Evaluation of the effects of nicorandil on the QT prolongation and myocardial damage induced by citalopram in rats

Objective: The aim of our study is to evaluate the protective role of nicorandil, a selective mitochondrial KATP (mito-KATP) channel opener, on the QT interval prolongation and myocardial damage model induced by citalopram, a selective serotonin reuptake inhibitör antidepressant. Methods: Experiments were carried out on 44 male Sprague Dawley rats. In the preliminary study, in order to determine the intraperitoneal (i.p) dosage of citalopram that prolongs the QT interval, i.p citalopram was administered at lower than the median lethal dose (MLD) (n=3), equal to MLD (102.2 mg/kg, n=1), higher than MLD (n=1) and cardiovascular parameters [heart rate (HR), QRS duration, QT interval and corrected QT interval (QTc)] were recorded. Following citalopram administration, the number of rat was completed to 5 at the dose (102.2 mg/kg i.p), in which prolongation of QT interval was detected and no death was observed. In the other part of this preliminary study, selective mito-KATP channel opener nicorandil (3 mg/kg i.p, n=3) and selective mito-KATP channel blocker 5-hydroxydecanoate (5-HD) (10 mg/kg i.p, n=3) were applied alone and cardiovascular parameters were recorded. Biochemical and histological data were evaluated in blood and heart tissue samples which were taken from 6 rats to record as control values. Malondialdehyde (MDA) and reduced glutathione (GSH) were measured by high pressure liquid chromatography (HPLC); glutathione peroxidase (GpX), superoxide dismutase (SOD) were measured by colorimetric spectrophotometric method from plasma and tissue samples. Histological examination of tissue damage was performed using a scoring system on hematoxylin-eosin and masson trichrome stained slides. Apoptosis in cardiomyocytes was evaluated immunohistochemically by Activated CASPASE-3 and TUNEL method. Rats were randomly divided into 4 groups in the experimental groups. Cardiovascular parameters were recorded for 120 minutes after injections of citalopram in all experimental groups. Citalopram dose (102 mg/kg i.p) tested in the preliminary study were administered to the rats of the saline (SF)+citalopram group (n=6) in order to evaluate the cardiovascular effects of citalopram alone. In the nicorandil+citalopram group (n=5), to evaluate the effect of nicorandil on citalopram-induced QT interval prolongation, 10 minutes after SF injection nicorandil (3 mg/kg i.p) was administered and citalopram (102 mg/kg i.p) was administered following 15 minutes after nicorandil injection. In the 5-HD+citalopram group (n=6), 10 minutes after 5-HD (selective mito-KATP channel blocker) (10 mg/kg i.p) injection SF was administered and citalopram (102 mg/kg i.p) was administered following 15 minutes after SF injection. In the 5-HD+nicorandil+citalopram group (n=6), 10 minutes after 5-HD (selective mito-KATP channel blocker) injection (10 mg/kg i.p) nicorandil (selective mito-KATP channel opener) (3 mg/kg i.p) was administered and citalopram (102 mg/kg i.p) was administered following 15 minutes after nicorandil injection and the effects of the selective mito-KATP channel opener and blocker drugs were evaluated when used together. HR, QRS duration, QT interval and QTc interval of rats were recorded during the follow-up period. Blood and heart samples were taken from the rats at the end of the experiment. MDA, GSH, GpX and SOD values were recorded from plasma and tissue samples. Histomorphological and immunohistochemical evaluations were made in the heart tissue. Statistical analysis of cardiovascular and biochemical parameters was performed by variance analysis (ANOVA) followed by Tukey's multiple comparison tests (Graphad Instat V2.05a 1994). Statistical analysis of histological parameters was performed by Kruskal Wallis and Mann Whitney U post hoc tests (SPSS 20.0 INC., Chicago, IL, USA). Results: In the preliminary study, the dose of citalopram that prolongs the QT interval and without death was found as 102 mg/kg, i.p.. Nicorandil and 5-HD alone, did not statistically difference for QT interval, QTc interval, QRS duration and HR values to the baseline (p>0.05). In ECG of rats administered citalopram following SF, while there was no significant difference in QRS duration and HR (p>0.05), there was statistically significant prolongation in QT and QTc intervals to the baseline (for QT interval; 40th, 50th, 60th, 70th, 80th, 90th, 100th, 110th, 120th minutes, respectively p<0.01, p<0.001, p<0.001, p<0.001, p<0.001, p<0.001, p<0.001, p<0.05, p<0.001; for QTc interval; 50th, 60th, 70th, 80th, 100th minutes, respectively p<0.05, p<0.001, p<0.01, p<0.05, p<0.05). Citalopram did not cause any significant difference in the oxidant / antioxidant parameters (MDA/GSH, GpX, SOD) of the rats compared to the control values (p>0.05). Histomorphological damage was observed in the myocardial cells of the rats and there was statistically significant increase in histomorphological and apoptosis scores when compared to the control values (p<0.01, p<0.001). In rats administered citalopram following nicorandil, nicorandil did not prevent the prolongation in citalopram-induced QT and QTc interval (p>0.05), did not cause any significant difference in the oxidant/antioxidant parameters (p>0.05), however it significantly reduced the increase of histomorphological score and apoptosis induced by citalopram (p<0.05, p<0.001). While citalopram injection following 5-HD, did not cause any significant change in the prolongation of QT and QTc interval induced by citalopram (p>0.05), it significantly increased the decrease of histomorphological score and apoptosis induced by nicorandil+citalopram (p<0.01, p<0.001). Citalopram injection following 5-HD+nicorandil, caused a statistically significant decrease in the QT interval prolongation at 60th minute, QTc interval prolongation at 50th and 60th minutes induced by citalopram; QTc interval prolongation at 40th and 50th minutes induced by 5-HD+citalopram (p<0.05, for all parameters). There was no statistically significant difference in oxidant/antioxidant parameters in all other experimental groups (p> 0.05). Conclusion: Citalopram caused cardiac toxicity by causing prolongation in QT-QTc intervals, histological damage in myocardial cells and an increase in apoptosis but the effect of oxidative stress was not observed in this cardiac toxicity model. Nicorandil, which is a selective mito-KATP channel opener, did not play a protective role in the prolongation of QT and QTc interval induced by citalopram, but it was shown to have a protective effect from myocardial damage. While the role of anti-apoptotic effect was shown in this protective effect of nicorandil, the contribution of anti-oxidant effect could not be shown. Our study suggests that mito-KATP channels may play a role in the mechanism of myocardial damage caused by citalopram and nicondil may have a protective effect. Keywords: Citalopram, nicorandil, cardiotoxicity, long QT syndrome, KATP channels.