Recently, we demonstrated that
melatonin reduced
protein kinase RNA (PKR)-like ER
kinase (PERK)-
eukaryotic initiation factor 2 alpha (eIF2α)-activating transcription factor-4 (ATF4)-mediated myocardial endoplasmic reticulum (ER) stress and apoptosis during
myocardial ischemia-reperfusion (MI/R) injury. However, the underlying mechanisms are still not clear.
Myocardial reperfusion injury salvage
kinase (RISK) pathway as well as survivor activating factor enhancement (SAFE) pathway are two pivotal intrinsic pro-survival signaling cascades. In this study, we performed in vivo and in vitro experiment to investigate the ameliorative effect of
melatonin on ER stress with a focus on RISK and SAFE pathways interaction. Male C57Bl/6 mice received
melatonin (300 μg/25 g/day, 3 days before MI/R surgery; 300 μg/25 g, 25 min before the onset of
ischemia) pre-treatment with or without the administration of
LY294002 (a PI3K/Akt inhibitor),
U0126 (an ERK1/2 inhibitor) or
AG490 (a STAT3 pathway inhibitor). H9c2 cells were pre-treated with
melatonin (100 μM, 8 h) in the presence or absence of
LY294002,
U0126 or
AG490. Compared with the I/R-injured group,
melatonin effectively reduced myocardial apoptosis, oxidative stress and improved cardiac function. In addition,
melatonin pre-treatment also increased the phosphorylation of Akt, GSK-3β, ERK1/2 and STAT3 and reduced PERK-eIF2α-ATF4-mediated ER stress. However, these effects were blocked by
LY294002,
U0126 or
AG490. Additionally, either
LY294002 or
U0126 treatment could inhibit STAT3 phosphorylation, whereas
AG490 administration also reduced both Akt and ERK1/2 phosphorylation, indicating an interplay exists between RISK and SAFE pathways in
melatonin's cardioprotective effect. In summary, our study demonstrates that RISK and SAFE pathways mediate the cardioprotective effect of
melatonin against MI/R injury.
Melatonin pre-treatment attenuates PERK-eIF2α-ATF4-mediated ER stress and apoptosis during MI/R injury via RISK and SAFE pathways interaction.