Effects of hsp70.1 gene knockout on the mitochondrial apoptotic pathway after focal cerebral ischemia.
OBJECTIVE
Murine heat-shock protein 70 (HSP70) protein, which is produced from 2 genes, hsp70.1 and hsp70.3, is known to protect the brain against ischemic injury. However, little information is available on the antiapoptotic mechanism of HSP70.1 protein after cerebral ischemia. To evaluate the role of HSP70.1 protein in ischemia, we analyzed the mitochondrial apoptotic pathway using hsp70.1 knockout (KO) mice and their wild-type (WT) mice.


METHODS
hsp70.1 KO and WT mice underwent focal ischemia for 120 minutes. DNA fragmentation was evaluated by TUNEL staining. Cytochrome c release and the activation of caspase-3 were analyzed by Western blotting and immunohistochemistry.


RESULTS
hsp70.1 mRNA was not detected in hsp70.1 KO mice after ischemia, and HSP70 protein expression was markedly suppressed versus WT mice. KO mice showed a significantly greater infarction volume and DNA fragmentation in the cortex than WT mice at 24 hours after ischemia. At 8 hours, cytochrome c release into the cytoplasm was markedly higher in KO mice than in WT mice. Caspase-3 activation was also significantly enhanced in KO mice versus WT mice, as evidenced by higher levels of activated caspase-3 and cleaved gelsolin.


CONCLUSIONS
These findings suggest that the deletion of the hsp70.1 gene increases cytochrome c release into the cytoplasm and subsequent caspase-3 activation, thereby exacerbating apoptosis after focal cerebral ischemia.
Lee
Seung-Hoon
SH
Department of Neurology, National University, Seoul, Republic of Korea.
Kwon
Hyung-Min
HM
Kim
Young-Ju
YJ
Lee
Kyung-Mi
KM
Kim
Manho
M
Yoon
Byung-Woo
BW
D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002544:Cerebral Infarction / Q000209:etiology / Q000473:pathology; D045304:Cytochromes c / Q000032:analysis; D053938:DNA Fragmentation; D004789:Enzyme Activation; D018260:Gelsolin / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D012333:RNA, Messenger / Q000096:biosynthesis
D018260:Gelsolin; D018840:HSP70 Heat-Shock Proteins; C498550:Hsp70.3 protein, mouse; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C081884:heat-shock protein 70.1; D045304:Cytochromes c; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases