Scopel-Guerra Adriele, Olivera-Severo Deiber, Staniscuaski Fernanda, Uberti Augusto F, Callai-Silva Natália, Jaeger Natália, Porto Bárbara N, Carlini Celia R
Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
Department of Biology, Universidade Regional Integrada do Alto Uruguai e das Missões, São Luiz Gonzaga, Brazil.
Front Microbiol. 2017 Dec 12;8:2447. doi: 10.3389/fmicb.2017.02447. eCollection 2017.
Gastric infection by is considered a risk factor for gastric and duodenal cancer, and extragastric diseases. Previous data have shown that, in a non-enzymatic way, urease (HPU) activates neutrophils to produce ROS and also induces platelet aggregation, requiring ADP secretion modulated by the 12-lipoxygenase pathway, a signaling cascade also triggered by the physiological agonist collagen. Here we investigated further the effects on platelets of recombinant versions of the holoenzyme HPU, and of its two subunits (HpUreA and HpUreB). Although HpUreA had no aggregating activity on platelets, it partially inhibited collagen-induced aggregation. HpUreB induced platelet aggregation in the nanomolar range, and also interfered dose-dependently on both collagen- and ADP-induced platelet aggregation. HPU-induced platelet aggregation was inhibited by antibodies against glycoprotein VI (GPVI), the main collagen receptor in platelets. Flow cytometry analysis revealed exposure of P-selectin in HPU-activated platelets. Anti-glycoprotein IIbIIIa (GPIIbIIIa) antibodies increased the binding of FITC-labeled HPU to activated platelets, whereas anti-GPVI did not. Evaluation of post-transcriptional events in HPU-activated platelets revealed modifications in the pre-mRNA processing of pro-inflammatory proteins, with increased levels of mRNAs encoding IL-1β and CD14. We concluded that HPU activates platelets probably through its HpUreB subunit. Activation of platelets by HPU turns these cells into a pro-inflammatory phenotype. Altogether, our data suggest that urease, besides allowing bacterial survival within the gastric mucosa, may have an important, and so far overlooked, role in gastric inflammation mediated by urease-activated neutrophils and platelets.
幽门螺杆菌（Helicobacter pylori，Hp）感染被认为是胃癌、十二指肠癌及胃外疾病的一个危险因素。既往数据表明，幽门螺杆菌脲酶（HPU）以非酶促方式激活中性粒细胞以产生活性氧（ROS），还诱导血小板聚集，这需要由12-脂氧合酶途径调节的二磷酸腺苷（ADP）分泌，该信号级联反应也由生理性激动剂胶原蛋白触发。在此，我们进一步研究了全酶HPU及其两个亚基（HpUreA和HpUreB）的重组形式对血小板的影响。尽管HpUreA对血小板没有聚集活性，但它部分抑制胶原蛋白诱导的聚集。HpUreB在纳摩尔范围内诱导血小板聚集，并且还剂量依赖性地干扰胶原蛋白和ADP诱导的血小板聚集。HPU诱导的血小板聚集被抗糖蛋白VI（GPVI）抗体抑制，GPVI是血小板中的主要胶原蛋白受体。流式细胞术分析显示HPU激活的血小板中有P-选择素暴露。抗糖蛋白IIbIIIa（GPIIbIIIa）抗体增加了异硫氰酸荧光素（FITC）标记的HPU与活化血小板的结合，而抗GPVI抗体则没有。对HPU激活的血小板中转录后事件的评估揭示了促炎蛋白前体mRNA加工的改变，编码白细胞介素-1β（IL-1β）和CD14的mRNA水平增加。我们得出结论，HPU可能通过其HpUreB亚基激活血小板。HPU对血小板的激活使这些细胞转变为促炎表型。总之，我们的数据表明，幽门螺杆菌脲酶除了使细菌在胃黏膜内存活外，可能在由脲酶激活的中性粒细胞和血小板介导的胃炎症中具有重要但迄今被忽视的作用。
