Clusterin associates with altered elastic fibers in human photoaged skin and prevents elastin from ultraviolet-induced aggregation in vitro

The Pigmentation of Blue Light Is Mediated by Both Melanogenesis Activation and Autophagy Inhibition through OPN3-TRPV1

Blue light, a high-energy radiation in the visible light spectrum, was recently reported to induce skin pigmentation. In this study, we investigated the involvement of TRPV1-mediated signaling along with OPN3 in blue light-induced melanogenesis as well as its signaling pathway. Operating downstream target of OPN3 in blue light-induced melanogenesis, blue light activated TRPV1 and upregulated its expression, resulting in calcium influx. Calcium ion induced the activation of calcium/calmodulin-dependent protein kinase II and MAPK. It also downregulated clusterin expression, leading to the nuclear translocation of PAX3, ultimately affecting melanin synthesis. In addition, blue light interfered with autophagy-mediated regulation of melanosomes by decreasing not only the interaction between clusterin and LC3B but the expression of activating transcription factor family. These findings demonstrate that the pigmenting effects of blue light are mediated by calcium/calmodulin-dependent protein kinase II- and MAPK-mediated signaling as well as clusterin-dependent inhibition of autophagy through OPN3-TRPV1-calcium influx, suggesting, to our knowledge, a previously unreported signaling pathway through which blue light regulates melanocyte biology. Furthermore, these results suggest that TRPV1 and clusterin could be potential therapeutic targets for blue light-induced pigmentation due to prolonged exposure to blue light.

Oxidative stress via UVC irradiation on the structural rearrangement of hen egg white lysozyme

Oxidative stress is a physiological condition where oxygen radicals are responsible for the conformational restructuring and loss of functionality of important biomacromolecules. Among the various external agents, UV irradiation is one of the sources that can induce oxidative stress. Here, we report an in vitro study to gauge the effect of ROS on the structural rearrangement of hen egg white lysozyme, a hydrolytic enzyme, via UVC exposure studied via various biophysical techniques. The investigations revealed a rise in the β-sheet content of the protein at the expense of a decrease in α-helix within ten minutes of exposure, thereby showing rapid changes in the secondary structure. While the unexposed sample showed partial reversibility after being subjected to a heating and cooling cycle, the newly formed structures via irradiation, on the other hand, were found to be more thermally stable. The aging of the samples via UVC exposure was reflected in both the UV-vis and PL spectra of the samples, as well as the loss of spectral features in the aliphatic and aromatic regions in the magnetic resonance spectrum. Finally, the increase in the hydrodynamic diameter of the samples shows cross-linking taking place due to the generated oxygen radicals.

Correction of age-related changes in the skin at the dermal and subdermal level using radiofrequency macroneedling therapy

BACKGROUND

The negative effects of skin aging are primarily related to the destruction of dermal architectural structure. More specifically, this includes changes in the spatial arrangement of collagen, elastin fibers, mucopolysaccharides, proteoglycans, and ground substances.

AIMS

The purpose of this study is to investigate the histologic effects of dermal and subdermal tissue after a controlled single treatment with radiofrequency (RF) macroneedling. This therapy provides a controlled, localized, thermal effect on the dermis whereby triggering the body's own healing processes of extracellular matrix remodeling. Clinically benefits include skin tightening.

METHODS

Biopsies were obtained for histologic evaluation from four patients (n = 4), 4 weeks after completing a single RF macroneedling facial treatment.

RESULTS

Age-related changes of the dermal and subdermal architecture were observed at baseline. After treatment, all biopsies demonstrated an increase in epidermal cells, collagen, elastin, fibroblasts, vasculature, and a decrease in inflammatory cells.

CONCLUSIONS

The results of this histologic study confirm a significant "subsurfacing" thermal effect from the noncoagulative ascendant thermal injury. The obtained results characterize RF macroneedling therapy as an effective method for correcting age-related changes in facial skin.

Anti-Aging and Depigmentation Effect of a Hyaluronic Acid Mechanically Stabilized Complex on Human Skin Explants

Solar radiation and environmental pollutants are factors that cause changes in the skin that trigger skin aging. The objective of the study is to evaluate the rejuvenating effects of a complex formed by hyaluronic acid supplemented with vitamins, amino acids and oligopeptides in explants of human skin. For this, surplus skin samples have been obtained from donors that have been resected and cultivated on slides with membrane inserts. The complex was administered to some skin explants and the percentage of cells with low, medium and high levels of melanin was evaluated as an indicator of the degree of pigmentation. Other skin segments were irradiated with UVA/UVB, then the product was administered on several slides and the levels of collagen, elastin, sulfated GAG and MMP1 were evaluated. The results show that the administration of the complex significantly reduces the percentage of skin cells with a high melanin content by 16%, and that in skin irradiated with UVA/UVB, there is a decrease in the content of collagen, elastin and sulfate GAGs, and the complex reverses this reduction without changing MMP1 levels. This suggests that the compound has anti-aging and depigmentation effects on the skin, giving a skin rejuvenation appearance.

Clusterin, other extracellular chaperones, and eye disease

Proteostasis refers to all the processes that maintain the correct expression level, location, folding and turnover of proteins, essential to organismal survival. Both inside cells and in body fluids, molecular chaperones play key roles in maintaining proteostasis. In this article, we focus on clusterin, the first-recognized extracellular mammalian chaperone, and its role in diseases of the eye. Clusterin binds to and inhibits the aggregation of proteins that are misfolded due to mutations or stresses, clears these aggregating proteins from extracellular spaces, and facilitates their degradation. Clusterin exhibits three main homeostatic activities: proteostasis, cytoprotection, and anti-inflammation. The so-called "protein misfolding diseases" are caused by aggregation of misfolded proteins that accumulate pathologically as deposits in tissues; we discuss several such diseases that occur in the eye. Clusterin is typically found in these deposits, which is interpreted to mean that its capacity as a molecular chaperone to maintain proteostasis is overwhelmed in the disease state. Nevertheless, the role of clusterin in diseases involving such deposits needs to be better defined before therapeutic approaches can be entertained. A more straightforward case can be made for therapeutic use of clusterin based on its proteostatic role as a proteinase inhibitor, as well as its cytoprotective and anti-inflammatory properties. It is likely that clusterin works together in this way with other extracellular chaperones to protect the eye from disease, and we discuss several examples. We end this article by predicting future steps that may lead to development of clusterin as a biological drug.

Increased Desmosine in the lens capsules is associated with augmented elastin turnover in Pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PXF) is an idiopathic disease with a high prevalence rate. The elastosis disorder is contributed by genetic and non-genetic factors. Elastin dysregulation associated with the disease mechanism is incompletely understood. This study evaluated the molecules of the elastogenesis machinery in PXF. Lens capsule and aqueous humor (aqH) samples (age/sex-matched) were collected from the eyes with PXF alone and PXF with glaucoma (PXF-G) undergoing Extra Capsular Cataract Extraction (ECCE) surgery. The Elastin turnover was assessed by estimating Desmosine levels in the lens capsules by HPLC analysis. Expression of elastogenesis genes [EMILIN1, CLU, FBN1, FN1, FBLN5, FBLN4 and LOXL1] were evaluated in the lens capsule by qPCR while the proteins were assessed in aqH by western blot analysis. The Desmosine content in the lens capsules were 3-fold and 6-fold elevated in PXF (P = 0.02) and PXF-G (P = 0.01) respectively compared to the cataract-alone, indicating increased elastin degradation. A significant increase in the transcript levels of the CLU, FBLN4, EMILIN1, FBLN5, FN1, FBN1, LOXL1 along with significant changes in protein expression of CLU, FBLN5, FBN1 and LOXL1 signified up-regulation of the elastogenesis machinery. The study provides direct evidence of augmented elastin degradation and turnover in the lens capsule of PXF marked by increased Desmosine content and the expression of proteins involved in mature elastin formation.

Protection of human γD-crystallin protein from ultraviolet C-induced aggregation by ortho-vanillin

Cataract is known as one of the leading causes of vision impairment worldwide. While the detailed mechanism of cataratogenesis remains unclear, cataract is believed to be correlated with the aggregation and/or misfolding of human ocular lens proteins called crystallins. A 173-residue structural protein human γD-crystallin is a major γ-crystallin protein in the human eye lens and associated with the development of juvenile and mature-onset cataracts. This work is aimed at investigating the effect of a small molecule, e.g., ortho-vanillin, on human γD-crystallin aggregation upon exposure to ultraviolet-C irradiation. According to the findings of right-angle light scattering, transmission electron microscopy, and gel electrophoresis, ortho-vanillin was demonstrated to dose-dependently suppress ultraviolet-C-triggered aggregation of human γD-crystallin. Results from the synchronous fluorescence spectroscopy, tryptophan fluorescence quenching, and molecular docking studies revealed the structural change of γD-crystallin induced by the interaction/binding between ortho-vanillin and protein. We believe the outcome from this work may contribute to the development of potential therapeutics for cataract.

Alterations of the pigmentation system in the aging process

Human skin aging is a natural phenomenon that results from continuous exposure to intrinsic (time, genetic factors, hormones) as well as extrinsic factors (UV exposure, pollution, tobacco). In areas that are frequently exposed to the sun, photoaging blends with the process of intrinsic aging, resulting in an increased senescent cells number and consequently accelerating the aging process. The severity of photodamage depends on constitutional factors, including skin phototype (skin color, tanning capacity), intensity, and duration of sunlight/UV exposure. Aging affects nearly every aspect of cutaneous biology, including pigmentation. Clinically, the phenotype of age pigmented skin has a mottled, uneven color, primarily due to age spots, with or without hypopigmentation. Uneven pigmentation might be attributed to the hyperactivation of melanocytes, altered distribution of pigment, and turnover. In addition to direct damage to pigment-producing cells, photodamage alters the physiological crosstalk between keratinocytes, fibroblasts, endothelial cells, and melanocytes responsible for natural pigmentation homeostasis. Interestingly, age-independent diffuse expression of senescence-associated markers in the dermal and epidermal compartment is also associated with vitiligo, suggesting that premature senescence plays an important role in the pathology.

Optimization of the saffron compound essence formula and its effect on preventing skin photoaging

OBJECTIVE

The main aim of this study was to optimize the formula of saffron compound essence (SCE) and investigate the protective effects and mechanisms of SCE against skin photoaging.

MATERIALS AND METHODS

The formula of SCE was optimized using single factor and orthogonal experiments. The optimized SCE was then applied on the back skin of mice under ultraviolet irradiation. The protective effect and possible mechanism of SCE on skin photoaging were investigated using macroscopic and histological evaluation, skin thickness tests, determination of skin microcirculation, and the skin content determination of type I and III collagen, matrix metalloproteinase-2 (MMP-2), and extracellular regulatory protein kinase (ERK1/2) on the skin of each group of photoaging mice model.

RESULTS

The SCE prepared using the optimal formula was golden yellow, uniform, fine, and viscous. The obtained results in the SCE high dose group indicated that SCE can inhibit the generation of wrinkles, decrease the skin thickness, reduce the microcirculation blood flow of the back skin of mice, alleviate the proliferation and abnormal accumulation of collagen fibers and elastic fibers, increase the content of skin type I and III collagen, up-regulate the expression MMP-2 protein, and down-regulate the expression ERK1/2 protein, when compared with the shave control group.

CONCLUSION

The results obtained in this study have indicated that the optimized SCE has the effect of preventing skin photoaging, and its mechanism may be associated with the ERK1/2 pathway. Therefore, SCE should be regarded as a potential therapeutic agent for preventing photoaging.

Decreased circulating clusterin reflects severe liver complications after hepatoportoenterostomy of biliary atresia

This study aimed to determine whether circulating levels of clusterin (CLU), an extracellular chaperone implicated in cholestatic and fibrotic processes, are associated with clinical parameters of post-operative BA patients and could serve as a BA biomarker. Ninety-six BA patients and 56 healthy controls were recruited. Circulating CLU levels were measured using enzyme-linked immunosorbent assay. Circulating CLU levels were significantly reduced in BA patients - especially those with worse outcomes including jaundice, severe liver fibrosis, and late-stage of hepatic dysfunction. Multivariate linear regression analysis revealed that circulating CLU levels were negatively associated with outcome parameters indicating jaundice status, degree of fibrosis, and liver dysfunction, but positively correlated with serum albumin and platelet number of BA patients. Lower circulating CLU levels were considerably associated with poor survival of post-operative BA patients. Receiver-operating characteristic curve analysis demonstrated a diagnostic value of circulating CLU as a non-invasive indicator for poor outcomes of BA patients (AUC = 0.85), with a sensitivity of 81.5% and a specificity of 73.5%. All findings indicate that reduced circulating CLU might reflect poor outcomes of BA patients and have potential as a novel biomarker for the disease severity following Kasai-operation.

Quantitative proteomics analysis of young and elderly skin with DIA mass spectrometry reveals new skin aging-related proteins

Skin aging is a specific manifestation of the physiological aging process that occurs in virtually all organisms. In this study, we used data independent acquisition mass spectrometry to perform a comparative analysis of protein expression in volar forearm skin samples from of 20 healthy young and elderly Chinese individuals. Our quantitative proteomic analysis identified a total of 95 differentially expressed proteins (DEPs) in aged skin compared to young skin. Enrichment analyses of these DEPs (57 upregulated and 38 downregulated proteins) based on the GO, KEGG, and KOG databases revealed functional clusters associated with immunity and inflammation, oxidative stress, biosynthesis and metabolism, proteases, cell proliferation, cell differentiation, and apoptosis. We also found that GAPDH, which was downregulated in aged skin samples, was the top hub gene in a protein-protein interaction network analysis. Some of the DEPs identified herein had been previously correlated with aging of the skin and other organs, while others may represent novel age-related entities. Our non-invasive proteomics analysis of human epidermal proteins may guide future research on skin aging to help develop treatments for age-related skin conditions and rejuvenation.

Alterations in extracellular matrix composition during aging and photoaging of the skin

Human skin is composed of the cell-rich epidermis, the extracellular matrix (ECM) rich dermis, and the hypodermis. Within the dermis, a dense network of ECM proteins provides structural support to the skin and regulates a wide variety of signaling pathways which govern cell proliferation and other critical processes. Both intrinsic aging, which occurs steadily over time, and extrinsic aging (photoaging), which occurs as a result of external insults such as solar radiation, cause alterations to the dermal ECM. In this study, we utilized both quantitative and global proteomics, alongside single harmonic generation (SHG) and two-photon autofluorescence (TPAF) imaging, to assess changes in dermal composition during intrinsic and extrinsic aging. We find that both intrinsic and extrinsic aging result in significant decreases in ECM-supporting proteoglycans and structural ECM integrity, evidenced by decreasing collagen abundance and increasing fibril fragmentation. Intrinsic aging also produces changes distinct from those produced by photoaging, including reductions in elastic fiber and crosslinking enzyme abundance. In contrast, photoaging is primarily defined by increases in elastic fiber-associated protein and pro-inflammatory proteases. Changes associated with photoaging are evident even in young (mid 20s) sun-exposed forearm skin, indicating that proteomic evidence of photoaging is present decades prior to clinical signs of photoaging. GO term enrichment revealed that both intrinsic aging and photoaging share common features of chronic inflammation. The proteomic data has been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier PXD015982.

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Intrinsic aging and photoaging both decrease ECM-supporting proteoglycans and structural ECM.

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Intrinsic aging produces reductions in elastic fiber and crosslinking enzyme abundance.

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Photoaging results in increases in pro-inflammatory proteases and elastic fiber abundance.

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Intrinsic aging and photoaging share common features associated with chronic inflammation.

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Proteomic changes associated with photoaging are evident decades prior to clinical aging signs.

Mass spectrometry-based proteomics reveals the distinct nature of the skin proteomes of photoaged compared to intrinsically aged skin

OBJECTIVE

With increasing age, skin is subject to alterations in its organization, which impact on its function as well as having clinical consequences. Proteomics is a useful tool for non-targeted, semi-quantitative simultaneous investigation of high numbers of proteins. In the current study, we utilize proteomics to characterize and contrast age-associated differences in photoexposed and photoprotected skin, with a focus on the epidermis, dermal-epidermal junction and papillary dermis.

METHODS

Skin biopsies from buttock (photoprotected) and forearm (photoexposed) of healthy volunteers (aged 18-30 or ≥65 years) were transversely sectioned from the stratum corneum to a depth of 250 μm. Following SDS-PAGE, each sample lane was segmented prior to analysis by liquid chromatography-mass spectrometry/mass spectrometry. Pathway analysis was carried out using Ingenuity IPA.

RESULTS

Comparison of skin proteomes at buttock and forearm sites revealed differences in relative protein abundance. Ageing in skin on the photoexposed forearm resulted in 80% of the altered proteins being increased with age, in contrast to the photoprotected buttock where 74% of altered proteins with age were reduced. Functionally, age-altered proteins in the photoexposed forearm were associated with conferring structure, energy and metabolism. In the photoprotected buttock, proteins associated with gene expression, free-radical scavenging, protein synthesis and protein degradation were most frequently altered.

CONCLUSION

This study highlights the necessity of not considering photoageing as an accelerated intrinsic ageing, but as a distinct physiological process.

A Role for Clusterin in Exfoliation Syndrome and Exfoliation Glaucoma?

The multifunctional protein clusterin (CLU) is a secreted glycoprotein ubiquitously expressed throughout the body, including in the eye. Its primary function is to act as an extracellular molecular chaperone, preventing the precipitation and aggregation of misfolded extracellular proteins. Clusterin is commonly identified at fluid-tissue interfaces, and has been identified in most body fluids. It is a component of exfoliation material, and CLU mRNA is reduced in eyes with exfoliation syndrome compared with controls. SNPs located in the CLU genomic region have been associated with Alzheimer disease (AD) at the genome-wide level and several CLU SNPs located in an apparent regulatory region have been nominally associated with XFS/XFG in Caucasians with European ancestry and in south Indians. Interestingly, clusterin associates with altered elastic fibers in human photoaged skin and prevents UV-induced elastin aggregation in vitro. In light of the known geographic risk factors for XFS/XFG, which could include UV light, investigations of CLU-geographic interactions could be of interest. Future studies investigating rare CLU variation and other complex interactions including gene-gene interactions in XFS/XFG cases and controls may also be fruitful. Although CLU has been considered as a therapeutic target in AD, cancer and dry eye, a role for clusterin in XFS/XFG needs to be better defined before therapeutic approaches involving CLU can be entertained.

Diverse functions of clusterin promote and protect against the development of pulmonary fibrosis

Pulmonary fibrosis is a progressive scarring disorder of the lung with dismal prognosis and no curative therapy. Clusterin, an extracellular chaperone and regulator of cell functions, is reduced in bronchoalveolar lavage fluid of patients with pulmonary fibrosis. However, its distribution and role in normal and fibrotic human lung are incompletely characterized. Immunohistochemical localization of clusterin revealed strong staining associated with fibroblasts in control lung and morphologically normal areas of fibrotic lung but weak or undetectable staining in fibrotic regions and particularly fibroblastic foci. Clusterin also co-localized with elastin in vessel walls and additionally with amorphous elastin deposits in fibrotic lung. Analysis of primary lung fibroblast isolates in vitro confirmed the down-regulation of clusterin expression in fibrotic compared with control lung fibroblasts and further demonstrated that TGF-β1 is capable of down-regulating fibroblast clusterin expression. shRNA-mediated down-regulation of clusterin did not affect TGF-β1-induced fibroblast-myofibroblast differentiation but inhibited fibroblast proliferative responses and sensitized to apoptosis. Down-regulation of clusterin in fibrotic lung fibroblasts at least partly due to increased TGF-β1 may therefore represent an appropriate but insufficient response to limit fibroproliferation. Reduced expression of clusterin in the lung may also limit its extracellular chaperoning activity contributing to dysregulated deposition of extracellular matrix proteins.

Medical implications of understanding the functions of human small heat shock proteins

Small heat shock proteins (sHsps) are ubiquitous molecular chaperones that are implicated in a variety of diseases. Upon stress, they stabilize unfolding proteins and prevent them from aggregating. However, under physiological conditions without severe stress, some sHsps interact with other proteins. In a perspective view, their ability to bind specific client proteins might allow them to fine-tune the availability of the client for other, client-dependent cellular processes. Additionally, some sHsps seem to interact with specific co-chaperones. These co-chaperones are usually part of large protein machineries that are functionally modulated upon sHsps interaction. Finally, secreted human sHsps seem to interact with receptor proteins, potentially as signal molecules transmitting the stress status from one cell to another. This review focuses on the mechanistic description of these different binding modes for human sHsps and how this might help to understand and modulate the function of sHsps in the context of disease.

Clusterin expression in gastrointestinal neuroendocrine tumours is highly correlated with location and is helpful in determining the origin of liver metastases

AIMS

Clusterin (CLU) is a sulphated glycoprotein implicated in many physiological and pathological processes, including tumorigenesis. We have previously demonstrated that CLU is highly expressed in pancreatic neuroendocrine tumours (NETs). The aims of this study were: to investigate CLU expression in gastrointestinal NETs; the potential correlation between this expression and different clinicopathological parameters; and its usefulness in the differential diagnosis of liver metastases.

METHODS AND RESULTS

Immunohistochemistry using an anti-CLU antibody was performed on paraffin sections from 108 primary NETs [G3 (13 cases), G2 (18 cases), and G1 (77 cases), according to the 2010 WHO classification] and 60 metastases. Cytoplasmic positivity was scored qualitatively and quantitatively. The pattern of staining was also assessed. Two-step statistical analyses (univariate and multivariate logistic regression) were performed. More than 90% of small-intestine NETs were completely negative. The probability of obtaining a positive CLU score was higher for the appendix, the stomach, the duodenum and the rectum than for the small intestine and colon. All G3 NETs and most G2 NETs were negative as compared with G1. CLU expression in the metastatic foci was identical to that of the primary tumour.

CONCLUSIONS

Clusterin expression in gastrointestinal NETs is highly correlated with location and probably also with grading, in both the primary tumour and metastases. Underexpression of CLU in small-intestine NETs is helpful for identifying the origin of liver metastases: a strong CLU score in a liver biopsy makes the small intestine highly unlikely as a primary site.

Meta-profiles of gene expression during aging: limited similarities between mouse and human and an unexpectedly decreased inflammatory signature

BACKGROUND

Skin aging is associated with intrinsic processes that compromise the structure of the extracellular matrix while promoting loss of functional and regenerative capacity. These processes are accompanied by a large-scale shift in gene expression, but underlying mechanisms are not understood and conservation of these mechanisms between humans and mice is uncertain.

RESULTS

We used genome-wide expression profiling to investigate the aging skin transcriptome. In humans, age-related shifts in gene expression were sex-specific. In females, aging increased expression of transcripts associated with T-cells, B-cells and dendritic cells, and decreased expression of genes in regions with elevated Zeb1, AP-2 and YY1 motif density. In males, however, these effects were contrasting or absent. When age-associated gene expression patterns in human skin were compared to those in tail skin from CB6F1 mice, overall human-mouse correspondence was weak. Moreover, inflammatory gene expression patterns were not induced with aging of mouse tail skin, and well-known aging biomarkers were in fact decreased (e.g., Clec7a, Lyz1 and Lyz2). These unexpected patterns and weak human-mouse correspondence may be due to decreased abundance of antigen presenting cells in mouse tail skin with age.

CONCLUSIONS

Aging is generally associated with a pro-inflammatory state, but we have identified an exception to this pattern with aging of CB6F1 mouse tail skin. Aging therefore does not uniformly heighten inflammatory status across all mouse tissues. Furthermore, we identified both intercellular and intracellular mechanisms of transcriptome aging, including those that are sex- and species-specific.

Influence of stress on extracellular matrix and integrin biology

Dynamic interactions between cells and extracellular matrix (ECM) through integrins influence most cellular functions. Normal cells, but even more, tumor cells are subjected to different forms of stress, including ischemia, radical oxygen species production, starvation, mechanical stress or genotoxic insults due to anti-cancer drugs or irradiation. In these situations, an adaptative cellular response occurs, integrating a complex network of intracellular signaling modules, which, depending on stress intensity, may result to either damage repair followed by complete restitution of cellular functions, or programmed cell death. Because of its implication in oncogenesis and anti-cancer therapy, cellular stress response has been thoroughly investigated. However, most of these studies have been performed in the context of isolated cells without taking into consideration that most cells are part of the tissue within which they interact with ECM through integrin. Few studies have described the influence of stress on cell-to-ECM interaction. However, one can speculate that, in these conditions, cells could functionally interact with protein microenvironment either to create positive interactions to survive (for example by facilitating protective pathways) or negative interaction to die (for example by facilitating detachment). In this review, we summarize the knowledge relative to the influence of different stress modalities on ECM remodeling, integrin expression and/or function modifications, and possible functional consequences, independently from the cellular model as these findings came from a large variety of cells (mesenchymal, endothelial, muscular, epithelial and glandular) and fields of application (cancer, vascular biology and tissue engineering). Most studies support the general notion that non-lethal stress favors ECM stiffness, integrin activation and enhanced survival. This field opens large perspectives not only in tumor biology but also in anti-cancer therapy by targeting one or several steps of the integrin-mediated signaling pathway, including integrin ligation, or activation of integrin-linked enzymes or integrin adaptors.

Examining the influence of ultraviolet C irradiation on recombinant human γD-crystallin

PURPOSE

Human γD crystallin is a principal protein component of the human eye lens and associated with the development of juvenile and mature-onset cataracts. Exposure to ultraviolet (UV) light is thought to perturb protein structure and eventually lead to aggregation. This work is aimed at exploring the effects of UV-C irradiation on recombinant human γD-crystallin (HGDC).

METHODS

Recombinant HGDC proteins were expressed in E. coli strain BL21(DE3) harboring plasmid pEHisHGDC and purified using chromatographic methods. The proteins were then exposed to UV-C light (λ(max)=254 nm, 15 W) at the intensity of 420, 800, or 1850 μW/cm(2). The UV-C-unexposed, supernatant fraction of UV-C-exposed, and re-dissolved precipitated fraction of UV-C exposed preparations were characterized by SDS-PAGE, turbidity measurement, CD spectroscopy, tryptophan fluorescence spectroscopy, acrylamide fluorescence quenching analysis, and sulfhydryl group measurements.

RESULTS

The turbidity of the HGDC sample solution was found to be positively correlated with HGDC concentration, UV-C irradiation intensity, and UV-C irradiation duration. When exposed to UV-C, HGDC sample solutions became visibly turbid and a noticeable amount of larger protein particle, perceptible to the naked eye, was observed upon prolonged irradiation. The precipitated fraction of irradiated HGDC sample was found to be re-dissolved by guanidine hydrochloride. Electrophoresis, acrylamide fluorescence quenching, and spectroscopic analyses revealed differences in structures among the non-irradiated HGDC, the supernatant fraction of irradiated HGDC, and the re-dissolved precipitated fraction of irradiated HGDC. Through the use of L-cysteine, the measurements of sulfhydryl contents, and the reducing as well as non-reducing SDS-PAGE, our data further suggested that disulfide bond formation and/or cleavage probably play an important role in aggregation and/or precipitation of HGDC elicited by UV-C irradiation.

CONCLUSIONS

Our findings highlight the close connections among disulfide bond cleavage and/or formation, intermolecular interactions, and the resultant formation of aggregates of HGDC induced by UV-C irradiation. The results from this research may not only contribute to the understanding of the environmental factors causing protein aggregation but also have implications for deciphering the molecular mechanism of cataractogenesis.

Morphological and Biochemical Changes During Aging and Photoaging of the Skin of C57BL/6J Mice

The differences between the dorsal skin of 11- and 16-week-old C57BL/6J mice were examined morphologically and biochemically. The dermis of the 16-week-old mice was thinner than that of the 11-week-old mice due to decreases in the amounts of soluble collagen and elastin. Next, the changes in dorsal skin exposed to UVA irradiation for 8 weeks (576 J/cm²) were examined in 3 (younger)- and 8 (older)-week-old C57BL/6J mice. The thickness of the dermis was not significantly different between the UVA-irradiated and control mice in either the younger or older group. The increase in the amount of collagen was related to the increase in the level of soluble collagen in the younger mice. In contrast, it was related to the increase in the level of insoluble collagen in the older mice. In the UVA-irradiated older mice, the activity of the latent form of MMP-13 was significantly higher than that in the control mice. These results suggest that aging and UVA-induced photoaging in the skin are histologically and biochemically different phenomena.

Chapter 9: Oxidative stress in malignant progression: The role of Clusterin, a sensitive cellular biosensor of free radicals

Clusterin/Apolipoprotein J (CLU) gene is expressed in most human tissues and encodes for two protein isoforms; a conventional heterodimeric secreted glycoprotein and a truncated nuclear form. CLU has been functionally implicated in several physiological processes as well as in many pathological conditions including ageing, diabetes, atherosclerosis, degenerative diseases, and tumorigenesis. A major link of all these, otherwise unrelated, diseases is that they are characterized by increased oxidative injury due to impaired balance between production and disposal of reactive oxygen or nitrogen species. Besides the aforementioned diseases, CLU gene is differentially regulated by a wide variety of stimuli which may also promote the production of reactive species including cytokines, interleukins, growth factors, heat shock, radiation, oxidants, and chemotherapeutic drugs. Although at low concentration reactive species may contribute to normal cell signaling and homeostasis, at increased amounts they promote genomic instability, chronic inflammation, lipid oxidation, and amorphous aggregation of target proteins predisposing thus cells for carcinogenesis or other age-related disorders. CLU seems to intervene to these processes due to its small heat-shock protein-like chaperone activity being demonstrated by its property to inhibit protein aggregation and precipitation, a main feature of oxidant injury. The combined presence of many potential regulatory elements in the CLU gene promoter, including a Heat-Shock Transcription Factor-1 and an Activator Protein-1 element, indicates that CLU gene is an extremely sensitive cellular biosensor of even minute alterations in the cellular oxidative load. This review focuses on CLU regulation by oxidative injury that is the common molecular link of most, if not all, pathological conditions where CLU has been functionally implicated.

Clusterin: a forgotten player in Alzheimer's disease

Clusterin, also known as apolipoprotein J, is a versatile chaperone molecule which contains several amphipathic and coiled-coil alpha-helices, typical characteristics of small heat shock proteins. In addition, clusterin has three large intrinsic disordered regions, so-called molten globule domains, which can stabilize stressed protein structures. Twenty years ago, it was demonstrated that the expression of clusterin was clearly increased in Alzheimer's disease (AD). Later it was observed that clusterin can bind amyloid-beta peptides and prevent their fibrillization. Clusterin is also involved in the clearance of amyloid-beta peptides and fibrils by binding to megalin receptors and enhancing their endocytosis within glial cells. Clusterin is a complement inhibitor and can suppress complement activation observed in AD. Clusterin is also present in lipoprotein particles and regulates cholesterol and lipid metabolism of brain which is disturbed in AD. Clusterin is a stress-induced chaperone which is normally secreted but in conditions of cellular stress, it can be transported to cytoplasm where it can bind to Bax protein and inhibit neuronal apoptosis. Clusterin can also bind to Smad2/3 proteins and potentiate the neuroprotective TGFbeta signaling. An alternative splicing can produce a variant isoform of clusterin which can be translocated to nuclei where it induces apoptosis. The role of nuclear clusterin in AD needs to be elucidated. We will review here the extensive literature linking clusterin to AD and examine the recent progress in clusterin research with the respect to AD pathology. Though clusterin can be viewed as a multipotent guardian of brain, it is unable to prevent the progressive neuropathology in chronic AD.

Clusterin expression in cholestasis, hepatocellular carcinoma and liver fibrosis

AIMS

Clusterin shares functional properties with small heat shock proteins. In contrast to other heat shock proteins, it is present in the extracellular space. Its expression is altered in various diseases. The aim was to evaluate the presence and distribution of clusterin in liver diseases associated with cholestasis, in fibrosis and in hepatocellular carcinoma.

METHODS AND RESULTS

Tissue microarrays and biopsy materials were used to evaluate immunohistochemically the expression of clusterin in hepatocellular carcinoma, primary sclerosing cholangitis, primary biliary cirrhosis, mechanical cholestasis, drug-induced cholestasis, liver fibrosis and cirrhosis. The presence of clusterin in human bile was assessed by Western blotting. Furthermore, real-time reverse transcriptase-polymerase chain reaction was performed on liver tissue with mechanical cholestasis. Clusterin colocalized with elastic fibres, but not with collagen, hepatocytes or bile duct epithelia. It was detected in bile plugs in cholestasis and hepatocellular carcinomas with pseudoglandular features within the lumina. Clusterin was demonstrated in bile by Western blotting and its mRNA was expressed in normal and cholestatic livers.

CONCLUSIONS

Clusterin may protect bile duct epithelium against offensive biliary components or inhibit precipitation of biliary proteins. The association of clusterin with elastic fibres could reflect an extracellular chaperone function by either protecting elastic fibres or shielding abnormal elastic material.

Ultraviolet radiation-A (366 nm) induced morphological and histological malformations during embryogenesis of Clarias gariepinus (Burchell, 1822)

Exposure to ultraviolet radiation has been associated with variety effects in many organisms ranging from molecular and tissue damage to population level effects. The exposure of embryos of the catfish, Clarias gariepinus (Burchell, 1822) to 366nm UVA at different doses 15, 30 and 60 min resulted in the hatching time delayed to 29 h-post-fertilization stage (29 h-PFS) in comparison with normal hatching time of 22h-PFS at 29 degrees C. In embryos exposed to 15 min/UVA, 30 min/UVA and 60 min/UVA the total percentage of hatched embryos/fertilized eggs were 90%, 89% and 85%, respectively, while in control was 95% at 29 h-PFS. The total percentage of mortality/ hatched embryos were (1-14)%, (2-22)%, (2-23)% and (3-40)% for control, 15 min, 30 min and 60 min groups, respectively, at 40 h-PFS. Also as a result some morphological malformations; (yolk sac oedema, body curvature, fin blistering, and dwarfism) were revealed. These destructive effects were also confirmed by histopathological changes in gills, eyes, intestinal tract, spinal cord, notochord, liver, skin and kidney. The results confirm that exposure to UVA caused an exposure time-dependent delay in hatching rate and reduced the percentage of the hatched embryos but the mortality rate increased with increase of the exposure time to UVA.