Tissue-resident trained immunity in hepatocytes protects septic-liver injury in zebrafish

Trained immunity is classically characterized by long-term epigenetic reprogramming of innate immune cells to combat infectious diseases. Infection-induced organ injury is a common clinical severity phenotype of sepsis. However, whether the induction of trained immunity plays a role in protecting septic-organ injury remains largely unknown. Here, through establishing an in vivo β-glucan training and secondary LPS challenge-induced organ injury model in zebrafish larvae, we observe that induction of trained immunity could inhibit the pyroptosis of hepatocytes to alleviate septic-liver injury, with an elevated epigenetic modification of trimethylation at histone 3 lysine 4 (H3K4me3) that targets mitophagy activation. Moreover, we identify a novel C-type lectin domain receptor in zebrafish, named DrDectin-1, which is revealed as the orchestrator in gating H3K4me3 rewiring-mediated mitophagy activation and alleviating the pyroptosis-engaged septic-liver injury in vivo. Taken together, our results uncover a tissue-resident trained immunity in maintaining tissue homeostasis at a whole animal level, and offer a facile in vivo model to efficiently integrate trained immunity for immunotherapies. ChIP-Seq for H3K4me3 in zebrafish liver (ZFL) cells after β-glucan treatment