The leukocyte cell adhesion cascade and its role in myocardial ischemia-reperfusion injury

A 3D culture system improves the yield of MSCs-derived extracellular vesicles and enhances their therapeutic efficacy for heart repair

BACKGROUND

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs), due to their inner functional substances, have shown great value in treating acute myocardial infarction (AMI). However, their clinical application is limited by a low yield. In the present study, we cultured EVs using a hollow fiber bioreactor-based three-dimensional (3D) system, and assessed their therapeutic effectiveness on AMI.

METHODS

The MSCs separated from fresh human umbilical cord were planted into the flasks of two systems: two-dimensional (2D) culture and hollow-fiber-bioreactor based 3D culture. EVs were extracted from the culture supernatants. Characteristics and yields of EVs from two culture systems, namely 2D-EVs and 3D-EVs, were compared. A rat model of AMI was built up to assess their therapeutic efficacy on AMI.

RESULTS

The yield of 3D-EVs was higher, with biofunctions similar to those of 2D-EVs. 3D-EVs repressed the apoptosis of cardiomyocytes, facilitated angiogenesis, and regulated the transition of macrophage subpopulations after myocardial infarction, and eventually improved cardiac function in the AMI rats.

CONCLUSIONS

The hollow fiber 3D culture system can increase the yield of MSCs-derived EVs to render a strong cardioprotective effect in AMI rats.

M3 subtype of muscarinic acetylcholine receptor promotes cardioprotection via the suppression of miR-376b-5p

The M₃ subtype of muscarinic acetylcholine receptors (M₃-mAChR) plays a protective role in myocardial ischemia and microRNAs (miRNAs) participate in many cardiac pathophysiological processes, including ischemia-induced cardiac injury. However, the role of miRNAs in M₃-mAChR mediated cardioprotection remains unexplored. The present study was designed to identify miRNAs that are involved in cardioprotective effects of M₃-mAChR against myocardial ischemia and elucidate the underlying mechanisms. We established rat model of myocardial ischemia and performed miRNA microarray analysis to identify miRNAs involved in the cardioprotection of M₃-mAChR. In H9c2 cells, the viability, intracellular free Ca²⁺ concentration ([Ca²⁺]i), intracellular reactive oxygen species (ROS), miR-376b-5p expression level, brain derived neurophic factor (BDNF) and nuclear factor kappa-B (NF-κB) levels were measured. Our results demonstrated that M₃-mAChR protected myocardial ischemia injury. Microarray analysis and qRT-PCR revealed that miR-376b-5p was significantly up-regulated in ischemic heart tissue and the M₃-mAChRs agonist choline reversed its up-regulation. In vitro, miR-376b-5p promoted H₂O₂-induced H9c2 cell injuries measured by cells viability, [Ca²⁺]i and ROS. Western blot and luciferase assay identified BDNF as a direct target of miR-376b-5p. M₃-mAChR activated NF-κB and thereby inhibited miR-376b-5p expression. Our data show that a novel M₃-mAChR/NF-κB/miR-376b-5p/BDNF axis plays an important role in modulating cardioprotection. MiR-376b-5p promotes myocardial ischemia injury possibly by inhibiting BDNF expression and M₃-mAChR provides cardioprotection at least partially mediated by the downregulation of miR-376b-5p through NF-κB. These findings provide new insight into the potential mechanism by which M₃-mAChR provides cardioprotection against myocardial ischemia injury.

Proteasome inhibitor attenuates skeletal muscle reperfusion injury by blocking the pathway of nuclear factor-kappaB activation

BACKGROUND

Nuclear factor-kappaB is a key transcriptional factor in the regulation of inflammatory factors that are involved in tissue reperfusion injury, but conflicting data have been presented in the literature. The proteasome regulates proteins that control cell-cycle progression and apoptosis, and inhibition of the proteasome has been shown to reduce nuclear factor-kappaB activation and reperfusion injury. Although bortezomib is a potent proteasome inhibitor, its role in skeletal muscle reperfusion injury has not been documented, and its effects on the regulation of inflammatory factors in reperfused tissue are unclear. In this study, the authors investigated the role of nuclear factor-kappaB in skeletal muscle reperfusion injury and the effect of bortezomib (a proteasome inhibitor) on reperfusion injury.

METHODS

Pedicled cremaster muscle flaps from bortezomib-treated and phosphate-buffered saline-treated control mice were subjected to 4.5 hours of ischemia and 90 minutes of reperfusion.

RESULTS

During reperfusion, arterial diameters and blood flow recovered earlier and more completely in bortezomib-treated muscle than in controls. Compared with controls, Western blot analysis demonstrated a significant reduction in degradation of nuclear factor-kappaB inhibitory protein and expression of inducible nitric oxide synthase protein in bortezomib-treated muscle at the end of reperfusion. Immunohistochemistry showed decreased nuclear factor-kappaB p65-binding activity and down-regulated protein expression of intercellular adhesion molecule-1 and nitrotyrosine, accompanied by less muscle edema and inflammation as proven by histologic examination.

CONCLUSIONS

Bortezomib effectively blocks nuclear factor-kappaB activation in attenuating muscle reperfusion injury through inhibiting nuclear factor-kappaB inhibitory protein degradation. Therefore, inhibition of proteasome activity may provide a novel therapeutic strategy for the treatment of skeletal muscle reperfusion injury.

The new face of bispecific antibodies: targeting cancer and much more

The term magic bullet was first coined by bacteriologist Paul Ehrlich in the late 1800s to describe a chemical with the ability to specifically target microorganisms while sparing normal host cells. His concept was later expanded to include treatments for cancer, but it is only in recent decades, with development and improvements in monoclonal antibody (mAb) technology, that the full therapeutic implications of "magic bullet" strategies have been realized. Expanding on the success of mAb-targeting, linking the specificity of two mAbs into a single agent, called a bispecific antibody (BiAb), allows for targeting of a therapeutic biological agent or cell to specific tissue antigens. Classically, BiAbs have been used for several decades to redirect cytotoxic T cells or other effector cells to kill tumor cells. Here, we review preclinical models and ongoing phase I clinical trials in which arming polyclonally activated T cells with BiAbs may provide anti-tumor activity without dose-limiting toxicities. Additionally, we review findings from this novel strategy that merges magic bullet technology with hematopoietic stem cells to repair injured myocardium. Arming stem cells with BiAbs directed at injury-associated antigens enhances specific homing and engraftment to myocardial infarctions and may significantly improve cardiac function, strongly suggesting new paradigms for BiAb-targeting applications in tissue repair.

Virtual reality of stem cell transplantation to repair injured myocardium

The search for the fountain of youth continues into the 21st century with hopes that embryonic or hematopoietic stem cells (SC) will repair injured tissues in the heart, lungs, pancreas, muscles, nerves, liver, or skin. This commentary focuses on the potential of SC for inducing cardiac regeneration after myocardial injury, the barriers to SC treatment that need to be overcome for ensuring successful cardiac repair, and the experimental approaches that can be applied to the problem.

Endotoxin elicits nitric oxide release in rat but prostacyclin synthesis in human and bovine vascular smooth muscle cells

Lipopolysaccharide (LPS) exposure to cells and tissues can mimic the biochemical events leading to septic shock. Previous data demonstrated a massive upregulation of prostaglandin endoperoxide H2 synthase (PGHS-2), but not NO synthase-2 (NOS-2) in bovine smooth muscle cells (SMC) between 2 and 12 h of LPS exposure. This caused an abundant release of prostacyclin (PGI2) by constitutive PGI2-synthase as a counterregulation to a dysfunctional endothelium. We here report that human as well as bovine SMC mainly respond by the induction of PGHS-2 and the subsequent release of PGI2, whereas rat SMC exhibited a distinct induction of NOS-2 and released significantly higher amounts of *NO compared with cattle and human. The induction of either PGHS-2 or NOS-2 in the three different species investigated seems to be mutually exclusive in the time window of 2-24 h. This finding should be considered in the setup of experimental models for the investigation of septic shock.

Glucocorticoid Treatment Prevents Progressive Myocardial Dysfunction Resulting From Experimental Coronary Microembolization

Background— The frequency and importance of microembolization in patients with acute coronary syndromes and during coronary interventions have recently been appreciated. Experimental microembolization induces immediate ischemic dysfunction, which recovers within minutes. Subsequently, progressive contractile dysfunction develops over several hours and is not associated with reduced regional myocardial blood flow (perfusion-contraction mismatch) but rather with a local inflammatory reaction. We have now studied the effect of antiinflammatory glucocorticoid treatment on this progressive contractile dysfunction.

Methods and Results— Microembolization was induced by injecting microspheres (42-μm diameter) into the left circumflex coronary artery. Anesthetized dogs were followed up for 8 hours and received placebo (n=7) or methylprednisolone 30 mg/kg IV either 30 minutes before (n=7) or 30 minutes after (n=5) microembolization. In addition, chronically instrumented dogs received either placebo (n=4) or methylprednisolone (n=4) 30 minutes after microembolization and were followed up for 1 week. In acute placebo dogs, posterior systolic wall thickening was decreased from 20.0±2.1% (mean±SEM) at baseline to 5.8±0.6% at 8 hours after microembolization. Methylprednisolone prevented the progressive myocardial dysfunction. Increased leukocyte infiltration in the embolized myocardium was prevented only when methylprednisolone was given before microembolization. In chronic placebo dogs, progressive dysfunction recovered from 5.0±0.7% at 4 to 6 hours after microembolization back to baseline (19.1±1.6%) within 5 days. Again, methylprednisolone prevented the progressive myocardial dysfunction.

Conclusions— Methylprednisolone, even when given after microembolization, prevents progressive contractile dysfunction.

Role of reactive oxygen species in ischemic preconditioning of subcellular organelles in the heart

Ischemic preconditioning (IPC) is an endogenous adaptive mechanism and is manifested by early and delayed phases of cardioprotection. Brief episodes of ischemia-reperfusion during IPC cause some subtle functional and structural alterations in sarcolemma, mitochondria, sarcoplasmic reticulum, myofibrils, glycocalyx, as well as nucleus, which render these subcellular organelles resistant to subsequent sustained ischemia-reperfusion insult. These changes occur in functional groups of various receptors, cation transporters, cation channels, and contractile and other proteins, and may explain the initial effects of IPC. On the other hand, induction of various transcriptional factors occurs to alter gene expression and structural changes in subcellular organelles and may be responsible for the delayed effects of IPC. Reactive oxygen species (ROS), which are formed during the IPC period, may cause these changes directly and indirectly and act as a trigger of IPC-induced cardioprotection. As ROS may be one of the several triggers proposed for IPC, this discussion is focused on the current knowledge of both ROS-dependent and ROS-independent mechanisms of IPC. Furthermore, some events, which are related to functional preservation of subcellular organelles, are described for a better understanding of the IPC phenomenon.

Exacerbation of myocardial injury in transgenic mice overexpressing FGF-2 is T cell dependent

Fibroblast growth factor-2 (FGF-2) is cardioprotective when added exogenously, stimulates cardiac myocyte proliferation, and is a mediator of tissue repair after injury. Furthermore, transgenic (TG) mice overexpressing FGF-2 in cardiac muscle demonstrate increased resistance to injury in an isolated heart model of ischemia-reperfusion. We investigated how increasing the endogenous FGF-2 levels in the heart affects the extent of myocardial damage induced by isoproterenol in vivo. Histopathological evaluation of hearts after intraperitoneal injection of isoproterenol yielded significantly higher scores for myocardial damage in FGF-2 TG lines compared with non-TG mice. After 1 day, FGF-2 TG mouse hearts displayed more cellular infiltration correlating with increased tissue damage. Immunostaining of non-TG and FGF-2 TG mouse hearts showed the presence of leukocytes in the infiltrate, including T cells expressing FGF receptor-1. Treatment of mice with T cell suppressors cyclosporin A and anti-CD3epsilon significantly decreased the level of myocardial injury observed after isoproterenol and equalized the histopathology scores in FGF-2 TG and non-TG hearts. These data demonstrate a direct T cell involvement in the response to isoproterenol-induced injury in vivo. Moreover, the findings indicate that the exacerbation of myocardial damage in FGF-2 TG mice was dependent on T cell infiltration, implicating FGF-2 in the inflammatory response seen in cardiac tissue after injury in vivo.

Na(+)/H(+) exchange inhibition prevents endothelial dysfunction after I/R injury

Whereas inhibition of the Na(+)/H(+) exchanger (NHE) has been demonstrated to reduce myocardial infarct size in response to ischemia-reperfusion injury, the ability of NHE inhibition to preserve endothelial cell function has not been examined. This study examined whether NHE inhibition could preserve endothelial cell function after 90 min of regional ischemia and 180 min of reperfusion and compared this inhibition with ischemic preconditioning (IPC). In a canine model either IPC, produced by one 5-min coronary artery occlusion (1 x 5'), or the specific NHE-1 inhibitor eniporide (EMD-96785, 3.0 mg/kg) was administered 15 min before a 90-min coronary artery occlusion followed by 3 h of reperfusion. Infarct size (IS) was determined by 2,3,5-triphenyl tetrazolium chloride staining and expressed as a percentage of the area-at-risk (IS/AAR). Endothelial cell function was assessed by measurement of coronary blood flow in response to intracoronary acetylcholine infusion at the end of reperfusion. Whereas neither control nor IPC-treated animals exhibited a significant reduction in IS/AAR or preservation of endothelial cell function, animals treated with the NHE inhibitor eniporide showed a marked reduction in IS/AAR and a significantly preserved endothelial cell function (P < 0.05). Thus NHE-1 inhibition is more efficacious than IPC at reducing IS/AAR and at preserving endothelial cell function in dogs.

Nuclear factor kappa-B and the heart

Nuclear factor kappa-B (NFkappaB), a redox-sensitive transcription factor regulating a battery of inflammatory genes, has been indicated to play a role in the development of numerous pathological states. Activation of NFkappaB induces gene programs leading to transcription of factors that promote inflammation, such as leukocyte adhesion molecules, cytokines, and chemokines, although some few substances with possible anti-inflammatory effects are also NFkappaB regulated. The present article reviews basic regulation of NFkappaB and its activation, cell biological effects of NFkappaB activation and the role of NFkappaB in apoptosis. Evidence involving NFkappaB as a key factor in the pathophysiology of ischemia-reperfusion injury and heart failure is discussed. Although activation of NFkappaB induces pro-inflammatory genes, it has lately been indicated that the transcription factor is involved in the signaling of endogenous myocardial protection evoked by ischemic preconditioning. A possible role of NFkappaB in the development of atherosclerosis and unstable coronary syndromes is discussed. Nuclear factor kappa-B may be a new therapeutic target for myocardial protection.

Cardioprotection: emerging pharmacotherapy

By the year 2020, it is predicted that acute coronary occlusion will be the major cause of death in the world. Recent advances in reperfusion therapy have substantially improved survival of patients with acute coronary syndromes. While early reperfusion reduces mortality, a time limitation exists with regard to myocardial salvage. In fact, the major limiting factor in further improving survival of patients with myocardial ischaemia is the susceptibility of the cardiomyocyte to ischaemic insult and lethal cell injury. Over the last decade substantial progress has been made in our understanding of the fundamental mechanisms of ischaemia/reperfusion injury. From this work novel means which limit or delay myocyte death have emerged and are currently under development as therapeutic candidates for the management of acute coronary syndromes. This report examines cardioprotective mechanisms and reviews clinical evidence for myocardial protective therapies.

Dynamic progression of contractile and endothelial dysfunction and infarct extension in the late phase of reperfusion

BACKGROUND

Myocardial injury during early reperfusion (R) has been well documented. However, the extent and time course of myocardial injury during late R are still unclear. The purpose of this study was to determine the extent of regional contractile and endothelial dysfunction and myocardial blood flow (MBF) defect as well as extension of infarction in association with neutrophil (PMN) actions during R.

MATERIALS AND METHODS

A total of 29 dogs underwent a protocol of 1 h LAD ischemia followed by 6, 24, 48, and 72 h of R, respectively. Regional contractile function (sonomicrometry), MBF (colored microspheres), infarct size (triphenyltetrazolium chloride staining), and PMN localization (immunohistochemistry) were determined.

RESULTS

Percentage segmental shortening at 6, 24, 48, and 72 h of R was significantly blunted (-1.8 +/- 1.2,* - 0.37 +/- 0. 6,* 0.04 +/- 0.2,* and 5.9 +/- 1.2* vs baseline 17.7 +/- 0.8). MBF (ml/min/g) was attenuated at 24 (0.27 +/- 0.03*), 48 (0.46 +/- 0. 07*), and 72 h of R (0.48 +/- 0.06*) vs 6 h of R (0.65 +/- 0.06). Infarct size increased from 6 (27 +/- 2%) to 24 h of R (41 +/- 2%*) with no further increase at 48 and 72 h of R, consistent with a peak of creatine kinase activity. PMN adherence (mm(2) endothelium) to left anterior descending coronary artery (LAD) segments was increased after 6 h of R (63 +/- 3*) vs nonischemic left circumflex coronary artery (LCX) segments (42 +/- 2) with a peak at 48 h of R (111 +/- 5*). Endothelium-dependent vascular relaxation in the LAD was also blunted at 6, 24, and 48 h of R. Immunostaining revealed CD18-positive PMNs were mainly accumulated in intravascular space during 6 h of R with an increase in migration of PMNs seen at 24 h of R, consistent with a peak of myeloperoxidase release. Myeloperoxidase activity in a given area at risk sample was significantly correlated with infarct extension during the first 24 h of R.

CONCLUSIONS

These results provide pathologic evidence for myocardial injury during the extended R and a basis for exploration of interventions designed to limit myocardial injury after ischemia. (*P < 0.05 vs Baseline, 6 h of R and LCX segments.)

Na(+)/H(+) exchange inhibition-induced cardioprotection in dogs: effects on neutrophils versus cardiomyocytes

Numerous studies have examined the effect of Na(+)/H(+) exchanger (NHE) inhibition on the myocardium; however, the effect of NHE-1 inhibition on neutrophil function has not been adequately examined. An in vivo canine model of myocardial ischemia-reperfusion injury in which 60 min of left anterior descending coronary artery occlusion followed by 3 h of reperfusion was used to examine the effect of NHE-1 inhibition on infarct size (IS) and neutrophil function. BIIB-513, a selective inhibitor of NHE-1, was infused before ischemia. IS was expressed as a percentage of area at risk (IS/AAR). NHE-1 inhibition significantly reduced IS/AAR and reduced neutrophil accumulation in the ischemic myocardium. NHE-1 inhibition attenuated both phorbol 12-myristate 13-acetate- and platelet-activating factor-induced neutrophil respiratory burst but not CD18 upregulation. Furthermore, NHE-1 inhibition directly protected cardiomyocytes against metabolic inhibition-induced lactate dehydrogenase release and hypercontracture. This study provides evidence that the cardioprotection induced by NHE-1 inhibition is likely due to specific protection of cardiomyocytes and attenuation of neutrophil activity.

Kallikrein-like amidase activity in renal ischemia and reperfusion

We assessed a kallikrein-like amidase activity probably related to the kallikrein-kinin system, as well as the participation of leukocyte infiltration in renal ischemia and reperfusion. Male C57BL/KSJmdb mice were subjected to 20 or 60 min of ischemia and to different periods of reperfusion. A control group consisted of sham-operated mice, under similar conditions, except for ischemia induction. Kallikrein-like amidase activity, Evans blue extravasation and myeloperoxidase activity were measured in kidney homogenates, previously perfused with 0.9% NaCl. Plasma creatinine concentration increased only in the 60-min ischemic group. After 20 min of ischemia and 1 or 24 h of reperfusion, no change in kallikrein-like amidase activity or Evans blue extravasation was observed. In the mice subjected to 20 min of ischemia, edema was evident at 1 h of reperfusion, but kidney water content returned to basal levels after 24 h of reperfusion. In the 60-min ischemic group, kallikrein-like amidase activity and Evans blue extravasation showed a similar significant increase along reperfusion time. Kallikrein-like amidase activity increased from 4 nmol PNA mg protein-1 min-1 in the basal condition to 15 nmol PNA mg protein-1 min-1 at 10 h of reperfusion. For dye extravasation the concentration measured was near 200 microg of Evans blue/g dry tissue in the basal condition and 1750 microg of Evans blue/g dry tissue at 10 h of reperfusion. No variation could be detected in the control group. A significant increase from 5 to 40 units of DeltaAbs 655 nm g wet tissue-1 min-1 in the activity of the enzyme myeloperoxidase was observed in the 60-min ischemic group, when it was evaluated after 24 h of reperfusion. Histological analysis of the kidneys showed migration of polymorphonuclear leukocytes from the vascular bed to the interstitial tissue in the 60-min ischemic group after 24 h of reperfusion. We conclude that the duration of ischemia is critical for the development of damage during reperfusion and that the increase in renal cortex kallikrein-like amidase activity probably released from both the kidney and leukocytes may be responsible, at least in part, for the observed effects, probably through direct induction of increased vascular permeability.

Optimization of ex vivo pressure mediated delivery of antisense oligodeoxynucleotides to ICAM-1 reduces reperfusion injury in rat cardiac allografts

BACKGROUND

Our purpose was to optimize hyperbaric pressure as a vector for ex vivo transfection of antisense oligodeoxynucleotides (AS-ODN) to intercellular adhesion molecule-1 to limit reperfusion injury (RI) in cardiac allografts. We investigated the effects of increased pressure, incubation time, and AS-ODN concentrations on transfection efficiency and toxicity.

METHODS AND RESULTS

PVG (RT1c) donor hearts were heterotopically transplanted to ACI (RT1a) recipients. Donor hearts were harvested and the various groups were treated at: (1) different pressure (1-9 atm) for 45 min with 80 micromol/liter AS-ODN; (2) different incubation times (15 min to 6 hr) at 5 atm with 80 micromol/liter AS-ODN; 3) different AS-ODN concentrations (80-240 micromol/liter) at 5 atm for 45 min. Hearts were procured 24 or 72 hr after transplantation. Transfection efficiency was determined with fluorescein-labeled AS-ODN. The degree of RI was determined with biochemical and histological analysis. Increasing pressure from ambient (1 atm) pressure to pressures as high as 9 atm leads to a increase in transfection efficiency from 1.7+/-.5 to 62+/-3.9% and a reduction in RI. Increased incubation time up to 45 min increased transfection efficiency and reduced RI, but longer incubation times induced significant toxicity to the allograft. Increased AS-ODN concentrations improved transfection and reduced RI.

CONCLUSIONS

Hyperbaric pressure is a safe and effective vector for the ex vivo delivery of AS-ICAM-1-ODN to rodent cardiac allografts and results in a reduction in reperfusion injury.

Ischemic cell death in brain neurons

This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell death occurs by a necrotic pathway characterized by either ischemic/homogenizing cell change or edematous cell change. Death also occurs via an apoptotic-like pathway that is characterized, minimally, by DNA laddering and a dependence on caspase activity and, optimally, by those properties, additional characteristic protein and phospholipid changes, and morphological attributes of apoptosis. Death may also occur by autophagocytosis. The cell death process has four major stages. The first, the induction stage, includes several changes initiated by ischemia and reperfusion that are very likely to play major roles in cell death. These include inhibition (and subsequent reactivation) of electron transport, decreased ATP, decreased pH, increased cell Ca(2+), release of glutamate, increased arachidonic acid, and also gene activation leading to cytokine synthesis, synthesis of enzymes involved in free radical production, and accumulation of leukocytes. These changes lead to the activation of five damaging events, termed perpetrators. These are the damaging actions of free radicals and their product peroxynitrite, the actions of the Ca(2+)-dependent protease calpain, the activity of phospholipases, the activity of poly-ADPribose polymerase (PARP), and the activation of the apoptotic pathway. The second stage of cell death involves the long-term changes in macromolecules or key metabolites that are caused by the perpetrators. The third stage of cell death involves long-term damaging effects of these macromolecular and metabolite changes, and of some of the induction processes, on critical cell functions and structures that lead to the defined end stages of cell damage. These targeted functions and structures include the plasmalemma, the mitochondria, the cytoskeleton, protein synthesis, and kinase activities. The fourth stage is the progression to the morphological and biochemical end stages of cell death. Of these four stages, the last two are the least well understood. Quite little is known of how the perpetrators affect the structures and functions and whether and how each of these changes contribute to cell death. According to this description, the key step in ischemic cell death is adequate activation of the perpetrators, and thus a major unifying thread of the review is a consideration of how the changes occurring during and after ischemia, including gene activation and synthesis of new proteins, conspire to produce damaging levels of free radicals and peroxynitrite, to activate calpain and other Ca(2+)-driven processes that are damaging, and to initiate the apoptotic process. Although it is not fully established for all cases, the major driving force for the necrotic cell death process, and very possibly the other processes, appears to be the generation of free radicals and peroxynitrite. Effects of a large number of damaging changes can be explained on the basis of their ability to generate free radicals in early or late stages of damage. Several important issues are defined for future study. These include determining the triggers for apoptosis and autophagocytosis and establishing greater confidence in most of the cellular changes that are hypothesized to be involved in cell death. A very important outstanding issue is identifying the critical functional and structural changes caused by the perpetrators of cell death. These changes are responsible for cell death, and their identity and mechanisms of action are almost completely unknown.

Renal ischemia-induced increase in vascular permeability is limited by hypothermia

The purpose of the present work was to evaluate the kallikrein-kinin system and effects of hypothermia during renal ischemia and reperfusion. Male C57BL/KSJmdb mice were subjected to 20 or 60 min ischemia for different periods of reperfusion. Our results demonstrate that short periods of ischemia followed by reperfusion did not cause significant alterations in kallikrein activity, Evans Blue (EB) extravasation, prokallikreins, myeloperoxidase activity or plasma creatinine concentration. Edema was evident at 1 h reperfusion in the treated mice, but returned to basal values after 24 h reperfusion. Kallikrein activities and EB extravasation showed a significant increase in 60 min ischemic mice. Myeloperoxidase activity in the kidney of the mice confirmed net infiltration in the group with 60 min ischemia and 24 h reperfusion. The generation of kinins and activation of matrix degrading enzymes by tissue kallikrein, liberated from both renal and infiltrated leukocytes, could be responsible at least in part for the damage observed in the kidney of mice subject to 60 min ischemia and reperfusion. The hypothermia significantly reduced the inflammatory process in the 60 min ischemic mice, and did prevent an increase in vascular permeability. Nevertheless, the tissue edema was not shown to change between normothermic and hypothermic ischemic mice.

Pressure delivery of AS-ICAM-1 ODN with LFA-1 mAb reduces reperfusion injury in cardiac allografts

BACKGROUND

The goal of this study is to determine the effects of ex vivo hyperbaric pressure administration of AS-ICAM-1 ODN and systemic anti-LFA-1 mAb treatment on reperfusion injury in the rat cardiac allograft model.

METHODS

A PVG to ACI functional heterotopic rat heart model was used. Donor hearts were treated with either saline or AS-ICAM-1 ODN and 5 atm of hyperbaric pressure for 45 minutes. Anti-LFA-1 mAb was administered systemically prior to reperfusion of the allograft. Allografts were procured 24 hours after transplantation for assessment of reperfusion injury or 72 hours to determine ICAM-1 protein expression.

RESULTS

Ex vivo administration of AS-ICAM-1 ODN led to decreases in percentage wet weight (77.1+/-0.83% vs 78.7+/-1.0%, p < 0.05), myeloperoxidase activity (3.14+/-0.72 vs 4.07+/-0.59, p < 0.05), contraction band necrosis (6.4+/-6.47% vs 21.1+/-7.43%, p < 0.01), and ICAM-1 protein expression determined by immunohistochemistry compared to saline controls. Treatment with anti-LFA-1 mAb resulted in decreases in wet weight ratio (76.7+/-0.63%, p < 0.05 vs saline), myeloperoxidase activity (3.58+/-0.39, p < 0.05 vs saline) and contraction band necrosis (11.8+/-3.56%, p < 0.05 vs saline). Combination of pressure administration of AS-ICAM-1 ODN and anti-LFA-1 mAb decreased wet weight ratios (77.1+/-0.93%, p < 0.05 vs saline), myeloperoxidase activity (2.88+/-0.44, p < 0.01 vs saline), and contraction band necrosis (6.75+/-5.67%, p < 0.05 vs saline).

CONCLUSIONS

Ex vivo pressure mediated delivery of AS-ICAM-1 ODN decreases ICAM-1 protein expression, reduces reperfusion injury in rodent cardiac allografts, and is more effective than anti-LFA-1 mAb treatment alone.

Thrombogenesis in myocardial infarction and related syndromes: the role of molecular markers in diagnosis and management

Anticoagulant therapy has undergone some major developments in recent years. Conventional drugs that produce anticoagulant effects such as heparin and oral anticoagulants are no longer considered the only candidates for the anticoagulant/antithrombotic management of patients. Recombinant hirudin, glycoproteins IIb/IIIa targeting antibodies, synthetic peptides such as Hirulog and efegatran are being tested for their efficacy. These drugs produce their effects at different sites. To monitor their overall effects on the hemostatic system, molecular markers offer a practical and reliable approach. Markers of thrombin generation are useful for the monitoring of antithrombin drugs whereas, the efficacy of antiplatelet drugs can be assessed by monitoring the platelet release products. Furthermore, polytherapy using several anticoagulant and antithrombotic drugs in combination has been considered. In these situations, the use of molecular markers may also prove to be invaluable. The introduction of simple technology such as the test strip or particle agglutination methods may be available for the measurement of many of these markers in the near future. This will be useful for ready availability and reduced cost for individual marker testing. Furthermore, this type of technology can be used at bedside, off-site, and in doctor's offices. It is clear that the molecular marker profiling provides useful information on the nature of pathophysiology of a given thrombotic disorder. However, for practical use, a cost-effective and simpler assay-based approach will enhance their use, and these tests will be readily accepted at the laboratory and clinical levels.

Neutrophil function in peripheral arterial occlusive disease: the effects of prostaglandin E1

The role of polymorph nuclear neutrophils (PMN) in limb ischemia and reperfusion has been recognized only in recent years. The present study aimed to investigate the systemic and local (in femoral venous blood) effects of intra-arterially or intravenously applied prostaglandin E1 (PGE1) on systemic and ischemia-induced local changes in neutrophil function. Thirty patients with intermittent claudication were randomly assigned to intra-arterial or intravenous infusion of prostaglandin E1 (10 microg i.a. or 15 microg i.v. over 30 min). Prior to infusion femoral arterial and venous blood samples were obtained from the predominantly affected leg under resting conditions and immediately after a 3-min period of ischemia induced by suprasystolic thigh compression. After 24 h additional blood samples were obtained at baseline, following infusion of prostaglandin E1, and again after another 3-min period of ischemia following the prostaglandin E1 infusion. Intra-arterially administered prostaglandin E1 caused an increase in the PMN count by 3.5 +/- 2% (p<0.05) and a decrease in free oxygen radical production by 13 +/- 8% (p<0.05) measured by whole blood chemiluminescence. Additionally, a trend for lower PMN filterabilities (9 +/- 12%, NS) was observed. Intra-arterially infused prostaglandin E1 significantly reduced the ischemia-induced decrease in neutrophil filterability (arterial and venous blood difference after ischemia -- control: 22 +/- 17% (p<0.05); IA PGE1: 8 +/- 11% (NS), each compared to baseline). Intravenously administered prostaglandin E1 showed similar systemic effects as the intra-arterial application, but did not affect the ischemia-induced changes in neutrophil filterability. In conclusion, prostaglandin E1 reduces PMN activation in patients with peripheral arterial occlusive disease.

Useful laboratory tests for studying thrombogenesis in acute cardiac syndromes

We review laboratory tests that evaluate thrombogenesis during acute coronary syndromes. These tests have been found to be valuable research tools in more clearly understanding the pathophysiology of acute coronary syndromes. In particular, we describe tissue factor, tissue factor pathway inhibitor, prothrombin fragment 1.2, thrombin-antithrombin complex, fibrinopeptide A, tissue plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), t-PA-PAI complex, Bβ 15–42-related peptides, fibrinogen degradation products, fibrin degradation products, D-dimer, platelet factor 4, β-thromboglobulin, 5-hydroxytryptamine, thromboxane B2, prostacyclin, endothelin, angiotensin-converting enzyme, soluble thrombomodulin, C1-esterase inhibitor, anaphylotoxins C3a, C4a, and C5a, bradykinin, tumor necrosis factor, leukotriene C4, platelet activating factor, anti-phospholipid antibody, and von Willebrand factor. Some of these tests may prove to be useful in clinical diagnosis and management of acute coronary syndromes. Clinical outcome studies are needed to determine which tests may be cost effective and medically useful.