Tsai Chia-Houng, Yang Sheng-Huei, Chien Ching-Ming, Lu Mei-Chin, Lo Chao-Sheng, Lin Yi-Hsiung, Hu Xiu-Wei, Lin Shinne-Ren
Faculty of Medicinal and Applied Chemistry, Graduate Institute of Natural Products and Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan, ROC.
Clin Exp Pharmacol Physiol. 2006 Mar;33(3):177-82. doi: 10.1111/j.1440-1681.2006.04334.x.
Cardiotoxin III (CTX III) is a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom. This is the first report on the mechanism of the anticancer effect of CTX III in human colorectal cancer Colo205 cells. 2. Cardiotoxin III-induced Colo205 cell apoptosis was confirmed by DNA fragmentation (DNA ladder and sub-G1 formation) with an IC(50) of 4 mg/mL at 48 h. 3. Further mechanistic analysis demonstrate that CTX III induced the loss of mitochondrial membrane potential (Dym), cytochrome c release from mitochondria into the cytosol and activation of capase-9, caspase 3, as well as markedly enhancing the expression of Bax, but not Bcl-2, protein in the cells. Moreover, the CTX III-induced apoptosis was significantly blocked by the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. 4. However, CTX III did not generate the formation of reactive oxygen species and anti-oxidants, including N-acetylcysteine, and catalase could not block CTX III-induced apoptosis in the Colo205 cells. 5. Taken together, these results suggest that CTX III may induce apoptosis through a mitochondrial- and caspase-dependent mechanism and alteration of Bax/Bcl-2 ratio in human colorectal Colo205 cancer cells.
心脏毒素III（CTX III）是一种从眼镜蛇毒中分离出来的含有60个氨基酸残基的碱性多肽。这是关于CTX III对人结肠癌细胞Colo205抗癌作用机制的首次报道。2. 通过DNA片段化（DNA梯状条带和亚G1峰形成）证实了CTX III诱导的Colo205细胞凋亡，48小时时的半数抑制浓度（IC50）为4毫克/毫升。3. 进一步的机制分析表明，CTX III诱导线粒体膜电位（ΔΨm）丧失、细胞色素c从线粒体释放到细胞质中以及激活半胱天冬酶-9、半胱天冬酶-3，同时显著增强细胞中Bax蛋白的表达，但不影响Bcl-2蛋白的表达。此外，广谱半胱天冬酶抑制剂苄氧羰基-Val-Ala-Asp-氟甲基酮可显著阻断CTX III诱导的凋亡。4. 然而，CTX III不会产生活性氧，包括N-乙酰半胱氨酸在内的抗氧化剂以及过氧化氢酶均不能阻断CTX III诱导的Colo205细胞凋亡。5. 综上所述，这些结果表明，CTX III可能通过线粒体和半胱天冬酶依赖性机制以及改变人结肠癌细胞Colo205中Bax/Bcl-2比值来诱导凋亡。
