Abstract P197: TRPM7 is Involved in the Effects of VEGF and EGF in Vascular Cells

Abstract

TRPM6 and 7 are channels important in Mg 2+ and Ca 2+ homeostasis. We demonstrated that TRPM7 is influenced by angiotensin II. TRPM6 is influenced by EGF and cancer patients treated with EGFR inhibitors exhibit hypomagnesemia and hypertension by unclear mechanisms. Whether growth factors influence vascular TRPM7 is unknown. Here we questioned if VEGF/EGF mediate vascular effects through TRPM7. Studies were performed in human VSMC, wild type (WT) and TRPM7-deficient (M7+/Δ) mice. VSMC were stimulated with VEGF or EGF (50ng/ml) in the absence/presence of vatalanib, gefitinib (1μM), 2APB (30μM) and NS8593 (40μM), inhibitors of VEGFR, EGFR and TRPM7 respectively. Ca 2+ and Mg 2+ levels were assessed by Cal-520 and Mg-green. VEGF/EGF signaling was assessed by immunoblotting and vascular function by myography in mesenteric arteries from WT and M7+/Δ mice and treated with EGF or VEGF (50ng/ml). TRPM7 expression in aortas and kidneys from WT treated with vatalanib or gefitinib (100mg/Kg/day, 2 weeks) was assessed by immunoblotting. VEGF and EGF increased TRPM7 expression (50% and 67% respectively) and phosphorylation (2-fold), promoted influx of Ca 2+ (8% and 10%) and Mg 2+ (8%), effects that were reduced by vatalanib, gefitinib, NS8593, and 2-APB. EGF but not VEGF increased phosphorylation of PKC (43%), p38MAPK (47%), and ERK1/2 (120%). These responses were reduced by gefitinib, however only ERK1/2 phosphorylation was inhibited by NS8593, and 2-APB. Mice treated with vatalanib or gefitinib showed reduced expression of TRPM7 in aortas (50% and 74% respectively) and kidneys (36% and 66% respectively). Vessels exposed to EGF were less responsive to acetylcholine (ACh)-induced relaxation, [Emax %: WT (veh 97±3 vs EGF 63±10, p<0.05), M7+/Δ (veh 89%±5% vs EGF 69%±5%, p<0.05)]. Vessels from M7+/Δ treated with VEGF were less sensitive to sodium nitroprusside (SNP)-induced relaxation [pD2: WT (veh 7±0.12 vs VEGF 7.4±0.12, p<0.05), M7+/Δ (veh 6.7±0.15 vs VEGF 6.9±0.09)]. EGF and VEGF regulate VSMCs through TRPM7-dependent pathways. These processes involve MAP kinases and influence vascular function. Our findings identify novel mechanisms whereby growth factors influence vascular contraction/relaxation and suggest that TRPM7-regulated Mg 2+ and Ca 2+ are important.