The activated caveolin‐3/μ‐opioid receptor complex drives morphine‐induced rescue therapy in failing hearts

Background and Purpose Opioid analgesics can alleviate ischaemia/reperfusion (I/R) injury in chronic heart failure. However, the underlying mechanisms and targets remain unknown. Here, we investigate if caveolin‐3 (Cav3) interacts with μ opioid receptors and if Cav3–μ receptor interactions play a role in morphine‐induced cardioprotection in failing hearts. Experimental Approach Cav3 and μ receptor proteins in human and rat heart tissue were determined by western blot, immunofluorescence and co‐immunoprecipitation. Methyl‐β‐cyclodextrin (MβCD), a destroyer of caveolae, and AAV‐Cav3 shRNA were used to reduce Cav3 expression in failing rat hearts. CTOP, a specific μ antagonist, was administrated before morphine preconditioning in perfused failing heart models of myocardial I/R injury. Key Results Levels of Cav3 and μ receptor proteins were significantly higher in human and rat myocardial tissues with heart failure than in control tissues. Cav3 and μ receptor expression levels were positively correlated with disease severity. The signal of the cardiac Cav3 protein was colocalized with μ receptor in both the human and rat heart sections. Disruption of caveolae in the failing heart by either MβCD or AAV‐Cav3 shRNA significantly inhibits morphine‐induced phosphorylation of ERK1/2 and cardioprotection. Administration of CTOP substantially reduced Cav3 expression and morphine‐induced cardioprotective effect in heart failure. Conclusion and Implications Our data suggest that up‐regulation of the Cav3/μ receptor complex is critical for morphine protection of the failing heart against I/R injury by regulating the ERK1/2 pathway. The activated Cav3/μ receptor complex is an understudied therapeutic target for opioid treatment of heart failure and ischaemic insult.