Vascular endothelial dysfunction (VED) is a key feature of vascular aging underlying the predisposition of old adults to CVD. Sustained oxidative stress is a major driving force for VED by synergically dysregulating the production of vasodilator NO and vasoconstrictor endothelin-1(ET-1). But the underlying redox mechanisms re- main unclear. Novel approaches to reversing oxidative stress are particularly compelling given the ineffective- ness of general antioxidant therapies that targets extremely short-lived ROS. Protein S-glutathionylation (PrS- SG), a stable but reversible oxidant-induced posttranslational modification dominates the molecular mechanisms for redox signaling. Reversal of PrS-SG is catalyzed specifically by glutaredoxin which thereby is critical in redox regulation of cellular function. Dysfunction of glutaredoxin-1 (Glrx-1), a major actor in the de-glutathionylation is implicated in cardiac, and brain aging. Its role in vascular aging is unknown. This application is built upon a strong premise. Our published and preliminary studies indicate that Glrx1 deficiency and PrS-SG induction promote endothelial dysfunction and aging-associated metabolic syndromes and that during aging, aortic Glrx1 is decreased with a concomitant increase in endothelial PrS-SG. Evidence in the literature also supports a causal role of Pr-SSG in VED in that S-glutathionylation can uncouple eNOS and activate p21Ras, which are known to impair NO bioavailability and stimulate Erk1/2 dependent-ET-1 expression. We thus hypothesize that age-related Glrx1 downregulation promotes VED by dysregulating the integrated redox signaling of eNOS and ET-1, which can be reversed by replenishing Grlx1 in endothelium. This central hypothesis is tested by pursuing two specific aims: 1) To understand the relationship between Glrx1/PrS-SG and the onset and progression of VED with aging. Using C57BL6J mice, a well-characterized model of aging we will measure the temporal changes in aortic Glrx1, PrS-SG, and endothelium-dependent vasorelaxation in young, middle-aged and old mice, and longitudinal changes of flow-mediated dilation of femoral artery in vivo using a non-invasive Optical-Coherence-Tomography technique. To test the causal role of Glrx1 downregulation in VED, we will test whether VED is aggravated in Glrx1 knockout mice; 2) To test a new concept that replenishing Glrx1 in endothelium can reverse VED in aging. Using a novel inducible endothelial specific Glrx1 transgenic mouse model, we will determine the impact on VED and the integrated signaling of eNOS and ET-1 of Glrx1 transgene expression in young, middle-aged, and old mice. The positive results in the R21 grant will help advance our understanding how redox signaling mediates the multifaceted effects of aging on ECs, promoting VED, and offer a new antioxidant therapeutic strategy to restore vascular function in older adults.
The proposed research is relevant to public health because, by 2050 the number of Americans aged 65 and older is projected to be 88.5 million, more than double its current population of 40.2 million, and aging dominates the risk factors for cardiovascular disease(CVD), which becomes a huge health issue in the older population. Although oxidative stress is a central mechanism for vascular endothelial dysfunction which predisposes the elderly to CVD, the underlying redox mechanisms remain unclear, and general antioxidant therapies have very limited benefit in CVD patients. Thus, the proposed research is relevant to the part of NIH's mission that pertains to developing fundamental knowledge that will help to preserve/restore cardiovascular function and reduce the burden of CVD in older patients.
