Abstract 13087: TRPM7 Kinase Regulates Inflammation in Hypomagnesemia-Induced Cardiac Diastolic Dysfunction

Abstract

Introduction: Hypomagnesemia (HypoMg) is commonly observed in heart failure and associated with inflammation. We have reported that inflammation contributes to mitochondrial oxidative stress and causes cardiac diastolic dysfunction (DD) in diabetic mice and that Mg supplementation shows therapeutic benefits. Meanwhile, diet-induced HypoMg alone can lead to DD. Transient receptor potential melastatin 7 (TRPM7), a Mg transporter with a kinase domain, regulates Mg homeostasis in different types of cells. Object: We aim to assess the role of TRPM7 in HypoMg-associated inflammation and DD. Methods: Wild type (WT) C57BL/6J and transgenic kinase dead TRPM7 K1646R mice (with a global homozygous K1646R mutation in the kinase domain) were fed with a normal (2 g/kg Mg) or a HypoMg diet (15-30 mg/kg Mg) for 6 weeks. Echocardiography was performed to monitor E/e’ (an DD indicator when increased). Hearts were collected for protein levels of TRPM7, inflammatory markers IL-1β and NLRP3, and total protein oxidation. Isolated cardiac macrophages (Mϕs) were used for phenotyping by flow cytometry. Raw264.7 cells (a Mϕ cell line) and RL-14 cells (a cardiomyocyte cell line) were treated with a normal (0.81 mM Mg) or a HypoMg medium (0.04 mM Mg) for 48 h. TRPM7 protein and IL-1β collected from the culture media or from cell lysates were tested. Results: In the WT-HypoMg mouse group, E/e’, protein levels of TRPM7, IL-1β and NLRP3, and total protein oxidation were all significantly elevated, which were not observed in the TRPM7 K1646R -HypoMg group. Cardiac Mϕs phenotype showed increased recruited pro-inflammatory Mϕs and decreased resident pro-resolving Mϕs, while the former was prevented by TRPM7 K1646R . TRPM7 protein levels in Raw264.7 and RL-14 cells were also significantly increased by HypoMg treatment, as well as Mϕ-secreted IL-1β (2.7±0.6 pg/mL vs. undetectable in control, P=0.012) and IL-1β in RL-14 cell lysates (2.6±0.2-fold of control, P=0.006). Conclusions: TRPM7 kinase function is upregulated under HypoMg in both Mϕs and cardiomyocytes. It contributes to inflammatory Mϕ activation, elevated IL-1β production, increased oxidative stress, and cardiac DD, suggesting inflammation as a potential mediator of HypoMg-induced DD.