Ginsenoside Rh2 and Rh3 induce differentiation of HL-60 cells into granulocytes:: modulation of protein kinase C isoforms during differentiation by ginsenoside Rh2

Ginsenoside Rh-1 or Rh-2 differentiated B16 melanoma or F9 teratocarnoma to phenotypic normal melanocyte-like cells or parietal endoderm-like cells. Ginsenoside Rh-3 and Rh-4 were recently isolated from Panax ginseng, but their biochemical and pharmacological effects remain unidentified. The present study investigated whether the ginsenoside Rh group (G-Rh-1, -Rh-2, -Rh-3 and -Rh-4) having similar structures induce differentiation of HL-60 cells and whether protein kinase C (PKC) is involved in differentiation by ginsenoside. Differentiation was assessed by Wright-Giemsa stain and nitroblue tetrazolium reduction. G-Rh-2 and G-Rh-3 induced differentiation of HL-60 cells into morphologically and functionally granulocytes but G-Rh-1 and G-Rh-4 did not. G-Rh-2 and G-Rh-3 arrested the cell cycle at the G1/S phase, consistent with the ability to induce differentiation in a decreasing order of retinoic acid > G-Rh-2 > G-Rh-3. During differentiation by G-Rh-2, Ca2+/phospholipid-dependent PKC activity was increased in both the cytosol and total cell extract and Ca2+/phospholipid-dependent phosphorylation of 38 and 200 kDa endogenous proteins increased, while phosphorylation of 60, 64, 66 and 97 kDa proteins was Ca2+/phospholipid-independent. When cytosolic PKC isoforms were analyzed by immunoblotting, no significant change was observed in the alpha level, however, the immunoreactive 60 kDa band of a similar mass to the PKC catalytic fragment appeared following treatment with G-Rh-2. The beta isoform was gradually increased with prolonged treatment. The gamma isoform was not detected in the cytosol of untreated cells, whereas a small amount was detected 5 days after treatment. It is concluded that G-Rh-2 and G-Rh-3 can induce differentiation of HL-60 cells into granulocytes and modulation of PKC isoform levels may contribute to differentiation of HL-60 cells by G-Rh-2. (C) 1998 Elsevier Science Ltd. All rights reserved.