Cardiovascular effects of a PEGylated apelin

► N-terminal conjugated 40kDa PEG apelin-36 was successfully produced. ► PEGylation had minimal effect on APJ receptor binding affinity. ► Comparable in vitro bioactivity was observed between PEG–apelin-36 and apelin-36. ► Inotropic effect and circulation time were prolonged with PEG–apelin-36. ► Apelin-36 and PEG–apelin-36 had no effect on blood pressure. Several studies have documented cardiovascular effects of apelin, including enhanced inotropy and vasodilation. However, these cardiovascular effects are short lived due to the predicted short circulating half-life of the apelin peptide. To address this limitation of apelin, we pursued N-terminal PEGylation of apelin and examined the cardiovascular effects of the PEGylated apelin. A 40kDa PEG conjugated apelin-36 (PEG–apelin-36) was successfully produced with N-terminal conjugation, high purity (>98%) and minimum reduction of APJ receptor binding affinity. Using an adenylate cyclase inhibition assay, comparable in vitro bioactivity was observed between the PEG–apelin-36 and unmodified apelin-36. In vivo evaluation of the PEG–apelin-36 was performed in normal rats and rats with myocardial infarction (MI). Cardiac function was assessed via echocardiography before, during a 20min IV infusion and up to 100min post peptide infusion. Similar increases in cardiac ejection fraction (EF) were observed during the infusion of PEG–apelin-36 and apelin-36 in normal rats. However, animals that received PEG–apelin-36 maintained significantly increased EF over the 100min post infusion monitoring period compared to the animals that received unmodified apelin-36. Interestingly, EF increases observed with PEG–apelin-36 and apelin-36 were greater in the MI rats. PEG–apelin-36 had a prolonged circulating life compared to apelin-36 in rats. There were no changes in aortic blood pressure when PEG–apelin-36 or apelin-36 was administered. To our knowledge this is the first report of apelin PEGylation and documentation of its cardiovascular effects.