Persistent mTORC1 activation due to loss of liver tuberous sclerosis complex 1 promotes liver injury in alcoholic hepatitis

IL-37d suppresses Rheb-mTORC1 axis independently of TCS2 to alleviate alcoholic liver disease

Tuberous sclerosis complex 2 (TSC2) crucially suppresses Rheb activity to prevent mTORC1 activation. However, mutations in TSC genes lead to mTORC1 overactivation, thereby causing various developmental disorders and cancer. Therefore, the discovery of novel Rheb inhibitors is vital to prevent mTOR overactivation. Here, we reveals that the anti-inflammatory cytokine IL-37d can bind to lysosomal Rheb and suppress its activity independent of TSC2, thereby preventing mTORC1 activation. The binding of IL-37d to Rheb switch-II subregion destabilizes the Rheb-mTOR and mTOR-S6K interactions, further halting mTORC1 signaling. Unlike TSC2, IL-37d is reduced under ethanol stimulation, which results in mitigating the suppression of lysosomal Rheb-mTORC1 activity. Consequently, the recombinant human IL-37d protein (rh-IL-37d) with a TAT peptide greatly improves alcohol-induced liver disorders by hindering Rheb-mTORC1 axis overactivation in a TSC2- independent manner. Together, IL-37d emerges as a novel Rheb suppressor independent of TSC2 to terminate mTORC1 activation and improve abnormal lipid metabolism in the liver.

Unraveling the complexities of fibrosis and ductular reaction in liver disease: pathogenesis, mechanisms, and therapeutic insights

Ductular reaction and fibrosis are hallmarks of many liver diseases including primary sclerosing cholangitis, primary biliary cholangitis, biliary atresia, alcoholic liver disease, and metabolic dysfunction-associated steatotic liver disease/metabolic dysfunction-associated steatohepatitis. Liver fibrosis is the accumulation of extracellular matrix often caused by excess collagen deposition by myofibroblasts. Ductular reaction is the proliferation of bile ducts (which are composed of cholangiocytes) during liver injury. Many other cells including hepatic stellate cells, hepatocytes, hepatic progenitor cells, mesenchymal stem cells, and immune cells contribute to ductular reaction and fibrosis by either directly or indirectly interacting with myofibroblasts and cholangiocytes. This review summarizes the recent findings in cellular links between ductular reaction and fibrosis in numerous liver diseases.

Alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a major cause of chronic liver disease worldwide, and comprises a spectrum of several different disorders, including simple steatosis, steatohepatitis, cirrhosis, and superimposed hepatocellular carcinoma. Although tremendous progress has been made in the field of ALD over the last 20 years, the pathogenesis of ALD remains obscure, and there are currently no FDA-approved drugs for the treatment of ALD. In this Review, we discuss new insights into the pathogenesis and therapeutic targets of ALD, utilizing the study of multiomics and other cutting-edge approaches. The potential translation of these studies into clinical practice and therapy is deliberated. We also discuss preclinical models of ALD, interplay of ALD and metabolic dysfunction, alcohol-associated liver cancer, the heterogeneity of ALD, and some potential translational research prospects for ALD.