Traffic-Related Air Pollution Contributes to Development of Facial Lentigines: Further Epidemiological Evidence from Caucasians and Asians

Epigenome-wide association study on short-, intermediate- and long-term ozone exposure in Han Chinese, the NSPT study

Epidemiological and epigenetic studies have acknowledged ambient ozone exposure associated with inflammatory and cardiovascular disease. However, the molecular mechanisms still remained unclear, and epigenome-wide analysis in cohort were lacking, especially in Chinese. We included blood-derived DNA methylation for 3365 Chinese participants from the NSPT cohort and estimated individual ozone exposure level of short-, intermediate- and long-term, based on a validated prediction model. We performed epigenome-wide association studies which identified 59 CpGs and 30 DMRs at a strict genome-wide significance (P < 5 ×10-8). We also conducted comparison on the DNA methylation alteration corresponding to different time windows, and observed an enhanced differentiated methylation trend for intermediate- and long-term exposure, while the short-term exposure associated methylation changes did not retain. The targeted genes of methylation alteration were involved in mechanism related to aging, inflammation disease, metabolic syndrome, neurodevelopmental disorders, and oncogenesis. Underlying pathways were enriched in biological activities including telomere maintenance process, DNA damage response and megakaryocyte differentiation. In conclusion, our study is the first EWAS on ozone exposure conducted in large-scale Han Chinese cohort and identified associated DNA methylation change on CpGs and regions, as well as related gene functions and pathways.

The Burden of Air Pollution on Skin Health: a Brief Report and Call to Action

INTRODUCTION

Air pollution in North America has intensified due to wildfires in recent years. In 2023, the wildfires in the Canadian province of Quebec caused a southward spread of pollutants, negatively affecting air quality and thereby aggravating certain health conditions in northeastern USA. This study examines the impact of air pollution on atopic dermatitis (AD) and skin health and how wildfires can exacerbate the burden of disease.

METHODS

Carbon monoxide levels measured by the U.S. Environmental Protection Agency (EPA) in the Boston region during the months following the Canadian wildfires of 2023 were collected from the U.S. EPA Outdoor Air Quality webpage. Patient records on dermatology clinic visits for dermatitis and eczema at the Mass General Brigham (MGB) hospital system, 300 miles from the wildfires, were examined, and the data compared with data from the corresponding months in 2019-2022 for historical control. No individual patient data were collected.

RESULTS

A notable rise and atypical summer peak in carbon monoxide (CO) levels in the Boston region during 2023 correlated with a spike in AD, dermatitis, and eczema-related dermatology clinic visits within the MGB hospital system, as compared with the prior 4 years.

CONCLUSION

The synchronized atypical peaks of CO levels and AD-related visits during the summer of 2023 highlight the potential impact of acute air pollution events such as wildfires on air quality and the consequences for skin health. Air pollution, exacerbated by wildfires, can damage the skin through the smoke and chemicals utilized for extinguishing fires, which contain multiple potential allergens and irritants to the skin, such as CO, particulate matter (PM2.5), and ammonium phosphates, triggering airway and skin inflammation and flares of AD. This issue disproportionately affects vulnerable populations, including low-income communities and the geriatric and pediatric populations. Healthcare professionals and government agencies must work together to improve air quality and purification policies and initiatives to lower the burden of skin disease, especially for vulnerable communities.

A combination of three antioxidants decreases the impact of rural particulate pollution in Normal human keratinocytes

OBJECTIVE

It is well established that exposure of human skin to airborne pollution, particularly in the form of particulate matter sized 2.5 μm (PM2.5 ), is associated with oxidative stress, DNA damage and inflammation, leading to premature signs of skin aging. Because much of the damage results from oxidative stress, we examined the effects of a topical composition containing three antioxidants in an in vitro model system to assess the potential for amelioration of premature aging. The use of multiple antioxidants was of interest based on the typical composition of therapeutic skincare products. It is important to determine the efficacy of multiple antioxidants together and develop a short-term assay for larger scale efficacy testing.

METHODS

Normal human epidermal keratinocytes were exposed to a rural-derived source of PM2.5 in the presence and absence of an antioxidant mixture of resveratrol, niacinamide and GHK peptide. Endpoints related to inflammation, premature aging and carcinogenicity were monitored after 5 h of exposure and included IL-6, CXCL10, MMP-1 and NRF2. Differentially expressed genes were monitored by RNA-seq.

RESULTS

Pre-treatment of keratinocytes with the antioxidant preparation in the absence of PM2.5 reduced baseline levels of MMP-1, IL-6 and CYP1A1 and reduced PM2.5 -induced increases in all four endpoints, MMP-1, IL-6, CXCL10 and CYP1A1. Antioxidants significantly increased NRF2 protein in the presence of PM2.5 , indicating a protective response. RNA-seq interrogation of antioxidant-treated cells further showed increased expression of NRF2 inducible genes. The expression of CYP1A1 and genes related to aryl hydrocarbon activation were induced by PM2.5 and suppressed by antioxidants.

CONCLUSIONS

Specific signalling pathways known to be correlated with skin inflammation and aging were examined based on their suitability for use in efficacy testing for the prevention of skin damage due to ambient hydrocarbon pollution. Endpoints examined after only 5 h of exposure provide a useful method amenable to high through-put screening. The results obtained reinforce the concept that a multiple antioxidant preparation, topically applied, may reduce pro-inflammatory signalling and cellular damage and thereby reduce premature skin aging due to exposure to rural-derived airborne pollution.

[Skin aging exposome]

The skin is a barrier organ and thus exposed to environmental factors from birth, which essentially determine skin aging. In order to describe and understand this complex process exactly, we applied the concept of the "exposome" to the environmentally induced skin aging process. In this review, we summarize current knowledge on the skin aging exposome. In this context, we characterize the most important exposomal factors, address their relative importance for skin aging and also the relevance of their mutual interactions. Finally, we discuss the clinical consequences resulting from this concept for an effective prevention of skin aging.

Climate Change, Skin Health, and Dermatologic Disease: A Guide for the Dermatologist

Climate change has a pervasive impact on health and is of clinical relevance to every organ system. Climate change-related factors impact the skin's capacity to maintain homeostasis, leading to a variety of cutaneous diseases. Stratospheric ozone depletion has led to increased risk of melanoma and keratinocyte carcinomas due to ultraviolet radiation exposure. Atopic dermatitis, psoriasis, pemphigus, acne vulgaris, melasma, and photoaging are all associated with rising levels of air pollution. Elevated temperatures due to global warming induce disruption of the skin microbiome, thereby impacting atopic dermatitis, acne vulgaris, and psoriasis, and high temperatures are associated with exacerbation of skin disease and increased risk of heat stroke. Extreme weather events due to climate change, including floods and wildfires, are of relevance to the dermatologist as these events are implicated in cutaneous injuries, skin infections, and acute worsening of inflammatory skin disorders. The health consequences as well as the economic and social burden of climate change fall most heavily on vulnerable and marginalized populations due to structural disparities. As dermatologists, understanding the interaction of climate change and skin health is essential to appropriately manage dermatologic disease and advocate for our patients.

Preventive Effect of Pharmaceutical Phytochemicals Targeting the Src Family of Protein Tyrosine Kinases and Aryl Hydrocarbon Receptor on Environmental Stress-Induced Skin Disease

The skin protects our body; however, it is directly exposed to the environment and is stimulated by various external factors. Among the various environmental factors that can threaten skin health, the effects of ultraviolet (UV) and particulate matter (PM) are considered the most notable. Repetitive exposure to ultraviolet and particulate matter can cause chronic skin diseases such as skin inflammation, photoaging, and skin cancer. The abnormal activation of the Src family of protein tyrosine kinases (SFKs) and the aryl hydrocarbon receptor (AhR) in response to UV and/or PM exposure are involved in the development and aggravation of skin diseases. Phytochemicals, chemical compounds of natural plants, exert preventive effects on skin diseases through the regulation of various signaling pathways. Therefore, this review aims to highlight the efficacy of phytochemicals as potential nutraceuticals and pharmaceutical materials for the treatment of skin diseases, primarily by targeting SFK and AhR, and to explore the underlying mechanisms of action. Future studies are essential to validate the clinical potential for the prevention and treatment of skin diseases.

Skin Aging Exposome in Skin of Color Populations: Review of the Literature

BACKGROUND

As life expectancy increases, the comorbidities related to aging require greater attention. Skin aging exposomes were only recently defined and need additional delineation, particularly in Skin of Color (SOC) populations.

OBJECTIVE

The primary objective is to shed the light and summarize the existing literature on skin aging exposome in SOC populations.

MATERIALS AND METHODS

We performed an extensive search in the PubMed and Google Scholar databases. We included peer-reviewed studies in SOC populations around the world regarding one or more of the skin aging exposome factors, and we grouped and organized the studies under each factor of the skin aging exposome.

RESULTS

Some environmental exposome factors are preventable or modifiable, for example, by applying broad-spectrum sunscreens with visible light protection, improving nutrition, and smoking cessation. Other factors such as air pollution will require more complex solutions. Our search revealed a paucity of references on skin aging exposome factors in SOC populations.

CONCLUSION

We identified the need for more dedicated studies in SOC populations to advance knowledge on skin aging exposome factors. This knowledge will provide a better understanding of approaches to minimize extrinsic skin aging in these populations.

The impact of airborne ultrafine particulate matter on human keratinocyte stem cells

OBJECTIVE

Air pollution is today fully acknowledged to be a significant public health problem. Rapid urbanization exposed us to a variety of unhealthy ambient air pollutants at high concentrations. The emergence of airborne ultrafine particles has added an additional dimension to this already complex problem of air pollution. The skin has different functions, one of them being the protection against the deleterious effect of external agents. The aim of this study is to evaluate the impact of airborne ultrafine particles (UFP) pollution on skin aging and on keratinocyte differentiation.

METHODS

Ex vivo human skin biopsies and cultured keratinocytes stem cells (KSC) were submitted to diesel exhaust-derived UFP. Reactive oxygen species (ROS) production was assessed with the MitoSOX™ probe. Keratinocyte stemness potential was evaluated by the immunodetection of keratin 15 (K15) and p63 (∆N isoforms). Effect of UFP on the epithelial niche maintenance was evaluated by immunodetection of Sox9. Reconstructed epidermis model was used to assess the impact of UFP on keratinocyte differentiation and aging.

RESULTS

UFP exposure induced ROS production and disturbed K15, ∆Np63 and Sox9 expression in KSC or ex vivo skin. Finally, investigations on reconstructed epidermis revealed a phenotype marked by impaired keratinocyte differentiation.

CONCLUSION

These results indicate that UFP pollution is a potent extrinsic factor of skin aging, affecting the keratinocyte stem cell potential and the skin renewal process.

Influence of environmental factors on facial pigmented spots: Epidemiological survey of women living in the northern and southern regions of Japan

BACKGROUND

Several epidemiological studies have been conducted to understand the relationship between environmental factors (including chronic sun exposure) and clinical signs of pigmented spots. However, no quantitative analysis has focused on the adverse effects of the detailed features of pigmented spots, including their color intensity, size, and number on the cheek. This study was performed to elucidate the adverse effects of environmental factors on clinical signs of pigmented spots.

METHODS

We conducted an epidemiological survey of 102 Japanese women in 2 regions of high and low sun exposure (southern and northern regions, respectively). Using image analysis of high-resolution digital facial photographs, individual pigmented spots were quantified according to color, size, and total number on the cheek. Each indicator was then compared between the groups.

RESULTS

For the number of pigmented spots on the cheek, the age-related increase curve showed a large slope in the southern group. For the size of pigmented spots, no significant difference was found between the two groups, and large pigmented spots were observed on the cheek even in the northern group. For the color intensity of the spots, the southern group showed a marked age-related change; among older subjects, the pigmented spots were significantly darker in the southern than northern group.

CONCLUSION

Our results may indicate that environmental factors, including chronic exposure to sunlight, mainly increase the number of pigmented spots and darkening of these spots. However, the occurrence of large pigmented spots may be related to intrinsic factors represented by heredity rather than environmental factors.

Protective effects of a day/night dual-antioxidant serum on skin: A randomized, regimen-controlled study in Chinese women exposed to air pollution

BACKGROUND

Chronic exposure to air pollution can negatively affect skin health.

AIMS

To assess the efficacy of the LUMIVIVE^® System (LVS), a skincare system consisting of individual day and night serums, in Chinese women exposed to air pollution.

PATIENTS/METHODS

In this single-center, vehicle-controlled study, eligible females (mean age, 49.02 years) were randomized 1:1 to treatment group (LVS plus basic moisturizer) or control group (basic moisturizer). Skin color, sebum content, barrier function, elasticity, and texture were measured at baseline and at each follow-up visit (days 28, 56, and 84). Air pollution parameters were collected throughout the study.

RESULTS

Air pollution levels, including PM_2.5 and NO₂ , were consistently high during the study. The treatment group showed significantly higher skin color L* (p ≤ 0.0001) and lower a* values (p ≤ 0.05) at all follow-up visits compared with the control group, indicating lower skin pigmentation and redness, respectively. Skin color L* and a* values remained unchanged over time for the control group but were significantly different at all follow-up visits compared to baseline (p ≤ 0.0001 and p ≤ 0.05, respectively) for the treatment group. There was an increasing trend for sebum content in the control group, which was not observed in the treatment group. Both groups showed improvements over time in other skin physiology parameters.

CONCLUSIONS

The current analysis demonstrates the efficacy of LVS plus basic moisturizer compared with basic moisturizer alone to reduce skin pigmentation and redness, as well as to mitigate sebum production, in Chinese women exposed to air pollution.

Genetic Variants in Telomerase Reverse Transcriptase Contribute to Solar Lentigines

Solar lentigines (SLs) are a hallmark of human skin aging. They result from chronic exposure to sunlight and other environmental stressors. Recent studies also imply genetic factors, but findings are partially conflicting and lack of replication. Through a multi-trait based analysis strategy, we discovered that genetic variants in telomerase reverse transcriptase were significantly associated with non-facial SL in two East Asian (Taizhou longitudinal cohort, n = 2,964 and National Survey of Physical Traits, n = 2,954) and one Caucasian population (SALIA, n = 462), top SNP rs2853672 (P-value for Taizhou longitudinal cohort = 1.32 × 10^‒28 and P-value for National Survey of Physical Traits = 3.66 × 10^‒17 and P-value for SALIA = 0.0007 and P_meta = 4.93 × 10^‒44). The same variants were nominally associated with facial SL but not with other skin aging or skin pigmentation traits. The SL-enhanced allele/haplotype upregulated the transcription of the telomerase reverse transcriptase gene. Of note, well-known telomerase reverse transcriptase‒related aging markers such as leukocyte telomere length and intrinsic epigenetic age acceleration were not associated with SL. Our results indicate a previously unrecognized role of telomerase reverse transcriptase in skin aging‒related lentigines formation.

Commentary: Facial Aesthetic Dermatological Procedures and Photoprotection in Chinese Populations

The medical literature on aesthetic dermatology has primarily focused on a light-skinned patient population, yet patients of darker skin types have different needs and priorities. In Chinese individuals, key concerns include altered pigmentation, which is perceived to age the individual, and also relates to the Chinese cultural standard of beauty of fair skin; many seek aesthetic treatment for this. Non-invasive cosmetic procedures such as lasers and injections are also gaining in popularity in the Chinese market, but this population is prone to hyperpigmentation as an adverse effect of such procedures. Considered and tailored approaches, both to primary concerns of photoaging and the side effects of cosmetic treatments, are warranted.

Aging in the sebaceous gland

Sebaceous glands (SGs) originate from hair follicular stem cells and secrete lipids to lubricate the skin. The coordinated effects of intrinsic and extrinsic aging factors generate degradation of SGs at a late age. Senescence of SGs could be a mirror of the late aging of both the human body and skin. The procedure of SG aging goes over an initial SG hyperplasia at light-exposed skin areas to end with SG atrophy, decreased sebum secretion, and altered sebum composition, which is related to skin dryness, lack of brightness, xerosis, roughness, desquamation, and pruritus. During differentiation and aging of SGs, many signaling pathways, such as Wnt/β-catenin, c-Myc, aryl hydrocarbon receptor (AhR), and p53 pathways, are involved. Random processes lead to random cell and DNA damage due to the production of free radicals during the lifespan and neuroendocrine system alterations. Extrinsic factors include sunlight exposure (photoaging), environmental pollution, and cigarette smoking, which can directly activate signaling pathways, such as Wnt/β-catenin, Notch, AhR, and p53 pathways, and are probably associated with the de-differentiation and hyperplasia of SGs, or indirectly activate the abovementioned signaling pathways by elevating the inflammation level. The production of ROS during intrinsic SG aging is less, the signaling pathways are activated slowly and mildly, and sebocytes are still differentiated, yet terminal differentiation is not completed. With extrinsic factors, relevant signaling pathways are activated rapidly and fiercely, thus inhibiting the differentiation of progenitor sebocytes and even inducing the differentiation of progenitor sebocytes into keratinocytes. The management of SG aging is also mentioned.

Detrimental correlation between air pollution with skin aging in Taiwan population

Dissecting the complex relationships between skin aging and air pollution has been an ongoing effort. The increased exposure to air pollution over time imposed a negative effect on skin. This study explores the correlation between skin aging in the Asian population and levels of air pollutants to show different relationship between the two. This study was retrospective and included 389 patients, age between 30 and 74, who planned to receive a session of laser treatment for skin disorders in Kaohsiung Medical University Hospital (KMUH) from 2006 to 2019. Preoperative skin condition quantified by VISIA Complexion Analysis System (Canfield Imaging Systems, Fierfield, NJ, US). Eight air pollutants such as carbon monoxide (CO), non-methane hydrocarbon (NMHC), nitrogen oxides (NO, NO2, and NOx), particulate matters (PM2.5 and PM10), ozone (O3), sulfur dioxide (SO2) and 8 skin condition such as spots, wrinkles, textures, pores, ultraviolet spots (UV spots), brown spots, red area, and porphyrin were analyzed to explore correlation between air pollution and skin aging. Strong correlation was found between NMHC exposure and texture, pores and brown spots formation. A positive correlation between O3 and better VISIA texture and pores scores was found. Brown spots was found to negatively associate with CO, NMHC, NO2, NOx, PM10, PM2.5, and SO2. The skin condition of population over age 45 affected by CO, NMHC, NO2, NOx, PM2.5, PM10, and SO2. Skin condition of the bottom 10% strongly correlates with exposure to PM10 and SO2, whereas skin condition of the top 10% was affected by PM10. Air pollutants such as CO, NO2, NOx, PM2.5, PM10, SO2, and NMHC were found to correlate with negative skin quality strongly. In contrast, O3 exposure is associated with less texture and pores. Future studies are warranted to further appreciate the relationships between air pollutants and skin condition.

Ultraviolet Light Protection: Is It Really Enough?

Our current understanding of the pathogenesis of skin aging includes the role of ultraviolet light, visible light, infrared, pollution, cigarette smoke and other environmental exposures. The mechanism of action common to these exposures is the disruption of the cellular redox balance by the directly or indirectly increased formation of reactive oxygen species that overwhelm the intrinsic antioxidant defense system, resulting in an oxidative stress condition. Altered redox homeostasis triggers downstream pathways that contribute to tissue oxinflammation (cross-talk between inflammation and altered redox status) and accelerate skin aging. In addition, both ultraviolet light and pollution increase intracellular free iron that catalyzes reactive oxygen species generation via the Fenton reaction. This disruption of iron homeostasis within the cell further promotes oxidative stress and contributes to extrinsic skin aging. More recent studies have demonstrated that iron chelators can be used topically and can enhance the benefits of topically applied antioxidants. Thus, an updated, more comprehensive approach to environmental or atmospheric aging protection should include sun protective measures, broad spectrum sunscreens, antioxidants, chelating agents, and DNA repair enzymes.

Association Between Short-term Exposure to Environmental Air Pollution and Psoriasis Flare

IMPORTANCE

Psoriasis is a chronic inflammatory disease with a relapsing-remitting course. Selected environmental factors such as infections, stressful life events, or drugs may trigger disease flares. Whether air pollution could trigger psoriasis flares is still unknown.

OBJECTIVE

To investigate whether short-term exposure to environmental air pollution is associated with psoriasis flares.

DESIGN, SETTING, AND PARTICIPANTS

This observational study with both case-crossover and cross-sectional design retrospectively analyzed longitudinal data from September 2013 to January 2020 from patients with chronic plaque psoriasis consecutively attending the outpatient dermatologic clinic of the University Hospital of Verona. For the case-crossover analysis, patients were included who had at least 1 disease flare, defined as Psoriasis Area and Severity Index (PASI) increase of 5 or greater between 2 consecutive assessments in a time frame of 3 to 4 months. For the cross-sectional analysis, patients were included who received any systemic treatment for 6 or more months, with grade 2 or higher consecutive PASI assessment.

MAIN OUTCOMES AND MEASURES

We compared the mean and cumulative (area under the curve) concentrations of several air pollutants (carbon monoxide, nitrogen dioxide, other nitrogen oxides, benzene, coarse particulate matter [PM; 2.5-10.0 μm in diameter, PM10] and fine PM [<2.5 μm in diameter, PM2.5]) in the 60 days preceding the psoriasis flare and the control visits.

RESULTS

A total of 957 patients with plaque psoriasis with 4398 follow-up visits were included in the study. Patients had a mean (SD) age of 61 (15) years and 602 (62.9%) were men. More than 15 000 measurements of air pollutant concentration from the official, open-source bulletin of the Italian Institute for Environmental Protection and Research (ISPRA) were retrieved. Among the overall cohort, 369 (38.6%) patients with psoriasis flare were included in the case-crossover study. We found that concentrations of all pollutants were significantly higher in the 60 days before psoriasis flare (median PASI at the flare 12; IQR, 9-18) compared with the control visit (median PASI 1; IQR, 1-3, P < .001). In the cross-sectional analysis, exposure to mean PM10 over 20 μg/m3 and mean PM2.5 over 15 μg/m3 in the 60 days before assessment were associated with a higher risk of PASI 5 or greater point worsening (adjusted odds ratio [aOR], 1.55; 95% CI, 1.21-1.99; and aOR, 1.25; 95% CI, 1.0-1.57, respectively). Sensitivity analyses that stratified for trimester of evaluation, with various lag of exposure and adjusting for type of treatment, yielded similar results.

CONCLUSIONS AND RELEVANCE

The findings of this case-crossover and cross-sectional study suggest that air pollution may be a trigger factor for psoriasis flare.

Cannabinoid receptors promote chronic intermittent hypoxia-induced breast cancer metastasis via IGF-1R/AKT/GSK-3β

The progression of breast cancer is closely related to obstructive sleep apnea-hypopnea syndrome (OSAHS). Low concentrations of cannabinoids promote tumor proliferation. However, the role of cannabinoid receptors (CBs) in chronic intermittent hypoxia (CIH)-induced breast cancer has not been reported. The migration and invasion of breast cancer cell lines (MCF-7 and T47D) were measured by scratch assay and transwell assay. Gene and protein expressions were analyzed by qPCR and western blotting. Tumor xenograft mice model were established to evaluate the function of CBs. We observed that chronic hypoxia (CH) and CIH increased CBs expression and promoted migration and invasion in breast cancer. Mice grafted with MCF-7 exhibited obvious tumor growth, angiogenesis, and lung metastasis in CIH compared with CH and control. In addition, CIH induced CBs expression, which subsequently activated insulin-like growth factor-1 receptor (IGF-1R)/AKT/glycogen synthase kinase-3β (GSK-3β) axis. Knockdown of CBs alleviated CIH-induced migration and invasion of breast cancer in vitro. Furthermore, CIH exaggerated the malignancy of breast cancer and silencing of CBs suppressed tumor growth and metastasis in vivo. Our study contributed to understanding the role of CIH in breast cancer development modulation.

Defining skin aging and its risk factors: a systematic review and meta-analysis

Skin aging has been defined to encompass both intrinsic and extrinsic aging, with extrinsic aging effected by environmental influences and overlaying the effects of chronological aging. The risk factors of skin aging have been studied previously, using methods of quantifying skin aging. However, these studies have yet to be reviewed. To better understand skin aging risk factors and collate the available data, we aimed to conduct a systematic review and meta-analysis. We conducted our systematic review in compliance with Preferred Reporting Item for Systematic Review and Meta-Analyses (PRISMA) guidelines. Embase, PubMed and Web of Science databases were searched in October 2020 using specific search strategies. Where odds ratios were reported, meta-analyses were conducted using the random effects model. Otherwise, significant factors were reported in this review. We identified seven notable risk factors for various skin aging phenotypes: age, gender, ethnicity, air pollution, nutrition, smoking, sun exposure. This review's results will guide future works, such as those aiming to examine the interaction between genetic and environmental influences.

The role of local retinoids in eliminating signs of skin aging

Skin aging is a complex process involving both internal (chronological aging) and external (biological aging) factors. Slowing down the proliferative and immune processes in the epidermis, reducing the activity of fibroblasts and vascularization of the dermis during chronological aging lead to thinning, dryness, hypersensitivity, vulnerability and superficial wrinkles. Exposure to ultraviolet rays, pollutants, climate, and thermal factors cause keratinocyte disorganization, enhanced melanogenesis, collagen dystrophy, solar elastosis, and disorder of microcirculation. The main signs of external skin aging are deep wrinkles, sagging, pigmentation, telangiectasia, skin neoplasms. Among the local anti-aging agents, retinoids occupy a leading place, as they eliminate the main signs of skin aging. Of the entire group of retinoids, retinoic acids are the most active. However, the possibility of skin irritation limits their use. Therapeutic and cosmetic products with retinol esters (retinol palmitate) have a minimal irritating effect and can be used both for the prevention of skin aging and the elimination of its signs. Oral use of isotretinoin as an anti-aging agent is undesirable due to the many side effects and contraindications.

How to prevent skin damage from air pollution part 2: Current treatment options

In the first part of this review, we have summarized the methods used to examine skin exposure to air pollution and the fundamental concept of skin-exposome interactions. Part 2 of this review focuses on dermatoses, whose aggravation or initiation by air pollution has been confirmed in evidence based medicine manner. Based on the model of photodermatology and photodermatoses, we propose a new concept of "polludermatoses." A key feature of this concept is identifying patients at risk, which will reveal the noxious effects of air pollutants on skin health. Identifying clinical signs of pollution-damaged skin could be beneficial in categorizing conditions caused or exacerbated by exposure to air pollution. Finally, we discuss the current treatment options and the pathogenetic processes targeted by these therapeutics or the development of novel treatment modalities.

Polycyclic aromatic hydrocarbons regulate the pigmentation pathway and induce DNA damage responses in keratinocytes, a process driven by systemic immunity

BACKGROUND

Urban pollution is correlated with an increased prevalence of skin pigmentation disorders, however the physiological processes underlying this association are unclear.

OBJECTIVES

To delineate the relationship between polycyclic aromatic hydrocarbons (PAHs), a key constituent of atmospheric pollution, and immunity/skin pigmentation pathways.

METHODS

We exposed peripheral blood mononuclear cells (PBMC) to PAHs and performed cytokines/chemokine profiling. We then examined the effect of immune activation on pigmentation by co-culturing PBMC and Benzo(a)pyrene (BaP) with reconstructed human pigmented epidermis (RHPE). To study the mechanism, we treated keratinocytes with conditioned medium from BaP-exposed PBMC and studied DNA damage responses, aryl hydrocarbon receptor (AhR) activation and pro-pigmentation factor, proopiomelanocortin (POMC) secretion.

RESULTS

PAHs induced up-regulation of inflammatory cytokines/chemokine in PBMC. Co-culturing of RHPE with PBMC+BaP resulted in increased melanin content and localization. BaP-conditioned medium significantly increased DNA damage, p53 stabilization, AhR activation and POMC secretion in keratinocytes. We found that IFNγ induced DNA damage, while TNFα and IL-8 potentiated POMC secretion in keratinocytes. Importantly, BaP-conditioned medium-induced DNA damage and POMC secretion is prevented by antioxidants vitamin E, vitamin C and sulforaphane, as well as the prototypical corticosteroid dexamethasone. Finally, vitamin C and sulforaphane enhanced the genome protective and depigmentation effects of dexamethasone, providing proof-of-concept for a combinatorial approach for the prevention and/or correction of PAH-induced pigment spots formation.

CONCLUSION

Our study reveals the importance of systemic immunity in regulating PAH-induced skin pigmentation, and provide a new keratinocyte DNA damage response mechanistic target for the prevention or reversal of pollution-associated skin pigmentation.

Short-term effect of NO2 on outpatient visits for dermatologic diseases in Xinxiang, China: a time-series study

OBJECTIVES

As the largest organ of the human body, the skin is the major exposure route of NO₂. However, the evidence for a relationship between NO₂ exposure and dermatologic diseases (DMs) is limited. This time-series study was conducted to assess the short-term effect of nitrogen dioxide (NO₂) exposure on DMs outpatient visits in Xinxiang, China.

METHODS

Daily recordings of NO₂ concentrations, meteorological data, and the outpatient visits data for DMs were collected in Xinxiang from January 1st, 2015, to December 31st, 2018. The analysis method used was based on the generalized additive model (GAM) with quasi-Poisson regression to investigate the relationship between NO₂ exposure and DMs outpatient visits. Several covariates, such as long-term trends, seasonality, and weather conditions were controlled.

RESULTS

A total of 164,270 DMs outpatients were recorded. A 10 μg/m³ increase in NO₂ concentrations during the period was associated with a 1.86% increase in DMs outpatient visits (95% confidence intervals [Cl]: 1.06-2.66%). The effect was stronger (around 6 times) in the cool seasons than in warmer seasons and younger patients (< 15 years of age) appeared to be more vulnerable.

CONCLUSIONS

The findings of this study indicate that short-term exposure to NO₂ increases the risk of DMs in Xinxiang, China, especially in the cool seasons. Policymakers should implement more stringent air quality standards to improve air quality.

Particulate matter-induced atmospheric skin aging is aggravated by UVA and inhibited by a topical l-ascorbic acid compound

Ambient particulate matter (PM) is a major contributor to environmental air pollution-associated skin damage. However, most published studies are observational or epidemiologic and have not mechanistically investigated the effects of air pollutants on cellular senescence and aging, particularly in combination with ultraviolet (UV) radiation. Herein, we analyzed whether UVA aggravates the PM-induced inflammatory cascade, which contributes to the aging of skin-derived cells. We hypothesized that cellular senescence is involved in PM&UVA-induced aging and tested whether an l-ascorbic acid compound (LAC), containing vitamin E and ferulic acid, can inhibit PM&UVA-induced aging. PM&UVA-exposed HDFs showed further elevated reactive oxygen species (ROS) levels detected by flow cytometry. We then demonstrated that PM induces MAPK signaling activation and the expression of AhR and NF-κB, responses that are both exacerbated by UVA. The levels of inflammatory cytokines, IL-1β and IL-6, were significantly higher in the PM&UVA-exposed group which resulted in increased transcription of MMPs, causing downregulation of type I collagen. Meanwhile, treatment with LAC reduced the levels of ROS and inflammatory cytokines. Additionally, PM&UVA-induced SA-β-gal production (staining assay) was reduced by LAC. These findings suggest a role of atmospheric pollution and UVA radiation in cellular senescence induction. Our findings also suggest a possible role of AhR inhibition by topical antioxidants to prevent atmospheric pollution-induced skin aging.

Differences between perceived age and chronological age in women: A multi-ethnic and multi-centre study

Objective

Accuracy in assessing age from facial cues is important in social perception given reports of strong negative correlations between perceived age and assessments of health and attractiveness. In a multi‐ethnic and multi‐centre study, we previously documented similar patterns of female facial age assessments across ethnicities, influenced by gender and ethnicity of assessors.

Methods

Here we extend these findings by examining differences between estimated age from digital portraits and chronological age (Δ age) for 180 women from three age groups (20–34, 35–49, 50–66 years) and five ethnicities (36 images of each ethnicity, assessed for age on a continuous scale by 120 female and male raters of each ethnicity).

Results

Across ethnicities, Δ age was smallest in French assessors and largest in South African assessors. Numerically, French women were judged oldest and Chinese women youngest relative to chronological age. In younger women, Δ age was larger than in middle‐aged and older women. This effect was particularly evident when considering the interaction of women's age with assessor gender and ethnicity, independently and together, on Δ age.

Conclusion

Collectively, our findings suggest that accuracy in assessments of female age from digital portraits depends on the chronological age and ethnicity of the photographed women and the ethnicity and gender of the assessor. We discuss the findings concerning ethnic variation in skin pigmentation and visible signs of ageing and comment on implications for cosmetic science.

In elderly Caucasian women, younger facial perceived age correlates with better forearm skin microcirculation reactivity

BACKGROUND

Visual and molecular changes occurring upon aging are rather well characterized. Still, aging signs show great significant inter-individual variations, and little is known concerning the link between perceived age and cutaneous microcirculation.

MATERIALS AND METHODS

To investigate this point, we recruited Caucasian women in their mid-50's to mid-70's and subsampled women looking older or younger than their age. We studied their facial skin color, as well as their microvascular reactivity to local heating assessed in the forearm skin. We also used skin biopsies from some of these women for gene expression or immunohistochemical analysis.

RESULTS

Clinical and instrumental analysis of skin color revealed that subjects who look 5 years younger differ only by a higher glowing complexion. Our most striking result is that subjects looking 5 years younger than their age present a higher microcirculation reactivity in forearm skin. Transcriptome comparison of skin samples from women looking older or younger than their age revealed 123 annotated transcripts differentially expressed, among which MYL9 relates to microcirculation. MYL9 is downregulated in the group of women looking younger than their real age. Microscopy shows that the labeling of MYL9 and CD31 are altered and heterogeneous with age, as is the morphology of microvessels.

CONCLUSION

Therefore, assessing generalized vascular reactivity in non-photo-exposed skin to focus on the intrinsic aging allows subtle discrimination of perceived age within elderly healthy subjects.

Alterations of the pigmentation system in the aging process

Human skin aging is a natural phenomenon that results from continuous exposure to intrinsic (time, genetic factors, hormones) as well as extrinsic factors (UV exposure, pollution, tobacco). In areas that are frequently exposed to the sun, photoaging blends with the process of intrinsic aging, resulting in an increased senescent cells number and consequently accelerating the aging process. The severity of photodamage depends on constitutional factors, including skin phototype (skin color, tanning capacity), intensity, and duration of sunlight/UV exposure. Aging affects nearly every aspect of cutaneous biology, including pigmentation. Clinically, the phenotype of age pigmented skin has a mottled, uneven color, primarily due to age spots, with or without hypopigmentation. Uneven pigmentation might be attributed to the hyperactivation of melanocytes, altered distribution of pigment, and turnover. In addition to direct damage to pigment-producing cells, photodamage alters the physiological crosstalk between keratinocytes, fibroblasts, endothelial cells, and melanocytes responsible for natural pigmentation homeostasis. Interestingly, age-independent diffuse expression of senescence-associated markers in the dermal and epidermal compartment is also associated with vitiligo, suggesting that premature senescence plays an important role in the pathology.

Clinical and biological impact of the exposome on the skin

The skin exposome is defined as the totality of environmental exposures over the life course that can induce or modify various skin conditions. Here, we review the impact on the skin of solar exposure, air pollution, hormones, nutrition and psychological factors. Photoageing, photocarcinogenesis and pigmentary changes are well-established consequences of chronic exposure of the skin to solar radiation. Exposure to traffic-related air pollution contributes to skin ageing. Particulate matter and nitrogen dioxide cause skin pigmentation/lentigines, while ozone causes wrinkles and has an impact on atopic eczema. Human skin is a major target of hormones, and they exhibit a wide range of biological activities on the skin. Hormones decline with advancing age influencing skin ageing. Nutrition has an impact on numerous biochemical processes, including oxidation, inflammation and glycation, which may result in clinical effects, including modification of the course of skin ageing and photoageing. Stress and lack of sleep are known to contribute to a pro-inflammatory state, which, in turn, affects the integrity of extracellular matrix proteins, in particular collagen. Hormone dysregulation, malnutrition and stress may contribute to inflammatory skin disorders, such as atopic dermatitis, psoriasis, acne and rosacea.

Skin exposome science in practice : current evidence on hair biomonitoring and future perspectives

The skin exposome, defined as the totality of environmental exposures from conception to death that can induce or modify various skin conditions, compiles environmental, lifestyle and psychosocial exposures, as well as the resulting internal biological and physiological responses to these exposures. Biomonitoring can be used to obtain information on the internal dose of pollutants. The concentration of biomarkers in body fluids is highly variable over time due to differential elimination kinetics of chemicals, whereas they accumulate in hair. Hair analysis thus provides information on cumulative exposure over a longer period of time, and so can be used for assessing chronic exposure to pollutants. Studies on hair samples collected from 204 women living in two cities in China with different levels of pollution demonstrated that hair damage and the skin microbiome are biomarkers of a polluted city and long-term exposure to pollution and UV can increase signs of facial ageing. Adopting an exposome approach to skin health requires assessing multiple exposures and biological consequences, possibly in relation to longitudinally followed-up health outcomes. Leveraging "omics" data (e.g. metabolomics, proteomics, genomics and microbiome) and big data analytics, in particular multivariate analysis, will help to further understand the impact of pollution on skin and the combined effects with other exposome factors, including solar radiation and other environmental exposures.

A Randomized Controlled Trial on the Effectiveness of Epidermal Growth Factor-Containing Ointment on the Treatment of Solar Lentigines as Adjuvant Therapy

Background and Objective: Little is known about the anti-pigmentation effects of whitening agents on solar lentigines. Epidermal growth factor (EGF) has been used as a booster for wound healing in the skin, and it has been suggested to have anti-pigmentation effects. This study aimed to evaluate the effect and safety of EGF-containing ointment for treating solar lentigines with a Q-switched (QS) 532 nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (Bluecore company, Seoul, Republic of Korea). Materials and Methods: Subjects who underwent QS 532 nm Nd:YAG laser treatment of solar lentigines were randomly assigned to treatment with an EGF ointment or petrolatum. After the laser procedure, the subjects were administered the test ointment twice a day for 4 weeks. The physician's assessment of the degree of pigment clearance and patient's satisfaction were assessed after 4 and 8 weeks. Additionally, the melanin index (MI), erythema index (EI), transepidermal water loss (TEWL), and post-inflammatory hyperpigmentation (PIH) were evaluated. This trial was registered with ClinicalTrials.gov (NCT04704245). Results: The blinded physician's assessment using 5-grade percentage improvement scale and patient's satisfaction were significantly higher in the study group than in the control group at the 4th and 8th weeks. The MI was significantly higher in the control group than in the study group at the 4th and 8th weeks. The EI and TEWL did not differ significantly between the two groups at either time point. The incidence of PIH was higher in the control group (37.5%) than in the EGF group (7.14%) at the 8th week. Conclusions: The application of EGF-containing ointment on facial solar lentigines with a QS 532 nm Nd:YAG laser showed efficient and safe therapeutic effects, with less PIH. Thus, EGF-containing ointment could be suggested as the promising adjuvant treatment strategy with a QS laser for solar lentigines.

Environmentally-Induced (Extrinsic) Skin Aging: Exposomal Factors and Underlying Mechanisms

As a barrier organ, the skin is an ideal model to study environmentally-induced (extrinsic) aging. In this review, we explain the development of extrinsic skin aging as a consequence of skin exposure to specific exposomal factors, their interaction with each other, and the modification of their effects on the skin by genetic factors. We also review the evidence that exposure to these exposomal factors causes extrinsic skin aging by mechanisms that critically involve the accumulation of macromolecular damage and the subsequent development of functionally altered and/or senescent fibroblasts in the dermal compartment of the skin.

Air pollution and skin disorders

Air pollution is being shown to play an increasing causation role in our most common skin diseases. Acne, hyperpigmentation, atopic dermatitis, and psoriasis have been shown to be influenced by air pollution. It is important for pollution to be added as a risk factor for these skin disorders, and thus we must discuss mitigating its negative affects with patients. Air pollution is the contamination of outdoor (ambient) and indoor (household) environments by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. Nearly all (90%) of the world's population experience daily pollution. In 2019, air pollution was considered by the World Health Organization to be the biggest environmental health risk to humans, responsible for killing more than 7 million people prematurely every year. Preliminary studies link air pollution to COVID-19 deaths, as there were high death tolls in some of the most globally polluted areas. Air pollution affects many organ systems such as cardiovascular, pulmonary, central nervous, reproductive, and integumentary systems. In this study, we detail the current evidence linking specific skin and health disorders to air pollution.

Deleterious Effects of an Air Pollutant (NO2) on a Selection of Commensal Skin Bacterial Strains, Potential Contributor to Dysbiosis?

The skin constitutes with its microbiota the first line of body defense against exogenous stress including air pollution. Especially in urban or sub-urban areas, it is continuously exposed to many environmental pollutants including gaseous nitrogen dioxide (gNO₂). Nowadays, it is well established that air pollution has major effects on the human skin, inducing various diseases often associated with microbial dysbiosis. However, very few is known about the impact of pollutants on skin microbiota. In this study, a new approach was adopted, by considering the alteration of the cutaneous microbiota by air pollutants as an indirect action of the harmful molecules on the skin. The effects of gNO₂ on this bacterial skin microbiota was investigated using a device developed to mimic the real-life contact of the gNO₂ with bacteria on the surface of the skin. Five strains of human skin commensal bacteria were considered, namely Staphylococcus aureus MFP03, Staphylococcus epidermidis MFP04, Staphylococcus capitis MFP08, Pseudomonas fluorescens MFP05, and Corynebacterium tuberculostearicum CIP102622. Bacteria were exposed to high concentration of gNO₂ (10 or 80 ppm) over a short period of 2 h inside the gas exposure device. The physiological, morphological, and molecular responses of the bacteria after the gas exposure were assessed and compared between the different strains and the two gNO₂ concentrations. A highly significant deleterious effect of gNO₂ was highlighted, particularly for S. capitis MFP08 and C. tuberculostearicum CIP102622, while S. aureus MFP03 seems to be the less sensitive strain. It appeared that the impact of this nitrosative stress differs according to the bacterial species and the gNO₂ concentration. Thus the exposition to gNO₂ as an air pollutant could contribute to dysbiosis, which would affect skin homeostasis. The response of the microbiota to the nitrosative stress could be involved in some pathologies such as atopic dermatitis.

Air Pollution and Skin Aging

PURPOSE OF THE REVIEW

The evidence on the role of air pollution on skin aging has increased in recent years. The accumulating evidence is based on both, epidemiological and mechanistic studies. The purpose of this review is to evaluate the recent evidence on the impacts of air pollution on skin aging as well as identify knowledge gaps for future research.

RECENT FINDINGS

Traffic-related air pollution exposure (particulate matter (PM), soot and nitrogen dioxide (NO₂)) has been associated with premature skin aging in several independent cohorts. In real life, human skin is additionally exposed to UV radiation, which is known for its effects on premature skin aging. More recent epidemiological findings suggest that (1) associations of PM can be altered by UV radiation with stronger PM associations at lower levels of UV, and (2) there is an association of tropospheric ozone with wrinkle formation, independent of NO₂, PM, and UV. The association between traffic-related air pollution and skin aging has been well-established. More recent epidemiological studies focused on the associations with ozone as well as interactions with of ambient air pollution with UV radiation, a research area that is becoming more important with the increase of global warming.

Mechanism underlying the effect of SO2-induced oxidation on human skin keratinocytes

This study aimed to study the effect and mechanism of action of SO2-induced oxidation on human skin keratinocytes.Different concentrations of SO2 derivatives (0, 25, 50, 100, 200, 400, and 800 μM) were used for treating HaCaT keratinocytes for 24 hours. MTT was used to evaluate the effect of each concentration on cell proliferation. HaCaT cells were randomly divided into control and SO2 groups. The control group received no treatment, whereas the SO2 group was treated with SO2 derivatives of selected concentrations for 24 hours. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD), tumor necrosis factor TNF-α (TNF-α), and interleukin-1 (IL-1-β) in cell supernatants were detected using enzyme-linked immunosorbent assay. Real-time polymerase chain reaction was used to detect the expression of nuclear transcription factor (Nrf2) and heme oxygenase (HO)-1 mRNA. The Western blot analysis was used to test the expression levels of Nrf2, HO-1, activated caspase-3, Bcl-2, Bax, IκB, NF-κB p65 (p65), ERK1/2, p38, phospho-NF-κB p65 (p-p65), p-ERK1/2, and p-p38.SO2 derivatives (100, 200, 400, and 800 μM) could inhibit cell proliferation. SO2 derivatives increased the level of ROS, MDA, TNF-α, IL-1β, Nrf2, HO-1, and p-p65/p65 and decreased the levels of SOD, IκB, p-ERK1/2/ERK1/2, and p-p38/p38 compared with the control group, but they had no effect on the levels of caspase-3, Bcl-2, and Bax.SO2 could inhibit the proliferation of human skin keratinocytes and induce oxidative stress and inflammation via the activation of the NF-κB pathway to inhibit the ERK1/2 and p38 pathways.

[Topical treatment of pigmentation disorders with cosmetic and pharmaceutical agents]

BACKGROUND

Esthetically unattractive hyperpigmentation can occur post-inflammatory or as a result of genetic or hormonal influences, UV exposure or medication. Important parameters for the quality of topical treatments are evidence-based in vivo and in vitro efficacy as well as scientifically verified wanted and unwanted effects.

OBJECTIVES

This paper will present cosmetic and pharmaceutical topical ingredients against hyperpigmentation that have been proven in scientific studies.

MATERIALS AND METHODS

A search of PubMed database was performed in October 2020 using the various ingredient names, "melasma" and "hyperpigmentation." Two reviewers independently screened titles, leading to the selection of 30 papers.

RESULTS

Hydroquinone, a tyrosinase inhibitor, has been used for over 40 years to treat hyperpigmentation. It is the most commonly studied agent for lightening pigment. Despite the limited evidence-based research on novel treatment approaches, several ingredients did show efficacy as depigmenting agents, including tyrosinase inhibitors, substances that increase cell turnover, and plant derivatives.

CONCLUSIONS

Hydroquinone is still the gold standard for the treatment of hyperpigmentation, along with the triple therapy of hydrochinon, tretinoin, and steroids in different modifications. In summary, hyperpigmentation is best treated using a combination therapy of different approaches that includes consequent UV protection.

Bioengineered Skin Intended as In Vitro Model for Pharmacosmetics, Skin Disease Study and Environmental Skin Impact Analysis

This review aims to be an update of Bioengineered Artificial Skin Substitutes (BASS) applications. At the first moment, they were created as an attempt to replace native skin grafts transplantation. Nowadays, these in vitro models have been increasing and widening their application areas, becoming important tools for research. This study is focus on the ability to design in vitro BASS which have been demonstrated to be appropriate to develop new products in the cosmetic and pharmacology industry. Allowing to go deeper into the skin disease research, and to analyze the effects provoked by environmental stressful agents. The importance of BASS to replace animal experimentation is also highlighted. Furthermore, the BASS validation parameters approved by the OECD (Organisation for Economic Co-operation and Development) are also analyzed. This report presents an overview of the skin models applicable to skin research along with their design methods. Finally, the potential and limitations of the currently available BASS to supply the demands for disease modeling and pharmaceutical screening are discussed.

Sulforaphane controls the release of paracrine factors by keratinocytes and thus mitigates particulate matter-induced premature skin aging by suppressing melanogenesis and maintaining collagen homeostasis

BACKGROUND

Skin aging, potentially caused by exposure to particulate matter (PM)_2.5, is characterized by wrinkling, abnormal pigmentation, and skin dryness triggered by several keratinocyte-derived paracrine factors. Sulforaphane (4-methylsulfinylbutyl isothiocyanate, SFN), commonly found in cruciferous vegetables, has diverse biological effects on skin tissue.

PURPOSE

In the present study, we have investigated whether SFN may alleviate PM_2.5-induced premature skin aging.

METHODS

We used keratinocyte/melanocyte or keratinocyte/fibroblast coculture models of skin cells and measured the parameters of melanogenesis, collagen homeostasis and inflammation.

RESULTS

SFN inhibited the development of reactive oxygen species in keratinocytes exposed to PM_2.5. In keratinocyte/melanocyte cocultures, it significantly inhibited the upregulation of melanogenic paracrine mediators (including endothelin-1 and prostaglandin E2) in keratinocytes exposed to PM_2.5; the synthesis of melanogenic proteins including microphthalmia-associated transcription factor, tyrosinase-related protein 1, and tyrosinase; and the levels of melanin in melanocytes. SFN treatment of keratinocyte/fibroblast cocultures significantly reduced the PM_2.5-induced expression of NF-κB-mediated cytokines including interleukin-1β, interleukin-6, tumor necrosis factor α, and cyclooxygenase-2. In fibroblasts of the keratinocyte/fibroblast coculture system, the expression levels of phospho-NF-κB, cysteine-rich protein 61, and matrix metalloproteinase-1 were significantly decreased whereas procollagen type I synthesis was significantly increased.

CONCLUSION

Collectively, our results suggest that SFN mitigates PM_2.5-induced premature skin aging by suppressing melanogenesis and maintaining collagen homeostasis. It acts by regulating the release of paracrine factors from keratinocytes.

Oxidative contribution of air pollution to extrinsic skin ageing

•Epidemiological evidence links exposure to poor air quality to lentigines and wrinkles. •Experimental studies provide mechanistic explanations involving oxidative stress. •Polluted air may hasten skin ageing through indirect systemic effects via the lung and/or direct effects on cutaneous tissue. •Prevention measures would need to combine strategies that target both ‘routes’. •Air pollution is one of several environmental stressors that combined, may have additive/synergistic effects on the skin.

An association between air pollution and daily most frequently visits of eighteen outpatient diseases in an industrial city

Toxic effects of air pollutants were individually identified in various organs of the body. However, the concurrent occurrences and the connection of diseases in multiple organs arise from air pollution has not been concurrently studied before. Here we hypothesize that there exist connected health effects arise from air pollution when diseases in various organs were considered together. We used medical data from hospital outpatient visits for various organs in the body with a disease-air pollution model that represents each of the diseases as a function of the environmental factors. Our results show that elevated air pollution risks (above 40%) concurrently occurred in diseases of spondylosis, cerebrovascular, pneumonia, accidents, chronic obstructive pulmonary disease (COPD), influenza, osteoarthritis (OA), asthma, peptic ulcer disease (PUD), cancer, heart, hypertensive, diabetes, kidney, and rheumatism. Air pollutants that were associated with elevated health risks are particular matters with diameters equal or less than 2.5 μm (PM_2.5), nitrogen dioxide (NO₂), ozone (O₃), particular matters with diameters equal or less than 10 μm (PM₁₀), carbon monoxide (CO), and nitrogen oxide (NO). Concurrent occurrences of diseases in various organs indicate that the immune system tries to connectively defend the body from persistent and rising air pollution.

Skin Irritation Testing beyond Tissue Viability: Fucoxanthin Effects on Inflammation, Homeostasis, and Metabolism

UV light catalyzes the ozone formation from air pollutants, like nitrogen oxides. Since ozone reacts with cutaneous sebum lipids to peroxides and, thus, promotes inflammation, tumorigenesis, and aging, even broad-spectrum sunscreens cannot properly protect skin. Meanwhile, xanthophylls, like fucoxanthin, proved their antioxidant and cytoprotective functions, but the safety of their topical application in human cell-based models remains unknown. Aiming for a more detailed insight into the cutaneous fucoxanthin toxicity, we assessed the tissue viability according to OECD test guideline no. 439 as well as changes in inflammation (IL-1α, IL-6, IL-8), homeostasis (EGFR, HSPB1) and metabolism (NAT1). First, we proved the suitability of our 24-well-based reconstructed human skin for irritation testing. Next, we dissolved 0.5% fucoxanthin either in alkyl benzoate or in ethanol and applied both solutions onto the tissue surface. None of the solutions decreased RHS viability below 50%. In contrast, fucoxanthin ameliorated the detrimental effects of ethanol and reduced the gene expression of pro-inflammatory interleukins 6 and 8, while increasing NAT1 gene expression. In conclusion, we developed an organ-on-a-chip compatible RHS, being suitable for skin irritation testing beyond tissue viability assessment. Fucoxanthin proved to be non-irritant in RHS and already showed first skin protective effects following topical application.

Role of the Aryl Hydrocarbon Receptor in Environmentally Induced Skin Aging and Skin Carcinogenesis

The skin is constantly exposed to a variety of environmental threats, including solar electromagnetic radiation, microbes, airborne particulate matter, and chemicals. Acute exposure to these environmental factors results in the activation of different signaling pathways that orchestrate adaptive stress responses to maintain cell and tissue homeostasis. Chronic exposure of skin to these factors, however, may lead to the accumulation of damaged macromolecules and loss of cell and tissue integrity, which, over time, may facilitate aging processes and the development of aging-related malignancies. One transcription factor that is expressed in all cutaneous cells and activated by various environmental stressors, including dioxins, polycyclic aromatic hydrocarbons, and ultraviolet radiation, is the aryl hydrocarbon receptor (AHR). By regulating keratinocyte proliferation and differentiation, epidermal barrier function, melanogenesis, and immunity, a certain degree of AHR activity is critical to maintain skin integrity and to adapt to acute stress situations. In contrast, a chronic activation of cutaneous AHR signaling critically contributes to premature aging and the development of neoplasms by affecting metabolism, extracellular matrix remodeling, inflammation, pigmentation, DNA repair, and apoptosis. This article provides an overview of the detrimental effects associated with sustained AHR activity in chronically stressed skin and pinpoints AHR as a promising target for chemoprevention.

Traffic-derived air pollution compromises skin barrier function and stratum corneum redox status: A population study

BACKGROUND

Since air pollution is only one of many environmental stressors that can affect skin, it has been challenging to identify skin appearance or functional features profoundly affected by chronic exposure to traffic-derived air pollution.

AIMS

The current population study focused on taxi drivers working in urban and rural areas in order to take advantage of difference in occupational exposure.

METHODS

The skin conditions of 100 middle-aged male taxi drivers from urban Shanghai and 66 from rural Chongming were measured with facial tape strips were collected for biomarker analyses.

RESULTS

Trans-epidermal water loss (TEWL) values before and after tape stripping were considerably higher in urban taxi drivers from Shanghai. Contrary to previous studies, there was no apparent detrimental effect on skin wrinkle or pigmentation from traffic pollution, which might be attributed to the higher than general public level of photo-exposure in this population. At the same time, pollution exposure especially the heavy traffic pollution exposure was found to associate with lower stratum corneum trypsin-like enzyme activity (SCTE), reduced catalase activity and total antioxidant capacity (TAOC) in tape strips.

CONCLUSION

The evidence suggests that traffic-derived air pollution could deteriorate skin's physical and antioxidant barrier, whereas factors like photo-exposure can be overwhelming against appearance aging. Therefore, in addition to photoprotection, skin barrier care should be considered for people with high air pollution exposure.

[Air pollution (particulate matter and nitrogen dioxide) and skin aging]

It has recently been discovered that air pollution can contribute to skin aging. This conclusion is based on both epidemiological and mechanistic evidence. Specifically, exposure to ambient relevant particulate matter and to nitrogen dioxide (NO₂) is associated with an increased risk to develop facial pigment spots. In addition, genetic studies indicate the involvement of gene-environment interactions because women carrying certain genetic variants of the aryl hydrocarbon receptor (AHR) signaling pathway have a higher risk to develop facial pigment spots in response to exposure to particulate matter (PM2.5). Mechanistic studies prove a cause/effect relationship because topical exposure of human skin ex vivo or in vivo to non-toxic concentrations of a standardized diesel exhaust mixture increased skin pigmentation by inducing melanin de novo synthesis via an oxidative stress response. In line with this, cosmetic anti-pollution products containing anti-oxidants, but also AHR antagonists are effective in reducing or preventing this increase in skin pigmentation. Ultraviolet (UV) radiation is another important environmental factor which can cause skin aging and pigment spot formation. In a real exposure situation, human skin is exposed to both environmental factors simultaneously. Corresponding epidemiological studies show that particulate matter present in the troposphere and solar UV radiation interact with each other. These results emphasize that environmentally induced skin aging results from a highly complex process.

A novel water-based anti-aging suncare formulation provides multifaceted protection and repair against environmental aggressors: evidence from in vitro, ex vivo, and clinical studies

Background

Ultraviolet (UV) radiation is an established cause of skin aging, and the role of pollution is increasingly acknowledged. In this study, we evaluated the efficacy of an antipollution and anti-aging suncare product in in vitro, ex vivo, and clinical studies.

Methods

We assessed 1) sunburn cell (SBC) and cyclobutane pyrimidine dimer (CPD) formation and gene expression profile in reconstructed human epidermis following solar irradiation, 2) malondialdehyde (MDA) level, Nrf2 immunostaining, and genetic expression in skin explants exposed to pollution, 3) carbon particle adhesion to healthy forearm skin in a clinical study, and 4) skin firmness, elasticity, and pigmentation spots in healthy women following 56 days of application.

Results

1) The product fully protected against CPD formation, and provided a high protection against SBC formation, with levels close to non-irradiated samples. Expression of genes encoding pro-inflammatory and oxidative stress response markers was lower in product-treated than untreated skin. 2) Compared with pollution-exposed untreated controls, product-treated skin had 23% lower MDA levels (P<0.01), weaker Nrf2 immunostaining, and attenuated upregulation of CYP1A1. 3) The product significantly decreased adhesion of carbon particles to the skin (15.2% less than control; P<0.01). 4) Clinically, product use led to a decrease in brown spots, with a relative reduction in the count of −1.9% (NS), and in area, −5.0% (P<0.01), and decrease in UV spots, with a relative reduction of −6.9% (P<0.01) and −9.3% (P=0.02) for count and area, respectively. Firmness increased significantly by 14.1% (P<0.01). Participants reported skin was more even in tone (80%), more moisturized (93%), and firmer (74%).

Conclusion

This water-based anti-aging SPF50 suncare formulation containing photolyase encapsulated in liposome, active biopeptides, antioxidants, and hyaluronic acid provides multifaceted protection and repair action against pollution and UV-induced skin aging, ideal for everyday use.

Environmental Stressors on Skin Aging. Mechanistic Insights

The skin is the main barrier that protects us against environmental stressors (physical, chemical, and biological). These stressors, combined with internal factors, are responsible for cutaneous aging. Furthermore, they negatively affect the skin and increase the risk of cutaneous diseases, particularly skin cancer. This review addresses the impact of environmental stressors on skin aging, especially those related to general and specific external factors (lifestyle, occupation, pollutants, and light exposure). More specifically, we have evaluated ambient air pollution, household air pollutants from non-combustion sources, and exposure to light (ultraviolet radiation and blue and red light). We approach the molecular pathways involved in skin aging and pathology as a result of exposure to these external environmental stressors. Finally, we reflect on how components of environmental stress can interact with ultraviolet radiation to cause cell damage and the critical importance of knowing the mechanisms to develop new therapies to maintain the skin without damage in old age and to repair its diseases.

Skin protective effects of an antipollution, antioxidant serum containing Deschampsia antartica extract, ferulic acid and vitamin C: a controlled single-blind, prospective trial in women living in urbanized, high air pollution area

Introduction: Air pollution causes skin damage and favors skin aging processes such as dark spots and wrinkles, through oxidative stress. Pollutant substances accelerate skin aging through a specific activation of intracellular receptors called AhR (aryl-hydrocarbon receptors). Deschampsia antartica aqueous extract (DAE) has shown to counteract the pollutant-induced AhR activation. Ferulic acid (FA) and vitamin C (VC) are potent antioxidant substances. A serum containing DAE/FA/VC has been recently developed. So far, no clinical data are available regarding the protective actions of this serum against the detrimental effects of air pollution on the skin. Objective: We conducted a prospective, single-blind, 28-day study to assess efficacy and protective effects against air pollution skin damage of a new serum containing Deschampsia antartica extract. Materials and methods: Twenty, photo type I-III, women (mean age 42 years) with at least three dark spots on the face, living in a homogenous urbanized, high pollution area (Rome) were evaluated. The objectives of the study were to evaluate the effects of treatment on skin barrier function, assessed by transepidermal water loss (TEWL) measurement (Tewameter), the effect on dark spots, evaluated by means of colorimetry (Colorimeter CL 400), and the effect on squalene peroxide (SQOOH)/squalene (SQ) skin ratio assessed with face swabs. Results: The trial was conducted between November 20 and December 19, 2018. In comparison with baseline, the product induced a significant improvement of skin hydration (-19% of TEWL), a significant improvement of dark spots (+7%) and a significant improvement of SQOOH/SQ ratio (-16%). The product was evaluated very well by >90% of the treated subjects regarding cosmetic acceptability. Discussion: A serum containing DAE/FA/VC has shown to improve skin barrier function, to reduce dark spots and to counteract the skin oxidative stress in women living in high pollution urban area.

Mitochondria's Role in Skin Ageing

Skin ageing is the result of a loss of cellular function, which can be further accelerated by external factors. Mitochondria have important roles in skin function, and mitochondrial damage has been found to accumulate with age in skin cells, but also in response to solar light and pollution. There is increasing evidence that mitochondrial dysfunction and oxidative stress are key features in all ageing tissues, including skin. This is directly linked to skin ageing phenotypes: wrinkle formation, hair greying and loss, uneven pigmentation and decreased wound healing. The loss of barrier function during skin ageing increases susceptibility to infection and affects wound healing. Therefore, an understanding of the mechanisms involved is important clinically and also for the development of antiageing skin care products.

The impact of airborne pollution on skin

Indoor and outdoor airborne pollutants modify our environment and represent a growing threat to human health worldwide. Airborne pollution effects on respiratory and cardiac health and diseases have been well established, but its impact on skin remains poorly described. Nonetheless, the skin is one of the main targets of pollutants, which reach the superficial and deeper skin layers by transcutaneous and systemic routes. In this review, we report the outcomes of basic and clinical research studies monitoring pollutant levels in human tissues including the skin and hair. We present a current understanding of the biochemical and biophysical effects of pollutants on skin metabolism, inflammatory processes and oxidative stress, with a focus on polyaromatic hydrocarbons and ground-level ozone that are widespread outdoor pollutants whose effects are mostly studied. We reviewed the literature to report the clinical effects of pollutants on skin health and skin ageing and their impact on some chronic inflammatory skin diseases. We also discuss the potential interactions of airborne pollutants with either ultraviolet radiation or human skin microbiota and their specific impact on skin health.