1996 Fiscal Year Final Research Report Summary
The pathogenesis and treatment of cerebral ischemia based on the mechanism of cytoskeletal changes
| Project/Area Number |
07457357
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Anesthesiology/Resuscitation studies
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| Research Institution | Yamaguchi University |
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Principal Investigator |
SAKABE Takefumi Yamaguchi Univ.School of Medicine, Professor, 医学部, 教授 (40035225)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIKAWA Toshizo Yamaguchi Univ.Sch.of Med., Research Associate, 医学部, 助手 (90034991)
MATSUMOTO Mishiya Yamaguchi Univ.Hospital., Assistant Professor, 医学部・附属病院, 講師 (60243664)
SANO Takanobu Yamaguchi Univ.Hospital., Recearch Associate, 医学部・附属病院, 助手 (40243670)
NAKAKIMURA Kazuhiko Yamaguchi Univ.Sch.of Med., Associate Professor, 医学部, 助教授 (50180261)
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| Project Period (FY) |
1995 – 1996
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| Keywords | cerebral ischemia / ischemic neuronal death / cytoskeleton / calpain / calpastatin / fodrin / calpain inhibitor-1 / hypothermia |
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| Research Abstract |
Introduction
Increase in intracellular calcium (Ca^<2+>) has been speculated to play a pivotal role in the progress of ischemic brain damage. Calpain, calcium-dependent neutral protease, and its endogenous inhibitor calpastatin, may be involved in the pathogenesis, by influencing the breakdown of fodrin, a major constituent of the membrane skeleton in the central nervous system (CNS). We examined the activity of calpain/calpastatin and the proteolysis of alpha-and beta-subunits of fodrin during ischemia in the rat.
Methods and Results
Decapitated heads of rats were incubated at 37ﾟC for 0-40 min. The proteolysis of fodrin in the homogenates were analyzed by Western blotting. The 100 000xg supernatant was applied to a DEAE-cellulose column, and the amount of m-calpain in the 0.4 M NaCl eluate was measured by spectrophotometry as the release of trichloroacetic acid-soluble peptides from azocasein in the presence of 5 mM Ca^<2+>. Calpastatin activity in the heat treated 100 000xg supernatant
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was determined by measuring the inhibition of bovine lung m-calpain.
Degradation of alpha-and beta-fodrin were progressively increased with ischemia time. The amount of m-calpain showed no significant changes, and calpastatin activity decreased significantly in 40 minute-period of ischemia.
When the heads of rats were incubated at 33ﾟC for 40 min, breakdown product (150-kD fagment) was decreased significantly comparing to that from the samples of normothermia (37ﾟC).
In the brain subjected to 30 minute-forebrain ischemia, the amount of calpain was significatnly decreased, and the breakdown of alpha-fodrin was significantly increased during and 60 min after ischemia.
Pretreatment with calpain inhibitor-1 (CAI) (iv.) showed the trend inhibition of calpain activation and significant attenuation of the breakdown of alpha-fodrin.
Zymography, applicable to smaller samples, showed the regional variation of the m-calpain activation and breakdown of fodrin, which were marked in the hippocampus during (15min) and (60min) after ischemia.
Conclusions
The results suggest that ischemia induces the proteolysis of alpha-and beta-fodrin chiefly through an activation of m-calpain. Hypothermia and CAI provide substantial protective effect by modifying the calpain activity and hence the breakdown of the cytoskeleton of CNS. Less
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