Psoriasis is a visible manifestation of the skin's defense against micro-organisms

Identification of gene signatures and molecular mechanisms underlying the mutual exclusion between psoriasis and leprosy

Leprosy and psoriasis rarely coexist, the specific molecular mechanisms underlying their mutual exclusion have not been extensively investigated. This study aimed to reveal the underlying mechanism responsible for the mutual exclusion between psoriasis and leprosy. We obtained leprosy and psoriasis data from ArrayExpress and GEO database. Differential expression analysis was conducted separately on the leprosy and psoriasis using DEseq2. Differentially expressed genes (DEGs) with opposite expression patterns in psoriasis and leprosy were identified, which could potentially involve in their mutual exclusion. Enrichment analysis was performed on these candidate mutually exclusive genes, and a protein-protein interaction (PPI) network was constructed to identify hub genes. The expression of these hub genes was further validated in an external dataset to obtain the critical mutually exclusive genes. Additionally, immune cell infiltration in psoriasis and leprosy was analyzed using single-sample gene set enrichment analysis (ssGSEA), and the correlation between critical mutually exclusive genes and immune cells was also examined. Finally, the expression pattern of critical mutually exclusive genes was evaluated in a single-cell transcriptome dataset. We identified 1098 DEGs in the leprosy dataset and 3839 DEGs in the psoriasis dataset. 48 candidate mutually exclusive genes were identified by taking the intersection. Enrichment analysis revealed that these genes were involved in cholesterol metabolism pathways. Through PPI network analysis, we identified APOE, CYP27A1, FADS1, and SOAT1 as hub genes. APOE, CYP27A1, and SOAT1 were subsequently validated as critical mutually exclusive genes on both internal and external datasets. Analysis of immune cell infiltration indicated higher abundance of 16 immune cell types in psoriasis and leprosy compared to normal controls. The abundance of 6 immune cell types in psoriasis and leprosy positively correlated with the expression levels of APOE and CYP27A1. Single-cell data analysis demonstrated that critical mutually exclusive genes were predominantly expressed in Schwann cells and fibroblasts. This study identified APOE, CYP27A1, and SOAT1 as critical mutually exclusive genes. Cholesterol metabolism pathway illustrated the possible mechanism of the inverse association of psoriasis and leprosy. The findings of this study provide a basis for identifying mechanisms and therapeutic targets for psoriasis.

Psoriasis and Leprosy: An Arcane Relationship

Purpose

Psoriasis (Ps) and leprosy are chronic inflammatory skin disorders, characterised by enhanced innate and adaptive immunity. Ps and leprosy rarely coexist. The molecular immune mechanism of the Ps and leprosy rarely coexistence is unclear.

Patients and Methods

RNA-sequencing (RNA-seq) was performed on 20 patients with Ps, 5 adults with lepromatous leprosy (L-lep), and 5 patients with tuberculoid leprosy (T-lep) to analyse the differentially expressed genes (DEGs) between them. Moreover, the biological mechanism of Ps and leprosy was explored by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, Gene Ontology (GO) analysis, Gene Set Enrichment Analysis analysis, and protein-protein interaction (PPI) analyses. Finally, 13 DEGs of 10 skin biopsies of Ps patients, 6 samples of L-lep patients, 6 samples of T-lep patients and 5 healthy controls were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The PPI network was constructed and primarily associated with immune response, IL-17 signalling, and Toll-like receptor pathway between Ps and leprosy. Th17 markers (interleukin (IL)-19, IL-20, IL-36A, IL-36G, IL-22, IL-17A, and lipocalin-2 (LCN2) had higher expression in Ps than in L-lep and T-lep, whereas macrophage biomarkers (CLEC4E and TREM2), SPP1, and dendritic cell (DC)-related hallmarks (ITGAX) and TNF-a had significantly lower expression across Ps and T-lep than in L-lep.

Conclusion

To put it simply, Ps patients with IL-17A, IL-19, IL-20, IL-36A, IL-36G, and IL-22 in conjunction with LCN2 with up-graduated expression might be not susceptible to L-lep. However, high levels of CLEC4E, TREM2, and SPP1 in L-lep patients indicated that they unlikely suffered from Ps.

Psoriasis with a dirt-adherent: A rare case report

Cutaneous dirt-adherent disease (CDAD) is a rare psychogenic dermatosis mainly occurring in young Japanese and Chinese women. It mainly occurs on cheeks, forehead, nipple, mammary areola and around mammary areola. To our knowledge, this is the first case of CDAD with the skin lesion of psoriasis rupioides to be reported. In our case, the patient, a 43-year-old Chinese man presented with thick, yellowish-brown adherent crusts on his face with severe painful 6-days duration. Histopathologic image: Parakeratosis, the epidermis demonstrates regular acanthosis with some thinning of the suprapapillary plates, neutrophils exocytosis are noted. As for the histopathologic diagnosis in his right crus, combined with the clinical manifestation of rupioides-shaped crusts, film phenomenon and Auspitz's sign, we considered Psoriasis rupioide.

Evaluation of candidal colonization and specific humoral responses against Candida albicans in patients with psoriasis

BACKGROUND

Psoriasis is an inflammatory skin disease that can considerably affect a patient's quality of life. Environmental and genetic factors, as well as superantigens and toxins from Candida species, may play various roles in the exacerbation and persistence of psoriasis. In the present study, we evaluated candidal colonization and specific humoral responses against Candida albicans in patients with psoriasis.

METHODS

A total of 100 patients with psoriasis vulgaris and 50 healthy control individuals were enrolled in the study. Skin and oral specimens from all participants were cultured on CHROMagar Candida medium. Isolated yeast-like fungi were identified using the sequence of the D1/D2 domain of the 26S rRNA gene. Enzyme-linked immunosorbent assays (ELISAs) were used to detect immunoglobulin M (IgM), IgA, and IgG antibodies against C. albicans in sera of patients and healthy individuals.

RESULTS

Candida species were isolated from the skin of 15% of patients and 4% of controls and from oral specimens of 60% of patients and 20% of controls. There was a significant difference in candidal colonization between patients and controls (P < 0.05). Serum IgM, IgA, and IgG levels against C. albicans were significantly lower in patients with psoriasis than in controls (P < 0.05). There was no significant association between serum levels of specific antibodies against C. albicans or the frequency of candidal colonization with the clinical severity of the disease (P > 0.05).

CONCLUSIONS

The results of the present study show a higher rate of candidal colonization in patients with psoriasis in comparison with controls and a reduction in humoral immune responses in patients.

Immunopathogenesis of psoriasis

This paper reviews the pathogenesis of psoriasis, in particular, the immunological cascade in psoriasis. Psoriasis is an immune-mediated skin disease where the T cell plays a pivotal role in the pathogenesis of the disease. The critical steps involved in the pathogenesis include Langerhans cell activation and maturation by antigens in the skin, activation of the T cell by mature Langerhans cells, differentiation and expansion of T cells within the lymph nodes, trafficking of activated T cells from the lymph node to the skin and the subsequent release of cytokines. These cytokines are responsible for epidermal and vascular hyperproliferation and pro-inflammatory effects. Each of these steps provides an opportunity for biological agents designed to block the psoriatic immunological cascade. This paper reviews the immunopathogenesis of psoriasis. Biologic agents in psoriasis, to be published separately, reviews the new biologic therapies that aim to selectively block the immunological steps implicated in the pathogenesis of psoriasis outlined in this paper.

Skin basement membrane zone: a depository for circulating microbial antigen evoking psoriasis and autoimmunity

BACKGROUND

Elevated levels of antibody to streptococcal exoenzymes have been found in patients with psoriasis or psoriatic arthritis. Research on the role of streptococcal antigen in psoriasis has been hampered by a potential molecular mimicry between streptococcal epitopes and human epidermal keratin.

OBJECTIVE AND METHODS

Evidence of microbial product was sought in skin biopsies of psoriasis patients thought clinically to have either streptococcal carrier state or gastrointestinal candidal colonization. A polyclonal antibody to streptococcal-derived exoenzymes unlikely to share antigenic structures with normal human skin, and an anticandidal antibody, were used with linked streptavidin biotin amplification stain.

RESULTS

The predicted microbial product appeared heavily in lesional epidermis, but unexpectedly also as a thin deposit along the skin basement membrane zone (SBMZ) of apparently unaffected skin. Staining was negative for nonpsoriatic subjects.

CONCLUSIONS

The findings support a direct effect of microbial antigen in psoriasis. They also suggest an important role for SBMZ as a very large adhesive surface in the first step of a process of percutaneous epidermal elimination of foreign antigens and microbial toxins. The many autoimmune phenomena seen so often at the SBMZ are probably a physiologic part of this important immune function. Efforts to enhance the adhesive properties of SBMZ should be exploitable for both diagnostic and therapeutic benefit.

A new therapeutic approach to treat psoriasis by inhibition of fatty acid oxidation by Etomoxir

BACKGROUND

The dogma in psoriasis is that due to pathogen-induced inflammatory responses, an autoreactive immune response is induced that leads to tissue destruction. However, this model might be too simplistic. Literature data suggest that the expression of enzymes crucial for fatty acid oxidation is upregulated in the skin of patients with psoriasis compared with healthy individuals.

OBJECTIVES

To examine the influence of fatty acid oxidation on psoriasis with regard to expression and activity of the key enzyme in fatty acid oxidation, carnitine palmitoyltransferase-1 (CPT-1) and the effect of the CPT-1 inhibitor, Etomoxir.

METHODS

Experiments were performed with homogenates of lesional and healthy skin, fibroblast cultures and a model of human psoriatic skin transplanted on immune-deficient BNX mice.

RESULTS

CPT-1 was highly active in lesional skin. Etomoxir was able to block CPT-1 activity in skin, implying that this antagonist may have the potential to suppress psoriasis when administered topically. In the mouse model, Etomoxir had an antipsoriatic effect that was at least as good as that of betamethasone, as evidenced by reduction of epidermal thickness, keratinocyte proliferation and differentiation.

CONCLUSIONS

We conclude that fatty acid metabolism and in particular CPT-1 may be an excellent target for treatment of psoriasis.

Innate immune-related receptors in normal and psoriatic skin

CONTEXT

A precise role for the innate immune system in psoriasis remains to be determined. Surface receptors, including Toll-like receptors (TLRs) that recognize bacterial ligands and CD91, which recognizes heat shock proteins (HSPs), are implicated in both innate and adaptive immunity.

OBJECTIVE

Since skin is exposed to various exogenous stimuli, which can provoke or exacerbate psoriasis, we characterized expression and function of TLRs, CD91, and HSPs in normal and psoriatic skin.

DESIGN

A variety of skin-derived cells and blood-derived cells were analyzed both in vivo and in vitro; samples were obtained from 24 different individuals for innate immune-related receptor expression and function. By comparing and contrasting individuals with healthy skin and psoriatic patients, several specific differences were identified.

RESULTS

Immunohistochemistry-based expression profiling revealed TLR1 expression in epidermal dendritic cells (DCs) and dermal dendritic cells (DDCs) in normal skin, as well as in pre-psoriatic skin and psoriatic plaques, with enhanced basal layer keratinocyte (KC) expression in pre-psoriatic and psoriatic plaques compared with normal skin; TLR2 expression primarily by DDCs; and TLR4 expression by epidermal DCs and DDCs, with mid-epidermal-layer KCs displaying cell surface staining. No TLR9 or CD14 was detected on DCs or KCs, although psoriatic plaques contained CD14-positive macrophages. Analysis of psoriatic epidermis revealed HSPs 27, 60, and 70. Keratinocytes were CD91 negative, but CD91 was expressed by fibroblasts and DDCs in normal and pre-psoriatic skin, with prominent accumulation of CD91-positive DDCs in psoriatic plaques. Cultured KCs revealed no surface expression of TLR2, TLR4, TLR9, or CD91. Exposure of fibroblasts, but not KCs, to lipopolysaccharide or HSPs triggered nuclear factor (NF)-kappaB activation. Heat shock proteins did induce maturation of blood-derived DCs accompanied by increased interleukin-12 production and enhanced antigen-presenting function.

CONCLUSIONS

These data demonstrate distinctive patterns of innate immune-related receptors by specific subsets of cells in normal and psoriatic skin, suggesting functional roles for HSPs and DCs in psoriasis.

Papulosquamous disorders of the elderly

Several papulosquamous skin conditions occur in the elderly, including inherited and acquired ichthyoses, psoriasis, cutaneous lymphoma, and cutaneous connective tissue diseases. The clinical presentations can be quite helpful in diagnosing these conditions, and confirmatory histology and immunologic testing can often better define the specific entities. Treatment often involves identifying underlying systemic causes, as well as specific approaches based on the diagnosis and severity of clinical presentation.

Interactions between non-immune host cells and the immune system during periodontal disease: role of the gingival keratinocyte

Periodontal disease and inflammatory dermatoses, such as psoriasis, are characterized by the accumulation of dense inflammatory infiltrates immediately beneath the epithelial cell layer of the gingiva and skin, respectively. Dermatologists are increasingly aware that the epidermal keratinocyte probably contributes to inflammatory disease progression by secreting a number of pro-inflammatory cytokines and expressing various adhesion molecules. In psoriatic lesions, it is now believed that epidermal keratinocytes may also act as antigen-presenting cells and participate directly in the superantigenic activation of T-cell clones, some of which may initiate, contribute to, or maintain the disease process. Although the role of the host response in periodontal disease has been extensively studied over the years, very little is known about the contribution of the gingival keratinocyte to the inflammatory response. The available published information is discussed in this review, and we suggest that, like its epidermal counterpart, the gingival keratinocyte may participate actively in the pathogenesis of periodontal disease.

[Mycoses in patients with psoriasis or atopic dermatitis]

Both, psoriasis and atopic dermatitis are multifactorial diseases with an unknown pathogenesis. To elucidate the influence of fungal infections in the onset or recurrence of those inflammatory skin disease we determined the frequencies of Candida and dermatophyte infections of the skin and orointestinal tract concomitantly seen in patients with psoriasis or atopic dermatitis. We analyzed the files of more than 40,000 in-patients of the Department of Dermatology, Kiel. Sex- and age-adjusted relative risk were calculated. The results demonstrate that patients with psoriasis (N = 3006) presented with a decreased rate of tinea. This was significant for tinea corporis (RR = 0.13, p < 0.01). Candida infections of the skin were seen more often in psoriasis patients compared to controls. Differentiating between Type I (early onset) and Type II (late onset) psoriasis only Type I psoriasis patients presented with decreased dermatophyte infections and increased Candida colonization of the intestinum. However, patients with Type II psoriasis demonstrated an increased rate of candidosis cutis and candidosis oris as compared to controls. Patients with atopic dermatitis (N = 1808) displayed a decreased overall incidence of tinea and Candida infections. Furthermore, in patients with atopic dermatitis a Candida colonization of the orointestinal tract was found elevated (RR = 1.51, p < 0.01), whereas tinea corporis (RR = 0.24, p < 0.01) and candidosis cutis (RR = 0.30, p < 0.001) was found decreased compared to controls. Our results show that the influence of fungal infections on the two skin diseases investigated is not as strong as often considered. The increased relative risk in patients with atopic dermatitis to present with Candida colonization in the digestive tract or vice versa may contribute to the pathogenesis of atopic dermatitis.