Involvement of CDK4, pRB, and E2F1 in ginsenoside Rg: protecting rat cortical neurons from β-amyloid-induced apoptosis

摘要

AIM: To explore the possible mechanism of β-amyloid (Aβ)-induced apoptosis in rat cortical neurons and the protective effect of ginsenoside Rg_1. METHODS: AO-EB staining was used to quantify the apoptotic cells. DNA fragmentation was observed by gel electrophoresis. The levels of cyclin-dependent kinases-4 (CDK4) and phos-phorylated pRB were detected by Western blot. RT-PCR was used to examine the expression of E2F1 mRNA. RESULTS: Treatment with Aβ_(1-40) at the concentration of 20, 40, 80 mg/L for 48 h induced rat cortical neuron apoptosis from 12.5 %+-1.5 % (control) to 22.3 %+-1.4 %, 38.8 %+-1.3 %, 36.7 %+-1.4 %, respectively. Pretreat-ment with Rg_1 at the dose of 0.5, 1, 2, 4, 8, 16 μmol/L for 24 h, then treatment with Aβ_(1-40) 40 mg/L for 24 h, thepercentage of apoptotic neurons decreased from 38.8 %+-1.3 % to 14.5 %+-1.3 %, 13.3 %+-1.0 %, 11.6 %+-0.29 %, 11.8 %+-1.0 %, 6.2 %+-0.8 %, 5.8 %+-0.8 %, respectively. After treatment with Aβ_(1-40) 40 mg/L for 24 h, there were transient increases in CDK4 and phosphorylated pRB protein level, as well as the expression of E2F1 mRNA. However, the above levels decreased markedly after pretreatment with Rg_1 8 μmol/L for 24 h. CONCLUSION: Ginsenoside Rg_1 attenuated Aβ_(1-40)-induced apoptosis in rat cortical neurons via inhibiting the activity of CDK4, decreasing the phosphorylation of pRB and downregulating the expression of E2F1 mRNA.