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Purpose: We found in previous study that metformin could treat sepsis myocarditis in a mouse model. We employed the zebrafish model organism to investigate the effect of metformin on sepsis myocarditis. Methods and Results: Wild-type zebrafish was used to establish a sepsis myocarditis model and combined with image software analysis and cytokine detection, the protective dose of metformin was determined. The results showed that immersion with Escherichia coli could cause 75% mortality in zebrafish and make larvae appear as characteristics of severe sepsis myocarditis. Pretreatment with 10 mM metformin for 3 hours could effectively reduce heart congestion and swelling in zebrafish with sepsis myocarditis and increased the heart rate. It could reduce the mortality and prolong the survival time of zebrafish with sepsis myocarditis; Tg(mpx: EGFP) transgenic zebrafish were adopted to explore the number of neutrophils in zebrafish heart before and after metformin protection, and metformin could maintain the number of neutrophils in zebrafish heart; quantitative real-time reverse transcription–polymerase chain reaction showed that metformin could reduce the expression of pro-inflammatory factors, tumor necrosis factor-α and interleukin (IL)-6, and could promote the anti-inflammatory factor, transforming growth factor-β and IL-10 expression. Conclusion: We established a zebrafish sepsis myocarditis model and applied metformin in advance to provide a protective effect on the zebrafish heart.

Purpose: Interferon regulatory factor 4 (IRF4) is identified as a transcriptional factor and plays an important role in the immune response in mammals; however, there are few reports about the function of zebrafish IRF4. Methods: We first amplified the coding sequence of irf4a from the testis of zebrafish. Besides, the fragments of irf4a , P2A , EGFP , and Tol2 vector were added for homologous recombination. By sequencing, we can get the Tol2-ef1α-irf4a-EGFP recombinant plasmid and it was microinjected into zebrafish embryos. Fluorescence observation was proceeded at days 3 post fertilization; F0 generations expressing green fluorescence in multiple tissues throughout the body were screened as the founder and raised them to sexual maturity. After mating with WT zebrafish to generate F1 offspring, polymerase chain reaction was used to identify whether irf4a was integrated into the zebrafish genome. Conclusion: We obtained the systematic overexpressed irf4a transgenic zebrafish with green fluorescence labeled in spine, eyes, heart, brain, and other tissues. The transgenic zebrafish will be used as a tool for the role of IRF4a in the immune response to the inflammation preconditioning in the future study.