Postischemic Myocardial Dysfunction Research Articles

Morphine induces physiological, structural, and molecular benefits in the diabetic myocardium.

The obesity epidemic has increased type II diabetes mellitus (T2DM) across developed countries. Cardiac T2DM risks include ischemic heart disease, heart failure with preserved ejection fraction, intolerance to ischemia-reperfusion (I-R) injury, and refractoriness to cardioprotection. While opioids are cardioprotective, T2DM causes opioid receptor signaling dysfunction. We tested the hypothesis that sustained opioid receptor stimulus may overcome diabetes mellitus-induced cardiac dysfunction via membrane/mitochondrial-dependent protection. In a murine T2DM model, we investigated effects of morphine on cardiac function, I-R tolerance, ultrastructure, subcellular cholesterol expression, mitochondrial protein abundance, and mitochondrial function. T2DM induced 25% weight gain, hyperglycemia, glucose intolerance, cardiac hypertrophy, moderate cardiac depression, exaggerated postischemic myocardial dysfunction, abnormalities in mitochondrial respiration, ultrastructure and Ca2+ -induced swelling, and cell death were all evident. Morphine administration for 5 days: (1) improved glucose homeostasis; (2) reversed cardiac depression; (3) enhanced I-R tolerance; (4) restored mitochondrial ultrastructure; (5) improved mitochondrial function; (6) upregulated Stat3 protein; and (7) preserved membrane cholesterol homeostasis. These data show that morphine treatment restores contractile function, ischemic tolerance, mitochondrial structure and function, and membrane dynamics in type II diabetic hearts. These findings suggest potential translational value for short-term, but high-dose morphine administration in diabetic patients undergoing or recovering from acute ischemic cardiovascular events.

ДИАГНОСТИЧЕСКИЕ ПРИЗНАКИ РЕПЕРФУЗИОННОГО ПОВРЕЖДЕНИЯ МИОКАРДА ПРИ КОРОНАРНОМ ШУНТИРОВАНИИ

One of the main causes for operative mortality and perioperative complications after coronary artery bypass grafting is myocardial reperfusion injury following the restoration of the coronary circulation in the ischemic zone of the myocardium and characterized by myocardial, electrophysiological and vascular dysfunction. In order to identify the diagnostic signs of myocardial reperfusion injury after coronary artery bypass grafting, a prospective study was conducted, which included 89 patients with ischemic heart disease and forthcoming coronary artery bypass grafting either on-pump or off-pump. Postischemic myocardial dysfunction was assessed using transesophageal echocardiography, morphological and functional signs of myocardial reperfusion injury were detected using cardiac magnetic resonance imaging, moreover, the level of highly sensitive troponin, myoglobin, creatine phosphokinase-MB, metalloproteinase-2, and highly sensitive C-reactive protein was measured to assess the contribution of biomarkers to the development of reperfusion injuries. The obtained data allowed us to assess the morphological and functional characteristics of postischemic myocardial dysfunction and identify diagnostic signs of irreversible reperfusion injuries.

Custodiol (Histidine-Tryptophan-Ketoglutarate) versus Modified St. Thomas Cold Crystalloid Cardioplegia: Short-term Results

Abstract Background: Myocardial protection refers to strategies used to avoid post-ischemic myocardial dysfunction. One dose approach for myocardial safety is attractive in long operations. Purpose: to assess differences among the custodial cardioplegia and the cold crystalloid cardioplegia according to myocardial protection in cases listed for Double Valve Replacement Surgery. Patient and methods: This prospective cohort trial included 50 cases had double valve replacement surgery between August 2017 and July 2019. Twenty-nine patients were males (58%), and the mean age was 57.66±8.81 years. The mean ejection fraction was 41.43±9.25 %. Results: The mean CPB time in custodial group was 99.4±8.46 while in cold crystalloid cardioplegia group was 95.6±12.27 minutes. The mean DC shocks that was required in custodial group was 9(36%) while in cold crystalloid cardioplegia group was 17 (68%) times. Mean days of ICU stay in custodial group were 1.28±0.46 while in cold crystalloid cardioplegia group were 1.72±0.61 days. The mean duration of mechanical ventilation in custodial group was 4.64±0.86 while in cold crystalloid cardioplegia group was 7.04±0.84 hours. Troponin elevation mean in the immediate post-operative: in custodiol group was 8.46±2.21 while in the cold crystalloid group was 10.08±2.18. Conclusion: This study showed that the evidence supporting the superiority of custodial over cold crystalloid cardioplegia are limited however, Custodiol cardioplegia is appealing as it gives lengthy myocardial protection with a single-dose. The present work demonstrated that Histidine-Tryptophan-Ketoglutarate cardioplegia is related with less ICU stay, mechanical ventilation, postoperative hospitalization and troponin T release in low-risk patients who had double valve replacement.

Benzolamide perpetuates acidic conditions during reperfusion and reduces myocardial ischemia-reperfusion injury.

During ischemia, increased anaerobic glycolysis results in intracellular acidosis. Activation of alkalinizing transport mechanisms associated with carbonic anhydrases (CAs) leads to myocardial intracellular Ca2+ increase. We characterize the effects of inhibition of CA with benzolamide (BZ) during cardiac ischemia-reperfusion (I/R). Langendorff-perfused isolated rat hearts were subjected to 30 min of global ischemia and 60 min of reperfusion. Other hearts were treated with BZ (5 μM) during the initial 10 min of reperfusion or perfused with acid solution (AR, pH 6.4) during the first 3 min of reperfusion. p38MAPK, a kinase linked to membrane transporters and involved in cardioprotection, was examined in hearts treated with BZ in presence of the p38MAPK inhibitor SB202190 (10 μM). Infarct size (IZ) and myocardial function were assessed, and phosphorylated forms of p38MAPK, Akt, and PKCε were evaluated by immunoblotting. We determined the rate of intracellular pH (pHi) normalization after transient acid loading in the absence and presence of BZ or BZ + SB202190 in heart papillary muscles (HPMs). Mitochondrial membrane potential (ΔΨm), Ca2+ retention capacity and Ca2+-mediated swelling after I/R were also measured. BZ, similarly to AR, reduced IZ, improved postischemic recovery of myocardial contractility, increased phosphorylation of Akt, PKCε, and p38MAPK, and normalized ΔΨm and Ca2+ homeostasis, effects abolished after p38MAPK inhibition. In HPMs, BZ slowed pHi recovery, an effect that was restored after p38MAPK inhibition. We conclude that prolongation of acidic conditions during reperfusion by BZ could be responsible for the cardioprotective benefits of reduced infarction and better myocontractile function, through p38MAPK-dependent pathways. NEW & NOTEWORTHY Carbonic anhydrase inhibition by benzolamide (BZ) maintains acidity, decreases infarct size, and improves postischemic myocardial dysfunction in ischemia-reperfusion (I/R) hearts. Protection afforded by BZ mimicked the beneficial effects elicited by an acidic solution (AR). Increased phosphorylation of p38MAPK occurs in I/R hearts reperfused with BZ or with AR. Mitochondria from I/R hearts possess abnormal Ca2+ handling and a more depolarized membrane potential compared with control hearts, and these changes were restored by treatment with BZ or AR.

Effects of Combined Milrinone and Levosimendan Treatment on Systolic and Diastolic Function During Postischemic Myocardial Dysfunction in a Porcine Model.

It is not known whether there are positive or negative interactions on ventricular function when a calcium-sensitizing inotrope is added to a phosphodiesterase inhibitor in the clinical setting of acute left ventricular (LV) dysfunction. We hypothesized that when levosimendan is added to milrinone treatment, there will be synergetic inotropic and lusitropic effects. This was tested in an anesthetized porcine postischemic global LV injury model, where ventricular pressures and volumes (conductance volumetry) were measured. A global ischemic injury was induced by repetitive left main stem coronary artery occlusions. Load-independent indices of LV function were assessed before and after ventricular injury, after milrinone treatment, and finally after addition of levosimendan to the milrinone treatment. Nonparametric, within-group comparisons were made. The protocol was completed in 12 pigs, 7 of which received the inotrope treatment and 5 of which served as controls. Milrinone led to positive lusitropic effects seen by improvement in tau after myocardial stunning. The addition of levosimendan to milrinone further increased lusitropic state. The latter effect could however not be attributed solely to levosimendan, since lusitropic state also improved spontaneously in time-matched controls at the same rate during the corresponding period. When levosimendan was added to milrinone infusion, there was no increase in systolic function (preload recruitable stroke work) compared to milrinone treatment alone. We conclude that in this model of postischemic LV dysfunction, there appears to be no clear improvement in systolic or diastolic function after addition of levosimendan to established milrinone treatment but also no negative effects of levosimendan in this context.

Epigenetic Modulation of Myocardial Angiogenic Balance: An Emerging Therapeutic Perspective for Adult Failing Heart

The term "Epigenetics" refers to chromatin-based pathways involved in the regulation of gene expression without altering DNA sequence. Suppression of angiogenesis may be related to cardiac dysfunction following alterations in capillary microvasculature. An understanding of the relationship between angiogenesis and cardiac remodeling remains the major limitation in order to address the weak self-renewal ability of the adult failing heart. In physiological conditions, genes responsible for sustaining the angiogenic ability of the mature endothelial cells can be categorized into pro- and anti-angiogenic genes. The balanced expression of angiogenic genes maintains a state of equilibrium in capillary density of the adult myocardium. In the context of post-ischemic myocardial dysfunction, transcriptional and posttranscriptional modifications of the gene pool are involved in alterations of angiogenic balance in capillary microvasculature, angiogenesis, myocardial perfusion/contractility match and contractile function. The regulation of angiogenic gene expression by different epigenetic modifications may induce the formation of new vessels from coronary mature endothelial cells rather than endothelial progenitor cells. The role of proangiogenic epigenetic activators is emerging as a new actor in the modulation of the angiogenic balance of failing heart. In fact, the development of an ideal method to promote myocardial revascularization, while attenuating cardiac remodeling, is still a challenging issue. The present review will examine emerging studies on the epigenetic mechanisms involved in the regulation of function and angiogenic ability of mature endothelial cells residing in the adult myocardium.

Mitochondrial energy metabolism plays a critical role in the cardioprotection afforded by intermittent hypobaric hypoxia

Intermittent hypobaric hypoxia (IHH) is an effective protective strategy against myocardial ischaemia-reperfusion (I/R) injury, but the precise mechanisms are far from clear. To understand the overall effects of IHH on the myocardial proteins during I/R, we analysed functional performance and the protein expression profile in isolated hearts from normoxic rats and from rats adapted to IHH (5000 m, 4 h day(-1), 4 weeks) following I/R injury (30 min/45 min). Intermittent hypobaric hypoxia significantly improved the postischaemic recovery of left ventricular function compared with the recovery in time-matched normoxic control hearts. Two-dimensional electrophoresis with matrix-assisted laser desorption/ionization and time-of-flight mass spectrometric analysis was then used to assess protein alterations in left ventricles from normoxic and IHH groups, with or without I/R. The expressions of 16 proteins changed by over fivefold; nine of these proteins are involved in energy metabolism. Immunoblot and real-time PCR analysis confirmed the IHH-increased expressions of the ATP synthase subunit β, mitochondrial aldehyde dehydrogenase and heat shock protein 27 in left ventricles. Furthermore, IHH significantly attenuated the reduction of myocardial ATP content, mitochondrial ATP synthase activity, membrane potential and respiratory control ratios due to I/R. In addition, inhibition of mitochondrial ATP synthase by oligomycin (1 μmol l(-1)) abolished the IHH-induced improvements in three parameters: postischaemic recovery of left ventricular function, mitochondrial membrane potential and respiratory control ratios. These results suggest that an improvement in mitochondrial energy metabolism makes an important contribution to the cardioprotection afforded by IHH against postischaemic myocardial dysfunction.

Alternative use of isoflurane and propofol confers superior cardioprotection than using one of them alone in a dog model of cardiopulmonary bypass

Our previous clinical study reported that isoflurane preconditioning and high-dose propofol posttreatment attenuated myocardial ischemia/reperfusion injury of patients in surgery with cardiopulmonary bypass (CPB). This study was designed to confirm this cardiac protection by use of a dog CPB model and to elucidate the related mechanism. Adult mongrel male dogs undergoing standard CPB were assigned into 4 groups: Sham group, Propofol group, Isoflurane (Iso) group and isoflurane in combination of propofol (pre-Iso+P) group. After induction, anesthesia was maintained with propofol (Propofol group), isoflurane (Iso group) or isoflurane preconditioning in combination with propofol posttreatment (pre-Iso+P group). After 2h cardiac arrest and CPB, aortic cross-clamping was released to allow 2h reperfusion. The results demonstrated that joint use of isoflurane and propofol facilitated cardiac functional recovery, improved myocardial oxygen utilization and decreased cardiac enzyme release. Also, the oxidative damage caused by ischemia/reperfusion injury was remarkably attenuated. Linear regression analysis showed that cardiac function performance and oxidative stress status were inversely correlated, indicating the improved cardiac function was in closed association with the attenuation of oxidative stress. In addition, the cardiac oxygen consumption (VO2) was found to be significantly associated with the above cardiac function and oxidative stress parameters, suggesting VO2 was predictive for the levels of cardiac damage and oxidative stress. Therefore, we conclude that alternative use of isoflurane and propofol confers superior cardioprotection against postischemic myocardial injury and dysfunction, and this protection was probably mediated by attenuation of cardiac oxidative damage.

The Role of Reactive Oxygen Species in Contractile Dysfunction Following Ischemia/Reperfusion

Myocardial stunning occurs following ischemia-reperfusion, and is characterized by depressed contractility and elevated resting tension that is distinct from dysfunction associated with tissue damage or death. A wide variety of factors have been shown to contribute to post-ischemic myocardial dysfunction including cytosolic Ca2+ overload, acidosis, and the damaging effects of degradative enzymes and free radicals such as reactive oxygen species (ROS). These mechanisms act over a wide range of timescales. Intracellular Ca2+, Na+, and pH return to near pre-ischemic levels within a matter of minutes, while ROS production persists for up to three hours. The symptoms of myocardial stunning can persist even longer, indicative of a modified redox environment in the myocyte. Studies have revealed a number of sources of ROS production during reperfusion, but the mitochondria's role in regulating the balance of electron-carrying redox couples implicates cellular respiration as a critical source of ROS. In the modeling work presented here, we link a mathematical model of mitochondrial respiration and ROS production with a model of excitation-contraction coupling in the guinea pig myocyte. Experimentally determined ROS-dependent modulation of ryanodine receptors, sarcoplasmic reticulum (SR) Ca2+ ATPase, Na+-K+ ATPase and myofilaments is incorporated into our model. Using this integrated model, we show that contractile dysfunction associated with myocardial stunning persists after ROS-mediated alterations in protein function. ROS-related changes in Na+-K+ ATPase flux lead to altered intracellular Na+, which modulates diastolic intracellular Ca+ via the Na+-Ca2+ exchanger. Reduced SR Ca2+ ATPase activity and increased ryanodine receptor leak cause decreased SR Ca2+ load. Finally, ROS-related alteration of myofilament proteins reduces their Ca2+ sensitivity, which also contributes to decreased contractile force. Taken together, all of these mechanisms lead to contractile dysfunction caused by mitochondria-derived ROS.

Protective Effects of Cyclo(L-Leu-L-Tyr) against Postischemic Myocardial Dysfunction in Guinea-Pig Hearts

The protective effects of cyclic dipeptides in alcoholic beverages were investigated in the perfused guinea-pig hearts subjected to ischemia and reperfusion. Subsequently, in order to determine the importance of cyclic dipeptide structure, the effects of cyclo(L-Leu-L-Tyr) (cLY) were compared with those of the newly synthesized non-cyclic dipeptides, L-Leu-L-Tyr (LY) and L-Tyr-L-Leu (YL). After reperfusion, pressure recovery (%) in the left ventricle reached a peak of over 90% in the presence of cLY (10(-6) M and 10(-5) M) (control: 22.9%). The recovery by LY and YL was significantly lower than that by cLY, and ATP levels simultaneously monitored using (31)P-NMR were already lower during the ischemic end period than those observed with cLY treatment. In perfused mitochondrial preparations, cLY significantly inhibited mitochondrial Ca(2+) ([Ca(2+)](m)) elevation in a similar way to that of the mitochondrial permeability transition pore (MPTP) inhibitor cyclosporin A. In vitro electron paramagnetic resonance (EPR) revealed that the active oxygen radicals quenching activity of cLY was greater than those of non-cyclic dipeptides. cLY inhibited caspase-3-induced apoptosis. The cyclic dipeptide structure inhibits opening of the MPTP by preventing [Ca(2+)](m) overload-induced apoptosis related to mitochondrial active oxygen radical accumulation in ischemia-reperfusion hearts.

Catestatin Improves Post-Ischemic Left Ventricular Function and Decreases Ischemia/Reperfusion Injury in Heart

The Chromogranin A (CgA)-derived anti-hypertensive peptide catestatin (CST) antagonizes catecholamine secretion, and is a negative myocardial inotrope acting via a nitric oxide-dependent mechanism. It is not known whether CST contributes to ischemia/reperfusion injury or is a component of a cardioprotective response to limit injury. Here, we tested whether CST by virtue of its negative inotropic activity improves post-ischemic cardiac function and cardiomyocyte survival. Three groups of isolated perfused hearts from adult Wistar rats underwent 30-min ischemia and 120-min reperfusion (I/R, Group 1), or were post-conditioned by brief ischemic episodes (PostC, 5-cycles of 10-s I/R at the beginning of 120-min reperfusion, Group 2), or with exogenous CST (75 nM for 20 min, CST-Post, Group-3) at the onset of reperfusion. Perfusion pressure and left ventricular pressure (LVP) were monitored. Infarct size was evaluated with nitroblue-tetrazolium staining. The CST (5 nM) effects were also tested in simulated ischemia/reperfusion experiments on cardiomyocytes isolated from young-adult rats, evaluating cell survival with propidium iodide labeling. Infarct size was 61 ± 6% of risk area in hearts subjected to I/R only. PostC reduced infarct size to 34 ± 5%. Infarct size in CST-Post was 36 ± 3% of risk area (P < 0.05 respect to I/R). CST-Post reduced post-ischemic rise of diastolic LVP, an index of contracture, and significantly improved post-ischemic recovery of developed LVP. In isolated cardiomyocytes, CST increased the cell viability rate by about 65% after simulated ischemia/reperfusion. These results suggest a novel cardioprotective role for CST, which appears mainly due to a direct reduction of post-ischemic myocardial damages and dysfunction, rather than to an involvement of adrenergic terminals and/or endothelium.

Opioid receptor agonist reduces myocardial ischemic injury when administered during early phase of myocardial ischemia

Aim of the study Postresuscitation myocardial dysfunction is one of the leading causes of early death after initial success of resuscitation, the mechanisms of postresuscitation myocardial dysfunction remain controversial. We hypothesize that ischemia injury, rather than reperfusion injury is the major cause of postresuscitation myocardial dysfunction. We proposed to investigate the separate effects of ischemia and reperfusion injury on postresuscitation myocardial dysfunction. Methods Thirty-three Langendorff-perfused isolated rat hearts were subjected to 15 min of global ischemia followed by 120 min of reperfusion. Pentazocine was utilized as a myocardial protective agent, either before ischemia or during reperfusion. All hearts were randomized into 3 groups: (1) “ischemia protection”, in which pentazocine was infused 10 min prior to global ischemia, (2) “reperfusion protection”, in which pentazocine was infused during 2 h of reperfusion and (3) “control”, with no pentazocine infusion. Left ventricular (LV) functions were measured by the maximal rate of LV pressure rise (d P/d t max) and decline (−d P/d t max), the maximal LV diastolic pressure (LVDP). The incidences of postischemic arrhythmias were measured. Results When pentazocine was administered before onset of ischemia, the LV systolic and diastolic functions were significantly greater, and the postischemic arrhythmias were significantly less in comparison to those with reperfusion protection ( p < 0.05) and the control group ( p < 0.05). Conclusions In this model, the severity of postischemic myocardial dysfunction was less when the heart was protected during ischemia. Ischemia injury may therefore be the major cause of postresuscitation myocardial dysfunction.

The influence of FGF2 high molecular weight (HMW) isoforms in the development of cardiac ischemia–reperfusion injury

Fibroblast growth factor 2 (FGF2) consists of multiple protein isoforms (low [LMW] and high molecular weight [HMW]), which are localized to different cellular compartments, indicating unique biological activity. We previously showed that the LMW isoform is important in protecting the heart from myocardial dysfunction associated with ischemia–reperfusion (I/R) injury, but the roles of the HMW isoforms remain unknown. To elucidate the role of HMW isoforms in I/R and cardioprotection, hearts from novel mouse models, in which the murine FGF2 HMWs are knocked out (HMWKO) or the human FGF2 24 kDa HMW isoform is overexpressed (HMW Tg) and their wildtype (Wt) or non-transgenic (NTg) cohorts were subjected to an ex vivo work-performing heart model of I/R. There was a significant improvement in post-ischemic recovery of cardiac function in HMWKO hearts (76±5%, p<0.05) compared to Wt hearts (55±5%), with a corresponding decrease in HMW Tg function (line 20: 38±6% and line 28: 33±4%, p<0.05) compared to non-transgenic hearts (68±9%). FGF2 LMW isoform was secreted from Wt and HMWKO hearts during I/R, and a FGF receptor (FGFR) inhibitor, PD173074 caused a decrease in cardiac function when administered in I/R in Wt and FGF2 HMWKO hearts (p<0.05), indicating that FGFR is involved in FGF2 LMW isoform's biological effect in ischemia–reperfusion injury. Moreover, overexpression of HMW isoform reduced FGFR1 phosphorylation/activation with no further decrease in the phosphorylation state in the presence of the FGFR inhibitor. Overall, our data indicate that HMW isoforms have a detrimental role in the development of post-ischemic myocardial dysfunction.

Effects of a protocol of ischemic postconditioning and/or captopril in hearts of normotensive and hypertensive rats

Brief periods (a few seconds) of cyclic coronary occlusions applied early in reperfusion induce a cardioprotection against infarct size, called postconditioning (PostC) in which B(2)-bradykinin receptors play a pivotal role. Since angiotensin-converting enzyme (ACE) inhibitors reduce degradation of kinins, we studied the effects of PostC on infarct size and postischemic myocardial dysfunction in both normotensive (WKY) and spontaneously hypertensive rats (SHR) acutely or chronically treated with the ACE inhibitor Captopril. Isolated hearts from SHR and WKY rats were subjected to the following protocols: (a) ischemia for 30- and 120-min reperfusion (I/R); (b) I/R + PostC protocol (5-cycles 10-s I/R); (c) pretreatment with Captopril for 4-weeks before to subject the hearts to I/R with or without PostC maneuvers. Some SHR hearts were treated with Captopril during the 20- or 40-min early reperfusion with or without PostC maneuvers. Cardiac function was assessed in vivo with echocardiography. Left ventricular pressure and infarct size were measured ex vivo. Chronic Captopril significantly reduced left ventricular hypertrophy in SHR, and reduced infarct size in both WKY and SHR hearts. PostC maneuvers significantly reduced infarct size in WKY, but not in SHR hearts. Yet, PostC slightly improved postischemic systolic function in untreated SHR. Captopril given in reperfusion was unable to limit I/R injury in SHR hearts. Data show that PostC protection against infarct size is blunted in SHR and that PostC is unable to add its protective effect to those of chronic Captopril, which per se reduces cardiac hypertrophy and heart susceptibility to I/R insult.

Plasma concentrations of TNF‐α and its soluble receptors sTNFR1 and sTNFR2 in patients with coronary artery disease

Tumour necrosis factor alpha (TNF-alpha) is implicated in post-ischemic myocardial dysfunction. Two distinct TNF-alpha receptors are shed from cell membranes and circulate in plasma as soluble sTNFR1 and sTNFR2 proteins. The aim of the study was to establish factors associated with plasma concentrations of TNF-alpha and its receptors in patients with coronary artery disease (CAD). Since adenosine inhibits the expression of TNF-alpha, two functional polymorphisms in genes encoding enzymes participating in adenosine metabolism, i.e. AMP deaminase-1 (AMPD1, C34T) and adenosine deaminase (ADA, G22A), were analyzed. Plasma concentrations of TNF-alpha, sTNFR1, and sTNFR2 were measured using ELISA in 167 patients with CAD. Common factors significantly associated with higher TNF-alpha, sTNFR1, and sTNFR2 were lower glomerular filtration rate (GFR), older age, higher BNP, lower blood haemoglobin, and the presence of asthma or chronic obstructive pulmonary disease (COPD). Higher TNF-alpha and sTNFR1 concentrations were also associated with the presence of heart failure (HF), lower ejection and shortening fraction, the presence of diabetes or metabolic syndrome, lower serum HDL cholesterol, and higher uric acid. In multivariate analysis the common independent predictors of higher TNF-alpha, sTNFR1, and sTNFR2 were lower GFR, lower HDL cholesterol, higher BNP, and the presence of asthma or COPD. There were no associations between AMPD1 C34T or ADA G22A genotypes and TNF-alpha or its receptors. In conclusion, the concentrations of TNF-alpha, sTNFR1, and sTNFR2 reflect the impairment of cardiac and renal function in patients with CAD. Metabolic syndrome and diabetes are associated with higher plasma concentrations of TNF-alpha and its receptors.

Abstract 1055: The 70 kDa Heat Shock Cognate Protein Plays A Novel Role In Myocardial Chemokine Expression And Cardiac Dysfunction Following Ischemia And Reperfusion Injury

Myocardial ischemia and reperfusion (I/R) causes the release of cellular proteins including heat shock proteins (HSPs). The inducible HSP70 induces cytokine production in monocytes and dendritic cells through Toll-like receptor 4 (TLR4) signaling. In evaluation of the role of HSPs in myocardial inflammatory response in a mouse heart global I/R model, we found that the 70 kDa heat shock cognate protein (HSC70), but not HSP70, was released into the extracellular space and the coronary effluent during I/R. These observations prompted us to hypothesize that HSC70 plays a novel role in postischemic myocardial inflammatory response and cardiac dysfunction. Methods: We subjected mouse hearts to global I/R (20 min/60 min) or perfusion using the Langendorff method. We examined: the effect of HSC70 antibody on myocardial chemokine expression and cardiac functional recovery following I/R, the effect of recombinant HSC70 on myocardial chemokine expression and cardiac function and the role of TLR4 and the HSC70 substrate-binding domain in the effect of HSC70 on the heart. Results: In comparison with non-immune IgG, anti-HSC70 reduced myocardial expression of KC and MCP-1 mRNAs and proteins following I/R. Moreover, treatment with anti-HSC70 improved postischemic cardiac functional recovery (66±5.4% of baseline vs. 28±5.1% of baseline in hearts treated with non-immune IgG, p&lt;0.01). Recombinant HSC70 induced myocardial expression of KC and MCP-1 mRNAs and proteins and caused cardiac dysfunction (72±2.6% of baseline vs. 98±3.9% of baseline in perfusion controls, p&lt;0.001) in hearts with competent TLR4 (C3H/HeN). Interestingly, these effects of HSC70 were abrogated in hearts with defective TLR4 (C3H/HeJ). The potency of HSC70 was completely lost in the absence of its substrate-binding domain. Conclusions: Taken together, our studies demonstrate, for the first time, that HSC70 plays an important role in the induction of myocardial chemokines and cardiac dysfunction during I/R. The effect of HSC70 is dependent on TLR4 and requires the presence of the substrate-binding domain. The results suggest that the release of HSC70 into the extracellular space elicits an inflammatory response and causes mechanic dysfunction in the heart.

Cardioprotective effects of stretch are mediated by activation of sarcolemmal, not mitochondrial, ATP-sensitive potassium channels

To determine whether sarcolemmal and/or mitochondrial ATP-sensitive potassium (K(ATP)) channels (sarcK(ATP), mitoK(ATP)) are involved in stretch-induced protection, isolated isovolumic rat hearts were assigned to the following protocols: nonstretched hearts were subjected to 20 min of global ischemia (Is) and 30 min of reperfusion, and before Is stretched hearts received 5 min of stretch + 10 min of no intervention. Stretch was induced by a transient increase in left ventricular end-diastolic pressure (LVEDP) from 10 to 40 mmHg. Other hearts received 5-hydroxydecanoate (5-HD; 100 microM), a selective inhibitor of mitoK(ATP), or HMR-1098 (20 microM), a selective inhibitor of sarcK(ATP), before the stretch protocol. Systolic function was assessed through left ventricular developed pressure (LVDP) and maximal rise in velocity of left ventricular pressure (+dP/dt(max)) and diastolic function through maximal decrease in velocity of left ventricular pressure (-dP/dt(max)) and LVEDP. Lactate dehydrogenase (LDH) release and ATP content were also measured. Stretch resulted in a significant increase of postischemic recovery and attenuation of diastolic stiffness. At 30 min of reperfusion LVDP and +dP/dt(max) were 87 +/- 4% and 92 +/- 6% and -dP/dt(max) and LVEDP were 95 +/- 9% and 10 +/- 4 mmHg vs. 57 +/- 6%, 53 +/- 6%, 57 +/- 10%, and 28 +/- 5 mmHg, respectively, in nonstretched hearts. Stretch increased ATP content and did not produce LDH release. 5-HD did not modify and HMR-1098 prevented the protection achieved by stretch. Our results show that the beneficial effects of stretch on postischemic myocardial dysfunction, cellular damage, and energetic state involve the participation of sarcK(ATP) but not mitoK(ATP).

The Effects of Propofol on Cardiac Function After 4 Hours of Cold Cardioplegia and Reperfusion

To examine whether propofol protects against postischemic myocardial dysfunction and apoptosis during reperfusion after prolonged cold ischemia in isolated rat hearts. A prospective, randomized, controlled study. A university laboratory. Animals. The isolated hearts of 40 Sprague-Dawley male rats were perfused with modified Krebs-Hennseleit solution for 15 minutes for a stabilization period and 15 minutes for a perfusion period and then underwent 4 hours of global cold ischemia followed by 60 minutes of reperfusion. Four groups were studied (n = 10 for each group). Ten hearts served as an untreated control group. Propofol (2 micromol/L) treatment was performed only before ischemia in the PRE group, only during reperfusion in the POST group, and both before and after ischemia in the ALL group. Infusion of propofol during reperfusion improved recovery of left ventricular-developed pressure (LVDP) from 61.2% +/- 8.5% (control) to 86.3% +/- 12.1% (POST) and 74.9% +/- 13.2% (ALL, both p < 0.05), whereas preischemic infusion of propofol (64.3% +/- 9.7%, PRE) did not improve recovery of LVDP. Infusion of propofol during reperfusion significantly reduced the number of apoptotic cells and led to a smaller infarct size than control and PRE groups (p < 0.05, respectively). Propofol infusion during the reperfusion period produced a cardioprotective effect and inhibited apoptosis of cardiomyocytes in the ischemia-reperfusion model, with prolonged cold ischemia, in isolated rat hearts.

Ranolazine, an Inhibitor of the Late Sodium Channel Current, Reduces Postischemic Myocardial Dysfunction in the Rabbit

Ranolazine is a selective inhibitor of the late sodium current relative to peak sodium channel current, and via this mechanism, it may decrease sodium-dependent intracellular calcium overload during ischemia and reperfusion. Ranolazine reduces the frequency of angina attacks, but there is little information on its effects on myocardial stunning after short-term ischemia. The objective of this study was to test the effects of ranolazine on left ventricular (LV) function and myocardial stunning after ischemia/reperfusion in rabbits. Myocardial stunning was induced in rabbits by 15 minutes of coronary artery occlusion (CAO) followed by 3 hours reperfusion. Ten minutes before CAO, rabbits were randomly assigned to vehicle (n = 15) or ranolazine (2 mg/kg bolus plus 60 microg/kg/min infusion, IV, n = 15). Myocardial stunning was assessed by LV 2-dimensional echocardiography using, as a marker of severity, ischemic free-wall fractional thickening (FWft; systolic wall thickness - diastolic wall thickness/diastolic wall thickness). Regional ejection fraction (EF) was also assessed. During CAO, FWft was depressed in both groups, indicating an ischemic insult (FWft was reduced from 0.62 +/- 0.05 at baseline to 0.10 +/- 0.04 in vehicle and from 0.73 +/- 0.05 to 0.26 +/- 0.07 in ranolazine, P < 0.05, ranolazine vs vehicle). After reperfusion, previously ischemic myocardium remained stunned; however, FWft recovered significantly better in ranolazine (0.51 +/- 0.05) than in vehicle (0.35 +/- 0.04, P = .027). Baseline EF was 0.65 +/- 0.02 in the ranolazine and 0.68 +/- 0.02 in vehicle (P = ns). During CAO, EF was reduced by 36% +/- 6% in vehicle versus only 20% +/- 6% in ranolazine (P < .05). At the end of reperfusion, EF remained depressed in both groups, but the reduction in the vehicle group (25% +/- 5%) was significantly worse than in ranolazine (9% +/- 4%, P = .017). Improvement in function was independent of necrosis (negligible) or differences in hemodynamics (no differences between groups). Ranolazine treatment reduced myocardial stunning following brief ischemia/reperfusion suggesting that inhibiting the late sodium channel current may be a novel approach to treating stunning independent of effects on hemodynamics.

O2delivery and redox state are determinants of compartment-specific reactive O2species in myocardial reperfusion

Reperfusion of the ischemic myocardium leads to a burst of reactive O(2) species (ROS), which is a primary determinant of postischemic myocardial dysfunction. We tested the hypothesis that early O(2) delivery and the cellular redox state modulate the initial myocardial ROS production at reperfusion. Isolated buffer-perfused rat hearts were loaded with the fluorophores dihydrofluorescein or Amplex red to detect intracellular and extracellular ROS formation using surface fluorometry at the left ventricular wall. Hearts were made globally ischemic for 20 min and then reperfused with either 95% or 20% O(2)-saturated perfusate. The same protocol was repeated in hearts loaded with dihydrofluorescein and perfused with either 20 or 5 mM glucose-buffered solution to determine relative changes in NADH and FAD. Myocardial O(2) delivery during the first 5 min of reperfusion was 84.7 +/- 4.2 ml O(2)/min with 20% O(2)-saturated buffer and 354.4 +/- 22.8 ml O(2)/min with 95% O(2) (n = 8/group, P < 0.001). The fluorescein signal (intracellular ROS) was significantly increased in hearts reperfused with 95% O(2) compared with 20% O(2). However, the resorufin signal (extracellular ROS) was significantly increased with 20% O(2) compared with 95% O(2) during reperfusion. Perfusion of hearts with 20 mM glucose reduced the (.)NADH during ischemia (P < 0.001) and the (.)ROS at reperfusion (P < 0.001) compared with 5.5 mM-perfused glucose hearts. In conclusion, initial O(2) delivery to the ischemic myocardium modulates a compartment-specific ROS response at reperfusion such that high O(2) delivery promotes intracellular ROS and low O(2) delivery promotes extracellular ROS. The redox state that develops during ischemia appears to be an important precursor for reperfusion ROS production.