Aqueous extracts of Tribulus terrestris protects against oxidized low-density lipoprotein-induced endothelial dysfunction

To investigate the role of aqueous extracts of Tribulus terrestris (TT) against oxidized low-density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs) dysfunction in vitro. HUVECs were pre-incubated for 60 min with TT (30 and 3 mu g/mL respectively) or 10(-5) mol/L valsartan (as positive controls) and then the injured endothelium model was established by applying 100 mu g/mL ox-LDL for 24 h. Cell viability of HUVECs was observed by real-time cell electronic sensing assay and apoptosis rate by Annexin V/PI staining. The cell migration assay was performed with a transwell insert system. Cytoskeleton remodeling was observed by immunofluorescence assay. The content of endothelial nitric oxide synthase (eNOS) was measured by enzyme-linked immunosorbent assay. Intracellular reactive oxygen species (ROS) generation was assessed by immunofluorescence and flow cytometer. Key genes associated with the metabolism of ox-LDL were chosen for quantitative real-time polymerase chain reaction to explore the possible mechanism of TT against oxidized LDL-induced endothelial dysfunction. TT suppressed ox-LDL-induced HUVEC proliferation and apoptosis rates significantly (41.1% and 43.5% after treatment for 3 and 38 h, respectively; P < 0.05). It also prolonged the HUVEC survival time and postponed the cell's decaying stage (from the 69th h to over 100 h). According to the immunofluorescence and transwell insert system assay, TT improved the endothelial cytoskeletal network, and vinculin expression and increased cell migration. Additionally, TT regulated of the synthesis of endothelial nitric oxide synthase and generation of intracellular reactive oxygen species (P < 0.05). Both 30 and 3 mu g/mL TT demonstrated similar efficacy to valsartan. TT normalized the increased mRNA expression of PI3K alpha and Socs3. It also decreased mRNA expression of Akt1, AMPK alpha 1, JAK2, LepR and STAT3 induced by ox-LDL. The most notable changes were JAK2, LepR, PI3K alpha, Socs3 and STAT3. TT demonstrated potential lowering lipid benefits, anti-hypertension and endothelial protective effects. It also suggested that the JAK2/STAT3 and/or PI3K/AKT pathway might be a very important pathway which was involved in the pharmacological mechanism of TT as the vascular protective agent.