Connexin 43 (
Cx43) deficiency increases myocardial tolerance to
ischemia-reperfusion injury and abolishes preconditioning protection. It is not known whether modifications in baseline signaling through protective RISK or SAFE pathways or in response to preconditioning may contribute to these effects. To answer this question we used
Cx43(Cre-ER(T)/fl) mice, in which
Cx43 expression is abolished after
4-hydroxytamoxifen (4-OHT) administration. Isolated hearts from
Cx43(Cre-ER(T)/fl) mice, or from
Cx43(fl/fl) controls, treated with vehicle or
4-OHT, were submitted to global
ischemia (40 min) and reperfusion.
Cx43 deficiency was associated with reduced
infarct size after
ischemia-reperfusion (11.17 ± 3.25 % vs. 65.04 ± 3.79, 59.31 ± 5.36 and 65.40 ± 4.91, in
Cx43(fl/fl) animals treated with vehicle,
Cx43(fl/fl) mice treated with 4-OHT, and
Cx43(Cre-ER(T)/fl) mice treated with vehicle, respectively, n = 8-9, p < 0.001). However, the ratio phosphorylated/total
protein expression for Akt, ERK-1/2, GSK3β and STAT3 was not increased in normoxic samples from animals lacking
Cx43. Instead, a reduction in the phosphorylation state of GSK3β was observed in Cx43-deficient mice (ratio: 0.15 ± 0.02 vs. 0.56 ± 0.11, 0.77 ± 0.15, and 0.46 ± 0.14, respectively, n = 5-6, p < 0.01). Furthermore, ischemic preconditioning (IPC, 4 cycles of 3.5 min of
ischemia and 5 min of reperfusion) increased phosphorylation of ERK-1/2, GSK3β, and STAT3 in all hearts without differences between groups (n = 5-6, p < 0.05), although
Cx43 deficient mice were not protected by either IPC or pharmacological preconditioning with
diazoxide. Our data demonstrate that modification of RISK and SAFE signaling does not contribute to the role of
Cx43 in the increased tolerance to
myocardial ischemia-
reperfusion injury and in preconditioning protection.