Neuroimmunopathology of Trypanosoma cruzi-induced megaoesophagus: Is there a role for mast cell proteases?

Tryptase and chymase are mast cell (MC)-specific proteases, which influence in the activation of inflammatory cells. In this study, we quantified tryptase- or chymase-expressing MCs in the oesophaguses of Chagas patients, and searched for a correlation between those data with area of nerve fibres that expressed either PGP9.5 (pan-marker) or vasoactive intestinal polypeptide (VIP), which is a neuromediator that has anti-inflammatory activity. Samples from the oesophaguses of 14 individuals Trypanosoma cruzi-infected and from six uninfected individuals were analysed by immunohistochemistry. It was demonstrated that the number of tryptase-IR MCs in infected individuals increased when compared with controls, regardless of whether the individuals had megaoesophagus, whereas the number of chymase-IR MCs increased only in infected individuals without megaoesophagus. Negative correlations were observed between tryptase-IR MCs and the density of nerve fibres that expressed VIP or PGP 9.5-IR. The participation of chymase and tryptase in this type of immunopathology is discussed.

An imbalance between substance P and vasoactive intestinal polypeptide might contribute to the immunopathology of megaesophagus after Trypanosoma cruzi infection.

Megaesophagus is one of the major causes of morbidity in chronic Chagas disease, and extensive denervation, associated with an inflammatory process, is recognized as the key factor for alterations in motility and disease development. Here, we analyzed esophagus samples from necropsied, infected individuals--6 cases with megaesophagus and 6 cases without megaesophagus--for the relative areas of expression of 2 neuromediators, substance P and vasoactive intestinal peptide, which are known to activate or inhibit, respectively, local immune cells. Samples from 6 noninfected individuals were used as controls. Esophageal sections were immunohistochemically stained for protein gene product 9.5, vasoactive intestinal peptide, and substance P, and the relative areas of expression of the latter 2 were calculated. Morphometric analyses revealed increased substance P and decreased vasoactive intestinal peptide relative areas in esophageal sections from patients with megaesophagus. Furthermore, in the group of patients without megaesophagus, the loss of vasoactive intestinal peptide positively correlated with the denervation process. We suggest that an imbalance between vasoactive intestinal peptide and substance P production results in the reestablishment and maintenance of the inflammatory process, leading to denervation and, consequently, promoting the development of megaesophagus.

Characterization of enteroglial cells and denervation process in chagasic patients with and without megaesophagus.

Chagas disease is caused by infestation with the parasite Trypanosoma cruzi, and some patients who are serologically positive develop chronic megaesophagus, whereas others are symptom-free. Gastrointestinal form of Chagas disease involves an inflammatory invasion of the enteric plexuses and degeneration of enteric neurons and previous works related that enteroglial cells would be involved in enteric inflammatory responses. Because of this, the aims of this study were to determine the relation of enteroglial cells with the denervation process in chagasic patients with and without megaesophagus and seronegative individuals. Our results indicated that the innervation of the esophageal muscle was substantially reduced in patients with megaesophagus, but asymptomatic seropositive subjects were not different to seronegative controls. Besides, patients with megaesophagus had significant decreased of enteroglial cells labeled with S-100 and glial fibrillary acidic protein, whereas patients without megaesophagus presented an increased of both labels. We believe that enteroglial cells would operate a mechanism of defense in the enteric nervous system against the Trypanosoma cruzi infection, which could prevent the organ denervation and preserve the esophagus function.