Sphingomyelinase-induced ceramide production stimulate calcium-independent JNK and PP2A activation following cerebral ischemia.
OBJECTIVE
Intracellular calcium overload is considered to be a key pathologic factor for ischemic stroke; however, there are other signal molecules produced in response to ischemic stimuli. The present study investigated the ceramide signal pathway, which is associated with cerebral ischemia in a calcium-independent manner.


METHODS
Male Sprague-Dawley rats were subjected to 10-minute four-vessel occlusion. Ketamine, a blocker of calcium-ion channels, or TPCK or fumonisin B1, inhibitors of ceramide production in the sphingomyelinase and de novo pathways, respectively, were administrated to the rats prior to inducing ischemia. Ceramide levels were determined by immunofluorescence, protein activity was assessed by immunoblotting and PP2A activity was measured using a protein phosphatase assay system.


RESULTS
The morphologic data indicated that ischemia-induced ceramide production was largely restricted to glia cells in the rat hippocampus. TPCK, but not ketamine or fumonisin B1, blocked the ceramide pathway and its downstream molecules, JNK and PP2A.


CONCLUSIONS
Cerebral ischemia up-regulates the sphingomyelin-ceramide pathway, which involves calcium-independent JNK and PP2A activation in hippocampal glia; this may play a significant role in cerebral lesions post-ischemia.
Tian
He-ping
HP
Nanjing Medical University, PR China.
Qiu
Tian-zhu
TZ
Zhao
Jie
J
Li
Li-xin
LX
Guo
Jun
J
D000818:Animals; D002545:Brain Ischemia / Q000139:chemically induced / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D048688:MAP Kinase Kinase 7 / Q000378:metabolism*; D008297:Male; D009457:Neuroglia / Q000378:metabolism; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002518:Ceramides; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D048688:MAP Kinase Kinase 7; D054648:Protein Phosphatase 2; D013108:Sphingomyelin Phosphodiesterase; D002118:Calcium