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

Oral Administration of Rosa gallica Prevents UVB-Induced Skin Aging through Targeting the c-Raf Signaling Axis

Rosa gallica is a widely used Rosa species for medicinal and culinary purposes. Rosa gallica has been reported to display antioxidant, anti−inflammatory, and antibacterial activities. However, the effect of Rosa gallica against skin aging in vivo is unknown and its active components have not been fully understood. Oral administration of Rosa gallica prevented UVB−mediated skin wrinkle formation and loss of collagen/keratin fibers in the dorsal skin of mice. Examination of biomarkers at the molecular level showed that Rosa gallica downregulates UVB−induced COX−2 and MMP−1 expression in the skin. Through a direct comparison of major compounds identified using the UHPLC−MS/MS system, we discovered gallic acid as the primary component contributing to the anti-skin aging effect exhibited by Rosa gallica. Examination of the molecular mechanism revealed that gallic acid can potently and selectively target the c−Raf/MEK/ERK/c−Fos signaling axis. In addition, both gallic acid and MEK inhibitor blocked UVB−induced MMP−1 expression and restored collagen levels in a reconstructed 3D human skin model. Collectively, Rosa gallica could be used as a functional ingredient in the development of nutraceuticals against skin aging.

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.

Luteolin prevents solar radiation-induced matrix metalloproteinase-1 activation in human fibroblasts: a role for p38 mitogen-activated protein kinase and interleukin-20 released from keratinocytes

Human skin is continuously exposed to solar radiation, which can result in photoaging, a process involving both dermal and, to a lesser extent, epidermal structures. Previously, we have shown that the flavonoid luteolin protects the epidermis from ultraviolet (UV)-induced damage by a combination of UV-absorbing, antioxidant, and antiinflammatory properties. The aim of the present study was to determine direct and indirect effects of luteolin on dermal fibroblasts as major targets of photoaging. Stimulation of fibroblasts with UVA light or the proinflammatory cytokine interleukin-20 (IL-20) is associated with wrinkled skin, increased IL-6 secretion, matrix metalloproteinase (MMP-1) expression, and hyaluronidase activity. All of these targets were inhibited by luteolin via interference with the p38 mitogen-activated protein kinase (MAPK) pathway. Next, we assessed the role of conditioned supernatants from keratinocytes irradiated with solar-simulated radiation (SSR) on nonirradiated dermal fibroblasts. In keratinocytes, luteolin inhibited SSR-induced production of IL-20, also via interference with the p38 MAPK pathway. Similarly, keratinocyte supernatant-induced IL-6 and MMP-1 expression in fibroblasts was reduced by pretreatment of keratinocytes with luteolin. Finally, these results were confirmed ex vivo on skin explants treated with luteolin before UV irradiation. Our results suggest that SSR-mediated production of soluble factors in keratinocytes is modulated by luteolin and may attenuate photoaging in dermal fibroblasts.

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.

New wrinkles on wrinkling: an 8-year longitudinal study on the progression of expression lines into persistent wrinkles

BACKGROUND

While cumulative lifetime sun exposure is well recognized as having an important role in the progression of facial wrinkling, the role of facial expression has largely been overlooked, in part due to the lack of comprehensive longitudinal data on the change in both expression lines and persistent wrinkles with age.

OBJECTIVES

To track the detailed pattern of facial wrinkling in the same group of people over several years and to verify that expression lines evolve into persistent wrinkles. In addition, to identify factors predictive of a faster or slower rate of wrinkling.

METHODS

Standardized images were captured at baseline and at 8 years of 122 women (ages 10-72 years, skin types I-VI) with and without a smiling expression. The wrinkle pattern with expression at baseline was compared with the pattern without expression at 8 years. Severity of facial wrinkling was quantified using computer-based image analysis. Skin colour, hydration, sebum and pH were measured at baseline. A structured questionnaire captured demographic and lifestyle data at baseline and at 8 years.

RESULTS

Each subject's unique pattern of persistent facial wrinkling observed without expression at year 8 was predicted by the pattern of lines observed with a smiling expression at baseline. Having a drier, more alkaline stratum corneum, a lighter complexion, being middle-aged (40s) or becoming menopausal were associated with faster persistent wrinkling.

CONCLUSIONS

Repeated skin flexure during facial expression causes persistent wrinkles. The pattern of expression lines predicts the pattern of future persistent wrinkles. Certain intrinsic and extrinsic factors are not causative, but influence the rate, of facial wrinkling.

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.

Relationship between dermal birefringence and the skin surface roughness of photoaged human skin

The dermal degeneration accompanying photoaging is considered to promote skin roughness features such as wrinkles. Our previous study demonstrated that polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) enabled noninvasive three-dimensional evaluation of the dermal degeneration of photoaged skin as a change in dermal birefringence, mainly due to collagenous structures. Our purpose is to examine the relationship between dermal birefringence and elasticity and the skin morphology in the eye corner area using PS-SD-OCT. Nineteen healthy male subjects in their seventees were recruited as subjects. A transverse dermal birefringence map, automatically produced by the algorithm, did not show localized changes in the dermal birefringence in the part of the main horizontal wrinkle. The averaged upper dermal birefringence, however, showed depth-dependent correlation with the parameters of skin roughness significantly, suggesting that solar elastosis is a major factor for the progress of wrinkles. Age-dependent parameters of skin elasticity measured with Cutometer did not correlate with the parameters. These results suggest that the analysis of dermal birefringence using PS-SD-OCT enables the evaluation of photoaging-dependent upper dermal degeneration related to the change of skin roughness.

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.

Topical dorsal skin immersion in seawater induces apoptosis and proliferation in hairless mice

Recreational and occupational exposure to seawater (SW), have increased but the effect of SW on skin has not been elucidated. The purpose of present study was to assess the effects of SW immersion on the dorsal skin in hairless mice. Adult hairless mice were individually immersed in SW for 3 h, 6 h and 12 h; then, full-thickness dorsal skin of 2 cm diameter was excised for pathological examination (light microscope), apoptosis detection (terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling [TUNEL]) and proliferation index evaluation (immunohistochemistry). Normal and normal saline (NS)-immersed skin were used as controls. Histological examination revealed that there were randomly distributed cell deaths, presenting cell shrinkage, condensation of nuclear chromatin and eosinophilic cytoplasm in the epidermis, and neutrophil infiltration in the dermis, after SW immersion. Moreover, TUNEL showed low levels of apoptosis in normal (9.07 +/- 0.70%) and NS-immersed skin (9.99 +/- 1.22%). There was an apparent increase in the 6-h and 12-h SW immersed groups (29.90 +/- 6.85%, P < 0.01; 45.46 +/- 6.12%, P < 0.01, respectively). Ki-67 antigen was located in the basal layer of the epidermis and hair follicles, the rates of Ki-67-positive cells were 7.90 +/- 1.45% and 7.76 +/- 1.52% in normal and NS-immersed skin, respectively, and in the 12-h SW immersed group, the rate of Ki-67-positive cells reached 23.85 +/- 4.21% (threefold, P < 0.01). In each group, the rate of apoptosis was higher than that of proliferation. We conclude that SW immersion can cause time-dependent apoptosis and proliferation in the epidermis, and the overall effect of SW immersion is injury to the epidermis.

Ultraviolet B light stimulates interleukin-20 expression by human epithelial keratinocytes

The proinflammatory cytokine interleukin-20 (IL-20) may exert the majority of its activity in the skin. We examined the effect of various treatments including several forms of phototherapy on IL-20 expression using cultured normal human epithelial keratinocytes (NHEK). Broadband UVB light, recombinant (r) IL-1 and rIL-8 increased, while hydrocortisone reduced, NHEK supernatant IL-20 levels. Elevation of NHEK IL-20 mRNA and maximal supernatant IL-20 levels occurred with a UVB light dose (40 mJ cm(-2)) that reduced cell viability by approximately 50%. While this UVB light dose also elevated supernatant IL-1 alpha and IL-8 levels, antibody neutralization studies indicated that neither of these cytokines was directly responsible for this increase in IL-20 expression. However, the elevation in IL-20 levels was fully inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580, suggesting involvement of this stress signaling pathway in this UVB light response. Photodynamic therapy (PDT) with the photosensitizer lemuteporfin, UVA light, cisplatin, lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) or recombinant interferon-gamma (rIFN-gamma) either had little effect or decreased NHEK supernatant IL-20 levels. Reduced IL-20 levels paralleled the cytotoxic actions of PDT, UVA light or cisplatin and the antiproliferative effect of rIFN-gamma. Neither rIL-20 supplementation nor anti-IL-20 antibody treatments affected cell viability indicating that soluble IL-20 did not affect the short-term survival of UVB light-irradiated NHEK. Stimulation of IL-20 expression in keratinocytes by UVB light suggests that this cytokine might participate in skin responses to this ever-present environmental factor and potentially has a role in UV light-associated dermatoses.

Protection of Human Keratinocytes from UVB-Induced Inflammation Using Root Extract of Lithospermum erythrorhizon

UVB irradiation is an important inducer of biological changes in skin and can activate inflammatory reactions and apoptotic pathways, leading to skin damage. A root extract of Lithospermum erythrorhizon (SK), which has naphthoquinone pigments containing shikonin and shikonin derivatives, is known for its anti-inflammatory, anti-bacterial, and anti-tumor activity, and for its scavenging of reactive oxygen species. However, the effect of SK against UV damage is not clear. The aim of this study was to evaluate the efficacy of SK against UVB induced damage in normal human epidermal keratinocytes (NHEK). UVB-irradiated NHEK showed decreased cell viability, increased production of interleukin (IL)-1alpha, IL-6, IL-8, and tumor necrosis factor-alpha, and induced apoptosis. In an apoptosis pathway assay, UVB-irradiated NHEK showed increased caspase-3 activity, p53 and its phosphorylation at serine 15 compared with non-irradiated cells. All these effects induced by UVB irradiation were clearly inhibited by treatment with SK before and after UVB irradiation for 24 h. It is suggested that SK can protect epidermal cells against harmful effects of UVB irradiation and that SK treatment is probably beneficial for photoprotection of the skin.