Photo-dermatology最新文献

Exposure of mouse skin to UV radiation in doses comparable to those commonly received by humans has been shown to diminish the capacity of irradiated skin to mediate the induction of contact hypersensitivity to dinitrofluorobenzene (DNFB). In other studies, contact sensitization reactions to the structurally related hapten, trinitrochlorobenzene (TNCB), have been used to test the immunogenic properties of haptenated subpopulations of epidermal cells. To extend the applicability of TNCB to experiments that examine UVB modulation of immunization by epidermal cells, we examined the sensitivity of TNCB-induced contact hypersensitivity to low doses of UVB radiation. Abdominal skin of C3H mice was exposed to daily doses of 660 J/m2 broad-band UV radiation for 4 successive days. Immediately following the final exposure, 7% TNCB was applied to irradiated or non-irradiated skin of designated mice. After 5 days, mice were ear-challenged with 2% TNCB, and incremental ear-swelling responses were measured. Mice sensitized with TNCB through irradiated skin exhibited significantly diminished responses compared with UVB-treated mice sensitized through non-irradiated skin. We also found that mice initially sensitized with TNCB through irradiated skin but subsequently painted with oxazolone on normal skin developed full responses to ear-challenge with oxazolone. In contrast, mice sensitized initially with TNCB through irradiated skin failed to fully immunize even after TNCB was repainted on normal skin at a later date. We conclude that low-dose UVB radiation interrupts the induction of contact hypersensitivity to TNCB, leading to hapten-specific nonresponsiveness rather than hypersensitivity, and that this capacity to prevent successful immunization with TNCB is limited to the site of irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of UV irradiation on the human stratum corneum (SC) were studied under both artificial and natural conditions. Artificial UV exposure was performed with a solar simulator. Single doses of radiation from 1 to 3 MED were delivered on the backs of volunteers and the measurements were recorded for a period of one month. Corneocytes were harvested from the skin surface by using a "turbine-machine". Their count and projected area were measured by image analysis. The evolution of corneocyte counts showed 3 steps: 1) a background level of desquamation until the 8th day; 2) a sharp increase from day 9 to day 11; and 3) a plateau until the 20th day. No evolution of the corneocyte size occurred at 1 MED, but a decrease was recorded at day 20 for 2 MED and earlier for 3 MED. Natural sun exposure was investigated in 2 different experiments: on a population living in a sunny coastline and on professional racing cyclists. In these natural conditions, the response of the SC to UV led to an increase in corneocyte count associated with a decreased size. Even though natural environment involves both weather and sun influences, results showed similar SC responses. In case of acute irradiation, the skin recovers its initial state one month later, but in the natural environment, it maintains altered features as long as the UV irradiation occurs.

Trimethylpsoralen (TMP) concentrations were determined in blood and skin of 21 patients given oral TMP therapy and were compared to data obtained from 5 patients treated with TMP baths. The quantitative determination was performed by gas chromatography with selected ion monitoring. Concentrations of up to 5.6 ng/ml were detected in whole blood from orally TMP treated patients, with about the same concentrations in patients given TMP baths. Whole skin biopsies from patients ingesting TMP showed concentrations in 14 patients that ranged from 30 to 1250 ng/g skin, median value 85 ng/g. Large interindividual variations were observed. Stripped skin from 5 patients after TMP baths showed a somewhat higher median value of 160 ng/g and their entire skin had fairly high concentrations, with a median value of 390 ng/g, probably mostly bound to stratum corneum. Different concentrations in different parts of the skin may explain the difference in phototoxic capacity when the drug is given locally.

A 65-year-old patient with xeroderma pigmentosum (XP), XP77TO, was assigned to complementation Group D by the cell-fusion study and comprised the fifth Group D case in Japan. The patient had mild solar sensitivity by age 7, dyspigmentation by 10 years, and he still currently has moderate symptoms. The skin phototest by 290, 300 and 305 nm monochromatic ultraviolet (UV) light revealed a delayed peak of erythema 48 h post-irradiation and lowered minimal erythemal doses. The XP77TO skin fibroblasts, as well as a reference Group D strain, exhibited the same 7-fold higher sensitivity to the lethal effect of 254 nm UV as did normal cells. Unscheduled DNA synthesis (UDS) induced in XP77TO cells by 254 nm UV (10 J/m2) was 42% of normal, falling into the Group D range of 25-50% UDS. In spite of such a similar cellular phenotype, XP77TO developed squamous cell carcinomas at 44 and 65 years of age and audiometric sensorineural deafness in a delayed fashion at advanced age.

The immediate pigment-darkening reaction (IPD) is a gray-brown discoloration of the skin induced mainly by long-wave ultraviolet (UVA) radiation. The threshold value of IPD can be used as an important parameter in a series of light tests. The principle mechanism of the reaction is a photo-oxidative process causing darkening of preformed melanin and the production of free radicals. It has also been suggested that the reaction involves micromorphological changes in the melanocytes and a changed distribution pattern of melanosomes in the keratinocytes. This concept has recently been questioned by independent investigators. The physiological function of IPD still remains largely unknown. No photoprotective effect of the reaction has been observed. It has been suggested that IPD might have been of value during human evolution.

UV-induced epidermal hyperplasia was investigated by measuring the optical transmission of the epidermis of hairless mice exposed daily to ultraviolet radiation. The effects of 2 different radiation sources were investigated: Philips TUV 40W, emitting mainly 254 nm radiation, and Philips TL01 40W, emitting radiation in a narrow band around 312 nm. With both lamps a number of groups of animals were used, each receiving a different daily dose. In the experiments with both types of lamps, hyperplasia appeared to be fully determined by the accumulated dose, irrespective of the daily dose administered. This implies reciprocity between the daily dose and the time elapsed since the first exposure. Moreover, the change of transmission with time and daily dose showed very characteristic behaviour. A simple mathematical model was used to describe these changes. In a previous study we used this model to describe the results of a similar experiment with Westinghouse FS40 sunlamps. The combined data from the present and the previous experiments were used to calculate a first approximation of the action spectrum for UV-induced hyperplasia. In addition, we calculated the dose-response relationship for UV-induced increase in tolerance against ultraviolet radiation for the 3 irradiation sources.

Exposure of mammalian skin to ultraviolet radiation (UVR) results in a transient inhibition of scheduled DNA synthesis. The wavelength dependence for this response was investigated in the epidermis of albino hairless mice. Groups of animals were exposed to narrow wavebands of UVR (HPBW 6.6 nm) from a monochromator in the 260-335 nm range. A dose-dependent inhibition of DNA synthesis was observed following exposure to all test wavebands except that centered at 335 nm. An action spectrum constructed from dose-response regression lines showed peak effectiveness at 290 nm. This spectrum bears a close resemblance to published action spectra for the induction of pyrimidine dimers in vivo, suggesting that DNA is the primary chromophore for both events. The DNA synthesis inhibition spectrum bears little resemblance to a published therapeutic action spectrum for the clearing of psoriasis.