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Increased phagocytic capacity in Chagas’ disease patients with heart failure

Muniz-Junqueira Imaculada; Aires Rodrigo; Mota Lícia; Junqueira Jr Luiz

University of Brasilia Department of Pathology and Department of Internal Medicine.
Laboratory of Cellular Immunology and Division of Cardiology. Brasilia. Brazil.

Abstract
Introduction
Objectives
Material and Methods
Results
Discussion and Conclusions

Abstract
Introduction: The pathophysiological disturbances associated to the increased cytokine production in Chagas’ heart disease patients with cardiac failure may alter the function of immune system cells. Moreover, the phagocytosed parasites in the macrophages may continuously to stimulate the immunological system and additionally alter the function of the immune cells. Objective: To evaluate the phagocytosis by monocytes and neutrophils in Chagas’ heart failure patients.
Subjects and Methods: We tested 11 Chagas’ disease patients with heart failure and other 11 without the syndrome, and 6 patients with heart failure of other etiology. Samples of peripheral blood were placed on laminas and incubated for 45 min in a wet chamber at 37° C. Thereafter, the phagocytes adhered to the laminas were incubated for 30 min with 5 or 20 Saccharomyces cerevisiae per phagocyte sensitized or not with serum of the patients. The phagocytic index (PI) was calculated multiplying the mean number of ingested yeast by the proportion of phagocytosing cells.
Results: Patients with Chagas’ heart failure showed increased median of PI of monocytes (18) in comparison to those without the syndrome (5.5), for 20 yeast non-sensitized per phagocyte (p = 0,04; Mann-Whitney test). Similar increase in phagocytosis by neutrophils was observed in chagasic patients with heart failure (PI median: 142 versus 86), for 5 sensitized yeast per phagocyte (p = 0,05; t test). The median PI of neutrophils from chagasic individuals with heart failure (97,5) was also higher than in patients with non-chagasic cardiopathy with heart failure (67), for 5 non-sensitized yeast per phagocyte (p = 0,04; Mann-Whitney test).
Conclusion: Chagas’ disease patients when in heart failure showed increased phagocytic capacity of immune cells. The syndrome combined with the chagasic infection appears to be the cause of the altered immune function since the other groups of patients did not showed the dysfunction. This improper immunological hyperfunction may facilitate infections in Chagas’ heart failure patients. (PIBIC-UnB/CNPq)

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Introduction:

Chagas’ disease, caused by the intracellular parasite Trypanosoma cruzi is an important problem of public health in several South America countries, and present high morbidity and mortality. The main cause of disability and death in Chagas’ disease is a peculiar cardiopathy which commonly result in severe congestive heart failure. It is possible that the haemodynamic and secretory disturbances present in the chagasic heart failure may alter the function of cells of the immune system. Macrophages play an important role in defense against the parasite. However such cells may also participate in the Chagas' disease, because the Trypanosoma cruzi may persist viable by years into these immune cells. The presence of parasites in cells may continuously to stimulate the immune system resulting in chronic inflammation of heart. Into the macrophage the parasite can escape from phagolysosomes to cytoplasm of the cell where it is protect of the mechanism of defense of the host. The presence of the parasite in the cytoplasm of macrophage may also alter the function of these cells. It is not yet fully clarified the phagocytic function of phagocytes in Chagas’ disease.

Objectives:

This work aimed to evaluate the phagocytic function of monocytes and neutrophils in Chagas’ heart disease patients with congestive heart failure in comparison to chagasic patients without the congestive syndrome and to patients with heart failure due to other cardiopathies.

Material and Methods:

We tested 11 Chagas’ heart disease patients with heart failure and other 11 chagasic without the congestive syndrome, and 6 patients with cardiopathy of other etiology also with heart failure, of both sexes, between 18 to 60 years old. The ethical rules of Helsinki Declaration and those from the Health Ministry of Brazil for experimentation in human beings were strictly followed throughout this work, and the patients gave their informed consent for participation. Samples of 40 m l per well of peripheral blood from individual volunteer were placed on slides and incubated for 45 minutes in a wet chamber at 37° C. After rinsing the slides with 0.15M phosphate buffered saline (PBS), pH 7.2, the adherent cells (>98% neutrophils and monocytes) were incubated with a suspension of 5 or 20 Saccharomyces cerevisiae in Hanks-triz pH, 7.2 for 30 min in a wet chamber at 37oC. The mean number of adhered cells per well were previously assessed. To evaluate the immune phagocytosis a suspension of Saccharomyces cerevisiae was previously incubated with 20% fresh serum from the same individual from which the phagocytes were obtained or 20% fetal calf serum (inactivated at 56o C), for 30 minutes at 37o C. Slides were then rinsed with PBS to eliminate non-phagocytosed particle, fixed with absolute methanol, stained with 10% buffered Giemsa solution and the number of bound and/or ingested particle by 200 monocytes and 200 neutrophils by individual preparation was assessed by microscopy. Microscopic fields distributed throughout the slides were randomly selected and all monocytes or neutrophils in each particular field were examined. The phagocytic index (PI) was calculated as the average number of attached plus ingested particle per phagocytosing monocyte or neutrophil multiplied by the percentage of these cells engaged in phagocytosis. The results were analyzed by the Student t test or the Mann-Whitney test to compare two independent samples with normal or non-normal distribution, respectively, employing the SigmaStat software package. A p value £ 0.05 was considered as significant.

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Results:

The patients with Chagas’ disease with heart failure showed higher median phagocytic index of monocytes (median = 18) in comparison to chagasic patients without the syndrome (median = 5.5), for the case of 20 non-sensitized yeast by phagocyte (p = 0.049 by the Mann-Whitney test). The Figure 1 illustrates these observations. A limitrophe statistical increase in phagocytosis by neutrophils, expressed by the median phagocytic index, was observed in chagasic patients with heart failure (mean = 142) as compared with those without the syndrome (mean = 86), in the case of 5 sensitized yeast by phagocyte (p = 0.05 by the Student t test). The Figure 2 shown these results. The median of neutrophils of Chagas’ heart disease individuals with heart failure (median = 97.5) was also higher than that observed in patients with non-chagasic cardiopathy with heart failure (median = 67), for 5 non-sensitized yeast by phagocyte (p = 0.04 by the Mann-Whitney test), as shown in
Figure 3.

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Fig. 1: Higher index of phagocytosis by monocytes in Chagas’ heart disease patients with congestive heart failure (n = 11) as compared to chagasic patients without the congestive syndrome (n = 11)  (p = 0.049, Mann-Whitney test). The data are shown as median, interquartile range and extreme values.

 

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Fig. 2: Higher index of phagocytosis by neutrophils in Chagas’ heart disease patients with congestive heart failure (n = 11) as compared to chagasic patients without the congestive syndrome (n = 11) (p = 0.05, Student t test). The data are shown as mean and range of 1 standard deviation.

 

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Fig. 3: Higher index of phagocytosis by neutrophils in Chagas’ heart disease patients with congestive heart failure (n = 11) as compared to patients with other cardiopathies also with heart failure (n = 6) (p = 0.039, Mann-Whitney test). The data are shown as median, interquartile range and extreme values.

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Discussion and conclusions:

The present data indicates immunological hyperfunction of monocytes and neutrophils in Chagas’ heart disease patients with congestive heart failure, characterized by increased phagocytic capacity of both immune cells, as compared to patients with the disease but without the congestive syndrome. The association between the heart failure syndrome to the Trypanosoma cruzi infection appears to be the cause of the altered immune function of the phagocytes, since the groups of patients with other cardiopathies also in phase of heart failure presents lower phagocytic index than the patients with chagasic heart failure. Chagas’ heart disease is a chronic infectious condition that may increase the production of several cytokines, as a-tumor necrosis factor and interferon-g, that are able to influence the phagocyte function. Heart failure cause haemodynamic, hydroelectrolytic, hormonal and autonomic neural disturbances and may also modify the cytokine production by these ways. The association of these different alterations is probably the cause of the increased immunological function of phagocytes. These immune cells are involved in the primary defense of organisms against infection and after distinctive stimulation they also produce a lot of substances that may interfere with their self function and with also the cardiac function. The improper increased response of these cells may participate in the aggravation of the heart function and may facilitate infections in chagasic patients with heart failure, possibly influencing the prognostic of the disease.

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Questions, contributions and commentaries to the Authors: send an e-mail message (up to 15 lines, without attachments) to chagas-pcvc@pcvc.sminter.com.ar , written either in English, Spanish, or Portuguese.

 


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Bioengineering
UNER

Update
Nov/09/1999