Activation of G alpha(s) mediates induction of tissue-type plasminogen activator gene transcription by epoxyeicosatrienoic acids

The epoxyeicosatrienoic acids (EETs) are products of cytochrome P450 (CYP) epoxygenases that have vasodilatory and anti-inflammatory properties. Here we report that EETs have additional fibrinolytic properties. In vascular en dothelial cells, physiological concentrations of EETs, particularly 11,12-E ET, or overexpression of the endothelial epoxygenase, CYP2J2, increased tis sue plasminogen activator (t-PA) expression by 2.5-fold without affecting p lasminogen activator inhibitor-1 expression. This increase in t-PA expressi on correlated with a 4-fold induction in t-PA gene transcription and a 3-fo ld increase in t-PA fibrinolytic activity and was blocked by the CYP inhibi tor, SKF525A, but not by the calcium-activated potassium channel blocker, c harybdotoxin, indicating a mechanism that does not involve endothelial cell hyperpolarization. The t-PA promoter is cAMP-responsive, and induction of t-PA gene transcription by EETs correlated with increases in intracellular cAMP levels and, functionally, with cAMP-driven promoter activity. To deter mine whether increases in intracellular cAMP levels were due to modulation of guanine nucleotide-binding proteins, we assessed the effects of EETs on G alpha (s) and G alpha (i2). Treatment with EETs increased G alpha (s), bu t not G alpha (i2), GTP-binding activity by 3.5-fold. These findings indica te that EETs possess fibrinolytic properties through the induction of t-PA and suggest that endothelial CYP2J2 may play an important role in regulatin g vascular hemostasis.