Psoriasis vulgaris: cutaneous lymphoid tissue supports T-cell activation and ‘Type 1’ inflammatory gene expression

Characterization of retinoic acid-inducible gene-I (RIG-I) expression corresponding to viral infection and UVB in human keratinocytes

BACKGROUND

Retinoic acid-inducible gene-I (RIG-I) is a cytoplasmic protein that recognizes viral double-stranded RNA to induce the type I interferon (IFN) response. In human keratinocytes, RIG-I is induced by IFN-γ and tumor necrosis factor-α stimulation, and is abundantly expressed in psoriatic keratinocytes of the spinous and basal layers.

OBJECTIVE

This study investigated the effects of extraneous stimuli including viral infection and UVB exposure on RIG-I expression in human keratinocytes.

METHODS

Human skin keratinocytes (HaCaT cells) were stimulated by polyinosinic-polycytidylic acid (poly(I:C)), which mimics viral infection, and UVB exposure. We assessed the expression of RIG-I and IFN-regulatory factor (IRF)-1 in HaCaT cells by RT-PCR and Western blot analysis. Moreover, we investigated the effect of IRF-1 binding site of RIG-I gene promoter on the regulation of RIG-I expression by luciferase promoter assay and electrophoretic mobility shift assay.

RESULTS

Poly(I:C) induced RIG-I expression, while UVB inhibited basal RIG-I expression and the poly(I:C)-induced RIG-I overexpression in HaCaT cells. IRF-1, which binds to a regulatory element located on the RIG-I gene promoter, was required for both inductions of RIG-I expression. IRF-1 expression was enhanced three hours after the poly(I:C) stimulation, consistent with the RIG-I response to poly(I:C), and thereafter was suppressed. Moreover, UVB exposure promptly decreased IRF-1 expression, resulting in decreased IRF-1 protein binding to the RIG-I promoter, and consequently, decreased RIG-I expression.

CONCLUSION

Thus, suppression of RIG-I and IRF-1 expression caused by UVB exposure may partly explain the inhibition of skin-based immune responses, leading to viral infection and recrudescence.

A single intradermal injection of IFN-γ induces an inflammatory state in both non-lesional psoriatic and healthy skin

Psoriasis is a chronic, debilitating, immune-mediated inflammatory skin disease. As IFN-γ is involved in many cellular processes, including activation of dendritic cells (DCs), antigen processing and presentation, cell adhesion and trafficking, and cytokine and chemokine production, IFN-γ-producing Th1 cells were proposed to be integral to the pathogenesis of psoriasis. Recently, IFN-γ was shown to enhance IL-23 and IL-1 production by DCs and subsequently induce Th17 cells, which are important contributors to the inflammatory cascade in psoriatic lesions. To determine whether IFN-γ indeed induces the pathways expressed in psoriatic lesions, a single intradermal injection of IFN-γ was administered to an area of clinically normal, non-lesional (NL) skin of psoriasis patients and biopsies were collected 24 hours later. Although there were no visible changes in the skin, IFN-γ induced many molecular and histological features characteristic of psoriatic lesions. IFN-γ increased a number of differentially expressed genes in the skin, including many chemokines concomitant with an influx of T cells and inflammatory DCs. Furthermore, inflammatory DC products tumor necrosis factor (TNF), inducible nitric oxide synthase, IL-23, and TNF-related apoptosis-inducing ligand were present in IFN-γ-treated skin. Thus, IFN-γ, which is significantly elevated in NL skin compared with healthy skin, appears to be a key pathogenic cytokine that can induce many features of the inflammatory cascade of psoriasis.

A single intradermal injection of IFN-γ induces an inflammatory state in both non-lesional psoriatic and healthy skin

Psoriasis is a chronic, debilitating, immune-mediated inflammatory skin disease. As IFN-γ is involved in many cellular processes, including activation of dendritic cells (DCs), antigen processing and presentation, cell adhesion and trafficking, and cytokine and chemokine production, IFN-γ-producing Th1 cells were proposed to be integral to the pathogenesis of psoriasis. Recently, IFN-γ was shown to enhance IL-23 and IL-1 production by DCs and subsequently induce Th17 cells, which are important contributors to the inflammatory cascade in psoriatic lesions. To determine whether IFN-γ indeed induces the pathways expressed in psoriatic lesions, a single intradermal injection of IFN-γ was administered to an area of clinically normal, non-lesional (NL) skin of psoriasis patients and biopsies were collected 24 hours later. Although there were no visible changes in the skin, IFN-γ induced many molecular and histological features characteristic of psoriatic lesions. IFN-γ increased a number of differentially expressed genes in the skin, including many chemokines concomitant with an influx of T cells and inflammatory DCs. Furthermore, inflammatory DC products tumor necrosis factor (TNF), inducible nitric oxide synthase, IL-23, and TNF-related apoptosis-inducing ligand were present in IFN-γ-treated skin. Thus, IFN-γ, which is significantly elevated in NL skin compared with healthy skin, appears to be a key pathogenic cytokine that can induce many features of the inflammatory cascade of psoriasis.

The pro-inflammatory role of TGFβ1: a paradox?

TGFβ1 was initially identified as a potent chemotactic cytokine to initiate inflammation, but the autoimmune phenotype seen in TGFβ1 knockout mice reversed the dogma of TGFβ1 being a pro-inflammatory cytokine to predominantly an immune suppressor. The discovery of the role of TGFβ1 in Th17 cell activation once again revealed the pro-inflammatory effect of TGFβ1. We developed K5.TGFβ1 mice with latent human TGFβ1 overexpression targeted to epidermal keratinocytes by keratin 5. These transgenic mice developed significant skin inflammation. Further studies revealed that inflammation severity correlated with switching TGFβ1 transgene expression on and off, and genome wide expression profiling revealed striking similarities between K5.TGFβ1 skin and human psoriasis, a Th1/Th17-associated inflammatory skin disease. Our recent study reveals that treatments alleviating inflammatory skin phenotypes in this mouse model reduced Th17 cells, and antibodies against IL-17 also lessen the inflammatory phenotype. Examination of inflammatory cytokines/chemokines affected by TGFβ1 revealed predominantly Th1-, Th17-related cytokines in K5.TGFβ1 skin. However, the finding that K5.TGFβ1 mice also express Th2-associated inflammatory cytokines under certain pathological conditions raises the possibility that deregulated TGFβ signaling is involved in more than one inflammatory disease. Furthermore, activation of both Th1/Th17 cells and regulatory T cells (Tregs) by TGFβ1 reversely regulated by IL-6 highlights the dual role of TGFβ1 in regulating inflammation, a dynamic, context and organ specific process. This review focuses on the role of TGFβ1 in inflammatory skin diseases.

A subset of methylated CpG sites differentiate psoriatic from normal skin

Psoriasis is a chronic inflammatory immune-mediated disorder affecting the skin and other organs including joints. Over 1,300 transcripts are altered in psoriatic involved skin compared to normal skin. However to our knowledge global epigenetic profiling of psoriatic skin is previously unreported. Here we describe a genome-wide study of altered CpG methylation in psoriatic skin. We determined the methylation levels at 27,578 CpG sites in skin samples from individuals with psoriasis (12 involved, 8 uninvolved) and 10 unaffected individuals. CpG methylation of involved skin differed from normal skin at 1,108 sites. Twelve mapped to the epidermal differentiation complex, upstream or within genes that are highly up-regulated in psoriasis. Hierarchical clustering of 50 of the top differentially methylated (DM) sites separated psoriatic from normal skin samples. CpG sites where methylation was correlated with gene expression are reported. Sites with inverse correlations between methylation and nearby gene expression include those of KYNU, OAS2, S100A12, and SERPINB3, whose strong transcriptional up-regulation are important discriminators of psoriasis. We observed intrinsic epigenetic differences in uninvolved skin. Pyrosequencing of bisulfite-treated DNA from skin biopsies at three DM loci confirmed earlier findings and revealed reversion of methylation levels towards the non-psoriatic state after one month of anti-TNF-α therapy.

In vitro induced CD8+ regulatory T cells inhibit skin inflammation

CD8(+) regulatory T cells appear impaired in number and/or function in some autoimmune diseases. However, the role of CD8(+) regulatory T cells in the pathogenesis of skin inflammation and psoriasis remains unknown. In this study, we set out to analyze the capability of CD8(+) regulatory T cells to inhibit skin inflammation in a murine model and to determine the frequency of CD8(+) regulatory T cells in patients with psoriasis. We demonstrate that murine fully competent CD8(+) regulatory T cells can be induced by stimulating naïve CD8(+) T cells in the presence of TGF-β and retinoic acid (RA). Importantly, in vitro induced CD8(+) regulatory T cells significantly suppressed skin inflammation in vivo. Furthermore, we found that the frequency of regulatory CD8(+)CD25(+)Foxp3(+) T cells is decreased in peripheral blood but increased in lesional psoriatic skin of patients with psoriasis. Thus, our study suggests a previously unappreciated role of CD8(+)CD25(+)Foxp3(+) T cells in skin disorders, and induction of these cells in vitro may be an effective immunotherapy for skin inflammation.

Serum cytokine profile in psoriasis-a case-control study in a tertiary care hospital from northern India

Psoriasis is chronic autoimmune hyperproliferative skin disease with a population prevalence of 1.5-3%. The cause of psoriasis is still not fully understood. It has been hypothesized to be an immune-mediated disorder in which the excessive reproduction of keratinocytes is due to cytokines such as interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha, secreted by infiltrating CD4(+) and CD8(+) T cells and natural killer cells. The aim of our study was to determine the serum levels of TNF-α, IL-4, IL-6 & IL-10 in psoriasis patients and compare it with healthy controls. 30 clinically diagnosed psoriasis patients and 30 age and sex matched healthy controls were included in the study. The serum cytokine levels were measured by solid phase sandwich ELISA (DIACLONE Research, France). TNF-α and IL-6 levels were significantly raised in patients and the results were statistically significant (P < 0.001). IL-4 levels were higher in patients than in controls (1.91 ± 4.7 pg/ml in cases & 0.9 ± 0.3 pg/ml in controls) but were not statistically significant. Interestingly, IL-10 levels were found to be higher in controls than in patients but again, it was not statistically significant. Pro-inflammatory cytokines play a pivotal role in the pathogenesis of psoriasis and it is the type 1(TH1) cytokine pattern, i.e., IL-6 & TNF-α, which predominate in the psoriatic T cell response. Further studies on IL-10 levels in psoriasis are recommended to establish their exact role in the pathogenesis of the disease.

Targeting chemokine receptors in chronic inflammatory diseases: an extensive review

The traffic of the different types of immune cells is an important aspect in the immune response. Chemokines are soluble peptides that are able to attract cells by interaction with chemokine receptors on their target cells. Several different chemokines and receptors exist enabling the specific trafficking of different immune cells. In chronic inflammatory disorders there is abundance of immune cells present at the inflammatory site. This review focuses on the role of chemokine receptors in chronic inflammatory disorders of the lungs, intestine, joints, skin and nervous system and the potential of targeting these receptors as therapeutic intervention in these disorders.

Function and regulation of retinoic acid-inducible gene-I

Antiviral innate immunity is triggered by sensing viral nucleic acids. RIG-I (retinoic acid-inducible gene-I) is an intracellular molecule that responds to viral nucleic acids and activates downstream signaling, resulting in the induction of members of the type I interferon (IFN) family, which are regarded among the most important effectors of the innate immune system. Although RIG-I is expressed ubiquitously in the cytoplasm, its levels are subject to transcriptional and post-transcriptional regulation. RIG-I belongs to the IFN-stimulated gene (ISG) family, but certain cells regulate its expression through IFN-independent mechanisms. Several lines of evidence indicate that deregulated RIG-I signaling is associated with autoimmune disorders. Further studies suggest that RIG-I has functions in addition to those directly related to its role in RNA sensing and host defense. We have much to learn and discover regarding this interesting cytoplasmic sensor so that we can capitalize on its properties for the treatment of viral infections, immune disorders, cancer, and perhaps other conditions.

Insulin-like growth factor-1 in psoriatic plaques treated with PUVA and methotrexate

BACKGROUND

The pathogenesis of psoriasis is thought to depend on the activation of immune cells and their secreted cytokines, chemokines and growth factors like IGF-1 which may contribute to the epidermal hyperplasia of psoriasis. Treatment of psoriasis with PUVA and methotrexate are associated with clinical improvement and decrease in epidermal hyperplasia.

OBJECTIVE

To examine the effects of PUVA and methotrexate therapy on IGF-1 expression in psoriatic plaques and whether this change correlates with clinical response.

METHODS

For 24 psoriatic patients, the PASI score and levels of lesional IGF-1 and its mRNA were determined by RT-PCR before and after treatment with either methotrexate or PUVA. Skin biopsies from 12 healthy volunteers served as control for IGF-1 levels in normal skin.

RESULTS

Lesional skin of psoriatic patients showed a statistically significant elevation in IGF-1 and its mRNA levels in comparison to control (P = 0.0001). Both methotrexate and PUVA treatment were associated with a significant decrease in both PASI scores and lesional IGF-1 after 10 month treatment.

CONCLUSION

Both methotrexate and PUVA therapy for psoriasis are associated with a decrease in PASI score and IGF-1. The IGF-1 down-regulation may possibly be a consequence of the decrease in cytokines and inflammatory cellular infiltrate that occur following treatment with either modalities or due to their effect on local fibroblast activity and proliferation.

The role of etanercept on the expression of markers of T helper 17 cells and their precursors in skin lesions of patients with psoriasis vulgaris

Very recently, it has been demonstrated that CD161, retinoic acid-related orphan receptor gamma-t (RORgamma-t) and CC-chemokin receptor 6 (CCR6) can be considered good surface markers to detect T helper 17 cells and their precursors, T cell populations that are considered to play an important role in the pathogenesis of psoriasis. In the present study, we evaluate the clinical involvement by calculating the PASI score and the number of CD4+, CD161+, RORgammat+ and CCR6+ cells before and after a 12-week course with etanercept or acitretin in patients with moderate-to-severe, plaque-type psoriasis vulgaris. Ten patients were given etanercept 50 mg twice weekly and 10 patients acitretin 0.4 mg/kg per day, both for 12 weeks. At the baseline and at the end of the treatment PASI was calculated, and skin biopsies were taken to evaluate the expression of CD4, CD161, RORgammat and CCR6 by immunohistochemistry. As controls, 10 patients with atopic dermatitis (AD) were included in the study. After 12 weeks, PASI was significantly lower than at the baseline for both groups. However, etanercept-treated patients showed lower PASI than acitretin-treated ones. While CD4+ cell numbers were similar in both diseases, all the other markers, that are considered more specific for Th17 cells and their precursors, were more expressed in psoriasis than in AD. Furthermore, only etanercept, but not acitretin, was able to significantly reduce CD161+, RORgammat+ and CCR6+ cells in skin lesions of patients with psoriasis. Our study provides further evidence of the role of Th17 pathway in the pathogenesis of psoriasis. Furthermore, our findings suggest that etanercept is able to downregulate the expression of the recently recognized markers of Th17 cells and their precursors CD161, RORgammat and CCR6, while acitretin is not. This activity on the Th17 lineage may contribute to the efficacy of etanercept in the treatment of psoriasis.

Distinct roles of IL-22 in human psoriasis and inflammatory bowel disease

IL-22, an IL-10 family cytokine, is produced by different leukocyte subsets, including T cells, NK cells and lymphoid tissue inducer (LTi) cells. IL-22 mediates the crosstalk between leukocytes and tissue epithelia because its receptor is preferentially expressed on various tissue epithelial cells. IL-22 is essential for host defense against infections of extracellular pathogens, such as bacteria and yeasts, by eliciting various innate defensive mechanisms from tissue epithelial cells and promoting wound-healing responses. In autoimmune diseases, however, diverse tissue microenvironments and underlying pathogenic mechanisms may result in opposing contributions of IL-22 in disease progression. For example, in psoriasis, IL-22 can synergize with other proinflammatory cytokines to induce many of the pathogenic phenotypes from keratinocytes and exacerbate disease progression. In contrast, IL-22 plays a beneficial role in IBD by enhancing barrier integrity and epithelial innate immunity of intestinal tract.

Eotaxin-3/CC chemokine ligand 26 is a functional ligand for CX3CR1

Eotaxin-3/CCL26 is a functional ligand for CCR3 and abundantly produced by IL-4-/IL-13-stimulated vascular endothelial cells. CCL26 also functions as a natural antagonist for CCR1, CCR2, and CCR5. In this study, we report that CCL26 is yet a functional ligand for CX3CR1, the receptor for fractalkine/CX3CL1, which is expressed by CD16(+) NK cells, cytotoxic effector CD8(+) T cells, and CD14(low)CD16(high) monocytes. Albeit at relatively high concentrations, CCL26 induced calcium flux and chemotaxis in mouse L1.2 cells expressing human CX3CR1 but not mouse CX3CR1 and competed with CX3CL1 for binding to CX3CR1. In chemotaxis assays using human PBMCs, CCL26 attracted not only eosinophils but also CD16(+) NK cells, CD45RA(+)CD27(-)CD8(+) T cells, and CD14(low)CD16(high) monocytes. Intraperitoneal injection of CCL26 into mice rapidly recruited mouse eosinophils and intravenously transferred human CD16(+) NK cells into the peritoneal cavity. IL-4-stimulated HUVECs produced CCL26 and efficiently induced adhesion of cells expressing CX3CR1. Real-time PCR showed that skin lesions of psoriasis consistently contained CX3CL1 mRNA but not CCL26 mRNA, whereas those of atopic dermatitis contained CCL26 mRNA in all samples but CX3CL1 mRNA in only about half of the samples. Nevertheless, the skin lesions from both diseases consistently contained CX3CR1 mRNA at high levels. Thus, CCL26 may be partly responsible for the recruitment of cells expressing CX3CR1 in atopic dermatitis particularly when the expression of CX3CL1 is low. Collectively, CCL26 is another agonist for CX3CR1 and may play a dual role in allergic diseases by attracting eosinophils via CCR3 and killer lymphocytes and resident monocytes via CX3CR1.

Psoriasis genetics: breaking the barrier

Psoriasis is a common incurable inflammatory skin disease affecting 2-3% of the European population. Psoriatic skin contains large numbers of immune cells which produce many cytokines, chemokines and inflammatory molecules. The epidermis divides much faster than normal and has a defective outer layer or barrier which under normal circumstances protects from infection and dehydration. Psoriatic skin is characterized by a distinct set of inflammation and epidermal proliferation and differentiation markers, and it has been unclear whether the genetic basis of psoriasis reflects defects of the immune system or of the skin. One genetic determinant lies within the major histocompatibility complex class 1 region. Genome-wide association studies have revealed genetic susceptibility factors that play a role in the formation of immune cells found in psoriasis lesions. Others affect epidermal proliferation and skin barrier formation. Hence, genetic components of both the immune system and the epidermis can predispose to disease.

The IFN-gamma-dependent suppressor of cytokine signaling 1 promoter activity is positively regulated by IFN regulatory factor-1 and Sp1 but repressed by growth factor independence-1b and Krüppel-like factor-4, and it is dysregulated in psoriatic keratinocytes

Epidermal keratinocytes can counteract the detrimental effects of IFN-gamma by inducing the expression of suppressor of cytokine signaling (SOCS)1, which plays an important anti-inflammatory and self-protective role. To date, limited information exists on its expression and regulation in human diseased keratinocytes. In this study, we compared the expression levels of SOCS1 in keratinocytes isolated from skin affected by psoriasis with cells obtained from healthy donors, unveiling that keratinocytes are more prone than healthy cells to upregulate SOCS1 mRNA expression in response to IFN-gamma. We explored the regulatory mechanisms involved in socs1 gene transcription, and found that Sp1 and IFN regulatory factor-1 transcription factors are, respectively, responsible for the basal and IFN-gamma-induced activity of human socs1 promoter. In parallel, we demonstrated that socs1 promoter is negatively regulated by two transcriptional repressors, namely, growth factor independence-1b and Krüppel-like factor 4, which tightly control SOCS1 transcription on IFN-gamma stimulation. Interestingly, although the expression of Sp1 and IFN regulatory factor-1 activators of socs1 promoter is unaltered, growth factor independence-1b and Krüppel-like factor 4 are significantly reduced in psoriatic compared with healthy keratinocytes. This reduction and the consequent unbalanced binding of transcriptional activators and repressors to socs1 promoter after IFN-gamma stimulation might be responsible for the enhanced expression of SOCS1 in psoriatic cells. We suggest that SOCS1 exaggerated upregulation in psoriatic keratinocytes could represent a mechanism through which these cells attempt to protect themselves from IFN-gamma effects. However, the SOCS1 increased levels in psoriatic keratinocytes are not sufficient to completely inhibit the expression of proinflammatory genes.

Progress in understanding the immunopathogenesis of psoriasis

This review emphasizes how translation from bench research to clinical knowledge and vice versa has resulted in considerable progress in understanding the immunopathogenesis of psoriasis. First, the journey in understanding the pathogenic mechanisms behind psoriasis is described. The roles of different components of the adaptive and innate immune systems involved in driving the inflammatory response are explained. Discovery of new immune pathways i.e. the IL23/Th17 axis and its subsequent impact on the development of novel biological therapies is highlighted. Identification of potential targets warranting further research for future therapeutic development are also discussed.

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.

Deficient SOCS3 and SHP-1 expression in psoriatic T cells

IFN-alpha and skin-infiltrating activated T lymphocytes have important roles in the pathogenesis of psoriasis. T cells from psoriatic patients display an increased sensitivity to IFN-alpha, but the pathological mechanisms behind the hyperresponsiveness to IFN-alpha remained unknown. In this study, we show that psoriatic T cells display deficient expression of the suppressor of cytokine signaling (SOCS)3 in response to IFN-alpha and a low baseline expression of the SH2-domain-containing protein-tyrosine phosphatase (SHP)-1 when compared with skin T cells from nonpsoriatic donors. Moreover, IFN-alpha-stimulated psoriatic T cells show enhanced activation of JAKs (JAK1 and TYK2) and signal transducers and activators of transcription. Increased expression of SOCS3 proteins resulting from proteasomal blockade partially inhibits IFN-alpha response. Similarly, forced expression of SOCS3 and SHP-1 inhibits IFN-alpha signaling in psoriatic T cells. In conclusion, our data suggest that loss of regulatory control is involved in the aberrant hypersensitivity of psoriatic T cells to IFN-alpha.

The Th17 cytokine IL-22 induces IL-20 production in keratinocytes: a novel immunological cascade with potential relevance in psoriasis

Psoriasis is a common chronic skin disease. Recent studies demonstrated that IL-20 and IL-22, cytokines produced by keratinocytes and T cells, respectively, both inhibit keratinocyte terminal differentiation and induce psoriasis-like epidermis alterations. Here, we investigated the relationship between these mediators. Although IL-20 was not able to regulate IL-22 production, IL-22 induced IL-20 mRNA and protein in human keratinocytes. However, IL-22 had only a minimal effect, if any, on IL-19 and IL-26. Cutaneous IL-20 was also elevated in mice following IL-22 application. Accordingly, some of IL-22's effects on differentiation-regulating genes were partially mediated by an endogenous, secreted protein and attenuated by anti-IL-20 Ab. Like IL-22, IL-17A and TNF-alpha induced IL-20 in keratinocytes, whereas IFN-gamma and IL-20 itself did not. Furthermore, IL-17A and TNF-alpha individually strengthened the IL-22-induced IL-20 production. In lesional skin of psoriasis patients, highly elevated IL-20 levels strongly correlated with IL-22, and to a lesser extent, with IL-17A and TNF-alpha. As previously shown for IL-22, IL-20 blood levels correlated with the disease severity, although with a lower significance. This study demonstrates that a T-cell mediator induces a tissue cell mediator with similar effects to its own and therefore suggests the existence of a novel type of pathogenetic cascade.

Psoriasis during interferon beta treatment for multiple sclerosis

Previous reports have suggested an increased risk of psoriasis in MS patients. Worsening of dermatologic lesions during interferon therapy has been rarely reported, but activation of psoriatic arthritis has not been described until now. The following is a case report. A 37-year-old woman affected by relapsing-remitting multiple sclerosis had severe worsening of cutaneous psoriasis and activation of psoriatic arthritis during interferon beta treatment. The symptoms resolved after therapy discontinuation. This case further supports that activation of psoriasis might be a rare side effect of IFNB therapy and suggests careful evaluation of concomitant morbidity to allow a patient-oriented treatment strategy.

Th17 cytokines stimulate CCL20 expression in keratinocytes in vitro and in vivo: implications for psoriasis pathogenesis

T helper (Th) 17 cells have recently been implicated in psoriasis pathogenesis, but mechanisms of how these cells traffic into inflamed skin are unknown. By immunostaining for interleukin (IL)-17A and IL-22, we show numerous cells present in psoriasis lesions that produce these cytokines. We next found that Th17 cytokines (IL-17A, IL-22, and tumor necrosis factor (TNF)-alpha) markedly increased the expression of CC chemokine ligand (CCL) 20, a CC chemokine receptor (CCR)6 ligand, in human keratinocyte monolayer and raft cultures in a dose- and time-dependent manner. Lastly, we showed in mice that subcutaneous injection with recombinant IL-17A, IL-22, or TNF-alpha led to the upregulation of both CCL20 and CCR6 expression in skin as well as cutaneous T-cell infiltration. Taken together, these data show that Th17 cytokines stimulate CCL20 production in vitro and in vivo, and thus provide a potential explanation of how CCR6-positive Th17 cells maintain their continual presence in psoriasis through a positive chemotactic feedback loop.

Psoriasis and streptococci: the natural selection of psoriasis revisited

We have previously postulated that surviving invasive streptococcal infections may have been a factor in psoriasis becoming a common skin disease in some parts of the world. Many of the candidate genes linked to psoriasis are associated with the acquired or innate immune system, which are also important in host defence to invasive streptococcal infections. High rates of positive streptococcal throat swabs among patients with chronic plaque psoriasis suggest that they are efficient at internalizing/carrying beta-haemolytic streptococci. Internalization of streptococci in the throat is dependent upon the transforming growth factor (TGF)-beta/fibronectin/alpha 5 beta 1 integrin pathway. The immune cell Th17 and its related cytokine network are important in mucosal defence, being very effective against extracellular microbes but having little effect on intracellular organisms. The TGF-beta/fibronectin/alpha 5 beta 1 integrin pathway and the Th17 cell network also appear to be operative in psoriasis, animal models of both TGF-beta and alpha 5 beta 1 cutaneous overexpression being associated with characteristic psoriasis lesions. We postulate that some of the genotypic/phenotypic changes in different immunological pathways in psoriasis, including the acquired T-cell response, the innate immune response, the TGF-beta/fibronectin/alpha 5 beta 1 integrin pathway and the Th17 cell system, confer protection against mortality during epidemics of invasive streptococcal infections, heightened efficiency in internalizing and allowing carriage of streptococci as well as predisposition to the development of psoriasis.

Histamine H1-receptor antagonists with immunomodulating activities: potential use for modulating T helper type 1 (Th1)/Th2 cytokine imbalance and inflammatory responses in allergic diseases

Being a first-line treatment for hypersensitivity allergic disease, histamine H1-receptor antagonists possess anti-inflammatory activity in addition to being H1-receptor antagonists. While it is not purely a histamine-related condition, hypersensitivity allergic disease is associated with an increase in the number of T helper type 2 (Th2) cells and Th2 cytokines, and a decrease in the number of Th1 cells and Th1 cytokines. Suppression of Th2-type cytokine production in addition to H1-receptor blockade may therefore represent a successful therapeutic strategy for the treatment of hypersensitivity allergic diseases. H1-receptor antagonists have been reported to modulate immune cascade at various points by acting on T cell-related inflammatory molecules, including adhesion molecules, chemokines and inflammatory cytokines. These effects of H1-receptor antagonists may be optimized for the treatment of allergic diseases. Besides their ability to regulate inflammatory molecules, some H1-receptor antagonists have been reported to down-regulate Th2 cytokine production. In particular, it has been shown that several H1-receptor antagonists specifically inhibit the production of Th2, but not Th1, cytokines. Accumulating evidence indicates a crucial role for Th1/Th2 cytokine imbalance on the development of allergic diseases. Accordingly, the use of H1-receptor antagonist with Th2 cytokine inhibitory activity to modulate Th1/Th2 cytokine imbalance might be a favourable strategy for the treatment of hypersensitivity allergic diseases. Furthermore, the identification of H1-receptor antagonists which possess immunoregulatory activities in addition to their anti-histamine activity will provide an important insight into the development of novel immunoregulatory drugs.

IL-22 and IL-20 are key mediators of the epidermal alterations in psoriasis while IL-17 and IFN-gamma are not

Psoriasis is a common chronic skin disease with a largely unknown pathogenesis. We demonstrate here that transgenic over-expression of interleukin (IL)-22 in mice resulted in neonatal mortality and psoriasis-like skin alterations including acanthosis and hypogranularity. This cutaneous phenotype may be caused by the direct influence of IL-22 on keratinocytes, since this cytokine did not affect skin fibroblasts, endothelial cells, melanocytes, or adipocytes. The comparison of cytokines with hypothesized roles in psoriasis pathogenesis determined that neither interferon (IFN)-gamma nor IL-17, but only IL-22 and, with lower potency, IL-20 caused psoriasis-like morphological changes in a three-dimensional human epidermis model. These changes were associated with inhibited keratinocyte terminal differentiation and with STAT3 upregulation. The IL-22 effect on differentiation-regulating genes was STAT3-dependent. In contrast to IL-22 and IL-20, IFN-gamma and IL-17 strongly induced T-cell and neutrophilic granulocyte-attracting chemokines, respectively. Tumor necrosis factor-alpha potently induced diverse chemokines and additionally enhanced the expression of IL-22 receptor pathway elements and amplified some IL-22 effects. This study suggests that different cytokines are players in the psoriasis pathogenesis although only the IL-10 family members IL-22 and IL-20 directly cause the characteristic epidermal alterations.

The IL-23/Th17 axis in the immunopathogenesis of psoriasis

Abnormal production of inflammatory mediators is believed to play an important role in the pathogenesis of psoriasis. Emerging data, both in mice and in humans, put the spotlight on a new subset of T helper (Th) cells, in part characterized by their production of IL-17 and accordingly named Th17 cells. Here, we review the development, characterization, and function of human Th17 cells as well as the crucial role of IL-23 in the context of Th17-cell-dependent chronic inflammation in psoriasis. We further discuss recent clinical trials targeting the IL-23/Th17 axis in psoriasis.

Serum levels of IL-17 and IL-22 are reduced by etanercept, but not by acitretin, in patients with psoriasis: a randomized-controlled trial

INTRODUCTION

There are no controlled trials comparing etanercept and acitretin efficacy and therapeutic mechanisms in psoriasis.

MATERIALS AND METHODS

In the present study, 30 patients were given etanercept 50 mg twice weekly and 30 patients acitretin 0.4 mg/kg per day, both for 12 weeks. Before and after treatment, psoriasis area and severity index was calculated, and serum levels of interleukin (IL)-17, IL-22, and IL-23 were investigated.

RESULTS

After treatment, psoriasis area and severity index was significantly lower for both groups. However, etanercept-treated patients showed lower psoriasis area and severity index than acitretin-treated ones. Psoriasis patients showed higher IL-17 and IL-22 levels than controls, while no IL-23 was found in any serum. Furthermore, a correlation between IL-17 levels and psoriasis severity was found. Only etanercept was able to reduce IL-17 and IL-22 levels.

CONCLUSIONS

Our findings suggest that etanercept is more effective than acitretin in the treatment of psoriasis and that it is able to affect Th17 system.

The Increased Expression of Matrix Metalloproteinase-9 Messenger RNA in the Non-lesional Skin of Patients with Large Plaque Psoriasis Vulgaris

BACKGROUND

A difference of the interleukin-18 (IL-18) mRNA expression among several proinflammatory genes was previously observed between large plaque (LP) psoriasis patients (more than 5 cm lesions are typical) and small plaque (SP) psoriasis patients (1~2 cm lesions are typical). Therefore, it is necessary to test whether there is any difference in the expression of the genes that activate IL-18 or the expression of genes that are induced by IL-18.

OBJECTIVE

To test the differential mRNA expressions of caspase-1, STAT-6, MMP-1, MMP-2, MMP-9 and TIMP-1 according to the clinical types of psoriasis vulgaris lesions in Korean patients, we have analyzed the skin samples of psoriasis vulgaris patients.

METHODS

The total cellular RNA of skin samples from groups of patient with LP and SP psoriasis was analyzed by performing real-time PCR (the Taqman method) to compare the differences in the mRNA expressions.

RESULTS

The caspase-1 and STAT-6 mRNA expression levels from the SP lesional skin of the patients were increased compared with the caspase-1 and STAT-6 mRNA expression levels from SP non-lesional skin or normal skin, but these expression levels from the SP non-lesional skin were not significantly different from those of the LP non-lesional skin. Among MMP-1, MMP-2, MMP-9 and TIMP-1, the expressions of MMP-1, MMP-2 and MMP-9 mRNA were increased in the SP lesional skin compared with those of the SP non-lesional skin. The MMP-1 mRNA expressions in both the LP and SP lesional skin were increased compared with those in the normal skin (p=0.028 and p=0.007 respectively). The MMP-9 mRNA expression in the LP non-lesional skin was elevated compared with the MMP-9 mRNA expression in the SP non-lesional skin (p=0.047). The TIMP-1 mRNA expression levels from the non-lesional skin and the lesional skin of the psoriasis patients and the normal skin samples were not significantly different.

CONCLUSION

The increased expression of MMP-9 mRNA in the LP non-lesional skin compared to that of the SP non-lesional skin in the psoriatic skin suggests that the increased MMP-9 mRNA expression is related to the large size type of lesion.

Induction and effector phase of allergic lung inflammation is independent of CCL21/CCL19 and LT-beta

The chemokines CCL21 and CCL19, and cell bound TNF family ligand lymphotoxin beta (LTbeta), have been associated with numerous chronic inflammatory diseases. A general role in chronic inflammatory diseases cannot be assumed however; in the case of allergic inflammatory disease, CCL21/CCL19 and LTbeta have not been associated with the induction, recruitment, or effector function of Th2 cells nor dendritic cells to the lung. We have examined the induction of allergic inflammatory lung disease in mice deficient in CCL21/CCL19 or LTbeta and found that both kinds of mice can develop allergic lung inflammation. To control for effects of priming differences in knockout mice, adoptive transfers of Th2 cells were also performed, and they showed that such effector cells had equivalent effects on airway hyper-responsiveness in both knockout background recipients. Moreover, class II positive antigen presenting cells (B cells and CD11c+ dendritic cells) showed normal recruitment to the peribronchial spaces along with CD4 T cells. Thus, the induction of allergic responses and recruitment of both effector Th2 cells and antigen presenting cells to lung peribronchial spaces can develop independently of CCL21/CCL19 and LTbeta.

Low expression of the IL-23/Th17 pathway in atopic dermatitis compared to psoriasis

The classical Th1/Th2 paradigm previously defining atopic dermatitis (AD) and psoriasis has recently been challenged with the discovery of Th17 T cells that synthesize IL-17 and IL-22. Although it is becoming evident that many Th1 diseases including psoriasis have a strong IL-17 signal, the importance of Th17 T cells in AD is still unclear. We examined and compared skin biopsies from AD and psoriasis patients by gene microarray, RT-PCR, immunohistochemistry, and immunofluorescence. We found a reduced genomic expression of IL-23, IL-17, and IFN-gamma in AD compared with psoriasis. To define the effects of IL-17 and IL-22 on keratinocytes, we performed gene array studies with cytokine-treated keratinocytes. We found lipocalin 2 and numerous other innate defense genes to be selectively induced in keratinocytes by IL-17. IFN-gamma had no effect on antimicrobial gene-expression in keratinocytes. In AD skin lesions, protein and mRNA expression of lipocalin 2 and other innate defense genes (hBD2, elafin, LL37) were reduced compared with psoriasis. Although AD has been framed by the Th1/Th2 paradigm as a Th2 polar disease, we present evidence that the IL-23/Th17 axis is largely absent, perhaps accounting for recurrent skin infections in this disease.

Possible pathogenic role of Th17 cells for atopic dermatitis

The critical role of IL-17 has recently been reported in a variety of conditions. Since IL-17 deeply participates in the pathogenesis of psoriasis and keratinocyte production of certain cytokines, the involvement of T helper cell 17 (Th17) in atopic dermatitis (AD) is an issue to be elucidated. To evaluate the participation of Th17 cells in AD, we successfully detected circulating lymphocytes intracellularly positive for IL-17 by flow cytometry, and the IL-17+ cell population was found exclusively in CD3+CD4+ T cells. The percentage of Th17 cells was increased in peripheral blood of AD patients and associated with severity of AD. There was a significant correlation between the percentages of IL-17+ and IFN-gamma+ cells, although percentage of Th17 cells was not closely related to Th1/Th2 balance. Immunohistochemically, IL-17+ cells infiltrated in the papillary dermis of atopic eczema more markedly in the acute than chronic lesions. Finally, IL-17 stimulated keratinocytes to produce GM-CSF, TNF-alpha, IL-8, CXCL10, and VEGF. A marked synergistic effect between IL-17 and IL-22 was observed on IL-8 production. The number of Th17 cells is increased in the peripheral blood and acute lesional skin of AD. Th17 cells may exaggerate atopic eczema.

Psoriasis is characterized by accumulation of immunostimulatory and Th1/Th17 cell-polarizing myeloid dendritic cells

Myeloid dermal dendritic cells (DCs) accumulate in chronically inflamed tissues such as psoriasis. The importance of these cells for psoriasis pathogenesis is suggested by comparative T-cell and DC-cell counts, where DCs outnumber T cells. We have previously identified CD11c(+)-blood dendritic cell antigen (BDCA)-1(+) cells as the main resident dermal DC population found in normal skin. We now show that psoriatic lesional skin has two populations of dermal DCs: (1) CD11c(+)BDCA-1(+) cells, which are phenotypically similar to those contained in normal skin and (2) CD11c(+)BDCA-1(-) cells, which are phenotypically immature and produce inflammatory cytokines. Although BDCA-1(+) DCs are not increased in number in psoriatic lesional skin compared with normal skin, BDCA-1(-) DCs are increased 30-fold. For functional studies, we FACS-sorted psoriatic dermal single-cell suspensions to isolate these two cutaneous DC populations, and cultured them as stimulators in an allogeneic mixed leukocyte reaction. Both BDCA-1(+) and BDCA-1(-) myeloid dermal DC populations induced T-cell proliferation, and polarized T cells to become T helper 1 (Th1) and T helper 17 (Th17) cells. In addition, psoriatic dermal DCs induced a population of activated T cells that simultaneously produced IL-17 and IFN-gamma, which was not induced by normal skin dermal DCs. As psoriasis is believed to be a mixed Th17/Th1 disease, it is possible that induction of these IL-17(+)IFN-gamma(+) cells is pathogenic. These cytokines, the T cells that produce them, and the inducing inflammatory DCs may all be important new therapeutic targets in psoriasis.

Type I interferon: potential therapeutic target for psoriasis?

Background

Psoriasis is an immune-mediated disease characterized by aberrant epidermal differentiation, surface scale formation, and marked cutaneous inflammation. To better understand the pathogenesis of this disease and identify potential mediators, we used whole genome array analysis to profile paired lesional and nonlesional psoriatic skin and skin from healthy donors.

Methodology/Principal Findings

We observed robust overexpression of type I interferon (IFN)–inducible genes and genomic signatures that indicate T cell and dendritic cell infiltration in lesional skin. Up-regulation of mRNAs for IFN-α subtypes was observed in lesional skin compared with nonlesional skin. Enrichment of mature dendritic cells and 2 type I IFN–inducible proteins, STAT1 and ISG15, were observed in the majority of lesional skin biopsies. Concordant overexpression of IFN-γ and TNF-α–inducible gene signatures occurred at the same disease sites.

Conclusions/Significance

Up-regulation of TNF-α and elevation of the TNF-α–inducible gene signature in lesional skin underscore the importance of this cytokine in psoriasis; these data describe a molecular basis for the therapeutic activity of anti–TNF-α agents. Furthermore, these findings implicate type I IFNs in the pathogenesis of psoriasis. Consistent and significant up-regulation of type I IFNs and their associated gene signatures in psoriatic skin suggest that type I IFNs may be potential therapeutic targets in psoriasis treatment.

Chemotactic activity of S100A7 (Psoriasin) is mediated by the receptor for advanced glycation end products and potentiates inflammation with highly homologous but functionally distinct S100A15

Human S100A7 (psoriasin) is overexpressed in inflammatory diseases. The recently discovered, co-evolved hS100A15 is almost identical in sequence and up-regulated with hS100A7 during cutaneous inflammation. The functional role of these closely related proteins for inflammation remains undefined. By generating specific Abs, we demonstrate that hS100A7 and hS100A15 proteins are differentially expressed by specific cell types in the skin. Although highly homologous, both proteins are chemoattractants with distinct chemotactic activity for leukocyte subsets. We define RAGE (receptor for advanced glycation end products) as the hS100A7 receptor, whereas hS100A15 functions through a Gi protein-coupled receptor. hS100A7-RAGE binding, signaling, and chemotaxis are zinc-dependent in vitro, reflecting the previously reported zinc-mediated changes in the hS100A7 dimer structure. When combined, hS100A7 and hS100A15 potentiate inflammation in vivo. Thus, proinflammatory synergism in disease may be driven by the diverse biology of these almost identical proteins that have just recently evolved. The identified S100A7 interaction with RAGE may provide a novel therapeutic target for inflammation.

Eczematous dermatosis and thrombocytosis induced by efalizumab: two new side effects

Efalizumab was authorized to be put on the market in France starting July 21, 2005. Its efficacy and tolerance profile in plaque psoriasis at a dose of 1 mg kg(-1) weekly in a subcutaneous injection have been studied in phase III trials. At the current moment, more than 3,500 patients have been included in clinical trials. Flu-like symptoms (fever, chills, headaches, nausea, vomiting, myalgia) are the most frequent adverse events. On the skin, a localized papular rash or the aggravation of the psoriasis in an edematous or even pustular form are the two most regularly observed complications. At the biological level, hyperlymphocytosis and a temporary increase in alkaline phosphatases without clinical consequences are the most frequent anomalies. We report 2 adverse events under efalizumab that to our knowledge have never been described: a case of an eczematous rash and a case of thrombocytosis.

Psoriasis vulgaris lesions contain discrete populations of Th1 and Th17 T cells

The importance of T helper 17 (Th17) cells in inflammation and autoimmunity is now being appreciated. We analyzed psoriasis skin lesions and peripheral blood for the presence of IL-17-producing T cells. We localized Th17 cells predominantly to the dermis of psoriasis skin lesions, confirmed that IL-17 mRNA increased with disease activity, and demonstrated that IL-17 mRNA expression normalized with cyclosporine therapy. IL-22 mRNA expression mirrored IL-17 and both were downregulated in parallel with keratin 16. Th17 cells are a discrete population, separate from Th1 cells (which are also in psoriasis lesions), and Th2 cells. Our findings suggest that psoriasis is a mixed Th1 and Th17 inflammatory environment. Th17 cells may be proximal regulators of psoriatic skin inflammation, and warrant further attention as therapeutic targets.