Abstract 508: TNFα Downregulates DNA Methylation and Increases Pulmonary Arterial Smooth Muscle Cell (PASMC) Proliferation
Background: Chronic cold exposure triggers robust TNFα production in the lungs and pulmonary arteries (PAs) and causes PA remodeling in rats. A hallmark of the PA remodeling is the over-proliferation of PASMCs. The purpose of this experiment was to investigate potential mechanisms of TNF-alpha induced PASMC proliferation.
Methods and Results: PASMCs were isolated from 8-week-old male Sprague Dawley rats and treated with 0, 20 or 200 ng/ml TNFα for 24 or 48 hours. After treatment, cell number, superoxide production, histone acetylation and DNA methylation were assessed. TNFα treatment significantly increased the number of PASMCs, indicating excessive proliferation. TNFα also increased NADPH oxidase activity and superoxide production compared with untreated controls. TNFα treatment however did not affect histone acetylation at either dose. Interestingly, DNA methylation was significantly decreased by TNFα treatment compared to controls. Unexpectedly, the activity of DNA methyltransferase-1, the major enzyme for DNA methylation, was not altered by TNFα treatment. Further investigation using QRT-RT-PCR revealed that TNFα upregulated several factors including Gadd45α that regulate DNA de-methylation.
Conclusions: Our results show that TNFα treatment induced cell proliferation and increased superoxide production in PASMCs. TNFα decreased DNA methylation and upregulated mediators of de-methylation in PASMCs. These findings suggest that TNF-alpha induced PASMCs proliferation may involve the DNA methylation mechanism. (Supported by NIH HL077490 and AHA 11PRE7830040).
- © 2012 by American Heart Association, Inc.