Research Papers: Pathology:
SIRT3 is attenuated in systemic sclerosis skin and lungs, and its pharmacologic activation mitigates organ fibrosis
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Kaname Akamata1,*, Jun Wei1,*, Mitra Bhattacharyya1, Paul Cheresh2, Michael Y. Bonner3, Jack L. Arbiser3,4, Kirtee Raparia5, Mahesh P. Gupta6, David W. Kamp2,7 and John Varga1
1 Division of Rheumatology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
2 Division of Pulmonary & Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
3 Department of Dermatology, Emory University School of Medicine, Atlanta, GA, USA
4 Atlanta Veterans Administration Medical Center and Winship Cancer, Atlanta, GA, USA
5 Department of Pathology, Northwestern University, Chicago, IL, USA
6 Department of Surgery, University of Chicago, Chicago, IL, USA
7 Jesse Brown VA Medical Center, Chicago, IL, USA
* These authors have contributed equally to this work
John Varga, email:
Keywords: fibrosis, SIRT3, TGF-β, myofibroblast, ROS, Pathology Section
Received: July 10, 2016 Accepted: September 29, 2016 Published: October 06, 2016
Constitutive fibroblast activation is responsible for organ fibrosis in fibrotic disorders including systemic sclerosis (SSc), but the underlying mechanisms are not fully understood, and effective therapies are lacking. We investigated the expression of the mitochondrial deacetylase sirtuin 3 (SIRT3) and its modulation by hexafluoro, a novel fluorinated synthetic honokiol analogue, in the context of fibrosis. We find that augmenting cellular SIRT3 by forced expression in normal lung and skin fibroblasts, or by hexafluoro treatment, blocked intracellular TGF-ß signaling and fibrotic responses, and mitigated the activated phenotype of SSc fibroblasts. Moreover, hexafluoro attenuated mitochondrial and cytosolic reactive oxygen species (ROS) accumulation in TGF-β-treated fibroblasts. Remarkably, we found that the expression of SIRT3 was significantly reduced in SSc skin biopsies and explanted fibroblasts, and was suppressed by TGF-β treatment in normal fibroblasts. Moreover, tissue levels of acetylated MnSOD, a sensitive marker of reduced SIRT3 activity, were dramatically enhanced in lesional skin and lung biopsies from SSc patients. Mice treated with hexafluoro showed substantial attenuation of bleomycin-induced fibrosis in the lung and skin. Our findings reveal a cell-autonomous function for SIRT3 in modulating fibrotic responses, and demonstrate the ability of a novel pharmacological SIRT3 agonist to attenuate fibrosis in vitro and in vivo. In light of the impaired expression and activity of SIRT3 associated with organ fibrosis in SSc, pharmacological approaches for augmenting SIRT3 might have therapeutic potential.
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