Abstract:
We have observed an inhibitory action of magnolol on the production of
leukotriene (LT) C4 and LTB4, important lipid mediators
in allergy and inflammation. IgE- and A23187-stimulated production of LTC
4 and LTB4 was measured by radioimmunoassay (RIA) in the
absence or presence of various concentrations of magnolol in intact rat basophilic
leukemia (RBL)-2H3 cells. Magnolol dose-dependently inhibited synthesis of
LTC4 and LTB4. Magnolol inhibited the IgE-mediated increase
of intracellular calcium ion concentration, resulting in the inhibition of
cytosolic phospholipase A2 (cPLA2) and possibly 5-lipoxygenase
(5-LO), both calcium ion-dependent enzymes. In cell-free studies magnolol
inhibited LTC4 synthase activity. LTA4 hydrolase activity
was only inhibited at the higher concentration (2.5 × 10-5 M). These results indicate that magnolol inhibits production
of LTs by inhibiting PLA2, 5-LO, LTC4 synthase and LTA
4 hydrolase which are essential for LT-synthesis. Magnolol may have
anti-allergic effect by blocking LT-synthesis.
Key words:
Magnolol - leukotriene (LT) - rat basophilic leukemia-2H3 cell (RBL-2H3) - cytosolic phospholipase A2 (PLA2) - 5-lipoxygenase (5-LO) -
Magnolia obovata Thunberg
