Geranylgeranylacetone and volatile anesthetic-induced cardiac protection synergism is dependent on caveolae and caveolin-3.

Purpose: Pharmacological preconditioning, including that with geranylgeranylacetone (GGA) and volatile anesthetics, has been shown to confer cardiac protection from ischemia/reperfusion injury although the mechanisms for this protection are poorly understood. Caveolins, integral membrane proteins that act as scaffolding proteins in caveolar membranes, localize molecules involved in cardiac protection. We have tested the hypothesis that caveolin-3 (Cav-3), the predominant isoform in cardiac myocytes, is essential for the synergistic effect observed between GGA and volatile anesthetics.

Methods: Mice were randomly assigned to receive GGA, isoflurane [0.5 and 1.0 minimum alveolar concentration (MAC)], or GGA + isoflurane (0.5 MAC). An in vivo mouse model of ischemia/reperfusion injury was tested in wild-type and Cav-3 knockout mice, and the infarct size was determined. Biochemical assays were also performed in excised hearts.

Results: Geranylgeranylacetone and therapeutic isoflurane (1.0 MAC) independently reduced infarct size (31.6 ± 6.1 and 28.0 ± 5.0% of the area at risk, respectively; n = 10) as compared to the controls (45.8 ± 9.4%; n = 10). The combination GGA + sub-therapeutic isoflurane (0.5 MAC) further decreased the infarct size to 19.3 ± 5.1% (n = 10). Preconditioning [GGA, isoflurane (1.0 MAC), and GGA + isoflurane] increased the amount of Cav-3 protein in the discontinuous sucrose-gradient buoyant fractions. Additionally, cardiac protection was not observed in Cav-3 knockout mice following the administration of GGA, isoflurane, and GGA + isoflurane.

Conclusions: Combined administration of GGA + isoflurane had a synergistic effect, enhancing the protection against myocardial infarction to a greater extent than either drug alone. This beneficial effect is mediated by Cav-3 expression.