Increased carnitine-dependent fatty acid uptake into mitochondria of human colon cancer cells induces apoptosis
Increased carnitine-dependent fatty acid uptake into mitochondria of human colon cancer cells induces apoptosis
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DOI：
10.1093/jn/135.6.1510
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发表时间：
2005-06-01
影响因子：
4.2
通讯作者：
Daniel, H
中科院分区：
文献类型：
--
作者：
Wenzel, U;Nickel, A;Daniel, H
肉毒碱依赖的脂肪酸输入到线粒体和β-氧化似乎在肿瘤细胞中受损。在本研究中，我们表明，供应棕榈酰肉毒碱与L-肉毒碱一起有效地诱导HT-29人结肠癌细胞的凋亡作为一个结果，加速脂肪酸氧化。Caspase-3样活性，测定的裂解率的荧光四肽底物和核碎片后，在固定的细胞DNA标记荧光显微镜，作为凋亡的指标。无论是L-肉毒碱，也没有棕榈酰肉毒碱单独能够增加半胱天冬酶-3样活性和DNA片段化，但当提供在一起，细胞凋亡发生。外源性肉毒碱确实能够增强脂肪酸摄取到线粒体中，这通过荧光棕榈酸类似物的流入增加来证明。线粒体中脂肪酸可用性的增强导致O-2（-）生成的增加，如O-2（-）敏感性荧光染料所检测到的，表明递送底物的氧化。苯醌，一种O-2（-）清除剂，阻断O-2的产生，并阻止由棕榈酰肉碱和肉碱的组合所引发的细胞凋亡。神经酰胺合成抑制剂伏马菌素对棕榈酰肉毒碱/肉毒碱诱导的细胞凋亡的作用的缺乏进一步支持了凋亡性细胞死亡具体是由于脂肪酸氧化的观点。与HT-29细胞相反，未转化的人结肠细胞对外源性棕榈酰肉碱/肉碱没有反应，也没有观察到细胞凋亡。总之，我们的研究提供的证据表明，有限的线粒体脂肪酸进口在人类结肠癌细胞防止高速率的线粒体O-2（-）生产和保护结肠癌细胞凋亡，可以克服由外源性肉毒碱供应。
Carnitine-dependent fatty acid import into mitochondria and beta-oxidation seem to be impaired in tumor cells. In the present study we show that a supply of palmitoylcarnitine together with L-carnitine potently induces apoptosis in HT-29 human colon cancer cells as a consequence of accelerated fatty acid oxidation. Caspase-3-like activities, measured by the cleavage rate of a fluorogenic tetrapepticle substrate and nuclear fragmentation determined after DNA labeling in fixed cells by fluorescence microscopy, served as indicators of apoptosis. Neither L-carnitine nor palmitoylcarnitine alone were able to increase caspase-3-like activities and DNA fragmentation, but when provided together, apoptosis occurred. That exogenous carnitine was indeed able to enhance fatty acid uptake into mitochondria was demonstrated by an increased influx of a fluorescent palmitic acid analog. Enhanced fatty acid availability in mitochondria led to an increased generation of 0(2)(-), as detected by a O-2(-) sensitive fluorogenic dye, indicating oxidation of delivered substrates. Benzoquinone, an O-2(-) scavenger, blocked O-2 generation and prevented apoptosis as initiated by the combination of palmitoylcarnitine and carnitine. The lack of effect of the ceramide synthesis inhibitor fumonisin on palmitoylcarnitine/carnitine-induced apoptosis further supports the notion that apoptotic cell death is specifically due to fatty acid oxidation. In contrast to HT-29 cells, nontransformed human colonocytes did not respond to exogenous palmitoylcarnitine/carnitine and no apoptosis was observed. In conclusion, our studies provide evidence that a limited mitochondrial fatty acid import in human colon cancer cells prevents high rates of mitochondrial O-2(-) production and protects colon cancer cells from apoptosis that can be overcome by an exogenous carnitine supply.