The aim of this study was to evaluate whether chronotropic incompetence (CI), the inability to re... more The aim of this study was to evaluate whether chronotropic incompetence (CI), the inability to reach 85% of the maximal predicted heart rate during exercise, affects the assessment of myocardial ischemia and prognosis in patients undergoing myocardial perfusion single-photon emission computed tomography (MPS). Patients undergoing exercise/rest MPS were studied. Those taking drugs with negative chronotropic properties were excluded. Summed stress, rest, and difference scores (SSS, SRS, and SDS, representing, respectively, the extent and severity of the total perfusion defect, fibrosis, or ischemia) were calculated. Patients were followed up for the occurrence of hard events (death or myocardial infarction) or myocardial revascularization for 36±20 months. A total of 391 patients were studied; among them, 11.5% had CI. All perfusion scores were higher in patients with CI. On logistic regression, history of myocardial infarction and SDS were found to be independent predictors of CI. On comparing patients with and without CI, the former more often had hard events (12.5 vs. 0.9%, P=0.007) and revascularization (20.0 vs. 8.1%, P=0.003). CI was associated with myocardial ischemia. Higher rates of hard events and revascularization were observed in patients with CI, in accordance with the larger extent of myocardial ischemia found in these patients. Performing MPS in the setting of CI may maintain the diagnostic and prognostic abilities of the test.
Abstract Deep water drilling is normally associated to narrow operational windows where gains and... more Abstract Deep water drilling is normally associated to narrow operational windows where gains and losses are frequent. drilling fluids are designed to gel when it is not submitted to shear stress. This is necessary to avoid cuttings to settle during circulation stops. When ...
Selenium is an essential trace element and its deficiency was implicated in heart diseases. We re... more Selenium is an essential trace element and its deficiency was implicated in heart diseases. We recently showed low Se levels in chronic chagasic patients with cardiomyopathy. Herein, mice were depleted in Se by feeding the mothers with chow containing only 0.005 mg Se/kg and maintaining this diet for offspring, that were further infected with Trypanosoma cruzi. Survival rate was significantly lower in Se deficient than in control mice. Parasitemia was similar in all groups. Necrotic heart lesions were found after infection (high CK-MB levels). No outbreaks of parasite growth were detected in chronic survivors submitted or not to a second Se depletion. The present results confirm our hypothesis that a nutritional deficiency in Se is associated to a higher mortality during T. cruzi infection. The potential beneficial effect of Se supplementation is a perspective. Hypothesis to explain the higher susceptibility of Se-depleted mice to T. cruzi infection are discussed.
Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a serious public health proble... more Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a serious public health problem in Latin America. In relation to digestive problems, 4.5% of patients show mega syndromes (megacolon) in the chronic phase. In this article, we evaluated intestinal motility at the acute phase of T. cruzi infection through charcoal ingestion in adult mice. After infection, Swiss mice were administered an aqueous suspension of charcoal in water by gavage. Decrease in intestinal motility was determined by increased time of appearance of charcoal in the feces. The uninfected group showed a mean time of charcoal elimination of 109.0 ± 14.6 min throughout the assay. On the other hand, infected mice presented a significant increase in charcoal defecation time during infection. At 15 days postinfection, infected mice showed a significant increase in charcoal defecation time, 310.2 ± 67.4 min when compared to the uninfected group, which presented 97.8 ± 31.8 min, indicating that the T. cruzi infection interferes with intestinal motility. Our results demonstrate that the use of charcoal is an ethical and efficient procedure to evaluate the intestinal motility in the murine model of T. cruzi infection.
Chagasic patients with cardiomyopathy have low levels of selenium (Se), a fundamental trace eleme... more Chagasic patients with cardiomyopathy have low levels of selenium (Se), a fundamental trace element. We evaluated the effect of supplementing infected mice with Se (0.25–16 ppm). Supplementation with 0.25 or 1 ppm Se led to parasitaemia and survival curves similar to those of the control group. Mice treated with 4–16 ppm showed a dose-dependent decrease of parasitaemia, significant for the highest concentration. This was probably due to a direct effect on the parasites, which were lysed after in vitro incubation with Se. Survival rates did not change significantly; however, heart damage was reduced in infected mice supplemented with 4 ppm Se, as indicated by a lower cardiac isoform of creatine kinase levels. Our results imply that Se supplementation does not lead to a general protection during infection, but may help protect the heart from inflammatory damage. The effect of Se supplementation in the course of T. cruzi infection depends on the host-parasite pair employed.
International Journal of Experimental Pathology, 2010
Understanding the dual participation of the immune response in controlling the invader and at the... more Understanding the dual participation of the immune response in controlling the invader and at the same time causing tissue damage might contribute to the design of effective new vaccines and therapies for Chagas disease. Perforin, a cytolytic protein product of killer cells, is involved in resistance to acute Trypanosoma cruzi infection. However, the contribution of perforin in parasite control and chronic chagasic cardiomyopathy is unclear. Perforin-positive cells were detected in the heart tissue during the acute and chronic phases of infection of C57BL/6 mice inoculated with low dose (102 parasites) of the Colombian T. cruzi strain. This protocol led to acute phase survival in both wild-type and perforin null (pfp−/−) mice lineages. During the chronic infection, parasitism and inducible nitric oxide synthase (iNOS) as well as interleukin (IL)-4+ and, mainly, interferon (IFN)-γ+ cells were more elevated in the heart tissue of pfp−/− mice. Higher levels of circulating NO and anti-parasite immunoglobulin (Ig)G2c and IgG3, paralleled by a prominent frequency of IFN-γ+ and IL-10+ splenocytes, were present in pfp−/−-infected mice. Therefore, although the perforin-dependent pathway plays a role, it is not crucial for anti-T. cruzi immunity and acute phase survival of mice infected with a low inoculum. Further, perforin deficiency resulted in lower activity of creatine kinase-muscle brain isoform (CK-MB) isoenzyme in serum and a more restricted connexin 43 loss, both of which are markers of the cardiomyocyte lesion. Moreover, perforin deficiency hampered the development of severe electrocardiographic abnormalities. Hence, our results corroborate that perforin-bearing cytotoxic cells might contribute to cardiomyocyte lesion and heart dysfunction during chronic T. cruzi infection, shedding light on immunopathogenesis of chronic chagasic cardiomyopathy.
Experimental acute infection with Trypanosoma cruzi in mice promotes an intense myocarditis and o... more Experimental acute infection with Trypanosoma cruzi in mice promotes an intense myocarditis and other systemic changes. However, the network of pathophysiological disorders and renal injury caused by the infection has not been elucidated. Our previous results with a murine model observed a discrete acute myocarditis and high mortality with significant inflammatory kidney injury with T. cruzi infection. The aim of this study was to investigate the mechanisms of kidney injury caused by the parasite in mice during the experimental acute phase. Results employing BALB/c mice infected with T. cruzi of Y strain showed renal injury on the 6th day postinfection (dpi) caused by a transitory decrease of renal blood flow. Acute kidney injury (AKI) was also observed similar to the model of ischemia/reperfusion lesion in these infected mice. The injury was not related to the presence (or multiplication) of parasites. Only rare nests were microscopically detected, and the presence of scattered parasites in renal parenchyma was seen on the 15th dpi. Thus, it was observed that during the acute phase of the disease, AKI in infected mice is linked to early cardiovascular effects, including heart failure, caused by striking inflammatory lesions in the myocardium, which lead to the high mortality rate of animals.
The elucidation of the intricate molecular network of costimulus and regulatory pathways of the i... more The elucidation of the intricate molecular network of costimulus and regulatory pathways of the immune system led to the design of molecular therapies that specifically inactivate some cellular responses and ameliorate some autoimmune and inflammatory diseases. This innovative concept opens a new class of therapies, and one of the central components that could be targeted in future molecular therapies is the Fas-based pathway. Both soluble and membrane-bound Fas and Fas-L molecules exert a wide range of proinflammatory functions through the secretion of cytokines and chemokines, cellular chemotaxis, transcriptional regulation, cellular death, and others. Accordingly, many chronic inflammatory diseases, including myocarditis, are attenuated in mice lacking either molecule. Although it is tempting to speculate that the Fas/Fas-L pathway could be targeted for in vivo myocarditis therapy, the plurality of Fas/Fas-L functions can be an obstacle, leading to important side effects. In this review, we suggest that the injection of nonagonistic antibodies raised against the Fas molecule or the inactivation of downstream Fas-1,4,5-inositol triphosphate cascade are possible targets for myocarditis treatment.
Trypanosoma cruzi infection induces diverse alterations in immunocompetent cells and organs, myoc... more Trypanosoma cruzi infection induces diverse alterations in immunocompetent cells and organs, myocarditis and congestive heart failure. However, the physiological network of disturbances imposed by the infection has not been addressed thoroughly. Regarding myocarditis induced by the infection, we observed in our previous work that Fas-L-/- mice (gld/gld) have very mild inflammatory infiltration when compared to BALB/c mice. However, all mice from both lineages die in the early acute phase. Therefore, in this work we studied the physiological connection relating arterial pressure, renal function/damage and cardiac insufficiency as causes of death. Our results show that a broader set of dysfunctions that could be classified as a cardio/anaemic/renal syndrome is more likely responsible for cardiac failure and death in both lineages. However, gld/gld mice had very early glomerular deposition of IgM and a more intense renal inflammatory response with reduced renal filtration, which is probably responsible for the premature death in the absence of significant myocarditis in gld/gld.
Immunisation with Amastigote Surface Protein 2 (asp-2) and trans-sialidase (ts) genes induces pro... more Immunisation with Amastigote Surface Protein 2 (asp-2) and trans-sialidase (ts) genes induces protective immunity in highly susceptible A/Sn mice, against infection with parasites of the Y strain of Trypanosoma cruzi. Based on immunological and biological strain variations in T. cruzi parasites, our goal was to validate our vaccination results using different parasite strains. Due to the importance of the CD8+ T cells in protective immunity, we initially determined which strains expressed the immunodominant H-2Kk-restricted epitope TEWETGQI. We tested eight strains, four of which elicited immune responses to this epitope (Y, G, Colombian and Colombia). We selected the Colombian and Colombia strains for our studies. A/Sn mice were immunised with different regimens using both T. cruzi genes (asp-2 and ts) simultaneously and subsequently challenged with blood trypomastigotes. Immune responses before the challenge were confirmed by the presence of specific antibodies and peptide-specific T cells. Genetic vaccination did not confer protective immunity against acute infection with a lethal dose of the Colombian strain. In contrast, we observed a drastic reduction in parasitemia and a significant increase in survival, following challenge with an otherwise lethal dose of the Colombia strain. In many surviving animals with late-stage chronic infection, we observed alterations in the heart's electrical conductivity, compared to naive mice. In summary, we concluded that immunity against T. cruzi antigens, similar to viruses and bacteria, may be strain-specific and have a negative impact on vaccine development.
The aim of this study was to evaluate whether chronotropic incompetence (CI), the inability to re... more The aim of this study was to evaluate whether chronotropic incompetence (CI), the inability to reach 85% of the maximal predicted heart rate during exercise, affects the assessment of myocardial ischemia and prognosis in patients undergoing myocardial perfusion single-photon emission computed tomography (MPS). Patients undergoing exercise/rest MPS were studied. Those taking drugs with negative chronotropic properties were excluded. Summed stress, rest, and difference scores (SSS, SRS, and SDS, representing, respectively, the extent and severity of the total perfusion defect, fibrosis, or ischemia) were calculated. Patients were followed up for the occurrence of hard events (death or myocardial infarction) or myocardial revascularization for 36±20 months. A total of 391 patients were studied; among them, 11.5% had CI. All perfusion scores were higher in patients with CI. On logistic regression, history of myocardial infarction and SDS were found to be independent predictors of CI. On comparing patients with and without CI, the former more often had hard events (12.5 vs. 0.9%, P=0.007) and revascularization (20.0 vs. 8.1%, P=0.003). CI was associated with myocardial ischemia. Higher rates of hard events and revascularization were observed in patients with CI, in accordance with the larger extent of myocardial ischemia found in these patients. Performing MPS in the setting of CI may maintain the diagnostic and prognostic abilities of the test.
Abstract Deep water drilling is normally associated to narrow operational windows where gains and... more Abstract Deep water drilling is normally associated to narrow operational windows where gains and losses are frequent. drilling fluids are designed to gel when it is not submitted to shear stress. This is necessary to avoid cuttings to settle during circulation stops. When ...
Selenium is an essential trace element and its deficiency was implicated in heart diseases. We re... more Selenium is an essential trace element and its deficiency was implicated in heart diseases. We recently showed low Se levels in chronic chagasic patients with cardiomyopathy. Herein, mice were depleted in Se by feeding the mothers with chow containing only 0.005 mg Se/kg and maintaining this diet for offspring, that were further infected with Trypanosoma cruzi. Survival rate was significantly lower in Se deficient than in control mice. Parasitemia was similar in all groups. Necrotic heart lesions were found after infection (high CK-MB levels). No outbreaks of parasite growth were detected in chronic survivors submitted or not to a second Se depletion. The present results confirm our hypothesis that a nutritional deficiency in Se is associated to a higher mortality during T. cruzi infection. The potential beneficial effect of Se supplementation is a perspective. Hypothesis to explain the higher susceptibility of Se-depleted mice to T. cruzi infection are discussed.
Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a serious public health proble... more Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a serious public health problem in Latin America. In relation to digestive problems, 4.5% of patients show mega syndromes (megacolon) in the chronic phase. In this article, we evaluated intestinal motility at the acute phase of T. cruzi infection through charcoal ingestion in adult mice. After infection, Swiss mice were administered an aqueous suspension of charcoal in water by gavage. Decrease in intestinal motility was determined by increased time of appearance of charcoal in the feces. The uninfected group showed a mean time of charcoal elimination of 109.0 ± 14.6 min throughout the assay. On the other hand, infected mice presented a significant increase in charcoal defecation time during infection. At 15 days postinfection, infected mice showed a significant increase in charcoal defecation time, 310.2 ± 67.4 min when compared to the uninfected group, which presented 97.8 ± 31.8 min, indicating that the T. cruzi infection interferes with intestinal motility. Our results demonstrate that the use of charcoal is an ethical and efficient procedure to evaluate the intestinal motility in the murine model of T. cruzi infection.
Chagasic patients with cardiomyopathy have low levels of selenium (Se), a fundamental trace eleme... more Chagasic patients with cardiomyopathy have low levels of selenium (Se), a fundamental trace element. We evaluated the effect of supplementing infected mice with Se (0.25–16 ppm). Supplementation with 0.25 or 1 ppm Se led to parasitaemia and survival curves similar to those of the control group. Mice treated with 4–16 ppm showed a dose-dependent decrease of parasitaemia, significant for the highest concentration. This was probably due to a direct effect on the parasites, which were lysed after in vitro incubation with Se. Survival rates did not change significantly; however, heart damage was reduced in infected mice supplemented with 4 ppm Se, as indicated by a lower cardiac isoform of creatine kinase levels. Our results imply that Se supplementation does not lead to a general protection during infection, but may help protect the heart from inflammatory damage. The effect of Se supplementation in the course of T. cruzi infection depends on the host-parasite pair employed.
International Journal of Experimental Pathology, 2010
Understanding the dual participation of the immune response in controlling the invader and at the... more Understanding the dual participation of the immune response in controlling the invader and at the same time causing tissue damage might contribute to the design of effective new vaccines and therapies for Chagas disease. Perforin, a cytolytic protein product of killer cells, is involved in resistance to acute Trypanosoma cruzi infection. However, the contribution of perforin in parasite control and chronic chagasic cardiomyopathy is unclear. Perforin-positive cells were detected in the heart tissue during the acute and chronic phases of infection of C57BL/6 mice inoculated with low dose (102 parasites) of the Colombian T. cruzi strain. This protocol led to acute phase survival in both wild-type and perforin null (pfp−/−) mice lineages. During the chronic infection, parasitism and inducible nitric oxide synthase (iNOS) as well as interleukin (IL)-4+ and, mainly, interferon (IFN)-γ+ cells were more elevated in the heart tissue of pfp−/− mice. Higher levels of circulating NO and anti-parasite immunoglobulin (Ig)G2c and IgG3, paralleled by a prominent frequency of IFN-γ+ and IL-10+ splenocytes, were present in pfp−/−-infected mice. Therefore, although the perforin-dependent pathway plays a role, it is not crucial for anti-T. cruzi immunity and acute phase survival of mice infected with a low inoculum. Further, perforin deficiency resulted in lower activity of creatine kinase-muscle brain isoform (CK-MB) isoenzyme in serum and a more restricted connexin 43 loss, both of which are markers of the cardiomyocyte lesion. Moreover, perforin deficiency hampered the development of severe electrocardiographic abnormalities. Hence, our results corroborate that perforin-bearing cytotoxic cells might contribute to cardiomyocyte lesion and heart dysfunction during chronic T. cruzi infection, shedding light on immunopathogenesis of chronic chagasic cardiomyopathy.
Experimental acute infection with Trypanosoma cruzi in mice promotes an intense myocarditis and o... more Experimental acute infection with Trypanosoma cruzi in mice promotes an intense myocarditis and other systemic changes. However, the network of pathophysiological disorders and renal injury caused by the infection has not been elucidated. Our previous results with a murine model observed a discrete acute myocarditis and high mortality with significant inflammatory kidney injury with T. cruzi infection. The aim of this study was to investigate the mechanisms of kidney injury caused by the parasite in mice during the experimental acute phase. Results employing BALB/c mice infected with T. cruzi of Y strain showed renal injury on the 6th day postinfection (dpi) caused by a transitory decrease of renal blood flow. Acute kidney injury (AKI) was also observed similar to the model of ischemia/reperfusion lesion in these infected mice. The injury was not related to the presence (or multiplication) of parasites. Only rare nests were microscopically detected, and the presence of scattered parasites in renal parenchyma was seen on the 15th dpi. Thus, it was observed that during the acute phase of the disease, AKI in infected mice is linked to early cardiovascular effects, including heart failure, caused by striking inflammatory lesions in the myocardium, which lead to the high mortality rate of animals.
The elucidation of the intricate molecular network of costimulus and regulatory pathways of the i... more The elucidation of the intricate molecular network of costimulus and regulatory pathways of the immune system led to the design of molecular therapies that specifically inactivate some cellular responses and ameliorate some autoimmune and inflammatory diseases. This innovative concept opens a new class of therapies, and one of the central components that could be targeted in future molecular therapies is the Fas-based pathway. Both soluble and membrane-bound Fas and Fas-L molecules exert a wide range of proinflammatory functions through the secretion of cytokines and chemokines, cellular chemotaxis, transcriptional regulation, cellular death, and others. Accordingly, many chronic inflammatory diseases, including myocarditis, are attenuated in mice lacking either molecule. Although it is tempting to speculate that the Fas/Fas-L pathway could be targeted for in vivo myocarditis therapy, the plurality of Fas/Fas-L functions can be an obstacle, leading to important side effects. In this review, we suggest that the injection of nonagonistic antibodies raised against the Fas molecule or the inactivation of downstream Fas-1,4,5-inositol triphosphate cascade are possible targets for myocarditis treatment.
Trypanosoma cruzi infection induces diverse alterations in immunocompetent cells and organs, myoc... more Trypanosoma cruzi infection induces diverse alterations in immunocompetent cells and organs, myocarditis and congestive heart failure. However, the physiological network of disturbances imposed by the infection has not been addressed thoroughly. Regarding myocarditis induced by the infection, we observed in our previous work that Fas-L-/- mice (gld/gld) have very mild inflammatory infiltration when compared to BALB/c mice. However, all mice from both lineages die in the early acute phase. Therefore, in this work we studied the physiological connection relating arterial pressure, renal function/damage and cardiac insufficiency as causes of death. Our results show that a broader set of dysfunctions that could be classified as a cardio/anaemic/renal syndrome is more likely responsible for cardiac failure and death in both lineages. However, gld/gld mice had very early glomerular deposition of IgM and a more intense renal inflammatory response with reduced renal filtration, which is probably responsible for the premature death in the absence of significant myocarditis in gld/gld.
Immunisation with Amastigote Surface Protein 2 (asp-2) and trans-sialidase (ts) genes induces pro... more Immunisation with Amastigote Surface Protein 2 (asp-2) and trans-sialidase (ts) genes induces protective immunity in highly susceptible A/Sn mice, against infection with parasites of the Y strain of Trypanosoma cruzi. Based on immunological and biological strain variations in T. cruzi parasites, our goal was to validate our vaccination results using different parasite strains. Due to the importance of the CD8+ T cells in protective immunity, we initially determined which strains expressed the immunodominant H-2Kk-restricted epitope TEWETGQI. We tested eight strains, four of which elicited immune responses to this epitope (Y, G, Colombian and Colombia). We selected the Colombian and Colombia strains for our studies. A/Sn mice were immunised with different regimens using both T. cruzi genes (asp-2 and ts) simultaneously and subsequently challenged with blood trypomastigotes. Immune responses before the challenge were confirmed by the presence of specific antibodies and peptide-specific T cells. Genetic vaccination did not confer protective immunity against acute infection with a lethal dose of the Colombian strain. In contrast, we observed a drastic reduction in parasitemia and a significant increase in survival, following challenge with an otherwise lethal dose of the Colombia strain. In many surviving animals with late-stage chronic infection, we observed alterations in the heart's electrical conductivity, compared to naive mice. In summary, we concluded that immunity against T. cruzi antigens, similar to viruses and bacteria, may be strain-specific and have a negative impact on vaccine development.
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Papers by gabriel oliveira