Acute phase response in zebrafish embryo/larva with special emphasis on LPS-induced changes in expression pattern of acute phase protein genes

Abstract

Acute phase response (APR) in developing embryos/larvae remains poorly studied in fish, and information regarding the expression and role of acute phase proteins (APPs) in developing embryos/larvae is rather limited in teleosts. In this study we investigated the APR in zebrafish (Danio rerio) embryos/larvae challenged with LPS by examining the expression of APP genes encoding CRP, SAA, LECT2, HAMP and HP and APP inducer genes encoding IL-1β and TNF-α. Expression of all the seven genes was up-regulated in embryos/larvae after challenge with LPS as revealed by q-RT-PCR. Whole-mount in situ hybridization (WISH) showed that all the genes displayed strong maternal expression in the cleavage and blastula stages, and ubiquitous expression in the gastrula and segmentation stage embryos, and then they were expressed differently in specific tissues in later developmental stages. Interestingly, challenge with LPS resulted in de novo expression of the SAA gene in the yolk sac and intestine, the LECT2 gene in the yolk sac, and the IL-1β gene in the yolk sac and the dispersed neutrophils of caudal vein, and visible enhanced expression of the LECT2 gene in the yolk sac. These are the first such data reported in teleosts, showing that LPS challenge is able to modify the expression patterns of APP and APP inducer genes. Altogether, these data suggest that zebrafish embryos/larvae are able to respond to acute infection though their immune system remains in a developing and immature state.