Insecticides and Bio-insecticides Modulate the Glutathione-related Antioxidant Defense System of Cowpea Storage Bruchid (Callosobruchus maculatus)

The possible cellular involvements of cowpea storage bruchid (Callosobruchus maculatus (Fab.) [Coleoptera: Chrysomelidae]) glutathione and its related enzymes system in the cellular defense against insecticides (Cypermethrin and λ-cyhalothrin) and bio-insecticides (ethanolic extract of Tithonia diversifolia, Cyperus rotundus, Hyptis suavolens leaves, and Jatropha curcas seed) were investigated. The results showed that the effect of insecticides and bio-insecticides on the C. maculatus is a function of oxidative and nitrosative stresses generated in vivo. A significant (p < 0.05) increase in carbonyl protein (CP) and lipid peroxidation (LPO) contents in bio-insecticides and insecticides exposed groups compared to the control indicates the extent of vital organs damage. These stresses caused similar and significant increase of glutathione peroxidase and glutathione synthetase in response to insecticides and bio-insecticide exposure in a dose-dependent manner. There was no post-translational modification of glutathione transferases expression induced. The alterations of the insect glutathione-dependent antioxidant enzyme activities reflect the presence of a functional defense mechanism against the oxidative and nitrosative stress and are related firmly to the glutathione demands and metabolism but appear inadequate by the significant reduction in glutathione reductase (GR) activity to prevent the damages. Exogenous application of reduced glutathione (GSH), to complement the in vivo demand, could not protect against the onslaught.