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Epidemiological studies in the developing world are frequently biased by the simultaneous presence of several infectious pathogens. In the present study, we examined the usefulness of circulating markers of oxidative stress and liver fibrosis to investigate the distinct forms of chronic liver inflammations associated with schistosomiasis and viral hepatitis, respectively. The study was performed in a Sudanese population exposed to Schistosoma. Circulating hyaluronic acid (HA) was used as a marker of liver fibrosis; the severity of schistosomiasis was determined by ultrasonic examination; viral hepatitis infection was ascertained by circulating anti-hepatitis antibodies. Serum markers were examined also in Sudanese subjects not exposed to Schistosoma infection and in French control subjects. We found a drastic decrease of lycopene levels in the subjects exposed to schistosomiasis in comparison with non-exposed Sudanese and French control subjects. Retinol, alpha-tocopherol and five carotenoids were unchanged. Lycopene depletion was unlikely to be due to variations of nutritional origin, since the lycopene/beta-carotene ratio was five-fold lower in the population at risk of schistosomiasis than in the other groups. We found that high HA serum levels were associated with severe periportal fibrosis but not with viral infection. Conversely, levels of the oxidized lipid malondialdehyde (MDA) were associated with viral infection but not with the severity of schistosomiasis, even though the two infections had additive effects. We concluded that serum markers are valuable tools for investigating the complex effects of co-existing factors of chronic liver inflammation.

Molecular hydrogen reacts with the hydroxyl radical, a highly cytotoxic species produced in inflamed tissues. It has been suggested therefore to use gaseous hydrogen in a new anti-inflammatory strategy. We tested this idea, with the aid of the equipment and skills of COMEX SA in Marseille, a group who experiments with oxygen-hydrogen breathing mixtures for professional deep-sea diving. The model used was schistosomiasis-associated chronic liver inflammation. Infected animals stayed 2 weeks in an hyperbaric chamber in a normal atmosphere supplemented with 0.7 MPa hydrogen. The treatment had significant protective effects towards liver injury, namely decreased fibrosis, improvement of hemodynamics, increased NOSII activity, increased antioxidant enzyme activity, decreased lipid peroxide levels and decreased circulating TNF-alpha levels. Under the same conditions, helium exerted also some protective effects, indicating that hydroxyl radical scavenging is not the only protective mechanism. These findings indicate that the proposed anti-inflammatory strategy deserves further attention.

We investigated the nitric oxide (NO) synthase and arginase pathways in resident peritoneal macrophages of mice infected with the tropical parasite Schistosoma mansoni. The two enzymes may have opposite effects, insofar as NO may be involved in the killing of the parasite whereas arginase may stimulate parasite growth via polyamine synthesis. We determined the effects of the infection on the expression and activity of the two enzymes in macrophages, before and after cytokine activation. Cells from infected mice expressed the hepatic type I arginase, whereas in control cells, the enzyme was expressed only after cytokine activation, as were NO synthase II and type II arginase in both groups of cells. Moreover, we found that in infected mice, arginase expression in macrophages was associated with a ten fold increase in the concentration of circulating ornithine-derived polyamines. This may be of pathological importance, since parasitic helminths are though to be dependent on their hosts for the uptake and interconversion of polyamines.

We investigated the involvement of nitric oxide in Schistosoma-induced liver injury. We found that inducible nitric oxide synthase mRNA became detectable in the liver at the onset of parasite egg laying and levels then increased as the eggs accumulated in the organ. Enzyme concentration and activity paralleled mRNA levels. The event was a direct effect of egg deposition, as it occurred in the liver after natural infection, or in the lungs after i.v. injection of the eggs. However, nitric oxide seems to have no direct effect on the eggs since in vitro assays showed that the nitric oxide donor SIN-1 did not alter the ability of the eggs to hatch. L-Arginine and L-NAME, a nitric oxide synthase inhibitor, were administered to infected mice in an attempt to increase or reduce nitric oxide production, respectively. Arginine had no effect on the disease, whereas the inhibitor led to a marked decrease of hepatic injury with, in particular, reduced fibrosis and decreased lipid peroxidation. In conclusion, not only is inducible nitric oxide synthase activity unlikely to exert an anti-microbicidal effect against the egg stage of S. mansoni but it might lead to deleterious effects in the liver and therefore contribute to the pathology.

We showed previously that infection by Schistosoma mansoni not only triggers the production of reactive oxygen species in mouse liver but also leads to the alteration of antioxidant defences. To determine whether such events occur in humans, we measured the serum markers of oxidative stress, i.e., lipid peroxides and protein carbonyl, as well as hyaluronate levels in subjects in the Managil area of the Sudan. Grades of fibrosis were determined by ultrasonographic examination. Two groups were used as controls, one Sudanese and the other European. We found that Sudanese subjects in the endemic area differed from the control groups, both Sudanese and European, insofar as they had higher levels of the serum metabolites measured. The latter increased with the grade of fibrosis. Moreover, protein carbonyl and hyaluronic acid levels correlated positively with lipid peroxide levels. These findings indicate that oxidative stress might contribute to S. mansoni-associated pathology in man. The serum markers considered in our study, obtained by relatively simple techniques, may provide a useful biochemical index for the identification of almost asymptomatic patients who, however, are at risk of developing severe schistosomiasis.

Background/aims: 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.

Background/aims: The tropical parasite Schistosoma mansoni causes granulomatous inflammation following lodging of eggs in portal capillaries. In vitro studies indicated that the host reaction should involve reactive oxygen intermediates; however, it is not known what occurs in vivo at the site of the disease. Moreover, the ultimate pathophysiological effects of oxidative processes depend upon antioxidant factors, which are investigated in this study., Methods: We explored the changes in the major enzyme activities involved in liver redox metabolism during the course of infection and, for some of them, the mRNA expression. We also measured the reduced glutathione and lipid peroxide levels in the liver., Results: We found that the deposition of parasite eggs triggers the release of endogenous eosinophil peroxidase; enzyme activity developed in the immediate vicinity of the eggs and it increased dramatically with time. However, Cu,Zn-superoxide dismutase, catalase and glutathione peroxidase activities decreased drastically. In contrast, glutathione transferase was unaffected. There was no proportional decrease in mRNA levels for the H2O2 scavenging enzymes. Reduced glutathione concentrations also dropped as a result of infection. Lastly, a two-fold increase in the levels of hepatic products generated by lipid peroxidation was observed., Conclusions: These results show that on the one hand oxidative processes occurred at the site of granulomatous inflammation and on the other hand the antioxidant capacity of the liver decreased, leading to the generation of lipid peroxides. The resulting imbalance between pro- and anti-oxidant processes may play a central role in the pathology associated with schistosomiasis.