TNF-Receptor-1 inhibition reduces liver steatosis, hepatocellular injury and fibrosis in NAFLD mice.

Non-alcoholic fatty liver disease (NAFLD) shows an increasing prevalence and is associated with the development of liver fibrosis and cirrhosis as the major risk factors of liver-related mortality in this disease. The therapeutic possibilities are limited and restricted to life style intervention, since specific drugs for NAFLD are unavailable so far. TNFα has been implicated as a major pathogenic driver of NAFLD. TNFα-mediated liver injury occurs mainly via TNF-receptor-1 (TNFR1) signaling, whereas TNFR2 mediates protective pathways. In this study, we analyzed the therapeutic effects of a novel antibody, which selectively inhibits TNFR1 while retaining protective TNFR2 signaling in a high-fat diet (HFD) mouse model of NAFLD. Mice were fed with HFD for 32 weeks and treated with anti-TNFR1-antibody or control-antibody for the last 8 weeks. We then investigated the mechanisms of TNFR1 inhibition on liver steatosis, inflammatory liver injury, insulin resistance and fibrosis. Compared to control-antibody treatment, TNFR1 inhibition significantly reduced liver steatosis and triglyceride content, which was accompanied by reduced expression and activation of the transcription factor SREBP1 and downstream target genes of lipogenesis. Furthermore, inhibition of TNFR1 resulted in reduced activation of the MAP kinase MKK7 and its downstream target JNK, which was associated with significant improvement of insulin resistance. Apoptotic liver injury, NAFLD activity and alanine aminotransferase (ALT) levels, as well as liver fibrosis significantly decreased by anti-TNFR1 compared to control-antibody treatment. Thus, our results suggest selective TNFR1 inhibition as a promising approach for NAFLD treatment.

Constitutive activation of the canonical NF-κB signaling pathway in EBV-associated gastric carcinoma.

EBV-associated gastric carcinoma (EBVaGC) is a specific subgroup of gastric carcinoma, and the multifunctional transcriptional factor NF-κB may contribute to its tumorigenesis. In this study, we comprehensively characterized NF-κB signaling in EBVaGC using qRT-PCR, western blot, immunofluorescence assays, ELISA, and immunohistochemistry staining. NF-κB-signaling inhibitors may inhibit the growth of EBVaGC cells and induce significant apoptosis. IκBα is a key regulatory molecule, and repression of IκBα can contribute to aberrant NF-κB activation. Overexpression of LMP1 and LMP2A in the EBV-negative GC cell line SGC7901 could inhibit the expression of IκBα and induce NF-κB activation. These findings indicate that the canonical NF-κB signal is constitutively activated and plays an important role in EBVaGC tumorigenesis.

miR-214 Down-Regulation Promoted Hypoxia/Reoxygenation-Induced Hepatocyte Apoptosis Through TRAF1/ASK1/JNK Pathway.

OBJECTIVE: This study investigated the role of miR-214 in the hepatocyte apoptosis induced by hypoxia/reoxygenation (H/R) injury. MATERIALS AND METHODS: In vivo hepatic ischemia/reperfusion (HIR) injury, mice model and in vitro HR model were established. miR-214, TRAF1, ASK1, and JNK expression levels were detected by qRT-PCR and western blot. The apoptosis of mouse hepatocyte AML12 was detected by flow cytometry analysis. The interaction between miR-214 and TRAF1 was confirmed by dual-luciferase reporter gene assay. RESULTS: Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were elevated in HIR injury mice compared with sham mice. miR-214 expression was down-regulated in liver tissues of HIR and H/R-induced hepatocytes, whereas TRAF1, ASK1, and JNK expressions were up-regulated in HIR and H/R groups. H/R stimulation promoted the apoptosis of hepatocytes, and miR-214 overexpression inhibited the apoptosis of hepatocytes. Besides, TRAF1 was a target of miR-214 and negatively regulated by miR-214. miR-214/TRAF1 pathway involved in the modulation of H/R-induced apoptosis of hepatocytes. In vivo study proved miR-214 reduced hepatic injury of HIR mice. CONCLUSION: miR-214 overexpression reduces hepatocyte apoptosis after HIR injury through negatively regulating TRAF1/ASK1/JNK pathway.

Targeting hepatic TRAF1-ASK1 signaling to improve inflammation, insulin resistance, and hepatic steatosis.

BACKGROUND & AIMS: Tumor necrosis factor receptor-associated factor 1 (TRAF1) is an important adapter protein that is largely implicated in molecular events regulating immunity/inflammation and cell death. Although inflammation is closely related to and forms a vicious circle with insulin dysfunction and hepatic lipid accumulation, the role of TRAF1 in hepatic steatosis and the related metabolic disorders remains unclear. METHODS: The participation of TRAF1 in the initiation and progression of hepatic steatosis was evaluated in high fat diet (HFD)-induced and genetic obesity. Mice with global TRAF1 knockout or liver-specific TRAF1 overexpression were employed to investigate the role of TRAF1 in insulin resistance, inflammation, and hepatic steatosis based on various phenotypic examinations. Molecular mechanisms underlying TRAF1-regulated hepatic steatosis were further explored in vivo and in vitro. RESULTS: TRAF1 expression was significantly upregulated in the livers of NAFLD patients and obese mice and in palmitate-treated hepatocytes. In response to HFD administration or in ob/ob mice, TRAF1 deficiency was hepatoprotective, whereas the overexpression of TRAF1 in hepatocytes contributed to the pathological development of insulin resistance, inflammatory response and hepatic steatosis. Mechanistically, hepatocyte TRAF1 promotes hepatic steatosis through enhancing the activation of ASK1-mediated P38/JNK cascades, as evidenced by the fact that ASK1 inhibition abolished the exacerbated effect of TRAF1 on insulin dysfunction, inflammation, and hepatic lipid accumulation. CONCLUSIONS: TRAF1 functions as a positive regulator of insulin resistance, inflammation, and hepatic steatosis dependent on the activation of ASK1-P38/JNK axis.

Curcumin suppresses proliferation and induces apoptosis in human biliary cancer cells through modulation of multiple cell signaling pathways.

Cholangiocarcinoma (CCA) is a tumor with poor prognosis that is resistant to all currently available treatments. Whether curcumin, a nutraceutical derived from turmeric (Curcuma longa), has potential therapeutic activity against human CCA was investigated using three CCA cell lines (KKU100, KKU-M156 and KKU-M213). Examination of mitochondrial dehydrogenase activity, phosphatidylserine externalization, esterase staining, caspase activation and poly-adenosine diphosphate ribose polymerase cleavage demonstrated that curcumin inhibited proliferation of and induced apoptosis in these biliary cancer cells. Colony-formation assay confirmed the growth-inhibitory effect of curcumin on CCA cells. When examined for the mechanism, curcumin was found to activate multiple cell signaling pathways in these cells. First, all CCA cells exhibited constitutively active nuclear factor (NF)-κB, and treatment with curcumin abolished this activation as indicated by DNA binding, nuclear translocation and p65 phosphorylation. Second, curcumin suppressed activation of signal transducer and activator of transcription-3 as indicated by decreased phosphorylation at both tyrosine(705) and serine(727) and inhibition of janus kinase-1 phosphorylation. Third, curcumin induced expression of peroxisome proliferator-activated receptor gamma. Fourth, curcumin upregulated death receptors, DR4 and DR5. Fifth, curcumin suppressed the Akt activation pathway. Sixth, curcumin inhibited expression of cell survival proteins such as B-cell lymphoma-2, B-cell leukemia protein xL, X-linked inhibitor of apoptosis protein, c-FLIP, cellular inhibitor of apoptosis protein (cIAP)-1, cIAP-2 and survivin and proteins linked to cell proliferation, such as cyclin D1 and c-Myc. Seventh, the growth inhibitory effect of curcumin was enhanced in the IκB kinase-deficient cells, the enzyme required for nuclear factor-kappaB activation. Overall, our results indicate that curcumin mediates its antiproliferative and apoptotic effects through activation of multiple cell signaling pathways, and thus, its activity against CCA should be further investigated.

Blockade of tumor necrosis factor (TNF) receptor type 1-mediated TNF-alpha signaling protected Wistar rats from diet-induced obesity and insulin resistance.

TNF-alpha plays an important role in the pathogenesis of obesity and insulin resistance in which the effect of TNF-alpha signaling via TNF receptor type 1 (TNFR1) largely remains controversial. To delineate the role of TNFR1-mediated TNF-alpha signaling in the pathogenesis of this disorder, a TNFR1 blocking peptide-Fc fusion protein (TNFR1BP-Fc) was used for the present study. Wistar rats were fed a high-fat/high-sucrose (HFS) diet for 16 wk until obesity and insulin resistance developed. In comparison with increased body weight and fat weight, enlarged adipocytes, and hypertriglyceridemia in the obese state, the subsequent 4-wk treatment with TNFR1BP-Fc resulted in significant weight loss characterized by decreased fat pad weight and adipocyte size and reduced plasma triglycerides. Furthermore, obesity-induced insulin resistance, including hyperinsulinemia, elevated C-peptide, higher degree of hyperglycemia after glucose challenge, and less hypoglycemic response to insulin, was markedly improved, and the compensatory hyperplasia and hypertrophy of pancreatic islets were reduced. Interestingly, treatment with TNFR1BP-Fc markedly suppressed systemic TNF-alpha release and its local expression in pancreatic islets and muscle and adipose tissues. In addition, blockage of TNFR1-mediated TNF-alpha signaling in obese rats significantly enhanced tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) in the muscle and fat tissues. Our results strongly suggest a pivotal role for TNFR1-mediated TNF-alpha signaling in the pathogenesis of obesity and insulin resistance. Thus, TNFR1BP-Fc may be a good candidate for the treatment of this disease.

4-1BBL induces TNF receptor-associated factor 1-dependent Bim modulation in human T cells and is a critical component in the costimulation-dependent rescue of functionally impaired HIV-specific CD8 T cells.

During chronic infection, HIV-specific CD8 T cells exhibit progressive signs of functional impairment, attributed to persistent antigenic stimulation, up-regulation of the inhibitory receptor PD-1, and declining T cell help. Strategies that directly improve CD8 T cell function offer the potential of restoring immune control of HIV. Although PD-1 expression has been identified as a cause of functional impairment in HIV, in this study, PD-1 expression was observed on only a subfraction of HIV-specific CD8 T cells in a subfraction of donors, whereas HIV-specific CTL from all donors exhibited a limited repertoire of effector functions. CD137L (4-1BBL) is emerging as an important stimulator of antiviral CD8 T cell responses. Regardless of the PD-1 status of the donors, here we show that 4-1BBL, when combined with CD80 or CD70, expands a population of Ag-specific CD8 T cells expressing multiple markers of effector function, from the functionally impaired starting population. In contrast, CD70 in combination with CD80 was insufficient for these effects and the related TNF family ligand, LIGHT, had negligible activity. The unique contribution of 4-1BBL correlated with down-regulation of the proapoptotic molecule Bim in activated CD8 T cells. Decreasing the level of TNFR-associated factor 1 in T cells using small interfering RNA resulted in increased levels of Bim in the 4-1BBL-stimulated T cells. Thus, costimulation via 4-1BBL leads to TNFR-associated factor 1-dependent Bim down-modulation in T cells, resulting in increased T cell expansion. These studies identify 4-1BBL as a critical component in therapeutic strategies aimed at improving CD8 T cell function.