Department of Biomedical Sciences, Iowa State University, Ames, IA, United States.
Immunobiology Interdepartmental Graduate Program, Iowa State University, Ames, IA, United States.
Front Cell Infect Microbiol. 2022 Apr 19;12:848773. doi: 10.3389/fcimb.2022.848773. eCollection 2022.
Agriculture workers report various respiratory symptoms owing to occupational exposure to organic dust (OD) and various gases. Previously, we demonstrated that pre-exposure to hydrogen sulfide (HS) alters the host response to OD and induces oxidative stress. Nrf2 is a master-regulator of host antioxidant response and exposures to toxicants is known to reduce Nrf2 activity. The OD exposure-induced lung inflammation is known to increase susceptibility to a secondary microbial infection. We tested the hypothesis that repeated exposure to OD or HS leads to loss of Nrf2, loss of epithelial cell integrity and that activation of Nrf2 rescues this epithelial barrier dysfunction. Primary normal human bronchial epithelial (NHBE) cells or mouse precision cut-lung slices (PCLS) were treated with media, swine confinement facility organic dust extract (ODE) or HS or ODE+HS for one or five days. Cells were also pretreated with vehicle control (DMSO) or RTA-408, a Nrf2 activator. Acute exposure to HS and ODE+HS altered the cell morphology, decreased the viability as per the MTT assay, and reduced the Nrf2 expression as well as increased the keap1 levels in NHBE cells. Repeated exposure to ODE or HS or ODE+HS induced oxidative stress and cytokine production, decreased tight junction protein occludin and cytoskeletal protein ezrin expression, disrupted epithelial integrity and resulted in increased invasion. RTA-408 (pharmacological activator of Nrf2) activated Nrf2 by decreasing keap1 levels and reduced ODE+HS-induced changes including reversing loss of barrier integrity, inflammatory cytokine production and microbial invasion in PCLS but not in NHBE cell model. We conclude that Nrf2 activation has a partial protective function against ODE and HS.
农业工人由于职业性接触有机粉尘（OD）和各种气体而报告有各种呼吸道症状。此前，我们已经证明，预先暴露于硫化氢（HS）会改变宿主对 OD 的反应，并诱导氧化应激。Nrf2 是宿主抗氧化反应的主要调节剂，已知暴露于毒物会降低 Nrf2 活性。OD 暴露引起的肺部炎症已知会增加对二次微生物感染的易感性。我们检验了以下假设：重复暴露于 OD 或 HS 会导致 Nrf2 丧失、上皮细胞完整性丧失，而激活 Nrf2 则可以挽救这种上皮屏障功能障碍。将原代正常人类支气管上皮（NHBE）细胞或小鼠精密切割肺切片（PCLS）用培养基、猪密闭设施有机粉尘提取物（ODE）或 HS 或 ODE+HS 处理 1 天或 5 天。细胞还分别用载体对照（DMSO）或 RTA-408（Nrf2 激活剂）预处理。急性暴露于 HS 和 ODE+HS 改变了细胞形态，根据 MTT 测定降低了细胞活力，并降低了 NHBE 细胞中的 Nrf2 表达以及增加了 keap1 水平。重复暴露于 ODE 或 HS 或 ODE+HS 会诱导氧化应激和细胞因子产生，降低紧密连接蛋白 occludin 和细胞骨架蛋白 ezrin 的表达，破坏上皮完整性，并导致侵袭增加。RTA-408（Nrf2 的药理学激活剂）通过降低 keap1 水平激活 Nrf2，并减少 ODE+HS 诱导的变化，包括逆转屏障完整性丧失、炎症细胞因子产生和微生物侵袭，这在 PCLS 中得到证实，但在 NHBE 细胞模型中则不然。我们得出结论，Nrf2 激活对 ODE 和 HS 具有部分保护作用。
