Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, 04023-062, São Paulo, SP, Brazil.
Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, 04023-062, São Paulo, SP, Brazil; Departamento de Ciências Farmacêuticas, Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, 09913-030, Diadema, SP, Brazil.
Exp Parasitol. 2022 Sep;240:108329. doi: 10.1016/j.exppara.2022.108329. Epub 2022 Jul 19.
Intestinal epithelial cells (IECs) reside in a highly anaerobic environment that is subject to daily fluctuations in partial oxygen pressure (pO), depending on intestinal tissue perfusion. This condition, known as physiological hypoxia, has a major impact on the maintenance of gut homeostasis, such as effects on the integrity and function of the intestinal epithelial barrier. Giardia lamblia is a microaerophilic protozoan parasite that infects and colonizes the small intestine of its host, causing watery diarrhea. The disease, known as giardiasis, is associated with enhanced intestinal permeability and disruption or reorganization of tight junction (TJ) proteins between IECs. Given the central role of oxygen in gut homeostasis, in this study, we aimed to evaluate whether pO affects intestinal permeability (flux of ions and macromolecules) and TJ protein expression in human IECs during G. lamblia infection. Using human cell lines HuTu-80 and Caco-2 as models of "loose" (low resistance) and "tight" (high resistance) intestines, respectively, we elucidated that low pO drives intestinal barrier dysfunction in IECs infected with trophozoites through dephosphorylation of protein kinase C (PKC α/β II). Additionally, we demonstrated that IECs infected with trophozoites in the presence of a pharmacological PKC activator (phorbol 12-myristate 13-acetate) partially restored the barrier function, which was correlated with increased protein expression levels of zonula occludens (ZO)-2 and occludin. Collectively, these results support the emerging theory that molecular oxygen impacts gut homeostasis during Giardia infection via direct host signaling pathways. These findings further our knowledge regarding Giardia-host interactions and the pathophysiological mechanisms of human giardiasis.
肠上皮细胞 (IECs) 位于高度厌氧的环境中，其局部氧分压 (pO) 会随肠道组织灌注而每天波动。这种情况被称为生理性缺氧，对维持肠道内环境稳态有重大影响，例如影响肠道上皮屏障的完整性和功能。蓝氏贾第鞭毛虫是一种微需氧的原生动物寄生虫，感染并定植于宿主的小肠，引起水样腹泻。这种疾病称为贾第虫病，与肠道通透性增强以及 IEC 之间紧密连接 (TJ) 蛋白的破坏或重组有关。鉴于氧在肠道内环境稳态中的核心作用，本研究旨在评估 pO 是否会影响 G. lamblia 感染期间人 IEC 中的肠道通透性（离子和大分子的通量）和 TJ 蛋白表达。我们使用人细胞系 HuTu-80 和 Caco-2 分别作为“疏松”（低电阻）和“紧密”（高电阻）肠道的模型，阐明低 pO 通过蛋白激酶 C (PKC α/β II) 的去磷酸化驱动感染滋养体的 IEC 肠道屏障功能障碍。此外，我们证明在存在药理学 PKC 激活剂 (佛波醇 12-肉豆蔻酸 13-乙酸盐) 的情况下，感染滋养体的 IEC 部分恢复了屏障功能，这与紧密连接蛋白 (ZO)-2 和闭合蛋白的蛋白表达水平增加相关。总之，这些结果支持了这样一种新兴理论，即分子氧通过直接的宿主信号通路影响贾第虫感染期间的肠道内环境稳态。这些发现进一步了解了贾第虫与宿主的相互作用以及人类贾第虫病的病理生理机制。
