Apoptosis and activation of Erkl/2 and Akt in astrocytes postischemia.
We have shown previously that in vitro ischemia could induce apoptosis in primary culture of astrocytes. In this paper we demonstrate that astrocytes in culture could undergo apoptosis during in vitro incubation postischemia. We also measured the changes of phosphorylated Erk1/2 (p-Erk1/2) and phosphorylated Akt (p-Akt) in order to determine whether these two pathways play a role in apoptosis. After 4 h in vitro ischemic incubation of cultured astrocytes, a limited amount of nuclear condensation was demonstrated by Hoechst 33342 staining. When ischemic incubation was halted and the cultures transferred to standard normoxic incubation (postischemia) conditions, DNA fragmentation and apoptosis were demonstrated by TUNEL and DNA laddering analysis. TUNEL-positive astrocytes began to appear at 6 h postischemia and increased in number from 12 h postischemia. Western blot analysis showed that both p-Erk1/2 and p-Akt were elevated in astrocytes subjected to 4 h of ischemia. Elevated p-Erk1/2 levels were sustained during the postischemia incubation for 12 h and decreased significantly afterward, but did not return to the levels in the control cultures that did not experience ischemic insult. In contrast, the p-Akt level continued to increase at 6 and 12 h postischemia before declining significantly. The changes in p-Erk1/2 and p-Akt correlated well with the appearance of apoptotic astrocytes in the culture.
Jiang
Zhongjian
Z
Neuroscience Research Institute, Peking University, Beijing, China.
Zhang
Yun
Y
Chen
Xiao Qian
XQ
Lam
Philip Yeung
PY
Yang
Hui
H
Xu
Qunyuan
Q
Yu
Albert Cheung Hoi
AC
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D001253:Astrocytes / Q000201:enzymology*; D002545:Brain Ischemia / Q000201:enzymology* / Q000473:pathology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000098:blood supply*; D004195:Disease Models, Animal; D004789:Enzyme Activation; D020287:In Situ Nick-End Labeling; D051379:Mice; D008813:Mice, Inbred ICR; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt
D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases