Background: Activation of innate immunity by gut-derived immunogens such as lipopolysaccharides (LPS) may play an important role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Whether NAFLD-associated lipid disturbances and polyunsaturated fatty acid (PUFA) metabolism in particular contribute to heightened innate immunity, remains to be determined.
Objective: To determine if oxylipins, metabolic products of PUFA metabolism, enhance innate immune reactivity alone and/or following exposure to LPS.
Methods: Plasma and peripheral blood mononuclear cells (PBMC) were collected from 35 NAFLD patients and 8 healthy controls. Oxylipin levels were documented by HPLC-MS/MS, cytokines (IL-1, IL-6, IL-10, and TNF-α) by ELISA, and chemokine receptors (CCR1 and CCR2) by flow cytometry.
Results: Mean plasma levels of four pro-inflammatory oxylipins (Tetranor 12-HETE, 20-HETE, 8-HETrE, and 7-HDoHE) were significantly elevated in NAFLD patients compared to healthy controls. However, the levels did not correlate with the severity of liver injury as reflected by serum aminotransferases, ck18M30, and Fib-4 determinations. In vitro, 20-HETE (0.01-100 nM), the plasma oxylipin with the most significantly elevated plasma levels, did not alter NAFLD or control PBMC cytokine release or enhance the increases in cytokine release following 24 h of LPS exposure. Similarly, 20-HETE alone did not alter PBMC CCR1 or CCR2 expression or LPS-induced downregulation of these receptors.
Conclusions: Pro-inflammatory oxylipin levels are increased in NAFLD, but these metabolites do not appear to drive short-term direct or LPS-induced increases in PBMC cytokine release or chemotaxis.
Keywords: Chemotaxis; Cytokines; Eicosanoids; Liver disease; NAFLD; Oxylipins; PUFA.