A New Era with the Development of Cytokine-Based Therapy for Pruritus

The Role and Implications of Epidermal Dysfunction in the Pathogenesis of Inflammaging

Inflammaging has long been linked to the pathogenesis of various aging-associated disorders, including cardiovascular disease, obesity, type 2 diabetes, and dementia. Yet, the origins of inflammaging remain unclear. Although inflammatory dermatoses such as psoriasis and atopic dermatitis predispose to the development of certain aging-associated disorders, suggesting a pathogenic role of cutaneous inflammation in these disorders, the great majority of aged humans do not have inflammatory dermatoses. Nonetheless, recent studies point to epidermal dysfunction as contributing to inflammaging, even in otherwise normal aged humans. Chronologically aged skin exhibits reduced stratum corneum hydration levels, delayed permeability barrier recovery, and an elevated stratum corneum pH, all of which can provoke and exacerbate cutaneous inflammation. Owing to the prolonged release of proinflammatory cytokines (including TNFα, IL-1β, and IL-6) from the epidermis into the circulation in response to these functional abnormalities, cutaneous inflammation can lead to extracutaneous inflammation, resulting in the downstream development of inflammaging and its accompanying disorders. In support of this concept, topical therapies that improve epidermal function can mitigate some aging-associated disorders, such as mild cognitive impairment. In this perspective, we discuss the link between epidermal dysfunction and inflammaging and highlight the potential management of inflammaging-associated sequelae by enhancing epidermal functions.

Molecular and cellular pruritus mechanisms in the host skin

Pruritus, also known as itching, is a complex sensation that involves the activation of specific physiological and cellular receptors. The skin is innervated with sensory nerves as well as some receptors for various sensations, and its immune system has prominent neurological connections. Sensory neurons have a considerable impact on the sensation of itching. However, immune cells also play a role in this process, as they release pruritogens. Disruption of the dermal barrier activates an immune response, initiating a series of chemical, physical, and cellular reactions. These reactions involve various cell types, including keratinocytes, as well as immune cells involved in innate and adaptive immunity. Collective activation of these immune responses confers protection against potential pathogens. Thus, understanding the molecular and cellular mechanisms that contribute to pruritus in host skin is crucial for the advancement of effective treatment approaches. This review provides a comprehensive analysis of the present knowledge concerning the molecular and cellular mechanisms underlying itching signaling in the skin. Additionally, this review explored the integration of these mechanisms with the broader context of itch mediators and the expression of their receptors in the skin.

Efficacy of Dupilumab in Children 6 Months to 11 Years Old With Atopic Dermatitis: A Retrospective Real-World Study in China

Background: Atopic dermatitis (AD) is a common skin disease that affects patients' quality of life, especially in the pediatric population. Dupilumab has shown good efficacy and safety in the treatment of AD in adolescents and adults, but the real data on younger children using dupilumab are scarce. Objectives: We investigated the doses, efficacy, and safety of dupilumab in children with moderate-to-severe AD aged ≥6 months to 11 years. Methods: This single-center retrospective cohort analysis included dupilumab-treated patients with severe AD under 12 years of age. Primary endpoints included the proportion of Validated Investigator Global Assessment (vIGA) 0/1 achieved and the percentage change from baseline in eczema area and severity index (EASI) and SCORing Atopic Dermatitis (SCORAD) at week 24 (W24). Secondary endpoints were mean change in pruritus numerical rating score (P-NRS) and body surface area (BSA) after W24 of treatment, description of adverse events, and Children's Dermatology Life Quality Index (CDLQI) improvement from baseline in endpoints. Results: Fifty-seven patients were included (mean age 7.2 ± 3.0 years). The primary endpoint (vIGA = 0/1) was achieved by 51 of 57 (89.5%) patients at W24. Significant improvements in EASI, SCORAD, P-NRS, and CDLQI scores were observed from baseline to W24 with dupilumab treatment and remained until W40. In different age groups, the endpoint vIGA achieved 0/1: 95.2% (20/21) of younger children and 88.9% (32/36) of older children. No serious adverse drug reactions were reported. Conclusions: This study aimed to describe the safety and efficacy of dupilumab in pediatric patients and examined differences of efficacy with various doses. The outcomes are comparable with those of existing clinical trials. Phase III Clinical Trial: NCT03346434.

Improvement in Cutaneous Conditions Can Benefit Some Health Conditions in the Elderly

As we are aging, a number of cutaneous and extracutaneous disorders will be developed. Although the pathogenesis of these aging-associated disorders is not clear yet, abnormalities in the skin are linked to some aging-associated disorders at least to some extent. Inflammatory dermatoses such as psoriasis and atopic dermatitis predispose to the development of cardiovascular diseases, obesity and type 2 diabetes. In addition, both chronologically aged skin and individuals with some aging-associated systemic conditions display altered epidermal function, such as reduced stratum corneum hydration levels, which can provoke cutaneous inflammation. Because aged skin exhibits higher expression levels of inflammatory cytokines, which play a pathogenic role in a variety of aging-associated health condition, the association of the skin with some aging-associated disorders is likely mediated by inflammation. This postulation is supported by the evidence that improvement in either epidermal function or inflammatory dermatoses can mitigate some aging-associated disorders such as mild cognitive impairment and insulin sensitivity. This perspective discusses the association of the skin with aging-associated disorders and highlights the potential of improvement in cutaneous conditions in the management of some health conditions in the elderly.

Divergent in situ expression of IL-31 and IL-31RA between bullous pemphigoid and pemphigus vulgaris

Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are two major autoimmune blistering skin diseases. Unlike PV, BP is accompanied by intense pruritus, suggesting possible involvement of the pruritogenic cytokine IL-31. However, the underlying mechanisms of the clinical difference between BP and PV in terms of pruritus are not fully understood. To compare the expression levels of IL-31 and its receptor IL-31RA in the lesional skin, including peripheral nerves in BP and PV patients, immunohistochemical staining for IL-31 and IL-31RA was performed in skin samples of BP and PV patients and healthy controls (HC). The IL-31RA-expressing area in epidermis and peripheral nerves was analysed using ImageJ and the percentage of positive cells for IL-31/IL-31RA in dermal infiltrating cells was manually quantified. Quantitative analyses revealed that IL-31/IL-31RA expressions in the epidermis and dermal infiltrate were significantly increased in BP compared to PV and HC. The difference between BP and PV became more obvious when advanced bullous lesions were compared. Peripheral nerves in BP lesions presented significantly higher IL-31RA expression compared to PV lesions. In conclusion, we found significantly augmented expressions of IL-31/IL-31RA in BP lesions, including peripheral nerves, in comparison to PV. These results suggest a possible contribution of IL-31/IL-31RA signalling to the difference between BP and PV in the facilitation of pruritus and local skin inflammation, raising the possibility of therapeutic targeting of the IL-31/IL-31RA pathway in BP patients.

Serum Mediators in Patients with Both Type 2 Diabetes Mellitus and Pruritus

Chronic pruritus is an unpleasant sensory perception that negatively affects quality of life and is common among patients with type 2 diabetes mellitus. Current antipruritic therapies are insufficiently effective. Thus, the mediation of diabetic pruritus by histamine-independent pathways is likely. The aim of this study was to identify possible mediators responsible for diabetic pruritus. A total of 87 patients with type 2 diabetes mellitus were analysed, of whom 59 had pruritus and 28 did not. The 2 groups were assessed for baseline demographics, serum biochemistry parameters, cytokines, and chemokines. This study also investigated the associations of these factors with the severity of itching. Neither haemoglobin A1c nor serum creatinine levels were correlated with severity of itching. Significantly higher levels of interleukin-4 (p = 0.004), interleukin-13 (p = 0.006), granulocyte-macrophage colony-stimulating factor (p < 0.001) and C-X-C motif chemokine ligand 10 (p = 0.028) were observed in the patients with pruritus than in those without pruritus. Moreover, the levels of these mediators were positively correlated with the severity of itching. Thus, novel antipruritic drugs can be developed to target these molecules. This is the first study to compare inflammatory mediators comprehensively in patients with diabetes mellitus with pruritus vs those without pruritus.

Apigenin: A Therapeutic Agent for Treatment of Skin Inflammatory Diseases and Cancer

The skin is the main barrier between the body and the environment, protecting it from external oxidative stress induced by ultraviolet rays. It also prevents the entrance of infectious agents such as viruses, external antigens, allergens, and bacteria into our bodies. An overreaction to these agents causes severe skin diseases, including atopic dermatitis, pruritus, psoriasis, skin cancer, and vitiligo. Members of the flavonoid family include apigenin, quercetin, luteolin, and kaempferol. Of these, apigenin has been used as a dietary supplement due to its various biological activities and has been shown to reduce skin inflammation by downregulating various inflammatory markers and molecular targets. In this review, we deal with current knowledge about inflammatory reactions in the skin and the molecular mechanisms by which apigenin reduces skin inflammation.

Cytokines and chemokines modulation of itch

Itch (pruritus) is a common cutaneous symptom widely associated with many skin complaints, and chronic itch can be a severe clinical problem. The onset and perpetuation of itch are linked to cytokines, such as interleukin (IL)-31, IL-4, IL-13, IL-33, thymic stromal lymphopoietin, and tumor necrosis factor-alpha, and chemokines, such as chemokine (C-C motif) ligand 2 and C-X-C motif chemokine ligand 10. This review highlights research that has attempted to determine the attributes of various cytokines and chemokines concerning the development and modulation of itch. Through such research, clinical approaches targeting cytokines and/or chemokines may arise, which may further the development of itch therapeutics.