Inhibition of cyclooxygenase-2 improves cardiac function after myocardial infarction in the mouse

Comparison of microsomal prostaglandin E synthase-1 deletion and COX-2 inhibition in acute cardiac ischemia in mice

The aim of the present study was to compare the effects of genetic mPGES-1 loss and COX-2 inhibition on myocardial damage after coronary occlusion. mPGES-1(-/-) mice and their wild-type littermates were injected with vehicle or COX-2 inhibitor (celecoxib), and 30min later the left coronary artery was surgically occluded. At 24h, myocardial infarct (MI) volume was measured histologically. Post-MI survival was reduced in WT mice receiving celecoxib (12/20) compared with vehicle-treated controls (12/12) or the loss of mPGES-1 (13/13) together with increased phosphokinase (CPK) and cardiac troponin-I release. Endogenous mPGES-1 expression was unchanged by ischemia in WT mice and absent in mPGES-1(-/-) hearts. COX-2 expression was markedly increased at 24h after MI in WT hearts; this upregulation was largely attenuated in mPGES-1(-/-) mice. We conclude that loss of mPGES-1 prevents the upregulation of COX-2 after myocardial infarct, and in contrast to inhibition of COX-2, does not increase ischemic myocardial damage.

Selective cyclooxygenase-2 inhibition protects against myocardial damage in experimental acute ischemia

BACKGROUND

Acute myocardial infarction is associated with tissue inflammation. Early coronary reperfusion clearly improves the outcome but may help propagate the inflammatory response and enhance tissue damage. Cyclooxygenase-2 is an enzyme that catalyzes the initial step in the formation of inflammatory prostaglandins from arachidonic acid. Cyclooxygenase-2 levels are increased when ischemic cardiac events occur. The overall function of COX-2 in the inflammatory process generated by myocardial ischemic damage has not yet been elucidated.

GOAL

The objective of this study was to determine whether a selective cyclooxygenase-2 inhibitor (rofecoxib) could alter the evolution of acute myocardial infarction after reperfusion.

METHODS AND RESULTS

This study was performed with 48 mongrel dogs divided into two groups: controls and those treated with the drug. All animals were prepared for left anterior descending coronary artery occlusion. The dogs then underwent 180 minutes of coronary occlusion, followed by 30 minutes of reperfusion. Blood samples were collected from the venous sinus immediately before coronary occlusion and after 30 minutes of reperfusion for measurements of CPK-MB, CPK-MBm and troponin I. During the experiment we observed the mean blood pressure, heart rate and coronary flow. The coronary flow and heart rate did not change, but in the control group, there was blood pressure instability, in addition to maximal levels of CPK-MB post-infarction. The same results were observed for CPK-MBm and troponin I.

CONCLUSION

In a canine model of myocardial ischemia-reperfusion, selective inhibition of Cyclooxygenase-2 with rofecoxib was not associated with early detrimental effects on the hemodynamic profile or the gross extent of infarction; in fact, it may be beneficial by limiting cell necrosis.

Overexpression of prostaglandin EP3 receptors activates calcineurin and promotes hypertrophy in the murine heart

AIMS

Prostaglandin E(2) (PGE(2)) has been shown to mediate anti-ischaemic effects and cardiomyocyte hypertrophy and there is evidence for an involvement of the prostaglandin EP(3)-receptor subtype. This study focuses on the EP(3)-mediated hypertrophic action and investigates intracellular signalling pathways of the EP(3)-receptor subtype in the murine heart.

METHODS AND RESULTS

Cardiac function was analyzed in vivo by magnetic resonance imaging (MRI) in transgenic (tg) mice with cardio-specific overexpression of the EP(3) receptor in comparison with wild-type (wt) mice. Left ventricular (LV) function was determined in isolated perfused hearts subjected to 60 min of zero-flow ischaemia and 45 min of reperfusion. Calcineurin activity and nuclear activity of nuclear factor of activated T-cells (NFAT) were determined by a modified malachite green assay and ELISA, respectively. Extracellular matrix compounds were analyzed by RT-PCR and histology. MRI indicated a significant increase in end-diastolic and end-systolic volume in tg hearts. LV ejection fraction was severely decreased in tg hearts while the relative LV mass was significantly increased. In Langendorff perfused hearts, EP(3)-receptor overexpression resulted in a marked blunting of the ischaemia-induced increase in LV end-diastolic pressure and creatine kinase release. Analysis of EP(3)-receptor-mediated signalling revealed significantly increased calcineurin activity and nuclear activity of NFAT in tg hearts. Moreover, elevated mRNA levels of collagen types I and III as well as the collagen-binding proteoglycans biglycan and decorin were detected in tg hearts.

CONCLUSION

EP(3)-receptor-mediated signalling results in a significant anti-ischaemic action and activation of the pro-hypertrophic calcineurin signalling pathway, suggesting the involvement of the EP(3) subtype in both PGE(2)-mediated cardioprotection as well as cardiac hypertrophy.

Effect of selective cyclooxygenase-2 inhibitor meloxicam on liver fibrosis in rats with ligated common bile ducts

AIM

Cholestasis triggers fibrogenesis in the liver. Hepatic cyclooxygenase-2 (COX-2) expression increases in various chronic liver diseases caused either by viruses or toxins. We hypothesized that selective COX-2 inhibitor meloxicam could suppress inflammation and fibrogenesis in a rat model of cholestasis induced by bile duct ligation (BDL).

METHODS

Forty-three Sprague-Dawley rats were assigned to one of four treatment groups (sham-operation, BDL, daily meloxicam injections following BDL, and daily meloxicam injection without BDL). Liver histopathology was analyzed with hematoxylin-eosin and Masson's trichrome staining. The expression of alpha-smooth muscle actin (alpha-SMA), transforming growth factor-beta1 (TGF-beta1), and COX-2 were measured with immunohistochemical staining. The levels of COX-2, TGF-beta1, and matrix metalloproteinase-9 (MMP-9) production were measured with the Western blot method and an enzyme immunoassay.

RESULTS

Meloxicam treatment attenuated the expression of alpha-SMA, TGF-beta1, and COX-2 in rats that were treated with BDL for 3 weeks. This was associated with a marked reduction in collagen accumulation and histological improvement. In addition, meloxicam treatment was found to downregulate the levels of hepatic COX-2, TGF-beta1, and MMP-9 production.

CONCLUSION

Cholestasis in BDL rats induces hepatic COX-2 expression. Selective COX-2 inhibitor meloxicam reduces BDL-induced hepatic fibrosis, and this is associated with reduced hepatic TGF-beta1 expression as well as decreased cyclooxygenase activity in the liver.

Cyclooxygenase in normal human tissues--is COX-1 really a constitutive isoform, and COX-2 an inducible isoform?

Cyclooxygenase (COX) is a key enzyme in prostanoid synthesis. It exists in two isoforms, COX-1 and COX-2. COX-1 is referred to as a ‘constitutive isoform’, and is considered to be expressed in most tissues under basal conditions. In contrast, COX-2 is referred to as an ‘inducible isoform’, which is believed to be undetectable in most normal tissues, but can be up-regulated during various conditions, many of them pathological. Even though the role of COX in homeostasis and disease in now well appreciated, controversial information is available concerning the distribution of COX isoforms in normal human tissues. There is mounting evidence that it is much more complex than generally believed. Our aim was therefore to analyse the expression and distribution of COX isoforms in normal human tissues, using immunohistochemistry, Western blotting and real-time RT-PCR. Autopsy samples from 20 healthy trauma victims and samples from 48 biopsy surgical specimens were included. COX-1 was found in blood vessels, interstitial cells, smooth muscle cells, platelets and mesothelial cells. In contrast, COX-2 was found predominantly in the parenchymal cells of many tissues, with few exceptions, for example the heart. Our results confirm the hypothesis that the distribution of COX isoforms in healthy tissues is much more complex than generally believed. This and previous studies indicate that both isoforms, not only COX-1, are present in many normal human tissues, and that both isoforms, not only COX-2, are up-regulated in various pathological conditions. We may have to revise the concept of ‘constitutive’ and ‘inducible’ COX isoforms.

Microsomal Prostaglandin E 2 Synthase-1 Deletion Leads to Adverse Left Ventricular Remodeling After Myocardial Infarction

Background— Pharmacological inhibition of cyclooxygenase-2 increases the risk of myocardial infarction (MI) and stroke. Microsomal prostaglandin (PG) E 2 synthase-1 (mPGES-1), encoded by the Ptges gene, functions downstream from cyclooxygenase-2 in the inducible PGE 2 biosynthetic pathway. We caused acute MI in Ptges +/+ and Ptges −/− mice to define the role of mPGES-1 in cardiac ischemic injury.

Methods and Results— Twenty-eight days after MI, Ptges −/− mice develop more left ventricular (LV) dilation, have worse LV systolic and diastolic function, and have higher LV end-diastolic pressure than Ptges +/+ mice but have similar pulmonary wet-to-dry weight ratios, cardiac mass, infarct size, and mortality. The length-to-width ratio of individual cardiomyocytes is significantly greater in Ptges −/− than Ptges +/+ mice after MI, a finding consistent with eccentric cardiomyocyte hypertrophy in Ptges −/− mice. Expression of atrial natriuretic peptide, brain natriuretic peptide, and α- and β-myosin heavy chain, markers of ventricular hypertrophy, is higher in the LV of Ptges −/− than Ptges +/+ mice after MI. Ptges +/+ mice express cyclooxygenase-2 and mPGES-1 protein in inflammatory cells adjacent to the infarct after MI but do not express these proteins in cardiomyocytes. Ptges −/− mice express cyclooxygenase-2 in inflammatory cells adjacent to the infarct and do not express mPGES-1 in any cells in the heart. Levels of PGE 2 but not PGD 2 , thromboxane A 2 , PGI 2 , or PGF 2α are higher in the infarct and LV remote from the infarct after MI in Ptges +/+ than Ptges −/− mice.

Conclusions— In Ptges +/+ mice, mPGES-1 in inflammatory cells catalyzes PGE 2 biosynthesis in the LV after MI. Deletion of mPGES-1 leads to eccentric cardiac myocyte hypertrophy, LV dilation, and impaired LV contractile function after acute MI.

Conjugated linoleic acid isomers inhibit platelet-derived growth factor-induced NF-kappaB transactivation and collagen formation in human vascular smooth muscle cells

BACKGROUND

Atherosclerosis is characterized by extensive thickening of the arterial intima partially resulting from deposition of collagen by vascular smooth muscle cells (SMCs). Polyunsaturated fatty acids stimulate collagen formation through NF-kappaB activation.

AIM OF THE STUDY

The present study aimed to explore the effect of conjugated linoleic acids (CLAs) which are known to inhibit NF-kappaB activation on collagen formation by SMCs.

METHODS

Vascular SMCs were cultured with 50 micromol/l of CLA isomers (c9t11-CLA, t10c12-CLA) or linoleic acid (LA) and analysed for collagen formation and NF-kappaB p50 transactivation.

RESULTS

Treatment with CLA isomers but not LA significantly reduced PDGF-stimulated [(3)H] proline incorporation into cell layer protein of SMCs without altering cell proliferation. Simultaneous treatment with the PPARgamma inhibitor T0070907 abrogated this effect. Treatment of SMCs with c9t11-CLA and t10c12-CLA significantly reduced PDGF-induced NF-kappaB p50 activation.

CONCLUSIONS

CLA isomers inhibit PDGF-stimulated collagen production by vascular SMCs, which is considered to be a hallmark of atherosclerosis, in a PPARgamma-dependent manner. Whether inhibition of the NF-kappaB-pathway is of significance for the reduction of collagen formation by CLA isomers needs further investigation.

Reduced cardiac remodeling and function in cardiac-specific EP4 receptor knockout mice with myocardial infarction

We have shown previously that cyclooxygenase-2 inhibition reduces cardiac hypertrophy and fibrosis postmyocardial infarction (MI) in a mouse model and that prostaglandin E(2) stimulates cardiomyocyte hypertrophy in vitro through its EP(4) receptor. Because the role of cardiac myocyte EP(4) in cardiac function and hypertrophy in vivo is unknown, we generated mice lacking EP(4) only in cardiomyocytes (CM- EP(4) knockout [KO]). Twelve- to 14-week-old mice were evaluated using echocardiography and histology. There were no differences in ejection fraction, myocyte cross-sectional area, and interstitial collagen fraction between KO mice and littermate controls. To test the hypothesis that EP(4) is involved in cardiac remodeling after MI, we induced MI by ligating the left anterior descending coronary artery. Two weeks later, the mice were subjected to echocardiography, and hearts were removed for histology and Western blot. There was no difference in infarct size between KO mice and controls; however, KO mice showed less myocyte cross-sectional area and interstitial collagen fraction than controls. Also, CM-EP4 KO mice had reduced ejection fraction. Because the transcription factor Stat-3 is involved in hypertrophy and protection from ischemic injury, we tested whether it was activated in control and KO mouse hearts after MI. Western blot indicated that Stat-3 was activated in control hearts after MI but not in KO hearts. Thus, CM-EP4 deletion decreased hypertrophy, fibrosis, and activation of Stat-3. However, cardiac function was unexpectedly worsened in these mice. We conclude that cardiac myocyte EP(4) plays a role in hypertrophy via activation of Stat-3, a process that seems to be cardioprotective.

Protective effects of parecoxib, a cyclo-oxygenase-2 inhibitor, in postinfarction remodeling in the rat

OBJECTIVE

Selective cyclo-oxygenase-2 (COX-2) inhibitors have been shown to preserve hemodynamic performance in experimental models of acute myocardial infarction (AMI) in rodents. The impact of COX-2 inhibition on apoptosis, vascular density, and postinfarction remodeling has not yet been fully characterized. The aim of the present study was to evaluate the effects of parecoxib, a selective COX-2 inhibitor, in an experimental AMI model in the rat.

METHODS

Twenty-four male Wistar rats (10 weeks of age, weighing 350-500 g) underwent surgical left coronary artery ligation. Four animals died within 24 hours. Starting on day 2, 10 rats received parecoxib (0.75 mg/kg intraperitoneal) daily for 5 days and the remaining 10 received NaCl-0.9%. Animals underwent transthoracic echocardiography before surgery and 7 days later for the measurement of end-diastolic and end-systolic diameter and wall thickness; thereafter, animals were sacrificed and histological analysis was performed to evaluate cardiomyocyte apoptosis and small arteriolar density. Data are expressed as mean and standard error.

RESULTS

Three saline-treated (30%) and zero parecoxib-treated animals died before day 7. Compared with saline-treated animals, rats treated with parecoxib had a smaller end-diastolic diameter (6.3 +/- 0.1 vs. 7.0 +/- 0.1 mm, P = 0.018) and end-systolic diameter (2.7 +/- 0.1 vs. 3.9 +/- 0.1 mm, P = 0.027), and had a greater fractional shortening (57 +/- 1 vs. 45 +/- 2%, P = 0.050). Systolic thickness in the anterior (infarct) wall was also significantly greater in the parecoxib-treated animals (3.2 +/- 0.1 vs. 2.7 +/- 0.1 mm, P = 0.008), while the posterior wall was not significantly affected (P = 0.08). Aneurysmal dilatation of the left ventricle was more frequent in saline-treated versus parecoxib-treated animals (43 vs. 0%, P = 0.025). Parecoxib treatment was associated with lower apoptotic rates (1.0 +/- 0.2 vs. 4.0 +/- 0.4%, P < 0.001) and preservation of arteriolar density (20 +/- 5 vs. 8 +/- 2 mm/mm3, P = 0.018) in the peri-infarct area, without differences in circulating interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, and interferon-gamma levels.

CONCLUSION

Administration of parecoxib significantly ameliorates the remodeling process after AMI, possibly through prevention of apoptosis and preservation of myocardial vascularity. These findings aid in the understanding of the role of COX-2 in ischemic damage and remodeling.

Induction of cardiovascular pathology in a novel model of low-grade chronic inflammation

OBJECTIVE

Epidemiological and clinical evidence indicate that inflammatory processes play a pivotal role in a number of conditions associated with aging, including osteoporosis and cardiovascular diseases. The purpose of this study was to evaluate cardiovascular pathology and select inflammatory mediators of interest in a model of low-grade inflammation-induced osteopenia.

METHODS

Slow-release pellets were subcutaneously implanted in male rats to deliver 0, 3.3, or 33.3 microg of lipopolysaccharide (LPS)/day for 90 days. Tail blood was collected at 1, 2, and 3 months for differential white cell counts, and at the end of the study, hearts were harvested for histological and immunohistochemical evaluation.

RESULTS

The low-grade inflammatory response was characterized by elevated peripheral blood neutrophils and monocytes. Histological examination of heart cross sections revealed increased fibrous tissue, infiltration of lymphocytes, accumulation of mast cells, and roughened intimal borders within the arteries and arterioles, consistent with vascular disease. Inflammatory mediators (cyclooxygenase-2, tumor necrosis factor-alpha, and interleukin-1 beta) were up-regulated, and increased expression of platelet endothelial cell adhesion molecule-1 and receptor activator for NF-kappaB ligand was localized to the microvasculature endothelium.

CONCLUSIONS

These findings suggest that inflammation induced by chronic exposure to LPS produces cardiovascular pathology in the smaller intramural arteries and arterioles and support the utility of this model for further mechanistic and therapeutic studies focused on the role of chronic inflammation in cardiovascular disease.

Expression of cyclooxygenase-1 and cyclooxygenase-2 in the normal human heart and in myocardial infarction

INTRODUCTION

Cyclooxygenase is a key enzyme in prostanoid synthesis. It exists in two isoforms: cyclooxygenase-1 (COX-1), which is constitutively expressed in cells and tissues maintaining normal homeostasis, and cyclooxygenase-2 (COX-2), which is normally not present in most cells, but can be induced by various stimuli. Little is known about the significance of COX isoforms in the normal human heart and in myocardial infarction (MI). Thus, we aimed to investigate the immunohistochemical expression of COX-1 and COX-2 in the normal human heart and in MI.

METHODS

Our study included autopsy samples of heart tissue from 15 healthy individuals who died in accidents, and from 40 patients with MI who died few hours to a month after the onset of symptoms. Immunohistochemistry was performed by a sensitive peroxidase-streptavidin method on formalin fixed, paraffin-embedded tissue, using monoclonal antibodies against COX-1 and COX-2.

RESULTS

In normal hearts, COX-1 was found in endothelial and smooth muscle cells of blood vessels and in endothelial cells of the endocardium. In MI, it was expressed in inflammatory cells, as well as in myofibroblasts and capillaries of granulation and fibrous tissue. COX-2 was either not present or it was present in occasional myocytes in the normal hearts. In MI, its expression was induced in cardiomyocytes as well as in interstitial inflammatory cells, and in capillaries and myofibroblasts in granulation tissue.

CONCLUSIONS

Our results suggest that COX-1 is associated with normal homeostasis in the heart, whereas COX-2 probably mediates inflammatory reaction in MI. It appears that both COX-1 and COX-2 are associated with the healing processes and scar formation after MI.

Cyclooxygenase-2 inhibitor ameliorates ureteric damage in rats with obstructed uropathy

To investigate the effect of cyclooxygenase-2 (COX-2) inhibitor on the tissue damage and fibrosis in obstructed ureters, 80 rats were studied. Celecoxib, a COX-2 inhibitor, was administered to 40 rats at the dose of 10 mg/kg per day 1 day before unilateral ligation of ureters and every day thereafter. The others, receiving unilateral ligation of ureters only, served as controls. Eight rats from each group were sacrificed for examination on days 7, 14, 21, 28 and 42 after ligation, respectively. The expressions of COX-2, prostaglandin E(2) (PGE(2)), transforming growth factor-beta(1) (TGFbeta(1)), alpha-smooth muscle actin (alpha-SMA), proliferation cell nuclear antigen (PCNA) and the apoptotic cells in the ureteric smooth muscle were examined. Hydroureter and fibrosis of the muscle layer became progressively aggravated during the period of obstruction in the ligated ureters of both groups. The severity of the hydroureter and fibrosis of muscle layer in the ligated ureters of the treated group was significantly milder than those of the control group. Expressions of COX-2 and PGE(2) were found in the smooth muscle layer of ligated ureters in the control group from day 14 after ureteric ligation, reached a peak on day 21, and then declined. Treatment with Celecoxib completely abolished the expression of COX-2 and PGE(2). The Celecoxib administration also decreased the expression of TGFbeta(1), alpha-SMA and the labeling index of apoptotic cells in the smooth muscle layer of ligated ureters in the treated group. In the contrast, treatment with Celecoxib significantly increased the expression of PCNA in the smooth muscle layer of ligated ureters in the treated group. We concluded that COX-2 inhibitor might ameliorate the damage of obstructed ureters, at least partly, via the inhibition of COX-2 and TGFbeta(1) expression.

Improvement of cardiac function with parecoxib, a cyclo-oxygenase-2 inhibitor, in a rat model of ischemic heart failure

OBJECTIVE

To assess changes in cardiac function in animals with ischemic congestive heart failure (CHF) treated with a selective cyclo-oxygenase-2 (COX-2) inhibitor.

BACKGROUND

In patients with CHF, COX-2 expression was associated with features of worsening failure. However, evidence of beneficial or detrimental functional effects of COX-2 inhibition in ischemic CHF is lacking.

METHODS

Thirty male Wistar rats underwent coronary ligation and were allowed to recover for 12 months. Five sham-operated animals were used as controls. After 12 months, six surviving animals underwent baseline echocardiogram to measure end-diastolic diameter (EDD), end-systolic diameters (ESD), fractional shortening (FS), and anterior and posterior diastolic and systolic wall thicknesses. The animals were thereafter treated by daily intraperitoneal parecoxib injections (0.75 mg/kg) for 7 days. On day 7, a repeat echocardiogram was performed.

RESULTS

When compared to baseline, repeat echocardiography after 7 days of parecoxib treatment showed no changes in the EDD (9.4 +/- 0.4 mm vs. 9.4 +/- 0.3 mm, P = 0.9), a significant reduction of ESD (5.5 +/- 0.8 mm vs. 6.4 +/- 0.3 mm, P = 0.028), and a significant improvement in the FS (43 +/- 3% vs. 32 +/- 5%, P = 0.027). Improvement of FS was associated with a significant change in systolic thickness in the infarct zone (3.6 +/- 0.4 mm vs. 3.0 +/- 0.1 mm, P = 0.046), whereas no significant changes in systolic thickness in the remote area were observed.

CONCLUSIONS

Administration of parecoxib in ischemic CHF provides functional improvement of the peri-infarct myocardium. This finding may prove useful in improving quality of life and, perhaps, survival in patients with ischemic heart disease.

Granulocyte colony-stimulating factor improves left ventricular function of doxorubicin-induced cardiomyopathy

It is not well-known yet how granulocyte colony-stimulating factor (G-CSF) affects nonischemic cardiomyopathy, though its beneficial effects on acute myocardial infarction are well-established. We hypothesize that G-CSF beneficially might affect nonischemic cardiomyopathy through the direct cardioprotective effects. Here, we show that a single injection of doxorubicin (DOX, 15 mg/kg) induced left ventricular dilatation and dysfunction in mice within 2 weeks, and that these effects were significantly attenuated by human recombinant G-CSF (100 microg/kg/day for 5 days). G-CSF also protected hearts against DOX-induced cardiomyocyte atrophy/degeneration, fibrosis, inflammatory cell infiltration and down regulation of GATA-4 and sarcomeric proteins, myosin heavy chain, troponin I and desmin, both in vivo and in vitro. Cardiac cyclooxygenase-2 was upregulated and G-CSF receptor was downregulated in DOX-induced cardiomyopathy, but both of those effects were largely reversed by G-CSF. No DOX-induced apoptotic effects were seen, nor were there any changes in tumor necrosis factor-alpha or transforming growth factor-beta1 levels. Among downstream mediators of G-CSF receptor signaling, DOX-induced cardiomyopathy involved inactivation of extracellular signal-regulated protein kinase (ERK); the ERK inactivation was reversed by G-CSF. Inhibition of ERK activation, but not cyclooxygenase-2 inhibition, completely abolished beneficial effect of G-CSF on cardiac function. G-CSF did not promote differentiation of bone marrow cells into cardiomyocytes according to the experiment using green fluorescent protein-chimeric mice, and inhibition of CXCR4+ cell homing using AMD3100 did not diminish the effect of G-CSF. Finally, G-CSF was also effective when administered after cardiomyopathy was established. In conclusion, these findings imply the therapeutic usefulness of G-CSF mainly through restoring ERK activation against DOX-induced nonischemic cardiomyopathy.

Downregulation of NADPH oxidase, antioxidant enzymes, and inflammatory markers in the heart of streptozotocin-induced diabetic rats by N-acetyl-l-cysteine

We investigated the effect of N-acetyl-l-cysteine (NAC) on the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, antioxidant enzymes, and inflammatory markers in diabetic rat hearts. Metabolic parameters, free 15-F2t-isoprostane level, protein expression of NADPH oxidase, superoxide dismutase (SOD), heme oxygenase (HO-1), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2) were analyzed in control and streptozotocin-induced diabetic rats treated with or without NAC in drinking water for 8 wk. The cardiac protein expression of p67phox and p22phox was increased in diabetic rats, accompanied by increased NADPH-dependent superoxide production. As a compensatory response to the increased NADPH oxidase, the protein expression of Cu-Zn-SOD and HO-1 and the total SOD activity were also increased in diabetic rat hearts. Consequently, cardiac free 15-F2t-isoprostane, an index of oxidative stress, was increased in diabetic rats, indicating that the production of reactive oxygen species becomes excessive in diabetic rat hearts. Cardiac inflammatory markers IL-6 and COX-2 were also increased in diabetic rats. NAC treatment prevented the increased expression of p22phox and translocation of p67phox to the membrane in diabetic rat hearts. Subsequently, the levels of cardiac free 15-F2t-isoprostane, HO-1, Cu-Zn-SOD, total SOD, IL-6, and COX-2 in diabetic rats were decreased by NAC. Consequently, cardiac hypertrophy was attenuated in diabetic rats treated with NAC. The protective effects of NAC on diabetic rat hearts may be attributable to its protection of hearts against oxidative damage induced by the increased NADPH oxidase and to its reduction in cardiac inflammatory mediators IL-6 and COX-2.

Developing Strategies to Link Basic Cardiovascular Sciences with Clinical Drug Development: Another Opportunity for Translational Sciences

Driven, at least in part, by the National Institutes of Health roadmap, an increasing number of studies has bridged the chasm between observations in the basic research laboratory and the clinical bedside. These studies have been an integral part in "translating" new discoveries into therapeutic initiatives. However, "translational medicine" has been used less frequently in the development of cardiovascular drugs or in predicting the potential cardiovascular toxicity of non-cardiac agents. Studies in animal models can provide important clues as to the potential cardiotoxicity of new therapeutic agents, as well as providing a template for the rational design of clinical trials. Three examples of drug development programs that might have been altered by clues available from laboratory studies include the development programs for the anti-cancer drug trastuzumab, the cyclooxygenase inhibitors, and the adenosine-receptor agonists and antagonists. Although mouse models may not always represent the physiology of humans, they provide important information that clinical scientists can utilize in designing safe programs for the evaluation of new pharmacologic agents.

Ischemic preconditioning via epsilon protein kinase C activation requires cyclooxygenase-2 activation in vitro

The signaling pathway of cyclooxygenase-2 (COX-2) induction following ischemic preconditioning (IPC) in brain remains undefined. To determine role of COX-2 in ischemic preconditioning, we used two in vitro models: mixed cortical neuron/astrocyte cell cultures and organotypic hippocampal slice cultures. We simulated IPC by exposing cell or slice cultures to 1 h or 15 min of oxygen/glucose deprivation (OGD), respectively, 48 h prior to ischemia. To mimic ischemia in vitro, we exposed cell or slice cultures to OGD of 4 h or 40 min, respectively. In cell cultures, these experiments revealed that COX-2 induction peaked at 24 h following IPC in cell culture. Inhibition of COX-2 activation with 50 microM NS-398 (a COX-2 selective inhibitor) abolished IPC-mediated neuroprotection in both in vitro models. Next, we tested whether epsilon protein kinase C (epsilonPKC) and extracellular signal regulated kinase 1/2 (ERK1/2) activation was involved in IPC-mediated neuroprotection and COX-2 expression in cell culture. Cell cultures were treated with an epsilonPKC-specific activating peptide (psiepsilonRACK, 100 nM) for 1 h, and 48 h later were exposed to OGD. epsilonPKC activation increased ERK1/2 phosphorylation and COX-2 induction and conferred neuroprotection similar to IPC. Additionally, inhibition of either epsilonPKC or ERK1/2 activation abolished COX-2 expression and neuroprotection due to ischemic preconditioning. These results demonstrate a crucial role for the epsilonPKC-->ERK1/2-->COX-2 pathway in the induction of neuroprotection via ischemic preconditioning.

Cyclooxygenase-2 Inhibition Increases Mortality, Enhances Left Ventricular Remodeling, and Impairs Systolic Function After Myocardial Infarction in the Pig

BACKGROUND

Cyclooxygenase (COX)-2 expression in the heart increases after myocardial infarction (MI). In murine models of MI, COX-2 inhibition preserves left ventricular dimensions and function. We studied the effect of selective COX-2 inhibition on left ventricular remodeling and function after MI in a pig model.

METHODS AND RESULTS

Twenty-two pigs were assigned to COX-2 inhibition with a COX-2 inhibitor (COX-2i; celecoxib 400 mg twice daily; n=14) or a control group (n=8). MI was induced by left circumflex coronary artery ligation, and the animals were euthanized 6 weeks later. Cardiac dimensions and function were assessed with echocardiography and conductance catheters. Infarct size and collagen density were analyzed with triphenyltetrazolium chloride staining and picrosirius red staining, respectively. COX-2 inhibition increased mortality compared with controls (50% versus 0%, P=0.022), whereas infarct size was similar (13.1+/-0.7% versus 14.1+/-0.1%, P=0.536). The decrease in thickness of the infarcted myocardial wall was more pronounced in the COX-2i group (60.6+/-9.6% versus 36.2+/-5.7%, P=0.001). End-diastolic volume was higher in the COX-2i group (133.9+/-33.5 versus 91.1+/-24.0 mL; P=0.021), as was the end-systolic volume at 100 mm Hg (81.7+/-27.8 versus 56.3+/-21.1 mL; P=0.037), which indicates that systolic function was more severely impaired. Infarct collagen density was lower after COX-2i treatment (25.3+/-3.9 versus 56.1+/-23.8 gray value/mm2; P=0.005).

CONCLUSIONS

In pigs, COX-2 inhibition after MI is associated with increased mortality, enhanced left ventricular remodeling, and impaired systolic function, probably due to decreased infarct collagen fiber density.

Roles of cyclooxygenase-2 and phosphorylated Akt (Thr308) in cardiac hypertrophy regression mediated by left-ventricular unloading

OBJECTIVES

Cyclooxygenase-2 is associated with cardiac hypertrophy during chronic heart failure and is regulated through the PI3K/Akt pathway. Cyclooxygenase-2-induced cell growth through Akt phosphorylation was demonstrated in vitro. In chronic heart failure, left ventricular assist devices lead to hypertrophy regression and molecular changes. Therefore, the expression of cyclooxygenase-2, phosphorylated Akt (p-Akt), and p-Erk 1/2, as well as cardiac hypertrophy before and after left ventricular assist device insertion, was investigated.

METHODS

In myocardial tissue before and after left ventricular assist device insertion, the expression of cyclooxygenase-2, p-Akt (Thr308), p-Akt (Ser473), and p-Erk 1/2 was demonstrated by immunohistochemistry and quantified by morphometry. Colocalization of cyclooxygenase-2 and p-Akt (Thr308) was investigated by immuno-doublestaining.

RESULTS

A significant decrease of cyclooxygenase-2, p-Akt (Thr308), p-Akt (Ser473), and p-Erk 1/2 protein expression and hypertrophy regression was observed after left ventricular assist device insertion. A significant correlation between cyclooxygenase-2 and p-Akt (Thr308) expression, as well as between cyclooxygenase-2 expression and cardiomyocyte diameter, was observed before, but not after, left ventricular assist device insertion. Only cyclooxygenase-2-positive cardiomyocytes showed significant hypertrophy regression on unloading. Sarcoplasmic colocalization of cyclooxygenase-2 and p-Akt (Thr308) is present before left ventricular assist device insertion and is decreased after unloading, whereas the normal myocardium is completely devoid of it.

CONCLUSIONS

Left ventricular assist device treatment is associated with a significant decrease of cyclooxygenase-2, p-Akt (Thr308), p-Akt (Ser473), and p-Erk 1/2, and cardiac hypertrophy regression of cyclooxygenase-2-positive cardiomyocytes. The significant correlation and colocalization in cardiomyocytes of cyclooxygenase-2 and p-Akt (Thr308) before left ventricular assist device insertion suggests a cross-talk between the 2 molecules in the progression of cardiac hypertrophy, which is reversibly regulated by the left ventricular assist device.

Infiltration of inflammatory cells plays an important role in matrix metalloproteinase expression and activation in the heart during sepsis

Septicemia is an emerging pathological condition involving, among other effects, refractory hypotension and heart dysfunction. Here we have investigated the contribution of resident nonmyocytic cells to heart alterations after lipopolysaccharide administration. These cells contributed to the rapid infiltration of additional inflammatory cells that enhance the onset of heart disease through the release of inflammatory mediators. Early activation of resident monocytic cells played a relevant role on the infiltration process, mainly of major histocompatibility complex class II- and CD11b-positive cells. This infiltration was significantly impaired in animals lacking the nitric-oxide synthase-2 (NOS-2) gene or after pharmacological in-hibition of NOS-2 or cylooxygenase-2, suggesting a significant contribution of nitric oxide and prostanoids to the infiltration process. Under these conditions, the expression of NOS-2 and cylooxygenase-2 in the whole organ was attenuated because cardiomyocytes failed to express these enzymes. However, cardiomyocytes expressed and activated matrix metalloproteinase-9 through mechanisms regulated, at least in part, by nitric oxide and prostaglandins in an additive way. These results directly link the inflammatory response in the heart and extracellular matrix remodeling by the matrix metalloproteinases released by the cardiomyocytes, suggesting that activation and recruitment of inflammatory cells to the heart is a major early event in cardiac dysfunction promoted by septicemia.

Role of the cyclooxygenase pathway in the protection against postischemic stunning in conscious sheep

OBJECTIVE

There are controversial reports in conscious animals regarding the role of cyclooxygenase-2 in late preconditioning (LP). This study analyzed the effect of COX-2 involvement in non-preconditioned hearts (NP) and in mediation of LP protection against stunning in conscious sheep submitted to a prolonged reversible ischemia.

METHODS

Six groups were considered: NP: 12 min ischemia and 120 min reperfusion; LP consisting of six periods of 5 min-ischemia-5 min reperfusion 24 h before the 12 min ischemia; NP and LP with either the non-selective COX-1 and COX-2 inhibitor, aspirin (20 mg/kg), or the specific COX-2 inhibitor, celecoxib (3 mg/kg) before the 12 min ischemic period.

RESULTS

Mean postischemic wall thickening fraction (as % of preischemic values) improved from 49.6 +/- 4.0% in NP to 72.5 +/- 3.5% in LP (p < 0.01) and a similar protection was obtained with aspirin and celecoxib in NP hearts (p < 0.01). Neither aspirin nor celecoxib administration prior to the prolonged ischemia on day 2 abrogated LP improvement of postischemic dysfunction. Moreover, LP with aspirin improved the protective response (80.7 +/- 2.6%) over that obtained with aspirin in NP hearts (66.6 +/- 4.7%, p < 0.05). This effect was not obtained with celecoxib.

CONCLUSIONS

Aspirin and celecoxib showed that COX-2 has a detrimental effect on mechanical cardioprotection in NP hearts of conscious sheep submitted to a prolonged reversible ischemia, and does not seem to participate as mediator of LP. Aspirin revealed a similar COX-1 deleterious action, since only when both COX-1 and COX-2 were inhibited, LP was put in evidence adding functional improvement over that obtained in NP hearts treated with aspirin.

THE RESPONSE OF NEONATAL RAT VENTRICULAR MYOCYTES TO LIPOPOLYSACCHARIDE-INDUCED STRESS

Sepsis induced by exposure to lipopolysaccharide (LPS) can be life-threatening and lead to multiple-organ dysfunction. Sepsis-associated cardiac dysfunction is a primary cause of mortality. The response of isolated cardiac myocytes to LPS exposure is poorly understood. Cultured neonatal rat ventricular cardiomyocytes were used to evaluate the response to LPS exposure. Other authors have reported that LPS exposure at doses sufficient to induce tumor necrosis factor alpha (TNF-alpha) production and apoptosis in adult cardiomyocytes do not induce apoptosis in neonatal cardiomyocytes. We therefore hypothesized that neonatal cardiomyocytes have innate protective mechanisms that protect from septic damage. Cultured neonatal rat ventricular cardiomyocytes were stimulated by exposure to LPS for varying lengths of time. NFkappaB signaling pathways, TNF-alpha production, and Akt activation were monitored. We also assessed the induction of apoptosis in these cells by monitoring caspase-3 activity. LPS rapidly stimulates nuclear translocation of NFkappaB and Akt activation. TNF-alpha production is also stimulated. However, high doses of LPS are unable to induce apoptosis in these cells, and protection is not a function of Akt activation. LPS treatment also stimulated the levels of cyclooxygenase-2 and the production of downstream metabolites, specifically PGE2 and 15deoxyDelta12-14PGJ2 (15dPGJ2). Specific inhibition of cyclooxygenase-2 activity induced apoptosis in the presence of LPS, whereas direct exposure to 15dPGJ2 at pharmacological levels induced apoptosis. Neonatal rat ventricular cardiomyocytes have innate protective mechanisms that prevent apoptotic cell death after LPS exposure. Metabolic products of arachidonic acid metabolized by the cyclooxygenase pathway can be potentially apoptotic or antiapoptotic. The balance of these products within these cells may define the cellular response to LPS exposure.

Disruption of COX-2 modulates gene expression and the cardiac injury response to doxorubicin

To determine the role of cyclooxygenase (COX)-2 in anthracycline-induced cardiac toxicity, we administered doxorubicin (Dox) to mice with genetic disruption of COX-2 (COX-2-/-). After treatment with Dox, COX-2-/- mice had increased cardiac dysfunction and cardiac cell apoptosis compared with Dox-treated wild-type mice. The expression of the death-associated protein kinase-related apoptosis-inducing protein kinase-2 was also increased in Dox-treated COX-2-/- animals. The altered gene expression, cardiac injury, and dysfunction after Dox treatment in COX-2-/- mice was attenuated by a stable prostacyclin analog, iloprost. Wild-type mice treated with Dox developed cardiac fibrosis that was absent in COX-2-/- mice and unaffected by iloprost. These results suggest that genetic disruption of COX-2 increases the cardiac dysfunction after treatment with Dox by an increase in cardiac cell apoptosis. This Dox-induced cardiotoxicity in COX-2-/- mice was attenuated by a prostacyclin analog, suggesting a protective role for prostaglandins in this setting.

PGE2 stimulates human brain natriuretic peptide expression via EP4 and p42/44 MAPK

Brain natriuretic peptide (BNP) produced by cardiac myocytes has antifibrotic and antigrowth properties and is a marker of cardiac hypertrophy. We previously showed that prostaglandin E2 (PGE2) is the main prostaglandin produced in myocytes treated with proinflammatory stimuli and stimulates protein synthesis by binding to its EP4 receptor. We hypothesized that PGE2, acting through EP4, also regulates BNP gene expression. We transfected neonatal ventricular myocytes with a plasmid encoding the human BNP (hBNP) promoter driving expression of a luciferase reporter gene. PGE2 increased hBNP promoter activity 3.5-fold. An EP4 antagonist reduced the stimulatory effect of PGE2 but not an EP1 antagonist. Because EP4 signaling can involve adenylate cyclase, cAMP, and protein kinase A (PKA), we tested the effect of H-89, a PKA inhibitor, on PGE2 stimulation of the hBNP promoter. H-89 at 5 muM decreased PGE2 stimulation of BNP promoter activity by 100%. Because p42/44 MAPK mediates the effect of PGE2 on protein synthesis, we also examined the role of MAPKs in the regulation of BNP promoter activity. PGE2 stimulation of the hBNP promoter was inhibited by a MEK1/2 inhibitor and a dominant-negative mutant of Raf, indicating that p42/44 MAPK was involved. In contrast, neither a p38 MAPK inhibitor nor a JNK inhibitor reduced the stimulatory effect of PGE2. Involvement of small GTPases was also studied. Dominant-negative Rap inhibited PGE2 stimulation of the hBNP promoter, but dominant-negative Ras did not. We concluded that PGE2 stimulates the BNP promoter mainly via EP4, PKA, Rap, and p42/44 MAPK.

Inhibition of cyclooxygenase-2 enhances myocardial damage in a mouse model of viral myocarditis

To determine critical role of cyclooxygenase-2 (COX-2) for development of viral myocarditis, a mouse model of encephalomyocarditis virus-induced myocarditis was used. The virus was intraperitoneally given to COX-2 gene-deficient heterozygote mice (COX-2+/-) and wild-type mice (WT). We examined differences in heart weights, cardiac histological scores, numbers of infiltrating or apoptotic cells in myocardium, cardiac expression levels of COX-2, tumor necrosis factor-alpha (TNF-alpha), and adiponectin mRNA, immunoreactivity of COX-2, TNF-alpha, and adiponectin in myocytes, cardiac concentrations of TNF-alpha and adiponectin, prostaglandin E2 (PGE2) levels in hearts, and viral titers in tissues between COX-2+/- and WT. We observed significantly decreased expression of COX-2 mRNA and reactivity in hearts from COX-2+/- on day 8 after viral inoculation as compared with that from WT, together with elevated cardiac weights and severe inflammatory myocardial damage in COX-2+/-. Cardiac expression of TNF-alpha mRNA, reactivity, and protein on day 8 was significantly higher in COX-2+/- than in WT, together with reciprocal expression of adiponectin mRNA, reactivity, and protein in hearts. Significantly reduced cardiac PGE2 levels on day 8 were found in COX-2+/- compared with those in WT. There was no difference in local viral titers between both groups on day 4. Infected WT treated with a selective COX-2 inhibitor, NS-398, also showed the augmented myocardial damage on day 8. These results suggest that inhibition of COX-2 may enhance myocardial damage through reciprocal cardiac expression of TNF-alpha and adiponectin in a mouse model of viral myocarditis.

PGE2-induced hypertrophy of cardiac myocytes involves EP4 receptor-dependent activation of p42/44 MAPK and EGFR transactivation

Upon induction of cyclooxygenase-2 (COX-2), neonatal ventricular myocytes (VMs) mainly synthesize prostaglandin E2 (PGE2). The biological effects of PGE2 are mediated through four different G protein-coupled receptor (GPCR) subtypes (EP1–4). We have previously shown that PGE2 stimulates cAMP production and induces hypertrophy of VMs. Because the EP4 receptor is coupled to adenylate cyclase and increases in cAMP, we hypothesized that PGE2 induces hypertrophic growth of cardiac myocytes through a signaling cascade that involves EP4-cAMP and activation of protein kinase A (PKA). To test this, we used primary cultures of VMs and measured [3H]leucine incorporation into total protein. An EP4 antagonist was able to partially block PGE2 induction of protein synthesis and prevent PGE2-dependent increases in cell surface area and activity of the atrial natriuretic factor promoter, which are two other indicators of hypertrophic growth. Surprisingly, a PKA inhibitor had no effect. In other cell types, G protein-coupled receptor activation has been shown to transactivate the epidermal growth factor receptor (EGFR) and result in p42/44 mitogen-activated protein kinase (MAPK) activation and cell growth. Immunoprecipitation of myocyte lysates demonstrated that the EGFR was rapidly phosphorylated by PGE2 in VMs, and the EP4 antagonist blocked this. In addition, the selective EGFR inhibitor AG-1478 completely blocked PGE2-induced protein synthesis. We also found that PGE2 rapidly phosphorylated p42/44 MAPK, which was inhibited by the EP4 antagonist and by AG-1478. Finally, the p42/44 MAPK inhibitor PD-98053 (25 μmol/l) blocked PGE2-induced protein synthesis. Altogether, we believe these are the first data to suggest that PGE2 induces protein synthesis in cardiac myocytes in part via activation of the EP4 receptor and subsequent activation of p42/44 MAPK. Activation of p42/44 MAPK is independent of the common cAMP-PKA pathway and involves EP4-dependent transactivation of EGFR.

Influence of scanning frequency and ultrasonic contrast agent on reproducibility of left ventricular measurements in the mouse

BACKGROUND

Mice are now widely used as models of cardiovascular disease. Their small size and fast heart rates are technically challenging to echocardiography. This study examined the influence of different scanning frequencies and ultrasonic contrast agent (UCA) on the accuracy and reproducibility of measurements of left ventricular (LV) structure and function.

METHODS

Normal mouse hearts (C57BL6) were imaged at 3 different scanning frequencies before and after intravenous injection of the UCA, Optison. Coronary artery ligation mice and sham-operated controls were scanned at 10-22 MHz with and without UCA.

RESULTS

Scanning frequency had no significant effect on intraobserver or interobserver variation of LV measurements in normal mice under baseline conditions. Use of UCA significantly reduced estimated ejection fraction at 10-22 MHz compared with baseline (baseline 50.8 +/- 7.6% vs UCA 39.7 +/- 7.6%; P = .03) and significantly increased values for LV cavity dimensions (eg, LV area diastole 20.74 +/- 1.20 vs 23.23 +/- 0.98 mm 2 ; P = .002). UCA significantly reduced intraobserver and interobserver variation in LV ejection fraction.

CONCLUSIONS

Scanning frequency had no significant effect on reproducibility of LV measurements in the mouse but UCA significantly reduced interobserver variation. Use of UCA could reduce the number of mice required in any given experiment to observe a statistically significant change in LV function.

Regulation of the membrane-localized prostaglandin E synthases mPGES-1 and mPGES-2 in cardiac myocytes and fibroblasts

The proinflammatory mediator cyclooxygenase (COX)-2 and its product PGE2 are induced in the ischemic heart, contributing to inflammatory cell infiltration, fibroblast proliferation, and cardiac hypertrophy. PGE2 synthesis coupled to COX-2 involves two membrane-localized PGE synthases, mPGES-1 and mPGES-2; however, it is not clear how these synthases are regulated in cardiac myocytes and fibroblasts. To study this, we used primary cultures of neonatal ventricular myocytes (VM) and fibroblasts (VF) treated with IL-1β for 24 h. To test for involvement of MAPKs in IL-1β regulation of mPGES-1 and-2, cells were pretreated with the pharmacological inhibitors of p42/44 MAPK, p38 MAPK, and c-Jun kinase (JNK). mRNA was analyzed by RT-PCR. Protein was analyzed by densitometry of Western blots. mPGES-1 was undetectable in untreated VF but induced by IL-1β; inhibition of either p42/44 MAPK or JNK, but not p38 MAPK, was almost completely inhibitory. In VM, inhibition of the three MAPKs reduced IL-1β-stimulated mPGES-1 protein by 70–90%. mPGES-2 was constitutively synthesized in both VM and VF and was not regulated by IL-1β or MAPKs. Confocal microscopy revealed colocalization of both mPGES-1 and mPGES-2 with COX-2 in the perinuclear area of both VF and VM. Finally, PGE2 production was higher in VM than VF. Our data show that 1) mPGES-1 is induced in both VF and VM, 2) regulation of mPGES-1 by MAPK family members is different in the two cell types, 3) mPGES-2 is constitutively synthesized in both VM and VF and is not regulated, and 4) mPGES-1 and mPGES-2 are colocalized with COX-2 in both cells. Thus differences in activity of mPGES-1 and COX-2 or coupling of COX-2 with mPGES-1 may contribute to differences in PGE2 production by myocytes and fibroblasts.