Progress in understanding the immunopathogenesis of psoriasis

The inhibitory mechanism by curcumin on the Zac1-enhanced cyclin D1 expression in human keratinocytes

BACKGROUND

ZAC, a zinc finger protein regulating cell cycle arrest and apoptosis, mRNA was found highly expressed in the hyper-proliferative epidermal compartment of psoriatic skin. On the other hand, curcumin has been tried for treatment of psoriasis partly due to its anti-proliferative property.

OBJECTIVES

Since cyclin D1 is a positive regulator for cell-cycle progression and its expression can be inhibited by curcumin, we would like to test whether the expression of cyclin D1 can be affected by Zac1. The cross-talk between curcumin and Zac1 upon the regulation of cyclin D1 expression will also be explored in the HaCaT cell line.

METHODS

Cyclin D1 promoter luciferase reporter was used to measure the transcriptional activity of Zac1 in the absence or presence of curcumin treatment for HaCaT cells. Likewise, RT-PCR, western blotting and flow cytometry were employed to evaluate the expression of Zac1, cyclin D1 and other negative regulators of S phase entry in cell-cycle.

RESULTS

Zac1 enhances the expression of cyclin D1, but curcumin decreases both the expression of Zac1 and cyclin D1. Interestingly, Zac1-induced cyclin D1 promoter activity is abolished by curcumin. Supportively, curcumin indeed exhibits an inhibitory effect to prevent cultured keratinocytes from entry into S phase in the cell cycle.

CONCLUSIONS

These findings revealed that Zac1 modulates not only cell differentiation and apoptosis but also cell proliferation. The experimental results implied that curcumin may inhibit the expression of ZAC, consequently down-regulate the cyclin D1 expression and decelerate cell-cycle progression of psoriatic keratinocytes.

Genetic and epigenetic basis of psoriasis pathogenesis

Psoriasis is a chronic inflammatory skin disease whose prevalence varies among different populations worldwide. It is a complex multi-factorial disease and the exact etiology is largely unknown. Family based studies have indicated a genetic predisposition; however they cannot fully explain the disease pathogenesis. In addition to genetic susceptibility, environmental as well as gender and age related factors were also been found to be associated. Recently, imbalances in epigenetic networks are indicated to be causative elements in psoriasis. The present knowledge of epigenetic involvement, mainly the DNA methylation, chromatin modifications and miRNA deregulation is surveyed here. An integrated approach considering genetic and epigenetic anomalies in the light of immunological network may explore the pathogenesis of psoriasis.

Non-adherence and measures to improve adherence in the topical treatment of psoriasis

Psoriasis is a chronic, recurrent immune-mediated skin disease with a 2-3% prevalence in the Western population, which severely affects patients' quality of life and poses a considerable socioeconomic challenge. The majority of individuals have psoriasis in limited areas and topical products are the mainstay of therapy according to existing guidelines. It is known that medication adherence rates are lower for topical treatment than for systemic treatment. Poor medication adherence is a major multidimensional problem for patients with chronic disorders as it is associated with unfavourable treatment outcomes, increased risk for development of concomitant diseases and inefficient use of health resources. Despite four decades of adherence research and the large number of studies that have identified the importance of medication non-adherence, there are relatively few studies reporting and designing effective strategies to improve adherence. The aim of this article was to report and describe non-adherence in the topical treatment of psoriasis, the factors that might contribute to this phenomenon, and which interventions have so far been developed for the management of chronic conditions. This article proposes that given that the barriers to medication adherence are complex and varied, solutions to improve adherence and thus clinical outcomes must be multifaceted and must also provide the possibility to be tailored according to each patient's individual needs. Such an individualized and comprehensive adherence-enhancing intervention would probably enable the successful long-term management of this disabling chronic condition.

Psoriasis

Psoriasis is a common chronic inflammatory skin disease with a spectrum of clinical phenotypes and results from the interplay of genetic, environmental, and immunological factors. Four decades of clinical and basic research on psoriasis have elucidated many of the pathogenic mechanisms underlying disease and paved the way to effective targeted therapies. Here, we review this progress and identify future directions of study that are supported by a more integrative research approach and aim at further improving the patients' life.

JAK inhibitors: treatment efficacy and safety profile in patients with psoriasis

Janus kinase (JAK) pathways are key mediators in the immunopathogenesis of psoriasis. Psoriasis treatment has evolved with the advent of targeted therapies, which inhibit specific components of the psoriasis proinflammatory cascade. JAK inhibitors have been studied in early phase trials for psoriasis patients, and the data are promising for these agents as potential treatment options. Tofacitinib, an oral or topically administered JAK1 and JAK3 inhibitor, and ruxolitinib, a topical JAK1 and JAK2 inhibitor, have been most extensively studied in psoriasis, and both improved clinical symptoms of psoriasis. Additional JAK1 or JAK3 inhibitors are being studied in clinical trials. In phase III trials for rheumatoid arthritis, tofacitinib was efficacious in patients with inadequate responses to tumor necrosis factor inhibitors, methotrexate monotherapy, or disease-modifying antirheumatic drugs. The results of phase III trials are pending for these therapies in psoriasis, and these agents may represent important alternatives for patients with inadequate responses to currently available agents. Further investigations with long-term clinical trials are necessary to verify their utility in psoriasis treatment and assess their safety in this patient population.

Balance of Treg vs. T-helper cells in the transition from symptomless to lesional psoriatic skin

BACKGROUND

In the pathogenesis of psoriasis, proinflammatory T cells are strongly involved in the inflammatory process, where regulatory T-cell (Treg) function is impaired.

OBJECTIVES

As effective Treg function is associated with a numerical balance between Treg and effector T cells, we wondered whether Treg/T-helper cell ratios may be associated with certain stages of the inflammatory process. We opted for the margin zone model as a dynamic approach.

METHODS

From nine patients with chronic plaque psoriasis, 3-mm punch biopsies were obtained from the centre and margin of the lesion, perilesional skin and distant uninvolved skin. Skin biopsies of 10 healthy volunteers were included as a control. Samples were analysed using immunohistochemistry and immunofluorescence.

RESULTS

In the transition from symptomless to lesional skin, a significant increase of CD3+, CD4+ and Foxp3+ cells was found. In seven of nine patients the ratio of Treg (Foxp3+) vs. CD4+ T cells was higher in the distant uninvolved skin than in the perilesional and lesional skin. Interestingly, the Foxp3/CD4 ratio in the distant uninvolved skin was even higher than in the skin of healthy controls. Notably, we found that most of the interleukin (IL)-17 expression was not related to CD4+ cells, but to mast cells.

CONCLUSIONS

The relatively high Foxp3/CD4 ratio in symptomless skin of patients with psoriasis suggests an active immune controlling mechanism distant from the psoriatic plaque. In the margin and centre of the plaque the ratio appears skewed towards effector cells associated with inflammation. IL-17, an important driver of the psoriatic process, is mostly related to mast cells, and only sporadically to T cells.

Severe skin forms of psoriasis in black africans: epidemiological, clinical, and histological aspects related to 56 cases

Bacground. Psoriasis is an erythematosquamous dermatosis of chronic development. In sub-Saharan Africa, few studies have been focused on complicated forms of psoriasis. Objective. The aim is to describe epidemiological, clinical, and histological features of severe skin forms of psoriasis in Cote d'Ivoire. Material and Methods. The study was both cross-sectional and descriptive, that focused on patient admitted to the dermatology unit for complicated psoriasis, from January 1st, 1986, to December 31th, 2007. Results. Fifty-six patients admitted to hospital for severe skin forms of psoriasis were recorded and included in our study over 7.503 patients hospitalized during the study period. They represented 0.75% of cases. The average age was 39.6 ± 3.3 years. There were 49 male (87.5%) and 7 female patients (12.5%) with a sex ratio of 7. At socioprofessional level, 48 patients (87.5%) were from category 1. Patients' history was dominated by the psoriasis vulgaris. Physical and general signs were dominated by itching (58.9%). The three severe skin forms were observed with predominant erythrodermic psoriasis (60.7%). Fifteen patients (34.9%) were HIV positive. Conclusion. Severe skin forms of psoriasis are rare in our setting. But in the quarter of HIV-positive patients, they are dominated by the erythrodermic psoriasis.

A randomized phase 2a efficacy and safety trial of the topical Janus kinase inhibitor tofacitinib in the treatment of chronic plaque psoriasis

BACKGROUND

Tofacitinib (CP-690,550) is a novel Janus kinase inhibitor in development as an oral formulation for the treatment of several inflammatory diseases including psoriasis.

OBJECTIVES

This phase 2a study aimed to assess the efficacy, systemic safety, local tolerability and systemic pharmacokinetics of topical tofacitinib in mild-to-moderate plaque psoriasis.

METHODS

Two tofacitinib ointment formulations were evaluated in this multicentre, double-blind, vehicle-controlled trial (NCT01246583). Seventy-one patients were randomized 2 : 1 : 2 : 1 to 2% tofacitinib ointment 1, vehicle 1, 2% tofacitinib ointment 2 and vehicle 2, each administered twice daily for 4 weeks to a single fixed 300 cm(2) treatment area containing a target plaque with or without one or more nontarget plaques and normal skin.

RESULTS

The primary endpoint of percentage change from baseline in the Target Plaque Severity Score at week 4 demonstrated statistically significant improvement for ointment 1 [least squares mean (LSM) -54.4%] vs. vehicle 1 (LSM -41.5%), but not ointment 2 (LSM -24.2%) vs. vehicle 2 (LSM -17.2%). Secondary endpoints (target plaque area and Itch Severity Item) improved similarly for tofacitinib ointment vs. corresponding vehicle. Adverse event (AE) occurrence was similar across treatment groups. All AEs were mild or moderate and none were serious or led to subject discontinuation. One application-site AE (erythema) was reported. Tofacitinib mean systemic exposure was minimal and was greater for ointment 1 than for ointment 2.

CONCLUSIONS

Tofacitinib ointment 1 was well tolerated and efficacious compared with vehicle for the treatment of plaque psoriasis. Further study of topical tofacitinib for psoriasis treatment is warranted.

Genetic Epidemiology of Psoriasis

Psoriasis is a chronic, inflammatory, immune-mediated skin condition with a prevalence of 0-11.8% across the world. It is associated with a number of cardiovascular, metabolic, and autoimmune disease co-morbidities. Psoriasis is a multifactorial disorder, influenced by both genetic and environmental factors. Its genetic basis has long been established through twin studies and familial clustering. The association of psoriasis with the HLA-Cw6 allele has been shown in many studies. Recent genome-wide association studies have identified a large number of other genes associated with psoriasis. Many of these genes regulate the innate and adaptive immune system. These findings indicate that a dysregulated immune system may play a major role in the pathogenesis of psoriasis. In this article, we review the clinical and genetic epidemiology of psoriasis with a brief description of the pathogenesis of disease.

Community differentiation of the cutaneous microbiota in psoriasis

BACKGROUND

Psoriasis is a common chronic inflammatory disease of the skin. We sought to characterize and compare the cutaneous microbiota of psoriatic lesions (lesion group), unaffected contralateral skin from psoriatic patients (unaffected group), and similar skin loci in matched healthy controls (control group) in order to discern patterns that govern skin colonization and their relationship to clinical diagnosis.

RESULTS

Using high-throughput 16S rRNA gene sequencing, we assayed the cutaneous bacterial communities of 51 matched triplets and characterized these samples using community data analysis techniques. Intragroup Unifrac β diversity revealed increasing diversity from control to unaffected to lesion specimens. Likewise, principal coordinates analysis (PCoA) revealed separation of the lesion samples from unaffected and control along the first axis, suggesting that psoriasis is a major contributor to the observed diversity. The taxonomic richness and evenness decreased in both lesion and unaffected communities compared to control. These differences are explained by the combined increased abundance of the four major skin-associated genera (Corynebacterium, Propionibacterium, Staphylococcus, and Streptococcus), which present a potentially useful predictor for clinical skin type. Psoriasis samples also showed significant univariate decreases in relative abundances and strong classification performance of Cupriavidus, Flavisolibacter, Methylobacterium, and Schlegelella genera versus controls. The cutaneous microbiota separated into two distinct clusters, which we call cutaneotypes: (1) Proteobacteria-associated microbiota, and (2) Firmicutes-associated and Actinobacteria-associated microbiota. Cutaneotype 2 is enriched in lesion specimens compared to control (odds ratio 3.52 (95% CI 1.44 to 8.98), P <0.01).

CONCLUSIONS

Our results indicate that psoriasis induces physiological changes both at the lesion site and at the systemic level, which select for specific differential microbiota among the assayed clinical skin types. These differences in microbial community structure in psoriasis patients are potentially of pathophysiologic and diagnostic significance.

The role of p38 MAPK in the aetiopathogenesis of psoriasis and psoriatic arthritis

The pathogenetic mechanisms responsible for the induction of immune-mediated disorders, such as psoriasis, remain not well characterized. Molecular signaling pathways are not well described in psoriasis, as well as psoriatic arthritis, which is seen in up to 40% of patients with psoriasis. Signaling pathway defects have long been hypothesized to participate in the pathology of psoriasis, yet their implication in the altered psoriatic gene expression still remains unclear. Emerging data suggest a potential pathogenic role for mitogen activated protein kinases p38 (p38 MAPK) extracellular signal-regulated kinase 1/2 (ERK1/2), and c-Jun N-terminal kinase (JNK) in the development of psoriasis. The data are still limited, though, for psoriatic arthritis. This review discusses the current data suggesting a crucial role for p38 MAPK in the pathogenesis of these disorders.

CD57 expression and cytokine production by T cells in lesional and unaffected skin from patients with psoriasis

BACKGROUND

The immunopathogenic mechanisms leading to psoriasis remain unresolved. CD57 is a marker of replicative inability and immunosenescence on CD8+ T cells and the proportion of CD57 expressing CD8+ T cells is increased in a number of inflammatory conditions.

METHODOLOGY

We examined the expression of CD57 on T cells in the skin of patients affected with psoriasis, comparing lesional and unaffected skin. We also assessed functionality of the T cells by evaluating the secretion of several inflammatory cytokines (IL-17A, IFN-gamma, IL-2, IL-33, TNF-alpha, IL-21, IL-22, and IL-27), from cell-sorted purified CD4+ and CD8+ T cells isolated from lesional and unaffected skin biopsies of psoriasis patients.

PRINCIPAL FINDINGS

We observed that the frequency of CD57+CD4+ and CD57+CD8+ T cells was significantly higher in unaffected skin of psoriasis patients compared to lesional skin. Sorted CD4+ T cells from psoriatic lesional skin produced higher levels of IL-17A, IL-22, and IFN-gamma compared to unaffected skin, while sorted CD8+ T cells from lesional skin produced higher levels of IL-17, IL-22, IFN-gamma, TNF-alpha, and IL-2 compared to unaffected skin.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that T cells in unaffected skin from psoriasis patients exhibit a phenotype compatible with replicative inability. As they have a lower replicative capacity, CD57+ T cells are less frequent in lesional tissue due to the high cellular turnover.

Th22 and related cytokines in inflammatory and autoimmune diseases

INTRODUCTION

Th22 and related cytokines regulate various processes and have been linked to diverse effects. The levels of Th22 and cytokine IL-22 are increased in several disorders and positively related to some autoimmune diseases. Preclinical studies have suggested that the inhibition or stimulation of IL-22 is an attractive approach to reverse the immune disorders. Simultaneously, considering many patients with refractory autoimmune diseases respond poorly to the therapies which are highly toxic, more effective therapies are to be examined.

AREAS COVERED

The role of Th22 cells and related cytokines and therapeutic strategies targeting them in many illnesses, especially inflammatory and autoimmune diseases.

EXPERT OPINION

Th22 cells and related cytokine IL-22 regulate multiple biological functions and play an important role in a number of inflammatory and autoimmune diseases. They have unique and attractive advantages for targeting. Targeting IL-22 has already been trialed in many mice experiments, showing better efficacy and fewer side effects compared with classical drugs. Targeting IL-22 or Th22 might provide pathogenetic treatment. However, Th22 subset is a recently identified Th subset and its associated research is extremely limited. Therefore, there are still many unanswered questions and further researches are warranted.

The pro-inflammatory cytokine IL-22 up-regulates keratin 17 expression in keratinocytes via STAT3 and ERK1/2

BACKGROUND

To investigate the regulation of K17 expression by the pro-inflammatory cytokine IL-22 in keratinocytes and its important role in our previously hypothesized "K17/T cell/cytokine autoimmune loop" in psoriasis.

MATERIALS AND METHODS

K17 expression was examined in the IL-22-treated keratinocytes by real-time quantitative PCR, ELISA, Western blot and Immunofluorescence. In addition, the signaling pathways involved in K17 regulation were investigated with related inhibitors and siRNAs. In addition, K17 expression was examined in the epidermis of IL-22-injected mouse skin.

RESULTS

IL-22-induced K17 expression was confirmed in keratinocytes and the epidermis of IL-22-injected mouse skin at both mRNA and protein levels, which is an important complement to the autoimmune loop. We further investigated the regulatory mechanisms and found that both STAT3 and ERK1/2 were involved in the up-regulation of K17 expression induced by IL-22.

CONCLUSION

IL-22 up-regulates K17 expression in keratinocytes in a dose-dependent manner through STAT3- and ERK1/2-dependent mechanisms. These findings indicated that IL-22 was also involved in the K17/T cell/cytokine autoimmune loop and may play an important role in the progression of psoriasis.

How genetic variation affects patient response and outcome to therapy for psoriasis

Psoriasis is a prevalent chronic inflammatory condition that affects the skin. There are many treatments available for psoriasis but they are not universally effective and some have associated toxicities. Pharmacogenetics and pharmacogenomics explore the relationship between individual genetic variation and drug effect to allow targeted 'personalized' therapy for patients. There has been very limited pharmacogenetic research regarding psoriasis, with most limited to small retrospective case-control studies looking at single-nucleotide polymorphisms in candidate genes involved in drug pharmacokinetics. We review the pharmacogenetic investigation of treatments for psoriasis to date, including emerging pharmacogenomic studies. In addition, we discuss how such genetic data could be incorporated into routine clinical practice and future areas for development in this field.