Anti-irritant and anti-inflammatory effects of glycerol and xylitol in sodium lauryl sulphate-induced acute irritation.

BACKGROUND: Glycerol is known to possess anti-irritant and hydrating properties and previous studies suggested that xylitol may also have similar effects. OBJECTIVE: Our aim was to study whether different concentrations of these polyols restore skin barrier function and soothe inflammation in sodium lauryl sulphate (SLS)-induced acute irritation. METHODS: The experiments were performed on male SKH-1 hairless mice. The skin of the dorsal region was exposed to SLS (5%) for 3 h alone or together with 5% or 10% of glycerol respectively. Further two groups received xylitol solutions (8.26% and 16.52% respectively) using the same osmolarities, which were equivalent to those of the glycerol treatments. The control group was treated with purified water. Transepidermal water loss (TEWL) and skin hydration were determined. Microcirculatory parameters of inflammation were observed by means of intravital videomicroscopy (IVM). Furthermore, accumulation of neutrophil granulocytes and lymphocytes, the expression of inflammatory cytokines and SLS penetration were assessed, as well. RESULTS: Treatment with the 10% of glycerol and both concentrations of xylitol inhibited the SLS-induced elevation of TEWL and moderated the irritant-induced increase in dermal blood flow and in the number of leucocyte-endothelial interactions. All concentrations of the applied polyols improved hydration and prevented the accumulation of lymphocytes near the treatment site. At the mRNA level, neither glycerol nor xylitol influenced the expression of interleukin-1 alpha. However, expression of interleukin-1 beta was significantly decreased by the 10% glycerol treatment, while expression of tumour necrosis factor-alpha decreased upon the same treatment, as well as in response to xylitol. Higher polyol treatments decreased the SLS penetration to the deeper layers of the stratum corneum. CONCLUSION: Both of the analysed polyols exert considerable anti-irritant and anti-inflammatory properties, but the effective concentration of xylitol is lower than that of glycerol.

Differences in corneocyte surface area in pre- and post-menopausal women. Assessment with the noninvasive videomicroscopic imaging of corneocytes method (VIC) under basal conditions.

The differences between pre- and postmenopausal women and men on corneocyte surface area were investigated by a noninvasive exfoliation method. Surface corneocytes were collected with a modified detergent scrub technique. Separated corneocytes were analyzed by videomicroscopy and image analyses (NIH Image 1.59). Additionally transepidermal water loss (TEWL) and stratum corneum hydration, water-holding capacity and moisture accumulation velocity were measured. 21 postmenopausal females without hormonal substitution (age 50.6 years), 33 premenopausal women (age 41.0 years) and 25 men matched for age (age 44.0 years) were included in this study. The smallest corneocyte surface area was seen in premenopausal women (368.0 pixels). For postmenopausal women and the male control population almost equal values could be detected (postmenopausal women 401.1 pixels; men 401.8 pixels). Significant differences were calculated with the ANOVA test (p = 0.0050) and post-hoc analyses (Dunn test); premenopausal vs. postmenopausal women (p < 0.05) and premenopausal women vs. men (p < 0.05), but not postmenopausal women vs. men (p > 0.05). No statistically significant differences could be detected for TEWL, stratum corneum hydration parameters. No correlation could be found between the corneocyte surface area and barrier or hydration parameters. The detected differences support the hypothesis that sexual hormones have an impact on corneocyte surface area, because sex hormone levels are higher in premenopausal women than in non-hormone-substituted postmenopausal women or men.

The efficiency of humectants as skin moisturizers in the presence of oil.

BACKGROUND/AIMS: The research on the treatment of "dry skin syndrome" is hampered by the lack of a suitable animal model. Formerly, we developed a validated guinea pig in vivo model in which the dry skin syndrome persists at least for 1 week. We can, therefore, compare the pharmacological effectiveness of known and potential moisturizers for the treatment of dry skin syndrome. Our aim is to study whether the moisturizing efficiency of humectants depends on the solvents in which they are dissolved. METHODS: "Dry skin syndrome" was induced on the shaved skin on one side of guinea pigs by daily application of 2% sodium lauryl sulphate in deionized water (SLS) for 3 days. The other shaved side was used as control. After ascertaining skin dryness, that side was treated for 6 days with glycerol or 1,2-hexanediol in different solvents: water, or medium chain triglycerides (MCT) or mixtures of MCT with isopropyl alcohol in different proportions. Measurement of the in vivo moisturizing effect was carried out by a Comeometer CM 825; erythema was measured by a Mexameter MX 16. RESULTS: Treatments with glycerol (1M) in water reversed the skin dryness shown by both instruments. When dissolving glycerol in MCT, no moisturizing effect was found, probably because glycerol does not dissolve in the oil. No moisturizing effect was found with different combinations of glycerol in the mixtures of MCT and isopropyl alcohol. No moisturizing effect was found using another polyol moisturizer: 1,2 hexanediol (1M) dissolved in MCT oil. Glycerol or 1,2-hexanediol abolished the erythema only when they were dissolved in water alone. CONCLUSION: Polyol moisturizers such as glycerol or 1,2-hexanediol do not act in the presence of oils against the sodium lauryl sulphate-induced dry skin in our guinea pig model. Since in an oil-in-water (O/W) emulsion, the water evaporates within several minutes, one has to question the ability of moisturizing emulsions to treat dry skin. In such instances, one cannot draw conclusions about the moisturizing efficiency of the preparation merely from the presence of the humectant. One has to study the effect of the finished preparation.

Measurement of croton oil induced rabbit ear swelling and evaluation of anti-inflammatory agents with a standard low pressure caliper.

BACKGROUND/AIMS: Carbobenzoxy-phenylalanyl-methionine (CBZ-Phe-Met), a known inhibitor of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) in vitro, has not been evaluated as a topical anti-inflammatory agent in vivo. In order to measure the effect of CBZ-phe-met, one needs a repeat-able, quantitative, easily obtainable standard measurement of the edema formation. In this study, a caliper designed for measuring soft materials was used to evaluate the edema, induced by croton oil on rabbit ears, as well as the effects of CBZ-phe-met. METHODS: The model used in this study was croton-induced inflammation on rabbit ears. A caliper for measuring soft materials (European standard DIN 863 part 3, manufactured by TESA Ltd., Renens, Switzerland) was used to evaluate the edema, which is part of the inflammatory effect. The action of CBZ-phe-met and two other anti-inflammatory agents; hydrocortisone and Na-ibuprofen, were compared. RESULTS: CBZ-phe-met 1-5% was found to reduce the edema on rabbit ears induced by croton oil by 15 to 93%. 5% CBZ-phe-met was found to be as effective as 5% Na-ibuprofen and 0.1% hydrocortisone. CONCLUSION: The caliper for soft materials was found to be suitable for measuring the edema induced by croton-oil, as well as the reducing edema due to anti-inflammatory treatment. It was also found that CBZ-phe-met is a potent topical anti-inflammatory agent in the croton-oil-induced inflammatory model. This may indicate a new approach in the treatment of inflammation.

Measurement of skin pH.

The knowledge of the skin surface pH-acid mantle is updated. The conviction that chronic alkalinization is damaging has been strengthened. Extensive skin surface pH data on the skin of non-white people are still missing. In the case of any measurement, the need for extensive infrastructural research and evaluation by non-parametric methods is emphasized. Infrastructural studies evaluate the range and change of the measured parameters for each test method according to sex, age and body area, as well as the sensitivity of the method to pharmacological influences. A detailed knowledge of the normal-representative range would make it possible to select those individuals whose measured parameter is outside the main 95% of the population; a detailed study of such individuals would be a very effective method of understanding the basic regulatory mechanism of the measured parameter.

An instrument for quantifying meibomian lipid on the lid margin: the Meibometer.

An instrument, the Meibometer, is described for estimating the casual level of meibomian lipid on the human eyelid margins, adapted from a commercially-available instrument used for measurement of skin surface lipid. A loop of plastic tape is pressed onto the everted lower lid margin to lift off a blot of lipid. The resultant change in light transmission of the tape is read by a photometer. Readings are not affected by side (R or L), time of day or lid surface temperature. After cleaning lipid from the lid margins with hexane, the rate of recovery per 10 blinks, as a percentage of the pre-cleaned level, was measured as 33.7 +/- 5.8 (mean +/- SE). This rate of delivery appears to provide enough lipid for complete resurfacing of the preocular tear film with every blink. Over short periods no detectable lipid was delivered in the absence of blinking.

The casual level of meibomian lipids in humans.

Using a modified skin surface lipid measuring instrument, the Meibometer, the amounts of meibomian lipid on the lid margins (the casual levels) of 421 subjects aged 1 to 94 years were measured. The lowest levels were found in children younger than 14 years (means +/- S.E.: males = 1.48 +/- 0.17, females = 1.53 +/- 0.17 micrograms lipid/mm2 lid margin surface) and rose with age, the highest levels being found in males aged 60-69 years (mean +/- S.E. = 3.26 +/- 0.18 micrograms lipid/mm2 lid margin surface). Male levels were higher than females in the 20-29 years age group but male and female levels became indistinguishable above the age of 50. These age- and sex-related changes differed markedly from those seen in skin surface lipid levels. The age-related changes in the casual levels of lid lipids remain unexplained although an endocrinological mechanism modified by morphological factors is considered.

Influence of ageing on the in vivo mechanics of the skin.

The response of the skin to common in vivo tests (in-plane uniaxial stretch, torsion, indentation and levarometry) is analyzed in terms of their suitability for ageing studies. The analysis suggests that low-load indentation and small deformation levarometry are well suited for ageing studies since the skin response under these tests can be directly related to its structure and constituent properties (known to be affected by ageing). The measured forehead skin response under these tests in 'young' (20-26 years) and 'old' (64-80 years) subjects is presented and compared with predictions of corresponding models. The results show that levarometry is more sensitive to ageing than indentometry.

Sebum measurements for rapid identification of hyperandrogenism due to an ovarian Leydig cell tumor.

Direct measurements of sebum with the Sebumeter were used in a patient with a benign androgen-producing tumor of the ovary. Androgen levels fell immediately after surgery, whereas the markedly elevated sebum levels found preoperatively dropped to normal after a delay of more than 2 weeks. Therefore, the Subumeter, due to its simplicity, may be useful for the preliminary screening and follow-up of patients with hyperandrogenic states.

In-vivo indentation of human skin.

Indentation tests were carried out on the forehead skin of volunteers under loading pressures of 0-5 KPa. The indentation was found to increase asymptomatically with loading pressure. In an attempt to develop a quantitative index for aging of the skin, its response to indentation loading was analyzed in reference to its glycosaminoglycan (GAG) containing ground substance and fibers' network microstructure. An analytic model that considers the skin as an incompressible solid-fluid mixture was developed and utilized to simulate the skin's indentation response. Following parameter fitting, the predicted results are in close agreement with the data. The model can thus serve as a tool for evaluating the effect of changes in the dermis components which accompany aging.

Study of skin ageing as a function of social and professional conditions: modification of the rheological parameters measured with a noninvasive method--indentometry.

Skin ageing was studied with a noninvasive method: indentometry. We measured two rheological parameters: resistance to pressure, indentation, under the pressure of 10 g/cm2, and elastic rebound, elasticity, after the removal of the pressure. We studied three different populations: cloistered nuns, white collar and blue collar workers. We found in all populations a steady decrease in elasticity as a function of age; this effect was always steeper in females. The working women lost their elasticity more rapidly than the nuns, and the male blue collar workers lost their elasticity more rapidly than the male white collar workers. The development of indentation as a function of age is somewhat different. The white collar males showed a steady loss of resistance to pressure with age much more rapidly than their blue collar counterparts. The females showed either a biphasic change (the nuns), no change at all (the white collar workers) or a loss of resistance to pressure (the blue collar workers). These results show that professional as well as social factors may influence skin ageing.

Comparison of different instruments for measuring stratum corneum moisture content.

Synopsis Stratum corneum moisturization was measured by two instruments simultaneously on the same subjects at different body sites. One instrument is based on the 1 GH(z) focused mirowave dielectric measurement; the other instrument measures impedance at 16 Hz. A linear relationship r = 0.86 was observed between the measurements by the two above-mentioned instruments. The 1 GHz focused microwave measurement is more accurate in measuring water concentration in the stratum corneum, especially in the upper layers relevant to "moisturization"; it is, however, an expensive research instrument. The low frequency impedance measurement involves a much simpler, cheaper and portable instrument which can be used routinely to evaluate 'moisturization' for the purpose of skin classification under field conditions.

The use of indentometry to study the effect of agents known to increase skin c-AMP content.

Local, externally applied pharmacological agents which are assumed to raise the c-AMP level, decrease the low pressure indentation value of the forehead skin of certain human volunteers.

Survival of isolated rabbit cornea and free radical scavengers.

The survival time of perfused endothelium is doubled in presence of the free radical scavengers superoxide dismutase and catalase.

The performance of a medico-cosmetic consultation unit.

Synopsis The facial skin of almost 500 women was measured by low pressure indentometry and surface pH-metry. The women's skin was also classified by visual observation by a well-trained cosmetician. Agreement between indentometry and cosmetic definition was found to be well correlated, except in the group of young women with dry skin. In this group, we believe, indentometry more accurately describes skin status. A significant relationship was found between high skin pH (>5.9) and lack of elasticity in the older age group with dry skin. It is hypothesized that high skin surface pH below the age of 70 is an expression of accelerated ageing process, and further, that chronic, high pH treatment of the skin leads to accelerated loss of skin elasticity.