UV light and skin aging

Antiphotoaging effects of solvent fractions isolated from Allomyrina dichotoma larvae extract

Skin aging is affected by a variety of factors, including ultraviolet rays, oxidative stress, medications, smoking, and genetics. Among them, photo-aging accounts for about 80% of skin aging. The present study was evaluated to verify the potential of Allomyrina dichotoma larvae, which has recently been attracting attention as an edible insect, as an anti-aging substance. UVB irradiation at 100 mJ/cm2 was sufficient to induce photo-aging of fibroblasts within 24 h, which was alleviated after treatment with 70% ethanol extract of Allomyrina dichotoma larvae extract (ADLE). To obtain an extract from ADLE, which has a relatively high content of polyphenol compounds containing physiological activity, fractional solvent extraction was carried out using organic solvents such as hexane, chloroform, ethyl acetate, and butanol. Additionally, ethyl acetate and butanol fractions contributed to the inhibition of UVB-induced ROS production, cell damage, and senescence of fibroblasts. It was also confirmed that the two fractions can regulate the expression of MMP-1 and AP-1. In particular, the ethyl acetate fraction showed an excellent effect in recovering collagen decomposed by UVB. Therefore, these results suggest that ADLE has potential as a natural insect-derived biomaterial to inhibit UVB-induced photo-aging.

Elimination of damaged mitochondria during UVB-induced senescence is orchestrated by NIX-dependent mitophagy

Skin aging is the result of two types of aging, "intrinsic aging" an inevitable consequence of physiologic and genetically determined changes and "extrinsic aging," which is dependent on external factors such as exposure to sunlight, smoking, and dietary habits. UVB causes skin injury through the generation of free radicals and other oxidative byproducts, also contributing to DNA damage. Appearance and accumulation of senescent cells in the skin are considered one of the hallmarks of aging in this tissue. Mitochondria play an important role for the development of cellular senescence, in particular stress-induced senescence of human cells. However, many aspects of mitochondrial physiology relevant to cellular senescence and extrinsic skin aging remain to be unraveled. Here, we demonstrate that mitochondria damaged by UVB irradiation of human dermal fibroblasts (HDF) are eliminated by NIX-dependent mitophagy and that this process is important for cell survival under these conditions. Additionally, UVB-irradiation of human dermal fibroblasts (HDF) induces the shedding of extracellular vesicles (EVs), and this process is significantly enhanced in UVB-irradiated NIX-depleted cells. Our findings establish NIX as the main mitophagy receptor in the process of UVB-induced senescence and suggest the release of EVs as an alternative mechanism of mitochondrial quality control in HDF.

Clinical Assessment, Diagnosis, and Management of Infraorbital Wrinkles and Pigmentation

Lower eyelid skin is unique and different from that of other areas. In addition to being an area of high exposure to the sun and elements, there are anatomic considerations and specific histologic characteristics that can cause the skin in this area to be more sensitive. These attributes can readily cause under-eye wrinkling and pigmentation. This review aims to present an updated overview of the current knowledge regarding the clinical characteristics, diagnosis, and management of wrinkles and pigmentation in this area. These disorders are usually caused by different factors, such as genetics, aging, sun exposure, lack of sleep, and stress.

ΔNp63α-mediated epigenetic regulation in keratinocyte senescence

Keratinocyte senescence contributes to skin ageing and epidermal dysfunction. According to the existing knowledge, the transcription factor ΔNp63α plays pivotal roles in differentiation and proliferation of keratinocytes. It is traditionally accepted that ΔNp63α exerts its functions via binding to promoter regions to activate or repress gene transcription. However, accumulating evidence demonstrates that ΔNp63α can bind to elements away from promoter regions of its target genes, mediating epigenetic regulation. On the other hand, several epigenetic alterations, including DNA methylation, histone modification and variation, chromatin remodelling, as well as enhancer-promoter looping, are found to be related to cell senescence. To systematically elucidate how ΔNp63α affects keratinocyte senescence via epigenetic regulation, we comprehensively compiled the literatures on the roles of ΔNp63α in keratinocyte senescence, epigenetics in cellular senescence, and the relation between ΔNp63α-mediated epigenetic regulation and keratinocyte senescence. Based on the published data, we conclude that ΔNp63α mediates epigenetic regulation via multiple mechanisms: recruiting epigenetic enzymes to modify DNA or histones, coordinating chromatin remodelling complexes (CRCs) or regulating their expression, and mediating enhancer-promoter looping. Consequently, the expression of genes related to cell cycle is modulated, and proliferation of keratinocytes and renewal of stem cells are maintained, by ΔNp63α. During skin inflammaging, the decline of ΔNp63α may lead to epigenetic dysregulation, resultantly deteriorating keratinocyte senescence.

Beneficial effect of ζ-carotene-like compounds on acute UVB irradiation by alleviating inflammation and regulating intestinal flora

ζ-Carotene is a key intermediate in the carotenoid pathway, but owing to its low content and difficulties in isolation, its application is restricted. In this study, three genes (pnCrtE, pnCrtB, and pnCrtP) in the carotenoid pathway of Antarctic moss were identified, recombined, and expressed in Escherichia coli (E. coli) BL21(DE3). The expression product was identified as one of the ζ-carotenes by UV absorbance spectrum, thin layer chromatography (TLC), and super-high-performance liquid chromatography-mass spectrum (UPLC-MS), and was called a ζ-carotene-like compound (CLC). Excessive exposure to ultraviolet B (UVB) irradiation is one of the main risk factors for skin photodamage. The purpose of this study was to investigate the preventive and therapeutic effects of CLC on UVB-induced skin photodamage in mice. In this paper, through histological examinations (hematoxylin-eosin, HE; Masson and TdT-mediated dUTP Nick-End Labeling, Tunel), biochemical index detection (reactive oxygen species, ROS; inflammatory factors; cyclobutyl pyrimidine dimers, CPDs and hyaluronic acid, HA), quantitative real time polymerase chain reaction (qRT-PCR), immunohistochemistry and intestinal content flora, etc., it is concluded that CLC has the potential to enhance skin antioxidant capacity by activating the nuclear transcription factor/antioxidant reaction element (Nrf2/ARE) pathway and also reduce skin inflammation and aging by inhibiting the mitogen-activated protein kinase (MAPK) pathway. Moreover, the regulation of intestinal flora may potentially mitigate skin damage induced by UVB radiation. This research not only developed a green and sustainable platform for the efficient synthesis of CLC but also laid a foundation for its application in functional food and medicine for skin resistance against UVB damage.

Preparation of Cod Skin Collagen Peptides/Chitosan-Based Temperature-Sensitive Gel and Its Anti-Photoaging Effect in Skin

Background

Photoaging decreases quality of life and increases the risk of skin cancer, underscoring the urgent need to explore natural, high-efficacy, anti-skin photoaging (SP) active substances.

Methods

In this study, a gel (CS/CSCPs/β-GP gel) was prepared using chitosan (CS) and sodium β-glycerophosphate (β-GP) through crosslinking with small molecular CSCPs as the carried drug. We evaluated its structural characteristics and properties. The effect of CS/CSCPs/β-GP gel on the degree of ultraviolet (UV)-induced skin aging of mice was investigated through comparative analysis of skin damage, the integrity of collagen tissues and elastic fibers, levels of reactive oxygen species (ROS) and key inflammatory factors (tumor necrosis factor [TNF]-α and interleukin [IL]-1β, IL-6, and IL-10), and tissue expression of matrix metalloproteinase-3 (MMP-3) after repeated UV irradiation in a nude mice SP model.

Results

The results showed that CS/CSCPs/β-GP gel was successfully prepared and had the desired characteristics. Compared with CSCPs alone, the CS/CSCPs/β-GP gel more evidently improved typical photoaging characteristics on mouse dorsal skin. It also increased the moisture content, causing the skin to become glossy and elastic. Pathological skin analysis revealed that this peptide-carrying gel can effectively inhibit epidermal thickening, reduce tissue inflammatory infiltration, suppress collagen fiber degradation, increase the collagen content, alleviate structural elastic fiber damage, and significantly inhibit abnormal MMP-3 expression. In addition, biochemical analysis showed that the CS/CSCPs/β-GP gel can effectively inhibit the elevated expressions of ROS and key proinflammatory factors (TNF-α, IL-1β, IL-6) in photoaging skin tissues and promote expression of the anti-inflammatory factor IL-10.

Conclusion

SP can cause many clinical skin diseases, such as solar freckle-like nevus, solar keratosis, cutaneous melanoma, and squamous cell carcinoma. CSCPs are a high-efficacy anti-SP natural active substance and CS/CSCPs/β-GP gel can synergistically enhance the CSCPs' anti-SP effect. The mechanism is likely related to the inhibited activation of ROS/nuclear transcription factor-κB signaling and the expression of downstream inflammatory factors.

Protective Effect of the Hydrophilic Extract of Polypodium leucotomos, Fernblock®, against the Synergistic Action of UVA Radiation and Benzo[a]pyrene Pollutant

Oxidative stress is a harmful effect induced on the skin by polycyclic aromatic hydrocarbons (PAH), including benzo[a]pyrene (BaP) air pollutants. This effect is amplified by the additive damaging effect of the sun, especially through the UVA light component. Besides being one of the main compounds that make up air pollution, BaP can also be found in tar, tobacco smoke, and various foods. In addition to its direct carcinogenic potential, BaP can act as a photosensitizer absorbing sunlight in the UVA range and thus generating ROS and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Fernblock^® (FB) is an aqueous extract from the leaves of Polypodium leucotomos that has been proven to exert photoprotective and antioxidant effects on skin cells. In this study, we evaluate the potential of FB to prevent the damage induced by a combination of BaP and UVA light on human keratinocyte and mouse melanocyte cell lines (HaCaT and B16-F10, respectively). In particular, we have analyzed the capacity of FB to counteract the alterations caused on cellular morphology, viability, oxidative stress and melanogenic signaling pathway activation. Our data indicate that FB prevented cell damage and reduced oxidative stress and melanogenic signaling pathway activation caused by a combination of BaP and UVA light irradiation. Altogether, our findings support the fact that FB is able to prevent skin damage caused by the exposure to a combination of UVA and the air pollutant BaP.

Cryptotanshinone protects skin cells from ultraviolet radiation-induced photoaging via its antioxidant effect and by reducing mitochondrial dysfunction and inhibiting apoptosis

The integrity of skin tissue structure and function plays an important role in maintaining skin rejuvenation. Ultraviolet (UV) radiation is the main environmental factor that causes skin aging through photodamage of the skin tissue. Cryptotanshinone (CTS), an active ingredient mianly derived from the Salvia plants of Lamiaceae, has many pharmacological effects, such as anti-inflammatory, antioxidant, and anti-tumor effects. In this study, we showed that CTS could ameliorate the photodamage induced by UV radiation in epidermal keratinocytes (HaCaT) and dermal fibroblasts (HFF-1) when applied to the cells before exposure to the radiation, effectively delaying the aging of the cells. CTS exerted its antiaging effect by reducing the level of reactive oxygen species (ROS) in the cells, attenuating DNA damage, activating the nuclear factor E2-related factor 2 (Nrf2) signaling pathway, and reduced mitochondrial dysfunction as well as inhibiting apoptosis. Further, CTS could promote mitochondrial biosynthesis in skin cells by activating the AMP-activated protein kinase (AMPK)/sirtuin-1 (SIRT1)/peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) signaling pathway. These findings demonstrated the protective effects of CTS against UV radiation-induced skin photoaging and provided a theoretical and experimental basis for the application of CTS as an anti-photodamage and anti-aging agent for the skin.

Activation of the JNKs/ATM-p53 axis is indispensable for the cytoprotection of dermal fibroblasts exposed to UVB radiation

Although UVB radiation is mainly absorbed by the epidermis, ~5-10% of its photons reach and affect the upper part of the dermis. Physiologically relevant UVB doses, able to provoke erythema, induce apoptosis in human dermal fibroblasts in vitro, as well as in the dermis of SKH-1 mice. Given the sparse and even contradictory existing information on the effect of UVB radiation on dermal fibroblasts' viability, aim of this work was to unravel the crucial signaling pathways regulating the survival of UVB-treated human dermal fibroblasts. We found that UVB radiation immediately stimulates the phosphorylation of MAPK family members, as well as Akt, and is genotoxic leading to the delayed ATM-p53 axis activation. Akt phosphorylation after UVB radiation is EGFR-mediated and EGFR inhibition leads to a further decrease of viability, while the Akt activator SC79 rescues fibroblasts to an extent by a mechanism involving Nrf2 activation. The known Nrf2 activator sulforaphane also exerts a partial protective effect, although by acting in a distinct mechanism from SC79. On the other hand, inhibition of JNKs or of the ATM-p53 axis leads to a complete loss of viability after UVB irradiation. Interestingly, JNKs activation is necessary for p53 phosphorylation, while the ATM-p53 pathway is required for the long-term activation of JNKs and Akt, reassuring the protection from UVB. Although UVB radiation results in intense and prolonged increase of intracellular ROS levels, classical anti-oxidants, such as Trolox, are unable to affect Akt, JNKs, or p53 phosphorylation and to reverse the loss of fibroblasts' viability. Collectively, here we provide evidence that the main viability-regulating UVB-triggered biochemical pathways act synergistically towards the protection of human dermal fibroblasts, with EGFR/Akt and Nrf2 serving as auxiliary anti-apoptotic machineries, while JNKs/ATM-p53 activation and interplay being overriding and indispensable for the perpetuation of cellular defense and the maintenance of cell viability.

Eisenia bicyclis Extract Repairs UVB-Induced Skin Photoaging In Vitro and In Vivo: Photoprotective Effects

Chronic exposure to ultraviolet B (UVB) is a major cause of skin aging. The aim of the present study was to determine the photoprotective effect of a 30% ethanol extract of Eisenia bicyclis (Kjellman) Setchell (EEB) against UVB-induced skin aging. By treating human dermal fibroblasts (Hs68) with EEB after UVB irradiation, we found that EEB had a cytoprotective effect. EEB treatment significantly decreased UVB-induced matrix metalloproteinase-1 (MMP-1) production by suppressing the activation of mitogen-activated protein kinase (MAPK)/activator protein 1 (AP-1) signaling and enhancing the protein expression of tissue inhibitors of metalloproteinases (TIMPs). EEB was also found to recover the UVB-induced degradation of pro-collagen by upregulating Smad signaling. Moreover, EEB increased the mRNA expression of filaggrin, involucrin, and loricrin in UVB-irradiated human epidermal keratinocytes (HaCaT). EEB decreased UVB-induced reactive oxygen species (ROS) generation by upregulating glutathione peroxidase 1 (GPx1) and heme oxygenase-1 (HO-1) expression via nuclear factor erythroid-2-related factor 2 (Nrf2) activation in Hs68 cells. In a UVB-induced HR-1 hairless mouse model, the oral administration of EEB mitigated photoaging lesions including wrinkle formation, skin thickness, and skin dryness by downregulating MMP-1 production and upregulating the expression of pro-collagen type I alpha 1 chain (pro-COL1A1). Collectively, our findings revealed that EEB prevents UVB-induced skin damage by regulating MMP-1 and pro-collagen type I production through MAPK/AP-1 and Smad pathways.

Protective effects of GLHP from Gracilaria lemaneiformis against UVB-induced photodamage in human immortalized keratinocytes cells and BALB/c mice

Our previous study showed that the water-soluble heteropolysaccharide extracted from Gracilaria lemaneiformis (GLHP) has excellent anti-inflammation and anti-oxidant properties. This study explored the efficacy of GLHP against skin anti-photoaging in human immortalized keratinocytes (HaCaT) cells and BALB/c mice under UVB irradiation. Cell viability, antiapoptotic, reactive oxygen species (ROS) scavenging activity, mitochondrial membrane potential, and cell wound scratch assays were conducted, as well as assessment of inflammation markers and sun protection factors. The in vitro results showed that GLHP pretreatment significantly inhibited UVB-induced apoptosis, reversed the decrease of cell viability via downregulating the expression of apoptosis-related protein caspase-3, accelerated the migration of HaCaT cells, and promoted wound healing. Notably, the protective effect of GLHP may be associated with the scavenging of ROS and the decrease of mitochondrial membrane potential. Moreover, GLHP pretreatment significantly restrained the upregulation of iNOS (UVB-induced inflammation marker), suppressed the expression of P-ERK and NF-κB, and decreased the activity of MMPs, suggesting that it exerts the therapeutic effects by inhibiting the MAPK/NF-κB signal pathway. Results obtained after conducting the in vivo assay confirmed that GLHP could reverse the UVB-induced increase of epidermal thickness in BALB/c mice. In conclusion, this study shows that GLHP can be utilized as a safer resource in the manufacture of anti-aging cosmetics because it exerts excellent anti-photoaging effects.

Pharmacological Activation of Autophagy Restores Cellular Homeostasis in Ultraviolet-(B)-Induced Skin Photodamage

Ultraviolet (UV) exposure to the skin causes photo-damage and acts as the primary etiological agent in photo-carcinogenesis. UV-B exposure induces cellular damage and is the major factor challenging skin homeostasis. Autophagy allows the fundamental adaptation of cells to metabolic and oxidative stress. Cellular dysfunction has been observed in aged tissues and in toxic insults to cells undergoing stress. Conversely, promising anti-aging strategies aimed at inhibiting the mTOR pathway have been found to significantly improve the aging-related disorders. Recently, autophagy has been found to positively regulate skin homeostasis by enhancing DNA damage recognition. Here, we investigated the geno-protective roles of autophagy in UV-B-exposed primary human dermal fibroblasts (HDFs). We found that UV-B irradiation to HDFs impairs the autophagy response in a time- and intensity-independent manner. However, improving autophagy levels in HDFs with pharmacological activators regulates the UV-B-induced cellular stress by decreasing the induction of DNA photo-adducts, promoting the DNA repair process, alleviating oxidative and ER stress responses, and regulating the expression levels of key cell cycle regulatory proteins. Autophagy also prevents HDFs from UV-B-induced nuclear damage as is evident in TUNEL assay and Acridine Orange/Ethidium Bromide co-staining. Salubrinal (an eIF2α phosphatase inhibitor) relieves ER stress response in cells and also significantly alleviates DNA damage and promotes the repair process in UV-B-exposed HDFs. P62-silenced HDFs show enhanced DNA damage response and also disturb the tumor suppressor PTEN/pAKT signaling axis in UV-B-exposed HDFs whereas Atg7-silenced HDFs reveal an unexpected consequence by decreasing the UV-B-induced DNA damage. Taken together, these results suggest that interventional autophagy offers significant protection against UV-B radiation-induced photo-damage and holds great promise in devising it as a suitable therapeutic strategy against skin pathological disorders.

Metabolomics study of fibroblasts damaged by UVB and BaP

We have recently shown that both UVB and BaP can induce the production of ROS, apoptosis and even cancer. However, the differences in the metabolic profiles of skin damaged by UVB, BaP or UVB combined with BaP have not been studied. Therefore, we examined the metabolic changes in the human foreskin fibroblast injured by UVB or BaP or the combination of the two, using ultra performance liquid chromatography (UPLC) coupled with quadrupole time-of-flight mass spectrometry (qTOF-MS). 24 metabolites were altered in the UVB damage group, 25 in the BaP damage group, and 33 in the UVB combined with BaP group. These alterations indicated that the metabolic mechanisms of HFF-1 cells treated with UVB or BaP are related to multiple main metabolites including glycerophosphocholine (PC), lactosylceramide (LacCer), guanidinosuccinic acid (GSA), glutathione(GSH), and lysophosphatidylcholine (LysoPC) and the main mechanisms involved glycerophospholipid and glutathione metabolism. Thus, our report provided useful insight into the underlying mechanisms of UVB and BaP damage to skin cells.

Therapeutic effect of concentrated growth factor preparation on skin photoaging in a mouse model

OBJECTIVE

To establish a nude mouse model of photoaging and study the therapeutic effect of a concentrated growth factor preparation (CGF) on skin photoaging.

METHODS

CGF was prepared from blood from Sprague-Dawley rats. A skin photoaging nude mouse model was developed using UV irradiation combined with the photosensitizer, 8-methoxypsoralen. Mice were divided randomly into seven groups (n = 6 per group): normal control, photoaging, mock treatment, saline treatment, CGF treatment, Filoca 135HA treatment, and plasma skin regeneration system irradiation (the latter two were positive controls). Body weight and skin appearance were observed and pathological changes were determined by hematoxylin and eosin staining. Fiber elasticity was evaluated by Weigert staining. Expression levels of proliferating cell nuclear antigen (PCNA) and matrix metalloproteinase 1 (MMP1) were determined by immunohistochemistry.

RESULTS

A mouse model with typical features of photoaging skin was successfully developed. CGF significantly improved the skin appearance, wrinkle scores, pathological changes, and fiber elasticity, and increased PCNA and decreased MMP1 expression levels in photoaging mice, comparable to the two positive controls.

CONCLUSION

CGF can improve the symptoms of skin photoaging in mice, suggesting that it may have applications in the treatment of skin aging in humans.

Potential Use of Amla (Phyllanthus emblica L.) Fruit Extract to Protect Skin Keratinocytes from Inflammation and Apoptosis after UVB Irradiation

Ultraviolet B (UVB) exposure is the primary risk factor for the deadliest type of skin cancer—melanoma. Incorporating natural antioxidants in skin protection products is currently a favored research theme. For this study, we selected Phyllanthus emblica L. fruit extract (PE) to assess its potential use in dermal protection against UVB-induced keratinocyte inflammation and apoptosis. High-performance liquid chromatography (HPLC) was used to investigate PE’s phytochemical constituents (ascorbic acid, ellagic acid, gallic acid, chlorogenic acid, and quercetin), while ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), total ROS, OH^•, O₂^•−, and H₂O₂-scavenging activities were used to determine the antioxidant properties. PE significantly increased the cell viability (MTT assay) and reduced apoptosis (Hoechst staining) in HaCaT cells exposed to UVB (40 mJ/cm²). PE abolished oxidative stress by reducing the production of intracellular ROS, O₂^•− and H₂O₂ production. Catalase activity (but not superoxide dismutase or glutathione peroxidase activity) was enhanced in keratinocytes incubated with PE prior to UVB exposure. Western blot analysis suggested that PE inhibited cytochrome c release and inhibited the dysregulation of PI3K/Akt without any impact on p38 activation. PE attenuated the inflammatory response to UVB irradiation by inhibiting AP-1, NF-κB, and the mediator PGE₂. Thus, PE is a candidate with great potential for use as an active ingredient in skin care products.

The impact of ultraviolet radiation on skin photoaging - review of in vitro studies

Background

Photoaging, ultra violet (UV) induced skin aging is a gradual process that depends on the time and intensity of solar radiation.

Aim

The aim of this paper was to review of the literature focused on in vitro studies explaining the mechanisms of photoaging.

Methods

Electronic databases, including PubMed and MEDLINE, were searched for in vitro studies on the importance of UV radiation in the skin photoaging process of peer‐reviewed scientific journals. Only articles available in English and full version publications were considered for this review.

Results

Three main modes of UV radiation action on skin cells which lead to photoaging, there are changes in cell metabolism, induction of oxidative stress due to the change in enzyme activity.

Conclusion

The information gathered in this publication will help to better understand the complex and multidirectional mechanism of skin photoaging, which will contribute to the development of research on potential cosmetic products that provide effective and safe sun protection or repair damage caused by UV radiation.

Ultraviolet B irradiation up-regulates MM1 and induces photoageing of the epidermis

BACKGROUND

ΔNp63α and c-Myc are key transcription factors controlling proliferation and senescence in epithelial cells. We previously reported that the c-Myc modulator MM1 and its E3 ligase, HERC3, together with the transcription factor ΔNp63α, compose a feedback loop, which regulates proliferative senescence in MCF-10A mammary epithelial cells. However, it is unknown whether this loop is involved in skin ageing. On the other hand, ultraviolet B (UVB) rays are assumed to be the main culprits for photoageing of the epidermis, but the underlying mechanisms are obscure.

AIMS

To investigate whether MM1/ΔNp63α axis is involved in UVB-induced photoageing of the epidermis.

MATERIALS AND METHODS

HaCaT human immortalized keratinocytes overexpressed with MM1, knocked down with c-Myc or irradiated with UVB, were subjected to MTT assays to measure cell proliferation, as well as RT-qPCR or immunoblot to detect the members of MM1/ΔNp63α loop and the cellular senescence markers. Meanwhile, primary normal human keratinocytes (NHKs) or mice were irradiated with UVB, followed by immunoblot analysis, SA-β-gal, haematoxylin-eosin or immunohistochemistry staining.

RESULTS

Overexpression of MM1 down-regulated ΔNp63α and induced proliferative senescence in the HaCaT cells. In the HaCaT cells, NHKs and the mouse epidermis, UVB irradiation increased MM1 mRNA level and led to a down-regulation of ΔNp63α, HERC3 and c-Myc, concomitant with cellular senescence or photoageing. Additionally, knock-down of c-Myc induced proliferative senescence in the HaCaT cells and abrogated UVB-induced cellular senescence.

CONCLUSIONS

UVB up-regulates MM1 and consequently modulates ΔNp63α and c-Myc, which may account for the proliferative senescence of keratinocytes and photoageing of the epidermis.

Skin Protective Activity of LactoSporin-the Extracellular Metabolite from Bacillus Coagulans MTCC 5856

Background: Probiotics and their products are increasingly used in skincare in recent years. Postbiotics are defined as any substance derived through the metabolic activity of a probiotic microorganism, which exerts a direct or indirect beneficial effect on the host. The extracellular metabolites of probiotic bacteria have antimicrobial activities, protect against acne, and improve skin condition. We studied skin protective activities of the extracellular metabolite (LactoSporin) of a spore-forming probiotic Bacillus coagulans MTCC 5856 in vitro. Methods: LactoSporin was evaluated for antioxidant activity by free radical scavenging activity and reactive oxygen quenching activity in human dermal fibroblast cells. Protection of fibroblasts from UV-induced apoptosis and cell death was studied by flow cytometry and neutral red uptake assays. Enzyme inhibition assays were carried out for collagenase, Elastase, and Hyaluronidase. Gene expression studies were carried out using polymerase chain reaction. Results: LactoSporin showed antioxidant activity and was found to protect skin cells from UV-induced apoptosis and cell death. LactoSporin inhibited collagenase, elastase, and hyaluronidase activity and upregulated the expression of hyaluronan synthase, transforming growth factor and epidermal growth factor, which are associated with extracellular matrix integrity. Conclusions: These results suggest LactoSporin is a skin protective postbiotic with wide application in cosmetic formulations.

Enzyme-Treated Zizania latifolia Ethanol Extract Protects from UVA Irradiation-Induced Wrinkle Formation via Inhibition of Lysosome Exocytosis and Reactive Oxygen Species Generation

Ultraviolet A (UVA) is a risk factor for photoaging and wrinkle formation. Zizania latifolia is an herbaceous perennial plant. It contains many bioactive compounds such as tricin that show antioxidative and anti-inflammatory effects. The aim of this study was to investigate the antiwrinkle effect of a mixture of hydrolytic enzyme (cellulase, hemicellulase and pectinase)-treated Z. latifolia extract (ZLE) and tricin on UVA-irradiated human dermal fibroblasts (HDFs) and SKH-1 hairless mice. Treatment of UVA-irradiated HDF cells with ZLE and tricin significantly decreased UVA induced-plasma membrane rupture, generation of ROS, expression levels of total and secreted lysosomal associated membrane protein (LAMP-1), cathepsin B and metalloproteinases (MMPs) and inhibited NF-κB activation. In the animal study, UVA-damaged epidermal and dermal tissues were repaired by the ZLE and tricin treatments. Administration of ZLE or tricin to UVA-irradiated animals recovered skin surface moisture and collagen fiber in dermal tissue. Treatment of ZLE or tricin decreased wrinkle formation, secretion of MMPs and expression levels of vascular endothelial growth factor (VEGF) and cathepsin B, and increased the expression level of collagen-1 in UVA-irradiated animals. Overall, the ZLE and tricin treatments decreased the skin damage induced by UVA irradiation via inhibition of lysosomal exocytosis and ROS generation. Therefore, ZLE and tricin are promising as antiwrinkle and antiphotoaging agents.

Topical Application of Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells in Combination with Sponge Spicules for Treatment of Photoaging

Purpose

The topical application of exosomes secreted by mesenchymal stem cells (MSC-Exos) on the skin is a very new and interesting topic in the medical field. In this study, we aimed to investigate whether marine sponge Haliclona sp. spicules (SHSs) could effectively enhance the skin delivery of human umbilical cord-derived MSC-Exos (hucMSC-Exos), and further evaluate the topical application of hucMSC-Exos combined with SHSs in rejuvenating photoaged mouse skin.

Materials and Methods

SHSs were isolated from the explants of sponge Haliclona sp. with our proprietary method, and hucMSC-Exos were prepared from the conditioned medium of hucMSCs using ultracentrifugation. The effects of SHSs on the skin penetration of fluorescently labeled hucMSC-Exos were determined using confocal microscopy in vitro (porcine skin) and in vivo (mouse skin). The therapeutic effects of hucMSC-Exos coupled with SHSs against UV-induced photoaging in mice were assessed by using microwrinkles analysis, pathohistological examination and real-time RT-PCR. We also tested the skin irritation caused by the combination of hucMSC-Exos and SHSs in guinea pigs.

Results

In vitro results showed that hucMSC-Exos could not readily penetrate through porcine skin by themselves. However, SHSs increased the skin absorption of exosomes by a factor of 5.87 through creating microchannels. Similar penetration enhancement of hucMSC-Exos was observed after SHSs treatment in mice. The combined use of hucMSC-Exos and SHSs showed significant anti-photoaging effects in mice, including reducing microwrinkles, alleviating histopathological changes, and promoting the expression of extracellular matrix constituents, whereas hucMSC-Exos alone produced considerably weaker effects. Skin irritation test showed that the combination of hucMSC-Exos and SHSs caused slight irritation, and the skin recovered shortly.

Conclusion

SHSs provide a safe and effective way to enhance the skin delivery of MSC-Exos. Moreover, the combination of MSC-Exos and SHSs may be of much use in the treatment of photoaging.

Effects of light on aging and longevity

Increasing evidence suggests an important role for light in regulation of aging and longevity. UV radiation is a mutagen that can promote aging and decrease longevity. In contrast, NIR light has shown protective effects in animal disease models. In invertebrates, visible light can shorten or extend lifespan, depending on the intensity and wavelength composition. Visible light also impacts human health, including retina function, sleep, cancer and psychiatric disorders. Possible mechanisms of visible light include: controlling circadian rhythms, inducing oxidative stress, and acting through the retina to affect neuronal circuits and systems. Changes in artificial lighting (e.g., LEDs) may have implications for human health. It will be important to further explore the mechanisms of how light affects aging and longevity, and how light affects human health.

Do We Utilize Our Knowledge of the Skin Protective Effects of Carotenoids Enough?

Due to their potential health-promoting effects, carotenoids have drawn both scientific and public attention in recent years. The primary source of carotenoids in the human skin is diet, mainly fruits, vegetables, and marine product, but they may originate from supplementation and topical application, too. In the skin, they accumulate mostly in the epidermis and act as a protective barrier to various environmental influences. Namely, the skin is exposed to numerous environmental factors, including ultraviolet radiation (UVR), air pollution, and smoking, that cause oxidative stress within the skin with consequent premature (extrinsic) aging. UVR, as the most prominent environmental factor, may cause additional detrimental skin effects, such as sunburn, DNA damage, and skin cancer. Therefore, photoprotection is the first line intervention in the prevention of premature aging and skin cancer. Numerous studies have demonstrated that carotenoids, particularly β-carotene, lycopene, lutein, and astaxanthin, have photoprotective effects, not only through direct light-absorbing properties, but also through their antioxidant effects (scavenging reactive oxygen species), as well as by regulation of UV light-induced gene expression, modulation of stress-dependent signaling, and/or suppression of cellular and tissue responses like inflammation. Interventional studies in humans with carotenoid-rich diet have shown its photoprotective effects on the skin (mostly by decreasing the sensitivity to UVR-induced erythema) and its beneficial effects in prevention and improvement of skin aging (improved skin elasticity and hydration, skin texture, wrinkles, and age spots). Furthermore, carotenoids may be helpful in the prevention and treatment of some photodermatoses, including erythropoietic protoporphyria (EPP), porphyria cutanea tarda (PCT) and polymorphous light eruption (PMLE). Although UVR is recognized as the main etiopathogenetic factor in the development of non-melanoma skin cancer (NMSC) and melanoma, and the photoprotective effects of carotenoids are certain, available studies still could not undoubtedly confirm the protective role of carotenoids in skin photocarcinogenesis.

Short-term high temperature treatment reduces viability and inhibits respiration and DNA repair enzymes in Araucaria angustifolia cells

We evaluated the effect of global warming on Araucaria angustifolia (Bert.) O. Kuntze, a critically endangered native tree of Southern Brazil, by studying the effects of short-term high temperature treatment on cell viability, respiration and DNA repair of embryogenic cells. Compared with control cells grown at 25°C, cell viability was reduced by 40% after incubation at 30 and 37°C for 24 and 6 h, respectively, while 2 h at 40 and 42°C killed 95% of the cells. Cell respiration was unaffected at 30-37°C, but dramatically reduced after 2 h at 42°C. The in vitro activity of enzymes of the base excision repair (BER) pathway was determined. Apurinic/apyrimidine endonuclease, measured in extracts from cells incubated for 2 h at 42°C, was completely inactivated while lower temperatures had no effect. The activities of three enzymes of the mitochondrial BER pathway were measured after 30-min preincubation of isolated mitochondria at 25-40°C and one of them, uracil glycosylase, was completely inhibited at 40°C. We conclude that cell viability, respiration and DNA repair have different temperature sensitivities between 25 and 37°C, and that they are all very sensitive to 40 or 42°C. Thus, A. angustifolia will likely be vulnerable to the short-term high temperature events associated with global warming.

Induction of angiogenic and inflammation-associated dermal biomarkers following acute UVB exposure on bio-engineered pigmented dermo-epidermal skin substitutes in vivo

PURPOSE

Ultraviolet (UV) radiation adversely affects skin health at cellular and molecular levels. Hence, UV radiation can directly induce inflammatory responses in the dermis by inducing erythema, edema, inflammation, dermal fibroblasts alterations, and extracellular matrix modifications.

METHODS

Human keratinocytes, melanocytes, and fibroblasts were isolated from skin biopsies, cultured, and expanded in vitro. Fibroblasts were seeded into collagen type I hydrogels that were subsequently covered by keratinocytes and melanocytes. These pigmented dermo-epidermal skin substitutes (pigmDESS) were transplanted for 5 weeks onto full-thickness skin wounds on the back of immuno-incompetent rats, exposed to a single UVB dose of 250 mJ/cm² or unexposed and excised after 1 week. The effects onto the dermis were assessed regarding cell number, cell phenotype, and cell proliferation. Local inflammation by granulocytes (HIS48) or macrophages (CD11b, iNOS) was analyzed by immunohistochemistry staining.

RESULTS

We observed a significantly enhanced ingrowth rate of blood capillaries, but not of lymphatic capillaries at 1 week post-irradiation. Moreover, the enhanced vascularization of pigmDESS after UVB exposure was concomitant with a high infiltration of granulocytes and monocytes/macrophages to the dermal part of grafts. In addition, a heterogeneous expression of HIF-1α and TNFα was detected at this early phase after UVB exposure. In local cellular response examination, results only show a moderate cell proliferation in the dermis.

CONCLUSIONS

We were able to define early markers of UVB-induced effects in the dermis of pigmDESS. Overall, a single UVB dose induces temporary acute angiogenic and immune responses during the early post-irradiation phase in vivo.

Protective Effects of Euphrasia officinalis Extract against Ultraviolet B-Induced Photoaging in Normal Human Dermal Fibroblasts

Ultraviolet (UV) radiation induces skin photoaging, which is associated with the elevation of matrix metalloproteinases (MMPs) and the impairment of collagen. The Euphrasia species play a well-known role in the treatment of certain eye disorders through their anti-oxidative and anti-inflammatory activities. However, their protective activity toward UVB-induced damage remains unclear. In the present study, we investigated the protective effect of Euphrasia officinalis (95% ethanol extract) on UVB-irradiated photoaging in normal human dermal fibroblasts (NHDFs). Our results show that Euphrasia officinalis extract exhibited obvious reactive oxygen species (ROS) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, enhanced NHDF cell migration, and reduced UVB-induced apoptosis. The UVB-induced increases in MMP-1 and MMP-3 and decrease in type I procollagen were ameliorated by Euphrasia officinalis treatment, which worked by suppressing the mitogen-activated protein kinase (MAPK) and nuclear transcription factor activator protein 1 (AP-1) signaling pathways. Taken together, our data strongly suggest that Euphrasia officinalis ethanol extract could reduce UVB-induced photoaging by alleviating oxidative stress, proinflammatory activity, and cell apoptosis.

Scopoletin downregulates MMP‑1 expression in human fibroblasts via inhibition of p38 phosphorylation

Irradiation of keratinocytes by ultraviolet B induces cytokine production, which in turn activates fibroblasts to produce cytokines and increase matrix metallopeptidase (MMP)‑1 protein expression. The present study investigated the effect and potential mechanisms of scopoletin on the regulation of MMP‑1 expression in fibroblasts. Scopoletin was isolated from Artemisia capillaris crude extract. Treatment of fibroblasts with scopoletin resulted in a decrease in the protein expression of MMP‑1 following stimulation with human keratinocyte (HaCaT) conditioned medium. To further explore the mechanism underlying this effect, the expression levels of proteins in the mitogen‑activated protein kinase (MAPK) and nuclear factor‑κB (NF‑κB) signaling pathways were evaluated via western blot analysis. The mRNA expression levels of interleukin (IL)‑1α and tumor necrosis factor (TNF) α were evaluated via reverse transcription‑quantitative polymerase chain reaction. The effect of scopoletin on cell viability was assessed with the MTT assay. The results demonstrated that scopoletin treatment markedly decreased MMP‑1, IL‑1α and TNFα mRNA expression in fibroblasts stimulated with HaCaT conditioned medium (40 mJ/cm2), without any apparent cell cytotoxicity, and in a dose‑dependent manner. In addition, western blot analysis demonstrated that scopoletin reduced the phosphorylation of p38 MAPK in fibroblasts. In summary, the present study demonstrated that scopoletin inhibited MMP‑1 and proinflammatory cytokine expression by inhibiting p38 MAPK phosphorylation. These findings suggest that scopoletin may have potential as a therapeutic agent to prevent and treat photoaging of the skin.

Aquatide Activation of SIRT1 Reduces Cellular Senescence through a SIRT1-FOXO1-Autophagy Axis

Ultraviolet (UV) irradiation is a relevant environment factor to induce cellular senescence and photoaging. Both autophagy- and silent information regulator T1 (SIRT1)-dependent pathways are critical cellular processes of not only maintaining normal cellular functions, but also protecting cellular senescence in skin exposed to UV irradiation. In the present studies, we investigated whether modulation of autophagy induction using a novel synthetic SIRT1 activator, heptasodium hexacarboxymethyl dipeptide-12 (named as Aquatide), suppresses the UVB irradiation-induced skin aging. Treatment with Aquatide directly activates SIRT1 and stimulates autophagy induction in cultured human dermal fibroblasts. Next, we found that Aquatide-mediated activation of SIRT1 increases autophagy induction via deacetylation of forkhead box class O (FOXO) 1. Finally, UVB irradiation-induced cellular senescence measured by SA-β-gal staining was significantly decreased in cells treated with Aquatide in parallel to occurring SIRT1 activation-dependent autophagy. Together, Aquatide modulates autophagy through SIRT1 activation, contributing to suppression of skin aging caused by UV irradiation.

Alleviation of Ultraviolet B-Induced Photodamage by Coffea arabica Extract in Human Skin Fibroblasts and Hairless Mouse Skin

Coffea arabica extract (CAE) containing 48.3 ± 0.4 mg/g of chlorogenic acid and a trace amount of caffeic acid was found to alleviate photoaging activity in human skin fibroblasts. In this study, polyphenol-rich CAE was investigated for its antioxidant and antiinflammatory properties, as well as for its capability to alleviate ultraviolet B (UVB)-induced photodamage in BALB/c hairless mice. The results indicated that 500 μg/mL of CAE exhibited a reducing power of 94.7%, ferrous ion chelating activity of 46.4%, and hydroxyl radical scavenging activity of 20.3%. The CAE dose dependently reduced UVB-induced reactive oxygen species (ROS) generation in fibroblasts. Furthermore, CAE inhibited the UVB-induced expression of cyclooxygenase-2 and p-inhibitor κB, and the translocation of nuclear factor-kappa B (NF-κB) to the nucleus of fibroblasts. In addition, CAE alleviated UVB-induced photoaging and photodamage in BALB/c hairless mice by restoring the collagen content and reduced UVB-induced epidermal hyperplasia. CAE also inhibited UVB-induced NF-κB, interleukin-6, and matrix metalloproteinase-1 expression in the hairless mouse skin. The results indicated that CAE exhibits antiphotodamage activity by inhibiting UV-induced oxidative stress and inflammation. Therefore, CAE is a candidate for use in antioxidant, antiinflammatory, and antiphotodamage products.

Cryptomphalus aspersa Mollusc Egg Extract Promotes Regenerative Effects in Human Dermal Papilla Stem Cells

The aim of this study was to test, by an in vitro approach, whether a natural extract derived from eggs of the mollusc Cryptomphalus aspersa (e-CAF) that seems to present regenerative properties, can enhance the mobilization of human hair dermal papilla cells (HHDPCs) and play a role on tissue repair and regeneration. We have tested HHDPCs proliferation by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium-bromide (MTT) assay; cell migration by using a wound healing assay, as well as the modulation of the expression of cytoskeletal (F-actin and vimentin) and cell adhesion to the extracellular matrix (ECM) (vinculin and P-FAK) proteins. We also explored whether e-CAF could lead HHDPCs to keratinocytes and/or fibroblasts by evaluating the expression of specific markers. We have compared these e-CAF effects with those induced by TGFβ₁, implicated in regulation of cell proliferation and migration. e-CAF promotes proliferation and migration of HHDPCs cells in a time- and dose-dependent manner; it also increases the migratory behavior and the expression of adhesion molecules. These results support the fact that e-CAF could play a role on skin regeneration and be used for the prevention or repair of damaged tissue, either due to external causes or as a result of cutaneous aging.

Molecular mechanisms of UVB-induced senescence of dermal fibroblasts and its relevance for photoaging of the human skin

Due to its ability to cross the epidermis and reach the upper dermis where it causes cumulative DNA damage and increased oxidative stress, UVB is considered the most harmful component of sunlight to the skin. The consequences of chronic exposition to UVB are related to photoaging and photocarcinogenesis. There are limitations to the study of human skin aging and for this reason the use of models is required. Human dermal fibroblasts submitted to mild and repeated doses of UVB are considered a versatile model to study UVB effects in the process of skin photoaging, which depends on the accumulation of senescent cells, in particular in the dermis. Here we provide updated information about the current model of UVB-induced senescence with special emphasis on the process of protein quality control.

[Epidermal aging and anti-aging strategies]

Epithelial senescence is a complex process depending on intrinsic as well as extrinsic factors (e.g., UV or IR light, tobacco smoke) and must be seen in the context of the aging process especially of the corium and the subcutis. Morphological alterations become apparent in the form of epithelial atrophy, structural changes within the basal membrane, and a decrease in cell count of melanocytes and Langerhans cells. Signs of cellular senescence are reduced proliferation of keratinocytes, cumulation of dysplastic keratinocytes, various mutations (e.g., c-Fos/c-Jun, STAT3, FoxO1), as well as multiple lipid or amino acid metabolic aberrations (e.g., production of advanced glycation endproducts). This causes functional changes within the physical (lipid deficiency, water distribution dysfunction, lack of hygroscopic substances), chemical (pH conditions, oxygen radicals), and immunological barrier. Prophylactically, barrier-protective care products, antioxidant substances (e.g., vitamin C, B3, E, polyphenols, flavonoids), sunscreen products/measurements, and retinoids are used. For correcting alterations in aged epidermis, chemical peelings (fruit acids, β-hydroxy acid, trichloroacetic acid, phenolic compounds), non-ablative (IPL, PDL, Nd:YAG) as well as ablative (CO2, Erbium-YAG) light-assisted methods are used.

Conditioned medium from human bone marrow-derived mesenchymal stem cells promotes skin moisturization and effacement of wrinkles in UVB-irradiated SKH-1 hairless mice

BACKGROUND

Mesenchymal stem cells (MSCs) are promising therapeutic agents for various diseases.

AIMS

To investigate the effects of conditioned medium from human bone marrow-derived mesenchymal stem cells (MSC-CdM) on pro-collagen production and wrinkle formation, we performed in vitro and in vivo experiments.

METHODS

We assessed the effects of MSC-CdM on proliferation and photo-aging in human dermal fibroblasts after UVB exposure using enzyme activity assays for collagen type I secretion and MMP-1. To determine the effect of topically applied MSC-CdM on wrinkle formation, MSC-CdM (1% and 10%) and vehicle (propylene glycol: ethanol, 7 : 3) were applied to the dorsal skin of UVB-irradiated hairless mice for 8 weeks. We examined the effects on wrinkle formation by assessing visual skin grading, replica, tape stripping, transepidermal water loss (TEWL), and skin hydration measurement. We also examined histology of the lesions using hematoxylin-eosin, Masson's trichrome, and immunohistochemical staining.

RESULTS

MSC-CdM markedly reduced UV-induced matrix metalloproteinase-1 expression and increased pro-collagen synthesis in a dose-dependent manner. Our findings suggest that MSC-CdM induces repair of dermal damage and effacement of wrinkles on UVB-irradiated hairless mice through protective effect of hydration.

CONCLUSION

These results support an anti-wrinkle effect of MSC-CdM that involves increased collagen synthesis and suggest that MSC-CdM might be a potential candidate for preventing UV-induced skin damage.

A systematic review on the role of environmental toxicants in stem cells aging

Stem cells are an important target for environmental toxicants. As they are the main source for replenishing of organs in the body, any changes in their normal function could affect the regenerative potential of organs, leading to the appearance of age-related disease and acceleration of the aging process. Environmental toxicants could exert their adverse effect on stem cell function via multiple cellular and molecular mechanisms, resulting in changes in the stem cell differentiation fate and cell transformation, and reduced self-renewal capacity, as well as induction of stress-induced cellular senescence. The present review focuses on the effect of environmental toxicants on stem cell function associated with the aging process. We categorized environmental toxicants according to their preferred molecular mechanism of action on stem cells, including changes in genomic, epigenomic, and proteomic levels and enhancing oxidative stress. Pesticides, tobacco smoke, radiation and heavy metals are well-studied toxicants that cause stem cell dysfunction via induction of oxidative stress. Transgenerational epigenetic changes are the most important effects of a variety of toxicants on germ cells and embryos that are heritable and could affect health in the next several generations. A better understanding of the underlying mechanisms of toxicant-induced stem cell aging will help us to develop therapeutic intervention strategies against environmental aging. Meanwhile, more efforts are required to find the direct in vivo relationship between adverse effect of environmental toxicants and stem cell aging, leading to organismal aging.

Dandelion Extracts Protect Human Skin Fibroblasts from UVB Damage and Cellular Senescence

Ultraviolet (UV) irradiation causes damage in skin by generating excessive reactive oxygen species (ROS) and induction of matrix metalloproteinases (MMPs), leading to skin photoageing. Dandelion extracts have long been used for traditional Chinese medicine and native American medicine to treat cancers, hepatitis, and digestive diseases; however, less is known on the effects of dandelion extracts in skin photoageing. Here we found that dandelion leaf and flower extracts significantly protect UVB irradiation-inhibited cell viability when added before UVB irradiation or promptly after irradiation. Dandelion leaf and flower extracts inhibited UVB irradiation-stimulated MMP activity and ROS generation. Dandelion root extracts showed less action on protecting HDFs from UVB irradiation-induced MMP activity, ROS generation, and cell death. Furthermore, dandelion leaf and flower but not root extracts stimulated glutathione generation and glutathione reductase mRNA expression in the presence or absence of UVB irradiation. We also found that dandelion leaf and flower extracts help absorb UVB irradiation. In addition, dandelion extracts significantly protected HDFs from H₂O₂-induced cellular senescence. In conclusion, dandelion extracts especially leaf and flower extracts are potent protective agents against UVB damage and H₂O₂-induced cellular senescence in HDFs by suppressing ROS generation and MMP activities and helping UVB absorption.

The protective effect of 18β-Glycyrrhetinic acid against UV irradiation induced photoaging in mice

It has been confirmed that repeated exposure of skin to ultraviolet (UV) radiation results in cutaneous oxidative stress and inflammation, which act in concert to cause premature skin aging, well known as photoaging. 18β-Glycyrrhetinic acid (GA), widely used to treat various tissue inflammations, is the main active component of licorice root, and has also been shown to possess favorable anti-oxidative property and modulating immunity function. In the present study, we investigated the potential protective effect of GA on UV-induced skin photoaging in a mouse model. During the experimental period of ten consecutive weeks, the dorsal depilated skin of mice was treated with topical GA for 2 hours prior to UV irradiation. The results showed that GA pretreatment significantly alleviated the macroscopic and histopathological damages in mice skin caused by UV. Meanwhile, the data also indicated that GA markedly up-regulated the activities of the antioxidant enzymes (SOD, GSH-Px), and increased the content of skin collagen, while obviously decreased malonaldehyde level and inhibited high expressions of matrix metalloproteinase-1 (MMP-1) and -3 (MMP-3), as well as down-regulated the expression of inflammatory cytokines such as IL-6, TNF-α and IL-10. Taken together, these findings amply demonstrate that GA observably attenuates UV-induced skin photoaging mainly by virtue of its antioxidative and anti-inflammatory properties, as well as regulating the abnormal expression of MMP-1 and MMP-3.