Microcystin-LR sensitizes the Oncorhynchus mykiss intestinal epithelium and interacts with paralytic shellfish toxins to alter oxidative balance

• Published in: Toxicology and applied pharmacology Vol. 485; p. 116891
• Main Authors: Painefilú, Julio C., González, Carolina, Krock, Bernd, Bieczynski, Flavia, Luquet, Carlos M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2024
• Subjects: ABCC transporters; Animals; Fish intestine; Glutathione - metabolism; Intestinal Mucosa - drug effects; Intestinal Mucosa - metabolism; Marine Toxins - toxicity; Microcystin; Microcystins - toxicity; Neurotoxin; Oncorhynchus mykiss - metabolism; Oxidative Stress; Oxidative Stress - drug effects; Reactive Oxygen Species - metabolism; Saxitoxin - toxicity; Toxins interaction; Microcystin; Fish intestine; ABCC transporters; Oxidative Stress; Neurotoxin; Toxins interaction
• ISSN: 0041-008X; 1096-0333
• DOI: 10.1016/j.taap.2024.116891

In the context of harmful algal blooms, fish can be exposed to the combined effects of more than one toxin. We studied the effects of consecutive exposure to Microcystin-LR (MCLR) in vivo and paralytic shellfish toxins (PST) ex vivo/in vitro (MCLR+PST) in the rainbow trout Oncorhynchus mykiss's middle intestine. We fed juvenile fish with MCLR incorporated in the feed every 12 h and euthanized them 48 h after the first feeding. Immediately, we removed the middle intestine to make ex vivo and in vitro preparations and exposed them to PST for one hour. We analyzed glutathione (GSH) and glutathione disulfide (GSSG) contents, glutathione S-transferase (GST), glutathione reductase (GR), catalase (CAT), and protein phosphatase 1 (PP1) activities in ex vivo intestinal strips; apical and basolateral ATP-biding cassette subfamily C (Abcc)-mediated transport in ex vivo everted and non- everted sacs; and reactive oxygen species (ROS) production in isolated enterocytes in vitro. MCLR+PST treatment decreased the GSH content, GSH/GSSG ratio, GST activity, and increased ROS production. GR activity remained unchanged, while CAT activity only increased in response to PST. MCLR inhibited PP1 activity and activated Abcc-mediated transport only at the basolateral side of the intestine. Our results show a combined effect of MCLR+PST on the oxidative balance in the O. mykiss middle intestine, which is not affected by the two toxins groups when applied individually. Basolateral Abcc transporters activation by MCLR treatment could lead to an increase in the absorption of toxicants (including MCLR) into the organism. Therefore, MCLR makes the O. mykiss middle intestine more sensitive to possibly co-occurring cyanotoxins like PST. [Display omitted] •Microcystin-LR and Paralytic Shellfish Toxins interact to produce oxidative stress.•Microcystin-LR induces ABCC-mediated transport in enterocytes' basolateral membrane.•Paralytic Shellfish Toxins do not affect MCLR-induced protein phosphatase inhibition.