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Background and purpose Cellular debris causes sterile inflammation after myocardial infarction. Mitochondria constitute about 30 percent of the human heart. Mitochondrial DNA (mtDNA) is a damage-associated-molecular-pattern that induce injurious sterile inflammation. Little is known about mtDNA's inflammatory signalling pathways in cardiomyocytes and how mtDNA is internalized to associate with its putative receptor, toll-like receptor 9 (TLR9). Experimental approach We hypothesized that mtDNA can be internalized in cardiomyocytes and induce an inflammatory response. Adult mouse cardiomyocytes were exposed to hypoxia-reoxygenation and extracellular DNA. Microscale thermophoresis was used to demonstrate binding between nucleolin and DNA. Key results Expression of the pro-inflammatory cytokines IL-1β and TNFα were upregulated by mtDNA, but not by nuclear DNA (nDNA), in cardiomyocytes exposed to hypoxia-reoxygenation. Blocking the RNA/DNA binding protein nucleolin with midkine reduced expression of IL-1β/TNFα and the nucleolin inhibitor AS1411 reduced interleukin-6 release in adult mouse cardiomyocytes. mtDNA bound 10-fold stronger than nDNA to nucleolin. In HEK293-NF-κB reporter cells, mtDNA induced NF-κB activity in normoxia, while CpG-DNA and hypoxia-reoxygenation, synergistically induced TLR9-dependent NF-κB activity. Protein expression of nucleolin was found in the plasma membrane of cardiomyocytes and inhibition of nucleolin with midkine inhibited cellular uptake of CpG-DNA. Inhibition of endocytosis did not reduce CpG-DNA uptake in cardiomyocytes. Conclusion and implications mtDNA, but not nDNA, induce an inflammatory response in mouse cardiomyocytes during hypoxia-reoxygenation. In cardiomyocytes, nucleolin is expressed on the membrane and blocking nucleolin reduce inflammation. Nucleolin might be a therapeutic target to prevent uptake of immunogenic DNA and reduce inflammation. Linked articles This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Ischemia-reperfusion (IR) injury of the heart generates reactive oxygen species that oxidize macromolecules including mitochondrial DNA (mtDNA). The 8-oxoguanine DNA glycosylase (OGG1) works synergistically with MutY DNA glycosylase (MYH) to maintain mtDNA integrity. Our objective was to study the functional outcome of lacking the repair enzymes OGG1 and MYH after myocardial IR and we hypothesized that OGG1 and MYH are important enzymes to preserve mtDNA and heart function after IR. Ex vivo global ischemia for 30min followed by 10min of reperfusion induced mtDNA damage that was removed within 60min of reperfusion in wild-type mice. After 60min of reperfusion the ogg1(-/-) mice demonstrated increased mtDNA copy number and decreased mtDNA damage removal suggesting that OGG1 is responsible for removal of IR-induced mtDNA damage and copy number regulation. mtDNA damage was not detected in the ogg1(-/-)/myh(-/-), inferring that adenine opposite 8-oxoguanine is an abundant mtDNA lesion upon IR. The level and integrity of mtDNA were restored in all genotypes after 35min of regional ischemia and six week reperfusion with no change in cardiac function. No consistent upregulation of other mitochondrial base excision repair enzymes in any of our knockout models was found. Thus repair of mtDNA oxidative base lesions may not be important for maintenance of cardiac function during IR injury in vivo. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease."

OBJECTIVES: Several studies have reported superior post-cardioplegic recovery after glutamate supplementation. The optimum dose of glutamate supplementation is unknown. The purpose of this study was to find the optimal protective concentration of glutamate supplementation in a model of ischaemia/cardioplegia and reperfusion.METHODS: Isolated rat hearts (n = 77) were perfused with the Krebs-Henseleit buffer. After stabilization, the hearts were subjected to 25 min of normothermic ischaemia followed by a single 3-min infusion of cold (4-6 °C) St. Thomas' Hospital II cardioplegia and 87 min of cardioplegic ischaemic arrest and 60 min of reperfusion. Sodium-l-glutamate was added to the perfusate (control group had zero glutamate) in increasing concentrations (0.01, 0.1, 1, 10, 20, 30 and 100 mM) and given throughout perfusion. Corresponding concentrations were added to the cardioplegic solution. A balloon in the left ventricle inserted via the left atrium measured left ventricular pressures isometrically. Left ventricular developed pressure was calculated. Myocardial exchange of glucose and lactate was measured prior to ischaemia and during reperfusion. Myocardial content of glycogen and glutamate was measured at the end of reperfusion.RESULTS: During reperfusion left ventricular developed pressure increased (P CONCLUSIONS: Even low concentrations of l-glutamate improved postischaemic and post-cardioplegic heart function and 1 mM seems to be optimal.

We aimed to study the cardiac expression of bone morphogenetic protein 2, its receptor 1 b, and connective tissue growth factor, factors implicated in cardiac embryogenesis, following ischemia/hypoxia, heart failure, and in remodeling hearts from humans and mice. Biopsies from the left ventricle of patients with end-stage heart failure due to dilated cardiomyopathy or coronary artery disease were compared with donor hearts and biopsies from patients with normal heart function undergoing coronary artery bypass grafting. Mouse model of post-infarction remodeling was made by permanent ligation of the left coronary artery. Hearts were analyzed by real-time polymerase chain reaction and Western blotting after 24 hours and after 2 and 4 weeks. Patients with dilated cardiomyopathy and mice post-infarction had increased cardiac expression of connective tissue growth factor. Bone morphogenetic protein 2 was increased in human hearts failing due to coronary artery disease and in mice post-infarction. Gene expression of bone morphogenetic protein receptor 1 beta was reduced in hearts of patients with failure, but increased two weeks following permanent ligation of the left coronary artery in mice. In conclusion, connective tissue growth factor is upregulated in hearts of humans with dilated cardiomyopathy, bone morphogenetic protein 2 is upregulated in remodeling due to myocardial infarction while its receptor 1 b in human failing hearts is downregulated. A potential explanation might be an attempt to engage regenerative processes, which should be addressed by further, mechanistic studies.

Aims Heart failure is associated with activation of fetal gene programs. Bone morphogenetic proteins (BMPs) regulate embryonic development through interaction with BMP receptors (BMPRs) on the cell surface. We investigated if the expression of BMP4 and its receptors BMPR1a and BMPR2 were activated in post-infarction remodeling and heart failure. Main methods Left ventricular biopsies were taken from explanted hearts of patients with end-stage heart failure due to dilated cardiomyopathy (CMP; n = 15) or ischemic heart disease (CAD; n = 9), and compared with homograft control preparations from organ donors deceased due to non-cardiac causes (n = 7). Other samples were taken from patients undergoing coronary artery bypass grafting (CABG; n = 11). Mice were subjected to induced infarction by permanent coronary artery ligation or sham operation, and hearts were sampled serially thereafter (n = 7 at each time point). Key findings Human and mouse hearts expressed BMP4 and both receptor subtypes. CABG and CMP patients had increased expression of mRNA encoding for BMP4, but unchanged protein. Mouse hearts had increased BMP4 precursor protein 24 h after infarction. BMPR1a protein decreased in CAD patients and initially in postinfarcted mouse hearts, but increased again in the latter after two weeks. Human recombinant BMP4 promoted survival after H 2 O 2 injury in HL-1 cells, and also protected adult mouse cardiomyocytes against hypoxia–reoxygenation injury. Significance Adult hearts express BMP4, the mRNA increasingly so in patients with coronary artery disease with good cardiac function. BMPRs are downregulated in cardiac remodeling and failure. Recombinant BMP4 has protective effects on cultured cardiomyocytes.

Myocardial connective tissue growth factor (CTGF/CCN2) is induced in heart failure, a condition associated with diminution of β-adrenergic receptor (β-AR) responsiveness. Accordingly, we aimed to investigate whether CTGF could play a mechanistic role in regulation of β-AR responsiveness. Concentration-response curves of isoproterenol-stimulated cAMP generation in cardiomyocytes from transgenic mice with cardiac-restricted overexpression of CTGF (Tg-CTGF) or cardiomyocytes pretreated with recombinant human CTGF (rec-hCTGF) revealed marked reduction of both β₁-AR and β₂-AR responsiveness. Consistently, ventricular muscle strips from Tg-CTGF mice stimulated with isoproterenol displayed attenuation of maximal inotropic responses. However, no differences of maximal inotropic responses of myocardial fibers from Tg-CTGF mice and nontransgenic littermate control (NLC) mice were discerned when stimulated with supramaximal concentrations of dibutyryl-cAMP, indicating preserved downstream responsiveness to cAMP. Congruent with a mechanism of desensitization of β-ARs, mRNA and protein levels of G protein-coupled receptor kinase 5 (GRK5) were found isoform-selective upregulated in both cardiomyocytes from Tg-CTGF mice and cardiomyocytes exposed to rec-hCTGF. Corroborating a mechanism of GRK5 in CTGF-mediated control of β-AR sensitivity, Chinese hamster ovary cells pretreated with rec-hCTGF displayed increased agonist- and biased ligand-stimulated β-arrestin binding to β-ARs. Despite increased sensitivity of cardiomyocytes from GRK5-knockout (KO) mice to β-adrenergic agonists, pretreatment of GRK5-KO cardiomyocytes with rec-hCTGF, as opposed to cardiomyocytes from wild-type mice, did not alter β-AR responsiveness. Finally, Tg-CTGF mice subjected to chronic exposure (14 days) to isoproterenol revealed blunted myocardial hypertrophy and preserved cardiac function versus NLC mice. In conclusion, this study uncovers a novel mechanism controlling β-AR responsiveness in cardiomyocytes involving CTGF-mediated regulation of GRK5.

Aquaporin-1 (AQP1) is expressed in human and mouse hearts, but little is known about its cellular and subcellular localization and regulation. The aim of this study was to investigate the localization of AQP1 in the mouse heart and to determine the effects of ischemia and hypoxia on its expression. Mouse myocardial cells were freshly isolated and split into cardiomyocyte and non-cardiomyocyte fractions. Isolated, Langendorff-perfused C57Bl6 mouse hearts (n=46) were harvested with no intervention, subjected to 35min of ischemia or ischemia followed by 60min of reperfusion. Eleven mouse hearts were perfusion-fixed for electron microscopy. Forty C57Bl6 mice were exposed to normobaric hypoxia for one or two weeks (n=12). Needle biopsies of human left ventricular myocardium were sampled (n=30) during coronary artery bypass surgery before cardioplegia and after 30min of reperfusion. Human umbilical vein endothelial cells (HUVECs) were subjected to 4h of hypoxia with reoxygenation for either 4 or 24h. AQP1 expression was studied by electron microscopy with immunogold labeling, Western blot, and qPCR. Expression of miR-214 and miR-320 in HUVECs with hypoxia was studied with qPCR. HUVECs were then transfected with precursors and inhibitors of miR-214. AQP1 expression was confined to cardiac endothelial cells, with no signal in cardiomyocytes or cardiac fibroblasts. Immunogold electron microscopy showed AQP1 expression in endothelial caveolae with equal distribution along the basal and apical membranes. Ischemia and reperfusion tended to decrease AQP1 mRNA expression in mouse hearts by 37±9% (p=0.06), while glycosylated AQP1 protein was reduced by 16±9% (p=0.03). No difference in expression was found between ischemia alone and ischemia-reperfusion. In human left ventricles AQP1 mRNA expression was reduced following cardioplegia and reperfusion (p=0.008). Hypoxia in mice reduced AQP1 mRNA expression by 20±7% (p

Acute myocardial infarction (AMI) causes sterile inflammation, which exacerbates tissue injury. Elevated levels of circulating mitochondrial DNA (mtDNA) have been associated with AMI. We hypothesized that mtDNA triggers an innate immune response via TLR9 and NF-κB activation, causing cardiomyocyte injury. Murine cardiomyocytes express TLR9 mRNA and protein and were able to internalize fluorescently labeled mouse mtDNA. Incubation of human embryonic kidney cells with serum from AMI patients containing naturally elevated levels of mtDNA induced TLR9-dependent NF-κB activity. This effect was mimicked by isolated mtDNA. mtDNA activated NF-κB in reporter mice both in vivo and in isolated cardiomyocytes. Moreover, incubation of isolated cardiomyocytes with mtDNA induced cell death after 4 and 24 h. Laser confocal microscopy showed that incubation of cardiomyocytes with mtDNA accelerated mitochondrial depolarization induced by reactive oxygen species. In contrast to mtDNA, isolated total DNA did not activate NF-κB nor induce cell death. In conclusion, mtDNA can induce TLR9-dependent NF-κB activation in reporter cells and activate NF-κB in cardiomyocytes. In cardiomyocytes, mtDNA causes mitochondrial dysfunction and death. Endogenous mtDNA in the extracellular space is a danger signal with direct detrimental effects on cardiomyocytes.

To evaluate if remote gene delivery of HMOX-1 prior to myocardial infarction can prevent cardiac remodeling and preserve function, without causing general angiogenesis.Right quadriceps muscles of mice were treated with DNA encoding for HMOX-1 or empty vector (pcDNA) and electroporated to enhance nuclear uptake, while a third group received saline. Transfection efficacy was evaluated by real time PCR and situ hybridization in transfected muscle, contralateral muscle, and heart. Seven days after transfection baseline echocardiography was performed. Myocardial infarction was induced by ligation of the left coronary artery. Six weeks later heart function was reassessed by echocardiography. Hearts were extracted for evaluation of infarct size. Immunoflorescent staining was used to evaluate angiogenesis using the endothelial marker CD31 in cross-sections of the transfected quadriceps muscle, the untreated muscle, and hearts.Gene delivery of HMOX-1 leads to a local expression of HMOX-1 in the treated muscle, but not in any other organ. HMOX-1 treated mice had reduced infarct size (p=0.03) and improved function evident as higher ejection fraction (p=0.001), improved fractional shortening (p0.0001) and higher stroke volume (p=0.002). HMOX-1 did not cause angiogenesis in the heart or skeletal muscle.Remote delivery of DNA encoding for HMOX-1 was cardioprotective, as evidenced by preserved cardiac structure and function. Angiogenesis was not induced by HMOX-1 treatment.

CCN2/connective tissue growth factor (CTGF), a CCN family matricellular protein repressed in healthy hearts after birth, is induced in heart failure of various etiologies. Multiple cellular and biological functions have been assigned to CCN2/CTGF depending on cellular context. However, the functions and mechanisms of action of CCN2/CTGF in the heart as well as its roles in cardiac physiology and pathophysiology remain unknown. Transgenic mice with cardiac-restricted overexpression of CTGF (Tg-CTGF) were generated and compared with nontransgenic littermate control (NLC) mice. Tg-CTGF mice displayed slightly lower cardiac mass and inconspicuous increase of myocardial collagen compared with NLC mice but no evidence of contractile dysfunction. Analysis of the myocardial transcriptome by DNA microarray revealed activation of several distinct gene programs in Tg-CTGF hearts involved in cardioprotection and growth inhibition. Indeed, Tg-CTGF mice subjected to ischemia-reperfusion injury by in situ transient occlusion of the left anterior descending coronary artery in vivo displayed reduced vulnerability with markedly diminished infarct size. These findings were recapitulated in isolated hearts perfused with recombinant human (h)CTGF before the ischemia-reperfusion procedure. Consistently, Tg-CTGF hearts, as well as isolated adult cardiac myocytes exposed to recombinant hCTGF, displayed enhanced phosphorylation and activity of the Akt/p70S6 kinase/GSK-3β salvage kinase pathway and induction of several genes with reported cardioprotective functions. Inhibition of Akt activities also prevented the cardioprotective phenotype of hearts from Tg-CTGF mice. This report provides novel evidence that CTGF confers cardioprotection by salvage phosphokinase signaling leading to inhibition of GSK-3β activities, activation of phospho-SMAD2, and reprogramming of gene expression.

To investigate whether human veins responded to surgical handling with acute remodelling by measuring matrix metalloproteinase 9 (MMP9) expression and activity.Saphenous veins were collected from 24 patients (12 stable angina, 12 unstable angina) undergoing coronary artery bypass grafting. Expression of MMP9 and its regulators (plasminogen activators, plasminogen activator inhibitor-1, tissue inhibitor of metalloproteinase-1) was evaluated by semiquantitative RT-PCR in veins sampled at the start of and after surgical preparation, while protein was detected by western blotting. The proteolytic activity of MMP9 was analyzed by zymography.Gene (p=0.01) and protein (p=0.001) expression of MMP9 increased after surgical manipulation of vein grafts in all patients, accompanied by increased pro-MMP9 (p=0.04), but not active MMP9 (p=0.6). Grafts from stable patients had increased gene (p=0.05) and protein (p=0.006) expression, as well as increased pro- (p=0.04) and active (p=0.04) MMP9. Grafts from unstable patients increased only in MMP9 protein expression (p=0.05). The MMP9 regulators were unchanged.Surgical handling of vein grafts increased expression and activity of MMP9. However, the surgery-induced increase was attenuated in veins from unstable patients.

Hyperoxic exposure in vivo (> 95% oxygen) attenuates ischemia-reperfusion injury, but the signaling mechanisms of this cardioprotection are not fully determined. We studied a possible role of nitric oxide (NO) and mitogen activated protein kinases (MAPK) in hyperoxic protection. Mice (n = 7–9 in each group) were kept in normoxic or hyperoxic environments for 15 min prior to harvesting the heart and Langendorff perfusion with global ischemia (45 min) and reperfusion (60 min). Endpoints were cardiac function and infarct size. Additional hearts were collected to evaluate MAPK phosphorylation (immunoblot). The nitric oxide synthase inhibitor L-NAME, the ERK1/2 inhibitor PD98059 and the p38 MAPK inhibitor FR167653 were injected intraperitoneally before hyperoxia or normoxia. Hyperoxia improved postischemic functional recovery and reduced infarct size (p < 0.05). Hyperoxic exposure caused cardiac phosphorylation of the MAPK family members p38 and ERK1/2, but not JNK. L-NAME, PD98059 and FR167653 all reduced the protection afforded by hyperoxic exposure, but did not influence performance or infarction in hearts of normoxic mice. The hyperoxia-induced phosphorylation of ERK1/2 and p38 was reduced by L-NAME and both MAPK inhibitors. Nitric oxide triggers hyperoxic protection, and ERK1/2 and p38 MAPK are involved in signaling of protection against ischemia-reperfusion injury.

Background Saphenous veins are often used for coronary artery bypass grafting (CABG), but loss of patency is a problem. The surgical procedure may contribute to graft injury. Our aim was to study the impact of surgical handling of saphenous veins on graft inflammation and vascular function. Methods Biopsy samples of saphenous veins were taken from 9 patients undergoing elective CABG at the start of vein harvesting (open technique) and after the last proximal anastomosis was sutured. Messenger RNA was extracted and amplified with semiquantitative reverse transcription polymerase chain reaction. Gene expression of proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β), leukocyte adhesion molecules (E-selectin, intercellular adhesion molecule-1), and vasoactive substances (endothelin-1, inducible and endothelial nitric oxide synthase) was investigated. Translocation of nuclear factor-κB (NFκB) was evaluated with electrophoretic mobility shift assay. Immunostaining for von Willebrand factor was performed to evaluate loss of endothelium, and in vitro vein reactivity to phenylephrine and endothelin-1 was studied. Results Gene expression of cytokines and leukocyte adhesion molecules increased after graft harvesting and storage, whereas vasoactive substances did not change. Nuclear translocation of NFκB occurred after surgical handling, concurrent with partial loss of endothelium and impaired contractile function. Conclusions Standard surgical handling of vein grafts induces NFκB-driven inflammation in the vessel wall and impairs vascular function. This may potentially contribute to both early and late graft occlusion.

The role of nuclear factor kappa-B (NF-kappaB) p105 for vascular inflammatory gene expression and neointima formation after arterial injury was studied. Mice carotid arteries were injured by ligation. Vascular NF-kappaB activation was monitored using a NF-kappaB luciferase reporter mouse. Mice with gene deletion of the NF-kappaB p105 subunit (p50 precursor) and the corresponding wild types were assessed for vascular gene expression and neointimal hyperplasia. NF-kappaB was activated in the injured vessel wall in wild type mice, and this was accompanied by increased expression of the proinflammatory genes tumor necrosis factor alpha, interleukin 1 beta, and inducible nitric oxide synthase. In contrast, NF-kappaB p105 knockout mice had reduced expression of the inflammatory genes and enhanced neointima formation four weeks after ligation. Basic fibroblast growth factor (bFGF) gene expression increased after arterial ligation. A higher percentage of bFGF positive cells were found in lesions from NF-kappaB p105 knock out mice. These data indicate that the p105 subunit of NF-kappaB plays an essential role in vascular healing, and defects in NF-kappaB p105 promote neointima hyperplasia.

Objectives: Aminosteroids of the lazaroid type protect organs from ischemia-reperfusion damage. The authors hypothesized that lazaroid U-83836E may be beneficial in a shock model with hemorrhage combined with limb ischemia. Furthermore, the authors hypothesized that lazaroids induce expression of heat shock proteins (HSPs) of the 72-kDa family. Methods: Rats were divided into two groups (lazaroid and control groups, n = 8 each) and pretreated with the lazaroid U-83836E (5 mg/kg) or with vehicle intraperitoneally at 12 and 24 hours before experiments. At the time of the experiment, rats were anesthetized, and the femoral artery of each rat was cannulated. After 20 minutes of stabilization, blood was shed from each rat to bring its mean arterial pressure to 24-28 mmHg for 2 hours. Bilateral tourniquets were tightened proximally on the rat thighs during those 2 hours and then released. Shed blood plus equal amounts of Ringer acetate then were infused to restore normal blood pressure, followed by a continuous infusion of Ringer acetate, the rate of which was regulated to maintain blood pressure, until 30 minutes after start of resuscitation. Fluid resuscitation was stopped, and rats were observed for another 3.5 hours. At the end of the observation period, the rats' hearts were collected for immunoblot analysis of HSP72. Additional hearts were collected from similarly pretreated rats not undergoing the episode of hemorrhagic shock and fluid resuscitation. Results: Pretreatment with U-83836E improved mean arterial blood pressure after hemorrhagic shock and fluid resuscitation (p = 0.02), combined with improvements in acid-base balance (improved base excess and standard bicarbonate; p = 0.02 and p = 0.01, respectively). Western blot of cardiac protein extracts demonstrated that lazaroid pretreatment increased expression of HSP72. Conclusions: Pretreatment with the lazaroid U-83836E improved outcome markers in this hemorrhagic shock model. The observed protection may be caused by increased expression of HSP72.

We hypothesized that intraperitoneal injections of anaesthetics or fluid per se might evoke a delayed preconditioning-like response in mice hearts isolated and Langendorff perfused 24 h later. To test this, mice were given opioid anaesthesia by intraperitoneal injections or sham treated and the hearts were harvested and subjected to global ischaemia and reperfusion 24 h later in series 1. In series 2, mice were subjected to intraperitoneal injection of Ringer, sham needle prick procedure, or no intervention 24 h before heart isolation. In series 3, intraperitoneal Ringer injection 24 h earlier was compared with the effects of classic preconditioning or no pretreatment of the isolated heart or no treatment. Heart function was measured in all series. At the end of reperfusion, hearts in series 1 and 2 were frozen and infarct size was estimated by triphenyltetrazolium chloride solution. In series 3, separate hearts were frozen for immunoblotting to detect phosphorylation of mitogen-activated protein (MAP) kinases. Cardiac activation of nuclear factor kappa B (NFκB) was measured using a NFκB luciferase firefly reporter mouse. The ischaemia-induced impairment of left ventricular function was attenuated by opioid anaesthesia injected 24 h earlier, which also reduced infarct size. Injection of fluid, but not the sham needle prick procedure, reduced infarct size. The functional protection afforded by classic preconditioning and Ringer pretreatment was comparable. Neither cardiac MAP kinases nor NFκB were influenced by the interventions. In conclusion, this study demonstrates a delayed preconditioning-like effect of the heart caused by intraperitoneal administration of opioid anaesthetics and of fluid only in the mouse. The mechanism of protection remains to be determined.

Background : The isolated perfused mouse heart is a useful experimental model, and cardiac troponin T (cTnT) in coronary effluent may be a sensitive marker of myocardial damage. In recent years, the apolipoprotein E/low-density lipoprotein receptor double knockout (apoE/LDLr KO) mice have become valuable tools in atherosclerosis research. The aim of the study was to validate measurements of cTnT in heart, skeletal muscle, and serum of apoE/LDLr KO mice. Methods : Wild-type C57BL/6J mice were fed with standard diet, and apoE/LDLr KO mice were fed an atherogenic diet. Blood was sampled from the jugular vein or the thoracic cavity. Heart and femoral skeletal muscle were sampled and homogenized. cTnT was measured with the third-generation cTnT assay (Troponin T STAT) on Elecsys 2010 immunoassay analyser (Roche Diagnostics). Results : Median serum cTnT in samples from the thoracic cavity of C57BL/6J mice was about 20–90 times higher, and from ApoE/LDLr KO mice about 30 times higher than serum cTnT in samples from the external jugular vein. There was no difference in cTnT content (μg cTnT/g heart muscle) in hearts from C57BL/6J and apoE/LDLr KO mice. The median cTnT content in skeletal muscle was less than 0.1% of the cTnT content in heart muscle. Conclusion : There is no difference in cTnT content of heart muscle comparing C57BL/6J and ApoE/LDLr KO mice, which have larger hearts. Sampling from the thoracic cavity causes unacceptably high cTnT levels. Serum cTnT in samples from the jugular vein is only slightly elevated. Elevated baseline levels of cTnT in mice are not caused by troponin T from skeletal muscle.

Objectives: Brief episodes of myocardial ischemia-reperfusion employed during reperfusion after a prolonged ischemic insult may attenuate the total ischemia-reperfusion injury. This phenomenon has been termed ischemic postconditioning. In the present study, we studied the possible effect of postconditioning on persistent reperfusion-induced ventricular fibrillation (VF) in the isolated rat heart model. Methods: Isolated Langendorff-perfused rat hearts ðn ¼ 46Þ were subjected to 30 min of regional ischemia and reperfusion. The hearts with persistent VF ðn ¼ 11Þ present after 15 min of reperfusion were then randomly assigned into one of the two groups: (1) control hearts ðn ¼ 6Þ; in which perfusion was continued without intervention; (2) postconditioned hearts ðn ¼ 5Þ subjected to 2 min of global ischemia followed by reperfusion. Left ventricular pressures, heart rate, coronary flow, and electrogram were monitored throughout the experiment. Results: Conversion of VF into regular rhythm was observed in all hearts subjected to postconditioning. Regular beating was maintained by all postconditioned hearts during the subsequent reperfusion. None of the hearts in the control group had normal rhythm at the end of the experiment. At the end of reperfusion, the left ventricular developed pressure was lower in beating postconditioned hearts compared to the hearts that did not develop persistent VF. Conclusions: Ischemic postconditioning possesses strong antiarrhythmic effect against persistent reperfusion-induced tachyarrhythmias. Postconditioning may be an interesting, novel adjunct strategy to protect the heart. q 2004 Elsevier B.V. All rights reserved.

Objective: Hyperoxia has been previously shown to protect the heart from ischemia-reperfusion injury. In the present study we investigated whether the cardioprotective effects of hyperoxia were dependent on the redox-sensitive transcription factor nuclear factor κB. Methods: Rats were kept in a hyperoxic (≥95% O 2 ) environment for 60 minutes. Their hearts were isolated immediately afterward, buffer perfused in a Langendorff apparatus, and subjected to 25 minutes of global ischemia and 60 minutes of reperfusion. Cardiac pressures and coronary flow were measured, and infarct size was determined by means of triphenyl tetrazolium chloride staining. Activation of nuclear factor κB was assessed by means of the electrophoretic mobility shift assay, whereas the inhibitor IκBα was evaluated by means of immunoblotting. Pharmacologic inhibition of nuclear factor κB was achieved with 2 different agents, SN50 and pyrrolidine dithiocarbamate. Results: Preischemic exposure to hyperoxia improved postischemic recovery of myocardial contractile function and coronary flow and reduced infarct size. Hyperoxia activated pulmonary and myocardial nuclear factor κB. Pretreatment with SN50 (400 μg/kg administered intraperitoneally) or pyrrolidine dithiocarbamate (100 mg/kg administered intraperitoneally) before hyperoxia abolished the functional and infarct-limiting protection. Hyperoxia reduced nuclear factor κB activation in the heart during sustained ischemia and reperfusion and increased the cytoplasmatic inhibitory factor IκBα. Administration of pyrrolidine dithiocarbamate or SN50 during ischemia and reperfusion to isolated hearts from normoxic control animals improved postischemic contractile function and coronary flow and reduced infarct size. Conclusions: Hyperoxia protects the rat heart against ischemia-reperfusion injury. The cardioprotection depends on myocardial activation of the transcription factor nuclear factor κB. Our results support evidence for a dual role of nuclear factor κB in the heart. J Thorac Cardiovasc Surg 2003;125:650-60

Heart rupture and heart failure are deleterious complications of myocardial infarction. The ShcA gene encodes for three protein isoforms, p46-, p52- and p66ShcA. p66ShcA induces oxidative stress. We studied the role of p66ShcA post-infarction. Expression of p66ShcA was analyzed in myocardium of patients with stable angina (n = 11), in explanted hearts with end-stage ischemic heart failure (n = 9) and compared to non-failing hearts not suitable for donation (n = 7). p66ShcA was increased in the patients with stable angina, but not in the patients with end-stage heart failure. Mice (n = 105) were subjected to coronary artery ligation. p66ShcA expression and phosphorylation were evaluated over a 6-week period. p66ShcA expression increased transiently during the first weeks post-infarction. p66ShcA knockout mice (KO) were compared to wild type (n = 82 in total). KO had improved survival and reduced occurrence of heart rupture post-infarction. Expression of cardiac matrix metalloproteinase 2 (MMP-2) was reduced; fibroblast activation and collagen accumulation were facilitated, while oxidative stress was attenuated in KO early post-infarction. 6 weeks post-infarction, reactive fibrosis and left ventricular dilatation were diminished in KO. p66ShcA regulation of MMP-2 was demonstrated in cultured fibroblasts: lack or overexpression of p66ShcA in vitro altered expression of MMP-2. Myocardial infarction induced cardiac p66ShcA. Deletion of p66ShcA improved early survival, myocardial healing and reduced cardiac fibrosis. Upon myocardial infarction p66ShcA regulates MMP-2 activation. The role of p66ShcA in human cardiac disease deserves further study as a potential target for reducing adverse cardiac remodeling post-infarction.

Objectives: Breathing a hyperoxic gas ($95% O2) protects against ischaemia-reperfusion injury in rat and mouse hearts. The present study investigated how oxygen concentration and duration of hyperoxic exposure influenced cardioprotection, and whether hyperoxia might induce delayed cardioprotection (after 24 h). Methods: Animals were kept in normal air or in a hyperoxic environment, and their hearts were isolated and Langendorff-perfused immediately or 24 h thereafter. Global ischaemia was induced for 25 min in rats and 40 min in mice, followed by 60 min of reperfusion. Infarct size was determined by triphenyl tetrazolium chloride staining. Results: In rats exposure to $95, 80, and 60%, but not to 40% of oxygen immediately before heart isolation and perfusion improved postischaemic functional recovery. Eighty or more percent of oxygen also reduced infarct size. A preconditioning-like effect could be evoked by 60 or 180 min of hyperoxia, giving both immediate and delayed protection. In the mouse heart protection could be induced by pretreatment for 15 or 30, but not by 60 min with $95% oxygen. The protective effect of hyperoxia in mice could be evoked in the immediate model only. Conclusions: Hyperoxia protects the isolated rat and mouse heart against ischaemia-reperfusion injury, but some species-different responses exist. The protection depends on both oxygen concentration in inspired air, and duration of hyperoxic exposure. q 2002 Elsevier Science B.V. All rights reserved.

Aims The cellular prion protein, PrPC, whose aberrant isoforms are related to prion diseases of humans and animals, has a still obscure physiological function. Having observed an increased expression of PrPC in two in vivo paradigms of heart remodelling, we focused on isolated mouse hearts to ascertain the capacity of PrPC to antagonize oxidative damage induced by ischaemic and non-ischaemic protocols. Methods and results Hearts isolated from mice expressing PrPC in variable amounts were subjected to different and complementary oxidative perfusion protocols. Accumulation of reactive oxygen species, oxidation of myofibrillar proteins, and cell death were evaluated. We found that overexpressed PrPC reduced oxidative stress and cell death caused by post-ischaemic reperfusion. Conversely, deletion of PrPC increased oxidative stress during both ischaemic preconditioning and perfusion (15 min) with H2O2. Supporting its relation with intracellular systems involved in oxidative stress, PrPC was found to influence the activity of catalase and, for the first time, the expression of p66Shc, a protein implicated in oxidative stress-mediated cell death. Conclusions Our data demonstrate that PrPC contributes to the cardiac mechanisms antagonizing oxidative insults.

Background . Coronary atherosclerosis has profound effects on vascular and myocardial biology, and it has been speculated that the atherosclerotic heart does not benefit from ischemic preconditioning. Methods . To investigate if atherosclerosis would influence the preconditioning response, Apolipoprotein E/low density lipoprotein (LDL) receptor double knockout mice (ApoE/LDLr−/−) were fed an atherogenic diet (21% fat, 0.15% cholesterol) for 6 to 8 months. At that time, extensive atherosclerotic lesions throughout the coronary tree were seen in transverse sections stained with Oil Red-O. Hearts of ApoE/LDLr−/− mice were Langendorff-perfused with 40 minutes of global ischemia and 60 minutes reperfusion, and compared with C57BL/6 controls. Preconditioning with two episodes of 2 minutes of ischemia and 5 minutes reperfusion, or exposing the mice to a hyperoxic environment (O 2 > 98%) for 60 minutes before heart perfusion, was performed. Results . Hearts of mice with coronary atherosclerosis had worse postischemic function, and increased infarct size and troponin T release compared to hearts of C57BL/6 mice. Ischemic preconditioning improved postischemic ventricular function, and reduced myocardial infarct size and troponin T release in both normal and ApoE/LDLr−/− mice. The effects were most pronounced in ApoE/LDLr−/− hearts. Exposure to hyperoxia exerted a similar protection of function and cell viability of ApoE/LDLr−/− mice hearts. Conclusions . These findings suggest that the severely atherosclerotic heart may be protected by preconditioning induced by ischemia or hyperoxia.

Cardioplegia and reperfusion may induce an inflammatory reaction, which may contribute to postoperative morbidity and mortality.Gene expression of cytokines, adhesion molecules, and vasoactive substances was evaluated in left ventricular biopsies taken before cardioplegia (lasting approximately 70 minutes) and after reperfusion (approximately 40 minutes) from 19 patients (5 with valvular or combined disease, 7 with stable angina pectoris, 7 with unstable angina). mRNA was extracted and amplified with a semiquantitative reverse transcription polymerase chain reaction.Cardioplegia-reperfusion increased mRNA for E-selectin by a factor of 17 +/- 5 (p0.002) (mean +/- SEM), interleukin-1beta, with 9 +/- 3 (p0.007), tumor necrosis factor-alpha with 6 +/- 3 (p0.05), interleukin-2 receptor alpha chain CD25 with 2 +/- 0.6 (p0.04), and intercellular adhesion molecule-1 with 2 +/- 0.4 (p0.005). Before cardioplegia, mRNA for endothelial nitric oxide synthase was predominantly detected in unstable angina patients, and increased by a factor of 11 +/- 6 (p0.02) during reperfusion. mRNA for endothelin-1 decreased by a factor of 0.5 +/- 0.1 (p0.0005). The changes were more pronounced in unstable patients. The transcription factor nuclear factor kappa B (NFkappaB), which regulates expression of inflammatory mediators, was activated during reperfusion (n = 10, p0.0001).Open heart surgery induces an inflammatory response in the human heart, which is more pronounced in patients with unstable angina. It involves NFkappaB activation and expression of several NFkappaB-regulated genes.

One hundred and ten patients were investigated prospectively in a study aimed at creating reference curves for inflammation markers (serum C-reactive protein (CRP), blood leukocyte count, iron, transthyretin and procalcitonin). Blood samples were taken daily and the patients were monitored for signs of infection. Ninety-six patients had no postoperative infections. CRP and leukocyte counts peaked on the third and second postoperative days, respectively. Neither patients operated on off-pump (n = 4) nor patients with minor infections (n = 11) differed from the non-infected group. Two out of three patients with major postoperative infection exhibited a secondary peak in CRP and leukocyte count. Iron and transthyretin decreased initially, followed by a slow increase without any difference between the groups. Procalcitonin was high in some non-infected patients and low in some infected patients. CRP and leukocyte count had a predictable course with a secondary peak in major infections but the other markers did not provide any valuable information.

The possible cardioprotective effects of preconditioning by ischaemia (IPC) or a low dose of H2O2 (HPC) prior to a high dose of H2O2 was investigated. Langendorff-perfused rat hearts (n = 10 in each group) were subjected to 10 min of 140 micromol/L H2O2 and 30 min recovery after either (1) control perfusion, (2) 20 micromol/L H2O2 for 10 min, recovery 10 min, or (3) 2 x 2 min global ischaemia and 5 min reperfusion. 140 micromol/L H2O2 increased left ventricular end-diastolic pressure from 0 to 68+/-8 mmHg in controls (mean+/-SEM), which was attenuated by IPC (46+/-9 mmHg, p

In studies of preconditioning, a variety of models have been used. The aim of the present study was to find the optimal preconditioning model for preservation of cardiac function during reperfusion of globally ischaemic, Langendorff-perfused rat hearts. Cardiac function was assessed by the occurrence of severe reperfusion arrhythmias (ventricular fibrillation or asystolia), heart rate (HR), left ventricular systolic (LVSP), end diastolic (LVEDP), and developed pressures (LVDP = LVSP - LVEDP), as well as coronary flow (CF). Series 1 (n = 17) in each group: control perfusion for 20 min without preconditioning or 2 episodes of 2, 3, 4, or 5 min of ischaemia, each followed by 5 min reperfusion, before 25 min ischaemia and 60 min reperfusion. Preconditioning reduced the incidence of reperfusion arrhythmias, attenuated the reperfusion-induced increase of LVEDP, and increased CF, but did not influence LVSP, LVDP, or rate x pressure-product (RPP = LVSP x HR) during reperfusion. The greatest effect was found by 2 min ischaemia and 5 min reperfusion. In series 2 (n = 17 in each group) control perfusion for 7 or 28 min, or preconditioning with 1-4 episodes of 2 min ischaemia and 5 min reperfusion before 35 min ischaemia and 60 min reperfusion were compared. Reduction of severe reperfusion arrhythmias and LVEDP elevation, as well as improvement of CF, LVDP, and HR in preconditioned hearts were observed in series 2. Optimal cardioprotection was achieved by only one episode of preconditioning. In conclusion, preconditioning before global ischaemia improved cardiac function during reperfusion of isolated rat hearts. The most marked effects were reduction of severe reperfusion arrhythmias and attenuation of diastolic dysfunction. Although all preconditioning models employed were cardioprotective, 1 episode of 2 min ischaemia provided optimal protection.

Cardioprotection can be evoked through extracardiac approaches. This prompted us to investigate whether remote transplantation of stem cells confers protection of the heart against ischemic injury. The cardioprotective effect of subcutaneous transplantation of naïve versus heme oxygenase-1 (HMOX-1)-overexpressing mouse mesenchymal stem cells (MSC) to mice was investigated in hearts subjected to ischemia-reperfusion in a Langendorff perfusion system. Mice were transplanted into the interscapular region with naïve or HMOX-1 transfected MSC isolated from transgenic luciferase reporter mice and compared to sham-treated animals. The fate of transplanted cells was followed by in vivo bioluminescence imaging, revealing that MSC proliferated, but did not migrate detectably from the injection site. Ex vivo analysis of the hearts showed that remote transplantation of mouse adipose-derived MSC (mASC) resulted in smaller infarcts and improved cardiac function after ischemia-reperfusion compared to sham-treated mice. Although HMOX-1 overexpression conferred cytoprotective effects on mASC against oxidative stress in vitro, no additive beneficial effect of HMOX-1 transfection was noted on the ischemic heart. Subcutaneous transplantation of MSC also improved left ventricular function when transplanted in vivo after myocardial infarction. Plasma analysis and gene expression profile of naïve- and HMOX-1-mASC after transplantation pointed toward pentraxin 3 as a possible factor involved in the remote cardioprotective effect of mASC. These results have significant implications for understanding the behavior of stem cells after transplantation and development of safe and noninvasive cellular therapies with clinical applications. Remote transplantation of MSC can be considered as an alternative procedure to induce cardioprotection. Stem Cells 2014;32:2123–2134

We thank Mezzaroma et al . and Jong and Zuurbier for their interest in our article,1 and also for their valuable comments and concerns regarding our results and interpretations. As stated by Mezzaroma et al ., several studies have now addressed the role of inflammasomes in the heart. We fully agree with the authors that in order to understand the role of NLRP3 in the myocardium, identification of the cell types involved in NLRP3-mediated responses is of great importance. We also share the authors' claim that cardiomyocytes are the most prominent cell type in the heart. Likewise, loss of contractile tissue is also the most important consequence of a myocardial infarction. However, this does not necessarily imply that the NLRP3 inflammasome needs to be functional in the cardiomyocytes. In fact, while we clearly do not exclude a functional role of NLRP3 inflammasome in cardiomyocytes, we, in line with the study of Kawaguchi et al. ,2 suggest that myocardial fibroblasts, being a potent inflammatory cell, could contribute to NLRP3-mediated inflammation …

Aims N ucleotide-binding oligomerization domain- L ike R eceptor with a P yrin domain 3 (NLRP3) is considered necessary for initiating a profound sterile inflammatory response. NLRP3 forms multi-protein complexes with A poptosis-associated S peck-like protein containing a C aspase recruitment domain (ASC) and Caspase-1, which activate pro-interleukin-1β (IL-1β) and pro-IL-18. The role of NLRP3 in cardiac cells is not known. Thus, we investigated the expression and function of NLRP3 during myocardial ischaemia. Methods and results Myocardial infarction (MI) was induced in adult C57BL/6 mice and Wistar rats by ligation of the coronary artery. A marked increase in NLRP3, IL-1β, and IL-18 mRNA expression was found in the left ventricle after MI, primarily located to myocardial fibroblasts. In vitro studies in cells from adult mice showed that myocardial fibroblasts released IL-1β and IL-18 when primed with lipopolysaccharide and subsequently exposed to the danger signal adenosine triphosphate, a molecule released after tissue damage during MI. When hearts were isolated from NLRP3-deficient mice, perfused and subjected to global ischaemia and reperfusion, a marked improvement of cardiac function and reduction of hypoxic damage was found compared with wild-type hearts. This was not observed in ASC-deficient hearts, potentially reflecting a protective role of other ASC-dependent inflammasomes or inflammasome-independent effects of NLRP3. Conclusion This study shows that the NLRP3 inflammasome is up-regulated in myocardial fibroblasts post-MI, and may be a significant contributor to infarct size development during ischaemia–reperfusion.

Tissue plasminogen activator (t-PA) is a potential marker of endothelial cell activation or injury. The relationship between duration of ischaemia and release of t-PA during reperfusion was investigated in isolated rat hearts exposed to either 5, 10, 20, 30, 40, or 60 min of global, normothermic ischaemia followed by 30 min of reperfusion (n = 8 in each group). t-PA activity was measured (chromogenic peptide substrate assay) in the effluent before ischaemia, and after 2.5, 5, 7.5, 10, 20, and 30 min of reperfusion. Release of lactate dehydrogenase (LD), a marker of myocyte injury, was measured before ischaemia and after 5 min reperfusion. Left ventricular pressures were measured by a balloon in the left ventricle. Ischaemia for 20 min or less had only minor effects on cardiac function. Thirty min or more of ischaemia induced ventricular fibrillation during reperfusion in most hearts. After ischaemia t-PA outflow increased, but without any significant difference between groups. Peak release occurred after either 2.5 or 5 min of reperfusion. After 10 min reperfusion the release was not different from the basal value. In contrast, postischaemic release of LD correlated to the length of ischaemia. To conclude, t-PA release from the ischaemic-reperfused rat heart is independent of the length of ischaemia. Thus the potential of t-PA to quantify endothelial injury appears to be limited.

Tumor necrosis factor α (TNFα) expression is strongly attenuated by the intracellular signaling mediator cyclic adenosine monophosphate (cAMP), which is synthesized by adenylyl cyclase (AC) enzymes. We have compared AC regulation and TNFα production in male and female monocytes, and characterized the role of monocyte AC isoforms in TNFα regulation. Males and females, age groups 20-30 years and 50-70 years donated blood for this study. In lipopolysaccharide-stimulated blood from young male donors, we observed significantly higher TNFα responses (6h, p=0.03) compared to females of the same age, a difference not observed in the older donors. Rapid down-regulation of the monocyte AC isoforms AC4, AC7 and AC9 were observed in young males. AC-directed siRNA experiments in the human monocyte cell line THP-1 demonstrated that AC7 and AC9 knock-down significantly induced TNFα release (p=0.01 for both isoforms). These data indicate that the stronger TNFα-responses in young males may be partly associated with male-specific down-regulation of adenylyl cyclases.

The role of histamine in cardiac physiology and pathophysiology is not clarified, but is dependent on species. The effects of exogenous histamine in Langendorff-perfused rat hearts were investigated. 1 mM, 100, 10, 1 and 0.1 microM of histamine (n = 7 each) as 15 min infusions were employed in a dose-response study, and compared to control perfused hearts (n = 7). In another experimental series, 100 microM histamine (n = 15) was added during reperfusion after 25 min global ischemia, and compared to control ischemia-reperfusion (n = 15). The maximal response to histamine in the dose-response study (100 microM) was an increase of left ventricular developed pressure to 126 +/- 8% of initial value (mean +/- SEM, p0.04), and increase of coronary flow to 152+6% (p0.02) after 5 min infusion. 100 microM histamine did not significantly influence heart rate or rhythm. The lowest concentration (0.1 microM) did not have effects cardiac performance. Reperfusion with histamine for 2 min after ischemia reduced left ventricular developed pressure to 68 +/- 10% of initial value versus 116+17% in ischemic controls (p0.05), and increased left ventricular end-diastolic pressure to 24 +/- 8 mmHg compared to 6 +/- 2 mmHg in controls (p0.04). Left ventricular pressures were similar in hearts reperfused with histamine and in ischemic controls for the rest of the observation. Coronary flow increased during reperfusion in hearts given histamine. Histamine had a dose-dependent positive inotropic and vasodilatory effect in isolated rat hearts. Exogenous histamine had only minor effects on post-ischemic cardiac function.

The roles of immune cells and their soluble products during myocardial infarction (MI) are not completely understood. Here, we observed that the percentages of IL-17, but not IL-22, producing cells are reduced in mice splenocytes after developing MI. To correlate this finding with the functional activity of IL-17, we sought to determine its effect on monocytes. In particular, we presumed that this cytokine might affect the chemotaxis of monocytes important for cardiac inflammation and remodeling. We observed that IL-17 tends to reduce the expression of two major chemokine receptors involved in monocyte chemotaxis, namely CCR2 and CXCR4. Further analysis showed that monocytes pretreated with IL-17 have reduced in vitro chemotaxis towards the ligand for CCR2, i.e., MCP-1/CCL2, and the ligand for CXCR4, i.e., SDF-1α/CXCL12. Our results support the possibility that IL-17 may be beneficial in MI, and this could be due to its ability to inhibit the migration of monocytes.

Aquaporins (AQPs) are channel-forming membrane proteins highly permeable to water. AQP4 is found in mammalian hearts; however, its expression sites, regulation and function are largely unknown. The aim was to investigate cardiac AQP4 expression in humans and mice, its regulation by ischemia and hypoxia, and in particular its role in cardiac ischemic injury using AQP4 knockout (KO) mice. Comparable levels of AQP4 were detected by Western blot and qPCR in biopsies from human donor hearts and wild type C57Bl6 mouse hearts. In mice, AQP4 was expressed on cardiomyocyte plasmalemma (qPCR, Western blot, immunogold), and its mRNA decreased following ischemia/reperfusion (isolated hearts, p = 0.02) and after normobaric hypoxia in vivo (oxygen fraction 10 % for 1 week, p < 0.001). Isolated hearts from AQP4 KO mice undergoing global ischemia and reperfusion had reduced infarct size (p = 0.05) and attenuated left ventricular end-diastolic pressure during reperfusion (p = 0.04). Infarct size was also reduced in AQP4 KO mice 24 h after left coronary artery ligation in vivo (p = 0.036). AQP4 KO hearts had no compensatory change in AQP1 protein expression. AQP4 KO cardiomyocytes were partially resisted to hypoosmotic stress in the presence of hypercontracture. AQP4 is expressed in human and mouse hearts, in the latter confined to the cardiomyocyte plasmalemma. AQP4 mRNA expression is downregulated by hypoxia and ischemia. Deletion of AQP4 is protective in acute myocardial ischemia–reperfusion, and this molecule might be a future target in the treatment of acute myocardial infarction.

Liver X receptor (LXR)-α and -β play a major role in lipid and glucose homeostasis. Their expression and function in the heart is not well characterized. Our aim was to describe the expression of LXRs in the murine heart, and to determine effects of cardiac LXR activation on target gene expression, lipid homeostasis and ischemia. Both LXRα and -β were expressed in heart tissues, HL-1 cells and isolated cardiomyocytes as determined by qRT-PCR. Elevated cardiac expression of LXR target genes and LXRβ was observed 24 h after in vivo permanent coronary artery ligation. The synthetic LXR agonist GW3965 induced mRNA expression of the LXR target genes in HL-1 cells and isolated cardiomyocytes. This was associated with a buildup of intracellular triglycerides and expanding lipid droplets as quantified by confocal microscopy. Mice injected with GW3965 had cardiac LXR activation as judged by increased target gene expression and lipid droplet accumulation. GW3965 in vivo and in vitro increased expression of genes inducing triglyceride synthesis, and altered expression of lipid droplet-binding protein genes. GW3965 protected HL-1 cells against hypoxia-reoxygenation induced apoptosis. LXR activation by GW3965 in vivo prior to heart isolation and perfusion with induced global ischemia and reperfusion improved left ventricular contractile function and decreased infarct size. In conclusion, LXRs are expressed in the murine heart in the basal state, and are activated by myocardial infarction. Activation of LXR by the synthetic agonist GW3965 is associated with intracardiac accumulation of lipid droplets and protection against myocardial ischemia–reperfusion injury.

The host inflammatory response in sepsis may be resolved by endogenous anti-inflammatory immune cell responses, avoiding fatal pathogenesis, organ injury, and death. The intracellular signaling mediator cyclic 3'5'-adenosine monophosphate is a potent modulator of inflammatory responses and initiates the polarization of immune cells in a direction that suppresses inflammatory activation. Cyclic 3'5'-adenosine monophosphate is enzymatically produced by adenylyl cyclases (ACs). The expression of ACs is previously shown to be reduced in rat organs after in vivo endotoxemia, concurrent with the progressing systemic inflammation. In the present study, tissue AC gene expression and regulation are explored in a rat model of cecal ligation and puncture (CLP) sepsis. Eighteen hours after CLP operation, expression of several AC isoforms in the liver, spleen, and kidney was reduced, significantly so for AC9 in all tissues. AC9 expression is regulated by the microRNA miR142-3p in T cells. When microRNA was extracted and amplified for miR142-3p expression, it was increasingly expressed 18 h after CLP. A correlation between increased miR142-3p and decreased AC9 expression was found in the liver, kidney, and spleen, and when hepatocytes, Kupffer cells (KCs), and liver sinusoidal endothelial cells were isolated after CLP, reduced AC expression and increased miR142-3p expression were found in KCs and liver sinusoidal endothelial cells. Transfecting a miR142-3p inhibitor probe in rat KCs abolished LPS-mediated AC9 inhibition in vitro. These results indicate that CLP leads to miR142-3p-mediated AC9 reduction in liver macrophages, which may further limit cyclic 3'5'-adenosine monophosphate signaling and the ability of macrophages to resolve the proinflammatory response.

The role of arachidonic acid metabolites in the cardiac effects of toxic oxygen metabolites (TOM) was investigated in buffer-perfused rat hearts (Langendorff model). Hydrogen peroxide (H 2 O 2 , 200 μM) was given for 10 min to generate TOM, followed by 30 min recovery. H 2 O 2 reduced left ventricular developed pressure (LVDP), increased left ventricular end-diastolic pressure (LVEDP), and increased coronary flow (CF). The hydroxyl radical scavenger thiourea inhibited the H 2 O 2 -induced effects. Perfusion with three lipoxgenase inhibitors, AA861, BWA4C, and diethylcarbamazine, in adition to H 2 O 2 , augmented the decrease of LVDP and the increase of LVEDP induced by H 2 O 2 . The cyclooxygenase inhibitor indomethacin had the same effects. The H 2 O 2 -induced increased in CF was not influenced by diethylcarbamazine, but inhibited by all other drugs. Control perfusion with drugs alone did not influence cardiac function. In conclusion, inhibition of lipoxygenase and cyclooxygenase augmented the depression of cardiac function induced by TOM. Leukotrienes and prostanoids appear to be protective against H 2 O 2 -induced cardiac injury.

Gene therapy of a peripheral organ to protect the heart is clinically attractive. The transcription factor hypoxia-inducible factor 1 alpha (HIF-1α) transactivates cardioprotective genes. We investigated if remote delivery of DNA encoding for HIF-1α is protective against myocardial ischemia-reperfusion injury in vivo.DNA encoding for human HIF-1α was delivered to quadriceps muscles of mice. One week later myocardial infarction was induced and four weeks later its size was measured. Echocardiography and in vivo pressure-volume analysis was performed. Coronary vascularization was evaluated through plastic casting. HL-1 cells, transfected with either HIF-1α or HMOX-1 or administered bilirubin or the carbon monoxide (CO) donor CORM-2, were subjected to lipopolysacharide (LPS)-induced cell death to compare the efficacy of treatments.After four weeks of reperfusion post infarction, animals pretreated with HIF-1α showed reduced infarct size and left ventricular remodeling (p0.05, respectively). Fractional shortening was preserved in mice pretreated with HIF-1α (p0.05). Invasive hemodynamic parameters indicated preserved left ventricular function after HIF-1α (p0.05), which also induced coronary vascularization (p0.05). HIF-1α downstream target heme oxygenase 1 (HMOX-1) was upregulated in skeletal muscle, while serum bilirubin was increased. Transfection of HL-1 cells with HIF-1α or HMOX-1 and administration of bilirubin or CORM-2 comparably salvaged cells from lipopolysacharide (LPS)-induced cell death (all p0.05).HIF-1α gene delivery to skeletal muscle preceding myocardial ischemia reduced infarct size and postischemic remodeling accompanied by an improved cardiac function and vascularization. Similar to HIF-1α, HMOX-1, bilirubin and CO were protective against LPS-induced injury. This observation may have clinical potential.

Objective: Exposure to normobaric hyperoxia protects the heart against ischemia—reperfusion injury ex vivo. In the present study, we investigated the effect of the early and late phase of hyperoxia on in vivo myocardial infarction and apoptosis. Methods: Rats were exposed to room air preoxygenation (O2 � 95%) followed by regional ischemia (30 min) and 0, 90, 180, and 360 min of reperfusion. Hyperoxic exposure was performed for 120 min either immediately or 24 h before coronaryocclusionfollowed by 360-min reperfusion. Infarct size was evaluated by Evans blue/triphenyltetrazolium chloride staining. Apoptosis in the infarcted area was evaluated by terminal deoxy-nucleotidyl transferase-mediated deoxy uridine triphosphate (dUTP) nick end-labeling (TUNEL). Caspase 3 activity was measured by fluorometric enzyme assay, Bcl-2 and Bax protein expression assessed by western blotting and DNA laddering assessed with DNA gel electrophoresis. Results: The infarct size did not increase with increasing duration of reperfusion. However, apoptosis as evaluated by Bcl-2/Bax ratio, caspase 3 activity, and TUNEL-positive cells increased with increasing time of reperfusion. Both early and delayed pretreatment with hyperoxia reduced infarct size (p = 0.0013, p = 0.046), ameliorated ischemic arrhythmias and increased Bcl-2/Bax ratio (p = 0.015, p = 0.0159). Only hyperoxia immediately before coronary occlusion decreased caspase 3 activity (p = 0.026) and decreased TUNEL-positive staining (p = 0.046) with no visible DNA laddering. Conclusions: Detection of myocardial apoptosis increased with prolongation of reperfusion time, as opposed to infarct detection where reperfusion was essentialto detectinfarction,but theinfarctsizedidnotincreasewith time.Pretreatmentwithhyperoxiasignificantlydecreasedinfarctsize and apoptotic cell death. Pretreatment, immediately before coronary occlusion, was most cardioprotective. # 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

We tested if remote gene delivery of hypoxia-inducible factor 1 alpha (HIF-1 alpha) protected hearts against induced ischemia, hypothesizing that gene delivery into skeletal muscle may lead to secretion of proteins with actions elsewhere. Murine quadriceps muscles were transfected with DNA encoding for human HIF-1 alpha, which resulted in a local, but lasting expression (mRNA and protein, where the latter had nuclear localization). Subjection of isolated hearts to global ischemia and reperfusion 1, 4, and 8 weeks after gene delivery resulted in infarct size reduction (p < 0.05). Supporting that this was due to paracrine effects, HL-1 cells treated with conditioned media from cells transfected with HIF-1 alpha or serum from HIF-1 alpha-treated mice were protected against H(2)O(2)-induced cell death (p < 0.05, respectively). The latter protection was reduced when a heme oxygenase activity blocker was used. Taqman low-density array of 47 HIF-1 alpha-regulated genes at the treatment site showed nine specific upregulations (p < 0.05). Of the corresponding proteins, PDGF-B and adrenomedullin were upregulated in the heart. HIF-1 alpha treatment induced an increased vascularization of the heart and skeletal muscle. In conclusion, remote delivery of DNA for HIF-1 alpha was cardioprotective, represented by consistent infarct size reduction, which may be due to release of paracrine factors from the transfected muscle.

The present study investigates whether the cardioprotection achieved by gene delivery of hypoxia-inducible factor-1 alpha (HIF-1 alpha) depends on the downstream factor haem oxygenase (HMOX)-1.Immortalized cardiomyocytes (HL-1 cells) were transfected with HIF-1 alpha or HMOX-1 and injured with hydrogen peroxide (H(2)O(2)), and death was evaluated by trypan blue staining. Quadriceps muscles of mice were treated with DNA for HIF-1 alpha and HMOX-1, or sham-treated and electroporated, and 3 days later, hearts were isolated and subjected to global ischaemia and reperfusion. Some HIF-1 alpha- and sham-treated mice received the HMOX blocker zinc deuteroporphyrin 2,4-bis-glycol (ZnBG) (n = 6-8 in each group). HL-1 cells were stimulated with bilirubin or the carbon monoxide donor CORM-2 before injury with H(2)O(2). HL-1 cells which were transfected with HIF-1 alpha or HMOX-1 had an increased survival to H(2)O(2)-induced injury compared with empty vector (n = 10-12 per group; P0.01 for both). When HMOX-1-luciferase reporter mice were treated with HIF-1 alpha in the quadriceps muscle, increased luciferase activity was found locally, but nowhere else. Mice pre-treated with HIF-1 alpha or HMOX-1 had a reduced infarct size, improved post-ischaemic function, and increased serum bilirubin (P0.05). ZnBG inhibited all these effects afforded by HIF-1 alpha. Stimulation of HL-1 cells with bilirubin and CORM-2 reduced cell death evoked by H(2)O(2) (P0.05 for both, n = 11-15 in each group).HIF-1 alpha and HMOX-1 provided protection against H(2)O(2)-induced damage in HL-1 cells. Remote gene delivery of HIF-1 alpha afforded cardioprotective effects. These were dependent on HMOX activity, as an HMOX blocker abolished the effects, and they were mimicked by pre-treatment with HMOX-1. Downstream to HMOX-1, bilirubin as well as carbon monoxide may be organ effectors.

Objective: Ischemic preconditioning reduces infarct size and improves hemodynamic function. Unstable angina may be a clinical analogue to ischemic preconditioning, and involve activation of gene programs. We hypothesized that preceding unstable angina and/or ischemic preconditioning activated genes regulated by nuclear factor kappa B (NFkB) or hypoxia-inducible factor 1 alpha in parallel to improved cardiac function. Methods: Patients undergoing coronary artery bypass grafting with stable or unstable angina were subjected to ischemic preconditioning or sham treatment (n = 10—11 in each group). Central hemodynamics were monitored. Left ventricular and atrial biopsies were harvested before cardioplegic arrest and after 25 min of reperfusion. Expression of heat shock protein 72 was evaluated by immunoblot, and activation of NFkB was detected by electrophoretic mobility shift assay. Real-time PCR was used to quantify expression of genes regulated by NFkB (inducible nitric oxide synthase, tumor necrosis factor-alpha, intercellular adhesion molecule 1) or by hypoxia-inducible factor 1 alpha (heme oxygenase-1, glucose transporter-1 and vascular endothelial growth factor-A). Results: Ischemic preconditioning improved postoperative cardiac index and left ventricular stroke work index in both stable and unstable groups on the first postoperative day. Expression of hypoxia-inducible factor 1 alpha regulated genes was not influenced by cardioplegia and reperfusion, ischemic preconditioning or unstable angina. Expression of the NFkBregulated genes increased after cardioplegia and reperfusion, but this was not influenced by ischemic preconditioning in stable patients. Inducible nitric oxide synthase and tumor necrosis factor expression were reduced after ischemic preconditioning in patients with unstable angina. There were no significant differences in gene expression between stable and unstable patients before cardioplegia and ischemic preconditioning. NFkB translocation at reperfusion was reduced in stable preconditioned and unstable control patients compared to stable controls. Heat shock protein 72 expression increased after preconditioning of unstable patients. Conclusion: Cardiac function was improved by ischemic preconditioning in both stable and unstable patients. Unstable angina per se had no effect. NFkB-regulated genes were influenced by ischemic preconditioning, but hypoxia-inducible genes were not. # 2008 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Objective: Corticosteroids and hyperoxia protect the heart against ischemia—reperfusion injury and may attenuate vascular reactivity. We hypothesized that (1) combining these two pretreatments induces an additive cardioprotection, (2) protection depends on activation of survival kinases and/or heat shock proteins, and (3) these interventions would change vascular reactivity into a more relaxed state. Methods: Male rats were randomized (n = 10 in each group): 1. control, 2. dexamethasone (3 mg/kg) injected 24 and 12 h before harvesting the hearts, 3. 60 min of hyperoxia (90—95% O2) immediately before harvest, 4. combination of dexamethasone and hyperoxia as in groups 2 and 3. The hearts were Langendorff-perfused and exposed to 30 min of global ischemia and reperfused for 120 min. Cardiac function was monitored and infarct size determined. Isometric tension to vasoconstrictive and vasodilatory agents was measured in femoral artery rings. Phosphorylation of survival kinases (protein kinase B/AKT, extracellular signal-regulated kinases (ERK1/2), the stress-activated/c-Jun NH2 terminal kinases (SAPK/JNK) and p38 MAPK), adenosine monophosphate dependent kinase (AMPK) and expression of heat shock protein 72 (HSP72) in hearts was evaluated by immunoblotting. Results: Infarct size was attenuated in all pretreated groups versus controls: 29% reduction in the combined group (p < 0.01), 23% in hyperoxia group (p < 0.05) and 31% in dexamethasone group (p < 0.01). There was no significant difference between the treated groups. Combined pretreatment improved postischemic left ventricular end diastolic pressure compared to all other groups (p < 0.001 vs controls, p = 0.002 vs dexamethasone, p = 0.005 vs hyperoxia). Combined pretreatment improved left ventricular developed pressure and coronary flow compared to controls (p < 0.001 for both) and hyperoxia (p = 0.0047 and p = 0.0024, respectively). Combined pretreatment enhanced endothelium-independent relaxation (p = 0.0032) compared to controls. Excepting ERK1/2 phosphorylation in the combined group during early reperfusion, there was no increased phosphorylation of the survival kinases AKT, p38, JNK, or AMPK and no increase of HSP72 expression. Conclusion: Combined pretreatment by hyperoxia and dexamethasone improved postischemic heart function, but did not reduce infarct size compared to single pretreatment groups. Except of a possible role of ERK1/2, protection depended neither on survival kinases nor heat shock protein 72. # 2007 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Aim: To examine cardiac function, body temperature and locomotor behaviour in the awake adenosine A 1 receptor knock out mouse of both sexes. Methods: Male and female A 1 R (+/+) and (-/-) mice, instrumented with telemetric devices, were recorded during basal conditions and after drug administration. Results: Female mice had higher heart rate, body temperature and locomotion, both during daytime and during the night. Awake A 1 R (-/-) mice had a slightly elevated heart rate, and this was more clear-cut in males. Heart rate was also higher in Langendorff-perfused denervated A 1 R (-/-) hearts. Body temperature was higher in A 1 R (-/-) males and females; locomotor activity was higher in A 1 R (-/-) females, but not in males. The adenosine receptor agonist R-PIA (0.2 mg kg -1 ) decreased heart rate and body temperature, but less in A 1 R (-/-) animals than in A 1 R (+/+) mice (P < 0.001 in both parameters). The unselective adenosine receptor antagonist caffeine had a minor stimulatory effect on heart rate in lower doses, but depressed it at a dose of 75 mg kg -1 . Body temperature was increased after a low dose (7.5 mg kg -1 ) of caffeine in both sexes and genotypes, and markedly reduced after a high dose (75 mg kg -1 ) of caffeine. An intermediary dose of caffeine 30 mg kg -1 increased or decreased body temperature depending on genotype and sex. Locomotor responses to caffeine were variable depending both on genotype and sex. Conclusion: Thus, the adenosine A 1 receptor is involved in the regulation of heart rate, body temperature and locomotor activity, but the magnitude of the involvement is different in males and females.

For subsequent studies on the molecular mechanisms of postconditioning, we aimed to identify a robust postconditioning protocol in rat and mouse heart.Isolated rat hearts were subjected to different postconditioning protocols (study 1 and 2). The protection was compared to preconditioning. Rats (study 3) in vivo in two different laboratories were postconditioned. Isolated mouse hearts (study 4) and mice in vivo (study 5) were postconditioned.Postconditioning did not protect isolated, perfused rat hearts, however, preconditioning improved function and reduced infarct size. Postconditioning tended to protect rat hearts in vivo in one laboratory (p = 0.10), whereas protection was seen in the other laboratory (infarct size 51+/-11% vs controls 62+/-3%, p = 0.01). Postconditioned mouse hearts were protected, both ex vivo (16+/-9% vs controls 33+/-18%, p = 0.02) and in vivo (21+/-5% vs 42+/-7%, p0.001).Rat hearts are less suitable for studies of mechanisms of postconditioning. The results suggest that the signaling pathways differ between pre- and postconditioning. Mouse hearts were strongly protected by postconditioning, and genetically engineered mice may be useful for postconditioning research.

Ischemic preconditioning may provide a systemic organ protection, evident as the phenomenon known as remote preconditioning. Unstable angina may be a clinical analogue to ischemic preconditioning. Vein graft harvesting induces inflammation of the graft wall. We hypothesized that preoperative unstable angina preconditions vein grafts and reduces the inflammatory response to graft harvesting. Consecutive patients with stable or unstable angina undergoing open heart surgery (n = 12 in each group) were studied. Saphenous vein biopsies were collected at the start of graft harvesting, and when the last proximal anastomosis to the aorta was finished (average 112 minutes later). Gene expression of inflammatory mediators (tumor necrosis factor alpha, interleukin-1beta (IL-1beta), E-selectin (CD62E), intercellular leukocyte adhesion molecule 1, inducible nitric oxide synthase, endothelin-1) increased after surgical handling (semiquantitative RT-PCR). In vein grafts from unstable patients the increase was attenuated for Il-1beta (p0.004) and CD62E (p0.001). In stable patients the protein expression of IkappaBalpha and heat shock protein72 was reduced by surgical handling (p0.04), but was not influenced in unstable patients (immunoblotting). In vitro relaxation to acetylcholine was enhanced, and contractions to phenylephrine and endothelin-1 were attenuated in veins rings from unstable patients (p0.003). In conclusion, surgical handling of vein grafts induces inflammation of the vessel wall. This response was reduced in grafts from patients with unstable angina, indicating a possible systemic preconditioning-like effect of acute coronary syndromes.

AIMS: The aim of this study was to test whether oral pre-treatment with rosuvastatin at a dosage giving clinically relevant plasma concentrations protects the myocardium against ischaemia/reperfusion injury and to investigate the involvement of nitric oxide (NO) and neutrophil infiltration. METHODS: Pigs were given placebo (n = 7), rosuvastatin (80 mg day(-1), n =7), rosuvastatin (160 mg day(-1), n = 7) or pravastatin (160 mg day(-1), n = 7) orally for 5 days before being subjected to coronary artery ligation and reperfusion. An additional group was given rosuvastatin 160 mg day(-1) and a nitric oxide synthase (NOS) inhibitor. RESULTS: Rosuvastatin 80 and 160 mg day(-1) resulted in plasma concentrations of 2.6 +/- 0.7 and 5.6 +/- 1.0 ng mL(-1), respectively. Serum cholesterol was not affected. Rosuvastatin 160 mg day(-1) and pravastatin limited the infarct size from 82 +/- 3% of the area at risk in the placebo group to 61 +/- 3% (P < 0.05), and to 61 +/- 2% (P < 0.05) respectively. Rosuvastatin 80 mg day(-1) limited the infarct size to 69 +/- 2%, however, this effect was not statistically significant. Rosuvastatin 160 mg day(-1) attenuated neutrophil infiltration in the ischaemic/reperfused myocardium. The protective effect of rosuvastatin 160 mg day(-1) was abolished by NOS inhibition. The expression of NOS2 and NOS3 in the myocardium did not differ between the groups. CONCLUSIONS: Oral pre-treatment with rosuvastatin limited infarct size following ischaemia/reperfusion without affecting cholesterol levels. The cardioprotective effect is suggested to be dependent on maintained bioactivity of NO, without influencing NOS expression.

Unstable coronary syndromes, initiated by rupture of an atherosclerotic plaque, may involve the activation of matrix metalloproteinases (MMPs). The regulation of MMP activity is complex and involves three steps. First, an inactive pro-MMP is transcriptionally regulated, a process that is likely to involve the transcription factor activator protein-1 (AP-1) and nuclear factor kappa B (NF-kappaB). Secondly, the pro-MMP is proteolytically cleaved into an active MMP. Plasmin has been suggested to be the major activator of MMPs in vivo. Thirdly, the activated MMP can be inhibited by tissue inhibitors of metalloproteinase (TIMPs). We investigated if expression of MMP9 and its potential regulators are induced in unstable coronary plaques. Atherosclerotic plaques from patients with stable (n=22) and unstable (n=39) angina were obtained by directional coronary atherectomy and analysed by semiquantitative RT-PCR and immunohisto-chemistry. Plasma was collected for ELISA analysis. mRNA for MMP9 as well as plasminogen activator inhibitor-1 (PAI-1) was increased in unstable plaques, while tissue type plasminogen activator (tPA) expression was similar in stable and unstable plaques. Plaques from unstable patients had an increased infiltration of macrophages and T-lymphocytes, nuclear localisation of AP-1 and the NF-kappaB subunit p65, as well as increased positive immunostaining for MMP9 and tPA. Plasma MMP9 antigen was elevated in unstable patients. MMP9 is expressed in the unstable coronary atherosclerotic plaque, as are its transcriptional and posttranscriptional regulators.