Differential Inflammatory-Response Kinetics of Human Keratinocytes upon Cytosolic RNA- and DNA-Fragment Induction

Inhibition of RNase 7 by RNase inhibitor promotes inflammation and Staphylococcus aureus growth: Implications for atopic dermatitis

BACKGROUND

The antimicrobial ribonuclease RNase 7 is abundantly expressed in the epidermis of lesional skin of atopic dermatitis (AD). Host RNase inhibitor (RI) binds to RNase 7 and blocks its ribonuclease activity. This study aimed to evaluate the impact of RNase 7-RI interactions on AD.

METHODS

Cultured human primary keratinocytes, with siRNA-mediated downregulation of RNase 7 and RI, were stimulated with the synthetic RNA polyinosinic-polycytidylic acid (poly I:C). Induction of proinflammatory mediators was analyzed by real-time PCR and ELISA. RI expression in AD non-lesional and lesional skin biopsies and healthy controls was analyzed by real-time PCR and immunostaining. RI protein release in vivo on the AD skin surface was determined by western blot. Antimicrobial and ribonuclease assays were used to investigate the functional role of RI.

RESULTS

RNase 7 inhibited the RNA-induced expression of proinflammatory mediators in keratinocytes. Accordingly, downregulation of RNase 7 in keratinocytes enhanced RNA-mediated induction of proinflammatory mediators, whereas downregulation of RI had the opposite effect. RI was released by damaged keratinocytes and epidermis. In vivo expression and release of RI on the skin surface were enhanced in lesional AD skin. Rinsing solution from the surface of lesional AD skin blocked the ribonuclease activity of RNase 7. The anti-Staphylococcus aureus activity of RNase 7 was abrogated by RI.

CONCLUSIONS

Our data suggest a novel role of RI as a trigger factor of inflammation in AD by blocking the ribonuclease and antimicrobial activity of RNase 7, thereby enhancing RNA-mediated inflammation and S. aureus growth.

Ex vivo cytokine production in psoriatic disease: Towards specific signatures in cutaneous psoriasis and peripheral psoriatic arthritis

Objectives

Psoriatic arthritis (PsA) and cutaneous psoriasis (PsO) are different phenotypes of psoriatic disease (PsD), whose underlying specific mechanisms remain incompletely understood. As cytokines are key elements to induce and tune up immune responses to drive inflammatory diseases, our objective was to assess whether clinical features, disease phenotype and PsA and PsO activity were associated with a particular ex vivo cytokine production profile.

Methods

Forty-eight patients (37 PsA and 11 PsO) and 11 healthy subjects (HS) were studied. Cytokine production by peripheral blood mononuclear cells (PBMC) that were either unstimulated, or stimulated with LPS or anti-CD3/CD28 antibodies, were analysed by multiplex assay in the culture supernatants.

Results

Cytokine signature of PsD includes a high level of TNFα in supernatants of LPS-stimulated PBMC, higher levels of IL-6 and lower levels of IFN-γ and IL-17A after CD3-CD28 stimulation, as well as higher spontaneous IL-1RA and TNFα production compared to HS. High body mass index (BMI) was associated with lower levels of IL-1β, and metabolic syndrome with lower levels of IFN-γ after LPS stimulation. In PsD, dermatological activity was related with higher IL-17A level, while rheumatic activity was linked with lower levels of IFN-γ and TNFα. Comparing each PsD subtype to HS, IL-1β and IL-6 productions are higher when using LPS stimulation in PsO patients with higher levels of IL-1β and IL-1α in peripheral PsA patients after CD3/CD28 stimulation. LPS stimulation induced high levels of IL-17A in peripheral PsA compared to axial PsA. PsA patients with axial PsA share some features with PsO but shows a distinct cytokine pattern compared to peripheral PsA.

Conclusion

PsO and the different PsA subtypes exhibit distinct ex vivo cytokine production profiles and common features of the so-called PsD. Analysis of IL-1 cytokine family and IL-6 seems to be of particular interest to distinguish PsO and peripheral PsA since it depends on monocytes in PsO and T-lymphocytes in peripheral PsA. Peripheral cytokine profiles are influenced by rheumatic and dermatological activity of the disease, and also by metabolic syndrome features. Our results highlight the crucial role of immune cell interactions with different patterns of interaction depending on clinical phenotype.

Psoriasis-Associated Inflammatory Conditions Induce IL-23 mRNA Expression in Normal Human Epidermal Keratinocytes

Psoriasis is a multifactorial, chronic inflammatory skin disease, the development of which is affected by both genetic and environmental factors. Cytosolic nucleic acid fragments, recognized as pathogen- and danger-associated molecular patterns, are highly abundant in psoriatic skin. It is known that psoriatic skin exhibits increased levels of IL-23 compared to healthy skin. However, the relationship between free nucleic acid levels and IL-23 expression has not been clarified yet. To examine a molecular mechanism by which nucleic acids potentially modulate IL-23 levels, an in vitro system was developed to investigate the IL-23 mRNA expression of normal human epidermal keratinocytes under psoriasis-like circumstances. This system was established using synthetic nucleic acid analogues (poly(dA:dT) and poly(I:C)). Signaling pathways, receptor involvement and the effect of PRINS, a long non-coding RNA previously identified and characterized by our research group, were analyzed to better understand the regulation of IL-23 in keratinocytes. Our results indicate that free nucleic acids regulate epithelial IL-23 mRNA expression through the TLR3 receptor and specific signaling pathways, thereby, contributing to the development of an inflammatory milieu favorable for the appearance of psoriatic symptoms. A moderate negative correlation was confirmed between the nucleic-acid-induced IL-23 mRNA level and the rate of its decrease upon PRINS overexpression.

TRAF3 and NBR1 both influence the effect of the disease-causing CYLD(Arg936X) mutation on NF-κB activity

Recently described Hungarian and Anglo-Saxon pedigrees that are affected by CYLD cutaneous syndrome (syn: Brooke-Spiegler syndrome (BSS)) carry the same disease-causing mutation (c.2806C>T, p.Arg936X) of the cylindromatosis (CYLD) gene but exhibit striking phenotypic differences. Using whole exome sequencing, missense genetic variants of the TRAF3 and NBR1 genes were identified in the affected family members of the Hungarian pedigree that are not present in the Anglo-Saxon pedigree. This suggested that the affected proteins (TRAF3 and NBR1) are putative phenotype-modifying factors. An in vitro experimental system was set up to clarify how wild type and mutant TRAF3 and NBR1 modify the effect of CYLD on the NF-κB signal transduction pathway. Our study revealed that the combined expression of mutant CYLD(Arg936X) with TRAF3 and NBR1 caused increased NF-κB activity, regardless of the presence or absence of mutations in TRAF3 and NBR1. We concluded that increased expression levels of these proteins further strengthen the effect of the CYLD(Arg936X) mutation on NF-κB activity in HEK293 cells and may explain the phenotype-modifying effect of these genes in CYLD cutaneous syndrome. These results raise the potential that detecting the levels of TRAF3 and NBR1 might help explaining phenotypic differences and prognosis of CCS.

Diosmin restores the skin barrier by targeting the aryl hydrocarbon receptor in atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is an inflammatory chronic skin disease that is characterized by the dysfunction or lack of skin barrier proteins. Recent studies have proposed that the pharmacological upregulation of skin barrier proteins is an effective treatment for AD. Aryl hydrocarbon receptor (AhR) is a transcription factor that positively regulates the expression of skin barrier proteins upon its activation.

PURPOSE

This study aimed to identify AhR agonists from phytochemicals and investigate its effect on skin barrier restoration as well as its mechanisms of action in AD.

STUDY DESIGN

A publicly available assay database and HaCaT cells stably transduced with a luciferase gene driven by an AhR-target gene promoter (CYP1A1) were used to screen for the activity of AhR agonists from phytochemicals. Normal human epidermal keratinocytes (NHEKs) and a human skin equivalent (HSE) model were used to investigate the effect of AhR agonists on skin restoration and its underlying mechanisms.

METHODS

A Gaussia luciferase assaywas performed to screen for AhR agonist activity. Western blotting, qRT-PCR analysis, immunofluorescence, drug affinity responsive target stability assay, and siRNA-mediated AhR knockdown were performed in NHEKs. Hematoxylin and eosin staining was performed to measure epidermal thickness in the HSE model.

RESULTS

Diosmin, a potential AhR agonist derived from natural products, upregulated the expression of skin barrier proteins (filaggrin and loricrin) and their upstream regulator (OVOL1) in NHEKs. Diosmin treatment also increased epidermal thickness in the HSE model. In addition, incubating NHEKs with diosmin restored the expression of skin barrier proteins and mRNAs that were suppressed by Th2 cytokines and inhibited STAT3 phosphorylation that was induced by Th2 cytokines. Diosmin also upregulated the expression of NQO1, a negative regulator of STAT3. Immunofluorescence results showed that diosmin stimulated AhR nuclear translocation, and the drug affinity responsive target stability assay revealed that this phytochemical directly bound to AhR. Furthermore, AhR knockdown abolished diosmin-induced filaggrin and loricrin expression.

CONCLUSION

These results suggest that diosmin is a potential treatment for AD that targets AhR.

Enhanced Wound Healing- and Inflammasome-Associated Gene Expression in TNFAIP3-Interacting Protein 1- (TNIP1-) Deficient HaCaT Keratinocytes Parallels Reduced Reepithelialization

TNIP1 protein is a widely expressed, cytoplasmic inhibitor of inflammatory signaling initiated by membrane receptors such as TLRs which recognize pathogen-associated and damage-associated molecular patterns (PAMPs and DAMPs). Keratinocyte TNIP1 deficiency sensitizes cells to PAMPs and DAMPs promoting hyperresponsive expression and secretion of cytokine markers (e.g., IL-8 and IL-6) relevant to cases of chronic inflammation, like psoriasis, where TNIP1 deficiency has been reported. Here, we examined the impact of TNIP1 deficiency on gene expression and cellular responses (migration and viability) relevant to acute inflammation as typically occurs in wound healing. Using siRNA-mediated TNIP1 expression knockdown in cultured HaCaT keratinocytes, we investigated TNIP1 deficiency effects on signaling downstream of TLR3 agonism with low-concentration poly (I:C), a representative PAMP/DAMP. The combination of TNIP1 knockdown and PAMP/DAMP signaling disrupted expression of specific keratinocyte differentiation markers (e.g., transglutaminase 1 and involucrin). These same conditions promoted synergistically increased expression of wound-associated markers (e.g., S100A8, TGFβ, and CCN2) suggesting potential benefit of increased inflammatory response from reduced TNIP1 protein. Unexpectedly, poly (I:C) challenge of TNIP1-deficient cells restricted reepithelialization and reduced cell viability. In these cells, there was not only increased expression for genes associated with inflammasome assembly (e.g., ASC, procaspase 1) but also for A20, a TNIP1 partner protein that represses cell-death signaling. Despite this possibly compensatory increase in A20 mRNA, there was a decrease in phospho-A20 protein, the form necessary for quenching inflammation. Hyperresponsiveness to poly (I:C) in TNIP1-deficient keratinocytes was in part mediated through p38 and JNK pathways. Taken together, we conclude that TNIP1 deficiency promotes enhanced expression of factors associated with promoting wound healing. However, the coupled, increased potential priming of the inflammasome and reduced compensatory activity of A20 has a net negative effect on overall cell recovery potential manifested by poor reepithelialization and viability. These findings suggest a previously unrecognized role for TNIP1 protein in limiting inflammation during successful progression through early wound healing stages.

Cartilage Oligomeric Matrix Protein Negatively Influences Keratinocyte Proliferation via α5β1-Integrin: Potential Relevance of Altered Cartilage Oligomeric Matrix Protein Expression in Psoriasis

In psoriasis, nonlesional skin shows alterations at the dermal-epidermal junction compared with healthy skin. Cartilage oligomeric matrix protein (COMP) is part of the papillary dermis of healthy skin, and its expression has not yet been studied in psoriatic skin. In this study, we found that COMP localization extended deeper into the dermis and formed a more continuous layer in psoriatic nonlesional skin compared with healthy skin, whereas in psoriatic lesions, COMP showed a partially discontinuous deposition at the dermal-epidermal junction. COMP and β1-integrin showed strong colocalization in nonlesional skin, where the laminin layer within the basement membrane is discontinuous. In in vitro models, the presence of exogenous COMP decreased the proliferation rate of keratinocytes, and this proliferation-suppressing effect was diminished by blocking α5β1-integrin. Our results suggest that COMP can interact with α5β1-integrin of basal keratinocytes through the disrupted basement membrane, and this interaction might stabilize the epidermis in the nonlesional state by contributing to the suppression of keratinocyte proliferation. The antiproliferative effect of COMP is likely to be relevant to other skin diseases in which chronic nonhealing wounds are coupled with massive COMP accumulation.

The use of leukocytes' secretome to individually target biological therapy in autoimmune arthritis: a case report

Background

Biological agents have allowed remarkable improvement in controlling autoimmune arthropathies, although none of the numerous biologics readily available represent a universal treatment standard. Moreover, classical and genetic predictors are currently unsatisfactory to predict individual response to a biologic, and the best treatment selection is still based on a trial-and-error approach. Here, we report a clinical case demonstrating the usefulness of examining the leukocytes’ secretome of patients. We set up and standardized a protocol that examines a patient’s immune responses to establish the secretome of the blood mononuclear leukocytes and personalize the biotherapy.

Case presentation

A 24-year-old woman was diagnosed with active early rheumatoid arthritis. The initial treatment regimen (prednisone, methotrexate, hydroxychloroquine, naproxen) was inefficient, as well as the anti-TNF adalimumab. The diagnosis was revised as possible rheumatoid arthritis-like psoriatic arthritis and adalimumab was replaced by abatacept (IgG1 Fc-CTLA-4) to no avail. Five years later, abatacept was replaced by the anti-IL-12/IL-23 ustekinumab with no objective control over the symptoms. The patient was thus enrolled in a prospective study based on the quantification of cytokines secreted by peripheral blood leukocytes stimulated with well-known immune activators of pattern recognition receptors and cytokine signalling. The results of this study revealed that plasma concentrations of cytokines were similar between the patient and healthy donors. In comparison to leukocytes from healthy donors, the patient’s secretome showed a unique overproduction of IL-6. The anti-IL-6 receptor tocilizumab was, therefore, administered with a rapid improvement of her active psoriatic arthritis that remained dependent on low prednisone dosage. Clinical parameters progressively returned to normal levels and her quality of life was greatly improved, despite the major delay to begin the present personalized treatment.

Conclusions

An efficient way to effectively treat patients with complex autoimmune arthropathies, and avoid irreversible disability, is to know their leukocytes’ secretome to identify abnormally secreted cytokines and personalize their biotherapy, as exemplified by this case report.