Uk. Hahn et al., Involvement of nitric oxide in killing of schistosoma mansoni sporocysts by hemocytes from resistant Biomphalaria glabrata, J PARASITOL, 87(4), 2001, pp. 778-785
In strains of the snail Biomphalaria glabrata (Gastropoda) that are resista
nt to the parasite Schistosoma mansoni (Trematoda), hemocytes in the hemoly
mph are responsible for elimination of S. mansoni sporocysts. The defensive
role of reactive nitrogen species was investigated in in vitro interaction
s between hemocytes derived from the resistant 13-16-R1 strain of B. glabra
ta and the parasite. The nitric oxide synthase (NOS) inhibitor N-omega-nitr
o-L-arginine methylester (L-NAME) and the nitric oxide (NO) scavenger 2-(4-
carboxyphenyl)-4,4,5,5 -tetramethylimidazoline-1-oxyl-3-oxide reduced cell-
mediated killing of S. mansoni sporocysts. To determine if peroxynitrite (O
NOO-) is involved in killing, assays were run in the presence of the ONOO-
scavengers uric acid and deferoxamine. These did not influence the rate of
parasite killing, indicating that NO is directly responsible for mediating
cytotoxicity, but ONOO- is not. The combination of the NOS inhibitor L-NAME
and catalase, an enzyme that detoxifies hydrogen peroxide (H2O2), reduced
average sporocyst mortality to a greater extent than L-NAME alone. Killing
of the sporocysts was, however, not totally inhibited. It is suggested that
NO and H2O2, are both involved in hemocyte-mediated toxicity of 13-16-R1 B
. glabrata against S. mansoni sporocysts.