Dermatomyositis autoantigen CHD4 forms immune stimulatory complexes with endogenous DNA.

Dermatomyositis (DM) is an idiopathic inflammatory myopathy belonging to the spectrum of autoimmune connective tissue diseases. DM patients present with antinuclear antibodies against Mi-2, also known as Chromodomain-helicase-DNA-binding protein 4 (CHD4). CHD4 is upregulated in DM skin biopsies and could potentially affect DM pathophysiology as it binds endogenous DNA with a high affinity (KD = 0.2 nM ± 0.076 nM) and forms CHD4-DNA complexes. The complexes are localized in the cytoplasm of UV-radiated and transfected HaCaTs and amplify the expression of interferon (IFN) regulated genes and the amount of functional CXCL10 protein stronger than DNA alone. The enhancement of the type I IFN pathway activation in HaCaTs through CHD4-DNA signalling suggests a possible mechanism for the sustainment of the pro-inflammatory vicious cycle in DM skin lesions.

JAK1/2 inhibition impairs the development and function of inflammatory dendritic epidermal cells in atopic dermatitis.

BACKGROUND: Janus kinase (JAK) inhibitors are a new class of therapeutic compounds for dermatological diseases. In atopic dermatitis (AD), data of clinical phase III trials show rapid improvement of pruritus and significant reduction of inflammation within the first weeks with a favorable safety profile. However, their mode of action in AD is not fully understood. OBJECTIVES: In our study, we investigate the effect of different JAK inhibitors on cell differentiation, phenotype, and function of inflammatory dendritic epidermal cells (IDECs). METHODS: We analyzed the JAK expression in IDEC from ex vivo skin and in vitro generated IDECs using flow cytometry and PCR. Further, we studied in vitro the effect of different JAK inhibitors on IDEC cell differentiation, phenotype, and maturation. RESULTS: IDECs express JAK1 and JAK2 ex vivo and in vitro. We found that JAK1 and JAK2 were upregulated during the differentiation from monocytes to IDECs. Conversely, JAK2 inhibition by ruxolitinib (JAK1/2 inhibitor) or BMS-911543 (JAK2 inhibitor) abrogated the differentiation from monocytes into IDECs. Differentiated IDECs can redifferentiate into a more monocyte-like phenotype in the presence of ruxolitinib or BMS-911543. Furthermore, we showed that concomitant inhibition of JAK1/2 rather than blocking JAK1 or JAK2 alone, impaired maturation and the release of proinflammatory cytokines on lipopolysaccharide stimulation. CONCLUSIONS: Our results suggest that inhibition of JAK1/2 impairs IDEC differentiation and function. We provide new insight into the mode of action of JAK inhibitors in AD and highlight the role of JAK1/2 inhibitors for the treatment of patients with AD.

NKG2D and its ligands as cytotoxic factors in cutaneous lupus erythematosus.

Cutaneous lupus erythematosus (CLE) is an autoimmune skin disorder that is characterized by an anti-epidermal lymphocytic infiltrate invading the dermo-epidermal junction, causing an interface dermatitis (ID). Pathogenesis of CLE has been linked to activation of innate immunity. NKG2D is an innate immune receptor on NK cells and distinct T-cell populations. The NKG2D ligands MHC class I polypeptide-related sequence A and B (MICA, MICB) have been associated to CLE susceptibility. Our gene microarray analyses of chronic discoid lupus erythematosus (CDLE) skin lesions, separated in epidermal, junctional and dermal skin areas via laser microdissection, revealed a high expression of NKG2D in the lymphocytic infiltrate and led us to further investigate the role of NKG2D in CLE. Pathway analyses showed a strong "interferon (IFN) signature" and vast activation of innate immune response pathways (TLR, RIG-I, cytosolic DNA sensing, JAK/STAT) in CDLE, that expressed the high NKG2D signal. Immunohistochemistry (IHC) confirmed the presence of NKG2D and its ligand MICB in CDLE and subacute cutaneous lupus erythematosus (SCLE) lesions. Finally, HaCaT cells were stimulated with nucleic acids and extracted RNA was sequenced with Illumina HiSeq and showed that stressed keratinocytes express typical NKG2D ligands MICA/B and ULBP2. This study provides first evidence that NKG2D is present in CDLE and SCLE skin lesions and could be relevant for cytotoxicity in IFN-driven skin lesions with upregulated innate immune response pathways present in CLE. It could furthermore play a role in CLE inflammation promoted by keratinocytes under cell stress.

Safety, pharmacokinetics and pharmacodynamics of a topical SYK inhibitor in cutaneous lupus erythematosus: A double-blind Phase Ib study.

The immunoregulator spleen tyrosine kinase (SYK) is upregulated in cutaneous lupus erythematosus (CLE). This double-blind, multicentre, Phase Ib study evaluated the safety, tolerability, pharmacokinetics, pharmacodynamics and clinical efficacy of the selective SYK inhibitor GSK2646264 in active CLE lesions. Two lesions from each participant (n = 11) were each randomized to topical application of 1% (w/w) GSK2646264 or placebo for 28 days; all participants received GSK2646264 and placebo. The primary endpoint was safety and tolerability of GSK2646264, assessed by adverse event incidence and a skin tolerability test. Secondary endpoints included change from baseline in clinical activity and mRNA expression of interferon-related genes in skin biopsies. Levels of several immune cell markers were evaluated over time. Eight (73%) participants experienced ≥ 1 adverse event (all mild in intensity), and maximal dermal response was similar for GSK2646264 and placebo. The expression of several interferon-related genes, including CXCL10 and OAS1, showed modest decreases from baseline after 28 days of treatment with GSK2646264 compared with placebo. Similar findings were observed for CD3 + T cell and CD11c + dendritic cell levels; however, overall clinical activity remained unchanged with GSK2646264 vs. placebo. Further studies are warranted to assess SYK inhibitors as potential treatment for CLE.

APRIL expression is upregulated in atopic dermatitis skin lesions and at sites of antigen driven allergic skin inflammation in mice.

Atopic dermatitis (AD) is the most common inflammatory skin disease. It is characterized by a defective skin barrier and a Th2 dominated skin inflammation. The TNF family member a proliferation-inducing ligand (APRIL) and its receptors transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) and B cell maturation antigen (BCMA) are expressed by immune cells and epithelial cells including keratinocytes. We demonstrate that APRIL expression is upregulated in the epidermis of skin lesions from patients with AD as well as in mouse skin undergoing allergic inflammation elicited by epicutaneous (EC) sensitization with the antigen ovalbumin. We show that APRIL from OVA sensitized mouse skin causes keratinocytes to upregulate the expression of IL-6, an inflammatory cytokine implicated in AD pathogenesis. These results suggest a role for APRIL in allergic skin inflammation and a potential role for APRIL blockade in treating AD.

Cutaneous lupus erythematosus: The impact of self-amplifying innate and adaptive immune responses and future prospects of targeted therapies.

Cutaneous lupus erythematosus (CLE) is a heterogeneous autoimmune disease encompassing a broad spectrum of skin conditions including localized plaques or widespread lesions, which may be accompanied by systemic involvement (systemic lupus erythematosus (SLE)). The disease is characterized by necroptotic keratinocytes and a cytotoxic immune cell infiltrate at the dermo-epidermal junction (DEJ), orchestrated by interferon (IFN)-regulated proinflammatory cytokines. Molecular analyses revealed a strong upregulation of innate and adaptive immune pathways in lesional skin including DNA-recognition pathways, chemokine signalling, antigen presentation and B- and T-cell activation, which are believed to interact in a complex self-amplifying network. Concerning adaptive immune signalling, particularly B cells are currently being studied as there is growing evidence for additional abilities besides autoantibody expression in skin autoimmunity. These detailed insights have paved the way for the development of drugs targeting crucial molecules of pathogenic immune cells and pathways. Moreover, they forwarded the understanding of distinct molecular mechanisms within CLE subtypes, which might enable a more mechanism-directed, stratified pharmacotherapy of LE skin lesions in the future.

High expression of B lymphocyte stimulator in lesional keratinocytes of patients with cutaneous lupus erythematosus.

Belimumab, an anti-B lymphocyte stimulator (BLyS) monoclonal antibody, is approved for systemic lupus erythematosus; however, it is unclear if it can be used to treat specific skin lesions in this disease. In this analysis, we investigated the expression of BLyS and its receptors in skin lesions of different subtypes of cutaneous lupus erythematosus (CLE) using immunohistochemistry and gene expression analyses. Compared to healthy controls, the expression of BLyS was significantly higher in skin lesions of all included CLE subtypes. Similar results were seen for the BLyS receptors BAFF-R and BCMA. Moreover, CLE-typical pro-inflammatory mediators (immunostimulatory DNAs) significantly enhanced the BLyS expression of keratinocytes in vitro. This study suggests a potential role for BLyS as therapeutic target in the treatment of CLE skin lesions.

JAK inhibitor ruxolitinib inhibits the expression of cytokines characteristic of cutaneous lupus erythematosus.

This study was stimulated by the clinical observation of a rapid response of a chilblain lupus patient to treatment with JAK1/2-kinase inhibitor ruxolitinib. We investigated the in vivo expression of phospho-JAK2 in CLE skin samples as well as the immunomodulatory in vitro effect of ruxolitinib in cultured immortalized keratinocytes and in a 3D human epidermis model (epiCS). Our results demonstrate that ruxolitinib significantly decreases the production of CLE-typical cytokines (CXCL10, CXCL9, MxA) and might be a promising drug for future clinical studies in patients with CLE and related autoimmune skin diseases.

Spleen tyrosine kinase (SYK) is a potential target for the treatment of cutaneous lupus erythematosus patients.

Spleen tyrosine kinase (SYK) is a protein kinase involved in cell proliferation and the regulation of inflammatory pathways. Due to the increasing evidence that kinase inhibitors have potential as specific anti-inflammatory drugs, we have investigated the potential for SYK inhibition as a therapeutic target in autoimmune diseases, particularly cutaneous lupus erythematosus (CLE). Skin samples of patients with different CLE subtypes and appropriate controls were analysed for the expression of SYK and SYK-associated pro-inflammatory mediators via gene expression analysis and immunohistochemistry. The functional role of SYK in keratinocytes was investigated in vitro, using LE-typical pro-inflammatory stimuli and a selective inhibitor of SYK. SYK-associated genes are strongly upregulated in CLE skin lesions. Importantly, phosphorylated SYK (pSYK) is strongly expressed by several immune cell types and also keratinocytes in CLE skin. In vitro, immunostimulatory nucleic acids are capable of inducing SYK phosphorylation in keratinocytes leading to the induction of pro-inflammatory cytokines, while small-molecule SYK inhibition decreases the expression of these proteins. The results demonstrate that pSYK is expressed by immune cells and keratinocytes in skin lesions of CLE patients. LE-typical stimuli induce the expression of pSYK in vitro. Small-molecule SYK inhibition leads to a reduction of pSYK expression and downregulation of pro-inflammatory cytokines in keratinocytes. We therefore believe that pSYK provides a potential future drug target for the treatment of patients who suffer from CLE and related skin disorders. Specifically, our study reveals evidence supporting the use of topical SYK inhibitors in treating lupus.

Genome-wide association study identifies new susceptibility loci for cutaneous lupus erythematosus.

Cutaneous lupus erythematosus (CLE) is a chronic autoimmune disease of the skin with typical clinical manifestations. Here, we genotyped 906 600 single nucleotide polymorphisms (SNPs) in 183 CLE cases and 1288 controls of Central European ancestry. Replication was performed for 13 SNPs in 219 case subjects and 262 controls from Finland. Association was particularly pronounced at 4 loci, all with genomewide significance (P < 5 × 10(-8) ): rs2187668 (PGWAS  = 1.4 × 10(-12) ), rs9267531 (PGWAS  = 4.7 × 10(-10) ), rs4410767 (PGWAS  = 1.0 × 10(-9) ) and rs3094084 (PGWAS  = 1.1 × 10(-9) ). All mentioned SNPs are located within the major histocompatibility complex (MHC) region of chromosome 6 and near genes of known immune functions or associations with other autoimmune diseases such as HLA-DQ alpha chain 1 (HLA-DQA1), MICA, MICB, MSH5, TRIM39 and RPP21. For example, TRIM39/RPP21 read through transcript is a known mediator of the interferon response, a central pathway involved in the pathogenesis of CLE and systemic lupus erythematosus (SLE). Taken together, this genomewide analysis of disease association of CLE identified candidate genes and genomic regions that may contribute to pathogenic mechanisms in CLE via dysregulated antigen presentation (HLA-DQA1), apoptosis regulation, RNA processing and interferon response (MICA, MICB, MSH5, TRIM39 and RPP21).

Ultraviolet light protection by a sunscreen prevents interferon-driven skin inflammation in cutaneous lupus erythematosus.

Irradiation with ultraviolet (UV) light is an important exacerbating factor in cutaneous lupus erythematosus (CLE) and induces various effects in the skin of patients with the disease, such as cell death and inflammation. Recently, we demonstrated the ability of a broad-spectrum sunscreen to prevent UV-induced damage both in patients with CLE and healthy controls (HCs). The aim of this study was to evaluate whether the UV-dependent activation of interferon (IFN)-driven inflammation in CLE can also be prevented by application of the sunscreen. In 20 patients with different subtypes of CLE and 10 HCs, defined areas on the upper back were treated with a broad-spectrum liposomal sunscreen 20 min prior to a combined standardized UVA/UVB irradiation. Immunohistological analyses using antibodies directed against MxA, CD11c, CD123 and CD68 were performed from skin biopsies taken from areas before UV irradiation as well as from sunscreen-treated and sunscreen-untreated areas 24 and 72 h after UV irradiation. The expression of MxA was completely prevented by the sunscreen applied prior to UV irradiation in CLE patients and HCs. Additionally, sunscreen protection significantly diminished the number of the CD11c- and CD123-positive dendritic cells, which are suggested to be a major source of type I/III IFNs, in UV-irradiated skin of patients with CLE. Moreover, the application of the sunscreen prevented the increase in CD68-positive macrophages in both groups 72 h after UV irradiation. The data of this study demonstrate that UV protection reduces lesional tissue damage and inhibits the typical IFN-driven inflammatory response in CLE.

Low-dose methotrexate - a therapeutical kick in TNF-alpha antagonist treatment for recalcitrant psoriasis vulgaris.

In contrast to the treatment of rheumatoid arthritis, there are few data in psoriasis vulgaris regarding the efficacy of combining tumor necrosis factor (TNF)-alpha inhibitors and methotrexate (MTX). Indeed, combination of MTX with different TNF-alpha inhibitors may enhance the therapeutic effects and reduce side effects because of less dosage of the single agent. The present authors present five cases in which low-dose MTX combined with TNF-alpha inhibitors led to impressive improvement in Psoriasis Area and Severity Index scores. Here, the present authors initiated very low-dose MTX treatment in addition to existing TNF-alpha inhibitor therapy to exhaust current therapy and prevent premature change of the biologic. These observations support the concept of combined treatment in recalcitrant cases of psoriasis, which need a systemically lifelong treatment when both first-line and second-line monotherapies fail to provide sufficient clinical response.

International exchange on the clinical practice and research of rheumatic skin diseases: A report of the 5th International Conference of Cutaneous Lupus Erythematosus.

The 5th International Conference of Cutaneous Lupus Erythematosus was held in Tokyo, Japan on May 9 and 10, 2023. The latest topics on the pathogenesis, diagnosis, assessment, and treatment of cutaneous lupus erythematosus, dermatomyositis, and scleroderma (systemic sclerosis, morphea) were presented by experts in each field and new developments discussed. In these rheumatic skin diseases, many clinical trials of novel therapies targeting cytokines, signaling molecules, plasmacytoid dendritic cells, B cells, and other molecules are currently underway, and standardization of outcome assessment was discussed. In addition, the selection of the therapeutic agents available for the diversity of each case is becoming more important, together with the ongoing pathophysiological analysis of the diseases. The achievements of this conference will further promote the development of clinical practice and research in rheumatic skin diseases through international exchange among researchers. We hope that by reporting a summary of the conference in this manuscript, we can share its contents with readers.

Severe autoimmune hemolytic anemia following immunotherapy with checkpoint inhibitors in two patients with metastatic melanoma: a case report.

Introduction: Over the past decade, immune checkpoint inhibitors such as antibodies against cytotoxicity T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) have become an important armamentarium against a broad spectrum of malignancies. However, these specific inhibitors can cause adverse autoimmune reactions by impairing self-tolerance. Hematologic side effects of immune checkpoint inhibitors, including autoimmune hemolytic anemia (AIHA), are rare but can be life-threatening. Case report: Herein, we report two patients on immune checkpoint inhibitors for metastatic melanoma who developed AIHA with symptoms of dyspnea and fatigue. In the first patient, symptoms alleviated after discontinuation of combined anti CTLA-4 and anti-PD-1 therapy, initiation of corticosteroids and application of a single red blood cell transfusion. Due to subsequent progress of melanoma, combinational anti-PD-1 and tyrosine kinase inhibitor therapy was initiated based on multidisciplinary tumor board decision. After two months, she again developed the described hematological and clinical signs of AIHA leading to cessation of anti-PD-1 therapy and initiation of corticosteroids, which again resulted in an alleviation of her symptoms. Due to further progression, the patient received dacarbazine for several months before she decided to stop any therapy other than palliative supportive care. In the second patient, discontinuation of anti-PD-1 therapy and initiation of corticosteroids entailed a complete alleviation of his symptoms. After refusing chemotherapy due to subsequent melanoma progression, he received radiotherapy of bone metastases and is currently enrolled in a clinical trial. The patient did not develop AIHA ever since. Conclusion: Hematologic immune-related adverse events due to treatment with immune checkpoint inhibitors are rare but can have life-threatening consequences. If dyspnea and other clinical symptoms are present, AIHA should be considered as a potential cause and treated promptly in a multidisciplinary setting. An expanded comprehension of risk factors and pathogenesis of AIHA is needed to identify high-risk patients beforehand, leading to more effective predictive and reactive treatment approaches.