Investigation of the immunosuppressive activity of artemether on T-cell activation and proliferation.
OBJECTIVE
Artemisinin and its derivatives exhibit potent immunosuppressive activity. The purpose of the current study was to examine the immunosuppressive activity of artemether directly on T lymphocytes and to explore its potential mode of action.


METHODS
In vitro, T-cell proliferation was measured using [(3)H]-thymidine incorporation assay in cells stimulated with ConA, alloantigen and anti-CD3 antibody. CFSE-labeled cell division and cell cycle distribution were monitored by flow cytometry. In vivo, the effects of artemether were evaluated in delayed-type hypersensitivity (DTH) and purified T-cell responses to ovalbumin in ovalbumin-immunized mice. The activation of extracellular signal-regulated kinase1/2 (ERK1/2) and Raf1 were assessed by Western blot analysis and the activation of Ras was tested in pull-down assays.


RESULTS
We show that, in vitro, artemether suppressed ConA- or alloantigen-induced splenocyte proliferation, influenced production of the cytokines IL-2 and IFN-gamma and inhibited cell cycle progression through the G0/G1 transition. In vivo, administration of artemether attenuated CD4 T-cell-mediated DTH reaction, and suppressed antigen-specific T-cell response in immunized mice. Further experiments showed that, treatment with artemether impaired both antigen- and anti-CD3-induced phosphorylation of ERK. In primary T cells, artemether profoundly inhibited anti-CD3-induced phosphorylation of Raf1 and activation of Ras.


CONCLUSIONS
This study provided experimental evidence of the immunosuppressive effects of artemether directly on T cells both in vitro and in vivo. Its immunosuppressive mechanism involved inhibition of the activation of the Ras-Raf1-ERK1/2 protein kinase cascade in T cells.
Wang
J-X
JX
First Department of Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China.
Tang
W
W
Shi
L-P
LP
Wan
J
J
Zhou
R
R
Ni
J
J
Fu
Y-F
YF
Yang
Y-F
YF
Li
Y
Y
Zuo
J-P
JP
D000818:Animals; D000077549:Artemether; D037621:Artemisinins / Q000494:pharmacology* / Q000627:therapeutic use; D017252:CD3 Complex / Q000276:immunology; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival; D003208:Concanavalin A / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D006968:Hypersensitivity, Delayed / Q000139:chemically induced / Q000276:immunology / Q000517:prevention & control*; D007111:Immunity, Cellular / Q000187:drug effects; D007156:Immunologic Memory / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000494:pharmacology* / Q000627:therapeutic use; D007371:Interferon-gamma / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008934:Mitogens / Q000494:pharmacology; D010047:Ovalbumin / Q000276:immunology; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D013997:Time Factors; D018631:ras Proteins / Q000378:metabolism
D037621:Artemisinins; D017252:CD3 Complex; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D008934:Mitogens; D003208:Concanavalin A; D007371:Interferon-gamma; D010047:Ovalbumin; D000077549:Artemether; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins