Involvement of changes in stratum corneum keratin in wrinkle formation by chronic ultraviolet irradiation in hairless mice

HPRT1 Most Suitable Reference Gene for Accurate Normalization of mRNA Expression in Canine Dermal Tissues with Radiation Therapy

Reference genes are crucial in molecular biological studies as an internal control for gene re-search as they exhibit consistent expression patterns across many tissue types. In canines, radiation therapy is the most important therapeutic tool to cure various diseases like cancer. However, when using radiation for therapeutic strategy, radiation exposure to healthy tissues leads to some possible side effects such as acute radiation-induced skin injury and alters gene expression. Therefore, the analysis of a change in reference gene expression during the skin recovery process after radiation therapy is essential in healthy canine tissue. In the present study, we analyzed eight reference genes (ACTB, GAPDH, YWHAZ, GUSB, HPRT1, RPL4, RPS5, and TBP) in canine dermal tissues at 0, 1, 2, 3, 4, 5, 7, and 9 weeks of radiation exposure that affected the skin condition of canines. The stability of reference genes is determined by evaluating radiation therapy’s effect on healthy canine dermal tissue. Epidermal marker, Keratin 10 expression varies each week after irradiation, and HPRT1 is found to be the most suitable for normalization of mRNA expression in radiation-exposed canine dermal tissues. Changes in the gene expression level were evaluated by using a reliable tool such as quantitative real-time polymerase chain reaction (qRT-PCR). In order to achieve a valid qRT-PCR result, the most stable reference genes used for normalization after the radiation exposure process are important. Therefore, the current study was designed to evaluate the most stable reference gene for the post-irradiation canine tissues. After radiation exposure, the alternation of reference gene expression was estimated by three algorithms (geNorm, Normfinder, and Bestkeeper). The RG validation programs (GeNorm and NormFinder) suggested that HPRT1, RPL4, and TBP were suitable for normalization in qRT-PCR. Furthermore, three algorithms suggested that HPRT1 was the most stable reference gene for normalization with qRT-PCR results, regardless of before and after radiation exposure. Whereas GAPDH was found to be the most unstable reference gene. In addition, the use of stable or unstable reference genes for the normalization of Keratin 10 expression showed statistical differences. Therefore, we observed that, to obtain accurate and suitable PCR results of the canine tissues with and without radiation exposure, the HPRT1 reference gene is recommended for normalization with its high stability. Additionally, the use of RGs such as HPRT1, RPL4, and TBP for normalization in qRT-PCR experiments is recommended for post-radiation canine tissues to generate more accurate and reliable data. These results will provide fundamental information regarding internal controls for gene expression studies and can be used for the analysis of gene patterns in regenerative medicine.

NRF2 in dermatological disorders: Pharmacological activation for protection against cutaneous photodamage and photodermatosis

The skin barrier and its endogenous protective mechanisms cope daily with exogenous stressors, of which ultraviolet radiation (UVR) poses an imminent danger. Although the skin is able to reduce the potential damage, there is a need for comprehensive strategies for protection. This is particularly important when developing pharmacological approaches to protect against photocarcinogenesis. Activation of NRF2 has the potential to provide comprehensive and long-lasting protection due to the upregulation of numerous cytoprotective downstream effector proteins that can counteract the damaging effects of UVR. This is also applicable to photodermatosis conditions that exacerbate the damage caused by UVR. This review describes the alterations caused by UVR in normal skin and photosensitive disorders, and provides evidence to support the development of NRF2 activators as pharmacological treatments. Key natural and synthetic activators with photoprotective properties are summarized. Lastly, the gap in knowledge in research associated with photodermatosis conditions is highlighted.

Effect of boron element on photoaging in rats

BACKGROUND

The present study further assessed the effects of oral and topical applications of boron, which is known to have antiinflammatory and wound healing effects, on photoaging.

METHODS

A total of 49 eight-week-old female Wistar albino rats randomly divided into seven groups (control, shaved control, shaved+UVB, topical dermabor 2% (D2), and %5 (D5), systemic sodium perborate tetrahydrate (SPT) 2% (SPT2) and 4% (SPT4). To induce an experimental photoaging, the rats were exposed to UVB at an emission spectrum of 290-320 nm. Biochemical, molecular, skin, histological, and collagen content analyzes were made at the end of the study.

RESULTS

Increased skin inflammatory parameters (COX-2, IL-8, NF-KB, IL-6, and TNF-α) levels in UVB-exposed groups were inhibited in all treatment groups. The tissue level of hydroxyproline and elastase was found to decrease in all UVB-exposed group. The level of hydroxyproline was significantly higher in the D2 and D5 groups than in the SPT2 and SPT4 groups. The level of elastase was significantly lower in the D2 and D5 groups than in the SPT2 and SPT4 groups.

CONCLUSIONS

In future, boron may be developed as a functionally protective treatment against photoaging caused by UVB, and may be included in sun protection systems.

Raman confocal microscopy and biophysics multiparametric characterization of the skin barrier evolution with age

Skin aging is a multifactorial phenomenon that involves alterations at the molecular, cellular and tissue levels. Our aim was to carry out a multiparametric biophysical and Raman characterization of skin barrier between individuals of different age groups (<24 and >70 years old). Our results showed a significant decrease of lipids to proteins ratio overall the thickness of the stratum corneum and higher lateral packing in the outer part of the SC for elderly. This can explain the decrease in trans epidermal water loss measured values rather than only SC thickening. Both age groups showed similar water content at SC surface while elderly presented higher water content in deep SC and viable epidermis. Mechanical measurements showed a decrease in the elasticity and an increase in the fatigability with age and were correlated with partially bound water. Highest correlation and anti-correlation values were observed for the deepest part of the SC and the viable epidermis.

Characterization of Permeability Barrier Dysfunction in a Murine Model of Cutaneous Field Cancerization Following Chronic UV-B Irradiation: Implications for the Pathogenesis of Skin Cancer

Simple Summary

In the present work, we developed an experimental preclinical model of skin with cutaneous field cancerization after chronic UV-B light exposure in an immunologically intact mouse model (SKH1 aged mice). We observed impairments in the transepidermal water loss, stratum corneum hydration, and surface pH. We also detected a marked hyperkeratotic hyperplasia of the epidermis, induction of keratinocyte hyperproliferation, incidental actinic keratosis, and in situ squamous cell carcinomas in the UV-B light-irradiated groups. In this context, the association between the permeability barrier impairment and keratinocyte hyperproliferation might be considered a new target in the management of skin with cutaneous field cancerization. As current therapeutic approaches to actinic keratosis and cutaneous field cancerization only focus on the direct antineoplastic, immunomodulatory, or photodynamic effects of approved topical drugs, this mouse model of skin with cutaneous field cancerization might be helpful for both the identification and screening of potentially new preventive strategies or treatments (e.g., skin barrier therapies).

Abstract

Chronic ultraviolet B (UV-B) irradiation is known to be one of the most important hazards acting on the skin and poses a risk of developing photoaging, skin with cutaneous field cancerization (CFC), actinic keratosis (AKs), and squamous cell carcinomas (SCCs). Most of the UV-B light is absorbed in the epidermis, affecting the outermost cell layers, the stratum corneum, and the stratum granulosum, which protects against this radiation and tries to maintain the permeability barrier. In the present work, we show an impairment in the transepidermal water loss, stratum corneum hydration, and surface pH after chronic UV-B light exposure in an immunologically intact mouse model (SKH1 aged mice) of skin with CFC. Macroscopic lesions of AKs and SCCs may develop synchronically or over time on the same cutaneous surface due to both the presence of subclinical AKs and in situ SCC, but also the accumulation of different mutations in keratinocytes. Focusing on skin with CFC, yet without the pathological criteria of AKs or SCC, the presence of p53 immunopositive patches (PIPs) within the epidermis is associated with these UV-B-induced mutations. Reactive epidermis to chronic UV-B exposure correlated with a marked hyperkeratotic hyperplasia, hypergranulosis, and induction of keratinocyte hyperproliferation, while expressing an upregulation of filaggrin, loricrin, and involucrin immunostaining. However, incidental AKs and in situ SCC might show neither hypergranulosis nor upregulation of differentiation markers in the upper epidermis. Despite the overexpression of filaggrin, loricrin, involucrin, lipid enzymes, and ATP-binding cassette subfamily A member 12 (ABCA12) after chronic UV-B irradiation, the permeability barrier, stratum corneum hydration, and surface pH were severely compromised in the skin with CFC. We interpret these results as an attempt to restore the permeability barrier homeostasis by the reactive epidermis, which fails due to ultrastructural losses in stratum corneum integrity, higher pH on skin surface, abundant mast cells in the dermis, and the common presence of incidental AKs and in situ SCC. As far as we know, this is the first time that the permeability barrier has been studied in the skin with CFC in a murine model of SCC induced after chronic UV-B irradiation at high doses. The impairment in the permeability barrier and the consequent keratinocyte hyperproliferation in the skin of CFC might play a role in the physiopathology of AKs and SCCs.

Epidermal and Dermal Hallmarks of Photoaging are Prevented by Treatment with Night Serum Containing Melatonin, Bakuchiol, and Ascorbyl Tetraisopalmitate: In Vitro and Ex Vivo Studies

INTRODUCTION

Photoaging is a complex process that is chiefly the result of oxidative stress caused by ultraviolet (UV)-generated reactive oxygen species. To counter this process, we developed a 3-in-1 night facial serum (3-in-1 NFS) containing a combination of direct and indirect antioxidants and polyphenols that is designed to attenuate UV-generated free radicals and stimulate dermal protein synthesis. In clinical trials 3-in-1 NFS improved the appearance of photoaged skin. In this study we sought to identify some of the main histologic changes responsible for this.

METHODS

We performed an immunolabeling analysis of some of the salient epidermal and dermal proteins in 3-in-1 NFS-treated primary epidermal keratinocytes (HEKs) and dermal fibroblasts (HDFs) in vitro, and in UV-exposed skin explants ex vivo. Numbers of apoptotic sunburn cells following exposure of 3-in-1 NFS-treated skin explants to UV radiation were also determined.

RESULTS

We demonstrate that 3-in-1 NFS increases levels of filaggrin and aquaporin 3 in HEKs, and levels of collagen I and collagen III in HDFs in vitro. Levels of precursor procollagen type I and tropoelastin were increased in ex vivo skin explants. Numbers of apoptotic sunburn cells were significantly reduced in UV-exposed skin explants. These effects were only observed with the combination of ingredients in 3-in-1 NFS, suggesting that they have a synergistic effect on photoaged skin biology.

CONCLUSION

Our results show that some of the histological hallmarks of photoaging are improved with the use of 3-in-1 NFS.

Skin Hydration Effects of Scale-Up Fermented Cyclopia intermedia against Ultraviolet B-Induced Damage in Keratinocyte Cells and Hairless Mice

Photoaging occurs by chronic skin exposure to the sun and ultraviolet irradiation and leads to skin aging accompanied by a lack of skin hydration. We previously demonstrated the photoprotective effect of fermented Cyclopia intermedia (honeybush) extract on the skin. In this study, we evaluated the skin hydration effects of scaled-up fermented honeybush extract (HU-018) against ultraviolet B (UVB) radiation in HaCaT immortalized human keratinocytes and hairless mice. Pretreating HaCaT cells with HU-018 attenuated the decreased hyaluronic acid (HA) levels and mRNA expression of genes encoding involucrin, filaggrin, and loricrin by UVB irradiation. HU-018 treatment also ameliorated the decreased stratum corneum (SC) hydration and the increased levels of transepidermal water loss (TEWL) and erythema index (EI) in hairless mice after UVB exposure. Microarray analysis revealed changes in gene expression patterns of hyaluronan synthase 2 (Has2), transforming growth factor-beta 3 (TGF-β3), and elastin induced by HU-018 in UVB-irradiated mice. Consistently, the mRNA expression of Has2, TGF-β3, and elastin was increased by HU-018 treatment. Moreover, HU-018 restored the increased epidermal thickness and collagen disorganization in skin tissue of UVB-irradiated mice. HU-018 treatment also decreased matrix metalloproteinase-1 (MMP-1) expression and increased procollagen type-1, elastin, and TGF-β1 expression. In conclusion, we found that HU-018 promoted skin hydration processes in UVB-irradiated keratinocytes and hairless mice by modulating involucrin, filaggrin, loricrin, and HA expression and ameliorating visible signs of photoaging. Thus, HU-018 may be a good skin hydration agent for skin care.

In vivo Change of Keratin-Bound Molecules in the Human Stratum Corneum following Exposure to Ultraviolet Radiation

BACKGROUND/OBJECTIVES

Ultraviolet (UV) radiation damages the stratum corneum (SC) and disrupts the skin barrier. The damaged skin changes in the molecular composition of the SC, including its water content. However, it is difficult to examine the in vivo SC changes with existing methods, so those have not been well characterized. Therefore, we investigated in vivo changes of UV-induced SC damage using confocal Raman spectroscopy.

METHOD

We irradiated the volar forearm of 10 subjects with 0.5, 1, and 1.5 minimal erythemal doses of UV radiation. Then, we examined erythema, the transepidermal water loss (TEWL), the water content, the natural moisturizing factor (NMF), and the lipids of the skin.

RESULTS

After UV irradiation, erythema and TEWL of the skin were both increased. The bound water content of the SC was also increased following UV irradiation. The NMF of the SC revealed different tendencies. All free amino acids (FAAs) of the NMF were increased after UV irradiation, except proline. trans-urocanic acid, pyrrolidone carboxylic acid, lactate, and urea, which are NMF components produced by the subsequent catabolism of FAAs and sweat, were decreased after UV irradiation. The amount of ceramide in the SC was also decreased after UV exposure, while cholesterol was increased.

CONCLUSIONS

The bound water content of the SC was increased by UV exposure along with increasing TEWL, several NMF components, and cholesterol. These in vivo results for UV-damaged SC obtained via Raman spectroscopy could be applied to research with regard to protecting the SC from UV radiation and treating UV-damaged SC.

Histological observation of hairless mice skin after exposure to Simulated Solar Light: Comparison between the histological findings with different methodologies and 3R principle correlations

BACKGROUND

Albino hairless mouse (AHM) has been used as a biological model in photodermatology. However, the experimental landscape is diverse to follow and need particular attention.

PURPOSE

Irradiation parameters were investigated for the development of a protocol to assess alterations in the AHM skin using Simulated Solar Light (SSL). The present study was compared with published articles (last 15 years) according to irradiation protocols, morphological findings to minimize animal suffering and UV exposure.

MATERIALS AND METHODS

Three groups: Control (G1), experimental - sunburn (G2) and skin photodamage assay (G3). G2 were immobilized and exposed to SSL once for 15, 30 and 45min. G3 were exposed to SSL, without immobilization, for 15min once a day for one week. The dorsal skin was analyzed using hematoxylin and eosin technique.

RESULTS

G2 displayed different sunburn degrees. Based on the profile of the observed morphological alterations, a 15min irradiation was chosen as the exposure time to expose G3, without immobilization, for 5 consecutive days.

CONCLUSION

These conditions produced the same morphological changes in the AHM with a shorter solar exposure time, without immobilizing the animals but using environmental exposure fluences, conforming to 3R (reduction - refinement - replacement) recommendations.

Photoprotective effects of topical ginseng leaf extract using Ultraflo L against UVB-induced skin damage in hairless mice

BACKGROUND

Abnormal activation of matrix metalloproteinases (MMPs) plays an important role in UV-induced wrinkle formation, which is a major dermatological problem. This formation occurs due to the degeneration of the extracellular matrix (ECM). In this study, we investigated the cutaneous photoprotective effects of Ultraflo L treated ginseng leaf (UTGL) in hairless mice.

METHODS

SKH-1 hairless mice (6 weeks of age) were randomly divided into four groups (8 mice/group). UTGL formulation was applied topically to the skin of the mice for 10 weeks. The normal control group received nonvehicle and was not irradiated with UVB. The UV control (UVB) group received nonvehicle and was exposed to gradient-UVB irradiation. The groups (GA) receiving topical application of UTGL formulation were subjected to gradient-UVB irradiation on 0.5 mg/cm2 [GA-low (GA-L)] and 1.0 mg/cm2 [(GA-high (GA-H)] of dorsal skin area, respectively.

RESULTS

We found that topical treatment with UTGL attenuated UVB-induced epidermal thickness and impairment of skin barrier function. Additionally, UTGL suppressed the expression of MMP-2, -3, and -13 induced by UVB irradiation. Our results show that topical application of UTGL protects the skin against UVB-induced damage in hairless mice and suggest that UTGL can act as a potential agent for preventing and/or treating UVB-induced photoaging.

CONCLUSION

UTGL possesses sunscreen properties and may exhibit photochemoprotective activities inside the skin of mice. Therefore, UTGL could be used as a potential therapeutic agent to protect the skin against UVB-induced photoaging.

Noninvasive Optical Imaging of UV-Induced Squamous Cell Carcinoma in Murine Skin: Studies of Early Tumor Development and Vitamin D Enhancement of Protoporphyrin IX Production

Better noninvasive techniques are needed to monitor protoporphyrin IX (PpIX) levels before and during photodynamic therapy (PDT) of squamous cell carcinoma (SCC) of the skin. Our aim was to evaluate (1) multispectral fluorescent imaging of ultraviolet light (UV)-induced cancer and precancer in a mouse model of SCC and (2) multispectral imaging and probe-based fluorescence detection as a tool to study vitamin D (VD) effects on aminolevulinic acid (ALA)-induced PpIX synthesis. Dorsal skin of hairless mice was imaged weekly during a 24-week UV carcinogenesis protocol. Hot spots of PpIX fluorescence were detectable by multispectral imaging beginning at 14 weeks of UV exposure. Many hot spots disappeared after cessation of UV at week 20, but others persisted or became visible after week 20, and corresponded to tumors that eventually became visible by eye. In SCC-bearing mice pretreated with topical VD before ALA application, our optical techniques confirmed that VD preconditioning induces a tumor-selective increase in PpIX levels. Fluorescence-based optical imaging of PpIX is a promising tool for detecting early SCC lesions of the skin. Pretreatment with VD can increase the ability to detect early tumors, providing a potential new way to improve efficacy of ALA-PDT.

Non-melanoma Skin Cancer in Canada Chapter 2: Primary Prevention of Non-melanoma Skin Cancer

BACKGROUND

Non-melanoma skin cancer (NMSC), including basal and squamous cell carcinoma (BCC and SCC), represents the most common malignancy.

OBJECTIVE

To provide guidance to Canadian health care practitioners regarding primary prevention of NMSC.

METHODS

Structured literature searches were conducted, using search terms including prevention, sunscreen, and sun prevention factor. All recommendations concern guidance that physicians should regularly discuss with their patients to help establish photoprotection habits. The GRADE system was used to assign strength to each recommendation.

RESULTS

Ultraviolet exposure is the major modifiable risk factor for NMSC. Aspects of photoprotection, including effective sunscreen use and avoidance of both the midday sun and artificial tanning, are discussed. Several widespread misunderstandings that undermine responsible public health measures related to sun safety are addressed.

CONCLUSIONS

Photoprotection represents both an individual priority and a public health imperative. By providing accurate information during routine patient visits, physicians reinforce the need for ongoing skin cancer prevention.

Effects of Collagen Tripeptide Supplement on Photoaging and Epidermal Skin Barrier in UVB-exposed Hairless Mice

Collagen tripeptide (CTP) is a functional food material with several biological effects such as improving dry skin and wound and bone fracture healing. This study focused on the anti-photoaging effects of CTP on a hairless mouse model. To evaluate the effects of CTP on UVB-induced skin wrinkle formation in vivo, the hairless mice were exposed to UVB radiation with oral administration of CTP for 14 weeks. Compared with the untreated UVB control group, mice treated with CTP showed significantly reduced wrinkle formation, skin thickening, and transepidermal water loss (TEWL). Skin hydration and hydroxyproline were increased in the CTP-treated group. Moreover, oral administration of CTP prevented UVB-induced MMP-3 and -13 activities as well as MMP-2 and -9 expressions. Oral administration of CTP increased skin elasticity and decreased abnormal elastic fiber formation. Erythema was also decreased in the CTP-treated group. Taken together, these results strongly suggest that CTP has potential as an anti-photoaging agent.

Short-term exposure to UV-A, UV-B, and UV-C irradiation induces alteration in cytoskeleton and autophagy in human keratinocytes

Ultraviolet radiation (UV) induces a series of morphological and ultrastructural alterations in human epidermis. Alterations observed in irradiated keratinocytes in morphological studies done before were cell retraction with loss of intercellular interactions, surface blebbing, and eventually cell death by apoptosis. The aim of this study was to investigate effect of UV-A, UV-B, and UV-C irradiation on the cytoskeleton of human keratinocytes. Keratinocytes were obtained by exfoliative scrubbing procedure from buccal mucosa of healthy individuals, and treated with UV-A, UV-B, and UV-C radiation. Afterward, treated cell were labeled with anti-alfa-tubulin and anti-human-cytokeratin and analyzed by light and confocal microscopy. The intensity of the cytokeratin labeling was found to be much higher in all irradiated cells than in control cells as observed by light microscope and measured with the Image J program. This measurement showed that with the decrease in the wavelengths of UV irradiation the intensity of the labeling of cells increases. Although the authors expected to find the collapse of microtubules toward the cell nucleus or their rearrangement in UV-treated cells, these alterations were not verified on cell smears labeled with anti-alfa tubulin observed by confocal microscope. When they used electron microscopy to examine in more detail the morphology of irradiated cells, they did not find apoptotic cells, but found features of autophagy in UV-treated keratinocytes. The authors assume that autophagy found as a result of UV radiation of human keratinocytes acts as a cytoprotective mechanism against UV-induced apoptosis.

Solar UV radiation reduces the barrier function of human skin

The ubiquitous presence of solar UV radiation in human life is essential for vitamin D production but also leads to skin photoaging, damage, and malignancies. Photoaging and skin cancer have been extensively studied, but the effects of UV on the critical mechanical barrier function of the outermost layer of the epidermis, the stratum corneum (SC), are not understood. The SC is the first line of defense against environmental exposures like solar UV radiation, and its effects on UV targets within the SC and subsequent alterations in the mechanical properties and related barrier function are unclear. Alteration of the SC's mechanical properties can lead to severe macroscopic skin damage such as chapping and cracking and associated inflammation, infection, scarring, and abnormal desquamation. Here, we show that UV exposure has dramatic effects on cell cohesion and mechanical integrity that are related to its effects on the SC's intercellular components, including intercellular lipids and corneodesmosomes. We found that, although the keratin-controlled stiffness remained surprisingly constant with UV exposure, the intercellular strength, strain, and cohesion decreased markedly. We further show that solar UV radiation poses a double threat to skin by both increasing the biomechanical driving force for damage while simultaneously decreasing the skin's natural ability to resist, compromising the critical barrier function of the skin.

In the shadow of the wrinkle: experimental models

Research on aging has run for decades, and knowledge on the biologic process of skin chronological and photoaging is still increasing thanks to read across results generated between human, animal, and in vitro studies. However, wrinkles should not be considered to result only from the aging process. There are few reports on specific wrinkle histological features compared to the surrounding skin, and there is thus a need in really wrinkling skin animal and in vitro models. UV-irradiated Hr mouse is a good model because it develops wrinkles. Nevertheless, as mouse skin is somehow different from human skin, the innovative model of wrinkling human skin xenograft on SCID mice seems to be really promising. Concerning in vitro and ex vivo models, although there have been considerable advances in reconstructing realistic aged skins, there is still a lack of in vitro wrinkling skin model, and unfortunately, this gap will probably be difficult to fill.

Essential role of microfibrillar-associated protein 4 in human cutaneous homeostasis and in its photoprotection

UVB-induced cutaneous photodamage/photoaging is characterized by qualitative and quantitative deterioration in dermal extracellular matrix (ECM) components such as collagen and elastic fibers. Disappearance of microfibrillar-associated protein 4 (MFAP-4), a possible limiting factor for cutaneous elasticity, was documented in photoaged dermis, but its function is poorly understood. To characterize its possible contribution to photoprotection, MFAP-4 expression was either augmented or inhibited in a human skin xenograft photodamage murine model and human fibroblasts. Xenografted skin with enhanced MFAP-4 expression was protected from UVB-induced photodamage/photoaging accompanied by the prevention of ECM degradation and aggravated elasticity. Additionally, remarkably increased or decreased fibrillin-1-based microfibril development was observed when fibroblasts were treated with recombinant MFAP-4 or with MFAP-4-specific siRNA, respectively. Immunoprecipitation analysis confirmed direct interaction between MFAP-4 and fibrillin-1. Taken together, our findings reveal the essential role of MFAP-4 in photoprotection and offer new therapeutic opportunities to prevent skin-associated pathologies.

Ultraviolet-B irradiation induces differential regulations of hyaluronidase expression and activity in normal human keratinocytes

Skin aging is a complex process determined by genetic factors (intrinsic aging) and environmental factors (extrinsic aging). One of the most influential environmental factor is UV-B irradiation. Hyaluronic acid (HA) is an abundant component of skin extracellular matrix where it plays many roles such as hydration and architectural support. Downregulation of HA during photoaging was reported previously. Changes in expression and function of its degrading enzymes, the hyaluronidases (Hyals) might be involved in this decrease. In the present study, normal human keratinocytes were submitted to increasing doses of UV-B. The mRNA expression of HYAL1, HYAL2 and HYAL3 and the hyaluronidase enzymatic activity were quantified using real-time PCR and a microtiter-based assay, respectively. After UV-B irradiation, HYAL1 mRNA expression was upregulated whereas HYAL2 and HYAL3 mRNAs were downregulated and hyaluronidase enzymatic activity was increased in both cell layer and culture medium. In parallel, immunohistochemical studies performed on UV-B irradiated reconstructed epidermis confirmed that Hyal-1, Hyal-2 and Hyal-3 protein expression were differently regulated by UV-B. Taken together, our results demonstrate that UV-B irradiation induces differential regulations of hyaluronidase expression and enzymatic activity in human keratinocytes. These differential modulations of hyaluronidase expression and activity by UV-B could contribute to cutaneous photoaging.

Profilometric and morphometric response of murine skin to cosmeceutical agents

OBJECTIVE

To investigate whether topical antiaging compounds can reduce wrinkle depth as noted at replica profilometry with comparable changes in histologic findings in hairless mice.

METHODS

Commercial retinoic acid cream, a peptide lotion, and a soy cream were applied to the dorsal skin for 4 weeks. Silicone-negative replicas of treated and untreated skin surface were photographed and evaluated for traditional features of surface roughness. Skin samples were processed using histomorphometry and immunohistochemistry of proliferating cell nuclear antigen. Quantitative light microscopic data were acquired for estimating replication of epidermal keratinocytes, epidermal thickness, and depth of dermal collagen bundles.

RESULTS

Data were analyzed by comparing means with 1-way analysis of variance, and significant changes in all measurements were noted. Augmented keratinocyte proliferation and thickening of viable epidermis were observed with all 3 compounds, although a greater effect was found in the retinoic acid and peptide treatment groups. A similar trend was noted with respect to widening of the collagen layer. Epidermal surface roughness manifested maximum smoothing after treatment with the peptide compound.

CONCLUSION

The pronounced effects noted with all 3 compounds indicate that topical agents other than retinoic acid may have comparative stimulating effects on the skin in nonirradiated mice.

Mechanistic effects of long-term ultraviolet B irradiation induce epidermal and dermal changes in human skin xenografts

UVB irradiation has been reported to induce photoaging and suppress systemic immune function that could lead to photocarcinogenesis. However, because of the paucity of an UVB-induced photodamaged skin model, precise and temporal mechanism(s) underlying the deleterious effects of long-term UVB exposure on human skin have yet to be delineated. In this study, we established a model using human skin xenografted onto severe combined immunodeficient mice, which were subsequently challenged by repeated UVB irradiation for 6 weeks. Three-dimensional optical image analysis of skin replicas and noninvasive biophysical measurements illustrated a significant increase in skin surface roughness, similar to premature photoaging, and a significant loss of skin elasticity after long-term UVB exposure. Resembling authentically aged skin, UVB-exposed samples exhibited significant increases in epithelial keratins (K6, K16, K17), elastins, and matrix metalloproteinases (MMP-1, MMP-9, MMP-12) as well as degradation of collagens (I, IV, VII). The UVB-induced deterioration of fibrous keratin intermediate filaments was also observed in the stratum corneum. Additionally, similarities in gene expression patterns between our model and chronologically aged skin substantiated the plausible relationship between photodamage and chronological age. Furthermore, severe skin photodamage was observed when neutralizing antibodies against TIMP-1, an endogenous inhibitor of MMPs, were administered during the UVB exposure regimen. Taken together, these findings suggest that our skin xenograft model recapitulates premature photoaged skin and provides a comprehensive tool with which to assess the deleterious effects of UVB irradiation.

Long-term alteration in the expression of keratins 6 and 16 in the epidermis of mice after chronic UVB exposure

The influences of chronic UVB exposure on epidermal differentiation have been poorly studied compared to dermal photo-aging although those effects are very important in terms of photo-damage to the skin. The purpose of this study was to investigate the effects of chronic UVB exposure on keratin expression in the epidermis. The effects on murine skin of chronic exposure to weak UVB (below 1 MED) was examined by immunoblotting for keratins K10, K5, K6, and K16, by immunohistochemistry using antibodies to K6, K16, and Ki67 as well as by conventional HE staining of skin sections. Alterations of keratin expression induced by the chronic UVB exposure were distinct from those elicited by a single acute UVB exposure. The expression of keratins K6 and K16 was quite long-lasting, continuing for 7 weeks after 6 weeks of chronic UVB exposure and for 6 weeks after 9 weeks of chronic UVB exposure. In contrast, K6 and K16 expression induced by a single UVB exposure at 0.5 MED or 3 MED almost ceased within 2 weeks after that exposure. Furthermore, the expression of the constructive keratins, K5 and K10, remained almost unchanged by chronic UVB exposure. Epidermal thickness was increased significantly immediately after the 9 weeks of chronic UVB exposure; however, it had returned to normal level 6 weeks later. The alterations in keratin expression accompanied the marked disruption of the ordered ultrastructure of keratin intermediate filaments, which were observed by TEM. Thus, chronic exposure to UVB has a deep impact on the biosynthetic regulation of different keratins in the epidermis, thereby interfering with the ordered ultrastructure of keratin intermediate filaments. Those events could have relevance to the mechanism of photo-damage, such as fine wrinkles observed in chronically UV-exposed skin in addition to dermal photo-aging.

Mechanisms of inhibitory effects of CoQ10 on UVB-induced wrinkle formation in vitro and in vivo

Photodamaged skin exhibits wrinkles, pigmented spots, dryness and tumors. Solar UV radiation induces cyclobutane pyrimidine dimers (CPD) and further produces base oxidation by reactive oxygen species (ROS). ROS are thought to be a major factor to initiate the up-regulation of matrix metalloproteinases (MMPs) in keratinocytes and fibroblasts via activation of receptor proteins on the cell membrane of keratinocytes and fibroblasts, and to degrade fiber components in dermis, leading to wrinkle formation. Coenzyme Q10 (CoQ10) was reported to reduce ROS production and DNA damage triggered by UVA irradiation in human keratinocytes in vitro. Further, CoQ10 was shown to reduce UVA-induced MMPs in cultured human dermal fibroblasts. We speculated that UVB radiation-induced cytokine production in keratinocytes may be inhibited by CoQ10, resulting in the reduction of MMPs in fibroblasts leading to wrinkle reduction. Our in vitro studies showed that UVB-induced IL-6 production of normal human keratinocyte (NHKC) decreased in the presence of CoQ10. Furthermore, MMP-1 production of fibroblasts cultured with the medium containing CoQ10 collected from UVB-irradiated NHKC significantly decreased during 24 h culture. In the clinical trial study, we found that the use of 1% CoQ10 cream for five months reduced wrinkle score grade observed by a dermatologist. Taken together, our results indicate that CoQ10 may inhibit the production of IL-6 which stimulate fibroblasts in dermis by paracrine manner to up-regulate MMPs production, and contribute to protecting dermal fiber components from degradation, leading to rejuvenation of wrinkled skin.

Establishment of a mouse skin model of the lichenification in human chronic eczematous dermatitis

BACKGROUND

Repeated mechanical stresses, such as scratching and rubbing, on a lesional skin area induce a rough skin condition known as lichenification in patients with chronic eczematous dermatitis. For ethical reasons, the pathomechanisms involved are difficult to study, so an animal model is required.

OBJECTIVES

To study the pathomechanisms of the unique rough skin changes seen in chronic eczematous dermatitis, we established a mouse skin model by repeated tape stripping to inflict stratum corneum (SC) barrier disruption. The skin characteristics of the model were investigated biologically, histologically and pharmacologically.

METHODS

Tape stripping was done on mouse back skin three times a week for 4 weeks. The skin changes were studied by obtaining negative replicas, haematoxylin and eosin staining, immunostaining for CD31 and BrdU, and measuring epidermal and cutaneous thickness and skin capacitance. Activities of matrix metalloproteinase (MMP)-2, 9 and urokinase-type plasminogen activator (uPA) in the skin tissues were analysed by zymography. The effects of MMP inhibitor and glycine were assessed.

RESULTS

The repeated tape stripping produced crusting and desquamation at 48 h, followed 1 week later by the formation of shallow furrows, which became much deeper after 4 weeks, appearing as fine and regular wrinkles. The resultant wrinkled skin resembled lichenified skin seen in patients with chronic eczematous dermatitis. Histopathologically, we found acanthosis, hypergranulosis and hyperkeratosis even at 48 h, and the skin was 2.5 times thicker than untreated control skin at 4 weeks. We observed angiogenesis in the upper dermis at 1 and 4 weeks. Skin capacitance, a parameter of SC hydration, displayed consistently low levels throughout the experimental period. Although the dermis was also thickened, the activity of MMP-9 was sharply increased only at 24 and 48 h after tape stripping, declining thereafter to the control level. Topical applications of CGS-27023A (CGS), an MMP inhibitor, failed to suppress this tape-stripping-induced wrinkle formation. In contrast, topical applications of a barrier recovery accelerator, glycine, effectively inhibited the wrinkle formation induced by repeated tape stripping.

CONCLUSIONS

The induction of fine and regular wrinkles by inflicting chronic SC barrier disruption in this model involves mainly epidermal changes, which is in sharp contrast to the mainly dermal changes induced by chronic ultraviolet B irradiation.

The formation of wrinkles caused by transition of keratin intermediate filaments after repetitive UVB exposure

It has been reported that the formation of wrinkles involves changes in the elastic properties of the dermis due to the denaturation of elastic fibers. Several studies have shown that the hydration condition of the stratum corneum is also important in wrinkle formation. It is, however, still unclear how the stratum corneum contributes to wrinkle formation. Here we investigated the relationship between the formation of wrinkles and changes in the physical properties and condition of the skin after repetitive ultraviolet B (UVB) irradiation of hairless mice (HR/ICR). Repetitive UVB irradiation caused wrinkles on the dorsal skin of the mice. The elasticity (E') of the stratum corneum of UVB-irradiated mice was significantly lower than that of age-matched control (unirradiated) mice. UVB exposure also caused a deterioration of the fibrous ultrastructure of keratin intermediate filaments (KIFs) in the skin. We conclude that the deterioration of KIFs in the stratum corneum caused by repetitive UVB irradiation decreases the elastic properties of the stratum corneum, resulting in the formation of wrinkles.

Ultraviolet-B Radiation Causes an Upregulation of Survivin in Human Keratinocytes and Mouse Skin¶

Understanding of the mechanism of ultraviolet (UV)-mediated cutaneous damages is far from complete. The cancer-specific expression of Survivin, a member of the inhibitor of apoptosis family of proteins, coupled with its importance in inhibiting cell death and in regulating cell division, makes it a target for cancer treatment. This study was designed to investigate the modulation of Survivin during UV response, both in vitro and in vivo. We used UV-B-mediated damages in normal human epidermal keratinocytes (NHEK) cells as an in vitro model and SKH-1 hairless mouse model for the in vivo studies. For in vitro studies, NHEK were treated with UV-B and samples were processed at 5, 15, 30 min, 1, 3, 6, 12 and 24 h after treatment. Our data demonstrated that UV-B exposure (50 mJ/cm2) to NHEK resulted in a significant upregulation in Survivin messenger RNA (mRNA) and protein levels. We also observed that UV-B exposure to NHEK resulted in significant (1) decrease in Smac/DIABLO and (2) increase in p53. For in vivo studies, the SKH-1 hairless mice were subjected to a single exposure of UV-B (180 mJ/cm2), and samples were processed at 3, 6, 12 and 24 h after UV-B exposure. UV-B treatment resulted in a significant increase in protein or mRNA levels (or both) of Survivin, phospho-Survivin and p53 and a concomitant decrease in Smac/DIABLO in mouse skin. This study demonstrated, for the first time, the involvement of Survivin (and the associated events) in UV-B response in vitro and in vivo in experimental models regarded to have relevance to human situations.

Ultraviolet radiation and melanogenesis

Light radiation is a part of the electromagnetic radiation, and it consists of the ultraviolet (UV) radiation, visible light, and infrared radiation. UV radiation energy is absorbed in the form of photons in biomolecules (chromophores) and induces various cellular reactions, out of which photochemical and photosensitizing are the most significant. In contact with the skin UV radiation incites protection mechanisms: the most important are stratum corneum thickening and melanin synthesis (melanogenesis). Basic role of melanin is absorption and scattering of UV rays and neutralization of free radicals. In this review physical characteristics of UV radiation, its biological effects, and relation to melanogenesis and carcinogenesis are discussed.