Angelica sinensis polysaccharides inhibit endothelial progenitor cell senescence through the reduction of oxidative stress and activation of the Akt/hTERT pathway

Context: Angelica sinensis (Oliv.) Diels (Apiaceae) polysaccharides (ASP) may play a key role in anti-ischemic activity. However, the anti-atherosclerotic activity and mechanism are unknown. Objective: This study investigated the protective effects of ASP against ox-LDL-induced senescence of EPCs and explored its underlying molecular mechanisms. Materials and methods: Mononuclear cells were isolated from bone marrow (BM) of SD rats and differentiated to EPCs. EPCs were exposed to oxidized low-density lipoprotein (ox-LDL, 10 mu g/mL, 24 h) and incubated with or without high-dose (100 mu g/mL, 48 h) or low-dose (20 mu g/mL, 48 h) ASP. Another group of EPCs was pre-treated with Wortmannin (100 nM, 45 min), a PI3K/Akt inhibitor. EPC senescence, telomerase activity, and superoxide anion levels were assessed using SA-beta-galactosidase staining, telomerase PCR-ELISA analysis, and DHE staining, respectively. The expression of related proteins, including Akt, p-Akt, hTERT, p-hTERT, and gp91phox, were detected using western blot. Results: EPCs (47.3%) were SA-beta-gal positive after treatment by ox-LDL, additionally, ox-LDL significantly increased superoxide anion levels (375% versus 100%), and inhibited telomerase activity (42% versus 100%). However, the pro-senescent effect of ox-LDL was attenuated about three-fold (16.7%), superoxide anion levels were decreased more than two-fold (148%), and telomerase activity was recovered partly (88% versus 42%) in the EPCs when treated with ASP (100 mu g/mL). The immunoblotting confirmed that ASP attenuated inhibition of phosphorylation of Akt and hTERT induced by ox-LDL and down-regulated increased the expression of gp91phox. Moreover, some effects of ASP were partially abrogated in the presence of Wortmannin. Discussion: Ox-LDL induced senescence of EPCs via inhibition of telomerase activity, which was influenced by oxidative stress and the Akt/hTERT pathway. The inhibition of EPC senescence by ASP could be important for potential therapeutics. Conclusion: Treatment of EPCs with ASP remarkably attenuates the harmful effects of ox-LDL via augmentation of Akt/hTERT phosphorylation and inhibition of oxidative stress.