title: Baicalin promotes cholesterol efflux by regulating the expression of SR-BI in macrophages.
abstract: Intake of a high dosage of baicalin has previously been shown to attenuate hyperlipidemia induced by a high-fat diet. Baicalin functions as an activator of peroxisome proliferator-activated receptor-γ (PPAR-γ), which is the key regulator of reverse cholesterol transport (RCT). The present study aimed to test the hypothesis that baicalin could promote cholesterol efflux in macrophages through activating PPAR-γ. Phorbol 12-myristate 13-acetate-stimulated THP-1 cells were treated with oxidized low-density lipoprotein and (3H)-cholesterol for 24 h, and the effects of baicalin on cholesterol efflux were evaluated in the presence of apolipoprotein A-1 (ApoA-1), or high-density lipoprotein subfraction 2 (HDL2) or subfraction 3 (HDL3). The expression levels of scavenger receptor class B type I (SR-BI), PPAR-γ and liver X receptor-α (LXRα) were detected and specific inhibitors or activators of SR-BI, PPAR-γ and LXRα were applied to investigate the mechanism. Treatment of THP-1 macrophages with baicalin significantly accelerated HDL-mediated, but not ApoA-1-mediated cholesterol efflux. However, baicalin treatment increased the expression of SR-BI at the mRNA and protein levels in a dose- and time-dependent manner, and pre-treatment with the SR-BI inhibitor BLT-1 and SR-BI small interfering RNA significantly inhibited baicalin-induced cholesterol efflux. Furthermore, baicalin increased the expression of PPAR-γ and LXRα, and the application of specific agonists and inhibitors of PPAR-γ and LXRα changed the expression of SR-BI, as well as cholesterol efflux. It may be concluded that baicalin induced cholesterol efflux from THP-1 macrophages via the PPAR-γ/LXRα/SR-BI pathway.
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Renchao
authors.initials: R
authors.lastname: Yu
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Yuexia
authors.initials: Y
authors.lastname: Lv
authors.affiliation: Clinical Skill Training Center, People's Hospital of Weifang, Weifang, Shandong 261041, P.R. China.
authors.forename: Juanling
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Nana
authors.initials: N
authors.lastname: Pan
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Xiaxia
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Haichu
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Tan
authors.affiliation: Department of Cardiology, Central Hospital of Zibo, Zibo, Shandong 255036, P.R. China.
authors.forename: Yunhe
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Cardiology, Central Hospital of Zibo, Zibo, Shandong 255036, P.R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
keywords: baicalin; cholesterol efflux; liver X receptor-α; peroxisome proliferator-activated receptor-γ; scavenger receptor class B type I