Ultraviolet radiation-induced injury, chemokines, and leukocyte recruitment: An amplification cycle triggering cutaneous lupus erythematosus

Systemic lupus erythematosus: pathogenesis and targeted therapy

Systemic lupus erythematosus (SLE) is a multifaceted autoimmune disorder characterized by dysregulated immune responses and autoantibody production, which affects multiple organs and varies in clinical presentation and disease severity. The development of SLE is intricate, encompassing dysregulation within the immune system, a collapse of immunological tolerance, genetic susceptibilities to the disease, and a variety of environmental factors that can act as triggers. This review provides a comprehensive discussion of the pathogenesis and treatment strategies of SLE and focuses on the progress and status of traditional and emerging treatment strategies for SLE. Traditional treatment strategies for SLE have mainly employed non-specific approaches, including cytotoxic and immunosuppressive drugs, antimalarials, glucocorticoids, and NSAIDs. These strategies are effective in mitigating the effects of the disease, but they are not a complete cure and are often accompanied by adverse reactions. Emerging targeted therapeutic drugs, on the other hand, aim to control and treat SLE by targeting B and T cells, inhibiting their activation and function, as well as the abnormal activation of the immune system. A deeper understanding of the pathogenesis of SLE and the exploration of new targeted treatment strategies are essential to advance the treatment of this complex autoimmune disease.

How underappreciated autoinflammatory (innate immunity) mechanisms dominate disparate autoimmune disorders

Historically inflammation against self was considered autoimmune which stems back to the seminal observations by Ehrlich who described serum factors, now known to be autoantibodies produced by B lineage cells that mediate "horror autotoxicus". The 20th century elucidation of B- and T-cell adaptive immune responses cemented the understanding of the key role of adaptive immune responses in mediating pathology against self. However, Mechnikov shared the Nobel Prize for the discovery of phagocytosis, the most rudimentary aspect of innate immunity. Fast forward some 100 years and an immunogenetic understanding of innate immunity led to the categorising of innate immunopathology under the umbrella term 'auto inflammation' and terminology such as "horror autoinflammaticus" to highlight the schism from the classical adaptive immune understanding of autoimmunity. These concepts lead to calls for a two-tiered classification of inflammation against self, but just as innate and adaptive immunity are functionally integrated, so is immunopathology in many settings and the concept of an autoimmune to autoinflammation continuum emerged with overlaps between both. Herein we describe several historically designated disorders of adaptive immunity where innate immunity is key, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still's disease (AOSD) where the immunopathology phenotype is strongly linked to major histocompatibility complex (MHC) class II associations and responds to drugs that target T-cells. We also consider MHC-I-opathies including psoriasis and Behcet's disease(BD) that are increasingly viewed as archetype CD8 T-cell related disorders. We also briefly review the key role of barrier dysfunction in eczema and ulcerative colitis (UC) where innate tissue permeability barrier dysfunction and microbial dysbiosis contributes to prominent adaptive immune pathological mechanisms. We also highlight the emerging roles of intermediate populations of lymphocytes including gamma delta (γδ) and mucosal-associated invariant T (MAIT) cells that represent a blend of adaptive immune plasticity and innate immune rapid responders that may also determine site specific patterns of inflammation.

Headache in systemic lupus erythematosus: The LUNA registry cross-sectional study

OBJECTIVES

This study investigated the clinically relevant factors for headaches in patients with systemic lupus erythematosus (SLE) using a registry from a Japanese multicenter cohort.

METHODS

This cross-sectional study analysed the clinical information of patients with SLE who experienced headache episodes using the Migraine Disability Assessment (MIDAS) questionnaire. Significant findings in the comparisons between patients with headache (HA patients) and those without headache (non-HA patients) and in the comparisons depending on the grades of headache-induced disability in daily life based on the MIDAS scores were evaluated. Multivariate logistic regression analyses were performed to identify the relevant factors for headache.

RESULTS

We analyzed 369 patients (median age, 45 years; female, 90.8%), including 113 HA patients who were significantly younger than non-HA patients (p < .005). HA patients had significantly higher frequencies of photosensitivity, rashes, and mucosal ulcers than non-HA patients (p < .05). Age and photosensitivity were significantly associated with headache (odds ratio (OR) 0.93, 95% confidence interval (CI) 0.95-0.99; OR 2.11, 95% CI 1.29-3.49, respectively). In the HA patients, hypocomplementemia was significantly associated with a disability of more than mild grade (OR 2.89, 95% CI 1.14-7.74), while rash was significantly observed in those presenting with moderate and severe disability.

CONCLUSION

This study suggests that photosensitivity is a relevant manifestation of headache in patients with SLE. Persistent hypocomplementemia can contribute to headache-induced disability in daily life, whereas a rash may be a dominant manifestation in patients presenting with moderate/severe headache-induced disability.

[Ultraviolet radiation in the pathogenesis of lupus erythematosus]

Photosensitivity represents an increased inflammatory reaction to sunlight, which can be observed particularly in the autoimmune disease lupus erythematosus. Cutaneous lupus erythematosus (CLE) can be provoked by ultraviolet (UV) radiation and can cause both acute, nonscarring and chronic, scarring skin changes. In systemic lupus erythematosus, on the other hand, provocation by UV radiation can lead to flare or progression of systemic involvement. The etiology of lupus erythematosus is multifactorial and includes genetic, epigenetic and immunologic mechanisms. In this review, we address the effect of UV radiation on healthy skin and photosensitive skin using the example of lupus erythematosus. We describe possible mechanisms of UV-triggered immune responses that could offer therapeutic approaches. Currently, photosensitivity can only be prevented by avoiding UV exposure itself. Therefore, it is important to better understand the underlying mechanisms in order to develop strategies to counteract the deleterious effects of photosensitivity.

An update on clinical trials for cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) comprises dermatologic manifestations that may occur independently or with systemic lupus erythematosus (SLE). Despite advancements in refining CLE classification, establishing precise subtype criteria remains challenging due to overlapping presentations and difficulty in distinguishing morphology. Current treatments encompass preventive measures, topical therapies, and systemic approaches. Hydroxychloroquine and glucocorticoids are the sole US Food and Drug Administration (FDA)-approved medications for CLE, with numerous off-label treatments available. However, these treatments are often not covered by insurance, imposing a significant financial burden on patients. The exclusion of most CLE patients, particularly those without concurrent SLE, from trials designed for SLE has resulted in a lack of targeted treatments for CLE. To develop effective CLE treatments, validated outcome measures for tracking patient responsiveness are essential. The Cutaneous Lupus Erythematosus Disease Area and Severity Index is widely utilized for its reliability, validity, and ability to differentiate between skin activity and damage. In contrast, the FDA mandates the use of the Investigator's Global Assessment, a five-point Likert scale related to lesion characteristics, for skin-related therapeutic trials. It requires the disease to resolve or almost completely resolve to demonstrate improvement, which can be difficult when there is residual erythema or incomplete clearance that is meaningfully improved from a patient perspective. Various classes of skin lupus medications target diverse pathways, allowing tailored treatment based on the patient's lupus inflammatory profile, resulting in improved outcomes. Promising targeted therapeutic drugs include anifrolumab (anti-type 1 interferon), deucravacitinib (allosteric tyrosine kinase 2 inhibitor), litifilimab (plasmacytoid dendritic cell-directed therapy), iberdomide (cereblon-targeting ligand), and belimumab (B-cell directed therapy). Despite the significant impact of CLE on quality of life, therapeutic options remain inadequate. While promising treatments for cutaneous lupus are emerging, it is crucial to underscore the urgency for skin-focused treatment outcomes and the implementation of validated measures to assess therapeutic effectiveness in clinical trials.

The role of vitamin D in pediatric systemic lupus erythematosus - a double pawn in the immune and microbial balance

Having increased popularity during the Covid-19 pandemic, vitamin D3 is currently impressing thanks to the numerous researches aimed at its interactions with the body's homeostasis. At the same time, there is a peak in terms of recommendations for supplementation with it. Some of the studies focus on the link between autoimmune diseases and nutritional deficiencies, especially vitamin D3. Since the specialized literature aimed at children (patients between 0-18 years old) is far from equal to the informational diversity of the adult-centered branch, this review aims to bring up to date the relationship between the microbial and nutritional balance and the activity of pediatric systemic lupus erythematosus (pSLE). The desired practical purpose resides in a better understanding and an adequate, individualized management of the affected persons to reduce morbidity. The center of the summary is to establish the impact of hypovitaminosis D in the development and evolution of pediatric lupus erythematosus. We will address aspects related to the two entities of the impact played by vitamin D3 in the pathophysiological cascade of lupus, but also the risk of toxicity and its effects when the deficiency is over supplemented (hypervitaminosis D). We will debate the relationship of hypovitaminosis D with the modulation of immune function, the potentiation of inflammatory processes, the increase of oxidative stress, the perfusion of cognitive brain areas, the seasonal incidence of SLE and its severity. Finally, we review current knowledge, post-pandemic, regarding the hypovitaminosis D - pSLE relationship.

Interferon alpha promotes caspase-8 dependent ultraviolet light-mediated keratinocyte apoptosis via interferon regulatory factor 1

Introduction

Ultraviolet (UV) light is a known trigger of both cutaneous and systemic disease manifestations in lupus patients. Lupus skin has elevated expression of type I interferons (IFNs) that promote increased keratinocyte (KC) death after UV exposure. The mechanisms by which KC cell death is increased by type I IFNs are unknown.

Methods

Here, we examine the specific cell death pathways that are activated in KCs by type I IFN priming and UVB exposure using a variety of pharmacological and genetic approaches. Mice that overexpress Ifnk in the epidermis were exposed to UVB light and cell death was measured. RNA-sequencing from IFN-treated KCs was analyzed to identify candidate genes for further analysis that could drive enhanced cell death responses after UVB exposure.

Results

We identify enhanced activation of caspase-8 dependent apoptosis, but not other cell death pathways, in type I IFN and UVB-exposed KCs. In vivo, overexpression of epidermal Ifnk resulted in increased apoptosis in murine skin after UVB treatment. This increase in KC apoptosis was not dependent on known death ligands but rather dependent on type I IFN-upregulation of interferon regulatory factor 1 (IRF1).

Discussion

These data suggest that enhanced sensitivity to UV light exhibited by lupus patients results from type I IFN priming of KCs that drives IRF1 expression resulting in caspase-8 activation and increased apoptosis after minimal exposures to UVB.

Dermoscopy for the Differentiation of Subacute Cutaneous Lupus Erythematosus from Other Erythematous Desquamative Dermatoses-Psoriasis, Nummular Eczema, Mycosis Fungoides and Pityriasis Rosea

Subacute cutaneous lupus erythematosus (SCLE) is a condition that might pose a diagnostic challenge. The aim of this study was to assess the usefulness of videodermoscopy in the differentiation of SCLE from other erythematous-desquamative dermatoses. Consecutive patients with SCLE (n = 27), psoriasis (n = 36), nummular eczema (n = 30), mycosis fungoides (n = 26), and pityriasis rosea (n = 20) referred to our Department of Dermatology were recruited for this study. A representative lesion was visualized using a Canfield D200EVO Videodermatoscope (Canfield Scientific GmbH, Bielefeld, Germany) and evaluated for the following parameters: vessels (morphology and distribution), scales (color and distribution), follicular findings, colors and morphologies, and presence of specific clues. SCLE was predominantly characterized by a polymorphous vascular pattern (92.6%) of unspecific distribution (92.6%) over a pink-red background (74.1%). Gray-brown dots were present in 10 (37.0%) cases, and pigmentation was noted in 15 (55.6%) patients, including peripheral pigmentation in 7 (25.9%) patients. Videodermoscopic evaluation showed significant differences between SCLE and psoriasis, which was characterized by regularly distributed dotted vessels. Although some common dermoscopic features with MF were noted, the presence of yellow structureless areas and red dots/globules favored the diagnosis of MF. In conclusion, a polymorphic vascular pattern, especially in association with gray-brown dots and/or peripheral pigmentation, is a valuable clue for the differentiation of SCLE from other erythematous-desquamative dermatoses.

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.

Biomarkers for systemic lupus erythematosus - a focus on organ damage

INTRODUCTION

Systemic lupus erythematosus (SLE) is complex autoimmune disease with heterogenous manifestations, unpredictable disease course and response to treatment. One of the critical needs in SLE management is the identification of reliable biomarkers that can aid in early diagnosis, accurate monitoring of disease activity, and assessment of treatment response.

AREAS COVERED

In the current review, we focus on the commonly affected organs (skin, kidney, and nervous system) in SLE to summarize the emerging biomarkers that show promise in disease diagnosis, monitoring and treatment response assessment. The subtitles within each organ domain were determined based on the most relevant and promising biomarkers for that specific organ damage.

EXPERT OPINION

Biomarkers have the potential to significantly benefit the management of SLE by aiding in diagnosis, disease activity monitoring, prognosis, and treatment response assessment. However, despite decades of research, none has been validated and implemented for routine clinical use. Novel biomarkers could lead to the development of precision medicine for SLE, guide personalized treatment, and improve patient outcomes. Challenges in biomarker research in SLE include defining clear and clinically relevant questions, accounting for the heterogeneity of SLE, and confirming initial findings in larger, multi-center, multi-ethnic, independent cohorts that reflect real-world clinical scenarios.

Molecular consideration relevant to the mechanism of the comorbidity between psoriasis and systemic lupus erythematosus (Review)

Systemic lupus erythematosus (SLE), a common autoimmune disease with a global incidence and newly diagnosed population estimated at 5.14 (range, 1.4-15.13) per 100,000 person-years and 0.40 million people annually, respectively, affects multiple tissues and organs; for example, skin, blood system, heart and kidneys. Accumulating data has also demonstrated that psoriasis (PS) can be a systemic inflammatory disease, which can affect organs other than the skin and occur alongside other autoimmune diseases, such as inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis and SLE. The current explanations for the possible comorbidity of PS and SLE include: i) The two diseases share susceptible gene loci; ii) they share a common IL-23/T helper 17 (Th17) axis inflammatory pathway; and iii) the immunopathogenesis of the two conditions is a consequence of the interactions between IL-17 cytokines with effector Th17 cells, T regulatory cells, as well as B cells. In addition, the therapeutic efficacy of IL-17 or TNF-α inhibitors has been demonstrated in PS, and has also become evident in SLE. However, the mechanisms have not been investigated. To the best of our knowledge, there remains a lack of substantial studies on the correlation between PS and SLE. In the present review, the literature, with regards to the epidemiology, genetic predisposition, inflammatory mechanisms and treatment of the patients with both PS and SLE, has been reviewed. Further investigations into the molecular pathogenic mechanism may provide drug targets that could benefit the patients with concomitant PS and SLE.

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.

Cutaneous Lupus Erythematosus: An Update on Pathogenesis and Future Therapeutic Directions

Lupus erythematosus comprises a spectrum of autoimmune diseases that may affect various organs (systemic lupus erythematosus [SLE]) or the skin only (cutaneous lupus erythematosus [CLE]). Typical combinations of clinical, histological and serological findings define clinical subtypes of CLE, yet there is high interindividual variation. Skin lesions arise in the course of triggers such as ultraviolet (UV) light exposure, smoking or drugs; keratinocytes, cytotoxic T cells and plasmacytoid dendritic cells (pDCs) establish a self-perpetuating interplay between the innate and adaptive immune system that is pivotal for the pathogenesis of CLE. Therefore, treatment relies on avoidance of triggers and UV protection, topical therapies (glucocorticosteroids, calcineurin inhibitors) and rather unspecific immunosuppressive or immunomodulatory drugs. Yet, the advent of licensed targeted therapies for SLE might also open new perspectives in the management of CLE. The heterogeneity of CLE might be attributable to individual variables and we speculate that the prevailing inflammatory signature defined by either T cells, B cells, pDCs, a strong lesional type I interferon (IFN) response, or combinations of the above might be suitable to predict therapeutic response to targeted treatment. Therefore, pretherapeutic histological assessment of the inflammatory infiltrate could stratify patients with refractory CLE for T-cell-directed therapies (e.g. dapirolizumab pegol), B-cell-directed therapies (e.g. belimumab), pDC-directed therapies (e.g. litifilimab) or IFN-directed therapies (e.g. anifrolumab). Moreover, Janus kinase (JAK) and spleen tyrosine kinase (SYK) inhibitors might broaden the therapeutic armamentarium in the near future. A close interdisciplinary exchange with rheumatologists and nephrologists is mandatory for optimal treatment of lupus patients to define the best therapeutic strategy.

Type I IFNs link skin-associated dysbiotic commensal bacteria to pathogenic inflammation and angiogenesis in rosacea

Rosacea is a common chronic inflammatory skin disease with a fluctuating course of excessive inflammation and apparent neovascularization. Microbial dysbiosis with a high density of Bacillus oleronius and increased activity of kallikrein 5, which cleaves cathelicidin antimicrobial peptide, are key pathogenic triggers in rosacea. However, how these events are linked to the disease remains unknown. Here, we show that type I IFNs produced by plasmacytoid DCs represent the pivotal link between dysbiosis, the aberrant immune response, and neovascularization. Compared with other commensal bacteria, B. oleronius is highly susceptible and preferentially killed by cathelicidin antimicrobial peptides, leading to enhanced generation of complexes with bacterial DNA. These bacterial DNA complexes but not DNA complexes derived from host cells are required for cathelicidin-induced activation of plasmacytoid DCs and type I IFN production. Moreover, kallikrein 5 cleaves cathelicidin into peptides with heightened DNA binding and type I IFN-inducing capacities. In turn, excessive type I IFN expression drives neoangiogenesis via IL-22 induction and upregulation of the IL-22 receptor on endothelial cells. These findings unravel a potentially novel pathomechanism that directly links hallmarks of rosacea to the killing of dysbiotic commensal bacteria with induction of a pathogenic type I IFN-driven and IL-22-mediated angiogenesis.

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.

Current concepts of photosensitivity in cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) represents a complex autoimmune disease with a broad phenotypic spectrum ranging from acute to chronic destructive cutaneous lesions. Patients with CLE exhibit high photosensitivity and ultraviolet (UV) irradiation can lead to systemic flares in systemic lupus erythematosus. However, the exact mechanisms how UV irradiation enhances cutaneous inflammation in lupus are not fully understood. Recently, new molecular mechanisms of UV-driven immune responses in CLE were identified, offering potential therapeutic approaches. Especially the induction of type I interferons, central cytokines in lupus pathogenesis which are released by various skin cells, have become the focus of current research. In this review, we describe current pathogenic concepts of photosensitivity in lupus erythematosus, including UV-driven activation of intracellular nucleic acid sensors, cellular cytokine production and immune cell activation. Furthermore, we discuss activated pathways contributing to enhanced apoptosis as well as intracellular translocation of autoantigens thereby promoting CLE upon UV light exposure.

Current Concepts on Pathogenic Mechanisms and Histopathology in Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an interferon (IFN)-driven autoimmune disease that may be limited to the skin or can be associated with systemic lupus erythematosus (SLE). CLE occurs in several morphologic subtypes ranging from isolated, disc-shaped plaques to disseminated skin lesions. The typical histopathologic pattern of skin lesions is named interface dermatitis and characterized by a lymphocytic infiltrate and necroptotic keratinocytes at the dermo-epidermal junction. Other histopathologic patterns primarily involve the dermis or subcutis, depending on the subtype. One critical mechanism in CLE is the chronic reactivation of innate and adaptive immune pathways. An important step in this process is the recognition of endogenous nucleic acids released from dying cells by various pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and other cytosolic receptors. Crucial cells in CLE pathogenesis comprise plasmacytoid dendritic cells (pDCs) as major producers of type I IFN, T cells exerting cytotoxic effects, and B cells, previously believed to contribute via secretion of autoantibodies. However, B cells are increasingly considered to have additional functions, supported by studies finding them to occur in highest numbers in chronic discoid lupus erythematosus (CDLE), a subtype in which autoantibodies are often absent. More precise knowledge of how CLE subtypes differ pathophysiologically may allow a tailored pharmacotherapy in the future, taking into account the specific molecular signature in relation to the morphologic subtype.

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.

Solar UVR and Variations in Systemic Immune and Inflammation Markers

The characterization of the effects of solar UVR on a broad set of circulating markers in systemic immunity and inflammation may provide insight into the mechanisms responsible for the UVR associations observed for several benign and malignant diseases. We examined the associations between exposure to solar UVR and circulating levels of 78 markers among 1,819 individuals aged 55–74 years who participated in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial using multiplex assays. Solar UVR was derived by linking the geocoded locations of 10 screening centers across the continental United States and the date of blood draw to the National Solar Radiation Database from 1993 to 2005. We assessed associations between ambient solar UVR and dichotomized marker levels using adjusted weighted logistic regression models and applied a 5% false discovery rate criterion to P-values. UVR exposure was associated (P < 0.05) with 9 of the 78 markers. CCL27, CCL4, FGF2, GM-CSF, IFN-γ, soluble IL4R, IL-7, and IL-11 levels were lower with increasing UVR tertile, with adjusted ORs ranging from 0.66 to 0.80, and the significant association for CCL27 withstood multiple comparison correction. In contrast, CRP levels were elevated with increasing UVR. Solar UVR was associated with alterations in systemic immune and inflammation marker levels.

C-X-C Motif Chemokine Ligand 9 and Its CXCR3 Receptor Are the Salt and Pepper for T Cells Trafficking in a Mouse Model of Gaucher Disease

Gaucher disease is a lysosomal storage disease, which happens due to mutations in GBA1/Gba1 that encodes the enzyme termed as lysosomal acid β-glucosidase. The major function of this enzyme is to catalyze glucosylceramide (GC) into glucose and ceramide. The deficiency of this enzyme and resultant abnormal accumulation of GC cause altered function of several of the innate and adaptive immune cells. For example, augmented infiltration of T cells contributes to the increased production of pro-inflammatory cytokines, (e.g., IFNγ, TNFα, IL6, IL12p40, IL12p70, IL23, and IL17A/F). This leads to tissue damage in a genetic mouse model (Gba1^9V/-) of Gaucher disease. The cellular mechanism(s) by which increased tissue infiltration of T cells occurs in this disease is not fully understood. Here, we delineate role of the CXCR3 receptor and its exogenous C-X-C motif chemokine ligand 9 (CXCL9) in induction of increased tissue recruitment of CD4⁺ T and CD8⁺ T cells in Gaucher disease. Intracellular FACS staining of macrophages (Mϕs) and dendritic cells (DCs) from Gba1^9V/- mice showed elevated production of CXCL9. Purified CD4⁺ T cells and the CD8⁺ T cells from Gba1^9V/- mice showed increased expression of CXCR3. Ex vivo and in vivo chemotaxis experiments showed CXCL9 involvement in the recruitment of Gba1^9V/- T cells. Furthermore, antibody blockade of the CXCL9 receptor (CXCR3) on T cells caused marked reduction in CXCL9- mediated chemotaxis of T cells in Gba1^9V/- mice. These data implicate abnormalities of the CXCL9-CXCR3 axis leading to enhanced tissue recruitment of T cells in Gaucher disease. Such results provide a rationale for blockade of the CXCL9/CXCR3 axis as potential new therapeutic targets for the treatment of inflammation in Gaucher disease.

Bioinformatics analyses of gene expression profile identify key genes and functional pathways involved in cutaneous lupus erythematosus

BACKGROUND

Lupus erythematosus is an autoimmune disease that causes damage to multiple organs ranging from skin lesions to systemic manifestations. Cutaneous lupus erythematosus (CLE) is a common type of lupus erythematosus (LE), but its molecular mechanisms are currently unknown. The study aimed to explore changes in the gene expression profiles and identify key genes involved in CLE, hoping to uncover its molecular mechanism and identify new targets for CLE.

METHOD

We analyzed the microarray dataset (GSE109248) derived from the Gene Expression Omnibus (GEO) database, which was a transcriptome profiling of CLE cutaneous lesions. The differentially expressed genes (DEGs) were identified, and the functional annotation of DEGs was performed with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Protein-protein interaction (PPI) network was also constructed to identify hub genes involved in CLE.

RESULT

A total of 755 up-regulated DEGs and 405 down-regulated DEGs were identified. GO enrichment analysis showed that defense response to virus, immune response, and type I interferon signaling pathway were the most significant enrichment items in DEGs. The KEGG pathway analysis identified 51 significant enrichment pathways, which mainly included systemic lupus erythematosus, osteoclast differentiation, cytokine-cytokine receptor interaction, and primary immunodeficiency. Based on the PPI network, the study identified the top 10 hub genes involved in CLE, which were CXCL10, CCR7, FPR3, PPARGC1A, MMP9, IRF7, IL2RG, SOCS1, ISG15, and GSTM3. By comparison between subtypes, the results showed that ACLE had the least DEGs, while CCLE showed the most gene and functional changes.

CONCLUSION

The identified hub genes and functional pathways found in this study may expand our understanding on the underlying pathogenesis of CLE and provide new insights into potential biomarkers or targets for the diagnosis and treatment of CLE. Key Points • The bioinformatics analysis based on CLE patients and healthy controls was performed and 1160 DEGs were identified • The 1160 DEGs were mainly enriched in biological processes related to immune responses, including innate immune response, type I interferon signaling pathway, interferon-γ-mediated signaling pathway, positive regulation of T cell proliferation, regulation of immune response, antigen processing, and presentation via MHC class Ib and so on • KEGG pathway enrichment analysis indicated that DEGs were mainly enriched in several immune-related diseases and virus infection, including systemic lupus erythematosus, primary immunodeficiency, herpes simplex infection, measles, influenza A, and so on • The hub genes such as CXCL10, IRF7, MMP9, CCR7, and SOCS1 may become new markers or targets for the diagnosis and treatment of CLE.

Regulation of cGAS-STING pathway - Implications for systemic lupus erythematosus

Type I interferon (IFN-I) is implicated in the pathogenesis of systemic lupus erythematosus (SLE) and the closely associated monogenic autoinflammatory disorders termed the “interferonopathies.” Recently, the cytosolic DNA sensor cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) and its downstream signaling adaptor stimulator of interferon genes (STING) have been identified as having important, if not central, roles in driving IFN-I expression in response to self-DNA. This review highlights the many ways in which this pathway is regulated in order to prevent self-DNA recognition and underlines the importance of maintaining tight control in order to prevent autoimmune disease. We will discuss the murine and human studies that have implicated the cGAS-STING pathway as being an important contributor to breakdown in tolerance in SLE and highlight the potential therapeutic application of this knowledge for the treatment of SLE.

Mechanisms of Photosensitivity in Autoimmunity

Aberrant responses to UV light frequently lead to the formation of skin lesions and the activation of systemic inflammation in some autoimmune diseases, especially systemic lupus erythematosus. Whereas the effects of UV light on the skin have been studied for decades, only recently have some of the mechanisms that contribute to abnormal responses to UV light in patients with autoimmune diseases been uncovered. This review will discuss the biology of UV in the epidermis and discuss the abnormal epidermal and inflammatory mechanisms that contribute to photosensitivity. Further research is required to fully understand how to normalize UV-mediated inflammation in patients with autoimmune diseases.

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.

Immune Cell-Stromal Circuitry in Lupus Photosensitivity

Photosensitivity is a sensitivity to UV radiation (UVR) commonly found in systemic lupus erythematosus (SLE) patients who have cutaneous disease. Upon even ambient UVR exposure, patients can develop inflammatory skin lesions that can reduce the quality of life. Additionally, UVR-exposed skin lesions can be associated with systemic disease flares marked by rising autoantibody titers and worsening kidney disease. Why SLE patients are photosensitive and how skin sensitivity leads to systemic disease flares are not well understood, and treatment options are limited. In recent years, the importance of immune cell-stromal interactions in tissue function and maintenance is being increasingly recognized. In this review, we discuss SLE as an anatomic circuit and review recent findings in the pathogenesis of photosensitivity with a focus on immune cell-stromal circuitry in tissue health and disease.

Type I Interferon as cardiovascular risk factor in systemic and cutaneous lupus erythematosus: A systematic review

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) have a high burden of cardiovascular disease (CVD) of multifactorial origin. The aim of this systematic review is to analyze the role of the interferon I (IFN-I) signature and fibroblast growth factor-23 (FGF-23) in patients with SLE or cutaneous lupus erythematosus (CLE) herein.

MATERIALS AND METHODS

We conducted a systematic literature search in PubMed and Scopus using keywords for major adverse cardiovascular events (MACE) and intermediate outcomes (endothelial dysfunction, subclinical atherosclerosis, platelet activation) associated with IFN-I or FGF-23 in patients with SLE and CLE.

RESULTS

4745 citations were screened, of which 12 studies were included. IFN-I was associated with MACE in two third of the studies and the association was strongest for cardiac events. An association of IFN-I was found in all studies investigating impaired vascular function, but only in 50% (respectively 40%) of reports examining the relation of IFN-I and platelet activation (respectively subclinical atherosclerosis). Altogether the reports were of variable bias and quality due to high variability of examined IFN-I biomarkers and inconsistent results for different outcome measures. No studies investigating the cardiovascular risk of circulating IFN-I in CLE, nor FGF-23 in SLE or CLE were found.

CONCLUSION

Clinical studies measuring the association between IFN-I and direct / intermediate measures of CVD are rare and ambiguous in SLE and nonexistent in CLE, hampering a definite conclusion.

Toxic epidermal necrolysis-like acute cutaneous lupus erythematosus: two cases report

Toxic epidermal necrolysis-like acute cutaneous lupus erythematosus (TEN-like ACLE) is a rare manifestation of systemic lupus erythematosus (SLE). Because of its rarity, little is known about this entity. In this report, we describe a case of two women previously diagnosed with SLE that presented TEN-like skin lesions. The common elements in both patients were the initial disposition of the lesions on the photoexposed areas, the positivity of Nikolsky´s sign, the discrete mucosal attrition compared to that observed during TEN, and the simultaneous appearance of dermatological lesions with an extra-cutaneous flare of lupus disease. The skin biopsy in both cases showed epidermal necrosis with an identification of lupus band on direct immunofluorescence. Systemic corticosteroids were used with a good evolution after 2 weeks. Skin damage is an indicator of disease activity, and careful search for extracutaneous involvement is obligatory to prevent further complications.

Immunopathogenesis of skin injury in systemic lupus erythematosus

PURPOSE OF REVIEW

Skin injury is the most common clinical manifestation of SLE and is disfiguring, difficult to treat, and incompletely understood. We provide an overview of recently published articles covering the immunopathogenesis of skin injury in SLE.

RECENT FINDINGS

Skin of SLE has an inherent susceptibility to apoptosis, the cause of which may be multifactorial. Chronic IFN overexpression leads to barrier disruption, infiltration of inflammatory cells, cytokine production, and release of autoantigens and autoantibody production that result in skin injury. Ultraviolet light is the most important CLE trigger and amplifies this process leading to skin inflammation and potentially systemic disease flares.

SUMMARY

The pathogenesis of skin injury in CLE is complex but recent studies highlight the importance of mechanisms driving dysregulated epidermal cell death likely influenced by genetic risk factors, environmental triggers (UV light), and cytotoxic cells and cellular signaling.

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.

CCL27 Signaling in the Tumor Microenvironment

Chemokines are a group of small proteins which play an important role in leukocyte migration and invasion. They are also involved in the cellular proliferation and migration of tumor cells.Chemokine CCL27 (cutaneous T cell-attracting chemokine, CTACK) is mainly expressed by keratinocytes of the normal epidermis. It is well known that this chemokine plays an important role in several inflammatory diseases of the skin, such as atopic dermatitis, contact dermatitis, and psoriasis. Moreover, several studies have shown an association between CCL27 expression and a variety of neoplasms including skin cancer.In this chapter, we address the role of chemokine CCL27 in the tumor microenvironment in the most relevant cancers of the skin and other anatomical locations. We also make a brief comment on future perspectives and the potential relation of CCL27 with different immunotherapeutic modalities.

The Role of Cutaneous Type I IFNs in Autoimmune and Autoinflammatory Diseases

IFNs are well known as mediators of the antimicrobial response but also serve as important immunomodulatory cytokines in autoimmune and autoinflammatory diseases. An increasingly critical role for IFNs in evolution of skin inflammation in these patients has been recognized. IFNs are produced not only by infiltrating immune but also resident skin cells, with increased baseline IFN production priming for inflammatory cell activation, immune response amplification, and development of skin lesions. The IFN response differs by cell type and host factors and may be modified by other inflammatory pathway activation specific to individual diseases, leading to differing clinical phenotypes. Understanding the contribution of IFNs to skin and systemic disease pathogenesis is key to development of new therapeutics and improved patient outcomes. In this review, we summarize the immunomodulatory role of IFNs in skin, with a focus on type I, and provide insight into IFN dysregulation in autoimmune and autoinflammatory diseases.

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.

The influence of interferon on healthy and diseased skin

Type I interferons (IFNs) are an immunomodulatory class of cytokines that serve to protect against viral and bacterial infection. In addition, mounting evidence suggests IFNs, particularly type I but also IFNγ, are important to the pathogenesis of autoimmune and inflammatory skin diseases, such as cutaneous lupus erythematosus (CLE). Understanding the role of IFNs is relevant to anti-viral responses in the skin, skin biology, and therapeutics for these IFN-related conditions. Type I IFNs (α and β) are produced by recruited inflammatory cells and by the epidermis itself (IFNκ) and have important roles in autoimmune and inflammatory skin disease. Here, we review the current literature utilizing a PubMed database search using terms [interferon/IFN/type I IFN AND lupus/ cutaneous lupus/CLE/dermatomyositis/Sjogrens/psoriasis/lichen planus/morphea/alopecia areata/vitiligo] with a focus on the role of IFNs in basic keratinocyte biology and their implications in the cutaneous autoimmune and inflammatory diseases: cutaneous lupus erythematosus, dermatomyositis, Sjogren's syndrome, psoriasis, lichen planus, alopecia areata and vitiligo. We provide information about genes and proteins induced by IFNs and how downstream mechanisms relate to clinical disease.

Current Insights in Cutaneous Lupus Erythematosus Immunopathogenesis

Cutaneous Lupus Erythematosus (CLE) is a clinically diverse group of autoimmune skin diseases with shared histological features of interface dermatitis and autoantibodies deposited at the dermal-epidermal junction. Various genetic and environmental triggers of CLE promote infiltration of T cells, B cells, neutrophils, antigen presenting cells, and NK cells into lesional skin. In this mini-review, we will discuss the clinical features of CLE, insights into CLE immunopathogenesis, and novel treatment approaches.

The early local and systemic Type I interferon responses to ultraviolet B light exposure are cGAS dependent

Most systemic lupus erythematosus (SLE) patients are photosensitive and ultraviolet B light (UVB) exposure worsens cutaneous disease and precipitates systemic flares of disease. The pathogenic link between skin disease and systemic exacerbations in SLE remains elusive. In an acute model of UVB-triggered inflammation, we observed that a single UV exposure triggered a striking IFN-I signature not only in the skin, but also in the blood and kidneys. The early IFN-I signature was significantly higher in female compared to male mice. The early IFN-I response in the skin was almost entirely, and in the blood partly, dependent on the presence of cGAS, as was skin inflammatory cell infiltration. Inhibition of cGAMP hydrolysis augmented the UVB-triggered IFN-I response. UVB skin exposure leads to cGAS-activation and both local and systemic IFN-I signature and could contribute to acute flares of disease in susceptible subjects such as patients with SLE.

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.

Staphylococcus aureus Colonization Is Increased on Lupus Skin Lesions and Is Promoted by IFN-Mediated Barrier Disruption

Cutaneous inflammation is recurrent in systemic lupus erythematosus (SLE), yet mechanisms that drive cutaneous inflammation in SLE are not well defined. Type I IFNs are elevated in nonlesional SLE skin and promote inflammatory responses. Staphylococcus aureus, known to induce IFN production, could play a role in cutaneous inflammation in SLE. We show here that active cutaneous lupus erythematosus lesions are highly colonized (∼50%) by S. aureus. To define the impact of IFNs on S. aureus colonization, we examined the effects of type I and type II IFNs on S. aureus adherence and invasion. An increase in adherent S. aureus was observed after exposure to both IFN-α and -γ, whereas IFN-γ appeared to inhibit invasion of S. aureus. Cutaneous lupus erythematosus lesional skin microarray data and RNA sequencing data from SLE keratinocytes identified repression of barrier gene expression, such as filaggrin and loricrin, and SLE keratinocytes exhibited increased S. aureus-binding integrins. These SLE-associated changes could be replicated by IFN treatment of keratinocytes. Further, SLE keratinocytes exhibited increased binding to S. aureus. Together, these data suggest that chronic exposure to IFNs induces barrier disruption that allows for higher S. aureus colonization in SLE skin.

Plucked hair follicles from patients with chronic discoid lupus erythematosus show a disease-specific molecular signature

OBJECTIVE

When faced with clinical symptoms of scarring alopecia-the standard diagnostic pathway involves a scalp biopsy which is an invasive and expensive procedure. This project aimed to assess if plucked hair follicles (HFs) containing living epithelial cells can offer a non-invasive approach to diagnosing inflammatory scalp lesions.

METHODS

Lesional and non-lesional HFs were extracted from the scalp of patients with chronic discoid lupus erythematosus (CDLE), psoriasis and healthy controls. RNA was isolated from plucked anagen HFs and microarray, as well as quantitative real-time PCR was performed.

RESULTS

Here, we report that gene expression analysis of only a small number of HF plucked from lesional areas of the scalp is sufficient to differentiate CDLE from psoriasis lesions or healthy HF. The expression profile from CDLE HFs coincides with published profiles of CDLE from skin biopsy. Genes that were highly expressed in lesional CDLE corresponded to well-known histopathological diagnostic features of CDLE and included those related to apoptotic cell death, the interferon signature, complement components and CD8+ T-cell immune responses.

CONCLUSIONS

We therefore propose that information obtained from this non-invasive approach are sufficient to diagnose scalp lupus erythematosus. Once validated in routine clinical settings and compared with other scarring alopecias, this rapid and non-invasive approach will have great potential for paving the way for future diagnosis of inflammatory scalp lesions.

T-cell positioning by chemokines in autoimmune skin diseases

Autoimmune skin diseases are complex processes in which autoreactive cells must navigate through the skin tissue to find their targets. Regulatory T cells in the skin help to mitigate autoimmune inflammation and may in fact be responsible for the patchy nature of these conditions. In this review, we will discuss chemokines that are important for global recruitment of T cell populations to the skin during disease, as well as signals that fine-tune their localization and function. We will describe prototypical disease responses and chemokine families that mediate these responses. Lastly, we will include an overview of chemokine-targeting drugs that have been tested as new treatment strategies for autoimmune skin diseases.

Effect of in vivo Hydroxychloroquine and ex vivo Anti-BDCA2 mAb Treatment on pDC IFNα Production From Patients Affected With Cutaneous Lupus Erythematosus

Objective: Plasmacytoid dendritic cells (pDCs) are a major source of Type-I Interferon (IFN-I), a key driver in cutaneous lupus erythematosus (CLE). Currently evaluated in Phase II clinical trial, 24F4A (BIIB059) is an antibody targeting BDCA2, an inhibitory receptor expressed on pDCs. Given that Hydroxychloroquine (HCQ), a widely-used CLE therapy, and 24F4A are both able to inhibit pDC-derived IFN-I production; this study aimed to determine whether 24F4A would show an additional inhibitory effect on pDC response after ex vivo or in vivo treatment with HCQ.

Methods: The effect of 24F4A on pDC-derived IFNα was measured from peripheral blood mononuclear cells (PBMC) either from healthy donors in presence or absence of HCQ or from CLE patients clinically exposed to various levels of HCQ. TLR7, TLR7/8, and TLR9 agonists (ssRNA, R848, and CpG-A) were used for pDC stimulation.

Results: PDCs were the only producers of IFNα in response to CpG-A, R848, and ssRNA stimulation in PBMC cultures. CLE patients with higher levels of blood HCQ showed lower ex vivo pDC responses to CpG-A, but not R848 or ssRNA. In contrast, 24F4A reduced the amount of IFNα produced by pDCs from CLE patients in response to all TLR agonists, irrespective of the blood HCQ level.

Conclusion: Our findings reveal that clinically-relevant HCQ concentrations partially inhibit the pDC response to TLR9 and weakly affect the response to TLR7/8 stimulation. 24F4A robustly inhibits pDC responses even in the presence of HCQ, highlighting its unique potential to disrupt pDC disease relevant biology, which could provide additional therapeutic benefit for CLE patients.

Hypersensitive IFN Responses in Lupus Keratinocytes Reveal Key Mechanistic Determinants in Cutaneous Lupus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease in which 70% of patients experience disfiguring skin inflammation (grouped under the rubric of cutaneous lupus erythematosus [CLE]). There are limited treatment options for SLE and no Food and Drug Administration-approved therapies for CLE. Studies have revealed that IFNs are important mediators for SLE and CLE, but the mechanisms by which IFNs lead to disease are still poorly understood. We aimed to investigate how IFN responses in SLE keratinocytes contribute to development of CLE. A cohort of 72 RNA sequencing samples from 14 individuals (seven SLE and seven healthy controls) were analyzed to study the transcriptomic effects of type I and type II IFNs on SLE versus control keratinocytes. In-depth analysis of the IFN responses was conducted. Bioinformatics and functional assays were conducted to provide implications for the change of IFN response. A significant hypersensitive response to IFNs was identified in lupus keratinocytes, including genes (IFIH1, STAT1, and IRF7) encompassed in SLE susceptibility loci. Binding sites for the transcription factor PITX1 were enriched in genes that exhibit IFN-sensitive responses. PITX1 expression was increased in CLE lesions based on immunohistochemistry, and by using small interfering RNA knockdown, we illustrated that PITX1 was required for upregulation of IFN-regulated genes in vitro. SLE patients exhibit increased IFN signatures in their skin secondary to increased production and a robust, skewed IFN response that is regulated by PITX1. Targeting these exaggerated pathways may prove to be beneficial to prevent and treat hyperinflammatory responses in SLE skin.

Anifrolumab effects on rash and arthritis: impact of the type I interferon gene signature in the phase IIb MUSE study in patients with systemic lupus erythematosus

Objective

This post hoc analysis compared anifrolumab 300 mg every 4 weeks with placebo on rash and arthritis measures with different stringency in patients with moderate to severe SLE (phase IIb; MUSE; NCT01438489). Subgroups were analysed by type I interferon gene signature (IFNGS test–high or test–low).

Methods

Rash was measured with the SLE Disease Activity Index 2000 (SLEDAI-2K), British Isles Lupus Assessment Group (BILAG) Index and modified Cutaneous Lupus Erythematosus Disease Area and Severity Index (mCLASI). Arthritis was evaluated using SLEDAI-2K, BILAG and swollen and tender joint counts. Outcomes were measured at week 52.

Results

More anifrolumab-treated patients demonstrated resolution of rash by SLEDAI-2K versus placebo: 39/88 (44.3%) versus 13/88 (14.8%), OR (90% CI) 4.56 (2.48 to 8.39), p<0.001; improvement of BILAG: 48/82 (58.5%) versus 24/85 (28.2%), OR (90% CI) 3.59 (2.08 to 6.19), p<0.001; and ≥50% improvement by mCLASI: 57/92 (62.0%) versus 30/89 (33.7%), OR (90% CI) 3.31 (1.97 to 5.55), p<0.001. More anifrolumab-treated patients had improved arthritis by SLEDAI-2K versus placebo: 55/97 (56.7%) versus 42/99 (42.4%), OR (90%  CI) 1.88 (1.16 to 3.04), p=0.032;  and BILAG: 65/94 (69.1%) versus 47/95 (49.5%), OR (90% CI) 2.47 (1.48 to 4.12), p=0.003; and mean (SD) swollen and tender joint reductions: –5.5 (6.3) versus –3.4 (5.9), p=0.004. Comparable results were demonstrated in IFNGS test–high patients (n=151). In IFNGS test–low patients (n=50), substantial numerical differences in partial rash and arthritis responses were observed in anifrolumab-treated patients versus placebo, with statistical significance only for rash by BILAG in this small population.

Conclusions

Anifrolumab treatment was associated with improvements versus placebo in specific SLE features of arthritis and rash using measures of different stringency. Although driven by robust data in the prevalent IFNGS test–high population, further evaluation in IFNGS test–low patients is warranted.

Anifrolumab effects on rash and arthritis: impact of the type I interferon gene signature in the phase IIb MUSE study in patients with systemic lupus erythematosus

OBJECTIVE

This post hoc analysis compared anifrolumab 300 mg every 4 weeks with placebo on rash and arthritis measures with different stringency in patients with moderate to severe SLE (phase IIb; MUSE; NCT01438489). Subgroups were analysed by type I interferon gene signature (IFNGS test-high or test-low).

METHODS

Rash was measured with the SLE Disease Activity Index 2000 (SLEDAI-2K), British Isles Lupus Assessment Group (BILAG) Index and modified Cutaneous Lupus Erythematosus Disease Area and Severity Index (mCLASI). Arthritis was evaluated using SLEDAI-2K, BILAG and swollen and tender joint counts. Outcomes were measured at week 52.

RESULTS

More anifrolumab-treated patients demonstrated resolution of rash by SLEDAI-2K versus placebo: 39/88 (44.3%) versus 13/88 (14.8%), OR (90% CI) 4.56 (2.48 to 8.39), p<0.001; improvement of BILAG: 48/82 (58.5%) versus 24/85 (28.2%), OR (90% CI) 3.59 (2.08 to 6.19), p<0.001; and ≥50% improvement by mCLASI: 57/92 (62.0%) versus 30/89 (33.7%), OR (90% CI) 3.31 (1.97 to 5.55), p<0.001. More anifrolumab-treated patients had improved arthritis by SLEDAI-2K versus placebo: 55/97 (56.7%) versus 42/99 (42.4%), OR (90%  CI) 1.88 (1.16 to 3.04), p=0.032;  and BILAG: 65/94 (69.1%) versus 47/95 (49.5%), OR (90% CI) 2.47 (1.48 to 4.12), p=0.003; and mean (SD) swollen and tender joint reductions: -5.5 (6.3) versus -3.4 (5.9), p=0.004. Comparable results were demonstrated in IFNGS test-high patients (n=151). In IFNGS test-low patients (n=50), substantial numerical differences in partial rash and arthritis responses were observed in anifrolumab-treated patients versus placebo, with statistical significance only for rash by BILAG in this small population.

CONCLUSIONS

Anifrolumab treatment was associated with improvements versus placebo in specific SLE features of arthritis and rash using measures of different stringency. Although driven by robust data in the prevalent IFNGS test-high population, further evaluation in IFNGS test-low patients is warranted.

Photosensitivity and type I IFN responses in cutaneous lupus are driven by epidermal-derived interferon kappa

OBJECTIVE

Skin inflammation and photosensitivity are common in patients with cutaneous lupus erythematosus (CLE) and systemic lupus erythematosus (SLE), yet little is known about the mechanisms that regulate these traits. Here we investigate the role of interferon kappa (IFN-κ) in regulation of type I interferon (IFN) and photosensitive responses and examine its dysregulation in lupus skin.

METHODS

mRNA expression of type I IFN genes was analysed from microarray data of CLE lesions and healthy control skin. Similar expression in cultured primary keratinocytes, fibroblasts and endothelial cells was analysed via RNA-seq. IFNK knock-out (KO) keratinocytes were generated using CRISPR/Cas9. Keratinocytes stably overexpressing IFN-κ were created via G418 selection of transfected cells. IFN responses were assessed via phosphorylation of STAT1 and STAT2 and qRT-PCR for IFN-regulated genes. Ultraviolet B-mediated apoptosis was analysed via TUNEL staining. In vivo protein expression was assessed via immunofluorescent staining of normal and CLE lesional skin.

RESULTS

IFNK is one of two type I IFNs significantly increased (1.5-fold change, false discovery rate (FDR) q<0.001) in lesional CLE skin. Gene ontology (GO) analysis showed that type I IFN responses were enriched (FDR=6.8×10-04) in keratinocytes not in fibroblast and endothelial cells, and this epithelial-derived IFN-κ is responsible for maintaining baseline type I IFN responses in healthy skin. Increased levels of IFN-κ, such as seen in SLE, amplify and accelerate responsiveness of epithelia to IFN-α and increase keratinocyte sensitivity to UV irradiation. Notably, KO of IFN-κ or inhibition of IFN signalling with baricitinib abrogates UVB-induced apoptosis.

CONCLUSION

Collectively, our data identify IFN-κ as a critical IFN in CLE pathology via promotion of enhanced IFN responses and photosensitivity. IFN-κ is a potential novel target for UVB prophylaxis and CLE-directed therapy.

Human and Murine Evidence for Mechanisms Driving Autoimmune Photosensitivity

Ultraviolet (UV) light is an important environmental trigger for systemic lupus erythematosus (SLE) patients, yet the mechanisms by which UV light impacts disease are not fully known. This review covers evidence in both human and murine systems for the impacts of UV light on DNA damage, apoptosis, autoantigen exposure, cytokine production, inflammatory cell recruitment, and systemic flare induction. In addition, the role of the circadian clock is discussed. Evidence is compared in healthy individuals and SLE patients as well as in wild-type and lupus-prone mice. Further research is needed into the effects of UV light on cutaneous and systemic immune responses to understand how to prevent UV-light mediated lupus flares.

The Role of CXCR3 and Its Chemokine Ligands in Skin Disease and Cancer

Chemokines and their receptors play an important role in the recruitment, activation and differentiation of immune cells. The chemokine receptor, CXCR3, and its ligands, CXCL9, CXCL10, and CXCL11 are key immune chemoattractants during interferon-induced inflammatory responses. Inflammation of the skin resulting from infections or autoimmune disease drives expression of CXCL9/10/11 and the subsequent recruitment of effector, CXCR3⁺ T cells from the circulation. The relative contributions of the different CXCR3 chemokines and the three variant isoforms of CXCR3 (CXCR3A, CXCR3B, CXCR3alt) to the inflammatory process in human skin requires further investigation. In skin cancers, the CXCR3 receptor can play a dual role whereby expression on tumor cells can lead to cancer metastasis to systemic sites while receptor expression on immune cells can frequently promote anti-tumor immune responses. This review will discuss the biology of CXCR3 and its associated ligands with particular emphasis on the skin during inflammation and carcinogenesis.