Survival and death-promoting events after transient spinal cord ischemia in rabbits: induction of Akt and caspase3 in motor neurons.
OBJECTIVE
The mechanism of spinal cord injury has been thought to be related to the vulnerability of spinal motor neuron cells to ischemia. However, the mechanisms of such vulnerability are not fully understood. We previously reported that spinal motor neurons might be lost as a result of programmed cell death and investigated a possible mechanism of neuronal death by means of immunohistochemical analysis for CPP32 (caspase3) and serine-threonine kinase (Akt).


METHODS
We used a rabbit spinal cord ischemia model with use of a balloon catheter. The spinal cord was removed at 8 hours or 1, 2, or 7 days after 15 minutes of transient ischemia, and histologic changes were studied with hematoxylin and eosin staining. Western blot analysis for Akt and caspase3, temporal profiles of Akt and caspase3 immunoreactivity, and double-label fluorescence immunocytochemical studies were performed.


RESULTS
The majority of motor neurons were preserved until 2 days but were selectively lost at 7 days of reperfusion. Western blot analysis revealed no immunoreactivity for Akt and caspase3 in the sham-operated spinal cords. However, such immunoreactivity became apparent at 8 hours after transient ischemia, decreased at 1 day, and returned to the baseline level at 2 days. A double-label fluorescence immunocytochemical study revealed that both Akt and caspase3 were positive at 8 hours of reperfusion in the same motor neurons, which eventually die.


CONCLUSIONS
These results suggests that transient spinal cord ischemia activates both cell death and survival pathways after ischemia. The activation of Akt protein at the early stage of reperfusion might be one of the factors responsible for the delay in neuronal death after spinal cord ischemia.
Sakurai
Masahiro
M
Department of Cardiovascular Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Nagata
Tatsuya
T
Abe
Koji
K
Horinouchi
Takashi
T
Itoyama
Yasuto
Y
Tabayashi
Koichi
K
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000032:analysis / Q000502:physiology*; D002404:Catheterization / Q000009:adverse effects; D002452:Cell Count; D002470:Cell Survival; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D009046:Motor Neurons / Q000201:enzymology*; D010264:Paraplegia / Q000145:classification / Q000209:etiology*; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000502:physiology*; D011817:Rabbits; D012720:Severity of Illness Index; D020760:Spinal Cord Ischemia / Q000150:complications* / Q000473:pathology*; D013997:Time Factors
D017346:Protein Serine-Threonine Kinases; D053148:Caspase 3; D020169:Caspases