Role and regulation of autophagy and apoptosis by nitric oxide in hepatic stellate cells during acute liver failure

Background & Aims We previously found that hepatic stellate cell (HSC) activation induced by autophagy maintains the liver architecture to prevent collapse during acute liver failure (ALF). Nitric oxide (NO) has shown to induce HSC apoptosis. Whether and how NO is involved in ALF and autophagy remains unclear. Methods ALF patients were recruited to investigate the correlation between plasma NO levels and clinical features. Liver tissues were collected from chronic hepatitis patients by biopsy and from ALF patients who had undergone liver transplantation. The expression of NO synthases and HSC activation (alpha-SMA), and autophagic activity (LC3) were investigated by immunohistochemistry. Autophagy and apoptosis were investigated by immunoblot analysis, confocal microscopy, and flow cytometry in HSCs treated with NO donors. Results Plasma NO level was significantly increased in patients with ALF compared to those with cirrhosis (53.60 ± 19.74 μM vs 19.40 ± 9.03 μM, Z = -7.384, p < 0.001) and positively correlated with MELD-Na score (r = 0.539, p < 0.001), implicating NO in ALF. At least some NO was produced by overexpression of inducible NO synthases (NOS) and endothelial NOS, but not neuronal NOS in the liver tissue. In vivo observation revealed that autophagy was inhibited in HSCs based on decreased LC3 immunostaining, and in vitro experiments demonstrated that NO can inhibit autophagy. Moreover, NO promoted HSC apoptosis, which was rescued by an autophagy inducer. Conclusions Increased NOS/NO promotes apoptosis through autophagy inhibition in HSCs during ALF, providing a novel strategy for the treatment of patients with ALF. This article is protected by copyright. All rights reserved.