Deletion Of ABRO1 Resists MCD-Induced Nonalcoholic Steatohepatitis And The Study Of Its Mechanism

Non-alcoholic fatty liver disease(NAFLD)has surpassed chronic viral hepatitis as the biggest liver disease in China,thus seriously affecting human health.From the steatosis alone at the beginning,developing to steatohepatitis,with the degree of pathologies deepen,appearing gradually hepatic fibrosis,resulting in liver cirrhosis eventually,and the happening of liver cancer at last.Nonalcoholic steatohepatitis(NASH)has a 20% chance of becoming liver cirrhosis.At present,there is a lack of effective clinical treatment measures.Revealing the pathogenesis of NASH and finding therapeutic targets will greatly promote the prevention and treatment of NASH.Methionine and choline‐deficient diet(MCD)model is a classic animal model of nonalcoholic steatohepatitis in the laboratory.The deficiency of methionine and choline in the diet leads to the blocked synthesis of very low density lipoprotein(VLDL),which transports hepatic triglycerides out of liver,and also blocked the synthesis of glutathione,a very important antioxidant.On the one hand,the deficiency induces a large amount of triglyceride accumulation in the liver to cause steatosis,and leads to the increase of ROS levels of lipid peroxidation and oxidative stress.On the other hand,the hepatic antioxidant barrier is impaired.The combination of the two ways will eventually lead to liver inflammation and hepatic cell apoptosis,which results in NASH seriously.ABRO1 is an important member of the deubiquitination enzyme BRISC complex.As a platform protein,it is responsible for recruiting BRCC36,MERIT40 and BRE,which are essential components for the deubiquitination activity of the BRISC complex to K63.Previous studies have reported that ABRO1 is involved in the regulation of a variety of biological processes,such as DNA damage repair,ischemia-reperfusion injury,cell cycle regulation,etc.,and plays an important role in the immune response induced by type I interferon receptor.The effect of ABRO1 on NASH induced by MCD was observed in ABRO1 knockout mice.Western-blot and real-time PCR showed that the expression of ABRO1 in the liver was up-regulated in the MCD model.H&E staining,oil red O staining,and intrahepatic triglyceride assays showed that MCD-induced lipid accumulation in the liver of ABRO1 knockout mice was significantly lower than that of normal mice.Detection of serum transaminase levels,liver inflammatory cell infiltration,and the expression and secretion of liver related inflammatory factors revealed that ABRO1 deficiency significantly reduced MCD-induced liver inflammation.In addition,massone staining and caspase-3 immunohistochemical detection showed that the MCD-induced liver fibrosis and apoptosis were significantly reduced in ABRO1 knockout mice.These results showed that ABRO1 knockout significantly inhibited the occurrence and development of NASH induced by MCD.In order to reveal the mechanism of ABRO1 in NASH,we established bone marrow chimeric mice by bone marrow transplantation,and the results showed that the ABRO1 knockout recipient mice receiving bone marrow cells from normal mice lost their original ability to resist MCD-induced NASH,suggesting that deficiency of ABRO1 mainly affects bone marrow-derived cells to resist MCD-induced NASH.Further,we use BRCC3(BRISC complex enzyme activity of subunits)knockout mice to observe the effect of ABRO1 rely on BRISC complex,it is found that unlike ABRO1 knock out,knockout BRCC3 has no significant effect on MCD induced steatosis,only have a certain influence on the inflammatory response in the late,explain that deficiency of ABRO1 resists to NASH induced by MCD may not rely on BRISC activity,but the function of ABRO1 is related to another mechanism.These studies provide important functional clues for understanding the molecular mechanism that ABRO1 promotes the occurrence and development of NASH.To sum up,this paper found that ABRO1 knockout mice significantly resisted the occurrence and development of MCD-induced NASH,and the mechanism study revealed that ABRO1 mainly affected the function of bone marrow-derived cells(most likely immune cells in the liver)by not relying on BRISC complex.Our study revealed the new pathogenesis of NASH and provided new ideas for the prevention and treatment of NASH.Further research will focus on the role of ABRO1 in human NASH and its molecular mechanism.