Cytoprotective effects of trimetazidine in carmustine cholestasis

Carmustine [1,3-bis(2-chloroethyl)- 1-nitrosurea (BCNU)] is an antitumour a gent, however, its usefulness has been limited by a side effect; which invo lves pericholangitis and intrahepatic cholestasis. The primary effects of c holestasis is well known; bile flow retention, intracellular Ca++ accumulat ion and acidosis although it may lead to hepatotoxicity by dose-dependent m anner. Recent studies provide evidence that lipoperoxidation (LPO) and alte rations in the antioxidant system may significantly contribute to BCNU indu ced hepatotoxicity. Trimetazidine, (1-[2,3,4-Trimethoxy-benzyl] piperazine, HCl; TMZ) introduced as an antianginal compound, is found to exhibit vario us cytoprotective features by preserving cellular ATP levels, limiting intr acellular acidosis and inorganic phosphate as well as Na+ and Ca++ accumula tion in ischemic cardiac injury. No study was undertaken to investigate the cytoprotective role of TMZ in cholestatic injury till today; therefore we initiated this study to investigate if its cytoprotective features also exh ibit in the liver and to characterize further the cholestatic response to B CNU administration. Male rats were randomly seperated to control (CONT) (n = 15), BCNU administered (BCNU) (n = 16) and BCNU+TMZ administered (BCNU+TM Z) (n = 12) groups. The control rats received a single dosage of 2ml/kg of corn oil (i.p.) while the BCNU group received a single dosage of BCNU (20 m g/kg,i.p.) in corn oil. In the BCNU +TMZ group 2,5 mg/kg/day (i.p.) of TMZ was administered for three days. This group also received BCNW (210 mg/kg, i.p.) in corn oil, 12 hours after the initial dose of TMZ. The cholestatic effect of BCNU was monitored by stasis markers such as ALP, GGT and total b ilirubin levels. Hepatic TEARS analysis was determined with the modified me thod of Okhawa et al, based on the reaction of Lipid peroxides with thiobar bituric acid. Oxidized (GSSG) and reduced (GSH) glutathione levels were mea sured by the modified enzymatic recycling method of Teare et al. Statistica l tests were performed using Kruskal Wallis one-way Anova test and posthoc analysis by Newman-Keuls test. The BCNU group and the BCNU + TMZ group show ed significant increases (p = 0.029) in hepatic TEARS levels compared to th e CONT group; however the difference between the BCNU and BCNU + TMZ groups in regard to TEARS was not significant. BCNU and BCNU + TMZ groups manifes ted a significant decrease (p = 0.0005) in GSH levels as compared to contro ls. GSH/GSSG ratios in the BCNU and BCNU + TMZ group also manifested a sign ificant decrease (p = 0.0013) as compared to the CONT group. TMZ administra tion caused a significant increase in total GSH levels (p = 0.0026) in BCNU + TMZ group when compared to the BCNU group. Our results support the hypot hesis that BCNU induced cholestasis partly involves LPO revealed by the dis tinct increase in the content of TEARS in the liver after BCNU administrati on. BCNU is a potent inhibitor of GSSG reductase altering the preservation of the thiol redox balance in the system. As a result, supranormal concentr ations of intracellular GSSG would accumulate in the hepatocyte and the ext rusion of this oxidized compound would require active transport leading to ATP hydrolysis. This would deplete the energy stores of the cell which woul d accelerate further the possible prooxidant status. Although administratio n of TMZ did not provoke any significant alterations in LPO, it preserved t he total GSH levels of the cell probably by improving the energy status of the cell by protection of ATP-producing processes at the mitochondrial leve l and provision of the necessary substrates for GSH synthesis. This protective role in the antioxidant system normalizes the altered GSH l evels by BCNU and hence proposes TMZ to be a promising agent in the cholest atic injury.