Abstract 12763: High Innate Aerobic Capacity Protects Against Angiotensin II-Induced Hypertension and Vascular Remodeling

Abstract

Low aerobic capacity is associated with increased cardiovascular morbidity and mortality. A heterogeneous rat population selectively bred to segregate genes that sustain innate aerobic exercise capacity, low capacity runners (LCR) show impaired cardiac function in old age and premature death versus high capacity runners (HCR). Here we investigated whether high innate aerobic capacity offers early protection against cardiovascular disease by examining the hypertensive response of 7-month-old LCR and HCR rats to angiotensin II (Ang II, 150 μg/kg/min for 14 days). LCR and HCR rats showed no difference in basal blood pressure (105 mmHg) or vessel wall morphology, but in LCRs the mean arterial blood pressure increased to 145 mmHg versus 125 mmHg in HCRs. Congruently, LCR rats had increased aortic medial thickness and fibrosis. Aortic cytosolic and mitochondrial superoxide levels were also significantly increased in LCRs. Vascular reactivity experiments revealed impaired endothelium-dependent and -independent relaxation of mesenteric arteries of LCRs. Ang II infusion significantly increased the infiltration of macrophages into the aortic adventitia of LCRs as determined by CD68 and Mac-3 staining. Gene expression analysis by qPCR showed that markers of classically-activated macrophages CD86 and TNF-α were unchanged in rat strains but markers of alternatively-activated macrophages CD163 and Arg-1 were upregulated only in LCRs. Plasma IL-6, RANTES, CCL2 and Ang II and aortic VCAM1 levels were elevated only in LCRs whereas no difference in eNOS levels was observed between the rat strains. Aortic sections of LCRs showed increased senescence in adventitia whereas vascular smooth muscle cells (VSMC) isolated from LCR rats were more susceptible to Ang II-induced senescence. LCRs also showed increased cardiac hypertrophy and fibrosis. These data support the “outside-in” hypothesis, in which vascular inflammation initiated in adventitia progresses inwards to media and intima, causing VSMC and endothelial dysfunction, and that fibroblasts play a critical role in Ang II-induced hypertension and vascular remodeling under low innate aerobic capacity conditions, whereas high innate aerobic capacity is potentially protective against hypertension.