Role of necroptosis in chronic hepatic inflammation and fibrosis in a mouse model of increased oxidative stress

• Published in: Free radical biology & medicine 2021-02, Vol.164, p.315-328
• Main Authors: Mohammed, Sabira, Nicklas, Evan H., Thadathil, Nidheesh, Selvarani, Ramasamy, Royce, Gordon H., Kinter, Michael, Richardson, Arlan, Deepa, Sathyaseelan S.
• Format: Article
• Language: English
• Subjects: Animals; Autophagy; Carcinoma, Hepatocellular - pathology; Cu/Zn superoxide dismutase; Disease Models, Animal; Fibrosis; Hepatocellular carcinoma; Inflammation; Inflammation - metabolism; Liver - metabolism; Liver Neoplasms - pathology; Mice; Mice, Inbred C57BL; Necroptosis; Necrostatin-1s; Non-alcoholic fatty liver disease; Non-alcoholic Fatty Liver Disease - metabolism; Non-alcoholic hepatosteatosis; Oxidative Stress
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2020.12.449

Mice deficient in the antioxidant enzyme Cu/Zn-superoxide dismutase (Sod1−/− or Sod1KO mice) have increased oxidative stress, show accelerated aging and develop spontaneous hepatocellular carcinoma (HCC) with age. Similar to humans, HCC development in Sod1KO mice progresses from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH) with fibrosis, which eventually progresses to HCC. Oxidative stress plays a role in NAFLD to NASH progression, and liver inflammation is the main mechanism that drives the disease progression from NASH to fibrosis. Because necroptosis is a major source of inflammation, we tested the hypothesis that increased necroptosis in the liver plays a role in increased inflammation and fibrosis in Sod1KO mice. Phosphorylation of MLKL (P-MLKL), a well-accepted marker of necroptosis, and expression of MLKL protein were significantly increased in the livers of Sod1KO mice compared to wild type (WT) mice indicating increased necroptosis. Similarly, phosphorylation of RIPK3 and RIPK3 protein levels were also significantly increased. Markers of pro-inflammatory M1 macrophages, NLRP3 inflammasome, and transcript levels of pro-inflammatory cytokines and chemokines, e.g., TNFα, IL-6, IL-1β, and Ccl2 that are associated with human NASH, were significantly increased. Expression of antioxidant enzymes and heat shock proteins, and markers of fibrosis and oncogenic transcription factor STAT3 were also upregulated and autophagy was downregulated in the livers of Sod1KO mice. Short term treatment of Sod1KO mice with necrostatin-1s (Nec-1s), a necroptosis inhibitor, reversed these conditions. Our data show for the first time that necroptosis-mediated inflammation contributes to fibrosis in a mouse model of increased oxidative stress and accelerated aging, that also exhibits progressive HCC development. •Inflammation and necroptosis are increased in the livers of Sod1KO mice, a mouse model of increased oxidative stress.•Blocking necroptosis reduced expression of proinflammatory cytokines in livers of Sod1KO mice.•Blocking necroptosis reduced fibrosis and activation of oncogenic transcription factor STAT3 in the livers of Sod1KO mice.•Necroptosis-mediated inflammation play a role in chronic liver disease in Sod1KO mice.