Effects of Microcystin toxicity present in the crude extract of cyanobacteria, Radiocystis fernandoi on liver of Neotropical fish (Hoplias malabaricus)

TAVARES D.; PAULINO M.G.; ROSSI P.A.; VENTURINI F.P.; BIECZYNSKI, F.; TEREZAN A.P.; SAKURAGUI M.M.; SOUZA N.E.S.; MORAES, G.; GIANI, A.; LUQUET, C.M.; FERNANDES J.P.; FERNANDES M.N.

PIRACICABA

Workshop; 1st International workshop of cyanobacterial natural products; 2016

Microcystins is toxic to fish. It can accumulate in the fish tissues causing and changes in liver structure. This study evaluated the bioaccumulation potential of the majority microcystins in the crude extract of the cyanobacteria Radiocystis fernandoi cepa R28 on the fish Hoplias malabaricus after subchronical exposure and their effect on the liver by assessing its structure and the detoxification process. Fish were intraperitoneally injected with 100 μg MC-LReq kg-1 every 72 hours during 30 days. Biochemical and morphological biomarkers were used to evaluate the action of toxins, structural and ultrastructural damage and the detoxification mechanisms. The activity of the SOD-CAT system increased by 31% and 68%, respectively, indicating the production of reactive oxygen species (ROS). Conversely, the activity of GPx decreased 58%, indicating the inhibition of enzyme synthesis or its activity. The reduction of MDA (63%) and protein carbonylation indicate an efficient SOD-CAT response. The alanine aminotransferase and aspartate activity in plasma and the serine protein phosphatase/threonine PP2A was inhibited in the liver indicating liver damage. Animals injected with MCs increased plasma activity of transaminases, ALT (101%) and AST (900%), and BD (137%). Increased ALT and AST activity in plasma showed liver injury, which was confirmed with increasing BD concentration in the blood. Macroscopically occurred changes in the color, texture and liver mass; microscopically the morphology of hepatocytes and intracellular organelles were altered and abundant fibrous tissue disrupted the architecture of the liver parenchyma. Moreover, the inhibition of detoxification process was evidenced by decreasing the GSH content and GST activity. In conclusion, although oxidative stress was not observed by the responses of the liver antioxidant system, the changes of the liver biochemical variables and structure evidenced functional impairment of the organ suggesting that the microcystin present in the crude extract of cyanobacteria R. fernandoi (R28 strain) compromise the animal health and may affect growth, reproduction and even survival after long term exposure.