Ursolic Acid Attenuates High Glucose-Mediated Mesangial Cell Injury by Inhibiting the Phosphatidylinositol 3-Kinase/Akt/Mammalian Target of Rapamycin (PI3K/Akt/mTOR) Signaling Pathway

Background: To investigate the protective effect of ursolic acid (UA) on high glucose (HG)-induced human glomerular mesangial cell injury and to determine whether UA inhibits cell proliferation and reactive oxygen species (ROS) production by suppressing PI3K/Akt/mTOR pathway activation. Material/Methods: Human mesangial cells were cultured with normal glucose (NG group), high glucose (HG group), mannitol (mannitol hypertonic control group), or high glucose with different concentrations (0.5, 1.0, and 2.0 mmol/L) of UA (HG+UA groups). Cell proliferation and intracellular ROS levels were assessed by methyl thiazolyl tetrazolium (MTT) and dichloro-dihydro-fluorescein diacetate (DCFH-DA) flow cytometry assays, respectively. Western blotting was used to detect mesangial cell expression of PI3K/Akt/mTOR pathway components, including Akt, p-Akt, mTOR, and p-mTOR, and proteins related to cell injury, including TGF-beta 1 and fibronectin (FN). mRNA expression of TGF-b1 and FN were evaluated using real-time quantitative polymerase chain reaction (PCR). Results: Abnormal proliferation was observed in human glomerular mesangial cells at 48 h after treatment with HG, and UA suppressed the HG-induced proliferation of mesangial cells in a dose-dependent manner. UA inhibited ROS generation and oxidative stress in mesangial cells and mitigated mesangial cell injury. Treatment with UA reduced Akt and mTOR phosphorylation levels in mesangial cells exposed to HG (p<0.05 vs. HG) and downregulated protein and mRNA expression of TGF-b1 and FN in these cells (p<0.05 vs. HG). Conclusions: UA attenuated mesangial cell proliferation and ROS generation by inhibiting HG-mediated PI3K/Akt/mTOR pathway activation, thereby ameliorating mesangial cell damage.