Abstractω3‐polyunsaturated free fatty acids (ω3‐PUFAs), particularly docosahexaenoic (DHA) and eicosapentaenoic acid (EPA), are thought to exert health promoting effects in metabolic and in inflammatory diseases. The molecular mechanisms of these beneficial effects are only partially understood. DHA and EPA activate Free Fatty Acid receptor 4 (GPR120/FFA4). Recently, the first orally available, synthetic ligand of FFA4, 3‐[2‐chloro‐5‐(trifluoromethoxy)phenyl]‐3‐azaspiro[5.5]undecane‐9‐acetic acid (“compound A”; cpd A) has been developed. Cpd A exhibits distinctly higher potency, efficiency, and selectivity at FFA4 than ω3‐PUFAs and ameliorates insulin resistance and adipose tissue inflammation in the mouse. With GPR120/FFA4 activation believed to also attenuate tissue inflammation in autoimmune diseases, cpd A may also have a beneficial effect in these diseases. We have therefore addressed the therapeutic potential of cpd A in mouse models of three prototypical autoimmune diseases, specifically psoriasis, rheumatoid arthritis, and bullous pemphigoid. The effect of cpd A on the course of Aldara™‐induced psoriasis‐like dermatitis, K/BxN serum transfer arthritis, and antibody transfer pemphigoid disease‐like dermatitis was scrutinized. Cpd A did not alter the course of Aldara‐induced psoriasis‐like dermatitis, K/BxN serum transfer arthritis, or antibody transfer pemphigoid disease‐like dermatitis. Our results suggest that therapeutic regimens solely relying on FFA4 activation do not bear the potential to treat inflammatory diseases. With cpd A distinctly more potent in activating GPR120/FFA4 than ω3‐PUFAs, this also suggests that GPR120/FFA4 activation by ω3‐PUFAs does not significantly contribute to the health‐promoting effects of ω3‐PUFAs in autoimmune diseases.

The drug dimethyl fumarate (DMF) is in clinical use for the treatment of psoriasis and multiple sclerosis. In addition, it has recently been demonstrated to ameliorate skin pathology in mouse models of pemphigoid diseases, a group of autoimmune blistering diseases of the skin and mucous membranes. However, the mode of action of DMF in inflammatory skin diseases has remained elusive. Therefore, we have investigated here the mechanisms by which DMF improves skin pathology, using the antibody transfer model of bullous pemphigoid-like epidermolysis bullosa acquisita (EBA). Experimental EBA was induced by transfer of antibodies against collagen VII that triggered the infiltration of immune cells into the skin and led to inflammatory skin lesions. DMF treatment reduced the infiltration of neutrophils and monocytes into the skin explaining the improved disease outcome in DMF-treated animals. Upon ingestion, DMF is converted to monomethyl fumarate that activates the hydroxycarboxylic acid receptor 2 (HCA2). Interestingly, neutrophils and monocytes expressed Hca2. To investigate whether the therapeutic effect of DMF in EBA is mediated by HCA2, we administered oral DMF to Hca2-deficient mice (Hca2−/−) and wild-type littermates (Hca2+/+) and induced EBA. DMF treatment ameliorated skin lesions in Hca2+/+ but not in Hca2−/− animals. These findings demonstrate that HCA2 is a molecular target of DMF treatment in EBA and suggest that HCA2 activation limits skin pathology by inhibiting the infiltration of neutrophils and monocytes into the skin.

Objectives Functional IgG autoantibodies against diverse G protein-coupled receptors, i.e. antibodies with agonistic or antagonistic activity at these receptors, are abundant in human serum. Their levels are altered in patients with SSc, and autoantibodies against angiotensin II receptor 1 (ATR1) and endothelin receptor A (ETA) have been suggested to drive SSc by inducing the chemokines CXCL8 and CCL18 in the blood. The objective of our study is to profile the effect of IgG in SSc (SSc-IgG) on the production of soluble mediators in monocytic cells. Methods Monocyte-like THP-1 cells were stimulated with SSc-IgG and their secretome was analysed. Furthermore, the significance of major pro-inflammatory pathways for the induction of CXCL8 and CCL18 in response to SSc-IgG was assessed by a pharmacological approach. Results Stimulation with SSc-IgG significantly alters the secretome of THP-1 cells towards a general pro-inflammatory and profibrotic phenotype, which includes an increase of CCL18 and CXCL8. The consequent expression profiles vary depending on the individual donor of the SSc-IgG. CCL18 and CXCL8 expression is thus regulated differentially, with AP-1 driving the induction of both CCL18 and CXCL8 and the TAK/IKK-β/NF-κB pathway and ERK1/2 driving that of CXCL8. Conclusions Our results suggest that SSc-IgG contributes to the generation of the pro-inflammatory/profibrotic tissue milieu characteristic of SSc by its induction of a respective phenotype in monocytes. Furthermore, our results highlight AP-1 as a critical regulator of gene transcription of CCL18 in monocytic cells and as a promising pharmacological therapeutic target for the treatment of SSc.

clear DEAF-1-related (NUDR) protein contains a novel DNA binding domain and represses transcription of the heterogeneous nuclear ribonucleoprotein A2/B1 promoter. J Biol Chem 1999;274:30510e9.

Background:Regulatory IgG autoantibodies directed against diverse G protein-coupled receptors (GPCR),i.e.antibodies with agonistic or antagonistic activity are abundant in human serum. The serum titers of autoantibodies targeting angiotensin II receptor 1 (AT1) and endothelin receptor A (ETA) are specifically altered in autoimmune diseases such as systemic sclerosis (SSc). Disease-promoting mechanisms regulated by anti-AT1and anti-ETAIgG are still elusive, but induction of pro-inflammatory and pro-fibrotic chemokines (CXCL8, CCL18) has been suggested to be one of them.Objectives:To determine the cytokine and phospho-kinase profiles induced in monocyte-like cells by IgG derived from SSc patients (SSc-IgG) enriched with anti-AT1and anti-ETAantibodies in comparison to IgG derived from healthy donors (IgG-HD).Methods:A monocyte-like cell line (THP-1) was culturedin vitroand stimulated with IgG (1 mg/ml) derived from SSc patients or HD in the presence of various inhibitors/blockers for 24h. Then, supernatants were analyzed by a human cytokine/chemokine array. Data were analyzed using bio-mathematical tools such as generalized t-test including the robust regression method from R/Bioconductor package LIMMA. In addition, THP-1 cells were culturedin vitroand stimulated with IgG (1 mg/ml) derived from SSc patients or HD for up to 30 minutes. Thereafter, cell lysates were assayed for the kinome employing a human phospho-kinase array. To validate potential effects of transcription factor inhibition, release of CXCL8 and CCL18 into the supernatant was measured by Elisa.Results:In general, SSc-IgG induced the release of most cytokines by THP-1 cells more pronouncedly than HD-IgG. The bio-mathematical analysis suggested that stimuli, responsible for the shift of the THP-1 cell cytokine profile, are more abundant in SSc-IgG than in HD-IgG. Based upon these findings a gene set enrichment analysis for transcription factors yielded the transcription factors NF-κB, AP-1, and PRDM1 (Blimp-1) as putative major regulatory hubs for the response of THP-1 cells to SSc-IgG. Further, SSc-IgG altered the phosphorylation status of several proteins, indicative of an involvement of MAPK and/or JAK/STAT pathways. Interestingly, a role for AP-1 was also proposed by the inhibition of CXCL8 and CCL18 release following pretreatment of THP-1 cells with an AP-1 blocker.Conclusion:Herein, we demonstrate that IgG of SSc patients, enriched with anti-AT1and anti-ETAautoantibodies drives THP-1 cells towards a general pro-inflammatory and pro-fibrotic phenotype, which is reflected by broad changes in the secretome and kinome of these cells. Furthermore, our results highlight AP-1 as critical regulator of gene transcription of CXCL8 and CCL18 in a monocyte-like cell line.References:[1]Cabral-Marques O, Marques A, Giil LM, De Vito R, Rademacher J, Günther J, Lange T, Humrich JY, Klapa S, Schinke S, et al. GPCR-specific autoantibody signatures are associated with physiological and pathological immune homeostasis.Nat Commun(2018)9:5224. doi:10.1038/s41467-018-07598-9[2]Günther J, Kill A, Becker MO, Heidecke H, Rademacher J, Siegert E, Radi M, Burmester G-R, Dragun D, Riemekasten G. Angiotensin receptor type 1 and endothelin receptor type A on immune cells mediate migration and the expression of IL-8 and CCL18 when stimulated by autoantibodies from systemic sclerosis patients.Arthritis Res Ther(2014)16:R65. doi:10.1186/ar4503Disclosure of Interests:Anja Dalmann: None declared, Sripriya Murthy: None declared, Melanie Wannick: None declared, Georgios Eleftheriadis: None declared, Antje Müller: None declared, Detlef Zillikens: None declared, Hauke Busch: None declared, Christian Sadik: None declared, Gabriela Riemekasten Consultant of: Cell Trend GmbH, Janssen, Actelion, Boehringer Ingelheim, Speakers bureau: Actelion, Novartis, Janssen, Roche, GlaxoSmithKline, Boehringer Ingelheim, Pfizer