Selective proteolysis by matrix metalloproteinases of photo-oxidised dermal extracellular matrix proteins

Protective effects of sugarcane polyphenol against UV-B-induced photoaging in Balb/c mouse skin: Antioxidant, anti-inflammatory, and anti-glycosylation Effects

Although the benefits of sugarcane polyphenol (SP) are well documented, its function in preventing photoaging has not yet been investigated. This study aimed to investigate the protective effects of SP in preventing ultraviolet (UV)-B-induced skin photoaging in Balb/c mice, as well as the underlying mechanism. Chlorogenic acid was determined to be the primary component of SP by using high-performance liquid chromatography-mass spectrometry. SP and chlorogenic acid were orally administrated to mice for 56 days, and UV-B radiation exposure was administered 14 days after SP and chlorogenic acid administration and lasted 42 days to cause photoaging. SP and chlorogenic acid administrations significantly alleviated the UV-B-induced mouse skin photoaging, as indicated by the decrease in epidermal thickness, increase in the collagen (COL) volume fraction, and elevation in type 1 and type 3 COL contents. Notably, both SP and chlorogenic acid effectively reversed the overexpression of matrix metalloproteinase induced by UV-B exposure in the mouse skin. Furthermore, SP and chlorogenic acid reduced the expression of receptor for advanced glycosylation end products in the mice; amplified the activities of antioxidant enzymes superoxide dismutase and catalase; reduced malondialdehyde levels; and decreased inflammatory cytokines interleukin 1β, interleukin 6, and tumor necrosis factor α levels. SP could be a prospective dietary supplement for anti-photoaging applications due to its antioxidant, anti-inflammatory, and anti-glycosylation attributes, and chlorogenic acid might play a major role in these effects. PRACTICAL APPLICATION: This study can provide a scientific basis for the practical application of sugarcane polyphenols. We expect that sugarcane polyphenols can be used in food and beverage products to provide flavor while combating skin aging.

Acute exposure to ultraviolet radiation targets proteins involved in collagen fibrillogenesis

Introduction: Exposure to chronic, low-dose UV irradiation (UVR) can lead to premature ageing of the skin. Understanding which proteins are affected by acute UVR and photo-dynamically produced reactive oxygen species (ROS) could help to inform strategies to delay photoageing. Conventional biochemical analyses can be used to characterize UVR/ROS-induced damage on a protein-by-protein basis and we have previously shown using SDS-PAGE that collagen I and plasma fibronectin are respectively resistant and susceptible to physiological doses of UVR. The aim of this study was to screen a complex proteome for UVR-affected proteins. Methods: This study employed a sensitive mass spectrometry technique (peptide location fingerprinting: PLF) which can identify structure associated differences following trypsin digestion to characterize the impact of UVR exposure on purified collagen I and tissue fibronectin and to identify UVR-susceptible proteins in an ECM-enriched proteome. Results: Using LC/MS-MS and PLF we show that purified mature type-I collagen is resistant to UVR, whereas purified tissue fibronectin is susceptible. UV irradiation of a human dermal fibroblast-deposited ECM-enriched proteome in vitro, followed by LC/MS-MS and PLF analysis revealed two protein cluster groups of UV susceptible proteins involved in i) matrix collagen fibril assembly and ii) protein translation and motor activity. Furthermore, PLF highlighted UV susceptible domains within targeted matrix proteins, suggesting that UV damage of matrix proteins is localized. Discussion: Here we show that PLF can be used to identify protein targets of UVR and that collagen accessory proteins may be key targets in UVR exposed tissues.

Anti-oxidative, anti-apoptotic, and anti-inflammatory activities of Connarus semidecandrus Jack ethanol extract in UVB-irradiated human keratinocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Connarus semidecandrus Jack (Family: connaraceae) is a medicinal plant known for its wide distribution throughout Southeast Asia. Renowned for its diverse therapeutic properties, it has been traditionally used for treating fever, skin irritation, and colic.

AIM OF THE STUDY

Numerous individuals suffer from skin issues, including wrinkles, hyperpigmentation, and inflammation, due to environmental factors. Although many drugs are available to treat skin problems, chemical drugs have many shortcomings and side effects. Therefore, natural products are attractive potential medicines for alleviating skin troubles. We recently showed that Connarus semidecandrus Jack ethanol extract (Cs-EE) has anti-alopecia potential. This paper aims to explore the potential skin-protective effects and underlying molecular mechanisms of Connarus semidecandrus Jack in UVB-induced human keratinocytes (HaCaT).

MATERIALS AND METHODS

Before utilization, Cs-EE was dissolved in dimethyl sulfoxide (DMSO) and was preserved at a temperature of -20 °C. The phytochemical constituents of Cs-EE were detected by gas chromatography-mass spectrometry analysis (GC-MS). Sequentially, HaCaT cells were exposed to varying concentrations of Cs-EE prior to ultraviolet B (UVB) irradiation. Evaluations of cellular responses in HaCaT cells, including assessments of cell viability, deoxyribonucleic acid (DNA) damage, and gene and protein expressions, were carried out. To explore the specific signaling pathway involved, we conducted a luciferase assay in addition to validating these pathways using Western blot analysis.

RESULTS

Nitric oxide (NO) and intracellular reactive oxygen species were decreased. Melanin production through the activation of melanocytes by α-melanocyte-stimulating hormone (MSH) was also inhibited by Cs-EE. Furthermore, the mRNA expression levels of key factors such as cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), MMP-1, MMP-3, and MMP-9 exhibited a remarkable decrease. In addition, the phosphorylation of TAK1 within the signaling cascade exhibited a decline, and the activities of the transcription factor AP-1 were decreased according to a luciferase reporter assay.

CONCLUSIONS

Taken together, these findings suggest that the anti-inflammatory, anti-aging, and anti-apoptotic effects of Cs-EE indicate the compound's potential usefulness as a natural component in pharmaceutical and cosmetic products.

Mesenchymal stem cell-derived exosomes and skin photoaging: From basic research to practical application

BACKGROUND

Skin photoaging is a condition caused by long-term exposure to ultraviolet irradiation, resulting in a variety of changes in the skin, such as capillary dilation, increased or absent pigmentation, dryness, sagging, and wrinkles. Stem cells possess a remarkable antioxidant capacity and the ability to proliferate, differentiate, and migrate, and their main mode of action is through paracrine secretion, with exosomes being the primary form of secretion. Stem cell-derived exosomes contain a variety of growth factors and cytokines and may have great potential to promote skin repair and delay skin ageing.

METHODS

This review focuses on the mechanisms of UV-induced skin photoaging, the research progress of stem cell exosomes against skin photoaging, emerging application approaches and limitations in the application of exosome therapy.

RESULT

Exosomes derived from various stem cells have the potential to prevent skin photoaging.

CONCLUSION

The combination with novel materials may be a key step for their practical application, which could be an important direction for future basic research and practical applications.

Cycloastragenol exerts protective effects against UVB irradiation in human dermal fibroblasts and HaCaT keratinocytes

BACKGROUND

Cycloastragenol (CAG) is a triterpene aglycone of astragaloside IV that possesses various pharmacological actions including improving telomerase activity, inhibiting inflammation and cell proliferation, inducing apoptosis.

OBJECTIVE

CAG has also shown effect to significantly improve the appearance of aging skin but, its molecular mechanism of protective effect against UVB induced-damage have not been elucidated. We investigated the potential effect of CAG on UVB wrinkle promoting activities and skin-moisturizing effects in human dermal fibroblasts (HDF) and HaCaT keratinocytes.

METHODS

After UVB irradiation or H2O2 treatment, the levels of matrix metalloproteinases (MMPs) and ROS generation were measured in CAG-treated HDF cells. In addition, after UVB irradiation, hyaluronic acid and skin hydration factors (filaggrin and SPT) were also analyzed in CAG (0-0.5-1-2 µM)-treated HDF and HaCaT cells.

RESULTS

We found that CAG caused a significant decrease in the levels of UVB-induced MMP-1, MMP-9, MMP-13 and ROS generation, also increased UVB-damaged Collagen Ⅰ. We also noted that CAG increased cell viability and can regulate MMP-1, MMP-9, MMP-13and Collagen Ⅰ in H2O2-damaged HDF cells. Moreover, we noticed that CAG effectively enhanced levels of hyaluronic acid and expression of skin hydration factors (filaggrin and serine palmitoyltransferase (SPT)) in UVB-damaged HDF and HaCaT cells.

CONCLUSION

This is first report indicating that CAG can exhibit protective effect against UVB and H2O2-induced damages and can contribute in maintenance of healthy skin.

Nanoscale Structural Comparison of Fibrillin-1 Microfibrils Isolated from Marfan and Non-Marfan Syndrome Human Aorta

Fibrillin-1 microfibrils are essential elements of the extracellular matrix serving as a scaffold for the deposition of elastin and endowing connective tissues with tensile strength and elasticity. Mutations in the fibrillin-1 gene (FBN1) are linked to Marfan syndrome (MFS), a systemic connective tissue disorder that, besides other heterogeneous symptoms, usually manifests in life-threatening aortic complications. The aortic involvement may be explained by a dysregulation of microfibrillar function and, conceivably, alterations in the microfibrils' supramolecular structure. Here, we present a nanoscale structural characterization of fibrillin-1 microfibrils isolated from two human aortic samples with different FBN1 gene mutations by using atomic force microscopy, and their comparison with microfibrillar assemblies purified from four non-MFS human aortic samples. Fibrillin-1 microfibrils displayed a characteristic "beads-on-a-string" appearance. The microfibrillar assemblies were investigated for bead geometry (height, length, and width), interbead region height, and periodicity. MFS fibrillin-1 microfibrils had a slightly higher mean bead height, but the bead length and width, as well as the interbead height, were significantly smaller in the MFS group. The mean periodicity varied around 50-52 nm among samples. The data suggest an overall thinner and presumably more frail structure for the MFS fibrillin-1 microfibrils, which may play a role in the development of MFS-related aortic symptomatology.

Shotgun proteomics of extracellular matrix in late senescent human dermal fibroblasts reveals a down-regulated fibronectin-centered network

Extracellular matrix (ECM) proteins play a pivotal role in cell growth and differentiation. To characterize aged ECM proteins, we compared the proteomes by shotgun method of young (passage #15) and late senescent (passage #40) human dermal fibroblasts (HDFs) using SDS-PAGE coupled with LC–MS/MS. The relative abundance of identified proteins was determined using mol% of individual proteins as a semi-quantitative index. Fifteen ECM proteins including apolipoprotein B (APOB) and high-temperature requirement factor 1 (HTRA1) were up-regulated, whereas 50 proteins including fibronectin 1 (FN1) and vitronectin (VTN) were down-regulated in late senescent HDFs. The identified ECM proteins combined with plasma membrane were queried to construct the protein–protein interaction network using Ingenuity Pathways Analysis, resulting in a distinct FN1-centered network. Of differentially abundant ECM proteins in shotgun proteomics, the protein levels of FN1, VTN, APOB, and HTRA1 were verified by immunoblot analysis. The results suggest that the aging process in HDFs might be finally involved in the impaired FN1 regulatory ECM network combined with altered interaction of neighboring proteins. Shotgun proteomics of highly aged HDFs provides insight for further studies of late senescence-related alterations in ECM proteins.

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.

Resveratrol Treats UVB-Induced Photoaging by Anti-MMP Expression, through Anti-Inflammatory, Antioxidant, and Antiapoptotic Properties, and Treats Photoaging by Upregulating VEGF-B Expression

UVB exposure is one of the primary factors responsible for the development of photoaging, and the aim of this study was to investigate the mechanism involved in the photoprotective properties of resveratrol (RES) in UVB-induced photoaging. Photoaging models of Hacat cells and ICR mice were established by UVB irradiation. The effect of RES on cell viability was then assessed using the MTT assay. The effect of RES on reactive oxygen species (ROS) production was detected through a fluorescent probe assay. The effect of RES on oxidized glutathione (GSSH) content, and superoxide dismutase (SOD) activity in photoaging Hacat cells, were measured separately, using kits. An enzyme-linked immunosorbent assay (ELISA) was used to measure the effect of RES on IL-6 secretion. The effect of VEGF-B on RES photoprotection was examined through the RT-qPCR method, after silencing VEGF-B through siRNA transfection. For animal experiments, the relative water content of the skin of ICR mice was determined using the Corneometer CM825 skin moisture tester. Starting from the third week of the study, the back skin of photoaging ICR mice was photographed weekly using the TIVI700 camera, and the depth of skin wrinkles in photoaging ICR mice was also analyzed. The thickness of the epidermis in photoaging ICR mice was assessed by the hematoxylin-eosin (HE) staining method. The content of collagen fibers in the skin dermis of photoaging ICR mice was measured by the Masson trichrome staining method. The content of collagen III in the dermis of the skin in photoaging ICR mice was measured through immunohistochemistry (IHC) techniques. The effect of RES on the mRNA expression levels of MMP-1, MMP-9, HO-1, GPX-4, IL-6, TNF-α, VEGF-B, caspase9, and caspase3 in photoaging Hacat cells, and that of MMP-3, Nrf2, HO-1, NQO1, SOD1, GPX-4, caspase9, caspase3, and IL-6 in the skin of photoaging ICR mice, was measured by RT-qPCR. The effects of RES on caspase3, Nrf2 (intranuclear), COX-2, P-ERK1/2, ERK1/2, P-P38MAPK, and P38MAPK in photoaging Hacat cells, and on MMP-9, caspase3, COX-2, P-JNK, P-ERK1/2, and P-P38MAPK protein expression in the skin of photoaging ICR mice, were assayed by the WB method. The results of this study, therefore, show that RES has a protective effect against UVB-induced photoaging in both Hacat cells and ICR mice. Its mechanism of action may include reducing the expression of MMPs and the secretion of collagen and inflammatory factors by inhibiting the ROS-mediated MAPK and COX-2 signaling pathways, balancing oxidative stress in the skin of Hacat cells and ICR mice by promoting the Nrf2 signaling pathway, inducing antiapoptotic effects by inhibiting caspase activation, and exerting antioxidant and antiapoptotic effects by targeting the VEGF-B, demonstrating its photoprotective effects against UVB irradiation-induced photoaging.

The Effects of Ionising and Non-Ionising Electromagnetic Radiation on Extracellular Matrix Proteins

Exposure to sub-lethal doses of ionising and non-ionising electromagnetic radiation can impact human health and well-being as a consequence of, for example, the side effects of radiotherapy (therapeutic X-ray exposure) and accelerated skin ageing (chronic exposure to ultraviolet radiation: UVR). Whilst attention has focused primarily on the interaction of electromagnetic radiation with cells and cellular components, radiation-induced damage to long-lived extracellular matrix (ECM) proteins has the potential to profoundly affect tissue structure, composition and function. This review focuses on the current understanding of the biological effects of ionising and non-ionising radiation on the ECM of breast stroma and skin dermis, respectively. Although there is some experimental evidence for radiation-induced damage to ECM proteins, compared with the well-characterised impact of radiation exposure on cell biology, the structural, functional, and ultimately clinical consequences of ECM irradiation remain poorly defined.

Peptide location fingerprinting reveals modification-associated biomarker candidates of ageing in human tissue proteomes

Although dysfunctional protein homeostasis (proteostasis) is a key factor in many age-related diseases, the untargeted identification of structurally modified proteins remains challenging. Peptide location fingerprinting is a proteomic analysis technique capable of identifying structural modification-associated differences in mass spectrometry (MS) data sets of complex biological samples. A new webtool (Manchester Peptide Location Fingerprinter), applied to photoaged and intrinsically aged skin proteomes, can relatively quantify peptides and map statistically significant differences to regions within protein structures. New photoageing biomarker candidates were identified in multiple pathways including extracellular matrix organisation (collagens and proteoglycans), protein synthesis and folding (ribosomal proteins and TRiC complex subunits), cornification (keratins) and hemidesmosome assembly (plectin and integrin α6β4). Crucially, peptide location fingerprinting uniquely identified 120 protein biomarker candidates in the dermis and 71 in the epidermis which were modified as a consequence of photoageing but did not differ significantly in relative abundance (measured by MS1 ion intensity). By applying peptide location fingerprinting to published MS data sets, (identifying biomarker candidates including collagen V and versican in ageing tendon) we demonstrate the potential of the MPLF webtool for biomarker discovery.

Daily photoprotection to prevent photoaging

BACKGROUND

Extrinsic skin aging or photoaging was previously thought to be almost exclusively due to solar ultraviolet (UV) radiation. However, recent literature has described other contributing factors and clarification is thus required as to what extent and what type of daily photoprotection is needed to mitigate extrinsic skin aging.

METHODS

We reviewed the existing scientific evidence on daily photoprotection, and specific requirements at the product level, to prevent extrinsic skin aging. We critically reviewed the existing evidence on potential ecological and toxicological risks which might be associated with daily photoprotection.

RESULTS

Evidence shows that broad protection against the entire solar range of UVB, UVA, UVA1, visible light, and short infrared (IRA) is required to prevent extrinsic aging. Other exposome factors, such as air pollution and smoking, also contribute to skin aging. Daily broad-spectrum sunscreen photoprotection should thus contain antioxidant ingredients for additional benefits against UV, IRA, and pollution-induced oxidative stress as well as anti-aging active ingredients to provide clinical benefits against skin aging signs, such as wrinkles and dark spots. Broad-spectrum sunscreen containing pigments, such as iron oxide, may be required for melasma prevention. There is no conclusive clinical evidence that daily sunscreen use is unsafe or that it compromises vitamin D synthesis.

CONCLUSION

Daily use of broad-spectrum sunscreen containing antioxidant and anti-aging active ingredients can effectively reduce extrinsic aging.

Predicting Proteolysis in Complex Proteomes Using Deep Learning

Both protease- and reactive oxygen species (ROS)-mediated proteolysis are thought to be key effectors of tissue remodeling. We have previously shown that comparison of amino acid composition can predict the differential susceptibilities of proteins to photo-oxidation. However, predicting protein susceptibility to endogenous proteases remains challenging. Here, we aim to develop bioinformatics tools to (i) predict cleavage site locations (and hence putative protein susceptibilities) and (ii) compare the predicted vulnerabilities of skin proteins to protease- and ROS-mediated proteolysis. The first goal of this study was to experimentally evaluate the ability of existing protease cleavage site prediction models (PROSPER and DeepCleave) to identify experimentally determined MMP9 cleavage sites in two purified proteins and in a complex human dermal fibroblast-derived extracellular matrix (ECM) proteome. We subsequently developed deep bidirectional recurrent neural network (BRNN) models to predict cleavage sites for 14 tissue proteases. The predictions of the new models were tested against experimental datasets and combined with amino acid composition analysis (to predict ultraviolet radiation (UVR)/ROS susceptibility) in a new web app: the Manchester proteome susceptibility calculator (MPSC). The BRNN models performed better in predicting cleavage sites in native dermal ECM proteins than existing models (DeepCleave and PROSPER), and application of MPSC to the skin proteome suggests that: compared with the elastic fiber network, fibrillar collagens may be susceptible primarily to protease-mediated proteolysis. We also identify additional putative targets of oxidative damage (dermatopontin, fibulins and defensins) and protease action (laminins and nidogen). MPSC has the potential to identify potential targets of proteolysis in disparate tissues and disease states.

Elastic fibers during aging and disease

Elastic fibers are essential constituents of the extracellular matrix of higher vertebrates and endow several tissues and organs including lungs, skin and blood vessels with elasticity and resilience. During the human lifespan, elastic fibers are exposed to a variety of enzymatic, chemical and biophysical influences, and accumulate damage due to their low turnover. Aging of elastin and elastic fibers involves enzymatic degradation, oxidative damage, glycation, calcification, aspartic acid racemization, binding of lipids and lipid peroxidation products, carbamylation and mechanical fatigue. These processes can trigger an impairment or loss of elastic fiber function and are associated with severe pathologies. There are different inherited or acquired pathological conditions, which influence the structure and function of elastic fibers and microfibrils predominantly in the cardiorespiratory system and skin. Inherited elastic-fiber pathologies have a direct or indirect impact on elastic-fiber formation due to mutations in the fibrillin genes (fibrillinopathies), in the elastin gene (elastinopathies) or in genes encoding proteins that are associated with microfibrils or elastic fibers. Acquired elastic-fiber pathologies appear age-related or as a result of multiple factors impairing tissue homeostasis. This review gives an overview on the fate of elastic fibers over the human lifespan in health and disease.

MiR-16-5p suppresses myofibroblast activation in systemic sclerosis by inhibiting NOTCH signaling

Systemic sclerosis (SSc) is a prototypic fibrotic disease characterized by localized or diffuse skin thickening and fibrosis. Tissue fibrosis is driven by myofibroblasts, and factors affecting myofibroblast activation may also be involved in the development of SSc. In this study, we examined molecular mechanisms underlying SSc by focusing on myofibroblast activation processes. Bioinformatics analysis conducted to identify differentially expressed miRNAs (DEMs) and genes (DEGs) revealed that microRNA-16-5p (miR-16-5p) was downregulated and NOTCH2 was upregulated in SSc patients. In vitro experiments confirmed that miR-16-5p was able to bind directly to NOTCH2 and inhibit myofibroblast activation. Moreover, miR-16-5p-dependent inhibition of NOTCH2 decreased collagen and α-SMA expression. MiR-16-5p downregulation and NOTCH2 upregulation was also confirmed in vivo in SSc patients, and NOTCH2 activation promoted fibrosis progression in vitro. These results indicate that miR-16-5p suppresses myofibroblast activation by suppressing NOTCH signaling.

The Human Epidermal Basement Membrane: A Shaped and Cell Instructive Platform That Aging Slowly Alters

One of the most important functions of skin is to act as a protective barrier. To fulfill this role, the structural integrity of the skin depends on the dermal-epidermal junction—a complex network of extracellular matrix macromolecules that connect the outer epidermal layer to the underlying dermis. This junction provides both a structural support to keratinocytes and a specific niche that mediates signals influencing their behavior. It displays a distinctive microarchitecture characterized by an undulating pattern, strengthening dermal-epidermal connectivity and crosstalk. The optimal stiffness arising from the overall molecular organization, together with characteristic anchoring complexes, keeps the dermis and epidermis layers extremely well connected and capable of proper epidermal renewal and regeneration. Due to intrinsic and extrinsic factors, a large number of structural and biological changes accompany skin aging. These changes progressively weaken the dermal–epidermal junction substructure and affect its functions, contributing to the gradual decline in overall skin physiology. Most changes involve reduced turnover or altered enzymatic or non-enzymatic post-translational modifications, compromising the mechanical properties of matrix components and cells. This review combines recent and older data on organization of the dermal-epidermal junction, its mechanical properties and role in mechanotransduction, its involvement in regeneration, and its fate during the aging process.

Investigation of fibrillin microfibrils in the canine cruciate ligament in dogs with different predispositions to ligament rupture

Cranial cruciate ligament disease (CCLD) is the most common cause of pelvic limb lameness in dogs but its precise aetiopathogenesis is uncertain. Fibrillin microfibrils (FM) are complex macro-molecular assemblies found in many tissues including ligaments, where they are thought to play an important mechanical role. We hypothesised that FM ultrastructural variation correlates with the differing predisposition of canine breeds to CCLD. Non-diseased cranial and caudal cruciate ligaments (CCLs and CaCLs) were obtained from Greyhound (GH) and Staffordshire Bull Terrier (SBT) cadavers. Fibrillin microfibrils were extracted from the ligaments by bacterial collagenase digestion, purified by size-exclusion chromatography and subsequently visualized by atomic force microscopy (AFM). With AFM, FMs have a characteristic beads-on-a-string appearance. For each FM, periodicity (bead-bead distance) and length (number of beads/FM) was measured. Fibrillin microfibril length was found to be similar for GH and SBT, with non-significant inter-breed and inter-ligament differences. Fibrillin microfibril periodicity varied when comparing GH and SBT for CCL (GH 60.2 ± 1.4 nm; SBT 56.2 ± 0.8 nm) and CaCL (GH 55.5 ± 1.6 nm; SBT 61.2 ± 1.2 nm). A significant difference was found in the periodicity distribution when comparing CCL for both breeds (P < 0.00001), further, intra-breed differences in CCL vs CaCL were statistically significant within both breeds (P < 0.00001). The breed at low risk of CCLD exhibited a periodicity profile which may be suggestive of a repair and remodelling within the CCL.

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.

Proteomic fingerprints of damage in extracellular matrix assemblies

In contrast to the dynamic intracellular environment, structural extracellular matrix (ECM) proteins with half-lives measured in decades, are susceptible to accumulating damage. Whilst conventional approaches such as histology, immunohistochemistry and mass spectrometry are able to identify age- and disease-related changes in protein abundance or distribution, these techniques are poorly suited to characterising molecular damage. We have previously shown that mass spectrometry can detect tissue-specific differences in the proteolytic susceptibility of protein regions within fibrillin-1 and collagen VI alpha-3. Here, we present a novel proteomic approach to detect damage-induced “peptide fingerprints” within complex multi-component ECM assemblies (fibrillin and collagen VI microfibrils) following their exposure to ultraviolet radiation (UVR) by broadband UVB or solar simulated radiation (SSR). These assemblies were chosen because, in chronically photoaged skin, fibrillin and collagen VI microfibril architectures are differentially susceptible to UVR. In this study, atomic force microscopy revealed that fibrillin microfibril ultrastructure was significantly altered by UVR exposure whereas the ultrastructure of collagen VI microfibrils was resistant. UVR-induced molecular damage was further characterised by proteolytic peptide generation with elastase followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Peptide mapping revealed that UVR exposure increased regional proteolytic susceptibility within the protein structures of fibrillin-1 and collagen VI alpha-3. This allowed the identification of UVR-induced molecular changes within these two key ECM assemblies. Additionally, similar changes were observed within protein regions of co-purifying, microfibril-associated receptors integrins αv and β1. This study demonstrates that LC-MS/MS mapping of peptides enables the characterisation of molecular post-translational damage (via direct irradiation and radiation-induced oxidative mechanisms) within a complex in vitro model system. This peptide fingerprinting approach reliably allows both the identification of UVR-induced molecular damage in and between proteins and the identification of specific protein domains with increased proteolytic susceptibility as a result of photo-denaturation. This has the potential to serve as a sensitive method of identifying accumulated molecular damage in vivo using conventional mass spectrometry data-sets.

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Mass spectrometry “peptide fingerprinting” can detect post-translational damage within extracellular matrix proteins.

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UVR-induced FBN1 and COL6A3 peptide fingerprints are reproducibly identified from purified microfibrils.

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Peptide mapping reveals increased regional susceptibilities to proteolysis in FBN1 and COL6A3 proteins.

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Regional changes are also observed in protein structures of microfibril-associated receptor integrins αv and β1.

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This “peptide fingerprinting” approach is applicable to conventional LC-MS/MS datasets.

Remodelling of fibrillin-rich microfibrils by solar-simulated radiation: impact of skin ethnicity

Cutaneous fibrillin-rich microfibrils (FRMs) should be considered as two distinct populations that differentially accrue damage in response to SSR. Furthermore, FRMs derived from black African skin show greater change following UVR challenge.

Circadian rhythms in skin and other elastic tissues

Circadian rhythms are daily oscillations that, in mammals, are driven by both a master clock, located in the brain, and peripheral clocks in cells and tissues. Approximately 10% of the transcriptome, including extracellular matrix components, is estimated to be under circadian control. Whilst it has been established that certain collagens and extracellular matrix proteases are diurnally regulated (for example in tendon, cartilage and intervertebral disc) the role played by circadian rhythms in mediating elastic fiber homeostasis is poorly understood. Skin, arteries and lungs are dynamic, resilient, elastic fiber-rich organs and tissues. In skin, circadian rhythms influence cell migration and proliferation, wound healing and susceptibility of the tissues to damage (from protease activity, oxidative stress and ultraviolet radiation). In the cardiovascular system, blood pressure and heart rate also follow age-dependent circadian rhythms whilst the lungs exhibit diurnal variations in immune response. In order to better understand these processes it will be necessary to characterise diurnal changes in extracellular matrix biology. In particular, given the sensitivity of peripheral clocks to external factors, the timed delivery of interventions (chronotherapy) has the potential to significantly improve the efficacy of treatments designed to repair and regenerate damaged cutaneous, vascular and pulmonary tissues.