Attenuation of fibroblast activation and fibrosis by adropin in systemic sclerosis

Fibrotic diseases impose a major socioeconomic challenge on modern societies and have limited treatment options. Adropin, a peptide hormone encoded by the energy homeostasis-associated (ENHO) gene, is implicated in metabolism and vascular homeostasis, but its role in the pathogenesis of fibrosis remains enigmatic. Here, we used machine learning approaches in combination with functional in vitro and in vivo experiments to characterize adropin as a potential regulator involved in fibroblast activation and tissue fibrosis in systemic sclerosis (SSc). We demonstrated consistent down-regulation of adropin/ENHO in skin across multiple cohorts of patients with SSc. The prototypical profibrotic cytokine TGFβ reduced adropin/ENHO expression in a JNK-dependent manner. Restoration of adropin signaling by therapeutic application of bioactive adropin34-76 peptides in turn inhibited TGFβ-induced fibroblast activation and fibrotic tissue remodeling in primary human dermal fibroblasts, three-dimensional full-thickness skin equivalents, mouse models of bleomycin-induced pulmonary fibrosis and sclerodermatous chronic graft-versus-host-disease (sclGvHD), and precision-cut human skin slices. Knockdown of GPR19, an adropin receptor, abrogated the antifibrotic effects of adropin in fibroblasts. RNA-seq demonstrated that the antifibrotic effects of adropin34-76 were functionally linked to deactivation of GLI1-dependent profibrotic transcriptional networks, which was experimentally confirmed in vitro, in vivo, and ex vivo using cultured human dermal fibroblasts, a sclGvHD mouse model, and precision-cut human skin slices. ChIP-seq confirmed adropin34-76-induced changes in TGFβ/GLI1 signaling. Our study characterizes the TGFβ-induced down-regulation of adropin/ENHO expression as a potential pathomechanism of SSc as a prototypical systemic fibrotic disease that unleashes uncontrolled activation of profibrotic GLI1 signaling.

TGFβ promotes fibrosis by MYST1-dependent epigenetic regulation of autophagy

Activation of fibroblasts is essential for physiological tissue repair. Uncontrolled activation of fibroblasts, however, may lead to tissue fibrosis with organ dysfunction. Although several pathways capable of promoting fibroblast activation and tissue repair have been identified, their interplay in the context of chronic fibrotic diseases remains incompletely understood. Here, we provide evidence that 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 and deregulated epigenetics in fibrotic diseases and may contribute to the development of therapeutic interventions in fibrotic diseases.

AB0091 INHIBITION OF AUTOPHAGY PREVENTS PROGRESSION OF FIBROSIS IN MURINE MODELS OF SYSTEMIC SCLEROSIS

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. Recent studies demonstrate that autophagy is activated in several fibrotic diseases such as liver fibrosis, renal interstitial fibrosis, cardiac fibrosis.

Objectives:

The objective of this work was to characterize the activation of autophagy in systemic sclerosis (SSc) and to decipher its role in the pathogenesis of SSc.

Methods:

Activation of autophagy in skin samples of patients and murine models of SSc was assessed by co-staining of LC3B and P62 with the lysosomal marker LAMP2. The role of the autophagy was investigated in the model of bleomycin-induced dermal fibrosis. Beclin1 was overexpressed using adenovirus encoding for Beclin1. To knockdown Atg7 in vivo was achieved by subcutaneous injections of Atg7 siRNA or non-targeting siRNA. In vivo, 3-methyladenine (3-MA) was administered i.p. in a concentration of 15 mg/kg ones daily. Protein expression was measured by Western blot. Target genes were analyzed by qPCR. To monitor the autophagic flux, we generated adenoviral vectors encoding for tandem fluorescent-tagged LC3 (mRFP-EGFP-LC3).

Results:

In the present study, we demonstrate that autophagy is activated in fibroblasts in SSc skin and also in experimental fibrosis models as compared to respective non-fibrotic control tissue with enhanced activity in in vivo and in vitro autophagy reporter studies. The aberrant activation of autophagy had profound stimulatory effects on fibroblasts. Activation of autophagy by forced expression of BECLIN1 promoted fibroblast-to-myofibroblast transition and stimulated the collagen release by cultured human fibroblasts and induced fibrosis in murine model. Nevertheless, inhibition of autophagy can deactivate myofibroblasts and induce regression of tissue fibrosis. Knockdown of ATG7 or BECLIN1 in human fibroblasts reduced the expression of αSMA and the number of stress fibers in myofibroblasts, indicating re-differentiation of myofibroblasts into resting fibroblasts upon inhibition of autophagy. Similar results were obtained with the autophagy inhibitors CQ and 3-MA. In vivo, siRNA mediated knockdown of Atg7 effectively prevented progression of fibrosis in a model of established bleomycin-induced skin fibrosis. Inactivation of autophagy decreased dermal thickness, myofibroblast counts and hydroxyproline content to below pretreatment levels, indicating regression of bleomycin-induced skin fibrosis. In addition, treatment of mice with the autophagy inhibitor 3-MA ameliorated bleomycin-induced skin fibrosis.

Conclusion:

We demonstrate that autophagy activity is enhanced in fibroblasts of SSc patients and in murine models of SSc. The increased activation of autophagy induces fibroblast-to-myofibroblast transition and promotes fibrotic tissue remodeling. However, inhibition of autophagy can deactivate myofibroblasts and induce regression of tissue fibrosis.

References:

[1]Wynn, T. Cellular and molecular mechanisms of fibrosis. J Pathol 214, 199-210 (2008).

[2]Klionsky DJ, Abeliovich H, Agostinis P, et al. Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes. Autophagy 4, 151-175 (2008).

[3]Wang, CW & Klionsky, DJ. The molecular mechanism of autophagy. Mol Med 9, 65-76 (2003).

[4]Hernández-Gea V, Ghiassi-Nejad Z, Rozenfeld R, 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, Yi-Nan Li: None declared, Neng-Yu Lin: None declared, Andrea-Hermina Györfi: None declared, Alina Soare: None declared, Christina Bergmann: None declared, Andreas Ramming: None declared, Georg Schett: None declared, Jörg H.W. Distler Consultant of: Actelion, Active Biotech, Anamar, ARXX, Bayer Pharma, Boehringer Ingelheim, Celgene, Galapagos, GSK, Inventiva, JB Therapeutics, Medac, Pfizer, RuiYi and UCB., Grant/research support from: Anamar, Active Biotech, Array Biopharma, aTyr, BMS, Bayer Pharma, Boehringer Ingel-heim, Celgene, Galapagos, GSK, Inventiva, Novartis, Sanofi-Aventis, RedX, UCB., Employee of: stock owner of 4D Science and Scientific head of FibroCure

X-linked inhibitor of apoptosis protein (XIAP) inhibition in systemic sclerosis (SSc)

OBJECTIVE

X-linked inhibitor of apoptosis protein (XIAP) is a multifunctional protein with important functions in apoptosis, cellular differentiation and cytoskeletal organisation and is emerging as potential target for the treatment of various cancers. The aim of the current study was to investigate the role of XIAP in the pathogenesis of systemic sclerosis (SSc).

METHODS

The expression of XIAP in human skin samples of patients with SSc and chronic graft versus host disease (cGvHD) and healthy individuals was analysed by quantitative PCR, immunofluorescence (IF) and western blot. XIAP was inactivated by siRNA-mediated knockdown and pharmacological inhibition. The effects of XIAP inactivation were analysed in cultured fibroblasts and in the fibrosis models bleomycin-induced and topoisomerase-I-(topoI)-induced fibrosis and in Wnt10b-transgenic mice.

RESULTS

The expression of XIAP, but not of other inhibitor of apoptosis protein family members, was increased in fibroblasts in SSc and sclerodermatous cGvHD. Transforming growth factor beta (TGF-β) induced the expression of XIAP in a SMAD3-dependent manner. Inactivation of XIAP reduced WNT-induced fibroblast activation and collagen release. Inhibition of XIAP also ameliorated fibrosis induced by bleomycin, topoI and overexpression of Wnt10b in well-tolerated doses. The profibrotic effects of XIAP were mediated via WNT/β-catenin signalling. Inactivation of XIAP reduces binding of β-catenin to TCF to in a TLE-dependent manner to block WNT/β-catenin-dependent transcription.

CONCLUSIONS

Our data characterise XIAP as a novel link between two core pathways of fibrosis. XIAP is overexpressed in SSc and cGvHD in a TGF-β/SMAD3-dependent manner and in turn amplifies the profibrotic effects of WNT/β-catenin signalling on fibroblasts via transducin-like enhancer of split 3. Targeted inactivation of XIAP inhibits the aberrant activation of fibroblasts in murine models of SSc.

SAT0284 EPIGENETIC DEREGULATION OF AUTOPHAGY PROMOTES FIBROSIS IN SYSTEMIC SCLEROSIS

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 generatedAtg7fl/flxCol1a2;CreER 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 forMyst1. 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 fluxin vitroandin vivowe 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 & rheumatology (Hoboken, N.J.) 69, 257-267 (2017).

[3]Gyorfi, A.H., Matei, A.E. & 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. & 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

Acyltransferase skinny hedgehog regulates TGFβ-dependent fibroblast activation in SSc

OBJECTIVES

Systemic sclerosis (SSc) is characterised by aberrant hedgehog signalling in fibrotic tissues. The hedgehog acyltransferase (HHAT) skinny hedgehog catalyses the attachment of palmitate onto sonic hedgehog (SHH). Palmitoylation of SHH is required for multimerisation of SHH proteins, which is thought to promote long-range, endocrine hedgehog signalling. The aim of this study was to evaluate the role of HHAT in the pathogenesis of SSc.

METHODS

Expression of HHAT was analysed by real-time polymerase chain reaction(RT-PCR), immunofluorescence and histomorphometry. The effects of HHAT knockdown were analysed by reporter assays, target gene studies and quantification of collagen release and myofibroblast differentiation in cultured human fibroblasts and in two mouse models.

RESULTS

The expression of HHAT was upregulated in dermal fibroblasts of patients with SSc in a transforming growth factor-β (TGFβ)/SMAD-dependent manner. Knockdown of HHAT reduced TGFβ-induced hedgehog signalling as well as myofibroblast differentiation and collagen release in human dermal fibroblasts. Knockdown of HHAT in the skin of mice ameliorated bleomycin-induced and topoisomerase-induced skin fibrosis.

CONCLUSION

HHAT is regulated in SSc in a TGFβ-dependent manner and in turn stimulates TGFβ-induced long-range hedgehog signalling to promote fibroblast activation and tissue fibrosis. Targeting of HHAT might be a novel approach to more selectively interfere with the profibrotic effects of long-range hedgehog signalling.

The tyrosine phosphatase SHP2 controls TGFβ-induced STAT3 signaling to regulate fibroblast activation and fibrosis

Uncontrolled activation of TGFβ signaling is a common denominator of fibrotic tissue remodeling. Here we characterize the tyrosine phosphatase SHP2 as a molecular checkpoint for TGFβ-induced JAK2/STAT3 signaling and as a potential target for the treatment of fibrosis. TGFβ stimulates the phosphatase activity of SHP2, although this effect is in part counterbalanced by inhibitory effects on SHP2 expression. Stimulation with TGFβ promotes recruitment of SHP2 to JAK2 in fibroblasts with subsequent dephosphorylation of JAK2 at Y570 and activation of STAT3. The effects of SHP2 on STAT3 activation translate into major regulatory effects of SHP2 on fibroblast activation and tissue fibrosis. Genetic or pharmacologic inactivation of SHP2 promotes accumulation of JAK2 phosphorylated at Y570, reduces JAK2/STAT3 signaling, inhibits TGFβ-induced fibroblast activation and ameliorates dermal and pulmonary fibrosis. Given the availability of potent SHP2 inhibitors, SHP2 might thus be a potential target for the treatment of fibrosis.