Abstract
The protozoan Entamoeba histolytica is the etiological agent of amoebiasis, which can spread to the liver and form amoebic liver abscesses. Histological studies conducted with resistant and susceptible models of amoebic liver abscesses (ALAs) have established that neutrophils are the first cells to contact invasive amoebae at the lesion site. Myeloperoxidase is the most abundant enzyme secreted by neutrophils. It uses hydrogen peroxide secreted by the same cells to oxidize chloride ions and produce hypochlorous acid, which is the most efficient microbicidal system of neutrophils. In a previous report, our group demonstrated that myeloperoxidase presents amoebicidal activity in vitro. The aim of the current contribution was to analyze in vivo the role of myeloperoxidase in a susceptible (hamsters) and resistant (Balb/c mice) animal models of ALAs. In liver samples of hamsters and mice inoculated intraportally with Entamoeba histolytica trophozoites, the number of neutrophils in ALAs was determined by enzymatic activity. The presence of myeloperoxidase was observed by staining, and its expression and activity were quantified in situ. A significant difference existed between the two animal models in the number of neutrophils and the expression and activity of myeloperoxidase, which may explain the distinct evolution of amoebic liver abscesses. Hamsters and mice were treated with an MPO inhibitor (4-aminobenzoic acid hydrazide). Hamsters treated with ABAH showed no significant differences in the percentage of lesions or in the percentage of amoebae damaged compared with the untreated hamsters. ABAH treated mice versus untreated mice showed larger abscesses and a decreased percentage of damaged amoebae in these lesion at all stages of evolution. Further studies are needed to elucidate the host and amoebic mechanisms involved in the adequate or inadequate activation and modulation of myeloperoxidase.
Highlights
The protozoan Entamoeba histolytica (E. histolytica) is the etiological agent of amoebiasis, which mainly affects the colon
The increase in the neutrophils in the infiltrates and the posterior reduction in the percentage was quite similar in both animal models, except that the reduction of neutrophils was more drastic in hamsters than in mice, as determined by Student’s t-test (ÃÃÃ p
We demonstrate for the first time that there was a smaller number of neutrophils positive for MPO in the inflammatory infiltrate of a resistant model of amoebic liver abscess (ALAs) (Balb/c mice), than in a susceptible model
Summary
The protozoan Entamoeba histolytica (E. histolytica) is the etiological agent of amoebiasis, which mainly affects the colon. It can spread to the liver and gives rise to amoebic liver abscess (ALAs)[1] [2]. It is known that there is a gender-based susceptibility to the development of invasive amoebiasis, being more frequent for adult males. This may be due to a greater male-related susceptibility to asymptomatic infectious [3]. Gender differences have been observed in animal models, whereas female C57BL/6 mice were resistant to ALA development, male mice presented a prolonged ALA recovery time [4]. The reasons for these differences are still unknown
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