Characterization of Superoxide Dismutase in the Metacestode of Echinococcus granulosus Sensu Stricto (s. s.) and Buffalo Liver.

Purpose: The present study assessed the level of superoxide dismutase (SOD) in the metacestode of Echinococcus granulosus sensu stricto (s. s.) as well as in the liver of Indian water buffalo (Bubalus bubalis).

Methods: SOD activity was analyzed by the pyrogallol autoxidation assay and electrophoretic fractionation by native polyacrylamide gel electrophoresis, followed by specific staining of the enzyme. Besides this, metallic co-factor of SOD was determined using different concentrations of inhibitors.

Results: The protoscoleces and cyst wall have appreciable amount of SOD, and the level of SOD was found to be significantly (p ≤ 0.001) higher in the fertile compared to non-fertile cyst wall and the infected than non-infected liver. Four SOD activity bands were observed in the protoscoleces, while one band each in the fertile and non-fertile cyst wall, suggesting the occurrence of isozymes in the protoscoleces but not in the cyst wall. Approximately 99% and 16% of enzyme activity were inhibited at 5 mM concentration of KCN and H₂O₂, respectively. Furthermore, no activity band of SOD was detected in the gels treated with 5 mM KCN whereas, the same concentration of H₂O₂ and NaN₃ does not affect the visibility of SOD activity band.

Conclusion: The present study indicated that the protoscoleces and cyst wall contain a significant amount of SOD, which likely contributes to their survival within the hostile microenvironment of the host. Inhibition studies revealed the presence of Cu/Zn SOD in the protoscoleces, cyst wall, and host liver. The elevated SOD levels in infected liver may be a protective adaptation against self-generated reactive oxygen species (ROS).