Caspase-3 is activated following axotomy of neonatal facial motoneurons and caspase-3 gene deletion delays axotomy-induced cell death in rodents.
In this report, we examined the possible functions of the cell death protease, caspase-3, in the axotomy-induced apoptosis of facial motoneurons in newborn rodents. Using in situ hybridization and Western blot, we found higher levels of caspase-3 mRNA and pro-caspase-3 protein expression in motoneurons of neonatal and 2-week-old rats than adult rats. Following facial motoneuron axotomy, caspase-3 mRNA and protein expression increased in motoneurons of both neonatal and adult rats. However, using an antibody directed to the activated form of the caspase-3 protease, we found that catalytically active caspase-3 was present only in axotomized neonatal motoneurons. As motoneurons in neonatal but not adult rodents are susceptible to axotomy-induced apoptosis, we hypothesized that caspase-3 may play a role in their demise. To determine the necessity of caspase-3 activation in axotomy-induced apoptosis, we counted the number of surviving motoneurons at 4 and 7 days following axotomy in wild type mice and caspase-3 gene-deleted mice. There were nearly three times more surviving motoneurons in caspase-3 gene-deleted mice than in wild type mice at both 4 days (mean 1074 vs. 464, P<0.005) and 7 days (mean 469 vs. 190, P<0.005) following injury, indicating a slower rate of death. Examination of the dying motoneurons using TUNEL staining (for fragmented DNA) and bisbenzimide staining (for nuclear morphology) revealed incomplete nuclear condensation in caspase-3-deficient motoneurons. These results demonstrate that caspase-3 activation plays important roles in the rapid demise of axotomized neonatal motoneurons.
Vanderluit
J L
JL
CORD (Collaboration on Repair Discoveries), University of British Columbia, Vancouver, British Columbia, Canada.
McPhail
L T
LT
Fernandes
K J
KJ
McBride
C B
CB
Huguenot
C
C
Roy
S
S
Robertson
G S
GS
Nicholson
D W
DW
Tetzlaff
W
W
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000235:genetics*; D019771:Axotomy; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D005154:Facial Nerve / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005333:Fetus; D017353:Gene Deletion; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology; D009410:Nerve Degeneration / Q000201:enzymology* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D012333:RNA, Messenger; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases