Endothelial cell injury in cardiovascular surgery: ischemia-reperfusion

Ginsenoside Rd: A promising target for ischemia-reperfusion injury therapy (A mini review)

Ischemia-reperfusion injury (IRI) represents a prevalent pathological phenomenon. Traditional treatment approaches primarily aim at restoring blood supply to ischemic organs, disregarding the consequent damage caused by IRI. Belonging to the class of protopanaxadiol ginsenosides that are found in Panax ginseng, ginsenoside Rd (GSRd) demonstrates notable safety alongside a diverse range of biological functions. Its active components exhibit diverse pharmacological effects, encompassing anti-inflammatory, anti-tumor, neuroprotective, cardiovascular-protective, and immune-regulatory properties, making it a promising candidate for addressing multiple medical conditions. GSRd shields against I/R injury by employing crucial cellular mechanisms, including the attenuation of oxidative stress, reduction of inflammation, promotion of cell survival signaling pathways, and inhibition of apoptotic pathways. Additionally, GSRd regulates mitochondrial function, maintains calcium homeostasis, and modulates the expression of genes involved in I/R injury. This review seeks to consolidate the pharmacological mechanism of action of GSRd within the context of IRI. Our objective is to contribute to the advancement of GSRd-related pharmaceuticals and provide novel insights for clinicians involved in developing IRI treatment strategies.

Improving vasculoprotective effects of MSCs in coronary microvessels - benefits of 3D culture, sub-populations and heparin

Introduction

Opening occluded coronary arteries in patients with myocardial infarction (MI) damages the delicate coronary microvessels through a process called myocardial ischaemia-reperfusion injury. Although mesenchymal stromal cells (MSCs) have the potential to limit this injury, clinical success remains limited. This may be due to (i) poor MSC homing to the heart (ii) infused MSCs, even if derived from the same site, being a heterogeneous population with varying therapeutic efficacy and (iii) conventional 2D culture of MSCs decreasing their homing and beneficial properties. This study investigated whether 3D culture of two distinctly different bone marrow (BM)-derived MSC sub-populations could improve their homing and coronary vasculoprotective efficacy.

Methods

Intravital imaging of the anaesthetised mouse beating heart was used to investigate the trafficking and microvascular protective effects of two clonally-derived BM-derived MSC lines, namely CD317neg MSCs-Y201 and CD317pos MSCs-Y202, cultured using conventional monolayer and 3D hanging drop methods.

Results

3D culture consistently improved the adhesive behaviour of MSCs-Y201 to various substrates in vitro. However, it was their differential ability to reduce neutrophil events within the coronary capillaries and improve ventricular perfusion in vivo that was most remarkable. Moreover, dual therapy combined with heparin further improved the vasculoprotection afforded by 3D cultured MSCs-Y201 by also modifying platelet as well as neutrophil recruitment, which subsequently led to the greatest salvage of viable myocardium. Therapeutic benefit could mechanistically be explained by reductions in coronary endothelial oxidative stress and intercellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1 (VCAM-1) expression. However, since this was noted by both 2D and 3D cultured MSCs-Y201, therapeutic benefit is likely explained by the fact that 3D cultured MSCs-Y201 were the most potent sub-population at reducing serum levels of several pro-inflammatory cytokines.

Conclusion

This novel study highlights the importance of not only 3D culture, but also of a specific CD317neg MSC sub-population, as being critical to realising their full coronary vasculoprotective potential in the injured heart. Since the smallest coronary blood vessels are increasingly recognised as a primary target of reperfusion injury, therapeutic interventions must be able to protect these delicate structures from inflammatory cells and maintain perfusion in the heart. We propose that relatively feasible technical modifications in a specific BM-derived MSC sub-population could achieve this.

Unusual severe hypoxemia due to unilateral pulmonary edema after conventional cardiopulmonary bypass salvaged by veno-venous extracorporeal membrane oxygenation: a case report

BACKGROUND

We report a case in which veno-venous extracorporeal membrane oxygenation (V-V ECMO) saved the life of a patient who developed severe hypoxemia due to unusual unilateral pulmonary edema (UPE) after cardiopulmonary bypass (CPB).

CASE PRESENTATION

A 69-year-old man underwent aortic valve replacement and coronary artery bypass grafting. Following uneventful weaning off CPB, he developed severe hypoxemia. The ratio of arterial oxygen tension to inspired oxygen fraction (PaO2/FiO2) decreased from 301 mmHg 5 min after CPB to 42 mmHg 90 min after CPB. A chest X-ray revealed right-sided UPE. Immediately established V-V ECMO increased PaO2/FiO2 to 170 mmHg. Re-expansion pulmonary edema (REPE) was likely, as the right lung remained collapsed during CPB following the accidental opening of the right chest cavity during graft harvesting.

CONCLUSIONS

V-V ECMO was effective in improving oxygenation and saving the life of a patient who had fallen into unilateral REPE unusually developing after conventional CPB.

Protective role of nitric oxide donors on endothelium in ischemia-reperfusion injury: a meta-analysis of randomized controlled trials

BACKGROUND

Decreased bioavailability of nitric oxide (NO) under hypoxic conditions can lead to endothelial dysfunction. NO supplementation may protect endothelial function in ischemia-reperfusion (IR) injury. Therefore, a meta-analysis of randomized controlled trials (RCTs) was performed to verify the protective effect of NO donors on endothelium in IR injury.

METHODS

Medline, Embase, Cochrane Library, and Web of Science databases were searched from inception to April 1, 2023. The specific inclusion criteria were as follows: (1) RCTs; (2) trials comparing NO donors with placebo control groups; and (3) trials reporting the effects of these interventions on vascular endothelial functional outcomes in IR injury. Random-effects models were used to assess pooled effect sizes, which were expressed as standardized mean differences (SMD).

RESULTS

Seven studies satisfied the inclusion criteria and consisted of a total of 149 participants. NO donors were protective of endothelial function in IR injury (SMD: - 1.60; 95% confidence interval [CI]: - 2.33, - 0.88, P < 0.0001; heterogeneity [I² = 66%, P = 0.001]). Results of the subgroup analysis showed the following: absence of protective effect of NO donor use following ischemia on endothelial function in IR injury - 1.78 (95% CI: - 2.50, - 1.07) and loss of protective effect on endothelial function after prolonged NO donor use - 0.89 (95% CI: - 2.06, 0.28).

CONCLUSION

The short-period use of NO donors before the onset of ischemia can protect endothelial function in IR injury.

Apoptotic Features in Non-Apoptotic Processes

Apoptosis is the most thoroughly studied type of regulated cell death. Certain events, such as externalization of phosphatidylserine (PS) into the outer leaflet of plasma membrane, mitochondrial outer membrane permeabilization, caspase cascade activation, DNA fragmentation and blebbing, are widely considered to be hallmarks of apoptosis as well as being traditionally viewed as irreversible. This review shows that under particular circumstances these events can also participate in physiological processes not associated with initiation of apoptosis, such as cell differentiation, division, and motility, as well as non-apoptotic types of cell death. Moreover, these events may often be reversible. This review focuses on three processes: phosphatidylserine externalization, blebbing, and activation of apoptotic caspases. Mitochondrial outer membrane permeabilization and DNA fragmentation are not discussed.

Effects of Dexmedetomidine Pretreatment, Posttreatment, and Whole-Course Pumping on Myocardial Damage during Cardiac Valve Replacement

To compare the effects of dexmedetomidine (DEX) pretreatment, posttreatment, and whole-course pumping on myocardial protection during cardiac valve replacement.One hundred and twenty patients undergoing cardiac valve replacement were randomly divided into the follow groups: DEX pretreatment (D1 group), DEX posttreatment (D2 group), DEX whole-course pumping (D3 group), and Control (C group). The concentrations of cardiac troponin I (cTnI), malondialdehyde (MDA), tumor necrosis factor alpha (TNF-α), rate of spontaneous heart rebound after aortic opening, time to heart rebound, incidence of arrhythmia, and use of sufentanil and vasoactive drugs were recorded.Compared with group C, the concentrations of cTnI, MDA, and TNF-α in the D1, D2, and D3 groups were lower, especially in the latter. The time to heart rebound was prolonged in all three groups (P < 0.05). The rate of automatic rebound was increased (P < 0.05) while the incidence of arrhythmia was decreased (P < 0.05) in all groups compared with group C. Group D3 had the highest rate of automatic rebound and the lowest incidence of arrhythmia. Compared with groups C and D2, the use of sufentanil and dopamine was lower in groups D1 and D3 (P < 0.05), especially in the latter.During cardiac valve replacement, DEX pretreatment, posttreatment, and whole-course pumping could have myocardial protective effects. The latter showed better effects.

Zebrafish as a New Tool in Heart Preservation Research

Heart transplantation became a reality at the end of the 1960s as a life-saving option for patients with end-stage heart failure. Static cold storage (SCS) at 4-6 °C has remained the standard for heart preservation for decades. However, SCS only allows for short-term storage that precludes optimal matching programs, requires emergency surgeries, and results in the unnecessary discard of organs. Among the alternatives seeking to extend ex vivo lifespan and mitigate the shortage of organs are sub-zero or machine perfusion modalities. Sub-zero approaches aim to prolong cold ischemia tolerance by deepening metabolic stasis, while machine perfusion aims to support metabolism through the continuous delivery of oxygen and nutrients. Each of these approaches hold promise; however, complex barriers must be overcome before their potential can be fully realized. We suggest that one barrier facing all experimental efforts to extend ex vivo lifespan are limited research tools. Mammalian models are usually the first choice due to translational aspects, yet experimentation can be restricted by expertise, time, and resources. Instead, there are instances when smaller vertebrate models, like the zebrafish, could fill critical experimental gaps in the field. Taken together, this review provides a summary of the current gold standard for heart preservation as well as new technologies in ex vivo lifespan extension. Furthermore, we describe how existing tools in zebrafish research, including isolated organ, cell specific and functional assays, as well as molecular tools, could complement and elevate heart preservation research.

The Problem of Apoptotic Processes Reversibility

Apoptosis is the best understood variant of regulated cell death, which has been considered irreversible for a long time. To date, an increasing amount of data has been accumulating indicating that key events of apoptosis, such as the externalization of phosphatidylserine, mitochondrial outer membrane permeabilization, caspase activation, DNA damage, and cytoplasmic blebbing are not irreversible and can be involved in the normal cell functioning not associated with the induction of apoptosis. Anastasis - cell recovery after induction of apoptosis - can occur following elimination of proapoptotic stimuli. This can facilitate survival of damaged or tumor cells. This review describes key processes of apoptosis, which do not necessarily lead to cell death during normal cell activity as well as anastasis. Understanding mechanisms and consequences of apoptotic processes reversibility, on the one hand, could contribute to the improvement of existing therapeutic approaches for various diseases, including malignant neoplasms, and, on the other hand, could open up new possibilities for protecting cellular elements of tissues and organs from death during treatment of degenerative pathologies.

Pharmacological activation of soluble guanylate cyclase improves vascular graft function

OBJECTIVES

Ischaemia-reperfusion injury impairs the nitric oxide/soluble guanylate cyclase/cyclic guanosine monophosphate (cGMP) signalling pathway and leads to vascular dysfunction. We assessed the hypothesis that the soluble guanylate cyclase activator cinaciguat would protect the vascular graft against ischaemia-reperfusion injury.

METHODS

In the treatment groups, rats (n = 8/group) were pretreated with either intravenous saline or intravenous cinaciguat (10 mg/kg) 2 h before an aortic transplant. Aortic grafts were stored for 2 h in saline and transplanted into the abdominal aorta of the recipients. Two hours after the transplant, the grafts were harvested and mounted in an organ bath. Vascular function of the grafts was investigated in the organ bath. Terminal deoxynucleotidyl transferase dUTP nick end labelling, cluster of differentiation 31, caspase-3, endothelial nitric oxide synthase, cGMP, nitrotyrosine and vascular cell adhesion molecule 1 immunochemical reactions were also investigated.

RESULTS

Pretreatment with cinaciguat significantly improved endothelium-dependent maximal relaxation 2 h after reperfusion compared with the saline group (maximal relaxation control: 96.5 ± 1%, saline: 40.4 ± 3% vs cinaciguat: 54.7 ± 2%; P < 0.05). Pretreatment with cinaciguat significantly reduced DNA fragmentation and nitro-oxidative stress; decreased the caspase-3 and vascular cell adhesion molecule 1 scores; and increased endothelial nitric oxide synthase, cGMP and cluster of differentiation 31 scores.

CONCLUSIONS

Our results demonstrated that enhancement of cGMP signalling by pharmacological activation of the soluble guanylate cyclase activator cinaciguat might represent a beneficial therapy for treating endothelial dysfunction of arterial bypass graft during cardiac surgery.

Total circulatory arrest as a support modality in congenital heart surgery: review and current evidence

The use of total circulatory arrest (TCA)/deep hypothermic circulatory arrest (DHCA) as a support modality in congenital heart surgery is a time-tested strategy. However, with technological advances, the widespread use of this technique has decreased. Adjunctive cerebral perfusion with continuous cardiopulmonary bypass (CPB) gradually has become more popular with a view to reduce the complications related to DHCA. In addition, better neuromonitoring and neuroprotective strategies have made DHCA much safer. However, the level of evidence to support the best way to protect the brain during congenital heart surgery is insufficient. This review analyzes the history, physiology, techniques of DHCA, as well as other alternative strategies like selective cerebral perfusion and presents the current available evidence.

Sarcopenia assessed by the quantity and quality of skeletal muscle is a prognostic factor for patients undergoing cardiac surgery

PURPOSE

Sarcopenia was assessed as a prognostic factor for patients undergoing cardiac surgery by evaluating the quantity and quality of skeletal muscle.

METHODS

Sarcopenia was assessed by perioperative abdominal computed tomography using the total psoas muscle index (TPI) and intra-muscular adipose tissue content (IMAC). Patients were classified into high- (HT, n = 143) and low- (LT, n = 63) TPI groups and low- (LI, n = 122) and high- (HI, n = 84) IMAC groups.

RESULTS

There were significantly more complications in the LT and HI groups than in the HT and LI groups. (HT 15.4% vs. LT 30.2%, P = 0.014) (LI 11.5% vs. HI 31.1%, P < 0.001). There were more respiratory complications in the LT group (HT 0% vs. LT 6.3%, P = 0.002) and more surgical site infections in the HI group than in the LI group (LI 0.8% vs. HI 7.1%, P = 0.014). A multivariable analysis showed that low TPI and high IMAC significantly predicted more major complications than other combinations (odds ratio [OR] 2.375; 95% confidence interval [CI] 1.152-5.783; P = 0.036, OR 3.973; 95% CI 1.737-9.088; P = 0.001).

CONCLUSIONS

Sarcopenia is a risk factor for complications. The quantity and quality of muscle must be assessed to predict operative outcomes.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000027077.

Childhood Obesity, Endothelial Cell Activation, and Critical Illness

Pediatric obesity is increasing in prevalence and is frequently an antecedent to adult obesity and adult obesity-associated morbidities such as atherosclerosis, type II diabetes, and chronic metabolic syndrome. Endothelial cell activation, one aspect of inflammation, is present in the early stages of atherosclerosis, often prior to the onset of symptoms. Endothelial activation is a pathological condition in which vasoconstricting, pro-thrombotic, and proliferative mediators predominate protective vasodilating, anti-thrombogenic, and anti-mitogenic mediators. Many studies report poor outcomes among obese children with systemic endothelial activation. Likewise, the link between childhood obesity and poor outcomes in critical illness is well-established. However, the link between obesity and severity of endothelial activation specifically in the setting of critical illness is largely unstudied. Although endothelial cell activation is believed to worsen disease in critically ill children, the nature and extent of this response is poorly understood due to the difficulty in measuring endothelial cell dysfunction and destruction. Based on the data available for the obese, asymptomatic population and the obese, critically ill population, the authors posit that obesity, and obesity-associated chronic inflammation, including oxidative stress and insulin resistance, may contribute to endothelial activation and associated worse outcomes among critically ill children. A research agenda to examine this hypothesis is suggested.

Microvolt T-wave alternans at the end of surgery is associated with postoperative mortality in cardiac surgery patients

Microvolt T-wave alternans (MTWA), which reflects electrical dispersion of repolarization, is known to be associated with arrhythmia or sudden cardiac death in high risk patients. In this study we investigated the relationship between MTWA and postoperative mortality in 330 cardiac surgery patients. Electrocardiogram, official national data and electric chart were analysed to provide in-hospital and mid-term outcome. MTWA at the end of surgery was significantly associated with in-hospital mortality in both univariate analysis (OR = 27.378, 95% CI 5.616-133.466, p < 0.001) and multivariate analysis (OR = 59.225, 95% CI 6.061-578.748, p < 0.001). Cox proportional hazards model revealed MTWA at the end of surgery was independently associated with mid-term mortality (HR = 4.337, 95% CI 1.594-11.795). The area under the curve of the model evaluating MTWA at the end of surgery was 0.764 (95% CI, 0.715-0.809) and it increased to 0.929 (95% CI, 0.896-0.954) when combined with the EuroSCORE II. MTWA positive at the end of surgery had a 60-fold increase in in-hospital mortality and a 4-fold increase in mid-term mortality. Moreover, MTWA at the end of surgery could predict in-hospital mortality and this predictability is more robust when combined with the EuroSCORE II.

Cytokines as biomarkers of inflammatory response after open versus endovascular repair of abdominal aortic aneurysms: a systematic review

The repair of an abdominal aortic aneurysm (AAA) is a high-risk surgical procedure related to hormonal and metabolic stress-related response with an ensuing activation of the inflammatory cascade. In contrast to open repair (OR), endovascular aortic aneurysm repair (EVAR) seems to decrease the postoperative stress by offering less extensive incisions, dissection, and tissue manipulation. However, these beneficial effects may be offset by the release of cytokines and arachidonic acid metabolites during intra-luminal manipulation of the thrombus using catheters in endovascular repair, resulting in systemic inflammatory response (SIR), which is clinically called post-implantation syndrome. In this systematic review we compared OR with EVAR in terms of the post-interventional inflammatory response resulting from alterations in the circulating cytokine levels. We sought to summarize all the latest evidence regarding post-implantation syndrome after EVAR. We searched Medline (PubMed), ClinicalTrials.gov and the Cochrane library for clinical studies reporting on the release of cytokines as part of the inflammatory response after both open/conventional and endovascular repair of the AAA. We identified 17 studies examining the cytokine levels after OR versus EVAR. OR seemed to be associated with a greater SIR than EVAR, as evidenced by the increased cytokine levels, particularly IL-6 and IL-8, whereas IL-1β, IL-10 and TNF-α showed conflicting results or no difference between the two groups. Polyester endografts appear to be positively correlated with the incidence of post-implantation syndrome after EVAR. Future large prospective studies are warranted to delineate the underlying mechanisms of the cytokine interaction in the post-surgical inflammatory response setting.

VascuTrainer: A Mobile and Disposable Bioreactor System for the Conditioning of Tissue-Engineered Vascular Grafts

In vitro tissue engineering of vascular grafts requires dynamic conditioning in a bioreactor system for in vitro tissue maturation and remodeling to receive a mechanically adequate and hemocompatible implant. The goal of the current work was to develop a bioreactor system for the conditioning of vascular grafts which is (i) able to create a wide range of flow, pressure and frequency conditions, including physiological ones; (ii) compact and easy to assemble; (iii) transportable; (iv) disposable. The system is driven by a small centrifugal pump controlled via a custom-made control unit, which can also be operated on batteries to allow for autonomous transportation. To show the potential of the newly developed bioreactor system small-caliber vascular composite grafts (n = 5, internal diameter = 3 mm, length = 12.5 cm) were fabricated using a fibrin scaffold embedding human umbilical artery smooth muscle cells and a polyvinylidene fluoride warp-knitted macroporous mesh. Subsequently, the vascular grafts were endothelialized and mounted in the bioreactor system for conditioning. The conditioning parameters remained within the predefined range over the complete conditioning period and during operation on batteries as tested for up to 25 h. Fabrication and pre-conditioning under arterial pressure and shear stress conditions resulted in robust and hemocompatible tissue-engineered vascular grafts. Analysis of immunohistochemical stainings against extracellular matrix and cell-specific proteins revealed collagen I and collagen III deposition. The luminal surface was confluently covered with endothelial cells. The developed bioreactor system showed cytocompatibility and pH, pO₂, pCO₂, glucose and lactate stayed constant. Sterility was maintained during the complete fabrication process of the vascular grafts. The potential of a versatile and mobile system and its functionality by conditioning tissue-engineered vascular grafts under physiological pressure and flow conditions could be demonstrated.

L-carnitine on myocardial function after coronary artery bypass grafting

Background

This study aims to evaluate the effect of L-carnitine on postoperative cardiac performance and morbidity and complications in patients undergoing coronary artery bypass grafting.

Methods

Between April 2005 and June 2008, a total of 60 patients (36 males, 24 females; mean age 60.6 years; range 57 to 65) who were scheduled for coronary artery bypass grafting were prospectively randomized to receive one of three different strategies of myocardial preservation. Group A (n=20) received antegrade crystalloid cardioplegia, Group B (n=20) received antegrade blood cardioplegia, and Group C (n=20) received antegrade blood cardioplegia with carnitine. Samples for lactate dehydrogenase (LDH), creatinine phosphokinase (CPK), creatinine phosphokinasemyocardial band (CK-MB), and Troponin-I were taken from coronary sinus during the operation and from peripheral venous line postoperatively. Blood samples were obtained before CPB, just after CPB and postoperative 1, 6, 12, 24 and 48 hours. Levels of CPK, CK-MB and Troponin-T levels were studied by immunoassay method.

Results

The patients who received carnitine had significantly improved cardiac output, cardiac index, and right and left ventricular stroke work immediately after cardiopulmonary bypass and at the first postoperative hour (p=0.01). Troponin-T levels decreased in all patients after 12 hours postoperatively, and this change was most prominent in Group C (p=0.001).

Conclusion

Intravenous supplementation of carnitine during cardioplegia provides better results on the recovery of cardiac function and metabolic parameters after coronary artery bypass grafting.

Correlation Between Flow-Mediated Dilatation of the Brachial Artery and Serum Endothelial Biomarkers in the Evaluation of Acute Endothelial Injury After Cardiopulmonary Bypass

OBJECTIVES

The purpose of this study was to investigate the correlation between flow-mediated dilatation of the brachial artery and serum endothelial biomarkers and to discuss the feasibility of sonographic evaluation of acute endothelial injury during cardiopulmonary bypass (CPB) surgery.

METHODS

Sonography was applied to determine the percentage of change in the brachial artery size during flow-mediated dilatation. Meanwhile, the plasma concentrations of endothelial-derived biomarkers, such as endothelin 1, nitric oxide, and von Willebrand factor, were measured to monitor the changes in endothelial function. We analyzed the correlation between flow-mediated dilatation and biomarkers during the perioperative period of CPB in 27 patients.

RESULTS

All of the biomarkers changed dramatically, especially during the CPB period. There was a negative correlation between flow-mediated dilatation and von Willebrand factor (P = .001; R = -0.31).

CONCLUSIONS

A CPB event has a substantial impact on endothelial function, and sonographic assessment of the percentage of change in the brachial artery size during flow-mediated dilatation allows early detection of acute endothelial function injury in cardiac surgery.

Glutamine Improves Myocardial Function following Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion injury is common during cardiac procedures. Glutamine may protect the myocardium by preserving metabolic substrates. Glutamine (0.52 g·kg−1) or Ringer's lactate solution (control group) was administered intraperitoneally to 63 Sprague-Dawley rats at 4 or 18 hours prior to experimental ischemia and reperfusion. The hearts were excised and perfused on an isolated working heart model, exposed to global ischemia for 15 min and reperfusion for 1 hour. Left atrial pressure, mean aortic pressure, cardiac flow, coronary flow, and aortic output were measured 15 min before ischemia and every 15 min during reperfusion. There was significantly better cardiac output in the glutamine pretreated groups. Pretreatment at 4 hours before the experiment was superior to pretreatment at 18 hours, with better maintenance of cardiac output and coronary flow. The enhanced protective effect of pretreatment at 4 hours highlights the importance of timing, and suggests a potential clinical benefit.

N-n-butyl haloperidol iodide ameliorates hypoxia/reoxygenation injury through modulating the LKB1/AMPK/ROS pathway in cardiac microvascular endothelial cells

Endothelial cells are highly sensitive to hypoxia and contribute to myocardial ischemia/reperfusion injury. We have reported that N-n-butyl haloperidol iodide (F2) can attenuate hypoxia/reoxygenation (H/R) injury in cardiac microvascular endothelial cells (CMECs). However, the molecular mechanisms remain unclear. Neonatal rat CMECs were isolated and subjected to H/R. Pretreatment of F2 leads to a reduction in H/R injury, as evidenced by increased cell viability, decreased lactate dehydrogenase (LDH) leakage and apoptosis, together with enhanced AMP-activated protein kinase (AMPK) and liver kinase B1 (LKB1) phosphorylation in H/R ECs. Blockade of AMPK with compound C reversed F2-induced inhibition of H/R injury, as evidenced by decreased cell viability, increased LDH release and apoptosis. Moreover, compound C also blocked the ability of F2 to reduce H/R-induced reactive oxygen species (ROS) generation. Supplementation with the ROS scavenger N-acetyl-L-cysteine (NAC) reduced ROS levels, increased cell survival rate, and decreased both LDH release and apoptosis after H/R. In conclusion, our data indicate that F2 may mitigate H/R injury by stimulating LKB1/AMPK signaling pathway and subsequent suppression of ROS production in CMECs.

Systemic Dosing of Thymosin Beta 4 before and after Ischemia Does Not Attenuate Global Myocardial Ischemia-Reperfusion Injury in Pigs

The use of cardiopulmonary bypass (CPB) and aortic cross-clamping causes myocardial ischemia-reperfusion injury (I-RI) and can lead to reduced postoperative cardiac function. We investigated whether this injury could be attenuated by thymosin beta 4 (TB4), a peptide which has showed cardioprotective effects. Pigs received either TB4 or vehicle and underwent CPB and aortic cross-clamping for 60 min with cold intermittent blood-cardioplegia and were then followed for 30 h. Myocardial function and blood flow was studied by cardiac magnetic resonance and PET imaging. Tissue and plasma samples were analyzed to determine the amount of cardiomyocyte necrosis and apoptosis as well as pharmacokinetics of the peptide. In vitro studies were performed to assess its influence on blood coagulation and vasomotor tone. Serum levels of the peptide were increased after administration compared to control samples. TB4 did not decrease the amount of cell death. Cardiac function and global myocardial blood flow was similar between the study groups. At high doses a vasoconstrictor effect on mesentery arteries and a vasodilator effect on coronary arteries was observed and blood clot firmness was reduced when tested in the presence of an antiplatelet agent. Despite promising results in previous trials the cardioprotective effect of TB4 was not demonstrated in this model for global myocardial I-RI.

Elevated free fatty acid level is a risk factor for early postoperative hypoxemia after on-pump coronary artery bypass grafting: association with endothelial activation

BACKGROUND

We aimed to investigate the relationship between increased free fatty acid (FFA) level and early postoperative hypoxemia after coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB).

METHODS

Ninety-eight consecutive patients undergoing CABG were enrolled. Early postoperative hypoxemia was defined as the lowest of the ratio of arterial oxygen tension (PaO2) to inspired oxygen fraction (FiO2) ≤ 200 mm Hg within 24 h without pleural effusion and pneumothorax. The 26 perioperative factors, serum levels of FFA and inflammatory cytokines between the hypoxemia and non-hypoxemia groups were recorded or detected using autoanalyzer and enzyme-linked immunosorbent assay, respectively. Additionally, the risk factors for early postoperative hypoxemia were evaluated using multiple logistic regression analysis.

RESULTS

The incidence rate of early postoperative hypoxemia was 37.8 %. Serum FFA levels were significantly higher in the hypoxemia group than in the non-hypoxemia group (P<0.001). Further, postoperative serum FFA levels were inversely related to the lowest of the ratio of PaO2/FiO2 at 24 h after CABG (r= - 0.367, P<0.001). Multiple logistic regression analysis confirmed that age, body mass index and postoperative serum FFA concentrations were independently associated with early postoperative hypoxemia. Notably, patients with hypoxemia had markedly higher serum intercellular adhesion molecule-1 (ICAM-1) levels than those without (P<0.001). Moreover, serum FFA levels at 2 h after CABG correlated positively with ICAM-1 concentrations (r=0.492, P<0.001).

CONCLUSIONS

Elevated FFA concentration is a risk factor for early postoperative hypoxemia after on-pump CABG, which may be closely associated with endothelial activation.

Dimethyloxalylglycine treatment of brain-dead donor rats improves both donor and graft left ventricular function after heart transplantation

OBJECTIVE

Hypoxia inducible factor (HIF)-1 pathway signalling has a protective effect against ischemia/reperfusion injury. The prolyl-hydroxylase inhibitor dimethyloxalylglycine (DMOG) activates the HIF-1 pathway by stabilizing HIF-1α. In a rat model of brain death (BD)-associated donor heart dysfunction we tested the hypothesis that pre-treatment of brain-dead donors with DMOG would result in a better graft heart condition.

METHODS

BD was induced in anesthetized Lewis rats by inflating a subdurally placed balloon catheter. Controls underwent sham operations. Then, rats were injected with an intravenous dose of DMOG (30 mg/kg) or an equal volume of physiologic saline. After 5 hours of BD or sham operation, hearts were perfused with a cold (4°C) preservation solution (Custodiol; Dr. Franz Köhler Chemie GmbH; Germany), explanted, stored at 4°C in Custodiol, and heterotopically transplanted. Graft function was evaluated 1.5 hours after transplantation.

RESULTS

Compared with control, BD was associated with decreased left ventricular systolic and diastolic function. DMOG treatment after BD improved contractility (end-systolic pressure volume relationship E'max: 3.7 ± 0.6 vs 3.1 ± 0.5 mm Hg/µ1; p < 0.05) and left ventricular stiffness (end-diastolic pressure volume relationship: 0.13 ± 0.03 vs 0.31 ± 0.06 mm Hg/µ1; p < 0.05) 5 hours later compared with the brain-dead group. After heart transplantation, DMOG treatment of brain-dead donors significantly improved the altered systolic function and decreased inflammatory infiltration, cardiomyocyte necrosis, and DNA strand breakage. In addition, compared with the brain-dead group, DMOG treatment moderated the pro-apoptotic changes in the gene and protein expression.

CONCLUSIONS

In a rat model of potential brain-dead heart donors, pre-treatment with DMOG resulted in improved early recovery of graft function after transplantation. These results support the hypothesis that activation of the HIF-1 pathway has a protective role against BD-associated cardiac dysfunction.

Endothelial dysfunction of bypass graft: direct comparison of in vitro and in vivo models of ischemia-reperfusion injury

Background

Although, ischemia/reperfusion induced vascular dysfunction has been widely described, no comparative study of in vivo- and in vitro-models exist. In this study, we provide a direct comparison between models (A) ischemic storage and in-vitro reoxygenation (B) ischemic storage and in vitro reperfusion (C) ischemic storage and in-vivo reperfusion.

Methods and Results

Aortic arches from rats were stored for 2 hours in saline. Arches were then (A) in vitro reoxygenated (B) in vitro incubated in hypochlorite for 30 minutes (C) in vivo reperfused after heterotransplantation (2, 24 hours and 7 days reperfusion). Endothelium-dependent and independent vasorelaxations were assessed in organ bath. DNA strand breaks were assessed by TUNEL-method, mRNA expressions (caspase-3, bax, bcl-2, eNOS) by quantitative real-time PCR, proteins by Western blot analysis and the expression of CD-31 by immunochemistry. Endothelium-dependent maximal relaxation was drastically reduced in the in-vivo models compared to ischemic storage and in-vitro reperfusion group, and no difference showed between ischemic storage and control group. CD31-staining showed significantly lower endothelium surface ratio in-vivo, which correlated with TUNEL-positive ratio. Increased mRNA and protein levels of pro- and anti-apoptotic gens indicated a significantly higher damage in the in-vivo models.

Conclusion

Even short-period of ischemia induces severe endothelial damage (in-vivo reperfusion model). In-vitro models of ischemia-reperfusion injury can be limitedly suited for reliable investigations. Time course of endothelial stunning is also described.

Cardiopulmonary bypass is associated with altered vascular reactivity of isolated pulmonary artery in a porcine model: therapeutic potential of inhaled tezosentan

OBJECTIVE

Whereas it is established that endothelin-1 elicits sustained deleterious effects on the cardiovascular system during cardiopulmonary bypass (CPB), presently it remains unknown whether the inhaled administration of the dual ETA and ETB antagonist tezosentan prevents the development of pulmonary endothelial dysfunction.

DESIGN

A prospective, randomized laboratory investigation.

SETTING

University research laboratory.

PARTICIPANTS

Landrace swine.

INTERVENTIONS

Three groups of animals underwent a 90-minute period of full bypass followed by a 60-minute period of reperfusion. Among treated groups, one received tezosentan through inhalation prior to CPB, whereas the other one received it intravenously at weaning from CPB; the third group remained untreated. Pulmonary vascular reactivity studies, realized on a total of 285 rings, were performed in all groups, including 1 sham.

MEASUREMENTS AND MAIN RESULTS

The contractility of pulmonary arteries to prostaglandin F2α and to the thromboxane A2 mimetic U46619 was preserved in animals submitted to CPB. By contrast, there were significant increases both in the maximal contraction to endothelin-1 and in the plasma levels of the peptide 60 minutes after reperfusion. Tezosentan administered by inhalation or intravenously did not prevent the development of pulmonary CPB-associated endothelial dysfunction. However, while hemodynamic disturbances were improved with both routes, the inhaled administration had a beneficial effect on oxygen parameters over intravenous administration.

CONCLUSIONS

Despite the blockade of the endothelin-1 pathway with tezosentan, the development of the pulmonary endothelial dysfunction associated with CPB still occurred. However, only the inhalation route had a significant impact on gas exchange during CPB.

Fluid Mechanical Forces and Endothelial Mitochondria: A Bioengineering Perspective

Endothelial cell dysfunction is the hallmark of every cardiovascular disease/condition, including atherosclerosis and ischemia/reperfusion injury. Fluid shear stress acting on the vascular endothelium is known to regulate cell homeostasis. Altered hemodynamics is thought to play a causative role in endothelial dysfunction. The dysfunction is associated with/preceded by mitochondrial oxidative stress. Studies by our group and others have shown that the form and/or function of the mitochondrial network are affected when endothelial cells are exposed to shear stress in the absence or presence of additional physicochemical stimuli. The present review will summarize the current knowledge on the interconnections among intracellular Ca²⁺ - nitric oxide - mitochondrial reactive oxygen species, mitochondrial fusion/fission, autophagy/mitophagy, and cell apoptosis vs. survival. More specifically, it will list the evidence on potential regulation of the above intracellular species and processes by the fluid shear stress acting on the endothelium under either physiological flow conditions or during reperfusion (following a period of ischemia). Understanding how the local hemodynamics affects mitochondrial physiology and the cell redox state may lead to development of novel therapeutic strategies for prevention or treatment of the endothelial dysfunction and, hence, of cardiovascular disease.

Protection of coronary endothelial function during cardiac surgery: potential of targeting endothelial ion channels in cardioprotection

Vascular endothelium plays a critical role in the control of blood flow by producing vasoactive factors to regulate vascular tone. Ion channels, in particular, K(+) channels and Ca(2+)-permeable channels in endothelial cells, are essential to the production and function of endothelium-derived vasoactive factors. Impairment of coronary endothelial function occurs in open heart surgery that may result in reduction of coronary blood flow and thus in an inadequate myocardial perfusion. Hyperkalemic exposure and concurrent ischemia-reperfusion during cardioplegic intervention compromise NO and EDHF-mediated function and the impairment involves alterations of K(+) channels, that is, KATP and KCa, and Ca(2+)-permeable TRP channels in endothelial cells. Pharmacological modulation of these channels during ischemia-reperfusion and hyperkalemic exposure show promising results on the preservation of NO and EDHF-mediated endothelial function, which suggests the potential of targeting endothelial K(+) and TRP channels for myocardial protection during cardiac surgery.

The effect of safflower yellow on spinal cord ischemia reperfusion injury in rabbits

Safflower yellow (SY) is the safflower extract and is the one of traditional Chinese medicine. The aim of the present work was to investigate the effect of SY on spinal cord ischemia reperfusion injury (SCIRI) in rabbits. The models of spinal cord ischemia reperfusion (SI/R) were constructed, and the degree of the post-ischemic injury was assessed by means of the neurological deficit scores and plasma levels of lipid peroxidation reactioin and neuronal morphologic changes. SCIRI remarkably affected the functional activities of the hind limbs and activated lipid peroxidation reaction. SY could attenuate apoptosis and SCIRI by enhancing Bcl-2 expression and inhibiting Bax and caspase-3 activation.

Liposomal encapsulation enhances in vivo near infrared imaging of exposed phosphatidylserine in a mouse glioma model

We have previously demonstrated that exposed phosphatidylserine (PS) on tumor vascular endothelial cells is highly tumor specific, and development of the PS targeted near infrared (NIR) optical probe enables successful in vivo optical imaging of U87 gliomas in a mouse model. Liposomes have been widely used as a nanovector for delivery of chemotherapeutics and imaging contrast agents due to their high payload and longer circulation time. In the current study, we have fabricated PS-targeted liposomal nanoprobes encapsulating a NIR dye, IRDye^® 800CW, aiming to enhance PS-targeted tumor imaging. Hydrophilic 800CW dye was packed into the core of polyethylene glycol (PEG)-coated liposomes functionalized with F(ab’)₂ fragments of PGN635, a fully human monoclonal antibody that binds PS. As expected, in vivo dynamic NIR imaging revealed significantly improved tumor/normal contrast (TNR = 20 ± 3; p < 0.01) of subcutaneous U87 gliomas in mice after injection of the liposomal nanoprobes. Markedly enhanced TNR was observed after the tumors were irradiated to increase PS exposure (TNR = 48 ± 6; p < 0.05). Intriguingly, the liposomal nanoprobes, PGN-L-800CW showed distinct biodistribution and pharmacokinetics compared to the 800CW-PGN probes used in our previous study. Our data further suggest the usefulness of PS-targeted imaging probes for sensitive tumor detection and the potential of utilizing liposomal platform for glioma theranostics.

[Critical conditions as a logical and appropriate series of events in iron methabolism disorders (the summary of experimental studies)]

It is revealed that in all models of critical conditions will activate the free-radical oxidation, decreasing the total antioxidant activity, the concentration of transferrin decreases in the serum of the blood, increase of the concentration of ferritin, the theological properties of the blood are violated and the signs of endothelial dysfunction are identified. Pre-entered deferoxamine in the dose of 80 mg/kg reduced the intensity of free-radical oxidation processes, restoring the antioxidant potential, concentration of the transferrin, and a lower level of ferritin, contributed to the normalization of blood theological properties and a reduction of the extent endothelium destruction as a result of the reduction Fe2+ concentration in blood serum.

Addition of vardenafil into storage solution protects the endothelium in a hypoxia-reoxygenation model

OBJECTIVE

Based upon the well known protective effect of intracellular cyclic guanosine monophosphate (cGMP) accumulation, we tested the hypothesis that storage solution enriched with optimal concentration of the phosphodiestherase-5 inhibitor vardenafil could provide better protection of vascular grafts against reperfusion injury after long-term cold ischaemic storage.

METHODS

Isolated thoracic aorta obtained from rats underwent 24-h cold ischaemic preservation in physiological saline or vardenafil (10(-11) M)-supplemented saline solution. Reperfusion injury was simulated by hypochlorite (200 μM) exposure for 30 minutes. Endothelium-dependent vasorelaxation was assessed, and histopathological and molecular-biological examination of the aortic tissue were performed.

RESULTS

Compared with the control group, the saline group showed significantly attenuated endothelium-dependent maximal relaxation (Rmax) to acetylcholine after hypoxia-reoxygenation, which was significantly improved by vardenafil supplementation (Rmax control: 98 ± 1%; saline: 48 ± 6%; vardenafil: 75 ± 4%; p < .05). Vardenafil treatment significantly reduced DNA strand breaks (control: 10.6 ± 6.2%; saline: 72.5 ± 4.0%; vardenafil: 14.2 ± 5.2%; p < .05) and increased cGMP score in the aortic wall (control: 8.2 ± 0.6; saline: 4.5 ± 0.3; vardenafil: 6.7 ± 0.6; p < .05).

CONCLUSIONS

Our results support the view that impairment of intracellular cGMP signalling plays a role in the pathogenesis of the endothelial dysfunction induced by cold storage warm reperfusion, which can be effectively reversed by pharmacological phosphodiesterase-5 inhibition.

Redox signaling pathways involved in neuronal ischemic preconditioning

There is extensive evidence that the restoration of blood flow following cerebral ischemia contributes greatly to the pathophysiology of ischemia mediated brain injury. The initiating stimulus of reperfusion injury is believed to be the excessive production of reactive oxygen (ROS) and nitrogen (RNS) species by the mitochondria. ROS and RNS generation leads to mitochondrial protein, lipid and DNA oxidation which impedes normal mitochondrial physiology and initiates cellular death pathways. However not all ROS and RNS production is detrimental. It has been demonstrated that low levels of ROS production are protective and may serve as a trigger for activation of ischemic preconditioning. Ischemic preconditioning is a neuroprotective mechanism which is activated upon a brief sublethal ischemic exposure and is sufficient to provide protection against a subsequent lethal ischemic insult. Numerous proteins and signaling pathways have been implicated in the ischemic preconditioning neuroprotective response. In this review we examine the origin and mechanisms of ROS and RNS production following ischemic/reperfusion and the role of free radicals in modulating proteins associated with ischemic preconditioning neuroprotection.

The effect of C1 inhibitor on myocardial ischemia and reperfusion injury

BACKGROUND

Activation of the complement system has been demonstrated to be an important mechanism in the mediation of myocardial ischemia and reperfusion (MIR) injury. C1 inhibitor (C1INH) has been shown to be beneficial in experimental MIR models. The underlying mechanism of this effect has been assumed to result primarily from inhibition of complement system activation. We recently demonstrated that C1INH plays a direct role in suppression of leukocyte transmigration in the mouse intestinal ischemia and reperfusion model. The purpose of this study was to investigate the mechanism of the beneficial effect of C1INH in mouse MIR model.

METHODS

C57BL/6, C1INH-deficient (C1INH(-/-)), and C3-deficient mice (C3(-/-)) were subjected to 30-min (C57BL/6 and C1INH(-/-)) or 60-min (C3(-/-)) occlusion of the left anterior descending branch of the coronary artery followed by 4-h reperfusion. C1INH or reactive center cleaved inactive C1INH (iC1INH) was injected intravenously 5 min before reperfusion.

RESULTS

Myocardial infarct size relative to the area at risk or relative to left ventricular area was significantly reduced in C1INH-treated wild-type, C1INH(-/-), and C3(-/-) mice compared with vehicle-treated mice. MIR induced an increase in myocardial polymorphonuclear neutrophil accumulation and plasma cardiac specific troponin I levels in vehicle-treated MIR mice, while C1INH treatment significantly attenuated these effects. iC1INH had a similar protective effect.

CONCLUSIONS

These results suggested that C1INH prevented MIR injury in mice and that this cardioprotective effect may not solely result from complement inhibition, but might be also contributed by inhibiting leukocyte recruitment into ischemic tissue, an effect that is not mediated via protease inhibition.

Cilostazol, a type III phosphodiesterase inhibitor, reduces ischemia/reperfusion-induced spinal cord injury

BACKGROUND

Spinal cord injury is still a devastating complication after surgical repair of thoracoabdominal aortic pathologies. In this study, we investigated the protective effect of cilostazol, a type III phosphodiesterase inhibitor, against ischemia/reperfusion (I/R)-induced spinal cord injury in rats.

METHODS

Twenty-four rats were assigned to 3 experimental study groups: the control group (sham operation, n = 8); the ischemia group (nontreated, n = 8), which underwent aortic occlusion without pharmacologic intervention; and the cilostazol-treated group (n = 8), which received 20 mg/kg cilostazol per day orally for 3 days before spinal ischemia. All animals underwent a 45-minute period of spinal cord ischemia via clamping of the abdominal aorta between the left renal artery and the aortic bifurcation; removal of the aortic clamp was followed by reperfusion. Neurologic status was assessed before spinal ischemia and at 48 hours after the operation. All animals were sacrificed at 48 hours after the operation. Spinal cords were harvested for histopathologic examination and biochemical analyses for the malondialdehyde (MDA) level and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities.

RESULTS

Tarlov scores at postoperative hour 48 tended to be higher in the cilostazol-treated group than in the nontreated ischemia group (mean ± SD, 3.66 ± 0.40 versus 2.32 ± 0.80; P = .08). Spinal cord tissue MDA levels (per gram protein) were lower in the cilostazol-treated group than in the nontreated ischemia group (0.27 ± 0.01 mmol/g versus 0.33 ± 0.04 mmol/g, P = .026), and the cilostazol-treated group had higher activities of tissue SOD (519.6 ± 56.3 U/g versus 438.9 ± 67.4 U/g, P = .016) and GSH-Px (4.07 ± 1.37 U/g versus 3.21 ± 1.02 U/g, P = .47) than the nontreated ischemia group. Histopathologic analyses demonstrated that cilostazol treatment attenuated I/R-induced cellular damage.

CONCLUSION

Administration of cilostazol before spinal cord ischemia reduced neurologic injury and produced clinical improvement by attenuating oxidative stress in this rat spinal cord I/R model.

Studies of isolated global brain ischaemia: I. A new large animal model of global brain ischaemia and its baseline perfusion studies

OBJECTIVES

Neurological injury after global brain ischaemia (i.e. sudden death) remains problematic, despite improving cardiac survival. Unfortunately, sudden death models introduce unwanted variables for studying the brain because of multiple organ injury. To circumvent this, a new minimally invasive large animal model of isolated global brain ischaemia, together with baseline perfusion studies is described.

METHODS

The model employs neck and small (3-4 inches) supra-sternal incisions to block inflow from carotid and vertebral arteries for 30 min of normothermic ischaemia. Neurological changes after 24 h in six pigs was compared with six Sham pigs assessing neurological deficit score (NDS, 0 = normal, 500 = brain death), brain oedema and cerebral infarction by 2,3,5-triphenyltetrazolium chloride (TTC) stain. Six other pigs had baseline perfusion characteristics in this new model evaluated at carotid flows of 750, 550 and 450 cc/min, with cerebral perfusion pressure, cerebral oximeter saturation [IN Vivo Optical Spectroscopy (INVOS)] and transcranial O(2) uptake measurements.

RESULTS

The model never altered cardiac or pulmonary function, and six Sham pigs had normal (NDS = 0) neurological recovery without brain injury. Conversely, 24 h analysis showed that 30 min of global normothermic brain ischaemia caused multiple post-reperfusion seizures (P < 0.001 versus Sham), raised NDS (231 ± 16; P < 0.001 versus Sham) in four of six survivors and caused marked post-brain oedema (P < 0.001 versus Sham) and extensive cerebral infarctions (TTC stain; P < 0.001 versus Sham). Baseline perfusion showed 750 cc/min flow rate produced normal INVOS levels and O(2) consumption at mean 90-100 mmHg carotid pressure. Carotid pressure and INVOS fell at mid- and low-flow rates. Although INVOS did not change, 450 cc/min flow lowered global O(2) consumption, which further decreased after transient ischaemia (30 s) and 5 min of reperfusion.

CONCLUSIONS

This new isolated global brain model consistently caused anatomic, biochemical and functional neurological damage in pigs after 30 min of ischaemia. Flows of 750 cc/min maintained normal mean systemic arterial (90-100 mmHg) pressure, INVOS levels and O(2) consumption. Cerebral pressure and INVOS fell in mid- and low-flow studies. A disparity existed between INVOS oxygen saturation and global O(2) consumption at lower flow rates of 450 cc/min following transient ischaemia, indicating that surface oxygen saturation measurement does not reflect global brain O(2) consumption.

Studies of isolated global brain ischaemia: I. Overview of irreversible brain injury and evolution of a new concept - redefining the time of brain death

Despite advanced cardiac life support (ACLS), the mortality from sudden death after cardiac arrest is 85-95%, and becomes nearly 100% if ischaemia is prolonged, as occurs following unwitnessed arrest. Moreover, 33-50% of survivors following ACLS after witnessed arrest develop significant neurological dysfunction, and this rises to nearly 100% in the rare survivors of unwitnessed arrest. Although, whole body (cardiac) survival improves to 30% following recent use of emergency cardiopulmonary bypass, sustained neurological dysfunction remains a devastating and unresolved problem. Our studies suggest that both brain and whole body damage reflect an ischaemic/reperfusion injury that follows the present reperfusion methods that use normal blood, which we term 'uncontrolled reperfusion'. In contrast, we have previously introduced the term 'controlled reperfusion', which denotes controlling both the conditions (pressure, flow and temperature) as well as the composition (solution) of the reperfusate. Following prolonged ischaemia of the heart, lung and lower extremity, controlled reperfusion resulted in tissue recovery after ischaemic intervals previously thought to produce irreversible cellular injury. These observations underlie the current hypothesis that controlled reperfusion will become an effective treatment of the otherwise lethal injury of prolonged brain ischaemia, such as with unwitnessed arrest, and we tested this after 30 min of normothermic global brain ischaemia. This review, and the subsequent three studies will describe the evolution of the concept that controlled reperfusion will restore neurological function to the brain following prolonged (30 min) ischaemia. To provide a familiarity and rationale for these studies, this overview reviews the background and current treatment of sudden death, the concepts of controlled reperfusion, recent studies in the brain during whole body ischaemia, and then summarizes the three papers in this series on a new brain ischaemia model that endorses our hypothesis that controlled reperfusion allows complete neurological recovery following 30 min of normothermic global brain ischaemia. These findings may introduce innovative management approaches for sudden death, and perhaps stroke, because the brain is completely salvageable following ischaemic times thought previously to produce infarction.

Development of bavituximab, a vascular targeting agent with immune-modulating properties, for lung cancer treatment

Bavituximab is a chimeric monoclonal antibody directed against the membrane phospholipid phosphatidylserine. Phosphatidylserine exposure is increased on endothelial cells and apoptotic cancer cells in solid tumors, allowing tumor-specific targeting of bavituximab. Bavituximab binding results in tumor vessel occlusion and enhanced antitumor immunity. Preclinical investigations have demonstrated efficacy as monotherapy and in combination with other modalities against multiple cancer types. Phase I clinical trials of bavituximab monotherapy and in combination with chemotherapy in adults with refractory solid tumors have been completed. Phase II trials of bavituximab in combination with chemotherapy for the first- and second-line treatment of advanced non-small-cell lung cancer are currently ongoing. This article summarizes the preclinical development and clinical experience with bavituximab in non-small-cell lung cancer.

Rosuvastatin, a new generation 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitor, reduces ischemia/reperfusion-induced spinal cord tissue injury in rats

BACKGROUND

Severe neurological injury still represents one of the most devastating complications occurring after surgical repair of thoracoabdominal aneurysms. We aimed to investigate the role of rosuvastatin (RSV) against ischemia/reperfusion injury in an experimental model of spinal cord ischemia in rats.

METHODS

Experimental groups included control group (n = 8), ischemia/reperfusion group (n = 8) undergoing aortic occlusion without pharmacologic treatment, and RSV-treated group (n = 8) receiving 10 mg/kg/day of RSV orally for 3 days before spinal cord ischemia. Spinal cord ischemia was induced by occlusion of the abdominal aorta between the left renal artery and aortic bifurcation for 45 minutes, followed by reperfusion. Neurological status was assessed before spinal ischemia and at 48 hours postoperatively. Spinal cords were harvested for histopathologic examination with hematoxylin-eosin staining and biochemical analysis for tissue malondialdehyde, superoxide dismutase, and glutathione peroxidase levels.

RESULTS

Decreased spinal cord tissue malondialdehyde levels (p = .01) and increased tissue superoxide dismutase (p = .01) and glutathione peroxidase (p = .09) levels were observed in the RSV-treated group, as compared with the ischemia group. Histopathologic analyses demonstrated typical changes of ischemic necrosis in the ischemia group; however, RSV attenuated tissue necrosis. Total injury score in the RSV-treated group was significantly decreased, as compared with the ischemia group (p < .05). The Tarlov scores at 48 hours postoperatively were higher in the RSV group as compared with the ischemia group.

CONCLUSION

RSV administration before spinal cord ischemia reduces spinal cord tissue injury by increasing antioxidant enzyme levels and may reduce the incidence of associated neurological dysfunction.

Toll-like receptor and its roles in myocardial ischemic/reperfusion injury

The innate immune system, mediated via toll-like receptors (TLRs), represents the first line of defensive mechanisms that protects hosts from invading microbial pathogens. TLRs are a family of pattern recognition receptors (PRRs), and are pathologically activated by a set of pathogen-associated microbial patterns (PAMPs) and damage-associated molecular patterns (DAMPs). TLRs deliver signals via a specific intracellular signaling pathway involving distinctive adaptor proteins and protein kinases, and ultimately initiate transcriptional factors resulting in inflammatory responses. TLR4 is a paramount type of TLRs, located in the heart, and plays an important role in mediating myocardial ischemic reperfusion (I/R) injury. Loss-of-function experiments and animal models using genetic techniques have found that the MyD88-independent and the MyD88-dependent pathways together participate in the pathological process of myocardial I/R injury. Some other distinctive signaling pathways, such as the PI3K/AKt and AMPK/ERK pathways, interacting with the TLR4 signaling pathway, were also found to be causes of myocardial I/R injury. These different pathways activate a series of downstream transcriptional factors, produced a great quantity of inflammatory cytokines, such as IL, TNF, and initiate inflammatory response. This results in cardiac injury and dysfunction, such as myocardial stunning, no reflow phenomenon, reperfusion arrhythmias and lethal reperfusion injury, and other related complication such as ventricular remodeling. In the future, blockades aimed at blocking the signaling pathway could benefit developments in pharmacology.

Epidermal growth factor-like domain 7 suppresses intercellular adhesion molecule 1 expression in response to hypoxia/reoxygenation injury in human coronary artery endothelial cells

BACKGROUND

Epidermal growth factor-like domain 7 (Egfl7) is a chemoattractant for endothelial cells, and its expression is restricted to endothelial cells. Hypoxia/reoxygenation (H/R) induced endothelial injury that occurs during transplantation contributes to the subsequent development of allograft vasculopathy. We investigated the effect of Egfl7 on endothelial cell intercellular adhesion molecule 1 expression in response to H/R injury.

METHODS AND RESULTS

Human coronary artery endothelial cells were submitted to hypoxia (0.1% O(2)) followed by normoxia (21% O(2)) in the presence or absence of Egfl7 (100 ng/mL). Hypoxia alone increased the expression of Egfl7×140±8% of control at 3 hours (n=6; P<0.05) and 385±50% of control at 6 hours (n=6; P<0.001). Incubation with Egfl7 during the reoxygenation period prevented intercellular adhesion molecule 1 upregulation (mean fluorescence intensity: 5.37±0.92 versus 3.81±0.21; P<0.05; n=4 per group). Nuclear factor-κB nuclear localization on H/R injury was blocked by Egfl7 administration (cytosolic/nuclear ratio of 0.93±0.01 versus 1.44±0.24; P<0.05; n=4 per group). Inhibitor of nuclear factor-κB protein level was significantly reduced on H/R injury (26±4.6% of control expression; P<0.05; n=4 per group); however, concurrent incubation with Egfl7 attenuated this reduction (46±6.2% of control expression; P<0.05 when compared with H/R injury alone; n=4 per group).

CONCLUSIONS

Our study reveals the novel observation that hypoxia upregulates human coronary artery endothelial cells expression of Egfl7 and that Egfl7 inhibits expression of intercellular adhesion molecule 1 subsequent to H/R injury. Mechanistically, Egfl7 prevented nuclear factor-κB nuclear localization and augmented inhibitor of nuclear factor-κB protein levels, suggesting that it inhibits nuclear factor-κB activation, a key step in the inflammatory activation of endothelial cells. Egfl7 may be protective against H/R injury incurred during transplantation and may modulate the events that lead to the development of graft vasculopathy.

The protective effects of Egr-1 antisense oligodeoxyribonucleotide on cardiac microvascular endothelial injury induced by hypoxia-reoxygenation

Early growth response 1 (Egr-1) over-expression has been demonstrated in myocardial ischemia-reperfusion injury, which is closely associated with endothelial dysfunction. In the present study we investigated the expression of Egr-1 on cultured cardiac microvascular endothelial cells (CMECs) to help define the mechanism of myocardial ischemia-reperfusion injury. A model of cultured CMECs exposed to hypoxia-reoxygenation was developed in which synthesized Egr-1 sense and antisense oligodeoxyribonucleotide were transfected into the cells. The expression of Egr-1 was examined by Western blot analysis. Lactate dehydrogenase, malondialdehyde, superoxide dismutase, tumor necrosis factor alpha, and intercellular adhesion molecule 1 were measured after hypoxia-reoxygenation to assess cell function and injury. Cell morphology, cell viability, and neutrophil adhesion to the CMECs were measured to assess the degree of injury and inflammation. Only cells transfected with Egr-1 antisense oligodeoxyribonucleotide showed a significant reduction in Egr-1 protein expression following hypoxia-reoxygenation. Consistent with the down-regulation of Egr-1 expression, other forms of cell injury were significantly reduced in this group of cells, as evidenced by less alteration in cell morphology, a decrease in expression of tumor necrosis factor alpha and intercellular adhesion molecule 1, improved cell survival, and reduced neutrophil adhesion.

Pre-conditioning with the soluble guanylate cyclase activator Cinaciguat reduces ischaemia-reperfusion injury after cardiopulmonary bypass

OBJECTIVE

Activation of the nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) pathway can induce potent cardioprotection-like effects against ischaemia-reperfusion injury and nitro-oxidative stress. We investigated the effects of pharmacological pre-conditioning with Cinaciguat (BAY 58-2667), a novel sGC activator on peroxynitrite-induced endothelial dysfunction in vitro, as well as on myocardial and coronary vascular function during reperfusion in a canine model of cardioplegic arrest and extracorporeal circulation.

METHODS

Isolated coronary arterial rings exposed to peroxynitrite were investigated for vasomotor function. Vehicle- and Cinaciguat-pre-treated (8.33 μg h(-1) or 25 μg h(-1) intravenous (IV) for 30 min) anaesthetised dogs (n = 6-7 per group) underwent hypothermic cardiopulmonary bypass with 60 min of hypothermic cardioplegic arrest. Left- and right-ventricular end-systolic pressure-volume relationship (ESPVR) was measured by a pressure-volume conductance catheter at baseline and after 60 min of reperfusion. Coronary blood flow, vasodilatation to acetylcholine and myocardial level of adenosine triphosphate were determined.

RESULTS

Pre-incubation of coronary rings with Cinaciguat improved peroxynitrite-induced endothelial dysfunction. Compared with control, pharmacological pre-conditioning with Cinaciguat (25 μg h(-1)) led to higher myocardial adenosine triphosphate content, to a better recovery of left- and right-ventricular contractility (Δ slope of left ventricular ESPVR given as percent of baseline: 102.4 ± 19.1% vs 56.0 ± 7.1%) and to a higher coronary blood flow (49.6 ± 3.5 ml min(-1) vs 28.0 ± 3.9 ml min(-1)). Endothelium-dependent vasodilatation to acetylcholine was improved in the treatment groups.

CONCLUSIONS

Pre-conditioning with Cinaciguat improves myocardial and endothelial function after cardiopulmonary bypass with hypothermic cardiac arrest. The observed protective effects imply that pharmacological sGC activation could be a novel therapeutic option in the protection against ischaemia-reperfusion injury in cardiac surgery.