ROS-JNK1/2-dependent activation of autophagy is required for the induction of anti-inflammatory effect of dihydroartemisinin in liver fibrosis

Accumulating evidence identifies autophagy as an inflammation-related defensive mechanism against diseases including liver fibrosis. Therefore, autophagy may represent a new pharmacologic target for drug development to treat liver fibrosis. In this study, we sought to investigate the effect of dihydroartemisinin (DHA) on autophagy, and to further examine the molecular mechanisms of DHA-induced anti-inflammatory effects. We found that DHA appeared to play an essential role in controlling excessive inflammation. DHA suppressed inflammation in rat liver fibrosis model and inhibited the expression of proinflammatory cytokines in activated hepatic stellate cells (HSCs). Interestingly, DHA increased the autophagosome generation and autophagic flux in activated HSCs, which is underlying mechanism for the anti-inflammatory activity of DHA. Autophagy depletion impaired the induction of anti-inflammatory effect of DHA, while autophagy induction showed a synergistic effect with DHA. Importantly, our study also identified a crucial role for reactive oxygen species (ROS) in the facilitation of DHA-induced autophagy. Antioxidants, such as glutathione and N-acetyl cysteine, significantly abrogated ROS production, and in turn, prevented DHA-induced autophagosome generation and autophagic flux. Besides, we found that c-Jun N-terminal kinase1/2 (JNK1/2) was a downstream signaling molecule of ROS that mediated the induction of autophagy by DHA. Down-regulation of JNK1/2 activity, using selective JNK1/2 inhibitor (SP600125) or siJNK1/2, led to an inhibition of DHA-induced autophagy. Overall, these results provide novel implications to reveal the molecular mechanism of DHA-induced anti-inflammatory effects, by which points to the possibility of using DHA based proautophagic drugs for the treatment of inflammatory diseases.