Idiopathic pulmonary fibrosis (IPF) is a deadly disease characterized by chronic
inflammation and excessive
collagen accumulation in the lung. Myofibroblasts are the primary
collagen-producing cells in
pulmonary fibrosis.
Histone deacetylase inhibitor (HDACi) can affect gene expression, and some, such as
suberoylanilide hydroxamic acid (SAHA), are US FDA approved for
cancer treatment. In this study, we investigated SAHA's effects on the expression of
collagen III alpha 1 (COL3A1) in primary human IPF fibroblasts and in a murine model of
pulmonary fibrosis. We observed that increased COL3A1 expression in IPF fibroblasts can be substantially reduced by SAHA treatment at the level of transcription as detected by RT-PCR;
collagen III
protein level was also reduced, as detected by Western blots and immunofluorescence. The deacetylation inhibitor effect of SAHA was verified by observing higher acetylation levels of both
histone H3 and H4 in treated IPF cells.
Chromatin immunoprecipitation (ChIP) experiments demonstrated that the reduced expression of COL3A1 by SAHA is with increased association of the repressive
chromatin marker, H3K27Me3, and decreased association of the active
chromatin marker, H3K9Ac. In our murine model of
bleomycin-induced
pulmonary fibrosis, the SAHA treated group demonstrated significantly less
collagen III, as detected by immunohistochemistry. Our data indicate that the HDACi SAHA alters the
chromatin associated with COL3A1, resulting in its decreased expression.