A specific peptide with immunomodulatory activity from Pseudostellaria heterophylla and the action mechanism

Pseudostellaria heterophylla protein hydrolysate has been reported to be a potential nutraceutical supplement to strengthen the immune system. A specific peptide from P. heterophylla protein hydrolysate with proliferation promotion effect on spleen lymphocytes was purified by RP-HPLC. The amino acid sequence of the peptide was determined to be RGPPP, with molecular weight of 522.29 Da. 100 mu g/mL of RP-5 achieved the highest stimulation index of 1.27 on spleen lymphocytes and activated RAW264.7 cells resulting in up-regulating tumor necrosis factor-alpha (TNF-alpha) secretion to 827.24 pg/mL and elevating pinocytosis rate to 123.81%. Results of western-blot and siRNA experiments indicated that RP-5 activated nuclear factor-kappa B (NF-kappa B) signaling pathway through combining to TLR2 expressed on RAW264.7 cells surface. Furthermore, TNF-alpha secretion increased by RP-5 could be decreased to 401.68 pg/mL by pyrrolidine dithiocarbamate or BAY11-7082. These findings further the research progress of peptide with immunomodulatory activity and its action mechanism.