Cardiac hyporesponsiveness in severe sepsis is associated with nitric oxide-dependent activation of G protein receptor kinase.

G protein-coupled receptor kinase isoform 2 (GRK2) has a critical role in physiological and pharmacological responses to endogenous and exogenous substances. Sepsis causes an important cardiovascular dysfunction in which nitric oxide (NO) has a relevant role. The present study aimed to assess the putative effect of inducible NO synthase (NOS2)-derived NO on the activity of GRK2 in the context of septic cardiac dysfunction. C57BL/6 mice were submitted to severe septic injury by cecal ligation and puncture (CLP). Heart function was assessed by isolated and perfused heart, echocardiography, and ß-adrenergic receptor binding. GRK2 was determined by immunofluorescence and Western blot analysis in the heart and isolated cardiac myocytes. Sepsis increased NOS2 expression in the heart, increased plasma nitrite + nitrate levels, and reduced isoproterenol-induced isolated ventricle contraction, whole heart tension development, and ß-adrenergic receptor density. Treatment with 1400W or with GRK2 inhibitor prevented CLP-induced cardiac hyporesponsiveness 12 and 24 h after CLP. Increased labeling of total and phosphorylated GRK2 was detected in hearts after CLP. With treatment of 1400W or in hearts taken from septic NOS2 knockout mice, the activation of GRK2 was reduced. 1400W or GRK2 inhibitor reduced mortality, improved echocardiographic cardiac parameters, and prevented organ damage. Therefore, during sepsis, NOS2-derived NO increases GRK2, which leads to a reduction in ß-adrenergic receptor density, contributing to the heart dysfunction. Isolated cardiac myocyte data indicate that NO acts through the soluble guanylyl cyclase/cGMP/PKG pathway. GRK2 inhibition may be a potential therapeutic target in sepsis-induced cardiac dysfunction.NEW & NOTEWORTHY The main novelty presented here is to show that septic shock induces cardiac hyporesponsiveness to isoproterenol by a mechanism dependent on nitric oxide and mediated by G protein-coupled receptor kinase isoform 2. Therefore, G protein-coupled receptor kinase isoform 2 inhibition may be a potential therapeutic target in sepsis-induced cardiac dysfunction.

Short-term and long-term models of doxorubicin-induced cardiomyopathy in rats: A comparison of functional and histopathological changes.

OBJECTIVES: Doxorubicin (DXR), an anthracyclic antineoplastic agent, is one of the most commonly drug utilized to induce dilated cardiomyopathy (DCM) and heart failure (HF), but the well optimized protocol for cardiomyopathy induction leading to development of cardiac systolic dysfunction is unclear. This study aims to critically compare short-term and long-term DXR injection protocols for the induction of DCM in rats. METHODS: Animals were allocated into 3 experimental groups: a ST (short-term DXR injection) group, in which animals received 6 intraperitoneal (i.p.) injections of DXR (2.5mg/kg per dose) over a period of 2 weeks (cumulative dose of 15mg/kg); a LT (long-term DXR injection) group in which animals received weekly i.p. injections of DXR (2mg/kg per dose) over a period of 9 weeks (cumulative dose of 18mg/kg); and a control group in which animals received an appropriate volume of 0.9% saline i.p. All animals were submitted to echocardiography analysis at baseline and after completion treatment. Afterwards, the hearts were collected for conventional light microscopy and collagen quantification. RESULTS: Morphological myocardial analysis of both DXR-treated groups showed an identical pattern of swollen and vacuolated cardiomyocytes and disorganization of myofibrils. There was pronounced interstitial fibrosis in both groups of DXR-treated hearts as compared to controls, as assessed by the interstitial collagen volume fraction. There was no difference in interstitial fibrosis between the ST and LT groups. The echocardiography analysis of the LT group showed structural and functional findings compatible with DCM, including increased left ventricular systolic (5.02±0.96mm) and diastolic (7.68±0.96mm) dimensions and reduction of ejection fraction (69.40±8.51%) as compared to the ST group (4.10±0.89mm, 7.32±0.84, and 79.68±7.23%, respectively) and control group (4.07±0.72mm, 7.17±0.68mm and 80.08±4.71%, respectively), ANOVA p<0.01. CONCLUSIONS: These results indicate that LT injection of DXR is more effective than ST injection in inducing left ventricular dysfunction and structural cardiac changes resembling those found in dilated cardiomyopathy.

Involvement of the microvasculature in the pathogenesis of terlipressin-related myocardial infarction.

We report an autopsy case of a 24-year-old man with diagnoses of advanced alcoholic liver cirrhosis, portal hypertension, and esophageal variceal bleeding that presented extensive myocardial infarction after treatment with terlipressin. On postmortem examination the cut surface of the heart presented myocardial infarction implicating the left ventricle free wall, apex of the heart and ventricular septum. Light microscopic examination revealed that the extensive area of cardiac infarction was the result of the sum of diffuse foci of microinfarction of various ages interspersed with small clusters of preserved myocytes. Moreover, the epicardial vessels were patent while the small intramyocardial vessels presented thickened wall, apparent reduction in lumen diameter and disruption of endothelial cells indicative of spasm. The observations in this case allow clear insight into the involvement of the microcirculation in the pathogenesis of myocardial infarction with the use of terlipressin.

Lipofuscin Granules in the Epileptic Human Temporal Neocortex with Age.

Lipofuscin granules (LGs), the "age pigments", are autofluorescent cell products from lysosomes that diverge in number and size among brain regions. Human temporal cortex from 20- to 55-year-old epileptic subjects were studied with the fat soluble dye Sudan Black, under confocal and electron microscopy. Ultrastructural analysis showed that with age LGs increase in area, but not in number. Proportionally to the LGs area, the electron lucid portion increases and the electron dense reduces over time. The robust increase in lipid components is possibly due to modifications in the neuronal metabolism with age in physiological and pathological conditions.

The acute phase of Trypanosoma cruzi infection is attenuated in 5-lipoxygenase-deficient mice.

In the present work we examine the contribution of 5-lipoxygenase- (5-LO-) derived lipid mediators to immune responses during the acute phase of Trypanosoma cruzi infection in 5-LO gene knockout (5-LO(-/-)) mice and wild-type (WT) mice. Compared with WT mice, the 5-LO(-/-) mice developed less parasitemia/tissue parasitism, less inflammatory cell infiltrates, and a lower mortality. This resistance of 5-LO(-/-) mice correlated with several differences in the immune response to infection, including reduced PGE2 synthesis; sustained capacity of splenocytes to produce high levels of interleukin (IL)-12 early in the infection; enhanced splenocyte production of IL-1ß, IL-6, and IFN-γ; rapid T-cell polarization to secrete high quantities of IFN-γ and low quantities of IL-10; and greater numbers of CD8(+)CD44(high)CD62L(low) memory effector T cells at the end of the acute phase of infection. The high mortality in WT mice was associated with increased production of LTB4/LTC4, T cell bias to produce IFN-γ, high levels of serum nitrite, and marked protein extravasation into the peritoneal cavity, although survival was improved by treatment with a cys-LT receptor 1 antagonist. These data also provide evidence that 5-LO-derived mediators negatively affect host survival during the acute phase of T. cruzi infection.

Role of dystrophin in acute Trypanosoma cruzi infection.

Previous studies have demonstrated loss/reduction of dystrophin in cardiomyocytes in both acute and chronic stages of experimental Trypanosoma cruzi (T. cruzi) infection in mice. The mechanisms responsible for dystrophin disruption in the hearts of mice acutely infected with T. cruzi are not completely understood. The present in vivo and in vitro studies were undertaken to evaluate the role of inflammation in dystrophin disruption and its correlation with the high mortality rate during acute infection. C57BL/6 mice were infected with T. cruzi and killed 14, 20 and 26 days post infection (dpi). The intensity of inflammation, cardiac expression of dystrophin, calpain-1, NF-κB, TNF-α, and sarcolemmal permeability were evaluated. Cultured neonatal murine cardiomyocytes were incubated with serum, collected at the peak of cytokine production and free of parasites, from T. cruzi-infected mice and dystrophin, calpain-1, and NF-κB expression analyzed. Dystrophin disruption occurs at the peak of mortality and inflammation and is associated with increased expression of calpain-1, TNF-α, NF-κB, and increased sarcolemmal permeability in the heart of T. cruzi-infected mice at 20 dpi confirmed by in vitro studies. The peak of mortality occurred only when significant loss of dystrophin in the hearts of infected animals occurred, highlighting the correlation between inflammation, dystrophin loss and mortality.

Cellular and molecular tissue response to triple antibiotic intracanal dressing.

INTRODUCTION: The aim of this study was to characterize the response of mouse subcutaneous tissue to triple antibiotic paste (TAP) using conventional light microscopy and real-time PCR (qRT-PCR). METHODS: Polyethylene tubes containing TAP or calcium hydroxide (CH) (ie, the control group) were implanted in mouse subcutaneous tissue. Animals that received empty tubes or no tubes were used as additional controls. After periods of 7, 21, and 63 days postimplantation, the specimens were removed and subjected to histologic processing. The number of inflammatory cells and vessels, vessel areas, vascular density, and relative percentage of collagen were evaluated. Gene expression of proinflammatory (interleukin-1 beta, tumor necrosis factor alpha, and interleukin 17) and anti-inflammatory (transforming growth factor beta) cytokines and angiogenic factors (vascular endothelial growth factor and hypoxia-inducible factor-1 alpha) was quantified by 7 and 21 days postimplantation. Results were analyzed using the Student t test, analysis of variance, and the Tukey test (α = 0.05). RESULTS: TAP induced an exuberant inflammatory and angiogenic response, with higher numbers of inflammatory cells, higher vascular area and density, and lower relative percentage of collagen compared with CH. In general, the expression of genes involved in inflammation and angiogenesis was higher in the TAP group compared with animals that received CH or empty tubes. CONCLUSIONS: The response of mouse subcutaneous tissue to TAP was characterized by exuberant and persistent inflammatory and angiogenic responses with no repair and high gene expression of biomarkers associated with inflammation and angiogenesis.

Haeme oxygenase activity protects the host against excessive cardiac inflammation during experimental Trypanosoma cruzi infection.

The infection with Trypanosoma cruzi induces a robust cardiac inflammation that plays a pathogenic role in the development of Chagas heart disease. In this study, we aimed at investigating the effects of Haem Oxygenase (HO) during experimental infection by T. cruzi in BALB/c and C57BL/6 mice. HO has recently emerged as a key factor modulating the immune response in diverse models of inflammatory diseases. In mice with two different genetic backgrounds, the pharmacologic inhibition of HO activity with zinc-protoporphyrin IX (ZnPPIX) induced enhanced myocarditis and reduced parasitaemia, which was accompanied by an amplified production of nitric oxide and increased influx of CD4(+), CD8(+) and IFN-γ(+) cells to the myocardium in comparison with the control group. Conversely, treatment with haemin (an activator of HO) lead to a decreased number of intracardiac CD4(+) (but not CD8(+)) cells compared to the control group. The mechanism involved in these observations is a modulation of the induction of regulatory T cells, because the stimulation or inhibition of HO was parallelled by an enhanced or reduced frequency of regulatory T cells, respectively. Hence, HO may be involved in the regulation of heart tissue inflammation and could be a potential target in conceiving future therapeutic approaches for Chagas disease.

Increase in parasympathetic tone by pyridostigmine prevents ventricular dysfunction during the onset of heart failure.

Heart failure (HF) is characterized by elevated sympathetic activity and reduced parasympathetic control of the heart. Experimental evidence suggests that the increase in parasympathetic function can be a therapeutic alternative to slow HF evolution. The parasympathetic neurotransmission can be improved by acetylcholinesterase inhibition. We investigated the long-term (4 wk) effects of the acetylcholinesterase inhibitor pyridostigmine on sympathovagal balance, cardiac remodeling, and cardiac function in the onset of HF following myocardial infarction. Myocardial infarction was elicited in adult male Wistar rats. After 4 wk of pyridostigmine administration, per os, methylatropine and propranolol were used to evaluate the cardiac sympathovagal balance. The tachycardic response caused by methylatropine was considered to be the vagal tone, whereas the bradycardic response caused by propranolol was considered to be the sympathetic tone. In conscious HF rats, pyridostigmine reduced the basal heart rate, increased vagal, and reduced sympathetic control of heart rate. Pyridostigmine reduced the myocyte diameter and collagen density of the surviving left ventricle. Pyridostigmine also increased vascular endothelial growth factor protein in the left ventricle, suggesting myocardial angiogenesis. Cardiac function was assessed by means of the pressure-volume conductance catheter system. HF rats treated with pyridostigmine exhibited a higher stroke volume, ejection fraction, cardiac output, and contractility of the left ventricle. It was demonstrated that the long-term administration of pyridostigmine started right after coronary artery ligation augmented cardiac vagal and reduced sympathetic tone, attenuating cardiac remodeling and left ventricular dysfunction during the progression of HF in rats.

Disruption of calcium homeostasis in cardiomyocytes underlies cardiac structural and functional changes in severe sepsis.

Sepsis, a major cause of morbidity/mortality in intensive care units worldwide, is commonly associated with cardiac dysfunction, which worsens the prognosis dramatically for patients. Although in recent years the concept of septic cardiomyopathy has evolved, the importance of myocardial structural alterations in sepsis has not been fully explored. This study offers novel and mechanistic data to clarify subcellular events that occur in the pathogenesis of septic cardiomyopathy and myocardial dysfunction in severe sepsis. Cultured neonatal mice cardiomyocytes subjected to serum obtained from mice with severe sepsis presented striking increment of [Ca(2+)]i and calpain-1 levels associated with decreased expression of dystrophin and disruption and derangement of F-actin filaments and cytoplasmic bleb formation. Severe sepsis induced in mice led to an increased expression of calpain-1 in cardiomyocytes. Moreover, decreased myocardial amounts of dystrophin, sarcomeric actin, and myosin heavy chain were observed in septic hearts associated with depressed cardiac contractile dysfunction and a very low survival rate. Actin and myosin from the sarcomere are first disassembled by calpain and then ubiquitinated and degraded by proteasome or sequestered inside specialized vacuoles called autophagosomes, delivered to the lysosome for degradation forming autophagolysosomes. Verapamil and dantrolene prevented the increase of calpain-1 levels and preserved dystrophin, actin, and myosin loss/reduction as well cardiac contractile dysfunction associated with strikingly improved survival rate. These abnormal parameters emerge as therapeutic targets, which modulation may provide beneficial effects on future vascular outcomes and mortality in sepsis. Further studies are needed to shed light on this mechanism, mainly regarding specific calpain inhibitors.

Doxycycline prevents acute pulmonary embolism-induced mortality and right ventricular deformation in rats.

PURPOSE: Acute pulmonary embolism (APE) is a critical cardiopulmonary condition associated with right ventricular (RV) failure and death. While pharmacological inhibition of matrix metalloproteinases (MMPs) attenuated APE-induced hemodynamic alterations, no previous study has evaluated whether this approach decreases APE-induced mortality and RV deformation. We tested this hypothesis in rats. METHODS: Wistar rats received an intraperitoneal injection of 30 mg/kg doxycycline (or saline) and after 30 min a sterile suspension of 300 µm microsphere (21 mg/kg or saline) was injected into the tail vein. After 24 h, surviving animals were killed and the RVs were collected and used for histological and morphometric analyses. RV samples were also homogenized and assayed by SDS-polyacrilamide gel electrophoresis gelatin zymography to evaluate MMP-2 and MMP-9 activity. In situ zymography was carried out in RV to assess MMP activity and neutrophil accumulation in myocardial tissue was determined by myeloperoxidase activity measurement. Dihydroethidium was used to assess RV reactive oxygen species concentrations. RESULTS: APE caused 72.5% mortality during the first hour of follow up. Pretreatment with doxycycline was associated with significant decrease in APE-induced mortality rate to 50% (P<0.05). Embolized animals showed significant RV dilation, and pretreatment with doxycycline blunted this alteration (P<0.05). APE increased the number of RV neutrophils and MMP-9 levels (P<0.05). Pretreatment with doxycycline blunted APE-induced increases in RV myocardial ROS concentrations and MMP gelatinolytic activity (both P<0.05). CONCLUSIONS: These findings show that MMP inhibition with doxycycline protects against APE-induced mortality and RV enlargement. These beneficial effects are probably due to attenuation of APE-induced oxidative stress and increases in ventricular proteolytic activity and suggest that doxycycline may have promising protective effects in patients with APE.

Sepsis: going to the heart of the matter.

Although myocardial depression is the predominant cause of death in severe sepsis/septic shock, it remains disputed whether the functional changes are a consequence of structural alterations. If we look at myocardial dysfunction from the perspective of a critically ill patient, there are a few questions to be asked: What causes myocardial dysfunction? What is the pathophysiology of cardiac dysfunction and death? Is there something that could be done to prevent the outcome? Each of these questions is interrelated and the answers will be more easily addressed if we continue to understand the basic mechanisms that are implicated. The principal mechanisms proposed for the pathogenesis of myocardial dysfunction support a prominent role for functional rather than anatomical abnormalities. However, attempts to reduce the high mortality in septic patients by manipulating the functional alterations have provided limited success. In recent years, the concept of septic cardiomyopathy has evolved, which implies alterations in the myocardial phenotype. This review includes an overview on the activation of the immune system and therapeutic approaches in sepsis, myocardial structural changes in the human septic heart, experimental models of sepsis, and cellular, molecular and functional myocardial changes seen in a variety of experimental sepsis models. The abnormal parameters discussed may emerge as therapeutic targets, for which modulation might provide beneficial effects on cardiovascular outcome and mortality in sepsis in the future.

Expression profile of peripheral tissue antigen genes in medullary thymic epithelial cells (mTECs) is dependent on mRNA levels of autoimmune regulator (Aire).

In the thymus of non-obese diabetic (NOD) mice, the expression of the autoimmune regulator (Aire) gene varies with age, and its down-regulation in young mice precedes the later emergence of type 1 diabetes mellitus (T1D). In addition, the insulin (Ins2) peripheral tissue antigen (PTA) gene, which is Aire-dependent, is also deregulated in these mice. Based in these findings, we hypothesized that the imbalance in PTA gene expression in the thymus can be associated with slight variations in Aire transcript levels. To test this, we used siRNA to knockdown Aire by in vivo electro-transfection of the thymus of BALB/c mice. The efficiency of the electro-transfection was monitored by assessing the presence of irrelevant Cy3-labeled siRNA in the thymic stroma. Importantly, Aire-siRNA reached medullary thymic epithelial cells (mTECs) down-regulating Aire. As expected, the in vivo Aire knockdown was partial and transient; the maximum 59% inhibition occurred in 48 h. The Aire knockdown was sufficient to down-regulate PTA genes; however, surprisingly, several others, including Ins2, were up-regulated. The modulation of these genes after in vivo Aire knockdown was comparable to that observed in NOD mice before the emergence of T1D. The in vitro transfections of 3.10 mTEC cells with Aire siRNA resulted in samples featuring partial (69%) and complete (100%) Aire knockdown. In these Aire siRNA-transfected 3.10 mTECs, the expression of PTA genes, including Ins2, was down-regulated. This suggests that the expression profile of PTA genes in mTECs is affected by fine changes in the transcription level of Aire.

Temporal changes in cardiac matrix metalloproteinase activity, oxidative stress, and TGF-ß in renovascular hypertension-induced cardiac hypertrophy.

Cardiovascular remodeling found in later phases of two-kidney, one-clip (2K1C) hypertension may involve key mechanisms particularly including MMP-2, oxidative stress, transforming growth factor-ß (TGF-ß), and inactivation of the endogenous MMP inhibitor, the tissue inhibitor of MMP (TIMP)-4. We examined whether temporal cardiac remodeling resulting from 2K1C hypertension occurs concomitantly with alterations in cardiac collagen, MMP activity, MMP-2, TIMP-4, TGF-ß, and reactive oxygen species (ROS) levels during the development of 2K1C hypertension. Sham-operated and 2K1C hypertensive rats were studied after 15, 30, and 75 days of hypertension. Systolic blood pressure was monitored weekly. Left ventricle (LV) morphometry and fibrosis were evaluated in hematoxylin/eosin and picrosirius red-stained sections, respectively. Cardiac MMP-2 levels/activity was determined by gelatin zymography, immunofluorescence, and in situ zymography. TIMP-4 levels were determined by western blotting. Cardiac TGF-ß levels were evaluated by immunofluorescence and ROS levels were evaluated with a dihydroethidium probe. 2K1C hypertension induced LV hypertrophy associated with augmented gelatinolytic activity at an early phase of hypertension and further increased after 75 days of hypertension. These alterations were associated with increased cardiac MMP-2, TGF-ß, and ROS in hypertensive rats. Higher TIMP-4 levels were found in hypertensive rats only after 75 days after surgery. Our findings show that increased MMP-2 activity is associated with concomitant development of LV hypertrophy and increased TGF-ß and ROS levels.

Tempol inhibits TGF-ß and MMPs upregulation and prevents cardiac hypertensive changes.

BACKGROUND: Increased oxidative stress upregulates matrix metalloproteinases (MMPs) and transforming grow factor (TGF-ß), which are involved in hypertensive cardiac remodeling. We tested the hypothesis that tempol (an antioxidant) could prevent these alterations in two-kidney, one-clip (2K1C) hypertension. METHODS: Sham-operated or hypertensive rats were treated with tempol (18 mg.kg(-1)day(-1) or vehicle) for 8 weeks. Systolic blood pressure was monitored weekly. At the end of the treatment, a catheter was inserted into the left carotid artery and into the left ventricle (LV) to assess arterial blood pressure and contractile function. Morphometry of the LV was carried out in hematoxylin/eosin sections and fibrosis was assessed in picrosirius red-stained sections. Cardiac TGF-ß level was evaluated by immunofluorescence. Cardiac MMP-2 levels and activity were determined by gelatin zymography, in situ zymography, and immunofluorescence. Cardiac superoxide production was evaluated by dihydroethidium probe. RESULTS: Tempol treatment attenuated 2K1C-induced hypertension and reversed the contractile dysfunction in 2K1C rats. Cardiac hypertrophy was ameliorated by antioxidant treatment. Hypertensive rats showed increased cardiac MMP-2 levels, however tempol did not decrease MMP-2 levels. Increased TGF-ß level, total gelatinolytic activity and oxidative stress were found in untreated 2K1C rats. Tempol treatment decreased oxidative stress, TGF-ß levels, and gelatinolytic activity in 2K1C rats to control levels. CONCLUSIONS: Tempol blunted the increases in TGF-ß, the proteolytic imbalance, and the morphological and functional alterations found in 2K1C-induced cardiac hypertrophy. These findings are consistent with the idea that antioxidants may help to prevent hypertension-induced cardiac hypertrophy.

Response of mice connective tissue to intracanal dressings containing chlorhexidine.

Substances containing chlorhexidine (CHX) have been studied as intracanal medicaments. The aim of the present study was to characterize the response of mouse subcutaneous connective tissue to CHX-containing medications by conventional optical microscopy. The tissue response was evaluated by implanting polyethylene tubes containing one of the substances evaluated: Calen paste + 0.5% CHX, Calen + 2% CHX, 2% CHX gel, and Calen paste (control). After experimental periods of 7, 21, and 63 days, the implants (n = 10) were removed along with the subcutaneous connective tissue. Tissue samples were subjected to histological processing, and sections were stained with hematoxylin and eosin. Qualitative and quantitative analyses of the number of inflammatory cells, blood vessels, and vascularized areas were performed. Results were analyzed by ANOVA and Tukey tests with the significance level set at 5%. We concluded that Calen + 0.5% CHX led to reparative tissue response in contrast with Calen + 2% CHX and 2% CHX gel, which induced persistent inflammatory response, pointing to the aggressive nature of this mixture. When Calen + 2% CHX and 2% CHX gel were compared, the latter induced more intense inflammatory response.

Early dystrophin disruption in the pathogenesis of experimental chronic Chagas cardiomyopathy.

Chronic Chagas cardiomyopathy evolves over a long period of time after initial infection by Trypanosoma cruzi. Similarly, a cardiomyopathy appears later in life in muscular dystrophies. This study tested the hypothesis that dystrophin levels are decreased in the early stage of T. cruzi-infected mice that precedes the later development of a cardiomyopathy. CD1 mice were infected with T. cruzi (Brazil strain), killed at 30 and 100 days post infection (dpi), and the intensity of inflammation, percentage of interstitial fibrosis, and dystrophin levels evaluated. Echocardiography and magnetic resonance imaging data were evaluated from 15 to 100 dpi. At 30 dpi an intense acute myocarditis with ruptured or intact intracellular parasite nests was observed. At 100 dpi a mild chronic fibrosing myocarditis was detected without parasites in the myocardium. Dystrophin was focally reduced or completely lost in cardiomyocytes at 30 dpi, with the reduction maintained up to 100 dpi. Concurrently, ejection fraction was reduced and the right ventricle was dilated. These findings support the hypothesis that the initial parasitic infection-induced myocardial dystrophin reduction/loss, maintained over time, might be essential to the late development of a cardiomyopathy in mice.

The vasculature in chagas disease.

The cardiovascular manifestations of Chagas disease are well known. However, the contribution of the vasculature and specifically the microvasculature has received little attention. This chapter reviews the evidence supporting the notion that alterations in the microvasculature especially in the heart contribute to the pathogenesis of chagasic cardiomyopathy. These data may also be important in understanding the contributions of the microvasculature in the aetiologies of other cardiomyopathies. The role of endothelin-1 and of thromboxane A(2) vascular spasm and platelet aggregation is also discussed. Further, these observations may provide target(s) for intervention.

Calpain-mediated dystrophin disruption may be a potential structural culprit behind chronic doxorubicin-induced cardiomyopathy.

The critical importance of dystrophin to cardiomyocyte contraction and sarcolemmal and myofibers integrity, led us to test the hypothesis that dystrophin reduction/loss could be involved in the pathogenesis of doxorubicin-induced cardiomyopathy, in order to determine a possible specific structural culprit behind heart failure. Rats received total cumulative doses of doxorubicin during 2 weeks: 3.75, 7.5, and 15 mg/kg. Controls rats received saline. Fourteen days after the last injection, hearts were collected for light and electron microscopy, immunofluorescence and western blot. The cardiac function was evaluated 7 and 14 days after drug or saline. Additionally, dantrolene (5 mg/kg), a calcium-blocking agent that binds to cardiac ryanodine receptors, was administered to controls and doxorubicin-treated rats (15 mg/kg). This study offers novel and mechanistic data to clarify molecular events that occur in the myocardium in doxorubicin-induced chronic cardiomyopathy. Doxorubicin led to a marked reduction/loss in dystrophin membrane localization in cardiomyocytes and left ventricular dysfunction, which might constitute, in association with sarcomeric actin/myosin proteins disruption, the structural basis of doxorubicin-induced cardiac depression. Moreover, increased sarcolemmal permeability suggests functional impairment of the dystrophin-glycoprotein complex in cardiac myofibers and/or oxidative damage. Increased expression of calpain, a calcium-dependent protease, was markedly increased in cardiomyocytes of doxorubicin-treated rats. Dantrolene improved survival rate and preserved myocardial dystrophin, calpain levels and cardiac function, which supports the opinion that calpain mediates dystrophin loss and myofibrils degradation in doxorubicin-treated rats. Studies are needed to further elucidate this mechanism, mainly regarding specific calpain inhibitors, which may provide new interventional pathways to prevent doxorubicin-induced cardiomyopathy.

Cell-free antigens from Paracoccidioides brasiliensis drive IL-4 production and increase the severity of paracoccidioidomycosis.

The thermally dimorphic fungus Paracoccidioides brasiliensis (Pb) is the causative agent of paracoccidioidomycosis (PCM), one of the most frequent systemic mycosis that affects the rural population in Latin America. PCM is characterized by a chronic inflammatory granulomatous reaction, which is consequence of a Th1-mediated adaptive immune response. In the present study we investigated the mechanisms involved in the immunoregulation triggered after a prior contact with cell-free antigens (CFA) during a murine model of PCM. The results showed that the inoculation of CFA prior to the infection resulted in disorganized granulomatous lesions and increased fungal replication in the lungs, liver and spleen, that paralleled with the higher levels of IL-4 when compared with the control group. The role of IL-4 in facilitating the fungal growth was demonstrated in IL-4-deficient- and neutralizing anti-IL-4 mAb-treated mice. The injection of CFA did not affect the fungal growth in these mice, which, in fact, exhibited a significant diminished amount of fungus in the tissues and smaller granulomas. Considering that in vivo anti-IL-4-application started one week after the CFA-inoculum, it implicates that IL-4-CFA-induced is responsible by the mediation of the observed unresponsiveness. Further, the characterization of CFA indicated that a proteic fraction is required for triggering the immunosuppressive mechanisms, while glycosylation or glycosphingolipids moieties are not. Taken together, our data suggest that the prior contact with soluble Pb antigens leads to severe PCM in an IL-4 dependent manner.