Endothelial Adherens Junctions and Endothelial Dysfunction in Aging Arteries

Abstract

Aging causes a systemic deterioration of the structure and function of the entire arterial network resulting in organ injury, dysfunction and failure. Endothelial dysfunction, including diminished NO activity, is thought to be a key contributor to pathological vascular aging. The normal protective phenotype of arterial endothelial cells is initiated in the immediate postnatal period and appears to be dependent on increased engagement and signaling of VE‐cadherin at Adherens Junctions (Flavahan S et al, 2013, Am J Physiol Heart Circ Physiol. 305(3):H321–9). The aim of the present study was to determine whether this process might be disrupted in aging arteries and contribute to aging‐induced endothelial dysfunction. Aortas and tail arteries were isolated from young (3 to 4 months) and old (22–24 months old) F344 rats and processed for immunofluorescent, biochemical and functional analysis. Arterial function was assessed using pressure myographs at a constant transmural pressure of 60 mmHg. During constriction with phenylephrine (to 70% of baseline), acetylcholine (1 to 1000 nM) caused dilatation that was significantly reduced in old compared to young arteries. Inhibition of NO synthase with LNAME markedly inhibited responses to acetylcholine, and there was no significant difference in the magnitude of the LNAME‐resistant dilatation between young and old arteries. There was also no significant difference in dilatation to the NO donor, DEA‐NONOate (1 to 1000 nM) between young and old arteries. These results are consistent with the presence of endothelial dysfunction and reduced endothelial NO activity in aging arteries. Immunofluorescent labeling followed by LSM analysis of VE‐cadherin demonstrated the presence of intense protein staining at endothelial Adherens Junctions in young arteries. This staining was significantly reduced in old arteries, which demonstrated a significant increase in intracellular localization of the protein. Immunoblot analysis confirmed a significant reduction in cell surface expression of VE‐cadherin in old compared to young arteries. A function‐blocking antibody to VE‐cadherin, which inhibits VE‐cadherin engagement and disrupts endothelial Adherens Junctions, significantly inhibited dilatation to acetylcholine in young but not in old arteries. A control antibody had no significant effects. After inhibition of VE‐cadherin engagement with the function‐blocking antibody, there was no longer any significant different in dilatation to acetylcholine between young and old arteries. These results demonstrate that there is morphological disruption of Adherens Junctions and reduced cell surface expression of VE‐cadherin in aging endothelial cells. Furthermore, the functional role of Adherens Junctions in contributing to endothelial dilatation is selectively lost in old arteries and likely contributes to endothelial dysfunction in these blood vessels.