Negative effects of rofecoxib treatment on cardiac function after ischemia-reperfusion injury in APOE*3Leiden mice are prevented by combined treatment with thromboxane prostanoid-receptor antagonist S18886 (terutroban)*:

Prostanoids in Cardiac and Vascular Remodeling

Prostanoids are biologically active lipids generated from arachidonic acid by the action of the COX (cyclooxygenase) isozymes. NSAIDs, which reduce the biosynthesis of prostanoids by inhibiting COX activity, are effective anti-inflammatory, antipyretic, and analgesic drugs. However, their use is limited by cardiovascular adverse effects, including myocardial infarction, stroke, hypertension, and heart failure. While it is well established that NSAIDs increase the risk of atherothrombotic events and hypertension by suppressing vasoprotective prostanoids, less is known about the link between NSAIDs and heart failure risk. Current evidence indicates that NSAIDs may increase the risk for heart failure by promoting adverse myocardial and vascular remodeling. Indeed, prostanoids play an important role in modulating structural and functional changes occurring in the myocardium and in the vasculature in response to physiological and pathological stimuli. This review will summarize current knowledge of the role of the different prostanoids in myocardial and vascular remodeling and explore how maladaptive remodeling can be counteracted by targeting specific prostanoids.

Cyclooxygenase-2-derived prostacyclin protective role on endotoxin-induced mouse cardiomyocyte mortality

Cardiovascular dysfunction characterizes septic shock, inducing multiple organ failure and a high mortality rate. In the heart, it has been shown an up-regulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions with subsequent overproduction of nitric oxide (NO) and eicosanoids. This study is focused on the links between these products of inflammation and cell loss of mouse cardiomyocytes during treatment by the Salmonella typhimurium lipopolysaccharide (LPS) in presence or in absence of NOS or COX inhibitors. LPS induced RelA/NF-κB p65 activation, iNOS and COX-2 up-regulations, resulting in NO and prostacyclin releases. These effects were reversed by the NO-synthase inhibitor and increased by the specific COX-2 inhibitor. Immunostainings with FITC-conjugated anti-Annexin-V and propidium iodide and caspase 3/7 activity assay showed that cardiomyocyte necrosis was inhibited by L-NA during LPS treatment challenge, while apoptosis was induced in presence of both LPS and NS-398. No effect on LPS cellular injury was observed using the specific cyclooxygenase-1 (COX-1) inhibitor, SC-560. These findings strongly support the hypothesis of a link between iNOS-dependent NO overproduction and LPS-induced cell loss with a selective protective role allotted to COX-2 and deriving prostacyclins.

Review: Antiplatelet Drugs: What Comes Next?

Antiplatelet drugs are important components in the management of atherothrombotic vascular disease. However, several limitations restrict the safety and efficacy of current antiplatelet therapy in clinical practice. Interpatient variability and resistance to aspirin and/or clopidogrel has spurred efforts for the development of novel agents. Indeed, several antiplatelet drugs are at various stages of evaluation; those at advanced stage of development are the focus of this review.

The thromboxane/endoperoxide receptor (TP): the common villain

The stimulation of thromboxane/endoperoxide receptors (TP) elicits diverse physiological/pathophysiological reactions, including platelet aggregation and contraction of vascular smooth muscle. Furthermore, the activation of endothelial TP promotes the expression of adhesion molecules and favors adhesion and infiltration of monocytes/macrophages. In various cardiovascular diseases, endothelial dysfunction is predominantly the result of the release of endothelium-derived contracting factors that counteract the vasodilator effect of nitric oxide produced by the endothelial nitric oxide synthase. Endothelium-dependent contractions involve the activation of cyclooxygenases, the production of reactive oxygen species along with that of endothelium-derived contracting factors, which diffuse toward the vascular smooth muscle cells and activate their TP. TP antagonists curtail the endothelial dysfunction in diseases such as hypertension and diabetes, are potent antithrombotic agents, and reduce vascular inflammation. Therefore, TP antagonists, because of this triple activity, may have a unique potential for the treatment of cardiovascular disorders.

Diclofenac: an update on its mechanism of action and safety profile

BACKGROUND

Diclofenac is a proven, commonly prescribed nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory, and antipyretic properties, and has been shown to be effective in treating a variety of acute and chronic pain and inflammatory conditions. As with all NSAIDs, diclofenac exerts its action via inhibition of prostaglandin synthesis by inhibiting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) with relative equipotency. However, extensive research shows the pharmacologic activity of diclofenac goes beyond COX inhibition, and includes multimodal and, in some instances, novel mechanisms of action (MOA).

DATA SOURCES

Literature retrieval was performed through PubMed/MEDLINE (through May 2009) using combinations of the terms diclofenac, NSAID, mechanism of action, COX-1, COX-2, and pharmacology. Reference citations resulting from publications identified in the literature search were reviewed when appropriate.

METHODS

This article reviews the established, putative, and emerging MOAs of diclofenac; compares the drug's pharmacologic and pharmacodynamic properties with other NSAIDs to delineate its potentially unique qualities; hypothesizes why it has been chosen for further recent formulation enhancement; and evaluates the potential effect of its MOA characteristics on safety.

DISCUSSION

Research suggests diclofenac can inhibit the thromboxane-prostanoid receptor, affect arachidonic acid release and uptake, inhibit lipoxygenase enzymes, and activate the nitric oxide-cGMP antinociceptive pathway. Other novel MOAs may include the inhibition of substrate P, inhibition of peroxisome proliferator activated receptor gamma (PPARgamma), blockage of acid-sensing ion channels, alteration of interleukin-6 production, and inhibition of N-methyl-D-aspartate (NMDA) receptor hyperalgesia. The review was not designed to compare MOAs of diclofenac with other NSAIDs. Additionally, as the highlighted putative and emerging MOAs do not have clinical data to demonstrate that these models are correct, further research is necessary to ascertain if the proposed pathways will translate into clinical benefits. The diversity in diclofenac's MOA may suggest the potential for a relatively more favorable profile compared with other NSAIDs.

Pathophysiology of cyclooxygenases in cardiovascular homeostasis

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandin H(2) (PGH(2)), which is subsequently converted to the prostanoids PGE(2), PGI(2), PGF(2alpha), and thromboxane A(2). COX has 2 distinct membrane-anchored isoenzymes: COX-1 and COX-2. COX-1 is constitutively expressed in most normal tissues; COX-2 is highly induced by proinflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include conventional nonselective nonsteroidal anti-inflammatory drugs and selective nonsteroidal anti-inflammatory drugs, such as COX-2 inhibitors. The adverse effects of COX inhibitors on the cardiovascular system have been addressed in the last few years. In general, COX inhibitors have many effects, but those most important to the cardiovascular system can be direct (through the effects of prostanoids) and indirect (through alterations in fluid dynamics). Despite reports of detrimental human cardiovascular events associated with COX inhibitors, short, long, and lifetime preclinical toxicology studies in rodents and nonrodents have failed to identify these risks. This article focuses on the expression and function of COX enzymes in normal and pathologic conditions of the cardiovascular system and discusses the cardiovascular pathophysiologic complications associated with COX inhibition.

Genome-wide mRNA expression analysis of hepatic adaptation to high-fat diets reveals switch from an inflammatory to steatotic transcriptional program

BACKGROUND

Excessive exposure to dietary fats is an important factor in the initiation of obesity and metabolic syndrome associated pathologies. The cellular processes associated with the onset and progression of diet-induced metabolic syndrome are insufficiently understood.

PRINCIPAL FINDINGS

To identify the mechanisms underlying the pathological changes associated with short and long-term exposure to excess dietary fat, hepatic gene expression of ApoE3Leiden mice fed chow and two types of high-fat (HF) diets was monitored using microarrays during a 16-week period. A functional characterization of 1663 HF-responsive genes reveals perturbations in lipid, cholesterol and oxidative metabolism, immune and inflammatory responses and stress-related pathways. The major changes in gene expression take place during the early (day 3) and late (week 12) phases of HF feeding. This is also associated with characteristic opposite regulation of many HF-affected pathways between these two phases. The most prominent switch occurs in the expression of inflammatory/immune pathways (early activation, late repression) and lipogenic/adipogenic pathways (early repression, late activation). Transcriptional network analysis identifies NF-kappaB, NEMO, Akt, PPARgamma and SREBP1 as the key controllers of these processes and suggests that direct regulatory interactions between these factors may govern the transition from early (stressed, inflammatory) to late (pathological, steatotic) hepatic adaptation to HF feeding. This transition observed by hepatic gene expression analysis is confirmed by expression of inflammatory proteins in plasma and the late increase in hepatic triglyceride content. In addition, the genes most predictive of fat accumulation in liver during 16-week high-fat feeding period are uncovered by regression analysis of hepatic gene expression and triglyceride levels.

CONCLUSIONS

The transition from an inflammatory to a steatotic transcriptional program, possibly driven by the reciprocal activation of NF-kappaB and PPARgamma regulators, emerges as the principal signature of the hepatic adaptation to excess dietary fat. These findings may be of essential interest for devising new strategies aiming to prevent the progression of high-fat diet induced pathologies.