Attenuation of neutrophil-mediated myocardial ischemia-reperfusion injury by a calpain inhibitor

Endoplasmic reticulum stress serves an important role in cardiac ischemia/reperfusion injury (Review)

Although acute myocardial infarction is one of the most common fatal diseases worldwide, the understanding of its underlying pathogenesis continues to develop. Myocardial ischemia/reperfusion (I/R) can restore myocardial oxygen and nutrient supply. However, a large number of studies have demonstrated that recovery of blood perfusion after acute ischemia causes reperfusion injury to the heart. With progress made in the understanding of the underlying mechanisms of myocardial I/R and oxidative stress, a novel area of research that merits greater study has been identified, that of I/R-induced endoplasmic reticulum (ER) stress (ERS). Cardiac I/R can alter the function of the ER, leading to the accumulation of unfolded/misfolded proteins. The resulting ERS then induces the activation of signal transduction pathways, which in turn contribute to the development of I/R injury. The mechanism of I/R injury, and the causal relationship between I/R and ERS are reviewed in the present article.

Neutrophil Cell Shape Change: Mechanism and Signalling during Cell Spreading and Phagocytosis

Perhaps the most important feature of neutrophils is their ability to rapidly change shape. In the bloodstream, the neutrophils circulate as almost spherical cells, with the ability to deform in order to pass along narrower capillaries. Upon receiving the signal to extravasate, they are able to transform their morphology and flatten onto the endothelium surface. This transition, from a spherical to a flattened morphology, is the first key step which neutrophils undergo before moving out of the blood and into the extravascular tissue space. Once they have migrated through tissues towards sites of infection, neutrophils carry out their primary role-killing infecting microbes by performing phagocytosis and producing toxic reactive oxygen species within the microbe-containing phagosome. Phagocytosis involves the second key morphology change that neutrophils undergo, with the formation of pseudopodia which capture the microbe within an internal vesicle. Both the spherical to flattened stage and the phagocytic capture stage are rapid, each being completed within 100 s. Knowing how these rapid cell shape changes occur in neutrophils is thus fundamental to understanding neutrophil behaviour. This article will discuss advances in our current knowledge of this process, and also identify an important regulated molecular event which may represent an important target for anti-inflammatory therapy.

Relevance of Endoplasmic Reticulum Stress Cell Signaling in Liver Cold Ischemia Reperfusion Injury

The endoplasmic reticulum (ER) is involved in calcium homeostasis, protein folding and lipid biosynthesis. Perturbations in its normal functions lead to a condition called endoplasmic reticulum stress (ERS). This can be triggered by many physiopathological conditions such as alcoholic steatohepatitis, insulin resistance or ischemia-reperfusion injury. The cell reacts to ERS by initiating a defensive process known as the unfolded protein response (UPR), which comprises cellular mechanisms for adaptation and the safeguarding of cell survival or, in cases of excessively severe stress, for the initiation of the cell death program. Recent experimental data suggest the involvement of ERS in ischemia/reperfusion injury (IRI) of the liver graft, which has been considered as one of major problems influencing outcome after liver transplantation. The purpose of this review is to summarize updated data on the molecular mechanisms of ERS/UPR and the consequences of this pathology, focusing specifically on solid organ preservation and liver transplantation models. We will also discuss the potential role of ERS, beyond the simple adaptive response and the regulation of cell death, in the modification of cell functional properties and phenotypic changes.

Calpain-1 induces endoplasmic reticulum stress in promoting cardiomyocyte apoptosis following hypoxia/reoxygenation

Both calpain activation and endoplasmic reticulum (ER) stress are implicated in ischemic heart injury. However, the role of calpain in ER stress remains largely elusive. This study investigated whether calpain activation causes ER stress, thereby mediating cardiomyocyte apoptosis in an in vitro model of hypoxia/re-oxygenation (H/R). In neonatal mouse cardiomyocytes and rat cardiomyocyte-like H9c2 cells, up-regulation of calpain-1 sufficiently induced ER stress, c-Jun N-terminal protein kinase1/2 (JNK1/2) activation and apoptosis. Inhibition of ER stress or JNK1/2 prevented apoptosis induced by calpain-1. In an in vitro model of H/R-induced injury in cardiomyocytes, H/R was induced by a 24-hour hypoxia followed by a 24-hour re-oxygenation. H/R activated calpain-1, induced ER stress and JNK1/2 activation, and triggered apoptosis. Inhibition of calpain and ER stress blocked JNK1/2 activation and prevented H/R-induced apoptosis. Furthermore, blockade of JNK1/2 signaling inhibited apoptosis following H/R. The role of calpain in ER stress was also demonstrated in an in vivo model of ischemia/reperfusion using transgenic mice over-expressing calpastatin. In summary, calpain-1 induces ER stress and JNK1/2 activation, thereby mediating apoptosis in cardiomyocytes. Accordingly, inhibition of calpain prevents ER stress, JNK1/2 activation and apoptosis in H/R-induced cardiomyocytes. Thus, ER stress/JNK1/2 activation may represent an important mechanism linking calpain-1 to ischemic injury.

Ca²⁺ and calpain control membrane expansion during the rapid cell spreading of neutrophils

Following adherence of neutrophils to the endothelium, neutrophils undergo a major morphological change that is a necessary prelude to their extravasation. We show here that this shape change is triggered by an elevation of cytosolic inositol (1,4,5)-trisphosphate (IP3), to provoke physiological Ca(2+) influx through a store-operated mechanism. This transition from a spherical to 'flattened' neutrophil morphology is rapid (∼100 seconds) and is accompanied by an apparent rapid expansion of the area of the plasma membrane. However, no new membrane is added into the plasma membrane. Pharmacological inhibition of calpain-activation, which is triggered by Ca(2+) influx during neutrophil spreading, prevents normal cell flattening. In calpain-suppressed cells, an aberrant form of cell spreading can occur where an uncoordinated and localised expansion of the plasma membrane is evident. These data show that rapid neutrophil spreading is triggered by Ca(2+) influx, which causes activation of calpain and release of furled plasma membrane to allow its apparent 'expansion'.

Relationship between white blood cell count and in-hospital outcomes in acute coronary syndrome patients from the Middle East

We evaluated the relationship between admission white blood cell (WBC) count and in-hospital outcomes in acute coronary syndrome (ACS) patients from the Middle East. Data were analyzed from 7806 consecutive patients with ACS who were divided into 4 groups (G) according to their WBC count (× 10(9)/L; G1: < 6.00; G2: 6.00-9.99; G3: 10.00-11.99; G4: ≥ 12.00). After significant covariate adjustment, those in G4 were 68% more likely to have cardiogenic shock than those in G1 (95% confidence interval [CI]: 1.05-2.68; P = .030) and G2 (odds ratio [OR], 2.02; 95% CI: 1.51-2.71; P < .001). Those in G4 were 2.02 times (95% CI: 1.11-3.67; P = .021) and 65% (95% CI: 1.17-2.32; P = .004) more likely to die in hospital than those in G1 and G2, respectively. Admission WBC count is an independent risk factor for in-hospital cardiogenic shock and mortality, in Middle Eastern patients with ACS. Novel therapeutic agents targeting WBCs in patients with ACS may improve outcomes.

Disruption of Rac1 signaling reduces ischemia-reperfusion injury in the diabetic heart by inhibiting calpain

Diabetes increases myocardial ischemia/reperfusion (I/R) injury. However, the underlying mechanisms remain incompletely understood. This study investigated the role of Rac1 signaling and calpain in exacerbated I/R injury in diabetic hearts. Mice with cardiac-specific deletion of Rac1 (Rac1-ko) and transgenic mice with cardiac-specific superoxide dismutase-2 (SOD2) or calpastatin overexpression were rendered diabetic with streptozotocin. Isolated perfused hearts were subjected to global I/R. After I/R, Rac1 activity was significantly enhanced in diabetic compared with nondiabetic hearts. Diabetic hearts displayed more severe I/R injury than nondiabetic hearts, as evidenced by more lactate dehydrogenase release and apoptosis and decreased cardiac function. These adverse impacts of diabetes were abrogated in Rac1-ko hearts or by perfusion with the Rac1 inhibitor NSC23766. In an in vivo I/R mouse model, infarct size was much smaller in diabetic Rac1-ko compared with wild-type mice. Inhibition of Rac1 signaling prevented NADPH oxidase activation, reactive oxygen species production, and protein carbonyl accumulation, leading to inhibition of calpain activation. Furthermore, SOD2 or calpastatin overexpression significantly reduced I/R injury in diabetic hearts and improved cardiac function after I/R. In summary, Rac1 activation increases I/R injury in diabetic hearts and the role of Rac1 signaling is mediated, at least in part, through calpain activation.

Extensive autolytic fragmentation of membranous versus cytosolic calpain following myocardial ischemia–reperfusion

We investigated calpain activation in the heart during ischemia–reperfusion (I–R) by immunologically mapping the fragmentation patterns of calpain and selected calpain substrates. Western blots showed the intact 78 kDa large subunit of membrane-associated calpain was autolytically fragmented to 56 and 43 kDa signature immunopeptides following I–R. Under these conditions, the 78 kDa calpain large subunit from crude cytosolic fractions was markedly less fragmented, with only weakly stained autolytic peptides detected at higher molecular weights (70 and 64 kDa). Western blots also showed corresponding calpain-like degradation products (150 and 145 kDa) of membrane-associated α-fodrin (240 kDa) following I–R, but in crude myofibrils α-fodrin degradation occurred in a manner uncharacteristic of calpain. For control hearts perfused in the absence of ischemia, autolytic fragmentation of calpain and calpain-like α-fodrin degradation were completely absent from most subcellular fractions. The exception was sarcolemma-enriched membranes, where significant calpain autolysis and calpain-like α-fodrin degradation were detected. In purified sarcoplasmic reticulum membranes, RyR2 and SERCA2 proteins were also highly degraded, but for RyR2 this did not occur in a manner characteristic of calpain. When I–R-treated hearts were perfused with peptidyl calpain inhibitors (ALLN or ALLM; 25 µmol/L), calpain autolysis and calpain-like degradation of α-fodrin were equally attenuated by each inhibitor. However, only ALLN protected against early loss of developed pressure in hearts following I–R, with no functionally protective effect of ALLM observed. Our studies suggest calpain is preferentially activated at membranes following I–R, possibly contributing to impaired ion channel function implicated by others in I–R injury.

Reduction of myocardial infarction by postischemic administration of the calpain inhibitor A-705253 in comparison to the Na(+)/H(+) exchange inhibitor Cariporide in isolated perfused rabbit hearts

The calpain inhibitor A-705253 and the Na(+)/H(+)-exchange inhibitor Cariporide were studied in isolated perfused rabbit hearts subjected to 60 min occlusion of the ramus interventricularis of the left coronary artery (below the origin of the first diagonal branch), followed by 120 min of reperfusion. The inhibitors were added to the perfusion fluid solely or in combination at the beginning of reperfusion. Hemodynamic monitoring and biochemical analysis of perfusion fluid from the coronary outflow were performed. Myocardial infarct size and area at risk (transiently not perfused myocardium) were determined from left ventricular slices after a special staining procedure with Evans blue and 2,3,5-triphenyltetrazolium chloride. The infarcted area (dead myocardium) was 72.7+/-4.0% of the area at risk in untreated controls, but was significantly smaller in the presence of the inhibitors. The largest effect was seen with 10(-6) m A-705253, which reduced the infarcted area to 49.2+/-4.1% of the area at risk, corresponding to a reduction of 33.6%. Cariporide at 10(-6) m reduced the infarct size to the same extent. The combination of both inhibitors, however, did not further improve cardioprotection. No statistical difference was observed between the experimental groups in coronary perfusion, left ventricular pressure, heart rate, and in the release of lactate dehydrogenase and creatin kinase from heart muscle.

Calpain inhibition attenuates iNOS production and midzonal hepatic necrosis in a repeat dose model of endotoxemia in rats

Systemic exposure to bacterial lipopolysaccharide (LPS, endotoxin) induces hypotension, disseminated intravascular coagulation and neutrophil infiltration in various organs including the lung, kidney and liver. A rat endotoxemic neutrophilic hepatitis model (repeat dose LPS, 10 mg/kg, i.v. 24 hours apart) was developed exhibiting hepatic neutrophil infiltration and mid-zonal hepatic necrosis. The goal of the study was to investigate the role of the intracellular enzyme calpain in the development of neutrophilic hepatitis with midzonal necrosis in this model. A second goal was to compare the observed protective effects of calpain inhibition with a relatively selective inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine (AG) and an inhibitor of coagulation, heparin. When compared to rats administered LPS alone, administration of calpain 1 inhibitor prior to LPS significantly reduced hepatic iNOS expression, hepatic neutrophil infiltration and attenuated midzonal hepatic necrosis. Administration of AG or heparin prior to LPS also decreased liver iNOS expression, hepatic neutrophil infiltration and liver pathology comparable to calpain inhibition. Blood neutrophil activation, as measured by the neutrophil adhesion molecule CD11b integrin, was upregulated in all the LPS treated groups regardless of inhibitor administration. We conclude that amelioration of liver pathology via calpain inhibition is likely dependent on the down-regulation of iNOS expression in the rat model of LPS-mediated hepatitis.

Intravenous injection of phagocytes transfected ex vivo with FGF4 DNA/biodegradable gelatin complex promotes angiogenesis in a rat myocardial ischemia/reperfusion injury model

Conventional gene therapies still present difficulties due to poor tissue-targeting, invasiveness of delivery, method, or the use of viral vectors. To establish the feasibility of using non-virally ex vivo transfected phagocytes to promote angiogenesis in ischemic myocardium, gene-transfection into isolated phagocytes was performed by culture with positively charged gelatin impregnated with plasmid DNA. A high rate of gene transfection was achieved in rat macrophages and human monocytes, but not in mouse fibroblasts. The efficiency was 68 +/- 11% in rat macrophages and 78 +/- 8% in human monocytes. Intravenously injected phagocytes accumulated predominantly in ischemic tissue (13 +/- 8%) and spleen (84 +/- 6%), but negligibly in other organs in rodents. The efficiency of accumulation in the target ischemic tissue reached more than 86% on direct local tissue injection. In a rat model of myocardial ischemia-reperfusion, intravenous injection of fibroblast growth factor 4 (FGF4)-gene-transfected macrophages significantly increased regional blood flow in the ischemic myocardium (78 +/- 7.1 % in terms of flow ratio of ischemic/non-ischemic myocardium) compared with intravenous administration of saline (36 +/- 11%) or nontransfected macrophages (42 +/- 12 %), or intramuscular administration of naked DNA encoding FGF4 (75 +/- 18 %). Enhanced angiogenesis in the ischemic tissue we confirmed histologically. Similarly, intravenous injection of FGF4-gene-transfected monocytes enhanced regional blood flow in an ischemic hindlimb model in mice (93 +/- 22 %), being superior to the three other treatments described above (38 +/- 12, 39 +/- 15, and 55 +/- 12%, respectively). Phagocytes transfected ex vivo with FGF4 DNA/gelatin promoted angiogenesis. This approach might have potential for non-viral angiogenic gene therapy.

Homocysteine-mediated activation and mitochondrial translocation of calpain regulates MMP-9 in MVEC

Hyperhomocysteinemia (HHcy) is associated with atherosclerosis, stroke, and dementia. Hcy causes extracellular matrix remodeling by the activation of matrix metalloproteinase-9 (MMP-9), in part, by inducing redox signaling and modulating the intracellular calcium dynamics. Calpains are the calcium-dependent cysteine proteases that are implicated in mitochondrial damage via oxidative burst. Mitochondrial abnormalities have been identified in HHcy. The mechanism of Hcy-induced extracellular matrix remodeling by MMP-9 activation via mitochondrial pathway is largely unknown. We report a novel role of calpains in mitochondrial-mediated MMP-9 activation by Hcy in cultured rat heart microvascular endothelial cells. Our observations suggested that calpain regulates Hcy-induced MMP-9 expression and activity. We showed that Hcy activates calpain-1, but not calpain-2, in a calcium-dependent manner. Interestingly, the enhanced calpain activity was not mirrored by the decreased levels of its endogenous inhibitor calpastatin. We presented evidence that Hcy induces the translocation of active calpain from cytosol to mitochondria, leading to MMP-9 activation, in part, by causing intramitochondrial oxidative burst. Furthermore, studies with pharmacological inhibitors of calpain (calpeptin and calpain-1 inhibitor), ERK (PD-98059) and the mitochondrial uncoupler FCCP suggested that calpain and ERK-1/2 are the major events within the Hcy/MMP-9 signal axis and that intramitochondrial oxidative stress regulates MMP-9 via ERK-1/2 signal cascade. Taken together, these findings determine the novel role of mitochondrial translocation of calpain-1 in MMP-9 activation during HHcy, in part, by increasing mitochondrial oxidative stress.

The anti-anginal drug trimetazidine reduces neutrophil-mediated cardiac reperfusion injury

Trimetazidine has no hemodynamic/antithrombotic actions. Hence, its anti-ischemic properties have been mostly attributed to its metabolic effects. However, this issue is not completely elucidated. We investigated whether inhibition of neutrophil activation may also contribute to its cardioprotective action. We first showed that trimetazidine inhibits neutrophil activation in vitro. We subsequently tested whether trimetazidine protects postischemic hearts from neutrophil-mediated injury. Four groups of rat hearts underwent 20 minutes of global ischemia: (1) controls, reperfused with neutrophil-enriched buffer for 5 minutes, followed by 40 minutes standard perfusate; (2) hearts from rats pretreated with trimetazidine for 1 week; (3) hearts in which 10 M trimetazidine was added to the perfusate, starting 5 minutes before ischemia and for the initial 15 minutes of reflow; (4) hearts from pretreated rats that also received trimetazidine in the perfusate. Postischemic impairment of contractile function was significantly attenuated by trimetazidine infusion (recovery of developed pressure: 68 +/- 7% versus 42 +/- 9% of baseline in controls; P < 0.05). Pretreatment alone was not effective, nor did it further improve the beneficial effects of infusion. Cardiac oxygen radical production at reflow (by electron paramagnetic resonance spectroscopy) was also reduced by trimetazidine, independently of direct scavenger effects. Thus, trimetazidine can protect postischemic hearts from neutrophil-mediated injury.

Calpains: a physiological regulator of the endothelial barrier?

The intracellular protease calpain, abundant in endothelial cells (EC), is assumed to be inactive under physiological conditions but may account for Ca2+ -linked pathophysiological events. However, nonstimulated EC contained autolyzed, activated calpain. Adding 12-48 microM calpain inhibitor I (CI) or 0.5-1 microM of the novel, membrane-permeable conjugate of calpastatin peptide-penetratin (CPP) caused rapid rounding and retraction of cultured EC (phase contrast, capacitance) and translocation of Syk, Rac, and Rho to the membrane, signifying activation upon inhibition of calpain. Isolated hearts (guinea pig) perfused with 12 microM CI or 0.5 muM CPP developed coronary leak. We conclude that calpain is constitutively active in EC and regulates vascular permeability by governing cell-cell attachment.

Changes in P-selectin expression on cardiac microvessels in blood-perfused rat hearts subjected to ischemia-reperfusion

BACKGROUND

During cardiac surgery involving cardiopulmonary bypass, activation of polymorphonuclear cells is believed to contribute to ischemia-reperfusion injury and subsequent myocardial impairment of function. The early tethering of polymorphonuclear cells to blood vessel walls depends upon recognition of the adhesion molecule P-selectin on endothelium. The purpose of this study was to define the kinetic changes in expression of P-selectin on myocardial vessels in a model of global ischemia-reperfusion injury.

METHODS

In a novel recirculating blood-based perfusion system, rat hearts were subjected to 30 minutes of aerobic perfusion, 60 minutes of global ischemia, and 60 minutes of reperfusion, or to 120 minutes of continuous aerobic blood perfusion (with or without leukocyte/platelet depletion). Heart function (left ventricular developed pressure), heart rate, and perfusion pressure were monitored throughout. Hearts were sampled at defined periods for microvascular expression of P-selectin, identified by immunohistochemistry.

RESULTS

In control (nonperfused) hearts and in hearts subjected to perfusion and ischemia, few cardiac vessels (8% to 16%) expressed P-selectin. After 15 minutes of reperfusion, P-selectin was present on the majority of vessels (77%; p < 0.05) but expression decreased subsequently throughout the remaining duration of reperfusion. Interestingly, upregulation of P-selectin also occurred when hearts were subjected to continuous perfusion alone (no ischemia), but this upregulation was less rapid. Depletion of leukocytes/platelets from the blood perfusate did not modify P-selectin expression.

CONCLUSIONS

The augmented expression of P-selectin on myocardial vessels during reperfusion of ischemic hearts probably reflects changes induced during global ischemia and by the duration of perfusion through the nonbiological tubing of the circuit. That is likely to mimic the effects initiated during cardiopulmonary bypass.

Calpain inhibitor-1 protects the rat heart from ischemia-reperfusion injury: analysis by mechanical work and energetics

We hypothesized that calpain inhibitor-1 protected left ventricular (LV) function from ischemia-reperfusion injury by inhibiting the proteolysis of α-fodrin. To test this hypothesis, we investigated the effect of calpain inhibitor-1 on LV mechanical work and energetics in the cross-circulated rat hearts that underwent 15-min global ischemia and 60-min reperfusion ( n = 9). After ischemia-reperfusion with calpain inhibitor-1, mean end-systolic pressure at midrange LV volume and systolic pressure-volume area (PVA) at midrange LV volume (total mechanical energy per beat) were hardly changed, although they were significantly ( P < 0.01) decreased after ischemia-reperfusion without calpain inhibitor-1. Mean myocardial oxygen consumption per beat (Vo2) intercepts (PVA-independent Vo2; Vo2 for the total Ca2+ handling in excitation-contraction coupling and basal metabolism) of Vo2-PVA linear relations were also unchanged after ischemia-reperfusion with calpain inhibitor-1, although they were significantly ( P < 0.01) decreased after ischemia-reperfusion without calpain inhibitor-1. There were no significant differences in O2 costs of LV PVA and contractility among the hearts in control (or normal) postischemia-reperfusion and postischemia-reperfusion with calpain inhibitor-1. Western blot analysis of α-fodrin and the immunostaining of 150-kDa products of α-fodrin confirmed that calpain inhibitor-1 almost completely protected the proteolysis of α-fodrin. Our results indicate that calpain inhibitor-1 prevents the heart from ischemia-reperfusion injury associated with the impairment of total Ca2+ handling by directly inhibiting the proteolysis of α-fodrin.

The calcium-dependent protease calpain causes endothelial dysfunction in type 2 diabetes

Cardiovascular complications are the leading cause of morbidity and mortality in diabetic patients. Endothelial dysfunction with impaired endothelial nitric oxide (NO) synthase (eNOS) activity is a widely accepted cause of diabetic vasculopathy. The mechanisms of endothelial dysfunction in diabetes remain elusive, thus limiting effective therapeutic interventions. We report novel evidence demonstrating that the calcium-dependent protease calpain causes endothelial dysfunction and vascular inflammation in the microcirculation of the ZDF (Zucker diabetic fatty) rat, a genetic rat model of type 2 diabetes. We found evidence of increased calpain activity and leukocyte trafficking in the microcirculation of ZDF rats. Inhibition of calpain activity significantly attenuated leukocyte-endothelium interactions in the vasculature of ZDF rats. Expression of cell adhesion molecules in the vascular endothelium of ZDF rats was consistently increased, and it was suppressed by calpain inhibition. In vivo measurement of endothelial NO availability demonstrated a 60% decrease in NO levels in the microcirculation of diabetic rats, which was also prevented by calpain inhibition. Immunoprecipitation studies revealed calpain-dependent loss of association between eNOS and the regulatory protein heat shock protein 90. Collectively, these data provide evidence for a novel mechanism of endothelial dysfunction and vascular inflammation in diabetes. Calpains may represent a new molecular target for the prevention and treatment of diabetic vascular complications.

[Calpains and cardiac diseases]

Calpains are a large family of cytosolic cysteine proteases composed of at least fourteen distinct isoforms. The family can be divided into two groups on the basis of distribution: ubiquitous and tissue-specific. Our current knowledge about calpains properties apply mainly to the ubiquitous isozymes, micro- and milli-calpain (classic calpains). These forms are activated after autolysis. Translocation and subsequent interactions with phospholipids of these enzymes increase their activity. Calpains are able to cleave a subset of substrates, as enzymes, structural and signalling proteins. Cardiac pathologies, such as heart failure, atrial fibrillation or clinical states particularly ischemia reperfusion, are associated with an increase of cytosolic calcium and in this regards, calpain activation has been evoked as one of the mediators leading to myocardial damage. Calpain activities have been shown to be increased in hearts experimentally subjected to ischemia reperfusion or during hypertrophy, but also in atrial tissue harvested from patients suffering from atrial fibrillations. These activities have been related to an increase of the proteolysis of different myocardial components, particularly, troponins, which are major regulators of the contraction of cardiomyocytes. Moreover, recent works have demonstrated that calpains are involved in the development of myocardial cell death by necrosis or apoptosis.

The remote ischemic preconditioning stimulus modifies inflammatory gene expression in humans

Remote ischemic preconditioning (IPC) reduces tissue injury caused by ischemia-reperfusion (IR) in distant organs. We tested the hypothesis that remote IPC (rIPC) modifies inflammatory gene transcription in humans. Using a microarray method, we demonstrated that a simple model of brief forearm ischemia suppresses proinflammatory gene expression in circulating leukocytes. Genes encoding key proteins involved in cytokine synthesis, leukocyte chemotaxis, adhesion and migration, exocytosis, innate immunity signaling pathways, and apoptosis were all suppressed within 15 min (early phase IPC) and more so after 24 h (second window IPC). Changes in leukocyte CD11b expression measured by flow cytometry mirrored this pattern, with there being a significant (P = 0.01) reduction at 24 h. The results of this study show that the rIPC stimulus modifies leukocyte inflammatory gene expression. This effect may contribute to the protective effect of IPC against IR injury and may have broader implications in other inflammatory processes. This is the first study of human gene expression following rIPC stimulus. rIPC stimulus suppressed proinflammatory gene transcription in human leukocytes.

Reduction of infarct size and preservation of endothelial function by multidose intravenous adenosine during extended reperfusion

It has been proposed that infarct extension is developed from the early to the late phase of reperfusion (R). This study compares the protective effect of single or multidose administration of adenosine (Ado) on infarct size during early and late phases of R by attenuating neutrophil (PMN) recruitment. Forty-one dogs underwent 60-min left anterior descending artery (LAD) ischemia followed by 6, 24, and 48 h of R, respectively. Infarct size (%) increased over 6 to 24 h (27 +/- 2 to 38 +/- 4; P < 0.05 24 h versus 6 h group), with a corresponding increase in creatine kinase activity. Transmural myocardial blood flow (mL/min/g) decreased from 6 to 24 h (0.47 +/- 0.02 to 0.29 +/- 0.02; P < 0.05 24 h versus 6 h group). PMN localization (mm(2) myocardium) in the perinecrotic tissue detected by immunohistochemistry with anti-CD18 antibody, and accumulation detected by myeloperoxidase (MPO, DeltaAbs/min/g) increased from 6 to 24 h (292 +/- 25 to 605 +/- 44; P < 0.05 24 h versus 6 h group; and 55 +/- 7 to 96 +/- 5; P < 0.05 24 h versus 6 h group), respectively. In in vitro analysis, PMN adherence (mm(2) endothelium) to postischemic LAD increased from 98 +/- 2 to 125 +/- 3 (P < 0.05 24 h versus 6 h group) and maximal LAD endothelium-dependent relaxation (%) impaired from 6 to 24 h (74 +/- 7 to 42 +/- 10; P < 0.05 24 h versus 6 h group). Intravenous Ado (140 microg/kg/min) for 2 h at R reduced infarct size (17 +/- 2; P < 0.05 Ado versus 6 h group), CD18 positive cells (130 +/- 10; P < 0.05 Ado versus 6 h group), MPO (14 +/- 3; P < 0.05 Ado versus 6 h group), PMN adherence (57 +/- 2; P < 0.05 Ado versus 6 h group), and augmented LAD vascular relaxation (102 +/- 5 versus 74 +/- 7; P < 0.05 Ado versus 6 h group). However, this protection by Ado was lost when R was extended to 24 h. Treatment with multiple infusion of Ado at 2, 6, 12, and 18 h R significantly preserved protective effects seen at 6 h R in the Ado group. Protection by multidose Ado was still preserved when R was extended to an additional 24 h. These data suggest that interventions aiming at permanently reducing R injury may thus need to be administered not only at early R, but also during late phase. A slow wave of PMN accumulation at late R may be involved in the extension of infarction and endothelial dysfunction.

A novel role for calpains in the endothelial dysfunction of hyperglycemia

Recent studies have reported that the activity of the calcium-dependent protease calpain is increased in acute inflammatory processes of the cardiovascular system. Because diabetes is associated with vascular inflammation, we hypothesized that increased calpain activity in response to hyperglycemia may play a role in diabetic cardiovascular disease. The effects of calpain inhibition on leukocyte-endothelium interactions induced by hyperglycemia were examined by intravital microscopy. Intraperitoneal administration of the selective calpain inhibitor benzyloxycarbonyl-leucyl-leucinal (5 micromol/L) prevented the up-regulation of leukocyte-endothelium interactions in response to 25 mmol/L D-glucose via a nitric oxide-dependent mechanism. Furthermore, treatment of rats with D-glucose significantly decreased basal endothelial NO release in mesenteric post-capillary venules, a phenomenon prevented by inhibition of calpain activity. Immunoprecipitation studies revealed that glucose induces loss of NO via a calpain-dependent decrease in the association of hsp90 with endothelial nitric oxide synthase. In addition, inhibition of calpain activity decreased endothelial cell surface expression of the pro-inflammatory adhesion molecules ICAM-1 and VCAM-1 during hyperglycemia. These data demonstrate that calpains contribute to important inflammatory events during hyperglycemia and that pharmacological inhibition of calpain activity attenuates leukocyte-endothelium interactions and preserves eNOS function.

Synthesis of 3,3'-(1-piperidino)substituted methylene-bis-isoxazoles preventing stimulus-induced leukocytes activation

Some 3,3'-(1-piperidino)substituted methylene-bis-isoxazoles were prepared via Mannich base and tested to verify their antiinflammatory-related activity. Human neutrophils stimulated with either PMA and f-MLP were used as the cellular model. The efficiency of eight differently substituted compounds (2-9) was established on their capacity to reduce the O(2)(-) production by activated human neutrophils. The rising hydrophobicity in the side-chain of methylene-bis-isoxazoles leads to a distinction in the neutrophil response against the two stimuli, favoring the inhibition of the PMA elicited cell activation and leaving inaffected the f-MLP induced cell responses. Compounds 8 and 9 are particularly active and abolish almost completely the neutrophil activation in the presence of PMA stimulus.