Scophthalmus maximus interleukin-1β limits Edwardsiella piscicida colonization in vivo

Interleukine-1 beta (IL-1 beta) is the first identified pro-inflammatory cytokine, which is cleaved by caspase-1 following the inflammasomes activation, playing critical roles in innate immunity. However, few studies have been performed to characterize the IL-1 beta in lower vertebrates. Herein, we distinguished the Scophthalmus maximus IL-1 beta (SmIL-1 beta) from three like sequences and found that SmIL-1 beta was cleaved by S. maximus caspase at a non-conserved Asp(86), then targeted to the plasma membrane. Moreover, during the immersion infection of Edwardsiella piscicida, we found that E. piscicida were mainly colonized in gills at early time points and invaded to systemic sites after 5 days post infection, which was consistent with the dynamic up-regulated transcription of SmIL-1 beta. Furthermore, knockdown of SrnIL-1 beta promotes the bacterial colonization in gills at early time points and result into systemic colonization, while overexpression of SmIL-1 beta hampers the bacterial colonization in both spleen and kidney. Taken together, these data provide new insights into the molecular mechanisms of SmIL-1 beta and reveal its role in limiting bacterial infection in vivo, which will support the idea for better understanding the evolutionary of IL-1 beta functions in teleost.