The Role of Lipoprotein-Associated Phospholipase A<Subscript>2</Subscript> as a Marker and Potential Therapeutic Target in Atherosclerosis

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is an enzyme that generates inflammatory mediators within atherosclerotic plaques. In epidemiologic studies there is an association between higher plasma Lp-PLA₂ activity and myocardial infarction, stroke and cardiovascular mortality. In animal models, darapladib, a specific inhibitor of Lp-PLA_2, decreases the size of the atheroma necrotic core and plaques with thin fibrous caps. Early clinical trials suggest darapladib effectively and safely inhibits Lp-PLA₂ activity both in plasma and in carotid atheroma. Two large phase III clinical trials that are currently in progress will determine whether darapladib will reduce the risk of myocardial infarction, stroke, and cardiovascular death by stabilizing atherosclerotic plaques.     

Lipoprotein-Associated Phospholipase A<Subscript>2</Subscript> and C-Reactive Protein for Measurement of Inflammatory Risk: Independent or Complementary?

The purpose of this article is to review the evidence concerning the utility of lipoprotein-associated phospholipase A₂ (Lp-PLA₂), a key promoter of vascular inflammation, as a biomarker of future risk of cardiovascular disease. In addition, the evidence of complementary action of Lp-PLA₂ and C-reactive protein (CRP) is evaluated. On balance, there is a great deal of consistency across studies supporting Lp-PLA₂ as a risk factor for coronary disease and ischemic stroke (independently of traditional risk factors and CRP) among persons with and without clinical coronary artery disease. On the other hand, there is yet limited and inconsistent evidence for a synergistic effect of Lp-PLA₂ and CRP on cardiovascular disease risk. Additional studies are thus needed before widespread Lp-PLA₂ and CRP testing with regard to incremental cardiovascular disease risk prediction can be recommended.     

Thromboxane A<Subscript>2</Subscript> Inhibition

Bronchial asthma is a disease defined by reversible airway obstruction, bronchial hyperresponsiveness and inflammation. In addition to histamine and acetylcholine, recent studies have emphasized the role of arachidonic acid metabolites (leukotrienes, prostaglandins and thromboxane A₂) in the pathogenesis of asthma. Among these mediators, thromboxane A₂ (TXA₂) has attracted attention as an important mediator in the pathophysiology of asthma because of its potent bronchoconstrictive activity. Thromboxane A₂ is believed to be involved not only in late asthmatic responses but also in bronchial hyperresponsiveness, a typical feature of asthma.Strategies for inhibition of TXA₂ include TXA₂ receptor antagonism and thromboxane synthase inhibition. Results of double-blind, placebo-controlled clinical trials have proven the efficacies of the thromboxane receptor antagonist seratrodast and the thromboxane synthase inhibitor ozagrel in the treatment of patients with asthma. Seratrodast and ozagrel are available in Japan for the treatment of asthma. Ramatroban, another thromboxane receptor antagonist, is currently under phase III clinical evaluation in Europe and Japan for the treatment of asthma.The pharmacological profiles of the thromboxane modulators may be improved by combination with leukotriene D₄ receptor antagonists. A multi-pathway inhibitory agent such as YM 158, which is a novel orally active dual antagonist for leukotriene D₄ and thromboxane A₂ receptors, may have potent therapeutic effects in the treatment of bronchial asthma. Large scale clinical trials are necessary to further define the role of thromboxane modulators in the treatment of patients with asthma.     

Lipoprotein Associated Phospholipase A<Subscript>2</Subscript> Inhibition Reduces Generation of Oxidized Fatty Acids

Purpose Lipoprotein associated phospholipase A₂ (Lp-PLA₂) is an emerging cardiovascular risk marker. After low-density lipoprotein (LDL) oxidation, Lp-PLA₂ generates oxidized nonesterified fatty acids and lysophosphatidylcholine, both of which have demonstrated proinflammatory and proapoptotic activities. Through the use of a selective inhibitor of Lp-PLA₂ (SB-677116), we investigated whether Lp-PLA₂ participates in the ex vivo generation of oxidized fatty acids (ox-FA). Methods Due to the higher correlation between Lp-PLA₂ activity and small LDL particles, we investigated the effects of a selective Lp-PLA₂ inhibition on production of ox-FA in metabolic syndrome subjects with small LDL size <20.5 nm. Whole blood samples were incubated with vehicle (0 μM) or SB-677116 for 6 h at two different concentrations (0.3, 3.0 μM) to determine the effects of inhibitor on Lp-PLA₂ activity, the formation of oxidized esterified and nonesterified hydroxy-fatty acid (OH-FA) or ox-FA in 24 subjects. Results Whole blood incubation with Lp-PLA₂ inhibitor (0.3, 3.0 μM) reduced multiple C-18 OH-FA subclasses (p < 0.05 versus control). For the highly redox-sensitive 9-OH-FA, there was a concentration-dependent reduction in Lp-PLA₂ activity and 9-OH-FA (p _trend = 0.0016) Conclusions In conclusion, selective inhibition of Lp-PLA₂ reduced levels of OH-FA generated in whole blood of metabolic syndrome patients. These novel findings suggest that Lp-PLA₂ inhibition may attenuate some noxious downstream effects of lipid peroxidation that potentially include inflammatory responses. Dr. Rosenson has stock ownership in LipoScience and he serves as a Consultant to LipoScience.     

Anthracycline-induced phospholipase A<Subscript>2</Subscript> inhibition

The purpose of this essay is to overview our findings that membrane-associated calcium-independent phospholipase A₂ is markedly inhibited by low, clinically relevant concentrations of anthracyclines. Our studies suggest that due to the essential role of this enzyme in membrane homeostasis, its inhibition can be one of the early culprits leading to anthracycline-induced cardiac dysfunction. The clinical importance and potential pharmaceutical use of this new phenomenon await further studies.     

Molecular basis of the A<Subscript>2</Subscript>B in Taiwan

Molecular genotyping of the ABO alleles has been widely used in ABO subgroups analysis and has been able to solve the rare ABO blood grouping discrepancies. The genotypes of sixty-one A(2)B phenotype donors recruited from the middle and south of Taiwan were analyzed by means of molecular methods. The A(2)B phenotype was initially identified by serological test. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to screen the ABO alleles at nucleotides (nt) 261 and 703 based on the nt differences found in the ABO alleles. The subgroups of the A(2) allele were determined by the PCR-RFLP and direct sequencing methods. The discrepancies between the phenotype and genotype of the A(2)B were then studied by subcloning and nucleotide sequence analysis. Our results show that 55 of the 61 A(2)B donors (90%) are A205/B allele and two are A201/B allele. Four cases were heterozygotes of the cis-AB/O or B alleles. Two were cis-AB04/O allele, one was cis-AB01/O allele and the other was cis-AB02/B allele. In conclusion, most A(2)B genotypes belong to the A205/B allele in Taiwan. In this study, we report for the first time the presence of the A205, A201, and cis-AB02 alleles in Taiwan.     

Ankylosing spondylitis monocyte-derived macrophages express increased level of A<Subscript>2A</Subscript> adenosine receptor and decreased level of ectonucleoside triphosphate diphosphohydrolase-1 (CD39), A<Subscript>1</Subscript> and A<Subscript>2B</Subscript> adenosine receptors

Macrophages play an important role in the ankylosing spondylitis (AS) auto-inflammatory responses and fibrocartilage destruction. Adenosine is a key modulator of inflammatory conditions. The various effects of adenosine are mediated by its interaction with adenosine receptors (AR). In this study, we investigated the mRNA expression of A₁, A_2A, A_2B, and A₃ adenosine receptors, ectonucleoside triphosphate diphosphohydrolase-1 (CD39), and ecto-5′-nucleotidase (CD73) in the monocyte-derived macrophages from AS patients in comparison to healthy controls. We also explored the correlation between analyzed gene expression and patients’ clinical manifestations. Whole blood-separated monocytes from 23 healthy controls and 23 active AS patients were stimulated by macrophage colony-stimulating factor (M-CSF) for 7 days and differentiated to macrophages. Monocyte and macrophage markers were analyzed by flow cytometry. Analysis of adenosine receptors (ADORA1? ADORA2A? ADORA2B? ADORA3), CD39 and CD73 gene expression was performed by SYBR green real-time PCR. Our results demonstrated monocyte-derived macrophages from AS patients expressed increased level of A_2AAR and reduced level of A₁, A_2BAR, and CD39 mRNA compared to healthy controls. We found an inverse correlation between A_2AAR mRNA expression and Bath Ankylosing Spondylitis Functional Index (BASFI) score in AS patients. According to our results, altered expression level of adenosine-relying system would be involved in AS macrophage dysfunction and inflammation and correlated with functional status in AS patients.     

Effects of Gabexate Mesilate (FOY) on Amylase and Phospholipase A<Subscript>2</Subscript> in Human Serum and Pancreatic Juice

The precise inhibitory action of gabexate mesilate (GM) on the various pancreatic enzymes remains unclear. We designed this study to investigate the enzyme inhibitory action of GM in the serum and directly in the pancreatic juice. We observed 16 cases with postoperative pancreatic drainage. Patients were randomly assigned to one of two groups, to receive GM at a dose of 600 mg/24 hr (treated group: 8 patients) or a physiological solution (control group: 8 patients) by continuous intravenous infusion. In both groups pancreatic juice and serum were sampled three times: before infusion began (T0) and at 12 hr (T1) and 24 hr after infusion ended (T2). At the end of the study, seven patients received octreotide and the volume of pancreatic secretion was determined. No statistical difference was observed in serum amylase and phospholipase A₂ activity in the treated and control groups. On the contrary, amylase and phospholipase A₂ activity in the pancreatic juice diminished significantly only in the treated group, and in these patients a GM metabolite was also detectable in the pancreatic secretion. The volume of pancreatic secretion decreased only after infusion of octreotide. The enzyme inhibition in the pancreatic gland itself and the central role of inhibition of phospholipase A₂ in the enzyme cascade responsible for activating other proteases, confirm the therapeutic use of GM in acute pancreatitis. An association of GM and octreotide during acute pancreatitis should be useful because of their different mechanisms.     

Adenosine A<Subscript>1</Subscript> antagonists and the cardiorenal syndrome

Adenosine A₁ antagonists are being developed for the treatment of renal dysfunction in patients with congestive heart failure. After early small studies prompted hope that these agents could increase urine output without worsening the glomerular filtration rate, larger studies published and presented in 2007 confirmed their beneficial impact on weight and renal function. However, in many studies the renal benefits disappear with higher doses, suggesting that specificity may be lost with higher doses of these drugs. Investigations in animals indicate that there may also be direct benefits on the myocardium and in the lung. Although studies have not shown adverse effects at optimal dosing, the widespread actions of adenosine mandate that safety be established. Ongoing studies should be able to demonstrate whether adenosine A₁ antagonists can be used to improve renal function without adversely affecting patients with heart failure.     

Serotonin mediates PGE<Subscript>2</Subscript> overexpression through 5-HT<Subscript>2A</Subscript> and 5-HT<Subscript>3</Subscript> receptor subtypes in serum-free tissue culture of macrophage-like synovial cells

Serotonin antagonists show impressive analgesic efficacy in rheumatoid arthritis, osteoarthritis (OA) or fibromyalgia; however, this effect is not well understood. We examined the mechanism of serotonin-induced inflammation and its antagonists in OA. Serotonin receptor subtypes and COX-2 were analysed by RT-PCR from synovial tissue. Serum-free cultures were stimulated with 10 muM serotonin and/or the antagonists ketanserin (5-HT(2A)), tropisetron (5-HT(3)) and parecoxib (COX-2). Prostaglandin E(2) (PGE(2)), tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta) and leukotriene B4 (LTB4) were measured by an immunoassay in the supernatants. RT-PCR results showed mRNA for 5-HT(2A) and 5-HT(3) receptors, and COX-2. PGE(2) in the supernatants increased by 261.2% +/- 56.7 (mean +/- SEM; P = 0.007) in response to serotonin. TNF-alpha, IL-1beta and LTB4 levels did not change. Ketanserin, tropisetron and parecoxib suppressed PGE(2). The serotonin-induced PGE(2) overexpression appeared thus to be mediated by 5-HT(2A) and 5-HT(3) receptors. This activation might involve COX-2. The findings may explain the potent benefit of 5-HT(3) antagonists.     

Effects of H<Subscript>2</Subscript>O<Subscript>2</Subscript> on Microfilaments of Cultured Endothelial Cells

Hydrogen peroxide (H₂O₂) is an important granulocyte derived mediator of endothelial cell injury. Alterations of the microfilaments system (especially of actin) in endothelial cells may be relevant for the pathogenesis of vascular leakage. In the study presented effects of H₂O₂ on actin monomers (G-actin) and filamentous actin (F-actin) were examined in cultured pulmonary artery endothelial cells. Phalloidin which blocks actin depolymerization by inhibiting actin monomer dissociation and C. Botulinum C2 toxin which ADP-ribosylates G-actin thereby inhibiting actin polymerization were used as tools for the study of H₂O₂–related actin alterations. Exposure of cells to 2 mM H₂O₂ resulted in a biphasic change of F-actin with an early decrease (15 min) and a subsequent doubling (120 min) paralleled by an inverse G-actin pattern. In endothelial cells with a 20% reduction of F-actin-brought about by preincubation with C2-toxin for 150 min- H₂O₂-related actin polymerization was unimpaired. In cells with completely dissolved F-actin (Bot. C2-toxin for 210 min) no actin polymerization occurred upon H₂O₂ application. Phalloidin blocked the early H₂O₂-induced F-actin decrease and slowed down late actin polymerization. Effects of H₂O₂ on endothelial actin were abolished in the presence of scavengers of oxygen metabolites (catalase) and by the poly (ADP) ribose-polymerase inhibitor aminobenzamid. The data presented are compatible with the concept that H₂O₂ stimulates actin turnover and actin nucleation which—in the long run—result in H₂O₂ related formation of new actin filaments. This process was blocked by oxygen metabolite scavengers and by inhibition of DNA strand break repair mechanisms.     

脂蛋白相关性磷脂酶A2与缺血性心脑血管病

脂蛋白相关性磷脂酶A2（Lp-PLA2）是一种主要由巨噬细胞产生的反映血管炎症的特异性标记物,在低密度脂蛋白的氧化、促进动脉粥样硬化以及冠心病和卒中的形成等方面发挥重要作用。Lp-PLA2水平升高是预测冠心病和卒中风险的一种独立危险因素。     

颈动脉粥样硬化与脂蛋白相关磷脂酶A2的相关性

目的 探讨脂蛋白相关磷脂酶A2水平与颈动脉硬化病变程度的关系,以及其与血脂及超敏C-反应蛋白之间的关系.方法 收集138例病例(男70例,女68例)采用彩色多普勒超声诊断仪检测患者双侧颈动脉,按超声检查结果分为三组:颈动脉正常组30例;颈动脉内膜中膜增厚组38例;斑块组70例.留取患者空腹血清采用ELISA法测定脂蛋白相关磷脂酶A2浓度,并同时测定超敏C-反应蛋白浓度及血脂系列.结果 斑块组的总胆固醇、超敏C-反应蛋白、脂蛋白相关磷脂酶A2浓度都明显高于颈动脉正常组及颈动脉内膜中膜增厚组,且差异有显著性(P<0.05);血清甘油三酯、低密度脂蛋白在三组内比较,差异无显著性(P>0.05).等级分析方法结果显示,脂蛋白相关磷脂酶A2浓度与总胆固醇、低密度脂蛋白、超敏C-反应蛋白呈显著正相关(r=0.279、0.187、0.176,P=0.001、0.028、0.039),与血清甘油三酯无显著正相关(r=0.100,P=0.244).结论 脂蛋白相关磷脂酶A2作为促动脉粥样硬化的一个因素,能够反映颈动脉粥样硬化病变的严重程度,尤其是斑块的有无,并且其发生作用的机制可能与脂类和炎症有关.     

Lipoprotein-associated phospholipase A<Subscript>2</Subscript> and future risk of subclinical disease and cardiovascular events in individuals with type 2 diabetes: the Cardiovascular Health Study

Aims/hypothesis  

Type 2 diabetes is an established risk factor for cardiovascular disease (CVD). This increased risk may be due in part to the increased levels of inflammatory factors associated with diabetes. Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a risk marker for CVD and has pro-inflammatory effects in atherosclerotic plaques. We therefore sought to determine whether Lp-PLA₂ levels partially explain the greater prevalence of subclinical CVD and greater incidence of CVD outcomes associated with type 2 diabetes in the Cardiovascular Health Study.     

The role of PGE<Subscript>2</Subscript> in human atherosclerotic plaque on platelet EP<Subscript>3</Subscript> and EP<Subscript>4</Subscript> receptor activation and platelet function in whole blood

Atherosclerosis has an important inflammatory component. Macrophages accumulating in atherosclerotic arteries produce prostaglandin E₂ (PGE₂), a main inflammatory mediator. Platelets express inhibitory receptors (EP₂, EP₄) and a stimulatory receptor (EP₃) for this prostanoid. Recently, it has been reported in ApoE^−/− mice that PGE₂ accumulating in inflammatory atherosclerotic lesions might contribute to atherothrombosis after plaque rupture by activating platelet EP₃, and EP₃ blockade has been proposed to be a promising new approach in anti-thrombotic therapy. The aim of our investigation was to study the role of PGE₂ in human atherosclerotic plaques on human platelet function and thrombus formation. Plaque PGE₂ might either activate or inhibit platelets depending on stimulation of either EP₃ or EP₄, respectively. We found that the two EP₃-antagonists AE5-599 (300 nM) and AE3-240 (300 nM) specifically and completely inhibited the synergistic effect of the EP₃-agonist sulprostone on U46619-induced platelet aggregation in blood. However, these two EP₃-antagonists neither inhibited atherosclerotic plaque-induced platelet aggregation, GPIIb/IIIa exposure, dense and alpha granule secretion in blood nor reduced plaque-induced platelet thrombus formation under arterial flow. The EP₄-antagonist AE3-208 (1–3 μM) potentiated in combination with PGE₂ (1 μM) ADP-induced aggregation, demonstrating that PGE₂ enhances platelet aggregation when the inhibitory EP₄-receptor is inactivated. However, plaque-induced platelet aggregation was not augmented after platelet pre-treatment with AE3-208, indicating that plaque PGE₂ does not stimulate the EP₄-receptor. We found that PGE₂ was present in plaques only at very low levels (15 pg PGE₂/mg plaque). We conclude that PGE₂ in human atherosclerotic lesions does not modulate (i.e. stimulate or inhibit) atherothrombosis in blood after plaque rupture.     

Cardiac-Specific Knockout of ET<Subscript>A</Subscript> Receptor Mitigates Paraquat-Induced Cardiac Contractile Dysfunction

Paraquat (1,1’-dimethyl-4-4’-bipyridinium dichloride), a highly toxic quaternary ammonium herbicide widely used in agriculture, exerts potent toxic prooxidant effects resulting in multi-organ failure including the lung and heart although the underlying mechanism remains elusive. Recent evidence suggests possible involvement of endothelin system in paraquat-induced acute lung injury. This study was designed to examine the role of endothelin receptor A (ET_A) in paraquat-induced cardiac contractile and mitochondrial injury. Wild-type (WT) and cardiac-specific ET_A receptor knockout mice were challenged to paraquat (45 mg/kg, i.p.) for 48 h prior to the assessment of echocardiographic, cardiomyocyte contractile and intracellular Ca²⁺ properties, as well as apoptosis and mitochondrial damage. Levels of the mitochondrial proteins for biogenesis and oxidative phosphorylation including UCP2, HSP90 and PGC1α were evaluated. Our results revealed that paraquat elicited cardiac enlargement, mechanical anomalies including compromised echocardiographic parameters (elevated left ventricular end-systolic and end-diastolic diameters as well as reduced factional shortening), suppressed cardiomyocyte contractile function, intracellular Ca²⁺ handling, overt apoptosis and mitochondrial damage. ET_A receptor knockout itself failed to affect myocardial function, apoptosis, mitochondrial integrity and mitochondrial protein expression. However, ET_A receptor knockout ablated or significantly attenuated paraquat-induced cardiac contractile and intracellular Ca²⁺ defect, apoptosis and mitochondrial damage. Taken together, these findings revealed that endothelin system in particular the ET_A receptor may be involved in paraquat-induced toxic myocardial contractile anomalies possibly related to apoptosis and mitochondrial damage.     

Lp-PLA<Subscript>2</Subscript> as a Marker of Cardiovascular Diseases

Inflammation lies at the base of endothelial dysfunction, eventually leading to plaque formation. The degree of inflammation defines the “vulnerability” of plaque to rupture. Numerous strategies have been adopted to identify and eventually treat high-risk vulnerable plaque. Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) has emerged as one such candidate marker of inflammation that may play a direct role in the formation of rupture-prone plaque. Epidemiologic studies have clearly demonstrated the prognostic ability of increased Lp-PLA₂ levels and their association with increased risk of future coronary and cerebrovascular events. Moreover, Lp-PLA₂ might have similar predictive power for both incident coronary heart disease in initially healthy individuals as well as for recurrent events in those with clinically manifest atherosclerosis. The latest evidence has also suggested its incremental value for risk determination over the well-established traditional risk factors and biomarkers in patients with congestive heart failure. These data support an integral role of Lp-PLA₂ activity in lipid peroxidation and cardiovascular risk assessment. This review summarizes the current body of evidence supporting the clinical utility of Lp-PLA₂ and its future applications in cardiovascular medicine.     

Effects of balneotherapy on serum IL-1, PGE<Subscript>2 </Subscript>and LTB<Subscript>4</Subscript> levels in fibromyalgia patients

The purpose of this study was to investigate the clinical effects of balneotherapy in the treatment of Fibromyalgia Syndrome (FMS) and to determine if balneotherapy influences serum levels of inflammation markers, IL-1, PGE₂ and LTB₄. 24 primary fibromyalgia female patients diagnosed according to American College of Rheumatology criteria were included to the study. Their ages ranged between 33 and 55 years. FMS patients were randomly assigned in two groups as, group 1 (n = 12) and group 2 (n = 12). Group 1 received 20-min bathing, once in a day for five days per week. Patients participated in the study for 3 weeks (total of 15 sessions) in Denizli. Group 2 did not receive balneotherapy. FMS patients were evaluated by tenderness measurements (tender point count and algometry), Visual Analogue Scale, Beck’s Depression Index, Fibromyalgia Impact Questionnaire. Ten healthy women recruited group three as the controls. Serum PGE₂, LTB₄ and IL1-α levels were measured in all three groups. The biochemical measurements and clinical assessments were performed before and at the end of general period of therapy. Statistically significant alterations in algometric score, Visual Analogue score, Beck’s Depression Index and PGE₂ levels (P < 0.001), numbers of tender points (P < 0.01) and Fibromyalgia Impact Questionnaire score (P < 0.05) were found after the balneotherapy between group 1 and 2. Mean PGE₂ level of FMS patients were higher compared to healthy control group (P < 0.0001) and decreased after the treatment period, only in group 1 (P < 0.05). As in the group 2 and 3, detectable IL-1 and LTB₄ measurements were insufficient, statistical analysis was performed, only in group 1. After balneotherapy IL-1 and LTB₄ significantly decreased in group 1 (P < 0.05). In conclusion, balneotherapy is an effective choice of treatment in patients with FMS relieving the clinical symptoms, and possibly influencing the inflammatory mediators.     

The p38 MAPK Inhibitor SB203580 Blocks Adenosine A<Subscript>1</Subscript> Receptor-Induced Attenuation of In Vivo Myocardial Stunning

Summary There is considerable evidence implicating a key role for p38 mitogen-activated protein kinase (MAPK) in ischemic and pharmacological preconditioning against myocardial infarction. However, there have been few, if any, studies examining the role of p38 MAPK in the protection of stunned myocardium. The purpose of this study was to determine whether p38 MAPK plays a role in the adenosine A₁ receptor anti-stunning effect in in vivo porcine myocardium. Regional myocardial stunning in anesthetized, open-chest pigs was induced by 15 min of left anterior descending coronary artery (LAD) occlusion and 3 h of reperfusion (RP). Animals were treated with either vehicle (n = 5), AMP579 (70 g/kg i.v.; 25 g/kg bolus + 1.5 g/kg/min for 30 min prior to ischemia, n = 5), the p38 MAPK inhibitor SB203580 (0.25 mg/kg i.v. bolus, n = 4) or a combination of SB203580 plus AMP579 (n = 5). Regional ventricular function was monitored by measurements of segment shortening and load insensitive parameters including preload recruitable stroke work (PRSW) and PRSW area (PRSWA). The ischemic area at risk was similar in all groups and there was no necrosis in any heart. Treatment with AMP579 significantly improved reperfusion regional PRSW and PRSWA compared to vehicle controls. The p38 inhibitor SB203580 alone did not alter the extent of myocardial stunning, but it abolished the beneficial effect of AMP579 pretreatment. These results provide the first evidence that p38 MAPK activation may play an important role in the mechanism by which adenosine agonists attenuate myocardial stunning.