bims-mameti 2021-01-03 papers

bims-mameti

Biomed News

on Macrophage metabolism in inflammation

Issue of 2021‒01‒03
thirty-four papers selected by
Alessio Menga
University of Turin

Human macrophages stimulate expression of inflammatory mediators in adipocytes; effects of second-generation antipsychotics and glucocorticoids on cellular cross-talk.
The versatile biochemistry of iron in macrophage effector functions.
Adipose-Derived Stem Cells from Obese Donors Polarize Macrophages and Microglia toward a Pro-Inflammatory Phenotype.
Zinc and Cadmium in the Aetiology and Pathogenesis of Osteoarthritis and Rheumatoid Arthritis.
Host-Derived Lipids from Tuberculous Pleurisy Impair Macrophage Microbicidal-Associated Metabolic Activity.
Resident and elicited murine macrophages differ in expression of their glycomes and glycan-binding proteins.
IL1β promotes immune suppression in the tumor microenvironment independent of the inflammasome and gasdermin D.
Microglial metabolic disturbances and neuroinflammation in cerebral infarction.
PLD1 and PLD2 differentially regulate the balance of macrophage polarization in inflammation and tissue injury.
Regulation of glycolytic genes in human macrophages by oxysterols: a potential role for Liver X receptors Oxysterols modulate glycolysis in human macrophages.
Molecular Crosstalk Between Macrophages and Mesenchymal Stromal Cells.
Tumor-Associated Macrophages in Tumor Immunity.
Myeloid Cells in Glioblastoma Microenvironment.
Short Term Acyl-CoA:Cholesterol Acyltransferase Inhibition, Combined with Apoprotein A1 Over-expression, Promotes Atherosclerosis Inflammation Resolution Mice.
Corticosterone Enhances the AMPK-Mediated Immunosuppressive Phenotype of Testicular Macrophages During Uropathogenic Escherichia coli Induced Orchitis.
Alterations of macrophage and neutrophil content in skeletal muscle of aged versus young mice.
The Acute Effects of 5 Fluorouracil on Skeletal Muscle Resident and Infiltrating Immune Cells in Mice.
Macrophage Reprogramming for Therapy.
Distinct Populations of Immune-Suppressive Macrophages Differentiate from Monocytic Myeloid-Derived Suppressor Cells in Cancer.
Aberrant RhoA activation in macrophages increases senescence-associated secretory phenotypes and ectopic calcification in muscular dystrophic mice.
Aging-Associated Alterations in Mammary Epithelia and Stroma Revealed by Single-Cell RNA Sequencing.
Binding of Macrophage Receptor MARCO, LDL, and LDLR to Disease-Associated Crystalline Structures.
Airway-Associated Macrophages in Homeostasis and Repair.
Plasticity of Epididymal Adipose Tissue in Response to Diet-Induced Obesity at Single-Nucleus Resolution.
Aging of the immune system and impaired muscle regeneration: A failure of immunomodulation of adult myogenesis.
Phagocytic activity of splenic macrophages is enhanced and accompanied by cytosolic alkalinization in TRPM7 kinase-dead mice.
Pharmacological activation of LXR alters the expression profile of tumor-associated macrophages and the abundance of regulatory T cells in the tumor microenvironment.
Stimulation of cholesterol biosynthesis in mitochondrial complex I-deficiency lowers reductive stress and improves motor function and survival in mice.
Circular dumbbell miR-34a-3p and -5p suppresses pancreatic tumor cell-induced angiogenesis and activates macrophages.
Aging Reprograms the Hematopoietic-Vascular Niche to Impede Regeneration and Promote Fibrosis.
Intracellular AIBP (Apolipoprotein A-I Binding Protein) Regulates Oxidized LDL (Low-Density Lipoprotein)-Induced Mitophagy in Macrophages.
Single-Cell Transcriptomics Reveal Immune Mechanisms of the Onset and Progression of IgA Nephropathy.
High-Throughput CRISPR Screening Identifies Genes Involved in Macrophage Viability and Inflammatory Pathways.
Immunogenic Chemotherapy Enhances Recruitment of CAR-T Cells to Lung Tumors and Improves Antitumor Efficacy when Combined with Checkpoint Blockade.

Psychoneuroendocrinology. 2020 Dec 11. pii: S0306-4530(20)30494-7. [Epub ahead of print]125 105071

Human macrophages stimulate expression of inflammatory mediators in adipocytes; effects of second-generation antipsychotics and glucocorticoids on cellular cross-talk.

Assel Sarsenbayeva, Priya Dipta, Martin Lundqvist, Kristina E Almby, Boaz Tirosh, Giada Di Nunzio, Jan W Eriksson, Maria J Pereira.

  OBJECTIVE: Adipose tissue inflammation and distorted macrophage-adipocyte communication are positively associated with metabolic disturbances. Some pharmacological agents, such as second-generation antipsychotics (SGAs) and synthetic glucocorticoid (GC) dexamethasone, tend to induce adverse metabolic side effects and the underlying mechanisms are not fully understood. Our work aimed to study whether SGAs and dexamethasone affect macrophage phenotype and macrophage-adipocyte communication on gene expression level. We selected the model involving THP-1-derived macrophages, polarized into M0, M1, and M2 phenotypes, and primary human mature subcutaneous adipocytes.METHODS: Abdominal subcutaneous adipose tissue needle biopsies were obtained from 6 healthy subjects (4F/2M; age: 22-64 yr; BMI: 21.7-27.6 kg/m2) followed by isolation of mature adipocytes. THP-1-human monocytic cell line was used for the study. THP-1 monocytes were differentiated and polarized into M0 (naïve), M1 (classically activated), and M2 (alternatively activated) macrophages. During and after polarization the macrophages were treated for 24 h without (control) or with therapeutic and supra-therapeutic concentrations of olanzapine (0.2 µM and 2.0 µM), aripiprazole (1.0 µM and 10 µM) and its active metabolite dehydroaripiprazole (0.4 µM and 4.0 µM). Isolated mature human adipocytes were co-incubated with THP-1-derived polarized macrophages pre-treated with SGAs after their polarization. Adipocytes and macrophages were collected before and after co-culture for mRNA expression analysis of genes involved in inflammation.
RESULTS: Co-incubation of mature human adipocytes with human macrophages, regardless of polarization, resulted in a marked induction of pro-inflammatory cytokines in adipocytes, including IL1B, IL6, TNFA, and IL10. Remarkably, it did not affect the expression of adipokines and genes involved in the regulation of energy, lipid, and glucose metabolism in adipocytes. Dexamethasone markedly reduced gene expression of pro-inflammatory cytokines in macrophages and prevented macrophage-induced inflammatory response in adipocytes. In contrast, SGAs did not affect macrophage-adipocyte communication and had a minute anti-inflammatory effect in macrophages at supra-therapeutic concentrations. Interestingly, the adipocytes co-incubated with M1 macrophages pre-treated with dexamethasone and SGAs particularly the supra-therapeutic concentration of olanzapine, reduced expression of LPL, LIPE, AKT1, and SLC2A4, suggesting that the expression of metabolic genes in adipocytes was dependent on the presence of pro-inflammatory M1 macrophages.
CONCLUSION: Together, these data suggest that macrophages induce expression of pro-inflammatory genes in human subcutaneous adipocytes without affecting the expression of adipokines or genes involved in energy regulation. Furthermore, our findings demonstrated that SGAs and dexamethasone had a mild effect on macrophage-adipocyte communication in M1 macrophage phenotype.

Keywords:  Adipose tissue; Glucocorticoids; Inflammation; Macrophages; Second-generation antipsychotics

DOI:  https://doi.org/10.1016/j.psyneuen.2020.105071
FEBS J. 2020 Dec 22.

The versatile biochemistry of iron in macrophage effector functions.

Jacques Behmoaras.

  Macrophages are mononuclear phagocytes with remarkable polarization ability that allow them to have tissue-specific functions during development, homeostasis, inflammatory and infectious disease. One particular trophic factor in the tissue environment is iron, which is intimately linked to macrophage effector functions. Macrophages have a well-described role in the control of systemic iron levels, but their activation state is also depending on iron-containing proteins/enzymes. Haemoproteins, dioxygenases and iron-sulfur (Fe-S) enzymes are iron-binding proteins that have bactericidal, metabolic and epigenetic-related functions, essential to shape the context-dependent macrophage polarization. In this review, I describe mainly pro-inflammatory macrophage polarization focussing on the role of iron biochemistry in selected haemoproteins and Fe-S enzymes. I show how iron, as part of haem or Fe-S clusters, participates in the cellular control of pro-inflammatory redox reactions in parallel with its role as enzymatic cofactor. I highlight a possible coordinated regulation of haemoproteins and Fe-S enzymes during classical macrophage activation. Finally, I describe tryptophan and α-ketoglutarate (αKG) metabolism as two essential effector pathways in macrophages that use diverse iron biochemistry at different enzymatic steps. Through these pathways, I show how iron participates in the regulation of essential metabolites that shape macrophage function.

Keywords:  Fe-S proteins; ROS; haemoprotein; iron; macrophage; metabolism; mitochondria

DOI:  https://doi.org/10.1111/febs.15682
Cells. 2020 Dec 25. pii: E26. [Epub ahead of print]10(1):

Adipose-Derived Stem Cells from Obese Donors Polarize Macrophages and Microglia toward a Pro-Inflammatory Phenotype.

Mark A A Harrison, Rachel M Wise, Brooke P Benjamin, Emily M Hochreiner, Omair A Mohiuddin, Bruce A Bunnell.

  Macrophages and microglia represent the primary phagocytes and first line of defense in the peripheral and central immune systems. They activate and polarize into a spectrum of pro- and anti-inflammatory phenotypes in response to various stimuli. This activation is tightly regulated to balance the appropriate immune response with tissue repair and homeostasis. Disruption of this balance results in inflammatory disease states and tissue damage. Adipose stem cells (ASCs) have great therapeutic potential because of the potent immunomodulatory capabilities which induce the polarization of microglia and macrophages to the anti-inflammatory, M2, phenotype. In this study, we examined the effects of donor heterogeneity on ASC function. Specifically, we investigated the impact of donor obesity on ASC stemness and immunomodulatory abilities. Our findings revealed that ASCs from obese donors (ObASCs) exhibited reduced stem cell characteristics when compared to ASCs from lean donors (LnASCs). We also found that ObASCs promote a pro-inflammatory phenotype in murine macrophage and microglial cells, as indicated by the upregulated expression of pro-inflammatory genes, increased nitric oxide pathway activity, and impaired phagocytosis and migration. These findings highlight the importance of considering individual donor characteristics such as obesity when selecting donors and cells for use in ASC therapeutic applications and regenerative medicine.

Keywords:  adipose stem cells (ASCs); adipose tissue; immunomodulation; inflammation; macrophage; microglia; obesity; polarization

DOI:  https://doi.org/10.3390/cells10010026
Nutrients. 2020 Dec 26. pii: E53. [Epub ahead of print]13(1):

Zinc and Cadmium in the Aetiology and Pathogenesis of Osteoarthritis and Rheumatoid Arthritis.

Theoharris Frangos, Wolfgang Maret.

  Osteoarthritis (OA) and rheumatoid arthritis (RA) are inflammatory articular conditions with different aetiology, but both result in joint damage. The nutritionally essential metal zinc (Zn2+) and the non-essential metal cadmium (Cd2+) have roles in these arthritic diseases as effectors of the immune system, inflammation, and metabolism. Despite both metal ions being redox-inert in biology, they affect the redox balance. It has been known for decades that zinc decreases in the blood of RA patients. It is largely unknown, however, whether this change is only a manifestation of an acute phase response in inflammation or relates to altered availability of zinc in tissues and consequently requires changes of zinc in the diet. As a cofactor in over 3000 human proteins and as a signaling ion, zinc affects many pathways relevant for arthritic disease. How it affects the diseases is not just a question of zinc status, but also an issue of mutations in the many proteins that maintain cellular zinc homoeostasis, such as zinc transporters of the ZIP (Zrt-/Irt-like protein) and ZnT families and metallothioneins, and the multiple pathways that change the expression of these proteins. Cadmium interferes with zinc's functions and there is increased uptake under zinc deficiency. Remarkably, cadmium exposure through inhalation is now recognized in the activation of macrophages to a pro-inflammatory state and suggested as a trigger of a specific form of nodular RA. Here, we discuss how these metal ions participate in the genetic, metabolic, and environmental factors that lead to joint destruction. We conclude that both metal ions should be monitored routinely in arthritic disease and that there is untapped potential for prognosis and treatment.

Keywords:  cadmium; osteoarthritis; rheumatoid arthritis; zinc

DOI:  https://doi.org/10.3390/nu13010053
Cell Rep. 2020 Dec 29. pii: S2211-1247(20)31536-9. [Epub ahead of print]33(13): 108547

Host-Derived Lipids from Tuberculous Pleurisy Impair Macrophage Microbicidal-Associated Metabolic Activity.

José Luis Marín Franco, Melanie Genoula, Dan Corral, Gabriel Duette, Malena Ferreyra, Mariano Maio, María Belén Dolotowicz, Omar Emiliano Aparicio-Trejo, Eduardo Patiño-Martínez, Alison Charton, Arnaud Métais, Federico Fuentes, Vanessa Soldan, Eduardo José Moraña, Domingo Palmero, Matías Ostrowski, Pablo Schierloh, Carmen Sánchez-Torres, Rogelio Hernández-Pando, José Pedraza-Chaverri, Yoann Rombouts, Denis Hudrisier, Emilie Layre, Christel Vérollet, Isabelle Maridonneau-Parini, Olivier Neyrolles, María Del Carmen Sasiain, Geanncarlo Lugo-Villarino, Luciana Balboa.

  Mycobacterium tuberculosis (Mtb) regulates the macrophage metabolic state to thrive in the host, yet the responsible mechanisms remain elusive. Macrophage activation toward the microbicidal (M1) program depends on the HIF-1α-mediated metabolic shift from oxidative phosphorylation (OXPHOS) toward glycolysis. Here, we ask whether a tuberculosis (TB) microenvironment changes the M1 macrophage metabolic state. We expose M1 macrophages to the acellular fraction of tuberculous pleural effusions (TB-PEs) and find lower glycolytic activity, accompanied by elevated levels of OXPHOS and bacillary load, compared to controls. The eicosanoid fraction of TB-PE drives these metabolic alterations. HIF-1α stabilization reverts the effect of TB-PE by restoring M1 metabolism. Furthermore, Mtb-infected mice with stabilized HIF-1α display lower bacillary loads and a pronounced M1-like metabolic profile in alveolar macrophages (AMs). Collectively, we demonstrate that lipids from a TB-associated microenvironment alter the M1 macrophage metabolic reprogramming by hampering HIF-1α functions, thereby impairing control of Mtb infection.

Keywords:  HIF-1α; aerobic glycolytic; eicosanoids; macrophages; oxygen consumption; pleural effusion; tuberculosis

DOI:  https://doi.org/10.1016/j.celrep.2020.108547
Cell Chem Biol. 2020 Dec 29. pii: S2451-9456(20)30514-6. [Epub ahead of print]

Resident and elicited murine macrophages differ in expression of their glycomes and glycan-binding proteins.

Diane D Park, Jiaxuan Chen, Matthew R Kudelka, Nan Jia, Carolyn A Haller, Revanth Kosaraju, Alykhan M Premji, Melina Galizzi, Alison V Nairn, Kelley W Moremen, Richard D Cummings, Elliot L Chaikof.

  The pleiotropic functions of macrophages in immune defense, tissue repair, and maintenance of tissue homeostasis are supported by the heterogeneity in macrophage sub-populations that differ both in ontogeny and polarization. Although glycans and glycan-binding proteins (GBPs) are integral to macrophage function and may contribute to macrophage diversity, little is known about the factors governing their expression. Here, we provide a resource for characterizing the N-/O-glycomes of various murine peritoneal macrophage sub-populations, demonstrating that glycosylation primarily reflects developmental origin and, to a lesser degree, cellular polarization. Furthermore, comparative analysis of GBP-coding genes in resident and elicited macrophages indicated that GBP expression is consistent with specialized macrophage functions and correlates with specific types of displayed glycans. An integrated, semi-quantitative approach was used to confirm distinct expression patterns of glycans and their binding proteins across different macrophages. The data suggest that regulation of glycan-protein complexes may be central to macrophage residence and recruitment.

Keywords:  glycan-binding proteins; glycomics; glycosylation; inflammation; macrophages; polarization

DOI:  https://doi.org/10.1016/j.chembiol.2020.12.005
Cancer Immunol Res. 2020 Dec 23. pii: canimm.0431.2020. [Epub ahead of print]

IL1β promotes immune suppression in the tumor microenvironment independent of the inflammasome and gasdermin D.

Mate Kiss, Lieselotte Vande Walle, Pedro H V Saavedra, Els Lebegge, Helena Van Damme, Aleksandar Murgaski, Junbin Qian, Manuel Ehling, Samantha Pretto, Evangelia Bolli, Jiri Keirsse, Pauline M R Bardet, Sana M Arnouk, Yvon Elkrim, Maryse Schmoetten, Jan Brughmans, Ayla Debraekeleer, Amelie Fossoul, Louis Boon, Geert Raes, Geert van Loo, Diether Lambrechts, Massimiliano Mazzone, Alain Beschin, Andy Wullaert, Mohamed Lamkanfi, Jo A Van Ginderachter, Damya Laoui.

Interleukin-1β (IL1β) is a central mediator of inflammation. Secretion of IL1β typically requires proteolytic maturation by the inflammasome and formation of membrane pores by gasdermin D (GSDMD). Emerging evidence suggests an important role for IL1β in promoting cancer progression in patients, but the underlying mechanisms are ill-defined. Here, we have shown a key role for IL1β in driving tumor progression in two distinct mouse tumor models. Notably, activation of the inflammasome, caspase-8 as well as the pore-forming proteins GSDMD and mixed lineage kinase domain-like protein (MLKL) in the host were dispensable for the release of intratumoral bioactive IL1β. Inflammasome-independent IL1β release promoted systemic neutrophil expansion and fostered accumulation of T-cell suppressive neutrophils in the tumor. Moreover, IL1β was essential for neutrophil infiltration triggered by antiangiogenic therapy, thereby contributing to treatment-induced immunosuppression. Deletion of IL1β allowed intratumoral accumulation of CD8+ effector T cells that subsequently activated tumor-associated macrophages. Depletion of either CD8+ T cells or macrophages abolished tumor growth inhibition in IL1β-deficient mice, demonstrating a crucial role for CD8+ T cell-macrophage crosstalk in the antitumor immune response. Overall, these results support a tumor-promoting role for IL1β through establishing an immunosuppressive microenvironment and show that inflammasome activation is not essential for release of this cytokine in tumors.

DOI: https://doi.org/10.1158/2326-6066.CIR-20-0431
J Pharmacol Sci. 2021 Jan;pii: S1347-8613(20)30113-4. [Epub ahead of print]145(1): 130-139

Microglial metabolic disturbances and neuroinflammation in cerebral infarction.

Haruna Takeda, Teruaki Yamaguchi, Hajime Yano, Junya Tanaka.

  Cerebral ischemia/reperfusion injury activates microglia, resident immune cells in the brain, and allows the infiltration of circulating immune cells into the ischemic lesions. Microglia play both exacerbating and protective roles in pathological processes and are thus often referred to as "double-edged swords." In ischemic brains, blood-borne macrophages play a role that is distinct from that of resident activated microglia. Recently, the metabolic alteration of immune cells in the pathogenesis of inflammatory disorders including cerebral infarction has become a critical target for investigation. We begin this review by describing the multifaceted functions of microglia in cerebral infarction. Next, we focus on the metabolic alterations that occur in microglia during pathological processes. We also discuss morphological changes that take place in the mitochondria, leading to functional disturbances, accompanied by alterations in microglial function. Moreover, we describe the involvement of the reactive oxygen species that are produced during aberrant metabolic activity. Finally, we discuss therapeutic strategies to ameliorate aggravative changes in metabolism.

Keywords:  Glycolysis; Macrophage; Nrf2; OXPHOS; ROS

DOI:  https://doi.org/10.1016/j.jphs.2020.11.007
J Cell Physiol. 2020 Dec 23.

PLD1 and PLD2 differentially regulate the balance of macrophage polarization in inflammation and tissue injury.

Won Chan Hwang, Seol Hwa Seo, Minju Kang, Rae Hee Kang, Gilbert Di Paolo, Kang-Yell Choi, Do Sik Min.

  Phospholipase D (PLD) isoforms PLD1 and PLD2 serve as the primary nodes where diverse signaling pathways converge. However, their isoform-specific functions remain unclear. We showed that PLD1 and PLD2 selectively couple to toll-like receptor 4 (TLR4) and interleukin 4 receptor (IL-4R) and differentially regulate macrophage polarization of M1 and M2 via the LPS-MyD88 axis and the IL-4-JAK3 signaling, respectively. Lipopolysaccharide (LPS) enhanced TLR4 or MyD88 interaction with PLD1; IL-4 induced IL-4R or JAK3 association with PLD2, indicating isozyme-specific signaling events. PLD1 and PLD2 are indispensable for M1 polarization and M2 polarization, respectively. Genetic and pharmacological targeting of PLD1 conferred protection against LPS-induced sepsis, cardiotoxin-induced muscle injury, and skin injury by promoting the shift toward M2; PLD2 ablation intensified disease severity by promoting the shift toward M1. Enhanced Foxp3+ regulatory T cell recruitment also influenced the anti-inflammatory phenotype of Pld1LyzCre macrophages. We reveal a previously uncharacterized role of PLD isoforms in macrophage polarization, signifying potential pharmacological interventions for macrophage modulation.

Keywords:  IL-4R; TLR-4; inflammation; macrophage polarization; phospholipase D; tissue homeostasis

DOI:  https://doi.org/10.1002/jcp.30224
Br J Pharmacol. 2020 Dec 29.

Regulation of glycolytic genes in human macrophages by oxysterols: a potential role for Liver X receptors Oxysterols modulate glycolysis in human macrophages.

Louise Ménégaut, Antoine Jalil, Thomas Pilot, Kevin van Dongen, Valentin Crespy, Eric Steinmetz, Jean Paul Pais de Barros, Audrey Geissler, Wilfried Le Goff, Nicolas Venteclef, Laurent Lagrost, Thomas Gautier, Charles Thomas, David Masson.

  BACKGROUND AND PURPOSE: Subset of macrophages within the atheroma plaque displays a high glucose uptake activity. Nevertheless, the molecular mechanisms as well as the pathophysiological significance of this high glucose need remain unclear. While a role for hypoxia and hypoxia inducible factor 1α has been demonstrated, the contribution of lipid microenvironment and more specifically oxysterols is yet to be explored.EXPERIMENTAL APPROACH: Human macrophages were conditioned in the presence of homogenates from human carotid plaques and expression of genes involved in glucose metabolism was quantified. Correlative analyses between gene expression and the oxysterol composition of plaques were performed.
KEY RESULTS: Conditioning of human macrophages by plaque homogenates induces expression of several genes involved in glucose uptake and glycolysis including glucose transporter 1 (GLUT1), and hexokinases 2 and 3 (HK2 and HK3), This activation is significantly correlated to the oxysterol content of the plaque samples and is associated with a significant increase in the glycolytic activity of the cells. Pharmacological inverse agonist of the oxysterol receptor Liver X Receptor (LXR) partially reverses the induction of glycolysis genes without affecting macrophage glycolytic activity. Chromatin immunoprecipitation analysis confirms the implication of LXR in the regulation of GLUT1 and HK2 CONCLUSIONS AND IMPLICATIONS: While our work supports a role of oxysterols and LXR in the modulation of macrophage metabolism in atheroma plaques, it also highlights some LXR-independent effects of plaques samples. Finally, this study identifies the hexokinase HK3 as a promising target in the context of atherosclerosis.

Keywords:  Liver X Receptors; Oxysterols; glycolysis; macrophages

DOI:  https://doi.org/10.1111/bph.15358
Front Cell Dev Biol. 2020 ;8 600160

Molecular Crosstalk Between Macrophages and Mesenchymal Stromal Cells.

Hazel Y Stevens, Annie C Bowles, Carolyn Yeago, Krishnendu Roy.

  Mesenchymal stromal cells (MSCs) have been widely investigated for regenerative medicine applications, from treating various inflammatory diseases as a cell therapy to generating engineered tissue constructs. Numerous studies have evaluated the potential effects of MSCs following therapeutic administration. By responding to their surrounding microenvironment, MSCs may mediate immunomodulatory effects through various mechanisms that directly (i.e., contact-dependent) or indirectly (i.e., paracrine activity) alter the physiology of endogenous cells in various disease pathologies. More specifically, a pivotal crosstalk between MSCs and tissue-resident macrophages and monocytes (TMφ) has been elucidated using in vitro and in vivo preclinical studies. An improved understanding of this crosstalk could help elucidate potential mechanisms of action (MOAs) of therapeutically administered MSCs. TMφ, by nature of their remarkable functional plasticity and prevalence within the body, are uniquely positioned as critical modulators of the immune system - not only in maintaining homeostasis but also during pathogenesis. This has prompted further exploration into the cellular and molecular alterations to TMφ mediated by MSCs. In vitro assays and in vivo preclinical trials have identified key interactions mediated by MSCs that polarize the responses of TMφ from a pro-inflammatory (i.e., classical activation) to a more anti-inflammatory/reparative (i.e., alternative activation) phenotype and function. In this review, we describe physiological and pathological TMφ functions in response to various stimuli and discuss the evidence that suggest specific mechanisms through which MSCs may modulate TMφ phenotypes and functions, including paracrine interactions (e.g., secretome and extracellular vesicles), nanotube-mediated intercellular exchange, bioenergetics, and engulfment by macrophages. Continued efforts to elucidate this pivotal crosstalk may offer an improved understanding of the immunomodulatory capacity of MSCs and inform the development and testing of potential MOAs to support the therapeutic use of MSCs and MSC-derived products in various diseases.

Keywords:  cell therapy; immunomodulation; macrophages (M1/M2); mechanism of action (MOA); mesenchymal stromal (or stem) cells

DOI:  https://doi.org/10.3389/fcell.2020.600160
Front Immunol. 2020 ;11 583084

Tumor-Associated Macrophages in Tumor Immunity.

Yueyun Pan, Yinda Yu, Xiaojian Wang, Ting Zhang.

  Tumor-associated macrophages (TAMs) represent one of the main tumor-infiltrating immune cell types and are generally categorized into either of two functionally contrasting subtypes, namely classical activated M1 macrophages and alternatively activated M2 macrophages. The former typically exerts anti-tumor functions, including directly mediate cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC) to kill tumor cells; the latter can promote the occurrence and metastasis of tumor cells, inhibit T cell-mediated anti-tumor immune response, promote tumor angiogenesis, and lead to tumor progression. Both M1 and M2 macrophages have high degree of plasticity and thus can be converted into each other upon tumor microenvironment changes or therapeutic interventions. As the relationship between TAMs and malignant tumors becoming clearer, TAMs have become a promising target for developing new cancer treatment. In this review, we summarize the origin and types of TAMs, TAMs interaction with tumors and tumor microenvironment, and up-to-date treatment strategies targeting TAMs.

Keywords:  immunosuppression; regulation; tumor microenvironment; tumor therapy; tumor-associated macrophages

DOI:  https://doi.org/10.3389/fimmu.2020.583084
Cells. 2020 Dec 24. pii: E18. [Epub ahead of print]10(1):

Myeloid Cells in Glioblastoma Microenvironment.

Alessandra De Leo, Alessio Ugolini, Filippo Veglia.

  Glioblastoma (GBM) is the most aggressive, malignant primary brain tumor in adults. GBM is notoriously resistant to immunotherapy mainly due to its unique immune microenvironment. High dimensional data analysis reveals the extensive heterogeneity of immune components making up the GBM microenvironment. Myeloid cells are the most predominant contributors to the GBM microenvironment; these cells are critical regulators of immune and therapeutic responses to GBM. Here, we will review the most recent advances on the characteristics and functions of different populations of myeloid cells in GBM, including bone marrow-derived macrophages, microglia, myeloid-derived suppressor cells, dendritic cells, and neutrophils. Epigenetic, metabolic, and phenotypic peculiarities of microglia and bone marrow-derived macrophages will also be assessed. The final goal of this review will be to provide new insights into novel therapeutic approaches for specific targeting of myeloid cells to improve the efficacy of current treatments in GBM patients.

Keywords:  brain cancers; dendritic cells; glioblastoma; glioma; microglia; myeloid cells; myeloid-derived suppressor cells; neutrophils; tumor-associated macrophages

DOI:  https://doi.org/10.3390/cells10010018
Mol Pharmacol. 2020 Dec 31. pii: MOLPHARM-AR-2020-000108. [Epub ahead of print]

Short Term Acyl-CoA:Cholesterol Acyltransferase Inhibition, Combined with Apoprotein A1 Over-expression, Promotes Atherosclerosis Inflammation Resolution Mice.

Jaume Amengual, Yoscar Ogando, Cyrus Nikain, Alexandra Quezada, Kun Qian, Tomas Vaisar, Edward A Fisher.

  Acyl-CoA:cholesterol acyltransferase (ACAT) mediates cellular cholesterol esterification. In atherosclerotic plaque macrophages, ACAT promotes cholesteryl ester accumulation, resulting in foam cell formation and atherosclerosis progression. Its complete inactivation in mice, however, showed toxic effects because of an excess of free cholesterol (FC) in macrophages, which can cause ER stress, cholesterol crystal formation, and inflammasome activation. Our previous studies showed that long-term partial ACAT inhibition, achieved by dietary supplementation with Fujirebio F1394, delays atherosclerosis progression in apoprotein E-deficient (Apoe-/- ) mice by reducing plaque foam cell formation without inflammatory or toxic effects. Here, we determined whether short-term partial inhibition of ACAT, in combination with an enhanced systemic FC acceptor capacity, has synergistic benefits. Thus, we crossbred Apoe-/- with human apoprotein A1-transgenic (APOA1tg/tg ) mice, which have elevated cholesterol-effluxing high-density lipoprotein particles, and subjected Apoe-/- and APOA1tg/tg/Apoe-/- mice to an atherogenic diet to develop advanced plaques. Then mice were either euthanized (baseline) or fed purified standard diet with or without F1394 for four more weeks. Plaques of APOA1tg/tg/Apoe-/- mice fed F1394 showed a 60% reduction of macrophages accompanied by multiple other benefits, such as reduced inflammation and favorable changes in extracellular composition, in comparison to Apoe-/- baseline mice. In addition, there was no accumulation of cholesterol crystals or signs of toxicity. Overall, these results show that short-term partial ACAT inhibition, coupled to increased cholesterol efflux capacity, favorably remodels atherosclerosis lesions, supporting the potential of these combined therapies in the treatment of advanced atherosclerosis. Significance Statement Short-term pharmacological inhibition of ACAT-mediated cholesterol esterification, in combination with increased free cholesterol efflux acceptors, has positive effects in mice by (1) reducing the inflammatory state of the plaque macrophages, and (2) favoring compositional changes associated with plaque stabilization. These effects occur without toxicity, showing the potential of these combined therapies in the treatment of advanced atherosclerosis.

Keywords:  apolipid proteins; atherosclerosis; cholesterol; cholesterol metabolism/lipoproteins; macrophages

DOI:  https://doi.org/10.1124/molpharm.120.000108
Front Immunol. 2020 ;11 583276

Corticosterone Enhances the AMPK-Mediated Immunosuppressive Phenotype of Testicular Macrophages During Uropathogenic Escherichia coli Induced Orchitis.

Zhengguo Zhang, Ziming Jiang, Yiming Zhang, Yu Zhang, Yan Yan, Sudhanshu Bhushan, Andreas Meinhardt, Zhihai Qin, Ming Wang.

  Testicular macrophages (TM) play a central role in maintaining testicular immune privilege and protecting spermatogenesis. Recent studies showed that their immunosuppressive properties are maintained by corticosterone in the testicular interstitial fluid, but the underlying molecular mechanisms are unknown. In this study, we treated mouse bone marrow-derived macrophages (BMDM) with corticosterone (50 ng/ml) and uncovered AMP-activated protein kinase (AMPK) activation as a critical event in M2 polarization at the phenotypic, metabolic, and cytokine production level. Primary TM exhibited remarkably similar metabolic and phenotypic features to corticosterone-treated BMDM, which were partially reversed by AMPK-inhibition. In a murine model of uropathogenic E. coli-elicited orchitis, intraperitoneal injection with corticosterone (0.1mg/day) increased the percentage of M2 TM in vivo, in a partially AMPK-dependent manner. This study integrates the influence of corticosterone on M2 macrophage metabolic pathways, phenotype, and function, and highlights a promising new avenue for the development of innovative therapeutics for orchitis patients.

Keywords:  AMPK; Corticosterone; Fatty acid oxidation (FAO); Orchitis; Testicular macrophage

DOI:  https://doi.org/10.3389/fimmu.2020.583276
Muscle Nerve. 2021 Jan 01.

Alterations of macrophage and neutrophil content in skeletal muscle of aged versus young mice.

Noriaki Kawanishi, Shuichi Machida.

  INTRODUCTION: Skeletal muscle inflammation and oxidative stress are associated with aging-related loss of muscle mass and may be attributable to alterations in the number and types of leukocytes in skeletal muscle. Here, we tested the hypothesis that aging changes the number and composition of leukocyte subsets in skeletal muscle tissue.METHODS: Skeletal muscle was sampled from 4-month-old (young) and 27-month-old (old) C57BL/6J mice. Mononuclear cells of the gastrocnemius muscle were isolated, and flow cytometry was used to characterize the number and types of immune cells.
RESULTS: The number of neutrophils and Ly-6C+ inflammatory macrophages in the skeletal muscle was significantly higher in old mice than in young mice. Inflammation and oxidative stress (measured using the markers phosphorylated JNK and nitrotyrosine) were also higher in the skeletal muscle of old mice than in that of young mice.
DISCUSSION: Increasing age promotes skeletal muscle inflammation and oxidative stress, as well as infiltration of inflammatory macrophages and neutrophils.

Keywords:  Increasing age; Inflammation; Loss of muscle mass; Macrophage; Oxidative stress

DOI:  https://doi.org/10.1002/mus.27158
Front Physiol. 2020 ;11 593468

The Acute Effects of 5 Fluorouracil on Skeletal Muscle Resident and Infiltrating Immune Cells in Mice.

Brandon N VanderVeen, Alexander T Sougiannis, Kandy T Velazquez, James A Carson, Daping Fan, E Angela Murphy.

  5 fluorouracil (5FU) has been a first-choice chemotherapy drug for several cancer types (e.g., colon, breast, head, and neck); however, its efficacy is diminished by patient acquired resistance and pervasive side effects. Leukopenia is a hallmark of 5FU; however, the impact of 5FU-induced leukopenia on healthy tissue is only becoming unearthed. Recently, skeletal muscle has been shown to be impacted by 5FU in clinical and preclinical settings and weakness and fatigue remain among the most consistent complaints in cancer patients undergoing chemotherapy. Monocytes, or more specifically macrophages, are the predominate immune cell in skeletal muscle which regulate turnover and homeostasis through removal of damaged or old materials as well as coordinate skeletal muscle repair and remodeling. Whether 5FU-induced leukopenia extends beyond circulation to impact resident and infiltrating skeletal muscle immune cells has not been examined. The purpose of the study was to examine the acute effects of 5FU on resident and infiltrating skeletal muscle monocytes and inflammatory mediators. Male C57BL/6 mice were given a physiologically translatable dose (35 mg/kg) of 5FU, or PBS, i.p. once daily for 5 days to recapitulate 1 dosing cycle. Our results demonstrate that 5FU reduced circulating leukocytes, erythrocytes, and thrombocytes while inducing significant body weight loss (>5%). Flow cytometry analysis of the skeletal muscle indicated a reduction in total CD45+ immune cells with a corresponding decrease in total CD45+CD11b+ monocytes. There was a strong relationship between circulating leukocytes and skeletal muscle CD45+ immune cells. Skeletal muscle Ly6cHigh activated monocytes and M1-like macrophages were reduced with 5FU treatment while total M2-like CD206+CD11c- macrophages were unchanged. Interestingly, 5FU reduced bone marrow CD45+ immune cells and CD45+CD11b+ monocytes. Our results demonstrate that 5FU induced body weight loss and decreased skeletal muscle CD45+ immune cells in association with a reduction in infiltrating Ly6cHigh monocytes. Interestingly, the loss of skeletal muscle immune cells occurred with bone marrow cell cycle arrest. Together our results highlight that skeletal muscle is sensitive to 5FU's off-target effects which disrupts both circulating and skeletal muscle immune cells.

Keywords:  bone marrow; chemotherapy; macrophages; monocytes; skeletal muscle

DOI:  https://doi.org/10.3389/fphys.2020.593468
Immunology. 2020 Dec 23.

Macrophage Reprogramming for Therapy.

Valentina M T Bart, Robert J Pickering, Philip R Taylor, Natacha Ipseiz.

  Dysfunction of the immune system underlies a plethora of human diseases, requiring the development of immunomodulatory therapeutic intervention. To date, most strategies employed have been focusing on the modification of T lymphocytes and although remarkable improvement have been obtained, results often fall short of the intended outcome. Recent cutting-edge technologies have highlighted macrophages as potential targets for disease control. Macrophages play central roles in development, homeostasis and host defence and their dysfunction and dysregulation have been implicated in the onset and pathogenesis of multiple disorders including cancer, neurodegeneration, autoimmunity, and metabolic diseases. Recent advancements have led to a greater understanding of macrophage origin, diversity and function, in both health and disease. Over the last few years, a variety of strategies targeting macrophages have been developed and these open new therapeutic opportunities. Here, we review the progress in macrophage reprogramming in various disorders and discuss the potential implications and challenges for macrophage-targeted approaches in human disease.

Keywords:  Macrophages; polarization; reprogramming

DOI:  https://doi.org/10.1111/imm.13300
Cell Rep. 2020 Dec 29. pii: S2211-1247(20)31560-6. [Epub ahead of print]33(13): 108571

Distinct Populations of Immune-Suppressive Macrophages Differentiate from Monocytic Myeloid-Derived Suppressor Cells in Cancer.

Taekyoung Kwak, Fang Wang, Hui Deng, Thomas Condamine, Vinit Kumar, Michela Perego, Andrew Kossenkov, Luis J Montaner, Xiaowei Xu, Wei Xu, Cathy Zheng, Lynn M Schuchter, Ravi K Amaravadi, Tara C Mitchell, Giorgos C Karakousis, Charles Mulligan, Brian Nam, Gregory Masters, Neil Hockstein, Joseph Bennett, Yulia Nefedova, Dmitry I Gabrilovich.

  Here, we report that functional heterogeneity of macrophages in cancer could be determined by the nature of their precursors: monocytes (Mons) and monocytic myeloid-derived suppressor cells (M-MDSCs). Macrophages that are differentiated from M-MDSCs, but not from Mons, are immune suppressive, with a genomic profile matching that of M-MDSCs. Immune-suppressive activity of M-MDSC-derived macrophages is dependent on the persistent expression of S100A9 protein in these cells. S100A9 also promotes M2 polarization of macrophages. Tissue-resident- and Mon-derived macrophages lack expression of this protein. S100A9-dependent immune-suppressive activity of macrophages involves transcription factor C/EBPβ. The presence of S100A9-positive macrophages in tumor tissues is associated with shorter survival in patients with head and neck cancer and poor response to PD-1 antibody treatment in patients with metastatic melanoma. Thus, this study reveals the pathway of the development of immune-suppressive macrophages and suggests an approach to their selective targeting.

Keywords:  S100A9; immune suppression; myeloid-derived suppressor cells; tumor associated macrophages; tumor immunology

DOI:  https://doi.org/10.1016/j.celrep.2020.108571
Aging (Albany NY). 2020 Dec 23. 12

Aberrant RhoA activation in macrophages increases senescence-associated secretory phenotypes and ectopic calcification in muscular dystrophic mice.

Xiaodong Mu, Chi-Yi Lin, William S Hambright, Ying Tang, Sudheer Ravuri, Aiping Lu, Polina Matre, Wanqun Chen, Xueqin Gao, Yan Cui, Ling Zhong, Bing Wang, Johnny Huard.

  Duchenne Muscular Dystrophy (DMD) patients often suffer from both muscle wasting and osteoporosis. Our previous studies have revealed reduced regeneration potential in skeletal muscle and bone, concomitant with ectopic calcification of soft tissues in double knockout (dKO, dystrophin-/-; utrophin-/-) mice, a severe murine model for DMD. We found significant involvement of RhoA/ROCK (Rho-Associated Protein Kinase) signaling in mediating ectopic calcification of muscles in dKO mice. However, the cellular identity of these RhoA+ cells, and the role that RhoA plays in the chronic inflammation-associated pathologies has not been elucidated. Here, we report that CD68+ macrophages are highly prevalent at the sites of ectopic calcification of dKO mice, and that these macrophages highly express RhoA. Macrophages from dKO mice feature a shift towards a more pro-inflammatory M1 polarization and an increased expression of various senescence-associated secretory phenotype (SASP) factors that was reduced with the RhoA/ROCK inhibitor Y-27632. Further, systemic inhibition of RhoA activity in dKO mice led to reduced number of RhoA+/CD68+ cells, as well as a reduction in fibrosis and ectopic calcification. Together, these data revealed that RhoA signaling may be a key regulator of imbalanced mineralization in the dystrophic musculoskeletal system and consequently a therapeutic target for the treatment of DMD or other related muscle dystrophies.

Keywords:  cellular senescence; chronic inflammation; heterotopic ossification; muscle dystrophy; muscle stem cell

DOI:  https://doi.org/10.18632/aging.202413
Cell Rep. 2020 Dec 29. pii: S2211-1247(20)31555-2. [Epub ahead of print]33(13): 108566

Aging-Associated Alterations in Mammary Epithelia and Stroma Revealed by Single-Cell RNA Sequencing.

Carman Man-Chung Li, Hana Shapiro, Christina Tsiobikas, Laura M Selfors, Huidong Chen, Jennifer Rosenbluth, Kaitlin Moore, Kushali P Gupta, G Kenneth Gray, Yaara Oren, Michael J Steinbaugh, Jennifer L Guerriero, Luca Pinello, Aviv Regev, Joan S Brugge.

  Aging is closely associated with increased susceptibility to breast cancer, yet there have been limited systematic studies of aging-induced alterations in the mammary gland. Here, we leverage high-throughput single-cell RNA sequencing to generate a detailed transcriptomic atlas of young and aged murine mammary tissues. By analyzing epithelial, stromal, and immune cells, we identify age-dependent alterations in cell proportions and gene expression, providing evidence that suggests alveolar maturation and physiological decline. The analysis also uncovers potential pro-tumorigenic mechanisms coupled to the age-associated loss of tumor suppressor function and change in microenvironment. In addition, we identify a rare, age-dependent luminal population co-expressing hormone-sensing and secretory-alveolar lineage markers, as well as two macrophage populations expressing distinct gene signatures, underscoring the complex heterogeneity of the mammary epithelia and stroma. Collectively, this rich single-cell atlas reveals the effects of aging on mammary physiology and can serve as a useful resource for understanding aging-associated cancer risk.

Keywords:  aging; endothelial cells; fibroblasts; luminal and myoepithelial cells; macrophages; mammary epithelia and stroma; single-cell RNA-seq

DOI:  https://doi.org/10.1016/j.celrep.2020.108566
Front Immunol. 2020 ;11 596103

Binding of Macrophage Receptor MARCO, LDL, and LDLR to Disease-Associated Crystalline Structures.

Anika Alberts, Annika Klingberg, Leonie Hoffmeister, Anne Kathrin Wessig, Korbinian Brand, Andreas Pich, Konstantin Neumann.

  Endogenous and exogenous crystalline structures are involved in various pathologies and diseases in humans by inducing sterile inflammation, mechanical stress, or obstruction of excretory organs. The best studied of these diseases is gout, in which crystallization of uric acid in the form of monosodium urate (MSU) mainly in synovial fluid of the joints leads to sterile inflammation. Though some of these diseases have been described for centuries, little is known about if and how the immune system recognizes the associated crystals. Thus, in this study we aimed at identifying possible recognition molecules of MSU using liquid chromatography-mass spectrometry (LC-MS) analysis of MSU-binding serum proteins. Among the strongest binding proteins, we unexpectedly found two transmembrane receptors, namely macrophage receptor with collagenous structure (MARCO) and low-density lipoprotein (LDL) receptor (LDLR). We show that recombinant versions of both human and mouse MARCO directly bind to unopsonized MSU and several other disease-associated crystals. Recombinant LDLR binds many types of crystals mainly when opsonized with serum proteins. We show that this interaction is predominantly mediated by LDL, which we found to bind to all crystalline structures tested except for cholesterol crystals. However, murine macrophages lacking LDLR expression do neither show altered phagocytosis nor interleukin-1β (IL-1β) production in response to opsonized crystals. Binding of LDL to MSU has previously been shown to inhibit the production of reactive oxygen species (ROS) by human neutrophils. We extend these findings and show that LDL inhibits neutrophil ROS production in response to most crystals tested, even cholesterol crystals. The inhibition of neutrophil ROS production only partly correlated with the inhibition of IL-1β production by peripheral blood mononuclear cells (PBMCs): LDL inhibited IL-1β production in response to large MSU crystals, but not small MSU or silica crystals. This may suggest distinct upstream signals for IL-1β production depending on the size or the shape of the crystals. Together, we identify MARCO and LDLR as potential crystal recognition receptors, and show that LDL binding to diverse disease-associated crystalline structures has variable effects on crystal-induced innate immune cell activation.

Keywords:  atherosclerosis; crystallopathies; gout; inflammasome; sterile inflammation; urate; uric acid

DOI:  https://doi.org/10.3389/fimmu.2020.596103
Cell Rep. 2020 Dec 29. pii: S2211-1247(20)31542-4. [Epub ahead of print]33(13): 108553

Airway-Associated Macrophages in Homeostasis and Repair.

Anna E Engler, Alexandra B Ysasi, Riley M F Pihl, Carlos Villacorta-Martin, Hailey M Heston, Hanne M K Richardson, Bibek R Thapa, Noah R Moniz, Anna C Belkina, Sarah A Mazzilli, Jason R Rock.

  There is an increasing appreciation for the heterogeneity of myeloid lineages in the lung, but relatively little is known about populations specifically associated with the conducting airways. We use single-cell RNA sequencing, flow cytometry, and immunofluorescence to characterize myeloid cells of the mouse trachea during homeostasis and epithelial injury/repair. We identify submucosal macrophages, similar to lung interstitial macrophages, and intraepithelial macrophages. Following injury, there are early increases in neutrophils and submucosal macrophages, including M2-like macrophages. Intraepithelial macrophages are lost after injury and later restored by CCR2+ monocytes. We show that repair of the tracheal epithelium is impaired in Ccr2-deficient mice. Mast cells and group 2 innate lymphoid cells are sources of interleukin-13 (IL-13) that polarize macrophages and directly influence basal cell behaviors. Their proximity to the airway epithelium establishes these myeloid populations as potential therapeutic targets for airway disease.

Keywords:  airway; macrophages; niche; regeneration; trachea

DOI:  https://doi.org/10.1016/j.celrep.2020.108553
Cell Metab. 2020 Dec 24. pii: S1550-4131(20)30659-8. [Epub ahead of print]

Plasticity of Epididymal Adipose Tissue in Response to Diet-Induced Obesity at Single-Nucleus Resolution.

Anitta Kinga Sárvári, Elvira Laila Van Hauwaert, Lasse Kruse Markussen, Ellen Gammelmark, Ann-Britt Marcher, Morten Frendø Ebbesen, Ronni Nielsen, Jonathan Richard Brewer, Jesper Grud Skat Madsen, Susanne Mandrup.

  Adipose tissues display a remarkable ability to adapt to the dietary status. Here, we have applied single-nucleus RNA-seq to map the plasticity of mouse epididymal white adipose tissue at single-nucleus resolution in response to high-fat-diet-induced obesity. The single-nucleus approach allowed us to recover all major cell types and to reveal distinct transcriptional stages along the entire adipogenic trajectory from preadipocyte commitment to mature adipocytes. We demonstrate the existence of different adipocyte subpopulations and show that obesity leads to disappearance of the lipogenic subpopulation and increased abundance of the stressed lipid-scavenging subpopulation. Moreover, obesity is associated with major changes in the abundance and gene expression of other cell populations, including a dramatic increase in lipid-handling genes in macrophages at the expense of macrophage-specific genes. The data provide a powerful resource for future hypothesis-driven investigations of the mechanisms of adipocyte differentiation and adipose tissue plasticity.

Keywords:  adipocyte differentiation; adipocyte subpopulations; adipose tissue plasticity; fibro-adipogenic progenitors; in vivo adipogenesis; lipid-associated macrophages; snRNA-seq

DOI:  https://doi.org/10.1016/j.cmet.2020.12.004
Exp Gerontol. 2020 Dec 23. pii: S0531-5565(20)30548-9. [Epub ahead of print] 111200

Aging of the immune system and impaired muscle regeneration: A failure of immunomodulation of adult myogenesis.

James G Tidball, Ivan Flores, Steven S Welc, Michelle Wehling-Henricks, Eisuke Ochi.

  Skeletal muscle regeneration that follows acute injury is strongly influenced by interactions with immune cells that invade and proliferate in the damaged tissue. Discoveries over the past 20 years have identified many of the key mechanisms through which myeloid cells, especially macrophages, regulate muscle regeneration. In addition, lymphoid cells that include CD8+ T-cells and regulatory T-cells also significantly affect the course of muscle regeneration. During aging, the regenerative capacity of skeletal muscle declines, which can contribute to progressive loss of muscle mass and function. Those age-related reductions in muscle regeneration are accompanied by systemic, age-related changes in the immune system, that affect many of the myeloid and lymphoid cell populations that can influence muscle regeneration. In this review, we present recent discoveries that indicate that aging of the immune system contributes to the diminished regenerative capacity of aging muscle. Intrinsic, age-related changes in immune cells modify their expression of factors that affect the function of a population of muscle stem cells, called satellite cells, that are necessary for normal muscle regeneration. For example, age-related reductions in the expression of growth differentiation factor-3 (GDF3) or CXCL10 by macrophages negatively affect adult myogenesis, by disrupting regulatory interactions between macrophages and satellite cells. Those changes contribute to a reduction in the numbers and myogenic capacity of satellite cells in old muscle, which reduces their ability to restore damaged muscle. In addition, aging produces changes in the expression of molecules that regulate the inflammatory response to injured muscle, which also contributes to age-related defects in muscle regeneration. For example, age-related increases in the production of osteopontin by macrophages disrupts the normal inflammatory response to muscle injury, resulting in regenerative defects. These nascent findings represent the beginning of a newly-developing field of investigation into mechanisms through which aging of the immune system affects muscle regeneration.

Keywords:  Aging; Muscle inflammation; Muscle injury; Muscle regeneration; Skeletal muscle

DOI:  https://doi.org/10.1016/j.exger.2020.111200
FEBS J. 2020 Dec 22.

Phagocytic activity of splenic macrophages is enhanced and accompanied by cytosolic alkalinization in TRPM7 kinase-dead mice.

Pavani Beesetty, Jananie Rockwood, Taku Kaitsuka, Tetyana Zhelay, Siham Hourani, Masayuki Matsushita, J Ashot Kozak.

  Transient receptor potential melastatin 7 (TRPM7) is a unique protein functioning as a cation channel as well as a serine/threonine kinase and is highly expressed in immune cells such as lymphocytes and macrophages. TRPM7 kinase-dead (KD) mouse model has been used to investigate the role of this protein in immune cells; these animals display moderate splenomegaly and ectopic hemopoiesis. The basal TRPM7 current magnitudes in peritoneal macrophages isolated from KD mice were higher, however the maximum currents, achieved after cytoplasmic Mg2+ washout were not different. In the present study, we investigated the consequences of TRPM7 kinase inactivation in splenic and peritoneal macrophages. We measured the basal phagocytic activity of splenic macrophages using fluorescent latex beads, pHrodo zymosan bioparticles and opsonized red blood cells. KD macrophages phagocytized more efficiently and had slightly higher baseline calcium levels compared to WT cells. We found no obvious differences in store-operated Ca2+ entry between WT and KD macrophages. By contrast, the resting cytosolic pH in KD macrophages was significantly more alkaline than in WT. Pharmacological blockade of sodium-hydrogen exchanger 1 (NHE1) reversed the cytosolic alkalinization and reduced phagocytosis in KD macrophages. Basal TRPM7 channel activity in KD macrophages was also reduced after NHE1 blockade. Cytosolic Mg2+ sensitivity of TRPM7 channels measured in peritoneal macrophages was similar in WT and KD mice. The higher basal TRPM7 channel activity in KD macrophages is likely due to alkalinization. Our results identify a novel role for TRPM7 kinase as a suppressor of basal phagocytosis and a regulator of cellular pH.

Keywords:  SLC9A1; alkalinization; erythrophagocytosis; ion channel; spleen

DOI:  https://doi.org/10.1111/febs.15683
Cancer Res. 2020 Dec 23. pii: canres.3360.2019. [Epub ahead of print]

Pharmacological activation of LXR alters the expression profile of tumor-associated macrophages and the abundance of regulatory T cells in the tumor microenvironment.

José M Carbó, Theresa E León, Joan Font-Díaz, Juan Vladimir De la Rosa, Antonio Castrillo, Felix R Picard, Daniel Staudenraus, Magdalena Huber, Lídia Cedó, Joan Carles Escolà-Gil, Lucía Campos, Latifa Bakiri, Erwin F Wagner, Carme Caelles, Thomas Stratmann, Jo A Van Ginderachter, Annabel F Valledor.

Liver X receptors (LXR) are transcription factors from the nuclear receptor family that are activated by oxysterols and synthetic high-affinity agonists. In this study, we assessed the anti-tumor effects of synthetic LXR agonist TO901317 in a murine model of syngeneic Lewis Lung carcinoma. Treatment with TO901317 inhibited tumor growth in wild-type but not in LXR-deficient mice, indicating that the anti-tumor effects of the agonist depends on functional LXR activity in host cells. Pharmacological activation of the LXR pathway reduced the intratumoral abundance of regulatory T cells (Treg) and the expression of the Treg-attracting chemokine Ccl17 by MHCIIhigh tumor-associated macrophages (TAM). Moreover, gene expression profiling indicated a broad negative impact of the LXR agonist on other mechanisms used by TAM for the maintenance of an immunosuppressive environment. In studies exploring the macrophage response to GM-CSF or IL-4, activated LXR repressed IRF4 expression, resulting in subsequent downregulation of IRF4-dependent genes including Ccl17. Taken together, this work reveals the combined actions of the LXR pathway in the control of TAM responses that contribute to the anti-tumoral effects of pharmacological LXR activation. Moreover, these data provide new insights for the development of novel therapeutic options for the treatment of cancer.

DOI: https://doi.org/10.1158/0008-5472.CAN-19-3360
Biochim Biophys Acta Mol Basis Dis. 2020 Dec 29. pii: S0925-4439(20)30410-5. [Epub ahead of print] 166062

Stimulation of cholesterol biosynthesis in mitochondrial complex I-deficiency lowers reductive stress and improves motor function and survival in mice.

Tom J J Schirris, Sergio Rossell, Ria de Haas, Sanne J C M Frambach, Charlotte A Hoogstraten, G Herma Renkema, Julien D Beyrath, Peter H G M Willems, Martijn A Huynen, Jan A M Smeitink, Frans G M Russel, Richard A Notebaart.

  The majority of cellular energy is produced by the mitochondrial oxidative phosphorylation (OXPHOS) system. Failure of the first OXPHOS enzyme complex, NADH:ubiquinone oxidoreductase or complex I (CI), is associated with multiple signs and symptoms presenting at variable ages of onset. There is no approved drug treatment yet to slow or reverse the progression of CI-deficient disorders. Here, we present a comprehensive human metabolic network model of genetically characterized CI-deficient patient-derived fibroblasts. Model calculations predicted that increased cholesterol production, export, and utilization can counterbalance the surplus of reducing equivalents in patient-derived fibroblasts, as these pathways consume considerable amounts of NAD(P)H. We show that fibrates attenuated increased NAD(P)H levels and improved CI-deficient fibroblast growth by stimulating the production of cholesterol via enhancement of its cellular efflux. In CI-deficient (Ndufs4-/-) mice, fibrate treatment resulted in prolonged survival and improved motor function, which was accompanied by an increased cholesterol efflux from peritoneal macrophages. Our results shine a new light on the use of compensatory biological pathways in mitochondrial dysfunction which may lead to novel therapeutic interventions for mitochondrial diseases for which currently no cure exists.

Keywords:  Leigh syndrome; NAD(P)H; Ndufs4(-/-) mice; cholesterol biosynthesis; complex I deficiency; metabolic network modelling

DOI:  https://doi.org/10.1016/j.bbadis.2020.166062
Oncol Lett. 2021 Jan;21(1): 75

Circular dumbbell miR-34a-3p and -5p suppresses pancreatic tumor cell-induced angiogenesis and activates macrophages.

Manu Gnanamony, Lusine Demirkhanyan, Liang Ge, Paresh Sojitra, Sneha Bapana, Joseph A Norton, Christopher S Gondi.

  Angiogenesis is a tightly regulated biological process by which new blood vessels are formed from pre-existing blood vessels. This process is also critical in diseases such as cancer. Therefore, angiogenesis has been explored as a drug target for cancer therapy. The future of effective anti-angiogenic therapy lies in the intelligent combination of multiple targeting agents with novel modes of delivery to maximize therapeutic effects. Therefore, a novel approach is proposed that utilizes dumbbell RNA (dbRNA) to target pathological angiogenesis by simultaneously targeting multiple molecules and processes that contribute to angiogenesis. In the present study, a plasmid expressing miR-34a-3p and -5p dbRNA (db34a) was constructed using the permuted intron-exon method. A simple protocol to purify dbRNA from bacterial culture with high purity was also developed by modification of the RNASwift method. To test the efficacy of db34a, pancreatic cancer cell lines PANC-1 and MIA PaCa-2 were used. Functional validation of the effect of db34a on angiogenesis was performed on human umbilical vein endothelial cells using a tube formation assay, in which cells transfected with db34a exhibited a significant reduction in tube formation compared with cells transfected with scrambled dbRNA. These results were further validated in vivo using a zebrafish angiogenesis model. In conclusion, the present study demonstrates an approach for blocking angiogenesis using db34a. The data also show that this approach may be used to targeting multiple molecules and pathways.

Keywords:  angiogenesis; circular RNA; db34a; dumbbell RNA; inflammation; miR-34a; pancreatic cancer; tumor-associated macrophage

DOI:  https://doi.org/10.3892/ol.2020.12336
Cell Metab. 2020 Dec 17. pii: S1550-4131(20)30654-9. [Epub ahead of print]

Aging Reprograms the Hematopoietic-Vascular Niche to Impede Regeneration and Promote Fibrosis.

Yutian Chen, Qiang Pu, Yongyuan Ma, Hua Zhang, Tinghong Ye, Chengjian Zhao, Xiaojuan Huang, Yafeng Ren, Lina Qiao, Han-Min Liu, Charles T Esmon, Bi-Sen Ding, Zhongwei Cao.

  Regenerative capacity is frequently impaired in aged organs. Stress to aged organs often causes scar formation (fibrosis) at the expense of regeneration. It remains to be defined how hematopoietic and vascular cells contribute to aging-induced regeneration to fibrotic transition. Here, we find that aging aberrantly reprograms the crosstalk between hematopoietic and vascular cells to impede the regenerative capacity and enhance fibrosis. In aged lung, liver, and kidney, induction of Neuropilin-1/hypoxia-inducible-factor 2α (HIF2α) suppresses anti-thrombotic and anti-inflammatory endothelial protein C receptor (EPCR) pathway, leading to formation of pro-fibrotic platelet-macrophage rosette. Activated platelets via supplying interleukin 1α synergize with endothelial-produced angiocrine chemokine to recruit fibrogenic TIMP1high macrophages. In mouse models, genetic targeting of endothelial Neuropilin-1-HIF2α, platelet interleukin 1α, or macrophage TIMP1 normalized the pro-fibrotic hematopoietic-vascular niche and restored the regenerative capacity of old organs. Targeting of aberrant endothelial node molecules might help propel "regeneration without scarring" in the repair of multiple organs.

Keywords:  aging; endothelial cell; endothelial protein C receptor; hypoxia-inducible factor 2 alpha; interleukin-1alpha; liver fibrosis; lung fibrosis; macrophage; neuropilin1; platelet; vascular niche

DOI:  https://doi.org/10.1016/j.cmet.2020.11.019
Arterioscler Thromb Vasc Biol. 2020 Dec 24. ATVBAHA120315485

Intracellular AIBP (Apolipoprotein A-I Binding Protein) Regulates Oxidized LDL (Low-Density Lipoprotein)-Induced Mitophagy in Macrophages.

Soo-Ho Choi, Colin Agatisa-Boyle, Ayelet Gonen, Alisa Kim, Jungsu Kim, Elena Alekseeva, Sotirios Tsimikas, Yury I Miller.

  OBJECTIVE: Atherosclerotic lesions are often characterized by accumulation of OxLDL (oxidized low-density lipoprotein), which is associated with vascular inflammation and lesion vulnerability to rupture. Extracellular AIBP (apolipoprotein A-I binding protein; encoded by APOA1BP gene), when secreted, promotes cholesterol efflux and regulates lipid rafts dynamics, but its role as an intracellular protein in mammalian cells remains unknown. The aim of this work was to determine the function of intracellular AIBP in macrophages exposed to OxLDL and in atherosclerotic lesions. Approach and Results: Using a novel monoclonal antibody against human and mouse AIBP, which are highly homologous, we demonstrated robust AIBP expression in human and mouse atherosclerotic lesions. We observed significantly reduced autophagy in bone marrow-derived macrophages, isolated from Apoa1bp-/- compared with wild-type mice, which were exposed to OxLDL. In atherosclerotic lesions from Apoa1bp-/- mice subjected to Ldlr knockdown and fed a Western diet, autophagy was reduced, whereas apoptosis was increased, when compared with that in wild-type mice. AIBP expression was necessary for efficient control of reactive oxygen species and cell death and for mitochondria quality control in macrophages exposed to OxLDL. Mitochondria-localized AIBP, via its N-terminal domain, associated with E3 ubiquitin-protein ligase PARK2 (Parkin), MFN (mitofusin)1, and MFN2, but not BNIP3 (Bcl2/adenovirus E1B 19-kDa-interacting protein-3), and regulated ubiquitination of MFN1 and MFN2, key components of mitophagy.CONCLUSIONS: These data suggest that intracellular AIBP is a new regulator of autophagy in macrophages. Mitochondria-localized AIBP augments mitophagy and participates in mitochondria quality control, protecting macrophages against cell death in the context of atherosclerosis.

Keywords:  atherosclerosis; autophagy; inflammation; macrophages; mitophagy

DOI:  https://doi.org/10.1161/ATVBAHA.120.315485
Cell Rep. 2020 Dec 22. pii: S2211-1247(20)31514-X. [Epub ahead of print]33(12): 108525

Single-Cell Transcriptomics Reveal Immune Mechanisms of the Onset and Progression of IgA Nephropathy.

Ying Zheng, Ping Lu, Yiyao Deng, Lu Wen, Yong Wang, Xin Ma, Zhongxin Wang, Lingling Wu, Quan Hong, Shuwei Duan, Zhong Yin, Bo Fu, Guangyan Cai, Xiangmei Chen, Fuchou Tang.

  IgA nephropathy (IgAN) is the leading cause of kidney failure due to an incomplete understanding of its pathogenesis. We perform single-cell RNA sequencing (RNA-seq) on kidneys and CD14+ peripheral blood mononuclear cells (PBMCs) collected from IgAN and normal samples. In IgAN, upregulation of JCHAIN in mesangial cells provides insight into the trigger mechanism for the dimerization and deposition of IgA1 in situ. The pathological mesangium also demonstrates a prominent inflammatory signature and increased cell-cell communication with other renal parenchymal cells and immune cells, suggesting disease progress from the mesangium to the entire kidney. Specific gene expression of kidney-resident macrophages and CD8+ T cells further indicates abnormal regulation associated with proliferation and inflammation. A transitional cell type among intercalated cells with fibrosis signatures is identified, suggesting an adverse outcome of interstitial fibrosis. Altogether, we systematically analyze the molecular events in the onset and progression of IgAN, providing a promising landscape for disease treatment.

Keywords:  IgA nephropathy; immune cellsmesangial cell; single-cell RNA seq

DOI:  https://doi.org/10.1016/j.celrep.2020.108525
Cell Rep. 2020 Dec 29. pii: S2211-1247(20)31530-8. [Epub ahead of print]33(13): 108541

High-Throughput CRISPR Screening Identifies Genes Involved in Macrophage Viability and Inflammatory Pathways.

Sergio Covarrubias, Apple Cortez Vollmers, Allyson Capili, Michael Boettcher, Aaron Shulkin, Michele Ramos Correa, Haley Halasz, Elektra K Robinson, Laura O'Briain, Christopher Vollmers, James Blau, Sol Katzman, Michael T McManus, Susan Carpenter.

  Macrophages are critical effector cells of the immune system, and understanding genes involved in their viability and function is essential for gaining insights into immune system dysregulation during disease. We use a high-throughput, pooled-based CRISPR-Cas screening approach to identify essential genes required for macrophage viability. In addition, we target 3' UTRs to gain insights into previously unidentified cis-regulatory regions that control these essential genes. Next, using our recently generated nuclear factor κB (NF-κB) reporter line, we perform a fluorescence-activated cell sorting (FACS)-based high-throughput genetic screen and discover a number of previously unidentified positive and negative regulators of the NF-κB pathway. We unravel complexities of the TNF signaling cascade, showing that it can function in an autocrine manner in macrophages to negatively regulate the pathway. Utilizing a single complex library design, we are capable of interrogating various aspects of macrophage biology, thus generating a resource for future studies.

Keywords:  3′ UTR; CRISPR screen; NF-kappaB; NF-κB; TNF; inflammation; macrophage; viability

DOI:  https://doi.org/10.1016/j.celrep.2020.108541
Cancer Cell. 2020 Dec 01. pii: S1535-6108(20)30597-3. [Epub ahead of print]

Immunogenic Chemotherapy Enhances Recruitment of CAR-T Cells to Lung Tumors and Improves Antitumor Efficacy when Combined with Checkpoint Blockade.

Shivani Srivastava, Scott N Furlan, Carla A Jaeger-Ruckstuhl, Megha Sarvothama, Carolina Berger, Kimberly S Smythe, Sarah M Garrison, Jennifer M Specht, Sylvia M Lee, Robert A Amezquita, Valentin Voillet, Vishaka Muhunthan, Sushma Yechan-Gunja, Smitha P S Pillai, Christoph Rader, A McGarry Houghton, Robert H Pierce, Raphael Gottardo, David G Maloney, Stanley R Riddell.

  Adoptive therapy using chimeric antigen receptor-modified T cells (CAR-T cells) is effective in hematologic but not epithelial malignancies, which cause the greatest mortality. In breast and lung cancer patients, CAR-T cells targeting the tumor-associated antigen receptor tyrosine kinase-like orphan receptor 1 (ROR1) infiltrate tumors poorly and become dysfunctional. To test strategies for enhancing efficacy, we adapted the KrasLSL-G12D/+;p53f/f autochthonous model of lung adenocarcinoma to express the CAR target ROR1. Murine ROR1 CAR-T cells transferred after lymphodepletion with cyclophosphamide (Cy) transiently control tumor growth but infiltrate tumors poorly and lose function, similar to what is seen in patients. Adding oxaliplatin (Ox) to the lymphodepletion regimen activates tumor macrophages to express T-cell-recruiting chemokines, resulting in improved CAR-T cell infiltration, remodeling of the tumor microenvironment, and increased tumor sensitivity to anti-PD-L1. Combination therapy with Ox/Cy and anti-PD-L1 synergistically improves CAR-T cell-mediated tumor control and survival, providing a strategy to improve CAR-T cell efficacy in the clinic.

Keywords:  CAR-T cells; CXCR3; CXCR6; KP; ROR1; alveolar macrophage; immunogenic cell death; lung adenocarcinoma; oxaliplatin

DOI:  https://doi.org/10.1016/j.ccell.2020.11.005