Chronic Ethanol Exposure Leads to Mild Inflammation, Complement Activation, and Fibrosis in Kidneys

Background: Acute kidney injury is related to higher mortality rates in patients with severe alcohol-related hepatitis (sAH). Chronic heavy ethanol consumption, and obesity, can contribute to kidney injury, but the mechanism by which they lead to tubular injury isn’t fully understood. Complement, a major component of innate immunity, is activated in patients with sAH. Since complement is known to be involved in kidney diseases of other etiologies, we hypothesize that complement activation and inflammatory cytokines contribute to kidney injury in response to chronic ethanol. Further, since many patients with sAH are also overweight/obese, we investigated the impact of chronic ethanol in the context of high fat diet on kidney injury in mice and the interaction of palmitic acid (PA) and ethanol on indicators of injury in HK-2 cells. Methods: Male C57BL/6 mice were allowed access to high fat Lieber-DeCarli liquid diet containing 5% (v/v) ethanol or pair-fed a control diet that isocalorically substituted maltose dextrin for ethanol for 4wks. Mice were euthanized and kidneys collected for histology, qPCR and western blot. Human tubular cells, HK-2, were cultured with or without 0.1mM PA with or without 100mM ethanol for 24h. Indicators of inflammation and fibrosis were assessed by qPCR. Results: Histologic analysis of kidneys of chronic ethanol-fed mice exhibited mild tubular vacuolization and hyalin casts. C3 cleavage fragments, an indicator of complement activation, were detected in kidneys of ethanol-fed mice as well as increased expression of complement factor collectin11 mRNA. Expression of inflammatory cytokines and chemokines, including monocyte chemoattractant protein-1, MIP1α, and pro-fibrotic genes, α-SMA, Tgfβ1 and collagen 3A1 mRNA, were increased in kidneys of ethanol-fed mice. Similar to ethanol-fed mice, PA and ethanol increased MCP1, TGFB1 and αSMA, as well as complement 5a Receptor 1 and C5, mRNA expression in HK-2 cells. Conclusion: Chronic ethanol exposure in the context of high fat diet induced complement activation and mild kidney injury. Culture with PA increased expression of inflammatory and fibrotic mRNA responses in HK-2 cells; challenge with ethanol increased this response to PA. Taken together, these results point to an interaction between high fat intake and chronic ethanol consumption to kidney impairment. Funding: Other NIH Support - NIH