Autophagosome Formation is Required for Cardioprotection by Chloramphenicol

Aims: Chloramphenicol (CAP), a broad spectrum antibiotic, was shown to protect the heart against ischemia/reperfusion (I/R) injury. CAP also induces autophagy, however, it is not known whether CAP-induced cardioprotection is mediated by autophagy. Therefore, here we aimed to assess whether activation of autophagy is required for the infarct size limiting effect of CAP and to identify which component of CAP-induced autophagy contributes to cardioprotection against I/R injury.

Main Methods: Hearts of Sprague-Dawley rats were perfused in Langendorff mode with Krebs-Henseleit solution containing either vehicle (CON), 300μM CAP (CAP), CAP and an inhibitor of autophagosome-lysosome fusion chloroquine (CAP+CQ), or an inhibitor of autophagosome formation, the functional null mutant TAT-HA-Atg5 protein (CAP+K130R), and K130R or CQ alone, respectively. After 35min of aerobic perfusion, hearts were subjected to 30min global ischemia and 2h reperfusion. Autophagy was determined by immunoblot against LC3 from left atrial tissue. Infarct size was measured by TTC staining, coronary flow was measured, and the release of creatine kinase (CK) was assessed from the coronary effluent.

Key Findings: CAP treatment induced autophagy, increased phosphorylation of Erk1/2 in the myocardium and significantly reduced infarct size and CK release. Autophagy inhibitor TAT-HA-Atg5 abolished cardioprotection by CAP, while in CAP+CQ hearts infarct size and CK release were reduced similarly to as seen in the CAP-treated group.

Conclusion: This is the first demonstration that autophagosome formation but not autophagosomal clearance is required for CAP-induced cardioprotection.

Significance: Inducing autophagy sequestration might yield novel therapeutic options against acute ischemia/reperfusion injury.