Elsevier

Human Pathology

Volume 40, Issue 2, February 2009, Pages 244-251
Human Pathology

Original contribution
Glial fibrillary acidic protein and S-100 colocalization in the enteroglial cells in dilated and nondilated portions of colon from chagasic patients

https://doi.org/10.1016/j.humpath.2008.04.025Get rights and content

Summary

After acute immunoreactive infestation with the Chagas' disease parasite, Trypanosoma cruzi, some patients develop chronic megacolon, whereas others remain asymptomatic. Chronic chagasic patients with gastrointestinal involvement exhibit inflammation and degeneration of enteric neurons. Our hypothesis is that enteric glial cells may be involved in the modulation of enteric inflammatory responses or even control the colon's dilatation. The aims of this study were to characterize the phenotype of enteric glial cells according to the expression of S-100 and glial fibrillary acidic protein and to look for correlation between these data and the neuronal loss in the colon of chagasic patients. We studied both dilated and nondilated portions of chagasic megacolon. We used a pan-enteric glial cell marker (anti-S-100), a subpopulation enteric glial cell marker (anti–glial fibrillary acidic protein), and a pan-neuronal marker (anti-Human protein C and protein D) with double-labeled sheets using a confocal microscope. Our results demonstrate that neuronal loss is similar in dilated and nondilated portions of chagasic megacolon. Moreover, the results indicate that neuronal destruction present in chagasic megacolon is preceded by glial component loss. The nondilated portion of chagasic megacolon exhibited increased expression of glial fibrillary acidic protein comparable with the dilated portion and also to the noninfected group. Our results suggest that glial fibrillary acidic protein enteric glial cells prevent dilatation of the organ and protect the enteric nervous system against the inflammatory process and neuronal destruction, preventing the destruction from expanding to unaffected areas of the colon.

Introduction

Chagas' disease (American trypanosomiasis), which is caused by the protozoan Trypanosoma cruzi, is endemic in Central and South America. The parasite is most commonly transmitted to humans by hematophagous insects of the Reduviidae family [1]. The infection has a self-limited acute phase, detected only in a minority of infected persons. In the chronic form of Chagas' disease, cardiac and gastrointestinal involvement may occur, depending on multiple factors, including the host immune response [2], [3], [4].

The gastrointestinal form of Chagas' disease is characterized mainly by the involvement of the esophagus and colon. Previous studies demonstrated that colon dilatation and lengthening lead to megacolon development. Abnormalities of the enteric nervous system (ENS), namely, degeneration and neuronal number reduction, seem to be essential elements in the pathogenesis of the gastrointestinal disorders [3], [5], [6]. Actually, it is thought that neuronal loss occurs because of immune cytotoxic mechanisms [6], [7] and parasite-induced lesions [7], [8], [9]. Ultramicroscopic studies of colon from acutely infected patients have demonstrated that T cruzi penetrates a variety of cells such as macrophages, neurons, and enteric glia cells (EGCs).

EGCs play an important role in the maintenance of gastrointestinal tract tissue integrity. The exact mechanisms by which EGCs contribute to gut homeostasis are still poorly understood [10], [11], although recent data have demonstrated that, when stimulated with proinflammatory cytokines, EGCs represent the main source of neurotrophic factors in the gut [12]. S-100 is a Ca2+-binding protein commonly used to identify EGCs, whereas glial fibrillary acidic protein (GFAP) is expressed by only a subpopulation of EGCs, principally in the presence of inflammatory factors [13]. It has been suggested that enhanced expression of GFAP by EGCs could represent a structural barrier against immune cytotoxic mechanisms to enteric neurons.

The present study was designed based on our hypothesis that in the colon of T cruzi–infected patients, the EGCs might have an active response because of inflammatory cytokines secreted by immune cells. If this is true, the functional state of EGCs might determine the level of neuronal loss and the development of megacolon. To test our hypothesis, we performed double-labeling immunohistochemistry for S-100 and GFAP to characterize the EGCs present in dilated and nondilated portions of colon from patients with chronic chagasic megacolon. We further looked for correlations between the EGC phenotype and the number of enteric neurons to determine the relationship between these ENS components in chagasic patients.

Section snippets

Patients and tissue collection

Colon tissue samples were collected from noninfected individuals (n = 5) and chagasic patients with megacolon (n = 10). Patient characteristics are shown in Table 1. The main reasons for tissue resection were colon complications caused by Chagas' disease in chagasic patients and adenocarcinoma or diverticular disease in noninfected individuals. All surgical specimens were collected from the same topographic regions of the colon (rectum and sigmoid) during low anterior resection or a Duhamel

Analysis of the inflammatory process

H&E sections of dilated and nondilated portions of the colon from patients with megacolon and from noninfected individuals were studied to determine the intensity of the inflammatory process. The dilated portions from chagasic patients demonstrated an intense inflammatory infiltrate with predominantly mononuclear cells. However, the nondilated portions from chagasic patients and from noninfected individuals did not show any significant inflammatory process. Histologic sections of colon samples

Discussion

The etiology of the pathogenesis and physiopathology of chagasic megacolon is the least understood clinical form of Chagas' disease. The relationship among colon dilatation, the extent of the numerical reduction in neurons, and the alteration of EGCs is an important feature that needs to be understood. Many studies on chagasic megacolon have evaluated only neuronal destruction [3], [5], [15]. In addition, EGCs in chagasic megacolon have not been investigated. This is the first report evaluating

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    This work was supported by funds from CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) Ministério da Ciência e Tecnologia, Brazil, and the National Health and Medical Research Council of Australia (grant 400020).

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