Bacterial DNA induces myocardial inflammation and reduces cardiomyocyte contractility: role of toll-like receptor 9

DNA sensors in metabolic and cardiovascular diseases: Molecular mechanisms and therapeutic prospects

DNA sensors generally initiate innate immune responses through the production of type I interferons. While extensively studied for host defense against invading pathogens, emerging evidence highlights the involvement of DNA sensors in metabolic and cardiovascular diseases. Elevated levels of modified, damaged, or ectopically localized self-DNA and non-self-DNA have been observed in patients and animal models with obesity, diabetes, fatty liver disease, and cardiovascular disease. The accumulation of cytosolic DNA aberrantly activates DNA signaling pathways, driving the pathological progression of these disorders. This review highlights the roles of specific DNA sensors, such as cyclic AMP-GMP synthase and stimulator of interferon genes (cGAS-STING), absent in melanoma 2 (AIM2), toll-like receptor 9 (TLR9), interferon gamma-inducible protein 16 (IFI16), DNA-dependent protein kinase (DNA-PK), and DEAD-box helicase 41 (DDX41) in various metabolic disorders. We explore how DNA signaling pathways in both immune and non-immune cells contribute to the development of these diseases. Furthermore, we discuss the intricate interplay between metabolic stress and immune responses, offering insights into potential therapeutic targets for managing metabolic and cardiovascular disorders. Understanding the mechanisms of DNA sensor signaling in these contexts provides a foundation for developing novel interventions aimed at mitigating the impact of these pervasive health issues.

Assessment of hemodynamic dysfunction in septic newborns by functional echocardiography: a systematic review

BACKGROUND

Neonatal sepsis remains a leading cause of mortality in neonatal units. Neonatologist-performed echocardiography (NPE) offers the potential for early detection of sepsis-associated cardiovascular dysfunction. This review examines available echocardiographic findings in septic neonates.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically reviewed prospective observational, cross-sectional, case control, and cohort studies on septic newborns with echocardiographic assessments from PubMed, Scopus and Embase. Quality assessment employed the Newcastle-Ottawa Scale, with results analyzed descriptively.

RESULTS

From an initial pool of 1663 papers, 12 studies met inclusion criteria after relevance screening and eliminating duplicates/excluded studies. The review encompassed 438 septic newborns and 232 controls. Septic neonates exhibited either increased risk of pulmonary hypertension or left ventricular diastolic dysfunction, and a warm shock physiology characterized by higher cardiac outputs.

DISCUSSION

The included studies exhibited heterogeneity in sepsis definitions, sepsis severity scores, echocardiographic evaluations, and demographic data of newborns. Limited sample sizes compromised analytical interpretability. Nonetheless, this work establishes a foundation for future high-quality echocardiographic studies.

CONCLUSION

Our review confirms that septic neonates show significant hemodynamic changes that can be identified using NPE. These findings underscore the need for wider NPE use to tailor hemodynamics-based strategies within this population.

IMPACT

1. Our study emphasizes the value of neonatologist-performed echocardiography (NPE) as a feasible tool for identifying significant hemodynamic changes in septic neonates. 2. Our study underscores the importance of standardized echocardiographic protocols and frequent monitoring of cardiac function in septic neonates. 3. The impact of the study lies in its potential to increase researchers' awareness for the need for more high-quality echocardiographic data in future studies. By promoting wider use of NPE, neonatologists can more accurately assess the hemodynamic status of septic newborns and tailor treatment approaches, potentially improving patient outcomes.

Effects of aging and lifelong aerobic exercise on expression of innate immune components in skeletal muscle of women

This study examined the effects of aging and lifelong aerobic exercise on innate immune system components in the skeletal muscle of healthy women in the basal state and after an unaccustomed resistance exercise (RE) challenge. We also made exploratory between-sex comparisons with our previous report on men. Three groups of women were studied: young exercisers (YE, n = 10, 25 ± 1 yr, V̇o2max: 44 ± 2 mL/kg/min), lifelong aerobic exercisers with a 48 ± 2 yr training history (LLE, n = 7, 72 ± 2 yr, V̇o2max: 26 ± 2 mL/kg/min), and old healthy nonexercisers (OH, n = 10, 75 ± 1 yr, V̇o2max: 18 ± 1 mL/kg/min). Ten Toll-like receptors (TLRs)1-10, TLR adaptors (Myd88, TRIF), and NF-κB pathway components (IκBα, IKKβ) were assessed at the mRNA level in vastus lateralis biopsies before and 4 h after RE [3×10 repetitions, 70% 1-repetition maximum (1RM)]. Basal TLR1-10 expression was minimally influenced by age or LLE in women (TLR9 only; OH > YE, +43%, P < 0.05; OH > LLE, +30%, P < 0.10) and was on average 24% higher in women versus men. Similarly, basal adaptor expression was not influenced (P > 0.05) by age or LLE in women but was on average 26% higher (myeloid differentiation primary response 88, Myd88) and 23% lower [Toll interleukin (IL)-1 receptor-containing adaptor-inducing interferon-γ, TRIF] in women versus men. RE-induced changes in women, independent of the group, in TLR3, TLR4, TLR6 (∼2.1-fold, P < 0.05), Myd88 (∼1.2-fold, P < 0.10), and IκBα (∼0.3-fold, P < 0.05). Although there were some similar RE responses in men (TLR4: 2.1-fold, Myd88: 1.2-fold, IκBα: 0.4-fold), several components responded only in men to RE (TLR1, TLR8, TRIF, and IKKβ). Our findings support the sexual dimorphism of immunity, with women having greater basal skeletal muscle TLR expression and differential response to unaccustomed exercise than men.NEW & NOTEWORTHY We recently reported that aging increases basal expression of many Toll-like receptors (TLRs) in men and lifelong aerobic exercise does not prevent this effect. In addition, a resistance exercise (RE) challenge increased the expression of many TLRs. Here we show that basal TLR expression is minimally influenced by aging in women and findings support the sexual dimorphism of immunity, with women having greater basal skeletal muscle TLR expression and a differential response to unaccustomed exercise than men.

Role of toll-like receptor-mediated pyroptosis in sepsis-induced cardiomyopathy

Sepsis, a life-threatening dysregulated status of the host response to infection, can cause multiorgan dysfunction and mortality. Sepsis places a heavy burden on the cardiovascular system due to the pathological imbalance of hyperinflammation and immune suppression. Myocardial injury and cardiac dysfunction caused by the aberrant host responses to pathogens can lead to cardiomyopathy, one of the most critical complications of sepsis. However, many questions about the specific mechanisms and characteristics of this complication remain to be answered. The causes of sepsis-induced cardiac dysfunction include abnormal cardiac perfusion, myocardial inhibitory substances, autonomic dysfunction, mitochondrial dysfunction, and calcium homeostasis dysregulation. The fight between the host and pathogens acts as the trigger for sepsis-induced cardiomyopathy. Pyroptosis, a form of programmed cell death, plays a critical role in the progress of sepsis. Toll-like receptors (TLRs) act as pattern recognition receptors and participate in innate immune pathways that recognize damage-associated molecular patterns as well as pathogen-associated molecular patterns to mediate pyroptosis. Notably, pyroptosis is tightly associated with cardiac dysfunction in sepsis and septic shock. In line with these observations, induction of TLR-mediated pyroptosis may be a promising therapeutic approach to treat sepsis-induced cardiomyopathy. This review focuses on the potential roles of TLR-mediated pyroptosis in sepsis-induced cardiomyopathy, to shed light on this promising therapeutic approach, thus helping to prevent and control septic shock caused by cardiovascular disorders and improve the prognosis of sepsis patients.

Inflammatory mechanisms and intervention strategies for sepsis-induced myocardial dysfunction

Sepsis-induced myocardial dysfunction (SIMD) is the leading cause of death in patients with sepsis in the intensive care units. The main manifestations of SIMD are systolic and diastolic dysfunctions of the myocardium. Despite our initial understanding of the SIMD over the past three decades, the incidence and mortality of SIMD remain high. This may be attributed to the large degree of heterogeneity among the initiating factors, disease processes, and host states involved in SIMD. Previously, organ dysfunction caused by sepsis was thought to be an impairment brought about by an excessive inflammatory response. However, many recent studies have shown that SIMD is a consequence of a combination of factors shaped by the inflammatory responses between the pathogen and the host. In this article, we review the mechanisms of the inflammatory responses and potential novel therapeutic strategies in SIMD.

Toll-like receptor 9 signaling after myocardial infarction: Role of p66ShcA adaptor protein

During myocardial infarction, cellular debris is released, causing a sterile inflammation via pattern recognition receptors. These reactions amplify damage and promotes secondary heart failure. The pattern recognition receptor, Toll-like receptor 9 (TLR9) detects immunogenic fragments of endogenous DNA, inducing inflammation by NFκB. The p66ShcA adaptor protein plays an important role in both ischemic myocardial damage and immune responses. We hypothesized that p66ShcA adaptor protein promotes DNA-sensing signaling via the TLR9 pathway after myocardial infarction. TLR9 protein expression increased in cardiac tissue from patients with end-stage heart failure due to ischemic heart disease. Myocardial ischemia in mice in vivo induced gene expression of key TLR9 pathway proteins (MyD88 and Unc93b1). In this model, a functional link between TLR9 and p66ShcA was revealed as; (i) ischemia-induced upregulation of TLR9 protein was abrogated in myocardium of p66ShcA knockout mice; (ii) when p66ShcA was overexpressed in NFkB reporter cells stably expressing TLR9, NFkB-activation increased during stimulation with the TLR9 agonist CpG B; (iii) in cardiac fibroblasts, p66ShcA overexpression caused TLR9 upregulation. Co-immunoprecipitation showed that ShcA proteins and TLR9 may be found in the same protein complex, which was dissipated upon TLR9 stimulation in vivo. A proximity assay confirmed the co-localization of TLR9 and ShcA proteins. The systemic immune response after myocardial ischemia was dampened in p66ShcA knockout mice as interleukin-4, -17 and -22 expression in mononuclear cells isolated from spleens was reduced. In conclusion, p66ShcA adaptor may be an interaction partner and a regulator of the TLR9 pathway post-infarction.

TLR9: A friend or a foe

The innate immune system is a primary protective line in our body. It confers its protection through different pattern recognition receptors (PRRs), especially toll like receptors (TLRs). Toll like receptor 9 (TLR9) is an intracellular TLR, expressed in different immunological and non-immunological cells. Release of cellular components, such as proteins, nucleotides, and DNA confers a beneficial inflammatory response and maintains homeostasis for removing cellular debris during normal physiological conditions. However, during pathological cellular damage and stress signals, engagement between mtDNA and TLR9 acts as an alarm for starting inflammatory and autoimmune disorders. The controversial role of TLR9 in different diseases baffled scientists if it has a protective or deleterious effect after activation during insults. Targeting the immune system, especially the TLR9 needs further investigation to provide a therapeutic strategy to control inflammation and autoimmune disorders.

PAMPs and DAMPs as the Bridge Between Periodontitis and Atherosclerosis: The Potential Therapeutic Targets

Atherosclerosis is a chronic artery disease characterized by plaque formation and vascular inflammation, eventually leading to myocardial infarction and stroke. Innate immunity plays an irreplaceable role in the vascular inflammatory response triggered by chronic infection. Periodontitis is a common chronic disorder that involves oral microbe-related inflammatory bone loss and local destruction of the periodontal ligament and is a risk factor for atherosclerosis. Periodontal pathogens contain numerous pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide, CpG DNA, and Peptidoglycan, that initiate the inflammatory response of the innate immunity depending on the recognition of pattern-recognition receptors (PRRs) of host cells. The immune-inflammatory response and destruction of the periodontal tissue will produce a large number of damage-associated molecular patterns (DAMPs) such as neutrophil extracellular traps (NETs), high mobility group box 1 (HMGB1), alarmins (S100 protein), and which can further affect the progression of atherosclerosis. Molecular patterns have recently become the therapeutic targets for inflammatory disease, including blocking the interaction between molecular patterns and PRRs and controlling the related signal transduction pathway. This review summarized the research progress of some representative PAMPs and DAMPs as the molecular pathological mechanism bridging periodontitis and atherosclerosis. We also discussed possible ways to prevent serious cardiovascular events in patients with periodontitis and atherosclerosis by targeting molecular patterns.

Targeting Toll-Like Receptors in Sepsis: From Bench to Clinical Trials

Significance: Sepsis is a critical clinical syndrome with life-threatening organ dysfunction induced by a dysregulated host response to infection. Despite decades of intensive research, sepsis remains a leading cause of in-hospital mortality with few specific treatments. Recent Advances: Toll-like receptors (TLRs) are a part of the innate immune system and play an important role in host defense against invading pathogens such as bacteria, virus, and fungi. Using a combination of genetically modified animal models and pharmacological agents, numerous preclinical studies during the past two decades have demonstrated that dysregulated TLR signaling may contribute to sepsis pathogenesis. However, many clinical trials targeting inflammation and innate immunity such as TLR4 have yielded mixed results. Critical Issues: Here we review various TLRs and the specific molecules these TLRs sense-both the pathogen-associated and host-derived stress molecules, and their converging signaling pathways. We critically analyze preclinical investigations into the role of TLRs in animal sepsis, the complexity of targeting TLRs for sepsis intervention, and the disappointing clinical trials of the TLR4 antagonist eritoran. Future Directions: Future sepsis treatments will depend on better understanding the complex biological mechanisms of sepsis pathogenesis, the high heterogeneity of septic humans as defined by clinical presentations and unique immunological biomarkers, and improved stratifications for targeted interventions.

The Central Role and Possible Mechanisms of Bacterial DNAs in Sepsis Development

The pathological roles of bacterial DNA have been documented many decades ago. Bacterial DNAs are different from mammalian DNAs; the latter are heavily methylated. Mammalian cells have sensors such as TLR-9 to sense the DNAs with nonmethylated CpGs and distinguish them from host DNAs with methylated CpGs. Further investigation has identified many other types of DNA sensors distributed in a variety of cellular compartments. These sensors not only sense foreign DNAs, including bacterial and viral DNAs, but also sense damaged DNAs from the host cells. The major downstream signalling pathways includeTLR-9-MyD88-IKKa-IRF-7/NF-κB pathways to increase IFN/proinflammatory cytokine production, STING-TBK1-IRF3 pathway to increase IFN-beta, and AIM2-ASC-caspas-1 pathway to release IL-1beta. The major outcome is to activate host immune response by inducing cytokine production. In this review, we focus on the roles and potential mechanisms of DNA sensors and downstream pathways in sepsis. Although bacterial DNAs play important roles in sepsis development, bacterial DNAs alone are unable to cause severe disease nor lead to death. Priming animals with bacterial DNAs facilitate other pathological factors, such as LPS and other virulent factors, to induce severe disease and lethality. We also discuss compartmental distribution of DNA sensors and pathological significance as well as the transport of extracellular DNAs into cells. Understanding the roles of DNA sensors and signal pathways will pave the way for novel therapeutic strategies in many diseases, particularly in sepsis.

CpG postconditioning after reperfused myocardial infarction is associated with modulated inflammation, less apoptosis, and better left ventricular function

Postconditioning attenuates inflammation and fibrosis in myocardial infarction (MI). The aim of this study was to investigate whether postconditioning with the cytosine-phosphate-guanine (CpG)-containing Toll-like receptor-9 (TLR9) ligand 1668-thioate (CpG) can modulate inflammation and remodeling in reperfused murine MI. Thirty minutes of left descending coronary artery (LAD) occlusion was conducted in 12-wk-old C57BL/6 mice. Mice were treated with CpG intraperitoneally 5 min before reperfusion. The control group received PBS; the sham group did not undergo ischemia. M-mode echocardiography (3, 7, and 28 days) and Millar left ventricular (LV) catheterization were performed (7 and 28 days) before the hearts were excised and harvested for immunohistochemical (6 h, 24 h, 3 days, 7 days, and 28 days), gene expression (6 h, 24 h, and 3 days; Taqman RT-qPCR), protein, and FACS analysis (24 h and 3 days). Mice treated with CpG showed significantly better LV function after 7 and 28 days of reperfusion. Protein and mRNA expressions of proinflammatory and anti-inflammatory cytokines were significantly induced after CpG treatment. Histology revealed fewer macrophages in CpG mice after 24 h, confirmed by FACS analysis with a decrease in both classically M1- and alternative M2a-monocytes. CpG treatment reduced apoptosis and cardiomyocyte loss and was associated with induction of adaptive mechanisms, e.g., of heme-oxigenase-1 and β-/α-myosin heavy chain (MHC) ratio. Profibrotic markers collagen type Iα (Col-Ια) and Col-III induction was abrogated in CpG mice, accompanied by fewer myofibroblasts. This led to the formation of a smaller scar. Differential matrix metalloproteinase (MMP)/tissue inhibitor of metalloproteinase (TIMP) expression contributed to attenuated remodeling in CpG, resulting in preserved cardiac function in a Toll-like receptor 1- and TLR9-dependent manner. Our study suggests a cardioprotective mechanism of CpG postconditioning, involving Toll-like receptor-driven modulation of inflammation. This is followed by attenuated remodeling and preserved LV function.NEW & NOTEWORTHY Cytosine-phosphate-guanine (CpG) postconditioning seems to mediate inflammation via Toll-like receptor-1 and Toll-like receptor-9 signaling. Enhanced cytokine and chemokine expressions are partly attenuated by IL-10 and matrix metalloproteinase-8 (MMP8) induction, being associated with lower macrophage infiltration and M1-monocyte differentiation. Furthermore, switch from α- to β-MHC and balanced MMP/TIMP expression led to lesser cardiomyocyte apoptosis, smaller scar size, and preserved cardiac function. Data of pharmacological postconditioning have been widely disappointing to date. Our study suggests a new pathway promoting myocardial postconditioning via Toll-like receptor activation.

DHA Supplementation Attenuates MI-Induced LV Matrix Remodeling and Dysfunction in Mice

Objective

Myocardial ischemia and reperfusion (I/R) injury is associated with oxidative stress and inflammation, leading to scar development and malfunction. The marine omega-3 fatty acids (ω-3 FA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are mediating cardioprotection and improving clinical outcomes in patients with heart disease. Therefore, we tested the hypothesis that docosahexaenoic acid (DHA) supplementation prior to LAD occlusion-induced myocardial injury (MI) confers cardioprotection in mice.

Methods

C57BL/6N mice were placed on DHA or control diets (CD) beginning 7 d prior to 60 min LAD occlusion-induced MI or sham surgery. The expression of inflammatory mediators was measured via RT-qPCR. Besides FACS analysis for macrophage quantification and subtype evaluation, macrophage accumulation as well as collagen deposition was quantified in histological sections. Cardiac function was assessed using a pressure-volume catheter for up to 14 d.

Results

DHA supplementation significantly attenuated the induction of peroxisome proliferator-activated receptor-α (PPAR-α) (2.3 ± 0.4 CD vs. 1.4 ± 0.3 DHA) after LAD occlusion. Furthermore, TNF-α (4.0 ± 0.6 CD vs. 1.5 ± 0.2 DHA), IL-1β (60.7 ± 7.0 CD vs. 11.6 ± 1.9 DHA), and IL-10 (223.8 ± 62.1 CD vs. 135.5 ± 38.5 DHA) mRNA expression increase was diminished in DHA-supplemented mice after 72 h reperfusion. These changes were accompanied by a less prominent switch in α/β myosin heavy chain isoforms. Chemokine mRNA expression was stronger initiated (CCL2 6 h: 32.8 ± 11.5 CD vs. 78.8 ± 13.6 DHA) but terminated earlier (CCL2 72 h: 39.5 ± 7.8 CD vs. 8.2 ± 1.9 DHA; CCL3 72 h: 794.3 ± 270.9 CD vs. 258.2 ± 57.8 DHA) in DHA supplementation compared to CD mice after LAD occlusion. Correspondingly, DHA supplementation was associated with a stronger increase of predominantly alternatively activated Ly6C-positive macrophage phenotype, being associated with less collagen deposition and better LV function (EF 14 d: 17.6 ± 2.6 CD vs. 31.4 ± 1.5 DHA).

Conclusion

Our data indicate that DHA supplementation mediates cardioprotection from MI via modulation of the inflammatory response with timely and attenuated remodeling. DHA seems to attenuate MI-induced cardiomyocyte injury partly by transient PPAR-α downregulation, diminishing the need for antioxidant mechanisms including mitochondrial function, or α- to β-MHC isoform switch.

TLR9 deficiency alleviates doxorubicin-induced cardiotoxicity via the regulation of autophagy

Doxorubicin is a commonly used anthracycline chemotherapeutic drug. Its application for treatment has been impeded by its cardiotoxicity as it is detrimental and fatal. DNA damage, cardiac inflammation, oxidative stress and cell death are the critical links in DOX-induced myocardial injury. Previous studies found that TLR9-related signalling pathways are associated with the inflammatory response of cardiac myocytes, mitochondrial dysfunction and cardiomyocyte death, but it remains unclear whether TLR9 could influence DOX-induced heart injury. Our current data imply that DOX-induced cardiotoxicity is ameliorated by TLR9 deficiency both in vivo and in vitro, manifested as improved cardiac function and reduced cardiomyocyte apoptosis and oxidative stress. Furthermore, the deletion of TLR9 rescued DOX-induced abnormal autophagy flux in vivo and in vitro. However, the inhibition of autophagy by 3-MA abolished the protective effects of TLR9 deletion on DOX-induced cardiotoxicity. Moreover, TLR9 ablation suppressed the activation of p38 MAPK during DOX administration and may promote autophagy via the TLR9-p38 MAPK signalling pathway. Our study suggests that the deletion of TLR9 exhibits a protective effect on doxorubicin-induced cardiotoxicity by enhancing p38-dependent autophagy. This finding could be used as a basis for the development of a prospective therapy against DOX-induced cardiotoxicity.

Depletion of β3-adrenergic receptor induces left ventricular diastolic dysfunction via potential regulation of energy metabolism and cardiac contraction

Left ventricular diastolic dysfunction (LVDD) is a central perturbation in heart failure with preserved ejection fraction, and there are currently no effective remedies to improve LVDD in clinical practice. The β3-adrenergic receptor (ADRB3) was reported to play protective effects on inhibiting myocardial fibrosis in response to hemodynamic stress. However, the effects of ADRB3 on LVDD and its underlying mechanisms are still undefined. In the current study, the role of ADRB3 in LVDD was identified in ADRB3-knockout mice. Echocardiography parameters showed that depletion of ADRB3 had little effect on cardiac systolic function but obviously led to cardiac diastolic dysfunction in vivo. Proteomics (including the global proteome, phosphorylated and acetylated proteome) and bioinformatics analysis (including GO analysis, KEGG pathway analysis, GO-Tree network, Pathway-Act network, and protein-protein interaction network) were performed on cardiac specimens of ADRB3-KO mice and wild-type mice. The results showed that the cardiac energy metabolism (especially the citrate cycle), actin cytoskeleton organization, and cardiac muscle contraction (related to mitogen-activated protein kinase, toll-like receptor, and ErbB signalling pathway) were potential core mechanisms underlying ADRB3-KO-induced LVDD. In addition, the protein-protein interaction network indicated that the core proteins associated with ADRB3-KO-induced LVDD were FGG, ALDH1A1, FGA, APOC3, SLC4A1, SERPINF2, HP, CTNNB1, and TKT. In conclusion, the absence of ADRB3 leads to LVDD, which is potentially associated with the regulation of cardiac energy metabolism, actin cytoskeleton organization, and cardiac muscle contraction.

The Relationship Between Sepsis-induced Immunosuppression and Serum Toll-like Receptor 9 Level

BACKGROUND/AIM

Our aim was to determine serum TLR-9 levels in sepsis and evaluate the relationship between sepsis and serum TLR-9 levels.

MATERIALS AND METHODS

The study group consisted of 80 consecutive patients with sepsis and 100 healthy individuals. The demographic characteristics, co-morbidities and hemodynamic data of all patients were recorded.

RESULTS

TLR-9 serum levels in sepsis were statistically significantly lower compared to the control group. It was also seen that when the lactate level was >5 mmol/l in patients in the sepsis group, the serum TLR-9 levels were substantially higher.

CONCLUSION

There is a relationship between sepsis-induced immunosuppression and serum TLR-9 levels. The host immunity system can be activated by means of TLR-9-related systems, while hyperlactatemia may play a stimulating role in the re-activation of the immune system.

Harmful Roles of TLR3 and TLR9 in Cardiac Dysfunction Developing during Polymicrobial Sepsis

We determined the roles of TLR3 and TLR9 in adverse events of polymicrobial sepsis, with a focus on development of septic cardiomyopathy, progression of which we have recently shown to be complement- and histones-dependent. So Wt, TLR3-knocked out (K.O.), and TLR9-K.O. mice were subjected to polymicrobial sepsis following cecal ligation and puncture (CLP). In the absence of either TLR3 or TLR9, the intensity of echocardiogram (Echo)-Doppler dysfunction during development of cardiomyopathy was substantially reduced in the K.O. mice. Based on our prior studies emphasizing the adverse effects of plasma C5a and histones in the cardiomyopathy of sepsis, in TLR3- and TLR9-K.O. mice, there were striking reductions in plasma levels of C5a and histones as well as reduced levels of cytokines in plasma and heart tissue after CLP. Since we know that histones cause cardiac dysfunction, rat cardiomyocytes (CMs) were exposed in vitro to the histones (purified from calf thymus), which caused bleb formation on the surfaces of CMs, suggesting histones may perturb the cell membrane of CMs. In vitro, exposure of CMs to the histones for 3 hours caused lactate dehydrogenase release from CMs. These data indicate that sepsis-induced cardiac dysfunction requires presence of TLR3 and TLR9 and may be linked to histone-induced damage of CMs.

Inhibition of TLR9-NF-κB-mediated sterile inflammation improves pressure overload-induced right ventricular dysfunction in rats

Aims

Recent accumulating evidence suggests that sterile inflammation plays a crucial role in the progression of various cardiovascular diseases. However, its contribution to right ventricular (RV) dysfunction remains unknown. The aim of this study was to elucidate whether toll-like receptor 9 (TLR9)-NF-κB-mediated sterile inflammation plays a critical role in the pathogenesis of RV dysfunction.

Methods and results

We performed main pulmonary artery banding (PAB) in rats to induce RV pressure overload and dysfunction. On Day 14 after PAB, the pressure overload impaired RV function as indicated by increased RV end-diastolic pressure concomitant with macrophage infiltration and fibrosis, as well as maximal activation of NF-κB and TLR9. Short-term administration (days 14–16 after PAB) of a specific TLR9 inhibitor, E6446, or an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC) significantly attenuated NF-κB activation. Furthermore, long-term administration of E6446 (treatment: days 14–28) or PDTC (prevention: days −1 to 28; treatment: days 14 to 28) improved RV dysfunction associated with mitigated macrophage infiltration and fibrosis in right ventricle and decreased serum brain natriuretic peptide levels.

Conclusion

Inhibition of TLR9-NF-κB pathway-mediated sterile inflammation improved PAB-induced RV dysfunction in rats. This pathway plays a major role in the progression of pressure overload-induced RV dysfunction and is potentially a novel therapeutic target for the disorder.

[Increased myocardial expression of Toll-like receptors 2 and 9 as a marker of active myocarditis and a possible predictor of therapeutic effectiveness]

AIM

to investigate the myocardial expression of some structural proteins and markers of cellular proliferation and innate immunity for assessing their possible diagnostic and prognostic role in patients with chronic myocarditis.

SUBJECTS AND METHODS

The investigation enrolled 23 patients (16 men; mean age, 52.0±12.4 years (range, 27 to 73) with various forms of noncoronarogenic myocardial injury who underwent right ventricular endomyocardial biopsy (n=4), intraoperative left ventricular biopsy (n=17) or autopsy (n=2). Prior to their morphological examination, the patients were divided into two groups: 1) 10 patients with dilated cardiomyopathy and presumptive myocarditis; 2) 13 patients with valvular heart disease, hypertrophic cardiomyopathy, myxoma, and chronic pulmonary thromboembolism, presumptively without myocarditis. Along with myocardial histological and immunohistochemical (IHC) examinations, the expression of vimentin, desmin, c-kit, Ki-67, and Toll-like receptors (TLR) 2 and 9 was determined. Polymerase chain reaction was used to identify whether herpes viruses of and parvovirus B19 genomes were present in the blood and myocardial samples; indirect ELISA was applied to estimate the blood level of antibodies against various cardiac antigens.

RESULTS

According to the histological findings, active/borderline lymphocytic myocarditis was diagnosed in all the patients (Group 1) and in 6 patients (Group 2) in conjunction with the underlying disease (only in 9 and 7 patients, respectively), viral genome was detected in the myocardium of 15 patients, including in 5 without morphological signs of myocarditis (parvovirus B19 (n=11), herpesvirus 6 (n=4), herpes simplex virus types 1 and 2 (n=1), Epstein-Barr virus (n=2), and cytomegalovirus (n=1)), and in the blood (n=4). A marked correlation was found between TLR2 and TLR9 expressions and the morphological pattern of active myocarditis in the absence of this correlation with the expression level of other studied markers. The expression level of TLR2 in patients with and without borderline myocarditis was 0 [0; 0,75] and in those with active myocarditis was 1.5 [1; 1,5] points; that of TLR9 was 2 [2; 2] and 4 [3; 4] points, respectively (p<0.001). The expression of TLR2 and TLR9 in patients with borderline myocarditis was lower than in those without myocarditis (0 [0; 0] versus 0 [0; 1] and 2 [1,5; 2] versus 2 [2; 3] points), which can reflect cardiomyocyte destruction/depletion at later stages of the disease. There was also a close correlation between the expression level of TLR2 and that of TLR9 (r=0.824; p<0.001) and with Ki-67 levels (r=-0.531 and r=-0.702; p<0.01). There was also a correlation of the expression of the studied markers with viral persistence (desmin), the degree of myocardial dysfunction and cardiosclerosis (c-kit), which calls for further investigations.

CONCLUSION

Determination of the myocardial expression level of TLR2 and TLR9 may serve as an immunohistochemical marker for myocarditis and preservation of its activity, which is especially valuable in patients with borderline forms. The marked expression of these markers for innate immunity may reflect both one of the mechanisms of genetic predisposition to myocarditis and its severe course and their secondary activation in the pathogenesis of the disease and is a potential target of therapy.

The Role of Toll-Like Receptor Signaling in the Progression of Heart Failure

Medical systems worldwide are being faced with a growing need to understand mechanisms behind the pathogenesis of heart failure (HF) that is considered as a leading cause of morbidity and mortality around the world. Elevated levels of inflammatory mediators have been identified in patients with HF, which are primarily manifestations of innate immune responses mediated by pattern recognition receptors (PRRs). Toll-like receptors (TLRs), which belong to PRRs, are subjected to the release of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) to generate innate immune responses. More and more emerging data indicate that TLR signaling pathway molecules are involved in the progression of HF. Herein, we present new data with regard to the activation of TLRs in the failing heart, focusing on TLR2, TLR3, TLR4, and TLR9, and suggest the potential use of TLRs in target therapy.

The Role of Toll-Like Receptors and Vitamin D in Cardiovascular Diseases-A Review

Cardiovascular diseases are the leading cause of mortality worldwide. Therefore, a better understanding of their pathomechanisms and the subsequent implementation of optimal prophylactic and therapeutic strategies are of utmost importance. A growing body of evidence states that low-grade inflammation is a common feature for most of the cardiovascular diseases in which the contributing factors are the activation of toll-like receptors (TLRs) and vitamin D deficiency. In this article, available data concerning the association of cardiovascular diseases with TLRs and vitamin D status are reviewed, followed by a discussion of new possible approaches to cardiovascular disease management.

Epigenetics, inflammation and metabolism in right heart failure associated with pulmonary hypertension

Right ventricular failure (RVF) is the most important prognostic factor for both morbidity and mortality in pulmonary arterial hypertension (PAH), but also occurs in numerous other common diseases and conditions, including left ventricle dysfunction. RVF remains understudied compared with left ventricular failure (LVF). However, right and left ventricles have many differences at the morphological level or the embryologic origin, and respond differently to pressure overload. Therefore, knowledge from the left ventricle cannot be extrapolated to the right ventricle. Few studies have focused on the right ventricle and have permitted to increase our knowledge on the right ventricular-specific mechanisms driving decompensation. Here we review basic principles such as mechanisms accounting for right ventricle hypertrophy, dysfunction, and transition toward failure, with a focus on epigenetics, inflammatory, and metabolic processes.

Extracellular mtDNA activates NF-κB via toll-like receptor 9 and induces cell death in cardiomyocytes

Acute myocardial infarction (AMI) causes sterile inflammation, which exacerbates tissue injury. Elevated levels of circulating mitochondrial DNA (mtDNA) have been associated with AMI. We hypothesized that mtDNA triggers an innate immune response via TLR9 and NF-κB activation, causing cardiomyocyte injury. Murine cardiomyocytes express TLR9 mRNA and protein and were able to internalize fluorescently labeled mouse mtDNA. Incubation of human embryonic kidney cells with serum from AMI patients containing naturally elevated levels of mtDNA induced TLR9-dependent NF-κB activity. This effect was mimicked by isolated mtDNA. mtDNA activated NF-κB in reporter mice both in vivo and in isolated cardiomyocytes. Moreover, incubation of isolated cardiomyocytes with mtDNA induced cell death after 4 and 24 h. Laser confocal microscopy showed that incubation of cardiomyocytes with mtDNA accelerated mitochondrial depolarization induced by reactive oxygen species. In contrast to mtDNA, isolated total DNA did not activate NF-κB nor induce cell death. In conclusion, mtDNA can induce TLR9-dependent NF-κB activation in reporter cells and activate NF-κB in cardiomyocytes. In cardiomyocytes, mtDNA causes mitochondrial dysfunction and death. Endogenous mtDNA in the extracellular space is a danger signal with direct detrimental effects on cardiomyocytes.

Proinflammatory Stimulation of Toll-Like Receptor 9 with High Dose CpG ODN 1826 Impairs Endothelial Regeneration and Promotes Atherosclerosis in Mice

Background

Toll-like receptors (TLR) of the innate immune system have been closely linked with the development of atherosclerotic lesions. TLR9 is activated by unmethylated CpG motifs within ssDNA, but also by CpG motifs in nucleic acids released during vascular apoptosis and necrosis. The role of TLR9 in vascular disease remains controversial and we sought to investigate the effects of a proinflammatory TLR9 stimulation in mice.

Methods and Findings

TLR9-stimulation with high dose CpG ODN at concentrations between 6.25nM to 30nM induced a significant proinflammatory cytokine response in mice. This was associated with impaired reendothelialization upon acute denudation of the carotid and increased numbers of circulating endothelial microparticles, as a marker for amplified endothelial damage. Chronic TLR9 agonism in apolipoprotein E-deficient (ApoE^-/-) mice fed a cholesterol-rich diet increased aortic production of reactive oxygen species, the number of circulating endothelial microparticles, circulating sca-1/flk-1 positive cells, and most importantly augmented atherosclerotic plaque formation when compared to vehicle treated animals. Importantly, high concentrations of CpG ODN are required for these proatherogenic effects.

Conclusions

Systemic stimulation of TLR9 with high dose CpG ODN impaired reendothelialization upon acute vascular injury and increased atherosclerotic plaque development in ApoE^-/- mice. Further studies are necessary to fully decipher the contradictory finding of TLR9 agonism in vascular biology.

Beneficial effects of exercise on age-related mitochondrial dysfunction and oxidative stress in skeletal muscle

Mitochondria are negatively affected by ageing leading to their inability to adapt to higher levels of oxidative stress and this ultimately contributes to the systemic loss of muscle mass and function termed sarcopenia. Since mitochondria are central mediators of muscle health, they have become highly sought-after targets of physiological and pharmacological interventions. Exercise is the only known strategy to combat sarcopenia and this is largely mediated through improvements in mitochondrial plasticity. More recently a critical role for mitochondrial turnover in preserving muscle has been postulated. Specifically, cellular pathways responsible for the regulation of mitochondrial turnover including biogenesis, dynamics and autophagy may become dysregulated during ageing resulting in the reduced clearance and accumulation of damaged organelles within the cell. When mitochondrial quality is compromised and homeostasis is not re-established, myonuclear cell death is activated and muscle atrophy ensues. In contrast, acute and chronic exercise attenuates these deficits, restoring mitochondrial turnover and promoting a healthier mitochondrial pool that leads to the preservation of muscle. Additionally, the magnitude of these exercise-induced mitochondrial adaptations is currently debated with several studies reporting a lower adaptability of old muscle relative to young, but the processes responsible for this diminished training response are unclear. Based on these observations, understanding the molecular details of how advancing age and exercise influence mitochondria in older muscle will provide invaluable insight into the development of exercise protocols that will maximize beneficial adaptations in the elderly. This information will also be imperative for future research exploring pharmacological targets of mitochondrial plasticity.

Tlr4 Deficiency Protects against Cardiac Pressure Overload Induced Hyperinflammation

Transverse aortic constriction provokes a pro-inflammatory reaction and results in cardiac hypertrophy. Endogenous ligands contribute to cardiac hypertrophy via toll-like receptor (TLR)-4 binding. A lack of TLR4 signaling diminishes hypertrophy and inflammation. Wild type mice undergoing aortic constriction respond to a lipopolysaccharide second-hit stimulus with hyperinflammation. The objective of this study was to assess whether other second-hit challenges utilizing TLR ligands provoke a comparable inflammatory reaction, and to find out whether this response is absent in TLR4 deficient mice. Assuming that cardiac stress alters the expression of pattern recognition receptors we analyzed the effects of transverse aortic constriction and second-hit virulence factor treatment on TLR expression, as well as cytokine regulation. Wild type and Tlr4-/- mice were subjected to three days of TAC and subsequently confronted with gram-positive TLR2 ligand lipoteichoic acid (LTA, 15 mg/g bodyweight) or synthetic CpG-oligodesoxynucleotide 1668 thioate (20 nmol/kg bodyweight, 30 min after D-galactosamin desensitization) signaling via TLR9. Hemodynamic measurements and organ preservation were performed 6 h after stimulation. Indeed, the study revealed a robust enhancement of LTA induced pattern recognition receptor and cytokine mRNA expression and a LTA-dependent reduction of hemodynamic pressure in TAC wild type mice. Second-Hit treatment with CpG-ODNs led to similar results. However, second-hit effects were abolished in Tlr4-/- mice. In total, these data indicate for the first time that cardiac stress increases the inflammatory response towards both, gram-negative and gram-positive, TLR ligands as well as bacterial DNA. The decrease of the inflammatory response upon TLR2 and -9 ligand challenge in TAC Tlr4-/- mice demonstrates that a lack of TLR4 signaling does not only prevent left ventricular hypertrophy but also protects the mice from a cardiac stress induced hyperinflammatory reaction.

Unmethylated CpG motifs inToxoplasma gondiiDNA induce TLR9- and IFN-β-dependent expression ofα-defensin-5 in intestinal epithelial cells

The gut epithelial barrier is a strategic place to prevent, or at least to limit, parasite dissemination upon oral infection withToxoplasma gondii. Innate immunity to this pathogen results from delicate interactions involving different components of the infecting agent and the host. We herein aimed to examine the molecular mechanism by which protozoan DNA boosts the production ofα-defensin-5 (DEFA-5), the main antimicrobial peptide at the target site of infection. The present study shows that DEFA-5 is rapidly upregulated in intestinal epithelial cells following intracellular Toll-like receptor 9 (TLR9) activation by unmethylated CpG motifs in DNA fromT. gondii(CpG-DNA). Concomitantly, CpG-DNA purified from the pathogen markedly increased TLR9 mRNA expression levels in the Caco-2 cell line. We further verified that DEFA-5 production was dependent on interferon-βreleased from these cells upon treatment with CpG-DNA prepared from tachyzoites. Our results suggest that, in protozoan DNA-stimulated intestinal epithelial cells, the TLR9/interferon-β/DEFA-5 pathway may initiate an innate anti-T. gondiiresponse without the need of parasite invasion. These findings highlight the key role of the gut epithelium in Toxoplasma recognition and amplification of local host defence against this microbe, thereby contributing to gain insight into immunoprotective mechanisms and to improve therapeutic strategies.

Sustained Toll-Like Receptor 9 Activation Promotes Systemic and Cardiac Inflammation, and Aggravates Diastolic Heart Failure in SERCA2a KO Mice

AIM

Cardiac inflammation is important in the pathogenesis of heart failure. However, the consequence of systemic inflammation on concomitant established heart failure, and in particular diastolic heart failure, is less explored. Here we investigated the impact of systemic inflammation, caused by sustained Toll-like receptor 9 activation, on established diastolic heart failure.

METHODS AND RESULTS

Diastolic heart failure was established in 8-10 week old cardiomyocyte specific, inducible SERCA2a knock out (i.e., SERCA2a KO) C57Bl/6J mice. Four weeks after conditional KO, mice were randomized to receive Toll-like receptor 9 agonist (CpG B; 2μg/g body weight) or PBS every third day. After additional four weeks, echocardiography, phase contrast magnetic resonance imaging, histology, flow cytometry, and cardiac RNA analyses were performed. A subgroup was followed, registering morbidity and death. Non-heart failure control groups treated with CpG B or PBS served as controls. Our main findings were: (i) Toll-like receptor 9 activation (CpG B) reduced life expectancy in SERCA2a KO mice compared to PBS treated SERCA2a KO mice. (ii) Diastolic function was lower in SERCA2a KO mice with Toll-like receptor 9 activation. (iii) Toll-like receptor 9 stimulated SERCA2a KO mice also had increased cardiac and systemic inflammation.

CONCLUSION

Sustained activation of Toll-like receptor 9 causes cardiac and systemic inflammation, and deterioration of SERCA2a depletion-mediated diastolic heart failure.

Microbial Nucleic Acid Sensing in Oral and Systemic Diseases

One challenge in studying chronic infectious and inflammatory disorders is understanding how host pattern recognition receptors (PRRs), specifically toll-like receptors (TLRs), sense and respond to pathogen- or damage-associated molecular patterns, their communication with each other and different components of the immune system, and their role in propagating inflammatory stages of disease. The discovery of innate immune activation through nucleic acid recognition by intracellular PRRs such as endosomal TLRs (TLR3, TLR7, TLR8, and TLR9) and cytoplasmic proteins (absent in melanoma 2 and DNA-dependent activator of interferon regulatory factor) opened a new paradigm: Nucleic acid sensing is now implicated in multiple immune and inflammatory conditions (e.g., atherosclerosis, cancer), viral (e.g., human papillomavirus, herpes virus) and bacterial (e.g., Helicobacter pylori, pneumonia) diseases, and autoimmune disorders (e.g., systemic lupus erythematosus, rheumatoid arthritis). Clinical investigations reveal the overexpression of specific nucleic acid sensors in diseased tissues. In vivo animal models show enhanced disease progression associated with receptor activation. The involvement of nucleic acid sensors in various systemic conditions is further supported by studies reporting receptor knockout mice being either protected from or prone to disease. TLR9-mediated inflammation is also implicated in periodontal diseases. Considering that persistent inflammation in the oral cavity is associated with systemic diseases and that oral microbial DNA is isolated at distal sites, nucleic acid sensing may potentially be a link between oral and systemic diseases. In this review, we discuss recent advances in how intracellular PRRs respond to microbial nucleic acids and emerging views on the role of nucleic acid sensors in various systemic diseases. We also highlight new information on the role of intracellular PRRs in the pathogenesis of oral diseases including periodontitis and oral cavity cancer, which might offer future possibilities for disease prevention and therapy.

Inhibition of Toll-like receptor 9 attenuates sepsis-induced mortality through suppressing excessive inflammatory response

Sepsis, a major clinical problem with high morbidity and mortality, is caused by overwhelming systemic host-inflammatory response. Toll-like receptors (TLRs) play a fundamental role in induction of hyperinflammation and tissue damage in sepsis. In this study, we demonstrate a protective role of TLR9 inhibition against the dysregulated inflammatory response and tissue injury in sepsis. TLR9 deficiency decreased the mortality of mice following cecal ligation and puncture (CLP)-induced sepsis. TLR9 knockout mice showed dampened p38 activation and augmented Akt phosphorylation in the spleen, lung and liver. In addition, TLR9 deficiency decreased the levels of inflammatory cytokines and attenuated splenic apoptosis after CLP. These results indicate that TLR9 inhibition might offer a novel therapeutic strategy for the management of sepsis.

Postconditioning with a CpG containing oligodeoxynucleotide ameliorates myocardial infarction in a murine closed-chest model

AIMS

Toll-like receptor (TLR)9 ligand CpG-oligodeoxynucleotide (CpG-ODN) exerts preconditioning in myocardial ischemia/reperfusion. We hypothesized a postconditioning effect of CpG-ODN in a murine closed-chest model of myocardial infarction.

MATERIALS AND METHODS

C57BL/6 (12 weeks, male, WT) mice were instrumented at the left anterior descending artery, then allowed 5d of recovery before 30 min ischemia. Treatments comprised: 1) PBS: 250 μl phosphate buffer solution intraperitoneally 5 min before reperfusion and 2) IPC (ischemic postconditioning): 3 twenty-second reperfusion and occlusion episodes at the end of ischemia 3) CpG-ODN: 1668 thioate 0.2 μmol/kg BW intraperitoneally 5 min before reperfusion. Infarct size was assessed via triphenyltetrazolium chloride (TTC) staining after 2 and 24h reperfusion. Myocardial mRNA-expression of cytokines was measured using real-time PCR after 2h reperfusion. Phosphatidylinositol-3 kinase (PI3K)-inhibitor wortmannin was injected intraperitoneally in WT 15 min before postconditioning and PBS in each group. Cardiac function in WT was assessed with a left-ventricular pressure-volume catheter at 24h reperfusion.

KEY FINDINGS

Following 30 min ischemia and 2h reperfusion, infarct size was diminished by 90% in WT postconditioned with CpG-ODN (2.4 ± 1.55 IS/AAR%) and IPC (1.98 ± 1.03 IS/AAR%) compared to PBS mice (23.2 ± 3.97 IS/AAR%). Infarct size increased following 24h reperfusion but the differences remained robust. Expression of TNF-α and IL-10 was increased in CpG-ODN. Wortmannin abolished the postconditioning effect of CpG-ODN and IPC. Ejection fraction and preload-recruitable stroke work were significantly greater in CpG-ODN mice.

SIGNIFICANCE

CpG-ODN confers postconditioning via activation of TLR9. Cardiac function is preserved following CpG-ODN postconditioning. The PI3K -inhibitor wortmannin attenuates CpG-ODN postconditioning.

Toll-like receptor 9 mediated responses in cardiac fibroblasts

Altered cardiac Toll-like receptor 9 (TLR9) signaling is important in several experimental cardiovascular disorders. These studies have predominantly focused on cardiac myocytes or the heart as a whole. Cardiac fibroblasts have recently been attributed increasing significance in mediating inflammatory signaling. However, putative TLR9-signaling through cardiac fibroblasts remains non-investigated. Thus, our aim was to explore TLR9-signaling in cardiac fibroblasts and investigate the consequence of such receptor activity on classical cardiac fibroblast cellular functions. Cultivated murine cardiac fibroblasts were stimulated with different TLR9 agonists (CpG A, B and C) and assayed for the secretion of inflammatory cytokines (tumor necrosis factor α [TNFα], CXCL2 and interferon α/β). Expression of functional cardiac fibroblast TLR9 was proven as stimulation with CpG B and -C caused significant CXCL2 and TNFα-release. These responses were TLR9-specific as complete inhibition of receptor-stimulated responses was achieved by co-treatment with a TLR9-antagonist (ODN 2088) or chloroquine diphosphate. TLR9-stimulated responses were also found more potent in cardiac fibroblasts when compared with classical innate immune cells. Stimulation of cardiac fibroblasts TLR9 was also found to attenuate migration and proliferation, but did not influence myofibroblast differentiation in vitro. Finally, results from in vivo TLR9-stimulation with subsequent fractionation of specific cardiac cell-types (cardiac myocytes, CD45+ cells, CD31+ cells and cardiac fibroblast-enriched cell-fractions) corroborated our in vitro data and provided evidence of differentiated cell-specific cardiac responses. Thus, we conclude that cardiac fibroblast may constitute a significant TLR9 responder cell within the myocardium and, further, that such receptor activity may impact important cardiac fibroblast cellular functions.

Sepsis-induced Cardiac Mitochondrial Damage and Potential Therapeutic Interventions in the Elderly

The incidence of sepsis and its attendant mortality risk are significantly increased with aging. Thus, severe sepsis in the elderly is likely to become an emerging concern in critical care units. Cardiac dysfunction is an important component of multi-organ failure after sepsis. In our laboratory, utilizing a pneumonia-related sepsis animal model, our research has been focused on the mechanisms underlying sepsis-induced cardiac failure. In this review, based on findings from others and ours, we discussed age-dependent decay in mitochondria and the role of mitochondrial reactive oxygen species (mtROS) in sepsis-induced cardiac inflammation and autophagy. Our recent discovery of a potential signal transduction pathway that triggers myocardial mitochondrial damage is also discussed. Because of the significance of mitochondria damage in the aging process and in sepsis pathogenesis, we hypothesize that specific enhancing mitochondrial antioxidant defense by mitochondria-targeted antioxidants (MTAs) may provide important therapeutic potential in treating elder sepsis patients. In this review, we summarized the categories of currently published MTA molecules and the results of preclinical evaluation of MTAs in sepsis and aging models.

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.

Translation of hemodynamic stress to sterile inflammation in the heart

Recently, growing evidence suggests that cardiac inflammation contributes to progression of heart failure (HF). However, the precise mechanism has been elusive. Autophagy is well-known phenomenon which plays essential roles in the maintenance of cardiomyocyte homeostasis by clearing damaged proteins and organelles, and dysfunction of this system evokes HF. Although emerging roles of mitochondria in inflammasome development are highlighted in immune cells, an involvement in the heart has not been defined until recently. This review discusses recent advances in understanding the complex mechanisms underlying cardiac inflammation: these studies have revealed that a combination of mitochondrial autophagy and innate immune responses to mitochondrial DNA during increased hemodynamic stress contribute to cardiac inflammation.

TLR2 stimulation induces cardiac inflammation but not cardiac depression in vivo

BACKGROUND

Bacteria such as Staphylococcus aureus induce myocardial dysfunction in vivo. To rectify conflicting evidence about the role of TLR2 signaling and cardiac dysfunction, we hypothesized that the specific TLR2 agonist purified lipoteichoic acid (LTA) from S. aureus contributes to cardiac dysfunction in vitro and in vivo.

METHODS

Wildtype (WT-) and TLR2-deficient (TLR2-D) mice were challenged with LTA and in comparison with equivalent doses of lipopolysaccharide (LPS) and CpG-oligodeoxynucleotide (CpG-ODN). TLR2-expression, NFκB as well as cytokine response were determined. Sarcomere shortening of isolated cardiomyocytes was analyzed in vitro and cardiac function in vivo after stimulation with LTA.

RESULTS

LTA induced up-regulation of TLR2 mRNA, activation of NFκB and cytokine expression within 2-6 h in WT-, but not in TLR2-D hearts. Cytokines were also elevated in the serum. LPS and CpG-ODN induced a more severe cardiac inflammation. In vitro incubation of cardiomyocytes with LTA reduced sarcomere shortening via NO at stimulation frequencies ≤ 8 Hz only in WT cells. However, hemodynamic parameters in vivo were not affected by LTA challenge.

CONCLUSIONS

LTA induced cardiac inflammation was relatively weak and sarcomere shortening was reduced only below physiological heart rates. This may explain the apparent contradiction between the in vivo and in vitro LTA effects.

Pre-conditioning with synthetic CpG-oligonucleotides attenuates myocardial ischemia/reperfusion injury via IL-10 up-regulation

The aim of the study was to investigate whether pre-conditioning with CpG-oligodeoxynucleotides (CpG-ODN) may change cardiac ischemia/reperfusion (I/R)-dependent inflammation and modulates infarct size and cardiac performance. WT and TLR9-deficient mice were pre-treated with 1668-, 1612- and H154-thioate or D-Gal as control. Priming with 1668-thioate significantly induced inflammatory mediators in the serum and a concomitant increase of immune cells in the blood and spleen of WT mice. Furthermore, it induced myocardial pattern recognition receptors and pro-inflammatory cytokines peaking 2 h after priming and a continuous increase of IL-10. 16 h after pre-conditioning, myocardial ischemia was induced for 1 h. Infarct size determined after 24 h of I/R was reduced by 75 % due to pre-conditioning with 1668-thioate but not in the other groups. During reperfusion, cytokine expression in 1668-thioate primed mice increased further with IL-10 exceeding the other mediators by far. These changes were observed neither in animals pre-treated with 1612- or H154-thioate nor in TLR9-deficient mice. The 1668-thioate-dependent increase of IL-10 was further supported by results of a micro-array analysis 3 h after begin of reperfusion. Block of IL-10 signaling increased I/R size and prevented influence of priming. In the group pre-treated with 1668-thioate, cardiac function was preserved 24 h, 14 days and 28 days after I/R, whereas animals without pre-conditioning exhibited impaired heart function 24 h and 14 days after I/R. The excessive 1668-thioate-dependent IL-10 up-regulation during pre-conditioning and after I/R seems to be the key factor for reducing infarct size and improving cardiac function. This is in agreement with the finding that IL-10 block prevents cardioprotection by pre-conditioning.

Toll-like receptor 9 promotes cardiac inflammation and heart failure during polymicrobial sepsis

Background. Aim was to elucidate the role of toll-like receptor 9 (TLR9) in cardiac inflammation and septic heart failure in a murine model of polymicrobial sepsis. Methods. Sepsis was induced via colon ascendens stent peritonitis (CASP) in C57BL/6 wild-type (WT) and TLR9-deficient (TLR9-D) mice. Bacterial load in the peritoneal cavity and cardiac expression of inflammatory mediators were determined at 6, 12, 18, 24, and 36 h. Eighteen hours after CASP cardiac function was monitored in vivo. Sarcomere length of isolated cardiomyocytes was measured at 0.5 to 10 Hz after incubation with heat-inactivated bacteria. Results. CASP led to continuous release of bacteria into the peritoneal cavity, an increase of cytokines, and differential regulation of receptors of innate immunity in the heart. Eighteen hours after CASP WT mice developed septic heart failure characterised by reduction of end-systolic pressure, stroke volume, cardiac output, and parameters of contractility. This coincided with reduced cardiomyocyte sarcomere shortening. TLR9 deficiency resulted in significant reduction of cardiac inflammation and a sustained heart function. This was consistent with reduced mortality in TLR9-D compared to WT mice. Conclusions. In polymicrobial sepsis TLR9 signalling is pivotal to cardiac inflammation and septic heart failure.

CpG-ODN attenuates pathological cardiac hypertrophy and heart failure by activation of PI3Kα-Akt signaling

Phosphoinositide-3-kinase α (PI3Kα) represents a potential novel drug target for pathological cardiac hypertrophy (PCH) and heart failure. Oligodeoxynucleotides containing CpG motifs (CpG-ODN) are classic agonists of Toll-like receptor 9 (TLR9), which typically activates PI3K-Akt signaling in immune cells; however, the role of the nucleotide TLR9 agonists in cardiac myocytes is largely unknown. Here we report that CpG-ODN C274 could both attenuate PCH and improve cardiac dysfunction by activating PI3Kα-Akt signaling cascade. In vitro studies indicated that C274 could blunt reactivation of fetal cardiac genes and cell enlargement induced by a hypertrophic agent, isoproterenol. The anti-hypertrophic effect of C274 was suppressed by a pan-PI3K inhibitor, LY294002, or a small interfering RNA targeting PI3Kα. In vivo studies demonstrated that PCH, as marked by increased heart weight (HW) and cardiac ANF mRNA, was normalized by pre-administration with C274. In addition, Doppler echocardiography detected cardiac ventricular dilation, and contractile dysfunction in isoproterenol-treated animals, consistent with massive replacement fibrosis, reflecting cardiac cell death. As expected, pre-treatment of mice with C274 could prevent cardiac dysfunction associated with diminished cardiac cell death and fibrosis. In conclusion, CpG-ODNs are novel cardioprotective agents possessing antihypertrophic and anti-cell death activity afforded by engagement of the PI3Kα-Akt signaling. CpG-ODNs may have clinical use curbing the progression of PCH and preventing heart failure.

In vivo TLR9 inhibition attenuates CpG-induced myocardial dysfunction

The involvement of toll-like receptor 9 (TLR9), a receptor for bacterial DNA, in septic cardiac depression has not been clarified in vivo. Thus, the aim of the study was to test possible TLR9 inhibitors (H154-thioate, IRS954-thioate, and chloroquine) for their ability to protect the cardiovascular system in a murine model of CpG oligodeoxynucleotide- (ODN-) dependent systemic inflammation. Sepsis was induced by i.p. application of the TLR9 agonist 1668-thioate in C57BL/6 wild type (WT) and TLR9-deficient (TLR9-D) mice. Thirty minutes after stimulation TLR9 antagonists were applied i.v. Survival was monitored up to 18 h after stimulation. Cardiac mRNA expression of inflammatory mediators was analyzed 2 h and 6 h after stimulation with 1668-thioate and hemodynamic parameters were monitored at the later time point. Stimulation with 1668-thioate induced a severe sepsis-like state with significant drop of body temperature and significantly increased mortality in WT animals. Additionally, there was a time-dependent increase of inflammatory mediators in the heart accompanied by development of septic heart failure. These effects were not observed in TLR9-D mice. Inhibition of TLR9 by the suppressive ODN H154-thioate significantly ameliorated cardiac inflammation, preserved cardiac function, and improved survival. This suppressive ODN was the most efficient inhibitor of the tested substances.

Small interfering RNA targeting Toll-like receptor 9 protects mice against polymicrobial septic acute kidney injury

BACKGROUND/AIMS

Although recent reports suggest that Toll-like receptor (TLR) 9 is associated with the pathogenesis of polymicrobial septic acute kidney injury (AKI), it is still unclear whether and how renal TLR9 is involved in the development of polymicrobial septic AKI. This study aimed to determine whether the expression of TLR9 in mouse renal cells is related to the development of polymicrobial septic AKI.

METHODS

The efficacy of small interfering RNA (siRNA) targeting TLR9 was tested in a cultured murine macrophage cell line (RAW264.7 cells). The most potent siRNA was transfected into mice using the hydrodynamic method prior to the induction of polymicrobial septic AKI being induced by cecal ligation and puncture (CLP). TLR9 knockdown was determined by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting in RAW264.7 cells and kidney tissues. The levels of serum creatinine and blood urea nitrogen (BUN) and the renal histopathology assessment were determined at 6-, 12-, and 24-hour time points after CLP, and renal cell apoptosis was studied at 24 h. The 4- and 7-day survival rates of mice were also observed.

RESULTS

We found that mice developed AKI in our model of polymicrobial sepsis, despite fluid and antibiotic resuscitation, which resembles human sepsis. siRNA to TLR9 successfully silenced the induction of renal TLR9 gene and protein expression following CLP. Effective silencing of renal TLR9 expression decreased renal cell apoptosis, mitigated the severity of AKI, and increased the survival of mice.

CONCLUSIONS

Our data demonstrates the induction of TLR9 expression in mouse kidney tissue following CLP. Renal cell apoptosis and AKI in our model of polymicrobial sepsis are dependent on TLR9. Thus, TLR9 may play a critical role in the pathophysiology of polymicrobial septic AKI.

Genomics in cardiovascular diseases: analysis of the importance of the toll-like receptor signaling pathway

The development of techniques for genomics study makes it possible for us to further our knowledge about the physiopathology of various immunological or infectious diseases. These techniques improve our understanding of the development and evolution of such diseases, including those of cardiovascular origin, whilst they help to bring about the design of new therapeutic strategies. We are reviewing the genetic alterations of immunity in said field, and focusing on the signaling pathway of toll-like receptors because not only does this play a decisive role in response to microorganisms, it is also heavily involved in modulating the inflammatory response to tissue damage, a side effect of numerous cardiovascular diseases. These alterations in tissue homeostasis are present under a wide range of circumstances, such as reperfusion ischemia (myocardial infarction) phenomena, arteriosclerosis, or valvulopathy.

Effect of prophylactically applied CpG ODN on the development of myocarditis in mice infected with Coxsackievirus B3

Coxsackievirus B3 was one of the major pathogens causing viral myocarditis. Toll-like receptor 9 activation contributed to the innate immune response in the process of CVB3-induced myocarditis. In order to find out how CpG oligodeoxynucleotide, known as a TLR-9 agonist, would affect the CVB3-induced myocarditis, we chose a C-type CpG oligodeoxynucleotide (YW002) injected to the mice one day before CVB3 challenge. On day 4 post CVB3 infection, 3 mice in each group were randomly sacrificed and their hearts were isolated to detect CVB3 replication. On day 10, the CVB3 neutralizing antibody and inflammatory change of the hearts were detected. The results indicated that the CVB3-induced myocarditis was aggravated with the declining body weight of mice, decreasing neutralizing antibody, and uncontrolling virus replication by injecting 20 μg YW002 per mouse. When adjusted the amount at 10 μg YW002 per mouse, there were no signs of aggravation in myocarditis. Plus, the mortality of the infected mice was reduced, the neutralizing antibody level was raised and the replication of virus was restrained. These results suggested that a proper amount of CpG oligodeoxynucleotide application could help to inhibit CVB3 infection.

Priming with synthetic oligonucleotides attenuates pressure overload-induced inflammation and cardiac hypertrophy in mice

AIMS

Inflammation and Toll-like receptor (TLR) signalling have been linked to the development of cardiac hypertrophy following transverse aortic constriction (TAC). In the present study, we investigated whether pre-treatment with the synthetic TLR9 ligands 1668-thioate or 1612-thioate modulates the progression of TAC-induced cardiac inflammation and hypertrophy.

METHODS AND RESULTS

C57BL/6N-mice were pre-treated with 1668-thioate, 1612-thioate (0.25 nmol/g, i.p.), or phosphate-buffered saline 16 h prior to TAC or sham surgery. Heart-weight/body-weight ratio (HW/BW), cardiomyocyte cell size, cellular macrophage accumulation, myofibroblast differentiation, and collagen deposition were investigated for up to 28 days. Cardiac function was monitored using a pressure-volume catheter and M-mode echocardiography. Inflammatory gene expression in the heart was analysed via gene array, while the time course of mRNA expression of key inflammatory mediators was assessed via RT-qPCR. TAC increased the HW/BW ratio and cardiomyocyte cell size and induced macrophage accumulation, myofibroblast differentiation, and collagen deposition. These changes were accompanied by cardiac inflammation and a significant loss of left ventricular function. Pre-treatment with cytosine-phosphate-guanine (CpG)-containing 1668-thioate attenuated the inflammatory response, the progression of cardiac hypertrophy, and cardiac remodelling, which resulted in a prolonged preservation of left ventricular function. These changes were induced to a smaller extent by the use of the non-CG-containing oligodeoxynucleotide 1612-thioate.

CONCLUSION

Pre-treatment with 1668-thioate attenuated cardiac hypertrophy following pressure overload, possibly by modifying the hypertrophy-induced inflammatory response, thereby reducing cardiac growth and fibrosis as well as delaying loss of cardiac function.

Vascular dysfunction following polymicrobial sepsis: role of pattern recognition receptors

AIMS

Aim was to elucidate the specific role of pattern recognition receptors in vascular dysfunction during polymicrobial sepsis (colon ascendens stent peritonitis, CASP).

METHODS AND RESULTS

Vascular contractility of C57BL/6 (wildtype) mice and mice deficient for Toll-like receptor 2/4/9 (TLR2-D, TLR4-D, TLR9-D) or CD14 (CD14-D) was measured 18 h following CASP. mRNA expression of pro- (Tumor Necrosis Factor-α (TNFα), Interleukin (IL)-1β, IL-6) and anti-inflammatory cytokines (IL-10) and of vascular inducible NO-Synthase (iNOS) was determined using RT-qPCR. Wildtype mice exhibited a significant loss of vascular contractility after CASP. This was aggravated in TLR2-D mice, blunted in TLR4-D animals and abolished in TLR9-D and CD14-D animals. TNF-α expression was significantly up-regulated after CASP in wildtype and TLR2-D animals, but not in mice deficient for TLR4, -9 or CD14. iNOS was significantly up-regulated in TLR2-D animals only. TLR2-D animals showed significantly higher levels of TLR4, -9 and CD14. Application of H154-ODN, a TLR9 antagonist, attenuated CASP-induced cytokine release and vascular dysfunction in wildtype mice.

CONCLUSIONS

Within our model, CD14 and TLR9 play a decisive role for the development of vascular dysfunction and thus can be effectively antagonized using H154-ODN. TLR2-D animals are more prone to polymicrobial sepsis, presumably due to up-regulation of TLR4, 9 and CD14.

[Use of the most recent reagent (CuFL) for stimulation of NO synthesis by the medicinal leech salivary cell secretion in the cultures of human endothelium cells (HUVEC) and in rat cardiomiocytes]

The medicinal leech salivary cell secretion (SCS) may stimulate NO-production in cultures of human endothelium cells (HUVEC) and rat cardiomiocytes (RCM). This effect was detected using a NO specific reagent, - the complex Cu2+ with a fluorescein derivative (Cu-Fl). NO had also been detected in the cells by fluorescent electronic microscopy and determined quantitatively in the cells and in culture fluid by the fluorescence method. SCS stimulated NO synthesis in HUVEC cells (but not in RCM) is accompanied by NO release into intercellular space. Localization of NO synthesis centers is presented and it is shown that the increase in NO levels during the SCS action on HUVEC and RCM is associated with the increase in the activity of eNOS/nNOS, but not iNOS. In endothelial cells SCS activates nitrosylation processes, assessed by the increase of nitrite-ions in the culture medium. It is therefore important to use Cu-Fl, other than Griss-reagent, during the first hour of analysis of NO synthesis. The NO-depended mechanism of SCS action on endothelial cells might be a factor in providing of its positive action in hirudotheraphy.

CpG-ODN, the TLR9 agonist, attenuates myocardial ischemia/reperfusion injury: involving activation of PI3K/Akt signaling

BACKGROUND

Toll-like receptors (TLRs) have been implicated in myocardial ischemia/reperfusion (I/R) injury. The TLR9 ligand, CpG-ODN has been reported to improve cell survival. We examined effect of CpG-ODN on myocardial I/R injury.

METHODS

Male C57BL/6 mice were treated with either CpG-ODN, control-ODN, or inhibitory CpG-ODN (iCpG-ODN) 1h prior to myocardial ischemia (60min) followed by reperfusion. Untreated mice served as I/R control (n=10/each group). Infarct size was determined by TTC straining. Cardiac function was examined by echocardiography before and after myocardial I/R up to 14days.

RESULTS

CpG-ODN administration significantly decreased infarct size by 31.4% and improved cardiac function after myocardial I/R up to 14days. Neither control-ODN nor iCpG-ODN altered I/R-induced myocardial infarction and cardiac dysfunction. CpG-ODN attenuated I/R-induced myocardial apoptosis and prevented I/R-induced decrease in Bcl2 and increase in Bax levels in the myocardium. CpG-ODN increased Akt and GSK-3β phosphorylation in the myocardium. In vitro data suggested that CpG-ODN treatment induced TLR9 tyrosine phosphorylation and promoted an association between TLR9 and the p85 subunit of PI3K. Importantly, PI3K/Akt inhibition and Akt kinase deficiency abolished CpG-ODN-induced cardioprotection.

CONCLUSION

CpG-ODN, the TLR9 ligand, induces protection against myocardial I/R injury. The mechanisms involve activation of the PI3K/Akt signaling pathway.

The Toll-like receptor 9 ligand CPG-C attenuates acute inflammatory cardiac dysfunction

Stimulation of toll-like receptor 9 (TLR9) by CpG-C containing oligonucleotides attenuates ischemic injury in the brain and liver. In this study, we investigate whether any of the three classes of CpG (A, B, or C) mitigate ischemia-induced cardiac dysfunction. We measured left ventricular ejection fraction (LVEF) in C57BL/6 mice using transthoracic echocardiography. Using LPS as an inflammatory stimulus, CpG-C was uniquely able to prevent cardiac dysfunction; its activity was confirmed through nuclear factor κB transcriptional activity assay in HL-1 cardiomyocytes. We went on to investigate CpG-C's efficacy and mechanism in the treatment of ischemia-reperfusion. Compared with baseline, no class of CpG significantly altered LVEF at 6 or 24 h; 40 mg/kg LPS induced a rapid, profound suppression of LVEF compared with baseline (26% ± 1.4% vs. 65% ± 1.4%), whereas pretreatment with CpG demonstrated that of the three classes, only CpG-C prevented the LPS -induced decrease in LVEF (51% ± 5.8%). In separate mice, 1-h ischemia followed by reperfusion of the left anterior descending artery resulted in a 7-day suppression of the LVEF (66% ± 5.2% at baseline; 46% ± 4.7% at day 1, and 46% ± 4.0% at day 7), whereas mice either pretreated with or begun on an infusion of CpG-C during the ischemia had no significant decline in LVEF. Gene expression microarray of CpG-C-stimulated cells revealed upregulation of the nuclear factor κB pathway inhibitors TNFAIP3, NFKBIA, TRIM30, and TNIP1. These may play a role in attenuation of cardiac inflammation. The TLR9 ligand CpG-C attenuates the acute inflammatory cardiac dysfunction induced by both LPS and ischemia-reperfusion of the left anterior descending artery.

Down-regulation of ATP-binding cassette transporter G1 expression by unmethylated CpG oligodeoxynucleotides in RAW 264.7 macrophages

We have investigated the effect of various forms of phosphodiester cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs) on the production of pro-inflammatory cytokines and related genes in RAW 264.7 macrophages. Treatment with the CpG ODNs increased the expression of tumor necrosis factor α (TNF-α), IL-6, and inducible nitric oxide synthase but not interleukin-1β (IL-1β). We also investigated the effect of CpG ODNs on the expression of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) genes which are known to facilitate cholesterol efflux from macrophages for anti-atherosclerosis. CpG 2006 significantly reduced the levels of ABCG1 mRNA as determined by real-time polymerase chain reaction, whereas ABCA1 mRNA level was not changed. Western blot analysis further confirmed the reduction of ABCG1 protein expression by CpG 2006. In addition, we also determined the protein level of peroxisome proliferator activated receptor γ (PPARγ), which is recognized as a transcriptional activator of ABC transporters, was also reduced by CpG 2006. Thus, these results suggest that ABCG1 is specifically down-regulated by CpG 2006 in a PPARγ-dependent manner in macrophages.