Loss of INK4a/Arf gene enhances ultraviolet radiation‐induced cutaneous tumor development

The CDKN2A locus encodes for tumor suppressor genes p16^INK4a and p14^Arf which are frequently inactivated in human skin tumors. The purpose of this study was to determine the relationship between loss of INK4a/Arf activity and inflammation in the development of ultraviolet (UV) radiation‐induced skin tumors. Panels of INK4a/Arf^‐/? mice and wild‐type (WT) mice were treated with a single dose of UVB (200 mJ/cm²). For long‐term studies, these mice were irradiated with UVB (200 mJ/cm²) three times weekly for 30 weeks. At the end of the experiment, tissues were harvested from mice and assayed for inflammatory biomarkers and cytokines. A single dose of UVB resulted in a significant increase in reactive oxygen species (ROS) and 8‐dihydroxyguanosine (8‐oxo‐dG) lesions in INK4a/Arf^?/? mice compared to WT mice. When subjected to chronic UVB, we found that 100% of INK4a/Arf^?/‐ mice had tumors, whereas there were no tumors in WT controls after 24 weeks of UVB exposure. The increase in tumor development correlated with a significant increase in nuclear factor (NF)‐κB, cyclooxygenase‐2 (COX‐2), prostaglandin E₂ (PGE₂) and its receptors both in UVB‐exposed skin and in the tumors. A significant increase was seen in inflammatory cytokines in skin samples of INK4a/Arf^‐/‐ mice following treatment with chronic UVB radiation. Furthermore, significantly more CD11b⁺Gr1⁺ myeloid cells were present in UVB‐exposed INK4a/Arf^‐/‐ mice compared to WT mice. Our data indicate that by targeting UVB‐induced inflammation, it may be possible to prevent UVB‐induced skin tumors in individuals that carry CDKN2A mutation.     

Astaxanthin,a xanthophyll carotenoid,inhibits ultraviolet‐induced apoptosis in keratinocytes

Intra‐cellular reactive nitrogen/oxygen species and apoptosis play important roles in ultraviolet (UV)‐induced inflammatory responses in the skin. Astaxanthin (AST), a xanthophyll carotenoid, exhibits diverse clinical benefits. The protective effects of AST against UV‐induced apoptosis were investigated in the present study. Astaxanthin (5 μm ) caused a significant decrease in the protein content and the mRNA levels of inducible nitric oxide (iNOS) and cyclooxygenase (COX)‐2, and decreased the release of prostaglandin E2 from HaCaT keratinocytes after UVB (20 mJ/cm²) or UVC (5 mJ/cm²) irradiation. No significant protective effects against UV‐induced reactive oxygen species (ROS) were observed in AST‐pretreated cells. Astaxanthin caused a significant inhibition of UV‐irradiation‐induced apoptosis, as evidence by a DNA fragmentation assay. Furthermore, we found that the treatment with AST caused a reduction in the UVB‐ or UVC‐induced protein and mRNA expression of macrophage migration inhibitory factor (MIF), IL‐1β and TNF‐α in HaCaT keratinocytes. These results suggest that AST effectively protects against UV‐induced inflammation by decreasing iNOS and COX‐2, and thereby inhibiting the apoptosis of keratinocytes.     

Opposing effects of ultraviolet B irradiation on interleukin-1 receptor antagonist and interleukin-1α messenger RNA expression in a human epidermoid carcinoma cell line

Interleukin-1 receptor antagonist (IL-1RA) is a cytokine that acts to antagonize IL-1 activity without agonist function. The expression of IL-1RA has been reported in many cell types, including the keratinocyte that covers the outer most part of the skin. However the modulation of IL-1RA by ultraviolet B (UVB), which is the most biologically active UV, has not been reported yet. We therefore selected a keratinocyte cell line with a cytokine-producing profile similar to that of keratinocytes and tested the effect of UVB on its ability to produce IL-1RA mRNA. IL-1RA mRNA was constitutively expressed in the cell line and began to be suppressed by 3 h after the UVB irradiation with 100 mJ/cm². The level of IL-1RA expression became lowest by 16 h after the irradiation with 100 mJ/cm². Simultaneously, IL-1α mRNA started to increase by 1 h and peaked by 3–16 h after the irradiation with 10–100 mJ/cm². The differential expression of IL-1α and IL-1RA mRNA following exposure to a high dose (100 mJ/cm²) of UVB may markedly potentiate the role of IL-1 in UV-induced inflammation.     

Topical cholesterol treatment ameliorates hapten‐evoked cutaneous hypersensitivity by sustaining expression of 11β‐HSD1 in epidermis

Changes in the stratum corneum extracellular matrix impair epidermal barrier function and may cause dermatoses. The aim of this study was to examine the effect of exogenous cholesterol application on skin barrier function and cutaneous inflammation. Skin barrier‐disrupted or hapten‐stimulated mice were treated with topical cholesterol. The effect of topical cholesterol application on an oxazolone (OXA)‐induced hypersensitivity reaction was evaluated. Topical application of cholesterol efficiently decreased transepidermal water loss in areas of barrier‐disrupted skin and ameliorated OXA‐induced cutaneous hypersensitivity. These favourable effects may have resulted from sustained expression of 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1) in the cholesterol‐treated skin. As 11β‐HSD1 is known to produce active cortisol, topical cholesterol may attenuate contact hypersensitivity by normalizing secretion of hormonally active cortisol from the skin.     

Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomized controlled trial

Background Previous epidemiological, animal and human data report that lycopene has a protective effect against ultraviolet radiation (UVR)‐induced erythema. Objectives We examined whether tomato paste – rich in lycopene, a powerful antioxidant – can protect human skin against UVR‐induced effects partially mediated by oxidative stress, i.e. erythema, matrix changes and mitochondrial DNA (mtDNA) damage. Methods In a randomized controlled study, 20 healthy women (median age 33 years, range 21–47; phototype I/II) ingested 55 g tomato paste (16 mg lycopene) in olive oil, or olive oil alone, daily for 12 weeks. Pre‐ and postsupplementation, UVR erythemal sensitivity was assessed visually as the minimal erythema dose (MED) and quantified with a reflectance instrument. Biopsies were taken from unexposed and UVR‐exposed (3 × MED 24 h earlier) buttock skin pre‐ and postsupplementation, and analysed immunohistochemically for procollagen (pC) I, fibrillin‐1 and matrix metalloproteinase (MMP)‐1, and by quantitative polymerase chain reaction for mtDNA 3895‐bp deletion. Results Mean ± SD erythemal D₃₀ was significantly higher following tomato paste vs. control (baseline, 26·5 ± 7·5 mJ cm^?2; control, 23 ± 6·6 mJ cm^?2; tomato paste, 36·6 ± 14·7 mJ cm^?2; P = 0·03), while the MED was not significantly different between groups (baseline, 35·1 ± 9·9 mJ cm^?2; control, 32·6 ± 9·6 mJ cm^?2; tomato paste, 42·2 ± 11·3 mJ cm^?2). Presupplementation, UVR induced an increase in MMP‐1 (P = 0·01) and a reduction in fibrillin‐1 (P = 0·03). Postsupplementation, UVR‐induced MMP‐1 was reduced in the tomato paste vs. control group (P = 0·04), while the UVR‐induced reduction in fibrillin‐1 was similarly abrogated in both groups, and an increase in pCI deposition was seen following tomato paste (P = 0·05). mtDNA 3895‐bp deletion following 3 × MED UVR was significantly reduced postsupplementation with tomato paste (P = 0·01). Conclusions Tomato paste containing lycopene provides protection against acute and potentially longer‐term aspects of photodamage.     

Antifungal effect of TONS504‐photodynamic therapy on Malassezia furfur

Numerous reports indicate therapeutic efficacy of photodynamic therapy (PDT) against skin tumors, acne and for skin rejuvenation. However, few reports exist regarding its efficacy for fungal skin diseases. In order to determine the antifungal effect, PDT was applied on Malassezia furfur. M. furfur was cultured in the presence of a novel cationic photosensitizer, TONS504, and was irradiated with a 670‐nm diode laser. TONS504‐PDT showed a significant antifungal effect against M. furfur. The effect was irradiation dose‐ and TONS504 concentration‐dependent and the maximal effect was observed at 100 J/cm² and 1 μg/mL, respectively. In conclusion, TONS504‐PDT showed antifungal effect against M. furfur in vitro, and may be a new therapeutic modality for M. furfur‐related skin disorders.     

Staphylococcal α‐toxin induces a functional upregulation of TLR‐2 on human peripheral blood monocytes

Resistance to bacterial skin infections, for example with Staphylococcus aureus (S. aureus), is based on the function of intact innate immune mechanisms. Toll‐like receptor (TLR)‐2 recognizes components of S. aureus and is known to be expressed on monocytes. Staphylococcal exotoxins such as staphylococcal enterotoxin B (SEB) or α‐toxin are produced by many S. aureus strains. To investigate TLR‐2 regulation and function on human monocytes upon stimulation with staphylococcal exotoxins to elucidate a putative feedback loop between different staphylococcal components. Monocytes were stimulated with α‐toxin or SEB, respectively. TLR‐2 expression and regulation as well as functional effects of TLR‐2 stimulation with Pam3Cys (TLR‐2/TLR‐1), lipoteichoic acid (LTA) (TLR‐2/TLR‐6) and peptidoglycan (PGN) (TLR‐2 and Nod) were then investigated both at the mRNA and protein level and compared to monocytes from patients with psoriasis. α‐toxin significantly upregulated TLR‐2 expression. TLR‐2 mediated IL‐1β, IL‐6 and IL‐8 secretion was significantly augmented after upregulation with staphylococcal exotoxins. CD36 expression was significantly more downregulated after TLR‐2 upregulation with SEB and consecutive LTA stimulation and TLR‐2 upregulation with α‐toxin following LTA and PGN stimulation, respectively. PGN enhanced CD54 expression after upregulation of the receptor with α‐toxin. Expression of HLA‐DR was unaffected. However, no differences were observed in monocytes from psoriasis patients compared to healthy controls. Together, our findings provide a new link between staphylococcal α‐toxin and TLR‐2 signalling in monocytes which may have implications for skin diseases where skin colonization with S. aureus and dysregulation of TLR‐2 have been described.     

Expression profiles of cortisol‐inactivating enzyme, 11β‐hydroxysteroid dehydrogenase‐2, in human epidermal tumors and its role in keratinocyte proliferation

The enzyme 11β‐hydroxysteroid dehydrogenase (11β‐HSD) catalyzes the interconversion between hormonally active cortisol and inactive cortisone within cells. There are two isozymes: 11β‐HSD1 activates cortisol from cortisone and 11β‐HSD2 inactivates cortisol to cortisone. 11β‐HSD1 was recently discovered in skin, and we subsequently found that the enzyme negatively regulates keratinocyte proliferation. We verified 11β‐HSD1 and 11β‐HSD2 expression in benign and malignant skin tumors and investigated the role of 11β‐HSD in skin tumor pathogenesis. Randomly selected formalin‐fixed sections of skin lesions of seborrheic keratosis (SK), squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) were stained with 11β‐HSD1 and 11β‐HSD2 antibodies, and 11β‐HSD expression was also evaluated in murine epidermis in which hyperproliferation was induced by 12‐O‐tetradecanoylphorbol‐13 acetate (TPA). We observed that 11β‐HSD1 expression was decreased in all SK, SCC, and BCC lesions compared with unaffected skin. Conversely, 11β‐HSD2 expression was increased in SK and BCC but not in SCC. Overexpression of 11β‐HSD2 in keratinocytes increased cell proliferation. In the murine model, 11β‐HSD1 expression was decreased in TPA‐treated hyperproliferative skin. Our findings suggest that 11β‐HSD1 expression is decreased in keratinocyte proliferative conditions, and 11β‐HSD2 expression is increased in basal cell proliferating conditions, such as BCC and SK. Assessing 11β‐HSD1 and 11β‐HSD2 expression could be a useful tool for diagnosing and characterizing skin tumors.     

NADPH oxidase is a novel target of delphinidin for the inhibition of UVB‐induced MMP‐1 expression in human dermal fibroblasts

We investigated the reported antiphotoaging effects of the major anthocyanidin delphidin and sought to identify its specific molecular target during UVB‐induced MMP‐1 expression. Delphinidin treatment significantly inhibited UVB‐induced MMP‐1 expression in primary cultured human dermal fibroblasts (HDF), an effect associated with the suppression of MKK4‐JNK1/2, MKK3/6‐p38 and MEK‐ERK1/2 phosphorylation. Further investigation revealed that delphinidin significantly inhibited UVB‐induced ROS production and NOX activity. Interestingly, the inhibitory effect of delphinidin on UVB‐induced NOX activity was stronger than that of apocynin, a pharmaceutical NOX inhibitor. Fractioned cell analysis results using a Western blot assay showed that this effect occurred through the inhibition of UVB‐induced P47^phox (a NOX subunit) translocation from the cytosol to the membrane. Pull down assays demonstrated that delphinidin binds directly to P47^phox in vitro. Collectively, our results suggest that delphinidin targets NOX, resulting in the suppression of UVB‐induced MMP‐1 expression in human dermal fibroblasts.     

Could colorimetric method replace the individual minimal erythemal dose (MED) measurements in determining the initial dose of narrow‐band UVB treatment for psoriasis patients with skin phototype III–V?

Background Assessment of minimal erythemal dose (MED) for individual patients has been used to guide the narrowband Ultraviolet B (NB‐UVB) phototherapy, which sometimes causes discomfort and additional time. The L* value (the lightness of color in Commission Internationlale de l’Eclairge L*a*b* color scale) measured by colorimeter was shown to be useful for predicting sensitivity to NB‐UVB irradiation. Objective To compare the efficacy and safety of NB‐UVB phototherapy between 50% of MED and colorimetric L* value starting dose regimens for skin phototype III–V Korean patients with psoriasis. Method Twenty seven patients determined starting doses based on colorimetric L* value, and 27 patients based on 50% of MED. Since correlation analysis showed that L* value had the most significant association with MED compared with skin phototypes, a*, and b* values, we designated starting doses of L* value regimen as follows: 300 mJ/cm² (L* >66), 400 mJ/cm² (62 < L*≤66), and 500 mJ/cm² (L*≤62). Results There was no significant difference between two groups in clinical efficacy including response rate, mean number of sessions, duration of treatment, maximum dose and cumulative dose until achieving the state of near clearance. The proportion of adverse effects was not also significantly different. Conclusions NB‐UVB starting dose determination based on colorimetric L* value was comparable with conventional MED based regimen in efficacy and safety for skin phototype III–V patients. Since it provides much convenience and ease for both patients and physicians, colorimetric L* value could partly substitute the MED checking methods in NB‐UVB phototherapy.     

Ultraviolet B stimulates proopiomelanocortin signalling in the arcuate nucleus of the hypothalamus in mice

We previously found that ultraviolet B (UVB) could stimulate the paraventricular nucleus (PVN) with activation the systemic hypothalamic–pituitary– adrenal (HPA) axis. To investigate whether UVB can also stimulate other hypothalamic nuclei, we tested its effect on the proopiomelanocortin (POMC) related signalling system in the arcuate nucleus (ARC) of female C57BL/6 and FVB albino mice. The shaved back skin of the mice was irradiated with either 100 or 400 mJ/cm² of UVB. After 1, 3, 6 and 12 h, blood and hypothalamus were collected and processed for gene and protein expression, and measurement of α‐MSH and β‐endorphin (β‐END) levels. An in situ immunohistochemical examination was performed for melanocortin receptor 4 (MC4R) and POMC‐derived α‐MSH. The expression of Pomc and MC4R mRNAs was stimulated, whereas that of AgRP was inhibited after exposure to UVB. It was accompanied by an increased number of both α‐MSH‐ and MC4R‐immunoreactive neurons in the ARC, and by increased levels of α‐MSH and β‐END (both found in the hypothalamus and plasma). This surprising discovery of UVB stimulating the POMC system in the ARC, accompanied by the increased plasma levels of α‐MSH and β‐END, paves the way for exciting areas of research on the communication between the skin and the brain, as well as is suggesting a new role for UVB in regulation of body metabolism.     

Isoflavones in aglycone solution enhance ultraviolet B‐induced DNA damage repair efficiency

The isoflavones daidzein and genistein are natural compounds which have anti‐inflammatory and photoprotective activities, and may be effective in the repair of ultraviolet (UV)‐induced photodamage. In this study, an alcoholic solution of aglycone isoflavones with a genistein:daidzein ratio of 1:4 [Rottapharm (RPH)‐aglycone] was examined for its effects on the repair of DNA damage induced by a single dose of UVB irradiation (20 mJ/cm²). For this purpose, human skin cells were first UVB‐irradiated and then treated with RPH‐aglycone. Comet assay analysis was used to estimate the UVB‐induced DNA damage at different time points after treatment by measuring the tail moment parameter. We found that treatment with 10 μmol/L RPH‐aglycone solution resulted in a significantly reduced tail moment at 1 h after treatment, and 34–35% enhancement of damage repair at 4 h after treatment. These results suggest that isoflavone aglycones are protective against UVB‐induced DNA damage.     

Ultraviolet B‐induced apoptosis of human skin fibroblasts involves activation of caspase‐8 and ‐3 with increased expression of vimentin

Background: After irradiation with a high dose of ultraviolet B (UVB), cells undergo apoptosis. Caspase‐8 and ‐3 are key mediators of apoptosis in many cells. Vimentin, an important cytoskeleton component, can be cleaved by caspase‐3, ‐6, ‐7 and ‐8. Cell apoptosis is promoted via caspase‐triggered proteolysis of vimentin. In this study, we explored the roles of caspase‐8 and ‐3 and the changes in vimentin expression in UVB‐induced apoptosis of human dermal fibroblasts. Methods: Skin fibroblasts were irradiated with 150 mJ/cm² UVB and cell death was monitored by the 3‐(4,5)‐dimethylthiahiazo(‐z‐y1)‐3,5‐diphenytetrazoliumromide assay and Hoechst staining. Caspase‐8 and ‐3 activities were detected by the caspase activity assay. Vimentin expression was assessed by immunofluorescence and Western blot. Results: Caspase‐8 and ‐3 were activated by 150 mJ/cm² UVB irradiation. Caspase‐8 and ‐3 activities changed in a time‐dependent way after UVB irradiation to induce apoptosis of fibroblasts, and caspase‐8 and ‐3 interacted with each other in this process. However, their substrate, vimentin, showed an enhanced expression over time after UVB irradiation. Conclusions: UVB‐triggered apoptosis of fibroblasts was dependent on the activation of caspase‐8 and ‐3 with an increased expression of vimentin.