ROS-activated MAPK/ERK pathway regulates crosstalk between Nrf2 and Hif-1α to promote IL-17D expression protecting the intestinal epithelial barrier under hyperoxia

Reactive oxygen species (ROS) damage to the intestinal barrier is a side effect of prolonged hyperoxia therapy in neonates, which impairs growth and development of the intestine and promotes intestinal diseases. However, the research on clinical prevention and treatment is lacking. Therefore, we investigated the molecular mechanisms of the neonate intestinal response against hyperoxia-derived ROS to find targets for intestinal barrier damage prevention. Human intestinal epithelial cells were incubated under hyperoxia (85% oxygen) to build an in vitro model. ROS and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway were inhibited to detect the MAPK/ERK pathway, nuclear factor erythroid factor 2-related factor 2 (Nrf2), hypoxia-inducible factor-1α (Hif-1α), and interleukin-17D (IL-17D) expression. Nrf2 was inhibited to detect Hif-1α and IL-17D expression. Hif-1α was inhibited to detect Nrf2, IL-17D, and tight junction proteins expression and apoptosis. Cells were treated with human recombinant IL-17D to detect TNF-α, IL-1β, IL-10, and tight junction proteins expression. ROS, Nrf2, Hif-1α, and IL-17D were upregulated and the MAPK/ERK pathway was activated under hyperoxia. But ROS inhibition downregulated the MAPK/ERK pathway, Nrf2, Hif-1α, and IL-17D. MAPK/ERK pathway inhibition downregulated Nrf2, Hif-1α, and IL-17D. Nrf2 inhibition downregulated Hif-1α and IL-17D. Hif-1α inhibition downregulated Nrf2, IL-17D, tight junction proteins, and exacerbated apoptosis. The recombinant IL-17D downregulated TNF-α, IL-1β, but upregulated IL-10 and tight junction proteins. We concluded that Hyperoxia-generated ROS activated the MAPK/ERK pathway to regulate Nrf2, Hif-1α, and IL-17D expression. Nrf2 and Hif-1α were interdependent and promoted IL-17D. Importantly, Hif-1α and IL-17D expression protected the intestinal epithelial barrier.