The toll-like receptor 4 antagonist transforming growth factor-ß-activated kinase(TAK)-242 attenuates taurocholate-induced oxidative stress through regulating mitochondrial function in mice pancreatic acinar cells.

ABSTRACT

BACKGROUND: Acute pancreatitis (AP) is a commonly occurring and potentially life-threatening disease. Recently, toll-like receptor 4 (TLR4) has been considered as a new clue for studying the pathogenesis of AP due to its important role in inflammatory response cascade. MATERIALS AND METHODS: The aim of this study was to investigate the potential protective effect of transforming growth factor-ß-activated kinase (TAK)-242, a novel TLR4 antagonist, in taurocholate-treated mice pancreatic acinar cells. The protective effects were measured by cell viability, lactate dehydrogenase release and apoptosis, and oxidative stress was assayed by lipid peroxidation and oxidative enzyme activities. To determine the potential underlying mechanisms, mitochondrial cytochrome c release, swelling, and calcium buffering capacity were measured in isolated mitochondria, and mitochondrial biogenesis and expression of mitochondrial dynamic proteins were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. RESULTS: Treatment with 6-mM taurocholate significantly increased the expression of TLR4 at both mRNA and protein levels. TAK-242 markedly increased cell viability, decreased lactate dehydrogenase release, and inhibited apoptotic cell death as measured by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining in pancreatic acinar cells. These protective effects were accompanied by the suppressed lipid peroxidation and enhanced endogenous antioxidative enzyme activity. Using isolated and purified mitochondria from pancreatic acinar cells, we found that TAK-242 treatment also inhibited cytochrome c release into the cytoplasm, mitochondrial swelling, and decrease in mitochondrial Ca2+ buffering capacity after taurocholate exposure. In addition, TAK-242 significantly promoted mitochondrial biogenesis, as evidenced by increased mtDNA and upregulated mitochondrial transcription factors. The results of Western blot analysis showed that TAK-242 also differently regulated the expression of mitochondrial fusion and fission proteins. CONCLUSIONS: All these data strongly indicated that blocking TLR4 activity via TAK-242 exerts protective effects in an in vitro AP model, and it could be a possible strategy to improve clinical outcome in AP patients.