Influenza a(H1N1) virus infection impairs syncytiotrophoblast functions by promoting ferroptosis through the TNF-α/ISG15/EGR1 axis.

Influenza A virus (IAV) is linked to adverse pregnancy outcomes like spontaneous abortion, preterm birth, and neonatal death. Inhibition of trophoblast cell fusion by IAV infection is a key factor contributing to these adverse pregnancy outcomes. Cytokine TNF-α modulates fusion defects in human trophoblast cells. Ferroptosis, a new form of programmed cell death, involves iron-dependent lipid peroxide buildup. It's unclear if the adverse outcomes of IAV infection on pregnant women are related to trophoblast cell ferroptosis. This study made a syncytiotrophoblast (STB) cell model by treating BeWo cells with forskolin (FSK) in vitro. We investigated the impact of H1N1 virus infection on trophoblast cell syncytialization. We found TNF-α expression rose significantly in H1N1-infected fused trophoblast cells, causing ferroptosis and disrupting syncytialization. ISG15 was identified as a downstream gene of TNF-α, and its knockdown reversed the effects of TNF-α. ISG15 overexpression enhanced ferroptosis-related gene transcription via EGR1, further disrupting syncytialization. EGR1 was found to promote TNF-α transcription, thereby forming a TNF-α, ISG15, EGR1 positive feedback loop. In vivo TNF-α inhibition reduced ferroptosis markers and improved trophoblast cell fusion. This investigation demonstrated that H1N1 infection initiates ferroptosis and compromises trophoblast cell fusion through the TNF-α/ISG15/EGR1 pathway. These findings imply a potential therapeutic approach for pregnancy complicated by influenza A virus infection.