Psoriasis is characterized by accumulation of immunostimulatory and Th1/Th17 cell-polarizing myeloid dendritic cells

Adenosine A2A receptor activation regulates the M1 macrophages activation to initiate innate and adaptive immunity in psoriasis

Psoriasis is a common inflammatory systemic disease characterized by pro-inflammatory macrophages activation (M1 macrophage) infiltrated in the dermal layer. How M1 macrophage contributes to psoriasis remains unknown. In this study, we found that adenosine A2A receptor (A2AR) agonist CGS 21680 HCl alleviated the imiquimod (IMQ) and mouse IL-23 Protein (rmIL-23)-induced psoriasis inflammation through reducing infiltration of M1. Conversely, Adora2a deletion in mice exacerbated psoriasis-like phenotype. Mechanistically, A2AR activation inhibited M1 macrophage activation via the NF-κB-KRT16 pathway to reduce the secretion of CXCL10/11 and inhibit Th1/17 differentiation. Notably, the KRT16 expression was first found in M1 macrophage in our study, not only in keratinocytes (KCs). CXCL10/11 are first identified as primarily derived from macrophages and dendritic cells (DCs) rather than KCs in psoriasis using single cell RNA sequencing (scRNA-Seq). In total, the study emphasizes the importance of M1 as an innate immune cell in pathogenesis of psoriasis.

Curcumin as a regulator of Th17 cells: Unveiling the mechanisms

Curcumin, a polyphenol natural product derived from turmeric, possesses diverse pharmacological effects due to its interactions with various cells and molecules. Recent studies have highlighted its immunomodulatory properties, including its impact on immune cells and mediators involved in immune responses. Th17 cells play a crucial role in promoting immune responses against extracellular pathogens by recruiting neutrophils and inducing inflammation. These cells produce inflammatory cytokines such as TNF-α, IL-21, IL-17A, IL-23, IL-17F, IL-22, and IL-26. Curcumin has been shown to significantly inhibit the proliferation of Th17 cells and reduce the production of inflammatory cytokines, including TNF-α, IL-22, and IL-17. This review aims to assess the effectiveness of curcumin and its underlying mechanisms in modulating Th17 cells.

Targeting STING in dendritic cells alleviates psoriatic inflammation by suppressing IL-17A production

Psoriasis is a common chronic inflammatory skin disease driven by the aberrant activation of dendritic cells (DCs) and T cells, ultimately leading to increased production of cytokines such as interleukin (IL)-23 and IL-17A. It is established that the cGAS-STING pathway is essential for psoriatic inflammation, however, the specific role of cGAS-STING signaling in DCs within this context remains unclear. In this study, we demonstrated the upregulation of cGAS-STING signaling in psoriatic lesions by analyzing samples from both clinical patients and imiquimod (IMQ)-treated mice. Using a conditional Sting-knockout transgenic mouse model, we elucidated the impact of cGAS-STING signaling in DCs on the activation of IL-17- and IFN-γ-producing T cells in psoriatic inflammation. Ablation of the Sting hampers DC activation leads to decreased numbers of IL-17-producing T cells and Th1 cells, and thus subsequently attenuates psoriatic inflammation in the IMQ-induced mouse model. Furthermore, we explored the therapeutic potential of the STING inhibitor C-176, which reduces psoriatic inflammation and enhances the anti-IL-17A therapeutic response. Our results underscore the critical role of cGAS-STING signaling in DCs in driving psoriatic inflammation and highlight a promising psoriasis treatment.

Comparative Proteomics Analysis Reveals Distinct Molecular Phenotype and Biomarkers in Patients with Erythrodermic Atopic Dermatitis and Erythrodermic Psoriasis

Erythrodermic atopic dermatitis (EAD) and erythrodermic psoriasis (EP) are rare yet debilitating inflammatory skin disorders that propose challenges in diagnosis and discovering effective therapeutic targets. Despite their clinical and histological similarities, the underlying molecular mechanisms and systemic biomarkers of these diseases are substantially unclear. In this study, we sought to investigate the differential serum proteome of EP and EAD patients and identify biomarkers for these two subtypes of erythroderma. We recruited 14 EAD patients, 14 EP patients and 14 healthy controls. Serum samples were collected and analyzed using the Olink high-throughput platform to assess the levels of 269 inflammation-/immune response-/cardiovascular-related biomarkers. Both EAD and EP patients exhibited enhanced immune activation and dysregulated cardiovascular profiles compared to healthy controls. EAD demonstrated a more pronounced inflammation tone, characterized by Th1/Th2/Th22/IL-1-dominant patterns, as well as increased TNF superfamily, Th17, and apoptosis markers. Conversely, EP displayed inflammation with Th1/Th17/TNF-skewing and mild Th2 upregulation, along with notable increases in epidermal-development markers. Disease severity in EAD was strongly correlated with apoptosis/Th2 markers, while correlated with Th17 markers in EP. Furthermore, a panel of eight markers (IL-17A/IL-17C/PI3/CCL20/SH2D1A/SIRT2/DFFA/IL-13) was identified that effectively discriminated between EP and EAD, with an Area Under the Curve greater than 0.8. Our study comprehensively characterizes the circulating molecular profiles in EAD and EP patients, providing insights into the similarities and complexities of their inflammation phenotypes. The identified serum biomarkers have the potential to differentiate between EP and EAD, which could aid in the diagnosis and guiding tailored therapeutics.

IFN-γ, IL-17A, IL-4, and IL-13: Potential Biomarkers for Prediction of the Effectiveness of Biologics in Psoriasis Patients

Biologics are widely used to treat moderate-to-severe psoriasis. However, we have unmet needs for predicting individual patient responses to biologics before starting psoriasis treatment. We investigate a reliable platform and biomarkers for predicting individual patient responses to biologics. In a cohort study between 2018 and 2023 from a referral center in Taiwan, twenty psoriasis patients with or without psoriatic arthritis who had ever experienced two or more biologics were enrolled. Peripheral blood mononuclear cells obtained from these patients were treated with Streptococcus pyogenes and different biologics. The PASI reduction rate was strongly correlated with the reduction rate in the IL-13 level (p = 0.001) and the ratios of IFN-γ to IL-13 (p < 0.001), IFN-γ to IL-4 (p = 0.019), and IL-17A to IL-13 (p = 0.001). The PASI reduction difference was strongly correlated with the difference in the IFN-γ level (p = 0.002), the difference in the ratios of IFN-γ to IL-4 (p = 0.041), the difference in the ratios of IFN-γ to IL-13 (p = 0.006), the difference in the ratios of IL-17A to IL-4 (p = 0.011), and the difference in the ratios of IL-17A to IL-13 (p = 0.029). The biomarkers IFN-γ, IL-13, IFN-γ/IL4, IFN-γ/IL13, IL-17A/IL-4, and IL-17A/IL-13 are representative of the effectiveness of psoriasis treatment.

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

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

A BET inhibitor, NHWD-870, can downregulate dendritic cells maturation via the IRF7-mediated signaling pathway to ameliorate imiquimod-induced psoriasis-like murine skin inflammation

Psoriasis is a chronic, recurrent, inflammatory dermatosis accompanied by excessive activation of dendritic cells (DCs), which are primarily responsible for initiating an immune response. The bromodomain and extraterminal domain (BET) family plays a pivotal role in the transcriptional regulation of inflammation and its inhibitors can downregulate DCs maturation and activation. Here we investigated the effect of NHWD-870, a potent BET inhibitor, on inflammation in an imiquimod (IMQ)-induced psoriasis-like mouse model and murine bone marrow-derived dendritic cells (BMDCs) stimulated by lipopolysaccharide (LPS) and IMQ. Application of NHWD-870 significantly ameliorated IMQ-triggered skin inflammation in mice, and markers associated with DC maturation (CD40, CD80 and CD86) were decreased in skin lesions, spleen and lymph nodes. Additionally, NHWD-870 reduced LPS or IMQ induced DCs maturation and activation in vitro, with lower expression of inflammatory cytokines [interleukin (IL)-12, IL-23, tumor necrosis factor-α, IL-6, IL-1β, chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10]. In addition, we found that interferon regulatory factor 7 (IRF7) significantly increased during DCs maturation, and inhibition of IRF7 could impair BMDCs maturation and activation. What's more, IRF7 was highly expressed in both psoriatic patients and IMQ-induced psoriasis-like mice. Single-cell RNA sequencing of normal and psoriatic skin demonstrated that IRF7 expression was increased in DCs of psoriatic skin. While NHWD-870 could inhibit IRF7 and phosphorylated-IRF7 expression in vivo and in vitro. These results indicate that NHWD-870 suppresses the maturation and activation of DCs by decreasing IRF7 proteins which finally alleviates psoriasis-like skin lesions, and NHWD-870 may be a potent therapeutic drug for psoriasis.

The Immunology of Psoriasis-Current Concepts in Pathogenesis

Psoriasis is one of the most common inflammatory skin diseases with a chronic, relapsing-remitting course. The last decades of intense research uncovered a pathological network of interactions between immune cells and other types of cells in the pathogenesis of psoriasis. Emerging evidence indicates that dendritic cells, TH17 cells, and keratinocytes constitute a pathogenic triad in psoriasis. Dendritic cells produce TNF-α and IL-23 to promote T cell differentiation toward TH17 cells that produce key psoriatic cytokines IL-17, IFN-γ, and IL-22. Their activity results in skin inflammation and activation and hyperproliferation of keratinocytes. In addition, other cells and signaling pathways are implicated in the pathogenesis of psoriasis, including TH9 cells, TH22 cells, CD8+ cytotoxic cells, neutrophils, γδ T cells, and cytokines and chemokines secreted by them. New insights from high-throughput analysis of lesional skin identified novel signaling pathways and cell populations involved in the pathogenesis. These studies not only expanded our knowledge about the mechanisms of immune response and the pathogenesis of psoriasis but also resulted in a revolution in the clinical management of patients with psoriasis. Thus, understanding the mechanisms of immune response in psoriatic inflammation is crucial for further studies, the development of novel therapeutic strategies, and the clinical management of psoriasis patients. The aim of the review was to comprehensively present the dysregulation of immune response in psoriasis with an emphasis on recent findings. Here, we described the role of immune cells, including T cells, B cells, dendritic cells, neutrophils, monocytes, mast cells, and innate lymphoid cells (ILCs), as well as non-immune cells, including keratinocytes, fibroblasts, endothelial cells, and platelets in the initiation, development, and progression of psoriasis.

Theoretical Studies of DNA Microarray Present Potential Molecular and Cellular Interconnectivity of Signaling Pathways in Immune System Dysregulation

Autoimmunity is defined as the inability to regulate immunological activities in the body, especially in response to external triggers, leading to the attack of the tissues and organs of the host. Outcomes include the onset of autoimmune diseases whose effects are primarily due to dysregulated immune responses. In past years, there have been cases that show an increased susceptibility to other autoimmune disorders in patients who are already experiencing the same type of disease. Research in this field has started analyzing the potential molecular and cellular causes of this interconnectedness, bearing in mind the possibility of advancing drugs and therapies for the treatment of autoimmunity. With that, this study aimed to determine the correlation of four autoimmune diseases, which are type 1 diabetes (T1D), psoriasis (PSR), systemic sclerosis (SSc), and systemic lupus erythematosus (SLE), by identifying highly preserved co-expressed genes among datasets using WGCNA. Functional annotation was then employed to characterize these sets of genes based on their systemic relationship as a whole to elucidate the biological processes, cellular components, and molecular functions of the pathways they are involved in. Lastly, drug repurposing analysis was performed to screen candidate drugs for repositioning that could regulate the abnormal expression of genes among the diseases. A total of thirteen modules were obtained from the analysis, the majority of which were associated with transcriptional, post-transcriptional, and post-translational modification processes. Also, the evaluation based on KEGG suggested the possible role of TH17 differentiation in the simultaneous onset of the four diseases. Furthermore, clomiphene was the top drug candidate for regulating overexpressed hub genes; meanwhile, prilocaine was the top drug for regulating under-expressed hub genes. This study was geared towards utilizing transcriptomics approaches for the assessment of microarray data, which is different from the use of traditional genomic analyses. Such a research design for investigating correlations among autoimmune diseases may be the first of its kind.

Regulation of the Immune Cell Repertoire in Psoriasis Patients Upon Blockade of IL-17A or TNFα

INTRODUCTION

Targeting of the proinflammatory cytokine interleukin 17A (IL-17A) or tumor necrosis factor alpha (TNFα) with the monoclonal antibodies (mAbs) ixekizumab or adalimumab, respectively, is a successful therapy for chronic plaque psoriasis. The effects of these treatments on immune cell populations in the skin are largely unknown.

METHODS

In this study, we compared the composition of cutaneous, lesional and non-lesional immune cells and blood immune cells in ixekizumab- or adalimumab-treated patients with psoriasis.

RESULTS

Our data reveal that both treatments efficiently downregulate T cells, macrophages and different subsets of dendritic cells (DCs) in lesional skin towards levels of healthy skin. In contrast to lesional skin, non-lesional areas in patients harbor only few or no detectable DCs compared to the skin of healthy subjects. Treatment with neither ixekizumab nor adalimumab reversed this DC imbalance in non-lesional skin of psoriatic patients.

CONCLUSION

Our study shows that anti-IL-17A and anti-TNFα therapy rebalances the immune cell repertoire of lesional skin in psoriatic patients but fails to restore the disturbed immune cell repertoire in non-lesional skin.

The Use of Microbial Modifying Therapies to Prevent Psoriasis Exacerbation and Associated Cardiovascular Comorbidity

Psoriasis has emerged as a systemic disease characterized by skin and joint manifestations as well as systemic inflammation and cardiovascular comorbidities. Many progresses have been made in the comprehension of the immunological mechanisms involved in the exacerbation of psoriatic plaques, and initial studies have investigated the mechanisms that lead to extracutaneous disease manifestations, including endothelial disfunction and cardiovascular disease. In the past decade, the involvement of gut dysbiosis in the development of pathologies with inflammatory and autoimmune basis has clearly emerged. More recently, a major role for the skin microbiota in establishing the immunological tolerance in early life and as a source of antigens leading to cross-reactive responses towards self-antigens in adult life has also been evidenced. Gut microbiota can indeed be involved in shaping the immune and inflammatory response at systemic level and in fueling inflammation in the cutaneous and vascular compartments. Here, we summarized the microbiota-mediated mechanisms that, in the skin and gut, may promote and modulate local or systemic inflammation involved in psoriatic disease and endothelial dysfunction. We also analyze the emerging strategies for correcting dysbiosis or modulating skin and gut microbiota composition to integrate systemically existing pharmacological therapies for psoriatic disease. The possibility of merging systemic treatment and tailored microbial modifying therapies could increase the efficacy of the current treatments and potentially lower the effect on patient's life quality.

Damage-Associated Molecular Patterns, a Class of Potential Psoriasis Drug Targets

Psoriasis is a chronic skin disorder that involves both innate and adaptive immune responses in its pathogenesis. Local tissue damage is a hallmark feature of psoriasis and other autoimmune diseases. In psoriasis, damage-associated molecular patterns (DAMPs) released by damaged local tissue act as danger signals and trigger inflammatory responses by recruiting and activating immune cells. They also stimulate the release of pro-inflammatory cytokines and chemokines, which exacerbate the inflammatory response and contribute to disease progression. Recent studies have highlighted the role of DAMPs as key regulators of immune responses involved in the initiation and maintenance of psoriatic inflammation. This review summarizes the current understanding of the immune mechanism of psoriasis, focusing on several important DAMPs and their mechanisms of action. We also discussed the potential of DAMPs as diagnostic and therapeutic targets for psoriasis, offering new insights into the development of more effective treatments for this challenging skin disease.

A Review of Dupilumab-Induced Adverse Events to Dermatologists and the Potential Pathogenesis in the Treatment of Atopic Dermatitis

Dupilumab, a monoclonal antibody targeting interleukin-4 antibody, is approved for use in many type 2 inflammatory diseases, including atopic dermatitis. It is generally well tolerated with no need of routine laboratory monitoring. However, several adverse events have been reported during real-world practice and in pivotal trials. We conducted a systematic literature research of the PubMed, Medline, and Embase databases to identify articles recording the clinical manifestation and potential pathogenesis of these adverse events with interests (AEIs) to dermatologists. In total, 547 cases from 134 studies have developed 39 AEIs 1 day to 2.5 years after dupilumab treatment. The most common AEIs are facial and neck dermatitis (299 cases), psoriasis (70 cases), arthralgia (56 cases), alopecia (21 cases), cutaneous T cell lymphoma (19 cases), severe ocular diseases (19 cases), and drug eruption (6 cases). Most of the AEIs recorded in this review resolved or improved after dupilumab discontinuation or the addition of another treatment, whereas 3 of the cases died of severe AEI. The potential pathogenesis included T help type 1 (Th1)/T help type 2 (Th2) imbalance, Th2/T help type 17 (Th17) imbalance, immune reconstitution, hypersensitivity reaction, transient hypereosinophilia related, and Th1 suppression. Clinicians should be alert of these AEIs for timely diagnosis and appropriate treatment.

Use of secukinumab in erythrodermic psoriasis: A single center experience

Background

Erythrodermic psoriasis is an acute inflammatory condition presenting as erythema and scaling involving more than 90% of body surface area in patients with a history of psoriasis vulgaris. If not treated promptly, metabolic complications and infections due to acute skin failure can cause significant morbidity and mortality in this condition. Interleukin-17 (IL-17) is considered to be the key player in initiating the inflammatory cascade in psoriasis. IL-17 blockers have been successfully used in the management of psoriasis vulgaris. However, its use in unstable erythrodermic psoriasis is limited to isolated case reports.

Methods

We hereby report an observational study of nine patients of unstable psoriatic erythroderma successfully managed with injection secukinumab and followed up over the next 24 months.

Results

Nine patients were managed during the study period, and a successful outcome was noted in all the patients. The Psoriasis Area and Severity Index response rate improved by at least 75% from baseline in 33.3% (3⁄9) at week 4 and improved to 88.9% (8⁄9) at week 12. None of the patients had a recurrence of erythroderma till 24 months of followup.

Conclusion

The study concluded that secukinumab is quick, safe, and efficient in psoriatic erythroderma, and there was no relapse of erythroderma in any of the patients in the 24 months of followup.

From the Skin to Distant Sites: T Cells in Psoriatic Disease

Human skin has long been known as a protective organ, acting as a mechanical barrier towards the external environment. More recent is the acquisition that in addition to this fundamental role, the complex architecture of the skin hosts a variety of immune and non-immune cells playing preeminent roles in immunological processes aimed at blocking infections, tumor progression and migration, and elimination of xenobiotics. On the other hand, dysregulated or excessive immunological response into the skin leads to autoimmune reactions culminating in a variety of skin pathological manifestations. Among them is psoriasis, a multifactorial, immune-mediated disease with a strong genetic basis. Psoriasis affects 2-3% of the population; it is associated with cardiovascular comorbidities, and in up to 30% of the cases, with psoriatic arthritis. The pathogenesis of psoriasis is due to the complex interplay between the genetic background of the patient, environmental factors, and both innate and adaptive responses. Moreover, an autoimmune component and the comprehension of the mechanisms linking chronic skin inflammation with systemic and joint manifestations in psoriatic patients is still a major challenge. The understanding of these mechanisms may offer a valuable chance to find targetable molecules to treat the disease and prevent its progression to severe systemic conditions.

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.

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.

Inflammatory Cues Direct Skin-Resident Type 1 Innate Lymphoid Cells to Adopt a Psoriasis-Promoting Identity

Innate lymphoid cells (ILCs) are gatekeepers in barrier organs, where they maintain tissue integrity and contribute to host defense as well as tissue repair. Inappropriate activation of ILCs, however, can lead to immunopathology with detrimental results. In this study, we focused on type 1 ILCs (ILC1s), which under inflammatory conditions constitute a poorly defined population with ambiguous functions. To delineate the properties of ILC1s in skin pathology, we used the well-established mouse model of imiquimod-induced psoriasis. Although ILC1s represented a minority among cutaneous lymphocytes in vehicle-treated controls, they rapidly expanded during early psoriasis and ultimately increased by >20-fold. This rapid increase was verified using two additional psoriasis models. Inflammatory ILC1s from imiquimod-treated skin were defined as CD44+, CXCR6+, and CD11b+ and substantially contributed to TNF-α and GM-CSF production, rendering them a potential candidate to shape the inflammatory infiltrate. In accordance with the psoriasis-specific microenvironment, skin ILC1s upregulated the IL-23 receptor whereas expression of the IL-12Rβ2 subunit was diminished. As a consequence, neutralization of IL-12 only had a minor impact, whereas blocking IL-23 reduced both ILC1 abundance and disease severity. Together, our findings identify skin ILC1s as a likely player in early psoriasis and a prospective target for therapeutic approaches.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

Conventional dendritic cells type 1 are strongly enriched, quiescent and relatively tolerogenic in local inflammatory arthritis

Introduction

Dendritic cells (DC) are crucial for initiating and shaping immune responses. So far, little is known about the functional specialization of human DC subsets in (local) inflammatory conditions. We profiled conventional (c)DC1, cDC2 and monocytes based on phenotype, transcriptome and function from a local inflammatory site, namely synovial fluid (SF) from patients suffering from a chronic inflammatory condition, Juvenile Idiopathic Arthritis (JIA) as well as patients with rheumatoid arthritis (RA).

Methods

Paired PB and SF samples from 32 JIA and 4 RA patients were collected for mononuclear cell isolation. Flow cytometry was done for definition of antigen presenting cell (APC) subsets. Cell sorting was done on the FACSAria II or III. RNA sequencing was done on SF APC subsets. Proliferation assays were done on co-cultures after CD3 magnetic activated cell sorting (MACS). APC Toll-like receptor (TLR) stimulation was done using Pam3CSK4, Poly(I:C), LPS, CpG-A and R848. Cytokine production was measured by Luminex.

Results

cDC1, a relatively small DC subset in blood, are strongly enriched in SF, and showed a quiescent immune signature without a clear inflammatory profile, low expression of pathogen recognition receptors (PRRs), chemokine and cytokine receptors, and poor induction of T cell proliferation and cytokine production, but selective production of IFNλ upon polyinosinic:polycytidylic acid exposure. In stark contrast, cDC2 and monocytes from the same environment, showed a pro-inflammatory transcriptional profile, high levels of (spontaneous) pro-inflammatory cytokine production, and strong induction of T cell proliferation and cytokine production, including IL-17. Although the cDC2 and monocytes showed an overlapping transcriptional core profile, there were clear differences in the transcriptional landscape and functional features, indicating that these cell types retain their lineage identity in chronic inflammatory conditions.

Discussion

Our findings suggest that at the site of inflammation, there is specific functional programming of human DCs, especially cDC2. In contrast, the enriched cDC1 remain relatively quiescent and seemingly unchanged under inflammatory conditions, pointing to a potentially more regulatory role.

Th17 Cells: Orchestrators of Mucosal Inflammation and Potential Therapeutic Targets

T helper 17 (Th17) cells represent a specialized subgroup of effector CD4+ T cells known for their role in provoking neutrophil-driven tissue inflammation, particularly within mucosal tissues. Although they are pivotal for defending the host against extracellular bacteria and fungi, they have also been associated with development of various T cell-mediated inflammatory conditions, autoimmune diseases, and even cancer. Notably, Th17 cells exhibit a dual nature, with different Th17 cell subtypes showcasing distinct effector functions and varying capacities to incite autoimmune tissue inflammation. Furthermore, Th17 cells exhibit significant plasticity, which carries important functional implications, both in terms of their expression of cytokines typically associated with other effector T cell subsets and in their interactions with regulatory CD4+ T cells. The intricate balance of Th17 cytokines can also be a double-edged sword in inflammation, autoimmunity, and cancer. Within this article, we delve into the mechanisms that govern the differentiation, function, and adaptability of Th17 cells. We culminate with an exploration of therapeutic potentials in harnessing the power of Th17 cells and their cytokines. Targeted interventions to modulate Th17 responses are emerging as promising strategies for autoimmunity, inflammation, and cancer treatment. By precisely fine-tuning Th17-related pathways, we may unlock new avenues for personalized therapeutic approaches, aiming to restore immune balance, alleviate the challenges of these disorders, and ultimately enhance the quality of life for individuals affected by them.

ETV3 and ETV6 enable monocyte differentiation into dendritic cells by repressing macrophage fate commitment

In inflamed tissues, monocytes differentiate into macrophages (mo-Macs) or dendritic cells (mo-DCs). In chronic nonresolving inflammation, mo-DCs are major drivers of pathogenic events. Manipulating monocyte differentiation would therefore be an attractive therapeutic strategy. However, how the balance of mo-DC versus mo-Mac fate commitment is regulated is not clear. In the present study, we show that the transcriptional repressors ETV3 and ETV6 control human monocyte differentiation into mo-DCs. ETV3 and ETV6 inhibit interferon (IFN)-stimulated genes; however, their action on monocyte differentiation is independent of IFN signaling. Instead, we find that ETV3 and ETV6 directly repress mo-Mac development by controlling MAFB expression. Mice deficient for Etv6 in monocytes have spontaneous expression of IFN-stimulated genes, confirming that Etv6 regulates IFN responses in vivo. Furthermore, these mice have impaired mo-DC differentiation during inflammation and reduced pathology in an experimental autoimmune encephalomyelitis model. These findings provide information about the molecular control of monocyte fate decision and identify ETV6 as a therapeutic target to redirect monocyte differentiation in inflammatory disorders.

Pathogenesis, multi-omics research, and clinical treatment of psoriasis

Psoriasis is a common inflammatory skin disease involving interactions between keratinocytes and immune cells that significantly affects the quality of life. It is characterized by hyperproliferation and abnormal differentiation of keratinocytes and excessive infiltration of immune cells in the dermis and epidermis. The immune mechanism underlying this disease has been elucidated in the past few years. Research shows that psoriasis is regulated by the complex interactions among immune cells, such as keratinocytes, dendritic cells, T lymphocytes, neutrophils, macrophages, natural killer cells, mast cells, and other immune cells. An increasing number of signaling pathways have been found to be involved in the pathogenesis of psoriasis, which has prompted the search for new treatment targets. In the past decades, studies on the pathogenesis of psoriasis have focused on the development of targeted and highly effective therapies. In this review, we have discussed the relationship between various types of immune cells and psoriasis and summarized the major signaling pathways involved in the pathogenesis of psoriasis, including the PI3K/AKT/mTOR, JAK-STAT, JNK, and WNT pathways. In addition, we have discussed the results of the latest omics research on psoriasis and the epigenetics of the disease, which provide insights regarding its pathogenesis and therapeutic prospects; we have also summarized its treatment strategies and observations of clinical trials. In this paper, the various aspects of psoriasis are described in detail, and the limitations of the current treatment methods are emphasized. It is necessary to improve and innovate treatment methods from the molecular level of pathogenesis, and further provide new ideas for the treatment and research of psoriasis.

The role of cells of the innate immune system in psoriasis

Psoriasis is an immune-mediated disease with a complex pathogenesis. The close relationship between the development of psoriasis and the adaptive immune response is already known. However, recent data have shown that innate immune cells also play an important role in the development of psoriasis. Congenital lymphoid cells, dendritic cells, T cells, NK cells, and NKT lymphocytes are activated in psoriasis, contributing to disease pathology through IL-17-dependent and independent mechanisms. During disease progression, T cells secrete proinflammatory cytokines that induce and exacerbate the course of psoriasis. T cells have memory cell properties that respond rapidly to secondary stimulation, which contributes to disease relapse. This article presents an overview of recent findings demonstrating the role of innate immunity in psoriasis.

Local IL-23 is required for proliferation and retention of skin-resident memory TH17 cells

The cytokine interleukin-23 (IL-23) is critical for development and maintenance of autoimmune inflammation in nonlymphoid tissues; however, the mechanism through which IL-23 supports tissue-specific immunity remains unclear. In mice, we found that circulating memory T cells were dispensable for anamnestic protection from Candida albicans skin infection, and tissue-resident memory (TRM) cell-mediated protection from C. albicans reinfection required IL-23. Administration of anti-IL-23 receptor antibody to mice after resolution of primary C. albicans infection resulted in loss of CD69+ CD103+ tissue-resident memory T helper 17 (TRM17) cells from skin, and clinical anti-IL-23 therapy depleted TRM17 cells from skin of patients with psoriasis. IL-23 receptor blockade impaired TRM17 cell proliferation but did not affect apoptosis susceptibility or tissue egress. IL-23 produced by CD301b+ myeloid cells was required for TRM17 maintenance in skin after C. albicans infection, and CD301b+ cells were necessary for TRM17 expansion during the development of imiquimod dermatitis. This study demonstrates that locally produced IL-23 promotes in situ proliferation of cutaneous TRM17 cells to support their longevity and function and provides mechanistic insight into the durable efficacy of IL-23 blockade in the treatment of psoriasis.

Human dendritic cell subsets: An updated view of their ontogeny and functional specialization

Human DCs have been divided into several subsets based on their phenotype and ontogeny. Recent high throughput single-cell methods have revealed additional heterogeneity within human DC subsets, and new subpopulations have been proposed. In this review, we provide an updated view of the human DC subsets and of their ontogeny supported by recent clinical studies . We also summarize their main characteristics including their functional specialization.

A role for whey acidic protein four-disulfide-core 12 (WFDC12) in the pathogenesis and development of psoriasis disease

Whey acidic protein four-disulfide core domain protein 12 (WFDC12) has been implicated in the pathogenesis of psoriasis but the specific molecular mechanism is not clearly defined. In this study, we found the expression of WFDC12 protein closely correlated with psoriasis. WFDC12 in keratinocyte might increase infiltration of Langerhans cells (LCs) and monocyte-derived dendritic cells (moDDCs), up-regulating the co-stimulation molecular CD40/CD86. Th1 cells in lymph nodes were higher in K14-WFDC12 transgenic psoiasis-like mice. Meanwhile, the mRNA of IL-12 and IFN-γ in the lesion skin was significantly increased in transgenic mice. Moreover, we found that the expression of the proteins that participated in the retinoic acid–related pathway and immune signaling pathway was more changed in the lesion skin of K14-WFDC12 transgenic psoriasis-like mice. Collectively, the results implied that WFDC12 might affect the activation of the retinoic acid signaling pathway and regulate the infiltration of DC cells in the skin lesions and lymph nodes, thereby inducing Th1 cells differentiation and increasing the secretion of IFN-γ to exacerbate psoriasis in mice.

A sharp decrease of Th17, CXCR3+-Th17, and Th17.1 in peripheral blood is associated with an early anti-IL-17-mediated clinical remission in psoriasis

Psoriasis-an immune-mediated skin disease-implicates in its pathophysiology by circulating pro-inflammatory cell populations, cytokines, and their interactions with the epidermis. The direct effect of approved anti-interleukin- (IL-)17A and anti-IL-17R biologic therapy on immunophenotyping of peripheral blood mononuclear lymphocytes' (PBMCs) relative sub-population frequencies in psoriasis patients has not yet been described. Using multiparameter flow cytometry we examined T-cell subpopulations characterized by CCR6, CCR4, and CXCR3 chemokine receptor surface expression at baseline and after initiation of biologic therapy in PBMCs collected from 30 psoriasis patients. Increased CD3+CD4+CXCR3+, CD3+CD4+CCR6+CCR4+CXCR3+(CXCR3+-Th17), and CD3+CD4+CCR6+CCR4-CXCR3+(Th17.1) cell populations were observed in patients with psoriasis in comparison to healthy individuals (n = 10). IL-17 therapeutic blockade decreased CD3+CD4+CCR6+, CD3+CD4+CXCR3+, CD3+CD4+CCR6-CXCR3+(Th1), CD3+CD4+CCR6+CCR4+(Th17), CD3+CD4+CCR6+CCR4+CXCR3+(CXCR3+-Th17), and CD3+CD4+CCR6+CCR4-CXCR3+(Th17.1) cell populations in responding psoriasis patients. Moreover, CD3+CD4-CCR6+, CD3+CD4-CXCR3+, CD3+CD4-CCR6+CCR4+(Tc17), and CD3+CD4-CCR6-CXCR3+(Tc1) percentages were also inhibited. Modulation of the same cell sub-populations was also assessed in patients treated with methotrexate (n = 4), apremilast (n = 4), and anti-IL-23 biologic treatment (n = 4). In our study, the levels and functional capacity of peripheral pro-inflammatory Th1, Th17, and additional CCR6+T cell sub-gated populations from psoriasis patients that were treated with anti-IL-17 or anti-IL-17R targeted biologic therapy were explored for the first time. Our data clearly demonstrate that early anti-IL-17 mediated clinical remission is accompanied by a significant decrease of Th1, Th17, CXCR3+-Th17, and Th17.1 cells.

From IL-17 to IFN-γ in inflammatory skin disorders: Is transdifferentiation a potential treatment target?

The targeted inhibition of effector cytokines such as interleukin 17 (IL-17) in psoriasis and IL-13 in atopic dermatitis offers impressive efficacy with a favorable side effect profile. In contrast, the downregulation of interferon gamma (IFN-γ) in T helper (Th) 1-dominant skin disorders may lead to more adverse events, given the crucial role of IFN-γ in antiviral and antitumoral immunity. Modulating Th17 and Th2 cell differentiation is performed by blocking IL-23 and IL-4, respectively, whereas anti-IL-12 antibodies are only moderately effective in downregulating Th1 lymphocyte differentiation. Therefore, a targeted approach of IFN-γ-driven disorders remains challenging. Recent literature suggests that certain pathogenic Th17 cell subsets with Th1 characteristics, such as CD4+CD161+CCR6+CXCR3+IL-17+IFN-y+ (Th17.1) and CD4+CD161+CCR6+CXCR3+IL-17-IFN-y+ (exTh17), are important contributors in Th1-mediated autoimmunity. Differentiation to a Th17.1 or exTh17 profile results in the upregulation of IFN-y. Remarkably, these pathogenic Th17 cell subsets are resistant to glucocorticoid therapy and the dampening effect of regulatory T cells (Treg). The identification of Th17.1/exTh17 cells in auto-immune disorders may explain the frequent treatment failure of conventional immunosuppressants. In this review, we summarize the current evidence regarding the cellular plasticity of Th17 cells in inflammatory skin disorders. A deeper understanding of this phenomenon may lead to better insights into the pathogenesis of various skin diseases and the discovery of a potential new treatment target.

The Dendritic Cell Dilemma in the Skin: Between Tolerance and Immunity

Dendritic cells (DC) are uniquely capable of initiating and directing immune responses. The range of their activities grounds in the heterogeneity of DC subsets and their functional plasticity. Numerical and functional DC changes influence the development and progression of disease, and correction of such dysregulations has the potential to treat disease causally. In this review, we discuss the major advances in our understanding of the regulation of DC lineage formation, differentiation, and function in the skin. We describe the alteration of DC in disease as well as possibilities for therapeutic reprogramming with a focus on tolerogenic DC. Because regulatory T cells (Treg) are indispensable partners of DC in the induction and control of tolerance, we pay special attention to the interactions with these cells. Above all, we would like to arouse fascination for this cell type and its therapeutic potential in skin diseases.

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.

Chrna5 is overexpressed in psoriasis patients and promotes psoriasis-like inflammation in mouse models

It is well known that psoriasis is closely related to smoking, and the cholinergic receptor nicotinic subunit alpha-5 (Chrna5) plays an important role in smoking-related diseases. However, studies on the relationship between Chrna5 and psoriasis are limited. This study aimed to examine the role of Chrna5 in psoriasis development and pathogenesis. Analysis in psoriatic tissues and imiquimod (IMQ)-induced mouse models showed that Chrna5 was highly expressed in psoriatic lesional skin. To further verify the function of Chrna5, we constructed Chrna5-knockout mice and induced the psoriasis model. We found that Chrna5 knockout significantly reduced the severity of psoriasis and could regulate inflammation via the mitogen-activated protein kinase kinase kinase 1 (MEKK1)/c-Jun NH(2)-terminal kinase (JNK)-MAPK/NF-κB pathway. The single-cell sequencing results revealed that after Chrna5 knockout, the keratinocyte subpopulation was significantly reduced and the related Janus kinase/signal transduction and activator of transcription (JAK/STAT) signaling pathway was downregulated, further indicating the importance of Chrna5 in psoriasis. Human keratinocytes were analyzed, and silencing Chrna5 inhibited keratinocyte proliferation and migration. In summary, Chrna5 played important roles in the development and pathogenesis of psoriasis, and targeting Chrna5 may be an effective strategy for the treatment of psoriasis.

Peroxisome proliferator-activator receptor γ and psoriasis, molecular and cellular biochemistry

The pathophysiology of psoriasis is complex and has not been completely elucidated. Better understanding of the pathogenesis may contribute to further improvement of our therapeutic strategies controlling psoriasis. Emerging evidence points to a causative relationship between altered activity of peroxisome proliferator-activated receptor γ (PPARγ) and psoriasis. The present review focuses on deeper understanding of the possible role of PPARγ in the pathogenesis of psoriasis and the potential of PPARγ agonist to improve the treatment of psoriasis. PPARγ is decreased in psoriasis. PPARγ possibly has effects on the multiple aspects of the pathogenesis of psoriasis, including abnormal lipid metabolism, insulin resistance, immune cells, pro-inflammatory cytokines, keratinocytes, angiogenesis, oxidative stress, microRNAs and nuclear factor kappa B. As defective activation of PPARγ is involved in psoriasis development, PPARγ agonists may be promising agents for treatment of psoriasis. Pioglitazone appears an effective and safe option in the treatment of patients with psoriasis, but there are still concerns about its potential side effects. Research effort has recently been undertaken to explore the PPARγ-activating potential of natural products. Among them some have been studied clinically or preclinically for treatment of psoriasis with promising results.

Suppression of IL-12/IL-23 p40 subunit in the skin and blood of psoriasis patients by Tofacitinib is dependent on active interferon-γ signaling in dendritic cells: implications for the treatment of psoriasis and interferon-driven diseases

Interleukin (IL)‐12 and IL‐23 are pro‐inflammatory cytokines produced by dendritic cells (DCs) and associated with Psoriasis (Pso) and Psoriatic Arthritis (PsA) pathogenesis. Tofacitinib, a Janus kinase inhibitor, effectively suppresses inflammatory cascades downstream the IL‐12/IL‐23 axis in Pso and PsA patients. Here, we investigated whether Tofacitinib directly regulates IL‐12/IL‐23 production in DCs, and how this regulation reflects responses to Tofacitinib in Pso patients. We treated monocyte‐derived dendritic cells and myeloid dendritic cells with Tofacitinib and stimulated cells with either lipopolysaccharide (LPS) or a combination of LPS and IFN‐γ. We assessed gene expression by qPCR, obtained skin microarray and blood Olink data and clinical parameters of Pso patients treated with Tofacitinib from public data sets. Our results indicate that in DCs co‐stimulated with LPS and IFN‐γ, but not with LPS alone, Tofacitinib leads to the decreased expression of IL‐23/IL‐12 shared subunit IL12B (p40). In Tofacitinib‐treated Pso patients, IL‐12 expression and psoriasis area and severity index (PASI) are significantly reduced in patients with higher IFN‐γ at baseline. These findings demonstrate for the first time that Tofacitinib suppresses IL‐23/IL‐12 shared subunit IL12B in DCs upon active IFN‐γ signaling, and that Pso patients with higher IFN‐γ baseline levels display improved clinical response after Tofacitinib treatment.

Relationship between Immune Cells, Depression, Stress, and Psoriasis: Could the Use of Natural Products Be Helpful?

Psoriasis is one of the most widespread chronic inflammatory skin diseases, affecting about 2%-3% of the worldwide adult population. The pathogenesis of this disease is quite complex, but an interaction between genetic and environmental factors has been recognized with an essential modulation of inflammatory and immune responses in affected patients. Psoriatic plaques generally represent the clinical psoriatic feature resulting from an abnormal proliferation and differentiation of keratinocytes, which cause dermal hyperplasia, skin infiltration of immune cells, and increased capillarity. Some scientific pieces of evidence have reported that psychological stress may play a key role in psoriasis, and the disease itself may cause stress conditions in patients, thus reproducing a vicious cycle. The present review aims at examining immune cell involvement in psoriasis and the relationship of depression and stress in its pathogenesis and development. In addition, this review contains a focus on the possible use of natural products, thus pointing out their mechanism of action in order to counteract clinical and psychological symptoms.

Psoriasis between Autoimmunity and Oxidative Stress: Changes Induced by Different Therapeutic Approaches

Psoriasis is defined as chronic, immune-mediated disease. Regardless of the development of new therapeutic approaches, the precise etiology of psoriasis remains unknown and speculative. The aim of this review was to systematize the results of previous research on the role of oxidative stress and aberrant immune response in the pathogenesis of psoriasis, as well as the impact of certain therapeutic modalities on the oxidative status in patients with psoriasis. Complex immune pathways of both the innate and adaptive immune systems appear to be major pathomechanisms in the development of psoriasis. Oxidative stress represents another important contributor to the pathophysiology of disease, and the redox imbalance in psoriasis has been reported in skin cells and, systemically, in plasma and blood cells, and more recently, also in saliva. Current immune model of psoriasis begins with activation of immune system in susceptible person by some environmental factor and loss of immune tolerance to psoriasis autoantigens. Increased production of IL-17 appears to be the most prominent role in psoriasis pathogenesis, while IL-23 is recognized as master regulator in psoriasis having a specific role in cross bridging the production of IL-17 by innate and acquired immunity. Other proinflammatory cytokines, including IFN-γ, TNF-α, IL-1β, IL-6, IL-22, IL-26, IL-29, or IL-36, have also been reported to play important roles in the development of psoriasis. Oxidative stress can promote inflammation through several signaling pathways. The most noticeable and most powerful antioxidative effects exert various biologics compared to more convenient therapeutic modalities, such as methotrexate or phototherapy. The complex interaction of redox, immune, and inflammatory signaling pathways should be focused on further researches tackling the pathophysiology of psoriasis, while antioxidative supplementation could be the solution in some refractory cases of the disease.

Hydrogel-mediated topical delivery of steroids can effectively alleviate psoriasis via attenuating the autoimmune responses

Psoriasis is a systemic, relapsing, and chronic autoimmune inflammatory disease of the skin. Topical use of betamethasone, a glucocorticoid, in the form of creams is a common treatment for psoriasis. However, topical use of these creams is challenging due to the ineffective entrapment of steroids, burst release of the entrapped drugs, poor skin permeability, and high toxicity. Herein, we present the engineering of a betamethasone-loaded topical hydrogel (B-Gel) that can efficiently entrap steroids with high spreadability, and can also maintain the sustained release of drugs. We used an imiquimod (IMQ) induced ear psoriasis model, and demonstrated that topical application of B-Gel can mitigate the autoimmune inflammation reactions, and leads to a reduction in erythema, induration, scaling, and ear thickness. As interleukin 17 (IL-17) secreting T helper 17 (Th17) cells and γδ⁺ T cells are responsible for psoriasis, B-Gel treatment witnessed a reduction in the infiltration of leukocytes, CD4⁺ T cells, Th17 T cells, and dermal γδ⁺ T cells. We further demonstrated that B-Gel mediated reduction of IL-1β, IL-17, and K16 (marker for keratinocyte proliferation) is responsible for alleviation of psoriasis. Therefore, the non-greasy nature of the hydrogel with a cooling effect provides an alternative for topical application of steroids.

Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells Alleviate Psoriasis-like Skin Inflammation

Immunomodulatory effects of mesenchymal stem cells (MSCs) in inflammatory diseases, including psoriasis, are well documented. However, the role of MSC-derived exosomes (MSCs-Exo) in psoriasis-like skin inflammation remains largely unknown. This study aimed to investigate whether MSCs-Exo play a regulatory role in psoriasis-like skin inflammation. We found that subcutaneous injection of human umbilical cord MSCs-Exo (hucMSCs-Exo) significantly suppressed the proliferation of epidermis and reduced Psoriasis Area and Severity Index (PASI) scores in imiquimod (IMQ)-induced mice. hucMSCs-Exo also reduced the expression of interleukin (IL)-17, IL-23, and chemokine C-C-motif ligand 20 (CCL20) and inhibited phosphorylation of signal transducer and activator of transcription 3 (STAT3) in the skin of IMQ-induced mice and in human keratinocyte (HaCaT) cells. In addition, co-cultured with hucMSCs-Exo in vitro, the maturation and activation of dendritic cells (DCs) were suppressed, and the expression level of IL-23 was decreased. These results indicate that hucMSCs-Exo can effectively ameliorate psoriasis-like skin inflammation in mice by regulating the expression of IL-23 and IL-17, and inhibiting the maturation and activation of DCs. Our data offer a promising therapeutic approach for psoriasis by leveraging the immunomodulatory effects of hucMSCs-Exo.

Biologics in Psoriasis: Updated Perspectives on Long-Term Safety and Risk Management

Biologics targeting Th1/Th17 cytokines have revolutionised psoriasis treatment. In addition to treatment effectiveness, it is important to define and understand the long-term risks of biologic therapy in order to guide therapy selection and minimise these risks for patients where possible. This review article summarises available evidence from trial data, observational studies and pharmacovigilance registries to explore key long-term risks of biologic treatment, and how these risks might be managed in clinical practice.

Participation of interferons in psoriatic inflammation

Interferons are multifunctional cytokines not expressed in the skin under normal physiological conditions. However, they are overexpressed in serum and skin lesions of patients with psoriasis and play an important role in the pathogenesis of the disease. Interferons act directly on skin resident cells and recruit and modulate inflammatory cells, thereby exacerbating psoriatic inflammation. They upregulate the expression of relevant cytokines and chemokines, facilitate excessive proliferation of keratinocytes, and enhance the formation of poorly differentiated dermal microvessels. In this review, we summarized the pathogenic effect of interferons on psoriasis and also discussed the therapeutic strategies targeting interferons.

Coordinated glucocorticoid receptor and MAFB action induces tolerogenesis and epigenome remodeling in dendritic cells

Glucocorticoids (GCs) exert potent anti-inflammatory effects in immune cells through the glucocorticoid receptor (GR). Dendritic cells (DCs), central actors for coordinating immune responses, acquire tolerogenic properties in response to GCs. Tolerogenic DCs (tolDCs) have emerged as a potential treatment for various inflammatory diseases. To date, the underlying cell type-specific regulatory mechanisms orchestrating GC-mediated acquisition of immunosuppressive properties remain poorly understood. In this study, we investigated the transcriptomic and epigenomic remodeling associated with differentiation to DCs in the presence of GCs. Our analysis demonstrates a major role of MAFB in this process, in synergy with GR. GR and MAFB both interact with methylcytosine dioxygenase TET2 and bind to genomic loci that undergo specific demethylation in tolDCs. We also show that the role of MAFB is more extensive, binding to thousands of genomic loci in tolDCs. Finally, MAFB knockdown erases the tolerogenic properties of tolDCs and reverts the specific DNA demethylation and gene upregulation. The preeminent role of MAFB is also demonstrated in vivo for myeloid cells from synovium in rheumatoid arthritis following GC treatment. Our results imply that, once directly activated by GR, MAFB plays a critical role in orchestrating the epigenomic and transcriptomic remodeling that define the tolerogenic phenotype.

IL-30 ameliorates imiquimod and K14-VEGF induced psoriasis-like disease by inhibiting both innate and adaptive immunity disorders

Psoriasis is a severe skin disease with significant physical and psychological health consequences. As a typical type of immune disease, both innate and adaptive immunity disorders play key roles in the development of psoriasis. Interleukin (IL)-30 was thought as a natural antagonist of gp130-mediated signaling that affects T helper type 1 and 17 cell polarization by inhibiting IL-6 and IL-27 signaling pathways. Here, we found that, in vitro, IL-30 reduced cytokine levels of HaCaT keratinocytes and dendritic cells (DCs), weakened the maturationS of DCs, inhibited DC-mediated T cell proliferation, and blocked the activation of nuclear factor-κB. In vivo, IL-30 inhibited the development of skin disease in two animal models: Krt14-Vegfa and imiquimod (IMQ)-induced psoriasis-like skin disease. Thus, IL-30 may be useful as a therapeutic agent for controlling psoriasis.

Clinicoprognostic and Histopathological Features of Guttate and Plaque Psoriasis Based on PD-1 Expression

Several studies have determined the correlation between programmed cell death protein-1 (PD-1) and chronic plaque psoriasis (CPP). However, limited studies have assessed the association between PD-1 expression and the clinicoprognostic and distinct clinicopathological characteristics of CPP and guttate psoriasis (GP). Twenty-nine patients with skin biopsy-confirmed CPP were recruited at the Asan Medical Center between January 2018 and June 2020, and 33 patients with biopsy-confirmed GP were enrolled between January 2002 and June 2020. The clinicoprognostic and histopathological characteristics were analyzed according to immunohistochemical PD-1 expression in the epidermal or dermal inflammatory infiltrates. The CPP and GP lesions were divided into PD-1-low and PD-1-high groups. The CPP epidermal PD-1-high group had typical histopathological changes and significantly higher psoriasis area and severity index scores (p = 0.014) and disease duration (p = 0.009) than the epidermal PD-1-low group. In patients with GP, compared with the dermal PD-1-high group, the dermal PD-1-low group exhibited significantly higher disease duration (p = 0.002) and relapse rate of plaque psoriasis (p = 0.005) and significantly lower relapse-free survival (p = 0.016). Upregulated epidermal PD-1 expression was correlated with the chronicity and severity of CPP, while downregulated dermal PD-1 expression was correlated with poor prognosis of GP.

Pulmonary and blood dendritic cells from sarcoidosis patients more potently induce IFNγ-producing Th1 cells compared with monocytes

Sarcoidosis is a systemic inflammatory disease mainly affecting the lungs. The hallmark of sarcoidosis are granulomas that are surrounded by activated T cells, likely targeting the disease-inducing antigen. IFNγ-producing Th1 and Th17.1 T cells are elevated in sarcoidosis and associate with disease progression. Monocytes and dendritic cells (DCs) are antigen-presenting cells (APCs) and required for T cell activation. Several subsets of monocytes and DCs with different functions were identified in sarcoidosis. However, to what extent different monocyte and DC subsets can support activation and skewing of T cells in sarcoidosis is still unclear. In this study, we performed a transcriptional and functional side-by-side comparison of sorted monocytes and DCs from matched blood and bronchoalveolar lavage (BAL) fluid of sarcoidosis patients. Transcriptomic analysis of all subsets showed upregulation of genes related to T cell activation and antigen presentation in DCs compared with monocytes. Allogeneic T cell proliferation was higher after coculture with monocytes and DCs from blood compared with BAL and DCs induced more T cell proliferation compared with monocytes. After coculture, proliferating T cells showed high expression of the transcription factor Tbet and IFNγ production. We also identified Tbet and RORγt coexpressing T cells that mainly produced IFNγ. Our data show that DCs rather than monocytes from sarcoidosis patients have the ability to activate and polarize T cells towards Th1 and Th17.1 cells. This study provides a useful in vitro tool to better understand the contribution of monocytes and DCs to T cell activation and immunopathology in sarcoidosis.

Mitochondrial Reactive Oxygen Species Are Essential for the Development of Psoriatic Inflammation

Psoriasis is a common immune-mediated, chronic, inflammatory skin disease that affects approximately 2-3% of the population worldwide. Although there is increasing evidence regarding the essential roles of the interleukin (IL)-23/IL-17 axis and dendritic cell (DC)-T cell crosstalk in the development of skin inflammation, the contributions of mitochondrial function to psoriasis are unclear. In a mouse model of imiquimod (IMQ)-induced psoriasiform skin inflammation, we found that hematopoietic cell-specific genetic deletion of p32/C1qbp, a regulator of mitochondrial protein synthesis and metabolism, protects mice from IMQ-induced psoriatic inflammation. Additionally, we demonstrate that p32/C1qbp is an important regulator of IMQ-induced DC activation, both in vivo and in vitro. We also found that p32/C1qbp-deficient DCs exhibited impaired production of IL-1β, IL-23, and mitochondrial reactive oxygen species (mtROS) after IMQ stimulation. Because the inhibition of mtROS suppressed IMQ-induced DC activation and psoriatic inflammation, we presume that p32/C1qbp and mtROS can serve as therapeutic targets in psoriasis.

Enhanced NF-κB signaling in type-2 dendritic cells at baseline predicts non-response to adalimumab in psoriasis

Biologic therapies have transformed the management of psoriasis, but clinical outcome is variable leaving an unmet clinical need for predictive biomarkers of response. Here we perform in-depth immunomonitoring of blood immune cells of 67 patients with psoriasis, before and during therapy with the anti-TNF drug adalimumab, to identify immune mediators of clinical response and evaluate their predictive value. Enhanced NF-κBp65 phosphorylation, induced by TNF and LPS in type-2 dendritic cells (DC) before therapy, significantly correlates with lack of clinical response after 12 weeks of treatment. The heightened NF-κB activation is linked to increased DC maturation in vitro and frequency of IL-17⁺ T cells in the blood of non-responders before therapy. Moreover, lesional skin of non-responders contains higher numbers of dermal DC expressing the maturation marker CD83 and producing IL-23, and increased numbers of IL-17⁺ T cells. Finally, we identify and clinically validate LPS-induced NF-κBp65 phosphorylation before therapy as a predictive biomarker of non-response to adalimumab, with 100% sensitivity and 90.1% specificity in an independent cohort. Our study uncovers important molecular and cellular mediators underpinning adalimumab mechanisms of action in psoriasis and we propose a blood biomarker for predicting clinical outcome.

Myeloid Dendritic Cells Are Major Producers of IFN-β in Dermatomyositis and May Contribute to Hydroxychloroquine Refractoriness

Dermatomyositis pathogenesis remains incompletely understood; however, recent work suggests a predominant IFN-1 response. We explored dermatomyositis pathogenesis by quantifying the inflammatory cells in the skin, comparing myeloid with plasmacytoid dendritic cell release of IFN-β, and assessing myeloid dendritic cell (mDC) contribution to hydroxychloroquine refractoriness. Immunohistochemistry was performed to assess cell-type expression in lesional skin biopsies from 12 patients with moderate-to-severe cutaneous dermatomyositis. Immunofluorescence, laser-capture microdissection, and flow cytometry were used to assess mDC release of IFN-β in lesional skin biopsies and blood of patients with dermatomyositis. Immunohistochemistry was utilized to determine whether myeloid or plasmacytoid dendritic cells were increased in hydroxychloroquine nonresponders. CD4+, CD11c+, and CD69+ cells were more populous in lesional skin of patients with dermatomyositis. mDCs colocalized with IFN-β by immunofluorescence and laser-capture microdissection revealed increased IFN-β mRNA expression by mDCs in lesional skin of patients with dermatomyositis. In blood, both mDCs and plasmacytoid dendritic cells were major producers of IFN-β in patients with dermatomyositis, whereas plasmacytoid dendritic cells predominately released IFN-β in healthy controls (P < 0.01). mDCs were significantly increased in the skin of hydroxychloroquine nonresponders compared with that in the skin of responders (P < 0.05). mDCs cells appear to play an important role in dermatomyositis pathogenesis and IFN-β production.

Potential Therapeutic Approaches through Modulating the Autophagy Process for Skin Barrier Dysfunction

Autophagy is an attractive process to researchers who are seeking novel potential treatments for various diseases. Autophagy plays a critical role in degrading damaged cellular organelles, supporting normal cell development, and maintaining cellular homeostasis. Because of the various effects of autophagy, recent human genome research has focused on evaluating the relationship between autophagy and a wide variety of diseases, such as autoimmune diseases, cancers, and inflammatory diseases. The skin is the largest organ in the body and provides the first line of defense against environmental hazards, including UV damage, chemical toxins, injuries, oxidative stress, and microorganisms. Autophagy takes part in endogenous defense mechanisms by controlling skin homeostasis. In this manner, regulating autophagy might contribute to the treatment of skin barrier dysfunctions. Various studies are ongoing to elucidate the association between autophagy and skin-related diseases in order to find potential therapeutic approaches. However, little evidence has been gathered about the relationship between autophagy and the skin. In this review, we highlight the previous findings of autophagy and skin barrier disorders and suggest potential therapeutic strategies. The recent research regarding autophagy in acne and skin aging is also discussed.

Depression and Obesity in Patients With Psoriasis and Psoriatic Arthritis: Is IL-17-Mediated Immune Dysregulation the Connecting Link?

Patients with psoriasis are frequently obese and experience anxiety or suffer from depressive disorders. The immunopathogenesis of psoriasis and indeed psoriatic arthritis is largely based on the pivotal role of IL-17/IL-23 axis, to an extent that currently monoclonal antibodies selectively inhibiting IL-17 or IL-23 are routinely used for the treatment of psoriatic diseases. Emerging data, demonstrating a decisive role for IL-17 and IL-17 producing cell subsets, such as Th17 in the induction and progression of obesity and depression has led authors to suggest that psoriatic disease, obesity and anxiety/depression may indeed be interconnected manifestation of a state of immunedysregulation, the linked being IL-17 and its related cells. We discuss this hypothetical link in depth taking into account the beneficial effects anti-IL17 and anti-IL-17 receptor inhibitors in treating psoriatic disease and the on-going debate as to whether these biologics may exert a direct or indirect effect in ameliorating concomitant obesity and depressive disorders, which are frequently noted in the same patient.

Thrombosis in Psoriasis: Cutaneous Cytokine Production as a Potential Driving Force of Haemostatic Dysregulation and Subsequent Cardiovascular Risk

Psoriasis (PsO) is a common T cell-mediated inflammatory disorder of the skin with an estimated prevalence of 2%. The condition manifests most commonly as erythematous plaques covered with scales. The aetiology of PsO is multifactorial and disease initiation involves interactions between environmental factors, susceptibility genes, and innate and adaptive immune responses. The underlying pathology is mainly driven by interleukin-17. In addition, various inflammatory mediators from specific T helper (T_H) cell subsets, namely T_H1, T_H17, and T_H22, are overexpressed in cutaneous lesions and may also be detected in the peripheral blood of psoriatic patients. Moreover, these individuals are also at greater risk, compared to the general population, of developing multiple comorbid conditions. Cardiovascular disease (CVD) has been recognised as a prominent comorbidity of PsO. A potential mechanism contributing to this association may be the presence of a hypercoagulable state in these individuals. Inflammation and coagulation are closely related. The presence of chronic, low-grade systemic inflammation may promote thrombosis – one of the major determinants of CVD. A pro-inflammatory milieu may induce the expression of tissue factor, augment platelet activity, and perturb the vascular endothelium. Altogether, these changes will result in a prothrombotic state. In this review, we describe the aetiology of PsO, as well as the pathophysiology of the condition. We also consider its relationship to CVD. Given the systemic inflammatory nature of PsO, we evaluate the potential contribution of prominent inflammatory mediators (implicated in PsO pathogenesis) to establishing a prothrombotic state in psoriatic patients.