Variants of Toll-like receptor 4 predict cardiac recovery in patients with dilated cardiomyopathy

Systematic Review, Meta-Analysis, and Population Study to Determine the Biologic Sex Ratio in Dilated Cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) appears to be diagnosed twice as often in male than in female patients. This could be attributed to underdiagnosis in female patients or sex differences in susceptibility. Up to 30% of cases have an autosomal dominant monogenic cause, where equal sex prevalence would be expected. The aim of this systematic review, meta-analysis, and population study was to assess the sex ratio in patients with DCM, stratified by genetic status, and evaluate whether this is influenced by diagnostic bias.

METHODS

A literature search identified DCM patient cohorts with discernible sex ratios. Exclusion criteria were studies with a small (n<100), pediatric, or peripartum population. Meta-analysis and metaregression compared the proportion of female participants for an overall DCM cohort and the following subtypes: all genetic DCM, individual selected DCM genes (TTN and LMNA), and gene-elusive DCM. Population DCM sex ratios generated from diagnostic codes were also compared with those from sex-specific means using the UK Biobank imaging cohort; this established ICD coded, novel imaging-first, and genotype first determined sex ratios.

RESULTS

A total of 99 studies, with 37 525 participants, were included. The overall DCM cohort had a 0.30 female proportion (95% CI, 0.28-0.32), corresponding to a male:female ratio (M:F) of 2.38:1. This was similar to patients with an identified DCM variant (0.31 [95% CI, 0.26-0.36]; M:F 2.22:1; P=0.56). There was also no significant difference when compared with patients with gene-elusive DCM (0.30 [95% CI, 0.24-0.37]; M:F 2.29:1; P=0.81). Furthermore, the ratio within autosomal dominant gene variants was not significantly different for TTN (0.28 [95% CI, 0.22-0.36]; M:F 2.51:1; P=0.82) or LMNA (0.35 [95% CI, 0.27-0.44]; M:F 1.84:1; P=0.41). Overall, the sex ratio for DCM in people with disease attributed to autosomal dominant gene variants was similar to the all-cause group (0.34 [95% CI, 0.28-0.40]; M:F 1.98:1; P=0.19). In the UK Biobank (n=47 549), DCM defined by International Classification of Diseases, 10th revision, coding had 4.5:1 M:F. However, implementing sex-specific imaging-first and genotype-first diagnostic approaches changed this to 1.7:1 and 2.3:1, respectively.

CONCLUSIONS

This study demonstrates that DCM is twice as prevalent in male patients. This was partially mitigated by implementing sex-specific DCM diagnostic criteria. The persistent male excess in genotype-positive patients with an equally prevalent genetic risk suggests additional genetic or environmental drivers for sex-biased penetrance.

REGISTRATION

URL: https://www.crd.york.ac.uk/prospero; Unique identifier: CRD42023451944.

Myeloid differentiation factor-2 activates monocytes in patients with dilated cardiomyopathy

Plasma levels of myeloid differentiation factor-2 (MD-2), a co-receptor of toll-like-receptor 4 (TLR4), independently predict mortality in patients with dilated cardiomyopathy (DCM). We tested whether monocyte-activation by MD-2 contributes to immune activation and inflammatory status in DCM patients. We found increased MD-2 plasma-levels in 25 patients with recent-onset DCM (1,250±80.7 ng/ml) compared to 25 age- and gender-matched healthy controls (793.4±52.0 ng/ml; p<0.001). Monocytes isolated from DCM-patients showed a higher expression (141.7±12.4 %; p=0.006 vs. controls) of the MD-2 encoding gene, LY96, and an increased NF-κB-activation. Further, the TLR4-activator lipopolysaccharide (LPS) caused a higher increase in interleukin (IL)-6 in monocytes from DCM-patients compared to controls (mean fluorescence intensity: 938.7±151.0 vs. 466.9±51.1; p=0.005). MD-2 increased IL-6 secretion in a TLR4/NF-κB-dependent manner in monocyte-like THP-1-cells as demonstrated by TLR4-siRNA and NF-κB-inhibition. Since endothelial cells (ECs) are responsible for recruiting monocytes to the site of inflammation, ECs were treated with MD-2 leading to an activation of Akt and increased secretion of monocyte-chemoattractant-protein-1 (MCP-1). Activation of ECs by MD-2 was accompanied by an increased expression of the adhesion-molecules CD54, CD106, and CD62E, resulting in an increased monocyte-recruitment, which was attenuated by CD54-inhibition. In addition, in murine WT but not LY96-KO bone marrow-derived macrophages LPS increased the amount of CD54 and CD49d/CD29. MD-2 facilitates a pro-inflammatory status of monocytes and EC-mediated monocyte-recruitment via TLR4/NF-κB. Elevated MD-2 plasma-levels are possibly involved in monocyte-related inflammation promoting disease-progression in DCM. Our results suggest that MD-2 contributes to increasing monocytic inflammatory activity and triggers recruitment of monocytes to ECs in DCM. This article is protected by copyright. All rights reserved.

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.

TLR4 Activation Promotes the Progression of Experimental Autoimmune Myocarditis to Dilated Cardiomyopathy by Inducing Mitochondrial Dynamic Imbalance

Mitochondrial dynamic imbalance associates with several cardiovascular diseases. However, the role of mitochondrial dynamics in TLR4 activation-mediated dilated cardiomyopathy (DCM) progress remains unknown. A model of experimental autoimmune myocarditis (EAM) was established in BALB/c mice on which TLR4 activation by LPS-EB or TLR4 inhibition by LPS-RS was performed to induce chronic inflammation for 5 weeks. TLR4 activation promoted the transition of EAM to DCM as demonstrated by increased cardiomyocyte apoptosis, myocardial fibrosis, ventricular dilatation, and declined heart function. TLR4 inhibition mitigated the above DCM changes. Transmission electron microscope study showed that mitochondria became fragmented, also with damaged crista in ultrastructure in EAM mice. TLR4 activation aggravated the above mitochondrial aberration, and TLR4 inhibition alleviated it. The mitochondrial dynamic imbalance and damage in DCM development were mainly associated with OPA1 downregulation, which may be caused by elevated TNF-α level and ROS stress after TLR4 activation. Furthermore, OMA1/YME1L abnormal degradation was involved in the OPA1 dysfunction, and intervening OMA1/YME1L in H9C2 significantly alleviated mitochondrial fission, ultrastructure damage, and cell apoptosis induced by TNF-α and ROS. These data indicate that TLR4 activation resulted in OPA1 dysfunction, promoting mitochondrial dynamic imbalance and damage, which may involve in the progress of EAM to DCM.

Toll-like receptor expression and apoptosis morphological patterns in female rat hearts with takotsubo syndrome induced by isoprenaline

AIMS

Toll-like receptors (TLR) and apoptosis were indicated as important factors in heart failure. Our aim was to characterize the morphological pattern of apoptosis, TLR2, TLR4, and TLR6 expression in female rat hearts in the model of takotsubo syndrome (TTS).

MAIN METHODS

60 Sprague-Dawley female rats were treated with a single dose of 150 mg/kg b.wt. of isoprenaline (ISO) or 0.9% NaCl (controls). Hearts were collected 24, 48, 72 h and 7 days post-ISO injection. 32/60 hearts were used in immunohistopathological studies and 28/60 in real time.

KEY FINDINGS

Apoptosis was observed 24 h post-ISO in cardiomyocytes, 24, 48, 72 h and 7 days post-ISO in infiltrating inflammatory cells, 7 days post-ISO in endothelial cells of vessels. Diffuse TLR4CD68 (CD68, a macrophage marker) and TLR6CD68 positive cells and TLR2, TLR4, TLR6 mononuclear cells were observed in both acute and recovery phase of TTS. In the foci located in the neighborhood of damaged (necrotic/apoptotic) cardiomyocytes in TTS, high (strong) protein expression of TLR2 (TLR2^high) was observed: 24, 48, 72 h post-ISO; TLR4^high - 48 and 72 h post-ISO; TLR6^high - 48 h post-ISO. Whereas in cardiomyocytes of remote myocardium: TLR2^high - 72 h post-ISO; TLR4^high - 24 and 72 h post-ISO; TLR6^high - 24 h post-ISO. TLR2 mRNA was down-regulated 48 and 72 h post-ISO whereas TLR4 up-regulated 7 days post-ISO.

SIGNIFICANCE

The expression pattern of apoptosis and TLR differs in the course of TTS in comparison with the control rats. We hypothesize that innate immunity and apoptosis may play a crucial role in TTS pathophysiology.

The Quest for New Approaches in Myocarditis and Inflammatory Cardiomyopathy

Myocarditis is a diverse group of heart-specific immune processes classified by clinical and histopathological manifestations. Up to 40% of dilated cardiomyopathy is associated with inflammation or viral infection. Recent experimental studies revealed complex regulatory roles for several microribonucleic acids and T-cell and macrophage subtypes. Although the prevalence of myocarditis remained stable between 1990 and 2013 at about 22 per 100,000 people, overall mortality from cardiomyopathy and myocarditis has decreased since 2005. The diagnostic and prognostic value of cardiac magnetic resonance has increased with new, higher-sensitivity sequences. Positron emission tomography has emerged as a useful tool for diagnosis of cardiac sarcoidosis. The sensitivity of endomyocardial biopsy may be increased, especially in suspected sarcoidosis, by the use of electrogram guidance to target regions of abnormal signal. Investigational treatments on the basis of mechanistic advances are entering clinical trials. Revised management recommendations regarding athletic participation after acute myocarditis have heightened the importance of early diagnosis.

Lack of Association Between Polymorphism rs4986791 in TLR4 and Primary Open-Angle Glaucoma in a Saudi Cohort

AIMS

To investigate whether single nucleotide polymorphism (SNP) rs4986791 (C>T) in the toll-like receptor 4 (TLR4) gene is a risk factor for primary open-angle glaucoma (POAG) in the Saudi population.

METHOD

A case-control study was performed to genotype a cohort of 85 POAG patients and 95 matched healthy controls utilizing TaqMan(®). The association between mutant genotypes and various POAG clinical indices were investigated.

RESULTS

The wild-type (C/C), heterozygous (C/T), and homozygous (T/T) genotypes were observed in 85.9%, 12.9%, and 1.2% POAG cases, respectively, compared to 91.6%, 8.4%, and none, respectively, among controls. The minor allele frequency was 0.076 in cases and 0.042 in controls. Both the genotype and allele frequency among POAG cases and controls did not vary significantly. With the exception of family history of glaucoma (p = 0.032), no significant association of genotypes was seen with age, intraocular pressure, cup/disc ratio, number of antiglaucoma medications, and other systemic comorbidities among the POAG cases.

CONCLUSION

We did not detect any direct association between genotypes or allele frequencies of SNP rs4986791 in the TLR4 gene and POAG.

The Toll of Vascular Insufficiency: Implications for the Management of Peripheral Arterial Disease

Peripheral artery disease (PAD) can result in limb loss within six months of diagnosis in a subset of patients who cannot undergo endovascular or surgical revascularization yet continues to maintain a marginal position in cardiovascular research. While a body of literature continues to grow describing the role of danger signaling and innate immunity in cardiac biology, the role of these pathways in the ischemic myopathy associated with PAD has not been extensively studied. The following report will review the current literature on the role of Toll-like receptor (TLR) signaling in cardiovascular biology as well as in nonischemic myopathy. While attenuation of TLR signaling has not been shown to be clinically useful in the treatment of infectious inflammation, it may show promise in the management of severe arterial insufficiency.

Innate immune receptors in heart failure: Side effect or potential therapeutic target?

Heart failure (HF) is a leading cause of mortality and morbidity in western countries and occasions major expenses for public health systems. Although optimal medical treatment is widely available according to current guidelines, the prognosis of patients with HF is still poor. Despite the etiology of the disease, increased systemic or cardiac activation of the innate immune system is well documented in several types of HF. In some cases there is evidence of an association between innate immune activation and clinical outcome of patients with this disease. However, the few large trials conducted with the use of anti-inflammatory medication in HF have not revealed its benefits. Thus, greater understanding of the relationship between alteration in the immune system and development and progression of HF is urgently necessary: prior to designing therapeutic interventions that target pathological inflammatory processes in preventing harmful cardiac effects of immune modulatory therapy. In this regard, relatively recently discovered receptors of the innate immune system, i.e., namely toll-like receptors (TLRs) and nod-like receptors (NLRs)-are the focus of intense cardiovascular research. These receptors are main up-stream regulators of cytokine activation. This review will focus on current knowledge of the role of TLRs and NLRs, as well as on downstream cytokine activation, and will discuss potential therapeutic implications.

Stiffness of left ventricular cardiac fibroblasts is associated with ventricular dilation in patients with recent-onset nonischemic and nonvalvular cardiomyopathy

BACKGROUND

Ventricular dilation is known as a pivotal predictor in recent-onset cardiomyopathy (ROCM), but its pathophysiology is not fully understood. In the present study we investigated whether single-cell stiffness of right and left ventricular-derived fibroblasts has an effect on cardiac phenotype in patients with ROCM.

METHODS AND RESULTS

Patients with endomyocardial biopsy-proven ROCM were included (n=10). Primary cardiac fibroblasts (CFBs) were cultured from left and right ventricular endomyocardial biopsies and their single-cell stiffness was analyzed by quantification of Young's modulus using colloidal probe atomic force microscopy. Cardiac fibrosis was analyzed by Masson's trichrome staining. CFBs from the left ventricle showed significantly decreased stiffness when compared with CFBs from the right ventricle, indexed by decreased stiffness (Young's modulus 3,374±389 vs. 4,837±690 Pa; P<0.05). Young's modulus of CFBs derived from the left ventricle correlated negatively with the left ventricular end-diastolic dimension derived from 2-dimensional echocardiography (R(2)=0.77; P<0.01). Neither left nor right ventricular fibrosis correlated with the respective ventricular dimensions.

CONCLUSIONS

Our data suggest that a decrease in single-cell stiffness of left ventricular fibroblasts could trigger left ventricular dilation in patients with ROCM. This implies a new potential mechanism for the ventricular dilation with this disease.

Almanac 2014: cardiomyopathies

Cardiomyopathies are myocardial disorders that are not explained by abnormal loading conditions and coronary artery disease. They are classified into a number of morphological and functional phenotypes that can be caused by genetic and non-genetic mechanisms. The dominant themes in papers published in 2012-2013 are similar to those reported in Almanac 2011, namely, the use (and interpretation) of genetic testing, development and application of novel non-invasive imaging techniques and use of serum biomarkers for diagnosis and prognosis. An important innovation since the last Almanac is the development of more sophisticated models for predicting adverse clinical events.

Therapeutic administration of the chemokine CXCL1/KC abrogates autoimmune inflammatory heart disease

Myocarditis, often due to an aberrant immune response to infection, is a major cause of dilated cardiomyopathy. Microbial pattern recognition receptors, such as TLRs, orchestrate the cytokine and chemokine responses that augment or limit the severity of myocarditis. Using the mouse model of experimental autoimmune myocarditis (EAM), in which disease is induced by immunization with a heart-specific self peptide and the agonist to multiple TLRs, complete Freund's adjuvant, we found that increased serum concentrations of the chemokine CXCL1/KC correlated directly with decreased severity of myocarditis. To directly test whether CXCL1/KC caused the amelioration of myocarditis, we treated mice, after challenge with heart-specific self peptide, with exogenous recombinant CXCL1/KC. We found that the administration of recombinant mouse CXCL1/KC completely abrogated heart inflammatory infiltration and cardiomyocyte damage. Moreover, we show that TLR4 signaling is required to increase serum protein concentrations of CXCL1/KC in EAM, and we demonstrate that the administration of the TLR4 agonist LPS significantly decreased severity and prevalence of EAM and reduced the number of heart-specific self peptide reactive effector T cells. These findings reveal a novel function of CXCL1/KC in the context of organ-specific autoimmune disease that may prove useful for the treatment of inflammatory conditions that underlie human heart disease.

Activation of toll-like receptors and inflammasome complexes in the diabetic cardiomyopathy-associated inflammation

Diabetic cardiomyopathy is defined as a ventricular dysfunction initiated by alterations in cardiac energy substrates in the absence of coronary artery disease and hypertension. Hyperglycemia, hyperlipidemia, and insulin resistance are major inducers of the chronic low-grade inflammatory state that characterizes the diabetic heart. Cardiac Toll-like receptors and inflammasome complexes may be key inducers for inflammation probably through NF-κB activation and ROS overproduction. However, metabolic dysregulated factors such as peroxisome proliferator-activated receptors and sirtuins may serve as therapeutic targets to control this response by mitigating both Toll-like receptors and inflammasome signaling.

HMGB1 and TLR4 mediate skeletal muscle recovery in a murine model of hindlimb ischemia

BACKGROUND

We have previously shown that the danger signal high-mobility group box 1 (HMGB1) promotes angiogenesis when administered to ischemic muscle. HMGB1 signals through Toll-like receptor 4 (TLR4) as well as the receptor for advanced glycation end-products (RAGE). However, the actions of these receptors in ischemic injury and muscle recovery are not known. We hypothesize that TLR4 mediates tissue recovery and angiogenesis in response to ischemia.

METHODS

Femoral artery ligation was performed in control, TLR4 competent (C3H/HeOuJ) and incompetent (C3H/HeJ) mice, as well as RAGE knockout mice and their C57B6 control counterparts. In other experiments, control mice were pretreated with anti-HMGB1 neutralizing antibody before femoral artery ligation. After 2 weeks, limb perfusion was evaluated using laser Doppler perfusion imaging and reported as the ratio of blood flow in the ischemic to nonischemic limb. Muscle necrosis, fat replacement, and vascular density in the anterior tibialis muscle were quantified histologically. In vitro, TLR4 and RAGE expression was evaluated in human dermal microvascular endothelial cells in response to hypoxia. Human dermal microvascular endothelial cells treated with HMGB1 alone and in the presence of anti-TLR4 antibody were probed for phosphorylated extracellular signal-regulated kinase (ERK), a signaling molecule critical to endothelial cell (EC) angiogenic behavior.

RESULTS

Both anti-HMGB1 antibody as well as defective TLR4 signaling in HeJ mice resulted in prominent muscle necrosis 2 weeks after femoral artery ligation. Control HeOuJ mice had less necrosis than TLR4 incompetent HeJ mice, but a greater amount of fat replacement. In contrast to control C3H mice, control C57B6 mice demonstrated prominent muscle regeneration with very little necrosis. Muscle regeneration was not dependent on RAGE. While vascular density did not differ between strains, mice with intact RAGE and TLR4 signaling had less blood flow in ischemic limbs compared with mutant strains. In vitro, EC TLR4 expression increased in response to hypoxia while TLR4 antagonism decreased HMGB1-induced activation of extracellular signal-regulated kinase.

CONCLUSIONS

Both HMGB1 and TLR4 protect against muscle necrosis after hindlimb ischemia. However, muscle regeneration does not appear to be tied to vascular density. HMGB1 likely activates angiogenic behavior in ECs in vitro, and this activation may be modulated by TLR4. The improvement in blood flow seen in mice with absent TLR4 and RAGE signaling may suggest anti-angiogenic roles for both receptors, or vasoconstriction induced by TLR4 and RAGE mediated inflammatory pathways.

Initial white blood cell count is an independent risk factor for survival in patients with dilated cardiomyopathy

BACKGROUND

The impact of white blood cell count (WBCc) on the outcome of patients with non-ischemic left ventricular (LV) dysfunction is unknown. In the present study we investigated the influence of WBCc on mortality and cardiac inflammation in patients with reduced LV systolic function in the absence of ischemic or valvular etiology.

METHODS AND RESULTS

We included 381 patients with reduced left ventricular (LV) ejection fraction (LVEF ≤ 45%) quantified by two-dimensional echocardiography. Coronary artery disease and valvular diseases were excluded by angiography and echo, respectively, in all patients. WBCc was quantified routinely upon first hospital admission. In 291 patients, endomyocardial biopsies from the right ventricle were performed upon first hospital admission for assessment of cardiac inflammation. Follow-up was up to 5.5 years (median 2.93 [1.7;4.0]). Information on vital status of patients was obtained from official resident data files. WBCc >11 Gpt/l was associated with significantly increased mortality in patients with severe LV dilation (end-diastolic diameter (LVEDD) >70 mm quantified by echocardiography) in comparison to patients showing WBCc ≤ 11 Gpt/l (41.7% vs 13.6%, p=0.02). Multivariable Cox regression analysis showed that WBCc predicts mortality independently of other cardiovascular risk factors and LVEF (hazard ratio 1.14; p=0.04). Doses of heart failure medication did not differ significantly in patients with LVEDD >70 mm and WBCc >11 Gpt/l when compared to LVEDD >70 mm and WBCc ≤ 11 Gpt/l (percent of maximum doses: ß-blockers p=0.51, ACE inhibitors p=0.56, AT1 antagonists p=0.77, aldosterone antagonists p=0.35). WBCc including its subpopulations (monocytes, lymphocytes and granulocytes) did not show a significant correlation with cardiac amounts of CD3(+)-lymphocytes (r=0.02, p=0.78) or CD68(+)-macrophages (r=1.0, p=0.09) (n=291).

CONCLUSION

WBCc at first hospital admission predicts long term-mortality in patients with dilated cardiomyopathy independently of cardiovascular risk factors.