Selective accumulation of the first component of complement and leukocytes in ischemic canine heart muscle. A possible initiator of an extra myocardial mechanism of ischemic injury

Growth factor therapy for cardiac repair: an overview of recent advances and future directions

Heart disease represents a significant public health burden and is associated with considerable morbidity and mortality at the level of the individual. Current therapies for pathologies such as myocardial infarction, cardiomyopathy and heart failure are unable to repair damaged tissue to an extent that provides restoration of function approaching that of the pre-diseased state. Novel approaches to repair and regenerate the injured heart include cell therapy and the use of exogenous factors. Improved understanding of the role of growth factors in endogenous cardiac repair processes has motivated the investigation of their potential as therapeutic agents for cardiac pathology. Despite the disappointing performance of other growth factors in historical clinical trials, insulin-like growth factor 1 (IGF-1), neuregulin and platelet-derived growth factor (PDGF) have recently emerged as new candidate therapies. These growth factors elicit tissue repair through anti-apoptotic, pro-angiogenic and fibrosis-modulating mechanisms and have produced clinically significant functional improvement in preclinical studies. Early human trials suggest that IGF-1 and neuregulin are well tolerated and yield dose-dependent benefit, warranting progression to later phase studies. However, outstanding challenges such as short growth factor serum half-life and insufficient target-organ specificity currently necessitate the development of novel delivery strategies.

The Lectin Pathway of Complement in Myocardial Ischemia/Reperfusion Injury-Review of Its Significance and the Potential Impact of Therapeutic Interference by C1 Esterase Inhibitor

Acute myocardial infarction (AMI) remains a leading cause of morbidity and mortality in modern medicine. Early reperfusion accomplished by primary percutaneous coronary intervention is pivotal for reducing myocardial damage in ST elevation AMI. However, restoration of coronary blood flow may paradoxically trigger cardiomyocyte death secondary to a reperfusion-induced inflammatory process, which may account for a significant proportion of the final infarct size. Unfortunately, recent human trials targeting myocardial ischemia/reperfusion (I/R) injury have yielded disappointing results. In experimental models of myocardial I/R injury, the complement system, and in particular the lectin pathway, have been identified as major contributors. In line with this, C1 esterase inhibitor (C1INH), the natural inhibitor of the lectin pathway, was shown to significantly ameliorate myocardial I/R injury. However, the hypothesis of a considerable augmentation of myocardial I/R injury by activation of the lectin pathway has not yet been confirmed in humans, which questions the efficacy of a therapeutic strategy solely aimed at the inhibition of the lectin pathway after human AMI. Thus, as C1INH is a multiple-action inhibitor targeting several pathways and mediators simultaneously in addition to the lectin pathway, such as the contact and coagulation system and tissue leukocyte infiltration, this may be considered as being advantageous over exclusive inhibition of the lectin pathway. In this review, we summarize current concepts and evidence addressing the role of the lectin pathway as a potent mediator/modulator of myocardial I/R injury in animal models and in patients. In addition, we focus on the evidence and the potential advantages of using the natural inhibitor of the lectin pathway, C1INH, as a future therapeutic approach in AMI given its ability to interfere with several plasmatic cascades. Ameliorating myocardial I/R injury by targeting the complement system and other plasmatic cascades remains a valid option for future therapeutic interventions.

Leucocytes and cardiopulmonary bypass: in vitro production of oxygen free radicals and trapping in the reperfused myocardium

The production of oxygen free radicals (OFR) by leucocytes was evaluated ex vivo by chemiluminescence (CL) before, during and after routine coronary artery bypass surgery (group A, n=11). The possibility of leucocyte trapping in the coronary circulation during the early reperfusion period was also investigated (group B, n=9). In group A, arterial blood samples were taken immediately before the start of surgery during anaesthesia, five minutes before and five and 30 minutes after the start of cardiopulmonary bypass (CPB), five minutes before and five and 30 minutes after the start of reperfusion of the heart, and then four and 24 hours after the end of CPB. In group B, arterial and coronary sinus blood samples were simultaneously drawn five and 30 minutes after the release of the aortic crossclamp. All blood samples were corrected for haemodilution. In group A, both CL and the level of circulating leucocytes declined during CPB. The lowest value of CL was measured 30 minutes after the start of CPB (69± 2% of baseline values) (mean±SEM). The lowest level of leucocytes was found after 30 minutes of CPB: 2.6±0.4 (109/l) vs 4.2±0.5 before surgery. Twenty-four hours after CPB, CL was increased to 170±49% and a leucocytosis was present (12.2±1.1). In group B, after five minutes of reperfusion the number of circulating leucocytes in arterial blood was 3.8±0.9 x 10 9/l as compared to 2.2±0.5 x 109/l in the coronary sinus (p<0.0017). However, no such difference was found after 30 minutes of reperfusion. The decreased CL during CPB was probably due to in vivo activation and exhaustion of leucocytes. The postischaemic trapping of these cells may play a pathogenetic role in reperfusion injury.

Influence of persistent organic pollutants on the complement system in a population-based human sample

BACKGROUND

Persistent organic pollutants (POPs) are toxic compounds generated through various industrial activities and have adverse effects on human health. Studies performed in cell cultures and animals have revealed that POPs can alter immune-system functioning. The complement system is part of innate immune system that helps to clear pathogens from the body. We performed a large-scale population-based study to find out associations between summary measures of different POPs and different complement system markers.

METHODS

In this cross-sectional study, 16 polychlorinated biphenyls (PCBs), 3 organochlorine (OC) pesticides, octachloro-p-dibenzodioxin, and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) were analyzed for their association with levels of protein complement 3 (C3), 3a (C3a), 4 (C4) and C3a/C3 ratio. A total of 992 individuals (all aged 70 years, 50% females) were recruited from the Prospective Investigation of the Vasculature in Uppsala Seniors cohort. Regression analysis adjusting for a variety of confounders was performed to study the associations of different POP exposures (total toxic equivalency value or TEQ and sum of 16 PCBs) with protein complements.

RESULTS

The TEQ values were found to be positively associated with C3a (β=0.07, 95% CI=0.017-0.131, p=0.01) and C3a/C3 ratio (β=0.07, 95% CI=0.015-0.126, p=0.01) taking possible confounders into account. The association observed was mainly driven by PCB-126.

CONCLUSION

In this study involving 992 elderly individuals from the general population, we showed that POPs, mainly PCB-126, were associated with levels of complement system markers indicating that the association of these toxic compounds with downstream disease could be mediated by activation of immune system.

Human C1 inhibitor attenuates liver ischemia-reperfusion injury and promotes liver regeneration

Liver ischemia-reperfusion injury (IRI) is a well-known cause of morbidity and mortality after liver transplantation (LT). Activation of the complement system contributes to the pathogenesis of IRI. Effective treatment strategies aimed at reducing hepatic IRI and accelerating liver regeneration could offer major benefits in LT. Herein, we investigated the effect of C1-esterase inhibitor (human) [C1-INH] on IRI and liver regeneration. Mice were subjected to 60-min partial IRI, with or without 70% partial hepatectomy, or CCl4-induced acute liver failure. Before liver injury, the animals were pretreated with intravenous C1-INH or normal saline. Liver IRI was evaluated using serum levels of alanine aminotransferase, serum interleukin-6, and histopathology. Liver samples were stained for specific markers of regeneration (5-bromo-2'-deoxyuridine [BrdU] staining and proliferating cell nuclear antigen [PCNA]). Histology, serum interleukin-6, and alanine aminotransferase release revealed that C1-INH treatment attenuated liver injury compared with controls. Improved animal survival and increased number of BrdU- and PCNA-positive cells were observed in C1-INH-treated animals which underwent IRI + partial hepatectomy or CCl4 injection compared with control group. These data indicate that complement plays a key role in IRI and liver regeneration. C1-INH represents a potential therapeutic strategy to reduce IRI and promote regeneration in LT.

Role of complement and perspectives for intervention in ischemia-reperfusion damage

Reperfusion of an organ following prolonged ischemia instigates the pro-inflammatory and pro-coagulant response of ischemia / reperfusion (IR) injury. IR injury is a wide-spread pathology, observed in many clinically relevant situations, including myocardial infarction, stroke, organ transplantation, sepsis and shock, and cardiovascular surgery on cardiopulmonary bypass. Activation of the classical, alternative, and lectin complement pathways and the generation of the anaphylatoxins C3a and C5a lead to recruitment of polymorphonuclear leukocytes, generation of radical oxygen species, up-regulation of adhesion molecules on the endothelium and platelets, and induction of cytokine release. Generalized or pathway-specific complement inhibition using protein-based drugs or low-molecular-weight inhibitors has been shown to significantly reduce tissue injury and improve outcome in numerous in-vitro, ex-vivo, and in-vivo models. Despite the obvious benefits in experimental research, only few complement inhibitors, including C1-esterase inhibitor, anti-C5 antibody, and soluble complement receptor 1, have made it into clinical trials of IR injury. The results are mixed, and the next objectives should be to combine knowledge and experience obtained in the past from animal models and channel future work to translate this into clinical trials in surgical and interventional reperfusion therapy as well as organ transplantation.

The giant danio (D. aequipinnatus) as a model of cardiac remodeling and regeneration

The paucity of mammalian adult cardiac myocytes (CM) proliferation following myocardial infarction (MI) and the remodeling of the necrotic tissue that ensues, result in non-regenerative repair. In contrast, zebrafish (ZF) can regenerate after an apical resection or cryoinjury of the heart. There is considerable interest in models where regeneration proceeds in the presence of necrotic tissue. We have developed and characterized a cautery injury model in the giant danio (GD), a species closely related to ZF, where necrotic tissue remains part of the ventricle, yet regeneration occurs. By light and transmission electron microscopy (TEM), we have documented four temporally overlapping processes: (1) a robust inflammatory response analogous to that observed in MI, (2) concomitant proliferation of epicardial cells leading to wound closure, (3) resorption of necrotic tissue and its replacement by granulation tissue, and (4) regeneration of the myocardial tissue driven by 5-EDU and [(3) H]thymidine incorporating CMs. In conclusion, our data suggest that the GD possesses robust repair mechanisms in the ventricle and can serve as an important model of cardiac inflammation, remodeling and regeneration.

Protective effects of Carthamus tinctorius injection on isoprenaline-induced myocardial injury in rats

CONTEXT

Carthamus tinctorius injection (CTI) is a traditional Chinese medicine (TCM) specifically used for the treatment of cerebral ischemia and myocardial ischemia.

OBJECTIVE

This study evaluated the protective effects of CTI on isoprenaline-induced acute myocardial ischemia (AMI) in rats and explored the underlying mechanisms.

MATERIALS AND METHODS

(i) Sprague-Dawley rats were randomly divided into 5 groups: control, myocardial ischemia model, and high-, low-dose of CTI groups (2.5 and 0.625 g/kg, respectively, i.p. for 5 days), and Xiang-Dan (20 g/kg) group (n = 10 in each group). AMI was induced by isoproterenol (5 mg/kg) by intraperitoneal injection. Assessment of electrocardiograms (ECG) was carried out. (ii) Another 40 rats were randomly divided into 5 groups, the concentration of IL-6 and TNF-α in serum were measured by radioimmunological assay; Bcl-2 and Bax protein expression were measured by immunohistochemistry.

RESULTS

CTI (2.5 and 0.625 g/kg) significantly inhibited the typical ECG S-T segment elevation, reduced concentration of IL-6 and TNF-α in serum, suppressed overexpression of Bax protein and also inhibited the reduction of Bcl-2 expression and markedly depressed the Bax/Bcl-2 ratio.

DISCUSSION AND CONCLUSION

These findings demonstrate that CTI is cardioprotective against AMI in rats and is likely to related to decrease inflammatory response mediated by TNF-α and IL-6, down-regulate protein level of Bax and up-regulate that of Bcl-2 in the heart tissue.

The axonal repellent, Slit2, inhibits directional migration of circulating neutrophils

In inflammatory diseases, circulating neutrophils are recruited to sites of injury. Attractant signals are provided by many different chemotactic molecules, such that blockade of one may not prevent neutrophil recruitment effectively. The Slit family of secreted proteins and their transmembrane receptor, Robo, repel axonal migration during CNS development. Emerging evidence shows that by inhibiting the activation of Rho-family GTPases, Slit2/Robo also inhibit migration of other cell types toward a variety of chemotactic factors in vitro and in vivo. The role of Slit2 in inflammation, however, has been largely unexplored. We isolated primary neutrophils from human peripheral blood and mouse bone marrow and detected Robo-1 expression. Using video-microscopic live cell tracking, we found that Slit2 selectively impaired directional migration but not random movement of neutrophils toward fMLP. Slit2 also inhibited neutrophil migration toward other chemoattractants, namely C5a and IL-8. Slit2 inhibited neutrophil chemotaxis by preventing chemoattractant-induced actin barbed end formation and cell polarization. Slit2 mediated these effects by suppressing inducible activation of Cdc42 and Rac2 but did not impair activation of other major kinase pathways involved in neutrophil migration. We further tested the effects of Slit2 in vivo using mouse models of peritoneal inflammation induced by sodium periodate, C5a, and MIP-2. In all instances, Slit2 reduced neutrophil recruitment effectively (P<0.01). Collectively, these data demonstrate that Slit2 potently inhibits chemotaxis but not random motion of circulating neutrophils and point to Slit2 as a potential new therapeutic for preventing localized inflammation.

The mannose-binding lectin pathway is a significant contributor to reperfusion injury in the type 2 diabetic heart

The severity of ischaemic heart disease is markedly enhanced in type 2 diabetes. We recently reported that complement activation exacerbates I/R injury in the type 2 diabetic heart. The purpose of this study was to isolate and examine MBL pathway activation following I/R injury in the diabetic heart. ZLC and ZDF rats underwent 30 minutes of left coronary artery occlusion followed by 120 minutes of reperfusion. Two different groups of ZDF rats were treated with either FUT-175, a broad complement inhibitor, or P2D5, a monoclonal antibody raised against rat MBL-A. ZDF rats treated with FUT175 and P2D5 had significantly decreased myocardial infarct size, C3 deposition and neutrophil accumulation compared with untreated ZDF controls. Taken together, these findings indicate that the MBL pathway plays a key role in the severity of complement-mediated I/R injury in the type 2 diabetic heart.

Ca2+/calmodulin-dependent kinase II triggers cell membrane injury by inducing complement factor B gene expression in the mouse heart

Myocardial Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibition improves cardiac function following myocardial infarction (MI), but the CaMKII-dependent pathways that participate in myocardial stress responses are incompletely understood. To address this issue, we sought to determine the transcriptional consequences of myocardial CaMKII inhibition after MI. We performed gene expression profiling in mouse hearts with cardiomyocyte-delimited transgenic expression of either a CaMKII inhibitory peptide (AC3-I) or a scrambled control peptide (AC3-C) following MI. Of the 8,600 mRNAs examined, 156 were substantially modulated by MI, and nearly half of these showed markedly altered responses to MI with CaMKII inhibition. CaMKII inhibition substantially reduced the MI-triggered upregulation of a constellation of proinflammatory genes. We studied 1 of these proinflammatory genes, complement factor B (Cfb), in detail, because complement proteins secreted by cells other than cardiomyocytes can induce sarcolemmal injury during MI. CFB protein expression in cardiomyocytes was triggered by CaMKII activation of the NF-kappaB pathway during both MI and exposure to bacterial endotoxin. CaMKII inhibition suppressed NF-kappaB activity in vitro and in vivo and reduced Cfb expression and sarcolemmal injury. The Cfb-/- mice were partially protected from the adverse consequences of MI. Our findings demonstrate what we believe is a novel target for CaMKII in myocardial injury and suggest that CaMKII is broadly important for the genetic effects of MI in cardiomyocytes.

C1 inhibitor: just a serine protease inhibitor? New and old considerations on therapeutic applications of C1 inhibitor

C1 inhibitor is a potent anti-inflammatory protein as it is the major inhibitor of proteases of the contact and the complement systems. C1-inhibitor administration is an effective therapy in the treatment of patients with hereditary angioedema (HAE) who are genetically deficient in C1 inhibitor. Owing to its ability to modulate the contact and complement systems and the convincing safety profile, plasma-derived C1 inhibitor is an attractive therapeutic protein to treat inflammatory diseases other than HAE. In the present review we give an overview of the biology of C1 inhibitor and its use in HAE. Furthermore, we discuss C1 inhibitor as an experimental therapy in diseases such as sepsis and myocardial infarction.

Beneficial effects of C1 esterase inhibitor in ST-elevation myocardial infarction in patients who underwent surgical reperfusion: a randomised double-blind study

BACKGROUND

The inflammatory cascade has been hypothesized to be an important mechanism of post-ischaemic myocardial reperfusion injury and several studies demonstrated that C1 esterase inhibitor (C1-INH) is effective in post-ischaemia myocardial protection. Therefore, we aimed to investigate prospectively in a randomised double-blind study the cardioprotective effects of C1-INH in ST segment elevation myocardial infarction (STEMI) in patients who underwent emergent reperfusion with coronary artery bypass grafting (CABG).

METHODS

In this study, we enrolled 80 patients affected with STEMI who underwent emergent CABG. Patients were assigned in two groups (C1-INH group: receive 1000 UI of C1-INH; and placebo group: receive a saline solution). The effects of C1-INH on complement inhibition, myocardial cell injury extension and clinical outcome were studied. Haemodynamic data and myocardial function were monitored. C1-INH, C3a, C4a complement activation fragments and cardiac troponin I (cTnI) serum levels were measured before, during and after surgery.

RESULTS

Patient characteristics were not different between the two groups. The overall in-hospital mortality rate was 6.2%. No statistical significant difference was observed between the two groups with regard to early mortality (p=0.36). Statistical significant difference between the two groups was showed for cardiopulmonary bypass support (p=0.04), administration of high dose of inotropes drugs (p=0.001), time of intubation (p=0.03), intensive care unit (ICU) stay (p=0.04) and in-hospital stay (p=0.03). A significant improvement in mean arterial pressure (p=0.03), cardiac index (p=0.02) and stroke volume (p=0.03) was showed in C1-INH group versus placebo group. The serum cTnI levels were significantly low in the C1-INH group versus placebo group after reperfusion, during the observation period. Plasma levels of C3a and C4a complement fragments were reduced significantly in C1-INH group. No drugs-related adverse effects were observed.

CONCLUSIONS

The inhibition of the classic complement pathway by C1-INH appears to be an effective mean of preserving ischaemic myocardium from reperfusion injury as demonstrated by low serum cTnI levels in C1-INH group. Therefore, the use of C1-INH during CABG as a rescue therapy in STEMI patients is probably an effective treatment to inhibit complement activity and to improve cardiac function and haemodynamic performance without impacting early mortality. Large randomised study should be performed to support our results.

Protective role of unconjugated bilirubin on complement-mediated hepatocytolysis

Hyperbilirubinemia and complement-mediated immune attack on hepatocyte membrane are common features of certain hepatic diseases. To assess whether unconjugated bilirubin (UB) counteracts complement-mediated hepatocytolysis, we first generated a rabbit polyclonal antibody (Ab) against rat hepatocyte plasma membrane (RHPM). An assay performed with isolated rat hepatocytes in the presence of the polyclonal Ab and rat serum as complement donor demonstrated that UB inhibits cell lysis, as lactate dehydrogenase release into the medium was inhibited by the pigment in a dose-dependent manner. Immunofluorescence microscopy studies showed that UB significantly attenuates the binding of C3 to the hepatocyte-Ab complex. Further enzyme immunoassay studies showed that UB interferes the binding of C1q to purified anti-RHPM IgG, also in a dose-dependent manner. A dot-blot assay showed that [14C]-UB binds to C1q and human serum albumin (HSA) to a similar extent. A differential spectrum analysis of UB in the presence of C1q further confirmed that the pigment interacts with this protein. In conclusion, we demonstrated an inhibitory action of UB on complement-mediated Ab-induced hepatocytolysis, this action being evidenced at pathophysiological pigment concentrations (171 microM and higher). A direct binding of the pigment to C1q is likely involved.

Anti-ischemia/reperfusion of C1 inhibitor in myocardial cell injury via regulation of local myocardial C3 activity

C3 is common to all pathways of complement activation augmenting ischemia/reperfusion (I/R)-induced myocardial injury and cardiac dysfunction. Complement inhibition with the complement regulatory protein, C1 inhibitor (C1INH), obviously exerts cardioprotective effects. Here, we examine whether C1INH regulates C3 activity in the ischemic myocardial tissue. C1INH markedly suppressed C3 mRNA expression and protein synthesis in both a model of I/R-induced rat acute myocardial infarction (AMI) and the cultured rat H9c2 heart myocytes. At least, this regulation was at the transcriptional level in response to oxygen tension. In vitro, C3 deposition on, and binding to, the surface of rat myocardial cells were significantly blocked by C1INH treatment. C1INH could inhibit classical complement-mediated cell lysis via suppressing the biological activity of C3. Therefore, C1INH, in addition to inhibition of the systemic complement activation, prevents myocardial cell injury via a direct inhibitory role in the local myocardial C3 activity.

Role of Adenosine as Adjunctive Therapy in Acute Myocardial Infarction

Although early reperfusion and maintained patency is the mainstay therapy for ST elevation myocardial infarction, experimental studies demonstrate that reperfusion per se induces deleterious effects on viable ischemic cells. Thus "myocardial reperfusion injury" may compromise the full potential of reperfusion therapy and may account for unfavorable outcomes in high-risk patients. Although the mechanisms of reperfusion injury are complex and multifactorial, neutrophil-mediated microvascular injury resulting in a progressive decrease in blood flow ("no-reflow" phenomenon) likely plays an important role. Adenosine is an endogenous nucleoside found in large quantities in myocardial and endothelial cells. It activates four well-characterized receptors producing various physiological effects that attenuate many of the proposed mechanisms of reperfusion injury. The cardio-protective effects of adenosine are supported by its role as a mediator of pre- and post-conditioning. In experimental models, administration of adenosine in the peri-reperfusion period results in a marked reduction in infarct size and improvement in ventricular function. The cardioprotective effects in the canine model have a narrow time window with the drug losing its effect following three hours of ischemia. Several small clinical studies have demonstrated that administration of adenosine with reperfusion therapy reduces infarct size and improves ventricular function. In the larger AMISTAD and AMISTAD II trials a 3-h infusion of adenosine as an adjunct to reperfusion resulted in a striking reduction in infarct size (55-65%). Post hoc analysis of AMISTAD II showed that this was associated with significantly improved early and late mortality in patients treated within 3.17 h of symptoms. An intravenous infusion of adenosine for 3 h should be considered as adjunctive therapy in high risk-patients undergoing reperfusion therapy.

Proteome analysis of myocardial tissue following ischemia and reperfusion--effects of complement inhibition

Myocardial ischemia-reperfusion injury can be related to complement activation with generation of chemotactic mediators, release of cytokines, leukocyte accumulation, and subsequent severe tissue injury. In this regard, activation of transcription factors (i.e., NFkappaB) and de novo protein synthesis or inflammatory protein degradation seems to play an important role. In the present study, we analyzed the cardiac protein expression following myocardial ischemia (60 min) and reperfusion (180 min) in a rabbit model utilizing two-dimensional electrophoresis and nanoHPLC/ESI-MS/MS for biochemical protein identification. To achieve cardioprotective effects, we used a novel highly selective small molecule C1s inhibitor administered 5 min prior to reperfusion. The reduction of myocardial injury was observed as diminished plasma creatine kinase activity in C1s-INH-248-treated animals (65.2+/-3 vs. 38.5+/-3 U/g protein after 3 h of reperfusion, P<0.05). With proteome analysis we were able to detect 509+/-21 protein spots on the gels of the 3 groups. A pattern of 480 spots with identical positions was found on every gel of myocardial tissue of sham animals, vehicle and C1s-INH-248-treated animals. We analyzed 11 spots, which were identified by mass spectrometry: Superoxide dismutase, alpha-crystallin-chain-B, mitochondrial stress protein, Mn SOD, ATP synthase A chain heart isoform, creatine kinase, and troponin T. All of these proteins were significantly decreased in the vehicle group when we compared to sham-treated animals. Treatment with C1s-INH-248 preserved levels of these proteins. Thus, blocking the classical complement pathway with a highly specific and potent synthetic inhibitor of the activated C1 complex archives cardio-protection by altering and preserving different anti-inflammatory and cytoprotective cascades.

Inhibition of classical complement activation attenuates liver ischaemia and reperfusion injury in a rat model

Activation of the complement system contributes to the pathogenesis of ischaemia/reperfusion (I/R) injury. We evaluated inhibition of the classical pathway of complement using C1-inhibitor (C1-inh) in a model of 70% partial liver I/R injury in male Wistar rats (n = 35). C1-inh was administered at 100, 200 or 400 IU/kg bodyweight, 5 min before 60 min ischaemia (pre-I) or 5 min before 24 h reperfusion (end-I). One hundred IU/kg bodyweight significantly reduced the increase of plasma levels of activated C4 as compared to albumin-treated control rats and attenuated the increase of alanine aminotransferase (ALT). These effects were not better with higher doses of C1-inh. Administration of C1-inh pre-I resulted in lower ALT levels and higher bile secretion after 24 h of reperfusion than administration at end-I. Immunohistochemical assessment indicated that activated C3, the membrane attack complex C5b9 and C-reactive protein (CRP) colocalized in hepatocytes within midzonal areas, suggesting CRP is a mediator of I/R-induced, classical complement activation in rats. Pre-ischaemic administration of C1-inh is an effective pharmacological intervention to protect against liver I/R injury.

Phase 2 ventricular arrhythmias in acute myocardial infarction: a neglected target for therapeutic antiarrhythmic drug development and for safety pharmacology evaluation

Ventricular fibrillation (VF), a cause of sudden cardiac death (SCD) in the setting of acute myocardial infarction (MI), remains a major therapeutic challenge. In humans, VF may occur within minutes or hours after the onset of chest pain, so its precise timing in relation to the onset of ischaemia is variable. Moreover, because VF usually occurs unobserved, out of hospital, and is usually lethal in the absence of intervention, its precise timing of onset is actually unknown in most patients. In animal models, the timing of susceptibility to VF is much better characterised. It occurs in two distinct phases. Early VF (defined as phase 1 VF, with possible subphases 1a and 1b in some animal species) occurs during the first 30 min of ischaemia when most myocardial injury is still reversible. Late VF, defined as phase 2 VF, occurs when myocardial necrosis is becoming established (after more than 90 min of ischaemia). Although much is known about the mechanisms and pharmacology of phase 1 VF, little is known about phase 2 VF. By reviewing a range of different types of data we have outlined the likely mechanisms and clinical relevance of phase 2 VF, and have evaluated possible future directions to help evolve a strategy for its suppression by drugs. The possibility that a proarrhythmic effect on phase 2 VF contributes to the adverse cardiac effects of certain cardiac and noncardiac drugs is also discussed in relation to the emerging field of safety pharmacology. It is concluded that suppression of phase 2 as well as phase 1 VF will almost certainly be necessary if drugs of the future are to achieve what drugs of the past and present have failed to achieve: full protection against SCD. Likewise, safety will require avoidance of exacerbation of phase 2 as well as phase 1 VF.

Locally targeted cytoprotection with dextran sulfate attenuates experimental porcine myocardial ischaemia/reperfusion injury

AIMS

Intravascular inflammatory events during ischaemia/reperfusion injury following coronary angioplasty alter and denudate the endothelium of its natural anticoagulant heparan sulfate proteoglycan (HSPG) layer, contributing to myocardial tissue damage. We propose that locally targeted cytoprotection of ischaemic myocardium with the glycosaminoglycan analogue dextran sulfate (DXS, MW 5000) may protect damaged tissue from reperfusion injury by functional restoration of HSPG.

METHODS AND RESULTS

In a closed chest porcine model of acute myocardial ischaemia/reperfusion injury (60 min ischaemia, 120 min reperfusion), DXS was administered intracoronarily into the area at risk 5 min prior to reperfusion. Despite similar areas at risk in both groups (39+/-8% and 42+/-9% of left ventricular mass), DXS significantly decreased myocardial infarct size from 61+/-12% of the area at risk for vehicle controls to 39+/-14%. Cardioprotection correlated with reduced cardiac enzyme release creatine kinase (CK-MB, troponin-I). DXS abrogated myocardial complement deposition and substantially decreased vascular expression of pro-coagulant tissue factor in ischaemic myocardium. DXS binding, detected using fluorescein-labelled agent, localized to ischaemically damaged blood vessels/myocardium and correlated with reduced vascular staining of HSPG.

CONCLUSION

The significant cardioprotection obtained through targeted cytoprotection of ischaemic tissue prior to reperfusion in this model of acute myocardial infarction suggests a possible role for the local modulation of vascular inflammation by glycosaminoglycan analogues as a novel therapy to reduce reperfusion injury.

Dermatan disulfate (Intimatan) prevents complement-mediated myocardial injury in the human-plasma-perfused rabbit heart

Intimatan (dermatan 4,6-O-disulfate), a heparin cofactor II agonist, is a highly sulfated negatively charged semisynthetic polysaccharide. The present study examined the hypothesis that Intimatan reduces complement-mediated myocardial injury. The rabbit isolated heart was perfused with 4% normal human plasma (NHP) as a source of complement in the absence or presence of Intimatan (5 microM). Heat-inactivated human plasma (HIHP) was used as a negative control. Previous studies demonstrated that contact of rabbit tissue with human plasma results in activation of the alternative pathway of the human complement system, leading to irreversible myocardial injury. In the presence of NHP, left ventricular end-diastolic pressure (LVEDP) was increased significantly to 61.8+/-11.7 mm Hg compared to a value of 17.2+/-6.1 mm Hg in hearts perfused in the presence of HIHP. Left ventricular developed pressure (LVDP) was reduced significantly upon exposure to NHP, 19.3+/-10.2 (NHP) vs. 54.0+/-8.0 mm Hg (HIHP). Functional impairment in the presence of NHP was accompanied by a significant release of cardiac troponin I (cTnI; 131.8+/-20.3 ng/ml) as compared to hearts exposed to HIHP (0.8+/-0.8). Intimatan treatment improved cardiac function and maintained viability of cardiac myocytes (LVEDP 14.6+/-5.6, LVDP 58.0+/-8.1 mm Hg and cTnI 6.7+/-5.2 ng/ml). Immunohistochemical staining demonstrated that Intimatan pretreatment prevented deposition of the human membrane attack complex (MAC) in hearts exposed to NHP. The results indicate that Intimatan, a glycosaminoglycan (GAG), can reduce tissue injury and preserve organ function that otherwise would be compromised during activation of the human complement cascade.

C-reactive protein and complement depositions in human infarcted myocardium are more extensive in patients with reinfarction or upon treatment with reperfusion

BACKGROUND

Impaired perfusion of the heart induces a local inflammatory response, which involves deposition of C-reactive protein and complement activation products C3d and C5b-9. We investigated whether reperfusion or reinfarction enhances these phenomena in humans.

MATERIALS AND METHODS

Depositions of C-reactive protein and complement were quantified in tissue samples of infarcted myocardium from 76 patients who had died after acute myocardial infarction. The extent of depositions in patients treated with reperfusion or suffering from reinfarction was compared with that in patients who had no reperfusion or reinfarction.

RESULTS

Patients with reinfarction had significantly more extensive depositions of C-reactive protein and complement (C3d and C5b-9) in the infarcted myocardium than patients without reinfarction. Similarly, patients who received reperfusion therapy had more extensive depositions also than those who had not received this therapy.

CONCLUSIONS

Both reinfarction and reperfusion therapy significantly increase the extent of C-reactive protein and complement depositions in human myocardial infarcts.

Amelioration of ischemia-reperfusion injury with cyclic peptide blockade of ICAM-1

Neutrophils are pivotal in the pathogenesis of ischemia-reperfusion (I/R) injury leading to muscle damage. Firm adhesion of neutrophils to the endothelium is initiated by an interaction between intercellular adhesion molecular-1 (ICAM-1) on the endothelium and beta(2)-integrins on neutrophils. Inhibition of ICAM-1-dependent binding using monoclonal antibodies has been shown to be efficacious in ameliorating I/R injury by preventing the influx of neutrophils into the ischemic tissue. We recently described a cyclic peptide that is a potent and selective inhibitor of ICAM-1 (IP25) in vitro. In this study, we tested the hypothesis that IP25-mediated blockade of ICAM-1 would inhibit neutrophil influx during reperfusion of ischemic tissue and consequently attenuate muscle injury in a tourniquet hindlimb murine model of I/R injury. Varying amounts of peptide drug were injected at the beginning of the reperfusion period. The neutrophil influx and size of infarction at the end of 2 h of reperfusion were compared with those in untreated control mice and contralateral nonischemic limbs. Mice receiving IP25 immediately before reperfusion showed a 56% reduction in neutrophil infiltration in the ischemic muscle, accompanied by a 40% reduction in the infarct size. No effect on I/R injury was seen if IP25 administration was delayed for 60 min after reperfusion. We conclude that IP25 effectively inhibits ICAM-1-mediated adhesion of neutrophils to the endothelium in mice leading to a protective effect and suggests that synthetic peptide antagonists have a potential role as therapeutic tools.

Pharmacologic Manipulation of the Labyrinth with Novel and Traditional Agents Delivered to the Inner Ear

We describe the methodology and rationale behind the delivery of therapeutic medicines to the inner ear. The inner ear has long been impervious to pharmacologic manipulation. This is most likely the result of a protective mechanism called the blood-labyrinth barrier, whose function closely resembles that of the blood-brain barrier. This protective barrier impedes the clinician's ability to treat inner ear diseases with systemically administered medications. Since 1935, otolaryngologists have attempted to manipulate the inner ear with transtympanically injected medicines. Success has varied widely, but medicinal ablation of vestibular function can be achieved in this manner. Unfortunately, the auditory system is also at great risk from any medicine that is delivered to the inner ear via the middle ear. Over the past 10 years, significant improvements in drug delivery have allowed for more “titratable” treatment, which has reduced (but not eliminated) the risk of permanent hearing loss. In this article, we discuss both novel and time-tested methods of delivering medicines to the inner ear. We also review the classes of medications that alter inner ear function and the attendant risks of such treatments.

Xanthine oxidase, but not neutrophils, contributes to activation of cardiac sympathetic afferents during myocardial ischaemia in cats

Activation of cardiac sympathetic afferents during myocardial ischaemia causes angina and induces important cardiovascular reflex responses. Reactive oxygen species (ROS) are important chemical stimuli of cardiac afferents during and after ischaemia. Iron-catalysed Fenton chemistry constitutes one mechanism of production of hydroxyl radicals. Another potential source of these species is xanthine oxidase-catalysed oxidation of purines. Polymorphonuclear leukocytes (PMNs) also contribute to the production of ROS in some conditions. The present study tested the hypothesis that both xanthine oxidase-catalysed oxidation of purines and neutrophils provide a source of ROS sufficient to activate cardiac afferents during ischaemia. We recorded single-unit activity of cardiac afferents innervating the ventricles recorded from the left thoracic sympathetic chain (T1-5) of anaesthetized cats to identify the afferents' responses to ischaemia. The role of xanthine oxidase in activation of these afferents was determined by infusion of oxypurinol (10 mg kg(-1), I.V.), an inhibitor of xanthine oxidase. The importance of neutrophils as a potential source of ROS in the activation of cardiac afferents during ischaemia was assessed by the infusion of a polyclonal antibody (3 mg ml(-1) kg(-1), I.V.) raised in rabbits immunized with cat PMNs. This antibody decreased the number of circulating PMNs and, to a smaller extent, platelets. Since previous data suggest that platelets release serotonin (5-HT), which activates cardiac afferents through a serotonin receptor (subtype 3,5-HT3 receptor) mechanism, before treatment with the antibody in another group, we blocked 5-HT3 receptors on sensory nerve endings with tropisetron (300 microg kg(-1), I.V.). We observed that oxypurinol significantly decreased the activity of cardiac afferents during myocardial ischaemia from 1.5 +/- 0.4 to 0.8 +/- 0.4 impulses s(-1). Similarly, the polyclonal antibody significantly reduced the discharge frequency of ischaemically sensitive cardiac afferents from 2.5 +/- 0.7 to 1.1 +/- 0.4 impulses s(-1). However, pre-blockade of 5-HT3 receptors eliminated the influence of the antibody on discharge activity of the afferents during ischaemia. This study demonstrates that ROS generated from the oxidation of purines contribute to the stimulation of ischaemically sensitive cardiac sympathetic afferents, whereas PMNs do not play a major role in this process.

Role of the complement system in ischaemic heart disease: potential for pharmacological intervention

The complement system is an innate, cytotoxic host defence system that normally functions to eliminate foreign pathogens. However, considerable evidence suggests that complement plays a key role in the pathophysiology of ischaemic heart disease (IHD). Experimental models of acute myocardial infarction (MI) and autopsy specimens taken from acute MI patients demonstrate that complement is selectively deposited in areas of infarction. Furthermore, inhibition of complement activation or depletion of complement components prior to myocardial reperfusion has been shown to reduce complement-mediated tissue injury in numerous animal models. IHD remains a leading cause of patient morbidity and mortality. Considerable effort in recent years has therefore been directed by biotechnology and pharmaceutical industries towards the development of novel, human complement inhibitors. Proposed anticomplement therapeutic strategies include the administration of naturally occurring or recombinant complement regulators, anticomplement monoclonal antibodies, and anticomplement receptor antagonists. Although data regarding the effectiveness of anticomplement therapy in humans is limited at present, a number of novel anticomplement therapeutic strategies are currently in clinical trials. The role of complement in IHD and potential for pharmacological intervention is reviewed.

Novel small molecule inhibitor of C1s exerts cardioprotective effects in ischemia-reperfusion injury in rabbits

Myocardial ischemia-reperfusion injury can be related to complement activation with generation of chemotactic agents, adhesion molecule expression, release of cytokines and oxygen-derived free radicals, and subsequent neutrophil accumulation. In the present study the cardioprotective effects of a novel highly selective small molecule C1s inhibitor (C1s-INH-248, Knoll) were examined in a rabbit model of myocardial ischemia (I) and reperfusion (R; i.e., 60 min I + 180 min R). In in vitro tests (enzyme activity and SRBC lysis) C1s-INH-248 demonstrated profound inhibitory potency. In vivo C1s-INH-248 (1 mg/kg body weight) administered 5 min before reperfusion significantly attenuated myocardial injury (31.9 +/- 2.5 vs 8.9 +/- 1.6% necrosis/area at risk; p < 0.01). The cardioprotective effect was dose dependent. The reduction of myocardial injury was also observed as diminished plasma creatine kinase activity in C1s-INH-248-treated animals (70.7 +/- 6.8 vs 45.1 +/- 3.9 U/g protein after 3 h of reperfusion, p < 0.05). Further, cardiac myeloperoxidase activity (i.e., a marker of PMN accumulation) in the ischemic and necrotic area was significantly reduced following C1s-INH-248 treatment (1.31 +/- 0.23 vs 0.4 +/- 0.05 U/100 mg tissue in necrotic area, p < 0.01). Thus, blocking the classical complement pathway with a highly specific and potent synthetic inhibitor of the activated C1 complex appears to be an effective mean to preserve ischemic myocardium from injury following reperfusion.

Complement and its implications in cardiac ischemia/reperfusion: strategies to inhibit complement

Although reperfusion of the ischemic myocardium is an absolute necessity to salvage tissue from eventual death, it is also associated with pathologic changes that represent either an acceleration of processes initiated during ischemia or new pathophysiological changes that were initiated after reperfusion. This so-called "reperfusion injury" is accompanied by a marked inflammatory reaction, which contributes to tissue injury. In addition to the well known role of oxygen free radicals and white blood cells, activation of the complement system probably represents one of the major contributors of the inflammatory reaction upon reperfusion. The complement may be activated through three different pathways: the classical, the alternative, and the lectin pathway. During reperfusion, complement may be activated by exposure to intracellular components such as mitochondrial membranes or intermediate filaments. Two elements of the activated complement contribute directly or indirectly to damages: anaphylatoxins (C3a and C5a) and the membrane attack complex (MAC). C5a, the most potent chemotactic anaphylatoxin, may attract neutrophils to the site of inflammation, leading to superoxide production, while MAC is deposited over endothelial cells and smooth vessel cells, leading to cell injury. Experimental evidence suggests that tissue salvage may be achieved by inhibition of the complement pathway. As the complement is composed of a cascade of proteins, it provides numerous sites for pharmacological interventions during acute myocardial infarction. Although various strategies aimed at modulating the complement system have been tested, the ideal approach probably consists of maintaining the activity of C3 (a central protein of the complement cascade) and inhibiting the later events implicated in ischemia/reperfusion and also in targeting inhibition in a tissue-specific manner.

Effects of endotoxin on neutrophil-mediated ischemia/reperfusion injury in the rat heart in vivo

We have previously shown that a nonlethal dose of lipopolysaccharide (LPS) decreases L-selectin expression of neutrophils (PMNs), thereby preventing PMN-mediated reperfusion injury in the isolated heart. In the present study we determined whether or not that dose of LPS would protect hearts during in vivo ischemia and reperfusion by preventing PMN-induced reperfusion injury. Rats receiving saline vehicle showed marked myocardial injury (necrotic area/area at risk = 82%+/-2%) and significant depression in left ventricular function as assessed in the isolated isovolumic heart preparation at constant flow rates of 5, 10, 15, and 20 ml/min. The administration of LPS (100 microg/kg body wt) 7 hr prior to ischemia resulted in a reduction in myocardial damage (necrotic area/area at risk = 42%+/-3%) and preservation of function. Myocardial function was similar to that of sham ischemic saline- and LPS-treated rats. Moreover, PMN infiltration as determined by histology was quantitatively more severe in hearts of saline-treated rats than in hearts of LPS-treated rats. Isolated hearts from vehicle- and LPS-treated animals undergoing sham ischemia in vivo recovered to the same extent after in vitro ischemia/reperfusion, suggesting that LPS did not induce protection by altering intrinsic properties of the heart. Our results indicate that LPS-induced protection of the heart from in vivo PMN-mediated ischemia/reperfusion injury may be due to decreased L-selectin expression of PMNs in LPS-treated animals.

alpha(4)-integrin mediates neutrophil-induced free radical injury to cardiac myocytes

Previous work has demonstrated that circulating neutrophils (polymorphonuclear leukocytes [PMNs]) adhere to cardiac myocytes via beta(2)-integrins and cause cellular injury via the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase enzyme system. Since PMNs induced to leave the vasculature (emigrated PMNs) express the alpha(4)-integrin, we asked whether (a) these PMNs also induce myocyte injury via NADPH oxidase; (b) beta(2)-integrins (CD18) still signal oxidant production, or if this process is now coupled to the alpha(4)-integrin; and (c) dysfunction is superoxide dependent within the myocyte or at the myocyte-PMN interface. Emigrated PMNs exposed to cardiac myocytes quickly induced significant changes in myocyte function. Myocyte shortening was decreased by 30-50% and rates of contraction and relaxation were reduced by 30% within the first 10 min. Both alpha(4)-integrin antibody (Ab)-treated PMNs and NADPH oxidase-deficient PMNs were unable to reduce myocyte shortening. An increased level of oxidative stress was detected in myocytes within 5 min of PMN adhesion. Addition of an anti-alpha(4)-integrin Ab, but not an anti-CD18 Ab, prevented oxidant production, suggesting that in emigrated PMNs the NADPH oxidase system is uncoupled from CD18 and can be activated via the alpha(4)-integrin. Addition of exogenous superoxide dismutase (SOD) inhibited all parameters of dysfunction measured, whereas overexpression of intracellular SOD within the myocytes did not inhibit the oxidative stress or the myocyte dysfunction caused by the emigrated PMNs. These findings demonstrate that profound molecular changes occur within PMNs as they emigrate, such that CD18 and associated intracellular signaling pathways leading to oxidant production are uncoupled and newly expressed alpha(4)-integrin functions as the ligand that signals oxidant production. The results also provide pathological relevance as the emigrated PMNs have the capacity to injure cardiac myocytes through the alpha(4)-integrin-coupled NADPH oxidase pathway that can be inhibited by extracellular, but not intracellular SOD.

Improved right ventricular function after intracoronary administration of a C1 esterase inhibitor in a right heart transplantation model

OBJECTIVE

Myocardial injury from ischemia can be augmented after reperfusion due to proinflammatory events including complement activation, leukocyte adhesion, and release of various chemical mediators. It has been shown that intracoronary administration of a C1 esterase inhibitor (C1 INH) significantly reduces myocardial necrosis in an experimental model of ischemia. Our study addresses the question whether the most susceptible region of the heart for ischemic injury, the right ventricle (RV), can benefit from the protective effects of C1 esterase inhibition after transplantation.

METHODS

To precisely control RV volume in vivo an isovolumic model was used in which the RV volume was regulated using an intracavity high compliance balloon inserted into donor hearts of domestic pigs (34+/-4 kg). After 4 h of ischemia, donor hearts were transplanted into recipient pigs (44+/-4 kg). Treatment groups, each with six animals, consisted of C1 INH treatment or control. After opening the cross clamp, the C1 INH group animals received 20 IU/kg body weight of C1 INH intracoronary over a 5 min period. The control animals received no drug therapy. The hearts were reperfused for 60 min, and thereafter the RV balloon volume was increased in 10 ml increments until RV failure occurred. These measurements were repeated after 120 min of reperfusion.

RESULTS

There was no significant difference in maximal RV developed pressure between the two groups (after 1 h, 35.7+/-5.9 vs. 40.6+/-12.7 mm Hg; after 2 h, 41.5+/-10.7 vs. 46.3+/-15.2 mm Hg; for C1 INH and control animals, respectively). However, the RV could be loaded with a significantly higher volume after both 1 h (60.0+/-20.0 ml (C1 INH) vs. 46.7+/-13.7 ml (control) balloon volume, P<0.05), and 2 h of reperfusion (70.0+/-8.9 ml vs. 60.0+/-6.3 ml; C1 INH and control animals, respectively; P<0.05).

CONCLUSIONS

Intracoronary administration of a C1 INH significantly improves right ventricular function in an experimental transplant model. Thus, inhibition of the classic complement cascade may be a promising therapeutic approach for effective protection of myocardium from reperfusion injury after transplantation.

Recombinant human complement C5a receptor antagonist reduces infarct size after surgical revascularization

OBJECTIVES

This study tested the hypothesis that a recombinant human C5a antagonist, CGS 32359, attenuates neutrophil activation and reduces infarct size in a porcine model of surgical revascularization.

METHODS

CGS 32359 (0.16-16 micromol/L) dose-dependently inhibited superoxide production by human C5a-activated porcine neutrophils (18 +/- 3.7 vs 1.6 +/- 0.5 nmol/5 min/5 x 10(6) neutrophils; P <.05) and reduced neutrophil adherence to coronary endothelium from 194 +/- 9 to 43 +/- 6 neutrophils/mm(2) (P <.05). The left anterior descending coronary artery was occluded for 50 minutes, after which saline solution (n = 8), mannitol-buffer vehicle (n = 9, 102 mg/kg bolus, 102 mg. kg(-1). h(-1)), or CGS 32359 (CGS, n = 7, 60 mg/kg bolus, 60 mg. kg(-1). h(-1)) was infused. After ischemia, 1-hour arrest was achieved by means of multidose hypothermic (4 degrees C) blood cardioplegia, followed by 2.5 hours of off-bypass reperfusion. The ligature on the left anterior descending artery was released before the second infusion of cardioplegic solution.

RESULTS

Area at risk was similar in all groups (saline solution, 27% +/- 2%; mannitol-buffer vehicle, 26% +/- 2%; CGS, 26% +/- 2% left ventricular mass). Infarct size (area necrosis/area at risk) was significantly reduced by CGS (18% +/- 6%, P <.05) versus saline solution (52% +/- 3%) and mannitol-buffer vehicle (60% +/- 4%). Postischemic systolic shortening (sonomicrometry) in the area at risk was significantly improved with CGS (0.8% +/- 0.9%) compared with saline solution (-3.7% +/- 1.1%) and mannitol-buffer vehicle (-6.4% +/- 1.0%). Myeloperoxidase activity from accumulated neutrophils was less in the ischemic zone of CGS (0.014 +/- 0.002 U/100 mg tissue; P <.05) than mannitol-buffer vehicle (0.133 +/- 0.012 U/100 mg tissue).

CONCLUSIONS

We conclude that the recombinant human C5a receptor antagonist CGS 32359 inhibits surgical ischemia-reperfusion injury after coronary occlusion.

Large, sustained cardiac lipid peroxidation and reduced antioxidant capacity in the coronary circulation after brief episodes of myocardial ischemia

OBJECTIVES

We sought to investigate whether a brief episode of myocardial ischemia produces a detectable cardiac oxidative stress in patients undergoing elective coronary angioplasty (PTCA).

BACKGROUND

Although cardiac oxidative stress has been clearly demonstrated in experimental models of ischemia-reperfusion, its presence in patients after transient myocardial ischemia is still unclear.

METHODS

In order to evaluate oxidative stress in ischemic cardiac regions, plasma conjugated dienes (CD), lipid hydroperoxides (ROOHs) and total antioxidant capacity (TRAP), independent indexes of oxidative stress, were measured in the aorta and great cardiac vein (GCV) before (t0), 1, (t1), 5 (t5) and 15 min (t15) after first balloon inflation in 15 patients undergoing PTCA on left anterior descending coronary artery (Group 1); six patients with right coronary artery stenosis (Group 2), which is not drained by the GCV, were studied as controls.

RESULTS

In Group 1 at baseline, CD and ROOHs levels were higher in GCV than in aorta (p < 0.01 for both), and TRAP levels were lower (p < 0.01). Aortic levels of CD, ROOHs and TRAP did not change at any time after to; venous levels of CD and ROOHs levels markedly increased at t1, at t5 and remained elevated at t15 (p < 0.01 for all comparisons vs. to); venous levels of TRAP decreased at t1 and t5 (p < 0.01 vs. t0) and returned to normal at t15. In Group 2, CD, ROOHs and TRAP levels were similar in the aorta and GCV and did not change throughout the study.

CONCLUSIONS

Short episodes of myocardial ischemia during PTCA induce a sustained oxidative stress, which is detectable in the venous effluent of reperfused myocardium.

Complement activation following oxidative stress

It is clear that complement plays an important role in the inflammatory process following oxidative stress in cellular and animal models. Clinical trials underway with novel complement inhibitors will establish the potential therapeutic benefit of complement inhibition in human disease. For as much as we understand about the role of complement in disease states, many questions remain. How is complement activated on endothelial cells following oxidative stress? What is the ligand for MBL on endothelial cells following oxidative stress? Will inhibition of MBL provide tissue protection to the extent observed with other complement inhibitors such as sCR1 or anti-C5 mAbs? These questions and more will undoubtedly be answered in the next millennium.

Reactive oxygen metabolites, antioxidants and head and neck cancer

This manuscript will review the probable role of reactive oxygen metabolites (ROM) in the etiopathogenesis of head and neck cancer (HNC). Cancer is a heterogeneous disorder with multiple etiologies including somatic and germ-line mutations, cellular homeostatic disturbances, and environmental triggers. Certain etiologies are characteristic of HNC and include infectious agents such as the Epstein-Barr virus, the use of tobacco, and consumption of alcohol. A large body of evidence implicates ROM in tumor formation and promotion. ROM species are formed in the process of cellular respiration, specifically during oxidative phosphorylation. These ubiquitous molecules are highly toxic in the cellular environment. Of the many effects of ROM, especially important are their effect on DNA. Specifically, ROM cause a variety of DNA damage, including insertions, point mutations, and deletions. Thus, it is hypothesized that ROM may be critically involved in the etiology of malignant disease through their possible impact on protooncogenes and tumor suppressor genes. Additionally, empirical evidence suggests that ROM may also affect the balance between apoptosis and cellular proliferation. If apoptotic mechanisms are overwhelmed, uncontrolled cellular proliferation may follow, potentially leading to tumor formation. Thus, this manuscript will critically review the evidence that supports the role of ROM in tumorigenesis. ROM scavengers and blockers have shown both in vivo and in vitro effects of attenuating the toxicity of ROM. Such compounds include the antioxidant vitamins (A, C, and E), nutrient trace elements (selenium), enzymes (superoxide dismutase, glutathione peroxidase, and catalase), hormones (melatonin), and a host of natural and synthetic compounds (lazaroids, allopurinol, gingko extract). Thus, this paper will also review the possible benefit derived from the use of such scavengers/blockers in the prevention of HNC.

Reduction of myocardial infarct size after ischemia and reperfusion by the glycosaminoglycan pentosan polysulfate

Activation of the complement system contributes to the tissue destruction associated with myocardial ischemia/reperfusion. Pentosan polysulfate (PPS), a negatively charged sulfated glycosaminoglycan (GAG) and an effective inhibitor of complement activation, was studied for its potential to decrease infarct size in an experimental model of myocardial ischemia/reperfusion injury. Open-chest rabbits were subjected to 30-min occlusion of the left coronary artery followed by 5 h of reperfusion. Vehicle (saline) or PPS (30 mg/kg/h) was administered intravenously immediately before the onset of reperfusion and every hour during the reperfusion period. Treatment with PPS significantly (p < 0.05) reduced infarct size as compared with vehicle-treated animals (27.5+/-2.9% vs. 13.34+/-2.6%). Analysis of tissue demonstrated decreased deposition of membrane-attack complex and neutrophil accumulation in the area at risk. The results indicate that, like heparin and related GAGs, PPS possesses the ability to decrease infarct size after an acute period of myocardial ischemia and reperfusion. The observations are consistent with the suggestion that PPS may mediate its cytoprotective effect through modulation of the complement cascade.

Complement activation and regulator expression after anoxic injury of human endothelial cells

Complement activation is involved in the ischemia-reperfusion injury of various organs, but the mechanisms leading to activation of the complement system are incompletely understood. In this study we show that EA.hy 926 human endothelial cells cultured under anoxic conditions (24 or 48 h) become activators of the homologous complement system. Flow cytometric analysis indicated that C1q, C3c, C3d, C4, C5, C9 components of complement are deposited on anoxic but not on normoxic cells after incubation with normal human serum. Cell membrane-associated regulators of complement, membrane cofactor protein (CD46), decay-accelerating factor (CD55) and protectin (CD59) were expressed on EA.hy 926 cells grown under normal oxygen tension. Under anoxic conditions the expression of protectin was clearly decreased, whereas the expression of CD46 and CD55 diminished only slightly. Our results suggest that anoxia can convert human endothelial cells to activators of the complement system. The diminished expression of protectin, CD46 and CD55 can sensitize the cells to complement-mediated damage. Activation of the complement system due to the anoxic injury of human endothelial cells might be an important triggering mechanism in the pathogenesis of ischemia-reperfusion injury of human heart.

Leucocyte filtration during cardiopulmonary bypass hardly changed leucocyte counts and did not influence myeloperoxidase, complement, cytokines or platelets

In some patients, coronary artery bypass surgery induces postoperative organ dysfunction despite an apparently adequate revascularization and good haemodynamic performance. This complication may be caused by activation of the body's inflammatory systems on blood contact with large foreign surfaces in the extracorporeal circuit. Activated leucocytes may play an important role in organ damage, and it is conceivable that leucocyte removal by filtration may decrease the potential side-effects of cardiopulmonary bypass (CPB). The aim of the present study was to investigate possible effects of leucocyte filtration during the whole CPB period in elective coronary artery bypass surgery on biochemical and clinical parameters. Forty patients were randomized to extracorporeal circulation using a leucocyte-depleting filter (group L, n = 20) or to extracorporeal circulation with no leucocyte filter (group C, n = 20). In the leucocyte-depleted group, the mean total white blood cell counts increased from 6.3 (95% confidence interval, 5.5-7.0) x 10(9)/l to 7.0 (5.7-8.3) x 10(9)/l during extracorporeal circulation and in the control group from 6.3 (5.2-7.3) x 10(9)/l to 8.5 (7.2-9.8) x 10(9)/l. The intergroup difference was not statistically significant (p = 0.84). A substantial increase in concentrations of interleukin-6, myeloperoxidase and complement activation products were observed in both groups without statistically significant intergroup differences. It is concluded that the leucocyte-depletion filter did not cause a significant reduction of circulating white blood cells during CPB, and there were no significant differences between the groups with respect to the inflammatory markers studied.

Rescue therapy with C1-esterase inhibitor concentrate after emergency coronary surgery for failed PTCA

Administration of C1-esterase inhibitor (C1-INH) attenuates myocardial necrosis and sustains normal cardiac performance after myocardial ischemia and reperfusion in animal experiments. We report on our first experience of C1-INH application as rescue therapy in patients undergoing emergency surgical revascularization after failed percutaneous transluminal coronary angioplasty. Three patients were treated, because post-operative hemodynamic stabilization could not be achieved despite prolonged reperfusion periods, high-dose inotropic support, inodilators and aortic counterpulsation. As there was no surgical or medical option remaining, C1-INH was administered starting with a 2000 unit bolus, followed by 1000 U 12 and 24 h after surgery. C1-INH therapy resulted in rapid hemodynamic stabilization of all patients; weaning from aortic counterpulsation and epinephrine support was possible within 1 day. All patients survived and were discharged from hospital. In this group of patients suffering from severe reperfusion injury after coronary surgery, C1-INH seemed to be an effective adjuvant therapy to restore myocardial function by blocking the complement cascade. These results should encourage the performance of controlled studies on the effects of prophylactic C1-INH substitution therapy in patients undergoing coronary surgery at high risk conditions.

Phagocytes in ischemia injury

We are now developing the means to evaluate components of this inflammatory response that may facilitate healing. A key event in the change in the inflammatory response is the development of a cytokine cascade that promotes phenotypic changes in the infiltrating leukocytes, which endow them with the ability to promote fibroblast proliferation and collagen deposition, the hallmarks of healing.

Post-ischaemic organ dysfunction: a review

OBJECTIVES

The aim of this review is to consider the pathophysiology of ischaemia-reperfusion in organs that may be affected by either its local or remote consequences. Potential therapeutic strategies are also considered.

DESIGN

A general discussion of the biochemical (including oxygen free radicals, complement, cytokines) and cellular events (endothelial cells, neutrophils) responsible for the mediation of reperfusion injury is presented, with special consideration of the organ-specific differences affecting the myocardium, central nervous system, gut, liver, kidney and skeletal muscle. Similarly, events which promote remote organ injury are described.

CONCLUSIONS

Although it is recognised that prolonged ischaemia results in tissue and organ damage, the concept of reperfusion-induced tissue injury, defined as tissue damage occurring as a direct consequence of revascularisation, is relatively recent. Such events may increase the morbidity and mortality of patients undergoing vascular reconstruction, trauma surgery and transplantation. A clear understanding of the factors responsible for its development is therefore vital if protocols that reduce its impact are to be developed.

Induction of cytokine expression in leukocytes in acute myocardial infarction

OBJECTIVES

This study sought to investigate whether cytokine expression in leukocytes may be induced by plasma from the reperfused heart of patients with an acute myocardial infarction (MI).

BACKGROUND

Reperfusion in acute MI is associated with deleterious local and systemic inflammatory responses that are regulated by cytokines. Induction of cytokine expression in resident leukocytes could contribute to inflammatory responses of the ischemic and reperfused heart.

METHODS

Blood samples of 10 patients with an acute MI were obtained simultaneously from the coronary sinus and the aorta before and 5 min after recanalization of the coronary occlusion. Ten patients with elective percutaneous transluminal coronary angioplasty served as a control group. We incubated leukocytes from healthy donors with plasma samples and analyzed mRNA expression of interleukin (IL)-1 beta, IL-6, IL-8 and tumor necrosis factor-alpha (TNF-alpha) by Northern blot analysis.

RESULTS

In patients with an acute MI, plasma obtained from the coronary sinus after recanalization increased the mRNA expression of IL-1 beta and IL-8 compared with that of plasma before recanalization (median [quartiles] difference before vs. after recanalization: 34.5 [4, 137], p = 0.017, for IL-1 beta; 18.5 [4, 35], p = 0.032, for IL-8) and simultaneously obtained aortic plasma (median [quartiles] coronary sinus-aortic differences after recanalization: 45.5 [-3, 115], p = 0.021, for IL-1 beta; 16 [4, 52], p = 0.005, for IL-8). No induction of IL-6 and TNF-alpha expression could be observed. No changes found in the study patients were detectable in the control group.

CONCLUSIONS

Plasma from the ischemic and reperfused heart stimulates the expression of IL-1 beta and IL-8 in leukocytes. Therefore, leukocyte-derived cytokines may contribute to the regulation of cardiac inflammatory responses in patients with an acute MI.

Membrane attack complex of complement and 20 kDa homologous restriction factor (CD59) in myocardial infarction

In order to investigate the mechanism of deposition of the complement membrane attack complex (MAC) in cardiomyocytes in areas of human myocardial infarction, the 20 kDA homologous restriction factor of complement (HRF20; CD59) and complement components (Clq. C3d and MAC) were analysed immunohistochemically using specific antibodies. Myocardial tissues obtained at autopsy from nine patients who died of acute myocardial infarction were fixed in acetone and embedded in paraffin. The ages of the infarcts ranged from about 3.5 h to 12 days. In cases of myocardial infarction of 20 h or less, MAC deposition was shown in the infarcted cardiomyocytes without loss of HRF20. Where the duration was 4 days or more, the cardiomyocytes with MAC deposition in the infarcted areas also showed complete loss of HRF20. Outside the infarcts, HRF20 in the cardiomyocytes was well preserved without MAC deposition. The present study suggests that the initial MAC deposition in dead cardiomyocytes can occur as a result of degradation of plasma-membrane by a mechanism independent of complement-mediated injury to the membrane. Loss of HRF20 from dead cardiomyocytes may not be the initial cause of MAC deposition, but may accelerate the deposition process of MAC in later stages of infarction.