Effects of tumour necrosis factor-alpha on the coronary circulation of the rat isolated perfused heart: a potential role for thromboxane A2 and sphingosine

MECHANISMS OF CARDIAC DYSFUNCTION IN SEPSIS

ABSTRACT

Studies in animal models of sepsis have elucidated an intricate network of signaling pathways that lead to the dysregulation of myocardial Ca 2+ handling and subsequently to a decrease in cardiac contractile force, in a sex- and model-dependent manner. After challenge with a lethal dose of LPS, male animals show a decrease in cellular Ca 2+ transients (ΔCa i ), with intact myofilament function, whereas female animals show myofilament dysfunction, with intact ΔCa i . Male mice challenged with a low, nonlethal dose of LPS also develop myofilament desensitization, with intact ΔCa i . In the cecal ligation and puncture (CLP) model, the causative mechanisms seem similar to those in the LPS model in male mice and are unknown in female subjects. ΔCa i decrease in male mice is primarily due to redox-dependent inhibition of sarco/endoplasmic reticulum Ca 2+ ATP-ase (SERCA). Reactive oxygen species (ROS) are overproduced by dysregulated mitochondria and the enzymes NADPH/NADH oxidase, cyclooxygenase, and xanthine oxidase. In addition to inhibiting SERCA, ROS amplify cardiomyocyte cytokine production and mitochondrial dysfunction, making the process self-propagating. In contrast, female animals may exhibit a natural redox resilience. Myofilament dysfunction is due to hyperphosphorylation of troponin I, troponin T cleavage by caspase-3, and overproduction of cGMP by NO-activated soluble guanylate cyclase. Depleted, dysfunctional, or uncoupled mitochondria likely synthesize less ATP in both sexes, but the role of energy deficit is not clear. NO produced by NO synthase (NOS)-3 and mitochondrial NOSs, protein kinases and phosphatases, the processes of autophagy and sarco/endoplasmic reticulum stress, and β-adrenergic insensitivity may also play currently uncertain roles.

Tumor Necrosis Factor-α in Heart Failure: an Updated Review

PURPOSE OF THE REVIEW

Proinflammatory cytokines are consistently elevated in congestive heart failure. In the current review, we provide an overview on the current understanding of how tumor necrosis factor-α (TNFα), a key proinflammatory cytokine, potentiates heart failure by overwhelming the anti-inflammatory responses disrupting the homeostasis.

RECENT FINDINGS

Studies have shown co-relationship between severity of heart failure and levels of the proinflammatory cytokine TNFα and one of its secondary mediators interleukin-6 (IL-6), suggesting their potential as biomarkers. Recent efforts have focused on understanding the mechanisms of how proinflammatory cytokines contribute towards cardiac dysfunction and failure. In addition, how unchecked proinflammatory cytokines and their cross-talk with sympathetic system overrides the anti-inflammatory response underlying failure. The review offers insights on how TNFα and IL-6 contribute to cardiac dysfunction and failure. Furthermore, this provides a forum to begin the discussion on the cross-talk between sympathetic drive and proinflammatory cytokines and its determinant role in deleterious outcomes.

Proinflammatory Cytokines Mediate GPCR Dysfunction

Proinflammatory reaction by the body occurs acutely in response to injury that is considered primarily beneficial. However, sustained proinflammatory cytokines observed with chronic pathologies such as metabolic syndrome, cancer, and arthritis are detrimental and in many cases is a major cardiovascular risk factor. Proinflammatory cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor α (TNFα) have long been implicated in cardiovascular risk and considered to be a major underlying cause for heart failure (HF). The failure of the anti-TNFα therapy for HF indicates our elusive understanding on the dichotomous role of proinflammatory cytokines on acutely beneficial effects versus long-term deleterious effects. Despite these well-described observations, less is known about the mechanistic underpinnings of proinflammatory cytokines especially TNFα in pathogenesis of HF. Increasing evidence suggests the existence of an active cross-talk between the TNFα receptor signaling and G-protein-coupled receptors such as β-adrenergic receptor (βAR). Given that βARs are the key regulators of cardiac function, the review will discuss the current state of understanding on the role of proinflammatory cytokine TNFα in regulating βAR function.

Rapid negative inotropic effect induced by TNF-α in rat heart perfused related to PKC activation

Myocardial depression, frequently observed in septic shock, is mediated by circulating molecules such as cytokines. TNF-α appears to be the most important pro-inflammatory cytokine released during the early phase of a septic shock. It was previously shown that TNF-α had a negative inotropic effect on myocardium. Now, the aim of this study was to investigate the effects of the activation of PKC by TNF-α on heart function, and to determine if this cytokine could induce a decrease of membrane excitability. Isolated rat hearts (n = 6) were perfused with Tyrode solution containing TNF-α at 20 ng/ml during 30 min by using a Langendorff technique. Expressions of PKC-α and PKC-ε were analysed by western blot on membrane and cytosol proteins extracted from ventricular myocardium. Patch clamp was performed on freshly isolated cardiomyocytes (n = 8). Compared to control situation, 30 min of TNF-α perfusion led to cardiac dysfunction with a decrease of the heart rate (-83%), the force (-20%) and speed of relaxation (-18%) and the coronary flow (-25%). This is associated with an activation and a membrane targeting of both PKC-α and PKC-ε isoforms in ventricle with respectively +123% and +54% compared to control hearts. Nevertheless, TNF-α had no significant effect on voltage-gated sodium current (109.0%+/- 12.5) after addition of the cytokine when compared to control. These results showed that TNF-α had a negative inotropic effect on the isolated rat heart and can induce PKC activation leading to an impaired contractility of the heart. However the early heart dysfunction induced by the cytokine was not associated to a decrease of cardiomyocytes membrane excitability as it has been evidenced in skeletal muscle fibres.

Xenon is not superior to isoflurane on cardiovascular function during experimental acute pulmonary hypertension

BACKGROUND

Acute right ventricular afterload increase is a known perioperative challenge for the anaesthetic regime especially for patients with a compromised right ventricle. The accused negative inotropic action of volatile anaesthetics, with the exception of xenon, might be crucial for the adaptation of the right ventricle.

METHODS

Reversible pulmonary hypertension (mean pressure 40 mmHg) was induced by an infusion of the stable thromboxane A(2) analog U46619 in a porcine model (n = 35). The effects of 70 vol% xenon and 0.9 vol% isoflurane on biventricular function were studied by conductance catheter technique. Inflammation and myocardial injury was quantified using serum probes [tumour necrosis factor α (TNFα), interleukin 6 (IL-6), troponin] and myocardial tissue [B natriuretic peptide (BNP), TNFα, activated caspase 3] by enzyme-linked immunosorbance assays and reverse-transcription polymerase chain reaction.

RESULTS

After wash in of xenon global haemodynamic parameters remained stable whereas isoflurane caused a systemic vasodilation. This led to a significant decrease in mean arterial pressure in the isoflurane group whereas cardiac output remained stable. Both substances did not alter the biventricular contractility nor did they induce changes in preload for both ventricles. Xenon led to an additional increase in right ventricular afterload, whereas isoflurane reduced pulmonary vascular resistance. No effects on systemic inflammatory response and myocardial injury were found, whereas higher apoptosis rate and expression of BNP and IL-6 was determined in the right ventricle.

CONCLUSIONS

These results do not support the idea that xenon is more beneficial than isoflurane in right ventricular failure during pulmonary hypertension. Isoflurane did not compromise systolic ventricular function during acute PHT it only led to vasodilation in contrast to xenon.

Role of sphingosine kinase 1 in allergen-induced pulmonary vascular remodeling and hyperresponsiveness

BACKGROUND

Immunologic processes might contribute to the pathogenesis of pulmonary arterial hypertension (PAH), a fatal condition characterized by progressive pulmonary arterial remodeling, increased pulmonary vascular resistance, and right ventricular failure. Experimental allergen-driven lung inflammation evoked morphologic and functional vascular changes that resembled those observed in patients with PAH. Sphingosine kinase 1 (SphK1) is the main pulmonary contributor to sphingosine-1-phosphate (S1P) synthesis, a modulator of immune and vascular functions.

OBJECTIVE

We sought to investigate the role of SphK1 in allergen-induced lung inflammation.

METHODS

SphK1-deficient mice and C57Bl/6 littermates (wild-type [WT] animals) were subjected to acute or chronic allergen exposure.

RESULTS

After 4 weeks of systemic ovalbumin sensitization and local airway challenge, airway responsiveness increased less in SphK1(-/-) compared with WT mice, whereas pulmonary vascular responsiveness was greatly increased and did not differ between strains. Acute lung inflammation led to an increase in eosinophils and mRNA expression for S1P phosphatase 2 and S1P lyase in lungs of WT but not SphK1(-/-) mice. After repetitive allergen exposure for 8 weeks, airway responsiveness was not augmented in SphK1(-/-) or WT mice, but pulmonary vascular responsiveness was increased in both strains, with significantly higher vascular responsiveness in SphK1(-/-) mice compared with that seen in WT mice. Increased vascular responsiveness was accompanied by remodeling of the small and intra-acinar arteries.

CONCLUSION

: The data support a role for SphK1 and S1P in allergen-induced airway inflammation. However, SphK1 deficiency increased pulmonary vascular hyperresponsiveness, which is a component of PAH pathobiology. Moreover, we show for the first time the dissociation between inflammation-induced remodeling of the airways and pulmonary vasculature.

Cytokine-Induced Modulation of Cardiac Function

Cytokines act in an autocrine and/or paracrine fashion to induce a diverse variety of biological responses. Several cardiac diseases are associated with cytokine activation, and such activation significantly influences several physiologic parameters, including cardiac mechanical function. This review summarizes the current concepts regarding the modulation of myocardial function by cytokines and provides rationale for the sometimes-conflicting results in the literature regarding underlying mechanisms and patterns of dysfunction. Although traditionally considered cardiodepressant mediators, contractile responses are complex and bimodal, with an early response (within minutes) of variable direction, stimulatory or depressant, depending on the ambient physiologic milieu and relative contributions of the underlying signaling pathways that are activated. These pathways include sphingomyelinase-, nitric oxide (NO)-, and phospholipase A2-dependent signaling with resultant combined effects on contraction and the Ca2+ transient. This is subsequently followed by a profoundly cardiodepressant late response lasting hours to days, depending on the production of secondary mediators and the combined influence of NO generated from inducible NO synthase, reactive oxygen species, and alterations in beta-adrenergic receptor signaling. The interrelationships between these pathways and the time-dependence of their activation are important considerations in the evaluation of cytokine-dependent dysfunction during both acute cardiac injury and chronic cardiac pathologies.

Endotoxin-induced myocardial dysfunction: evidence for a role of sphingosine production

OBJECTIVE

To determine whether sphingomyelinase pathway activation would participate in myocardial depression induced by endotoxin.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Male Sprague-Dawley rats, isolated rat heart, and cardiac myocytes.

INTERVENTIONS

Cardiovascular function was evaluated in rats injected with saline, endotoxin (10 mg/kg, intravenously), and N-oleoylethanolamine (NOE; 10 mg/kg, intravenously). In ex vivo experiments, isolated rat hearts were perfused with endotoxin (5 microg/mL). For pharmacologic intervention, NOE (1 micromol/L) was admixed to the perfusate 20 mins before endotoxin. In in vitro experiments, ventricular myocytes were incubated with sphingosine (20 microM). Myocyte cell shortening and calcium transient were measured. Mitochondrial membrane potential was measured using the cationic dye tetramethylrhodamine methylester fluorescence technique.

MEASUREMENTS AND MAIN RESULTS

Endotoxin treatment at 4 hrs did not alter mean arterial pressure and abdominal blood flow compared with control rats. Left ventricle developed pressure (LVDP) and its first derivatives (i.e., maximal and minimal change in pressure over time [dP/dtmax and dP/dtmin]) were decreased after 4 hrs in endotoxin-treated rats compared with control rats. NOE (10 mg/kg) treatment largely prevented left ventricular systolic function alterations of endotoxin-treated hearts (n = 6 in each group). In isolated rat heart, endotoxin (5 microg/mL) caused increases in tumor necrosis factor-alpha perfusate concentration and delayed depression of LVDP, dP/dtmax, and dP/dtmin after 60 mins, which was partially abrogated in the presence of the ceramidase inhibitor NOE (1 micromol/L). Sphingosine (20 microM) caused decreases in cell fractional shortening, calcium transient, and mitochondrial membrane potential of cardiac myocytes.

CONCLUSION

These observations suggest that the sphingomyelinase pathway participates in endotoxin-induced myocardial depression.

Resident cardiac mast cells and ischemia-reperfusion injury

BACKGROUND

The intense inflammatory reaction following reperfusion of ischemic myocardium has been implicated as a factor in the extension of myocardial injury. One of the therapeutic goals of modern cardiology is to design strategies to limit the infarct size following myocardial infarction. A sound understanding of the inflammatory cascade that involves the release of various proinflammatory mediators from cardiac cells is necessary before a specific intervention is pursued.

OBSERVATION

Summarized is the role of resident cardiac mast cells, which are noted to release inflammatory mediators, in ischemia-reperfusion-induced myocardial injury. Various pharmacologic interventions, such as disodium cromoglycate and ketotifen, that stabilize cardiac mast cells, or agents such as chlorpheniramine and cetirizine that prevent their degranulation during ischemia and reperfusion, may prove to be potential therapeutic agents to limit or salvage ischemia-reperfusion-induced injury.

CONCLUSION

On the basis of the effects of histamine H1 antagonists, adrenoceptor blockers, cellular calcium and nitric oxide modulators, as well as inhibitors of phosphodiesterase and mitogen-activated protein kinase on mast cells, cardiac resident mast cells may represent a novel target for the development of cardioprotective agents.

Leukotriene-mediated coronary vasoconstriction and loss of myocardial contractility evoked by low doses of Escherichia coli hemolysin in perfused rat hearts

OBJECTIVE

hemolysin has been implicated as an important pathogenic factor in extraintestinal infections including sepsis. We investigated the effects of coronary administration of hemolysin on cardiac function in isolated rat hearts perfused at constant flow.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Isolated hearts from male Wistar rats.

INTERVENTIONS

Isolated hearts were perfused with purified hemolysin for 60 min.

MEASUREMENTS AND MAIN RESULTS

Low concentrations of the toxin in the perfusate (0.1-0.2 hemolytic units/mL) caused a dose-dependent coronary vasoconstriction with a marked increase in coronary perfusion pressure, which was paralleled by a decrease in left ventricular developed pressure (and the maximum rate of left ventricular pressure increase). Moreover, 0.2 hemolytic units/mL hemolysin evoked ventricular fibrillation within 10 mins of toxin application. These events were accompanied by the liberation of leukotrienes (LTC4, LTD4, LTE4, and LTB4), thromboxane A2, prostaglandin I2, and the cell necrosis markers lactate dehydrogenase and creatine kinase into the recirculating perfusate. The lipoxygenase inhibitor MK-886 fully blocked the toxin-induced coronary vasoconstrictor response and the loss of myocardial contractility and reduced the release of lactate dehydrogenase and creatine kinase. In contrast to this, the cyclooxygenase inhibitor indomethacin was entirely ineffective. In addition, hemolysin elicited an increase in heart weight and left ventricular end-diastolic pressure, the latter again being suppressed by MK-886.

CONCLUSIONS

Low doses of hemolysin cause strong coronary vasoconstriction, linked with loss of myocardial performance, release of cell injury enzymes, and electrical instability, with all events being largely attributable to toxin-elicited leukotriene generation in the coronary vasculature. Bacterial exotoxins such as hemolysin thus may be implicated in the cardiac abnormalities encountered in septic shock.

Haemodynamic effects of endothelin receptor antagonist, tezosentan, in tumour necrosis factor-alpha treated anaesthetized rats

Administration of tumour necrosis factor-alpha (TNF-alpha) produces progressive reduction in cardiac output (CO) by affecting preload, afterload and cardiac contractility. We have examined the effect of an endothelin receptor antagonist, tezosentan (1, 3 or 10 mg/kg), on CO, heart rate (HR), blood pressure (BP), mean circulatory filling pressure (P(mcf)), resistance to venous return (RVR), arterial resistance (AR), dP/dt, stroke volume (SV), plasma levels of NO(2)(-)/NO(3)(-), and inducible nitric oxide synthase (iNOS) activity in lungs, ex vivo, following treatment with TNF-alpha (30 microg/kg) in anaesthetized rats. Treatment with TNF-alpha alone resulted in significant reduction in CO (40+/-4%), dP/dt (24+/-2%), P(mcf) (24+/-2%), BP (21+/-3%) and SV (38+/-5%) ( n=6; mean +/- SEM), and significant increases in RVR (38+/-9%) and AR (45+/-6%). There were no significant changes in HR or in plasma levels of NO(2)(-)/NO(3)(-) in animals treated with TNF-alpha but there was a modest but significant increase in iNOS activity. Tezosentan alone did not have any effect on haemodynamics, plasma levels of NO(2)(-)/NO(3)(-) or iNOS activity. Tezosentan at the highest dose abolished the effects of TNF-alpha on dP/dt, AR, and RVR. In animals treated with a combination of TNF-alpha and highest dose of tezosentan CO, P(mcf), BP, and SV were reduced by 28+/-5%, 16+/-3%, 21+/-4%, and 27+/-5%, respectively. Tezosentan was able to inhibit the negative impact of TNF-alpha on AR and dP/dt but not on P(mcf). It is likely that the negative impact of TNF-alpha on CO in tezosentan-treated animals could be entirely attributed to reduction in preload.

Role of ceramide in TNF-alpha-induced impairment of endothelium-dependent vasorelaxation in coronary arteries

The present study tested the hypothesis that ceramide, a sphingomylinase metabolite, serves as an second messenger for tumor necrosis factor-alpha (TNF-alpha) to stimulate superoxide production, thereby decreasing endothelium-dependent vasorelaxation in coronary arteries. In isolated bovine small coronary arteries, TNF-alpha (1 ng/ml) markedly attenuated vasodilator responses to bradykinin and A-23187. In the presence of N(G)-nitro-L-arginine methyl ester, TNF-alpha produced no further inhibition on the vasorelaxation induced by these vasodilators. With the use of 4,5-diaminofluorescein diacetate fluorescence imaging analysis, bradykinin was found to increase nitric oxide (NO) concentrations in the endothelium of isolated bovine small coronary arteries, which was inhibited by TNF-alpha. Pretreatment of the arteries with desipramine (10 microM), an inhibitor of acidic sphingomyelinase, tiron (1 mM), a superoxide scavenger, and polyethylene glycol-superoxide dismutase (100 U/ml) largely restored the inhibitory effect of TNF-alpha on bradykinin- and A-23187-induced vasorelaxation. In addition, TNF-alpha activated acidic sphingomyelinase and increased ceramide levels in coronary endothelial cells. We conclude that TNF-alpha inhibits NO-mediated endothelium-dependent vasorelaxation in small coronary arteries via sphingomyelinase activation and consequent superoxide production in endothelial cells.

Sphingosine modulates myocyte electrophysiology, induces negative inotropy, and decreases survival after myocardial ischemia

Contractility studies in isolated feline myocytes have demonstrated that sphingosine, a metabolite stimulated by tumor necrosis factor (TNF) binding, decreases intracellular calcium release and depresses inotropic activity. This study investigated the electrophysiologic effects of sphingosine in isolated cat myocytes as well as the cardiodynamic consequence of TNF, sphingosine, and its metabolic precursors in vivo. In cat myocytes, sphingosine markedly decreased action potential duration, lowered action potential plateau, and inhibited L-type calcium current (I(Ca-L)). After administration of TNF, sphingomyelin, C2-ceramide, or sphingosine, only C2-ceramide and sphingosine depressed cardiac function in normal rats. Negative inotropic effects of C2-ceramide were attenuated by N-oleoylethanolamine (NOE), a ceramidase inhibitor that blocks sphingosine formation. Rats pretreated with NOE before undergoing 30 min of acute regional myocardial ischemia followed by 150 min of reperfusion exhibited improved survival. Most deaths could be attributed to acute pump failure accompanied by bradycardia. Myocardial infarct size and peak serum TNF were not different between NOE- and vehicle-treated groups (3,908 +/- 1097 pg/ml and 3,027 +/- 846 pg/ml, respectively). These results indicate that sphingosine exerts direct inhibitory effects on the action potential and I(Ca-L) in isolated feline myocytes, consistent with previously reported sphingosine activity on I(Ca-L) in isolated rat myocytes. The in vivo study suggests that reducing sphingosine production with N-oleoylethanolamine attenuates cardiodepression and can improve overall survival after ischemic injury. Clearly, agents that modulate sphingosine production limit cardiodepression and may provide a therapeutic benefit in clinical conditions of myocardial inflammatory injury.

Biosynthesis of constitutive nitric oxide synthase-derived nitric oxide attenuates coronary vasoconstriction and myocardial depression in a model of septic heart failure induced by Staphylococcus aureus alpha-toxin

OBJECTIVE

Myocardial depression, which frequently occurs in the course of septic shock, has been attributed to the cardiodepressant properties of nitric oxide (NO) generated by either the inducible NO synthase (iNOS) or the constitutive isoform (cNOS). We have previously demonstrated that alpha-toxin from Staphylococcus aureus induces thromboxane-mediated vasoconstriction accompanied by severe cardiodepression in isolated rat hearts. In the present study, we investigated the role of NO in the alpha-toxin-induced vascular and contractile abnormalities.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Isolated hearts from male Wistar rats.

INTERVENTIONS

Isolated hearts were perfused with purified staphylococcal alpha-toxin for 60 mins.

MEASUREMENTS AND MAIN RESULTS

At a concentration of 0.25 and 0.5 microg/mL, alpha-toxin induced a rise in coronary perfusion pressure, depressed myocardial contractility, and caused edema formation. Simultaneously, a time- and dose-dependent rapid release of NO into the perfusate was noted as quantified by a chemiluminescence technique. L-NMMA, a nonselective inhibitor of NOS, but not PBITU, an iNOS-selective inhibitor, blocked NO synthesis, markedly increased the rise in coronary perfusion pressure and the loss in contractility, and enhanced edema formation in response to alpha-toxin. In contrast, zaprinast, a selective inhibitor of phosphodiesterase type V that is used for stabilization of cyclic guanosine monophosphate, attenuated the toxin-induced coronary vasoconstrictor response and the myocardial depression. L-arginine, the substrate of NOS, had similar, yet less potent, effects as zaprinast and slightly increased the release of NO caused by alpha-toxin. Immunohistochemical analysis of the myocardium at the end of the perfusion period demonstrated a positive staining for cNOS but not for iNOS. In addition, no up-regulation of iNOS mRNA was detected in the tissue of toxin-exposed hearts.

CONCLUSIONS

Staphylococcal alpha-toxin provokes NO biosynthesis via activation of cNOS in rat hearts. NO partly antagonizes the deleterious effects of this pathogenicity factor on coronary vasoregulation and myocardial performance.

Effects of tumor necrosis factor-alpha on basal and stimulated endothelium-dependent vasomotion in human resistance vessel

The aim of this study was to determine whether tumor necrosis factor (TNF)-alpha would impair basal and stimulated endothelium-dependent vasomotion in human resistance vessel. Changes in baseline and acetylcholine (ACh)-induced forearm vascular resistance (FVR) were measured plethysmographically before and after a low-dose intraarterial forearm infusion of TNF-alpha according to the following three protocols in healthy volunteers. In the condition without pretreatment, basal FVR was significantly increased by TNF-alpha (from 30.5 +/- 4.8 to 39.9 +/- 5.9 units; p < 0.01), whereas ACh-induced minimal FVR did not differ between pre- and post-TNF-alpha states. In the condition after pretreatment with the cyclooxygenase inhibitor acetylsalicylic acid, although the vascular effects of TNF-alpha on basal FVR appeared to be blocked (37.1 +/- 5.3 vs. 37.6 +/- 5.2; NS), ACh-induced minimal FVR did not differ between pre- and post-TNF-alpha states. In the condition after pretreatment with the nitric oxide (NO) synthase inhibitor N(G)-monomethyl-L-arginine, the vascular effect of TNF-alpha on basal FVR was diminished, and the ACh-induced maximal dilatory response was significantly blunted after TNF-alpha compared with before TNF-alpha (minimal FVR: 30.4 +/- 12.0 vs. 12.3 +/- 4.2 units; p < 0.05). These findings suggest that brief exposure of the human forearm resistance artery to TNF-alpha may increase basal bioavailability of the vasoconstrictor prostaglandin and reduce basal bioavailability of NO. In the stimulated condition, TNF-alpha-induced vascular dysfunction may be overwhelmed by increased NO bioavailability in healthy humans.

Blood product use in cardiac revascularization: comparison of on- and off-pump techniques

BACKGROUND

Cardiac revascularization on a beating heart avoids the side effects of cardiopulmonary bypass (eg, neurologic injury, hemodilution, and coagulopathy). We examined perioperative bleeding and use of blood products during coronary artery bypass grafting using either on-pump or off-pump techniques.

METHOD

The charts of 126 patients who had coronary artery bypass grafting were reviewed. Data from 66 patients revascularized off pump and 60 patients with cardiopulmonary bypass (on pump) were analyzed using unpaired Student's t test.

RESULTS

Average age was 62.5 years in either group. More patients received heparin preoperatively in the off-pump group that resulted in mild elevation of preoperative partial thromboplastin time and activated clotting time (40.4 +/- 2.9 seconds and 150.1 +/- 5.3 seconds, respectively). However, the off-pump group had less perioperative (intraoperative or postoperative) bleeding (2312 +/- 212 mL versus 3251 +/- 155 mL, p < 0.05) and required fewer blood products compared with the on-pump group. Hemoglobin and platelets decreased more in the conventional on-pump group.

CONCLUSIONS

Avoiding cardiopulmonary bypass decreases perioperative bleeding and, consequently, reduces the use of blood products after coronary artery bypass grafting, which might result in fewer transfusion-related complications.

Ceramide-induced vasorelaxation: An inhibitory action on protein kinase C

Experiments were designed to examine the role of sphingosine, PP2A phosphatases, and protein kinase C (PKC) inhibition in mediating the vasodilatory effects of ceramide in rat thoracic aorta. Sphingosine did not cause vasorelaxation, and oleoylethanol-amine, a ceramidase inhibitor, did not affect sphingomyelinase-induced relaxation. Okadaic acid potentiated the relaxation response to ceramide. These observations rule out involvement of sphingosine and PP2A phosphatases in mediating ceramide-induced relaxation. Sphingomyelinase attenuated contractile and single-cell intracellular calcium responses to phorbol ester. Chelerythrine incubation potentiated the relaxation response to ceramide. These observations support a role for PKC inhibition in mediating the vasodilatory effects of ceramide.

Effects of tumour necrosis factor-alpha on left ventricular function in the rat isolated perfused heart: possible mechanisms for a decline in cardiac function

1. The cardiac depressant actions of TNF were investigated in the isolated perfused rat heart under constant flow (10 ml min(-1)) and constant pressure (70 mmHg) conditions, using a recirculating (50 ml) mode of perfusion. 2. Under constant flow conditions TNF (20 ng ml(-1)) caused an early (< 25 min) decrease in left ventricular developed pressure (LVDP), which was maintained for 90 min (LVDP after 90 min: control vs TNF; 110 +/- 4 vs 82 +/- 10 mmHg, P < 0.01). 3. The depression in cardiac function seen with TNF under constant flow conditions, was blocked by the ceramidase inhibitor N-oleoylethanolamine (NOE), 1 microM, (LVDP after 90 min: TNF vs TNF with NOE; 82 +/- 10 vs 11 +/- 5 mmHg, P < 0.05). 4. In hearts perfused at constant pressure, TNF caused a decrease in coronary flow rate (change in flow 20 min after TNF: control vs TNF; -3.0 +/- 0.9 vs -8.7 +/- 1.2 ml min(-1), P < 0.01). This was paralleled by a negative inotropic effect (change in LVDP 20 min after TNF: control vs TNF; -17 +/- 7 vs -46 +/- 6 mmHg, P < 0.01). The decline in function was more rapid and more severe than that seen under conditions of constant flow. 5. These data indicate that cardiac function can be disrupted by TNF on two levels, firstly via a direct, ceramidase dependant negative inotropic effect, and secondly via an indirect coronary vasoconstriction.