Study Of The Neuroprotective Mechanisms Of Ginsenoside Rg1 And Genistein On SK-N-SH Cells

Phytoestrogens are plant-derived compounds that structurally or functionally mimic mammalian estrogens. They have been shown to possess a variety of beneficial effects on human health, including antioxidant and free redical scavenging. Ginsenosides Rg1 is the principal active component of ginseng. Genistein is the major components of soy isoflavone. Both of them are known phytoestrogens and have neuroprotective effects on the nervous system, but the detail mechanism is not very clear. Our present study aims at investigating the neuroprotective effects of ginsenoside Rg1 and genistein against the 6-OHDA-induced neurotoxicity in human dopaminergic neuroblastoma SK-N-SH cells and the blocking effects of insulin like growth factor I receptor (IGF-IR) antagonist JB-1 or estrogen receptor (ER) antagonist ICI182,780 by using MTT assay, flowcytometry, RT-PCR, western blot, confocal and dual luciferase assay. Results were as follows:1. 6-OHDA induced cell death in a dose-dependent manner (P<0.01) . Rg1 and genistein had neuroprotective effects on cell viability against 6-OHDA-induced neurotoxicity in SK-N-SH cells (P<0.05) .2. 6-OHDA arrested the cells at G₀G₁ phase, prevented S phase entry. Rg1 and genistein pretreatment could reverse the toxic effect of 6-OHDA. These effects could be completely blocked by IGF-IR antagonist JB-1 or ER antagonist ICI182,7803. 6-OHDA increased the ratio of the mRNA expression of Bax/Bcl-2 (P<0.01). Pretreatment with Rg1 and genistein could reverse the 6-OHDA-induced increase of the ratio of Bax/Bcl-2.4. 6-OHDA increased the Bax protein expression (P<0.01) and decreased the Bcl-2 protein expression (P<0.05). These effects could be reversed by Rg1 and genistein pretreatment.5. Rg1 and genistein could partly attenuate 6-OHDA-induced the decrease in mitochondrial membrane potential (P<0.01). These effects could be completely blocked by IGF-IR antagonist JB-1 or ER antagonist ICI182,780 (P<0.01).6. Rg1 and genistein could increase the activity of estrogen responsive elements (ERE) and IGF-IR promoter (P<0.01).These data demonstrated that ginsenoside Rg1 and genistein have neuroprotective effects against the 6-OHDA-induced neurotoxicity in SK-N-SH cells and their actions might involve activation of IGF-IR and ER signaling pathway and anti-apoptosis. These results not only provide new mechanism for the neuroprotective effects of Rg1 and gensitein, but also provide experimental evidence for the clinical application of ginsenoside Rg1 and genistein for prevention and treatment of Parkinson's disease.