Possible involvement of protein kinase c inhibition in the reduction of phorbol ester-induced neutrophil aggregation by magnolol in the rat

J Pharm Pharmacol. 1998 Oct;50(10):1167-72. doi: 10.1111/j.2042-7158.1998.tb03329.x.


The influence of the plant product magnolol on neutrophil aggregation has been investigated in the rat. Magnolol inhibited phorbol 12-myristate 13-acetate (PMA)-activated rat neutrophil aggregation in a concentration-dependent manner with an IC50 (concentration resulting in 50% inhibition) of 24.2 +/- 1.7 microM. Magnolol suppressed the enzyme activity of neutrophil cytosolic and rat brain protein kinase C (PKC) over the same range of concentrations at which it inhibited the aggregation. Magnolol did not affect PMA-induced cytosolic PKC-alpha and -delta membrane translocation or trypsin-treated rat-brain PKC activity, but attenuated [3H]phorbol 12,13-dibutyrate binding to neutrophil cytosolic PKC. These results suggest that the inhibition of PMA-induced rat neutrophil aggregation by magnolol is probably attributable, at least in part, to the direct suppression of PKC activity through blockade of the regulatory region of PKC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Biphenyl Compounds / pharmacology*
  • Enzyme Inhibitors / pharmacology*
  • In Vitro Techniques
  • Lignans*
  • Neutrophils / drug effects*
  • Neutrophils / physiology
  • Platelet Aggregation Inhibitors / pharmacology
  • Protein Kinase C / antagonists & inhibitors*
  • Protein Kinase C / metabolism
  • Rats
  • Tetradecanoylphorbol Acetate / pharmacology*
  • Tritium
  • Trypsin / metabolism


  • Biphenyl Compounds
  • Enzyme Inhibitors
  • Lignans
  • Platelet Aggregation Inhibitors
  • magnolol
  • Tritium
  • Protein Kinase C
  • Trypsin
  • Tetradecanoylphorbol Acetate