Antioxidative responses in Galleria mellonella larvae infected with the entomopathogenic nematode Heterorhabditis sp. beicherriana

The effects of a new species Heterorhabditis sp. beicherriana on the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and malondialdehyde (MDA) content of the host were studied. Last-instar larvae of Galleria mellonella were used as host insects and were experimentally infected with H. beicherriana at 0, 20, 40, 80 infective juveniles (IJs) per insect. At 0, 8, 16, 24, 32 and 40 h after infection, activities of SOD, POD, CAT and MDA content were determined in extracts from infected and control insects. We found that H. beicherriana infection resulted in gradually increased activities of SOD, POD and CAT the first day and decreased activities of these enzymes thereafter. However, MDA content in the insects of both control and IJ-inoculated groups stayed at a similar level at 24 h post-infection, but a significant decrease of MDA content in inoculated groups was recorded after 32 h of the infection, which is 8 hours later than the activities of SOD, POD and CAT were significantly increased. Our results suggest that H. beicherriana infection increases the level of oxidative stress and antioxidative responses in the larval G. mellonella, and it seems that oxidative damage contributes to cell death in this host.