Abstract 10246: Hydroxychloroquine Pretreatment Reduces Myocardial Ischemia-Reperfusion Injury: Role of Cardiac Extracellular-Signal-Regulated Kinase 5 and Autophagy

Abstract

Background: Hydroxychloroquine (HCQ) is an antimalarial drug, which is also widely used to treat chronic rheumatologic diseases. Since HCQ was reported to inhibit cell autophagy and to activate extracellular-signal-regulated kinase 5 (ERK5) in vascular endothelial cells, we designed the current study to determine the effects of HCQ on cardiac ischemia-reperfusion (I-R) injury and post-I-R expression of ERK5 and autophagy marker proteins. Methods: Adult C57BL/6J mice of both genders were pretreated with HCQ (50 mg/kg, i.p.) 1 hour prior to isolation of the hearts, which were subjected to 30 min of no-flow global ischemia followed by 60 min of reperfusion in Langendorff mode. Ventricular function was continuously assessed and myocardial infarct size was determined at the end of I-R. Heart samples were collected following normoxic perfusion (no-ischemic controls), I-R, or I-R with HCQ for assessing ERK5 and autophagy-related proteins with Western blots. Results: HCQ pretreatment reduced infarct size significantly in the female hearts (P<0.05) as compared with the male hearts (Fig. A). Post-I-R cardiac function was better in HCQ-treated males (Fig. B). I-R resulted in a robust increase in total ERK5 (Fig. C) and phosphorylated ERK5 (Thr218/Tyr220) in both genders, which was abolished in HCQ-treated groups. Conversely, either I-R or HCQ did not affect the post-I-R cardiac expression of autophagy-related proteins (e.g., Atg5, Beclin-1, LC3II/LC3I ratio), except Beclin-1 phosphorylation was inhibited in HCQ-treated male hearts, but not females (Fig. D). Conclusions: Acute HCQ pretreatment affords cardioprotection against I-R injury in both genders. Interestingly, cardioprotective effects of HCQ are associated with a strong inhibitory effect on the induction of ERK5 following I-R in the heart, indicating a novel molecular mechanism underlying the HCQ-induced cardioprotection. However, the cardioprotective dose of HCQ has no major impact on cardiac autophagy.