Collagen Production in Cardiac Fibroblasts During Inhibition of Aminopeptidase B

Tumor exosomal RNPEP promotes lung metastasis of liver cancer via inducing cancer-associated fibroblast activation

Cancer-associated fibroblasts (CAFs) are essential players in the tumor microenvironment (TME) due to their roles in facilitating tumor progression and metastasis. It is worth noting that the high-metastatic hepatocellular carcinoma (HCC) cell-derived exosomes have exhibited the ability to transform normal fibroblasts into CAFs, which further fosters the lung metastasis of low-metastatic HCC cells. Yet, the mechanisms underlying this tumor exosome-induced metastatic niche formation are poorly explored. In this study, the secreted protein arginyl aminopeptidase (RNPEP) was highly expressed in the plasma of patients with HCC. In addition, high-metastatic HCC cells showed augmented RNPEP expression levels in their exosomes. These exosomes induced obvious CAF-like properties in the human fibroblast cell line MRC-5, as evidenced by the increased CAF marker expression, and enhanced migratory ability. More strikingly, the secretions from high-metastatic tumor exosome-educated MRC-5 cells increased tumor stemness and promoted epithelial-mesenchymal transition (EMT) in MHCC-97L cells, a low-metastatic HCC cell line. However, the knockdown of RNPEP in exosomes from high-metastatic HCC cells abated the changes described above. Animal studies in vivo highlighted the pro-tumor and pro-metastatic effects of exosomal RNPEP on MHCC-97L cells by inducing CAF activation. Furthermore, tumor-derived exosomal RNPEP induced the activation of NF-κB signaling in MRC-5 cells, a critical pathway associated with CAF activation. Collectively, these results provide novel insight into tumor-derived exosomal RNPEP for its crosstalk with CAFs during HCC lung metastasis.

Role of the lysyl oxidase enzyme family in cardiac function and disease

Heart diseases are a major cause of morbidity and mortality world-wide. Lysyl oxidase (LOX) and related LOX-like (LOXL) isoforms play a vital role in remodelling the extracellular matrix (ECM). The LOX family controls ECM formation by cross-linking collagen and elastin chains. LOX/LOXL proteins are copper-dependent amine oxidases that catalyse the oxidation of lysine, causing cross-linking between the lysine moieties of lysine-rich proteins. Dynamic changes in LOX and LOXL protein-expression occur in a variety of cardiac pathologies; these changes are believed to be central to the associated tissue-fibrosis. An awareness of the potential pathophysiological importance of LOX has led to the evaluation of interventions that target LOX/LOXL proteins for heart-disease therapy. The purposes of this review article are: (i) to summarize the basic biochemistry and enzyme function of LOX and LOXL proteins; (ii) to consider their tissue and species distribution; and (iii) to review the results of experimental studies of the roles of LOX and LOXL proteins in heart disease, addressing involvement in the mechanisms, pathophysiology and therapeutic responses based on observations in patient samples and relevant animal models. Therapeutic targeting of LOX family enzymes has shown promising results in animal models, but small-molecule approaches have been limited by non-specificity and off-target effects. Biological approaches show potential promise but are in their infancy. While there is strong evidence for LOX-family protein participation in heart failure, myocardial infarction, cardiac hypertrophy, dilated cardiomyopathy, atrial fibrillation and hypertension, as well as potential interest as therapeutic targets, the precise involvement of LOX-family proteins in heart disease requires further investigation.

Reprint of "The complex dynamics of myocardial interstitial fibrosis in heart failure. Focus on collagen cross-linking"

Myocardial interstitial fibrosis (MIF) is a common finding in heart failure (HF) patients, both with preserved and reduced ejection fraction, as well as in HF animal models. MIF is associated with impaired cardiac function and worse clinical outcome. The impact of MIF is influenced not only by the quantity but also by changes in the quality of collagen fibers and in the extracellular matrix components, such as a shift in collagen types proportion, increased fibronectin polymerization and increased degree of collagen cross-linking (CCL). In particular, CCL, a process that renders collagen fibers stiffer and more resistant to degradation, is increased both in patients and animal models of HF. Importantly, in HF patients increased cardiac CCL is directly associated with increased left ventricular stiffness and a higher risk of hospitalization for HF. The aim of this review is to address the complexity of MIF in HF, focusing on CCL.

The complex dynamics of myocardial interstitial fibrosis in heart failure. Focus on collagen cross-linking

Myocardial interstitial fibrosis (MIF) is a common finding in heart failure (HF) patients, both with preserved and reduced ejection fraction, as well as in HF animal models. MIF is associated with impaired cardiac function and worse clinical outcome. The impact of MIF is influenced not only by the quantity but also by changes in the quality of collagen fibers and in the extracellular matrix components, such as a shift in collagen types proportion, increased fibronectin polymerization and increased degree of collagen cross-linking (CCL). In particular, CCL, a process that renders collagen fibers stiffer and more resistant to degradation, is increased both in patients and animal models of HF. Importantly, in HF patients increased cardiac CCL is directly associated with increased left ventricular stiffness and a higher risk of hospitalization for HF. The aim of this review is to address the complexity of MIF in HF, focusing on CCL.

Role of lysyl oxidase in myocardial fibrosis: from basic science to clinical aspects

Because of its dynamic nature, the composition and structure of the myocardial collagen network can be reversibly modified to adapt to transient cardiac injuries. In response to persistent injury, however, irreversible, maladaptive changes of the network occur leading to fibrosis, mostly characterized by the excessive interstitial and perivascular deposition of collagen types I and III fibers. It is now becoming apparent that myocardial fibrosis directly contributes to adverse myocardial remodeling and the resulting alterations of left ventricular (LV) anatomy and function present in the major types of cardiac diseases. The enzyme lysyl oxidase (LOX) is a copper-dependent extracellular enzyme that catalyzes lysine-derived cross-links in collagen and elastin. LOX-mediated cross-linking of collagen types I and III fibrils leads to the formation of stiff collagen types I and III fibers and their subsequent tissue deposition. Evidence from experimental and clinical studies shows that the excess of LOX is associated with an increased collagen cross-linking and stiffness. It is thus conceivable that LOX upregulation and/or overactivity could underlie myocardial fibrosis and altered LV mechanics and contribute to the compromise of LV function in cardiac diseases. This review will consider the molecular aspects related to the regulation and actions of LOX, namely, in the context of collagen synthesis. In addition, it will address the information related to the role of myocardial LOX in heart failure and the potential benefits of controlling its expression and function.

Impact of treatment on myocardial lysyl oxidase expression and collagen cross-linking in patients with heart failure

The aim of this study was to investigate whether torasemide modifies collagen cross-linking in the failing human heart. We analyzed the degree of cross-linking and the expression of the enzyme lysyl oxidase, which regulates cross-linking, in the myocardium of patients with chronic heart failure at baseline and after 8 months of treatment with either torasemide or furosemide in addition to their standard heart failure therapy. Whereas lysyl oxidase protein expression was very scarce in normal hearts, it was highly expressed in failing hearts. Cross-linking was increased (P<0.001) in heart failure patients compared with normal hearts. These 2 parameters decreased (P=0.021 and P=0.034) in torasemide-treated patients and remained unchanged in furosemide-treated patients. In addition, more (P=0.009) patients showed normalization of left ventricular chamber stiffness in the torasemide subgroup than in the furosemide subgroup after treatment. Lysyl oxidase expression correlated with cross-linking (r=0.661; P<0.001), and cross-linking correlated with left ventricular chamber stiffness (r=0.452; P=0.002) in all patients. These findings show for the first time that lysyl oxidase overexpression is associated with enhanced collagen cross-linking in the failing human heart. In addition, we report that the ability of torasemide to correct both lysyl oxidase overexpression and enhanced collagen cross-linking results in normalization of left ventricular chamber stiffness in patients with heart failure. Lysyl oxidase may thus represent a target for reduction of stiff collagen and improvement of left ventricular mechanical properties in heart failure patients.

Dystrophin-deficient cardiomyopathy in mouse: expression of Nox4 and Lox are associated with fibrosis and altered functional parameters in the heart

Duchenne muscular dystrophy (DMD; dystrophin-deficiency) causes dilated cardiomyopathy in the second decade of life in affected males. We studied the dystrophin-deficient mouse heart (mdx) using high-frequency echocardiography, histomorphometry, and gene expression profiling. Heart dysfunction was prominent at 9-10months of age and showed significantly increased LV internal diameter (end systole) and decreased posterior wall thickness. This cardiomyopathy was associated with a 30% decrease in shortening fraction. Histologically, there was a 10-fold increase in connective tissue volume (fibrosis). mRNA profiling with RT-PCR validation showed activation of key pro-fibrotic genes, including Nox4 and Lox. The Nox gene family expression differed in mdx heart and skeletal muscle, where Nox2 was specifically induced in skeletal muscle while Nox4 was specifically induced in heart. This is the first report of an altered profibrotic gene expression profile in cardiac tissue of dystrophic mice showing echocardiographic evidence of cardiomyopathy.