Narrowband ultraviolet B radiation suppresses contact hypersensitivity

Background/purpose: A main mechanism responsible for the efficacy of narrowband ultraviolet (UV)B is thought to be the induction of apoptosis in pathogenetically relevant cells. Narrowband UVB therapy, however, generally induces a relatively long remission period. Recently, evidence that UVB radiation induces regulatory T (Treg) cells was reported. Based on these findings, we examined whether narrowband UVB suppresses contact hypersensitivity (CHS) by inducing Treg cells. Methods: The shaved abdomens of C3H/HeN mice were irradiated with broadband or narrowband UVB. CHS was defined as an ear‐swelling response. To examine whether tolerance can be induced by adoptive transfer, lymph node cells from UVB‐irradiated mice were injected into naïve mice before sensitization and CHS challenge. Results: Narrowband UVB exposure dose dependently suppressed CHS. Significant suppression was observed at doses between 1000 and 3000 mJ/cm² (P<0.05). The suppressive effect achieved with 1000 mJ/cm² narrowband UVB was very similar to the effect achieved with 100 mJ/cm² broadband UVB. The suppressive effects on CHS were transferred to naïve mice by the injection of lymph node cells from tolerant mice. Conclusion: Narrowband UVB induced local and systemic suppression of CHS. In addition, narrowband UVB induces tolerance to CHS and the suppressive effects were transferable to naïve mice.     

Interaction of ultraviolet-B-rich and ultraviolet-A-rich radiation in ketoprofen-induced photohemolysis

Interactions between different wavelengths can cause inhibition or enhancement of various biological reactions. We evaluated in vitro the effect of UVB-rich irradiation on UVA-induced phototoxicity. Suspensions of human erythrocytes were incubated with ketoprofen, a phototoxic nonsteroidal anti-inflammatory drug. These samples were exposed to 0, 20, 40, 80, 160 or 320 mJ/cm² UVB followed by irradiation with 0 or 6 J/cm² UVA. Photo-induced hemolysis was calculated as a percentage of complete hemolysis. Ketoprofen-dependent hemolysis due to UVA alone was 63% (median). UVB did not induce ketoprofen-dependent photohemolysis at doses <80 mJ/cm². Exposure to UVB at all doses enhanced significantly (P<0.01) UVA-induced ketoprofen-dependent hemolysis in samples from 9 of 15 donors. However, with erythrocytes from the other 6 donors, 20 or 40 mJ/cm² UVB reduced the median of UVA-induced photohemolysis by 69% (P<0.05) or 47% (not significant), respectively. Co-incubation of samples with ascorbic acid resulted in a profound inhibition of ketoprofen-dependent photohemolysis. These results indicate that the effect of low UVB doses on UVA-induced phototoxicity depends on individual, yet unknown characteristics of the target cells.     

Tegafur-induced photosensitivity — evaluation of provocation by UVB irradiation

Dermatology, A 75-year-old Japanese man with photodistributed erythematous lichen planus like eruptions visited the dermatology clinic of Kobe University in November 1994. He had had an operation for gastric cancer in July 1992, and thereafter he had been taking 600 mg/d of tegafur. In July 1994, he was exposed to the sun for 2 h and the following day noticed an itchy rash in the areas exposed to the sun. He consulted his surgeon and stopped i taking the tegafur In October. Thereafter his eruption gradually improved. A biopsy J specimen taken on the initial visit to our hospital, 22 days after the cessation of tegafur, revealed perivascular collections of mononuclear cells in the upper dermis and slight liquefaction degeneration of the epidermal basal cells with some civatte bodies. Immunofluorescent staining showed no deposits of immunoglobulins or complements. Photosensitivity studies were performed with a bank of 7 fluorescent sunlamps (Toshiba FL20SE) emitting 280–370 nm (nnainly UVB energy, peaKing at 305 nm) and a bank ot 14 fluorescent black lights (Toshiba FL32SBL) emitting 300–420 nm (mainly UVA energy peaking at 365 nm). His minimal erythema doses (MEDs) of 58.5 mJ/cm² in UVB and of large dose of UVA over 12.6 J/cm² were in the normal range. Patch tests and two sets of photopatch tests were made with 5% tegafur and 5-fluorouracil (5-FU) in white petrolatum using Finn chambers. One set was exposed to 6.3 J/cm² of UVA, and a second set to a suberythemal dose of UVB, 40 mJ/cm², after 24 h of closed patch tests. Twenty four hours after UV irradiation for photopatch tests, and 48 h after the initial patch for patch tests, the reaction was evaluated. No abnormal reactions in patch and photopatch tests were detected. Tegafur was readministered at a dose of 200 mg every eight hours. After a total dose of 2400 mg (day 4), the skin of the back was exposed to UVB (6–120 mJ/cm²) and UVA (2–12.6 J/cm²) two hours after the last oral intake of tegafur. No decrease in MED or any abnormal reaction was observed. After a total of 3600 mg (day 6), a new skin site on the back was exposed to 3 MED of UVB. The next day (day 7, after a total dose of 4200 mg), 3 MED of UVB was irradiated on the same site and 5 MED of UVB was irradiated at a new site. Lastly, after a total dose of 4800 mg (day 8), 3 MED and 5 MED of UVB was again irradiated on the same sites that were irradiated on the previous day, and 10 MED UVB and 21 J/cm² UVA were irradiated at new individual sites. Eight days after the last irradiation (day 16, after 9600 mg of drug intake) the 10 MED UVB irradiated site revealed miliar-sized papules with a faint red hue after sunburn reaction. Simultaneously, an edematous erythema recurred on the face, neck, upper back, and hands, where the rash had previously been, without exposure to UVB or UVA. These tests were conducted while the patient was hospitalized and he was very careful not to be exposed to the sun, even through glass. The biopsy specimens of 10 MED irradiated sites and the flare-up lesion of his upper back revealed liquefaction degeneration of the epidermal basal cells with civatte bodies. Immunofluorescent staining study showed IgM, IgA, and C4 deposition of the civatte bodies in the flare-up lesion which had not been exposed to any UV irradiation.     

UV irradiation induces downregulation of bcl-2 expression in vitro and in vivo

Abstract Recently, the proto-oncogenes bcl-2 and bax have emerged as important regulators of the apoptotic form of cell death. We examined UV irradiation-elicited apoptosis and regulation of bcl-2 and bax expression both in vivo in human skin and in vitro in HeLa cells. Using flow cytometric analysis, HeLa cells were found to undergo apoptosis at the 12-h time-point after exposure to UVB irradiation (100 mJ/cm²). The expression of bcl-2 mRNA was found to decrease after a single dose of UVB radiation (doses 10–200 mJ/ cm²). In contrast, the expression of bax mRNA was not significantly changed. When human skin was irradiated with a single dose of solar-simulated radiation (40 mJ/cm²), Bcl-2-positive cells were significantly reduced in the epidermis at the 3- and 6-h time-points. Our results suggest that UV irradiation downregulates bcl-2 expression both in vitro at the mRNA level and in vivo at the protein level, and that downregulation of bcl-2 constitutes a mechanism of potential importance in UV-induced apoptosis in human epidermis. Received: 1 July 1998 / Received after revision: 12 October1998 / Accepted: 2 November 1998     

UVA does not photoreactivate pyrimidine dimers in cultured human fibroblasts

Abstract Pyrimidine dimers were induced in duplicates of cultured human skin fibroblasts by irradiation with various doses of UVB radiation. Subsequently, one set of cells was further exposed to either 5 or 10 J/cm² of UVA radiation to assess the photoreactivating activity of this spectral range in a human cell system. Following irradiation, pyrimidine dimers were quantified in all cells by determining the number of endonuclease-sensitive sites (ESS). No difference in the yield of ESS was observed between cells which had been irradiated with UVB only as compared to cells which subsequently had been exposed to 5 or 10 J/cm² UVA. In contrast, subsequent exposure of UVB-irradiated cells of Monodelphis domestica to 10 J/cm² UVA resulted in an almost 50% reduction of UVB-induced pyrimidine dimers. These data indicate that UVA does not induce photoenzymatic repair in human fibroblasts.     

Studies on the effects of a high dose UVA-1 radiation therapy on surface markers and function of epidermal Langerhans cells

Recently, high-dose UVA-1 therapy (340–400 nm) was introduced as an effective treatment of severe exacerbated atopic dermatitis. Since the target of this type of radiation in the skin is not known we investigated using the mouse model whether surface markers of the antigen-presenting function of epidermal Langerhans cells are affected by UVA-1 radiation. Even repeated high doses of UVA-1 radiation (up to 50 J/cm²) had no detectable effect on surface ATPase activity and Ia antigen expression on Langerhans cells. Also, the contact allergen oxazolone was presented normally in skin treated with UVA-1 radiation. In contrast, if the mice were injected 1 h before irradiation with 8-methoxypsoralen a dramatic reduction in ATPase activity and Ia antigen expression on Langerhans cells was observed and the induction of contact sensitivity was suppressed (PUVA effect). These results show that epidermal Langerhans cells are not impaired either in structure or function and that these cells probably do not represent the primary target of UVA-1 radiation in the skin. No side effects resulting from a diminished Langerhans cell function should result from high-dose UVA-1 therapy.     

UVB irradiation induces changes in the distribution and release of 14C-arachidonic acid in human keratinocytes in culture

Summary Following labeling of human keratinocytes in culture for 48 h with ¹⁴C-arachidonic acid (800,000 cpm), 86.8±0.5% (mean±SEM) of the radioactivity was incorporated into the cells. Two hours after exposure to UVB irradiation at doses up to 392 mJ/cm² of erythemally effective (EE) UVB irradiation, only slight changes in the distribution of arachidonic acid could be detected. However, 24 h after irradiation the release of arachidonic acid into the culture medium was significantly increased. The distribution of arachidonic acid was also changed: there was a considerable loss in the amount of radioactivity associated with phosphatidylethanolamine. With doses up to 174 mJ/cm² (EE) of UVB, the decrease in the labeling of phospholipids was accompanied by an increased arachidonic acid content in the nonphosphorus lipids, especially in the triacylglycerols. Following a high dose of UVB (392 mJ/cm², EE), a substantial release of label was detected, but the labeling of triacylglycerols was unaltered. The present study suggests that in human keratinocytes UVB irradiation induces the release of arachidonic acid from the cellular lipids and that the major source of the released arachidonic acid is phosphatidylethanolamine.This study was financially supported by the Research and Science Foundation of Farmos (Finland), the Finnish Allergy Research Foundation, and the Finnish Dermatological Society     

Protective effect of topically applied conjugated hexadienes against ultraviolet radiation-induced chronic skin damage in the hairless mouse

Albino hairless mice (SkH:HR-1) exposed chronically to suberythemal doses of ultraviolet B (UVB) radiation display visible skin wrinkling and tumors. Topical treatment of mice with solutions of conjugated dienes (2,4-hexadien-1-ol and derivatives of it) prior to each UVB radiation exposure reduces significantly the severity of these visible alterations. Chronic suberythemal doses of ultraviolet A radiation induce skin sagging, a distinctly different visible skin alteration. The severity of skin sagging is not reduced by topical application of the conjugated dienes tested here.     

Antioxidant defence mechanism of the skin against UV irradiation: Study of the role of catalase using acatalasaemia fibroblasts

To clarify the role of catalase, an antioxidant enzyme, in response to UV irradiation, we compared the effects of irradiation on cytotoxicity, activities of antioxidant enzymes, total glutathione concentrations, lipid peroxidation and the rate of collagen synthesis in skin fibroblasts from a patient with acatalasaemia and in those from a normal individual. The cells were irradiated with UVA (6 and 12 J/cm² or UVB (0.5 and 1 J/cm²). Cell survival curves after UV irradiation were similar in cells from both subjects. Although superoxide dismutase activity in acatalasaemia cells was higher than in the control cells before irradiation, after irradiation the activity decreased in acatalasaemia cells (76% with 12 J/cm² UVA, 47% with 1 J/cm² UVB), but remained unchanged in control cells. Total glutathione concentrations also decreased in acatalasaemia cells (60% with 12 J/cm²) in response to UVA irradiation, but remained unchanged in control cells. Lipid peroxidation did not increase significantly in either cell type. The rate of collagen synthesis decreased to a similar extent in response to UV exposure in the two cell types (60–80% with 8.2 J/cm² UVA, 40–50% with 10 mJ/cm² UVB). We conclude from the results of cytotoxicity and lipid peroxidation that although acatalasaemia cells were killed by hydrogen peroxide at low concentrations with a single UV exposure, catalase functions only to a small degree as an antioxidant enzyme. There remains the possibility, however, that a deficiency of catalase may chronically damage the skin resulting in a reduced defence function of Superoxide dismutase and glutathione with repeated exposures to UV, which is becoming more common in our daily life.     

Higher cyclobutane pyrimidine dimer and (6-4) photoproduct yields in epidermis of normal humans with increased sensitivity to ultraviolet B radiation

Cyclobutane pyrimidine dimer (CPD) and (6-4) photoproduct induced in the epidermis of five Japanese volunteers exposed to ultraviolet (UVB) radiation were measured with monoclonal antibodies specific for each photoproduct. The volunteers comprised two individuals who are sensitive to solar irradiation (low minimal erythema dose [MED]) and three who are less sensitive. The yields of CPD and (6-4) photoproduct were within similar ranges after 1 MED or 3 MED doses. The yields of both photoproducts after the same dose of irradiation (120 mJ/cm²) were higher in UV-sensitive individuals than in less sensitive individuals. By 24 h after irradiation, an average of 60% of CPD had been removed after the 1 MED dose, 27% after the 3 MED dose and 34% after 120 mJ/cm². The (6-4) photoproduct was removed within 24 h, independently of the dose of UVB tested. These data suggest that DNA photoproducts participate in initiating UVB-induced erythema, and partially explain why individuals with higher sensitivity to UVB have a higher risk of UV-induced skin cancer.     

The Effects of Sunscreens on UVB Erythema and Langerhans Cell Depression

Langerhans cells (LCs) are epidermal antigen-presenting cells capable of initiating a specific T lymphocyte-mediated immune response. It is a well known fact that ultraviolet light B (UVB) suppresses LC number and function. In this study, we confirmed that the sunscreens CITY BLOCK, and TOTAL SUN SHIELD 28 (Clinique Laboratories Tokyo, Japan) protected the epidermis against the depletion of LC number. We also investigated whether or not sunscreens could provide LC protection from ultraviolet ray (UVR) damage other than the prevention of the decrease in the total number of cells. Our data showed that the LC population was depressed after irradiation by 100 mJ/cm² or 10 mJ/cm² of UVB, but recovered to within normal levels after 16 days. Both sunscreens provided protection against erythema and LC depression due to UVB irradiation. However, despite the fact that these sunscreens had completely suppressed UVB erythema, shrinkage of LC dendrites was seen. Apparently, sunscreens prevent UVB erythema, but do not protect against functional changes in LC due to UVB. Recently, it has been reported that sunscreens are less effective in protecting against systemic immunosuppression that against inflammation. The shrinkage of LC dendrites despite sunscreen application may help explain this discrepancy.     

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.     

Erythemal and therapeutic response of psoriasis to PUVA using high-dose UVA

In PUVA treatment of psoriasis, clinical observation suggests that uninvolved skin is more susceptible to PUVA erythema than lesions of psoriasis. If this is the case, then the efficacy of PUVA treatment might be increased by using localized high-dose UVA restricted to lesional skin. We have therefore studied the erythemal and therapeutic response of psoriasis to PUVA using high-dose UVA and, for comparison, the erythemal response to UVB. In 14 patients, an area of psoriasis and adjacent uninvolved skin were exposed to a series of UVA doses (350 ± 30 nm, 1–16 J/cm²), using an irradiation monochromator. Six other patients were similarly phototested with a series of UVB doses (300 ± 5 nm, 20–112 mJ/cm²) to both uninvolved and lesional skin. Erythema was judged visually at 72 h for psoralen–UVA, and at 24 h for UVB, and measured using a scanning laser–Doppler velocimeter. In 10 patients, PUVA therapy using high-dose UVA was subsequently given to lesional skin (8–16 J/cm² twice weekly) in addition to conventional whole-body PUVA. For psoralen–UVA, the minimal phototoxic dose within psoriasis was increased by a factor of 4 compared with non-lesional skin (P < 0.01, Wilcoxon signed-rank test). For UVB, the minimal erythema dose within psoriasis was higher than that for non-lesional skin (medians > 112 and 28 respectively, P < 0.05). Laser–Doppler measurements confirmed that the reduced erythemal sensitivity was not due to masking of response by pre-existing increased blood flux within psoriasis. In six patients, the sites subsequently treated twice weekly with PUVA, using high-dose UVA, cleared faster (median number of treatments 3), but with a similar cumulative UVA dose, compared with adjacent lesional skin treated with conventional PUVA (median number of treatments 12). This study demonstrates that psoriasis may clear rapidly, without burning, using high-dose UVA. Availability of a suitable irradiation apparatus would allow rapid and effective PUVA treatment to be used for localized, resistant disease.     

Interdependence between body surface area and ultraviolet B dose in vitamin D production: a randomized controlled trial

Background Ultraviolet (UV) B radiation increases serum vitamin D level expressed as 25‐hydroxyvitamin‐D₃ [25(OH)D], but the relationship to body surface area and UVB dose needs investigation. Objective To investigate the importance of body surface area and UVB dose on vitamin D production after UVB exposure. Methods We randomized 92 participants to have 6%, 12% or 24% of their skin exposed to 0·75 (7·5 mJ cm^?2 at 298 nm using the CIE erythema action spectrum), 1·5 (15 mJ cm^?2) or 3·0 (30 mJ cm^?2) standard erythema doses (SED) of UVB. Each participant underwent four UVB exposures at intervals of 2–3 days. Skin pigmentation and 25(OH)D levels were measured before and 48 h after the final exposure. Results The increase in 25(OH)D after irradiation [Δ25(OH)D] was positively correlated with body surface area (P = 0·006; R² = 0·08) and UVB dose (P < 0·0001; R² = 0·28), and negatively correlated with baseline 25(OH)D (P < 0·0001; R² = 0·18), for the entire data sample. However, when analysing each body surface area separately, we found a significant UVB response correlation for 6% (P < 0·0001; R² = 0·48) and 12% (P = 0·0004; R² = 0·35), but not for 24%. We also found a significant skin area response correlation for 0·75 SED (P < 0·0001; R² = 0·56), but not for 1·5 and 3·0 SED when analysing each UVB dose separately. The relationships did not change significantly after adjustment of Δ25(OH)D for baseline 25(OH)D. Conclusion The increase in 25(OH)D depends mainly on the UVB dose; however, for small UVB doses the area of irradiated body surface is important.     

In vivo PUVA and UVB sensitivity of various human epidermal Langerhans cell markers (ATPase, HLA-DR and T6)—Dose-response and time-sequence studies

To form a comprehensive view of the UV-sensitivity of human epidermal Langerhans cells (LC), the time-sequence and close response effects of single doses of UVB or 8-methoxypsoralen plus UVA (PUVA) radiation on three different LC surface markers were studied with histochemical and immunohistochemical staining. An increasing PUVA dose from 1 to 10 J/cm² caused an almost linear decrease in the surface enzyme (ATPase) positive LC count, whereas the cell surface antigens (HLA-DR and T6) were rather more resistant, up to a PUVA dose of 5 J/cm². A single dose of 5 J/cm² of PUVA induced an LC depletion that was similar during the 21 days of observation, irrespective of whether the cells were visualized with ATPase staining or with monoclonal antibodies against the cell surface antigens HLA-DR or T6. In each case, the nadir was reached 14 days after irradiation; the average residual LC count was then 57%. The cell counts 21 days after PUVA irradiation were still only approximately 74% of the nontreated skin counts. Langerhans cell depletion induced by an erythemagenic dose of UVB irradiation was swifter and more pronounced than that induced by 5 J/cm² of PUVA but, again, a similar time schedule was recorded with ATPase, HLA-DR and T6 staining.     

人参皂苷Rg1对UVB损伤PG12及成纤维细胞的保护作用

目的研究人参皂苷Rg1对中波紫外线（UVB）损伤皮肤成纤维细胞以及作为皮肤神经细胞模型的PC12细胞的保护作用。方法实验分为UVB模型组、UVB＋Rg1三个不同浓度保护组、对照组,分别以60mJ／cm^2、100mJ／cm^2强度UVB造成培养的皮肤成纤维细胞、皮肤神经细胞模型PC12（神经元化）细胞损伤,用MTT法检测细胞增殖活性,酶生化法检测光损伤前后细胞培养上清SOD活性、MDA含量。结果强度为60mJ／cm^2、100mJ／cm^2的中波紫外线分别可以造成体外培养的人皮肤成纤维细胞、神经元化PC12细胞增殖活性降低,细胞培养上清SOD活性降低,MDA含量升高,与UVB模型组相比均P〈0．05。给定浓度范围的Rg1能增加细胞的增殖活性,增加细胞培养上清SOD活性、降低MDA含量。结论紫外线可以造成体外培养的人皮肤成纤维细胞及PC12细胞氧化损伤,人参皂苷Rg1对损伤的细胞具有一定保护作用,其机制可能与它的抗氧化、增强细胞活力有关