Abstract 17239: Ifn-γ Aggravated Neointimal Hyperplasia By Inducing Er Stress-mediated Apoptosis in Macrophages Through Accelerating Lxr-α Degradation

Introduction: Neointimal hyperplasia is the major cause of restenosis after percutaneous coronary interventions, which is characterized by thicken arterial wall and decreased arterial lumen space. Both interferon-γ (IFN-γ) and macrophages play nonredundant roles in pathogenesis of vascular intimal hyperplasia. But until now, the underlying mechanisms remain elusive and need to be further addressed. Methods and Results: IFN-γ decreased the protein expression of liver X receptor (LXR)-α dose-dependently, but not LXR-β, in Raw264.7 and mouse peritoneal macrophages. IFN-γ did not influence the mRNA expression of LXR-α. IFN-γ increased polyubiquitin chain formation on LXR-α, resulting accelerated degradation of LXR-α in macrophages which could be prevented by MG-132, a proteasome inhibitor. Immunoprecipitation and Western blot analysis showed that LXR-α bound both with p-STAT1 and PIAS1 in macrophages under the action of IFN-γ. STAT1 inhibition by fludarabine or PIAS1 knockout by transfection of shRNA lentivirus not only reduced ubiquitination but also up-regulated the protein expression of LXR-α in macrophages treated by IFN-γ. Moreover, IFN-γ increased expression of p-PERK, p-eIF2α and CHOP, which could be partially reversed by LXR agonist T0901317. IFN-γ augmented apoptosis of macrophages, which was assessed by Annexin V and PI staining. Inhibition of ER stress by 4-phenylbutyric acid (4-PBA) and treatment with T0901317 alleviated apoptosis induced by IFN-γ in macrophages. The thickness of carotid intima increased obviously after ligation for 4 weeks in male ApoE -/- mice and was suppressed notably by T0901317 and 4-PBA treatment. Meanwhile, T0901317 and 4-PBA treatment reduced expression of p-eIF2α and CHOP of CD68 + macrophages and cellular apoptosis in hyperplastic neointimal tissue, which were evaluated by immunofluorescence and TUNEL staining, respectively. Conclusions: These results defined an unexpected role of IFN-γ and LXR-α in the development of neointimal hyperplasia. IFN-γ accelerated the degradation of LXR-α through STAT1/PIAS1 dependent way and promoted ER stress-mediated apoptosis in macrophages. Ameliorate restenosis and vascular remodeling after PCI by targeting LXR-α may be a promising new strategy.