APT070 (Mirococept), a membrane-localised complement inhibitor, inhibits inflammatory responses that follow intestinal ischaemia and reperfusion injury

Activation of the complement system has been shown to play a major role in the mediation of reperfusion injury. Here, we assessed the effects of APT070 (Mirococept), a novel membrane-localised complement inhibitor based on a recombinant fragment of soluble CR1, on the local, remote and systemic injuries following intestinal ischaemia and reperfusion (I/R) in the rat. In a model of mild I/R injury (30 min of ischaemia and 30 min of reperfusion), APT070 dose-dependently (1-10 mg kg(-1)) inhibited the increase in vascular permeability of and neutrophil influx into intestine and lungs. Maximal inhibition occurred at 10 mg kg(-1). Following severe I/R injury (120 min of ischaemia and 120 min of reperfusion), APT070 (10 mg kg(-1)) markedly prevented neutrophil influx and the increase in vascular permeability both in the intestine and the lungs.APT070 also effectively suppressed the increase of tissue (intestine and lungs) and serum concentrations of TNF-alpha and IL-6, but not those of IL-1beta or IL-10. There was no significant reduction of mortality in the APT070 group. In conclusion, treatment with the membrane-targeted complement inhibitor APT070 significantly reduced the hyperinflammatory response after mild and severe ischaemia and reperfusion injury (I/RI) in rats. APT070 may be effective in therapeutic indications involving gut I/RI.     

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.     

Comparative anti-inflammatory activities of antagonists to C3a and C5a receptors in a rat model of intestinal ischaemia/reperfusion injury

1. Complement activation is implicated in the pathogenesis of intestinal ischaemia-reperfusion injury (I/R), although the relative importance of individual complement components is unclear. A C3a receptor antagonist N(2)-[(2,2-diphenylethoxy)acetyl]-l-arginine (C3aRA) has been compared with a C5a receptor antagonist (C5aRA), AcF-[OPdChaWR], in a rat model of intestinal I/R. 2. C3aRA (IC(50)=0.15 microm) and C5aRA (IC(50)=0.32 microm) bound selectively to human polymorphonuclear leukocyte (PMN) C3a and C5a receptors, respectively. Effects on circulating neutrophils and blood pressure in the rat were also assessed. 3. Anaesthetised rats, subjected to intestinal ischaemia (30 min) and reperfusion (120 min), were administered intravenously with either (A) the C3aRA (0.1-1.0 mg x kg(-1)); the C5aRA (1.0 mg x kg(-1)); the C3aRA+C5aRA (each 1.0 mg x kg(-1)); or vehicle, 45 min prior, or (B) the C3aRA (1.0 mg x kg(-1)) or vehicle, 120 min prior to reperfusion. 4. The C3aRA and C5aRA, administered 45 min prior to reperfusion, displayed similar efficacies at ameliorating several disease markers (increased oedema, elevated ALT levels and mucosal damage) of rat intestinal I/R. The combination drug treatment did not result in greater injury reduction than either antagonist alone. However, doses of the C3aRA (0.01-10 mg x kg(-1)) caused transient neutropaenia, and the highest dose (10 mg x kg(-1)) also caused a rapid and transient hypertension. 5. The C3aRA (1.0 mg x kg(-1)), delivered 120 min prior to reperfusion to remove the global effect of C3aRA-induced neutrophil sequestration, did not attenuate the markers of intestinal I/R, despite persistent C3aR antagonism at this time. 6. C3aR antagonism does not appear to be responsible for the anti-inflammatory actions of this C3aRA in intestinal I/R in the rat. Instead, C3aRA-mediated global neutrophil tissue sequestration during ischaemia and early reperfusion may account for the protective effects observed.     

Mechanisms of the anti-inflammatory effects of the natural secosteroids physalins in a model of intestinal ischaemia and reperfusion injury

Reperfusion of an ischaemic tissue is associated with an intense inflammatory response and inflammation-mediated tissue injury. Physalins, a group of substances with secosteroidal chemical structure, are found in Physalis angulata stems and leaves. Here, we assessed the effects of physalins on the local, remote and systemic injuries following intestinal ischaemia and reperfusion (I/R) in mice and compared with the effects of dexamethasone. Following I/R injury, dexamethasone (10 mg kg(-1)) or physalin B or F markedly prevented neutrophil influx, the increase in vascular permeability in the intestine and the lungs. Maximal inhibition occurred at 20 mg kg(-1). Moreover, there was prevention of haemorrhage in the intestine of reperfused animals. Dexamethasone or physalins effectively suppressed the increase in tissue (intestine and lungs) and serum concentrations of TNF-alpha. Interestingly, treatment with the compounds was associated with enhancement of IL-10. The anti-inflammatory effects of dexamethasone or physalins were reversed by pretreatment with the corticoid receptor antagonist RU486 (25 mg kg(-1)). The drug compounds suppressed steady-state concentrations of corticosterone, but did not alter the reperfusion-associated increase in levels of corticosterone. The IL-10-enhancing effects of the drugs were not altered by RU486. In conclusion, the in vivo anti-inflammatory actions of physalins, natural steroidal compounds, appear to be mostly due to the activation of glucocorticoid receptors. Compounds derived from these natural secosteroids may represent novel therapeutic options for the treatment of inflammatory diseases.     

Genistein, a protein tyrosine kinase inhibitor, inhibits thromboxane A2-mediated human platelet responses

An isoflavone compound, genistein, which is known as a protein tyrosine kinase inhibitor, concentration-dependently (0.1-30 micrograms/ml) suppressed human platelet aggregation, serotonin secretion, and protein tyrosine phosphorylation induced by collagen or stable thromboxane A2 analogs [U46619 and 9,11-epithio-11,12-methano-thromboxane A2 (STA2)]. However, genistein did not inhibit these thrombin (0.1 unit/ml)-induced platelet responses. Although thrombin induced an increase in the platelet phosphotyrosine content, genistein at 100 micrograms/ml only slightly attenuated thrombin-induced protein tyrosine phosphorylation. Genistein competitively inhibited [3H]U46619 binding to washed platelets, in a concentration-dependent fashion. Daidzein (another isoflavone compound), which does not have a hydroxyl group at the 5-position of genistein and lacks inhibitory activity for protein tyrosine kinase, was found to suppress [3H]U46619 binding, leading to the inhibition of collagen- or STA2-induced platelet responses. These results indicate that the blockage by genistein of platelet responses induced by collagen or thromboxane A2 is due to its preventive action on thromboxane A2 binding to the receptor, rather than via inhibition of protein tyrosine phosphorylation, and that the drug does not appear to be a particularly good inhibitor of tyrosine phosphorylation in intact platelets.     

Cardioprotective effect of TY-12533, a novel Na(+)/H(+) exchange inhibitor, on ischemia/reperfusion injury

The effects of 6,7,8, 9-tetrahydro-2-methyl-5H-cyclohepta[b]pyridine-3-carbonylguanidine maleate (TY-12533) on myocardial ischemia/reperfusion injury were evaluated in rats. Inhibitory effects of TY-12533, TY-50893 (the 9-chloro derivative of TY-12533) and cariporide on the platelet Na(+)/H(+) exchanger in vitro were almost equal at pH 6.2 and decreased at pH 6.7; but TY-12533 was four times more potent than TY-50893 and cariporide at pH 6.7. TY-12533, TY-50893 and cariporide administered before ischemia (0.01-1 mg/kg, i.v.) suppressed the ischemia/reperfusion-induced arrhythmias to the same extent in vivo; but TY-12533 was more effective than cariporide and TY-50893 when they were administered during ischemia (0.1-1 mg/kg). Similar results were obtained for the inhibitory effects of these drugs administered before ischemia (0.03-0.1 mg/kg, i.v.) and during ischemia (0.1-1 mg/kg) on the ischemia/reperfusion-induced myocardial infarction. These differences between TY-12533 and the other drugs in vitro and in vivo may be ascribed to the pK(a) values of the guanidinium moiety of TY-12533 (6.93), TY-50893 (6.35) and cariporide (6.28).     

Mitochondrial function in ischaemia and reperfusion of the ageing heart

1. In addition to Ca2+-dependent mediation of excitation-contraction coupling during cardiac work and ATP hydrolysis, Ca2+ also stimulates the Krebs' cycle and mitochondrial matrix dehydrogenases to maintain the nicotinamide adenine dinucleotide redox potential and ATP synthesis. Thus, the balance between energy demand and supply is maintained during increases in cardiac work by elevated cytosolic Ca2+ that is transmitted to the mitochondrial matrix via regulation of uniporter and antiporter pathways across the inner mitochondrial membrane. 2. Brief ischaemia perturbs Ca2+ homeostasis but mitochondrial buffering of Ca2+ permits maintained mitochondrial function. However, prolonged ischaemia and reperfusion causes Ca2+ 'overload' at supramicromolar levels. The onset of vicious cycles that abrogate contractile function and, ultimately, may cause irreversible cell injury involves: (i) loss of ionic homeostasis, energy production and anti-oxidant enzyme activity; (ii) activation of phospholipases; and (iii) accumulation of free radicals, membrane lipid peroxidation products and protein adducts. 3. Increased permeability of the inner mitochondrial membrane to solutes occurs causing mitochondrial swelling, 'proton leak', reduced efficiency of the respiratory chain and uncoupling of oxidative phosphorylation. The opening of the mitochondrial permeability transition pore is potentiated by high mitochondrial Ca2+ and inducers, such as Pi, long-chain acyl coenzyme (Co)A and oxygen free radicals. Opening of this channel depolarizes the mitochondrion and dissipates the H+ electrochemical gradient (delta muH), preventing oxidative phosphorylation. Together with the release of cytochrome c and subsequent activation of caspase pathways, these events precede cell death. 4. Compared with younger counterparts, the senescent myocardium has a reduced capacity to recover from ischaemia and reperfusion. The consequent events described above are augmented in ageing. Elevated mitochondrial Ca2+ and increased dehydrogenase activation are linked to inefficient mitochondrial function and limited postischaemic recovery of contractile function. 5. Notably, a distinct decrease in the ratio of mitochondrial membrane omega-3 to omega-6 polyunsaturated fatty acids (PUFA) and a decrease in the mitochondrial phospholipid cardiolipin occurs in aged rat hearts. A diet rich in omega-3 PUFA directly increases membrane omega-3:omega-6 PUFA and cardiolipin content and also facilitates improved tolerance of ischaemia and reperfusion. A major consequence of dietary omega-3 PUFA may be the effect of altered mitochondrial Ca2+ flux and Ca2+-dependent processes.     

Cardioprotective actions of oligotide, a single stranded polydeoxyribonucleotide complex, in myocardial ischaemia and reperfusion injury.

1. The efficacy of oligotide, a single stranded polydeoxyribonucleotide complex, was examined in a feline model of myocardial ischaemia (MI: 90 min) and reperfusion (R: 270 min). Oligotide (15 mg kg-1 bolus) was administered intravenously 80 min after occlusion of the left anterior descending (LAD) coronary artery (i.e., 10 min prior to R) and continued for an additional 280 min (10 mg kg-1 h-1 infusion). 2. Oligotide-treated cats showed significantly smaller myocardial necroses and lower cardiac myeloperoxidase activities (significantly lower neutrophil infiltration) in the necrotic zone as compared to MI+R cats receiving only vehicle. 3. LAD coronary arteries isolated from MI+R cats exhibited a significant endothelial dysfunction (i.e., reduced endothelium-dependent relaxation), and significantly increased adherence of polymorphonuclear neutrophils (PMNs) ex vivo. However, oligotide significantly preserved endothelial function and attenuated PMN adherence in ischaemic LAD coronary arteries. 4. Oligotide attenuated P-selectin expression on thrombin-stimulated platelets as well as PMN adherence to thrombin-stimulated coronary endothelium. Immunohistochemical examination in vivo revealed that oligotide treatment also significantly inhibited coronary endothelial P-selectin expression after 90 min MI and 20 min R. 5. Oligotide exerted a significant cardioprotection in MI+R injury. The mechanism appears to be related to attenuation of PMN-endothelial interaction and eventual infiltration into the ischaemic myocardium.     

Role of the bradykinin B2 receptor for the local and systemic inflammatory response that follows severe reperfusion injury

1. Bradykinin (BK) appears to play an important role in the development and maintenance of inflammation. Here, we assessed the role of the BK B(2) receptor for the injuries that occur after ischemia and reperfusion (I/R) of the territory irrigated by the superior mesenteric artery. 2. Tissue (lung and duodenum) kallikrein activity increased after ischemia with greater enhancement after reperfusion. A selective inhibitor of tissue kallikrein, Phenylacetyl-Phe-Ser-Arg-N-(2,3-dinitrophenyl)-ethylenediamine (TKI, 0.001-10 mg ml(-1)), inhibited kallikrein activity in a concentration-dependent manner in vitro. In vivo, pretreatment with TKI (30 mg kg(-1)) prevented the extravasation of plasma and the recruitment of neutrophils. 3. Similarly, the bradykinin B(2) receptor antagonists, HOE 140 (0.01-1.0 mg kg(-1)) or FR173657 (10.0 mg kg(-1)), inhibited reperfusion-induced increases in vascular permeability and the recruitment of neutrophils in the intestine and lungs. 4. In a model of more severe I/R injury, HOE 140 (1.0 mg kg(-1)) inhibited the increase in vascular permeability, neutrophil recruitment, haemorrhage and tissue pathology. Furthermore, HOE 140 significantly inhibited the elevations of TNF-alpha in tissue and serum and partially prevented lethality. This was associated with an increase in the concentrations of IL-10 in tissue and serum. 5. Thus, our results demonstrate that, following intestinal I/R injury, there is an increase in tissue kallikrein activity and activation of BK B(2) receptors. B(2) receptor activation is essential for the development of inflammatory tissue injury and lethality. These results contrast with those of others showing that BK mostly exerts a protective role during I/R injury.     

Ozone oxidative preconditioning inhibits inflammation and apoptosis in a rat model of renal ischemia/reperfusion injury

Ischemia/reperfusion injury, which is commonly seen in the field of renal surgery or transplantation, is a major cause of acute renal failure. Previous studies showed that ozone oxidative preconditioning (OzoneOP) attenuated renal ischemia/reperfusion injury. The objective of this study was to examine the role of the OzoneOP in modulating inflammation and apoptosis after renal ischemia/reperfusion injury. Rats were subjected to 45 min of renal ischemia, with or without treatment with OzoneOP (1 mg/kg). Renal function, inflammation and apoptosis were compared at 24 h after renal injury. OzoneOP improved the renal dysfunction and reduced inflammation and apoptosis after ischemia/reperfusion injury. In conclusion, OzoneOP has potent anti-apoptotic and anti-inflammatory properties. These findings may have major implications in the treatment of human ischemic acute renal failure.     

SB-656933, a novel CXCR2 selective antagonist, inhibits ex vivo neutrophil activation and ozone-induced airway inflammation in humans

AIMS

To determine the safety and tolerability of a novel selective CXCR2 antagonist and assess its pharmacodynamic effects using measures of neutrophil activation and function, including CD11b expression in whole blood and ozone-induced airway inflammation in healthy subjects.

METHODS

Flow cytometric determination of ex vivo CXCL1-induced CD11b expression on peripheral blood neutrophils was performed following single dose oral administration of SB-656933 (dose range 2–1100 mg). A subsequent randomized study (placebo, 50 mg and 150 mg) was performed to explore the dose–response for ozone-induced airway inflammation, as measured by sputum biomarkers.

RESULTS

Oral administration of SB-656933 resulted in significant inhibition of CXCL1-induced CD11b expression on peripheral blood neutrophils at single doses greater than or equal to 50 mg. Maximum inhibition (70%) relative to placebo was observed following administration of SB-656933 400 mg (95% CI 60%, 77%). This was sustained up to a dose of 1100 mg. Single doses of SB-656933 reduced ozone-induced airway inflammation in a dose-dependent manner. Relative to placebo, there were 55% (95% CI 20%, 75%) and 74% (95% CI 55%, 85%) fewer neutrophils in the sputum of subjects after a single dose of 50 mg or 150 mg, respectively. There was a corresponding reduction in myeloperoxidase concentrations in the sputum supernatant of 32.8% (95% CI 9.2, 50.3) and 50.5% (95% CI 33.3, 63.3). SB-656933 was safe and well-tolerated at all doses.

CONCLUSIONS

SB-656933 is a CXCR2 antagonist that demonstrates dose-dependent effects on neutrophil activation and recruitment within a well-tolerated dose range. These data suggest that SB-656933 may be an effective agent in neutrophil-predominant diseases.     

Immunoferon, a glycoconjugate of natural origin, inhibits LPS-induced TNF-alpha production and inflammatory responses

We have analyzed the effect of a patented glycoconjugate (GC) of natural origin, Inmunoferon, in the development of the response to endotoxemia induced by administration of LPS in rodents. We have observed that oral treatment with the drug reduced the levels of serum TNF-alpha induced by an intravenous pulse of LPS. The serum of pretreated mice blocked TNF-alpha production by peritoneal macrophages. The drug increased the levels of TNF-alpha regulators such as IL-10 and corticosteroids, whereas it inhibited TNF-alpha-dependent IL-6 production. Further TNF-alpha-dependent responses, such as cell extravasation, was decreased in treated mice. According to these results, Inmunoferon is postulated as an inhibitor of the systemic response to LPS. Correlation of the observations made in mice with a rat model suggests the efficacy of this product in reducing TNF-alpha production in a species-independent fashion and opens the possibility of its trial as an adjuvant of antibiotics in treatment against gram-negative bacterial infection.     

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.     

Hydroxysafflor yellow a protects neuron against hypoxia injury and suppresses inflammatory responses following focal ischemia reperfusion in rats

Previous data demonstrated that hydroxysafflor yellow A (HSYA), a yellow color pigments extracted from the safflower, was an effective agent against focal cerebral ischemia. In the present study we demonstrated that HSYA prevented the injury in cultured cerebral cortical neurons induced by oxygen-glucose deprivation and increased the cell viability, as shown by the inhibition of both LDH and NO efflux. Further, HSYA administered orally 3 d before middle cerebral artery occlusion has the capacity to reduce cerebral infarct size and edema after 2 h cerebral ischemia followed by 24 h reperfusion in rats, and to significantly improve neurological behavior scores. Mean while, treatment with HSYA significantly decreased both mRNA and protein levels of IL-1beta, TNF-alpha in ischemic brain tissue. These results suggested that the protection of HSYA results from, at least in part, suppression of inflammatory responses following focal ischemia reperfusion.     

Treatment with DF 2162, a non-competitive allosteric inhibitor of CXCR1/2, diminishes neutrophil influx and inflammatory hypernociception in mice

BACKGROUND AND PURPOSE: Neutrophil migration into tissues is involved in the genesis of inflammatory pain. Here, we addressed the hypothesis that the effect of CXC chemokines on CXCR1/2 is important to induce neutrophil migration and inflammatory hypernociception. EXPERIMENTAL APPROACH: Mice were treated with a non-competitive allosteric inhibitor of CXCR1/2, DF 2162, and neutrophil influx and inflammatory hypernociception were assessed by myeloperoxidase assay and electronic pressure meter test, respectively, in various models of inflammation. KEY RESULTS: DF 2162 inhibited neutrophil chemotaxis induced by CXCR1/2 ligands but had no effect on CXCL8 binding to neutrophils. A single mutation of the allosteric site at CXCR1 abrogated the inhibitory effect of DF 2162 on CXCL-8-induced chemotaxis. Treatment with DF 2162 prevented influx of neutrophils and inflammatory hypernociception induced by CXCL1 in a dose-dependent manner. The compound inhibited neutrophil influx and inflammatory hypernociception induced by carrageenan, lipopolysaccharide and zymosan, but not hypernociception induced by dopamine and PGE(2). DF 2162 had a synergistic effect with indomethacin or the absence of TNFR1 to abrogate carrageenan-induced hypernociception. Treatment with DF 2162 diminished neutrophil influx, oedema formation, disease score and hypernociception in collagen-induced arthritis. CONCLUSIONS AND IMPLICATIONS: CXCR1/2 mediates neutrophil migration and is involved in the cascade of events leading to inflammatory hypernociception. In addition to modifying fundamental pathological processes, non-competitive allosteric inhibitors of CXCR1/2 may have the additional benefit of providing partial relief for pain and, hence, may be a valid therapeutic target for further studies aimed at the development of new drugs for the treatment of rheumatoid arthritis.     

Inhibition of interleukin-8 (CXCL8/IL-8) responses by repertaxin, a new inhibitor of the chemokine receptors CXCR1 and CXCR2

Repertaxin is a new non-competitive allosteric blocker of interleukin-8 (CXCL8/IL-8) receptors (CXCR1/R2), which by locking CXCR1/R2 in an inactive conformation prevents receptor signaling and human polymorphonuclear leukocyte (PMN) chemotaxis. Given the unique mode of action of repertaxin it was important to examine the ability of repertaxin to inhibit a wide range of biological activities induced by CXCL8 in human leukocytes. Our results show that repertaxin potently and selectively blocked PMN adhesion to fibrinogen and CD11b up-regulation induced by CXCL8. Reduction of CXCL8-mediated PMN adhesion by repertaxin was paralleled by inhibition of PMN activation including secondary and tertiary granule release and pro-inflammatory cytokine production, whereas PMN phagocytosis of Escherichia coli bacteria was unaffected. Repertaxin also selectively blocked CXCL8-induced T lymphocyte and natural killer (NK) cell migration. These data suggest that repertaxin is a potent and specific inhibitor of a wide range of CXCL8-mediated activities related to leukocyte recruitment and functional activation in inflammatory sites.     

Systemic administration of Zn2+ during the reperfusion phase of transient cerebral ischaemia protects rat hippocampus against iron-catalysed postischaemic injury

1. The aim of the present study was to test the protective role of intravenous Zn(2+) against iron-catalysed reperfusion injury in the hippocampus of ischaemic rats. 2. One hundred adult male Wistar albino rats were randomly divided into five groups. Rats in the first group were subjected to surgery (sham operation) without induction of cerebral ischaemia and injected with normal saline (i.v.). The second group of sham-operated rats were injected with 6 mg/kg, i.v., ZnCl(2). In the third group, rats were subjected to cerebral ischaemia for 60 min. Animals in the fourth group were subjected to cerebral ischaemia for 60 min followed by 8 h reperfusion. In the fifth group, rats were subjected to cerebral ischaemia for 60 min, followed by 8 h reperfusion with injection of a single dose of ZnCl(2) (6 mg/kg, i.v.) during the first 5 min of the reperfusion period. After reperfusion, animals were killed, their brains were dissected out on ice and the two hippocampi from each animal were isolated and analysed. 3. Cerebral ischaemia induced an increase in the iron content, lipidic peroxidation, apoptosis and metallothionein (MT) in the hippocampus. These effects were significantly increased in the hippocampus of ischaemic rats subjected to 8 h reperfusion compared with ischaemic non-reperfused rats. Intravenous administration of ZnCl(2)decreased the accumulation of iron, lipidic peroxidation and apoptosis produced by reperfusion, but increased the level of MT. 4. Data from the present study suggest that, after 1 h ischaemia, there is an increase in the permeability of the blood-brain barrier and this allows penetration of i.v. injected ZnCl(2), which can induce expression of brain MT, increase the anti-oxidant capacity and diminish iron-catalysed lipid peroxidation and apoptosis. This may give new insights as to how to improve the outcome for stroke patients.     

Protective effects of M40403, a selective superoxide dismutase mimetic,in myocardial ischaemia and reperfusion injury in vivo

1. Myocardial injury caused by ischaemia and reperfusion comes from multiple pathogenic events, including endothelial damage, neutrophil extravasation into tissue, mast cell activation, and peroxidation of cell membrane lipids. These events are followed by myocardial cell alterations resulting eventually in cell necrosis. An enhanced formation of reactive oxygen species is widely accepted as a stimulus for tissue destruction and cardiac failure. 2. In this study, we have investigated the cardioprotective effects of M40403 in myocardial ischaemia-reperfusion injury. M40403 is a low molecular weight, synthetic manganese containing superoxide dismutase mimetic (SODm) that selectively removes superoxide anion. Ischaemia was induced in rat hearts in vivo by ligating the left anterior descending coronary artery. Thirty minutes after the induction of ischaemia, the ligature was removed and reperfusion allowed to occur for at least 60 min. M40403 (0.1-1 mg kg(-1)) was given intravenously 15 min before ischaemia. 3. The results obtained in this study showed that M40403 significantly reduced the extent of myocardial damage, mast cell degranulation and the incidence of ventricular arrhythmias. Furthermore, M40403 significantly attenuated, in a dose-dependent manner, neutrophil infiltration in the myocardium as well as the associated induction of lipid peroxidation. Calcium overload seen post-reperfusion of the ischaemic myocardium was also reduced by M40403. 4. Immunohistochemical analysis for nitrotyrosine revealed a positive staining in cardiac tissue taken after reperfusion: this was attenuated by M40403. Moreover reperfused cardiac tissue sections showed positive staining for P-selectin and for anti-intercellular adhesion molecule (ICAM-1) in the vascular endothelial cells. M40403 treatment markedly reduced the intensity and degree of P-selectin and ICAM-1 in these tissues. No staining for nitrotyrosine, P-selectin or ICAM-1 was found in cardiac tissue taken at the end of the ischaemic period. 5. Overall, M40403 treatment reduced the morphological signs of myocardial cell injury and significantly improved survival. 6. Taken together, these results clearly indicate that M40403 treatment exerts a protective effect against ischaemia-reperfusion-induced myocardial injury, supporting a key role for superoxide anion in reperfusion injuries. This suggests that synthetic enzymes of SOD such as M40403, offer a novel therapeutic approach for the treatment of ischaemic heart disease where superoxide anion plays a dominant role.