Ischemic preconditioning (IPC) is a protective mechanism against ischemia/reperfusion injury in brain and heart. Our previous studies have shown that IPC via epsilon PKC activation induced the phosphorylation of extracelluar signal regulated kinase1/2 (ERK1/2) and cyclooxygenase-2 (COX-2) leading to the neuroprotection (1). However, transcriptional signal pathways by which IPC regulates COX-2 in brain remain undefined. The signal transducers and activators of transcription (STATs) upregulate COX-2 expression during cardioprotection (2). A previous study with epsilon PKC knock out mouse model suggests that serine-727-STAT3 phosphorylation was mediated by epsilon PKC activation (3). Therefore, in this study, we tested the hypothesis that IPC via epsilon PKC activates STATs transcriptional signaling pathways. Methods: Mixed cortical neuron/astrocyte cell cultures are prepared from rat embryo/neonatal rat (18-19 days old/ 1-2 days old) respectively. Cell cultures were exposed to 1 h of IPC and 48 h of reperfusion later. Epsilon PKC specific activating peptide (100 nM) was administrated to cell culture for 1 h. Cell lysates were isolated from different intervals of reperfusion after IPC or epsilon PKC specific activating peptide treatment for immunoblotting with antibody against p-ERK1/2 and P- ser727-STAT3. Results: Ischemic preconditioning induced the serine-727 phosphorylation of STAT3 from 15 min and was sustained for 2 h of reperfusion. STAT3 phosphorylation was accompanied by the phosphorylation of ERK1/2 (15 min-1 h of reperfusion). Similarly, epsilon PKC specific activating peptide (100 nM) also induced the phosphorylation of STAT3 and ERK1/2. To test whether IPC-induced STAT3 activation is mediated by ERK1/2 activation or by directly PKC activation, PD98059 (MAPK-K inhibitor,0.01 mM) was administrated to cell cultures during and after IPC. PD98059 prevented the IPC-induced phosphorylation of STAT3. Our previous studies showed that Inhibition of ERK1/2 prevented IPC-induced COX-2 expression (1). Based on our findings in future studies, we will further define whether STAT3 activation induces COX-2 expression after IPC. Conclusion: Our findings suggest that IPC via epsilon PKC activation is mediated by ERK1/2->STAT3 pathway and the signaling pathways of epsilon PKC->ERK1/2->STAT3 might be involved COX-2 expression following IPC.
|Journal||Journal of Cerebral Blood Flow and Metabolism|
|Issue number||SUPPL. 1|
|State||Published - Nov 13 2007|
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism