Tumor necrosis factor: a mechanistic link between angiotensin-II-induced cardiac inflammation and fibrosis

Cardiac and perivascular myofibroblasts, matrifibrocytes, and immune fibrocytes in hypertension; commonalities and differences with other cardiovascular diseases

Hypertension is a major cause of cardiovascular diseases such as myocardial infarction and stroke. Cardiovascular fibrosis occurs with hypertension and contributes to vascular resistance, aortic stiffness, and cardiac hypertrophy. However, the molecular mechanisms leading to fibroblast activation in hypertension remain largely unknown. There are two types of fibrosis: replacement fibrosis and reactive fibrosis. Replacement fibrosis occurs in response to the loss of viable tissue to form a scar. Reactive fibrosis occurs in response to an increase in mechanical and neurohormonal stress. Although both types of fibrosis are considered adaptive processes, they become maladaptive when the tissue loss is too large, or the stress persists. Myofibroblasts represent a subpopulation of activated fibroblasts that have gained contractile function to promote wound healing. Therefore, myofibroblasts are a critical cell type that promotes replacement fibrosis. Although myofibroblasts were recognized as the fibroblasts participating in reactive fibrosis, recent experimental evidence indicated there are distinct fibroblast populations in cardiovascular reactive fibrosis. Accordingly, we will discuss the updated definition of fibroblast subpopulations, the regulatory mechanisms, and their potential roles in cardiovascular pathophysiology utilizing new knowledge from various lineage tracing and single-cell RNA sequencing studies. Among the fibroblast subpopulations, we will highlight the novel roles of matrifibrocytes and immune fibrocytes in cardiovascular fibrosis including experimental models of hypertension, pressure overload, myocardial infarction, atherosclerosis, aortic aneurysm, and nephrosclerosis. Exploration into the molecular mechanisms involved in the differentiation and activation of those fibroblast subpopulations may lead to novel treatments for end-organ damage associated with hypertension and other cardiovascular diseases.

Cardiac fibrogenesis: an immuno-metabolic perspective

Cardiac fibrosis is a major and complex pathophysiological process that ultimately culminates in cardiac dysfunction and heart failure. This phenomenon includes not only the replacement of the damaged tissue by a fibrotic scar produced by activated fibroblasts/myofibroblasts but also a spatiotemporal alteration of the structural, biochemical, and biomechanical parameters in the ventricular wall, eliciting a reactive remodeling process. Though mechanical stress, post-infarct homeostatic imbalances, and neurohormonal activation are classically attributed to cardiac fibrosis, emerging evidence that supports the roles of immune system modulation, inflammation, and metabolic dysregulation in the initiation and progression of cardiac fibrogenesis has been reported. Adaptive changes, immune cell phenoconversions, and metabolic shifts in the cardiac nonmyocyte population provide initial protection, but persistent altered metabolic demand eventually contributes to adverse remodeling of the heart. Altered energy metabolism, mitochondrial dysfunction, various immune cells, immune mediators, and cross-talks between the immune cells and cardiomyocytes play crucial roles in orchestrating the transdifferentiation of fibroblasts and ensuing fibrotic remodeling of the heart. Manipulation of the metabolic plasticity, fibroblast-myofibroblast transition, and modulation of the immune response may hold promise for favorably modulating the fibrotic response following different cardiovascular pathological processes. Although the immunologic and metabolic perspectives of fibrosis in the heart are being reported in the literature, they lack a comprehensive sketch bridging these two arenas and illustrating the synchrony between them. This review aims to provide a comprehensive overview of the intricate relationship between different cardiac immune cells and metabolic pathways as well as summarizes the current understanding of the involvement of immune-metabolic pathways in cardiac fibrosis and attempts to identify some of the previously unaddressed questions that require further investigation. Moreover, the potential therapeutic strategies and emerging pharmacological interventions, including immune and metabolic modulators, that show promise in preventing or attenuating cardiac fibrosis and restoring cardiac function will be discussed.

GPCRs and fibroblast heterogeneity in fibroblast-associated diseases

G protein-coupled receptors (GPCRs) are the largest and most diverse class of signaling receptors. GPCRs regulate many functions in the human body and have earned the title of "most targeted receptors". About one-third of the commercially available drugs for various diseases target the GPCRs. Fibroblasts lay the architectural skeleton of the body, and play a key role in supporting the growth, maintenance, and repair of almost all tissues by responding to the cellular cues via diverse and intricate GPCR signaling pathways. This review discusses the dynamic architecture of the GPCRs and their intertwined signaling in pathological conditions such as idiopathic pulmonary fibrosis, cardiac fibrosis, pancreatic fibrosis, hepatic fibrosis, and cancer as opposed to the GPCR signaling of fibroblasts in physiological conditions. Understanding the dynamics of GPCR signaling in fibroblasts with disease progression can help in the recognition of the complex interplay of different GPCR subtypes in fibroblast-mediated diseases. This review highlights the importance of designing and adaptation of next-generation strategies such as GPCR-omics, focused target identification, polypharmacology, and effective personalized medicine approaches to achieve better therapeutic outcomes for fibrosis and fibrosis associated malignancies.

TNF superfamily control of tissue remodeling and fibrosis

Fibrosis is the result of extracellular matrix protein deposition and remains a leading cause of death in USA. Despite major advances in recent years, there remains an unmet need to develop therapeutic options that can effectively degrade or reverse fibrosis. The tumor necrosis super family (TNFSF) members, previously studied for their roles in inflammation and cell death, now represent attractive therapeutic targets for fibrotic diseases. In this review, we will summarize select TNFSF and their involvement in fibrosis of the lungs, the heart, the skin, the gastrointestinal tract, the kidney, and the liver. We will emphasize their direct activity on epithelial cells, fibroblasts, and smooth muscle cells. We will further report on major clinical trials targeting these ligands. Whether in isolation or in combination with other anti-TNFSF member or treatment, targeting this superfamily remains key to improve efficacy and selectivity of currently available therapies for fibrosis.

Rapid kidney function decline and increased risk of heart failure in patients with type 2 diabetes: findings from the ACCORD cohort : Rapid kidney function decline and heart failure in T2D

BACKGROUND

Impaired kidney function and albuminuria are associated with increased risk of heart failure (HF) in patients with type 2 diabetes (T2D). We investigated whether rapid kidney function decline over time is an additional determinant of increased HF risk in patients with T2D, independent of baseline kidney function, albuminuria, and other HF predictors.

METHODS

Included in the study were 7,539 participants in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study with baseline urinary albumin-to-creatinine ratio (UACR) data, who had completed 4 years of follow-up and had ≥ 3 eGFR measurements during that period (median eGFR/year = 1.9, IQR 1.7-3.2). The association between rapid kidney function decline (eGFR loss ≥ 5 ml/min/1.73 m2/year) and odds of HF hospitalization or HF death during the first 4 years of follow-up was estimated by logistic regression. The improvement in risk discrimination provided by adding rapid kidney function decline to other HF risk factors was evaluated as the increment in the area under the Receiving Operating Characteristics curve (ROC AUC) and integrated discrimination improvement (IDI).

RESULTS

Over 4 years of follow-up, 1,573 participants (20.9%) experienced rapid kidney function decline and 255 (3.4%) experienced a HF event. Rapid kidney function decline was associated with a ~ 3.2-fold increase in HF odds (3.23, 95% CI, 2.51-4.16, p < 0.0001), independent of baseline CVD history. This estimate was not attenuated by adjustment for potential confounders, including eGFR and UACR at baseline as well as at censoring (3.74; 95% CI 2.63-5.31). Adding rapid kidney function decline during follow-up to other clinical predictors (WATCH-DM score, eGFR, and UACR at study entry and end of follow-up) improved HF risk classification (ROC AUC = + 0.02, p = 0.027; relative IDI = + 38%, p < 0.0001).

CONCLUSIONS

In patients with T2D, rapid kidney function decline is associated with a marked increase in HF risk, independent of starting kidney function and/or albuminuria. These findings highlight the importance of serial eGFR measurements over time to improve HF risk estimation in T2D.

Role of resveratrol in inhibiting pathological cardiac remodeling

Cardiovascular disease is a group of diseases with high mortality in clinic, including hypertension, coronary heart disease, cardiomyopathy, heart valve disease, heart failure, to name a few. In the development of cardiovascular diseases, pathological cardiac remodeling is the most common cardiac pathological change, which often becomes a domino to accelerate the deterioration of the disease. Therefore, inhibiting pathological cardiac remodeling may delay the occurrence and development of cardiovascular diseases and provide patients with greater long-term benefits. Resveratrol is a non-flavonoid polyphenol compound. It mainly exists in grapes, berries, peanuts and red wine, and has cardiovascular protective effects, such as anti-oxidation, inhibiting inflammatory reaction, antithrombotic, dilating blood vessels, inhibiting apoptosis and delaying atherosclerosis. At present, the research of resveratrol has made rich progress. This review aims to summarize the possible mechanism of resveratrol against pathological cardiac remodeling, in order to provide some help for the in-depth exploration of the mechanism of inhibiting pathological cardiac remodeling and the development and research of drug targets.

Evaluating the adverse outcome of subtypes of heart failure with preserved ejection fraction defined by machine learning: A systematic review focused on defining high risk phenogroups

The ability to distinguish clinically meaningful subtypes of heart failure with preserved ejection fraction (HFpEF) has recently been examined by machine learning techniques but studies appear to have produced discordant results. The objective of this study is to synthesize the types of HFpEF by examining their features and relating them to phenotypes with adverse prognosis. A systematic search was conducted using the search terms "Diastolic Heart Failure" OR "heart failure with preserved ejection fraction" OR "heart failure with normal ejection fraction" OR "HFpEF" AND "machine learning" OR "artificial intelligence" OR 'computational biology'. Ten studies were identified and they varied in their prevalence of ten clinical variables: age, sex, body mass index (BMI) or obesity, hypertension, diabetes mellitus, coronary artery disease, atrial fibrillation, chronic kidney disease, chronic obstructive pulmonary disease or symptom severity (NYHA class or BNP). The clinical findings associated with the different phenotypes in > 85 % of studies were age, hypertension, atrial fibrillation, chronic kidney disease and worse symptoms severity; an adverse outcome was in 65 % to 85 % of studies identified diabetes mellitus and female sex and in less than 65 % of studies was body mass index or obesity, and coronary artery disease. COPD was a relevant factor in only 33 % of studies. Adverse clinical outcome - death or admission to hospital (for heart failure) defined phenogroups with the worst outcome. Combining the 4 studies that calculated the MAGGIC score showed a significant (p<0.05) linear relationship between MAGGIC score and outcome, using the one-year event rate. A new score based on strength of the evidence of the HFpEF studies analyzed here, using 9 variables (eliminating COPD), showed a significant (p<0.009) linear relationship with one-year event rate. Three studies examined biomarkers in detail and the ones most prominently related to outcome or consistently found in the studies were GDF15, FABP4, FGF23, sST2, renin and TNF. The dominant factors that identified phenotypes of HFpEF with adverse outcome were hypertension, atrial fibrillation, chronic kidney disease and worse symptoms severity. A new simplified score, based on clinical factors, was proposed to assess prognosis in HFpEF. Several biomarkers were consistently elevated in phenogroups with adverse outcomes and may indicate the underlying mechanism or pathophysiology specific for phenotypes with an adverse prognosis.

Exploring the Pattern of Metabolic Alterations Causing Energy Imbalance via PPARα Dysregulation in Cardiac Muscle During Doxorubicin Treatment

Cardiotoxicity by anthracycline antineoplastic drug doxorubicin is one of the systemic toxicity of the cardiovascular system. The mechanism responsible for doxorubicin cardiotoxicity and lipid metabolism remains elusive. The current study tested the hypotheses that the role of peroxisome proliferator-activated receptor α (PPARα) in the progress of doxorubicin-induced cardiomyopathy and its mechanism behind lipid metabolism. In the present study, male rats were subjected to intraperitoneal injection (5-week period) of doxorubicin with different dosages such as low dosage (1.5 mg/kg body weight) and high dosage (15 mg/kg body weight) to induce doxorubicin cardiomyopathy. Myocardial PPARα was impaired in both low dosage and high dosage of doxorubicin-treated rats in a dose-dependent manner. The attenuated level of PPARα impairs the expression of the genes involved in mitochondrial transporter, fatty acid transportation, lipolysis, lipid metabolism, and fatty acid oxidation. Moreover, it disturbs the reverse triacylglycerol transporter apolipoprotein B-100 (APOB) in the myocardium. Doxorubicin elevates the circulatory lipid profile and glucose. Further aggravated lipid profile in circulation impedes the metabolism of lipid in cardiac tissue, which causes a lipotoxic condition in the heart and subsequently associated disease for the period of doxorubicin treatment. Elevated lipids in the circulation translocate into the heart dysregulates lipid metabolism in the heart, which causes augmented oxidative stress and necro-apoptosis and mediates lipotoxic conditions. This finding determines the mechanistic role of doxorubicin-disturbed lipid metabolism via PPARα, which leads to cardiac dysfunction.

Cardiac fibrosis and curcumin: a novel perspective on this natural medicine

BACKGROUND

According to WHO statistics, cardiovascular disease are the leading causes of death in the world. One of the main factors which is causing heart failure, systolic and diastolic dysfunction, and arrythmias is a condition named cardiac fibrosis. This condition is defined by the accumulation of fibroblast-produced ECM in myocardium layer of the heart.

OBJECTIVE

Accordingly, the current review aims to depict the role of curcumin in the regulation of different signaling pathways that are involved in cardiac fibrosis.

RESULTS

A great number of cellular and molecular mechanisms such as oxidative stress, inflammation, and mechanical stress are acknowledged to be involved in cardiac fibrosis. Despite the available therapeutic procedures which are designed to target these mechanisms in order to prevent cardiac fibrosis, still, effective therapeutic methods are needed. Curcumin is a natural Chinese medicine which currently has been declared to have therapeutic properties such as anti-oxidant and immunomodulatory activities. In this review, we have gathered several experimental studies in order to represent diverse impacts of this turmeric derivative on pathogenic factors of cardiac fibrosis.

CONCLUSION

Curcumin might open new avenues in the field of cardiovascular treatment.

Low-intensity pulsed ultrasound ameliorates angiotensin II-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway

OBJECTIVES

Cardiac hypertrophy and fibrosis are major pathological manifestations observed in left ventricular remodeling induced by angiotensin II (AngII). Low-intensity pulsed ultrasound (LIPUS) has been reported to ameliorate cardiac dysfunction and myocardial fibrosis in myocardial infarction (MI) through mechano-transduction and its downstream pathways. In this study, we aimed to investigate whether LIPUS could exert a protective effect by ameliorating AngII-induced cardiac hypertrophy and fibrosis and if so, to further elucidate the underlying molecular mechanisms.

METHODS

We used AngII to mimic animal and cell culture models of cardiac hypertrophy and fibrosis. LIPUS irradiation was applied in vivo for 20 min every 2 d from one week before mini-pump implantation to four weeks after mini-pump implantation, and in vitro for 20 min on each of two occasions 6 h apart. Cardiac hypertrophy and fibrosis levels were then evaluated by echocardiographic, histopathological, and molecular biological methods.

RESULTS

Our results showed that LIPUS could ameliorate left ventricular remodeling in vivo and cardiac fibrosis in vitro by reducing AngII-induced release of inflammatory cytokines, but the protective effects on cardiac hypertrophy were limited in vitro. Given that LIPUS increased the expression of caveolin-1 in response to mechanical stimulation, we inhibited caveolin-1 activity with pyrazolopyrimidine 2 (pp2) in vivo and in vitro. LIPUS-induced downregulation of inflammation was reversed and the anti-fibrotic effects of LIPUS were absent.

CONCLUSIONS

These results indicated that LIPUS could ameliorate AngII-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway, providing new insights for the development of novel therapeutic apparatus in clinical practice.

Cancer therapy-related cardiac dysfunction: is endothelial dysfunction at the heart of the matter?

Significant improvements in cancer survival have brought to light unintended long-term adverse cardiovascular effects associated with cancer treatment. Although capable of manifesting a broad range of cardiovascular complications, cancer therapy-related cardiac dysfunction (CTRCD) remains particularly common among the mainstay anthracycline-based and human epidermal growth factor receptor-targeted therapies. Unfortunately, the early asymptomatic stages of CTRCD are difficult to detect by cardiac imaging alone, and the initiating mechanisms remain incompletely understood. More recently, circulating inflammatory markers, cardiac biomarkers, microRNAs, and extracellular vesicles (EVs) have been considered as early markers of cardiovascular injury. Concomitantly, the role of the endothelium in regulating cardiac function in the context of CTRCD is starting to be understood. In this review, we highlight the impact of breast cancer therapies on the cardiovascular system with a focus on the endothelium, and examine the status of circulating biomarkers, including inflammatory markers, cardiac biomarkers, microRNAs, and endothelial cell-derived EVs. Investigation of these emerging biomarkers may uncover mechanisms of injury, detect early stages of cardiovascular damage, and elucidate novel therapeutic approaches.

Inflammatory markers and incident heart failure in older men: the role of NT-proBNP

Aim:

To determine the relationship between baseline inflammation (CRP and IL-6) with natriuretic peptide (NP) activity (measured by NT-proBNP) and incident heart failure (HF) in older men.

Methods & results:

In the British Regional Heart Study, 3569 men without prevalent myocardial infarction or HF were followed for mean 16.3 years; 327 developed HF. Baseline CRP and IL-6 were significantly and positively associated with NT-proBNP. Those in the highest CRP and IL-6 quartiles had an elevated risk of HF after age and BMI adjustment (HR = 1.42 [1.01–1.98] and 1.71 [1.24–2.37], respectively), which markedly attenuated after NT-proBNP adjustment (HR = 1.15 [0.81–1.63] and 1.25 [0.89–1.75], respectively).

Conclusion:

NP activity is associated with pro-inflammatory biomarkers and may explain the link between inflammation and incident HF.

Inflammation describes the body’s natural response to infections, injuries and toxins. Inflammation is a helpful response in the short term, but it is thought that long-lasting inflammation – for example, due to illnesses such as diabetes or obesity – may have harmful effects. Previous studies have found that people with higher levels of inflammatory molecules in the blood seem to be more likely to develop heart failure (HF) later on. The amount of fluid in the body is controlled, in part, by molecules in the blood known as ‘natriuretic peptides' (NPs). People with HF have much higher levels of NPs in their blood, and these are used to help diagnose HF. There are suggestions that inflammation and natriuretic peptides are linked to one another. Using a sample of men aged 60–79 years, who did not have HF, we compared blood markers of inflammation and NPs at a baseline examination. Men with higher blood inflammatory markers tended to have higher blood NP levels. We then followed these men up for an average of 16.3 years. Men with higher blood inflammatory markers at baseline were more likely to develop HF, as expected, even after accounting for differences in age and BMI. However, when we accounted for NP levels at baseline, the increased risk of HF with inflammation disappeared. This suggests that NP activity is important in the relationship between inflammation and the risk of HF. Future studies should account for this when examining the link. It is possible that NPs or, more likely, whatever is driving their release, may explain why people with inflammation are more likely to get HF.

Berry-Derived Polyphenols in Cardiovascular Pathologies: Mechanisms of Disease and the Role of Diet and Sex

Cardiovascular disease (CVD) prevalence, pathogenesis, and manifestation is differentially influenced by biological sex. Berry polyphenols target several signaling pathways pertinent to CVD development, including inflammation, oxidative stress, and cardiac and vascular remodeling, and there are innate differences in these pathways that also vary by sex. There is limited research systematically investigating sex differences in berry polyphenol effects on these pathways, but there are fundamental findings at this time that suggest a sex-specific effect. This review will detail mechanisms within these pathological pathways, how they differ by sex, and how they may be individually targeted by berry polyphenols in a sex-specific manner. Because of the substantial polyphenolic profile of berries, berry consumption represents a promising interventional tool in the treatment and prevention of CVD in both sexes, but the mechanisms in which they function within each sex may vary.

Role of the Renin-Angiotensin-Aldosterone System in Dystrophin-Deficient Cardiomyopathy

Dystrophin-deficient cardiomyopathy (DDC) is currently the leading cause of death in patients with dystrophinopathies. Targeting myocardial fibrosis (MF) has become a major therapeutic goal in order to prevent the occurrence of DDC. We aimed to review and summarize the current evidence about the role of the renin-angiotensin-aldosterone system (RAAS) in the development and perpetuation of MF in DCC. We conducted a comprehensive search of peer-reviewed English literature on PubMed about this subject. We found increasing preclinical evidence from studies in animal models during the last 20 years pointing out a central role of RAAS in the development of MF in DDC. Local tissue RAAS acts directly mainly through its main fibrotic component angiotensin II (ANG2) and its transducer receptor (AT1R) and downstream TGF-b pathway. Additionally, it modulates the actions of most of the remaining pro-fibrotic factors involved in DDC. Despite limited clinical evidence, RAAS blockade constitutes the most studied, available and promising therapeutic strategy against MF and DDC. Conclusion: Based on the evidence reviewed, it would be recommendable to start RAAS blockade therapy through angiotensin converter enzyme inhibitors (ACEI) or AT1R blockers (ARBs) alone or in combination with mineralocorticoid receptor antagonists (MRa) at the youngest age after the diagnosis of dystrophinopathies, in order to delay the occurrence or slow the progression of MF, even before the detection of any cardiovascular alteration.

Cardiac dysfunction after preeclampsia; an overview of pro- and anti-fibrotic circulating effector molecules

Preeclampsia (PE) is strongly associated with heart failure (HF) later in life. The aberrant cardiac remodelling is likely initiated or amplified during preeclamptic pregnancy. Aberrant remodelling often persists after delivery and is known to relate strongly to cardiac fibrosis. This review provides an overview of pro- and anti- fibrotic circulating effector molecules that are involved in cardiac fibrosis and their association with PE. Women with PE complicated pregnancies show increased ANG-II sensitivity and elevated levels of the pro-fibrotic factors IL-6, TNF-α, TGs and FFAs compared to uncomplicated pregnancies. In the postpartum period, PE pregnancies compared to uncomplicated pregnancies have increased ANG-II sensitivity, elevated levels of the pro-fibrotic factors IL-6, TNF-α, LDL cholesterol and leptin, as well as decreased levels of the anti-fibrotic factor adiponectin. The review revealed several profibrotic molecules that associate to cardiac fibrosis during and after PE. The role that these fibrotic factors have on the heart during and after PE may improve the understanding of the link between PE and HF. Furthermore they may provide insight into the pathways in which the relation between both diseases can be understood as potential mechanisms which interfere in the process of cardiovascular disease (CVD). Unravelling the molecular mechanism and pathways involved might bring the diagnostic and therapeutic abilities of those factors a step closer.

Panax Notoginseng Saponins Inhibits Ventricular Remodeling after Myocardial Infarction in Rats Through Regulating ATF3/MAP2K3/p38 MAPK and NF κ B Pathway

OBJECTIVE

To explore whether Panax notoginseng saponins (PNS) exhibits heart protective effect in myocardial infarction (MI) rats and to identify the potential signaling pathways involved.

METHODS

MI rats induced by ligating the left anterior descending (LAD) coronary artery were assigned to sham coronary artery ligation or coronary artery ligation. Totally 36 Sprague-Dawley rats were randomly divided into sham group (distilled water, n=9), MI group (distilled water, n=9), PNS group (PNS, 40 mg/kg daily, n=9) and fosinopril group (FIP, 1.2 mg/kg daily, n=9) according to a random number table. The left ventricular morphology and function were conducted by echocardiography. Histological alterations were evaluated by the stainings of HE and Masson. The serum levels of C reactive protein (CRP), tumor necrosis factor α (TNF-α), growth differentiation factor-15 (GDF-15) and the ratio of metalloproteinase-9 (MMP-9) and tissue inhibitor of MMP-9 (TIMP-1) were determined by ELISA. The levels of activating transcription factor 3 (ATF3), mitogen-activated protein kinase kinase 3 (MAP2K3), p38 mitogen-activated protein kinase (p38 MAPK), phosphorylation of p38 MAPK (p-p38 MAPK), transforming growth factor-β (TGF-β1), collagen I, nuclear factor kappa B p65 (NFκB p65), phosphorylation of NFκB p65 (p-NFκB p65), and phosphorylation of inhibitory kappa Bα (p-Iκ Bα) in hearts were measured by Western blot and immunohistochemical staining, respectively.

RESULTS

PNS improved cardiac function and fibrosis in MI rats (P<0.05). The serum levels of CRP, TNF-α, GDF-15 and the ratio of MMP9/TIMP1 were reversed by PNS in MI rats. The expressions of TGF-β1, collagen I, MAP2K3, p38 MAPK, p-p38 MAPK, NFκB p65, p-NFκB p65, and p-IκBα were down-regulated, while ATF3 increased with the treatment of PNS (P<0.05).

CONCLUSIONS

PNS may improve cardiac function and fibrosis in MI rats via regulating ATF3/MAP2K3/p38 MAPK and NFκB signaling pathways. These results suggest the potential of PNS in preventing the development of ventricular remodeling in MI rats.

Thioridazine aggravates skeletal myositis, systemic and liver inflammation in Trypanosoma cruzi-infected and benznidazole-treated mice

While thioridazine (Tio) inhibits the antioxidant defenses of Trypanosoma cruzi, the gold standard antitrypanosomal drug benznidazole (Bz) has potent anti-inflammatory and pro-oxidant properties. The combination of these drugs has never been tested to determine the effect on T. cruzi infection. Thus, we compared the impact of Tio and Bz, administered alone and in combination, on the development of skeletal myositis and liver inflammation in T. cruzi-infected mice. Swiss mice were randomized into six groups: uninfected untreated, infected untreated, treated with Tio (80 mg/kg) alone, Bz (50 or 100 mg/kg) alone, or a combination of Tio and Bz. Infected animals were inoculated with a virulent T. cruzi strain (Y) and treated by gavage for 20 days. Mice untreated or treated with Tio alone developed the most intense parasitemia, highest parasitic load, elevated IL-10, IL-17, IFN-γ, and TNF-α plasma levels, increased N-acetylglucosaminidase and myeloperoxidase activity in the liver and skeletal muscle, as well as severe myositis and liver inflammation (P < 0.05). All parameters were markedly attenuated in animals receiving Bz alone (P < 0.05). However, the co-administration of Tio impaired the response to Bz chemotherapy, causing a decrease in parasitological control (parasitemia and parasite load), skeletal muscle and liver inflammation, and increased microstructural damage, when compared to the group receiving Bz alone (P < 0.05). Altogether, our findings indicated that Tio aggravates systemic inflammation, skeletal myositis and hepatic inflammatory damage in T. cruzi-infected mice. By antagonizing the antiparasitic potential of Bz, Tio limits the anti-inflammatory, myoprotectant and hepatoprotective effects of the reference chemotherapy, aggravating the pathological remodeling of both organs. As the interaction of T. cruzi infection, Bz and Tio is potentially toxic to the liver, inducing inflammation and microvesicular steatosis; this drug combination represents a worrying pharmacological risk factor in Chagas disease.

Non-ischemic dilated cardiomyopathy and cardiac fibrosis

Cardiac fibrosis is associated with non-ischemic dilated cardiomyopathy, increasing its morbidity and mortality. Cardiac fibroblast is the keystone of fibrogenesis, being activated by numerous cellular and humoral factors. Macrophages, CD4+ and CD8+ T cells, mast cells, and endothelial cells stimulate fibrogenesis directly by activating cardiac fibroblasts and indirectly by synthetizing various profibrotic molecules. The synthesis of type 1 and type 3 collagen, fibronectin, and α-smooth muscle actin is rendered by various mechanisms like transforming growth factor-beta/small mothers against decapentaplegic pathway, renin angiotensin system, and estrogens, which in turn alter the extracellular matrix. Investigating the underlying mechanisms will allow the development of diagnostic and prognostic tools and discover novel specific therapies. Serum biomarkers aid in the diagnosis and tracking of cardiac fibrosis progression. The diagnostic gold standard is cardiac magnetic resonance with gadolinium administration that allows quantification of cardiac fibrosis either by late gadolinium enhancement assessment or by T1 mapping. Therefore, the goal is to stop and even reverse cardiac fibrosis by developing specific therapies that directly target fibrogenesis, in addition to the drugs used to treat heart failure. Cardiac resynchronization therapy had shown to revert myocardial remodeling and to reduce cardiac fibrosis. The purpose of this review is to provide an overview of currently available data.

Mind the gap (junction): cGMP induced by nitric oxide in cardiac myocytes originates from cardiac fibroblasts

Background and Purpose

The intracellular signalling molecule cGMP, formed by NO‐sensitive GC (NO–GC), has an established function in the vascular system. Despite numerous reports about NO‐induced cGMP effects in the heart, the underlying cGMP signals are poorly characterized.

Experimental Approach

Therefore, we analysed cGMP signals in cardiac myocytes and fibroblasts isolated from knock‐in mice expressing a FRET‐based cGMP indicator.

Key Results

Whereas in cardiac myocytes, none of the known NO–GC‐activating substances (NO, GC activators, and GC stimulators) increased cGMP even in the presence of PDE inhibitors, they induced substantial cGMP increases in cardiac fibroblasts. As cardiac myocytes and fibroblasts are electrically connected via gap junctions, we asked whether cGMP can take the same route. Indeed, in cardiomyocytes co‐cultured on cardiac fibroblasts, NO‐induced cGMP signals were detectable, and two groups of unrelated gap junction inhibitors abolished these signals.

Conclusion and Implication

We conclude that NO‐induced cGMP formed in cardiac fibroblasts enters cardiac myocytes via gap junctions thereby turning cGMP into an intercellular signalling molecule. The findings shed new light on NO/cGMP signalling in the heart and will potentially broaden therapeutic opportunities for cardiac disease.

CaMKII Activity in the Inflammatory Response of Cardiac Diseases

Inflammation is a physiological process by which the body responds to external insults and stress conditions, and it is characterized by the production of pro-inflammatory mediators such as cytokines. The acute inflammatory response is solved by removing the threat. Conversely, a chronic inflammatory state is established due to a prolonged inflammatory response and may lead to tissue damage. Based on the evidence of a reciprocal regulation between inflammation process and calcium unbalance, here we described the involvement of a calcium sensor in cardiac diseases with inflammatory drift. Indeed, the Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is activated in several diseases with an inflammatory component, such as myocardial infarction, ischemia/reperfusion injury, pressure overload/hypertrophy, and arrhythmic syndromes, in which it actively regulates pro-inflammatory signaling, among which includes nuclear factor kappa-B (NF-κB), thus contributing to pathological cardiac remodeling. Thus, CaMKII may represent a key target to modulate the severity of the inflammatory-driven degeneration.

Single-cell expression profiling reveals dynamic flux of cardiac stromal, vascular and immune cells in health and injury

Besides cardiomyocytes (CM), the heart contains numerous interstitial cell types which play key roles in heart repair, regeneration and disease, including fibroblast, vascular and immune cells. However, a comprehensive understanding of this interactive cell community is lacking. We performed single-cell RNA-sequencing of the total non-CM fraction and enriched (Pdgfra-GFP⁺) fibroblast lineage cells from murine hearts at days 3 and 7 post-sham or myocardial infarction (MI) surgery. Clustering of >30,000 single cells identified >30 populations representing nine cell lineages, including a previously undescribed fibroblast lineage trajectory present in both sham and MI hearts leading to a uniquely activated cell state defined in part by a strong anti-WNT transcriptome signature. We also uncovered novel myofibroblast subtypes expressing either pro-fibrotic or anti-fibrotic signatures. Our data highlight non-linear dynamics in myeloid and fibroblast lineages after cardiac injury, and provide an entry point for deeper analysis of cardiac homeostasis, inflammation, fibrosis, repair and regeneration.

In our bodies, heart attacks lead to cell death and inflammation. This is then followed by a healing phase where the organ repairs itself. There are many types of heart cells, from muscle and pacemaker cells that help to create the beating motion, to so-called fibroblasts that act as a supporting network. Yet, it is still unclear how individual cells participate in the heart's response to injury.

All cells possess the same genetic information, but they turn on or off different genes depending on the specific tasks that they need to perform. Spotting which genes are activated in individual cells can therefore provide clues about their exact roles in the body. Until recently, technological limitations meant that this information was difficult to access, because it was only possible to capture the global response of a group of cells in a sample.

A new method called single-cell RNA sequencing is now allowing researchers to study the activities of many genes in thousands of individual cells at the same time. Here, Farbehi, Patrick et al. performed single-cell RNA sequencing on over 30,000 individual cells from healthy and injured mouse hearts. Computational approaches were then used to cluster cells into groups according to the activities of their genes.

The experiments identified over 30 distinct sub-types of cell, including several that were previously unknown. For example, a group of fibroblasts that express a gene called Wif1 was discovered. Previous genetic studies have shown that Wif1 is essential for the heart's response to injury. Further experiments by Farbehi, Patrick et al. indicated that this new sub-type of cells may control the timing of the different aspects of heart repair after damage.

Tens of millions of people around the world suffer from heart attacks and other heart diseases. Knowing how different types of heart cells participate in repair mechanisms may help to find new targets for drugs and other treatments.

Beneficial effects of andrographolide in a rat model of autoimmune myocarditis and its effects on PI3K/Akt pathway

The study is to investigate effects of andrographolide on experimental autoimmune myocarditis (EAM). Lewis rats were immunized on day 0 with porcine cardiac myosin to establish EAM. The EAM rats were treated with either andrographolide (25, 50, 100 mg/kg/day) or vehicle for 21 days. An antigen-specific splenocytes proliferation assay was performed by using the cells from control rats immunized with cardiac myosin. Survival rates, myocardial pathology and myocardial functional parameters (left ventricle end-diastolic pressure, ± dP/dt and left ventricular internal dimension) of EAM rats received andrographolide were significantly improved. Andrographolide treatment caused an decrease in the infiltration of CD3⁺ and CD14⁺ positive cells in myocardial tissue. Moreover, andrographolide treatment caused a reduction in the plasma levels of tumor necrosis factor-alpha, interleukin-17 (IL-17) and myosin-antibody, and an increase in the level of IL-10 in EAM rats. Oral administration of andrographolide resulted in the decreased expression of p-PI3K, p-Akt without any change of PI3K and Akt. Further results indicate andrographolide significantly inhibited myosin-induced proliferation in splenocytes, and this effect was inhibited by co-treatment of SC79 (Akt activator). Our data indicate andrographolide inhibits development of EAM, and this beneficial effect may be due to powerful anti-inflammatory activity and inhibitory effect on PI3K/Akt pathway.

Differential Expression of Transforming Growth Factor-β1 Is Associated With Fetal Regeneration After Myocardial Infarction

BACKGROUND

Global extracellular matrix (ECM)-related gene expression is decreased after myocardial infarction (MI) in fetal sheep when compared with adult sheep. Transforming growth factor (TGF)-β1 is a key regulator of ECM; therefore we hypothesize that TGF-β1 is differentially expressed in adult and fetal infarcts after MI.

METHODS

Adult and fetal sheep underwent MI via ligation of the left anterior descending coronary artery. Expression of TGF-β1 and ECM-related genes was evaluated by ovine-specific microarray and quantitative polymerase chain reaction. Fibroblasts from the left ventricle of adult and fetal hearts were treated with TGF-β1 or a TGF-β1 receptor inhibitor (LY36497) to evaluate the effect of TGF-β1 on ECM-related genes.

RESULTS

Col1a1, col3a1, and MMP9 expression were increased in adult infarcts 3 and 30 days after MI but were upregulated in fetal infarcts only 3 days after MI. Three days after MI elastin expression was increased in adult infarcts. Despite upregulation in adult infarcts both 3 and 30 days after MI, TGF-β1 was not upregulated in fetal infarcts at any time point. Inhibition of the TGF-β1 receptor in adult cardiac fibroblasts decreased expression of col1a1, col3a1, MMP9, elastin, and TIMP1, whereas treatment of fetal cardiac fibroblasts with TGF-β1 increased expression of these genes.

CONCLUSIONS

TGF-β1 is increased in adult infarcts compared with regenerative, fetal infarcts after MI. Although treatment of fetal cardiac fibroblasts with TGF-β1 conveys an adult phenotype, inhibition of TGF-β1 conveys a fetal phenotype to adult cardiac fibroblasts. Decreasing TGF-β1 after MI may facilitate myocardial regeneration by "fetalizing" the otherwise fibrotic, adult response to MI.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

CaMKIIδ-mediated inflammatory gene expression and inflammasome activation in cardiomyocytes initiate inflammation and induce fibrosis

Inflammation accompanies heart failure and is a mediator of cardiac fibrosis. CaMKIIδ plays an essential role in adverse remodeling and decompensation to heart failure. We postulated that inflammation is the mechanism by which CaMKIIδ contributes to adverse remodeling in response to nonischemic interventions. We demonstrate that deletion of CaMKIIδ in the cardiomyocyte (CKO) significantly attenuates activation of NF-κB, expression of inflammatory chemokines and cytokines, and macrophage accumulation induced by angiotensin II (Ang II) infusion. The inflammasome was activated by Ang II, and this response was also diminished in CKO mice. These events occurred prior to any evidence of Ang II-induced cell death. In addition, CaMKII-dependent inflammatory gene expression and inflammasome priming were observed as early as the third hour of infusion, a time point at which macrophage recruitment was not evident. Inhibition of either the inflammasome or monocyte chemoattractant protein 1 (MCP1) signaling attenuated macrophage accumulation, and these interventions, like cardiomyocyte CaMKIIδ deletion, diminished the fibrotic response to Ang II. Thus, activation of CaMKIIδ in the cardiomyocyte represents what we believe to be a novel mechanism for initiating inflammasome activation and an inflammatory gene program that leads to macrophage recruitment and ultimately to development of fibrosis.

Alamandine attenuates sepsis-associated cardiac dysfunction via inhibiting MAPKs signaling pathways

Sepsis-induced myocardial dysfunction represents a major cause of death. Alamandine is an important biologically active peptide. The present study evaluated whether alamandine improves cardiac dysfunction, inflammation, and apoptosis, and affects the signaling pathways involved in these events. Experiments were carried out in mice treated with lipopolysaccharide (LPS) or alamandine, and in neonatal rat cardiomyocytes. Alamandine increased the ejection fraction and fractional shortening, both of which were decreased upon LPS infusion in mice. LPS and alamandine reduced blood pressure, and increased the expression of inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) in the heart in mice. The LPS-induced decrease in α-myosin heavy chain (MHC) and β-MHC, and increase in S100 calcium binding protein A8 (S100A8) and S100A9, were reversed by alamandine pre-treatment. Alamandine pre-treatment prevented LPS-induced myocardial inflammation, apoptosis and autophagy. LPS increased p-ERK, p-JNK, and p-p38 levels, which were inhibited by alamandine. Dibutyryl cyclic AMP (db-cAMP) increased p-ERK, p-JNK, and p-p38 levels, and reversed the inhibitory effects of alamandine on the LPS-induced increase in p-ERK, p-JNK, and p-p38. Moreover, db-cAMP reduced the expression of α-MHC and β-MHC in cardiomyocytes, and reversed the almandine-induced attenuation of the LPS-induced decrease in α-MHC and β-MHC. These results indicate that alamandine attenuates LPS-induced cardiac dysfunction, resulting in increased cardiac contractility, and reduced inflammation, autophagy, and apoptosis. Furthermore, alamandine attenuates sepsis induced by LPS via inhibiting the mitogen-activated protein kinases (MAPKs) signaling pathways.

Immune cells in repair of the infarcted myocardium

The immune system plays a critical role in both repair and remodeling of the infarcted myocardium. Danger signals released by dying cardiomyocytes mobilize, recruit, and activate immune cells, triggering an inflammatory reaction. CXC chemokines containing the ELR motif attract neutrophils, while CC chemokines mediate recruitment of mononuclear cell subpopulations, contributing to clearance of the infarct from dead cells and matrix debris. Immune cell subsets also participate in suppression and containment of the postinfarction inflammatory response by secreting anti-inflammatory mediators, such as IL-10 and TGF-β. As proinflammatory signaling is suppressed, macrophage subpopulations, mast cells and lymphocytes, activate fibrogenic and angiogenic responses, contributing to scar formation. In the viable remodeling myocardium, chronic activation of immune cells may promote fibrosis and hypertrophy. This review discusses the role of immune cells in repair and remodeling of the infarcted myocardium. Understanding the role of immune cells in myocardial infarction is critical for the development of therapeutic strategies aimed at protecting the infarcted heart from adverse remodeling. Moreover, modulation of immune cell phenotype may be required in order to achieve the visionary goal of myocardial regeneration.

TIMP3 deficiency exacerbates iron overload-mediated cardiomyopathy and liver disease

Chronic iron overload results in heart and liver diseases and is a common cause of morbidity and mortality in patients with genetic hemochromatosis and secondary iron overload. We investigated the role of tissue inhibitor of metalloproteinase 3 (TIMP3) in iron overload-mediated tissue injury by subjecting male mice lacking Timp3 ( Timp3^-/-) and wild-type (WT) mice to 12 wk of chronic iron overload. Whereas WT mice with iron overload developed diastolic dysfunction, iron-overloaded Timp3^-/- mice showed worsened cardiac dysfunction coupled with systolic dysfunction. In the heart, loss of Timp3 was associated with increased myocardial fibrosis, greater Timp1, matrix metalloproteinase ( Mmp) 2, and Mmp9 expression, increased active MMP-2 levels, and gelatinase activity. Iron overload in Timp3^-/- mice showed twofold higher iron accumulation in the liver compared with WT mice because of constituently lower levels of ferroportin. Loss of Timp3 enhanced the hepatic inflammatory response to iron overload, leading to greater neutrophil and macrophage infiltration and increased hepatic fibrosis. Expression of inflammation-related MMPs (MMP-12 and MMP-13) and inflammatory cytokines (IL-1β and monocyte chemoattractant protein-1) was elevated to a greater extent in iron-overloaded Timp3^-/- livers. Gelatin zymography demonstrated equivalent increases in MMP-2 and MMP-9 levels in WT and Timp3^-/- iron-overloaded livers. Loss of Timp3 enhanced the susceptibility to iron overload-mediated heart and liver injury, suggesting that Timp3 is a key protective molecule against iron-mediated pathology. NEW & NOTEWORTHY In mice, loss of tissue inhibitor of metalloproteinase 3 ( Timp3) was associated with systolic and diastolic dysfunctions, twofold higher hepatic iron accumulation (attributable to constituently lower levels of ferroportin), and increased hepatic inflammation. Loss of Timp3 enhanced the susceptibility to iron overload-mediated injury, suggesting that Timp3 plays a key protective role against iron-mediated pathology.

Detection of Pathological Changes in the Aorta during Thoracic Aortic Aneurysm Progression on Molecular Level

The progression of thoracic aortic aneurysm depends on regulation of aortic wall homeostasis and on changes in the structural components of the extracellular matrix, which are affected by multiple molecular signalling pathways. We decided to correlate the diameter of ascending thoracic aneurysm with gene expression of inflammation markers (IL-6, CRP), cytokine receptors (IL-6R, TNFR1, and TNFR2), and extracellular matrix components (Emilin-1, MMP9, and TIMP) for detection of the degree of pathological process of TAA formation. The experimental group was divided into three groups according to the diameter of the aortic aneurysm. Whole blood and tissue samples were properly collected and used for nucleic acid, chromatin, and protein isolation. The mRNA levels were detected by qRT-PCR. For the detection of protein levels a Cytokine Array IV assay kit was used in combination with a biochip analyzer. In aortic tissue, significant positive correlations were found between increased mRNA levels of inflammatory cytokines (CRP and IL-6) on both mRNA levels in tissue and protein from the blood with maximum in stage 3. Changes of gene expression of selected genes can be used for the experimental study of the inflammatory receptor inhibitors during trials targeted on slowing down the progress of aortic wall aneurysm.

Integrin α4β1 and TLR4 Cooperate to Induce Fibrotic Gene Expression in Response to Fibronectin's EDA Domain

Alternative splicing of fibronectin increases expression of the EDA⁺ isoform of fibronectin (EDA⁺Fn), a damage-associated molecular pattern molecule, which promotes fibro-inflammatory disease through the activation of toll-like receptors. Our studies indicate that the fibronectin EDA domain drives two waves of gene expression in human dermal fibroblasts. The first wave, seen at 2 hours, consisted of inflammatory genes, VCAM1, and tumor necrosis factor. The second wave, evaluated at 24 hours, was composed of the fibrosis-associated cytokines IL-10 and IL-13 and extracellular matrix genes fibronectin and osteopontin. Gene expression was coordinately regulated by the α4β1 integrin and the innate immune receptor toll-like receptor 4. Additionally, we found a significant toll-like receptor 4/α4β1-dependent enrichment in the ratio of EDA⁺Fn to total fibronectin in response to EDA, consistent with EDA⁺Fn initiating further production of EDA⁺Fn. Our data also suggest that the EDA/α4β1 integrin interaction primes the cell for an enhanced response to toll-like receptor 4 ligands. Our studies provide evidence that remodeling of the fibronectin matrix in injured or diseased tissue elicits an EDA-dependent fibro-inflammatory response in dermal fibroblasts. The data suggest a paradigm of damage-associated molecular pattern-based signaling whereby damage-associated molecular pattern binding integrins cooperate with innate immune receptors to stimulate inflammation and fibrosis.

Dissecting the role of myeloid and mesenchymal fibroblasts in age-dependent cardiac fibrosis

Aging is associated with increased cardiac interstitial fibrosis and diastolic dysfunction. Our previous study has shown that mesenchymal fibroblasts in the C57BL/6J (B6J) aging mouse heart acquire an inflammatory phenotype and produce higher levels of chemokines. Monocyte chemoattractant protein-1 (MCP-1) secreted by these aged fibroblasts promotes leukocyte uptake into the heart. Some of the monocytes that migrate into the heart polarize into M2a macrophages/myeloid fibroblasts. The number of activated mesenchymal fibroblasts also increases with age, and consequently, both sources of fibroblasts contribute to fibrosis. Here, we further investigate mechanisms by which inflammation influences activation of myeloid and mesenchymal fibroblasts and their collagen synthesis. We examined cardiac fibrosis and heart function in three aged mouse strains; we compared C57BL/6J (B6J) with two other strains that have reduced inflammation via different mechanisms. Aged C57BL/6N (B6N) hearts are protected from oxidative stress and fibroblasts derived from them do not develop an inflammatory phenotype. Likewise, these mice have preserved diastolic function. Aged MCP-1 null mice on the B6J background (MCP-1KO) are protected from elevated leukocyte infiltration; they develop moderate but reduced fibrosis and diastolic dysfunction. Based on these studies, we further delineated the role of resident versus monocyte-derived M2a macrophages in myeloid-dependent fibrosis and found that the number of monocyte-derived M2a (but not resident) macrophages correlates with age-related fibrosis and diastolic dysfunction. In conclusion, we have found that ROS and inflammatory mediators are necessary for activation of fibroblasts of both developmental origins, and prevention of either led to better functional outcomes.

Role of Circulating Fibrocytes in Cardiac Fibrosis

OBJECTIVE

It is revealed that circulating fibrocytes are elevated in patients/animals with cardiac fibrosis, and this review aims to provide an introduction to circulating fibrocytes and their role in cardiac fibrosis.

DATA SOURCES

This review is based on the data from 1994 to present obtained from PubMed. The search terms were "circulating fibrocytes " and "cardiac fibrosis ".

STUDY SELECTION

Articles and critical reviews, which are related to circulating fibrocytes and cardiac fibrosis, were selected.

RESULTS

Circulating fibrocytes, which are derived from hematopoietic stem cells, represent a subset of peripheral blood mononuclear cells exhibiting mixed morphological and molecular characteristics of hematopoietic and mesenchymal cells (CD34+/CD45+/collagen I+). They can produce extracellular matrix and many cytokines. It is shown that circulating fibrocytes participate in many fibrotic diseases, including cardiac fibrosis. Evidence accumulated in recent years shows that aging individuals and patients with hypertension, heart failure, coronary heart disease, and atrial fibrillation have more circulating fibrocytes in peripheral blood and/or heart tissue, and this elevation of circulating fibrocytes is correlated with the degree of fibrosis in the hearts.

CONCLUSIONS

Circulating fibrocytes are effector cells in cardiac fibrosis.

The antifibrogenic effect of etanercept on development of liver cirrhosis induced by thioacetamide in rats

Liver cirrhosis is an elevating cause of morbidity and mortality worldwide. TNF-α/TNF-R1 signal is implicated in progression of many liver diseases. This study provides histological and ultrastructural view that clarifies the effect of etanercept, a TNF-α inhibitor, on development of thioacetamide (TAA)-induced liver cirrhosis and the accompanied hemosiderosis in rats, highlighting the implication and distribution pattern of hepatic TNF-R1. Sixty male albino rats (Rattus norvegicus) were equally randomized into three groups. Group I served as the control. Liver cirrhosis was triggered in the other two groups by intraperitoneal injection of TAA twice a week for five months. Group II received TAA only, while group III subcutaneously injected with etanercept one hour before TAA, along five months. At the end of the experiment, blood was collected for biochemical analysis and livers were excised for histological, immunohistochemical, and electron microscopical preparations. Rats treated with TAA only developed hepatic cirrhosis accompanied by massive deposition of hemosiderin; strong and widespread expression of hepatic TNF-R1 in sinusoidal endothelial cells (SECs), Kupffer cells (KCs), and many hepatocytes; and frequent appearance of fibrogenic, plasma, and mast cells, at the ultrastructural level. By contrast, administration of etanercept diminished the expression of TNF-R1, attenuated the accumulation of collagen and hemosiderin, and preserved the hepatic histoarchitecture. In conclusion, TNF-α signal via TNF-R1 may be implicated in the mechanism of fibrogenesis and the associated hemosiderosis. Etanercept may provide a promising therapeutic approach not only for attenuating the progression of fibrogenesis, but also for hepatic iron overload-associated disorders.

Identification and functional characterization of tumor necrosis factor receptor 1 (TNFR1) of grass carp (Ctenopharyngodon idella)

Tumor necrosis factor-alpha (TNF-α) exerts its regulatory effects by binding one of two TNF receptors, TNF-α receptor 1 (TNFR1) or TNFR2. In this study, we isolated and identified the cDNA sequence of grass carp TNFR1 (gcTNFR1). Similar to its homologs in other fish species, the putative protein of gcTNFR1 possessed an extracellular region containing three TNF homology domains, a transmembrane region and a cytoplasmic region with a conserved death domain. Consistent with the widespread expression of mammalian TNFR1, gcTNFR1 transcripts ubiquitously expressed in spleen, thymus, liver, heart, gill, intestine, brain and head kidney with the highest expression levels in head kidney. To reveal its inductive expression patterns in inflammatory response, effect of in vivo bacterial infection on gcTNFR1 gene expression was examined, showing a rapid increase of gcTNFR1 expression in head kidney, gill, liver and intestine, which is consistent with the role of TNF-α as an early response gene during immune challenges. To define the functional role of gcTNFR1, recombinant extracellular region of gcTNFR1 (rgcTNFR1) was prepared and used to perform in vitro binding assay, demonstrating its ability to interact with recombinant grass carp TNF-α (rgcTNF-α). Furthermore, to characterize the function of gcTNFR1 in affecting rgcTNF-α actions, the effect of overexpressing gcTNFR1 on rgcTNF-α-induced grass carp IL-1β (gcIL-1β) promoter activity was determined in COS7 cells. Results showed that gcTNFR1 was involved in the regulation of rgcTNF-α on gcIL-1β transcription. Consistently, rgcTNFR1 was effective in attenuating the effect of rgcTNF-α on IL-1β mRNA expression in grass carp head kidney leukocytes, providing evidence for the involvement of TNFR1 in TNF-α signaling in grass carp. These data facilitate a better understanding of TNF-α receptor signaling in grass carp.

Novel therapeutic strategies targeting fibroblasts and fibrosis in heart disease

Our understanding of the functions of cardiac fibroblasts has moved beyond their roles in heart structure and extracellular matrix generation and now includes their contributions to paracrine, mechanical and electrical signalling during ontogenesis and normal cardiac activity. Fibroblasts also have central roles in pathogenic remodelling during myocardial ischaemia, hypertension and heart failure. As key contributors to scar formation, they are crucial for tissue repair after interventions including surgery and ablation. Novel experimental approaches targeting cardiac fibroblasts are promising potential therapies for heart disease. Indeed, several existing drugs act, at least partially, through effects on cardiac connective tissue. This Review outlines the origins and roles of fibroblasts in cardiac development, homeostasis and disease; illustrates the involvement of fibroblasts in current and emerging clinical interventions; and identifies future targets for research and development.

TNF/Ang-II synergy is obligate for fibroinflammatory pathology, but not for changes in cardiorenal function

Angiotensin‐II (Ang‐II) infusion is associated with the development of interstitial fibrosis in both heart and kidney as a result of chemokine‐dependent uptake of monocytes and subsequent development of myeloid fibroblasts. This study emphasizes on the synergistic role of tumor necrosis factor (TNF) on the time course of Ang‐II‐induced fibrosis and inflammation in heart and kidney. In wild‐type (WT) hearts, Ang‐II‐induced fibrosis peaked within 1 week of infusion and remained stable over a 6‐week period, while the myeloid fibroblasts disappeared; TNF receptor‐1‐knockout (TNFR1‐KO) hearts did not develop a myeloid response or cardiac fibrosis during this time. WT hearts developed more accelerated cardiac hypertrophy and remodeling than TNFR1‐KO. In the kidney, 1‐week Ang‐II infusion did not evoke a fibrotic response; however, after 6 weeks, WT kidneys displayed modest but significant tubulointerstitial collagen deposition associated with the appearance of myeloid cells and profibrotic gene activation. Renal fibrosis was not seen in Ang‐II‐infused TNFR1‐KO. By contrast, while hypertension increased and cardiac function decreased more slowly in TNFR1‐KO than WT, they were equivalently abnormal at 6 weeks. Similarly, serum markers for renal dysfunction were not different after 6 weeks. In conclusion, Ang‐II infusion initiated fibroinflammatory responses with different time courses in heart and kidney, both requiring TNFR1 signaling, and both associated with monocyte‐derived myeloid fibroblasts. TNFR1 deletion obviated the fibroinflammatory effects of Ang‐II, but did not alter changes in blood pressure and cardiorenal function after 6 weeks. Thus, the synergy of TNF with Ang‐II targets the fibroinflammatory component of Ang‐II signaling.

Cardiac Fibrosis: The Fibroblast Awakens

Myocardial fibrosis is a significant global health problem associated with nearly all forms of heart disease. Cardiac fibroblasts comprise an essential cell type in the heart that is responsible for the homeostasis of the extracellular matrix; however, upon injury, these cells transform to a myofibroblast phenotype and contribute to cardiac fibrosis. This remodeling involves pathological changes that include chamber dilation, cardiomyocyte hypertrophy and apoptosis, and ultimately leads to the progression to heart failure. Despite the critical importance of fibrosis in cardiovascular disease, our limited understanding of the cardiac fibroblast impedes the development of potential therapies that effectively target this cell type and its pathological contribution to disease progression. This review summarizes current knowledge regarding the origins and roles of fibroblasts, mediators and signaling pathways known to influence fibroblast function after myocardial injury, as well as novel therapeutic strategies under investigation to attenuate cardiac fibrosis.

Mesenchymal stem cell-derived inflammatory fibroblasts mediate interstitial fibrosis in the aging heart

Pathologic fibrosis in the aging mouse heart is associated with dysregulated resident mesenchymal stem cells (MSC) arising from reduced stemness and aberrant differentiation into dysfunctional inflammatory fibroblasts. Fibroblasts derived from aging MSC secrete higher levels of 1) collagen type 1 (Col1) that directly contributes to fibrosis, 2) monocyte chemoattractant protein-1 (MCP-1) that attracts leukocytes from the blood and 3) interleukin-6 (IL-6) that facilitates transition of monocytes into myeloid fibroblasts. The transcriptional activation of these proteins is controlled via the farnesyltransferase (FTase)-Ras-Erk pathway. The intrinsic change in the MSC phenotype acquired by advanced age is specific for the heart since MSC originating from bone wall (BW-MSC) or fibroblasts derived from them were free of these defects. The potential therapeutic interventions other than clinically approved strategies based on findings presented in this review are discussed as well. This article is a part of a Special Issue entitled "Fibrosis and Myocardial Remodeling".

Cardiac fibroblasts as sentinel cells in cardiac tissue: Receptors, signaling pathways and cellular functions

Cardiac fibroblasts (CF) not only modulate extracellular matrix (ECM) proteins homeostasis, but also respond to chemical and mechanical signals. CF express a variety of receptors through which they modulate the proliferation/cell death, autophagy, adhesion, migration, turnover of ECM, expression of cytokines, chemokines, growth factors and differentiation into cardiac myofibroblasts (CMF). Differentiation of CF to CMF involves changes in the expression levels of various receptors, as well as, changes in cell phenotype and their associated functions. CF and CMF express the β2-adrenergic receptor, and its stimulation activates PKA and EPAC proteins, which differentially modulate the CF and CMF functions mentioned above. CF and CMF also express different levels of Angiotensin II receptors, in particular, AT1R activation increases collagen synthesis and cell proliferation, but its overexpression activates apoptosis. CF and CMF express different levels of B1 and B2 kinin receptors, whose stimulation by their respective agonists activates common signaling transduction pathways that decrease the synthesis and secretion of collagen through nitric oxide and prostacyclin I2 secretion. Besides these classical functions, CF can also participate in the inflammatory response of cardiac repair, through the expression of receptors commonly associated to immune cells such as Toll like receptor 4, NLRP3 and interferon receptor. The activation by their respective agonists modulates the cellular functions already described and the release of cytokines and chemokines. Thus, CF and CMF act as sentinel cells responding to a plethora of stimulus, modifying their own behavior, and that of neighboring cells.