Résumé
This study was designed to test the hypothesis that fenofibrate, the peroxisome proliferator-activated receptor α (PPARα) activator, improves age-related endothelial dysfunction in small mesenteric arteries (SMA). Adult and aged rats were treated with fenofibrate and then endothelium-dependent relaxations of SMA; expressions of endothelial NO synthase (eNOS), cyclo-oxygenase (COX-1 and COX-2) and superoxide dismutases (SOD) (Cu/Zn SOD, Mn SOD and EC SOD) proteins and release of TXB
2 and 6-keto-PGF
1α were assessed. Fenofibrate improved endothelium-dependent vasodilatation of arteries from old rats and decreased participation of endothelial vasoconstrictor products, sensitive to COX-1 and COX-2 inhibitors and acting on Tp receptor. Fenofibrate decreased expressions of COX-1 and COX-2, and generation of TXA
2. Release of vasodilator PGI
2 and U46619-induced contraction remained unaltered. Neither NO-mediated vasodilatation nor eNOS expression was affected. The addition of the scavengers, SOD and catalase increased relaxation only in SMA from control rats. Finally, fenofibrate did not change expressions of Cu/Zn SOD and Mn SOD but it increased EC SOD towards that observed in arteries from adult rats. Fenofibrate improves endothelial function in resistance arteries from aged rats by decreasing expression of COX-1 and COX-2 together with enhancing anti-oxidant capacity of the vessel wall probably through the increased expression of EC SOD. This study provides evidence that PPARα may have clinical applications toward maintaining endothelial function during ageing.