Visualization of oxygen radical production in mouse liver in response to infection with Schistosoma mansoni.
OBJECTIVE
The tropical parasite S. mansoni induces granulomatous inflammation in the liver, following the lodging of eggs in this organ. In vitro studies suggested that the host's response might involve the production of oxygen radicals.


METHODS
In an attempt to investigate the situation at the site of inflammation, under disease conditions, livers of infected mice were treated with dichlorodihydrofluorescein diacetate which fluoresces after oxidation.


RESULTS
Fluorescence of the oxidized tracer revealed that oxygen radicals were produced by granulomatous inflammatory cells. The phenomenon reached its highest intensity close to the eggs. The membranes of the cells were strongly labelled, probably reflecting membrane-associated NADPH oxidase activity. The cytoplasm of hepatocytes was also fluorescent but with lower intensity; hepatocyte membranes or nuclei were not labelled. Fluorescence was reduced drastically by treatment with catalase and antioxidants, indicating the occurrence of H2O2. Treatment with superoxide dismutase had no effect. Neither the livers of uninfected animals nor those of infected animals before parasite egg deposition were labelled. Eosinophil peroxidase activity was released in the areas of inflammatory cells, but was not found in hepatocytes.


CONCLUSIONS
The H2O2/peroxidase system, which is the cornerstone of the antimicrobial defense associated with inflammation, is activated in close contact with parasite eggs. The process does contribute to egg killing in vivo. Moreover, hepatocytes undergo oxidative stress in the entire organ. This finding is in agreement with the parasite-induced decrease of liver antioxidant defenses demonstrated previously.
Abdallahi
O M
OM
INSERM U399, Univ Mediterranee, Marseille, France.
Hanna
S
S
De Reggi
M
M
Gharib
B
B
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D047209:Eosinophil Peroxidase; D005260:Female; D005452:Fluoresceins / Q000378:metabolism; D005453:Fluorescence; D015745:Granuloma, Foreign-Body / Q000378:metabolism / Q000469:parasitology / Q000473:pathology; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D007124:Immunoenzyme Techniques; D008109:Liver Diseases, Parasitic / Q000378:metabolism* / Q000469:parasitology / Q000473:pathology; D051379:Mice; D008808:Mice, Inbred CBA; D010084:Oxidation-Reduction; D010270:Parasite Egg Count; D010544:Peroxidases / Q000378:metabolism / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012550:Schistosoma mansoni / Q000472:pathogenicity*; D012555:Schistosomiasis mansoni / Q000378:metabolism* / Q000469:parasitology / Q000473:pathology
C110400:2',7'-dichlorodihydrofluorescein diacetate; D000975:Antioxidants; D005452:Fluoresceins; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D047209:Eosinophil Peroxidase; D010544:Peroxidases; D002374:Catalase