Mechanisms of cellular death pattern induced by the ingredients of areca nut

• Main Authors: Yung-Chih Cheng, 鄭詠之
• Other Authors: Young-Chau Liu
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/40292082003546988398

碩士 === 嘉南藥理科技大學 === 生物科技系暨研究所 === 98 === Abstract Arecoline, the major alkaloid of areca nut (AN), was known to induce apoptosis; however, we found that AN extract (ANE) itself and its 30-100 kDa fraction (ANE 30-100K) caused autophagy-like responses in oral cancer OECM-1 cells, including microtubule-associated protein 1 light chain 3 (LC3)-II accumulation and morphological changes distinct to those of apoptosis. Therefore, we were interested in assessing whether ANE 30-100K stimulates autophagic flux and the possible involved mechanisms. We found that ANE- and ANE 30-100K-induced LC-II accumulation was further elevated in the presence of lysosomal protease inhibitors in oral fibroblasts CMT415, suggesting autophagic flux induction by these two AN components. After specific inhibition by RNAi strategies in OECM-1cells, ANE 30-100K-mediated cytotoxicity and LC3-II accumulation were significantly attenuated in Atg5 knocked down clones, but not evidently affected in Beclin-1 knocked down clones. In contrast, Beclin-1, but not Atg5, knocked down clones were more resistant to glucose starvation. On the other hand, ANE 30-100K was known to stimulate the phosphorylation of AMP-activated protein kinase (AMPK) in Jurkat T cells, whereas arecoline exerts a contrary effect on this kinase; however, our preliminary results showed that ANE 30-100K only mildly upregulated AMPK phosphorylation in OECM-1, and ANE 30-100K-induced LC3-II accumulation and cytotoxicity in an AMPK RNAi-inhibited OECM-1 clone were similar to control cells. Interestingly, the AMPK activator, AICAR, restored arecoline-inhibited AMPK phosphorylation and cell viability in Jurkat T cells. These results suggest that Atg5 may play a more important role than Beclin-1 and AMPK in the ANE 30-100K-induced autophagy, whereas AMPK may be required for arecoline-induced apoptosis in OECM-1 cells. Keywords: Areca nut, Arecoline, AMPK, Beclin-1, Atg5, Autophagy