Homocysteine (Hcy) is one of the independent risk factors of cardiovascular disease. Sodium tanshinone IIA sulfonate (STS) is a hydrophilic derivate of tanshinone IIA which is the main active constitute of Chinese Materia Medica Salviae Miltiorrhizae Radix et Rhizoma, and exhibits multiple pharmacological activities. However, whether STS could prevent from Hcy-induced endothelial cell injury is unknown.

We found that STS dramatically reversed Hcy-induced cell death concentration dependently in human umbilical vascular endothelial cells (HUVECs). STS ameliorated the endothelial cell cycle progression, proliferation and cell migratory function impaired by Hcy, which might be co-related to the inhibition of intracellular oxidative stress and mitochondrial dysfunction. STS also elevated the phosphorylation of AKT and MAPKs and protein expression of sirtuin1 (SIRT1), NRF2 and HO-1 which were suppressed by Hcy. The protective effect of STS against Hcy-induced endothelial cell toxicity was partially attenuated by PI3K, AKT, MEK, ERK, SIRT1, NRF2 and HO-1 inhibitors. Besides, knockdown of SIRT1 by its siRNA dramatically decreased the endothelial protective effect of STS accompanied with suppression of SIRT1, NRF2, HO-1 and phosphorylated AKT. The activation of AKT or NRF2 partially reversed SIRT1-knockdown impaired cyto-protective effect of STS against Hcy-induced cell injury. Furthermore, STS prevented from Hcy-induced intracellular nicotinamide N-methyltransferase (NNMT) reduction along with elevation of intracellular methylnicotinamide (MNA), and MNA enhanced STS protecting against Hcy induced endothelial death. Knockdown of NNMT reduced the protective effect of STS against Hcy induced endothelial cell injury.

Collectively, STS presented potent endothelial protective effect against Hcy and the underlying molecular mechanisms were involved in the suppression of intracellular oxidative stress and mitochondria dysfunction by activation of AKT/MAPKs, SIRT1/NRF2/HO-1 and NNMT/MNA signaling pathways.