Objectives Polydatin, one of the major active ingredients in Rhizoma Polygonl Cuspidatl, has been recently shown to possess extensive cardiovascular pharmacological activities. However, a direct effect of Polydatin on the uptake of ox-LDL by macrophages and formation of foam cells has not yet been elucidated. And the mechanism of the anti-atherosclerotic effect of Polydatin is unclear. In present study we examined the effect of Polydatin on peritoneal macrophage-derived foam cells in Apolipoprotein E gene knockout mice (ApoE-/-) and explored the potential underlying mechanisms.
Methods Peritoneal macrophages of ApoE-/- mice were collected and divided into four groups: Control group (calf serum 250ul was administrated), Model group (calf serum 250ul and ox-LDL 250µg were administrated), Lovastatin group (calf serum 250µl, ox-LDL 250µg and 110µg/ml lovastatin were administrated) and Polydatin group (calf serum 250µl, ox-LDL 250µg and 8.9µg/ml polydatin were administrated). After 0h, 24h and 48h of incubation, some indexes was detected.
Results The results suggested that Polydatin and Lovastatin could protect the ultrastructure of peritoneal macrophage. Polydatin and Lovastatin significantly reduced cholesterol accumulation in ox-LDL loaded macrophages, P<0.01. There was no difference between Polydatin and Lovastatin groups.
To further investigate the potential effect of Polydatin on inflammatory factors, the protein expression of TNF-α and IL-1β in the peritoneal macrophage cells were evaluated by ELISA analysis. After ox-LDL treatment for 24h and 48h, the level of TNF-α and IL-1β protein expression were significantly increased, P<0.01. However, compared to ox-LDL treatment group, Polydatin and Lovastatin reduced the protein expression of TNF-α and IL-1β, P<0.01 or P<0.05. And there is no difference between Polydatin and Lovastatin groups.
The effect of Ploydatin on TLR4 and NF-kB expression at the protein level was examined by western blotting. Polydatin and Lovastatin significantly attenuated the expression of TLR4 and NF-κB proteins, P<0.01. There was no difference between Polydatin and Lovastatin groups.
The expression of PPAR-γ, ABCA1 and CD36 was examined by RT-PCR to determine if Polydatin has a suppressive effect on the PPAR-γ pathway in the peritoneal macrophage cells. Polydatin and Lovastatin could up-regulate the mRNA expression of PPAR-γ and ABCA1, and down-regulate the mRNA expression of CD36, P<0.01. There was no difference between the Polydatin and Lovastatin groups.
Conclusions Macrophage-derived foam cells play integral roles in all stages of atherosclerosis. Elucidation of molecular and cellular processes involving macrophages has led to numerous therapeutic targets being suggested. In our study, we showed that Polydatin could increase cholesterol efflux from macrophage and decrease the uptake of ox-LDL, thus resulting in the inhibition of cholesterol accumulation in macrophage. Its mechanism is possibly induced in a PPAR-γ dependent manner. And the study also illustrated that Polydatin had the anti-inflammatory effect through TLR4/NF-κB pathway. Thus, Polydatin could inhibit the foam cells formation.
Our results demonstrated that Polydatin significantly inhibited the foam cell formation in peritoneal macrophages, it had the anti-inflammatory effect and regulating the metabolism of lipid, possibly through the TLR4 and PPAR-g signal pathway.