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Pharmacological activation of the prostaglandin E2 receptor EP4 improves cardiac function after myocardial ischaemia/reperfusion injury.

ABSTRACT: Increased expression of several subtypes of prostaglandin E(2) receptors (EP1-4) has recently been described in clinical and experimental myocardial ischaemia/reperfusion (I/R) injury. However, their pathophysiological significance in I/R remains obscure. Thus, we determined whether the activation of the prostanoid receptor, EP4, suppresses myocardial I/R injury.To analyse the role of EP4, we administered an EP4 selective agonist (EP4RAG, 1 or 3 mg/kg) or vehicle to rats with myocardial I/R injury. After 7 days of reperfusion, I/R rats exhibited left ventricular (LV) dilatation and contractile dysfunction with myocyte hypertrophy and interstitial fibrosis. EP4RAG significantly reduced infarction area/ischaemic myocardium (72.4 +/- 0.7 vs. 23.3 +/- 0.6%; P < 0.05) and improved LV contraction and dilatation compared with that of the vehicle. EP4RAG also attenuated the recruitment of inflammatory cells, especially macrophages, and interstitial fibrosis in hearts. Monocyte chemoattractant protein (MCP)-1 and other cytokines were increased in both non-ischaemic (area not at risk, ANAR) and ischaemic (area at risk, AAR) myocardium; however, western blot analysis and RNase protection assay showed that EP4RAG suppressed these changes. Gelatin zymography revealed EP4RAG significantly reduced matrix metalloproteinase-2 and -9 activities in both ANAR and AAR. Chemoattractant assay demonstrated that EP4RAG suppressed the migration of cytokine-stimulated macrophages and decreased the level of MCP-1 production in the supernatant (587.3 +/- 55.3 vs. 171.5 +/- 47.5 pg/mL; P < 0.05).The data suggest that the EP4 agonist is effective for attenuation of I/R injury by suppressing MCP-1 and the infiltration of inflammatory cells, especially macrophages.

SUBMITTER: Hishikari K

PROVIDER: S-EPMC2721641 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature

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Pharmacological activation of the prostaglandin E2 receptor EP4 improves cardiac function after myocardial ischaemia/reperfusion injury.

Hishikari Keiichi K Suzuki Jun-ichi J Ogawa Masahito M Isobe Kazuya K Takahashi Teisuke T Onishi Michihito M Takayama Kiyoshi K Isobe Mitsuaki M

Cardiovascular research 20080918 1

<h4>Aims</h4>Increased expression of several subtypes of prostaglandin E(2) receptors (EP1-4) has recently been described in clinical and experimental myocardial ischaemia/reperfusion (I/R) injury. However, their pathophysiological significance in I/R remains obscure. Thus, we determined whether the activation of the prostanoid receptor, EP4, suppresses myocardial I/R injury.<h4>Methods and results</h4>To analyse the role of EP4, we administered an EP4 selective agonist (EP4RAG, 1 or 3 mg/kg) or ...[more]

PMID: 18805784

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Project description:AimsNo effective therapy is available in clinics to protect the heart from ischaemia/reperfusion (I/R) injury. Endothelial cells are activated after I/R, which may drive the inflammatory response by releasing ATP through pannexin1 (Panx1) channels. Here, we investigated the role of Panx1 in cardiac I/R.Methods and resultsPanx1 was found in cardiac endothelial cells, neutrophils, and cardiomyocytes. After in vivo I/R, serum Troponin-I, and infarct size were less pronounced in Panx1-/- mice, but leukocyte infiltration in the infarct area was similar between Panx1-/- and wild-type mice. Serum Troponin-I and infarct size were not different between mice with neutrophil-specific deletion of Panx1 and Panx1fl/fl mice, suggesting that cardioprotection by Panx1 deletion rather involved cardiomyocytes than the inflammatory response. Physiological cardiac function in wild-type and Panx1-/- hearts was similar. The time to onset of contracture and time to maximal contracture were delayed in Panx1-/- hearts, suggesting reduced sensitivity of these hearts to ischaemic injury. Moreover, Panx1-/- hearts showed better recovery of left ventricle developed pressure, cardiac contractility, and relaxation after I/R. Ischaemic preconditioning failed to confer further protection in Panx1-/- hearts. Panx1 was found in subsarcolemmal mitochondria (SSM). SSM in WT or Panx1-/- hearts showed no differences in morphology. The function of the mitochondrial permeability transition pore and production of reactive oxygen species in SSM was not affected, but mitochondrial respiration was reduced in Panx1-/- SSM. Finally, Panx1-/- cardiomyocytes had a decreased mitochondrial membrane potential and an increased mitochondrial ATP content.ConclusionPanx1-/- mice display decreased sensitivity to cardiac I/R injury, resulting in smaller infarcts and improved recovery of left ventricular function. This cardioprotective effect of Panx1 deletion seems to involve cardiac mitochondria rather than a reduced inflammatory response. Thus, Panx1 may represent a new target for controlling cardiac reperfusion damage.

Project description:Aims:Myocardial ischaemia followed by reperfusion (IR) causes an oxidative burst resulting in cellular dysfunction. Little is known about the impact of oxidative stress on cardiomyocyte lipids and their role in cardiac cell death. Our goal was to identify oxidized phosphatidylcholine-containing phospholipids (OxPL) generated during IR, and to determine their impact on cell viability and myocardial infarct size. Methods and results:OxPL were quantitated in isolated rat cardiomyocytes using mass spectrophotometry following 24 h of IR. Cardiomyocyte cell death was quantitated following exogenously added OxPL and in the absence or presence of E06, a 'natural' murine monoclonal antibody that binds to the PC headgroup of OxPL. The impact of OxPL on mitochondria in cardiomyocytes was also determined using cell fractionation and Bnip expression. Transgenic Ldlr-/- mice, overexpressing a single-chain variable fragment of E06 (Ldlr-/--E06-scFv-Tg) were used to assess the effect of inactivating endogenously generated OxPL in vivo on myocardial infarct size. Following IR in vitro, isolated rat cardiomyocytes showed a significant increase in the specific OxPLs PONPC, POVPC, PAzPC, and PGPC (P < 0.05 to P < 0.001 for all). Exogenously added OxPLs resulted in significant death of rat cardiomyocytes, an effect inhibited by E06 (percent cell death with added POVPC was 22.6 ± 4.14% and with PONPC was 25.3 ± 3.4% compared to 8.0 ± 1.6% and 6.4 ± 1.0%, respectively, with the addition of E06, P < 0.05 for both). IR increased mitochondrial content of OxPL in rat cardiomyocytes and also increased expression of Bcl-2 death protein 3 (Bnip3), which was inhibited in presence of E06. Notably cardiomyocytes with Bnip3 knock-down were protected against cytotoxic effects of OxPL. In mice exposed to myocardial IR in vivo, compared to Ldlr-/- mice, Ldlr-/--E06-scFv-Tg mice had significantly smaller myocardial infarct size normalized to area at risk (72.4 ± 21.9% vs. 47.7 ± 17.6%, P = 0.023). Conclusions:OxPL are generated within cardiomyocytes during IR and have detrimental effects on cardiomyocyte viability. Inactivation of OxPL in vivo results in a reduction of infarct size.

Project description:The alterations in mitochondrial protein glycosylation in myocardial ischaemia reperfusion (I/R) injury are still unclear. Therefore, based on a lectin microarray and liquid chromatograph-mass spectrometer/mass spectrometer (LC‒MS/MS) technology combined with a bioinformatics analysis, we studied the changes in mitochondrial protein glycosylation during I/R injury. This study revealed significant differences in mitochondrial glycoprotein during I/R injury. Compared with the sham operation group, the model group, which underwent ischaemia for 30 min, showed a high expression of glycan structures recognized by lectins, such as WFA, PTL-I, LTL, GSL-I, SBA and SNA, and a low expression of glycan structures recognized by ConA, VVA and RCA120. The model group, which underwent ischaemia for 45 min, showed a high expression of glycan structures recognized by LTL and SNA and a low expression of glycan structures recognized by ECA. Further analysis showed that the Siaα2-6Gal/N-acetylgalactosamine (GalNAc) structures recognized by SNA were significantly increased. In total, 91 differential proteins were identified by LC‒MS/MS, and 8 hub genes were screened by Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment and protein interaction analyses. Compared with the Gene Expression Omnibus (GEO) database genes, two differential genes, Pros1 and Vtn, were obtained. Pros1 is a key regulator of the inflammatory response and vascular injury response. The Vtn gene variant is associated with the risk of myocardial infarction. This study is expected to provide a new method for the treatment of I/R injury and could provide new ideas for the postoperative prognosis of patients. Highlights • Changes in the mitochondrial glycoprotein glycan profile in Myocardial Ischaemia Reperfusion Injury.• Expression of Siaα2-6Gal/GalNAc structures recognized by SNA increased in the process of I/R injury.• Proteins identified by LC‒MS/MS in the sham-operated group and the 30-min ischaemia group.• By comparison with the GEO database, two candidate genes, Pros1 and Vtn, were obtained.

Project description:AimsEmpagliflozin (EMPA), a potent inhibitor of the renal sodium-glucose cotransporter 2 and an effective treatment for Type 2 diabetes, has been shown to have cardioprotective effects, independent of improved glycaemic control. Several non-canonical mechanisms have been proposed to explain these cardiac effects, including increasing circulating ketone supply to the heart. This study aims to test whether EMPA directly alters cardiac ketone metabolism independent of supply.Methods and resultsThe direct effects of EMPA on cardiac function and metabolomics were investigated in Langendorff rat heart perfused with buffer containing 5 mM glucose, 4 mM β-hydroxybutyrate (βHb) and 0.4 mM intralipid, subject to low flow ischaemia/reperfusion. Cardiac energetics were monitored in situ using 31P NMR spectroscopy. Steady-state 13C labelling was performed by switching 12C substrates for 13C1 glucose or 13C4 βHb and 13C incorporation into metabolites determined using 2D 1H-13C HSQC NMR spectroscopy. EMPA treatment improved left ventricular-developed pressure during ischaemia and reperfusion compared to vehicle-treated hearts. In EMPA-treated hearts, total adenosine triphosphate (ATP) and phosphocreatine (PCr) levels, and Gibbs free energy for ATP hydrolysis were significantly higher during ischaemia and reperfusion. EMPA treatment did not alter the incorporation of 13C from glucose into glycolytic products lactate or alanine neither during ischaemia nor reperfusion. In ischaemia, EMPA led to a decrease in 13C1 glucose incorporation and a concurrent increase in 13C4 βHb incorporation into tricarboxylic acid (TCA) cycle intermediates succinate, citrate, and glutamate. During reperfusion, the concentration of metabolites originating from 13C1 glucose was similar to vehicle but those originating from 13C4 βHb remained elevated in EMPA-treated hearts.ConclusionOur findings indicate that EMPA causes a switch in metabolism away from glucose oxidation towards increased ketone utilization in the rat heart, thereby improving function and energetics both during ischaemia and recovery during reperfusion. This preference of ketone utilization over glucose was observed under conditions of constant supply of substrate, suggesting that EMPA acts directly by modulating cardiac substrate preference, independent of substrate availability. The mechanisms underlying our findings are currently unknown, warranting further study.

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Pharmacological activation of the prostaglandin E2 receptor EP4 improves cardiac function after myocardial ischaemia/reperfusion injury.

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Pharmacological activation of the prostaglandin E2 receptor EP4 improves cardiac function after myocardial ischaemia/reperfusion injury.

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