Hepatic Sirt6 activation abrogates acute liver failure.

Acute liver failure (ALF) is a deadly illness due to insufficient detoxification in liver induced by drugs, toxins, and other etiologies, and the effective treatment for ALF is very limited. Among the drug-induced ALF, acetaminophen (APAP) overdose is the most common cause. However, the molecular mechanisms underlying APAP hepatoxicity remain incompletely understood. Sirtuin 6 (Sirt6) is a stress responsive protein deacetylase and plays an important role in regulation of DNA repair, genomic stability, oxidative stress, and inflammation. Here, we report that genetic and pharmacological activation of Sirt6 protects against ALF in mice. We first observed that Sirt6 expression was significantly reduced in the liver tissues of human patients with ALF and mice treated with an overdose of APAP. Then we developed an inducible Sirt6 transgenic mice for Cre-mediated overexpression of the human Sirt6 gene in systemic (Sirt6-Tg) and hepatic-specific (Sirt6-HepTg) manners. Both Sirt6-Tg mice and Sirt6-HepTg mice exhibited the significant protection against APAP hepatoxicity. In contrast, hepatic-specific Sirt6 knockout mice exaggerated APAP-induced liver damages. Mechanistically, Sirt6 attenuated APAP-induced hepatocyte necrosis and apoptosis through downregulation of oxidative stress, inflammation, the stress-activated kinase JNK activation, and apoptotic caspase activation. Moreover, Sirt6 negatively modulated the level and activity of poly (ADP-ribose) polymerase 1 (PARP1) in APAP-treated mouse liver tissues. Importantly, the specific Sirt6 activator MDL-800 exhibited better therapeutic potential for APAP hepatoxicity than the current drug acetylcysteine. Furthermore, in the model of bile duct ligation induced ALF, hepatic Sirt6-KO exacerbated, but Sirt6-HepTg mitigated liver damage. Collectively, our results demonstrate that Sirt6 protects against ALF and suggest that targeting Sirt6 activation could be a new therapeutic strategy to alleviate ALF.

SIRT6 Protects Against Lipopolysaccharide-Induced Inflammation in Human Pulmonary Lung Microvascular Endothelial Cells.

Inflammatory response in the pulmonary endothelium drives the pathogenesis of acute lung injury and sepsis. Sirtuin 6 (SIRT6), a member of class III NAD+-dependent deacetylases belonging to the sirtuin family, regulates senescence, metabolism, and inflammation and extends lifespan in mice and model organisms. However, the role of SIRT6 in pulmonary endothelial inflammation is unknown. Thus, we hypothesized that SIRT6 suppresses inflammatory response in human lung microvascular cells (HLMEC) and ensues monocyte adhesion to endothelial cells. Primary HLMECs were treated with control or SIRT6 adenovirus or SIRT6 agonist, with or without lipopolysaccharide (LPS) treatment. We observed that treatment with LPS did not affect the protein expression of SIRT6 in HLMECs. However, adenovirus-mediated SIRT6 overexpression attenuated LPS-induced VCAM1 gene and protein expression, followed by decreased monocyte adhesion to endothelial cells. Similarly, activation of SIRT6 by a recently reported SIRT6 activator UBCS039, but not the regioisomer negative control compound UBCS060, ameliorated LPS-induced VCAM1 mRNA and protein expression as well as monocyte adhesion. Moreover, luciferase assay revealed that SIRT6 adenovirus decreased the activity of NF-κB, the master regulator of vascular inflammation. Taken together, these results indicate that molecular and pharmacological activation of SIRT6 protects against lung microvascular inflammation via suppressing NF-κB activation, implicating the therapeutic potential of the SIRT6 activators for lung disorders associated with microvascular inflammation.

SIRT6 Mitigates Heart Failure With Preserved Ejection Fraction in Diabetes.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a growing health problem without effective therapies. Epidemiological studies indicate that diabetes is a strong risk factor for HFpEF, and about 45% of patients with HFpEF are suffering from diabetes, yet the underlying mechanisms remain elusive. METHODS: Using a combination of echocardiography, hemodynamics, RNA-sequencing, molecular biology, in vitro and in vivo approaches, we investigated the roles of SIRT6 (sirtuin 6) in regulation of endothelial fatty acid (FA) transport and HFpEF in diabetes. RESULTS: We first observed that endothelial SIRT6 expression was markedly diminished in cardiac tissues from heart failure patients with diabetes. We then established an experimental mouse model of HFpEF in diabetes induced by a combination of the long-term high-fat diet feeding and a low-dose streptozocin challenge. We also generated a unique humanized SIRT6 transgenic mouse model, in which a single copy of human SIRT6 transgene was engineered at mouse Rosa26 locus and conditionally induced with the Cre-loxP technology. We found that genetically restoring endothelial SIRT6 expression in the diabetic mice ameliorated diastolic dysfunction concurrently with decreased cardiac lipid accumulation. SIRT6 gain- or loss-of-function studies showed that SIRT6 downregulated endothelial FA uptake. Mechanistically, SIRT6 suppressed endothelial expression of PPARγ through SIRT6-dependent deacetylation of histone H3 lysine 9 around PPARγ promoter region; and PPARγ reduction mediated SIRT6-dependent inhibition of endothelial FA uptake. Importantly, oral administration of small molecule SIRT6 activator MDL-800 to diabetic mice mitigated cardiac lipid accumulation and diastolic dysfunction. CONCLUSIONS: The impairment of endothelial SIRT6 expression links diabetes to HFpEF through the alteration of FA transport across the endothelial barrier. Genetic and pharmacological strategies that restored endothelial SIRT6 function in mice with diabetes alleviated experimental HFpEF by limiting FA uptake and improving cardiac metabolism, thus warranting further clinical evaluation.

Rutaecarpine derivative R3 attenuates atherosclerosis via inhibiting NLRP3 inflammasome-related inflammation and modulating cholesterol transport.

Atherosclerosis is a chronic disease characterized by lipid deposition and inflammatory response. NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome-facilitated inflammatory responses are crucial in the pathogenesis of atherosclerosis, and thus new therapeutic approaches are emerging that target NLRP3 and inflammation. Here, we explored the anti-atherosclerotic effect and mechanisms of a new rutaecarpine derivative, 5-deoxy-rutaecarpine (R3) in vitro and in vivo. R3 treatment attenuated atherosclerosis development and increased plaque stability in Apoe-/- mice fed a high-fat diet, and decreased levels of inflammatory mediators, such as interleukin-1ß, in the serum of Apoe-/- mice and in oxidized low-density lipoprotein (ox-LDL)-stimulated murine macrophages. R3 treatment inhibited NLRP3 inflammasome activation in the livers of Apoe-/- mice and ox-LDL-stimulated murine macrophages by inhibiting NF-κB and MAPK pathways. Additionally, R3 significantly decreased total cholesterol in the serum and livers of Apoe-/- mice and promoted cholesterol efflux in murine macrophages through upregulating protein expression of ATP-binding cassette subfamily A member 1 and scavenger receptor class B type I/human CD36 and lysosomal integral membrane protein-II analogous-1. Our results demonstrated that R3 prevented atherosclerotic progression via attenuating NLRP3 inflammasome-related inflammation and modulating cholesterol transport.

Nuclear Factor Erythroid 2 Related Factor 2 Activator JC-5411 Inhibits Atherosclerosis Through Suppression of Inflammation and Regulation of Lipid Metabolism.

Phenethyl isothiocyanate is widely present in cruciferous vegetables with multiple biological effects. Here we reported the antiatherogenic effects and the underlying mechanisms of JC-5411 (Phenethyl isothiocyanate formulation) in vitro and in vivo. Luciferase reporter assay showed that JC-5411 increased the activity of nuclear factor erythroid 2-related factor 2 (Nrf2) and antioxidant response element (ARE). JC-5411 treatment significantly increased the protein expression of Nrf2 and its downstream target gene hemeoxygenase 1 (HO-1) in liver of apolipoprotein E deficient (ApoE-/-) mice. Importantly, JC-5411 treatment significantly reduced atherosclerotic plaque area in both en face aorta and aortic sinus when compared with model group in WD induced ApoE-/- mice. JC-5411 obviously decreased proinflammatory factors' levels in serum of ApoE-/- mice, LPS stimulated macrophages and TNFα induced endothelial cells, respectively. JC-5411 significantly decreased the levels of total cholesterol (TC) and triglyceride (TG) in both serum and liver of ApoE-/- mice and hyperlipidemic golden hamsters. Mechanism studies showed that JC-5411 exerted anti-inflammatory effect through activating Nrf2 signaling and inhibiting NF-κB and NLRP3 inflammasome pathway. JC-5411 exerted regulating lipid metabolism effect through increasing cholesterol transfer proteins (ABCA1 and LDLR) expression, regulating fatty acids synthesis related genes (p-ACC, SCD1 and FAS), and increasing fatty acids ß-oxidation (CPT1A) in vivo. Furthermore, JC-5411 treatment had a favorable antioxidant effect in ApoE-/- mice by increasing the antioxidant related genes expression. Taken together, we conclude that JC-5411 as a Nrf2 activator has anti-inflammatory, rebalancing lipid metabolism, and antioxidant effects, which makes it as a potential therapeutic agent against atherosclerosis.

Regulation of SRF protein stability by an autophagy-dependent pathway.

Serum response factor (SRF), a key transcription factor, plays an important role in regulating cell functions such as proliferation and differentiation. Most proteins are unstable, and protein stability is regulated through the ubiquitin-proteasome system (UPS) or the autophagy lysosome pathway (ALP). Whether SRF is degraded and what mechanisms control SRF protein stability remain unexplored. Western blot analyses of cells treated with cycloheximide (CHX), a protein synthesis inhibitor, showed that SRF was degraded in a time-dependent manner. Moreover, we observed that SRF undergoes autophagy-dependent destruction, which is accelerated by serum deprivation. Through bioinformatics screening, we found that SRF contains the GSK3ß phosphorylation motif (T/SPPXS): SPDSPPRSDPT, which is conserved from zebrafish to humans. Serum deprivation stimulated GSK3ß activation that then potentiates SRF degradation through the autophagy lysosome pathway. Since SRF is important for numerous cellular activities, our results suggest that the autophagy-dependent SRF degradation pathway may provide a new avenue to modulate SRF-mediated cell functions.

The novel coronary artery disease risk gene JCAD/KIAA1462 promotes endothelial dysfunction and atherosclerosis.

AIMS: Recent genome-wide association studies (GWAS) have identified that the JCAD locus is associated with risk of coronary artery disease (CAD) and myocardial infarction (MI). However, the mechanisms whereby candidate gene JCAD confers disease risk remain unclear. We addressed whether and how JCAD affects the development of atherosclerosis, the common cause of CAD. METHODS AND RESULTS: By mining data in the Genotype-Tissue Expression (GTEx) database, we found that CAD-associated risk variants at the JCAD locus are linked to increased JCAD gene expression in human arteries, implicating JCAD as a candidate causal CAD gene. We therefore generated global and endothelial cell (EC) specific-JCAD knockout mice, and observed that JCAD deficiency attenuated high fat diet-induced atherosclerosis in ApoE-deficient mice. JCAD-deficiency in mice also improved endothelium-dependent relaxation. Genome-wide transcriptional profiling of JCAD-depleted human coronary artery ECs showed that JCAD depletion inhibited the activation of YAP/TAZ pathway, and the expression of downstream pro-atherogenic genes, including CTGF and Cyr61. As a result, JCAD-deficient ECs attracted fewer monocytes in response to lipopolysaccharide (LPS) stimulation. Moreover, JCAD expression in ECs was decreased under unidirectional laminar flow in vitro and in vivo. Proteomics studies suggest that JCAD regulates YAP/TAZ activation by interacting with actin-binding protein TRIOBP, thereby stabilizing stress fiber formation. Finally, we observed that endothelial JCAD expression was increased in mouse and human atherosclerotic plaques. CONCLUSION: The present study demonstrates that the GWAS-identified CAD risk gene JCAD promotes endothelial dysfunction and atherosclerosis, thus highlighting the possibility of new therapeutic strategies for CAD by targeting JCAD.

Cholinergic system is involved in the therapeutic effect of madecassoside on collagen-induced arthritis in rats.

Our previous studies demonstrated that oral administration of madecassoside could markedly attenuate collagen-induced arthritis in rats, a rodent model of rheumatoid arthritis. As the autonomic nervous system is critically involved in the modulation of peripheral inflammation and immune response, the present study aims to explore the possible involvement of adrenergic and cholinergic nerves in the effect of madecassoside on rheumatoid arthritis. Arthritis was induced by chicken collagen in rats, and madecassoside was orally administered daily for two weeks from day 14 after the primary immunization. The antagonists of adrenoceptor and cholinergic receptors were co-administered with madecassoside, respectively. Unilateral cervical vagotomy was performed four days before the arthritis induction. The results showed that madecassoside (30 mg/kg) treatment markedly ameliorated arthritis symptoms in rats, mainly evidenced by the reduction of paw swelling and arthritis index scores. Co-administration of madecassoside with atropine (an antagonist of the muscarinic acetylcholine receptor) or hexamethonium (an antagonist of the nicotinic acetylcholine receptor) markedly diminished the therapeutic effects of madecassoside in arthritis. However, co-administration with phentolamine (an antagonist of the α-adrenoceptor) or propranolol (an antagonist of the ß-adrenoceptor) did not alter the effect of madecassoside on arthritis. Furthermore, unilateral cervical vagotomy significantly reduced the anti-arthritis efficacy of madecassoside, including the amelioration of clinical symptoms, as well as the inhibition of the production of pro-inflammatory cytokines except T lymphocytes-related cytokines. These findings suggest that madecassoside exerts inhibitory effects on collagen-induced arthritis through, at least partially, the peripheral cholinergic system.

E3317 promotes cholesterol efflux in macrophage cells via enhancing ABCA1 expression.

Reverse cholesterol transport (RCT) plays an important role in cholesterol and lipid metabolism. Regulating the activities of key transporters and receptors in RCT, such as ATP-binding cassette transporter A1 (ABCA1), helps to prevent atherosclerotic cardiovascular disease. In this study, we used an ABCA1 promoter luciferase reporter assay to screen 20,000 compounds for ABCA1 upregulators. Compound E3317 (N-(6-butylbenzo[d]thiazol-2(3H)-ylidene)-3-(N-(2-cyanoethyl)sulfamoyl)benzamide)) was identified as a positive hit with an EC50 value of 0.2 µM in ABCA1p-LUC HepG2 cells. Thus, we hypothesized that E3317 might have cholesterol- and lipid metabolism-regulating effects through ABCA1 upregulation. E3317 significantly increased ABCA1 mRNA and protein expression in hepatic L02 cells and RAW264.7 macrophages. E3317 promoted cholesterol efflux to apolipoprotein A-I in RAW264.7 macrophages and significantly decreased lipid accumulation in oxidized low-density lipoprotein-induced murine RAW264.7 macrophages. Further studies using ABCA1 siRNA showed that the promotion of cholesterol efflux and decrease of lipid accumulation by E3317 depended on ABCA1 expression. Mechanistic studies indicated that E3317 regulated ABCA1 expression via activating nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ), which plays an important role in the regulation of glucose homeostasis and lipid metabolism. The structure of E3317 was docked in the ligand-binding domain of PPARγ (PBD code: 4EMA) to find the key binding amino acids. Site mutation assays confirmed that Y327 and F363 were the key PPARγ binding epitopes of E3317. Our results revealed that E3317 upregulates ABCA1 expression and thereby promotes cholesterol efflux. E3317 may regulate ABCA1 expression through PPARγ. Our findings provide a new compound, E3317, which may have beneficial cardiovascular effects.

SIRT1 activator E1231 protects from experimental atherosclerosis and lowers plasma cholesterol and triglycerides by enhancing ABCA1 expression.

BACKGROUND AND AIMS: Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide-dependent protein deacetylase. Recent studies have demonstrated that enhancing SIRT1 expression or activity may modulate cholesterol and lipid metabolism. However, pharmacological and molecular regulators for SIRT1 are scarce. Here, we aimed to find novel small molecule modulators of SIRT1 to regulate cholesterol and lipid metabolism. METHODS: A high-throughput screening assay was established to identify SIRT1 activators. Surface plasmon resonance and immunoprecipitation were performed to confirm the interaction of E1231 with SIRT1. Cholesterol assay was performed to demonstrate the in vitro effect of E1231. The in vivo effect of E1231 was evaluated in experimental models. RESULTS: E1231, a piperazine 1,4-diamide compound, was identified as a SIRT1 activator with EC50 value of 0.83 µM. E1231 interacted with recombinant human SIRT1 protein and deacetylated liver X receptor-alpha (LXRα). E1231 increased ATP-binding cassette transporter A1 (ABCA1) expression in RAW 264.7 cells dependent on SIRT1 and LXRα. E1231 promoted cholesterol efflux and inhibited lipid accumulation in RAW 264.7 cells via SIRT1 and ABCA1. In the golden hamster hyperlipidemia model, E1231 treatment decreased total cholesterol and triglyceride levels in both serum and the liver, while increased cholesterol content in feces. Moreover, E1231 increased ABCA1 and SIRT1 protein expression in the liver. In ApoE-/- mice, E1231 treatment reduced atherosclerotic plaque development compared with untreated ApoE-/- mice. CONCLUSIONS: We identified a novel SIRT1 activator E1231 and elucidated its beneficial effects on lipid and cholesterol metabolism. Our study suggests that E1231 might be developed as a novel drug for treating atherosclerosis.

A novel SIRT1 activator E6155 improves insulin sensitivity in type 2 diabetic KKAy mice.

Sirtuin 1 (SIRT1) is an NAD+-dependent protein deacetylase that plays a critical role in controlling energy metabolism, stress response and aging. Hence, enhancing SIRT1 activity could be a potential therapeutic strategy to treat metabolic diseases such as diabetes. However, pharmacological activators for SIRT1 are scarce to date. In this study, using the optimized high throughput screening, we identified E6155, a piperazine 1, 4- diamide compound, as a new small molecular activator of SIRT1. We further found that E6155 significantly upregulated glucose uptake in cultured normal liver cells and skeletal muscle cells through increasing SIRT1 deacetylase activity. In type 2 diabetic KKAy mice, E6155 treatment markedly decreased the level of fasting glucose. Moreover, E6155 improved oral glucose tolerance and insulin tolerance. Euglycemic clamp and the homeostasis model assessment of insulin resistance index showed that E6155 ameliorated the insulin resistance and increased insulin sensitivity in diabetic mice. Mechanistically, we observed that the antidiabetic effects of E6155 were involved in SIRT1 dependent activation of LKB1/AMPK and IRS1/AKT pathways. In conclusion, our findings identified E6155 as a novel SIRT1 activator and suggested that E6155 could be a promising drug candidate for treating insulin resistance and diabetes.

Curcumin attenuates collagen-induced inflammatory response through the "gut-brain axis".

BACKGROUND: Previous studies have demonstrated that oral administration of curcumin exhibited an anti-arthritic effect despite its poor bioavailability. The present study aimed to explore whether the gut-brain axis is involved in the therapeutic effect of curcumin. METHODS: The collagen-induced arthritis (CIA) rat model was induced by immunization with an emulsion of collagen II and complete Freund's adjuvant. Sympathetic and parasympathetic tones were measured by electrocardiographic recordings. Unilateral cervical vagotomy (VGX) was performed before the induction of CIA. The ChAT, AChE activities, and serum cytokine levels were determined by ELISA. The expression of the high-affinity choline transporter 1 (CHT1), ChAT, and vesicular acetylcholine transporter (VAChT) were determined by real-time PCR and immunohistochemical staining. The neuronal excitability of the vagus nerve was determined by whole-cell patch clamp recording. RESULTS: Oral administration of curcumin restored the imbalance between the sympathetic and parasympathetic tones in CIA rats and increased ChAT activity and expression of ChAT and VAChT in the gut, brain, and synovium. Additionally, VGX eliminated the effects of curcumin on arthritis and ACh biosynthesis and transport. Electrophysiological data showed that curcumin markedly increased neuronal excitability of the vagus nerve. Furthermore, selective α7 nAChR antagonists abolished the effects of curcumin on CIA. CONCLUSIONS: Our results demonstrate that curcumin attenuates CIA through the "gut-brain axis" by modulating the function of the cholinergic system. These findings provide a novel approach for mechanistic studies of anti-arthritic compounds with low oral absorption and bioavailability.

Arctigenin functions as a selective agonist of estrogen receptor ß to restrict mTORC1 activation and consequent Th17 differentiation.

Arctigenin was previously proven to inhibit Th17 cell differentiation and thereby attenuate colitis in mice by down-regulating the activation of mechanistic target of rapamycin complex 1 (mTORC1). The present study was performed to address its underlying mechanism in view of estrogen receptor (ER). The specific antagonist PHTPP or siRNA of ERß largely diminished the inhibitory effect of arctigenin on the mTORC1 activation in T cell lines and primary CD4+ T cells under Th17-polarization condition, suggesting that arctigenin functioned in an ERß-dependent manner. Moreover, arctigenin was recognized to be an agonist of ERß, which could bind to ERß with a moderate affinity, promote dissociation of ERß/HSP90 complex and nuclear translocation and phosphorylation of ERß, and increase the transcription activity. Following activation of ERß, arctigenin inhibited the activity of mTORC1 by disruption of ERß-raptor-mTOR complex assembly. Deficiency of ERß markedly abolished arctigenin-mediated inhibition of Th17 cell differentiation. In colitis mice, the activation of ERß, inhibition of mTORC1 activation and Th17 response by arctigenin were abolished by PHTPP treatment. In conclusion, ERß might be the target protein of arctigenin responsible for inhibition of mTORC1 activation and resultant prevention of Th17 cell differentiation and colitis development.

DGAEE, a newly synthesized derivative of glycyrrhetinic acid, potently attenuates mouse septic shock via its main metabolite DGA in an IL-10-dependent manner.

Endotoxin can stimulate inflammatory cytokine release from monocytes/macrophages and result in septic shock. Glycyrrhetinic acid (GA), the main bioactive component of licorice, possesses substantial anti-inflammatory activity. Here, we explored effect of 11-deoxy-18α-glycyrrhetinic acid-30-ethyl ester (DGAEE), a newly synthesized derivative of GA, on septic shock. DGAEE and its main metabolite 11-deoxy-18α-glycyrrhetinic acid (DGA) significantly alleviated septic shock as evidenced by improvements of survival rates, lung histopathological changes and wet/dry ratio in lipopolysaccharide (LPS)/D-galactosamine-stimulated mice, and decreased blood pressure in LPS/D-galactosamine-stimulated rats. The two compounds decreased serum levels of NO, TNF-α, IL-6, IL-1ß, and increased the level of IL-10 more potently in mice. In LPS-stimulated RAW 264.7 cells, DGA but not DGAEE showed marked regulation of NO, TNF-α, IL-6 and IL-10 levels, suggesting that DGAEE display anti-shock effect by DGA rather than itself. Moreover, the neutralizing antibody against IL-10 markedly prohibited the inhibitory effect of DGA on the production of cytokines from RAW 264.7 cells, and AS101 (an inhibitor of IL-10 biosynthesis) almost completely reversed the anti-shock effect of DGA in mice. In addition, DGA did not affect activation of NF-κB-p65 and p38 MAPK as well as IκBα degradation, but moderately reduced activation of ERK and JNK, and markedly increased phosphorylation of GSK3ß in LPS-stimulated RAW 264.7 cells. LY294002 (an inhibitor of GSK3ß phosphorylation) and LiCl (an inhibitor of GSK3ß activity) diminished and potentiated increase of IL-10 levels by DGA, respectively. In conclusion, DGAEE alleviates septic shock through DGA in an IL-10-dependent manner, and the mechanism is related to inactivation of GSK3ß.

Arctigenin exerts anti-colitis efficacy through inhibiting the differentiation of Th1 and Th17 cells via an mTORC1-dependent pathway.

Arctigenin, the main effective constituent of Arctium lappa L. fruit, has previously been proven to dramatically attenuate dextran sulfate sodium (DSS)-induced colitis in mice, a frequently used animal model of inflammatory bowel disease (IBD). As Th1 and Th17 cells play a crucial role in the pathogenesis of IBD, the present study addressed whether and how arctigenin exerted anti-colitis efficacy by interfering with the differentiation and activation of Th1/Th17 cells. In vitro, arctigenin was shown to markedly inhibit the differentiation of Th17 cells from naïve T cells, and moderately inhibit the differentiation of Th1 cells, which was accompanied by lowered phosphorylation of STAT3 and STAT4, respectively. In contrast, arctigenin was lack of marked effect on the differentiation of either Th2 or regulatory T cells. Furthermore, arctigenin was shown to suppress the mammalian target of rapamycin complex 1 (mTORC1) pathway in T cells as demonstrated by down-regulated phosphorylation of the downstream target genes p70S6K and RPS6, and it functioned independent of two well-known upstream kinases PI3K/AKT and ERK. Arctigenin was also able to inhibit the activity of mTORC1 by dissociating raptor from mTOR. Interestingly, the inhibitory effect of arctigenin on T cell differentiation disappeared under a status of mTORC1 overactivation via knockdown of tuberous sclerosis complex 2 (TSC2, a negative regulator of mTORC1) or pretreatment of leucine (an agonist of mTOR). In DSS-induced mice, the inhibition of Th1/Th17 responses and anti-colitis effect of arctigenin were abrogated by leucine treatment. In conclusion, arctigenin ameliorates colitis through down-regulating the differentiation of Th1 and Th17 cells via mTORC1 pathway.