Ipratropium bromide-mediated myocardial injury in in vitro models of myocardial ischaemia/reperfusion

Ipratropium bromide, a nonselective muscarinic antagonist, is widely prescribed for the treatment of chronic obstructive pulmonary disease (COPD). Analyses of COPD patients, with underlying ischaemic heart disease, receiving anticholinergics, have indicated increased risk of severity and occurrence of cardiovascular events (including myocardial infarction). The present study explored whether ipratropium bromide induces myocardial injury in nonclinical models of simulated myocardial ischaemia/reperfusion injury. Adult Sprague Dawley rat hearts/primary ventricular myocytes were exposed to simulated ischaemia/hypoxia prior to administration of ipratropium at the onset of reperfusion/reoxygenation. Infarct to risk ratio and cell viability was measured via triphenyl tetrazolium chloride staining and thiazolyl blue tetrazolium bromide (MTT) assay. The involvement of Apoptosis and necrosis was evaluated by flow cytometry. Mitochondrial-associated responses were detected by tetramethylrhodamine methyl ester fluorescence and myocyte contracture. Ipratropium (1 × 10⁻¹¹ M - 1 × 10⁻⁴ M) significantly increased infarct/risk ratio and decreased cell viability in a dose-dependent manner. Increased levels of necrosis and Apoptosis were observed via flow cytometry, accompanied by increased levels of cleaved Caspase-3 following ipratropium treatment. Levels of endogenous myocardial acetylcholine were verified via use of an acetylcholine assay. In these experimental models, exogenous acetylcholine (1 × 10⁻⁷ M) showed protective properties, when administered alone, as well as abrogating the exacerbation of myocardial injury during ischaemia/reperfusion following ipratropium coadministration. In parallel experiments, under conditions of myocardial ischaemia/reperfusion, a similar injury was observed following atropine (1 × 10⁻⁷ M) administration. These data demonstrate for the first time in a nonclinical setting that ipratropium exacerbates ischaemia/reperfusion injury via apoptotic- and necrotic-associated pathways.