Abstract 13147: Formate Stimulates S-Nitrosylation and Mitochondrial Activity to Induce Cardioprotection

Abstract

Formate (FM) is a substrate in one-carbon metabolism, and recent studies implicate its function in both health and disease, but a role in the heart remains unexplored. Research from our group demonstrates that the loss of formaldehyde dehydrogenase, which oxidizes formaldehyde into FM, ameliorates sex-dependent cardioprotection against ischemia-reperfusion (I/R) injury in the female mouse heart. Considering that FM depletion may be detrimental, we tested the hypothesis that FM yields cardioprotective benefit in a model of I/R injury. Hearts from male and female mice (n=5-10/group) were subjected to ex vivo I/R injury with or without FM via Langendorff perfusion. FM significantly enhanced post-ischemic functional recovery in male hearts (27.1%, 95% CI 10.8 to 45.9, p=0.0023; females: 9.5%, 95% CI -6.9 to 27.8, p=0.2020) and decreased infarct size (males: -24.6%, 95% CI -35.1 to -12.2, p<0.0001; females: -3.7%, 95% CI -9.6 to -0.3, p=0.1128), indicating that FM protects the myocardium against I/R injury. Although FM had a greater protective effect in male hearts than in female hearts, plasma FM levels were greater in female mice, suggesting that FM-mediated cardioprotection may already exist near steady state in females. Mechanistically, cardiomyoblasts stimulated with FM exhibited a significant increase in total protein S-nitrosylation (SNO) without changing nitric oxide synthase (NOS) phosphorylation or protein expression; this was suppressed by NOS inhibition, suggesting that FM contributes to NOS-dependent NO cycling in the heart. FM-treated cardiomyocytes and cardiomyoblasts also exhibited significant increases in mitochondrial marker protein expression, metabolic activity, and maximal oxygen consumption, demonstrating an enhanced respiratory capacity to respond to increased energetic demand. Furthermore, FM treatment significantly increased phospho-activation of the energy regulator AMPKα and the protein expression of PGC-1α targets, indicating a potential upregulation in mitochondrial biogenesis. Taken together, these data suggest that FM may stimulate protein SNO and mitochondrial activity to protect the heart against I/R injury.