| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Carnitine is a substance important in the translocating of free fatty acids into the mitochondria matrix for β-oxidation. Accumulated evidences have shown that mitochondrial permeability transition (MPT) is induced by mitochondrial dysfunction, thereby leading to cytochrome (cyt.) c release from mitochondria into the cytosol, activating cysteine proteases (caspases), resulting in apoptosis. In our previous report (Kashiwagi et al., 2001), MPT is in part thought to be regulated by a balance between long chain free fatty acids and L-carnitine in and around the mitochondrial membrane. The present study attempts to clarify the role of acetyl-L-carnitine (ALC) during T_3-induced tadpole tail apoptosis. TK stage X tadpoles of Rana (R.) japonica were exposed to L-3,5,3'-triiodothyronine (T3) in the presence or absence of ALC. Changes in lipid peroxidation, lysosomal acid DNase activity, genomic DNA fragmentation and ladder formation were investigated biochemically using tadpole tails undergoing regression during T_3 enhancement. Increases in lipid peroxide, acid DNase activity, genomic DNA fragmentation and ladder formation with concomitant shortening of T_3-treated tadpole tail were observed. ALC was found to suppress the enhancing effects of T_3 on tail shortening, lipid peroxidation, acid DNase activity, genomic DNA fragmentation and ladder formation. It was also found that acid DNase activity during T_3-induced tadpole tail shortening in culture system was suppressed by an addition of a cysteine protease inhibitor L-trans-epoxysuccinyl-leucylamido-(4-guanidinobutane) (E-64) to culture medium. These results suggested that T_3 induces lipid peroxidation and cyt. c release from mitochondria, thereby activating cysteine protease including lysosomal enzymes and caspase-3, which might elicit acid DNase activation, resulting in tail apoptosis, and ALC was seen to suppress the effects of T_3.
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