ADAM17 AND AGING-RELATED VASCULAR DYSFUNCTION

Abstract

A disintegrin and metalloproteinase ADAM17 (tumor necrosis factor–converting enzyme) regulates soluble TNF levels. We tested the hypothesis that aging-induced activation in adipose tissue (AT)-expressed ADAM17 contributes to the development of remote coronary microvascular dysfunction in obesity. We found that the increased activity of endothelial ADAM17 is mediated by a diminished inhibitory interaction with caveolin-1, due to age-related decline in caveolin-1 expression in obese patients and mice or to genetic deletion of caveolin-1. Coronary arterioles (CA) and AT were examined in patients who underwent heart surgery. Excess, ADAM17-shed TNF from AT arteries in older obese patients was sufficient to impair CA dilation in a bioassay in which the AT artery was serially connected to a CA. CA and AT were also studied in 6-month and 24-month lean and obese mice. We found that obesity elicited impaired endothelium-dependent CA dilations only in older patients and in aged obese mice. Transplantation of AT from aged obese, but not from young or aged, mice increased serum cytokine levels, including TNF, and impaired CA dilation in the young recipient mice. In patients and mice, obesity was accompanied by age-related activation of ADAM17, which was attributed to vascular endothelium–expressed ADAM17. Additionally, ADAM17 mediates shedding of JAM-A (junctional adhesion molecule-A). We hypothesized that ADAM17 activation, via increased JAM-A shedding impairs flow mechanosensing and induces abnormal artery remodeling in aging. We found a reduced lumen diameter and increased wall thickness in AT of aged patients. ECs using plasmid JAM-A were aligned to flow direction earlier than GFP treated control cells. Site-directed mutagenesis was employed to generate JAM-A cleavage resistant mutants, we detected soluble JAM-A in the supernatants from cells transfected with plasmid JAM-A, but not from cells expressing mutant JAM-A plasmids. Importantly, soluble JAM-A is significantly increased in the supernatant from cells with combined action of plasmid JAM-A and recombinant ADAM17, when compared to cells with plasmid JAM-A alone. Collectively, our data revealed that age-related reduction in Cav-1 expression and subsequently increased the activity of endothelial ADAM17 led to excess TNF production, which acts remotely to promote coronary arteriole dysfunction. Whereas activation of ADAM17 in vascular endothelium mediates increased JAM-A shedding and causes ECs misalignment. Our data suggest that the combined action of TNF and JAM-A lead to development of CMD and its related vascular remodeling in older obese patients.