Hydrogen peroxide preconditioning is of dual role in cardiac ischemia/reperfusion.

Moderate reactive oxygen species (ROS) at reperfusion would trigger cardioprotection and various antioxidants for pharmacological preconditioning failed to achieve cardioprotection. The causes for different roles of preischemic ROS during cardiac ischemia/reperfusion (I/R) require reevaluation. We investigated the precise role of ROS and its working model in this study. Different doses of hydrogen peroxide (H2O2, the most stable form of ROS) were added 5 min before ischemia using isolated perfused rat hearts, only moderate-dose H2O2 preconditioning (H2O2PC) achieved contractile recovery, whereas the low dose and high dose led to injury. Similar results were observed in isolated rat cardiomyocytes on cytosolic free Ca2+ concentration ([Ca2+]c) overload, ROS production, the recovery of Ca2+ transient, and cell shortening. Based on the data mentioned above, we set up a mathematics model to describe the effects of H2O2PC with the fitting curve by the percentage of recovery of heart function and Ca2+ transient in I/R. Besides, we used the two models to define the initial thresholds of H2O2PC achieving cardioprotection. We also detected the expression of redox enzymes and Ca2+ signaling toolkits to explain the mathematics models of H2O2PC in a biological way. The expression of tyrosine 705 phosphorylation of STAT3, Nuclear factor E2-related factor 2, manganese superoxide dismutase, phospholamban, catalase, ryanodine receptors, and sarcoendoplasmic reticulum calcium ATPase 2 were similar with the control I/R and low-dose H2O2PC but were increased in the moderate H2O2PC and decreased in the high-dose H2O2PC. Thus, we concluded that preischemic ROS are of dual role in cardiac I/R.

Pharmacological preconditioning with intralipid in patients undergoing off-pump coronary artery bypass surgery.

Aims and Objectives: The objective of the study was to determine the preconditioning myocardial protective effects of intralipid (IL) in off-pump coronary artery bypass (OPCAB) surgery by measuring highly sensitive troponin T (hsTnT) and cardiac-specific creatine kinase (CK-MB) as markers of myocardial injury. Materials and Methods: : Thirty patients, scheduled to undergo elective OPCAB surgery, were randomly assigned to the IL group (n = 15) or control (C) group (n = 15); the IL group received an infusion of 20% IL 2 ml/kg, 30 min prior to revascularization and the control group received an equivalent volume of normal saline. Serum levels of hsTnT and CK-MB were measured before surgery and at 6 h, 24 h, 48 h, and 72 h postoperatively. Also, intraoperative hemodynamic parameters, inotrope use, ventilatory hours, ICU stay, postoperative left ventricular ejection fraction, postoperative lipid profile, renal and hepatic function tests were measured. Results: The hsTnT values at the 24 h, 48 h, and 72 h in IL group were significantly lower as compared with the control group. The decline in plasma levels of CK-MB mirrored the hsTnT levels post revascularization at 24 h and 48 h in the IL group compared with the control group; however, at 72 h, level was comparable in both the groups. None of the treated patients had abnormal lipid metabolism, deranged renal, and hepatic function. Conclusion: The study revealed Intralipid as a safe pharmacological preconditioning agent for OPCAB surgeries which can reduce the postischemic myocardial injury indicated by the reduction in postischemic cardiac enzymes hsTnT and CK-MB.

Preconditioning with hyperbaric oxygen and calcium and potassium channel modulators in the rat heart.

The aim of this study was to establish the effect of combined therapy with hyperbaric oxygen (HBO2) therapy and verapamil, amlodipine or nicorandil on functional recovery and oxidative stress markers after ischemia in the isolated rat heart. The study included 48 rats (Wistar albino, male gender, eight weeks old, body weight 200±50g). All animals were exposed to HBO2 treatment over 14 days. Isolated heart rats were perfused by the Langendorff retrograde method at a constant coronary pressure of 70 cm H2O. After stabilization period the hearts were divided into the following groups: HBO2 group (animals exposed to only HBO2 preconditioning); HBO2 + verapamil; HBO2 + amlodipine; andHBO2 + nicorandil (animals pretreated with HBO2 and appropriate pharmacological agent). Afterward, the hearts in all groups were subjected to 20-minute global ischemia and 30-minute reperfusion. Parameters of heart function were registered, including maximum and minimum rate of pressure development, systolic and diastolic left ventricular pressure, heart rate and coronary flow. Levels of pro-oxidants such as index of lipid peroxidation, measured as thiobarbituric acid-reactive substances, nitrites, levels of superoxide anion radicals and hydrogen peroxide were determined in coronary venous effluent. Changes in cardiac tissue were evaluated by hematoxylin and eosin staining. Obtained results clearly indicate that blockage of calcium channel or the activation of adenosine triphosphate-sensitive potassium (KATP) in combination with HBO2 prevented ischemia/reperfusion-induced cardiac deleterious effects, thus contributing to improvement of functional recovery of the heart. However, future studies are certainly necessary for better understanding the mechanisms through which combination of these two maneuvers of preconditioning triggers cardioprotection.

[Protective effect of acupuncture preconditioning on oxidative stress injury induced by myocardial ischemia-reperfusion injury in rats].

OBJECTIVE: To observe the protective effect of acupuncture preconditioning at "Jiaji" (EX-B 2) on acute myocardial ischemia-reperfusion injury (MIRI) in the rats and explore the mechanism. METHODS: Fifty Wistar rats were randomly divided into a control group, a model group, a Jiaji group, a Neiguan group and a Quchi group, 10 rats in each one. In the Jiaji group, the Neiguan group and the Quchi group, electroacupuncture was given for preconditioning at "Jiaji" T4~T5 (EX-B 2), "Neiguan" (PC 6) and "Quchi" (LI 11) for 7 days before modeling. In the control group and the model group, the regular feeding was given, without any acupuncture. At the end of acupuncture, except the control group, ligating the left anterior descending coronary artery (LAD) was adopted to duplicate MIRI models in the rest groups. Electrocardio-gram (ECG) was monitored and ST-segment shift was analyzed. HE staining method was adopted to observe the morphology of cardiac tissue in the rats of the groups. The transmission electron microscope was used to observe myocardial cell ultrastructure. WST-1 method was used to determine the activity of serum superoxide dismutase (SOD), TBA method was used to determine the content of serum malondialehyde (MDA) and the real-time fluorescent quantitative PCR method to determine the expressions of Nrf 2 in ischemic myocardial tissue and downstream HO-1 gene. RESULTS: Compared with the control group, after LAD ligation, ST-segment was elevated and depressed in ECG apparently after reperfusion in the rest groups (all P<0.05). The ST-segment elevation in the Jiaji group and the Neiguan group was less than that in the model group (both P<0.05). Compared with the model group, SOD activity was increased apparently in the Jiaji group and the Neiguan group (both P<0.05), and MDA content was reduced apparently (both P<0.05). The effects in the Jiaji group were better than those in the Neiguan group (both P<0.05). Pathologically, "Jiajia" (EX-B 2) and "Neiguan" (PC 6) all improved the morphology of cardiac tissue and cell ultrastructure. The effects in the Jiaji group were much more significant and the improvements in the Quchi group were not apparent. Compared with the control group, the expressions of Nrf 2 and HO-1 gene in myocardial tissue were down-regulated in the model group (both P<0.05). Those were up-regulated apparently in the Jiaji group and the Neiguan group as compared with the model group (P<0.05, P<0.01). The up-regulation times of the expressions of Nrf 2 and HO-1 gene in the Jiajia group were the highest in comparison. CONCLUSIONS: Acupuncture preconditioning at "Jiaji" (EX-B 2) has the protective effect on cardiac ischemia and reperfusion damage, which is probably relevant with the up-regulation of Nrf 2-ARE pathway expression, the activation of endogenous anti-oxidative pathway, the improvement of oxygen free radical scavenging capacity and the alleviation of lipid peroxide damage.

[Effects of electroacupuncture preconditioning on expression of aquaporin-1 and activity of protein kinase C in myocardium of rats with acute myocardial ischemia-reperfusion injury].

OBJECTIVE: To explore the partial action mechanism and the myocardial protective effect differences between electroacupuncture (EA) preconditioning at "Neiguan"(PC 6) and "Taiyuan"(LU 9) in rats with acute myocardial ischemia-reperfusion injury. METHODS: Ninety-six Wistar rats were randomly assigned into a sham-operation group, a model group, a Neiguan group and a Taiyuan group, 24 rats in each one. The rats in the Neiguan group and Taiyuan group were treated with EA (2 Hz in frequency, 1 mA in intensity) at "Neiguan" (PC 6) and "Taiyuan" (LU 9) respectively, 20 min per treatment, once a day for consecutive 7 days. The rats in the sham-operation group and model group were treated with immobilization for the same time, and no EA was given. The model of myocardial ischemia-reperfusion injury was established in the model group, Neiguan group and Taiyuan group 24 h after the end of EA, while the rats in the sham-operation group were treated with sham operation (no ligation was made during surgery). The myocardial ischemic size, infarction size, activity of protein kinase C (PKC) and expression of aquaporin1 (AQP1) in each group were detected. RESULTS: Compared with sham-operation group, the myocardial ischemic size, infarction size, AQP1 expression and PKC activity in the model group were significantly increased (all P<0.01); compared with the model group and Taiyuan group, the myocardial ischemic size, infarction size, PKC activity and AQP1 expression were significantly decreased in the Neiguan group (P<0.01, P<0.05). By Pearson correlation analysis, the changes of AQP1 expression were positively correlated with those of PKC activity after EA preconditioning. CONCLUSIONS: EA preconditioning at "Neiguan" (PC 6) could significantly decrease myocardial AQP1 expression and PKC activity in rats with acute myocardial ischemia-reperfusion injuing, but the effect of EA preconditioning at "Taiyuan"(LU 9) is not obvious; its protective effect is likely to be achieved by inhibiting PKC activity and AQP1 expression.

Nitrite-Nitric Oxide Signaling and Cardioprotection.

Cardioprotective strategies to prevent damage to mitochondria in acute myocardial infarction are warranted to reduce lethal myocardial ischemia/reperfusion (I/R) injury. Mitochondrial antagonists in I/R are reactive oxygen species (ROS), deteriorated calcium signaling, permeabilization of the mitochondrial outer membrane (MOM) and deranged mitochondrial structural dynamism (fusion and fission). Nitric oxide (NO) related signaling can protect hearts from I/R. Albeit the underlying signaling is incompletely resolved, recent data point to a particular involvement of protective posttranslational modification of mitochondrial elements. We and others have demonstrated that hypoxic NO signaling in cardiomyocytes is associated with a posttranslational mitochondrial complex I modification to reduce the burden of ROS. Induction of cardioprotective NO signaling may occur through several pathways. These include (i) the supplementation with mitochondria unspecific and specific NO-donors, (ii) the administration of the 'hypoxic-NO donors nitrate and nitrite' and (iii) the enhancement of endogenous NO formation, e.g. by remote ischemic preconditioning maneuvers (rIPC). In this chapter, we outline how NO signaling is activated in the cardiomyocyte, characterize the downstream signaling pathways and discuss how this could translate into a tractable therapeutic approach in patients requiring cardioprotection.

Cardioprotection: Where to from here?

The size of the myocardial infarction remains an important therapeutic target, because heart attack size correlates with mortality and heart failure. In this era, myocardial infarct size is reduced primarily by timely reperfusion of the infarct related coronary artery. Whereas numerous pre-clinical studies have shown that certain pharmacologic agents and therapeutic maneuvers reduce myocardial infarction size greater than reperfusion alone, very few of these therapies have translated to successful clinical trials or standard clinical use. In this review we discuss both the recent successes as well as recent disappointments, and describe some of the newer potential therapies from the preclinical literature that have not yet been tested in clinical trials.

Low-Level Laser Irradiation Precondition for Cardiac Regenerative Therapy.

OBJECTIVE: The purpose of this article was to review the molecular mechanisms of low-level laser irradiation (LLLI) preconditioning for heart cell therapy. BACKGROUND DATA: Stem cell transplantation appears to offer a better alternative to cardiac regenerative therapy. Previous studies have confirmed that the application of LLLI plays a positive role in regulating stem cell proliferation and in remodeling the hostile milieu of infarcted myocardium. Greater understanding of LLLI's underlying mechanisms would be helpful in translating cell transplantation therapy into the clinic. METHODS: Studies investigating LLLI preconditioning for cardiac regenerative therapy published up to 2015 were retrieved from library sources and Pubmed databases. RESULTS: LLLI preconditioning stimulates proliferation and differentiation of stem cells through activation of cell proliferation signaling pathways and alteration of microRNA expression. It also could stimulate paracrine secretion of stem cells and alter cardiac cytokine expression in infarcted myocardium. CONCLUSIONS: LLLI preconditioning provides a promising approach to maximize the efficacy of cardiac cell-based therapy. Although many studies have reported possible molecular mechanisms involved in LLLI preconditioning, the exact mechanisms are still not clearly understood.

Protective effects of hyperbaric oxygen therapy (HBO2) in cardiac care--A proposal to conduct a study into the effects of hyperbaric pre-conditioning in elective coronary artery bypass graft surgery (CABG).

We review and report on accumulated data showing the benefits offered by hyperbaric oxygen (HBO2) therapy as an adjunct in the treatment of coronary artery bypass graft (CABG) patients. It has been shown that ischemia-reperfusion injury is deleterious to the myocardium, causing left ventricular dysfunction, structural damage to the myocytes and endothelial cells, myocardial stunning, reperfusion arrhythmias and potentially irreversible injury. There is a substantial body of evidence pointing to the role of HBO2 in mitigating the harmful effects of ischemia-reperfusion injury. Specifically, we review evidence from a number of studies which clearly point to both clinical and cost benefits HBO2 offers when used to precondition non-emergent patients having on-pump coronary arterial bypass graft surgery. Study data show that adding adjunctive HBO2 into the plan of care leads to improved myocardial function, reduces length of stay in the ICU, and limits post-surgical complications. Further, it has only minimal impact on the presurgical preparation, i.e., time must be allowed for the hyperbaric treatment(s), and no role in the surgery or post-surgical care of the patient. The studies pointing to clinical and cost benefit of preconditioning have been conducted outside the United States. Given the pressure on costs in all areas of health care, it seems that a therapeutic approach, which has been shown to be of benefit in both animal and human trials over the course of many years, should attract funding for a properly structured study designed to test whether significant and simultaneous improvements in clinical outcomes and cost reductions can be achieved within the framework of a U.S. healthcare facility.

The NHLBI-sponsored Consortium for preclinicAl assESsment of cARdioprotective therapies (CAESAR): a new paradigm for rigorous, accurate, and reproducible evaluation of putative infarct-sparing interventions in mice, rabbits, and pigs.

RATIONALE: Despite 4 decades of intense effort and substantial financial investment, the cardioprotection field has failed to deliver a single drug that effectively reduces myocardial infarct size in patients. A major reason is insufficient rigor and reproducibility in preclinical studies. OBJECTIVE: To develop a multicenter, randomized, controlled, clinical trial-like infrastructure to conduct rigorous and reproducible preclinical evaluation of cardioprotective therapies. METHODS AND RESULTS: With support from the National Heart, Lung, and Blood Institute, we established the Consortium for preclinicAl assESsment of cARdioprotective therapies (CAESAR), based on the principles of randomization, investigator blinding, a priori sample size determination and exclusion criteria, appropriate statistical analyses, and assessment of reproducibility. To validate CAESAR, we tested the ability of ischemic preconditioning to reduce infarct size in 3 species (at 2 sites/species): mice (n=22-25 per group), rabbits (n=11-12 per group), and pigs (n=13 per group). During this validation phase, (1) we established protocols that gave similar results between centers and confirmed that ischemic preconditioning significantly reduced infarct size in all species and (2) we successfully established a multicenter structure to support CAESAR's operations, including 2 surgical centers for each species, a Pathology Core (to assess infarct size), a Biomarker Core (to measure plasma cardiac troponin levels), and a Data Coordinating Center-all with the oversight of an external Protocol Review and Monitoring Committee. CONCLUSIONS: CAESAR is operational, generates reproducible results, can detect cardioprotection, and provides a mechanism for assessing potential infarct-sparing therapies with a level of rigor analogous to multicenter, randomized, controlled clinical trials. This is a revolutionary new approach to cardioprotection. Importantly, we provide state-of-the-art, detailed protocols ("CAESAR protocols") for measuring infarct size in mice, rabbits, and pigs in a manner that is rigorous, accurate, and reproducible.

[Effects of preconditioning of wufu jingfang on ischemia/reperfusion injury induced apoptosis in rats].

OBJECTIVE: To observe the protective effect of Wufu Jingfang (WJ, containing Aconitum carmichaeli Debx, Radix Aconiti Lateralis Preparatae, Rhizoma Pinelliae, and snakegourd fruit) on myocardial ischemia-reperfusion injury (I/R) of rats, thus exploring the feasibility of recipes containing eighteen incompatible pairs for specific pathological conditions. METHODS: Fifty male Wistar rats were randomly divided into five groups, i.e., the sham-operative control group (the SH group), the I/R group, the low dose WJ I/R group (the I/R +JFL group), the middle dose WJ I/R group (the I/R +JFM group), the high dose WJ I/R group (the I/R +JFH group), 10 in each group. Rats in the latter three groups were administered with WJ at 0.75 mL/100 g, 1.50 mL/100 g, and 3.00 mL/100 g body weight for 14 consecutive days by gastrogavage. All groups except the SH group received ligation of left anterior descending branch of coronary artery for 30-min ischemia followed by 120-min reperfusion. The micro-structural changes of myocardial mitochondria were observed by transmission electron microscope. The ischemic cardiomyocyte apoptosis was detected in each group using one-step terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL). The mRNA expressions of B-cell leukemia/lymphoma 2 (Bcl-2) and Bcl-2 associated x protein (Bax) were detected by RT-PCR. The activities of lactic dehydrogenase (LDH) and creatine kinase (CK) were detected using ELISA. The myocardial infarct size was detected. RESULTS: Compared with the I/R group, WJ pretreatment significantly suppressed the release of LDH and CK (Besides, the release of LDH and CK reduced along with increased dose.), reduced the myocardial infarct size, and lowered myocardial apoptosis index (P < 0.05). WJ pretreatment also modulated Bcl-2/Bax ratio by up-regulating Bcl-2 expression level while decreasing Bax expression level. CONCLUSIONS: WJ pretreatment might protect the heart from I/R injury via decreasing myocardial cell apoptosis. The results suggested that eighteen incompatible pairs is not absolute, but relative. Chinese medical preparation containing opposite Chinese herbs could be used in specific pathological states such as ischemic cardiomyopathy.

High dose remifentanil increases myocardial oxidative stress and compromises remifentanil infarct-sparing effects in rats.

Chronic administration of high dose opioids such as morphine is known to create intracellular oxidative stress via an opioid receptor dependent mechanism and this can interfere with cellular function. This study aimed at examining whether such changes can occur following short term exposure to high concentration of remifentanil, a potent short acting opioid. We conducted a experimental study using rat myocardium and systematically quantified tissue levels of superoxide anions, malondialdehyde (MDA) and nitrotyrosine following exposure to increasing duration (15 min, 1 or 2 h) or escalating doses of remifentanil (1 µg, 5 µg, 10 µg or 20 µg/kg/min). Concurrently the susceptibility of the heart to ischaemia reperfusion injury was assessed under the similar conditions. For any given duration of remifentanil infusion, there was increasing superoxide anions generated as the dose of remifentanil was increased. MDA concentrations were significantly increased when the animal was exposed to 10 µg/kg/min for 2h or 20 µg/kg/min for any duration. There was a trend towards an increased nitrotyrosine concentration with increasing dose of remifentanil, becoming significant when the dose was 20 µg/kg/min. The infarct limiting ability of remifentanil was compromised when the dihydroethidium fluorescence positive cell percentage exceeded 50%, MDA concentration greater than 2 nmol/mg of protein and nitrotyrosine content exceeding 1.5 µg/mg of protein. Short term high dose opioid exposure can induce oxidative changes seen previously only with chronic opioid use and this high oxidative stress environment corrupts the heart's sensitivity to be preconditioned by opioids.

Electroacupuncture reduces myocardial infarct size and improves post-ischemic recovery by invoking release of humoral, dialyzable, cardioprotective factors.

Previous studies have shown that electroacupuncture (EA) can induce cardioprotection against ischemia-reperfusion (IR) injury, but its mechanisms are incompletely understood. We have previously shown that several other forms of remote preconditioning of the heart work, at least in part, via the release of circulating cardioprotective factors into the bloodstream, that can be dialyzed and subsequently shown to reduce IR injury in isolated hearts. We used the same methods to assess whether EA leads to similar humoral cardioprotection. EA rabbits were subjected to 60 min of bilateral stimulation at the Neiguan point, following which their blood was drawn, dialyzed, and used to perfuse hearts in Langendorff preparation and subsequently subjected to 60 min of global ischemia and 120 min of reperfusion. Compared to controls, dialysate from EA animals led to significant reduction in infarct size and improved functional recovery. The degree of cardioprotection was no different to that seen in animals randomized to receive remote preconditioning using transient limb ischemia (4 cycles of 5 min ischemia/5 min reperfusion). These results suggest that EA recapitulates the cardioprotection achieved by remote preconditioning, by similarly leading to release of circulating cardioprotective factors.

[Effect of Gingkgo biloba leaf extract induced delayed preconditioning on cytochrome c oxidase expression during myocardial ischemia-reperfusion in rats].

OBJECTIVE: To determine the effect of Gingkgo biloba leaf extract (EGb761) induced delayed preconditioning on cytochrome c oxidase (CcO) expression during myocardial ischemia-reperfusion in rats. METHODS: Four groups (10 in each) of Sprague-Dawley male rats were studied. In the sham group, the rats received no treatment. Rats in the ischemia-reperfusion (IR) group were treated with NS (1.0 mL/kg intravenously) 24 h before ischemia. Rats in the M group were treated with EGb761 (100 mg/kg intravenously) 24 h before the ischemia. In the D group , EGb761-treated rats that received the 5-hydroxydecanoate (5-HD), an inhibitor of mitochondrial KATP channels 15 min before the ischemia. The IR, M, and D groups were subjected to ischemia by 30 min of coronary artery occlusion before 2 h of reperfusion. At the end of the reperfusion, myocardial infarct size was measured. CcO was measured by Western blot. The myocardial ultrastructure was observed under the electron microscope. RESULTS: The infarct size was significantly smaller in the M group [(23.78 ± 4.82)%] than in the I/R group [(37.87 ± 5.92)%] (P<0.05). The CcO protein expression in the myocardium was significantly higher in the M group than in the I/R group(P<0.05). Microscopic examination showed less myocardial damage in the M group than that in the I/R group. The infarct size, CcO protein expression, and myocardial damage had no significant difference between the D group and the I/R group (P>0.05). CONCLUSION: EGb761 induced delayed preconditioning attenuates myocardial ischemia-reperfusion injury possibly through up-regulating CcO expression in rats.