Clinical and experimental studies of octocrylene's allergenic potency

Octocrylene: From Sunscreens to the Degradation Pathway during Chlorination Processes: Formation of Byproducts and Their Ecotoxicity Assessment

Octocrylene is an organic sunscreen whose main action is to absorb UVB radiation and short UVA wavelengths; it is used in various cosmetic products in order to provide an adequate sun-protection factor or to protect the cosmetic formulations themselves from UV radiation. This filter is believed to be a possible endocrine disruptor and is also questioned due to its allergic and/or photoallergic potential. However, it continues to be widely used, and it has been found in various environments, not least those of swimming pools, where it is evidently released by consumers, to the point that it is now considered an emerging micropollutant. The present investigation presents the possible chemical fate of octocrylene in the typical chlorination conditions of wastewater or swimming pools. A total of 11 disinfection byproducts were identified, and 6 were identified for the first time, and separated by HPLC. These products were identified through careful mass spectrometry studies and 1D and 2D NMR experiments. A formation mechanism has been proposed that justifies the chemical structures of all of the compounds identified. The ecotoxicological assessment of octocrylene and their products was carried out by employing Phaeodactylum tricornutum, Brachionus plicatilis and Aliivibrio fischeri as bioindicators. The ecotoxicity results reveal that toxic byproducts might be generated during the oxidation process, increasing the potential risk to the marine environment.

Expansion of the Cosmetics Europe skin sensitisation database with new substances and PPRA data

The assessment of skin sensitisation is a key requirement in all regulated sectors, with the European Union's regulation of cosmetic ingredients being most challenging, since it requires quantitative skin sensitisation assessment based on new approach methodologies (NAMs). To address this challenge, an in-depth and harmonised understanding of NAMs is fundamental to inform the assessment. Therefore, we compiled a database of NAMs, and in vivo (human and local lymph node assay) reference data. Here, we expanded this database with 41 substances highly relevant for cosmetic industry. These structurally different substances were tested in six NAMs (Direct Peptide Reactivity Assay, KeratinoSens™, human Cell Line Activation Test, U-SENS™, SENS-IS, Peroxidase Peptide Reactivity Assay). Our analysis revealed that the substances could be tested without technical limitations, but were generally overpredicted when compared to reference results. Reasons for this reduced predictivity were explored through pairwise NAM comparisons and association of overprediction with hydrophobicity. We conclude that more detailed understanding of how NAMs apply to a wider range of substances is needed. This would support a flexible and informed choice of NAMs to be optimally applied in the context of a next generation risk assessment framework, ultimately contributing to the characterisation and reduction of uncertainty.

Occurrence of Allergens in Cosmetics for Sensitive Skin

Sensitive skin is characterized by symptoms such as stinging and tingling in response to stimuli that usually do not cause unpleasant sensations. Epidemiological studies show that individuals with sensitive skin are more prone to developing skin allergies, although the link between both conditions is unknown. Aiming to evaluate the presence of allergens in facial-skin products for sensitive skin, a pool of 88 cosmetic products from international brands marketed in pharmacies and parapharmacies was analyzed. A list of allergens identified in product labels was compiled and grouped according to their function. Fragrances were the most common allergens, followed by skin-conditioning agents, surfactants, and preservatives. Fragrances presenting the highest use percentages were linalool, benzyl alcohol, geraniol, and citronellol. Overall, the majority of cosmetic formulations were absent of fragrance allergens, being present only in 7% of products. Other allergens were found in most products (95%). This finding should be interpreted with caution, since many of these compounds are rare sensitizers and studies demonstrating their risk for individuals with sensitive skin are lacking. With this study, useful information for health professionals is provided to support their advice and to help consumers choosing cosmetic products.

Contact allergy to fragrance mix I and its components in individuals with photocontact allergy to ketoprofen

BACKGROUND

Contact allergy to fragrance mix I (FM I) is over-represented in patients photoallergic to ketoprofen. The prevalence of contact allergy to two components of FM I, cinnamal and cinnamyl alcohol, in ketoprofen-photoallergic patients is higher than in dermatitis patients.

OBJECTIVE

To explore the prevalence of contact allergy to FM I and its individual components in patients with photocontact allergy to ketoprofen, and to compare with a dermatitis and the general population.

METHODS

Data on patch and photopatch tests performed between 2009-2018 were collected. Ketoprofen-photoallergic patients were compared with dermatitis patients and published data on the general population regarding the prevalence and the distribution of contact allergy to FM I and its components.

RESULTS

A higher prevalence of contact allergy to cinnamyl alcohol compared with cinnamal (23.3% vs 10.0%), and eugenol compared with isoeugenol (23.3% vs 6.7%), was observed in ketoprofen-photoallergic patients, while the relationship was the opposite in the dermatitis group (0.7% vs 1.05%; 0.4% vs 0.9%). The overall prevalence of contact allergy to several components of FM I was significantly higher in ketoprofen-photoallergic patients.

CONCLUSIONS

Contact allergy to FM I and many of its components is over-represented in patients photoallergic to ketoprofen compared with dermatitis patients and the general population.

Unravelling the Photoprotective Mechanisms of Nature-Inspired Ultraviolet Filters Using Ultrafast Spectroscopy

There are several drawbacks with the current commercially available ultraviolet (UV) filters used in sunscreen formulations, namely deleterious human and ecotoxic effects. As a result of the drawbacks, a current research interest is in identifying and designing new UV filters. One approach that has been explored in recent years is to use nature as inspiration, which is the focus of this review. Both plants and microorganisms have adapted to synthesize their own photoprotective molecules to guard their DNA from potentially harmful UV radiation. The relaxation mechanism of a molecule after it has been photoexcited can be unravelled by several techniques, the ones of most interest for this review being ultrafast spectroscopy and computational methods. Within the literature, both techniques have been implemented on plant-, and microbial-inspired UV filters to better understand their photoprotective roles in nature. This review aims to explore these findings for both families of nature-inspired UV filters in the hope of guiding the future design of sunscreens.

Ultraviolet filters in sunscreen products labeled for use in children and for sensitive skin

BACKGROUND

The active ingredients in sunscreen products are ultraviolet (UV) filters, many of which are known potential allergens. The use of sunscreen in younger children and individuals with sensitive skin requires special attention, since absorption and allergen sensitization are of concern.

OBJECTIVE

This study aims to evaluate the ultraviolet filters in sunscreen products labeled specifically for "kids" or as "sensitive/hypoallergenic" and compare these to general sunscreen products.

METHODS

From December 2017 to March 2018, the ingredient labels on commercially available sunscreen products in Bangkok, Thailand, were analyzed.

RESULTS

Two hundred and forty-six sunscreen products were examined. Of these, twenty products (8.1%) were marketed for "kids." Forty-one products (16.6%) were labeled as "sensitive" or "hypoallergenic." Ethylhexyl methoxycinnamate (EHMC) and benzophenone-3 (BP3) were less prevalent in products for children [(P = .004) and (P = .029), respectively]. Eighty-five percent of sunscreen products labeled for kids contained at least one chemical UV filter. There was no significant difference between BP3, butyl methoxydibenzoylmethane (BMDM), and octocrylene (OCR) in products labeled for sensitive skin compared to products with no specific labels. Moreover, methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT) was more commonly found in products for sensitive skin than in nonsensitive products (P = .001).

CONCLUSIONS

Common allergenic UV filters were found in sunscreens labeled as sensitive and for children. Regulations for displaying these specific labels should be established for improved benefits and safety to allergy-prone skin.

Unravelling photoprotection in microbial natural products

Mycosporine-like amino acids have long been known as a natural form of photoprotection for fungi and cyanobacteria. This review will highlight the key time-resolved experimental and theoretical techniques unravelling their photochemistry and photophysics, and directly link this to their use in commercial skin-care products, namely as sunscreen filters. Three case studies have been selected, each having aided advancement in this burgeoning field of research. We discuss these studies in the context of photoprotection and conclude by evaluating the necessary future steps towards translating the photochemistry and photophysics insight of these nature derived sunscreen filters to commercial application.

Glutathione as a photo-stabilizer of avobenzone: an evaluation under glass-filtered sunlight using UV-spectroscopy

Avobenzone is the most widely used UVA filter in sunscreen lotion and it is prone to degradation in the presence of sunlight/UV radiation. To overcome the photo-instability of avobenzone, various photostabilizers have been used as additives, including antioxidants such as vitamin C, vitamin E, and ubiquinone. In the present study, the well known antioxidant, glutathione, was evaluated for protecting avobenzone from photodegradation in the presence of glass-filtered sunlight. The features of glutathione as a skin whitener and a radical scavenger in cells have prompted the assessment of the photostabilzing activity of glutathione on avobenzone. Glutathione significantly attenuated the glass-filtered sunlight-induced degradation of avobenzone at equimolar or higher ratios of glutathione and avobenzone. Mutational studies have been undertaken to investigate the role of the thiol group and the isopeptide bond of glutathione on its photoprotection activity towards avobenzone. The thiol group of glutathione plays a vital role in exhibiting the photoprotection activity, which was further supported by the studies on photodegradation of avobonzone in the presence of β-mercaptoethanol. The dual role of glutathione as a skin whitening agent and a photostabilizer of avobenzone may be useful for the development of multipurpose cosmetic lotions.

Molecular photoprotection of human keratinocytes in vitro by the naturally occurring mycosporine-like amino acid palythine

Background

Solar ultraviolet radiation (UVR) induces molecular and genetic changes in the skin, which result in skin cancer, photoageing and photosensitivity disorders. The use of sunscreens is advocated to prevent such photodamage; however, most formulations contain organic and inorganic UVR filters that are nonbiodegradable and can damage fragile marine ecosystems. Mycosporine‐like amino acids (MAAs) are natural UVR‐absorbing compounds that have evolved in marine species for protection against chronic UVR exposure in shallow‐water habitats.

Objectives

To determine if palythine, a photostable model MAA, could offer protection against a range of UVR‐induced damage biomarkers that are important in skin cancer and photoageing.

Methods

HaCaT human keratinocytes were used to assess the photoprotective potential of palythine using a number of end points including cell viability, DNA damage (nonspecific, cyclobutane pyrimidine dimers and oxidatively generated damage), gene expression changes (linked to inflammation, photoageing and oxidative stress) and oxidative stress. The antioxidant mechanism was investigated using chemical quenching and Nrf2 pathway activation assays.

Results

Palythine offered statistically significant protection (P < 0·005) against all end points tested even at extremely low concentrations (0·3% w/v). Additionally, palythine was found to be a potent antioxidant, reducing oxidatively generated stress, even when added after exposure.

Conclusions

Palythine is an extremely effective multifunctional photoprotective molecule in vitro that has potential to be developed as a natural and biocompatible alternative to currently approved UVR filters.

What's already known about this topic?

Mycosporine‐like amino acids (MAAs) are photoprotective molecules found in marine organisms but there are few data on their ability to protect skin cells from the adverse effects of solar ultraviolet radiation (UVR).

The European Chemicals Agency (ECHA) is concerned about the potential adverse health and ecotoxic effects of eight of 16 commonly used sunscreen filters in Europe. The Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme has expressed similar concerns.

What does this study add?

Palythine, an MAA extracted from an edible seaweed, affords photoprotection against a wide range of adverse effects in HaCaT keratinocytes exposed to solar simulating and ultraviolet A radiation. Of note is protection against two types of DNA photolesions; cyclobutane pyrimidine dimers and 8‐oxo‐7,8‐dihydroguanine.

Palythine is also a potent antioxidant that offers protection even when added after UVR exposure.

What is the translational message?

MAAs should be considered for development as natural biocompatible sunscreens that may address the concerns of the ECHA and EEAP.

Linked Comment: https://doi.org/10.1111/bjd.16598.

https://goo.gl/Uqv3dl

Ketoprofen-induced formation of amino acid photoadducts: possible explanation for photocontact allergy to ketoprofen

Photocontact allergy is a well-known side effect of topical preparations of the nonsteroidal anti-inflammatory drug ketoprofen. Photocontact allergy to ketoprofen appears to induce a large number of photocross allergies to both structurally similar and structurally unrelated compounds. Contact and photocontact allergies are explained by structural modification of skin proteins by the allergen. This complex is recognized by the immune system, which initiates an immune response. We have studied ketoprofen's interaction with amino acids to better understand ketoprofen's photoallergenic ability. Irradiation of ketoprofen and amino acid analogues resulted in four different ketoprofen photodecarboxylation products (6-9) together with a fifth photoproduct (5). Dihydroquinazoline 5 was shown to be a reaction product between the indole moiety of 3-methylindole (Trp analogue) and the primary amine benzylamine (Lys analogue). In presence of air, dihydroquinazoline 5 quickly degrades into stable quinazolinone 12. The corresponding quinazolinone (17) was formed upon irradiation of ketoprofen and the amino acids N-acetyl-l-Trp ethyl ester and l-Lys ethyl ester. The formation of these models of an immunogenic complex starts with the ketoprofen-sensitized formation of singlet oxygen, which reacts with the indole moiety of Trp. The formed intermediate subsequently reacts with the primary amino functionality of Lys, or its analogue, to form a Trp-Lys adduct or a mimic thereof. The formation of a specific immunogenic complex that does not contain the allergen but that can still induce photocontact allergy would explain the large number of photocross allergies with ketoprofen. These allergens do not have to be structurally similar as long as they can generate singlet oxygen. To the best of our knowledge, there is no other suggested explanation for ketoprofen's photoallergenic properties that can account for the observed photocross allergies. The formation of a specific immunogenic complex that does not contain the allergen is a novel hypothesis in the field of contact and photocontact allergy.

Photoallergy

Abstract Photoallergic contact dermatitis (PACD) is a hypersensitivity reaction mounting from skin exposure to generally harmless amounts of ultraviolet and/or visible light in the presence of a photoreactive allergen. These reactions are typically delayed type (Gell and Coombs type IV) reactions and require pre-sensitization to photoallergens. Phototoxic reactions are clinically similar and often difficult to differentiate from photoallergies, but they are caused by interaction of light with photoirritants and do not require sensitization. The main investigative technique to diagnose PACD is photopatch testing, which is not commonly used; therefore, PACD may be overlooked in many patients. Currently, leading contact photosensitizers are sunscreens and topical non-steroidal anti-inflammatory drugs. This article provides an overview on photocontact allergies.

Computer models versus reality: how well do in silico models currently predict the sensitization potential of a substance

National legislations for the assessment of the skin sensitization potential of chemicals are increasingly based on the globally harmonized system (GHS). In this study, experimental data on 55 non-sensitizing and 45 sensitizing chemicals were evaluated according to GHS criteria and used to test the performance of computer (in silico) models for the prediction of skin sensitization. Statistic models (Vega, Case Ultra, TOPKAT), mechanistic models (Toxtree, OECD (Q)SAR toolbox, DEREK) or a hybrid model (TIMES-SS) were evaluated. Between three and nine of the substances evaluated were found in the individual training sets of various models. Mechanism based models performed better than statistical models and gave better predictivities depending on the stringency of the domain definition. Best performance was achieved by TIMES-SS, with a perfect prediction, whereby only 16% of the substances were within its reliability domain. Some models offer modules for potency; however predictions did not correlate well with the GHS sensitization subcategory derived from the experimental data. In conclusion, although mechanistic models can be used to a certain degree under well-defined conditions, at the present, the in silico models are not sufficiently accurate for broad application to predict skin sensitization potentials.

Photopatch testing: recommendations for a European photopatch test baseline series

In order to establish a consensus recommendation for performing photopatch testing, a photopatch test taskforce group was established under the joint umbrella of the European Society for Contact Dermatitis and the European Society for Photodermatology in 2000. After proposing the most adequate methodology in 2004 and completing a European multicentre photopatch test study in 2011, this taskforce is recommending a list of photoallergens that should form part of a baseline series for photopatch testing in Europe. It contains mainly ultraviolet filters and drugs, mostly non-steroidal anti-inflammatory drugs. The choice of chemicals was based on the results of a recent multicentre study, previous published cases of photoallergy, and use of the substances in the European market. It is suggested that an extended list of photoallergens should be photopatch tested in selected cases, along with patients' own products. Two contact allergens, cinnamyl alcohol and decyl glucoside, should be simultaneously patch tested in order to clarify photopatch and patch test reactions, respectively, to ketoprofen and methylene bis-benzotriazolyl tetramethylbutylphenol (Tinosorb M™).