Activation of Galpha 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 endothelial cells, physiological concentrations of EETs, particularly 11,12-EET, or overexpression of the endothelial epoxygenase, CYP2J2, increased tissue plasminogen activator (t-PA) expression by 2.5-fold without affecting plasminogen activator inhibitor-1 expression. This increase in t-PA expression correlated with a 4-fold induction in t-PA gene transcription and a 3-fold increase in t-PA fibrinolytic activity and was blocked by the CYP inhibitor, SKF525A, but not by the calcium-activated potassium channel blocker, charybdotoxin, 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 determine whether increases in intracellular cAMP levels were due to modulation of guanine nucleotide-binding proteins, we assessed the effects of EETs on Galpha(s) and Galpha(i2). Treatment with EETs increased Galpha(s), but not Galpha(i2), GTP-binding activity by 3.5-fold. These findings indicate that EETs possess fibrinolytic properties through the induction of t-PA and suggest that endothelial CYP2J2 may play an important role in regulating vascular hemostasis.