Antioxidative Effect of the Herbal Remedy Qin Huo Yi Hao and Its Active Component Tetramethylpyrazine on High Glucose-treated Endothelial Cells

Aims: 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.

Main Methods: 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.

Key Findings: 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.

Significance: All of the data, taken together, point to some therapeutic potential of QHYH and TMP for vascular complications of diabetes.