Defective neuropeptide processing and ischemic brain injury: a study on proprotein convertase 2 and its substrate neuropeptide in ischemic brains.
Using a focal cerebral ischemia model in rats, brain ischemia-induced changes in expression levels of mRNA and protein, and activities of proprotein convertase 2 (PC2) in the cortex were examined. In situ hybridization analyses revealed a transient upregulation of the mRNA level for PC2 at an early reperfusion hour, at which the level of PC2 protein was also high as determined by immunocytochemistry and western blotting. When enzymatic activities of PC2 were analyzed using a synthetic substrate, a significant decrease was observed at early reperfusion hours at which levels of PC2 protein were still high. Also decreased at these reperfusion hours were tissue levels of dynorphin-A(1-8) (DYN-A(1-8)), a PC2 substrate, as determined by radioimmunoassay. Further examination of PC2 protein biosynthesis by metabolic labeling in cultured neuronal cells showed that in ischemic cells, the proteolytic processing of PC2 was greatly attenuated. Finally, in mice, an intracerebroventricular administration of synthetic DYN-A(1-8) significantly reduced the extent of ischemic brain injury. In mice those lack an active PC2, exacerbated brain injury was observed after an otherwise non-lethal focal ischemia. We conclude that brain ischemia attenuates PC2 and PC2-mediated neuropeptide processing. This attenuation may play a role in the pathology of ischemic brain injury.
Zhan
Shuqin
S
Robert S. Dow Neurobiology Laboratories, Legacy Research, Portland, Oregon 97232, USA.
Zhao
Hongbo
H
J White
Aaron
A
Minami
Manabu
M
Pignataro
Giuseppe
G
Yang
Tao
T
Zhu
Xiaorong
X
Lan
Jingquan
J
Xiong
Zhigang
Z
Steiner
Donald F
DF
Simon
Roger P
RP
Zhou
An
A
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D004399:Dynorphins / Q000008:administration & dosage / Q000032:analysis* / Q000627:therapeutic use; D017403:In Situ Hybridization; D009479:Neuropeptides; D010446:Peptide Fragments / Q000008:administration & dosage / Q000032:analysis* / Q000627:therapeutic use; D045706:Proprotein Convertase 2 / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D015424:Reperfusion; D020521:Stroke; D013997:Time Factors; D015854:Up-Regulation / Q000235:genetics
D009479:Neuropeptides; D010446:Peptide Fragments; D012333:RNA, Messenger; D004399:Dynorphins; C026770:dynorphin (1-8); D045706:Proprotein Convertase 2