title: Saikosaponin a inhibits lipopolysaccharide-oxidative stress and inflammation in Human umbilical vein endothelial cells via preventing TLR4 translocation into lipid rafts.
abstract: Saikosaponin a (SSa), the major triterpenoid saponin derivatives from Radix bupleuri (RB), has been reported to have anti-inflammatory effects. The aim of this study was to investigate the effects of SSa on lipopolysaccharide (LPS)-induced oxidative stress and inflammatory response in human umbilical vein endothelial cells (HUVECs). HUVECs were stimulated with LPS in the presence or absence of SSa. The levels of TNF-α and IL-8 were detected by ELISA. The expression of COX-2 and iNOS, NF-κB and IκB protein were determined by Western blotting. To investigate the protective mechanisms of SSa, TLR4 expression was detected by Western blotting and membrane lipid rafts were separated by density gradient ultracentrifugation and analyzed by immunoblotting with anti-TLR4 antibody. The results showed that SSa dose-dependently inhibited the production of ROS, TNF-α, IL-8, COX-2 and iNOS in LPS-stimulated HUVECs. Western blot analysis showed that SSa suppressed LPS-induced NF-κB activation. SSa did not affect the expression of TLR4 induced by LPS. However, translocation of TLR4 into lipid rafts and oligomerization of TLR4 induce by LPS was inhibited by SSa. Furthermore, SSa disrupted the formation of lipid rafts by depleting cholesterol. Moreover, SSa activated LXRα-ABCA1 signaling pathway, which could induce cholesterol efflux from lipid rafts. Knockdown of LXRα abrogated the anti-inflammatory effects of SSa. In conclusion, the effects of SSa is associated with activating LXRα-ABCA1 signaling pathway which results in disrupting lipid rafts by depleting cholesterol and reducing translocation of TLR4 to lipid rafts and oligomerization of TLR4, thereby attenuating LPS mediated oxidative and inflammatory responses.
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
authors.forename: Yunhe
authors.initials: Y
authors.lastname: Fu
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Hu
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
authors.forename: Yongguo
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
authors.forename: Zecai
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China. Electronic address: zhangns61@163.com.
authors.forename: Naisheng
authors.initials: N
authors.lastname: Zhang
mesh_terms: D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D008070:Lipopolysaccharides; D021962:Membrane Microdomains / Q000378:metabolism; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism; D012503:Saponins / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014162:Transfection
chemical_list: D000893:Anti-Inflammatory Agents; D008070:Lipopolysaccharides; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D012503:Saponins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D009828:Oleanolic Acid; C025759:saikosaponin D
keywords: ABCA1; NF-κB; ROS; cholesterol; lipid raft