Schistosomicidal activities ofLymnaea stagnalishaemocytes: the role of oxygen radicals

Abstract

Macrophage-like defence cells (haemocytes) of the pond snail Lymnaea stagnalis mediate cytotoxicity through reactive oxygen intermediates (ROIs). This activity is NADPH-oxidase dependent, as in mammalian phagocytes during the respiratory burst. In this study, mother sporocysts of schistosomes, the compatible Trichobilharzia ocellata and the incompatible Schistosoma mansoni evoke in vitro ROI activities (detected by luminol dependent chemiluminescence, LDCL) from L. stagnalis haemocytes. S. mansoni is encapsulated by haemocytes and eliminated, whereas T. ocellata escapes encapsulation and survives. Both schistosomes were equally susceptible to in vitro oxidative damage from exposure to hydrogen peroxide and to ROIs generated by a xanthine/xanthine oxidase system. Protocatechuic acid, a specific antagonist of NADPH-oxidase, delayed the killing of T. ocellata and S. mansoni sporocysts by haemocytes of resistant snails (Biomphalaria glabrata and L. stagnalis, respectively). We conclude that ROIs take part in haemocyte-mediated cytotoxicity. However, neither a snail's capability to generate ROIs, nor a schistosome's susceptibility to ROIs, determine snail/schistosome incompatibility. Snail/schistosome compatibility is rather determined by the parasite's ability to modulate haemocyte behaviour such that effective encapsulation and the generation of lethal concentrations of ROIs are prevented.

Ultrastructural study of the in vitro interaction between Biomphalaria glabrata hemocytes and Schistosoma mansoni miracidia

“…The invertebrate host defense response may include migration, super-oxide anions production associated with an encapsulation process or cell-mediated cytotoxicity reactions (Dikkeboom et al 1988, Adema et al 1994, Loverde 1998. All of these responses can occur indifferently in both resistant and susceptible molluscs, especially at the beginning of the interaction.…”

Stress and immune responses in abalone: Limitations in current knowledge and investigative methods based on other models

“…It proceeds through well-defined stages, including recognition, chemotaxis, attachment, ingestion and destruction of foreign particles [30,55,71,81,[88][89][90]. After internalisation, foreign particles are enclosed in a primary phagosome, which then fuses with lysosomes to form a phagolysosome.…”

β-1, 3-glucan modulates PKC signalling inLymnaea stagnalisdefence cells: a role for PKC in H2O2 production and downstream ERK activation

“…Haemolymph was then obtained by head-foot retraction (Sminia, 1972). This natural defence reflex involves the snail withdrawing into its shell following continual prodding of its head-foot; haemolymph is then expelled through the haemal pore (Sminia, 1972 (Adema et al, 1994) was then added to the extracted haemolymph (2 parts haemolymph: 1 part SSS) which was kept on ice to prevent haemocyte clumping.…”

“…This work was prompted because H 2 O 2 is a highly cytotoxic molecule that participates in the elimination of pathogens. Lymnaea stagnalis is intermediate host to schistosomes of the genus Trichobillharzia and H 2 O 2 might possess schistosomicidal activity (Dikkeboom et al, 1987;Adema et al, 1994); thus knowledge of the molecular control of H 2 O 2 production by molluscan haemocytes is crucial to our understanding of snail-schistosome host-parasite interactions. Laminarin stimulated H 2 O 2 production by L. stagnalis haemocytes, effects were dose-dependent and, when used at 10·mg·ml -1 , a tenfold increase in H 2 O 2 output occurred after 30·min challenge.…”