Cyclic GMP/protein kinase G phosphorylation of Smad3 blocks transforming growth factor-beta-induced nuclear Smad translocation: a key antifibrogenic mechanism of atrial natriuretic peptide

Use of Statins in Heart Failure with Preserved Ejection Fraction: Current Evidence and Perspectives

Systemic inflammation and coronary microvascular endothelial dysfunction are essential pathophysiological factors in heart failure (HF) with preserved ejection fraction (HFpEF) that support the use of statins. The pleiotropic properties of statins, such as anti-inflammatory, antihypertrophic, antifibrotic, and antioxidant effects, are generally accepted and may be beneficial in HF, especially in HFpEF. Numerous observational clinical trials have consistently shown a beneficial prognostic effect of statins in patients with HFpEF, while the results of two larger trials in patients with HFrEF have been controversial. Such differences may be related to a more pronounced impact of the pleiotropic properties of statins on the pathophysiology of HFpEF and pro-inflammatory comorbidities (arterial hypertension, diabetes mellitus, obesity, chronic kidney disease) that are more common in HFpEF. This review discusses the potential mechanisms of statin action that may be beneficial for patients with HFpEF, as well as clinical trials that have evaluated the statin effects on left ventricular diastolic function and clinical outcomes in patients with HFpEF.

Molecular mechanisms of Chengshi Beixie Fenqing Decoction based on network pharmacology: pivotal roles of relaxin signaling pathway and its associated target proteins against Benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a common disease that affects the quality of life of middle-aged and older men. We investigated the therapeutical effects of Chengshi Beixie Fenqing Decoction (CBFD), a classic traditional Chinese medicine prescription, on BPH through in vivo model and network pharmacology. Bioactives in CBFD were detected through UPLC-Q-Tof-MS/MS and GC-MS, and filtered by the modified Lipinski's rule. Target proteins associated with the filtered compounds and BPH are selected from public databases. Venn diagram identified the overlapping target proteins between the bioactives-interacted target proteins and the BPH-targeted proteins. The bioactive-protein interactive networking of BPH was analyzed through the KEGG pathway on STRING to identify potential ligand-target and visualized the rich factors on the R packet. After that, the molecular docking test (MDT) was performed between bioactives and target proteins. It showed that the mechanism of CBFD against BPH was related to 104 signaling pathways of 42 compounds. AKT1, 6-demethyl-4'-methyl-N-methylcoclaurine and relaxin signaling pathways were selected as a hub target, key bioactivitie and hub signaling pathway, respectively. In addition, three major compounds, 6-demethyl-4'-methyl-N-methylcoclaurine, isoliensinine and liensinine, had the highest affinity on MDT for the three crucial target proteins, AKT1, JUN and MAPK1. These proteins were associated with the relaxin signaling pathway, which regulated the level of nitric oxide and is implicated in both BPH development and CBFD. We concluded that the three key bioactivities found in Plumula nelumbinis of CBFD may contribute to improving BPH condition by activating the relaxin signaling pathways.Communicated by Ramaswamy H. Sarma.

The effect of exenatide (a GLP-1 analogue) and sitagliptin (a DPP-4 inhibitor) on asymmetric dimethylarginine (ADMA) metabolism and selected biomarkers of cardiac fibrosis in rats with fructose-induced metabolic syndrome

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis, is a risk factor for endothelial dysfunction, a common pathophysiological denominator for both atherogenesis and cardiac fibrosis. We aimed to investigate whether the cardioprotective and antifibrotic effects of incretin drugs, exenatide and sitagliptin, may be associated with their ability to affect circulating and cardiac ADMA metabolism. Normal and fructose-fed rats were treated with sitagliptin (5.0/10 mg/kg) or exenatide (5/10 µg/kg) for 4 weeks. The following methods were used: LC-MS/MS, ELISA, Real-Time-PCR, colorimetry, IHC and H&E staining, PCA and OPLS-DA projections. Eight-week fructose feeding resulted in an increase in plasma ADMA and a decrease in NO concentration. Exenatide administration into fructose-fed rats reduced the plasma ADMA level and increased NO level. In the heart of these animals exenatide administration increased NO and PRMT1 level, reduced TGF-ß1, α-SMA levels and COL1A1 expression. In the exenatide treated rats renal DDAH activity positively correlated with plasma NO level and negatively with plasma ADMA level and cardiac α-SMA concentration. Sitagliptin treatment of fructose-fed rats increased plasma NO concentration, reduced circulating SDMA level, increased renal DDAH activity and reduced myocardial DDAH activity. Both drugs attenuated the myocardial immunoexpression of Smad2/3/P and perivascular fibrosis. In the metabolic syndrome condition both sitagliptin and exenatide positively modulated cardiac fibrotic remodeling and circulating level of endogenous NOS inhibitors but had no effects on ADMA levels in the myocardium.

N-butyldeoxynojirimycin (miglustat) ameliorates pulmonary fibrosis through inhibition of nuclear translocation of Smad2/3

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease. The disease involves excessive accumulation of fibroblasts and myofibroblasts, and myofibroblasts differentiated by pro-fibrotic factors promote the deposition of extracellular matrix proteins such as collagen and fibronectin. Transforming growth factor-β1 is a pro-fibrotic factor that promotes fibroblast-to-myofibroblast differentiation (FMD). Therefore, inhibition of FMD may be an effective strategy for IPF treatment. In this study, we screened the anti-FMD effects of various iminosugars and showed that some compounds, including N-butyldeoxynojirimycin (NB-DNJ, miglustat, an inhibitor of glucosylceramide synthase (GCS)), a clinically approved drug for treating Niemann-Pick disease type C and Gaucher disease type 1, inhibited TGF-β1-induced FMD by inhibiting the nuclear translocation of Smad2/3. N-butyldeoxygalactonojirimycin having GCS inhibitory effect did not attenuate the TGF-β1-induced FMD, suggesting that NB-DNJ exerts the anti-FMD effects by GCS inhibitory effect independent manner. N-butyldeoxynojirimycin did not inhibit TGF-β1-induced Smad2/3 phosphorylation. In a mouse model of bleomycin (BLM)-induced pulmonary fibrosis, intratracheal or oral administration of NB-DNJ at an early fibrotic stage markedly ameliorated lung injury and deterioration of respiratory functions, such as specific airway resistance, tidal volume, and peak expiratory flow. Furthermore, the anti-fibrotic effects of NB-DNJ in the BLM-induced lung injury model were similar to those of pirfenidone and nintedanib, which are clinically approved drugs for the treatment of IPF. These results suggest that NB-DNJ may be effective for IPF treatment.

Genetic Disruption of Guanylyl Cyclase/Natriuretic Peptide Receptor-A Triggers Differential Cardiac Fibrosis and Disorders in Male and Female Mutant Mice: Role of TGF-β1/SMAD Signaling Pathway

The global targeted disruption of the natriuretic peptide receptor-A (NPRA) gene (Npr1) in mice provokes hypertension and cardiovascular dysfunction. The objective of this study was to determine the mechanisms regulating the development of cardiac fibrosis and dysfunction in Npr1 mutant mice. Npr1 knockout (Npr1^-/-, 0-copy), heterozygous (Npr1^+/-, 1-copy), and wild-type (Npr1^+/+, 2-copy) mice were treated with the transforming growth factor (TGF)-β1 receptor (TGF-β1R) antagonist GW788388 (2 µg/g body weight/day; ip) for 28 days. Hearts were isolated and used for real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blot, and immunohistochemical analyses. The Npr1^-/- (0-copy) mice showed a 6-fold induction of cardiac fibrosis and dysfunction with markedly induced expressions of collagen-1α (3.8-fold), monocyte chemoattractant protein (3.7-fold), connective tissue growth factor (CTGF, 5.3-fold), α-smooth muscle actin (α-SMA, 6.1-fold), TGF-βRI (4.3-fold), TGF-βRII (4.7-fold), and phosphorylated small mothers against decapentaplegic (pSMAD) proteins, including pSMAD-2 (3.2-fold) and pSMAD-3 (3.7-fold), compared with wild-type mice. The expressions of phosphorylated extracellular-regulated kinase ERK1/2 (pERK1/2), matrix metalloproteinases-2, -9, (MMP-2, -9), and proliferating cell nuclear antigen (PCNA) were also significantly upregulated in Npr1 0-copy mice. The treatment of mutant mice with GW788388 significantly blocked the expression of fibrotic markers, SMAD proteins, MMPs, and PCNA compared with the vehicle-treated control mice. The treatment with GW788388 significantly prevented cardiac dysfunctions in a sex-dependent manner in Npr1 0-copy and 1-copy mutant mice. The results suggest that the development of cardiac fibrosis and dysfunction in mutant mice is predominantly regulated through the TGF-β1-mediated SMAD-dependent pathway.

Shexiang Tongxin Dropping Pill Protects Against Chronic Heart Failure in Mice via Inhibiting the ERK/MAPK and TGF-β Signaling Pathways

Background: Chronic heart failure (CHF) is a major public health problem with high mortality and morbidity worldwide. Shexiang Tongxin Dropping Pill (STDP) is a widely used traditional Chinese medicine preparation for coronary heart disease and growing evidence proves that STDP exerts beneficial effects on CHF in the clinic. However, the molecular mechanism of the therapeutic effects of STDP on CHF remains largely unknown.

Objective: This study aimed to elucidate the mechanism of action of STDP against CHF by integrating network pharmacology analysis and whole-transcriptome sequencing.

Methods: First, the mouse model of CHF was established by the transverse aortic constriction (TAC) surgery, and the efficacy of STDP against CHF was evaluated by assessing the alterations in cardiac function, myocardial fibrosis, and cardiomyocyte hypertrophy with echocardiography, Masson’s trichrome staining, and wheat germ agglutinin staining. Next, a CHF disease network was constructed by integrating cardiovascular disease-related genes and the transcriptome sequencing data, which was used to explore the underlying mechanism of action of STDP. Then, the key targets involved in the effects of STDP on CHF were determined by network analysis algorithms, and pathway enrichment analysis was performed to these key genes. Finally, important targets in critical pathway were verified in vivo.

Results: STDP administration obviously improved cardiac function, relieved cardiomyocyte hypertrophy, and ameliorated myocardial fibrosis in CHF mice. Moreover, STDP significantly reversed the imbalanced genes that belong to the disease network of CHF in mice with TAC, and the number of genes with the reverse effect was 395. Pathway analysis of the crucial genes with recovery efficiency revealed that pathways related to fibrosis and energy metabolism were highly enriched, while TGF-β pathway and ERK/MAPK pathway were predicted to be significantly affected. Consistently, validation experiments confirmed that inhibiting ERK/MAPK and TGF-β signaling pathways via reduction of the phosphorylation level of Smad3 and ERK1/2 is the important mechanism of STDP against CHF.

Conclusion: Our data demonstrated that STDP can recover the imbalanced CHF network disturbed by the modeling of TAC through the multi-target and multi-pathway manner in mice, and the mechanisms are mainly related to inhibition of ERK/MAPK and TGF-β signaling pathways.

The cGMP system: components and function

The cyclic guanosine monophosphate (cGMP) signaling system is one of the most prominent regulators of a variety of physiological and pathophysiological processes in many mammalian and non-mammalian tissues. Targeting this pathway by increasing cGMP levels has been a very successful approach in pharmacology as shown for nitrates, phosphodiesterase (PDE) inhibitors and stimulators of nitric oxide-guanylyl cyclase (NO-GC) and particulate GC (pGC). This is an introductory review to the cGMP signaling system intended to introduce those readers to this system, who do not work in this area. This article does not intend an in-depth review of this system. Signal transduction by cGMP is controlled by the generating enzymes GCs, the degrading enzymes PDEs and the cGMP-regulated enzymes cyclic nucleotide-gated ion channels, cGMP-dependent protein kinases and cGMP-regulated PDEs. Part A gives a very concise introduction to the components. Part B gives a very concise introduction to the functions modulated by cGMP. The article cites many recent reviews for those who want a deeper insight.

Chlorogenic Acid Alleviates Hyperglycemia-Induced Cardiac Fibrosis through Activation of the NO/cGMP/PKG Pathway in Cardiac Fibroblasts

SCOPE

Hyperglycemia-induced cardiac fibrosis is one of the main causes of diabetic cardiomyopathy (DM). Chlorogenic acid (CGA) found in many foods has excellent hypoglycemic effectiveness, but it is not known whether CGA can improve DM by inhibiting cardiac fibrosis caused by hyperglycemia.

METHODS AND RESULTS

Type I diabetic mice are induced by streptozotocin, and after treatment with CGA for 12 weeks, cardiac functions and fibrosis are determined. CGA significantly attenuates hyperglycemia-induced cardiac fibrosis and improves cardiac functions. The mechanism of CGA on fibrotic inhibition is further studied by immunofluorescence, western blot and RNA interference technology in vivo and in vitro. The results show CGA exerted its anti-fibrotic effects through activating the cyclic GMP/protein kinase G pathway (cGMP/PKG) to block hyperglycemia-induced nuclear translocation of p-Smad2/3, and then inhibiting pro-fibrotic gene expression in cardiac fibroblasts without depending on its hypoglycemic function. Moreover, the data also revealed that CGA increased cGMP level and activated PKG in cardiac fibroblasts by enhancing endothelial nitric oxide synthase (eNOS) activity and NO production.

CONCLUSION

Besides lowering blood glucose, CGA also has an independent ability to inhibit cardiac fibrosis. Therefore, long-term consumption of foods rich in CGA for diabetic patients will have great benefits to improve diabetic cardiomyopathy.

Epigallocatechin-3-gallate (EGCG) inhibits myofibroblast transformation of human Tenon's fibroblasts

Myofibroblast transformation of human Tenon's fibroblasts severely challenges the outcome of glaucoma filtration surgery. epigallocatechin-3-gallate (EGCG) is considered as a potential reagent to overcome this issue for its anti-fibrosis effect on various human diseases, but it is unclear on the fibrosis of Tenon's fibroblasts. This study was conducted to investigate the effect of EGCG on TGF-β1-induced myofibroblast transformation of human Tenon's fibroblasts. The human Tenon's fibroblasts were incubated in the medium containing 10 ng/mL TGF-β1, and subsequently treated with EGCG or mitomycin C (MMC). The cell proliferation and migration were analyzed. The expression of alpha-smooth muscle actin (α-SMA), type I collagen (Col-I), and p-Smad2/3 were also evaluated. It showed that EGCG and MMC strongly inhibited the elevation in cell number in tissue explants compared to the tissues treated with TGF-β1 alone. Scratch-Wound assay showed that 48 h after TGF-β1 induction, only 10% of the wound width remained. But cells treated with EGCG still showed over 93% wound width. Further, EGCG effectively inhibited TGF-β1-induced expression of α-SMA and Col-I as well as phosphorylation of Smad2/3 in Tenon's fibroblasts. Altogether, we concluded that EGCG suppressed the myofibroblast transformation in Tenon's fibroblasts through inactivating TGF-β1/Smad signaling. These findings demonstrate that EGCG can be considered as one of the possible antifibrotic reagents for preventing postoperative scarring in glaucoma filtration surgery.

A concise discussion of the regulatory role of cGMP kinase I in cardiac physiology and pathology

The underlying cause of cardiac hypertrophy, fibrosis, and heart failure has been investigated in great detail using different mouse models. These studies indicated that cGMP and cGMP-dependent protein kinase type I (cGKI) may ameliorate these negative phenotypes in the adult heart. Recently, evidence has been published that cardiac mitochondrial BKCa channels are a target for cGKI and that activation of mitoBKCa channels may cause some of the positive effects of conditioning in ischemia/reperfusion injury. It will be pointed out that most studies could not present convincing evidence that it is the cGMP level and the activity cGKI in specific cardiac cells that reduces hypertrophy or heart failure. However, anti-fibrotic compounds stimulating nitric oxide-sensitive guanylyl cyclase may be an upcoming therapy for abnormal cardiac remodeling.

Roles of PDE1 in Pathological Cardiac Remodeling and Dysfunction

Pathological cardiac hypertrophy and dysfunction is a response to various stress stimuli and can result in reduced cardiac output and heart failure. Cyclic nucleotide signaling regulates several cardiac functions including contractility, remodeling, and fibrosis. Cyclic nucleotide phosphodiesterases (PDEs), by catalyzing the hydrolysis of cyclic nucleotides, are critical in the homeostasis of intracellular cyclic nucleotide signaling and hold great therapeutic potential as drug targets. Recent studies have revealed that the inhibition of the PDE family member PDE1 plays a protective role in pathological cardiac remodeling and dysfunction by the modulation of distinct cyclic nucleotide signaling pathways. This review summarizes recent key findings regarding the roles of PDE1 in the cardiac system that can lead to a better understanding of its therapeutic potential.

ω3-Polyunsaturated fatty acids for heart failure: Effects of dose on efficacy and novel signaling through free fatty acid receptor 4

Heart failure (HF) affects 5.7 million in the U.S., and despite well-established pharmacologic therapy, the 5-year mortality rate remains near 50%. Furthermore, the mortality rate for HF has not declined in years, highlighting the need for new therapeutic options. Omega-3 polyunsaturated fatty acids (ω3-PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are important regulators of cardiovascular health. However, questions of efficacy and mechanism of action have made the use of ω3-PUFAs in all cardiovascular disease (CVD) controversial. Here, we review recent studies in animal models of HF indicating that ω3-PUFAs, particularly EPA, are cardioprotective, with the results indicating a threshold for efficacy. We also examine clinical studies suggesting that ω3-PUFAs improve outcomes in patients with HF. Due to the relatively small number of clinical studies of ω3-PUFAs in HF, we discuss EPA concentration-dependency on outcomes in clinical trials of CVD to gain insight into the perceived questionable efficacy of ω3-PUFAs clinically, with the results again indicating a threshold for efficacy. Ultimately, we suggest that the main failing of ω3-PUFAs in clinical trials might be a failure to reach a therapeutically effective concentration. We also examine mechanistic studies suggesting that ω3-PUFAs signal through free fatty acid receptor 4 (Ffar4), a G-protein coupled receptor (GPR) for long-chain fatty acids (FA), thereby identifying an entirely novel mechanism of action for ω3-PUFA mediated cardioprotection. Finally, based on mechanistic animal studies suggesting that EPA prevents interstitial fibrosis and diastolic dysfunction, we speculate about a potential benefit for EPA-Ffar4 signaling in heart failure preserved with ejection fraction.

Role of TGFβ signaling in the pathogenesis of Alzheimer's disease

Aging is the main risk factor for Alzheimer’s disease (AD); being associated with conspicuous changes on microglia activation. Aged microglia exhibit an increased expression of cytokines, exacerbated reactivity to various stimuli, oxidative stress, and reduced phagocytosis of β-amyloid (Aβ). Whereas normal inflammation is protective, it becomes dysregulated in the presence of a persistent stimulus, or in the context of an inflammatory environment, as observed in aging. Thus, neuroinflammation can be a self-perpetuating deleterious response, becoming a source of additional injury to host cells in neurodegenerative diseases. In aged individuals, although transforming growth factor β (TGFβ) is upregulated, its canonical Smad3 signaling is greatly reduced and neuroinflammation persists. This age-related Smad3 impairment reduces protective activation while facilitating cytotoxic activation of microglia through several cellular mechanisms, potentiating microglia-mediated neurodegeneration. Here, we critically discuss the role of TGFβ-Smad signaling on the cytotoxic activation of microglia and its relevance in the pathogenesis of AD. Other protective functions, such as phagocytosis, although observed in aged animals, are not further induced by inflammatory stimuli and TGFβ1. Analysis in silico revealed that increased expression of receptor scavenger receptor (SR)-A, involved in Aβ uptake and cell activation, by microglia exposed to TGFβ, through a Smad3-dependent mechanism could be mediated by transcriptional co-factors Smad2/3 over the MSR1 gene. We discuss that changes of TGFβ-mediated regulation could at least partially mediate age-associated microglia changes, and, together with other changes on inflammatory response, could result in the reduction of protective activation and the potentiation of cytotoxicity of microglia, resulting in the promotion of neurodegenerative diseases.

Angiotensin-converting enzyme-2 overexpression improves atrial remodeling and function in a canine model of atrial fibrillation

BACKGROUND

Atrial fibrosis is an important factor in initiating and maintaining atrial fibrillation. The purpose of this study was to test the hypothesis that atrial angiotensin-converting enzyme-2 (ACE2) overexpression might inhibit atrial collagen accumulation and improve atrial remodeling in a canine atrial pacing model.

METHODS AND RESULTS

Thirty-two mongrel dogs of both genders were divided randomly into 4 groups: sham-operated, control, gene therapy with adenovirus-enhanced green fluorescent protein (Ad-EGFP), and gene therapy with Ad-ACE2. All of the dogs in the control, Ad-EGFP, and Ad-ACE2 groups were paced at 450 bpm for a period of 14 days. The dogs in the sham group were instrumented without pacing. After 2 weeks, all of the dogs underwent a thoracotomy operation and received epicardial gene painting. On post-gene transfer day 21, the animals underwent electrophysiology, histology, and molecular studies. The percentage of fibrosis in the Ad-ACE2 group was markedly lower than the percentage in the control and Ad-EGFP groups. Compared with the other groups, ACE2 expression was increased significantly in the Ad-ACE2 group. Compared with the sham and Ad-ACE2 groups, the expression levels of transforming growth factor-β1 and Smad3 were significantly higher in the Ad-EGFP and control groups; however, the expression levels of Smad7 were lower in the atrial tissue as detected by Western blot and reverse transcription polymerase chain reaction.

CONCLUSIONS

Our results demonstrate that the overexpression of ACE2 inhibits atrial collagen accumulation and improves left atrial remodeling and function in a canine model of atrial fibrillation. Thus, targeted gene ACE2 therapy provides a promising approach for the treatment of atrial fibrillation.

Chronic inhibition of cyclic guanosine monophosphate-specific phosphodiesterase 5 prevented cardiac fibrosis through inhibition of transforming growth factor β-induced Smad signaling

Recent evidences suggested that cyclic guanosine monophosphate-specific phosphodiesterase 5 (PDE5) inhibitor represents an important therapeutic target for cardiovascular diseases. Whether and how it ameliorates cardiac fibrosis, a major cause of diastolic dysfunction and heart failure, is unknown. The purpose of this study was to investigate the effects of PDE5 inhibitor on cardiac fibrosis. We assessed cardiac fibrosis and pathology in mice subjected to transverse aortic constriction (TAC). Oral sildenafil, a PDE5 inhibitor, was administered in the therapy group. In control mice, 4 weeks of TAC induced significant cardiac dysfunction, cardiac fibrosis, and cardiac fibroblast activation (proliferation and transformation to myofibroblasts). Sildenafil treatment markedly prevented TAC-induced cardiac dysfunction, cardiac fibrosis and cardiac fibroblast activation but did not block TAC-induced transforming growth factor-β1 (TGF-β1) production and phosphorylation of Smad2/3. In isolated cardiac fibroblasts, sildenafil blocked TGF-β1-induced cardiac fibroblast transformation, proliferation and collagen synthesis. Furthermore, we found that sildenafil induced phosphorylated cAMP response element binding protein (CREB) and reduced CREB-binding protein 1 (CBP1) recruitment to Smad transcriptional complexes. PDE5 inhibition prevents cardiac fibrosis by reducing CBP1 recruitment to Smad transcriptional complexes through CREB activation in cardiac fibroblasts.

Gualou Xiebai Decoction prevents myocardial fibrosis by blocking TGF-beta/Smad signalling

OBJECTIVES

The present study is aimed to investigate the effect of Gualou Xiebai Decoction (GXD) ethanol extract on myocardial fibrosis and clarify the possible mechanism.

METHODS

Rats with ligated left anterior descending coronary artery were treated with GXD ethanol extract (1.14 g/kg, 2.27 g/kg, 4.53 g/kg) daily via gavage for 4 weeks. Histopathological changes and collagen distribution were evaluated by haematoxylin and eosin and Masson staining. The mRNA levels of Collagen I and Collagen III were detected by real-time PCR. The expressions of TGF-β1, TGFβ receptor (TGFβR)I, TGFβRII, P-Smad2/3 and Smad7 were determined by Western blot.

RESULTS

GXD treatment was significantly reduced the heart weight/body weight ratio (P < 0.05) as well as the left ventricle weight/body weight ratio (P < 0.05). It also significantly alleviated the degree of inflammation, decreased myocardial collagen volume fraction (P < 0.05 ∼ 0.01), together with markedly prevented the upregulations of Collagen I and Collagen III (P < 0.05 ∼ 0.01). Moreover, GXD downregulated expressions of TGF-β1, TGFβRI, TGFβRII, Smad2/3 whereas improved Smad7 expression in the myocardial fibrosis rats.

CONCLUSIONS

GXD ameliorates myocardial fibrosis induced by cardiac infarction with ligated left anterior descending coronary artery, the mechanism maybe involve in inhibiting the TGF-β1 signalling pathway.

CCL2/CCR2 chemokine signaling coordinates survival and motility of breast cancer cells through Smad3 protein- and p42/44 mitogen-activated protein kinase (MAPK)-dependent mechanisms

Increased cell motility and survival are important hallmarks of metastatic tumor cells. However, the mechanisms that regulate the interplay between these cellular processes remain poorly understood. In these studies, we demonstrate that CCL2, a chemokine well known for regulating immune cell migration, plays an important role in signaling to breast cancer cells. We report that in a panel of mouse and human breast cancer cell lines CCL2 enhanced cell migration and survival associated with increased phosphorylation of Smad3 and p42/44MAPK proteins. The G protein-coupled receptor CCR2 was found to be elevated in breast cancers, correlating with CCL2 expression. RNA interference of CCR2 expression in breast cancer cells significantly inhibited CCL2-induced migration, survival, and phosphorylation of Smad3 and p42/44MAPK proteins. Disruption of Smad3 expression in mammary carcinoma cells blocked CCL2-induced cell survival and migration and partially reduced p42/44MAPK phosphorylation. Ablation of MAPK phosphorylation in Smad3-deficient cells with the MEK inhibitor U0126 further reduced cell survival but not migration. These data indicate that Smad3 signaling through MEK-p42/44MAPK regulates CCL2-induced cell motility and survival, whereas CCL2 induction of MEK-p42/44MAPK signaling independent of Smad3 functions as an alternative mechanism for cell survival. Furthermore, we show that CCL2-induced Smad3 signaling through MEK-p42/44MAPK regulates expression and activity of Rho GTPase to mediate CCL2-induced breast cancer cell motility and survival. With these studies, we characterize an important role for CCL2/CCR2 chemokine signaling in regulating the intrinsic relationships between breast cancer cell motility and survival with implications on the metastatic process.

DHA derivatives of fish oil as dietary supplements: a nutrition-based drug discovery approach for therapies to prevent metabolic cardiotoxicity

INTRODUCTION

During the early 1970s, Danish physicians Jorn Dyerberg and colleagues observed that Greenland Eskimos consuming fatty fishes exhibited low incidences of heart disease. Fish oil is now one of the most commonly consumed dietary supplements. In 2004, concentrated fish oil was approved as a drug by the FDA for the treatment of hyperlipidemia. Fish oil contains two major omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). With advancements in lipid concentration and purification techniques, EPA- or DHA-enriched products are now commercially available, and the availability of these components in isolation allows their individual effects to be examined. Newly synthesized derivatives and endogenously discovered metabolites of DHA exhibit therapeutic utility for obesity, metabolic syndrome and cardiovascular disease.

AREAS COVERED

This review summarizes our current knowledge on the distinct effects of EPA and DHA to prevent metabolic syndrome and reduce cardiotoxicity risk. Since EPA is an integral component of fish oil, we will briefly review EPA effects, but our main theme will be to summarize effects of the DHA derivatives that are available today. We focus on using nutrition-based drug discovery to explore the potential of DHA derivatives for the treatment of obesity, metabolic syndrome and cardiovascular diseases.

EXPERT OPINION

The safety and efficacy evaluation of DHA derivatives will provide novel biomolecules for the drug discovery arsenal. Novel nutritional-based drug discoveries of DHA derivatives or metabolites may provide realistic and alternative strategies for the treatment of metabolic and cardiovascular disease.

Molecular mechanisms underlying cardiac antihypertrophic and antifibrotic effects of natriuretic peptides

Natriuretic peptides (NPs) exert well-characterized protective effects on the cardiovascular system, such as vasorelaxation, natri- and diuresis, increase of endothelial permeability, and inhibition of renin-angiotensin-aldosterone system. It has been reported that they also possess antihypertrophic and antifibrotic properties and contribute actively to cardiac remodeling. As a consequence, they are involved in several aspects of cardiovascular diseases. Antihypertrophic and antifibrotic actions of NPs appear to be mediated by specific signaling pathways within a more complex cellular network. Elucidation of the molecular mechanisms underlying the effects of NPs on cardiac remodeling represents an important research objective in order to gain more insights on the complex network leading to cardiac hypertrophy, ventricular dysfunction, and transition to heart failure, and in the attempt to develop novel therapeutic agents. The aim of the present article is to review well-characterized molecular mechanisms underlying the antihypertrophic and antifibrotic effects of NPs in the heart that appear to be mainly mediated by guanylyl cyclase type A receptor. In particular, we discuss the calcineurin/NFAT, the sodium exchanger NHE-1, and the TGFβ1/Smad signaling pathways. The role of guanylyl cyclase type B receptor, along with the emerging functional significance of natriuretic peptide receptor type C as mediators of CNP antihypertrophic and antifibrotic actions in the heart are also considered.

Omega-3 fatty acids prevent pressure overload-induced cardiac fibrosis through activation of cyclic GMP/protein kinase G signaling in cardiac fibroblasts

BACKGROUND

Omega-3 polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid) from fish oil ameliorate cardiovascular diseases. However, little is known about the effects of ω-3 polyunsaturated fatty acids on cardiac fibrosis, a major cause of diastolic dysfunction and heart failure. The present study assessed the effects of ω-3 polyunsaturated fatty acids on cardiac fibrosis.

METHODS AND RESULTS

We assessed left ventricular fibrosis and pathology in mice subjected to transverse aortic constriction after the consumption of a fish oil or a control diet. In control mice, 4 weeks of transverse aortic constriction induced significant cardiac dysfunction, cardiac fibrosis, and cardiac fibroblast activation (proliferation and transformation into myofibroblasts). Dietary supplementation with fish oil prevented transverse aortic constriction-induced cardiac dysfunction and cardiac fibrosis and blocked cardiac fibroblast activation. In heart tissue, transverse aortic constriction increased active transforming growth factor-β1 levels and phosphorylation of Smad2. In isolated adult mouse cardiac fibroblasts, transforming growth factor-β1 induced cardiac fibroblast transformation, proliferation, and collagen synthesis. Eicosapentaenoic acid and docosahexaenoic acid increased cyclic GMP levels and blocked cardiac fibroblast transformation, proliferation, and collagen synthesis. Eicosapentaenoic acid and docosahexaenoic acid blocked phospho-Smad2/3 nuclear translocation. DT3, a protein kinase G inhibitor, blocked the antifibrotic effects of eicosapentaenoic acid and docosahexaenoic acid. Eicosapentaenoic acid and docosahexaenoic acid increased phosphorylated endothelial nitric oxide synthase and endothelial nitric oxide synthase protein levels and nitric oxide production.

CONCLUSION

Omega-3 fatty acids prevent cardiac fibrosis and cardiac dysfunction by blocking transforming growth factor-β1-induced phospho-Smad2/3 nuclear translocation through activation of the cyclic GMP/protein kinase G pathway in cardiac fibroblasts.

Atrial fibrillation induces myocardial fibrosis through angiotensin II type 1 receptor-specific Arkadia-mediated downregulation of Smad7

RATIONALE

Tachycardia-induced atrial fibrosis is a hallmark of structural remodeling of atrial fibrillation (AF). The molecular mechanisms underlying the AF-induced atrial fibrosis remain unclear.

OBJECTIVE

To determine the role of angiotensin II (Ang II)/Ang II type 1 (AT(1)) receptor-coupled transforming growth factor (TGF)-β(1)/Smad signaling pathway in the AF-induced atrial fibrosis.

METHODS AND RESULTS

Rapid atrial pacing (1000 ppm) was applied to the left atrium of rabbit heart to induce atrial fibrillation and fibrosis. Quantitative PCR and Western blot analysis revealed that rapid atrial pacing caused a marked increase in the expression of Ang II, TGF-β(1), phosphorylated Smad2/3 (P-Smad2/3), Arkadia, and hydroxyproline synthesis. However, the expression of Smad7, a key endogenous antagonist of the TGF-β(1)/Smad-mediated fibrosis, was significantly decreased. These changes were dose-dependently reversed by AT(1) receptor antagonist losartan, implicating the involvement of AF-induced release of Ang II and activation of AT(1) receptor-specific pathway. In the adult rabbit cardiac fibroblasts, Ang II increased the expression of TGF-β(1), P-Smad2/3, Smad4, Arkadia, and collagen I synthesis and significantly reduced Smad7 expression. These effects of Ang II were reversed by losartan but not by the AT(2) antagonist (PD123319). In addition, extracellular signal-regulated kinase inhibitor and anti-TGF-β(1) antibody also blocked the Ang II-induced downregulation of Smad7. Silencing of Smad7 gene by small interfering RNA abolished the antagonism of losartan on the fibrogenic effects of Ang II on cardiac fibroblasts, whereas overexpression of Smad7 blocked Ang II-induced increase in collagen I synthesis.

CONCLUSIONS

Ang II/AT(1) receptor-specific activation of Arkadia-mediated poly-ubiquitination and degradation of Smad7 may decrease the inhibitory feedback regulation of TGF-β(1)/Smad signaling and serves as a key mechanism for AF-induced atrial fibrosis.

Inhibition of transforming growth factor-beta signaling induces left ventricular dilation and dysfunction in the pressure-overloaded heart

This study utilized a transgenic mouse model that expresses an inducible dominant-negative mutation of the transforming growth factor (TGF)-beta type II receptor (DnTGFbetaRII) to define the structural and functional responses of the left ventricle (LV) to pressure-overload stress in the absence of an intact TGF-beta signaling cascade. DnTGFbetaRII and nontransgenic (NTG) control mice (male, 8-10 wk) were randomized to receive Zn(2+) (25 mM ZnSO(4) in drinking H(2)O to induce DnTGFbetaRII gene expression) or control tap H(2)O and then further randomized to undergo transverse aortic constriction (TAC) or sham surgery. At 7 days post-TAC, interstitial nonmyocyte proliferation (Ki67 staining) was greatly reduced in LV of DnTGFbetaRII+Zn(2+) mice compared with the other TAC groups. At 28 and 120 days post-TAC, collagen deposition (picrosirius-red staining) in LV was attenuated in DnTGFbetaRII+Zn(2+) mice compared with the other TAC groups. LV end systolic diameter and end systolic and end diastolic volumes were markedly increased, while ejection fraction and fractional shortening were significantly decreased in TAC-DnTGFbetaRII+Zn(2+) mice compared with the other groups at 120 days post-TAC. These data indicate that interruption of TGF-beta signaling attenuates pressure-overload-induced interstitial nonmyocyte proliferation and collagen deposition and promotes LV dilation and dysfunction in the pressure-overloaded heart, thus creating a novel model of dilated cardiomyopathy.