Abstract 237: Role of Runx2 in Vascular Responses to Angiotensin II-Induced Hypertension

Abstract

Increases in local angiotensin II (ANGII) signaling have been implicated in a number of diseases, including atherosclerosis, hypertension, and aneurysm. Endothelial dysfunction is strongly associated with increased ANGII signaling and the pathogenesis of these diseases. While increases in Runx2 have been implicated in cardiovascular calcification and vascular stiffening in diabetes, little is known regarding the role of Runx2 in the regulation of endothelial function. In the present study, we hypothesized that Runx2 is a key mediator of impaired vascular function and increased vascular wall stiffness provoked by ANGII. Wild-type mice (WT) and littermates that were deficient in one copy of Runx2 (HET) were implanted with osmotic minipumps containing saline or a pressor dose of ANGII (1000 ng/kg/min). Blood pressure was measured non-invasively using tail-cuff methods (CODA) and mice were sacrificed following 14 days of treatment. Changes in endothelium-dependent relaxation (relaxation to acetylcholine, R ACH ) and passive pressure-diameter relationships were measured in vitro (Living Systems arteriograph). In WT mice, treatment with ANGII for 14 days resulted in profound impairment in R ACH (85 ± 4% vs 47 ± 14% p<0.05) and slight reductions in vascular diameter at high distending pressures (~10% reduction in maximal diameter). While Runx2 deficiency did not alter R ACH or vascular distensibility/compliance in saline-treated mice, loss of one copy of Runx2 in ANGII-treated mice dramatically improved R ACH compared to their wild-type, ANGII-treated littermates. Interestingly, impairments in the pressure-diameter relationship with ANGII infusion were not affected by loss of one copy of Runx2. Critically, reductions in Runx2 did not significantly alter the pressor response to ANGII. In conclusion, our data suggest that Runx2 may play an integral role in the pathogenesis of ANGII-induced endothelial dysfunction, with these changes occurring independently of alterations in extracellular matrix remodeling and vascular stiffness. These data suggest that Runx2 may play a key, context-dependent role mediating vascular responses to ANGII.