Immunosuppressive Effects Of Ginsenoside Rd On Skin Allograft Rejection In Rats

Aims:Organ transplantation is an effective and necessary procedure for patients with organ failure.However,the acute and chronic immunological rejection is a major problem of successful transplantation.At present,many immunosuppressive agents were used in clinical care,such as FK506 and Cyclosporine A.Although these drugs have powerful immunosuppressive effect,their low specificity,serious drug toxicity and side effect also remain major obstacles for their chronic use.Therefore,immunosuppressive agents with low toxicity and high efficacy are eagerly waited.Ginsenoside-Rd(Rd)is one of the six major compounds in the total saponins from Panax notoginseng,and the total saponins have been demonstrated to play a role in bidirectional regulation for immune.In this study,we aimed to demonstrate the immunosuppressive effects of Rd in organ,cell and molecular levels,and provide theoretical foundation for its clinical application.Methods:The first part:(1)We testified that Rd exerts the immunosuppressive effect through the model of delayed type hypersensitivity(DTH)in mice.(2)We detected the effect of Rd on mitogen-induced mouse spleen lymphocyte proliferation in vitro.The second part:Skin transplantation was performed between Wistar rats serving as recipients and SD rats serving as donors.Wistar rats were randomly divided into 6 groups,namely normal group(NS,0.2 ml/100g),model group(55%1,2-propylene glycol),positive control group(CsA,5 mg/kg),and Rd low dose(12.5mg/kg,Rd L),medium dose(25mg/kg,Rd M)and high dose(50 mg/kg,Rd H)groups.Three days or one day before skin transplantation,the recipients were treated with medicine via intramuscular injection once per day for 14 consecutive days.The mean survival time of grafted skin was recorded after skin grafting operation.Histopathological change,serum level of cytokines(IL-1β,IL-2,IL-10,IL-12,IL-15,TNF-α and INF-γ)and T cell subset were also estimated to confirm the immunosuppressive effects of Rd.Results:The first part:(1)Effect of Rd on the DTH reaction to DNCB after different treatment:① Effects of Rd on the DTH reaction to DNCB after once treatment with drugs before the sensitization phase:In the model group,the mouse ear thickness was significantly increased(P<0.01),while there was no significant difference in the spleen index and the thymus index(P>0.05)of mice as compared with that of normal group.Compared with the model group,the levels of ear swelling,spleen index and thymus index in mice of the DXM group were obviously decreased(P<0.05,P<0.01,P<0.05,respectively),but these parameters were not markedly altered in mice treated with Rd(P>0.05).② Effects of Rd on the DTH reaction to DNCB in mice treated with drugs in the phases of both sensitization and effector or treated in the effector phase continuously:The ear thickness and thymus index in mice of model group were significantly increased(P<0.01,P<0.01,respectively)as compared with that of the normal group.The ear thickness was markedly reduced as compared with the model group(P<0.01)after treatment with DXM or Rd in both sensitization phase and effector phase.As compared with model group,the thymus index was reduced in Rd H group(P<0.01),and the spleen index(P<0.01)and the thymus index(P<0.01)were significantly decreased in DXM group but not in Rd L and M groups.However,the results of another four groups that continuously treated in the effector phase were obviously different from those above experiment:The three parameters of the DXM group were all obviously dropped compared with the model group(P<0.01,equally).Especially,the ear swelling and spleen index were significantly decreased in Rd L,M or H groups as compared with that of model group.(2)The results showed that Rd could markedly inhibit Concanavalin A(ConA)-induced mouse spleen T lymphocyte proliferation(P<0.01,equally),but it did not affect LPS-induced mouse spleen B lymphocyte proliferation.The second part:The indices on 7 day after rat allogeneic skin grafting:① The survival time of grafted skin in model group,DXM group,RD L,M and H groups was 9.60 ± 2.46 d,17.75 ± 3.15 d,11.60 ± 2.80 d,15.20 ± 2.78 d and 16.13 ± 3.09 d;respectively.Compared with model group,CsA,Rd M and Rd H could significantly prolong the mean survival time of skin allograft(P<0.01),but Rd L had no effect on the mean survival time of skin allograft(P>0.05).② Rd could mitigate skin tissue damage and reduce inflammatory cell infiltration in tissues.③ Rd could obviously reduce the serum levels of IL-1β,IL-2,IL-12,IL-15,TNF-α and INF-γ(P<0.01 or P<0.05),especially IL-2,and up-regulate the expression of IL-10(P<0.01).④ The percent of CD4+ T cells in rat peripheral blood was markedly reduced in Rd L,M and H groups(P<0.01).Conclusions:(1)Ginsenoside Rd could suppress the DTH reaction in mice treated in the phases of both sensitization and effector or treated in the effector phase continuously.(2)Ginsenoside Rd could markedly inhibit ConA-induced mouse spleen T lymphocyte proliferation.(3)Ginsenoside-Rd could effectively antagonize skin allograft rejection in rats.(4)Ginsenoside-Rd might exert immnuosuppression through regulating the expression of cytokines,such as IL-2 etc.