Jarbas E. Cardoso

Impaired Production of Proinflammatory Cytokines and Host Resistance to Acute Infection with Trypanosoma cruzi in Mice Lacking Functional Myeloid Differentiation Factor 88

Studies performed in vitro suggest that activation of Toll-like receptors (TLRs) by parasite-derived molecules may initiate inflammatory responses and host innate defense mechanisms against Trypanosoma cruzi. Here, we evaluated the impact of TLR2 and myeloid differentiation factor 88 (MyD88) deficiencies in host resistance to infection with T. cruzi. Our results show that macrophages derived from TLR2 −/− and MyD88−/− mice are less responsive to GPI-mucin derived from T. cruzi trypomastigotes and parasites. In contrast, the same cells from TLR2−/− still produce TNF-α, IL-12, and reactive nitrogen intermediates (RNI) upon exposure to live T. cruzi trypomastigotes. Consistently, we show that TLR2−/− mice mount a robust proinflammatory cytokine response as well as RNI production during the acute phase of infection with T. cruzi parasites. Further, deletion of the functional TLR2 gene had no major impact on parasitemia nor on mortality. In contrast, the MyD88−/− mice had a diminished cytokine response and RNI production upon acute infection with T. cruzi. More importantly, we show that MyD88−/− mice are more susceptible to infection with T. cruzi as indicated by the higher parasitemia and accelerated mortality, as compared with the wild-type mice. Together, our results indicate that T. cruzi parasites elicit an alternative inflammatory pathway independent of TLR2. This pathway is partially dependent on MyD88 and necessary for mounting optimal inflammatory and RNI responses that control T. cruzi replication during the early stages of infection.

Glycosylphosphatidylinositol-Anchored Mucin-Like Glycoproteins from Trypanosoma cruzi Bind to CD1d but Do Not Elicit Dominant Innate or Adaptive Immune Responses Via the CD1d/NKT Cell Pathway

It has been proposed that self and protozoan-derived GPI anchors are natural ligands of CD1d. In this study, we investigated the ability of GPI anchors from Trypanosoma cruzi to bind to CD1d and mediate activation of NKT cells. We observed that GPI-anchored mucin-like glycoproteins (GPI mucins), glycoinositolphospholipids (GIPLs), and their phosphatidylinositol moieties bind to rCD1d and inhibit the stimulation of a NKT hybridoma by the α-galactosylceramide-CD1 complex. However, these GPI anchors and related structures were unable to activate NKT cells in vitro or in vivo. We found that high titers of Ab anti-GPI mucins, but not anti-GIPLs, were detected in sera from wild-type as well as in TAP1−/−, CD1d−/−, and MHC class II−/− mice after immunization. However, T-dependent anti-GPI mucin Ab isotypes, such as IgG1, IgG2a, IgG2b, and IgG3, were absent on MHC class II−/−, but were conserved in CD1d−/− and TAP1−/− mice. Furthermore, we found that CD1d−/− mice presented a robust cytokine as well as anti-GPI mucins and anti-GIPL Ab responses, upon infection with T. cruzi parasites. These results indicate that, despite binding to CD1d, GPI mucins and related structures expressed by T. cruzi appear not to evoke dominant CD1d-restricted immune responses in vivo. In contrast, MHC class II is critical for the production of the major Ig G isotypes against GPI mucins from T. cruzi parasites.

Factor V Leiden and increased risk for arterial thrombotic disease in young Brazilian patients.

The contribution of mutations in the prothrombin (FII G20210A), methylenetetrahydrofolate reductase (C677T) genes and factor V Leiden (FVL) to the pathogenesis of arterial thrombosis remains controversial. In this study, these polymorphisms were investigated by polymerase chain reaction–restriction fragment length polymorphism in a group of 53 patients that presented arterial thrombosis other than myocardial infarction as a first thrombotic event and 275 control subjects living in the state of Minas Gerais, Brazil. Odds ratio (OR) and χ2 tests were applied for statistical comparisons. Similar frequencies were detected among patients and control subjects for the C677T mutation. The 20210A mutation was present in 3.6% of the control subjects but was not detected among ischemic stroke patients. Significant differences were detected only for factor V Leiden (odds ratio 7.11; 95% confidence interval 1.55–32.73). Our data indicate that, among these genetic factors, factor V Leiden was identified as an important risk factor for arterial thrombosis in this group of patients. In addition, our results indicate regional differences in the incidence of these genetic factors in Brazil, as compared to the incidences reported in other studies.

Plasma Total Homocysteine Levels and Methylenetetrahydrofolate Reductase Gene Polymorphism in Patients with Type 2 Diabetes Mellitus

Background: Thrombotic episodes account for approximately 80% of deaths in type 2 diabetic patients. Hyperhomocysteinaemia is a well recognized independent risk factor for atherosclerosis and thromboembolism. Increased homocysteine levels may occur due to a number of factors including inherited gene polymorphism of methylenetetrahydrofolate reductase (MTHFR) C677T. Here, we evaluate plas- ma total homocysteine (tHcy) levels and frequency of the MTHFR C677T gene polymorphism in asymptomatic healthy volunteers and type 2 diabetic patients with hypertension but without nephropathy. We have also investigated the relationship between tHcy levels and the presence of MTHFR C677T gene polymorphism. Methods: Plasma tHcy levels and MTHFR C677T genotype were investigated in a total of 53 subjects. These included asymptomatic healthy volunteers (n = 16), patients with type 2 diabetes (n = 7), subjects with hypertension (n = 12) and patients with both type 2 diabetes and hypertension (n = 18). Renal function, serum lipids and other metabolites were also assessed. Results: There was no significant difference in tHcy levels between the groups studied. The frequency of MTHFR C677T gene polymorphism observed was similar to that obtained for the general Brazilian population. In patients with type 2 diabetes and hypertension but without impaired renal function, we observed no meaningful correlation between increased tHcy levels and the presence of MTHFR C677T gene polymorphism. Conclusions: Type 2 diabetics who are homozygous or heterozygous for the MTHFR C677T gene polymorphism showed normal tHcy levels. Our results further suggest that diabetes without an associated adverse risk profile is not an independent correlate of increased tHcy levels.

Effect of oral hormone replacement therapy on plasma homocysteine levels

Background. Various inherited or acquired conditions can lead to mild or severe hyperhomocysteinemia, which has toxic effects on the vascular endothelium. It has been reported that hormone replacement therapy is associated with decreased homocysteine plasma levels, but this is still a controversial issue. Purpose. To compare homocysteine plasma levels in women before and after 3 months of oral hormone replacement therapy. Methods. Twenty‐four women were selected to take part in the study. Blood samples were collected immediately before hormone replacement therapy (cyclic association of 2 mg of estradiol valerate and 1 mg of cyproterone acetate) and three months after the beginning of hormone replacement therapy. Samples collected before hormone replacement therapy were used as controls. Plasma homocysteine levels and the presence of C677T mutation in the methylene tetrahydrofolate reductase gene were evaluated in all participants. Results. The methylene tetrahydrofolate reductase gene mutation was detected in 8 women (33.3%) in heterozygosis, in 3 (12.5%) in homozygosis, and 13 women (54.2%) did not present the mutation. No significant differences were observed in homocysteine levels before and after three months of oral hormone replacement therapy, regardless of the C677T genotype. Conclusions. The results obtained indicate that homocysteine plasma levels are not affected after three months of oral hormone replacement therapy.

Avaliação da incidência das mutações G1691A no gene do fator V (fator V Leiden) e G20210A no gene da protrombina em pacientes com diabetes mellitus tipo 2

Em virtude da alta prevalencia de Diabetes mellitus tipo 2 (DM2) na populacao mundial e da alta taxa de mortalidade decorrente de eventos tromboticos, e de extrema importância o conhecimento das alteracoes no sistema hemostatico em pacientes portadores deste disturbio. A mutacao no gene do fator V (G1691A - fator V Leiden) em heterozigose ou homozigose confere aos portadores o fenotipo de resistencia a proteina C ativada, situacao que aumenta em sete vezes o risco de desenvolver uma trombose. A mutacao G20210A no gene da protrombina resulta no quadro de hiperprotrombinemia, aumentando o risco de trombose em tres vezes. A pesquisa dessas mutacoes de interesse em trombofilia e de grande relevância considerando que a presenca das mesmas pode exacerbar o estado de hipercoagulabilidade acelerando as complicacoes no diabetes. O presente estudo teve como objetivo avaliar a incidencia dessas mutacoes em individuos higidos (Controle, n=16), pacientes com DM2 (n=7), com hipertensao (HAS, n=12) e com DM2+HAS (n=18), atraves da tecnica de PCR-RFLP. As frequencias encontradas nos grupos estudados foram baixas e similares aquelas observadas na populacao brasileira em geral. Nao foi possivel estabelecer correlacao entre a presenca da mutacao e caracteristicas especificas de cada grupo. Dessa forma, ainda nao esta claro se ha ou nao uma maior prevalencia dessas mutacoes em individuos diabeticos e se a presenca das mesmas contribui para o aumento do risco de desenvolver trombose nesses individuos, sendo necessario estudos mais amplos para a elucidacao da questao.

Epidermal growth factor receptors, testosterone levels and parotid gland changes in rats infected with Trypanosoma cruzi

It has been demonstrated that parotid glands of rats infected with Trypanosoma cruzi present severe histological alterations; changes include reduction in density and volume of the acini and duct systems and an increase in connective tissue. We evaluated the association between morphological changes in parotid glands, circulating testosterone levels and epidermal growth factor receptor (EGF-R) expression in experimental Chagas disease in rats. Animals at 18 days of infection (acute phase) showed a significant decrease in body weight, serum testosterone levels and EGF-R expression in the parotid gland compared with a control group. Since decreases in body weight could lead to a reduction in circulating testosterone concentration, we believe that the reduction in EGF-R expression in parotid glands of infected rats is due to alterations in testosterone levels and atrophy of parotid glands is caused by changes in EGF-R expression. Additionally, at 50 days (chronic phase) of infection parotid glands showed a normal histological aspect likely due to the normalization of the body weight. These findings suggest that the testosterone-EGF-R axis is involved in the histological changes.

Frequência do polimorfismo da glicoproteína IIIa de plaquetas (PlA2) em mulheres com diabetes mellitus tipo 2

The platelet glycoprotein IIIa polymorphism is associated to an increased risk of coronary heart disease. Type 2 diabetic women present a fivefold higher risk of coronary heart disease compared to non-diabetic women. The aim of this study was to verify the frequency of the glycoprotein IIIa polymorphism (PlA2) in type 2 diabetic women and compare this result with the frequency reported for the general population. The PlA polymorphisms of 62 type 2 diabetic women were determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). The resulting frequencies were 81% for PlA1A1, 18% for PlA1A2 and 1% for PlA2A2. There was no significant difference between observed frequencies and the frequencies described in the literature. Our results suggest that the frequency of the glycoprotein IIIa polymorphism, PlA2, in type 2 diabetic women is similar to that observed in general population