Cyclosporin-A reduces leukocyte accumulation and protects against myocardial ischaemia reperfusion injury in rats

Organ-Specific Mitochondrial Alterations Following Ischemia-Reperfusion Injury in Post-Cardiac Arrest Syndrome: A Comprehensive Review

BACKGROUND

Mitochondrial dysfunction, which is triggered by systemic ischemia-reperfusion (IR) injury and affects various organs, is a key factor in the development of post-cardiac arrest syndrome (PCAS). Current research on PCAS primarily addresses generalized mitochondrial responses, resulting in a knowledge gap regarding organ-specific mitochondrial dynamics. This review focuses on the organ-specific mitochondrial responses to IR injury, particularly examining the brain, heart, and kidneys, to highlight potential therapeutic strategies targeting mitochondrial dysfunction to enhance outcomes post-IR injury.

METHODS AND RESULTS

We conducted a narrative review examining recent advancements in mitochondrial research related to IR injury. Mitochondrial responses to IR injury exhibit considerable variation across different organ systems, influenced by unique mitochondrial structures, bioenergetics, and antioxidative capacities. Each organ demonstrates distinct mitochondrial behaviors that have evolved to fulfill specific metabolic and functional needs. For example, cerebral mitochondria display dynamic responses that can be both protective and detrimental to neuronal activity and function during ischemic events. Cardiac mitochondria show vulnerability to IR-induced oxidative stress, while renal mitochondria exhibit a unique pattern of fission and fusion, closely linked to their susceptibility to acute kidney injury. This organ-specific heterogeneity in mitochondrial responses requires the development of tailored interventions. Progress in mitochondrial medicine, especially in the realms of genomics and metabolomics, is paving the way for innovative strategies to combat mitochondrial dysfunction. Emerging techniques such as mitochondrial transplantation hold the potential to revolutionize the management of IR injury in resuscitation science.

CONCLUSIONS

The investigation into organ-specific mitochondrial responses to IR injury is pivotal in the realm of resuscitation research, particularly within the context of PCAS. This nuanced understanding holds the promise of revolutionizing PCAS management, addressing the unique mitochondrial dysfunctions observed in critical organs affected by IR injury.

Targeting Inflammation After Myocardial Infarction

PURPOSE OF REVIEW

Inflammation plays a key role in clearing cellular debris and recovery after acute myocardial infarction (AMI). Dysregulation of or prolonged inflammation may result in adverse cardiac remodeling and major adverse clinical events (MACE). Several pre-clinical studies and moderate sized clinical trials have investigated the role of immunomodulation in improving clinical outcomes in patients with AMI.

RECENT FINDINGS

Clinical data from the Canakinumab Atherothrombosis Outcome (CANTOS) and Colchicine Cardiovascular Outcomes Trial (COLCOT) have provided encouraging results among patients with AMI. Several other clinical and pre-clinical trials have brought about the prospect of modulating inflammation at various junctures of the inflammatory cascade including inhibition of complement cascade, interleukins, and matrix metalloproteinases. In patients with AMI, modulation of residual inflammation via various inflammatory pathways and mediators may hold promise for further reducing MACE. Learning from current data and understanding the nuances of immunomodulation in AMI are key for future trials and before widespread dissemination of such therapies.

Mitochondrial ion channels as targets for cardioprotection

Acute myocardial infarction (AMI) and the heart failure (HF) that often result remain the leading causes of death and disability worldwide. As such, new therapeutic targets need to be discovered to protect the myocardium against acute ischaemia/reperfusion (I/R) injury in order to reduce myocardial infarct (MI) size, preserve left ventricular function and prevent the onset of HF. Mitochondrial dysfunction during acute I/R injury is a critical determinant of cell death following AMI, and therefore, ion channels in the inner mitochondrial membrane, which are known to influence cell death and survival, provide potential therapeutic targets for cardioprotection. In this article, we review the role of mitochondrial ion channels, which are known to modulate susceptibility to acute myocardial I/R injury, and we explore their potential roles as therapeutic targets for reducing MI size and preventing HF following AMI.

Anti-inflammatory therapies in myocardial infarction: failures, hopes and challenges

In the infarcted heart, the damage-associated molecular pattern proteins released by necrotic cells trigger both myocardial and systemic inflammatory responses. Induction of chemokines and cytokines and up-regulation of endothelial adhesion molecules mediate leukocyte recruitment in the infarcted myocardium. Inflammatory cells clear the infarct of dead cells and matrix debris and activate repair by myofibroblasts and vascular cells, but may also contribute to adverse fibrotic remodelling of viable segments, accentuate cardiomyocyte apoptosis and exert arrhythmogenic actions. Excessive, prolonged and dysregulated inflammation has been implicated in the pathogenesis of complications and may be involved in the development of heart failure following infarction. Studies in animal models of myocardial infarction (MI) have suggested the effectiveness of pharmacological interventions targeting the inflammatory response. This article provides a brief overview of the cell biology of the post-infarction inflammatory response and discusses the use of pharmacological interventions targeting inflammation following infarction. Therapy with broad anti-inflammatory and immunomodulatory agents may also inhibit important repair pathways, thus exerting detrimental actions in patients with MI. Extensive experimental evidence suggests that targeting specific inflammatory signals, such as the complement cascade, chemokines, cytokines, proteases, selectins and leukocyte integrins, may hold promise. However, clinical translation has proved challenging. Targeting IL-1 may benefit patients with exaggerated post-MI inflammatory responses following infarction, not only by attenuating adverse remodelling but also by stabilizing the atherosclerotic plaque and by inhibiting arrhythmia generation. Identification of the therapeutic window for specific interventions and pathophysiological stratification of MI patients using inflammatory biomarkers and imaging strategies are critical for optimal therapeutic design.

Plant-based foods containing cell wall polysaccharides rich in specific active monosaccharides protect against myocardial injury in rat myocardial infarction models

Many cohort studies have shown that consumption of diets containing a higher composition of foods derived from plants reduces mortality from coronary heart disease (CHD). Here, we examined the active components of a plant-based diet and the underlying mechanisms that reduce the risk of CHD using three rat models and a quantitative proteomics approach. In a short-term myocardial infarction (MI) model, intake of wheat extract (WE), the representative cardioprotectant identified by screening approximately 4,000 samples, reduced myocardial injury by inhibiting apoptosis, enhancing ATP production, and maintaining protein homeostasis. In long-term post-MI models, this myocardial protection resulted in ameliorating adverse left-ventricular remodelling, which is a predictor of heart failure. Among the wheat components, arabinose and xylose were identified as active components responsible for the observed efficacy of WE, which was administered via ingestion and tail-vein injections. Finally, the food components of plant-based diets that contained cell wall polysaccharides rich in arabinose, xylose, and possibly fucose were found to confer protection against myocardial injury. These results show for the first time that specific monosaccharides found in the cell wall polysaccharides in plant-based diets can act as active ingredients that reduce CHD by inhibiting postocclusion steps, including MI and heart failure.

Soluble guanylate cyclase activation during ischemic injury in mice protects against postischemic inflammation at the mitochondrial level

The aim was to determine whether treatment with BAY 60-2770, a selective activator of oxidized soluble guanylate cyclase (sGC), near the end of an ischemic event would prevent postischemic inflammation and mitochondrial dysfunction in wild-type (WT) and heme oxygenase-1 KO (HO-1(-/-)) mice. This protocol prevented increases in leukocyte rolling (LR) and adhesion (LA) to intestinal venules along with elevated TNFα and circulating neutrophil levels that accompany ischemia-reperfusion (I/R) in both animal models. We further hypothesized that a component of BAY 60-2770 treatment involves maintenance of mitochondrial membrane integrity during I/R. Measurements on isolated enterocytes of calcein fluorescence (mitochondrial permeability) and JC-1 fluorescence ratio (mitochondrial membrane potential) were reduced by I/R, indicating formation of mitochondrial permeability transition pores (mPTP). These effects were abrogated by BAY 60-2770 as well as cyclosporin A and SB-216763, which prevented mPTP opening and inhibited glycogen synthase kinase-3β (GSK-3β), respectively. Western blots of WT and HO-1(-/-) enterocytes indicated that GSK-3β phosphorylation on Ser(9) (inhibitory site) was reduced by half following I/R alone (increased GSK-3β activity) and increased by one-third (reduced GSK-3β activity) following BAY 60-2770. Other investigators have associated phosphorylation of the GSK-3β substrate cyclophilin D (pCyPD) with mPTP formation. We observed a 60% increase in pCyPD after I/R, whereas BAY 60-2770 treatment of sham and I/R groups reduced pCyPD by about 20%. In conclusion, selective activation of oxidized sGC of WT and HO-1(-/-) during ischemia protects against I/R-induced inflammation and preserves mucosal integrity in part by reducing pCyPD production and mPTP formation.

Intravenous xenogeneic transplantation of human adipose-derived stem cells improves left ventricular function and microvascular integrity in swine myocardial infarction model

OBJECTIVES

The potential for beneficial effects of adipose-derived stem cells (ASCs) on myocardial perfusion and left ventricular dysfunction in myocardial ischemia (MI) has not been tested following intravenous delivery.

METHODS

Surviving pigs following induction of MI were randomly assigned to 1 of 3 different groups: the placebo group (n = 7), the single bolus group (SB) (n = 7, 15 × 10(7) ASCs), or the divided dose group (DD) (n = 7, 5 × 10(7) ASCs/day for three consecutive days). Myocardial perfusion defect area and coronary flow reserve (CFR) were compared during the 28-day follow-up. Also, serial changes in the absolute number of circulating CD4(+) T and CD8(+) T cells were measured.

RESULTS

The increases in ejection fraction were significantly greater in both the SB and the DD groups compared to the placebo group (5.4 ± 0.9%, 3.7 ± 0.7%, and -0.4 ± 0.6%, respectively), and the decrease in the perfusion defect area was significantly greater in the SB group than the placebo group (-36.3 ± 1.8 and -11.5 ± 2.8). CFR increased to a greater degree in the SB and the DD groups than in the placebo group (0.9 ± 0.2, 0.8 ± 0.1, and 0.2 ± 0.2, respectively). The circulating number of CD8(+) T cells was significantly greater in the SB and DD groups than the placebo group at day 7 (3,687 ± 317/µL, 3,454 ± 787/µL, and 1,928 ± 457/µL, respectively). The numbers of small vessels were significantly greater in the SB and the DD groups than the placebo group in the peri-infarct area.

CONCLUSIONS

Both intravenous SB and DD delivery of ASCs are effective modalities for the treatment of MI in swine. Intravenous delivery of ASCs, with its immunomodulatory and angiogenic effects, is an attractive noninvasive approach for myocardial rescue.

Signalling pathways and mechanisms of protection in pre- and postconditioning: historical perspective and lessons for the future

Ischaemic pre- and postconditioning are potent cardioprotective interventions that spare ischaemic myocardium and decrease infarct size after periods of myocardial ischaemia/reperfusion. They are dependent on complex signalling pathways involving ligands released from ischaemic myocardium, G-protein-linked receptors, membrane growth factor receptors, phospholipids, signalling kinases, NO, PKC and PKG, mitochondrial ATP-sensitive potassium channels, reactive oxygen species, TNF-α and sphingosine-1-phosphate. The final effector is probably the mitochondrial permeability transition pore and the signalling produces protection by preventing pore formation. Many investigators have worked to produce a roadmap of this signalling with the hope that it would reveal where one could intervene to therapeutically protect patients with acute myocardial infarction whose hearts are being reperfused. However, attempts to date to show efficacy of such an intervention in large clinical trials have been unsuccessful. Reasons for this inability to translate successes in the experimental laboratory to the clinical arena are evaluated in this review. It is suggested that all patients with acute coronary syndromes currently presenting to the hospital and being treated with platelet P2Y12 receptor antagonists, the current standard of care, are indeed already benefiting from protection from the conditioning pathways outlined earlier. If that proves to be the case, then future attempts to further decrease infarction will have to rely on interventions which protect by a different mechanism.

Attenuation of skeletal muscle and renal injury to the lower limb following ischemia-reperfusion using mPTP inhibitor NIM-811

Introduction

Operation on the infrarenal aorta and large arteries of the lower extremities may cause rhabdomyolysis of the skeletal muscle, which in turn may induce remote kidney injury. NIM-811 (N-metyl-4-isoleucine-cyclosporine) is a mitochondria specific drug, which can prevent ischemic-reperfusion (IR) injury, by inhibiting mitochondrial permeability transition pores (mPTP).

Objectives

Our aim was to reduce damages in the skeletal muscle and the kidney after IR of the lower limb with NIM-811.

Materials and methods

Wistar rats underwent 180 minutes of bilateral lower limb ischemia and 240 minutes of reperfusion. Four animal groups were formed called Sham (receiving vehicle and sham surgery), NIM-Sham (receiving NIM-811 and sham surgery), IR (receiving vehicle and surgery), and NIM-IR (receiving NIM-811 and surgery). Serum, urine and histological samples were taken at the end of reperfusion. NADH-tetrazolium staining, muscle Wet/Dry (W/D) ratio calculations, laser Doppler-flowmetry (LDF) and mean arterial pressure (MAP) monitoring were performed. Renal peroxynitrite concentration, serum TNF-α and IL-6 levels were measured.

Results

Less significant histopathological changes were observable in the NIM-IR group as compared with the IR group. Serum K⁺ and necroenzyme levels were significantly lower in the NIM-IR group than in the IR group (LDH: p<0.001; CK: p<0.001; K⁺: p = 0.017). Muscle mitochondrial viability proved to be significantly higher (p = 0.001) and renal function parameters were significantly better (creatinine: p = 0.016; FENa: p<0.001) in the NIM-IR group in comparison to the IR group. Serum TNF-α and IL-6 levels were significantly lower (TNF-α: p = 0.003, IL-6: p = 0.040) as well as W/D ratio and peroxynitrite concentration were significantly lower (p = 0.014; p<0.001) in the NIM-IR group than in the IR group.

Conclusion

NIM-811 could have the potential of reducing rhabdomyolysis and impairment of the kidney after lower limb IR injury.

Mesenchymal stem cell therapy for cardiac repair

OPINION STATEMENT

Owing to the prevalence of heart disease and the lack of effective long-term solutions for managing cardiac injury, research has turned to cell therapy as a potential mechanism for myocardial repair. Mesenchymal stem cells (MSC) in particular have become popular because their differentiative ability and their angiogenic and immunomodulatory properties make them attractive candidates for transplantation. However, there is still debate regarding the optimal strategy for the delivery of these cells. Recent clinical studies have isolated MSCs from a variety of tissue origins and have also tested the benefits of pretreatment with cardiogenic growth factors. Meanwhile, a newer school of thought instead supports the utilization of cardiomyocytes generated from MSC-derived induced pluripotent stem cells. This review will examine the promise of MSC therapy, discuss the results of past work, and propose steps that must be taken in the future.

Cardioprotection against myocardial reperfusion injury: successes, failures, and perspectives

The past few decades have witnessed an enormous number of research strategies aimed at protecting the heart against myocardial ischemia-reperfusion injury. Several randomized clinical trials are nowadays in progress testing whether promising therapeutic strategies aimed at preventing lethal reperfusion injury can be translated from bench to bedside. Many of these interventions, either pharmacological or mechanical, are targeting mitochondria as the final effectors of cardioprotection. Despite encouraging pre-clinical studies and small proof of concept clinical trials, there are still several limitations that may jeopardize the efficacy of cardioprotective strategies. These limitations include clinical setting, patient profile, drug administration, and methods for evaluating treatment efficacy. Identifying potential mechanistic and methodological pitfalls in the field may improve future translational research.

Targeting reperfusion injury in acute myocardial infarction: a review of reperfusion injury pharmacotherapy

INTRODUCTION

Acute myocardial infarction (AMI) (secondary to lethal ischemia-reperfusion [IR]) contributes to much of the mortality and morbidity from ischemic heart disease. Currently, the treatment for AMI is early reperfusion; however, this itself contributes to the final myocardial infarct size, in the form of what has been termed 'lethal reperfusion injury'. Over the last few decades, the discovery of the phenomena of ischemic preconditioning and postconditioning, as well as remote preconditioning and remote postconditioning, along with significant advances in our understanding of the cardioprotective pathways underlying these phenomena, have provided the possibility of successful mechanical and pharmacological interventions against reperfusion injury.

AREAS COVERED

This review summarizes the evidence from clinical trials evaluating pharmacological agents as adjuncts to standard reperfusion therapy for ST-elevation AMI.

EXPERT OPINION

Reperfusion injury pharmacotherapy has moved from bench to bedside, with clinical evaluation and ongoing clinical trials providing us with valuable insights into the shortcomings of current research in establishing successful treatments for reducing reperfusion injury. There is a need to address some key issues that may be leading to lack of translation of cardioprotection seen in basic models to the clinical setting. These issues are discussed in the Expert opinion section.

Cyclosporin A and cardioprotection: from investigative tool to therapeutic agent

Ischaemic heart disease (IHD) is the leading cause of death and disability worldwide. The pathophysiological effects of IHD on the heart most often result from the detrimental effects of acute ischaemia-reperfusion injury (IRI) on the myocardium. Therefore, novel therapeutic targets for protecting the myocardium against acute IRI are required to reduce injury to the heart, preserve cardiac function and improve clinical outcomes in patients with IHD. In this regard, the mitochondrial permeability transition pore (mPTP) has emerged as a critical target for cardioprotection which is readily amenable to intervention at the time of myocardial reperfusion. The formation and opening of the mPTP at the onset of myocardial reperfusion is a major determinant of mitochondrial dysfunction and cardiomyocyte death in the setting of acute IRI. The seminal discovery in the late 1980s that mPTP opening could be pharmacologically inhibited by the immunosuppressive agent, cyclosporin A (CsA), has been fundamental in the elucidation of the critical role of the mPTP as a mediator of acute IRI and, therefore, a viable target for cardioprotection. Its initial role as an investigative tool was used to identify mitochondrial cyclophilin D to be a regulatory component of the mPTP. The mPTP as a viable target for cardioprotection has recently been translated into the clinical setting with CsA reducing myocardial infarct size in patients. In this article, we review the intriguing role of CsA as a tool for investigating the mPTP as a target for cardioprotection and its potential role as a therapeutic agent for patients with IHD.

Cyclosporin variably and inconsistently reduces infarct size in experimental models of reperfused myocardial infarction: a systematic review and meta-analysis

Cyclosporin is an immunosuppressant that has recently been proposed as a treatment to prevent reperfusion injury in acute myocardial infarction (MI). We aimed to determine the overall efficacy of cyclosporin in experimental studies of acute reperfused MI. We conducted a systematic review and stratified meta-analysis of published studies describing the efficacy of cyclosporin in experimental models of acute reperfused MI. We included all in vivo publications of cyclosporin where infarct size was measured. A literature search identified 29 potential studies of which 20 fulfilled the eligibility criteria. In these studies (involving four species of animals), cyclosporin reduced myocardial infarct size by a standardized mean (95% confidence interval) difference of -1.60 (-2.17, -1.03) compared with controls. Cyclosporin failed to demonstrate a convincing benefit in studies involving pigs. Despite this observation, the overall efficacy of cyclosporin did not differ across species (P= 0.358). The dose of cyclosporin given did not affect final infarct size (P= 0.203). Funnel plots of these data suggested heterogeneity among the studies. Cyclosporin had variable effects on infarct size compared with placebo. Cyclosporin had no effect on myocardial infarct size in swine, raising a question over the potential cardioprotective effects of cyclosporin in man.

Cyclosporin-A does not prevent cold ischemia/reperfusion injury of rat livers

Cyclosporin-A (CsA) has been reported to protect livers from warm ischemia/reperfusion (I/R) injury. To study if CsA has also a protective effect on cold I/R injury, two models were used: the isolated perfused rat liver (IPRL) and the orthotopic rat liver transplantation (ORLT). (1) IPRL: Livers were preserved for 24 h (5°C) in University of Wisconsin (UW) solution alone (group 1), with CsA (400 nM) dissolved in dimethylsulfoxide (50 μM) (group 2), and with dimethylsulfoxide (DMSO) alone (group 3). Livers were reperfused for 60 min (37°C) (n = 8/group). Cell necrosis was evaluated by trypan blue uptake and apoptosis by laddering and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and by caspase-3 activation. Marked and similar sinusoidal endothelial cell necrosis was found in the three groups while apoptosis was found similarly deceased in groups 2 and 3 compared with group 1. (2) ORLT: Donors received either CsA (5 mg/kg) or corn oil 24 h before transplantation. Recipients were sacrificed after 240 min; cell necrosis and apoptosis were then evaluated. No difference was found between treated and control groups. The current data strongly suggest that CsA has no protective effect on hepatic cold I/R injury. Hepatocyte apoptosis can be reduced by antioxidants, as occurred with DMSO, but introduction of CsA does not provide additional protective effect.

Ischemic postconditioning: from receptor to end-effector

Ischemic preconditioning, a robust cardioprotective intervention, has limited clinical efficacy because it must be initiated before myocardial ischemia. Conversely, ischemic postconditioning, repeated brief reocclusions of a coronary artery after release of prolonged coronary occlusion, provides cardioprotection in clinically feasible settings, that is, coronary angioplasty. Ischemic postconditioning's signaling is being investigated to identify pharmacological triggers that could be used without angioplasty. In initial minutes of reperfusion H(+) washes out of previously ischemic cells. pH rises enabling mitochondrial permeability transition pores (MPTPs) to form leading to cessation of ATP production and cell necrosis. Coronary reocclusions maintain sufficient acidosis to keep MPTP closed while signaling is initiated that can generate endogenous antagonists of MPTP formation even after cellular pH normalizes. Reintroduction of oxygen generates reactive oxygen species that activate protein kinase C to increase sensitivity of adenosine A(2b) receptors allowing adenosine released from ischemic cells to bind leading to activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase 1/2. Phosphatidylinositol 3-kinase activation results in phosphorylation of Akt promoting activation of nitric oxide synthase and nitric oxide production, which inhibits glycogen synthase kinase-3β, perhaps the final cytosolic signaling step before inhibition of MPTP formation. Interference with MPTP may be the final step that determines cell salvage.

Novel bisindolylmaleimide derivative inhibits mitochondrial permeability transition pore and protects the heart from reperfusion injury

Despite major advances in treating patients with coronary heart disease, reperfusion injury is still considered to be a major problem, especially in surgical settings. Here, we demonstrate the protective effects of a novel bisindolylmaleimide derivative, MS1 (2-[1-(3-aminopropyl)indol-3-yl]-3-(indol-3-yl)-N-methylmaleimide), against reperfusion injury of the heart. After anesthesia and artificial ventilation, Wistar rats were subjected to 30 min of left coronary artery occlusion followed by 120 min of reperfusion with or without treating the rats with MS1 (2.25 mumol.L-1.kg-1) before left coronary artery occlusion. Compared with the untreated hearts, MS1 treatment significantly reduced myocardial infarct size (35.1% +/- 3% vs. 75.5% +/- 5%, p < 0.001), reduced prevalence of apoptotic cells (2.6% +/- 0.5% vs. 12.2% +/- 2.1%, p < 0.001), prevented mitochondrial swelling and cytochrome c release, inhibited downregulation of antiapoptotic protein Bcl-2 expression, and suppressed caspase-3 activation. In contrast, pretreatment with atractyloside, a mitochondrial permeability transition pore opener, abolished the protective effects of MS1. In conclusion, MS1 inhibits pathologic opening of permeability transition pores and protects the heart against reperfusion injury and pathologic apoptosis.

Microcirculatory changes in experimental mesenteric longitudinal ulcers of the small intestine in rats

Rats receiving intracolonic administration of indomethacin develop longitudinal ulcers on the mesenteric side of the small intestine that are similar to those seen in the acute phase of Crohn's disease. To investigate the causative role of microcirculatory disturbances and to elucidate the therapeutic effect of antioxidants on this enteropathy in rats, we serially evaluated changes in regional blood flow of the small intestine using laser Doppler perfusion imaging and the colored microsphere injection method. Both methods disclosed stepwise hyperperfusion limited to the mesenteric side of the small intestine following transient ischemia during the initial 30-60 minutes. In addition, both a radical scavenger and a radical production inhibitor significantly ameliorated the mesenteric longitudinal ulcers. We concluded that ischemia-reperfusion on the mesenteric side accompanying excessive production of radicals might be strongly involved in indomethacin-induced longitudinal ulcers of the small intestine in rats.

Cardioprotective effects of cyclosporine A in an in vivo model of myocardial ischemia and reperfusion

BACKGROUND

Recent evidence indicates that reperfusion of the heart after a period of ischemia leads to the opening of the mitochondrial permeability transition pore (MPTP). The aim of this study was to investigate cardioprotective effects of cyclosporine A (CsA), an inhibitor of the MPTP, in an in vivo model of myocardial ischemia and reperfusion.

METHODS

Male Sprague-Dawley rats were subjected to occlusion of the left anterior descending coronary artery for 30 min followed by 180 min of reperfusion. CsA (10 mg/kg) or vehicle was given 10 min prior to ischemia via the femoral vein. Sham myocardial ischemia-reperfusion rats (sham-operation group) were used as controls. Infarct size was measured using the staining agent TTC (2,3,5-triphenyl tetrazolium chloride) and myocardial apoptosis by caspase-3 activity was determined by fluorescent assay. The myocardium mitochondria ultrastructure was observed through a transmission electron microscope.

RESULTS

CsA significantly reduced infarct size (48.8 +/- 5.8% of left ventricle in vehicle + I/R group and 30.3 +/- 2.7% of left ventricle in CsA + I/R, respectively) and decreased caspase-3 activity in the myocardium [(0.62 +/- 0.17)/microg of protein and (0.42 +/- 0.15)/microg of protein, respectively] and relieved the injury of mitochondria.

CONCLUSION

CsA reduced the cardiac damage associated with ischemia-reperfusion injury of the heart. The cardioprotective effects of CsA might be associated with the protection of mitochondria and the inhibition of caspase-3 activity. It also suggests that the MPTP might play an important role in cardiomyocytes death after ischemia-reperfusion injury.

Mitochondrial membrane permeabilization in cell death

Irrespective of the morphological features of end-stage cell death (that may be apoptotic, necrotic, autophagic, or mitotic), mitochondrial membrane permeabilization (MMP) is frequently the decisive event that delimits the frontier between survival and death. Thus mitochondrial membranes constitute the battleground on which opposing signals combat to seal the cell's fate. Local players that determine the propensity to MMP include the pro- and antiapoptotic members of the Bcl-2 family, proteins from the mitochondrialpermeability transition pore complex, as well as a plethora of interacting partners including mitochondrial lipids. Intermediate metabolites, redox processes, sphingolipids, ion gradients, transcription factors, as well as kinases and phosphatases link lethal and vital signals emanating from distinct subcellular compartments to mitochondria. Thus mitochondria integrate a variety of proapoptotic signals. Once MMP has been induced, it causes the release of catabolic hydrolases and activators of such enzymes (including those of caspases) from mitochondria. These catabolic enzymes as well as the cessation of the bioenergetic and redox functions of mitochondria finally lead to cell death, meaning that mitochondria coordinate the late stage of cellular demise. Pathological cell death induced by ischemia/reperfusion, intoxication with xenobiotics, neurodegenerative diseases, or viral infection also relies on MMP as a critical event. The inhibition of MMP constitutes an important strategy for the pharmaceutical prevention of unwarranted cell death. Conversely, induction of MMP in tumor cells constitutes the goal of anticancer chemotherapy.

Myocardial infarct-sparing effect of adenosine A2A receptor activation is due to its action on CD4+ T lymphocytes

BACKGROUND

We previously used adenosine A2A receptor (A2AR) knockout (KO) mice and bone marrow transplantation to show that the infarct-sparing effect of A2AR activation at reperfusion is primarily due to effects on bone marrow-derived cells. In this study we show that CD4+ but not CD8+ T lymphocytes contribute to myocardial ischemia/reperfusion injury.

METHOD AND RESULTS

After a 45-minute occlusion of the left anterior descending coronary artery and reperfusion, T cells accumulate in the infarct zone within 2 minutes. Addition of 10 microg/kg of the A2AR agonist ATL146e 5 minutes before reperfusion produces a significant reduction in T-cell accumulation and a significant reduction in infarct size (percentage of risk area) measured at 24 hours. In Rag1 KO mice lacking mature lymphocytes, infarct size is significantly smaller than in C57BL/6 mice. Infarct size in Rag1 KO mice is increased to the level of B6 mice by adoptive transfer of 50 million CD4+ T lymphocytes derived from C57BL/6 or A2AR KO but not interferon-gamma KO mice. ATL146e completely blocked the increase in infarct size in Rag1 KO mice reconstituted with B6 but not A2AR KO CD4+ T cells. The number of neutrophils in the reperfused heart at 24 hours after infarction correlated well with the number of lymphocytes and infarct size.

CONCLUSIONS

These results strongly suggest that the infarct-sparing effect of A2AR activation is primarily due to inhibition of CD4+ T-cell accumulation and activation in the reperfused heart.

Macrophage inhibitor, semapimod, reduces tumor necrosis factor-alpha in myocardium in a rat model of ischemic heart failure

Pharmaceutical agents aimed at reducing tumor necrosis factor-alpha (TNF-alpha) levels appeared to be attractive possibilities in the medical management of heart failure, as heart failure was shown to be associated with high TNF-alpha levels. However, therapies specifically targeting TNF-alpha failed to show any survival benefit. We examined whether a broad inhibition of inflammatory cytokine production secondary to macrophage inhibition would be more effective at improving cardiac function in the setting of heart failure. To this end, we studied Semapimod (formerly known as CNI-1493), a synthetic guanylhydrazone that inhibits macrophage activation and the production of several inflammatory cytokines. Left anterior descending coronary ligation surgery was performed on each animal to induce a myocardial infarction. After confirming heart failure by echocardiography, the animals were randomly assigned to one of four groups: (1) rats with myocardial infarct receiving high-dose Semapimod, 10 mg/kg/d (MI-H, N = 13); (2) rats with myocardial infarct receiving low-dose Semapimod, 3 mg/kg/d (MI-L, N = 9); (3) rats with myocardial infarct receiving vehicle treatment, 2.5% mannitol in water (MI-0, N = 9); and (4) control rats with sham operation and vehicle treatment (Sham, N = 10). Both Semapimod and vehicle treatments were administered by daily tail vein injections over a course of five days. Echoes were repeated at 2, 5, and 9 weeks following treatment. At 9 weeks, hemodynamic data were collected and the animals were euthanized. Trichrome staining was done to assess infarct, and immunohistochemistry was performed to assess TNF-alpha levels. Prior to drug administration, serum was taken from 5 random rats. No detectable level of TNF-alpha was seen (lower limit of detection for the assay used = 12.5 pg/mL). Also prior to any treatment, echocardiography confirmed significant cardiac impairment of rats undergoing LAD ligation as compared with sham. Over the course of the 9 weeks, there were 4 deaths, all in the MI-H group. There was no difference between Semapimod-treated animals and vehicle-treated MI animals in any echocardiographic or hemodynamic parameter. TNF-alpha staining in the noninfarcted region was evident only in the MI groups, not the sham group. When blindly compared on a semiquantitative scale (ie, 0 = no visible staining to 3 = marked staining), a significant difference in staining was observed between MI-0 versus MI-H (1.19 +/- 0.32 versus 0.33 +/- 0.14; P = 0.03) and between MI-0 and MI-L (1.19 +/- 0.32 versus 0.39 +/- 0.22; P = 0.05). In this setting, despite the fact that Semapimod treatment decreased tissue TNF-alpha levels, it did not improve cardiac function, and at high doses it was associated with higher mortality. These results in a rodent model confirm the results of clinical trials with etanercept and infliximab (ie, that decreasing TNF levels in plasma or tissues does not improve cardiac function and may actually increase mortality).

Cyclosporine protects against ischemia/reperfusion injury in rat kidneys

Renal ischemia followed by reperfusion leads to acute renal failure in both native kidneys and renal allografts. Cyclosporine A (CsA) has been used as an immunosuppressive agent in organ transplantation. In the present study, the effect of CsA on ischemia/reperfusion (I/R)-induced injury in the kidney was investigated. Ischemia/reperfusion injury caused a significant deterioration in the renal function, morphology and gave rise to a severe oxidative stress in the kidney. At 3 mg/kg i.v., CsA significantly improved the functional and histological parameters and attenuated the oxidative stress induced by renal ischemia/reperfusion. From the results of our study, it can be concluded that low-dose CsA pretreatment preconditions the rat kidneys against subsequent ischemia/reperfusion injury.

Down-regulation of Connexin43 in Early Myocardial Ischemia and Protective Effect by Ischemic Preconditioning in Rat Hearts In Vivo

Connexin 43 (Cx43), a primary component of gap junctions, contributes to intercellular electrochemical communication. Cx43 undergoes dephosphorylation in early ischemia. We examined whether Cx43 is degraded in association with dephosphorylation during early myocardial ischemia and whether ischemic preconditioning (IP) affects the degradation after rat coronary artery occlusion. Male Sprague-Dawley rats underwent coronary artery occlusion for 1, 2, or 3 hours, or for 1 hour following treatment either with a calcineurin inhibitor (cyclosporine A), proteasome inhibitor (PSI), or lysosomal inhibitor (E64c), or following IP alone or after protein kinase C (PKC) inhibitor (chelerythrine) pretreatment. The IP was afforded by three cycles of 3 minute ischemia and 5 minute reperfusion. A large portion of the phosphorylated Cx43 (pCx43) in the membrane fraction was dephosphorylated, while a small portion was degraded at 1 hour of ischemia. The effects of the inhibitors were dephosphorylation and degradation by calcineurin and proteasome/lysosome, respectively. IP suppressed the decrease in pCx43 and increase in dCx43, while only the former was inhibited by the PKC inhibitor chelerythrine. The Cx43 mRNA level was reduced at 3 hours, but not at 1 hour of ischemia, irrespective of IP. We believe that Cx43 is dephosphorylated and degraded in early ischemia, whereas Cx43 transcription was suppressed at a later phase of ischemia.

Protective effects of immunosuppressants and steroids against ischemia-reperfusion injury in cremaster muscle flap at microcirculatory level

The sequential events between leukocytes and endothelium have significant implications in surgical procedures, trauma, vascular injury, and wound healing. These sequential events are mediated by free oxygen radicals, leukocytes, red blood cells, and endothelial cells. In this study, we investigated the protective effects of steroids and immunosuppressants against ischemia-reperfusion injury in cremaster muscle flaps at the microcirculatory level. In this experimental study, 50 male Sprague-Dawley rats, weighing about 120-130 g, were used. The rats were divided into five groups of 10 rats each: the control group (group 1, n = 10), methyl prednisolone group (group 2, n = 10), dexamethasone group (group 3, n = 10), cyclosporin A group (group 4, n = 10), and azathioprine (group 5, n = 10). Surgical procedures were divided into two stages. In the first stage, a cremaster muscle end-organ tube flap was created by extracting the testes and spermatic cord. The flap was placed into a subcutaneous tunnel in the anteromedial aspect of the ipsilateral limb. In the experimental groups, ischemia was performed by clamping the femoral artery and vein above and below the cremaster pedicle for 4 h. Then the clamps were removed, and perfusion of the cremaster muscle was allowed for 24 h. In the second stage, a round flap was obtained from the cremaster muscle tube-flap to evaluate microcirculation after 24 h of reperfusion, and dissected along its front wall using cauterization. Vessel diameter, red blood cell velocities, leukocyte activation, perfused capillaries, and endothelial edema index were measured and evaluated statistically. There was a significant decrease in the number of rolling, sticking, and transmigrating neutrophils of groups 2 (cyclosporin A), 4 (methylprednisolone), and 3 (azathioprine) (P < 0.05), whereas those of group 5 (dexamethasone) were not decreased (P > 0.05). There was a significant increase in the number of perfused capillaries of groups 2 (cyclosporin A), 4 (methylprednisolone), and 3 (azathioprine) (P < 0.05), nearly 0.75-, 0.5-, and 0.75-fold, respectively. We conclude that cyclosporin and azathioprine showed a protective effect on muscle tissue against ischemia-reperfusion injury by inhibiting leukocyte infiltration, and that methylprednisolone had a beneficial effect against ischemia-reperfusion injury by reducing the synthesis of eicosanoids, edema formation, and leukocyte infiltration. However, we believe that dexamethasone might have a salutary effect due to reducing the synthesis of eicosanoids, edema formation, and release of free oxygen radicals, but not due to leukocyte infiltration.

Docosahexaenoic acid ameliorates murine ischemic acute renal failure and prevents increases in mRNA abundance for both TNF-alpha and inducible nitric oxide synthase

This study demonstrates that intraperitoneal injections of DHA (all cis 4,7,10,13,16,19 docosahexaenoic acid C22: n-3) bound to bovine serum albumin ameliorate murine acute renal failure (ARF) induced by temporary occlusion of the renal artery. Three micromoles of DHA decreased serum creatinine (Scr) from 2.3 mg/dl to 1.1 mg/dl 24 h after reperfusion (n = 15; P < 0.05). Scr of the treated animals were significantly lower than controls throughout a 7-d time course. Although lower doses of DHA were less effective, higher doses were not more effective. Ribonuclease (RNase) protection assays showed that ischemia increased mRNA abundance for TNF-alpha and inducible nitric oxide synthase (iNOS) at 24 h. This increase was prevented by DHA administration. Because TNF-alpha and iNOS contribute to renal ischemic injury, their inhibition may contribute to DHA's salutary effect. In addition, the data may have therapeutic implications, because the DHA improves ARF even when administered at 4 h after reperfusion.

Intercellular adhesion molecule-1 in the heart

Intercellular adhesion molecule-1 (ICAM-1) belongs to the superfamily of immunoglobulin-like adhesion molecules. Up-regulation of ICAM-1 occurs in many different pathophysiological processes. Also, cardiomyocytes can express ICAM-1-for example, in acute myocardial infarction. Moreover, inhibition of ICAM-1 expression in the heart dramatically reduces infarct size. Hence, inhibitors of ICAM-1 may provide a novel therapeutic option for acute myocardial infarction.

Oxidative stress and neutrophil activation—the two keystones of ischemia/reperfusion injury

The widespread introduction of fibrinolytics and recently also PTCA in the treatment of myocardial infarction has changed the picture of modern cardiology. But this therapy also raises new problems and challenges. One of them is the occurrence of extensive tissue injury caused by reperfusion. Reinstitution of oxygen to the ischemic tissues initiates various processes leading to generation of reactive oxygen species (ROSs). Acting on the plasma membrane ROS damage its organization and release various proinflammatory agents. Different proteins, including receptors, ionic channels, transporters or components of transduction pathways are substrates of oxidation by ROSs. Their changed structure results in altered functioning and disruption of vital cellular processes. Another key factor of reperfusion injury is activation and infiltration of infarcted area by polymorphonuclear leukocytes (PMNs). Multiple studies identified consecutive stages of PMN activation and substances being involved in it. Main interest lies in cellular adhesion molecules, particularly selectins and beta2 integrins, as their antagonists were repeatedly found to diminish neutrophil activation and infarct size. Nevertheless new publications strike at the foundations of the established order and confront the relation between neutrophil infiltration and infarct size. PMNs are linked by close ties to other cells involved in inflammatory response. Seemingly also in cardiac ischemia-reperfusion injury, the activity of neutrophils is modulated by lymphocytes and macrophages. The article describes mutual interactions between different factors involved in the reperfusion injury that may enable preparing new treatments, hopefully as effective and successful as reperfusion therapy.

Close association between the reduction in myocardial energy metabolism and infarct size: dose-response assessment of cyclosporine

Cyclosporine protects the heart against ischemia/reperfusion injury, but its effect on cardiac metabolism is largely unknown. We assessed cyclosporine-induced metabolic changes in the rat heart prior to occlusion using magnetic resonance spectroscopy (MRS) and correlated effects with infarct size in a coronary occlusion/reperfusion model. The two study groups were cyclosporine and cyclosporine + coronary occlusion (n = 20/group). Rats were pretreated with cyclosporine (5, 10, 15, and 25 mg/kg/day) or the vehicle by oral gavage for 3 days (n = 4/dose). On day 4, hearts of rats in the cyclosporine group were excised, and extracted cell metabolites were measured using (1)H and (31)P MRS. The second group was subjected to 30 min of coronary artery occlusion followed by 24 h of reperfusion. Infarct size and area at risk were measured using a double staining method. In the cyclosporine group, cyclosporine reduced cardiac energy metabolism (ATP: r = -0.89, P < 0.001) via depression of oxidative phosphorylation and the Krebs' cycle in a dose-dependent manner. The decrease of ATP levels was positively correlated with changes of NAD(+) (r = 0.89), glutamate (r = 0.95), glutamine (r = 0.84), and glucose concentrations (r = 0.92, all P < 0.002). It was inversely correlated with lactate (r = -0.93, P < 0.001). In the coronary occlusion group, cyclosporine dose dependently reduced the ratio [area of infarct/area of the left ventricle] (r = -0.86, P < 0.01), with 15 mg/kg/day being the most effective cyclosporine dose. The reduction in infarct size correlated with the reduction in oxidative phosphorylation (ATP: r = 0.97; NAD(+): r = 0.82, P < 0.01). The reduction in cardiac energy metabolism before occlusion may be the cause of myocardial preservation during ischemia/reperfusion.

Cyclosporine A protects against apoptosis in ischaemic/reperfused rat kidneys

1. Renal ischaemia followed by reperfusion leads to acute renal failure in both native kidneys and renal allografts. Cyclosporine A (CsA) has been used as an immunosuppressive agent in organ transplantation. In the present study, the effect of CsA on ischaemia/reperfusion-induced apoptosis in the kidney was investigated. 2. Ischaemia/reperfusion injury caused widespread apoptosis primarily in the medulla of the kidney. At 1.5 mg/kg per day, CsA significantly reduced the number of apoptotic cells in rat kidney after ischaemia/reperfusion injury. 3. Low-dose CsA treatment did not affect the levels of creatinine in the serum of rats after ischaemia/reperfusion injury.

Comparison of the effects of cyclosporin a on the metabolism of perfused rat brain slices during normoxia and hypoxia

The authors evaluated and compared the metabolic effects of cyclosporin A in the rat brain during normoxia and hypoxia/reperfusion. Ex vivo 31P magnetic resonance spectroscopy experiments based on perfused rat brain slices showed that under normoxic conditions, 500 microg/L cyclosporin A significantly reduced mitochondrial energy metabolism (nucleotide triphosphate, 83 +/- 9% of controls; phosphocreatine, 69 +/- 9%) by inhibition of the Krebs cycle (glutamate, 77 +/- 5%) and oxidative phosphorylation (NAD+, 65 +/- 14%) associated with an increased generation of reactive oxygen species (285 +/- 78% of control). However, the same cyclosporin A concentration (500 microg/L) was found to be the most efficient concentration to inhibit the hypoxia-induced mitochondrial release of Ca2+ in primary rat hippocampal cells with cytosolic Ca2+ concentrations not significantly different from normoxic controls. Addition of 500 microg/L cyclosporin A to the perfusion medium protected high-energy phosphate metabolism (nucleotide triphosphate, 11 +/- 15% of control vs. 35 +/- 9% with 500 microg/L cyclosporin A) and the intracellular pH (6.2 +/- 0.1 control vs. 6.6 +/- 0.1 with cyclosporin A) in rat brain slices during 30 minutes of hypoxia. Results indicate that cyclosporin A simultaneously decreases and protects cell glucose and energy metabolism. Whether the overall effect was a reduction or protection of cell energy metabolism depended on the concentrations of both oxygen and cyclosporin A in the buffer solution.

Protective effects of cyclosporin A from endotoxin-induced myocardial dysfunction and apoptosis in rats

Myocardial depression can be demonstrated following administration of endotoxin. Proposed mechanisms of endotoxin-induced myocardial dysfunction include the release of proinflammatory mediators, focal myocardial ischemia, and the presence of activated leukocytes within the myocardium. Recently, myocardial caspase activation and mitochondria-related apoptotic events (i.e., release of cytochrome c) were demonstrated in the failing septic heart. Here, we tested the hypothesis that immunosuppressors, cyclosporin A and tacrolimus (FK 506), would improve inflammation, heart nuclear apoptosis, and myocardial dysfunction in endotoxin-treated rats. Myocardial contractility was assessed using an isolated heart preparation. Heart leukocyte infiltration was assessed by measurement of heart myeloperoxidase activity. Leukocyte activation was studied using the intravital microscopy of the mesenteric venule. Apoptosis was detected as myocardial DNA fragmentation, downstream caspase activation, and mitochondrial cytochrome c release. Both cyclosporin A and FK 506 reduced heart leukocyte sequestration and venular adhesion in endotoxin-treated rats. Cyclosporin A, which blocks mitochondrial cytochrome c release, was able to reduce endotoxin-induced myocardial end-stage nuclear apoptosis and heart dysfunction, whereas tacrolimus had no such effects. These effects could be related to the unique properties of cyclosporin A to act on mitochondria.

Cyclosporin A pretreatment in a rat model of warm ischaemia/reperfusion injury

BACKGROUND/AIMS

These studies investigated the role of apoptosis following ischaemia/reperfusion (I/R) injury to the liver and the effect of pretreatment with Cyclosporin A.

METHODS

Male Sprague-Dawley rats received 30 min of warm ischaemia followed by a period of reperfusion of 6 h. Rats were given olive oil or Cyclosporin A (30 mg/kg p.o.) the day before surgery. Neutrophil numbers were assessed in haematoxylin-eosin-stained sections of liver. In situ staining of sections using TdT-mediated dUTP-fluorescein nick-end labelling was carried out to determine the extent of apoptosis, followed by electron microscopy. Semi-quantitative polymerase chain reaction (PCR) analysis of the transcript for Fas antigen was performed.

RESULTS AND CONCLUSIONS

High levels of apoptosis were observed in I/R injury, which were greatly ameliorated in Cyclosporin A-pretreated groups. PCR analysis indicated a reduction in the level of expression of Fas transcript in Cyclosporin A-treated rats. Histological analysis showed a significant increase in the number of neutrophils infiltrating I/R-injured tissue (62 +/- 10.69, n=16), which was markedly reduced by Cyclosporin A pretreatment (16 +/- 7, n=6, P<0.05). These results indicate a role of parenchymal apoptosis in the pathogenesis of I/R injury, which occurs in association with neutrophil infiltration, both of which can be significantly reduced by Cyclosporin A pretreatment.

Cyclosporine induces myocardial connective tissue growth factor in spontaneously hypertensive rats on high-sodium diet

BACKGROUND

The introduction of cyclosporine (CsA) has led to an improvement in the prognosis of solid organ transplantation. However, drug-induced hypertension and nephrotoxicity, associated with the development of atherosclerosis and coronary heart disease, still worsen the long-term outcome of CsA-treated patients. Whether the CsA-induced myocardial changes are associated with the induction of connective tissue growth factor (CTGF), a recently found polypeptide implicated in extracellular matrix synthesis, is not known.

METHODS

Spontaneously hypertensive rats (8-9 weeks old) were treated with CsA (5 mg x kg(-1) x d(-1) subcutaneously) for 6 weeks. The influence of angiotensin-converting enzyme inhibition (enalapril 30 mg x kg(-1) x d(-1) orally) and angiotensin-1 receptor blockade (valsartan 3 and 30 mg x kg(-1) x d(-1) orally) on CsA toxicity was also investigated. Myocardial morphology was examined, and vascular lesions were scored. Localization and the quantitative expression of CTGF, as well as collagen I and collagen III, mRNA were evaluated by in situ hybridization and Northern blot.

RESULTS

CsA-induced hypertension and nephrotoxicity were associated with myocardial infarcts and vasculopathy of the coronary arteries. CsA increased myocardial CTGF, collagen I, and collagen III mRNA expressions by 91%, 198%, and 151%, respectively. CTGF mRNA expression colocalized with the myocardial lesions. Blockade of the renin-angiotensin system prevented vascular damage and the CsA-induced CTGF, collagen I, and collagen III mRNA overexpressions in the heart.

CONCLUSIONS

CsA increases CTGF, collagen I, and collagen III mRNA expressions in the heart. The induction of CTGF gene is mediated, at least in part, by angiotensin II.

Limited use of cyclosporin A in skeletal muscle ischemia--reperfusion injury

Reperfusion injury is propagated by an inflammatory-mediated tissue edema and damage after reestablishment of vascular flow following an initial ischemic insult. In the field of transplantation, cyclosporin A(CsA) provides protection against chronic graft rejection through lymphocyte immunosuppression. Evidence for an independent protective effect of CsA against ischemia-reperfusion (IR) injury during organ transfer has prompted studies showing the benefit of CsA in various ischemia-exposed visceral organs. The authors hypothesized that CsA administration may similarly benefit IR injury after skeletal muscle amputations. To determine the effects of CsA on IR injury the authors induced 4 hours of ischemia on the gracilis muscle in a rat model. CsA (15 mg per kilogram orally) was administered in two experimental groups: (1) preischemic (N = 6): 48, 24, and 3 hours before ischemia; and (2) postischemic (N = 6): 30 minutes after induction of ischemia. The effects of CsA on IR muscle injury were observed in each of the experimental groups as well as a control group (N = 6) exposed to similar ischemia and administered a saline vehicle. Muscle viability (nitro blue tetrazolium staining) and muscle edema (wet-to-dry weight ratio) were assessed 24 hours after reperfusion. The preischemic CsA-treated gracilis muscle group demonstrated improved muscle viability (39.1 +/- 4.8%) when compared with the ischemic control muscle group (23.8 +/- 7.1%; p = 0.039). Furthermore, the preischemic CsA-treated muscle group demonstrated decreased edema (1.137 +/- 0.095 times the contralateral nonischemic muscle) when compared with the control ischemic muscle group (1.248 +/- 0.045 times the contralateral nonischemic muscle; p = 0.011). Although a trend toward improved muscle viability (32.1 +/- 4.2%) and decreased edema formation (1.200 +/- 0.062 times the contralateral nonischemic muscle) was observed in the peri-ischemic CsA-treated group when compared with the control ischemic muscle group, these differences were not significant. These observations confirm the beneficial effects of preischemic CsA therapy observed in organ transplantation research and suggest limited clinical use of peri-ischemic CsA therapy for patients with musculoskeletal amputations.

Free radicals, cytokines and nitric oxide in cardiac failure and myocardial infarction

Myocardial infarction is the most common cause of congestive cardiac failure. Free radicals, cytokines, nitric oxide (NO) and antioxidants play a major role both in atherosclerosis and myocardial damage and preservation. In the early stages of atherosclerosis, neutrophils and monocytes infiltrate the intima and generate free radicals which damage the endothelial cells. As a result, production of NO and prostacyclin by the endothelial cells declines, which have cardioprotective actions. This also has relevance to the beneficial action of aspirin since, it can modulate both prostanoid and L-arginine-NO systems and NF-kB translocation. In both acute myocardial infarction and chronic congestive cardiac failure, the plasma levels of various inflammatory mediators such as interleukins and tumour necrosis factor-alpha (TNFalpha) are elevated. TNFalpha, produced by the inflammatory cells and the myocardium, can suppress myocardial contractility and induce the production of free radicals, which in turn can further damage the myocardium. Transforming growth factor beta (TGFbeta), polyunsaturated fatty acids and the glucose-insulin-potassium regimen can antagonize the harmful actions of TNFalpha and protect the myocardium. This explains why efforts made to reduce the levels of pro-inflammatory cytokines have beneficial action and preserve the myocardium.

Cardioprotection by the phytoestrogen genistein in experimental myocardial ischaemia-reperfusion injury

1. Soybean phytoestrogens have no oestrogen agonist effects on the reproductive system and therefore it is reasonable to explore the potential of these naturally occurring plant oestrogens in the cardiovascular pathology. We therefore investigated the effects of genistein in a rat model of myocardial ischaemia-reperfusion injury. 2. Anaesthetized rats were subjected to total occlusion (45 min) of the left main coronary artery followed by 5 h reperfusion (MI/R). Sham operated rats were used as controls. Myocardial necrosis, myocardial myeloperoxidase activity (MPO), serum creatinine phosphokinase activity (CPK), serum and macrophage Tumour Necrosis Factor-alpha (TNF-alpha), cardiac intercellular adhesion molecule-1 (ICAM-1) immunostaining, cardiac mRNA for ICAM-1 evaluated by the means of reverse transcriptase polymerase chain reaction (RT - PCR), ventricular arrhythmias and myocardial contractility (left ventricle dP/dt(max)) were evaluated. 3. Myocardial ischaemia and reperfusion in untreated rats produced marked myocardial necrosis, increased serum CPK activity and MPO activity both in the area-at-risk and in the necrotic area, reduced myocardial contractility, caused ventricular arrhythmias and induced a marked increase in serum and macrophage TNF-alpha. Furthermore myocardial ischaemia-reperfusion injury increased ICAM-1 expression in the myocardium. 4. Administration of genistein (1 mg kg(-1), i.v., 5 min after coronary artery occlusion) lowered myocardial necrosis and MPO activity in the area-at-risk and in the necrotic area, decreased serum CPK activity, increased myocardial contractility, decreased the occurrence of ventricular arrhythmias, reduced serum and macrophages levels of TNF-alpha and blunted ICAM-1 expression in the injured myocardium. Finally genistein added in vitro to peritoneal macrophages collected from untreated rats subjected to myocardial ischaemia-reperfusion injury significantly reduced TNF-alpha production. 5. Our data suggest that genistein limits the inflammatory response and protects against myocardial ischaemia-reperfusion injury.