Inhibition of Glucose Metabolism Abrogates the Effector Phase of Bullous Pemphigoid-Like Epidermolysis Bullosa Acquisita

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.

Autoimmune blistering diseases: promising agents in clinical trials

INTRODUCTION

Treatment options for autoimmune bullous diseases (AIBD) are currently limited to corticosteroids and traditional immunomodulants and immunosuppressants that are associated with unfavorable adverse effect profiles. The most frequent AIBDs, i.e. bullous pemphigoid, pemphigus vulgaris, and mucous membrane pemphigoid, impose a high disease burden onto affected patients and can be detrimental due to infections, exsiccosis, and impaired food intake. Significant progress has been made in elucidating disease mechanisms and key mediators by in vivo and in vitro models, thus identifying a multifaceted range of possible drug targets. However, except for rituximab for pemphigus vulgaris, no new drugs have been approved for the treatment of AIBDs in the last decades.

AREAS COVERED

This review covers new drug developments and includes ongoing or completed phase 2 and 3 clinical trials. Studies were identified by querying the registries of ClinicalTrials.gov and Cochrane Library.

EXPERT OPINION

Promising results were shown for a variety of new agents including nomacopan, efgartigimod, omalizumab, dupilumab, as well as chimeric autoantibody receptor T cells. Clinical translation in the field of AIBDs is highly active, and we anticipate significant advances in the treatment landscape.

Dapsone Suppresses Disease in Preclinical Murine Models of Pemphigoid Diseases

Epidermolysis bullosa acquisita and mucous membrane pemphigoid are autoimmune blistering diseases characterized by mucocutaneous blisters elicited by an autoantibody-mediated immune response against specific proteins of the epidermal basement membrane. The antibiotic dapsone is frequently used to treat both diseases, but its therapeutic effectiveness is uncertain, and its mode of action in these diseases is largely unknown. We evaluated the effect of dapsone in antibody transfer mouse models of epidermolysis bullosa acquisita and mucous membrane pemphigoid, which do not allow the drawing of conclusions on clinical treatment regimens but can be instrumental to partially uncover the mode(s) of action of dapsone in these diseases. Dapsone significantly mitigated inflammation in both models, reducing the recruitment of neutrophils into the skin and disrupting their release of leukotriene B4 (LTB4) and ROS in response to immune complexes. LTB4 has been implicated in numerous diseases, but effective LTB4 inhibitors for clinical use are not available. Our findings indicate that the mode of action of dapsone in these models may be based on the inhibition of LTB4 and ROS release from neutrophils. Moreover, they encourage testing the use of dapsone as an effective, albeit nonspecific, inhibitor of LTB4 biosynthesis in other LTB4-driven diseases.