title: Protection of glycyrrhizic acid against AGEs-induced endothelial dysfunction through inhibiting RAGE/NF-κB pathway activation in human umbilical vein endothelial cells.
abstract: BACKGROUND
  Licorice (Glycyrrhiza uralensis roots) is used as a traditional medicine for the treatment of diabetes mellitus and its vascular complications. Glycyrrhizic acid (GA, also known as Glycyrrhizin), a triterpenoid saponin glycoside, is considered to be a bioactive component in Licorice and is beneficial to diabetic vascular complications.
  
  
  OBJECTIVE
  The present study was conducted to evaluate the potential protective activities on AGEs-induced endothelial dysfunction, including anti-apoptosis, antioxidant stress and anti-proinflammatory responses, and explore the underlying mechanism.
  
  
  METHODS
  Human umbilical vein endothelial cells (HUVECs) were incubated and pre-treated with GA (10(-9)-10(-6)M) or RAGE-Ab (5μg/ml) in the presence or absence of 200μg/ml AGEs. AO/EB fluorescence staining assay was performed to evaluate anti-apoptosis activity. The superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in cell supernatant were detected by kits while the intracellular reactive oxygen species (ROS) generation was determined by 2,7-dichlorodihydrofluorescin diacetate (DCFH-DA) kit. Immunocytochemistry analysis was designed to determine transforming growth factor beta1(TGF-β1) protein expression while immunofluorescence analysis for RAGE and NF-kB. The protein expressions of TGF-β1, RAGE and NF-kB were analyzed by Western blot analysis.
  
  
  RESULTS
  Pretreatment with GA at a concentration of 10(-8)-10(-6)M significantly reduced the AGEs-induced apoptosis in HUVECs. GA significantly increased antioxidant enzyme SOD activity and decreased peroxide degradation product MDA level in a dose-dependent manner. Furthermore, GA also remarkably inhibited the overgeneration of AGEs-induced ROS. Both immunocytochemistry analysis and western blot analysis showed that GA significantly decreased the protein expression of poinflammatory cytokine TGF-β1 in a similar manner which RAGE-Ab did. Additionally, AGEs-induced RAGE and NF-kB protein expressions were down-regulated significantly by the pretreatment with GA or RAGE-Ab.
  
  
  CONCLUSIONS
  These findings provide evidences that GA possesses protective activity on AGEs-induced endothelial dysfunction, including anti-apoptosis, anti-inflammation and antioxidant stress, via inhibiting RAGE/NF-kB pathway. GA might be an alternative for the prevention and treatment of diabetic vascular complications in an appropriate dosage.
authors.affiliation: Key Laboratory of Delivery Systems of Chinese Meteria Medica, Jiangsu Provincial Academy of Chinese Medicine, Jiangsu, Nanjing 210028, China. wenmoxiushi@163.com
authors.forename: Liang
authors.initials: L
authors.lastname: Feng
authors.forename: Mao-Mao
authors.initials: MM
authors.lastname: Zhu
authors.forename: Ming-Hua
authors.initials: MH
authors.lastname: Zhang
authors.forename: Ru-Shang
authors.initials: RS
authors.lastname: Wang
authors.forename: Xiao-Bin
authors.initials: XB
authors.lastname: Tan
authors.forename: Jie
authors.initials: J
authors.lastname: Song
authors.forename: Shu-Min
authors.initials: SM
authors.lastname: Ding
authors.forename: Xiao-Bin
authors.initials: XB
authors.lastname: Jia
authors.forename: Shao-Ying
authors.initials: SY
authors.lastname: Hu
mesh_terms: D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis; D002478:Cells, Cultured; D017127:Glycation End Products, Advanced; D019695:Glycyrrhizic Acid / Q000494:pharmacology*; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008315:Malondialdehyde / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D000067759:Receptor for Advanced Glycation End Products / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000893:Anti-Inflammatory Agents; D000975:Antioxidants; D017127:Glycation End Products, Advanced; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D000067759:Receptor for Advanced Glycation End Products; D008315:Malondialdehyde; D019695:Glycyrrhizic Acid; D013482:Superoxide Dismutase