Formate reduces ischemic injury in female hearts lacking alcohol dehydrogenase 5

Ischemic heart disease is a primary cause of death for men and women in the United States. Recent epidemiologic findings, however, suggest that pre-menopausal women have inherent protection from many cardiovascular pathologies compared to age-matched men, which is lost with menopause. We and others have documented similar protective signaling in animal models, with females exhibiting protection from ischemic injury that is lost with ovariectomy (OVX). Furthermore, in recent studies, we demonstrated that the loss of alcohol dehydrogenase 5 (ADH5) blocked sex-specific cardioprotection in females, but activation of aldehyde dehydrogenase 2 (ALDH2) provided a rescue. ADH5 and ALDH2 both metabolize formaldehyde to formate, potentially implicating formate in female-specific cardioprotection. Therefore, the objective of this study was to examine a role for formate during ischemic injury in female hearts using wild-type (WT) and ADH5 ^-/- mice. We also aimed to explore estrogen-dependent effects by using ovariectomized (OVX) WT mice. To assess the protective effects of formate in intact female WT and ADH5 ^-/- hearts, as well as OVX WT hearts, hearts were Langendorff-perfused and subjected to ischemia/reperfusion (I/R) injury. Since formate is used in one-carbon metabolism (OCM), select OCM enzymes were also probed via western blot. Importantly, we found that formate significantly reduced infarct size in female ADH5 ^-/- hearts subjected to I/R injury, but formate was without effect in intact female WT hearts. Additionally, formate failed to reduce I/R injury in OVX WT hearts, despite OVX WT hearts exhibiting reduced ADH5 and ALDH2 activity. However, we noted that the expression of certain OCM enzymes was downregulated in OVX WT hearts vs. intact WT females, which may prevent proper formate utilization by OCM in OVX WT hearts. Furthermore, blockage of formate import into OCM in intact female WT hearts also exacerbated I/R injury. Taken together, our findings support formate utilization by OCM as a key component of cardioprotective signaling in female hearts, with estrogen acting as a potential mediator.