Thomas J. Stephens

The Living Dermal Equivalent as an In Vitro Model for Predicting Ocular Irritation

AbstractThe Living Dermal Equivalent (LDE), composed of human dermal fibroblasts in a collagen-containing matrix, was used as a model system for examining toxic responses to a broad range of test chemicals and final product formulations. The thiazolyl blue (MTT) assay for mitochondrial function and the release of proinflammatory eicosanoids (prostaglandin E2 and prostacyclin) were used as end points to rank order the relative irritancy of test samples. In these studies a total of 65 test samples including liquids, creams, emulsions, and solids were applied topically to the air-exposed surface of the LDE. Protocols were designed to maximize the discrimination between samples with known ocular irritation potentials. For a given set of samples, altering the experimental conditions, including the dosage and time of exposure, is shown to influence the degree to which responses of the LDE agree with in vivo data. Strategies for using the LDE as an in vitro ocular irritation model are presented and recommendatio...

Fundamental Concepts in Photoimmunology and Photoallergy

AbstractExposure to sunlight, particularly ultraviolet light (UV), can produce changes in the status of the immune system. Photoimmunology is the study of the distortions in “normal” immune responses that may be produced by UV and/or visible light exposure. Photoallergy, on the other hand, is an acquired im-munologically mediated reactivity to a chemical or drug precipitated by the formation of photoproducts. This article reviews the key principles with supporting evidence from both photoimmunology and photoallergy. Reviews of the fundamental concepts of cutaneous structure and function, inflammation, immunology, and allergic contact dermatitis are presented as introduction. Subsequent sections discuss the capacity of UV to alter allergic contact dermatitis. The second part of the article presents an overview of past clinical observations and important laboratory animal studies relevant to photoallergy, including new techniques for predictive testing for photoallergic contact dermatitis in animals and hel...

In Vitro Skin Irritation Testing of Petroleum-Based Compounds in Reconstituted Human Skin Models

AbstractSeven petroleum-based test materials were evaluated for skin irritation potential using full-thickness reconstituted human skin models (skin2 Model ZK1300 from Advanced Tissue Sciences, Inc., and Living Skin Equivalent (LSE) from Organogenesis, Inc.). Test materials were dosed undiluted in triplicate onto the epidermal side of the tissues that were incubated in polyethylene bags designed to minimize cross-contamination and loss of volatile constituents. The endpoints measured were thiazolyl blue (MTT) reduction and lactate dehydrogenase (LDH), prostaglandin E2 (PGE2), and interleukin-1 alpha (IL-1 α) release into spent media from treated and untreated tissues. Data from these tests were correlated with Draize primary dermal irritation index (PDII) scores using Coopers criteria. Results showed that all endpoints measured approximated the skin irritation potential of the test materials, with the exception of IL-1 α in the skin2 Model ZK1300, in which significant levels of IL-1 α could not be detect...

Alternatives to the Draize Eye Test Including the Use of Tissue Cultured Corneal Cells

In recent years there have been major efforts to develop alternative procedures to the Draize eye test. Just as adjustments have been made to improve the usefulness of the Draize eye test, similar trends are being observed with alternative test procedures. In vitro test methods appear to be useful either as a screening tool before continuing to animal and human testing or as a mechanistic model to better define the nature of the ocular injury. Progress has been made in identifying in vitro tests to replace the Draize eye test; however, a universally accepted test or battery of tests has yet to be identified. Most likely, the test battery will consist of test(s) that will predict cytotoxicity, non-cytotoxicity-induced inflammation, and, possibly, effects on nutrition and metabolism of cells. Problems related to in vitro testing, such as non-water-soluble preparations in tissue culture, must also be addressed. It is anticipated that with continued research, it will be possible to develop a battery of endpoi...

Use of A Reconstituted Human Skin Model for Predicting the Inflammation Potential of Wound Care Products

AbstractUnited States Pharmacopoeia protocols for cytotoxicity are conducted using a monolayer of cultured rodent fibroblasts. Major disadvantages of these tests are that they are conducted with nonhuman cells and that noncytotoxic inflammatory events go undetected. In our studies a commercially available hydrogel wound dressing and povidone-iodine were dosed onto a reconstituted human skin model. Cytotoxicity was determined by punch biopsying dosed tissues and extracting a vital dye. Inflammation potential was assessed by measuring prostaglandin E2 from the spent media of treated tissues. Results showed that povidone-iodine has a substantially greater potential to produce cytotoxicity and biochemical inflammation in human tissue than hydrogel wound dressing. This information may assist physicians in selecting the best treatment modality for wounds.

Comparative Skin Irritation of High and Low Spf Sunscreen Products

AbstractThe Food and Drug Administration has recently held public meetings to discuss specific recommendations pertaining to over-the-counter products. Among the more controversial issues in these discussions is the question of the need for sunscreen products with sunscreen protection factors (SPF) greater than 15.Proponents of very high SPF products argue that current SPF 15 sunscreen products are not truly “sunblocks,” and that increasing the SPF level further will offer a significant improvement in protection from the adverse effects of sunlight. Those opposed to products with SPF values exceeding 15 suggest that the dermatologic hazard from the increased levels of ultraviolet radiation (W)-absorbing ingredients in these products may outweigh the benefits of marginally improving the level of sunscreen protection.The purpose of this paper was to examine the irritation potential of several commercially available sunscreens, and to determine if dermal irritation potential does increase as a function of SP...

Assessing Acnegenic and Acne-Aggravating Potential

AbstractSome individuals with acne-prone skin appear to react negatively to certain external factors. Past observations have pointed to a variety of such factors including friction, utraviolet light, and certain cosmetics and medications. Having tests in place to screen potential new products on this skin type is of importance to the dermatologic, cosmetic, and pharmaceutical communities.Based on current knowledge in this area, we have set out to design tests intended to help detect potential problems. This paper will detail human assays recently used to assess comedogenicity, pustulogenicity, and other phenomena that could possibly create or worsen acne. These tests combine clinical and noninvasive laboratory evaluations. Methods and data from assays conducted on both the back and face will be presented.

Localized Eye Area Sensitivity Syndrome

AbstractLocalized eye area sensitivity syndrome (LEASS) describes a collection of subjective and objective symptoms that occur when susceptible individuals apply moisturizers, eye creams, and wrinkle creams containing certain chemicals to the periocular area. Women experiencing this syndrome complain of symptoms ranging from itchy, burning, stinging, and watery eyes to foreign body sensations. Ophthalmologic and dermatologic examinations reveal erythematous skin reactions and bulbar conjunctival chemosis and injection. Ocular surface changes are not observed in patients with LEASS. Onset of symptoms occurs within minutes following the application of the cosmetic and may last up to 48 hr. During the latter stages of LEASS, the patient may complain of a dull, aching feeling in the periocular area.

Assessing the Irritation Potential of Eye Area Products in the Human Eye

AbstractCurrent safety testing programs for consumer products generally include a test to evaluate potential eye damage by assessing objective irritation in the conjunctivum, iris, or cornea. However, the potential for a product to cause eye discomfort in the form of subjective irritation through burning, itching, or tearing cannot be measured by standard eye safety tests. A protocol has been developed to test for these subjective irritation responses. Results indicate that, with the application of proper statistical treatment, differences in factors measuring subjective irritation of the eyes by different test materials can be detected.