Functional and toxicological characterization of ABCC transporters in the rainbow trout (Oncorhynchus mykiss) intestine

BIECZYNSKI F.; PAINEFILÚ, J.C.; DE ANNA, J.S.; LUQUET, C.M.

Gothenborg

Simposio; 21 st International Symposium on Gothenburg is the largest nonP ollutant R esponses I n M arine Gothenburg O rganisms ( PRIMO 21 ); 2021

University of Gothenburg

ABCC proteins are membrane transporters that work together with biotransformation enzymes to eliminate endogenous and exogenous toxic compounds. The apical ABCC transporters (Abcc2) of polarized epithelia, like the intestinal mucosa, function as a barrier against pollutants. Basolateral ABCCs export compounds into the blood. We aim to integrate our studies on pollutants detoxification by fish intestinal ABCC proteins and related biotransformation enzymes and nuclear receptors, emphasizing the experimental design and considering the epithelial polarity when determining the organism’s defence capacity against a toxic compound. We studied intestine ABCC function with in vivo, ex vivo, and in vitro O. mykiss intestine preparations exposed to relevant pollutants: microcystin-LR (MCLR), paralytic shellfish toxins (PST), AsIII, and chlorpyrifos (CPF). Results: ex vivo preparations indicate that MCLR inhibits apical and basolateral ABCC proteins transport. Coexposure with the specific ABCC inhibitor MK571 increases MCLR toxicity. AsIII has similar effects only at the apical membrane. In vivo exposure to AsIII for 48 h induces Abcc2 activity and expression. This effect reduces the toxicity of MCLR applied ex vivo. In vivo exposure to MCLR increases GST activity and decreases ABCC transport at 12 h. The transport activity rate recovers at 48 h but is higher than in control fish preparations only at the basolateral side.Ex vivo preparations exposed to PST showed lysosomal damage and inhibition of basolateral ABCC transport. However, MK571 did not increase lysosomal damage. Ex vivo exposure to CPF for 1 h increased Abcc2 transport, and 12 h in vivo exposure to CPF induced the expression of intestine abcc2, the nuclear receptor PXR, and other PXR-regulated genes, and downregulated the AhR pathway.Discussion-Conclusion: MCLR and AsIII are ABCC substrates. AsIII induces intestinal Abcc2 gene expression, indicating the activation of a pathway that favours its excretion and that of other pollutants such as MCLR. Contrarily, the incremented activity of basolateral ABCCs after in vivo exposure to MCLR can increase MCLR transport into the blood and to other tissues. PST and CPF affect ABCC transporters but not as transport substrates. The inhibition of basolateral ABCCs by PST can lead to intracellular accumulation of toxic substrates. CPF increases Abcc2 activity and expression through a regulatory pathway which could increase the excretion of toxic compounds.