Modulation of LPS-mediated inflammation by fenofibrate via the TRIF-dependent TLR4 signaling pathway in vascular smooth muscle cells

Abstract

Lipopolysaccharide (LPS) induced-vascular inflammation plays a central role in vasculitis and atherosclerosis. The stimulation of toll-like receptor 4 (TLR4) by LPS elicits the release of major proinflammatory cytokines that aggravates cardiovascular disorders. Peroxisome proliferator- activated receptor alpha (PPARalpha) agonists have been shown to reduce cardiovascular events by controlling lipid metabolism as well as inflammation. However, the role of PPARalpha agonist fenofibrate in modulating LPS-mediated inflammatory responses in vascular smooth muscle cells (VSMCs) remains elusive. The present study demonstrated that fenofibrate exerted a potent anti-inflammatory action through reducing interleckin-1(IL-18), tissue inhibitor of metalloproteinase-1(TIMP-1), TLR4 and enhancing PPARalpha in LPS-stimulated VSMCs. Additionally, treatment of VSMCs with the TLR4 inhibition or TLR4 small-interfering RNA illustrated that the modulatory effects of fenofibrate on LPS-mediated inflammatory responses in VSMCs were reliant on TLR4. Especially, the results suggested that beneficial effects of fenofibrate on LPS-stimulated inflammatory responses in VSMCs were mediated through interference of TLR4 and its downstream signaling components such as Toll-interleckin-1(IL-1) receptor domain- containing adaptor inducing interferon-beta (TRIF), interferon regulatory factor 3 (IRF3) and interferon-gamma inducible protein 10 (IP-10). In conclusion, PPARalpha agonist fenofibrate exerts anti-inflammatory property by antagonizing LPS-mediated inflammatory responses in VSMCs. More importantly, the modulation of the TRIF-dependent signaling pathway (TLR4/TRIF/IRF3/IP-10) might be a useful and novel anti-inflammatory strategy of fenofibrate.