Recent insights into the immunopathogenesis of psoriasis provide new therapeutic opportunities

Influence of ustekinumab on body weight of patients with psoriasis: an initial report

Introduction

Many recent epidemiological studies have shown the influence of treatment with anti-TNF-α on body mass of patients with psoriasis but there are no reports in the literature on the influence of ustekinumab on that parameter.

Aim

To review the effect of ustekinumab therapy on body weight in patients with psoriasis.

Material and methods

The examined group consisted of 11 patients with psoriasis treated at the Department and Clinic of Dermatology in Olsztyn. Patients’ body mass and body mass index (BMI) were evaluated prior to the first administration of the ustekinumab dose and at week 28 of treatment (the day of the fourth dose).

Results

Body mass increase was determined in 7 patients (64%), on average by 2.27 kg (p < 0.05), and the BMI increased by 3.35% (p < 0.1).

Conclusions

Observing a correlation between ustekinumab application and body mass increase, similar to the treatment with anti-TNF-α preparations, an attempt was undertaken at explaining that correlation by analysing the role of IL-12 and IL-23 in psoriasis pathogenesis. IL-12 and IL-23, by influencing the naïve lymphocytes T and stimulating their diversification towards Th1 and Th17, also, indirectly, cause an increase in TNF-α and other cytokines production (IL-2, IFN-γ, IL-17, IL-10, IL-22). Ustekinumab will then have a significant influence on decreasing the production of cytokines, which are important for metabolism and body mass.

Study on Certain Biomarkers of Inflammation in Psoriasis Through "OMICS" Platforms

Background:

In recent years, research on psoriasis has focused on the identification of biomarkers for the diagnosis, pathogenesis, prognosis, or therapeutic response of the disease. These studies could provide insights into the susceptibility and natural history of psoriasis. The identification of biomarkers related to comorbidities in psoriasis, such as arthritis, cardiovascular disease, and the metabolic syndrome, is of special clinical interest.

Materials and Methods:

We performed an extensive review on psoriasis biomarkers, including cytokine and growth factors, in the literature published between 1997 and 2013, including cross-references of any retrieved articles. We also included some data from our own studies.

Results:

This review presents current knowledge of soluble biomarkers in psoriasis, including cytokines, chemokines, proangiogenic mediators, growth factors, antimicrobial proteins, neuropeptides, and oxidative stress markers.

Conclusion:

In conclusion, a number of studies have been conducted with the aim of establishing soluble biomarkers for psoriasis. Most of the biomarkers that have been studied do not meet the criteria for a clinically useful biomarker. Further work is needed to establish a role for soluble biomarkers in the diagnosis and treatment of psoriasis, with a special focus on biomarkers for psoriasis comorbidities, such as arthritis, cardiovascular disease, and the metabolic syndrome.

Patient considerations and targeted therapies in the management of psoriasis in Chinese patients: role of ustekinumab

Psoriasis is an immune-mediated disease affecting approximately 0.1% to 0.5% of the population in the People's Republic of China. Multiple therapeutic options are available for the treatment of moderate to severe psoriasis although they all have their respective disadvantages. The application of biological agents has brought significant efficacy in psoriasis treatment. Ustekinumab, a human monoclonal antibody targeting the interleukin-12/23 pathway, shows its superiority in efficacy, long duration of drug action, and good tolerance in patients. Phase III clinical trials of ustekinumab have been completed in Mainland China, and the drug is available in Taiwan and Hong Kong. Meanwhile, its long-term safety and efficacy merit further investigation.

Suppression of molecular inflammatory pathways by Toll-like receptor 7, 8, and 9 antagonists in a model of IL-23-induced skin inflammation

Psoriasis is a complex inflammatory disease resulting from the activation of T helper (Th) 1 and Th17 cells. Recent evidence suggests that abnormal activation of Toll-like receptors (TLRs) 7, 8 and 9 contributes to the initiation and maintenance of psoriasis. We have evaluated the effects of TLR antagonists on the gene expression profile in an IL-23-induced skin inflammation model in mice. Psoriasis-like skin lesions were induced in C57BL/6 mice by intradermal injection of IL-23 in the dorsum. Two TLR antagonists were compared: IMO-3100, an antagonist of TLRs 7 and 9, and IMO-8400, an antagonist of TLRs 7, 8 and 9, both of which previously have been shown to reduce epidermal hyperplasia in this model. Skin gene expression profiles of IL-23-induced inflammation were compared with or without TLR antagonist treatment. IL-23 injection resulted in alteration of 5100 gene probes (fold change ≥ 2, FDR < 0.05) including IL-17 pathways that are up-regulated in psoriasis vulgaris. Targeting TLRs 7, 8 and 9 with IMO-8400 resulted in modulation of more than 2300 mRNAs while targeting TLRs 7 and 9 with IMO-3100 resulted in modulation of more than 1900 mRNAs. Both agents strongly decreased IL-17A expression (>12-fold reduction), normalized IL-17 induced genes such as beta-defensin and CXCL1, and normalized aberrant expression of keratin 16 (indicating epidermal hyperplasia). These results suggest that IL-23-driven inflammation in mouse skin may be dependent on signaling mediated by TLRs 7, 8, and 9 and that these receptors represent novel therapeutic targets in psoriasis vulgaris and other diseases with similar pathophysiology.

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.

Associations between tumor necrosis factor-α polymorphisms and risk of psoriasis: a meta-analysis

Background

Tumor necrosis factor-α (TNF-α) may play an important role in the recalcitrant inflammatory and hyperproliferative dermatosis of psoriasis, and there may be a relationship between TNF-α polymorphisms and psoriasis risk.

Methods

We performed a meta-analysis to evaluate the associations between TNF-α polymorphisms and psoriasis. Electronic searches of Pubmed, Embase, and Web of Science were performed for all publications on the associations between TNF-α polymorphisms and psoriasis through September 26, 2012. The pooled odds ratios (ORs) with their 95% confidence interval (95%CIs) were calculated to assess the associations.

Results

Sixteen case-control studies with a total of 2,253 psoriasis cases and 1,947 controls on TNF-α 308 G/A polymorphism and fourteen studies on TNF-α 238 G/A polymorphism with 2,104 cases and 1,838 controls were finally included into the meta-analysis. Overall, TNF-α 308 G/A polymorphism was significantly associated with decreased risk of psoriasis under three genetic comparison models (for A versus G: fixed-effects OR 0.71, 95%CI 0.62-0.82, P < 0.001; for AG versus GG: fixed-effects OR 0.67, 95%CI 0.57-0.78, P < 0.001; for AA/AG versus GG: fixed-effects OR 0.67, 95%CI 0.58-0.78, P < 0.001). In addition, TNF-α 238 G/A polymorphism was associated with increased risk of psoriasis under three genetic models (for A versus G: fixed-effects OR 2.46, 95%CI 2.04-2.96, P < 0.001; for AG versus GG: fixed-effects OR 2.69, 95%CI 2.20-3.28, P < 0.001; for AA/AG versus GG: fixed-effects OR 2.68, 95%CI 2.20-3.26, P < 0.001). Subgroup analysis by ethnicity identified a significant association between TNF-α 308 G/A polymorphism and decreased risk of psoriasis in both Caucasians and Asians and a significant association between TNF-α 238 G/A polymorphism and increased risk of psoriasis in Caucasians.

Conclusions

The meta-analysis suggests that TNF-α 308 G/A polymorphism is associated with decreased risk of psoriasis, while TNF-α 238 G/A is associated with increased risk of psoriasis.

Metabolic syndrome and skin: psoriasis and beyond

Metabolic syndrome (Met S) is a clustering of risk factors comprising of abdominal obesity, dyslipidemia, elevated blood pressure, and abnormal glucose tolerance. The prevalence of Met S has been increasing in the last few years throughout the world. Psoriasis has consistently been associated with Met S as well as its various components. However, the association is no longer limited to psoriasis alone. Various dermatological conditions such as lichen planus, androgenetic alopecia, systemic lupus erythematosus, skin tags, acanthosis nigricans, and even cutaneous malignancies have also been found to be associated with this syndrome. Though chronic inflammation is thought to be the bridging link, the role of oxidative stress and endocrine abnormalities has recently been proposed in bringing them together.

Psoriasis and uveitis: a literature review

Psoriasis is a systemic, chronic, immunologically mediated disease, with significant genetic and environmental influences. It affects from 1 to 3% of the world population. Recently, the relation between psoriasis and different comorbidities, particularly metabolic syndrome, has become extremely relevant. Uveitis is characterized by a process of intraocular inflammation resulting from various causes. Considering psoriasis and uveitis as immune-mediated diseases, this study aims to evaluate the possible association of psoriasis and/or psoriatic arthritis with uveitis and its subtypes. Few studies have evaluated the association of uveitis and psoriasis without joint involvement. It seems that psoriasis without arthropathy is not a risk factor for the development of uveitis. Uveitis tends to develop more frequently in patients with arthropathy or pustular psoriasis than in patients with other forms of psoriasis. Ophthalmic examination should be performed periodically in patients with psoriasis and uveitis. If ophthalmopathy is diagnosed, the patient should receive adequate treatment with anti-inflammatory drugs or immunomodulators to prevent vision loss.

Psoralen-ultraviolet A treatment with Psoralen-ultraviolet B therapy in the treatment of psoriasis

OBJECTIVE

To compare the conventional psoralen-ultraviolet A treatment with psoralen-ultraviolet B therapy in the treatment of psoriasis.

METHODOLOGY

We studied 50 patients of plaque type psoriasis who were selected to receive either conventional psoralen-ultraviolet A or psoralen-ultraviolet B treatment.

RESULTS

There was no significant difference between the two treatment groups in the number of patients whose skin cleared of psoriasis or the number of exposures required for clearance. Profile of side effects and disease status was also similar after three months of follow up.

CONCLUSION

Psoralen-ultraviolet B treatment is as effective as conventional psoralen-ultraviolet A in the treatment of psoriasis. Further long term studies are needed to assess the safety of psoralen-ultraviolet B.

The psoriasis-associated D10N variant of the adaptor Act1 with impaired regulation by the molecular chaperone hsp90

Act1 is an essential adaptor in interleukin 17 (IL-17)-mediated signaling and is recruited to the receptor for IL-17 after stimulation with IL-17. Here we found that Act1 was a 'client' protein of the molecular chaperone hsp90. The D10N variant of Act1 (Act1(D10N)) that is linked to susceptibility to psoriasis was defective in its interaction with hsp90, which resulted in a global loss of Act1 function. Act1-deficient mice modeled the mechanistic link between loss of Act1 function and susceptibility to psoriasis. Although Act1 was necessary for IL-17-mediated inflammation, Act1-deficient mice had a hyperactive response of the T(H)17 subset of helper T cells and developed spontaneous IL-22-dependent skin inflammation. In the absence of IL-17 signaling, IL-22 was the main contributor to skin inflammation, which provides a molecular mechanism for the association of Act1(D10N) with psoriasis susceptibility.

Prevalence of metabolic syndrome in South Indian patients with psoriasis vulgaris and the relation between disease severity and metabolic syndrome: a hospital-based case-control study

Background:

Psoriasis is a chronic inflammatory disease of the skin and joints with an increased cardiovascular risk. Previous studies have shown a higher prevalence of metabolic syndrome (MS) in psoriatic patients.

Objective:

To investigate the prevalence of MS in patients with psoriasis and healthy controls, and to determine the relation between disease severity and the presence of MS.

Materials and Methods:

We performed a hospital-based case-control study on 118 adult patients with psoriasis vulgaris and 120 controls matched for age, sex and body mass index. MS was diagnosed by the presence of three or more of the South Asian Modified National Cholesterol Education Program's Adult Panel III criteria.

Results:

MS was significantly more common in psoriatic patients than in controls (44.1% vs. 30%, P value = 0.025). Psoriatic patients also had a higher prevalence of triglyceridemia (33.9% vs. 20.8%, P value = 0.011), abdominal obesity (34.7% vs. 32.5%, P value = 0.035) and elevated blood sugar. There was no difference in the high density lipoprotein (HDL) levels and presence of hypertension among patients with psoriasis and normal controls. There was no correlation between the severity and duration of psoriasis with MS.

Conclusion:

MS is frequent in patients with psoriasis. We have found no relationship between disease severity and presence of MS. Hence, we suggest that all patients must be evaluated for the MS, irrespective of the disease severity.

Psoriasis and increased prevalence of hypertension and diabetes mellitus

Background:

Psoriasis is an autoimmune skin disease and associated with other diseases such as cardiovascular, hypertension, and diabetes mellitus.

Aim:

Our aim was to explore the prevalence of diabetes mellitus and hypertension in psoriatic patients.

Materials and Methods:

Between April 2008 and May 2010, a total of 304 psoriatic and 300 nonpsoriatic patients were enrolled in this cross sectional study. Data were obtained on age, sex, weight, heights, etc; documented medical history of diabetes mellitus and hypertension; family history of diabetes mellitus and hypertension in first relatives, history of smoking.

Results:

There was no significant difference in age and gender distribution between two groups. There was also no difference in body mass index between two groups. Within psoriatic group, 79.3% of patients present with plaque type of the disease and 20.7% present with other types. The results showed that within psoriatic patients, the prevalence of diabetes in women is significantly higher than in men (OR=1.93, CI95%: 1.1–3.6, P=0.004) but this difference is not present in nonpsoriatic patients. The results also showed that the prevalence of diabetes in psoriatic patients is significantly higher than nonpsoriatic patients (OR=1.76, CI95%: 1.11–2.8, P=0.015). The data showed that psoriatic patients were more likely to develop hypertension compared with nonpsoriatic patients (OR=2.2, CI95%: 1.2–4.6, P=0.003). According to results, although smoking rate within psoriatic patients is higher than the other group but the difference was not significant.

Conclusion:

Psoriatic patients have an increased risk of developing metabolic syndrome and hypertension in comparison to nonpsoriatic patients.

Effect of Biologic Agents on Non-PASI Outcomes in Moderate-to-Severe Plaque Psoriasis: Systematic Review and Meta-Analyses

Introduction

The objective of this review was to conduct a systematic review with meta-analysis and Bayesian mixed treatment comparisons (MTC) evaluating the impact of biologics on non-Psoriasis Area and Severity Index (PASI) health outcomes in patients with moderate-to-severe plaque psoriasis.

Methods

MEDLINE and Cochrane Central Register of Controlled Trials were searched from 1966 to May 2009. Citations were screened for randomized, controlled trials of biologics versus either placebo or each other in adults with moderate-to-severe plaque psoriasis and reported any of several outcomes. Traditional and Bayesian MTC meta-analyses were conducted for each endpoint using either a random- or fixed-effect model where appropriate.

Results

Thirty-eight studies met eligibility criteria. All biologics showed significant improvement in achieving a good response on the static physician’s global assessment (PGA) versus placebo while, in the MTC, differences were noted between individual drugs. In achieving a good response on the dynamic PGA, all biologics showed significant improvements over placebo, while the MTC showed significant improvements with the anti-interleukins versus anti-T cells. Relative to placebo, antitumor necrosis factor (TNF) agents and anti-interleukins showed significant improvements in the Dermatology Life Quality Index (DLQI). Compared with placebo, the anti-TNF agents showed significant improvements in both 36-item Medical Outcomes Study Short-Form General Health Survey (SF-36) mental and physical component scores, while anti-T cell agents showed no improvements. The MTC showed no differences between any biologics for either the DLQI or SF-36.

Conclusion

Individual biologics and classes showed consistent benefits across non-PASI health outcomes in patients with moderate-to-severe plaque psoriasis while MTC meta-analyses suggested that some differences exist.

Ustekinumab in psoriasis immunopathology with emphasis on the Th17-IL23 axis: a primer

Psoriasis is a chronic relapsing immunoinflammatory dermatosis that is commonly associated with systemic comorbidities. The pathogenic importance of interleukin (IL)-12 and IL-23 is beyond doubt, as well as the involvement of T helper cells (Th)1 and Th17 cells. There is upregulation of the p40 subunit shared by IL-12 and IL-23 and of the IL-23 p19 subunit, but not an increased expression of the IL-12 p35 subunit. This indicates that IL-23 appears more involved than IL-12 in the pathogenesis of psoriatic plaques. Ustekinumab is a fully human monoclonal antibody of the immunoglobulin (Ig) G1 class targeting the p40 subunit common to both IL-12 and IL-23, thus inhibiting both IL-12 and IL-23 receptor-mediated signalling. Ustekinumab is part of the recent biologic therapies active in psoriasis, autoimmune arthritides, and inflammatory bowel diseases.

Synovial tissue response to treatment in psoriatic arthritis

Following its validation and wide application in rheumatoid arthritis (RA), synovial tissue analysis has recently been applied to studies on Psoriatic Arthritis (PsA). Such studies aim to thereby clarify its distinctive features and the nature of specific responses upon administration of disease modifying anti-rheumatic drug (DMARD) or biologic agents. In consequence, insights to disease pathogenesis, drugs' mechanisms of action (MOA) and biomarkers of response have emerged. Data from pilot and open-label studies, and recently from randomized controlled trials, have helped in refining the therapeutic approaches to PsA patients, by improving understanding of MOA and in provision of biomarkers of response. The availability of less invasive and reproducible analysis techniques to obtain and evaluate synovial biopsies will further enhance the utility of this approach in due course.

Immune-regulatory mechanisms in systemic autoimmune and rheumatic diseases

Systemic autoimmune and rheumatic diseases (SAIRDs) are thought to develop due to the failure of autoimmune regulation and tolerance. Current therapies, such as biologics, have improved the clinical results of SAIRDs; however, they are not curative treatments. Recently, new discoveries have been made in immune tolerance and inflammation, such as tolerogenic dendritic cells, regulatory T and B cells, Th 17 cells, inflammatory and tolerogenic cytokines, and intracellular signaling pathways. They lay the foundation for the next generation of the therapies beyond the currently used biologic therapies. New drugs should target the core processes involved in disease mechanisms with the aim to attain complete cure combined with safety and low costs compared to the biologic agents. Re-establishment of autoimmune regulation and tolerance in SAIRDs by the end of the current decade should be the final and realistic target.

Infliximab for the treatment of plaque psoriasis

Infliximab is a monoclonal antibody that targets tumor necrosis factor-α (TNFα). It is used in the treatment of a number of inflammatory disorders including severe plaque psoriasis. TNFα is thought to have a major role in psoriasis by promoting an inflammatory infiltrate into the skin and inducing keratinocyte proliferation and preventing keratinocyte apoptosis, which directly contributes to the characteristic plaque skin lesions. Based on four randomized, placebo-controlled, double-blind clinical trials and nine open-label uncontrolled trials of the use of infliximab in plaque psoriasis, it was found that infliximab is a highly efficacious, rapid, sustainable, and relatively safe therapy. Yet as with any biologic, caution is recommended in its use as infusion reactions, lupus-like syndromes, infections, malignancies including lymphomas, as well as other rare events have been reported.

Protecting the boundary: the sentinel role of host defense peptides in the skin

The skin is our primary shield against microbial pathogens and has evolved innate and adaptive strategies to enhance immunity in response to injury or microbial insult. The study of antimicrobial peptide (AMP) production in mammalian skin has revealed several of the elegant strategies that AMPs use to prevent infection. AMPs are inducible by both infection and injury and protect the host by directly killing pathogens and/or acting as multifunctional effector molecules that trigger cellular responses to aid in the anti-infective and repair response. Depending on the specific AMP, these molecules can influence cytokine production, cell migration, cell proliferation, differentiation, angiogenesis and wound healing. Abnormal production of AMPs has been associated with the pathogenesis of several cutaneous diseases and plays a role in determining a patient's susceptibility to pathogens. This review will discuss current research on the regulation and function of AMPs in the skin and in skin disorders.

Low-frequency sonophoresis: application to the transdermal delivery of macromolecules and hydrophilic drugs

IMPORTANCE OF THE FIELD

Transdermal delivery of macromolecules provides an attractive alternative route of drug administration when compared to oral delivery and hypodermic injection because of its ability to bypass the harsh gastrointestinal tract and deliver therapeutics non-invasively. However, the barrier properties of the skin only allow small, hydrophobic permeants to traverse the skin passively, greatly limiting the number of molecules that can be delivered via this route. The use of low-frequency ultrasound for the transdermal delivery of drugs, referred to as low-frequency sonophoresis (LFS), has been shown to increase skin permeability to a wide range of therapeutic compounds, including both hydrophilic molecules and macromolecules. Recent research has demonstrated the feasibility of delivering proteins, hormones, vaccines, liposomes and other nanoparticles through LFS-treated skin. In vivo studies have also established that LFS can act as a physical immunization adjuvant. LFS technology is already clinically available for use with topical anesthetics, with other technologies currently under investigation.

AREAS COVERED IN THIS REVIEW

This review provides an overview of mechanisms associated with LFS-mediated transdermal delivery, followed by an in-depth discussion of the current applications of LFS technology for the delivery of hydrophilic drugs and macromolecules, including its use in clinical applications.

WHAT THE READER WILL GAIN

The reader will gain an insight into the field of LFS-mediated transdermal drug delivery, including how the use of this technology can improve on more traditional drug delivery methods.

TAKE HOME MESSAGE

Ultrasound technology has the potential to impact many more transdermal delivery platforms in the future due to its unique ability to enhance skin permeability in a controlled manner.

CCR6 as a possible therapeutic target in psoriasis

IMPORTANCE OF THE FIELD

Psoriasis is a common, chronic autoimmune disease of the skin. Despite a number of effective treatments, new therapies are needed with enhanced efficacy, safety and convenience. Chemokine receptors are GPCRs that control leukocyte trafficking, and like other GPCRs, are good potential drug targets. The chemokine receptor CCR6 is expressed on the T(H)17 subset of CD4(+) T cells, which produces IL-17A/F, IL-22, TNF-alpha and other cytokines, and which has been implicated in the pathogenesis of psoriasis. CCR6 and its ligand, CCL20/MIP-3alpha, are highly expressed in psoriatic skin and CCR6 is necessary for the pathology induced in a mouse model of psoriasis-like inflammation.

AREAS COVERED IN THIS REVIEW

This review summarizes the evidence for the importance of the IL-23/T(H)17 axis, and in particular CCR6 and CCL20 in psoriasis, dating from 2000 to the present, and discusses the possibility of inhibiting CCR6 as a treatment for the disease.

WHAT THE READER WILL GAIN

The review informs the reader of the current thinking on the mechanisms of inflammation in psoriasis and the possible roles for CCR6 (and CCL20) in disease pathogenesis.

TAKE HOME MESSAGE

We conclude that CCR6 should be investigated as a potential therapeutic target in psoriasis.

Pathogenic mechanisms shared between psoriasis and cardiovascular disease

Psoriasis is associated with an increased risk of cardiovascular disease, a hallmark of which is atherosclerosis. The objective of this study was to review the pertinent literature and highlight pathogenic mechanisms shared between psoriasis and atherosclerosis in an effort to advocate early therapeutic or preventive measures. We conducted a review of the current literature available from several biomedical search databases focusing on the developmental processes common between psoriasis and atherosclerosis. Our results revealed that the pathogenic mechanisms shared between the two diseases converged onto "inflammation" phenomenon. Within the lymph nodes, antigen-presenting cells activate naive T-cells to increase expression of LFA-1 following which activated T-cells migrate to blood vessel and adhere to endothelium. Extravasation occurs mediated by LFA-1 and ICAM-1 (or CD2 and LFA-3) and activated T-cells interact with dendritic cells (and macrophages and keratinocytes in psoriasis or smooth muscle cells in atherosclerosis). These cells further secrete chemokines and cytokines that contribute to the inflammatory environment, resulting in the formation of psoriatic plaque or atherosclerotic plaque. Additionally, some studies indicated clinical improvement in psoriasis condition with treatment of associated hyperlipidemia. In conclusion, therapeutic or preventive strategies that both reduce hyperlipidemia and suppress inflammation provide potentially useful approaches in the management of both diseases.

Genetic background of psoriasis

Psoriasis is a chronic inflammatory dermatosis that contributes to approximately 1-5% of all skin disorders in Saudi Arabia. The genetic basis of psoriasis is supported by family based investigations; population based epidemiological studies, association studies with human leucocyte antigens (HLAs), genome-wide linkage scans, and candidate gene studies within and outside the major histocompatibility complex. Psoriasis represents a complex disease at the cellular, genomic and genetic levels, with infiltration of many types of leukocytes into the skin, altered growth and differentiation of skin-resident cells, and altered expression of more than 1,300 genes in psoriatic lesions. It is also apparent that there is considerable overlap between the molecular pathways that are involved in psoriasis and those that lead to other inflammatory or autoimmune diseases in humans. In this review article, we describe the immune-genetic basis of psoriasis, the molecular pathways of pathogenic inflammation and the potential role of the genes that confer increased susceptibility to psoriasis.

Plasmacytoid dendritic cells and dermatological disorders: focus on their role in autoimmunity and cancer

Dendritic cells (DC), considered as immunological sentinels of the organism since they are antigen presenting cells, create the link between innate and adaptive immunity. DC include myeloid dendritic cells (MDC) and plasmacytoid dendritic cells (PDC). The presence of PDC, cells capable of producing large quantities of interferon alpha (IFN-alpha) in response to pathogenic agents or danger signals, seems to be closely related to pathological conditions. PDC have been observed in inflammatory immunoallergic dermatological disorders, in malignant cutaneous tumours and in cutaneous lesions of infectious origin. They seem to play a crucial role in the initiation of the pathological processes of autoimmune diseases such as lupus or psoriasis. Their function within a tumour context is not as well known and is controversial. They could have a tolerogenic role towards tumour cells in the absence of an activator but they also have the capacity to become activated in response to Toll-like receptor (TLR) ligands and could therefore be useful for therapeutic purposes.

Angiogenesis drives psoriasis pathogenesis

Psoriasis pathogenesis is closely associated with disease-inducing Th1 and Th17 cells. Yet, several studies suggest that aberrant keratinocyte or endothelial cell signalling significantly contributes to disease manifestation. Histological hallmarks of psoriatic skin include the infiltration of multiple immune cells, keratinocyte proliferation and increased dermal vascularity. Formation of new blood vessels starts with early psoriatic changes and disappears with disease clearance. Several angiogenic mediators like vascular endothelial growth factor, hypoxia-inducible factors, angiopoietins and pro-angiogenic cytokines, such as tumour necrosis factor (TNF), interleukin (IL)-8 and IL-17, are up-regulated in psoriasis development. Contact- and mediator-dependent factors derived from keratinocytes, mast cells and immune cells may contribute to the strong blood vessel formation of psoriasis. New technologies and experimental models provide new insights into the role of angiogenesis in psoriasis pathogenesis. Interestingly, many therapies target not only immune cells, but also protein structures of endothelial cells. Here we summarize the role of pro-angiogenic factors in psoriasis development and discuss angiogenesis as a potential target of novel therapies.

CCR6 is required for IL-23-induced psoriasis-like inflammation in mice

Psoriasis is a common immune-mediated chronic inflammatory skin disorder, but the mechanisms of pathogenesis are still poorly understood. IL-23 is expressed in psoriatic skin, and IL-23 injection produces IL-22-dependent psoriasiform changes in mouse skin. Th17 cells produce IL-22 and display CCR6, the CCL20 receptor; CCR6+ T cells and CCL20 are abundant in psoriatic skin. We investigated a possible role for CCR6 in recruiting Th17 cells and producing psoriasiform pathology by injecting IL-23 into the skin of WT and Ccr6-/- mice. Unlike for WT mice, IL-23-injected ears of Ccr6-/- mice showed neither substantial epidermal/dermal changes nor increased Il22 mRNA expression. However, injection of IL-22 yielded equivalent psoriasiform changes in WT and Ccr6-/- mice. Surprisingly, IL-23-injected ears of WT and Ccr6-/- mice contained similar numbers of Th cells able to make IL-17A and/or IL-22. Furthermore, in ears of Rag1-/- mice, IL-23 initially induced skin changes and levels of Il22 mRNA that were indistinguishable from WT mice, revealing at least one non-T cell source for IL-22. We conclude that CCR6 is essential in a model of IL-23-induced, IL-22-mediated dermatitis, which develops in sequential T cell-independent and T cell-dependent phases. These findings reveal an expanded role for CCR6 in IL-23-related responses and identify CCR6 as a potential therapeutic target in psoriasis.

The caspase-cleaved form of LYN mediates a psoriasis-like inflammatory syndrome in mice

We showed previously that Lyn is a substrate for caspases, a family of cysteine proteases, involved in the regulation of apoptosis and inflammation. Here, we report that expression of the caspase-cleaved form of Lyn (LynDeltaN), in mice, mediates a chronic inflammatory syndrome resembling human psoriasis. Genetic ablation of TNF receptor 1 in a LynDeltaN background rescues a normal phenotype, indicating that LynDeltaN mice phenotype is TNF-alpha-dependent. The predominant role of T cells in the disease occurring in LynDeltaN mice was highlighted by the distinct improvement of LynDeltaN mice phenotype in a Rag1-deficient background. Using pan-genomic profiling, we also established that LynDeltaN mice show an increased expression of STAT-3 and inhibitory members of the NFkappaB pathway. Accordingly, LynDeltaN alters NFkappaB activity underlying a link between inhibition of NFkappaB and LynDeltaN mice phenotype. Finally, analysis of Lyn expression in human skin biopsies of psoriatic patients led to the detection of Lyn cleavage product whose expression correlates with the activation of caspase 1. Our data identify a new role for Lyn as a regulator of psoriasis through its cleavage by caspases.

Interleukin-1 regulates keratinocyte expression of T cell targeting chemokines through interleukin-1 receptor associated kinase-1 (IRAK1) dependent and independent pathways

IL-1 is a potent pro-inflammatory cytokine that activates intracellular signaling cascades some of which may involve IL-1 receptor associated kinase-1 (IRAK1). Psoriasis is a T cell dependent chronic inflammatory condition of the skin of unknown cause. IL-1 has been implicated in psoriasis pathology, but the mechanism has not been elucidated. Interestingly, expression of IRAK1 is elevated in psoriatic skin. To identify a potential link between IL-1, keratinocytes and T cells in skin inflammation we employed pathway-focused microarrays to evaluate IL-1 dependent gene expression in keratinocytes. Several candidate mRNAs encoding known T cell chemoattractants were identified in primary keratinocytes and the stable keratinocyte cell line HaCaT. CCL5 and CCL20 mRNA and protein levels were confirmed up-regulated by IL-1 in concentration and time-dependent manners. Furthermore IL-1 synergized with IFN-gamma and TNF-alpha. Expression of CXCL9, CXCL10 and CXCL11 mRNAs was also increased in response to IL-1, but protein could only be detected in medium from cells treated with IFN-gamma alone or in combination with IL-1. Over-expression of IRAK1 led to increased constitutive and cytokine induced production of CCL5 and CCL20. Inhibition of IRAK1 activity through RNAi or expression of a dominant negative mutant blocked production of CCL5 and CCL20 but had no effect upon the IL-1 enhancement of IFN-gamma induced CXCL9, CXCL10 and CXCL11 production. In conclusion IL-1 regulates T cell targeting chemokine production in keratinocytes through IRAK1 dependent and independent pathways. These pathways may contribute to acute and chronic skin inflammation.

The PKC inhibitor AEB071 may be a therapeutic option for psoriasis

PKC isoforms tau, alpha, and beta play fundamental roles in the activation of T cells and other immune cell functions. Here we show that the PKC inhibitor AEB071 both abolishes the production of several cytokines by activated human T cells, keratinocytes, and macrophages in vitro and inhibits an acute allergic contact dermatitis response in rats. To translate these findings into humans, single and multiple ascending oral doses of AEB071 were administered to healthy volunteers and patients with psoriasis, respectively. AEB071 was well tolerated with no clinically relevant laboratory abnormalities. Ex vivo stimulation of lymphocytes from subjects exposed to single doses of AEB071 resulted in a dose-dependent inhibition of both lymphocyte proliferation and IL2 mRNA expression. Clinical severity of psoriasis was reduced up to 69% compared with baseline after 2 weeks of treatment, as measured by the Psoriasis Area Severity Index (PASI) score. The improvement in psoriasis patients was accompanied by histological improvement of skin lesions and may be partially explained by a substantial reduction of p40+ dermal cells, which are known to mediate psoriasis. These data suggest that AEB071 could be an effective novel treatment regimen for psoriasis and other autoimmune diseases, and that AEB071 warrants long-term studies to establish safety and efficacy.

Epigenetics in human autoimmunity. Epigenetics in autoimmunity - DNA methylation in systemic lupus erythematosus and beyond

Epigenetic mechanisms are essential for normal development and function of the immune system. Similarly, a failure to maintain epigenetic homeostasis in the immune response due to factors including environmental influences, leads to aberrant gene expression, contributing to immune dysfunction and in some cases the development of autoimmunity in genetically predisposed individuals. This is exemplified by systemic lupus erythematosus, where environmentally induced epigenetic changes contribute to disease pathogenesis in those genetically predisposed. Similar interactions between genetically determined susceptibility and environmental factors are implicated in other systemic autoimmune diseases such as rheumatoid arthritis and scleroderma, as well as in organ specific autoimmunity. The skin is exposed to a wide variety of environmental agents, including UV radiation, and is prone to the development of autoimmune conditions such as atopic dermatitis, psoriasis and some forms of vitiligo, depending on environmental and genetic influences. Herein we review how disruption of epigenetic mechanisms can alter immune function using lupus as an example, and summarize how similar mechanisms may contribute to other human autoimmune rheumatic and skin diseases.

Reactive oxygen species in tumor necrosis factor-alpha-activated primary human keratinocytes: implications for psoriasis and inflammatory skin disease

The multifunctional cytokine tumor necrosis factor-alpha (TNF-alpha) is known to play an important role in inflammatory and immunological responses in human skin. Although it has been documented that reactive oxygen species (ROS) are involved in TNF-alpha-induced signaling pathways associated with certain inflammatory diseases, their role in TNF-alpha signaling cascades has not been examined in primary human keratinocytes used as a model of inflammatory skin disease and psoriasis. Employing a series of in vitro and in cellulo approaches, we have demonstrated that in primary human keratinocytes (i) TNF-alpha rapidly induces ROS generation, IkappaB degradation, NF-kappaB p65 nuclear translocation, and ultimately production of inflammatory cytokines; (ii) TNF-alpha-induced cytokine production is mediated both by the mammalian target of rapamycin signaling pathway via NF-kappaB activation and by ROS; (iii) TNF-alpha-dependent NF-kappaB activation (that is, IkappaB degradation and NF-kappaB p65 nuclear translocation) is not mediated by ROS; and (iv) a cell-penetrating derivative of the antioxidant enzyme, catalase, as well as taurine and N-acetyl-cysteine attenuate the TNF-alpha-induced production of cytokines. These latter results suggest that catalase and perhaps other antioxidants should be considered as part of a more specific and effective therapy for the treatment of inflammatory skin diseases, including psoriasis.

Immunopathogenesis of psoriasis

Investigations into the cause and treatment of psoriasis remain at the forefront of basic and applied clinical research efforts around the world. The purpose for this review is to provide an up-to-date synopsis of recent progress in ten sections exploring the immunological and inflammatory basis for psoriasis. Given the breadth of this topic in investigative skin biology and frequent paradigm shifts, it should not be surprising that the bibliography contains more than 150 references; many of which have been published in the last 5 years. Whereas considerable progress has been made into the immunopathogenesis of psoriasis, many fundamentally important questions remain regarding the role of cells located in both epidermal and dermal compartments. Attempts to characterize various animal models of psoriasis, delineation of the mechanism of action for biological agents, and consideration of molecular links between skin inflammation and various extracutaneous comorbidities are likely to continue challenging investigators and clinicians for many years to come.

Innate immunity and antimicrobial defense systems in psoriasis

Psoriasis is a chronic inflammatory disorder that is mediated by elements of the innate and adaptive immune systems. Its characteristic features in the skin consist of inflammatory changes in both dermis and epidermis, with abnormal keratinocyte differentiation and proliferation. Despite the elucidation of many aspects of psoriasis pathogenesis, some puzzling questions remain to be answered. A major question currently debated is whether psoriasis is a primary abnormality of the epidermal keratinocyte or a reflection of dysregulated bone marrow-derived immunocytes. In this review we will focus on understanding the role of the innate immune system in psoriasis and how this provides a rational solution to address the origin of this multifactorial disease. Innate immunity is nonspecific and genetically based. It protects the body against the constant risk of pathogens through the use of rapidly mobilized defenses that are able to recognize and kill a variety of threats (bacteria, fungi, viruses, etc). The key mechanisms of innate immune responses are the existence of receptors to recognize pathogens and the production of factors that kill pathogens, such as antimicrobial peptides and proteins. Any combination of excessive sensitivity of the innate detection system, or dysregulation of the response system, can manifest both an epidermal phenotype and an abnormal T-cell function. Thus, the multidimensional action of the innate immune system, its triggers, and its recently understood role in T-cell function argue for an important role for innate mechanisms of recognition and response in the pathogenesis of psoriasis.

Activator protein 1 (Fos/Jun) functions in inflammatory bone and skin disease

Activator protein 1 (AP-1) (Fos/Jun) is a transcriptional regulator composed of members of the Fos and Jun families of DNA binding proteins. The functions of AP-1 were initially studied in mouse development as well as in the whole organism through conventional transgenic approaches, but also by gene targeting using knockout strategies. The importance of AP-1 proteins in disease pathways including the inflammatory response became fully apparent through conditional mutagenesis in mice, in particular when employing gene inactivation in a tissue-specific and inducible fashion. Besides the well-documented roles of Fos and Jun proteins in oncogenesis, where these genes can function both as tumor promoters or tumor suppressors, AP-1 proteins are being recognized as regulators of bone and immune cells, a research area termed osteoimmunology. In the present article, we review recent data regarding the functions of AP-1 as a regulator of cytokine expression and an important modulator in inflammatory diseases such as rheumatoid arthritis, psoriasis and psoriatic arthritis. These new data provide a better molecular understanding of disease pathways and should pave the road for the discovery of new targets for therapeutic applications.

IL-10 implications in psoriasis

Interleukin (IL)-10 is a pluripotent cytokine with effects on numerous cell populations, in particular circulating and resident immune cells as well as epithelial cells. With its potent immunoregulatory capacities, its main biological function seems to be the limitation and termination of inflammatory responses. Hence, its low level expression found in psoriasis may have pathophysiological relevance to this immune disease. Remarkably, the induction of IL-10 expression was found by conventional antipsoriatic therapies, supporting the hypothesis that it may be a key cytokine in psoriasis. Furthermore, the first use in clinical trials in patients with established psoriasis showed that it had moderate antipsoriatic effects and was well tolerated. Moreover, long-term application in psoriatic patients in remission showed that it decreases the incidence of relapse and prolongs the disease free interval. The IL-10 antipsoriatic activity is suggested to be due to the effects on different cell populations, including antigen presenting cells and T-cells (type 1 / type 2 balance shift), but not through direct effects on keratinocytes. In conclusion, IL-10 seems to have major clinical and therapeutic implications in psoriasis. Further multicenter, placebo-controlled, double blind trials are required to be an established antipsoriatic therapy. We can come to the conclusion that IL-10 genetic polymorphism and expression is potentially a key immune marker in psoriasis.

Targeting TNFalpha rapidly reduces density of dendritic cells and macrophages in psoriatic plaques with restoration of epidermal keratinocyte differentiation

BACKGROUND

The cytokine network theory for psoriasis postulates a key role for TNFalpha in mediating inflammation and altered epidermal differentiation.

OBJECTIVE

This study defines responses following administration of adalimumab, a TNFalpha inhibitor, in pre-psoriatic skin (PN) and lesional psoriatic plaques (PP) skin.

METHODS

PN and PP skin before and after treatment were biopsied at days 2, 7, 28 and 84 (n=6 different patients). Cryosections were immunohistochemically stained to detect TNFalpha and other relevant markers in epidermal and dermal compartments. Detection of apoptosis utilized antibody specific for activated caspase 3. Semiquantitative assessments and statistical analysis was performed for each staining profile.

RESULTS

TNFalpha+ cells were increased in PP skin. PP skin was also characterized by a four-fold increase in number of CD68+ macrophages as well as eight-fold increase in CD11c+ dermal dendritic cells (DCs) compared to PN skin. By two-color immunofluorescence staining, both CD68+ cells as well as CD11c+ cells expressed TNFalpha. Following initiation of adalimumab therapy, CD11c+ cells, significantly decreased in PP skin at days 7, 28, and 84, while CD68+ and CD14+ cells decreased at days 28 and 84. Other markers for DCs (CD83, CD86) showed decreases at days 7, 28, and 84. Reduction in DCs, macrophages or T cells was not accompanied by increased activated caspase 3-positive cells. When a keratinocyte terminal differentiation marker was examined, adalimumab triggered rapid restoration of loricrin expression (beginning on day 2), with loss of aberrant differentiation marker, keratin 17 (K17).

CONCLUSION

Adalimumab impacts dermal-based immunocytes, and the epidermal compartment also responds by restoration of normal differentiation without detectable apoptosis.

The role of dendritic cells in the immunopathogenesis of psoriasis

Psoriasis vulgaris is a chronic inflammatory skin disease that is marked by a complex interplay of dendritic cells (DCs), T-cells, cytokines, and downstream transcription factors as part of a self-sustaining type 1 cytokine network. As integral players of the immune system, DCs represent antigen-presenting cells that are crucial for efficient activation of T-cells and B-cells. DCs have also been linked to distinct chronic inflammatory conditions, including psoriasis. In the setting of psoriasis therapy, DC/T cell interactions serve as a potential target for biologic response modifiers. Here we describe the major DC subsets as well as the immunologic involvement of DCs within the context of psoriatic lesions.

Fulminant ulcerative colitis associated with steroid-resistant minimal change disease and psoriasis: A case report

A 43-year-old Chinese patient with a history of psoriasis developed fulminant ulcerative colitis after immunosuppressive therapy for steroid-resistant minimal change disease was stopped. Minimal change disease in association with inflammatory bowel disease is a rare condition. We here report a case showing an association between ulcerative colitis, minimal change disease, and psoriasis. The possible pathological link between 3 diseases is discussed.

Expression of the chemokine receptor CCR5 in psoriasis and results of a randomized placebo controlled trial with a CCR5 inhibitor

Several reports have indicated that the chemokine receptor CCR5 and its ligands, especially CCL5 (formerly known as RANTES), may play a role in the pathogenesis of psoriasis. The purpose of this investigation was to examine the expression of CCR5 and its ligands in chronic plaque psoriasis and to evaluate the clinical and immunohistochemical effect of a CCR5 receptor inhibitor. Immunohistochemical analysis showed low but significant increased total numbers of CCR5 positive cells in epidermis and dermis of lesional skin in comparison to non-lesional skin. However, relative expression of CCR5 proportional to the cells observed revealed that the difference between lesional and non-lesional skin was only statistically significant in the epidermis for CD3 positive cells and in the dermis for CD68 positive cells. Quantification of mRNA by reverse transcriptase-polymerase chain reaction only showed an increased expression of CCL5 (RANTES) in lesional skin. A randomized placebo-controlled clinical trial in 32 psoriasis patients revealed no significant clinical effect and no changes at the immunohistochemical level comparing patients treated with placebo or a CCR5 inhibitor SCH351125. We conclude that although CCR5 expression is increased in psoriatic lesions, this receptor does not play a crucial role in the pathogenesis of psoriasis.

Antipsoriatic effects of avarol-3'-thiosalicylate are mediated by inhibition of TNF-alpha generation and NF-kappaB activation in mouse skin

BACKGROUND AND PURPOSE

Avarol is a marine sesquiterpenoid hydroquinone with anti-inflammatory and antipsoriatic properties. The aim of this study was to evaluate the in vitro and in vivo pharmacological behaviour of the derivative avarol-3'-thiosalicylate (TA) on some inflammatory parameters related to the pathogenesis of psoriasis.

EXPERIMENTAL APPROACH

Human neutrophils and monocytes as well as the human keratinocyte cell line HaCaT were used to study the effect of TA on oxidative stress, the arachidonic acid pathway, tumour necrosis factor-alpha (TNF-alpha) release and nuclear factor-kappaB (NF-kappaB) activation. All these parameters were also determined in vivo using the zymosan induced mouse air pouch model and the 12-O-tetradecanoylphorbol-13-acetate (TPA) induced mouse epidermal hyperplasia model.

KEY RESULTS

TA showed antioxidant properties in human neutrophils and in the hypoxanthine/xanthine oxidase assay. This compound reduced, in a concentration-dependent manner, leukotriene B(4), prostaglandin E(2) and TNF-alpha production in activated leukocytes. Oral and intrapouch administration of TA in the mouse air pouch model produced a dose-dependent reduction of all these inflammatory mediators. TA also inhibited secretory phospholipase A(2) activity and NF-kappaB DNA-binding in HaCaT keratinocytes. In TPA-induced mouse epidermal hyperplasia, topical administration of TA reduced oedema, leukocyte infiltration, eicosanoid levels and TNF-alpha in skin. In addition, interleukin (IL)-1beta and IL-2 production were also inhibited. Finally, TA was also capable of suppressing NF-kappaB nuclear translocation in vivo.

CONCLUSIONS AND IMPLICATIONS

TA inhibited several key biomarkers up-regulated in the inflammatory response of psoriatic skin and this compound could be a promising antipsoriatic agent.

Sequence variants in the genes for the interleukin-23 receptor (IL23R) and its ligand (IL12B) confer protection against psoriasis

Psoriasis is an inflammatory skin disorder that is inherited as a multifactorial trait. Genetic analyses have repeatedly identified a primary disease susceptibility locus lying within the major histocompatibility complex (MHC), on chromosome 6p21. A small number of non-MHC susceptibility loci have also been identified. These regions tend to overlap with susceptibility intervals for Crohn's disease and atopic dermatitis, suggesting the possibility that genetic variants affecting inflammatory pathways may contribute to the pathogenesis of multiple disorders. Here, we report a genetic analysis of the interleukin 23 receptor gene (IL23R), which was recently identified as a susceptibility determinant for Crohn's disease. We initially examined the results of a whole-genome association scan, carried out on 318 cases and 288 controls. We observed a significant increase of a non-synonymous substitution (p.Arg381Gln) among controls (P = 0.00036). We validated this finding by extending our cohort to include a further 519 cases and 528 controls. In the overall sample, the frequency of the 381Gln allele was 3.6% in cases and 7% in controls, yielding a P value of 0.00014. Next, we examined genetic variation at the IL12RB1, IL23A and IL12B genes, respectively, encoding the second subunit of the IL23R receptor and the two subunits of its ligand. This analysis identified independent associations for IL12B SNPs rs10045431 (P value for the extended dataset = 0.0001) and rs3212227 (P = 0.036). Altogether, these findings indicate that genes participating in IL23 signalling play a significant role in the pathogenesis of chronic epithelial inflammation.

Immunobiologics in the treatment of psoriasis

The pathogenesis of various inflammatory cutaneous diseases such as psoriasis, atopic dermatitis and mycosis fungoides relies greatly on the abnormal function of T cells. Fundamental knowledge of the role of T cells in the cutaneous immune response has led to the development and production of biologic molecules designed to block T cell function at various steps, specifically activation (i.e. alefacept, efalizumab), trafficking into inflamed skin (i.e. efalizumab) and effector function under cytokine control (i.e. etanercept, infliximab, adalimumab, and anti-IL-12 antibody). We review the immune abnormalities and the role of T cells in psoriasis, and the recent biologic therapies, which share the common mission to hinder T cell activity in inflammatory diseases. An advantage from the preciseness of these biologic therapies is the potential limit of non-specific and potentially devastating organ toxicity, which commonly plagues other systemic therapies.

IL-23 stimulates epidermal hyperplasia via TNF and IL-20R2-dependent mechanisms with implications for psoriasis pathogenesis

Aberrant cytokine expression has been proposed as an underlying cause of psoriasis, although it is unclear which cytokines play critical roles. Interleukin (IL)-23 is expressed in human psoriasis and may be a master regulator cytokine. Direct intradermal administration of IL-23 in mouse skin, but not IL-12, initiates a tumor necrosis factor-dependent, but IL-17A-independent, cascade of events resulting in erythema, mixed dermal infiltrate, and epidermal hyperplasia associated with parakeratosis. IL-23 induced IL-19 and IL-24 expression in mouse skin, and both genes were also elevated in human psoriasis. IL-23-dependent epidermal hyperplasia was observed in IL-19-/- and IL-24-/- mice, but was inhibited in IL-20R2-/- mice. These data implicate IL-23 in the pathogenesis of psoriasis and support IL-20R2 as a novel therapeutic target.

Approaches to discontinuing efalizumab: an open-label study of therapies for managing inflammatory recurrence

Background

Efalizumab is a humanised recombinant monoclonal IgG1 antibody for the treatment of moderate-to-severe plaque psoriasis. When treatment discontinuation is necessary, however, some patients may experience inflammatory recurrence of the disease, which can progress to rebound if untreated. This analysis evaluated approaches for managing inflammatory recurrence after discontinuation of efalizumab.

Methods

An open-label, multicentre, investigational study was performed in 41 patients with moderate-to-severe plaque psoriasis who had recently completed clinical studies with efalizumab and had developed signs of inflammatory recurrence following abrupt cessation of treatment. Patients were assigned by the attending physicians to receive one of five standardised alternative systemic psoriasis treatment regimens for 12 weeks. Efficacy of the different therapy options was assessed using the physician's global assessment (PGA) of change over time.

Results

More favourable PGA responses were observed in patients changing to cyclosporin (PGA of 'good', 'excellent' or 'cleared': 7/10 patients, 70.0%) or methotrexate (9/20, 45.0%), compared with those receiving systemic corticosteroids (2/8, 25.0%), retinoids (0/1, 0.0%) or combined corticosteroids plus methotrexate (0/2, 0.0%). While the majority (77.8%) of patients showed inflammatory morphology at baseline, following 12 weeks of the alternative therapies the overall prevalence of inflammatory disease was decreased to 19.2%.

Conclusion

Inflammatory recurrence after discontinuation of efalizumab therapy is a manageable event, with a number of therapies and approaches available to physicians, including short courses of cyclosporin or methotrexate.

Platelet-activating factor is crucial in psoralen and ultraviolet A-induced immune suppression, inflammation, and apoptosis

Psoralen plus UVA (PUVA) is used as a very effective treatment modality for various diseases, including psoriasis and cutaneous T-cell lymphoma. PUVA-induced immune suppression and/or apoptosis are thought to be responsible for the therapeutic action. However, the molecular mechanisms by which PUVA acts are not well understood. We have previously identified platelet-activating factor (PAF), a potent phospholipid mediator, as a crucial substance triggering ultraviolet B radiation-induced immune suppression. In this study, we used PAF receptor knockout mice, a selective PAF receptor antagonist, a COX-2 inhibitor (presumably blocking downstream effects of PAF), and PAF-like molecules to test the role of PAF receptor binding in PUVA treatment. We found that activation of the PAF pathway is crucial for PUVA-induced immune suppression (as measured by suppression of delayed type hypersensitivity to Candida albicans) and that it plays a role in skin inflammation and apoptosis. Downstream of PAF, interleukin-10 was involved in PUVA-induced immune suppression but not inflammation. Better understanding of PUVA's mechanisms may offer the opportunity to dissect the therapeutic from the detrimental (ie, carcinogenic) effects and/or to develop new drugs (eg, using the PAF pathway) that act like PUVA but have fewer side effects.

Recombinant integrin CD11b A-domain blocks polymorphonuclear cells recruitment and protects against skeletal muscle inflammatory injury in the rat

The beta2 integrin CD11b/CD18 (CR3) is a major adhesion receptor of neutrophils, normally utilized to fend off infections. This receptor contributes, however, to multiple forms of non-infectious inflammatory injury when dysregulated as shown in gene knock-outs and through the use of blocking monoclonal antibodies. The major ligand recognition site of CR3 has been mapped to the A-domain in the CD11b subunit (CD11bA). The recombinant form of this domain exhibits a ligand binding profile similar to that of the holoreceptor. To assess the potential anti-inflammatory activity of CD11bA as a competitive antagonist of CR3 in vivo, we assessed its effects on a developed animal model of traumatic skeletal muscle injury in the rat. Recombinant soluble rat CD11bA-domain fused to glutathione-S-transferase (GST) was administered intravenously in a single dose at 1 mg/kg to nine groups of Wistar rats, five in each group, 30 min before inducing traumatic skeletal muscle injury. Control animals received either a function-blocking anti-CD11b/CD18 monoclonal antibody (1 mg/kg), non-functional mutant forms of the CD11bA (D140GS/AGA, T209/A, D242/A), recombinant GST or buffer alone. In control animals, the wounded muscle showed oedema, erythrocyte extravasation and myonecrosis both within and outside the immediate wounded area (5-10 mm zone) and influx of neutrophils was detected 30 min post-wound, followed by a second wave 3 hr later. Wild-type CD11bA- or anti-CD11b monoclonal antibody (mAb)-treated rats showed a comparable and significant decrease in the number of infiltrating PMN (78 + 4%, n = 70 and 86 +/- 2%, n = 50, respectively) and preservation of the muscular fibres outside the immediate zone of necrosis (75 + 4%, n = 70, 84 +/- 1%, n = 50, respectively), compared to controls. These data demonstrate that CD11bA can be an effective tissue-preserving agent in acute inflammatory muscular injury.

The importance of disease associations and concomitant therapy for the long-term management of psoriasis patients

It is well established that several inflammatory-type conditions, such as arthritis, diabetes, cardiovascular disease, and irritable bowel disease exist comorbidly and at an increased incidence in patients with psoriasis. Psoriasis and other associated diseases are thought to share common inflammatory pathways. Conditions such as these, with similar pathogenic mechanisms involving cytokine dysregulation, are referred to as immune-mediated inflammatory diseases (IMIDs). Considerable evidence for the genetic basis of comorbidities in psoriasis exists. The WHO has reported that the occurrence of chronic diseases, including IMIDs, are a rising global burden. In addition, conditions linked with psoriasis have been associated with increasing rates of considerable morbidity and mortality. The presence of comorbid conditions in psoriasis patients has important implications for clinical management. QoL, direct health care expenditures and pharmacokinetics of concomitant therapies are impacted by the presence of comorbid conditions. For example, methotrexate is contraindicated in hepatic impairment, while patients on cyclosporin should be monitored for kidney function. In addition, some agents, such as beta blockers, lithium, synthetic antimalarial drugs, NSAIDs and tetracycline antibiotics, have been implicated in the initiation or exacerbation of psoriasis. Consequently, collaboration between physicians in different specialties is essential to ensuring that psoriasis treatment benefits the patient without exacerbating associated conditions.

CXCR2 ligands and G-CSF mediate PKCalpha-induced intraepidermal inflammation

Transgenic mice overexpressing PKCalpha in the epidermis (K5-PKCalpha mice) exhibit an inducible severe intraepidermal neutrophilic inflammation and systemic neutrophilia when PKCalpha is activated by topical 12-O-tetradecanoylphorbol-13-acetate (TPA). This inducible model of cutaneous inflammation was used to define mediators of skin inflammation that may have clinical relevance. Activation of cutaneous PKCalpha increased the production of the chemotactic factors cytokine-induced neutrophil chemoattractant (KC) and macrophage inflammatory protein 2 (MIP-2) in murine plasma. TPA treatment of cultured K5-PKCalpha keratinocytes also released KC and MIP-2 into culture supernatants through an NF-kappaB-dependent pathway. MIP-2 and KC mediated the infiltration of neutrophils into the epidermis, since this was prevented by ablating CXCR2 in K5-PKCalpha mice or administering neutralizing antibodies against KC or MIP-2. The neutrophilia resulted from PKCalpha-mediated upregulation of cutaneous G-CSF released into the plasma independent of CXCR2. These responses could be inhibited by topical treatment with a PKCalpha-selective inhibitor. Inhibiting PKCalpha also reduced the basal and TNF-alpha- or TPA-induced expression of CXCL8 in cultured psoriatic keratinocytes, suggesting that PKCalpha activity may contribute to psoriatic inflammation. Thus, skin can be the source of circulating factors that have both local and systemic consequences, and these factors, their receptors, and possibly PKCalpha could be therapeutic targets for inhibition of cutaneous inflammation.

Activated macrophages are essential in a murine model for T cell-mediated chronic psoriasiform skin inflammation

The CD18 hypomorphic (CD18hypo) PL/J mouse model clinically resembling human psoriasis is characterized by reduced expression of the common chain of beta2 integrins (CD11/CD18) to only 2-16% of WT levels. Previously we found that this chronic psoriasiform skin inflammation also depends on the presence of CD4+ T cells. Herein we investigated the role of macrophages in this CD18hypo mouse model. Activated macrophages were significantly increased in lesional skin as well as in inflamed skin draining lymph nodes (DLNs) of affected CD18hypo mice and were identified as being an important source of TNF-alpha in vivo. Both depletion of macrophages and neutralization of TNF-alpha resulted in a significant alleviation of psoriasiform skin inflammation. As monocyte chemotactic protein 1 was enhanced in lesional skin of affected CD18hypo mice, we intradermally injected recombinant murine monocyte chemotactic protein-1 (rJE/MCP-1) alone or in combination with rTNF-alpha into the skin of healthy CD18hypo mice. Only simultaneous injection of rJE/MCP-1 and rTNF-alpha, but neither substance alone, resulted in the induction of psoriasiform skin inflammation around the injection sites with recruitment and activation of macrophages. Collectively, our data suggest that maintenance of psoriasiform skin inflammation critically depends on efficient recruitment and activation of macrophages with sufficient release of TNF-alpha.