Effects of depuration on histopathological changes in tilapia (Oreochromis niloticus) after exposure to cylindrospermopsin

Cylindrospermopsin (CYN) is a highly water-soluble cytotoxin produced by several species of freshwater cyanobacteria and it is considered the second most studied cyanotoxin worldwide. CYN acts as a potent protein and glutathione synthesis inhibitor, as well as inducing genotoxicity, oxidative stress and histopathological alterations. Studies concerning the depuration of cyanobacterial toxins in aquatic organisms, especially in fish, are of great interest for fish economy and public health, but are scarce in the case of CYN. This is the first study reporting the ability of depuration (3 − 7 days) in reversing or ameliorating the histopathological lesions induced in liver, kidney, heart, intestines, and gills of tilapia (Oreochromis niloticus) due to exposure by immersion to repeated doses of a CYN-containing culture of A. ovalisporum for 14 days. The main histopathological changes induced by CYN were glucogenic degeneration and loss of the normal hepatic cord-structure (liver), hyperemia, dilated Bowman's capsule and cellular tumefaction (kidney), myofibrolysis, hemorrhages and edema (heart), necrosis and partial loss of microvilli (gastrointestinal tract), and hyperemia and inflammatory cells infiltrates (gills). After 3 days of depuration, gills were totally recovered, while the liver, kidney, and gastrointestinal tract required 7 days, and longer depuration periods may be needed for a full recovery of the heart. In addition, the morphometric study indicated that depuration managed to reverse the affectation in the hepatocytes nuclear diameters and cross sections of the proximal and distal convoluted tubules induced in CYN-exposed fish. In general, these results validate depuration as an effective practice for detoxification of fish contaminated with CYN. © 2016 Wiley Periodicals, Environ Toxicol 32: 1318–1332, 2017. © 2016 Wiley Periodicals,

This work was supported by the Ministerio de Ciencia e Innovación of Spain (AGL2009‐10026 and AGL2015‐64558‐R), co‐financed with FEDER funds, and the Junta de Andalucía (P09‐AGR‐4672). The authors would like to acknowledge the European Cooperation in Science and Technology, COST Action ES 1105 “CYANOCOST‐Cyanobacterial blooms and toxins in water resources: Occurrence, impacts and management” for adding value to this study through networking and knowledge sharing with European experts and researchers in the field. Remedios Guzmán Guillén also gratefully acknowledges the Spanish Ministerio de Educación for her grant “Formación del Profesorado Universitario (FPU)”.