Carotenoid supplementation reduces erythema in human skin after simulated solar radiation exposure

Excessive exposure to solar radiation, especially ultraviolet A (UVA: 320-400 nm) and ultraviolet B (UVB: 290-320 nm) radiation, may induce UV-carcinogenesis and erythema in the skin. Although the protective effects of carotenoids against skin lesions are still unclear, beta-carotene has been proposed as an oral sun protectant. The purpose of this study was to determine the magnitude of the protective effects of oral alpha- and beta-carotene supplementation for 24 weeks on UVA- and UVB-induced erythema in humans. While being exposed to UVA and UVB radiation, 22 subjects (11 men and 11 women) were supplemented with natural carotenoids for 24 weeks. Each day for the first 8 weeks, subjects were given 30 mg of natural carotenoids containing 29.4 mg of beta-carotene, 0.36 mg of alpha-carotene, and traces of other carotenoids in vegetable oil. The natural carotenoid dose was progressively raised by 30-mg increments, at every 8 weeks, from 30 mg to 90 mg. Small areas (1 cm2) of the skin were exposed to increasing doses of UV light (16-42 mJ/cm2) to determine the minimal erythema dose (MED). MED was defined as a uniform pink color with well-defined borders. MED readings were obtained by visual inspection 24 hr postirradiation. Blood samples taken during supplementation were used to determine alpha- and beta-carotene serum levels and for a lipid peroxidation analysis. During natural carotenoid supplementation, the MED of solar simulator radiation increased significantly (P<0.05). After 24 weeks of supplementation, serum beta-carotene levels were increased from 0.22 microg/ml (95% CI; 0.16-0.27) to 1.72 microg/ml (95% CI;1.61-1.83). Similarly, alpha-carotene serum levels increased from 0.07 microg/ml (95% CI;0.048-0.092) to 0.36 microg/ml (95% CI; 0.32-0.40). Serum lipid peroxidation was significantly (P<0.05) inhibited in a dose-dependent manner during natural carotenoid supplementation. The present data suggest that supplementation with natural carotenoids may partially protect human skin from UVA- and UVB-induced erythema, although the magnitude of the protective effect is modest.     

Ultraviolet radiation-induced erythema in human skin

We have evaluated UVR-induced erythema in previously unexposed buttock skin of volunteers of skin types I, II, III, and IV. Studies were done with solar-simulated radiation (SSR), UVB, and UVAI and we determined the just perceptible minimal erythema dose (MED) and, in some cases, quantified erythema with a reflectance device. The results show that there is a trend for increased SSR MED with skin type, with the MED of skin type IV being approximately twice that of skin type I, a smaller difference than one might have expected. However, there is a very considerable overlap of MED between skin types which shows that MED is a very poor indictor of skin type. Quantitative dose-response and time course studies with SSR and UVAI showed broadly similar responses when comparable MED-based exposures were given. We used our data to test the new concept of the standard erythema dose (SED) with two different erythema action spectra, and confirmed that the SED approach works with the different UVR sources that we studied.     

Inhibition of UV radiation-induced DNA damage by a 5-methoxypsoralen tan in human skin

Previously untanned buttock skin of 4 volunteers (skin type II; tan with difficulty as they sunburn easily) was treated with various sunscreen preparations and solar--simulated radiation (SSR) or SSR alone for 2 weeks. One week later, the treatment sites were challenged with a DNA-damaging dose of SSR--twice the minimal erythema dose (2 MED). Skin biopsy samples were assayed for the levels of unscheduled DNA synthesis (a measure of DNA damage), melanin distribution, and skin thickening. 5-Methoxypsoralen-containing sunscreen preparations plus SSR or SSR alone induced melanogenesis and increased the stratum corneum thickness, but only the former regimen afforded a high degree of protection against subsequent SSR-induced DNA damage. 5-Methoxypsoralen-free sunscreen preparations plus SSR induced negligible tanning, skin thickening, and photoprotection. These findings are relevant to the risk-benefit analysis of sunscreen preparations, especially in skin type II, as they provide evidence that a 5-methoxypsoralen-induced tan is protective against the DNA-damaging effects of solar UV radiation, and thus has the potential to reduce the carcinogenic risk of exposure to such radiation.     

The impact of skin colour on human photobiological responses

Terrestrial solar ultraviolet radiation (UVR) exerts both beneficial and adverse effects on human skin. Epidemiological studies show a lower incidence of skin cancer in people with pigmented skins compared to fair skins. This is attributed to photoprotection by epidermal melanin, as is the poorer vitamin D status of those with darker skins. We summarize a wide range of photobiological responses across different skin colours including DNA damage and immunosuppression. Some studies show the generally modest photoprotective properties of melanin, but others show little or no effect. DNA photodamage initiates non‐melanoma skin cancer and is reduced by a factor of about 3 in pigmented skin compared with white skin. This suggests that if such a modest reduction in DNA damage can result in the significantly lower skin cancer incidence in black skin, the use of sunscreen protection might be extremely beneficial for susceptible population. Many contradictory results may be explained by protocol differences, including differences in UVR spectra and exposure protocols. We recommend that skin type comparisons be done with solar‐simulated radiation and standard erythema doses or physical doses (J/m²) rather than those based solely on clinical endpoints such as minimal erythema dose (MED).     

Determination of erythema-effective solar radiation in Japan and Germany with a spore monolayer film optimized for the detection of UVB and UVA – results of a field campaign

The available physical and biological broadband radiometers designed to determine erythema-effective radiation do not show any response or over/underestimate the biologically effective radiation to a high extent in the ultraviolet (UV)A spectral region. The data presented in this paper demonstrate that the biological system used in this study is the first one to make possible measurements of erythema-effective radiation in the sun in the UVA and UVB spectral region. These measurements were performed with a spore-film filter system as well as with spectroradiometers. It was demonstrated that this biotechnological method could be used to determine exact values expressed as minimal erythemal dose (MED). The spore-film system was tested in various field campaigns performed in Germany and in Japan. The seasonal daily variation of UV radiation in Germany determined in the period November 1995 to December 1996 using the spore-film filter system in sunny conditions tallied well with model calculations. The daily dose in Germany measured with the spore-film system close to the summer solstice, in sunny conditions (20.45 MED), was approximately 20 times higher than the lowest value measured close to the winter solstice (0.82 MED), a result which was in accordance with model calculations. The data determined with the spore-film filter system in Sapporo and Naha, Japan, fitted to the erythema-weighted data calculated from spectroradiometric measurements (Brewer), even at low solar radiation angles in a solar spectrum with less UVB but significant UVA. The spore-film dosimeter values were about 103 ± 8% of the integrated dose of the Brewer instrument. The standard deviation of the spore-film measurements obtained in Japan was 12.8%. The responsivity of the spore-film system towards longer wavelengths within the UVA spectrum was tested with the Okasaki Large Spectrograph with monochromatic radiation. At a wavelength of 365 nm – in a spectral region which is dominant in many tanning lamps and with minor importance for solar radiation in summer conditions – the tested spore-film system gave results that were close (112% compared to the calibration dose) to the calibration dose which was used for irradiation. Received: 27 January 1998 / Received last revision: 21 July 1998 / Accepted: 29 July 1998     

Modulation of UV-light-induced skin inflammation by d-alpha-tocopherol and l-ascorbic acid: a clinical study using solar simulated radiation

Objective: In this clinical trial we studied whether oral supplementation with d-alpha-tocopherol (α-Toc), l-ascorbic acid (Asc), or α-Toc combined with Asc influenced the solar simulated radiation (SSR) induced skin inflammation in healthy volunteers. Methods: We investigated the following groups in a prospective, randomized and placebo controlled study: Group (1) α-Toc 2 g / day, group (2) Asc 3 g / day, group (3) α-Toc 2 g / day combined with Asc 3 g / day, and group (4) placebo. Before and 50 days after supplementation we analyzed α-Toc and Asc concentrations in keratinocytes. The dose response curve of UV erythema was determined by reflectance spectrophotometry and the minimal erythema dose (MED) by visual grading before and after supplementation. Results: 50 days after supplementation α-Toc keratinocyte levels were increased in groups (1) and (3), Asc concentrations were elevated in groups (2) and (3), and the a/γ-Toc ratio increased in groups (1) and (3). The dose response curve of UVR induced erythema showed a significant flattening and the MED increased from 103 ± 29 mJ/cm² (before supplementation) to 183 ± 35 mJ/cm² (after supplementation) in group (3), while there were no significant changes in groups (1) and (2) after vitamin supplementation. Conclusion: α-Toc and Asc act synergistically in suppression of the sunburn reaction.     

Effects of whole body UV-irradiation on oxygen delivery from the erythrocyte

In 16 healthy caucasian volunteers (mean age: 22.2 years) the influence of whole body UV-irradiation on the oxygen transport properties of erythrocytes was investigated. Four hours after irradiation with UV (using the minimal erythema dose, MED) no variation of haemoglobin concentration, hematocrit, mean corpuscular haemoglobin concentration, pH or standard bicarbonate could be found, whereas inorganic plasma phosphate (Pi), calcium, the intraerythrocytic 2,3-diphosphoglycerate (2,3-DPG), the activity of erythrocytic phosphofructokinase (PFK) and pyruvatekinase (PK) increased significantly. The half saturation tension of oxygen (P50-value) tended to increase. The increase of Pi causes--via a stimulation of the glycolytic pathway--an increase in 2,3-DPG concentration and thus results in a shift of the oxygen dissociation curve. It is therefore possible to enhance tissue oxygenation by whole body UV-irradiation.     

Modulation of catalase in human skin in vivo by acute and chronic UV radiation.

In this study, we demonstrate that catalase is differently regulated either by acute, or chronic UV radiation during the photoaging process. 2MED of UV radiation decreased the activity and expression of catalase gradually in the epidermis and dermis at between 24 and 48 h after the UV exposure. These levels then returned to near normal by 72 h after exposure. The catalase mRNA was also decreased in the skin 24 h after UV irradiation to 50% of the control level, and then started to recover. In contrast, chronic UV irradiation over a lifetime (approximately 50 years) increased the catalase activity in the epidermis and dermis of the human skin in vivo. Our results suggest that catalase might be one of the important enzymes in the skin aging process, and that it plays an important role in the photoprotection of the skin from UV light.     

Relationship between skin response to ultraviolet exposure and skin color type

Sun exposure is responsible for detrimental damage ranging from sunburn to photoaging and skin cancer. This damage is likely to be influenced by constitutive pigmentation. The relationship between ultraviolet (UV) sensitivity and skin color type was analyzed on 42 ex vivo skin samples objectively classified from light to dark skin, based on their values of individual typology angle (ITA) determined by colorimetric parameters. The biologically efficient dose (BED) was determined for each sample by quantifying sunburn cells after exposure to increasing doses of UV solar-simulated radiation. Typical UV-induced biologic markers, other than erythema, such as DNA damage, apoptosis and p53 accumulation, were analyzed. A statistically significant correlation was found between ITA and BED and, ITA and DNA damage. Interestingly, DNA lesions were distributed throughout the whole epidermal layers and the uppermost dermal cells in light, intermediate and tanned skin while they were restricted to suprabasal epidermal layers in brown or dark skin. Our data support, at the cellular level, the relationship between UV sensitivity and skin color type. They emphasize the impact of DNA damage accumulation in basal layer in relation to the prevalence of skin cancer.     

Alteration of the immune response to Mycobacterium bovis BCG in mice exposed chronically to low doses of UV radiation

BALB/c mice were exposed on shaved dorsal skin to 1 minimal erythemal dose (MED) of UVB radiation (2.25 kJ/m2) from a bank of six FS-40 sunlamps three times per week. The total number of irradiations ranged from 1 to 27. At regular intervals, groups of mice were injected in the left hind foot pad with 1 x 10(6) live mycobacteria (Mycobacterium bovis BCG) 3 days after the last UVB exposure. The mice were tested 21 and 42 days after infection for a delayed type hypersensitivity (DTH) response to the purified protein derivative (PPD) of tubercle bacilli by injecting PPD into the right hind foot pad and measuring the foot pad swelling 24 hr later. The course of infection was followed by assessing the number of bacterial colony forming units in the lymph node draining the site of BCG infection and the spleen. Mice exposed from 1 to 15 times to 1 MED of UV radiation showed a significant suppression in their DTH response to PPD compared with the unirradiated mice. At the same time, the number of bacterial colony-forming units in the lymph node and spleen of the UV-irradiated mice was greater than in control mice. With continued exposure to UVB, however, the DTH response recovered to a normal level, and there was no longer an increase in the number of viable bacteria in the lymphoid organs. These results indicate that early in the course of chronic UV irradiation, mice were impaired in their ability to mount a DTH response to BCG and to clear these bacteria from their lymphoid organs; later the mice recovered from these effects of UV, with continued treatment. A dose-response study using single doses of UV radiation indicated that a dose of 2.7 kJ/m2 suppressed the DTH response by 50%. Thus, exposure of mice to a single or multiple low doses of UV radiation prior to infection can interfere with systemic immunity to mycobacteria.     

Migration of Langerhans cells and gammadelta dendritic cells from UV-B-irradiated sheep skin

Depletion of dendritic cells from UV-B-irradiated sheep skin was investigated by monitoring migration of these cells towards regional lymph nodes. By creating and cannulating pseudoafferent lymphatic vessels draining a defined region of skin, migrating cells were collected and enumerated throughout the response to UV-B irradiation. In the present study, the effects of exposing sheep flank skin to UV-B radiation clearly demonstrated a dose-dependent increase in the migration of Langerhans cells (LC) from the UV-B-exposed area to the draining lymph node. The range of UV-B doses assessed in this study included 2.7 kJ/m2, a suberythemal dose; 8 kJ/m2, 1 minimal erythemal dose (MED); 20.1 kJ/m2; 40.2 kJ/m2; and 80.4 kJ/m2, 10 MED. The LC were the cells most sensitive to UV-B treatment, with exposure to 8 kJ/m2 or greater reproducibly causing a significant increase in migration. Migration of gammadelta+ dendritic cells (gammadelta+ DC) from irradiated skin was also triggered by exposure to UV-B radiation, but dose dependency was not evident within the range of UV-B doses examined. This, in conjunction with the lack of any consistent correlation between either the timing or magnitude of migration peaks of these two cell types, suggests that different mechanisms govern the egress of LC and gammadelta+ DC from the skin. It is concluded that the depression of normal immune function in the skin after exposure to erythemal doses of UV-B radiation is associated with changes in the migration patterns of epidermal dendritic cells to local lymph nodes.     

Carotenoids and Flavonoids Contribute to Nutritional Protection against Skin Damage from Sunlight

The concept of photoprotection by dietary means is gaining momentum. Plant constituents such as carotenoids and flavonoids are involved in protection against excess light in plants and contribute to the prevention of UV damage in humans. As micronutrients, they are ingested with the diet and are distributed into light-exposed tissues, such as skin or the eye where they provide systemic photoprotection. β-Carotene and lycopene prevent UV-induced erythema formation. Likewise, dietary flavanols exhibit photoprotection. After about 10–12 weeks of dietary intervention, a decrease in the sensitivity toward UV-induced erythema was observed in volunteers. Dietary micronutrients may contribute to life-long protection against harmful UV radiation.     

Keratinocytes exposed to ultraviolet radiation reveal three down-regulated genes with potential function in differentiation and cell cycle control

The incidence of skin cancer is increasing in epidemic proportion. Although solar UV radiation is known to be the major risk factor, much information is lacking about the molecular mechanisms leading to skin cancer. To gain a deeper insight into these mechanisms, we have examined cells of a human keratinocyte cell line (HaCat) after exposure to 0.16 minimal erythema doses of UVB radiation. This dose led to an S-phase delay that was reversible 22 h postirradiation. To examine gene expression 10 h after UV irradiation, a nonradioactive differential display was employed. Three genes were identified as being down-regulated significantly. The first encodes for topoisomerase-IIbeta-binding protein 1 (expression level 5% 6 h after irradiation). This protein is associated with human topoisomerase IIbeta and appears to be necessary for DNA replication during the onset of S phase. The second gene product has previously been reported to be involved in differentiation and is therefore known as differentiation-dependent A4 protein (28% 8 h after irradiation). The third gene is XPO1 (also known as CRM1) (5% 8 h after irradiation), whose protein is involved in nuclear export of mRNA molecules. Differential expression of these genes after UV irradiation has not been reported. Because of their potential involvement in cell cycle control and differentiation, these proteins could be important for understanding the reaction of keratinocytes after exposure to UV radiation.     

Ultraviolet light induced alteration to the skin

Solar light is the primary source of UV radiation for all living systems. UV photons can mediate damage through two different mechanisms, either by direct absorption of UV via cellular chromophores, resulting in excited states formation and subsequent chemical reaction, or by phosensitization mechanisms, where the UV light is absorbed by endogenous (or exogenous) sensitizers that are excited and their further reactions lead to formation of reactive oxygen species (ROS). These highly reactive species can interact with cellular macromolecules such as DNA, proteins, fatty acids and saccharides causing oxidative damage. Direct and indirect injuries result in a number of harmful effects such as disrupted cell metabolism, morphological and ultrastructural changes, attack on the regulation pathways and, alterations in the differentiation, proliferation and apoptosis of skin cells. Processes like these can lead to erythema, sunburn, inflammation, immunosuppression, photoaging, gene mutation, and development of cutaneous malignancies. The endogenous and exogenous mechanisms of skin photoprotection are discussed.     

Methods for exposure of laboratory animals to ultraviolet radiation

Two different sources of ultraviolet B (UVB) radiation, an electronically controlled UVB exposure unit, containing FS40 tubes, and a hand-held Kromayer lamp, were evaluated for actual irradiance in W/m2 and spectra (physical dosimetry and biological dosimetry (skin effects in rodents)). The technical studies of the FS40 sources demonstrated that the flux intensity of the lamps could be changed electronically, without affecting the spectrum. Thus it was possible to standardize UVB exposure electronically. The biologically effective doses of these sources were analysed in RIV-Tox Wistar rats and BALB/c mice. After low doses of UVB radiation, histopathological changes such as acanthosis, hyperkeratosis and dermal inflammation were observed in the skin without the presence of major side effects such as erythema and oedema. After higher doses of UVB radiation erythema and oedema were clearly visible. Quantitative studies showed that the minimal erythema dose, as a biological parameter, correlated well to the emission in J/m2. In addition, biological parameters such as acanthosis and inflammation in the skin correlated well to the actual exposure in J/m2 and were sensitive biomarkers for UVB-induced skin toxicity. Thus, in addition to minimal erythemal doses, acanthosis and inflammation may also be applied as biologically relevant doses for studies of the biological effects of UVB radiation.     

Photobiological implications of melanin photoprotection after UVB‐induced tanning of human skin but not UVA‐induced tanning

Repetitive suberythemal UVA and/or UVB exposures were used to generate comparable UV‐induced tans in human skin over the course of 2 weeks. To evaluate the potential photoprotective values of those UVA‐ and/or UVB‐ induced tans and to avoid the confounding issue of residual UV‐induced DNA damage, we waited 1 week before challenging those areas with a 1.5 MED of UVA+UVB after which we measure DNA damage. The results show that the type of UV used to induce skin pigmentation affects the redistribution of melanin in the skin and/or de novo melanin synthesis. The UVA‐induced tans failed to even provide a minimal SPF of 1.5, which suggests that producing a tan with UVA‐rich sunlamps prior to a holiday or vacation is completely counterproductive.     

One to Two Year Treatment of Parkinson's Disease with Levodopa

One hundred patients with Parkinson''s disease were treated with levodopa for more than a year at UCLA Medical Center. They were examined at given intervals and their improvement was graded. The optimum therapeutic dose was attained by balancing side effects against relief of symptoms and ranged from 1.5 grams to 8.0 grams per day (average 4.3 grams). There is no doubt that levodopa is the most effective treatment now available for Parkinson''s disease. At the end of the first year, 60 percent of the patients improved 50 percent or better, and 10 percent were considered symptom-free. All major symptoms of this disease, including rigidity, akinesia and tremor, improved in variable degree.There were no serious abnormalities in the routine clinical laboratory tests. The comon side effects included nausea, vomiting and choreoathetoid dyskinesias. The side effects were not life threatening, but occasionally were major therapeutic challenges.Maximal benefits with minimal side effects were achieved only by careful adjustments of the levodopa dosage as the months went by. This needed careful management by the physician and cooperation by the patient. Anticholinergic medications or amantadine hydrochloride, sometimes both, usually supplemented the effect of the levodopa.