Although the phosphatidyl-inositol-3-kinase (PI3K)/Akt pathway is essential for conferring cardioprotection in response to ischemic preconditioning (IP), the role of PI3K/Akt signaling in the infarcted heart for mediating the
anti-arrhythmic effects in response to IP remains unclear. We explored the involvement of PI3K/Akt in the IP-like effect of
connexin 43 and proangiogenic factors with particular regard to its role in protecting against
ischemia-induced
arrhythmia,
heart failure, and myocardial remodeling. Groups of pigs were administered
phosphate-buffered saline (PBS) or
LY294002 solution. Before induction of
myocardial infarction (MI), pigs were grouped according to whether or not they underwent IP. Next, all animals underwent MI induction by
ligation of the left anterior descending (LAD) coronary artery. Myocardial tissues from the pig hearts at 7 days after MI were used to assess myocardium
myeloperoxidase and reaction
oxygen species,
infarct size,
collagen content, blood vascular density, expression of Akt,
connexin 43, and proangiogenic
growth factors, using spectrophotometer, histology, immunohistochemistry, real-time RT-PCR, and western blot. At 7 days after MI, IP significantly reduced animal mortality and malignant ventricular
arrhythmia, myocardial
inflammation,
infarct size, and
collagen content, and improved cardiac function and remodeling; use of the PI3K inhibitor
LY294002 diminished these effects. In parallel with a decline in Akt expression and phosphorylation by MI,
LY294002 injection resulted in significant suppression of
connexin 43 and proangiogenic factor expression, and a reduction of angiogenesis and collateral circulation. These findings demonstrate that the cardioprotective effects of IP on antiventricular
arrhythmia and myocardial repair occur through upregulation of PI3K/Akt-mediated
connexin 43 and
growth factor signaling.