Figure 1.

M1 macrophages in liver ischemia-reperfusion injury. In liver ischemia-reperfusion, liver cells produce a large amount of ROS due to hypoxia and apoptosis occurs. Apoptotic liver cells secrete a series of DAMPs such as HMGB1, and promote the polarization of macrophages to M1 macrophages by stimulating TLR4 and other receptors on macrophages. Macrophages polarized to M1 can further secrete ROS to promote liver cell apoptosis and cause liver damage, or they can recruit neutrophils and cause liver damage by secreting TNF-α and other pro-inflammatory factors.