Chemotactic responses of fibroblasts to tropoelastin and elastin-derived peptides

Preparation and characterization of PVA/chitosan nanofibers loaded with Dragon's blood or poly helixan as wound dressings

Nanofibers have been investigated in regenerative medicine. Dragon's blood (DB)- and poly helixan PF (PHPF) are natural materials used in cosmetics. Herein, we generated DB- and PHPF-loaded polyvinyl alcohol/chitosan (PVA/CS/DB and PVA/CS/PHPF, respectively) nanofibers. PVA/CS/DB and PVA/CS/PHPF nanofibers had an average diameter of 547.5 ± 17.13 and 521 ± 24.67 nm, respectively as assessed by SEM, and a degradation rate of 43.1 and 47.6 % after 14 days, respectively. PVA/CS/DB and PVA/CS/PHPF nanofibers had a hemolysis rate of 0.10 and 0.39 %, respectively, and a water vapor transmission rate of ∼2200 g.m-2.day-1. These nanofibers exhibited favorable antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis in vitro. PVA/CS/DB and PVA/CS/PHPF nanofibers demonstrated a sustained release of 77.91 and 76.55 % over 72 h. PVA/CS/DB and PVA/CS/PHPF nanofibers had a high rate of cytocompatibility and significantly improved the viability of NIH/3T3 cells as compared with free drugs or unloaded nanofibers. Histological inspection via H&E and Verhoeff's staining demonstrated PVA/CS/DB and PVA/CS/PHPF nanofibers enhanced the wound healing and damaged tissue recovery of unsplinted wound models by promoting epithelial layer formation, collagen deposition, and enhancing the presence of fibroblasts. Conclusively, PVA/CS/DB and PVA/CS/PHPF can be introduced as potential wound dressing candidates with favorable properties.

Extracellular Matrix Remodeling in Vascular Disease: Defining Its Regulators and Pathological Influence

Because of structural and cellular differences (ie, degrees of matrix abundance and cross-linking, mural cell density, and adventitia), large and medium-sized vessels, in comparison to capillaries, react in a unique manner to stimuli that induce vascular disease. A stereotypical vascular injury response is ECM (extracellular matrix) remodeling that occurs particularly in larger vessels in response to injurious stimuli, such as elevated angiotensin II, hyperlipidemia, hyperglycemia, genetic deficiencies, inflammatory cell infiltration, or exposure to proinflammatory mediators. Even with substantial and prolonged vascular damage, large- and medium-sized arteries, persist, but become modified by (1) changes in vascular wall cellularity; (2) modifications in the differentiation status of endothelial cells, vascular smooth muscle cells, or adventitial stem cells (each can become activated); (3) infiltration of the vascular wall by various leukocyte types; (4) increased exposure to critical growth factors and proinflammatory mediators; and (5) marked changes in the vascular ECM, that remodels from a homeostatic, prodifferentiation ECM environment to matrices that instead promote tissue reparative responses. This latter ECM presents previously hidden matricryptic sites that bind integrins to signal vascular cells and infiltrating leukocytes (in coordination with other mediators) to proliferate, invade, secrete ECM-degrading proteinases, and deposit injury-induced matrices (predisposing to vessel wall fibrosis). In contrast, in response to similar stimuli, capillaries can undergo regression responses (rarefaction). In summary, we have described the molecular events controlling ECM remodeling in major vascular diseases as well as the differential responses of arteries versus capillaries to key mediators inducing vascular injury.

In Vitro and In Silico Studies on Angiotensin I-Converting Enzyme Inhibitory Peptides Found in Hydrophobic Domains of Porcine Elastin

One of the most striking aspects of the primary structure in the hydrophobic domains of the tropoelastin molecule is the occurrence of the VAPGVG repeating sequence. Since the N-terminal tripeptide VAP of VAPGVG showed a potent ACE inhibitory activity, the ACE inhibitory activity of various derivatives of VAP was examined in vitro. The results showed that VAP derivative peptides VLP, VGP, VSP, GAP, LSP, and TRP exhibited potent ACE inhibitory activities, while the non-derivative peptide APG showed only weak activity. In in silico studies, the docking score S value showed that VAP derivative peptides VLP, VGP, VSP, LSP, and TRP had stronger docking interactions than APG. Molecular docking in the ACE active pocket showed that TRP, the most potent ACE inhibitory peptide among the VAP derivatives, had a larger number of interactions with ACE residues in comparison with APG and that the TRP molecule appeared to spread widely in the ACE pocket, while the APG molecule appeared to spread closely. Differences in molecular spread may be a reason why TRP exhibits more potent ACE inhibitory activity than APG. The results suggest that the number and strength of interactions between the peptide and ACE are important for the ACE- inhibitory potency of the peptide.

An artificially designed elastin-like recombinant polypeptide improves aging skin

BACKGROUND

As a substrate for cell growth, elastin can promote the regeneration and remodeling of the epidermis, which plays an important role in delaying skin aging. However, elastin proteins are more than 700 amino acids long and cannot be absorbed through the skin, which prevents the direct utilization of elastin in the prevention and treatment of aging skin.

METHODS

We designed an elastin-like recombinant polypeptide (ELR) which could be absorbed through the skin based on the property of hexapeptide VGVAPG. Thirty healthy Chinese Han female participants which met the criteria were enrolled in this study and all of them completed the tests including elasticity, tightness, and wrinkle detection. The participants used this polypeptide for 4 weeks and were tested in three visits: one day before trial started (D0), and 14 and 28 days after the trial (D14 and D28, respectively). Paired t-tests or Wilcoxon signed-rank tests for non-parametric measures were used to determine the difference between D0 and D14, or D0 and D28.

RESULTS

The skin elasticity level in the thirty participants was significantly increased after using ELR for 28 days (P=0.024), and the average value of skin firmness (Uf) declined from 3.313 (D0) to 3.292 (D14) and 3.265 (D28), although there was no statistically significant difference between treatment and pre-treatment. Furthermore, the wrinkle count (D14: P<0.001; D28: P<0.001), wrinkles volume (D14: P<0.001; D28: P=0.008), and wrinkles area (D14: P<0.001; D28: P<0.001) of Crow's feet were significantly improved by using ELR for 14 days or 28 days.

CONCLUSION

Continuous use of ELR could significantly improve skin elasticity and reduce wrinkles.

Characterization and Cytocompatibility of Collagen-Gelatin-Elastin (CollaGee) Acellular Skin Substitute towards Human Dermal Fibroblasts: In Vitro Assessment

Full-thickness skin wounds have become a serious burden to patients, medical care, and the socio-economic environment. The development of a safe and effective acellular skin substitute that can rapidly restore intact physiological skin is required. Natural bioactive materials including collagen, gelatin, and elastin possess significant advantages over synthetic biomaterials regarding biodegradability and biocompatibility. However, low mechanical strength, a faster biodegradation rate, and thermally unstable biomaterials lead to slow-healing and a high rate of post-implantation failure. To overcome these concerns, naturally occurring genipin (GNP) flavonoids were added to improve the mechanical strength, degradation rate, and thermal properties. Therefore, this study aimed to fabricate and characterize collagen−gelatin−elastin (CollaGee) biomaterials cross-linked with GNP as an acellular skin substitute potentially used in full-thickness wound healing. CollaGee at different ratios was divided into non-cross-linked and cross-linked with 0.1% GNP (w/v). The physicochemical, mechanical, and biocompatibility properties of CollaGee were further investigated. The results demonstrated that GNP-cross-linked CollaGee has better physicochemical (>50% porosity, pore size range of 100−200 µm, swelling ratio of >1000%) and mechanical properties (resilience and cross-linking degree of >60%, modulus of >1.0 GPa) compared to non-cross-linked CollaGee groups. Furthermore, both cross-linked and non-cross-linked CollaGee demonstrated pivotal cellular compatibility with no toxicity and sustained cell viability until day 7 towards human dermal fibroblasts. These findings suggest that GNP-cross-linked CollaGee could be a promising ready-to-use product for the rapid treatment of full-thickness skin loss.

Severe Pulmonary Arterial Hypertension Is Characterized by Increased Neutrophil Elastase and Relative Elafin Deficiency

BACKGROUND

Preclinical evidence implicates neutrophil elastase (NE) in pulmonary arterial hypertension (PAH) pathogenesis, and the NE inhibitor elafin is under early therapeutic investigation.

RESEARCH QUESTION

Are circulating NE and elafin levels abnormal in PAH and are they associated with clinical severity?

STUDY DESIGN AND METHODS

In an observational Stanford University PAH cohort (n = 249), plasma NE and elafin levels were measured in comparison with those of healthy control participants (n = 106). NE and elafin measurements were then related to PAH clinical features and relevant ancillary biomarkers. Cox regression models were fitted with cubic spline functions to associate NE and elafin levels with survival. To validate prognostic relationships, we analyzed two United Kingdom cohorts (n = 75 and n = 357). Mixed-effects models evaluated NE and elafin changes during disease progression. Finally, we studied effects of NE-elafin balance on pulmonary artery endothelial cells (PAECs) from patients with PAH.

RESULTS

Relative to control participants, patients with PAH were found to have increased NE levels (205.1 ng/mL [interquartile range (IQR), 123.6-387.3 ng/mL] vs 97.6 ng/mL [IQR, 74.4-126.6 ng/mL]; P < .0001) and decreased elafin levels (32.0 ng/mL [IQR, 15.3-59.1 ng/mL] vs 45.5 ng/mL [IQR, 28.1-92.8 ng/mL]; P < .0001) independent of PAH subtype, illness duration, and therapies. Higher NE levels were associated with worse symptom severity, shorter 6-min walk distance, higher N-terminal pro-type brain natriuretic peptide levels, greater right ventricular dysfunction, worse hemodynamics, increased circulating neutrophil levels, elevated cytokine levels, and lower blood BMPR2 expression. In Stanford patients, NE levels of > 168.5 ng/mL portended increased mortality risk after adjustment for known clinical predictors (hazard ratio [HR], 2.52; CI, 1.36-4.65, P = .003) or prognostic cytokines (HR, 2.63; CI, 1.42-4.87; P = .001), and the NE level added incremental value to established PAH risk scores. Similar prognostic thresholds were identified in validation cohorts. Longitudinal NE changes tracked with clinical trends and outcomes. PAH PAECs exhibited increased apoptosis and attenuated angiogenesis when exposed to NE at the level observed in patients' blood. Elafin rescued PAEC homeostasis, yet the required dose exceeded levels found in patients.

INTERPRETATION

Blood levels of NE are increased while elafin levels are deficient across PAH subtypes. Higher NE levels are associated with worse clinical disease severity and outcomes, and this target-specific biomarker could facilitate therapeutic development of elafin.

Integrative transcriptome analysis deciphers mechanisms of nickel contact dermatitis

Background

Nickel‐induced allergic contact dermatitis (nACD) remains a major occupational skin disorder, significantly impacting the quality of life of suffering patients. Complex cellular compositional changes and associated immunological pathways are partly resolved in humans; thus, the impact of nACD on human skin needs to be further elucidated.

Methods

To decipher involved immunological players and pathways, human skin biopsies were taken at 0, 2, 48, and 96 hours after nickel patch test in six nickel‐allergic patients. Gene expression profiles were analyzed via microarray.

Results

Leukocyte deconvolution of nACD‐affected skin identified major leukocyte compositional changes at 48 and 96 hours, including natural killer (NK) cells, macrophage polarization, and T‐cell immunity. Gene set enrichment analysis mirrored cellular‐linked functional pathways enriched over time. NK cell infiltration and cytotoxic pathways were uniquely found in nACD‐affected skin compared to sodium lauryl sulfate–induced irritant skin reactions.

Conclusion

These results highlight key immunological leukocyte subsets as well as associated pathways in nACD, providing insights into pathophysiology with the potential to unravel novel therapeutic targets.

Elastases and elastokines: elastin degradation and its significance in health and disease

Elastin is an important protein of the extracellular matrix of higher vertebrates, which confers elasticity and resilience to various tissues and organs including lungs, skin, large blood vessels and ligaments. Owing to its unique structure, extensive cross-linking and durability, it does not undergo significant turnover in healthy tissues and has a half-life of more than 70 years. Elastin is not only a structural protein, influencing the architecture and biomechanical properties of the extracellular matrix, but also plays a vital role in various physiological processes. Bioactive elastin peptides termed elastokines - in particular those of the GXXPG motif - occur as a result of proteolytic degradation of elastin and its non-cross-linked precursor tropoelastin and display several biological activities. For instance, they promote angiogenesis or stimulate cell adhesion, chemotaxis, proliferation, protease activation and apoptosis. Elastin-degrading enzymes such as matrix metalloproteinases, serine proteases and cysteine proteases slowly damage elastin over the lifetime of an organism. The destruction of elastin and the biological processes triggered by elastokines favor the development and progression of various pathological conditions including emphysema, chronic obstructive pulmonary disease, atherosclerosis, metabolic syndrome and cancer. This review gives an overview on types of human elastases and their action on human elastin, including the formation, structure and biological activities of elastokines and their role in common biological processes and severe pathological conditions.

Inclusion of Cross-Linked Elastin in Gelatin/PEG Hydrogels Favourably Influences Fibroblast Phenotype

The capacity of a biomaterial to innately modulate cell behavior while meeting the mechanical property requirements of the implant is a much sought-after goal within bioengineering. Here we covalently incorporate soluble elastin into a gelatin–poly (ethylene glycol) (PEG) hydrogel for three-dimensional (3D) cell encapsulation to achieve these properties. The inclusion of elastin into a previously optimized gelatin–PEG hydrogel was then evaluated for effects on entrapped fibroblasts, with the aim to assess the hydrogel as an extracellular matrix (ECM)-mimicking 3D microenvironment for cellular guidance. Soluble elastin was incorporated both physically and covalently into novel gelatin/elastin hybrid PEG hydrogels with the aim to harness the cellular interactivity and mechanical tunability of both elastin and gelatin. This design allowed us to assess the benefits of elastin-containing hydrogels in guiding fibroblast activity for evaluation as a potential dermal replacement. It was found that a gelatin–PEG hydrogel with covalently conjugated elastin, supported neonatal fibroblast viability, promoted their proliferation from 7.3% to 13.5% and guided their behavior. The expression of collagen alpha-1(COL1A1) and elastin in gelatin/elastin hybrid gels increased 16-fold and 6-fold compared to control sample at day 9, respectively. Moreover, cells can be loaded into the hydrogel precursor solution, deposited, and the matrix cross-linked without affecting the incorporated cells adversely, thus enabling a potential injectable system for dermal wound healing.

Erythromycin Prevents Elastin Peptide-Induced Emphysema and Modulates CD4+T Cell Responses in Mice

Purpose

Elastin peptides (EP) can induce lung inflammation and emphysema. Erythromycin has been shown to decrease acute exacerbation frequency and delay lung function decline in chronic obstructive pulmonary disease patients and ameliorate emphysema in murine models; however, the mechanism remains unclear. We aimed to observe the preventive and immunomodulatory effects of erythromycin in a mouse model of EP-induced emphysema.

Methods

In the in vivo study, Balb/c mice were treated with EP intranasally on day 0, and then administered erythromycin (100 mg/kg) or vehicle orally on day 1, which was continued every other day. Mice exposed to cigarette smoke were used as an emphysema positive control. The severity of emphysema and inflammation in the lungs of EP-exposed mice with or without erythromycin treatment were observed on day 40 after EP administration. In the in vitro study, naïve CD4⁺T cells were isolated from healthy mice spleens and stimulated by EP with or without erythromycin incubation. Flow cytometry was used to measure the proportions of Th1, Th17, and Treg cells. ELISA was used to detect cytokine levels of IFN-γ, IL-17, IL-6, and TGF-β. Transcript levels of Ifnγ, IL17a, and Foxp3 were evaluated by qRT-PCR.

Results

After exposure to EP, Th1 and Th17 cell percentages and the levels of inflammatory cytokines increased in vivo and in vitro, while Treg cells decreased in vivo. Erythromycin reduced IFN-γ, IL-17, IL-6 inflammatory cytokines, MLI, and the inflammation score in the lungs of EP-exposed mice. In vitro, erythromycin also limited Th17 and Th1 cell differentiation and downregulated transcript levels of Ifnγ and IL17a in the EP-stimulated CD4⁺T cells.

Conclusion

The Th1 and Th17 cell responses were increased in EP-induced emphysema. Prophylactic use of erythromycin effectively ameliorated emphysema and modulated CD4⁺T cells responses in EP-induced lung inflammation in mice.

Matrix metalloproteinases in emphysema

Several studies have implicated a causative role for specific matrix metalloproteinases (MMPs) in the development and progression of cigarette smoke-induced chronic obstructive pulmonary disease (COPD) and its severe sequela, emphysema. However, the precise function of any given MMP in emphysema remains an unanswered question. Emphysema results from the degradation of alveolar elastin - among other possible mechanisms - a process that is often thought to be caused by elastolytic proteinases made by macrophages. In this article, we discuss the data suggesting, supporting, or refuting causative roles of macrophage-derived MMPs, with a focus on MMPs-7, -9, -10, -12, and 28, in both the human disease and mouse models of emphysema. Findings from experimental models suggest that some MMPs, such as MMP-12, may directly breakdown elastin, whereas others, particularly MMP-10 and MMP-28, promote the development of emphysema by influencing the proteolytic and inflammatory activities of macrophages.

Elastin purification and solubilization

The functional form of elastin is a highly cross-linked polymer that organizes as sheets or fibers in the extracellular matrix. Purification of the mature protein is problematic because its insolubility precludes its isolation using standard wet-chemistry techniques. Instead, relatively harsh experimental approaches designed to remove nonelastin "contaminates" are employed to generate an insoluble product that has the amino acid composition expected of elastin. Although soluble, tropoelastin also presents problems for isolation and purification. The protein's extreme stickiness and susceptibility to proteolysis require careful attention during purification and in tropoelastin-based assays. This chapter describes the most common approaches for purification of elastin and for preparing solubilized forms of the protein.

The Elastin Receptor Complex: A Unique Matricellular Receptor with High Anti-tumoral Potential

Elastin, one of the longest-lived proteins, confers elasticity to tissues with high mechanical constraints. During aging or pathophysiological conditions such as cancer progression, this insoluble polymer of tropoelastin undergoes an important degradation leading to the release of bioactive elastin-derived peptides (EDPs), named elastokines. EDP exhibit several biological functions able to drive tumor development by regulating cell proliferation, invasion, survival, angiogenesis, and matrix metalloproteinase expression in various tumor and stromal cells. Although, several receptors have been suggested to bind elastokines (α_vβ₃ and α_vβ₅ integrins, galectin-3), their main receptor remains the elastin receptor complex (ERC). This heterotrimer comprises a peripheral subunit, named elastin binding protein (EBP), associated to the protective protein/cathepsin A (PPCA). The latter is bound to a membrane-associated protein called Neuraminidase-1 (Neu-1). The pro-tumoral effects of elastokines have been linked to their binding onto EBP. Additionally, Neu-1 sialidase activity is essential for their signal transduction. Consistently, EDP-EBP interaction and Neu-1 activity emerge as original anti-tumoral targets. Interestingly, besides its direct involvement in cancer progression, the ERC also regulates diabetes outcome and thrombosis, an important risk factor for cancer development and a vascular process highly increased in patients suffering from cancer. In this review, we will describe ERC and elastokines involvement in cancer development suggesting that this unique receptor would be a promising therapeutic target. We will also discuss the pharmacological concepts aiming at blocking its pro-tumoral activities. Finally, its emerging role in cancer-associated complications and pathologies such as diabetes and thrombotic events will be also considered.

Induction and regulation of murine emphysema by elastin peptides

Emphysema is the major component of chronic obstructive pulmonary disease (COPD). During emphysema, elastin breakdown in the lung tissue originates from the release of large amounts of elastase by inflammatory cells. Elevated levels of elastin-derived peptides (EP) reflect massive pulmonary elastin breakdown in COPD patients. Only the EP containing the GXXPG conformational motif with a type VIII β-turn are elastin receptor ligands inducing biological activities. In addition, the COOH-terminal glycine residue of the GXXPG motif seems a prerequisite to the biological activity. In this study, we endotracheally instilled C57BL/6J mice with GXXPG EP and/or COOH-terminal glycine deleted-EP whose sequences were designed by molecular dynamics and docking simulations. We investigated their effect on all criteria associated with the progression of murine emphysema. Bronchoalveolar lavages were recovered to analyze cell profiles by flow cytometry and lungs were prepared to allow morphological and histological analysis by immunostaining and confocal microscopy. We observed that exposure of mice to EP elicited hallmark features of emphysema with inflammatory cell accumulation associated with increased matrix metalloproteinases and desmosine expression and of remodeling of parenchymal tissue. We also identified an inactive COOH-terminal glycine deleted-EP that retains its binding-activity to EBP and that is able to inhibit the in vitro and in vivo activities of emphysema-inducing EP. This study demonstrates that EP are key actors in the development of emphysema and that they represent pharmacological targets for an alternative treatment of emphysema based on the identification of EP analogous antagonists by molecular modeling studies.

Elafin Reverses Pulmonary Hypertension via Caveolin-1-Dependent Bone Morphogenetic Protein Signaling

RATIONALE

Pulmonary arterial hypertension is characterized by endothelial dysfunction, impaired bone morphogenetic protein receptor 2 (BMPR2) signaling, and increased elastase activity. Synthetic elastase inhibitors reverse experimental pulmonary hypertension but cause hepatotoxicity in clinical studies. The endogenous elastase inhibitor elafin attenuates hypoxic pulmonary hypertension in mice, but its potential to improve endothelial function and BMPR2 signaling, and to reverse severe experimental pulmonary hypertension or vascular pathology in the human disease was unknown.

OBJECTIVES

To assess elafin-mediated regression of pulmonary vascular pathology in rats and in lung explants from patients with pulmonary hypertension. To determine if elafin amplifies BMPR2 signaling in pulmonary artery endothelial cells and to elucidate the underlying mechanism.

METHODS

Rats with pulmonary hypertension induced by vascular endothelial growth factor receptor blockade and hypoxia (Sugen/hypoxia) as well as lung organ cultures from patients with pulmonary hypertension were used to assess elafin-mediated reversibility of pulmonary vascular disease. Pulmonary arterial endothelial cells from patients and control subjects were used to determine the efficacy and mechanism of elafin-mediated BMPR2 signaling.

MEASUREMENTS AND MAIN RESULTS

In Sugen/hypoxia rats, elafin reduced elastase activity and reversed pulmonary hypertension, judged by regression of right ventricular systolic pressure and hypertrophy and pulmonary artery occlusive changes. Elafin improved endothelial function by increasing apelin, a BMPR2 target. Elafin induced apoptosis in human pulmonary arterial smooth muscle cells and decreased neointimal lesions in lung organ culture. In normal and patient pulmonary artery endothelial cells, elafin promoted angiogenesis by increasing pSMAD-dependent and -independent BMPR2 signaling. This was linked mechanistically to augmented interaction of BMPR2 with caveolin-1 via elafin-mediated stabilization of endothelial surface caveolin-1.

CONCLUSIONS

Elafin reverses obliterative changes in pulmonary arteries via elastase inhibition and caveolin-1-dependent amplification of BMPR2 signaling.

Preclinical validation and imaging of Wnt-induced repair in human 3D lung tissue cultures

Chronic obstructive pulmonary disease (COPD) is characterised by a progressive loss of lung tissue. Inducing repair processes within the adult diseased lung is of major interest and Wnt/β-catenin signalling represents a promising target for lung repair. However, the translation of novel therapeutic targets from model systems into clinical use remains a major challenge.

We generated murine and patient-derived three-dimensional (3D) ex vivo lung tissue cultures (LTCs), which closely mimic the 3D lung microenvironment in vivo. Using two well-known glycogen synthase kinase-3β inhibitors, lithium chloride (LiCl) and CHIR 99021 (CT), we determined Wnt/β-catenin-driven lung repair processes in high spatiotemporal resolution using quantitative PCR, Western blotting, ELISA, (immuno)histological assessment, and four-dimensional confocal live tissue imaging.

Viable 3D-LTCs exhibited preserved lung structure and function for up to 5 days. We demonstrate successful Wnt/β-catenin signal activation in murine and patient-derived 3D-LTCs from COPD patients. Wnt/β-catenin signalling led to increased alveolar epithelial cell marker expression, decreased matrix metalloproteinase-12 expression, as well as altered macrophage activity and elastin remodelling. Importantly, induction of surfactant protein C significantly correlated with disease stage (per cent predicted forced expiratory volume in 1 s) in patient-derived 3D-LTCs.

Patient-derived 3D-LTCs represent a valuable tool to analyse potential targets and drugs for lung repair. Enhanced Wnt/β-catenin signalling attenuated pathological features of patient-derived COPD 3D-LTCs.

Elastin-derived peptides stimulate trophoblast migration and invasion: a positive feedback loop to enhance spiral artery remodelling

Elastin breakdown in the walls of uterine spiral arteries during early pregnancy facilitates their transformation into dilated, high-flow, low-resistance channels. Elastin-derived peptides (EDP) can influence cell migration, invasion and protease activity, and so we hypothesized that EDP released during elastolysis promote extravillous trophoblast (EVT) invasion and further elastin breakdown. Treatment of the trophoblast cell line SGHPL4 with the elastin-derived matrikine VGVAPG (1 μg/ml) significantly increased total elastase activity, promoted migration in a wound healing assay and increased invasion through Matrigel-coated transwells compared with vehicle control (0.1% DMSO) or the scrambled sequence VVGPGA. Furthermore, treatment of first-trimester placental villous explants with this EDP significantly increased both the area of trophoblast outgrowth and distance of migration away from the villous tips. Primary first-trimester cytotrophoblast exposed to VGVAPG (1 μg/ml) for 30 min showed increased phosphorylation of endothelial nitric oxide synthase and activation of the mitogen activated protein kinase pathway, events also associated with tumour cell migration and invasion. These in vitro observations suggest liberation of bioactive EDP during induction of elastolysis in the uterine spiral arteries may orchestrate a positive feedback loop that promotes EVT invasion and further elastin breakdown, contributing to the process of vascular remodelling.

Inhibition of elastin peptide-mediated angiogenic signaling mechanism(s) in choroidal endothelial cells by the α6(IV)NC1 collagen fragment

PURPOSE

The inhibitory effects and mechanism(s) of type IV collagen α-6 chain-derived noncollagenous domain (α6[IV]NC1 or hexastatin) on elastin-derived peptide (EDP)-activated choroidal endothelial cell migration, kinase signaling, and membrane type 1 metalloproteinase (MT1-MMP) activation are explored.

METHODS

Mouse choroidal endothelial cells (MCECs) were incubated in media with soluble EDPs (kappa elastin, mouse elastin, and Val-Gly-Val-Ala-Pro-Gly [VGVAPG] hexapeptide) for different time intervals with or without α6(IV)NC1. The MCECs proliferation, migration, tube formation, MT1-MMP expression, and angiogenic signaling were analyzed in cells subjected to EDP and α6(IV)NC1 treatments. The MCECs also were subjected to EDPs, and specific inhibitors for evaluation of focal adhesion kinase (FAK) and protein kinase B (Akt) phosphorylation.

RESULTS

Kappa elastin, mouse elastin, and VGVAPG enhanced the migration, without affecting the proliferation of MCECs. The α6(IV)NC1 inhibited survival and EDP-activated migration of MCECs. The EDP-activated MCEC tube formation on matrigel also was inhibited by α6(IV)NC1. Further, EDP-activated MT1-MMP expression and FAK/phosphoinositide-3-kinase (PI-3K)/mammalian target of rapamycin (mToR)/Akt phosphorylation in MCECs, were reduced by α6(IV)NC1. The EDP-induced FAK and Akt phosphorylation was blocked by FAK- and Akt-specific inhibitors.

CONCLUSIONS

The EDPs and α6(IV)NC1 are identified to exhibit opposing effects on MCEC angiogenic behavior and signaling. The α6(IV)NC1 inhibited cell survival, EDP-mediated migration, MT1-MMP expression and, FAK/PI-3K/mToR/Akt phosphorylation in MCECs. This work demonstrates α6(IV)NC1 as a prospective endogenous molecule for the treatment of diseases involving choroidal neovascularization in the eye.

A novel cell adhesion region in tropoelastin mediates attachment to integrin αVβ5

Tropoelastin protein monomers assemble to form elastin. Cellular integrin αVβ3 binds RKRK at the C-terminal tail of tropoelastin. We probed cell interactions with tropoelastin by deleting the RKRK sequence to identify other cell-binding interactions within tropoelastin. We found a novel human dermal fibroblast attachment and spreading site on tropoelastin that is located centrally in the molecule. Inhibition studies demonstrated that this cell adhesion was not mediated by either elastin-binding protein or glycosaminoglycans. Cell interactions were divalent cation-dependent, indicating integrin dependence. Function-blocking monoclonal antibodies revealed that αV integrin(s) and integrin αVβ5 specifically were critical for cell adhesion to this part of tropoelastin. These data reveal a common αV integrin-binding theme for tropoelastin: αVβ3 at the C terminus and αVβ5 at the central region of tropoelastin. Each αV region contributes to fibroblast attachment and spreading, but they differ in their effects on cytoskeletal assembly.

Acute Myocardial Infarction and Pulmonary Diseases Result in Two Different Degradation Profiles of Elastin as Quantified by Two Novel ELISAs

BACKGROUND

Elastin is a signature protein of the arteries and lungs, thus it was hypothesized that elastin is subject to enzymatic degradation during cardiovascular and pulmonary diseases. The aim was to investigate if different fragments of the same protein entail different information associated to two different diseases and if these fragments have the potential of being diagnostic biomarkers.

METHODS

Monoclonal antibodies were raised against an identified fragment (the ELM-2 neoepitope) generated at the amino acid position '552 in elastin by matrix metalloproteinase (MMP) -9/-12. A newly identified ELM neoepitope was generated by the same proteases but at amino acid position '441. The distribution of ELM-2 and ELM, in human arterial plaques and fibrotic lung tissues were investigated by immunohistochemistry. A competitive ELISA for ELM-2 was developed. The clinical relevance of the ELM and ELM-2 ELISAs was evaluated in patients with acute myocardial infarction (AMI), no AMI, high coronary calcium, or low coronary calcium. The serological release of ELM-2 in patients with chronic obstructive pulmonary disease (COPD) or idiopathic pulmonary fibrosis (IPF) was compared to controls.

RESULTS

ELM and ELM-2 neoepitopes were both localized in diseased carotid arteries and fibrotic lungs. In the cardiovascular cohort, ELM-2 levels were 66% higher in serum from AMI patients compared to patients with no AMI (p<0.01). Levels of ELM were not significantly increased in these patients and no correlation was observed between ELM-2 and ELM. ELM-2 was not elevated in the COPD and IPF patients and was not correlated to ELM. ELM was shown to be correlated with smoking habits (p<0.01).

CONCLUSIONS

The ELM-2 neoepitope was related to AMI whereas the ELM neoepitope was related to pulmonary diseases. These results indicate that elastin neoepitopes generated by the same proteases but at different amino acid sites provide different tissue-related information depending on the disease in question.

Elastin signaling in wound repair

Skin is an important organ to the human body as it functions as an interface between the body and environment. Cutaneous injury elicits a complex wound healing process, which is an orchestration of cells, matrix components, and signaling factors that re-establishes the barrier function of skin. In adults, an unavoidable consequence of wound healing is scar formation. However, in early fetal development, wound healing is scarless. This phenomenon is characterized by an attenuated inflammatory response, differential expression of signaling factors, and regeneration of normal skin architecture. Elastin endows a range of mechanical and cell interactive properties to skin. In adult wound healing, elastin is severely lacking and only a disorganized elastic fiber network is present after scar formation. The inherent properties of elastin make it a desirable inclusion to adult wound healing. Elastin imparts recoil and resistance and induces a range of cell activities, including cell migration and proliferation, matrix synthesis, and protease production. The effects of elastin align with the hallmarks of fetal scarless wound healing. Elastin synthesis is substantial in late stage in utero and drops to a trickle in adults. The physical and cell signaling advantages of elastin in a wound healing context creates a parallel with the innate features of fetal skin that can allow for scarless healing.

Elastin sequences trigger transient proinflammatory responses by human dermal fibroblasts

Following penetrating injury of the skin, a highly orchestrated and overlapping sequence of events helps to facilitate wound resolution. Inflammation is a hallmark that is initiated early, but the reciprocal relationship between cells and matrix molecules that triggers and maintains inflammation is poorly appreciated. Elastin is enriched in the deep dermis of skin. We propose that deep tissue injury encompasses elastin damage, yielding solubilized elastin that triggers inflammation. As dermal fibroblasts dominate the deep dermis, this means that a direct interaction between elastin sequences and fibroblasts would reveal a proinflammatory signature. Tropoelastin was used as a surrogate for elastin sequences. Tropoelastin triggered fibroblast expression of the metalloelastase MMP-12, which is normally expressed by macrophages. MMP-12 expression increased 1056 ± 286-fold by 6 h and persisted for 24 h. Chemokine expression was more transient, as chemokine C-X-C motif ligand 8 (CXCL8), CXCL1, and CXCL5 transcripts increased 11.8 ± 2.6-, 10.2 ± 0.4-, and 8593 ± 996-fold, respectively, by 6-12 h and then decreased. Through the use of specific inhibitors and protein truncation, we found that transduction of the tropoelastin signal was mediated by the fibroblast elastin binding protein (EBP). In silico modeling using a predictive computational fibroblast model confirmed the up-regulation, and simulations revealed PKA as a key part of the signaling circuit. We tested this prediction with 1 μM PKA inhibitor H-89 and found that 2 h of exposure correspondingly reduced expression of MMP-12 (63.9±12.3%) and all chemokine markers, consistent with the levels seen with EBP inhibition, and validated PKA as a novel node and druggable target to ameliorate the proinflammatory state. A separate trigger that utilized C-terminal RKRK of tropoelastin reduced marker expression to 65.0-76.5% and suggests the parallel involvement of integrin αVβ3. We propose that the solubilization of elastin as a result of dermal damage leads to rapid chemokine up-regulation by fibroblasts that is quenched when exposed elastin is removed by MMP-12.

Tropoelastin modulates TGF-β1-induced expression of VEGF and CTGF in airway smooth muscle cells

Elastin is predominantly comprised of crosslinked tropoelastin. For many years elastin was considered to serve a solely structural role but is now being increasingly identified as causal in cell signaling, development and repair. We introduced tropoelastin into an in vitro model in which airway smooth muscle cells (ASMCs) were stimulated with transforming growth factor (TGF)-β1 to examine the modulatory effect of this modular elastin sequence on release of angiogenic factors and matrix metalloproteinases (MMPs). Human ASMCs were presented to surfaces coated with tropoelastin or collagen and controls, then stimulated with TGF-β1. Transcript levels of vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) were quantified 4 and 24 h after TGF-β1 stimulation. Protein VEGF release from cells and CTGF sequestered at cell surfaces were measured by ELISA at 24 and 48 h. TGF-β1 increased VEGF mRNA 2.4 fold at 4 h and 5 fold at 24 h, accompanied by elevated cognate protein release 3 fold at 24 h and 2.5 fold at 48 h. TGF-β1 stimulation increased CTGF mRNA 6.9 fold at 4 h and 11.8 fold at 24 h, accompanied by increased sequestering of its protein counterpart 1.2 fold at 24 h and 1.4 fold at 48 h. Pre-incubation of cells with tropoelastin did not modulate VEGF or CTGF mRNA expression, but combined with TGF-β1 stimulation it led to enhanced VEGF release 5.1-fold at 24h and 4.4-fold at 48 h. Pre-incubation with tropoelastin decreased CTGF sequestering 0.6-fold at 24 and 48 h, and increased MMP-2 production. Collagen pre-incubation under the same conditions displayed no effect on TGF-β1 stimulation apart from a slightly decreased (0.9 fold) sequestered CTGF at 48 h. As CTGF is known to anchor VEGF to the matrix and inhibit its angiogenic activity, a process which can be reversed by digestion with MMP-2, these findings reveal that elastin sequences can disrupt the balance of angiogenic factors, with implications for aberrant angiogenesis. The results suggest a model of molecular crosstalk and support an active role for elastin in vascular remodeling.

Serum elastin-derived peptides and anti-elastin antibody in patients with systemic sclerosis

The elastin metabolism in systemic sclerosis (SSc) has been known to be abnormal. The authors investigated relationship between the clinical manifestations of systemic sclerosis (SSc) and serum levels of soluble elastin-derived peptide (S-EDP) and anti-elastin antibodies. Serum samples were obtained from 79 patients with SSc and 79 age- and sex-matched healthy controls. Concentrations of serum S-EDP and anti-elastin antibodies were measured by ELISA. The serum concentrations of S-EDP in SSc patients were significantly higher than in healthy controls (median, 144.44 ng/mL vs 79.59 ng/mL, P < 0.001). Serum EDP concentrations were found to be correlated with disease duration in SSc (P = 0.002) and particularly in diffuse cutaneous SSc (P = 0.005). Levels of anti-elastin antibodies were found to be more elevated in SSc patients than in healthy controls (median, 0.222 U vs 0.191 U, P = 0.049), more increased in diffuse cutaneous SSc than limited cutaneous SSc (median, 0.368 U vs 0.204 U, P = 0.031). In addition, levels of anti-elastin antibodies were also found to be negatively associated with presence of anti-centromere antibody (P = 0.023). The S-EDP levels were not found to be correlated with levels of anti-elastin antibodies. The increased S-EDP and anti-elastin antibody levels and association with clinical and laboratory characteristics may reflect the abnormal metabolism in SSc.

Elastin in asthma

Extracellular matrix is generally increased in asthma, causing thickening of the airways which may either increase or decrease airway responsiveness, depending on the mechanical requirements of the deposited matrix. However, in vitro studies have shown that the altered extracellular matrix produced by asthmatic airway smooth muscle cells is able to induce increased proliferation of non-asthmatic smooth muscle cells, which is a process believed to contribute to airway hyper-responsiveness in asthma. Elastin is an extracellular matrix protein that is altered in asthmatic airways, but there has been no systematic investigation of the functional effect of these changes. This review reveals divergent reports of the state of elastin in the airway wall in asthma. In some layers of the airway it has been described as increased, decreased and/or fragmented, or unchanged. There is also considerable evidence for an imbalance of matrix metalloproteinases, which degrade elastin, and their respective inhibitors the tissue inhibitors of metalloproteinases, which collectively help to explain observations of both increased elastin and elastin fragments. A loss of lung elastic recoil in asthma suggests a mechanical role for disordered elastin in the aetiology of the disease, but extensive studies of elastin in other tissues show that elastin fragments elicit cellular effects such as increased proliferation and inflammation. This review summarises the current understanding of the role of elastin in the asthmatic airway.

The action of neutrophil serine proteases on elastin and its precursor

This study aimed to investigate the degradation of the natural substrates tropoelastin and elastin by the neutrophil-derived serine proteases human leukocyte elastase (HLE), proteinase 3 (PR3) and cathepsin G (CG). Focus was placed on determining their cleavage site specificities using mass spectrometric techniques. Moreover, the release of bioactive peptides from elastin by the three proteases was studied. Tropoelastin was comprehensively degraded by all three proteases, whereas less cleavage occurred in mature cross-linked elastin. An analysis of the cleavage site specificities of the three proteases in tropoelastin and elastin revealed that HLE and PR3 similarly tolerate hydrophobic and/or aliphatic amino acids such as Ala, Gly and Val at P(1), which are also preferred by CG. In addition, CG prefers the bulky hydrophobic amino acid Leu and accepts the bulky aromatic amino acids Phe and Tyr. CG shows a strong preference for the charged amino acid Lys at P(1) in tropoelastin, whereas Lys was not identified at P(1) in CG digests of elastin due to extensive cross-linking at Lys residues in mature elastin. All three serine proteases showed a clear preference for Pro at P(2) and P(4)'. With respect to the liberation of potentially bioactive peptides from elastin, the study revealed that all three serine proteases have a similar ability to release bioactive sequences, with CG producing the highest number of these peptides. In bioactivity studies, potentially bioactive peptides that have not been investigated on their bioactivity to date, were tested. Three new bioactive GxxPG motifs were identified; GVYPG, GFGPG and GVLPG.

Cellular responses to patterned poly(acrylic acid) brushes

We use patterned poly(acrylic acid) (PAA) polymer brushes to explore the effects of surface chemistry and topography on cell-surface interactions. Most past studies of surface topography effects on cell adhesion have focused on patterned feature sizes that are larger than the dimensions of a cell, and PAA brushes have been characterized as cell repellent. Here we report cell adhesion studies for RBL mast cells incubated on PAA brush surfaces patterned with a variety of different feature sizes. We find that when patterned at subcellular dimensions on silicon surfaces, PAA brushes that are 30 or 15 nm thick facilitate cell adhesion. This appears to be mediated by fibronectin, which is secreted by the cells, adsorbing to the brushes and then engaging cell-surface integrins. The result is detectable accumulation of plasma membrane within the brushes, and this involves cytoskeletal remodeling at the cell-surface interface. By decreasing brush thickness, we find that PAA can be 'tuned' to promote cell adhesion with down-modulated membrane accumulation. We exemplify the utility of patterned PAA brush arrays for spatially controlling the activation of cells by modifying brushes with ligands that specifically engage IgE bound to high-affinity receptors on mast cells.

Binding of the cell adhesive protein tropoelastin to PTFE through plasma immersion ion implantation treatment

The interaction of proteins and cells with polymers is critical to their use in scientific and medical applications. In this study, plasma immersion ion implantation (PIII) was used to modify the surface of polytetrafluorethylene (PTFE), enabling the covalent binding of a cell adhesive protein, tropoelastin, without employing chemical linking molecules. Tropoelastin coating of untreated or PIII treated PFTE simultaneously promoted and blocked cell interactions respectively, i.e. PIII treatment of the PTFE surface completely inverses the cell interactive properties of bound tropoelastin. This activity persisted over long term storage of the PIII treated surfaces. The integrin binding C-terminus of tropoelastin was markedly less solvent exposed when bound to PIII treated PTFE than untreated PTFE, accounting for the modulation of cell adhesive activity. This presents a new methodology to specifically modulate cell behavior on a polymer surface using a simple one step treatment process, by adjusting the adhesive activity of a single extracellular matrix protein.

Elastin peptides prepared from piscine and mammalian elastic tissues inhibit collagen-induced platelet aggregation and stimulate migration and proliferation of human skin fibroblasts

We obtained pure elastin peptides from bovine ligamentum nuchae, porcine aorta, and bonito bulbus arteriosus. The inhibitory activity of these elastin peptides on platelet aggregation induced by collagen and the migratory and proliferative responsivenesses of human skin fibroblasts to these elastin peptides were examined. All of bonito, bovine, and porcine elastin peptides found to inhibit platelet aggregation, but bonito elastin peptides showed a higher inhibitory activity than bovine and porcine elastin peptides did. All elastin peptides enhanced the proliferation of fibroblasts 3.5- to 4.5-fold at a concentration of 10 µg/ml. Bovine and porcine elastin peptides stimulated the migration of fibroblasts, with the optimal response occurring at 10(-1) µg/ml, while maximal response was at 10(2) µg/ml for bonito elastin peptides. Furthermore, pretreatment of fibroblasts by lactose depressed their ability to migrate in response to all elastin peptides, suggesting the involvement of elastin receptor in cell response. These results suggest that both mammalian and piscine elastin peptides can be applied as useful biomaterials in which elasticity, antithrombotic property, and the enhancement of cell migration and proliferation are required.

Characterization of peptide fragments from lung elastin degradation in chronic obstructive pulmonary disease

This study presents a method for detecting and characterizing peptides of elastin that result from lung matrix injury in chronic obstructive pulmonary disease (COPD). Lung elastin degradation was studied by two representative in vivo elastases, human neutrophil elastase (HNE) and macrophage metalloproteinase (MMP12). The resulting peptide mixtures were analyzed by high-performance liquid chromatography/electrospray tandem mass spectrometry (LC/MSMS) to characterize 40 elastin-derived peptides (EDPs), 24 from HNE and 16 from MMP12 digestions. The peptides constitute major EDPs that are solubilized by the enzymatic digestion. Using the selected reaction monitoring (SRM) from LC/MSMS analysis, the transition ions of the peptides were used to investigate the presence of the peptides in selected body fluids of chronic obstructive pulmonary disease (COPD) patients. Four peptides, GYPI, APGVGV, GLGAFPA, and VGVLPGVPT, were detected in plasma or sputum of some COPD patients but not in normal controls. A hexapeptide VGVAPG, which had been widely studied for its chemotactic activity for a possible pathogenic role in COPD, was not detected in lung EDPs by HNE or MMP12 digestion, but only by porcine pancreatic elastase (PPE) digestion. This study demonstrates a practical methodology to study peptides from matrix degradations in pulmonary disease and a means of investigating their pathogenesis.

Hypertrophy of the lumbar ligamentum flavum is associated with inflammation-related TGF-β expression

BACKGROUND

Despite the significance of hypertrophy of the ligamentum flavum (HLF) in the disease progress of neurogenic claudication, the cellular mechanisms underlying the gradual fibrotic thickening of the ligamentum flavum remain poorly understood. The aim of our study was to get insight into the contribution of inflammatory mechanisms to the development of hypertrophy.

METHODS

Specimens of hypertrophied ligamenta flava were obtained at surgery from 20 patients with acquired lumbar osteoligamentous spinal canal stenosis from the central part of the ligament. Paraffin sections were stained with hematoxylin and eosin and Elastica van Gieson to evaluate extracellular matrix architecture, and immunohistochemistry was performed to characterize the inflammatory reaction and the sources of transforming growth factor beta (TGF-β) expression. Sections of normal ligamenta flava obtained from corresponding anatomical sites and stained in parallel served as a control.

RESULTS

HLF was characterized by a considerable distortion of the elastic matrix and fibrotic transformation by extracellular collagen deposition. All specimens showed highly inflammatory cellular infiltrates confined to regions exhibiting marked degeneration of the elastic matrix composed mainly of macrophages, scattered T lymphocytes, and neovascularization, thus representing a chronic inflammation. Surprisingly, macrophages as well as vascular endothelial cells but not fibroblasts showed a strong expression of TGF-β, a strong inducer of extracellular collagen deposition.

CONCLUSIONS

Macrophages were identified as a major cellular source of TGF-β in advanced HLF and may perpetuate further hypertrophy. This finding suggests that modulating the immune response locally or systemically could prove to be effective for impeding the disease progress.

Linker-free covalent attachment of the extracellular matrix protein tropoelastin to a polymer surface for directed cell spreading

Polymers are used for the fabrication of many prosthetic implants. It is desirable for these polymers to promote biological function by promoting the adhesion, differentiation and viability of cells. Here we have used plasma immersion ion implantation (PIII) treatment of polystyrene to modify the polymer surface, and so modulate the binding of the extracellular matrix protein tropoelastin. PIII treated, but not untreated polystyrene, bound tropoelastin in a sodium dodecyl sulfate (SDS)-resistant manner, consistent with previous enzyme-binding data that demonstrated the capability of these surfaces to covalently attach proteins without employing chemical linking molecules. Furthermore sulfo-NHS acetate (SNA) blocking of tropoelastin lysine side chains eliminated the SDS-resistant binding of tropoelastin to PIII-treated polystyrene. This implies tropoelastin is covalently attached to the PIII-treated surface via its lysine side chains. Cell spreading was only observed on tropoelastin coated, PIII-treated polystyrene surfaces, indicating that tropoelastin was more biologically active on the PIII-treated surface compared to the untreated surface. A contact mask was used to pattern the PIII treatment. Following tropoelastin attachment, cells spread preferentially on the PIII-treated sections of the polystyrene surface. This demonstrates that PIII treatment of polystyrene improves the polymer's tropoelastin binding properties, with advantages for tissue engineering and prosthetic design.

Primary human dermal fibroblast interactions with open weave three-dimensional scaffolds prepared from synthetic human elastin

We present an elastic, fibrous human protein-based and cell-interactive dermal substitute scaffold based on synthetic human elastin. Recombinant human tropoelastin promoted primary human dermal fibroblast attachment, spreading and proliferation. Tropoelastin was cross-linked to form a synthetic elastin (SE) hydrogel matrix and electrospun into fibrous SE scaffolds. Fibroblasts attached to and proliferated across SE hydrogel scaffold surfaces for at least 14 days and deposited the extracellular matrix proteins fibronectin and collagen type I. To allow for the benefit of greater cell infiltration, SE was electrospun into open weave, fibrous scaffolds that closely mimic the fibrous nature of the skin dermis. 3D SE scaffolds were robust and consisted of flat, ribbon-like fibers with widths that are similar to native dermal elastic fibers. The scaffolds displayed elasticity close to that of natural elastin. 3D SE retained the ability to interact with primary human dermal fibroblasts, which consistently attached and proliferated to form monolayers spanning the entire scaffold surface. The open weave design, with larger spaces between individual fibers and greater fiber diameters beneficially allowed for substantial cell infiltration throughout the scaffolds.

Cell adhesion to tropoelastin is mediated via the C-terminal GRKRK motif and integrin alphaVbeta3

Elastin fibers are predominantly composed of the secreted monomer tropoelastin. This protein assembly confers elasticity to all vertebrate elastic tissues including arteries, lung, skin, vocal folds, and elastic cartilage. In this study we examined the mechanism of cell interactions with recombinant human tropoelastin. Cell adhesion to human tropoelastin was divalent cation-dependent, and the inhibitory anti-integrin alpha(V)beta(3) antibody LM609 inhibited cell spreading on tropoelastin, identifying integrin alpha(V)beta(3) as the major fibroblast cell surface receptor for human tropoelastin. Cell adhesion was unaffected by lactose and heparin sulfate, indicating that the elastin-binding protein and cell surface glycosaminoglycans are not involved. The C-terminal GRKRK motif of tropoelastin can bind to cells in a divalent cation-dependent manner, identifying this as an integrin binding motif required for cell adhesion.

Elastin receptor (spliced galactosidase) occupancy by elastin peptides counteracts proinflammatory cytokine expression in lipopolysaccharide-stimulated human monocytes through NF-kappaB down-regulation

In inflammatory diseases, strong release of elastinolytic proteases results in elastin fiber degradation generating elastin peptides (EPs). Chemotactic activity for inflammatory cells was, among wide range of properties, the former identified biological activity exerted by EPs. Recently, we demonstrated the ability of EPs to favor a Th1 cytokine (IL-2, IFN-gamma) cell response in lymphocytes and to regulate IL-1beta expression in melanoma cells. We hypothesized that EPs might also influence inflammatory cell properties by regulating cytokine expression by these cells. Therefore, we investigated the influence of EPs on inflammatory cytokine synthesis by human monocytes. We evidenced that EPs down-regulated both at the mRNA and protein levels the proinflammatory TNF-alpha, IL-1beta, and IL-6 expression in LPS-activated monocytes. Such negative feedback loop could be accounted solely for EP-mediated effects on proinflammatory cytokine production because EPs did not affect anti-inflammatory IL-10 or TGF-beta secretion by LPS-activated monocytes. Furthermore, we demonstrated that EP effect on proinflammatory cytokine expression by LPS-stimulated monocytes could not be due either to a decrease of LPS receptor expression or to an alteration of LPS binding to its receptor. The inhibitory effects of EPs on cytokine expression were found to be mediated by receptor (spliced galactosidase) occupancy, as being suppressed by lactose, and to be associated with the decrease of NF-kappaB-DNA complex formation. As a whole, these results demonstrated that EP/spliced galactosidase interaction on human monocytes down-regulated NF-kappaB-dependent proinflammatory cytokine expression and pointed out the critical role of EPs in the regulation of inflammatory response.

Proteolytic digest derived from bovine Ligamentum Nuchae stimulates deposition of new elastin-enriched matrix in cultures and transplants of human dermal fibroblasts

BACKGROUND

Diverse topical products and injectable fillers used for correcting facial wrinkles induce rather short-lived effects because they target replacement of dermal collagen and hyaluronan, matrix components of limited biologic durability.

OBJECTIVE

Present studies were aimed at stimulation of fully differentiated human dermal fibroblasts to resume deposition of new extracellular matrix rich of elastin, the most durable and metabolically inert component of dermal ECM.

METHODS

We have created a novel proteolytic digest of bovine ligamentum nuchae (ProK-60), and tested its potential biological effect on dermal fibroblasts derived from females of different ages. Northern blots, quantitative immunohistochemistry and metabolic assays were used to assess effects of ProK-60 on proliferation and matrix production in primary cultures of dermal fibroblasts, in cultures of skin explants and after implantation of stimulated fibroblasts into the skin of athymic nude mice.

RESULTS

ProK-60 increased proliferation (25-30%) of cultured dermal fibroblasts and significantly enhanced their production of new elastic fibers (>250%) and collagen fibers (100%). These effects were mostly mediated by stimulation of cellular elastin receptor. In contrast, ProK-60 inhibited production of fibronectin (-30%) and chondroitin sulfate proteoglycans (-50%). ProK-60 also activated proliferation of dermal fibroblasts, mostly derived from the stratum basale and induced deposition of elastic fibers in cultures of skin explants. Moreover, human fibroblasts pre-treated with ProK-60 produced abundant elastic fibers after their injection into the skin of athymic nude mice.

CONCLUSION

The described biological effects of ProK-60, including its unique elastogenic property, encourage use of this compound in cosmetic formulations stimulating rejuvenation of aged skin.

Cellular interactions with elastin

Elastin is a key structural component of the extracellular matrix. Tropoelastin is the soluble precursor of elastin. In addition to providing elastic recoil to various tissues such as the aorta and lung, elastin, tropoelastin and elastin degradation products are able to influence cell function and promote cellular responses. These responses include chemotaxis, proliferation and cell adhesion. The interaction of elastin products with cells has been attributed to the elastin receptor. However, additional cell-surface receptors have also been identified. These include G protein-coupled receptors and integrins. The potential roles of these receptors in cell-elastin interactions, with particular focus on elastin formation are discussed.

Elastin-derived peptides induce a T-helper type 1 polarization of human blood lymphocytes

OBJECTIVE

Increased level of elastin-derived peptides (EDPs) is observed in the serum of patients with manifestations of arterial diseases. We here investigated whether EDPs might exert, at systemic level, a regulatory role for the T-helper type 1 (Th-1)/Th-2 cellular immune response by human peripheral blood lymphocytes (PBLs) expressing the spliced-galactosidase (S-gal)-elastin receptor.

METHODS AND RESULTS

Using flow cytometry and Western blot analysis, we demonstrated that EDPs led to an activation of the S-gal-elastin receptor associated with cytokine production on PBLs and CD4+ T cell subpopulations. The constitutive expression of the S-gal-elastin receptor at the surface of human PBLs was upregulated at the mRNA (RT-PCR) and protein (ELISA) levels on cell activation. In nonactivated and phytohemagglutinin-activated conditions, expressions of the predominant Th-2 cytokine interleukin-5 (IL-5) and IL-10 were reduced, whereas those of the major Th-1 cytokines interferon-gamma and IL-2 were enhanced by EDPs. Furthermore, we evidenced that EDPs could not only potentiate the IL-12-induced Th-1 profile but also could reverse the Th-2 (over Th-1) profile induced by IL-4. Finally, Th-1 cytokine upregulation was associated to an increased activator protein-1 DNA binding and enhanced pro-matrix metalloproteinase-9 secretion.

CONCLUSIONS

This study highlights the importance of EDPs as stimuli for Th-1 differentiation, whether T cells are in an inactivated state or already orientated toward a Th-1 (IL-12) or Th-2 (IL-4) response.

What is the contribution of respiratory viruses and lung proteases to airway remodelling in asthma and chronic obstructive pulmonary disease?

It is well known that the lungs of asthmatics show airway wall remodelling and that asthma exacerbations are linked to respiratory infections. There is some evidence that respiratory infections in early childhood may increase the risk of developing asthma later in life. Chronic obstructive pulmonary disease (COPD), by definition, involves structural changes to the airways. However, very little is known about what role virus infections play in the development of this remodelling. This review considers the role of matrix metalloproteases and neutrophil elastase in remodelling, and whether the induction of proteases and other mediators during respiratory virus infections may contribute to the development of airway remodelling.

Elastin

Elastin is a key extracellular matrix protein that is critical to the elasticity and resilience of many vertebrate tissues including large arteries, lung, ligament, tendon, skin, and elastic cartilage. Tropoelastin associates with multiple tropoelastin molecules during the major phase of elastogenesis through coacervation, where this process is directed by the precise patterning of mostly alternating hydrophobic and hydrophilic sequences that dictate intermolecular alignment. Massively crosslinked arrays of tropoelastin (typically in association with microfibrils) contribute to tissue structural integrity and biomechanics through persistent flexibility, allowing for repeated stretch and relaxation cycles that critically depend on hydrated environments. Elastin sequences interact with multiple proteins found in or colocalized with microfibrils, and bind to elastogenic cell surface receptors. Knowledge of the major stages in elastin assembly has facilitated the construction of in vitro models of elastogenesis, leading to the identification of precise molecular regions that are critical to elastin-based protein interactions.

Elastin induces myofibrillogenesis via a specific domain, VGVAPG

A hallmark of vascular smooth muscle cells (VSMCs) is their dynamic ability to assemble and disassemble contractile proteins into sarcomeric units depending upon their phenotypic state. This phenotypic plasticity plays an important role during vascular development and in obstructive vascular disease. Previously, we showed that the Elastin gene product, tropoelastin, activates myofibrillar organization of VSMCs. Recently, others have suggested that elastin does not have a direct signaling role but rather binds to and alters the interactions of other matrix proteins with their cognate receptors or disrupts the binding of growth factors and cytokines. In contrast, we provide evidence that tropoelastin directly regulates contractile organization of VSMCs. First, we show that a discrete domain within tropoelastin, VGVAPG, induces myofibrillogenesis in a time- and dose-dependent fashion. We confirm specificity using a closely related control peptide that fails to stimulate actin stress fiber formation. Second, the activity of VGVAPG is not affected by the presence or absence of other serum or matrix components. Third, both the elastin hexapeptide and tropoelastin stimulate actin polymerization through a common pertussis toxin-sensitive G protein pathway that activates RhoA-GTPase and results in the conversion of G to F actin. Collectively, these data support a model whereby the elastin gene product, signaling through the VGVAPG domain, directly induces VSMC myofibrillogenesis.

Involvement of matrix metalloproteinases and tenascin-C in elastin calcification

Elastin degeneration and calcification occur in many cardiovascular diseases, including medial arterial elastocalcinosis, atherosclerosis, and bioprosthetic heart valve mineralization. In the present study, we tested the hypothesis that the onset and progression of elastin-oriented calcification is associated with matrix remodeling and elastin degradation events. We studied whether aluminum ions inhibit elastin calcification by reducing elastin degradation and altering remodeling events. Subdermal implantation of pure elastin in juvenile rats resulted in a time-dependent calcification of elastin, reaching high levels 21 days after implantation. In situ hybridization showed that elastin calcification was associated with an up-regulation of matrix metalloproteinase (MMP) mRNA expression, specifically MMP-9 and MMP-2. Gelatin zymography demonstrated increased MMP-9 and MMP-2 enzyme activities in early stages of elastin calcification. Calcified elastin displayed a time-dependent pattern of tenascin-C (TN-C) and alkaline phosphatase (AP) expression. Pretreatment of pure elastin with aluminum ions prior to implantation resulted in complete inhibition of elastin calcification. Aluminum ion binding to elastin was found to protect elastin against MMP-mediated degradation in vitro. Noncalcified, explanted aluminum-pretreated elastin exhibited reduced activities of MMPs. TN-C expression in elastin implants exhibited a time-dependent pattern that was also affected by pretreatment of elastin with aluminum ions. In conclusion, elastin calcification is accompanied by matrix remodeling events, and the efficacy of aluminum pretreatment in inhibiting elastin calcification may be related in part to its effects on elastin remodeling.

Peptides and hormesis

The article provides a broad assessment of the occurrence of hormetic-like biphasic dose-response relationships by over 30 peptides representing many major peptide classes. These peptide-induced biphasic dose responses were observed to occur in a extensive range of tissues, affecting an diverse range of biological endpoints. Despite diversity of peptides, models and endpoints, the quantitative features of the biphasic dose responses are remarkably similar with respect to the amplitude and width of the stimulatory response. These findings strongly suggest that hormetic-like biphasic dose responses represent a broadly generalizable biological phenomenon.

Characterization of an in vitro model of calcification in retinal pigmented epithelial cells

Little is known about the relationship at the molecular and cellular levels between vascular calcification and elastic fibers essential for elasticity. To gain a better understanding of the physiological function of elastin in vascular calcification, we developed a calcification model on cultured bovine retinal-pigmented-epithelial cells (RPEs) that do not express endogenous tropoelastin. The addition of inorganic phosphate (NaH2PO4; Pi) induced calcium deposition in RPEs. The Pi-induced calcification, as assessed by the o-cresolphthalein complexone method, Goldenbergs method, and von Kossa staining, was completely inhibited by treatment with clodronate (DMDP) and phosphonoformic acid (PFA) and was weakly suppressed by treatment with levamisole. Moreover, the osteopontin mRNA expression was upregulated in the Pi-induced calcification of RPEs. These reactions in RPEs were characteristically consistent with those already established in cultured bovine aortic smooth muscle cells (BASMCs). Furthermore, bacterially expressed tropoelastin inhibited calcium deposition in RPEs as well as in BASMCs. Finally, Pi-induced calcification was partially suppressed after the addition of tropoelastin due to elastic fiber formation. In conclusion, we suggest that this calcification model in RPEs is useful for analyzing the relation between elastic fibers and vascular calcification, and that tropoelastin and elastic fibers may contribute to the inhibition of vascular calcification.

Monocyte chemotactic activity in human abdominal aortic aneurysms: role of elastin degradation peptides and the 67-kD cell surface elastin receptor

BACKGROUND

Chronic inflammation is a characteristic feature of abdominal aortic aneurysms (AAAs), but the molecular signals responsible for recruiting monocytes into the outer aortic wall are unresolved. The purpose of this study was to examine whether AAA tissues elaborate chemotactic activity for mononuclear phagocytes and to determine whether this activity is attributable to interactions between elastin degradation peptides (EDPs) and their cell surface receptor, the 67-kD elastin binding protein (EBP).

MATERIAL AND METHODS

Soluble proteins were extracted from human AAA tissues, and chemotactic activity for differentiated U937 mononuclear phagocytes was measured by use of a modified Boyden chamber. Chemotactic activity induced by N -formyl-Met-Leu-Phe was used as a positive control and checkerboard analysis was used to distinguish chemotaxis from chemokinesis. Inhibition of chemotaxis was tested by peptide competition, blocking antibodies and galactosugar-mediated dissociation of the 67-kD EBP.

RESULTS

AAA extracts stimulated a concentration-dependent increase in monocyte migration that reached up to 24% of the maximal effect induced by N -formyl-Met-Leu-Phe. Checkerboard analysis demonstrated that AAA extracts stimulated chemotaxis without a chemokinetic effect. AAA-derived chemotactic activity was eliminated by competition with Val-Gly-Val-Arg-Pro-Gly (VGVAPG), a repetitive peptide found in human elastin that binds to cellular elastin receptors, and decreased nearly 40% in the presence of BA-4, an antielastin monoclonal antibody that can block EDP-mediated chemotactic activity. Monocyte chemotaxis in response to both VGVAPG and AAA extracts was abolished in the presence of lactose, a galactosugar that specifically dissociates the 67-kD EBP, but it was unaffected by either glucose, fructose, or mannose.

CONCLUSIONS

These findings indicate that soluble EDPs released within human AAA tissue can subsequently attract mononuclear phagocytes through ligand-receptor interactions with the 67-kD EBP, thereby providing a plausible molecular mechanism to explain the inflammatory response that accompanies aneurysmal degeneration. Better understanding of factors regulating inflammatory cell recruitment may lead to novel forms of therapy for early stages of aneurysmal degeneration.