bims-imicid Biomed News
on Immunometabolism of infection, cancer and immune-mediated disease
Issue of 2022‒02‒13
twenty papers selected by
Dylan Ryan
University of Cambridge

  1. Science. 2022 Feb 11. 375(6581): 671-677
      The extension of life span driven by 40% caloric restriction (CR) in rodents causes trade-offs in growth, reproduction, and immune defense that make it difficult to identify therapeutically relevant CR-mimetic targets. We report that about 14% CR for 2 years in healthy humans improved thymopoiesis and was correlated with mobilization of intrathymic ectopic lipid. CR-induced transcriptional reprogramming in adipose tissue implicated pathways regulating mitochondrial bioenergetics, anti-inflammatory responses, and longevity. Expression of the gene Pla2g7 encoding platelet activating factor acetyl hydrolase (PLA2G7) is inhibited in humans undergoing CR. Deletion of Pla2g7 in mice showed decreased thymic lipoatrophy, protection against age-related inflammation, lowered NLRP3 inflammasome activation, and improved metabolic health. Therefore, the reduction of PLA2G7 may mediate the immunometabolic effects of CR and could potentially be harnessed to lower inflammation and extend the health span.
  2. Cell. 2022 Feb 03. pii: S0092-8674(22)00068-X. [Epub ahead of print]
      Rapid neutrophil recruitment to sites of inflammation is crucial for innate immune responses. Here, we reveal that the G-protein-coupled receptor GPR35 is upregulated in activated neutrophils, and it promotes their migration. GPR35-deficient neutrophils are less recruited from blood vessels into inflamed tissue, and the mice are less efficient in clearing peritoneal bacteria. Using a bioassay, we find that serum and activated platelet supernatant stimulate GPR35, and we identify the platelet-derived serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) as a GPR35 ligand. GPR35 function in neutrophil recruitment is strongly dependent on platelets, with the receptor promoting transmigration across platelet-coated endothelium. Mast cells also attract GPR35+ cells via 5-HIAA. Mice deficient in 5-HIAA show a loss of GPR35-mediated neutrophil recruitment to inflamed tissue. These findings identify 5-HIAA as a GPR35 ligand and neutrophil chemoattractant and establish a role for platelet- and mast cell-produced 5-HIAA in cell recruitment to the sites of inflammation and bacterial clearance.
    Keywords:  5-HIAA; GPCRs; GPR35; SSRI; inflammation; mast cells; migration; neutrophil; platelets; serotonin metabolite
  3. Nat Commun. 2022 Feb 10. 13(1): 790
      High-calorie diet-induced nutrient stress promotes thiol oxidative stress and the reprogramming of blood monocytes, giving rise to dysregulated, obesogenic, proatherogenic monocyte-derived macrophages. We report that in chow-fed, reproductively senescent female mice but not in age-matched male mice, deficiency in the thiol transferase glutaredoxin 1 (Grx1) promotes dysregulated macrophage phenotypes as well as rapid weight gain and atherogenesis. Grx1 deficiency derepresses distinct expression patterns of reactive oxygen species and reactive nitrogen species generators in male versus female macrophages, poising female but not male macrophages for increased peroxynitrate production. Hematopoietic Grx1 deficiency recapitulates this sexual dimorphism in high-calorie diet-fed LDLR-/- mice, whereas macrophage-restricted overexpression of Grx1 eliminates the sex differences unmasked by high-calorie diet-feeding and protects both males and females against atherogenesis. We conclude that loss of monocytic Grx1 activity disrupts the immunometabolic balance in mice and derepresses sexually dimorphic oxidative stress responses in macrophages. This mechanism may contribute to the sex differences reported in cardiovascular disease and obesity in humans.
  4. Front Immunol. 2022 ;13 773261
      Short-chain fatty acids (SCFAs) are metabolites produced mainly by the gut microbiota with a known role in immune regulation. Acetate, the major SCFA, is described to disseminate to distal organs such as lungs where it can arm sentinel cells, including alveolar macrophages, to fight against bacterial intruders. In the current study, we explored mechanisms through which acetate boosts macrophages to enhance their bactericidal activity. RNA sequencing analyses show that acetate triggers a transcriptomic program in macrophages evoking changes in metabolic process and immune effector outputs, including nitric oxide (NO) production. In addition, acetate enhances the killing activity of macrophages towards Streptococcus pneumoniae in an NO-dependent manner. Mechanistically, acetate improves IL-1β production by bacteria-conditioned macrophages and the latter acts in an autocrine manner to promote NO production. Strikingly, acetate-triggered IL-1β production was neither dependent of its cell surface receptor free-fatty acid receptor 2, nor of the enzymes responsible for its metabolism, namely acetyl-CoA synthetases 1 and 2. We found that IL-1β production by acetate relies on NLRP3 inflammasome and activation of HIF-1α, the latter being triggered by enhanced glycolysis. In conclusion, we unravel a new mechanism through which acetate reinforces the bactericidal activity of alveolar macrophages.
    Keywords:  IL-1β; Streptococcus pneumoniae; alveolar macrophages; immunometabolism; innate immunity; nitric oxide; short chain fatty acid
  5. Immunology. 2022 Feb 08.
      Obesity is accompanied by and accelerated with chronic inflammation in adipose tissue, especially visceral adipose tissue (VAT). This low-level inflammation predisposes the host to the development of metabolic disease, most notably type 2 diabetes. We have focused on the capacity of glycolipid-reactive, CD1d-restricted natural killer T (NKT) cells to modulate obesity and its associated metabolic sequelae. We previously reported that CD1d knockout (KO) mice are partially protected against the development of obesity-associated insulin-resistance, and these findings were recapitulated in mice with an adipocyte-specific CD1d deficiency, suggesting that NKT cell-adipocyte interactions play a critical role in exacerbating disease. However, many other CD1d-expressing cells contribute to the in vivo responses of NKT cells to lipid antigens. In the present study, we examined the role of CD1d expression by macrophages (Mϕ) to the development of obesity-associated metabolic inflammation using LysMcre-cd1d1f/f mice where the CD1d1 gene is disrupted in a Mϕ-specific manner. Unexpectedly, these animals contained a higher frequency of T-bet+ CD4+ T cells in VAT with increased production of Th1-cytokines that aggravated VAT inflammation. Mϕ from mutant mice displayed increased production of IL-12p40, suggesting M1 polarization. These findings indicate that interactions of CD1d on Mϕ with NKT cells play a beneficial role in obesity-associated VAT inflammation and insulin resistance with a sharp contrast to an aggravating role of CD1d on another type of antigen presenting cell, dendritic cells.
  6. J Clin Invest. 2022 Feb 10. pii: e155224. [Epub ahead of print]
      The functional integrity of CD8+ T cells is tightly coupled to metabolic reprogramming, but how oxidative stress directs CD8+ T cell metabolic fitness in the tumor microenvironment (TME) remains elusive. Here, we report that SUMO-specific protease 7 (SENP7) senses oxidative stress to maintain the CD8+ T cell metabolic state and antitumor functions. SENP7-deficient CD8+ T cells exhibited decreased glycolysis and oxidative phosphorylation, resulting in attenuated proliferation in vitro and dampened antitumor functions in vivo. Mechanistically, CD8+ T cell-derived reactive oxygen species (ROS) triggered cytosolic SENP7-mediated PTEN deSUMOylation, thereby promoting PTEN degradation and preventing PTEN-dependent metabolic defects. Importantly, lowering T cell-intrinsic ROS restricted SENP7 cytosolic translocation and repressed CD8+ T cell metabolic and functional activity in human colorectal cancer samples. Our findings reveal that SENP7, as an oxidative stress sensor, sustains CD8+ T cell metabolic fitness and effector functions and unveil an oxidative stress-sensing machinery in tumor-infiltrating CD8+ T cells.
    Keywords:  Adaptive immunity; Cancer immunotherapy; Immunology; Metabolism; T cells
  7. Immunology. 2022 Feb 09.
      The NLRP3 inflammasome is a multi-protein complex that regulates caspase-1 activation and subsequent interleukin (IL)-1β and IL-18 release from innate immune cells in response to infection or injury. Derivatives of the metabolites itaconate and fumarate, dimethyl itaconate (DMI), 4-octyl itaconate (4OI) and dimethyl fumarate (DMF), limit both expression and release of IL-1β following NLRP3 inflammasome activation. However, the direct effects of these metabolite derivatives on NLRP3 inflammasome responses require further investigation. Using murine bone marrow-derived macrophages, mixed glia and organotypic hippocampal slice cultures (OHSCs), we demonstrate that DMI, 4OI and DMF pre-treatment inhibit pro-inflammatory cytokine production in response to lipopolysaccharide (LPS), as well as inhibiting subsequent NLRP3 inflammasome activation induced by nigericin. DMI, 4OI, DMF and monomethyl fumarate (MMF), another fumarate derivative, also directly inhibited biochemical markers of NLRP3 activation in LPS-primed macrophages, mixed glia, OHSCs and human macrophages in response to nigericin and imiquimod, including ASC speck formation, caspase-1 activation, gasdermin D cleavage and IL-1β release. DMF, an approved treatment for multiple sclerosis, as well as DMI, 4OI and MMF, inhibited NLRP3 activation in macrophages in response to lysophosphatidylcholine, which is used to induce demyelination, suggesting a possible mechanism for DMF in multiple sclerosis through NLRP3 inhibition. The derivatives also reduced pro-IL-1α cleavage in response to the calcium ionophore ionomycin. Together, these findings reveal the immunometabolic regulation of both the priming and activation steps of NLRP3 activation in macrophages. Furthermore, we highlight itaconate and fumarate derivatives as potential therapeutic options in NLRP3- and IL-1α-driven diseases, including in the brain.
    Keywords:  NLRP3; fumarate; inflammasome; interleukin; itaconate
  8. Endocrinology. 2022 Feb 05. pii: bqac014. [Epub ahead of print]
      Obesity-linked diabetes is associated with accumulation of pro-inflammatory macrophages into adipose tissue leading to inflammasome activation and pyroptotic secretion of IL-1β and IL-18. Targeting fatty acid binding protein 4 (FABP4) uncouples obesity from inflammation, attenuates characteristics of type II diabetes and is mechanistically linked to the cellular accumulation of monounsaturated fatty acids in macrophages. Herein we show that pharmacologic inhibition or genetic deletion of FABP4 activates SIRT1 and deacetylates its downstream targets p53 and STAT3. Pharmacologic inhibition of fatty acid synthase or stearoyl CoA desaturase inhibits, whereas exogenous addition of C16:1 or C18:1 but not their saturated acyl chain counterparts, activates SIRT1 and p53/STAT3 signaling and IL-1β/IL-18 release. Expression of the p53 target gene ASC required for assembly of the NLRP3 inflammasome is down regulated in FABP4 null mice and macrophage cell lines leading to loss of pro-caspase 1 activation and pyroptosis. Concomitant with loss of ASC expression in FABP4 -/- macrophages, inflammasome activation, gasdermin D processing and functional activation of pyroptosis are all diminished in FABP4 null macrophages but can be rescued by silencing SIRT1 or exogenous expression of ASC. Taken together, these results reveal a novel lipid-regulated pathway linking to SIRT1-p53-ASC signaling and activation of inflammasome action and pyroptosis.
    Keywords:  ASC; SIRT1; fatty acid binding protein 4; inflammasome; p53; pyroptosis
  9. Cell Immunol. 2022 Feb 07. pii: S0008-8749(22)00009-0. [Epub ahead of print]373 104485
      The metabolite itaconate plays a critical role in modulating inflammatory responses among macrophages infected with intracellular pathogens. However, the ability of itaconate to influence developing T cells responses is poorly understood. To determine if itaconate contributes to the quality of T cell mediated immunity against intracellular infection, we used Francisella tularensis as a model of vaccine induced immunity. Following vaccination with F. tularensis live vaccine strain, itaconate deficient mice (ACOD KO) had a prolonged primary infection but were more resistant to secondary infection with virulent F. tularensis relative to wild type controls. Improved resistance to secondary challenge was associated with both increased numbers and effector function of CD4+ and CD8+ T cells in ACOD KO mice. However, additional data suggest that improved T cell responses was not T cell intrinsic. These data underscore the consequences of metabolic perturbations within antigen presenting cells on the development of vaccine-elicited immune responses.
    Keywords:  Francisella tularensis; Immunometabolism; Itaconate; Lung; Macrophage; T cell
  10. Infect Immun. 2022 Feb 07. IAI0047021
      Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen that causes nosocomial pneumonia, urinary tract infections, and bacteremia. A hallmark of P. aeruginosa pathogenesis is disruption of host cell function by the type III secretion system (T3SS) and its cognate exoenzyme effectors. The T3SS effector ExoU is phospholipase A2 (PLA2) that targets the host cell plasmalemmal membrane to induce cytolysis, and is an important virulence factor that mediates immune avoidance. In addition, ExoU has been shown to subvert the host inflammatory response in a non-cytolytic manner. In primary bone marrow-derived macrophages (BMDMs), P. aeruginosa infection is sensed by the nucleotide-binding domain containing leucine rich repeats-like receptor 4 (NLRC4) inflammasome, which triggers caspase-1 activation and inflammation. ExoU transiently inhibits NLRC4 inflammasome-mediated activation of caspase-1 and its downstream target, IL-1β, to suppress activation of inflammation. In the present study, we sought to identify additional non-cytolytic virulence functions for ExoU and discovered an unexpected association between ExoU, host mitochondria, and NLRC4. We show that infection of BMDMs with P. aeruginosa strains expressing ExoU elicited mitochondrial oxidative stress. In addition, mitochondria and mitochondria-associated membrane fractions enriched from infected cells exhibited evidence of autophagy activation, indicative of damage. The observation that ExoU elicited mitochondrial stress and damage suggested that ExoU may also associate with mitochondria during infection. Indeed, ExoU phospholipase A2 enzymatic activity was present in enriched mitochondria and mitochondria-associated membrane fractions isolated from P. aeruginosa-infected BMDMs. Intriguingly, enriched mitochondria and mitochondria-associated membrane fractions isolated from infected Nlrc4 homozygous knockout BMDMs displayed significantly lower levels of ExoU enzyme activity, suggesting NLRC4 plays a role in the ExoU-mitochondria association. These observations prompted us to assay enriched mitochondria and mitochondria-associated membrane fractions for NLRC4, caspase-1, and IL-1β. NLRC4 and pro-caspase-1 were detected in enriched mitochondria and mitochondria-associated membrane fractions isolated from non-infected BMDMs, and active caspase-1 and active IL-1β were detected in response to P. aeruginosa infection. Interestingly, ExoU inhibited mitochondria-associated caspase-1 and IL-1β activation. The implications of ExoU-mediated effects on mitochondria and the NLRC4 inflammasome during P. aeruginosa infection are discussed.
  11. Int Immunol. 2022 Feb 08. pii: dxac004. [Epub ahead of print]
      Prostaglandin E2 (PGE2), a product of the cyclooxygenase (COX) pathway, is produced by tumors and surrounding stromal cells. It stimulates tumor progression, promotes angiogenesis, and suppresses the antitumor response. Pharmacological inhibition of PGE2 synthesis has been shown to suppress tumor initiation and growth in vivo. In the current study, we demonstrated that the growth of the Ptgs2-deficient the 3LL lung adenocarcinoma cell line was downregulated in vivo through natural killer (NK) cell activation and a reduction in the population of polymorphonuclear leukocyte-myeloid-derived suppressor cells (PMN-MDSCs) and tumor associated macrophages (TAMs). Based on these results, the therapeutic effect of ONO-AE3-208 (EP4i), an inhibitor of EP4 (a PGE2 receptor), combined with anti-PD-1Ab was evaluated. EP4i, but not anti-PD-1 Ab, decreased tumor metabolism including glycolysis, fatty acid oxidation, and oxidative phosphorylation. EP4i induced IFNγ production from only NK cells (not from T cells) and a shift from M2- to M1-like macrophages in TAMs. These effects were further enhanced by anti-PD-1 Ab treatment. Although CD8T cell infiltration was increased, IFNγ production was not significantly altered, even with combination therapy. Tumor hypoxia was ameliorated by either EP4i or anti-PD-1 Ab treatment, which was further affected by the combination. Normalization of tumor vessels was significant only for the combination therapy. The results indicate a novel effect of EP4i for the metabolic reprogramming of tumors, revealed unique features of EP4i that can synergize with anti-PD-1Ab to promote IFNγ production of NK cells, polarize TAMs into the M1-phenotype, and reduce hypoxia through normalization of the tumor vasculature. (250 words).
    Keywords:  NK cells; Prostaglandin; tumor immunity; tumor metabolism; tumor vessels
  12. Cancer Res. 2022 Feb 08. pii: canres.0003.2021. [Epub ahead of print]
      Macrophages perform key and distinct functions in maintaining tissue homeostasis by finely tuning their activation state. Within the tumor microenvironment, macrophages are reshaped to drive tumor progression. Here we report that tumor necrosis factor α-induced protein 8-like 1 (TIPE1) is highly expressed in macrophages, and that depletion of TIPE1 impedes alternative activation of macrophages. TIPE1 enhanced activation of the PI3K/Akt pathway in macrophages by directly binding with and regulating the metabolism of phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3). Accordingly, inhibition of the PI3K/Akt pathway significantly attenuated the effect of TIPE1 on macrophage alternative activation. Tumor-associated macrophages (TAM) in human liver cancer and melanoma tissues showed significantly upregulated TIPE1 expression that negatively correlated with patient survival. In vitro and in vivo, TIPE1 knockdown in macrophages retarded the growth and metastasis of liver cancer and melanoma. Furthermore, blockade or depletion of TGF-β signaling in macrophages abrogated the effects of TIPE1 on tumor cell growth and migration. Together, these results highlight that the phosphoinositide-related signaling pathway involves reprogramming tumor-associated macrophages to optimize the microenvironment for cancer progression.
  13. Acta Pharm Sin B. 2022 Jan;12(1): 182-196
      Hepatic ischemia/reperfusion injury (HIRI) is a serious complication that occurs following shock and/or liver surgery. Gut microbiota and their metabolites are key upstream modulators of development of liver injury. Herein, we investigated the potential contribution of gut microbes to HIRI. Ischemia/reperfusion surgery was performed to establish a murine model of HIRI. 16S rRNA gene sequencing and metabolomics were used for microbial analysis. Transcriptomics and proteomics analysis were employed to study the host cell responses. Our results establish HIRI was significantly increased when surgery occurred in the evening (ZT12, 20:00) when compared with the morning (ZT0, 08:00); however, antibiotic pretreatment reduced this diurnal variation. The abundance of a microbial metabolite 3,4-dihydroxyphenylpropionic acid was significantly higher in ZT0 when compared with ZT12 in the gut and this compound significantly protected mice against HIRI. Furthermore, 3,4-dihydroxyphenylpropionic acid suppressed the macrophage pro-inflammatory response in vivo and in vitro. This metabolite inhibits histone deacetylase activity by reducing its phosphorylation. Histone deacetylase inhibition suppressed macrophage pro-inflammatory activation and diminished the diurnal variation of HIRI. Our findings revealed a novel protective microbial metabolite against HIRI in mice. The potential underlying mechanism was at least in part, via 3,4-dihydroxyphenylpropionic acid-dependent immune regulation and histone deacetylase (HDAC) inhibition in macrophages.
    Keywords:  3,4-Dihydroxyphenylpropionic acid; Diurnal variation; Gut microbiota; Hepatic ischemia/reperfusion injury
  14. Nat Commun. 2022 Feb 10. 13(1): 805
      T follicular helper (Tfh) cells provide signals to initiate and maintain the germinal center (GC) reaction and are crucial for the generation of robust, long-lived antibody responses, but how the GC microenvironment affects Tfh cells is not well understood. Here we develop an in vivo T cell-intrinsic CRISPR-knockout screen to evaluate Tfh and Th1 cells in an acute viral infection model to identify regulators of Tfh cells in their physiological setting. Using a screen of druggable-targets, alongside genetic, transcriptomic and cellular analyses, we identify a function of HIF-1α in suppressing mTORC1-mediated and Myc-related pathways, and provide evidence that VHL-mediated degradation of HIF-1α is required for Tfh development; an expanded in vivo CRISPR screen reveals multiple components of these pathways that regulate Tfh versus Th1 cells, including signaling molecules, cell-cycle regulators, nutrient transporters, metabolic enzymes and autophagy mediators. Collectively, our data serve as a resource for studying Tfh versus Th1 decisions, and implicate the VHL-HIF-1α axis in fine-tuning Tfh generation.
  15. Stem Cell Reports. 2022 Feb 01. pii: S2213-6711(22)00055-8. [Epub ahead of print]
      Mitochondria are fundamental but complex determinants for hematopoietic stem cell (HSC) maintenance. However, the factors involved in the regulation of mitochondrial metabolism in HSCs and the underlying mechanisms have not been fully elucidated. Here, we identify sterol regulatory element binding factor-1c (Srebf1c) as a key factor in maintaining HSC biology under both steady-state and stress conditions. Srebf1c knockout (Srebf1c-/-) mice display increased phenotypic HSCs and less HSC quiescence. In addition, Srebf1c deletion compromises the function and survival of HSCs in competitive transplantation or following chemotherapy and irradiation. Mechanistically, SREBF1c restrains the excessive activation of mammalian target of rapamycin (mTOR) signaling and mitochondrial metabolism in HSCs by regulating the expression of tuberous sclerosis complex 1 (Tsc1). Our study demonstrates that Srebf1c plays an important role in regulating HSC fate via the TSC1-mTOR-mitochondria axis.
    Keywords:  Srebf1c; TSC1; hematopoietic stem cell; mTOR; mitochondrial metabolism
  16. Gut. 2022 Feb 09. pii: gutjnl-2021-325150. [Epub ahead of print]
      OBJECTIVE: Follistatin-like protein 1 (FSTL1) is widely recognised as a secreted glycoprotein, but its role in modulating macrophage-related inflammation during liver fibrosis has not been documented. Herein, we aimed to characterise the roles of macrophage FSTL1 in the development of liver fibrosis.DESIGN: Expression analysis was conducted with human liver samples obtained from 33 patients with liver fibrosis and 18 individuals without fibrosis serving as controls. Myeloid-specific FSTL1-knockout (FSTL1M-KO) mice were constructed to explore the function and mechanism of macrophage FSTL1 in 3 murine models of liver fibrosis induced by carbon tetrachloride injection, bile duct ligation or a methionine-deficient and choline-deficient diet.
    RESULTS: FSTL1 expression was significantly elevated in macrophages from fibrotic livers of both humans and mice. Myeloid-specific FSTL1 deficiency effectively attenuated the progression of liver fibrosis. In FSTL1M-KO mice, the microenvironment that developed during liver fibrosis showed relatively less inflammation, as demonstrated by attenuated infiltration of monocytes/macrophages and neutrophils and decreased expression of proinflammatory factors. FSTL1M-KO macrophages exhibited suppressed proinflammatory M1 polarisation and nuclear factor kappa B pathway activation in vivo and in vitro. Furthermore, this study showed that, through its FK domain, FSTL1 bound directly to the pyruvate kinase M2 (PKM2). Interestingly, FSTL1 promoted PKM2 phosphorylation and nuclear translocation, reduced PKM2 ubiquitination to enhance PKM2-dependent glycolysis and increased M1 polarisation. Pharmacological activation of PKM2 (DASA-58) partially countered FSTL1-mediated glycolysis and inflammation.
    CONCLUSION: Macrophage FSTL1 promotes the progression of liver fibrosis by inducing M1 polarisation and inflammation based on the intracellular PKM2 reprogramming function of macrophages.
    Keywords:  hepatic fibrosis; inflammation; macrophages; signaling
  17. Immunobiology. 2022 Feb 02. pii: S0171-2985(22)00012-2. [Epub ahead of print]227(2): 152186
      In this study, we have identified Interferon-stimulated genes (ISGs), especially IFIT1, 2 and 3, as target genes of propionate-induced signalling in the human epithelial cell line A549, the monocytic cell line THP-1 as well as in primary, human peripheral blood-derived macrophages (PBMs). Induction of the IFIT gene family by propionate negatively regulates TLR-induced signalling. Propionate stimulation results in downregulation of pro-inflammatory cytokine and chemokine expression as well as MHC class II expression upon TLR1/2 and TLR4 re-stimulation in A549 and THP-1 cells as well as in PBMs, demonstrating that propionate-induced signalling is involved in the induction of TLR cross-tolerance. Signalling pathway analysis clearly demonstrates that propionate-induced IFIT expression is mediated by FFAR2 in a Gαq/11 signalling pathway-dependent manner. Furthermore, propionate-induced IFIT expression is dependent on IFN type I and/or type III-mediated signalling since pre-treatment of A549 cells with Ruxolitinib, a specific JAK1/2 tyrosine kinase inhibitor, prior to stimulation with propionate, inhibited the upregulation of IFIT1 expression. The hypo-responsiveness towards TLR1/2 and TLR4 agonists seems to be mediated by different members of the IFIT gene family in a cell type-specific manner. Collectively, our data indicate that propionate-induced signalling controls pro-inflammatory responses by activation of IFN type I and/or type III-induced and IFIT-mediated counter-regulatory mechanisms in order to protect against exacerbating inflammatory reactions.
    Keywords:  Bacterial metabolites; IFITs; Immune regulation; Interferon-stimulated genes; TLR tolerance
  18. Cell Death Dis. 2022 Feb 08. 13(2): 127
      MitoNEET (mitochondrial protein containing Asn-Glu-Glu-Thr (NEET) sequence) is a 2Fe-2S cluster-containing integral membrane protein that resides in the mitochondrial outer membrane and participates in a redox-sensitive signaling and Fe-S cluster transfer. Thus, mitoNEET is a key regulator of mitochondrial oxidative capacity and iron homeostasis. Moreover, mitochondrial dysfunction and oxidative stress play critical roles in inflammatory diseases such as sepsis. Increased iron levels mediated by mitochondrial dysfunction lead to oxidative damage and generation of reactive oxygen species (ROS). Increasing evidence suggests that targeting mitoNEET to reverse mitochondrial dysfunction deserves further investigation. However, the role of mitoNEET in inflammatory diseases is unknown. Here, we investigated the mechanism of action and function of mitoNEET during lipopolysaccharide (LPS)-induced inflammatory responses in vitro and in vivo. Levels of mitoNEET protein increased during microbial or LPS-induced sepsis. Pharmacological inhibition of mitoNEET using mitoNEET ligand-1 (NL-1) decreased the levels of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α in animal models of sepsis, as well as LPS-induced inflammatory responses by macrophages in vitro. Inhibition of mitoNEET using NL-1 or mitoNEET shRNA abrogated LPS-induced ROS formation and mitochondrial dysfunction. Furthermore, mitochondrial iron accumulation led to generation of LPS-induced ROS, a process blocked by NL-1 or shRNA. Taken together, these data suggest that mitoNEET could be a key therapeutic molecule that targets mitochondrial dysfunction during inflammatory diseases and sepsis.
  19. Elife. 2022 02 09. pii: e72182. [Epub ahead of print]11
      Targeting endoplasmic reticulum (ER) stress, inflammation, and metabolic dysfunctions may halt the pathogenesis of obesity and thereby reduce the prevalence of diabetes, cardiovascular disesases, and cancers. The present study was designed to elucidate the mechnaisms by which plant-derived celastrol ameliorated inflammation and lipid accumulation in obesity. The mouse model of diet-induced obesity was induced by feeding high-fat diet for 3 months and subsequently intervented with celastrol for 21 days. Hepatic and adipose tissues were analyzed for lipid accumulation, macrophage activation, and biomarker expression. As result, celastrol effectively reduced body weight, suppressed ER stress, inflammation, and lipogenesis while promoted hepatic lipolysis. RNA-sequencing revealed that celastrol-loaded nanomicelles restored the expression of 49 genes that regulate ER stress, inflammation, and lipid metabolism. On the other hand, celastrol-PEG4-alkyne was synthesized for identifying celastrol-bound proteins in RAW264.7 macrophages. ER chaperone GRP78 (78 kDa glucose-regulated protein) was identified by proteomics approach for celastrol binding to the residue Cys41. Upon binding and conjugation, celastrol diminished the chaperone activity of GRP78 by 130-fold and reduced ER stress in palmitate-challenged cells, while celastrol analog lacking quinone methide failed to exhibit antiobesity effects. Thus, covalent GRP78 inhibition may induce the reprograming of ER signaling, inflammation, and metabolism against diet-induced obesity.
    Keywords:  ER stress; GRP78; biochemistry; celastrol; chemical biology; inflammation; lipid accumulation; medicine; mouse; obesity