Abstract
Chagas' myocardiopathy, caused by the intracellular protozoan Trypanosoma cruzi, is characterized by microvascular alterations, heart failure and arrhythmias. Ischemia and arrythmogenesis have been attributed to proteins shed by the parasite, although this has not been fully demonstrated. The aim of the present investigation was to study the effect of substances shed by T. cruzi on ischemia/reperfusion-induced arrhythmias. We performed a triple ischemia-reperfusion (I/R) protocol whereby the isolated beating rat hearts were perfused with either Vero-control or Vero T. cruzi-infected conditioned medium during the different stages of ischemia and subsequently reperfused with Tyrode's solution. ECG and heart rate were recorded during the entire experiment. We observed that triple I/R-induced bradycardia was associated with the generation of auricular-ventricular blockade during ischemia and non-sustained nodal and ventricular tachycardia during reperfusion. Interestingly, perfusion with Vero-infected medium produced a delay in the reperfusion-induced recovery of heart rate, increased the frequency of tachycardic events and induced ventricular fibrillation. These results suggest that the presence of parasite-shed substances in conditioned media enhances the arrhythmogenic effects that occur during the I/R protocol.
Chagas' disease; Arrhythmias; Ischemia
Introduction
Chagas' disease is a tropical disease, initially confined to Central and South
America, caused by the intracellular protozoan Trypanosoma cruzi.
This illness is characterized by an acute phase, which is generally asymptomatic or
oligosymptomatic; an indeterminate phase, which may persist for several years, and a
chronic phase, when dilated cardiomyopathy and arrhythmias are primarily observed.
Chagasic cardiomyopathy has been attributed to an imbalance between adrenergic or
cholinergic innervations, cellular and humoral autoimmunity, parasitic effects, or
microischemic disturbances (11. Higuchi Mde L, Benvenuti LA, Martins Reis M, Metzger M.
Pathophysiology of the heart in Chagas' disease: current status and new
developments. Cardiovasc Res 2003: 60: 96-107, doi:
10.1016/S0008-6363(03)00361-4.
https://doi.org/10.1016/S0008-6363(03)00...
).
The phenomenon of microvascular alterations and the generation of microischemic foci have been studied extensively during the acute and chronic phases of Chagas' disease. Several researchers have described changes indicative of ischemia in the hearts of chagasic patients, mainly associated with platelet aggregation 22. Rossi MA, Carobrez SG. Experimental Trypanosoma cruzi cardiomyopathy in BALB/c mice: histochemical evidence of hypoxic changes in the myocardium. Br J Exp Pathol 1985: 66: 155-160., thinning of the capillary basement membranes 33. Andrade ZA, Andrade SG, Sadigursky M, Wenthold RJ Jr, Hilbert SL, Ferrans VJ. The indeterminate phase of Chagas' disease: ultrastructural characterization of cardiac changes in the canine model. Am J Trop Med Hyg 1997: 57: 328-336., and areas of focal vascular constriction, microaneurysms, and dilatation of vascular beds in murine hearts during the acute phase of this infection (44. Factor SM, Cho S, Wittner M, Tanowitz H. Abnormalities of the coronary microcirculation in acute murine Chagas' disease. Am J Trop Med Hyg 1985: 34: 246-253.). These disturbances could generate or enhance arrhythmias that are observed during chronic Chagas' disease.
Cardiac arrhythmias are one of the most important disorders occurring during Chagas'
disease. Traditionally, arrhythmias have been considered to be a consequence of
cardiac structural changes that occur during the chronic phase. In this respect, the
main alterations reported are atrial and ventricular extrasystoles, intraventricular
and/or AV conduction disturbances, and primary ST-T wave changes 55. Elizari MV, Chiale PA. Cardiac arrhythmias in Chagas' heart
disease. J Cardiovasc Electrophysiol 1993: 4: 596-608, doi:
10.1111/j.1540-8167.1993.tb01247.x.
https://doi.org/10.1111/j.1540-8167.1993...
). However, ST and T abnormalities, ventricular
and supraventricular arrhythmias and low-voltage QRS have been reported in a recent
acute oral outbreak characterized by high parasitemia (66. Alarcon de Noya B, Diaz-Bello Z, Colmenares C, Ruiz-Guevara R,
Mauriello L, Zavala-Jaspe R, et al. Large urban outbreak of orally acquired
acute Chagas disease at a school in Caracas, Venezuela. J Infect Dis 2010: 201:
1308-1315, doi: 10.1086/651608.
https://doi.org/10.1086/651608...
), which suggest that the parasite may have a role in
arrhythmia generation. The mechanisms associated with non-structural-related
arrhythmias in Chagas' disease are poorly understood.
Soluble factors that are generated during ischemia have been linked to cardiac
arrhythmias, which are observed in isolated beating chagasic hearts 77. Alvarado-Tapias E, Rivas-Coppola M, Alvarado A, Bello M, Briceno
M, Rodriguez-Bonfante C, et al. [Adenosine induces ventricular arrythmias in
hearts with chronic chagas cardiomyopathy]. Rev Esp Cardiol 2010: 63: 478-482,
doi: 10.1016/S0300-8932(10)70069-5.
https://doi.org/10.1016/S0300-8932(10)70...
). Moreover, it is known that T.
cruzi can release several substances into the extracellular milieu that
produce alterations in microvascular (88. Libby P, Alroy J, Pereira ME. A neuraminidase from
Trypanosoma cruzi removes sialic acid from the surface of
mammalian myocardial and endothelial cells. J Clin Invest 1986: 77: 127-135,
doi: 10.1172/JCI112266.
https://doi.org/10.1172/JCI112266...
) and
intracellular calcium homeostasis (99. Dorta ML, Ferreira AT, Oshiro ME, Yoshida N. Ca2+
signal induced by Trypanosoma cruzi metacyclic trypomastigote
surface molecules implicated in mammalian cell invasion. Mol Biochem Parasitol
1995: 73: 285-289, doi: 10.1016/0166-6851(94)00123-5.
https://doi.org/10.1016/0166-6851(94)001...
,
1010. Manque PM, Neira I, Atayde VD, Cordero E, Ferreira AT, da
Silveira JF, et al. Cell adhesion and Ca2+ signaling activity in
stably transfected Trypanosoma cruzi epimastigotes expressing
the metacyclic stage-specific surface molecule gp82. Infect Immun 2003: 71:
1561-1565, doi: 10.1128/IAI.71.3.1561-1565.2003.
https://doi.org/10.1128/IAI.71.3.1561-15...
), thereby contributing to
arrhythmogenesis. Nevertheless, the association between proteins that are secreted
and/or shed by T. cruzi and the disturbances in heart conduction
system and arrhythmias has not been fully elucidated. The aim of the present study
was to determine whether perfusion of non-chagasic beating hearts with substances
released by T. cruzi can potentiate arrhythmias under ischemic
conditions. Therefore, we performed a triple ischemia/reperfusion (I/R) protocol to
induce the ischemic and pro-arrhythmic conditions that are present in chronic
chagasic hearts. To obtain quantitative information, the effects on heart rate (HR)
were analyzed by fitting against a double-logistic model, and the results were
compared to the changes observed in the ECG recordings during the different protocol
stages.
Material and Methods
Cell culture and conditioned medium
Vero cells were plated in a 75-cm2 Easy Flask in 20-mL complete minimum essential medium (MEM) supplemented with 10% (v/v) fetal bovine serum (FBS), and were infected with 2 × 105 trypomastigotes/mL of the EP strain at a ratio of 2 parasites per cell. Noninvasive parasites were removed after 24 h and the initial medium was changed at this time. The conditioned media were collected on the 5th or 6th day post-infection. The criteria for medium collection were that a minimum of 75% Vero cells should have adhered and that at least 2.5 × 106 trypomastigotes/mL should be present in the supernatant. The medium was centrifuged at 1500 g for 10 min to separate the parasites, and the supernatant was subsequently filtered using a 0.2-µM membrane filter (Millipore®, USA) and stored at -20°C until use.
Preparation of isolated Langendorff hearts
For the isolated beating heart experiments, hearts were removed from adult female Sprague Dawley rats weighing 300-400 g anesthetized ip with 40 mg/kg pentobarbital. The isolated hearts were placed in cold Tyrode's solution (25 mM sodium bicarbonate, 10 mM glucose, 116 mM sodium chloride, 3.3 mM potassium chloride, 2.5 mM calcium chloride, and 1 mM magnesium sulfate), cannulated through the aorta, and perfused in a retrograde manner with warm Tyrode's solution (37°C) for 30 min by using the isolated beating heart system (AD Instruments, Australia). The presence of sinus rhythm, HR greater than 180 bpm, perfusion pressure higher than 30 mmHg, and a flow rate of 8-10 mL/min were considered to be stable values for all experiments. All procedures were approved by the Institutional Committee of the Venezuelan Institute for Scientific Research.
After stabilization was achieved, a protocol consisting of three consecutive I/R cycles (10 and 20 min, respectively) was initiated. During each ischemic cycle, deoxygenated complete MEM (1.8 mM calcium chloride, 0.81 mM magnesium sulfate, 5.33 mM potassium chloride, 117.24 mM sodium chloride, 1.01 mM sodium phosphate monobasic, 5.56 mM D-glucose, plus L-glutamine, phenol red and essential amino acids) supplemented with 24 mM sodium bicarbonate was perfused at a low flow rate (2 mL/min) for 10 min, followed by reperfusion with oxygenated Tyrode's solution for 20 min (flow of 8 to 10 mL/min). During the ischemic periods, the hearts were perfused with medium that was conditioned with either control Vero cells (Vero-control medium, n = 12) or infected Vero cells (Vero-infected medium, n = 14). Both of these media contained 10% FBS (v/v).
Measurement of enzyme activity
For biochemical analysis of the I/R process, we determined aspartate aminotransferase (AST) activity by sampling the effusate to indicate cardiac damage. The samples were collected every 2 min for a period of 30 min. The samples were immediately frozen and stored at -20°C until further processing. The enzyme activity was measured with a commercially available ELISA kit (Invelab™, Venezuela) according to manufacturer specifications.
Curve fitting
In this study, we used a double-logistic model (1111. Head GA, Lukoshkova EV, Mayorov DN, van den Buuse M.
Non-symmetrical double-logistic analysis of 24-h blood pressure recordings in
normotensive and hypertensive rats. J Hypertens 2004: 22: 2075-2085, doi:
10.1097/00004872-200411000-00008.
https://doi.org/10.1097/00004872-2004110...
)
Statistical analysis
Data are reported as means ± SE. The Student t-test was used to determine statistical significance, and results with P < 0.05 were considered to be statistically significant. The χ2 test was used to compare the ventricular fibrillation rate between the groups. Data analysis was performed using the Prism5® software (GraphPad Software, Inc., USA).
Results
Validation of the ischemia-reperfusion model
To evaluate cardiac damage during the I/R cycles, we collected the media after heart reperfusion and measured AST activity (Figure 1). A rapid increase in enzymatic activity was observed during the three ischemic phases (0-10, 30-40 and 60-70 min; Figure 1, thick black lines), which returned to basal levels during reperfusion. The enzymatic activity was not found to be different between the different ischemic cycles; therefore, these results suggest that our protocol produced a transient damage to the isolated beating hearts. Similarly, no significant differences were observed between the hearts that were perfused with Vero-control or Vero-infected medium (Figure 1).
Average evolution of enzymatic activity (AST) in ischemia-reperfusion cycles. The graph shows the values of enzymatic activity measured every 2 min during the three ischemia-reperfusion cycles. Thick horizontal lines (top) indicate the different ischemia stages and are identified as I1 (ischemia 1), I2 (ischemia 2), and I3 (ischemia 3) and match the increased AST activity. The graph averages the data of Vero-control (n = 12) and Vero-infected hearts (n = 14).
Effect of conditioned medium on ECG values and recordings during I/R
Figure 2 demonstrates the fitting of Equation 1 to HR kinetics during the I/R protocol for perfusion with Vero-control (A) or Vero-infected conditioned (B) medium (r2 = 0.94 and 0.92, respectively). The plot shows that HR recovery (P5) was significantly slower in hearts perfused with Vero-infected medium compared to Vero-control medium (0.53 ± 0.1422 vs 2.87 ± 0.36555, P = 0.0006). Interestingly, these results were associated with bradyarrhythmias, particularly sinus arrest during the reperfusion period (middle portion of Figure 3), and were not observed in hearts perfused with Vero-control (top portion of Figure 3) that showed AV blockade during the final phase of ischemia.
Average heart rate (HR) during the ischemia-reperfusion process. Dotted lines represent the mean ± SE HR in all ischemia-reperfusion cycles. Panel A shows the data of Vero-control-perfused hearts (n = 12), and Panel B shows data of Vero-infected-perfused hearts (n = 14). Continuous lines are the results of the fitting of Equation 1, and parameters are shown in the inset.
Panel A shows representative ECG recordings of the ischemia-reperfusion process for different perfused media. The figure shows the ECG recordings during the different stages of ischemia-reperfusion processes, which were identified as I1, I2, I3 for the three ischemia stages and as R1, R2, and R3 for the reperfusion ones. The upper recording shows the ECG of an isolated beating heart perfused with Vero cell-conditioned medium (Vero-control), and the middle and bottom recordings show ECGs of two different isolated beating hearts perfused with Vero-infected-conditioned medium. Panel B shows a numerical comparison of tachyarrhythmia and ventricular fibrillation events between Vero-control and Vero-infected perfused hearts. The P value was 0.0138 in tachyarrhythmia comparison (Student t-test) and 0.0441 in ventricular fibrillation comparison (chi-square test).
In addition, tachyarrhythmias and the low-voltage QRS complex generated during perfusion of Vero-infected medium are displayed in Figure 3A (Vero-infected “2”, bottom). Ventricular tachycardia was observed during the first reperfusion phase, whereas ventricular fibrillation was noted during the last reperfusion phase. Hearts perfused with Vero-infected medium demonstrated atrial flutter and nodal and ventricular tachycardia during the I/R stages, whereas in hearts perfused with Vero-control medium, nodal and ventricular tachycardia was observed in the reperfusion stage only. Overall, 1.5 ± 0.43 tachyarrhythmic events/record were recorded in hearts perfused with Vero-infected medium, whereas 0.25 ± 0.13 tachyarrhythmic events/record were recorded in hearts perfused with Vero-control medium (P = 0.0156). Ventricular fibrillation was detected in 4 of 14 hearts perfused with Vero-infected medium compared to 0 of 12 hearts perfused with Vero-control medium (P = 0.0441).
Discussion
Ischemia-reperfusion can lead to arrhythmias and sudden death. In particular,
ischemia can lead to ventricular tachycardia and, finally, ventricular fibrillation
(1212. Cascio WE. Myocardial ischemia: what factors determine
arrhythmogenesis? J Cardiovasc Electrophysiol 2001: 12: 726-729, doi:
10.1046/j.1540-8167.2001.00726.x.
https://doi.org/10.1046/j.1540-8167.2001...
). These events correlate with a
concomitant increase in the intracellular H+, Na+, and
Ca2+ levels (1212. Cascio WE. Myocardial ischemia: what factors determine
arrhythmogenesis? J Cardiovasc Electrophysiol 2001: 12: 726-729, doi:
10.1046/j.1540-8167.2001.00726.x.
https://doi.org/10.1046/j.1540-8167.2001...
), affecting the
cardiac action potential and thereby generating arrhythmias. Furthermore,
microvascular alterations observed in Chagas' disease could produce transient
ischemia (22. Rossi MA, Carobrez SG. Experimental Trypanosoma
cruzi cardiomyopathy in BALB/c mice: histochemical evidence of
hypoxic changes in the myocardium. Br J Exp Pathol 1985: 66:
155-160.), and this is probably due to
parasite-shed proteins (1313. Yoshida N, Cortez M. Trypanosoma cruzi:
parasite and host cell signaling during the invasion process. Subcell Biochem
2008: 47: 82-91, doi: 10.1007/978-0-387-78267-6_6.
https://doi.org/10.1007/978-0-387-78267-...
). However, their
participation in arrythmogenesis, which is observed in Chagas' disease, are still
unclear.
The fitting of a double-logistic equation (Equation 1) to model the I/R process is suitable to quantify and compare the different situations explained above. Despite the high complexity of the heart dynamics, the tendency shown allows us to use this tool to have an idea of the kinetics of the process with a reasonable degree of precision. However, a full mathematical description of the heart is far from being obtained and is out of the scope of the present study.
During our experiments, we observed an increase in the frequency of tachyarrhythmias
during perfusion with Vero-infected medium; therefore, we suggest that proteins
present in the conditioned medium have the ability to enhance arrhythmias, probably
by increasing the intracellular calcium levels. During parasite-host cell
interaction, several secreted or released proteins can bind to the host cell
receptors and modify cellular signaling. The different mucins present on the surface
of trypomastigotes have been associated with the process of invasion. The protein
gp82, a surface mucin of T. cruzi, causes an increase in
intracellular calcium in Hela cells infected with metacyclic trypomastigotes, an
effect mediated by IP3, phospholipase C and protein tyrosine kinase (99. Dorta ML, Ferreira AT, Oshiro ME, Yoshida N. Ca2+
signal induced by Trypanosoma cruzi metacyclic trypomastigote
surface molecules implicated in mammalian cell invasion. Mol Biochem Parasitol
1995: 73: 285-289, doi: 10.1016/0166-6851(94)00123-5.
https://doi.org/10.1016/0166-6851(94)001...
,
1414. Yoshida N, Favoreto S Jr, Ferreira AT, Manque PM. Signal
transduction induced in Trypanosoma cruzi metacyclic
trypomastigotes during the invasion of mammalian cells. Braz J Med Biol Res
2000: 33: 269-278, doi: 10.1590/S0100-879X2000000300003.
https://doi.org/10.1590/S0100-879X200000...
). Gp90 and gp35/50 proteins are involved
in the modulation of calcium increase in the host cell and the invasiveness of the
strain of the parasite in which they are present (1515. Ruiz RC, Favoreto S Jr, Dorta ML, Oshiro ME, Ferreira AT, Manque
PM, et al. Infectivity of Trypanosoma cruzi strains is
associated with differential expression of surface glycoproteins with
differential Ca2+ signalling activity. Biochem J 1998: 330 (Part 1):
505-511.). On the other hand, it has been reported that protein members of the
transialidase and mucin family attach to the host cells and increase the
intracellular calcium levels (1313. Yoshida N, Cortez M. Trypanosoma cruzi:
parasite and host cell signaling during the invasion process. Subcell Biochem
2008: 47: 82-91, doi: 10.1007/978-0-387-78267-6_6.
https://doi.org/10.1007/978-0-387-78267-...
). Similarly,
parasite cysteine proteases can cleave extracellular precursors, such as kininogens,
which in turn bind to the host cell BK2R receptors and increase the
intracellular calcium concentration (1616. Scharfstein J, Andrade D. Infection-associated vasculopathy in
experimental chagas disease pathogenic roles of endothelin and kinin pathways.
Adv Parasitol 2011: 76: 101-127, doi:
10.1016/B978-0-12-385895-5.00005-0.
https://doi.org/10.1016/B978-0-12-385895...
). These
phenomena facilitate the entry of the parasite into its respective host cell.
Interestingly, the existence of calcium overload in the ventricular myocytes of
chagasic patients was recently reported (1717. Lopez JR, Espinosa R, Landazuru P, Linares N, Allen P, Mijares
A. [Dysfunction of diastolic [Ca(2)(+)] in cardiomyocytes isolated from chagasic
patients]. Rev Esp Cardiol 2011: 64: 456-462, doi:
10.1016/j.recesp.2011.01.008.
https://doi.org/10.1016/j.recesp.2011.01...
).
It is well known that increases in the intracellular calcium levels are responsible
for the extension of the plateau phase of the cardiac action potential. This
phenomenon contributes to the generation of re-entry circuits and therefore the
appearance of malignant ventricular arrhythmias (1818. Sipido KR, Bito V, Antoons G, Volders PG, Vos MA. Na/Ca exchange
and cardiac ventricular arrhythmias. Ann N Y Acad Sci 2007: 1099: 339-348, doi:
10.1196/annals.1387.066.
https://doi.org/10.1196/annals.1387.066...
). It is possible that the calcium overload that occurs during
parasitic invasion of the cardiac cells can potentiate the proarrhythmogenic status
produced by the ischemia due to microvascular alterations, which is observed in
Chagas' disease.
Ventricular arrhythmias observed in the isolated beating chagasic hearts have been
attributed to the activation of adenosine and adrenergic systems, both of which are
present during ischemia (77. Alvarado-Tapias E, Rivas-Coppola M, Alvarado A, Bello M, Briceno
M, Rodriguez-Bonfante C, et al. [Adenosine induces ventricular arrythmias in
hearts with chronic chagas cardiomyopathy]. Rev Esp Cardiol 2010: 63: 478-482,
doi: 10.1016/S0300-8932(10)70069-5.
https://doi.org/10.1016/S0300-8932(10)70...
). To our knowledge,
this is the first report that demonstrates a causal link between
trypomastigote-conditioned medium and arrythmogenesis in Chagas' disease.
Other ionic currents may be associated with electrical alterations produced by
T. cruzi-conditioned medium. Pacioretty et al. (1919. Pacioretty LM, Barr SC, Han WP, Gilmour RF Jr. Reduction of the
transient outward potassium current in a canine model of Chagas' disease. Am J
Physiol 1995: 268: H1258-H1264.) reported a reduction of transient outward
potassium current in epicardial myocytes during the acute phase of Chagas' disease.
This reduction was associated with the parasitemia peak, suggesting that a direct
action of the parasite may be involved in this effect. Also, sera from chagasic
patients with beta-adrenergic activity shortened the QT interval and the action
potential duration and increased slow inward potassium current (IKs) and inward
calcium current (Ica) (2020. Medei EH, Nascimento JH, Pedrosa RC, Barcellos L, Masuda MO,
Sicouri S, et al. Antibodies with beta-adrenergic activity from chronic chagasic
patients modulate the QT interval and M cell action potential duration. Europace
2008: 10: 868-876, doi: 10.1093/europace/eun138.
https://doi.org/10.1093/europace/eun138...
).
On the other hand, parasite-cell interaction relies on specific signaling pathways in
the host cells that facilitate the entry of the parasite, which could contribute to
the physiopathology of the disease. Andrade et al. (2121. Andrade D, Serra R, Svensjo E, Lima AP, Ramos ES Jr, Fortes FS,
et al. Trypanosoma cruzi invades host cells through the
activation of endothelin and bradykinin receptors: a converging pathway leading
to chagasic vasculopathy. Br J Pharmacol 2012: 165: 1333-1347, doi:
10.1111/j.1476-5381.2011.01609.x.
https://doi.org/10.1111/j.1476-5381.2011...
) reported that exogenous endothelin-1 (ET-1) potentiated T.
cruzi uptake in vitro and was associated with
interstitial edema elicited by extracellular trypomastigotes. ET-1 is a potent
vasoconstrictor and is present in high levels in the serum of chagasic patients.
ET-1 induces vasospasm in T. cruzi-infected mice, consequently
contributing to the development of myocardial ischemia and myonecrosis (1616. Scharfstein J, Andrade D. Infection-associated vasculopathy in
experimental chagas disease pathogenic roles of endothelin and kinin pathways.
Adv Parasitol 2011: 76: 101-127, doi:
10.1016/B978-0-12-385895-5.00005-0.
https://doi.org/10.1016/B978-0-12-385895...
). Additionally, other non-protein soluble
mediators are secreted by the parasite and may be related to ischemic and electrical
disturbances in chagasic hearts. T. cruzi-derived thromboxane A2
(TXA2) has been detected in the circulation of infected mice (2222. Ashton AW, Mukherjee S, Nagajyothi FN, Huang H, Braunstein VL,
Desruisseaux MS, et al. Thromboxane A2 is a key regulator of pathogenesis during
Trypanosoma cruzi infection. J Exp Med 2007: 204: 929-940,
doi: 10.1084/jem.20062432.
https://doi.org/10.1084/jem.20062432...
). Interestingly, TXA2 has been associated with reperfusion
arrhythmias (2323. Parratt JR, Coker SJ, Wainwright CL. Eicosanoids and
susceptibility to ventricular arrhythmias during myocardial ischaemia and
reperfusion. J Mol Cell Cardiol 1987: 19 (Suppl 5): 55-66, doi:
10.1016/S0022-2828(87)80610-7.
https://doi.org/10.1016/S0022-2828(87)80...
). Therefore, it could be
involved in the arrythmogenesis observed in Chagas' disease.
Perfusion with conditioned media produced a delay in HR recovery during the early
reperfusion phase (see Figures 2 and 3). This is particularly relevant because it has
been widely reported that Chagas' disease is characterized by an alteration in the
heart conduction pathways, which leads to AV block and sinus arrest among other
complications (2424. Garzon SA, Lorga AM, Nicolau JC. Electrocardiography in Chagas'
heart disease. São Paulo Med J 1995: 113: 802-813, doi:
10.1590/S1516-31801995000200011.
https://doi.org/10.1590/S1516-3180199500...
). In addition, it has been
reported that sera obtained from chronic chagasic patients who suffer from complex
cardiac arrhythmias show depressed electrogenesis and conduction when used in
different isolated beating heart preparations (2525. Costa PC, Fortes FS, Machado AB, Almeida NA, Olivares EL, Cabral
PR, et al. Sera from chronic chagasic patients depress cardiac electrogenesis
and conduction. Braz J Med Biol Res 2000: 33: 439-446, doi:
10.1590/S0100-879X2000000400010.
https://doi.org/10.1590/S0100-879X200000...
). It has been suggested that dampening of electrogenesis and
bradyarrhythmias is due to the presence of autoantibodies against the second
extracellular loop of cardiac M2 acetylcholine receptor and β2 adrenoceptor (2626. Escobar AL, Fernandez-Gomez R, Peter JC, Mobini R, Hoebeke J,
Mijares A. IgGs and Mabs against the beta2-adrenoreceptor block A-V conduction
in mouse hearts: A possible role in the pathogenesis of ventricular arrhythmias.
J Mol Cell Cardiol 2006: 40: 829-837, doi:
10.1016/j.yjmcc.2006.03.430.
https://doi.org/10.1016/j.yjmcc.2006.03....
,
2727. Mijares A, Verdot L, Peineau N, Vray B, Hoebeke J, Argibay J.
Antibodies from Trypanosoma cruzi infected mice recognize the
second extracellular loop of the beta 1-adrenergic and M2-muscarinic receptors
and regulate calcium channels in isolated cardiomyocytes. Mol Cell Biochem 1996:
163-164: 107-112, doi: 10.1007/BF00408646.
https://doi.org/10.1007/BF00408646...
). Interestingly, some investigators have
reported a decrease in the expression of connexin 43, a gap junction protein, in the
infected cardiac myocytes (2828. Adesse D, Goldenberg RC, Fortes FS, Jasmin, Iacobas DA, Iacobas
S, et al. Gap junctions and Chagas disease. Adv Parasitol 2011: 76: 63-81, doi:
10.1016/B978-0-12-385895-5.00003-7.
https://doi.org/10.1016/B978-0-12-385895...
). This implies a
causal relationship between parasitic infection and cardiac conduction disorders.
However, to our knowledge, this is the first report that demonstrates the
association of cardiac bradyarrhythmias with the perfusion of T.
cruzi-conditioned medium.
We developed an experimental protocol to reproduce the ischemic and pro-arrhythmic conditions that exist in chronic chagasic hearts. The application of a double-logistic model allows the comparison of HR in the different media perfused. Our results suggest that substances present in the conditioned media have the ability to enhance I/R-induced arrhythmic and conduction disorders, which are similar to those observed in chagasic cardiomyopathy.
Research supported by IVIC, project #N-305, and by Misión Ciencia, Ministerio del Poder Popular para la Ciencia y Tecnología, Fondo Nacional de Ciencia y Tecnología (FONACIT), project #2007001425.
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2Rossi MA, Carobrez SG. Experimental Trypanosoma cruzi cardiomyopathy in BALB/c mice: histochemical evidence of hypoxic changes in the myocardium. Br J Exp Pathol 1985: 66: 155-160.
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3Andrade ZA, Andrade SG, Sadigursky M, Wenthold RJ Jr, Hilbert SL, Ferrans VJ. The indeterminate phase of Chagas' disease: ultrastructural characterization of cardiac changes in the canine model. Am J Trop Med Hyg 1997: 57: 328-336.
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4Factor SM, Cho S, Wittner M, Tanowitz H. Abnormalities of the coronary microcirculation in acute murine Chagas' disease. Am J Trop Med Hyg 1985: 34: 246-253.
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5Elizari MV, Chiale PA. Cardiac arrhythmias in Chagas' heart disease. J Cardiovasc Electrophysiol 1993: 4: 596-608, doi: 10.1111/j.1540-8167.1993.tb01247.x.
-
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First published online January 11, 2013.
Publication Dates
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Publication in this collection
11 Jan 2013 -
Date of issue
Jan 2013
History
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Received
25 May 2012 -
Accepted
3 Sept 2012