We investigated the effectiveness of perconditioning (Perc) applied at different time points along with the role of RISK, SAFE, STAT5 and eNOS pathways.
METHODS AND RESULTS: Anesthetized rabbits were subjected to 30-min
ischemia/3-hour reperfusion. Perc, consisted of 4 cycles of 1-min
ischemia/reperfusion, was applied in the carotid artery at different time points. Perc was started and ended during
ischemia, started during
ischemia and ended at the beginning of reperfusion, started at the end of
ischemia and ended at reperfusion and started and ended during reperfusion. The PI3K inhibitor
wortmannin, or the JAK-2 inhibitor
AG490, was also applied and the
infarct size was assessed. In another series assigned to the previous groups, the phosphorylation of Akt, PI3K, ERKs1/2, GSK3β, STAT3, and STAT5 was evaluated. All Perc groups had smaller
infarction compared to those without Perc, independently of PI3K or JAK-2 inhibition. STAT5 was the only molecule that was phosphorylated in parallel with cardioprotection. Since Src and
angiotensin II mediate the STAT5 pathway, we administered the Scr inhibitor PP1 and the
angiotensin II receptor antagonist valsartan. PP1 and
valsartan prevented STAT5 phosphorylation, but did not abrogate the effect of Perc. Furthermore, the NOS inhibitor
L-NAME was administered and abrogated the
infarct size limiting effect of Perc. In parallel, the expression of cleaved
caspase-3 was elevated only in the control and Perc-A-
L-NAME groups.
CONCLUSION: