FOXO转录因子调控银屑病表皮增殖的分子机制

The fact, which the epidermal defect without T cell activition could produce psoriasis-like animal models and patients with AIDS can have severe psoriasis without Th cell activation,indicates that Th17 cell activation is not an only factor in the pathogenesis of psoriasis.The cause of hyperproliferation of psoriatic keratinocytes including cell cycle acceleration and abnormal apoptosis needs further study.FOXO transcription factors inhibit cell proliferation by inhibition cell cycle from progress and promotion cell apoptosis by regulatling the expressions of genes related to cell cycle and apoptosis.The relationship between FOXO and the proliferation of psoriatic keratinocytes has not been reported. We found that, increased activity of PI3K/Akt in psoriatic lesions in our previous study,which might make FOXO phosphorylated leading to its molecular conformation change and transition from nucleus to cytoplasm,might prevent its function.The present study might provide a clue for investigating the molecular mechanisms of hyperproliferation of psoriatic keratinocytes through the FOXO function study in vivo and searching unknow target genes from three aspects of phosphorylated FOXO level and cell localization,Its transcription activity in vivo and the expressions of its target genes related to cell cycle and apoptosis by the methods of tissue microarrays,antibody arrays and immunoprecipitation.

无T细胞活化只有表皮缺陷仍可产生银屑病样动物模型，无Th细胞活化的艾滋病患仍可患严重的银屑病，说明Th17细胞活化不是银屑病发病的唯一因素。导致银屑病表皮增殖失调-细胞周期加速及凋亡异常的原因仍待进一步研究。FOXO转录因子因能通过调控细胞周期和凋亡相关基因的表达来阻抑细胞周期和促进细胞凋亡而抑制细胞增殖，但与银屑病表皮增殖的关系未见报道。我们以前的研究发现：银屑病皮损内FOXO上游通路PI3K/Akt活化，可导致FOXO的磷酸化使其分子构象改变而发生胞核到胞浆的转位，阻抑其对细胞增殖的抑制。为探讨FOXO功能改变与银屑病表皮增殖的相关性，本项目拟采用组织芯片、抗体芯片、染色质免疫沉淀等方法，从磷酸化FOXO的水平及亚细胞定位、FOXO的体内活性及其调控的靶基因的水平三方面，研究FOXO在银屑病表皮增殖失调中可能的作用，为探索揭示银屑病表皮增殖的分子机制提供线索。

为探讨FOXOs功能改变与银屑病表皮增殖的关系，本研究留取87例寻常型银屑病患者皮损、非皮损组织和75例正常对照的皮肤组织样本进行对照：通过实时定量聚合酶链反应、蛋白质免疫印迹法、凝胶迁移率实验检测，检测样本中FOXOs mRNA水平；FOXOs（FOXO1、FOXO3、FOXO4）总蛋白、胞浆蛋白及胞核蛋白表达水平；FOXOs蛋白的转录活性。通过免疫组化检测31例寻常型银屑病皮损及30例正常对照组织中FOXOs下游凋亡相关因子（Bcl-6、Bim、PUMA、TRAIL、BNIP3、BNIP3L）与细胞周期因子（p27、p21、p15、p19、p130、cyclinG、cyclinD1）的表达情况。.结果表明：.①.与正常对照组相比，银屑病皮损中FOXOs的mRNA表达无明显差异；.②.银屑病皮肤组织总蛋白中FOXO1和FOXO4蛋白表达低于正常组织；.③患者皮损胞浆蛋白中FOXOs蛋白表达水平高于正常对照；患者皮损细胞核蛋白中FOXOs（FOXO1、FOXO3、FOXO4）水平显著低于正常对照组；④患者皮损中总磷酸化FOXOs蛋白水平高于正常对照，但无统计学差异；.⑤患者皮损细胞核蛋白FOXOs的DNA结合活性显著降低，皮肤组织中FOXOs转录活性可能主要和FOXO1亚类相关；.⑥下游凋亡蛋白Bcl-6及BNIP3表达水平明显高于正常对照，Bim的表达水平明显低于正常对照组。. 研究结果提示：银屑病皮损中FOXOs表达降低，核浆定位发生改变，可能导致FOXOs转录活性下降，导致下游细胞凋亡蛋白异常，引起银屑病角质形成细胞凋亡失调，参与银屑病皮损的形成。