SAT0284 EPIGENETIC DEREGULATION OF AUTOPHAGY PROMOTES FIBROSIS IN SYSTEMIC SCLEROSIS
Authors: A. Zehender, N. Y. Lin, Y. N. LI, A. H. Györfi, C. Bergmann, A. Ramming, G. Schett, J. Distler
Journal: Annals of the Rheumatic Diseases (2020)

Background: Autophagy is catabolic process allowing cells to degrade unnecessary or dysfunctional cellular organelles. Failure of appropriate regulation of autophagy, however, can severely perturb tissue homeostasis. Several stimuli present in fibrosis such as pro-fibrotic cytokines are known to activate autophagy. Objectives: The objective of this work was to characterize the regulation of autophagy in systemic sclerosis (SSc) and to decipher its role in the pathogenesis of SSc. Methods: Activation of autophagy in SSc skin and matched tissue samples from healthy individuals was assessed by immunofluorescence staining for ATG7, BECLIN1 and P62. We generated Atg7 fl/fl x Col1a2 ; Cre ER mice to selectively disable autophagy in fibroblasts. The role of the autophagy was investigated in the model of bleomycin- and TβRIact-induced dermal and pulmonary fibrosis. Overexpression of Myst1 was achieved by adenovirus encoding for Myst1 . Collagen release and protein expression were measure by Western blot. Target genes were analyzed by RT-PCR. Co-immunoprecipitation and reporter assay were performed to study physical and functional interactions between MYST1 and SMAD3. To monitor the autophagic flux in vitro and in vivo we generated adenoviral vectors encoding for tandem fluorescent-tagged LC3 (mRFP-EGFP-LC3). Results: Transforming growth factor-β (TGFβ) activates autophagy by an epigenetic mechanism to amplify its profibrotic effects. TGFβ induces autophagy in fibrotic diseases by SMAD3-dependent downregulation of the H4K16 histone acetyltransferase MYST1, which regulates the expression of core components of the autophagy machinery such as ATG7 and BECLIN1. Activation of autophagy in fibroblasts promotes collagen release and is both, sufficient and required, to induce tissue fibrosis. Forced expression of MYST1 abrogates the stimulatory effects of TGFβ on autophagy and re-establishes the epigenetic control of autophagy in fibrotic conditions. Interference with the aberrant activation of autophagy inhibits TGFβ-induced fibroblast activation and ameliorates experimental dermal and pulmonary fibrosis. These findings link uncontrolled TGFβ signaling to aberrant autophagy, deregulated epigenetics in fibrotic diseases and may open new avenues for therapeutic intervention in fibrotic diseases. Conclusion: We demonstrate that the epigenetic control of autophagy is disturbed by a TGFβ-dependent downregulation of the H4K16 histone acetyltransferase MYST1. The increased activation of autophagy induces fibroblast-to-myofibroblast transition and promotes fibrotic tissue remodeling. Re-expression of MYST1 prevents aberrant autophagy, limits the profibrotic effects of TGFβ and ameliorates experimental fibrosis. Restoration of the epigenetic control of autophagy might thus be a novel approach to ameliorate fibrotic tissue remodeling. References: [1]Wynn, T.A. Cellular and molecular mechanisms of fibrosis. J Pathol 214, 199-210 (2008). [2]Distler, J.H., et al. Review: Frontiers of Antifibrotic Therapy in Systemic Sclerosis. Arthritis &amp; rheumatology (Hoboken, N.J.) 69, 257-267 (2017). [3]Gyorfi, A.H., Matei, A.E. &amp; Distler, J.H.W. Targeting TGF-beta signaling for the treatment of fibrosis. Matrix biology: journal of the International Society for Matrix Biology 68-69, 8-27 (2018). [4]Wang, C.W. &amp; Klionsky, D.J. The molecular mechanism of autophagy. Mol Med 9, 65-76 (2003). [5]Hernandez-Gea, V., et al. Autophagy releases lipid that promotes fibrogenesis by activated hepatic stellate cells in mice and in human tissues. Gastroenterology 142, 938-946 (2012). Disclosure of Interests: Ariella Zehender: None declared, Neng Yu Lin: None declared, Yi-Nan Li: None declared, Andrea-Hermina Györfi: None declared, Christina Bergmann: None declared, Andreas Ramming Grant/research support from: Pfizer, Novartis, Consultant of: Boehringer Ingelheim, Novartis, Gilead, Pfizer, Speakers bureau: Boehringer Ingelheim, Roche, Janssen, Georg Schett Speakers bureau: AbbVie, BMS, Celgene, Janssen, Eli Lilly, Novartis, Roche and UCB, Jörg Distler Grant/research support from: Boehringer Ingelheim, Consultant of: Boehringer Ingelheim, Paid instructor for: Boehringer Ingelheim, Speakers bureau: Boehringer Ingelheim