The Role of Interleukin-10 Family Members in Inflammatory Skin Diseases. Understanding the mechanism of action of interferon lambda and interleukin-22 on human primary keratinocytes and dermal fibroblasts with a focus on healing responses in inflammatory skin diseases

Cutaneous lupus erythematosus (CLE) is an autoimmune disease that resolves with or without permanent scars depending on the subtype. Interferons (IFNs), including the skin specific IFNλ mainly activate STAT1, which results in inflammation in CLE and may play a significant role in scar formation in chronic discoid CLE. IL-22 activates STAT3 and it is emerging as a mediator with significant impact on normal wound repair, epidermal hyperproliferation and prevention of fibrosis. This work focussed on understanding the regulation and functional impact of IL-22 and IFNλ on skin cells. The counter-regulatory effect of IL-22 on the activities of IFNλ was assessed through downstream interferon stimulated genes (ISGs) expression in healthy and CLE keratinocytes. Cell proliferation and gap closure were investigated in skin resident cells using cell trace dye and scratch assay. Dermal fibroblasts were assessed for the presence of IFNλR1 and IL-22R1, downstream activities of the receptors. Results showed that IL-22 accelerated “scratch” closure in keratinocytes while IFNλ caused a delay in closure. IL-22 significantly downregulated IFNλ-induced chemokines expression in healthy, but not CLE keratinocytes. Reduced IL-22R1 expression and “STAT3 signature genes” was observed in CLE keratinocytes. A key finding of this project is that dermal fibroblasts respond to both IFNλ and IL-22. This work shows that IL-22 can reduce the damaging effect of IFNs in inflamed skin and also identifies dermal fibroblasts as important cells in skin immune responses. In conclusion, IL-10 family members can have both beneficial and destructive effects on the skin organ depending on the micro milieu and cell-type involved. Manipulating the balance of IL-10 family members in the skin may offer new therapeutic approach for both psoriasis and CLE.University of Bradford and Centre for Skin Science

IL-36γ has proinflammatory effects on human endothelial cells

Interleukin-36 cytokines are predominantly expressed by epithelial cells. Significant upregulation of epidermal IL-36 is now a recognised characteristic of psoriatic skin inflammation. IL-36 is known to induce inflammatory responses in dendritic cells, fibroblasts and epithelial cells. Although vascular alterations are a hallmark of psoriatic lesions and dermal endothelial cells are well known to play a critical role in skin inflammation, the effects of IL-36 on endothelial cells are unexplored. We here show that endothelial cells including dermal microvascular cells express a functionally active IL-36 receptor. Adhesion molecules VCAM-1 and ICAM-1 are upregulated by IL-36γ stimulation and this is reversed by the presence of the endogenous IL-36 receptor antagonist. IL-36γ stimulated endothelial cells secrete the proinflammatory chemokines IL-8, CCL2 and CCL20. Chemotaxis assays showed increased migration of T cells following IL-36γ stimulation of endothelial cells. These results suggest a role for IL-36γ in the dermal vascular compartment and it is likely to enhance psoriatic skin inflammation by activating endothelial cells and promoting leukocyte recruitment. This article is protected by copyright. All rights reserved

Antimicrobial peptide LL-37 facilitates intracellular uptake of RNA aptamer Apt 21-2 without inducing an inflammatory or interferon response

RNA aptamers are synthetic single stranded RNA oligonucleotides that function analogously to antibodies. Recently, they have shown promise for use in treating inflammatory skin disease as, unlike antibody-based biologics, they are able to enter the skin following topical administration. However, it is important to understand the inflammatory milieu into which aptamers are delivered, as numerous immune-modulating mediators will be present at abnormal levels. LL-37 is an important immune-modifying protein upregulated in several inflammatory skin conditions, including psoriasis, rosacea and eczema. This inflammatory antimicrobial peptide is known to complex nucleic acids and induce both inflammatory and interferon responses from keratinocytes. Given the attractive notion of using RNA aptamers in topical medication and the prevalence of LL-37 in these inflammatory skin conditions, we examined the effect LL-37 had on the efficacy and safety of the anti-IL-17A RNA aptamer, Apt 21-2. LL-37 was demonstrated to complex with the RNA aptamer by electrophoretic mobility shift and filter binding assays. In contrast to free Apt 21-2, LL-37-complexed Apt 21-2 was observed to efficiently enter both keratinocytes and fibroblasts by confocal microscopy. Despite internalisation of LL-37-complexed aptamers, measurement of inflammatory mediators and interferon stimulated genes showed LL-37-complexed Apt 21-2 remained immunologically inert in keratinocytes, fibroblasts, and peripheral blood mononuclear cells including infiltrating dendritic cells and monocytes. The findings of this study suggest RNA aptamers delivered into an inflammatory milieu rich in LL-37 may become complexed and subsequently internalised by surrounding cells in the skin. Whilst the results of this study indicate delivery of RNA aptamers into tissue rich in LL-37 should not cause an unwarranted inflammatory of interferon response, these results have significant implications for the efficacy of aptamers with regards to extracellular vs intracellular targets that should be taken into consideration when developing treatment strategies utilising RNA aptamers in inflamed tissue

Interleukin-33 modulates the expression of human β-defensin 2 in human primary keratinocytes and may influence the susceptibility to bacterial superinfection in acute atopic dermatitis.

noBackground  Interleukin (IL)-33 is a member of the IL-1 family and has been implicated in Th2-driven allergic diseases such as atopic dermatitis (AD) and asthma. The principal Th2 cytokine IL-4, found highly expressed in acute allergic eczema, is known to downregulate human β-defensin 2 (hBD2) expression in human keratinocytes and this is associated with superinfection in patients with AD. Objectives  To investigate the effect of IL-33 on the expression of hBD2 in human keratinocytes. Methods  hBD2 production by stimulated keratinocytes was measured by enzyme-linked immunosorbent assay. Results  Our results showed that serum is a very potent inducer of hBD2 and 2·5% human serum was much more potent in inducing hBD2 than 20 ng mL−1 of tumour necrosis factor-α. Interestingly, serum from patients with AD showed an impaired ability to induce hBD2 in normal keratinocytes. IL-33 significantly downregulated serum-induced hBD2. The downregulatory capacity of IL-33 was found to be 1·5- to 2-fold weaker compared with IL-4. Conclusions  Our data suggest that IL-33 can significantly contribute to the decreased expression of hBD2 in acute eczematous reaction clinically characterized by spongiosis and oozing – thus indicative for contact of the epidermis with serum components

Gene expression and autoantibody analysis reveals distinct ancestry-specific profiles associated with response to rituximab in refractory systemic lupus erythematosus

Objective Gene expression profiles are associated with the clinical heterogeneity of SLE but are not well studied as biomarkers for therapy. Many clinical and demographic features influence treatment responses. We studied gene expression and response to rituximab in a multi-ethnic UK cohort refractory to standard therapy. Methods Baseline expression of transcripts known to associate with clinical features of SLE was evaluated in whole blood by 96-probe Taqman® array in patients (n=213) with active SLE, prospectively enrolled in British Isles Lupus Assessment Group (BILAG) Biologics Registry. Autoantibodies were measured using immunoprecipitation and ELISA. Response to first cycle rituximab (n=110) was determined by BILAG-2004 criteria at 6 months. Results Interferon scores were lower in European ancestry patients than all other groups. The relationship between blood interferon scores and plasmablast, neutrophil, myeloid, inflammation and erythropoiesis-annotated scores differed between patients of European and non-European ancestries. Hierarchical clustering revealed 3 distinct non-European ancestry patient subsets with stratified response to rituximab which was not explained by sociodemographic and clinical variables. Response was lowest in an interferon-low, neutrophil-high cluster and highest in a cluster with high expression across all signatures (p<0.001). Clusters within European ancestry patients did not predict response to rituximab but segregated patients by global disease activity and renal involvement. In both ancestral groups, interferon-high clusters associated with U1RNP-Sm antibodies. Conclusion Ancestry appears central to the immunological and clinical heterogeneity in SLE. These results suggest that ancestry, disease activity and transcriptional signatures could each assist predict the effectiveness of B-cell depletion

IFNλ stimulates MxA production in human dermal fibroblasts via a MAPK-dependent STAT1-independent mechanism

Interferon lambda (IFNλ) is important for epidermal defence against viruses. It is produced by, and acts on, keratinocytes, whereas fibroblasts were previously considered to be unresponsive to this type III IFN. Herein we report findings revealing cell type-specific differences in IFNλ signalling and function in skin resident cells. In dermal fibroblasts, IFNλ induced the expression of MxA, a potent antiviral factor, but not other IFN signature genes as it does in primary keratinocytes. In contrast to its effect on keratinocytes, IFNλ did not phosphorylate STAT1 in fibroblasts, but instead activated MAPKs. Accordingly, inhibition of MAPK activation (p38 and p42/44) blocked the expression of MxA protein in fibroblasts but not in keratinocytes. Functionally, IFNλ inhibited proliferation in keratinocytes but not in fibroblasts. Moreover, IFNλ upregulated the expression of TGFβ1-induced collagens in fibroblasts. Taken together, our findings identify primary human dermal fibroblasts as responder cells to IFNλ. Our study shows cutaneous cell type-specific IFN signalling and suggests that IFNλ, whilst important for epidermal anti-viral competence, may also have a regulatory role in the dermal compartment balancing type I IFN-induced inhibition of tissue repair processes.Journal of Investigative Dermatologyaccepted article preview online, 19 August 2015. doi:10.1038/jid.2015.317