Effects of dietary heavy metals on the immune and antioxidant systems of Galleria mellonella larvae

In this work, we analyzed the effects of chromium (Cr) and lead (Pb) on immune and antioxidant systems of Galleria mellonella. In particular, after exposure to diets containing environmentally relevant concentrations (5, 50 and 100 μg/g) of Cr or Pb for 7 d, alterations in innate immune parameters and the activity of endogenous enzymes were measured in larvae. The results showed that 1) compared with the control, the lowest doses (5 μg/g) of Cr and Pb significantly increased the levels of innate immune parameters (total hemocyte count, THC; phagocytic activity; extent of encapsulation) of the larvae and hemolymph immune enzyme activities (acid phosphatase, ACP; alkaline phosphatase, AKP; phenoloxidase, PO), whereas the highest doses (100 μg/g) of Cr and Pb inhibited them; 2) the activity of antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT) showed significant increases with increasing concentrations of dietary Cr and Pb, and were significantly higher than those of the control; and 3) feeding the larvae with experimental concentrations of either Cr or Pb resulted similar patterns of changes of all the parameters examined. The current study suggested that moderate amounts of Cr and Pb enhance the innate immunity of G. mellonella, but that large amounts led to the inhibition of larval immune function, and also indicated that the experimental concentrations of Cr and Pb used caused strong oxidative stresses in the larvae.