Contribution of In Vivo and Organotypic 3D Models to Understanding the Role of Macrophages and Neutrophils in the Pathogenesis of Psoriasis

Advances in the mechanism of action of short-chain fatty acids in psoriasis

Psoriasis is a prevalent chronic inflammatory and immunological disorder. Its lesions are present as scaly erythema or plaques. Disruptions in the body's immune system play a significant role in developing psoriasis. Recent evidence suggests a potential role of the gut microbiome in autoimmune diseases. Short-chain fatty acids (SCFAs) are the primary metabolites created by gut microbes and play a crucial fuction in autoimmunity. SCFAs act on various cells by mediating signaling to participate in host physiological and pathological processes. These processes encompass body metabolism, maintenance of intestinal barrier function, and immune system modulation. SCFAs can regulate immune cells to enhance the body's immune function, potentially influencing the prevention and treatment of psoriasis. However, the mechanisms underlying the role of SCFAs in psoriasis remain incompletely understood. This paper examines the relationship between SCFAs and psoriasis, elucidating how SCFAs influence the immune system, inflammatory response, and gut barrier in psoriasis. According to the study, in psoriasis, SCFAs have been shown to regulate neutrophils, macrophages, and dendritic cells in the adaptive immune system, as well as T and B cells in the innate immune system. Additionally, we explore the role of SCFAs in psoriasis by maintaining intestinal barrier function, restoring intestinal ecological homeostasis, and investigating the potential therapeutic benefits of SCFAs for psoriasis.

Exploring shared mechanisms between ulcerative colitis and psoriasis and predicting therapeutic natural compounds through bioinformatics and molecular docking

Introduction

Previous studies have suggested a potential correlation between psoriasis (PS) and ulcerative colitis (UC). However, studies exploring the shared mechanisms of both diseases remain limited. Current treatments primarily involve using immunosuppressive drugs, which can lead to potential side effects and drug resistance. Traditional Chinese medicine has demonstrated favorable efficacy in treating UC and PS with fewer side effects. This study aims to elucidate the shared biological mechanisms underlying UC and PS and to predict natural compounds effective for treating both disorders.

Method

We collected and validated differentially expressed genes associated with UC and PS from the Gene Expression Omnibus database. A protein-protein interaction network was constructed using the STRING database, aiding in identifying core targets. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases were utilized to analyze the functions and genomic enrichment of the identified core targets. The CIBERSORT method was employed to assess the correlation of core targets with immune cells. Compounds with potential therapeutic values were selected from the Coremine and TCMSP databases, and their therapeutic efficacy was predicted via molecular docking.

Results

In UC and PS, 20 common core targets were identified, with matrix metalloproteinase 9 (MMP9), matrix metalloproteinase 1 (MMP1), cluster of differentiation 274 (CD274), C-X-C motif chemokine ligand 10 (CXCL10), and topoisomerase II alpha (TOP2A) emerging as the most relevant targets shared between both conditions. Elevated levels of macrophages and dendritic cells were observed in UC and PS, with CXCL10 exhibiting the closest association with macrophages. UC and PS shared common signaling pathways, including IL-17, TNF, and chemokine signaling pathways, among others. Molecular docking revealed that quercetin, baicalen, irisolidone, rutaecarpine, epigallocatechin-3-gallate, and others held potential as natural compounds for treating both disorders.

Conclusion

MMP9, MMP1, and CXCL10, central mediators in the inflammatory pathways of UC and PS, establish a shared mechanism by triggering cytokine and chemokine activation, leading to tissue damage and positioning them as promising therapeutic targets for both conditions. Compounds such as quercetin, luteolin, irisolidone, rutaecarpine, and so on may be key drugs for treating both conditions. These findings suggest the potential advancement of therapeutic strategies and the enhancement of patient care by exploring shared mechanisms and predicting promising natural compounds for treating UC and PS.

Neutrophil extracellular traps promote macrophage inflammation in psoriasis

Psoriasis is a chronic inflammatory skin disease connected with immune dysregulation. Macrophages are key inflammatory cells in psoriasis but the specific mechanism of their activation is not fully understood. Neutrophil extracellular traps (NETs) have been shown to regulate macrophage function. Here, we found that NET deposition was increased in psoriasis lesions. Peptidylarginine deaminase 4 (PAD4, a key enzyme for NET formation) deficiency attenuated skin lesions and inflammation in an imiquimod-induced psoriatic mouse model. Furthermore, the STING signaling pathway was markedly activated in psoriasis and abolished by PAD4 deficiency. PAD4-deficient mice treated with the STING agonist DMXAA exhibited more severe symptoms and inflammation than control mice. Mechanistically, the STING inhibitor C-176 inhibited NET-induced macrophage inflammation and further inhibited the proliferation of HaCaT cells. Our findings suggest an important role of NETs in the pathogenesis of psoriasis, and activation of macrophage STING/NF-κB signaling pathway might involve in NETs related psoriasis.

RNA-binding proteins potentially regulate alternative splicing of immune/inflammatory-associated genes during the progression of generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a rare but severe form of psoriasis. However, the pathogenesis of GPP has not been fully elucidated. Although RNA-binding proteins (RBPs) and the alternative splicing (AS) process are essential for regulating post-transcriptional gene expression, their roles in GPP are still unclear. We aimed to elucidate the regulatory mechanisms to identify potential new therapeutic targets. Here, We analyzed an RNA sequencing (RNA-seq) dataset (GSE200977) of peripheral blood mononuclear cells (PBMCs) of 24 patients with GPP, psoriasis vulgaris (PV), and healthy controls (HCs) from the Gene Expression Omnibus (GEO) database. We found that the abnormal alternative splicing (AS) events associated with GPP were mainly "alt3p/alt5p", and 15 AS genes were differentially expressed. Notably, the proportions of different immune cell types were correlated with the expression levels of regulatory alternatively spliced genes (RASGs): significant differences were observed in expression levels of DTD2, NDUFAF3, NBPF15, and FBLN7 in B cells and ARFIP1, IPO11, and RP11-326L24.9 in neutrophils in the GPP samples. Furthermore, We identified 32 differentially expressed RNA-binding proteins (RBPs) (18 up-regulated and 14 down-regulated). Co-expression networks between 14 pairs of differentially expressed RBPs and RASGs were subsequently constructed, demonstrating that these differentially expressed RBPs may affect the progression of GPP by regulating the AS of downstream immune/inflammatory-related genes such as LINC00989, ENC1 and MMP25-AS1. Our results were innovative in revealing the involvement of inflammation-related RBPs and RASGs in the development of GPP from the perspective of RBP-regulated AS.

Cornuside alleviates psoriasis-like skin lesions in mice by relieving inflammatory effects

Psoriasis is a chronic inflammatory skin disease substantially affecting the quality of life, with no complete cure owing to its complex pathogenesis. Cornuside, a major bioactive compound present in Cornus officinalis Sieb. et Zucc., which is a well-known traditional Chinese medicine with a variety of biological and pharmacological activities, such as anti-apoptotic, antioxidant, and anti-inflammatory properties. However, its effects on psoriasis remain unclear. Our preliminary analysis of network pharmacology showed that cornuside may be involved in psoriasis by regulating the inflammatory response and IL-17 signaling pathway. Thus, we investigated the protective role and mechanism of cornuside in the pathogenesis of psoriasis in an imiquimod (IMQ)-induced psoriasis mouse model. In-vivo experiments demonstrated that cornuside-treated mice had reduced skin erythema, scales, thickness, and inflammatory infiltration. The Psoriasis Area Severity Index score was significantly lower than that of the IMQ group. Flow cytometry analysis indicated that cornuside effectively inhibited Th1- and Th17-cell infiltration and promoted aggregation of Th2 cells in skin tissues. Cornuside also inhibited the infiltration of macrophages to the skin. Furthermore, in-vitro experiments indicated that cornuside also decreased the polarization of M1 macrophages and reduced the levels of associated cytokines. Western blotting demonstrated that cornuside suppressed the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular receptor kinase (ERK) in bone marrow-derived macrophages. Our findings indicate that cornuside has a protective effect against IMQ-induced psoriasis by inhibiting M1 macrophage polarization through the ERK and JNK signaling pathways and modulating the infiltration of immune cells as well as the expression of inflammatory factors.

Integrated bioinformatics combined with machine learning to analyze shared biomarkers and pathways in psoriasis and cervical squamous cell carcinoma

Background

Psoriasis extends beyond its dermatological inflammatory manifestations, encompassing systemic inflammation. Existing studies have indicated a potential risk of cervical cancer among patients with psoriasis, suggesting a potential mechanism of co-morbidity. This study aims to explore the key genes, pathways, and immune cells that may link psoriasis and cervical squamous cell carcinoma (CESC).

Methods

The cervical squamous cell carcinoma dataset (GSE63514) was downloaded from the Gene Expression Omnibus (GEO). Two psoriasis-related datasets (GSE13355 and GSE14905) were merged into one comprehensive dataset after removing batch effects. Differentially expressed genes were identified using Limma and co-expression network analysis (WGCNA), and machine learning random forest algorithm (RF) was used to screen the hub genes. We analyzed relevant gene enrichment pathways using GO and KEGG, and immune cell infiltration in psoriasis and CESC samples using CIBERSORT. The miRNA-mRNA and TFs-mRNA regulatory networks were then constructed using Cytoscape, and the biomarkers for psoriasis and CESC were determined. Potential drug targets were obtained from the cMAP database, and biomarker expression levels in hela and psoriatic cell models were quantified by RT-qPCR.

Results

In this study, we identified 27 key genes associated with psoriasis and cervical squamous cell carcinoma. NCAPH, UHRF1, CDCA2, CENPN and MELK were identified as hub genes using the Random Forest machine learning algorithm. Chromosome mitotic region segregation, nucleotide binding and DNA methylation are the major enrichment pathways for common DEGs in the mitotic cell cycle. Then we analyzed immune cell infiltration in psoriasis and cervical squamous cell carcinoma samples using CIBERSORT. Meanwhile, we used the cMAP database to identify ten small molecule compounds that interact with the central gene as drug candidates for treatment. By analyzing miRNA-mRNA and TFs-mRNA regulatory networks, we identified three miRNAs and nine transcription factors closely associated with five key genes and validated their expression in external validation datasets and clinical samples. Finally, we examined the diagnostic effects with ROC curves, and performed experimental validation in hela and psoriatic cell models.

Conclusions

We identified five biomarkers, NCAPH, UHRF1, CDCA2, CENPN, and MELK, which may play important roles in the common pathogenesis of psoriasis and cervical squamous cell carcinoma, furthermore predict potential therapeutic agents. These findings open up new perspectives for the diagnosis and treatment of psoriasis and squamous cell carcinoma of the cervix.

Adenosine and Its Receptors in the Pathogenesis and Treatment of Inflammatory Skin Diseases

Inflammatory skin diseases highlight inflammation as a central driver of skin pathologies, involving a multiplicity of mediators and cell types, including immune and non-immune cells. Adenosine, a ubiquitous endogenous immune modulator, generated from adenosine triphosphate (ATP), acts via four G protein-coupled receptors (A1, A2A, A2B, and A3). Given the widespread expression of those receptors and their regulatory effects on multiple immune signaling pathways, targeting adenosine receptors emerges as a compelling strategy for anti-inflammatory intervention. Animal models of psoriasis, contact hypersensitivity (CHS), and other dermatitis have elucidated the involvement of adenosine receptors in the pathogenesis of these conditions. Targeting adenosine receptors is effective in attenuating inflammation and remodeling the epidermal structure, potentially showing synergistic effects with fewer adverse effects when combined with conventional therapies. What is noteworthy are the promising outcomes observed with A2A agonists in animal models and ongoing clinical trials investigating A3 agonists, underscoring a potential therapeutic approach for the management of inflammatory skin disorders.

Macrophage Functions in Psoriasis: Lessons from Mouse Models

Psoriasis is a systemic autoimmune/autoinflammatory disease that can be well studied in established mouse models. Skin-resident macrophages are classified into epidermal Langerhans cells and dermal macrophages and are involved in innate immunity, orchestration of adaptive immunity, and maintenance of tissue homeostasis due to their ability to constantly shift their phenotype and adapt to the current microenvironment. Consequently, both macrophage populations play dual roles in psoriasis. In some circumstances, pro-inflammatory activated macrophages and Langerhans cells trigger psoriatic inflammation, while in other cases their anti-inflammatory stimulation results in amelioration of the disease. These features make macrophages interesting candidates for modern therapeutic strategies. Owing to the significant progress in knowledge, our review article summarizes current achievements and indicates future research directions to better understand the function of macrophages in psoriasis.

Single-cell and bulk RNAseq unveils the immune infiltration landscape and targeted therapeutic biomarkers of psoriasis

Background

Psoriasis represents a multifaceted and debilitating immune-mediated systemic ailment afflicting millions globally. Despite the continuous discovery of biomarkers associated with psoriasis, identifying lysosomal biomarkers, pivotal as cellular metabolic hubs, remains elusive.

Methods

We employed a combination of differential expression analysis and weighted gene co-expression network analysis (WGCNA) to initially identify lysosomal genes. Subsequently, to mitigate overfitting and eliminate collinear genes, we applied 12 machine learning algorithms to screen robust lysosomal genes. These genes underwent further refinement through random forest (RF) and Lasso algorithms to ascertain the final hub lysosomal genes. To assess their predictive efficacy, we conducted receiver operating characteristic (ROC) analysis and verified the expression of diagnostic biomarkers at both bulk and single-cell levels. Furthermore, we utilized single-sample gene set enrichment analysis (ssGSEA), CIBERSORT, and Pearson's correlation analysis to elucidate the association between immune phenotypes and hub lysosomal genes in psoriatic samples. Finally, employing the Cellchat algorithm, we explored potential mechanisms underlying the participation of these hub lysosomal genes in cell-cell communication.

Results

Functional enrichment analyses revealed a close association between psoriasis and lysosomal functions. Subsequent intersection analysis identified 19 key lysosomal genes, derived from DEGs, phenotypic genes of WGCNA, and lysosomal gene sets. Following the exclusion of collinear genes, we identified 11 robust genes, further refined through RF and Lasso, yielding 3 hub lysosomal genes (S100A7, SERPINB13, and PLBD1) closely linked to disease occurrence, with high predictive capability for disease diagnosis. Concurrently, we validated their relative expression in separate bulk datasets and single-cell datasets. A nomogram based on these hub genes may offer clinical advantages for patients. Notably, these three hub genes facilitated patient classification into two subtypes, namely metabolic-immune subtype 1 and signaling subtype 2. CMap analysis suggested butein and arachidonic fasudil as preferred treatment agents for subtype 1 and subtype 2, respectively. Finally, through Cellchat and correlation analysis, we identified PRSS3-F2R as potentially promoting the expression of hub genes in the psoriasis group, thereby enhancing keratinocyte-fibroblast interaction, ultimately driving psoriasis occurrence and progression.

Conclusion

Our study identifies S100A7, SERPINB13, and PLBD1 as potential diagnostic biomarkers, offering promising prospects for more precisely tailored psoriatic immunotherapy designs.

SPRR1B is Related to the Immune Microenvironment and Can Be Used as a Biomarker for the Diagnosis of Psoriasis

Background

Psoriasis, a chronic inflammatory disorder with an unknown cause, significantly impacts the physical and psychological well-being of patients. However, current biomarkers related to psoriasis lack clinical specificity, sensitivity, and predictive ability.

Methods

In this study, we collected skin lesion tissues from 20 psoriasis patients and 20 normal skin samples. Additionally, we obtained four datasets from the GEO database, which included human psoriasis and healthy specimens. We utilized SVM-RFE analysis and the LASSO regression model to identify potential biomarkers. Furthermore, we examined the composition of immune cell types in psoriasis and their correlation with specific genes.

Results

Our investigation revealed 57 differentially expressed genes (DEGs), and we identified significantly enriched pathways through KEGG pathway analysis. The results of machine learning and WGCNA suggested that LCE3D and SPRR1B could potentially be used as marker genes for diagnosing psoriasis. RT-PCR and immunohistochemical detection confirmed the abnormally high expression of the SPRR1B gene in psoriasis. Analysis of immune cell infiltration revealed a strong positive correlation between SPRR1B and Macrophages M0 and T cells follicular helper, while showing the strongest negative correlation with resting Mast cells. In addition, we found that silencing SPRR1B in IFN-γ-treated HaCat cells could significantly reduce the increase in IL-17, IL-22, KRT6, and KRT16 caused by IFN-γ.

Conclusion

These findings suggest that SPRR1B may have a significant role in the pathogenesis of psoriasis and could be employed as a novel immunomarker for its development.

Histological and functional characterization of 3D human skin models mimicking the inflammatory skin diseases psoriasis and atopic dermatitis

Three-dimensional (3D) human skin equivalents have emerged as valuable tools in skin research, replacing animal experimentation and precluding the need for patient biopsies. In this study, we advanced 3D skin equivalents to model the inflammatory skin diseases atopic dermatitis and psoriasis by cytokine stimulation, and were successful in integrating TH1 T cells into skin models to develop an immunocompetent 3D psoriasis model. We performed in-depth histological and functional characterization of 3D skin equivalents and validated them in terms of tissue architecture, pathological changes, expression of antimicrobial peptides and Staphylococcus aureus colonization using 3D reconstruction by multiphoton microscopy and phenotyping by highly multiplexed 'co-detection by indexing' (CODEX) microscopy. We show that our skin equivalents have a structural architecture with a well-developed dermis and epidermis, thus resembling human skin. In addition, the skin models of atopic dermatitis and psoriasis show several phenotypic features of inflammatory skin disease, including disturbed epidermal differentiation and alterations in the expression of epidermal barrier genes and antimicrobial peptides, and can be reliably used to test novel treatment strategies. Therefore, these 3D equivalents will be a valuable tool in experimental dermatological research.

Importance of PLD2 in an IL-23 driven psoriasiform dermatitis model and potential link to human psoriasis

Phospholipase D2 (PLD2), a major isoform of the PLD family, has been reported to regulate inflammatory responses. Thus far, the relevance of PLD2 in psoriasis, an inflammatory skin disease, has not been explored. In the current study, we examined PLD2 expression in the skin of psoriasis patients and the role of PLD2 in an interleukin (IL)-23-induced mouse model of psoriasiform dermatitis. Both in situ hybridization and bulk RNA sequencing showed PLD2 gene expression is significantly higher in lesional relative to non-lesional skin of psoriasis patients or the skin of healthy subjects. PLD2 expression is also enriched in residual lesions from patients on biologic therapies. Murine in vivo studies showed that PLD2 deficiency significantly reduced psoriasiform inflammation in IL-23-injected ears, as reflected by decreases in ear thickness, expression of defensin beta 4A and the S100 calcium binding protein A7A, macrophage infiltrate, and expression of CXCL10 and IL-6. However, the expression of type 17 cytokines, IL-17A and IL-17F, were not reduced. Dual knockout of PLD1 and PLD2 offered little additional protection compared to PLD2 knockout alone in the IL-23 model. In addition, pharmacological inhibition with a pan-PLD1/PLD2 inhibitor also suppressed IL-23-induced psoriasiform dermatitis. Bone-marrow-derived macrophages from wild type (WT) and PLD2 knockout (KO) mice exhibited little difference in viability and sensitivity to lipopolysaccharide and/or interferon gamma, or resiquimod (R848). PLD2 deficiency did not alter the differentiation and function of Th17 cells in an ex vivo study with splenocytes isolated from WT and PLD2 KO mice. Overall, these data suggest that PLD2 may play a role in the pathophysiology of psoriasis. Reducing macrophage infiltrate and cytokine/chemokine production might contribute to an anti-inflammatory effect observed in PLD2 knockout mice. Further studies are required to better understand the mechanisms by which PLD2 contributes to skin lesions in psoriasis patients and psoriasiform dermatitis models.

Cellular Mechanisms of Psoriasis Pathogenesis: A Systemic Review

Psoriasis is a common inflammatory skin disease characterized by abnormal proliferation of epidermal keratinocytes and massive infiltration of inflammatory cells. Many kinds of cells, including keratinocytes, T lymphocytes, dendritic cells, neutrophils, and macrophages, are reported to play critical roles in the pathogenesis and progression of psoriasis. However, to date, the role of each kind of cell in the pathogenesis and development of psoriasis has not been systematically reviewed. In addition, although antibodies developed targeting cytokines (e.g. IL-23, IL-17A, and TNF-α) released by these cells have shown promising results in the treatment of psoriasis patients, these targeted antibodies still do not cure psoriasis and only provide short-term relief of symptoms. Furthermore, long-term use of these antibodies has been reported to have adverse physical and psychological effects on psoriasis patients. Therefore, gaining a deeper understanding of the cellular and molecular pathogenesis of psoriasis and providing new thoughts on the development of psoriasis therapeutic drugs is of great necessity. In this review, we summarize the roles of various cells involved in psoriasis, aiming to provide new insights into the pathogenesis and development of psoriasis at the cellular level and hoping to provide new ideas for exploring new and effective psoriasis treatments.

The Role of Inflammation in the Pathogenesis of Psoriasis

"Psoriasis is a chronic inflammatory skin condition with genetic determinism characterized by the presence of welldefined, erythematous plaques, covered by white, pearly, stratified scales, located on the extension areas, the skin of the scalp, intertriginous regions. The origin of psoriasis is multifactorial, involving hereditary and environmental pathogenic mechanisms. It is triggered by various risk factors involving a variety of processes, such as inflammation, antigen presentation, cell signaling, and transcriptional regulation. "

The SELP, CD93, IL2RG, and VAV1 Genes Associated with Atherosclerosis May Be Potential Diagnostic Biomarkers for Psoriasis

Purpose

Psoriasis and atherosclerosis are immunometabolic diseases. This study aimed to integrate bioinformatics and updated public resources to find potential biological markers associated with atherosclerosis that can cause psoriasis.

Patients and Methods

Microarray datasets were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were screened, and functional enrichment analysis was performed. We identified psoriasis and atherosclerosis common immune-related genes (PA-IRGs) by overlapping immune-related genes (IRGs) with genes in the module most associated with psoriasis and atherosclerosis obtained by weighted gene co-expression network analysis (WGCNAs). Receiver operating characteristic (ROC) was conducted to evaluate the predictive ability. The skin expression levels of diagnostic biomarkers were further verified by immunohistochemical staining. CIBERSORT, single-sample gene set enrichment analysis (ssGSEA), and Pearson's correlation analysis were applied to evaluate immune and lipid metabolism relationships in psoriatic tissues. In addition, a lincRNA-miRNA-mRNA network was constructed to find the pathogenesis in which diagnostic markers may be involved.

Results

Four PA-IRGs (SELP, CD93, IL2RG, and VAV1) demonstrated the optimal diagnostic value, with an AUC above 0.8. The immune cell infiltration analysis showed that dendritic resting cells, NK cell activation, neutrophils, macrophages M2, macrophages M0, and B-cell memory were highly abundant in psoriasis. Immune response analysis showed that TNF family members, chemokine receptors, interferons, natural killer cells, and TGF-β family members might be involved in psoriasis. Diagnostic biomarkers are strongly associated with various infiltrating immune cells, immune responses, and lipid metabolism. A lincRNA-miRNA-mRNA regulatory network consisting of 31 lincRNAs and 23 miRNAs was constructed. LINC00662 is involved in modulating four diagnostic biomarkers.

Conclusion

This study identified atherosclerosis-related genes SELP, CD93, VAV1, and IL2RG as potential psoriasis diagnostic markers. Provide novel insights into the possible regulatory mechanisms involved in psoriasis.

Looking beyond the Skin: Pathophysiology of Cardiovascular Comorbidity in Psoriasis and the Protective Role of Biologics

Psoriasis is a chronic systemic inflammatory disease associated with a higher incidence of cardiovascular disease, especially in patients with moderate to severe psoriasis. It has been estimated that severe psoriasis confers a 25% increase in relative risk of cardiovascular disease, regardless of traditional risk factors. Although the underlying pathogenic mechanisms relating psoriasis to increased cardiovascular risk are not clear, atherosclerosis is emerging as a possible link between skin and vascular affection. The hypothesis that the inflammatory cascade activated in psoriasis contributes to the atherosclerotic process provides the underlying basis to suggest that an anti-inflammatory therapy that improved atherosclerosis would also reduce the risk of MACEs. In this sense, the introduction of biological drugs which specifically target cytokines implicated in the inflammatory cascade have increased the expectations of control over the cardiovascular comorbidity present in psoriasis patients, however, their role in vascular damage processes remains controversial. The aim of this paper is to review the mechanistic link between psoriasis and cardiovascular disease development, as well as analyzing which of the biological treatments could also reduce the cardiovascular risk in these patients, fueling a growing debate on the modification of the general algorithm of treatment.

Dendritic Cells and Macrophages in the Pathogenesis of Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by scaly indurated erythema. This disease impairs patients’ quality of life enormously. Pathological findings demonstrate proliferation and abnormal differentiation of keratinocytes and massive infiltration of inflammatory immune cells. The pathogenesis of psoriasis is complicated. Among immune cells, dendritic cells play a pivotal role in the development of psoriasis in both the initiation and the maintenance phases. In addition, it has been indicated that macrophages contribute to the pathogenesis of psoriasis especially in the initiation phase, although studies on macrophages are limited. In this article, we review the roles of dendritic cells and macrophages in the pathogenesis of psoriasis.

Current Concepts of Psoriasis Immunopathogenesis

Psoriasis is a recurrent, chronic, immune-mediated, systemic inflammatory disease of the skin, joints, and other organic systems. After atopic dermatitis, chronic stationary psoriasis is the most common inflammatory skin disease, affecting an average of 2-4% of the world's population. The disease carries a significant burden due to its numerous comorbidities and the major impact on patients' social and emotional aspects of life. According to current knowledge, psoriasis is a multifactorial disease that occurs in genetically predisposed individuals under various environmental factors, which trigger an immune response disorder with a series of complex inflammatory cascades. The disease is initiated and maintained by mutual interaction of the innate and adaptive immune cells, primarily dendritic cells, T lymphocytes, and keratinocytes, whose leading role alternates at different stages of the disease, consisting mainly in the IL-23/Th17 pathway. Inflammatory events result in consequent epidermal and dermal changes and evolution of the characteristic psoriatic phenotype, respectively. This paper aims to present a comprehensive overview of current knowledge on psoriasis genetic and environmental etiological factors, immunopathogenesis, and the leading cellular and cytokine participants in the inflammatory pathways of this disease.

IFN-γ Drives Human Monocyte Differentiation into Highly Proinflammatory Macrophages That Resemble a Phenotype Relevant to Psoriasis

As key cells of the immune system, macrophages coordinate the activation and regulation of the immune response. Macrophages present a complex phenotype that can vary from homeostatic, proinflammatory, and profibrotic to anti-inflammatory phenotypes. The factors that drive the differentiation from monocyte to macrophage largely define the resultant phenotype, as has been shown by the differences found in M-CSF- and GM-CSF-derived macrophages. We explored alternative inflammatory mediators that could be used for in vitro differentiation of human monocytes into macrophages. IFN-γ is a potent inflammatory mediator produced by lymphocytes in disease and infections. We used IFN-γ to differentiate human monocytes into macrophages and characterized the cells at a functional and proteomic level. IFN-γ alone was sufficient to generate macrophages (IFN-γ Mϕ) that were phagocytic and responsive to polarization. We demonstrate that IFN-γ Mϕ are potent activators of T lymphocytes that produce IL-17 and IFN-γ. We identified potential markers (GBP-1, IP-10, IL-12p70, and IL-23) of IFN-γ Mϕ and demonstrate that these markers are enriched in the skin of patients with inflamed psoriasis. Collectively, we show that IFN-γ can drive human monocyte to macrophage differentiation, leading to bona fide macrophages with inflammatory characteristics.

Artemisinin ameliorates intestinal inflammation by skewing macrophages to the M2 phenotype and inhibiting epithelial-mesenchymal transition

BACKGROUND

Inflammatory bowel disease (IBD) is a self-destructive intestinal disease whose etiology is unclear but complex and the effective treatment is deficient. Increasing evidences have indicated that immune dysfunction and epithelial-mesenchymal transition (EMT)-related intestinal mucosal barrier impaired hold critical position in the pathogenesis of IBD. Artemisinin (ART) is a sesquiterpenoid compound extracted from Chinese herbal medicine which has good immunomodulatory effects. Studies have shown that artemisinin and its analogues have therapeutic effects on a variety of tumors and immune-related disorders. The purpose of current study was to research the effect and mechanism about artemisinin-induced macrophage polarization to M2 phenotype and inhibiting the process of EMT.

METHODS

In vitro, the anti-inflammatory effect of artemisinin is mainly verified by RAW264.7 cells and tissue (colon tissue and PBMC) from CD patients with active intestinal inflammation. RAW264.7 cells stimulated with LPS to induce inflammatory state and ART were used as therapeutic treatment in different concentration. Then the expression levels of pro-inflammatory factors, macrophage polarization and ERK pathway were analyzed. Colon tissue and PBMC from CD patients were treated with ART in different concentrations and macrophage polarization, pro-inflammatory factors expression, EMT-related protein were analyzed. In vivo, DSS-induced colitis mice were treated by ART for seven days. The DAI score was calculated and the colons and spleens were harvested after the animals were sacrificed. The expression of macrophage markers and EMT-related markers in the intestines of mice in each group were monitored by qPCR and western blot.

RESULT

ART treatment could decrease the levels of pro-inflammatory coefficient expressed in theRAW264.7 cells and human PBMC. Moreover, ART could ameliorate the intestinal inflammation in vivo through down-regulating the expression of pro-inflammatory factors, promoting macrophage polarization to M2 phenotype and inhibiting the process of EMT.

CONCLUSION

Taken together, our findings demonstrated that artemisinin might ameliorate inflammation by inducing macrophage polarization to M2 phenotype and inhibiting the process of EMT, suggesting that ART may be applied to the rehabilitation of IBD in the future.

Role of Neutrophils in Psoriasis

Psoriasis is a common inflammatory disease that can involve the skin, joints, or both. The abnormalities of innate immunity play crucial roles in the pathogenesis of psoriasis. Neutrophils are the most abundant leukocytes in the circulation. Emerging evidences have demonstrated that neutrophils may play a role in autoimmune diseases. The neutrophil-to-lymphocyte ratio (NLR), the activity of neutrophils, and the number of NETotic cells were significantly higher in psoriasis patients compared to healthy controls. The number of low-density granulocytes (LDGs) in the blood of psoriasis patients was significantly higher than those in the control blood. Furthermore, neutrophils may play important roles in the cardiovascular risk in psoriasis. However, the exact role of neutrophils in psoriasis remains unclear. In this review, we highlight the role of neutrophils in the pathogenesis of psoriasis.

Current Developments in the Immunology of Psoriasis

Psoriasis is a frequent inflammatory skin disease. Fundamental research on the pathogenesis of psoriasis has substantially increased our understanding of skin immunology, which has helped to introduce innovative and highly effective therapies. Psoriasis is a largely T lymphocyte-mediated disease in which activation of innate immune cells and pathogenic T cells result in skin inflammation and hyperproliferation of keratinocytes. B cells have thus far largely been neglected regarding their role for the pathogenesis of psoriasis. However, recent data shed light on their role in inflammatory skin diseases. Interestingly, interleukin (IL)-10-producing regulatory B cells have been assumed to ameliorate psoriasis. In this review, we will discuss the development of disease, pathogenicity, and current developments in therapeutic options. We describe different roles of T cells, B cells, and cytokines for the immunopathology and disease course of psoriasis.

CD200-CD200R1 signalling attenuates imiquimod-induced psoriatic inflammation by inhibiting the activation of skin inflammatory macrophages

Psoriasis is an autoimmune skin disease caused by interactions between keratinocytes and immune cells, such as macrophages. CD200 is expressed on the surface of various cell types, and its receptor, CD200R1, belongs to a family of immunosuppressive receptors that are mainly expressed on myeloid cells. CD200/CD200R1 signalling is associated with the prevention of autoimmune diseases; however, the role of CD200/CD200R1 signalling in the pathogenesis of psoriasis remains unknown. In this study, we detected in vivo effect of the CD200 protein on psoriasis and in vitro effects of CD200 on macrophages and keratinocytes co-cultured with macrophages were also evaluated. Our data showed that the expression of CD200 and CD200R1 was decreased and the expression of macrophage-related pro-inflammatory factors (IL-6, IL-1β, TNF-α) was increased in IMQ-induced psoriasis-like skin of mice. After subcutaneous injection of CD200, the symptoms were alleviated, local expression of CD200R1 was markedly induced, infiltrated CD68⁺ cells were significantly reduced and the expression levels of IL-6, IL-1β, and TNF-α were strongly downregulated. In in vitro experiments, CD200 suppressed the migration of macrophages, induced CD200R1 expression on the surface of macrophages, and decreased the levels of pro-inflammatory factors. Western blot (WB) data showed that the CD200-CD200R1 reaction controlled the activation of inflammatory macrophages by inhibiting the NF-κB signalling pathway. These results demonstrate that CD200-CD200R1 signalling can reduce IMQ-induced psoriasis-like skin inflammation by inhibiting the activation of macrophages.

Inhibition of NLRP3 inflammasome-mediated pyroptosis in macrophage by cycloastragenol contributes to amelioration of imiquimod-induced psoriasis-like skin inflammation in mice

Psoriasis is a common chronic inflammatory skin disease, and the infiltrated macrophages in psoriatic skin lesions play a key role in the progression of this uncontrolled cutaneous inflammation. However, the current therapeutic strategies for patients with psoriasis are not satisfactory. Here, we report that cycloastragenol (CAG), a natural active small compound isolated from Astragalus membranaceus, significantly ameliorated imiquimod (IMQ)-induced psoriasiform dermatitis in mice by targeting proinflammatory macrophages. CAG significantly reduced the clinical scores, decreased the epidermal thickness, and ameliorated the deteriorating histopathology observed in IMQ-induced mice. CAG treatment specifically reduced the dermal infiltration of macrophages, rather than of dendritic cells, neutrophils, or T lymphocytes, into psoriatic skin. CAG dose-dependently decreased the level of proinflammatory cytokines, including IL-1β, TNF-α and IL-6, in murine psoriatic skin and serum, as well as in IMQ-stimulated, bone-marrow-derived macrophages. When compared to the control group, CAG significantly decreased IMQ-triggered NLRP3 inflammasome activation and gasdermin D-mediated cell pyroptosis in these proinflammatory macrophages. CAG also suppressed the assembly of the NLRP3 inflammasome complex. Taken together, the results show that CAG selectively modulates macrophage function by inhibiting NLRP3 inflammasome-mediated pyroptosis to ameliorate IMQ-induced psoriasis-like skin inflammation in mice. Our findings also identify an effective drug candidate for the treatment of psoriasis.

Transient receptor potential ankyrin 1 (TRPA1) positively regulates imiquimod-induced, psoriasiform dermal inflammation in mice

Transient receptor potential ankyrin 1 (TRPA1), a membrane protein ion channel, is known to mediate itch and pain in skin. The function of TRPA1, however, in psoriasiform dermatitis (PsD) is uncertain. Herein, we found that expression of TRPA1 is highly up-regulated in human psoriatic lesional skin. To study the role of TRPA1 in PsD, we assessed Psoriasis Severity Index (PSI) scores, transepidermal water loss (TEWL), skin thickness and pathology, and examined dermal inflammatory infiltrates, Th17-related genes and itch-related genes in c57BL/6 as wild-type (WT) and TRPA1 gene knockout (KO) mice following daily application of topical IMQ cream for 5 days. Compared with WT mice, clinical scores, skin thickness change and TEWL scores were similar on day 3, but were significantly decreased on day 5 in IMQ-treated TRPA1 KO mice (vs WT mice), suggesting reduced inflammation and skin barrier defects. Additionally, the relative area of epidermal Munro's microabscesses and mRNA levels of neutrophil inducible chemokines (S100A8, S100A9 and CXCL1) were decreased in the treated skin of TRPA1 KO mice, suggesting that neutrophil recruitment was impaired in the KO mice. Furthermore, mast cells, CD31⁺ blood vascular cells, CD45⁺ leukocytes and CD3⁺ T cells were all reduced in the treated skin of TRPA1 KO mice. Lastly, mRNA expression levels of IL-1β, IL-6, IL-23, IL-17A, IL-17F and IL-22 were decreased in TRPA1 KO mice. In summary, these results suggest a key role for TRPA1 in psoriasiform inflammation and raising its potential as a target for therapeutic intervention.

Transcription Factor Retinoid-Related Orphan Receptor γt: A Promising Target for the Treatment of Psoriasis

Psoriasis, which is a common chronic inflammatory skin disease, endangers human health and brings about a major economic burden worldwide. To date, treatments for psoriasis remain unsatisfied because of their clinical limitations and various side effects. Thus, developing a safer and more effective therapy for psoriasis is compelling. Previous studies have explicitly shown that psoriasis is an autoimmune disease that is predominantly mediated by T helper 17 (Th17) cells, which express high levels of interleukin-17 (IL-17) in response to interleukin-23 (IL-23). The discovery of the IL-23–Th17–IL-17 axis in the development of psoriasis has led to the paradigm shift of understanding pathogenesis of psoriasis. Although anti-IL-17 antibodies show marked clinical efficacy in treating psoriasis, compared with antibodies targeting IL-17A or IL-17R alone, targeting Th17 cells themselves may have a maximal benefit by affecting multiple proinflammatory cytokines, including IL-17A, IL-17F, IL-22, and granulocyte-macrophage colony-stimulating factor, which likely act synergistically to drive skin inflammation in psoriasis. In this review, we mainly focus on the critical role of Th17 cells in the pathogenesis of psoriasis. Especially, we explore the small molecules that target retinoid-related orphan receptor γt (RORγt), a vital transcription factor for Th17 cells. Given that RORγt is the lineage-defining transcription factor for Th17 cell differentiation, targeting RORγt via small molecular inverse agonists may be a promising strategy for the treatment of Th17-mediated psoriasis.

MiR-876-5p suppresses cell proliferation by targeting Angiopoietin-1 in the psoriasis

Psoriasis is an autoimmune disease characterized by abnormal differentiation and hyper-proliferation of epidermal keratinocytes. The object of the study is to investigate the role of miRNA-876-5p in psoriasis. It reported that MicroRNAs (miRNAs) played roles in the malignant progression in psoriasis development. The expression of miR-876-5p was found to be down-regulated in psoriasic tissue and blood of patients. The luciferase assay verified the targeting role of miR-876-5p to 3'UTR of Angiopoietin-1 (Ang-1). Proliferation of psoriasic cells were inhibited by miR-876-5p and hold on G0/G1 phase. Further studies showed that miR-876-5p suppressed proliferation by restraining the expression of Ang-1, which would regulate the phosphorylation level of PI3K, AKT, mTOR and ERK in psoriasic cells. Invasion and adhesion, serving as important behavioral traits of epidermal keratinocytes cells, were suppressed by excessive miR-876-5p in psoriasic cells also. MiR-876-5p would be expected to be biomarker and potential therapeutic targets for the treatment of psoriasis.

Systemic Inflammation and Cardiovascular Comorbidity in Psoriasis Patients: Causes and Consequences

Psoriasis is a common inflammatory skin disease characterized by the appearance of red scaly plaques that can affect any part of the body. High prevalence, chronicity, disfiguration, disability, and associated comorbidity make it a challenge for clinicians of multiple specialties. Likewise, its complex pathogenesis, comprising inflammation, hyperproliferation, and angioneogenesis, intrigues numerous scientific disciplines, namely, immunology. From a clinical perspective, the severity of psoriasis is highlighted by its increased mortality, with cardiovascular diseases contributing the highest excess risk. From a scientific point of view, psoriasis has to be considered a systemic inflammatory condition, as blood biomarkers of inflammation are elevated and imaging techniques document sites of inflammation beyond the skin. While the association of psoriasis with cardiovascular diseases is now widely accepted, causes and consequences of this association are controversially discussed. This review comments on epidemiologic, genetic, and mechanistic studies that analyzed the relation between psoriasis and cardiovascular comorbidity. The hypothesis of psoriasis potentially being an independent cardiovascular risk factor, driving atherosclerosis via inflammation-induced endothelial dysfunction, will be discussed. Finally, consequences for the management of psoriasis with the objective to reduce the patients’ excess cardiovascular risk will be pointed out.