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

FLAVIA BIECZYNSKI; PAINEFILÚ, JULIO C.; DE ANNA, JULIETA S; CARLOS M. LUQUET

Gothenburg

Congreso; The 21st International Symposium on Pollutant Responses In Marine Organisms; 2022

ABCC proteins are membrane transporters that work together with biotransformation enzymesto eliminate endogenous and exogenous toxic compounds. The apical ABCC transporters(Abcc2) of polarized epithelia, like the intestinal mucosa, function as a barrier againstpollutants. Basolateral ABCCs export compounds into the blood.We aim to integrate our studies on pollutants detoxification by fish intestinal ABCC proteinsand related biotransformation enzymes and nuclear receptors, emphasizing the experimentaldesign and considering the epithelial polarity when determining the organism?s defencecapacity 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 ABCCproteins transport. Coexposure with the specific ABCC inhibitor MK571 increases MCLRtoxicity. AsIII has similar effects only at the apical membrane. In vivo exposure to AsIII for 48h induces Abcc2 activity and expression. This effect reduces the toxicity of MCLR applied exvivo. In vivo exposure to MCLR increases GST activity and decreases ABCC transport at 12h. The transport activity rate recovers at 48 h but is higher than in control fish preparationsonly at the basolateral side.Ex vivo preparations exposed to PST showed lysosomal damage and inhibition of basolateralABCC transport. However, MK571 did not increase lysosomal damage. Ex vivo exposure toCPF for 1 h increased Abcc2 transport, and 12 h in vivo exposure to CPF induced theexpression of intestine abcc2, the nuclear receptor PXR, and other PXR-regulated genes, anddownregulated the AhR pathway.Discussion-Conclusion: MCLR and AsIII are ABCC substrates. AsIII induces intestinalAbcc2 gene expression, indicating the activation of a pathway that favours its excretion andthat of other pollutants such as MCLR. Contrarily, the incremented activity of basolateralABCCs after in vivo exposure to MCLR can increase MCLR transport into the blood and toother tissues. PST and CPF affect ABCC transporters but not as transport substrates. Theinhibition of basolateral ABCCs by PST can lead to intracellular accumulation of toxicsubstrates. CPF increases Abcc2 activity and expression through a regulatory pathway whichcould increase the excretion of toxic compounds.