Role of Cell-generated Hydrogen Peroxide in Granulocyte-mediated Killing of Schistosomula of Schistosoma mansoni In Vitro

Abstract

A B S T R A C T Human as well as murine granulocytes have been shown to kill the larval stages of helminth parasites; the mechanism of this cell-mediated cytotoxicity is, however, poorly understood. The present study was designed to assess the role of peroxidative processes in killing of schistosomula of Schistosoma mansoni by human granulocytes in vitro. The rate of H202 production by human neutrophils, eosinophils, and basophils was measured upon incubation with schistosomula alone or in the presence of specific antibody or complement. Opsonized parasites (antibody and/or complement) increased the rate of H202 production by neutrophils, eosinophils, and basophils by respective percentages of 500, 500, and 371. The rate of H202 release was directly related to the number of granulocytes and to the proportion of cells attached to the surface of the schistosomula. Increased hydrogen peroxide release occurred by 10 min of incubation and was demonstrable up to 16 h after addition of leukocytes to schistosomula. The primary source of this oxygen product was found to be the granulocytes adherent to the schistosomula and not those that remained unattached. Hydrogen peroxide production by neutrophils and eosinophils was quantitatively similar (schistosomula coated with antibody plus complement stimulated 5 x 106 neutrophils and eosinophils to release H202 at respective rates of 0.35 and 0.40 nmol/min). Granulocyte-mediated parasite killing correlated with rate of H202 generation; both processes were inhibited by catalase. To define further the role of oxidative metabolites, neutrophils and eosinophils of two subjects with chronic granThis work was presented, in part, at the national meeting of the Association of American Physicians, Washington, D. C. 1980.Receivedfor publication 24 April 1980 and in revisedform 12 September 1980. ulomatous disease were used; marked reduction of granulocyte-mediated parasite mortality was observed.Peroxidase was required for H202-mediated killing. Addition of the peroxidase inhibitors azide (1 mM), cyanide (1 mM), or aminotriazole (1 cM) to neutrophilschistosomula mixtures significantly reduced parasite cytotoxicity (P < 0.01); similar reduction was observed when eosinophils were used (P <0.01). Fixation of halide (iodide) to trichloroacetic acid-precipitable protein (2.4-6.0 nmol/h per 107 neutrophils) was demonstrated in the presence of granulocytes, opsonins, and parasites; this process was completely inhibited by 1 mM azide.These data indicate that contact between the surfaces of human granulocytes and schistosomula results in release of cellular hydrogen peroxide and iodination. The generation of H202 and its interaction with peroxidase appear to be crucial in effecting in vitro granulocyte-mediated parasite cytotoxicity.

Species-related innate resistance to Schistosoma mansoni. Role of mononuclear phagocytes in schistosomula killing in vitro.

“…These cells were demonstrated to adhere to the parasite surface and to cause morphologically evident damage to (23,24); its activity against multicellular parasites is, however, poorly defined (25,26). Klebanoff (20) (27). While rat mononuclear phagocyte-mediated parasite killing was inhibited by catalase, rabbit monocyte cytotoxicity was not blocked by this enzyme, which may be related to the lack of cytochemically demonstrable peroxidase in their granules (20).…”

Eosinophils generate brominating oxidants in allergen-induced asthma

“…In vitro studies demonstrate that the EPO-H 2 O 2 -Br -system possesses potent antibacteriacidal, -fungicidal, -parasitic, and -viricidal activities (1,11,12,14,15,20). However, the potential beneficial aspects of these activities within the setting of an allergen-triggered asthma exacerbation are less clear.…”

“…A structurally and functionally distinct enzyme from neutrophil myeloperoxidase (MPO) (17)(18)(19), it shares with MPO the unique ability to use halides or pseudohalides (X -) and H 2 O 2 derived from the respiratory burst to generate cytotoxic hypohalous acids (HOX): H 2 O 2 + X -+ H + → HOX + H 2 O; where X = Cl -, Br -, I -, or SCN -). In cellfree models, halogenating oxidants formed by the EPO-H 2 O 2 -X -system are effective cytotoxins for multiple targets such as multicellular worms or parasites, bacteria, viruses, and host cells (1,(11)(12)(13)(14)(15)(16)20).…”

Pulmonary immune cells in health and disease: the eosinophil leucocyte (Part I)

“…These data suggest that the mature eosinophil is not only capable of releasing de novo generated lipid mediators and oxygen radicals but can also synthesize new proteins. [104,105,[108][109][110], and probably 1O 2 as well as OH· [111,112]. With most stimuli, the respiratory burst of eosinophils is greater than that of equivalent numbers of neutrophils [104,105,107,109,113].…”