TOXICITY OF HELICOBACTER PYLORI VACA TOXIN THROUGH ITS CELLULAR RECEPTOR

幽门螺杆菌VacA可能是至少一个导致细胞凋亡的因素，这在幽门螺杆菌感染中观察到。为了阐明p38在VacA处理的细胞损伤中的作用，我们检测了VacA对p38 MAP激酶磷酸化的影响。VacA以浓度依赖性的方式刺激p38磷酸化。p38抑制剂SB203580在10μM浓度下对vaca诱导的细胞空泡化、线粒体膜电位降低或线粒体释放细胞色素C没有抑制作用。这些结果与p38信号通路可能与细胞死亡无关的观点一致。此外，为了研究幽门螺杆菌引起的胃炎的炎症机制，我们给小鼠注射了VacA。接种VacA导致上皮空泡化，肥大细胞和单核细胞明显浸润粘膜上皮。此外，VacA诱导骨髓源性肥大细胞产生促炎细胞因子，另一方面，VacA与其细胞表面受体酪氨酸磷酸酶受体(rtp) β结合，导致胃上皮AZ-521细胞细胞质空泡化。含有胎牛血清（PCS）的细胞培养基抑制了VacA与细胞表面的结合和VacA依赖的空泡化。这些数据表明，FCS的高分子量部分通过其阻断毒素与AZ-521细胞上的受体RPTPβ结合的能力来抑制VacA的作用。

H. pylori VacA might be at least one factor causing the cell death by apoptosis, that is observed in H. Pylori infection. To elucidate the function of p38 in the damage of VacA-treated cells, we examined the effect of VacA on phosphorylation of p38 MAP kinase. VacA stimulated p38 phosphorylation in a concentration-dependent manner. The p38 inhibitor, SB203580, at concentration of 10μM did not inhibit VacA-induced cellular vacuolation, decrease in mitochondrial Membrane potential, or cytochrome C release from mitochondria. These results are consistent with the notion that p38 signaling pathway might not contribute to cell death.Also, to examine the mechanisms of inflammation in H. pylori-induced gastritis, we administered VacA to the mice. Inoculation of VacA resulted in epithelium vacuolization and marked infiltrations of mast cells and mononuclear cells into the mucosal epithelium. In addition, VacA induced bone marrow-derived mast cells to produce proinflammatory cytokinesOn the other hand, VacA binds to its cell surface receptor, receptor tyrosine phosphatase (RPTP) β, leading to cytoplasmic vacuolization of gastric epithelial AZ-521 cells. VacA binding to the cell surface and VacA-dependent vacuolization were inhibited by cell culture media containing fetal calf serum (PCS). These data show that the high molecular weight fraction of FCS inhibits VacA action though its ability to block toxin binding to its receptor, RPTPβ, on AZ-521 cells.