Bile acid and bile acid transporters are involved in the pathogenesis of acute hepatopancreatic necrosis disease in white shrimp Litopenaeus vannamei.

Acute hepatopancreas necrosis disease is a recently emerged shrimp disease that is caused by virulent strains of Vibrio parahaemolyticus. Although AHPND poses a serious threat to the shrimp industry, particularly in Asia, its underlying pathogenic mechanisms are not well characterized. Since a previous transcriptomic study showed upregulation of the apical sodium bile acid transporter (LvASBT), our objective here was to explore the role of bile acids and bile acid transporters in AHPND infection. We confirmed that mRNA expression of LvASBT was upregulated in the stomach of AHPND-infected shrimps. Bile acid concentrations were also higher in the stomach of AHPND-infected shrimp and correlated with high expression of pVA plasmid and Pir toxins. In vitro assays showed that bile acids enhanced biofilm formation and increased the release of PirABvp toxins in AHPND-causing V. parahaemolyticus, while in vivo inhibition of LvASBT by GSK2330672 reduced the copy numbers of pVA plasmid, Pir toxin and reduced the amounts of bile acids in AHPND-infected shrimp stomach. Transcriptomics data for AHPND-causing V. parahaemolyticus treated with bile acids showed upregulation of various genes involved in membrane transport, RND efflux pumps and a bacterial secretion system. Taken together, our results show that AHPND-causing V. parahaemolyticus virulence is positively regulated by bile acids and that LvASBT and bile acids in shrimp stomach have important roles in AHPND pathogenesis.

Metabolic Alterations in Shrimp Stomach During Acute Hepatopancreatic Necrosis Disease and Effects of Taurocholate on Vibrio parahaemolyticus.

Acute hepatopancreatic necrosis disease (AHPND), a recently emerged bacterial shrimp disease, has increased shrimp mortality and caused huge economic losses in many Asian countries. However, molecular factors underlying pathogenesis of this disease remain largely unknown. Our objective was to characterize metabolic alterations in shrimp stomach during AHPND and determine effects of taurocholate on AHPND-causing Vibrio parahaemolyticus. Based on metabolomics, pathways for lipid metabolism and for primary bile acid (BA) synthesis were majorly affected following AHPND infection. Bile acid metabolites, namely taurocholate, were downregulated in the metabolomics database. This prompted us to study effects of taurocholate on biofilm formation, PirAB vp toxin release and biofilm detachment capabilities in AHPND-causing V. parahaemolyticus. Treatment of this bacterium with high concentration of taurocholate, a primary bile acid, induced biofilm formation, PirAB vp toxin release and facilitated the dispersion of bacterial cells. Taken together, our findings suggest that AHPND infection can affect the lipid metabolites in shrimp stomach, and further suggest that the primary bile acid taurocholate is important for the virulence of AHPND-causing V. parahaemolyticus.