In vivo skin treatment with tissue-tolerable plasma influences skin physiology and antioxidant profile in human stratum corneum

The antimicrobial treatment of wounds is still a major problem. Tissue-tolerable electrical plasma (TTP) is a new approach for topical microbial disinfection of the skin surface. The aim of the present study was to investigate the influence of TTP on a carotenoid profile in relation to skin physiology parameters (epidermal barrier function, stratum corneum (SC) hydration, surface temperature and irritation parameters). We were interested in the interaction of TTP and the antioxidative network, as well as the consequences for skin physiology parameters. These parameters are also indicative of TTP safety in vivo. For plasma application, 'Kinpen 09' was used (surface exposure 30-43°C) for 3 s. Beta-carotene and water profiles were assessed by in vivo Raman microspectroscopy (skin composition analyzer 3510). Skin physiology parameters were measured with Tewameter TM 300, Corneometer CM 825, skin thermometer and Chromameter CR 300. All parameters were assessed non-invasively on seven healthy volunteers before and after plasma application in vivo. We could show that TTP application leads to a decrease in beta-carotene especially in the superficial SC. Skin-surface temperature increased by 1.74°C, while the transepidermal water loss (TEWL) increase indicated an impaired barrier function. SC hydration decreased as seen in water profile especially in the superficial layers and capacitance values. A slight increase in skin redness was measurable. The induction of reactive oxygen species is probably the major contributor of TTP efficacy in skin disinfection. Skin physiology parameters were influenced without damaging the skin or skin functions, indicating the safety of TTP under in vivo conditions.

Infrared radiation does not enhance the frequency of ultraviolet radiation-induced skin tumors, but their growth behaviour in mice

There is increasing concern about the interaction between infrared radiation (IR) and ultraviolet radiation (UVR) with regard to carcinogenesis because prolonged solar exposure is associated with an increased cumulative load not only of UVR but also of IR. We recently demonstrated that IR-pretreatment reduces UVR-induced apoptosis. As this might support the survival of UVR-damaged cells and thus carcinogenesis, we performed an in vivo photocarcinogenesis study. One group of mice were treated with IR prior to each UVR exposure; additional groups were treated with IR or UVR alone. IR alone did not induce skin cancer. UVR-induced tumor formation was not enhanced in IR-pretreated mice, but, in contrast, seemed to occur with delay. This correlated with a reduction of p53 mutated clones in the skin. However, once developed, tumors in IR-pretreated mice grew faster which was confirmed by their enhanced Ki-67 expression. The enhanced aggressiveness of tumors derived from IR-pretreated mice was associated with a higher prevalence of sarcomas than epithelial tumors. Hence, the impact of IR on UVR-induced carcinogenesis has to be interpreted with caution. Although IR may delay the onset of UVR-induced tumors, it might contribute to a worse outcome by shifting these tumors into a more aggressive phenotype.

Uptake of antioxidants by natural nutrition and supplementation: pros and cons from the dermatological point of view

The pros and cons of the systemic and topical application of antioxidant substances are a subject of intense discussion among experts, with resulting confusion for consumers and producers. The objective of the present article is to clarify the various uncertainties relating to the use of antioxidant substances in dermatology. Whereas inappropriate application of antioxidant substances (concerning their concentration and composition) might induce harmful effects, the consumer will definitively benefit from physiological concentrations and compositions of antioxidants. The most suitable method is the consumption of natural antioxidants in the form of fruit and vegetables, for example. In addition, the skin, which also accumulates antioxidant substances, may profit from a sufficient antioxidative level, as damage induced by sun radiation in addition to skin aging is reduced.

Interaction between carotenoids and free radicals in human skin

Environmental factors like air pollutants, radiation of the sun and stress factors such as illness, smoking, or alcohol abuse produce free radicals in the human tissue as well as in the skin. Free radicals serve as the main cause for premature skin aging. Additionally, they also contribute towards immunosuppression and the formation of skin diseases including cancer. The human organism has developed a protection system against the destructive action of free radicals by means of the antioxidant network. In the present study, the interaction of free radicals and carotenoid antioxidants in the human skin under in vivo conditions was investigated and summarized. The measurement of carotenoids in human skin was performed in vivo using resonance Raman spectroscopy.

Carotenoids in human skin

The interaction of free radicals with antioxidants is a topic of increasing interest in the development of prevention strategies against skin ageing. Carotenoids can serve as marker substances for the complete antioxidative network of human skin. Recently, it has become possible to measure the carotenoids non-invasively and online using resonance Raman spectroscopy. This method has been used in various studies to investigate the interaction of carotenoid antioxidants and free radicals in human skin. In this review, the results of the selected studies are summarized and compared. It could be demonstrated that the carotenoid concentration of the skin reflects the lifestyle of individuals. A high level of carotenoids can be achieved with a healthy diet rich, for instance, in fruit and vegetables. Stress factors such as illness, UV and IR radiation of the sun, and smoking and alcohol consumption reduce the concentration of the carotenoids in the skin. It could be demonstrated that premature skin ageing was less in people with a high level of antioxidants in their tissue. Consequently, the furrows and wrinkles were not so deep and dense as in the skin of individuals with a low antioxidant level. The measurements are highly suited for the development of anti-ageing strategies and can be efficiently used in the medical diagnostics and therapy control.

Determination of the antioxidative capacity of the skin in vivo using resonance Raman and electron paramagnetic resonance spectroscopy

BACKGROUND

Non-invasive measurements are of major interest for investigating the effects of stress, nutrition, diseases or pharmaceuticals on the antioxidative capacity of the human skin. However, only a few non-invasive methods are available.

MATERIAL AND METHODS

The resonance Raman spectroscopy is well established to monitor carotenoids in the skin, but correlations with other antioxidants have not yet been described. Electron paramagnetic resonance spectroscopy used for measurements of free radicals has already been used elsewhere to investigate the reduction of applied long-living nitroxide radicals, caused by skin antioxidants and UV irradiation, but only a single or up to four volunteers were included in these studies. Therefore, in this study, the two methods were applied in parallel on 17 volunteers, and the rate constant of the nitroxide decrease was correlated with the cutaneous carotenoid concentration.

RESULTS AND DISCUSSION

A correlation with R = 0.65 was found, supporting the thesis that different antioxidants protect each other and build an antioxidative network in the skin. The results also give first indications that the carotenoids serve as marker substances for the antioxidative capacity, if the nutrition is well balanced.

Kinetics of carotenoid distribution in human skin in vivo after exogenous stress: disinfectant and wIRA-induced carotenoid depletion recovers from outside to inside

The human organism has developed a protection system against the destructive effect of free radicals. The aim of the present study was to investigate the extent of exogenous stress factors such as disinfectant and IR-A radiation on the skin, and their influence on the kinetics of carotenoids distribution during the recovery process. Ten healthy volunteers were assessed with resonance spectroscopy using an Argon-laser at 488 nm to excite the carotenoids in vivo. Additionally, Raman-confocal-micro-spectroscopy measurements were performed using a model 3510 Skin Composition Analyzer with spatially resolved measurements down to 30 μm. The measurements were performed at a baseline of 20, 40, 60, and 120 min after an external stressor consisting either of water-filtered infrared A (wIRA) with 150 mW∕cm(2) or 1 ml∕cm(2) of an alcoholic disinfectant. Both Raman methods were capable to detect the infrared-induced depletion of carotenoids. Only Raman-microspectroscopy could reveal the carotenoids decrease after topical disinfectant application. The carotenoid-depletion started at the surface. After 60 min, recovery starts at the surface while deeper parts were still depleted. The disinfectant- and wIRA-induced carotenoid depletion in the epidermis recovers from outside to inside and probably delivered by sweat and sebaceous glands. We could show that the Raman microscopic spectroscopy is suited to analyze the carotenoid kinetic of stress effects and recovery.

Determination of the influence of IR radiation on the antioxidative network of the human skin

Production of free radicals in the human skin subsequent to IR irradiation has been demonstrated by means of two different methods. The first technique, based on resonance Raman spectroscopy, enables the non-invasive measurements of the kinetics of cutaneous carotenoid antioxidants beta-carotene and lycopene, subsequent to IR irradiation. Obtained degradation of the cutaneous carotenoids was a hint but not evidence that IR irradiation can produce free radicals in the skin. Therefore, the direct observation sustaining the production of free radicals subsequent to IR irradiation in the skin was performed in-vitro by electron paramagnetic resonance spectroscopy. Enzymatic processes as well as heat shock-induced radicals in the human skin are presumably involved in the energy transfer from IR irradiation into the molecules of the skin. Protection strategy for human skin against IR-induced free radicals based on the increase in the concentration of antioxidants by means of antioxidant-rich supplementation is discussed.

Can physical stress be measured in urine using the parameter antioxidative potential?

Although regular exercise is known to promote health, it is also well known that competetive sports can lead to an increase of free radical production, and thus to a drop in antioxidative potential. Thus, the present study examined the effect of competetive sports on the antioxidative potential (AOP).

Using chemoluminescence, the AOP was measured in the spontaneous urine of leisure and semi-professional athletes during a training camp. Further, the parameters creatinin and uric acid were measured.

It was shown that physical stress led to a drop in the antioxidant potential of up to approximately 50%. To compensate for this decline, special antioxidant food is recommended.