Activation of myeloid dendritic cells, effector cells and regulatory T cells in lichen planus

Lichen Planus: What is New in Diagnosis and Treatment?

Lichen planus (LP), an idiopathic, multifaceted chronic inflammatory disease with a heterogeneous clinical presentation, affects approximately 0.5-1% of the population. The various clinical manifestations of LP fall into three broad categories, namely cutaneous, appendageal, and mucosal, with further subclassification depending on the morphology and distribution patterns of individual lesions. There is mounting evidence that LP has systemic associations, including autoimmune conditions, glucose intolerance, dyslipidemia, and cardiovascular disorders. Cutaneous hypertrophic and mucosal forms of LP are at a heightened risk for malignant transformation. Familiarity with these potential associations in conjunction with long-term follow-up and regular screening could lead to a timely diagnosis and management of concomitant conditions. In addition, the frequent quality of life (QoL) impairment in LP underscores the need for a comprehensive approach including psychological evaluation and support. Several treatment strategies have been attempted, though most of them have not been adopted in clinical practice because of suboptimal benefit-to-risk ratios or lack of evidence. More recent studies toward pathogenesis-driven treatments have identified Janus kinase inhibitors such as tofacitinib, phosphodiesterase-4 inhibitors such as apremilast, and biologics targeting the interleukin-23/interleukin-17 pathway as novel therapeutic options, resulting in a dramatic change of the treatment landscape of LP. This contemporary review focuses on the diagnosis and management of LP, and places emphasis on more recently described targeted treatment options.

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 attentive focus on T cell-mediated autoimmune pathogenesis of psoriasis, lichen planus and vitiligo

T cell-mediated autoimmune skin diseases develop as a result of the aberrant immune response to the skin cells with T cells playing a central role. These chronic inflammatory skin diseases encompass various types including psoriasis, lichen planus and vitiligo. These diseases show similarities in their immune-pathophysiology. In the last decade, immunomodulating agents have been very successful in the management of these diseases thanks to a better understanding of the pathophysiology. In this review, we will discuss the immunopathogenic mechanisms and highlight the role of T lymphocytes in psoriasis, lichen planus and vitiligo. This study could provide new insights into a better understanding of targeted therapeutic pathways and biological therapies.

Staphylococcal enterotoxins modulate the effector CD4+ T cell response by reshaping the gene expression profile in adults with atopic dermatitis

Staphylococcus aureus colonizes the skin of atopic dermatitis (AD) individuals, but the impact of its enterotoxins on the chronic activation of CD4⁺ T cells demands further analysis. We aimed to analyze the CD4⁺ T cell anergy profile and their phenotypic and functional features through differential expression of cellular activation markers, cytokine production and response to staphylococcal enterotoxin A (SEA). A panel of 84 genes relevant to T cell anergy was assessed by PCR array in FACS-sorted CD4⁺ T cells, and the most prominent genes were validated by RT-qPCR. We evaluated frequencies of circulating CD4⁺ T cells secreting single or multiple (polyfunctional) cytokines (IL-17A, IL-22, TNF, IFN-γ, and MIP-1β) and expression of activation marker CD38 in response to SEA stimulation by flow cytometry. Our main findings indicated upregulation of anergy-related genes (EGR2 and IL13) promoted by SEA in AD patients, associated to a compromised polyfunctional response particularly in CD4⁺CD38⁺ T cells in response to antigen stimulation. The pathogenic role of staphylococcal enterotoxins in adult AD can be explained by their ability to downmodulate the activated effector T cell response, altering gene expression profile such as EGR2 induction, and may contribute to negative regulation of polyfunctional CD4⁺ T cells in these patients.

Lichen planus and lichenoid dermatoses: Clinical overview and molecular basis

Deriving from the Greek word λειχήν for "tree moss" and the Latin word planus for "planar," lichen planus is a relatively uncommon and heterogeneous cutaneous disorder that typically develops in middle-aged adults. Despite the significant clinical burden associated with the disorder, little well-conducted molecular research has been undertaken, possibly because of heterogeneity impeding consistent and confident phenotyping. The multiple variants of lichenoid disease bear overlapping clinical and pathologic features despite manifesting as distinct clinical disorders. The first article in this 2-part continuing medical education series provides a comprehensive overview of the clinical and pathologic characteristics of cutaneous lichenoid dermatoses and links these manifestations to recent advances in our understanding of the underlying pathobiology of such diseases.

Matrine alleviates imiquimod-induced psoriasiform dermatitis in BALB/c mice via dendritic cell regulation

Matrine, is a bioactive compound isolated from Sophora flavescens (Ku shen), an herb used in Chinese traditional medicine that possesses wide-reaching pharmacological action. Psoriasis is a chronic relapsing inflammatory disorder with an incompletely understood pathophysiology, and dendritic cells (DCs) play a central role in the disease. This study aimed to explore DCs related potential mechanisms based on the effect of matrine on imiquimod (IMQ)-induced psoriasiform dermatitis in BALB/c mice and DCs simulated by resiquimod. Mice with IMQ-induced psoriasiform cutaneous lesions were treated with matrine [12.5, 25 or 50 mg/(kg·d), for 6 days]. Morphology, histological changes, keratinocyte proliferation and differentiation, inflammatory cell infiltration, protein expression levels of myeloid differentiation factor 88 (MyD88), and mRNA expression levels of inflammatory factors [interleukin (IL)-12, IL-23, and IL-1β] in lesional skin were assessed. The application of matrine decreased the proliferation of IMQ-induced keratinocytes. The treatment attenuated the infiltration of PCNA⁺ and CD3⁺ cells in the lesions. Matrine reduced the expression of the MyD88 protein and the inflammatory factors' mRNA in lesional skin, but also in BMDCs (bone marrow derived dendritic cells). These results indicated that matrine suppressed expression of the inflammatory factors by decreasing the expression of the MyD88 protein on the surface of BMDCs, finally alleviating psoriasiform skin lesions. Therefore, the findings suggest that matrine might be a potential candidate for treating psoriasis.

The measurement of serum TNF-α levels in patients with lichen planus

BACKGROUND

Lichen planus is a common mucocutaneous inflammatory skin disease with a multifactorial etiology. Cytokines play a key role in lichen planus pathogenesis. This study investigates the relationship between disease severity and levels of tumor necrosis factor-α (TNF-α), which is considered a primary cytokine that initiates cytotoxicity.

MATERIAL AND METHODS

Serum TNF-α levels were compared between a patient group (n = 34) and a control group (n = 20). TNF-α serum levels were measured using human TNF-α Enzyme-Linked Immunosorbent Assay (ELISA) test kits, and the two groups were statistically compared to each other.

RESULTS

Mean serum TNF-α levels were found to be significantly higher in the patient group than in the control group (p < 0.005). However, no significant association was observed between TNF-α levels and oral mucosal involvement (p > 0.005). No relationship was detected between TNF-α levels and patients' sex.

CONCLUSION

It is thought that TNF-α, a proinflammatory cytokine, may play an important role in the pathogenesis of lichen planus. TNF-α may be a simple and effective predictor to illustrate the inflammatory status in patients with lichen planus.

Paeonol ameliorates imiquimod-induced psoriasis-like skin lesions in BALB/c mice by inhibiting the maturation and activation of dendritic cells

Paeonol, an active component derived from the traditional Chinese medicine Cortex Moutan, possesses anti-inflammatory, analgesic, antioxidant and anti-allergic properties. Psoriasis is a chronic, recurrent, inflammatory dermatosis accompanied by excessive activation of Toll-like receptors (TLRs) in dendritic cells (DCs), which are primarily responsible for initiating an immune response. We investigated the effect of paeonol on inflammation in an imiquimod (IMQ)-induced psoriasis-like mouse model and murine bone marrow-derived dendritic cells (BMDCs) stimulated by R848. Mice were intragastrically administered 100 mg/kg (high), 50 mg/kg (medium) and 25 mg/kg (low) paeonol, respectively. We evaluated inflammation of psoriasis-like lesions based on histological changes, protein levels of myeloid differentiation factor 88 (MyD88) and TLR8 in skin lesions by western blotting, and levels of CD11c⁺ DCs in skin by immunoassay and in spleens by flow cytometry. Inflammatory cytokines [interleukin (IL)-23, IL-12 and IL-1β] in skin lesions and BMDCs were also assessed by RT-PCR and ELISA. Application of paeonol decreased IMQ-induced keratinocyte proliferation, and infiltration of CD3⁺ cells, while the treatment ameliorated CD11c⁺ cells in the spleen and skin, and reduced MyD88 and TLR8 proteins in skin lesions. Paeonol inhibited IMQ-induced mRNA expression of IL-23, but not IL-12 and IL-1β in BMDCs, along with significantly lower levels of DCs expressing MHCII, CD80 and CD86 in vitro. These results indicate that paeonol suppresses the maturation and activation of DCs by decreasing MyD88 and TLR8 proteins in the TLR7/8 signaling pathway which finally alleviates psoriasis-like skin lesions. The TLR7/8 signaling pathway in DCs provides an important insight into the mechanism of psoriasis, and paeonol may be a potent therapeutic drug for psoriasis.