Difelikefalin suppresses itch and reduces scratching independent of inflammation in a murine model of atopic dermatitis.

BACKGROUND: Therapies specifically targeting nonhistaminergic pruritus are largely lacking. Difelikefalin (DFK) has been found to reduce itch in various chronic pruritic conditions, including atopic dermatitis (AD). OBJECTIVE: We sought to investigate the ability of DFK to impact scratching behavior, inflammatory mediators, and neuronal signaling in a murine model of AD. METHODS: The ears of C57BL/6 mice were topically treated with MC903 for 12 consecutive days to induce AD-like inflammation and itch. Before MC903 treatment, mice were treated with either DFK (0.5 mg/kg, intraperitoneal injection twice daily) or vehicle (saline). Skin ear thickness, histological analysis, flow cytometry, RNA-sequencing, and differential gene expression analyses of mouse ear skin were used to examine the effect of DFK on skin inflammation. Scratching behavior was quantified to measure itch behavior in mice that were topically treated with MC903 for 6 consecutive days; then, mice received a single injection of either DFK (1.0 mg/kg, intraperitoneal injection) or saline. Calcium imaging and single-cell RNA-sequencing were used in mouse dorsal root ganglia neurons to determine the size of the neurons activated with DFK treatment. Statistical significance was determined by Mann-Whitney test, unless otherwise noted. RESULTS: DFK rapidly suppressed itch without altering AD-like skin inflammation in MC903 (calcipotriol)-treated mice. In vitro Ca2+ influx trace of dorsal root ganglia suggested that a major target for DFK is the larger-diameter mechanoreceptors (eg, Aꞵ-fibers), rather than small-diameter pruriceptive C-fibers. CONCLUSIONS: These studies support a potential neuromodulatory role of DFK for reducing itch associated with AD in mice.

Oral difelikefalin reduces moderate to severe pruritus and expression of pruritic and inflammatory biomarkers in subjects with atopic dermatitis.

BACKGROUND: Pruritus is the most common and burdensome symptom of atopic dermatitis (AD). Pruritus-targeted treatments in AD are lacking, particularly for patients with milder skin disease. OBJECTIVE: We sought to evaluate the impact of the selective κ-opioid receptor agonist difelikefalin (DFK) on pruritus intensity and pruritus- and immune-related biomarkers in subjects with moderate to severe AD-related pruritus. METHODS: A phase 2 clinical trial investigated the efficacy and safety of oral DFK 0.25, 0.5, and 1.0 mg in subjects with moderate to severe AD-related pruritus. A biomarker substudy evaluated the effects of DFK on the expression of pruritus, TH2-associated genes, and skin barrier-related genes. RESULTS: In the clinical trial (N = 401), all DFK doses reduced itch versus placebo; however, the results were not statistically significant at week 12. In a subgroup of subjects in the trial with mild to moderate skin inflammation and moderate to severe itch (itch-dominant AD phenotype), DFK reduced itch at week 12 versus placebo. In the biomarker substudy, DFK downregulated the expression of key pruritus-related genes (eg, IL-31 and TRPV1) and the AD phenotype (eg, CCL17). Gene set variation analysis confirmed that DFK, but not placebo, downregulated pruritus-related genes and TH2 pathways. DFK improved skin barrier integrity markers and upregulated the expression of claudins and lipid metabolism-associated genes (eg, SEC14L6, ELOVL3, CYP1A2, and AKR1D1). CONCLUSIONS: DFK treatment reduced itch in subjects with moderate to severe AD-related pruritus, particularly those with an "itch-dominant" AD phenotype, and had an impact on the expression of pruritus, TH2-associated genes, and skin barrier-related genes. DFK is a promising therapy for AD-related pruritus; further clinical studies are warranted.

Burden of Disease and Unmet Needs in Atopic Dermatitis: Results From a Patient Survey.

Background: Atopic dermatitis (AD) affects 2%-10% of adults worldwide. Occurrence and severity of symptoms and treatment success vary among patients. Objective: To determine disease severity, burden, and treatment use and satisfaction in adults with AD. Methods: An international internet-based survey was conducted (October 5-November 1, 2021) in participants with AD from Canada, France, Germany, Italy, Japan, Spain, the United Kingdom, and the United States. Results: Of 2005 AD patients surveyed, 92% had body surface area (BSA) involvement <10%. Itch was the most bothersome symptom; 48.5% of participants reported severe itch in the past week (Itch Numerical Rating Scale [NRS] 7-10; 45.9% for BSA <10%, 75.0% for BSA ≥10%). Most participants reported moderate or severe sleep disturbance in the past week (Sleep NRS 4-10; 67.1% for BSA <10%, 92.3% for BSA ≥10%). Itch was the top reason for participants' most recent health care provider visit; reducing itching was their top treatment goal. Topical therapies, which were most commonly used, resulted in low treatment satisfaction. Conclusions: Itch was the most bothersome AD symptom. Although clinical development has focused on improving skin lesions, improving itch is patients' top treatment goal. This survey highlights the need for systemic antipruritic therapies that could reduce itch in nonlesional and lesional skin.

Phase 2 Trial of Difelikefalin in Notalgia Paresthetica.

BACKGROUND: Notalgia paresthetica is a neuropathic disorder characterized by pruritus in a circumscribed region of the upper back. Difelikefalin, a selective kappa opioid receptor agonist, has shown efficacy in other chronic pruritic conditions and is being investigated for the treatment of notalgia paresthetica. METHODS: In this phase 2, double-blind, placebo-controlled trial, we randomly assigned, in a 1:1 ratio, patients with moderate-to-severe pruritus caused by notalgia paresthetica to receive 2 mg of oral difelikefalin or placebo twice daily for 8 weeks. The primary outcome was the change from baseline at week 8 in the weekly mean score on the daily Worst Itch Numeric Rating Scale (WI-NRS; scores range from 0 [no itch] to 10 [worst itch imaginable]). The secondary clinical outcomes were itch-related quality-of-life and itch-related sleep measures. RESULTS: A total of 126 patients were enrolled; 62 patients were assigned to receive difelikefalin, and 63 were assigned to receive placebo. One patient who had been assigned to receive difelikefalin withdrew consent before the first dose and is not included in the main analyses. The mean baseline WI-NRS score was 7.6 (indicating severe itch) in each group. The change from baseline in the weekly mean WI-NRS score at week 8 was -4.0 points in the difelikefalin group and -2.4 points in the placebo group (difference in change, -1.6 points; 95% confidence interval, -2.6 to -0.6; P = 0.001). The results for the secondary outcomes generally did not support those of the primary analysis. Headache, dizziness, constipation, and increased urine output occurred more frequently in the difelikefalin group than in the placebo group. CONCLUSIONS: Among patients with notalgia paresthetica, oral treatment with difelikefalin resulted in modestly greater reductions in itch intensity scores than placebo over a period of 8 weeks but was associated with adverse events. Larger and longer trials are needed to assess the efficacy and safety of difelikefalin treatment in this disorder. (Funded by Cara Therapeutics; KOMFORT ClinicalTrials.gov number, NCT04706975.).

Understanding the patient experience of living with notalgia paresthetica: A qualitative interview study.

Background: Notalgia paresthetica (NP) is a chronic sensory neuropathy that causes intense pruritus, typically affecting the upper portion of the back and lasting for months to years. The impacts of pruritus and the full symptom experience are not well documented. Objective: To describe patients' NP symptom experience and the impacts of living with NP-related itch. Methods: Semistructured, one-to-one qualitative telephone interviews were conducted in adults living with NP. The worst itch severity during the previous 24 hours was assessed using an 11-point numerical rating scale. Results: Thirty participants (23 females; aged 41-80 years) completed interviews. Seventeen NP-related symptoms were described, with daily itch being the most common. Participants' itch ranged from severe to very severe (50%) and was experienced for a median of 2.8 years. Most (73%) participants were not receiving treatment for NP at the time of the study. Other reported symptoms included skin pain or sensitivity and secondary symptoms from itching (skin discoloration, lumps or bumps, bleeding or scabbing). NP-related itch was frequently reported to affect mood, interfere with sleep, and disrupt self-care. Limitations: Only English-speaking participants living in the United States were included. Conclusion: This study highlights the patient experience of living with NP and findings reveal that there remains an unmet need for effective therapeutic options to address NP-related itch.

Qualitative analysis and reproducibility assessment of the Scalp Itch Numeric Rating Scale among patients with moderate to severe plaque psoriasis of the scalp.

Background: Pruritus is a prevalent and bothersome symptom of scalp psoriasis. Validated scales assessing scalp itch are needed to evaluate treatment efficacy. Objective: To evaluate comprehensibility and reproducibility of the Scalp Itch Numeric Rating Scale (NRS), a novel scale being used in a phase 3 study of apremilast. Methods: The Scalp Itch NRS, Modified Whole Body Itch NRS, Global Assessment of Psoriasis Severity-Scalp (GAPS-S), and Global Impression of Change-Scalp Itch (GIC-SI) were assessed among patients with moderate to severe scalp psoriasis. Convergent validity and test-retest reliability between two visits (7 ± 3 days apart) were assessed using intra-class and Spearman's correlations. Results: Patients found the Scalp Itch NRS easy to use and understand. Convergent validity (Modified Whole Body Itch NRS Visit 1: rs = 0.71, Visit 2: rs = 0.92, p< .0001; GAPS-S Visit 1: rs = 0.62, Visit 2: rs = 0.63, p< .0001), and consistency with changes (Modified Whole Body Itch NRS: rs = 0.69, p< .0001; GAPS-S: rs = 0.42, p = .0029) were demonstrated. The Scalp Itch NRS showed strong test-retest reliability (intra-class correlation coefficient = 0.87; rs = 0.89). Change scores on the Scalp Itch NRS were consistent with change scores on the GIC-SI. Conclusions: The Scalp Itch NRS is a valid and reproducible measure of scalp itch in patients with moderate to severe scalp psoriasis. ClinicalTrials.gov: NCT03123471.

A Phase 2 Randomized Trial of Apremilast in Patients with Atopic Dermatitis.

A phase 2, double-blind, placebo-controlled trial evaluated apremilast efficacy, safety, and pharmacodynamics in adults with moderate to severe atopic dermatitis. Patients were randomly assigned to receive placebo, apremilast 30 mg twice daily (APR30), or apremilast 40 mg twice daily (APR40) for 12 weeks. During weeks 12-24, all patients received APR30 or APR40. A biopsy substudy evaluated atopic dermatitis-related biomarkers. Among 185 randomly assigned intent-to-treat patients at week 12, a dose-response relationship was observed; APR40 (n = 63), but not APR30 (n = 58), led to statistically significant improvements (vs. placebo, n = 64) in Eczema Area and Severity Index (mean [standard deviation] percent change from baseline = -31.6% [44.6] vs. -11.0% [71.2], P < 0.04; primary endpoint). mRNA expression of T helper type 17/T helper type 22-related markers (IL-17A, IL-22, and S100A7/A8; P < 0.05) showed the highest reductions with APR40, with minimal changes in other immune axes. Safety with APR30 was largely consistent with apremilast's known profile (common adverse events: nausea, diarrhea, headache, and nasopharyngitis). With APR40, adverse events were more frequent, and cellulitis occurred (n = 6). An independent safety monitoring committee discontinued the APR40 dosage. APR40 showed modest efficacy and decreased atopic dermatitis-related biomarkers in moderate to severe atopic dermatitis patients. Adverse events, including cellulitis, were more frequent with APR40, which was discontinued during the trial. Clinical Trial Registration Number: NCT02087943 (clinicaltrials.gov).

Tildrakizumab versus placebo or etanercept for chronic plaque psoriasis (reSURFACE 1 and reSURFACE 2): results from two randomised controlled, phase 3 trials.

BACKGROUND: Tildrakizumab is a high-affinity, humanised, IgG1 κ antibody targeting interleukin 23 p19 that represents an evolving treatment strategy in chronic plaque psoriasis. Previous research suggested clinical improvement with inhibition of interleukin 23 p19. We did two phase 3 trials to investigate whether tildrakizumab is superior to placebo and etanercept in the treatment of chronic plaque psoriasis. METHODS: We did two three-part, parallel group, double-blind, randomised controlled studies, reSURFACE 1 (at 118 sites in Australia, Canada, Japan, the UK, and the USA) and reSURFACE 2 (at 132 sites in Europe, Israel, and the USA). Participants aged 18 years or older with moderate-to-severe chronic plaque psoriasis (body surface area involvement ≥10%, Physician's Global Assessment [PGA] score ≥3, and Psoriasis Area and Severity Index [PASI] score ≥12) were randomised (via interactive voice and web response system) to tildrakizumab 200 mg, tildrakizumab 100 mg, or placebo in reSURFACE 1 (2:2:1), or to tildrakizumab 200 mg, tildrakizumab 100 mg, placebo, or etanercept 50 mg (2:2:1:2). Randomisation was done by region and stratified for bodyweight (≤90 kg or >90 kg) and previous exposure to biologics therapy for psoriasis. Investigators, participants, and study personnel were blinded to group allocation and remained blinded until completion of the studies. Assigned medication was identical in appearance and packaging. Tildrakizumab was administered subcutaneously at weeks 0 and 4 during part 1 and at week 16 during part 2 (weeks 12 and 16 for participants re-randomised from placebo to tildrakizumab; etanercept was given twice weekly in part 1 of reSURFACE 2 and once weekly during part 2). The co-primary endpoints were the proportion of patients achieving PASI 75 and PGA response (score of 0 or 1 with ≥2 grade score reduction from baseline) at week 12. Safety was assessed in the all-participants-as-treated population, and efficacy in the full-analysis set. These trials are registered with ClinicalTrials.gov, numbers NCT01722331 (reSURFACE 1) and NCT01729754 (reSURFACE 2). These studies are completed, but extension studies are ongoing. FINDINGS: reSURFACE 1 ran from Dec 10, 2012, to Oct 28, 2015. reSURFACE 2 ran from Feb 12, 2013, to Sept 28, 2015. In reSURFACE 1, 772 patients were randomly assigned, 308 to tildrakizumab 200 mg, 309 to tildrakizumab 100 mg, and 155 to placebo. At week 12, 192 patients (62%) in the 200 mg group and 197 patients (64%) in the 100 mg group achieved PASI 75, compared with 9 patients (6%) in the placebo group (p<0·0001 for comparisons of both tildrakizumab groups vs placebo). 182 patients (59%) in the 200 mg group and 179 patients (58%) in the 100 mg group achieved PGA responses, compared with 11 patients (7%) in the placebo group (p<0·0001 for comparisons of both tildrakizumab groups vs placebo). In reSURFACE 2, 1090 patients were randomly assigned, 314 to tildrakizumab 200 mg, 307 to tildrakizumab 100 mg, 156 to placebo, and 313 to etanercept. At week 12, 206 patients (66%) in the 200 mg group, and 188 patients (61%) in the 100 mg group achieved PASI 75, compared with 9 patients (6%) in the placebo group and 151 patients (48%) in the etanercept group (p<0·0001 for comparisons of both tildrakizumab groups vs placebo; p<0·0001 for 200 mg vs etanercept and p=0·0010 for 100 mg vs etanercept). 186 patients (59%) in the 200 mg group, and 168 patients (59%) [corrected] in the 100 mg group achieved a PGA response, compared with 7 patients (4%) in the placebo group and 149 patients (48%) in the etanercept group (p<0·0001 for comparisons of both tildrakizumab groups vs placebo; p=0·0031 for 200 mg vs etanercept and p=0·0663 for 100 mg vs etanercept). Serious adverse events were similar and low in all groups in both trials. One patient died in reSURFACE 2, in the tildrakizumab 100 mg group; the patient had alcoholic cardiomyopathy and steatohepatitis, and adjudication was unable to determine the cause of death. INTERPRETATION: In two phase 3 trials, tildrakizumab 200 mg and 100 mg were efficacious compared with placebo and etanercept and were well tolerated in the treatment of patients with moderate-to-severe chronic plaque psoriasis. FUNDING: Merck & Co.

Comparative genomic profiling of synovium versus skin lesions in psoriatic arthritis.

OBJECTIVE: To our knowledge, there is no broad genomic analysis comparing skin and synovium in psoriatic arthritis (PsA). Also, there is little understanding of the relative levels of cytokines and chemokines in skin and synovium. The purpose of this study was to better define inflammatory pathways in paired lesional skin and affected synovial tissue in patients with PsA. METHODS: We conducted a comprehensive analysis of cytokine and chemokine activation and genes representative of the inflammatory processes in PsA. Paired PsA synovial tissue and skin samples were obtained from 12 patients on the same day. Gene expression studies were performed using Affymetrix HGU133 Plus 2.0 arrays. Confirmatory quantitative real-time polymerase chain reaction (PCR) was performed on selected transcripts. Cell populations were assessed by immunohistochemistry and immunofluorescence. RESULTS: Globally, gene expression in PsA synovium was more closely related to gene expression in PsA skin than to gene expression in synovium in other forms of arthritis. However, PsA gene expression patterns in skin and synovium were clearly distinct, showing a stronger interleukin-17 (IL-17) gene signature in skin than in synovium and more equivalent tumor necrosis factor (TNF) and interferon-γ gene signatures in both tissues. These results were confirmed with real-time PCR. CONCLUSION: This is the first comprehensive molecular comparison of paired lesional skin and affected synovial tissue samples in PsA. Our results support clinical trial data showing that PsA skin and joint disease are similarly responsive to TNF antagonists, while IL-17 antagonists have better results in PsA skin than in PsA joints. Genes selectively expressed in PsA synovium might direct future therapies for PsA.

IL-17 induces an expanded range of downstream genes in reconstituted human epidermis model.

BACKGROUND: IL-17 is the defining cytokine of the Th17, Tc17, and γδ T cell populations that plays a critical role in mediating inflammation and autoimmunity. Psoriasis vulgaris is an inflammatory skin disease mediated by Th1 and Th17 cytokines with relevant contributions of IFN-γ, TNF-α, and IL-17. Despite the pivotal role IL-17 plays in psoriasis, and in contrast to the other key mediators involved in the psoriasis cytokine cascade that are capable of inducing broad effects on keratinocytes, IL-17 was demonstrated to regulate the expression of a limited number of genes in monolayer keratinocytes cultured in vitro. METHODOLOGY/PRINCIPAL FINDINGS: Given the clinical efficacy of anti-IL-17 agents is associated with an impressive reduction in a large set of inflammatory genes, we sought a full-thickness skin model that more closely resemble in vivo epidermal architecture. Using a reconstructed human epidermis (RHE), IL-17 was able to upregulate 419 gene probes and downregulate 216 gene probes. As possible explanation for the increased gene induction in the RHE model is that C/CAAT-enhancer-binding proteins (C/EBP) -ß, the transcription factor regulating IL-17-responsive genes, is expressed preferentially in differentiated keratinocytes. CONCLUSIONS/SIGNIFICANCE: The genes identified in IL-17-treated RHE are likely relevant to the IL-17 effects in psoriasis, since ixekizumab (anti-IL-17A agent) strongly suppressed the "RHE" genes in psoriasis patients treated in vivo with this IL-17 antagonist.

Nonlesional atopic dermatitis skin is characterized by broad terminal differentiation defects and variable immune abnormalities.

BACKGROUND: Atopic dermatitis (AD) is a common inflammatory skin disease with a T(H)2 and "T22" immune polarity. Despite recent data showing a genetic predisposition to epidermal barrier defects in some patients, a fundamental debate still exists regarding the role of barrier abnormalities versus immune responses in initiating the disease. An extensive study of nonlesional AD (ANL) skin is necessary to explore whether there is an intrinsic predisposition to barrier abnormalities, background immune activation, or both in patients with AD. OBJECTIVE: We sought to characterize ANL skin by determining whether epidermal differentiation and immune abnormalities that characterize lesional AD (AL) skin are also reflected in ANL skin. METHODS: We performed genomic and histologic profiling of both ANL and AL skin lesions (n = 12 each) compared with normal human skin (n = 10). RESULTS: We found that ANL skin is clearly distinct from normal skin with respect to terminal differentiation and some immune abnormalities and that it has a cutaneous expansion of T cells. We also showed that ANL skin has a variable immune phenotype, which is largely determined by disease extent and severity. Whereas broad terminal differentiation abnormalities were largely similar between involved and uninvolved AD skin, perhaps accounting for the "background skin phenotype," increased expression of immune-related genes was among the most obvious differences between AL and ANL skin, potentially reflecting the "clinical disease phenotype." CONCLUSION: Our study implies that systemic immune activation might play a role in alteration of the normal epidermal phenotype, as suggested by the high correlation in expression of immune genes in ANL skin with the disease severity index.

Contrasting pathogenesis of atopic dermatitis and psoriasis--part I: clinical and pathologic concepts.

Atopic dermatitis and psoriasis are 2 of the most common inflammatory skin diseases. They are similar in that they are complex inherited diseases involving genes that encode immune components and structural proteins that regulate differentiation of epidermal cells. Each disease is characterized by proliferation of epidermal keratinocytes and abnormal cornification or terminal differentiation in the epidermis; skin lesions contain immune infiltrates of T cells, dendritic cells, and other types of leukocytes. We review similarities between the diseases and differences in epidermal barrier defects and immune cells. We also propose mechanisms of pathogenesis based on differences in the balance of immune cell subsets that could cause the phenotypes that distinguish these diseases. The first part of this 2-part review focuses on the clinical and pathologic features of the diseases; the second part discusses differences in immune cell subsets between atopic dermatitis and psoriasis and recent therapeutic strategies.

Contrasting pathogenesis of atopic dermatitis and psoriasis--part II: immune cell subsets and therapeutic concepts.

Atopic dermatitis (AD) and psoriasis are among the most common inflammatory skin diseases. In the first part of this 2-part review, we discussed the similarities and differences between AD and psoriasis with respect to clinical features and pathology. The diseases are characterized by infiltration of skin lesions by large numbers of inflammatory cells; the second part of this review focuses on immune cell subsets that distinguish each disease and the therapeutic strategies that might be used or developed based on this information. We discuss the interactions among different populations of immune cells that ultimately create the complex inflammatory phenotype of AD and compare these with psoriasis. Therapeutic strategies have been developed for psoriasis based on the cytokine network that promotes inflammation in this disease. Antibodies against IL-12 and IL-23p40 antibody and antagonists of TNF are used to treat patients with psoriasis, and studies are underway to test specific antagonists of IL-23, IL-17, IL-17 receptor, IL-20, and IL-22. We discuss how these therapeutic approaches might be applied to AD.

Anti-cytokine therapies for psoriasis.

Current approaches for the treatment of psoriasis with anti-cytokine therapies involve the blockade of TNF-α, or the p40 sub-unit of IL-12 and IL-23. However, the field is currently evolving to test more selective antagonists, such as anti-IL-23p19, IL-17 and other inflammatory cytokines. Here we discuss our current understanding of dendritic cell and T cell subsets that are relevant in psoriasis, and the pharmacologic strategies that temper their activity in this disease.

Integrative responses to IL-17 and TNF-α in human keratinocytes account for key inflammatory pathogenic circuits in psoriasis.

Psoriasis is a complex inflammatory disease mediated by tumor necrosis factor (TNF)-α and cytokines secreted by specialized T-cell populations, e.g., IL-17, IL-22, and IFN-γ. The mechanisms by which innate and adaptive immune cytokines regulate inflammation in psoriasis are not completely understood. We sought to investigate the effects of TNF-α and IL-17 on keratinocyte (KC) gene profile, to identify genes that might be coregulated by these cytokines and determine how synergistically activated genes relate to the psoriasis transcriptome. Primary KCs were stimulated with IL-17 or TNF-α alone, or in combination. KC responses were assessed by gene array analysis, followed by reverse transcriptase-PCR confirmation for significant genes. We identified 160 genes that were synergistically upregulated by IL-17 and TNF-α, and 196 genes in which the two cytokines had at least an additive effect. Synergistically upregulated genes included some of the highest expressed genes in psoriatic skin with an impressive correlation between IL-17/TNF-α-induced genes and the psoriasis gene signature. KCs may be key drivers of pathogenic inflammation in psoriasis through integrating responses to TNF-α and IL-17. Our data predict that psoriasis therapy with either TNF or IL-17 antagonists will produce greater modulation of the synergistic/additive gene set, which consists of the most highly expressed genes in psoriasis skin lesions.

A subpopulation of CD163-positive macrophages is classically activated in psoriasis.

Macrophages are important cells of the innate immune system, and their study is essential to gain greater understanding of the inflammatory nature of psoriasis. We used immunohistochemistry and double-label immunofluorescence to characterize CD163(+) macrophages in psoriasis. Dermal macrophages were increased in psoriasis compared with normal skin and were identified by CD163, RFD7, CD68, lysosomal-associated membrane protein 2 (LAMP2), stabilin-1, and macrophage receptor with collagenous structure (MARCO). CD163(+) macrophages expressed C-lectins CD206/macrophage mannose receptor and CD209/DC-SIGN, as well as costimulatory molecules CD86 and CD40. They did not express mature dendritic cell (DC) markers CD208/DC-lysosomal-associated membrane glycoprotein, CD205/DEC205, or CD83. Microarray analysis of in vitro-derived macrophages treated with IFN-γ showed that many of the genes upregulated in macrophages were found in psoriasis, including STAT1, CXCL9, Mx1, and HLA-DR. CD163(+) macrophages produced inflammatory molecules IL-23p19 and IL-12/23p40 as well as tumor necrosis factor (TNF) and inducible nitric oxide synthase (iNOS). These data show that CD163 is a superior marker of macrophages, and identifies a subpopulation of "classically activated" macrophages in psoriasis. We conclude that macrophages are likely to contribute to the pathogenic inflammation in psoriasis, a prototypical T helper 1 (Th1) and Th17 disease, by releasing key inflammatory products.

Identification of TNF-related apoptosis-inducing ligand and other molecules that distinguish inflammatory from resident dendritic cells in patients with psoriasis.

BACKGROUND: Previous work has identified CD11c(+)CD1c(-) dendritic cells (DCs) as the major "inflammatory" dermal DC population in patients with psoriasis vulgaris and CD1c(+) DCs as the "resident" cutaneous DC population. OBJECTIVE: We sought to further define molecular differences between these 2 myeloid dermal DC populations. METHODS: Inflammatory and resident DCs were single-cell sorted from lesional skin biopsy specimens of patients with psoriasis, and the transcriptome of CD11c(+)CD1c(-) versus CD1c(+) DCs was determined. Results were confirmed with RT-PCR, flow cytometry, immunohistochemistry, and double-labeled immunofluorescence. Human keratinocytes were cultured for functional studies. RESULTS: TNF-related apoptosis-inducing ligand (TRAIL), Toll-like receptors 1 and 2, S100A12/ENRAGE, CD32, and many other inflammatory products were differentially expressed in inflammatory DCs compared with resident DCs. Flow cytometry and immunofluorescence confirmed higher protein expression on CD1c(-) versus CD1c(+) DCs. TRAIL receptors, death receptor 4, and decoy receptor 2 were expressed in keratinocytes and dermal cells. In vitro culture of keratinocytes with TRAIL induced CCL20 chemokine. CONCLUSIONS: CD11c(+)CD1c(-) inflammatory DCs in psoriatic lesional skin express a wide range of inflammatory molecules compared with skin-resident CD1c(+) DCs. Some molecules made by inflammatory DCs, including TRAIL, could have direct effects on keratinocytes or other skin cell types to promote disease pathogenesis.

New insights in the immunologic basis of psoriasis.

Psoriasis vulgaris is a multifactorial heritable disease characterized by severe inflammation resulting in poorly differentiated, hyperproliferative keratinocytes. Recent advances in genetic analyses have implicated components regulating the interleukin (IL)-23 and nuclear factor-kappaB pathways as risk factors for psoriasis. These inflammatory pathways exhibit increased activity in skin lesions, and promote secretion of various cytokines, such as IL-17 and IL-22. Unrestrained, the activated inflammatory cytokine network in psoriasis may trigger a vicious cycle of inflammation and cellular proliferation that ultimately results in lesion formation. These advances in genetic analyses, together with the progress made in targeted biological therapy, pave the path to tailor treatment on the basis of an individual's genetic and immunologic profile.