Modulation of Protein Kinase C Activity in NIH 3T3 Cells by Plant Glycosides from Panax ginseng

Abstract

The involvement of ginsenosides in the signal cascade that stimulates cellular growth was investigated. It was found that ginsenosides Rh₁ and Rh₂ extracted from the root of Panax ginseng inhibited cellular proliferation in NIH 3T3 fibroblasts. Both ginsenosides Rh₁ and Rh₂ effectively reduced phospholipase C activity resulting in a decrease in the intracellular level of diacylglycerol, an endogenous activator of protein kinase C. The treatment of cells with Rh₁ or Rh₂ was thus found to reduce intracellular protein kinase C activity. We also observed that the phosphorylation of myristoylated alanine-rich C kinase substrate, one of the major substrates of protein kinase C in cells, was inhibited by the ginsenosides. Data suggest that the ginsenoside Rh₁ or Rh₂ exerts antiproliferative effects by inhibiting phospholipase C, which produces second messengers necessary for the activation of protein kinase C.

key words

Panax ginseng - Araliaceae - ginsenoside - phospholipase C - protein kinase C - myristoylated alanine-rich C kinase substrate