Kynurenic Acid Protects Against Myocardial Ischemia/Reperfusion Injury by Activating GPR35 Receptors and Preserving Mitochondrial Structure and Function

Acute myocardial infarction, often associated with ischemia/reperfusion injury (I/R), is a major healthcare issue ranking among the leading causes of death globally. Although kynurenic acid (KYNA), an endogenous tryptophan metabolite, has been previously shown to protect the cardiac tissue against I/R injury, its mechanism of action remains unclear. Therefore, here, we examined whether KYNA administration rescues H9c2 cardiac cells exposed to I/R through the preservation of the structural and functional integrity of the mitochondria. In addition, we assessed whether KYNA-derived agonism on G-protein coupled receptor 35 (GPR35) is involved in the protection of cardiac cells against simulated I/R (SI/R)-induced cellular demise. Our results demonstrated that KYNA attenuated the SI/R-induced calcium overload as well as impairments in the mitochondrial ultrastructure. Furthermore, administration of KYNA was shown to reduce mitochondrial superoxide production and preserve mitochondrial function in cells exposed to SI/R. Activation of the GPR35 receptors using an agonist other than KYNA rescued cardiac cells undergoing SI/R, attenuated the apoptotic activity, and improved various parameters of mitochondrial respiration. The administration of a synthetic GPR35 antagonist in parallel with KYNA attenuated the KYNA-induced cytoprotection. Our findings provide evidence that the protective effect of KYNA against SI/R-induced cardiac cell injury involves mitoprotective mechanisms, acting, at least in part, through the activation of GPR35 receptors.