Role of nitric oxide in host defense against Hymenolepis nana infection.

The defensive role of nitric oxide (NO) against Hymenolepis nana was investigated in vivo and in vitro studies. Serum NO levels were increased (P < 0.001) in mice 5 days (cysticercoid stage) and 15 days (adult stage) after H. nana induced oral infection with 1000 eggs/mouse, compared with normal controls. Meanwhile, L-NAME, a NO synthase inhibitor, oral administration in drinking water to infected mice caused a non significant decrease in serum NO levels (P > 0.05) compared with normal controls, and was associated with a significant increase in number of both cysticercoids and adult worms (P < 0.001) compared to that in infected mice 5 and 15 days post infection. In an in vitro study, the NO donor; sodium nitroprusside caused an increased mortality rate of H. nana cysticercoids and adult worms (P < 0.001) compared with controls without NO donor, and this was in a concentration-dependent manner (P < 0.001). Implications of these results are discussed.