Cardioprotective and endothelial protective effects of [Ala-IL8]77 in a rabbit model of myocardial ischaemia and reperfusion

Investigation of the underlying hub genes and mechanisms of reperfusion injury in patients undergoing coronary artery bypass graft surgery by integrated bioinformatic analyses

Background

Although coronary artery bypass graft (CABG) surgery is the main method to revascularize the occluded coronary vessels in coronary artery diseases, the full benefits of the operation are mitigated by ischemia-reperfusion (IR) injury. Although many studies have been devoted to reducing IR injury in animal models, the translation of this research into the clinical field has been disappointing. Our study aimed to explore the underlying hub genes and mechanisms of IR injury.

Methods

A weighted gene co-expression network analysis (WGCNA) was executed based on the expression profiles in patients undergoing CABG surgery (GSE29396). Functional annotation and protein-protein interaction (PPI) network construction were executed within the modules of interest. Potential hub genes were predicted, combining both intramodular connectivity (IC) and degrees. Meanwhile, potential transcription factors (TFs) and microRNAs (miRNAs) were predicted by corresponding bioinformatics tools.

Results

A total of 336 differentially expressed genes (DEGs) were identified. DEGs were mainly enriched in neutrophil activity and immune response. Within the modules of interest, 5 upregulated hub genes (IL-6, CXCL8, IL-1β, MYC, PTGS-2) and 6 downregulated hub genes (C3, TIMP1, VSIG4, SERPING1, CD163, and HP) were predicted. Predicted miRNAs (hsa-miR-333-5p, hsa-miR-26b-5p, hsa-miR-124-3p, hsa-miR-16-5p, hsa-miR-98-5p, hsa-miR-17-5p, hsa-miR-93-5p) and TF (STAT1) might have regulated gene expression in the most positively related module, while hsa-miR-333-5p and HSF-1 were predicted to regulate the genes within the most negatively related module.

Conclusions

Our study illustrates an overview of gene expression changes in human atrial samples from patients undergoing CABG surgery and might help translate future research into clinical work.

Serum IL8 is not associated with cardiovascular events but with all-cause mortality

BACKGROUND

The aim of this study is to investigate if IL8 levels were associated with incident cardiovascular (CV) events (CVE) and mortality (all-cause, CV, and cancer) in a cohort of 60 years old men and women from Stockholm (60YO).

METHODS

The 60YO comprises 4232 participants; baseline period: 1997-1999. The cohort is matched annually to population registries to record deaths and incident CVE. Serum IL8 was measured in 4011 participants and categorized in quartiles. Cox proportional hazard models were used to estimate the CVE and mortality risk, expressed as hazard ratios (HR) with 95% confidence intervals (CI). Potential confounding was addressed by adjusting for traditional CV risk factors (CVE estimates) and by sex, life style habits, metabolic factors (mortality estimates). Laplace regression was used to calculate the difference in time until a certain percentage of the cohort died according to IL8 levels.

RESULTS

During 16.5 years follow up, 522 incident CVE were recorded and 647 study participants died. IL8 was not associated with CVE risk (IL8 Q4 vs Q1, HR of 0.95; 95% CI 0.75-1.22). Compared to Q1, IL8 Q4 was associated with all-cause mortality (adjusted HR 1.28; 95% CI 1.02-1.63). No association was observed with CV and cancer related mortality in the fully adjusted model. Participants with IL8 above the median died of any cause ≈1.3 years before the 15% of the population had died.

CONCLUSION

Elevated IL8 levels were not associated with CVE risk and CV mortality, but were associated with an increased risk of all-cause mortality regardless of the underlying cause.

Duffy antigen receptor genetic variant and the association with Interleukin 8 levels

The aim of this study is to identify loci associated with circulating levels of Interleukin 8 (IL8). We investigated the associations of 121,445 single nucleotide polymorphisms (SNPs) from the Illumina 200K CardioMetabochip with IL8 levels in 1077 controls from the Stockholm Heart Epidemiology Program (SHEEP) study, using linear regression under an additive model of inheritance. Five SNPs (rs12075A/G, rs13179413C/T, rs6907989T/A, rs9352745A/C, rs1779553T/C) reached the pre-defined threshold of genome-wide significance (p<1.0×10(-5)) and were tested for in silico replication in three independent populations, derived from the PIVUS, MDC-CC and SCARF studies. IL8 was measured in serum (SHEEP, PIVUS) and plasma (MDC-CC, SCARF). The strongest association was found with the SNP rs12075 A/G, Asp42Gly (p=1.6×10(-6)), mapping to the Duffy antigen receptor for chemokines (DARC) gene on chromosome 1. The minor allele G was associated with 15.6% and 10.4% reduction in serum IL8 per copy of the allele in SHEEP and PIVUS studies respectively. No association was observed between rs12075 and plasma IL8.

CONCLUSION

rs12075 was associated with serum levels but not with plasma levels of IL8. It is likely that serum IL8 represents the combination of levels of circulating plasma IL8 and additional chemokine liberated from the erythrocyte DARC reservoir due to clotting. These findings highlight the importance of understanding IL8 as a biomarker in cardiometabolic diseases.

Is serum Interleukin-17 associated with early atherosclerosis in obese patients?

Atherosclerosis is a chronic inflammatory process of the vessel walls, and CD4+ T-cells are peculiar to both human and murine atherosclerotic lesions. There is a recent line of research favoring hypothetic allergic mechanisms in the genesis of atherosclerosis and, consequently, coronary artery disease (CAD), among which Interleukin (IL)-17 appears to be a key cytokine regulating local tissue inflammation. The objective was to add a piece of information on the role of IL-17 in the genesis of atherosclerosis. Eighty obese patients with normal liver enzyme levels but presenting with ultrasonographic evidence of NAFLD formed the population of this cross-sectional study. Anthropometric measures, data on excess adiposity, metabolic profile, serum concentrations of IL-17, eotaxin-3, IL-8, and CCL4/MIP1β, C-reactive protein, fibrinogen, ferritin, TNF-α, as well carotid intima-media thickness (IMT), a marker of atherosclerosis, and the main risk factors for CAD, such as blood pressure and smoking status, but also less determinant ones such as degree of NAFLD severity, Intramuscular Triglyceride storage and Resting Metabolic Rate were evaluated. Serum concentrations of Il-17 were detected as related to those of inflammatory cytokines, IL-6, IFN-γ and TNF-α. Furthermore, circulating levels of IL-17 were linked to those mirroring allergic process, IL-8, CCL4/MIP1β and eotaxin. Early atherosclerosis, evidenced as increased IMT, was not associated with circulating IL-17 levels. At multiple regression,IMT was predicted, other than by age, by the amount of the visceral adiposity, expressed as visceral adipose tissue at ultrasonography, and by serum eotaxin. In conclusion, a strong relationship was found between the IL-17-related chemokine eotaxin and IMT. The association found between the amount of visceral fat and circulating levels of eotaxin on the one hand, and IMT on the other, could reinforce the hypothesis that IL-17, released by the visceral adipose tissue, induces eotaxin secretion via the smooth muscle cells present in the atheromatosus vessels.

Association of interleukin 8 with myocardial infarction: results from the Stockholm Heart Epidemiology Program

BACKGROUND

Interleukin 8 (IL8) has been contradictorily associated with the risk of myocardial infarction (MI).

AIM

To investigate the association of IL8 serum levels with the risk of MI and the association of the IL8 (IL8) and IL8 receptors (CXCR1 and CXCR2) genetic variants with IL8 levels and MI risk in a large case control study, the Stockholm Heart Epidemiology Program.

METHODS AND RESULTS

IL8 levels (pg/mL) were divided into quartiles and the MI risk was calculated by logistic regression and expressed as odds ratio (OR) and 95% CI. Two IL8 SNPs (rs4073A/T, rs2227306C/T) and three SNPs tagging CXCR1 and CXCR2 (rs4674258C/T, rs1008563C/T, rs6723449T/C) were analyzed for association with IL8 levels and with MI risk. Multivariate adjusted ORs for MI risk by IL8 levels in the highest quartiles indicated reduced point estimates in both women (OR 0.37; 95% CI 0.2-0.8) and men when compared to the lowest quartile. In female cases, IL8 levels decreased progressively in the six months after MI (p=0.03). IL8, CXCR1 and CXCR2 genetic variants were not associated with IL8 levels. In men, the T allele at the IL8 SNP rs4073 was associated with a slight increase in the MI risk under an additive and a recessive model of inheritance.

CONCLUSIONS

IL8 serum levels were associated with a reduced occurrence of MI among women, whereas IL8 was associated with a slightly increased risk among men, possibly through different mechanisms. These data suggest that the biological effects of IL8 on MI risk may vary over time and warrant further cohort studies with repetitive IL8 measurements.

High cerebrospinal fluid antioxidants and interleukin 8 are protective of hypoxic brain damage in newborns

The objective was to explain the discrepancy in the development of hypoxic ischemic brain injury (HIE) in some asphyxiated newborns rather than others. Forty newborns were classified according to their cerebrospinal neuron-specific-enolase (CSF-NSE) levels on their 5th-day of life; group 1 with low-NSE (n = 25). The remaining 15 newborns had high-NSE and were further divided into a group with no HIE (n = 10, group 2) and another with HIE (n = 5, group 3). CSF-NSE, total-hydroperoxide (TH), biological-antioxidant-potentials (BAPs), 12 cytokines and erythropoietin (EPO) were measured. The TH/BAP gave the oxidative-stress-index (OSI). The BAPs of serial dilutions of three types of EPO were tested. CSF-NSE and TH and mean OSIs were higher in group 3. IL-8 and mean BAPs were higher in group 2 than in group 1. EPO was less detected in group 3. Serial EPO dilutions correlated with their BAPs. Compensatory antioxidants and IL-8 elevation could be protective of perinatal asphyxic brain injury. Antioxidative effect of EPO could be neuroprotective.

The sex differences of cerebrospinal fluid levels of interleukin 8 and antioxidants in asphyxiated newborns

Newborn males are more sensitive to brain injury than newborn females are. The aim of the present study was to find an explanation for this. We used the neuron-specific enolase (NSE) levels in the cerebrospinal fluid (CSF) for the classification of 32 newborns (19 males and 13 females) on their fifth postnatal day. The NSE levels were higher than normal (8.4 +/- 1.6 ng/mL) in 10 newborn males and 6 females and were, respectively, considered asphyxiated male and female groups. The remaining newborns, 9 males and 7 females, had normal CSF levels of NSE and were considered normal newborn male and female groups. The CSF samples were measured for 12 cytokines, using a cytokine array kit, and for total hydroperoxide and biological antioxidant potentials (BAPs), using the free radical analytic system. Among the 12 cytokines measured, only interleukin 8 (IL-8) was properly detected. The CSF levels of IL-8 were higher in the asphyxiated newborn females than in the other three groups. The mean CSF levels of BAPs in the asphyxiated newborn females were higher compared with the other three groups, but significance was detected only in comparison with the BAP levels in the CSF samples of the normal newborn males. There were no differences in total hydroperoxide levels among the groups. There are sex-related differences in the CSF levels of IL-8 and antioxidants in asphyxiated newborns, with higher levels in newborn females; this might contribute in the sexual dimorphism regarding the fact that females have better protection from brain injury than the males.

An apparent paradox: Chemokine receptor agonists can be used for anti-inflammatory therapy

Inflammation plays an important role in a wide range of human diseases. Chemokines are a group of proteins which control the migration and activation of the immune cells involved in all aspects of the inflammatory response. Chemokines bind to specific receptors of the seven-transmembrane spanning type on target leukocytes and also bind to cell-surface glycosaminoglycans (GAG). Leukocytes express a range of chemokine receptors which can cross-desensitise each other, potentially allowing a single chemokine receptor agonist to desensitise all the chemokine receptors on a cell. If an appropriate single receptor agonist is engineered to be non-chemotactic itself, then a treated cell will lose the potential to migrate in response to chemokines towards any developing site of inflammation. A non-GAG-binding but receptor agonistic form of the chemokine CCL7 can inhibit leukocyte recruitment in response to a diverse range of chemokines in vitro and in vivo. We hypothesise that this modified chemokine mediates its effect by inducing homologous and heterologous receptor desensitisation and further propose that other suitable candidates could include agonistic chemokine receptor-specific antibodies or small molecule chemokine receptor agonists. Hence, an appropriate chemokine receptor agonist could be used to inhibit multiple chemokine receptors, thereby producing a powerful and robust anti-inflammatory effect. This review considers the mechanisms leading to chemokine receptor desensitisation and discusses the potential to develop a new class of anti-inflammatory agents based on targeted stimulation of chemokine receptors.

Comparison of inflammatory responses after off-pump and on-pump coronary surgery using surface modifying additives circuit

BACKGROUND

Cardiac surgery is followed by various degrees of inflammation, which have harmful consequences. Because of the central role of extracorporeal circulation (EC), off-pump coronary bypass surgery is deemed preferable. Do different modalities of EC challenge this view?

METHODS

Four groups of similar patients underwent coronary surgery: (group 1) on-pump, EC with closed surface modifying additives (SMA) circuit and no pump suckers (n = 20); (group 2) on-pump, EC with open SMA circuit and pump suckers (n = 20); (group 3) off-pump (beating heart) and heparin 3 mg/kg (n = 20); (group 4) off-pump (beating heart) and heparin 1 mg/kg (n = 20). Interleukins (IL)-6, IL-8, IL-10, myeloperoxidase, elastase, and terminal complex of the complement (TCC) were analyzed at various times: at induction (time I); after heparin (time II); after complete revascularization (time III); after protamine (time IV); and 24 hours later (time V).

RESULTS

The TCC was significantly higher in groups 1 and 2 at time III. The pattern of IL-6 was the same for the four groups. No significant difference in myeloperoxydase content was noted; however, elastase was significantly higher in the two EC (on-pump) groups.

CONCLUSIONS

Except for the complement system and elastase, on-pump surgery with SMA-coated circuits did not elicit any greater inflammatory response than off-pump surgery.

Activation of the Nrf2/antioxidant response pathway increases IL-8 expression

Oxidant stress can initiate or enhance inflammatory responses during tissue injury, possibly through activation of redox-sensitive chemokines. Because the transcription factor Nrf2 (NF-E2-related factor 2) is responsive to oxidative stress, and induces expression of cytoprotective and antioxidant genes that attenuate tissue injury, we postulated that Nrf2 may also regulate chemokine expression. To test this hypothesis, Nrf2 expression was directly increased in primary human kidney mesangial cells and aortic endothelial cells, or cell lines with an adenoviral construct, and the effects on the pro-inflammatory chemokine interleukin-8 (IL-8) were assessed. Nrf2 expression significantly increased IL-8 mRNA levels and protein secretion. Nrf2 caused only a weak induction of IL-8 transcription, but significantly increased the half-life of IL-8 mRNA. These data demonstrate that activation of the Nrf2/antioxidant response pathway induces expression of IL-8. The dominant mechanism of Nrf2-mediated IL-8 induction is through mRNA stabilization. Considering the evidence that Nrf2 activation is mainly cytoprotective, these observations raise the possibility that under certain circumstances IL-8 may serve an anti-inflammatory role and thereby contribute to the resolution of tissue injury.

The in situ expression of interleukin-8 in the normal human kidney and in different morphological forms of glomerulonephritis

BACKGROUND

Interleukin-8 (IL-8) is considered a deleterious chemokine involved in renal injury in glomerulonephritis (GN). IL-8 may be released as a 77-amino acid (AA) peptide or 72-AA protein.

METHODS

We evaluated gene and protein expression of IL-8 in 53 renal biopsy specimens from patients with GN and 9 control kidneys. Nonradioactive in situ hybridization and reverse-transcriptase polymerase chain reaction (RT-PCR) were applied to detect IL-8 messenger RNA (mRNA). In immunohistochemistry, a double-staining technique with the use of antibodies against the 77-AA and 72-AA forms of IL-8, as well as glomerular cell antigens, was used.

RESULTS

By in situ hybridization, IL-8 mRNA was detected in normal glomerular, tubular, and some interstitial cells. The RT-PCR study showed that IL-8 mRNA expression in control kidneys significantly exceeds that in specimens with GN (0.89 +/- 0.82 versus 0.21 +/- 0.20; P < 0.003). In control kidneys, major sources of 77-AA IL-8 were podocytes and endothelial cells of interstitial vessels, whereas tubular epithelial cells expressed minute amounts of 72-AA IL-8. In GN specimens, podocyte expression of 72-AA IL-8 varied notably, with the greatest level found in minimal change disease and the lowest level found in acute endocapillary GN. Conversely, increased glomerular expression of the 72-AA form of IL-8 was a general feature of GN, with its level significantly exceeding that of the 77-AA form in acute endocapillary GN (P < 0.01).

CONCLUSION

Our results suggest that intrinsic glomerular cell production of IL-8, in particular the 77-AA form, may be relevant for preservation of the glomerular architecture.

IL-8-induced migratory responses through CXCR1 and CXCR2: association with phosphorylation and cellular redistribution of focal adhesion kinase

CXCR1 and CXCR2 mediate migratory activities in response to IL-8 and other ELR+-CXC chemokines (e.g., GCP-2 and NAP-2). In vitro, activation of migration is induced by low IL-8 concentrations (10-50 ng/mL), whereas migratory shut-off is induced by high IL-8 concentrations (1000 ng/mL). The stimulation of CXCR1 and CXCR2 by IL-8 concentrations that result in migratory activation induced focal adhesion kinase (FAK) phosphorylation in a G(alpha)i-dependent manner. The expression of FRNK, a dominant negative mutant of FAK, perturbed migratory responses to the activating dose of 50 ng/mL IL-8. The migration-activating concentrations of 50 ng/mL GCP-2 and NAP-2 induced less potent migratory responses and FAK phosphorylation in CXCR2-expressing cells as compared with IL-8. These results indicate that FAK is phosphorylated, and required, for the chemotactic response under conditions of migratory activation by ELR+-CXC chemokines. In addition, FAK phosphorylation was determined following exposure to migration-attenuating concentrations of IL-8. In CXCR1-RBL cells this treatment resulted in FAK phosphorylation, in similar levels to those induced by activating concentrations of IL-8. In contrast, in CXCR2-RBL cells the migration-attenuating concentrations of IL-8 induced promoted levels of FAK phosphorylation and different patterns of FAK phosphorylation on its six potential tyrosine phosphorylation sites, as compared to activating concentrations of the chemokine. Exposure to IL-8 resulted not only in FAK phosphorylation but also in its cellular redistribution, indicated by the formation of defined contact regions with the substratum, enriched in phosphorylated FAK and vinculin. Overall, FAK phosphorylation was associated with, and found to be differently regulated upon, ELR+-CXC chemokine-induced migration.

CXC chemokine redundancy ensures local neutrophil recruitment during acute inflammation

Previous publications demonstrated that elevated systemic levels of interleukin (IL)-8 decrease local neutrophil recruitment. We tested whether sustained, high plasma levels of IL-8 would prevent local inflammation after inflammatory insults. Mice carrying the transgene for human IL-8 were separated on the basis of their plasma levels of IL-8 into IL-8-positive (plasma levels >90 ng/ml) and IL-8-negative (IL-8 below detection). Presence of the IL-8 transgene did not improve survival or morbidity nor did it alter peritoneal neutrophil recruitment induced by the cecal ligation and puncture model of sepsis. In an acute lung injury model created by intratracheal injection of acid, IL-8-positive mice showed no reduction in alveolar neutrophil recruitment. There was no difference in the local recruitment of neutrophils when either thioglycollate or glycogen was injected intraperitoneally. We examined the chemotactic response to murine chemokines to test how neutrophil recruitment occurs in the setting of elevated plasma IL-8 and found that neutrophils from both IL-8-positive and -negative mice respond equally well to recombinant KC or macrophage inflammatory protein (MIP)-2. We measured KC and MIP-2 in the peritoneum after thioglycollate injection and demonstrated that IL-8-positive mice have significantly higher levels of the chemokines compared to the IL-8-negative mice. Antibody inhibition of KC and MIP-2 in the IL-8-positive mice significantly decreased peritoneal neutrophil recruitment in response to thioglycollate, clarifying their important role in the local neutrophil recruitment. Our data demonstrate that despite the presence of high plasma levels of IL-8, neutrophils may still be recruited to sites of local inflammation because of chemokine redundancy.

Interleukin-1, interleukin-6 and myocardial enzyme response after coronary artery bypass grafting - a prospective randomized comparison of the conventional and three minimally invasive surgical techniques

OBJECTIVE

In order to evaluate the traumatic effects of median sternotomy and cardiopulmonary bypass (CPB) in conventional and minimally invasive coronary artery bypass grafting, inflammatory response was studied in a prospective randomized trial in patients referred to single-vessel coronary artery bypass grafting.

METHODS

Four surgical techniques were compared: group 1, median sternotomy with CPB in ten patients (eight male, two female; aged 59.6+/-11.0 years (mean+/-SD)); group 2, median sternotomy and off-pump in ten patients (seven male, three female; aged 65.1+/-10.0 years); group 3, minithoracotomy with CPB in ten patients (seven male, three female, aged 61.2+/-10.4 years); group 4, minithoracotomy and off-pump in ten patients (nine male, one female, aged 62.9+/-9.8 years). All patients received a left internal mammary artery graft to the left anterior descending artery (LAD). Clinical data, perioperative values of cytokines and cardiac enzymes were monitored.

RESULTS

There were no major complications. Troponin-T and creatine kinase isoenzyme MB (CK-MB) levels were significantly higher in CPB procedures (P<0.0056; multivariate general linear model). Interleukin-6 (IL-6) levels were significantly higher in minithoracotomy procedures. Interleukin-1 (IL-1) was significantly increased in all patients compared with the preoperative values.

CONCLUSIONS

The use of CPB is combined with higher levels of troponin-T and CK-MB as signs of myocardial damage. Surgical access was identified as a trigger of inflammatory response, as minithoracotomy is related to higher levels of IL-6. IL-1 increased in all procedures and this occurred independently of the surgical access or the use of CPB, which points out a potential relationship between inflammatory response and anesthesia. Neither CPB nor surgical access influenced the clinical outcome in the treatment of coronary artery single-vessel bypass grafting.

Effect of ursodeoxycholic acid on ischemia/reperfusion injury in isolated rat heart

In this study, the effects of ursodeoxycholic acid (UDCA) on ischemia/reperfusion injury were investigated on isolated heart perfusion model. Hearts were perfused with oxygenated Krebs-Henseleit solution (pH 7.4, 37 degrees C) on a Langendorff apparatus. After equilibration, isolated hearts were treated with UDCA 20 to 160 microM or vehicle (0.04% DMSO) for 10 min before the onset of ischemia. After global ischemia (30 min), ischemic hearts were reperfused and allowed to recover for 30 min. The physiological (i.e. heart rate, left ventricular developed pressure, coronary flow, double product and time to contracture formation) and biochemical (lactate dehydrogenase; LDH) parameters were evaluated. In vehicle-treated group, time to contracture formation was 21.4 min during ischemia, LVDP was 18.5 mmHg at the endpoint of reperfusion and LDH activity in total reperfusion effluent was 54.0 U/L. Cardioprotective effects of UDCA against ischemia/reperfusion consisted of a reduced TTC (EC25=97.3 microM), reduced LDH release and enhanced recovery of cardiac contractile function during reperfusion. Especially, the treatments of UDCA 80 and 160 microM significantly increased LVDP and reduced LDH release. Our findings suggest that UDCA ameliorates ischemia/reperfusion-induced myocardial damage.

Chemotactic gradients predict neutrophilic alveolitis in endotoxin-treated rats

We hypothesized that the intensity of neutrophilic alveolitis is related to establishing a gradient of neutrophil attractant chemokines across the alveolar-capillary barrier. In these experiments, a positive chemokine gradient toward the alveoli was induced by intratracheal instillation of endotoxin in rats (IT LPS). Alteration of the chemotactic gradient was induced by combining IT LPS (0.1 mg/kg) with an intraperitoneal injection of endotoxin (IP LPS, 6.0 mg/kg). Bronchoalveolar lavage (BAL) and peripheral blood cell counts and differentials, and lavage and serum CXC chemokines were measured 4 h after LPS treatment. Compared with IT LPS treatment alone, IP + IT LPS resulted in a 30-fold reduction in neutrophil (PMN) count in BAL and a decreased percentage of PMNs in lavage (from 82 to 24%, p < 0.01). Total lung myeloperoxidase activity, a reflection of total PMN burden, was increased in all three treatment groups compared with the control group, but differences were not apparent between treatment groups. For the rat CXC chemokines MIP-2 and CINC, high concentrations were detected in BAL from both IT and IP + IT LPS groups; however, significantly higher concentrations were found in the sera of rats treated with IP + IT LPS compared with IT LPS alone. The calculated chemokine BAL-serum gradients were significantly higher for both MIP-2 and CINC in the IT LPS group than in the IT + IP LPS or IP LPS group, and correlated with neutrophil influx into the alveolar spaces 4 h after LPS treatment. In addition, the BAL-serum MIP-2 gradient was found to be increased 24 h after IP LPS, which is the time point of peak neutrophilic alveolitis. In summary, these data show that local chemokine gradients predict the intensity of neutrophilic alveolitis after treatment with endotoxin. Interventions to limit neutrophilic alveolitis could either be targeted to block local lung chemokine production or, paradoxically, to increase systemic production of chemokines.

Pharmacology and cardiovascular implications of the kinin-kallikrein system

Kinins are peptide hormones that can exert a significant influence on the regulation of blood pressure and vascular tone due to their vasodilatatory, natriuretic and growth modulating activity. Their cardiovascular involvement in physiological and pathophysiological situations has been studied intensively since inhibitors for angiotensin I-converting enzyme and selective receptor antagonists have become available for pharmacologically potentiating or inhibiting kinin-mediated reactions. Molecular biological analysis and the establishment of genetically modified animal models have also allowed newer information to be acquired on this subject. In this review, the components and cardiovascularly relevant mechanisms of the kinin-kallikrein system shall be described. Organ-specific effects concerning the kidneys, the vascular system, the heart and nervous tissue shall also be illustrated. On this issue, the physiological functions and pathophysiological implications of the kinin-kallikrein system should be clearly distinguished from the many, mostly endothelium-mediated protective effects which occur during ACE inhibition due to the potentiation of kinin effects. Finally, a view shall also be cast upon newly discovered targets of action, which could be exploited for therapeutically altering the kinin-kallikrein system.

Reperfusion injury: a review of the pathophysiology, clinical manifestations and therapeutic options

Lack of blood supply or ischaemia underlies many of the most important cardiovascular and cerebrovascular diseases faced by clinicians in their daily practice. Many of these ischaemic episodes can be reversed at an early stage by surgical or pharmacological means with the ultimate aim of preventing infarction and cell necrosis in the ischaemic tissues. However, reperfusion of ischaemic areas, in particular the readmission of oxygen, may contribute to further tissue damage (reperfusion injury). For example, the use of thrombolytic therapy in acute myocardial infarction and other revascularisation procedures, such as percutaneous transluminal angioplasty and coronary artery bypass surgery, may be associated with reperfusion of ischaemic myocardium. Such ischaemia and reperfusion may result in injury to one of more of the biochemical, cellular and microvascular components of the heart. Our understanding of the significance of reperfusion injury is however restricted by the profuse literature in animal models and limited literature in the clinical situation. This article reviews the pathophysiology, clinical manifestations of reperfusion injury to the heart and discusses the possible therapeutic approaches to avoiding any adverse effects.

Reduction of rat myocardial ischaemia/reperfusion injury by a synthetic selectin oligopeptide

Neutrophils infiltrate into myocardial tissue subjected to ischaemia followed by reperfusion and play a major role in myocardial reperfusion injury. The infiltration of neutrophils begins within 2 h after reperfusion, indicating the engagement of rapidly inducible adhesion molecules, such as P-selectin, on vascular endothelial cells of myocardial tissue. To investigate the essential role of P-selectin in myocardial reperfusion injury, this study examined the expression of P-selectin in rat hearts subjected to 30 min of ischaemia followed by reperfusion. The induction of P-selectin was also evaluated on the surface of cultured rat vascular endothelial cells subjected to 60 min of hypoxia, followed by reoxygenation in vitro. Finally, the effects of in vivo administration of a synthetic selectin oligopeptide on myocardial necrosis were analysed. Reperfusion of ischaemic myocardial tissue resulted in enhanced expression of P-selectin on the luminal surface of vascular endothelium and surface expression of P-selectin was induced on cultured vascular endothelial cells by hypoxia/reoxygenation in vitro. The in vivo administration of a synthetic selectin oligopeptide significantly reduced the area of myocardial infarction produced by 30 min of ischaemia, followed by 48 h of reperfusion. These data offer therapeutic possibilities for acute myocardial infarction.

Human cytokine responses to cardiac transplantation and coronary artery bypass grafting

Cardiac surgery with cardiopulmonary bypass triggers an inflammatory response involving proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-6, and interleukin-8. To elucidate the pathophysiology of this cytokine response, we explored the possible differences in cytokine responses between patients undergoing heart transplantation and those undergoing coronary artery bypass grafting. Plasma levels of tumor necrosis factor-alpha, interleukin-6, interleukin-8, and interleukin-10 were measured in eight patients undergoing heart transplantation (mean age 44 years) and eight patients undergoing coronary artery bypass grafting (mean age 61 years). Duration of cardiopulmonary bypass and ischemic time were both longer in the heart transplantation group than in the coronary artery bypass grafting group (133 +/- 26 min vs 100 +/- 31 min, p < 0.05, and 130 +/- 47 min vs 58 +/- 21 min, p < 0.005, respectively). Samples were collected before heparin administration, at aortic crossclamping and declamping, and at 0.5, 1, 1.5, 2, 4, 12, and 24 hours after declamping. Tumor necrosis factor-alpha levels were significantly higher 30 minutes after aortic declamping in the heart transplantation group than in the coronary artery bypass grafting group (68 +/- 30 vs 18 +/- 5 pg/ml, p < 0.05). Interleukin-6 and interleukin-8 levels were also significantly higher 90 minutes after declamping in patients undergoing heart transplantation than in those undergoing coronary artery bypass grafting (310 +/- 63 vs 169 +/- 24 pg/ml, p < 0.05, and 73 +/- 17 vs 24 +/- 5 pg/ml, p < 0.01, respectively). Furthermore, interleukin-6 and interleukin-8 values 90 minutes after declamping were significantly correlated with the ischemic time (r = 0.72 and r = 0.82, respectively, both p < 0.05). Interleukin-10 levels in both groups rose to reach a peak value of around 115 pg/ml 1 hour after declamping. Patients undergoing heart transplantation exhibited a second peak of tumor necrosis factor-alpha, interleukin-8, and interleukin-10 levels 12 hours after declamping, probably related to the administration of rabbit antihuman thymocyte immunoglobulin (Thymoglobuline) 3 hours after declamping. Interleukin-6 levels decreased more significantly 12 and 24 hours after declamping in patients undergoing heart transplantation, probably related to methylprednisolone therapy. In conclusion, cardiopulmonary bypass is associated with the production of both proinflammatory and antiinflammatory cytokines. The production of proinflammatory cytokines in patients undergoing heart transplantation is higher than that in patients undergoing coronary artery bypass grafting, and this increase could be related to the longer duration of ischemia in the former group. The later course of cytokine levels after heart transplantation may be further influenced by immunosuppressive therapy.

Chemokines and tissue injury

Accumulation of leukocytes at sites of inflammation is essential for host defense, yet secretory products of the white cells may augment injury by damaging surrounding healthy tissues. Members of the chemokine family of chemotactic cytokines play a fundamental role in this process by attracting and stimulating specific subsets of leukocytes. In vitro studies suggest that chemokines participate in at least three phases of leukocyte recruitment. First, they foster tight adhesion of circulating leukocytes to the vascular endothelium by activating leukocytic integrins. Second, because of their chemoattractant properties, chemokines guide leukocytes through the endothelial junctions and underlying tissue to the inflammatory focus. Finally, chemokines activate effector functions of leukocytes, including production of reactive oxygen intermediates and exocytosis of degradative enzymes. Animal studies in which antibodies are used to neutralize the activity of individual members of the chemokine family confirm that these mediators contribute to the development of both acute and chronic inflammatory conditions. A number of mechanisms may operate in vivo to limit the proinflammatory properties of chemokines. Therapies that target chemokines directly or enhance the body's mechanisms for controlling their activity may prove to be reasonable approaches for treatment of inflammatory diseases.

Transient increase of cytokine-induced neutrophil chemoattractant, a member of the interleukin-8 family, in ischemic brain areas after focal ischemia in rats

BACKGROUND AND PURPOSE

We have indicated that neutrophils play an important role in cerebral ischemia-reperfusion injury. Neutrophils are also known to adhere to the endothelial wall through adhesion molecules and to infiltrate into the tissue, and this neutrophilic invasion correlates with the concentration gradient of chemotactic factors. The aim of the present study was to evaluate the role of cytokine-induced neutrophil chemoattractant (CINC) on brain damage in rats from transient ischemia.

METHODS

The brain water content was measured to evaluate postischemic brain injury in rats with 60 minutes of middle cerebral artery occlusion with perfusion. An enzyme-linked immunosorbent assay was used to evaluate the blood and brain concentrations of CINC, and enzymatic and histological techniques were used to measure the neutrophilic infiltration into the brain.

RESULTS

The increase of water content was first observed at 6 hours after reperfusion, after which this increase was gradual, with brain edema peaking from 24 to 48 hours after reperfusion. Neutrophilic infiltration into the parenchyma and myeloperoxidase activity were first noted 12 hours after reperfusion, after which a marked increase occurred from 24 to 48 hours after reperfusion. In the ischemic brain areas, CINC was first detected at 3 hours after reperfusion. The CINC level peaked at 12 hours after reperfusion (9.15 +/- 0.45 ng/g wet wt, n = 5 and then gradually reduced from 24 to 48 hours after reperfusion (5.35 +/- 0.95 ng/g wet wt, n = 5, and 1.25 +/- 0.10 ng/g wet wt, n = 5, respectively). Interestingly, the serum CINC concentration was transiently elevated from 3 to 6 hours after reperfusion. No CINC production was detected in the brain of rats subjected to 60 minutes of ischemia without reperfusion.

CONCLUSIONS

A marked increase in CINC concentration was detected in brain and serum during early reperfusion. This suggests that the time course of CINC production precedes brain edema formation and neutrophilic infiltration. It thus appears that CINC may play an important role in neutrophilic infiltration in ischemic lesion and in brain edema formation after ischemia-reperfusion injury.

Myocardial ischaemia: what happens to the coronary arteries?

Study of the effects of myocardial ischaemia and reperfusion has largely been confined to the impairment of cardiac contractility. However, emerging recognition of the importance of endothelium-derived vasoactive factors in blood flow regulation has stimulated interest in the effect of pathological states such as ischaemia on coronary vascular function and is discussed in this review by Christopher Sobey and Owen Woodman. Neutrophils may play a key role in impaired reperfusion and endothelial damage, and pharmacological intervention to preserve endothelial function could significantly improve coronary blood flow and cardiac function after an ischaemic attack.

Prevention of lung reperfusion injury in rabbits by a monoclonal antibody against interleukin-8

Re-establishing blood flow to ischaemic tissues causes greater injury than that induced during the ischaemic period. This type of tissue injury, reperfusion injury, is involved in frostbite, multiple organ failure after hypovolaemia and in myocardial infarction. Depletion of neutrophils alleviates reperfusion injury, implying a causal role of neutrophil infiltration. Among members of the recently discovered family of chemotactic cytokines (chemokines), interleukin-8 (IL-8) is a major neutrophil chemotactic and activating factor produced by various types of human cells. We investigated its pathophysiological role in a rabbit model of a lung reperfusion injury. Reperfusion of ischaemic lung caused neutrophil infiltration and destruction of pulmonary structure, as well as local production of IL-8. Furthermore, the administration of a neutralizing monoclonal antibody against IL-8 prevented neutrophil infiltration and tissue injury, proving a causal role of locally produced IL-8 in this model.

Dissociation of the anti-ischaemic effects of cloricromene from its anti-platelet activity

1. Cloricromene is a non-anticoagulant coumarin derivative with anti-platelet and anti-leukocyte properties, which has beneficial effects in various models of ischaemia and shock. 2. We have assessed the effects of cloricromene on (a) ex vivo platelet aggregation, and (b) infarct size using a model of myocardial ischaemia in the anaesthetized rabbit. 3. Cloricromene (1-1000 micrograms kg-1 min-1 for 15 min) induced a dose-dependent inhibition of ex vivo platelet aggregation, causing only a minimal increase in heart rate and no change in mean arterial blood pressure. The inhibitory activity was considerably stronger when platelet aggregation was induced by collagen than by ADP. 4. Cloricromene inhibited ex vivo platelet aggregation in rabbits pretreated with indomethacin (5 mg kg-1) and this inhibition persisted for 30-60 min. 5. The model of myocardial ischaemia involved 1 h occlusion of the first antero-lateral branch of the left coronary artery followed by 2 h of reperfusion. Infusion of cloricromene (30 or 300 micrograms kg-1 min-1), ibuprofen (80 micrograms kg-1 min-1) or vehicle began 15 min prior to occlusion, and continued throughout the experiment. 6. While area at risk was similar for all groups studied, cloricromene (30 or 300 micrograms kg-1 min-1) or ibuprofen caused a reduction in infarct size, and decreased myeloperoxidase activity in the tissue of the infarcted myocardium. 7. Cloricromene at 300 micrograms kg-1 min-1 also reduced the occlusion-induced elevation of the ST-segment of the rabbit electrocardiogram, and inhibited platelet aggregation ex vivo. Ibuprofen or cloricromene at 30 fg kg-1 min-1 had no effect on either the ST-elevation or platelet reactivity.8. Thus, cloricromene exhibits a cardioprotective activity via an inhibition of leukocyte infiltration, in the presence (300 microg kg-l min-1) or absence (30 microg kg-1 min-1) of inhibition of platelet activity ex vivo.The anti-aggregatory activity of cloricromene acts via a mechanism that is either different from, or in addition to, inhibition of cyclo-oxygenase, and is of long duration.

Reduction of myocardial leukocyte accumulation and myocardial infarct size following administration of BAY u3405, a thromboxane A2 receptor antagonist, in myocardial ischaemia-reperfusion injury

We investigated the effect of BAY u3405, a thromboxane A2 receptor antagonist in pentobarbital anaesthetized rats subjected to left main coronary artery ligation (1 h) followed by reperfusion (1 h; MI/R). Sham operated rats were used as controls (Sham MI/R). Survival rate, myocardial necrosis, myocardial myeloperoxidase activity (investigated as an index of leukocyte adhesion and accumulation) and serum creatine phosphokinase activity were studied. Ischaemia-reperfusion injury significantly reduced the survival rate (45%), caused a marked myocardial necrosis, increased serum creatine phosphokinase activity (Sham MI/R = 26 +/- 10.2 U/ml; MI/R = 213 +/- 19 U/ml) and produced a rise in myocardial myeloperoxidase activity in the area-at-risk and in the necrotic area (6.1 +/- 0.4 U x 10(-3)/g tissue and 6.7 +/- 0.9 U x 10(-3)/g of tissue, respectively). The administration of BAY u3405 (30 and 60 mg/kg/i.v., 30 min before occlusion) significantly increased survival rate, lowered the area of myocardial necrosis, blunted the increase in serum creatine phosphokinase activity and reduced the increase in myeloperoxidase activity in both the area-at-risk and the necrotic area. Furthermore, the protective effect of BAY u3405 was dose-dependent. These data are consistent with an involvement of TXA2 in myocardial ischaemia-reperfusion injury and suggest that BAY u3405 may represent a novel therapeutic approach to the treatment of acute ischaemia-reperfusion injury.

Tumor necrosis factor involvement in myocardial ischaemia-reperfusion injury

The role of tumor necrosis factor-alpha was investigated in an anaesthetized rat model of coronary artery ligation (60 min) and reperfusion (MI/R). Sham-occluded rats (sham MI/R) were used as controls. Survival rate, myocardial necrosis, myocardial myeloperoxidase activity, serum creatinine kinase activity and serum and macrophage tumor necrosis factor-alpha were studied. Ischaemia-reperfusion injury significantly reduced survival rate (45%), produced marked myocardial injury, increased serum creatinine kinase activity and increased myocardial myeloperoxidase activity in the area-at-risk and in the necrotic area. Serum tumor necrosis factor-alpha was undetectable during the occlusion period, but increased significantly upon release of the coronary artery. At the end of reperfusion, macrophage tumor necrosis factor-alpha was also increased. Passive immunization with a hyperimmune serum containing antibodies against murine tumor necrosis factor-alpha significantly increased survival rate (80%), lowered myocardial necrosis, reduced the increase in serum creatinine kinase activity and decreased myeloperoxidase activity in the area-at-risk and in the necrotic area. These data are consistent with an involvement of tumor necrosis factor-alpha in myocardial ischaemia-reperfusion injury.

Allopurinol and amlodipine improve coronary vasodilatation after myocardial ischaemia and reperfusion in anaesthetized dogs

1. We have assessed the effect of allopurinol, amlodipine and propranolol pretreatment on both endothelium-dependent and endothelium-independent coronary vasodilatation in vivo, by comparing pre-ischaemic responses with those measured after 60 min of coronary artery occlusion and 30 min of reperfusion in anaesthetized dogs. 2. In 15 untreated dogs ischaemia and reperfusion attenuated the increases in coronary blood flow produced by either acetylcholine (0.01-0.05 micrograms kg-1, i.a.) or glyceryl trinitrate (0.05-0.2 micrograms kg-1, i.a.), to an average of 39 +/- 4% and 42 +/- 5% of the pre-ischaemic control response, respectively (both P < 0.05). 3. In 5 dogs treated with allopurinol (25 mg kg-1, orally, 24 h previously, plus 50 mg kg-1, i.v., 5 min before occlusion), the increases in coronary blood flow after ischaemia and reperfusion (acetylcholine: 78 +/- 12%, glyceryl trinitrate: 60 +/- 3% of pre-ischaemic response) were significantly larger than post-ischaemic responses in untreated dogs (both P < 0.05). 4. Similarly, amlodipine treatment (3 micrograms kg-1 min-1, i.v., starting 90 min before occlusion) in 5 dogs improved post-ischaemic increases in blood flow (acetylcholine: 58.5%, glyceryl trinitrate: 66 +/- 6% of pre-ischaemic response, significantly greater than post-ischaemic responses in untreated dogs, P < 0.05). 5. In contrast, in a further 6 dogs pretreated with propranolol (1 mg kg-1, i.v., 30 min before occlusion,plus 0.5 mg kg-1 h-1, i.v.), blood flow responses after ischaemia and reperfusion were not different from post-ischaemic responses in untreated dogs (acetylcholine: 46 +/- 6%, glyceryl trinitrate: 46 +/-6% of pre-ischaemic response).6. These results suggest that allopurinol and amlodipine protect against the post-ischaemic impairment of endothelium-dependent and endothelium-independent coronary vasodilatation in vivo by mechanisms additional to endothelial protection.

The effect of cloricromene, a coumarine derivative, on leukocyte accumulation, myocardial necrosis and TNF-alpha production in myocardial ischaemia-reperfusion injury

The effects of cloricromene, a coumarine derivative, were studied in an anaesthetized rat model of coronary artery ligation (60 min) followed by reperfusion (60 min; MI/R). Sham operated rats were used as controls (Sham MI/R). Myocardial ischaemia-reperfusion injury produced a marked myocardial injury (necrotic area/area-at-risk = 68 +/- 4%; necrotic area/total area = 48 +/- 3%) high serum creatinphosphokinase activity (Sham MI/R = 29 +/- 8 U/ml; MI/R = 205 +/- 11 U/ml) and elevated myocardial myeloperoxidase activity (investigated as an index of leukocyte adhesion and accumulation), in the area-at-risk (6.3 +/- 0.2 U x 10(-3)/g tissue) and in necrotic area (6.5 +/- 0.5 U x 10(-3)/g tissue). Furthermore, serum TNF-alpha was undetectable during the occlusion period, but upon the release of the coronary artery significantly increased. At the end of reperfusion, macrophage TNF-alpha was also enhanced. The administration of cloricromene (2 mg/kg, 5 minutes after the onset of reperfusion) significantly reduced myocardial injury (necrotic area/area-at-risk 30 +/- 1.3%; necrotic area/total area = 25 +/- 1.5) blunted the increase in serum creatinphosphokinase activity (92 +/- 5 U/ml) and lowered myeloperoxidase activity in area-at-risk (2.5 +/- 0.2 U x 10(-3)/g tissue) and in necrotic area (2.2 +/- 0.3 U x 10(-3)/g tissue) and decreased the serum and macrophage levels of TNF-alpha. These data indicate that cloricromene exerts beneficial effects on myocardial ischaemia/reperfusion injury. Finally, since we measured increased serum levels of TNF-alpha that were blunted by the cloricromene treatment, our data are consistent with an involvement of TNF-alpha in the reperfusion injury induced by myocardial ischaemia.