Abstract P228: Protective Role of TRPM7-kinase Against Vascular Dysfunction and Fibrosis Induced by Aldosterone and Salt

TRPM7 is a cationic ion channel and with a serine/threonine kinase important for cellular Mg 2+ homeostasis. We recently showed that TRPM7-kinase plays a role in aldosterone-mediated vascular effects and inflammation. Here we explored the role of TRPM7-kinase in cardiac fibrosis and vascular function in aldosterone-induced hypertension in mice. Wild-type (WT) or heterozygote TRPM7-kinase domain (TRPM7+/-) were treated with infused aldosterone (600 μg/Kg/day) and NaCl 1% in drinking water (aldo/salt) for 4 weeks. Blood pressure (BP) was evaluated by tail-cuff. Vessel function was investigated in mesenteric arteries by wire and pressure myography. Protein expression was assessed in cardiac tissue by western-blot and histology. Aldo/salt increased BP in TRPM7+/- and WT to similar levels (137mmHg vs control 118mmHg). Mesenteric arteries from untreated TRPM7+/- mice were more sensitive to relaxation induced by acetylcholine (LogEC50: 7.6±0.1 vs 7.1±0.2, TRPM7+/- and WT, respectively), effects that were reduced by Aldo/salt treatment (LogEC50: 7.2±0.1). Phenylephrine-contraction and sodium nitroprusside-relaxation curves were similar among groups. Pressure myography showed that in WT, aldo/salt increase the diameter (26%) and cross-sectional area (40%), resulting in hypertrophic outward remodelling, whereas in TRPM7+/-, the treatment decreased the diameter (16%) and increase the wall/lumen ration (82%), resulting in eutrophic inward remodelling. Hearts from TRPM7+/- presented decreased expression of annexin-1, which is a target protein of TRPM7-kinase, that was further decreased by aldo-salt. Hearts from untreated TRPM7+/- mice had increased fibrotic markers: plasma galectin-3 (2.5ng/mL) vs WT (1.4ng/mL) and protein expression for fibronectin (2.4-fold) and TGFβ (2-fold), and the aging marker p-P66Sch (47%) which were similar to WT-aldo/salt. Aldo/salt induced higher collagen expression in TRPM7+/- than in WT animals (15%), as observed by picrosirius red staining. Our findings provide some insights into aldosterone signalling through TRPM7-kinase and suggest that this chanzyme may have protective actions, which when downregulated, promotes vascular remodelling and cardiac fibrosis in aldosterone-induced hypertension.