A Novel HIF-2a/ARNT Signaling Pathway Protects Against Microvascular Dysfunction and heart failure After Myocardial Infarction

Experiments were conducted with mice carrying an inducible EC-specific Hif2a-knockout (ecHif2a–/–) mutation, with mouse cardiac microvascular endothelial cells (CMVECs) isolated from the hearts of ecHif2a–/– mice after the mutation was induced, and with human CMVECs and umbilical-vein endothelial cells transfected with ecHif2a siRNA. After MI induction, echocardiographic assessments of cardiac function were significantly lower, while measures of cardiac microvascular leakage (Evans blue assay), plasma IL6 levels, and cardiac neutrophil accumulation and fibrosis (histology) were significantly greater, in ecHif2a–/– mice than in control mice, and RNA-sequencing analysis of heart tissues from both groups indicated that the expression of genes involved in vascular permeability and collagen synthesis was enriched in ecHif2a–/– hearts. In cultured ECs, ecHif2a deficiency was associated with declines in endothelial barrier function (electrical cell impedance assay) and the reduced abundance of tight-junction proteins, as well as an increase in the expression of inflammatory markers, all of which were largely reversed by the overexpression of ARNT. We also found that ARNT, but not Hif2a, binds directly to the IL6 promoter and suppresses IL6 expression. Overall design: To assess the functional role of HIF2a in ischemic heart injury, we ligated the proximal left anterior descending coronary artery to induce MI in tamoxifen inducible adult ecHIF2a-/- and control (Hif2aflox/flox) mice. Total RNA from controls and Hif2a-/- heart tissues was isolated 28 days after MI using RNeasy Fibrous Tissue Mini Kit (74704, Qiagen, MD) according to the manufacturer's protocol.