Regulatory effect of ginsenoside Rd on regulatory T cells/helper T cell 17 imbalance in experimental autoimmune encephalomyelitis mice models

Abstract

Objective To explore the effect of ginsenoside Rd on regulatory T cells (Tregs)/helper T cell 17 (Th17) imbalance in experimental autoimmune encephalomyelitis (EAE) mice models. Methods Fifty-four female C57BL/6 mice, aged 6-8 weeks, were randomly divided into ginsenoside Rd group, phosphate buffered saline (PBS) group and blank-control group (n=18). The EAE mice models in the first two groups were induced by classical Mog35-55 peptide immunoinduction method; ginsenoside Rd of 40 mg/(kg·d) was dissolved in PBS and intraperitoneally injected into the mice daily in the ginsenoside Rd group on 13th d of immunization; the mice in the PBS group and control group were intraperitoneally injected with same dose of PBS. Daily clinical symptom scale scores were obtained from the first d to the 20th d of immunization, and the lumbar spinal cords of the mice were taken for histological evaluation (inflammation scale and demyelinating scale) after the last symptom scale. On the 20th d of immunization, the spleens of each group were taken for cultivation; splenocytes were cultured in vitro for 48 h, and the culture supernatant was taken for detecting interleukin (IL)-10 and IL-17 levels by enzyme-linked immunosorbent assay (ELISA); the proportions of Tregs and Th17 in spleen tissues were detected by flow cytometry; real-time quantitative PCR was used to detect the mRNA expressions of Janus kinase 1 (JAK1), Janus kinase 2 (JAK2), signal transduction and activator of transcription 3 (STAT3), retinoic acid-related orphan nuclear receptors γt (ROR-γt) and forkhead gene p3 (Foxp3) in the lumbar spinal cords of mice in each group. Results (1) The clinical symptom scale scores and inflammation scale scores of ginsenoside Rd group were significantly lower than those of PBS group (P<0.05); there were a large number of inflammatory cells infiltration and loss of myelin in the lumbar spinal cord of PBS group, while the loss of myelin sheath in ginsenoside Rd group was obviously decreased as compared with that in PBS group; the demyelination scale scores between the two groups showed statistical differences (P<0.05). (2) As compared with those in the PBS group, the IL-10 level was significantly increased and the IL-17 level was significantly decreased in the splenocyte culture supernatant of ginsenoside Rd group (P<0.05). (3) As compared with the PBS group, the ginsenoside Rd group had significantly decreased proportion of CD4+IL-17+ cells and significantly increased proportion of CD4+CD25+Foxp3+ cells in the spleen (P<0.05). (4) As compared with those in the PBS group, the mRNA expression levels of JAK1, JAK2, STAT3 and ROR-γt were significantly decreased, and Foxp3 mRNA expression level was significantly increased in the lumbar spinal cords of the ginsenoside Rd group (P< 0.05). Conclusion Ginsenoside Rd can improve the condition of EAE mice models by altering the expressions of Foxp3/RORγt/STAT3 signaling pathway molecules related to differentiation of Tregs/Th17, increasing the IL-10 level and Tregs ratio, and decreasing the IL-17 level and Th17 ratio. Key words: Ginsenoside Rd; Experimental autoimmune encephamyelitis; Regulatory T cell; Helper T cell 17; Cell imbalance