Abstract:In the present study, the distribution of the carotenoids as a marker for the complete antioxidative potential in human skin was investigated before and after the topical application of carotenoids by in vivo Raman spectroscopy with an excitation wavelength of 785 nm. The carotenoid profile was assessed after a short term topical application in 4 healthy volunteers. In the untreated skin, the highest concentration of natural carotenoids was detected in different layers of the stratum corneum (SC) close to the skin surface. After topical application of carotenoids, an increase in the antioxidative potential in the skin could be observed. Topically applied carotenoids penetrate deep into the epidermis down to approximately 24 μm. This study supports the hypothesis that antioxidative substances are secreted via eccrine sweat glands and/or sebaceous glands to the skin surface. Subsequently they penetrate into the different layers of the SC.
Systemic and topical application of antioxidant substances for the medical treatment and prophylaxis of many diseases as well as additional protection of the skin against the destructive action of free radicals and other reactive species has become very popular during the past years. Stimulated by the positive results of a fruit and vegetable diet in supporting medical treatment and in cosmetics, artificial and extracted antioxidant substances have been broadly applied. Surprisingly, not only positive but also strong negative results have been obtained by different authors. According to study reports artificial and extracted antioxidant substances support different kinds of medical therapies, if they are applied in mixtures of different compounds at low concentration levels. In the case of the application of high concentration of some single compounds, side effects were often observed. Regarding skin treatment by systemically applied antioxidant substances for cosmetic purposes, positive cosmetic effects as well as no effects, but almost no side effects, apart from a number of allergic reactions, were reported. One reason for this seems to be the lower concentration of systemically applied antioxidant substances in comparison with a medical application. Topical application of antioxidant substances is closely related to cosmetic treatment for skin protection and anti-aging. Positive results were also obtained in this case. The present review is an attempt to classify and summarize the published literature concerning the efficiency of action of systemic and topical applications of antioxidant substances, such as carotenoids and vitamins, on human organism and especially on the skin. The available literature on this topic is very extensive and the results are often contradictory. Nevertheless, there are some clear tendencies concerning systemic and topical application of antioxidant substances in medicine and cosmetics, and we summarize them in the present paper.
In real life, at the beach, very little sunscreen remains present on the skin.
The recent European recommendation on the efficacy of sunscreen products requests now a minimum ratio of UVA/UVB protection. However, the visible and the infrared (IR) parts of the sun spectrum have received little attention concerning their possible contribution to skin damage. A common biophysical answer for the different wavelengths of the sun spectrum can be found in the creation of excess free radicals – mainly reactive oxygen species (ROS). Thanks to electron spin resonance spectroscopy applied to skin biopsies, we determined for the first time the free radical action spectrum covering UV and visible light (280–700 nm). Convolution of the action spectrum with sunlight spectral irradiance showed that 50% of the total skin oxidative burden was generated by visible light. Creation of ROS by visible light was experimentally confirmed by varying the illuminance of a spotlight. We also evidenced the creation of excess free radicals by near-IR radiation. In that case, free radical generation does not depend exclusively on the dose, but also on the skin temperature increase initiated by near-IR light. Some phenomena which are still unclear, such as the question about the deleterious or beneficial role of sunlight, are reviewed, implying the research on new protection strategies for the prevention of skin cancer.
The influence of the ultraviolet (UV) irradiation of the sun on the formation of free radicals in human skin is well investigated. Up to now, only small amounts of data are available stating that infrared (IR) irradiation can produce free radicals in the skin. In the present study, the formation of free radicals in human skin, subsequent to IRA irradiation (600–1,500 nm), has been demonstrated by means of two different methods. Firstly, the radical formation was detected indirectly by the degradation of the cutaneous carotenoid antioxidants β-carotene and lycopene, which was investigated in vivo by resonance Raman spectroscopic measurements. Secondly, the direct observation of produced radicals subsequent to IRA irradiation of the skin was performed in vitro by electron paramagnetic resonance spectroscopy. Taking into account the results of the present study and previous UV light studies, it can be expected that also solar irradiation in the visible spectral range will produce free radicals in the human skin. Therefore, the current sun protection strategies should be reconsidered. Furthermore, it was shown in the present study that the side effect in the form of radical formation could be significantly reduced by increasing the protection system of the human organism in form of the antioxidant network.
Constant exposure to solar UV irradiation and environmental hazards produces free radicals in the skin (Darr and Fridovich, 1994; Zastrow et al., 2004). The human organism has developed a protection system against the destructive action of free radicals, consisting mostly of vitamins, carotenoids, and enzymes (Stahl and Sies, 2003; Sander et al., 2004;Darvin et al., 2006). Approximately 70% of carotenoids in human skin are b-carotene and lycopene (Hata et al., 2000), which can serve as markers for the whole antioxidative potential (Darvin et al., 2008).Recently, Darvin et al. (2007) presented a laser spectroscopic method for the noninvasive determination of carotenoids in human skin, based on resonance Raman spectroscopy (RRS). The authors suggested that IR irradiation can give rise to the production of free radicals in the skin, which they measured by the degradation of the cutaneous carotenoids b-carotene and lycopene. Schroeder et al. (2008) showed in an in vivo study that IRA (760-1,440 nm) irradiation of the skin can elicit a retrograde mitochondrial signaling response that leads to the expression of matrix metalloproteinase-1. Given that expression of matrix metalloproteinase-1 was initiated through the generation of reactive oxygen species, which originated from the mitochondrial electron transport chain, the production of free radicals in the skin subsequent to IR irradiation could be expected.This supposition can be confirmed via direct detection of free radical formation using electron paramagnetic resonance (EPR) spectroscopy (Herrling et al., 2003). Until recently-in contrast to RRS measurements-EPR analysis could be performed only in vitro.
The influence of stress factors on human skin induces the production of free radicals. Free radicals react immediately with antioxidants contained in the skin, giving rise to their depletion and with the surrounding molecules, resulting in their damage, disorganization and even destruction. High amounts of free radicals are produced in the upper skin layers, i.e. mainly in the epidermis, subsequent to sun irradiation. Irradiation of the skin in the infra-red (IR) range of the spectra, applied at physiological doses, can produce free radicals. The magnitude of destruction of antioxidants, such as carotenoids, can serve as a marker of the extent of the stress factor, characterized by the quantity of produced free radicals. In this study, measurements on the degradation of cutaneous carotenoids following IR skin irradiation of 12 healthy volunteers (skin type II), with two IR sources (standard infrared radiator = SIR and water filter infrared = wIRA) were taken using resonance Raman spectroscopy. Topical application of the antioxidant beta-carotene (2 mg ⁄ cm 2 ) provided protection for the human skin when exposed to IR radiation. The magnitude of the degradation of dermal carotenoids after IR irradiation was significantly higher for SIR than for wIRA irradiation, for both non-treated and creamtreated skin areas. The amount of destroyed carotenoids after IR irradiation was higher in the case of pretreatment with betacarotene than for the untreated skin, indicating that the superficial part of antioxidants is most important for protecting against external stressors. The direct comparison of beta-carotene content was significantly higher for the cream-treated compared to untreated areas for all pairs: baseline, wIRA, after wIRA, baseline SIR and after SIR. Additionally, topically applied carotenoids as a single antioxidant component are less stable than the carotenoids in the skin incorporated by nutrition and accumulated in a mixture with different antioxidant substances. Resonance Raman spectroscopy can be used for the non-invasive measurements of carotenoids, which can be rated as marker substances of redox processes.
Resonance Raman spectroscopy was used as a fast and non-invasive optical method for the determination of the influence of IR radiation on the degradation of carotenoid antioxidant substances beta-carotene and lycopene in the human skin. It was found that the beta-carotene and lycopene concentration in the skin are decreased almost immediately subsequent to IR irradiation. The magnitude of degradation of carotenoids in the skin was determined at 27% for beta-carotene and 38% for lycopene on average. A strong correlation between the individual level of beta-carotene and lycopene in the skin of volunteers and the magnitude of destruction of carotenoids beta-carotene and lycopene in the skin was found to be R 2 = 0.78 and R 2 = 0.89 correspondingly. Taking into consideration the absence of absorption in the infrared range of spectra and the relative heat stability of carotenoids up to 50• C, the action of free radicals, which can be produced subsequent to IR irradiation in the skin, can be the main purpose for the degradation of carotenoid substances in the skin.
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