STAT3α interacts with nuclear GSK3beta and cytoplasmic RISK pathway and stabilizes rhythm in the anoxic-reoxygenated embryonic heart

Abstract

Activation of the Janus Kinase 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) pathway is known to play a key role in cardiogenesis and to afford cardioprotection against ischemia-reperfusion in adult. However, involvement of JAK2/STAT3 pathway and its interaction with other signaling pathways in developing heart transiently submitted to anoxia remains to be explored. Hearts isolated from 4-day-old chick embryos were submitted to anoxia (30 min) and reoxygenation (80 min) with or without the antioxidant MPG, the JAK2/STAT3 inhibitor AG490 or the PhosphoInositide-3-Kinase (PI3K)/Akt inhibitor LY-294002. Time course of phosphorylation of STAT3α(tyrosine705) and Reperfusion Injury Salvage Kinase (RISK) proteins [PI3K, Akt, Glycogen Synthase Kinase 3beta (GSK3beta), Extracellular signal-Regulated Kinase 2 (ERK2)] was determined in homogenate and in enriched nuclear and cytoplasmic fractions of the ventricle. STAT3 DNA-binding was determined. The chrono-, dromo- and inotropic disturbances were also investigated by electrocardiogram and mechanical recordings. Phosphorylation of STAT3α(tyr705) was increased by reoxygenation, reduced (~50%) by MPG or AG490 but not affected by LY-294002. STAT3 and GSK3beta were detected both in nuclear and cytoplasmic fractions while PI3K, Akt and ERK2 were restricted to cytoplasm. Reoxygenation led to nuclear accumulation of STAT3 but unexpectedly without DNA-binding. AG490 decreased the reoxygenation-induced phosphorylation of Akt and ERK2 and phosphorylation/inhibition of GSK3beta in the nucleus, exclusively. Inhibition of JAK2/STAT3 delayed recovery of atrial rate, worsened variability of cardiac cycle length and prolonged arrhythmias as compared to control hearts. Thus, besides its nuclear translocation without transcriptional activity, oxyradicals-activated STAT3α can rapidly interact with RISK proteins present in nucleus and cytoplasm, without dual interaction, and reduce the anoxia-reoxygenation-induced arrhythmias in the embryonic heart.

Interplay Between SAFE and RISK Pathways in Sphingosine-1-Phosphate–Induced Cardioprotection

“…Whether the inactivation of FOXO-1 by STAT-3 is direct or consecutive to Akt activation remains to be confirmed. These data confirm similar findings reported in the literature, with inactivation of other pro-apoptotic proteins such as GSK-3β and Bad by STAT-3 [9,34]. However, additional work is required to confirm that the inactivation of these proteins effectively contributes to the cardioprotective effect of the SAFE pathway.…”

The effects of curcumin post-treatment against myocardial ischemia and reperfusion by activation of the JAK2/STAT3 signaling pathway

“…Additionally, in vitro studies have demonstrated that STAT3 potentiates anti-apoptotic signals through the induction of Bcl2 and the inhibition of Caspase3 protein expression [15,16,51]. AG, a JAK2-specific inhibitor, has been used to inhibit the phosphorylation of STAT3 in many experimental studies [8,35]. We used 1-lM AG to investigate the role of the JAK2/STAT3 pathway in mediating Cur posttreatment protection against myocardial IR injury.…”

Remote Limb Ischaemic Postconditioning Protects Against Myocardial Ischaemia/Reperfusion Injury in Mice: Activation of JAK/STAT3-Mediated Nrf2-Antioxidant Signalling

“…Furthermore, the RIPostC group showed more pronounced increase in p-STAT3 Tyr705 expression than the IR group, and that elevation may contribute to the decreased number of apoptotic cardiomyocytes and the attenuation of myocardial infarct size. Although the downstream protective targets activated by STAT3 have not been systematically investigated, some research has reported that phosphorylation of STAT3 can activate downstream protective substrates, including Akt, eNOS, and GSK3β [18, 40]. STAT3, Akt and eNOS have been shown to inhibit opening of the mPTP during reperfusion [41-43], which can maintain mitochondrial membrane integrity and inhibit the activation of the mitochondrial apoptosis pathway.…”