Ferulate inhibits mixed lymphocyte reaction stimulated cell proliferation and inhibits IL-2 and IL-2 receptor expression

Abstract

Introduction. We have previously shown that curcumin (di-feruloyl methane) has immunosuppressive properties in addition to its anti-oxidant, anti-inflammation, and anti-mutagenic properties. Ferulic acid is a metabolic product of phenylalanine and tyrosine and also a degradation product of curcumin. In this experiment we investigated whether ferulic acid retained the immunosuppressive properties of curcumin. We used ethyl--ferulic acid (FE, from Sigma) in all our experiments due to its higher water solubility than free ferulic acid and therefore more bioavailable. Methods. Lymphocytes were isolated from human spleen. Mixed lymphocyte reaction (MLR), exogenous IL-2, and PHA-stimulated human lymphocyte proliferation were assayed by 3H-thymidine incorporation. Cell-secreted IL-2 in the culture medium was assayed by ELISA, and IL-2 Receptor (IL-2R) expression was assayed by flow-cytometry. Trypan Blue exclusion was used to rule out direct cytotoxic effects of FE. Microsoft Excel T-test program was used for statistics. P values less than 0.05 were considered statistically significant. Results. MLR stimulated cell proliferation > 8 times over the control response cells. FE at 10, 20, 40 and 80 μM inhibited MLR stimulated 3H-thymidine uptake (CPM/well) from 5349 ± 178 to 4635 ± 119, 4294 ± 125, 3450 ± 79, and 1756 ± 62, respectively ( P < 0.01, n = 6). MLR stimulated IL-2 secretion in the culture medium from control (pg/ml) 24 ± 5.2 to 214.8 ± 5.5. FE at 40 and 80 μM significantly inhibited IL-2 level from 214.8 ± 5.5 to 161.8 ± 6.6 and 138.5 ± 9.6, respectively ( P < 0.04, n = 3). Exogenous IL-2 (0.5 nM) stimulated IL-2 receptor (IL-2R) expression in human lymphocytes from control of 10.52 to 19.95%. FE at 80 μM inhibited exogenous IL-2-stimulated IL-2R expression to 10.95%. Mitogen PHA (5 μg/ml) stimulated IL-2R expression in the lymphocytes from control 10.52 to 58.34%, FE at 80 μM inhibited IL-2R expression to 25.5%. (This experiment has been done once.) Conclusion. FE has immunosuppressive properties like its precursor curcumin but possesses the additional advantage of being bioavailable. These effects warrant further investigation.