METABOLIC SYNDROME-ASSOCIATED MURINE AORTIC WALL STIFFENING IS ASSOCIATED WITH PREMATURE ELASTIC FIBERS AGING.

Type 2 diabetes (T2D) constitutes a major public health problem, and despite prevention efforts, this pandemic disease is 'one of the deadliest diseases in the world. In 2022, 6.7 million T2D patients died prematurely from vascular complications. Indeed, diabetes increases the risk of myocardial infarction or stroke eightfold. The identification of the molecular actors involved in the occurrence of cardiovascular complications and their prevention are therefore major axes. Our hypothesis is that factors brought into play during physiological aging appear prematurely with diabetes progression. Our study focused on the aging of the extracellular matrix (ECM), a major element in the maintenance of vascular homeostasis. We characterized the morphological and functional aspects of aorta, with a focus on the collagen and elastic fibers of diabetic mice aged from 6 months to non-diabetic mice aged 6 months and 20 months. The comparison with the two non-diabetic models (young and old) highlighted an exacerbated activity of proteases, which could explain a disturbance in the collagen accumulation and an excessive degradation of elastic fibers. Moreover, the generation of circulating elastin-derived peptides reflects premature aging of the ECM. These extracellular elements contribute to the appearance of vascular rigidity, often the origin of pathologies such as hypertension and atherosclerosis. In conclusion, we show that diabetic mice aged 6 months present the same characteristics of ECM wear as those observed in mice aged 20 months. This accelerated aortic wall remodeling could then explain the early onset of cardiovascular diseases and, therefore, the premature death of DT2 patients.

Structural and physical basis for the elasticity of elastin.

Elastin function is to endow vertebrate tissues with elasticity so that they can adapt to local mechanical constraints. The hydrophobicity and insolubility of the mature elastin polymer have hampered studies of its molecular organisation and structure-elasticity relationships. Nevertheless, a growing number of studies from a broad range of disciplines have provided invaluable insights, and several structural models of elastin have been proposed. However, many questions remain regarding how the primary sequence of elastin (and the soluble precursor tropoelastin) governs the molecular structure, its organisation into a polymeric network, and the mechanical properties of the resulting material. The elasticity of elastin is known to be largely entropic in origin, a property that is understood to arise from both its disordered molecular structure and its hydrophobic character. Despite a high degree of hydrophobicity, elastin does not form compact, water-excluding domains and remains highly disordered. However, elastin contains both stable and labile secondary structure elements. Current models of elastin structure and function are drawn from data collected on tropoelastin and on elastin-like peptides (ELPs) but at the tissue level, elasticity is only achieved after polymerisation of the mature elastin. In tissues, the reticulation of tropoelastin chains in water defines the polymer elastin that bears elasticity. Similarly, ELPs require polymerisation to become elastic. There is considerable interest in elastin especially in the biomaterials and cosmetic fields where ELPs are widely used. This review aims to provide an up-to-date survey of/perspective on current knowledge about the interplay between elastin structure, solvation, and entropic elasticity.

Prediction, screening and characterization of novel bioactive tetrapeptide matrikines for skin rejuvenation.

BACKGROUND: Extracellular matrices play a critical role in tissue structure and function and aberrant remodelling of these matrices is a hallmark of many age-related diseases. In skin, loss of dermal collagens and disorganization of elastic fibre components are key features of photoageing. Although the application of some small matrix-derived peptides to aged skin has been shown to beneficially affect in vitro cell behaviour and, in vivo, molecular architecture and clinical appearance, the discovery of new peptides has lacked a guiding hypothesis. OBJECTIVES: To identify, using protease cleavage site prediction, novel putative matrikines with beneficial activities for skin composition and structure. METHODS: Here, we present an in silico (peptide cleavage prediction) to in vitro (proteomic and transcriptomic activity testing in cultured human dermal fibroblasts) to in vivo (short-term patch test and longer-term split-face clinical study) discovery pipeline, which enables the identification and characterization of peptides with differential activities. RESULTS: Using this pipeline we showed that cultured fibroblasts were responsive to all applied peptides, but their associated bioactivity was sequence-dependent. Based on bioactivity, toxicity and protein source, we further characterized a combination of two novel peptides, GPKG (glycine-proline-lysine-glycine) and LSVD (leucine-serine-valine-aspartate), that acted in vitro to enhance the transcription of matrix -organization and cell proliferation genes and in vivo (in a short-term patch test) to promote processes associated with epithelial and dermal maintenance and remodelling. Prolonged use of a formulation containing these peptides in a split-face clinical study led to significantly improved measures of crow's feet and firmness in a mixed population. CONCLUSIONS: This approach to peptide discovery and testing can identify new synthetic matrikines, providing insights into biological mechanisms of tissue homeostasis and repair and new pathways to clinical intervention.

Like other organs and tissues, the skin is composed of both cells and a complex network of molecules and proteins called an extracellular matrix. This matrix contains proteins such as collagen and elastin and undergoes many changes when the skin is damaged by the sun. We know from previous studies that small parts of matrix proteins (called peptide 'matrikines') can help to treat the signs of sun-related skin ageing. In this UK study, we show that new beneficial peptides (with matrikine activity) can be identified using machine learning (artificial intelligence) techniques that predict where common matrix proteins might be 'cut' by skin enzymes. Candidate peptides were first made in the laboratory and then applied to skin cells in culture. These cell culture screens demonstrated that, while all the peptides showed some matrikine activity, two were particularly promising. These two peptides were then tested in a short-term study on the forearm skin of volunteers and, in a longer-term study, on the face. We found that the combination of these two peptides can prompt forearm skin cells to express genes that are involved in many different aspect of skin health and, over the longer 6-month period, produce visible benefits in the appearance of fine lines and wrinkles and firmness on the face. Our findings suggest that this approach may be able to identify beneficial peptide treatments for not only skin ageing and diseases, but also unwanted changes in the extracellular matrix of other tissues and organs.

Matrikines as mediators of tissue remodelling.

Extracellular matrix (ECM) proteins confer biomechanical properties, maintain cell phenotype and mediate tissue repair (via release of sequestered cytokines and proteases). In contrast to intracellular proteomes, where proteins are monitored and replaced over short time periods, many ECM proteins function for years (decades in humans) without replacement. The longevity of abundant ECM proteins, such as collagen I and elastin, leaves them vulnerable to damage accumulation and their host organs prone to chronic, age-related diseases. However, ECM protein fragmentation can potentially produce peptide cytokines (matrikines) which may exacerbate and/or ameliorate age- and disease-related ECM remodelling. In this review, we discuss ECM composition, function and degradation and highlight examples of endogenous matrikines. We then critically and comprehensively analyse published studies of matrix-derived peptides used as topical skin treatments, before considering the potential for improvements in the discovery and delivery of novel matrix-derived peptides to skin and internal organs. From this, we conclude that while the translational impact of matrix-derived peptide therapeutics is evident, the mechanisms of action of these peptides are poorly defined. Further, well-designed, multimodal studies are required.

Early Alterations of Intra-Mural Elastic Lamellae Revealed by Synchrotron X-ray Micro-CT Exploration of Diabetic Aortas.

Diabetes is a major concern of our society as it affects one person out of 11 around the world. Elastic fiber alterations due to diabetes increase the stiffness of large arteries, but the structural effects of these alterations are poorly known. To address this issue, we used synchrotron X-ray microcomputed tomography with in-line phase contrast to image in three dimensions C57Bl6J (control) and db/db (diabetic) mice with a resolution of 650 nm/voxel and a field size of 1.3 mm3. Having previously shown in younger WT and db/db mouse cohorts that elastic lamellae contain an internal supporting lattice, here we show that in older db/db mice the elastic lamellae lose this scaffold. We coupled this label-free method with automated image analysis to demonstrate that the elastic lamellae from the arterial wall are structurally altered and become 11% smoother (286,665 measurements). This alteration suggests a link between the loss of the 3D lattice-like network and the waviness of the elastic lamellae. Therefore, waviness measurement appears to be a measurable elasticity indicator and the 3D lattice-like network appears to be at the origin of the existence of this waviness. Both could be suitable indicators of the overall elasticity of the aorta.

Investigation of Antiparasitic Activity of 10 European Tree Bark Extracts on Toxoplasma gondii and Bioguided Identification of Triterpenes in Alnus glutinosa Barks.

Toxoplasmosis is a worldwide parasitosis that affects one-third of the population. People at risk, such as immunocompromised patients (AIDS, chemotherapy treatment) or fetuses (maternal-fetal transmission) can develop severe forms of the disease. The antiparasitic activity of extracts of different polarities (n-heptane, MeOH, MeOH/H2O) of 10 tree species endemic to temperate regions was investigated against Toxoplasma gondii infection in vitro. Our results showed that the n-heptane extract of the black alder (Alnus glutinosa) exhibited a significant antiparasitic activity without any cytotoxicity at the tested concentrations, with an IC50 of up to 25.08 µg/mL and a selectivity index higher than 3.99. The chemical profiling of this extract revealed triterpenes as major constituents. The ability of commercially available triterpene (betulin, betulinic acid, and betulone) to inhibit the growth of T. gondii was evaluated and showed growth inhibition rates of 44%, 49%, and 99% at 10 µM, respectively.

X-ray microtomography reveals a lattice-like network within aortic elastic lamellae.

The arterial wall consists of three concentric layers: intima, media, and adventitia. Beyond their resident cells, these layers are characterized by an extracellular matrix (ECM), which provides both biochemical and mechanical support. Elastin, the major component of arterial ECM, is present in the medial layer and organized in concentric elastic lamellae that confer resilience to the wall. We explored the arterial wall structures from C57Bl6 (control), db/db (diabetic), and ApoE-/- (atherogenic) mice aged 3 months using synchrotron X-ray computed microtomography on fixed and unstained tissues with a large image field (8 mm3 ). This approach combined a good resolution (0.83 µm/voxel), large 3D imaging field. and an excellent signal to noise ratio conferred by phase-contrast imaging. We determined from 2D virtual slices that the thickness of intramural ECM structures was comparable between strains but automated image analysis of the 3D arterial volumes revealed a lattice-like network within concentric elastic lamellae. We hypothesize that this network could play a role in arterial mechanics. This work demonstrates that phase-contrast synchrotron X-ray computed microtomography is a powerful technique which to characterize unstained soft tissues.

Structural Analysis of Nonapeptides Derived from Elastin.

Elastin-derived peptides are released from the extracellular matrix remodeling by numerous proteases and seem to regulate many biological processes, notably cancer progression. The canonical elastin peptide is VGVAPG, which harbors the XGXXPG consensus pattern, allowing interaction with the elastin receptor complex located at the surface of cells. Besides these elastokines, another class of peptides has been identified. This group of bioactive elastin peptides presents the XGXPGXGXG consensus sequence, but the reason for their bioactivity remains unexplained. To better understand their nature and structure-function relationships, herein we searched the current databases for this nonapeptide motif and observed that the XGXPGXGXG elastin peptides define a specific group of tandemly repeated patterns. Further, we focused on four tandemly repeated human elastin nonapeptides, i.e., AGIPGLGVG, VGVPGLGVG, AGVPGLGVG, and AGVPGFGAG. These peptides were analyzed by means of optical spectroscopies and molecular dynamics. Ultraviolet-circular dichroism and Raman spectra are consistent with a mixture of ß-turn, ß-strand, and random-chain secondary elements in aqueous media. Quantitative analysis of their conformations suggested that turns corresponded to half of the total population of structural elements, whereas the remaining half were equally distributed between ß-strand and unordered chains. These distributions were confirmed by molecular dynamics simulations. Altogether, our data suggest that these highly dynamic peptides harbor a type II ß-turn located in their central part. We hypothesize that this structural element could explain their specific bioactivity.

Elastin molecular aging promotes MDA-MB-231 breast cancer cell invasiveness.

Elastin is a long-lived extracellular matrix protein responsible for the structural integrity and function of tissues. Breast cancer elastosis is a complex phenomenon resulting in both the deposition of elastotic masses and the local production of elastin fragments. In invasive human breast cancers, an increase in elastosis is correlated with severity of the disease and age of the patient. Elastin-derived peptides (EDPs) are a hallmark of aging and are matrikines - matrix fragments having the ability to regulate cell physiology. They are known to promote processes linked to tumor progression, but their effects on breast cancer cells remain unexplored. Our data show that EDPs enhance the invasiveness of MDA-MB-231 breast cancer cells through the engagement of matrix metalloproteases 14 and 2. We therefore suggest that elastosis and/or an aged stroma could promote breast cancer cell invasiveness.

Production of Elastin-Derived Peptides Contributes to the Development of Nonalcoholic Steatohepatitis.

Affecting more than 30% of the Western population, nonalcoholic fatty liver disease (NAFLD) is the most common liver disease and can lead to multiple complications, including nonalcoholic steatohepatitis (NASH), cancer, hypertension, and atherosclerosis. Insulin resistance and obesity are described as potential causes of NAFLD. However, we surmised that factors such as extracellular matrix remodeling of large blood vessels, skin, or lungs may also participate in the progression of liver diseases. We studied the effects of elastin-derived peptides (EDPs), biomarkers of aging, on NAFLD progression. We evaluated the consequences of EDP accumulation in mice and of elastin receptor complex (ERC) activation on lipid storage in hepatocytes, inflammation, and fibrosis development. The accumulation of EDPs induces hepatic lipogenesis (i.e., SREBP1c and ACC), inflammation (i.e., Kupffer cells, IL-1ß, and TGF-ß), and fibrosis (collagen and elastin expression). These effects are induced by inhibition of the LKB1-AMPK pathway by ERC activation. In addition, pharmacological inhibitors of EDPs demonstrate that this EDP-driven lipogenesis and fibrosis relies on engagement of the ERC. Our data reveal a major role of EDPs in the development of NASH, and they provide new clues for understanding the relationship between NAFLD and vascular aging.

New Insights into Molecular Organization of Human Neuraminidase-1: Transmembrane Topology and Dimerization Ability.

Neuraminidase 1 (NEU1) is a lysosomal sialidase catalyzing the removal of terminal sialic acids from sialyloconjugates. A plasma membrane-bound NEU1 modulating a plethora of receptors by desialylation, has been consistently documented from the last ten years. Despite a growing interest of the scientific community to NEU1, its membrane organization is not understood and current structural and biochemical data cannot account for such membrane localization. By combining molecular biology and biochemical analyses with structural biophysics and computational approaches, we identified here two regions in human NEU1 - segments 139-159 (TM1) and 316-333 (TM2) - as potential transmembrane (TM) domains. In membrane mimicking environments, the corresponding peptides form stable α-helices and TM2 is suited for self-association. This was confirmed with full-size NEU1 by co-immunoprecipitations from membrane preparations and split-ubiquitin yeast two hybrids. The TM2 region was shown to be critical for dimerization since introduction of point mutations within TM2 leads to disruption of NEU1 dimerization and decrease of sialidase activity in membrane. In conclusion, these results bring new insights in the molecular organization of membrane-bound NEU1 and demonstrate, for the first time, the presence of two potential TM domains that may anchor NEU1 in the membrane, control its dimerization and sialidase activity.

Impact of sialic acids on the molecular dynamic of bi-antennary and tri-antennary glycans.

Sialic acids (SA) are monosaccharides that can be located at the terminal position of glycan chains on a wide range of proteins. The post-translational modifications, such as N-glycan chains, are fundamental to protein functions. Indeed, the hydrolysis of SA by specific enzymes such as neuraminidases can lead to drastic modifications of protein behavior. However, the relationship between desialylation of N-glycan chains and possible alterations of receptor function remains unexplored. Thus, the aim of the present study is to establish the impact of SA removal from N-glycan chains on their conformational behavior. We therefore undertook an in silico investigation using molecular dynamics to predict the structure of an isolated glycan chain. We performed, for the first time, 3 independent 500 ns simulations on bi-antennary and tri-antennary glycan chains displaying or lacking SA. We show that desialylation alters both the preferential conformation and the flexibility of the glycan chain. This study suggests that the behavior of glycan chains induced by presence or absence of SA may explain the changes in the protein function.

Pregnancy outcome following frozen embryo transfer after artificial cycle or treatment by clomiphene citrate.

The optimal method to prepare endometrium before frozen embryo transfer (FET) is not yet established. We retrospectively studied 4496 FET and detailed pregnancy and miscarriage rates in three groups of patients according to the endometrium preparation they have followed before their successive FET: clomifene citrate (CC, group 1), artificial cycle (AC, group 2) or switch between CC and AC (group 3). The overall pregnancy rates per transfer were 24.3, 20.8 and 17.3% while the miscarriage rates reached 23.2, 29.8 and 42.5%, respectively. Group 1 experienced the highest ongoing pregnancy rate (18.6%), the lowest being observed in group 3 (10.0%, p < 0.001). Here we propose several alternatives to improve our AC protocol (group 2) that seemed less effective than CC (group 1) and we consider the use of a gonadotrophin-stimulated treatment for patients with the lowest reproductive outcomes (group 3).

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 (αvß3 and αvß5 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.

Matrix ageing and vascular impacts: focus on elastin fragmentation.

Cardiovascular diseases (CVDs) are the leading cause of death worldwide and represent a major problem of public health. Over the years, life expectancy has considerably increased throughout the world, and the prevalence of CVD is inevitably rising with the growing ageing of the population. The normal process of ageing is associated with progressive deterioration in structure and function of the vasculature, commonly called vascular ageing. At the vascular level, extracellular matrix (ECM) ageing leads to molecular alterations in long half-life proteins, such as elastin and collagen, and have critical effects on vascular diseases. This review highlights ECM alterations occurring during vascular ageing with a specific focus on elastin fragmentation and also the contribution of elastin-derived peptides (EDP) in age-related vascular complications. Moreover, current and new pharmacological strategies aiming at minimizing elastin degradation, EDP generation, and associated biological effects are discussed. These strategies may be of major relevance for preventing and/or delaying vascular ageing and its complications.

Protein carbamylation is a hallmark of aging.

Aging is a progressive process determined by genetic and acquired factors. Among the latter are the chemical reactions referred to as nonenzymatic posttranslational modifications (NEPTMs), such as glycoxidation, which are responsible for protein molecular aging. Carbamylation is a more recently described NEPTM that is caused by the nonenzymatic binding of isocyanate derived from urea dissociation or myeloperoxidase-mediated catabolism of thiocyanate to free amino groups of proteins. This modification is considered an adverse reaction, because it induces alterations of protein and cell properties. It has been shown that carbamylated proteins increase in plasma and tissues during chronic kidney disease and are associated with deleterious clinical outcomes, but nothing is known to date about tissue protein carbamylation during aging. To address this issue, we evaluated homocitrulline rate, the most characteristic carbamylation-derived product (CDP), over time in skin of mammalian species with different life expectancies. Our results show that carbamylation occurs throughout the whole lifespan and leads to tissue accumulation of carbamylated proteins. Because of their remarkably long half-life, matrix proteins, like type I collagen and elastin, are preferential targets. Interestingly, the accumulation rate of CDPs is inversely correlated with longevity, suggesting the occurrence of still unidentified protective mechanisms. In addition, homocitrulline accumulates more intensely than carboxymethyl-lysine, one of the major advanced glycation end products, suggesting the prominent role of carbamylation over glycoxidation reactions in age-related tissue alterations. Thus, protein carbamylation may be considered a hallmark of aging in mammalian species that may significantly contribute in the structural and functional tissue damages encountered during aging.

Autophagy is decreased in triple-negative breast carcinoma involving likely the MUC1-EGFR-NEU1 signalling pathway.

Triple-negative breast carcinoma (TN) is a heterogeneous cancer type expressing EGFR in 75% of cases. MUC1 is a large type I sialylated glycoprotein comprising two subunits (α and ß chains, also called respectively MUC1-VNTR and MUC1-CT), which was found to regulate EGFR activity through endocytic internalisation. Endocytosis and autophagy use the lysosome pathway involving NEU1. Recently, a molecular EGFR-MUC1-NEU1 complex was suggested to play a role in EGFR pathway. In the aim to understand the relationship between EGFR-MUC1-NEU1 complex and autophagy in breast carcinoma, we compared triple negative (TN) showing a high-EGFR expression with luminal (LUM) presenting low-EGFR level. We studied the expression of MUC1-VNTR, MUC1-CT and NEU1 in comparison with those of two molecular actors of autophagy, PI3K (p110ß) and Beclin1. A total of 87 breast cancers were split in two groups following the immunohistochemical classification of breast carcinoma: 48 TN and 39 LUM. Our results showed that TN presented a high expression of EGFR and a low expression of MUC1-VNTR, MUC1-CT, NEU1, Beclin-1 and PI3Kp110ß. Moreover, in TN, a positive statistical correlation was observed between Beclin-1 or PI3Kp110ß and MUC1-VNTR or NEU1, but not with EGFR. In conclusion, our data suggest that autophagy is reduced in TN leading likely to the deregulation of EGFR-MUC1-NEU1 complex and its associated cellular pathways.

Uncoupling of Elastin Complex Receptor during In Vitro Aging Is Related to Modifications in Its Intrinsic Sialidase Activity and the Subsequent Lactosylceramide Production.

Degradation of elastin leads to the production of elastin-derived peptides (EDP), which exhibit several biological effects, such as cell proliferation or protease secretion. Binding of EDP on the elastin receptor complex (ERC) triggers lactosylceramide (LacCer) production and ERK1/2 activation following ERC Neu-1 subunit activation. The ability for ERC to transduce signals is lost during aging, but the mechanism involved is still unknown. In this study, we characterized an in vitro model of aging by subculturing human dermal fibroblasts. This model was used to understand the loss of EDP biological activities during aging. Our results show that ERC uncoupling does not rely on Neu-1 or PPCA mRNA or protein level changes. Furthermore, we observe that the membrane targeting of these subunits is not affected with aging. However, we evidence that Neu-1 activity and LacCer production are altered. Basal Neu-1 catalytic activity is strongly increased in aged cells. Consequently, EDP fail to promote Neu-1 catalytic activity and LacCer production in these cells. In conclusion, we propose, for the first time, an explanation for ERC uncoupling based on the age-related alterations of Neu-1 activity and LacCer production that may explain the loss of EDP-mediated effects occurring during aging.

Elastin-derived peptides are new regulators of thrombosis.

OBJECTIVE: Elastin is the major structural extracellular matrix component of the arterial wall that provides the elastic recoil properties and resilience essential for proper vascular function. Elastin-derived peptides (EDP) originating from elastin fragmentation during vascular remodeling have been shown to play an important role in cell physiology and development of cardiovascular diseases. However, their involvement in thrombosis has been unexplored to date. In this study, we investigated the effects of EDP on (1) platelet aggregation and related signaling and (2) thrombus formation. We also characterized the mechanism by which EDP regulate thrombosis. APPROACH AND RESULTS: We show that EDP, derived from organo-alkaline hydrolysate of bovine insoluble elastin (kappa-elastin), decrease human platelet aggregation in whole blood induced by weak and strong agonists, such as ADP, epinephrine, arachidonic acid, collagen, TRAP, and U46619. In a mouse whole blood perfusion assay over a collagen matrix, kappa-elastin and VGVAPG, the canonical peptide recognizing the elastin receptor complex, significantly decrease thrombus formation under arterial shear conditions. We confirmed these results in vivo by demonstrating that both kappa-elastin and VGVAPG significantly prolonged the time for complete arteriole occlusion in a mouse model of thrombosis and increased tail bleeding times. Finally, we demonstrate that the regulatory role of EDP on thrombosis relies on platelets that express a functional elastin receptor complex and on the ability of EDP to disrupt plasma von Willebrand factor interaction with collagen. CONCLUSIONS: These results highlight the complex nature of the mechanisms governing thrombus formation and reveal an unsuspected regulatory role for circulating EDP in thrombosis.

Elastin-derived peptides potentiate atherosclerosis through the immune Neu1-PI3Kγ pathway.

AIMS: Elastin is degraded during vascular ageing and its products, elastin-derived peptides (EP), are present in the human blood circulation. EP binds to the elastin receptor complex (ERC) at the cell surface, composed of elastin-binding protein (EBP), a cathepsin A and a neuraminidase 1. Some in vitro functions have clearly been attributed to this binding, but the in vivo implications for arterial diseases have never been clearly investigated. METHODS AND RESULTS: Here, we demonstrate that chronic doses of EP injected into mouse models of atherosclerosis increase atherosclerotic plaque size formation. Similar effects were observed following an injection of a VGVAPG peptide, suggesting that the ERC mediates these effects. The absence of phosphoinositide 3-kinase γ (PI3Kγ) in bone marrow-derived cells prevented EP-induced atherosclerosis development, demonstrating that PI3Kγ drive EP-induced arterial lesions. Accordingly, in vitro studies showed that PI3Kγ was required for EP-induced monocyte migration and ROS production and that this effect was dependent upon neuraminidase activity. Finally, we showed that degradation of elastic lamellae in LDLR(-/-) mice fed an atherogenic diet correlated with atherosclerotic plaque formation. At the same time, the absence of the cathepsin A-neuraminidase 1 complex in cells of the haematopoietic lineage abolished atheroma plaque size progression and decreased leucocytes infiltration, clearly demonstrating the role of this complex in atherogenesis and suggesting the involvement of endogenous EP. CONCLUSION: Altogether, this work identifies EP as an enhancer of atherogenesis and defines the Neuraminidase 1/PI3Kγ signalling pathway as a key mediator of this function in vitro and in vivo.