Cellular Senescence and the Associated Secretome Contribute to Age‐Related Vascular Dysfunction

Abstract

Age‐related vascular dysfunction (e.g., large elastic artery [aorta] stiffening and endothelial dysfunction) is mediated by excess reactive oxygen species (ROS) leading to lower nitric oxide (NO) bioavailability. The upstream mechanisms mediating excess ROS are mostly unknown. Cellular senescence is a principal mechanism of aging and the senescence associated secretory phenotype (SASP) may exacerbate ROS.PurposeTo: 1) determine if senescent cell clearance (senolysis) lowers aortic stiffness (pulse wave velocity [PWV]) and increases endothelial function (endothelium‐dependent dilation [EDD]), and if these effects are mediated by reduced ROS and increased NO bioavailability; and 2) isolate the influence of the circulating SASP on age‐related vascular dysfunction.Methods and ResultsYoung (6 mo) and old (27 mo) adult male and female p16‐3MR mice were treated with vehicle ([V]; saline) or a p16‐3MR senolytic, ganciclovir (GCV; 25 mg/kg/day) injected intraperitoneally for 5 days. This resulted in 4 groups/sex (Young‐V [YV], n = 23; Young‐GCV [Y‐GCV]; n = 16, Old‐V [OV]; n = 22, Old‐GCV [O‐GCV]; n = 21). No sex differences were observed, so results were combined.Aortic Stiffness. Aortic PWV (aPWV) was assessed pre and post V and GCV treatment. Old mice had higher aPWV at baseline vs young (aPWV [cm/sec]: O‐GCV, 450 ± 16; OV, 441 ± 13; YV, 352 ± 7; Y‐GCV, 351 ± 12; P<.05). Following GCV treatment, old mice had reduced aPWV (pre: 441 ± 13 vs post: 375 ± 5 cm/sec, P< .05), which was not different from YV (P= .63) or Y‐GCV (P= .72). These data suggest that cellular senescence mediates aortic stiffening with advancing age.Endothelial function. OV animals had impaired ex vivocarotid artery EDD to acetylcholine (an established assay of endothelial function) relative to young and GCV treatment resulted in greater peak EDD (Peak EDD [%]: O‐GCV, 95 ± 1; OV, 83 ± 4; YV, 93 ± 4; Y‐GCV, 95 ± 1; P<.05). Addition of the NO‐synthase inhibitor, L‐NAME, abolished group differences suggesting the age‐related increase in cellular senescence reduced EDD by lowering NO bioavailability. Administration of the ROS scavenger TEMPOL eliminated group differences in EDD, implying that cellular senescence causes endothelial dysfunction with aging by amplifying ROS.SASP. To determine the effect of the circulating SASP on aortic stiffness, we incubated aortic rings from young adult (6 mo) male and female C57BL/6 mice, with plasma from sex‐matched OV and O‐GCV mice, or under fetal bovine serum (control). Following a 48h incubation, we assessed intrinsic mechanical wall stiffness (elastic modulus [EM]), an established ex vivomeasure of aortic stiffness. OV plasma resulted in 1.5 ± .01‐fold greater EM vs control (P< .05), which did not occur in O‐GCV plasma (P= 0.84 vs control), suggesting the SASP may increase age‐related aortic stiffening.Conclusion. The circulating SASP factors may be a mechanism by which cellular senescence induces age‐related vascular dysfunction, and as such, these processes represent novel therapeutic targets.