22-S-Hydroxycholesterol protects against ethanol-induced liver injury by blocking the auto/paracrine activation of MCP-1 mediated by LXRα

Chronic ethanol consumption causes hepatic steatosis and inflammation, which are associated with liver hypoxia. Monocyte chemoattractant protein-1 (MCP-1) is a hypoxia response factor that determines recruitment and activation of monocytes to the site of tissue injury. The level of MCP-1 is elevated in the serum and liver of patients with alcoholic liver disease (ALD); however, the molecular details regarding the regulation of MCP-1 expression are not yet understood completely. Here, we show the role of liver X receptor (LXR) in the regulation of MCP-1 expression during the development of ethanol-induced fatty liver injury, using an antagonist, 22-S-hydroxycholesterol (22-S-HC). First, administration of 22-S-HC attenuated the signs of liver injury with decreased levels of MCP-1 and its receptor CCR2 in ethanol-fed mice. Second, hypoxic conditions or treatment with the LXR agonist GW3965 significantly induced the expression of MCP-1, which was completely blocked by treatment with 22-S-HC or infection by shLXR lentivirus in the primary hepatocytes. Third, over-expression of LXR or GW3965 treatment increased MCP-1 promoter activity by increasing the binding of hypoxia-inducible factor-1 to the hypoxia response elements, together with LXR. Finally, treatment with recombinant MCP-1 increased the level of expression of LXR and LXR-dependent lipid droplet accumulation in both hepatocytes and Kupffer cells. These data show that LXR and its ligand-induced up-regulation of MCP-1 and MCP-1-induced LXR-dependent lipogenesis play a key role in the autocrine and paracrine activation of MCP-1 in the pathogenesis of alcoholic fatty liver disease, and that this activation may provide a promising new target for ALD therapy.Copyright (c) 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.