Modulation of protein kinase C activity in NIH 313 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 Rh-1 and Rh-2 extracted from the root of Panax ginseng inhibited cellular proliferation in NIH 3T3 fibroblasts. Both ginsenosides Rh-1 and Rh-2 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 Rh-1 or Rh-2 was thus found to reduce intracellular protein Itinase C activity. We also observed that the phosphorylation of myristoylated alanine-rich C kinase substrate, one of the major substrates of protein Itinase C in cells, was inhibited by the ginsenosides. Data suggest that the ginsenoside Rh-1 or Rh-2 exerts antiproliferative effects by inhibiting phospholipase C, which produces second messengers necessary for the activation of protein kinase C.