Apolipoprotein (a)/Lipoprotein(a)‐Induced Oxidative‐Inflammatory <i>α</i>7‐nAChR/p38 MAPK/IL‐6/RhoA‐GTP Signaling Axis and M1 Macrophage Polarization Modulate Inflammation‐Associated Development of Coronary Artery Spasm
Yen‐Kuang Lin, Chi‐Tai Yeh, Kuang-Tai Kuo, Iat-Hang Fong, Vijesh Kumar Yadav, Nicholas G. Kounis, Patrick Hu, Ming‐Yow Hung
Abstract
Objective . Apolipoprotein (a)/lipoprotein(a) (Lp(a)), a major carrier of oxidized phospholipids, and α 7‐nicotinic acetylcholine receptor ( α 7‐nAChR) may play an important role in the development of coronary artery spasm (CAS). In CAS, the association between Lp(a) and the α 7‐nAChR‐modulated inflammatory macrophage polarization and activation and smooth muscle cell dysfunction remains unknown. Methods . We investigated the relevance of Lp(a)/ α 7‐nAChR signaling in patient monocyte‐derived macrophages and human coronary artery smooth muscle cells (HCASMCs) using expression profile correlation analyses, fluorescence‐assisted cell sorting flow cytometry, immunoblotting, quantitative real‐time polymerase chain reaction, and clinicopathological analyses. Results . There are increased serum Lp(a) levels (3.98‐fold, p = 0.011) and macrophage population (3.30‐fold, p = 0.013) in patients with CAS compared with patients without CAS. Serum Lp(a) level was positively correlated with high‐sensitivity C‐reactive protein ( r 2 = 0.48, p < 0.01), IL‐6 ( r 2 = 0.38, p = 0.03), and α 7‐nAChR ( r 2 = 0.45, p < 0.01) in patients with CAS, but not in patients without CAS. Compared with untreated or low‐density lipoprotein‐ (LDL‐) treated macrophages, Lp(a)‐treated macrophages exhibited markedly enhanced α 7‐nAChR mRNA expression ( p < 0.01) and activity ( p < 0.01), in vitro and ex vivo . Lp(a) but not LDL preferentially induced CD80+ macrophage (M1) polarization and reduced the inducible nitric oxide synthase expression and the subsequent NO production. While shRNA‐mediated loss of α 7‐nAChR function reduced the Lp(a)‐induced CD80+ macrophage pool, both shRNA and anti‐IL‐6 receptor tocilizumab suppressed Lp(a)‐upregulated α 7‐nAChR, p‐p38 MAPK, IL‐6, and RhoA‐GTP protein expression levels in cultures of patient monocyte‐derived macrophages and HCASMCs. Conclusions . Elevated Lp(a) levels upregulate α 7‐nAChR/IL‐6/p38 MAPK signaling in macrophages of CAS patients and HCASMC, suggesting that Lp(a)‐triggered inflammation mediates CAS through α 7‐nAChR/p38 MAPK/IL‐6/RhoA‐GTP signaling induction, macrophage M1 polarization, and HCASMC activation.