Circadian clock molecules CLOCK and CRYs modulate fibrinolytic activity by regulating the PAI-1 gene expression.

Disruptions of circadian rhythms are associated with the development of many disorders. However, whether a disruption of the circadian clock can cause anomalies of the hemostatic balance remains unknown. The present study examines coagulation and fibrinolytic activities in circadian clock mutants, a homozygous Clock mutant and Cry1/Cry2 double knockout (Cry1/2-deficient) mice. The euglobulin clot lysis time (ELT) showed circadian variations that peaked at 21:00 (early night) in wild-type mice, suggesting that fibrinolytic activity is lowest at this time. The ELT was continuously reduced in Clock mutants, while the ELT was significantly increased and did not differ between day and night (9:00 and 21:00) in Cry1/2-deficient mice. The prothrombin time (PT) and activated partial prothrombin time (APTT) were constant in all genotypes. To identify which factors cause the loss of ELT rhythm, we measured fibrinolytic parameters in Clock mutant and Cry1/2-deficient mice. The robust circadian fluctuation of plasma plasminogen activator inhibitor 1 (PAI-1) that peaked at early night was damped to trough levels in Clock mutant mice. On the other hand, PAI-1 levels in Cry1/2-deficient mice remained equivalent to the peak levels of those in wild-type mice at both 9:00 and 21:00. Circadian changes in plasma PAI-1 levels seemed to be regulated at the level of gene expression, because the plasma PAI-1 levels in Clock mutant and Cry1/2-deficient mice were closely correlated with the level of PAI-1 mRNA transcript in these mice. Plasma plasminogen and hepatic mRNA levels were not rhythmic in wild-type mice, and continuously higher in Clock mutant than in wild-type or Cry1/2-deficient mice. In contrast, the activity and mRNA levels of tissue type plasminogen activator (t-PA), plasma levels and mRNA levels of plasminogen, and plasma levels of alpha2 plasmin inhibitor (alpha2PI) in all genotypes were constant throughout the day. Coagulation parameters such as factor VII, factor X, prothrombin and fibrinogen remained constant throughout the day, and were not affected by clock gene mutations. These results suggest that circadian clock molecules play an important role in hemostatic balance by regulating the fibrinolytic systems.

Early de novo gene expression is required for 15-deoxy-Delta 12,14-prostaglandin J2-induced apoptosis in breast cancer cells.

Cyclopentenone prostaglandin derivatives of arachidonic acid are potent inducers of apoptosis in a variety of cancer cell types. Several investigators have shown that the terminal derivative of prostaglandin J(2) (PGJ(2)) metabolism, 15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)), induces apoptosis in breast cancer cells and is a potent activator of the nuclear hormone receptor peroxisome proliferator-activated receptor gamma (PPARgamma), but 15dPGJ(2) effects can be mediated by PPARgamma-dependent and PPARgamma-independent mechanisms. Here we report that 15dPGJ(2) regulates early gene expression critical to apoptosis. Specifically, 15dPGJ(2) induces potent and irreversible S phase arrest that is correlated with expression of genes critical to cell cycle arrest and apoptosis, including the cyclin-dependent kinase inhibitor p21(Waf1/Cip1) (p21). Inhibition of RNA or protein synthesis abrogates apoptosis induced by 15dPGJ(2) in breast cancer cells but potentiates apoptosis induced by tumor necrosis factor-alpha or CD95/Fas ligand. Additionally, 15dPGJ(2) induces caspase activation that is blocked by peptide caspase inhibitors. These data show that de novo gene transcription is necessary for 15dPGJ(2)-induced apoptosis in breast cancer cells. Critical candidate genes are likely to be revealed through analysis of differential cDNA array expression.