We examined the role for the JAK/STAT signaling pathway in acute
opioid-induced cardioprotection (OIC) and whether
opioid-induced
glycogen synthase kinase-3beta (GSK-3 beta) inhibition is mediated by the JAK/STAT pathway. Rats underwent 30 min of
ischemia and either 5 min or 2 h of reperfusion, followed by tissue isolation for molecular analysis or
infarct size assessment, respectively. Rats were treated with vehicle,
morphine (300 microg/kg), the delta-
opioid agonist
fentanyl isothiocynate (FIT, 10 microg/kg), or the GSK inhibitor
SB-216763 (SB21, 600 microg/kg) 10 min before
ischemia. Five minutes before
opioid or SB21 treatment, some rats received the putative JAK2 inhibitor
AG-490 (3 mg/kg) or the putative JAK3 inhibitor ZM-449829 (3 mg/kg). H9C2 cardiomyoblast cells were also used to investigate FIT-induced signaling (1 microM) in vitro via molecular analysis.
Morphine induced the phosphorylation of JAK2, yet not JAK1, in the area at risk.
Morphine, FIT, and SB21 also reduced
infarct size compared with vehicle (water) when administered before
ischemia [43.0 +/- 2.8, 39.1 +/- 3.1, and 42.1 +/- 2.5 (*P < 0.001, respectively) vs. 58.1 +/- 1.3%, respectively].
AG-490 abrogated OIC, whereas ZM-449829 had no effect on OIC. Cardioprotection was afforded by SB21 even in the presence of
AG-490.
Morphine phosphorylated STAT3, Akt, and
GSK-3beta, and phosphorylation was abrogated by
AG-490. FIT stimulation of H9C2 cells also caused a time-dependent phosphorylation of STAT3, Akt, and
GSK-3beta, and this effect was abrogated by
AG-490. STAT3 phosphorylation was also dependent on
phosphatidylinositol 3-kinase (PI3K) activation in both tissue and H9C2 cells. These data suggest that OIC occurs via the JAK2 regulation of PI3K pathway-dependent STAT3, Akt, and
GSK-3 beta, with
GSK-3 beta contributing a central role in acute OIC.