Interleukin-6 derived from hypoxic myocytes promotes neutrophil-mediated reperfusion injury in myocardium

Inhibition of sarcoplasmic reticular function by chronic interleukin-6 exposure via iNOS in adult ventricular myocytes

Interleukin (IL)-6 has been shown to decrease cardiac contractility via a nitric oxide synthase (NOS)-dependent pathway during acute exposure. We previously reported that IL-6 decreases contractility and increases inducible NOS (iNOS) in adult rat ventricular myocytes (ARVM) after 2 h exposure. The goal of this study was to investigate the cellular mechanism underlying this chronic IL-6-induced negative inotropy and the role of iNOS. Pretreatment for 2 h with 10 ng ml-1 IL-6 decreased the kinetics of cell shortening (CS) and contractile responsiveness to Ca2+o ([Ca2+]o from(0) to 2 mM) in ARVM. We first examined whether IL-6 reduced Ca2+ influx via L-type Ca2+ -channel current (ICa,L). Whole-cell ICa,L in ARVM was measured under conditions similar to those used for CS measurements, and it was found to be unaltered by IL-6. The sarcoplasmic reticular (SR) function was then assessed by examining postrest potentiation (PRP) and caffeine responsiveness of CS. Results showed that treatment with IL-6 for 2 h significantly decreased PRP, which was concomitant with a decrease in the phosphorylation of phospholamban. Following removal of IL-6, PRP and responsiveness to 10 mM caffeine were also reduced. Meanwhile, the IL-6-induced increase in nitric oxide (NO) production after 2 h (but not 1 h) was abolished by NG-monomethyl-l-arginine (l-NMMA) and 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT; a selective inhibitor of iNOS). Furthermore, IL-6-elicited suppressions of PRP and responsiveness to caffeine and Ca2+o were abolished by L-NMMA and AMT. Thus, these results suggest that activation of iNOS mediates IL-6-induced inhibition of SR function in ARVM during chronic exposure.

New developments in IL-6 dependent biology and therapy: where do we stand and what are the options?

Interleukin-6 (IL-6) is a four-helical protein which, on target cells, binds to a specific IL-6-receptor and two molecules of the promiscuous signal transducing protein gp130. Structure-function analysis defined three molecular contact sites between IL-6 and its receptor subunits. Using this information, competitive antagonistic proteins as well as hyperagonistic proteins were developed. Possible therapeutic applications of IL-6 antagonists are in IL-6 dependent haematological disorders (Castleman's disease, POEMS syndrome, multiple myeloma) and bone diseases (Paget's disease, osteoporosis). Designer IL-6 antagonists could suppress inflammatory activity in rheumatic and autoimmune diseases and could prevent secondary amyloidosis. IL-6 antagonists could also prove advantageous in myocardial infarction and unstable angina pectoris. IL-6 antagonists might slow down development of (mesangioproliferative) glomerulonephritis. On the other hand, hyperagonistic variants of IL-6 have a potential in ex vivo expansion of bone marrow stem cells and as thrombopoietic agents. They might also be developed into drugs to support liver regeneration in vivo and to treat stress-induced cardiac insufficiency.

Effects of unfractionated heparin, low molecular weight heparin and r-hirudin on leukocyte adhesion in ischemia/reperfusion

Activation of the coagulation cascade during myocardial ischemia and reperfusion may contribute to the post-ischemic inflammatory response, mostly via generation of thrombin. We assessed the effect of the anticoagulants unfractionated heparin (UFH), low molecular weight heparin (LMWH) and r-hirudin on leukocyte adhesion and emigration after ischemia and reperfusion in rats. The rat cremaster muscle was prepared for intravital microscopy. One hundred and twenty minutes of ischemia were followed by 90 min of reperfusion. Saline (control), UFH, LMWH or r-hirudin were given 15 min prior to reperfusion and infused for the rest of the observation period. Dosages per kilogram of body weight were (bolus, infusion): saline, 3 ml, 3 ml/h; UFH, 400 IU, 100 IU/h; LMWH, 100 IU, 3 ml/h saline; or r-hirudin, 0.3 mg, 0.15 mg/h. In collecting venules, rolling, adherent, and extravasated leukocytes were counted from recordings of the intravital microscopy. All three anticoagulants similarly attenuated post-ischemic endothelial leukocyte adhesion. In contrast, emigration of leukocytes was only attenuated by r-hirudin. The emigration efficiency of adherent leukocytes (control, 1.21) was unchanged after UFH (1.74), and LMWH (1.51) but decreased after r-hirudin treatment (0.12). The different efficacy of the three anticoagulants in affecting emigration of adherent leukocytes suggests a specific role for the direct thrombin inhibitor r-hirudin in attenuating the post-ischemic inflammatory response. This effect may contribute to the benefits of direct thrombin inhibitors seen in clinical studies after treatment for acute coronary syndromes.

Differential Cytokine Gene Expression in the Diaphragm in Response to Strenuous Resistive Breathing

Strenuous resistive breathing induces plasma cytokines that do not originate from circulating monocytes. We hypothesized that cytokine production is induced inside the diaphragm in response to resistive loading. Anesthetized, tracheostomized, spontaneously breathing Sprague-Dawley rats were subjected to 1, 3, or 6 hours of inspiratory resistive loading, corresponding to 45-50% of the maximum inspiratory pressure. Unloaded sham-operated rats breathing spontaneously served as control animals. The diaphragm and the gastrocnemius muscles were excised at the end of the loading period, and messenger ribonucleic acid expression of tumor necrosis factor-alpha, tumor necrosis factor-beta, interleukin (IL)-1alpha, IL-1beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, IFN-gamma, and two housekeeping genes was analyzed using multiprobe RNase protection assay. IL-6, IL-1beta, and, to lesser extents, tumor necrosis factor-alpha, IL-10, IFN-gamma, and IL-4 were significantly increased in a time-dependent fashion in the diaphragms but not the gastrocnemius of loaded animals or in the diaphragm of control animals. Elevation of protein levels of IL-6 and IL-1beta in the diaphragm of loaded animals was confirmed with immunoblotting. Immunostaining revealed IL-6 protein localization inside diaphragmatic muscle fibers. We conclude that increased ventilatory muscle activity during resistive loading induces differential elevation of proinflammatory and antiinflammatory cytokine gene expression in the ventilatory muscles.

Anesthetic myocardial protection with sevoflurane

OBJECTIVE

To examine the role of sevoflurane in myocardial protection in patients undergoing coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective, randomized, controlled, double-blinded study.

SETTING

Veterans Administration Medical Center (VAMC), Buffalo, New York.

SUBJECTS

Twenty-one patients undergoing CABG were included in the study. Eleven patients were randomized to receive sevoflurane, and 10 patients served as controls.

INTERVENTION

Total intravenous anesthesia was provided for both study and control groups by infusion of propofol, fentanyl, and midazolam. Sevoflurane 2% was added to the cardioplegia solution in the experimental group.

MEASUREMENTS AND MAIN RESULTS

Neutrophil beta-integrins (CD11b/CD18), tumor necrosis factor alpha (TNF-alpha), and interleukin (IL)-6 were measured as indicators of the inflammatory response to myocardial ischemia-reperfusion injury. Blood samples were obtained from the aorta and coronary sinus before (T1) and immediately after cardiopulmonary bypass (CPB) (T2) and, in addition, from a peripheral artery 6 hours (T3) after CPB. Myocardial function was determined in all patients at each time point. Left ventricular stroke work index (LVSWI) was calculated as an estimation of left ventricular function. Left ventricular regional wall motion abnormality (RWMA) was assessed by transesophageal echocardiography at T1 and T2 time points. TNF-alpha was detectable only in the control group in arterial samples at T3. IL-6 levels (pg/mL) were found to be lower in the sevoflurane group compared with controls at T2 arterial circulation (38.2 +/- 21.1 v 60.6 +/- 19.1, p < 0.05) as well as in the coronary circulation (38.4 +/- 19.9 v 118.2 +/- 23.5, p < 0.01) at T2. CD11b/CD18 increased 79% after CPB in the control group while only increasing 36% in the sevoflurane group (p < 0.05). The post-CPB LVSWI was back to its baseline values in the sevoflurane group, whereas it was still significantly depressed in the control group. Eight of 10 patients in the control group showed a transient new-onset RWMA in either the septal or anteroseptal regions. Only 2 of 11 patients in the sevoflurane group showed transient RWMA of the LV.

CONCLUSIONS

Sevoflurane decreases the inflammatory response after CPB, as measured by the release of IL-6, CD11b/CD18, and TNF-alpha. Myocardial function after CPB, as assessed by RWMA and LVSWI, was also improved with sevoflurane. The role of sevoflurane in myocardial protection and the inflammatory response to myocardial reperfusion should be considered.

Pharmacologic preconditioning of JTE-607, a novel cytokine inhibitor, attenuates ischemia-reperfusion injury in the myocardium

BACKGROUND

Myocardial ischemia-reperfusion injury is a main cause of postoperative cardiac dysfunction, and a burst of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin 1 beta, interleukin 6, and interleukin 8, plays a pivotal role. Recently, JTE-607 has been reported as a potent inhibitor of the multiple inflammatory cytokines in the endotoxin shock mouse model. In this study we proved the hypothesis that JTE-607 might attenuate myocardial ischemia-reperfusion injury in a rat model.

METHODS

The isolated rat hearts in the JTE-607 preconditioning group (J group, n = 8) or control group (C group, n = 8) were subjected to warm ischemia (37 degrees C) for 30 minutes, followed by 60 minutes of reperfusion with the Langendorff perfusion system.

RESULTS

Left ventricular developed pressure and maximum dp/dt after reperfusion were significantly improved in the J group than in the C group (P <.01). Creatine phosphokinase leakage is significantly lower in the J group (P <.05). Moreover, the tissue cytokine levels, such as tumor necrosis factor alpha, interleukin 6, and interleukin 8, in the myocardium were significantly lower in the J group than in the C group (P <.05).

CONCLUSION

These results suggested that the pharmacologic preconditioning of JTE-607 inhibits a burst of endogenous cytokines in the myocardium, resulting in the improvement of cardiac function after ischemia-reperfusion injury. Thus JTE-607 might be a novel therapeutic strategy for the protection of postoperative cardiac dysfunction in cardiac surgery.

Hemocompatibility of PMEA Coated Oxygenators Used for Extracorporeal Circulation Procedures

An inflammatory response to cardiopulmonary bypass (CPB) caused by bioincompatibility of extracorporeal circuits is one of the major clinical issues in cardiac surgery. Recently a new coating material, poly-2-methoxyethylacrylate (PMEA), was developed to improve the biocompatibility of blood contacting surfaces. In a simulated cardiopulmonary bypass model, using fresh human whole blood, 15 membrane oxygenators (Capiox SX18, Terumo Corp., Tokyo, Japan) were compared. Five of them had the PMEA coating, five had a heparin-coated surface, and five had no surface treatment. Blood samples were taken at several time-points during a 90 minute circulation period. Changes in coagulation, complement, and blood cell alteration factors were measured by ELISA methods, plasma bradykinin levels were measured by radioimmunoassay, and expression of genes encoding cytokines TNF-alpha, interleukin-1beta, interleukin-6, and interleukin-8 was determined by semiquantitative real time RT-PCR. Platelet adhesion was significantly reduced in both the PMEA and the heparin coated circuits. Release of platelet activation marker beta-thromboglobulin was significantly higher in the uncoated control group (p < 0.01). After 5 minutes of blood circulation bradykinin levels significantly increased in all three groups (p < 0.01); however, the group with the PMEA coated oxygenators showed the lowest values. Expression of genes encoding proinflammatory cytokines in monocytes was increased in all groups, with the lowest being in the PMEA coated group. PMEA coated CPB surfaces in an in vitro experimental model showed an improved thrombogenicity, reduced bradykinin release, less platelet activation and less proinflammatory cytokines gene expression in comparison with a noncoated group. The authors assume that PMEA coating may ameliorate some of intra- and postperfusion syndromes, particularly hypotension, unspecific inflammation, hyperfibrinolysis, and blood loss.

Nafamostat mesilate suppresses NF-kappaB activation and NO overproduction in LPS-treated macrophages

Nafamostat mesilate (NM), a clinically used serine protease inhibitor, suppressed the overproduction of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) in RAW264.7 murine macrophages treated with lipopolysaccharide (LPS, 100 ng/ml); however, it had little effect on endothelial NOS (eNOS) in human umbilical vein endothelial cells (HUVEC). Electrophoretic mobility shift assay (EMSA) revealed that LPS activated nuclear factor-kappaB (NF-kappaB) in RAW264.7 cells and that this activation was suppressed by nafamostat mesilate. Western blotting showed that nafamostat mesilate suppressed the phosphorylation and degradation of inhibitor kappaB-alpha (IkappaB-alpha), which holds NF-kappaB in the cytoplasm in an inactivated state. Our observations suggest that nafamostat mesilate is a candidate agent for various diseases such as ischemia-reperfusion, graft rejection, inflammatory diseases, and autoimmune diseases, in which iNOS and/or NF-kappaB are upregulated.

JAK2/STAT3, not ERK1/2, mediates interleukin-6-induced activation of inducible nitric-oxide synthase and decrease in contractility of adult ventricular myocytes

Interleukin (IL)-6 decreases cardiac contractility via a nitric oxide (NO)-dependent pathway. However, mechanisms underlying IL-6-induced NO production remain unclear. JAK2/STAT3 and ERK1/2 are two well known signaling pathways activated by IL-6 in non-cardiac cells. However, these IL-6-activated pathways have not been identified in adult cardiac myocytes. In this study, we identified activation of these two pathways during IL-6 stimulation and examined their roles in IL-6-induced NO production and decrease in contractility of adult ventricular myocytes. IL-6 increased phosphorylation of STAT3 (at Tyr(705)) and ERK1/2 (at Tyr(204)) within 5 min that peaked at 15-30 min and returned to basal levels at 2 h. Phosphorylation of STAT3 was blocked by genistein, a protein tyrosine kinase inhibitor, and AG490, a JAK2 inhibitor, but not PD98059, an ERK1/2 kinase inhibitor. The phosphorylation of ERK1/2 was blocked by PD98059 and genistein but not AG490. Furthermore, IL-6 enhanced de novo synthesis of iNOS protein, increased NO production, and decreased cardiac contractility after 2 h of incubation. These effects were blocked by genistein and AG490 but not PD98059. We conclude that IL-6 activated independently the JAK2/STAT3 and ERK1/2 pathways, but only JAK2/STAT3 signaling mediated the NO-associated decrease in contractility.

Release of pro-inflammatory mediators during myocardial ischemia/reperfusion in coronary artery bypass graft surgery

Inflammation has been reported to play an important role in cardiac surgery under cardiopulmonary bypass due to systemic endotoxemia. In order to develop strategies against this injury in future we studied the combined effect of a number of inflammatory mediators in myocardial ischemia/reperfusion. Coronary sinus blood samples of ten patients undergoing coronary artery bypass graft surgery (CABG) were obtained at three time intervals (1) before onset of bypass (2) 30 min after cross clamp, and (3) 10 min after removal of cross clamp. The samples were subjected to evaluate levels of nitric oxide byproducts (nitrite and nitrate and citrulline), inflammatory cytokines (interleukin-2, interferon-gamma and interleukin-6), adhesion molecules, (CD62L and CD54), ratio of cell surface markers (CD4/CD8 and TCRalphabeta/gammadelta) cell activation markers (CD69 and HLA DR) and second messengers (protein kinase C, inositol 1,4,5 triphosphate and intracellular calcium levels). Ischemia and further reperfusion resulted in significant rise in nitrite and nitrate levels (p < 0.001), interleukin-6 (p < 0.01), CD62L (p < 0.001), CD69 (p < 0.05), protein kinase C (p < 0.001) and intracellular calcium (p < 0.001). A fall in CD4/CD8 ratio was observed on reperfusion. These changes during CABG show that ischemia/reperfusion leads to a release of an array of pro-inflammatory mediators of tissue injury, which could lead to pathophysiological changes. Hence the study suggests the need of some protective therapies against these inflammatory markers.

Cytokine gene expression in monocytes of patients undergoing cardiopulmonary bypass surgery evaluated by real-time PCR

Cardiopulmonary bypass (CPB) surgery induces systemic release of proinflammatory cytokines causing unspecific inflammatory reactions. This study deals with the development of a sensitive technique for detecting changes at the mRNA level in monocytes of patients undergoing CPB surgery, by using real-time PCR. Blood samples from patients undergoing elective coronary artery bypass grafting were obtained at six different time points. RNA was extracted from isolated monocytes and cDNA was synthesized by reverse transcriptase. CPB surgery induced gene expression of IL-1beta, IL-6, IL-8, and TNF-alpha, followed by a decrease below the preoperative expression values 6 h post CPB. High significant increases in gene expression for IL-8 at the end of surgery (p = 0.001) were detected. Real-time PCR is a powerful tool for getting simultaneously numerous sensitive, accurate, and reliable results from small amounts of biological material. This method avoids time-consuming and hazardous post-PCR manipulations and decreases the potential risk of PCR contamination.

Correlation between inflammatory response and markers of neuronal damage in coronary revascularization with and without cardiopulmonary bypass

Off-pump coronary artery bypass graft (CABG) surgery may reduce the inflammatory response and the neuronal damage associated with conventional CABG on cardiopulmonary bypass. The purpose of this study was to explore the protective effect of off-pump surgery by assessing plasma inflammatory and neuronal injury markers. Forty-one patients with coronary artery disease undergoing elective CABG were examined: 21 on-pump (Group I) and 20 off-pump (Group II). The perioperative release of interleukin-2 receptor (IL-2r), IL-6, tumor necrosis factor-alpha, S-100 protein (S-100) and neuron-specific enolase (NSE) were measured. Postoperative peak values of NSE (p < 0.001) and S-100 (p < 0.05) were significantly lower in Group II. IL-6 showed significantly lower values in off-pump patients (p < 0.001). A significant correlation was found between NSE and IL-6 (p < 0.001). In conclusion, off-pump surgery reduces the inflammatory response as well as the perioperative release of neuronal damage markers. Correlation between inflammatory activation and neuronal markers may suggest a link between inflammation and release of markers of neuronal clinical and subclinical injury.

Expression of FHL2 and cytokine messenger RNAs in human myocardium after cardiopulmonary bypass

BACKGROUND

Proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and IL-8 have been implicated in myocardial injury following cardiopulmonary bypass (CPB). However, little evidence is currently available to directly confirm such a relationship. We have previously documented that a newly discovered 'four and a half LIM-only protein 2' (FHL2) is exclusively expressed in myofibres. We hypothesized that the upregulation of FHL2 is proportional to the degree of myocardial injury and investigated the myocardial expression of FHL2 together with these cytokine messenger RNAs (mRNAs) during clinical CPB.

METHODS

Intermittent hypothermic blood cardioplegia was used in all patients. Atrial myocardial biopsies were obtained immediately at the onset and at the end of CPB in 33 consecutive patients undergoing valvular or coronary artery surgery. TNF-alpha, IL-6, and IL-8 mRNA expressions in these myocardial samples were determined by semi-quantitative reverse transcription-polymerase chain reaction. Myocardial FHL2 expression was determined by Western blot analysis. Serum levels of the MB isoenzyme of creatine kinase (CK-MB) and cardiac troponin-I (cTnI) before surgery and 24 h after the end of CPB were also measured.

RESULTS

The duration of aortic crossclamping and CPB was 70+/-33 and 99+/-37 min, respectively. No elevated myocardial TNF-alpha mRNA expression was found after CPB. IL-6 mRNA expressions were detected in 14 pairs of the myocardial biopsies and were elevated in 11 (33%) post-CPB biopsies. Similarly, IL-8 mRNA expressions were detected in 19 pairs of samples and were elevated in 14 (42%) post-CPB biopsies. Among the 17 pairs of biopsies with positive FHL2 expression, FHL2 levels were increased in 11 (33%) post-CPB samples. Moreover, the elevated FHL2 expression was associated with an increase in IL-6 (P=0.018) and IL-8 (P=0.024) mRNA expression after CPB. Postoperative CK-MB and cTnI levels were significantly higher in patients with myocardial FHL2 expressions than those without (CK-MB, 13.5+/-2.3 vs. 6.5+/-0.8 ng/ml, P=0.022; cTnI, 10.7+/-2.0 vs. 3.5+/-0.6 ng/ml, P=0.0013).

CONCLUSIONS

Our findings demonstrate for the first time that both IL-6 and IL-8 mRNAs are upregulated in human cardiac myocytes following CPB and these cytokines may be involved in myocardial ischemia-reperfusion injury, as reflected by their association with an increased expression of FHL2.

The role of transsignalling via the agonistic soluble IL-6 receptor in human diseases

The activation of cells that do not express the membrane bound interleukin-6 6 receptor (IL-6R) by IL-6 and the soluble IL-6 receptor (sIL-6R) is termed transsignalling. Transsignalling may be an pathogenetic factor in human diseases as diverse as multiple myeloma (MM), Castleman's disease, prostate carcinoma, Crohn's disease, systemic sclerosis, Still's disease, osteoporosis and cardiovascular diseases. IL-6 and sIL-6R may directly or indirectly enhance their own production on endothelial or bone marrow stromal cells. Positive feedback autocrine loops thus created in affected organs may either cause or maintain disease progression. In autoimmune or vasculitic disease, the ability of the IL-6/sIL-6R complex to inhibit apoptosis of autoreactive T-cells may be central to the development of tissue specific autoimmunity. The anti-apoptotic effect of the IL-6/sIL-6R complex may be involved in tumour genesis and resistance to chemotherapy. Only in rare cases, where counterregulation has failed, there is a notable systemic effect of IL-6/sIL-6R. Appropriate animal models are necessary to establish the pathogenetic role of the IL-6/sIL-6R complex. A specific treatment option for diseases influenced by the sIL-6R could be based on gp130-Fc, a soluble gp130 (sgp130) linked to the Fc-fragment of IgG1. gp130-Fc has shown efficacy in vivo in animal models of Crohn's disease.

Systematic organ protection in coronary artery surgery with or without cardiopulmonary bypass

Coronary artery bypass grafting with cardiopulmonary bypass (CPB) is known to be associated with a systemic inflammatory response, which contributes to the development of postoperative complications including multiple organ dysfunction. Off-pump coronary surgery has been shown to attenuate the inflammatory injury compared to the conventional approach, thereby reducing the incidence of postoperative cardiopulmonary, renal, or neurological dysfunction. It is believed that off-pump experience may greatly impact on improving the outcome of coronary surgery in certain high-risk patients. Moreover, a better understanding of the underlying mechanism would also help to improve our current CPB management. Accumulating evidence to date indicates that a balance between pro- and antiinflammatory responses is crucial in limiting the extent of such systemic inflammatory injury following surgical myocardial revascularization.

Production of proinflammatory cytokines and myocardial dysfunction after arterial switch operation in neonates with transposition of the great arteries

OBJECTIVE

Neonates undergoing cardiac surgery have a systemic inflammatory reaction with release of proinflammatory cytokines, which could be responsible for myocardial dysfunction as a result of myocardial cell damage. The purpose of this study was to test the hypothesis that the production of proinflammatory cytokines during cardiac surgery would be associated with myocardial dysfunction after the arterial switch operation in neonates.

METHODS

A total of 63 neonates with transposition of the great arteries were operated on with combined deep hypothermic circulatory arrest and low-flow cardiopulmonary bypass at a median age of 7 days. Perioperative plasma concentrations of interleukins 6 and 8 were correlated with myocardial dysfunction, as assessed clinically and by echocardiography within 24 hours after the operation, and with perioperative cardiac troponin T blood levels as a marker of myocardial cell damage.

RESULTS

Myocardial dysfunction was observed in 11 patients (17.5%), and 2 of them died. Durations of cardiopulmonary bypass and aortic crossclamping, but not of circulatory arrest, were correlated with myocardial dysfunction. Patients with myocardial dysfunction had significantly higher cardiac troponin T blood levels at the end of cardiopulmonary bypass and 4 and 24 hours after the operation than did patients without myocardial dysfunction. Patients with myocardial dysfunction also had higher interleukin 6 plasma concentrations after cardiopulmonary bypass and 4 hours after the operation, as well as higher interleukin 8 plasma concentrations 4 and 24 hours after the operation, than did those without myocardial dysfunction. Postoperative interleukin 6 and 8 plasma concentrations were significantly correlated with postoperative cardiac troponin T blood levels. Multivariable analysis of independent risk factors for myocardial dysfunction comprising cytokine and troponin levels and bypass duration revealed interleukin 6 levels 4 hours after the operation as significant (P =.047).

CONCLUSIONS

Cardiac operations in neonates stimulate the production of proinflammatory cytokines, which may contribute to myocardial cell damage and myocardial dysfunction.

Role of the complement system in ischaemic heart disease: potential for pharmacological intervention

The complement system is an innate, cytotoxic host defence system that normally functions to eliminate foreign pathogens. However, considerable evidence suggests that complement plays a key role in the pathophysiology of ischaemic heart disease (IHD). Experimental models of acute myocardial infarction (MI) and autopsy specimens taken from acute MI patients demonstrate that complement is selectively deposited in areas of infarction. Furthermore, inhibition of complement activation or depletion of complement components prior to myocardial reperfusion has been shown to reduce complement-mediated tissue injury in numerous animal models. IHD remains a leading cause of patient morbidity and mortality. Considerable effort in recent years has therefore been directed by biotechnology and pharmaceutical industries towards the development of novel, human complement inhibitors. Proposed anticomplement therapeutic strategies include the administration of naturally occurring or recombinant complement regulators, anticomplement monoclonal antibodies, and anticomplement receptor antagonists. Although data regarding the effectiveness of anticomplement therapy in humans is limited at present, a number of novel anticomplement therapeutic strategies are currently in clinical trials. The role of complement in IHD and potential for pharmacological intervention is reviewed.

Cariporide (HOE 642) attenuates leukocyte activation in ischemia and reperfusion

Cariporide (HOE 642) ameliorates myocardial ischemia/reperfusion (I/R) injury, by the well established reduction of cytosolic [Ca(2+)] in cardiac myocytes through inhibition of Na(+)/H(+) exchange. However, postischemic inflammation also contributes to I/R injury. We tested the hypothesis that cariporide also modulates the inflammatory response. The effect of cariporide on L-selectin expression by human leukocytes in vitro and leukocyte adhesion and emigration in the reperfused rat cremaster muscle in vivo were studied. The rat cremaster muscle was exteriorized for intravital videomicroscopy, induction of ischemia (90 min), and reperfusion (90 min). Eleven rats were pretreated with cariporide (9 mg/kg body weight IV) whereas 11 rats received saline. Leukocyte adhesion was quantified offline. Human venous blood was incubated with cariporide (3 micromol/L) or saline, stimulated with formyl- methionine-leucine-phenylalanine (10(-10)-10(-6) mol/L), and granulocyte L-selectin expression was analyzed by flow cytometry. Cariporide reduced leukocyte rolling and adhesion by approximately 35% and 45%, respectively, after 30 min of reperfusion. Leukocyte extravasation was decreased by approximately 85% after 90 min. Cariporide increased L-selectin shedding at each formyl-methionine-leucine-phenylalanine concentration, reducing the 50% effective dose from 9.95 to 4.68 nmol/L. Thus, cariporide may ameliorate I/R injury not only by the known reduction of cytosolic [Ca(2+)] in cardiomyocytes, but also by attenuating leukocyte-dependent inflammatory responses. Promotion of L-selectin shedding from activated leukocytes may present a mechanism underlying this newly detected effect.

IMPLICATIONS

This study provides evidence that inhibition of Na(+)/H(+) exchange by cariporide (HOE 642) attenuates the postischemic inflammatory response. Leukocyte adhesion and emigration, assessed by in vivo microscopy, were markedly reduced in rat cremaster muscle, possibly because of increased L-selectin shedding of activated leukocytes as demonstrated by flow cytometry.

Intraoperative metabolic monitoring of the heart: I. Clinical assessment of coronary sinus metabolites

Numerous clinical studies have corroborated the ability of intraoperative sampling of coronary sinus blood to measure changes in myocardial metabolism induced by ischemia and reperfusion. Among other changes, cardiac arrest induces a period of obligate myocardial lactate production that persists for an indeterminate amount of time after reperfusion. Coronary sinus lactate assays have been established as a standard method to compare various myocardial protection strategies. Current methodology requires detailed sample processing, precluding real-time feedback in the operating room. Newer devices hold promise in allowing the online assessment of myocardial metabolism; however, these methods await precise validation.

The effects of aprotinin and steroids on generation of cytokines during coronary artery surgery

OBJECTIVE

To compare the efficacy of aprotinin and methylprednisolone in reducing cardiopulmonary bypass (CPB)-induced cytokine release, to evaluate the effect of myocardial cytokine release on systemic cytokine levels, and to determine the influence of cytokine release on perioperative and postoperative hemodynamics.

DESIGN

Prospective, randomized clinical trial.

SETTING

University teaching hospital and clinics.

PARTICIPANTS

Thirty patients undergoing elective coronary artery bypass graft surgery.

INTERVENTION

Patients were randomly allocated into groups treated with aprotinin (n = 10) or methylprednisolone (n = 10) or into an untreated control group (n = 10). Aprotinin-treated patients received aprotinin as a high-dose regimen (6 x 10(6) KIU), and methylprednisolone-treated patients received methylprednisolone (30 mg/kg intravenously) before CPB.

MEASUREMENTS AND MAIN RESULTS

Patients were analyzed for hemodynamic changes and alveolar-arterial PO2 difference (AaDO2) until the first postoperative day. Plasma levels of proinflammatory cytokines (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-6, and IL-8) were measured in peripheral arterial blood immediately before the induction of anesthesia, 5 minutes before CPB, 3 minutes after the start of CPB, 2 minutes after the release of the aortic cross-clamp, 1 hour after CPB, 6 hours after CPB, and 24 hours after CPB; and in coronary sinus blood immediately before CPB and 2 minutes after the release of the aortic cross-clamp. The hemodynamic parameters did not differ among the groups throughout the study. After CPB, AaDO2 significantly increased (p < 0.05) in all groups. A significant decrease in AaDO2 was observed in aprotinin-treated patients at 24 hours after CPB compared with the other groups (p < 0.05). TNF-alpha level from peripheral arterial blood significantly increased in control patients 1 hour after CPB (p < 0.01) and did not significantly increase in methylprednisolone-treated patients throughout the study. In all groups, IL-6 levels increased after the release of the aortic cross-clamp and reached peak values 6 hours after CPB. At 6 hours after CPB, the increase in IL-6 levels in methylprednisolone-treated patients was significantly less compared with levels measured in control patients and aprotinin-treated patients (p < 0.001). In control patients, IL-8 levels significantly increased 2 minutes after the release of the aortic cross-clamp (p < 0.05), and peak values were observed 1 hour after CPB (p < 0.01). IL-8 levels in control patients were significantly higher compared with patients treated with aprotinin and patients treated with methylprednisolone 1 hour after CPB (p < 0.05).

CONCLUSION

This study showed that methylprednisolone suppresses TNF-alpha, IL-6, and IL-8 release; however, aprotinin attenuates IL-8 release alone. Methylprednisolone does not produce any additional positive hemodynamic and pulmonary effects. An improved postoperative AaDO2 was observed with the use of aprotinin.

Aprotinin reduces the IL-8 after coronary artery bypass grafting

The effect of aprotinin, a protease inhibitor, on myocardial interleukin-8 (IL-8) production after ischemia-reperfusion injury was investigated. Twenty patients who had elective coronary artery bypass grafting were included in this study. Patients were randomly divided into two groups (n = 10 in each). Group A patients received high dose aprotinin (20,000 IU/kg as pretreatment followed by 7500 IU/kg for 6 h) and Group B patients received normal saline as a control. Serum IL-8 levels after the termination of cardiopulmonary bypass (CPB) showed a significant improvement in aprotinin treated group compared to control group (70 +/- 42.6 vs 360.71 +/- 87.9 ng/ml) (P < 0.005). Levels were also significantly higher at post-operative 24th hour in patients who did not received aprotinin (340.16 +/- 92.10 vs 96.13 +/- 34.33 ng/ml). However at post-operative 48th hour levels were again higher in control (untreated) group, but the difference was not statistically significant (78.8 +/- 34.4 vs 42.8 +/- 9.29 ng/ml). Aprotinin prevented the IL-8 release from myocytes in ischemia-reperfusion injury. The mechanism is highly dependent on anti-protease activity of aprotinin.

Myocardial heat shock proteins during the development of heart failure

When cardiomyocytes are exposed to stresses, production of heat shock proteins (HSPs) in the cells is enhanced. Such increase in cellular HSP production is considered to bring about tolerance against stress-induced cell damage. The exact role of the cellular HSPs remains unclear. In the present study, HSPs in the viable left ventricular myocardium were determined during the development of heart failure following coronary artery ligation (CAL). The rats after CAL showed symptoms of chronic heart failure (CHF) at the 8th week, but not at the 1st and 2nd weeks. Myocardial HSP27, which may bind to cytoskeletal protein, at the 1st, 2nd, and 8th weeks after CAL was approximately 180, 160, and 125% of the control, respectively. Myocardial HSP60, one of mitochondrial proteins, at the 8th week increased to 140% of the control, whereas those at the 1st and 2nd weeks did not change. Myocardial HSP72, an inducible form of HSP70 family, at the 1st week after CAL increased to 180% of the control, whereas that at the 2nd or 8th week was similar to control. Myocardial heat shock constitutive protein 73 (HSC73), a constitutively expressed form of HSP70 family, and HSP90, which may bind to steroid hormone receptor and actin fiber, of CAL rats did not alter throughout the experiment. These findings show that diverse changes in the production of myocardial HSPs occur during the development of heart failure. Only the increase in myocardial HSP60 production was associated with the development of CHF.

Can statins reduce the inflammatory response to cardiopulmonary bypass? A clinical study

OBJECTIVE

In addition to lowering lipid levels, statins might reduce leukocyte-endothelial cell interactions. Therefore, we assessed whether this effect could limit the inflammatory response to cardiopulmonary bypass (CPB) in cardiac surgical patients.

METHODS

Twenty patients undergoing valve or coronary operations with tepid (34 degrees C) CPB were randomized to receive an oral dose of atorvastatin (40 mg the evening before and 40 mg the morning of surgery) or to serve as controls. Pre- and post-CPB blood samples were assayed for neutrophil CD11b surface adhesion molecule and oxidative burst. Plasma levels of interleukins 6 and 8, P-selectin, soluble intercellular adhesion molecule-1, and lactoferrin were measured by enzyme-linked immunosorbent assay (ELISA). In addition, right atrial biopsies were taken before and at the end of CPB, and processed for the expression of the transcription nuclear factor-kappa B (NF-kappaB).

RESULTS

The two groups did not differ with regard to pre- and intraoperative data. Except for P-selectin, postbypass values of all markers significantly increased over baseline values, but atorvastatin therapy failed to attenuate the magnitude of this increase. In the two groups, the expression of NF-kappaB significantly (p = 0.004) increased over baseline without group effect. Postoperative clinical outcomes did not differ either between the two groups.

CONCLUSION

These data show that acute preoperative statin therapy fails to limit the inflammatory response to CPB; however, the data also document a major upregulation of NF-kappaB during cardiac operations, thereby providing a sound rationale for interventions targeted at inactivating this key component of the inflammatory cascade.

Therapeutic applications of antiflammin peptides in experimental ocular inflammation

Antiflammins are synthetic peptides derived from the region of highest local similarity between uteroglobulin and lipocortin. These peptides have shown anti-inflammatory activity on carrageenan-induced rat footpad edema. They are potent inhibitors for phospholipase A2 activation both in vitro and in vivo. Previously, we have demonstrated the effectiveness of topical antiflammins in suppressing acute ocular inflammation and allergic response in rodent endotoxin-induced uveitis and murine allergic conjunctivitis. The mechanisms by which antiflammins protect against inflammation and allergy in these ocular models may involve inhibition of phospholipase A2 and inducible nitric oxide synthase (iNOS) as well as the production of proinflammatory cytokine, interleukin-6.

Cytokine Responses in Low-Risk Coronary Artery Bypass Surgery

Inflammatory cytokines have been implicated in myocardial function, severe congestive heart failure and sepsis. The present study tested the hypothesis that cytokine levels are elevated after low-risk coronary artery bypass surgery (CABG), and that they may be associated with postoperative cardiac dysfunction. Twenty male patients undergoing elective CABG in cardiopulmonary bypass (CPB) were studied. Plasma levels of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-8, and IL-10 were measured before anesthesia induction, 5 minutes after, and 1, 4, and 20 hours after reperfusion to the myocardium. Levels of the MB isoenzyme of creatine kinase (CK-MB) were measured postoperatively. Hemodynamic data were also recorded. Myocardial ischemia was followed by an increase in the plasma levels of IL-6, IL-8, and IL-10. The duration of IL-6 response lasted throughout the postoperative period studied. Plasma cytokine levels at 1 hour after reperfusion correlated with the maximum CK-MB value (IL-6, r = 0.587, p < 0.01; IL-8, r = 0.460, p < 0.05; IL-10, r = 0.570, p < 0.05). Higher plasma IL-6 and IL-8 levels after reperfusion tended to be linked with lower cardiac index. The present results confirm that the levels of inflammatory cytokines IL-6, IL-8, and IL-10 are elevated after CABG. Increased systemic pro-inflammatory cytokine levels were partially associated with postoperative myocardial dysfunction. </hea

Systemic hypoxia increases leukocyte emigration and vascular permeability in conscious rats

We recently observed that acute systemic hypoxia produces rapid increases in leukocyte adherence in the mesenteric microcirculation of the anesthetized rat Wood JG, Johnson JS, Mattioli LF, and Gonzalez NC. J Appl Physiol 87: 1734-1740, 1999; Wood JG, Mattioli LF, and Gonzalez NC. J Appl Physiol 87: 873-881, 1999. Hypoxia-induced leukocyte adherence is associated with an increase in reactive oxygen species (ROS) generation and is attenuated by antioxidants or interventions that increase tissue levels of nitric oxide (NO). These results suggest that the acute effects of hypoxia on leukocyte-endothelial interactions are caused by a change in the ROS-NO balance. The present experiments were designed to extend our observations of the initial microcirculatory response to hypoxia; specifically, we wanted to determine whether the response to systemic hypoxia involves increased microvascular permeability and leukocyte emigration and whether ROS generation and decreased NO levels contribute to these responses. At this time, there is conflicting evidence, from in vitro studies, regarding the effect of hypoxia on these indexes of vascular function. Our studies were carried out in the physiological setting of the conscious animal, in which a prolonged hypoxic exposure is possible without the adverse effects that may develop under anesthesia. The central observation of these studies is that conscious animals exposed for 4 h to environmental hypoxia show increased microvascular permeability and emigration of leukocytes into the extravascular space of the mesenteric circulation. Furthermore, these events are dependent on increased ROS generation and, possibly, a subsequent decrease in tissue NO levels during systemic hypoxia. Our results show that systemic hypoxia profoundly affects vascular endothelial function through changes in the ROS-NO balance in the conscious animal.

Increased homocyst(e)ine associated with smoking, chronic inflammation, and aging may reflect acute-phase induction of pyridoxal phosphatase activity

Smokers, patients with chronic inflammatory disorders, and the elderly, are characterized by increased production of IL-6 as well as increased plasma levels of homocyst(e)ine. Analysis of cirrhotic livers suggests that IL-6 may stimulate the activity of pyridoxal phosphatase in hepatocytes, thereby diminishing pyridoxal phosphate levels, compromising cystathionine beta-synthase activity, and raising plasma homocyst(e)ine. Adequate supplemental intakes of pyridoxine may be corrective in this regard.

Interleukin 6 induction in the canine myocardium after cardiopulmonary bypass

OBJECTIVE

Interleukin 6 is a proinflammatory cytokine with a plasma concentration that has been noted to increase in response to cardiopulmonary bypass. The source of interleukin 6 after cardiopulmonary bypass is unknown. This study examined the myocardium as a potential source of interleukin 6 in this context.

METHODS

Dogs underwent 90 minutes of hypothermic cardiopulmonary bypass with 60 minutes of cardioplegic arrest. After rewarming, they were reperfused with the chest open for either 3 (n = 4) or 6 (n = 4) hours, at the end of which myocardial samples were obtained. Four additional animals undergoing open thoracotomy without bypass served as time-matched controls. Northern blot analysis, reverse transcriptase-polymerase chain reaction, and in situ hybridization were used to examine the myocardium for the induction of interleukin 6 and intercellular adhesion molecule-1.

RESULTS

Northern blot analysis and reverse transcriptase-polymerase chain reaction demonstrated a marked increase in myocardial interleukin 6 messenger RNA in 3 of 4 dogs at 3 hours after bypass and 3 of 4 dogs at 6 hours after bypass, which was not present in sham-bypass control animals. Northern blots at 3 hours after cardiopulmonary bypass also demonstrated myocardial intercellular adhesion molecule-1 induction. In situ hybridization studies confirmed that cardiac myocytes were a principal source of interleukin 6 messenger RNA early after cardiopulmonary bypass. Northern blots of messenger RNA extracted from isolated neutrophils and mononuclear leukocytes obtained from blood samples before bypass, at the end of bypass, and 3 hours after bypass failed to demonstrate interleukin 6 induction.

CONCLUSION

Despite protection with cold cardioplegic arrest, the myocardium was a significant source of interleukin 6 synthesis after cardiopulmonary bypass. Local production of interleukin 6 may play a pivotal role in postoperative myocardial function.

Leukocyte-depleted reperfusion after long cardioplegic arrest attenuates ischemia-reperfusion injury of the coronary endothelium and myocardium in rabbit hearts

OBJECTIVE

Cardiopulmonary bypass activates leukocytes, which should injure the coronary endothelium and myocardium during reperfusion especially after long cardioplegic arrest with long cardiopulmonary bypass time. The present study was designed to determine the protective efficacy of leukocyte-depleted reperfusion in blood-perfused parabiotic isolated rabbit hearts as a surgically relevant model with long cardioplegic arrest.

METHODS

Each isolated rabbit heart, with a latex balloon inserted in the left ventricle, was parabiotically blood-perfused using a modified Langendorff column. The left ventricular developed pressure (DP), rate of pressure development (dP/dT), and coronary flow with a left ventricular end-diastolic pressure of 10 mmHg were measured before ischemia and after 15, 30, 45, and 60 min reperfusion after 4 h cardioplegic arrest kept at 20 degrees C (control, n=10). Leukocyte-depleted reperfusion was done in the test group (n=10). The endothelium of the coronary artery was observed by scanning electron microscopy (SEM) with percent injured area of endothelial cells measured to evaluate the extent of endothelial ischemia-reperfusion injury.

RESULTS

The control hearts showed 53.3, 54.3, 48.4, and 39.0% recovery of DP compared to the pre-ischemia baseline data at 15, 30, 45, and 60 min after reperfusion began respectively. Leukocyte-depleted reperfusion enhanced the recovery of DP at 45 min (81.3%, P=0.0021) and 60 min (85.8%, P=0.0005) after reperfusion compared with that in the control group. The control hearts revealed 58.8%, 59.8%, 52.6%, and 43.4% recovery of dP/dT compared to the pre-ischemia baseline data at 15, 30, 45, and 60 min after reperfusion began, respectively. Leukocyte-depleted reperfusion also enhanced the recovery of dP/dT at 45 min (93.2%, P=0.0071) and 60 min (98.8%, P=0.0011) after reperfusion compared with that in the control group. There was also improvement of the recovery of coronary flow by leukocyte-depleted reperfusion (97.2%) compared with that in the control group (58.3%) after 60 min reperfusion (P=0.0121). Scanning electron microscopy showed that 69. 7% of coronary endothelial cells were morphologically injured in the control group. In contrast, leukocyte-depleted reperfusion prevented the extent of coronary endothelial damage with less injured area (0. 5%, P=0.0002).

CONCLUSIONS

Leukocyte-depleted reperfusion improved functional recovery with reduced coronary endothelial injury after long cardioplegic arrest.

Reperfusion injury after focal myocardial ischaemia: polymorphonuclear leukocyte activation and its clinical implications

The only way to rescue ischaemic tissue is to re-instate the oxygen supply to the tissue. However reperfusion of the ischaemic area not only oxygenates the tissue but also initiates a cascade of processes, which may in some cases result in temporary dysfunction of the myocardium. In order to devise protective measures, it is essential to understand the mechanisms and the triggers of this reperfusion phenomenon. In this review we will mainly focus on the inflammatory response caused by reperfusion. We will cover the different steps of polymorphonuclear leukocyte activation and will briefly discuss the molecular biology of the receptors involved. The currently used pharmacological medications in acute cardiology will be reviewed and in particular their actions on polymorphonuclear leukocyte activation, adhesion and degranulation. This review is a compilation of the current knowledge in the field and the therapeutic progress in the prevention of reperfusion injury made today.

Therapeutic potential of complement inhibitors in myocardial ischaemia

Under normal conditions, the complement system functions to eradicate microbes and other membrane bound pathogens. In other situations, complement activation comprises a pivotal mechanism for mediating tissue demolition in inflammatory disorders, including ischaemia/reperfusion injury. Complement-mediated tissue damage has long been recognised as a significant contributor to myocardial reperfusion injury. However, clinical use of complement inhibitors to reduce the extent of irreversible tissue injury related to reperfusion, remains in the early stages of development. Activation of the complement system generates anaphylatoxins, opsonins and the lytic moiety known as the membrane attack complex (MAC). In addition, fragments of the complement cascade proteins (e.g., C3a and C5a) secondarily initiate processes deleterious to myocytes by recruiting and stimulating inflammatory cells, such as neutrophils and macrophages, within the area of reperfusion. Damaged tissue itself, is capable of upregulating the genes that encode the formation of complement proteins leading to assembly of the MAC, which in turn further advances tissue injury. All of these factors contribute to the development of myocardial infarction subsequent to ischaemia and reperfusion. This paper provides an overview of how the complement system operates and examines the various inhibitors, both endogenous and exogenous, that regulate the complement cascade. Activation and inhibition of the complement system will be discussed primarily in the context of myocardial ischaemia and reperfusion injury.

Modified ultrafiltration lowers adhesion molecule and cytokine levels after cardiopulmonary bypass without clinical relevance in adults

OBJECTIVE

Cardiac surgery with cardiopulmonary bypass (CPB) results in expression of cytokines and adhesion molecules (AM) with subsequent inflammatory response. The purpose of the study was to evaluate the clinical impact of modified ultrafiltration (MUF) and its efficacy in reducing cytokines and AM following coronary artery bypass grafting (CABG) in adults.

METHODS

A prospective randomized study of 97 patients undergoing elective CABG was designed. Fifty patients were operated on using normothermic and 47 patients using hypothermic CPB. The normothermic group was subdivided into a group with modified ultrafiltration (n = 30) and a group without MUF (n = 20). In the hypothermic group 30 patients received MUF compared to 17 patients serving as controls. MUF was instituted after CPB for 15 min through the arterial and venous bypass circuit lines. Cytokines (IL-6, IL-8, TNF-alpha, IL-2R) and adhesion molecules (sE-selectin, sICAM-1) were measured preoperatively, pre-MUF, in the ultrafiltrate, 24 h, 48 h and 6 days after surgery by chemiluminescent enzyme immunometric assay or enzyme-linked immunosorbent assay (ELISA). Clinical parameters were collected prospectively until discharge.

RESULTS

In all patients AM and cytokines were significantly elevated after normothermic and hypothemic CPB. AM and cytokines were significantly higher in hypothermia compared to normothermia. In hypothermic CPB sE-selectin was decreased after 24 h by 37% (P < 0.0063) and by 40% (P < 0.0027) after 48 h postoperatively. ICAM-1 was reduced by 43% (P < 0.0001) after 24 h and by 60% (P < 0.0001) after 6 days. Similar results were seen in cytokines with reduction up to 60% after 24 h. Changes after 48 h were noticeable but not significant. Reduction of AM and cytokines after normothermic CPB was minimal. Neither in normothermia, nor in hypothermia has sIL-2R been effectively removed from the circulation. There were no significant differences in the clinical variables between the patients with or without MUF.

CONCLUSION

AM and cytokines are significantly elevated after hypothermic CPB compared to normothermic CPB. MUF led to a significant reduction in cytokine and AM levels after hypothermic CPB, except for IL-2R. MUF showed minimal effect in normothermia. We conclude that MUF is an efficient way to remove cytokines and AM. However, we were unable to demonstrate any significant impact of MUF in outcome of adults after elective CABG.

Influence of age on hypoxia/reoxygenation-induced DNA fragmentation and bcl-2, bcl-xl, bax and fas in the rat heart and brain

To test the hypothesis that the aging mammalian heart and brain might have increased vulnerability to acute stress, DNA fragmentation was studied after hypoxia-reoygenation in young adult (6 months) and old (22-24 months) F344 rats. Heart and brain tissue were examined at the following time points: 30, 60, or 90 min of hypoxia (H, 5% O2, 95% N2) plus 2 h of reoxygenation (R, room air, 21% O2). With increasing duration of hypoxia preceding the reoxygenation, the extent of DNA fragmentation (in situ terminal dUTP nick end labeling, TUNEL, positive cells) was progressively higher in both age groups, greater in the old compared to that of the young adult rat. The levels of the anti-apoptotic proteins bcl-2 and bcl-xL, were similar in young and old at baseline and tended to increase in both age groups after hypoxia/reoxygenation. The pro-apoptotic protein, bax, was higher at baseline in the old; it rose after hypoxia/reoxygenation in the young adult heart and brain, but was unchanged in the old heart and was decreased in the old brain. The ratios of bcl-2/bax and of bcl-xL/bax were higher in the old heart and brain compared to that in the young adult after hypoxia/reoxygenation. Thus, compared to that of the young adult, the heart and brain of the old rat have lower thresholds and are more vulnerable to injury induced by hypoxia/reoxygenation, despite rapid and heightened expression of the anti-apoptotic proteins bcl-2 and bcl-xl. This could be due partly to the age-associated increase in the basal expression of the pro-apoptotic protein bax, as well as possibly other factors.

Avoiding cardiopulmonary bypass in multivessel CABG reduces cytokine response and myocardial injury

BACKGROUND

Proinflammatory cytokines play a key role in the inflammatory cascade after cardiopulmonary bypass and may induce cardiac dysfunction. We compared the production of cytokines and the degree of postoperative myocardial injury in patients with multivessel coronary artery disease undergoing coronary artery bypass grafting through median sternotomy with or without cardiopulmonary bypass.

METHODS

Forty-four consecutive patients were studied. Patients were selected for off-pump coronary artery bypass grafting whenever complete revascularization was technically feasible. There were no differences between the two groups with respect to age, sex, symptoms, or functional class. Plasma levels of tumor necrosis factor-alpha, interleukin (IL)-6, IL-8, and IL-10 were measured before the operation, at the end of the procedure, and 2, 4, 8, 24, and 48 hours thereafter. Levels of the MB isoenzyme of creatine kinase and cardiac troponin-I were also measured after the operation.

RESULTS

The number of grafts was 2+/-0.7 in the off-pump group (n = 18) and 3+/-0.8 in the cardiopulmonary bypass group (n = 26). There were no deaths or major complications in either group. Levels of tumor necrosis factor-alpha were low in both groups. No significant intergroup differences were noted regarding serial IL-6 measurements. However, IL-8 and IL-10 levels after the operation were lower in the off-pump group (IL-8, 4+/-1 versus 38+/-12 pg/mL, p < 0.01; IL-10, 5+/-2 versus 191+/-33 pg/mL, p < 0.001). Whereas postoperative creatine kinase-MB values were similar in the two groups, cardiac troponin-I levels were significantly lower in the off-pump group (8 hours, p < 0.005; 24 hours, p < 0.02, respectively). Moreover, cardiac troponin-I values 24 hours after operation correlated strongly with IL-8 levels (r = 0.61, p < 0.005), indicating that the degree of myocardial injury may be related to IL-8 production.

CONCLUSIONS

Compared with conventional coronary artery bypass grafting, coronary revascularization without cardiopulmonary bypass is associated with reduced cytokine responses and less myocardial injury.

The heart produces but the lungs consume proinflammatory cytokines following cardiopulmonary bypass

OBJECTIVE

Proinflammatory cytokines, such as interleukin-6 (IL-6), and soluble adhesion molecules, such as E-selectin, may play an important role in patient response to cardiopulmonary bypass (CPB). We sought to define whether the heart and the lungs serve as important sources of these inflammatory mediators under clinical conditions of myocardial revascularization using CPB and cardioplegic arrest.

METHODS

Plasma levels of IL-6 and E-selectin were measured in coronary sinus (CS), arterial, pulmonary arterial (PA) and left atrial (LA) blood samples taken from 12 consecutive patients (68.3 +/- 11 years; five females) undergoing coronary artery bypass grafting (CABG). Blood samples were collected preoperatively, after reperfusion, and 1, 6, 12 and 18 h following surgery. CS and LA blood was drawn using transcutaneous catheters. PA artery blood was obtained through a Swan-Ganz catheter. Cytokine levels were determined by standard enzyme linked immunosorbent assay (ELISA) technique.

RESULTS

A mean of 3.8 +/- 1 coronary anastomoses were performed. The CPB time and aortic X-clamp time were 91 +/- 15 and 45 +/- 10 min, respectively. IL-6 levels increased significantly after CPB and peaked 6 h postoperatively. There was also a significant increase of E-selectin levels with an onset at 1 h and a peak at 12 h postoperatively. At all time points the IL-6 and E-selectin concentrations were significantly higher in the CS than in arterial blood. In contrast, the levels of both mediators measured in the LA were significantly lower than those in the PA.

CONCLUSION

The reperfusion of ischemic myocardium during CABG results in a significant increase in plasma levels of IL-6 and E-selectin. Our data indicate that the myocardium, but not the lungs, is a predominant source of IL-6 and E-selectin release following CPB. The lungs may consume rather than release those mediators during reperfusion. Not the CPB per se, but the myocardial ischemia seems to be crucial in the pathogenesis of the inflammatory response observed following open heart surgery.