Nonanticoagulant heparin inhibits NF-kappaB activation and attenuates myocardial reperfusion injury

Coagulation Activation and Organ Dysfunction Following Cardiac Surgery

STUDY OBJECTIVES

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with major inflammatory triggers that cause marked activation of the microcirculation. This inflammatory response is associated with significant organ dysfunction. How this response causes organ dysfunction is not well understood; consequently, few interventions exist to prevent or treat it. In other acute inflammatory conditions, such as sepsis, increased coagulation activation in the microcirculation may be a cause of organ injury. We documented the association between coagulation activation and organ dysfunction to investigate whether coagulation activation also plays a role in organ injury following cardiac surgery with CPB.

DESIGN

Prospective study of 30 patients undergoing cardiac surgery with CPB. Prothrombin fragment (PTF) 1 + 2 and plasminogen activator inhibitor (PAI) activity were measured, and levels correlated with postoperative measures of organ function including the left-ventricular stroke work index, the Pao(2)/fraction of inspired oxygen (Fio(2)) ratio, and creatinine levels.

RESULTS

PTF levels increased eightfold (p < 0.05), and PAI activity increased threefold (p < 0.05) over the first 4 h after CPB. PTF levels were correlated with deteriorations in the left-ventricular stroke work index (p = 0.04), the Pao(2)/Fio(2) ratio (p = 0.02), and creatinine levels (p = 0.02).

CONCLUSIONS

Levels of coagulation activation are associated with markers of postoperative organ dysfunction. Additional studies are warranted to investigate whether strategies that limit coagulation activation are associated with reductions in postoperative organ dysfunction.

Cytokine gene expression and production by human LPS-stimulated mononuclear cells are inhibited by sulfated heparin-like semi-synthetic derivatives

BACKGROUND

The K5 polysaccharide obtained from Escherichia coli strain 010:K5:H4 is a polymer of the disaccharidic unit formed by D-glucuronic acid and N-acetylglucosamine. This structure is akin to N-acetylheparosan, the precursory polymer of heparin and of heparan sulfate. This structural affinity with N-acetylated heparin and with de-sulfated heparin makes the K5 polysaccharide extremely useful for the preparation of sulfated heparin-like semi-synthetic derivatives. It has been demonstrated that heparins are able to inhibit tissue factor and cytokine production and expression by human monocytes.

OBJECTIVE

The aim of this study was to evaluate the effects of four different heparin-like semi-synthetic derivatives on inflammatory cytokine production and expression by human mononuclear cells.

RESULTS

The simultaneous addition of lipopolysaccharide (LPS; 0.2 and 10 micro g mL(-1)) and the K5 polysaccharide did not inhibit interleukin (IL)-1beta, IL-6 or tumor necrosis factor (TNF)-alpha production by stimulated mononuclear cells. IL-1beta, IL-6 and TNF-alpha concentrations in supernatants of LPS-stimulated mononuclear cells were not influenced by the addition of N,O-sulfated K5 polysaccharide (K5-N, OS) and epimerized N-sulfated K5 polysaccharide (K5 NS epi) at 5 and 10 microg mL(-1), whereas the addition of epimerized N,O-sulfated K5 polysaccharide (K5-N, OS epi) (5 and 10 microg mL(-1)) and O-sulfated K5 polysaccharide (K5-OS) (5 and 10 microg mL(-1)) to LPS-stimulated cells caused a significant dose-dependent inhibition of IL-1beta, IL-6 and TNF-alpha. All sulfated heparin-like semi-synthetic derivatives did not influence the IL-10 production by LPS-stimulated mononuclear cells. In LPS-stimulated cells (0.2 and 10 microg mL(-1)), K5-OS or K5-N, OS epi at 5 and 10 microg mL(-1) markedly decreased TNF-alpha mRNA expression.

CONCLUSIONS

These results indicate that the sulfated heparin-like semi-synthetic derivatives K5-OS and K5-N, OS epi are able to inhibit both expression and production of inflammatory cytokines, whereas they do not influence the anti-inflammatory cytokine IL-10, suggesting a potential role for these products as modulators of inflammatory reactions.

Nuclear factor kappa B—molecular biomedicine: the next generation

Nuclear factor kappa B (NFkappaB) as a transcription factor plays an important integrating role in the intracellular regulation of immune response, inflammation and cell cycle regulation. Nouvelle insights into the structure and regulation of activation of NFkappaB have brought a detailed picture of the function of this transcription factor. In this review the findings of interactions of NFkappaB with its inhibitors, tumour necrosis factor alpha and glucocorticoids are presented. The results from the latest in vivo studies show the capability of specific NFkappaB inhibitors in the clinical use. This article summarizes the most important facts regarding NFkappaB participation in the pathogenesis of diseases and its potential as a target of pharmacological agents.

Cardiopulmonary bypass in man: role of the intestine in a self-limiting inflammatory response with demonstrable bacterial translocation

BACKGROUND

Cardiopulmonary bypass provokes a systemic inflammatory reaction that, in 1% to 2% of all cases, leads to multiorgan disfunction. The aim of this study was to evaluate the possible role of the intestine in the pathogenesis and development of this reaction.

METHODS

Eleven selected patients scheduled for elective coronary artery bypass graft surgery were enrolled in a open, prospective clinical study. Gastric tonometry, chromium-labeled test and double sugar intestinal absorption tests, polymerase chain reaction microbial DNA test, and measurement of cytokines and transcriptional factor (nuclear factor kappaB) activation were performed.

RESULTS

During the postoperative period, gastric pH remained stable (range,7.2 to 7.3). The partial pressure for carbon dioxide gradient between the gastric mucosa and arterial blood increased significantly (from 1 to 23 mm Hg), peaking in the sixth postoperative hour. Interleukin 6 increased significantly over basal levels, peaking 3 hours after cardiopulmonary bypass (96.3 versus 24 pg/mL). Nuclear factor kappaB never reached levels higher than those observed after lipopolysaccharide stimulation. Escherichia coli translocation was documented in 10 patients: in eight cases from removal of aortic cross-clamps and in two cases from the first postoperative hour. With respect to basal value (6.4%), the urine collection revealed a significant increase in excretion of the radioisotope during the first 24 hours after surgery (39.1%), although there were no significant variations with the double sugar test.

CONCLUSIONS

The results obtained showed a correlation between the damage of the gastrointestinal mucosa, subsequent increased permeability, E coli bacteremia, and the activation of a self-limited inflammatory response in the absence of significant macrocirculatory changes and postoperative complications.

Gene transfer of IkappaBalpha limits infarct size in a mouse model of myocardial ischemia-reperfusion injury

Nuclear factor-kappaB (NF-kappaB) plays a central role in myocardial ischemia-reperfusion (MI/R) injury. The inhibitory protein IkappaBalpha prevents its activation. We investigated the effects of adeno-associated viral vector-mediated IkappaBalpha gene transfer in MI/R injury. Male C57BL/6 mice were randomized to receive a recombinant adeno-associated virus (rAAV) encoding the gene for the NF-kappaB inhibitory protein IkappaBalpha (rAAV- IkappaBalpha) or the beta-galactosidase gene (a control and inert gene; rAAV-LacZ), both at a dose of 10(11) copies. Four weeks later anesthetized animals were subjected to total occlusion (45 minutes) of the left main coronary artery followed by 5 hours of reperfusion. MI/R produced a wide infarct size (IF/area-at-risk = 56 +/- 8%; IF/left ventricle = 44 +/- 5%) and tissue neutrophil infiltration, studied by means of elastase activity (area-at-risk = 2.5 +/- 0.4 micro g/gm tissue; infarct area = 2.9 +/- 0.6 micro g/gm tissue). Furthermore MI/R caused peak message for intercellular adhesion molecule-1 (ICAM-1) in the area-at-risk at 3 hours of reperfusion (1.2 +/- 0.4 relative amount of cardiac ICAM-1 mRNA). NF-kappaB activation was evident at 0.5 hours of reperfusion and reached its maximum increase at 2 hours of reperfusion. rAAV-IkappaBalpha injection reduced infarct size (IF/area-at-risk = 19 +/- 3%; IF/left ventricle = 10 +/- 2%; p < 0.001), blocked NF-kappaB activation, diminished cardiac ICAM-1 expression (0.4 +/- 0.02 relative amount of cardiac ICAM-1 mRNA; p < 0.001), and blunted leukocyte accumulation (area-at-risk = 0.6 +/- 0.05 micro g/gm tissue; infarct area = 0.4 +/- 0.02 micro g/gm tissue; p < 0.001). Our data indicate that rAAV-IkappaBalpha may be useful for MI/R gene therapy.

Effects of heparin and related molecules upon neutrophil aggregation and elastase release in vitro

1 Neutrophil-derived elastase is an enzyme implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Heparin inhibits the enzymatic activity of elastase and here we provide evidence for the first time that heparin can inhibit the release of elastase from human neutrophils. 2 Unfractionated and low molecular weight heparins (UH and LMWH, 0.01-1000 U ml(-1)) and corresponding concentrations (0.06-6000 micro g ml(-1)) of nonanticoagulant O-desulphated heparin (ODH), dextran sulphate (DS) and nonsulphated poly-L-glutamic acid (PGA) were compared for their effects on both elastase release from and aggregation of neutrophils. 3 UH, ODH and LMWH inhibited (P<0.05) the homotypic aggregation of neutrophils, in response to both N-formyl-methionyl-leucyl-phenylalanine (fMLP, 10(-6) M) and platelet-activating factor (PAF, 10(-6) M), as well as elastase release in response to these stimuli, in the absence and presence of the priming agent tumour necrosis factor-alpha (TNF-alpha, 100 U ml(-1)). 4 DS inhibited elastase release under all the conditions of cellular activation tested (P<0.05) but had no effect on aggregation. PGA lacked efficacy in either assay, suggesting general sulphation to be important in both effects of heparin on neutrophil function and specific patterns of sulphation to be required for inhibition of aggregation. 5 Further investigation of the structural requirements for inhibition of elastase release confirmed the nonsulphated GAG hyaluronic acid and neutral dextran, respectively, to be without effect, whereas the IP(3) receptor antagonist 2-aminoethoxydiphenylborate (2-APB) mimicked the effects of heparin, itself an established IP(3) receptor antagonist, suggesting this to be a possible mechanism of action.

Recombinant human erythropoietin protects the myocardium from ischemia-reperfusion injury and promotes beneficial remodeling

Erythropoietin (EPO), originally identified for its critical hormonal role in promoting erythrocyte survival and differentiation, is a member of the large and diverse cytokine superfamily. Recent studies have identified multiple paracrineautocrine functions of EPO that coordinate local responses to injury by maintaining vascular autoregulation and attenuating both primary (apoptotic) and secondary (inflammatory) causes of cell death. Experimental evidence also supports a role for EPO in repair and regeneration after brain and spinal cord injury, including the recruitment of stem cells into the region of damage. Tissue expression of the EPO receptor is widespread, especially during development, and includes the heart. However, it is currently unknown as to whether EPO plays a physiological function in adult myocardial tissue. We have assessed the potential protective role of EPO in vitro with adult rat cardiomyocytes, and in vivo in a rat model of myocardial infarction with reperfusion. The results show that EPO markedly prevents the apoptosis of cultured adult rat myocardiocytes subjected to 28 h of hypoxia (approximately 3% normal oxygen). Additional studies employing a rat model of coronary ischemia-reperfusion showed that the administration of recombinant human EPO (5,000 units/kg of body weight; i.p. daily for 7 days) reduces cardiomyocyte loss by approximately 50%, an extent sufficient to normalize hemodynamic function within 1 week after reperfusion. These observations not only suggest a potential therapeutic role for recombinant human EPO in the treatment of myocardial ischemia and infarction by preventing apoptosis and attenuating postinfarct deterioration in hemodynamic function, but also predict that EPO is likely a tissue-protective cytokine in other organs as well.

Longitudinal evaluation of markers of endothelial cell dysfunction and hemostasis in treated antiphospholipid syndrome and in healthy pregnancy

OBJECTIVE

The purpose of this study was to determine whether primary antiphospholipid syndrome pregnancies are associated with endothelial cell activation in the maternal circulation.

STUDY DESIGN

Markers of endothelial cell activation were measured every 4 weeks during pregnancy in the blood of 23 women with primary antiphospholipid syndrome and 19 control subjects. All women with antiphospholipid syndrome received anticoagulant treatment. Plasma concentrations of plasminogen activator inhibitor type 1, tissue plasminogen activator, soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and soluble thrombomodulin were determined by enzyme-linked immunoassay. Concentrations of prothrombin fragments 1+2 and D-dimers were also determined.

RESULTS

Three antiphospholipid syndrome pregnancies (13%) were complicated by intrauterine growth restriction and preeclampsia; one antiphospholipid syndrome pregnancy (4%) was complicated by preterm rupture of membranes. Six women with antiphospholipid syndrome (26%) had thrombotic events. Differences in concentrations of endothelial cell activation markers between antiphospholipid syndrome and control pregnancies were not significant.

CONCLUSION

Despite poorer pregnancy outcome, there was no evidence of greater endothelial cell activation in antiphospholipid syndrome pregnancies that were treated.

Effect of N-desulfated heparin on hepatic/renal ischemia reperfusion injury in rats

AIM: To investigate the effect of N-desulfated heparin on hepatic/renal ischemia and reperfusion injury in rats.

METHODS: Using rat models of 60 min hepatic or renal ischemia followed by 1 h, 3 h, 6 h and 24 h reperfusion, animals were randomly divided into following groups, the sham operated controls, ischemic group receiving only normal saline, and treated group receiving N-desulfated heparin at a dose of 12 mg/kg at 5 min before reperfusion. P-selectin expression was detected in hepatic/renal tissues with immunohistochemistry method.

RESULTS: P-selectin expression, serum ALT, AST, BUN and Cr levels were significantly increased during 60 minute ischemia and 1 h, 3 h, 6 h and 24 h reperfusion, while the increment was significantly inhibited, and hepatic/renal pathology observed by light microscopy was remarkably improved by treatment with the N-desulfated heparin. Furthermore, the heparin was found no effects on PT and KPTT.

CONCLUSION: P-selectin might mediate neutrophil infiltration and contribute to hepatic/renal ischemia and reperfusion. The N-desulfated heparin might prevent hepatic/renal damage induced by ischemia and reperfusion injury without significant anticoagulant activity.

Endotoxin stress-response in cardiomyocytes: NF-kappaB activation and tumor necrosis factor-alpha expression

Although tumor necrosis factor (TNF)-alpha is implicated in numerous cardiac pathologies, the intracellular events leading to its production by heart cells are largely unknown. The goal of the present study was to identify the role of the transcription factor nuclear factor (NF)-kappaB in this process. Among the many inducers of TNF-alpha expression in myeloid cells, only lipopolysaccharide (LPS) led to its induction in cultured neonatal myocytes. LPS also activated the NF-kappaB pathway, as evidenced by the degradation of the inhibitory protein IkappaB and the appearance of NF-kappaB-binding complexes in nuclear extracts. Furthermore, inhibitors of NF-kappaB activation, such as lactacystin, MG132, and pyrrolidine dithiocarbamate, were found to completely block the production of TNF-alpha in response to LPS stimulation, indicating a requirement of NF-kappaB for TNF-alpha expression. However, interleukin-1beta and phorbol 12-myristate 13-acetate also activated NF-kappaB but did not evoke TNF-alpha expression, revealing that this factor is not sufficient for cytokine production. Detailed examination of the NF-kappaB cascade revealed that cardiac cells displayed a unique pattern of IkappaB degradation in response to LPS, with IkappaBbeta but not IkappaBalpha being degraded upon stimulation. Additionally, two specific p65-containing DNA-binding complexes were observed in the nuclear extracts of neonatal cardiomyocytes: an inducible complex that is necessary for TNF-alpha expression and a constitutive species. Taken together, these results reveal that NF-kappaB is not only involved in cytokine production but also may be linked to other pathways that subserve a constitutive, protective mechanism for the heart cell.

Complement and its implications in cardiac ischemia/reperfusion: strategies to inhibit complement

Although reperfusion of the ischemic myocardium is an absolute necessity to salvage tissue from eventual death, it is also associated with pathologic changes that represent either an acceleration of processes initiated during ischemia or new pathophysiological changes that were initiated after reperfusion. This so-called "reperfusion injury" is accompanied by a marked inflammatory reaction, which contributes to tissue injury. In addition to the well known role of oxygen free radicals and white blood cells, activation of the complement system probably represents one of the major contributors of the inflammatory reaction upon reperfusion. The complement may be activated through three different pathways: the classical, the alternative, and the lectin pathway. During reperfusion, complement may be activated by exposure to intracellular components such as mitochondrial membranes or intermediate filaments. Two elements of the activated complement contribute directly or indirectly to damages: anaphylatoxins (C3a and C5a) and the membrane attack complex (MAC). C5a, the most potent chemotactic anaphylatoxin, may attract neutrophils to the site of inflammation, leading to superoxide production, while MAC is deposited over endothelial cells and smooth vessel cells, leading to cell injury. Experimental evidence suggests that tissue salvage may be achieved by inhibition of the complement pathway. As the complement is composed of a cascade of proteins, it provides numerous sites for pharmacological interventions during acute myocardial infarction. Although various strategies aimed at modulating the complement system have been tested, the ideal approach probably consists of maintaining the activity of C3 (a central protein of the complement cascade) and inhibiting the later events implicated in ischemia/reperfusion and also in targeting inhibition in a tissue-specific manner.