Prostacyclin (PGI2) is a vasodilator and platelet inhibitor, properties consistent with cardioprotection. More than a decade ago, inhibition of cyclooxygenase-2 (COX-2) by the nonsteroidal anti-inflammatory drugs (NSAIDs) rofecoxib and celecoxib was found to reduce the amount of the major metabolite of PGI2 (PGI-M) in the urine of healthy volunteers. This suggested that NSAIDs might cause adverse cardiovascular events by reducing production of cardioprotective PGI2. This prediction was based on the assumption that the concentration of PGI-M in urine likely reflected vascular production of PGI2 and that other cardioprotective mediators, especially nitric oxide (NO), were not able to compensate for the loss of PGI2. Subsequently, eight placebo-controlled clinical trials showed that NSAIDs that block COX-2 increase adverse cardiovascular events. We connect tissue-specific effects of NSAID action and functional correlates in mice with clinical outcomes in humans by showing that deletion of COX-2 in the mouse vasculature reduces excretion of PGI-M in urine and predisposes the animals to both hypertension and thrombosis. Furthermore, vascular disruption of COX-2 depressed expression of endothelial NO synthase and the consequent release and function of NO. Thus, suppression of PGI2 formation resulting from deletion of vascular COX-2 is sufficient to explain the cardiovascular hazard from NSAIDs, which is likely to be augmented by secondary mechanisms such as suppression of NO production.

Continuous measurement and servo control (SC) of total body weight of unrestrained rats were used to investigate the role of volume expansion in the development of hypertension in Dahl salt-resistant (SR) and Dahl salt-sensitive (SS) rats. A change in sodium intake from 1 to 20 meq/day was associated with an increase in total body weight of 7.2% in both SS and SR rats over 96 h. Plasma sodium (pNa) increased from 145.0 to 147.4 meq/l in both SS (n = 10) and SR (n = 10) rats. Only in the SS rats was the volume expansion associated with an increase in arterial pressure of 27 +/- 3 mmHg. Prevention of the volume expansion by SC blocked the rise in arterial pressure in the SS rats (n = 10) but increased pNa from 143.5 to 152.4 meq/l. Hematocrit fell from 36.6 to 27.5% in both non-SC groups but decreased less in SC groups (35.7 to 32.0%). Plasma volume expansion from 17.6 +/- 0.6 to 25.2 +/- 0.8 ml in non-SC rats was greatly blunted by SC. In non-SC rats, SS (n = 10) and SR (n = 9) rats an increase in salt intake was associated with a rise in cardiac output from 413 +/- 6 to 507 +/- 12 ml.min-1.kg-1 in both groups. These results indicate that fluid retention is required to trigger the rise of pressure in Dahl SS rats.

Nonsteroidal anti-inflammatory drugs selective for inhibition of COX-2 increase heart failure and elevate blood pressure. The COX-2 gene was floxed and crossed into merCremer mice under the ␣-myosin heavy-chain promoter. Tamoxifen induced selective deletion of COX-2 in cardiomyocytes depressed cardiac output, and resulted in weight loss, diminished exercise tolerance, and enhanced susceptibility to induced arrhythmogenesis. The cardiac dysfunction subsequent to pressure overload recovered progressively in the knockouts coincident with increasing cardiomyocyte hypertrophy and interstitial and perivascular fibrosis. Inhibition of COX-2 in cardiomyocytes may contribute to heart failure in patients receiving nonsteroidal anti-inflammatory drugs specific for inhibition of COX-2.arrhythmia ͉ heart failure ͉ knockout ͉ NSAIDs ͉ fibrosis R andomized, placebo-controlled trials indicate that nonsteroidal antinflammatory drugs (NSAIDs) specific for inhibition of cyclooxygense (COX)-2 confer an increased risk of myocardial infarction and stroke (1-5), effects explicable by suppression of COX-2-derived products, such as prostacyclin (PGI 2 ) and prostaglandia E 2 (PGE 2 ) (6). While, the clinical spectrum of hazard is dominated by a predisposition to thrombosis, an additional feature has been congestive heart failure (1-4). NSAIDs may variably increase blood pressure (7): studies in rodents (8, 9) and a meta-analysis of clinical studies (10) suggest that this reflects inhibition of COX-2 and the specificity with which this is attained (11). Elevation of blood pressure by manipulation of the prostaglandin pathway is conditioned by genetic background in rodents (12). However, given this caveat, deletion or inhibition of COX-2 (8, 13) and deletion of the E prostanoid (EP)-2 receptor (14, 15) or the I-prostanoid receptor (IP) (16) for the COX-2 products, PGE 2 and PGI 2 respectively, may each result in hypertension. Indeed, deletion of the IP in these mice also results in cardiac hypertrophy and fibrosis, effects ameliorated by coincident deletion of the receptor for thromboxane A 2 , the TP, a maneuver that does not, alone, affect blood pressure (16). By contrast, inhibition or deletion of COX-1 attenuates the hypertensive response to infusion of angiotensin II (8) or treatment with a COX-2 inhibitor (13). Although placebo-controlled trials provide unequivocal evidence that COX-2-specific NSAIDs confer a cardiovascular hazard, the number of events within each trial are insufficient to permit analysis of covariates. Thus, it is unknown whether congestive heart failure on NSAIDs results solely from or is exacerbated by hypertension.Although suppression of COX-2-derived prostanoids is sufficient to explain the cardiovascular hazard conferred by purposedesigned and older NSAIDs specific for inhibition of COX-2 (17), there has been interest in the possibility that some or all of these effects might reflect ''off target'' effects. One such example was an overview-trial analysis interpreted to suggest that arrhythmia, cardiac arrest, ...

Background Microsomal (m) prostaglandin (PG) E2 synthase (S)-1 catalyzes the formation of PGE2 from PGH2, a cyclooxygenase (COX) product that is derived from arachidonic acid. Previous studies in mice suggest that targeting mPGES-1 may be less likely to cause hypertension or thrombosis than COX-2 selective inhibition or deletion in vivo. Indeed, deletion of mPGES-1 retards atherogenesis and angiotensin II-induced aortic aneurysm formation. The role of mPGES-1 in the response to vascular injury is unknown. Methods and Results Mice were subjected to wire injury of the femoral artery. Both neointimal area and vascular stenosis were reduced significantly four weeks after injury in mPGES-1 knock out (KO) mice compared to wild type (WT) controls (65.6±5.7 vs 37.7±5.1×103 pixel area and 70.5±13.4% vs 47.7±17.4%, respectively; p < 0.01). Induction of tenascin C (TN-C) after injury, a pro-proliferative and promigratory extracellular matrix protein, was attenuated in the KOs. Consistent with in vivo rediversion of PG biosynthesis, mPGES-1 deleted vascular smooth muscle cells (VSMC) generated less PGE2, but more PGI2 and expressed reduced TN-C when compared with WT cells. Both suppression of PGE2 and augmentation of PGI2 attenuate TN-C expression, VSMC proliferation and migration in vitro. Conclusions Deletion of mPGES-1 in mice attenuates neointimal hyperplasia after vascular injury, in part by regulating TN-C expression. This raises for consideration the therapeutic potential of mPGES-1 inhibitors as adjuvant therapy for percutaneous coronary intervention.