Little is known about the effect of epigallocatechin-3 gallate (EGCG), a major constituent of
green tea, on the expression of
cyclooxygenase (COX)-2. Here, we studied the role of
phospholipase D (
PLD)
isozymes in EGCG-induced COX-2 expression. Stimulation of human
astrocytoma cells (U87) with EGCG induced formation of
phosphatidylbutanol, a specific product of
PLD activity, and synthesis of COX-2
protein and its product,
prostaglandin E(2) (
PGE(2)). Pretreatment of cells with
1-butanol, but not 3-butanol, suppressed EGCG-induced COX-2 expression and
PGE synthesis. Furthermore, evidence that
PLD was involved in EGCG-induced COX-2 expression was provided by the observations that COX-2 expression was stimulated by overexpression of PLD1 or PLD2
isozymes and treatment with
phosphatidic acid (PA), and that prevention of PA dephosphorylation by 1-propranolol significantly potentiated COX-2 expression induced by EGCG. EGCG induced activation of
p38 mitogen-activated protein kinase (
p38 MAPK), and specific inhibition of
p38 MAPK dramatically abolished EGCG-induced
PLD activation, COX-2 expression, and
PGE(2) formation. Moreover,
protein kinase C (PKC) inhibition suppressed EGCG-induced
p38 MAPK activation, COX-2 expression, and
PGE(2) accumulation. The same pathways as those obtained (2)in the
astrocytoma cells were active in primary rat astrocytes, suggesting the relevance of the findings. Collectively, our results demonstrate for the first time that
PLD isozymes mediate EGCG-induced COX-2 expression through PKC and p38 in immortalized astroglial line and normal astrocyte cells.