Anti-atherogenic effect of laminar shear stress via Nrf2 activation

Nrf2-keap1 system versus NF-κB: the good and the evil in chronic kidney disease?

Inflammation and oxidative stress are two major components involved in the atherogenic process generated by the innate immune response to lipoprotein peroxidation, which is accelerated in patients with chronic kidney disease (CKD). Whereas the redox-sensitive transcription factor nuclear factor-κB (NF-κB) plays an important role in the coordinated expression of inflammatory genes, the nuclear factor E2-related factor 2 (Nrf2) is the transcription factor that is responsible for both constitutive and inducible expression of antioxidant response element (ARE)-regulated genes. Thus, Nrf2 can regulate antioxidant and anti-inflammatory cellular responses of this system, playing an important protective role on the development of the uremic phenotype. This review describes the Nrf2 system and its possible role in CKD patients.

Crosstalk between Nrf2 and the proteasome: therapeutic potential of Nrf2 inducers in vascular disease and aging

Excessive reactive oxygen species (ROS) generation is as a major cause of oxidative stress and is implicated in cellular dysfunction in aging, cardiovascular disease and other pathologies. As antioxidant trials have largely failed to provide protection in humans, research focus has shifted to activating endogenous antioxidant defenses. In vascular models, activators of the transcription factor NF-E2 related factor 2 (Nrf2) pathway have been shown to restore redox homeostasis by increasing antioxidant/electrophilic response element-mediated (ARE/EpRE) expression of phase II and antioxidant enzymes, including NAD(P)H:quinone oxidoreductase-1 (NQO1), heme oxygenase-1 (HO-1) and γ-glutamate cysteine ligase catalytic subunit (GCLC). Nrf2 activators disrupt basal ubiquitin-dependent degradation of Nrf2 by the 26S proteasome, leading to nuclear Nrf2 accumulation and gene induction. This review examines the evidence for crosstalk between Nrf2 and the proteasome, highlighting the mechanisms by which select Nrf2 activators regulate stress-induced proteasomal activity and removal of oxidized proteins. Exploiting the dual action of natural Nrf2 inducers may provide a novel therapeutic strategy for restoring cellular redox homeostasis in aging and cardiovascular related diseases such diabetes, atherosclerosis and stroke.

α1AMP-activated protein kinase mediates vascular protective effects of exercise

OBJECTIVE

We investigated whether AMP-activated protein kinase (AMPK) may be involved in the signaling processes leading to exercise-mediated vascular protection.

METHODS AND RESULTS

The effects of voluntary exercise on AMPK activity, endothelial NO synthase expression and phosphorylation, vascular reactive oxygen species formation, and cell senescence were tested in α1AMPK knockout and corresponding wild-type mice. Exercise significantly improved endothelial function, and increased plasma nitrite production in wild-type mice, associated with an activation of aortic AMPK assessed by its phosphorylation at threonine 172. In addition, regular physical activity resulted in an upregulation of endothelial NO synthase protein, serine 1177 endothelial NO synthase phosphorylation, and an increase of circulating Tie-2(+)Sca-1(+)Flk-1(+) myeloid progenitor cells. All these changes were absent after α1AMPK deletion. In addition, exercise increased the expression of important regulators of the antioxidative defense including heme oxygenase-1 and peroxisome proliferator-activated receptor γ coactivator 1α, decreased aortic reactive oxygen species levels, and prevented endothelial cell senescence in an α1AMPK-dependent manner.

CONCLUSIONS

Intact α1AMPK signaling is required for the signaling events leading to the manifestation of vascular protective effects during exercise. Pharmacological AMPK activation might be a novel approach in the near future to simulate the beneficial vascular effects of physical activity.

Redox going with vascular shear stress

Shear stress plays a critical role in the regulation of vascular biology and diseases, such as atherosclerosis, via modulation of signal transduction and redox balance. Atherosclerosis preferentially occurs in a site-specific manner linked to disturbed flow. In this Forum on Vascular Shear Stress, emerging role of redox-dependent molecular mechanisms by which shear stress regulates pro- and antiatherogenic responses in endothelial cells both in vitro and in vivo are reviewed in depth by experts. This Forum also provides comprehensive reviews regarding experimental apparatus and in vivo, ex vivo, and in vitro systems used for shear stress studies.