Psoriasin (S100A7) promotes stress-induced angiogenesis.

BACKGROUND: Vascular modifications occur early in the development of psoriasis, and angiogenesis is one of the key features in the pathogenesis of the disease. OBJECTIVES: To identify the role of the S100 protein psoriasin in psoriasis-associated angiogenesis. METHODS: The role of psoriasin in mediating angiogenesis was investigated by silencing psoriasin with small interfering RNA (siRNA) and measuring psoriasis-associated angiogenic factors in human epidermal keratinocytes. The secretion of psoriasin and the effect of psoriasin on general regulators of angiogenesis in keratinocytes, and on endothelial cell migration, proliferation, tube formation and production of angiogenic mediators, was evaluated. RESULTS: Reactive oxygen species (ROS) and hypoxia induced the expression of psoriasin. Downregulation of psoriasin in keratinocytes using siRNA altered the ROS-induced expression of the psoriasis-associated angiogenic factors vascular endothelial growth factor (VEGF), heparin-binding epidermal growth factor-like growth factor, matrix metalloproteinase 1 and thrombospondin 1. Overexpression of psoriasin altered several regulators of angiogenesis and led to the secretion of psoriasin. Treatment with extracellular psoriasin induced proliferation, migration and tube formation in dermal-derived endothelial cells to a similar extent as VEGF and interleukin-17, and induced the expression and release of proangiogenic mediators. These effects were suggested to be mediated by the PI3K and nuclear factor kappa B pathways. CONCLUSIONS: These findings suggest that psoriasin expression is promoted by oxidative stress in keratinocytes and amplifies the ROS-induced expression of angiogenic factors relevant to psoriasis. Moreover, extracellularly secreted psoriasin may act on dermal endothelial cells to contribute to key features angiogenesis.

Genetic variations of NLRP1: susceptibility in psoriasis.

BACKGROUND: NACHT, LRR and PYD domain-containing protein (NLRP)1 is part of the inflammasome multiprotein complex involved in the production of interleukin (IL)-1ß and IL-18, two cytokines strongly implicated in psoriasis pathogenesis. Genetic variations in NLRP1 are associated with a predisposition for chronic inflammatory conditions. OBJECTIVES: The aim of the study was to investigate the role of genetic variation in the NLRP1 inflammasome in psoriasis susceptibility. MATERIAL AND METHODS: Four haplotype-tagging single-nucleotide polymorphisms (SNPs) (rs6502867, rs8079034, rs878329 and rs12150220) were investigated by TaqMan allelic discrimination in a patient sample comprising 1847 individuals from 478 families and 802 healthy controls. RESULTS: Using the transmission disequilibrium test, a significant increase in the transmission of the NLRP1 rs8079034C and rs878329C alleles to patients with psoriasis was demonstrated (P = 0·006 and P = 0·033, respectively). Furthermore, homozygosity for the rs878329C allele correlated with a younger age of onset. We also observed an increase in the expression of NLRP1 mRNA in the peripheral blood cells of patients with psoriasis. This was accompanied by a higher level of circulating IL-18 and appeared to be associated with the rs878329C allele. CONCLUSIONS: Our data support the involvement of NLRP1 and the NLRP1 inflammasome in psoriasis susceptibility and further support the role of innate immunity in psoriasis.

Systemic up-regulation of TLR4 causes lipopolysaccharide-induced augmentation of nasal cytokine release in allergic rhinitis.

BACKGROUND: Allergic rhinitis is a systemic disorder, and it is clinically well recognized that it can be aggravated by infection. Activation of the innate immune system constitutes a critical element in the process. Toll-like receptors (TLRs) comprise a part of the innate immune system, and lipopolysaccharide (LPS)-induced activation of TLR4 represents bacterial-induced interactions in various model systems. The present study examines how TLR2 and TLR4 expression is affected by symptomatic allergic rhinitis, and if LPS added upon allergen affects nasal cytokine release. METHODS: In patients with pollen-induced allergic rhinitis and healthy non-allergic volunteers, nasal lavage (NAL), peripheral blood and bone marrow were sampled before and during the pollen season. TLR2 and TLR4 expression was determined flow cytometrically. Changes in the TLR receptor expression pattern were evaluated by a nasal challenge with allergen followed by LPS, or vice versa. Symptoms along with cells and cytokines in NAL were analyzed. RESULTS: TLR4 expression increased in leukocytes in NAL, peripheral blood and bone marrow during symptomatic allergic rhinitis. A similar increase was seen for TLR2 in neutrophils in blood. Nasal challenge with allergen followed by LPS augmented the release of IL-4, IL-5, IL-10, IL-13, IFN-γ and TNF-α. CONCLUSION: A systemic up-regulation of TLR4 in symptomatic allergic rhinitis may explain why LPS preceded by allergen increases nasal cytokine release.

Airway inflammation evaluated in a human nasal lipopolysaccharide challenge model by investigating the effect of a CXCR2 inhibitor.

BACKGROUND: The existence of a link between inflammation in upper and lower airways is well established. It may therefore be assumed that the nose could be used to study inflammatory events in the lower airways. OBJECTIVE: This study aimed to evaluate a lipopolysaccharide (LPS) nasal challenge model by investigating the effect of the CXCR2 inhibitor AZD8309 on neutrophilic inflammation. METHODS: A total of 18 healthy volunteers were randomized in a placebo-controlled, double-blind, cross-over study. AZD8309 or placebo was dosed for 3 days. Subjects were challenged nasally with LPS (50 µg/nostril), and nasal lavage was performed 6 and 24 h later. Leucocytes, neutrophils and inflammatory mediators were assessed in the lavage fluid. The outcome was compared with data from analogous experiments performed in a model of inhaled LPS followed by induced sputum. This trial was registered in the Current Controlled Trials register (ISRCTN trial number: ISRCTN46666382). RESULTS: The leucocytes in nasal lavage consisted to 99% of neutrophils on average. Treatment with AZD8309 reduced the leucocyte count to 48% of placebo 6 h after the LPS challenge. There was also a reduction in LTB4 levels to 45% of placebo after 6 h and in the neutrophil elastase activity after 24 h. No major adverse events were seen with either AZD8309 or placebo. The nasal LPS model induced only minimal local irritation and no signs of systemic inflammation. CONCLUSIONS AND CLINICAL RELEVANCE: LPS-induced neutrophil recruitment was reduced by inhibition of CXCR2. This outcome mimicked the response previously seen in a lower airway LPS model. Hence, the nasal model offers a convenient and well-tolerated alternative for pharmacological evaluation of anti-inflammatory drugs affecting neutrophilic migration and activity.