RIG-I and MDA5 are members of RIG-I-like receptors (RLRs) that detect viral RNA within the cytoplasm and
subsequently initiate antiviral immune responses. Necroptosis is a form of programmed cell death (PCD)
executed by mixed lineage kinase domain-like (MLKL), which, upon phosphorylation by receptor-interacting
protein kinase 3 (RIPK3), causes necrotic cell death. To date, no link between RLRs and necroptosis has been
observed during bacterial infection. Edwardsiella tarda is a zoonotic bacterial pathogen that can thrive in host
macrophages. In a previous study, we identified RIG-I and MDA5 as two hub factors of RAW264.7 cells
responsive to E. tarda infection. The present study aimed to determine th... More
RIG-I and MDA5 are members of RIG-I-like receptors (RLRs) that detect viral RNA within the cytoplasm and
subsequently initiate antiviral immune responses. Necroptosis is a form of programmed cell death (PCD)
executed by mixed lineage kinase domain-like (MLKL), which, upon phosphorylation by receptor-interacting
protein kinase 3 (RIPK3), causes necrotic cell death. To date, no link between RLRs and necroptosis has been
observed during bacterial infection. Edwardsiella tarda is a zoonotic bacterial pathogen that can thrive in host
macrophages. In a previous study, we identified RIG-I and MDA5 as two hub factors of RAW264.7 cells
responsive to E. tarda infection. The present study aimed to determine the specific form of cell death triggered by
E. tarda and explore the association between RIG-I/MDA5 and PCD in the context of bacterial infection. Our
results showed that E. tarda infection induced RIPK3-MLKL-mediated necroptosis, rather than pyroptosis or
apoptosis, in RAW264.7 cells. Meanwhile, E. tarda promoted RIG-I/MDA5 production and activated the RIG-I/
MDA5 pathways that led to IRF3 phosphorylation, IFN-β secretion, and interferon-stimulated gene (ISG) and
cytokine expression. Both RIG-I and MDA5 were essential for E. tarda-triggered necroptosis and required for
effective inhibition of intracellular bacterial replication. Furthermore, the regulatory effect of RIG-I/MDA5 on
necroptosis was not affected by type I IFN or TNF-α signaling blockage. Together these results revealed that
necroptosis could be triggered by intracellular bacterial infection through the RIG-I/MDA5 pathways, and that
there existed intricate interplays between PCD and RLRs induced by bacterial pathogen