IL-17 and IL-22 Promote Keratinocyte Stemness in the Germinative Compartment in Psoriasis.

Psoriasis is an inflammatory skin disorder characterized by the hyperproliferation of basal epidermal cells. It is regarded as T-cell mediated, but the role of keratinocytes (KCs) in the disease pathogenesis has reemerged, with genetic studies identifying KC-associated genes. We applied flow cytometry on KCs from lesional and nonlesional epidermis to characterize the phenotype in the germinative compartment in psoriasis, and we observed an overall increase in the stemness markers CD29 (2.4-fold), CD44 (2.9-fold), CD49f (2.8-fold), and p63 (1.4-fold). We found a reduced percentage of cells positive for the early differentiation marker cytokeratin 10 and a greater fraction of CD29+ and involucrin+ cells in the psoriasis KCs than in nonlesional KCs. The up-regulation of stemness markers was more pronounced in the K10+ cells. Furthermore, the psoriasis cells were smaller, indicating increased proliferation. Treatment with IL-17 and IL-22 induced a similar expression pattern of an up-regulation of p63, CD44, and CD29 in normal KCs and increased the colony-forming efficiency and long-term proliferative capacity, reflecting increased stem cell-like characteristics in the KC population. These data suggest that IL-17 and IL-22 link the inflammatory response to the immature differentiation and epithelial regeneration by acting directly on KCs to promote cell stemness.

Decreased Systemic Levels of Endocan-1 and CXCL16 in Psoriasis Are Restored following Narrowband UVB Treatment.

BACKGROUND: In psoriasis, a common immune-mediated disease affecting 2-3% of the population worldwide, there is an increased prevalence of extracutaneous diseases including obesity, the metabolic syndrome, and cardiovascular disease. This is believed to be linked to systemic inflammation. In previous studies, we have explored various markers in plasma and serum to characterize the ongoing systemic inflammation in psoriasis patients compared to controls. We have identified several markers that were altered in psoriasis patients, but which all were unresponsive to narrowband UVB (NB-UVB) treatment. OBJECTIVE: The objective of the study was to evaluate the effect of NB-UVB treatment on markers of cardiovascular risk and systemic inflammation in psoriasis. METHODS: The levels of 17 potential biomarkers with an association with cardiovascular risk were quantitated in plasma from 37 age- and gender-matched psoriasis patients and controls at baseline and in 21 psoriasis patients after 12 weeks of NB-UVB treatment to identify a systemic treatment response. RESULTS: We identified the mediators endocan-1, CXCL16, and sVEGFR1, which were systemically decreased in psoriasis at baseline, as well as FABP3, FABP4, and sIL-1R1, which showed normal baseline levels. After 10-12 weeks of NB-UVB treatment, endocan-1 and CXCL16 were restored to normal levels, while sVEGFR1, FABP3, FABP4, and sIL-1R1 showed a significant reduction. CONCLUSION: The current study expands the number of potential biomarkers in psoriasis by including a greater number and variety of mediators, approaching the systemic inflammation from additional vantage points, including soluble immune receptors and adipocyte contribution, to provide a more complete picture of the systemic inflammatory state in psoriasis.

Genome-Wide DNA Methylation Profiling Identifies Differential Methylation in Uninvolved Psoriatic Epidermis.

Psoriasis is a chronic inflammatory skin disease with both local and systemic components. Genome-wide approaches have identified more than 60 psoriasis-susceptibility loci, but genes are estimated to explain only one-third of the heritability in psoriasis, suggesting additional, yet unidentified, sources of heritability. Epigenetic modifications have been linked to psoriasis and altered DNA methylation patterns in psoriatic versus healthy skin have been reported in whole-skin biopsies. In this study, focusing on epigenetic modifications in the psoriatic uninvolved skin, we compared the lesional and non-lesional epidermis from psoriasis patients with epidermis from healthy controls. We performed an exhaustive genome-wide DNA methylation profiling using reduced representation bisulfite sequencing, which interrogates the methylation status of approximately 3-4 million CpG sites. More than 2,000 strongly differentially methylated sites were identified and a striking overrepresentation of the Wnt and cadherin pathways among the differentially methylated sites was found. In particular, we observe a strong differential methylation in several psoriasis candidate genes. A substantial number of differentially methylated sites present in the uninvolved versus healthy epidermis suggests the presence of a pre-psoriatic state in the clinically healthy skin type. Our exploratory study represents a starting point for identifying biomarkers for psoriasis-prone skin before disease onset.

Overexpression of Psoriasin (S100A7) Contributes to Dysregulated Differentiation in Psoriasis.

Psoriasin, which is highly expressed in psoriasis, is encoded by a gene located within the epidermal differentiation complex. The aim of this study was to investigate the effect of endogenous psoriasin on disturbed keratinocyte differentiation in psoriasis. Immunohistochemical staining revealed a gradient of psoriasin expression in the psoriatic epidermis with highest expression in the suprabasal, differentiated layers. Induction of keratinocyte differentiation caused concurrent expression of psoriasin and the differentiation marker involucrin. The differentiation-induced psoriasin expression was found to be mediated by the protein kinase C pathway. The downregulation of psoriasin expression by small interfering RNA revealed that psoriasin mediates the expression of involucrin, desmoglein 1, transglutaminase 1 and CD24 in normal differentiation. The lentivirus-mediated overexpression of psoriasin, mimicking the psoriatic milieu, gave rise to an altered regulation of differentiation genes and an expression pattern reminiscent of that in psoriatic epidermis. These findings suggest that psoriasin contributes to the dysregulated differentiation process in the psoriasis epidermis.

Systemic treatment and narrowband ultraviolet B differentially affect cardiovascular risk markers in psoriasis.

BACKGROUND: Psoriasis is associated with a systemic inflammation and an increased frequency of the metabolic syndrome, both of which are believed to link psoriasis to an increased risk of cardiovascular disease. OBJECTIVE: The study aimed to investigate the systemic expression of markers of cardiovascular risk and determine their response to ultraviolet B therapy and treatment with the tumor necrosis factor-alfa inhibitor, etanercept. METHODS: Six markers of cardiovascular risk were measured in 28 patients with psoriasis and 28 control subjects. RESULTS: Five of the 6 investigated markers were elevated in patients with psoriasis. Four of these correlated to the body mass index and waist-hip ratio, suggesting a link to the metabolic syndrome. Total plasminogen activator inhibitor-1 remained elevated independently of these factors. The levels of the investigated risk markers decreased considerably after tumor necrosis factor-alfa inhibitor treatment but remained unaffected by ultraviolet therapy. LIMITATIONS: A relatively limited study population and nonrandomization are limitations. CONCLUSION: These findings suggest that the choice of treatment in psoriasis may influence the cardiovascular risk in patients with psoriasis and the metabolic syndrome.

Systemically elevated Th1-, Th2- and Th17-associated chemokines in psoriasis vulgaris before and after ultraviolet B treatment.

Chemokines may contribute to the systemic inflammation that is linked to the increased risk of co-morbidities in patients with psoriasis. The aim of this study was to investigate circulating chemokines in patients with psoriasis and their relationship to disease severity. Analysis of plasma levels of chemokines in patients with psoriasis before narrowband ultraviolet B (UVB) therapy revealed increased expression of Th1-associated CXCL9 and -10, Th2-associated CCL17 and CCL22, and Th17-associated CCL20. CCL20 correlated with disease severity. UVB therapy reduced skin symptoms, but did not affect the chemokine levels in plasma. Anti-CD3 and anti-CD28-mediated activation of peripheral blood mononuclear cells (PBMCs) caused a higher secretion of Th2 cytokine interleukin (IL)-13 by PBMCs from patients with psoriasis than from healthy controls. The sustained high expression of inflammatory chemokines is a potential link to systemic inflammation in psoriasis. UVB therapy may be a more effective treatment of local rather than systemic inflammation.

Genetic support for the role of the NLRP3 inflammasome in psoriasis susceptibility.

NACHT leucine-rich repeat- and PYD-containing (NLRP)3 protein controls the inflammasome by regulating caspase-1 activity and interleukin (IL)-1ß processing. The contribution of IL-1ß in the pathogenesis of psoriasis is well recognized. Polymorphisms in NLRP3 and caspase recruitment domain-containing protein (CARD)8, a negative regulator of caspase-1 activity, have been associated with susceptibility to common inflammatory diseases, such as Crohn's disease and rheumatoid arthritis. To investigate the role for genetic variants in the NLRP3 inflammasome in psoriasis susceptibility. In a patient sample comprising 1988 individuals from 491 families and 1002 healthy controls, genotypes for four selected single-nucleotide polymorphisms (SNPs) in NLRP3 (three SNPs) and CARD8 (one SNP) were determined by TaqMan(®) Allelic Discrimination. Using the transmission disequilibrium test (TDT), a significant increase in the transmission of the NLRP3 rs10733113G genotype to a subgroup of patients with more widespread psoriasis was demonstrated (P = 0.015). Using logistic regression analysis in 741 patients with psoriasis and 1002 controls, the CARD8 rs2043211 genotype was significantly different in cases and controls in overall terms [OR 1.3 (1.1-1.5), P = 0.004] and for both genders. Our data support the hypothesis that the inflammasome plays a role in psoriasis susceptibility.

Allergen-induced accumulation of CD68-,CD123+ dendritic cells in the nasal mucosa.

BACKGROUND: Dendritic cells are antigen-presenting cells central to the immune system. They activate and orchestrate the innate and the adaptive immune systems. This phenotypically diverse group can be further divided into 2 subsets, the CD11c+ myeloid dendritic cells (mDCs) and the CD123+ plasmacytoid dendritic cells (pDCs). The aim of the study was to investigate the effect of allergen exposure on dendritic cells in subjects with allergic rhinitis. METHODS: Atopic and non-atopic subjects were challenged intranasally with birch or timothy allergen. Nasal biopsies were taken before and 24 h after challenge, and were, after CD68 exclusion, stained for expression of CD11c and CD123 to identify dendritic cell subsets. The effect of allergic mediators on CD68⁻,CD123+ cells was studied with flow cytometry analysis in peripheral blood. RESULTS: The amount of CD68⁻,CD123+ cells increased in the nasal sub-epithelium upon allergen challenge, whereas the number of CD68⁻,CD11c+ cells was unaffected. In vitro study of the effect of inflammatory mediators on pDC phenotype showed an increased activation in response TNF-α, IL-4 and CpG. Furthermore, TNF-α caused a higher activation among atopic than non-atopic subjects. CONCLUSIONS: An increased number of CD68⁻,CD123+ dendritic cells along with the positive pDC response following stimulation with inflammatory mediators suggest that the increased pDCs may be of an activated phenotype. It also suggests that the inflammatory response by pDCs to mediators such as TNF-α may be markedly higher in atopic subjects. These data support the notion of pDCs as important participants in allergic rhinitis.

Toll-like receptor 7 activation reduces the contractile response of airway smooth muscle.

Viral respiratory infections are a major cause of asthma exacerbations. The mechanisms by which such infections aggravate airway inflammation and hyperresponsiveness are complex and not fully understood. Toll-like receptor 7 is particularly relevant in the defence against common respiratory viruses, as it recognizes single-stranded viral RNA. The present study was designed to investigate the effect of Toll-like receptor 7 stimulation on airway smooth muscle reactivity. The presence of Toll-like receptor 7 within guinea pig airways was ensured with immunohistochemistry. The effects induced by 3days of culture of tracheal segments with the Toll-like receptor 7 agonist R837 or the Toll-like receptor 7/8 agonist R848 were evaluated in a myograph organ bath system. The intracellular mechanisms involved were dissected using inhibitors of intracellular mitogen-activated protein kinase (MAPK) activity. Toll-like receptor 7 immunoreactivity was observed across the epithelial cell layer and in the airway smooth muscle cells. Treatment with R837 and R848 reduced the airway contractile responses to 5-hydroxytryptamine (5-HT). This effect was abolished upon treatment with inhibitors of the p38 MAPK pathway and nuclear factor (NF)-κB pathways. According to the present model, activation of Toll-like receptor 7 might prevent development of airway hyperresponsiveness by acting on the airway smooth muscle. The presented data support the idea that individuals with defect Toll-like receptor 7 function might be more prone to respond to virus infections with asthmatic exacerbations. Further, they suggest that inhaled Toll-like receptor 7 ligand might be an effective treatment alternative for asthma.

The expression and function of Nod-like receptors in neutrophils.

Neutrophils make up an essential part of the innate immune system, and are involved both in the initial responses to pathogens, and in orchestrating later immune responses. Neutrophils recognize pathogens through pattern-recognition receptors (PRRs), which are activated by microbial motifs. The Nod-like receptors (nucleotide-binding domain leucine-rich repeat containing family; NLRs) constitute a recently discovered group of PRRs whose role in the neutrophil immune responses is not yet characterized. The present study aimed to investigate the expression and function of NLRs in neutrophils. Neutrophils were isolated from human peripheral blood, and the presence of nucleotide-binding oligomerization domain 1 (NOD1), NOD2 and NACHT-LRR-PYD-containing protein 3 (NLRP3) was evaluated with flow cytometry and immunohistochemistry. The expression of NOD1, NOD2 and NLRP3 messenger RNA was determined using real-time reverse transcription-polymerase chain reaction. Changes in neutrophil cytokine secretion, phenotype and migration following agonist-induced activation were studied using enzyme-linked immunosorbent assay, flow cytometry and a chemotaxis assay, respectively. No expression of NOD1 was found in isolated neutrophils and stimulation with the NOD1 ligand gamma-d-glutamyl-meso-diaminopimelic acid induced no signs of activity. In contrast, a marked expression of NOD2 and NLRP3 was found. NOD2 activation with MurNAc-l-Ala-d-isoGln (MDP) resulted in interleukin-8 secretion, CD62 ligand down-regulation, CD11b up-regulation and increased migration towards an inflammatory stimulus. NLRP3 activation with alum caused interleukin-1beta secretion and facilitated migration. Altogether, this suggests that NLRs may be a previously unknown pathway for neutrophil activation.

Nasal challenge with LPS stimulates the release of macrophage inflammatory protein 1alpha.

BACKGROUND: Bacterial infections can cause a variety of airway diseases. Toll-like receptors (TLRs) directly respond to the presence of microbes and partake in the innate immune defense. TLR4 is activated by lipopolysaccharide (LPS), and has been detected in sinonasal tissue, epithelial cells and various inflammatory cells. Macrophage inflammatory protein 1alpha (MIP-1alpha) is a chemokine released during the inflammatory process. The present study investigated the potential role and regulation of MIP-1alpha in LPS-induced nasal inflammation. METHODS: Thirty-two healthy individuals were intranasally challenged with LPS or vehicle. Nasal lavage was performed, followed by a nasal biopsy. Inflammatory cells were counted, MIP-1alpha levels analyzed and expression of MIP-1alpha mRNA in biopsies quantified. Neutrophils isolated from peripheral blood were treated with LPS and effects on MIP-1alpha release, cell survival, and the involved signal pathways, were investigated. RESULTS: LPS challenge caused an increase of MIP-1alpha in nasal lavage. No corresponding change in mRNA expression was seen in nasal biopsies, suggesting the increase was not due to epithelial synthesis. Neutrophil numbers increased after LPS provocation. Treatment of isolated neutrophils with LPS delayed neutrophil apoptosis and resulted in a time- and concentration-dependent release of MIP-1alpha, which was reduced by inhibitors of transcription and of nuclear factor (NF)-kappaB, protein kinase C (PKC) and p38 MAPK pathways. CONCLUSIONS: Nasal LPS challenge results in release of MIP-1alpha. The release most likely originates from recruited neutrophils, via NF-kappaB-, PKC- and p38 MAPK-dependent pathways. LPS stimulation delayed neutrophil apoptosis. MIP-1alpha may constitute an important mediator in neutrophilic airway disease.