Chaire de Recherche sur les Agents Anticancéreux d'Origine Naturelle, Laboratoire LASEVE, Université du Québec à Chicoutimi, Département des Sciences Fondamentales, 555 boul. de l'Université, Chicoutimi (Québec), Canada.
INRS-Institut Armand-Frappier, Université du Québec, 531 boul. des Prairies, Laval (Québec), Canada.
PLoS One. 2018 Mar 14;13(3):e0193386. doi: 10.1371/journal.pone.0193386. eCollection 2018.
Betulin has a wide range of biological and pharmacological properties with its anticancer activity attracting most of the attention as it offers a possible alternative treatment to chemotherapy. However, betulin's in vivo biological effectiveness is limited by its poor solubility. As such, we synthesized polar glycosylated derivatives to increase its hydrosolubility and enhance its pharmacological properties. Among these synthesized compounds, 28-O-α-l-rhamnopyranosylbetulin 3β-O-α-l-rhamnopyranoside (Bi-L-RhamBet) was assessed for its cytotoxic effects against a suite of lung cancer cell lines. We also investigated its mechanism of action using an A549 lung cancer cell line. Our results showed that Bi-L-RhamBet exhibited potent cytotoxic activity toward lung cancer cell lines including A549, NCI-H2087, NCI-H522, NCI-H1993 NCI-H1755, and LLC1 having IC50 values ranging from 2.9 to 5.9 μM. Moreover, Bi-L-RhamBet (50 mg/kg) significantly inhibited tumor growth with a treatment-to-control ratio (T/C) of 0.54 and a tumor growth inhibition rate of 46% at day 18 (p < 0.05). Microscopic observations of A549 cells, double stained with acridine orange and ethidium bromide, showed apoptotic features. Bi-L-RhamBet induced activation of pro-apoptotic caspases 8, 9, and 3/7 as well as causing DNA fragmentation. Moreover, a marked increase in mitochondrial ROS (mROS) was coupled with a reduction of mitochondrial potential. Interestingly, the presence of mitochondrial electron transport chain (ETC) inhibitors, including rotenone, malonate, and antimycin A, reduced mROS production, and the activation of caspases suggesting that Bi-L-RhamBet disturbs the ETC. Finally, dichloroacetate, a pyruvate dehydrogenase kinase inhibitor potentiated the cytotoxicity of Bi-L-RhamBet against A549 cells. Taken together, these data suggest that Bi-L-RhamBet can induce apoptotic cell death via disturbance of mitochondrial electron transfer chain, reduced ROS production, and decreased membrane potential.
白桦脂具有广泛的生物学和药理学特性，其抗癌活性引起了广泛关注，因为它为化疗提供了一种可能的替代治疗方法。然而，白桦脂的体内生物有效性受到其较差的水溶性的限制。因此，我们合成了极性糖基化衍生物以增加其水溶解度并增强其药理特性。在这些合成的化合物中，28-O-α-l-鼠李吡喃糖苷白桦脂醇 3β-O-α-l-鼠李吡喃糖苷（Bi-L-RhamBet）被评估了对一系列肺癌细胞系的细胞毒性作用。我们还使用 A549 肺癌细胞系研究了其作用机制。我们的结果表明，Bi-L-RhamBet 对包括 A549、NCI-H2087、NCI-H522、NCI-H1993、NCI-H1755 和 LLC1 在内的肺癌细胞系具有很强的细胞毒性作用，IC50 值范围为 2.9 至 5.9 μM。此外，Bi-L-RhamBet（50 mg/kg）在第 18 天显著抑制肿瘤生长，治疗对照比（T/C）为 0.54，肿瘤生长抑制率为 46%（p<0.05）。吖啶橙和溴化乙锭双重染色的 A549 细胞的显微镜观察显示出凋亡特征。Bi-L-RhamBet 诱导了促凋亡半胱天冬酶 8、9 和 3/7 的激活，并导致 DNA 片段化。此外，线粒体 ROS（mROS）的显著增加伴随着线粒体电势的降低。有趣的是，存在线粒体电子传递链（ETC）抑制剂，包括鱼藤酮、丙二酸和抗霉素 A，可减少 mROS 的产生和半胱天冬酶的激活，表明 Bi-L-RhamBet 扰乱了 ETC。最后，丙酮酸脱氢酶激酶抑制剂二氯乙酸增强了 Bi-L-RhamBet 对 A549 细胞的细胞毒性。总之，这些数据表明，Bi-L-RhamBet 可以通过干扰线粒体电子传递链、减少 ROS 产生和降低膜电位来诱导细胞凋亡死亡。
