Mechanism by Which Inflammation and Oxidative Stress Induce Mineralocorticoid Receptor Gene Expression in Aging Vascular Smooth Muscle Cells

Background:Vascular MR (mineralocorticoid receptor) expression increases with age driving aging-associated vascular stiffness and hypertension. MR has two isoforms (1 alpha and 1 beta) with distinct 5 '-untranslated and promoter sequences (P1 and P2), but the gene regulatory mechanisms remain unknown. We investigated mechanisms driving MR gene transcriptional regulation in aging human smooth muscle cells (SMC). Methods:MR was quantified in aortic tissue and primary human aortic SMC (HASMC) comparing adult and aged donors and adult HASMC treated with H2O2, to induce aging. Predicted transcription factor (TF) binding sites in the MR gene were validated using chromatin immunoprecipitations and reporter assays. The impact of TF inhibitors on MR isoforms and fibrosis target gene expression was examined. Results:Expression of both MR mRNA isoforms increased with donor age or H2O2 treatment in HASMCs. HIF1 alpha (hypoxia-inducible factor) and the inflammatory TF NF kappa B (nuclear factor kappa B) both increased with age in HASMCs and are predicted to bind MR promoters. H2O2 induced HIF1 alpha and NF kappa B expression and DNA binding of HIF1 alpha to the MR P1 promoter and of NF kappa B to both MR promoters in HASMCs. HIF1 alpha inhibition decreased MR-1 alpha isoform expression while NF kappa B inhibition decreased both MR isoforms. HIF1 alpha, NF kappa B, and MR inhibition decreased the expression of a SMC-MR target gene implicated in vascular fibrosis. In human aortic tissues, expression of HIF1 alpha and NF kappa B each positively correlated with donor age and MR expression (P<0.0001). Conclusions:These data implicate the inflammatory TF, NF kappa B, and oxidative stress-induced TF, HIF1 alpha, in regulating SMC MR transcription in aging HASMCs, which drives aging-related vascular stiffness and cardiovascular disease.