Involvement of EGF receptor activation in the induction of cyclooxygenase-2 in HaCaT keratinocytes after UVB

The impact of temperature on the skin barrier and atopic dermatitis

Climate change is a global threat to public health and causes or worsens various diseases including atopic dermatitis (AD), allergic, infectious, cardiovascular diseases, physical injuries, and mental disorders. The incidence of allergy, such as AD, has increased over the past several decades, and environmental factors such as climate change have been implicated as a potential mechanism. A substantial amount of literature has been published on the impact of climate factors, including cold and hot temperatures, on the skin barrier and AD. Studies in several countries have found a greater incidence of AD in children born in the colder seasons of fall and winter. The effect of cold and warm temperatures on itch, skin flares, increased outpatient visits, skin barrier dysfunction, development of AD, and asthma exacerbations have been reported. Understanding mechanisms by which changes in temperature influence allergies is critical to the development of measures for the prevention and treatment of allergic disorders, such as AD and asthma. Low and high temperatures induce the production of proinflammatory cytokines and lipid mediators such as interleukin-1β, thymic stromal lymphopoietin, and prostaglandin E2, and cause itch and flares by activation of TRPVs such as TRPV1, TRPV3, and TRPV4. TRPV antagonists may attenuate temperature-mediated itch, skin barrier dysfunction, and exacerbation of AD.

Fermented Kamut Sprout Extract Decreases Cell Cytotoxicity and Increases the Anti-Oxidant and Anti-Inflammation Effect

Kamut sprouts (KaS) contain several biologically active compounds. In this study, solid-state fermentation using Saccharomyces cerevisiae and Latilactobacillus sakei was used to ferment KaS (fKaS-ex) for 6 days. The fKaS-ex showed a 26.3 mg/g dried weight (dw) and 46.88 mg/g dw of polyphenol and the β-glucan contents, respectively. In the Raw264.7 and HaCaT cell lines, the non-fermented KaS (nfKaS-ex) decreased cell viability from 85.3% to 62.1% at concentrations of 0.63 and 2.5 mg/mL, respectively. Similarly, the fKaS-ex decreased cell viability, but showed more than 100% even at 1.25 and 5.0 mg/mL concentrations, respectively. The anti-inflammatory effect of fKaS-ex also increased. At 600 µg/mL, the fKaS-ex exhibited a significantly higher ability to reduce cytotoxicity by suppressing COX-2 and IL-6 mRNA expressions as well as that for IL-1β mRNA. In summary, fKaS-ex exhibited significantly lower cytotoxicity and increased anti-oxidant and anti-inflammatory properties, indicating that fKaS-ex is beneficial for use in food and other industries.

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.

7‑MEGA™ 500 regulates the expression of COX‑2, MMP‑3 and type 1 procollagen in UVB‑irradiated human keratinocytes and dermal fibroblasts

AlaskOmega® Omega 7 500, also known as Omega‑7 fatty acid or 7‑MEGA™, is a highly concentrated palmitoleic acid (C16:1). Little is known about how 7‑MEGA regulates skin inflammation and wrinkle formation in cultured skin cells. The present study aimed to investigate the effects of 7‑MEGA on the expression of cyclooxygenase‑2 (COX‑2), matrix metallopeptidase (MMP)‑1/3 and type 1 procollagen, which are markers of skin inflammation and wrinkle formation, in ultraviolet B (UVB)‑irradiated human dermal fibroblasts (HDFs) and keratinocytes (HaCaT). No toxicity was observed upon treatment of HDFs and HaCaT cells with 0.5‑2.5 µl/ml 7‑MEGA. The exposure of HaCaT cells to 10 mJ/cm2 UVB for 6 h resulted in increased protein and/or mRNA expression of COX‑2 and MMP‑3. Treatment of HaCaT cells with 2.5 µl/ml 7‑MEGA suppressed the UVB‑induced expression of COX‑2 and MMP‑3 in these cells. In addition, treatment with 2.5 µl/ml 7‑MEGA attenuated the UVB‑induced expression and phosphorylation levels of c‑Fos and c‑Jun, two components of the activator protein‑1 (AP‑1) transcription factor, in HaCaT cells. Exposure of HDFs to 60 mJ/cm2 UVB for 6 h significantly decreased the expression of type 1 procollagen protein, whereas treatment with 2.5 µl/ml 7‑MEGA partially reversed the effects of UVB on the expression of type 1 procollagen protein. These results demonstrated for the first time that 7‑MEGA regulated the expression of COX‑2, MMP‑3 and type 1 procollagen in UVB‑irradiated skin cells. The present study suggested that 7‑MEGA may serve as a novel agent against UVB‑induced skin inflammation and damage.

Anti-Inflammatory Effects of Phenolic Compounds Isolated from Quercus Mongolica Fisch. ex Ledeb. on UVB-Irradiated Human Skin Cells

Quercus mongolica Fisch. ex Ledeb. (QM) has been used as an oriental traditional medicine to relieve hemorrhoids, fever, and enteritis. We screened the inhibitory activities of the extracts and compounds (1–6) isolated from QM on the production of inflammatory cytokines and chemokines to evaluate their anti-inflammatory activities. Further, we evaluated the expression levels of cytokines, chemokines, and immune factors on pedunculagin (PC, 1), which was selected from isolated compounds (1–6) because of its potential anti-inflammation effect. Additionally, we evaluated whether the inflammation mitigation effects of PC (1) following UVB exposure in keratinocytes occurred because of nuclear factor (NF)-κB and signal transducer and activator of transcription (STAT)/Janus kinase (JAK) activation. PC (1) remarkably suppressed interleukin (IL)-6, IL-10, IL-13, and monocyte chemoattractant protein-1 (MCP-1) mRNA expression and reduced the mRNA expression level of Cyclooxygenase-2 (COX-2) and also reduced the phosphorylation of p38 mitogen-activated protein kinases (p38), c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) in a concentration-dependent manner.

Role of PGE-2 and Other Inflammatory Mediators in Skin Aging and Their Inhibition by Topical Natural Anti-Inflammatories

Human skin aging is due to two types of aging processes, “intrinsic” (chronological) aging and “extrinsic” (external factor mediated) aging. While inflammatory events, triggered mainly by sun exposure, but also by pollutants, smoking and stress, are the principle cause of rapid extrinsic aging, inflammation also plays a key role in intrinsic aging. Inflammatory events in the skin lead to a reduction in collagen gene activity but an increase in activity of the genes for matrix metalloproteinases. Inflammation also alters proliferation rates of cells in all skin layers, causes thinning of the epidermis, a flattening of the dermo-epidermal junction, an increase in irregular pigment production, and, finally, an increased incidence of skin cancer. While a large number of inflammatory mediators, including IL-1, TNF-alpha and PGE-2, are responsible for many of these damaging effects, this review will focus primarily on the role of PGE-2 in aging. Levels of this hormone-like mediator increase quickly when skin is exposed to ultraviolet radiation (UVR), causing changes in genes needed for normal skin structure and function. Further, PGE-2 levels in the skin gradually increase with age, regardless of whether or not the skin is protected from UVR, and this smoldering inflammation causes continuous damage to the dermal matrix. Finally, and perhaps most importantly, PGE-2 is strongly linked to skin cancer. This review will focus on: (1) the role of inflammation, and particularly the role of PGE-2, in accelerating skin aging, and (2) current research on natural compounds that inhibit PGE-2 production and how these can be developed into topical products to retard or even reverse the aging process, and to prevent skin cancer.

A comprehensive review of agrimoniin

Plant tannins are a unique class of polyphenols with relatively high molecular weights. Within the ellagitannins group, agrimoniin--dimeric ellagitannin--is one of the most representative compounds found in many plant materials belonging to the Rosaceae family. Agrimoniin was first isolated in 1982 from roots of Agrimonia pilosa Ledeb. (Rosaceae), a plant traditionally used in Japan and China as an antidiarrheal, hemostatic, and antiparasitic agent. Agrimoniin is a constituent of medicinal plants, which are often applied orally in the form of infusions, decoctions, or tinctures. It is also present in commonly consumed food products, such as strawberries and raspberries. It is metabolized by human gut microbiota into a series of low-molecular-weight urolithins with proven anti-inflammatory and anticancer in vivo and in vitro bioactivities. The compound has received widespread interest owing to some interesting biological effects and therapeutic activities, which we elaborate in the present review. Additionally, we present an overview of the techniques used for the analysis, isolation, and separation of agrimoniin from the practical perspective.

Attenuation of UV-B exposure-induced inflammation by abalone hypobranchial gland and gill extracts

Exposure to solar ultraviolet B (UV-B) is a known causative factor for many skin complications such as wrinkles, black spots, shedding and inflammation. Within the wavelengths 280–320 nm, UV-B can penetrate to the epidermal level. This investigation aimed to test whether extracts from the tropical abalone [Haliotis asinina (H. asinina)] mucus-secreting tissues, the hypobranchial gland (HBG) and gills, were able to attenuate the inflammatory process, using the human keratinocyte HaCaT cell line. Cytotoxicity of abalone tissue extracts was determined using an AlamarBlue viability assay. Results showed that HaCaT cells could survive when incubated in crude HBG and gill extracts at concentrations between <11.8 and <16.9 μg/ml, respectively. Subsequently, cell viability was compared between cultured HaCaT cells exposed to serial doses of UV-B from 1 to 11 (x10) mJ/cm² and containing 4 different concentrations of abalone extract from both the HBG and gill (0, 0.1, 2.5, 5 μg/ml). A significant increase in cell viability was observed (P<0.001) following treatment with 2.5 and 5 μg/ml extract. Without extract, cell viability was significantly reduced upon exposure to UV-B at 4 mJ/cm². Three morphological changes were observed in HaCaT cells following UV-B exposure, including i) condensation of cytoplasm; ii) shrunken cells and plasma membrane bubbling; and iii) condensation of chromatin material. A calcein AM-propidium iodide live-dead assay showed that cells could survive cytoplasmic condensation, yet cell death occurred when damage also included membrane bubbling and chromatin changes. Western blot analysis of HaCaT cell COX-2, p38, phospho-p38, SPK/JNK and phospho-SPK/JNK following exposure to >2.5 μg/ml extract showed a significant decrease in intensity for COX-2, phospho-p38 and phospho-SPK/JNK. The present study demonstrated that abalone extracts from the HGB and gill can attenuate inflammatory proteins triggered by UV-B. Hence, the contents of abalone extract, including cellmetabolites and peptides, may provide new agents for skin anti-inflammation, preventing damage due to UV-B.

Photoprotective Effects of Cycloheterophyllin against UVA-Induced Damage and Oxidative Stress in Human Dermal Fibroblasts

Ultraviolet (UV) radiation, particularly ultraviolet A (UVA), is known to play a major role in photoaging of the human skin. Many studies have demonstrated that UV exposure causes the skin cells to generate reactive oxygen species and activates the mitogen-activated protein kinase (MAPK) pathway. Previous studies have also demonstrated that cycloheterophyllin has an antioxidant effect and can effectively scavenge free radicals. Extending the aforementioned investigations, in this study, human dermal fibroblasts were used to investigate the protective effect of cycloheterophyllin against UV-induced damage. We found that cycloheterophyllin not only significantly increased cell viability, but also attenuated the phosphorylation of MAPK after UVA exposure. Furthermore, cycloheterophyllin could reduce hydrogen peroxide (H₂O₂) generation and down-regulate H₂O₂-induced MAPK phosphorylation. In the in vivo studies, the topical application of cycloheterophyllin before UVA irradiation significantly decreased trans-epidermal water loss (TEWL), erythema, and blood flow rate. These results indicate that cycloheterophyllin is a photoprotective agent that inhibits UVA-induced oxidative stress and damage, and could be used in the research on and prevention of skin photoaging.

Anti-Inflammatory Effects of Agrimoniin-Enriched Fractions of Potentilla erecta

Potentilla erecta (PE) is a small herbaceous plant with four yellow petals belonging to the Rosaceae family. The rhizome of PE has traditionally been used as an antidiarrheal, hemostatic and antihemorrhoidal remedy. PE contains up to 20% tannins and 5% ellagitannins, mainly agrimoniin. Agrimoniin is a hydrolyzable tannin that is a potent radical scavenger. In this study we tested the anti-inflammatory effect of four PE fractions with increasing amounts of agrimoniin obtained by Sephadex column separation. First, we analyzed in HaCaT keratinocytes the expression of cyclooxygenase-2 (COX-2) induced by ultraviolet-B (UVB) irradiation. As COX-2 catalyzes the metabolism of arachidonic acid to prostanoids such as PGE₂, we also measured the PGE₂ concentration in cell culture supernatants. PE inhibited UVB-induced COX-2 expression in HaCaT cells and dose-dependently reduced PGE₂. The PE fraction with the highest agrimoniin amount (PE4) was the most effective in this experiment, whereas fraction PE1 containing mainly sugars had no effect. PE4 also dose dependently inhibited the phosphorylation of the epidermal growth factor receptor (EGFR) which plays a crucial role in UVB-mediated COX-2 upregulation. A placebo-controlled UV-erythema study with increasing concentrations of PE4 demonstrated a dose dependent inhibition of UVB-induced inflammation in vivo. Similarly, PE4 significantly reduced UVB-induced PGE₂ production in suction blister fluid in vivo. In summary, PE fractions with a high agrimoniin content display anti-inflammatory effects in vitro and in vivo in models of UVB-induced inflammation.

Fisetin Ameliorated Photodamage by Suppressing the Mitogen-Activated Protein Kinase/Matrix Metalloproteinase Pathway and Nuclear Factor-κB Pathways

Ultraviolet (UV) irradiation is one of the most important extrinsic factors contributing to skin photodamage. After UV irradiation, a series of signal transductions in the skin will be activated, leading to inflammatory response and photoaged skin. In this study, fisetin, a flavonol that exists in fruits and vegetables, was investigated for its photoprotective effects. The results revealed that 5-25 μM fisetin inhibits cyclooxygenase-2 (COX-2) and matrix metalloproteinase (MMP)-1, MMP-3, MMP-9 expression induced by ultraviolet B (UVB) irradiation in human skin fibroblasts. In addition, fisetin suppressed UVB-induced collagen degradation. With regard to its effect on upper-stream signal transduction, we found that fisetin reduced the expression of ultraviolet (UV)-induced ERK, JNK, and p38 phosphorylation in the mitogen-activated protein kinase (MAP kinase) pathway. Furthermore, fisetin reduced inhibitor κB (IκB) degradation and increased the amount of p65, which is a major subunit of nuclear factor-κB (NF-κB), in cytoplasm. It also suppressed NF-κB translocated to the nucleus and inhibited cAMP response element-binding protein (CREB) Ser-133 phosphorylation level in the phosphoinositide 3-kinase/protein kinase B/CREB (PI3K/AKT/CREB) pathway. Finally, fisetin inhibited UV-induced intracellular reactive oxygen species (ROS), prostaglandin E2 (PGE2), and nitric oxide (NO) generation. The mentioned effects and mechanisms suggest that fisetin can be used in the development of photoprotective agents.

Protective effect of ixerisoside A against UVB-induced pro-inflammatory cytokine production in human keratinocytes

Human skin is the first line of defense for the protection of the internal organs of the body from different stimuli. Ultraviolet B (UVB), one of the harmful radiations for skin, is widely known to induce abnormally increased cytokine release from keratinocytes leading to inflammatory skin disorders. IL-6 and IL-8 induce an acute-phase response and stimulate leukocyte infiltration in the skin. Previous studies have shown that chronic exposure to UVB radiation increases cyclooxygenase-2 (COX‑2) expression through various cell signaling pathways, resulting in skin cancer. Recent studies have shown that the activation of extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 MAPK is strongly correlated with acute inflammation and development of skin cancer caused by an increased expression of COX-2. Ixerisoside A (IXA) is an active constituent of Ixeris dentata of the Compositae (Asteraceae) family. The effect of IXA on skin inflammation has yet to be elucidated. To determine the anti-inflammatory effects of IXA, we examined its effect on UVB-induced pro-inflammatory cytokine production in human keratinocytes (HaCaT cells) by observing these cells in the presence or absence of IXA. In this study, pro-inflammatory cytokine production was determined by enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (rt-pcr), and western blot analysis to evaluate the activation of mitogen-activated protein kinases (MAPKs). IXA inhibited UVB-induced production of the pro-inflammatory cytokines IL-6 and IL-8 in a dose-dependent manner. Moreover, IXA inhibited the expression of COX-2, ERK, JNK, and p38 MAPKs, indicating that the secretion of the pro-inflammatory cytokines IL-6 and IL-8, and COX-2 expression was inhibited by blocking MAPK phosphorylation. These results indicated that IXA potentially protects against UVB-induced skin inflammation.

Effect of glutathione reductase knockdown in response to UVB-induced oxidative stress in human lung adenocarcinoma

Background

Glutathione reductase (GR) plays a critical role in the maintenance of physiological redox status in cells. However, the comprehensive investigations of GR-modulated oxidative stress have not been reported.

Methods

In the present study, we cultured a human lung adenocarcinoma line CL1-0 and its GR-knockdown derivative CL1-0ΔGR to evaluate their differential responses to UVB-irradiation.

Results

We identified 18 proteins that showed significant changes under UVB-irradiation in CL1-0ΔGR cells rather than in CL1-0 cells. Several proteins involving protein folding, metabolism, protein biosynthesis and redox regulation showed significant changes in expression.

Conclusions

In summary, the current study used a comprehensive lung adenocarcinoma-based proteomic approach for the identification of GR-modulated protein expression in response to UVB-irradiation. To our knowledge, this is the first global proteomic analysis to investigate the role of GR under UVB-irradiation in mammalian cell model.

Sargassum fulvellum Protects HaCaT Cells and BALB/c Mice from UVB-Induced Proinflammatory Responses

Ultraviolet (UV) radiation has been reported to induce cutaneous inflammation such as erythema and edema via induction of proinflammatory enzymes and mediators. Sargassum fulvellum is a brown alga of Sargassaceae family which has been demonstrated to exhibit antipyretic, analgesic, antiedema, antioxidant, antitumor, fibrinolytic, and hepatoprotective activities. The purpose of this study is to investigate anti-inflammatory effects of ethylacetate fraction of ethanol extract of Sargassum fulvellum (SFE-EtOAc) in HaCaT keratinocytes and BALB/c mice. In HaCaT cells, SFE-EtOAc effectively inhibited UVB-induced cytotoxicity (60 mJ/cm²) and the expression of proinflammatory proteins such as cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS). Furthermore, SFE-EtOAc significantly reduced UVB-induced production of proinflammatory mediators including prostaglandin E₂ (PGE₂) and nitric oxide (NO). In BALB/c mice, topical application of SFE-EtOAc prior to UVB irradiation (200 mJ/cm²) effectively suppressed the UVB-induced protein expression of COX-2, iNOS, and TNF-α and subsequently attenuated generation of PGE₂ and NO as well. In another experiment, SFE-EtOAc pretreatment suppressed UVB-induced reactive oxygen species production and exhibited an antioxidant potential by upregulation of antioxidant enzymes such as catalase and Cu/Zn-superoxide dismutase in HaCaT cells. These results suggest that SFE-EtOAc could be an effective anti-inflammatory agent protecting against UVB irradiation-induced skin damages.

The epidermal growth factor receptor increases cytokine production and cutaneous inflammation in response to ultraviolet irradiation

The epidermal growth factor receptor (EGFR) is activated in cutaneous keratinocytes upon ultraviolet (UV) exposure and has been implicated in ultraviolet-(UV-)induced inflammation and skin tumorigenesis. Egfr mutant mice and EGFR inhibitors were used to investigate the hypothesis that EGFR activation augments inflammation following UV irradiation. Topical treatment of mouse skin with the EGFR inhibitor AG1478 before UV exposure suppressed UV-induced erythema, edema, mast cell infiltration, and neutrophil infiltration. Genetic ablation of Egfr and EGFR inhibition by AG1478 also suppressed the increase in the proinflammatory cytokines tumor necrosis factor α (TNF-α), interleukin-1α, KC (murine IL-8), and cyclooxygenase-2 (COX-2) after UV exposure of cultured keratinocytes. Finally, genetic ablation of inhibition of EGFR in cultured keratinocytes decreased p38 activation after UV, while inhibition of p38 kinase reduced COX-2 expression after UV. These data demonstrate that EGFR regulates multiple aspects of UV-induced inflammation and suggest activation of p38 kinase leading to increased COX-2 and cytokine expression as one mechanism through which it acts.

Sunlight UV-induced skin cancer relies upon activation of the p38α signaling pathway

The activation of cellular signal transduction pathways by solar ultraviolet (SUV) irradiation plays a vital role in skin tumorigenesis. Although many pathways have been studied using pure ultraviolet A (UVA) or ultraviolet B (UVB) irradiation, the signaling pathways induced by SUV (i.e., sunlight) are not understood well enough to permit improvements for prevention, prognosis, and treatment. Here, we report parallel protein kinase array studies aimed at determining the dominant signaling pathway involved in SUV irradiation. Our results indicated that the p38-related signal transduction pathway was dramatically affected by SUV irradiation. SUV (60 kJ UVA/m(2)/3.6 kJ UVB/m(2)) irradiation stimulates phosphorylation of p38α (MAPK14) by 5.78-fold, MSK2 (RPS6KA4) by 6.38-fold, and HSP27 (HSPB1) by 34.56-fold compared with untreated controls. By investigating the tumorigenic role of SUV-induced signal transduction in wild-type and p38 dominant-negative (p38 DN) mice, we found that p38 blockade yielded fewer and smaller tumors. These results establish that p38 signaling is critical for SUV-induced skin carcinogenesis.

Taxifolin suppresses UV-induced skin carcinogenesis by targeting EGFR and PI3K

Skin cancer is one of the most commonly diagnosed cancers in the United States. Taxifolin reportedly exerts multiple biologic effects, but the molecular mechanisms and direct target(s) of taxifolin in skin cancer chemoprevention are still unknown. In silico computer screening and kinase profiling results suggest that the EGF receptor (EGFR), phosphoinositide 3-kinase (PI3K), and Src are potential targets for taxifolin. Pull-down assay results showed that EGFR, PI3K, and Src directly interacted with taxifolin in vitro, whereas taxifolin bound to EGFR and PI3K, but not to Src in cells. ATP competition and in vitro kinase assay data revealed that taxifolin interacted with EGFR and PI3K at the ATP-binding pocket and inhibited their kinase activities. Western blot analysis showed that taxifolin suppressed UVB-induced phosphorylation of EGFR and Akt, and subsequently suppressed their signaling pathways in JB6 P+ mouse skin epidermal cells. Expression levels and promoter activity of COX-2 and prostaglandin E(2) (PGE(2)) generation induced by UVB were also attenuated by taxifolin. The effect of taxifolin on UVB-induced signaling pathways and PGE(2) generation was reduced in EGFR knockout murine embryonic fibroblasts (MEF) compared with EGFR wild-type MEFs. Taxifolin also inhibited EGF-induced cell transformation. Importantly, topical treatment of taxifolin to the dorsal skin significantly suppressed tumor incidence, volume, and multiplicity in a solar UV (SUV)-induced skin carcinogenesis mouse model. Further analysis showed that the taxifolin-treated group had a substantial reduction in SUV-induced phosphorylation of EGFR and Akt in mouse skin. These results suggest that taxifolin exerts chemopreventive activity against UV-induced skin carcinogenesis by targeting EGFR and PI3K.

Cutaneous epidermal growth factor receptor system following ultraviolet irradiation: exploring the role of molecular mechanisms

BACKGROUND/PURPOSE

The epidermal growth factor receptor (EGFR) pathway appears to be essential in many cutaneous disorders. It is well established that ultraviolet (UV) irradiation activates the EGFR in the animal and human skin; however, the molecular mechanisms involved in such activation remain unclear. Our aim is to review and analyse them.

METHODS

Computerized search and selection of original papers in the MEDLINE database (PubMed) from 1988 to 2009 were performed. Systematic analysis and breakdown of the information selected were carried out.

RESULTS

Full manuscripts were retrieved for 32 citations. It was proven that UV light acts directly and indirectly on EGFR (ErbB1/ErbB2) and on numerous intermediaries of extracellular and intracellular signalling. The most closely observed changes imply concentrations and/or molecular activity of the reactive oxygen species group, hydrogen peroxide, matrix metalloproteinases, p38MAPKinase, p21WAF1, p53, signal transducers and activators of transcription 3 and telomerase.

CONCLUSION

Our results help to clarify the working and importance of the UV-EGFR system in the human skin.

Ultraviolet-radiation induced skin inflammation: dissecting the role of bioactive lipids

Acute exposure of human skin to the ultraviolet radiation (UVR) in sunlight results in the sunburn response. This is mediated in part by pro-inflammatory eicosanoids and other bioactive lipids, which are in turn produced via mechanisms including UVR-induction of oxidative stress, cell signalling and gene expression. Sunburn is a self-limiting inflammation offering a convenient and accessible system for the study of human cutaneous lipid metabolism. Recent lipidomic applications have revealed that a wider diversity of eicosanoids may be involved in the sunburn response than previously appreciated. This article reviews the effects of UVR on cutaneous lipids and examines the contribution of bioactive lipid mediators in the development of sunburn. Since human skin is an active site of polyunsaturated fatty acid (PUFA) metabolism, and these macronutrients can influence the production of eicosanoids/bioactive lipids, as well as modulate cell signalling, gene expression and oxidative stress, the application of PUFA as potential photoprotective agents is also considered.

cis-Urocanic acid enhances prostaglandin E2 release and apoptotic cell death via reactive oxygen species in human keratinocytes

Urocanic acid (UCA) is a major UVR-absorbing skin molecule that undergoes trans to cis photoisomerization in the epidermis following UVR exposure. Murine studies have established that cis-UCA is an important mediator of UVR-induced immune suppression, but little is known about its signaling pathway. We have previously demonstrated that treatment of normal human epidermal keratinocytes with cis-UCA resulted in increased synthesis of prostaglandin E(2) (PGE(2)) and cell death. Here, using immortalized human keratinocytes, we report that cis-UCA but not trans-UCA generates reactive oxygen species (ROS) in a dose-dependent manner and that the natural antioxidant α-tocopherol can reduce this ROS generation, subsequent PGE(2) release, and apoptotic cell death. Western blot analysis revealed that cis-UCA leads to a transient phosphorylation of EGFR as well as downstream mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK) and p38. Pharmacological inhibition of their activity attenuated PGE(2) release induced by cis-UCA. After transient activation, cis-UCA downregulated EGFR protein expression that corresponded to activation of caspase-3. In addition, pretreatment with α-tocopherol inhibited EGFR downregulation and caspase-3 activation induced by cis-UCA. These results suggest that cis-UCA exerts its effects on human keratinocytes via intracellular ROS generation that modulates EGFR signaling and subsequently induces PGE(2) synthesis and apoptotic cell death.

Anti-photoaging effects of soy isoflavone extract (aglycone and acetylglucoside form) from soybean cake

Soy isoflavones, found in soybean and soybean products, have been reported to possess many physiological activities such as antioxidant activity, inhibition of cancer cell proliferation, reduction of cardiovascular risk, prevention of osteoporosis and alleviation of postmenopausal syndrome. In our previous study, soy isoflavone extract ISO-1 (containing 12 soy isoflavones) from soybean cake was demonstrated to prevent skin damage caused by UVB exposure. In this study, soy isoflavone extract from soybean cake was further purified and evaluated for the protective effects on UVB-induced damage. The results revealed that Fraction 3, which contains the aglycone group (daidzein, genistein and glycitein) and acetylglucoside group (acetyldaidzin, acetylgenistin and acetylglycitin) of soy isoflavones, could inhibit UVB-induced death of human keratinocytes and reduce the level of desquamation, transepidermal water loss (TEWL), erythema and epidermal thickness in mouse skin. Furthermore, topical application of Fraction 3 increased the activity of catalase and suppressed cyclooxygenase-2 (COX-2) and proliferating cell nuclear antigen (PCNA) expression in mice exposed to UVB. In addition, in comparison with ISO-1 and genistein, the Fraction 3 possessed much greater protective effects on both UVB-induced oxidative stress and keratinocyte death than other fractions. Therefore, the soy isoflavone extract Fraction 3 from soybean cake is a desirable anti-photoaging agent for skin care.

Suppression of gamma-tocotrienol on UVB induced inflammation in HaCaT keratinocytes and HR-1 hairless mice via inflammatory mediators multiple signaling

Tocopherol (Toc) such as alpha-Toc has been expected to act as photochemopreventive agent of skin, but the effect of the other vitamin E forms [tocotrienols (T3)] has not been fully understood. We evaluated the anti-inflammatory effect of T3 on UVB-induced inflammatory reaction using immortalized human keratinocytes and hairless mice. gamma-T3 suppressed UVB-induced PGE(2) production while similar alpha-Toc doses had no effect. The anti-inflammatory actions of gamma-T3 were explained by its ability to reduce UVB-induced inflammatory gene and protein expression [cyclooxgenase-2 (COX-2), interleukin (IL)-1beta, IL-6, and monocyte chemotactic protein-1]. Western blot analysis revealed gamma-T3 inhibited p38, extracellular signal-regulated kinase, and c-Jun N-terminal kinase/stress-activated protein kinase activation. In HR-1 hairless mice, oral T3 suppressed UVB-induced changes in skin thickness, COX-2 protein expression, and hyperplasia, but alpha-Toc did not. These results suggest T3 has potential use to protect against UVB-induced skin inflammation.

The peroxisome proliferator-activated receptor gamma system regulates ultraviolet B-induced prostaglandin e(2) production in human epidermal keratinocytes

Studies using PPARgamma agonists in mouse skin have suggested that peroxisome proliferator-activated receptor gamma (PPARgamma) is irrelevant to cutaneous photobiology. However, in several epithelial cell lines, ultraviolet B (UVB) has been shown to induce the nonenzymatic production of oxidized phospholipids that act as PPARgamma agonists. UVB is also a potent inducer of prostaglandin E(2) (PGE(2)) production and COX-2 expression in keratinocytes and PPARgamma is coupled to increased PGE(2) production in other cell lines. In this current study, we demonstrate that PPARgamma agonists, but not PPARalpha or PPARbeta/delta agonists, induce PGE(2) production and COX-2 expression in primary human keratinocytes (PHKs). Importantly, PPARgamma agonist-induced COX-2 expression and PGE(2) production were partially inhibited by the PPARgamma antagonist, GW9662, indicating that both PPARgamma-dependent and -independent pathways are likely involved. GW9662 also suppressed UVB and tert-butylhydroperoxide- (TBH-) induced PGE(2) production in PHKs and intact human epidermis and partially inhibited UVB-induced COX-2 expression in PHKs. These findings provide evidence that PPARgamma is relevant to cutaneous photobiology in human epidermis.

The UV response of the skin: a review of the MAPK, NFkappaB and TNFalpha signal transduction pathways

The sun emits different types of ultraviolet (UV) light. Our skin is a natural target of UV radiation which is involved in vitamin D3 production in our body. UV radiation at high doses is an environmental carcinogen which can elicit skin damage as well as inducing skin cancer. It can mediate inflammatory and immunological reactions through activation of receptors, DNA/RNA damage and production of reactive oxygen species. It is also involved in the release of pro-inflammatory cytokines, of which TNFalpha has been implicated in tumorigenic activities. In order to mediate its effects, UV radiation is known to activate multiple signalling cascades such as the p38 MAPK, Jun N-terminal kinase, extracellular signal-regulated kinase 1/2 and NFkappaB pathways in skin cells. The role each of these pathways plays in mediating the release of cytokines such as TNFalpha remains to be fully characterized. Once the function of these pathways is known, this information may provide for the formulation of therapy which will prevent the release of immunosuppressive cytokines resulting in a reduction in skin cancer formation.

Waveband and dose dependency of sunlight-induced immunomodulation and cellular changes

Both the UVB and UVA wavebands within sunlight are immunosuppressive. This article reviews the relationship between wavebands and dose in UV-induced immunosuppression mainly concentrating on responses in humans. It also contrasts the effects of UVB and UVA on cellular changes involved in immunosuppression. Over physiological sunlight doses to which humans can be exposed during routine daily living or recreational pursuits, both UVA and UVB suppress immunity. While there is a linear dose relationship with UVB commencing at doses less than half of what is required to cause sunburn, UVA has a bell-shaped dose response over the range to which humans can be realistically exposed. At doses too low for either waveband to be suppressive, interactions between UVA and UVB augment each other, enabling immunosuppression to occur. At doses beyond where UVA is immunosuppressive, it still contributes to sunlight-induced immunosuppression via this interaction with UVB. While there is little research comparing the mechanisms by which UVB, UVA and their interactions can cause immunosuppression, it is likely that different chromophores and early molecular events are involved. There is evidence that both wavebands disrupt antigen presentation and effect T cell responses. Different individuals are likely to have different immunomodulatory responses to sunlight.

Reactive oxygen species produced by NADPH oxidase, xanthine oxidase, and mitochondrial electron transport system mediate heat shock-induced MMP-1 and MMP-9 expression

In addition to ultraviolet radiation, human skin is also exposed to infrared radiation (IR) from natural sunlight. IR typically increases the skin temperature. This study examined whether or not heat shock-induced ROS stimulates MMPs in keratinocyte HaCaT cells. In HaCaT cells, heat shock was found to increase the intracellular ROS levels, including hydrogen peroxide and superoxide. The heat shock treatment induced MMP-1 and MMP-9, but not MMP-2, at the mRNA and protein levels. Moreover, heat shock caused the rapid activation of the three distinct MAPKs, ERK, JNK, and p38 kinase. The heat shock-induced expression of MMP-1 and MMP-9 was significantly suppressed by a pretreatment with the antioxidant NAC or catalase. On the other hand, SOD inhibited heat shock-induced activity of MMP-9 induction, but not MMP-1. A pretreatment with NAC or catalase, but not SOD, attenuated the phosphorylation of ERK, JNK, and p38 kinase by heat shock. The potential sites of ROS generation by heat shock along with its role in the heat shock-induced expression of MMP-1 and MMP-9 were next analyzed. These results indicate that heat shock-induced ROS is promoted via NADPH oxidase, xanthine oxidase, and mitochondria. Indeed, the NADPH oxidase and xanthine oxidase activities were increased by heat shock. Overall, the ROS produced by heat shock may play an important role in the heat shock-induced activation of MAPKs, which can induce MMP-1 and-9 expressions.

Effects of thioredoxin reductase-1 deletion on embryogenesis and transcriptome

Thioredoxin reductases (Txnrd) maintain intracellular redox homeostasis in most organisms. Metazoan Txnrds also participate in signal transduction. Mouse embryos homozygous for a targeted null mutation of the txnrd1 gene, encoding the cytosolic thioredoxin reductase, were viable at embryonic day 8.5 (E8.5) but not at E9.5. Histology revealed that txnrd1-/- cells were capable of proliferation and differentiation; however, mutant embryos were smaller than wild-type littermates and failed to gastrulate. In situ marker gene analyses indicated that primitive streak mesoderm did not form. Microarray analyses on E7.5 txnrd-/- and txnrd+/+ littermates showed similar mRNA levels for peroxiredoxins, glutathione reductases, mitochondrial Txnrd2, and most markers of cell proliferation. Conversely, mRNAs encoding sulfiredoxin, IGF-binding protein 1, carbonyl reductase 3, glutamate cysteine ligase, glutathione S-transferases, and metallothioneins were more abundant in mutants. Many gene expression responses mirrored those in thioredoxin reductase 1-null yeast; however, mice exhibited a novel response within the peroxiredoxin catalytic cycle. Thus, whereas yeast induce peroxiredoxin mRNAs in response to thioredoxin reductase disruption, mice induced sulfiredoxin mRNA. In summary, Txnrd1 was required for correct patterning of the early embryo and progression to later development. Conserved responses to Txnrd1 disruption likely allowed proliferation and limited differentiation of the mutant embryo cells.

Usnea barbata extract prevents ultraviolet-B induced prostaglandin E2 synthesis and COX-2 expression in HaCaT keratinocytes

Usnea barbata and its major constituent usnic acid are potent antimicrobial agents. Here, we have investigated anti-inflammatory properties of an U. barbata extract (UBE) containing 4% usnic acid in an ultraviolet-B (UVB) model with HaCaT keratinocytes. UVB irradiation induced PGE(2) production and COX-2 expression in a time and dose-dependent manner. UBE inhibited PGE(2) production at a half-maximal concentration of 60 microg/ml (2.4 microg/ml usnic acid) that did not affect the UVB-induced upregulation of COX-2, suggesting an effect on enzyme activity rather than on protein expression. The inhibition of PGE(2) production by UBE was not due to cytotoxicity. Besides its known antimicrobial properties, UBE displays specific UVB protective effects that might be useful in the topical treatment of UVB-mediated inflammatory skin conditions.

Prostaglandin E2 suppresses bacterial killing in alveolar macrophages by inhibiting NADPH oxidase

Prostaglandin E2 (PGE2) is a potent lipid mediator that effects changes in cell functions through ligation of four distinct G protein-coupled E prostanoid (EP) receptors (EP1-EP4). PGE2 inhibits bacterial killing and reactive oxygen intermediate (ROI) production by alveolar macrophages (AMs), although little is known about the operative molecular mechanisms. The aims of this study were to evaluate the molecular mechanisms and the specific EP receptors through which PGE2 inhibits killing of Klebsiella pneumoniae by AMs. The treatment of AMs with PGE2 suppressed the killing of K. pneumoniae, and this effect was blocked by an adenylyl cyclase inhibitor and mimicked by agonists for the stimulatory G protein (G(s))-coupled EP2 and EP4 receptors. Conversely, microbicidal activity was augmented by pretreatment with the cyclooxygenase inhibitor, indomethacin, and antagonists of EP2 and EP4. Similar results were found when ROI production was examined. PGE2 inhibition of killing and ROI generation was associated with its activation of the cAMP effectors, protein kinase A and exchange protein directly activated by cAMP-1, as well as attenuation of the phosphorylation and translocation of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase component, p47phox, to the phagosomal membrane. We conclude that PGE2 suppresses the microbicidal activity of AMs through the G(s)-coupled EP2/EP4 receptors, with increased cAMP inhibiting the assembly and activation of p47phox.

Lightening up the UV response by identification of the arylhydrocarbon receptor as a cytoplasmatic target for ultraviolet B radiation

UVB radiation-induced signaling in mammalian cells involves two major pathways: one that is initiated through the generation of DNA photoproducts in the nucleus and a second one that occurs independently of DNA damage and is characterized by cell surface receptor activation. The chromophore for the latter one has been unknown. Here, we report that the UVB response involves tryptophan as a chromophore. We show that through the intracellular generation of photoproducts, such as the arylhydrocarbon receptor (AhR) ligand 6-formylindolo[3,2-b]carbazole, signaling events are initiated, which are transferred to the nucleus and the cell membrane via activation of the cytoplasmatic AhR. Specifically, AhR activation by UVB leads to (i) transcriptional induction of cytochrome P450 1A1 and (ii) EGF receptor internalization with activation of the EGF receptor downstream target ERK1/2 and subsequent induction of cyclooxygenase-2. The role of the AhR in the UVB stress response was confirmed in vivo by studies employing AhR KO mice.

[6]-Gingerol prevents UVB-induced ROS production and COX-2 expression in vitro and in vivo

[6]-Gingerol, a naturally occurring plant phenol, is one of the major components of fresh ginger (Zingiber officinale Roscoe, Zingiberaceae) and has diverse pharmacologic effects. Here, we describe its novel anti-oxidant, anti-apoptotic, and anti-inflammatory activities in vitro and in vivo. In vitro, pre-treatment with [6]-gingerol reduced UVB-induced intracellular reactive oxygen species levels, activation of caspase-3, -8, -9, and Fas expression. It also reduced UVB-induced expression and transactivation of COX-2. Translocation of NF-kappaB from cytosol to nucleus in HaCaT cells was inhibited by [6]-gingerol via suppression of IkappaBalpha phosphorylation (ser-32). Examination by EMSAs and immunohistochemistry showed that topical application of [6]-gingerol (30 microM) prior to UVB irradiation (5 kJ/m(2)) of hairless mice, also inhibited the induction of COX-2 mRNA and protein, as well as NF-kappaB translocation. These results suggest that [6]-gingerol could be an effective therapeutic agent providing protection against UVB-induced skin disorders.

NFAT3 is Required for EGF-Induced COX-2 Transcription, but Neither iNOS Transcription Nor Cell Transformation in Cl 41 Cells

Epidermal growth factor (EGF) has been reported to act as a tumor promoter in several tissues, such as skin, in association with the induction of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). However, molecular mechanisms involved in these regulations are not well defined. This study addressed a potential role of nuclear factor of activated T cells 3 (NFAT3) in EGF-induced COX-2 and iNOS transcription and cell transformation in mouse epidermal Cl 41 cells. We found that EGF markedly induced anchorage-independent growth (cell transformation) of Cl 41 cells, as well as COX-2 (> 6-fold) and iNOS (> 5-fold) promoter-dependent transcription. The EGF-induced COX-2 transcription was blocked by knockdown of NFAT3 with NFAT3 siRNA, whereas the transcription of iNOS and cell transformation induced by EGF were not affected. Although our recent studies supported that NFAT3 plays an essential role in chemical carcinogen benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE)-induced cell transformation, the data presented here demonstrated that NFAT3 is required for EGF-induced COX-2 transcription, but neither iNOS transcription nor cell transformation, indicating that the role of NFAT3 in regulating cell transformation is carcinogen-specific.

Human keratinocytes acquire cellular cytotoxicity under UV-B irradiation. Implication of granzyme B and perforin

Ultraviolet (UV) radiation from the sun is widely considered as a major cause of human skin photoaging and skin cancer. Granzyme B (GrB) and perforin (PFN) are two proteins contained in granules and implicated in one of the mechanisms by which cytotoxic lymphocytes and natural killer cells exert their cytotoxicity against virus-infected, alloreactive, or transformed cells. The distribution of GrB and PFN in the skin has received little attention. However, Berthou and co-workers (Berthou, C., Michel, L., Soulie, A., Jean-Louis, F., Flageul, B., Dubertret, L., Sigaux, F., Zhang, Y., and Sasportes, M. (1997) J. Immunol. 159, 5293-5300) described that, whereas freshly isolated epidermal cells did not express GrB or PFN, keratinocyte growth to confluence was associated with GrB and PFN mRNA and protein synthesis. In this work, we have investigated the possible role of UV-B on GrB and PFN expression in keratinocytes. We found that UV-B induces GrB and PFN expression in these cells through redox-, epidermal growth factor receptor-, and mitogen-activated protein kinase-dependent signaling. Furthermore, under UV irradiation, keratinocytes acquire a significant cytotoxicity, which is GrB and PFN dependent, toward a variety of cellular targets including transformed T-lymphocytes, melanocytes, and keratinocytes. This phenomenon may have important functional consequences in the regulation of skin inflammatory response and in the emergence of cancer skin.

p38 and EGF receptor kinase-mediated activation of the phosphatidylinositol 3-kinase/Akt pathway is required for Zn2+-induced cyclooxygenase-2 expression

Cyclooxygenase 2 (COX-2) expression is induced by physiological and inflammatory stimuli. Regulation of COX-2 expression is stimulus and cell type specific. Exposure to Zn2+ has been associated with activation of multiple intracellular signaling pathways as well as the induction of COX-2 expression. This study aims to elucidate the role of intracellular signaling pathways in Zn2+-induced COX-2 expression in human bronchial epithelial cells. Inhibitors of the phosphatidylinositol 3-kinase (PI3K) potently block Zn2+-induced COX-2 mRNA and protein expression. Overexpression of adenoviral constructs encoding dominant-negative Akt kinase downstream of PI3K or wild-type phosphatase and tensin homolog deleted on chromosome 10, an important PI3K phosphatase, suppresses COX-2 mRNA expression induced by Zn2+. Zn2+ exposure induces phosphorylation of the tyrosine kinases, including Src and EGF receptor (EGFR), and the p38 mitogen-activated protein kinase. Blockage of these kinases results in inhibition of Zn2+-induced Akt phosphorylation as well as COX-2 protein expression. Overexpression of dominant negative p38 constructs suppresses Zn2+-induced increase in COX-2 promoter activity. In contrast, the c-Jun NH2-terminal kinase and the extracellular signal-regulated kinases have minimal effect on Akt phosphorylation and COX-2 expression. Inhibition of p38, Src, and EGFR kinases with pharmacological inhibitors markedly reduces Akt phosphorylation induced by Zn2+. However, the PI3K inhibitors do not show inhibitory effects on p38, Src, and EGFR. These data suggest that p38 and EGFR kinase-mediated Akt activation is required for Zn2+-induced COX-2 expression and that the PI3K/Akt signaling pathway plays a central role in this event.

Ultraviolet radiation-induced apoptosis in keratinocytes: on the role of cytosolic factors

Epidemiological and experimental evidences have established solar ultraviolet (UV) radiation as the leading cause of skin cancers. Specifically, the frequency of non-melanoma skin cancer, one of the malignancies with the most rapidly increasing incidence, is directly related to the total exposure to solar UV light. As part of a general effort to elucidate the components of cellular signal transduction pathways, the mechanisms of cellular responses to UV radiation have received considerable attention over the last few years. These efforts were driven mainly by the conviction that understanding how normal cells respond to extracellular stimuli such as exposure to UV radiation will undoubtedly help in deciphering what goes wrong in a variety of clinical disorders including skin cancers and will assist in the development of novel therapeutic strategies. Studies over the last decade have established that UV radiation induces a bewildering array of signal transduction pathways, some of which could lead to apoptotic cell death. UV-induced cell death by apoptosis is considered to be a natural protective mechanism that removes damaged keratinocytes and circumvents the risk of malignant transformation. In this review, we summarize some of the most important findings regarding the response and role of mitogen-activated protein kinases in UVA and UVB radiation-induced signaling to apoptosis in keratinocytes. We will also briefly discuss what is known about the role of the BCL-2 family of proteins, the emerging role of lysosomal proteases and other important cytosolic signaling proteins in UV-induced apoptosis.

Role of p38 MAPK in UVB-Induced Inflammatory Responses in the Skin of SKH-1 Hairless Mice

The p38 mitogen-activated protein kinase (MAPK) signaling pathway is activated by numerous inflammatory mediators and environmental stresses. We assessed the effects of ultraviolet B (UVB) on the p38 MAPK pathway and determined whether cyclooxygenase (COX)-2 expression is downstream of this kinase in the skin of UVB-irradiated SKH-1 mice. SKH-1 mice were irradiated with a single dose of UVB (360 mJ per cm2), and activation of the epidermal p38 MAPK pathway was assessed. UVB-induced phosphorylation of p38 MAPK occurred in a time-dependent manner. Phosphorylation of MAPK-activated protein kinase-2 (MAPKAPK-2) also was detected and correlated with an increase in its kinase activity. Phosphorylation of heat shock protein 27 (HSP27), a substrate for MAPKAPK-2, also was detected post-irradiation. Oral administration of the p38 inhibitor, SB242235, prior to UVB irradiation, blocked activation of the p38 MAPK cascade, and abolished MAPKAPK-2 kinase activity and phosphorylation of HSP27. Moreover, SB242235 inhibited expression of the pro-inflammatory cytokines interleukin (IL)-6 and KC (murine IL-8) and COX-2. Our data demonstrate that UVB irradiation of murine skin activates epidermal p38 MAPK signaling and induces a local pro-inflammatory response. Blockade of the p38 MAPK pathway may offer an effective approach to reducing or preventing skin damage resulting from acute solar radiation.

Modulation of light-induced skin tumors by N -acetylcysteine and/or ascorbic acid in hairless mice

The light emitted by halogen quartz bulbs contains a broad spectrum of UV wavelengths, is strongly genotoxic and is a potent inducer of skin tumors in hairless mice. By using a UVC filter, this light mimics solar radiation and induces a variety of genomic and transcriptional alterations in mouse skin. UV-related carcinogenesis involves depletion of antioxidants and glutathione in skin cells. On this basis, we evaluated modulation of carcinogenicity of UVC-filtered halogen lamps in SKH-1 hairless mice by the antioxidants N-acetyl-l-cysteine (NAC) and ascorbic acid (AsA). Both agents were given in the drinking water, either individually or in combination. The earliest skin lesions were detected after 300 days' exposure to light and became confluent in a number of mice after 480 days. NAC administration prolonged the latency time by 90 days. Moreover, NAC considerably and significantly decreased both incidence and multiplicity of light-induced skin tumors, prevented the occurrence of malignant lesions (squamocellular carcinomas) and reduced the tumor size. In contrast, AsA, which may behave as a prooxidant rather than an antioxidant, increased the multiplicity of total skin tumors, carcinomas in situ and squamocellular carcinomas. Co-administration of NAC with AsA significantly attenuated the negative effect of AsA, presumably due to the ability of this thiol to maintain a reduced environment. Therefore, in agreement with our previous in vitro findings, oral NAC is able to attenuate the detrimental effects of AsA.

Targeted delivery of antisense oligodeoxynucleotides to folate receptor-overexpressing tumor cells

A major problem in exploring the full potential of antisense ODN is the lack of a safe and efficient delivery system. In this study a new method has been developed that is highly efficient in encapsulating ODN inside folate receptor (FR)-targeted lipid vesicles. ODN formulated in these vesicles were efficiently protected from degradation by nucleases compared to free ODN. Folate efficiently mediated intracellular delivery of ODN to KB tumor cells that overexpress FR. Delivery of EGFR antisense ODN via FR-targeted lipid vesicles resulted in a significant down-regulation of EGFR expression in KB cells and cell growth inhibition, far more efficient than that with free ODN or ODN encapsulated in ligand-free lipid vesicles. Intracellular delivery of EGFR antisense ODN also sensitized KB cells to doxorubicin (DOX) treatment. Thus targeted delivery of ODN via this novel lipid vector may have potential in treating tumors that overexpress FR.