The protective role of epidermal melanin in a patient with porphyria variegata and vitiligo

To assess the role of epidermal melanin in a patient with porphyria variegata and vitiligo, the MED was determined in pigmented and vitiliginous skin for wavelengths of 310, 405 and 500 nm. The energy required to elicit erythema by irradiating vitiliginous skin at 310 nm was half that for pigmented skin. For 405 nm the differences was 4-fold and at 500 nm 2-fold. A possible explanation for the different protection by melanin against light of 310, 405 and 500 nm is given. UV-B irradiation, as a potent stimulus for melanization of the skin, is proposed as an additive measure in the protection against photosensitivity reactions in porphyria patients.     

The influence of pre-irradiation on the predictability of in vivo UVA protection with a new in vitro method

BACKGROUND/PURPOSE: UVA protection of sunscreen formulations is becoming increasingly important especially because of recent investigations on the long-term skin damage associated with UVA light. The development of a new in vitro method to measure UVA protection performance made it possible to predict reliably the in vivo UVA protection performance of representative sunscreen formulations found presently in the European and US market (1). This study was performed in order to determine the applicability of the method developed by Wendel et al. (1) to photostable and photolabile filter combinations and in order to measure the influence of sample pre-irradiation on predicting the in vivo performance. This was done by subjecting six photostable and six photolabile filter combinations to a standard irradiation. Then the in vitro UVA protection afforded by each combination was measured and compared with the persistent pigment darkening (PPD) values determined in vivo. RESULTS: The results clearly showed that pre-irradiation does not affect the in vitro PPD factor of the photostable and photolabile samples in the same way. Almost identical values were determined for the stable filter combinations with and without pre-irradiation, whereas distinct reductions in the in vitro factors by as much as 93% were observed after irradiation in the group of less stable filter combinations. Comparison of the in vivo and in vitro PPD factors showed that all 12 samples comprise a homogeneous distribution with identical factors before irradiation. After pre-irradiation only the factors for the six less stable products were selectively reduced. The correlation with the data determined on the skin was clearly poorer for these products after irradiation. CONCLUSION: Overall, the results showed that pre-irradiation should not to be used for the assessment of UVA protection using this method. Furthermore, it can be assumed that normalizing the in vitro absorbance curves to the labelled SPF of the sunscreen will adequately take into account the photochemical behaviour of UV filters on the skin during sun exposure.     

Tobacco smoke is phototoxic

BACKGROUND: Both cigarette smoke and ultraviolet (UV) radiation are known to cause changes of the skin which can be regarded as premature ageing. OBJECTIVES: To assess the theory that the effects of these two exposures could be linked by a phototoxic action of cigarette smoke. METHODS: A photohaemolysis test was used, in which human erythrocytes were incubated with cigarette smoke condensate, followed by UV irradiation and measurement of exposure-dependent haemolysis. RESULTS: Cigarette smoke condensate was clearly phototoxic. Photohaemolysis depended on the concentration of the condensate and UV dose and was more pronounced after exposure to UVA-rich than UVB-rich radiation. CONCLUSIONS: Phototoxicity may be a mechanism by which cigarette smoking causes premature skin ageing. An enhancing effect on photocarcinogenesis has also to be considered.     

Possible functional impairment of Langerhans' cells in vitiliginous skin. Reduced ability to elicit dinitrochlorobenzene contact sensitivity reaction and decreased stimulatory effect in the allogeneic mixed skin cell lymphocyte culture reaction

We used patch testing to compare the ability to elicit contact sensitivity to dinitrochlorobenzene (DNCB) of uninvolved with vitiliginous skin of 31 patients with vitiligo. The induction of DNCB contact sensitivity was possible in the vitiliginous skin in the same way as in normal skin. The DNCB contact sensitivity reactions, however, were generally diminished in vitiliginous skin, although the number of cases showing similar DNCB contact reactivity between normal and vitiliginous skin increased when the sensitization procedure was performed in vitiliginous skin instead of normal skin. On the other hand, delayed skin reactions to intradermally injected Candida albicans antigen were not suppressed in vitiliginous skin. The number of Langerhans' cells was not decreased in vitiliginous skin as compared with that of normal skin. The epidermal cells derived from vitiliginous skin, however, tended to show a lower stimulatory effect in the allogeneic mixed skin cell lymphocyte culture reaction than those from normal skin. These results suggest a possibility of functional impairment of Langerhans' cells in vitiliginous skin.     

Evaluation of phototoxic properties of fragrances

Fragrances are widely used in topical formulations and can cause photoallergic or phototoxic reactions. To identify phototoxic effects, 43 fragrances were evaluated in vitro with a photohaemolysis test using suspensions of human erythrocytes exposed to radiation sources rich in ultraviolet (UV) A or B in the presence of the test compounds. Haemolysis was measured by reading the absorbance values, and photohaemolysis was calculated as a percentage of total haemolysis. Oakmoss caused photohaemolysis of up to 100% with radiation rich in UVA and up to 26% with radiation rich in UVB. Moderate UVA-induced haemolysis (5-11%) was found with benzyl alcohol, bergamot oil, costus root oil, lime oil, orange oil, alpha-amyl cinnamic aldehyde and laurel leaf oil. Moderate UVB-induced haemolysis was induced by hydroxy citronellal, cinnamic alcohol, cinnamic aldehyde, alpha-amyl cinnamic aldehyde and laurel leaf oil. The phototoxic effects depended on the concentration of the compounds and the UV doses administered. We conclude that some, but not all, fragrances exert phototoxic effects in vitro. Assessment of the correlation of the clinical effects of these findings could lead to improved protection of the skin from noxious compounds.     

Diminished contact sensitivity response in vitiliginous skin

Thirty patients with vitiligo (ten of the segmental type and 20 of the generalized type) were sensitized with dinitrochlorobenzene (DNCB) in a normal skin site on the upper medial aspect of the arm. Challenge tests with dinitrochlorobenzene were performed in vitiliginous patches and in normal skin sites. In vitiliginous patches diminished contact sensitivity reactions to dinitrochlorobenzene were noted in both patient groups, while in normal skin sites a normal delayed hypersensitivity response to the same antigen developed in the same patients. Tuberculin reactivity was not suppressed in vitiliginous lesions. We suggest that diminished contact reactivity in vitiliginous skin might be due to functional changes in Langerhans' cells, or to an alteration of carrier (skin) proteins in the lesions.     

Protective effects of a topical antioxidant mixture containing vitamin C,ferulic acid,and phloretin against ultraviolet‐induced photodamage in human skin

Background Ultraviolet (UV) irradiation of the skin leads to acute inflammatory reactions, such as erythema, sunburn, and chronic reactions, including premature skin aging and skin cancer. Aim In this study, the effects of a topical antioxidant mixture consisting of vitamin C, ferulic acid, and phloretin on attenuating the harmful effects of UV irradiation on normal healthy volunteers were studied using biomarkers of skin damage. Subjects/methods Ten subjects (age, 18–60 years; Fitzpatrick skin types II and III) were randomized and treated with antioxidant product or vehicle control on the lower back for four consecutive days. On day 3, the minimal erythema dose (MED) was determined for each subject at a different site on the back. On day 4, the two test sites received solar‐simulated UV irradiation 1–5× MED at 1× MED intervals. On day 5, digital images were taken, and 4‐mm punch biopsies were collected from the two 5× MED test sites and a control site from each subject for morphology and immunohistochemical studies. Results UV irradiation significantly increased the erythema of human skin in a linear manner from 1× to 5× MED. As early as 24 h after exposure to 5× MEDs of UV irradiation, there were significant increases in sunburn cell formation, thymine dimer formation, matrix metalloproteinase‐9 expression, and p53 protein expression. All these changes were attenuated by the antioxidant composition. UV irradiation also suppressed the amount of CD1a‐expressing Langerhans cells, indicating immunosuppressive effects of a single 5× MED dose of UV irradiation. Pretreatment of skin with the antioxidant composition blocked this effect. Conclusion This study confirms the protective role of a unique mixture of antioxidants containing vitamin C, ferulic acid, and phloretin on human skin from the harmful effects of UV irradiation. Phloretin, in addition to being a potent antioxidant, may stabilize and increase the skin availability of topically applied vitamin C and ferulic acid. We propose that antioxidant mixture will complement and synergize with sunscreens in providing photoprotection for human skin.     

Topical vitamin C protects porcine skin from ultraviolet radiation-induced damage

Ultraviolet radiation damage to the skin is due, in part, to the generation of reactive oxygen species. Vitamin C (L-ascorbic acid) functions as a biological co-factor and antioxidant due to its reducing properties. Topical application of vitamin C has been shown to elevate significantly cutaneous levels of this vitamin in pigs, and this correlates with protection of the skin from UVB damage as measured by erythema and sunburn cell formation. This protection is biological and due to the reducing properties of the molecule. Further, we provide evidence that the vitamin C levels of the skin can be severely depleted after UV irradiation, which would lower this organ's innate protective mechanism as well as leaving it at risk of impaired healing after photoinduced damage. In addition, vitamin C protects porcine skin from UVA-mediated phototoxic reactions (PUVA) and therefore shows promise as a broad-spectrum photoprotectant.     

Epidermal photoprotection: comparative study of narrowband ultraviolet B minimal erythema doses with and without stratum corneum stripping in normal and vitiligo skin

Background. Recent accumulating data in the literature have indicated a complex photoprotective role of the epidermis, and the role of melanin as the major epidermal photoprotective mechanism has become debatable. Aim. Comparative assessment of the photoprotective roles played by different epidermal structures and compounds. Methods. In total, 64 participants, comprising patients with vitiligo (n = 32) and healthy volunteers (n = 32), with skin phototypes (SPTs) II to V, were enrolled in the study. Areas of skin were delineated; for both lesional and nonlesional skin, the stratum corneum (the SC) was stripped, followed 24 h later by exposure to narrowband ultraviolet B (NB‐UVB) irradiation, to measure the minimal erythema dose (MED) in normal, stripped normal, vitiliginous and stripped vitiliginous skin models. These MED values were used to assess the photoprotective role of epidermal structures: melanin, viable epidermis (VE) and the SC. Results. In the vitiligo group, the MED values were significantly (P < 0.05) different between the skin models, being highest in normal skin, followed by stripped normal, vitiliginous and stripped vitiliginous skin. A similar significance level was found within each SPT for almost all comparisons. There was also a significant (P < 0.001) positive correlation between MED and SPTs. There were also significant (P < 0.05) differences in MED values calculated for epidermal structures, being highest for VE, followed by melanin and then the SC, and there was a significant (P < 0.05) positive correlation between MED and SPTs. Conclusion. Epidermal photoprotection may extend beyond melanin production, involving several factors such as epidermal layer thickness, optical properties and chromophores. Such a role was perceived to be reactive to UV irradiation, and more efficient in those with higher SPTs.     

Phototoxic and contact toxic reactions of the exocarp of sweet oranges: a common cause of cheilitis?

Irritant skin reactions were produced within 1 h after application of the exocarp of sweet oranges or alchoholic extracts therefrom. Such reactions faded within 48 h. The exocarp. or extracts thereof, induced phototoxic reactions which were strongest at 72 h after exposure. The phototoxic reactions were only induced in natural blondes and only with some oranges.
The in vivo phototoxic reactions were confirmed in vitro , causing a slight but clear photo-inhibition of Candida albicans. Only some oranges inhibited growth.     

Factors influencing methoxsalen phototoxicity in vitiliginous skin.

A series of experiments were conducted to determine the optimum conditions required to induce methoxsalen phototoxicity in vitiliginous skin. The results revealed that optimum phototoxicity could be obtained only when a lapse of at least 15 minutes was allowed between the application of the drug and exposure to long-wave ultraviolet light (UVA). The duration of methoxsalen's phototoxic potentially, after its application to skin, varied in direct proportion to chemical concentration. Although a high chemical concentration and low dosage of UVA was a less time-consuming method of inducing phototoxicity, our results indicate that lower concentration and longer UVA exposure were less likely to induce undersirable blistering reactions.     

Photodegradation products of sulphonamide-derived oral antidiabetics and diuretics are not phototoxic in vitro

The oral antidiabetics glibenclamide and glipizide, and the diuretics bendroflumethiazide and furosemide, all sulphonamide derived drugs, were investigated in vitro for phototoxic properties. Irradiation with broad-band UV induced phototoxic inhibition of colony forming ability in cell cultures. During irradiation, the substances lost one absorption maximum in the UVA region, demonstrated by UV spectroscpoy. These findings correlate well with the UV applied, the action spectrum being in the UVA region. Photoproducts detected during and after irradiation showed a decomposition of the substances due to ionization and fragmentation. Incubation of these preirradiated drugs with the cell cultures revealed no phototoxic effects.     

Phototoxic reaction to xanthene dyes induced by visible light

Many dyes, for instance methylene blue, rose bengal, and eosin, are known as photosensitizers, and in the presence of molecular oxygen they induce cell lethality and skin photosensitivity (1-4). Several dyes are used in cosmetic products, particularly in lipsticks. Human lip skin is therefore exposed to potential danger from dye-sensitized phototoxic reactions. Using an in vivo system of mammalian skin, such as the abdominal skin of rabbits, we established screening tests for the phototoxic potential of synthetic dyes in two ways: (a) intracutaneous injection; (b) topical application with and without damaging the barrier property of the stratum corneum. In the intracutaneous injection assay, distinct phototoxic reactions were induced by rose bengal, eosin Y.S., and dibromofluorescein. When these dyes were applied topically to intact skin, no phototoxic reactions were observed. Phototoxic reactions were, however, elicited when the dye solutions were applied to abraded or scratched skin. The intensity of phototoxic reaction was found to be influenced by the vehicle in which the dyes were suspended. Phototoxic reaction to the dyes was induced by artificial light as well as by sunlight. By using commercially available fluorescent lamps with different spectral emissions, the action spectra for the phototoxic reaction to these dyes were investigated and it was found that the maximum phototoxicities of the dyes were manifested by light within a spectral range of 400-600 nm. Further studies on action spectra, using a monochromatic irradiation system, revealed a high correlation between the action spectra of the dyes and their absorption spectra. Maximum effective wavelength for the phototoxic reaction of eosin Y.S. was 525 nm. This topical as well as intradermal assay for assesing phototoxic reaction to synthetic dyes in living skin will be a practical and useful measure for studying the phototoxicity of the dyes.     

Failure of coconut oil to accelerate psoriasis clearance in narrow-band UVB phototherapy or photochemotherapy

Despite a widely held belief that the use of emollients prior to broad-band UVB irradiation accelerates clearance of psoriasis, only one single-blind controlled study exists in support of this. No similar study has been carried out with photochemotherapy (PUVA) or narrow-band UVB (311–313 nm) phototherapy. As some emollients absorb UV radiation, and thereby inhibit psoriasis clearance, there is a need to identify emollients suitable for pre-irradiation use. Coconut oil may be useful in this respect. In two randomized groups of patients with chronic plaque psoriasis undergoing either routine PUVA(n=14) or narrow-band UVB phototherapy (n=15), a single-blind controlled (half-body) study was undertaken to assess the died of pre-irradiation application of coconut oil. Patients were given PUVA twice weekly, or TL-01 therapy thrice weekly. The initial UV dose was 70% of previously determined minimal phototoxic (MPD) or minimal erythema doses (MED), with 40% incremental steps at each visit (reduced if adverse effects occurred). Psoriasis severity was scored on each side after every three treatments. No significant acceleration of psoriasis clearance was seen in either group. We do not, therefore, recommend the routine use of emollients prior to PUVA or TL-01 therapy when using near erythemogenic irradiation regimens.     

Effects of UV irradiation with one minimal erythema dose on human afferent skin lymph in vivo

Ultraviolet (UV) irradiation of the skin induces complex local and systemic immunomodulatory reactions. The biological effects of UV irradiation on human skin derived afferent lymph however are unknown. The aim of this study was to examine the effects of a single combined UV-A and UV-B irradiation with 1 minimal erythema dose (MED) on human skin derived lymph in vivo. After cannulation of a superficial lymph vessel on the lower leg, lymph flow and cell output per hour were determined before and for 6 days after UV irradiation of the lymph draining skin area in 5 volunteers. Furthermore, expression of CDla, CD4, CD8, CD28, CD54, CD80, CD86 and HLA-DR on migrating lymph cells and cytokine levels (IL-1α, IL-1β, IL-2, IL-6, IL-8, IL-10, IL-13, TNF-α and IFN-γ) in the afferent lymph were analyzed by cytofluorometry and ELISA. After UV irradiation a small initial enhancement in the daily lymph flow per hour was noticed in correlation with the slight erythematous skin reaction. Following resolution of the skin reaction, a delayed increase in cell output in correlation with an additional peak in the lymph flow was found between the 4th and 6th day after UV irradiation. However, no changes in the expression of CDla, CD4, CD8, CD28, CD54, CD80, CD86 and HLA-DR on migrating lymph cells were detectable. Interestingly, in parallel to the increased lymph flow and cell output, only elevated IL-8 protein levels were reproducibly detected in the afferent lymph after UV irradiation. Furthermore, using immunohistochemistry positive staining for IL-8 was found on migrating mononuclear lymph cells. In conclusion, our data demonstrate that a single UV irradiation of the skin with 1 minimal erythema dose leads to a delayed enhancement of lymph flow, number of migrating lymph cells and cytokine levels of IL-8. Moreover, we provide evidence that migrating lymph cells, besides resident epidermal and dermal cells, may contribute to the detected levels of IL-8 in the afferent lymph.     

Do OKT6 positive Langerhans cells play a role in the suppression of ultraviolet-induced carcinogenesis?

Langerhans cells (LC) in epidermis are antigen presenting cells. LC may play a role in immune surveillance system and are considered to suppress development of ultraviolet (UV) induced skin cancers. We studied effect of UVB irradiation to LC of xeroderma pigmentosum (XP) and normal subjects by using OKT6 monoclonal antibody. When 3 minimal erythema dose (MED) of UVB were irradiated, density of OKT6 positive LC of XP began to decrease 6 hours after irradiation, and showed the least numbers on day 2 and returned completely to the pre-irradiation level on day 14. Further, after 3 MED irradiation, LCs of both normal subjects became the least on day 3 and returned to the pre-irradiation level on day 14. In XP variant and normal subjects, the number of LC in chronic sun-exposed skin decreased significantly in a similar way comparing to that of non-exposed skin. These results suggest that epidermal LC may not play an essential role in prevention of UV-induced tumor development.     

窄谱中波紫外线围白斑照射治疗难治性白癜风的临床疗效观察

【摘要】 目的 探讨窄谱中波紫外线围白斑照射治疗难治性白癜风的临床疗效。方法 回顾2019年6月至2020年11月南京医科大学第一附属医院皮肤科治疗的126例难治性白癜风,分别采用遮盖白斑、窄谱中波紫外线照射围白斑区域皮肤和常规照射白斑治疗,每周2次,持续3个月。治疗结束后评估2组的疗效。运用倾向性评分匹配分析,按1∶1匹配。采用单因素和多因素Logistic回归分析、分层分析围白斑照射法对于难治性白癜风的临床疗效。结果 采用围白斑照射组皮损420处,常规照射组257处,倾向性评分匹配后每组各190处,匹配前后,围白斑照射组有效率（71.9%、67.9%）均高于常规照射组（31.9%、30.0%,均P < 0.05）。倾向性评分匹配后单因素Logistic回归分析显示,围白斑照射与常规照射对疗效的影响差异有统计学意义（OR = 4.9,95% CI：3.2,7.6,P < 0.001）;多因素分析显示,围白斑照射与常规照射对疗效的影响差异亦有统计学意义（OR = 12.0,95% CI：6.5,22.3,P < 0.001）。对不同毛发类型与照射方法对白斑疗效的影响进行分层分析,匹配前,毛白白斑采用常规照射187处,围白斑照射246处,毛黑白斑采用常规照射70处,围白斑照射174处;匹配后,毛白白斑两照射组各140处,毛黑白斑各50处。对于毛白白斑,匹配前后围白斑照射组的有效率（77.6%、72.8%）均好于常规照射组（19.3%、20.7%,P < 0.01）。对于毛黑白斑,匹配后两组疗效差异无统计学意义（P = 0.908）。结论 围白斑窄谱中波紫外线对于治疗难治性白癜风尤其是白斑处毛发变白的皮损疗效优于一般照射方法。     

A study of oil of bergamot and its importance as a phototoxic agent

Using a standardized open photopatch test technique, the phototoxic reactions produced by bergamot oil bergapten (5-methoxypsoralen) the active component of the oil, and xanthotoxin (8-methoxypsoralen) were studied. The reaction was affected by a range of factors such as the vehicle (PMF or ethanol), the concentration of ethanol in the vehicle, the skin site, the interval between application of the psoralen and irradiation, the hydration of the skin, and the degree of natural or sun-induced pigmentation. Repeated photopatch testing at the same skin site produced an increase in sensitivity. Eye colour, natural susceptibility to suntanning, age, and sex, had no effect on the phototoxic response to psoralens.     

Skin temperature and phototest evaluation

The degree of erythema following UV irradiation is known to depend upon skin temperature at the time of UV exposure. We investigated whether changes in skin temperature at the time of erythema assessment influenced the level of erythema. Twenty-two healthy people (mean age 26 years) were irradiated with solar simulated radiation on previously UV un-exposed buttock skin. The erythematous reactions were evaluated 20–24 h after irradiation by visual scoring and by measurements of skin reflectance and laser Doppler flowmetry. The readings were done at the baseline level at 21°C room temperature where skin temperature was 30.0±1.7°C and subsequently after skin warming to 37.2±2.5°C and after cooling to 22.8±2.6°C. After skin warming, a clinically evaluated erythema grade [0, (+), +, + +, +++] was scored higher for at least one reaction in 10 of 22 individuals (45%). In the same proportion of subjects, changes to lower erythema grades were detected upon cooling. Skin warming caused an increase in laser Doppler blood flux, but skin cooling did not have a significant effect on cutaneous perfusion. Skin redness measured by skin reflectance was relatively stable during the cooling phase, but a significant increase in skin redness was noted for 0 reaction upon skin warming. For + + and + + + reactions a small but significant decrease in reflectance was noted. Our results indicate that alterations in skin temperature, especially a temperature increase, modulates the degree of UV-induced erythema moderately. The temperature-dependent changes as an assessment of the (+) reaction are of practical significance, since this reaction is used for the assessment of cutaneous photosensitivity.     

Possible role of cutaneous metallothionein in protection against photo-oxidative stress--epidermal localization and scavenging activity for superoxide and hydroxyl radicals.

It is reported that increasing metallothionein (MT) synthesis suppressed sunburn cell formation in the mouse skin after ultraviolet B (UVB) irradiation, implying a photo-protective effect of the cysteine-rich protein. To understand the mechanism of the defense by cutaneous MT against UVB injury, an immunohistological localization of MT in human normal skin was studied following examination of lesional skin. MT in the skin was localized in granular layer with diffuse staining pattern in normal skin, defect in psoriatic lesions, positive but thin in granular cells in the lesions of lichen planus. MT treatment showed a significant decrease in chemiluminescence induced by superoxide radicals and depressed signal intensity of hydroxyl radicals derived from the Fenton reaction system. From the viewpoint of characteristic localization and probable role in scavenging activity for reactive oxygen species, MT in the epidermis may contribute to the protection against phototoxic injury in association with enzymatic and non-enzymatic antioxidants. These findings may support the previous results of UV defense by cadmium-induced MT in the skin.