Jp. Wang et al., Possible involvement of protein kinase C inhibition in the reduction of phorbol ester-induced neutrophil aggregation by magnolol in the rat, J PHARM PHA, 50(10), 1998, pp. 1167-1172
The influence of the plant product magnolol on neutrophil aggregation has b
een investigated in the rat.
Magnolol inhibited phorbol 12-myristate 13-acetate (PMA)-activated fat neut
rophil aggregation in a concentration-dependent manner with an IC50 (concen
tration resulting in 50% inhibition) of 24.2 +/- 1.7 mu M. Magnolol suppres
sed the enzyme activity of neutrophil cytosolic and rat brain protein kinas
e C (PKC) over the same range of concentrations at which it inhibited the a
ggregation. Magnolol did not affect PMA-induced cytosolic PKC-a and -delta
membrane translocation or trypsin-treated rat-brain PKC activity, but atten
uated [H-3]phorbol 12,13-dibutyrate binding to neutrophil cytosolic PKC.
These results suggest that the inhibition of PMA-induced rat neutrophil agg
regation by magnolol is probably attributable, at least in part, to the dir
ect suppression of PKC activity through blockade of the regulatory region o
f PKC.