Effects of solar radiation on cutaneous detoxification pathways

Seabuckthorn pulp extract alleviates UV-B-induced skin photo-damage by significantly reducing oxidative stress-mediated endoplasmic reticulum stress and DNA Damage in human primary skin fibroblasts and Balb/c mice skin

Skin homeostasis is predominantly compromised by exposure to UV-B irradiation, leading to several physiopathological processes at cellular and tissue levels that deteriorate skin function and integrity. The current study investigated the photo-protective role of seabuckthorn fruit pulp (SBT) extract against UV-B-induced damage in primary human skin fibroblasts (HDFs) and Balb/C mice skin. We subjected HDFs and Balb/C mice to UV-B irradiation and measured multiple cellular damage indicators. We found that UV-B-irradiated HDFs treated with SBT had a considerably greater survival rate than cells exposed to UV-B radiation alone. The UV-B irradiation-induced ROS generation led to the degradation of the extracellular matrix, inflammation, DNA damage, endoplasmic reticulum (ER) stress, and apoptosis. SBT treatment significantly reduced these manifestations. Topical application of SBT alleviated UV-B-induced epidermal thickening, leukocyte infiltration, and degradation of extracellular matrix in Balb/c mice skin. Based on our results, we conclude that SBT has the potential to be developed as a therapeutic/cosmetic remedy for the prevention of skin photo-damage.

Investigating the Impact of Sun/UV Protection and Ease of Skin Tanning on the Risk of Pseudoexfoliation Glaucoma: A Mendelian Randomization Study

Purpose

To investigate the potential causal associations between the use of sun/ultraviolet (UV) protection and ease of skin tanning and the risk of pseudoexfoliation glaucoma (PXG) in European populations.

Methods

Single nucleotide polymorphisms (SNPs) associated with the use of sun/UV protection and ease of skin tanning were selected from the UK Biobank genome-wide association study database consisting of 498,751 European participants. SNPs of PXG were obtained from the FinnGen study including 3424 PXG cases and 326,434 controls. Two-sample Mendelian randomization (MR) analyses were performed to assess the association between the use of sun/UV protection and ease of skin tanning and risk of PXG.

Results

Inverse variance weighted regression of genetic susceptibility predicted that both use of sun/UV protection and ease of skin tanning were potentially positively associated with the decreased risk of PXG in the European ancestry (use of sun/UV protection: odds ratio [OR] = 0.47; 95% confidence interval [CI], 0.24-0.92; P = 0.028; ease of skin tanning: OR = 0.81; 95% CI, 0.67-0.97; P = 0.025).

Conclusions

We found genetic evidence supporting a potential causal association between UV protection and a decreased risk of PXG in European population. Further research will help elucidate the underlying mechanisms and promote UV protection for eyes, especially in people with a high risk of PXG.

Preparation of enzymolysis porous corn starch composite microcapsules embedding organic sunscreen agents and its UV protection performance and stability

In this paper, a natural composite wall material sunscreen microcapsule was prepared, which significantly improved the SPF value and photostability of the embedded sunscreen agents. Using modified porous corn starch and whey protein as wall materials, the sunscreen agents 2-[4-(diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl ester and ethylhexyl methoxycinnamate were embedded by adsorption, emulsion, encapsulation and solidification. The embedding rate of the obtained sunscreen microcapsules was 32.71 % and the average size was 7.98 μm; the enzymatic hydrolyzed starch formed a porous structure, its X-ray diffraction pattern did not change significantly, and the specific volume and oil absorption rate increased by 39.89 % and 68.32 %, respectively, compared with those before enzymatic hydrolyzed; The porous surface of the starch after embedding the sunscreen was covered and sealed with whey protein. 120 h sunscreen penetration rate was lower than 12.48 %; Compared with the lotion containing the same amount of sunscreen but not encapsulated, the SPF value of the lotion containing sunscreen microcapsules increased by 62.24 %, and the photostability of sunscreen microcapsules increased by 66.28 % within 8 h under the irradiation intensity of 25 w/m². The wall material and the preparation method are natural and environmentally friendly, and have a good application prospect in low-leakage drug delivery system.

Obacunone Photoprotective Effects against Solar-Simulated Radiation-Induced Molecular Modifications in Primary Keratinocytes and Full-Thickness Human Skin

Solar radiation can cause damage to the skin, leading to various adverse effects such as sunburn, reactive oxygen species production, inflammation, DNA damage, and photoaging. To study the potential of photoprotective agents, full-thickness skin models are increasingly being used as in vitro tools. One promising approach to photoprotection involves targeting the redox-sensitive transcription factor Nrf2, which is responsible for regulating various cellular defense mechanisms, including the antioxidant response, inflammatory signaling, and DNA repair. Obacunone, a natural triterpenoid, has been identified as a potent Nrf2 agonist. The present study aims to evaluate the relevance of full-thickness (FT) skin models in photoprotection studies and to explore the potential photoprotective effects of obacunone on those models and in human keratinocytes. Phenion^® full-thickness skin models and keratinocytes were incubated with increasing concentrations of obacunone and irradiated with solar-simulated radiation (SSR). Various photodamage markers were evaluated, including histological integrity, oxidative stress, apoptosis, inflammation, photoaging-related dermal markers, and photocarcinogenesis markers. Increasing doses of SSR were found to modulate various biomarkers related to sun damage in the FT skin models. However, obacunone attenuated cytotoxicity, inflammation, oxidative stress, sunburn reaction, photoaging, and photocarcinogenesis in both keratinocytes and full thickness skin models exposed to SSR. These results suggest that obacunone may have potential as a photoprotective agent for preventing the harmful effects of solar radiation on the skin.

Photoprotective Effects of Dendrobium nobile Lindl. Polysaccharides against UVB-Induced Oxidative Stress and Apoptosis in HaCaT Cells

Acute ultraviolet (UV)-B radiation is the major external factor causing photodamage. In this study, we aimed to determine the effects of Dendrobium nobile Lindl. polysaccharides (DNPs) on photodamage in HaCaT keratinocytes after UVB irradiation and the underlying mechanisms. We found that DNPs significantly attenuated the decline in the viability and proliferation of HaCaT cells after UVB irradiation. Moreover, DNPs scavenged reactive oxygen species (ROS), improved the activities of endogenous antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase, and reduced the levels of malondialdehyde, while partially attenuating cell cycle arrest, suggesting their antioxidant and anti-apoptotic properties. The mitogen-activated protein kinase (MAPK) pathway was found to be important for the attenuation of UVB-induced photodamage in the HaCaT cells. Furthermore, DNPs exerted cytoprotective effects by downregulating UVB-induced ROS-mediated phosphorylation of MAPKs, including p38, c-Jun N-terminal kinase, and extracellular signal-regulated kinase, and by inhibiting p53 expression as well as the apoptotic cascade response. Therefore, DNPs ameliorated UVB-induced oxidative damage and apoptosis in HaCaT cells via the regulation of MAPKs. Our findings thus highlight the Dendrobium nobile Lindl polysaccharides as promising therapeutic candidates for UVB-induced photodamage.

Assessment of Inflammation in 3D Reconstructed Human Skin Exposed to Combined Exposure to Ultraviolet and Wi-Fi Radiation

In the human environment, the increasing exposure to radiofrequency (RF) radiation, especially that emitted by wireless devices, could be absorbed in the body. Recently, mobile and emerging wireless technologies (UMTS, DECT, LTE, and Wi-Fi) have been using higher frequencies than 2G GSM systems (900/1800 MHz), which means that most of the circulating RF currents are absorbed into the skin and the superficial soft tissue. The harmful genotoxic, cytotoxic, and mutagenic effects of solar ultraviolet (UV) radiation on the skin are well-known. This study aimed at investigating whether 2422 MHz (Wi-Fi) RF exposure combined with UV radiation in different sequences has any effect on the inflammation process in the skin. In vitro experiments examined the inflammation process by cytokines (IL-1α, IL-6, IL-8) and MMP-1 enzyme secretion in a 3D full-thickness human skin model. In the first study, UV exposure was immediately followed by RF exposure to measure the potential additive effects, while in the second study, the possible protective phenomenon (i.e., adaptive response) was investigated when adaptive RF exposure was challenged by UV radiation. Our results suggest that 2422 MHz Wi-Fi exposure slightly, not significantly increased cytokine concentrations of the prior UV exposure. We could not detect the adaptive response phenomenon.

Purple Corn Silk Extract Attenuates UVB-Induced Inflammation in Human Keratinocyte Cells

UVB is a causative factor for severe skin damage, such as cell aging, death, and inflammation. UVB easily permeates into the epidermis layer of human skin, which is mainly composed of keratinocyte cells. In previous results, we found that purple corn silk (PCS) extract showed the potential to inhibit keratinocyte damages of UVB-treated cells. Thus, in this study, we aimed to evaluate the preventive effects of PCS extract against the inflammation of UVB-induced keratinocyte cells using the HaCaT cell line. HaCaT cells were treated with PCS extract at various concentrations for 1 h, then exposed to 25 mJ/cm2 UVB before subsequent experiments. Fragmented DNA was observed using flow cytometry. The inflammatory response was investigated through NF-κB activity by immunofluorescence staining and related protein expression by Western blotting. The results demonstrated that PCS extract decreased the sub-G1 DNA content. Interestingly, PCS extract attenuated NF-κB activity via suppressed NF-κB nuclear translocation and protein expression. Moreover, PCS extract remarkably decreased c-Jun phosphorylation and decreased proinflammatory cytokines, along with iNOS and COX-2 levels in UVB-treated cells compared to the UVB-control group. This finding exhibited that PCS extract minimized inflammation in keratinocyte cells induced by UVB radiation.

Carbon Nanofibers versus Silver Nanoparticles: Time-Dependent Cytotoxicity, Proliferation, and Gene Expression

Carbon nanofibers (CNFs) are one-dimensional nanomaterials with excellent physical and broad-spectrum antimicrobial properties characterized by a low risk of antimicrobial resistance. Silver nanoparticles (AgNPs) are antimicrobial metallic nanomaterials already used in a broad range of industrial applications. In the present study these two nanomaterials were characterized by Raman spectroscopy, transmission electron microscopy, zeta potential, and dynamic light scattering, and their biological properties were compared in terms of cytotoxicity, proliferation, and gene expression in human keratinocyte HaCaT cells. The results showed that both AgNPs and CNFs present similar time-dependent cytotoxicity (EC50 of 608.1 µg/mL for CNFs and 581.9 µg/mL for AgNPs at 24 h) and similar proliferative HaCaT cell activity. However, both nanomaterials showed very different results in the expression of thirteen genes (superoxide dismutase 1 (SOD1), catalase (CAT), matrix metallopeptidase 1 (MMP1), transforming growth factor beta 1 (TGFB1), glutathione peroxidase 1 (GPX1), fibronectin 1 (FN1), hyaluronan synthase 2 (HAS2), laminin subunit beta 1 (LAMB1), lumican (LUM), cadherin 1 CDH1, collagen type IV alpha (COL4A1), fibrillin (FBN), and versican (VCAN)) treated with the lowest non-cytotoxic concentrations in the HaCaT cells after 24 h. The AgNPs were capable of up-regulating only two genes (SOD1 and MMP1) while the CNFs were very effective in up-regulating eight genes (FN1, MMP1, CAT, CDH1, COL4A1, FBN, GPX1, and TGFB1) involved in the defense mechanisms against oxidative stress and maintaining and repairing tissues by regulating cell adhesion, migration, proliferation, differentiation, growth, morphogenesis, and tissue development. These results demonstrate CNF nanomaterials' unique great potential in biomedical applications such as tissue engineering and wound healing.

Protective effect of purple corn silk extract against ultraviolet-B-induced cell damage in human keratinocyte cells

Ultraviolet-B (UVB) could lead to inflammation and cell death induction. Purple corn silk (PCS), part of female flower of corn has multiple pharmacological properties. This investigation focused on determining the preventive effects of PCS extract on human keratinocyte HaCaT cell damage induced by UVB irradiation. Cells were irradiated with 25 mJ/cm² UVB after pre-treated with PCS extract for 1 h. Then, the cells were then placed in culture medium followed by subsequent experiments. Cell survival was determined by MTT assay. The immunofluorescence, DCFH-DA, JC-1, and Hoeshst33342 staining assays were used to determine γ-H2AX, intracellular reactive oxygen species (ROS), membrane potential of mitochondria, and nuclear condensation, respectively. Western blot analysis was used to investigate the proteins expression. The statistically significant comparison was calculated by analysis of variance at P < 0.05. The fluorescence and protein band intensity were quantified by Image J densitometer. The results indicated cell survival was increased upon PCS extract pretreatment followed by UVB exposure. PCS extract decreased γ-H2AX expression, intracellular ROS overproduction, and nuclear condensation in cells induced by UVB. Furthermore, The PCS extract pretreatment attenuated apoptosis response through stabilized mitochondrial membrane potential, decreased apoptosis mediator proteins including Bax, Bak, cleaved-caspases, and cleaved-PARP, and increased Bcl-2 and Bcl-xL expression comparing to the UVB-treated control. This finding demonstrated that the PCS extract can reduce the deleterious effects from UVB exposure through decreased intracellular ROS, DNA damage, and apoptosis induction on HaCaT cells.

Melaleuca leucadendron (L.) L. flower extract exhibits antioxidant and photoprotective activities in human keratinocytes exposed to ultraviolet B radiation

Recently, there has been a demand for the replacement of chemical sunscreens with natural compounds that could prevent or restore UV-induced skin damage. Here, we investigated the photoprotective influence of the Melaleuca leucadendron ethanolic flower extract (EEMec) on factors involved in cellular and molecular UVB-induced oxidative stress in human skin keratinocytes (HaCaT). The phytochemical constituents, antioxidant potential by DPPH assay, content of total phenolic and flavonoid compounds in EEMec were evaluated. HaCaT cells were treated with EEMec followed by irradiation with UVB. CAT activity; GSH and ROS levels; and SOD1, GPx, CAT and COX-2 expression assays were employed to verify the oxidative stress, as well as EEMec effect on transmembrane transport, and pro-inflammatory and pro-apoptotic protein expression. EEMec reverted the viability loss of HaCaT cells after irradiation with UVB, exhibited significant antioxidant capacity and free radical scavenging activity in vitro, inhibited COX-2 expression and ensure protection of DNA-damage. EEMec shown a great photoprotective property to prevent keratinocytes damage induced by UV radiation and, thus a candidate potential to application as an adjuvant in sunscreen formulations as a strategy to reduce risk of sunburn and prevent skin diseases associated with UV-induced inflammation and cancer.

Fabrication of polyvinyl alcohol hydrogels with excellent shape memory and ultraviolet-shielding behavior via the introduction of tea polyphenols

Shape-memory hydrogels are expected to be used not only in an ordinary environment, but also in some special environments, such as under ultraviolet (UV) irradiation. Developing novel shape-memory polyvinyl alcohol (PVA)/tea polyphenol (TP) hydrogels with UV shielding performance is realistically important in application fields. Herein, we designed functional PVA/TP hydrogels with excellent UV-shielding ability and improved the shape memory on hot water stimuli. This study shows that the abundant hydrogen bonds between PVA and TP are the source of shape memory. The PVA hydrogels with 8 wt% TP loading could approximately recover their original shape after deformation when immersed in water at 50 °C for 30 s. Meanwhile, the hydrogels also had excellent UV shielding capacity. After ageing under UV for 16 days, the observed shape of the hydrogel with 8 wt% TP loading retained 74.7% of the original, and the hydrogel could effectively protect the skin of mice from damage under 10 mW cm-2 UV irradiation. With the understanding of the UV-shielding behavior of hydrogels, this study has been able to generate biomedical materials for human skin protection, specifically skin covering the joint areas, where shape memory of the applied materials is essential.

Regulation of Anti-Oxidative, Anti-Inflammatory, and Anti-Apoptotic Activity of Advanced Cooling Composition (ACC) in UVB-Irradiated Human HaCaT Keratinocytes

We recently demonstrated that advanced cooling composition (ACC) has effective ingredients that exhibit anti-inflammatory effects in RAW 264.7 cells stimulated with lipopolysaccharide (LPS) and exhibit strong antimicrobial effects on Pseudomonas aeruginosa, Staphylococcus aureus, MRSA (methicillin-resistant Staphylococcus aureus), Candida albicans, and Streptococcus mutans. To further investigate whether ACC has beneficial effects in ultraviolet B (UVB)-irradiated human keratinocytes (HaCaT cells), HaCaT cells were pretreated with ACC prior to UVB irradiation. Our data showed that ACC, which is effective at 100 µg/mL, is nontoxic and has an antioxidative effect against UVB-induced intracellular reactive oxygen species (ROS) in HaCaT cells. In addition, ACC exerts cytoprotective effects against UVB-induced cytotoxicity in HaCaT cells by inhibiting abnormal inflammation and apoptosis through the regulation of mitogen-activated protein kinase (MAPK) signals, such as jun-amino-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK). Therefore, these results indicate that ACC is a potentially beneficial raw material that possesses antioxidative, anti-inflammatory, and antiapoptotic effects against UVB-induced keratinocytes and may have applications in skin health.

Emerging Strategies to Protect the Skin from Ultraviolet Rays Using Plant-Derived Materials

Sunlight contains a significant amount of ultraviolet (UV) ray, which leads to various effects on homeostasis in the body. Defense strategies to protect from UV rays have been extensively studied, as sunburn, photoaging, and photocarcinogenesis are caused by excessive UV exposure. The primary lines of defense against UV damage are melanin and trans-urocanic acid, which are distributed in the stratum corneum. UV rays that pass beyond these lines of defense can lead to oxidative damage. However, cells detect changes due to UV rays as early as possible and initiate cell signaling processes to prevent the occurrence of damage and repair the already occurred damage. Cosmetic and dermatology experts recommend using a sunscreen product to prevent UV-induced damage. A variety of strategies using antioxidants and anti-inflammatory agents have also been developed to complement the skin's defenses against UV rays. Researchers have examined the use of plant-derived materials to alleviate the occurrence of skin aging, diseases, and cancer caused by UV rays. Furthermore, studies are also underway to determine how to promote melanin production to protect from UV-induced skin damage. This review provides discussion of the damage that occurs in the skin due to UV light and describes potential defense strategies using plant-derived materials. This review aims to assist researchers in understanding the current research in this area and to potentially plan future studies.

An Evaluation of the Effects of Photoactivation of Bithionol, Amiodarone and Chlorpromazine on Human Keratinocytes In Vitro

Human skin is a continual target for chemical toxicity, due to its constant exposure to xenobiotics. The skin possesses a number of protective antioxidant systems, including glutathione and enzymic pathways, which are capable of neutralising reactive oxygen species (ROS). In combination with certain chemicals, the presence of ROS might augment the levels of toxicity, due to photoactivation of the chemical or, alternatively, due to an oxidatively-stressed state in the skin which exisited prior to exposure to the chemical. Bithionol is a phototoxic anti-parasitic compound. The mechanism of its toxicity and the possible methods of protection from its damaging effects have been explored. The capacity of keratinocytes to protect themselves from bithionol and other phototoxic chemicals has been investigated. In addition, the potential of endogenous antioxidants, such as vitamin C and E, to afford protection to the cells, has been evaluated. The intracellular glutathione stores of HaCaT keratinocytes were reduced following treatment with biothionol. Following photoactivation, both bithionol and chlorpromazine had similar effects, which suggests that glutathione is important in the detoxification pathway of these chemicals. This was confirmed by means of the visual identification of fluorescently-labelled glutathione. Endogenous antioxidants were unable to protect the HaCaT keratinocytes from bithionol toxicity or chlorpromazine phototoxicity. Amiodarone was shown to have no effect on cellular glutathione levels, which suggests that an alternative mechanism of detoxification was occurring in this case. This was supported by evidence of the protection of HaCaT cells from amiodarone phototoxicity via endogenous antioxidants. Thus, it appears that amiodarone toxicity is dependent on the levels of non-gluathione antioxidants present, whilst bithionol and chlorpromazine detoxification relies on the glutathione antioxidant system. This type of approach could indicate the likely mechanisms of phototoxicity of chemicals in vitro, with relevance to potential effects in vivo.

A Review of the Role of Green Tea (Camellia sinensis) in Antiphotoaging, Stress Resistance, Neuroprotection, and Autophagy

Tea is one of the most widely consumed beverages worldwide, and is available in various forms. Green tea is richer in antioxidants compared to other forms of tea. Tea is composed of polyphenols, caffeine, minerals, and trace amounts of vitamins, amino acids, and carbohydrates. The composition of the tea varies depending on the fermentation process employed to produce it. The phytochemicals present in green tea are known to stimulate the central nervous system and maintain overall health in humans. Skin aging is a complex process mediated by intrinsic factors such as senescence, along with extrinsic damage induced by external factors such as chronic exposure to ultraviolet (UV) irradiation—A process known as photoaging—Which can lead to erythema, edema, sunburn, hyperplasia, premature aging, and the development of non-melanoma and melanoma skin cancers. UV can cause skin damage either directly, through absorption of energy by biomolecules, or indirectly, by increased production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Green tea phytochemicals are a potent source of exogenous antioxidant candidates that could nullify excess endogenous ROS and RNS inside the body, and thereby diminish the impact of photoaging. Several in vivo and in vitro studies suggest that green tea supplementation increases the collagen and elastin fiber content, and suppresses collagen degrading enzyme MMP-3 production in the skin, conferring an anti-wrinkle effect. The precise mechanism behind the anti-photoaging effect of green tea has not been explored yet. Studies using the worm model have suggested that green tea mediated lifespan extension depends on the DAF-16 pathway. Apart from this, green tea has been reported to have stress resistance and neuroprotective properties. Its ROS scavenging activity makes it a potent stress mediator, as it can also regulate the stress induced by metal ions. It is known that tea polyphenols can induce the expression of different antioxidant enzymes and hinder the DNA oxidative damage. Growing evidence suggests that green tea can also be used as a potential agent to mediate neurodegenerative diseases, including Alzheimer’s disease. EGCG, an abundant catechin in tea, was found to suppress the neurotoxicity induced by Aβ as it activates glycogen synthase kinase-3β (GSK-3β), along with inhibiting c-Abl/FE65—the cytoplasmic nonreceptor tyrosine kinase which is involved in the development of the nervous system and in nuclear translocation. Additionally, green tea polyphenols induce autophagy, thereby revitalizing the overall health of the organism consuming it. Green tea was able to activate autophagy in HL-60 xenographs by increasing the activity of PI3 kinase and BECLIN-1. This manuscript describes the reported anti-photoaging, stress resistance, and neuroprotective and autophagy properties of one of the most widely known functional foods—green tea.

Drug delivery strategies for chemoprevention of UVB-induced skin cancer: A review

Annually, more skin cancer cases are diagnosed than the collective incidence of the colon, lung, breast, and prostate cancer. Persistent contact with sunlight is a primary cause for all the skin malignancies. UVB radiation induces reactive oxygen species (ROS) production in the skin which eventually leads to DNA damage and mutation. Various delivery approaches for the skin cancer treatment/prevention have been evolving and are directed toward improvements in terms of delivery modes, therapeutic agents, and site-specificity of therapeutics delivery. The effective chemoprevention activity achieved is based on the efficiency of the delivery system used and the amount of the therapeutic molecule deposited in the skin. In this article, we have discussed different studies performed specifically for the chemoprevention of UVB-induced skin cancer. Ultra-flexible nanocarriers, transethosomes nanocarriers, silica nanoparticles, silver nanoparticles, nanocapsule suspensions, microemulsion, nanoemulsion, and polymeric nanoparticles which have been used so far to deliver the desired drug molecule for preventing the UVB-induced skin cancer.

DNA Damage and Deficiencies in the Mechanisms of Its Repair: Implications in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a perplexing and potentially severe disease, the pathogenesis of which is yet to be understood. SLE is considered to be a multifactorial disease, in which genetic factors, immune dysregulation, and environmental factors, such as ultraviolet radiation, are involved. Recently, the description of novel genes conferring susceptibility to develop SLE even in their own (monogenic lupus) has raised the interest in DNA dynamics since many of these genes are linked to DNA repair. Damage to DNA induces an inflammatory response and eventually triggers an immune response, including those targeting self-antigens. We review the evidence that indicates that patients with SLE present higher levels of DNA damage than normal subjects do and that several proteins involved in the preservation of the genomic stability show polymorphisms, some of which increase the risk for SLE development. Also, the experience from animal models reinforces the connection between DNA damage and defective repair in the development of SLE-like disease including characteristic features such as anti-DNA antibodies and nephritis. Defining the role of DNA damage response in SLE pathogenesis might be strategic in the quest for novel therapies.

Natural Antioxidants: Multiple Mechanisms to Protect Skin From Solar Radiation

Human skin exposed to solar ultraviolet radiation (UVR) results in a dramatic increase in the production of reactive oxygen species (ROS). The sudden increase in ROS shifts the natural balance toward a pro-oxidative state, resulting in oxidative stress. The detrimental effects of oxidative stress occur through multiple mechanisms that involve alterations to proteins and lipids, induction of inflammation, immunosuppression, DNA damage, and activation of signaling pathways that affect gene transcription, cell cycle, proliferation, and apoptosis. All of these alterations promote carcinogenesis and therefore, regulation of ROS levels is critical to the maintenance of normal skin homeostasis. Several botanical products have been found to exhibit potent antioxidant capacity and the ability to counteract UV-induced insults to the skin. These natural products exert their beneficial effects through multiple pathways, including some known to be negatively affected by solar UVR. Aging of the skin is also accelerated by UVR exposure, in particular UVA rays that penetrate deep into the epidermis and the dermis where it causes the degradation of collagen and elastin fibers via oxidative stress and activation of matrix metalloproteinases (MMPs). Because natural compounds are capable of attenuating some of the UV-induced aging effects in the skin, increased attention has been generated in the area of cosmetic sciences. The focus of this review is to cover the most prominent phytoproducts with potential to mitigate the deleterious effects of solar UVR and suitability for use in topical application.

Protective effect of curcumin against ultraviolet A irradiation‑induced photoaging in human dermal fibroblasts

Ultraviolet (UV) radiation induces DNA damage, oxidative stress, and inflammatory processes in skin, resulting in photoaging. Natural botanicals have gained considerable attention due to their beneficial protection against the harmful effects of UV irradiation. The present study aimed to evaluate the ability of curcumin (Cur) to protect human dermal fibroblasts (HDFs) against ultraviolet A (UVA)-induced photoaging. HDFs were treated with 0–10 µM Cur for 2 h and subsequently exposed to various intensities of UVA irradiation. The cell viability and apoptotic rate of HDFs were investigated by MTT and flow cytometry assays, respectively. The effect of UVA and Cur on the formation of reactive oxygen species (ROS), malondialdehyde levels, which are an indicator of ROS, and the levels/activity of antioxidative defense proteins, including glutathione, superoxide dismutase and catalase, were evaluated using 2′,7′-dichlorofluorescin diacetate and commercial assay kits. Furthermore, western blotting was performed to determine the levels of proteins associated with endoplasmic reticulum (ER) stress, the apoptotic pathway, inflammation and the collagen synthesis pathway. The results demonstrated that Cur reduced the accumulation of ROS and restored the activity of antioxidant defense enzymes, indicating that Cur minimized the damage induced by UVA irradiation in HDFs. Furthermore, western blot analysis demonstrated that Cur may attenuate UVA-induced ER stress, inflammation and apoptotic signaling by downregulating the protein expression of glucose-regulated protein 78, C/EBP-homologous protein, nuclear factor-κB and cleaved caspase-3, while upregulating the expression of Bcl-2. Additionally, it was demonstrated that Cur may regulate collagen metabolism by decreasing the protein expression of matrix metalloproteinase (MMP)-1 and MMP-3, and may promote the repair of cells damaged as a result of UVA irradiation through increasing the protein expression of transforming growth factor-β (TGF-β) and Smad2/3, and decreasing the expression of the TGF-β inhibitor, Smad7. In conclusion, the results of the present study indicate the potential benefits of Cur for the protection of HDFs against UVA-induced photoaging and highlight the potential for the application of Cur in skin photoprotection.

3-Amino-1,2,4-triazole Limits the Oxidative Damage in UVA-Irradiated Dysplastic Keratinocytes

Reactive oxygen species (ROS) generated by UVA irradiation affect the keratinocyte cell membrane, DNA, and proteins and may cause serious injury to the skin. Treating human dysplastic keratinocytes (DOK) with 3-amino-1,2,4-triazole (AMT), a common catalase inhibitor, induced a compensatory mechanism for the hydrogen peroxide detoxification, which included a rise in glutathione peroxidase and glutathione reductase activities. Here, we examined a possible role of AMT in protecting a human DOK cell line against UVA-induced damage. In DOK cells exposed to UVA irradiation, we observed a substantial decrease in antioxidant enzymatic activities, such as catalase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase and an increase in lipid peroxidation and protein oxidation levels. Treating DOK cells with AMT prior to UVA exposure enhanced the activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase, relative to nontreated cells. The enhanced antioxidant activities were correlated with decreased protein oxidation levels. Based on these results, we suggest that AMT may protect dysplastic keratinocytes against the harmful effects of UVA radiation.

Mycosporine-Like Amino Acids: Potential Health and Beauty Ingredients

Human skin is constantly exposed to damaging ultraviolet radiation (UVR), which induces a number of acute and chronic disorders. To reduce the risk of UV-induced skin injury, people apply an additional external protection in the form of cosmetic products containing sunscreens. Nowadays, because of the use of some chemical filters raises a lot of controversies, research focuses on exploring novel, fully safe and highly efficient natural UV-absorbing compounds that could be used as active ingredients in sun care products. A promising alternative is the application of multifunctional mycosporine-like amino acids (MAAs), which can effectively compete with commercially available filters. Here, we outline a complete characterization of these compounds and discuss their enormous biotechnological potential with special emphasis on their use as sunscreens, activators of cells proliferation, anti-cancer agents, anti-photoaging molecules, stimulators of skin renewal, and functional ingredients of UV-protective biomaterials.

Protective effect of a hydrogel containing Achyrocline satureioides extract-loaded nanoemulsion against UV-induced skin damage

Achyrocline satureioides is a medicinal plant widely used in South America that exhibits a well-documented antioxidant activity. Such activity has been related to their main aglycone flavonoids quercetin, luteolin, and 3-O-methylquercetin (3MQ). This study addresses the development of antioxidant hydrogels containing an A. satureioides extract-loaded nanoemulsions aimed at topical application. The systems investigated were A. satureioides extract-loaded nanoemulsions (ASNE) obtained by spontaneous emulsification procedure formulated in semisolid hydrogels composed of Carbopol® Ultrez 20 (HASNE). Hydrogels exhibit a non-Newtonian pseudoplastic behavior. A higher release of 3MQ from ASNE (3.61μg/cm(2)/h) was observed when compared with HASNE (2.83μg/cm(2)/h). Different parameters that may have an influence on the retention of flavonoids into the skin were investigated by using a Franz-type diffusion cells. Indeed, the amount of formulation applied on donor compartment was found to play a crucial role. At the optimized conditions, retention of approximately 2μg/cm(2) of flavonoids was detected into the skin. A higher retention of 3MQ was detected (approximately 1.0μg/cm(2)) in comparison with the other flavonoids. Finally, a protection the porcine ear skin by formulations, against oxidative stress generated by UVA/UVB light was demonstrated by means of TBARS, protein carbonylation, and protein thiol content assays. The overall results showed the potential of the formulations developed in this study for the prevention of oxidative stress on the skin.

UVB exposure enhanced the dermal penetration of zinc oxide nanoparticles and induced inflammatory responses through oxidative stress mediated by MAPKs and NF-κB signaling in SKH-1 hairless mouse skin

Besides titanium dioxide (TiO2), zinc oxide (ZnO) nanoparticles (NPs) are commonly used in sunscreen formulations as protective agents against exposure to ultraviolet radiation. Although the majority of prior studies have concluded that NPs do not penetrate healthy skin, compromised skin slightly enhanced metal oxide NP penetration. However, a question arises regarding the possible toxic consequences if consumers who had applied sunscreens containing ZnO-NPs were exposed to environmentally relevant doses of UVB. Considering this, we planned a study where SKH-1 hairless mice were topically exposed to a 5% and/or 10% dose of ZnO-NPs (<50 nm and <100 nm) either alone or along with UVB (50 mJ cm-2). In two additional groups, mice were treated with either bulk ZnO-NPs (<5 μm) or with ZnO-NPs (<5 μm) and subsequently UVB (50 mJ cm-2). Animals of all groups were sacrificed after 6, 24 and 48 h and the Zn ion content in the skin was measured. In addition, estimation of ROS generation, histopathology, myeloperoxidase (MPO) activity, immunohistochemistry for COX-2 and western blot analysis for MAPKs, p-IκBα, p-NF-κB, and COX-2 were also carried out. Significant increases in the Zn ion in exposed skin were seen. Enhanced ROS generation and MPO activity were also found in ZnO-NPs followed by UVB exposed groups at all three time points. Similarly, hyperplasia and over-expression of COX-2 were also greater in ZnO-NPs and UVB exposed groups than in the ZnO-NPs and UVB only groups. The expression of MAPKs, and transcription factors NF-κB along with COX-2 were also enhanced significantly in ZnO-NPs and the UVB treated group. Collectively, our findings suggest that UVB exposure enhanced ZnO-NP penetration in mouse skin and possibly dissolution of these ZnO-NPs takes place during this process, causing significant Zn ion generation leading to oxidative stress by ROS generation which subsequently activates MAPK-NF-κB signaling and increases COX-2 and inflammation.

Elevated 8-Isoprostane Levels in Basal Cell Carcinoma and in Uva Irradiated Skin

Isoprostanes are prostaglandin isomers produced from the peroxidation of polyunsaturated fatty acids from the cellular membrane. They have been used as a specific index of cellular lipoperoxidation and as an indirect measure of oxidative stress. However, these molecules also present several biological activities. An oxidative environment measured as the presence of other indirect measurements of reactive oxygen species lipoperoxidation has recently been described in basal cell carcinoma, the most frequent type of non-melanoma skin cancer. This study aims to measure the levels of 8-isoprostaglandin F2α, an isoprostane widely studied in other models as a by-product of ROS-induced lipid peroxidation, in basal cell carcinoma and in UVA irradiated healthy skin. We found that 8-iso-PGF2α is present in higher levels in BCC specimens compared to healthy non sun-exposed skin, confirming previous studies on the production of lipoperoxidation in this tumor. Moreover, we demonstrated that topical pre-treatment with a compound containing vitamin E is capable of reducing 8-iso-PGF2α formation in UV irradiated skin suggesting a role for isoprostanes in UV induced inflammation and eventually carcinogenesis and confirming the function of vitamin E as an antioxidant in this model.

The Effect of Lycopene Preexposure on UV-B-Irradiated Human Keratinocytes

Lycopene has been reported as the antioxidant most quickly depleted in skin upon UV irradiation, and thus it might play a protective role. Our goal was to investigate the effects of preexposure to lycopene on UV-B-irradiated skin cells. Cells were exposed for 24 h to 10 M lycopene, and subsequently irradiated and left to recover for another 24 h period. Thereafter, several parameters were analyzed by FCM and

RT-PCR

genotoxicity/clastogenicity by assessing the cell cycle distribution; apoptosis by performing the Annexin-V assay and analyzing gene expression of apoptosis biomarkers; and oxidative stress by ROS quantification. Lycopene did not significantly affect the profile of apoptotic, necrotic and viable cells in nonirradiated cells neither showed cytostatic effects. However, irradiated cells previously treated with lycopene showed an increase in both dead and viable subpopulations compared to nonexposed irradiated cells. In irradiated cells, lycopene preexposure resulted in overexpression of BAX gene compared to nonexposed irradiated cells. This was accompanied by a cell cycle delay at S-phase transition and consequent decrease of cells in G0/G1 phase. Thus, lycopene seems to play a corrective role in irradiated cells depending on the level of photodamage. Thus, our findings may have implications for the management of skin cancer.

Evaluating the clinical and physiological effects of long term ultraviolet B radiation on guinea pigs (Cavia porcellus)

Vitamin D is an important hormone in vertebrates. Most animals acquire this hormone through their diet, secondary to exposure to ultraviolet B (UVB) radiation, or a combination thereof. The objectives for this research were to evaluate the clinical and physiologic effects of artificial UVB light supplementation on guinea pigs (Cavia porcellus) and to evaluate the long-term safety of artificial UVB light supplementation over the course of six months. Twelve juvenile acromelanic Hartley guinea pigs were randomly assigned to one of two treatment groups: Group A was exposed to 12 hours of artificial UVB radiation daily and Group B received only ambient fluorescent light for 12 hours daily. Animals in both groups were offered the same diet and housed under the same conditions. Blood samples were collected every three weeks to measure blood chemistry values, parathyroid hormone, ionized calcium, and serum 25-hydroxyvitamin D3 (25-OHD3) levels. Serial ophthalmologic examinations, computed tomography scans, and dual energy x-ray absorptiometry scans were performed during the course of the study. At the end of the study the animals were euthanized and necropsied. Mean ± SD serum 25-OHD3 concentrations differed significantly in the guinea pigs (p<0.0001) between the UVB supplementation group (101.49±21.81 nmol/L) and the control group (36.33±24.42 nmol/L). An increased corneal thickness in both eyes was also found in the UVB supplementation compared to the control group (right eye [OD]: p<0.0001; left eye [OS]: p<0.0001). There were no apparent negative clinical or pathologic side effects noted between the groups. This study found that exposing guinea pigs to UVB radiation long term significantly increased their circulating serum 25-OHD3 levels, and that this increase was sustainable over time. Providing guinea pigs exposure to UVB may be an important husbandry consideration that is not currently recommended.

Modulation of PPARγ provides new insights in a stress induced premature senescence model

Peroxisome proliferator-activated receptor gamma (PPARγ) may be involved in a key mechanism of the skin aging process, influencing several aspects related to the age-related degeneration of skin cells, including antioxidant unbalance. Therefore, we investigated whether the up-modulation of this nuclear receptor exerts a protective effect in a stress-induced premature senescence (SIPS) model based on a single exposure of human dermal fibroblasts to 8-methoxypsoralen plus + ultraviolet-A-irradiation (PUVA). Among possible PPARγ modulators, we selected 2,4,6-octatrienoic acid (Octa), a member of the parrodiene family, previously reported to promote melanogenesis and antioxidant defense in normal human melanocytes through a mechanism involving PPARγ activation. Exposure to PUVA induced an early and significant decrease in PPARγ expression and activity. PPARγ up-modulation counteracted the antioxidant imbalance induced by PUVA and reduced the expression of stress response genes with a synergistic increase of different components of the cell antioxidant network, such as catalase and reduced glutathione. PUVA-treated fibroblasts grown in the presence of Octa are partially but significantly rescued from the features of the cellular senescence-like phenotype, such as cytoplasmic enlargement, the expression of senescence-associated-β-galactosidase, matrix-metalloproteinase-1, and cell cycle proteins. Moreover, the alterations in the cell membrane lipids, such as the decrease in the polyunsaturated fatty acid content of phospholipids and the increase in cholesterol levels, which are typical features of cell aging, were prevented. Our data suggest that PPARγ is one of the targets of PUVA-SIPS and that its pharmacological up-modulation may represent a novel therapeutic approach for the photooxidative skin damage.

Phototoxicity of narrowband ultraviolet (UV) B (311 nm) compared with broadband UVB in the photo hen's egg test

BACKGROUND

Broadband ultraviolet B (BB-UVB) is a well-established treatment option in dermatology. However, during the last decade BB-UVB has increasingly been replaced by narrowband UVB 311 nm (NB-UVB), especially in the therapy of psoriasis, atopic eczema and vitiligo. Several studies have indicated a better therapeutic response for almost all indications compared with BB-UVB.

OBJECTIVES

The aim of our study was to investigate the phototoxic effects of NB-UVB in comparison with BB-UVB in vivo.

METHODS

Therefore, we employed the photo hen's egg test (PHET), an established phototoxic model, based on the yolk sac blood vessel system of incubated hen's eggs. NB-UVB and BB-UVB dosages increasing from 30 up to 1200 mJ cm(-2) were applied on 17 test groups (each n = 12 eggs) and two unirradiated test groups served as controls. Twenty-four hours after irradiation we observed the following test parameters: lethality, membrane discoloration and haemorrhages.

RESULTS

Following our results, the lethal half dose (LD50) was 60 and 720 mJ cm(-2) for BB-UVB and NB-UVB, respectively. These LD50 dosages provoked severe membrane discoloration and haemorrhaging. Summarizing our results, the LD50 of NB-UVB was 12-fold higher than BB-UVB.

CONCLUSIONS

Interestingly, these findings are in good accordance with the literature, where the minimal erythema dose (MED) of NB-UVB in human skin is up to 14 times higher than the MED of BB-UVB. These results show that the PHET is a valid test model to evaluate the phototoxic effects of various UVB wavelengths. Moreover, our results indicate that regarding the investigation of phototoxic effects the PHET might serve as a model representative for human skin, which might reduce the extent of photoprovocation in humans in the future.

EGb-761 prevents ultraviolet B-induced photoaging via inactivation of mitogen-activated protein kinases and proinflammatory cytokine expression

BACKGROUND

EGb-761 is an antioxidant and anticarcinogen; however, its role as a photoprotector remains unknown.

OBJECTIVE

To determine whether EGb-761 photoprotects human dermal fibroblasts and BALB/c mice skin against ultraviolet B (UVB) light irradiation.

METHODS

To simulate chronic photodamage, shaved BALB/c mice were exposed to UVB irradiation (90mJ/cm(2)) thrice weekly for 3 months. EGb-761 (2mg/cm(2)) was topically applied 1h before irradiation to evaluate its effect. The mechanisms by which EGb-761 protects the skin from photodamage were evaluated by immunohistochemical analysis, enzyme-linked immunosorbent assay (ELISA), and Western blotting.

RESULTS

In BALB/c mice, the signs of photoaging or photodamage, such as coarse wrinkle formation, epidermal hyperplasia, and elastic fiber degeneration, markedly reduced with the topical application of EGb-761. Western blot and ELISA revealed that the activation of MMP-1 in cultured fibroblasts markedly diminished after pretreatment with EGb-761. In addition, EGb-761 inhibited UVB-induced overexpression by the fibroblasts of the proinflammatory cytokines, such as interleukin (IL)-1α, IL-1β, IL-6, and tumor necrosis factor-α. The phosphorylation of the mitogen-activated protein kinase (MAPK) signal transduction pathway components, including extracellular signal-regulated kinase, C-Jun N-terminal kinase, and p38, which are induced by UV irradiation, was significantly inhibited in vivo and in vitro. EGb-761 also diminished the generation of UVB-induced reactive oxygen species (ROS).

CONCLUSIONS

EGb-761 photoprotects mice and cultured fibroblasts, inhibits the UVB-induced phosphorylation of MAPK pathway components, and reduces the expression of the proinflammatory cytokines by suppressing ROS generation. Thus, topically applied EGb-761 may be a promising photoprotective agent.

Gardenia jasminoides Extract Attenuates the UVB-Induced Expressions of Cytokines in Keratinocytes and Indirectly Inhibits Matrix Metalloproteinase-1 Expression in Human Dermal Fibroblasts

Ultraviolet radiation (UV) is a major cause of photoaging, which also involves inflammatory cytokines and matrix metalloproteinases (MMP). The present study was undertaken to examine the UVB-protecting effects of yellow-colored plant extracts in cell-based assays. HaCaT keratinocytes were exposed to UVB in the absence or presence of plant extracts, and resulting changes in cell viability and inflammatory cytokine expression were measured. Of the plant extracts tested, Gardenia jasminoides extract showed the lowest cytotoxicity and dose-dependently enhanced the viabilities of UVB-exposed cells. Gardenia jasminoides extract also attenuated the mRNA expressions of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in HaCaT cells stimulated by UVB. Conditioned medium from UVB-exposed HaCaT cells was observed to stimulate MMP-1 protein expression in human dermal fibroblasts, and this effect was much smaller for the conditioned medium of HaCaT cells exposed to UVB in the presence of Gardenia jasminoides extract. Gardenia jasminoides extract also exhibited antioxidative and antiapoptotic effects in HaCaT cells exposed to UVB. These results indicated that UVB-induced injury and inflammatory responses of skin cells can be attenuated by yellow-colored plant extracts, such as Gardenia jasminoides extract.

Characterization and release studies of liposomal gels containing glutathione/cyclodextrins complexes potentially useful for cutaneous administration

The aim of this work is to develop and characterize a formulation intended for the cutaneous administration of glutathione (γ-glutamylcysteinylglycine, GSH), potentially useful for cellular defense against UV-induced damage. For this purpose, liposomes containing GSH or GSH/cyclodextrins(CDs) inclusion complexes as well as liposomes dispersed within a hydrophilic gel, were evaluated. These formulations were designed in order to obtain a system combining the advantages of liposomes as vehicles for topical drug delivery with those of CDs as penetration enhancers. The studied CDs were the natural (β-CD) and chemically modified (i.e., HP-β-CD and CH3 -β-CD) cyclodextrins. The prepared liposomes showed homogeneous size distribution, mean diameter in the range 622-1435 nm, small positive charge (+3.1 to +6.6 mV), and encapsulation efficiency of the peptide in the range 13.6%-23.7%. Release studies showed that the presence of the oligosaccharide may influence to some extent the amount of drug released, whereas stability studies clearly point out that the incorporation in a hydrophilic gel of 2-hydroxyethylcellulose insures a stable formulation maintaining unchanged the characteristics of liposomal vesicles.

α-Tocopherol protects keratinocytes against ultraviolet A irradiation by suppressing glutathione depletion, lipid peroxidation and reactive oxygen species generation

This study aimed to investigate whether α-tocopherol is able to protect keratinocytes against ultraviolet A (UVA) radiation by increasing glutathione (γ-glutamylcysteinylglycine; GSH) levels or decreasing lipid peroxidation and reactive oxygen species (ROS) generation. The cell survival fraction was 43.6% when keratinocytes were irradiated with UVA at a dose of 8 J/cm². α-Tocopherol was added prior to UVA irradiation and the cell viability was assayed. The cell survival fractions were 60.2, 77.1, 89.0, 92.9 and 96.2% when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. These results suggested that α-tocopherol is capable of protecting keratinocytes against UVA irradiation. Furthermore, the levels of GSH, lipid peroxidation and ROS were measured. The levels of GSH were 0.354 and 0.600 mmol/g protein in keratinocytes irradiated with UVA (8 J/cm²) and in non-irradiated cells, respectively, whereas they were 0.364, 0.420, 0.525, 0.540 and 0.545 mmol/g protein when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. The levels of lipid peroxidation were 20.401 or 5.328 μmol/g [malondialdehyde (MDA)/protein] in keratinocytes irradiated with UVA (8 J/cm²) and in non-irradiated cells, respectively, whereas they were 11.685, 6.544, 5.847, 4.390 and 2.164 μmol/g (MDA/protein) when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. The levels of ROS were 3,952.17 or 111.87 1/mg protein in keratinocytes irradiated with UVA (8 J/cm²) and in non-irradiated cells, respectively, whereas they were 742.48, 579.36, 358.16, 285.63 and 199.82 1/mg protein when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. These findings suggested that α-tocopherol protects keratinocytes against UVA irradiation, possibly through increasing the levels of GSH or decreasing the levels of lipid peroxidation and ROS generation.

Differential effects of topical vitamin E and C E Ferulic® treatments on ultraviolet light B-induced cutaneous tumor development in Skh-1 mice

Because of the ever-increasing incidence of ultraviolet light B (UVB)-induced skin cancer, considerable attention is being paid to prevention through the use of both sunscreens and after sun treatments, many of which contain antioxidants. Vitamin E is included as an antioxidant in many sunscreens and lotions currently on the market. Studies examining the efficacy of vitamin E as a topical preventative agent for UVB-induced skin cancer have yielded conflicting results. A likely contributor to differences in study outcome is the stability of vitamin E in the particular formulation being tested. In the current study we examined the effects of topical vitamin E alone as well as vitamin E combined with vitamin C and ferulic acid in a more stable topical formula (C E Ferulic®). Mice were exposed to UVB for 10 weeks in order to induce skin damage. Then, before the appearance of any cutaneous lesions, mice were treated for 15 weeks with a topical antioxidant, without any further UVB exposure. We found that topical C E Ferulic decreased tumor number and tumor burden and prevented the development of malignant skin tumors in female mice with chronically UVB-damaged skin. In contrast, female mice chronically exposed to UVB and treated topically with vitamin E alone showed a trend towards increased tumor growth rate and exhibited increased levels of overall DNA damage, cutaneous proliferation, and angiogenesis compared to vehicle-treated mice. Thus, we have demonstrated that topical 5% alpha tocopherol may actually promote carcinogenesis when applied on chronically UVB-damaged skin while treating with a more stable antioxidant compound may offer therapeutic benefits.

Melanin and urate act to prevent ultraviolet damage in the integument of the silkworm, Bombyx mori

The phenomenon that epidermal cells under the white stripes rather than black stripes contain many uric acid granules was found in larvae of several Lepidopteran species. However, the biological mechanism of this phenomenon is still unknown. In the present study, we take advantage of several silkworm (Bombyx mori) body color mutant strains to investigate the deposition patterns and biological mechanism of urate and melanin in the integuments of these mutant larvae. By imaging with transmission electron microscope, we found that there were some melanin granules in the larval cuticle in black body color mutant plain Black (p(B) ), but not in background strain plain (p) with white larval body color. In contrast, the larval epidermal cell of background strain had much more urate granules than that of black one. Furthermore, the uric acid content under the black stripes was significantly lower than that under the white stripes in a single individual of mottled stripe (p(S) ) with black and white stripes in each segment. Ultraviolet A (UVA) exposure experiments showed that the distinct oily (od) mutant individuals with translucent larval integument were more sensitive to the UVA damage than black body color mutant and background strain without any pigmentation in the larval cuticle. This is likely due to the absence of melanin granules and few urate granules in the integument of od mutant. Thus, both the deposited melanin granules in the cuticle and the abundant urate granules in the epidermis cells constitute effective barriers for the silkworm to resist UVA-induced damage.

Antagonizing effects and mechanisms of afzelin against UVB-induced cell damage

Ultraviolet (UV) radiation induces DNA damage, oxidative stress, and inflammatory processes in human keratinocytes, resulting in skin inflammation, photoaging, and photocarcinogenesis. Adequate protection of skin against the harmful effects of UV irradiation is essential. Therefore, in this study, we investigated the protective effects of afzelin, one of the flavonoids, against UV irradiation in human keratinocytes and epidermal equivalent models. Spectrophotometric measurements revealed that the afzelin extinction maxima were in the UVB and UVA range, and UV transmission below 376 nm was <10%, indicating UV-absorbing activity of afzelin. In the phototoxicity assay using the 3T3 NRU phototoxicity test (3T3-NRU-PT), afzelin presented a tendency to no phototoxic potential. In addition, in order to investigate cellular functions of afzelin itself, cells were treated with afzelin after UVB irradiation. In human keratinocyte, afzelin effectively inhibited the UVB-mediated increase in lipid peroxidation and the formation of cyclobutane pyrimidine dimers. Afzelin also inhibited UVB-induced cell death in human keratinocytes by inhibiting intrinsic apoptotic signaling. Furthermore, afzelin showed inhibitory effects on UVB-induced release of pro-inflammatory mediators such as interleukin-6, tumor necrosis factor-α, and prostaglandin-E2 in human keratinocytes by interfering with the p38 kinase pathway. Using an epidermal equivalent model exposed to UVB radiation, anti-apoptotic activity of afzelin was also confirmed together with a photoprotective effect at the morphological level. Taken together, our results suggest that afzelin has several cellular activities such as DNA-protective, antioxidant, and anti-inflammatory as well as UV-absorbing activity and may protect human skin from UVB-induced damage by a combination of UV-absorbing and cellular activities.

Photoprotective and antioxidant effects of Rhubarb: inhibitory action on tyrosinase and tyrosine kinase activities and TNF-α, IL-1α and α-MSH production in human melanocytes

BACKGROUND

Exposure to ultraviolet (UV) radiation causes various forms of acute and chronic skin damage, including immunosuppression, inflammation, premature aging and photodamage. Furthermore, it induces the generation of reactive oxygen species, produces proinflammatory cytokines and melanocyte-stimulating hormone (MSH) and increases tyrosinase activity. The aim of this study was to evaluate the potential photoprotective effects of Rheum rhaponticum L. rhizome extract on human UV-stimulated melanocytes.

METHODS

The effects of Rheum rhaponticum rhizome extract on tyrosine kinase activity, and on interleukin-1α (IL-1α), tumour necrosis factor α (TNF-α), and α-MSH production in human epidermal melanocytes were evaluated under UV-stimulated and non-stimulated conditions. Antioxidant activity was evaluated by lipid peroxidation and 1,1-dyphenyl-2-picryl-hydrazyl (DPPH) assays, while anti-tyrosinase activity was evaluated by the mushroom tyrosinase method.

RESULTS

Rheum rhaponticum L. rhizome extract showed in vitro antioxidant properties against lipid peroxidation, free radical scavenging and anti-tyrosinase activities, and inhibited the production of IL-1α, TNF-α, α-MSH, and tyrosine kinase activity in melanocytes subjected to UV radiation.

CONCLUSIONS

These results support the inclusion of Rheum rhaponticum L. rhizome extract into cosmetic, sunscreen and skin care products for the prevention or reduction of photodamage.

Study on the UV-Protective Performance of Cotton Fabrics Dyed with Natural Dyes

In this study, the ultraviolet protective properties of the cotton fabrics dyed with natural dyes were investigated. It was observed that cotton fabrics dyed with natural dyes could absorb about 80% of the ultraviolet rays. It was demonstrated that the UV-protective effects were strongly dependent on the absorption characteristics of natural dyes for UV radiation.

The effects of grape seeds polyphenols on SKH-1 mice skin irradiated with multiple doses of UV-B

The study investigated the protective activity of red grape seeds (Vitis vinifera L, Burgund Mare variety) (BM) extracts in vivo on multiple doses of ultraviolet radiation (UV)-B-induced deleterious effects in SKH-1 mice skin. Eighty 8-weeks-old female SKH-1 mice were divided into 8 groups: control, vehicle, UV-B irradiated, vehicle+UV-B irradiated, BM 2.5mg polyphenols (PF)/cm(2)+UV-B irradiated, BM 4 mg PF/cm(2)+UV-B irradiated, UV-B+BM 2.5mg PF/cm(2), UV-B+BM 4 mg PF/cm(2). The extract was applied topically before or after each UV-B exposure (240 mJ/cm(2)), for 10 days consecutively. The antioxidant activity of BM extract is higher than gallic acid (k(BM)=0.017, k(gallic acid)=0.013). Multiple doses of UV-B generated the formation of cyclobutane pyrimidine dimers (CPDs) and sunburn cells, increased glutathione peroxidase (GPx) and catalase (CAT) activities respectively glutathione (GSH) and IL-1β levels in skin. In group treated with 2.5mg PF/cm(2) before UV-B irradiation BM extract inhibited UV-B-induced sunburn cells, restored the superoxide dismutase (MnSOD) activity, increased insignificantly CAT and GPx activities and reduced IL-1β level. The BM 4.0 mg PF/cm(2) treatment decreased GSH level and reduced the percentage of CPDs positive cells in skin. Both doses of BM extract administered after UV-B irradiation increased the MnSOD and GPx activities and reduced the formation of sunburn cells in skin. Our results suggest that BM extract might be a potential chemo-preventive candidate in reducing the oxidative stress and apoptosis induced by multiple doses of UV-B in skin.