Corrigendum: Cutaneous kinase activity correlates with treatment outcomes following PI3K delta inhibition in mice with experimental pemphigoid diseases.

[This corrects the article DOI: 10.3389/fimmu.2022.865241.].

Cutaneous kinase activity correlates with treatment outcomes following PI3K delta inhibition in mice with experimental pemphigoid diseases.

Chronic blistering at the skin and/or mucous membranes, accompanied by a varying degree of inflammation, is the clinical hallmark of pemphigoid diseases that impose a major medical burden. Pemphigoid diseases are caused by autoantibodies targeting structural proteins of the epithelial basement membrane. One major pathogenic pathway of skin blistering and inflammation is activation of myeloid cells following Fc gamma receptor-dependent binding to the skin-bound immune complexes. This process requires activation of specific kinases, such as PI3Kδ, which have emerged as potential targets for the treatment of pemphigoid diseases. Yet, it is unknown if global cutaneous kinase activity present in lesional pemphigoid disease correlates with therapeutic effects following treatment with a given target-selective kinase inhibitor. To address this, we here first determined the kinase activity in three different mouse models of pemphigoid diseases: Antibody transfer-induced mucous membrane pemphigoid (MMP), antibody transfer-induced epidermolysis bullosa acquisita (EBA) and immunization-induced EBA. Interestingly, the kinome signatures were different among the three models. More specifically, PI3Kδ was within the kinome activation network of antibody transfer-induced MMP and immunization-induced EBA, but not in antibody transfer-induced EBA. Next, the therapeutic impact of the PI3Kδ-selective inhibitor parsaclisib was evaluated in the three model systems. In line with the kinome signatures, parsaclisib had therapeutic effects in antibody transfer-induced MMP and immunization-induced EBA, but not in autoantibody-induced EBA. In conclusion, kinase activation signatures of inflamed skin, herein exemplified by pemphigoid diseases, correlate with the therapeutic outcomes following kinase inhibition, demonstrated here by the PI3Kδ inhibitor parsaclisib.

Pathogenic Activation and Therapeutic Blockage of FcαR-Expressing Polymorphonuclear Leukocytes in IgA Pemphigus.

Pathomechanisms in IgA pemphigus are assumed to rely on Fc-dependent cellular activation by antigen-specific IgA autoantibodies; however, models for the disease and more detailed pathophysiologic data are lacking. In this study, we aimed to establish in vitro models of disease for IgA pemphigus, allowing us to study the effects of the interaction of anti-keratinocyte IgA with cell surface FcαRs. Employing multiple in vitro assays, such as a skin cryosection assay and a human skin organ culture model, in this study, we present mechanistic data for the pathogenesis of IgA pemphigus, mediated by anti-desmoglein 3 IgA autoantibodies. Our results reveal that this disease is dependent on FcαR-mediated activation of leukocytes in the epidermis. Importantly, this cell-dependent pathology can be dose-dependently abrogated by peptide-mediated inhibition of FcαR:IgA-Fc interaction, as confirmed in an additional model for IgA-dependent disease, that is, IgA vasculitis. These data suggest that IgA pemphigus can be modeled in vitro and that IgA pemphigus and IgA vasculitis are FcαR-dependent disease entities that can be specifically targeted in these experimental systems.

Propranolol Is an Effective Topical and Systemic Treatment Option for Experimental Epidermolysis Bullosa Acquisita.

Propranolol is an ADRB2 blocker that regulates heart muscle contractions, smooth muscle relaxation, and glycogenolysis. In addition, an increasing number of applications in dermatology have been described, most prominently, the use as a first-line treatment for infantile hemangiomas. We here show that propranolol enhances IL-8-induced neutrophil chemotaxis and reduces the release of ROS after immune complex stimulation. To obtain further molecular insights into the modulatory effects of propranolol in activated neutrophils, we performed RNA sequencing of immune complex-stimulated neutrophils in the absence and presence of the drug. We identified the transcriptomic signature of propranolol and demonstrated an ADR2-independent immunomodulatory effect. To determine if the anti-inflammatory transcriptomic signature of propranolol also translates into clinical effects, we next evaluated the impact of propranolol in a prototypical neutrophil-dependent skin disease, specifically, antibody transfer-induced epidermolysis bullosa acquisita in mice. To validate the identified propranolol gene signature obtained in human neutrophils, we analyzed a selection of genes by RT-PCR in mouse epidermolysis bullosa acquisita skin and confirmed TNF, among others, to be differentially regulated by propranolol treatment. Our data clearly indicate that, based on its molecular impact on immune complex-activated neutrophils, propranolol is a potential treatment option for neutrophil-mediated inflammatory skin diseases.

Protective effect of TSLP and IL-33 cytokines in ulcerative colitis.

PURPOSE: Inflammatory bowel disease (IBD) primarily includes ulcerative colitis (UC) and Crohn's disease (CD). Thymic stromal lymphopoietin (TSLP) is a cytokine produced by intestinal epithelial cells (IECs) with immunomodulatory properties that plays an important role in the development of regulatory T cell (Treg) responses and tolerance in the gut. On the other hand, IL-33 has been considered as a cytokine with two different properties, inflammatory and anti-inflammatory functions, the latter may play a protective role against chronic intestinal inflammation. In the present study, we investigated the relative gene expression levels of TSLP and IL-33 molecules in ulcerative colitis. METHODS: Patients with clinical symptoms of colitis undergoing a routine diagnostic colonoscopy were included in this study. Biopsy specimens were collected and divided into two parts. One part was fixed and processed for routine histopathological examinations and the other part was stored for RNA extraction. TSLP and IL-33 gene expression were determined using the SYBR Green qRT-PCR. RESULTS: The expression level of TSLP and IL-33 were significantly lower in UC patients compared with the control group. Moreover, the expressions of these cytokines were more down-regulated in severe UC patients compared with mild and moderate ones and the control group. We also showed a positive correlation between low expression of TSLP and IL-33 and the severity of UC disease. CONCLUSIONS: In this study, we showed decreased mRNA expression levels of TSLP and IL-33 in UC patients and also a negative correlation between expression of TSLP and IL-33 and severity of UC disease.

Calcitriol Treatment Ameliorates Inflammation and Blistering in Mouse Models of Epidermolysis Bullosa Acquisita.

A link between hypovitaminosis D and development of autoimmune bullous disorders has been suggested recently, but this association has not been elaborated experimentally. Here, the role of vitamin D was investigated in epidermolysis bullosa acquisita (EBA), an anti-type VII collagen autoantibody-induced blistering skin disease. Oral administration of the hormonally active vitamin D metabolite calcitriol ameliorated clinical disease severity and dermal neutrophil infiltration in both an antibody transfer- and immunization-induced EBA mouse model. Mechanistically, calcitriol hindered immune effector cell activation as evidenced by increased L-selectin expression on Gr-1+ cells in calcitriol-treated mice with antibody transfer-induced EBA, as well as suppressed in vitro immune complex-induced reactive oxygen species production in calcitriol-treated murine neutrophils. Additionally, calcitriol administration was associated with an increase of regulatory T (CD4+FoxP3+) and B (CD19+IL10+) cells as well as reduction of pro-inflammatory T helper 17 (CD4+IL-17+) cells in mice with immunization-induced EBA. In line, levels of circulating anti-type VII collagen autoantibodies were lower in mice that received calcitriol compared to solvent-treated animals. Together with the observed state of hypovitaminosis D in most cases of an analyzed EBA patient cohort, the results of this study support the use of vitamin D derivatives or analogs for patients with EBA and related diseases.

PDE4 Inhibition as Potential Treatment of Epidermolysis Bullosa Acquisita.

Pemphigoid diseases such as epidermolysis bullosa acquisita (EBA) may be difficult to treat. In pemphigoid diseases, mucocutaneous blistering is caused by autoantibodies to hemidesmosomal antigens; in EBA the autoantigen is type VII collagen. Despite growing insights into pemphigoid disease pathogenesis, corticosteroids are still a mainstay of treatment. In experimental EBA, myeloid cell activation is a key event leading to blistering. Activation of these cells depends on phosphodiesterase (PDE) 4. We therefore evaluated the potential for PDE4 inhibition in EBA: PDE4 was highly expressed in inflammatory cells and in the epidermis of patients compared with healthy skin samples. PDE4 inhibitors rolipram, roflumilast, and roflumilast N-oxide prevented the release of immune complex-induced reactive oxygen species from polymorphonuclear leukocytes and separation of the dermal-epidermal junction of skin incubated with antibodies to collagen type VII and polymorphonuclear leukocytes. The PDE4 inhibitors also impaired CD62L shedding and decreased CD11b expression on immune complex-stimulated polymorphonuclear leukocytes. For in vivo validation, experimental EBA was induced in mice by transfer of anti-collagen type VII IgG or immunization with collagen type VII. Roflumilast dose-dependently reduced blistering in antibody transfer-induced EBA and also hindered disease progression in immunization-induced EBA. PDE4 inhibition emerges as a new treatment modality for EBA and possibly other neutrophil-driven pemphigoid diseases.