Investigation into the effect of gut motility drug cisapride on myocardial ischaemia reperfusion injury

Mayel Gharanei, Afthab Hussain, Helen Maddock. Coventry University, CV1 5FB, United Kingdom.

Drug induced cardiotoxicity is a major concern to the pharmacological industry and it is one of the main reasons for non-approval, relabeling, warnings and withdrawal of pharmaceutical compounds from the market. This can form a financial burden to the companies and a serious threat to those who build up adverse effects to it. Cisapride was developed by the pharmaceutical industry for the treatment of gastroesophageal reflux which causes heart burn and acid damage to the oesophagus. In 2000 Cisapride was withdrawn from the UK market because of serious cardiovascular side effects.

The current study aimed to investigate the effects of Cisapride (1µM) on the myocardium subjected to normoxic and ischaemia-reperfusion (I/R). Studies were undertaken in Langendorff hearts and adult/neonatal ventricular myocytes. Isolated hearts were subjected to either normoxic conditions or 35 min regional ischemia and 120 min reperfusion. Hearts underwent triphenyl tetrazolium staining for infarct size assessment. Treatment groups (n=7-10) were perfused in the presence or absence of Cisapride (1µM). Following isolation, neonatal or adult cardiomyocytes were subjected to simulated ischaemia-reoxygenation and Cisapride (1µM) was administered at reoxygenation. Cellular injury was subsequently determined by measurement of live/death ratio and apoptosis using flow cytometry. In separate experiments adult and neonatal myocytes were subjected to laser illumination loaded with the fluorophore, Tetramethyl rhodamine methyl ester (TMRM). These conditions generate oxidative stress, represented by mitochondrial membrane depolarisation followed by rigour contracture. The neonatal or adult cardiac myocytes were subjected to oxidative stress in the presence and absence of Cisapride (1μM), Carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP, 1μM) or vehicle controls.

Administration of Cisapride in normoxic conditions significantly increased infarct size to risk ratio (%) compared to respective non-treated controls (35 ± 12% Cisapride vs. 13 ± 3% control, P<0.01). When

Cisapride was administered during reperfusion following ischaemia infarct size to risk ratio (%) was also significantly increased compared to respective non-treated controls (64 ± 8% Cisapride vs. 47 ± 2% control, P<0.05). Cisapride (1μM) significantly reduced the time required for depolarization and hypercontracture of the cardiac myocytes (Table 1, n&equals;7-10). Vehicle controls had no significant effect on depolarisation or hypercontracture in comparison to the control (data not shown). FCCP, known to cause ATP depletion significantly reduced the time taken to depolarisation and hypercontracture in both cell models. Cisapride also significantly increased apoptosis and decreased cell viability after reoxygenation compared to control. Statistical analysis were evaluated by one way anova.

Table 1: The effect of Cisapride on Depolarisation and Hypercontracture of adult myocytes

*P<0.05 vs. Control, **P<0.01 vs. Cisapride, #P<0.01 vs. FCCP

This is the first study to show that Cisapride exacerbates myocardial ischaemia reperfusion injury. We are currently undertaking further studies to determine the cellular mechanism via which Cisapride mediates increased myocardial injury in conditions of ischaemia-reperfusion.