Antioxidative effect of the herbal remedy Qin Huo Yi Hao and its active component tetramethylpyrazine on high glucose-treated endothelial cells

This study was designed to gain insights into the antioxidant mechanism of a Chinese herbal remedy, Qing Huo Yi Hao (QHYH), and its active components against oxidative stress induced by high glucose in endothelial cells.Effects of QHYH on reactive oxygen species (ROS) production and nitric oxide (NO) generation were measured with the fluorescent markers H(2)DCF-DA and DAF-FM DA, respectively. Phosphorylation of Akt (protein kinase B)/eNOS (endothelial nitric oxide synthase) and uncoupling protein 2 (UCP2) expression were studied by Western blot techniques. Influences of QHYH and one of the active components (tetramethylpyrazine, TMP) on UCP2 expression were subsequently evaluated by quantitative real-time reverse transcription-polymerase chain reaction. Using RNA interference techniques, the involvement of UCP2 in high glucose-induced ROS production in mouse brain microvascular (bEnd.3) cells and its correlation with the antioxidant effect of QHYH were further assessed.Our results showed that QHYH could protect endothelial cells from high glucose-induced damages, such as ROS production, down-regulation of Akt/eNOS phosphorylation and reduction of NO generation. The protective properties of QHYH were partially attributed to UCP2 mRNA/protein expression, because silence of UCP2 gene by siRNAs (small interfering RNAs) abolished such effects. A total of 28 extracts and 11 active components isolated from QHYH were functionally analyzed. Of which, TMP displayed comparable antioxidant and endothelial protective effects as QHYH.All of the data, taken together, point to some therapeutic potential of QHYH and TMP for vascular complications of diabetes.