P0016EFFECT OF GEMFIBROZIL ON KYNURENINE AMINOTRANSFERASE ACTIVITY AND KYNURENIC ACID PRODUCTION IN RAT KIDNEY

Abstract

Abstract Background and Aims Hypertriglyceridemia is the most common lipid disorder in chronic kidney disease. Lifestyle changes and fibrates administration are main methods of lowering triglycerides’ level. PPARα (peroxisome proliferator-activated receptor-α) activation is the primary mechanism of action of fibrates. A tryptophan metabolite, kynurenic acid (KYNA), is produced from L-kynurenine (L-KYN) by kynurenine aminotransferases (KATs). KAT I and KAT II isoenzymes are the best analyzed KATs. KYNA acts predominantly as a nonselective antagonist of ionotropic glutamatergic receptors, particularly N-methyl-D-aspartate (NMDA) type, which are highly expressed in the kidney. Natriuretic and hypotensive effects of KYNA are well described. Diet rich in fatty acids was reported to elevate central and peripheral KYNA level. The goal of presented study was to analyze the influence of gemfibrozil, one of the fibrates given to treat hypertriglyceridemia, on KYNA production and the activity of KAT isoenzymes: KAT I and KAT II, in rat kidney in vitro. Additionally, the molecular docking of gemfibrozil to KAT I and KAT II structures was performed to study drug-enzyme interaction. On the final step the microarray datamining was carried out to investigate whether gemfibrozil affects the expression of KAT-coding genes. Method The effect of gemfibrozil on KYNA synthesis together with KAT I and KAT II activity was tested in rat kidney homogenates in vitro after 2 hours incubation in the presence of L-KYN and gemfibrozil. The drug was examined at the concentration of 1 µM, 10 µM, 50 µM, 100 µM, 500 µM and 1 mM. Production of KYNA was analyzed using the high performance liquid chromatography (HPLC) with fluorometric detector. Results Gemfibrozil at 100 µM, 500 µM and 1 mM decreased KYNA production in kidney homogenates in vitro to 66% (P < 0.05), 58% (P < 0.01) and 41% (P < 0.01) of control value, respectively. At 100 µM, 500 µM and 1 mM concentration gemfibrozil lowered renal KAT I activity in vitro to 68% (P < 0.05), 56% (P < 0.01) and 52% (P < 0.01) of control value, respectively. Moreover, gemfibrozil at 500 µM and 1 mM concentration decreased kidney KAT II activity in vitro to 47% (P < 0.001) and 26% (P < 0.001) of control value, respectively. Results of the molecular docking suggested that gemfibrozil may affect the active site of both KAT I and KAT II. Publicly available microarray datasets suggested that the expression of KAT-coding genes does not change after gemfibrozil administration. Conclusion Gemfibrozil decreases KYNA production in rat kidney in vitro through inhibition of KAT I and KAT II isoenzymes. Presented results indicate a novel mechanism of gemfibrozil’s action in the kidney. Its potential role in nephrotoxicity needs verification in upcoming studies.