Lipid metabolism: a central modulator of RORt-mediated Th17 cell differentiation.

Among the T helper cell subsets, Th17 cells contribute to the development of various inflammatory and autoimmune diseases, including psoriasis, rheumatoid arthritis, inflammatory bowel disease, steroid-resistant asthma, and multiple sclerosis. Retinoid-related orphan receptor gamma t (RORγt), a nuclear hormone receptor, serves as a master transcription factor for Th17 cell differentiation. Recent findings have shown that modulating the metabolic pathway is critical for Th17 cell differentiation, particularly through the engagement of de novo lipid biosynthesis. Suppression of lipid biosynthesis, either through the pharmacological inhibition or gene deletion of related enzymes in CD4+ T cells, results in significant impairment of Th17 cell differentiation. Mechanistic studies indicate that metabolic fluxes through both the fatty acid and cholesterol biosynthetic pathways have a pivotal role in the regulation of RORγt activity through the generation of endogenous RORγt lipid ligands. This review discusses recent discoveries highlighting the importance of lipid metabolism in Th17 cell differentiation and function, as well as exploring specific molecular pathways involved in RORγt activation through cellular lipid metabolism. We further elaborate on a pioneering therapeutic approach to improve inflammatory and autoimmune disorders via the inhibition of RORγt.

The integration of metabolic and proteomic data uncovers an augmentation of the sphingolipid biosynthesis pathway during T-cell differentiation.

Recent studies have highlighted the significance of cellular metabolism in the initiation of clonal expansion and effector differentiation of T cells. Upon exposure to antigens, naïve CD4+ T cells undergo metabolic reprogramming to meet their metabolic requirements. However, only few studies have simultaneously evaluated the changes in protein and metabolite levels during T cell differentiation. Our research seeks to fill the gap by conducting a comprehensive analysis of changes in levels of metabolites, including sugars, amino acids, intermediates of the TCA cycle, fatty acids, and lipids. By integrating metabolomics and proteomics data, we discovered that the quantity and composition of cellular lipids underwent significant changes in different effector Th cell subsets. Especially, we found that the sphingolipid biosynthesis pathway was commonly activated in Th1, Th2, Th17, and iTreg cells and that inhibition of this pathway led to the suppression of Th17 and iTreg cells differentiation. Additionally, we discovered that Th17 and iTreg cells enhance glycosphingolipid metabolism, and inhibition of this pathway also results in the suppression of Th17 and iTreg cell generation. These findings demonstrate that the utility of our combined metabolomics and proteomics analysis in furthering the understanding of metabolic transition during Th cell differentiation.

IL-27 regulates the differentiation of follicular helper NKT cells via metabolic adaptation of mitochondria.

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes that express an invariant T cell receptor α chain and contribute to bridging innate and acquired immunity with rapid production of large amounts of cytokines after stimulation. Among effecter subsets of iNKT cells, follicular helper NKT (NKTFH) cells are specialized to help B cells. However, the mechanisms of NKTFH cell differentiation remain to be elucidated. In this report, we studied the mechanism of NKTFH cell differentiation induced by pneumococcal surface protein A and α-galactosylceramide (P/A) vaccination. We found that Gr-1+ cells helped iNKT cell proliferation and NKTFH cell differentiation in the spleen by producing interleukin-27 (IL-27) in the early phase after vaccination. The neutralization of IL-27 impaired NKTFH cell differentiation, which resulted in compromised antibody production and diminished protection against Streptococcus pneumoniae infection by the P/A vaccine. Our data indicated that Gr-1+ cell-derived IL-27 stimulated mitochondrial metabolism, meeting the energic demand required for iNKT cells to differentiate into NKTFH cells. Interestingly, Gr-1+ cell-derived IL-27 was induced by iNKT cells via interferon-γ production. Collectively, our findings suggest that optimizing the metabolism of iNKT cells was essential for acquiring specific effector functions, and they provide beneficial knowledge on iNKT cell-mediated vaccination-mediated therapeutic strategies.

ACC1-mediated fatty acid biosynthesis intrinsically controls thymic iNKT cell development.

To meet the energetic requirements associated with activation, proliferation, and survival, T cells switch their metabolic signatures from energetically quiescent to activated. However, little is known about the role of metabolic pathway controlling the development of invariant natural killer T (iNKT) cells. In the present study, we found that acetyl-CoA carboxylase 1 (ACC1), a rate-limiting enzyme for the fatty acid biosynthesis pathway, plays an essential role in the development of iNKT cells in the thymus. Mice lacking T-cell specific ACC1 showed a reduced number of iNKT cells with an increased proportion of iNKT cells at immature stages 0 and 1. Furthermore, mixed bone marrow (BM) chimera experiments revealed that T-cell intrinsic ACC1 expression was selectively important for the development of thymic iNKT cells, especially for the differentiation of the NKT1 cell subset. Our single-cell RNA-sequencing (scRNA-seq) data and functional analysis demonstrated that ACC1 is responsible for survival of developing iNKT cells. Thus, these findings highlighted a novel role of ACC1 in controlling thymic iNKT cell development mediated by the control of cell survival.

1-Oleoyl-lysophosphatidylethanolamine stimulates RORγt activity in TH17 cells.

Metabolic fluxes involving fatty acid biosynthesis play essential roles in controlling the differentiation of T helper 17 (TH17) cells. However, the exact enzymes and lipid metabolites involved, as well as their link to promoting the core gene transcriptional signature required for the differentiation of TH17 cells, remain largely unknown. From a pooled CRISPR-based screen and unbiased lipidomics analyses, we identified that 1-oleoyl-lysophosphatidylethanolamine could act as a lipid modulator of retinoid-related orphan receptor gamma t (RORγt) activity in TH17 cells. In addition, we specified five enzymes, including Gpam, Gpat3, Lplat1, Pla2g12a, and Scd2, suggestive of the requirement of glycerophospholipids with monounsaturated fatty acids being required for the transcription of Il17a. 1-Oleoyl-lysophosphatidylethanolamine was reduced in Pla2g12a-deficient TH17 cells, leading to the abolition of interleukin-17 (IL-17) production and disruption to the core transcriptional program required for the differentiation of TH17 cells. Furthermore, mice with T cell-specific deficiency of Pla2g12a failed to develop disease in an experimental autoimmune encephalomyelitis model of multiple sclerosis. Thus, our data indicate that 1-oleoyl-lysophosphatidylethanolamine is a lipid metabolite that promotes RORγt-induced TH17 cell differentiation and the pathogenicity of TH17 cells.

Lipid metabolism in Th17 cell function.

Among the subset of T helper cells, Th17 cells are known to play a crucial role in the pathogenesis of various autoimmune disorders, such as psoriasis, rheumatoid arthritis, inflammatory bowel disease, steroid-resistant asthma, and multiple sclerosis. The master transcription factor retinoid-related orphan receptor gamma t (RORγt), a nuclear hormone receptor, plays a vital role in inducing Th17-cell differentiation. Recent findings suggest that metabolic control is critical for Th17-cell differentiation, particularly through the engagement of de novo lipid biosynthesis. Inhibition of lipid biosynthesis, either through the use of pharmacological inhibitors or by the deficiency of related enzymes in CD4+ T cells, results in significant suppression of Th17-cell differentiation. Mechanistic studies indicate that metabolic fluxes through both the fatty acid and cholesterol biosynthetic pathways are essential for controlling RORγt activity through the generation of a lipid ligand of RORγt. This review highlights recent findings that underscore the significant role of lipid metabolism in the differentiation and function of Th17 cells, as well as elucidating the distinctive molecular pathways that drive the activation of RORγt by cellular lipid metabolism. We further elaborate on a pioneering therapeutic approach for ameliorating autoimmune disorders via the inhibition of RORγt.

Characterization of proteogenomic signatures of differentiation of CD4+ T cell subsets.

Functionally distinct CD4+ helper T (Th) cell subsets, including Th1, Th2, Th17, and regulatory T cells (Treg), play a pivotal role in the regulation of acquired immunity. Although the key proteins involved in the regulation of Th cell differentiation have already been identified how the proteogenomic landscape changes during the Th cell activation remains unclear. To address this issue, we characterized proteogenomic signatures of differentiation to each Th cell subsets by RNA sequencing and liquid chromatography-assisted mass spectrometry, which enabled us to simultaneously quantify more than 10,000 protein-coding transcripts and 8,000 proteins in a single-shot. The results indicated that T cell receptor activation affected almost half of the transcript and protein levels in a low correlative and gene-specific manner, and specific cytokine treatments modified the transcript and protein profiles in a manner specific to each Th cell subsets: Th17 and Tregs particularly exhibited unique proteogenomic signatures compared to other Th cell subsets. Interestingly, the in-depth proteome data revealed that mRNA profiles alone were not enough to delineate functional changes during Th cell activation, suggesting that the proteogenomic dataset obtained in this study serves as a unique and indispensable data resource for understanding the comprehensive molecular mechanisms underlying effector Th cell differentiation.

SCD2-mediated cooperative activation of IRF3-IRF9 regulatory circuit controls type I interferon transcriptome in CD4+ T cells.

Type I interferons (type I-IFN) are critical for the host defense to viral infection, and at the same time, the dysregulation of type I-IFN responses leads to autoinflammation or autoimmunity. Recently, we reported that the decrease in monounsaturated fatty acid caused by the genetic deletion of Scd2 is essential for the activation of type I-IFN signaling in CD4+ Th1 cells. Although interferon regulatory factor (IRF) is a family of homologous proteins that control the transcription of type I-IFN and interferon stimulated genes (ISGs), the member of the IRF family that is responsible for the type I-IFN responses induced by targeting of SCD2 remains unclear. Here, we report that the deletion of Scd2 triggered IRF3 activation for type I-IFN production, resulting in the nuclear translocation of IRF9 to induce ISG transcriptome in Th1 cells. These data led us to hypothesize that IRF9 plays an essential role in the transcriptional regulation of ISGs in Scd2-deleted (sgScd2) Th1 cells. By employing ChIP-seq analyses, we found a substantial percentage of the IRF9 target genes were shared by sgScd2 and IFNß-treated Th1 cells. Importantly, our detailed analyses identify a unique feature of IRF9 binding in sgScd2 Th1 cells that were not observed in IFNß-treated Th1 cells. In addition, our combined analyses of transcriptome and IRF9 ChIP-seq revealed that the autoimmunity related genes, which increase in patient with SLE, were selectively increased in sgScd2 Th1 cells. Thus, our findings provide novel mechanistic insights into the process of fatty acid metabolism that is essential for the type I-IFN response and the activation of the IRF family in CD4+ T cells.

Fatty acid metabolism in T-cell function and differentiation.

Immunometabolism has recently emerged as a field of study examining the intersection between immunology and metabolism. Studies in this area have yielded new findings on the roles of a diverse range of metabolic pathways and metabolites, which have been found to control many aspects of T-cell biology, including cell differentiation, function and fate. A particularly important finding has been the discovery that to meet the energy requirements associated with their proliferation, activation and specific functions, T cells switch their metabolic signatures during differentiation. For example, whereas the induction of de novo fatty acid biosynthesis and fatty acid uptake programs are required for antigen-stimulation-induced proliferation and differentiation of effector T cells, fatty acid catabolism via ß-oxidation is essential for the generation of memory T cells and the differentiation of regulatory T cells. In this review, we discuss recent advances in our understanding of the metabolism in different stages of T cells and how fatty acid metabolism in these cells controls their specific functions.

Acsbg1-dependent mitochondrial fitness is a metabolic checkpoint for tissue Treg cell homeostasis.

Regulatory T (Treg) cells are critical for immunological tolerance and immune homeostasis. Treg cells strongly rely on mitochondrial metabolism and show a lower level of glycolysis. However, little is known about the role of lipid metabolism in the regulation of Treg cell homeostasis. Some members of the ACSL family of acyl-coenzyme A (CoA) synthases are expressed in T cells, but their function remains unclear. A combination of RNA-sequencing and proteome analyses shows that Acsbg1, a member of ACSL, is selectively expressed in Treg cells. We show that the genetic deletion of Acsbg1 not only causes mitochondrial dysfunction, but it also dampens other metabolic pathways. The extrinsic supplementation of Acsbg1-deficient Treg cells with oleoyl-CoA restores the phenotype of the Treg metabolic signature. Furthermore, this pathway in ST2+ effector Treg cells enhances immunosuppressive capacity in airway inflammation. Thus, Acsbg1 serves as a metabolic checkpoint governing Treg cell homeostasis and the resolution of lung inflammation.

ACC1-expressing pathogenic T helper 2 cell populations facilitate lung and skin inflammation in mice.

T cells possess distinguishing effector functions and drive inflammatory disorders. We have previously identified IL-5-producing Th2 cells as the pathogenic population predominantly involved in the pathology of allergic inflammation. However, the cell-intrinsic signaling pathways that control the pathogenic Th2 cell function are still unclear. We herein report the high expression of acetyl-CoA carboxylase 1 (ACC1) in the pathogenic CD4+ T cell population in the lung and skin. The genetic deletion of CD4+ T cell-intrinsic ACC1 dampened eosinophilic and basophilic inflammation in the lung and skin by constraining IL-5 or IL-3 production. Mechanistically, ACC1-dependent fatty acid biosynthesis induces the pathogenic cytokine production of CD4+ T cells via metabolic reprogramming and the availability of acetyl-CoA for epigenetic regulation. We thus identified a distinct phenotype of the pathogenic T cell population in the lung and skin, and ACC1 was shown to be an essential regulator controlling the pathogenic function of these populations to promote type 2 inflammation.

SCD2-mediated monounsaturated fatty acid metabolism regulates cGAS-STING-dependent type I IFN responses in CD4+ T cells.

Host lipid metabolism and viral responses are intimately connected. However, the process by which the acquired immune systems adapts lipid metabolism to meet demands, and whether or not the metabolic rewiring confers a selective advantage to host immunity, remains unclear. Here we show that viral infection attenuates the expression of genes related to lipid metabolism in murine CD4+ T cells, which in turn increases the expression of antiviral genes. Inhibition of the fatty acid synthesis pathway substantially increases the basal expression of antiviral genes via the spontaneous production of type I interferon (IFN). Using a combination of CRISPR/Cas9-mediated genome editing technology and a global lipidomics analysis, we found that the decrease in monounsaturated fatty acid caused by genetic deletion of Scd2 in mice was crucial for the induction of an antiviral response through activation of the cGAS-STING pathway. These findings demonstrate the important relationship between fatty acid biosynthesis and type I IFN responses that enhances the antiviral response.

ACC1 determines memory potential of individual CD4+ T cells by regulating de novo fatty acid biosynthesis.

Immunological memory is central to adaptive immunity and protection from disease. Changing metabolic demands as antigen-specific T cells transition from effector to memory cells have been well documented, but the cell-specific pathways and molecules that govern this transition are poorly defined. Here we show that genetic deletion of ACC1, a rate-limiting enzyme in fatty acid biosynthesis, enhances the formation of CD4+ T memory cells. ACC1-deficient effector helper T (Th) cells have similar metabolic signatures to wild-type memory Th cells, and expression of the gene encoding ACC1, Acaca, was inversely correlated with a memory gene signature in individual cells. Inhibition of ACC1 function enhances memory T cell formation during parasite infection in mice. Using single-cell analyses we identify a memory precursor-enriched population (CCR7hiCD137lo) present during early differentiation of effector CD4+ T cells. Our data indicate that fatty acid metabolism directs cell fate determination during the generation of memory CD4+ T cells.

DUSP10 constrains innate IL-33-mediated cytokine production in ST2hi memory-type pathogenic Th2 cells.

ST2hi memory-type Th2 cells are identified as a pathogenic subpopulation in eosinophilic airway inflammation. These ST2hi pathogenic Th2 cells produce large amount of IL-5 upon T cell receptor stimulation, but not in response to IL-33 treatment. By contrast, IL-33 alone induces cytokine production in ST2+ group 2 innate lymphoid cells (ILC2). Here we show that a MAPK phosphatase Dusp10 is a key negative regulator of IL-33-induced cytokine production in Th2 cells. In this regard, Dusp10 is expressed by ST2hi pathogenic Th2 cells but not by ILC2, and Dusp10 expression inhibits IL-33-induced cytokine production. Mechanistically, this inhibition is mediated by DUSP10-mediated dephosphorylation and inactivation of p38 MAPK, resulting in reduced GATA3 activity. The deletion of Dusp10 renders ST2hi Th2 cells capable of producing IL-5 by IL-33 stimulation. Our data thus suggest that DUSP10 restricts IL-33-induced cytokine production in ST2hi pathogenic Th2 cells by controlling p38-GATA3 activity.

Amphiregulin-Producing Pathogenic Memory T Helper 2 Cells Instruct Eosinophils to Secrete Osteopontin and Facilitate Airway Fibrosis.

Memory T cells provide long-lasting protective immunity, and distinct subpopulations of memory T cells drive chronic inflammatory diseases such as asthma. Asthma is a chronic allergic inflammatory disease with airway remodeling including fibrotic changes. The immunological mechanisms that induce airway fibrotic changes remain unknown. We found that interleukin-33 (IL-33) enhanced amphiregulin production by the IL-33 receptor, ST2hi memory T helper 2 (Th2) cells. Amphiregulin-epidermal growth factor receptor (EGFR)-mediated signaling directly reprogramed eosinophils to an inflammatory state with enhanced production of osteopontin, a key profibrotic immunomodulatory protein. IL-5-producing memory Th2 cells and amphiregulin-producing memory Th2 cells appeared to cooperate to establish lung fibrosis. The analysis of polyps from patients with eosinophilic chronic rhinosinusitis revealed fibrosis with accumulation of amphiregulin-producing CRTH2hiCD161hiCD45RO+CD4+ Th2 cells and osteopontin-producing eosinophils. Thus, the IL-33-amphiregulin-osteopontin axis directs fibrotic responses in eosinophilic airway inflammation and is a potential target for the treatment of fibrosis induced by chronic allergic disorders.

Nutritional control of IL-23/Th17-mediated autoimmune disease through HO-1/STAT3 activation.

The nutritional curcumin (CUR) is beneficial in cell-mediated autoimmune diseases. The molecular mechanisms underlying this food-mediated silencing of inflammatory immune responses are poorly understood. By investigating antigen-specific immune responses we found that dietary CUR impairs the differentiation of Th1/Th17 cells in vivo during encephalomyelitis and instead promoted Th2 cells. In contrast, feeding CUR had no inhibitory effect on ovalbumin-induced airway inflammation. Mechanistically, we found that CUR induces an anti-inflammatory phenotype in dendritic cells (DC) with enhanced STAT3 phosphorylation and suppressed expression of Il12b and Il23a. On the molecular level CUR readily induced NRF2-sensitive heme oxygenase 1 (HO-1) mRNA and protein in LPS-activated DC. HO-1 enhanced STAT3 phosphorylation, which enriched to Il12b and Il23a loci and negatively regulated their transcription. These findings demonstrate the underlying mechanism through which a nutritional can interfere with the immune response. CUR silences IL-23/Th17-mediated pathology by enhancing HO-1/STAT3 interaction in DC.

Health effects of a farming program to foster community social capital of a temporary housing complex of the 2011 great East Japan earthquake.

OBJECTIVE: We launched a health promotion program called the Hamarassen ("let's get together") Farm, which provided farming opportunities for the victims of the Great East Japan Earthquake who resided in temporary housing. The aim of this study was to evaluate the effects of this program on physical and mental health in terms of bone mineral density (BMD) and a sense of purpose in life. METHODS: Among 39 female participants in whom BMD was evaluated, there were 12 Hamarassen participants, 8 self-farming control subjects, and 19 non-farming control subjects. BMD was measured by calcaneal quantitative ultrasound immediately after the project launch and 5 months later. A sense of purpose in life prior to and 2 months after the project's commencement was measured in 21 additional Hamarassen participants by use of the K-I Scale. Interviews were also conducted to qualitatively evaluate the effects of the Hamarassen program. RESULTS: The mean BMD T-score improved by 0.43 in the Hamarassen group, by 0.33 in the self-farming group, and by 0.06 in the controls (p=0.02). Among the 21 Hamarassen participants in whom mental health was evaluated, the average score for a sense of purpose in life improved from 20.5 to 24.9 (p=0.001). CONCLUSIONS: The Hamarassen Farm provided disaster victims with opportunities for social participation, interpersonal interaction, and physical exercise; such opportunities may improve physical and psychosocial well-being.

Hydrogen sulfide-mediated regulation of contractility in the mouse ileum with electrical stimulation: roles of L-cysteine, cystathionine ß-synthase, and K+ channels.

Hydrogen sulfide (H2S) is considered to be a signaling molecule. The precise mechanisms underlying H2S-related events, including the producing enzymes and target molecules in gastrointestinal tissues, have not been elucidated in detail. We herein examined the involvement of H2S in contractions induced by repeated electrical stimulations (ES). ES-induced contractions were neurotoxin-sensitive and increased by aminooxyacetic acid, an inhibitor of cystathionine ß-synthase (CBS) and cystathionine γ-lyase, but not by D,L-propargylglycine, a selective inhibitor of cystathionine γ-lyase, in an ES trial-dependent manner. ES-induced contractions were markedly decreased in the presence of L-cysteine. This response was inhibited by aminooxyacetic acid and an antioxidant, and accelerated by L-methionine, an activator of CBS. The existence of CBS was confirmed. NaHS transiently inhibited ES- and acetylcholine-induced contractions, and sustainably decreased basal tone for at least 20 min after its addition. The treatment with glibenclamide, an ATP-sensitive K+ channel blocker, reduced both the L-cysteine response and NaHS-induced inhibition of contractions. The NaHS-induced decrease in basal tone was inhibited by apamin, a small conductance Ca2+-activated K+ channel blocker. These results suggest that H2S may be endogenously produced via CBS in ES-activated enteric neurons, and regulates contractility via multiple K+ channels in the ileum.

Intracellular calcium increases in growth cones exposed to tetracaine.

UNLABELLED: Neurotoxicity of local anesthetics has been reported for both matured and growing neurons. In the present study, we examined if tetracaine increases Ca(2+) concentration during growth cone collapse. Intracellular Ca(2+) concentration was measured by fura 2/AM after exposure to tetracaine. Tetracaine (1-2 mM) induced increases in intra-growth cone Ca(2+) concentration (P < 0.01). The Ca(2+) hot spot was expanded into the neurite from the periphery towards the cell body. When tetracaine was applied to growth cones in Ca(2+) free media, the increase was minor. However, tetracaine induced growth cone collapse even in the culture media, which did not contain Ca(2+). Ni(2+) (100 microM; a general Ca(2+) channel inhibitor) and BAPTA-AM (5 microM; intracellular Ca(2+) chelator) could not inhibit growth cone collapse induced by 1-2 mM tetracaine. Tetracaine (>1 mM) induces collapse and Ca(2+) increase at growth cones simultaneously; however, these two phenomena might be provoked independently. IMPLICATIONS: Tetracaine induced intracellular Ca(2+) increases and growth cone collapse in dorsal root ganglion neurons. The Ca(2+) hot spot in the growth cone expanded into the neurite from periphery towards the cell body.