Barbara Z. Zmudzka

UV-induced DNA damage and melanin content in human skin differing in racial/ethnic origin

DNA damage induced by UV radiation is a critical event in skin photocarcinogenesis. However, the role of racial/ethnic origin in determining individual UV sensitivity remains unclear. In this study, we examined the relationships between melanin content and DNA damage induced by UV exposure in situ in normal human skin of different racial/ethnic groups, phototypes, and UV sensitivities. The minimal erythema dose (MED) was established for each subject exposed to UVA/UVB radiation, and skin was biopsied before as well as 7 min, 1 day, and 1 wk after UV exposure. There was great variation among individuals in the amount of DNA damage incurred and rates of its removal. The results show that after exposure to 1 MED of UV, the skin of subjects from all groups suffered significant DNA damage, and that increasing content of constitutive melanin inversely correlated with the amount of DNA damage. It is clear from these results that measured erythemal UV sensitivity of the skin (MED) is a more useful predictor of DNA photodamage than is racial/ethnic origin or skin phototype and that rates of DNA damage removal following UV radiation may be the critical determinant of the UV sensitivity (including predisposition to cancer) of the skin.

Human skin responses to UV radiation: pigment in the upper epidermis protects against DNA damage in the lower epidermis and facilitates apoptosis

Melanin plays an important role in protecting the skin against UV radiation, and melanomas and basal/squamous cell carcinomas occur more frequently in individuals with fair/light skin. We previously reported that levels of melanin correlate inversely with amounts of DNA damage induced by UV in normal human skin of different racial/ethnic groups. We have now separately examined DNA damage in the upper and lower epidermal layers in various types of skin before and after exposure to UV and have measured subsequent apoptosis and phosphorylation of p53. The results show that two major mechanisms underlie the increased photocarcinogenesis in fair/light skin. First, UV‐induced DNA damage in the lower epidermis (including keratinocyte stem cells and melanocytes) is more effectively prevented in darker skin, suggesting that the pigmented epidermis is an efficient UV filter. Second, UV‐induced apoptosis is significantly greater in darker skin, which suggests that UV‐damaged cells may be removed more efficiently in pigmented epidermis. The combination of decreased DNA damage and more efficient removal of UV‐damaged cells may play a critical role in the decreased photocarcinogenesis seen in individuals with darker skin.—Yamaguchi, Y., Takahashi, K., Zmudzka, B. Z., Kornhauser, A., Miller, S. A., Tadokoro, T., Berens, W., Beer, J. Z., Hearing, V. J. Human skin responses to UV radiation: pigment in the upper epidermis protects against DNA damage in the lower epidermis and facilitates apoptosis. FASEB J. 20, E630–E639 (2006)

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.

Activation of human immunodeficiency virus by ultraviolet radiation

Two years ago Valerie et al. (1988) reported that 254 nm ultraviolet radiation (UVR)* or sunlight can induce the human immunodeficiency virus (HIV) promoter. The same authors observed that UVR can stimulate growth of the complete virus in human cells. These observations attracted considerable attention. It is known that seroconversion and the acquired immunodeficiency syndrome (AIDS) develop with different dynamics in different individuals (Moss and Bacchetti, 1989). This may be influenced by human exposure to inducing agents including a variety of UVR sources. Studies related to HIV activation by UVR are continuing in several laboratories including this one. The significance of such studies reaches far beyond the AIDS problems. Information gained from them broadens our knowledge of activation of other pathogenic and nonpathogenic viruses as well as of the cellular control of gene regulation in human cells. It also contributes to our understanding of possible associations between DNA damage and repair, mutagenesis, and oncogenesis. This article will review the current status of the knowledge about UV-induced HIV activation. A brief description of HIV structure and, in particular, its gene promoter will be given. The effects of UVR exposure of cells on HIV activation and HIV promoter induction will be reviewed. Some events that follow production of DNA damage and lead, via activation of an oncogene, to HIV promoter induction will be discussed. Possible consequences of promoter induction and HIV activation for the cell and

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.

Cyclobutane pyrimidine dimer formation and p53 production in human skin after repeated UV irradiation

Abstract:  Substantial differences in DNA damage caused by a single UV irradiation were found in our previous study on skin with different levels of constitutive pigmentation. In this study, we assessed whether facultative pigmentation induced by repeated UV irradiation is photoprotective. Three sites on the backs of 21 healthy subjects with type II–III skin were irradiated at 100–600 J/m2 every 2–7 days over a 4‐ to 5‐week period. The three sites received different cumulative doses of UV (1900, 2900 or 4200 J/m2) and were biopsied 1 day after the last irradiation. Biomarkers examined included pigment content assessed by Fontana–Masson staining, melanocyte function by expression of melanocyte‐specific markers, DNA damage as cyclobutane pyrimidine dimers (CPD), nuclear accumulation of p53, apoptosis determined by TUNEL assay, and levels of p21 and Ser46‐phosphorylated p53. Increases in melanocyte function and density, and in levels of apoptosis were similar among the 3 study sites irradiated with different cumulative UV doses. Levels of CPD decreased while the number of p53‐positive cells increased as the cumulative dose of UV increased. These results suggest that pigmentation induced in skin by repeated UV irradiation protects against subsequent UV‐induced DNA damage but not as effectively as constitutive pigmentation.

ACTIVATION OF THE HUMAN IMMUNODEFICIENCY VIRUS PROMOTER BY UVA RADIATION IN COMBINATION WITH PSORALENS OR ANGELICINS

Abstract— 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′‐trimethyl‐psoralen, AMT) and four angelicins (angelicin; 4,5′‐diniethylangclicin, 4,5′‐DMA; 6,4′‐dimethylangelicin, 6,4′‐DMA; and 4,6,4′‐trimethylangelicin, TMA). The drugs alone and UVA radiation alone showed no erect on the HIV promoter. However, when the cells were incubated with the furocoumarins at 0.1–40 μg/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 μg/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 unexposcd samples), and (3) as the fluence was further increased, the promoter activity decreased. Similar (although shifted on the fluence scale) pattcrns 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 hence. The HIV promoter response patterns were similar for monofunctional angelicins and bifunctional psoralens. This indicated that the furocoumarin‐DNA crosslinks are not a prerequisite for the promoter activation and that the monoadducts suffice to elicit the HIV promoter response. The HIV promoter‐activating effectiveness of diKcrent drugs correlated with their photosensitizing potential. Thus, among psoralens the effectiveness order was AMT >. 5‐MOP >8‐MOP, and among angelicins: TMA > 6,4′‐DMA > 4,5′‐DMA > angelicin. The ektiveness did not vary substantially for 5‐MOP, 8‐MOP, 4,5′‐DMA, and 6,4′‐DMA. The combined drug and UVA radiation doses were higher than those that elicit cellular responses or those that may be received by the human white blood cells during cxtracorporeal PUVA therapy (photopheresis).

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.

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 (290–320nm) (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 (320–400nm) (an initial and an advanced stage of therapy, respectively), and the 8‐methoxypsoralen concentration in the blood is 0.1 μg/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 patients 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.

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)