José Clóvis do Prado Júnior

Dehydroepiandrosterone increases resistance to experimental infection by Trypanosoma cruzi

Dehydroepiandrosterone (DHEA) enhances immune responses against a wide range of viral, bacterial, and parasitic pathogens. In a previous study, we reported that administration of DHEA significantly decreased the numbers of blood parasites in Trypanosoma cruzi experimental infection. The present study was undertaken to determine the effectiveness of DHEA in reducing the severity of acute phase T. cruzi infection of male and female Wistar rats. Animals were treated subcutaneously with 40 mg/kg body weight/day of DHEA. The concentration of nitric oxide (NO) was determined in spleen peritoneal cavity. Interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) were determined in the sera of uninfected and infected animals. DHEA treatment augments NO production for both sexes after in vitro LPS treatment for uninfected animals. Infection triggered enhanced NO levels although not significant. IL-2 and IFN-gamma were detectable in higher concentrations in treated and infected rats of both genders when compared to untreated controls. These data suggest that DHEA may have a potent immunoregulatory function that can affect the course of T. cruzi infection.

Endocrine and immune system interactions during pregnancy

Pregnancy is known to induce a transient depression of maternal cell-mediated immunity, to prevent rejection of the fetus, while at the same time it keeps adequate maternal host defense mechanisms to fight infection. Presently, the aim of this paper was to investigate a possible endocrine and immunologic alteration observed during a successful pregnancy. This study consistently showed that plasma corticosterone levels were significantly higher (P<0.0001) in pregnant Wistar rats than in virgin female. An increased number of peritoneal macrophages was also detected in pregnant females when compared to non-pregnant ones. Macrophages play an important role in the production of bioactive proteins and lipids such as nitric oxide. Then, in support of the latter, the present study showed increased levels of endogenous NO in pregnant rats when compared to non-pregnant ones, thereby mediating the vasodilatation process of normal gestation. Furthermore, our FACS analysis clearly indicated the correlation between reduced CD161 expression on NK cells (P<0.0001) in pregnant rats when compared to virgin females. It was found that pregnancy appears to be associated with depressed cell immunity, as evidenced by a significant inhibition of lymphocyte proliferation. Understanding the immunological paradox of maternal tolerance, as well as the hormonal modulation of the immune environment during pregnancy is essential for future studies to investigate the potential for these processes to be modulated by diet or effective therapeutics during pregnancy.

Effects of dehydroepiandrosterone-sulfate (DHEA-S) and benznidazole treatments during acute infection of two different Trypanosoma cruzi strains.

A significant role for hormones in regulating the balance of Th1- and Th2-associated cytokines with a role in modulating diseases has been accumulating. Previously, we reported that dehydroepiandrosterone (DHEA), the most abundant steroid hormone synthesized by the adrenal cortex, markedly reduced the blood and tissue parasites in experimentally Trypanosoma cruzi-infected rats. Based on these findings, the main purpose of this study was to investigate the effect of dehydroepiandrosterone-sulfate ester (DHEA-S) therapy alone or in combination with benznidazole (BNZ) (recommended in Brazil for the treatment of T. cruzi infection) will be effective during the acute phase of two different lineages of T. cruzi strains: type I (Y strain) and type II (Bolivia strain) of T. cruzi. Administration of either DHEA-S or BNZ alone or in combination significantly reduced the Y strain parasite load as compared with untreated. Furthermore treatment with DHEA-S resulted in Bolivia strain clearance. This protective effect of DHEA-S was associated with the hosts immune response, as evidence by enhanced levels of interferon-gamma and interleukin-2. DHEA-S treatment also increased peritoneal macrophages levels and nitrite production. DHEA-S treatment was effective in reducing the mortality rate as compared to BNZ alone or to combiner DHEA-S+BNZ treatment of T. cruzi Bolivia strain infected animals. These findings suggest that hormonal therapy may have a protective effect in the treatment of T. cruzi infection.

Does l-arginine availability during the early pregnancy alters the immune response of Trypanosoma cruzi infected and pregnant Wistar rats?

Chagas disease induces a strong immune response and L-arginine is an essential amino acid which plays an important role in homeostasis of the immune system. The aims of this study were to evaluate parasitemia, corticosterone levels, production of nitric oxide (NO), fetal morphological measurements, and histology of heart and placenta. Twenty pregnant Wistar rats (180-220 g) were grouped in: pregnant control (PC), pregnant control and L-arginine supplied (PCA), pregnant infected (PI), pregnant infected and L-arginine supplied (PIA). Females were infected with 1×10(5) trypomastigotes of the Y strain (3rd day of pregnancy). Animals were supplied with 21 mg of L-arginine/kg/day during 14 days. PIA showed significant decreased levels of corticosterone and parasitemia. For control groups, any alteration in NO production was found with L-arginine supplementation; for PIA, enhanced nitrite concentrations were observed as compared to PI. Weights and lengths of fetuses were higher in L-arginine treated and infected pregnant rats as compared to untreated ones. Placental weight from the PIA group was significantly increased when compared to PI. In L-arginine treated animals, cardiac tissue showed reduced amastigote burdens. PIA and PI displayed similar placental parasitism. Based on these results, L-arginine supplementation may be potentially useful for the protection against Trypanosoma cruzi during pregnancy.

Estudo comparativo do comportamento da infecção de camundongos, através da inoculação subcutânea e intraperitoneal, utilizando-se duas cepas do Trypanosona cruzi

By means of comparative studies of the infection of mice with T. cruzi using intraperitoneal and subcutaneous inoculation, it was concluded that more uniform and virulent infections are obtained after subcutaneous inoculation. This is due to an immediate cellular response, when intraperitoneal inoculations are used. With the aim of making comparative studies as between the two methods of inoculation, the intraperitoneal using two, morfologically distinct, strains of T. cruzi: Y with predominance of thin forms and Bolivia with predominance of broad forms. White mice of approximately 18g were required for these tests. The groups of animals received 2 x 103, 2 x 104 and 2 x 105 trypanossomes per animal, and the course of the infection was subsequently observed. The results revealed that after subcutaneous inoculation when the Y strain was used in the tests, some significant differences appear, with more virulent and uniform infections. However, these did not appear when the Bolivia strain was used, because the animals showed the same standard parasitemy and other morpho-biological features, whether by subcutaneous or intraperitoneal inoculation. This incident suggests the existence of interrelation between the factors: method of inoculation represented by a greater or lesser presence of macrophages in the inoculated area, and the morphology of the blood forms represented by a greater or lesser capacity for cellular penetration.Foram utilizados camundongos brancos, pesando em media 18g e duas cepas de Trypanosoma cruzi, morfologicamente distintas: Y com predominância de formas sanguineas delgadas e Bolivia com predominio de formas largas. Os lotes de animais receberam 2 x 10³, 2 x 10(4) e 2 x 10(5) tripanossomos por animal e as vias de inoculacao utilizadas foram a intraperitoneal e a subcutânea. Nos animais foi observado o curso de infeccao. Os resultados obtidos revelaram que, nos experimentos em que se utilizou a cepa Y, existem algumas diferencas significantes, com infeccoes mais uniformes e virulentas, apos inoculacao subcutânea de 2 x 10³ e 2 x 10(4) formas sanguineas de T. cruzi. Entretanto, isto nao ocorreu com a cepa Bolivia, pois os animais apresentaram o mesmo padrao de parasitemia e os demais caracteres morfologicos, quer se utilizasse a via subcutânea ou intraperitoneal. Tal fato permite sugerir a existencia de interrelacao entre os fatores via de inoculacao traduzida pela maior ou menor presenca de macrofagos no sitio de inoculacao, e a morfologia das formas sanguineas representada pela maior ou menor capacidade de penetracao celular.

Effect of zinc supplementation in pregnant mice during experimental Trypanosoma cruzi infection.

Zinc is an essential micronutrient and has significant effects on human growth, development, and immune function. Zinc supplementation or deficiency may affect the course of infection. Zinc enhances immune response against a wide range of viral, bacterial, and parasitic pathogens. In the present study, we investigated the effects of zinc sulphate (ZnSO(4)) supplementation (20mg/kg/day) during pregnancy in mice, Swiss Webster strain infected by the Y strain of Trypanosoma cruzi. Oral supplementation of zinc sulphate in pregnant and non-pregnant infected animals did not affect the count of blood parasites as well as tissue parasitism in the heart, liver, and spleen. Zinc supplementation did not alter female body weight, the length of fetuses and neonates, placental size/weight and mortality rate. Among zinc supplied animals, no significant plasmatic zinc concentrations were observed. Concerning to tissue zinc concentrations, only the liver displayed enhanced values as compared to other organs. For placental parasitism, zinc supplied group displayed a significant decrease in amastigote burdens (P<0.05). However due to the reduced number of parasite burdens in placenta of animals supplied with zinc, these data suggest that zinc was partially effective in up-regulating the hosts immune response against parasite, probably attenuating the infection in fetuses.

Comportamento de formas sangüícolas do Trypanosoma cruzi obtidas de camundongos utilizados como filtros biológicos, em cultura e em triatomíneo

Camundongos normais, utilizados como filtros biologicos, foram inoculados endovenosamente, com tripomastigotas sanguicolas da derivada RCL da cepa RC do T. cruzi. Decorridas 48 horas, os animais foram submetidos ao xenodiagnostico e a puncao cardiaca para semeadura do sangue em meio de Warren. No estomago dos triatomineos e em cultura a 28°C, os tripomastigotas diferenciaram-se em formas arredondadas (esferomastigotas e/ou amastigotas). Esse comportamento das formas sanguicolas largas tem sido observado com frequencia e nos leva a inferir que a biologia do T. cruzi nao estaria apenas relacionada com a cepa, mas, eventualmente, com populacoes do parasita.