Piceatannol对佛波酯诱导MCF-10A细胞NF-κB激活和COX-2表达的抑制作用

【作者】 刘丹；

【导师】 毕开顺； 徐荣俊；

【作者基本信息】 沈阳药科大学 ， 药学， 2008， 硕士

【摘要】 现已有大量研究表明,慢性炎症与癌症的发生发展有着密切的联系。炎性细胞缓慢发展为肿瘤的病因已成为癌症研究的热点之一。环氧合酶2(cyclooxygenase-2,COX-2)是前列腺素(PG)合成过程中一个重要的限速酶,主要在炎症细胞表达。COX-2在人类许多癌前病变和恶性肿瘤中均有高表达,从而促进肿瘤细胞增殖,抑制凋亡。前期研究表明,葡萄中大量存在的白藜芦醇(3,4,5-三羟基二苯乙烯,Resveratrol)可以有效抑制cox-2基因转录的调控转录因子NF-κB,从而起到抗炎,抗肿瘤的作用。白藜芦醇羟基衍生物Piceatannol(反-3,4,3′,5′-四羟基二苯乙烯),是在大戟属植物中被首次发现的,具有很强的抗炎、抗增殖等多种药理活性,但其内在的分子机制还不是很清楚。本课题旨在研究Piceatannol是否与其结构衍生物白藜芦醇一样具有抑制COX-2表达和NF-κB活化的药理活性,以及对其内在的分子机制进行初步的探讨。本实验研究表明,Piceatannol可有效拮抗佛波酯(12-O-十四烷酰佛波醇-13-醋,TPA)诱导正常乳腺上皮细胞(MCF10A)cox-2基因的mRNA转录因子和蛋白表达水平。经Piceatannol处理过的MCF10A细胞可对TPA诱导的NF-κB DNA元件结合活性有很强的抑制作用,此作用在一定程度上超越了白藜芦醇和另一同类衍生物Oxyresveratrol(反-2,3′,4,5′-四羟基二苯乙烯)。因此,苯环上羟基数量的增加或减少以及羟基位置的改变对抑制NF-κB活性起重要作用。Piceatannol能够抑制TPA诱导的IκB的磷酸化与降解,从而阻止了p65亚基由胞质转移至核内。巯基还原剂二硫苏糖醇(DTT)可逆转Piceatannol对NF-κB DNA元件结合活性的抑制作用,其发生机制可能与调节IKK激酶结构域上半胱氨酸的还原态有关。Piceatannol对NF-κB转录活性的直接抑制作用及可能机制还在进一步的研究当中。更多还原

【Abstract】 There are multiple lines of evidence supporting that inflammation is causally linked to carcinogenesis.Abnormal upregulation of cyclooxygenase-2(COX-2),a rate-limiting enzyme in the prostaglandin biosynthesis,has been implicated in carcinogenesis.Previously,it has been reported that resveratrol(trans-3,4’,5-trihydroxystilbene)suppresses the activation of the nuclear transcription factor NF-κB,one of the major transcription factors that regulate cox-2 gene transcription.Piceatannol,(trans-3,4,3’,5’-tetrahydroxystilbene)primarily derived from the seeds of Euphorbia lagascae,exhibits potent anti-inflammatory and anti-proliferative activities,but the underlying molecular mechanisms remain largely unresolved.In the present study,we examined whether piceatannol,structurally analogous to resveratrol,could also suppress both COX-2 expression and NF-κB activation.Piceatannol abrogated the expression of 12-O-teradecanoylphorbol-13-acetate(TPA)-induced expression of COX-2 and its mRNA transcript in human mammary epithelial(MCF-10A)cells.The treatment of MCF-10A cells with piceatannol suppressed TPA-induced NF-κB DNA binding activity to a greater extent than did resveratrol and another stilbene analog oxyresveratrol(trans-2,3’,4,5’-tetrahydroxystilbene), indicative of the critical role of the orientation as well as the number of hydroxyl groups in its NF-κB inhibitoty activity.Piceatannol also inhibited TPA-induced phosphorylation and degradation of IκBαas well as nuclear translocation of p65.The thiol reducing agent dithiothreitol(DTT)abrogated the inhibitory effects of piceatannol on NF-κB DNA binding, presumably by keeping the cysteine residues in the kinase domain of IKKβin a reduced state.The possibility of direct inhibition of NF-κB transcriptional activity by piceatannol is under investigation.更多还原