Changes in sodium-potassium ratio in guinea pig epidermis in n-hexadecane-induced hyperplasia

A transient epidermal hyperplasia was induced in guinea pig epidermis by a single application of n-hexadecane. The epidermal response was analysed by light microscopy and by energy dispersive X-ray microanalysis (EDX). The epidermal hyperplasia reached a maximum between 96 and 192 h after the application. The hyperplastic response was associated with a depressed sodium-potassium ratio (increased potassium, decreased sodium) in the keratinocytes at 96 h, beginning already at 48 h. At 24 h there were no major differences in elemental content, compared the controls. The result of the present study is consistent with the hypothesis that alterations in the functional state of the epidermal keratinocytes are associated with changes in the sodium-potassium ratio in the cells. The absence of major elemental changes at 24 h indicates that the initiation of the hyperplastic response occurred prior to this time point.     

Pathological findings in cumulative irritation induced by SLS and croton oil in hairless mice

It is known that the pathological features of acute irritant contact dermatitis are specific according to the irritant. However, in chronic irritant contact dermatitis, it is not clear whether specific patterns exist. To investigate whether the specific pathology of acute irritant contact dermatitis is sustained in chronic irritant contact dermatitis, sodium lauryl sulfate (SLS) and croton oil were applied 3x a week for 2 weeks on the dorsal skin of hairless mice using Finn Chambers. The pathologic changes induced by irritants at various concentrations were evaluated using H&E and Luna's staining, as well as immunohistochemistry for 5-bromo-2-deoxyuridine (BrdU), keratin 6 and loricrin. Our results showed that epidermal hyperplasia and inflammatory infiltration were relatively marked in the groups treated with higher concentrations of irritants. These features were more prominent in the 1% croton oil treated group than in the 0.25% SLS treated group. However, lower concentrations of irritants resulted in very similar histological changes, characterized by epidermal hyperplasia with minimal inflammatory infiltration, irrespective of the chemical. Our results suggest that the histological responses to irritants vary with concentration in cumulative irritation, as in acute irritation, but repetitive mild irritation may evoke common histological changes, characterized by epidermal hyperplasia with minimal inflammatory infiltration, irrespective of the chemical used.     

Dynamic changes in the epidermal OKT6 positive cells at mild irritant reactions in human skin

In the present study we induced mild irritant contact reactions by using 0.5% sodium lauryl sulphate (SLS) in distilled water or with distilled water in patch tests for 6 or 24 hours. The biopsies were taken at 6, 24, 48 and 96 hours. Light and electron microscopy were used to assess the irritant reactions produced and the monoclonal antibody OKT6 was used for the detection of the LCs. The number of the epidermal OKT6 positive dendritic cells was found to be increased at 48 and 96 hours after the exposure to SLS and at 96 hours in the water patch tests. It is concluded that mild irritant stimuli cause an increase in the LCs (OKT6 positive cells) and thus might influence and modulate the response to subsequent exposures to allergens.     

Fluorescence confocal laser scanning microscopy for in vivo imaging of epidermal reactions to two experimental irritants

Background: Fibre‐optic fluorescence confocal laser scanning microscopy (CLSM) is a novel non‐invasive technique for in vivo imaging of skin. The cellular structure of the epidermis can be studied. A fluorophore, e.g. fluorescein sodium, is introduced by an intradermal injection or applied to the skin surface before scanning. Images are horizontal optical sections parallel to the skin surface. Fluorescence CLSM has hitherto not been applied to experimental contact dermatitis. Objective: The aim was to study the applicability of fluorescence CLSM for in situ imaging of irritant contact dermatitis reactions caused by established model irritants, e.g. sodium lauryl sulphate (SLS) and pelargonic acid (PA). Methods: Twelve healthy individuals volunteered. The flexor aspect of the right and the left forearm was exposed to SLS in water and PA in isopropanol and occluded under Finn Chambers for 24 h. The reactions were rated clinically and, following epicutaneous and intra‐dermal application of fluorescein sodium, studied by fluorescence CLSM, magnification × 1000. Results: Both irritants disturbed the epidermal intercellular borders, which became blurred, thickened and variably altered. This was interpreted as being a result of chemical damage to cellular membranes. Cell borders might show a double contour as a result of inter‐cellular oedema. PA might increase the size of individual keratinocytes interpreted as a result of intra‐cellular disturbance with oedema. SLS‐exposed sites showed clusters of keratinocytes with visible nuclei in the outer layers of the epidermis, e.g. a parakeratotic shift supposed to be due to increased cell proliferation elicited by SLS. The isopropanol vehicle and PA did not interfere with the CLSM imaging technique or the experimental procedures. SLS, being a detergent, however, modified the physico‐chemical properties of the skin surface and both disturbed epicutaneous labelling with the flurophore and immersion oil coupling between the skin surface and the optical system. Thus, SLS was technically more difficult to study by CLSM than PA. Conclusions: This preliminary study demonstrated the applicability of fluorescence CLSM for a detailed study of experimental skin irritants in vivo. Essential findings were disturbed and widened cell borders, swelling of keratinocytes by PA and induction of a parakeratotic shift by SLS with clusters of keratinocytes holding nuclei in the epidermis. Fluorescence CLSM offers a unique opportunity to study the inter‐ and intracellular water compartments directly in the epidermis in situ and an opportunity to visualize cell proliferation manifested as parakeratosis. Fibre‐optic fluorescence CLSM of irritant reactions is, however, technically more complicated than reflectance CLSM and may not be applicable to any irritant. SLS applied epicutaneously interacted with the skin surface and coupling to the microscope and was thus found to be more difficult to study technically than PA. PA dissolved in isopropanol is for technical reasons, and with SLS as alternative, considered the preferred model irritant.     

免疫磁性技术分离提纯酵母样真菌的研究

用包被有羊抗鼠ＩｇＧ的磁珠结合鼠抗白念单抗后，对白念珠菌，类星形念珠菌，类星形念珠菌，热带念珠菌，新生隐球菌，光滑念珠菌菌悬液及白念珠菌与新生隐球菌两菌混悬液进行了分离纯化研究。结果：免疫磁球和白念珠菌，类星形念珠菌结合尤为明显，与热带念珠菌少量结合而不和新生隐球菌，光滑念珠菌结合。     

Effect of sodium lauryl sulfate-induced skin irritation on in vivo percutaneous penetration of four drugs.

The influence of sodium lauryl sulfate-induced irritant contact dermatitis on in vivo percutaneous penetration was investigated for four 14C-labeled compounds with diverse physicochemical properties: hydrocortisone (HC), indomethacin (IM), ibuprofen (IB), and acitretin (AC). Hairless guinea pigs were pretreated for 24 h with either 0.5% sodium lauryl sulfate (SLS) to induce irritant contact dermatitis or with water (controls). Twenty-four hours after pretreatment, 450 microliters saturated solutions of HC, IM, IB, or AC in isopropylmyristate were applied to the pretreated skin for 24 h. Systemic absorption was determined by urinary and fecal excretion of compounds. Drug concentrations in stratum corneum (obtained by tape cellophane stripping after decontamination of the application site) and in epidermis/dermis (punch biopsy) were also investigated. Systemic absorption of topically applied drugs (as evaluated by urinary and fecal excretion) in SLS-irritated skin was significantly increased for HC (factor 2.6) followed by IB (1.9 times) and IM (1.6 times) but not increased for AC. However, drug concentrations in the viable epidermis and dermis were 70% lower in SLS-irritated than normal skin for HC, but not different for IB, IM, and AC. Thus, the influence of the state of the skin (irritant dermatitis versus healthy) on percutaneous penetration was different for diverse drugs. The general assumption that percutaneous penetration and drug tissue concentrations were higher in diseased versus healthy skin was not found to be true in our irritated-skin model.     

Epidermal hyperplasia induced in guinea pig flank skin by intradermal injection of Sudan red.

Studies of dermal-epidermal interactions were conducted with guinea pig flank skin and intradermal injections of the irritant, Sudan IV dye in olive oil. These injections led to epidermal hyperplasia in areas overlying the irritant and the effect was most significant when the irritant was placed in the upper dermis. Basal cell mitotic activity and thymidine uptake reached a peak by 24 h and thereafter dropped rapidly. Maximal epidermal thickness (4.3 times the control) resulting from an increase in cell number occurred within 2-4 days. Despite the very short period of increased cell growth, epidermal thickness returned to control values only after a 24-day period. A similar growth response could not be induced by saline injections. A single topical application of the irritant showed a qualitatively and quantitatively different epidermal response. These experiments indicate that an intradermal irritant can lead to epidermal hyperplasia and a long-lasting epidermal thickening.     

Effect of some irritants on human epidermal mitosis

Studies on how irritant materials might induce epidermal hyperplasia were initiated by investigating their influence on epidermal mitosis. 5% hydrochloric acid, neat dimethyl acetamide and 1% benzalkonium chloride had no effect. 5% benzalkonium chloride, however, produced a 10-fold increase in mitotic activity, while a dose response curve was seen with sodium lauryl sulphate (SLS) peaking at 1%. 1% SLS produced a remarkably uniform response for this type of assay and it is suggested that it might provide a useful model for situations of increased epidermal cell turnover such as psoriasis. It is also noted that there was apparently no direct relationship between gross inflammation and the mitotic response.     

Elemental changes in guinea-pig epidermis in the hyperplastic response to irritant stimuli

A mild irritant reaction was induced by application of sodium lauryl sulphate to the skin of guinea-pigs. The response was analysed at 24 and 48 h after application using light microscopy, transmission electron microscopy and energy dispersive X-ray microanalysis (EDX). It was found that the sodium lauryl sulphate induced a hyperplastic response in the epidermis with an increased number of keratinocytes. This response was associated with significantly increased levels of intracellular sodium and chloride. The elemental changes were most marked at 24 h, whereas the number of keratinocytes was highest at 48 h. The pattern of the elemental changes and the ultrastructural alterations are compatible with initial membrane damage followed by a transient increase in proliferative activity. The present results demonstrate that EDX is a useful tool for the analysis of functional alterations in epidermal keratinocytes under pathological conditions.     

SLS-irritated human skin shows no correlation between degree of proliferation and TEWL increase

Abstract It is well known that cutaneous irritants influence epidermal proliferation but the pathogenesis is poorly understood. Recent investigations have shown that the skin barrier integrity influences the proliferation of the basal keratinocytes. Our question was whether the proliferating activity of keratinocytes is indeed regulated by the degree of skin barrier damage or by a direct toxic action of the irritant on the keratinocytes. Therefore various degrees of skin irritation were induced by the application of 0.1%, 0.5% and 2% sodium lauryl sulphate (SLS) solution to the forearm skin of six healthy volunteers. This experiment was performed to evaluate the relationship between SLS concentration and epidermal proliferation. In a second experiment another 14 volunteers were treated with a single SLS concentration (0.5%) to look for interindividual differences in the patterns of skin reaction and susceptibility to the irritant. Skin barrier function was evaluated by measurements of transepidermal water loss (TEWL) before and after irritation. Punch biopsies were taken after 96 h from exposed areas and from unexposed normal skin. Dividing keratinocytes were identified immunocytochemically using three different monoclonal antibodies: PCNA, MIB 1 and KiS1. Exposure to SLS resulted in concentration-dependent increases in both TEWL and epidermal proliferation. However, no significant correlation could be found between the degree of hyperproliferation and the TEWL changes. The results suggest that epidermal proliferation is modulated by a direct interaction of the surfactant with the keratinocytes and/or by release of mediators rather than the consequence of a barrier disturbance. Received: 5 February 1997 / Received after revision: 12 August 1998 / Accepted: 24 August 1998     

Epidermal Langerhans cell apoptosis is induced in vivo by nonanoic acid but not by sodium lauryl sulphate

Exposure to irritants may cause chronic irritant contact dermatitis (ICD), characterized by irregular epidermal thickening and a predominantly dermal mononuclear cell infiltrate. The mechanisms involved, and why only certain individuals are affected, are not clearly understood. Different irritants may trigger different cellular and molecular interactions between resident skin cells and recruited inflammatory cells. In some individuals these interactions may become self-perpetuating resulting in persistent inflammation in the absence of continued exposure. This study examined Langerhans cell (LC) density in clinically normal skin of 46 patients with chronic ICD and 10 healthy individuals, and compared the action of the two irritants nonanoic acid (NA) and sodium lauryl sulphate (SLS) on the LCs and keratinocytes of clinically normal skin in patients with chronic ICD. There was a higher number of LCs/mm basement membrane in patients compared with controls, although there was no difference in the number of dendrites/LC nor in dendrite length. SLS induced keratinocyte proliferation after 48 h exposure, had no effect on LC number or distribution, and induced keratinocyte apoptosis after 24 and 48 h exposure. In contrast, NA decreased keratinocyte proliferation after 24 h exposure but this returned to basal levels after 48 h, and induced epidermal cell apoptosis after only 6 h exposure. NA dramatically decreased LC number after 24 and 48 h exposure, which was accompanied by basal redistribution and decreased dendrite length. Most significantly, NA induced apoptosis in over half of the LCs present after 24 and 48 h exposure.     

Distributional changes of Langerhans cells in human skin during irritant contact dermatitis

We used light and electron microscopic immunocytochemistry to study distributional changes in the human Langerhans cell (LC) system during the first 14 days of a mild irritancy caused by sodium lauryl sulphate (SLS). A marked initial decrease in epidermal LC was noted possibly resulting from migration from the epidermis to the dermis and from irreversible cell damage. Several studies have previously found an unchanged number of LC in SLS-induced contact irritant dermatitis, but these studies may not have taken into account the fact that SLS is effectively absorbed from the test chamber. Unless certain precautions are taken the SLS concentration rapidly falls to topical levels that have no effect on the LC system. Simultaneously with the decrease in the epidermis we observed an increase in dermal CD1a+ cells, confirming an often reported finding. There is, however, no consensus as to the identity of these cells, and several authors have reported that such cells lack LC granules and thus these cells have often been classed as indeterminate cells. We found that, during irritant contact dermatitis, provided an adequate number of sections were scrutinized in the electron microscope, all dermal CD1+ cells contained Birbeck granules.     

Electrical impedance measured to five skin depths in mild irritant dermatitis induced by sodium lauryl sulphate

The non-invasive electrical impedance technique used in this study reflects structural changes in a tissue, and provides an estimate of the level of oedema by a simple impedance index. Sodium lauryl sulphate (SLS), dissolved in water at concentrations of 0.1, 0.5 and 2.0%, was applied for 24 h in 12 mm Finn chambers® on both volar forearms of 12 healthy volunteers. An unoccluded area was used as a reference site. Readings from all sites were taken before the application of the irritant, and 24 h after its removal. After the last reading, a 3-mm punch biopsy was taken from each test site for histological examination. The results obtained from electrical impedance measurements at five different skin depths were correlated with those obtained from histological examination, visual scoring and transepidermal water loss (TEWL). For all of the methods used the responses were proportional to the concentration of the irritant. Statistically significant changes of electrical impedance were found for all depths and concentrations, except for 0.1% SLS at the most superficial depth. The histological changes were focused in the epidermis, and mainly consisted of oedema. Alterations in the thickness of the epidermis due to oedema were used as a quantitative parameter for correlation with the assessment of irritation using the electrical impedance technique. For the detection of irritant reactions, TEWL and electrical impedance are more sensitive than visual scoring, and selection of the optimum depth penetration further increases the sensitivity of the electrical impedance measurement.     

Profile of irritant patch testing with detergents: sodium lauryl sulfate,sodium laureth sulfate and alkyl polyglucoside

The cutaneous reaction to detergents follows distinct kinetic rules: the duration of application and the irritant concentration are of major importance. The aim of this study was to evaluate the differences in kinetics of skin reaction between the standard irritant sodium lauryl sulfate (SLS), and 2 modern detergents: sodium laureth sulfate (SLES) and alkyl polyglucoside (APG). We performed patch testing with SLS and SLES (or APG) at different concentrations (0.125, 0.25, 0.5, 1.0 and 2.0%) and with different exposure times (6, 12 and 24 h). Evaluation was conducted by measurement of transepidermal water loss (TEWL) and laser Doppler flowmetry (LD) 24 h, 7 and 10 days after patch removal. We found a pronounced reaction to SLS, and a far milder one to SLES. Even at the highest concentration the skin reaction to APG was hard to detect. During the regeneration period (day 3-10) SLS showed even at day 10 an increased TEWL at all concentrations tested. The irritation due to SLES was convincingly detectable only up to day 7, whereas the APG-tested skin areas showed no significant reaction even at day 3. These results demonstrate the improvement in reduction of skin irritation achieved by development of novel detergents.     

Irritant patch testing with sodium lauryl sulphate: interrelation between concentration and exposure time

BACKGROUND: It is well known that the degree of skin reaction to an irritant depends on its concentration and exposure time. OBJECTIVES: To determine the interrelationship between the concentration of sodium lauryl sulphate (SLS) and exposure time in both weak (subclinical) and severe reactions. METHODS: Patch testing with SLS was performed at different concentrations (0.125%, 0.25%, 0.5%, 1.0% and 2.0%) and with different exposure times (3, 6, 12, 24 and 48 h). Evaluation was conducted by measurement of transepidermal water loss and by laser-Doppler flowmetry both 30 min and 24 h after patch removal. RESULTS: We found more reliable and constant skin reactions 24 h after patch removal, and a higher correlation between SLS concentration and skin reaction. CONCLUSIONS: We conclude that the concentration of SLS influences the test outcome to a larger degree than the exposure time. We present formulae by which the outcome of SLS patch testing at various SLS concentrations ranging from 0.125% to 2% and any exposure time between 3 and 24 h can be estimated.     

Artificial disruption of skin barrier prior to irritant patch testing does not improve test design

BACKGROUND: Irritant patch testing is often performed as a 24- or 48-h occlusive patch test with low concentrations of sodium lauryl sulphate (SLS). OBJECTIVES: The aim of this study was to investigate potential ways to shorten this test procedure and obtain precise test results. PATIENTS AND METHODS: Thirty-six healthy volunteers underwent irritant patch testing with different pretreatments (PT) of the test fields. Occlusive test chambers were applied on the upper back with SLS 0.5%, 1%, 2% and 5% in large Finn Chambers(R). The patches were removed after 4 and 24 h, respectively, depending on the concentration used. Test fields were pretreated as follows: PT 0, field without any PT (control); PT 1, prick with lancet; PT 2, prick with test stamp; PT 3, scratch with lancet; PT 4, incision with standardized incision instrument (0.1-0.2 mm depth). Skin reactions were evaluated by transepidermal water loss (TEWL), skin erythema and skin hydration and as well by a visual score (VS) at 4, 24 and 72 h. RESULTS: Our data show an obvious distinction between PT 0-2 and PT 3-4 at all measurement methods. The average TEWL values with PT 3-4 were higher than those with PT 0-2, especially on the 4-h course. This distinction may derive from the shape and size of the skin impairment achieved by PT 3-4, leading to a mechanical barrier disruption. However, SLS may infiltrate directly into deeper skin layers supported by capillarity. Consequently, no or little penetration through the epidermis and interaction with its structures occurs, which is responsible for irritant skin reactions. The SLS dose in the upper skin layers is therefore lower at these PTs. The lower remaining dose of SLS also explains this distinction, especially for the VS. Additionally, there are presumed reactions in deeper layers of the epidermis and dermis at PT 3-4. CONCLUSIONS: In summary, all data suggest a different reaction pattern from the classical irritant response. Therefore, application without any PT seems to be best suited for irritancy skin testing, especially for visual assessment. PTs prior to irritant patch testing have been shown to be unjustifiable.     

Topical retinoic acid changes the epidermal cell surface glycosylation pattern towards that of a mucosal epithelium

Topical all-trims retinoic acid (RA) produces a number of epidermal changes which are indistinguishable from those observed following treatment with a local irritant, namely sodium lauryl sulphate (SI. S). This observation has led to criticism that the efficacy of RA in disorders such as photoageing. Is merely a result of irritancy. In stratified epithelia, the cellular differentiation process is characterized by a stepwise synthesis of cell surface carbohydrates, and each type of stratified epithelium has its own specific pattern of carbohydrate expression. Glycosyltransferases, which are responsible for carbohydrate synthesis, are influenced by retinoids. Thus, we investigated whether epidermal cell surface glycosylation is altered in skin treated with topical RA, and contrasted it with changes induced by topical SLS Skin biopsies were obtained from seven normal volunteers who had been treated, on three separate areas of buttock skin, with single applications of 0·1% RA. 2% SLS, or vehicle creams, followed by 4-day occlusion. Biopsies were assessed immunohistologically using highly specific monoclonal antibodies to cell surface carbohydrates (types 1, 2 and 3 chain structures), previously demonstrated in the epidermis and in oral mucosal epithelium. Although type 1 chain structures were not demonstrated in any of the samples, the distribution of type 2 and 3 chain structures in RA-treated epidermis was altered towards that seen in a mucosal epithelium. T antigen, a mucin-type cell surface carbohydrate structure normally expressed throughout the epidermis, was only observed in the granular layer of RA-treated epidermis-a feature of mucosal epithelia. Le^y, normally only seen in non-keratinized buccal epithelium, was strongly expressed in RA-treated epidermis. In contrast, the glycosylation pattern of the SLS-treated epidermis was not significantly different from that observed after vehicle treatment. Thus, RA treatment converts normal stratified epithelium towards the phenotype of mucosal epithelium with a decrease in T antigen and a concomitant increase in Le^y. These changes the not observed following treatment with SLS and identify an important difference between RA effects and irritancy.     

健康成人皮肤对十二烷基硫酸钠刺激反应的反射式共聚焦显微镜特征分析

目的 观察十二烷基硫酸钠（SLS）刺激后18 ~ 60岁健康人皮肤反射式共聚焦扫描显微镜（RCM）特征的差异,分析年龄和性别对皮肤反应的影响,同时初步探讨RCM在客观评价皮肤反应中的价值。方法 采用封闭式斑贴试验,分别将0.1%和0.5% SLS贴敷于120例健康受试者背部48 h,并于去除后不同时间点进行临床评估和RCM检测。结果 0.1%和0.5% SLS组皮肤刺激反应的RCM特征主要有角化不全、角质层结构不清、棘层海绵水肿、表皮炎症细胞浸润和真皮乳突毛细血管扩张等。去除0.1%和0.5%SLS 刺激后24 h,RCM特征发生率达到高峰,其中真皮毛细血管扩张的发生率分别高达66.7%和95.0%。0.5% SLS去除后24 h,男性海绵水肿的发生率为68.9%（42/61）,显著低于女性［84.7%（50/59）,χ2 = 4.24,P < 0.05］; 0.1%SLS去除后24 h,18 ~ 40岁年龄组人群棘层海绵水肿的发生率为53.3%（32/60）,显著高于41 ~ 60岁［35.0%（21/60）,χ2 = 4.09,P < 0.05］;其余RCM参数,在0.1%和0.5% SLS刺激去除后,不同性别或不同年龄组之间差异均无统计学意义（P > 0.05）。临床评估显示去除0.1%和0.5% SLS后24 h,男女皮肤刺激反应发生率差异均无统计学意义（均P > 0.05）,18 ~ 40岁和41 ~ 60岁两个年龄组之间差异也无统计学意义（均P > 0.05）。Spearman相关性分析显示,临床评估结果与RCM特征之间具有良好的相关性,其中,去除0.1% SLS后24 h,海绵水肿和真皮毛细血管扩张与临床评估结果的相关系数均高达0.77（P < 0.001）。但去除SLS 0.5 h后,0.1%和0.5% SLS组表现出2项以上RCM特征的受试者比例分别为17.5%（21/120）和51.7%（62/120）,比同一时刻临床评估的阳性率［2.5%（3/120）和12.5%（15/120）］更接近去除SLS 24 h后的临床评估结果34.2%（41/120）和85.0%（102/120）。结论 性别和年龄对0.1%和0.5% SLS诱导的皮肤刺激反应无明显影响;相对临床评估,RCM在刺激反应早期能更加客观准确地评估皮肤反应。