bims-imseme Biomed News
on Immunosenescence and T cell metabolism
Issue of 2020‒09‒13
twenty-one papers selected by
Pierpaolo Ginefra
Ludwig Institute for Cancer Research


  1. Cell Signal. 2020 Sep 04. pii: S0898-6568(20)30248-5. [Epub ahead of print] 109771
    Salminen A, Kaarniranta K, Kauppinen A.
      Exosomes represent an evolutionarily conserved signaling pathway which can act as an alarming mechanism in responses to diverse stresses, e.g. chronic inflammation activates the budding of exosomal vesicles in both immune and non-immune cells. Exosomes can contain both pro- and anti-inflammatory cargos but in chronic inflammation, exosomes mostly carry immunosuppressive cargos, e.g. enzymes and miRNAs. The aging process is associated with chronic low-grade inflammation and the accumulation of pro-inflammatory senescent cells into tissues. There is clear evidence that aging increases the number of exosomes in both the circulation and tissues. Especially, the secretion of immunosuppressive exosomes robustly increases from senescent cells. There are observations that the exosomes from senescent cells are involved in the expansion of senescence into neighbouring cells. Interestingly, the age-related exosomes contain immune suppressive cargos which enhance the immunosuppression within recipient immune cells, i.e. tissue-resident and recruited immune cells including M2 macrophages, myeloid-derived suppressor cells (MDSC), and regulatory T cells (Treg). It seems that increased immunosuppression with aging impairs the clearance of senescent cells and their accumulation within tissues augments the aging process.
    Keywords:  Aging; Extracellular vesicles; Immune evasion; Immunometabolism; Inflammaging; SASP
    DOI:  https://doi.org/10.1016/j.cellsig.2020.109771
  2. Aging Cell. 2020 Sep 11. e13188
    Fielder E, Tweedy C, Wilson C, Oakley F, LeBeau FEN, Passos JF, Mann DA, von Zglinicki T, Jurk D.
      Chronic inflammation is a common feature of many age-related conditions including neurodegenerative diseases such as Alzheimer's disease. Cellular senescence is a state of irreversible cell-cycle arrest, thought to contribute to neurodegenerative diseases partially via induction of a chronic pro-inflammatory phenotype. In this study, we used a mouse model of genetically enhanced NF-κB activity (nfκb1-/- ), characterized by low-grade chronic inflammation and premature aging, to investigate the impact of inflammaging on cognitive decline. We found that during aging, nfkb1-/- mice show an early onset of memory loss, combined with enhanced neuroinflammation and increased frequency of senescent cells in the hippocampus and cerebellum. Electrophysiological measurements in the hippocampus of nfkb1-/- mice in vitro revealed deficits in gamma frequency oscillations, which could explain the decline in memory capacity. Importantly, treatment with the nonsteroidal anti-inflammatory drug (NASID) ibuprofen reduced neuroinflammation and senescent cell burden resulting in significant improvements in cognitive function and gamma frequency oscillations. These data support the hypothesis that chronic inflammation is a causal factor in the cognitive decline observed during aging.
    Keywords:  aging; cognitive decline; hippocampus; memory; neuroinflammation; senescence
    DOI:  https://doi.org/10.1111/acel.13188
  3. Nat Commun. 2020 09 08. 11(1): 4454
    Sandu I, Cerletti D, Claassen M, Oxenius A.
      Chronic viral infections are often associated with impaired CD8+ T cell function, referred to as exhaustion. Although the molecular and cellular circuits involved in CD8+ T cell exhaustion are well defined, with sustained presence of antigen being one important parameter, how much T cell receptor (TCR) signaling is actually ongoing in vivo during established chronic infection is unclear. Here, we characterize the in vivo TCR signaling of virus-specific exhausted CD8+ T cells in a mouse model, leveraging TCR signaling reporter mice in combination with transcriptomics. In vivo signaling in exhausted cells is low, in contrast to their in vitro signaling potential, and despite antigen being abundantly present. Both checkpoint blockade and adoptive transfer of naïve target cells increase TCR signaling, demonstrating that engagement of co-inhibitory receptors curtails CD8+ T cell signaling and function in vivo.
    DOI:  https://doi.org/10.1038/s41467-020-18256-4
  4. J Clin Invest. 2020 Sep 08. pii: 137712. [Epub ahead of print]
    Helmin KA, Morales-Nebreda L, Torres Acosta MA, Anekalla KR, Chen SY, Abdala-Valencia H, Politanska Y, Cheresh P, Akbarpour M, Steinert EM, Weinberg SE, Singer BD.
      Regulatory T (Treg) cells require Foxp3 expression and induction of a specific DNA hypomethylation signature during development, after which Treg cells persist as a self-renewing population that regulates immune system activation. Whether maintenance DNA methylation is required for Treg cell lineage development and stability and how methylation patterns are maintained during lineage self-renewal remain unclear. Here, we demonstrate that the epigenetic regulator Uhrf1 is essential for maintenance of methyl-DNA marks that stabilize Treg cellular identity by repressing effector T cell transcriptional programs. Constitutive and induced deficiency of Uhrf1 within Foxp3+ cells resulted in global yet non-uniform loss of DNA methylation, derepression of inflammatory transcriptional programs, destabilization of the Treg cell lineage, and spontaneous inflammation. These findings support a paradigm in which maintenance DNA methylation is required in distinct regions of the Treg cell genome for both lineage establishment and stability of identity and suppressive function.
    Keywords:  Autoimmune diseases; Autoimmunity; Epigenetics; Immunology; T cells
    DOI:  https://doi.org/10.1172/JCI137712
  5. Mech Ageing Dev. 2020 Sep 07. pii: S0047-6374(20)30147-0. [Epub ahead of print] 111351
    Panwar A, Jhun M, Rentsendorj A, Mardiros A, Cordner R, Birch K, Yeager N, Duvall G, Golchian D, Koronyo-Hamaoui M, Cohen R, Ley E, Black K, Wheeler C.
      Mitigating effects of aging on human health remains elusive because aging impacts multiple systems simultaneously, and because experimental animals exhibit critical aging differences relative to humans. Separation of aging into discrete processes may identify targetable drivers of pathology, particularly when applied to human-specific features. Gradual homeostatic expansion of CD8 T cells dominantly alters their function in aging humans but not in mice. Injecting T cells into athymic mice induces rapid homeostatic expansion, but its relevance to aging remains uncertain. We hypothesized that homeostatic expansion of T cells injected into T-deficient hosts models physiologically relevant CD8 T cell aging in young mice, and aimed to analyze age-related T cell phenotype and tissue pathology in such animals. Indeed, we found that such injection conferred uniform age-related phenotype, genotype, and function to mouse CD8 T cells, heightened age-associated tissue pathology in young athymic hosts, and humanized amyloidosis after brain injury in secondary wild-type recipients. This validates a model conferring a human-specific aging feature to mice that identifies targetable drivers of tissue pathology. Similar examination of independent aging features should promote systematic understanding of aging and identify additional targets to mitigate its effects on human health.
    Keywords:  CD8 T cell; Cellular immunity; Homeostatic expansion; Immune aging; Neurodegeneration; Resident memory T cell
    DOI:  https://doi.org/10.1016/j.mad.2020.111351
  6. Ageing Res Rev. 2020 Sep 05. pii: S1568-1637(20)30300-7. [Epub ahead of print] 101165
    Li PH, Zhang R, Cheng LQ, Liu JJ, Chen HZ.
      The process of ageing includes molecular changes within cells and interactions between cells, eventually resulting in age-related diseases. Although various cells (immune cells, parenchymal cells, fibroblasts and endothelial cells) in tissues secrete proinflammatory signals in age-related diseases, immune cells are the major contributors to inflammation. Many studies have emphasized the role of metabolic dysregulation in parenchymal cells in age-related inflammatory diseases. However, few studies have discussed metabolic modifications in immune cells during ageing. In this review, we introduce the metabolic dysregulation of major nutrients (glucose, lipids, and amino acids) within immune cells during ageing, which leads to dysfunctional NAD + metabolism that increases immune cell senescence and leads to the acquisition of the corresponding senescence-associated secretory phenotype (SASP). We then focus on senescent immune cell interactions with parenchymal cells and the extracellular matrix and their involvement in angiogenesis, which lead to proinflammatory microenvironments in tissues and inflammatory diseases at the systemic level. Elucidating the roles of metabolic modifications in immune cells during ageing will provide new insights into the mechanisms of ageing and therapeutic directions for age-related inflammatory diseases.
    Keywords:  ageing; immune cell; inflammatory disease; metabolism; senescence-associated secretory phenotype (SASP)
    DOI:  https://doi.org/10.1016/j.arr.2020.101165
  7. Exp Mol Med. 2020 Sep 11.
    Lee WS, Yang H, Chon HJ, Kim C.
      Cancer immunotherapy with immune checkpoint inhibitors (ICIs) has revolutionized the treatment of advanced cancers. However, the tumor microenvironment (TME) functions as a formidable barrier that severely impairs the efficacy of ICIs. While the crosstalk between tumor vessels and immune cells determines the nature of anti-tumor immunity, it is skewed toward a destructive cycle in growing tumors. First, the disorganized tumor vessels hinder CD8+ T cell trafficking into the TME, disable effector functions, and even kill T cells. Moreover, VEGF, the key driver of angiogenesis, interferes with the maturation of dendritic cells, thereby suppressing T cell priming, and VEGF also induces TOX-mediated exhaustion of CD8+ T cells. Meanwhile, a variety of innate and adaptive immune cells contribute to the malformation of tumor vessels. Protumoral M2-like macrophages as well as TH2 and Treg cells secrete pro-angiogenic factors that accelerate uncontrolled angiogenesis and promote vascular immaturity. While CD8+ T and CD4+ TH1 cells suppress angiogenesis and induce vascular maturation by secreting IFN-γ, they are unable to infiltrate the TME due to malformed tumor vessels. These findings led to preclinical studies that demonstrated that simultaneous targeting of tumor vessels and immunity is a viable strategy to normalize aberrant vascular-immune crosstalk and potentiate cancer immunotherapy. Furthermore, this combination strategy has been evidently demonstrated through recent pivotal clinical trials, granted approval from FDA, and is now being used in patients with kidney, liver, lung, or uterine cancer. Overall, combining anti-angiogenic therapy and ICI is a valid therapeutic strategy that can enhance cancer immunity and will further expand the landscape of cancer treatment.
    DOI:  https://doi.org/10.1038/s12276-020-00500-y
  8. Cell Metab. 2020 Aug 31. pii: S1550-4131(20)30424-1. [Epub ahead of print]
    Kim CS, Ding X, Allmeroth K, Biggs LC, Kolenc OI, L'Hoest N, Chacón-Martínez CA, Edlich-Muth C, Giavalisco P, Quinn KP, Denzel MS, Eming SA, Wickström SA.
      Stem cells reside in specialized niches that are critical for their function. Upon activation, hair follicle stem cells (HFSCs) exit their niche to generate the outer root sheath (ORS), but a subset of ORS progeny returns to the niche to resume an SC state. Mechanisms of this fate reversibility are unclear. We show that the ability of ORS cells to return to the SC state requires suppression of a metabolic switch from glycolysis to oxidative phosphorylation and glutamine metabolism that occurs during early HFSC lineage progression. HFSC fate reversibility and glutamine metabolism are regulated by the mammalian target of rapamycin complex 2 (mTORC2)-Akt signaling axis within the niche. Deletion of mTORC2 results in a failure to re-establish the HFSC niche, defective hair follicle regeneration, and compromised long-term maintenance of HFSCs. These findings highlight the importance of spatiotemporal control of SC metabolic states in organ homeostasis.
    Keywords:  Akt; Hif1; cell fate; glutamine; hair follicle; hypoxia; mTOR; mTORC2; metabolism; stem cell
    DOI:  https://doi.org/10.1016/j.cmet.2020.08.011
  9. Exp Eye Res. 2020 Sep 02. pii: S0014-4835(20)30461-9. [Epub ahead of print] 108203
    Suvas P, Liu L, Rao P, Steinle JJ, Suvas S.
      The involvement of leukocytes in the pathophysiology of DR has mostly examined the role of monocytes and neutrophils with little emphasis on other immune cell types. In this study, we determined the systemic alterations in T cell subsets, myeloid cell types, NK cells, and NKT cells in the streptozotocin (STZ) mouse model of diabetic retinopathy (DR), and the role of NKT cells on retinal leukostasis and permeability changes. C57BL/6 J mice were made diabetic with 60 mg/kg dose of STZ given for 5-days. Flow cytometry assay measured the frequency of leukocyte subsets in the peripheral blood, spleen, and bone marrow of STZ- and vehicle-treated C57BL/6 J mice. Our results showed an increased proportion of memory CD8 T cells and interferon-gamma (IFN-γ) secreting CD8 T cells in the bone marrow of STZ-treated compared to control mice. Subsequently, increased production of inflammatory monocytes in the bone marrow and an enhanced frequency of CD11b + cells in the diabetic retina were seen in STZ-treated compared to control mice. The diabetic mice also exhibited a decrease in total NKT and CD4+NKT cells. A monoclonal antibody-based approach depleted NKT cells from STZ-treated mice, followed by measurements of retinal vascular permeability and leukostasis. The depletion of NKT cells in STZ-treated mice resulted in a significant increase in vascular permeability in the retinal tissue. Together, our results strongly imply the involvement of NKT cells in regulating the pathophysiology of the diabetic retina.
    Keywords:  Diabetic retinopathy; Leukocytes; NKT cells; Retina
    DOI:  https://doi.org/10.1016/j.exer.2020.108203
  10. Proc Natl Acad Sci U S A. 2020 Sep 10. pii: 202007224. [Epub ahead of print]
    Odagiu L, Boulet S, Maurice De Sousa D, Daudelin JF, Nicolas S, Labrecque N.
      Enhancing long-term persistence while simultaneously potentiating the effector response of CD8+ T cells has been a long-standing goal in immunology to produce better vaccines and adoptive cell therapy products. NR4A3 is a transcription factor of the orphan nuclear receptor family. While it is rapidly and transiently expressed following T cell activation, its role in the early stages of T cell response is unknown. We show that NR4A3-deficient murine CD8+ T cells differentiate preferentially into memory precursor and central memory cells, but also produce more cytokines. This is explained by an early influence of NR4A3 deficiency on the memory transcriptional program and on accessibility of chromatin regions with motifs for bZIP transcription factors, which impacts the transcription of Fos/Jun target genes. Our results reveal a unique and early role for NR4A3 in programming CD8+ T cell differentiation and function. Manipulating NR4A3 activity may represent a promising strategy to improve vaccination and T cell therapy.
    Keywords:  NR4A3; T cell function; T cell memory; early CD8+ T cell response; nuclear receptors
    DOI:  https://doi.org/10.1073/pnas.2007224117
  11. Int Immunol. 2020 Sep 10. pii: dxaa063. [Epub ahead of print]
    Masuhara K, Akatsuka H, Tokusanai M, Li C, Iida Y, Okada Y, Suzuki T, Ohtsuka M, Inoue I, Kimura M, Hosokawa H, Hozumi K, Sato T.
      AMBRA1 is a member of the BECN1 (BECLIN1) complex protein, and it plays a role in autophagy, cell death, tumorigenesis, and proliferation. We recently reported that on TCR stimulation, AMBRA1 controlled both autophagy and the cell cycle with metabolic regulation. Accumulating evidence has shown that autophagy and metabolic control are pivotal for T cell activation, clonal expansion, and effector/memory cell fate decision. However, it is unknown whether AMBRA1 is involved in T cell function under physiological conditions. We found that T cells in Ambra1-conditional knockout (cKO) mice induced exacerbated graft versus host response when they were transplanted into allogeneic BALB/c mice. Furthermore, Ambra1-deficient T cells showed increased proliferation and cytotoxic capability towards specific antigens in response to in vivo stimulation using allogeneic spleen cells. This enhanced immune response mainly contributed to naïve T cell hyperactivity. The T cell hyperactivity observed in this study were similar to those in some metabolic factor-deficient mice, but not those in other pro-autophagic factor-deficient mice. Under the static condition, however, naïve T cells were reduced in Ambra1-cKO mice, as same as in pro-autophagic factor-deficient mice. Collectively, these results suggested that AMBRA1 was involved in regulating T cell-mediated immune responses through autophagy-dependent and -independent mechanisms.
    Keywords:  Ambra1; Autophagy; CD8 + T cell; Naïve T cell; Proliferation
    DOI:  https://doi.org/10.1093/intimm/dxaa063
  12. Nat Rev Immunol. 2020 Sep 11.
    Hosokawa H, Rothenberg EV.
      Recent evidence has elucidated how multipotent blood progenitors transform their identities in the thymus and undergo commitment to become T cells. Together with environmental signals, a core group of transcription factors have essential roles in this process by directly activating and repressing specific genes. Many of these transcription factors also function in later T cell development, but control different genes. Here, we review how these transcription factors work to change the activities of specific genomic loci during early intrathymic development to establish T cell lineage identity. We introduce the key regulators and highlight newly emergent insights into the rules that govern their actions. Whole-genome deep sequencing-based analysis has revealed unexpectedly rich relationships between inherited epigenetic states, transcription factor-DNA binding affinity thresholds and influences of given transcription factors on the activities of other factors in the same cells. Together, these mechanisms determine T cell identity and make the lineage choice irreversible.
    DOI:  https://doi.org/10.1038/s41577-020-00426-6
  13. JCI Insight. 2020 Sep 08. pii: 138215. [Epub ahead of print]
    Pan W, Sharabi A, Ferretti AP, Zhang Y, Burbano C, Yoshida N, Tsokos MG, Tsokos GC.
      Protein phosphatase 2A is a ubiquitously expressed serine/threonine phosphatase which comprises a scaffold, a catalytic and multiple regulatory subunits and has been shown to be important in the expression of autoimmunity. We considered that a distinct subunit may account for the decreased production of interleukin-2 (IL-2) in people and mice with systemic autoimmunity. We show that the regulatory subunit PPP2R2D is increased in T cells from people with systemic lupus erythematosus and regulates IL-2 production. Mice lacking PPP2R2D only in T cells produce more IL-2 because the IL-2 gene and genes coding for IL-2 enhancing transcription factors remain open and the levels of the enhancer phosphorylated CREB are high. Mice with T cell-specific PPP2R2D deficiency display less systemic autoimmunity when exposed to a TLR7 stimulator. While genes related to regulatory T cell function do not change in the absence of PPP2R2D, regulatory T cells exhibit high suppressive function in vitro and in vivo. Because the ubiquitous expression of protein phosphatase 2A cannot permit systemic therapeutic manipulation, the identification of regulatory subunits able to control specific T cell functions opens the way for the development of novel, function-specific drugs.
    Keywords:  Autoimmune diseases; Autoimmunity; Immunology; Phosphoprotein phosphatases; T cells
    DOI:  https://doi.org/10.1172/jci.insight.138215
  14. Int J Mol Sci. 2020 Sep 05. pii: E6497. [Epub ahead of print]21(18):
    Kim C, Jin J, Weyand CM, Goronzy JJ.
      The transcription factor T cell factor 1 (TCF1), a pioneer transcription factor as well as a downstream effector of WNT/β-catenin signaling, is indispensable for T cell development in the thymus. Recent studies have highlighted the additional critical role of TCF1 in peripheral T cell responses to acute and chronic infections as well as cancer. Here, we review the regulatory functions of TCF1 in the differentiation of T follicular helper cells, memory T cells and recently described stem-like exhausted T cells, where TCF1 promotes less differentiated stem-like cell states by controlling common gene-regulatory networks. These studies also provide insights into the mechanisms of defective T cell responses in older individuals. We discuss alterations in TCF1 expression and related regulatory networks with age and their consequences for T cell responses to infections and vaccination. The increasing understanding of the pathways regulating TCF1 expression and function in aged T cells holds the promise of enabling the design of therapeutic interventions aiming at improving T cell responses in older individuals.
    Keywords:  T cell aging; T cell differentiation; T cell exhaustion; T follicular helper cells; TCF1; WNT/β-catenin; immunosenescence; memory T cells; stem-like CD8 T cells
    DOI:  https://doi.org/10.3390/ijms21186497
  15. Exp Cell Res. 2020 Sep 02. pii: S0014-4827(20)30509-7. [Epub ahead of print] 112260
    Hu F, Wang W, Fang C, Bai C.
      CD8+ T cells are considered a critical component of antitumor immunity. However, tumor-infiltrating CD8+ T cells may express more than one checkpoint molecules that have the potential to inhibit effector responses alone or cooperatively. Here, we focused on the expression dynamic of TIGIT and PD-1 in CD8+ T cells. TIGIT+ subset presented significantly higher PD-1 expression than TIGIT- subset in circulating CD8+ T cells. The expression dynamic of TIGIT and PD-1 was then tracked. In total CD8+ T cells, TIGIT mRNA increased more rapidly than PD-1 mRNA, and TIGIT+ CD8+ T cells upregulated PD-1 more rapidly than TIGIT- CD8+ T cells. Next, 24-h-stimulated CD8+ T cells were re-sorted into TIGIT+ and TIGIT- subsets, and the TIGIT+ cells that came from TIGIT- cells also presented significantly more rapid PD-1 induction than persistent TIGIT- CD8+ T cells. In non-small cell lung cancer (NSCLC) patients, the expression of PD-1 was more enriched in TIGIT+ cells than in TIGIT- cells in both circulating CD8+ T cells and tumor-infiltrating CD8+ T cells. Function analysis revealed that TIGIT+ CD8 T cells presented lower interferon-gamma, perforin 1, and granzyme B upregulation than TIGIT- CD8 T cells, especially in NSCLC patients. Overall, these data indicated that TIGIT presented earlier expression dynamic than PD-1 in activated CD8+ T cells and was upregulated in NSCLC patients.
    Keywords:  CD8(+) T cell; Non-small cell lung cancer; PD-1; TIGIT
    DOI:  https://doi.org/10.1016/j.yexcr.2020.112260
  16. Nat Commun. 2020 Sep 09. 11(1): 4520
    Peng DH, Rodriguez BL, Diao L, Chen L, Wang J, Byers LA, Wei Y, Chapman HA, Yamauchi M, Behrens C, Raso G, Soto LMS, Cuentes ERP, Wistuba II, Kurie JM, Gibbons DL.
      Tumor extracellular matrix has been associated with drug resistance and immune suppression. Here, proteomic and RNA profiling reveal increased collagen levels in lung tumors resistant to PD-1/PD-L1 blockade. Additionally, elevated collagen correlates with decreased total CD8+ T cells and increased exhausted CD8+ T cell subpopulations in murine and human lung tumors. Collagen-induced T cell exhaustion occurs through the receptor LAIR1, which is upregulated following CD18 interaction with collagen, and induces T cell exhaustion through SHP-1. Reduction in tumor collagen deposition through LOXL2 suppression increases T cell infiltration, diminishes exhausted T cells, and abrogates resistance to anti-PD-L1. Abrogating LAIR1 immunosuppression through LAIR2 overexpression or SHP-1 inhibition sensitizes resistant lung tumors to anti-PD-1. Clinically, increased collagen, LAIR1, and TIM-3 expression in melanoma patients treated with PD-1 blockade predict poorer survival and response. Our study identifies collagen and LAIR1 as potential markers for immunotherapy resistance and validates multiple promising therapeutic combinations.
    DOI:  https://doi.org/10.1038/s41467-020-18298-8
  17. Aging (Albany NY). 2020 Sep 07.
    Jiang S.
      
    Keywords:  N-acetylcysteine; NFAT; T cell exhaustion; mitochondrial oxidative phosphorylation
    DOI:  https://doi.org/10.18632/aging.103995
  18. Geroscience. 2020 Sep 10.
    Kim SJ, Miller B, Kumagai H, Silverstein AR, Flores M, Yen K.
      A decline in mitochondrial quality and activity has been associated with normal aging and correlated with the development of a wide range of age-related diseases. Here, we review the evidence that a decline in the levels of mitochondrial-derived peptides contributes to aging and age-related diseases. In particular, we discuss how mitochondrial-derived peptides, humanin and MOTS-c, contribute to specific aspects of the aging process, including cellular senescence, chronic inflammation, and cognitive decline. Genetic variations in the coding region of humanin and MOTS-c that are associated with age-related diseases are also reviewed, with particular emphasis placed on how mitochondrial variants might, in turn, regulate MDP expression and age-related phenotypes. Taken together, these observations suggest that mitochondrial-derived peptides influence or regulate a number of key aspects of aging and that strategies directed at increasing mitochondrial-derived peptide levels might have broad beneficial effects.
    Keywords:  Age-related diseases; Aging; Humanin; MOTS-c; Mitochondria; Mitochondrial-derived peptides
    DOI:  https://doi.org/10.1007/s11357-020-00262-5
  19. Cell Death Dis. 2020 Sep 07. 11(9): 725
    Martínez-Limón A, Calloni G, Ernst R, Vabulas RM.
      Tumor cells adapt their metabolism to meet the energetic and anabolic requirements of high proliferation and invasiveness. The metabolic addiction has motivated the development of therapies directed at individual biochemical nodes. However, currently there are few possibilities to target multiple enzymes in tumors simultaneously. Flavin-containing enzymes, ca. 100 proteins in humans, execute key biotransformations in mammalian cells. To expose metabolic addiction, we inactivated a substantial fraction of the flavoproteome in melanoma cells by restricting the supply of the FMN and FAD precursor riboflavin, the vitamin B2. Vitamin B2 deficiency affected stability of many polypeptides and thus resembled the chaperone HSP90 inhibition, the paradigmatic multiple-target approach. In support of this analogy, flavin-depleted proteins increasingly associated with a number of proteostasis network components, as identified by the mass spectrometry analysis of the FAD-free NQO1 aggregates. Proteome-wide analysis of the riboflavin-starved cells revealed a profound inactivation of the mevalonate pathway of cholesterol synthesis, which underlines the manifold cellular vulnerability created by the flavoproteome inactivation. Cell cycle-arrested tumor cells became highly sensitive to alkylating chemotherapy. Our data suggest that the flavoproteome is well suited to design synthetic lethality protocols combining proteostasis manipulation and metabolic reprogramming.
    DOI:  https://doi.org/10.1038/s41419-020-02929-5
  20. Sci Rep. 2020 Sep 10. 10(1): 14928
    Nojima I, Eikawa S, Tomonobu N, Hada Y, Kajitani N, Teshigawara S, Miyamoto S, Tone A, Uchida HA, Nakatsuka A, Eguchi J, Shikata K, Udono H, Wada J.
      The metabolic changes and dysfunction in CD8 + T cells may be involved in tumor progression and susceptibility to virus infection in type 2 diabetes (T2D). In C57BL/6JJcl mice fed with high fat-high sucrose chow (HFS), multifunctionality of CD8 + splenic and tumor-infiltrating lymphocytes (TILs) was impaired and associated with enhanced tumor growth, which were inhibited by metformin. In CD8 + splenic T cells from the HFS mice, glycolysis/basal respiration ratio was significantly reduced and reversed by metformin. In the patients with T2D (DM), multifunctionality of circulating CD8 + PD-1 + T cells stimulated with PMA/ionomycin as well as with HLA-A*24:02 CMV peptide was dampened, while metformin recovered multifunctionality. Both glycolysis and basal respiration were reduced in DM, and glycolysis was increased by metformin. The disturbance of the link between metabolism and immune function in CD8 + PD-1 + T cells in T2D was proved by recovery of antigen-specific and non-specific cytokine production via metformin-mediated increase in glycolytic activity.
    DOI:  https://doi.org/10.1038/s41598-020-71946-3
  21. Oxid Med Cell Longev. 2020 ;2020 2015920
    Bu W, Hao X, Yang T, Wang J, Liu Q, Zhang X, Li X, Gong Y, Shao C.
      Autophagy has been well documented to play an important role in maintaining genomic stability. However, in addition to directly engulfing and digesting the damaged organelles and chromatin fragments, autophagy can affect many cellular processes including DNA damage response, regulation of redox homeostasis, and cell division; it remains to be determined to what extent each of those processes contributes to the maintenance of genomic stability. We here examined the role of autophagy-dependent redox regulation in the maintenance of genomic stability in two cancer cell lines (HT1080 and U2OS) and mesenchymal stem cells (MSCs) using micronuclei MN, also referred to as cytoplasmic chromatin fragments, as a marker. Our results showed that the spontaneous and genotoxic stress-induced frequencies of MN in cancer cells were significantly reduced by autophagy activators rapamycin and Torin1, and the reduction in MN was accompanied by a reduction in reactive oxygen species (ROS). Increased micronucleation in senescent MSCs, in which autophagic flux is blocked, was also attenuated by rapamycin, together with a reduction in ROS. Inhibition of autophagy by chloroquine (CQ) or ATG5 depletion, on the other hand, resulted in an increased frequency of MN, though a ROS elevation in response to autophagy inhibition was only observed in MSCs. Importantly, the induction of MN by autophagy inhibition in MSCs could be abrogated by antioxidant N-acetylcysteine (NAC). In contrast to the reported impairment of CHK1 activation in Atg7-deficient mouse embryonic fibroblasts, we found that the level of phosphorylated CHK1 was increased by CQ or ATG5 depletion but decreased by rapamycin or Torin1, suggesting that the increased genomic instability by defective autophagy is not caused by insufficient activation of CHK1-homologous recombination cascade. Together, our findings suggest that redox homeostasis regulated by autophagy contributes substantially to the maintenance of genomic stability in certain contexts.
    DOI:  https://doi.org/10.1155/2020/2015920