Bullous pemphigoid: What's ahead?

Eosinophil-derived galectin-10 upregulates matrix metalloproteinase expression in bullous pemphigoid blisters

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune bullous disease in which abundant eosinophils accumulate in the blisters. Galectin-10 abounds in the cytoplasm of eosinophils and is released as a result of eosinophil extracellular trap cell death (EETosis).

OBJECTIVE

To identify EETosis and the pathological roles of galectin-10 in BP.

METHODS

EETosis and galectin-10 in BP blisters were confirmed by immunofluorescence and transmission electron microscopy. The concentrations of galectin-10 in serum and blister fluid from BP patients were studied by ELISA. The matrix metalloproteinase (MMP) expression in BP blisters was immunohistochemically compared to that in healthy controls. As an in vitro assay, normal human epidermal keratinocytes (NHEKs) and normal human dermal fibroblasts (NHDFs) were stimulated with galectin-10, followed by MMP expression measurement by real-time PCR and ELISA. The signaling pathways activated by galectin-10 were studied using Western blotting and confirmed by inhibition assays.

RESULTS

Galectin-10-containing eosinophil infiltration and the extracellular deposition of major basic protein were observed in BP blisters. The ultrastructural characteristics of tissue eosinophils indicated piecemeal degranulation and EETosis. In the BP patients, the concentration of galectin-10 was higher in the blister fluid than in the serum. Several types of MMPs were upregulated in BP blisters. Galectin-10 upregulated the production of MMPs through the pathways of p38 MAPK, ERK and JNK in NHEKs and NHDFs.

CONCLUSION

In the BP blisters, the eosinophils underwent EETosis and released galectin-10. Galectin-10 might contribute to BP blister formation through the production of MMPs by keratinocytes and fibroblasts.

Targeting type 2 inflammation in bullous pemphigoid: current and emerging therapeutic approaches

Bullous pemphigoid (BP) is one of the most common autoimmune bullous diseases and mainly affects an elderly population with multi-morbidity. Due to the frailty of many BP patients, existing treatment options are limited. The blisters associated with BP result from IgG and IgE autoantibodies binding to the central components of hemidesmosome, BP180, and BP230, stimulating a destructive inflammatory process. The known characteristic features of BP, such as intense pruritus, urticarial prodrome, peripheral eosinophilia, elevated IgE, as well as recent expanding evidence from in vitro and in vivo studies implicate type 2 inflammation as an important driver of BP pathogenesis. Type 2 inflammation is an inflammatory pathway involving a subset of CD4+ T cells that secrete IL-4, IL-5, and IL-13, IgE-secreting B cells, and granulocytes, such as eosinophils, mast cells, and basophils. It is believed that effectors in type 2 inflammation may serve as novel and effective treatment targets for BP. This review focuses on recent understandings of BP pathogenesis with a particular emphasis on the role of type 2 inflammation. We summarize current clinical evidence of using rituximab (B-cell depletion), omalizumab (anti-IgE antibody), and dupilumab (anti-IL-4/13 antibody) in the treatment of BP. The latest advances in emerging targeted therapeutic approaches for BP treatment are also discussed.

Three cases of refractory bullous pemphigoid in the elderly treated successfully with ultra‐low‐dose rituximab

Rituximab has proven effective for the treatment of steroid-refractory bullous pemphigoid (BP), but there is controversy over the dosing protocol. We report three cases of refractory BP treated successfully with ultra-low-dose rituximab (100 mg weekly for 4 weeks). Our cases confirmed the efficacy and good follow-up outcomes of this treatment strategy for refractory BP. The ultra-low-dose rituximab regimen (100 mg weekly for 4 weeks) may be a useful alternative therapy in patients with refractory BP.

Case report: Bullous pemphigoid arising in a patient with scleroderma and multiple sclerosis

Background

Bullous pemphigoid (BP) is the most common autoimmune-blistering disease, clinically characterized by erythematous urticarial plaques, blisters, and intense pruritus, induced by autoantibodies against two proteins of the dermo-epidermal junction, BP180 and BP230. A large number of autoimmune diseases are reported in the literature as BP comorbidities, such as multiple sclerosis, but only a few cases are in association with scleroderma and none in association with both.

Case presentation

We present the case of a 68-year-old woman affected by multiple sclerosis and scleroderma who developed severe bullous pemphigoid with a bullous pemphigoid disease area index of 60 and high titers of anti-BP180 and anti-BP230 autoantibodies by enzyme-linked immunosorbent assays. After 2 months of therapy with both intravenous and oral corticosteroids, the active lesions of bullous pemphigoid were remitted with no relapse.

Conclusion

Autoimmune diseases affecting the skin or organs where BP180 and BP230 are present could trigger an immune response to these antigens through an epitope-spreading phenomenon and, over the years, induce bullous pemphigoid onset.

NET Formation in Bullous Pemphigoid Patients With Relapse Is Modulated by IL-17 and IL-23 Interplay

Background: DNA extracellular traps (ETs), released by neutrophils (NETs), or eosinophils (EETs), play a pathogenic role in several autoimmune disorders. However, to date, NETs have never been investigated in bullous pemphigoid (BP) with respect to clinical and immunological activities, both at baseline and at time of relapse which have been characterized with specific IL-17 and IL-23 patterns. Objective: We sought to assess whether ETs were associated with BP as well as the relative contribution of IL-17 axis cytokines to NET induction. Methods: Skin biopsy specimens were obtained from 11 patients with BP. Immuno-detection of neutrophils and eosinophils combined to DNA staining allowed us to investigate the in-situ presence of NETs and EETs using confocal scanning microscopy. NETs release was evaluated ex vivo by stimulating polymorphonuclear cells from BP patients with BP biological fluids in presence of IL-17A and IL-23 or of glucocorticoids. Results: At baseline, ETs were observed in BP lesions at the site of dermal-epidermal cleavage. Despite an important infiltrate of eosinophils, ETs were essentially associated with neutrophils in situ and were not related to BP clinical activity at diagnosis. In situ observation of NETs was associated in 6 among 8 patients with serum capacity of NET induction. Notably both blister fluid and sera from BP patients at diagnosis and at time of relapse could induce NET formation ex vivo. In contrast, a longitudinal investigation showed a decrease of NET formation with time of treatment in patients undergoing remission. Mimicking relapse, complementation of sera from BP patients with ongoing remission with either IL-17A or IL-23 increased NET formation. Conversely, IL-17A inhibited NET formation induced by serum from BP patients with relapse supplemented or not with IL-23. Finally, glucocorticoids also inhibited NET formation ex vivo in BP. Conclusion: NET formation is an associated phenomenon with BP. Furthermore, we showed that IL-23 favored NET formation, whereas the effects of IL-17A are environment dependent. Indeed, IL-17A displayed a protective effect on NET formation when associated with IL-23, showing for the first-time differential effects of these two cytokines in BP.

BP180 Is Critical in the Autoimmunity of Bullous Pemphigoid

Bullous pemphigoid (BP) is by far the most common autoimmune blistering dermatosis that mainly occurs in the elderly. The BP180 is a transmembrane glycoprotein, which is highly immunodominant in BP. The structure and location of BP180 indicate that it is a significant autoantigen and plays a key role in blister formation. Autoantibodies from BP patients react with BP180, which leads to its degradation and this has been regarded as the central event in BP pathogenesis. The consequent blister formation involves the activation of complement-dependent or -independent signals, as well as inflammatory pathways induced by BP180/anti-BP180 autoantibody interaction. As a multi-epitope molecule, BP180 can cause dermal-epidermal separation via combining each epitope with specific immunoglobulin, which also facilitates blister formation. In addition, some inflammatory factors can directly deplete BP180, thereby leading to fragility of the dermal-epidermal junction and blister formation. This review summarizes recent investigations on the role of BP180 in BP pathogenesis to determine the potential targets for the treatment of patients with BP.