Continuous tepid blood cardioplegia can preserve coronary endothelium and ameliorate the occurrence of cardiomyocyte apoptosis

OBJECTIVE: In modern cardiac surgery, crystalloid or blood cardioplegic solutions have been used widely for myocardial protection; however, ischemia does occur during protection with intermittent infusion of cold crystalloid or blood cardioplegic solutions. The present study was designed to evaluate the effect of different cardioplegic methods on myocardial apoptosis and coronary endothelial injury after global ischemia, cardiopulmonary bypass (CPB), and reperfusion in anesthetized open-chest dogs. METHODS: The dogs were classified into five groups to identify the injury of myocardium and coronary endothelium: group 1, normothermic CPB without cardiac arrest; group 2, hypothermic CPB with continuous tepid blood cardioplegia, and with cardiac arrest; group 3, hypothermic CPB with intermittent cold blood cardioplegia, and with cardiac arrest; group 4, hypothermic CPB with intermittent cold crystalloid cardioplegia, and with cardiac arrest; and group 5, sham-operated control group. During CPB, cardiac arrest was achieved with different cardioplegia solutions for 60 min, followed by reperfusion for 4 h before the myocardium and coronary arteries were harvested. Coronary arteries were harvested immediately and analyzed by scanning electron microscopy. Cardiomyocytic apoptosis was detected using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling, Western blot, and DNA ladder methods. RESULTS: Regardless of the detection method used, significantly higher percentages of apoptotic cardiomyocytes were found in group 3 and group 4 than in other groups. Expression of caspase-3 correlated with increased apoptosis. Scanning electron microscopy revealed severe endothelial injury of coronary arteries in group 3 and group 4. CONCLUSION: These results point to an important explanation for the difference in cardiac recovery after hypothermic ischemia and arrest with various cardioplegic solutions.     

Remote ischemic preconditioning reduces myocardial injury after coronary artery bypass surgery with crystalloid cardioplegic arrest

Remote ischemic preconditioning (RIPC) with transient upper limb ischemia reduces myocardial injury in patients undergoing on-pump coronary artery bypass grafting (CABG) with cross-clamp fibrillation or blood cardioplegia for myocardial protection. Whether or not such protection is still operative when standard crystalloid cardioplegic arrest is used is uncertain. Fifty-three consecutive, non-diabetic patients with triple-vessel disease and 64 ± 12 years of age (mean ± SD), who underwent elective CABG surgery with crystalloid (Bretschneider) cardioplegic arrest, were allocated in a prospective, randomized, single-blinded protocol to receive either a RIPC protocol (3 cycles of 5 min transient left upper arm ischemia induced by inflating a blood pressure cuff to 200 mmHg with 5 min of reperfusion) or control, respectively, after induction of anesthesia. Cardiac troponin I (cTnI) concentration was measured preoperatively and over 72 h postoperatively, and the area under the curve (AUC) was calculated. Peak postoperative cTnI concentration was significantly reduced from 13.7 ± 7.7 ng/mL in controls to 8.9 ± 4.4 ng/mL in RIPC (P = 0.008). Mean cTnI concentration was significantly lower at 6, 12, 24, and 48 h after surgery (ANOVA; P < 0.0001) in the RIPC patients (N = 27) than in controls (N = 26), resulting in a 44.5% reduction of cTnI (AUC at 72 h). RIPC by repetitive inflation of a cuff around the left upper arm before surgery enhances myocardial protection in patients undergoing CABG surgery with antegrade cold crystalloid cardioplegia.     

大鼠体外循环基础上应用停跳液心脏停跳模型的建立

目的:在大鼠普通体外循环(CPB)模型基础上,建立灌注心停跳液心脏停跳(CA)模型,比较CA模型与普通CPB模型实验大鼠心肌缺血再灌注损伤情况;观察CA模型大鼠术后的存活和恢复情况。方法:借助血管穿刺置管技术,在大鼠普通CPB模型基础上,通过右侧颈总动脉置入双腔气囊导管,充气套囊、阻断升主动脉及灌注心脏停跳液使心脏停搏。比较CPB模型大鼠(n=6)和CA模型大鼠(n=15)心肌缺血再灌注损伤的区别;分别在术后1 d、1周和2周3个时点观察CA模型大鼠恢复情况(n=5)。结果:CA大鼠在心脏缺血再灌注60 min后,心型脂肪酸结合蛋白(HFABP)和心肌肌钙蛋白I(cTnI)明显高于术前基础值和普通CPB组水平,在复灌后3 h达到顶峰,术后1 d降低,在术后1周和2周的观察时点回降至术前水平。左心室射血分数(EF)在2组动物之间差别不大;舒张早期血流峰值/舒张晚期血流峰值比值(E/A比值)在CPB后降低,而在CA后进一步下降。CA组大鼠均存活,但术后质量明显降低,在术后1周时最为显著,2周时大鼠质量已经恢复,并且超过术前水平。结论:本实验在普通的CPB模型基础上成功的建立了CA模型。同普通CPB模型大鼠相比,CA模型大鼠在CPB心脏缺血再灌注后,出现了明显的心肌损伤。CA大鼠具有较高的存活率。     

Progressive loss of myocardial contractile function despite unimpaired coronary blood flow after cardiac surgery

Objective Mild to moderate transient contractile dysfunction is frequently observed after cardiac surgery on cardiopulmonary bypass (CPB) but may also lead to low–cardiac–output (LCO) failure especially in patients with unstable angina, and is often referred to represent myocardial stunning. Whether time course of contractile dysfunction after cardiac surgery is similar to that of myocardial stunning was investigated in pigs. Methods After baseline measurements of systemic hemodynamics (micromanometry), myocardial contractile function (sonomicrometry), cardiac output and coronary flow (ultrasonic probe), CPB was instituted. Control animals (n = 7) were weaned after 3 h from CPB. In LCO animals (n = 8), global ischemia was induced for 10 min by aortic crossclamping, followed by 1 h of cardioplegic cardiac arrest. After declamping and reperfusion, CPB was terminated after a total of 3 h. Measurements were repeated at 15 min, 4 h and 8 h after CPB. Systemic TNF–plasma concentrations were measured (ELISA) and left ventricular biopsies were analyzed with respect to myocardial TNF (immunohistochemistry) and irreversible cellular damage (light/electron microscopy). Results Contractile function decreased in LCO (75 ± 12%) and control (83 ± 17%) at 15 min compared to baseline (p < 0.05). Thereafter, contractile function remained unchanged in control, but progressively decreased in LCO (52 ± 12% at 4 h; 36 ± 5% at 8 h; p < 0.05). Coronary flow remained unchanged in both groups. Cardiac output progressively decreased to 2.8 ± 0.9 l/min at 8 h in the LCO group compared to baseline (5.9 ± 1.1 l/min, p < 0.05) and control (5.7 ± 1.4 l/min, p < 0.05). There was no evidence for myocardial infarction. TNF–plasma concentrations and myocardial TNF–staining were increased at 8 h after CPB in the LCO group compared to baseline and control (p < 0.05). Conclusions The progressive pattern of myocardial dysfunction apart from ongoing ischemia after cardiac surgery suggested underlying mechanisms at least partially different from those of myocardial stunning.     

Single-Dose del Nido Cardioplegia Compared With Standard Cardioplegia During Coronary Artery Bypass Grafting at a Veterans Affairs Hospital

Del Nido cardioplegic solution (DNC), used chiefly in pediatric patients, rapidly induces prolonged cardiac arrest during cardiac surgery. To determine whether surgical outcomes after coronary artery bypass grafting in a United States military veteran population differed when DNC was used instead of our standard Plegisol cardioplegia, we retrospectively reviewed 155 consecutive operations performed from July 2016 through June 2017. Del Nido cardioplegia was used to induce cardiac arrest in 70 patients, and Plegisol in 85.Compared with the Plegisol group, the DNC group had a shorter mean cardiopulmonary bypass time (96.8 vs 117 min; P <0.01) and aortic cross-clamp time (63.9 vs 71.7 min; P=0.02). On multiple linear regression, DNC use and number of bypasses performed were predictors of cardiopulmonary bypass time. The groups were similar in median number of bypasses performed, median time to extubation, intensive care unit stay, and total postoperative stay; however, the DNC group had a shorter mean operating room time (285.8 vs 364.5 min; P <0.01). Del Nido cardioplegia, number of bypasses, cardiopulmonary bypass time, and red blood cell transfusion were predictors of operating room time. Outcomes in the groups were similar for 30- and 180-day death, stroke, renal failure, ventilation time >48 hours, atrial fibrillation, tracheostomy, reintubation, and mechanical circulatory support. We conclude that single-dose DNC is safe, effective, and cost-effective for achieving cardiac arrest in U.S. veteran populations.     

Effects of beta-blockers and Ca2+ -antagonists on the response of the isolated working rat heart to adrenergic stimulants after cardioplegic arrest

Summary During coronary artery bypass graft (CABG) surgery, patients pretreated with the combination of beta-blocking drugs and Ca²⁺ antagonists for control of myocardial ischemia often respond inadequately to adrenergic stimulants administered after cardioplegic arrest. In this study, the effects of the combination of a beta-blocker (propranolol) and a Ca²⁺ antagonist (nifedipine) on the spontaneous recovery, as well as the adrenergic response of the isolated, perfused, working rat heart after a period of cardioplegic arrest were evaluated. After pretreatment of the animals with propranolol and/or nifedipine, hearts were removed, perfused in the presence of pretreatment drugs, subjected to 45 minutes of normothermic cardioplegic arrest, reperfused, and finally stimulated with exponentially increasing concentrations of a sympathomimetic drug. Propranolol, and to a lesser extent nifedipine, protected the hearts during cardioplegic arrest, as indicated by the improved recovery and maximum response to adrenergic stimulation after cardioplegia. Isoprenaline, a beta-stimulant, (at a 100 × higher than conventional concentration), elicited an adequate inotropic and chronotropic response. Stimulation by the alpha, beta-stimulant adrenaline or dobutamine improved only the inotropic response of propranolol and combination treated hearts. Cautious extrapolation of the results to human may suggest continuation of drug therapy of patients before CABG surgery.     

Activated protein C in the cardioplegic solution on a porcine model of coronary ischemia-reperfusion has deleterious hemodynamic effects

Summary Purpose: In reperfusion injury activation of coagulation and inflammation contribute to organ dysfunction. Activated protein C (APC) exhibits anticoagulant and anti-inflammatory properties in models of reperfusion injury. We hypothesized that APC could be cardioprotective after ischemia and cardiopulmonary bypass (CPB). Methods: 20 pigs, undergoing 120 min of CPB and aortic cross-clamping, were randomized to receive 1 mg of human APC or placebo to the last cardioplegic solution given 15 min before declamping to the systemic circulation. After aortic declamping the heart was supported by continuing CPB for 30 min followed by 30 min surveillance. Thrombin-antithrombin complexes, neutrophil L-selectin expression in blood and myeloperoxidase activity (MPO) of myocardial biopsies were measured. Results: There was no indication of APC-induced increased bleeding. Thrombin levels were significantly lower in the APC group than in the placebo group and so were the rates of thrombin formation during the first 3 min of reperfusion and between 10 and 30 min after declamping. There were no differences in MPO or in the proportion of L-selectin (+) to L-selectin (−) neutrophils between groups. Significant systolic hypotension in the APC group was observed at 30 and 45 min compared with the placebo group which associated with the increased mortality observed in the APC group (p = 0.019). Conclusions: Human APC in cardioplegic solution during CPB in pigs, decreased reperfusion induced thrombin formation with no associated bleeding. No anti-inflammatory effects of human APC were seen. However, in this setting, APC caused hemodynamic deterioration. The observed phenomenon could be explained by systolic hypotension potentially produced by the release of vasoactive substances generated by the APC activation of PARs in the endothelium.     

Remote intermittent ischemia before coronary artery bypass graft surgery: a strategy to reduce injury and inflammation?

Perioperative myocardial ischemia contributes to postoperative morbidity and mortality. Remote intermittent ischemia (RI) has been shown to benefit patients undergoing coronary artery bypass graft (CABG) surgery by decreasing postoperative cardiac troponin levels. In addition, there is evidence that volatile anesthetics may provide myocardial protection. In this prospective randomized controlled trial we tested the hypothesis that RI is cardioprotective under a strict anesthetic regime with volatile anesthesia until cardiopulmonary bypass (CPB). We also assessed whether RI modulates postoperative cytokine and growth factor concentrations. Fifty-four patients referred for elective CABG surgery without concomitant valve or aortic surgery were randomized to three 5-min cycles of left upper limb ischemia by cuff inflation (RI) or placebo without cuff inflation (Plac). All patients received the volatile anesthetic isoflurane (1.15–1.5 vol%) before CPB and the intravenous anesthetic propofol (3–4 mg/kg/h) thereafter until the end of surgery. Cardiac arrest during CPB was induced by intermittent cross-clamp fibrillation, or by blood cardioplegia. We excluded patients older than 85 years, with unstable angina, significant renal disease, and those taking sulfonylureas. Troponin I (cTnI) was measured preoperatively and after 6, 12, 24 and 48 h. In addition, brain natriuretic peptide (BNP), creatine kinase (CKMB) and a panel of cytokines and growth factors were analyzed perioperatively. Although cTnI, BNP and CKMB all increased post-CABG, there were no significant differences between RI and Plac groups; area under the curve for cTnI 189.4 (183.6) ng/mL/48 h and 183.0 (155.2) ng/mL/48 h mean (SD), p = 0.90, respectively, despite a tendency to a shorter (p < 0.07) cross-clamp time in the treatment group. Similarly, there were no differences between groups in the central venous concentrations of numerous cytokines and growth factors. In patients undergoing CABG surgery RI does not provide myocardial protection under a strict anesthetic regime with volatile anesthesia until CPB, and RI was not associated with changes in cytokines.     

Role of IL-1b and TNF-a in the regulation of NGF in experimentally induced arthritis in mice

The aim of this study was to investigate the effects of IL-1β and TNF-α on NGF levels in the knee joint in experimentally induced arthritis in adult mice. Out data showed that IL-1β, but not TNF-α, induces an increase in NGF levels, while concomitant injection of both cytokines enhances the effect of IL-1β on NGF presence. Analysis of NGF levels in the knee joint of carrageenan- and IL-1β-induced inflammation after administration of antibodies against TNF-α supports this hypothesis. Our studies also showed that exogenous administration of NGF antibody reduces the enhanced level of TNF-α occurring in arthritic mice. This latter observation indirectly suggests that NGF is implicated in the upregulation of TNF-α in these animal models of joint inflammation. The functional significance of NGF or NGF antibody in inflammatory arthritis is discussed. Received: 16 March 1998 / Accepted: 2 July 1998     

Dose-Dependent Effect of Aprotinin on Aggravated Pro-Inflammatory Cytokines in Patients with Pulmonary Hypertension Following Cardiopulmonary Bypass

Background: To investigate the dose dependent effect of aprotinin on aggravated pro-inflammatory cytokines in patients with pulmonary hypertension (PH) after cardiopulmonary bypass (CPB). Methods: Thirty-two patients with pulmonary arterial pressure (PAP) above 60 mmHg were recruited. They were assigned randomly to control (Group A, n = 8), and treated groups (Group B with aprotinin = 0.5 × 10⁵ KIU/Kg, and Group C with aprotinin = 1.0 × 10⁵ KIU/Kg, n = 12 each group). Blood samples were collected at various intervals of time and analyzed, from 0 hour (before CPB as baseline), at the completion of CPB, 4 hours and 24 hours after CPB, to measure the concentrations of interleukin 1 (IL-1), interleukin-8 (IL-8), interleukin-10 (IL-10) and tumor necrosis factor- (TNF-). Results: All the biomarkers significantly increased after CPB. There was no significant difference in cytokine levels between Group A and group B after CPB. But IL-1, IL-8 and TNF- of Group C were not only significantly lower than Group A (p < 0.05), but also lower than Group B at various time points after CPB (p < 0.05). IL-10 of group C was significantly higher than Group A and Group B after CPB (p < 0.05). Conclusions: High dose aprotinin can suppress the release of pro-inflammatory cytokines IL-1, IL-8 and TNF-, and enhance the release of IL-10 in patients with PH after CPB. For patients having PH, there exists a simple and potential way to reduce the inflammatory response by applying high dose aprotinin.     

Effect of edaravone, a novel free radical scavenger, supplemented to cardioplegia on myocardial function after cardioplegic arrest: in vitro study of isolated rat heart

Cardioplegic arrest has been the main mechanism of myocardial protection during open-heart surgery; however, it causes myocardial injury during ischemia-reperfusion. Free radical scavengers are widely known to attenuate ischemia-reperfusion injury in various settings. We investigated the effects of edaravone, a novel free radical scavenger that was originally used for cerebral protection, on myocardial function during ischemia-reperfusion after cardioplegic arrest. Rat hearts were excised and perfused using Langendorff apparatus. The hearts were cardioplegically arrested for 90 min using St. Thomas’ Hospital cardioplegic solution (ST solution) at 4°C every 45 min and then reperfused for 20 min. The hearts were divided into 4 groups (n = 13 in each group). In Group ST, the hearts were arrested using the ST solution alone. In Groups L, M, and H, the hearts were arrested using the ST solution supplemented with a low-dose (1 μM), moderate dose (10 μM), and high dose (100 μM) of edaravone, respectively. Left ventricular function (+dp/dt _max) and the levels of the cardiac enzymes released were measured before and after cardioplegic arrest. At the end of the study, the water content and the tissue oxidative stress (8-hydroxy-2′-deoxyguanosine) of the heart were measured. During reperfusion, the edaravone-treated groups showed a greater functional recovery with regard to the +dp/dt _max (P < 0.05). The lactate level was the lowest (P < 0.01) in Group M. The water content of the hearts in the edaravone-treated groups was significantly lower (P < 0.05) than that in Group ST. Oxidative stress was significantly lower (P < 0.01) in the edaravone-treated hearts than in Group ST, and it was the lowest in Group M. The addition of edaravone to the cardioplegic solution ameliorates the impairment in myocardial function by reducing the oxidative stress after cardioplegic arrest. In this study, the maximum improvement in the myocardial function was achieved by addition of a moderate dose (10 μM) of edaravone.     

The ghrelin O-acyltransferase–ghrelin system reduces TNF-α-induced apoptosis and autophagy in human visceral adipocytes

Aims/hypothesis  

Proinflammatory and proapoptotic cytokines such as TNF-α are upregulated in human obesity. We evaluated the association between ghrelin isoforms (acylated and desacyl ghrelin) and TNF-α in obesity and obesity-associated type 2 diabetes, as well as the potential role of ghrelin in the control of apoptosis and autophagy in human adipocytes.     

Moderation of myocardial ischemia reperfusion injury by calcium channel and calmodulin receptor inhibition

Summary Intracellular Ca²⁺ accumulation is implicated in the pathogenesis of myocardial reperfusion injury. To study approaches designed to modify Ca²⁺ uptake during coronary revascularization after acute infarction, a pig heart surgical infarct model (left anterior descending artery occlusion for 60 min) was subjected to 60 min hypothermic potassium cardioplegic arrest, followed by 60 min of global reperfusion. Four groups of six hearts each were studied in a randomized manner, i.e., cardioplegia alone (control), cardioplegia + 10 µM diltiazem (Ca²⁺ slow channel blocker), cardioplegia + 10 µM trifluoperazine (TFP), (a Ca²⁺-calmodulin antagonist), and cardioplegia + diltiazem (10 µM) + TFP (10 µM). Left ventricular contractility (global and segmental), metabolism (coronary blood flow and O₂ consumption), and creatine kinase generation were measured during reperfusion. Both the Ca²⁺ channel blocker, diltiazem, and the calmodulin antagonist, TFP, improved myocardial global and regional function as well as myocardial metabolism. While diltiazem better restored global and regional contractility, trifluoperazine had a greater effect on coronary blood flow and myocardial oxygen consumption. Enzyme release and lipid peroxidation were equally moderated by both drugs. From this study it can be concluded that Ca²⁺ influx does play a role in ischemic and reperfusion injury. The mechanisms of its effect are complex, but can be successfully antagonized by Ca²⁺ blockers as well as by calmodulin antagonists, with improved myocardial preservation.Supported in part by grants NIH HL 22559 and HL 34360     

Attenuation of myocardial injury by postconditioning: role of hypoxia inducible factor-1α

Postconditioning (PostC) has regenerated interest as a mechanical intervention against myocardial ischemia/reperfusion injury, but its molecular mechanisms remain elusive. This study tested the hypothesis that hypoxia inducible factor-1α (HIF-1α) plays a role in PostC-induced cardioprotection. Male Wistar rats were subjected to 30 min ischemia followed by 3 h of reperfusion (Control). PostC with 3 cycles of 10 s reperfusion and 10 s re-occlusion was applied at the onset of reperfusion. Relative to the Sham group, HIF-1α protein level was increased by 2.9-fold in the Control group, but its level was enhanced by 5.8-fold with PostC (P < 0.01 vs. Control). However, HIF-1α protein level was further augmented by 2.0-fold and 3.3-fold, respectively, when the prolyl hydroxylase inhibitor, dimethyloxalylglycine (DMOG, 40 mg/kg, i.p.) was given at 24 h before ischemia in both Control and PostC groups. PostC reduced infarct size by 24% compared with the Control (27 ± 4.2% vs. 36 ± 5.2%, P < 0.01), consistent with significant lower levels of plasma creatine kinase activity, index of cardiomyocyte apoptosis and caspase-3 activity. Although pretreatment with DMOG significantly reduced infarct size relative to the Control, the infarct-sparing effect of PostC was remarkably enhanced when DMOG was given before PostC (18 ± 2.0% vs. 27 ± 4.2% in PostC alone, P < 0.05). There was a significant linear inverse relationship between HIF-1α protein level and infarct size (r = −0.799, P < 0.01) among all groups. Furthermore, along with up-regulated HIF-1α expression, the levels of iNOS mRNA and protein were significantly increased in the PostC alone and DMOG plus PostC groups. In conclusion, these data suggest that HIF-1α is involved in cardioprotection by PostC and pharmacological augmentation of HIF-1α expression that enhances the infarct-sparing effect of PostC; iNOS, the downstream gene of HIF-1α, may participate in signaling pathways in mediating PostC’s protection.     

Differentiation profile of peripheral blood-derived vascular progenitor cell predicts intimal hyperplasia after coronary stenting

In-stent restenosis is largely due to intimal hyperplasia (IH). The number of vascular progenitor cells (VPCs) mobilized at the acute phase after stenting is associated with IH. This study sought to determine whether the differentiation profile of VPC predicts the development of IH. Peripheral blood was collected in 58 patients after bare-metal stenting to culture VPCs. Intravascular ultrasound was performed to estimate the area of IH 6 months after stenting. VPC differentiation was determined using flow cytometry. VE-cadherin (VE-Cad) and α-smooth muscle actin (α-SMA) were used to identify endothelial and smooth muscle cell lineages, respectively. After culturing, VPCs differentiated into four different phenotypes (α-SMA⁻VE-Cad⁺, α-SMA⁺VE-cad^high, α-SMA⁺VE-cad^low, and α-SMA⁺VE-Cad⁻). IH was correlated with gender (P = 0.04), smoking status (P = 0.04), reference diameter (P = 0.03), minimal lumen diameter (P = 0.03), stent area (P < 0.0001), and parameters in the VPC differentiation profile (P < 0.05). Multivariate analysis controlling for stent area, smoking status, and gender revealed that IH was positively and independently associated with the number of differentiated α-SMA⁺VE-Cad ^low/− VPCs (P < 0.0001), and the ratio of α-SMA⁺VE-Cad ^low/− VPCs to α-SMA⁻VE-Cad⁺ VPCs (P = 0.001). These parameters in the VPC differentiation profile independently predicted the IH and provided additive information to traditional risk factors. In conclusion, the profile of VPC differentiation predicts the severity of post-stent IH and may be a potential tool in the future for clinicians to identify patients at risk of post-stent restenosis.     

Preceding unstable angina affects inflammatory response and hemodynamics after coronary artery bypass surgery

The authors set out to investigate the inflammatory response and its impact on the hemodynamic function in stable and unstable coronary artery bypass (CABG) patients. Nineteen stable and twenty unstable patients were included in this prospective study. Serum IL-6, IL-8, TNF-, and IL-10 were measured before, during and after cardiopulmonary bypass (CPB). Hemodynamic data was also collected. TNF- was detected more often in unstable patients than in stable patients before (p=0.03) and after CPB (p<0.01). TNF- response after CPB was evident (p=0.03). Serum IL-6 and IL-8 level were significantly increased after 10 minutes of CPB, reaching the peak value at 6 hours after declamping. IL-10 level reached the highest, 6.8 × the baseline at 6 hours after declamping in the unstable, but 3.3 × of baseline on the first post-operative day (POD) in the stable patients (p=0.04). CI was better preserved in unstable patients (p=0.04). Serum TNF- was more likely to be found in patients with recent unstable episodes. CPB induces a release of serum IL-6, IL-8 and IL-10. Recent unstable angina seems to modify the cytokine response and hemodynamic outcome.     

TNFα protects cardiac mitochondria independently of its cell surface receptors

Our novel proposal is that TNFα exerts a direct effect on mitochondrial respiratory function in the heart, independently of its cell surface receptors. TNFα-induced cardioprotection is known to involve reactive oxygen species (ROS) and sphingolipids. We therefore further propose that this direct mitochondrial effect is mediated via ROS and sphingolipids. The protective concentration of TNFα (0.5 ng/ml) was added to isolated heart mitochondria from black 6 × 129 mice (WT) and double TNF receptor knockout mice (TNFR1&2^−/−). Respiratory parameters and inner mitochondrial membrane potential were analyzed in the presence/absence of two antioxidants, N-acetyl-l-cysteine or N-tert-butyl-α-(2-sulfophenyl)nitrone or two antagonists of the sphingolipid pathway, N-oleoylethanolamine (NOE) or imipramine. In WT, TNFα reduced State 3 respiration from 279.3 ± 3 to 119.3 ± 2 (nmol O₂/mg protein/min), increased proton leak from 15.7 ± 0.6% (control) to 36.6 ± 4.4%, and decreased membrane potential by 20.5 ± 3.1% compared to control groups. In TNFR1&2^−/− mice, TNFα reduced State 3 respiration from 205.2 ± 4 to 75.7 ± 1 (p < 0.05 vs. respective control). In WT mice, both antioxidants added with TNFα restored State 3 respiration to 269.2 ± 2 and 257.6 ± 2, respectively. Imipramine and NOE also restored State 3 respiration to 248.4 ± 2 and 249.0 ± 2, respectively (p < 0.01 vs. TNFα alone). Similarly, both antioxidant and inhibitors of the sphingolipid pathway restored the proton leak to pre-TNF values. TNFα-treated mitochondria or isolated cardiac muscle fibers showed an increase in respiration after anoxia–reoxygenation, but this effect was lost in the presence of an antioxidant or NOE. Similar data were obtained in TNFR1&2^−/− mice. TNFα exerts a protective effect on respiratory function in isolated mitochondria subjected to an anoxia–reoxygenation insult. This effect appears to be independent of its cell surface receptors, but is likely to be mediated by ROS and sphingolipids.     

Effect of a Calcium-Sensitizing Agent, Levosimendan, on the Postcardioplegic Inotropic Response of the Myocardium

Myocardial contractile function after coronary artery bypass graft surgery is often depressed and may require inotropic support, particularly in patients on treatment with beta-adrenergic and Ca²⁺ blockers. In view of the increase in cytosolic Ca²⁺ during early reperfusion, use of Ca²⁺ sensitizing agents may be preferable to adrenergic agonists for enhancement of contractile function after cardioplegic arrest. The aim of this study was to assess the efficacy of the Ca²⁺ sensitizer, levosimendan, as an inotrope on the mechanical recovery of hearts after normothermic and hypothermic cardioplegic arrest in the absence and presence of Ca²⁺ and beta-blockers. Isolated perfused working guinea pig hearts were perfused in the absence or presence of propranolol (10^–6 M) and/or nifedipine (10^–8 M), subjected to 45 minutes of normothermic or 180 minutes of hypothermic cardioplegic arrest, reperfused, and exposed to increasing concentrations of levosimendan (10^–9 to 10^–6 M). Levosimendan (10^–7 to 10^–6 M) has positive inotropic, chronotropic, and vasodilatory effects on normoxic perfused control hearts, as well as during reperfusion after 45 minutes of normothermic cardioplegic arrest. Similar effects were elicited in the presence of the blockers. Levosimendan had no stimulatory effect during reperfusion of hearts subjected to prior hypothermic arrest. Except for the increase in heart rate, the effects of levosimendan on functional performance during reperfusion were comparable with those of adrenaline. Levosimendan elicits a positive inotropic and chronotropic response during reperfusion of hearts after normothermic cardioplegic arrest, both in the absence and presence of Ca²⁺ and beta-adrenergic blockers.     

Cardioprotective effect of diadenosine tetraphosphate (AP4A) cardioplegia in isolated rat hearts

Preischemic administration of diadenosine tetraphosphate (AP4A) has been shown to be cardioprotective. We evaluated the protective effect of AP4A when used as a cardioplegic adjuvant and tested contributions of the ATP-sensitive potassium channel (K_ATP channel), adenosine receptor (AR), and purine 2y receptor (P2yR) to the effect of AP4A. Isolated buffer-perfused rat hearts were subjected to 23 min of ischemia (37°C) followed by 20 min of reperfusion. Cardioplegia solution (St. Thomas Hospital solution) was infused during the first 3 min of ischemia. AP4A (10 μM) or AP4A with glibenclamide (K_ATP channel blocker, 100 μM), 8-SPT (AR antagonist, 300 μM) or reactive blue (P2yR antagonist, 13 nM) were added to the cardioplegia solution. Compared with the cardioplegia solution alone, administration of AP4A with the solution significantly increased the recovery of rate-pressure production (75% ± 11% vs 58% ± 10%; P < 0.05) and dp/dt at the end of reperfusion, and reduced the leakage of creatine kinase (3.2 ± 3.7 vs 13.2 ± 10.1 IU/g; P < 0.05) during reperfusion. This effect was reversed by coadministration of glibenclamide or reactive blue but not 8-SPT. The addition of AP4A into the cardioplegia solution led to an added cardioprotective effect, either by opening the K_ATP channel or by activating P2yR. Received: November 2, 1999 / Accepted: March 3, 2000