The immunosuppressive effect of Buchang-tang through inhibition of mitogen-activated protein kinase and nuclear factor activation in MOLT-4 cells

Buchang-tang (BCT) has been known to suppress inflammatory and autoimmune responses. Accordingly, BCT has been clinically used in Korea as an immunomodulatory oriental medicine. Here, we report on the mechanism of action of BCT in activated MOLT-4 cells by determining the affected signaling pathways. BCT inhibits extracellular signal-regulated kinases (ERK)l/2 and p38 activation but does not interfere with phosphorylation of other mitogen-activated protein kinases, c-Jun NH₂-terminal kinases 1/2 in MOLT-4 cells. The nuclear localization of nuclear factor of activated T cells 2 (NFATc) was blocked by BCT. Also, degradation of inhibitor κB-α and transactivation by nuclear factor-κ B (NF-κB)/Rel A were impaired. Furthermore, interlukin (IL)-2 mRNA and protein levels were significantly diminished by BCT treatment. Our data indicate that BCT inhibits ERK1/2, p38 activation, nuclear translocation of NFATc, and NF-κB, resulting in diminished secretion of IL-2.