Stereospecificity Of Ginsenoside Rg3in The Promotion Of Cellular Immunity And Antioxidation In Hepatoma H22-bearing Mice

Ginseng (Panax ginseng C.A.Mey.), which has been widely used to treat or preventdiseases, is known as "The King of Herbs" and plays an important position in traditionalChinese medicine. Ginsenoside Rg3is one of the active ingredient in Panax ginseng,belongs to protopanaxadiol type saponin. It is responsible for most of the pharmacologicalactions of ginseng, including immunomodulation, anti-cancer, and anti-oxidative activities.Rg3exists as two epimers,20(S)-ginsenoside Rg3[20(S)-Rg3] and20(R)-ginsenoside Rg3[20(R)-Rg3] in Panax ginseng due to the differential chemical structure. Recent studieshave shown that they performed differentially in many biological activities, such as effects on ion channel currents and immunomodulatory. In order to make a safe and rationalenvironment for ginseng in clinical treatment, this study was designed to compare thedifferences of anti-tumor effect, immunomodulatory activity as well as antioxidationbetween20(S)-Rg3and20(R)-Rg3using a H22hepatoma-bearing mice model.1. Effect of20(S)-Rg3and20(R)-Rg3on cellular immunity in hepatoma-bearing miceObjective: To investigate the effects of20(S)-Rg3and20(R)-Rg3on cellularimmunity in hepatoma H22-bearing mice using a H22hepatoma-bearing mice model.Methods: After transplanting H22cells, mice were randomly and equally divided intothree groups: model group,20(S)-Rg3group, and20(R)-Rg3group (n=10). Another10mice without transplanted tumors were served as a normal group. After24h,20(S)-Rg3and20(R)-Rg3groups were injected intraperitoneally administered with20(S)-Rg3and20(R)-Rg3(3mg/kg BW, ip), once a day for10consecutive days, respectively. Mice in thenormal and model groups were given an equal volume of normal saline (0.2ml/10g BW,ip). All of the mice were weighed and sacrificed by removing the eyeballs to obtain serumafter the last administration. At the same time, the splenocytes were separated from theabove treated mice and the splenocyte proliferation was determined by MTT. The solidtumors were also dissected and weighed. The expression of cytokines in spleen and thymusas well as serum was checked by ELISA. Results: The tumor weights in the20(S)-Rg3and20(R)-Rg3treatment group were1.69±0.15g and1.32±0.20g. Compared with themodel group (2.21±0.16g), tumor weights were significantly reduced in H22-bearingmice after20(S)-Rg3and20(R)-Rg3treatment, and the inhibitory rates of tumor growth in20(S)-Rg3and20(R)-Rg3group were23.6%and40.9%, respectively. The ConA-inducedlymphocyte proliferations of the20(S)-Rg3and20(R)-Rg3group were0.11±0.004and0.13±0.003, respectively. Compared with the model group (0.066±0.002), Rg3significantly augmented ConA-induced lymphocyte proliferation in tumor-bearing mice (P<0.05). The levels of IFN-γ and IL-2significantly increased after treatment withginsenoside Rg3(P <0.05). In addition, compared with the20(S)-Rg3group,20(R)-Rg3significantly inhibited the growth of H22transplanted tumors and enhanced the splenocyteproliferative responses to ConA, as well as the levels of IFN-γ and IL-2in tumor-bearing mice. Taken together, these results illustrated that Rg3had an activity in immunoregulatory,and significantly inhibited H22tumor growth in vivo at least partly via improving the host’scellular immunity by enhancing lymphocyte proliferation ability and promoting theexpression of cytokines in a stereospecific manner, and the clinical efficacy of20(R)-Rg3may be better than that of20(S)-Rg3.2. Effect of20(S)-Rg3and20(R)-Rg3on antioxidantion in hepatoma-bearing miceObjective: Since host’s immune system is most likely to be affected by antioxidantcapacities. The present study was designed to assess the effects of20(S)-Rg3and20(R)-Rg3on oxidative stress in hepatoma H22-bearing mice using the above animalmodel, and explore the functional mechanisms of Rg3. Methods: The animal model, themethods and doses were consistent with the part one. All of the mice were weighed andsacrificed by cervical dislocation after the last administration. The thymus, spleen andserum were gathered to check the indices of immune organs and oxidativeparameters．Results: The indices of the thymus and spleen in20(S)-Rg3group were3.85±0.05and6.26±0.17, respectively. The indices of the thymus and spleen in20(S)-Rg3group were4.32±0.12and7.24±0.19, respectively. The indices of the thymus and spleenin20(S)-Rg3or20(R)-Rg3were significantly increased comparing to the model group（P <0.05）. Compare with the model group,20(S)-Rg3or20(R)-Rg3also significantlyincreased SOD activities, decreased XOD activities and the levels of MDA. Compared withthe20(S)-Rg3group,20(R)-Rg3showed a stronger antioxidant effect. These findingsillustrated that two epimers of Rg3had strong antioxidant activity, and significantlysuppressed the growth of H22implanted tumor. The possible mechanism might be relatedto the improved host’s immune function, which is caused by enhanced antioxidantactivities. Finally,20(R)-Rg3showed a stronger antioxidant effect than that of20(S)-Rg3in tumor-bearing mice.In summary, ginsenoside Rg3had strong antitumor effects, immunomodulatory andantioxidant activities in mice. Compared with the20(S)-Rg3group,20(R)-Rg3may be anideal prodrug of antitumor, immunomodulatory and antioxidant candidate.