(VP124) TRPM7 IS PROTECTIVE AGAINST CARDIOVASCULAR FIBROSIS BY REGULATING CARDIAC FIBROBLASTS ACTIVATION PHENOTYPE

Background: TRPM7 is a cation channel permeable to Mg2+ and Ca2+ bound to an alpha-kinase domain with important role in cell homeostasis. We demonstrated that TRPM7 is protective against cardiac inflammation and dysfunction. Here, we investigated the importance of TRPM7-Mg2+ in inflammatory response and oxidative stress in cardiac fibroblasts in the context of hypertension induced by aldosterone and salt.

METHODS AND RESULTS: Wild-type (WT) and TRPM7-deficient (M7+/Δ) mice were treated with aldosterone (600µg/Kg/day) plus NaCl (1% drinking-water), 4-weeks. Blood pressure (BP) was evaluated by tail-cuff. Molecular mechanisms were investigated in primary culture of cardiac fibroblasts (CF). Ca2+ influx was assessed by fluorescence microscopy. Gene and protein expression was assessed by real-time PCR immunoblotting respectively. H2O2 production was assessed by Amplex-red kit. M7+/Δ mice exhibited reduced TRPM7 expression (30%), phospho-TRPM7(62%) and total tissue [Mg2+] (28%). Levels that were recapitulated in WT-aldo-salt. M7+/Δ mice exhibited increased BP by aldo, salt and aldo-salt (135-140mmHg). In WT, only aldo-salt increased BP (134mmHg). Cardiac collagen deposition (68%), expression of IL-6, TGFβ, p-Smad3 and p-ERK1/2 were increased (1.5-1.8 fold) in aldo-salt TRPM7+/Δ versus WT. CF from M7+/Δ exhibit increased mineralocorticoid target gene SGK1 (3-fold vs WT), which was increased by aldosterone (10-fold vs WT-aldo 5.4-fold). CF from TRPM7+/Δ had reduced aldosterone-induced calcium influx (peak-response 105±0.7 vs WT:149±10). CF M7+/Δ exhibited reduced proliferation (30%), and protein expression of TGFβ, IL-6, p-Smad3 and p-ERK1/2 (1.4-2.0-fold) vs WT. Nox2 (170%) and Nox4 (220%) expression was increased in CF TRPM7+/Δ vs WT. Aldosterone increased Nox4 (154%) only in CF WT. These effects were associated with increased expression of peroxiredoxin-3 oxidation. Mg2+ supplementation normalized intracellular [Mg2+], cell proliferation, protein phosphorylation and Nox4 expression in CF TRPM7+/Δ (p < 0.05).

Conclusion: We define a novel protective role of TRPM7 in the cardiovascular system, which when downregulated, causes cardiac fibrosis by altering the fibroblast inflammatory response and oxidative stress through Mg2+ -dependent mechanisms.