Ventricular TLR4 Levels Abrogate TLR2-Mediated Adverse Cardiac Remodeling upon Pressure Overload in Mice

Toll-like receptor 2 deficiency ameliorates obesity-induced cardiomyopathy via inhibiting NF-κB signaling pathway

Growing evidence demonstrates that chronic low-grade inflammation, which is induced by high-fat diet (HFD) or saturated fatty acid, plays an important role in the obesity-induced cardiomyopathy (OIC) process. Moreover, obesity is associated with the activation of different inflammatory pathways, including nuclear factor-κB (NF-κB), Toll-like-receptor-2 (TLR2) and Toll-like-receptor-4 (TLR4). In this study, we established an HFD-induced cardiac injury mouse model and palmitate (PA)-induced myocardial cell model to evaluate the role of TLR2 in OIC. Our data show that TLR2 blockade using TLR2 knockout (KO) mice or a TLR2-specific inhibitor, C29, markedly ameliorated HFD- or PA-induced inflammation, myocardial fibrosis, and hypertrophy both in vivo and in vitro. Moreover, the PA-induced myocardial cell injury was mediated via inducing the formation of TLR2-MyD88 complex in a TLR4-independent manner in cardiomyocytes. Our data prove the critical role of cardiac TLR2 in the pathogenesis of HFD- and saturated fatty acid-induced myocarditis, fibrosis, myocardial hypertrophy, and cardiac dysfunction. Inhibition of TLR2 pathway may be a therapeutic strategy of OIC.

Toll-like Receptor 4 Differentially Modulates Cardiac Function in Response to Chronic Exposure to High-Fat Diet and Pressure Overload

BACKGROUND/AIM

The impact of myocardial stressors such as high-fat diet (HFD) and pressure overload has been extensively studied. Toll-like receptor 4 (TLR4) deficiency has been suggested to have a protective role in response to these stressors, although some conflicting data exist. Furthermore, there is limited information about the role of TLR4 on cardiac remodeling in response to long-term exposure to stressors. This study aims to investigate the effects of TLR4 deficiency on cardiac histology and physiology in response to chronic stressors.

METHODS

TLR4-deficient (TLR4-/-) and wild-type (WT) mice were subjected to either HFD or a normal diet (ND) for 28 weeks. Another group underwent abdominal aortic constriction (AAC) or a sham procedure and was monitored for 12 weeks. Inflammatory markers, histology, and echocardiography were used to assess the effects of these interventions.

RESULTS

TLR4-/- mice exhibited reduced cardiac hypertrophy and fibrosis after long-term HFD exposure compared to ND without affecting cardiac function. On the other hand, TLR4 deficiency worsened cardiac function in response to AAC, leading to decreased ejection fraction (EF%) and increased end-systolic volume (ESV).

CONCLUSIONS

TLR4 deficiency provided protection against HFD-induced myocardial inflammation but impaired hemodynamic cardiac function under pressure overload conditions. These findings highlight the crucial role of TLR4 and its downstream signaling pathway in maintaining cardiac output during physiologic cardiac hypertrophy in response to pressure overload.

The Chinese herbal medicine Fufang Zhenzhu Tiaozhi ameliorates diabetic cardiomyopathy by regulating cardiac abnormal lipid metabolism and mitochondrial dynamics in diabetic mice

Diabetic cardiomyopathy (DCM) is an important complication leading to the death of patients with diabetes, but there is no effective strategy for clinical treatments. Fufang Zhenzhu Tiaozhi (FTZ) is a patent medicine that is a traditional Chinese medicine compound preparation with comprehensive effects for the prevention and treatment of glycolipid metabolic diseases under the guidance of "modulating liver, starting pivot and cleaning turbidity". FTZ was proposed by Professor Guo Jiao and is used for the clinical treatment of hyperlipidemia. This study was designed to explore the regulatory mechanisms of FTZ on heart lipid metabolism dysfunction and mitochondrial dynamics disorder in mice with DCM, and it provides a theoretical basis for the myocardial protective effect of FTZ in diabetes. In this study, we demonstrated that FTZ protected heart function in DCM mice and downregulated the overexpression of free fatty acids (FFAs) uptake-related proteins cluster of differentiation 36 (CD36), fatty acid binding protein 3 (FABP3) and carnitine palmitoyl transferase 1 (CPT1). Moreover, FTZ treatment showed a regulatory effect on mitochondrial dynamics by inhibiting mitochondrial fission and promoting mitochondrial fusion. We also identified in vitro that FTZ could restore lipid metabolism-related proteins, mitochondrial dynamics-related proteins and mitochondrial energy metabolism in PA-treated cardiomyocytes. Our study indicated that FTZ improves the cardiac function of diabetic mice by attenuating the increase in fasting blood glucose levels, inhibiting the decrease in body weight, alleviating disordered lipid metabolism, and restoring mitochondrial dynamics and myocardial apoptosis in diabetic mouse hearts.

Impact of myeloid differentiation protein 1 on cardiovascular disease

Cardiovascular disease remains the leading cause of disability and mortality worldwide and a significant global burden. Many lines of evidence suggest complex remodeling responses to cardiovascular disease, such as myocardial ischemia, hypertension and valve disease, which lead to poor clinical outcomes, including heart failure, arrhythmia and sudden cardiac death (SCD). The mechanisms underlying cardiac remodeling are closely related to reactive oxygen species (ROS) and inflammation. Myeloid differentiation protein 1 (MD1) is a secreted glycoprotein known as lymphocyte antigen 86. The complex of MD1 and radioprotective 105 (RP105) is an important regulator of inflammation and is involved in the modulation of vascular remodeling and atherosclerotic plaque development. A recent study suggested that the expression of MD1 in hypertrophic cardiomyopathy (HCM) patients is decreased compared with that in donor hearts. Therefore, MD1 may play an important role in the pathological processes of cardiovascular disease and have potential clinical value. Here, this review aims to discuss the current knowledge regarding the role of MD1 in the regulation of cardiac pathophysiology.

A Simplified Herbal Formula Improves Cardiac Function and Reduces Inflammation in Mice Through the TLR-Mediated NF-κB Signaling Pathway

Nuanxinkang tablet (NXK), a Chinese herbal formula, can improve heart function and quality of life in patients with chronic heart failure (CHF). However, the mechanisms of action of NXK are not fully understood. In this study, we investigated the effects of NXK on inflammation in the CHF mouse model. This model was established by transverse aortic constriction (TAC) and treated with NXK for 8 weeks. Then, the cardiac function and myocardial fibrosis were evaluated. The monocytes/macrophages were evaluated by immunofluorescence. The mRNA levels of IL-1β, IL-6, TNF-α, ICAM-1, and VCAM-1 were measured by quantitative real-time polymerase chain reaction (qRT-PCR), while TLR4, MyD88, NF-κB p65, P-IκBα, TLR2, TLR7 and TLR9 protein levels were evaluated by Western blot. The results showed that NXK improved the left ventricular ejection fraction (LVEF) and left ventricular end-systolic dimension, reversed myocardial fibrosis, and inhibited pro-inflammatory (CD11b + Ly6C+) monocytes/macrophages in the TAC mouse model. NXK also reduced the mRNA and protein levels of the above markers. Taken together, NXK improved heart function and reduced inflammation through the TLR-mediated NF-κB signaling pathway, suggesting that it might be used as an innovative treatment strategy for CHF.

Clinical Phenotypes of Heart Failure With Preserved Ejection Fraction to Select Preclinical Animal Models

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To better define HFpEF clinically, patients are nowadays often clustered into phenogroups, based on their comorbidities and symptoms

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Many animal models claim to mimic HFpEF, but phenogroups are not yet regularly used to cluster them

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HFpEF animals models often lack reports of clinical symptoms of HF, therefore mainly presenting as extended models of LVDD, clinically seen as a prestate of HFpEF

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We investigated if clinically relevant phenogroups can guide selection of animal models aiming at better defined animal research

At least one-half of the growing heart failure population consists of heart failure with preserved ejection fraction (HFpEF). The limited therapeutic options, the complexity of the syndrome, and many related comorbidities emphasize the need for adequate experimental animal models to study the etiology of HFpEF, as well as its comorbidities and pathophysiological changes. The strengths and weaknesses of available animal models have been reviewed extensively with the general consensus that a “1-size-fits-all” model does not exist, because no uniform HFpEF patient exists. In fact, HFpEF patients have been categorized into HFpEF phenogroups based on comorbidities and symptoms. In this review, we therefore study which animal model is best suited to study the different phenogroups—to improve model selection and refinement of animal research. Based on the published data, we extrapolated human HFpEF phenogroups into 3 animal phenogroups (containing small and large animals) based on reports and definitions of the authors: animal models with high (cardiac) age (phenogroup aging); animal models focusing on hypertension and kidney dysfunction (phenogroup hypertension/kidney failure); and models with hypertension, obesity, and type 2 diabetes mellitus (phenogroup cardiometabolic syndrome). We subsequently evaluated characteristics of HFpEF, such as left ventricular diastolic dysfunction parameters, systemic inflammation, cardiac fibrosis, and sex-specificity in the different models. Finally, we scored these parameters concluded how to best apply these models. Based on our findings, we propose an easy-to-use classification for future animal research based on clinical phenogroups of interest.