Immunological Aspects of Skin Aging in Atopic Dermatitis

The novel house dust mite allergen Der p 39 exacerbates atopic dermatitis-like inflammation in mice by inducing skin barrier dysfunction

Background

House dust mite (HDM) allergens can induce or exacerbate allergic inflammation, including atopic dermatitis (AD). Substances that damage the epithelial barrier can trigger or worsen AD. The mechanism by which the novel HDM allergen Der p 39 induces allergic inflammation remains unclear. Our aim was to investigate the effects of Der p 39 on AD-like inflammation and associated mechanisms.

Methods

Dinitrochlorobenzene (DNCB) and Der p 39 were utilized to establish AD model mice. Inflammation severity was evaluated with physiological and morphological assays. The effects of Der p 39 on inflammatory cytokine release and skin barrier protein expression were examined in HaCaT cells (human epidermal keratinocytes). Mitogen-activated protein kinase (MAPK) activation was examined by western blots. MAPK inhibitors were employed to assess MAPK involvement in filaggrin expression.

Results

Der p 39 worsened allergic inflammation (tissue thickness) in murine ears pretreated with 1% DNCB. Compared to controls, Der p 39-sensitized tissues showed epidermal and dermal thickening with elevated numbers of mast cells and eosinophils in inflammatory lesions. Der p 39 increased transcription and production of pro-inflammatory interleukins (ILs), down-regulated expression of the skin barrier proteins filaggrin and loricrin, and upregulated phosphorylation of ERK, JNK and p38 in HaCaT cells. Inhibition of MAPK signaling rescued filaggrin expression in Der p 39-treated cells.

Conclusions

The HDM allergen Der p 39 enhances allergic inflammation and promotes MAPK pathway-mediated epidermal barrier dysfunction, suggesting that Der p 39 may possess pathogenic and clinically relevant immunomodulatory potential.

Upadacitinib Dose Reduction Regimen in Elderly Patients with Atopic Dermatitis, Guided by Treat-to-Target Consensus Recommendations

BACKGROUND

The effectiveness of Janus kinase (JAK) inhibitors in treating atopic dermatitis (AD) is well established. However, little is known about whether disease control can be maintained with longer dosing intervals, especially in older patients who are at higher risk of adverse events from JAK inhibitors. The treat-to-target (T2T) consensus was established to guide systemic treatment in adults with AD, aiming to achieve disease control promptly and sustain it in the long term.

OBJECTIVE

The aim of this study was to evaluate the efficacy and safety of extended JAK inhibitor dosing intervals based on the T2T consensus in older adults.

METHODS

A prospective observational cohort study was conducted from July 2022 to February 2024. Fifty-eight elderly patients (aged ≥ 65 years) were included in the study and received upadacitinib with gradually longer dosing intervals. The primary outcome was the proportion of patients maintaining different treatment dosing intervals at the end of the follow-up, as well as the assessment of six scales at every visit.

RESULTS

Among the 58 patients (median [IQR] age, 70 [68-77] years) included in the study, 86.2% completed the 1-year follow-up. By the last visit, among those who completed the follow-up, 26.0% maintained a dosing interval of every 3 days, and 72.0% maintained a dosing interval of every 2 days. The overall incidence of adverse events (AEs) was 29.3% among all patients, with the most common AE reported being herpes virus infection (13.8%).

CONCLUSIONS

The dose reduction regimen guided by the T2T consensus was well tolerated in elderly patients with moderate-to-severe AD. Prolonging dosing intervals offers potential benefits for both patients and socioeconomic outcomes.

Influences on Skin and Intrinsic Aging: Biological, Environmental, and Therapeutic Insights

BACKGROUND/AIM

Aging involves a progressive deterioration in physiological functions and increased disease susceptibility, impacting all organs and tissues, especially the skin. Skin aging is driven by intrinsic factors (genetics, cellular metabolism) and extrinsic factors (environment, lifestyle). Understanding these mechanisms is vital for promoting healthy aging and mitigating skin aging effects. This review aims to summarize the key factors influencing skin and intrinsic aging, providing a comprehensive understanding of the underlying mechanisms and contributing elements.

METHODS

A comprehensive literature review was conducted, focusing on peer-reviewed journals, clinical studies, and scientific reviews published within the last two decades. The inclusion criteria prioritized studies that addressed intrinsic and extrinsic mechanisms of skin aging. To ensure the relevance and quality of the selected sources, a systematic approach was used to assess study design, sample size, methodology, and the significance of the findings in the context of skin aging.

FINDINGS

The review identifies major internal factors, such as cellular senescence, genetic predisposition, telomere shortening, oxidative stress, hormonal changes, metabolic processes, and immune system decline, as pivotal contributors to intrinsic aging. External factors, including UV radiation, pollution, lifestyle choices (diet, smoking, alcohol consumption, and sleep patterns), and skincare practices, significantly influence extrinsic skin aging. The interplay between these factors accelerates aging processes, leading to various clinical manifestations like wrinkles, loss of skin elasticity, pigmentation changes, and texture alterations.

CONCLUSION

A comprehensive understanding of both extrinsic and intrinsic factors contributing to skin aging is essential for developing effective prevention and intervention strategies. The insights gained from this review highlight the importance of a multifaceted approach, incorporating lifestyle modifications, advanced skincare routines, and emerging therapeutic technologies, to mitigate the effects of aging and promote healthier, more resilient skin.

Achievement of Optimal Treatment Targets with Oral Janus Kinase Inhibition in Elderly Patients with Atopic Dermatitis: A Real-world, Multicenter, Retrospective Study

Objective

Oral Janus kinase inhibitors (JAKi) have demonstrated high levels of efficacy with acceptable safety in patients with atopic dermatitis (AD), yet there remains significant hesitancy among the dermatologic community to use JAKi in elderly populations due to the potential increased risk of serious adverse events in this population. We aimed to perform a retrospective review to describe real-world outcomes for the use of selective JAK-1 inhibitors in patients with AD aged 65 years or older.

Methods

We conducted a multicenter retrospective review. AD cases were identified by ICD-10-CM codes L20.8/L20.89/L20.9. Patients aged 65 years or older years treated with a selective JAK-1 inhibitor were included. Body surface area (BSA), Investigator Global Assessment (IGA), and Peak Pruritus Numerical Rating Scale (NRS) were collected and evaluated independently.

Results

Thirty-eight AD cases in patients aged 65 years or older treated with a selective JAK-1 inhibitor were identified. Patients were aged 65 to 96 years, and treatment duration ranged from 4 to 28 months. Thirty-six out of 38 patients (94.7%) tolerated treatment well; one was switched to another JAKi due to mood lability and another paused therapy during hospitalization for septic pneumonia. Thirty-five out of 37 (94.6%) patients achieved an IGA of 0/1, 28/30 (93.3%) achieved an NRS of 0/1, and 30/30 (100%) had a peak pruritus response with improvement of ≥4 points on NRS. There were no clinically meaningful laboratory abnormalities throughout the treatment course. No laboratory abnormality resulted in treatment discontinuation.

Limitations

Limitations of this retrospective review include selection bias and missing data.

Conclusion

We demonstrate the ability to achieve optimal treatment targets and safety of selective JAKi-1 inhibitors in elderly patients with AD.

Preparation and Properties of the Sodium Hyaluronate Composite Hydrogel for Medical Cosmetology

As society advances, an increasing number of people are focusing on the antiaging process of the body and seeking ways to maintain youthful facial features. Intradermal injection has been used to effectively improve the rough and wrinkled skin, playing a role in skin rejuvenation. However, the main component of intradermal injection products is cross-linked sodium hyaluronate (SHA), which has biological toxicity and potential carcinogenicity. In this study, amino acids were used as hyaluronidase inhibitors and combined with non-cross-linked SHA to prepare a synergically stable SHA composite hydrogel. The effects of amino acids on the viscosity and enzyme activity of the hydrogel were investigated. To determine the stability and antioxidant properties of the composite hydrogel, the effects of the introduction of stabilizer and antioxidant on the hydrogel properties were systematically studied. The results of the in vitro study showed that the introduction of amino acids effectively reduced the activity of hyaluronidase, addressing the problem of rapid hydrolysis and the short half-life of SHA hydrogel in vivo. In addition, the results revealed that NaCl stabilizer, niacinamide, and vitamin B12 antioxidants effectively maintained the stability and antioxidant properties of the hydrogels. In vivo results showed that SHA composite hydrogels had no irritating effect on the skin, and the subcutaneous experiments of mice showed that SHA composite hydrogel still retained a high content after 4 weeks. Therefore, the SHA composite hydrogels have promising applications in the field of medical cosmetology.

Quantum Sensing Unravels Antioxidant Efficacy Within PCL/Matrigel Skin Equivalents

Skin equivalents (SE) that recapitulate biological and mechanical characteristics of the native tissue are promising platforms for assessing cosmetics and studying fundamental biological processes. Methods to achieve SEs with well-organized structure, and ideal biological and mechanical properties are limited. Here, the combination of melt electrowritten PCL scaffolds and cell-laden Matrigel to fabricate SE is described. The PCL scaffold provides ideal structural and mechanical properties, preventing deformation of the model. The model consists of a top layer for seeding keratinocytes to mimic the epidermis, and a bottom layer of Matrigel-based dermal compartment with fibroblasts. The compressive modulus and the biological properties after 3-day coculture indicate a close resemblance with the native skin. Using the SE, a testing system to study the damage caused by UVA irradiation and evaluate antioxidant efficacy is established. The effectiveness of Tea polyphenols (TPs) and L-ascorbic acid (Laa) is compared based on free radical generation. TPs are demonstrated to be more effective in downregulating free radical generation. Further, T1 relaxometry is used to detect the generation of free radicals at a single-cell level, which allows tracking of the same cell before and after UVA treatment.

Exploring mechanisms of skin aging: insights for clinical treatment

The skin is the largest organ in the human body and is made up of various cells and structures. Over time, the skin will age, which is not only influenced by internal factors, but also by external environmental factors, especially ultraviolet radiation. Aging causes immune system weakening in the elderly, which makes them more susceptible to dermatosis, such as type 2 inflammatory mediated pruritus. The immune response in this condition is marked by senescent cells consistently releasing low amounts of pro-inflammatory cytokines through a senescence-associated secretory phenotype (SASP). This continuous inflammation may accelerate immune system aging and establish a connection between immune aging and type 2 inflammatory skin diseases. In addition, two chronic pigmentation disorders, vitiligo and chloasma, are also associated with skin aging. Aged cells escape the immune system and accumulate in tissues, forming a microenvironment that promotes cancer. At the same time, "photoaging" caused by excessive exposure to ultraviolet radiation is also an important cause of skin cancer. This manuscript describes the possible links between skin aging and type 2 inflammation, chronic pigmentation disorders, and skin cancer and suggests some treatment options.

Real-world efficacy of 2% crisaborole ointment on chronic hyperplasia lesions in 49 patients with atopic dermatitis

BACKGROUND

Crisaborole, as a phosphodiesterase 4 (PDE4) inhibitor (PDE4i), effectively inhibits inflammatory pathways, showing promising results in atopic dermatitis (AD), particularly in chronic hyperplasia lesions.

OBJECTIVES

Based on real-world data from China, this study assesses the effectiveness and safety of 2% PDE4i ointment as monotherapy for chronic hyperplastic AD lesions.

MATERIALS AND METHODS

A total of 49 AD patients aged 12 and above with chronic hyperplastic lesions and Investigator's Static Global Assessment scores of mild or moderate were enrolled. They received 2% PDE4i ointment twice daily until the lesions completely cleared. The effectiveness endpoints comprised the onset time of pruritus and lesion remission and the time of complete lesion clearance.

RESULTS

PDE4i demonstrated high effectiveness with minimal irritation, notable improvement in hyperpigmentation, and early remission of pruritus and lesions. The response varied across age groups; elderly patients experienced quicker pruritus relief compared to adolescents and adults, while adolescents showed earlier lesion remission by about 3 days. No significant difference was observed across age groups in the time for complete lesion clearance. Additionally, AD duration (less or more than 3 years) did not significantly impact pruritus or lesion remission.

CONCLUSIONS

PDE4i monotherapy is effective and safe for chronic hyperplasia lesions in AD across all age groups, and its effectiveness appears to be independent of AD duration.

Diagnosis and Management of Common Inflammatory Skin Diseases in Older Adults

Inflammatory skin conditions affect people of all ages, genders, and races. These common conditions are frequent causes of visits to the dermatologist. The geriatric population is often afflicted by these conditions because many are chronic and relapsing diseases. These inflammatory conditions include but are not limited to psoriasis, atopic dermatitis, contact dermatitis, seborrheic dermatitis, rosacea, and Grover disease. Chronic inflammatory skin conditions place a large burden on the health care system in the United States and have many associated comorbidities. This article discusses these inflammatory dermatoses that affect the geriatric population and common therapeutic options.

The efficacy and immunological effects of upadacitinib in the treatment of moderate-to-severe Chinese atopic dermatitis patients

Upadacitinib has received approval for the treatment of atopic dermatitis (AD) with favorable response in clinical trials. However, real-world research on its efficacy remains relatively limited. To bridge this gap, we conducted a prospective cohort study involving 25 Chinese patients with moderate-to-severe AD. These patients received a daily dose of 15 mg of upadacitinib. Our objective was to assess the real-world efficacy of upadacitinib and its impact on the immune system. Clinical assessments were conducted at baseline, 4 weeks, 8 weeks, and 12 weeks following treatment initiation. The findings revealed that upadacitinib treatment significantly improved the clinical scores of the patients. Regarding immunological markers, upadacitinib led to a significant reduction in peripheral blood eosinophils, as well as a decrease in neutrophil count. Furthermore, upadacitinib treatment resulted in an overall decrease in Th1, Th2, and Th17/22-type cytokines, as well as other inflammatory factors. Importantly, for the first time, we observed a notable reduction in both IL-22+CD4+ T cells and serum IL-22 levels in all treated patients, including those with recalcitrant AD who had previously shown inadequate responses to systemic treatments like dupilumab. Currently, international guidelines position upadacitinib as a second-line option following the failure of systemic treatments like dupilumab. Our findings provide valuable insights into the real-world effectiveness and immunological impacts of upadacitinib, which can aid in better understanding and implementation of the drug in clinical practice.

Current and Emerging Therapies for Atopic Dermatitis in the Elderly

Atopic dermatitis (AD) in the elderly has recently emerged as a distinct subgroup of AD, garnering widespread concern due to its increasing global incidence rate. Epidermal barrier dysfunction, inflammatory response, and chronic pruritus interact with each other, contributing to the pathogenesis and pathophysiology of AD in the elderly. Although fundamental medications are essential for managing AD in the elderly, older adults often struggle with regular usage of moisturizing emollients, topical medications, and avoidance of environmental triggers, leading to recurrent or even exacerbated disease progression. Therefore, a systematic medication approach is necessary to control pruritus and skin lesions. Traditional systemic treatments may not adequately meet the treatment needs of moderate and severe AD in the elderly and may even pose certain safety risks. Biologics and Janus kinase (JAK) inhibitors, exhibiting excellent clinical efficacy, have made significant breakthroughs in AD treatment. Existing evidence suggests that dupilumab, a human monoclonal IgG4 antibody, has been confirmed as an effective and safe first-line systematic treatment for moderate to severe AD in the elderly, with no notable differences between adults and the elderly. However, the limited inclusion of elderly patients in related clinical studies hinders the generalizability of these findings. As older patients face a higher risk of adverse events with JAK inhibitors, JAK inhibitors are recommended when no other suitable treatment options are available. Obtaining population-specific data is crucial for making evidence-based treatment choices when managing AD in older adults with JAK inhibitors.

Gene signature from cutaneous autoimmune diseases provides potential immunotherapy-relevant biomarkers in melanoma

Immune checkpoint inhibitors (ICIs) are promising agents for treating melanoma. Given that autoimmune skin diseases exhibit hyper immune reaction, investigation of immune cells from autoimmune skin disease is crucial to validate the effectiveness of ICIs in melanoma treatment. We employed multipanel markers to predict the response to immune checkpoint inhibitors by characterizing the gene expression signatures of skin immune cells in systemic lupus erythematosus (SLE), atopic dermatitis (AD), and psoriasis (PS). By analyzing single-cell RNA sequencing data from each dataset, T cell gene signatures from autoimmune skin diseases exhibit a complex immune response in tumors that responded to immunotherapy. Based on that CD86 and CD80 provide essential costimulatory signals for T cell activation, we observed that interaction of CD86 signaling has been enhanced in the T cells of patients with SLE, AD, and PS. Our analysis revealed a common increase in CD86 signals from dendritic cells (DCs) to T cells in patients with SLE, AD, and PS, confirming that dendritic cells produce pro-inflammatory cytokines to activate T cells. Thus, we hypothesize that T cell gene signatures from autoimmune skin diseases exhibit a pro-inflammatory response and have the potential to predict cancer immunotherapy. Our study demonstrated that T cell gene signatures derived from inflammatory skin diseases, particularly SLE and PS, hold promise as potential biomarkers for predicting the response to immune checkpoint blockade therapy in patients with melanoma. Our data provide an understanding of the immune-related characteristics and differential gene expression patterns in autoimmune skin diseases, which may represent promising targets for melanoma immunotherapy.

Atopic Dermatitis and the Risk of Myocardial Infarction and All-Cause Mortality: A Nationwide Population-Based Cohort Study

PURPOSE

Atopic dermatitis (AD) is a chronic inflammatory skin disorder associated with various comorbidities. However, inconsistent results on the risk of myocardial infarction (MI) and mortality have been reported in patients with AD. This study was aimed to evaluate the risk of MI and all-cause mortality in patients with AD.

METHODS

This nationwide population-based retrospective cohort study enrolled 56,205 adults ≥ 20 years of age with AD and 3,825,609 controls without AD from the Korean National Health Service (NHIS) database from 2009 to 2016.

RESULTS

The risk of MI (adjusted hazard ratio [aHR], 1.111, 95% confidence interval [CI], 1.050-1.176) was increased in patients with AD. By AD severity, patients with moderate-to-severe AD had a higher risk of MI (aHR, 1.163, 95% CI, 1.080-1.251) than individuals without AD. The risk of all-cause mortality was only increased for patients with moderate-to-severe AD (aHR, 1.096, 95% CI, 1.040-1.155) compared to individuals without AD. In subgroup analysis, an increased risk of MI was observed in female, non-obese, non-smoking, non-diabetic, and non-dyslipidemic patients with moderate-to-severe AD compared to individuals without AD. An increased risk of all-cause mortality was observed in patients with moderate-to-severe AD compared to non-AD controls among individuals ≥60 years of age and non-smokers.

CONCLUSIONS

The risk of MI and all-cause death was increased in patients with moderate-to-severe AD. Even without well-known risk factors for MI and mortality, patients with AD require the proper management and screening for comorbidities to prevent MI and decrease all-cause mortality.

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.

The role of cytokines/chemokines in an aging skin immune microenvironment

Reversing or slowing down the skin aging process is one of the most intriguing areas of focus across the social and scientific communities around the world. While aging is considered a universal and inevitable natural process of physiological decline, the aging of the skin is the most apparent visual representation of an individual's health. Aging skin may be objectively defined by epidermal thinning; increased transepidermal water loss; decreased cutaneous barrier function; loss of elasticity, laxity, and textured appearance; and gradual deterioration of the epidermal immune environment. As the largest structure of the immune system and of the body as a whole, the skin is the most vulnerable barrier of defense against the environment. The skin reflects an individual's exposures, lifestyle habits, and overall health. From an immunological perspective, cytokines and chemokines act as a central character in the communicating of the immunity in skin aging. These cell signaling proteins serve as the intercellular communication link. This review aims to elucidate how cell-cell crosstalk through cytokines and chemokines, and the interplay between host cells, infiltrating immune cells, and exogenous factors contribute to the overall aging skin.

High expression level of homocitrulline is correlated with seborrheic keratosis and skin aging

BACKGROUD

Homocitrulline (Hcit), is involved in the pathological processes of some diseases. However, the role and function of Hcit (CBL) in human skin remains largely obscure.

OBJECTIVE

To investigate the correlation of the level of Hcit in seborrheic keratosis, skin aging, and its clinical significance.

METHODS

Immunohistochemistry was used to analyze the level of Hcit in skin lesions of seborrheic keratosis (SK), unaffected skin (distant 0.5 centimeters from SK lesion), and normal skin of healthy subjects in the control group. ELISA test was used to detect the serum level of CBL in SK patients and healthy subjects of different ages.

RESULTS

Hcit was mainly localized in the nucleus of epidermal cells. In healthy control skin, the expression of Hcit increased with age and showed a positive correlation with age (the correlation coefficient was 0.806, p = 0.0002). The expressional level of Hcit in SK lesions was higher than that in healthy control skin (Z = -3.703, p = 0.0002). The serum level of CBL in healthy subjects and in SK patients increased with age (the correlation coefficient were 0.5763, p = 0.0032; 0.682, p = 0.004. respectively). The serum level of CBL in SK patients was higher than that in healthy subjects (Z = -2.19, p = 0.030).

STUDY LIMITATIONS

The small serum sample size in the study.

CONCLUSION

The high expressional level of Hcit is correlated with seborrheic keratosis and skin aging. Hcit may be one of the potential biomarkers of skin aging.

Neuroendocrine signaling in the skin with a special focus on the epidermal neuropeptides

The skin, which is comprised of the epidermis, dermis, and subcutaneous tissue, is the largest organ in the human body and it plays a crucial role in the regulation of the body's homeostasis. These functions are regulated by local neuroendocrine and immune systems with a plethora of signaling molecules produced by resident and immune cells. In addition, neurotransmitters, endocrine factors, neuropeptides, and cytokines released from nerve endings play a central role in the skin's responses to stress. These molecules act on the corresponding receptors in an intra-, juxta-, para-, or autocrine fashion. The epidermis as the outer most component of skin forms a barrier directly protecting against environmental stressors. This protection is assured by an intrinsic keratinocyte differentiation program, pigmentary system, and local nervous, immune, endocrine, and microbiome elements. These constituents communicate cross-functionally among themselves and with corresponding systems in the dermis and hypodermis to secure the basic epidermal functions to maintain local (skin) and global (systemic) homeostasis. The neurohormonal mediators and cytokines used in these communications regulate physiological skin functions separately or in concert. Disturbances in the functions in these systems lead to cutaneous pathology that includes inflammatory (i.e., psoriasis, allergic, or atopic dermatitis, etc.) and keratinocytic hyperproliferative disorders (i.e., seborrheic and solar keratoses), dysfunction of adnexal structure (i.e., hair follicles, eccrine, and sebaceous glands), hypersensitivity reactions, pigmentary disorders (vitiligo, melasma, and hypo- or hyperpigmentary responses), premature aging, and malignancies (melanoma and nonmelanoma skin cancers). These cellular, molecular, and neural components preserve skin integrity and protect against skin pathologies and can act as "messengers of the skin" to the central organs, all to preserve organismal survival.

Immunological Pathomechanisms of Spongiotic Dermatitis in Skin Lesions of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic pruritic skin disease with a complex pathogenesis underlying its heterogeneous clinical phenotypes and endotypes. The skin manifestation of AD reflects the cytokine milieu of a type-2-dominant immunity axis induced by genetic predisposition, innate immunity dysregulation, epidermal barrier defects, and allergic inflammation. However, the detailed pathomechanism of eczematous dermatitis, which is the principal characteristic of AD, remains unclear. This review examines previous studies demonstrating research progress in this area and considers the immunological pathomechanism of “spongiotic dermatitis”, which is the histopathological hallmark of eczematous dermatitis. Studies in this field have revealed the importance of IgE-mediated delayed-type hypersensitivity, the Fas/Fas-ligand system, and cell-mediated cytotoxicity in inducing the apoptosis of keratinocytes in spongiotic dermatitis. Recent studies have demonstrated that, together with infiltrating CD4 T cells, IgE-expressing dendritic cells (i.e., inflammatory dendritic epidermal cells and Langerhans cells) that capture specific allergens (i.e., house dust mites) are present in the spongiotic epidermis of lichenified eczema in patients with IgE-allergic AD. These findings suggest that IgE-mediated delayed-type hypersensitivity plays a pivotal role in the pathogenesis of spongiotic dermatitis in the skin lesions of AD.

Revisiting the Roles of Filaggrin in Atopic Dermatitis

The discovery in 2006 that loss-of-function mutations in the filaggrin gene (FLG) cause ichthyosis vulgaris and can predispose to atopic dermatitis (AD) galvanized the dermatology research community and shed new light on a skin protein that was first identified in 1981. However, although outstanding work has uncovered several key functions of filaggrin in epidermal homeostasis, a comprehensive understanding of how filaggrin deficiency contributes to AD is still incomplete, including details of the upstream factors that lead to the reduced amounts of filaggrin, regardless of genotype. In this review, we re-evaluate data focusing on the roles of filaggrin in the epidermis, as well as in AD. Filaggrin is important for alignment of keratin intermediate filaments, control of keratinocyte shape, and maintenance of epidermal texture via production of water-retaining molecules. Moreover, filaggrin deficiency leads to cellular abnormalities in keratinocytes and induces subtle epidermal barrier impairment that is sufficient enough to facilitate the ingress of certain exogenous molecules into the epidermis. However, although FLG null mutations regulate skin moisture in non-lesional AD skin, filaggrin deficiency per se does not lead to the neutralization of skin surface pH or to excessive transepidermal water loss in atopic skin. Separating facts from chaff regarding the functions of filaggrin in the epidermis is necessary for the design efficacious therapies to treat dry and atopic skin.

Opioidergic Signaling-A Neglected, Yet Potentially Important Player in Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin diseases, the prevalence of which is especially high among children. Although our understanding about its pathogenesis has substantially grown in recent years, and hence, several novel therapeutic targets have been successfully exploited in the management of the disease, we still lack curative treatments for it. Thus, there is an unmet societal demand to identify further details of its pathogenesis to thereby pave the way for novel therapeutic approaches with favorable side effect profiles. It is commonly accepted that dysfunction of the complex cutaneous barrier plays a central role in the development of AD; therefore, the signaling pathways involved in the regulation of this quite complex process are likely to be involved in the pathogenesis of the disease and can provide novel, promising, yet unexplored therapeutic targets. Thus, in the current review, we aim to summarize the available potentially AD-relevant data regarding one such signaling pathway, namely cutaneous opioidergic signaling.

Skin Immunosenescence and Type 2 Inflammation: A Mini-Review With an Inflammaging Perspective

Skin-resident stromal cells, including keratinocytes, fibroblasts, adipocytes, and immune cells including Langerhans cells, dendritic cells, T cells, and innate lymphoid cells, and their functional products work in concert to ensure the realization of skin barrier immunity. However, aging-induced immunosenescence predisposes the elderly to pruritic dermatoses, including type 2 inflammation-mediated. Inflammaging, characterized by chronic low level of pro-inflammatory cytokines released from senescent cells with the senescence-associated secretory phenotype (SASP), may drive immunosenescence and tangle with type 2 inflammatory dermatoses. The present mini-review summarizes current evidence on immunosenescence and type 2 inflammation in the skin and further focuses on future needs from an inflammaging perspective to clarify their complexity.

Protective Role of Melatonin and Its Metabolites in Skin Aging

The skin, being the largest organ in the human body, is exposed to the environment and suffers from both intrinsic and extrinsic aging factors. The skin aging process is characterized by several clinical features such as wrinkling, loss of elasticity, and rough-textured appearance. This complex process is accompanied with phenotypic and functional changes in cutaneous and immune cells, as well as structural and functional disturbances in extracellular matrix components such as collagens and elastin. Because skin health is considered one of the principal factors representing overall “well-being” and the perception of “health” in humans, several anti-aging strategies have recently been developed. Thus, while the fundamental mechanisms regarding skin aging are known, new substances should be considered for introduction into dermatological treatments. Herein, we describe melatonin and its metabolites as potential “aging neutralizers”. Melatonin, an evolutionarily ancient derivative of serotonin with hormonal properties, is the main neuroendocrine secretory product of the pineal gland. It regulates circadian rhythmicity and also exerts anti-oxidative, anti-inflammatory, immunomodulatory, and anti-tumor capacities. The intention of this review is to summarize changes within skin aging, research advances on the molecular mechanisms leading to these changes, and the impact of the melatoninergic anti-oxidative system controlled by melatonin and its metabolites, targeting the prevention or reversal of skin aging.

Epidermal Barrier Function and Skin Homeostasis in Atopic Dermatitis: The Impact of Age

Skin is damaged in atopic dermatitis (AD) patients. Age is also believed to have a negative effect on epidermal barrier function. The aim of this study was to investigate skin barrier function changes with age in AD patients. A cross-sectional study was conducted including 162 participants, 81 AD patients and 81 healthy volunteers. Skin barrier function parameters, such as transepidermal water loss (TEWL), erythema, temperature, stratum corneum hydration (SCH), pH, and elasticity, were evaluated. Healthy volunteers were evaluated on the volar forearm. AD patients were measured on two regions: on an eczematous lesion on the volar forearm and on a non-involved area 5 cm from the affected area. TEWL was lower on healthy skin than uninvolved AD skin (9.98 vs. 25.51 g·m⁻²·h⁻¹, p < 0.001) and AD eczematous lesions (9.98 vs. 28.38 g·m⁻²·h⁻¹, p < 0.001). SCH was lower on AD eczematous lesions than uninvolved AD skin (24.23 vs. 39.36 AU, p < 0.001) and healthy skin (24.23 vs. 44.36 AU, p < 0.001). Elasticity was lower on AD eczematous lesions than uninvolved AD skin (0.69 vs. 0.74, p = 0.038) and healthy skin (0.69 vs. 0.77, p = 0.014). A negative correlation was found between age and elasticity in all the population (r = −0.383, p < 0.001). This correlation was stronger in AD patients (r = −0.494, p < 0.001) than in controls (r = −0.266, p = 0.092). After conducting a linear regression model in AD patients adjusted by age, sex, and SCORing Atopic Dermatitis (SCORAD), it was found that elasticity was impaired by an increasing age (β = −0.004, p < 0.001) and a higher SCORAD (β = −0.003, p < 0.001). The skin barrier function is impaired by age and AD, reflected mainly in poor elasticity values in older AD patients.

The Impact of Vitamin D on Skin Aging

The active metabolites of vitamin D₃ (D₃) and lumisterol (L₃) exert a variety of antiaging and photoprotective effects on the skin. These are achieved through immunomodulation and include anti-inflammatory actions, regulation of keratinocytes proliferation, and differentiation programs to build the epidermal barrier necessary for maintaining skin homeostasis. In addition, they induce antioxidative responses, inhibit DNA damage and induce DNA repair mechanisms to attenuate premature skin aging and cancerogenesis. The mechanism of action would involve interaction with multiple nuclear receptors including VDR, AhR, LXR, reverse agonism on RORα and -γ, and nongenomic actions through 1,25D₃-MARRS receptor and interaction with the nongenomic binding site of the VDR. Therefore, active forms of vitamin D₃ including its canonical (1,25(OH)₂D₃) and noncanonical (CYP11A1-intitated) D₃ derivatives as well as L₃ derivatives are promising agents for the prevention, attenuation, or treatment of premature skin aging. They could be administrated orally and/or topically. Other forms of parenteral application of vitamin D₃ precursor should be considered to avoid its predominant metabolism to 25(OH)D₃ that is not recognized by CYP11A1 enzyme. The efficacy of topically applied vitamin D₃ and L₃ derivatives needs further clinical evaluation in future trials.