POS0428 REGULATION OF IFN SIGNATURE BY HDAC CLASS IIa-CD52 AXIS IN SYSTEMIC SCLEROSIS
Authors: M. Rudnik, A. Hukara, P. Blyszczuk, O. Distler, G. Kania
Journal: Annals of the Rheumatic Diseases (2021)

Background: Systemic sclerosis (SSc) is associated with an interferon (IFN) signature, which is defined by a higher expression of IFN-stimulated genes (mainly in response to IFNα). Histone deacetylases (HDACs) are a family of epigenetic modifiers mediating immune function. HDACs function via diverse molecular mechanisms, including direct inhibition of gene transcription or indirectly through modulation of nuclear transcription factors such as NF- κ B and STATs. CD52 protein regulates T cell receptor and NF- κ B signalling. Previously, we showed downregulation of CD52 in SSc monocytes, however, the influence of CD52 on IFN signalling has not been studied yet. Objectives: We investigated the role of CD52 in the regulation of IFN response in monocytes. Moreover, we explored the regulatory mechanisms of CD52 expression to identify the involvement of HDACs in that process. Methods: RNAseq of CD14 + monocytes isolated from peripheral blood of lcSSc (n=5, age=54.4±6.7), dcSSc patients (n=5, age=51.8±7.2) and age- and sex-matched healthy controls (HC) (n=5, age=50.8±9.7) was performed using Illumina HiSeq 4000 platform. Differentially expressed genes were computed using DeSEQ2 algorithm. Gene ontology and pathway analysis were performed using Metacore software and ShinyApp. CD52 activity in monocytes was blocked by monoclonal antibody Alemtuzumab [10ug/ml] and IFN signature genes expression was assessed upon IFNα stimulation [1ng/ml] by qPCR and ELISA. HDAC-dependent regulation of CD52 expression in CD14 + monocytes from HC was analysed on mRNA and protein levels after treatment with pan-HDAC inhibitor valproic acid and HDAC class IIa inhibitor TMP269 [both 2.5μM]. Results: Pathway analysis revealed significant alterations in interferon signalling in SSc monocytes. Monocytes treated with Alemtuzumab and IFNα showed induced expression of STAT1 (p=0.023, N=4), CXCL9 (p=0.062, N=4) and CXCL10 (p=0.005, N=4). RNAseq revealed a specific HDAC expression pattern in SSc monocytes with induced expression of HDAC4, 6, 10, 11 (p&lt;0.05) and reduced HDAC1, 3 and 8 (p&lt;0.05). CD52 mRNA was significantly decreased after IFNα stimulation (p=0.001, N=3). Treatment with valproic acid and HDAC class IIa inhibitor TMP269 resulted in decreased phosphorylation of STAT1 (p&lt;0.01, N=4) followed by a declined level of CXCL10 (p&lt;0.01, N=4) and restored level of CD52 mRNA (p&lt;0.001, N=4). Conclusion: Our findings demonstrated a new aspect of pro-inflammatory type I IFN signalling in SSc. We described a novel regulation feedback loop in monocytes, in which CD52 suppresses IFN signature, while its expression is inhibited by IFN-induced HDAC activity (mainly HDAC class IIa). Therefore, targeting the CD52-IFN-HDAC axis might serve as a novel therapeutic strategy in SSc. Disclosure of Interests: Michal Rudnik: None declared, Amela Hukara: None declared, Przemyslaw Blyszczuk: None declared, Oliver Distler Speakers bureau: Actelion, Bayer, Boehringer Ingelheim, Medscape, Novartis, Roche, Menarini, Mepha, MSD, iQone, Novartis, Pfizer, Consultant of: Abbvie, Actelion, Acceleron Pharma, Amgen, AnaMar, Arxx Therapeutics, Bayer, Baecon Discovery, Blade Therapeutics, Boehringer, CSL Behring, ChemomAb, Corpuspharma, Curzion Pharmaceuticals, Ergonex, Galapagos NV, GSK, Glenmark Pharmaceuticals, Inventiva, Italfarmaco, iQvia, Kymera, Medac, Medscape, Mitsubishi Tanabe Pharma, MSD, Roche, Sanofi, UCB, Lilly, Target BioScience, Pfizer, Grant/research support from: Actelion, Bayer, Boehringer Ingelheim, Kymera Therapeutics, Mitsubishi Tanabe, Gabriela Kania: None declared