Modulation of sebum oxidation and interleukin-1α levels associates with clinical improvement of mild comedonal acne

Association of different cell types and inflammation in early acne vulgaris

Acne vulgaris, one of the most common skin diseases, is a chronic cutaneous inflammation of the upper pilosebaceous unit (PSU) with complex pathogenesis. Inflammation plays a central role in the pathogenesis of acne vulgaris. During the inflammatory process, the innate and adaptive immune systems are coordinately activated to induce immune responses. Understanding the infiltration and cytokine secretion of differential cells in acne lesions, especially in the early stages of inflammation, will provide an insight into the pathogenesis of acne. The purpose of this review is to synthesize the association of different cell types with inflammation in early acne vulgaris and provide a comprehensive understanding of skin inflammation and immune responses.

Die Bedeutung von Mikrokomedonen bei der Akne: Von der Beschreibung bis zum Behandlungsansatz?: The role of microcomedones in acne: Moving from a description to treatment target?

Ein wichtiger Faktor in der Pathogenese der Akne vulgaris ist die duktale Hyperproliferation der Talgdrüsen. Diese beginnt mit der Bildung unsichtbarer Mikrokomedonen und führt im weiteren Verlauf zur Ausbildung sowohl entzündlicher als auch nicht‐entzündlicher klinischer Läsionen. Die Mikrokomedonen stehen am Anfang der zyklischen Entwicklung einer Akne, die als Komedogenese bezeichnet wird. Mikrokomedonen können mithilfe von Cyanoacrylat‐Hautablösungen, Elektronenmikroskopie, konfokaler Reflexionsmikroskopie und anderen Techniken nachgewiesen werden. Es wird angenommen, dass die Dichte und Größe von Mikrokomedonen positiv mit dem Schweregrad der Akne korreliert. Ziel dieser Übersichtsarbeit ist es, die Ursachen der Akne zusammenzufassen und darauf hinzuweisen, dass die Behandlung von Mikrokomedonen zumindest teilweise Akneläsionen beseitigen und Rückfälle verhindern könnte.

The role of microcomedones in acne: Moving from a description to treatment target?

A major factor in the pathogenesis of acne is ductal hyperproliferation in the pilosebaceous glands. This takes the form of invisible microcomedones and leads to the subsequent formation of both inflammatory and non-inflammatory clinical lesions. Microcomedones are the initial stage in the cyclical development of acne, so called comedogenesis. Microcomedones can be detected using cyanoacrylate skin surface stripping, electron microscopy, reflection confocal microscopy and other techniques. It has been proposed that the density and the size of microcomedones are positively correlated with acne severity. Thus, the purpose of this review is to summarize the root causes of acne, and suggest that treatment of microcomedones could, at least in part, resolve acne lesions and prevent relapse.

The role of in vivo reflectance confocal microscopy for the management of acne: A systematic review

Acne diagnosis, severity assessment and treatment follow-up rely primarily on clinical examination. In vivo reflectance confocal microscopy (RCM) provides non-invasively, real-time images of skin lesions with a level of detail close to histopathology. This systematic literature review aims to provide an overview of RCM utility in acne and a summary of specific features with clinical application that may increase objectivity in evaluating this condition. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for reporting our results. We systematically searched three databases: PubMed, Clarivate and Google Scholar (January 2022). All included studies used RCM to investigate acne in human patients and reported the investigated skin area and type (acne lesions or clinically uninvolved skin), the substance used in the case of treatment. Our search identified 2184 records in the three databases investigated. After duplicate removal, 1608 records were screened, 35 were selected for full-text assessment, and 14 were included in this review. We used the QUADAS-2 tool to evaluate the risk of bias and applicability concerns. RCM was selected as the index test and clinical examination as the reference standard. The total number of patients from all studies was 291, with 216 acne patients and 60 healthy participants aged between 13 and 45 years. The 14 considered studies analysed 456 follicles from healthy participants, 1445 follicles from uninvolved skin in acne patients and 1472 acne lesions. Consistent RCM findings concerning follicles of acne patients reported across studies were increased follicular infundibulum size, thick, bright border, intrafollicular content and inflammation. Our analysis indicates that RCM is a promising tool for acne evaluation. Nevertheless, standardization, a unified terminology, consistent research methods and unitary reporting of RCM findings are necessary. PROSPERO registration number CRD42021266547.

Oxygen Exposure and Tolerance Shapes the Cell Wall-Associated Lipids of the Skin Commensal Cutibacterium acnes

Cutibacterium acnes is one of the most abundant bacteria on the skin. Being exposed to oxygen and oxic stress, the secretion of the bacterial antioxidant protein RoxP ensures an endogenous antioxidant system for the preservation of skin health. To investigate the impact of the antioxidant RoxP on oxidation of the bacteria, wildtype and an isogenic roxp mutant were cultured in anaerobic and oxic conditions. The carbonylated status of proteins were recorded, as were the most significant modifications in a relative intensity of free fatty acids (FFA) and lipids containing fatty acids (FA), such as di- (DG) and triglycerides (TG), di- (DGDG) and sulfoquinozyldiacylglycerol (SQDG) and ceramides. Concerning the fatty acid types, it was observed that the free fatty acids contained mainly C12:0-C26:0 in hydroxy and acylated forms, the DG contained mainly C29:0-C37:0, the TG contained mainly C19:0-C33:0, and the DGDG/SQDGs contained very long fatty acids (C29:0-C37:0) demonstrating the interdependence of de novo synthesis of lipids and RoxP. The area of DGDG peaks (924.52, 929.56 and 930.58) were affected by bacterial growth conditions, with the exception of m/z 910.61. Moreover, the FFA unsaturation is wider in the SQDG species (C30:0 to C36:6) than in DG, TG or free FFA species. It could be concluded that both environmental oxidative statuses, as well as the prevalence of bacterial antioxidant systems, significantly shape the lipidome of C. acnes.

An optimal method for quantifying the facial sebum level and characterizing facial sebum features

BACKGROUND

Evidence suggests that sebum content is important in skin disorders such as acne. However, sebum levels change depending on the external environment, and quantifying skin sebum levels is challenging. Here, we propose an optimal method for quantifying the facial sebum level.

MATERIALS AND METHODS

Four hundred and sixty participants (160 males and 300 females) aged 20-40 were enrolled in this study. A Sebumeter SM 810 was used to measure the sebum level at five facial locations: the forehead, the chin, the left cheek, the right cheek, and the nose. The participants were divided into two groups; one group underwent a one-time measurement (n = 390, male: female = 120: 270), and the other underwent three consecutive measurements (n = 70, male: female = 40: 30). The casual sebum level (CSL) was measured in all patients after a 30-min acclimatization; subsequently, the sebum removal process was conducted, followed by a resting period of 1 h to determine the sebum excretion rate (SER). Spearman's correlation analysis and the Wilcoxon signed-rank test were used to compare the sebum level consistency and differences between the groups.

RESULTS

Although three consecutive measurements better reflected the sebum content, the one-time measurement also represented the relative sebum level. One hour after sebum removal, the sebum level recovered to 70%-90%; thus, this method was applicable for use in SER quantification. Of the five testing points, the sebum content was highest in the nose and lowest in the cheeks (both left and right). In addition, the cheeks were the most stable sites in terms of testing points, testing times, and CSL/SER values. A one-time measurement of the CSL could represent the SER 1 h after the sebum removal. In our cohort, the sebum level of males with oily skin was decreased at age 32-35, and that of males with non-oily skin increased at 28-35. The opposite trend was observed in female participants.

CONCLUSION

Sebum measurement methods were assessed, including testing times, indices (interval of time) and sites in a conditioned external environment. A one-time measurement of the CSL 1 h after sebum removal was sufficient to determine the sebum level and SER, and the cheeks are recommended as the testing site. Sex and skin type differences were observed in sebum level changes with age.

Markers of Oxidative Stress in Patients with Acne: A Literature Review

Acne vulgaris is a chronic inflammatory skin disease of the pilosebaceous unit. Its pathogenesis is multifactorial and involves the overlap between four main processes: alteration of the keratinization, increased sebum production, colonization with Cutibacterium acnes, and inflammation. The role of oxidative stress (OS) has been intensively studied in inflammatory skin conditions such as psoriasis, vitiligo, or atopic dermatitis. However, the involvement of OS in the pathogenesis of acne is less known. The evidence accumulated over the last decade suggests that in the case of acne patients, there is an imbalance between oxidants and antioxidants. In this review, we analyzed studies that evaluated markers of OS in patients with acne, published in the last ten years, with the aim of providing new insights into the pathogenesis of acne.

Environmental Air Pollutants Affecting Skin Functions with Systemic Implications

The increase in air pollution worldwide represents an environmental risk factor that has global implications for the health of humans worldwide. The skin of billions of people is exposed to a mixture of harmful air pollutants, which can affect its physiology and are responsible for cutaneous damage. Some polycyclic aromatic hydrocarbons are photoreactive and could be activated by ultraviolet radiation (UVR). Therefore, such UVR exposure would enhance their deleterious effects on the skin. Air pollution also affects vitamin D synthesis by reducing UVB radiation, which is essential for the production of vitamin D3, tachysterol, and lumisterol derivatives. Ambient air pollutants, photopollution, blue-light pollution, and cigarette smoke compromise cutaneous structural integrity, can interact with human skin microbiota, and trigger or exacerbate a range of skin diseases through various mechanisms. Generally, air pollution elicits an oxidative stress response on the skin that can activate the inflammatory responses. The aryl hydrocarbon receptor (AhR) can act as a sensor for small molecules such as air pollutants and plays a crucial role in responses to (photo)pollution. On the other hand, targeting AhR/Nrf2 is emerging as a novel treatment option for air pollutants that induce or exacerbate inflammatory skin diseases. Therefore, AhR with downstream regulatory pathways would represent a crucial signaling system regulating the skin phenotype in a Yin and Yang fashion defined by the chemical nature of the activating factor and the cellular and tissue context.

Protective Effects of Naringenin and Apigenin in Ameliorating Skin Damage via Mediating the Nrf2 and NF-κB Pathways in Mice

Naringenin and apigenin are common flavonoids derived from edible plants with the potential to alleviate inflammation and improve skin antioxidation. This study aimed to evaluate the effects of naringenin and apigenin on oleic acid-induced skin damage in mice and compare their underlying mechanisms of action. Triglycerides and non-esterified fatty acids were significantly decreased by naringenin and apigenin, while apigenin intervention resulted in a better recovery of skin lesions. Naringenin and apigenin improved the antioxidative abilities of the skin by increasing catalase and total antioxidant capacity levels and decreasing malondialdehyde and lipid peroxide levels. The release of skin proinflammatory cytokines, such as interleukin (IL)-6, IL-1β, and tumor necrosis factor α, was inhibited after naringenin and apigenin pretreatments, but naringenin only promoted the excretion of IL-10. Additionally, naringenin and apigenin regulated antioxidant defense and inflammatory response by activating nuclear factor erythroid-2 related factor 2-dependent mechanisms and suppressing the expression of nuclear factor-kappa B. In summary, naringenin and apigenin are prospective ingredients that contribute to the amelioration of skin damage by activating anti-inflammatory and antioxidative responses.

Confocal microscopy and optical coherence tomography of inflammatory skin diseases in hairs and pilosebaceous units: A systematic review

Common skin disorders such as acne vulgaris, rosacea and folliculitis are bothersome prevalent inflammatory diseases of hair follicles that can easily be investigated bedside using optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) with micrometre resolution, opening a novel era for high-resolution hair follicle diagnostics and quantitative treatment evaluation. EMBASE, PubMed and Web of Science were searched until 5 January 2023 to identify all studies imaging hair follicle characteristics by RCM and OCT for diagnosis and monitoring of treatment in hair follicle-based skin disorders. This study followed PRISMA guidelines. After inclusion of articles, methodological quality was assessed using the QUADAS-2 critical appraisal checklist. Thirty-nine in vivo studies (33 RCM and 12 OCT studies) were included. The studies focused on acne vulgaris, rosacea, alopecia areata, hidradenitis suppurativa, folliculitis, folliculitis decalvans, lichen planopilaris, discoid lupus erythemasus, frontal fibrosing alopecia and keratosis pilaris. Inter- and perifollicular morphology including number of demodex mites, hyperkeratinization, inflammation and vascular morphology could be assessed by RCM and OCT in all included skin disorders. Methodological study quality was low, and interstudy outcome variability was high. Quality assessment showed high or unclear risk of bias in 36 studies. Both RCM and OCT visualize quantitative features as size, shape, content and abnormalities of hair follicles, and have potential to support clinical diagnosis and evaluate treatment effects. However, larger studies with better methodological quality are needed to implement RCM and OCT directly into clinical practice.

Reactive Oxygen Species and Antioxidant System in Selected Skin Disorders

The skin has a solid protective system that includes the stratum corneum as the primary barrier and a complete antioxidant defence system to maintain the skin's normal redox homeostasis. The epidermal and dermal cells are continuously exposed to physiological levels of reactive oxygen species (ROS) originating from cellular metabolic activities. Environmental insults, such as ultraviolet (UV) rays and air pollutants, also generate ROS that can contribute to structural damage of the skin. The antioxidant defence system ensures that the ROS level remains within the safe limit. In certain skin disorders, oxidative stress plays an important role, and there is an established interplay between oxidative stress and inflammation in the development of the condition. Lower levels of skin antioxidants indicate that oxidative stress may mediate the pathogenesis of the disorder. Accordingly, the total antioxidant level was also found to be lower in individuals with skin disorders in individuals with normal skin conditions. This review attempts to summarise the skin oxidant sources and antioxidant system. In addition, both skin and total antioxidant status of individuals with psoriasis, acne vulgaris, vitiligo and atopic dermatitis (AD), as well as their associations with the progression of these disorders will be reviewed.

Dermoscopy, Reflectance Confocal Microscopy and Optical Coherence Tomography Features of Acne: A Systematic Review

Noninvasive imaging techniques have recently outlined precise microscopic features of acne elementary lesions and accurate quantifications for disease severity staging and therapeutical efficacy follow-up. The aim of this review is to systematically describe current applications of dermoscopy, reflectance confocal microscopy (RCM), and optical coherence tomography (OCT) in acne vulgaris assessment and management. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. We included studies conducted on human subjects with elementary lesions of acne vulgaris, reporting assessment of the lesions with dermoscopy, RCM, and/or OCT. At present there are few large studies regarding acne and noninvasive imaging techniques, representing the main limitation of this review. Clinical examination represents the first line in acne diagnosis and treatment. However, dermoscopy, RCM, and OCT are further tools that can improve acne classification, monitoring of treatment, and pathophysiologic characterization. In the near future, dermoscopy, RCM, and OCT could become routinely used for the evaluation of acne vulgaris to provide a deeper knowledge of the disease and to guide the clinician in the prescription of tailored treatment protocols based on each patient’s characteristics.

Lipidomics of facial sebum in the comparison between acne and non-acne adolescents with dark skin

Lipidomics is advantageous in the study of sebum perturbations occurring in acne. An extended evaluation of the sebum lipid profiles in acne-prone sebaceous areas is lacking in dark skin. Yet, there is a void space in understanding how the building blocks of sebum lipids, i.e. individual fatty acids (FAs), are intertwined with acne-prone skin. We aimed to determine the sebum lipidome in facial areas of adolescents with and without acne in Nigeria. A cross-sectional analytical study was conducted in 60 adolescents/young adults divided in 30 acne patients (15F, 15M) and 30 age and sex-matched controls. Sebum samples obtained from foreheads and cheeks were analysed separately by gas chromatography–mass spectrometry (GCMS) and thin layer chromatography (HPTLC). Distributions of sebum components were investigated with multivariate ANOVA-simultaneous component analysis (ASCA). Sebum incretion in acne was paralleled by significantly higher abundance of triglycerides, wax esters, and squalene together with monounsaturated FAs (MUFAs), and straight chain saturated FAs (SFAs), especially those with odd-carbon chain, i.e. C13:0, C15:0, and C17:0. Profiling weight/weight percentage of individual components revealed that, in acne, the free FAs (FFAs) array was shifted towards higher relative abundance of the SFAs C15:0, C16:0, and C17:0 and lower percentage of the anteiso-branched FFAs with 12, 14, 16, and 18 carbons. In acne patients, MUFAs and PUFAs were quantitatively increased and decreased on foreheads and cheeks, respectively. Relative abundance of fatty alcohols was decreased in acne independent on the site. The results indicated that acne associates with site-specific derangement of the pathways regulating the balance among odd straight-chain and branched-chain SFAs, MUFAs, which included sapienate (C16:1n-10), PUFAs, and squalene.

Hidradenitis suppurativa is an autoinflammatory keratinization disease: A review of the clinical, histologic, and molecular evidence

The pathogenic model of hidradenitis suppurativa is in the midst of a paradigm shift away from a disorder of primary follicular occlusion to an autoinflammatory keratinization disease. Observational, experimental, and therapeutic evidence supports the concept of hidradenitis suppurativa as a primarily inflammatory disorder, a disorder of autoimmunity, or both, in contrast to the current prevailing paradigm of primary follicular occlusion. The lack of reliable and high-fidelity disease models has limited the available experimental and mechanistic evidence to support or refute one pathogenic model over another. This scholarly review synthesizes the existing clinical, histologic, and molecular data to evaluate the extant evidence supporting the autoinflammatory paradigm and further informing the molecular mechanisms of hidradenitis suppurativa pathogenesis. Follicular hyperkeratosis/occlusion and perifollicular inflammation coexist in histologic specimens, with interleukin 1α demonstrated to stimulate comedogenesis in the infundibulum. pH elevation in occluded body sites alters the microbiome and amplifies existing T-helper cell type 17 immunoresponses. Known metabolic comorbidities and smoking are known to upregulate interleukin 1α in follicular keratinocytes. Identified genetic variants may alter epidermal growth factor receptor signaling, leading to upregulated keratinocyte inflammatory responses. The process of follicular rupture and dermal tunnel formation can be explained as secondary responses to inflammatory activation of fibroblasts and epithelial-mesenchymal transition, with antibody production associated with inflammatory amplification in advanced disease. This review aims to reevaluate and integrate the current clinical, histologic, and molecular data into a pathogenic model of hidradenitis suppurativa. This is essential to advance our understanding of the disease and identify novel therapeutic targets and approaches.

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.

Current Insights into the Biological Action of Squalene

Squalene is a triterpenic compound found in a large number of plants and other sources with a long tradition of research since it was first reported in 1926. Herein a systematic review of studies concerning squalene published in the last 8 years is presented. These studies have provided further support for its antioxidant, anti-inflammatory, and anti-atherosclerotic properties in vivo and in vitro. Moreover, an antineoplastic effect in nutrigenetic-type treatments, which depends on the failing metabolic pathway of tumors, has also been reported. The bioavailability of squalene in cell cultures, animal models, and in humans has been well established, and further progress has been made in regard to the intracellular transport of this lipophilic molecule. Squalene accumulates in the liver and decreases hepatic cholesterol and triglycerides, with these actions being exerted via a complex network of changes in gene expression at both transcriptional and post-transcriptional levels. Its presence in different biological fluids has also been studied. The combination of squalene with other bioactive compounds has been shown to enhance its pleiotropic properties and might lead to the formulation of functional foods and nutraceuticals to control oxidative stress and, therefore, numerous age-related diseases in human and veterinary medicine.

Influence of the sebaceous gland density on the stratum corneum lipidome

The skin surface lipids (SSL) result from the blending of sebaceous and epidermal lipids, which derive from the sebaceous gland (SG) secretion and the permeability barrier of the stratum corneum (SC), respectively. In humans, the composition of the SSL is distinctive of the anatomical distribution of the SG. Thus, the abundance of sebum biomarkers is consistent with the density of the SG. Limited evidence on the influence that the SG exerts on the SC lipidome is available. We explored the differential amounts of sebaceous and epidermal lipids in areas at different SG density with lipidomics approaches. SC was sampled with adhesive patches from forearm, chest, and forehead of 10 healthy adults (8F, 2M) after mechanical removal of sebum with absorbing paper. Lipid extracts of SC were analysed by HPLC/(-)ESI-TOF-MS. In the untargeted approach, the naïve molecular features extraction algorithm was used to extract meaningful entities. Aligned and normalized data were evaluated by univariate and multivariate statistics. Quantitative analysis of free fatty acids (FFA) and cholesterol sulfate (CHS) was performed by targeted HPLC/(-)ESI-TOF-MS, whereas cholesterol and squalene were quantified by GC-MS. Untargeted approaches demonstrated that the relative abundance of numerous lipid species was distinctive of SC depending upon the different SG density. The discriminating species included FFA, CHS, and ceramides. Targeted analyses confirmed that sebaceous FFA and epidermal FFA were increased and decreased, respectively, in areas at high SG density. CHS and squalene, which are biomarkers of epidermal and sebaceous lipid matrices, respectively, were both significantly higher in areas at elevated SG density. Overall, results indicated that the SG secretion intervenes in shaping the lipid composition of the epidermal permeability barrier.

Perianal Comedones: A Rare Incidental Finding

Comedones occur when an overproliferation of keratinocytes blocks sebum secretion in a pilosebaceous duct. Comedones have multiple possible etiologies and contributing factors. While comedones are common to acne, they are also seen in occupational exposures and are associated with certain syndromes. We describe a particularly rare case of comedones at the perianus that is not associated with any known exposure or disease and is a rare incidental finding.