Regulation of the Cardiac Fibroblast Transcriptome by Aldosterone In Vivo

Primary aldosteronism is characterized by excess autonomous secretion of aldosterone (ALDO) independent of the renin‐angiotensin system and accounts for ~10% of hypertensive patients. Excess ALDO causes hypertension and cardiac hypertrophy, inflammation and fibrosis that lead to cardiac dysfunction. We previously reported that ALDO in the presence of high salt intake (ALDO/SALT) dynamically modulates rat left ventricle (LV) transcriptome in vivo . The heart is a complex tissue composed primarily of cardiomyocytes, cardiac fibroblasts (CF), endothelial cells, vascular smooth muscle cells and infiltrating immune cells. Most of these cells are presumed to be direct or indirect targets of ALDO in vivo . The CF plays a critical role in ALDO/SALT‐mediated cardiac injury and dysfunction and may be an excellent therapeutic target to counteract ALDO/SALT‐mediated cardiac deleterious effects. However, the CF transcriptome regulation by ALDO/SALT in vivo remains to be elucidated. We aim to elucidate the genes, pathways and networks regulated by ALDO/SALT in CF in vivo . Eight‐week old uninephrectomized male Sprague Dawley rats were treated with ALDO (0.75 μg/h) and SALT (1.0% NaCl + 0.3% KCl) or vehicle for 2 weeks (N=6/group). LV CFs were isolated and CD90+ cells sorted by flow cytometry. Whole genome transcriptome was probed with Rat Gene 2.0‐ST Affymetrix arrays. Gene expression was analyzed with SAM software. Downstream bioinformatics analysis were performed with DAVID, Ingenuity and Enrichr software packages. Gene expression regulation was validated by qRT‐PCR. Sorted cells tested positive for CF markers (Thy1, vimentin, Fsp1, Ddr2) while negative for cardiomyocyte markers (Tnnt2). ALDO/SALT significantly regulated 950 genes (FC ≥ 1.5‐fold, FDR=10; 740 UP and 210 DOWN) in LV CFs. Upregulated genes were enriched in gene ontology categories such as immune response, inflammatory response, cell cycle, chemotaxis and cell migration. Surprisingly, downregulated genes were significantly enriched in the gene ontology category “detection of chemical stimulus involved in sensory perception of smell” with 47 distinct GPCR olfactory receptors downregulated. Furthermore, several Regulator of G‐protein Signaling proteins (RGS1, RGS2, RGS18 and RGS19), negative regulators of GPCR intracellular signaling, were upregulated by ALDO/SALT. These results suggest a concerted dowregulated response of the olfactory receptor family by ALDO/SALT in CF in vivo . Bioinformatics analysis of ALDO/SALT regulated metabolic pathways in CF in vivo , showed that the top upregulated pathways include D‐myo‐inositol‐5‐phosphate metabolism, citrulline‐nitric oxide cycle and aspartate degradation; while top downregulated ones include palmitate biosynthesis and fatty acid biosynthesis initiation. In silico analysis identified the transcription factors Yy1, Lef1, Jun, Runx1, Irf8, Foxc1, Mef2a, Cbepb and Nr5a2, some previously implicated in cardiac pathologies, as upstream candidate regulators of the ALDO/SALT‐regulated CF transcriptome. Our results show that the LV CF transcriptome is dynamically regulated by ALDO in vivo despite recent controversy in the field. Furthermore, we identified not only novel genes but completely new gene families, pathways and networks that are targeted by ALDO in CFs in vivo , suggesting novel therapeutic approaches for patients suffering from primary aldosteronism‐induced cardiac injury and dysfunction. Support or Funding Information Supported by American Heart Association Grant 12SDG8980032 (DGR).