Active NF-E2-related Factor (Nrf2) Contributes to Keep Endothelial NO Synthase (eNOS) in the Coupled State

Abstract

The aim of our study was to examine in detail the impact of NF-E2-related factor (Nrf2) activation on endothelial cell function with focus on redox homeostasis and the endothelial nitric oxide synthase (eNOS) system. We administered 2-cyano-3,12-dioxooleana-1,9-dien-28-oic imidazolide (CDDO-IM), a known activator of Nrf2, to primary human umbilical vein endothelial cells. Activation of Nrf2 by CDDO-IM increased the amount of bioavailable nitric oxide (NO), a major contributor to vascular homeostasis, in naive and stressed cells. Concomitantly, intracellular reactive oxygen species were dose-and timedependently reduced. In apparent contrast to elevated NO levels, eNOS protein expression was transiently decreased in an Nrf2-dependent manner. Employing pharmacological inhibitors as well as a small interfering RNA approach, we identified de novo protein synthesis of heme oxygenase 1 (HO-1) and its enzymatic activity as cause for the observed reduction of eNOS. We hypothesize that under redox stress, when the availability of tetrahydrobiopterin, a pivotal stoichiometric cofactor for eNOS, is limited, activation of Nrf2 leads (a) to transient reduction of eNOS protein levels and (b) to an antioxidant defense in human umbilical vein endothelial cells. Both activities ensure that a stoichiometric ratio of eNOS and tetrahydrobiopterin is sustained and that the risk of eNOS uncoupling is reduced. Our study is the first to provide a causal link between Nrf2 activation and eNOS expression and NO levels, respectively.

Synthetic Oleanane Triterpenoids: Multifunctional Drugs with a Broad Range of Applications for Prevention and Treatment of Chronic Disease

“…The reduction by this SO in the production of ROS/reactive nitrogen species, which is induced by angiotensin II activation of NADPH oxidase, in these cells is eliminated with knockdown of Nrf2 . Moreover, by inducing expression of HO-1, CDDO-Im increases the availability of NO and decreases levels of ROS and endothelial NOS in naive or stressed endothelial cells, thus mediating endothelial NOS coupling and vascular homeostasis (Heiss et al, 2009). Although cigarette smoking triggers cardiac dysfunction in the right ventricle that is worse in Nrf2(Ϫ/Ϫ) mice than in Nrf2(ϩ/ϩ) mice, CDDO-Im prevents the cardiac damage from smoking.…”

Targeting the KEAP1-NRF2 System to Prevent Kidney Disease Progression

“…Importantly, the improvement of eGFR was sustained at 4 weeks after stopping CDDO-methyl ester administration. It is now thought that CDDO-methyl ester improves the eGFR of kidney disease patients because of the restoration of endothelial function and/or vasodilation, followed by the preservation of the filtration bed area in the glomerulus [75,76,77]. Additionally, the inhibition of glomerular contraction and activation of glomerular filtration may occur.…”

Geniposide Induces the Expression of Heme Oxygenase-1 via PI3K/Nrf2-Signaling to Enhance the Antioxidant Capacity in Primary Hippocampal Neurons

“…28,29) To probe whether geniposide could activate Nrf2, primary hippocampal neurons were treated with geniposide for the indicated times and concentrations and followed by the analysis of expression of nuclear and cytosolic proteins by western blotting. Treatment with geniposide induced the expression of Nrf2 in cytoplasm and accumulation in nucleus.…”