Acceleration of the activation of hepatic stellate cells by bacteria via ROS

Background/Objectives: We recently reported an association of reactive oxygen species (ROS)-producing fungi and E. coli with enhanced nuclear transglutaminase activity in hepatic cells leading to apoptosis (Sci Rep, in press).... [ view full abstract ]

Background/Objectives: We recently reported an association of reactive oxygen species (ROS)-producing fungi and E. coli with enhanced nuclear transglutaminase activity in hepatic cells leading to apoptosis (Sci Rep, in press). Here, we examined if these bacteria-derived ROS might affect the activation of hepatic stellate cells (HSCs). Materials/Methods: Primary rat HSCs were incubated with E. coli BL21 for 5 days on a plastic dish and extent of the activation was estimated by changes in morphology as well as expression of alpha smooth muscle actin (αSMA) and TGF-β signalling at gene and/or protein levels. Results: The presence of bacteria accelerated morphological changes and proliferation of HSCs (1.5-fold) in a dose-dependent manner, being accompanied by 5-fold increases in pSmad3 in the nucleus and cellular αSMA as observed under immunofluorescent staining although its mRNA levels did not alter. Addition of N-acetyl cysteine (NAC) and S-allylmercaptocysteine (SAMC), which are known to trap ROS, blocked these changes. The levels of MMP9 mRNA were also increased 20-fold in HSCs following E. coli incubation. We are now exploring a possibility of enhanced proteolytic activation of TGF-β. Conclusion: Bacteria-derived ROS not only caused hepatocyte death via induction of nuclear transglutaminase, but also accelerated the activation of HSCs, which may explain a molecular mechanism of pathogenesis in ASH/NASH patients.