Current Insights in Cutaneous Lupus Erythematosus Immunopathogenesis

Hepatitis E Virus Infection in Patients with Systemic and Cutaneous Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by a multifactorial etiology in which genetic and environmental factors interplay. An exclusively cutaneous condition has been described and defined as cutaneous lupus erythematosus (CLE). In Italy, a nationwide blood donor survey found an overall HEV prevalence of 8.7%, with an interregional variation from 2.2% to 22.8%. In this study, we aimed to estimate HEV seroprevalence in a cohort of patients affected by SLE and CLE attending the Lupus Clinic, Sapienza University of Rome. Serum samples were tested for anti-HEV immunoglobulin Ig G and M antibodies using commercial enzyme-linked immunosorbent assay (ELISA) kits. Statistical analysis was performed. In total, 138 patients were enrolled, 92 (67%) affected by SLE and 46 by CLE. The prevalence of HEV infection was 23.9% in the CLE group and 7.6% in the SLE group. The anti-HEV+ prevalence was significantly more frequent in CLE. Some mechanisms may be linked to increased susceptibility to HEV such as a molecular mimicry associated with the CLE condition or with the skin compartment/skin self-antigens, as well as the involvement of the genetic background. Regarding the possible risk factors, no association was found, although, of note, the odds of HEV+ relative to contact with animals and to eating raw seafood were strongly higher than the unit in the CLE group.

UBE2N Is Essential for Maintenance of Skin Homeostasis and Suppression of Inflammation

UBE2N, a Lys63 ubiquitin-conjugating enzyme, plays critical roles in embryogenesis and immune system development and function. However, its roles in adult epithelial tissue homeostasis and pathogenesis are unclear. We generated conditional mouse models that deleted Ube2n in skin cells in a temporally and spatially controlled manner. We found that Ube2n knockout in the adult skin keratinocytes induced a range of inflammatory skin defects characteristic of psoriatic and actinic keratosis. These included inflammation, epidermal and dermal thickening, parakeratosis, and increased immune cell infiltration as well as signs of edema and blistering. Single-cell transcriptomic analyses and RT-qPCR showed that Ube2n-knockout keratinocytes expressed elevated myeloid cell chemoattractants such as Cxcl1 and Cxcl2 and decreased the homeostatic T lymphocyte chemoattractant Ccl27a. Consistently, the infiltrating immune cells were predominantly myeloid-derived cells, including neutrophils and M1-like macrophages, which expressed high levels of inflammatory cytokines such as Il1β and Il24. Pharmacological blockade of the IL-1 receptor associated kinases (IRAK1/4) alleviated inflammation, epidermal and dermal thickening, and immune infiltration of the Ube2n-mutant skin. Together, these findings highlight a key role of keratinocyte UBE2N in maintenance of epidermal homeostasis and skin immunity and identify IRAK1/4 as potential therapeutic target for inflammatory skin disorders.

Oral lupus erythematosus: Immunohistochemical evaluation of CD1a, CD21, CD123, and langerin expression in dendritic cells

BACKGROUND

Dendritic cells participate in the pathophysiology of lupus erythematosus (LE), which are studied in systemic and cutaneous forms; however, little is known about their oral manifestations.

METHODS

The expressions of dendritic cell markers (including CD1a, CD21, CD123, and langerin) were investigated by immunohistochemistry technique. Sixty intraoral and lower lip LE lesions, and additional 10 control samples were collected from 2003 to 2019. They were topographically analyzed in the epithelium (EP), lamina propria (LP), epithelial junction (JUN), and deep perivascular (PV) areas.

RESULTS

The expression of CD1a was decreased in the EP (p = 0.003) and increased in the deep PV area (p = 0.002). Langerin immunostaining showed no significant decrease in EP (p = 0.944); however, it increased in LP (p = 0.012) and JUN (p = 0.006). CD21 was expressed in only two specimens (EP, p = 0.012; LP, p < 0.001; deep PV area, p = 0.018). CD123 expression increased in all topographies (EP, p < 0.005; LP, p < 0.001, JUN, p < 0.001; deep PV, p < 0.001). The comparison between vermilion and intraoral mucosa LE lesions suggested that sun-exposed sites showed higher expression of CD123 (EP, p = 0.024; LP, p = 0.047; JUN, p = 0.001).

CONCLUSIONS

CD1a, langerin, and CD123 expressions were detected coincidently surrounding the inflammatory infiltrate in oral LE, suggesting that these cells may play an important role in immune response. Interestingly, plasmacytoid dendritic cells showed increased CD123 expression in sun-exposed site lesions, which point out a possible function in their pathogenesis. Further studies are needed to confirm this hypothesis.

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.

UBE2N is essential for maintenance of skin homeostasis and suppression of inflammation

UBE2N, a Lys63-ubiquitin conjugating enzyme, plays critical roles in embryogenesis and immune system development and function. However, its roles in adult epithelial tissue homeostasis and pathogenesis are unclear. We generated conditional mouse models that deleted Ube2n in skin cells in a temporally and spatially controlled manner. We found that Ube2n-knockout (KO) in the adult skin keratinocytes induced a range of inflammatory skin defects characteristic of psoriatic and actinic keratosis. These included eczematous inflammation, epidermal and dermal thickening, parakeratosis, and increased immune cell infiltration, as well as signs of edema and blistering. Single cell transcriptomic analyses and RT-qPCR showed that Ube2n KO keratinocytes expressed elevated myeloid cell chemo-attractants such as Cxcl1 and Cxcl2 and decreased the homeostatic T lymphocyte chemo-attractant, Ccl27a. Consistently, the infiltrating immune cells of Ube2n-KO skin were predominantly myeloid-derived cells including neutrophils and M1-like macrophages that were highly inflammatory, as indicated by expression of Il1β and Il24. Pharmacological blockade of the IL-1 receptor associated kinases (IRAK1/4) alleviated eczema, epidermal and dermal thickening, and immune infiltration of the Ube2n mutant skin. Together, these findings highlight a key role of keratinocyte-UBE2N in maintenance of epidermal homeostasis and skin immunity and identify IRAK1/4 as potential therapeutic target for inflammatory skin disorders.

Polyautoimmunity in patients with cutaneous lupus erythematosus: A nationwide sex- and age-matched cohort study from Denmark

Background

Polyautoimmunity is defined as having 2 or more autoimmune diseases. Little is known about polyautoimmunity in patients with cutaneous lupus erythematosus (CLE).

Objectives

To estimate prevalence and 5-year incidence of non-lupus erythematosus (LE) autoimmune diseases in patients with CLE.

Methods

Patients with CLE were identified In the Danish National Patient Registry and each patient was age- and sex-matched with 10 general population controls. Outcome information on non-LE autoimmune diseases was obtained by register-linkage between Danish National Patient Registry and the National Prescription Register. The risk ratio (RR) for prevalent non-LE autoimmune disease at time of CLE diagnosis was calculated in modified Poisson regression; and hazard ratios (HRs) for incident non-LE autoimmune disease were estimated in Cox regression analyses.

Results

Overall, 1674 patients with CLE had a higher prevalence of a non-LE autoimmune disease than the comparators (18.5 vs 7.9%; RR 2.4; 95% CI, 2.1 to 2.6). Correspondingly, the cumulative incidence of a non-LE autoimmune disease during 5 years of follow-up was increased for the patients with CLE: HR 3.5 (95% CI, 3.0 to 4.0).

Limitations

Risk of detection and misclassification bias, mainly pertaining to the CLE group.

Conclusion

Patients with CLE had higher prevalence and 5-year cumulative incidence of a non-LE autoimmune disease than the general population.

Cutaneous Toll-like Receptor 9 Pre-Defines Hydroxychloroquine Dosage in Patients with Both Discoid and Subacute Lupus Erythematosus

Background and Objectives: Cutaneous lupus erythematosus (CLE) presents clinically heterogeneous manifestations, partially explained by the different expression of Toll-like receptors (TLRs) type 8 and 9, located to endosomal compartments where they are poised to recognize microbial nucleic acids. This disease is empirically treated with hydroxychloroquine (HCQ), which is hallmarked with a safe and effective profile, but induces a slow and sometimes clinically insufficient therapeutic response. Currently, no biomarkers predictive of response are validated or even proposed in the scientific literature. We aimed to evaluate endosomal TLR type 7, 8 and 9 as predictive biomarkers of HCQ efficacy. Materials and Methods: We conducted a case-control study comparing CLE patients retrospectively assigned to three subgroups based on 3-6-month Cutaneous LE Disease Area and Severity Index (CLASI) reduction upon treatment with HCQ (I = <40% vs. II = 40-80% vs. III = >80%). Before HCQ, lesional skin specimens were collected in untreated CLE and through immunohistochemistry; TLR-7, -8 and -9 expression was evaluated in the epidermis and the lymphocytic infiltrate was evaluated in the dermis. Results: Sixty-six lesional skin biopsies were compared with healthy controls. CLE patients displayed lower epidermal expression of total TLR 8 and 9 as well as infiltrating TLR-8, TLR9 + lymphocytes compared to controls. High HCQ responders differed from low responders for TLR-9 positivity (high vs. low) and for the lymphocytic dermal infiltrate (high vs. low). Conclusions: TLR9 could be envisaged as a possible biomarker to predict HCQ response level and dosage in CLE patients.

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.

Prolidase Deficiency Causes Spontaneous T Cell Activation and Lupus-like Autoimmunity

Prolidase deficiency (PD) is a multisystem disorder caused by mutations in the PEPD gene, which encodes a ubiquitously expressed metallopeptidase essential for the hydrolysis of dipeptides containing C-terminal proline or hydroxyproline. PD typically presents in childhood with developmental delay, skin ulcers, recurrent infections, and, in some patients, autoimmune features that can mimic systemic lupus erythematosus. The basis for the autoimmune association is uncertain, but might be due to self-antigen exposure with tissue damage, or indirectly driven by chronic infection and microbial burden. In this study, we address the question of causation and show that Pepd-null mice have increased antinuclear autoantibodies and raised serum IgA, accompanied by kidney immune complex deposition, consistent with a systemic lupus erythematosus-like disease. These features are associated with an accumulation of CD4 and CD8 effector T cells in the spleen and liver. Pepd deficiency leads to spontaneous T cell activation and proliferation into the effector subset, which is cell intrinsic and independent of Ag receptor specificity or antigenic stimulation. However, an increase in KLRG1+ effector CD8 cells is not observed in mixed chimeras, in which the autoimmune phenotype is also absent. Our findings link autoimmune susceptibility in PD to spontaneous T cell dysfunction, likely to be acting in combination with immune activators that lie outside the hemopoietic system but result from the abnormal metabolism or loss of nonenzymatic prolidase function. This knowledge provides insight into the role of prolidase in the maintenance of self-tolerance and highlights the importance of treatment to control T cell activation.

Cutaneous lupus erythematosus: a review of etiopathogenic, clinical, diagnostic and therapeutic aspects

Cutaneous lupus erythematosus is an autoimmune disease of varied clinical expression, which may present as an exclusively cutaneous disease or be one of the multiple manifestations of systemic lupus erythematosus. Its classification includes acute, subacute, intermittent, chronic and bullous subtypes, which are usually identified based on clinical features and histopathological and laboratory findings. Other non-specific cutaneous manifestations may be associated with systemic lupus erythematosus and are usually related to disease activity. Environmental, genetic and immunological factors play a role in the pathogenesis of skin lesions in lupus erythematosus. Recently, considerable progress has been made in elucidating the mechanisms involved in their development, which allows for foreseeing future targets for more effective treatments. This review proposes to discuss the main etiopathogenic, clinical, diagnostic and therapeutic aspects of cutaneous lupus erythematosus, aiming to update internists and specialists from different areas.

Granzyme B in Autoimmune Skin Disease

Autoimmune diseases often present with cutaneous symptoms that contribute to dysfunction, disfigurement, and in many cases, reduced quality-of-life. Unfortunately, treatment options for many autoimmune skin diseases are limited. Local and systemic corticosteroids remain the current standard-of-care but are associated with significant adverse effects. Hence, there is an unmet need for novel therapies that block molecular drivers of disease in a local and/or targeted manner. Granzyme B (GzmB) is a serine protease with known cytotoxic activity and emerging extracellular functions, including the cleavage of cell-cell junctions, basement membranes, cell receptors, and other structural proteins. While minimal to absent in healthy skin, GzmB is markedly elevated in alopecia areata, interface dermatitis, pemphigoid disease, psoriasis, systemic sclerosis, and vitiligo. This review will discuss the role of GzmB in immunity, blistering, apoptosis, and barrier dysfunction in the context of autoimmune skin disease. GzmB plays a causal role in the development of pemphigoid disease and carries diagnostic and prognostic significance in cutaneous lupus erythematosus, vitiligo, and alopecia areata. Taken together, these data support GzmB as a promising therapeutic target for autoimmune skin diseases impacted by impaired barrier function, inflammation, and/or blistering.

Where Microneedle Meets Biomarkers: Futuristic Application for Diagnosing and Monitoring Localized External Organ Diseases

Extracellular tissue fluids are interesting biomatrices that have recently attracted scientists' interest. Many significant biomarkers for localized external organ diseases have been isolated from this biofluid. In the diagnostic and disease monitoring context, measuring biochemical entities from the fluids surrounding the diseased tissues may give more important clinical value than measuring them at a systemic level. Despite all these facts, pushing tissue fluid-based diagnosis and monitoring forward to clinical settings faces one major problem: its accessibility. Most extracellular tissue fluid, such as interstitial fluid (ISF), is abundant but hard to collect, and the currently available technologies are invasive and expensive. This is where novel microneedle technology can help tackle this significant obstacle. The ability of microneedle technology to minimally invasively access tissue fluid-containing biomarkers will enable ISF and other tissue fluid utilization in the clinical diagnosis and monitoring of localized diseases. This review attempts to present the current pursuit of the application of microneedle systems as a diagnostic and monitoring platform, along with the recent progress of biomarker detection in diagnosing and monitoring localized external organ diseases. Then, the potential use of various microneedles in future clinical diagnostics and monitoring of localized diseases is discussed by presenting the currently studied cases.

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.

Clinical aspects of cutaneous lupus erythematosus

Lupus erythematosus (LE) is an autoimmune inflammatory disease with a wide clinical spectrum from life-threatening multi-organ inflammation in systemic lupus erythematosus (SLE) to limited skin disease in cutaneous LE (CLE). The etiology of CLE is still not fully understood but a multifactorial genesis with genetic predisposition and certain environmental factors as triggers for the development are generally accepted features. Lesions can be induced and aggravated by UV-irradiation and smoking is linked to more severe forms of skin disease and to co-morbidity. Drugs, including many common medicines like antihypertensives, are known to induce subacute CLE (SCLE). The mechanisms involved have recently been shown to be part of the IFN-I pathway and new, specific treatments are currently in clinical trials. CLE is currently classified in subtypes based on clinical presentation and duration into acute CLE (ACLE), SCLE, and chronic CLE (CCLE). Distinct subtypes can be seen in individual patients or coexist within the same patient. Because of the confluent and overlapping picture between these subsets, serology, and histopathology constitute an important role guiding towards correct diagnose and there is ongoing work to update the classification. The Cutaneous Lupus Area Severity Index (CLASI) is a validated tool to measure activity and damage both in clinical trials but also for the clinician to evaluate treatment and follow the course of the disease among patients. CLE is known to have substantial impact on the life of those affected. Several tools have been proposed to measure QoL in these patients, currently Skindex-29 is probably the most used. Patient education is an important part of prevention of flares, including UV-protection and smoking cessation. First-line treatment includes topical corticosteroids as well as topical calcineurin inhibitors with the addition of systemic treatment with antimalarials in more severe or therapy resistant cases. Treatment specifically targeting CLE has been lacking, however novel potential therapies are in later phase clinical trials. In this review we aim to describe the different subsets of the cutaneous form in LE with focus on clinical aspects.

Molecular Characterization of Hepatitis B Virus Infection in a Patient with Cutaneous Lupus Erythematosus

Hepatitis B virus (HBV) infection is a serious global health problem. Patients with autoimmune diseases, such as Lupus Erythematosus, are exposed to a higher risk of acquiring infections. In this study, a molecular characterization, genomic investigation of the Hepatitis B virus, polymerase (P) and surface (S) genes, from a patient affected by Cutaneous Lupus Erythematosus (CLE), was presented. Viral DNA was extracted from 200 μL of serum, and the HBV-DNA was amplified by real-time polymerase chain reaction (PCR) with the Platinum Taq DNA Polymerase. The PCR products were purified and sequencing reactions were performed. A phylogenetic analysis was performed through maximum likelihood and Bayesian approaches. The HBV CLE isolate was classified as sub-genotype D3 and related to other Italian HBV D3 genomes, and some from foreign countries. No drug resistant mutations were identified. One mutation (a.a. 168 M) was located in the last part of the major hydrophilic region (MHR) of the surface antigen (HBsAg). Moreover, three sites (351G, 526Y, 578C) in the polymerase were exclusively present in the CLE patient. The mutations identified exclusively in the HBsAg of our CLE patient may have been selected because of the Lupus autoantibodies, which are characteristic in the Lupus autoimmune disease, using a possible molecular mimicry mechanism.

Modulation of Immune Cells as a Therapy for Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune disorder like systemic lupus erythematosus (SLE). Both SLE and CLE characterize autoantibody secretion and immune cell recruitment. In particular, CLE can be divided into three more frequent types, varying in the severity of the skin lesions they present. The role of type I IFN was shown to be one of the leading causes of the development of this pathology in the skin. Different treatments have been developed and tested against these different variants of CLE to decrease the increasing levels of CLE in humans. In this article, a literature revision discussing the similarities between SLE and CLE is carried out. In addition, new advances in understanding the development of CLE and the leading treatments being evaluated in animal models and clinical trials are reviewed.

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.

Medicinal Plant Extracts and Natural Compounds for the Treatment of Cutaneous Lupus Erythematosus: A Systematic Review

Cutaneous lupus erythematosus (CLE) is a group of autoimmune connective tissue disorders that significantly impact quality of life. Current treatment approaches typically use antimalarial medications, though patients may become recalcitrant. Other treatment options include general immunosuppressants, highlighting the need for more and more targeted treatment options. The purpose of this systematic review was to identify potential compounds that could be repurposed for CLE from natural products since many rheumatologic drugs are derived from natural products, including antimalarials. This study was registered with PROSPERO, the international prospective register of systematic reviews (registration number CRD42021251048). We comprehensively searched Ovid Medline, Cochrane Library, and Scopus databases from inception to April 27th, 2021. These terms included cutaneous lupus erythematosus; general plant, fungus, bacteria terminology; selected plants and plant-derived products; selected antimalarials; and JAK inhibitors. Our search yielded 13,970 studies, of which 1,362 were duplicates. We screened 12,608 abstracts, found 12,043 to be irrelevant, and assessed 565 full-text studies for eligibility. Of these, 506 were excluded, and 59 studies were included in the data extraction. The ROBINS-I risk of bias assessment tool was used to assess studies that met our inclusion criteria. According to our findings, several natural compounds do reduce inflammation in lupus and other autoimmune skin diseases in studies using in vitro methods, mouse models, and clinical observational studies, along with a few randomized clinical trials. Our study has cataloged evidence in support of potential natural compounds and plant extracts that could serve as novel sources of active ingredients for the treatment of CLE. It is imperative that further studies in mice and humans are conducted to validate these findings.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=251048.

Using Gene Expression Analysis to Understand Complex Autoimmune Skin Disease Patients: A Series of Four Canine Cutaneous Lupus Erythematosus Cases

Cutaneous Lupus Erythematosus (CLE) is an autoimmune skin disease that occurs in almost two-thirds of people with Systemic Lupus Erythematosus (SLE) and can exist as its own entity. Despite its negative impact on the quality of life of patients, lupus pathogenesis is not fully understood. In recent years, the role of gene expression analysis has become important in understanding cellular functions and disease causation within and across species. Interestingly, dogs also develop CLE, providing a spontaneous animal model of disease. Here, we present a targeted transcriptomic analysis of skin biopsies from a case series of four dogs with complex autoimmunity with suspected CLE. We identified 92 differentially expressed genes (DEGs), including type 1 interferon, B cell, and T cell-related genes, in the four cases compared to healthy skin margin controls. Additionally, we compared our results with existing CLE datasets from humans and mice and found that humans and canines share 49 DEGs, whereas humans and mice shared only 25 DEGs in our gene set. Immunohistochemistry of IFNG and CXCL10, two of the most highly upregulated inflammatory mediators, confirmed protein-level expression and revealed immune cells as the primary source of CXCL10 in dogs with SLE, whereas keratinocytes stained strongly for CXCL10 in dogs without SLE. We propose that gene expression analysis may aid the diagnosis of complex autoimmune skin diseases and that dogs may provide important insights into CLE and SLE pathogeneses, or more broadly, skin manifestations during systemic autoimmunity.

B Cell Signatures Distinguish Cutaneous Lupus Erythematosus Subtypes and the Presence of Systemic Disease Activity

Cutaneous lupus erythematosus (CLE) is a chronic inflammatory skin disease characterized by a diverse cadre of clinical presentations. CLE commonly occurs in patients with systemic lupus erythematosus (SLE), and CLE can also develop in the absence of systemic disease. Although CLE is a complex and heterogeneous disease, several studies have identified common signaling pathways, including those of type I interferons (IFNs), that play a key role in driving cutaneous inflammation across all CLE subsets. However, discriminating factors that drive different phenotypes of skin lesions remain to be determined. Thus, we sought to understand the skin-associated cellular and transcriptional differences in CLE subsets and how the different types of cutaneous inflammation relate to the presence of systemic lupus disease. In this study, we utilized two distinct cohorts comprising a total of 150 CLE lesional biopsies to compare discoid lupus erythematosus (DLE), subacute cutaneous lupus erythematosus (SCLE), and acute cutaneous lupus erythematosus (ACLE) in patients with and without associated SLE. Using an unbiased approach, we demonstrated a CLE subtype-dependent gradient of B cell enrichment in the skin, with DLE lesions harboring a more dominant skin B cell transcriptional signature and enrichment of B cells on immunostaining compared to ACLE and SCLE. Additionally, we observed a significant increase in B cell signatures in the lesional skin from patients with isolated CLE compared with similar lesions from patients with systemic lupus. This trend was driven primarily by differences in the DLE subgroup. Our work thus shows that skin-associated B cell responses distinguish CLE subtypes in patients with and without associated SLE, suggesting that B cell function in skin may be an important link between cutaneous lupus and systemic disease activity.

Resident Memory T Cells in Autoimmune Skin Diseases

Tissue resident memory T cells (TRM) are a critical component of the immune system, providing the body with an immediate and highly specific response against pathogens re-infecting peripheral tissues. More recently, however, it has been demonstrated that TRM cells also form during autoimmunity. TRM mediated autoimmune diseases are particularly destructive, because unlike foreign antigens, the self-antigens are never cleared, continuously activating self-reactive TRM T cells. In this article, we will focus on how TRMs mediate disease in autoimmune skin conditions, specifically vitiligo, psoriasis, cutaneous lupus erythematosus, alopecia areata and frontal fibrosing alopecia.

Shared inflammatory and skin-specific gene signatures reveal common drivers of discoid lupus erythematosus in canines, humans and mice

Autoimmune skin diseases are complex and are thought to arise from a combination of genetics and environmental exposures, which trigger an ongoing immune response against self-antigens. Companion animals including cats and dogs are known to develop inflammatory skin conditions similar to humans and share the same environment, providing opportunities to study spontaneous disease that encompasses genetic and environmental factors with a One Health approach. A strength of comparative immunology approaches is that immune profiles may be assessed across different species to better identify shared or conserved pathways that might drive inflammation. Here, we performed a comparative study of skin from canine discoid lupus erythematosus (DLE) using NanoString nCounter technology. We compared these gene expression patterns to those of human DLE and a mouse model of cutaneous lupus. We found strong interferon signatures, with CXCL10, ISG15, and an S100 gene family member among the highest, most significant DEGs upregulated across species. Cell type analysis revealed marked T-cell and B-cell infiltration. Interestingly, canine DLE samples also recapitulated downregulated skin homeostatic genes observed in human DLE. We conclude that spontaneous DLE in dogs captures many features that are present in human disease and may serve as a more complete model for conducting further genomic and/or transcriptomic studies.

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Canine DLE lesions express known drivers of pathogenesis including CXCL10, IFNG, FAS.

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Enrichment of key cell types, including T, B, NK cells, is observed in canine DLE.

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Canine, mouse and human DLE share similar proinflammatory profiles.

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Canine DLE exhibits downregulated skin homeostatic and immune regulatory genes.

Lichenoid dermatoses involving the vulva: A clinical-pathologic correlation✰

The lichenoid tissue reaction pattern generally signifies cytotoxic damage to the epithelium. When such reaction pattern occurs on vulvar skin or mucosa, the effects can result in considerable morbidity. None of the entities discussed in this review are entirely unique to the vulva, however, some entities may classically occur at this site, while others tend to be widespread diseases that may incidentally affect vulvar skin and mucosa. Given the complex anatomy of the vulva and the bridging of a site showing both keratinizing squamous epithelium and non-keratinizing squamous mucosa, histopathologic features may display variation in presentation. Although identification of a "lichenoid reaction pattern" alone may provide insight into the disease process, understanding of clinical presentation and specific sites of involvement, along with recognition of the nuanced features of the disease entities can help establish a specific diagnosis. Accurate histopathologic diagnoses by pathologists can improve the ability for treating clinicians to implement timely and effective treatment.