Hydrophobic extracts of a Chinese herb (CMX-13) exhibit potent immunosuppressive properties and prevent acute rejection in a highly histoincompatible model of rat lung transplantation

Background. The potential of higher plants as sources for new immunosuppressive medications is well recognized. In our experiments we investigated the immunosuppressive effect of a highly refined and potent extract of a Chinese herbal preparation, CMX-13, on inhibiting acute allograft rejection (AR) in a highly histoincompatible rat lung transplant model, BN→LEW, and on lymphocyte activation and cytokine gene expression in vitro. Methods. Left lung transplants: the control group (group 1) received only dimethylsulfoxide (DMSO) which is the solvent for CMX-13. Group 2 received intramuscular cyclosporin A (CsA, 25 mg/kg) on day 2 posttransplant. Group 3 and 4 received i.p. CMX-13 (0.5 mg/day, low dose and 5 mg/day, high dose, respectively) on day 1, 2, and 3 posttransplant. All animals were killed on day 6 posttransplant. Several pathological categories of inflammation were examined. In vitro experiments: rat spleen cells were incubated with Con A or irradiated stimulator cells with/without serial dilutions of CMX-13 or CsA. Cell proliferation was measured by ³H-thymidine incorporation. mRNA expression of interleukin-2 and interferon-γ was examined by reverse transcriptase-polymerase chain reaction. Results. The severity of AR in animals receiving high dose CMX-13 was significantly reduced (stage II, P < 0.05) compared with controls (stage IV). Significant differences were also seen when more specific parameters of inflammation were examined (necrosis, 0 vs. 1.7±1.0, P < 0.05; interalveolar hemorrhage, 0 vs. 3.0±0.9, P < 0.05). The responses seen in the animals treated with high dose CMX-13 were similar to those in the CsA group. CMX-13 inhibited T cell proliferative responses induced by Con A and alloantigen stimulation in a dose-dependent manner that were similar to CsA. Interleukin-2, and interferon-γmRNA expression in Con A-stimulated spleen cells was not inhibited by CMX-13 although CsA showed significant inhibition. Conclusions. 1) CMX-13 significantly reduces the stage of AR and parameters of inflammation in a highly histoincompatible rat lung transplant model. 2) CMX-13 has equal potency to CsA in the inhibition of Con A and alloantigen stimulated rat spleen cell proliferation. 3) CMX-13 showed no inhibitory effects on IL-2 and γ-IFN mRNA expression, suggesting that its mechanism of action is different from CsA. 4) CMX-13 or derivatives may have potential utility as an immunosuppressive agent(s) in modulation of AR and management of other inflammatory and immunological disorders.