Adenosine reduces cardiac TNF-alpha production and human myocardial injury following ischemia-reperfusion

The Role of Pro-Inflammatory Cytokines in the Pathogenesis of Cardiovascular Disease

With cardiovascular disease (CVD) being a primary source of global morbidity and mortality, it is crucial that we understand the molecular pathophysiological mechanisms at play. Recently, numerous pro-inflammatory cytokines have been linked to several different CVDs, which are now often considered an adversely pro-inflammatory state. These cytokines most notably include interleukin-6 (IL-6),tumor necrosis factor (TNF)α, and the interleukin-1 (IL-1) family, amongst others. Not only does inflammation have intricate and complex interactions with pathophysiological processes such as oxidative stress and calcium mishandling, but it also plays a role in the balance between tissue repair and destruction. In this regard, pre-clinical and clinical evidence has clearly demonstrated the involvement and dynamic nature of pro-inflammatory cytokines in many heart conditions; however, the clinical utility of the findings so far remains unclear. Whether these cytokines can serve as markers or risk predictors of disease states or act as potential therapeutic targets, further extensive research is needed to fully understand the complex network of interactions that these molecules encompass in the context of heart disease. This review will highlight the significant advances in our understanding of the contributions of pro-inflammatory cytokines in CVDs, including ischemic heart disease (atherosclerosis, thrombosis, acute myocardial infarction, and ischemia-reperfusion injury), cardiac remodeling (hypertension, cardiac hypertrophy, cardiac fibrosis, cardiac apoptosis, and heart failure), different cardiomyopathies as well as ventricular arrhythmias and atrial fibrillation. In addition, this article is focused on discussing the shortcomings in both pathological and therapeutic aspects of pro-inflammatory cytokines in CVD that still need to be addressed by future studies.

Drug-based mobilisation of mesenchymal stem/stromal cells improves cardiac function post myocardial infarction

There is an unmet need for treatments that prevent the progressive cardiac dysfunction following myocardial infarction. Mesenchymal stem/stromal cells (MSCs) are under investigation for cardiac repair; however, culture expansion prior to transplantation is hindering their homing and reparative abilities. Pharmacological mobilisation could be an alternative to MSC transplantation. Here, we report that endogenous MSCs mobilise into the circulation at day 5 post myocardial infarction in male Lewis rats. This mobilisation can be significantly increased by using a combination of the FDA-approved drugs mirabegron (β3-adrenoceptor agonist) and AMD3100 (CXCR4 antagonist). Blinded cardiac magnetic resonance imaging analysis showed the treated group to have increased left ventricular ejection fraction and decreased end systolic volume at 5 weeks post myocardial infarction. The mobilised group had a significant decrease in plasma IL-6 and TNF-α levels, a decrease in interstitial fibrosis, and an increase in the border zone blood vessel density. Conditioned medium from blood-derived MSCs supported angiogenesis in vitro, as shown by tube formation and wound healing assays. Our data suggest a novel pharmacological strategy that enhances myocardial infarction-induced MSC mobilisation and improves cardiac function after myocardial infarction.

Adenosine 5'-Triphosphate Metabolism in Red Blood Cells as a Potential Biomarker for Post-Exercise Hypotension and a Drug Target for Cardiovascular Protection

The importance of adenosine and ATP in regulating many biological functions has long been recognized, especially for their effects on the cardiovascular system, which may be used for management of hypertension and cardiometabolic diseases. In response to ischemia and cardiovascular injury, ATP is broken down to release adenosine. The effect of adenosine is very short lived because it is rapidly taken up by erythrocytes (RBCs), myocardial and endothelial cells, and also rapidly catabolized to oxypurine metabolites. Intracellular adenosine is phosphorylated back to adenine nucleotides via a salvage pathway. Extracellular and intracellular ATP is broken down rapidly to ADP and AMP, and finally to adenosine by 5′-nucleotidase. These metabolic events are known to occur in the myocardium, endothelium as well as in RBCs. Exercise has been shown to increase metabolism of ATP in RBCs, which may be an important mechanism for post-exercise hypotension and cardiovascular protection. The post-exercise effect was greater in hypertensive than in normotensive rats. The review summarizes current evidence in support of ATP metabolism in the RBC as a potential surrogate biomarker for cardiovascular protection and toxicities. It also discusses the opportunities, challenges, and obstacles of exploiting ATP metabolism in RBCs as a target for drug development and precision medicine.

New Insights into the Immunobiology of Mononuclear Phagocytic Cells and Their Relevance to the Pathogenesis of Cardiovascular Diseases

Macrophages are the primary immune cells that reside within the myocardium, suggesting that these mononuclear phagocytes are essential in the orchestration of cardiac immunity and homeostasis. Independent of the nature of the injury, the heart triggers leukocyte activation and recruitment. However, inflammation is harmful to this vital terminally differentiated organ with extremely poor regenerative capacity. As such, cardiac tissue has evolved particular strategies to increase the stress tolerance and minimize the impact of inflammation. In this sense, growing evidences show that mononuclear phagocytic cells are particularly dynamic during cardiac inflammation or infection and would actively participate in tissue repair and functional recovery. They respond to soluble mediators such as metabolites or cytokines, which play central roles in the timing of the intrinsic cardiac stress response. During myocardial infarction two distinct phases of monocyte influx have been identified. Upon infarction, the heart modulates its chemokine expression profile that sequentially and actively recruits inflammatory monocytes, first, and healing monocytes, later. In the same way, a sudden switch from inflammatory macrophages (with microbicidal effectors) toward anti-inflammatory macrophages occurs within the myocardium very shortly after infection with Trypanosoma cruzi, the causal agent of Chagas cardiomyopathy. While in sterile injury, healing response is necessary to stop tissue damage; during an intracellular infection, the anti-inflammatory milieu in infected hearts would promote microbial persistence. The balance of mononuclear phagocytic cells seems to be also dynamic in atherosclerosis influencing plaque initiation and fate. This review summarizes the participation of mononuclear phagocyte system in cardiovascular diseases, keeping in mind that the immune system evolved to promote the reestablishment of tissue homeostasis following infection/injury, and that the effects of different mediators could modulate the magnitude and quality of the immune response. The knowledge of the effects triggered by diverse mediators would serve to identify new therapeutic targets in different cardiovascular pathologies.

Cardioprotection requires flipping the 'posttranslational modification' switch

Minimizing damage during reperfusion of the heart following an ischemic event is an important part of the recovery process, as is preventing future recurrences; however, restoring blood perfusion to the heart following ischemia can lead to apoptosis, necrosis, and finally, diminished cardiac function. Exercise reduces risk of heart disease and has been shown to improve the recovery of the heart following ischemia and reperfusion. Brief intermittent ischemic events administered prior to or following a myocardial infarction have also been demonstrated to reduce the infarct size and improve cardiac function, thereby providing cardioprotection. Many signaling transduction pathways are known to regulate cardioprotection, including but not limited to calcium regulation, antioxidant scavenging, and kinase activation. Although posttranslational modifications (PTM) such as phosphorylation, O-GlcNAcylation, methylation, and acetylation are essential regulators of these pathways, their contributions are often overlooked in the literature. This review will examine how PTMS are important regulators of cardioprotection and demonstrate why they should be targeted when developing future therapies for the minimization of damage caused by cardiac ischemia and reperfusion.

Hypothermia down-regulates the LPS-induced norepinephrine (NE) release in ischaemic human heart cells

Hypothermia has been widely acknowledged as the fundamental component of myocardial protection during cardiac operations. In this work, we studied in human atrial tissue the effect of the common hypothermic protection used in cardiac surgery, and we assessed this effect by comparing catecholamine release among normoxic, ischaemic, and inflammatory conditions. Our results provide the first evidence that lipopolysaccharide treatment results in an extremely dramatic and significant increase in the resting norepinephrine release under ischaemic conditions that can be normalised by hypothermia. These findings demonstrate that inflammatory conditions increase the temperature sensitivity of the norepinephrine transporter in human cardiac tissue. When the possible pharmacological interventions are taken into consideration, the results presented here provide new insight into the protection against ischaemia/reperfusion injury during cardiac surgery.

Effects of CXCR4 gene transfer on cardiac function after ischemia-reperfusion injury

Acute coronary occlusion is the leading cause of death in the Western world. There is an unmet need for the development of treatments to limit the extent of myocardial infarction (MI) during the acute phase of occlusion. Recently, investigators have focused on the use of a chemokine, CXCL12, the only identified ligand for CXCR4, as a new therapeutic modality to recruit stem cells to individuals suffering from MI. Here, we examined the effects of overexpression of CXCR4 by gene transfer on MI. Adenoviruses carrying the CXCR4 gene were injected into the rat heart one week before ligation of the left anterior descending coronary artery followed by 24 hours reperfusion. Cardiac function was assessed by echocardiography couple with 2,3,5-Triphenyltetrazolium chloride staining to measure MI size. In comparison with control groups, rats receiving Ad-CXCR4 displayed an increase in infarct area (13.5% +/- 4.1%) and decreased fractional shortening (38% +/- 5%). Histological analysis revealed a significant increase in CXCL12 and tumor necrosis factor-alpha expression in ischemic area of CXCR4 overexpressed hearts. CXCR4 overexpression was associated with increased influx of inflammatory cells and enhanced cardiomyocyte apoptosis in the infarcted heart. These data suggest that in our model overexpressing CXCR4 appears to enhance ischemia/reperfusion injury possibly due to enhanced recruitment of inflammatory cells, increased tumor necrosis factor-alpha production, and activation of cell death/apoptotic pathways.

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

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

Adenosine receptors and neurological disease: neuroprotection and neurodegeneration

Adenosine receptors modulate neuronal and synaptic function in a range of ways that may make them relevant to the occurrence, development and treatment of brain ischemic damage and degenerative disorders. A(1) adenosine receptors tend to suppress neural activity by a predominantly presynaptic action, while A(2A) adenosine receptors are more likely to promote transmitter release and postsynaptic depolarization. A variety of interactions have also been described in which adenosine A(1) or A(2) adenosine receptors can modify cellular responses to conventional neurotransmitters or receptor agonists such as glutamate, NMDA, nitric oxide and P2 purine receptors. Part of the role of adenosine receptors seems to be in the regulation of inflammatory processes that often occur in the aftermath of a major insult or disease process. All of the adenosine receptors can modulate the release of cytokines such as interleukins and tumor necrosis factor-alpha from immune-competent leukocytes and glia. When examined directly as modifiers of brain damage, A(1) adenosine receptor (AR) agonists, A(2A)AR agonists and antagonists, as well as A(3)AR antagonists, can protect against a range of insults, both in vitro and in vivo. Intriguingly, acute and chronic treatments with these ligands can often produce diametrically opposite effects on damage outcome, probably resulting from adaptational changes in receptor number or properties. In some cases molecular approaches have identified the involvement of ERK and GSK-3beta pathways in the protection from damage. Much evidence argues for a role of adenosine receptors in neurological disease. Receptor densities are altered in patients with Alzheimer's disease, while many studies have demonstrated effects of adenosine and its antagonists on synaptic plasticity in vitro, or on learning adequacy in vivo. The combined effects of adenosine on neuronal viability and inflammatory processes have also led to considerations of their roles in Lesch-Nyhan syndrome, Creutzfeldt-Jakob disease, Huntington's disease and multiple sclerosis, as well as the brain damage associated with stroke. In addition to the potential pathological relevance of adenosine receptors, there are earnest attempts in progress to generate ligands that will target adenosine receptors as therapeutic agents to treat some of these disorders.

The comparison of mitogen-activated protein kinases that become activated within the left ventricular and right atrial tissues following heart transplantation in canine model

The activation of p38 mitogen-activated protein kinase (MAPK) plays an important role in ischemia/reperfusion injury. Some reports have documented MAPKs activation of the myocardium in human models, using right atrial (RA) tissue for samples. This study compared the activation of MAPKs in left ventricle (LV) and RA tissues in canine heart transplantation. Four dogs were used as baseline data at two points, before and 20 min after warm ischemia (baseline model), and eight dogs (four pairs of donor and recipient) were used at other points: 4 h after cold ischemia, and at 10, 60, and 180 min after reperfusion (transplantation model). In the transplantation model, donor hearts were left in situ for 20 min after cardiac arrest, and were immersed in Celsior solution for 4 h after coronary flushing. Orthotopic heart transplantation was then performed. Two groups were created: the LV and RA groups (n = 4 in each group). Heart tissue was harvested from the left ventricular wall in the LV group and from the right atrial appendage in the RA group. The activation of MAPKs, including p38 MAPK, c-Jun N-terminal protein kinase (JNK), and extracellular signal-regulated protein kinase (ERK), was evaluated at each point. The activation patterns of p38 MAPK and ERK were similar in the RA and LV groups, but JNK activation was different in the two groups, after ischemia and reperfusion. Thus, RA tissue may be deliberately used as a substitute for LV tissue when investigating the activation of MAPKs in a human model.

HPLC assay with UV detection for determination of RBC purine nucleotide concentrations and application for biomarker study in vivo

ATP and other purine nucleotides are important biomarkers for ischemia and may have considerable potential as targets for management of ischemic heart disease and stroke. The main objective of the study is to develop a rapid HPLC assay, which has adequate sensitivity and specificity for measuring concentrations of ATP, ADP, AMP, GTP, GDP and GMP in erythrocytes (RBC). The assays used ion-pair chromatography coupled with ultraviolet detection at 254 nm to separate and detect the purine nucleotides. Using 50-100 microL of RBC lysate as blank biologic matrix, the assay was linear from 100 to 2000 microg/mL for ATP and ADP, and 20-400 microg/mL for AMP, GTP, and GDP with coefficients of determination (r(2)) >0.99. GDP and GMP were not measurable in the study because of low concentrations and interference from endogenous materials, respectively. The intra-assay and inter-assay variations over a period of 1 year were less than 10% and 20%, respectively for most of the nucleotides. The assay was successfully applied to two pilot biomarker studies to measure RBC concentrations of the purine nucleotides in rats under restraining and exercise conditions. Preliminary results showed that the RBC concentrations of ATP and GTP were higher in the spontaneously hypertensive rats (SHR) compared to the Sprague-Dawley (SD) rats, and that exercise increased RBC concentrations of ATP in rats treated with the calcium channel blocker diltiazem.

Females exhibit relative resistance to depressive effects of tumor necrosis factor-alpha on the myocardium

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) plays a critical role in myocardial dysfunction following acute injury. It is unknown, however, if a gender-specific response to TNF infusion exists in isolated rat hearts. Elucidating such mechanisms is important to understanding the myocardial gender differences during acute injury. We hypothesize that females will exhibit a relative resistance to TNF-induced myocardial dysfunction compared to males and that menstrual cycle would influence the degree of female myocardial resistance to TNF-induced myocardial functional depression.

MATERIALS AND METHODS

Adult male, proestrus female, and metestrus/diestrus female hearts were subjected to 60 min of TNF infusion at 10,000 pg/mL.min via Langendorff. Myocardial contractile function (left ventricular developed pressure, and the positive/negative first derivative of pressure) was continuously recorded.

RESULTS

10,000 pg/mL.min of TNF markedly depressed myocardial function in males compared with other doses of TNF. Myocardial function was significantly decreased in males compared to females following TNF infusion. Additionally, both the proestrus and the metestrus/diestrus females exhibited equal resistance to TNF-induced myocardial dysfunction.

CONCLUSION

Our study shows that females exhibit a significantly greater degree of resistance to TNF-induced myocardial depression. Moreover, data from this study suggest that fluctuations in estrogen during the reproductive cycle may have little to no influence on TNF-induced myocardial depression.

Potential role and mechanisms of subcellular remodeling in cardiac dysfunction due to ischemic heart disease

Several studies have revealed varying degrees of changes in sarcoplasmic reticular and myofibrillar activities, protein content, gene expression and intracellular Ca-handling during cardiac dysfunction due to ischemia-reperfusion (I/R); however, relatively little is known about the sarcolemmal and mitochondrial alterations, as well as their mechanisms in the I/R hearts. Because I/R is associated with oxidative stress and intracellular Ca-overload, it has been indicated that changes in subcellular activities, protein content and gene expression due to I/R are related to both oxidative stress and Ca-overload. Intracellular Ca-overload appears to induce changes in subcellular activities, protein contents and gene expression (subcellular remodeling) by activation of proteases and phospholipases, as well as by affecting the genetic apparatus, whereas oxidative stress is considered to cause oxidation of functional groups of different subcellular proteins in addition to modifying the genetic machinery. Ischemic preconditioning, which is known to depress the development of both intracellular Ca-overload and oxidative stress due to I/R, was observed to attenuate the I/R-induced subcellular remodeling and improve cardiac performance. It is suggested that a combination therapy with antioxidants and interventions, which reduce the development of intracellular Ca-overload, may improve cardiac function by preventing or attenuating the occurrence of subcellular remodeling due to ischemic heart disease. It is proposed that defects in the activities of subcellular organelles may serve as underlying mechanisms for I/R-induced cardiac dysfunction under acute conditions, whereas subcellular remodeling due to alterations in gene expression may explain the impaired cardiac performance under chronic conditions of I/R.

Inflammation, proinflammatory mediators and myocardial ischemia-reperfusion Injury

Ischemic myocardium must be reperfused to terminate the ischemic event; otherwise the entire myocardium involved in the area at risk will not survive. However, there is a cost to reperfusion that may offset the intended clinical benefits of minimizing infarct size, postischemic endothelial and microvascular damage, blood flow defects, and contractile dysfunction. There are many contributors to this reperfusion injury. Targeting only one factor in the complex web of reperfusion injury is not effective because the untargeted mechanisms induce injury. An integrated strategy of reducing reperfusion injury in the catheterization laboratory involves controlling both the conditions and the composition of the reperfusate. Mechanical interventions such as gradually restoring blood flow or applying postconditioning may be used independently in or conjunction with various cardioprotective pharmaceuticals in an integrated strategy of reperfusion therapeutics to reduce postischemic injury.

Tumor necrosis factor alpha influences the inflammatory response after coronary surgery

BACKGROUND

A systemic inflammatory response is not uncommonly observed after coronary revascularization. Tumor necrosis factor alpha is one of a number of modulators of this response. A functional polymorphism within the TNFalpha gene at position G-308A has been associated with increased TNFalpha levels. The relationship between predicted TNFalpha genotype and circulating TNFalpha levels in patients undergoing coronary revascularization surgery has yet to be defined. We examined the relationship between TNFalpha G-308A polymorphism, TNFalpha postoperative levels, and clinical outcome after coronary revascularization surgery.

METHODS

We obtained DNA from 96 consecutive patients who underwent elective coronary revascularization. Patients were genotyped for TNFalpha G-308A polymorphism using sequence specific primer-polymerase chain reaction (SSP-PCR). Tumor necrosis factor alpha levels were measured on serum samples taken 3 hours postoperatively using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The prevalence of AA, AG, and GG TNFalpha-308 genotype was 12%, 40%, and 48%, respectively. Patients homozygous for A had higher circulating levels of TNFalpha (p = 0.009). Higher levels of TNFalpha were significantly associated with prolonged intensive care unit stay (p = 0.008), increase usage of an inotropic agent (p = 0.024), increased mortality risk (p = 0.018), and diabetes (p = 0.019). These remained statistically significant after risk stratification.

CONCLUSIONS

Patients of the AA-308 TNFalpha genotype showed significantly higher TNFalpha plasma levels. Higher plasma levels of TNFalpha were associated with less favorable outcome after coronary revascularization surgery. It may prove useful to utilize TNFalpha serum levels as a marker for identifying high-risk patients in the future.

Adenosine 5'-triphosphate and adenosine as endogenous signaling molecules in immunity and inflammation

Human health is under constant threat of a wide variety of dangers, both self and nonself. The immune system is occupied with protecting the host against such dangers in order to preserve human health. For that purpose, the immune system is equipped with a diverse array of both cellular and non-cellular effectors that are in continuous communication with each other. The naturally occurring nucleotide adenosine 5'-triphosphate (ATP) and its metabolite adenosine (Ado) probably constitute an intrinsic part of this extensive immunological network through purinergic signaling by their cognate receptors, which are widely expressed throughout the body. This review provides a thorough overview of the effects of ATP and Ado on major immune cell types. The overwhelming evidence indicates that ATP and Ado are important endogenous signaling molecules in immunity and inflammation. Although the role of ATP and Ado during the course of inflammatory and immune responses in vivo appears to be extremely complex, we propose that their immunological role is both interdependent and multifaceted, meaning that the nature of their effects may shift from immunostimulatory to immunoregulatory or vice versa depending on extracellular concentrations as well as on expression patterns of purinergic receptors and ecto-enzymes. Purinergic signaling thus contributes to the fine-tuning of inflammatory and immune responses in such a way that the danger to the host is eliminated efficiently with minimal damage to healthy tissues.

Reduction of apoptosis in the amygdala by an A2A adenosine receptor agonist following myocardial infarction

It has been observed that a cytokine synthesis inhibitor, pentoxifylline, prevents the apoptotic processes taking place in the amygdala following myocardial infarction. However, it is unknown if the cardioprotective effect of A(2A) adenosine receptor agonist, CGS21680, which reduces cytokine synthesis, would lead to such amygdala apoptosis regression. Thus, this study was designed to investigate whether cardioprotective A(2A) adenosine receptor activation reduces apoptosis in the amygdala following myocardial infarction. Anesthetized rats were subjected to left anterior descending coronary artery occlusion for 40 min, followed by 72 h of reperfusion. The A(2A) agonist CGS21680 (0.2 mug/kg/min i.v.) was administered continuously for 120 min, starting (1) five minutes prior to instituting reperfusion (Early) or (2) five minutes after the beginning of reperfusion (Late). After reperfusion, myocardial infarct size was determined and the amygdala was dissected from the brain. Infarct size was reduced significantly in the Early compared to the Control group (34.6 +/- 1.8% and 52.3 +/- 2.8% respectively; p < 0.05), with no difference compared to the Late group (40.1 +/- 6.1%). Apoptosis regression was documented in the amygdala of the Early group by an enhanced phosphatidylinositol 3-kinase-Akt pathway activation and Bcl-2 expression concurrently to a caspase-3 activation limitation and reduction in TUNEL-positive cells staining. On the other hand, amygdala TUNEL-positive cell numbers were not reduced in the Late group. Moreover, TNFalpha was significantly reduced in the amygdala of the Early group compared to the Control and Late groups. These results indicate that A(2A) adenosine receptor stimulation is associated with apoptosis regression in the amygdala following myocardial infarction.

Inhibitory effects of edaravone on the production of tumor necrosis factor-α in the isolated heart undergoing ischemia and reperfusion

We evaluated the effects of edaravone, a hydroxyl radical scavenging agent, on the production of tumor necrosis factor-alpha (TNF-alpha) in myocardium, and the release of TNF-alpha and P-selectin from myocardium after ischemia-reperfusion injury in isolated Langendorff-perfused rat hearts. Cardiodynamic function at stable points during perfusion and 5, 15, 30, and 60 min after the initiation of reperfusion was evaluated by left ventricular developed pressure, rate of increase in left ventricular pressure and rate of decrease in ventricular pressure, coronary flow, and heart rate. At 60 min after the initiation of reperfusion, myocardial infarct size was estimated microscopically using triphenyltetrazolium chloride staining, and expression of TNF-alpha in myocardium was detected by Western blot and immunohistochemistry. At the same time points as the measurement of cardiodynamic function, TNF-alpha and the soluble form of P-selectin in coronary effluent were measured by enzyme immunoassay. At all time points during reperfusion, edaravone markedly improved cardiodynamic function and reduced myocardial infarct size in comparison to the control. In myocardium in the control, TNF-alpha was detected in the endothelial cells and other cells bearing some resemblance to interstitial cells and monocyte cells. Edaravone suppressed this cytokine expression in the corresponding sites. P-selectin as well as TNF-alpha was found in the coronary effluent of the control, and edaravone significantly decreased soluble P-selectin levels in comparison to the control (P < 0.01). Edaravone might have protective effects on cardiac function through reduction of infarct size via decrease of production of TNF-alpha in myocardium induced by ischemia-reperfusion injury and through reduction of the release of adhesion molecules such as P-selectin from vascular endothelial cells.

The Effects of Pentoxifylline on the Myocardial Inflammation and Ischemia-Reperfusion Injury During Cardiopulmonary Bypass

BACKGROUND

Pentoxifylline (Ptx) decreases necessity of cell energy and inflammatory reactions via inhibition of 5'-nucleotidase (5'-NT). The aim of this study is to investigate whether the addition of Ptx into the cardioplegic solutions avoids myocardial inflammatory reactions and ischemia/reperfusion (I/R) injury during extracorpereal circulation.

METHODS

Between December 1999 and February 2002, we operated 75 patients with the diagnoses of atrial septal defect (ASD), ventricular septal defect (VSD), valve disease, and coronary disease. The average age of patients was 42.4 and male-female ratio was 1: 1.5. The patients were divided into two groups, which were the study group (n = 40) and the control group (n = 35). We used cold blood cardioplegia mixed with St. Thomas' Hospital II cardioplegic solution for both of the groups. Ptx was added into the cardioplegic solution (500 mg/L) in the study group. Interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrotisis factor-alpha (TNF-alpha) levels in coronary sinus blood samples during cross-clamp time (X-clamp) and after releasing of it and tissue TNF-alpha in the right atrial appendix biopsy material that was taken after X-clamp were studied to compare the both groups.

RESULTS

After releasing X-clamp, results of blood TNF-alpha, IL-6, and IL-8 of both groups were statistically significant (p < 0.005). At the pathological examination, we also observed that the amount of tissue TNF-alpha in the control group (66 +/- 17.1) was much higher than the study group (16.6 +/- 5.9, p <0.005).

CONCLUSIONS

These results show that Ptx may be added into cardioplegic solution to avoid the myocardial inflammation and I/R injury during open heart surgery.

The beneficial effect of insulin, glucose, and dipyridamole on regional left ventricular function early after acute myocardial infarction

BACKGROUND

High-dose glucose-insulin-potassium (GIK) solution has beneficial effects on reducing mortality in acute myocardial infarction. Dipyridamole (DIP) is a powerful antioxidant and increases adenosine concentration. Experimentally, GIK and DIP have additive protective effects in ischemia-reperfusion injury.

AIM

This work aims to assess the acute effects of DIP alone, GIK alone, and GIK+DIP on left ventricular function in patients evaluated early after an acute myocardial infarction.

METHODS

Ten male patients (age 63+/-11 years) with uncomplicated acute myocardial infarction were evaluated within 3 days after admission. All had been treated with systemic thrombolysis and were on full therapy (including beta-blockers) at the time of testing. They underwent stress echocardiography [2D echo, with wall motion score index (WMSI) evaluated in a 16-segment model of the left ventricle, with each segment scored from 1=normal to 4=dyskinetic] during low-dose DIP alone (0.28 mg/kg in 4 min); GIK alone (4-h infusion of glucose 30%, 25 insulin units, and 40 mEq of KCl, at an infusion rate of 1.5 ml/kg/h); and GIK+DIP.

RESULTS

Regional systolic function (baseline WMSI=1.69+/-0.2) improved after DIP (1.54+/-0.1), GIK (1.54+/-0.1), and, to a greater extent, after GIK+DIP (1.33+/-0.2; p<0.001 vs. baseline; p<0.05 vs. DIP; p<0.05 vs. GIK).

CONCLUSION

High-dose GIK has an acute beneficial effect on regional left ventricular function in patients with acute myocardial infarction. This beneficial effect is potentiated by low-dose DIP coadministration.

Pentoxifylline attenuates cardiac dysfunction and reduces TNF-alpha level in ischemic-reperfused heart

Although pentoxifylline (PTXF), a phosphodiesterase inhibitor, has been reported to exert beneficial effects in cardiac bypass surgery, its effect and mechanisms against ischemia-reperfusion (I/R) injury in heart are poorly understood. Because I/R is known to increase the level of tumor necrosis factor (TNF)-alpha in myocardium and PTXF has been shown to depress the production of TNF-alpha in failing heart, this study examined the hypothesis that PTXF may attenuate cardiac dysfunction and reduce TNF-alpha content in I/R heart. For this purpose, isolated rat hearts were subjected to global ischemia for 30 min followed by reperfusion for 2-30 min. Although cardiac dysfunction due to ischemia was not affected, the recovery of heart function upon reperfusion was markedly improved by PTXF treatment. This cardioprotective effect of PTXF was dose dependent; maximal effect was seen at a concentration of 125 microM. TNF-alpha, nuclear factor-kappaB (NF-kappaB), and phosphorylated NF-kappaB contents were decreased in ischemic heart but were markedly increased within 2 min of starting reperfusion. The ratio of cytosolic-to-homogenate NF-kappaB was decreased, whereas the ratio of particulate-to-homogenate NF-kappaB was increased in I/R hearts. These changes in TNF-alpha and NF-kappaB protein contents as well as in NF-kappaB redistribution due to I/R were significantly attenuated by PTXF treatment. The results of this study indicate that the cardioprotective effects of PTXF against I/R injury may be due to reductions in the activation of NF-kappaB and the production of TNF-alpha content.

TNF-α as a potential mediator of cardiac dysfunction due to intracellular Ca2+-overload

TNF-alpha has been shown to be involved in cardiac dysfunction during ischemia/reperfusion injury; however, no information regarding the status of TNF-alpha production in myocardial injury due to intracellular Ca2+-overload is available in the literature. The intracellular Ca2+-overload was induced in the isolated rat hearts subjected to 5 min Ca2+-depletion and 30 min Ca2+-repletion (Ca2+-paradox). The Ca2+-paradox hearts exhibited a dramatic depression in left ventricular developed pressure, a marked elevation in left ventricular end diastolic pressure, and more than a 4-fold increase in TNF-alpha content. The ratio of cytosolic to homogenate nuclear factor-kappaB (NFkappaB) was decreased whereas the ratio of phospho-NFkappaB to total NFkappaB was increased in the Ca2+-paradox hearts. All these changes due to Ca2+-paradox were significantly attenuated upon treating the hearts with 100 microM pentoxifylline. These results suggest that activation of NFkappaB and increased production of TNF-alpha may play an important role in cardiac injury due to intracellular Ca2+-overload.

Functional and clinical repercussions of myocyte apoptosis in the multifaceted damage by ischemia/reperfusion injury: old and new concepts after 10 years of contributions

Ten years ago, the first finding of apoptotic cell death on the 'crime scene' of cardiac ischemia/reperfusion injury profoundly dismayed the scientific community. This observation jarred with the deeply rooted conviction that cardiac myocytes stoically 'break, but do not bend' in the fight against ischemia, instead of spontaneously accepting a peaceful demise for the greater good. Ten years later, a number of studies not only proved right the coexistence of necrosis and apoptosis on the ischemic battle field, but also implicated myocyte apoptosis in the pathogenesis of all the shapes and shades that cardiac ischemic injury can take on.

Acute adenosinergic cardioprotection in ischemic-reperfused hearts

Cells of the cardiovascular system generate and release purine nucleoside adenosine in increasing quantities when constituent cells are "stressed" or subjected to injurious stimuli. This increased adenosine can interact with surface receptors in myocardial, vascular, fibroblast, and inflammatory cells to modulate cellular function and phenotype. Additionally, adenosine is rapidly reincorporated back into 5'-AMP to maintain the adenine nucleotide pool. Via these receptor-dependent and independent (metabolic) paths, adenosine can substantially modify the acute response to ischemic insult, in addition to generating a more sustained ischemia-tolerant phenotype (preconditioning). However, the molecular basis for acute adenosinergic cardioprotection remains incompletely understood and may well differ from more widely studied preconditioning. Here we review current knowledge and some controversies regarding acute cardioprotection via adenosine and adenosine receptor activation.

Purines and neuroprotection

The activation of adenosine A1, A2 andA3 receptors can protect neurones against damage generated by mechanical or hypoxic/ischaemic insults as well as excitotoxins. A1 receptors are probably effective by suppressing transmitter release and producing neuronal hyperpolarisation. They are less likely to be of therapeutic importance due to the plethora of side effects resulting from A1 agonism, although the existence of receptor subtypes and recent synthetic chemistry efforts to increase ligand selectivity, may yet yield clinically viable compounds. Activation of A2A receptors can protect neurons, although there is much uncertainty as to whether agonists are acting centrally or via a peripheral mechanism such as altering blood flow or immune cell function. Selective antagonists at the A2A receptor, such as 4-(2-[7-amino-2-(2-furyl)(1,2,4)triazolo(2,3-a)(1,3,5)triazin-5-yl-amino]ethyl)phenol (ZM 241385) and 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3e]-1,2,4-triazolo[1,5-c]pyrimidine (SCH 58261), can also protect against neuronal death produced by ischaemia or excitotoxicity. In addition, A2A receptor antagonists can reduce damage produced by combinations of subthreshold doses of the endogenous excitotoxin quinolinic acid and free radicals. Since the A2A receptors do not seem to be activated by normal endogenous levels of adenosine, their blockade should not generate significant side effects, so that A2A receptor antagonists appear to be promising candidates as new drugs for the prevention of neuronal damage. Adenosine A3 receptors have received less attention to date, but agonists are clearly able to afford protection against damage when administered chronically. Given the disappointing lack of success of NMDA receptor antagonists in human stroke patients, despite their early promise in animal models, it is possible that A2A receptor antagonists could have a far greater clinical utility.

On-pump coronary artery bypass surgery activates human myocardial NF-kappaB and increases TNF-alpha in the heart

PURPOSE

Myocardial tumor necrosis factor alpha (TNF) production and nuclear factor kappa B (NF-kappaB) activation has been demonstrated in chronic heart failure and experimental models of acute ischemia-reperfusion injury. Further, a cause and effect relationship has been established between these events and cardiomyocyte apoptosis following such conditions. It remains unknown, however, whether the myocardial injury associated with coronary artery bypass surgery (CAB) results in myocardial NF-kappaB activation and TNF production. We hypothesized that CAB with cardiopulmonary bypass ("on-pump") activates human myocardial NF-kappaB and increases TNF in the heart.

METHODS

Patients, 18 to 65 years of age, scheduled for elective cardiac surgery but without other preexisting disease were considered eligible for the study. Biopsies of human myocardium were obtained before and after cardiopulmonary bypass and myocardial TNF levels were determined by ELISA and cytotoxicity assay, and NF-kappaB activation was determined by electrophoretic mobility shift assay (n = 6 patients). NF-kappaB activation was quantitated with gel densitometry.

RESULTS

The clinical characteristics of the study patients were as follows (means +/- SEM): mean age (y) 50.0 +/- 5.7, male 6 (100%), cardiopulmonary bypass time (min) 107 +/- 37.7, cross-clamp time (min) 68 +/- 17.6, number of CAB 3.0 +/- 1.1, and length of hospital stay (d) 4.8 +/- 0.9. Before CAB, myocardial TNF-alpha levels were 251 +/- 22 pg/g and 33 +/- 9 U/g, as determined by ELISA and cytotoxicity assay, respectively. Following CAB, human myocardial TNF-alpha levels increased to 892 +/- 71 pg/g (P = 0.0008) and 141 +/- 11 U/g (P = 0.0042), as determined by ELISA and cytotoxicity assay, respectively. Before CAB, the ratio of bound to unbound NF-kappaB DNA was 0.009 +/- 0.0007 and after CAB the ratio was 0.24 +/- 0.01 (P < 0.0001).

CONCLUSIONS

This study represents the initial demonstration that coronary artery bypass grafting results in an activation of NF-kappaB and an increase of TNF in the heart.

Endothelial injury: cause and effect of alloimmune inflammation

This review discusses the concept that endothelial cells may facilitate inflammation, but are also targets of the inflammatory response. Endothelial cells express several molecules that promote leukocyte recruitment, and other molecules, such as MHC class I that enable endothelial injury. Circulating alloantibodies produced following transplantation may also target the endothelium for injury. It has been shown that the expression of select protective genes within endothelial cells, including anti-apoptotic genes, may provide resistance to immune-mediated injury. Thus, an understanding of the mechanisms by which endothelial cells are injured and by which endothelial cells are protected is important for our understanding of allograft rejection.

The interaction between Hsp70 and TNF-alpha expression: a novel mechanism for protection of the myocardium against post-injury depression

Tumor necrosis factor-alpha (TNF-alpha) depresses myocardial contractility, and overexpression of TNF-alpha in the myocardium contributes to cardiac dysfunction caused by both systemic and local insults. Sepsis, endotoxemia, hemorrhagic shock, and myocardial ischemia-reperfusion all promote cardiac dysfunction in part by a TNF-alpha-mediated mechanism. Thus, TNF-alpha represents an appealing therapeutic target for myocardial protection against multiple clinically relevant insults. The inducible 70-kD heat shock protein (Hsp70) is expressed in the myocardium in response to stress and has been linked to enhanced myocardial resistance to depression associated with ischemia-reperfusion or sepsis. The mechanism by which Hsp70 protects cardiac function against a subsequent insult remains obscure. In vitro induction of Hsp70 in monocytes or macrophages inhibits TNF-alpha production following bacterial lipopolysaccharide stimulation, and in vivo induction of Hsp70 down-regulates tissue TNF-alpha production following an injurious insult. Understanding of the regulatory role of Hsp70 in the myocardial inflammatory response will provide insights into the mechanism by which Hsp70 preserves cardiac function and may yield therapies for protection of the myocardium against depression associated injurious insults.

Pharmacological antagonism of fumonisin B1 cytotoxicity in porcine renal epithelial cells (LLC-PK1): a model for reducing fumonisin-induced nephrotoxicity in vivo

Fumonisin B1 is a mycotoxin commonly found on corn. It is hepatotoxic and nephrotoxic in domestic and experimental animals, and causes equine leukoencephalomalacia and porcine pulmonary oedema. It is a potent inhibitor of ceramide synthase. Inhibition leads to accumulation of free sphingoid bases in cells and tissues. In pig kidney epithelial cells (LLC-PK1), fumonisin B1 induces increased tumour necrosis factor alpha (TNFalpha) expression independent of the accumulation of sphingoid bases. The objective of this study was to investigate pharmacological approaches for intervening in fumonisin B1 toxicity using the LLC-PK1 cell model. The toxicity of fumonisin B1 was assayed using cell viability and lactate dehydrogenase (lactate dehydrogenase) release. Pretreatment of cells with myriocin, preventing sphinganine accumulates, prevented the fumonisin B1-induced decrease in cell viability and increased lactate dehydrogenase release. Modulation of adenosine receptor activity did not reduce the fumonisin B1 cytotoxicity. As with myriocin, silymarin pretreatment prevented the fumonisin B1-induced effects on cell viability and lactate dehydrogenase release. When added 6 or 24 hr after treatment of cells with fumonisin B1, both myriocin and silymarin reversed the decreased cell viability and suppressed the increased lactate dehydrogenase release. Myriocin, but not silymarin, blocked the accumulation of sphinganine in fumonisin B1-treated cells. Silymarin, unlike myriocin, induced expression of TNFalpha to an extent similar to fumonisin B1, but pretreatment with silymarin decreased the fumonisin B1-induced TNFalpha expression in LLC-PK1 cells. Results suggest that the mechanisms by which myriocin and silymarin protect renal cells are different, and silymarin potentially prevents fumonisin B1-induced toxicity by modulating TNFalpha expression or signals downstream of the inhibition of ceramide synthase.

The inhibition of pro-inflammatory cytokines with pentoxifylline in the cardiopulmunary bypass lung

In addition to preventing tissue energy loss during cardiopulmonary bypass, pentoxifylline (Ptx) prevents the production of pro-inflammatory cytokines as well. The aim of this study was to investigate whether Ptx decreases the inflammatory effects of cardiopulmonary bypass on the lungs during open-heart surgery. The patients in the study group (n = 15) who were going through an open-heart surgery had 500 mg l(-1) of Ptx added to their prime solution, whereas the patients in the control group (n = 10) only received prime solution. Pre-pump and post-pump blood samples were obtained from both groups and assayed for interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor alpha (TNFalpha). Lung tissue samples that were obtained after the pump were examined with light microscopy and stained for tissueTNFalpha. Non-parametric Wilcoxon test was utilized for statistical evaluation. In the post-pump period, the difference in the IL-6, IL-8 and TNFalpha levels of the two groups was found to be statistically significant (P<0.005). The tissue samples from the control group had significant staining with TNFalpha. We think that Ptx has important protective effects on the lungs during cardiopulmonary bypass.

Adenosine in myocardial protection given through three windows of opportunity. An experimental study with pigs

OBJECTIVE

Adenosine (ADO) has been shown to have beneficial effects against tissue injury after myocardial ischemia. However, the timing and dose of ADO administration have not been defined. This study was designed to determine the cardioprotective effect of exogenous ADO in an experimental open heart surgery model in pigs.

DESIGN

The animals were openly divided into two groups both undergoing 30 min of total cardiac arrest. In the control group animals received cold crystalloid cardioplegic solution. In the ADO group ADO was added to cardioplegic solution and in addition ADO was infused to the superior vena cava for 2 h starting 30 min before cardiac arrest. The pumping function of the heart was measured with echocardiography and myocardial blood flow was measured with microspheres and positron emission tomography (PET). Cardiomyocyte apoptosis was detected and tumor necrosis factor (TNF) levels were measured.

RESULTS

Better post-ischemic pumping function was found in the ADO group (relative decrease 43.7% vs 55.4%, p = 0.20 between the groups). The cardiac output decreased significantly from the baseline values (p < 0.05 in both groups). There was a temporary decrease in myocardial blood flow post-ischemically, followed by a compensatory increase during the later reperfusion period. The cardiomyocyte apoptosis was induced significantly in both groups.

CONCLUSIONS

In this experiment two important details were noticed. Firstly, cardiomyocyte apoptosis is involved in ischemia-reperfusion injury associated with open heart surgery. Secondly, PET is a comparable method with the microsphere technique when coronary flow is studied. No significant effects of ADO against ischemia-reperfusion injury could be shown. However, there were some signsof positive outcome, even though statistical significance could not be reached.

Novel targets for interleukin 18 binding protein

BACKGROUND

Interleukin 18 (IL18) is related to the IL1 family by structure, receptors, signalling molecules, and function. IL18 induces gene expression and synthesis of tumour necrosis factor (TNF), IL1, Fas ligand, several chemokines, and vascular adhesion molecules. Similar to IL1beta, IL18 is synthesised as a biologically inactive precursor molecule lacking a signal peptide. The IL18 precursor requires cleavage into an active, mature molecule by the intracellular cysteine protease, IL1beta converting enzyme (ICE, or caspase-1). Inhibitors of ICE activity limit the biological activity of IL18 in animals and may be useful in reducing the activity of IL18 in human disease. However, a constitutively secreted IL18 binding protein (IL18BP) exists which functions as a natural inhibitor of IL18 activity. IL18BP binds IL18 with a high affinity (Kd of 400 pM) and, at equimolar ratios, inhibits 50-70% of IL18; at twofold molar excess, IL18BP neutralises nearly all IL18 activity.

METHOD

IL18 was investigated for its role in human myocardial function. An ischaemia/reperfusion (I/R) model of suprafused human atrial myocardium was used to assess myocardial contractile force.

RESULTS

The addition of IL18BP to the perfusate during and after I/R resulted in improved post-I/R contractile function from 35% of control to 76% with IL18BP. Also, IL18BP treatment preserved intracellular tissue creatine kinase levels (by 420%). Because active IL18 requires cleavage of its precursor form by ICE, inhibition of ICE attenuated the depression in contractile force after I/R (from 35% of control compared with 75.8% in treated atrial muscle, p<0.01).

CONCLUSION

Myocardial ischaemia is a target for IL18BP and use of IL18BP may thereby reduce ischaemia-induced myocardial dysfunction.

Apoptosis in the ischemic reperfused myocardium

Recovery of the myocardium from an ischemic event depends on the reperfusion of the ischemic area. Resumed blood flow to the tissue restores the metabolic substrates necessary for energy production and cell survival. Paradoxically, ischemic reperfusion (I/R) can result in further damage to the myocardium (I/R injury) through an acute inflammatory response mediated by cytokines, neutrophils, macrophages, and reactive oxygen species. These events can trigger cardiomyocyte death through either necrosis or apoptosis. This report will focus on the apoptosis process, which is an organized, active, and gene-directed process of cell self-destruction that can be initiated by intracellular genetic programs, or second messenger pathways inside the cell upon extracellular stimulation by signaling molecules or stress. Awareness of the apoptotic process in cardiomyocytes and endothelial cells is relevant to myocardial preservation during cardiopulmonary bypass compared with off-pump cornary artery bypass procedures. Pharmacological interventions of the signaling pathways that control apoptosis provide an opportunity for new therapeutic approaches to reduce I/R injury in the heart. This review of apoptosis will introduce the perfusionist to apoptosis in the I/R heart, discuss some of the metabolic pathways that initiate it, and report on developing strategies to prevent it.

Cardioprotective effect of adenosine pretreatment in coronary artery bypass grafting

OBJECTIVE

There are several reports of the use of adenosine as a cardioprotective agent during cardiac surgery. Adenosine treatment might affect neutrophils and inflammatory mediators. The present prospective randomized study was designed to investigate the effect of adenosine pretreatment on myocardial recovery and inflammatory response in patients undergoing elective coronary artery bypass surgery.

DESIGN

A prospective, randomized, controlled study.

SETTING

Operative unit and ICU in a university hospital in Finland.

PATIENTS

Thirty male patients undergoing primary, elective coronary revascularization.

INTERVENTIONS

Patients in the adenosine group received a 7-min infusion of adenosine (total, 650 microg/kg) before the initiation of cardiopulmonary bypass.

MEASUREMENTS

Postoperative creatine kinase (CK)-MB release and hemodynamics were recorded. Perioperative leukocyte and cytokine release were measured.

RESULTS

Adenosine pretreatment resulted in less CK-MB release and an improved postbypass cardiac index. Similar leukocyte counts and cytokine responses were seen in both groups perioperatively. Neutrophil counts were similar between the groups before and after myocardial ischemia when measured simultaneously in arterial and coronary sinus blood.

CONCLUSIONS

The present results support the hypothesis that adenosine pretreatment is cardioprotective in humans, but the present dose failed to regulate the inflammatory responses after coronary artery bypass grafting.

Inhibition of caspase 1 reduces human myocardial ischemic dysfunction via inhibition of IL-18 and IL-1beta

The proinflammatory cytokine IL-18 was investigated for its role in human myocardial function. An ischemia/reperfusion (I/R) model of suprafused human atrial myocardium was used to assess myocardial contractile force. Addition of IL-18 binding protein (IL-18BP), the constitutive inhibitor of IL-18 activity, to the perifusate during and after I/R resulted in improved contractile function after I/R from 35% of control to 76% with IL-18BP. IL-18BP treatment also preserved intracellular tissue creatine kinase levels (by 420%). Steady-state mRNA levels for IL-18 were elevated after I/R, and the concentration of IL-18 in myocardial homogenates was increased (control, 5.8 pg/mg vs. I/R, 26 pg/mg; P < 0.01). Active IL-18 requires cleavage of its precursor form by the IL-1beta-converting enzyme (caspase 1); inhibition of caspase 1 also attenuated the depression in contractile force after I/R (from 35% of control to 75.8% in treated atrial muscle; P < 0.01). Because caspase 1 also cleaves the precursor IL-1beta, IL-1 receptor blockade was accomplished by using the IL-1 receptor antagonist. IL-1 receptor antagonist added to the perifusate also resulted in a reduction of ischemia-induced contractile dysfunction. These studies demonstrate that endogenous IL-18 and IL-1beta play a significant role in I/R-induced human myocardial injury and that inhibition of caspase 1 reduces the processing of endogenous precursors of IL-18 and IL-1beta and thereby prevents ischemia-induced myocardial dysfunction.

Local and systemic effects of peritoneal lavage with high concentrations of adenosine in rats

BACKGROUND

Adenosine exerts actions which may be beneficial in treating diseases of the gastrointestinal tract. However, administered systemically, adenosine causes a 'stress reaction' and may adversely affect blood pressure and cardiac and renal function.

AIM

To determine whether peritoneal lavage with adenosine provides pharmacological levels of adenosine in the intestines without elevating adenosine levels in the systemic circulation.

METHODS

Rats received an intramesenteric artery infusion of angiotensin II (30 ng/min) plus methoxamine (3 microg/min) to reduce mesenteric blood flow by approximately 60%, and adenosine solutions were instilled into the abdominal cavity. In a second study, microdialysis probes were placed in the mesenteric vein and aortic arch of rats, and the peritoneal cavity was continuously lavaged with adenosine solutions.

RESULTS

High concentrations (10(-3)M) of adenosine normalized the mesenteric blood flow without affecting blood pressure or heart rate. High concentrations of adenosine (10(-3)M) induced micromolar levels of adenosine and inosine in the mesenteric vein, without affecting adenosine or inosine levels in the aorta.

CONCLUSIONS

Peritoneal lavage with high concentrations of adenosine provides pharmacological levels of adenosine in the gastrointestinal tract without systemic side-effects. Peritoneal lavage with high concentrations of adenosine may be useful for the treatment of a number of diseases of the gastrointestinal tract.

Adenosine inhibits IL-12 and TNF-[alpha] production via adenosine A2a receptor-dependent and independent mechanisms

Interleukin 12 (IL-12) is a crucial cytokine in the regulation of T helper 1 vs. T helper 2 immune responses. In the present study, we investigated the effect of the endogenous purine nucleoside adenosine on the production of IL-12. In mouse macrophages, adenosine suppressed IL-12 production. Although the order of potency of adenosine receptor agonists suggested the involvement of A2a receptors, data obtained with A2a receptor-deficient mice showed that the adenosine suppression of IL-12 and even TNF-alpha production is only partly mediated by A2a receptor ligation. Studies with adenosine receptor antagonists or the adenosine uptake blocker dipyridamole showed that adenosine released endogenously also decreases IL-12. Although adenosine increases IL-10 production, the inhibition of IL-12 production is independent of the increased IL-10. The mechanism of action of adenosine was not associated with alterations of the activation of the p38 and p42/p44 mitogen-activated protein kinases or the phosphorylation of the c-Jun terminal kinase. Adenosine failed to affect steady-state levels of either IL-12 p35 or p40 mRNA, but augmented IL-10 mRNA levels. In summary, adenosine inhibits IL-12 production via various adenosine receptors. These results support the notion that adenosine-based therapies might be useful in certain autoimmune and/or inflammatory diseases.

Adenosine prevents activation of transcription factor NF-kappa B and enhances activator protein-1 binding activity in ischemic rat heart

BACKGROUND

Adenosine prevents myocardial TNF-alpha production induced by ischemia/reperfusion, but the mechanisms are poorly understood. Transcription factors NF-kappa B and AP-1 have been implicated in the regulation of a variety of inducible gene expressions in response to oxidative stress and cellular defense. The effects of adenosine on NF-kappa B and AP-1 activation have not been clearly defined. This study demonstrated differential effects of adenosine on NF-kappa B and AP-1 nuclear binding activity in ischemic myocardium.

METHODS

Isolated working rat hearts were subjected to 0, 1, 2, 3, 4, 5, 7.5, 10, 15, and 30 minutes of ischemia, with 4 to 6 hearts for each time point with and without adenosine (100 mumol/L). NF-kappa B and AP-1 binding activity in the nucleus were analyzed by electrophoretic mobility shift assay (EMSA). I kappa B alpha levels in the cytoplasm were measured by Western blot analysis. TNF-alpha mRNA levels were determined by RT-PCR.

RESULTS

NF-kappa B binding activity in the nucleus significantly increased after 4 minutes of ischemia and remained to 30 minutes. The levels of I kappa B alpha protein in the cytoplasm markedly decreased after 4, 5, 7.5, and 10 minutes of ischemia. TNF-alpha mRNA levels peaked after 10 minutes of ischemia. AP-1 DNA binding activity was induced and persisted during all ischemic periods. Adenosine significantly inhibited NK-kappa B binding activity in the nucleus, markedly prevented the loss of I kappa B alpha proteins from the cytoplasm, and concomitantly down-regulated TNF-alpha mRNA expression, but enhanced AP-1 binding activity in the nucleus of ischemic myocardium.

CONCLUSIONS

Adenosine modulation of NF-kappa B activation may be the cellular molecular mechanism of down-regulation of TNF-alpha mRNA expression. The cardioprotective properties of adenosine may be involved in the differential modulation of NF-kappa B and AP-1 activation during myocardial ischemia.

Ligand-activation of the adenosine A2a receptors inhibits IL-12 production by human monocytes

Adenosine (ADO) exerts potent anti-inflammatory and immunosuppressive effects. In this paper we address the possibility that these effects are partly mediated by inhibition of the secretion of IL-12, a proinflammatory cytokine and a major inducer of Th1 responses. We demonstrate that 5'-N-ethylcarboxamidoadenosine (NECA), a nonspecific ADO analogue, and 2-p-(2-carbonyl-ethyl)phenylethylamino-5'-N-ethylcarboxamidoadenos ine (CGS-21680), a specific A2a receptor agonist, dose-dependently inhibited, in whole blood ex vivo and monocyte cultures, the production of human IL-12 induced by LPS and Stapholococcus aureus Cowan strain 1. However, the A1 receptor agonist 2-Chloro-N6-cyclopentyladenosine and the A3 receptor agonists N6-Benzyl-NECA and 1-deoxy-1-[6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-N-methyl-be ta-d -ribofuranuronamide expressed only weak inhibitory effects. On the other hand, NECA and CGS-21680 dose-dependently potentiated the production of IL-10. The differential effect of these drugs on monocyte IL-12 and IL-10 production implies that these effects are mediated by A2a receptor signaling rather than by intracellular toxicity of ADO analogue's metabolites. Moreover, CGS-21680 inhibited IL-12 production independently of endogenous IL-10 induction, because anti-IL-10 Abs failed to prevent its effect. The selective A2a antagonist 8-(3-Chlorostyryl) caffeine prevented the inhibitory effect of CGS-21680 on IL-12 production. The phosphodiesterase inhibitor Ro 20-1724 dose-dependently potentiated the inhibitory effect of CGS-21680 and, furthermore, Rp-cAMPS, a protein kinase A inhibitor, reversed the inhibitory effect of CGS-21680, implicating a cAMP/protein kinase A pathway in its action. Thus, ligand activation of A2a receptors simultaneously inhibits IL-12 and stimulates IL-10 production by human monocytes. Through this mechanism, ADO released in excess during inflammatory and ischemic conditions, or tissue injury, may contribute to selective suppression of Th1 responses and cellular immunity.

Exogenous calcium preconditions myocardium from patients taking oral sulfonylurea agents

We have previously reported that atrial trabeculae from patients taking oral sulfonylurea hypoglycemic agents cannot be preconditioned by transient ischemia, which may, in part, explain the increased cardiovascular mortality historically associated with the use of these agents (J. C. Cleveland et al., 1997, Circulation 96, 29-32). Recently, we reported that clinically accessible and acceptable exogenous Ca(2+) pretreatment protects human atrial trabeculae from subsequent ischemia (B. S. Cain et al., 1998, Ann. Thoracic Surg. 65, 1065-1070). It remains unknown whether this preconditioning strategy could confer protection to trabeculae from patients taking oral sulfonylurea drugs. We therefore hypothesized that exogenous Ca(2+) confers ischemic protection to trabeculae from patients taking oral sulfonylureas. Human atrial trabeculae were suspended in organ baths and field stimulated at 1 Hz, and force development was recorded. Following 90 min equilibration, trabeculae from patients taking oral sulfonylurea agents (n = 6 patients) were subjected to ischemia/reperfusion (I/R; 45/120 min) with or without Ca(2+) (1 mM increase x 5 min) 10 min prior to I/R. I/R decreased postischemic human myocardial contractility in trabeculae from patients on oral hypoglycemics to 15.3 +/- 2.0% baseline developed force (%BDF). Ca(2+) pretreatment increased postischemic human myocardial developed force to 35.3 +/- 2.9 %BDF in these patients (P < 0.05 vs I/R, ANOVA and Bonferroni/Dunn). We conclude that atrial muscle from patients taking oral hypoglycemic agents can be preconditioned with exogenous Ca(2+). This therapy may offer a clinically relevant means to precondition the myocardium of diabetics taking oral hypoglycemic agents prior to clinical interventions such as coronary angioplasty or cardiac bypass.

Inhibition of myocardial TNF-alpha production by heat shock. A potential mechanism of stress-induced cardioprotection against postischemic dysfunction

Overproduction of tumor necrosis factor-alpha (TNF-alpha) contributes to cardiac dysfunction associated with systemic or myocardial stress, such as endotoxemia and myocardial ischemia/reperfusion (I/R). Heat shock has been demonstrated to enhance cardiac functional resistance to I/R. However, the protective mechanisms remain unclear. The purpose of this study was to determine: (1) whether cardiac macrophages express heat shock protein 72 (HSP72) after heat shock, (2) whether induced cardiac HSP72 suppresses myocardial TNF-alpha production during I/R, and (3) whether preservation of postischemic myocardial function by heat shock is correlated with attenuated TNF-alpha production during I/R. Rats were subjected to heat shock (42 degrees C for 15 min) and 24 h recovery. Immunoblotting confirmed the expression of cardiac HSP72. Immunofluorescent staining detected HSP72 in cardiac interstitial cells including resident macrophages rather than myocytes. Global I/R caused a significant increase in myocardial TNF-alpha. The increase in myocardial TNF-alpha was blunted by prior heat shock and the reduced myocardial TNF-alpha level was correlated with improved cardiac functional recovery. This study demonstrates for the first time that heat shock induces HSP72 in cardiac resident macrophages and inhibits myocardial TNF-alpha production during I/R. These observations suggest that inhibition of myocardial TNF-alpha production may be a mechanism by which HSP72 protects the heart against postischemic dysfunction.

p38 MAPK inhibition decreases TNF-alpha production and enhances postischemic human myocardial function

INTRODUCTION

TNF-alpha is a proinflammatory cytokine implicated in myocardial dysfunction following ischemia/reperfusion (I/R). I/R results in myocardial production of TNF-alpha and TNF-alpha suppresses myocardial contractility. p38 mitogen-activated protein kinase (MAPK) is a redox-sensitive protein kinase involved in intracellular signaling leading to TNF-alpha production. It remains unknown if the human heart produces TNF-alpha after I/R and, if so, whether p38 MAPK is involved.

HYPOTHESIS

p38 MAPK inhibition enhances human myocardial post-I/R contractile function by inhibition of myocardial TNF-alpha production.

METHODS

Human atrial trabeculae were suspended in organ baths, field simulated at 1 Hz, and force development was recorded. Following a 90-min equilibration, trabeculae were exposed to a p38 MAPK inhibitor (SB 203580, 1 microM) or vehicle (each n = 6) prior to simulated ischemia (45 min hypoxia, substrate-free, rapid pacing at 3 Hz) followed by 120 min reoxygenation. Myocardial TNF-alpha levels were measured by ELISA at end reoxygenation.

RESULTS

I/R increased human myocardial TNF-alpha levels from 26.9 +/- 9.3 to 83.9 +/- 19.2 pg/g wet tissue (P < 0.05 perfusion vs I/R; ANOVA Bonferroni/Dunn), while p38 MAPK inhibition decreased post-I/R myocardial TNF-alpha levels to 32.3 +/- 8.0 pg/g wet tissue (P > 0.05 p38 MAPK inhibition vs I/R). p38 MAPK inhibition improved postischemic force development from 18.5 +/- 2.1 to 37.0 +/- 2.0% baseline developed force (%BDF; P < 0.05 I/R vs p38 MAPK inhibition).

CONCLUSIONS

(1) The human heart produces TNF-alpha after I/R, (2) p38 MAPK mediates myocardial I/R-induced TNF-alpha production, (3) p38 MAPK inhibition limits functional impairment after I/R, and (4) inhibition of ischemia-induced TNF-alpha production may represent a potent therapeutic strategy for improving myocardial function after angioplasty, coronary bypass, or heart transplantation.