Loss of BReast CAncer Susceptibility Gene 2 Exacerbates Angiotensin‐II‐induced Endothelial Dysfunction

Abstract

Background Germ-line mutations in the tumour suppressor genes BRCA1 and BRCA2 (BReast CAncer susceptibility genes 1 & 2) predispose carriers to breast cancer. BRCA1 and BRCA2 help maintain genomic integrity by tracking DNA damage, and evoking DNA damage repair or cell cycle arrest pathways. These pathways play important roles in not only cancer, but also in the development of endothelial dysfunction, an early event in the progression of CVD like hypertension. However, the roles of BRCA1 and BRCA2 in hypertension-associated endothelial dysfunction has not been evaluated. We hypothesize that loss of endothelial BRCA2 exacerbates Angiotensin-II (Ang-II)-induced endothelial dysfunction. Methods and Results Ang-II treatment is a robust model of endothelial dysfunction in vitro and hypertension in vivo. We measured baseline and Ang-II induced expression of BRCA1 and BRCA2 in Human Umbilical Vein Endothelial Cells (HUVECs) and observed a significant up-regulation of only BRCA2 in Ang-II-treated HUVECs. BRCA2 was silenced and biomarkers for endothelial function (inflammation, migration and proliferation) were evaluated following Ang-II treatment. Our data showed a significant up-regulation of the endothelial inflammation markers: ICAM-1, VCAM-1 and E-selectin in Ang-II-treated BRCA2-silenced HUVECs compared to Ang-II-treated control HUVECs. Next, we evaluated angiogenic potential by evaluating the migratory capacity by scratch assay, which demonstrated reduced migration in Ang-II-treated BRCA2-silenced HUVECs compared to Ang-II-treated control HUVECs. At the molecular level, reduced migration was associated with significantly reduced Akt and eNOS activation in Ang-II-treated BRCA2-silenced HUVECs compared to Ang-II-treated control HUVECs. Loss of BRCA2 in endothelial cells following Ang-II treatment inhibited cell proliferation due to significant up-regulation of p21, an essential regulator of endothelial cell proliferation, in Ang-II-treated BRCA2-silenced HUVECs compared to Ang-II-treated control HUVECs. Conclusion We demonstrate a novel role for BRCA2 as a regulator for endothelial function and show that loss of BRCA2 significantly exacerbates Ang-II induced inhibition of angiogenic, migratory & proliferative potential, and increases inflammation in endothelial cells. These findings indicate an increased susceptibility of BRCA2-mutation carriers for hypertension-associated endothelial dysfunction and warrant further translational investigations.