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

Characteristics of penile growth in pubertal rats and a non-invasive method to lengthen the penis

BACKGROUND

Males with short penises may suffer from sexual dysfunction and psychological problems. However, currently, managing short penis is a huge challenge.

OBJECTIVES

To explore whether inhibition of lysyl oxidase (LOX) activity (anti-LOX) combined with a vacuum device could lengthen the penis of pubertal rat.

MATERIALS AND METHODS

Male rats of different ages were purchased, their exposed penile lengths and weights were measured, and protein expression and lysyl oxidase activity in the corpus cavernosum were analyzed. Fifteen-day-old rats were then purchased and divided into six groups: control, Anti-lysyl oxidase, -200 mm Hg (vacuum device under -200 mm Hg value), -200 mm Hg + Anti-lysyl oxidase, -300 mm Hg, and -300 mm Hg + Anti-lysyl oxidase groups. After the intervention duration of 7 weeks, rats' penile length was measured and erectile function was assessed. The corpus cavernosum was harvested for histopathology and molecular assessments.

RESULTS

Exposed penile length and weight significantly increased with age, especially between 4 and 8 weeks. Both the protein expression and lysyl oxidase activity in corpus cavernosum were the highest at 2 weeks; however, they quickly decreased with age and slowly declined after 8 weeks. Anti-lysyl oxidase significantly increased the penile length by 10.79% over controlled rats, -200 mm Hg + Anti-lysyl oxidase lengthened it by 14.05%, and -300 mm Hg + Anti-lysyl oxidase increased it by 19.84%. Anti-lysyl oxidase significantly reduced lysyl oxidase activity to decrease pyridinoline concentration; however, it did not change desmosine (P = .28), hydroxyproline (P = .14), and total elastin (P = .06) levels. Anti-lysyl oxidase with or without a vacuum device did not diminish erectile function or impair the normal microstructure of corpus cavernosum.

DISCUSSION AND CONCLUSION

The rats' penile growth peaks occurred between 4 and 8 weeks. Anti-lysyl oxidase with a vacuum device promoted penile lengthening by inhibiting pyridinoline production to induce tunica albuginea remodeling. The penile lengthening effect was more obvious in pubertal rats than the adult rats. None of the procedures decreased erectile function.

Toxic effects of a mancozeb-containing commercial formulation at environmental relevant concentrations on zebrafish embryonic development

The toxicological knowledge of mancozeb (MZ)-containing commercial formulations on non-target species is scarce and limited. Therefore, the objective of this work was to represent a realistic application scenario by evaluating the toxicity of environmental relevant and higher concentrations of a commercial formulation of MZ using zebrafish embryos. Following determination of the 96-h LC₅₀ value, the embryos at the blastula stage (~ 2 h post-fertilisation, hpf) were exposed to 0.5, 5, and 50 μg L^-1 of the active ingredient (~ 40× lower than the 96-h LC₅₀). During the exposure period (96 h), lethal, sublethal, and teratogenic parameters, as well as behaviour analysis, at 120 hpf, were assayed. Biochemical parameters such as oxidative stress-linked enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR)), reactive oxygen species (ROS) levels, and glutathione levels (GSH and GSSG), as well as the activity of degradation (glutathione S-transferase (GST) and carboxylesterase (CarE)), neurotransmission (acetylcholinesterase (AChE)), and anaerobic respiration (lactate dehydrogenase (LDH))-related enzymes, were analysed at the end of the exposure period. Exposed embryos showed a marked decrease in the hatching rate and many malformations (cardiac and yolk sac oedema and spinal torsions), with a higher prevalence at the highest concentration. A dose-dependent decreased locomotor activity and a response to an aversive stimulus, as well as a light-dark transition decline, were observed at environmental relevant concentrations. Furthermore, the activities of SOD and GR increased while the activity of GST, AChE, and MDA contents decreased. Taken together, the involvement of mancozeb metabolites and the generation of ROS are suggested as responsible for the developmental phenotypes. While further studies are needed to fully support the hypothesis presented, the potential cumulative effects of mancozeb-containing formulations and its metabolites could represent an environmental risk which should not be disregarded.

Role of the lysyl oxidase family in organ development (Review)

Lysyl oxidase proteins (LOXs) are amine oxidases, which are mainly located in smooth muscle cells and fibroblasts and serve an important role in the formation of the extracellular matrix (ECM) in a copper-dependent manner. Owing to the ability of LOX proteins to modulate crosslinking between collagens and to promote the deposition of other fibers, they serve crucially in organogenesis and the subsequent organ development, as well as disease initiation and progression. In addition, ECM formation significantly influences organ morphological formation in both cancer- and non-tumor-related diseases, in addition to cellular epigenetic transformation and migration, under the influence of LOXs. A number of different signaling pathways regulate the LOXs expression and their enzymatic activation. The tissue remodeling and transformation process shares some resemblance between oncogenesis and embryogenesis. Additionally the roles that LOXs serve appeared to be stressed during oncogenesis and tumor metastasis. It has also been indicated LOXs have a noteworthy role in non-tumor diseases. Nonetheless, the role of LOXs in systemic or local organ development and disease control remains unknown. In the present study, the essential roles that LOXs play in embryogenesis were unveiled partially, whereas the role of LOXs in organ or systematic development requires further investigations. The present review aimed to discuss the roles of members of the LOX family in the context of the remodeling of organogenesis and organ development. In addition, the consequences of the malfunction of these proteins related to the development of abnormalities and resulting diseases is discussed.

Molecular Insights Into Lysyl Oxidases in Cartilage Regeneration and Rejuvenation

Articular cartilage remains among the most difficult tissues to regenerate due to its poor self-repair capacity. The lysyl oxidase family (LOX; also termed as protein-lysine 6-oxidase), mainly consists of lysyl oxidase (LO) and lysyl oxidase-like 1-4 (LOXL1-LOXL4), has been traditionally defined as cuproenzymes that are essential for stabilization of extracellular matrix, particularly cross-linking of collagen and elastin. LOX is essential in the musculoskeletal system, particularly cartilage. LOXs-mediated collagen cross-links are essential for the functional integrity of articular cartilage. Appropriate modulation of the expression or activity of certain LOX members selectively may become potential promising strategy for cartilage repair. In the current review, we summarized the advances of LOX in cartilage homeostasis and functioning, as well as copper-mediated activation of LOX through hypoxia-responsive signaling axis during recent decades. Also, the molecular signaling network governing LOX expression has been summarized, indicating that appropriate modulation of hypoxia-responsive-signaling-directed LOX expression through manipulation of bioavailability of copper and oxygen is promising for further clinical implications of cartilage regeneration, which has emerged as a potential therapeutic approach for cartilage rejuvenation in tissue engineering and regenerative medicine. Therefore, targeted regulation of copper-mediated hypoxia-responsive signalling axis for selective modulation of LOX expression may become potential effective therapeutics for enhanced cartilage regeneration and rejuvenation in future clinical implications.

Lysyl oxidase-a possible role in systemic sclerosis-associated pulmonary hypertension: a multicentre study

OBJECTIVE

Lysyl oxidase (LOX) is an extracellular enzyme that cross-links collagen fibrils. LOX was found to be increased in serum of SSc patients and was suggested to be related to skin fibrosis, yet a vascular source of LOX has been demonstrated in idiopathic pulmonary arterial hypertension (iPAH). We aimed to validate elevated LOX serum levels in SSc and to study its correlation with clinical characteristics and investigate its main source at the tissue level.

METHODS

A total of 86 established SSc patients were compared with 86 patients with very early diagnosis of systemic sclerosis (VEDOSS), 110 patients with primary RP (PRP) and 80 healthy controls. LOX serum levels were determined by ELISA. Five lung and 12 skin biopsies from SSc patients were stained for LOX and compared with controls.

RESULTS

Serum levels of LOX in SSc were significantly higher than in VEDOSS, PRP and healthy controls (P < 0.001). LOX inversely correlated with the diffusing capacity of the lung for carbon monoxide diffusing capacity (DLCO) in diffuse SSc (r = -0.376, P = 0.02). Patients with moderate to severe estimated systolic PAH had higher LOX levels (P < 0.01). Lung biopsies demonstrated intense LOX staining in SSc patients with PAH that was predominantly located in the endothelium of the remodelled pulmonary vessels.

CONCLUSION

Serum LOX levels are increased in established SSc and inversely correlate with the DLCO. LOX is elevated in patients with moderate to severe PAH and is located in the proliferating endothelium in lung arterioles, suggesting a possible role for LOX in SSc-associated PAH.

Mix and (mis-)match - The mechanosensing machinery in the changing environment of the developing, healthy adult and diseased heart

The composition and the stiffness of cardiac microenvironment change during development and/or in heart disease. Cardiomyocytes (CMs) and their progenitors sense these changes, which decides over the cell fate and can trigger CM (progenitor) proliferation, differentiation, de-differentiation or death. The field of mechanobiology has seen a constant increase in output that also includes a wealth of new studies specific to cardiac or cardiomyocyte mechanosensing. As a result, mechanosensing and transduction in the heart is increasingly being recognised as a main driver of regulating the heart formation and function. Recent work has for instance focused on measuring the molecular, physical and mechanical changes of the cellular environment - as well as intracellular contributors to the passive stiffness of the heart. On the other hand, a variety of new studies shed light into the molecular machinery that allow the cardiomyocytes to sense these properties. Here we want to discuss the recent work on this topic, but also specifically focus on how the different components are regulated at various stages during development, in health or disease in order to highlight changes that might contribute to disease progression and heart failure.

Moderate Loss of the Extracellular Matrix Proteoglycan Lumican Attenuates Cardiac Fibrosis in Mice Subjected to Pressure Overload

INTRODUCTION

The heart undergoes myocardial remodeling during progression to heart failure following pressure overload. Myocardial remodeling is associated with structural and functional changes in cardiac myocytes, fibroblasts, and the extracellular matrix (ECM) and is accompanied by inflammation. Cardiac fibrosis, the accumulation of ECM molecules including collagens and collagen cross-linking, contributes both to impaired systolic and diastolic function. Insufficient mechanistic insight into what regulates cardiac fibrosis during pathological conditions has hampered therapeutic so-lutions. Lumican (LUM) is an ECM-secreted proteoglycan known to regulate collagen fibrillogenesis. Its expression in the heart is increased in clinical and experimental heart failure. Furthermore, LUM is important for survival and cardiac remodeling following pressure overload. We have recently reported that total lack of LUM increased mortality and left ventricular dilatation, and reduced collagen expression and cross-linking in LUM knockout mice after aortic banding (AB). Here, we examined the effect of LUM on myocardial remodeling and function following pressure overload in a less extreme mouse model, where cardiac LUM level was reduced to 50% (i.e., moderate loss of LUM).

METHODS AND RESULTS

mRNA and protein levels of LUM were reduced to 50% in heterozygous LUM (LUM+/-) hearts compared to wild-type (WT) controls. LUM+/- mice were subjected to AB. There was no difference in survival between LUM+/- and WT mice post-AB. Echocardiography revealed no striking differences in cardiac geometry between LUM+/- and WT mice 2, 4, and 6 weeks post-AB, although markers of diastolic dysfunction indicated better function in LUM+/- mice. LUM+/- hearts revealed reduced cardiac fibrosis assessed by histology. In accordance, the expression of collagen I and III, the main fibrillar collagens in the heart, and other ECM molecules central to fibrosis, i.e. including periostin and fibronectin, was reduced in the hearts of LUM+/- compared to WT 6 weeks post-AB. We found no differences in collagen cross-linking between LUM+/- and WT mice post-AB, as assessed by histology and qPCR.

CONCLUSIONS

Moderate lack of LUM attenuated cardiac fibrosis and improved diastolic dysfunction following pressure overload in mice, adding to the growing body of evidence suggesting that LUM is a central profibrotic molecule in the heart that could serve as a potential therapeutic target.

The peptide compound urantide regulates collagen metabolism in atherosclerotic rat hearts and inhibits the JAK2/STAT3 pathway

The aim of the present study was to investigate the effect of urantide on collagen metabolism in the hearts of rats with atherosclerosis (AS) by evaluating the expression of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway constituents. Urantide was delivered to rats with AS via tail vein injection for 3, 7 and 14 days. Serological indicators were identified by an automated biochemical analyzer. Histomorphological changes in the cardiac tissue of rats were observed by pathological staining techniques. The expression of genes and proteins was assessed using reverse transcription-quantitative PCR and western blot analysis, respectively. Localization of proteins was detected by immunofluorescence. Overexpression of urotensin II (UII) and its receptor, G protein-coupled receptor 14 (GPR14), was observed in the hearts of rats with AS and the expression of both proteins significantly declined after urantide administration. Triglyceride, total cholesterol, low-density lipoprotein, high-density lipoprotein and calcium levels were improved in rats with AS following treatment with urantide. Notably, urantide was able to antagonize the UII/GPR14 system. Urantide treatment resulted in markedly decreased expression levels of matrix metalloproteinase 2 (MMP-2), collagen type I/III, and genes and proteins in the JAK2/STAT3 pathway. By contrast, TIMP metallopeptidase inhibitor 2 (TIMP-2) levels were increased. In addition, the MMP-2/TIMP-2 protein ratio was significantly decreased in rats treated with urantide compared with AS rats with no urantide treatment. Constituents of the JAK2/STAT3 pathway and collagen type I/III were found to be localized in the diseased tissue and blood vessels of the hearts of rats with AS. In conclusion, urantide was able to effectively block the UII/GPR14 system by regulating the JAK2/STAT3 pathway and collagen metabolism. Inhibition of the UII/GPR14 system may prevent and potentially treat atherosclerotic myocardial fibrosis. Based on the current results, it was hypothesized that collagen metabolism may be associated with the JAK2/STAT3 pathway.

Generating cell-derived matrices from human trabecular meshwork cell cultures for mechanistic studies

Ocular hypertension has been attributed to increased resistance to aqueous outflow often as a result of changes in trabecular meshwork (TM) extracellular matrix (ECM) using in vivo animal models (for example, by genetic manipulation) and ex vivo anterior segment perfusion organ cultures. These are, however, complex and difficult in dissecting molecular mechanisms and interactions. In vitro approaches to mimic the underlying substrate exist by manipulating either ECM topography, mechanics, or chemistry. These models best investigate the role of individual ECM protein(s) and/or substrate property, and thus do not recapitulate the multifactorial extracellular microenvironment; hence, mitigating its physiological relevance for mechanistic studies. Cell-derived matrices (CDMs), however, are capable of presenting a 3D-microenvironment rich in topography, chemistry, and whose mechanics can be tuned to better represent the network of native ECM constituents in vivo. Critically, the composition of CDMs may also be fine-tuned by addition of small molecules or relevant bioactive factors to mimic homeostasis or pathology. Here, we first provide a streamlined protocol for generating CDMs from TM cell cultures from normal or glaucomatous donor tissues. Second, we document how TM cells can be pharmacologically manipulated to obtain glucocorticoid-induced CDMs and how generated pristine CDMs can be manipulated with reagents like genipin. Finally, we summarize how CDMs may be used in mechanistic studies and discuss their probable application in future TM regenerative studies.

The Role of Lysyl Oxidase Enzymes in Cardiac Function and Remodeling

Lysyl oxidase (LOX) proteins comprise a family of five copper-dependent enzymes (LOX and four LOX-like isoenzymes (LOXL1-4)) critical for extracellular matrix (ECM) homeostasis and remodeling. The primary role of LOX enzymes is to oxidize lysyl and hydroxylysyl residues from collagen and elastin chains into highly reactive aldehydes, which spontaneously react with surrounding amino groups and other aldehydes to form inter- and intra-catenary covalent cross-linkages. Therefore, they are essential for the synthesis of a mature ECM and assure matrix integrity. ECM modulates cellular phenotype and function, and strikingly influences the mechanical properties of tissues. This explains the critical role of these enzymes in tissue homeostasis, and in tissue repair and remodeling. Cardiac ECM is mainly composed of fibrillar collagens which form a complex network that provides structural and biochemical support to cardiac cells and regulates cell signaling pathways. It is now becoming apparent that cardiac performance is affected by the structure and composition of the ECM and that any disturbance of the ECM contributes to cardiac disease progression. This review article compiles the major findings on the contribution of the LOX family to the development and progression of myocardial disorders.

Anti-lysyl oxidase combined with a vacuum device induces penile lengthening by remodeling the tunica albuginea

This study aimed to explore whether and how anti-lysyl oxidase (anti-LOX) combined with a vacuum device (VD) could promote penile lengthening and to evaluate the effect on erectile function. This study was performed on four groups of adult rats: control, anti-LOX, VD (negative pressure value of −300 mmHg), and anti-LOX + VD. Penile length was measured by a modified VD method and verified on exposed length data. Intracavernous pressure (ICP) and maximum ICP/mean arterial pressure (MAP) ratio were recorded to assess erectile function. For corpus cavernosum, LOX activity and concentrations of pyridinoline, desmosine, hydroxyproline, and elastin were analyzed; transmission electron microscope and Hart's elastin staining were performed to monitor microstructural changes. Anti-LOX and VD significantly lengthened the penis by 10.8% (3.75 mm) and 8.2% (2.48 mm) compared with the control group, respectively, while anti-LOX + VD achieved the longest penile size (40.58 ± 0.40 mm) which was 17.4% longer than the control group (34.58 ± 0.54 mm). After 1-week washout, no penile retraction was observed. Meanwhile, exposed penile length data confirmed that the penis in the anti-LOX + VD group was also significantly longer. Anti-LOX inhibited LOX activity to reduce pyridinoline level, which led the penile tunica albuginea remodeling. However, it had no effect on hydroxyproline, desmosine, and elastin levels. Moreover, anti-LOX had no impact on erectile function, which was determined by ICP and ICP/MAP ratio. These results suggest that anti-LOX elongates the penis by reducing pyridinoline, which induces tunica albuginea remodeling. This lengthening effect was more obvious when combined with a VD. All procedures had no impact on erectile function.

Effects of 6-mercaptopurine in pressure overload induced right heart failure

Background

Several antineoplastic drugs have been proposed as new compounds for pulmonary arterial hypertension treatment but many have cardiotoxic side effects. The chemotherapeutic agent 6-mercaptopurine may have an effect in treatment of pulmonary arterial hypertension but at the same time, its effects on the afterload adaption of the right ventricle is unpredictable due to interaction with multiple downstream signalling pathways in the cardiomyocytes. We investigated the direct cardiac effects of 6-mercaptopurine in rats with isolated right heart failure caused by pulmonary trunk banding (PTB).

Methods

Male Wistar rat weanlings (112±2 g) were randomized to sham operation (sham, n = 10) or PTB. The PTB animals were randomized to placebo (PTB-control, n = 10) and 6-mercaptopurine (7.5 mg/kg/day) groups with treatment start before the PTB procedure (PTB-prevention, n = 10) or two weeks after (PTB-reversal, n = 10). Right ventricular effects were evaluated by echocardiography, cardiac MRI, invasive pressure-volume measurements, and histological and molecular analyses.

Results

PTB increased right ventricular afterload and caused right ventricular hypertrophy and failure. 6-mercaptopurine did not improve right ventricular function nor reduce right ventricular remodelling in both prevention and reversal studies compared with placebo-treated rats.

Conclusion

Treatment with 6-mercaptopurine did not have any beneficial or detrimental effects on right ventricular function or remodelling. Our data suggest that treatment of pulmonary arterial hypertension with 6-mercaptopurine is not harmful to the failing right ventricle.

Hypoxia and collagen crosslinking in the healthy and affected sites of periodontitis patients

Present study suggests that diseased sites of periodontitis with stage 3 grade B and C had decreased fibroblast cell density, hypoxia-inducible factor (HIF) and vascular endothelial growth factor (VEGF) expressions while increased inflammatory cell counts compared to both healthy sites of the periodontitis patients and healthy controls. Collagen maturation enzymes also decreased in the diseased sites. Objective: The present study aimed at determining markers of hypoxia and collagen crosslinking in healthy and diseased gingiva from healthy individuals and periodontitis patients. Methods: Group-1; healthy individuals, Group-2; healthy sites of periodontitis patients-stage 3 grade B, (H-GradeB) Group-3; diseased sites of periodontitis patients-stage 3 grade B, (D-GradeB). Group-4; healthy sites of periodontitis patients-stage 3 grade C, (H-GradeC). Group-5; diseased sites of periodontitis patients-stage 3 grade C, (D-GradeC). Plaque index (PI), gingival index (GI) and clinical attachment levels (CALs) were recorded. Gingival biopsies were obtained. Fibroblast and inflammatory cells were counted. HIF-1α, prolyl hydroxylase (PH), VEGF, lysyl oxidase (LOX) and lysyl hydroxylase (LH) levels were determined via immunohistochemistry. Results: Fibroblast cell counts were lower in D-GradeC and D-GradeB than other groups. C group had highest fibroblast cell counts. Inflammatory cell counts were highest in the D-GradeC and lowest in C group. HIF-1α levels were highest in C group and decreased in diseased sites. Lowest value was observed in D-GradeC group. VEGF, PH, and LH levels were higher in the control group compared to other groups. LOX levels were similar in the groups except for D-GradeC. LOX levels were similar in the groups except for D-GradeC which is significantly lower than those of the control group and healthy sites. Conclusions: The results revealed that diseased sites of periodontitis patients had decreased fibroblast cells, HIF and VEGF expressions while increased inflammatory cells. Collagen crosslinking tend to decrease with disease regardless of stage and grade of disease.

Identification of genes involved in glaucoma pathogenesis using combined network analysis and empirical studies

Glaucoma is a leading cause of blindness. We aimed in this study to identify genes that may make subtle and cumulative contributions to glaucoma pathogenesis. To this end, we identified molecular interactions and pathways that include transcription factors (TFs) FOXC1, PITX2, PAX6 and NFKB1 and various microRNAs including miR-204 known to have relevance to trabecular meshwork (TM) functions and/or glaucoma. TM tissue is involved in glaucoma pathogenesis. In-house microarray transcriptome results and data sources were used to identify target genes of the regulatory molecules. Bioinformatics analyses were done to filter TM and glaucoma relevant genes. These were submitted to network-creating softwares to define interactions, pathways and a network that would include the genes. The network was stringently scrutinized and minimized, then expanded by addition of microarray data and data on TF and microRNA-binding sites. Selected features of the network were confirmed by empirical studies such as dual luciferase assays, real-time PCR and western blot experiments and apoptosis assays. MYOC, WDR36, LTPBP2, RHOA, CYP1B1, OPA1, SPARC, MEIS2, PLEKHG5, RGS5, BBS5, ALDH1A1, NOMO2, CXCL6, FMNL2, ADAMTS5, CLOCK and DKK1 were among the genes included in the final network. Pathways identified included those that affect ECM properties, IOP, ciliary body functions, retinal ganglion cell viability, apoptosis, focal adhesion and oxidative stress response. The identification of many genes potentially involved in glaucoma pathology is consistent with its being a complex disease. The inclusion of several known glaucoma-related genes validates the approach used.

Lysyl Oxidases: Functions and Disorders

Lysyl oxidases (LOX) are copper-dependent enzymes that oxidize lysyl and hydroxylysyl residues in collagen and elastin, as a first step in the stabilization of these extracellular matrix proteins through the formation of covalent cross-linkages, an essential process for connective tissue maturation. Five different LOX enzymes have been identified in mammals, LOX and LOX-like (LOXL) 1 to 4, being genetically different protein products with a high degree of homology in the catalytic carboxy terminal end and a more variable amino terminal proregion. Intensive investigation in the last years has delineated the main biological functions of these enzymes and their involvement in several pathologies including fibrosis, cancer, and ocular disorders. This review article summarizes the major findings on the role of LOX isoforms, with particular focus on their contribution to the development and progression of human disorders.

Amelioration of Cavernosal Fibrosis and Erectile Function by Lysyl Oxidase Inhibition in a Rat Model of Cavernous Nerve Injury

BACKGROUND

Cavernous nerve injury (CNI) causes fibrosis and loss of smooth muscle cells (SMCs) in the corpus cavernosum and leads to erectile dysfunction, and lysyl oxidase (LOX) activation has been found to play an important role in fibrotic diseases.

AIM

To evaluate the role of LOX in penile fibrosis after bilateral CNI (BCNI).

METHODS

Rats underwent BCNI or a sham operation and were treated with vehicle or β-aminopropionitrile, a specific LOX activity inhibitor. 30 days after BCNI, rats were tested for erectile function before penile tissue harvest. LOX and extracellular matrix component expression levels in the corpus cavernosum, including matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), fibronectin (FN), collagen (COL) I, and COL IV, were evaluated by real-time quantitative polymerase chain reaction and western blot. Corporal fibrosis was evaluated by Masson trichrome staining. Localization of LOX and SMC content in the corpus cavernosum were assessed by immunohistochemistry.

OUTCOMES

Ratio of intracavernous pressure to mean arterial blood pressure; LOX, MMPs, TIMPs, COL I, COL IV, and FN expression; penile fibrosis; penile SMC content.

RESULTS

After BCNI, there was an increase in penile LOX expression and activity, increased penile fibrosis, decreased SMC content, and impaired erectile function. TIMP1, TIMP2, COL I, COL IV, and FN expression was markedly upregulated, whereas the enzyme activity of MMPs was decreased after BCNI. β-Aminopropionitrile treatment, at least in part, prevented a decrease in the ratio of intracavernous pressure to mean arterial blood pressure, decreased penile expression of TIMP1, TIMP2, COL I, COL IV, and FN, increased MMP activity, prevented corporal fibrosis, and preserved SMC content.

CLINICAL TRANSLATION

LOX over-activation contributes to penile fibrosis and LOX inhibition could be a promising strategy in preventing the progression of CNI-induced erectile dysfunction.

STRENGTHS AND LIMITATIONS

This is the 1st study to demonstrate the role of LOX activation in penile fibrosis. However, the exact mechanism of how LOX influences extracellular matrix protein synthesis and SMC content preservation awaits further investigation.

CONCLUSION

CNI induced LOX over-activation in cavernous tissue, and inhibition of LOX preserved penile morphology and improved erectile function in a rat model of BCNI. Wan Z-H, Li G-H, Guo Y-L, et al. Amelioration of Cavernosal Fibrosis and Erectile Function by Lysyl Oxidase Inhibition in a Rat Model of Cavernous Nerve Injury. J Sex Med 2018;15:304-313.

Targeting metabolic dysregulation for fibrosis therapy

Fibrosis is the abnormal deposition of extracellular matrix, which can lead to organ dysfunction, morbidity, and death. The disease burden caused by fibrosis is substantial, and there are currently no therapies that can prevent or reverse fibrosis. Metabolic alterations are increasingly recognized as an important pathogenic process that underlies fibrosis across many organ types. As a result, metabolically targeted therapies could become important strategies for fibrosis reduction. Indeed, some of the pathways targeted by antifibrotic drugs in development - such as the activation of transforming growth factor-β and the deposition of extracellular matrix - have metabolic implications. This Review summarizes the evidence to date and describes novel opportunities for the discovery and development of drugs for metabolic reprogramming, their associated challenges, and their utility in reducing fibrosis. Fibrotic therapies are potentially relevant to numerous common diseases such as cirrhosis, non-alcoholic steatohepatitis, chronic renal disease, heart failure, diabetes, idiopathic pulmonary fibrosis, and scleroderma.

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.

Caught between a "Rho" and a hard place: are CCN1/CYR61 and CCN2/CTGF the arbiters of microvascular stiffness?

The extracellular matrix (ECM) is a deformable dynamic structure that dictates the behavior, function and integrity of blood vessels. The composition, density, chemistry and architecture of major globular and fibrillar proteins of the matrisome regulate the mechanical properties of the vasculature (i.e., stiffness/compliance). ECM proteins are linked via integrins to a protein adhesome directly connected to the actin cytoskeleton and various downstream signaling pathways that enable the cells to respond to external stimuli in a coordinated manner and maintain optimal tissue stiffness. However, cardiovascular risk factors such as diabetes, dyslipidemia, hypertension, ischemia and aging compromise the mechanical balance of the vascular wall. Stiffening of large blood vessels is associated with well-known qualitative and quantitative changes of fibrillar and fibrous macromolecules of the vascular matrisome. However, the mechanical properties of the thin-walled microvasculature are essentially defined by components of the subendothelial matrix. Cellular communication network (CCN) 1 and 2 proteins (aka Cyr61 and CTGF, respectively) of the CCN protein family localize in and act on the pericellular matrix of microvessels and constitute primary candidate markers and regulators of microvascular compliance. CCN1 and CCN2 bind various integrin and non-integrin receptors and initiate signaling pathways that regulate connective tissue remodeling and response to injury, the associated mechanoresponse of vascular cells, and the subsequent inflammatory response. The CCN1 and CCN2 genes are themselves responsive to mechanical stimuli in vascular cells, wherein mechanotransduction signaling converges into the common Rho GTPase pathway, which promotes actomyosin-based contractility and cellular stiffening. However, CCN1 and CCN2 each exhibit unique functional attributes in these processes. A better understanding of their synergistic or antagonistic effects on the maintenance (or loss) of microvascular compliance in physiological and pathological situations will assist more broadly based studies of their functional properties and translational value.

Induction of LOX by TGF-β1/Smad/AP-1 signaling aggravates rat myocardial fibrosis and heart failure

This study aims to evaluate the efficacy of lysyl oxidase (LOX) inhibition in regulating rat myocardial fibrosis and chronic heart failure (CHF) and to validate the regulation of LOX by TGF-β1/Smad2/3 signaling in this process. A rat model of CHF was established by abdominal aortic coarctation. The renin-angiotensin-aldosterone system (RAAS) indexes (PRA, ACE2, Ang II, and ALD), cardiac function indicators (LVEF, LVFS, SAP, DAP, and LVEDP), ventricular remodeling- and fibrosis-related indicators (hydroxyproline, collagen deposition,and MMP-2/9), and morphological changes of myocardial tissues were examined. Rat cardiac fibroblasts (RCFs) were used in vitro assays. CHF patients showed increased LOX activity, accompanied by activated RAAS and TGF-β1. Furthermore, inhibition of LOX by β-aminopropionitrile (BAPN) mitigated the RAAS activation and attenuated cardiac dysfunction, ventricular remodeling, myocardial fibrosis, and collagen deposition in CHF rats. Moreover, TGF-β1 signaling diminished the LOX inhibition-mediated antiheart failure effect. Further assays showed that TGF-β1/Smad2/3 signaling increased expression of c-jun (AP-1 transcription factor subunit), which transcriptionally induced LOX expression. Additionally, BAPN abrogated the TGF-β1-mediated increase in cell proliferation and levels of MMP-2/9 and collagen I/III in RCFs. In conclusion, LOX can be induced by TGF-β1/Smad/AP-1 signaling and LOX inhibition attenuates rat myocardial fibrosis and CHF.

Mechanisms of cardiac collagen deposition in experimental models and human disease

The inappropriate deposition of extracellular matrix within the heart (termed cardiac fibrosis) is associated with nearly all types of heart disease, including ischemic, hypertensive, diabetic, and valvular. This alteration in the composition of the myocardium can physically limit cardiomyocyte contractility and relaxation, impede electrical conductivity, and hamper regional nutrient diffusion. Fibrosis can be grossly divided into 2 types, namely reparative (where collagen deposition replaces damaged myocardium) and reactive (where typically diffuse collagen deposition occurs without myocardial damage). Despite the widespread association of fibrosis with heart disease and general understanding of its negative impact on heart physiology, it is still not clear when collagen deposition becomes pathologic and translates into disease symptoms. In this review, we have summarized the current knowledge of cardiac fibrosis in human patients and experimental animal models, discussing the mechanisms that have been deduced from the latter in relation to the former. Because assessment of the extent of fibrosis is paramount both as a research tool to further understanding and as a clinical tool to assess patients, we have also summarized the current state of noninvasive/minimally invasive detection systems for cardiac fibrosis. Albeit not exhaustive, our aim is to provide an overview of the current understanding of cardiac fibrosis, both clinically and experimentally.

Fibrostenotic eosinophilic esophagitis might reflect epithelial lysyl oxidase induction by fibroblast-derived TNF-α

BACKGROUND

Fibrosis and stricture are major comorbidities in patients with eosinophilic esophagitis (EoE). Lysyl oxidase (LOX), a collagen cross-linking enzyme, has not been investigated in the context of EoE.

OBJECTIVE

We investigated regulation of epithelial LOX expression as a novel biomarker and functional effector of fibrostenotic disease conditions associated with EoE.

METHODS

LOX expression was analyzed by using RNA-sequencing, PCR assays, and immunostaining in patients with EoE; cytokine-stimulated esophageal 3-dimensional organoids; and fibroblast-epithelial cell coculture, the latter coupled with fluorescence-activated cell sorting.

RESULTS

Gene ontology and pathway analyses linked TNF-α and LOX expression in patients with EoE, which was validated in independent sets of patients with fibrostenotic conditions. TNF-α-mediated epithelial LOX upregulation was recapitulated in 3-dimensional organoids and coculture experiments. We find that fibroblast-derived TNF-α stimulates epithelial LOX expression through activation of nuclear factor κB and TGF-β-mediated signaling. In patients receiver operating characteristic analyses suggested that LOX upregulation indicates disease complications and fibrostenotic conditions in patients with EoE.

CONCLUSIONS

There is a novel positive feedback mechanism in epithelial LOX induction through fibroblast-derived TNF-α secretion. Esophageal epithelial LOX might have a role in the development of fibrosis with substantial translational implications.

Copper Deficiency in Liver Diseases: A Case Series and Pathophysiological Considerations

Copper is an indispensable trace element. It serves as a cofactor for enzymes involved in cellular energy metabolism, antioxidant defense, iron transport, and fibrogenesis. Although these processes are central in the pathogenesis of liver disorders, few studies have attributed them to copper deficiency. We herein describe in detail a case series of liver disease patients (n = 12) who presented with signs of copper deficiency based on serum and liver copper measurements. Median age of the group at the time of presentation was 39 (range 18‐64 years). Six patients were female. The median serum copper was 46 μg/dL (normal range: 80‐155 μg/dL for women and 70‐140 μg/dL for men). Seven of the 12 patients had hepatic copper concentration less than 10 μg/g dry weight (normal range: 10‐35 μg/g). Most cases presented with acute‐on‐chronic liver failure (n = 4) and decompensated cirrhosis (n = 5). Only 3 patients had a condition known to be associated with copper deficiency (ileocolonic Crohn’s disease following resection n = 1, Roux‐en‐Y gastric bypass n = 2) before presenting with hepatic dysfunction. Notable clinical features included steatohepatitis, iron overload, malnutrition, and recurrent infections. In 2 of the 3 patients who received copper supplementation, there was an improvement in serum copper, ceruloplasmin, and liver function parameters. Conclusion: Copper deficiency in the serum or liver occurs in a wide range of liver diseases. Given the biological essentiality of copper, the mechanism and clinical significance of this association require systematic study.

This case series describes copper deficiency in the serum and liver tissue in patients presenting with advanced liver diseases. We discuss the clinical implication of this phenomenon based on existing basic and translational studies. We also describe the effect of supplementation in three subjects.

The Extracellular Matrix in Ischemic and Nonischemic Heart Failure

The ECM (extracellular matrix) network plays a crucial role in cardiac homeostasis, not only by providing structural support, but also by facilitating force transmission, and by transducing key signals to cardiomyocytes, vascular cells, and interstitial cells. Changes in the profile and biochemistry of the ECM may be critically implicated in the pathogenesis of both heart failure with reduced ejection fraction and heart failure with preserved ejection fraction. The patterns of molecular and biochemical ECM alterations in failing hearts are dependent on the type of underlying injury. Pressure overload triggers early activation of a matrix-synthetic program in cardiac fibroblasts, inducing myofibroblast conversion, and stimulating synthesis of both structural and matricellular ECM proteins. Expansion of the cardiac ECM may increase myocardial stiffness promoting diastolic dysfunction. Cardiomyocytes, vascular cells and immune cells, activated through mechanosensitive pathways or neurohumoral mediators may play a critical role in fibroblast activation through secretion of cytokines and growth factors. Sustained pressure overload leads to dilative remodeling and systolic dysfunction that may be mediated by changes in the interstitial protease/antiprotease balance. On the other hand, ischemic injury causes dynamic changes in the cardiac ECM that contribute to regulation of inflammation and repair and may mediate adverse cardiac remodeling. In other pathophysiologic conditions, such as volume overload, diabetes mellitus, and obesity, the cell biological effectors mediating ECM remodeling are poorly understood and the molecular links between the primary insult and the changes in the matrix environment are unknown. This review article discusses the role of ECM macromolecules in heart failure, focusing on both structural ECM proteins (such as fibrillar and nonfibrillar collagens), and specialized injury-associated matrix macromolecules (such as fibronectin and matricellular proteins). Understanding the role of the ECM in heart failure may identify therapeutic targets to reduce geometric remodeling, to attenuate cardiomyocyte dysfunction, and even to promote myocardial regeneration.

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.

A Global Assessment of Circulating Prolysyl Oxidase in Nonischemic Patients With Garden-variety Heart Failure With Preserved Ejection Fraction

INTRODUCTION AND OBJECTIVES

Lysyl oxidase is overexpressed in the myocardium of patients with hypertensive cardiomyopathy. We aimed to explore whether patients with hypertensive-metabolic heart failure with preserved ejection fraction (HM-HFpEF) also have increased concentrations of circulating prolysyl oxidase (cpLOX) and its possible consequences.

METHODS

We quantified cpLOX concentrations in 85 nonischemic patients with stage C, HM-HFpEF, and compared them with those of 51 healthy controls. We also assessed the correlations of cpLOX with myocardial stiffness parameters, collagen turnover products and fibrogenic cytokines, as well as the predictive value of plasma proenzyme levels at 1-year of follow-up.

RESULTS

We detected raised cpLOX values and found that they correlated with calculated E/E' ratios and stiffness constants. The subgroup of patients with type I diastolic dysfunction showed a single negative correlation between cpLOX and B-type natriuretic peptide whereas patients with a restrictive diastolic pattern showed a strong correlation between cpLOX and galectin-3. Kaplan-Meier analysis revealed that cpLOX > 52.20 ng/mL slightly increased the risk of a fatal outcome (log-rank = 4.45; P = .034). When Cox regression was used, cpLOX was found to be a significant independent predictor of cardiovascular death or hospitalization due to the decompensation of HM-HFpEF (HR, 1.360; 95%CI, 1.126-1.638; P = .046).

CONCLUSIONS

Patients with symptomatic HM-HFpEF show high cpLOX serum levels associated with restrictive diastolic filling indices. These levels represent a moderate risk factor for poor clinical outcome. Throughout the natural history of HM-HFpEF, we observed that cpLOX concentrations were initially negatively correlated with B-type natriuretic peptide but positively correlated with galectin-3 as advanced diastolic dysfunction developed.

Cardio-omentopexy Reduces Cardiac Fibrosis and Heart Failure After Experimental Pressure Overload

BACKGROUND

The pedicled greater omentum has been shown to offer benefit in ischemic heart disease for both animal models and human patients. The impact of cardio-omentopexy in a pressure overload model of left ventricular hypertrophy (LVH) is unknown.

METHODS

LVH was created in rats by banding the ascending aorta after right thoracotomy (n = 23). Sham surgery was performed in 12 additional rats. Six weeks after banding, surviving LVH rats were assigned to cardio-omentopexy by left thoracotomy (LVH+Om, n = 8) or sham left thoracotomy (LVH, n = 8). Sham rats also underwent left thoracotomy for cardio-omentopexy (Sham+Om, n = 6); the remaining rats underwent sham left thoracotomy (Sham, n = 6).

RESULTS

Echocardiography 10 weeks after cardio-omentopexy revealed LV end-systolic diameter, cardiomyocyte diamter, and myocardial fibrosis in the LVH group were significantly increased compared with the LVH+Om, Sham+Om, and Sham groups (p < 0.01). LV ejection fraction of the LVH group was lower than the LVH+Om group (p < 0.01). Gene expression analysis revealed significantly lower levels of sarcoendoplasmic reticulum calcium adenosine triphosphatase 2b in LVH rats than in the LVH+Om, Sham+Om, and Sham groups (p < 0.01). In contrast, collagen type 1 α 1 chain, lysyl oxidase-like protein 1, nuclear protein-1, and transforming growth factor- β1 in the LVH group were significantly higher than in the LVH+Om cohort (p < 0.01), consistent with a reduced fibrotic phenotype after omentopexy. Lectin staining showed myocardial capillary density of the LVH group was significantly lower than all other groups (p < 0.01).

CONCLUSIONS

Cardio-omentopexy reduced cardiac dilation, contractile dysfunction, cardiomyocyte hypertrophy, and myocardial fibrosis, while maintaining other molecular indicators of contractile function in this LVH model.

ATP7A delivers copper to the lysyl oxidase family of enzymes and promotes tumorigenesis and metastasis

Lysyl oxidase (LOX) and LOX-like (LOXL) proteins are copper-dependent metalloenzymes with well-documented roles in tumor metastasis and fibrotic diseases. The mechanism by which copper is delivered to these enzymes is poorly understood. In this study, we demonstrate that the copper transporter ATP7A is necessary for the activity of LOX and LOXL enzymes. Silencing of ATP7A inhibited LOX activity in the 4T1 mammary carcinoma cell line, resulting in a loss of LOX-dependent mechanisms of metastasis, including the phosphorylation of focal adhesion kinase and myeloid cell recruitment to the lungs, in an orthotopic mouse model of breast cancer. ATP7A silencing was also found to attenuate LOX activity and metastasis of Lewis lung carcinoma cells in mice. Meta-analysis of breast cancer patients found that high ATP7A expression was significantly correlated with reduced survival. Taken together, these results identify ATP7A as a therapeutic target for blocking LOX- and LOXL-dependent malignancies.

Cardiomyocyte calcineurin is required for the onset and progression of cardiac hypertrophy and fibrosis in adult mice

Previous studies have demonstrated that activation of calcineurin induces pathological cardiac hypertrophy (CH). In these studies, loss-of-function was mostly achieved by systemic administration of the calcineurin inhibitor cyclosporin A. The lack of conditional knockout models for calcineurin function has impeded progress toward defining the role of this protein during the onset and the development of CH in adults. Here, we exploited a mouse model of CH based on the infusion of a hypertensive dose of angiotensin II (AngII) to model the role of calcineurin in CH in adulthood. AngII-induced CH in adult mice was reduced by treatment with cyclosporin A, without affecting the associated increase in blood pressure, and also by induction of calcineurin deletion in adult mouse cardiomyocytes, indicating that cardiomyocyte calcineurin is required for AngII-induced CH. Surprisingly, cardiac-specific deletion of calcineurin, but not treatment of mice with cyclosporin A, significantly reduced AngII-induced cardiac fibrosis and apoptosis. Analysis of profibrotic genes revealed that AngII-induced expression of Tgfβ family members and Lox was not inhibited by cyclosporin A but was markedly reduced by cardiac-specific calcineurin deletion. These results show that AngII induces a direct, calcineurin-dependent prohypertrophic effect in cardiomyocytes, as well as a systemic hypertensive effect that is independent of calcineurin activity.

Maternal cardiac messenger RNA expression of extracellular matrix proteins in mice during pregnancy and the postpartum period

IMPACT STATEMENT

This study provides the first comprehensive analysis of extracellular matrix protein (ECM) gene expression combined with echocardiographic analyses of heart functional parameters in the murine heart during pregnancy and the early postpartum period. Our findings show regulation of all Timp, selected Mmps, and Col1a1, Col3a1, and Col8a1 mRNA levels with reproductive status, with the greatest number of significant changes occurring in the early postpartum period. Left ventricle cardiac diastolic parameters were the first to change during pregnancy and remained elevated postpartum, whereas systolic parameters were increased in late pregnancy and began to recover during the first week postpartum. These novel findings indicate that although some ECM genes are elevated during late pregnancy, that the postpartum period is a time of robust altered ECM gene expression. These studies provide a basis for examining ECM proteins and their activities in the normal pregnant and postpartum heart and in models of postpartum cardiomyopathy.

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

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

The extracellular matrix proteoglycan fibromodulin is upregulated in clinical and experimental heart failure and affects cardiac remodeling

Pressure overload of the heart leads to cardiac remodeling that may progress into heart failure, a common, morbid and mortal condition. Increased mechanistic insight into remodeling is instrumental for development of novel heart failure treatment. Cardiac remodeling comprises cardiomyocyte hypertrophic growth, extracellular matrix alterations including fibrosis, and inflammation. Fibromodulin is a small leucine-rich proteoglycan that regulates collagen fibrillogenesis. Fibromodulin is expressed in the cardiac extracellular matrix, however its role in the heart remains largely unknown. We investigated fibromodulin levels in myocardial biopsies from heart failure patients and mice, subjected fibromodulin knock-out (FMOD-KO) mice to pressure overload by aortic banding, and overexpressed fibromodulin in cultured cardiomyocytes and cardiac fibroblasts using adenovirus. Fibromodulin was 3-10-fold upregulated in hearts of heart failure patients and mice. Both cardiomyocytes and cardiac fibroblasts expressed fibromodulin, and its expression was increased by pro-inflammatory stimuli. Without stress, FMOD-KO mice showed no cardiac phenotype. Upon aortic banding, left ventricles of FMOD-KO mice developed mildly exacerbated hypertrophic remodeling compared to wild-type mice, with increased cardiomyocyte size and altered infiltration of leukocytes. There were no differences in mortality, left ventricle dilatation, dysfunction or expression of heart failure markers. Although collagen amount and cross-linking were comparable in FMOD-KO and wild-type, overexpression of fibromodulin in cardiac fibroblasts in vitro decreased their migratory capacity and expression of fibrosis-associated molecules, i.e. the collagen-cross linking enzyme lysyl oxidase, transglutaminase 2 and periostin. In conclusion, despite a robust fibromodulin upregulation in clinical and experimental heart failure, FMOD-KO mice showed a relatively mild hypertrophic phenotype. In cultured cardiac fibroblasts, fibromodulin has anti-fibrotic effects.

Inhibitor of lysyl oxidase improves cardiac function and the collagen/MMP profile in response to volume overload

The cardiac extracellular matrix is a complex architectural network that serves many functions, including providing structural and biochemical support to surrounding cells and regulating intercellular signaling pathways. Cardiac function is directly affected by extracellular matrix (ECM) composition, and alterations of the ECM contribute to the progression of heart failure. Initially, collagen deposition is an adaptive response that aims to preserve tissue integrity and maintain normal ventricular function. However, the synergistic effects of proinflammatory and profibrotic responses induce a vicious cycle, which causes excess activation of myofibroblasts, significantly increasing collagen deposition and accumulation in the matrix. Furthermore, excess synthesis and activation of the enzyme lysyl oxidase (LOX) during disease increases collagen cross-linking, which significantly increases collagen resistance to degradation by matrix metalloproteinases (MMPs). In the present study, the aortocaval fistula model of volume overload (VO) was used to determine whether LOX inhibition could prevent adverse changes in the ECM and subsequent cardiac dysfunction. The major findings from this study were that LOX inhibition 1) prevented VO-induced increases in left ventricular wall stress; 2) partially attenuated VO-induced ventricular hypertrophy; 3) completely blocked the increases in fibrotic proteins, including collagens, MMPs, and their tissue inhibitors; and 4) prevented the VO-induced decline in cardiac function. It remains unclear whether a direct interaction between LOX and MMPs exists; however, our experiments suggest a potential link between the two because LOX inhibition completely attenuated VO-induced increases in MMPs. Overall, our study demonstrated key cardioprotective effects of LOX inhibition against adverse cardiac remodeling due to chronic VO. NEW & NOTEWORTHY Although the primary role of lysyl oxidase (LOX) is to cross-link collagens, we found that elevated LOX during cardiac disease plays a key role in the progression of heart failure. Here, we show that inhibition of LOX in volume-overloaded rats prevented the development of cardiac dysfunction and improved ventricular collagen and matrix metalloproteinase/tissue inhibitor of metalloproteinase profiles.

Lysyl oxidase family members in urological tumorigenesis and fibrosis

Lysyl oxidase (LOX) is an extracellular copper-dependent monoamine oxidase that catalyzes crosslinking of soluble collagen and elastin into insoluble, mature fibers. Lysyl oxidase-like proteins (LOXL), LOX isozymes with partial structural homology, exhibit similar catalytic activities. This review summarizes recent findings describing the roles of LOX family members in urological cancers and fibrosis. LOX/LOXL play key roles in extracellular matrix stability and integrity, which is essential for normal female pelvic floor function. LOX/LOXL inhibition may reverse kidney fibrosis and ischemic priapism. LOX and LOXL2 reportedly promote kidney carcinoma tumorigenesis, while LOX, LOXL1 and LOXL4 suppress bladder cancer growth. Multiple studies agree that the LOX propeptide may suppress tumor growth, but the role of LOX in prostate cancer remains controversial. Further studies are needed to clarify the exact effects and mechanism of LOX/LOXL on urological malignancies.

Pharmacologic inhibition of the enzymatic effects of tissue transglutaminase reduces cardiac fibrosis and attenuates cardiomyocyte hypertrophy following pressure overload

Tissue transglutaminase (tTG) is a multifunctional protein with a wide range of enzymatic and non-enzymatic functions. We have recently demonstrated that tTG expression is upregulated in the pressure-overloaded myocardium and exerts fibrogenic actions promoting diastolic dysfunction, while preventing chamber dilation. Our current investigation dissects the in vivo and in vitro roles of the enzymatic effects of tTG on fibrotic remodeling in pressure-overloaded myocardium. Using a mouse model of transverse aortic constriction, we demonstrated perivascular and interstitial tTG activation in the remodeling pressure-overloaded heart. tTG inhibition through administration of the selective small molecule tTG inhibitor ERW1041E attenuated left ventricular diastolic dysfunction and reduced cardiomyocyte hypertrophy and interstitial fibrosis in the pressure-overloaded heart, without affecting chamber dimensions and ejection fraction. In vivo, tTG inhibition markedly reduced myocardial collagen mRNA and protein levels and attenuated transcription of fibrosis-associated genes. In contrast, addition of exogenous recombinant tTG to fibroblast-populated collagen pads had no significant effects on collagen transcription, and instead increased synthesis of matrix metalloproteinase (MMP)3 and tissue inhibitor of metalloproteinases (TIMP)1 through transamidase-independent actions. However, enzymatic effects of matrix-bound tTG increased the thickness of pericellular collagen in fibroblast-populated pads. tTG exerts distinct enzymatic and non-enzymatic functions in the remodeling pressure-overloaded heart. The enzymatic effects of tTG are fibrogenic and promote diastolic dysfunction, but do not directly modulate the pro-fibrotic transcriptional program of fibroblasts. Targeting transamidase-dependent actions of tTG may be a promising therapeutic strategy in patients with heart failure and fibrosis-associated diastolic dysfunction.

Lysyl oxidase and adipose tissue dysfunction

BACKGROUND/OBJECTIVES

Lysyl oxidase (LOX) is an enzyme crucial for collagen fibre crosslinking and thus for fibrosis development. Fibrosis is characterised by a surplus of collagen fibre accumulation and is amongst others also a feature of obesity-associated dysfunctional adipose tissue (AT) which has been linked with type 2 diabetes. We hypothesised that in type 2 diabetes and obesity LOX expression and activity will be increased as a consequence of worsening AT dysfunction. This study aimed to provide a comprehensive characterisation of LOX in human AT.

METHODS

LOX mRNA expression was analysed in omental and abdominal subcutaneous AT obtained during elective surgery from subjects with a wide range of BMI, with and without diabetes. In addition, LOX expression was studied in subcutaneous AT before and 9.5months after bariatric surgery. To study the mechanism of LOX changes, its expression and activity were assessed after either hypoxia, recombinant human leptin or glucose treatment of AT explants. In addition, LOX response to acute inflammation was tested after stimulation by a single injection of lipopolysaccharide versus saline solution (control) in healthy men, in vivo. Quantity of mRNA was measured by RT-qPCR.

RESULTS

LOX expression was higher in obesity and correlated with BMI whilst, in vitro, leptin at high concentrations, as a potential feedback mechanism, suppressed its expression. Neither diabetes status, nor hyperglycaemia affected LOX. Hypoxia and lipopolysaccharide-induced acute inflammation increased LOX AT expression, latter was independent of macrophage infiltration.

CONCLUSIONS

Whilst LOX may not be affected by obesity-associated complications such as diabetes, our results confirm that LOX is increased by hypoxia and inflammation as underlying mechanism for its upregulation in adipose tissue with obesity.

Hypoxia-inducible factor-1α regulates epithelial-to-mesenchymal transition in paraquat-induced pulmonary fibrosis by activating lysyl oxidase

Pulmonary fibrosis (PF) is one of the most prevalent causes of death following paraquat (PQ) poisoning. As demonstrated in previous studies by the present authors, epithelial-to-mesenchymal transition (EMT) is associated with PQ-induced PF. In addition, hypoxia-inducible factor-1α (HIF-1α) and lysyl oxidase (LOX) promote EMT following PQ poisoning. However, the association between HIF-1α- and LOX-mediated regulation of EMT remains unclear. The present study investigated the association between HIF-1α and LOX with regard to PQ-induced EMT. A549 and RLE-6TN cells were treated with PQ, and HIF-1α and LOX expression was silenced with short interfering RNAs. Changes in the expression of HIF-1α, LOX, β-catenin and EMT-related makers were detected using real-time quantitative polymerase chain reaction, immunofluorescence, and western blotting. HIF-1α and LOX were associated with PQ-induced EMT, and their expression levels were significantly increased (P<0.05). LOX expression was significantly decreased following PQ poisoning when HIF-1α expression was inhibited (P<0.05). However, the level of HIF-1α did not change significantly when LOX was silenced. The expression level of β-catenin and the degree of EMT were significantly decreased following HIF-1α and LOX silencing in both cell lines (P<0.05). The association between HIF-1α and LOX in regulating EMT during PQ-induced PF may be unidirectional. HIF-1α may regulate PQ-induced EMT through the LOX/β-catenin pathway.

Pyridoxamine improves survival and limits cardiac dysfunction after MI

Advanced glycation end products (AGEs) play a key role in the progression of heart failure. Whether treatments limiting AGEs formation would prevent adverse left ventricular remodeling after myocardial infarction (MI) remain unknown. We investigated whether pyridoxamine (PM) could limit adverse cardiac outcome in MI. Rats were divided into MI, MI + PM and Sham. Echocardiography and hemodynamic parameters were used to assess cardiac function 8 weeks post-surgery. Total interstitial collagen, collagen I and collagen III were quantified using Sirius Red and polarized light microscopy. PM improved survival following LAD occlusion. Pre-treatment with PM significantly decreased the plasma AGEs levels. MI rats treated with PM displayed reduced left ventricular end-diastolic pressure and tau compared to untreated MI rats. Deformation parameters were also improved with PM. The preserved diastolic function was related to the reduced collagen content, in particular in the highly cross-linked collagen type I, mainly in the peri-infarct region, although not via TGF-β1 pathway. Our data indicate that PM treatment prevents the increase in AGEs levels and reduces collagen levels in a rat model of MI, resulting in an improved cardiac phenotype. As such, therapies targeting formation of AGEs might be beneficial in the prevention and/or treatment of maladaptive remodeling following MI.

Increased serum lysyl oxidase-like 2 levels correlate with the degree of left atrial fibrosis in patients with atrial fibrillation

Atrial fibrillation (AF) progression is generally accompanied by increased atrial fibrosis and atrial structural remodeling. Lysyl oxidase-like 2 (LOXL2) is known to play an important role in many fibrotic conditions, including cardiac fibrosis. The present study aimed to explore the relationship between serum LOXL2 levels and AF. Fifty-four AF patients and 32 control subjects were enrolled in the study. High-density three-dimensional electroanatomic mapping was performed, and mean bipolar voltage was assessed in AF patients. LOXL2 levels were measured by enzyme-linked immunosorbent assay. All patients underwent echocardiography to assess left atrium size and left ventricle function. Serum LOXL2 levels were significantly elevated in AF patients compared with the control group (526.81 ± 316.82 vs 240.94 ± 92.51 pg/ml, P<0.01). In addition, serum LOXL2 level was significantly correlated with the size of the left atrium (LAD) (r² = 0.38, P<0.01). Furthermore, the serum LOXL2 levels were significantly higher in AF patients with LAD ≥ 40 mm compared with those with LAD < 40 mm (664.34 ± 346.50 vs 354.90 ± 156.23 pg/ml, P<0.01). And the Spearman's correlation analysis further revealed that the mean bipolar left atrial voltage was inversely correlated with the LOXL2 (r² = -0.49, P<0.01) in AF patients. Multivariate regression analysis further demonstrated that serum LOXL2 [odds ratio (OR) 1.013, 95% confidence interval (CI) 1.002-1.024, P<0.05] and LAD (OR 1.704, 95% CI 1.131-2.568, P<0.01) were independent predictors of AF. In conclusion, serum LOXL2 levels were significantly elevated and were correlated with the degree of left atrial fibrosis in AF patients.

Periodontal-induced chronic inflammation triggers macrophage secretion of Ccl12 to inhibit fibroblast-mediated cardiac wound healing

Chronic inflammatory diseases, such as periodontal disease, associate with adverse wound healing in response to myocardial infarction (MI). The goal of this study was to elucidate the molecular basis for impaired cardiac wound healing in the setting of periodontal-induced chronic inflammation. Causal network analysis of 168 inflammatory and extracellular matrix genes revealed that chronic inflammation induced by a subseptic dose of Porphyromonas gingivalis lipopolysaccharide (LPS) exacerbated infarct expression of the proinflammatory cytokine Ccl12. Ccl12 prevented initiation of the reparative response by prolonging inflammation and inhibiting fibroblast conversion to myofibroblasts, resulting in diminished scar formation. Macrophage secretion of Ccl12 directly impaired fibronectin and collagen deposition and indirectly stimulated collagen degradation through upregulation of matrix metalloproteinase-2. In post-MI patients, circulating LPS levels strongly associated with the Ccl12 homologue monocyte chemotactic protein 1 (MCP-1). Patients with LPS levels ≥ 1 endotoxin units (EU)/ml (subseptic endotoxemia) at the time of hospitalization had increased end diastolic and systolic dimensions compared with post-MI patients with < 1 EU/ml, indicating that low yet pathological concentrations of circulating LPS adversely impact post-MI left ventricle (LV) remodeling by increasing MCP-1. Our study provides the first evidence to our knowledge that chronic inflammation inhibits reparative fibroblast activation and generates an unfavorable cardiac-healing environment through Ccl12-dependent mechanisms.