Arlete Rita Penitente

Trypanosoma cruzi infection induces morphological reorganization of the myocardium parenchyma and stroma, and modifies the mechanical properties of atrial and ventricular cardiomyocytes in rats

BACKGROUND This study investigates morphofunctional adaptations of the heart stroma and parenchyma in rats that are chronically infected with Trypanosoma cruzi. METHODS Four-month-old male Wistar rats were randomized into control (n=14) and infected (n=14) groups. Infected animals were inoculated with T. cruzi Y strain. After 9 weeks, the animals were euthanized, and the right atrium (RA) and left ventricle (LV) were removed for biochemical, stereological, and cardiomyocyte mechanical analyses. RESULTS Infected animals presented cardiomyocyte atrophy and myocardial fibrosis. For these animals, the total volume, length, surface area, and cross-sectional area of cardiomyocytes were significantly reduced, and the total interstitial and collagen volumes were significantly increased in the RA and LV compared to the controls. The total volume and length of blood vessels were significantly increased in the LV, and the total blood vessel surface area was significantly higher in the RA of infected animals. RA and LV cardiomyocytes from infected animals exhibited a significant reduction in cell shortening (43.02% and 24.98%, respectively), prolongation of the time to the peak of contraction (17.09%) and the time to half relaxation (23.68%) compared to non-infected animals. Lipid hydroperoxides, but not mineral concentrations, were significantly increased in the RA and LV from infected animals, showing an inverse correlation with cell shortening. CONCLUSIONS T. cruzi infection induces global structural remodeling of the RA and LV in rats. This remodeling coexists with cardiomyocyte contractility dysfunction, which is possibly related to the abnormal organization of the myocardial stroma and increased cellular lipid peroxidation.

Effects of Trypanosoma cruzi infection on myocardial morphology, single cardiomyocyte contractile function and exercise tolerance in rats

The aim of this study was to investigate the effects of Trypanosoma cruzi (T. cruzi) infection on myocardial morphology, single cardiomyocyte contractile function and exercise tolerance in rats. Adult Wistar rats were randomized into control (n = 14) and infected (n = 14) groups. Infected animals were inoculated with T. cruzi Y strain (300,000 trypomastigotes/50 g body weight). After 9 weeks, the animals were subjected to a treadmill running protocol. Then, the right atrium (RA) and left ventricle (LV) were removed for morphological and cell contractile evaluation. The infected animals exhibited a significant reduction in distance travelled, total time to fatigue and workload. In addition, these animals had hypertrophy, increased myocardial cellularity, and an increase in the proportion of collagen and blood vessels. RA and LV myocytes from infected animals showed marked contractile dysfunction under basal conditions and a reduced contractile response to β‐adrenergic stimulation. The workload of infected animals was correlated closely with the amplitude of cell shortening of RA and LV myocytes. T. cruzi infection influenced the myocardial morphology and the mechanical properties of RA and LV single myocytes negatively and reduced exercise tolerance. Single cardiomyocyte contractile dysfunction could constitute an additional mechanism of cardiac impairment and reduced exercise tolerance in this infection.

Swimming training attenuates contractile dysfunction in diabetic rat cardiomyocytes

BACKGROUND Experimental diabetes promotes contractile dysfunction in cardiomyocytes, but the effects of swimming in this disorder are not known. OBJECTIVE To test the effects of a swimming training program (STP) on cardiomyocyte contractile dysfunction in rats with experimental diabetes. METHODS Wistar rats (age: 30 days; mean body weight: 84.19 g) with diabetes induced by streptozotocin (60 mg/kg body weight; glucose > 300 mg/dl) were divided into sedentary diabetic rats (SD, n = 10) and exercised diabetic rats (ED, n = 13). Animals of same age and weight served as sedentary controls (SC, n = 10) and exercised controls (EC, n = 06). Animals and ED and EC underwent a STP (05 days/week, 90 min/day) for 08 weeks. Left ventricular (LV) myocytes were isolated and electrically stimulated at 3.0 Hz at room temperature (∼ 25º C). RESULTS Diabetes reduced contractile function in cardiomyocytes of animals compared to controls (i.e., lower amplitude of contraction, longer duration of contraction and relaxation). The STP attenuated the reduced amplitude of contraction (SC, 11 ± 0.2% vs ED, 11.6 ± 0.2%), time to peak contraction (SC, 319 ± 5.8 ms vs ED, 333 ± 4.8 ms) and time to 50.0% of relaxation (SC, 619 ± 22.2 ms vs ED 698 ± 18.6 ms) of cardiomyocytes of diabetic rats. Diabetes reduced the size of cardiomyocytes, however, the STP minimized the reduction of cell volume and width, without changing length. CONCLUSION The swimming training program attenuated the contractile dysfunction of the LV myocytes of rats with experimental diabetes.FUNDAMENTO: O diabete experimental promove disfuncao contratil em cardiomiocitos, mas os efeitos do treinamento em natacao nesta disfuncao nao sao conhecidos. OBJETIVO: Testar os efeitos de um programa de treino em natacao (PTN) sobre a disfuncao contratil de cardiomiocitos de ratos com diabete experimental. METODOS: Ratos Wistar (idade: 30 dias; peso corporal medio: 84,19 g) com diabete induzida por estreptozotocina (60 mg/kg de peso corporal; glicemia > 300 mg/dl) foram alocados em diabeticos sedentarios (DS, n = 10) e diabeticos exercitados (DE, n = 13). Animais da mesma idade e peso serviram de controles sedentarios (CS, n = 10) e controles exercitados (CE, n = 06). Os animais DE e CE foram submetidos a um PTN (05 dias/semana, 90 min/dia), por 08 semanas. Os miocitos do ventriculo esquerdo (VE) foram isolados e estimulados eletricamente a 3,0 Hz em temperatura ambiente (∼ 25o C). RESULTADOS: O diabete reduziu a funcao contratil nos cardiomiocitos dos animais em relacao aos controles (i.e., menor amplitude de contracao, maior tempo de contracao e relaxamento). O PTN atenuou a reducao na amplitude de contracao (CS, 11 ± 0,2% vs DE, 11,6 ± 0,2%), o tempo para o pico de contracao (CS, 319 ± 5,8 ms vs DE, 333 ± 4,8 ms) e o tempo para 50% de relaxamento (CS, 619 ± 22,2 ms vs DE, 698 ± 18,6 ms) dos cardiomiocitos dos animais diabeticos. O diabete reduziu as dimensoes dos cardiomiocitos, porem, o PTN minimizou a reducao da largura e volume celular, sem alterar o comprimento. CONCLUSAO: O programa de treino em natacao atenuou a disfuncao contratil dos miocitos do VE de ratos com diabete experimental.

Modulation of inflammatory and oxidative status by exercise attenuates cardiac morphofunctional remodeling in experimental Chagas cardiomyopathy.

AIMS The rational basis that explains the benefits of exercise therapy on Chagas cardiomyopathy (ChC) is poorly understood. This study investigated the impact of an exercise program on exercise performance, heart parasitism, immunoinflammatory response, fibrogenesis, oxidative damage, and cardiomyocytes contractility in experimental ChC. MAIN METHODS Wistar rats were subjected to a 9-week treadmill running training and challenged with Trypanosoma cruzi. Control animals remained sedentary. Physical and metabolic performance, cardiac morphology, cytokines, chemokines, nitric oxide, oxidative tissue damage, cardiomyocyte morphology and contractility were analyzed. KEY FINDINGS Exercise training was efficient to improve physical performance and anaerobic threshold in trained animals. By increasing cardiac and serum levels of cytokines (TNF-α, IFN-γ, and IL-6), chemokines (MCP-1 and CX3CL1), the myocardial activity catalase and superoxide dismutase, and reducing lipid and protein oxidation in cardiac tissue, exercise training seem to be a beneficial strategy to mitigate the progression and severity of Chagas-associated cardiomyopathy. SIGNIFICANCE The protective adaptations to the host triggered by exercise training contributed to reduce cardiac parasitism, inflammation, fibrosis and cardiomyocytes atrophy. Although exercise training does not affect nitric oxide levels in cardiac tissue from infected animals, this strategy enhanced the efficiency of endogenous antioxidant mechanisms, restricting oxidative tissue damage with positive repercussions to cardiomyocytes biomechanics in rats.

Uso de fluorescência em um método de dissector modificado para estimar o número de miócitos no tecido cardíaco

BACKGROUND Conventional disector methods currently require considerable financial, technical and operational costs to estimate the number of cells, including cardyomyocytes, in a 3D area. OBJECTIVE To use fluorescence microscopy in a modified disector method to determine the number of myocytes in cardiac tissue in normal and pathological conditions. METHODS The study employed four-month-old male Wistar rats with weight of 366.25 ± 88.21g randomized in control (CG, n=8) and infected (IG, n=8) groups. IG animals were inoculated with T. cruzi Y strain (300,000 trypomastigotes/50g wt). After eight weeks, the animals were weighted and euthanized. The left ventricles (LV) were removed for stereological analysis of numerical density of cardiomyocytes (Nv[c]) and total number of these cells in the LV (N[c]). These parameters were estimated using a fluorescent disector (FD) and compared with the conventional optical (OD) and physical (PD) disector methods. RESULTS In both disector methods, IG animals presented significant decrease of Nv[c] and N[c] compared to CG animals (P< 0.05). There was no significant difference in these variables despite the disector method applied in CG and IG animals (P> 0.05). A strong correlation, equal or above 96%, was obtained between FD, OD and PD. CONCLUSION The FD method seems to be equally reliable to determine Nv[c] and N[c] in normal and pathological conditions and presents some advantages compared to conventional disector methods: reduction of histological slices and images in the stereological analysis, reduction of time to analyze the images, construction of FD in simple microscopes using the epifluorescence mode, distinction of disector planes in lower magnifications.FUNDAMENTO: Metodos convencionais de dissector atualmente requerem consideraveis custos financeiros, tecnicos e operacionais para estimar o numero de celulas, incluindo cardiomiocitos, em uma area de 3D. OBJETIVO: Usar a microscopia de fluorescencia em um metodo de dissector modificado para determinar o numero de miocitos no tecido cardiaco em condicoes normais e patologicas. METODOS: O estudo empregou camundongos Wistar machos com quatro meses de idade e peso de 366,25 ± 88,21 g randomizados em grupos controles (GC, n = 8) e infectados (GI, n = 8). Os animais do GI foram inoculados com cepa Y de T. cruzi (300.000 tripomastigotas/50 g). Apos oito semanas, os animais foram pesados e sacrificados. Os Ventriculos Esquerdos (VE) foram removidos para analise estereologica da densidade numerica de cardiomiocitos (Nv [c]) e o numero total dessas celulas no VE (N [c]). Esses parâmetros foram estimados usando um dissector fluorescente (DF) e comparados com os metodos convencionais de dissector optico (DO) e dissector fisico (DFi). RESULTADOS: Em ambos os metodos de dissector, os animais do GI apresentaram queda significativa de Nv[c] e N[c] em comparacao com os animais do GC (P > 0,05). Uma correlacao forte, igual ou superior a 96%, foi obtida entre DF, DO e DFi. CONCLUSAO: O metodo DF parece ser igualmente confiavel para determinar Nv[c] e N[c] em condicoes normais e patologicas, apresentando algumas vantagens em relacao aos metodos convencionais de dissector: reducao de cortes histologicos e imagens na analise estereologica, reducao do tempo de analise das imagens, a construcao de DF em microscopios simples, utilizando o modo de epifluorescencia, distincao de planos de dissector em ampliacoes inferiores.

Modulation of oxidative and inflammatory cardiac response by nonselective 1- and 2-cyclooxygenase inhibitor and benznidazole in mice.

This study investigated the combined effects of benznidazole (BZ) and ibuprofen (IB) on the oxidative and inflammatory status of the cardiac tissue in vivo.

Treinamento em natação atenua a disfução contrátil de cardiomiócitos de ratos diabéticos

BACKGROUND Experimental diabetes promotes contractile dysfunction in cardiomyocytes, but the effects of swimming in this disorder are not known. OBJECTIVE To test the effects of a swimming training program (STP) on cardiomyocyte contractile dysfunction in rats with experimental diabetes. METHODS Wistar rats (age: 30 days; mean body weight: 84.19 g) with diabetes induced by streptozotocin (60 mg/kg body weight; glucose > 300 mg/dl) were divided into sedentary diabetic rats (SD, n = 10) and exercised diabetic rats (ED, n = 13). Animals of same age and weight served as sedentary controls (SC, n = 10) and exercised controls (EC, n = 06). Animals and ED and EC underwent a STP (05 days/week, 90 min/day) for 08 weeks. Left ventricular (LV) myocytes were isolated and electrically stimulated at 3.0 Hz at room temperature (∼ 25º C). RESULTS Diabetes reduced contractile function in cardiomyocytes of animals compared to controls (i.e., lower amplitude of contraction, longer duration of contraction and relaxation). The STP attenuated the reduced amplitude of contraction (SC, 11 ± 0.2% vs ED, 11.6 ± 0.2%), time to peak contraction (SC, 319 ± 5.8 ms vs ED, 333 ± 4.8 ms) and time to 50.0% of relaxation (SC, 619 ± 22.2 ms vs ED 698 ± 18.6 ms) of cardiomyocytes of diabetic rats. Diabetes reduced the size of cardiomyocytes, however, the STP minimized the reduction of cell volume and width, without changing length. CONCLUSION The swimming training program attenuated the contractile dysfunction of the LV myocytes of rats with experimental diabetes.FUNDAMENTO: O diabete experimental promove disfuncao contratil em cardiomiocitos, mas os efeitos do treinamento em natacao nesta disfuncao nao sao conhecidos. OBJETIVO: Testar os efeitos de um programa de treino em natacao (PTN) sobre a disfuncao contratil de cardiomiocitos de ratos com diabete experimental. METODOS: Ratos Wistar (idade: 30 dias; peso corporal medio: 84,19 g) com diabete induzida por estreptozotocina (60 mg/kg de peso corporal; glicemia > 300 mg/dl) foram alocados em diabeticos sedentarios (DS, n = 10) e diabeticos exercitados (DE, n = 13). Animais da mesma idade e peso serviram de controles sedentarios (CS, n = 10) e controles exercitados (CE, n = 06). Os animais DE e CE foram submetidos a um PTN (05 dias/semana, 90 min/dia), por 08 semanas. Os miocitos do ventriculo esquerdo (VE) foram isolados e estimulados eletricamente a 3,0 Hz em temperatura ambiente (∼ 25o C). RESULTADOS: O diabete reduziu a funcao contratil nos cardiomiocitos dos animais em relacao aos controles (i.e., menor amplitude de contracao, maior tempo de contracao e relaxamento). O PTN atenuou a reducao na amplitude de contracao (CS, 11 ± 0,2% vs DE, 11,6 ± 0,2%), o tempo para o pico de contracao (CS, 319 ± 5,8 ms vs DE, 333 ± 4,8 ms) e o tempo para 50% de relaxamento (CS, 619 ± 22,2 ms vs DE, 698 ± 18,6 ms) dos cardiomiocitos dos animais diabeticos. O diabete reduziu as dimensoes dos cardiomiocitos, porem, o PTN minimizou a reducao da largura e volume celular, sem alterar o comprimento. CONCLUSAO: O programa de treino em natacao atenuou a disfuncao contratil dos miocitos do VE de ratos com diabete experimental.

Protein Restriction after Weaning Modifies the Calcium Kinetics and Induces Cardiomyocyte Contractile Dysfunction in Rats

Protein restriction (PR) is associated with cardiovascular diseases. The purpose of this study was to investigate the effects on single ventricular cardiomyocyte contractile function of a short-term PR after weaning. Male Fischer rats that were 28 days old were randomly divided into a control group (CG, n = 16) and a protein-restricted group (PRG, n = 16). After weaning, CG and PRG animals received isocaloric diets containing 15 and 6% protein, respectively, for 35 days. Biometric parameters were then measured, and the hearts were removed for the analysis of contractile function and calcium transient in isolated cardiomyocytes of the left ventricule (LV), and the quantification of calcium and collagen fibers in LV myocardium. PRG animals had lower body weight (BW) and LV weight (LVW), an increased LVW to BW ratio and a higher proportion of collagen fibers than CG animals. PRG animals exhibited reduced tissue levels of calcium, reduced the length, width and volume of cardiomyocytes and their sarcomere length compared to CG animals. Cardiomyocytes from PRG animals had a lower amplitude of shortening, a slower time to the peak of shortening and a longer time to half-relaxation than those from the CG. Cardiomyocytes from PRG animals also presented a lower peak of calcium transient and a longer calcium transient decay time than CG animals. Taken together, the results indicate that short-term PR after weaning induces a marked structural remodeling of the myocardium parenchyma and stroma that coexists with contractile dysfunctions in single LV cardiomyocytes of rats, which is probably associated with pathological changes of the intracellular calcium kinetics, rather than inadequate available amounts of this mineral in cardiac tissue.

Use of fluorescence in a modified disector method to estimate the number of myocytes in cardiac tissue

BACKGROUND Conventional disector methods currently require considerable financial, technical and operational costs to estimate the number of cells, including cardyomyocytes, in a 3D area. OBJECTIVE To use fluorescence microscopy in a modified disector method to determine the number of myocytes in cardiac tissue in normal and pathological conditions. METHODS The study employed four-month-old male Wistar rats with weight of 366.25 ± 88.21g randomized in control (CG, n=8) and infected (IG, n=8) groups. IG animals were inoculated with T. cruzi Y strain (300,000 trypomastigotes/50g wt). After eight weeks, the animals were weighted and euthanized. The left ventricles (LV) were removed for stereological analysis of numerical density of cardiomyocytes (Nv[c]) and total number of these cells in the LV (N[c]). These parameters were estimated using a fluorescent disector (FD) and compared with the conventional optical (OD) and physical (PD) disector methods. RESULTS In both disector methods, IG animals presented significant decrease of Nv[c] and N[c] compared to CG animals (P< 0.05). There was no significant difference in these variables despite the disector method applied in CG and IG animals (P> 0.05). A strong correlation, equal or above 96%, was obtained between FD, OD and PD. CONCLUSION The FD method seems to be equally reliable to determine Nv[c] and N[c] in normal and pathological conditions and presents some advantages compared to conventional disector methods: reduction of histological slices and images in the stereological analysis, reduction of time to analyze the images, construction of FD in simple microscopes using the epifluorescence mode, distinction of disector planes in lower magnifications.FUNDAMENTO: Metodos convencionais de dissector atualmente requerem consideraveis custos financeiros, tecnicos e operacionais para estimar o numero de celulas, incluindo cardiomiocitos, em uma area de 3D. OBJETIVO: Usar a microscopia de fluorescencia em um metodo de dissector modificado para determinar o numero de miocitos no tecido cardiaco em condicoes normais e patologicas. METODOS: O estudo empregou camundongos Wistar machos com quatro meses de idade e peso de 366,25 ± 88,21 g randomizados em grupos controles (GC, n = 8) e infectados (GI, n = 8). Os animais do GI foram inoculados com cepa Y de T. cruzi (300.000 tripomastigotas/50 g). Apos oito semanas, os animais foram pesados e sacrificados. Os Ventriculos Esquerdos (VE) foram removidos para analise estereologica da densidade numerica de cardiomiocitos (Nv [c]) e o numero total dessas celulas no VE (N [c]). Esses parâmetros foram estimados usando um dissector fluorescente (DF) e comparados com os metodos convencionais de dissector optico (DO) e dissector fisico (DFi). RESULTADOS: Em ambos os metodos de dissector, os animais do GI apresentaram queda significativa de Nv[c] e N[c] em comparacao com os animais do GC (P > 0,05). Uma correlacao forte, igual ou superior a 96%, foi obtida entre DF, DO e DFi. CONCLUSAO: O metodo DF parece ser igualmente confiavel para determinar Nv[c] e N[c] em condicoes normais e patologicas, apresentando algumas vantagens em relacao aos metodos convencionais de dissector: reducao de cortes histologicos e imagens na analise estereologica, reducao do tempo de analise das imagens, a construcao de DF em microscopios simples, utilizando o modo de epifluorescencia, distincao de planos de dissector em ampliacoes inferiores.

Parasite control and skeletal myositis in Trypanosoma cruzi-infected and exercised rats

Non-pharmacological strategies have been rarely described in the treatment of infectious diseases. Although exercise training has been recently incorporated in the clinical management of Chagas disease, the rationale basis that supports this indication is poorly understood. Thus, we investigated the effect of an aerobic exercise on the parasitism, inflammation and oxidative tissue damage in a murine model of Trypanosoma cruzi-induced skeletal myositis. Wistar rats were randomized into four groups: trained not infected (TNI) and infected (TI), sedentary not infected (SNI) and infected (SI). A running training program was administered 5days/week for 9 weeks. Then, infected animals were inoculated with T. cruzi and followed up for another 9 weeks. Exercise training induced beneficial adaptations by increasing time to fatigue and lactate threshold in TNI and TI animals. SI animals presented higher parasitemia, skeletal muscle parasitism, cell necrosis, leukocyte infiltration, cytokines levels, reactive oxygen species and nitric oxide production, thiobarbituric acid reactive substances, carbonyl proteins, myosin heavy chain I depletion, and increased catalase (CAT) and superoxide dismutase (SOD) activities. Beyond attenuation in all these variables, TI animals showed reduced TNF-α, CCL-2/MCP-1 and CX3CL1, and increased IL-10 muscle levels. Furthermore, these animals presented higher CAT and SOD activities and reduced lipid and protein oxidation. Taken together, our findings indicated that exercise training induced a protective phenotype in T. cruzi-infected mice, enhancing host defenses against the parasite and attenuating the pathological remodeling associated with skeletal myositis, aspects potentially associated to an improved immunological and redox balance in infected animals.