Formate reduces ischemic injury in the male heart by increasing protein S-nitrosation

Ischemic heart disease is a leading cause of death for both men and women in the United States. We and others have demonstrated that nitric oxide (NO) signaling and associated protein S-nitrosation (SNO) play a key role in reducing ischemic injury in the heart. We also find that while females typically exhibit endogenous protection from ischemic injury, this protection is abrogated with the loss of the formate-generating enzyme alcohol dehydrogenase 5 (ADH5), but formate supplementation provided a rescue. Here, we investigate the cardioprotective efficacy of formate in male hearts. Hearts were Langendorff-perfused and subjected to ischemia/reperfusion (I/R) injury with and without formate. Formate-mediated protection was also examined using an in vitro model of coverslip-induced ischemic injury to identify molecular underpinnings. We found that formate yields protection from I/R injury in ex vivo and in vitro models by increasing post-ischemic protein SNO levels, while NO synthase inhibition blocked this formate-mediated increase in protein SNO in vitro, and attenuated protection from I/R injury ex vivo. Moreover, post-ischemic levels of tetrahydrobiopterin (BH4), a cofactor necessary for NOS function, were preserved in formate-treated hearts. Furthermore, inhibition of dihydrofolate reductase (DHFR), a one-carbon enzyme critical for BH4 recycling, blunted formate-mediated protection ex vivo. Collectively, our findings suggest that formate is a potent cardioprotective agent that confers protection by preserving post-ischemic BH4 levels, and enhancing protein SNO levels through a NOS-dependent mechanism. These findings have significant implications for the clinical prevention and treatment of ischemic heart disease in males.