Entamoeba histolytica: Production of nitric oxide and in situ activity of NADPH diaphorase in amebic liver abscess of hamsters

La Salle University, Filadelfia, Pennsylvania, United States
Parasitology Research (Impact Factor: 2.1). 02/2001; 87(1):49-56. DOI: 10.1007/s004360000287
Source: PubMed


Entamoeba histolytica trophozoites were inoculated into the liver of hamsters and serum nitrate/nitrite levels [expressed as nitric oxide (NO) production] were determined at different times during amebic liver abscess (ALA) development. We also tested the effects of NO synthase (NOS) inhibitors such as N(G)-nitro-L-arginine methyl ester (L-NAME), aminoguanidine, and dexamethasone during ALA production. Since NOS activity has been correlated with expression of reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) in tissues, we performed histochemistry studies to determine the activity of the latter in livers infected with E. histolytica trophozoites. Production of NO in serum was directly proportional to the size of ALAs, and NOS inhibitors caused low levels of NO and smaller ALAs. Our data suggest that NO does not have any lytic effect on E. histolytica trophozoites and is therefore incapable of providing protection against the amebic liver infection. In addition, NADPHd activity was detected histochemically in hepatocytes and inflammatory cells associated with focal necrosis containing trophozoites. The positive reactivity observed in these parasites may be attributable to a close biochemical similarity of NADPHd to the NADPH:flavin oxidoreductase described in E. histolytica by other investigators.

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Available from: Jesus Serrano-Luna, Jul 03, 2014
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    • "There is no direct in vivo evidence of ONOO−, probably due to its high reactivity [69, 70]. However, nitrate and nitrite, the products of spontaneous decomposition of this molecule, have been detected in the serum of hamsters with ALA [52, 53]. "
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    • "Serum samples were incubated overnight and cell culture supernatants for 1 h [16]. In the second procedure supernatants were deproteinized with 30% w/v ZnSO 4 by incubating 100-l samples with 5 l ZnSO 4 [17]. In both cases, to sediment the precipitated proteins, the samples were centrifuged at 12,000g for 10 min at 4 °C and nitrite concentration was determined in the supernatant. "
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