Abstract: OBJECTIVE: To investigate the effects of ginsenoside Rb1 on high glucose-induced neurotoxicity and the underlying molecular mechanism in primary cultured Schwann cells(SCs).METHODS: Cultured SCs were divided into six groups that received(a) normal glucose,(b) osmotic control,(c) high glucose,(d) high glucose plus 1μM ginsenoside Rb1,(e) high glucose plus 10 μM ginsenoside Rb1, or(f) high glucose plus 100 μM alpha lipoic acid(ALA). Intracellular reactive oxygen species(ROS) generation and mitochondrial transmembrane potential(ΔΨm) were detected by flow cytometric analyses. Apoptosis was confirmed by the annexin V-FITC/propidium iodide(PI) method,and the concentration of 8-hydroxy-2-deoxy guanosine(8-OHd G) was detected by an enzyme-linked immunosorbent assay. Western blotting was performed to analyze the expression levels of important transcription factors such as cytochrome c, bcl-2, bax, activated caspase-3, and activated poly(ADP-ribose) polymerase(PARP).RESULTS: Ginsenoside Rb1 inhibited high glucose-induced oxidative stress by decreasing ROS and 8-OHd G levels as well as mitochondrial depolarization in SCs. 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide and annexin V-FITC/PI assays showed that incubating SCs with high glucose decreased cell viability and increased the number of apoptotic cells, whereas treatment with ginsenoside Rb1 protected SCs against high glucose-induced cell damage. Furthermore, ginsenoside Rb1 down-regulated the expression of high glucose-induced bax and cytochrome c release but up-regulated bcl-2 expression. In addition, ginsenoside Rb1 attenuated high glucose-induced activation of caspase-3 and minimized cleavage of PARP in SCs.CONCLUSION: These results suggest that ginsenoside Rb1 antagonizes high glucose-induced oxidative stress and activation of the mitochondrial apoptosis pathway in SCs.

Key words: Diabetic neuropathies, Oxidative stress, Ginsenosides, Apoptosis inducing factor, Schwann cells