Assessment of cypermethrin induced hepatic toxicity in Catla catla: A multiple biomarker approach

The study was designed to evaluate chronic toxicity of pyrethroid pesticide cypermethrin through biochemical, histopathological, ultrastructural and molecular biomarkers in liver of freshwater carp Catla catla. The fish were exposed to two sub-lethal concentrations (0.21 μg/L and 0.41 μg/L) for a period of 45 days. Compared to the control, a significant (p < 0.05) increase in the activity of enzymatic antioxidants catalase (CAT), superoxide dismutase (SOD) and glutathione-S-transferase (GST), and glutathione content (GSH) was registered after initial 15 days of exposure to the toxicant, followed by decline on 30th and 45th day. Whereas, MDA level remained elevated throughout the exposure duration at both the tested concentrations. Light microscopy revealed changes like sinusoidal dilation, vacuolation, pycnosis, karyolysis, nuclear pleomorphism, lymphocyte infiltration in liver of the exposed fish, with highest mean degree of tissue change (DTC) value of 58.6 ± 3.19 on 45th day. Ultrastructurally, cytopasmic vacuolation, reduced glycogen granules, dilated RER, deformed nuclear membrane, swollen & distorted mitochondria and augmentation in lipid bodies were the prominently observed cytopathological alterations. These anomalies increased in time-concentration dependent manner, being most severe after 45 days at higher concentration. The gene expression levels of Gadd-45α and Bcl-2 depicted altered patterns. Gadd-45α exhibited significant upregulation by 45th day, while Bcl-2 demonstrated initial upregulation, with subsequent downregulation on 30th and 45th day. Principal component analysis (PCA) generated two components, PC1 (SOD, GSH, MDA and DTC) and PC2 (CAT and GST). The findings suggest that cypermethrin inflicts marked hepatototoxic effects on Catla catla even at sub-lethal concentrations.