Role of interleukin-6 and endothelin-1 receptors in enhanced melanocyte dendricity of facial spots and suppression of their ligands by niacinamide and tranexamic acid

BACKGROUND

Hyperpigmented spots are common issues in all ethnicities with a hallmark characteristic of increased melanocyte dendricity.

OBJECTIVES

To determine (1) potential receptors and/or cytokines that are involved in increased melanocyte dendricity in multiple facial spot types; (2) treatment effects of skin-lightening compounds on identified cytokine release from keratinocytes and on dendricity in melanocytes.

METHODS

Facial spots (melasma, solar lentigo, acne-induced post-inflammatory hyperpigmentation) and adjacent non-spot skin biopsies were collected from Chinese women (age 20-70). The epidermal supra and basal layers were laser dissected to enrich keratinocyte or melanocyte biology respectively for transcriptome analysis. Melanocyte dendricity was assessed histologically by immunofluorescent staining. Effect of interleukin-6 (IL-6) and endothelin-1 (ET-1) on melanocyte dendricity and melanosome transfer were assessed in human melanocytes or melanocyte-keratinocyte co-culture models. Treatment effects of skin-lightening compounds (niacinamide, tranexamic acid [TxA], sucrose laurate/dilaurate mixture [SDL]) were assessed on IL-6 or ET-1 release from keratinocytes and on dendricity in melanocytes.

RESULTS

Transcriptome analysis revealed IL-6 receptor and ET-1 receptor were significantly upregulated compared to the adjacent normal skin, visually confirmed at the protein level through immunostaining. Melanocytes in spot areas are more dendritic than melanocytes in adjacent non-spot skin. The addition of IL-6 and ET-1 to cell culture models increased melanocyte dendricity and melanosome transfer. IL-6 release was significantly suppressed by niacinamide and its combination, while ET-1 release was significantly reduced by both niacinamide and TxA. In contrast, SDL acted directly upon melanocytes to reduce dendricity.

CONCLUSION

Interleukin-6 and ET-1 receptors are significantly upregulated in multiple facial spot types. The in vitro testing demonstrated their respective ligands increased melanocyte dendricity. Tested skin-lightening compounds showed reduction in release of IL-6/ET-1 from epidermal keratinocytes and/or inhibition of melanocyte dendricity. This work sheds light on pathophysiological mechanism of facial spots and potential new mechanisms of these skin-lightening compounds which warrant further human clinical validation.

A case of nivolumab-induced acute-onset type 1 diabetes mellitus in melanoma

Nivolumab, an anti-PD-1 antibody, is now considered an important therapeutic agent in several advanced malignancies. However, immune-related adverse events such as endocrinopathies have been reported with its use. Thyroid disorder and isolated adrenocorticotropic hormone deficiency have frequently been reported as nivolumab-induced immune-related adverse events. Another endocrinopathy is nivolumab-induced type 1 diabetes mellitus (t1dm), described as diabetes mellitus with rapid onset and complete insulin insufficiency, at times leading to fulminant t1dm. We report the case of a 68-year-old woman who developed pancreatic islet-related autoantibody-negative t1dm, possibly induced by nivolumab, under continuous glucocorticoid administration. She was treated with nivolumab for advanced malignant melanoma, concomitant with 10 mg prednisolone daily for thrombophlebitis tapered to 5 mg after 13 courses of nivolumab therapy. At approximately the 27th course of nivolumab therapy, she showed elevated plasma glucose levels despite preserved insulin secretion. A month later, she developed diabetic ketoacidosis. Her insulin secretion decreased and finally was exhausted. She was diagnosed with acute-onset rather than fulminant t1dm because of a rapidly progressive course to diabetic ketoacidosis during just more than 1 week. She is currently receiving insulin replacement. There has been no recurrence of the melanoma. Thus, nivolumab might induce autoimmune diabetes mellitus, with patients having t1dm-sensitive human leucocyte antigen being more susceptible even when receiving glucocorticoids. Physicians should be aware that nivolumab could potentially induce t1dm as a critical immune-related adverse event.

The IL-13/periostin/IL-24 pathway causes epidermal barrier dysfunction in allergic skin inflammation

BACKGROUND

Barrier dysfunction is an important feature of atopic dermatitis (AD) in which IL-4 and IL-13, signature type 2 cytokines, are involved. Periostin, a matricellular protein induced by IL-4 or IL-13, plays a crucial role in the onset of allergic skin inflammation, including barrier dysfunction. However, it remains elusive how periostin causes barrier dysfunction downstream of the IL-13 signal.

METHODS

We systematically identified periostin-dependent expression profile using DNA microarrays. We then investigated whether IL-24 downregulates filaggrin expression downstream of the IL-13 signals and whether IL-13-induced IL-24 expression and IL-24-induced downregulation of filaggrin expression are dependent on the JAK/STAT pathway. To build on the significance of in vitro findings, we investigated expression of IL-24 and activation of STAT3 in mite-treated mice and in AD patients.

RESULTS

We identified IL-24 as an IL-13-induced molecule in a periostin-dependent manner. Keratinocytes are the main IL-24-producing tissue-resident cells stimulated by IL-13 in a periostin-dependent manner via STAT6. IL-24 significantly downregulated filaggrin expression via STAT3, contributing to barrier dysfunction downstream of the IL-13/periostin pathway. Wild-type mite-treated mice showed significantly enhanced expression of IL-24 and activation of STAT3 in the epidermis, which disappeared in both STAT6-deficient and periostin-deficient mice, suggesting that these events are downstream of both STAT6 and periostin. Moreover, IL-24 expression was enhanced in the epidermis of skin tissues taken from AD patients.

CONCLUSIONS

The IL-13/periostin pathway induces IL-24 production in keratinocytes, playing an important role in barrier dysfunction in AD.

The pruritogenic mediator endothelin-1 shifts the dendritic cell-T-cell response toward Th17/Th1 polarization

Endothelin-1 (ET-1) is associated with skin diseases such as atopic dermatitis (AD) and psoriasis. ET-1 is enhanced in the skin of patients AD and psoriasis. In addition, plasma levels of ET-1 are elevated in AD and psoriasis. Although both AD and psoriasis are T-cell-mediated skin diseases, the association between ET-1 and the T-cell immune response has not been clarified. To evaluate the role of ET-1 in inflammatory skin disease, we sought to investigate the effects of ET-1 on the functions of dendritic cells (DCs) and subsequent immune responses. For this purpose, we immunohistochemically confirmed the upregulation of ET-1 in the epidermis of patients with AD or psoriasis. ET-1 directly induced phenotypic maturation of bone marrow-derived DCs (BMDCs). In addition, ET-1 augmented the production of several cytokines and allogeneic stimulatory capacity of BMDCs. Interestingly, ET-1-activated BMDCs primed T cells to produce Th1 and Th17 cytokines, but not Th2 cytokines. These findings indicate that ET-1 polarizes the DC-T-cell response toward Th17/1 differentiation and may augment the persistent course of inflammatory skin diseases.

Emerging role of interleukin-31 and interleukin-31 receptor in pruritus in atopic dermatitis

Atopic dermatitis (AD) is a chronic or chronically relapsing, eczematous, severely pruritic skin disorder associated with skin barrier dysfunction. The lesional skin of AD exhibits T helper 2 (T_H 2)-deviated immune reactions. Interleukin-31 (IL-31), preferentially produced from T_H 2 cells, is a potent pruritogenic cytokine, and its systemic and local administration induces scratching behavior in rodents, dogs and monkeys. Recent clinical trials have revealed that administration of an anti-IL-31 receptor antibody significantly alleviates pruritus in patients with AD. In this review, we summarize recent topics related to IL-31 and its receptor with special references to atopic itch.

The first trial of CIM331, a humanized antihuman interleukin-31 receptor A antibody, in healthy volunteers and patients with atopic dermatitis to evaluate safety, tolerability and pharmacokinetics of a single dose in a randomized, double-blind, placebo-controlled study

BACKGROUND

The cytokine interleukin-31 (IL-31) is considered to be responsible for the development of pruritus in humans. At present, no available evidence has been provided on the safety and efficacy of blocking the IL-31 signal in humans for the amelioration of pruritus in atopic dermatitis (AD). CIM331 is a humanized antihuman IL-31 receptor A (IL-31RA) monoclonal antibody, which binds to IL-31RA to inhibit subsequent IL-31 signalling.

OBJECTIVES

To assess the tolerability, safety, pharmacokinetics and preliminary efficacy of CIM331 in healthy Japanese and white volunteers, and Japanese patients with AD.

METHODS

In this randomized, double-blind, placebo-controlled phase I/Ib study, CIM331 was administered in a single subcutaneous dose. The primary outcomes were safety and tolerability; the exploratory analysis was efficacy.

RESULTS

No deaths, serious adverse events (AEs) or discontinuations due to AEs were reported in any part of the study. No dose-dependent increase in the incidence of AEs occurred in any part of the study. In healthy volunteers, all AEs occurred once in the placebo groups, and increased creatine phosphokinase was more common in the CIM331 groups. In patients with AD, CIM331 reduced pruritus visual analogue scale score to about -50% at week 4 with CIM331 compared with -20% with placebo. CIM331 increased sleep efficiency and decreased the use of hydrocortisone butyrate.

CONCLUSIONS

A single subcutaneous administration of CIM331 was well tolerated in healthy volunteers and patients with AD. It decreased pruritus, sleep disturbance and topical use of hydrocortisone. CIM331 may become a novel therapeutic option for AD by inhibiting IL-31.