Molecular indices of apoptosis after intermittent blood and crystalloid cardioplegia.

BACKGROUND: We investigated whether intermittent blood and crystalloid cardioplegia differentially affect myocardial apoptosis and apoptosis gene-related proteins. METHODS AND RESULTS: Rabbit hearts were perfused with Krebs-Henseleit buffer on a Langendorff apparatus. Control hearts (n=6) were perfused for 120 minutes without cardioplegic ischemia. Hearts were arrested for 60 minutes with warm (37 degrees C) crystalloid cardioplegia (iW-CCP) (n=8) or with warm blood cardioplegia (iW-BCP) (n=8) administered intermittently. In cold (0 to 4 degrees C) groups, hearts were arrested for 60 minutes with cold crystalloid cardioplegia (iC-CCP; n=8) or with cold blood cardioplegia (iC-BCP; n=6) administered intermittently. The hearts were reperfused for 30 minutes with Krebs-Henseleit buffer. iC-BCP significantly preserved the recovery of left ventricular and microvascular function compared with the other 3 experimental groups. There were no significant differences in total protein levels of caspase 3, Bcl-2, Bad, and Bax among the groups. iC-BCP significantly induced greater phosphorylation of Bad (5.6+/-0.8-fold) as compared with the other 3 groups (3.4+/-0.6-fold in iC-CCP, P<0.05; 2.5+/-0.3 in iW-BCP, P<0.05; and 1.4+/-0.2 in iW-CCP, P<0.01). iC-BCP induced less caspase 3 activation and apoptosis than the other 3 groups. CONCLUSIONS: iC-BCP is superior to the other cardioplegic solutions in increasing the phosphorylation of Bad, inhibiting the activation of caspase 3, and preventing apoptosis. These effects of iC-BCP were associated with preserved left ventricular function and endothelium-dependent relaxation of coronary microvessels.

Bradykinin preconditioning improves the profile of cell survival proteins and limits apoptosis after cardioplegic arrest.

BACKGROUND: We hypothesized that preconditioning the heart with bradykinin (BK) would improve the profile of antiapoptotic proteins and inhibit myocardial apoptosis. METHODS AND RESULTS: Eighteen rabbit hearts were retrogradely perfused with Krebs-Henseleit buffer (KHB). Six control hearts were perfused with KHB for 90 minutes without cardioplegia ischemia. Six hearts were arrested for 30 minutes (37 degrees C) with crystalloid cardioplegia (CCP). Six BK preconditioning (BKPC) hearts received a 10-minute coronary infusion of 10(-8) M BK-enriched KHB followed by a 5-minute recovery period and were then arrested for 30 minutes with CCP. The hearts were reperfused for 30 minutes with KHB. BKPC significantly improved the recovery of left ventricular pressure (73+/-5 versus 51+/-4 mm Hg; P<0.05) and reduced the percentage of myocardial apoptosis (3.4+/-0.3% versus 1.2+/-0.2%; P<0.05) as compared with CCP. There were no significant differences in total protein levels of caspase 3, Bcl-2, Bad, and Bax, among the groups. Both BKPC and CCP induced phosphorylation of Bad at Ser112, but the BKPC group had higher phosphorylated Bad than CCP (4.4+/-0.5 versus 2.0+/-0.3; P<0.05). Both BKPC and CCP alone increased caspase 3 cleavage and activity as compared with controls (P<0.05 and P<0.01, respectively), but BKPC caused less cleavage and activation of caspase 3 than CCP alone (P<0.05). CONCLUSIONS: BKPC increased Bad phosphorylation, inhibited caspase 3 activation, and limited myocardial apoptosis, which were associated with improvement of left-ventricular performance. These results identify novel molecular mechanisms underlying the protective effects of BKPC during cardiac surgery.