Studies On The Establishment Of β-cell Apoptosis Model And The Anti-apoptotic Mechanism Of Ginseng Saponins

Ginseng has been used as an anti-diabetic herb for several thousand years in Asia with ginsenoside Rgl and ginsenoside Rbl as important active ingredients. However, there is no reported result concerning the anti-apoptotic function of Rbl and Rgl on pancreatic β-cells. The aim of the study was to investigate the effects of ginsenosides Rbl and Rgl on stimuli-induced pancreatic B-cell apoptosis and explore its mechanisms regarding signal transduction pathway. Results were shown below:1. In the study, Rin-m5F cells were cultured in different concentrations of glucose (5,10,15,25mmol/L) respectively for48hr. The results revealed as follow:compared with control group (10mmol/L), NO concentration of groups which contained5,15,25mmol/L glucose increased23.81(P<0.05),91.09(P<0.01),134.64(P<0.01) μmol/L, while apoptosis rate increased9.45%(P<0.05),8.35%(P<0.01),30.98%(P<0.01). Insulin secretion was enhanced when the concentrations of glucose were5-15mmol/L, that it reached the highest value at15mmol/L. Therefore,25mmol/L as the best glucose concentration were chosen to induced apoptosis of Rin-m5F cell line.2. In the study, Rin-m5F cells were cultured in RMPI1640medium contained50U/ml IL-1B+1000U/ml TNF-a+1000U/ml IFN-y for48hr. The results revealed that: compared with control group, NO concentration and apoptosis rate of cytokine group increased225.48μmol/L,58.60%(P<0.01) while the insulin secretion was enhanced0.83mU/L (P<0.01). The conclusion was that this concentration of cytokine could construct a stabilized apoptotic cell model.3. In the study, the two apoptotic models were treated by ginsenoside Rgl or ginsenoside Rbl for48hr respectively, the results revealed as follow:Rgl, Rb1could protect the toxic effect of high glucose and cytokine well. The effects of Rg1and Rb1on insulin secretion, NO concentration and apoptosis rate of RIN-m5F cell models were different. The promotion strength of Rgl, Rb1on insulin secretion of high glucose cell model was:Rgl>Rgl+Rbl>Rbl; the effect of Rgl+Rbl on inhibiting NO was better than that of Rgl and Rbl alone; the inhibition strength on apoptosis rate was:Rgl+Rb1> Rb1> Rg1; the promotion strength of Rg1, Rb1on insulin secretion of apoptosis cell model induced by cytokine was:Rg1>Rb1>Rg1+Rb1; the effects of Rgl+Rbl on apoptosis rate and NO inhibition while Rbl were stronger than Rgl. 4. Bcl-2, Bax, FAS, iNOS and Caspase-3mRNA expression were studied in this part. The results showed that:compared with control group, Bax, Fas, Caspase-3and iNOS gene expressions were up-regulated by high glucose, whereas only Bax, Caspase-3and iNOS gene expressions were elevated by cytokines. In addition, cytokines instead of high glucose down-regulated Bcl-2gene expression. As a conclusion, Fas signal pathway is important in high glucose-induced apoptosis, while mitochondria pathway plays a key role in cytokine-induce apoptosis. In high glucose-induced apoptotic cells, Rgl down-regulated Fas and iNOS gene expressions, while Rb1decreased Caspase-3and iNOS gene expressions. Similar result was observed in the cytokines-induced apoptotic cells. Of note, in these cells, the impaired Bcl-2/Bax ratio (0.53) was protected by Rgl with the value1.04, which is comparable to control condition.