Adenosine decreases post-ischaemic cardiac TNF-alpha production: anti-inflammatory implications for preconditioning and transplantation

AMP deaminase 1 gene polymorphism and heart disease-a genetic association that highlights new treatment

Nucleotide metabolism and signalling is directly linked to myocardial function. Therefore analysis how diversity of genes coding nucleotide metabolism related proteins affects clinical progress of heart disease could provide valuable information for development of new treatments. Several studies identified that polymorphism of AMP deaminase 1 gene (AMPD1), in particular the common C34T variant of this gene was found to benefit patients with heart failure and ischemic heart disease. However, these findings were inconsistent in subsequent studies. This prompted our detailed analysis of heart transplant recipients that revealed diverse effect: improved early postoperative cardiac function associated with C34T mutation in donors, but worse 1-year survival. Our other studies on the metabolic impact of AMPD1 C34T mutation revealed decrease in AMPD activity, increased production of adenosine and de-inhibition of AMP regulated protein kinase. Thus, genetic, clinical and biochemical studies revealed that while long term attenuation of AMPD activity could be deleterious, transient inhibition of AMPD activity before acute cardiac injury is protective. We suggest therefore that pharmacological inhibition of AMP deaminase before transient ischemic event such as during ischemic heart disease or cardiac surgery could provide therapeutic benefit.

Dual effects of tumor necrosis factor alpha on myocardial injury following prolonged hypoperfusion of the heart

OBJECTIVE

To examine the dose response of TNFα in an ex vivo rat model of myocardial ischemia reperfusion.

METHODS AND RESULTS

Seventy-two rat hearts were mounted on Langendorff apparatus and perfused with oxygenated Krebs-Henseleit solutions. Ischemia was induced by reducing the perfusate flow rate. During reperfusion, incremental doses of recombinant TNFα were infused as a part of perfusate. TNFα was blocked with monoclonal TNFα antibody. Myocardial function was measured by dP/dT and relaxation time (IVRT). Cellular injury was assessed by released myoglobin and tissue concentration of malondialdehyde activity of the heart homogenates. Baseline +dP/dT was 1645 ± 125 mmHg/sec, -dP/dT was 945 ± 73 mmHg/sec and IVRT was 65 ± 5 msec. At the conclusion of reperfusion period, lower doses of TNFα increased +dP/dT and lowered IVRT. In contrast, the higher doses of TNFα decreased +dP/dT and prolonged IVRT. Pretreating the hearts with monoclonal TNFα antibody completely abolished the effects of TNFα on myocardial contractility and relaxation comparable to ischemia controls.

CONCLUSION

Low dose TNFα improved myocardial function and decreased resultant cellular injury while high dose TNFα decreased myocardial function and increased myocardial injury following ischemia and reperfusion.

Protective effect of Salvia miltiorrhiza aqueous extract on myocardium oxidative injury in ischemic-reperfusion rats

Salvia miltiorrhiza has strong antioxidative activity. They may have a strong potential as cardioprotective agents in ischemic-reperfusion injury. Experiments were carried out in Sprague-Dawley rats with myocardium ischemia reperfusion (IR). Myocardial injuries during IR were determined by changes in electrocardiogram analysis of arrhythmias, antioxidant enzyme activities, AST, CK-MB, lactate dehydrogenase (LDH) levels, and myocyte apoptosis. Results showed that S. miltiorrhiza aqueous extract (SAME) pre-treatment significantly decreased the ST-segment (ΣST120) and myocardium MDA, AST, CK-MB, lactate dehydrogenase (LDH) levels, increased myocardium antioxidant enzyme activities, and inhibit myocardium cell apoptosis. Furthermore, the SAME pre-treatment significantly upregulated p-JAK2 and p-STAT3 protein expression, decreased myocardium TNF-α and IL-6 concentrations in IR rats. The levels of TNF-α and IL-6 were positively correlated with the changes in myocardium p-JAK2 and p-STAT3 protein expression levels in IR rats. It can be concluded that the SAME pre-treatment has anti-ischemic and anti-apoptosis activity in heart IR rats. SAME pre-treatment protects heart against IR injury, at least in part, through its stimulating effects on injury-induced deactivation of JAK2/STAT3 signaling pathway.

Ischemia/reperfusion injury: The role of immune cells

Ischemia/reperfusion (I/R) injury is an inflammatory condition that is characterized by innate immunity and an adaptive immune response. This review is focused on the acute inflammatory response in I/R injury, and also the adaptive immunological mechanisms in chronic ischemic disease that lead to increased vulnerability during acute events, in relation to the cell types that have been shown to mediate innate immunity to an adaptive immune response in I/R, specifically myocardial infarction. Novel aspects are also highlighted in respect to the mechanisms within the cardiovascular system and cardiovascular risk factors that may be involved in the inflammatory response accompanying myocardial infarction. Experimental myocardial I/R has suggested that immune cells may mediate reperfusion injury. Specifically, monocytes, macrophages, T-cells, mast cells, platelets and endothelial cells are discussed with reference to the complement cascade, toll-like receptors, cytokines, oxidative stress, renin-angiotensin system, and in reference to the microvascular system in the signaling mechanisms of I/R. Finally, the findings of the data summarized in this review are most important for possible translation into clinical cardiology practice and possible avenues for drug development.

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 EXTRACELLULAR CARDIAC PURINE METABOLOME IN SEPSIS

The total cardiac purine metabolome includes all of the adenine and guanine nucleoside and nucleosides and related molecules involved throughout the intracellular and extracellular compartments and various cell types in the heart. In considering purines as molecules involved in autocrine and paracrine communication, effective interstitial concentrations of the nucleoside adenosine, or purine metabolites, are of greatest interest. These molecules arise from the complex interactions between cardiac-specific cell types, including fibroblasts and myocytes, and noncardiac cells, such as tissue-resident macrophages and other immune cells that have vascular access. In the interstitial environment, adenosine can regulate vascular resistance, contractile function, and immunochemical interactions. The breakdown of purines can produce reactive oxygen species that also influence autocrine and paracrine interactions. A central enzyme in this paradigm, adenosine deaminase, is a pivotal molecule in regulating the balance between pro-inflammatory and anti-inflammatory signaling cascades. A new role for adenosine deaminase as an allosteric regulator of relevant membrane proteins has yet to be explored in the heart.

The interaction between myocardial depressant factors in endotoxemic cardiac dysfunction: role of TNF-alpha in TLR4-mediated ICAM-1 expression

Multiple pro-inflammatory mediators contribute to cardiac dysfunction caused by bacterial lipopolysaccharide (LPS). The rapid TNF-alpha response is likely involved in the induction of down-stream myocardial depressant factors. Studies by our laboratory and others indicate an important role for ICAM-1 in endotoxemic cardiac dysfunction through leukocyte-independent mechanisms. The purpose of this study was to determine: whether ICAM-1 knockout improves cardiac function during endotoxemia and whether TLR4 and TNF-alpha regulate LPS-induced myocardial ICAM-1 expression.

METHODS AND RESULTS

Mice were treated with Escherichia coli LPS (0.5mg/kg iv). Myocardial ICAM-1 levels were analyzed by immunoblotting and left ventricular developed pressure (LVDP) was assessed by the Langendorff technique. In wild-type mice, peak ICAM-1 levels were observed at 4h when myocardial contractility was depressed. Myocardial contractility was improved following LPS in mice lacking functional TLR4, TNF-alpha or ICAM-1. TLR4 mutation abolished ICAM-1 expression with abrogation of precedent TNF-alpha response. Similarly, TNF-alpha knockout reduced myocardial ICAM-1 level following LPS treatment.

CONCLUSIONS

ICAM-1 contributes to the mechanism of endotoxemic cardiac dysfunction. TNF-alpha is involved in the regulation of myocardial ICAM-1 expression by TLR4.

TNFα is required to confer protection in an in vivo model of classical ischaemic preconditioning

Although Tumor Necrosis Factor alpha (TNFalpha) is used as a preconditioning mimetic in vitro, its role in ischaemic preconditioning (IPC) has not been clearly defined. Here, we propose to use an in vivo model (that takes into account the activation of leukocytes which may affect levels of TNFalpha) to demonstrate that i) TNFalpha acts as a trigger in IPC and ii) the dose-dependent nature of this cardioprotective effect of TNFalpha. Male Wistar rats were subjected to 30 min of left coronary artery occlusion (index ischaemia), followed by 24 h reperfusion. In the presence or absence of a soluble TNFalpha receptor (sTNFalpha-R), preconditioning was induced by 3 cycles of ischaemia (3 min)/reperfusion (5 min) (IPC) or various doses (0.05-4 microg/kg) of exogenous TNFalpha. Following 24 h reperfusion, infarct size (IS, expressed as % of the area at risk (AAR)) was assessed. Tissue levels of TNFalpha from the AAR, following IPC and TNFalpha stimulus were determined using Western Blot. IPC caused decrease in IS (4.5+/-1.3% vs 30.8+/-4.3% in ischaemic rats; P<0.001) and increase of TNFalpha levels following the IPC stimulus. The protective effect of IPC was abrogated in the presence of the sTNFalpha-R. In addition, exogenous TNFalpha dose-dependently reduced IS with maximal protection at a dose of 0.1 microg/kg (IS=12.6%, P<0.01 vs ischaemic). In conclusion our data provide strong evidence for a role of TNFalpha during the trigger phase of IPC. In addition, exogenous TNFalpha mimics IPC by providing a dose-dependent cardioprotective effect against ischaemia-reperfusion injury in vivo.

Tumor necrosis factor-alpha production by human islets leads to postisolation cell death

BACKGROUND

Recent successes in islet transplantation highlight the importance of islet isolation by experienced centers and minimization of cell injury as crucial to the achievement of insulin independence. Islet injury may manifest as cell death by apoptosis, shorter graft survival, and the need for retransplantation. Although an inflammatory cytokine response at the graft site is known to inhibit engraftment, recent evidence indicates that islet cells may contribute to this response.

METHODS

Isolated human islets were cultured for up to one week in serum-free CMRL-1066 with 25 microM of tumor necrosis factor (TNF)alpha inhibitor RDP58. Gene expression was measured by reverse transcriptase polymerase chain reaction, apoptosis and TNFalpha secretion by enzyme-linked immunosorbent assay and enzyme-linked immunospot, and islet function by stimulated insulin secretion.

RESULTS

Isolation induced a twofold increase in TNFalpha expression between days one and three (P<0.05), while TNFalpha secretion peaked at day one. RDP58 reduced TNFalpha secretion by 70.6% (P<0.02), though TNFalpha gene expression was unaffected. RDP58 reduced the frequency of TNFalpha-secreting islets by 64.4% (P<0.05) and reduced apoptotic levels by 26.4% within 24 hr postisolation (P<0.05). The reduction in apoptosis was maintained throughout the week (P<0.01), while apoptosis increased in control cultures. Finally, RDP58-treated islets displayed increased insulin secretion in response to both elevated glucose (1915.0+/-396.6 vs. 825.3+/-261.1 mU/L, P<0.01) and secretagogues (2294.3+/-529.5 vs. 939.8+/-333.7 mU/L, P<0.02).

CONCLUSIONS

These data demonstrate that intraislet cytokine production should be considered as a factor leading to islet cell death postisolation and postengraftment, and strategies aimed at countering islet cytokine production represent a novel target for improving islet viability and function.

Biologics in the treatment of transplant rejection and ischemia/reperfusion injury: new applications for TNFalpha inhibitors?

Tumor necrosis factor (TNF)-alpha inhibitors have proven efficacy in various autoimmune diseases such as Crohn disease, rheumatoid arthritis, psoriasis, and ankylosing spondylitis. Indeed, some TNFalpha inhibitors have already been approved for the management of the inflammatory manifestations associated with Crohn disease and rheumatoid arthritis. These agents are increasingly used for treatment of corticosteroid-resistant graft-versus-host disease after bone marrow transplantation, and case reports have documented their efficacy in treating corticosteroid- and muromonab-resistant rejection after intestinal transplantation. Thus, the potential role of TNFalpha inhibitors in transplantation of other vascularized solid organs is worthy of investigation. Experimental evidence indicates that TNFalpha plays a key role in mediating ischemia/reperfusion (IR) injury after liver, kidney, intestine, heart, lung, and pancreas transplantation. TNFalpha was also identified as a marker cytokine during organ rejection. Single-center studies evaluating the role of TNFalpha inhibitors in kidney transplantation have been initiated but the results are not yet available. TNFalpha is known to be a contributing factor in kidney allograft rejection, and may have value in predicting the onset of steroid-resistant acute rejection after liver transplantation. Experimental and preliminary clinical data have shown that circulating levels of TNFalpha are increased during cardiac graft rejection, and indicate that TNFalpha plays a role in the pathogenesis of acute cardiac allograft rejection. Anti-TNFalpha therapy was shown to prolong cardiac allograft survival when used alone or in combination with other drugs. TNFalpha genotype has been strongly associated with mortality in humans due to acute cell-mediated heart transplant rejection. In addition, there is evidence for a genetic predisposition toward acute rejection after kidney and simultaneous kidney-pancreas transplantation. TNFalpha inhibition has been used successfully as part of an induction therapy for pancreatic islet cell transplantation. Apart from IR injury and acute rejection after lung transplantation, TNFalpha was also found to be involved in the pathoimmunology of obliterative bronchiolitis. In conclusion, a substantial body of experimental evidence and preliminary clinical data suggest that TNFalpha inhibitors may play an important role in solid-organ transplantation, both in the amelioration of IR injury and in the treatment and prevention of acute rejection. Pharmacodynamic monitoring and pharmacogenetic screening may help to identify patients most likely to benefit from TNFalpha blockade. Randomized controlled trials in patients undergoing solid-organ transplantation are needed to further elucidate the clinical value of TNFalpha inhibition.

Nicorandil attenuates NF-kappaB activation, adhesion molecule expression, and cytokine production in patients with coronary artery bypass surgery

Nicorandil (NCR), a KATP channel opener, has been reported to preserve microvascular integrity in patients with reperfused myocardial infarction. We tested the hypothesis that NCR suppresses myocardial ischemia and reperfusion injury via the attenuation of cytokine production. Forty patients who underwent coronary artery bypass graft surgery were studied. The patients were randomly divided into two groups, i.e., the patients with NCR (4-6 mg/h; N group, n = 20) or without NCR (C group, n = 20). Cardiac surgery was performed under anesthesia using fentanyl and propofol. Blood were sampled at the time of induction of anesthesia, pre-cardiopulmonary bypass, 60 min after aortic occlusion, and 60, 120, and 180 min after declamping the aorta. The activation of NF-kappaB, expression of adhesion molecules, and cytokine production were evaluated in blood samples from the control volunteers by flow cytometric analysis with or without lipopolysaccharide (LPS) stimulation in vitro. Serum IL-6 and IL-8 levels in both groups increased 60 min after declamping the aorta compared with the preoperative value (P < 0.001); the increases of these parameters in N group were lower than those in C group (P < 0.05). Serum creatine kinase with muscle and brain subunits and troponin-T levels increased 60 min after declamping the aorta in two groups (P < 0,001), but the increases of both parameters in N group were lower than those in C group (P < 0.05). NF-kappaB activation, CD11b/CD18 expression, and the production of TNF-alpha, IL-8, and IL-6 in monocytes and granulocytes were inhibited by NCR in vitro. NCR suppressed the increase of inflammatory cytokines such as IL-6 and IL-8 levels, and reduced myocardial reperfusion injury. The inhibition on NF-kappaB activation, adhesion molecule expression, and cytokine production may be one of the important mechanisms of myocardial protection of NCR.

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.

Upregulation of A2A adenosine receptor expression by TNF-alpha in PBMC of patients with CHF: a regulatory mechanism of inflammation

BACKGROUND

Tumor necrosis factor (TNF)-alpha plays a role in congestive heart failure (CHF). A2A adenosine receptor (A(2A)R) activation on immune cells putatively reduces the release of cytokines contributing to CHF progression. The study is aimed at determining the role of the A(2A)R in the modulation of TNF-alpha production, and the ex vivo effect of TNF-alpha on A(2A)R in peripheral blood mononuclear cells (PBMC) from CHF patients.

METHODS AND RESULTS

Plasma levels of TNF-alpha and TNF-alpha production from lipopolysaccharide (LPS)-stimulated PBMC were evaluated in 26 CHF patients in comparison to controls. The effects of the A(2A)R agonist CGS-21680 and antagonist ZM-241385 on TNF-alpha production from PBMC were also evaluated. Finally, reverse transcriptase-polymerase chain reaction and Western blot analyses of A(2A)R in PBMC were performed in TNF-alpha-treated and untreated cells. TNF-alpha production from LPS-stimulated PBMC was enhanced in CHF patients with respect to controls. CGS-21680 blunted TNF-alpha production in both groups; ZM-241385 reverted this effect. A(2A)R expression in PBMC was higher in CHF patients than in controls. TNF-alpha addition produced an increase in A(2A)R in PBMC from controls but not in PBMC from CHF patients.

CONCLUSIONS

PBMC from CHF patients show an upregulation of A(2A)R-mediated inhibition of TNF-alpha, which may represents a mechanism of protection against inappropriate cytokine production.

A1 adenosine receptor knockout mice exhibit increased mortality, renal dysfunction, and hepatic injury in murine septic peritonitis

Sepsis is a leading cause of multiorgan dysfunction and death in hospitalized patients. Dysregulated inflammatory processes and apoptosis contribute to the pathogenesis of sepsis-induced organ dysfunction and death. A(1) adenosine receptor (A(1)AR) activation reduces inflammation and apoptosis after ischemia-reperfusion injury. Therefore, we questioned whether A(1)AR-mediated reduction of inflammation and apoptosis could improve mortality and organ dysfunction in a murine model of sepsis. A(1)AR knockout mice (A(1) knockout) and their wild-type (A(1) wild-type) littermate controls were subjected to cecal ligation and double puncture (CLP) with a 20-gauge needle. A(1) knockout mice or A(1) wild-type mice treated with 1,3-dipropyl-8-cyclopentylxanthine (a selective A(1)AR antagonist) had a significantly higher mortality rate compared with A(1) wild-type mice following CLP. Mice lacking endogenous A(1)ARs demonstrated significant elevations in plasma creatinine, alanine aminotransferase, aspartate aminotransferase, keratinocyte-derived chemokine, and tumor necrosis factor-alpha 24 h after induction of sepsis compared with wild-type mice. The renal corticomedullary junction from A(1) knockout mice also exhibited increased myeloperoxidase activity, intercellular adhesion molecule-1 protein, and mRNA encoding proinflammatory cytokines compared with renal samples from A(1) wild-type littermate controls. No difference in renal tubular apoptosis was detected between A(1) knockout and A(1) wild-type mice. We conclude that endogenous A(1)AR activation confers a protective effect in mice from septic peritonitis primarily by attenuating the hyperacute inflammatory response in sepsis.

Sex differences in the myocardial inflammatory response to ischemia-reperfusion injury

The myocardium generates inflammatory mediators during ischemia-reperfusion (I/R), and these mediators contribute to cardiac functional depression and apoptosis. The great majority of these data have been derived from male animals and humans. Sex has a profound effect over many inflammatory responses; however, it is unknown whether sex affects the cardiac inflammatory response to acute myocardial I/R. We hypothesized the existence of inherent sex differences in myocardial function, expression of inflammatory cytokines, and activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway after I/R. Isolated rat hearts from age-matched adult males and females were perfused (Langendorff), and myocardial contractile function was continuously recorded. After I/R, myocardium was assessed for expression of TNF-alpha, IL-1beta, and IL-6 (RT-PCR, ELISA); IL-1alpha and IL-10 mRNA (RT-PCR); and activation of p38 MAPK (Western blot). All indexes of postischemic myocardial function [left ventricular developed pressure, left ventricular end-diastolic pressure, and maximal positive (+dP/dt) and negative (-dP/dt) values of the first derivative of pressure] were significantly improved in females compared with males. Compared with males, females had decreased myocardial TNF-alpha, IL-1beta, and IL-6 (mRNA, protein) and decreased activation of p38 MAPK pathway. These data demonstrate that hearts from age-matched adult females are relatively protected against I/R injury, possibly due to a diminished inflammatory response.

Signaling for myocardial depression in hemorrhagic shock: roles of Toll-like receptor 4 and p55 TNF-alpha receptor

Hemorrhagic shock causes myocardial contractile depression. Although this myocardial disorder is associated with increased expression of tumor necrosis factor-alpha (TNF-alpha), the role of TNF-alpha as a myocardial depressant factor in hemorrhagic shock remains to be determined. Moreover, it is unclear which TNF-alpha receptor mediates the myocardial depressive effects of TNF-alpha. Toll-like receptor 4 (TLR4) regulates cellular expression of proinflammatory mediators following lipopolysaccharide stimulation and may be involved in the tissue inflammatory response to injury. The contribution of TLR4 signaling to tissue TNF-alpha response to hemorrhagic shock and TLR4's role in myocardial depression during hemorrhagic shock are presently unknown. We examined the relationship of TNF-alpha production to myocardial depression in a mouse model of nonresuscitated hemorrhagic shock, assessed the influence of TLR4 mutation, resulting in defective signaling, on TNF-alpha production and myocardial depression, and determined the roles of TNF-alpha and TNF-alpha receptors in myocardial depression using a gene knockout (KO) approach. Hemorrhagic shock resulted in increased plasma and myocardial TNF-alpha (4.9- and 4.5-fold, respectively) at 30 min and induced myocardial contractile depression at 4 h. TLR4 mutation abolished the TNF-alpha response and attenuated myocardial depression (left ventricular developed pressure of 43.0 +/- 6.2 mmHg in TLR4 mutant vs. 30.0 +/- 3.6 mmHg in wild type, P < 0.05). TNF-alpha KO also attenuated myocardial depression in hemorrhagic shock, and the p55 receptor KO, but not the p75 receptor KO, mimicked the effect of TNF-alpha KO. The results suggest that TLR4 plays a novel role in signaling to the TNF-alpha response during hemorrhagic shock and that TNF-alpha through the p55 receptor activates a pathway leading to myocardial depression. Thus TLR4 and the p55 TNF-alpha receptor represent therapeutic targets for preservation of cardiac mechanical function during hemorrhagic shock.

TNF-α is required for late ischemic preconditioning but not for remote preconditioning of trauma

BACKGROUND

Ischemic preconditioning (IPC) and remote IPC are cardioprotective phenomena in which ischemia of the myocardium or of a remote tissue, respectively, induces cardioprotection. Despite clinical evidence that surgical trauma can remotely affect myocardial infarction, to date there are no basic science studies addressing the effect of nonischemic trauma at distant sites upon cardiac ischemia/reperfusion (I/R) injury. The objectives of this study were to determine the effects of nonischemic remote surgical trauma upon infarct size after myocardial I/R and to determine the effects of TNF-alpha ablation upon cardioprotective phenomena.

MATERIALS AND METHODS

A minimally traumatic mouse model was used to ascertain the effect of remote nonischemic surgical trauma upon I/R injury. TNF-alpha knockout mice were employed to determine the effect of TNF-alpha ablation.

RESULTS

Carotid artery vascular surgery remotely exacerbates cardiac I/R injury increasing infarct size by 287% (remote cardiac injury or RCI). Nonischemic, nonvascular trauma (abdominal incision) results in remote preconditioning of trauma (RPCT), decreasing infarct size by 81% (early phase) and 40% (late phase) relative to controls. Finally, TNF-alpha is required for late IPC but is not necessary for RCI or for RPCT.

CONCLUSIONS

We show that late IPC is TNF-alpha-dependent and describe two unique TNF-alpha-independent remote effects of nonischemic trauma upon myocardial infarction. Understanding the mechanism of these remote effects will allow the development of novel therapies for the treatment of ischemic heart disease. RPCT and TNF-alpha ablation have an additive protective effect suggesting that combinations of complementary approaches may be a useful strategy for maximizing the clinical efficacy of cardioprotective therapies.

A common variant of the AMPD1 gene predicts improved survival in patients with ischemic left ventricular dysfunction

BACKGROUND

A recent retrospective study suggested that the adenosine monophosphate deaminase (AMPD)-1 gene variant C34T predicts outcome in heart failure patients. This variant might lead to ischemic preconditioning by increasing tissue adenosine. We tested whether the survival benefit of C34T occurs preferentially in the setting of ischemic left ventricular dysfunction.

METHODS AND RESULTS

A consecutive cohort of patients (n=390) with left ventricular ejection fraction <40% was evaluated. In the ischemic patient subgroup (n=210) multivariate analysis identified AMPD1 T allele carriage (hazard ratio=0.43, confidence interval=0.20-0.94, P=.035) as an independent predictor of transplant-free cardiovascular survival. No benefit was found in the nonischemic group although the number of events was too small to reliably exclude a benefit by genotype.

CONCLUSION

The AMPD1 C34T polymorphism influences transplant-free cardiovascular survival in the setting of ischemic left ventricular dysfunction.

The role of estrogen in cardiovascular disease

Cardiovascular disease is the number one cause of death among women, accounting for nearly 50% of female deaths. Statistics show that women on average develop cardiovascular disease 10 to 15 years later in life than men, and that the risk may increase after menopause. This observation has led to much speculation as to what physiological change(s) associated with menopause is responsible for the higher risk of atherosclerosis. Estrogen, with its potential as a cardioprotective agent and as an immunomodulator of the inflammatory response in atherosclerosis, has received the most attention. Understanding the mechanisms that lead to these differences may allow beneficial therapeutic intervention to enhance this effect in females and evoke this protection in males. This review will do the following: (1) characterize mechanisms of atherosclerosis, (2) explore the role of estrogen-replacement therapy, (3) define the effect of gender on inflammation, (4) compare and contrast the effects of estrogen and testosterone on endothelial functional, and (5) suggest mechanistic based therapeutic opportunities.

Preconditioning the Myocardium: From Cellular Physiology to Clinical Cardiology

Yellon, Derek M., and James M. Downey. Preconditioning the Myocardium: From Cellular Physiology to Clinical Cardiology. Physiol Rev 83: 1113-1151, 2003; 10.1152/physrev.00009.2003.—The phenomenon of ischemic preconditioning, in which a period of sublethal ischemia can profoundly protect the cell from infarction during a subsequent ischemic insult, has been responsible for an enormous amount of research over the last 15 years. Ischemic preconditioning is associated with two forms of protection: a classical form lasting ∼2 h after the preconditioning ischemia followed a day later by a second window of protection lasting ∼3 days. Both types of preconditioning share similarities in that the preconditioning ischemia provokes the release of several autacoids that trigger protection by occupying cell surface receptors. Receptor occupancy activates complex signaling cascades which during the lethal ischemia converge on one or more end-effectors to mediate the protection. The end-effectors so far have eluded identification, although a number have been proposed. A range of different pharmacological agents that activate the signaling cascades at the various levels can mimic ischemic preconditioning leading to the hope that specific therapeutic agents can be designed to exploit the profound protection seen with ischemic preconditioning. This review examines, in detail, the complex mechanisms associated with both forms of preconditioning as well as discusses the possibility to exploit this phenomenon in the clinical setting. As our understanding of the mechanisms associated with preconditioning are unravelled, we believe we can look forward to the development of new therapeutic agents with novel mechanisms of action that can supplement current treatment options for patients threatened with acute myocardial infarction.

Serum tumour necrosis factor-alpha, interleukin-2 and interleukin-10 activation in stable angina and acute coronary syndromes

BACKGROUND

Dynamic instability of coronary atherosclerotic plaque results in the development of both unstable angina and myocardial infarction. The aim of the study was to investigate the dynamics of serum concentrations of tumour necrosis factor (TNF)alpha, interleukin (IL)-10, and IL-2 in patients with myocardial infarction (MI) and unstable angina (UA) as compared to stable angina (SA) patients and healthy volunteers.

METHODS

A total of 189 patients with coronary artery disease (CAD) were studied: 100 patients with SA (class II/III according to CCS), 57 patients with UA (Braunwald class IIIB; determinations at 6, 24, and 48 h after chest pain), and 32 patients with MI (determinations at admission, on the 7th and 30th days after MI). Twenty healthy volunteers acted as controls.

RESULTS

Serum TNFalpha levels were elevated in all CAD groups (SA: 17.3+/-4; UA: 18.7+/-4; MI: 22.0+/-3 pg/ml; p<0.001) in comparison to the controls (8.3+/-1.4 pg/ml). However, the highest values were characteristic of MI patients, especially values obtained at admission (p<0.01 versus SA and UA). Mean serum concentrations of IL-2 were significantly higher in patients with MI and UA (89.6+/-40; 87.0+/-24 pg/ml, respectively; p<0.01) when compared to SA and the control group (58.3+/-49; and 51.5+/-39, respectively). Serum IL-10 levels were also higher in MI and UA patients. Levels of IL-2 and IL-10 measured following chest pain in unstable patients, as well as their consecutive determinations in MI patients did not show any change dynamics, that is, they were persistently elevated.

CONCLUSIONS

When compared to stable CAD and healthy subjects, acute coronary syndromes are associated with long-term increase of serum concentrations of pro- and anti-inflammatory cytokines. It seems likely that sudden CAD progression leading to acute coronary syndromes is triggered/accompanied by prolonged immune 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.

Changes of peripheral A2A adenosine receptors in chronic heart failure and cardiac transplantation

Peripheral blood mononuclear cells of chronic heart failure (CHF) patients produce great amounts of pro-inflammatory cytokines, indicating that circulating cells are activated and could mirror changes occurring in inflammatory cells infiltrating the failing heart. Adenosine is a regulatory metabolite acting through four membrane receptors that are linked to adenylyl cyclase: activation of the A2A receptor subtype has been reported to inhibit cytokine release. Changes of the adenosinergic system may play a role in CHF development. Here we report an increase of A2A receptor expression, density, and coupling to adenylyl cyclase in blood circulating cells of CHF patients. A2A receptor up-regulation was also found in the explanted hearts of these patients, suggesting that changes of peripheral adenosine receptors mirror changes occurring in the disease target organ. In a cohort of patients followed longitudinally after heart transplantation, alterations of peripheral A2A adenosine receptor progressively normalized to control values within 6 months, suggesting that improvement of cardiac performance is accompanied by progressive restoration of a normal adenosinergic system. These results validate the importance of the A2A receptor in human diseases characterized by a marked inflammatory/immune component and suggest that the evaluation of this receptor in peripheral blood cells may be useful for monitoring hemodynamic changes and the efficacy of pharmacological and non-pharmacological treatments in CHF patients.

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.

Selected cytokines and soluble forms of cytokine receptors in coronary artery disease

Background: Cytokines may play a role in the pathogenesis of atherosclerosis and coronary artery disease (CAD). Methods: We examined serum concentrations of selected pro- (TNFalpha, IL-2) and anti-inflammatory (IL-10) cytokines, and soluble forms of TNF receptors (sTNFR 1 and sTNFR 2) by ELISA in 45 patients with stable exertional angina (group 1), 32 patients with unstable angina (group 2), and 20 healthy subjects (group C). Results: Serum concentrations of both TNFalpha (group 1, 18.3; group 2, 17.2 pg/ml; P<0.001) and IL-10 (group 1, 46.1; group 2, 41.5 pg/ml; P<0.05) were significantly higher in patients with CAD than in group C (8.3 and 14.3 pg/ml, respectively). sTNFR 1 serum level was higher in group 1 (1399.6; P<0.05) than in healthy volunteers (1093.9 pg/ml). In turn, the serum level of IL-2 was significantly higher in unstable patients than it was in groups 1 and C (89.4, 59.8 and 52.8 pg/ml, respectively). In group 1, both TNFalpha and IL-2 correlated with serum lipids. Conclusions: Patients with CAD, irrespective of the form of the disease, have higher serum levels of pro- and anti-inflammatory cytokines than control subjects. Increased concentrations of IL-2 in unstable angina may suggest additional immunologic activation. The pro-inflammatory cytokine levels seem to be related to lipid disturbances.

The endothelium in clinical cardiac transplantation

Cardiac transplantation is the most successful therapy for refractory heart failure, but clinical transplantation is still confronted with the problems of acute rejection and acute pump failure. The limiting factor in achieving prolonged survival remains cardiac allograft vasculopathy. In recent years it has become apparent that from brain death onward, the cardiac endothelium plays a key role in these acute and chronic events. Brain death is associated with an inflammatory response that primes the endothelium for cumulative injury during the subsequent stages of ischemic cold storage, reperfusion and allorecognition. As a structural and functional interface, the endothelium is the site at which inflammatory cells move from the bloodstream through the vessel wall into the parenchyma. The endothelium interacts with the complement system, the coagulation and inflammatory cascades, circulating leukocytes, the immune system, the smooth muscle in the vessel wall, and the surrounding matrix and cardiomyocytes. A better understanding of its many roles may lead to expansion of our therapeutic possibilities and better outcomes overall. This article reviews the possible roles of the endothelium in relation to cardiac transplantation, and discusses the diagnostic and therapeutic modalities that are available to date.

Ischemia alone is sufficient to induce TNF-alpha mRNA and peptide in the myocardium

Over-production of tumor necrosis factor-alpha (TNF-alpha) following myocardial ischemia-reperfusion contributes to cardiac dysfunction, and anti-TNF-alpha has therapeutic potential for myocardial protection in cardiac surgery with obligatory ischemia. It remains unclear, however, whether myocardial TNF-alpha production occurs during ischemia and whether cardiac myocytes constitute a source of myocardial TNF-alpha. Ischemia alone has been shown to activate myocardial NF-kappaB. We hypothesized that ischemia alone is sufficient to induce myocardial TNF-alpha gene expression and peptide synthesis. We examined TNF-alpha production and NF-kappaB activation in the isolated rat heart subjected to global normothermic ischemia. Myocardial ischemia resulted in rapid IkappaB-alpha degradation and NF-kappaB activation. Immunofluorescence staining detected NF-KB intranuclear translocation primarily in myocardial interstitial cells. Ischemia alone induced a time-dependent increase in myocardial TNF-alpha. TNF-alpha peptide increased to 20.3+/-3.0 pg/mg after 25 min of ischemia (P < 0.05 vs 8.9+/-2.0 pg/mg in perfusion control). TNF-alpha was also localized to myocardial interstitial cells. Increased TNF-alpha peptide level correlated with TNF-alpha mRNA expression. We conclude that ischemia alone induces TNF-a gene expression and peptide synthesis in the myocardium that are associated with NF-kappaB activation. Non-myocytes constitute the main source of myocardial TNF-alpha following ischemia. The results suggest that therapeutic strategies attempting to decrease myocardial TNF-alpha production need to be applied before or in the early phase of ischemia.

p38 MAPK mediates renal tubular cell TNF-alpha production and TNF-alpha-dependent apoptosis during simulated ischemia

Ischemia causes renal tubular cell loss through apoptosis; however, the mechanisms of this process remain unclear. Using the renal tubular epithelial cell line LLC-PK(1), we developed a model of simulated ischemia (SI) to investigate the role of p38 MAPK (mitogen-activated protein kinase) in renal cell tumor necrosis factor-alpha (TNF-alpha) mRNA production, protein bioactivity, and apoptosis. Results demonstrate that 60 min of SI induced maximal TNF-alpha mRNA production and bioactivity. Furthermore, 60 min of ischemia induced renal tubular cell apoptosis at all substrate replacement time points examined, with peak apoptotic cell death occurring after either 24 or 48 h. p38 MAPK inhibition abolished TNF-alpha mRNA production and TNF-alpha bioactivity, and both p38 MAPK inhibition and TNF-alpha neutralization (anti-porcine TNF-alpha antibody) prevented apoptosis after 60 min of SI. These results constitute the initial demonstration that 1) renal tubular cells produce TNF-alpha mRNA and biologically active TNF-alpha and undergo apoptosis in response to SI, and 2) p38 MAPK mediates renal tubular cell TNF-alpha production and TNF-alpha-dependent apoptosis after SI.

The role of anti-cytokine therapy in the failing heart

The understanding of the role of "neurohormones" in the progression of heart failure has led to the utilization of agents that antagonize the activation of neurohormonal systems as effective therapy in patients with heart failure. As more evidence emerges linking proinflammatory cytokines to disease progression in heart failure, there is an increasing interest in developing anti-cytokine strategies that might be used as adjunctive therapy in patients with heart failure. Accordingly, the focus of the present review is to summarize the experimental and clinical studies that have attempted to modulate the effects of cytokines in heart failure. Strategies have been employed to either suppress cytokine production or to prevent their toxic effects by interfering with the binding of cytokines to their cognate receptors.

Intravenous theophylline--an alternative to temporary pacing in the management of bradycardia secondary to AV nodal block

OBJECTIVE

To report a case of bradycardia secondary to atrioventricular nodal block (AVNB) successfully treated with intravenous theophylline. Intravenous theophylline was used as an alternative to temporary pacing in a patient with sepsis secondary to thermal injury.

CASE SUMMARY

A 79-year-old white woman with significant cardiac history was admitted with 14.5% total body surface area burns after a house fire. Cardiac events included intermittent episodes of sinus bradycardia complicated by the development of second-degree AVNB and periods of sinus arrest. Intravenous theophylline initiation maintained normal sinus rhythm without further episodes of sinus bradycardia or heart block, thus preventing the need for cardiac pacemaker placement.

DISCUSSION

This is the first case published in the English-language literature describing the use of intravenous theophylline as an alternative therapy to temporary pacing in a patient with sepsis secondary to thermal injury. Bradyarrhythmic events in sepsis patients have been associated with catecholamine production increasing adenosine formation. High concentrations of adenosine in the areas of the sinoatrial or atrioventricular nodal regions may induce sinus bradycardia or AVNB. Theophylline, an adenosine antagonist, has been identified as a treatment option for such bradyarrhythmic events.

CONCLUSIONS

Theophylline, a methylxanthine derivative, may represent an alternative to other pharmacologic therapies and temporary pacing in the treatment of bradycardia secondary to AVNB. These agents may represent a pharmacologic alternative in patients in whom other pharmacologic strategies or cardiac pacemaker insertion may be contraindicated.

Bench to bedside: tumor necrosis factor-alpha: from inflammation to resuscitation

Proinflammatory mediators such as tumor necrosis factor-alpha (TNF) have been implicated in the pathophysiology in a number of acute disease states. Tumor necrosis factor-alpha can contribute to cell death, apoptosis, and organ dysfunction. Tumor necrosis factor-alpha can be generated with sepsis or ischemia-reperfusion by activation of cell mitogen-activated protein kinases and nuclear factor kappa B, leading to TNF production. A number of strategies to modulate TNF have been recently explored, including factors directed toward mitogen-activated protein kinases, TNF transcription, anti-inflammatory ligands, heat shock proteins, and TNF-binding proteins. However, TNF may also play an important role in the adaptive response to injury and inflammation. Control of the deleterious effects of TNF and other proinflammatory cytokines represents a realistic goal for clinical emergency medicine. The purpose of this article is to provide a background of relevance to emergency medicine academicians on the production and regulation of TNF, the acute effects of TNF on pathophysiology, and the rationale for therapeutic interventions directed toward TNF and the clinical experience with these strategies.

Attenuation of reperfusion injury by renal ischaemic preconditioning: the role of nitric oxide

OBJECTIVE

To determine the effect on nitric oxide (NO) release and renal NO synthase (endothelial, eNOS and inducible, iNOS) activity of renal ischaemia-reperfusion (I/R) in vivo in an animal model, and to examine the possible involvement of NO in ischaemic preconditioning (IP) of the kidney.

MATERIALS AND METHODS

In a right-nephrectomized rat model, 42 animals were randomized in four groups: controls; IP-only (4 min of ischaemia followed by 11 min of reperfusion, total of four cycles); renal warm ischaemia (45 min) and 6 h reperfusion; ischaemia (45 min) preceded by IP pretreatment. Serum NO metabolites were assayed 2 and 6 h after ischaemia or the control equivalent. NOS expression in the kidney was detected immuno-histochemically, and damage assessed morphologically in sections stained with haematoxylin and eosin. Kidney function was assessed by the levels of serum creatinine, urea and electrolytes.

RESULTS

Compared with before ischaemia, the concentration of serum NO metabolites at 6 h was increased in the IP-only animals (P = 0. 016) and in the IP + I/R group (P = 0.002). There was greater eNOS expression in the IP-only group (P = 0.009) and in the IP + I/R group than in controls (P = 0.050). iNOS expression was greater in the IP-only animals than in the control group (P = 0.050). Histological assessment showed less evidence of cellular damage in IP + I/R animals than in the I/R-alone group (P = 0.020). Serum creatinine level was not significantly different between the IP-only group and the control. There were no differences after 2 h of reperfusion.

CONCLUSION

Ischaemic preconditioning has a protective effect on renal structure and function, which may be produced by increased NO release arising from increased NOS expression by 6 h after reperfusion.

Adenosine preconditioning reduces both pre and postischemic arrhythmias in human myocardium

INTRODUCTION

Consistently, clinical series record supraventricular tachyarrhythmias in approximately 30% of patients following coronary artery bypass surgery (CABG). Ischemic preconditioning and adenosine preconditioning (Ado-PC) decrease postischemia/reperfusion (I/R) myocardial stunning, infarct size, and pharmacologically induced arrhythmias in all species including man. We hypothesized that adenosine preconditioning would decrease spontaneous pre- and postischemic atrial arrhythmias in human myocardium. The purposes of this study were to determine the effect of in vivo and in vitro Ado-PC on atrial arrhythmias.

METHODS

Human atrial trabeculae were harvested from CABG patients, placed in organ baths, and paced (1 Hz). Developed force (DF) was recorded during simulated I/R (30/45 min). Prior to I/R, trabeculae were treated with Ado (125 microM) for 5 min (in vitro), or patients were treated with Ado (12 mg iv) 5 min (in vivo) prior to harvest of trabeculae. Contraction frequency >4 Hz (defined as atrial tachyarrhythmias) was recorded in all groups pre- and postischemia.

RESULTS

Control trabeculae exhibited increased tachyarrhythmias pre- and postischemia. In vivo and in vitro Ado-PC suppressed both pre- and postischemic arrhythmias.

CONCLUSIONS

Adenosine preconditioning suppresses the frequency of pre- and postischemic tachyarrhythmias against an ischemia/reperfusion insult in human myocardium. This antiarrhythmic effect occurs with both in vitro and in vivo administration of adenosine. Preconditioning with adenosine prior to elective ischemia/reperfusion is a promising strategy of reducing spontaneous atrial arrhythmias in patients undergoing myocardial revascularization.

Early renal ischemia, with or without reperfusion, activates NFkappaB and increases TNF-alpha bioactivity in the kidney

PURPOSE

Acute tubular necrosis (ATN) and the ensuing renal failure induced by ischemia and reperfusion injury (I/R) remain a major cause of morbidity and mortality among patients in the intensive care unit. Although it is well established that exogenous tumor necrosis factor-alpha (TNF) induces renal injury, it remains unknown whether ischemia and/or reperfusion activates the signaling mechanisms required for renal TNF production. We hypothesized that ischemia and/or reperfusion would activate the oxidant sensitive TNF transcription factor, nuclear factor kappa B (NFkappaB), and thereby lead to renal TNF production.

MATERIALS AND METHODS

Male Sprague-Dawley rats were anesthetized with sodium pentobarbital, after which various periods of renal ischemia, with or without reperfusion, were induced in rats. At different time intervals, kidneys were harvested and NFkappaB activation (electrophoretic mobility shift assay), TNF mRNA content (RT-PCR), and TNF bioactivity (WEHI-164 cell clone cytotoxicity assay) were determined.

RESULTS

Results indicate that 15 minutes of ischemia alone activates NFkappaB, whereas peak activation occurred at 30 minutes of ischemia alone. NFkappaB remained activated through 60 minutes reperfusion. Thirty minutes of ischemia is required to induce renal TNF mRNA production; however, renal TNF protein expression and bioactivity peaked following 1 hour of ischemia and 2 hours reperfusion.

CONCLUSIONS

These results are the initial demonstration that renal ischemia, with or without reperfusion, activates the TNF transcription factor NFkappaB and increases TNF bioactivity in the kidney.

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.

Early kidney TNF-alpha expression mediates neutrophil infiltration and injury after renal ischemia-reperfusion

The purpose of this study was to determine whether isolated renal ischemia and reperfusion (I/R) induces renal tumor necrosis factor (TNF) mRNA production, TNF protein expression, or TNF bioactivity and, if so, whether local/early TNF production acts as mediator of ischemia-induced, neutrophil-mediated renal injury. After rats were anesthetized, varying periods of renal ischemia, with or without reperfusion, were induced. Kidney mRNA content (RT-PCR), TNF protein expression (ELISA), TNF bioactivity (WEHI-164 cell clone cytotoxicity assay), and neutrophil infiltration [myeloperoxidase (MPO) assay] were determined. In other animals, renal MPO and serum creatinine were assessed after TNF was neutralized [binding protein (TNF-BP)]. Thirty minutes of ischemia induced renal TNF mRNA. TNF protein expression and bioactivity peaked after 1 h ischemia and 2 h reperfusion, whereas neutrophil infiltration peaked at 4 h reperfusion. TNF-BP neutralized TNF bioactivity, reduced neutrophil infiltration, and protected postischemic function. These results constitute the initial demonstration that 1) early renal tissue TNF expression contributes to neutrophil infiltration and injury after I/R and 2) TNF-BP may offer a new adjunctive therapy in renal preservation prior to planned ischemic insults.

Gene therapy in transplantation

Facilitation of solid organ and cell transplantation depends on metabolic and immunologic factors that can be manipulated ex vivo and in vivo using gene transfer technology. Vectors have been developed which can optimally transfer relevant genes to various tissues and organs. Interventions aimed at promoting tissue preservation before transplantation, prevention of oxidative stress and immunological rejection have recently become attractive options using viral and nonviral gene delivery vehicles. Further understanding of the mechanisms involved in tolerance induction as well as the facilitation of xenogeneic engraftment have made possible a variety of avenues that can be exploited using gene transfer technology.

Cytokines in heart failure: pathogenetic mechanisms and potential treatment

Recent studies have shown that patients with heart failure overexpress a class of biologically active molecules, generically referred to as pro-inflammatory cytokines. This article will review recent clinical and experimental material that suggests that pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6) may play a role in the pathogenesis of congestive heart failure. In addition, we will review recent studies that suggest that antagonizing cytokines may represent a novel target for heart failure therapy.

Role of TNF in mediating renal insufficiency following cardiac surgery: evidence of a postbypass cardiorenal syndrome

Recent evidence has implicated proinflammatory mediators such as TNF-alpha in the pathophysiology of ischemia-reperfusion (I/R) injury. Clinically, serum levels of TNF-alpha are increased after myocardial infarction and after cardiopulmonary bypass. Both cardiopulmonary bypass and renal ischemia-reperfusion injury induce a cascade of events leading to cellular damage and organ dysfunction. Tumor necrosis factor (TNF), a potent proinflammatory cytokine, is released from both the heart and the kidney in response to ischemia and reperfusion. TNF released during cardiopulmonary bypass induces glomerular fibrin deposition, cellular infiltration, and vasoconstriction, leading to a reduction in glomerular filtration rate (GFR). The signaling cascade through which renal ischemia-reperfusion induces TNF production is beginning to be elucidated. Oxidants released following reperfusion activate p38 mitogen-activated protein kinase (p38 MAP kinase) and the TNF transcription factor, NFkappaB, leading to subsequent TNF synthesis. In a positive feedback, proinflammatory fashion, binding of TNF to specific TNF membrane receptors can reactivate NFkappaB. This provides a mechanism by which TNF can upregulate its own expression as well as facilitate the expression of other genes pivotal to the inflammatory response. Following its production and release, TNF results in both renal and myocardial apoptosis and dysfunction. An understanding of these mechanisms may allow the adjuvant use of anti-TNF therapeutic strategies in the treatment of renal injury. The purposes of this review are: (1) to evaluate the evidence which indicates that TNF is produced by the heart following cardiopulmonary bypass; (2) to examine the effect of TNF on myocardial performance; (3) to outline the mechanisms by which the kidney produces significant TNF in response to ischemia and reperfusion; (5) to investigate the role of TNF in renal ischemia-reperfusion injury, (6) to describe the mechanisms of TNF-induced renal cell apoptosis, and (7) to suggest potential anti-TNF strategies designed to reduce renal insufficiency following cardiac surgery.

Calcium preconditioning, but not ischemic preconditioning, bypasses the adenosine triphosphate-dependent potassium (KATP) channel

BACKGROUND

Recent evidence has implicated the KATP channel as an important mediator of ischemic preconditioning (IPC). Indeed, patients taking oral sulfonylurea hypoglycemic agents (i.e., KATP channel inhibitors) for treatment of diabetes mellitus are resistant to the otherwise profoundly protective effects of IPC. Unfortunately, many cardiopulmonary bypass patients, who may benefit from IPC, are chronically exposed to these agents. Calcium preconditioning (CPC) is a potent form of similar myocardial protection which may or may not utilize the KATP channel in its mechanism of protection. The purpose of this study was to determine whether CPC may bypass the KATP channel in its mechanism of action. If so, CPC may offer an alternative to IPC in patients chronically exposed to these agents.

METHODS

Isolated rat hearts (n = 6-8/group) were perfused (Langendorff) and received KATP channel inhibition (glibenclamide) or saline vehicle 10 min prior to either a CPC or IPC preconditioning stimulus or neither (ischemia and reperfusion, I/R). Hearts were subjected to global warm I/R (20 min/40 min). Postischemic myocardial functional recovery was determined by measuring developed pressure (DP), coronary flow (CF), and compliance (end diastolic pressure, EDP) with a MacLab pressure digitizer.

RESULTS

Both CPC and IPC stimuli protected myocardium against postischemic dysfunction (P < 0.05 vs I/R; ANOVA with Bonferroni/Dunn): DP increased from 52 +/- 4 (I/R) to 79 +/- 2 and 83 +/- 4 mmHg; CF increased from 11 +/- 0.7 to 17 +/- 2 and 16 +/- 1 ml/min; and EDP decreased (compliance improved) from 50 +/- 7 to 27 +/- 5 and 31 +/- 7 mmHg. However, KATP channel inhibition abolished protection in hearts preconditioned with IPC (P < 0.05 vs IPC alone), but not in those preconditioned with CPC (P > 0.05 vs CPC alone).

CONCLUSIONS

(1) Both IPC and CPC provide similar myocardial protection; (2) IPC and CPC operate via different mechanisms; i.e., IPC utilizes the KATP channel whereas CPC does not; and (3) CPC may offer a means of bypassing the deleterious effects of KATP channel inhibition in diabetic patients chronically exposed to oral sulfonylurea hypoglycemic agents.

Review article: the role of tumor necrosis factor in renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury induces a cascade of events leading to cellular damage and organ dysfunction. Tumor necrosis factor-alpha (TNF), a potent proinflammatory cytokine, is released from the kidney in response to, and has been implicated in the pathogenesis of, renal ischemia-reperfusion injury. TNF induces glomerular fibrin deposition, cellular infiltration and vasoconstriction, leading to a reduction in glomerular filtration rate (GFR). The signaling cascade through which renal ischemia-reperfusion induces TNF production is beginning to be elucidated. Oxidants released following reperfusion activate p38 mitogen activated protein kinase (p38 MAP kinase) and the TNF transcription factor, NFkappaB, leading to subsequent TNF synthesis. In a positive feedback, proinflammatory fashion, binding of TNF to specific TNF membrane receptors can reactivate NFkappaB. This provides a mechanism by which TNF can upregulate its own expression as well as facilitate the expression of other genes pivotal to the inflammatory response. TNF receptor binding can also induce renal cell apoptosis, the major form of cell death associated with renal ischemia-reperfusion injury. Anti-TNF strategies targeting p38 MAP kinase, NFkappaB, and TNF itself are being investigated as methods of attenuating renal ischemic injury. The control of TNF production and activity represents a realistic goal for clinical medicine.

Protective effect of preconditioning and adenosine pretreatment in experimental skeletal muscle reperfusion injury

BACKGROUND

Prolonged ischaemia followed by reperfusion (I/R) of skeletal muscle results in significant tissue injury. Ischaemic preconditioning (IPC), achieved by repeated brief periods of I/R before prolonged ischaemia or adenosine pretreatment, can prevent I/R injury in cardiac muscle. The aim of this study was to ascertain in a rodent model if damage to skeletal muscle due to global hindlimb tourniquet-induced I/R could be similarly attenuated.

METHODS

Anaesthetized rats were randomized (n = 6-10 per group) to five groups: sham-operated controls; I/R (4 h of ischaemia, 2 h of reperfusion); IPC (three cycles of 10 min of ischaemia/10 min of reperfusion) alone; IPC immediately preceding I/R; or adenosine 1000 microg/kg immediately before I/R. At the end of reperfusion, biopsies were taken from the left gastrocnemius muscle for measurement of myeloperoxidase (MPO) and reduced glutathione (GSH). Before ischaemia and at the end of reperfusion, blood samples were taken for measurement of nitric oxide metabolites, tumour necrosis factor (TNF) alpha and macrophage inflammatory protein (MIP) 2.

RESULTS

IPC before I/R resulted in lower levels of MPO (P < 0.001) and TNF-alpha (P = 0.004), and higher levels of GSH (P < 0.001) and nitric oxide metabolites (P = 0.002) than I/R alone. Adenosine had effects comparable to IPC pretreatment (P < 0.001 for MPO, P = 0.002 for GSH, P = 0.02 for nitric oxide metabolites and P = 0.001 for TNF-alpha). There was no difference in the blood pressure or the MIP-2 concentration among the groups.

CONCLUSION

IPC or pretreatment with adenosine ameliorates the I/R injury of skeletal muscle.

Clinical effects of ischemic preconditioning

A variety of experimental studies have confirmed that preconditioning the myocardium by brief periods of ischemia represents a powerful cardioprotective effect resulting in a reduction of infarct size. After 15 years of research in the experimental laboratory, some evidence shows the existence of preconditioning in human patients with coronary artery disease: repeated balloon inflations before coronary angioplasty induce preconditioning-like effects; moreover, some studies demonstrate better clinical outcome in patients with angina before acute myocardial infarction, resembling a preconditioning effect. So far, a few drugs have been identified as potential mediators of preconditioning, e.g., adenosine, adenosine receptor agonists, and adenosine triphosphate-sensitive potassium channel openers. Before coronary angioplasty and heart surgery, these preconditioning mimetics might be used to protect myocardial tissue by means of preconditioning. Further research is required before preconditioning mimetics could be used for therapy in patients with chronic myocardial ischemia. Possible antipreconditioning effects of several drugs, e.g., sulfonylurea drugs have to be considered in the treatment of patients with coronary artery disease.

Tumor necrosis factor-alpha and interleukin-1beta synergistically depress human myocardial function

OBJECTIVE

Proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta have been implicated in the pathogenesis of myocardial dysfunction in ischemia-reperfusion injury, sepsis, chronic heart failure, viral myocarditis, and cardiac allograft rejection. Although circulating TNF-alpha and IL-1beta are both often elevated in septic shock, it remains unknown whether TNF-alpha or IL-1beta are the factors induced during sepsis that directly depress human myocardial function, and if so, whether the combination synergistically depresses myocardial function. Furthermore, the mechanism(s) by which these cytokines induce human myocardial depression remain unknown. We hypothesized the following: a) TNF-alpha and IL-1beta directly depress human myocardial function; b) together, TNF-alpha and IL-1beta act synergistically to depress human myocardial function; and c) inhibition of ceramidase or nitric oxide synthase attenuates myocardial depression induced by TNF-alpha or IL-1beta by limiting proximal cytokine signaling or production of myocardial nitric oxide (NO).

DESIGN

Prospective, randomized, controlled study.

SETTING

Experimental laboratory in a university hospital.

SUBJECTS

Freshly obtained human myocardial trabeculae.

INTERVENTIONS

Human atrial trabeculae were obtained at the time of cardiac surgery, suspended in organ baths, and field simulated at 1 Hz, and the developed force was recorded. After a 90-min equilibration, TNF-alpha (1.25, 12.5, 125, or 250 pg/mL for 20 mins), IL-1beta (6.25, 12.5, 50, or 200 pg/mL for 20 mins), or TNF-alpha (1.25 pg/mL) plus IL-1beta (6.25 pg/mL) were added to the bath, and function was measured for the subsequent 100 mins after the 20-min exposure. To assess the roles of the sphingomyelin and NO pathways in TNF-alpha and IL-1beta cross-signaling, the ceramidase inhibitor N-oleoyl ethanolamine (1 microM) or the NO synthase inhibitor N(G)-monomethyl-L-arginine (10 microM) was added before TNF-alpha (125 pg/mL) or IL-1beta (50 pg/mL).

MEASUREMENTS AND MAIN RESULTS

TNF-alpha and IL-1beta each depressed human myocardial function in a dose-dependent fashion (maximally depressing to 16.2 + 1.9% baseline developed force for TNF-alpha and 25.7 + 6.3% baseline developed force for IL-1beta), affecting systolic relatively more than diastolic performance (each p < .05). However, when combined, TNF-alpha and IL-1beta at concentrations that did not individually result in depression (p > .05 vs. control) resulted in contractile depression (p < .05 vs. control). Inhibition of myocardial sphingosine or NO release abolished the myocardial depressive effects of either TNF-alpha or IL-1beta.

CONCLUSIONS

TNF-alpha and IL-1beta separately and synergistically depress human myocardial function. Sphingosine likely participates in the TNF-alpha and IL-1beta signal leading to human myocardial functional depression. Therapeutic strategies to reduce production or signaling of either TNF-alpha or IL-1beta may limit myocardial dysfunction in sepsis.

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.

An overview of tumor necrosis factor alpha and the failing human heart

Recent studies have identified the importance of biologically active molecules (e.g., neurohormones) in disease progression in heart failure. In addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggest that the cytokines (e.g., tumor necrosis factor alpha), much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.

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.