Effects of the PAF receptor antagonist UK74505 on local and remote reperfusion injuries following ischaemia of the superior mesenteric artery in the rat

The effects of the long lasting and potent PAF receptor antagonist UK74505 were assessed on the local and remote injuries following ischaemia and reperfusion (I/R) of the superior mesenteric artery (SMA) in rats. In a severe model of ischaemia (120 min) and reperfusion (120) injury, in addition to the local and remote increases in vascular permeability and neutrophil accumulation, there was significant tissue haemorrhage, blood neutropenia, systemic hypotension and elevated local and systemic TNF-alpha levels. Post-ischaemic treatment with the selectin blocker fucoidin (10 mg kg(-1)) prevented neutrophil accumulation in tissue and, in consequence, all the local and systemic injuries following severe I/R. Treatment with an optimal dose of UK74505 (1 mg kg(-1)) also reversed local and remote neutrophil accumulation, increases in vascular permeability and intestinal haemorrhage. UK74505 partially inhibited blood neutropenia and reperfusion-induced hypotension. Interestingly, both fucoidin and UK74505 prevented the local, but not systemic, increases of TNF-alpha levels following severe I/R injury, demonstrating an important role of migrating cells for the local production of TNF-alpha. However, the results do not support a role for PAF as an intermediate molecule in the production of systemic TNF-alpha. The beneficial effects of UK74505 and other PAF receptor antagonists in models of I/R injury in animals and the safety of UK74505 use in man warrant further investigations of the use of this drug as preventive measure for I/R injury in humans.     

Role of tachykinin NK receptors on the local and remote injuries following ischaemia and reperfusion of the superior mesenteric artery in the rat

Neuropeptides acting on tachykinin NK receptors play an important role in the amplification of inflammatory responses. We have assessed the effects of tachykinin NK receptor blockade on the injuries following intestinal ischaemia and reperfusion (I/R) in rats. The tachykinin NK(1) receptor antagonist SR140333 dose-dependently (0.05 to 0.5 mg kg(-1)) suppressed the local (intestine) and remote (lung) increases in vascular permeability and neutrophil recruitment following mild I/R injury. A structurally-distinct NK(1) receptor antagonist, CP99,994, but not tachykinin NK(2) or NK(3) receptor antagonists also suppressed mild I/R injury. Neonatal pretreatment with capsaicin effectively depleted sensory neurons and abrogated the injuries following mild I/R. Treatment with SR140333 (0.5 mg kg(-1)) significantly reversed severe reperfusion-induced local and remote increases in vascular permeability, neutrophil recruitment, intestinal haemorrhage and blood neutropaenia, but did not prevent the lethality associated with severe I/R. Post-ischaemic treatment with SR140333 significantly inhibited the elevations of TNF-alpha in the intestine and lung, but not serum, following severe I/R. The increase in the concentrations of IL-10 in the lung and serum were also suppressed. Post-ischaemic blockade of tachykinin NK(1) receptors markedly inhibited the local and remote injuries, but not lethality, following reperfusion of the SMA in rats. Neuropeptides, possibly substance P, released from sensory nerves appear to account for the activation of these tachykinin NK(1) receptors. Antagonists of the tachykinin NK(1) receptor may be useful adjuncts in the treatment of the injuries which occur following reperfusion of an ischaemic vascular territory.     

线粒体与心肌缺血/再灌注损伤

心肌缺血/再灌注损伤会破坏线粒体稳态平衡引起功能紊乱,如线粒体ATP合成减少、ROS生成增加、Ca2+超载、膜通透性增加、线粒体片段化等,这些事件相互作用从多条途径参与I/R过程,是心肌I/R损伤的重要原因。对I/R中线粒体病理变化及I/R损伤线粒体保护途径的最新研究进展进行综述,为基于线粒体途径的心血管疾病药物防治研究提供参考。     

Structural apelin analogues: mitochondrial ROS inhibition and cardiometabolic protection in myocardial ischaemia reperfusion injury

Background and Purpose

Mitochondria-derived oxidative stress is believed to be crucially involved in cardiac ischaemia reperfusion (I/R) injury, although currently no therapies exist that specifically target mitochondrial reactive oxygen species (ROS) production. The present study was designed to evaluate the potential effects of the structural analogues of apelin-12, an adipocyte-derived peptide, on mitochondrial ROS generation, cardiomyocyte apoptosis, and metabolic and functional recovery to myocardial I/R injury.

Experimental Approach

In cultured H9C2 cardiomyoblasts and adult cardiomyocytes, oxidative stress was induced by hypoxia reoxygenation. Isolated rat hearts were subjected to 35 min of global ischaemia and 30 min of reperfusion. Apelin-12, apelin-13 and structural apelin-12 analogues, AI and AII, were infused during 5 min prior to ischaemia.

Key Results

In cardiac cells, mitochondrial ROS production was inhibited by the structural analogues of apelin, AI and AII, in comparison with the natural peptides, apelin-12 and apelin-13. Treatment of cardiomyocytes with AI and AII decreased cell apoptosis concentration-dependently. In a rat model of I/R injury, pre-ischaemic infusion of AI and AII markedly reduced ROS formation in the myocardial effluent and attenuated cell membrane damage. Prevention of oxidative damage by AI and AII was associated with the improvement of functional and metabolic recovery after I/R in the heart.

Conclusions and Implications

These data provide the evidence for the potential of the structural apelin analogues in selective reduction of mitochondrial ROS generation and myocardial apoptosis and form the basis for a promising therapeutic strategy in the treatment of oxidative stress-related heart disease.     

Effects of a BLT receptor antagonist on local and remote reperfusion injuries after transient ischemia of the superior mesenteric artery in rats

Reperfusion of ischemic vascular beds may lead to recruitment and activation of leukocytes, release of mediators of the inflammatory process and further injury to the affected vascular bed and to remote sites. Neutrophils appear to play a major role in the pathophysiology of reperfusion injury. Amongst inflammatory mediators shown to activate neutrophils and induce their recruitment in vivo, much interest has been placed on the role of leukotriene (LT)B(4). Here, we have assessed the effects of the BLT receptor antagonist (+)-1-(3S, 4R)-[3-(4-phenyl-benzyl)-4-hydroxy-chroman-7-yl]-cyclopentane carboxylic acid (CP 105,696) in a model of neutrophil-dependent ischemia and reperfusion injury in the rat. The superior mesenteric artery was isolated and ischemia was induced by its total occlusion for 30 min. After 30 min of reperfusion, injury was assessed by evaluating the extravasation of Evans blue, an index of vascular permeability, and the levels of myeloperoxidase, an index of neutrophil accumulation, in the intestine, mesentery and lung. The neutrophil-dependence of the local (intestine and mesentery) and remote (lung) injury was confirmed by using fucoidin, a selectin blocker, and WT-3, an anti-CD18 monoclonal antibody. Post-ischemic treatment with CP 105,696 dose-dependently inhibited vascular permeability and neutrophil accumulation in the intestine and mesentery. CP 105,696 also blocked the vascular permeability changes, but not neutrophil accumulation, in the lungs after reperfusion injury. Virtually identical results were obtained with another BLT receptor antagonist, 1-(5-ethyl-2-hydroxy-4-(6-methyl-6-(1H-tetrazol-5-yl)-heptoxy++ +)-phenyl )ethanone (LY255283). Our results suggest that post-ischemic treatment with BLT receptor antagonists may inhibit local and remote ischemia and reperfusion injury by blocking both the accumulation and/or activation of neutrophils.     

Riboflavin (vitamin B-2) reduces hepatocellular injury following liver ischaemia and reperfusion in mice

Riboflavin has been shown to exhibit anti-inflammatory and antioxidant properties in the settings of experimental sepsis and ischaemia/reperfusion (I/R) injury. We investigated the effect of riboflavin on normothermic liver I/R injury. Mice were submitted to 60 min of ischaemia plus saline or riboflavin treatment (30 μmoles/kg BW) followed by 6 h of reperfusion. Hepatocellular injury was evaluated by aminotransferase levels, reduced glutathione (GSH) content and the histological damage score. Hepatic neutrophil accumulation was assessed using the naphthol method and by measuring myeloperoxidase activity. Hepatic oxidative/nitrosative stress was estimated by immunohistochemistry. Liver endothelial and inducible nitric oxide synthase (eNOS/iNOS) and nitric oxide (NO) amounts were assessed by immunoblotting and a chemiluminescence assay. Riboflavin significantly reduced serum and histological parameters of hepatocellular damage, neutrophil infiltration and oxidative/nitrosative stress. Furthermore, riboflavin infusion partially recovered hepatic GSH reserves and decreased the liver contents of eNOS/iNOS and NO. These data indicate that riboflavin exerts antioxidant and anti-inflammatory effects in the ischaemic liver, protecting hepatocytes against I/R injury. The mechanism of these effects appears to be related to the intrinsic antioxidant potential of riboflavin/dihydroriboflavin and to reduced hepatic expression of eNOS/iNOS and reduced NO levels, culminating in attenuation of oxidative/nitrosative stress and the acute inflammatory response.     

Effects of defibrotide,a novel oligodeoxyribonucleotide,on ischaemia and reperfusion injury of the rat liver

1. The purpose of this study was to investigate the protective effects of defibrotide, a single-stranded polydeoxyribonucleotide, on ischaemia-reperfusion injury to the liver using a rat model. 2. Ischaemia of the left and median lobes was created by total inflow occlusion for 30 min followed by 60 min of reperfusion. Hepatic injury was assessed by the release of liver enzymes (alanine transferase, ALT and lactic dehydrogenase, LDH). Hepatic oxidant stress was measured by superoxide production, lipid peroxidation and nitrite/nitrate formation. Leukocyte-endothelium interaction and Kupffer cell mobilization were quantified by measuring hepatic myeloperoxidase (MPO), polymorphonuclear leukocyte adherence to superior mesenteric artery (SMA) and immunostaining of Kupffer cell. 3. Defibrotide treatment resulted in a significant inhibition of postreperfusion superoxide generation, lipid peroxidation, serum ALT activity, serum LDH activity, MPO activity, serum nitrite/nitrate level, leukocyte adherence to SMA, and Kupffer cell mobilization, indicating a significant attenuation of hepatic dysfunction. 4. A significant correlation existed between liver ischaemia/reperfusion and hepatic injury, suggesting that liver ischaemia/reperfusion injury is mediated predominantly by generation of oxygen free radicals and mobilization of Kupffer cells. 5. We conclude that defibrotide significantly protects the liver against liver ischaemia/reperfusion injury by interfering with Kupffer cell mobilization and formation of oxygen free radicals. This study provides strong evidence that defibrotide has important beneficial effects on acute inflammatory tissue injury such as that occurring in the reperfusion of the ischaemic liver.     

Effects of the endothelin receptor antagonist Bosentan on ischaemia/reperfusion injury in rat skeletal muscle

We examined the role of endothelin in ischaemia/reperfusion injury in skeletal muscle, using the endothelin receptor antagonist Bosentan. In the rat hindlimb tourniquet ischaemia model, one hindlimb was rendered ischaemic for 2 h at 36 degrees C, then blood flow was re-established for either 24 h to assess muscle survival or 1.5 h for a study of capillary perfusion. In the first set of rats, the gastrocnemius muscle was removed from the postischaemic limb and assessed for viability histochemically using the nitro blue tetrazolium stain. Tissue water content (a measure of oedema) and myeloperoxidase activity (a measure of neutrophil accumulation) were also assessed in the ischaemic muscle, the contralateral non-ischaemic muscle and the lungs. In the second set of rats, the hind limb was infused with India ink after 2-h ischaemia and 1.5-h reperfusion and the muscle was harvested, fixed and cleared. In control rats, muscle viability was 17+/-2% (S.E.M.). In rats treated with Bosentan (10 mg/kg, i.p.) 30 min before release of the tourniquet, muscle viability (48+/-7%) was significantly increased compared to the control group (P<0.01). Bosentan treatment had no significant effect on tissue water content or myeloperoxidase activity in the ischaemic muscle, the contralateral non-ischaemic muscle or the lung. Immunoreactive endothelin levels in serum increased to a peak at 90 min of reperfusion and returned to control levels by 24-h reperfusion. India ink studies demonstrated a significantly increased functional capillary density in postischaemic Bosentan-treated muscles compared with postischaemic control muscles (P<0.05). These results suggest that endothelin plays an important role in the necrosis which results from a period of ischaemia and reperfusion in skeletal muscle, by mediating a decrease in postischaemic microvascular perfusion.     

The role of cycloxygenase-2 in the rodent kidney following ischaemia/reperfusion injury in vivo

The role of cyclooxygenase-2 (COX-2) in the pathophysiology of renal ischaemia/reperfusion injury is still not fully understood. In order to elucidate the role of COX-2 in ischaemia/reperfusion injury of the kidney, we have evaluated the effects of ischaemia/reperfusion on renal dysfunction and injury in (i) rats treated with either vehicle or the selective COX-2 inhibitor parecoxib, and (ii) wild-type mice or mice in which the gene for COX-2 has been deleted (COX-2 knock-out mice or COX-2(-/-)). Rats were subjected to bilateral renal ischaemia (45 min) and reperfusion (6 h), and received parecoxib (20 mg/kg, i.v.) 30 min prior to ischaemia and 3 h after the commencement of reperfusion. Serum urea, serum creatinine, serum aspartate aminotransferase, creatinine clearance and fractional excretion of sodium were all used as indicators of renal dysfunction and injury. Mice (wild-type and COX-2(-/-)) were subjected to bilateral renal ischaemia (30 min) and reperfusion (24 h) after which renal dysfunction (serum urea and creatinine) and renal injury was assessed by histological analysis. Parecoxib significantly augmented the degree of renal dysfunction and injury caused by ischaemia/reperfusion in the rat. In addition, the degree of renal injury and dysfunction caused by ischaemia/reperfusion was also significantly augmented in COX-2(-/-) mice when compared to their wild-type littermates. These findings support the view that metabolites of COX-2 protect the kidney against ischaemia/reperfusion injury, and (ii) that selective inhibitors of COX-2 may worsen renal dysfunction and injury in conditions associated with renal ischaemia.     

Suppression of human inflammatory cell function by subtype-selective PDE4 inhibitors correlates with inhibition of PDE4A and PDE4B

1. Of the four major phosphodiesterase 4 (PDE4) subtypes, PDE4A, PDE4B and PDE4D are widely expressed in human inflammatory cells, including monocytes and T lymphocytes. We explored the functional role of these subtypes using ten subtype-selective PDE4 inhibitors, each belonging to one of two classes: (i) dual PDE4A/PDE4B inhibitors or (ii) PDE4D inhibitors. 2. These compounds were evaluated for their ability to inhibit antigen-stimulated T-cell proliferation and bacterial lipopolysaccharide (LPS)-stimulated tumour necrosis factor alpha (TNFalpha) release from peripheral blood monocytes. 3. All compounds inhibited T-cell proliferation in a concentration-dependent manner; with IC50 values distributed over an approximately 50 fold range. These compounds also inhibited TNFalpha release concentration-dependently, with a wider ( approximately 1000 fold) range of IC50 values. 4. In both sets of experiments, mean IC50 values were significantly correlated with compound potency against the catalytic activity of recombinant human PDE4A or PDE4B when analysed by either linear regression of log IC50 values or by Spearman's rank-order correlation. The correlation between inhibition of inflammatory cell function and inhibition of recombinant PDE4D catalytic activity was not significant in either analysis. 5. These results suggest that PDE4A and/or PDE4B may play the major role in regulating these two inflammatory cell functions but do not rule out PDE4D as an important mediator of other activities in mononuclear leukocytes and other immune and inflammatory cells. Much more work is needed to establish the functional roles of the PDE4 subtypes across a broader range of cellular functions and cell types.     

Effects of zaprinast and rolipram on platelet aggregation and arrhythmias following myocardial ischaemia and reperfusion in anaesthetized rabbits.

1. This study was designed to compare the effects of two selective inhibitors of certain phosphodiesterase (PDE) isoenzymes on arrhythmias induced by coronary artery occlusion and reperfusion. The drugs used were zaprinast which inhibits guanosine 3':5'-cyclic monophosphate (cyclic GMP)-specific PDE (PDE V) and rolipram which inhibits cyclic GMP-insensitive, adenosine 3':5'-cyclic monophosphate (cyclic AMP)-specific PDE (PDE IV). 2. Pretreatment of anaesthetized rabbits with zaprinast (300 micrograms kg-1 plus 30 micrograms kg-1 min-1) had no significant effect on ischaemia- or reperfusion-induced ST-segment changes, or arrhythmias. In contrast, rolipram (30 micrograms kg-1 plus 3 micrograms kg-1 min-1) and (100 micrograms kg-1 plus 10 micrograms kg-1 min-1) increased the severity of arrhythmias. With the higher dose of rolipram, ST-segment changes were increased in magnitude and mortality due to ventricular fibrillation during ischaemia or reperfusion was increased to 80% compared with 30% in controls (n = 10 per group). 3. Zaprinast caused small but significant increases in heart rate and arterial blood pressure whereas rolipram decreased diastolic arterial pressure, increased left ventricular (LV) dP/dtmax and substantially increased heart rate. 4. At the end of each experiment platelet aggregation was measured ex vivo. Pretreatment of rabbits with either dose of rolipram had no significant effect on platelet aggregation induced by adenosine diphosphate (ADP), collagen, arachidonic acid or thrombin or on isoprenaline- or prostacyclin-induced inhibition of aggregation. Aggregatory responses to ADP and collagen were increased in platelets obtained from rabbits which had received zaprinast.(ABSTRACT TRUNCATED AT 250 WORDS)     

Apolipoproteins and apolipoprotein agonists for the treatment of ischaemia/reperfusion injury

The use of agents and methods for the prevention, reduction or treatment of ischaemia/reperfusion (I/R) injury is claimed. The claimed agents can be any apolipoprotein, an apolipoprotein variant or fragment, paraoxonase, or lecithin:cholesterol acyltransferase. The agents are indicated to be useful in any condition where protection from, or treatment of, I/R injury is needed.     

4-型磷酸二酯酶与局部cAMP信号调节（英文）

Of the eleven families of cyclic nucleotide phosphodiesterases(PDEs) present in the human body,PDE4s represent the most widely expressed family of PDEs. A large body of work has been published on the expression and function of these PDEs,which preferentially hydrolyze cAMP in all cells studied,including neurons and supporting cells of the CNS. Four distinct genes termed PDE4 A,PDE4B,PDE4C and PDE4D encode PDE4 proteins. However,the number of PDE4s identified in different tissues and cells is estimated to be more than 30. Differences in regulation and localization explain this extreme heterogeneity. PDE4 hydrolytic activity is regulated by phosphorylation,and protein kinase A(PKA) was the first kinase identified. This PKA-dependent regulation establishes a feedback loop where cAMP regulates its own degradation to control the intensity and localization of the hormone and neurotransmitter signal. In addition,numerous additional kinases phosphorylate PDE4s to modulate the PKA-dependent activation and fine tune cAMP levels by growth factors and other extracellular cues. Thus,PDE4 can be considered a coincidence detector that integrates multiple signaling pathways. Finally,different PDE4s are involved in numerous macromolecular complexes targeting the cAMP hydrolytic activity to different subcellular domains. Thus,PDE4s function in different subcellular compartments,and inhibition of different isoforms affects cAMP levels in different subdomains with consequently different functions. The dyad space and the control of excitation/contraction will be used as examples of these localized regulations.     

3',4'-Dihydroxyflavonol reduces infarct size and injury associated with myocardial ischaemia and reperfusion in sheep

1 The antioxidant properties of flavonols in vivo and their potential benefits in myocardial ischaemia/reperfusion (I/R) injury have been little investigated. We evaluated the ability of a synthetic flavonol, 3',4'-dihydroxyflavonol (DiOHF) to scavenge superoxide in post-I/R myocardium and to prevent myocardial I/R injury. 2 Anaesthetized sheep were studied in four groups (n=5-6): control, ischaemic preconditioning (IPC), vehicle and DiOHF (before reperfusion, 5 mg kg(-1), i.v.). The left anterior descending coronary artery was occluded distal to the second diagonal branch for 1 h followed by 2 h of reperfusion. Infarct size, myocardial function, NADPH-activated superoxide generation and biochemical markers of injury were measured. 3 DiOHF (10(-8)-10(-4) m) incubated in vitro with post-I/R myocardium from the vehicle group suppressed superoxide production dose-dependently. 4 DiOHF administered in vivo also significantly reduced superoxide generation in vitro. DiOHF and IPC markedly reduced infarct size, which was 73+/-2% of the area at risk in vehicle, 50+/-4% in DiOHF, 75+/-5% in control and 44+/-4% in IPC. Post-I/R segment shortening within the ischaemic zone was greater in DiOHF (2.3+/-0.7%; P<0.01) and IPC (1.7+/-0.5%; P<0.01) than those in corresponding controls (-1.7+/-0.4; -2.1+/-0.4%). 5 DiOHF and IPC improved coronary blood flow to the ischaemic area and preserved higher levels of nitric oxide metabolites in the venous outflow from the ischaemic zone. 6 DiOHF attenuated superoxide production in post-I/R myocardium, and significantly reduced infarct size and injury following I/R in anaesthetized sheep. The extent of protection by DiOHF is comparable to that afforded by IPC. Thus, DiOHF has clinical potential for improving recovery from acute myocardial infarction and other ischaemic syndromes.     

Exendin-4 protects the hearts of rats from ischaemia/reperfusion injury by boosting antioxidant levels and inhibition of JNK/p66Shc/NADPH axis

Exendin-4, a glucagon-like peptide-1 receptor agonist, was shown to protect against cardiac ischaemia/reperfusion (I/R) injury by suppressing oxidative stress. p⁶⁶Shc, a pro-oxidant and an apoptotic protein, is activated in the infarcted left ventricles (LVs) after induction of I/R. This study investigated if the cardiac protective effect of Exendin-4 against I/R injury in rats involves inhibition of p⁶⁶Shc and to determine the underlying mechanisms behind this. Adult male rats (n = 12/group) were divided into four groups as a sham, a sham + Exendin-4, an I/R, and an I/R + Exendin-4. Exendin-4 was administered to rats 7 days before the induction of I/R. Ischaemia was induced by ligating the left anterior descending (LAD) coronary artery for 40 minutes followed by reperfusion for 10 minutes. The infarct myocardium was used for further analysis. Exendin-4 significantly reduced infarct area (by 62%), preserved LV function and lowered serum levels of LDH and CK-MB in I/R-induced rats. Also, it significantly reduced LV levels of ROS and MDA and protein levels of cytochrome-c and cleaved caspase-3 but significantly increased levels of glutathione (GSH) and manganese superoxide dismutase (MnSOD) in LVs of I/R rats indicating antioxidant and anti-apoptotic effects. Furthermore, it inhibited JNK and p⁶⁶Shc activation and downregulated protein levels of p⁶⁶Shc and NADPH oxidase with no effect on protein levels/activity of p53 and PKCβII. Of note, Exendin-4 also increased GSH and MnSOD in LVs of control rats. In conclusion, Exendin-4 cardioprotective effect in I/R hearts is mediated mainly by antioxidant effect and inhibition of JNK/P⁶⁶Shc/NADPH oxidase.     

Protective effects of n-6 fatty acids-enriched diet on intestinal ischaemia/reperfusion injury involve lipoxin A4 and its receptor

Background and Purpose

Long-term intake of dietary fatty acids is known to predispose to chronic inflammation, but their effects on acute intestinal ischaemia/reperfusion (I/R) injury is unknown. The aim of this study was to determine the consequences of a diet rich in n-3 or n-6 polyunsaturated fatty acids (PUFA) on intestinal I/R-induced damage.

Experimental Approach

Mice were fed three different isocaloric diets: a balanced diet used as a control and two different PUFA-enriched diets, providing either high levels of n-3 or of n-6 PUFA. Intestinal injury was evaluated after intestinal I/R. PUFA metabolites were quantitated in intestinal tissues by LC-MS/MS.

Key Results

In control diet-fed mice, intestinal I/R caused inflammation and increased COX and lipoxygenase-derived metabolites compared with sham-operated animals. Lipoxin A₄ (LxA₄) was significantly and selectively increased after ischaemia. Animals fed a high n-3 diet did not display a different inflammatory profile following intestinal I/R compared with control diet-fed animals. In contrast, intestinal inflammation was decreased in the I/R group fed with high n-6 diet and level of LxA₄ was increased post-ischaemia compared with control diet-fed mice. Blockade of the LxA₄ receptor (Fpr2), prevented the anti-inflammatory effects associated with the n-6 rich diet.

Conclusions and Implications

This study indicates that high levels of dietary n-6, but not n-3, PUFAs provides significant protection against intestinal I/R-induced damage and demonstrates that the endogenous production of LxA₄ can be influenced by diet.     

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

The present study was designed to evaluate the effect of cyclosporin A in a rat model of myocardial ischaemia reperfusion injury (MI/R). Anaesthetized rats were subjected to total occlusion (20 min) of the left main coronary artery followed by 5 h reperfusion (MI/R). Sham myocardial ischaemia-reperfusion rats (Sham MI/R) were used as controls. Myocardial necrosis, myocardial myeloperoxidase activity (MPO), serum creatinine phosphokinase activity (CPK), serum tumor necrosis factor (TNF-α), cardiac mRNA for TNF-α, cardiac intercellular adhesion molecule-1 (ICAM-1) immunostaining and myocardial contractility (left ventricle dP/dt_max) were evaluated. Myocardial ischaemia plus reperfusion in untreated rats produced marked myocardial necrosis, increased serum CPK activity and myeloperoxidase activity (a marker of leukocyte accumulation) both in the area-at-risk and in the necrotic area, reduced myocardial contractility and induced a marked increase in the serum levels of the TNF-α. Furthermore increased cardiac mRNA for TNF-α was measurable within 10 to 20 min of left main coronary artery occlusion in the area-at-risk and increased levels were generally sustained for 0.5 h. Finally, myocardial ischaemia-reperfusion injury increased ICAM-1 staining in the myocardium. Administration of cyclosporin A (0.25, 0.5 and 1 mg/kg as an i.v. infusion 5 min after coronary artery occlusion) lowered myocardial necrosis and myeloperoxidase activity in the area-at-risk and in the necrotic area, decreased serum CPK activity, increased myocardial contractility, reduced serum levels of TNF-α and the cardiac cytokine mRNA levels, and blunted ICAM-1 immunostaining in the injured myocardium. The data suggest that cyclosporin A suppresses leukocyte accumulation and protects against myocardial ischaemia-reperfusion injury.