Abstract 129: TRPM7 α-kinase Deficiency Causes Cardiovascular Inflammation and Fibrosis.

Abstract

We previously demonstrated that TRPM7, a Mg 2+ /cation channel fused to an α-kinase domain, is regulated by vasoactive mediators and plays a protective role in hypertension. Here we questioned whether TRPM7-kinase influences vascular inflammation and fibrosis. We used Wild-type (WT) and heterozygote mutant mice for TRPM7-kinase (M7+/-). Vascular inflammatory responses were assessed ex vivo by intravital microscopy. Immune cells were investigated by flow cytometry. Fibrosis was investigated by sirius-red staining. Bone-marrow derived macrophages (BMDM) and Cardiac fibroblasts (CF) were obtained from WT and M7+/. [Mg 2+ ]i in cardiac tissue, cardiac macrophages and circulating monocytes was significantly reduced (30-50%) in M7+/- vs WT mice. In small arteries studied by intravital microscopy, leukocytes from M7+/- showed reduced velocity (47%), increased adhesion (222%) and transmigration (480%). Expression of vascular pro-inflammatory markers including VCAM-1(33-fold), iNOS (12-fold), and IL-12 (6.8-fold) was increased in M7+/- vs WT. Cardiac galectin-3 (Gal-3) levels (16.6±3.6 vs WT 9.2±1.2 cells/field), collagen area (6.7% vs WT 2.6%), infiltration of CD45+ cells (6±0.6% vs WT 4±0.4%) and protein expression of fibronectin (280%), TGFβ (125%), and p-Smad3 (66%), were increased in M7+/- mice. BMDM macrophages from M7+/- exhibited increased levels of Gal-3 (2.6±0.05 vs WT 2.1±0.09ng/mL), IL-10 (807±92 vs WT 305±37 pg/mL) and IL-6 (84±8 vs WT 13±5 pg/mL). A similar profile was demonstrated in resident peritoneal macrophages. CF treated with supernatant of macrophages from M7+/- increased fibronectin (43%) and PCNA (36%) vs WT. To evaluate whether these processes are Mg 2+ -sensitive, we examined effects of Mg 2+ treatment and demonstrated that Mg 2+ ameliorated pro-fibrotic and pro-inflammatory signalling evident in TRPM7+/- mice. In conclusion, TRPM7-kinase deficiency is associated with cardiac and vascular inflammation and fibrosis, processes associated with cellular Mg 2+ deficiency. Our findings highlight an important cardiovascular protective role of TRPM7 and Mg 2+ .