FIGURE 2.

The dual role of hepatic macrophages in the progression and regression of liver fibrosis. KCs are activated by damaged hepatocytes and upregulate TGF-β, PDGF, CCL2/ CCR2, TNF-α, IL-1β, and so on. The increased levels of CCL2/CCR2 promote the recruitment of Ly-6C^hi monocytes to the liver injury. The activated KCs and Ly6C^hi monocytes both exert profibrotic effects by promoting the activation of HSCs, leading to the excessive deposition of ECM and scar formation. On the contrary, under various exogenous stimuli, KCs and Ly6C^lo monocytes can degrade ECM by producing MMPs and IL-10 to exert antifibrotic effects. In addition, autophagy and phagocytosis of KCs can promote the regression of liver fibrosis. Abbreviations: CCL2/CCR2, chemokine ligand 2/chemokine receptor 2; ECM, extracellular matrix; MMPs, matrix metalloproteinases; NLRs, nod-like receptors; PRRs, pattern recognition receptors; TLRs, toll-like receptors.