Abstract 109: Protective Effects of Nuclear Factor E2-related Factor 2 Activation on Angiotensin II Induced Microvascular Endothelial Dysfunction

Abstract

Background: Nuclear factor E2-related factor 2 (Nrf2) is a regulator of the cellular adaptive response to oxidative stress, but its effects on microvascular function are poorly characterized. Our previous studies in human glomerular endothelial cells found that tert-butylhydroquinone (tBHQ; a Nrf2 activator) reduced ROS, asymmetric dimethylarginine (ADMA, an endogenous NOS inhibitor) and increased eNOS. We hypothesized that tBHQ would prevent microvascular endothelial dysfunction via activation of Nrf2 / antioxidant responses in angiotensin II (ANG II) induced hypertension.

Methods: Mesenteric resistance arterioles (MRAs) were isolated from mice infused for 14 days with ANG II (400 ng/kg/min) or vehicle and given oral tBHQ (0.1% of water) or vehicle (n=6 mice/group). Acetylcholine-induced endothelium dependent relaxation (EDR), endothelial derived relaxation factor (EDRF) and contracting factor (EDCF) of MRAs were assessed by myograph. Vascular nitric oxide (NO), and ROS were assessed by RatioMaster. ROS biomarkers (urinary excretion of malondialdehyde [MDA]) and 8-isoprotane [8-Iso]), ADMA and protein expressions of MRAs were measured.

Results: tBHQ prevented the effects (all P<0.05) of ANG II infusion-induced the increases of urinary MDA (50±3 vs 83±11 nmol/mg creatine) and 8-Iso (1.4±0.1 vs 3.8±0.3 vs ng/mg creatinine) and decreases of EDR (75 ± 3 vs 53±5%), EDRF (23± 2 vs 17± 3%) and NO (0.3 ± 0.02 vs 0.2 ± 0.03 units), and enhanced EDCF (7 ± 1 vs 13 ± 2%) and associated ROS production (0.11 ± 0.03 vs 0.3 ± 0.08 units) and microvascular ADMA (18 ± 1 vs 13 ± 1 nmol/mg protein). ANG II increased the MRAs protein expressions (of β-actin, all P<0.05) for NOX1 (0.60 ± 0.03 vs 0.38± 0.04) and NOX2 (0.80 ± 0.04 vs 0.36± 0.05) and reduced phosphorylated eNOS (0.26 ±0.07 vs 0.53±0.09), whereas tBHQ increased Nrf2 expression (0.44 ±0.03 vs 0.73±0.04) and prevented these changes with ANG II infusion.

Conclusions: tBHQ upregulates Nrf2 and thereby engages the antioxidant responses to protect microvessels of ANG II-infused mice from the adverse effectors of ROS, NO deficiency and ADMA. This is a novel potential therapeutic target that activates Nrf2/antioxidant response element to protect against vascular oxidative stress, endothelial dysfunction and CVD.