Regulation of hydrogen peroxide release in circulating hemocytes of the planorbid snail Biomphalaria glabrata

Biomphalaria spp. serve as obligate intermediate hosts for the human blood fluke Schistosoma mansoni. Following S. mansoni penetration of Biomphalaria glabrata, hemocytes of resistant snails migrate towards the parasite, encasing the larva in a multicellular capsule resulting in its destruction via a cytotoxic reaction. Recent studies have revealed the importance of hydrogen peroxide (H2O2) and nitric oxide (NO) in parasite killing [Hahn UK, Bender RC, Bayne CJ. Killing of Schistosoma mansoni sporocysts by hemocytes from resistant Biomphalaria glabrata: role of reactive oxygen species. J Parasitol 2001;87:292–9; Hahn UK, Bender RC, Bayne CJ. Involvement of nitric oxide in killing of Schistosoma mansoni sporocysts by hemocytes from resistant Biomphalaria glabrata. J Parasitol 2001;87:778–85]. It is assumed that H2O2 and NO production is tightly regulated although the specific molecules involved remain largely unknown. Consequently, the potential role of cell signaling pathways in B. glabrata hemocyte H2O2 production was investigated by evaluating the effects of specific inhibitors of selected signaling proteins. Results suggest that both ERK and p38 MAPKs are involved in the regulation of B. glabrata H2O2 release in response to stimulation by PMA and galactose-conjugated BSA. However, the involvement of the signaling proteins PKC, PI3 kinase and PLA2 differs between PMA- and BSA-gal-induced H2O2 production.