Accumulation of free cholesterol and oxidized low-density lipoprotein is associated with portal inflammation and fibrosis in nonalcoholic fatty liver disease

BACKGROUND: Macrophages engulf oxidized-LDL (oxLDL) leading to accumulation of cellular cholesterol and formation of foam cells, which is a hallmark of atherosclerosis. Moreover, recent studies showed that accumulation of free cholesterol in macrophages leading to activation of NLRP3 inflammasome and production of interleukin-1β (IL-1β) has been linked to atherosclerosis-associated inflammation. However, it is not clear if cholesterol accumulation is associated with hepatic inflammation and fibrosis in the liver. In this study, we investigated the association of free cholesterol and oxLDL accumulation in portal vein with the inflammation, atherosclerosis, and fibrosis in human nonalcoholic fatty liver disease (NAFLD). METHODS: Serial sections derived from surgical specimens of NAFLD were stained with filipin and antibodies against IL-1β, CD68, α-smooth muscle actin (α-SMA), oxLDL and lectin-like oxLDL receptor-1 (LOX-1). RESULTS: We show that free cholesterol was colocalized with oxLDL in the wall of portal vein, and which was associated with lumen narrowing, plaque formation, endothelium deformation, and portal venous inflammation. The inflammation was evidenced by the colocalization of Kupffer cells and IL-1β and the expression of LOX-1. Notably, ruptured plaque was closely associated with portal venous inflammation. Moreover, free cholesterol and oxLDL accumulation in periportal and sinusoidal fibrosis, which was associated with regional stellate cell activation and chicken-wire fibrosis. CONCLUSION: These findings reveal a direct association between cholesterol accumulation, portal venous inflammation and fibrosis in NAFLD. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12950-019-0211-5) contains supplementary material, which is available to authorized users.