Toll-like receptor-2 and interleukin-6 mediate cardiomyocyte protection from apoptosis during Trypanosoma cruzi murine infection

Trypanosoma cruzi Dysregulates piRNAs Computationally Predicted to Target IL-6 Signaling Molecules During Early Infection of Primary Human Cardiac Fibroblasts

Trypanosoma cruzi, the etiological agent of Chagas disease, is an intracellular protozoan parasite, which is now present in most industrialized countries. About 40% of T. cruzi infected individuals will develop severe, incurable cardiovascular, gastrointestinal, or neurological disorders. The molecular mechanisms by which T. cruzi induces cardiopathogenesis remain to be determined. Previous studies showed that increased IL-6 expression in T. cruzi patients was associated with disease severity. IL-6 signaling was suggested to induce pro-inflammatory and pro-fibrotic responses, however, the role of this pathway during early infection remains to be elucidated. We reported that T. cruzi can dysregulate the expression of host PIWI-interacting RNAs (piRNAs) during early infection. Here, we aim to evaluate the dysregulation of IL-6 signaling and the piRNAs computationally predicted to target IL-6 molecules during early T. cruzi infection of primary human cardiac fibroblasts (PHCF). Using in silico analysis, we predict that piR_004506, piR_001356, and piR_017716 target IL6 and SOCS3 genes, respectively. We validated the piRNAs and target gene expression in T. cruzi challenged PHCF. Secreted IL-6, soluble gp-130, and sIL-6R in condition media were measured using a cytokine array and western blot analysis was used to measure pathway activation. We created a network of piRNAs, target genes, and genes within one degree of biological interaction. Our analysis revealed an inverse relationship between piRNA expression and the target transcripts during early infection, denoting the IL-6 pathway targeting piRNAs can be developed as potential therapeutics to mitigate T. cruzi cardiomyopathies.

The expression of TLR2 and TLR4 in the kidneys and heart of mice infected with Acanthamoeba spp

Background

Acanthamoeba spp. are cosmopolitan protozoans that cause infections in the brain, as well as extracerebral infections in the cornea, lungs and skin. Little is known about the mechanisms of the immunological response to these parasites in organs which are not their main biotope. Therefore, the purpose of this study was to determine the expression of TLR2 and TLR4 in the kidneys and heart of Acanthamoeba spp.-infected mice, with respect to the host’s immunological status.

Methods

The mice were grouped into four groups: immunocompetent control mice; immunosuppressed control mice; immunocompetent Acanthamoeba spp.-infected mice; and immunosuppressed Acanthamoeba spp. infected mice. In the study, we used the amoebae T16 genotype which was isolated from a patient. The TLRs expressions in the kidneys and heart of mice were assessed by quantitative real-time polymerase chain reaction. Moreover, we visualized TLR2 and TLR4 proteins in the organs by immunohistochemical staining.

Results

In the kidneys, we observed a higher TLR2 expression in immunosuppressed mice at 24 days post-Acanthamoeba spp. infection (dpi) compared to the uninfected mice. There were no statistically significant differences in TLR4 expression in the kidneys between the immunocompetent and immunosuppressed mice, both of infected and uninfected mice. In the heart, we observed a difference in TLR2 expression in immunocompetent mice at 24 dpi compared to immunocompetent mice at 8 dpi. The immunocompetent Acanthamoeba spp.-infected mice had higher TLR4 expression at 8 dpi compared to the immunocompetent uninfected mice.

Conclusions

Our results indicate that TLR2 is involved in response to Acanthamoeba spp. infection in the kidneys, whereas in the heart, both studied TLRs are involved.

Trypanosoma cruzi Promotes Transcriptomic Remodeling of the JAK/STAT Signaling and Cell Cycle Pathways in Myoblasts

Chagas disease is responsible for more than 10,000 deaths per year and about 6 to 7 million infected people worldwide. In its chronic stage, patients can develop mega-colon, mega-esophagus, and cardiomyopathy. Differences in clinical outcomes may be determined, in part, by the genetic background of the parasite that causes Chagas disease. Trypanosoma cruzi has a high genetic diversity, and each group of strains may elicit specific pathological responses in the host. Conflicting results have been reported in studies using various combinations of mammalian host-T. cruzi strains. We previously profiled the transcriptomic signatures resulting from infection of L6E9 rat myoblasts with four reference strains of T. cruzi (Brazil, CL, Y, and Tulahuen). The four strains induced similar overall gene expression alterations in the myoblasts, although only 21 genes were equally affected by all strains. Cardiotrophin-like cytokine factor 1 (Clcf1) was one of the genes found to be consistently upregulated by the infection with all four strains of T. cruzi. This cytokine is a member of the interleukin-6 family that binds to glycoprotein 130 receptor and activates the JAK/STAT signaling pathway, which may lead to muscle cell hypertrophy. Another commonly upregulated gene was tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein theta (Ywhaq, 14-3-3 protein Θ), present in the Cell Cycle Pathway. In the present work, we reanalyzed our previous microarray dataset, aiming at understanding in more details the transcriptomic impact that each strain has on JAK/STAT signaling and Cell Cycle pathways. Using Pearson correlation analysis between the expression levels of gene pairs in biological replicas from each pathway, we determined the coordination between such pairs in each experimental condition and the predicted protein interactions between the significantly altered genes by each strain. We found that although these highlighted genes were similarly affected by all four strains, the downstream genes or their interaction partners were not necessarily equally affected, thus reinforcing the idea of the role of parasite background on host cell transcriptome. These new analyses provide further evidence to the mechanistic understanding of how distinct T. cruzi strains lead to diverse remodeling of host cell transcriptome.

Identification of Candidate Signature Genes and Key Regulators Associated With Trypanotolerance in the Sheko Breed

African animal trypanosomiasis (AAT) is caused by a protozoan parasite that affects the health of livestock. Livestock production in Ethiopia is severely hampered by AAT and various controlling measures were not successful to eradicate the disease. AAT affects the indigenous breeds in varying degrees. However, the Sheko breed shows better trypanotolerance than other breeds. The tolerance attributes of Sheko are believed to be associated with its taurine genetic background but the genetic controls of these tolerance attributes of Sheko are not well understood. In order to investigate the level of taurine background in the genome, we compare the genome of Sheko with that of 11 other African breeds. We find that Sheko has an admixed genome composed of taurine and indicine ancestries. We apply three methods: (i) The integrated haplotype score (iHS), (ii) the standardized log ratio of integrated site specific extended haplotype homozygosity between populations (Rsb), and (iii) the composite likelihood ratio (CLR) method to discover selective sweeps in the Sheko genome. We identify 99 genomic regions harboring 364 signature genes in Sheko. Out of the signature genes, 15 genes are selected based on their biological importance described in the literature. We also identify 13 overrepresented pathways and 10 master regulators in Sheko using the TRANSPATH database in the geneXplain platform. Most of the pathways are related with oxidative stress responses indicating a possible selection response against the induction of oxidative stress following trypanosomiasis infection in Sheko. Furthermore, we present for the first time the importance of master regulators involved in trypanotolerance not only for the Sheko breed but also in the context of cattle genomics. Our finding shows that the master regulator Caspase is a key protease which plays a major role for the emergence of adaptive immunity in harmony with the other master regulators. These results suggest that designing and implementing genetic intervention strategies is necessary to improve the performance of susceptible animals. Moreover, the master regulatory analysis suggests potential candidate therapeutic targets for the development of new drugs for trypanosomiasis treatment.

Deficiency of CD73 activity promotes protective cardiac immunity against Trypanosoma cruzi infection but permissive environment in visceral adipose tissue

Damaged cells release the pro-inflammatory signal ATP, which is degraded by the ectonucleotidases CD39 and CD73 to the anti-inflammatory mediator adenosine (ADO). The balance between ATP/ADO is known to determine the outcome of inflammation/infection. However, modulation of the local immune response in different tissues due to changes in the balance of purinergic metabolites has yet to be investigated. Here, we explored the contribution of CD73-derived ADO on the acute immune response against Trypanosoma cruzi parasite, which invades and proliferates within different target tissues. Deficiency of CD73 activity led to an enhanced cardiac microbicidal immune response with an augmented frequency of macrophages with inflammatory phenotype and increased CD8+ T cell effector functions. The increment of local inducible nitric oxide (NO) synthase (iNOS)⁺ macrophages and the consequent rise of myocardial NO production in association with reduced ADO levels induced protection against T. cruzi infection as observed by the diminished cardiac parasite burden compared to their wild-type (WT) counterpart. Unexpectedly, parasitemia was substantially raised in CD73KO mice in comparison with WT mice, suggesting the existence of tissue reservoir/s outside myocardium. Indeed, CD73KO liver and visceral adipose tissue (VAT) showed increased parasite burden associated with a reduced ATP/ADO ratio and the lack of substantial microbicidal immune response. These data reveal that the purinergic system has a tissue-dependent impact on the host immune response against T. cruzi infection.

MyD88 activation in cardiomyocytes contributes to the heart immune response to acute Trypanosoma cruzi infection with no effect on local parasite control

Cardiomyopathy is the most serious consequence of Chagas disease, a neglected human disorder caused by Trypanosoma cruzi infection. Because T. cruzi parasites invade cardiomyocytes, we sought to investigate whether these cells recognize the parasite in vivo by receptors signaling through the MyD88 adaptor, which mediates the activation pathway of most Toll-like receptors (TLRs) and IL-1/IL-18 receptors, and influence the development of acute cardiac pathology. First, we showed that HL-1 cardiac muscle cell line expresses MyD88 gene and protein at resting state and after T. cruzi infection. To evaluate the role in vivo of MyD88 expression in cardiomyocytes, we generated Mer+MyD88flox+/+ mice in which tamoxifen treatment is expected to eliminate the MyD88 gene exclusively in cardiomyocytes. This Cre-loxP model was validated by both PCR and western blot analysis; tamoxifen treatment of Mer+MyD88flox+/+ mice resulted in decreased MyD88 gene and protein expression in the heart, but not in the spleen, while had no effect on littermates. The elimination of MyD88 in cardiomyocytes determined a lower increase in CCL5, IFNγ and TNFα gene transcription during acute infection by T. cruzi parasites of the Y strain, but it did not significantly modify heart leukocyte infiltration and parasitism. Together, our results show that cardiomyocytes can sense T. cruzi infection through MyD88-mediated molecular pathways and contribute to the local immune response to the parasite. The strong pro-inflammatory response of heart-recruited leukocytes may overshadow the effects of MyD88 deficiency in cardiomyocytes on the local leukocyte recruitment and T. cruzi control during acute infection.

Interleukin-6 signalling mediates Galectin-8 co-stimulatory activity of antigen-specific CD4 T-cell response

Galectin-8 (Gal-8) is a mammalian lectin endowed with the ability to co-stimulate antigen-specific immune responses. We have previously demonstrated that bone-marrow-derived dendritic cells produce high levels of interleukin-6 (IL-6) in response to Gal-8 stimulation. As IL-6 is a pleiotropic cytokine that has a broad effect on cells of the immune system, we aimed to elucidate whether IL-6 was involved in Gal-8-dependent co-stimulatory signals during antigen recognition by specific CD4 T cells. With this aim, splenocytes from DO11.10 mice were incubated with a low dose of the cognate ovalbumin peptide in combination with Gal-8. Interleukin-6 was found significantly increased in cultures stimulated with Gal-8 alone or Gal-8 plus cognate peptide. Moreover, IL-6 signalling was triggered during Gal-8-induced co-stimulation, as determined by phosphorylation of signal transducer and activator of transcription 3. Interleukin-6 blockade by neutralizing monoclonal antibody precluded Gal-8 co-stimulatory activity but did not affect the antigen-specific T-cell receptor activation. Different subsets of dendritic cells, as well as macrophages and B cells, were identified as the cellular source of IL-6 during Gal-8-induced co-stimulation. To confirm that IL-6 mediated the Gal-8 co-stimulatory effect, antigen-presenting cells from IL-6-deficient or wild-type mice were co-cultured with purified CD4 T cells from OTII mice in the presence of cognate peptide and Gal-8. Notably, Gal-8-induced co-stimulation, but not the antigen-specific response, was significantly impaired in the presence of IL-6-deficient antigen-presenting cells. In addition, exogenous IL-6 fully restored Gal-8-induced co-stimulation. Taken together, our results demonstrate that IL-6 signalling mediates the Gal-8 immune-stimulatory effect.

New Insights into the Immunobiology of Mononuclear Phagocytic Cells and Their Relevance to the Pathogenesis of Cardiovascular Diseases

Macrophages are the primary immune cells that reside within the myocardium, suggesting that these mononuclear phagocytes are essential in the orchestration of cardiac immunity and homeostasis. Independent of the nature of the injury, the heart triggers leukocyte activation and recruitment. However, inflammation is harmful to this vital terminally differentiated organ with extremely poor regenerative capacity. As such, cardiac tissue has evolved particular strategies to increase the stress tolerance and minimize the impact of inflammation. In this sense, growing evidences show that mononuclear phagocytic cells are particularly dynamic during cardiac inflammation or infection and would actively participate in tissue repair and functional recovery. They respond to soluble mediators such as metabolites or cytokines, which play central roles in the timing of the intrinsic cardiac stress response. During myocardial infarction two distinct phases of monocyte influx have been identified. Upon infarction, the heart modulates its chemokine expression profile that sequentially and actively recruits inflammatory monocytes, first, and healing monocytes, later. In the same way, a sudden switch from inflammatory macrophages (with microbicidal effectors) toward anti-inflammatory macrophages occurs within the myocardium very shortly after infection with Trypanosoma cruzi, the causal agent of Chagas cardiomyopathy. While in sterile injury, healing response is necessary to stop tissue damage; during an intracellular infection, the anti-inflammatory milieu in infected hearts would promote microbial persistence. The balance of mononuclear phagocytic cells seems to be also dynamic in atherosclerosis influencing plaque initiation and fate. This review summarizes the participation of mononuclear phagocyte system in cardiovascular diseases, keeping in mind that the immune system evolved to promote the reestablishment of tissue homeostasis following infection/injury, and that the effects of different mediators could modulate the magnitude and quality of the immune response. The knowledge of the effects triggered by diverse mediators would serve to identify new therapeutic targets in different cardiovascular pathologies.

Atrial Fibrillation Promotion in a Rat Model of Rheumatoid Arthritis

Background

The prevalence of atrial fibrillation (AF) is significantly higher in rheumatoid arthritis (RA) patients, but the underlying mechanisms remain poorly understood. The goal of this study was to assess the effects of RA on AF susceptibility and atrial arrhythmogenic remodeling in a rat model of RA.

Methods and Results

Collagen‐induced arthritis was induced in rats by immunization with type II collagen in Freund's incomplete adjuvant. Among the rats that developed arthritis, AF susceptibility and atrial remodeling were examined 8 weeks after the primary immunization. AF inducibility and duration were substantially increased in collagen‐induced arthritis rats, and AF duration was significantly and positively correlated with the serum IL‐6 and TNF‐α levels. Rats with collagen‐induced arthritis showed prolonged atrial conduction time with no changes in the atrial effective refractory period. Atrial conduction delay was accompanied by significantly increased atrial fibrosis. In addition, atrial structural and autonomic remodeling, including left atrial dilation, apoptosis and autophagy of atrial myocytes, and atrial heterogeneous sympathetic hyperinnervation, was observed. Interestingly, we found that collagen‐induced arthritis had no significant effects on connexins, Nav1.5, and the main ion channels' protein expressions in atria.

Conclusions

We demonstrated that RA increased AF susceptibility by inducing AF‐promoting atrial remodeling. This study may provide insights into mechanisms underlying RA‐induced AF and validate a model that is suitable for further mechanistic and therapeutic exploration.

Ex vivo infection of human placental chorionic villi explants with Trypanosoma cruzi and Toxoplasma gondii induces different Toll-like receptor expression and cytokine/chemokine profiles

PROBLEM

Trypanosoma cruzi and Toxoplasma gondii present, respectively, low and high congenital transmission rates. The placenta as an immune regulatory organ expresses TLRs, leading to the secretion of cytokines. Both parasites are recognized by TLR-2, TLR-4, and TLR-9. Here, we studied if the parasites induce differences in TLR protein expression, cytokine profiles, and whether receptor inhibition is related to parasite infection.

METHOD OF STUDY

Placental tissue explants were infected ex vivo with each parasite, TLRs protein expression, cytokine profile and parasite infection were determined by Western blotting, ELISA and qPCR.

RESULTS

Trypanosoma cruzi and Toxoplasma gondii infection is related to TLR-2 and TLR-4/TLR-9, respectively. Trypanosoma cruzi elicits an increase in TNF-α, IL-1β, IL-6, IL-8 and IL-10 cytokine secretion whereas T. gondii only increases the secretion of IL-8.

CONCLUSION

The susceptibility of the placenta to each parasite is mediated partially by the innate immune response.

IL-6 promotes M2 macrophage polarization by modulating purinergic signaling and regulates the lethal release of nitric oxide during Trypanosoma cruzi infection

The production of nitric oxide (NO) is a key defense mechanism against intracellular pathogens but it must be tightly controlled in order to avoid excessive detrimental oxidative stress. In this study we described a novel mechanism through which interleukin (IL)-6 mediates the regulation of NO release induced in response to Trypanosoma cruzi infection. Using a murine model of Chagas disease, we found that, in contrast to C57BL/6 wild type (WT) mice, IL-6-deficient (IL6KO) mice exhibited a dramatic increase in plasma NO levels concomitant with a significantly higher amount of circulating IL-1β and inflammatory monocytes. Studies on mouse macrophages and human monocytes, revealed that IL-6 decreased LPS-induced NO production but this effect was abrogated in the presence of anti-IL-1β and in macrophages deficient in the NLRP3 inflammasome. In accordance, while infected WT myocardium exhibited an early shift from microbicidal/M1 to anti-inflammatory/M2 macrophage phenotype, IL6KO cardiac tissue never displayed a dominant M2 macrophage profile that correlated with decreased expression of ATP metabolic machinery and a lower cardiac parasite burden. The deleterious effects of high NO production-induced oxidative stress were evidenced by enhanced cardiac malondialdehyde levels, myocardial cell death and mortality. The survival rate was improved by the treatment of IL-6-deficient mice with a NO production-specific inhibitor. Our data revealed that IL-6 regulates the excessive release of NO through IL-1β inhibition and determines the establishment of an M2 macrophage profile within infected heart tissue.

IL-6 Improves the Nitric Oxide-Induced Cytotoxic CD8+ T Cell Dysfunction in Human Chagas Disease

Reactive oxygen and nitrogen species are important microbicidal agents and are also involved in lymphocyte unresponsiveness during experimental infections. Many of the biological effects attributed to nitric oxide are mediated by peroxynitrites, which induce the nitration of immune cells, among others. Our group has demonstrated that nitric oxide is involved in the suppressive activity of myeloid-derived suppressor cells in Trypanosoma cruzi-infected mice, with a higher number of CD8+ T cells suffering surface-nitration compared to uninfected controls. Studying the functional and phenotypic features of peripheral CD8+ T cells from chagasic patients and human cells experimentally infected with T. cruzi, we found that different regulatory mechanisms impaired the effector functions of T cytotoxic population from seropositive patients. Peripheral leukocytes from chagasic patients showed increased nitric oxide production concomitant with increased tyrosine nitration of CD8+ T cells. Additionally, this cytotoxic population exhibited increased apoptotic rate, loss of the TCRζ-chain, and lower levels of CD107a, a marker of degranulation. Strikingly, IL-6 stimulation of in vitro-infected peripheral blood mononuclear cells obtained from healthy donors, blunted T. cruzi-induced nitration of CD3+CD8+ cells, and increased their survival. Furthermore, the treatment of these cultures with an IL-6 neutralizing antibody increased the percentage of T. cruzi-induced CD8+ T cell nitration and raised the release of nitric oxide. The results suggest that the under-responsiveness of cytotoxic T cell population observed in the setting of long-term constant activation of the immune system could be reverted by the pleiotropic actions of IL-6, since this cytokine improves its survival and effector functions.

CD73 Inhibition Shifts Cardiac Macrophage Polarization toward a Microbicidal Phenotype and Ameliorates the Outcome of Experimental Chagas Cardiomyopathy

Increasing evidence demonstrates that generation of extracellular adenosine from ATP, which is hydrolyzed by the CD39/CD73 enzyme pair, attenuates the inflammatory response and deactivates macrophage antimicrobial mechanisms. Although CD73 is emerging as a critical pathway and therapeutic target in cardiovascular disorders, the involvement of this ectonucleotidase during myocardial infection has not been explored. Using a murine model of infection with Trypanosoma cruzi, the causal agent of Chagas cardiomyopathy, we observed a sudden switch from the classical M1 macrophage (microbicidal) phenotype toward an alternative M2 (repairing/anti-inflammatory) phenotype that occurred within the myocardium very shortly after BALB/c mice infection. The observed shift in M1/M2 rate correlated with the cardiac cytokine milieu. Considering that parasite persistence within myocardium is a necessary and sufficient condition for the development of the chronic myocarditis, we hypothesized that CD73 activity may counteract cardiac macrophage microbicidal polarization, rendering the local immune response less effective. In fact, a transient treatment with a specific CD73 inhibitor (adenosine 5'-α,β-methylene-diphosphate) enhanced the microbicidal M1 subset predominance, diminished IL-4- and IL-10-producing CD4(+) T cells, promoted a proinflammatory cytokine milieu, and reduced parasite load within the myocardium during the acute phase. As a direct consequence of these events, there was a reduction in serum levels of creatine kinase muscle-brain isoenzyme, a myocardial-specific injury marker, and an improvement in the electrocardiographic characteristics during the chronic phase. Our results demonstrate that this purinergic system drives the myocardial immune response postinfection and harbors a promising potential as a therapeutic target.

Trypanosoma cruzi infection induces the expression of CD40 in murine cardiomyocytes favoring CD40 ligation-dependent production of cardiopathogenic IL-6

The inflammatory response in the myocardium is an important aspect of the pathogenesis of Chagas' heart disease raised by Trypanosoma cruzi. CD40, a transmembrane type I receptor belonging to the tumor necrosis factor receptor (TNFR) family, is expressed in a broad spectrum of cell types and is crucial in several inflammatory and autoimmune diseases. Activation of CD40 through ligation to CD40L (CD154) induces multiple effects, including the secretion of proinflammatory molecules. In the present study, we examined the ability of T. cruzi to trigger the expression of CD40 in cardiac myocytes in vitro and in a murine model of chagasic cardiomyopathy. Our results indicate, for the first time, that T. cruzi is able to induce the expression of CD40 in HL-1 murine cardiomyocytes. Moreover, ligation of CD40 receptor upregulated interleukin-6 (IL-6), associated with inflammation. Furthermore, the induction of this costimulatory molecule was demonstrated in vivo in myocardium of mice infected with T. cruzi. This suggests that CD40-bearing cardiac muscle cells could interact with CD40L-expressing lymphocytes infiltrating the heart, thus contributing to inflammatory injury in chagasic cardiomyopathy.

Reduced apoptosis after acute myocardial infarction by simvastatin

To observe the effect of simvastatin in patients with acute myocardial infarction in rabbits against myocardial apoptosis, and to explore its possible mechanism. Male New Zealand white rabbits were randomized into three groups, including the myocardial infarction group (12 rabbits), the simvastatin treatment group (15 rabbits), and the sham group (12 rabbits). In the simvastatin treatment and myocardial infarction groups, the rabbits received myocardial infarction surgeries. While in the sham group, loose knots were tied in the left anterior descending coronary artery branches. The simvastatin treatment group was given simvastatin by oral gavage 24 h after surgery. Parameters, which included left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left ventricular ejection fraction, and left ventricular mass index, were recorded in these three groups. Edge myocardial infarction and myocardial cell apoptosis were analyzed using TUNEL assay, and Bcl-2, Bax, and Caspase-3 protein levels were detected by Western blot. Acute myocardial infarction model was successfully established in rabbits by ligation of the left anterior descending coronary artery. Compared with the myocardial infarction group, left ventricular end-diastolic diameter (LVEDD) and left ventricular end systolic diameter (LVESD) were significantly reduced and left ventricular ejection fraction (LVEF) increased in the simvastatin treatment group. Compared with the sham group, LVEDD and LVESD were significantly increased and LVEF decreased in the simvastatin treatment group. All the differences were statistically significant (P < 0.05). Left ventricular mass index in the simvastatin treatment group was statistically lower than the myocardial infarction group. Compared with the sham group, left ventricular mass index in both the simvastatin treatment and myocardial infarction groups was significantly increased. The differences of the above comparisons were statistically significant (P < 0.05). Compared with the sham group, the apoptosis rate of the myocardial infarction group and the simvastatin treatment groups was significantly increased as shown by TUNEL assay, however, the apoptosis rate of the simvastatin treatment group was significantly lower than that of the myocardial infarction group. All the differences among above comparisons were statistically significant (P < 0.05). Bcl-2 levels significantly increased in the simvastatin treatment group compared with the myocardial infarction group, but Bcl-2 levels in both groups were significantly lower than the sham group. However, Bax protein levels showed inverse expression with Bcl-2. Meanwhile, Caspase-3 protein expression showed similar trend with Bcl-2. Simvastatin can improve cardiac function after myocardial infarction and reduce apoptosis of myocardial cells, possibly by decreasing Bax and Caspase-3 expression and increasing the expression level of Bcl-2.

Trypanosoma cruzi parasites fight for control of the JAK-STAT pathway by disarming their host

The zoonotic Chagas' disease is caused by infections with the hemoflagellate Trypanosoma cruzi (T. cruzi) which is endemic in Latin America. Despite recent advances in our understanding of the pathogenesis of the disease, the underlying molecular processes involved in host-parasite interactions are only poorly understood. In particular, the mechanisms for parasite persistence in host cells remain largely unknown. Cytokine-driven transcription factors from the family of STAT (signal transducer and activator of transcription) proteins appear to play a central role in the fight against T. cruzi infection. However, amastigotes proliferating in the cytoplasm of infected host cells develop effective strategies to circumvent the attack executed by STAT proteins. This review highlights the interactions between T. cruzi parasites and human host cells in terms of cytokine signaling and, in particular, discusses the impact of STATs on the balance between parasite invasion and clearance.

The innate immune response status correlates with a divergent clinical course in congenital Chagas disease of twins born in a non-endemic country

The innate immune response from diamniotic and dichorionic twin brothers congenitally infected with Trypanosoma. cruzi (strain DTU-V) who displayed different clinical symptomatology was studied. While Brother I manifested severe cardiac and digestive disorders, the Brother II showed slight splenomegaly. The secretion level of IL-1β, TNF-α, IL-12, IL-10, IFN-α and IL-6 cytokines produced after stimulation of peripheral blood cells with TLR-2, TLR-4 and TLR-9 ligands was determined pre- and post-benznidazole treatment. Cells from 10 uninfected infants born to mothers seropositive for Chagas disease were included as control. The obtained data show that the cells of Brother I secreted lower levels of the pro-inflammatory cytokines IL-1β and TNF-α (upon TLR-2 and TLR-4 stimulation) relative to those secreted by cells from Brother II and uninfected controls. The cells from Brother II secreted high levels of the IL-1β cytokine following TLR-2 stimulation relative to uninfected controls. The cells from both brothers secreted a higher level of IL-6, following TLR-4 stimulation, than that secreted by uninfected infant cells. After treatments, the cytokine secretion levels were similar in both children and comparable to those of uninfected donors. Treatment success in Brother I and treatment interruption in Brother II was detected by the use of serological biomarkers (KMP11, HSP70, PFR2, Tgp63) as well as follow-up done by PCR. Therefore, the Brother II required a second treatment. The data presented suggest that benznidazol treatment allows the innate immune system to reach a fully functional status similar to that of uninfected subjects.

Cellular and molecular mechanisms of cartilage damage and repair

Cartilage breakdown is the disabling outcome of rheumatic diseases, whether prevalently inflammatory such as rheumatoid arthritis or prevalently mechanical such as osteoarthritis (OA). Despite the differences between immune-mediated arthritides and OA, common mechanisms drive cartilage breakdown. Inflammation, chondrocyte phenotype and homeostatic mechanisms have recently been the focus of research and will be summarised in this review.

Innate immunity and cardiomyocytes in ischemic heart disease

Myocardial ischemia/reperfusion (I/R) is the most common cause of myocardial inflammation, which is primarily a manifestation of the innate immune responses. Innate immunity is activated when pattern recognition receptors (PRRs) respond to molecular patterns common to microbes and to danger signals expressed by injured or infected cells, so called pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). The expression of various PRRs in cardiomyocytes and the release of DAMPs from cardiomyocytes subjected to I/R injury, through active mechanisms as well as passive processes, enable cardiomyocytes to generate innate immune responses. Studies in isolated heart and cardiomyocytes have confirmed the inflammatory and functional effects of cardiac PRRs especially Toll-like receptors in response to I/R-derived DAMPs, such as heat shock proteins. This review addresses the active role of cardiomyocytes in mediating innate inflammatory responses to myocardial I/R. We propose that cardiomyocytes act as innate immune cells in myocardial I/R injury.