Alterations in the intestine of Patagonian silverside (Odontestheshatcheri) exposed to microcystin-LR: Changes in the glycosylationpattern of the intestinal wall and inhibition of multidrug resistanceproteins efflux activity

BIECZINSKY, FLAVIA; TORRES, WALTER; PAINEFILU, JULIO; CASTRO, JUAN M.; BIANCHI, VIRGINIA A.; FRONTERA, JIMENA; PAZ, DANTE; GONZÁLES, CAROLINA; MARTÍN, ALEJANDRO; VILLANUEVA, SILVINA; LUQUET, CARLOS

AQUATIC TOXICOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 178 p. 106 - 117

0166-445X

Accumulation and toxicity of cyanobacterial toxins, particularly microcystin-LR (MCLR) have been exten-sively studied in fish and aquatic invertebrates. However, MCLR excretion mechanisms, which couldreduce this toxin?s effects, have received little attention. The Patagonian silverside, Odontesthes hatcheri,is an omnivorous-planktivorous edible fish, which has been shown to digest cyanobacterial cells absorb-ing MCLR and eliminating the toxin within 48 h without suffering significant toxic effects. We studiedthe effects of MCLR on glycoconjugate composition and the possible role of multidrug resistance associ-ated proteins (Abcc) in MCLR export from the cells in O. hatcheri intestine. We treated O. hatcheri with5 g MCLR g−1body mass administered with the food. Twenty four hours later, the intestines of treatedand control fish were processed for lectin-histochemistry using concanavalin A (ConA), Triticum vulgarisagglutinin (WGA), and Dolichos biflorus agglutinin (DBA). MCLR affected the distribution of glycoconju-gates by augmenting the proportion of ConA-positive at the expense of WGA-positive cells. We studiedMCLR effects on the transport of the Abcc-like substrates 2,4-dinitrophenyl-S-glutathione (DNP-SG) andcalcein in ex vivo intestine preparations (everted and no-everted sacs and strips). In treated preparations,CDNB together with MCLR (113 g MCLR g−1intestine, equivalent to 1.14 mol L−1when applied in thebath) or the Abcc inhibitor, MK571 was applied for one hour, during which DNP-SG was measured in thebath every 10 min in order to calculate mass-specific DNP-SG transport rate. MCLR significantly inhibitedDNP-SG transport (p < 0.05), especially in middle intestine (47 and 24%, for luminal and serosal transport,respectively). In middle intestine strips, MCLR and MK571inhibited DNP-SG transport in a concentrationdependent fashion (IC503.3 and 0.6 mol L−1, respectively). In middle intestine strips incubated withcalcein-AM (0.25 mol L−1), calcein efflux was inhibited by MCLR (2.3 mol L−1) and MK571 (3 mol L−1)by 38 and 27%, respectively (p < 0.05). Finally, middle intestine segments were incubated with differentconcentrations of MCLR applied alone or together with 3 M MK571. After one hour, protein phosphatase1 (PP1) activity, the main target of MCLR, was measured. 2.5 M MCLR did not produce any significanteffect, while the same amount plus MK571 inhibited PP1 activity (p < 0.05). This effect was similar to that of 5 M MCLR. Our results suggest that in O. hatcheri enterocytes MCLR is conjugated with GSH via GST andthen exported to the intestinal lumen through Abcc-like transporters. This mechanism would protect thecell from MCLR toxicity, limiting toxin transport into the blood, which is probably mediated by basolateral Abccs. From an ecotoxicological point of view, elimination of MCLR through this mechanism would reducethe amount of toxin available for trophic transference.