Background/Purpose:

Autophagy (Atg) is catabolic process allowing cells to degrade unnecessary or dysfunctional cellular organelles. Aberrant activation of Atg has been implicated into the pathogenesis of various diseases.

Methods:

We generated Atg7^fl/flx Col1a2;CreER mice with selective inactivation of Atg in fibroblasts. The role of the Atg was investigated in the model of bleomycin- and TβRIact-induced dermal and pulmonary fibrosis. Overexpression of Myst1 and Beclin1 was achieved by adenoviral overexpression. ChIP and reporter assays were performed to study physical and functional interactions between MYST1 and SMAD3.

Results:

Atg is strongly activated in fibroblasts from SSc skin and also in experimental dermal and pulmonary fibrosis as compared to respective non-fibrotic control tissue with overexpression of ATG7 and of BECLIN, downregulation of the autophagy substrate p62 and activation of autophagy-dependent reporter activity. The aberrant activation of Atg has profound stimulatory effects on fibroblasts. Activation of Atg by forced expression of BECLIN1 promoted fibroblast-to-myofibroblast transition and stimulates the collagen release in vitro and in vivo. Moreover, inactivation of autophagy by fibroblast-specific knockout of Atg7prevented myofibroblast differentiation and ameliorated fibrosis, demonstrating that activation of Atg is both, sufficient and required, for fibroblast activation and tissue fibrosis. We also provide evidence that TGFβ activates Atg by an epigenetic mechanism to amplify its profibrotic effects. TGFβ induces Atg in fibrotic diseases by SMAD3-dependent downregulation of the H4K16-histoneacetlytransferase MYST1, which controls the expression of core components of the Atg machinery such as ATG7 and BECLIN1. Forced expression of MYST1 abrogates the stimulatory effects of TGFβ on Atg and re-establishes the epigenetic control of autophagy in fibrotic conditions. Overexpression of MYST1 prevents the aberrant activation of Atg, inhibits TGFβ-induced fibroblast activation and ameliorates experimental dermal and pulmonary fibrosis.

Conclusion:

We demonstrate that the epigenetic control of Atg is disturbed by a TGFβ-dependent downregulation of MYST1 in SSc. The resulting uncontrolled activation of Atg promotes fibroblast-to-myofibroblast transition and tissue fibrosis. Restoration of the epigenetic control of autophagy limits the profibrotic effects of TGFβ and ameliorates experimental fibrosis. These findings link uncontrolled TGFβ signaling to aberrant autophagy and altered epigenetics in fibrotic diseases.

« Back to ACR/ARHP Annual Meeting 2017

ACR Meeting Abstracts - https://acrabstracts.org/abstract/tgf%ce%b2-promotes-fibrosis-by-myst1-dependent-epigenetic-regulation-of-autophagy/