Dominant Th1 and minimal Th17 skewing in discoid lupus revealed by transcriptomic comparison with psoriasis

Transcriptomic studies unravel the molecular and cellular complexity of systemic lupus erythematosus: A review

Transcriptomic analysis plays a vital role in investigating Systemic Lupus Erythematosus (SLE), a complex autoimmune disease characterized by diverse clinical manifestations. This approach has yielded valuable insights into gene expression patterns and molecular regulatory mechanisms involved in SLE pathogenesis. Notably, interferon-stimulated gene (ISG) signatures are significantly upregulated in immune cells, skin, and kidney. Although a correlation with serological parameters and clinical symptoms has been proposed, the association with global disease activities remains controversial. Key findings in the field include an upregulated plasmablast signature, which positively correlates with disease activity; a neutrophil signature associated with lupus nephritis; and a decreased lymphocyte signature, reflecting lymphopenia. Tissue-level studies highlight the critical role of infiltrating immune cells in organ damage. Future research should leverage advanced technologies and integrate multi-omics data to deepen our understanding of SLE's molecular underpinnings, facilitating the development of targeted therapies.

The interferon-rich skin environment regulates Langerhans cell ADAM17 to promote photosensitivity in lupus

The autoimmune disease lupus erythematosus (lupus) is characterized by photosensitivity, where even ambient ultraviolet radiation (UVR) exposure can lead to development of inflammatory skin lesions. We have previously shown that Langerhans cells (LCs) limit keratinocyte apoptosis and photosensitivity via a disintegrin and metalloprotease 17 (ADAM17)-mediated release of epidermal growth factor receptor (EGFR) ligands and that LC ADAM17 sheddase activity is reduced in lupus. Here, we sought to understand how the lupus skin environment contributes to LC ADAM17 dysfunction and, in the process, differentiate between effects on LC ADAM17 sheddase function, LC ADAM17 expression, and LC numbers. We show through transcriptomic analysis a shared IFN-rich environment in non-lesional skin across human lupus and three murine models: MRL/lpr, B6.Sle1yaa, and imiquimod (IMQ) mice. IFN-I inhibits LC ADAM17 sheddase activity in murine and human LCs, and IFNAR blockade in lupus model mice restores LC ADAM17 sheddase activity, all without consistent effects on LC ADAM17 protein expression or LC numbers. Anti-IFNAR-mediated LC ADAM17 sheddase function restoration is associated with reduced photosensitive responses that are dependent on EGFR signaling and LC ADAM17. Reactive oxygen species (ROS) is a known mediator of ADAM17 activity; we show that UVR-induced LC ROS production is reduced in lupus model mice, restored by anti-IFNAR, and is cytoplasmic in origin. Our findings suggest that IFN-I promotes photosensitivity at least in part by inhibiting UVR-induced LC ADAM17 sheddase function and raise the possibility that anifrolumab ameliorates lupus skin disease in part by restoring this function. This work provides insight into IFN-I-mediated disease mechanisms, LC regulation, and a potential mechanism of action for anifrolumab in lupus.

Immune cells in skin inflammation, wound healing, and skin cancer

Given the self-evident importance of cutaneous immunity in the maintenance of body-surface homeostasis, disturbance of the steady-state skin is inextricably intertwined with dysfunction in cutaneous immunity. It is often overlooked by people that skin, well-known as a solid physical barrier, is also a strong immunological barrier, considering the abundant presence of immune cells including lymphocytes, granulocytes, dendritic cells, and macrophages. What's more, humoral immune components including cytokines, immunoglobulins, and antimicrobial peptides are also rich in the skin. This review centers on skin inflammation (acute and chronic, infection and aseptic inflammation), wound healing, and skin cancer to elucidate the elaborate network of immune cells in skin diseases.

Efferocytosis: Current status and future prospects in the treatment of autoimmune diseases

Billions of apoptotic cells are swiftly removed from the human body daily. This clearance process is regulated by efferocytosis, an active anti-inflammatory process during which phagocytes engulf and remove apoptotic cells. However, impaired clearance of apoptotic cells is associated with the development of various autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease. In this review, we conducted a comprehensive search of relevant studies published from January 1, 2000, to the present, focusing on efferocytosis, autoimmune disease pathogenesis, regulatory mechanisms governing efferocytosis, and potential treatments targeting this process. Our review highlights the key molecules involved in different stages of efferocytosis-namely, the "find me," "eat me," and "engulf and digest" phases-while elucidating their relevance to autoimmune disease pathology. Furthermore, we explore the therapeutic potential of modulating efferocytosis to restore immune homeostasis and mitigate autoimmune responses. By providing theoretical underpinnings for the targeting of efferocytosis in the treatment of autoimmune diseases, this review contributes to the advancement of therapeutic strategies in this field.

Spatial characterization of interface dermatitis in cutaneous lupus reveals novel chemokine ligand-receptor pairs that drive disease

Chemokines play critical roles in the recruitment and activation of immune cells in both homeostatic and pathologic conditions. Here, we examined chemokine ligand-receptor pairs to better understand the immunopathogenesis of cutaneous lupus erythematosus (CLE), a complex autoimmune connective tissue disorder. We used suction blister biopsies to measure cellular infiltrates with spectral flow cytometry in the interface dermatitis reaction, as well as 184 protein analytes in interstitial skin fluid using Olink targeted proteomics. Flow and Olink data concordantly demonstrated significant increases in T cells and antigen presenting cells (APCs). We also performed spatial transcriptomics and spatial proteomics of punch biopsies using digital spatial profiling (DSP) technology on CLE skin and healthy margin controls to examine discreet locations within the tissue. Spatial and Olink data confirmed elevation of interferon (IFN) and IFN-inducible CXCR3 chemokine ligands. Comparing involved versus uninvolved keratinocytes in CLE samples revealed upregulation of essential inflammatory response genes in areas near interface dermatitis, including AIM2. Our Olink data confirmed upregulation of Caspase 8, IL-18 which is the final product of AIM2 activation, and induced chemokines including CCL8 and CXCL6 in CLE lesional samples. Chemotaxis assays using PBMCs from healthy and CLE donors revealed that T cells are equally poised to respond to CXCR3 ligands, whereas CD14+CD16+ APC populations are more sensitive to CXCL6 via CXCR1 and CD14+ are more sensitive to CCL8 via CCR2. Taken together, our data map a pathway from keratinocyte injury to lymphocyte recruitment in CLE via AIM2-Casp8-IL-18-CXCL6/CXCR1 and CCL8/CCR2, and IFNG/IFNL1-CXCL9/CXCL11-CXCR3.

Cytotoxic dermatitis: Review of the interface dermatitis pattern in veterinary skin diseases

Interface dermatitis or lichenoid interface dermatitis refers to a cutaneous inflammatory pattern in which keratinocyte cell death is the essential feature. These terms have evolved from the originally described lichenoid tissue reaction. These lesions are the basis for an important group of skin diseases in animals and people where cytotoxic T-cell-mediated epidermal damage is a major pathomechanism. Yet, for largely historical reasons these commonly used morphological diagnostic terms do not reflect the essential nature of the lesion. An emphasis on subsidiary lesions, such as the presence of a lichenoid band, and definitions based on anatomical features, such as location at the dermo-epidermal location, may cause confusion and even misdiagnosis. This review covers historical aspects of the terminology, including the origin of terms such as "lichenoid." The types of cell death involved and the histopathologic lesions are described. Etiopathogenesis is discussed in terms of aberrations of immune/inflammatory mechanisms focusing on cutaneous lupus erythematosus, erythema multiforme, and Stevens-Johnson syndrome/toxic epidermal necrolysis. Mechanisms have most extensively been studied in humans and laboratory animals and the discussion is centered on these species. As interface dermatitis is firmly entrenched in dermatological parlance, rather than using "cytotoxic" as its substitute, the terminologies "interface cytotoxic dermatitis" and "panepidermal cytotoxic dermatitis" are recommended, based on location and extent of epithelium affected.

HIF-1 regulates pathogenic cytotoxic T cells in lupus skin disease

Cutaneous lupus erythematosus (CLE) is a disfiguring autoimmune skin disease characterized by an inflammatory infiltrate rich in T cells, which are strongly implicated in tissue damage. How these cells adapt to the skin environment and promote tissue inflammation and damage is not known. In lupus nephritis, we previously identified an inflammatory gene program in kidney-infiltrating T cells that is dependent on HIF-1, a transcription factor critical for the cellular and developmental response to hypoxia as well as inflammation-associated signals. In our present studies using a mouse model of lupus skin disease, we find that skin-infiltrating CD4+ and CD8+ T cells also express high levels of HIF-1. Skin-infiltrating T cells demonstrated a strong cytotoxic signature at the transcript and protein levels, and HIF-1 inhibition abrogated skin and systemic diseases in association with decreased T cell cytotoxic activity. We also demonstrate in human CLE tissue that the T cell-rich inflammatory infiltrate exhibited increased amounts of HIF-1 and a cytotoxic signature. Granzyme B-expressing T cells were concentrated at sites of skin tissue damage in CLE, suggesting relevance of this pathway to human disease.

LncRNA UCA1 promotes keratinocyte-driven inflammation via suppressing METTL14 and activating the HIF-1α/NF-κB axis in psoriasis

Keratinocytes are closely associated with innate immunity and inflammatory responses, and are dysregulated during the development of psoriasis, but the underlying mechanisms are not yet fully understood. This work aims to reveal the effects of long non-coding RNA (lncRNA) UCA1 in psoriatic keratinocytes. UCA1 was identified as a psoriasis-related lncRNA that highly expressed in psoriatic lesions. The transcriptome and proteome data of keratinocyte cell line HaCaT showed that UCA1 could positively regulate inflammatory functions, such as response to cytokine. Furthermore, UCA1 silencing decreased inflammatory cytokine secretion and innate immunity gene expression in HaCaT, its culture supernatant also decreased the migration and tube formation ability of vascular endothelial cells (HUVECs). Mechanistically, UCA1 activated the NF-κB signaling pathway, which is regulated by HIF-1α and STAT3. We also observed a direct interaction between UCA1 and N6-methyladenosine (m⁶A) methyltransferase METTL14. Knocking down METTL14 counteracted the effects of UCA1 silencing, indicating that it can suppress inflammation. In addition, the levels of m⁶A-modified HIF-1α were decreased in psoriatic lesions, indicating that HIF-1α is a potential target of METTL14. Taken together, this work indicates that UCA1 positively regulates keratinocyte-driven inflammation and psoriasis development by binding to METTL14, and activating HIF-1α and NF-κB signaling pathway. Our findings provide new insights into the molecular mechanisms of keratinocyte-driven inflammation in psoriasis.

Circulating and skin biopsy-present cytokines related to the pathogenesis of cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) is a common disease that may appear as a separate entity from systemic lupus erythematosus (SLE), precede SLE development, or occur as a manifestation of this systemic disease. It has a complex pathophysiology that involves genetic, environmental, and immune-mediated factors creating a self-amplification pro-inflammatory cycle. CLE is characterized by prominent type I interferons (IFNs) inflammation which are considered as the first precursors of the inflammatory cascade generated within the pathophysiology of CLE. TNF-α enhances the production of antibodies through the activation of B cells, and favors the expression of surface nuclear antigens on keratinocytes. UV light exposure favors keratinocyte apoptosis or necroptosis, which results in the release of multiple proinflammatory cytokines, including IL-6, IL-1α, IL-1β, TNF-α, IFNs, and CXCL10. Serum levels of IL-17 are elevated in patients with ACLE, SCLE, and DLE. Evidence suggests IL-22 plays a role primarily in tissue repair rather than in inflammation. High expression of BAFF and its receptors have been found in lesioned keratinocytes of patients with CLE, and patients with CLE have lower serum levels of the regulatory cytokines TGF-β and IL-10. The chemokines CXCL9 and CXCL10 (CXCR3 ligands) have an increased expression among these patients, and their expression is correlated with IFNs levels. CXCR3 ligands recruit cytotoxic type I cells through this receptor, further supporting the death of keratinocytes via necroptosis with the subsequent release of eNAs perpetuating the inflammatory cycle. Interface dermatitis is characterized by the presence of CXCR3-positive lymphocytes. This review describes the leading cytokines and chemokines present in the circulation and skin that play a fundamental role in the pathogenesis of CLE.

Current Knowledge of the Molecular Pathogenesis of Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune disease, which can be limited to the skin or associated with systemic lupus erythematosus (SLE). Gene expression analysis has revealed that both the innate and adaptive immune pathways are activated in CLE. Ultraviolet (UV) light, the predominant environmental factor associated with CLE, induces apoptosis in keratinocytes, and the endogenous nucleic acids released from the apoptotic cells are recognized via pattern recognition receptors, including Toll-like receptors. This leads to the production of type I interferon, a major contributor to the pathogenesis of CLE, by plasmacytoid dendritic cells. UV irradiation can also induce the externalization of autoantigens, such as SS-A/Ro, exposing them to circulating autoantibodies. T-helper 1 cells have been reported to play important roles in the adaptive immune response to CLE. Other environmental factors associated with CLE include drugs and cigarette smoke. Genetic factors also confer a predisposition to the development of CLE, and many susceptibility genes have been identified. Monogenetic forms of CLE also exist. This article aims to review current knowledge about the pathogenesis of CLE. A better understanding of the environmental, genetic, and immunoregulatory factors that drive CLE may provide important insights for the treatment of CLE.

Novel role of long non-coding RNAs in autoimmune cutaneous disease

Systemic autoimmune rheumatic diseases (SARDs) are a heterogeneous group of chronic multisystem inflammatory disorders that are thought to have a complex pathophysiology, which is not yet fully understood. Recently, the role of non-coding RNAs, including long non-coding RNA (lncRNA), has been of particular interest in the pathogenesis of SARDs. We aimed to summarize the potential roles of lncRNA in SARDs affecting the skin including, systemic sclerosis (SSc), dermatomyositis (DM) and cutaneous lupus erythematosus (CLE). We conducted a narrative review summarizing original articles published until July 19, 2021, regarding lncRNA associated with SSc, DM, and CLE. Several lncRNAs were hypothesized to play an important role in disease pathogenesis of SSc, DM and CLE. In SSc, Negative Regulator of IFN Response (NRIR) was thought to modulate Interferon (IFN) response in monocytes, anti-sense gene to X-inactivation specific transcript (TSIX) to regulate increased collagen stability, HOX transcript antisense RNA (HOTAIR) to increase numbers of myofibroblasts, OTUD6B-Anti-Sense RNA 1 to decrease fibroblast apoptosis, ncRNA00201 to regulate pathways in SSc pathogenesis and carcinogenesis, H19X potentiating TGF-β-driven extracellular matrix production, and finally PSMB8-AS1 potentiates IFN response. In DM, linc-DGCR6-1 expression was hypothesized to target the USP18 protein, a type 1 IFN-inducible protein that is considered a key regulator of IFN signaling. Additionally, AL136018.1 is suggested to regulate the expression Cathepsin G, which increases the permeability of vascular endothelial cells and the chemotaxis of inflammatory cells in peripheral blood and muscle tissue in DM. Lastly, lnc-MIPOL1-6 and lnc-DDX47-3 in discoid CLE were thought to be associated with the expression of chemokines, which are significant in Th1 mediated disease. In this review, we summarize the key lncRNAs that may drive pathogenesis of these connective tissue diseases and could potentially serve as therapeutic targets in the future.

Recent advances in cutaneous lupus

Cutaneous lupus erythematosus (CLE) is an inflammatory and autoimmune skin condition that affects patients with systemic lupus erythematosus (SLE) and exists as an isolated entity without associated SLE. Flares of CLE, often triggered by exposure to ultraviolet (UV) light result in lost productivity and poor quality of life for patients and can be associated with trigger of systemic inflammation. In the past 10 years, the knowledge of CLE etiopathogenesis has grown, leading to promising targets for better therapies. Development of lesions likely begins in a pro-inflammatory epidermis, conditioned by excess type I interferon (IFN) production to undergo increased cell death and inflammatory cytokine production after UV light exposure. The reasons for this inflammatory predisposition are not well-understood, but may be an early event, as ANA + patients without criteria for autoimmune disease exhibit similar (although less robust) findings. Non-lesional skin of SLE patients also exhibits increased innate immune cell infiltration, conditioned by excess IFNs to release pro-inflammatory cytokines, and potentially increase activation of the adaptive immune system. Plasmacytoid dendritic cells are also found in non-lesional skin and may contribute to type I IFN production, although this finding is now being questioned by new data. Once the inflammatory cycle begins, lesional infiltration by numerous other cell populations ensues, including IFN-educated T cells. The heterogeneity amongst lesional CLE subtypes isn't fully understood, but B cells appear to discriminate discoid lupus erythematosus from other subtypes. Continued discovery will provide novel targets for additional therapeutic pursuits. This review will comprehensively discuss the contributions of tissue-specific and immune cell populations to the initiation and propagation of disease.

The Genetic Landscape of Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune connective tissue disease that can exist as a disease entity or within the context of systemic lupus erythematosus (SLE). Over the years, efforts to elucidate the genetic underpinnings of CLE and SLE have yielded a wealth of information. This review examines prior studies investigating the genetics of CLE at the DNA and RNA level and identifies future research areas. In this literature review, we examined the English language literature captured within the MEDLINE and Embase databases using pre-defined search terms. First, we surveyed studies investigating various DNA studies of CLE. We identified three predominant areas of focus in HLA profiling, complement deficiencies, and genetic polymorphisms. An increased frequency of HLA-B8 has been strongly linked to CLE. In addition, multiple genes responsible for mediating innate immune response, cell growth, apoptosis, and interferon response confer a higher risk of developing CLE, specifically TREX1 and SAMHD1. There was a strong association between C2 complement deficiency and CLE. Second, we reviewed literature studying aberrations in the transcriptomes of patients with CLE. We reviewed genetic aberrations initiated by environmental insults, and we examined the interplay of dysregulated inflammatory, apoptotic, and fibrotic pathways in the context of the pathomechanism of CLE. These current learnings will serve as the foundation for further advances in integrating personalized medicine into the care of patients with CLE.

Machine learning reveals distinct gene signature profiles in lesional and nonlesional regions of inflammatory skin diseases

Analysis of gene expression from cutaneous lupus erythematosus, psoriasis, atopic dermatitis, and systemic sclerosis using gene set variation analysis (GSVA) revealed that lesional samples from each condition had unique features, but all four diseases displayed common enrichment in multiple inflammatory signatures. These findings were confirmed by both classification and regression tree analysis and machine learning (ML) models. Nonlesional samples from each disease also differed from normal samples and each other by ML. Notably, the features used in classification of nonlesional disease were more distinct than their lesional counterparts, and GSVA confirmed unique features of nonlesional disease. These data show that lesional and nonlesional skin samples from inflammatory skin diseases have unique profiles of gene expression abnormalities, especially in nonlesional skin, and suggest a model in which disease-specific abnormalities in "prelesional" skin may permit environmental stimuli to trigger inflammatory responses leading to both the unique and shared manifestations of each disease.

CRABP1 in Non-Canonical Activities of Retinoic Acid in Health and Diseases

In this review, we discuss the emerging role of Cellular Retinoic Acid Binding Protein 1 (CRABP1) as a mediator of non-canonical activities of retinoic acid (RA) and relevance to human diseases. We first discuss the role of CRABP1 in regulating MAPK activities and its implication in stem cell proliferation, cancers, adipocyte health, and neuro-immune regulation. We then discuss an additional role of CRABP1 in regulating CaMKII activities, and its implication in heart and motor neuron diseases. Through molecular and genetic studies of Crabp1 knockout (CKO) mouse and culture models, it is established that CRABP1 forms complexes with specific signaling molecules to function as RA-regulated signalsomes in a cell context-dependent manner. Gene expression data and CRABP1 gene single nucleotide polymorphisms (SNPs) of human cancer, neurodegeneration, and immune disease patients implicate the potential association of abnormality in CRABP1 with human diseases. Finally, therapeutic strategies for managing certain human diseases by targeting CRABP1 are discussed.

The neuropeptide Substance P facilitates the transition from an inflammatory to proliferation phase associated responses in dermal fibroblasts

The wound healing process is a product of three successive and overlapping phases of inflammation, proliferation and remodeling. Considerable efforts have been invested in deconstructing the intercellular crosstalk that orchestrates tissue repair and we investigated the role of neuropeptides released from peripheral neurons upon injury in mediating these interactions. Amongst the most abundant of these neuropeptides secreted by nerves in the skin, is Substance P (SP). Given the role of dermal fibroblasts in coordinating multiple processes in the wound healing program, the effect of SP on human dermal fibroblasts of different ages was evaluated. The use of a substrate that recapitulates the mechanical properties of the in vivo tissue revealed novel effects of SP on dermal fibroblasts, including a block in inflammatory cytokine expression. Moreover, SP can promote expression of some extracellular matrix components and generates signals that regulate angiogenesis. Interestingly, the response of fibroblasts to SP was reduced concomitant with donor age. Altogether, SP acts to inhibit the inflammatory responses and promote proliferation associated responses in an age-dependent manner in dermal fibroblasts, suggesting a role as a molecular switch between the inflammatory and proliferative phases of the wound healing response.

Targeting Bcl6 in the TREX1 D18N murine model ameliorates autoimmunity by modulating T follicular helper cells and Germinal center B cells

The Three Prime Repair EXonuclease I (TREX1) is critical for degrading post‐apoptosis DNA. Mice expressing catalytically inactive TREX1 (TREX1 D18N) develop lupus‐like autoimmunity due to chronic sensing of undegraded TREX1 DNA substrates, production of the inflammatory cytokines, and the inappropriate activation of innate and adaptive immunity. This study aimed to investigate Thelper (Th) dysregulation in the TREX1 D18N model system as a potential mechanism for lupus‐like autoimmunity. Comparison of immune cells in secondary lymphoid organs, spleen and peripheral lymph nodes (LNs) between TREX1 D18N mice and the TREX1 null mice revealed that the TREX1 D18N mice exhibit a Th1 bias. Additionally, the T‐follicular helper cells (Tfh) and the germinal celter (GC) B cells were also elevated in the TREX1 D18N mice. Targeting Bcl6, a lineage‐defining transcription factor for Tfh and GC B cells, with a commercially available Bcl6 inhibitor, FX1, attenuated Tfh, GC, and Th1 responses, and rescued TREX1 D18N mice from autoimmunity. The study presents Tfh and GC B‐cell responses as potential targets in autoimmunity and that Bcl6 inhibitors may offer therapeutic approach in TREX1‐associated or other lupus‐like diseases.

Applying Early Intervention Strategies to Autoimmune Skin Diseases. Is the Window of Opportunity Preclinical? A Dermato-Rheumatology Perspective

Many inflammatory skin diseases exhibit a chronic course with unsatisfactory long-term outcomes. Insights into early intervention approaches in other autoimmune contexts could improve the trajectory of lifelong diseases in terms of sustained remission or minimal disease activity, reduced requirement for therapy and medical resource use, and improved QoL. In both rheumatoid arthritis (RA) and psoriatic arthritis (PsA), we have learned that the timing and intensity of early interventions can influence later outcomes. Investigation into early RA, PsA, and systemic lupus erythematosus has shown that the optimal window of opportunity may even extend into asymptomatic preclinical phases of diseases. Notably, early and preclinical diseases may have pathogenic mechanisms and therapeutic targets that differ from those of the established disease. In this paper, we review the literature on these insights and discuss how similar research and therapeutic strategies may be investigated in cutaneous autoimmunity. We highlight the contribution of skin-resident cells to diseases that were previously thought to be initiated in the primary and secondary lymphoid organs of the immune system. We focus on two dermato‒rheumatology conditions-lupus and psoriasis-which share the commonality that effective early cutaneous disease therapy may have far-reaching implications on abrogating potentially severe systemic disease.

Establishment and validation of psoriasis evaluation models

Psoriasis is a common inflammatory skin disease that seriously affects the patient's quality of life. The diagnosis of psoriasis is mainly based on clinical and pathological features, and the assessment depends on the psoriasis area and severity index (PASI). However, there are few reliable and accurate evaluation methods to assess lesion severity and therapeutic effects. This work identified 17 model genes from GEO datasets and established 6 psoriasis evaluation models by LASSO regression, linear regression, and random forest separately. Models were trained and evaluated in different GEO datasets. All 6 models accurately classified psoriatic lesions and non-lesional skin in training and testing data, and showed good AUC. In biologics-treated samples, the model scores were positively correlated with the severity of lesions and negatively correlated with treatment length. Thus, models have the potential to assess the therapeutic effects. In addition, the expression of model genes was examined in keratinocytes, skin of IMQ-induced psoriatic mice, and lesions of psoriasis patients. The RNA and protein levels of model genes increased in cytokine-stimulated keratinocytes and psoriatic lesions as expected. This work provides new methods to assess the lesion severity and therapeutic effects of biologics in psoriasis.

Epigallocatechin-3-gallate exhibits anti-inflammatory effects in a human interface dermatitis model-implications for therapy

BACKGROUND

Epigallocatechin-3-gallate (EGCG) has been proven effective in treating viral warts. Since anticarcinogenic as well as anti-inflammatory properties are ascribed to the substance, its use has been evaluated in the context of different dermatoses. The effect of EGCG on interface dermatitis (ID), however, has not yet been explored.

OBJECTIVES

In this study, we investigated the effect of EGCG on an epidermal human in vitro model of ID.

METHODS

Via immunohistochemistry, lesional skin of lichen planus patients and healthy skin were analysed concerning the intensity of interferon-associated mediators, CXCL10 and MxA. Epidermal equivalents were stained analogously upon ID-like stimulation and EGCG treatment. Monolayer keratinocytes were treated likewise and supernatants were analysed via ELISA while cells were processed for vitality assay or transcriptomic analysis.

RESULTS

CXCL10 and MxA are strongly expressed in lichen planus lesions and induced in keratinocytes upon ID-like stimulation. EGCG reduces CXCL10 and MxA staining intensity in epidermis equivalents and CXCL10 secretion by keratinocytes upon stimulation. It furthermore minimizes the cytotoxic effect of the stimulus and downregulates a magnitude of typical pro-inflammatory cytokines that are crucial for the perpetuation of ID.

CONCLUSIONS

We provide evidence concerning anti-inflammatory effects of EGCG within a human in vitro model of ID. The capacity to suppress mediators that are centrally involved in disease perpetuation suggests EGCG as a potential topical therapeutic in lichen planus and other autoimmune skin diseases associated with ID.

Variability of the rs333 in Polish patients with lupus erythematosus

Introduction

Lupus erythematosus (LE) is an autoimmune disease with a strong influence of genetic and environmental factors. C-C motif chemokine receptor 5 (CCR5) gene expression may affect the development and intensity of LE.

Aim

To evaluate the possible association between the 32bp deletion in rs333 locus located within the CCR5 gene and the development of LE or the occurrence of various clinical symptoms in the course of the disease.

Material and methods

One hundred and twenty patients with LE (77 with systemic lupus erythematosus (SLE) and 43 with discoid lupus erythematosus (DLE)) and 100 healthy controls from the Polish population were genotyped for deletion in rs333.

Results

32 bp deletion in the rs333 was significantly more frequent among healthy individuals than DLE patients. Moreover, heterozygotes and homozygotes with deletion in rs333 were significantly more frequent within the control group than the group of patients with discoid lupus erythematosus. In contrast, any statistically significant differences in allele or genotype frequencies between healthy persons and SLE patients were observed. Furthermore, nucleotide sequence variability of rs333 was not associated with certain clinical symptoms of LE patients.

Conclusions

Deletion in the rs333 might be a protective factor for DLE, but not SLE in the Polish population. Nevertheless further studies performed on larger populations are needed to confirm these observations.

Follicular Regulatory T Cells in Systemic Lupus Erythematosus

Follicular regulatory T (Tfr) cells are the regulatory T cell subset mainly localized in the germinal center (GC), acting as modulators of GC responses. They can disrupt Tfh cell- and B cell-linked recognition, induce Tfh apoptosis, and suppress B cell function. Evidences show that dysregulated Tfr cells are associated with the disease activity index and serum autoantibody levels, influencing the development of systemic lupus erythematosus (SLE). This review focuses on the interaction among Tfr, Tfh, and B cells, summarizes the characterization and function of Tfr cells, concludes the imbalance of CD4⁺T subsets in SLE, and presents potential therapies for SLE. In general, we discuss the roles of Tfr cells in the progress of SLE and provide potential treatments.

Regulation of exosome secretion by cellular retinoic acid binding protein 1 contributes to systemic anti-inflammation

Background

Intercellular communications are important for maintaining normal physiological processes. An important intercellular communication is mediated by the exchange of membrane-enclosed extracellular vesicles. Among various vesicles, exosomes can be detected in a wide variety of biological systems, but the regulation and biological implication of exosome secretion/uptake remains largely unclear.

Methods

Cellular retinoic acid (RA) binding protein 1 (Crabp1) knockout (CKO) mice were used for in vivo studies. Extracellular exosomes were monitored in CKO mice and relevant cell cultures including embryonic stem cell (CJ7), macrophage (Raw 264.7) and hippocampal cell (HT22) using Western blot and flow cytometry. Receptor Interacting Protein 140 (RIP140) was depleted by Crispr/Cas9-mediated gene editing. Anti-inflammatory maker was analyzed using qRT-PCR. Clinical relevance was accessed by mining multiple clinical datasets.

Results

This study uncovers Crabp1 as a negative regulator of exosome secretion from neurons. Specifically, RIP140, a pro-inflammatory regulator, can be transferred from neurons, via Crabp1-regulated exosome secretion, into macrophages to promote their inflammatory polarization. Consistently, CKO mice, defected in the negative control of exosome secretion, have significantly elevated RIP140-containing exosomes in their blood and cerebrospinal fluid, and exhibit an increased vulnerability to systemic inflammation. Clinical relevance of this pathway is supported by patients’ data of multiple inflammatory diseases. Further, the action of Crabp1 in regulating exosome secretion involves its ligand and is mediated by its downstream target, the MAPK signaling pathway.

Conclusions

This study presents the first evidence for the regulation of exosome secretion, which mediates intercellular communication, by RA-Crabp1 signaling. This novel mechanism can contribute to the control of systemic inflammation by transferring an inflammatory regulator, RIP140, between cells. This represents a new mechanism of vitamin A action that can modulate the homeostasis of system-wide innate immunity without involving gene regulation.

The tweety Gene Family: From Embryo to Disease

The tweety genes encode gated chloride channels that are found in animals, plants, and even simple eukaryotes, signifying their deep evolutionary origin. In vertebrates, the tweety gene family is highly conserved and consists of three members—ttyh1, ttyh2, and ttyh3—that are important for the regulation of cell volume. While research has elucidated potential physiological functions of ttyh1 in neural stem cell maintenance, proliferation, and filopodia formation during neural development, the roles of ttyh2 and ttyh3 are less characterized, though their expression patterns during embryonic and fetal development suggest potential roles in the development of a wide range of tissues including a role in the immune system in response to pathogen-associated molecules. Additionally, members of the tweety gene family have been implicated in various pathologies including cancers, particularly pediatric brain tumors, and neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. Here, we review the current state of research using information from published articles and open-source databases on the tweety gene family with regard to its structure, evolution, expression during development and adulthood, biochemical and cellular functions, and role in human disease. We also identify promising areas for further research to advance our understanding of this important, yet still understudied, family of genes.

Phosphatidylserine-specific phospholipase A1: A friend or the devil in disguise

Various human tissues and cells express phospholipase A1 member A (PLA1A), including the liver, lung, prostate gland, and immune cells. The enzyme belongs to the pancreatic lipase family. PLA1A specifically hydrolyzes sn-1 fatty acid of phosphatidylserine (PS) or 1-acyl-lysophosphatidylserine (1-acyl-lysoPS). PS externalized by activated cells or apoptotic cells or extracellular vesicles is a potential source of substrate for the production of unsaturated lysoPS species by PLA1A. Maturation and functions of many immune cells, such as T cells, dendritic cells, macrophages, and mast cells, can be regulated by PLA1A and lysoPS. Several lysoPS receptors, including GPR34, GPR174 and P2Y10, have been identified. High serum levels and high PLA1A expression are associated with autoimmune disorders such as Graves' disease and systemic lupus erythematosus. Increased expression of PLA1A is associated with metastatic melanomas. PLA1A may contribute to cardiometabolic disorders through mediating cholesterol transportation and producing lysoPS. Furthermore, PLA1A is necessary for hepatitis C virus assembly and can play a role in the antivirus innate immune response. This review summarizes recent findings on PLA1A expression, lysoPS and lysoPS receptors in autoimmune disorders, cancers, cardiometabolic disorders, antivirus immune responses, as well as regulations of immune cells.

Gene expression profiling in skin reveals strong similarities between subacute and chronic cutaneous lupus that are distinct from lupus nephritis

Subacute cutaneous lupus erythematosus (SCLE) and chronic cutaneous lupus erythematosus (CCLE) are represented in the majority of cutaneous lupus subtypes, each of which has variable implications for systemic manifestations such as lupus nephritis. On dermatologic exam, SCLE and CCLE are distinct. However, it is often difficult to diagnose the subtype from histology alone. Our study utilized whole-genome microarray expression analysis on human skin samples of SCLE, CCLE, and healthy controls, along with human samples of lupus nephritis and normal kidney tissue to compare cutaneous lupus subtypes to each other, as well as lupus nephritis. The data revealed that cutaneous lupus subtypes were distinct from healthy control skin, with gene expression predominantly characterized by upregulation of type 1 interferon and T-cell chemotactic genes. However, the cutaneous lupus subtypes were very similar to one another; comparative analyses revealed few statistically significant differences in gene expression. There were also distinct differences between the gene signatures of cutaneous lupus and lupus nephritis. Cutaneous lupus samples revealed gene signatures demonstrating a prominent inflammatory component that may suggest the skin as an early site of initiation of lupus pathogenesis, while lupus nephritis reflected recruitment and activation of M2 macrophages and a wound healing signature.

Cutaneous and systemic connections in lupus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with multiple manifestations, with a majority of SLE patients having cutaneous involvement. Despite ongoing research, the relationship between SLE and cutaneous lupus erythematosus (CLE) pathogeneses remains unknown. This review will compare advances in understanding the cause and pathogenesis of SLE and CLE.

RECENT FINDINGS

Recently, mechanisms by which immune cell populations contribute to the pathogenesis of SLE and CLE have been queried. Studies have pointed to transitional B cells and B-cell activating factor (BAFF) signaling as potential drivers of SLE and CLE, with belimumab clinical data supporting these hypotheses. Ustekinumab trials and an exciting regulatory T cell (Treg) adoptive transfer in an SLE patient with cutaneous disease have suggested a role for T-cell-targeted therapies. The theory that neutrophil extracellular traps may be a source of autoantigens in SLE remains controversial, while neutrophils have been suggested as early drivers of cutaneous disease. Finally, plasmacytoid dendritic cells (pDCs) have been studied as a potential therapeutic target in SLE, and anti-blood DC antigen (anti-BDCA) antibody clinical trials have shown promise in treating cutaneous disease.

SUMMARY

Although recent findings have contributed to understanding SLE and CLE pathogenesis, the mechanistic link between these diseases remains an area requiring further research.

RNA tape sampling in cutaneous lupus erythematosus discriminates affected from unaffected and healthy volunteer skin

Objective

Punch biopsy, a standard diagnostic procedure for patients with cutaneous lupus erythematosus (CLE) carries an infection risk, is invasive, uncomfortable and potentially scarring, and impedes patient recruitment in clinical trials. Non-invasive tape sampling is an alternative that could enable serial evaluation of specific lesions. This cross-sectional pilot research study evaluated the use of a non-invasive adhesive tape device to collect messenger RNA (mRNA) from the skin surface of participants with CLE and healthy volunteers (HVs) and investigated its feasibility to detect biologically meaningful differences between samples collected from participants with CLE and samples from HVs.

Methods

Affected and unaffected skin tape samples and simultaneous punch biopsies were collected from 10 participants with CLE. Unaffected skin tape and punch biopsies were collected from 10 HVs. Paired samples were tested using quantitative PCR for a candidate immune gene panel and semi-quantitative immunohistochemistry for hallmark CLE proteins.

Results

mRNA collected using the tape device was of sufficient quality for amplification of 94 candidate immune genes. Among these, we found an interferon (IFN)-dominant gene cluster that differentiated CLE-affected from HV (23-fold change; p<0.001) and CLE-unaffected skin (sevenfold change; p=0.002), respectively. We found a CLE-associated gene cluster that differentiated CLE-affected from HV (fourfold change; p=0.005) and CLE-unaffected skin (fourfold change; p=0.012), respectively. Spearman’s correlation between per cent area myxovirus 1 protein immunoreactivity and IFN-dominant mRNA gene cluster expression was highly significant (dermis, rho=0.86, p<0.001). In total, skin tape-derived RNA expression comprising both IFN-dominant and CLE-associated gene clusters correlated with per cent area immunoreactivity of some hallmark CLE-associated proteins in punch biopsies from the same lesions.

Conclusions

A non-invasive tape RNA collection technique is a potential tool for repeated skin biomarker measures throughout a clinical trial.

Associations between COVID-19 and skin conditions identified through epidemiology and genomic studies

BACKGROUND

Coronavirus disease 2019 (COVID-19) is commonly associated with skin manifestations, and may also exacerbate existing skin diseases, yet the relationship between COVID-19 and skin diseases remains unclear.

OBJECTIVE

By investigating this relationship through a multiomics approach, we sought to ascertain whether patients with skin conditions are more susceptible to COVID-19.

METHODS

We conducted an epidemiological study and then compared gene expression across 9 different inflammatory skin conditions and severe acute respiratory syndrome coronavirus 2-infected bronchial epithelial cell lines, and then performed a genome-wide association study transdisease meta-analysis between COVID-19 susceptibility and 2 skin diseases (psoriasis and atopic dermatitis).

RESULTS

Skin conditions, including psoriasis and atopic dermatitis, increase the risk of COVID-19 (odds ratio, 1.55; P = 1.4 × 10-9) but decrease the risk of mechanical ventilation (odds ratio, 0.22; P = 8.5 × 10-5). We observed significant overlap in gene expression between the infected normal bronchial epithelial cells and inflammatory skin diseases, such as psoriasis and atopic dermatitis. For genes that are commonly induced in both the severe acute respiratory syndrome coronavirus 2 infection and skin diseases, there are 4 S100 family members located in the epidermal differentiation complex, and we also identified the "IL-17 signaling pathway" (P = 4.9 × 10-77) as one of the most significantly enriched pathways. Furthermore, a shared genome-wide significant locus in the epidermal differentiation complex was identified between psoriasis and severe acute respiratory syndrome coronavirus 2 infection, with the lead marker being a significant expression quantitative trait locus for S100A12 (P = 3.3 × 10-7).

CONCLUSIONS

Together our findings suggest association between inflammatory skin conditions and higher risk of COVID-19, but with less severe course, and highlight shared components involved in anti-COVID-19 immune response.

Immunostimulatory Endogenous Nucleic Acids Perpetuate Interface Dermatitis-Translation of Pathogenic Fundamentals Into an In Vitro Model

Interface dermatitis is a histopathological pattern mirroring a distinct cytotoxic immune response shared by a number of clinically diverse inflammatory skin diseases amongst which lichen planus and cutaneous lupus erythematosus are considered prototypic. Interface dermatitis is characterized by pronounced cytotoxic immune cell infiltration and necroptotic keratinocytes at the dermoepidermal junction. The initial inflammatory reaction is established by cytotoxic immune cells that express CXC chemokine receptor 3 and lesional keratinocytes that produce corresponding ligands, CXC motif ligands 9/10/11, recruiting the effector cells to the site of inflammation. During the resulting anti-epithelial attack, endogenous immune complexes and nucleic acids are released from perishing keratinocytes, which are then perceived by the innate immune system as danger signals. Keratinocytes express a distinct signature of pattern recognition receptors and binding of endogenous nucleic acid motifs to these receptors results in interferon-mediated immune responses and further enhancement of CXC chemokine receptor 3 ligand production. In this perspective article, we will discuss the role of innate nucleic acid sensing as a common mechanism in the perpetuation of clinically heterogeneous diseases featuring interface dermatitis based on own data and a review of the literature. Furthermore, we will introduce a keratinocyte-specific in vitro model of interface dermatitis as follows: Stimulation of human keratinocytes with endogenous nucleic acids alone and in combination with interferon gamma leads to pronounced production of distinct cytokines, which are essential in the pathogenesis of interface dermatitis. This experimental approach bears the capability to investigate potential therapeutics in this group of diseases with unmet medical need.

Modular gene analysis reveals distinct molecular signatures for subsets of patients with cutaneous lupus erythematosus

BACKGROUND

Cutaneous lupus erythematosus (CLE) is a heterogeneous autoimmune disease with clinical sequelae such as itching, dyspigmentation and scarring.

OBJECTIVES

We applied a previously described modular analysis approach to assess the molecular heterogeneity of patients with CLE.

METHODS

Whole-blood transcriptomes of RNA sequencing data from a racially and ethnically diverse group of patients with CLE (n = 62) were used to calculate gene co-expression module scores. An unsupervised cluster analysis and k-means clustering based on these module scores were then performed. We used Fisher's exact tests and Kruskal-Wallis tests to compare characteristics between patient clusters.

RESULTS

Six unique clusters of patients with CLE were identified from the cluster analysis. We observed that seven inflammation modules were elevated in two clusters of patients with CLE. Additionally, these clusters were characterized by interferon, neutrophil and cell-death signatures, suggesting that interferon-related proteins, neutrophils and cell-death processes could be driving the inflammatory response in these subgroups. Three different clusters had a predominant T-cell signature, which were supported by lymphocyte counts.

CONCLUSIONS

Our data support a diverse molecular profile in CLE that further adds to the clinical variations of this skin disease, and may affect disease course and treatment selection. Future studies with a larger and diverse cohort of patients with CLE are warranted to confirm these findings.

Macrophage Migration Inhibitory Factor (MIF) and Its Homologue d-Dopachrome Tautomerase (DDT) Inversely Correlate with Inflammation in Discoid Lupus Erythematosus

Discoid Lupus Erythematosus (DLE) is a chronic cutaneous disease of unknown etiology and of immunoinflammatory origin that is characterized by inflammatory plaques and may lead to disfiguring scarring and skin atrophy. Current treatments are limited, with a large proportion of patients either poorly or not responsive, which makes DLE an unmet medical need. Macrophage migration inhibitory factor (MIF) is the prototype of a pleiotropic family of cytokine that also includes the recently discovered homologue D-dopachrome tautomerase (DDT) or MIF2. MIF and DDT/MIF-2 exert several biological properties, primarily, but not exclusively of a proinflammatory nature. MIF and DDT have been suggested to play a key role in the pathogenesis of several autoimmune diseases, such as multiple sclerosis and type 1 diabetes, as well as in the development and progression of certain forms of cancers. In the present study, we have performed an immunohistochemistry analysis for the evaluation of MIF in DLE lesions and normal skin. We found high levels of MIF in the basal layer of the epidermis as well as in the cutaneous appendage (eccrine glands and sebocytes) of normal skin. In DLE lesions, we observed a significant negative correlation between the expression of MIF and the severity of inflammation. In addition, we performed an analysis of MIF and DDT expression levels in the skin of DLE patients in a publicly available microarray dataset. Interestingly, while these in silico data only evidenced a trend toward reduced levels of MIF, they demonstrated a significant pattern of expression and correlation of DDT with inflammatory infiltrates in DLE skins. Overall, our data support a protective role for endogenous MIF and possibly DDT in the regulation of homeostasis and inflammation in the skin and open up novel avenues for the treatment of DLE.

MicroRNAs in Several Cutaneous Autoimmune Diseases: Psoriasis, Cutaneous Lupus Erythematosus and Atopic Dermatitis

MicroRNAs (miRNAs) are endogenous small non-coding RNA molecules that regulate the gene expression at a post-transcriptional level and participate in maintaining the correct cell homeostasis and functioning. Different specific profiles have been identified in lesional skin from autoimmune cutaneous diseases, and their deregulation cause aberrant control of biological pathways, contributing to pathogenic conditions. Detailed knowledge of microRNA-affected pathways is of crucial importance for understating their role in skin autoimmune diseases. They may be promising therapeutic targets with novel clinical implications. They are not only present in skin tissue, but they have also been found in other biological fluids, such as serum, plasma and urine from patients, and therefore, they are potential biomarkers for the diagnosis, prognosis and response to treatment. In this review, we discuss the current understanding of the role of described miRNAs in several cutaneous autoimmune diseases: psoriasis (Ps, 33 miRNAs), cutaneous lupus erythematosus (CLE, 2 miRNAs) and atopic dermatitis (AD, 8 miRNAs). We highlight their role as crucial elements implicated in disease pathogenesis and their applicability as biomarkers and as a novel therapeutic approach in the management of skin inflammatory diseases.

Gene Co-expression Networks Identifies Common Hub Genes Between Cutaneous Sarcoidosis and Discoid Lupus Erythematosus

In this study we analyzed gene co-expression networks of three immune-related skin diseases: cutaneous sarcoidosis (CS), discoid lupus erythematosus (DLE), and psoriasis. We propose that investigation of gene co-expression networks may provide insights into underlying disease mechanisms. Microarray expression data from two cohorts of patients with CS, DLE, or psoriasis skin lesions were analyzed. We applied weighted gene correlation network analysis (WGCNA) to construct gene-gene similarity networks and cluster genes into modules based on similar expression profiles. A module of interest that was preserved between datasets and corresponded with case/control status was identified. This module was related to immune activation, specifically leukocyte activation, and was significantly increased in both CS lesions and DLE lesions compared to their respective controls. Protein-protein interaction (PPI) networks constructed for this module revealed seven common hub genes between CS lesions and DLE lesions: TLR1, ITGAL, TNFRSF1B, CD86, SPI1, BTK, and IL10RA. Common hub genes were highly upregulated in CS lesions and DLE lesions compared to their respective controls in a differential expression analysis. Our results indicate common gene expression patterns in the immune processes of CS and DLE, which may have indications for future therapeutic targets and serve as Th1-mediated disease biomarkers. Additionally, we identified hub genes unique to CS and DLE, which can help differentiate these diseases from one another and may serve as unique therapeutic targets and biomarkers. Notably, we find common gene expression patterns in the immune processes of CS and DLE through utilization of WGCNA.

Characterization of autoantibodies and cytokines related to cutaneous lupus erythematosus

OBJECTIVE

To investigate the profiles of anti-RPLP0, anti-galectin3 antibodies, interferon-α (IFN-α), interferon-λ1(IFN-λ1) and interleukin-17A/F(IL-17A/F) in the subtypes of cutaneous lupus erythematosus (CLE) including acute CLE (ACLE), subacute CLE (SCLE) and discoid lupus erythematosus (DLE).

METHODS

Serum levels of autoantibodies and cytokines were determined by enzyme-linked immunoabsorbent assay (ELISA). Lupus lesions were evaluated by cutaneous lupus erythematosus disease area and severity index (CLASI).

RESULTS

Serum anti-RPLP0, anti-galectin3 antibodies and IFN-λ1 were higher in systemic lupus erythematosus (SLE) patients with skin lesions than those without skin lesions, compared to healthy controls. IFN-α, IL-17A and IL-17F was elevated in all patients regardless of skin lesions. The two antibodies, IFN-α and IL-17A were positively correlated with the CLASI score in all patients with CLE. In addition, serum IL-17A was positively correlated to the CLASI score of ACLE, SCLE and DLE, while anti-RPLP0 and anti-galectin3 antibodies were only correlated to the score of SCLE and IL-17F to DLE.

CONCLUSION

Serum anti-RPLP0, anti-galectin3 antibodies, IFN-α, IFN-λ1 and IL-17A/F are associated with the occurrence of lupus skin lesions regardless of the systemic complications, whereas the profiles of these inflammatory mediators vary with the subtypes of lupus skin lesions.

The pathogenesis of cutaneous lupus erythematosus: The aberrant distribution and function of different cell types in skin lesions

Cutaneous lupus erythematosus (CLE) is an autoimmune disease with a broad range of cutaneous manifestations. In skin lesions of CLE, keratinocytes primarily undergo apoptosis. Interferon-κ(IFN-κ) is belonged to type I interferons (type I IFNs) and is selectively produced by keratinocytes. Recently, keratinocytes selectively produced IFN-κ is identified to be a key to trigger type I interferon responses in CLE. Other immune cells such as plasmacytoid dendritic cells (pDCs) are identified to be relevant origin of type I interferons (type I IFNs) which are central to the development of CLE lesions and responsible for mediating Th1 cell activity. Other types of cells such as neutrophils, B cells and Th17 cells also are involved in the development of this disease. The close interaction of those cells composes a comprehensive and complicated network in CLE. In this review, we discussed the aberrant distribution and function of different cells types involved in this disease and will offer a new direction for research and therapy in the near future.

An Update on the Pathogenesis of Cutaneous Lupus Erythematosus and Its Role in Clinical Practice

PURPOSE OF REVIEW

Understanding the pathogenesis of cutaneous lupus erythematosus (CLE) is an important step in developing new medications and providing effective treatment to patients. This review focuses on novel research within CLE pathogenesis, as well as some of the medications being developed based on this knowledge.

RECENT FINDINGS

The subtle differences between systemic lupus erythematosus (SLE) and CLE pathogenesis are highlighted by differences in the circulating immune cells found in each disease, as well as the specific pathways activated by ultraviolet light. Plasmacytoid dendritic cells and the related type I interferon pathway are major components of CLE pathogenesis, and as such, therapies targeting components of this pathway have been successful in recent clinical trials. B cell-depleting therapies have shown success in SLE; however, their role in CLE is less clear. Understanding the differences between these manifestations of lupus allows for the development of therapies that are more effective in skin-specific disease. Discovering key pathways in CLE pathogenesis is critical for understanding the clinical features of the disease and ultimately developing new and effective therapies.

Cutaneous lupus erythematosus and cardiovascular disease: current knowledge and insights into pathogenesis

Multiple autoinflammatory diseases, including psoriasis, psoriatic arthritis, and systemic lupus erythematosus, have been linked to increased risk of cardiovascular disease. Inflammation is known to play a key role in the pathogenesis of atherosclerosis, thus the contribution of systemic immune dysregulation, which characterizes such inflammatory conditions, towards the development of cardiovascular disease has garnered considerable interest. Cutaneous lupus erythematosus (CLE) is a chronic inflammatory skin disease, but risk of cardiovascular disease amongst patients with cutaneous lupus is less well known. Observational studies, including those of large nationwide cohorts, have been conducted to examine cardiovascular disease risk in CLE, with varying findings. As with other inflammatory diseases, immunologic mechanisms may provide plausible causal links between CLE and cardiovascular risk. On a macrolevel, several disease-related characteristics may also contribute to cardiovascular risk amongst CLE patients. This represents an area of research that should be prioritized, as understanding cardiovascular disease risk has important clinical implications for CLE patients.

Rethinking the Pathogenesis of Cutaneous Lupus

Knowledge of the etiology of cutaneous lupus is rapidly evolving. Dissection of the pathologic events in lesional skin has led to knowledge of important cell populations and transcriptional changes contributing to disease. Recently, the study of nonlesional skin in patients with systemic lupus has also identified key abnormalities that likely contribute to a propensity for inflammation. These include an elevated type I IFN signature, overproduction of IFNs, and an absence of Langerhans cells. These changes promote aberrant inflammation in response to known triggers of disease, such as UV light. Further research will undoubtedly accelerate our understanding of this disfiguring disease.

[Lupus erythematosus-a clinico-pathological heterogeneous disease]

Lupus erythematosus (LE) is an autoimmune disorder where immune tolerance towards nucleic acids is lost and a hyperactivated type I interferon system drives chronic immune activation. Typically, signs, symptoms, and clinical disease course are very variable between patients. Cutaneous LE can be associated with or precede systemic involvement or be limited to the skin, necessitating careful examination and follow-up of patients. LE skin disease includes a wide range of manifestations and precise classification for clinical studies is challenging. In this review article we discuss common and rare manifestations of cutaneous lupus with its clinical presentation and histopathological characteristics.

Scarring alopecia in chronic cutaneous lupus erythematosus with neutrophils: A new scenario with therapeutic connotations

The relationship between autoinflammatory and autoimmune conditions has been demonstrated in recent decades. Several autoimmune conditions exhibit an autoinflammatory component, which can manifest in various ways. Neutrophilic dermatosis in the context of lupus erythematosus (LE) is one example. Otherwise, neutrophils are rare in LE, except for the bullous variant and nonbullous neutrophilic LE. In this paper, we describe a case of scarring alopecia due to LE that stopped responding to a treatment that had been effective for years. The biopsy specimen demonstrated the presence of neutrophils in the inflammatory infiltrate. A treatment with dapsone was prescribed and yielded rapid improvement. This first case of scarring alopecia in the context of nonbullous neutrophilic LE emphasizes the importance of the infiltrate in determining the optimal therapeutic choice.

An Update on the Pathogenesis of Skin Damage in Lupus

PURPOSE OF REVIEW

Lupus erythematosus (LE) is characterized by broad and varied clinical forms ranging from a localized skin lesion to a life-threatening form with severe systemic manifestations. The overlapping between cutaneous LE (CLE) and systemic LE (SLE) brings difficulties to physicians for early accurate diagnosis and sometimes may lead to delayed treatment for patients. We comprehensively review recent progress about the similarities and differences of the main three subsets of LE in pathogenesis and immunological mechanisms, with a particular focus on the skin damage.

RECENT FINDINGS

Recent studies on the mechanisms contributing to the skin damage in lupus have shown a close association of abnormal circulating inflammatory cells and abundant production of IgG autoantibodies with the skin damage of SLE, whereas few evidences if serum autoantibodies and circulating inflammatory cells are involved in the pathogenesis of CLE, especially for the discoid LE (DLE). Till now, the pathogenesis and molecular/cellular mechanism for the progress from CLE to SLE are far from clear. But more and more factors correlated with the differences among the subsets of LE and progression from CLE to SLE have been found, such as the mutation of IRF5, IFN regulatory factors and abnormalities of plasmacytoid dendritic cells (PDCs), Th1 cells, and B cells, which could be the potential biomarkers for the interventions in the development of LE. A further understanding in pathogenesis and immunological mechanisms for skin damage in different subsets of LE makes us think more about the differences and cross-links in the pathogenic mechanism of CLE and SLE, which will shed a light in predictive biomarkers and therapies in LE.

Cutaneous Lupus Erythematosus: Current and Future Pathogenesis-Directed Therapies

Cutaneous lupus erythematosus (CLE) is an autoimmune disease of the skin with significant morbidity. Current treatments are often inadequate to control disease and there are no Food and Drug Administration (FDA)-approved therapies for this potentially debilitating disease, underscoring an unmet medical need. Recent insights into disease pathogenesis have implicated innate and adaptive immune components, including type I and type III interferons in the development of CLE. Promising clinical trials based on these insights are now underway. However, the full spectrum of immune cells, cytokines, and environmental triggers contributing to disease remain to be elucidated. In this review, we will highlight the current understanding of CLE immunopathogenesis, the ongoing clinical trial landscape, and provide a framework for designing future therapeutic strategies for CLE based on new insights into disease pathogenesis.

Integrated, multicohort analysis reveals unified signature of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease that follows an unpredictable disease course and affects multiple organs and tissues. We performed an integrated, multicohort analysis of 7,471 transcriptomic profiles from 40 independent studies to identify robust gene expression changes associated with SLE. We identified a 93-gene signature (SLE MetaSignature) that is differentially expressed in the blood of patients with SLE compared with healthy volunteers; distinguishes SLE from other autoimmune, inflammatory, and infectious diseases; and persists across diverse tissues and cell types. The SLE MetaSignature correlated significantly with disease activity and other clinical measures of inflammation. We prospectively validated the SLE MetaSignature in an independent cohort of pediatric patients with SLE using a microfluidic quantitative PCR (qPCR) array. We found that 14 of the 93 genes in the SLE MetaSignature were independent of IFN-induced and neutrophil-related transcriptional profiles that have previously been associated with SLE. Pathway analysis revealed dysregulation associated with nucleic acid biosynthesis and immunometabolism in SLE. We further refined a neutropoiesis signature and identified underappreciated transcripts related to immune cells and oxidative stress. In our multicohort, transcriptomic analysis has uncovered underappreciated genes and pathways associated with SLE pathogenesis, with the potential to advance clinical diagnosis, biomarker development, and targeted therapeutics for SLE.

Review-Current Concepts in Inflammatory Skin Diseases Evolved by Transcriptome Analysis: In-Depth Analysis of Atopic Dermatitis and Psoriasis

During the last decades, high-throughput assessment of gene expression in patient tissues using microarray technology or RNA-Seq took center stage in clinical research. Insights into the diversity and frequency of transcripts in healthy and diseased conditions provide valuable information on the cellular status in the respective tissues. Growing with the technique, the bioinformatic analysis toolkit reveals biologically relevant pathways which assist in understanding basic pathophysiological mechanisms. Conventional classification systems of inflammatory skin diseases rely on descriptive assessments by pathologists. In contrast to this, molecular profiling may uncover previously unknown disease classifying features. Thereby, treatments and prognostics of patients may be improved. Furthermore, disease models in basic research in comparison to the human disease can be directly validated. The aim of this article is not only to provide the reader with information on the opportunities of these techniques, but to outline potential pitfalls and technical limitations as well. Major published findings are briefly discussed to provide a broad overview on the current findings in transcriptomics in inflammatory skin diseases.

The pathogenesis of systemic lupus erythematosus: Harnessing big data to understand the molecular basis of lupus

Systemic lupus erythematosus (SLE) is a chronic, systemic autoimmune disease that causes damage to multiple organ systems. Despite decades of research and available murine models that capture some aspects of the human disease, new treatments for SLE lag behind other autoimmune diseases such as Rheumatoid Arthritis and Crohn's disease. Big data genomic assays have transformed our understanding of SLE by providing important insights into the molecular heterogeneity of this multigenic disease. Gene wide association studies have demonstrated more than 100 risk loci, supporting a model of multiple genetic hits increasing SLE risk in a non-linear fashion, and providing evidence of ancestral diversity in susceptibility loci. Epigenetic studies to determine the role of methylation, acetylation and non-coding RNAs have provided new understanding of the modulation of gene expression in SLE patients and identified new drug targets and biomarkers for SLE. Gene expression profiling has led to a greater understanding of the role of myeloid cells in the pathogenesis of SLE, confirmed roles for T and B cells in SLE, promoted clinical trials based on the prominent interferon signature found in SLE patients, and identified candidate biomarkers and cellular signatures to further drug development and drug repurposing. Gene expression studies are advancing our understanding of the underlying molecular heterogeneity in SLE and providing hope that patient stratification will expedite new therapies based on personal molecular signatures. Although big data analyses present unique interpretation challenges, both computationally and biologically, advances in machine learning applications may facilitate the ability to predict changes in SLE disease activity and optimize therapeutic strategies.

SLE Plasma Profiling Identifies Unique Signatures of Lupus Nephritis and Discoid Lupus

Systemic lupus erythematosus (SLE) impacts multiple organ systems, although the causes of many individual SLE pathologies are poorly understood. This study was designed to elucidate organ-specific inflammation by identifying proteins that correlate with SLE organ involvement and to evaluate established biomarkers of disease activity across a diverse patient cohort. Plasma proteins and autoantibodies were measured across seven SLE manifestations. Comparative analyses between pathologies and correlation with the SLE Disease Activity Index (SLEDAI) were used to identify proteins associated with organ-specific and composite disease activity. Established biomarkers of composite disease activity, SLE-associated antibodies, type I interferon (IFN), and complement C3, correlated with composite SLEDAI, but did not significantly associate with many individual SLE pathologies. Two clusters of proteins were associated with renal disease in lupus nephritis samples. One cluster included markers of infiltrating leukocytes and the second cluster included markers of tissue remodelling. In patients with discoid lupus, a distinct signature consisting of elevated immunoglobulin A autoantibodies and interleukin-23 was observed. Our findings indicate that proteins from blood samples can be used to identify protein signatures that are distinct from established SLE biomarkers and SLEDAI and could be used to conveniently monitor multiple inflammatory pathways present in different organ systems.

Molecular Profiling of Cutaneous Lupus Lesions Identifies Subgroups Distinct from Clinical Phenotypes

Cutaneous lupus erythematosus (CLE) is a common manifestation of systemic lupus erythematosus (SLE), and CLE can also develop without systemic involvement. CLE can be difficult to treat and negatively contributes to quality of life. Despite the importance of CLE, our knowledge of what differentiates cutaneous lupus subtypes is limited. Here, we utilized a large cohort of 90 CLE lesional biopsies to compare discoid lupus erythematosus (DLE) and subacute cutaneous lupus (SCLE) in patients with and without associated SLE in order to discern the drivers of disease activity and possibly uncover better treatment targets. Overall, we found that DLE and SCLE share many differentially expressed genes (DEG) reflecting type I interferon (IFN) signaling and repression of EGFR pathways. No differences between CLE only and SLE-associated CLE lesions were found. Of note, DLE uniquely expresses an IFN-γ node. Unbiased cluster analysis of the DEGs identified two groups separated by neutrophilic vs. monocytic signatures that did not sort the patients based on clinical phenotype or disease activity. This suggests that unbiased analysis of the pathobiology of CLE lesions may be important for personalized medicine and targeted therapeutic decision making.