Hydroxysafflor yellow A enhances survival of vascular endothelial cells under hypoxia via upregulation of the HIF-1 alpha-VEGF pathway and regulation of Bcl-2/Bax.

Hydroxysafflor yellow A (HSYA) is a component of the flower Carthamus tinctorius L. The present investigation determines whether HSYA can modify the effects of hypoxia on vascular endothelial cells (EC) and its mechanisms. Human EC line (EAhy926) viability was determined using the MTT assay. EC cycle phase distribution was done with PI staining and flow cytometric analysis, and EC apoptosis was done by AnnexinV-FITC detection and the TUNEL assay. The protein levels of VEGF, Bcl-2, Bax, and HIF-1 alpha were determined by ELISA or Western blot analysis, and the mRNA expression of these genes by RT-PCR analysis. HIF-1 alpha transcriptional activity was measured using a reporter gene assay. HSYA improved cell viability under hypoxia in a concentration-dependent manner by attenuating its cycle arrest and inhibiting its apoptosis. HSYA upregulated the bcl-2/bax ratio, which is downregulated under hypoxia, increased VEGF protein concentration and VEGF mRNA expression and enhanced HIF-1 alpha protein accumulation and its transcriptional activity. In conclusion, HSAY could enhance the survival of ECs under hypoxia, which may be correlated with its effect of upregulating the bcl-2/bax ratio and promoting HIF-1 alpha protein accumulation, which increases VEGF. These findings provide evidence for the mechanisms by which HSYA maintains EC survival under hypoxia.