Antioxidant defense system, immune response and erythron profile modulation in gold fish, Carassius auratus, after acute manganese treatment

The manganese contamination has become a global problem, recently, because it is perceived as a real threat to the human health and the environment. It is well-known that overexposure to Mn2+ may have negative physiological effects on fish and other organisms inhabiting heavy metal polluted waters. To the best of our knowledge, studies relating with manganese effects on fish antioxidant enzyme response in the blood, immunocompetence and erythron profile alteration, are scarce. In this study, the acute sub-lethal effects of manganese on blood antioxidant response, immune status and erythron profile were determined by exposing the freshwater model organism, Carassius auratus, to two doses of this metal (3.88 ± 0.193 mg/L and 7.52 ± 0.234 mg/L Mn2+) for 96 h. Significant increases in blood antioxidant enzyme activity like superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST), were observed in fish exposed to manganese. Furthermore, plasmatic glucose and cortisol levels increased, while total protein decreased significantly. White blood cell differential count revealed a significant increase in monocyte and neutrophil number and a significant decrease of lymphocyte's number in fish exposed to manganese compared with those of control group. That can be considered as a clear evidence of altered immune system. Measured of erythron profile revealed a significant increasing of cellular and nuclear alteration of red blood cells, with karryorhectic, dividing and micronucleated erythrocytes in exposed fish, indicating the cytotoxic and genotoxic effects Mn2+ ions. Our data shown also that manganese could trigger antioxidant response, modulate immune response and induce erythron profile modification leading to eryptosis, compromising the blood oxygen carrying capacity, and overall health status in fish. This may suggest those parameters consider as useful biomarkers for monitoring effects of sub-lethal metal exposure on fish.