Higher concentrations of dithranol appear to induce hair growth even in severe alopecia areata

Review on Alopecia Areata in the Middle East and Africa: Landscape and Unmet Needs

BACKGROUND

Alopecia areata (AA) is an autoimmune disease characterized by non-scarring hair loss in adults and children. Clinical manifestations range from hair loss in small, well-circumscribed patches to total hair loss on the scalp or any other hair-bearing areas. Although the exact pathogenesis of AA is not fully understood, it is thought that loss of immune privilege caused by immunological dysregulation of the hair follicle is key. Genetic susceptibility also plays a role. Response to currently available treatments is widely variable, causing patient dissatisfaction and creating an unmet need. AA is frequently associated with multiple comorbidities, further affecting patient quality of life.

AIMS AND FINDINGS

AA causes a significant burden on dermatologists and healthcare systems in the Middle East and Africa. There is a lack of data registries, local consensus, and treatment guidelines in the region. Limited public awareness, availability of treatments, and patient support need to be addressed to improve disease management in the region. A literature review was conducted to identify relevant publications and highlight regional data on prevalence rates, diagnosis, quality of life, treatment modalities, and unmet needs for AA in the Middle East and Africa.

IL-33 Contributes to the Pathological Changes of Hair Follicles in Psoriasis: A Potential Target for Psoriatic Alopecia

Purpose

IL-33 is constitutively expressed in skin tissues. Alopecia, a T cells-driven disorder of the hair follicles (HFs), is a common complication in the development of psoriasis. However, the role of IL-33 in psoriatic alopecia remains uncovered. Here, we investigated the roles of IL-33 in inducing pathological changes of hair follicles in psoriasis.

Patients and Methods

Clinical samples and imiquimod (IMQ)-induced psoriatic mice samples were used to investigate the pathological changes and T-cell infiltration of HFs. By using immunohistochemistry staining, the distribution and expression alteration of IL-33 in HFs were determined. Next, by using IL-33 and ST2 knockout mice, we investigated the role of IL-33/ST2 axis in the pathological changes of HFs in psoriasis. Meanwhile, recombinant IL-33 protein was subcutaneous injected to confirm its effect. Finally, RNA sequencing was used to clarify the genes and signaling pathways that involved in this process. Differentially expressed genes were further verified by RT-PCR in cultured HFs in vitro.

Results

We found that the pathological changes of HFs and T cells infiltration in imiquimod-induced psoriatic mice were similar to that in psoriasis patients. The IL-33 positive keratinocytes in the outer root sheath of HFs were increased in both psoriasis patients and psoriatic model mice compared with the controls. By using gene knockout mice, we found that the pathological changes and T cell infiltration were attenuated in IL-33^-/- and ST2^-/- psoriatic model mice. In addition, subcutaneous injection of recombinant IL-33 exacerbated the pathological changes of HFs and T cell infiltration. RNA sequencing and RT-RCR revealed that IL-33 upregulated the transcription of genes related to keratinocytes proliferation and T lymphocytes chemotaxis.

Conclusion

Our study identifies that IL-33 promotes the pathological changes of HFs in psoriasis, which contributes to psoriatic alopecia. Inhibition of IL-33 may be a potential therapeutic approach for psoriatic alopecia.

A systematic review on the treatment of pediatric severe alopecia areata by topical immunotherapy or Anthralin (contact sensitization) or low-level light/laser therapy (LLLT): focus on efficacy, safety, treatment duration, recurrence, and follow-up based on clinical studies

INTRODUCTION

Alopecia areata (AA) in its extensive and severe forms is treatment-challenging, especially in pediatrics.

METHOD

A PRISMA-compliant systematic review of seven electronic databases was searched by the terms "alopecia areata," "pediatric," "topical immunotherapy," "Anthralin," and "light therapy" from inception until March 2021. All the alternative names of the disease and therapies have been included in the search terms. 790 articles went to title abstract review by two independent reviewers. In the subsequent level, a review of the full text of studies was conducted.

RESULTS

Finally, 10 relevant articles in terms of content structure, subject coverage, and purpose, were selected for further review. The highest percentages of complete hair regrowth were 79.6% and 63.61% by SADBE (topical immunotherapy) and laser therapy. By Anthralin (contact sensitization), the complete response rate was below 50% (between 30 and 35%). Regarding average response, the most effective methods were local immunotherapy (with an average effectiveness of 53.8%), laser therapy (52.55%), and the use of Anthralin-induced contact dermatitis (30.86%), respectively. However, recurrence rate-after treatment with induced contact dermatitis by topical medications like Anthralin (contact sensitization)-was lower (mean 43.53%) in comparison with local immunotherapy (57%). In topical immunotherapy, light base therapy, and contact sensitization, the highest percentage of complete hair regrowth and the average response rate were (63.61% and 52.55%), (79.6% and 53.8%) and (32% and 30.8%), respectively. These methods are considered safe in children.

CONCLUSION

A high and more than 50% efficacy in hair regrowth could be expected by topical immunotherapy and light/laser therapy method. No serious side effects have been observed by these methods that are well tolerated in children. Therefore, a combination of local immunotherapy and light/laser therapy could be suggested for the treatment of extensive AA in children. The use of Anthralin could be associated with a lower but more durable response. These points are important for patient selection in individualized situations.

The hair follicle-psoriasis axis: Shared regulatory mechanisms and therapeutic targets

It has long been known that there is a special affinity of psoriasis for the scalp: Here, it occurs most frequently, lesions terminate sharply in frontal skin beyond the hair line and are difficult to treat. Yet, surprisingly, scalp psoriasis only rarely causes alopecia, even though the pilosebaceous unit clearly is affected. Here, we systematically explore the peculiar, insufficiently investigated connection between psoriasis and growing (anagen) terminal scalp hair follicles (HFs), with emphasis on shared regulatory mechanism and therapeutic targets. Interestingly, several drugs and stressors that can trigger/aggravate psoriasis can inhibit hair growth (e.g. beta-blockers, chloroquine, carbamazepine, interferon-alpha, perceived stress). Instead, several anti-psoriatic agents can stimulate hair growth (e.g. cyclosporine, glucocorticoids, dithranol, UV irradiation), while skin/HF trauma (Köbner phenomenon/depilation) favours the development of psoriatic lesions and induces anagen in "quiescent" (telogen) HFs. On this basis, we propose two interconnected working models: (a) the existence of a bidirectional "hair follicle-psoriasis axis," along which keratinocytes of anagen scalp HFs secrete signals that favour the development and maintenance of psoriatic scalp lesions and respond to signals from these lesions, and (b) that anagen induction and psoriatic lesions share molecular "switch-on" mechanisms, which invite pharmacological targeting, once identified. Therefore, we advocate a novel, cross-fertilizing and integrative approach to psoriasis and hair research that systematically characterizes the "HF-psoriasis axis," focused on identification and therapeutic targeting of selected, shared signalling pathways in the future management of both, psoriasis and hair growth disorders.

Induction of IL-1β and antimicrobial peptides as a potential mechanism for topical dithranol

Topical dithranol is effective in autoimmune conditions like alopecia areata, inducing hair regrowth in a high percentage of cases. Exact mechanisms of dithranol in alopecia areata, with seemingly healthy epidermis besides altered hair follicles, are not well understood. To better understand dithranol's mechanisms on healthy skin, we analysed its effect on normal murine as well as xenografted human skin. We found a strong increase in mRNA expression of anti-microbial peptides (AMPs) (eg Lcn2, Defb1, Defb3, S100a8, S100a9), keratinocyte differentiation markers (eg Serpinb3a, Flg, Krt16, Lce3e) and inflammatory cytokines (eg Il1b and Il17) in healthy murine skin. This effect was paralleled by inflammation and disturbed skin barrier, as well as an injury response resulting in epidermal hyperproliferation, as observed in murine and xenografted adult human skin. This contact response and disturbed barrier induced by dithranol might lead via a vicious loop between AMPs such as S100a8/a9 (that led to skin swelling itself after topical application) and cytokines such as IL-1β to an immune suppressive environment in the skin. A better understanding of the skin's physiologic response to dithranol may open up new avenues for the establishment of novel therapeutics (including AMP-related/interfering molecules) for certain skin conditions, such as alopecia areata.

Dithranol targets keratinocytes, their crosstalk with neutrophils and inhibits the IL-36 inflammatory loop in psoriasis

Despite the introduction of biologics, topical dithranol (anthralin) has remained one of the most effective anti-psoriatic agents. Serial biopsies from human psoriatic lesions and both the c-Jun/JunB and imiquimod psoriasis mouse model allowed us to study the therapeutic mechanism of this drug. Top differentially expressed genes in the early response to dithranol belonged to keratinocyte and epidermal differentiation pathways and IL-1 family members (i.e. IL36RN) but not elements of the IL-17/IL-23 axis. In human psoriatic response to dithranol, rapid decrease in expression of keratinocyte differentiation regulators (e.g. involucrin, SERPINB7 and SERPINB13), antimicrobial peptides (e.g. ß-defensins like DEFB4A, DEFB4B, DEFB103A, S100 proteins like S100A7, S100A12), chemotactic factors for neutrophils (e.g. CXCL5, CXCL8) and neutrophilic infiltration was followed with much delay by reduction in T cell infiltration. Targeting keratinocytes rather than immune cells may be an alternative approach in particular for topical anti-psoriatic treatment, an area with high need for new drugs.

Practical compendium for psoriasis management

Psoriasis management is complex and challenging. It should be tailored for each patient. Treatment strategy differs according to patient's age, sex, disease type, disease severity, burden on patient's quality of life, comorbidities, involvement of specific sites, and pregnancy. The choice of the appropriate therapeutic must take into consideration the availability, the price, and the patient's preferences. It is very important that the chosen treatment is not more unpleasant, intolerable, or dangerous than the disease itself. According to the disease type, severity, and effect on patient's quality of life, dermatologist chooses whether to start with topical therapy, phototherapy or systemic therapy, or a combination of two or more of them. Under each category, there are different types of therapies that can be the first line therapeutics, second line, or even contraindicated. In this compendium, we provide dermatologists with different treatment plans considering all the mentioned variables so that a dermatologist can choose the optimum plan for the patient.