(S)-Armepavine inhibits human peripheral blood mononuclear cell activation by regulating Itk and PLCγ activation in a PI-3K-dependent manner

Chinese herbs are useful edible and medicinal plants for their immune modulatory functions. We have proven that (S)‐armepavine (C19H23O3N; MW313) from Nelumbo nucifera inhibits the proliferation of human PBMCs activated with PHA and improves autoimmune diseases in MRL/MpJ‐lpr/lpr mice. In the present study, the pharmacological activities of (S)‐armepavine were evaluated in PHA‐activated PBMCs. The results showed that (S)‐armepavine suppressed PHA‐induced PBMC proliferation and genes expression of IL‐2 and IFN‐γ without direct cytotoxicity. Inhibition of NF‐AT and NF‐κB activation suggested phospholipase Cγ (PLCγ)‐mediated Ca2+ mobilization and protein kinase C activation were blocked by (S)‐armepavine. Phosphorylation of PLCγ is regulated by lymphocyte‐specific kinase (Lck), ZAP‐70, and IL‐2‐inducible T cell kinase (Itk). We found (S)‐armepavine inhibited PHA‐induced phosphorylation of Itk and PLCγ efficiently but did not influence Lck or ZAP‐70 phosphorylation. In addition, ZAP‐70‐mediated pathways, such as the association of linker for activation of T cells with PLCγ and activation of ERK, were also intact in the presence of (S)‐armepavine. Finally, reduction of phosphoinositide 3,4,5‐trisphosphate formation and Akt phosphorylation suggested that (S)‐armepavine inhibited Itk, and PLCγ phosphorylation might be a result of the influence of PI‐3K activation. Addition of exogenous IL‐2 or PMA/A23187 rescued PBMC proliferation in the presence of (S)‐armepavine. Therefore, we concluded that (S)‐armepavine inhibited PHA‐induced cell proliferation and cytokine production in a major way by blocking membrane‐proximal effectors such as Itk and PLCγ in a PI‐3K‐dependent manner.