Curcumin inhibits mitogen stimulated lymphocyte proliferation, NFkappaB activation, and IL-2 signaling.
BACKGROUND
T cell mediated acute rejection of transplanted organ continues to be a noticeable problem in solid organ transplantation. We showed that Curcumin is a potent inhibitor of Cyclosporin A resistant T cell CD28 co-stimulation pathway. Here we report the inhibitory effects of Curcumin on mitogen-stimulated lymphocyte proliferation, IL-2 synthesis/signaling, and NFkappaB (transcription factor of IL-2 promoter) activation.


METHODS
Human lymphocytes were isolated from fresh human spleen (SP-L). Mitogens [final concentrations of 2 microg/ml concanavalin A (Con A), 5 microg/ml phytohemagglutinin (PHA), and 20 ng/ml of phorbol-12-myristate-13-acetate (PMA)] were added to the designated wells in a 96-well plate with 0.2 million SP-L and cultured for 48 h and then assayed for IL-2 synthesis by ELISA and 3H-thymidine uptake. In another parallel experiment we added IL-2 (0.5 nM) to stimulate the cells to check if Curcumin's inhibition of IL-2 synthesis is the sole reason for inhibition of cell proliferation. Electrophoretic mobility shift assay (EMSA) was performed in PMA (20 ng/ml, 1 h) stimulated cells with or without Curcumin to assay NFkappaB activation.


RESULTS
Curcumin at 2.5 microg/ml inhibited Con A, PHA, and PMA stimulated SP-L proliferation at 77, 23, and 48%, respectively, over controls and Curcumin at 5 microg/ml completely (nearly 100%) inhibited the mitogen stimulated proliferation. Curcumin inhibited IL-2 synthesis in Con A, PHA, and PMA stimulated SP-L in a concentration-dependent manner with an ED50 (concentration required for 50% inhibition) measured at 3.5 microg/ml. Exogenous IL-2 stimulated SP-L proliferation was also inhibited by Curcumin in a concentration-dependent manner with an ED50 of 2 microg/ml. EMSA assay indicated that PMA at 20 ng/ml stimulated NFkappaB activation 253% over control, which was inhibited by 24, 38, and 73%, respectively, with Curcumin at final concentrations of 2.5, 5, and 10 microg/ml, respectively.


CONCLUSIONS
Curcumin has profound immunosuppressive effects mediated via inhibition of IL-2 synthesis, mitogen, and IL-2 induced activation of human lymphocytes. This effect may be mediated via NFkappaB inhibition.
Ranjan
Dinesh
D
Transplant Section, Department of Surgery, University of Kentucky, College of Medicine, Lexington, Kentucky 40536, USA. dranj1@uky.edu
Chen
Changguo
C
Johnston
Thomas D
TD
Jeon
Hoonbae
H
Nagabhushan
Moolky
M
D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology*; D004586:Electrophoresis; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology* / Q000502:physiology; D008934:Mitogens / Q000494:pharmacology*; D016328:NF-kappa B / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D013154:Spleen / Q000166:cytology
D007166:Immunosuppressive Agents; D007376:Interleukin-2; D008934:Mitogens; D016328:NF-kappa B; D003474:Curcumin