Herbal melanin inhibits colorectal cancer cell proliferation by altering redox balance, inducing apoptosis, and modulating MAPK signaling
Herbal melanin inhibits colorectal cancer cell proliferation by altering redox balance, inducing apoptosis, and modulating MAPK signaling
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DOI：
10.1186/s12935-020-01206-x
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发表时间：
2020-04-16
影响因子：
5.8
通讯作者：
Abdulla, Maha-Hamadien
中科院分区：
文献类型：
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作者：
Al-Obeed, Omar;El-Obeid, Adila Salih;Abdulla, Maha-Hamadien
结直肠癌是最需要安全有效化疗的恶性肿瘤之一。评价天然产物为基础的抗癌药物作为辅助治疗，副作用少，在很大程度上是未开发的研究领域。草药黑色素（HM）是黑种草子种皮的提取物，通过Toll样受体4（TLR 4）调节炎症反应。该TLR 4受体也参与细胞凋亡的调节。因此，我们探讨了HM的抗癌潜力，特别是其对腺癌和转移性结直肠癌（mCRC）细胞死亡的分子机制的影响。方法MTT法检测细胞活力;细胞活性氧（ROS），谷胱甘肽水平和凋亡状态进行了评估，使用荧光和比色检测方法。采用Western blot技术和线粒体过渡孔分析试剂盒研究HM诱导的细胞凋亡和其他信号通路。分别使用siRNA技术和中和抗体进行TLR 4受体下调和阻断。结果HM对结肠癌细胞株HT 29和mCRC SW 620的增殖有明显的抑制作用。此外，HM增强ROS产生并降低谷胱甘肽水平。HM诱导的细胞凋亡与线粒体外膜通透性和细胞色素c释放、Bcl 2家族蛋白的抑制和caspase-3/-7的激活相关。此外，HM通过激活JNK通路和抑制ERK磷酸化来调节MAPK通路。TLR 4受体下调增强HM诱导的细胞凋亡，而TLR 4受体阻断剂部分减轻HM抑制的ERK磷酸化。结论HM可通过TLR 4抑制MAPK信号通路，促进结直肠癌细胞凋亡，是一种有前景的天然药物。
Background Colorectal carcinoma is one of the most deadly cancers that requests effective and safe chemotherapy. Evaluation of natural product-based anticancer drugs as adjuvant treatment with fewer side effects is largely unexplored research fields. Herbal melanin (HM) is an extract of the seed coats of Nigella sativa that modulates an inflammatory response through toll-like receptor 4 (TLR4). This TLR4 receptor is also involved in the modulation of apoptosis. We therefore explored the anticancer potential of HM and specifically its effect on the molecular mechanisms underlying adenocarcinoma and metastatic colorectal cancer (mCRC) cell death in vitro. Methods Cell viability was evaluated using the MTT assay. Cellular reactive oxygen species (ROS), glutathione levels, and apoptotic status were assessed using fluorometric and colorimetric detection methods. HM-induced apoptotic and other signaling pathways were investigated using Western blot technology and mitochondrial transition pore assay kit. TLR4 receptor downregulation and blockade were performed using siRNA technology and neutralizing antibody, respectively. Results Our results showed that HM inhibited the proliferation of the colorectal adenocarcinoma HT29 and mCRC SW620 cell lines. Furthermore, HM enhanced ROS production and decreased glutathione levels. HM-induced apoptosis was associated with mitochondrial outer membrane permeability and cytochrome c release, inhibition of the Bcl2 family proteins, and activation of caspase-3/-7. In addition, HM modulated MAPK pathways by activating the JNK pathway and by inhibiting ERK phosphorylation. TLR4 receptor downregulation enhanced HM-induced apoptosis while TLR4 receptor blockade partially alleviated HM-inhibited ERK phosphorylation. Conclusion Altogether, these findings indicate that HM exerts pro-apoptotic effects and inhibits MAPK pathway through TLR4 in mCRC and colorectal adenocarcinoma cells, suggesting HM as a promising natural-based drug for the treatment of colorectal cancer.