Kynurenic acid- a key metabolite protecting the heart from an ischemic damage

Abstract

Abstract Background Myocardial ischemia is a major cause of death in patients with renal dysfunction. In order to identify a key metabolite which may protect cardiac function following renal injury, we have recently performed a metabolomics profiling analysis of LV lysates and plasma samples derived from animals that underwent an acute kidney injury (AKI) 1 or 7 days earlier, versus sham-operated controls. The analysis revealed that the kynurenic acid (kynurenate, KYNA) metabolite levels are highly elevated in all tested experimental samples relative to control. Purpose We wished to analyze whether KYNA may protect cardiomyocytes' survival and cardiac function upon an ischemic event and if so, to characterize whether the protecting effect may be linked to better preservation of the cardiac mitochondria. Methods Cellular viability of H9C2 rat cardiac myoblasts grown under normoxic or anoxic conditions with or without KYNA was determined by flow cytometry following Annexin-PI staining. The mitochondrial structure of the cells was determined by live cell staining with green (FITC) and deep red (Cy5) mito-tracker dyes. The potential effect of the metabolite on cardiac function following acute MI was tested in a murine model by echocardiography followed by histological staining of the cardiac sections with Picro Sirius Red. Results KYNA given at 10 mM concentration hardly affected the viability of H9C2 grown under normoxia, however the metabolite rescued the viability of the anoxic cells by 63% and largely improved their mitochondrial structure. Moreover, KYNA diluted in the drinking water of post-MI animals (250mg/ml), highly enhanced their cardiac recovery compared to untreated-animals as determined by echocardiography and collagen staining. Conclusions 1. KYNA may represent a key metabolite absorbed by the heart following AKI. 2. KYNA can enhance cardiac cell viability following an ischemic event both in vitro and in vivo in a mechanism which is mediated, at least in part, by protection of the cardiac mitochondria. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Weizmann Institute-Tel-Aviv Sourasky Medical Center joint research grant KYNA's protection of cardiac cells