Volatile
anesthetics protect the heart from
ischemia/reperfusion injury but the mechanisms for this protection are poorly understood. Caveolae, sarcolemmal invaginations, and
caveolins, scaffolding
proteins in caveolae, localize molecules involved in cardiac protection. We tested the hypothesis that caveolae and
caveolins are essential for volatile
anesthetic-induced cardiac protection using cardiac myocytes (CMs) from adult rats and in vivo studies in
caveolin-3 knockout mice (Cav-3(-/-)). We incubated CM with
methyl-beta-cyclodextrin (MbetaCD) or
colchicine to disrupt caveolae formation, and then exposed the myocytes to the volatile
anesthetic isoflurane (30 min, 1.4%), followed by simulated
ischemia/reperfusion (SI/R).
Isoflurane protected CM from SI/R [23.2+/-1.6% vs. 71.0+/-5.8% cell death (assessed by
trypan blue exclusion), P<0.001] but this protection was abolished by MbetaCD or
colchicine (84.9+/-5.5% and 64.5+/-6.1% cell death, P<0.001). Membrane fractionation by
sucrose density gradient centrifugation of CM treated with MbetaCD or
colchicine revealed that buoyant (caveolae-enriched) fractions had decreased phosphocaveolin-1 and
caveolin-3 compared to control CM. Cardiac protection in vivo was assessed by measurement of
infarct size relative to the area at risk and cardiac
troponin levels.
Isoflurane-induced a reduction in
infarct size and cardiac
troponin relative to control (
infarct size: 26.5%+/-2.6% vs. 45.3%+/-5.4%, P<0.01;
troponin: 27.7+/-4.4 vs. 77.7+/-11.8 ng/ml, P<0.05).
Isoflurane-induced cardiac protection was abolished in Cav-3(-/-) mice (
infarct size: 53.4%+/-6.1% vs. 53.2%+/-3.5%, P<0.01;
troponin: 102.1+/-22.3 vs. 105.9+/-8.2 ng/ml, P<0.01).
Isoflurane-induced cardiac protection is thus dependent on the presence of caveolae and the expression of
caveolin-3. We conclude that caveolae and
caveolin-3 are critical for volatile
anesthetic-induced protection of the heart from
ischemia/reperfusion injury.