Differential Activation of p38 MAPKs in Microglia and Astrocytes of Gerbil Brain after Global Ischemia

초록

Background and Purpose: The p38 kinase, a member of the mitogen-activated protein kinase (MAPK), is implicated in pathological changes in the course of inflammatory and apoptotic processes in various cell types including neurons. Induction of p38 MAPK has been reported after global (1) and focal ischemia (2), in which anti-ACTIVE-p38 antibody was utilized to assess the activity of p38 MAPKs, therefore giving us a limited information on the roles of p38 isoforms. Previously, we demonstrated that two p38 MAPK isoforms, p38a and p38b, among four isoforms were abundantly but differentially expressed in normal mouse brain (3). Here we demonstrated evidence for the changes in the expression as well as the induction of p38 kinase isoforms in pathological states. Differential activation of p38a and p38b was observed in microglia and astrocytes, respectively, at different time points after transient global ischemia. Methods: Adult male Mongolian gerbils, weighing 60-70 g, were anesthetized with ketamine (50 mg/kg) and xylazine hydrochloride (2.5 mg/kg). Bilateral common carotid arteries were dissected and occluded with microaneurysmal clips for 10 min. During the operation and until they were awake, body temperature was monitored by the rectal thermometer, and maintained at 37 oC. In sham-operated group, the same procedure was performed without carotid occlusion. 1hr, 4hr, 1d, 2d, and 4d after ischemia hippocampus extracts were prepared and Western analysis and kinase assay were employed to assess the induction and activation of p38a and p38b in post ischemic brain. Cellular localization of p38 MAPMK isoforms in post-ischemic brain was also examined by immunohistological staining by using anti-p38a and p38b specific antibodies. Results: Kinase activities of both p38a and p38b were induced in hippocampus after global ischemia at different time points. The induction of p38a was proceeded and reached to peak activation at 1-2d after ischemia, whereas the activation of p3