Targeted deletion of MMP-9 attenuates myocardial contractile dysfunction in heart failure

Exosomes as biomarkers and therapy in type 2 diabetes mellitus and associated complications

Type 2 diabetes mellitus (T2DM) is one of the most prevalent metabolic disorders worldwide. However, T2DM still remains underdiagnosed and undertreated resulting in poor quality of life and increased morbidity and mortality. Given this ongoing burden, researchers have attempted to locate new therapeutic targets as well as methodologies to identify the disease and its associated complications at an earlier stage. Several studies over the last few decades have identified exosomes, small extracellular vesicles that are released by cells, as pivotal contributors to the pathogenesis of T2DM and its complications. These discoveries suggest the possibility of novel detection and treatment methods. This review provides a comprehensive presentation of exosomes that hold potential as novel biomarkers and therapeutic targets. Additional focus is given to characterizing the role of exosomes in T2DM complications, including diabetic angiopathy, diabetic cardiomyopathy, diabetic nephropathy, diabetic peripheral neuropathy, diabetic retinopathy, and diabetic wound healing. This study reveals that the utilization of exosomes as diagnostic markers and therapies is a realistic possibility for both T2DM and its complications. However, the majority of the current research is limited to animal models, warranting further investigation of exosomes in clinical trials. This review represents the most extensive and up-to-date exploration of exosomes in relation to T2DM and its complications.

Prognostic role of tissue plasminogen activator in coronary artery disease with or without aortic valve sclerosis

AIMS

We sought to investigate the relationship between circulating tissue plasminogen activator (t-PA) level and long-term outcomes in stable coronary artery disease patients with or without aortic valve sclerosis (AVSc).

METHODS AND RESULTS

Serum levels of t-PA were determined in 347 consecutive stable angina patients with (n = 183) or without (n = 164) AVSc. Outcomes were prospectively recorded as planned clinic evaluations every 6 months up to 7 years. The primary endpoint was a composite of cardiovascular death and rehospitalization due to heart failure. The secondary endpoint included all-cause mortality, cardiovascular death, and rehospitalization due to heart failure. Serum t-PA was significantly higher in AVSc than in non-AVSc patients (2131.22 pg/mL vs. 1495.85 pg/mL, P < 0.001). For patients with AVSc, those with t-PA level above the median (>1840.68 pg/mL) were more likely to meet the primary and secondary endpoints (all P < 0.001). After adjusting for potential confounding factors, serum t-PA level remained significantly predictive for each endpoint in the Cox proportional hazard models. The prognostic value of t-PA was good, with an AUC-ROC of 0.753 (P < 0.001). The combination of t-PA with traditional risk factors improved the risk reclassification of AVSc patients, with a net reclassification index of 0.857 and an integrated discrimination improvement of 0.217 (all P < 0.001). However, for patients without AVSc, both primary and secondary endpoints were similar, irrespective of t-PA levels.

CONCLUSIONS

Elevated circulating t-PA confers an increased risk for poor long-term clinical outcomes in stable coronary artery disease patients with AVSc.

Elevated serum matrix metalloproteinase-2 levels in heart failure patients with reduced ejection fraction and Cheyne-Stokes respiration

STUDY OBJECTIVES

Cheyne-Stokes respiration (CSR), a kind of central sleep apnea (CSA), is referred to as a poor prognostic factor in heart failure patients with reduced ejection fraction (HFrEF). Matrix metalloproteinase (MMP) and B-type natriuretic peptide (BNP) play important roles in HFrEF patients and are markers of poor prognosis. However, there is no literature mentioning the changes in MMP and BNP in HFrEF patients with CSR.

METHODS

From June 2018 to June 2019, 41 adult patients with stable heart failure and left ventricular ejection fraction (LVEF) <50% were enrolled from the cardiology clinic. After history taking and medication review to exclude possible central nervous system or medication related CSA, an overnight polysomnography study was performed, and CSR was identified. The morning serum MMP-2, MMP-9 and BNP levels were determined using enzyme-linked immunosorbent assay and fluorescence immunoassay techniques. A positive airway pressure (PAP) device was applied to 7 patients for 3 months.

RESULTS

The serum MMP-2 and BNP levels were significantly higher in HFrEF patients with CSR than in patients without CSR. In addition, elevated serum MMP-2 levels correlated well with the severity of sleep apnea and intermittent hypoxia, which were represented as the apnea-hypopnea index and the oxygen-desaturation index. No positive correlation was found between those markers and LVEF. Finally, the treatment of sleep apnea with CPAP for 3 months tended to reduce the elevated serum MMP-2 levels.

CONCLUSIONS

Higher serum MMP-2 and BNP levels were found in HFrEF patients with CSR. Elevated MMP-2 levels were correlated with the severity of sleep apnea and intermittent hypoxia.

MMP9 inhibition increases autophagic flux in chronic heart failure

Increased matrix metalloprotease 9 (MMP9) after myocardial infarction (MI) exacerbates ischemia-induced chronic heart failure (CHF). Autophagy is cardioprotective during CHF; however, whether increased MMP9 suppresses autophagic activity in CHF is unknown. This study aimed to determine whether increased MMP9 suppressed autophagic flux and MMP9 inhibition increased autophagic flux in the heart of rats with post-MI CHF. Sprague-Dawley rats underwent either sham surgery or coronary artery ligation 6-8 wk before being treated with MMP9 inhibitor for 7 days, followed by cardiac autophagic flux measurement with lysosomal inhibitor bafilomycin A1. Furthermore, autophagic flux was measured in vitro by treating H9c2 cardiomyocytes with two independent pharmacological MMP9 inhibitors, salvianolic acid B (SalB) and MMP9 inhibitor-I, and CRISPR/cas9-mediated MMP9 genetic ablation. CHF rats showed cardiac infarct, significantly increased left ventricular end-diastolic pressure (LVEDP), and increased MMP9 activity and fibrosis in the peri-infarct areas of left ventricular myocardium. Measurement of the autophagic markers LC3B-II and p62 with lysosomal inhibition showed decreased autophagic flux in the peri-infarct myocardium. Treatment with SalB for 7 days in CHF rats decreased MMP9 activity and cardiac fibrosis but increased autophagic flux in the peri-infarct myocardium. As an in vitro corollary study, measurement of autophagic flux in H9c2 cardiomyocytes and fibroblasts showed that pharmacological inhibition or genetic ablation of MMP9 upregulates autophagic flux. These data are consistent with our observations that MMP9 inhibition upregulates autophagic flux in the heart of rats with CHF. In conclusion, the results in this study suggest that the beneficial outcome of MMP9 inhibition in pathological cardiac remodeling is in part mediated by improved autophagic flux.NEW & NOTEWORTHY This study elucidates that the improved cardiac extracellular matrix (ECM) remodeling and cardioprotective effect of matrix metalloprotease 9 (MMP9) inhibition in chronic heart failure (CHF) are via increased autophagic flux. Autophagy is cardioprotective; however, the mechanism of autophagy suppression in CHF is unknown. We for the first time demonstrated here that increased MMP9 suppressed cardiac autophagy and ablation of MMP9 increased cardiac autophagic flux in CHF rats. Restoring the physiological level of autophagy in the failing heart is a challenge, and our study addressed this challenge. The novelty and highlights of this report are as follows: 1) MMP9 regulates cardiomyocyte and fibroblast autophagy, 2) MMP9 inhibition protects CHF after myocardial infarction (MI) via increased cardiac autophagic flux, 3) MMP9 inhibition increased cardiac autophagy via activation of AMP-activated protein kinase (AMPK)α, Beclin-1, Atg7 pathway and suppressed mechanistic target of rapamycin (mTOR) pathway.

Role of the ADCY9 gene in cardiac abnormalities of the Rubinstein-Taybi syndrome

BACKGROUND

Rubinstein-Taybi syndrome (RTS) is a rare, congenital, plurimalformative, and neurodevelopmental disorder. Previous studies have reported that large deletions contribute to more severe RTS phenotypes than those caused by CREBBP point mutations, suggesting a concurrent pathogenetic role of flanking genes, typical of contiguous gene syndromes, but the detailed genetics are unclear.

RESULTS

This study presented a rare case of Rubinstein-Taybi (RT) syndrome with serious cardiac abnormalities. Based on the clinical and genetic analysis of the patient, the ADCY9 gene deletion was highlighted as a plausible explanation of cardiac abnormalities. In adcy9 morphant zebrafish, cardiac malformation was observed. Immunofluorescence study disclosed increased macrophage migration and cardiac apoptosis. RNA sequencing in zebrafish model highlighted the changes of a number of genes, including increased expression of the mmp9 gene which encodes a matrix metalloproteinase with the main function to degrade and remodel extracellular matrix.

CONCLUSIONS

In this study, we identified a plausible new candidate gene ADCY9 of CHD through the clinical and genetic analysis of a rare case of Rubinstein-Taybi (RT) syndrome with serious cardiac abnormalities. By functional study of zebrafish, we demonstrated that deletion of adcy9 is the causation for the cardiac abnormalities. Cardiac apoptosis and increased expression of the MMP9 gene are involved in the pathogenesis.

Cardiac remodeling secondary to chronic volume overload is attenuated by a novel MMP9/2 blocking antibody

Objective

Monoclonal antibody derivatives are promising drugs for the treatment of various diseases due to their high matrix metalloproteinases (MMP) active site specificity. We studied the effects of a novel antibody, SDS3, which specifically recognizes the mature active site of MMP9/2 during ventricular remodeling progression in a mouse model of chronic volume overload (VO).

Methods

VO was induced by creating an aortocaval fistula (ACF) in 10- to 12-week-old C57BL male mice. The VO-induced mice were treated with either vehicle control (PBS) or with SDS3 twice weekly by intraperitoneal (ip) injection. The relative changes in cardiac parameters between baseline (day 1) and end-point (day 30), were evaluated by echocardiography. The effects of SDS3 treatment on cardiac fibrosis, cardiomyocyte volume, and cardiac inflammation were tested by cardiac staining with Masson's trichrome, wheat Germ Agglutinin (WGA), and CD45, respectively. Serum levels of TNFα and IL-6 with and without SDS3 treatment were tested by ELISA.

Results

SDS3 significantly reduced cardiac dilatation, left ventricular (LV) mass, and cardiomyocyte hypertrophy compared to the vehicle treated animals. The antibody also reduced the heart-to-body weight ratio of the ACF animals to values comparable to those of the controls. Interestingly, the SDS3 group underwent significant reduction of cardiac inflammation and pro-inflammatory cytokine production, indicating a regulatory role for MMP9/2 in tissue remodeling, possibly by tumor necrosis factor alpha (TNFα) activation. In addition, significant changes in the expression of proteins related to mitochondrial function were observed in ACF animals, these changes were reversed following treatment with SDS3.

Conclusion

The data suggest that MMP9/2 blockage with SDS3 attenuates myocardial remodeling associated with chronic VO by three potential pathways: downregulating the extracellular matrix proteolytic cleavage, reducing the cardiac inflammatory responses, and preserving the cardiac mitochondrial structure and function.

Perivascular fibrosis and the microvasculature of the heart. Still hidden secrets of pathophysiology?

Perivascular fibrosis, the deposition of connective tissue around the vessels, has been demonstrated crucially involved in the development of cardiac dysfunction. Although cardiac fibrosis has been shown to be reversible under certain experimental conditions, effective anti-fibrotic therapies remain largely elusive. Therefore, perivascular fibrosis currently represents a major therapeutic target for cardiovascular diseases. The main topic of this review will be to address the mechanisms underlying perivascular fibrosis of the vasculature within the myocardium, with a special focus on perivascular fibrosis of small vessels, microvascular dysfunction and disease.

GYY4137, a Hydrogen Sulfide Donor Modulates miR194-Dependent Collagen Realignment in Diabetic Kidney

The relationship between hydrogen sulfide (H₂S), microRNAs (miRs), matrix metalloproteinases (MMPs) and poly-ADP-ribose-polymerase-1 (PARP-1) in diabetic kidney remodeling remains mostly obscured. We aimed at investigating whether alteration of miR-194-dependent MMPs and PARP-1 causes renal fibrosis in diabetes kidney, and whether H₂S ameliorates fibrosis. Wild type, diabetic Akita mice as well as mouse glomerular endothelial cells (MGECs) were used as experimental models, and GYY4137 as H₂S donor. In diabetic mice, plasma H₂S levels were decreased while ROS and expression of its modulator (ROMO1) were increased. In addition, alteration of MMPs-9, −13 and −14 expression, PARP-1, HIF1α, and increased collagen biosynthesis as well as collagen cross-linking protein, P4HA1 and PLOD2 were observed along with diminished vascular density in diabetic kidney. These changes were ameliorated by GYY4137. Further, downregulated miRNA-194 was normalized by GYY4137 in diabetic kidney. Similar results were obtained in in vitro condition. Interestingly, miR-194 mimic also diminished ROS production, and normalized ROMO1, MMPs-9, −13 and −14, and PARP-1 along with collagen biosynthesis and cross-linking protein in HG condition. We conclude that decrease H₂S diminishes miR-194, induces collagen deposition and realignment leading to fibrosis and renovascular constriction in diabetes. GYY4137 mitigates renal fibrosis in diabetes through miR-194-dependent pathway.

Mechanisms of TFAM-mediated cardiomyocyte protection

Although mitochondrial transcription factor A (TFAM) is a protective component of mitochondrial DNA and a regulator of calcium and reactive oxygen species (ROS) production, the mechanism remains unclear. In heart failure, TFAM is significantly decreased and cardiomyocyte instability ensues. TFAM inhibits nuclear factor of activated T cells (NFAT), which reduces ROS production; additionally, TFAM transcriptionally activates SERCA2a to decrease free calcium. Therefore, decreasing TFAM vastly increases protease expression and hypertrophic factors, leading to cardiomyocyte functional decline. To examine this hypothesis, treatments of 1.0 μg of a TFAM vector and 1.0 μg of a CRISPR-Cas9 TFAM plasmid were administered to HL-1 cardiomyocytes via lipofectamine transfection. Western blotting and confocal microscopy analysis show that CRISPR-Cas9 knockdown of TFAM significantly increased proteases Calpain1, MMP9, and regulators Serca2a, and NFAT4 protein expression. CRISPR knockdown of TFAM in HL-1 cardiomyocytes upregulates degradation factors, leading to cardiomyocyte instability. Hydrogen peroxide oxidative stress decreased TFAM expression and increased Calpain1, MMP9, and NFAT4 protein expression. TFAM overexpression normalizes pathological hypertrophic factor NFAT4 in the presence of oxidative stress.

Long-term dietary quercetin enrichment as a cardioprotective countermeasure in mdx mice

NEW FINDINGS

What is the central question of this study? The central question of this study is to understand whether dietary quercetin enrichment attenuates physiologic, histological, and biochemical indices of cardiac pathology. What is the main finding and its importance? Novel findings from this investigation, in comparison to prior published studies, suggest that mouse strain-dependent cardiac outcomes in performance and remodelling exist. Unlike Mdx/Utrn^-/+ mice, mdx mice receiving lifelong quercetin treatment did not exhibit improvements cardiac function. Similar to prior work in Mdx/Utrn^-/+ mice, histological evidence of remodelling suggests that quercetin consumption may have benefited hearts of mdx mice. Positive outcomes may be related to indirect markers that suggest improved mitochondrial wellbeing and to selected indices of inflammation that were lower in hearts from quercetin-fed mice. Duchenne muscular dystrophy causes a decline in cardiac health, resulting in premature mortality. As a potential countermeasure, quercetin is a polyphenol possessing inherent anti-inflammatory and antioxidant effects that activate proliferator-activated γ coactivator 1α (PGC-1α), increasing the abundance of mitochondrial biogenesis proteins. We investigated the extent to which lifelong 0.2% dietary quercetin enrichment attenuates dystrophic cardiopathology in mdx mice. Dystrophic animals were fed a quercetin-enriched or control diet for 12 months, while control C57 mice were fed a control diet. Cardiac function was assessed via 7 T magnetic resonance imaging at 2, 10 and 14 months. At 14 months, hearts were harvested for histology and Western blotting. The results indicated an mdx strain-dependent decline in cardiac performance at 14 months and that dietary quercetin enrichment did not attenuate functional losses. In contrast, histological analyses provided evidence that quercetin feeding was associated with decreased fibronectin and indirect damage indices (Haematoxylin and Eosin) compared with untreated mdx mice. Dietary quercetin enrichment increased cardiac protein abundance of PGC-1α, cytochrome c, electron transport chain complexes I-V, citrate synthase, superoxide dismutase 2 and glutathione peroxidase (GPX) versus untreated mdx mice. The protein abundance of the inflammatory markers nuclear factor-κB, phosphorylated nuclear factor kappa beta (P-NFκB) and phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (P-IKBα) was decreased by quercetin compared with untreated mdx mice, while preserving nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha( IKBα) compared with mdx mice. Furthermore, quercetin decreased transforming growth factor-β1, cyclooxygenase-2 (COX2) and macrophage-restricted F4/80 protein (F4/80) versus untreated mdx mice. The data suggest that long-term quercetin enrichment does not impact physiological parameters of cardiac function but improves indices of mitochondrial biogenesis and antioxidant enzymes, facilitates dystrophin-associated glycoprotein complex (DGC) assembly and decreases inflammation in dystrophic hearts.

Increased ADAMTS1 mediates SPARC-dependent collagen deposition in the aging myocardium

Secreted protein acidic and rich in cysteine (SPARC) is a collagen-binding matricellular protein highly expressed during fibrosis. Fibrosis is a prominent component of cardiac aging that reduces myocardial elasticity. Previously, we reported that SPARC deletion attenuated myocardial stiffness and collagen deposition in aged mice. To investigate the mechanisms by which SPARC promotes age-related cardiac fibrosis, we evaluated six groups of mice (n = 5-6/group): young (3-5 mo old), middle-aged (10-12 mo old), and old (18-29 mo old) C57BL/6 wild type (WT) and SPARC-null (Null) mice. Collagen content, determined by picrosirius red staining, increased in an age-dependent manner in WT but not in Null mice. A disintegrin and metalloproteinase with thrombospondin-like motifs 1 (ADAMTS1) increased in middle-aged and old WT compared with young, whereas in Null mice only old animals showed increased ADAMTS1 expression. Versican, a substrate of ADAMTS1, decreased with age only in WT. To assess the mechanisms of SPARC-induced collagen deposition, we stimulated cardiac fibroblasts with SPARC. SPARC treatment increased secretion of collagen I and ADAMTS1 (both the 110-kDa latent and 87-kDa active forms) into the conditioned media as well as the cellular expression of transforming growth factor-β1-induced protein (Tgfbi) and phosphorylated Smad2. An ADAMTS1 blocking antibody suppressed the SPARC-induced collagen I secretion, indicating that SPARC promoted collagen production directly through ADAMTS1 interaction. In conclusion, ADAMTS1 is an important mediator of SPARC-regulated cardiac aging.

Ablation of Matrix Metalloproteinase-9 Prevents Cardiomyocytes Contractile Dysfunction in Diabetics

Elevated expression and activity of matrix metalloproteinase-9 (MMP9) and decreased contractility of cardiomyocytes are documented in diabetic hearts. However, it is unclear whether MMP is involved in the regulation of contractility of cardiomyocytes in diabetic hearts. In the present study, we tested the hypothesis that MMP9 regulates contractility of cardiomyocytes in diabetic hearts, and ablation of MMP9 prevents impaired contractility of cardiomyocytes in diabetic hearts. To determine the specific role of MMP9 in cardiomyocyte contractility, we used 12–14 week male WT (normoglycemic sibling of Akita), Akita, and Ins^2+∕−/MMP9^−∕− (DKO) mice. DKO mice were generated by cross-breeding male Ins2^+∕− Akita (T1D) with female MMP9 knockout (MMP9^−∕−) mice. We isolated cardiomyocytes from the heart of the above three groups of mice and measured their contractility and calcium transients. Moreover, we determined mRNA and protein levels of sarco-endoplasmic reticulum calcium ATPase-2a (SERCA-2a), which is involved in calcium handling during contractility of cardiomyocytes in WT, Akita, and DKO hearts using QPCR, Western blotting and immunoprecipitation, respectively. Our results revealed that in Akita hearts where increased expression and activity of MMP9 is reported, the rates of shortening and re-lengthening (±dL/dt) of cardiomyocytes were decreased, time to 90% peak height and baseline during contractility was increased, rate of calcium decay was increased, and calcium transient was decreased as compared to WT cardiomyocytes. However, these changes in Akita were blunted in DKO cardiomyocytes. The molecular analyses of SERCA-2a in the hearts showed that it was downregulated in Akita as compared to WT but was comparatively upregulated in DKO. These results suggest that abrogation of MMP9 gene prevents contractility of cardiomyocytes, possibly by increasing SERCA-2a and calcium transients. We conclude that MMP9 plays a crucial role in the regulation of contractility of cardiomyocytes in diabetic hearts.

Regulation of cardiac microRNAs induced by aerobic exercise training during heart failure

Exercise training (ET) has beneficial effects on the myocardium in heart failure (HF) patients and in animal models of induced cardiac hypertrophy and failure. We hypothesized that if microRNAs (miRNAs) respond to changes following cardiac stress, then myocardial profiling of these miRNAs may reveal cardio-protective mechanisms of aerobic ET in HF. We used ascending aortic stenosis (AS) inducing HF in Wistar rats. Controls were sham-operated animals. At 18 wk after surgery, rats with cardiac dysfunction were randomized to 10 wk of aerobic ET (HF-ET) or to a heart failure sedentary group (HF-S). ET attenuated cardiac remodeling as well as clinical and pathological signs of HF with maintenance of systolic and diastolic function when compared with that of the HF-S. Global miRNA expression profiling of the cardiac tissue revealed 53 miRNAs exclusively dysregulated in animals in the HF-ET, but only 11 miRNAs were exclusively dysregulated in the HF-S. Out of 23 miRNAs that were differentially regulated in both groups, 17 miRNAs exhibited particularly high increases in expression, including miR-598, miR-429, miR-224, miR-425, and miR-221. From the initial set of deregulated miRNAs, 14 miRNAs with validated targets expressed in cardiac tissue that respond robustly to ET in HF were used to construct miRNA-mRNA regulatory networks that revealed a set of 203 miRNA-target genes involved in programmed cell death, TGF-β signaling, cellular metabolic processes, cytokine signaling, and cell morphogenesis. Our findings reveal that ET attenuates cardiac abnormalities during HF by regulating cardiac miRNAs with a potential role in cardio-protective mechanisms through multiple effects on gene expression.

Cardiosome mediated regulation of MMP9 in diabetic heart: role of mir29b and mir455 in exercise

'Cardiosomes' (exosomes from cardiomyocytes) have recently emerged as nanovesicles (30-100 nm) released in the cardiosphere by myocytes and cardiac progenitor cells, though their role in diabetes remains elusive. Diabetic cardiovascular complications are unequivocally benefitted from exercise; however, the molecular mechanisms need exploration. This novel study is based on our observation that exercise brings down the levels of activated (Matrix Metalloprotease 9) in db/db mice in a model of type 2 diabetes. We hypothesize that exosomes that are released during exercise contain microRNAs (mir455, mir29b, mir323-5p and mir466) that bind to the 3' region of MMP9 and downregulate its expression, hence mitigating the deleterious downstream effects of MMP9, which causes extracellular matrix remodeling. First, we confirmed the presence of exosomes in the heart tissue and serum by electron microscopy and flow cytometry, respectively, in the four treatment groups: (i) db/control, (ii) db/control+exercise, (iii) db/db and (iv) db/db+exercise. Use of exosomal markers CD81, Flottilin 1, and acetylcholinesterase activity in the isolated exosomes confirmed enhanced exosomal release in the exercise group. The microRNAs isolated from the exosomes contained mir455, mir29b, mir323-5p and mir466 as quantified by qRTPCR, however, mir29b and mir455 showed highest upregulation. We performed 2D zymography which revealed significantly lowered activity of MMP9 in the db/db exercise group as compared to non-exercise group. The immunohistochemical analysis further confirmed the downregulated expression of MMP9 after exercise. Since MMP9 is involved in matrix degradation and leads to fibrosis and myocyte uncoupling, the present study provides a strong evidence how exercise can mitigate these conditions in diabetic patients.

Histological and biochemical outcomes of cardiac pathology in mdx mice with dietary quercetin enrichment

NEW FINDINGS

What is the central question of this study? Does dietary quercetin enrichment improve biochemical and histological outcomes in hearts from mdx mice? What is the main finding and what is its importance? Biochemical and histological findings suggest that chronic quercetin feeding of mdx mice may improve mitochondrial function and attenuate tissue pathology. Patients with Duchenne muscular dystrophy suffer from cardiac pathology, which causes up to 40% of all deaths because of fibrosis and cardiac complications. Quercetin is a flavonol with anti-inflammatory and antioxidant effects and is also an activator of peroxisome proliferator-activated receptor γ coactivator 1α capable of antioxidant upregulation, mitochondrial biogenesis and prevention of cardiac complications. We sought to determine the extent to which dietary quercetin enrichment prevents (experiment 1) and rescues cardiac pathology (experiment 2) in mdx mice. In experiment 1, 3-week-old mdx mice were fed control chow (C3w6m, n = 10) or chow containing 0.2% quercetin for 6 months (Q3w6m, n = 10). In experiment 2, 3-month-old mdx mice were fed control chow (C3m6m, n = 10) or 0.2% chow containing 0.2% quercetin for 6 months (Q3m6m, n = 10). Hearts were excised for histological and biochemical analyses. In experiment 1, Western blot targets for mitochondrial biogenesis (cytochrome c, P = 0.007) and antioxidant expression (superoxide dismutase 2, P = 0.014) increased in Q3w6m mice compared with C3w6m. Histology revealed increased utrophin (P = 0.025) and decreased matrix metalloproteinase 9 abundance (P = 0.040) in Q3w6m mice compared with C3w6m. In experiment 2, relative (P = 0.023) and absolute heart weights (P = 0.020) decreased in Q3m6m mice compared with C3m6m. Indications of damage (Haematoxylin- and Eosin-stained sections, P = 0.007) and Western blot analysis of transforming growth factor β1 (P = 0.009) were decreased in Q3m6m mice. Six months of quercetin feeding increased a mitochondrial biomarker, antioxidant protein and utrophin and decreased matrix metalloproteinase 9 in young mice. Given that these adaptations are associated with attenuated cardiac pathology and damage, the present findings may indicate that dietary quercetin enrichment attenuates dystrophic cardiac pathology, but physiological confirmation is needed.

Phenanthrene exposure produces cardiac defects during embryo development of zebrafish (Danio rerio) through activation of MMP-9

Phenanthrene (Phe) is one of the most abundant polycyclic aromatic hydrocarbons in the aquatic environment as a result of human activities. It is widely accepted that Phe has cardiotoxic effects. Even so, knowledge concerning the mechanism(s) of cardiac development toxicity is still limited. In this study, we exposed zebrafish embryos to environmentally relevant concentrations of Phe and then investigated its cardiotoxic effects and the mechanism(s) involved. Some cardiac morphogenetic defects, which was characterized by an abnormally looped and enlarged heart, dilated and thinner ventricular wall, and increased interstitial fibrosis, were observed in the Phe treated groups. The mRNA and protein expression levels of matrix metalloproteinase-9 (MMP-9), as well as the MMP-9 activity, were induced. Moreover, during co-treatment of the zebrafish embryos with MMP-9 inhibitor, the cardiac defects caused by Phe were attenuated. In addition, Phe exposure led to an up-regulation of transforming growth factor β (TGF-β), which plays a crucial role in mediating cardiac fibrosis. Taken together, our data indicated that the exposure to Phe of zebrafish embryos disrupted normal cardiac development, and that the cardiac defects induced by Phe were mediated by the MMP-9, while TGF-β was also involved in these cardiac defects.

Membrane-associated matrix proteolysis and heart failure

The extracellular matrix (ECM) is a complex entity containing a large portfolio of structural proteins, signaling molecules, and proteases. Changes in the overall integrity and activational state of these ECM constituents can contribute to tissue structure and function, which is certainly true of the myocardium. Changes in the expression patterns and activational states of a family of ECM proteolytic enzymes, the matrix metalloproteinases (MMPs), have been identified in all forms of left ventricle remodeling and can be a contributory factor in the progression to heart failure. However, new clinical and basic research has identified some surprising and unpredicted changes in MMP profiles in left ventricle remodeling processes, such as with pressure or volume overload, as well as with myocardial infarction. From these studies, it has become recognized that proteolytic processing of signaling molecules by certain MMP types, particularly the transmembrane MMPs, actually may facilitate ECM accumulation and modulate fibroblast transdifferentiation; both are critical events in adverse left ventricle remodeling. Based on the ever-increasing substrates and diversity of biological actions of MMPs, it is likely that continued research about the relationship of left ventricle remodeling in this family of proteases will yield new insights into the ECM remodeling process and new therapeutic targets.

Nampt secreted from cardiomyocytes promotes development of cardiac hypertrophy and adverse ventricular remodeling

Nicotinamide phosphoribosyltransferase (Nampt) is an important coenzyme involved in cellular redox reactions. Inside the cell, Nampt (iNampt) functions as a rate-limiting enzyme in the NAD salvage pathway, and outside the cell (eNampt), it acts as a proinflammatory cytokine. High-circulating levels of Nampt are reported in different pathological conditions. This study was designed to examine the role of Nampt in the development of cardiac hypertrophy and ventricular remodeling. We studied the hypertrophic response in Nampt heterozygous (+/-) knockout and cardiac-specific overexpressing Nampt transgenic mice. Whereas Nampt(+/-) mice were protected against agonist (isoproterenol and angiotensin II)-induced hypertrophy, Nampt transgenic mice spontaneously developed cardiac hypertrophy at 6 mo of age. Experiments conducted to gain insight into the mechanism revealed that treatment of cardiomyocytes with recombinant (eNampt) or overexpression with Nampt-synthesizing adenovirus vector (Ad.Nampt) induced cardiomyocyte hypertrophy. The prohypertrophic effects of eNampt and Ad.Nampt were blocked by the addition of a Nampt-blocking antibody into cultures, thus suggesting that Nampt was in fact invoking hypertrophic response of cardiomyocytes by acting on the cell surface receptors. We also found increased Nampt levels in the supernatant of cardiomyocyte cultures subjected to stress by either serum starvation or H(2)O(2) treatment. Exploration of signaling pathways in Nampt-induced cardiac hypertrophy and fibrosis revealed increased activation of mitogen-activated protein kinases, namely, JNK1, p38, and ERK. This was also associated with increased calcineurin levels and nuclear factor of activated T-cell localization into the nucleus. From these studies we conclude that cardiomyocytes are capable of secreting Nampt during stress, and exogenous Nampt is a positive regulator of cardiac hypertrophy and adverse ventricular remodeling.

Mitochondrial mitophagic mechanisms of myocardial matrix metabolism and remodelling

High levels of homocysteine (Hcy), known as hyperhomocysteinmia (HHcy), are correlated with an increase in extracellular matrix remodelling (ECM) via the matrix metalloproteinases (MMPs) and plasminogen/plasmin system. This results in an increase deposition of collagen that leads to endothelial-myocyte (EM) and myocyte-myocyte (MM) uncoupling; the physiological consequences are a plethora of cardiovascular pathologies. Homocysteine-induced increase in intracellular and mitochondrial Ca(2+) plays an important role in increasing reactive oxygen species (ROS) within mitochondria and instigating mitophagy within the cell. This occurs via several Hcy-mitigated processes: agonizing N-methyl-d-aspartate receptor-1 (NMDA-R1), decreasing expression of peroxisome proliferator activator receptor (PPAR) [thereby increasing oxidation], impairing Ca(2+) handling via Na(+)/Ca(2+) exchanger (NCX1) and Sarco endoplasmic reticulum Ca(2+) ATPase (SERCA-2a). The end result is an increase in ROS that directly or indirectly lead to MMP activation within mitochondria or the cytoplasm. Hcy induces a mitochondrial permeability transition that allows MMPs to be released from mitochondria thereby metabolizing matrix and impairing cardiac function. Further work remains to be elucidated concerning the specific mitochondrial mitophagic mechanisms under which matrix metabolism and remodelling occurs. Moreover, the therapeutic implications of NMDA and PPAR ligands are some promise to patient.

Novel effects of macrolide antibiotics on cardiovascular diseases

Macrolide antibiotics are broadly used for the treatment of various microbial infections. However, they are also known to have multiple biologic effects, such as alteration of inflammatory factors and matrix metalloproteinases (MMPs). Because of controversial results in clinical trials, the effects of macrolides on cardiovascular diseases are still to be elucidated. It has been reported that MMP activity is upregulated in various cardiovascular diseases, such as myocarditis, cardiac transplant rejection and myocardial infarction. However, little is known about the effects of macrolides on cardiovascular diseases. We have reported that clarithromycin suppressed the development of myocarditis, cardiac rejection and myocardial ischemia using animal models. In this article, we reviewed the roles of MMPs in cardiovascular diseases and the effects of macrolides on the prevention of adverse tissue remodeling.

Salvianolic acid B functioned as a competitive inhibitor of matrix metalloproteinase-9 and efficiently prevented cardiac remodeling

Background

Infarct-induced left ventricular (LV) remodeling is a deleterious consequence after acute myocardial infarction (MI) which may further advance to congestive heart failure. Therefore, new therapeutic strategies to attenuate the effects of LV remodeling are urgently needed. Salvianolic acid B (SalB) from Salviae mitiorrhizae, which has been widely used in China for the treatment of cardiovascular diseases, is a potential candidate for therapeutic intervention of LV remodeling targeting matrix metalloproteinase-9 (MMP-9).

Results

Molecular modeling and LIGPLOT analysis revealed in silico docking of SalB at the catalytic site of MMP-9. Following this lead, we expressed truncated MMP-9 which contains only the catalytic domain, and used this active protein for in-gel gelatin zymography, enzymatic analysis, and SalB binding by Biacore. Data generated from these assays indicated that SalB functioned as a competitive inhibitor of MMP-9. In our rat model for cardiac remodeling, western blot, echocardiography, hemodynamic measurement and histopathological detection were used to detect the effects and mechanism of SalB on cardio-protection. Our results showed that in MI rat, SalB selectively inhibited MMP-9 activities without affecting MMP-9 expression while no effect of SalB was seen on MMP-2. Moreover, SalB treatment in MI rat could efficiently increase left ventricle wall thickness, improve heart contractility, and decrease heart fibrosis.

Conclusions

As a competitive inhibitor of MMP-9, SalB presents significant effects on preventing LV structural damage and preserving cardiac function. Further studies to develop SalB and its analogues for their potential for cardioprotection in clinic are warranted.

Intravenous hMSCs improve myocardial infarction in mice because cells embolized in lung are activated to secrete the anti-inflammatory protein TSG-6

Quantitative assays for human DNA and mRNA were used to examine the paradox that intravenously (i.v.) infused human multipotent stromal cells (hMSCs) can enhance tissue repair without significant engraftment. After 2 x 10(6) hMSCs were i.v. infused into mice, most of the cells were trapped as emboli in lung. The cells in lung disappeared with a half-life of about 24 hr, but <1000 cells appeared in six other tissues. The hMSCs in lung upregulated expression of multiple genes, with a large increase in the anti-inflammatory protein TSG-6. After myocardial infarction, i.v. hMSCs, but not hMSCs transduced with TSG-6 siRNA, decreased inflammatory responses, reduced infarct size, and improved cardiac function. I.v. administration of recombinant TSG-6 also reduced inflammatory responses and reduced infarct size. The results suggest that improvements in animal models and patients after i.v. infusions of MSCs are at least in part explained by activation of MSCs to secrete TSG-6.

Isoproterenol disperses distribution of NADPH oxidase, MMP-9, and pPKCepsilon in the heart, which are mitigated by endothelin receptor antagonist CPU0213

AIM

Spatial dispersion of bioactive substances in the myocardium could serve as pathological basis for arrhythmogenesis and cardiac impairment by beta-adrenoceptor stimulation. We hypothesized that dispersed NADPH oxidase, protein kinase Cepsilon (PKCepsilon), early response gene (ERG), and matrix metalloproteinase 9(MMP-9) across the heart by isoproterenol (ISO) medication might be mediated by the endothelin (ET) - ROS pathway. We aimed to verify if ISO induced spatially heterogeneous distribution of pPKCepsilon, NAPDH oxidase, MMP-9 and ERG could be mitigated by either an ET receptor antagonist CPU0213 or iNOS inhibitor aminoguanidine.

METHODS

Rats were treated with ISO (1 mg/kg sc) for 10 days, and drug interventions (mg/kg) either CPU0213 (30 sc) or aminoguanidine (100 ip) were administered on days 8-10. Expression of NADPH oxidase, MMP-9, ERG, and PKCepsilon in the left and right ventricle (LV, RV) and septum (S) were measured separately.

RESULTS

Ventricular hypertrophy was found in the LV, S, and RV, in association with dispersed QTc and oxidative stress in ISO-treated rats. mRNA and protein expression of MMP-9, PKCepsilon, NADPH oxidase and ERG in the LV, S, and RV were obviously dispersed, with augmented expression mainly in the LV and S. Dispersed parameters were re-harmonized by either CPU0213, or aminoguanidine.

CONCLUSION

We found at the first time that ISO-induced dispersed distribution of pPKCepsilon, NADPH oxidase, MMP-9, and ERG in the LV, S, and RV of the heart, which were suppressed by either CPU0213 or aminoguanidine. It indicates that the ET-ROS pathway plays a role in the dispersed distribution of bioactive substances following sustained beta-receptor stimulation.

Hydrogen sulfide ameliorates hyperhomocysteinemia-associated chronic renal failure

Elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), is associated with end-stage renal diseases. Hcy metabolizes in the body to produce hydrogen sulfide (H(2)S), and studies have demonstrated a protective role of H(2)S in end-stage organ failure. However, the role of H(2)S in HHcy-associated renal diseases is unclear. The present study was aimed to determine the role of H(2)S in HHcy-associated renal damage. Cystathionine-beta-synthase heterozygous (CBS+/-) and wild-type (WT, C57BL/6J) mice with two kidney (2-K) were used in this study and supplemented with or without NaHS (30 micromol/l, H(2)S donor) in the drinking water. To expedite the HHcy-associated glomerular damage, uninephrectomized (1-K) CBS(+/-) and 1-K WT mice were also used with or without NaHS supplementation. Plasma Hcy levels were elevated in CBS(+/-) 2-K and 1-K and WT 1-K mice along with increased proteinuria, whereas, plasma levels of H(2)S were attenuated in these groups compared with WT 2-K mice. Interestingly, H(2)S supplementation increased plasma H(2)S level and normalized the urinary protein secretion in the similar groups of animals as above. Increased activity of matrix metalloproteinase (MMP)-2 and -9 and apoptotic cells were observed in the renal cortical tissues of CBS(+/-) 2-K and 1-K and WT 1-K mice; however, H(2)S prevented apoptotic cell death and normalized increased MMP activities. Increased expression of desmin and downregulation of nephrin in the cortical tissue of CBS(+/-) 2-K and 1-K and WT 1-K mice were ameliorated with H(2)S supplementation. Additionally, in the kidney tissues of CBS(+/-) 2-K and 1-K and WT 1-K mice, increased superoxide (O(2)(*-)) production and reduced glutathione (GSH)-to-oxidized glutathione (GSSG) ratio were normalized with exogenous H(2)S supplementation. These results demonstrate that HHcy-associated renal damage is related to decreased endogenous H(2)S generation in the body. Additionally, here we demonstrate with evidence that H(2)S supplementation prevents HHcy-associated renal damage, in part, through its antioxidant properties.

Ciglitazone, a PPARgamma agonist, ameliorates diabetic nephropathy in part through homocysteine clearance

Diabetes and hyperhomocysteinemia (HHcy) are two independent risk factors for glomeruloslerosis and renal insufficiency. Although PPARgamma agonists such as ciglitazone (CZ) are known to modulate diabetic nephropathy, the role of CZ in diabetes-associated HHcy and renopathy is incompletely defined. We tested the hypothesis that induction of PPARgamma by CZ decreases tissue Hcy level; this provides a protective role against diabetic nephropathy. C57BL/6J mice were administered alloxan to create diabetes. Mice were grouped to 0, 1, 10, 12, and 16 wk of treatment; only 12- and 16-wk animals received CZ in drinking water after a 10-wk alloxan treatment. In diabetes, PPARgamma cDNA, mRNA, and protein expression were repressed, whereas an increase in plasma and glomerular Hcy levels was observed. CZ normalized PPARgamma mRNA and protein expression and glomerular level of Hcy, whereas plasma level of Hcy remained unchanged. GFR was dramatically increased at 1-wk diabetic induction, followed by hypofiltration at 10 wk, and was normalized by CZ treatment. This result corroborated with glomerular and preglomerular arteriole histology. A steady-state increase of RVR in diabetic mice became normal with CZ treatment. CZ ameliorated decrease bioavailability of NO in the diabetic animal. Glomerular MMP-2 and MMP-9 activities as well as TIMP-1 expression were increased robustly in diabetic mice and normalized with CZ treatment. Interestingly, TIMP-4 expression was opposite to that of TIMP-1 in diabetic and CZ-treated groups. These results suggested that diabetic nephropathy exacerbated glomerular tissue level of Hcy, and this caused further deterioration of glomerulus. CZ, however, protected diabetic nephropathy in part by activating PPARgamma and clearing glomerular tissue Hcy.