Dynamics of pigmentation induction by repeated ultraviolet exposures: dose, dose interval and ultraviolet spectrum dependence.

BACKGROUND: The dynamics of ultraviolet (UV)-induced melanogenesis have been well characterized for single UV exposures. However, our knowledge of the effects of repeated UV exposures on the development of new pigmentation is limited. OBJECTIVES: To characterize the dynamics and dose dependence of pigmentation induction by repeated UV exposures using two different UV sources. METHODS: A total of 40 healthy subjects participated in the study: 21 were exposed to a 5% UVB/95% UVA source and 19 were exposed to a 2% UVB/98% UVA source. Skin phototypes 2-3 were represented. Subjects were exposed one to three times per week. The minimal erythemal dose and minimal melanogenic dose of all subjects were determined, and both visual and instrumental observations of the development of pigmentation and erythema were recorded. RESULTS: Dark-brown pigmentation could be produced by a cumulative UV dose of 4200 J m(-2) given as 10 exposures over 5 weeks. However, comparable pigmentation could also be induced by a cumulative dose of 2900 J m(-2) given as eight exposures over 4 weeks. The lowest cumulative dose of 1900 J m(-2) given over 4 weeks produced moderate pigmentation. The 2% UVB source led to earlier and darker pigmentation than the 5% UVB source did for equally erythemogenic doses. CONCLUSIONS: These observations show that the dynamics of melanogenesis induced by repeated exposures depends on UV dose, dose interval and emission spectrum. They also indicate that increasing the UV dose above a certain level of cumulative exposure does not significantly increase the level of UV-induced pigmentation.

In vivo measurement of skin erythema and pigmentation: new means of implementation of diffuse reflectance spectroscopy with a commercial instrument.

BACKGROUND: Various physical, chemical and biological insults, including exposure to ultraviolet (UV) radiation, cause erythema and change in pigmentation in human skin. These reactions provide an important measure of the cutaneous response to the insult. OBJECTIVES: To present a new implementation of a method for objective in vivo measurement of erythema and pigmentation. METHODS: The method is based on acquisition of reflectance spectra in the visible range using a commercially available spectrophotometer. The probe of this instrument incorporates an integrating sphere that captures the light remitted from the skin in a wide range of angles. We corrected the acquired reflectance spectra for the contribution of specular reflections by an amount given by the Fresnel equation and verified this correction experimentally. This correction is particularly important when measurements are performed on heavily pigmented skin. The corrected reflectance spectra are then transformed into absorbance spectra. To analyse these spectra, we developed an algorithm which can be used to calculate apparent concentrations of oxyhaemoglobin, deoxyhaemoglobin and melanin. This method was tested in clinical studies of skin reactions induced by exposure to UV radiation. These experiments involved three groups of subjects with progressively darker complexion (constitutive pigmentation). Each group consisted of 10 subjects. Erythema was measured 1 day after UV exposure, and pigmentation (melanin content) 1 week later. Results Distinct apparent absorbance spectra were obtained for dark, intermediate and fair skin. There was good agreement between reconstructed spectra and experimental data at relevant wavelengths. Difference absorption spectra were able to show the dose dependence of UV-induced responses, and erythema and pigmentation values obtained by the spectroscopic method showed good correlation with those derived by subjective visual grading. CONCLUSIONS: The results demonstrate that the presented methodology provides an objective noninvasive way of measuring UV-induced reactions independently of the level of constitutive pigmentation.

Basal cell proliferation in female SKH-1 mice treated with alpha- and beta-hydroxy acids.

Alpha- and beta-hydroxy acids are compounds that have been used extensively in cosmetic and dermatological formulations. Clinical and qualitative effects of alpha- and beta-hydroxy acids have been well characterized, but little is known about their mechanism of action or acute and chronic biochemical effects. In the present study, we examined the acute proliferative effects of glycolic and salicylic acids on cell proliferation in the epidermis of SKH-1 female mice, using BrdU incorporation as a marker of epidermal proliferation. In preliminary experiments, we observed an increase in the rate of proliferation after 3 days of treatment with 10% glycolic acid-containing cream and this was sustained throughout a 6.5-week (treatment 5 days/week) time course compared with untreated control animals. After each treatment with cream containing glycolic acid there was a wave of proliferation that was maximal 12 to 16 h (significant at p < 0.05) after treatment, followed by a subsequent increase in epidermal thickness at 18 to 20 h (significant at p < 0.05). The effects of the concentration and pH level of glycolic acid- and salicylic acid-containing creams on the rate of proliferation and increases in skin thickness in SKH-1 epidermis were also investigated. We observed a dose-dependent increase in epidermal proliferation of animals treated with either glycolic or salicylic acid. A similar time-dependent response was observed in the epidermal thickness in animals treated with salicylic acid, but not with glycolic acid. Differences in pH (3.5 or 4.0) had no significant effect on either epidermal proliferation or skin thickness. The data that we present here should be useful in characterizing not only the beneficial but also the adverse effects that occur following acute or chronic usage of alpha-hydroxy acids.

Lack of consensus among experts on the choice of UV therapy for psoriasis.

CONTEXT: Each year tens of thousands of patients in the United States are treated with UV-B radiation or psoralen plus UV-A radiation (PUVA) for a variety of skin disorders. Although PUVA is generally considered more effective, it is also more toxic and more expensive. The degree of consensus among experts in prescribing these alternative treatments has not been quantified. OBJECTIVES: To quantify variation among specialty clinics in the type of ultraviolet therapy used to treat specific skin conditions and assess factors associated with the use of specific treatments. DESIGN: Survey conducted during two 2-week periods in the late fall of 1994 and early spring of 1995. SETTING: Thirty-nine specialty clinics in 17 US geographic areas in 14 states and Washington, DC. PARTICIPANTS: A total of 3401 patients treated with UV radiation one or more times. OUTCOME MEASURES: Type of UV therapy used and indications for treatment, age, sex, number of patients treated, and geographic location of each clinic. RESULTS: The proportion of patients at each center treated with PUVA ranged from 0% to 93% (mean, 41%). Clinic size and geographic location, demographic characteristics of the patients, and diagnosis did not explain these large intercenter differences. CONCLUSIONS: Among specialized clinics, there is little consistency in the use of alternative therapies, which differ substantially in safety and cost, but whose relative efficacy is not well quantified. There is a lack of consensus among experts about the circumstances in which the greater risks and costs of PUVA are outweighed by its possibly greater efficacy, especially in the treatment of psoriasis.

HIV-positive patients differ from HIV-negative patients in indications for and type of UV therapy used.

BACKGROUND: Treatments using UV, UVB, or oral psoralen and UVA (PUVA) have been advocated for the care of HIV-infected persons with skin diseases. Concerns about the safety of these treatments exist. OBJECTIVE: We attempted to determine the characteristics of HIV infected persons receiving UV therapy and establish the reasons for and type of treatment administered. METHODS: During two 2-week periods, we prospectively ascertained basic information on all patients treated at 40 phototherapy clinics and detailed clinical information on patients known to be infected with HIV. RESULTS: We identified 3716 persons receiving UV therapy, including 311 known to be infected with HIV. When compared with patients not known to be infected with HIV, HIV-positive patients were significantly more likely to be treated with UVB rather than PUVA and were more likely to be treated for pruritic conditions rather than psoriasis. CONCLUSION: There were great variations in the relative reliance on UVB and PUVA among centers. There appears to be no agreement as to which type of UV therapy is optimal for patients infected with HIV. Most patients known to the treating clinician to be HIV positive are in the advanced stages of HIV disease. The number of persons with less advanced HIV disease receiving treatment remains unquantified but may be even more clinically important.

Ultraviolet therapy of HIV-infected individuals: a panel discussion.

Patients infected with the human immunodeficiency virus (HIV) frequently develop skin diseases that are responsive to ultraviolet (UV) radiation. Studies on the effects of UV on HIV and on the immune system in vitro and in transgenic animals have raised questions regarding the safety of UV exposure in these patients. In this article, invited experts address issues concerning the safety of ultraviolet therapy in HIV-infected patients by discussing their clinical and/or research experience.

Photosensitized decontamination of blood with the silicon phthalocyanine Pc 4: no activation of the human immunodeficiency virus promoter.

Photochemical decontamination of red blood cell concentrates (RBCC) with the silicon phthalocyanine Pc 4 and red light is being studied to enhance the viral safety of blood transfusion. Recent reports indicate that treatments with radiation and various phototsensitizing agents can activate the promoter of human immunodeficiency virus (HIV). This raises the possibility that an inadequate, sublethal photochemical treatment of RBCC could induce HIV in latently infected cells. This question has been addressed using HeLa cells stably transfected with the chloramphenicol acetyl transferase gene under the control of the HIV promoter. In control studies, 8-methoxypsoralen (8-MOP) excited by UVA light caused activation of the HIV promoter in a dose- and time-dependent manner. At 0.1 microgram/mL of 8-MOP, maximal activation occurred with 18 J/cm2, 30 h after light exposure, With Pc 4 at 20 nM, over 90% of HeLa cells were killed after 24 h when exposed to 1 J/cm2 of red light. During that time interval and over a wide range of light doses no activation of the HIV promoter occurred. It is concluded that RBCC sterilization with Pc 4 and red light is unlikely to induce HIV production in latently infected cells.

Medical UV exposures and HIV activation.

This paper presents the first attempt to evaluate the potential of clinical UV exposures to induce the human immunodeficiency (HIV) promoter and, thus, to upregulate HIV growth in those skin cells that are directly affected by the exposure. Using the data for HIV promoter activation in vitro, we computed UVB and psoralen plus UVA (PUVA) doses that produce 50% of the maximal promoter activation (AD50). Then, using (a) literature data for UV transmittance in the human skin, (b) a composite action spectrum for HIV promoter and pyrimidine dimer induction by UVB and (c) an action spectrum for DNA synthesis inhibition by PUVA, we estimated the distribution of medical UVB and PUVA doses in the skin. This allowed us to estimate how deep into the skin the HIV-activating doses might penetrate in an initial and an advanced stage of UVB or PUVA therapy. Such analysis was done for normal type II skin and for single exposures. The results allow us to predict where in the skin the HIV promoter may be induced by selected small and large therapeutic UVB or PUVA doses. To accommodate changes in skin topography due to disease and UV therapy, our considerations would require further refinements. For UVB we found that, when the incident dose on the surface of the skin is 500 J/m2 (290-320 nm) (initial stage of the therapy), the dose producing 50% of the maximal HIV promoter activation (ADUVB50) is limited to the stratum corneum. However, with an incident dose of 5000 J/m2 (an advanced stage of the therapy), ADUVB50) may be delivered as far as the living cells of the epidermis and even to some parts of the upper dermis. For PUVA we found that, when the incident UVA doses are 25 or 100 kJ/m2 (320-400 nm) (an initial and an advanced stage of therapy, respectively), and the 8-methoxypsoralen concentration in the blood is 0.1 microgram/mL (the desired level), the combined doses to the mid epidermis (and some areas of the upper dermis) are well below the 50% HIV promoter-activating PUVA dose (ADPUVA50). Only under the worst scenario conditions, i.e. an exceptionally high drug concentration in the patient's tissues and localization of HIV in the nearest proximity to the skin surface, would the combined PUVA dose expected during photochemotherapy exceed ADPUVA50. These results suggest that the probability of HIV activation in the epidermis by direct mechanisms is higher for UVB than for PUVA treatment. However, complexities of the UV-inducible HIV activation and immunomodulatory phenomena are such that our results by themselves should not be taken as an indication that UVB therapy carries a higher risk than PUVA therapy when administered to HIV-infected patients.

Neoplastic transformation of neonatal human fibroblasts exposed in vitro to radiation from a quartz-halogen lamp.

The use of unfiltered quartz-halogen lamps exposes human skin to radiation that spans much of the ultraviolet (UV) spectrum. Reports indicate that exposure to quartz-halogen lamps is erythemogenic, mutagenic, and carcinogenic. To compare the carcinogenic potential of quartz-halogen lamps with that of other UV sources, we determined the dose dependence for cytotoxicity and neoplastic transformation in neonatal human fibroblasts exposed in vitro to: a 15 W germicidal lamp (primarily 254 nm radiation), a 15 W Cool White fluorescent lamp, and an unfiltered 20 W quartz-halogen lamp. Fluence-survival relationships were multiphasic with linear dose response below about 40% survival, and all three sources produced fluence-dependent transformation as indicated by induction of anchorage-independent growth. Maximum transformation frequencies were observed at fluences of 5-8 J/m2 for the germicidal lamp, 6.3 kJ/m2 for the fluorescent lamp, and 300 J/m2 for the quartz-halogen lamp. These data confirm the carcinogenic potential of the quartz-halogen lamp.

Relationships between mitotic delay and the dose rate of X radiation.

Upon exposure of cells to radiation delivered at a continuous low dose rate, cell proliferation may be sustained with the cells exhibiting a constant doubling time that is independent of the total dose. The doubling time or mitotic delay under these conditions has been shown to depend on the dose rate in HeLa, V79 and P388F cells (Mitchell et al., Radiat. Res. 79, 520-536, 1979; Fox and Gilbert, Int. J. Radiat. Biol. 11, 339-347, 1966). Reanalysis of the data for these particular cell lines shows that there is a threshold dose rate for mitotic delay, and that above the threshold there is a linear relationship between the length of mitotic delay and the logarithm of the dose rate which is referred to as the dose-rate response. We have observed the same relationships for L5178Y (LY)-R and LY-S cells exposed to low-dose-rate radiation. The threshold dose rates for LY-R, LY-S and P388F cells are similar (0.01-0.02 Gy/h) and are much lower than for V79 and HeLa cells. The slope of the dose-rate response curve is the greatest for HeLa cells, followed in order by LY-S, V79 and P388F cells, and finally by LY-R cells. The slopes for HeLa and LY-R cells differ by a factor of 35.

Effects of psoralen plus UVA radiation (PUVA) on HIV-1 in human beings: a pilot study.

BACKGROUND: Laboratory data document the activation of the HIV-1 genome on exposure to UV radiation, including PUVA. The overall effects of UV radiation exposure on HIV-1 infection in human beings are unknown. OBJECTIVE: Our purpose was to observe CD4 cell counts and quantitative markers of HIV-1 load in late-stage HIV-1-infected human beings receiving PUVA for various cutaneous diseases. METHODS: Samples of peripheral blood were obtained on days 0, 14, 30, and 60 of PUVA administered in therapeutic doses. Number of CD4+ T lymphocytes was determined by flow cytometry, and HIV-1 load was measured by semiquantitative polymerase chain reaction for viral genome in peripheral blood mononuclear cells, semiquantitative RNA-polymerase chain reaction for HIV-1 RNA in serum, and determination of p24 in serum. RESULTS: No significant changes in the measurements were observed. CONCLUSION: This study did not detect a deleterious effect on CD4 cell count or HIV-1 load during 2 months of PUVA treatment for patients in late stages of infection, with low CD4 cell counts and high HIV-1 loads.

Reassessment of the differential effects of ultraviolet and ionizing radiation on HIV promoter: the use of cell survival as the basis for comparisons.

Effects of different radiation treatments on the human immunodeficiency virus-1 (HIV) promoter were reassessed for exposures comparable to those encountered in clinical or cosmetic practice, using survival of the host cell as a basis for comparisons. The exposures were performed with two ultraviolet radiation sources commonly used as medical or cosmetic devices (UVASUN 2000 and FS20 lamps), a germicidal (G15T8) lamp and an X-ray machine. The UVC component of the FS20 lamp was filtered out. The emission spectra of the lamps were determined. The characteristics of these sources allowed us to discriminate among effects of UVA1 (340-400 nm), UVB + UVA2 (280-340 nm) and UVC (254 nm) radiations. Effects of irradiation were ascertained using cultures of HeLa cells stably transfected with the HIV promoter linked to a reporter-chloramphenicol acetyl transferase-gene. The exposures used caused at least two logs of cell killing. In this cytotoxicity range, UVA1 or X radiations had no effect on the HIV promoter, whereas UVB + UVA2 or UVC radiations activated the HIV promoter in a fluence-dependent manner. Survivals following exposure to UVB + UVA2 or UVC radiation were (1) at the lowest measurable HIV promoter activation, 30 and 20%, respectively, (2) at one-half maximal activation, 6 and 3%, respectively and (3) at the maximal activation, 0.5 and 0.2%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Slow clones, reduced clonogenicity, and intraclonal recovery in X-irradiated L5178Y-S cell cultures.

Profound, long-lasting growth disturbances and reduced viability and clonogenicity were observed in suspension cultures of L5178Y-S (LY-S) murine leukemic lymphoblasts exposed to 0.25-6 Gy of X rays. In most cases, uncloned cultures grew at a reduced rate for periods corresponding to at least 100 cell generations, even when viability of such cultures returned to the normal level. These disturbances were analyzed in clones isolated using agar-supplemented medium. A slow phenotype was much more frequent among surviving clones isolated from LY-S cell cultures irradiated with 3 Gy of X rays than among clones isolated from nonirradiated controls. Growth of individual LY-S clones was affected to different extents, regardless of the clone's viability. The slowest clones had doubling time twice as long (22 h) as that of the control (10-12 h). More than 100 slow clones isolated from irradiated and nonirradiated cultures were followed for prolonged times, and some of them were further subcloned. The slow clones showed a high degree of heterogeneity, and selection for the slowest clone produced clones with increasing proliferative impairment and decreasing cloning efficiency. These results showed that progeny of X-irradiated LY-S cells contained many slowly growing cells, and that their presence affected the growth rate for scores of cell generations. The prolonged impairment of growth rate, viability, and clonogenicity appeared to depend on heritable lesions that were overcome as a result of intraclonal recovery. All slow clones were capable of such recovery, which for clones derived from irradiated cultures typically required periods corresponding to several scores of, but in some cases > 200, cell generations. Intraclonal recovery was much more rapid in slow clones isolated from nonirradiated cultures. This finding indicated that either slow phenotype depended on different cellular changes in the two groups of clones or mechanisms of intraclonal recovery were affected by radiation.

Non-nuclear damage and cell lysis are induced by UVA, but not UVB or UVC, radiation in three strains of L5178Y cells.

The potential to induce non-nuclear changes in mammalian cells has been examined for (1) UVA1 radiation (340-400 nm, UVASUN 2000 lamp), (2) UVA+UVB (peak at 313 nm) radiation (FS20 lamp), and (3) UVC (254 nm) radiation (G15T8 lamp). The effects of irradiation were monitored in vitro using three strains of L5178Y (LY) mouse lymphoma cells that markedly differ in sensitivity to UV radiation. Comparisons were made for the effects of approximately equitoxic fluences that reduced cell survival to 1-15%. Depending on the cell strain, the fluences ranged from 830 to 1600 kJ/m2 for the UVASUN lamp, 75 to 390 J/m2 for the FS20 lamp and 3.8 to 17.2 J/m2 for the G15T8 lamp. At the exposure level used in this study, irradiation with the UVASUN, but not the FS20 or G15T8, lamp induced a variety of non-nuclear changes including damage to cytoplasmic organelles and increased plasma membrane permeability and cell lysis. Cell lysis and membrane permeabilization were induced by the UVA1 emission of the UVASUN lamp, but not by its visible+IR components (> 400 nm). The results show that the plasma membrane and other organelles of LY cells are highly sensitive to UVA1 but not to UVB or UVC radiation. Also UVA1, but not UVB or UVC radiation, causes rapid and extensive lysis of LY cells. In conclusion, non-nuclear damage contributes substantially to UVA cytotoxicity in all three strains of LY cells.

Activation of the human immunodeficiency virus promoter by UVA radiation in combination with psoralens or angelicins.

The effects of mono- and bifunctional furocoumarins plus UVA radiation (PUVA and related treatments) on the human immunodeficiency virus-1 (HIV-1) promoter were studied using HeLa cells stably transfected with the chloramphenicol acetyl transferase gene under the control of the HIV-1 promoter. The experiments were performed with three psoralens (5-methoxypsoralen, 5-MOP; 8-methoxypsoralen, 8-MOP; and 4'-aminomethyl-4,8,5'-trimethylpsoralen, AMT) and four angelicins (angelicin; 4,5'-dimethylangelicin, 4,5'-DMA; 6,4'-dimethylangelicin, 6,4'-DMA; and 4,6,4'-trimethylangelicin, TMA). The drugs alone and UVA radiation alone showed no effect on the HIV promoter. However, when the cells were incubated with the furocoumarins at 0.1-40 micrograms/mL and then irradiated, the HIV promoter was activated in distinct fluence ranges, i.e. (1) no promoter activity was discernible at low fluences (e.g. at 0.1 microgram/mL of 8-MOP up to 100 kJ/m2), (2) as the fluence was increased, the promoter activity increased to reach a maximum (10-50-fold with respect to the unexposed samples), and (3) as the fluence was further increased, the promoter activity decreased. Similar (although shifted on the fluence scale) patterns were observed with either > 340-nm UVA radiation or with UVA radiation contaminated with a small amount of UVB radiation (typical for PUVA lamps). The effective fluences were inversely related to the drug concentration. Experiments with 5-MOP and 8-MOP indicated reciprocity of the drug concentration and radiation fluence. The HIV promoter response patterns were similar for monofunctional angelicins and bifunctional psoralens.(ABSTRACT TRUNCATED AT 250 WORDS)

Spectral effects in activation of the human immunodeficiency virus promoter by psoralens plus ultraviolet A treatment.

The effects of PUVA treatment on HIV promoter activation and cell killing in HIV cat/HeLa cells were studied using two UV sources, a UVASUN sunlamp and a UVAR Photoactivation Chamber. A 4 to 5 times higher dose of ultraviolet radiation was required from the UVASUN lamp than from the UVAR lamps: 1) to activate the HIV promoter in the presence of 0.1 or 1.0 microgram/ml 8-MOP and 2) to reduce cell survival to a level of 10%, in the presence of 0.1 or 1.0 microgram/ml 8-MOP. In addition, exposures performed with a fixed dose of 20 kJ/m2 at varying concentrations of 8-MOP, required a 4.7 times higher combined PUVA dose from the UVASUN lamp than from the UVAR lamps. Two possible sources of these differences were analyzed: (1) the presence of UVB + UVA2 (280-340 nm) in the radiation emitted by the UVAR, but not the UVASUN lamp, and its potential biological activity independent of 8-MOP, and (2) the difference in the overlap of the emission spectra of the two lamps with the absorption spectrum of 8-MOP. The area of overlap was higher for the UVAR lamp than for the UVASUN lamp by a factor of 4.6, which is close to the difference between these two lamps in induction of the HIV promoter and killing HeLa cells. This indicates that the effectiveness of a particular UVA source used in combination with 8-MOP can be predicted by its congruence to the absorption spectrum of the photosensitizing drug.