Dapsone Suppresses Disease in Preclinical Murine Models of Pemphigoid Diseases

Mitochondrial DNA variants and microbiota: An experimental strategy to identify novel therapeutic potential in chronic inflammatory diseases

We previously demonstrated that mice carrying natural mtDNA variants of the FVB/NJ strain (m.7778 G>T in the mt-Atp8 gene in mitochondrial complex V), namely C57BL/6 J-mtFVB/NJ (B6-mtFVB), exhibited (i) partial protection from experimental skin inflammatory diseases in an anti-murine type VII collagen antibody-induced skin inflammation model and psoriasiform dermatitis model; (ii) significantly altered metabolites, including short-chain fatty acids, according to targeted metabolomics of liver, skin and lymph node samples; and (iii) a differential composition of the gut microbiota according to bacterial 16 S rRNA gene sequencing of stool samples compared to wild-type C57BL/6 J (B6) mice. To further dissect these disease-contributing factors, we induced an experimental antibody-induced skin inflammatory disease in gnotobiotic mice. We performed shotgun metagenomic sequencing of caecum contents and untargeted metabolomics of liver, CD4+ T cell, and caecum content samples from conventional B6-mtFVB and B6 mice. We identified D-glucosamine as a candidate mediator that ameliorated disease severity in experimental antibody-induced skin inflammation by modulating immune cell function in T cells, neutrophils and macrophages. Because mice carrying mtDNA variants of the FVB/NJ strain show differential disease susceptibility to a wide range of experimental diseases, including diet-induced atherosclerosis in low-density lipoprotein receptor knockout mice and collagen antibody-induced arthritis in DBA/1 J mice, this experimental approach is valuable for identifying novel therapeutic options for skin inflammatory conditions and other chronic inflammatory diseases to which mice carrying specific mtDNA variants show differential susceptibility.

Intravenous Ig Ameliorates Disease in a Murine Model of Anti-Laminin 332 Mucous Membrane Pemphigoid

Intravenous Ig (IVIg) is used to treat mucous membrane pemphigoid, although its therapeutic effectivity is not sufficiently supported by randomized controlled clinical trials, and its mode of action is only insufficiently understood. We have examined the effect of IVIg in a mouse model of anti-laminin 332 mucous membrane pemphigoid and found that IVIg ameliorates both cutaneous and mucosal inflammatory lesions. Our investigation into the modes of action of IVIg in mucous membrane pemphigoid indicated effective anti-inflammatory mechanisms beyond the enhanced degradation of IgG mediated through inhibition of the FcRn. Our results suggest that IVIg curbs the activation of neutrophils at several levels. This includes a direct, immediate inhibitory effect on neutrophil activation by immune complexes but not C5a, which blunts the release of ROS and leukotriene B4 from neutrophils. IVIg also suppresses the formation of neutrophil extracellular traps in response to calcium ion ionophore. In vivo treatment with IVIg altered the transcriptome of blood leukocytes and bone marrow neutrophils toward less proinflammatory phenotypes. Collectively, our results support the effectivity of IVIg in the treatment of mucous membrane pemphigoid and indicate that effects on neutrophils at multiple levels may significantly contribute to its therapeutic effects.

Immune-mediated oral mucosal pathology: a comprehensive review and update for clinicians - part II

The oral mucosa can be involved in a wide variety of mucocutaneous conditions that may present primarily in the mouth or affect other cutaneous or mucosal sites. Many of these conditions are immune mediated and typically present as inflammatory mucosal pathology. Patients experiencing such conditions usually seek medical evaluation and treatment due to the associated pain and discomfort, and occasionally taste disturbance or dysphagia and the overall deterioration in the oral health-related quality of life. These conditions share some common features and there could be some overlap in their clinical presentation, which can lead to delays in diagnosis and proper management of patients. Clinicians dealing with such disorders, including dermatologists, need to be aware of the oral manifestations of mucocutaneous conditions, their clinical features, underlying mechanisms, diagnostic approaches, and treatment options, as well as the recent advances in the research on these conditions. This review provides a comprehensive, evidence-based reference for clinicians, with updated insights into a group of immune mediated conditions known to cause oral mucosal pathology. Part one will cover oral lichen planus, erythema multiforme and systemic lupus erythematosus, while part two will cover recurrent aphthous stomatitis, pemphigus vulgaris and mucous membrane pemphigoid, in addition to the less common disorders linear IgA disease, dermatitis herpetiformis and epidermolysis bullosa.

A life for autoimmune blistering diseases: in memoriam Detlef Zillikens

Detlef Zillikens, MD, director and chair of the Department of Dermatology at the University of Lübeck, Lübeck, Germany, died in September 2022, aged only 64. He dedicated his professional life to autoimmune blistering diseases (AIBDs) and built his department into one of the world's leading centers for these diseases. Herein, his professional life and the impact on the field of AIBDs and the research landscape at the University of Lübeck are addressed. With his warm, integrative, open-minded, ever-optimistic attitude, he was a highly reliable colleague, mentor, and friend to many in the field including each of the authors. Combined with his in-depth knowledge of dermatology, interest in many fields of life science, and hard work, Detlef Zillikens initiated the founding of two independent research institutes, the Lübeck Institute of Experimental Dermatology and the Institute and Comprehensive Center for Inflammation Medicine. He was also instrumental in establishing the Center for Research on Inflammation of the Skin, where in a new research building, over 140 scientists pursue research questions related to skin inflammation. By inviting numerous researchers and clinicians to his department and hosting two large international meetings, he brought the field of AIBDs much closer together and inspired multiple national and international research initiatives. His ideas will live on and grow in many of his colleagues and mentees.

Autoimmunity against laminin 332

Laminin 332 is a heterotrimeric structural protein of the basal membrane zone (BMZ) of the skin and adjacent mucosal tissues. The importance of laminin 332 for the structural integrity of the BMZ is demonstrated by mutations in any of the three genes encoding for its three chains causing variants of junctional epidermolysis bullosa. Autoimmunity against laminin 332 is observed in mucous membrane pemphigoid (MMP) and in the rare patients with orf-induced pemphigoid. MMP is an autoimmune blistering disease with predominant mucosal manifestations and autoantibodies against the BMZ of the skin and orifice-close mucous membranes. The main autoantigens of MMP are type XVII collagen (BP180) and laminin 332 targeted in about 80% and 10-20% of patients, respectively. An increasing number of studies has highlighted the association of anti-laminin 332 MMP and malignancies that can be revealed in about a quarter of these patients. This data has led to the recommendation of current guidelines to assay for anti-laminin 332 reactivity in all MMP patients. The present review focuses on anti-laminin 332 MMP describing clinical features, its pathophysiology, and detection of serum anti-laminin 332 IgG. In addition, the available data about the occurrence of malignancies in anti-laminin 332 MMP, the underlying tumor entities, and its biology are detailed.

[Immunopathogenesis of mucous membrane pemphigoid]

A detailed understanding of the immunopathogenesis of mucous membrane pemphigoid (MMP) is of particular importance in view of the mostly difficult diagnostics and treatment of this blistering autoimmune dermatosis. A still unknown disturbance of the body's own immune tolerance leads to the formation of autoreactive cells. As the disease progresses these produce autoantibodies which are directed against structural proteins in the basement membrane zone (BMZ). After they bind to the target antigen, complement factors are deposited along the BMZ and inflammatory cells invade the underlying tissue and produce the characteristic subepithelial blistering. This inflammatory response is associated with fibrosis and scarring in many affected tissues. Most phases of MMP pathogenesis are poorly understood; however, the last few years have shed more light on this processes. These advances are mostly the result of animal and cell culture models. Typical clinical and immunopathological characteristics of MMP, such as oral, conjunctival and skin lesions, are reflected, for example, in an antibody transfer-induced mouse model for anti-laminin 332 MMP in adult mice. Dapsone, as first-line treatment for MMP patients, significantly reduced the severity of these symptoms, and fibrosis in the skin and mucous membranes was also found histologically, which makes the model well-suited for testing new therapeutic approaches for MMP patients and might be of help for further elucidation of the immunopathogenesis of MMP.

The cytokine milieu of bullous pemphigoid: Current and novel therapeutic targets

Bullous pemphigoid (BP) is the most common autoimmune bullous disease, characterized by severe pruritus and skin blistering. The loss of tolerance against Collagen XVII, also referred to as BP180, is the main pathogenic event of BP, leading to production of IgG autoantibodies which mainly target the juxtamembranous extracellular non-collagenous 16th A (NC16A) domain of BP180. A complex inflammatory network is activated upon autoantibody binding to the basement membrane zone; this inflammatory loop involves the complement cascade and the release of several inflammatory cytokines, chemokines and proteases from keratinocytes, lymphocytes, mast cells and granulocytes. Collectively, these events disrupt the integrity of the dermal-epidermal junction, leading to subepidermal blistering. Recent advances have led to identify novel therapeutic targets for BP, whose management is mainly based on the long-term use of topical and systemic corticosteroids. As an example, targeting type-2 T-helper cell-associated cytokines, such as Interleukin-4 and interleukin-13 has shown meaningful clinical efficacy in case series and studies; targeting IL-17 and IL-23 has also been tried, owing to an important role of these cytokines in the chronic maintenance phase of BP. In this review article, we discuss the complex cytokine milieu that characterized BP inflammation, highlighting molecules, which are currently investigated as present and future therapeutic targets for this life-threatening disease.

A comprehensive insight into the anti-inflammatory properties of dapsone

The 4,4'-diaminodiphenyl sulfone (DDS), also known as dapsone, is traditionally used as a potent anti-bacterial agent in clinical management of leprosy. For decades, dapsone has been among the first-line medications used in multidrug treatment of leprosy recommended by the World Health Organization (WHO). Shortly after dapsone's discovery as an antibiotic in 1937, the dual function of dapsone (anti-microbial and anti-inflammatory) was elucidated. Dapsone exerts its anti-bacterial effects by inhibiting dihydrofolic acid synthesis, leading to inhibition of bacterial growth, while its anti-inflammatory properties are triggered by inhibiting reactive oxygen species (ROS) production, reducing the effect of eosinophil peroxidase on mast cells and downregulating neutrophil-mediated inflammatory responses. Among the leading mechanisms associated with its anti-microbial/anti-protozoal effects, dapsone clearly has multiple antioxidant, anti-inflammatory, and anti-apoptotic functions. In this regard, it has been described in treating a wide variety of inflammatory and infectious skin conditions. Previous reports have explored different molecular targets for dapsone and provided insight into the anti-inflammatory mechanism of dapsone. This article reviews several basic, experimental, and clinical approaches on anti-inflammatory effect of dapsone.

The relevance of complement in pemphigoid diseases: A critical appraisal

Pemphigoid diseases are autoimmune chronic inflammatory skin diseases, which are characterized by blistering of the skin and/or mucous membranes, and circulating and tissue-bound autoantibodies. The well-established pathomechanisms comprise autoantibodies targeting various structural proteins located at the dermal-epidermal junction, leading to complement factor binding and activation. Several effector cells are thus attracted and activated, which in turn inflict characteristic tissue damage and subepidermal blistering. Moreover, the detection of linear complement deposits in the skin is a diagnostic hallmark of all pemphigoid diseases. However, recent studies showed that blistering might also occur independently of complement. This review reassesses the importance of complement in pemphigoid diseases based on current research by contrasting and contextualizing data from in vitro, murine and human studies.

Unmet Medical Needs in Chronic, Non-communicable Inflammatory Skin Diseases

An estimated 20-25% of the population is affected by chronic, non-communicable inflammatory skin diseases. Chronic skin inflammation has many causes. Among the most frequent chronic inflammatory skin diseases are atopic dermatitis, psoriasis, urticaria, lichen planus, and hidradenitis suppurativa, driven by a complex interplay of genetics and environmental factors. Autoimmunity is another important cause of chronic skin inflammation. The autoimmune response may be mainly T cell driven, such as in alopecia areata or vitiligo, or B cell driven in chronic spontaneous urticaria, pemphigus and pemphigoid diseases. Rare causes of chronic skin inflammation are autoinflammatory diseases, or rheumatic diseases, such as cutaneous lupus erythematosus or dermatomyositis. Whilst we have seen a significant improvement in diagnosis and treatment, several challenges remain. Especially for rarer causes of chronic skin inflammation, early diagnosis is often missed because of low awareness and lack of diagnostics. Systemic immunosuppression is the treatment of choice for almost all of these diseases. Adverse events due to immunosuppression, insufficient therapeutic responses and relapses remain a challenge. For atopic dermatitis and psoriasis, a broad spectrum of innovative treatments has been developed. However, treatment responses cannot be predicted so far. Hence, development of (bio)markers allowing selection of specific medications for individual patients is needed. Given the encouraging developments during the past years, we envision that many of these challenges in the diagnosis and treatment of chronic inflammatory skin diseases will be thoroughly addressed in the future.

Evaluation of Nomacopan for Treatment of Bullous Pemphigoid: A Phase 2a Nonrandomized Controlled Trial

Importance

Bullous pemphigoid is a difficult-to-treat autoimmune blistering skin disease that predominantly affects older adults and is associated with an increased mortality rate.

Objective

To examine the safety and therapeutic potential of nomacopan, an inhibitor of leukotriene B4 and complement C5, in patients with bullous pemphigoid.

Design, Setting, and Participants

This multicenter, single-group, phase 2a nonrandomized controlled trial was conducted in the dermatology departments of universities in the Netherlands and Germany. Participants were enrolled between September 2018 and April 2020. Older adult patients (aged ≥55 years) with mild to moderate, new-onset or relapsing bullous pemphigoid were recruited into the study.

Interventions

Patients received nomacopan, 90 mg, subcutaneously on day 1 and 30 mg subcutaneously daily until day 42.

Main Outcomes and Measures

The primary end point was the proportion of patients with grade 3 to 5 (severe) adverse events associated or possibly associated with nomacopan. Secondary end points included mean absolute and percentage changes in the Bullous Pemphigoid Disease Area Index (BPDAI) activity score, the BPDAI pruritus score, and the patient-reported outcome measures Dermatology Life Quality Index (DLQI) and Treatment of Autoimmune Bullous Disease Quality of Life (TABQOL).

Results

A total of 9 patients (median [range] age, 75 [55-85] years) with bullous pemphigoid were included in the trial, of whom 5 were women (55.6%). No serious adverse events associated with nomacopan were found. The mean (90% CI) BPDAI activity score decreased from 32.0 (8.7) points on day 1 to 19.6 (9.0) points on day 42. Seven of 9 patients (77.8%) responded to nomacopan with a reduction in the BPDAI activity score of at least 8 points between days 1 and 42; in 3 responders, the reduction was 80% or greater. On day 42, the mean (90% CI) BPDAI pruritus score had decreased by 6.8 (4.6) points from 17.6 (4.0) points on day 1. The mean (90% CI) DLQI score decreased from 11.3 (4.2) points at baseline to 6.4 (3.8) points by day 42, and the mean (90% CI) TABQOL score decreased from 14.6 (5.4) points at baseline to 10.3 (5.0) points on day 42.

Conclusions and Relevance

Results of this nonrandomized controlled trial suggest that nomacopan can be well tolerated in older patients with bullous pemphigoid and may have therapeutic benefits for suppressing acute flares of this disease. A larger, placebo-controlled randomized clinical trial is warranted to confirm this safety profile and to establish nomacopan as a new therapeutic option for bullous pemphigoid.

Trial Registration

ClinicalTrials.gov Identifier: NCT04035733.

Increased Fibrosis in a Mouse Model of Anti-Laminin 332 Mucous Membrane Pemphigoid Remains Unaltered by Inhibition of Aldehyde Dehydrogenase

Mucous membrane pemphigoid (MMP) is an autoimmune blistering disease characterized by autoantibodies against the basal membrane zone of skin and surface-close epithelia and predominant mucosal lesions. The oral cavity and conjunctivae are most frequently affected, albeit clinical manifestations can also occur on the skin. MMP-associated lesions outside the oral cavity typically lead to scarring. Mechanisms underlying scarring are largely unknown in MMP and effective treatment options are limited. Herein, we assessed the collagen architecture in tissue samples of an antibody-transfer mouse model of anti-laminin-332 MMP. In MMP mice, increased collagen fibril density was observed in skin and conjunctival lesions compared to mice injected with normal rabbit IgG. The extracellular matrix of MMP skin samples also showed altered post-translational collagen cross-linking with increased levels of both lysine- and hydroxylysine-derived collagen crosslinks supporting the fibrotic phenotype in experimental MMP compared to control animals. In addition, we evaluated a potential anti-fibrotic therapy in experimental anti-laminin-332 MMP using disulfiram, an inhibitor of the aldehyde dehydrogenase (ALDH), which has been implicated in immune-mediated mucosal scarring. In addition, disulfiram also acts as a copper chelator that was shown to block lysyl oxidase activity, an enzyme involved in formation of collagen crosslinks. Topical use of disulfiram (300 μM in 2% [w/v] methocel) did not improve ocular lesions in experimental MMP over the 12-day treatment period in disulfiram-treated mice compared to vehicle-treated mice (n=8/group). Furthermore, C57BL6/J mice (n=8/group) were treated prophylactically with 200 mg/kg p.o. disulfiram or the solvent once daily over a period of 12 days. Systemic treatment did not show any reduction in the severity of oral and ocular lesions in MMP mice, albeit some improvement in skin lesions was observed in disulfiram- vs. vehicle-treated mice (p=0.052). No reduction in fibrosis was seen, as assessed by immunohistochemistry. Whilst blocking of ALDH failed to significantly ameliorate disease activity, our data provide new insight into fibrotic processes highlighting changes in the collagenous matrix and cross-linking patterns in IgG-mediated MMP.

Mucous membrane pemphigoid

Mucous membrane pemphigoid (MMP) is a clinically and immunopathologically heterogenous disease with an incidence of about 2/million inhabitants/year in central Europe. Pemphigoid diseases are characterized by autoantibodies against structural proteins of the epidermis and/or surface-close epithelia. MMP has been defined as pemphigoid disease with predominant mucosal lesions. Most frequently, the oral cavity and the conjunctivae are affected. Lesions outside the mouth tend to heal with scarring leading to visual impairment and finally blindness, as well as, more rarely, impairment of breathing and food intake. Autoantibodies target BP180 (collagen type XVII), laminin 332, BP230 (nearly always in conjunction with other antigens), and type VII collagen in about 75%, 10-20%, 10-30%, and <5% of MMP patients, respectively. While the main autoantibody isotype is IgG, additional, and less frequently, exclusive IgA autoantibodies can be detected in the majority of patients. Assaying for anti-laminin 332 reactivity is pivotal, since in about a quarter of patients with anti-laminin 332 MMP, a malignancy, mainly solid cancers, is associated. The pathophysiology of MMP is yet incompletely understood. A recent mouse model of anti-laminin 332 MMP replicating characteristic clinical and immunopathological findings of the human disease may be helpful to close this knowledge gap. Diagnosis is established by the clinical picture with predominant mucosal lesions and visualization of tissue-bound anti-basement membrane zone antibodies by direct immunofluorescence microscopy. In recent S3 guidelines initiated by the European Academy of Dermatology and Venereology, the clinical spectrum and diagnostic strategies are detailed. In addition, treatment regimens for different clinical situations including patients with exclusive oral or ocular involvement are outlined. Future studies are needed to better understand the clinal complexity and associations as well as to establish widely available diagnostic assays and evidence-based therapeutic strategies.