Alterations in cardiac beta-adrenergic receptors in chagasic mice and their association with circulating beta-adrenoceptor-related autoantibodies.
OBJECTIVE: Cardiac tissue from chagasic mice was studied to evaluate the expression and biological activity of beta-adrenoceptors in association with circulating beta-adrenoceptor-related autoantibodies. METHODS: BALB/c inbred mice that were either treated or not treated with atenolol (2.5 mg/kg) and infected or not infected with 1 x 10(4) trypomastigotes (CA-1 strain) were sacrificed weekly up to week nine. Morphological, binding and contractility studies were performed on the four different groups of animals. The effect of their serum antibodies was also assayed in binding and contractility studies on normal heart preparations. RESULTS: Hearts from chagasic myocarditis mice showed a beta-adrenoceptor-related dysfunction, with a decrease in heart contractility, impaired response to exogenous beta-adrenoceptor agonist and a significant reduction in beta-adrenergic binding sites. Those effects were maximum at eight-nine weeks post-infection and were improved by treating infected mice with atenolol. In addition, serum or IgG from chagasic myocarditis mice was capable of interacting with cardiac beta-adrenoceptors, reducing the number of binding sites and inhibiting the contractile response to exogenous norepinephrine. IgG effects that were observed in normal myocardium, were highest in sera from mice eight-nine weeks post-infection and correlate with the degree of myocarditis. Moreover, chagasic autoantibodies from infected mice recognized a peptide corresponding to the sequence of the second extracellular loop of the human beta 1-adrenoceptor. CONCLUSIONS: (1) The development of alterations in beta-adrenergic receptors, related to cardiac dysfunction, may be associated with the presence of circulating antibodies against these receptors and (2) it is possible that the chronic deposits of these autoantibodies in cardiac beta-adrenoceptors could lead to a progressive blockade with sympathetic denervation, a phenomenon that has been described in the course of chagasic myocarditis. (+info)
Myocardial parasite persistence in chronic chagasic patients.
The persistence of Trypanosoma cruzi tissue forms was detected in the myocardium of seropositive individuals clinically diagnosed as chronic chagasic patients following endomyocardial biopsies (EMBs) processed by immunohistochemical (peroxidase-anti-peroxidase [PAP] staining) and molecular (polymerase chain reaction [PCR]) techniques. An indirect immunofluorescent technique revealed antigenic deposits in the cardiac tissue in 24 (88.9%) of 27 patients. Persistent T. cruzi amastigotes were detected by PAP staining in the myocardium of 22 (84.6%) of 26 patients. This finding was confirmed with a PCR assay specific for T. cruzi in 21 (91.3%) of 23 biopsy specimens from the same patients. Statistical analysis revealed substantial agreement between PCR and PAP techniques (k = 0.68) and the PCR and any serologic test (k = 0.77). The histopathologic study of EMB specimens from these patients revealed necrosis, inflammatory infiltrates, and fibrosis, and made it possible to detect heart abnormalities not detected by electrocardiogram and/or cineventriculogram. These indications of myocarditis were supported by the detection of T. cruzi amastigotes by the PAP technique or its genome by PCR. They suggest that although the number of parasites is low in patients with chronic Chagas' disease, their potential for heart damage may be comparable with those present during the acute phase. The urgent necessity for testing new drugs with long-term effects on T. cruzi is discussed in the context of the present results. (+info)
Parasite persistence correlates with disease severity and localization in chronic Chagas' disease.
The protozoan parasite Trypanosoma cruzi infects up to 20 million people in Latin America, and the resulting disease (Chagas' disease) is a leading cause of heart disease and death in young adults in areas endemic for the parasite. The clinical symptoms of Chagas' disease have been attributed to autoimmune reactivity to antigens shared by the parasite and host muscle or neuronal tissue. In the present study, in situ polymerase chain reaction analysis was used in murine models of Chagas' disease to demonstrate an absolute correlation between the persistence of parasites and the presence of disease in muscle tissue. Clearance of parasites from tissues, presumably by immunologic mechanisms, correlated with the abatement of inflammatory responses and the resolution of disease. These data provide strong evidence for parasite persistence as a primary cause of Chagas' disease and argue for efforts to eliminate T. cruzi from the host as a means for prevention and treatment of Chagas' disease. (+info)
Cardiac M(2) muscarinic cholinoceptor activation by human chagasic autoantibodies: association with bradycardia.
OBJECTIVE: To assess whether exposure of cardiac muscarinic acetylcholine receptors (mAChR) to activating chagasic antimyocardial immunoglobulins results in bradycardia and other dysautonomic symptoms associated with the regulation of heart rate. METHODS: Trypanosoma cruzi infected patients with bradycardia and other abnormalities in tests of the autonomic nervous system were studied and compared with normal subjects. Antipeptide antibodies in serum were demonstrated by an enzyme linked immunosorbent assay using a synthetic 24-mer-peptide corresponding antigenically to the second extracellular loop of the human heart M(2) mAChR. The functional effect of affinity purified antipeptide IgG from chagasic patients on spontaneous beating frequency and cAMP production of isolated normal rat atria was studied. RESULTS: There was a strong association between the finding of antipeptide antibodies in chagasic patients and the presence of basal bradycardia and an altered Valsalva manoeuvre (basal bradycardia: chi(2) = 37.5, p < 0. 00001; Valsalva manoeuvre: chi(2) = 70.0, p < 0.00001). The antipeptide autoantibodies also showed agonist activity, decreasing the rate of contraction and cAMP production. The effects on rat atria resembled the effects of the authentic agonist and those of the total polyclonal chagasic IgG, being selectively blunted by atropine and AF-DX 116, and neutralised by the synthetic peptide corresponding in amino acid sequence to the second extracellular loop of the human M(2) mAChR. CONCLUSIONS: There is an association between circulating antipeptide autoantibodies in chagasic patients and the presence of bradycardia and other dysautonomic symptoms. Thus these autoantibodies are a marker of autoimmune cardiac autonomic dysfunction. The results support the hypothesis that autoimmune mechanisms play a role in the pathogenesis of chagasic cardioneuromyopathy. (+info)
Different microcirculatory and interstitial matrix patterns in idiopathic dilated cardiomyopathy and Chagas' disease: a three dimensional confocal microscopy study.
OBJECTIVE: To analyse the morphological aspects of the extracellular matrix and microcirculation to clarify whether chronic Chagas' cardiopathy (CCC) is an accurate model to study the pathogenesis of idiopathic dilated cardiomyopathy (IDCM). DESIGN: Thick histological myocardial sections were prepared to analyse collagen, and microcirculation was examined during confocal laser and light microscopy. SETTING: The specimens were prepared at the pathology service of the Heart Institute of Sao Paulo, Brazil. PATIENTS: Nine control hearts, eight IDCM hearts, and 10 CCC hearts were studied after necropsy. MAIN OUTCOME MEASURES: The number of collagen struts per 100x field, the area of fibrosis (%), and the diameters of arterioles and capillaries were measured in each heart to establish outcome. RESULTS: A smaller number (mean (SD)) of collagen struts was seen in the hearts in the IDCM group (9.1 (4.1)) than in the control (22.4 (3.2)) (p < 0.05) or CCC (15.7 (7.4)) (p > 0.05) groups. Fibrosis was greater in the CCC hearts (13.8 (10.5)%) than in the IDCM hearts (5.9 (6.6)%) (p > 0.05). Major increases in arteriole (65.4 (9.9) microm) and capillary (9.9 (1.7) microm) diameters were seen in the CCC hearts but not in the IDCM hearts (arteriole diameter 40.3 (7.9) microm; capillary diameter 7.9 (1.3) microm). CONCLUSIONS: Hearts demonstrating CCC and IDCM present different extracellular and microvessel alterations. This suggests that distinct pathogenic mechanisms are responsible for each condition and that CCC is not an effective model to study IDCM. (+info)
Application of cardiac gated magnetic resonance imaging in murine Chagas' disease.
To evaluate the role of gated cardiac magnetic imaging resonance (MRI) in Chagas' disease, we infected mice with Trypanosoma cruzi (Brazil strain). Two models were chosen for study, the CD1 and the inducible nitric oxide synthase knockout (NOS2-/-) mice. Infection of CD1 mice was associated with a significant increase in the right ventricular inner diameter (RVID) that was reversed in some mice by verapamil. Expression of cardiac NOS2 has been associated with myocardial dysfunction. Therefore, we evaluated chagasic cardiomyopathy in NOS2-/- and syngeneic wild type (WT) mice. Infected WT mice exhibited an increase in RVID in the acute phase (< 60 days postinfection) that was more marked during chronic infection (>100 days postinfection). Chronically infected NOS2-/- mice had an increase in RVID. The RVID in infected WT mice was greater than in NOS2-/- mice. These data demonstrate that MRI is a useful tool in the serial evaluation of the heart in murine Chagas' disease. In addition, it supports the notion that the NOS2-/-/NO pathway may contribute to the pathogenesis of murine chagasic cardiomyopathy. (+info)
Chronic Chagas' heart disease in a Japanese-Brazilian traveler. A case report.
A 57-year-old Japanese-Brazilian man, visiting Japan for only 9 days, was admitted to our hospital due to syncope and frequent ventricular premature beats. He grew up in a rural area of Brazil and moved to Sao Paulo in 1959 when he was 20 years old. We suspected chronic Chagas' heart disease, i.e., dilated cardiomyopathy with apical ventricular aneurysm, right bundle branch block with left anterior fascicular block, and various arrhythmias including supraventricular premature beats, ventricular premature beats and non-sustained ventricular tachycardia because he showed typical echo- and electrocardiographic features of the disease. Coronary arteriograms were normal, and left ventriculogram confirmed the existence of apical ventricular aneurysm. A left ventricle biopsy specimen showed hypertrophic cardiac muscle with mild fibrosis. The diagnosis of chronic Chagas' disease was finally confirmed by the demonstration of Trypanosoma cruzi itself in the blood as well as Trypanosoma cruzi antibodies. (+info)
Immunopathology of Chagas disease.
The main clinical forms of Chagas disease (acute, indeterminate and chronic cardiac) present strong evidences for the participation of the immune system on pathogenesis. Although parasite multiplication is evident during acute infection, the intense acute myocarditis of this phase exhibits clear ultrastructural signs of cell-mediated immune damage, inflicted to parasitized and non-parasitized myocardiocytes and to the endothelium of myocardial capillaries (microangiopathy). Inflammation subsides almost completely when immunity decreases parasite load and suppressor factors modulate host reaction, but inflammation does not disappear when the disease enters the indeterminate phase. Inflammation becomes mild and focal and undergoes cyclic changes leading to complete resolution. However, the process is maintained because the disappearance of old focal lesions is balanced by the upsurge of new ones. This equilibrium allows for prolonged host survival in the absence of symptoms or signs of disease. The chronic cardiac form is represented by a delayed-type, cell-mediated diffuse myocarditis, that probably ensues when the suppressive mechanisms, operative during the indeterminate phase, become defaulted. The mechanism responsible for the transition from the indeterminate to the cardiac form, is poorly understood. (+info)