The effect of nitric oxide and hydrogen peroxide in the activation of the systemic immune response of Anopheles albimanus infected with Plasmodium berghei.

The expression of genes encoding the antimicrobial peptides (AMPs) attacin, cecropin and gambicin, as well as the effects of NO and H(2)O(2) on their expression was investigated in midguts and fat bodies of Anopheles albimanus during the midgut infection with Plasmodium berghei. Midgut infection induced an increase in the expression of the three AMPs in both tissues; while NO and H(2)O(2) were present in haemolymph. Treatment with L-NAME and vitamin C reduced the effect of P. berghei infection on the AMP's expression, and exogenous NO and H(2)O(2) induced their expression in the mosquito fat body. The induction of AMPs in abdominal tissues, while the malaria parasites are in the mosquito midgut, suggests communication between the midgut epithelial cells and the abdominal tissue which has not yet had direct contact with the parasites. Free radical production in mosquito midgut and haemolymph during Plasmodium infection and their inductive effect on AMPs in abdominal tissues indicates the possible participation of these radicals in mediating a systemic immune response in this mosquito.