Cutaneous Irritation Research Articles

Cosmetic selection in the sensitive-skin patient

The incidence of sensitive skin is increasing with great rapidity in the United States and Japan. This increase may be due in part to recognition of the condition, an increase in the number of skin products used on a daily basis by persons in developed countries, and other unidentified influences. Sensitive skin may be due to enhanced immune responsiveness, altered neurosensory input, and/or diminished barrier function. Guidelines for cosmetic and skin care product selection in the sensitive-skin patient include a paucity of ingredients, a minimum of potential allergens, a reduction in cutaneous irritants, and restoration of the cutaneous barrier. This article presents a thought pattern for addressing cosmetics issues in the sensitive-skin patient.

Regional variations in skin barrier function and cutaneous irritation due to iontophoresis in human subjects

The effect of saline iontophoresis on skin barrier function and irritation was investigated on three body sites (abdomen, chest and upper arm) in order to select an appropriate site for iontophoretic delivery of drugs. Thirty healthy human volunteers were recruited according to specific entry criteria. Ten subjects, five males and five females, were assigned to each body site group. Skin barrier function and irritation was examined after 4 h of saline iontophoresis at a current density of 0.2 mA/cm 2 on a 6.5 cm 2 area in terms of the measured responses: transepidermal water loss (TEWL), skin capacitance, skin temperature and visual scores. Alterations in TEWL due to iontophoresis were not observed in the upper arm and chest; however, changes in TEWL at the abdomen were observed and returned to baseline 2 h after patch removal. Similarly, changes in capacitance due to iontophoresis returned to baseline ( P>0.05) at the three body sites 2 h after patch removal except under the anode at the abdomen ( P<0.05). There was a significant increase in skin temperature due to iontophoresis at the anode and the cathode ( P<0.05) at the upper arm. Edema was not observed. At patch removal, the erythema score was significantly ( P<0.001) elevated in comparison to baseline at the three body sites. Erythema resolved within 24 h except at the chest under the anode, where the erythema score was still higher ( P<0.01) than the baseline. Papules appeared in five subjects at the active anode site on the chest. In three of the subjects, these papules did not resolve until 24 h post patch removal. Thus, there was regional variation in the function of the skin and irritation due to iontophoresis. Irritation was greater at the chest than at the abdomen or upper arm.

A comparative trial of two retinoids commonly used in the treatment of acne vulgaris

BACKGROUND: Topical retinoids are highly effective treatments for acne vulgaris. The various formulations and concentrations available allow physicians to tailor therapies to individual patient's needs and minimize the cutaneous irritation that is often observed with the use of these drugs. OBJECTIVE: To compare the efficacy and safety of tretinoin gel microsphere 0.1% with adapalene gel 0.1% in the treatment of acne vulgaris. METHODS: A 12-week double-blind study was conducted, and patients were evaluated at baseline and at weeks 2, 3, 4, 6, 8, 10, and 12. RESULTS: Although the two drugs displayed similar efficacy in the resolution of acne lesions at 12 weeks, a significantly greater reduction in the number of comedones was seen at week 4 among patients treated with tretinoin gel microsphere ( p = 0.047). Patients receiving tretinoin gel microsphere had an increased incidence of dryness (weeks 8 and 10) and peeling (weeks 3, 6, 8, and 10) compared with those patients treated with adapalene gel, but the two groups were comparable with respect to erythema, burning/stinging, and itching. CONCLUSION: Both drugs have similar efficacy in the resolution of acne lesions but tretinoin gel microsphere may result in a faster onset of action in the reduction of comedones compared to adapalene.

In vitro and in vivo assessment of the irritation potential of different spin traps in human skin

No clinical data are available on the acute cutaneous toxicity of spin traps which are frequently used in combination with the electron paramagnetic resonance (EPR) technique for detection of free radicals and reactive oxygen/nitrogen species. The purpose of this study was to evaluate the acute dermatotoxicity of the following spin traps in human skin: C-phenyl- N-tert.-butyl nitrone (PBN), C-(4-pyridinyl- N-oxide)- N-tert.-butylnitrone (POBN), 5,5-dimethyl-l-pyrroline- N-oxide(DMPO), 5 diethoxyphosphoryl-5-methyl-l-pyrroline- N-oxide (DEPMPO), diethyldithiocarbamate (DDC) and N-methyl- d-glucamine dithiocarbamate (MGD). The corrosivity of the test substances was first assessed in human skin in vitro by measurement of transcutaneous electrical resistance (TER). In this assay all spin traps were non-corrosive at 500 mM concentration. Subsequently cutaneous irritation of the spin traps was determined at different concentrations (50, 250 and 500 mM) in human skin according to a routine four h human patch test in comparison to the standardized irritant sodium laurylsulfate (SLS, 20%). The response was evaluated clinically as well as by a biophysical method analyzing transepidermal water loss (TEWL). PBN and DEPMPO caused a transient and weak inflammatory reaction at 500 mM in four of 17 and in two of 17 volunteers, respectively. DMPO, POBN, DDC, MGID, and the iron complexes of DDC and MGD were clinically non-irritant at all concentrations tested and no delayed-acute inflammatory reactions were observed. However, the TEWL values were significantly increased by all spin traps except DMPO at 500 mM, indicating disturbed epidermal barrier function. We conclude that the spin traps investigated have a low potential to cause acute skin toxicity and may be used safely for in vivo EPR studies in human skin.

Effect of saline iontophoresis on skin barrier function and cutaneous irritation in four ethnic groups

The effect of saline iontophoresis on skin barrier function and irritation was investigated in four ethnic groups (Caucasians, Hispanics, Blacks and Asians). Forty healthy human volunteers were recruited according to specific entry criteria. Ten subjects, five males and five females, were assigned to each ethnic group. Skin barrier function was examined after 4 hours of saline iontophoresis at a current density of 0.2 mA/cm 2 on a 6.5 cm 2 area in terms of the measured responses: transepidermal water loss (TEWL), skin capacitance, skin temperature and visual scores. There were significant differences in TEWL among the ethnic groups prior to patch application. TEWL at baseline in ethnic groups was in the rank order: Caucasian>Asian>Hispanic>Black. Iontophoresis was generally well tolerated, and skin barrier function was not irreversibly affected by iontophoresis in any group. There was no significant skin temperature change, compared to baseline, in any ethnic groups at any observation point. Edema was not observed. At patch removal, the erythema score was elevated in comparison to baseline in all ethnic groups; erythema resolved within 24 hours. Thus, saline iontophoresis produced reversible changes in skin barrier function and irritation in healthy human subjects.

Evaluation of Dermal Irritancy Potential of Benzanthrone-Derived Dye Analogs: Structure Activity Relationship

The twelve structural analogs of benzanthrone-derived dyes of commercial use were screened for their dermal irritation potential response using the Draize occlusive patch test. The test dyes, dissolved in DMSO as vehicle, were topically applied on the skin of the male Druckery rats (160 ± 10 g) according to the OECD protocol. The potential dermal hazard was assessed in terms of the primary cutaneous irritation (PCI) index and irritancy. Irritancy was evaluated according to the AFNOR scale. In terms of irritancy, the twelve benzanthrone dyes qualified as moderately irritant (3.0–5.0) according to the above scale. In decreasing order, PCI index of the various dyes was: Navy Blue R (4.5); Jade Green XBN (4.25); 16, 17-dihydroxydibenzanthrone (3.84); Black NB (3.75), Jade Green 2G (3.75); 3-bromobenzanthrone (3.58); Brilliant Purple 4R (3.58); Olive D (3.50); Dark Blue 2R (3.41); Olive Green B (3.33); isodibenzanthrone (3.33), and benzanthrone (3.16). These results indicate that benzanthrone-derived dyes/dye intermediates caused dermal toxicity which appears to be influenced by the number of carbonyl and amino-anthraquinone groups as well as by the presence of functional groups like halogen, nitro, hydroxy and methoxy in the parent molecule, benzanthrone.

Contact allergy, irritancy and 'danger'.

Conventional models of the immune response are based on distinguishing self and non-self. However, we consider that the more recently proposed 'danger' model may be an illuminating alternative for studying allergic contact dermatitis. In this model, an antigenic signal on its own would tend to produce tolerance. In contrast, in the presence of a 'danger' signal, which, in the case of allergic contact dermatitis, we suggest is usually cutaneous irritancy, the immune system would become activated, leading first to the induction of sensitization and then subsequently to the elicitation of a contact hypersensitivity response. In most cases, both the antigenic signal and irritant signal will come from the hapten, although, e.g., in an occupational setting, traumiterative dermatitis would be the source of the 'danger' signal. Typically, the irritant signal tends to be more concentration-dependent and thus is the overriding factor in the determination of the effective sensitizing and eliciting concentrations of the hapten. A further prediction of this hypothesis is that successful experiments demonstrating low-dose tolerance with contact allergens may be explained by the loss of the irritant effect at lower dilutions, whilst an antigenic stimulus remains present.

Otoplasty: anterior scoring technique and results in 500 cases.

Corrective otoplasty is a commonly performed procedure to change the shape of the auricular cartilage. Many techniques use permanent sutures to maintain the cartilage folding, whereas other techniques rely on cartilage incisions (partial thickness or full thickness). At this institution, a cartilage cutting and anterior scoring technique has been used for more than 30 years with pleasing results. The surgical techniques published in the past have been reviewed and compared with the procedure used at this institution to point out the advantages, disadvantages, and differences of these various techniques. Also reviewed were 500 consecutive cases operated on under local or general anesthesia between January of 1993 and December of 1995 to determine the incidence of early and late complications. The patients were contacted by mail to return for a follow-up examination or answer a questionnaire, at least 2 years after the procedure. Early complications were bleeding in 13 cases (2.6 percent) and hematoma in 2 cases (0.4 percent). There were no infections or ear necrosis. A small cutaneous wound was present on the anterior skin in three patients (0.6 percent), and there was one wound dehiscence (0.2 percent). Late complications were keloids in two cases and inclusion cysts in three cases. Residual deformity was noted in 22 cases and asymmetry in 28 cases. Secondary surgery was performed in six cases. The questionnaire was answered by 387 patients (77.4 percent response rate): pain when the ear is touched was present in 22 cases (5.7 percent), hypesthesia in 15 cases (3.9 percent), occasional cutaneous irritation in 38 cases (9.8 percent), asymmetry in 71 cases (18.4 percent), and abnormal ear shape in 17 cases (4.4 percent). Twenty-nine patients (7.5 percent) also noted that the ear was more sensitive to cold or touch. The satisfaction rate was 94.8 percent: very satisfied, 74 percent; satisfied, 20.8 percent; dissatisfied, 4.2 percent; and very dissatisfied, 1 percent. These results were compared with other published series of complications and late results after otoplasty; the complication rates are similar or lower in this study. Therefore, it can be concluded that the cartilage cutting and anterior scoring technique otoplasty is a safe procedure with a high patient-parent-surgeon satisfaction rate.

Analysis by GC-MS of monocyclic and polycyclic aromatic hydrocarbons in thermolysed waste products

Thermolysis is a new thermal decomposition process of waste products. This process involves a partial vacuum and oxygen free environment inerted under a stream of nitrogen. This technique allows for the recuperation and valorisation of recyclable materials without producing any dust or clinkers. Wastes decomposition is carried out in an oven in presence of recycled gas of thermolysis, circulating in a continuous flow, at 650 °C. Gas issued from thermolysis are cooled and treated: gaseous fraction is directly used as energy source and, water and hydrocarbon fractions are collected after decantation on a lamellar layer separator. Hydrocarbons are conditionned to be used in the thermal cycle as an energy source. So it is important to know the nature and the rates of these hydrocarbons in order to anticipate the degree of risk for the environment and to evaluate the best conditions of their recycling. The aim of this study was to analyse these hydrocarbons, obtained after thermolysis of waste compounds. Monoaromatic hydrocarbons (MAH) and polyaromatic hydrocarbons (PAH) are known to be toxic compounds, bronchopulmonary and cutaneous irritants, with risks of carcinogenicity and mutagenicity. Cases of cutaneous, bronchopulmonary and vesical tumors have been linked with aromatic hydrocarbons. The degree of risk depends on the compounds, benzo[a]pyrene is shown to be the most toxic [1,2].

Final Report on the Safety Assessment of Isostearamidopropyl Morpholine Lactate

Isostearamidopropyl Morpholine Lactate is the lactic acid salt of isostearamidopropyl morpholine used as an antistatic agent in 20 cosmetic formulations, mostly hair preparations. The concentration of use in hair preparations is in the 1-5% range- Isostearamidopropyl Morpholine Lactate was nontoxic in acute oral toxicity studies in rats. Although Morpholine is considered a cutaneous, ocular, and mucous membrane irritant, and a sensitizer, Isostearamidopropyl Morpholine Lactate exhibits none of the sensitization and irritant reactions observed with Morpholine. Isostearamidopropyl Morpholine Lactate was minimally irritating to rabbit eyes, and mildly irritating to intact and abraded rabbit skin. Although sensitization was not seen in clinical tests, some irritancy was noted. Isostearamidopropyl Morpholine Lactate was not mutagenic in the Ames test, with or without metabolic activation, although cell killing was seen at most test concentrations. Although Morpholine is readily nitrosated to form carcinogenic nitrosamines, N-nitroso impurities were not detected in Isostearamidopropyl Morpholine Lactate. Mutagenicity data on Isostearamidopropyl Morpholine Lactate in a mammalian system were not available, nor were data available on skin penetration or toxicity associated with inhalation exposures. Accordingly, the safety of this ingredient in leave-on cosmetic formulations could not be determined. Based on the available data, this ingredient was considered safe for use in rinse-off cosmetic products. Additional data needed for assessing the safety of leave-on uses include: (i) skin penetration; if there is significant skin penetration, then both a 28-day dermal toxicity study to assess general skin and systemic toxicity, and a reproductive and developmental toxicity study are needed; (ii) one genotoxicity study in a mammalian system; if positive, then a 2-year dermal carcinogenesis study using National Toxicology Program (NTP) methods may be needed; and (iii) inhalation toxicity data.

Use of skin cell cultures for in vitro assessment of corrosion and cutaneous irritancy.

Skin cell culture is one of the most promising tools for in vitro evaluation of both cutaneous irritancy and corrosion. New culture methodologies, including three-dimensional reconstruction of skin, allow the evaluation of a wide range of compounds and complex formulations. A number of tests have already been developed for the evaluation of cytotoxicity and many end-points are now currently used, including cell viability, alteration of cell growth or cell function. In recent years parameters more closely related to in vivo irritancy effects such as synthesis of inflammatory mediators and/or their release by keratinocytes after exposure to potential skin irritants have been evaluated. This paper reviews technological aspects and results of validation using skin cell culture for in vitro assessment of corrosion and skin irritancy. Advantages and limits of skin cell cultures are also presented. Current questions about the validation process of cutaneous irritation and corrosion are also considered.

The biological basis of grooming in moose: programmed versus stimulus-driven grooming

In domestic and wild mammals, tick infestation can be a significant fitness cost. Grooming behaviour has been shown to be effective in removing ticks. We studied grooming by moose,Alces alces, infested with winter ticks,Dermacentor albipictus, to determine which of two nonexclusive models for the regulation of tick-removal grooming, programmed or stimulus driven, best fit this host–parasite relationship. The programmed grooming model states that most grooming is driven by an internal timing mechanism which periodically evokes a bout a grooming independent of peripheral stimulation from tick bites. Because programmed grooming is preventive, the model predicts that those animals that groom the most will carry the fewest ticks, and a baseline level of programmed grooming is predicted even in a tick-sparse or tick-free environment. The stimulus-driven grooming model, on the other hand, states that grooming is a direct response to cutaneous irritation caused by tick bites and other sources of irritation. This stimulus-driven model predicts that (1) animals showing the highest rate of grooming will carry the most ticks and (2) animals will groom little when tick challenge is low. Both predictions of the stimulus-driven model were supported for moose: (1) calves oral-groomed three times more than cows, and tick densities on calves were three times higher than on cows; and (2) although all moose carried high densities of immature winter ticks (larvae, nymphs) from October through to February, grooming rate was very low until adult ticks started feeding in March–April. Peak grooming rates occurred during adult tick engorgement in March–April. Because an engorging adult female tick produces far more irritation than an engorging nymphal or larval tick, moose appeared to groom in direct proportion to the degree of cutaneous irritation and did not show a baseline level of grooming. The predominance of stimulus-driven grooming and apparent absence of programmed grooming may be the result of relaxed selection pressure for grooming in the evolutionary history of moose. Because the winter tick appears to have been introduced to moose from deer relatively recently, moose may not have had the time to adapt to winter ticks. The coevolutionary relationship between moose and winter ticks may be of insufficient duration for the evolution and/or maintenance of programmed grooming.

Applications of reconstructed skin models in pharmaco-toxicological trials.

The development of new cosmetic formulations requires precise assessment of their safety and efficacy. Today, legislation demands quality control combined with severe safety measures, as well as a limited use of animals for such testing (European Community directive 93/35/EEC). Consequently, safety assessment protocols are oriented towards in vivo tests on human volunteers and in vitro alternative methods to animal use, especially tissue engineered skin substitutes. In this paper, dermal and skin equivalents developed in the laboratory are described. The applications of reconstructed epidermis and skin substitutes for pharmaco-toxicological trials are also discussed. These tissue models have been shown to be very useful tools to assess cutaneous irritation, phototoxicity, photoprotection and to perform efficacy tests of cosmetic molecules and finished products. In conclusion, the authors are confident that these in vitro models can contribute to reduce animal use for routine toxicity testing.

Baseline biophysical parameters in subjects with sensitive skin

Sensitive skin has been described as a skin type showing higher reactivity than normal skin and developing exaggerated reactions when exposed to external factors. The stinging test, performed by applying lactic acid to the nasolabial fold and evaluating the intensity of subjective symptoms, is widely accepted as a marker of sensitivity and employed for the selection of subjects experiencing invisible cutaneous irritation. However, this test is based on self-perceived assessment and lacks objectivity. In order to contribute to the finding of objective descriptors, we assessed baseline biophysical parameters in subjects with sensitive skin by means of transepidermal water loss (TEWL), capacitance, pH, sebum and skin colour measurements, and compared the data with those obtained in normal subjects, also correlating the results with those of clinical assessments and functional tests. Subjects with sensitive skin showed a trend towards higher scores at all assessment times both for the stinging and the washing test. The skin of sensitive subjects was described as less supple, less hydrated and more erythematous and telangiectatic with respect to the skin of normal subjects. A trend towards an increase in TEWL, pH and colorimetric a* values, and a decrease in capacitance, sebum and colorimetric L* values on the face of subjects with sensitive skin was observable. However, significances were only present for capacitance and a* values. Thus, alterations of baseline capacitance values indicate the tendency to barrier impairment and support the view that skin hyperreactivity to water-soluble irritants is induced by a greater amount of irritants absorbed, whereas the increase in the erythema parameter shows that cutaneous vascular hyperreactivity in subjects with sensitive skin also corresponds to baseline vasodilation.

Topical treatment of acne vulgaris: Retinoids and cutaneous irritation

cles that involves a multifactored pathophysiology.1 Excessive sebum production, combined with abnormal desquamation of follicular epithelium, leads to an accumulation of these materials such that the lumina of sebaceous follicles become distended. This precursor, microscopic stage is known as a microcomedo. In this environment, Propionibacterium acnes proliferates and its production of proinflammatory chemotactic and cytokine factors is responsible for the inflammation of acne.2-4 Our therapeutic menu includes a variety of drugs, both topical and systemic, that can affect these areas of pathophysiology. The abnormal desquamation of follicular epithelium can be normalized by topical tretinoin and salicylic acid. These agents decrease the cohesion of corneocytes, minimize microcomedo formation and, in time, decrease both clinical noninflammatory and inflammatory lesions. The newer synthetic retinoid derivatives, adapalene and tazarotene, have also demonstrated effectiveness in the treatment of acne. Despite differences in physical characteristics and receptor affinity, their molecular and cellular mechanisms of action are thought to be similar to those of tretinoin.5 The major disadvantage of topical therapy for the treatment of acne is that many of the agents used cause tolerability problems. Significant erythema, dryness, peeling, scaling, and irritation may result in discontinuation of treatment,6 and in patients who continue treatment, irritation may lead to compliance problems.7 Tretinoin-induced irritation, for example, is generally doseand vehicle-related, and the level of irritation ranges from high to low with the solution, gel, and cream formulations, respectively.8 Unfortunately, efficacy is frequently dose-related as well, and some patients do not progress to an optimal tretinoin concentration because of tolerance problems.7 With this in mind, pharmaceutical research programs have focused on methods of minimizing the irritation caused by topical retinoids while preserving or improving their therapeutic benefits. The results of these programs have yielded several new developments. Modified tretinoin delivery systems, which minimize irritant effects and provide therapeutic benefit, are now available. These include complexes of tretinoin with polymer molecules and incorporation of tretinoin in microsponge particles. Two new agents, adapalene and tazarotene, bind with nuclear retinoid receptors and exert retinoid effects in a variety of systems. They have been found to be clinically effective in acne and have been approved by the FDA. From the Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia. Reprint requests: James J. Leyden, MD, Department of Dermatology, University of Pennsylvania Hospital, 3400 Spruce St., Philadelphia, PA 19104. J Am Acad Dermatol 1998;38:S1-4. Copyright © 1998 by the American Academy of Dermatology, Inc. 0190-9622/98/$5.00 + 0 16/0/88698 Topical treatment of acne vulgaris: Retinoids and cutaneous irritation

Comparative efficacy and safety of two 0.025% tretinoin gels: Results from a multicenter, double-blind, parallel study

Background: The addition of polyolprepolymer-2 in tretinoin formulations may reduce tretinoin-induced cutaneous irritation. Objective: This study compared the efficacy and safety of a new 0.025% tretinoin gel containing polyolprepolymer-2, its vehicle, and a commercially-available 0.025% tretinoin gel in patients with mild to moderate acne vulgaris. Methods: In this 12-week multicenter, double-blind, parallel group study, efficacy was evaluated by objective lesion counts and the investigators’ global evaluations. Subjective assessment of cutaneous irritation by the investigators and patients evaluated safety. Results: The efficacy of the two active treatments in this 215 patient study was comparable, and both treatments were statistically significantly more effective than vehicle. When compared with the commercially-available tretinoin gel, the formulation containing polyolprepolymer-2 demonstrated statistically significantly less peeling at days 28, 56, and 84, statistically significantly less dryness by day 84, and statistically significantly less itching at day 14. Irritation scores for the formulation containing polyolprepolymer-2 were numerically lower but not statistically different from those of the commercially-available gel for erythema and burning. The number of cutaneous and noncutaneous adverse events were similar for both active medications. Conclusion: The two 0.025% gels studied demonstrated comparable efficacy. However, the gel formulation containing polyolprepolymer-2 caused significantly less peeling and drying than the commercially-available formulation by day 84 of the study. (J Am Acad Dermatol 1998;38:S17-23.)

A physical method for preservation of cosmetic products

To date, the microbiological stability of cosmetics products is assured by means of chemical preservatives, with well-known possible side effects such as irritation or cutaneous allergic events. This paper describes a new concept to protect all types of cosmetic formulae from microbiological contamination: the osmotic effect of a particular form of glycerylpolyacrylate gels. The latter allows the formulator to conceive numerous preservative-free formulae. The basis of its activity lies in the strong osmotic properties of the hydrogel: it absorbs water from its surroundings, thus depriving germs of the vital aqueous environment needed for survival. Challenge tests on various microorganisms, repeat insult challenges and time-stability tests performed on these hydrogels in cosmetic formulas were carried out. At the same time, the hydrogel exhibited high skin moisturizing power. The hydrogel is non-toxic and non-irritant as the Primary Cutaneous Irritation Index observed after 48 h of occlusive patches in 10 adult volunteers is only of 0.10.

Cutaneous Tolerance to Nitroxide Free Radicals in Human Skin

No data are available on the irritant effect of nitroxide free radicals in human skin. Nitroxides are important biomedical skin probes used in Electron Paramagnetic Resonance spectroscopy and imaging. Our purpose was to study the skin irritation potential of different nitroxide free radical structures in skin of healthy human subjects. We investigated the following nitroxides: Tempo (2,2,6,6-tetramethyl-1-piperidinoxy), Doxo (2,2,5,5-tetramethyl-3-oxazolidinoxy), Proxo (2,2,5,5-tetramethyl-1-dihydro-pyrrolinoxy), and Imidazo (2,2,3,4,5,5-hexamethyl-imidazoline-1-yloxyl). Cutaneous irritation was determined in human skin following a single application and after repetitive applications in comparison to the standardized irritant sodium lauryl sulfate (SLS). The response was evaluated clinically as well as by a bioengineering method analyzing transepidermal water loss (TEWL) and skin hydration (capacitance). The nitroxides were classified clinically from nonirritant (Imidazo, Proxo), to slightly irritant (Doxo, 100 mM), or moderately irritant (Tempo 100 mM) after a single application. The TEWL values were significantly increased by Doxo and Tempo, but capacitance values were not changed significantly. In the cumulative irritation test Tempo was scored as a slight irritant (10 mM). TOLH (2,2,6,6-tetramethyl-1-hydroxypiperidin), the hydroxylamine of Tempo, which is the major skin metabolite, did not cause skin irritation after a single or repetitive applications. This may indicate that a loss of cellular reducing equivalents may be involved in the inflammation process caused by Tempo. The order of nitroxide irritation potency (Tempo > Doxo >> Imidazo = Proxo) is inverse to the order of nitroxide biostability in human skin (Imidazo = Proxo >> Doxo > Tempo). In conclusion, nitroxide free radicals are classified as nonirritant to moderately irritant in human skin. Particularily, the pyrrolidine and imidazoline type nitroxides have a low potential to cause acute or subacute skin toxicity.

Cutaneous tolerance to nitroxide free radicals and nitrone spin traps in the guinea pig

The attempts to use nitroxide free radicals and nitrone spin traps topically in skin requires analysis of their potential cutaneous adverse effects. The objective of this study was to investigate the skin irritation and sensitizing potential of nitroxides and nitrones in the guinea pig. The following unsubstituted nitroxides were investigated: 2,2,6,6-tetramethyl-1-piperidinoxyl (Tempo), 2,2,5,5-tetramethyl-3-oxazolidinoxyl (Doxo), 2,2,5,5-tetramethyl-1-dihydro-pyrrolinoxyl (Proxo), 2,2,3,4,5,5-hexamethyl-imidazoline-1-yloxyl (Imidazo) and the nitrones: 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) and N- tert.-butyl-phenylnitrone (PBN). Cutaneous irritation was determined following the modified Draize protocol. The response was evaluated clinically as well as by a biophysical method analyzing transepidermal water loss (TEWL). The nitroxides and nitrones were classified clinically from non-irritant (Proxo, Imidazo, DMPO) to slightly irritant (Tempo, Doxo, PBN) according to the Draize protocol. In agreement with the clinical scoring, the TEWL values were significantly increased by Tempo, Doxo and PBN. TOLH, the hydroxylamine of Tempo and its major skin metabolite, did not cause skin irritation. The sensitizing effect was evaluated according to the Magnusson and Kligman test. The results showed no cutaneous hypersensitivity to all nitroxides and nitrones, indicating a weak sensitizing potential. That concludes that the nitroxides and nitrones tested in this study have a low potential of acute skin intolerance.

Antiangiogenic properties of a novel shark cartilage extract: potential role in the treatment of psoriasis.

A number of inflammatory and immune diseases are associated with vascular changes. Psoriasis, as an example, is a common inflammatory skin disease with dilation of capillaries as an early histological change. In more developed psoriatic lesions there is proliferation of blood vessels and neovascularization. The use of agents that target these vascular changes represents a novel therapeutic strategy in the treatment of inflammatory diseases. Since cartilage is an avascular tissue, it has been hypothesized that there may be factors found in cartilage that inhibit blood vessel formation. The objectives of this study were 1) to determine whether extracts of cartilage could inhibit angiogenesis, and 2) since altered angiogenesis is associated with certain diseases, including psoriasis, to examine whether inhibition of angiogenesis could potentially contribute to the treatment of psoriasis. Extracts of shark cartilage were prepared by homogenization and ultrafiltration to derive the active agent termed AE -941. This agent was tested for antiangiogenesis activity using the embryonic vascularization test, which is a modification of the ex vivo chick embryo culture (CAM). Since one of the first steps in angiogenesis is degradation by metalloproteinases of the basement membrane of capillaries, AE -941 was tested for collagenase activity using a fluorogenic peptide substrate. Anti-inflammatory properties were tested using a cutaneous irritation model in humans. A dose dependent inhibition in embryonic neovascularization as well as in collagenase activity by AE -941 was demonstrated. When test compounds were applied on the forearms of test subjects, AE -941 was shown to have anti-inflammatory properties. Anecdotal data suggested that topical AE -941 had a beneficial effect in psoriasis. Our results show that AE -941 has anti-angiogenic and anti-inflammatory properties. Antiangiogenesis agents such as AE -941 provide an entirely new class of agents to treat cutaneous and systemic diseases associated with altered vascularity.