Myocardial Release Research Articles

Assessment of myocardial necrosis biomarker release after acute myocardial infarction determined by kinetic modeling and correlation with infarct size determined by magnetic resonance imaging

Infarct size (IS) is a key determinant of cardiovascular events and is ideally assessed by cardiac MRI. MRI availability is limited and many studies used necrosis biomarkers (CK, troponin) as a surrogate marker of IS by determination of their peak concentration and/or their area under the concentration versus time curve (AUC). These biological methods, excluding biomarkers kinetic data may provide inaccurate results. We recently developed a compartmental kinetic model allowing estimation of the total amount of necrosis biomarker released during ST-segment elevation myocardial infarction (STEMI), noted A0. The aim of this study was to determine the correlation level between the amount of biomarkers released in STEMI patients obtained with this kinetic modeling and cardiac MRI measurements of IS. We retrospectively included all patients admitted for STEMI in Tours University Hospital (France) from February 2015 to September 2017, that were treated by primary percutaneous coronary intervention and who had had a cardiac MRI in the days following their admission. CK, troponin I (cTnI) and troponin T (cTnT) concentrations data were collected and kinetics of these biomarkers were described by our kinetic model. For each biomarker, we compared the maximum concentration (Cmax), AUC and A0 determined by the model to cardiac MRI measurements of IS. Among the 41 patients included, all had CK assays available, 16 had cTnI assays (cTnI subgroup) and 25 hadcTnT assays (cTnT subgroup) available. The model described satisfactorily biomarker kinetic data with only 3 values of each biomarker. IS was correlated with all CK and cTnT parameters, particularly with CK Cmax (R2 = 64,8%) and cTnT A0 (R2 = 67,1%). For cTnI, there was no correlation between IS and cTnI Cmax (R2 = 2%). Furthermore, in cTnI subgroup, IS correlation was stronger with CK parameters than with cTnI parameters. This model allows an accurate description of necrosis biomarkers kinetics following STEMI, which only few measurements. Estimated parameters, particularly CK peak concentration and the total amount of cTnT released by the injured myocardium, were highly correlated to IS measured by cardiac MRI. This method may be used in future clinical trials on the assessment of therapies aiming to reduce IS, such as conditioning therapies.

Protective effect of insulin on myocardial ischemia-reperfusion injury in diabetic rats based on PI3K/Akt signaling pathway

Objective To study the effect of insulin on phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway in diabetic rats with myocardial ischemia reperfusion injury. Methods Diabetic rats were induced by high-sugar and high-fat diet plus intraperitoneal injection of streptozotocin (40 mg/kg). They were randomly divided into diabetic sham group (group A), diabetes ischemic reperfusion group (group B), diabetes ischemic reperfusion insulin treatment group (group C) and diabetic ischemia reperfusion+ insulin Wortmaninn (PI3K inhibitors) group (group D), 10 in each group. Myocardial ischemia reperfusion model in diabetic rats: heart was exposed between the third and fourth ribs of the left chest, 2 mm from the lower edge of the left atrial ear, and 5-0 sterile suture was used to ligate the anteri-or descending coronary artery (LAD) and the great cardiac vein for 30 min, and then the perfusion was resumed for 120 min.Wortmannin (15 μg/kg) was given through femoral vein 20 min before ligation in group D, and the same amount of normal saline was given in the other 3 groups.Insulin (2 U/kg) was injected subcutaneously in group C and D 10 min before ligation, and the same amount of normal saline was injected subcutaneously in group A and group B. Plasma creatine kinase MB (CK-MB)and troponin I (cTnI) levels were measured in arterial blood after 120 min of reperfusion, and PI3K and Akt expression in myocardial tissue were detected by Western blot. Results Compared with the group A, the plasma levels of cTnI and CK-MB increased and the expressions of PI3K and phosphorylated protein kinase B (p-Akt) in myocardium decreased in the group B (P<0.05). After insulin treatment, the plasma cTnI [(0.89±0.26)μg/L], CK-MB [(9.24±3.16)μg/L] in the myocardial tissue of the group C decreased, while the expression of PI3K (0.341 8±0.03 1) and p-Akt (0.673 1±0.028) in the myocardial tissue increased (P<0.05). After insulin+ Wortmaninn administration, the plasma cTnI [(1.16±0.29)μg/L] and CK-MB [(12.57±3.01)μg/L] in the group D increased , while the expression of PI3K (0.292 7±0.036) and p-Akt (0.531 4±0.030) in the myocardial tissue decreased, with statistically significant difference (P<0.05). Conclusions Insulin can reduce serum CK-MB and cTnI levels in diabetic rats with myocardial ischemia reperfusion injury, possibly by activating PI3K/Akt signal transduction pathway, inhibiting myocardial enzyme release, and improving myocardial ischemia reperfusion injury in diabetic rats to play a protective role in myocardial cells. Key words: 1-phosphatidylinositol 3-kinase; Protein kinases; Insulin; Diabetes mellitus; Reperfusion injury; Rats

Accentuated antagonism of vagal heart rate control and less potent prejunctional inhibition of vagal acetylcholine release during sympathetic nerve stimulation in the rat.

Complex interactions are known to occur between the sympathetic and parasympathetic controls of the heart. Although sympathetic nerve stimulation (SNS) usually augments the heart rate (HR) response to vagal nerve stimulation (VNS), exogenously administered norepinephrine (NE) can attenuate the HR response as well as the myocardial interstitial acetylcholine (ACh) release during VNS. To provide a basis for an integrative knowledge about the opposing adrenergic effects on the vagal control of the heart, we examined whether SNS significantly attenuates VNS-induced myocardial interstitial ACh release in the in vivo beating heart. In nine anesthetized rats, changes in HR and myocardial interstitial ACh release in response to 5- and 20-Hz VNS were examined in both the absence and presence of a 5-Hz background SNS. The SNS significantly enhanced the VNS-induced HR reduction during 20-Hz VNS (-101.2 ± 33.1 vs. -163.0 ± 34.9 beats/min, P < 0.001, a 60% augmentation). By contrast, the SNS significantly attenuated the ACh release during 20-Hz VNS (4.30 ± 0.72 vs. 3.80 ± 0.75 nM, P < 0.01, a 12% attenuation). In conclusion, SNS exerted only a moderate inhibitory effect on the VNS-induced myocardial interstitial ACh release in the in vivo beating heart.

Increased Cardiac Uptake of Ketone Bodies and Free Fatty Acids in Human Heart Failure and Hypertrophic Left Ventricular Remodeling.

Deranged energy metabolism contributes to the pathophysiology of heart failure (HF). Recent studies showed diminished free fatty acid (FFA) oxidation in experimental HF models with a shift towards oxidation of ketone bodies. However, conflicting clinical data on FFA metabolism and limited knowledge on ketone body metabolism in human HF mandate additional metabolic profiling studies. We, therefore, investigated cardiac uptake of FFAs and ketone bodies (β-hydroxybutyrate and acetoacetate) in patients with HF with reduced ejection fraction (HFrEF) or with aortic stenosis (AS)-induced left ventricular hypertrophy. We hypothesized that FFA oxidation is impaired in HFrEF and in AS and results in decreased concentrations of free carnitine, the necessary carrier for mitochondrial entry of activated FFAs, and in accumulation of metabolic intermediates. We collected arterial and coronary sinus blood samples in patients with HFrEF (n=15), in AS patients with preserved systolic function (n=15), and in control patients (n=15). Plasma concentration gradients across the heart show significantly greater uptake of ketone bodies in patients with HFrEF than in controls. Patients with AS show significantly increased uptake of β-hydroxybutyrate and FFAs. Free carnitine concentration and concentration gradients of intermediates of FFA oxidation were comparable between groups. In conclusion, our results show significantly increased cardiac uptake of ketone bodies in patients with stable HFrEF and AS and increased uptake of FFAs in AS compared with control patients. The lack of myocardial release of acyl-carnitine species or change in free carnitine uptake suggests no impairment of FFA oxidation.

Troponin I Changes in Patients with Subarachnoid Hemorrhage

Background : Subarachnoid hemorrhage (SAH) is a catastrophic neurological event. Aside from its neurological morbidities, SAH is associated with significant medical complications. Cardiac manifestations are common and can impact morbidity and mortality in SAH patients. Myocardial enzyme release occur frequently after Subarachnoid hemorrhage that reflect adverse intracranial events .These changes often are unrecognized or misinterpreted, potentially placing patients at risk for inappropriate management.Objective : The aim of this study was to assess Troponin I changes after acute SAH and these changes were compared with neurological severity. The result of the study might be helpful for better understanding diagnostic and therapeutic implications of acute neurocardiogenic injury after SAH.Patients and methods : This cross sectional descriptive study was conducted over 30 patients with SAH in medicine, neuromedicine and intensive care unit of Rajshahi Medical College Hospital during the period of January 2015 to December 2016. Predictor variables reflecting demographic (age, sex, occupation), hemodynamic (pulse, systolic and diastolic blood pressure) and neurological (WFNS score) informations were recorded. We evaluated their cTnI level, which had been measured at admission. A cTnI level above 0.12 ng/ml was defined as an indicator of cardiac injury following SAH.Results : Out of 30 patients 26.7% were both in between 40-49 years and 60-69 years age group &amp; 50% were male and 50% were female. Among the risk factors 60% of patient had history of hypertension, 40% smoking, 10% Diabetes mellitus and 3.3% alcohol abuse. On admission the mean GCS was 12.53±2.69,. The most frequently occurring WFNS grading were grade 1 and grade 4 (both were 43.3% of patients). Out of Thirty, 43.3% of patients demonstrated elevations of Troponin I. WFNS score ≥ 3 (92.3%, p = &lt;0.001) significantly correlated with elevated Troponin I concentration.Conclusion : serum troponin I reveal a higher incidence of myocardial injury in patients with SAH. The present study also demonstrates that raised serum cTnI is associated with more severe neurological injury. These findings support a neurocardiogenic cause of cardiac injury after SAH.TAJ 2014; 27(2): 39-43

The relationships among monocyte subsets, miRNAs and inflammatory cytokines in patients with acute myocardial infarction.

Acute myocardial infarction (AMI) causes irreversible myocardial damage and release of inflammatory mediators, including cytokines, chemokines and miRNAs. We aimed to investigate changes in the levels of cytokines (IL-6, TNF-α and IL-10), miRNAs profiles (miR-146 and miR-155) and distribution of different monocyte subsets (CD14++CD16-, CD14++CD16+, CD14+CD16++) in the acute and post-healing phases of AMI. In eighteen consecutive AMI patients (mean age 56.78 ± 12.4 years, mean left ventricle ejection fraction - LVEF: 41.9 ± 9.8%), treated invasively, monocyte subsets frequencies were evaluated (flow cytometry), cytokine concentrations were analyzed (ELISA) as well as plasma miRNAs were isolated twice - on admission and after 19.2 ± 5.9 weeks of follow-up. Measurements were also performed among healthy volunteers. AMI patients presented significantly decreased frequencies of classical cells in comparison to healthy controls (median 71.22% [IQR: 64.4-79.04] vs. 84.35% [IQR: 81.2-86.7], p = 0.001) and higher percent of both intermediate and non-classical cells, yet without statistical significance (median 6.54% [IQR: 5.14-16.64] vs. 5.87% [IQR: 4.48-8.6], p = 0.37 and median 5.99% [IQR: 3.39-11.5] vs. 5.26% [IQR: 3.62-6.2], p = 0.42, respectively). In AMI patients both, analyzed plasma miRNA concentrations were higher than in healthy subjects (miR-146: median 5.48 [IQR: 2.4-11.27] vs. 1.84 [IQR: 0.87-2.53], p = 0.003; miR-155: median 25.35 [IQR: 8.17-43.15] vs. 8.4 [IQR: 0.08-16.9], p = 0.027, respectively), and returned back to the values found in the control group in follow-up. miR-155/miR-146 ratio correlated with the frequencies of classical monocytes (r=0.6, p = 0.01) and miR-155 correlated positively with the concentration of inflammatory cytokines - IL-6 and TNF-α. These results may suggest cooperation of both pro-inflammatory and anti-inflammatory signals in AMI in order to promote appropriate healing of the infarcted myocardium.

FGF23 in Cardiovascular Disease: Innocent Bystander or Active Mediator?

Fibroblast growth factor−23 (FGF23) is a mainly osteocytic hormone which increases renal phosphate excretion and reduces calcitriol synthesis. These renal actions are mediated via alpha-klotho as the obligate co-receptor. Beyond these canonical “mineral metabolism” actions, FGF23 has been identified as an independent marker for cardiovascular risk in various patient populations. Previous research has linked elevated FGF23 predominantly to left-ventricular dysfunction and consecutive morbidity and mortality. Moreover, some experimental data suggest FGF23 as a direct and causal stimulator for cardiac hypertrophy via specific myocardial FGF23-receptor activation, independent from alpha-klotho. This hypothesis offers fascinating prospects in terms of therapeutic interventions, specifically in patients with chronic kidney disease (CKD) in whom the FGF23 system is strongly stimulated and in whom left-ventricular dysfunction is a major disease burden. However, novel data challenges the previous stand-alone hypothesis about a one-way road which guides unidirectionally skeletal FGF23 toward cardiotoxic effects. In fact, recent data point toward local myocardial production and release of FGF23 in cases where (acute) myocardial damage occurs. The effects of this local production and the physiological meaning are under current examination. Moreover, epidemiologic studies suggest that high FGF-23 may follow, rather than induce, myocardial disease in certain conditions. In summary, while FGF23 is an interesting link between mineral metabolism and cardiac function underlining the meaning of the bone-heart axis, more research is needed before therapeutic interventions may be considered.

Cold crystalloid versus warm blood cardioplegia in patients undergoing aortic valve replacement.

Myocardial protection techniques during cardiac arrest have been extensively investigated in the clinical setting of coronary revascularization. Fewer studies have been carried out of patients affected by left ventricular hypertrophy, where the choice of type and temperature of cardioplegia remain controversial. We have retrospectively investigated myocardial injury and short-term outcome in patients undergoing aortic valve replacement plus or minus coronary artery bypass grafting with using cold crystalloid cardioplegia (CCC) or warm blood cardioplegia (WBC). From January 2015 to October 2016, 191 consecutive patients underwent aortic valve replacement plus or minus coronary artery bypass grafting in normothermic cardiopulmonary bypass. Cardiac arrest was obtained with use of intermittent antegrade CCC group (n=32) or WBC group (n=159), according with the choice of the surgeon. As compared with WBC group, in CCC group creatine-kinase-MB (CK-MB), cardiac troponin I (cTnI), aspartate aminotransferase (AST) release, and their peak levels, were lower during each time points of evaluation, with the greater statistically significant difference at time 0 (P<0.05, for all comparisons). A time 0, CK-MB/CK ratio >10% was 5.9% in CCC group versus 7.8% in WBC group (P<0.0001). At time 0 CK-MB/CK ratio >10% in patients undergoing isolated aortic valve replacement was 6.0% in CCC group versus 8.0% in WBC group (P<0.01). No any difference was found in perioperative myocardial infarction (0% versus 3.8%), postoperative (PO) major complications (15.6% versus 16.4%), in-hospital mortality (3.1% versus 1.3%). In aortic valve surgery a significant decrease of myocardial enzymes release is observed in favor of CCC, but this difference does not translate into different clinical outcome. However, this study suggests that in presence of cardiac surgical conditions associated with significant left ventricular hypertrophy, i.e., the aortic valve disease, a better myocardial protection can be achieved with the use of a cold rather than a warm cardioplegia. Therefore, CCC can be still safely used.

Preconditioning potential of purmorphamine: a hedgehog activator against ischaemic reperfusion injury in ovariectomised rat heart.

The present study was been designed to investigate the role and pharmacological potential of hedgehog in oestrogen-deficient rat heart. Oestrogen deficiency was produced in female Wistar rats by the surgical removal of both ovaries and these animals were used four weeks later. Isolated rat heart was subjected to 30 min ischaemia followed by 120 min of reperfusion (I/R). The heart was subjected to pharmacological preconditioning with the hedgehog agonist purmorphamine (1μM) and GDC-0449, a hedgehog antagonist, in the last episode of reperfusion before I/R. Myocardial infarction was assessed in terms of the increase in lactate dehydrogenase (LDH), creatinine kinase-MB (CK-MB), myeloperoxidase (MPO) level and infarct size (triphenyltetrazolium chloride staining). Immunohistochemistry analysis was done for the assessment of tumour necrosis factor (TNF)-α level in cardiac tissue. eNOS expression was estimated by rt-PCR. Pharmacological preconditioning with purmorphamine significantly attenuated I/R-induced myocardial infarction, TNF-α, MPO level and release of LDH and CK-MB compared to the I/R control group. However, GDC-0449 prevented the ameliorative preconditioning effect of estradiol. It may be concluded that the hedgehog agonist purmorphamine prevents the ovariectomised heart from ischaemic reperfusion injury.

Inverse Association Between Myocardial B-Type Natriuretic Peptide Release and Functional Capacity in Healthy Humans

B-type natriuretic peptide (BNP) has been found to be inversely related to peak oxygen consumption (peak VO2) in various patient populations. However, in these studies, circulating plasma BNP, i.e. the net effect of release and elimination, rather than cardiac BNP release has been measured. We assessed the relationship between the transcardiac BNP gradient [ΔBNPCS-A, i.e. the difference between BNP in coronary sinus (BNPCS) and arterial (BNPA) plasma] and peak VO2 in healthy subjects with a view to better understanding the regulation of cardiac BNP release in humans. We studied 10 asymptomatic subjects (age 64±11 years, two females) with preserved left ventricular function (left ventricular ejection fraction 62±5%, averaged early diastolic mitral annular velocity 9±3cm/s) and low BNP (BNP in venous plasma [BNPV] <100ng/l). Subjects underwent measurement of BNPA and BNPCS for the calculation of ΔBNPCS-A, maximal cardiopulmonary exercise testing, echocardiography and resting and submaximal exercise right heart catheterisation. The median (range) BNPV, BNPA, BNPCS, and ΔBNPCS-A were 62 (14, 82), 60 (13, 79), 110 (25, 157), and 44 (1, 103) ng/l. The median peak VO2 during cardiopulmonary exercise testing was 21.5 (18, 54) ml/min/kg. There was an inverse correlation between higher ΔBNPCS-A and lower peak VO2 (r=-0.84; p=0.002) and oxygen pulse (r=-0.64, p=0.049). There was a trend towards an inverse correlation between ΔBNPCS-A and the exercise arteriovenous oxygen content difference (r=-0.58; p=0.08). In healthy humans, there is an inverse association between myocardial BNP release and peak VO2, which may be due to cardiac and non-cardiac mechanisms.

CaMKII inhibition mitigates ischemia/reperfusion-elicited calpain activation and the damage to membrane skeleton proteins in isolated rat hearts

Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been implicated in myocardial ischemia/reperfusion (IR) injury. The aim of this study was to determine the effect of CaMKII on the damage to membrane skeleton proteins, which is an important cause of IR injury. Isolated rat hearts were subjected to 45-min global ischemia/2-h reperfusion. Both KN-62 and KN-93 were used to inhibit CaMKII. Compared with controls, the hearts in the IR group exhibited remarkable myocardial injury area, LDH release, cell apoptosis and contractile dysfunction, along with an increase in the phosphorylation of CaMKII and its substrate phospholamban. Treatment with either KN-62 or KN-93 mitigated both the heart injury and the phosphorylation of CaMKII and phospholamban. The analysis of cell skeleton proteins revealed that IR injury resulted in an increase in the 150-kDa fragments resulting from the degradation of α-fodrin and dystrophin translocating from the sarcolemmal membrane to the cytosol and a decrease in the 220-kDa isoform of ankyrin-B. As expected, Evans blue dye staining showed an increase in membrane permeability or membrane rupture in the IR group. All of these alterations were alleviated by treatment with either KN-62 or KN-93. In addition, both KN-62 and KN-93 blocked the activity and membrane recruitment of calpain, a key protease responsible for destroying cell skeleton proteins during IR injury. In conclusion, our data provide evidence that damage to membrane skeleton proteins via calpain is a destructive downstream event of CaMKII activation in the setting of myocardial IR injury.

Cardioprotective effects of combined therapy with diltiazem and superoxide dismutase on myocardial ischemia-reperfusion injury in rats

AimsOur experiments were designed to study the effect of diltiazem (DIL) combined with superoxide dismutase (SOD) on myocardial ischemia-reperfusion (MIRI) injury in a rat model. Main methodsFifty rats were randomly separated into sham, ischemia-reperfusion (IR), DIL (5mg/kg), SOD (10,000U/kg) and combinatorial therapy (DIL plus SOD) groups. MIRI was induced by ligating the left anterior descending coronary artery for 30min and then reperfusing for 60min. The cardioprotective effects of combinatorial therapy were evaluated using hemodynamics, biochemical indices, histopathology and apoptotic-related proteins and gene expression. Key findingsCompared with the IR group, combinatorial therapy significantly improved cardiac function and decreased arrhythmia, myocardial infarction area and release of myocardial enzyme. In addition, combinatorial therapy protected the myocardial cell structure as well as markedly alleviated oxidative stress, resulting in upregulation of Bcl-2 and adenine nucleotide transporter-1 expression as well as downregulation of Bax, caspase-3 and cleaved caspase-3 expression. SignificanceOur results indicated that DIL combined with SOD can provide protection against MIRI in rats, and these effects may be attributed to a reduction in oxygen stress damage, attenuation of calcium overload, and inhibition of cell apoptosis.

Lysophosphatidic Acid Pretreatment Attenuates Myocardial Ischemia/Reperfusion Injury in the Immature Hearts of Rats.

The cardioprotection of the immature heart during cardiac surgery remains controversial due to the differences between the adult heart and the newborn heart. Lysophosphatidic acid (LPA) is a small bioactive molecule with diverse functions including cell proliferation and survival via its receptor: LPA1–LPA6. We previously reported that the expressions of LPA1 and LPA3 in rat hearts were much higher in immature hearts and then declined rapidly with age. In this study, we aimed to investigate whether LPA signaling plays a potential protective role in immature hearts which had experienced ischemia/reperfusion (I/R) injury. The results showed that in Langendorff-perfused immature rat hearts (2 weeks), compared to I/R group, LPA pretreatment significantly enhanced the cardiac function, attenuated myocardial infarct size and CK-MB release, decreased myocardial apoptosis and increased the expression of pro-survival signaling molecules. All these effects could be abolished by Ki16425, an antagonist to LPA1 and LPA3. Similarly, LPA pretreatment protected H9C2 from hypoxia-reoxygenation (H/R) induced apoptosis and necrosis in vitro. The mechanisms underlying the anti-apoptosis effects were related to activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinas B (AKT) signaling pathways as well as phosphorylation of the downstream effector of AKT, glycogen synthase kinase 3 beta (GSK3β), through LPA1 and/or LPA3. What's more, we found that LPA preconditioning increased glucose uptake of H9C2 subjected to H/R by the activation of AMP-Activated Protein Kinase (AMPK) but not the translocation of GLUT4. In conclusion, our study indicates that LPA is a potent survival factor for immature hearts against I/R injuries and has the potential therapeutic function as a cardioplegia additive for infantile cardiac surgery.

High sensitivity cardiac troponins: Can they help in diagnosing myocardial ischaemia?

Cardiac troponin is the most sensitive marker of myocardial injury, but controversy still exists about its role in detecting ischaemia. To investigate the role of troponin as a marker of stress-induced ischaemia, circulating high sensitivity cardiac troponin T (hs-cTnT) was measured and compared with the MB fraction of creatine kinase (CK-MB) in 125 patients undergoing a stress test (53 electrocardiogram/echo exercise, 42 echo dipyridamole and 30 echo dobutamine tests). Plasma concentrations of hs-cTnT increased after the tests in 90/125 patients, while an increase of CK-MB was seen in 31/125 patients ( p<0.0001). Overall, hs-cTnT significantly increased from 17.5±16.9 ng/l to 25.5±27.9 ng/l ( p<0.0001), without significant changes of CK-MB. Significant increments in hs-cTnT were documented after exercise test (from 15.9±11.9 ng/l to 19.5±13.6 ng/l, p<0.0001) and dobutamine test (from 20.6±20.8 ng/l to 37.8±31.1 ng/l, p=0.0006), in absence of changes in CK-MB according to each stressor. Among the 125 tests, 84 were diagnosed as negative and 41 as positive for myocardial ischaemia. Significant increments in hs-cTnT were detected after both negative (from 18.6±19.2 ng/l to 27.1±32.1 ng/l, p=0.0018) and positive test (from 15.2±10.8 ng/l to 22.3±16.2 ng/l, p=0.0005), without significant changes of CK-MB according to the test result. Despite a positive correlation between stress-induced increase of hs-cTnT and obstructive coronary artery disease, the release of troponin was observed also in a significant proportion of patients without coronary stenoses. Left ventricular hypertrophy markedly enhanced myocardial release of troponin. Circulating troponin increases in most patients undergoing a stress test, irrespective of the test result and of coronary artery disease. Plasma release of troponin depends on multiple pathogenetic mechanisms, making the biomarker a not reliable tool in detecting transient ischaemia.

Remifentanil functions in the adaptive protection of cardiac function following ischemia.

The present study aimed to investigate the effects of remifentanil during adaptation followinsg myocardial ischemia, and its possible clinical applications. Remifentanil was used during the simulation of adaptation following ischemia, which was performed using a Langendorff heart perfusion system. A total of 75 rats were divided into five groups, and the coronary flow, cardiac output and the cardiac enzyme content in coronary effluent prior to ischemia and post-reperfusion were recorded. Electron microscopy was used to observe myocardial ultrastructure, and the volume of aortic and coronary effluent was also measured. The recovery of cardiac output upon reperfusion was significantly higher following remifentanil treatment (91%), as compared with the ischemic control group (78%; P<0.05). The coronary flow of the experimental group following reperfusion decreased by 4 ml/min compared with the control group not exposed to ischemia, whilst the coronary flow of the ischemic control group was reduced by 20-24 ml/min. Flameng scoring of the mitochondria demonstrated improved mitochondrial ultrastructure following remifentanil treatment (score, 1.25±0.31), as compared the ischemic control group (score, 3.14±0.17). Lactate dehydrogenase (LDH) levels in the remifentanil-treated group were significantly lower at 10 and 30 min post-reperfusion (15.3±7.1 and 10.2±6.8 U/l, respectively), as compared with the control group (29.7±8.3 and 20.6±6.8 U/l, respectively; P<0.05). The results of the present study suggested that the application of remifentanil following ischemia protected heart function via the opioid receptors by reducing myocardial enzyme release, and attenuating ischemia-induced changes to the myocardial cell and mitochondrial structure.

N-Acetylcysteine Attenuates Diabetic Myocardial Ischemia Reperfusion Injury through Inhibiting Excessive Autophagy

Background. Excessive autophagy is a major mechanism of myocardial ischemia reperfusion injury (I/RI) in diabetes with enhanced oxidative stress. Antioxidant N-acetylcysteine (NAC) reduces myocardial I/RI. It is unknown if inhibition of autophagy may represent a mechanism whereby NAC confers cardioprotection in diabetes. Methods and Results. Diabetes was induced in Sprague-Dawley rats with streptozotocin and they were treated without or with NAC (1.5 g/kg/day) for four weeks before being subjected to 30-minute coronary occlusion and 2-hour reperfusion. The results showed that cardiac levels of 15-F2t-Isoprostane were increased and that autophagy was evidenced as increases in ratio of LC3 II/I and protein P62 and AMPK and mTOR expressions were significantly increased in diabetic compared to nondiabetic rats, concomitant with increased postischemic myocardial infarct size and CK-MB release but decreased Akt and eNOS activation. Diabetes was also associated with increased postischemic apoptotic cell death manifested as increases in TUNEL positive cells, cleaved-caspase-3, and ratio of Bax/Bcl-2 protein expression. NAC significantly attenuated I/RI-induced increases in oxidative stress and cardiac apoptosis, prevented postischemic autophagy formation in diabetes, and reduced postischemic myocardial infarction (all p < 0.05). Conclusions. NAC confers cardioprotection against diabetic heart I/RI primarily through inhibiting excessive autophagy which might be a major mechanism why diabetic hearts are less tolerant to I/RI.

Apoptotic Protease Activating Factor-1 Inhibitor Mitigates Myocardial Ischemia Injury via Disturbing Procaspase-9 Recruitment by Apaf-1.

(2S,3S,4S,5R,6R)-6-(4-((4-guanidinobutoxy)carbonyl)-2,6-dihydroxyphenoxy)-3,4,5-trihydroxytetrahydro-2H-pyran-2-carboxylic acid (ZYZ-488) was discovered as a novel inhibitor of apoptotic protease activating factor-1 (Apaf-1). In present work, a surface plasmon resonance (SPR) assay confirms the direct binding between ZYZ-488 and Apaf-1 and this interaction was found to be able to block the recruitment of procaspase-9 by Apaf-1. This study also shows that the treatment of MI (myocardial infarction) mice with this novel Apaf-1 inhibitor remarkably reduces the infarct size, improves cardiac functions, and attenuates the histopathology changes caused by MI. Meanwhile, here it is shown that ZYZ-488 decreases myocardial enzyme release, inhibits cardiomyocyte apoptosis, and suppresses the activation of the downstream cascade of caspases. Moreover, in silico prediction validated the drug-like properties of ZYZ-488. In conclusion, our findings present the first piece of evidence indicating the interaction between Apaf-1 and procaspase-9 as a novel therapeutic target in myocardial infarction and suggesting ZYZ-488 as a promising therapeutic option for myocardial infarction disease.

NLRP3 Inflammasome Activation-Mediated Pyroptosis Aggravates Myocardial Ischemia/Reperfusion Injury in Diabetic Rats.

The reactive oxygen species- (ROS-) induced nod-like receptor protein-3 (NLRP3) inflammasome triggers sterile inflammatory responses and pyroptosis, which is a proinflammatory form of programmed cell death initiated by the activation of inflammatory caspases. NLRP3 inflammasome activation plays an important role in myocardial ischemia/reperfusion (MI/R) injury. Our present study investigated whether diabetes aggravated MI/R injury through NLRP3 inflammasome-mediated pyroptosis. Type 1 diabetic rat model was established by intraperitoneal injection of streptozotocin (60 mg/kg). MI/R was induced by ligating the left anterior descending artery (LAD) for 30 minutes followed by 2 h reperfusion. H9C2 cardiomyocytes were exposed to high glucose (HG, 30 mM) conditions and hypoxia/reoxygenation (H/R) stimulation. The myocardial infarct size, CK-MB, and LDH release in the diabetic rats subjected to MI/R were significantly higher than those in the nondiabetic rats, accompanied with increased NLRP3 inflammasome activation and increased pyroptosis. Inhibition of inflammasome activation with BAY11-7082 significantly decreased the MI/R injury. In vitro studies showed similar effects, as BAY11-7082 or the ROS scavenger N-acetylcysteine, attenuated HG and H/R-induced H9C2 cell injury. In conclusion, hyperglycaemia-induced NLRP3 inflammasome activation may be a ROS-dependent process in pyroptotic cell death, and NLRP3 inflammasome-induced pyroptosis aggravates MI/R injury in diabetic rats.

Myocardial Production and Release of Stem Cell Factor Following Myocardial Infarction

Background: Stem cell homing to the heart is mediated by the release of chemo-attractant cytokines, including stem cell factor (SCF). SCF is detectable in peripheral blood in patients early after myocardial infarction (MI). However, whether the increased circulating SCF in these patients is released from the heart or another source remains unknown. Methods: Murine hearts were studied for the expression of SCF at day 3 following MI. The coronary artery and coronary sinus (venous) blood from patients following MI was used to determine whether SCF is released from the heart into the systemic circulation following MI. Patients with normal coronary arteries, stable coronary artery disease (CAD) and unstable angina served as controls. Results: In mice, SCF mRNA was constitutively expressed in the left ventricular myocardium at baseline. Following MI, SCF expression was suppressed in the infarct zone and border zone, but unchanged in the myocardium remote from the MI. In humans, SCF was not released from the heart at baseline, but was increased in response to MI. Interestingly, SCF was also released from the heart in stable CAD and in unstable angina without infarction. However, there was no significant correlation between the heart release of SCF and myocardial damage, and human cardiac release of SCF did not change with time following MI. Conclusions: Release of SCF from the heart into the circulation is increased in humans in all stages of CAD. Myocardial damage, per se, does not result in increased release of SCF into the circulation. This is consistent with the mouse model where SCF production does not increase after MI. Our findings suggest that the damaged myocardium does not contribute to human cardiac release of SCF.

Myocardial protection during minimally invasive cardiac surgery through right mini-thoracotomy.

Myocardial damage is an independent predictor of adverse outcome following cardiac surgery and myocardial protection is one of the key factors to achieve successful outcomes. Cardioplegia with Custodiol is currently the most used cardioplegia during minimally invasive cardiac surgery (MICS). Different randomized controlled trials compared blood and Custodiol cardioplegia in the context of traditional cardiac surgery. No data are available for MICS. The aim of this study was to compare the efficacy of cold blood versus Custodiol cardioplegia during MICS. We retrospectively evaluated 90 patients undergoing MICS through a right mini-thoracotomy in a three-year period. Myocardial protection was performed using cold blood (44 patients, CBC group) or Custodiol (46 patients, Custodiol group) cardioplegia, based on surgeon preference and complexity of surgery. The primary outcomes were post-operative cardiac troponin I (cTnI) and creatine kinase MB (CKMB) serum release and the incidence of Low Cardiac Output Syndrome (LCOS). Aortic cross-clamp and cardiopulmonary bypass times were higher in the Custodiol group. No difference was observed in myocardial injury enzyme release (peak cTnI value was 18±46 ng/ml in CBC and 21±37 ng/ml in Custodiol; p=0.245). No differences were observed for mortality, LCOS, atrial or ventricular arrhythmias onset, transfusions, mechanical ventilation time duration, intensive care unit and total hospital stay. Custodiol and cold blood cardioplegic solutions seem to assure similar myocardial protection in patients undergoing cardiac surgery through a right mini-thoracotomy approach.