Palmitate induces interleukin-8 expression in human aortic vascular smooth muscle cells via Toll-like receptor 4/nuclear factor-κB pathway

BackgroundRecent evidence demonstrates that saturated free fatty acids (FFAs) induce the inflammatory response via the Toll-like receptor 4 (TLR4) pathway. Interleukin-8 (IL-8) is a proinflammatory cytokine that induces vascular smooth muscle cell proliferation and migration in vitro. However, the regulation of IL-8 expression by palmitate in human vascular smooth muscle cells (HVSMCs) has not been clarified. The aim of this study was to investigate the regulation of IL-8 expression by free fatty acids and determine the underlying mechanisms in HVSMCs. MethodsHuman vascular smooth muscle cells were cultured and treated with palmitate, various signaling inhibitors or TLR4 shRNA adenovirus, and the mRNA and protein expression levels of IL-8, nuclear factor B (NF-B) luciferase activity and NF-B p65 binding activity were studied. ResultsPalmitate induced IL-8 mRNA expression and secretion in a dose-dependent manner. Palmitate significantly stimulated both nuclear factor B (NF-B) luciferase activity and NF-B p65 binding activity, which were markedly diminished by pretreatment with the NF-B inhibitor, parthenolide. Parthenolide pretreatment also abolished IL-8 mRNA and protein induction by palmitate. By contrast, disrupting the ceramide and phosphoinositide-3 kinase (PI3K) pathways with myriocin and wortmannin did not affect palmitate-induced IL-8 expression. Inhibition of protein kinase C (PKC) activation with calphostin C and chelerythrine partially suppressed palmitate-stimulated IL-8 expression, but it had no effect on palmitate-induced NF-B activation. Finally, knockdown of TLR4 markedly abolished palmitate-induced NF-B activation and IL-8 expression. ConclusionsPalmitate induces IL-8 gene expression in HVSMCs through the TLR4/NF-B pathway.