Apoptosis-inducing activity of plant lectins and specific application to tumor cells

凝集素是一种非免疫来源的蛋白质，对糖缀合物的碳水化合物部分具有特异性结合亲和力。我们已经开发了一种新的方法来分离凝集素使用亲和凝胶结合猪血浆蛋白。在这项研究中，我们研究了生物活性的凝集素分离，我们的方法。乌藤中的心叶木凝集素（ACL）具有增强Caco-2细胞中促炎细胞因子IL-8基因和蛋白表达的活性。我们的研究结果还表明，日本槲寄生凝集素，虹膜凝集素，和蝇蕈凝集素在人白血病U937细胞的凋亡诱导活性。此外，我们还发现黑川蘑菇中的白黑牛肝菌凝集素（Boletopsis leucomelas lectin，BLL）诱导U937细胞凋亡的机制包括G2/M期阻滞和p21/Waf 1基因表达上调。bcl-2表达的降低是由于p21/Waf 1表达上调，并与细胞色素c从线粒体释放到细胞质的增加有关，导致BLL处理细胞中caspase-9的激活。这些数据表明，我们的新方法的凝集素的分离和检查在各种动物系统中的植物凝集素的生物活性的重要性。

Lectins are proteins of non-immune origin with specific binding affinity for carbohydrate moiety of glycoconjugates. We have developed a new method to isolate lectins using affinity gels conjugated with porcine plasma proteins. In this study, we examined biological activities of lectins isolated by our method. Aralia cordate lectin (ACL) from udo showed activity to enhance gene and protein expression of proinflammatory cytokine IL-8 in Caco-2 cells. Our results also showed apoptosis inducing activity of Japanese mistletoe lectin, iris lectin, and muscari lectin in human leukemia U937 cells. In addition, we found that Boletopsis leucomelas lectin (BLL) from the edible mushroom kurokawa induced apoptosis in U937 cells by the mechanism incuding the G2/M cell cycle arrest in assocation with up-regulation of p21/Waf1 gene expression. The observed decrease in expression of bcl-2 was ascribable to the up-regulated expression of p21/Waf1 and correlated to the enhanced release of cytochrome c from mitochondria to cytoplasm, leading to the activation of caspase-9 in BLL-treated cells. These data suggest usefulness of our new method for lectin isolation and importance of examining biological activities of plant lectins in various animal systems.