Influence of the environmental relative humidity on the inflammatory response of skin model after exposure to various environmental pollutants

Toward Standardization of a Lung New Approach Model for Toxicity Testing of Nanomaterials

This study represents an attempt toward the standardization of pulmonary NAMs and the development of a novel approach for toxicity testing of nanomaterials. Laboratory comparisons are challenging yet essential for identifying existing limitations and proposing potential solutions. Lung cells cultivated and exposed at the air-liquid interface (ALI) more accurately represent the physiology of human lungs and pulmonary exposure scenarios than submerged cell and exposure models. A triculture cell model system was used, consisting of human A549 lung epithelial cells and differentiated THP-1 macrophages on the apical side, with EA.hy926 endothelial cells on the basolateral side. The cells were exposed to silver nanoparticles NM-300K for 24 h. The model used here showed to be applicable for assessing the hazards of nanomaterials and chemicals, albeit with some limitations. Cellular viability was measured using the alamarBlue assay, DNA damage was assessed with the enzyme-modified comet assay, and the expression of 40 genes related to cell viability, inflammation, and DNA damage response was evaluated through RT2 gene expression profiling. Despite harmonized protocols used in the two independent laboratories, however, some methodological challenges could affect the results, including sensitivity and reproducibility of the model.

The effect of dietary oxidation balance scores and volatile organic compounds exposures on inflammation

BACKGROUND

Inflammation is a significant factor in adverse health outcomes, but the combined effects of diets with varying oxidation levels and exposure to volatile organic compounds (VOCs) on inflammation are not well understood. This study aimed to elucidate the effects of the recognized Dietary Oxidative Balance Score (DOBS) and five VOCs on the systemic immune-inflammation index (SII) and C-reactive protein (CRP).

METHODS

This cross-sectional study included data from participants in three cycles (2003-2004, 2005-2006, 2009-2010) of the National Health and Nutrition Examination Survey (NHANES). We used Spearman correlation, logistic regression, and trend tests to explore the associations between DOBS, VOCs, SII, and CRP. Additionally, we conducted restricted cubic spline (RCS) analysis to assess dose-response relationships between exposure and effect. G-computation and stratified analyses were performed to further elucidate these associations.

RESULTS

We included 7033 eligible participants, with 48.8 % males and 51.2 % females. Spearman correlation revealed that DOBS was negatively correlated with SII and CRP, while the five VOCs were positively correlated with SII and CRP. Although fully adjusted logistic regression models did not yield statistically significant results, trend tests indicated a gradual decrease in SII and CRP with increasing DOBS, a finding validated by RCS analysis. G-computation results demonstrated that the combined effect of DOBS and VOCs on inflammation was positive, with DOBS exerting a negative effect and benzene, ethylbenzene, and 1,4-dichlorobenzene exerting positive effects. Stratified analysis showed that maintaining physical activity significantly influenced the effects of DOBS and VOCs on inflammation.

CONCLUSION

This study suggests that adjusting dietary structure and reducing daily exposure to VOCs can effectively reduce inflammation in the body.

Road-traffic-related air pollution contributes to skin barrier alteration and growth defect of sensory neurons

The effects of air pollution on health are gaining increasing research interest with limited data on skin alterations available. It was suggested that air pollution is a trigger factor for sensitive skin (SS). However, this data was based on surveys with a lack of experimental data. SS is related to altered skin nerve endings and cutaneous neurogenic inflammation. TTe present study was to assess the in vitro effect of particulate matter (PM) on epidermis and nerve ending homeostasis. PM samples were collected according to a validated protocol. Reconstructed human epidermis (RHE, Episkin®) was exposed to PM and subsequently the supernatants were transferred to a culture of PC12 cells differentiated into sensory neurons (SN). Cell viability, axonal growth and neuropeptide-release were measured. The modulation of the expression of different inflammatory, keratinocytes differentiation and neurites growth markers was assessed. PM samples contained a high proportion of particles with a size below 1 μm and a complex chemical composition. Transcriptomic and immunohistochemical analyses revealed that PM altered keratinocytes terminal differentiation and induced an inflammatory response. While viability and functionality of the SN were not modified, their outgrowth was significantly decreased after incubation with PM-exposed Episkin® supernatants. This was closely related to the modification of nerve growth factor/semaphorin 3A balance. This study showed that air pollutants have negative effects on keratinocytes and sensory nerve endings including inflammatory responses. These effects are probably involved in the SS pathophysiology and might be involved in inflammatory skin disorders.

Mechanistic insight into the adjuvant effect of co-exposure to ultrafine carbon black and high humidity on allergic asthma

Respiratory diseases continue to be a major global concern, with allergies and asthma often discussed as critical areas of study. While the role of environmental risk factors, such as non-allergenic pollutants and high humidity, in asthma induction is often mentioned, there is still a lack of thorough research on their co-exposure. This study aims to investigate the adjuvant effect of ultrafine carbon black (30-50 nm) and high humidity (70% relative humidity) on the induction of allergic asthma. A mouse model of asthma was established using ovalbumin, and airway hyperresponsiveness, remodeling, and inflammation were measured as the endpoint effects of asthma. The mediating role of the oxidative stress pathway and the transient receptor potential vanilloid 1 pathway in asthma induction was validated using pathway inhibitors vitamin E and capsaicin, respectively. Co-exposure to ultrafine carbon black and high humidity had a significant impact on metabolic pathways in the lung, including aminoacyl-tRNA biosynthesis, glycerophospholipid metabolism, and ATP-binding cassette transporters. However, administering vitamin E and capsaicin altered the effects of co-exposure on the lung metabolome. These results offer new insights into the health risk assessment of co-exposure to environmental risk factors and provide an important reference point for the prevention and treatment of allergic asthma.

Promoting New Approach Methodologies (NAMs) for research on skin color changes in response to environmental stress factors: tobacco and air pollution

Aging is one of the most dynamic biological processes in the human body and is known to carry significant impacts on individuals' self-esteem. Skin pigmentation is a highly heritable trait made possible by complex, strictly controlled cellular and molecular mechanisms. Genetic, environmental and endocrine factors contribute to the modulation of melanin's amount, type and distribution in the skin layers. One of the hallmarks of extrinsic skin aging induced by environmental stress factors is the alteration of the constitutive pigmentation pattern clinically defined as senile lentigines and/or melasma or other pigmentary dyschromias. The complexity of pollutants and tobacco smoke as environmental stress factors warrants a thorough understanding of the mechanisms by which they impact skin pigmentation through repeated and long-term exposure. Pre-clinical and clinical studies demonstrated that pollutants are known to induce reactive oxygen species (ROS) or inflammatory events that lead directly or indirectly to skin hyperpigmentation. Another mechanistic direction is provided by Aryl hydrocarbon Receptors (AhR) which were shown to mediate processes leading to skin hyperpigmentation in response to pollutants by regulation of melanogenic enzymes and transcription factors involved in melanin biosynthesis pathway. In this context, we will discuss a diverse range of New Approach Methodologies (NAMs) capable to provide mechanistic insights of the cellular and molecular pathways involved in the action of environmental stress factors on skin pigmentation and to support the design of raw ingredients and formulations intended to counter their impact and of any subsequently needed clinical studies.

Development and Characterization of a 96-Well Exposure System for Safety Assessment of Nanomaterials

In this study, a 96-well exposure system for safety assessment of nanomaterials is developed and characterized using an air-liquid interface lung epithelial model. This system is designed for sequential nebulization. Distribution studies verify the reproducible distribution over all 96 wells, with lower insert-to-insert variability compared to non-sequential application. With a first set of chemicals (TritonX), drugs (Bortezomib), and nanomaterials (silver nanoparticles and (non-)fluorescent crystalline nanocellulose), sequential exposure studies are performed with human lung epithelial cells followed by quantification of the deposited mass and of cell viability. The developed exposure system offers for the first time the possibility of exposing an air-liquid interface model in a 96-well format, resulting in high-throughput rates, combined with the feature for sequential dosing. This exposure system allows the possibility of creating dose-response curves resulting in the generation of more reliable cell-based assay data for many types of applications, such as safety analysis. In addition to chemicals and drugs, nanomaterials with spherical shapes, but also morphologically more complex nanostructures can be exposed sequentially with high efficiency. This allows new perspectives on in vivo-like and animal-free approaches for chemical and pharmaceutical safety assessment, in line with the 3R principle of replacing and reducing animal experiments.

Human skin responses to environmental pollutants: A review of current scientific models

Whatever the exposure route, chemical, physical and biological pollutants modify the whole organism response, leading to nerve, cardiac, respiratory, reproductive, and skin system pathologies. Skin acts as a barrier for preventing pollutant modifications. This review aims to present the available scientific models, which help investigate the impact of pollution on the skin. The research question was "Which experimental models illustrate the impact of pollution on the skin in humans?" The review covered a period of 10 years following a PECO statement on in vitro, ex vivo, in vivo and in silico models. Of 582 retrieved articles, 118 articles were eligible. In oral and inhalation routes, dermal exposure had an important impact at both local and systemic levels. Healthy skin models included primary cells, cell lines, co-cultures, reconstructed human epidermis, and skin explants. In silico models estimated skin exposure and permeability. All pollutants affected the skin by altering elasticity, thickness, the structure of epidermal barrier strength, and dermal extracellular integrity. Some specific models concerned wound healing or the skin aging process. Underlying mechanisms were an exacerbated inflammatory skin reaction with the modulation of several cytokines and oxidative stress responses, ending with apoptosis. Pathological skin models revealed the consequences of environmental pollutants on psoriasis, atopic dermatitis, and tumour development. Finally, scientific models were used for evaluating the safety and efficacy of potential skin formulations in preventing the skin aging process or skin irritation after repeated contact. The review gives an overview of scientific skin models used to assess the effects of pollutants. Chemical and physical pollutants were mainly represented while biological contaminants were little studied. In future developments, cell hypoxia and microbiota models may be considered as more representative of clinical situations. Models considering humidity and temperature variations may reflect the impact of these changes.