Roles of liver innate immune cells in nonalcoholic fatty liver disease

Figure 1 Mechanisms for the role of Kupffer cells in the development of nonalcoholic fatty liver disease. (1) Activated Kupffer cells (KCs) produce reactive oxygen species (ROS), interleukin-6 and tumor necrosis factor-α (TNF-α), which induce insulin resistance, leading to hepatocyte steatosis; (2) Activated KC-derived ROS causes lipid peroxidation production. Lipid peroxidation products and KC-derived TNF-α result in hepatocyte injury. Failure to repair hepatocytes after injury promotes the development of steatohepatitis; and (3) Activated KCs produce transforming growth factor-β1, which activates hepatic stellate cells. Activated hepatic stellate cells produce large quantities of extracellular matrix, leading to fibrosis.