Endothelial nitric oxide synthase impairment is restored by clofibrate treatment in an animal model of hypertension

Adequate production of nitric oxide (NO) by endothelial nitric oxide synthase (eNOS) requires eNOS coupling promoted by tetrahydrobiopterin (BH4). Under pathological conditions such as hypertension, BH4 is diminished, avoiding eNOS coupling. When eNOS is “uncoupled”, it yields a superoxide anion instead of NO. Peroxisome proliferator activated receptors (NR1C) are a family of nuclear receptors activated by ligand. Clofibrate, a member of a hypolipidemic class of drugs, acts by activating the alpha isoform of NR1C. To determine the participation of NR1C1 activation in BH4 and dihydrobiopterin (BH2) metabolism and its implications on eNOS coupling in hypertension, we performed aortic coarctation (AoCo) at inter-renal level on male Wistar rats in order to have a hypertensive model. Rats were divided into the following groups: Sham + vehicle (Sham-V); AoCo + vehicle (AoCo-V); Sham + clofibrate (Sham-C), and AoCo + clofibrate (AoCo-C). Clofibrate (7 days) increased eNOS coupling in the AoCo-C group compared with AoCo-V. Clofibrate also recovered the BH4:BH2 ratio in control values and prevented the rise in superoxide anion production, lipoperoxidation, and reactive oxygen species production. In addition, clofibrate increased GTP cyclohydrolase-1 (GTPCH-1) protein expression, which is related with BH4 recovered production. NR1C1 stimulation re-establishes eNOS coupling, apparently through recovering the BH4:BH2 equilibrium and diminishing oxidative stress. Both can contribute to high blood pressure attenuation in hypertension secondary to AoCo.