PPARδ agonist GW501516 prevents uncoupling of endothelial nitric oxide synthase in cerebral microvessels of hph-1 mice

Peroxisome proliferator-activated receptor delta (PPAR delta) is ubiquitously expressed in the vasculature, including cerebral circulation. The role of PPAR delta in metabolism of tetrahydrobiopterin (BH4) has not been studied in the cerebral microvasculature. In the present study, the effects of PPAR delta agonist GW501516 on uncoupling of endothelial nitric oxide synthase (eNOS) were determined in cerebral microvessels of BH4-deficient hph-1 mice. Wild-type (B6CBA) and hph-1 mice were orally gavaged with a selective PPAR delta activator, GW501516 (2 mg/kg/day) for 14 days, and thereafter, cerebral microvessels were isolated and studied. Treatment of hph-1 mice with GW501516 significantly reduced oxidation of BH4 and increased the ratio of BH4 to 7,8-BH2 (P<0.05, n=6-9). Attenuation of L-NAME-inhibitable superoxide anion levels by GW501516 demonstrated that activation of PPAR delta might prevent uncoupling of endothelial nitric oxide synthase (eNOS, P<0.05, n=6-9). Western blotting studies demonstrated that GW501516 selectively increased the endothelial expressions of CuZn superoxide dismutase (P<0.05, n=6-9) and catalase (P<0.05, n=6-8). PPAR delta activation increased the total nitrite and nitrate (NO2+NO3) content in cerebral microvessels (P<0.05, n=6). Obtained results suggest that in vivo activation of PPAR delta prevents eNOS uncoupling, restores bioavailability of NO and may help preserve endothelial function in the BH4-deficient cerebral circulation. (C) 2012 Elsevier B.V. All rights reserved.