Abstract 15774: Impaired Autophagy Contributes to Toll Like Receptor-4 Induced Osteogenesis in Human Aortic Valve Interstitial Cells
Objective: Stimulation of Toll-like receptor 4 (TLR4) induces inflammatory and osteogenic responses in aortic valve interstitial cells (AVICs). Autophagy protects against vascular calcification. We therefore hypothesized that LPS impairs autophagy, and this contributes to osteogenesis in human AVICs via mTOR signaling.
Methods: AVICs were isolated from the adult explanted heart transplant recipients without aortic valve abnormalities. Cells were treated with LPS. Autophagy activity was investigated using chemical inhibitors and genetic techniques. The osteogenic markers bone morphogenetic protein 2 (BMP-2) and alkaline phosphatase (ALP), as well as mTOR associated signaling molecules, were analyzed.
Results: LPS inhibited autophagy as indicated by changes of protein levels of LC3-II. Suppression of autophagy by 3-methyladenine, bafilomycin, or short hairpin-mediated silencing of Becn1 gene increased the expression of BMP-2 and ALP. Conversely, upregulation of autophagy with rapamycin or overexpression of Becn1 decreased the levels of BMP-2 and ALP in response to LPS and decreased ALP activity and calcium nodule formation. Mechanistically, inhibition of autophagy was mediated at least partly by increased mTOR signaling.
Conclusions: LPS suppressed autophagy and induced mTOR-mediated osteogenic responses in human AVICs. The results suggest that autophagy regulates inflammation-induced osteogenic responses in human AVICs. Inhibition of mTOR by rapamycin may have a therapeutic implication for initiation and progression of calcific aortic valve disease.
Author Disclosures: X. Deng: None. X. Meng: None. D. Fullerton: None. J. Jaggers: None.
- © 2014 by American Heart Association, Inc.