ORIGINAL ARTICLE IL-19 Is a Component of the Pathogenetic IL-23/IL-17 Cascade in Psoriasis Ellen Witte1,2, Georgios Kokolakis1,2,KatrinWitte1,2,SandraPhilipp1,2, Wolf-Dietrich Doecke3, Nina Babel4,5,BiancaM.Wittig6, Katarzyna Warszawska1, Agata Kurek1,2, Magdalena Erdmann-Keding1,2, Stefanie Kunz1,2, Khusru Asadullah3,MarshallE.Kadin7, Hans-Dieter Volk4,8, Wolfram Sterry9, Kerstin Wolk1,2,10 and Robert Sabat1,2,10 Psoriasis is a common chronic inflammatory disease with characteristic skin alterations and functions as a model of immune-mediated disorders. Cytokines have a key role in psoriasis pathogenesis. Here, we demonstrated that out of 30 individually quantified cytokines, IL-19 showed the strongest differential expression between psoriatic lesions and healthy skin. Cutaneous IL-19 overproduction was reflected by elevated IL-19 blood levels that correlated with psoriasis severity. Accordingly, anti-psoriatic therapies substantially reduced both cutaneous and systemic IL-19 levels. IL-19 production was induced in keratinocytes by IL-17A and was further amplified by tumor necrosis factor-a and IL-22. Among skin cells, keratinocytes were found to be important targets of IL-19. IL-19 alone, however, regulated only a few keratinocyte functions. While increasing the production of S100A7/8/9 and, to a moderate extent, also IL-1b, IL-20, chemokine C-X-C motif ligand 8, and matrix metalloproteinase 1, IL-19 had no clear influence on the differentiation, proliferation, or migration of these cells. Importantly, IL-19 amplified many IL-17A effects on keratinocytes, including the induction of b-defensins, IL-19, IL-23p19, and T helper type 17- cell- and neutrophil-attracting chemokines. In summary, IL-19 as a component of the IL-23/IL-17 axis strengthens the IL-17A action and might be a biomarker for the activity of this axis in chronic inflammatory disorders. Journal of Investigative Dermatology (2014) 134, 2757–2767; doi:10.1038/jid.2014.308; published online 11 September 2014 INTRODUCTION dilatation of dermal papillae vessels underlie the psoriatic skin Psoriasis vulgaris (referred to as psoriasis) is a common, alterations that appear as sharply demarcated, erythematous, chronic, inflammatory skin disease frequently accompanied scaly plaques (Schon and Boehncke, 2005; Griffiths and by arthritis as well as endocrine, cardiovascular, and meta- Barker, 2007). Despite the disturbed barrier function of these bolic alterations (Schon and Boehncke, 2005; Griffiths and lesions, they are highly protected against bacterial and viral Barker, 2007; Armstrong et al., 2013). Hyperproliferation and infections, which is due to the strong local upregulation of disturbed differentiation of keratinocytes as well as growth and anti-bacterial and anti-viral proteins (Ong et al., 2002; Wolk et al., 2013). 1Interdisciplinary Group of Molecular Immunopathology, Dermatology/ Although the pathogenesis of psoriasis is not fully under- 2 Medical Immunology, University Hospital Charite´, Berlin, Germany; Psoriasis stood, it is widely accepted that cytokines play a key role in Research and Treatment Center, University Hospital Charite´, Berlin, Germany; 3Global Biomarker, Bayer Pharma AG, Berlin, Germany; 4Berlin-Brandenburg both emergence and maintenance of psoriatic lesions. Accord- Center for Regenerative Therapies, University Hospital Charite´, Berlin, ingly, numerous immune mediators play been described as Germany; 5Department of Nephrology, University Hospital Charite´, Berlin, being elevated in the diseased skin of these patients (Sabat 6 Germany; Medical Clinic 1 (Gastroenterology, Rheumatology, Infectiology), et al., 2007). Among them are members of the IL-10 cytokine University Hospital Charite´, Berlin, Germany; 7Department of Dermatology, Boston University, Roger Williams Medical Center, Providence, Rhode Island, family—namely, IL-19, IL-20, IL-24, IL-22, IL-26, and IL-29 USA; 8Institute of Medical Immunology, University Hospital Charite´, Berlin, (Romer et al., 2003; Wolk et al., 2004; Kunz et al., 2006; Germany; 9Department of Dermatology and Allergy, University Hospital 10 Wolk et al., 2013). The cellular sources of these family Charite´, Berlin, Germany and Research Center Immunosciences, University members differ; in fact, IL-22, IL-26, and IL-29 are secreted Hospital Charite´, Berlin, Germany by T cells and innate lymphoid cells, whereas IL-24 is Correspondence: Robert Sabat, Interdisciplinary Group of Molecular Immunopathology, Dermatology/Medical Immunology, University Hospital preferentially produced by dendritic cells/macrophages and Charite´, Charite´platz 1, Berlin D-10117, Germany. keratinocytes (Romer et al., 2003; Donnelly et al., 2010; E-mail: [email protected] Kumari et al., 2013; Wolk et al., 2013; Sabat et al., 2014). Abbreviations: BD, b-defensin; CXCL8, chemokine C-X-C motif ligand 8; IL-19 and IL-20 expression in psoriasis has been solely located GM-CSF, granulocyte-macrophage-CSF; M-CSF, macrophage colony-stimulating in keratinocytes as impressively demonstrated by the Kragballe factor; mRNA, messenger RNA; TNF-a, tumor necrosis factor-a group (Romer et al.,2003).WiththeexceptionofIL-10,the Received 27 March 2013; revised 10 June 2014; accepted 30 June 2014; accepted article preview online 21 July 2014; published online 11 September IL-10 family members do not act on immune cells but instead 2014 target certain tissue cells (Sabat, 2010). Despite this, transgenic & 2014 The Society for Investigative Dermatology www.jidonline.org 2757 EWitteet al. Role of IL-19 in Psoriasis overexpression of IL-20, IL-22, and IL-24 in mice led to very of these cytokines’ action reduced cutaneous pathological similar psoriatic-like skin alterations (Blumberg et al., 2001; alterations in murine dermatitis models (Ma et al., 2008; Wolk et al., 2009a; He and Liang, 2010). Moreover, inhibition Stenderup et al., 2009; Kumari et al., 2013). This appears IL-19 IL-1β IL-6 IL-12p35 IL-20 IL-23p19 p40 1 *** 1 1 1 1 1 1 *** *** 0.1 0.1 0.1 0.1 0.1 0.1 0.1 *** *** 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ** Skin mRNA, 0.001 0.001 0.001 0.001 0.001 0.001 0.001 relative to HPRT relative 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 IL-25 IL-27p28 EBI3 IL-33 IL-36γ TNF-α M-CSF 1 1 1 1 100 1 1 ** *** *** 0.1 0.1 0.1 *** 0.1 10 0.1 0.1 0.01 0.01 *** 0.01 0.01 1 0.01 0.01 ** Skin mRNA, 0.001 0.001 0.001 0.001 0.1 0.001 0.001 relative to HPRT relative 0.0001 0.0001 0.0001 0.0001 0.01 0.0001 0.0001 IFN-γ OSM IL-4 IL-17A IL-21 IL-22 1 1 1 1 1 1 0.1 0.1 0.1 0.1 0.1 0.1 *** *** *** Healthy 0.01 0.01 *** 0.01 0.01 0.01 0.01 *** Psoriasis Skin mRNA, 0.001 0.001 0.001 0.001 0.001 0.001 relative to HPRT relative 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 IL-19 IL-19 IL-20 IL-22 Corr. with PASI 1,600 500 50 100 –1 rs P –1 *** 400 40 80 1,200 * * *** IL-19 0.653 0.000 Healthy 300 30 60 800 Psoriasis 200 20 40 IL-20 0.570 0.004 400 100 10 20 Skin protein, pg ml IL-22 0.624 0.001 Serum protein, pg ml 0 0 0 0 IL-19 IL-19 500 1,000 1,000 125 125 –1 400 100 100 100 100 * 300 75 * 75 10 10 * 200 50 50 * UV therapy * 1 1 % of 0 weeks 100 *** 25 25 etanercept therapy mRNA, % of 0 wks * mRNA, % of 0 weeks Serum protein, pg ml *** 0 0.1 0.1 0 0 0 weeks 4 weeks 0 weeks 2–5 weeks 0 weeks 0 weeks of ustekinumab therapy of UV-based therapy Healthy Asthma 1 week 12 week 4–6 weeks 24 weeks Serum IL-19 PASI Transplanted Crohn’s disease Crohn’s 2758 Journal of Investigative Dermatology (2014), Volume 134 EWitteet al. Role of IL-19 in Psoriasis to be caused by the direct effects of these mediators these patients. Importantly, IL-19 blood levels positively and on the keratinocytes, leading to their disturbed differentiation most significantly correlated with the disease severity repre- and chemokine production as demonstrated by in vitro sented by the psoriasis area and severity index value studies (Wolk et al., 2006; Sa et al., 2007; Wolk et al., (Figure 1d). Virtually no systemic levels of IL-19 were found 2009a; Kumari et al., 2013). Moreover, some IL-10 in healthy participants (Figure 1c and e). Analysis of further family members might have an essential role in the immune-mediated conditions revealed that patients suffering elevated anti-microbial competence of psoriatic lesions: from asthma and Crohn’s disease, but not those after renal IL-20, IL-22, and IL-24 strongly enhance the expression transplantation, also showed increased IL-19 blood levels, of anti-bacterial proteins in keratinocytes (Wolk et al., 2004; which, however, were far from reaching those of psoriasis Sa et al., 2007; Kumari et al., 2013), whereas the elevated patients (Figure 1e). anti-viral defense of psoriatic lesions seems to be dependent Next, we investigated the influence of anti-psoriatic thera- on IL-29 (Wolk et al., 2013). In contrast to IL-20, IL-22, IL-24, pies on the IL-19 levels in the skin and blood of psoriasis and IL-29, the roles of IL-19 and IL-26 were largely patients. A pronounced drop of cutaneous IL-19 mRNA to unexplored so far. below 1% of the initial expression levels was induced by UV In this study, we compared the expression of a broad range radiation and TNF-a inhibition–based therapies (Figure 1f). of cytokines belonging to different cytokine families (including Strikingly, only a single application of ustekinumab induced a the IL-1, IL-12/IL-23, IL-10, and IL-17 families) in psoriatic marked decrease in blood IL-19 concentrations (Figure 1g).