Characterization of AHR1 and its functional activity in Atlantic sturgeon and shortnose sturgeon

Abstract

Sturgeon species are imperiled world-wide by a variety of anthropogenic stressors including chemical contaminants. Atlantic sturgeon, Acipenser oxyrinchus, and shortnose sturgeon, Acipenser brevirostrum, are largely sympatric acipenserids whose young life-stages are often exposed to high levels of benthic-borne PCBs and PCDD/Fs in large estuaries along the Atlantic Coast of North America. In previous laboratory studies, we demonstrated that both sturgeon species are sensitive to early life-stage toxicities from exposure to environmentally relevant concentrations of coplanar PCBs and TCDD. The sensitivity of young life-stages of fishes to these contaminants varies among species by three orders of magnitude and often is due to variation in the structure and function of the aryl hydrocarbon receptor (AHR) pathway. Unlike mammals, fishes have two forms of AHR (AHR1 and AHR2) with AHR2 usually being more highly expressed across tissues and functional in mediating toxicities. Based on previous studies in white sturgeon, A. transmontanus, we hypothesized that sturgeon taxa are unusually sensitive to these contaminants because of higher levels of expression and functional activity of AHR1 than in other fish taxa. To address this possibility, we characterized AHR1 in both Atlantic Coast sturgeon species, evaluated its’ in vivo expression in young life-stages and in multiple tissues of shortnose sturgeon, and tested its ability to drive reporter gene expression in AHR-deficient cells treated with graded doses of PCB126 and TCDD. Similar to white sturgeon and lake sturgeon, AHR1 amino acid sequences in Atlantic sturgeon and shortnose sturgeon were more similar to mammalian AHRs and avian AHR1s than to AHR1 in other fishes, suggesting their greater functionality in sturgeon species than in other fishes. Exposure to graded doses of coplanar PCBs and TCDD usually failed to significantly induce AHR1 expression in young life-stages or most tissues of shortnose sturgeon. However, in reporter gene assays, AHR1 drove higher levels of gene expression than AHR2 alone, but their binary combination failed to drive higher levels of expression than either AHR alone. In total, our results suggest that AHR1 may be more functional in sturgeon species than in other fishes, but probably does not explain their heightened sensitivity to these contaminants.

Molecular and Functional Properties of the Atlantic Cod (Gadus morhua) Aryl Hydrocarbon Receptors Ahr1a and Ahr2a

“…Significant differences in E max values between gmAhr1a and gmAhr2a were observed for B­[a]­P, PCB126, and BNF, where gmAhr1a produced higher maximum responses for PCB126 and BNF. The higher transactivation activity of Ahr1a compared with Ahr2a after PCB126 exposure is in line with previous findings in Atlantic sturgeon and shortnose sturgeon …”

“…The higher transactivation activity of Ahr1a compared with Ahr2a after PCB126 exposure is in line with previous findings in Atlantic sturgeon and shortnose sturgeon. 82 Differences in gmAhr1a and gmAhr2a binding to [ 3 H]TCDD and [ 3 H]BNF were found in in vitro expressed proteins. In accordance with the luciferase reporter gene assay with TCDD and BNF, gmAhr1a was the receptor with the highest binding to both compounds.…”

The use of active coal feed supplement in the young fish feeding

“…Sturgeons are fish species with biological and economic importance, and most of them are endangered, vulnerable or rare due to their large size, late sexual maturity, long period between spawning and longevity (Hao, 2018;Jafari, 2018). Considering individual sectors of aquaculture, we note that, along with traditional technologies for growing commercial fish, the most important place is occupied by intensive forms of fish farming, in which the organization questions of full-fledged feeding is of paramount importance (Wang, 2016;Roy, 2018) Improving the efficiency of the fish farming industry, along with solving technical problems, urgently requires the most serious attention to the feeding process and the use of cost-effective feed products for all age groups of bred fish (Doering, 2014;Krymov, 2018;Mugetti, 2020). The interest of scientists and practitioners in the use of new feed supplements, biologically active substances, including sorbents in the cultivation of fish, has been significantly increasing in recent years (Molina-Ruiz, 2015).…”