PP2A/PI3k/Akt调控FBW7表达在腹泻性贝毒暴露引起结肠上皮增生中的作用研究

Diarrhea shellfish poisoning (DSP) toxins is a type of common algal toxin accumulated in shellfish. Besides causing symptoms of diarrheal poisoning after human consumption, it can also interfere with many physiological processes, such as cell cycle regulation, and seriously endanger the safety of shellfish farming and food safety. Our previous study found that repeated exposures of DSP toxins caused the hyperproliferation of human colon epithelium, and that the ubiquitin ligase FBW7 was down-regulated, but its regulatory mechanism was unclear. As DSP toxin has a specific inhibitory effect on protein PP2A, we speculate that the PP2A/PI3k/Akt pathway may be involved in the regulation of repeated exposures of DSP toxins and promote the proliferation of colon epithelial cells after FBW7 reduced expression. In order to validate our hypothesis, firstly we intend to use knockdown and overexpression of FBW7 to detect the proliferation of colonic epithelial cells and the survival and proliferation ability under the action of DSP toxins. Secondly detect the phosphorylation and activity of PI3k/Akt pathway proteins under the action of DSP toxin stress, and handle colonic epithelial cells with PI3k/Akt inhibitor and activator to detect the proliferation of colonic epithelium and FBW7 expression to study the effect of PP2A/PI3k/Akt pathway on FBW7 expression and the promotion of colonic epithelial hyperplasia.

腹泻性贝毒（DSP）是贝体积累的一类常见藻毒素，除引起腹泻性中毒症状外，还可干扰细胞周期调控等生理过程，严重危害贝类养殖和食用安全。我们前期研究发现，细胞周期调控蛋白泛素化连接酶FBW7在DSP毒素多次暴露引起人结肠上皮细胞增生中表达降低，但其调控机制不清。鉴于DSP毒素显著降低PP2A活性，我们推测PP2A/PI3k/Akt通路可能在下调FBW7表达参与DSP毒素重复暴露诱发结肠上皮增生中有重要作用。本实验拟采取敲低和过表达FBW7，检测结肠上皮细胞增殖及在DSP毒素胁迫下的生存能力；DSP毒素胁迫下PI3k/Akt通路蛋白磷酸化水平及活性，通过PI3k/Akt抑制剂及激活剂刺激结肠上皮细胞，检测结肠上皮增生及FBW7表达变化等，明确PI3k/Akt通路调控FBW7表达，促进结肠上皮增生的作用机制。

大田软海绵酸(OA) 是一种分布于世界各地的亲脂性藻毒素，会导致腹泻性中毒 (DSP)，甚至诱导胃肠道和皮肤肿瘤的发展。目前，食用受污染的海产品可能造成慢性OA暴露，引起胃肠道增生等改变，但目前相关数据严重缺乏。在这里，我们的研究表明亚慢性口服摄入OA（100 µg kg-1）会干扰 SD 大鼠的结肠粘膜完整性并诱发慢性腹泻及结肠炎症。结肠紧密连接蛋白 (TJPs)，主要是密蛋白，被破坏并导致形成珠状结构。此外，体外体内实验表明，长期摄入OA能诱导结肠上皮细胞加速增殖，长期摄入一定计量的OA 有促进肿瘤启动活性的风险。进一步研究表明 OA 是通过激活P53和Jak/stat3通路促进细胞增殖的。总之，这些发现表明，亚慢性 OA 给药可诱发结肠炎症，并可能通过影响水和离子的重吸收最终导致慢性腹泻。这些数据产生的明显风险表明，应更加关注经常食用被 DSP 毒素污染的海产品的风险。