Anti-tumor necrosis factor-alpha prevents decreased ventricular contractility in endotoxemic pigs

Regulatory role of the TLR4/JNK signaling pathway in sepsis‑induced myocardial dysfunction

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and is a leading cause of mortality worldwide. Myocardial dysfunction is associated with poor prognosis in patients with sepsis and contributes to a high risk of mortality. However, the pathophysiological mechanisms underlying sepsis-induced myocardial dysfunction are not completely understood. The aim of the present study was to investigate the role of toll-like receptor 4 (TLR4)/c-Jun N-terminal kinase (JNK) signaling in pro-inflammatory cytokine expression and cardiac dysfunction during lipopolysaccharide (LPS)-induced sepsis in mice. C57BL/6 mice were pretreated with TAK-242 or saline for 1 h and then subjected to LPS (12 mg/kg, intraperitoneal) treatment. Cardiac function was assessed using an echocardiogram. The morphological changes of the myocardium were examined by hematoxylin and eosin staining and transmission electron microscopy. The serum protein levels of cardiac troponin I (cTnI) and tumor necrosis factor-α (TNF-α) were determined by an enzyme-linked immunosorbent assay (ELISA). The TLR4 and JNK mRNA levels were analyzed via reverse transcription-quantitative PCR. TLR4, JNK and phosphorylated-JNK protein levels were measured by western blotting. In response to LPS, the activation of TLR4 and JNK in the myocardium was upregulated. There were significant increases in the serum levels of TNF-α and cTnI, as well as histopathological changes in the myocardium and suppressed cardiac function, following LPS stimulation. Inhibition of TLR4 activation using TAK-242 led to a decrease in the activation of JNK and reduced the protein expression of TNF-α in plasma, and alleviated histological myocardial injury and improved cardiac function during sepsis in mice. The present data suggested that the TLR4/JNK signaling pathway played a critical role in regulating the production of pro-inflammatory cytokines and myocardial dysfunction induced by LPS.

Melatonin alleviates lipopolysaccharide-induced myocardial injury by inhibiting inflammation and pyroptosis in cardiomyocytes

Background

Melatonin (MT) has been shown to protect against various cardiovascular diseases. However, the effect of MT on lipopolysaccharide (LPS)-induced myocardial injury is poorly understood. This study aims to evaluate the effects of MT on LPS-induced myocardial injury in vitro.

Methods

H9C2 cells were divided into a control group, MT group, LPS group, and MT + LPS group. The control group was treated with sterile saline solution, the LPS group received 8 µg/mL LPS for 24 h, MT + LPS cells were pretreated with 200 µmol/L MT for 2 h then with 8 µg/mL LPS for 24 h, and the MT group received only 200 µmol/L MT for 2 h. The CCK-8 assay and lactate dehydrogenase (LDH) activity assay were used to analyze cell viability and LDH release, respectively. Intracellular reactive oxygen species (ROS) and the rate of pyroptosis were measured using the fluorescent probe dichloro-dihydro-fluorescein diacetate (DCFH-DA) and propidium iodide (PI) staining, respectively. The cell supernatants were used to measure the levels of inflammatory cytokines, including IL-6, TNF-α, and IL-1β by enzyme-linked immunosorbent assay (ELISA). The protein levels of iNOS, COX-2, NF-κB, p-NF-κB, NLRP3, caspase-1, and GSDMD were detected by western blot.

Results

MT pretreatment significantly improved LPS-induced myocardial injury by inhibiting inflammation and pyroptosis in H9C2 cells. Moreover, MT inhibited the activation of the NF-κB pathway, and reduced the expression of inflammation-related proteins (iNOS and COX-2), and pyroptosis-related proteins (NLRP3, caspase-1, and GSDMD).

Conclusions

Our data suggests that MT can alleviate LPS-induced myocardial injury, providing novel insights into the treatment of sepsis-induced myocardial dysfunction.

The extract from Agkistrodon halys venom protects against lipopolysaccharide (LPS)-induced myocardial injury

BACKGROUND

Snake venoms contain various bioactive constituents which possess potential therapeutic effects. The aim of this work was to investigate the effect of the extract from Agkistrodon halys venom on lipopolysaccharide (LPS)-induced myocardial injury.

METHODS

Thirty male Sprague-Dawley rats were randomly assigned to three groups (10 rats per group): control group, LPS group and LPS + extract group. Rats in control and the LPS groups were intravenously injected with sterile saline solution, and rats in the LPS + extract group with the extract. After 2 h, rats of the control group were intraperitoneally injected sterile saline solution, and rats in the LPS and the LPS + extract groups were treated with LPS (20 mg per kg body weight). Levels of creatine kinase (CK) and lactate dehydrogenase (LDH) in serum were determined. Anti-inflammation of the extract was analyzed via determination of TNF-α and IL-6 in serum, and expression of TNF-α, IL-6, COX-2 and p-ERK protein in hearts. Heme oxygenase-1 (HO-1) and p-NF-κB protein expression in hearts, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in serum were used to evaluate the anti-oxidative properties of the extract.

RESULTS

Extract pretreatment significantly decreased the level of serum CK and LDH, reduced the generation of inflammatory cytokines such as TNF-α and IL-6, and also reduced serum level of MDA in the LPS + extract group compared with the LPS group. In addition, the extract increased SOD activity in serum, HO-1 protein expression in hearts, and decreased TNF-α, IL-6, COX-2, p-NF-κB and p-ERK1/2 protein expression.

CONCLUSION

Our results suggested that beneficial effect of this extract might be associated with an improved anti-oxidation and anti-inflammatory effect via downregulation of NF-κB/COX-2 signaling by activating HO-1/CO in hearts.

Gas6 attenuates lipopolysaccharide‑induced TNF‑α expression and apoptosis in H9C2 cells through NF‑κB and MAPK inhibition via the Axl/PI3K/Akt pathway

Therapeutic agents used to treat sepsis‑induced cardiac dysfunction are designed to suppress tumor necrosis factor (TNF)‑α release and inhibit cell apoptosis. Exogenous administration of growth arrest‑specific 6 (Gas6) exerts several biological and pharmacological effects; however, the role of Gas6 in sepsis‑induced myocardial dysfunction remains unclear. In this study, H9C2 cardiomyocytes were stimulated with LPS (10 µg/ml) to mimic septic cardiac dysfunction and Gas6 (100 ng/ml) was applied exogenously. Subsequently, mitogen‑activated protein kinase (MAPK) and nuclear factor (NF)‑κB activation, TNF‑α expression, and apoptosis in the presence or absence of TP‑0903 (15 nM) and Wortmannin (3 nM) were evaluated. The morphological alterations of H9C2 cells were visualized by phase‑contrast microscopy. Cell viability was determined using the Cell Counting kit 8 assay and lactate dehydrogenase release, and TNF‑α release was analyzed by ELISA analysis. Cell apoptosis was analyzed by flow cytometry and TUNEL assay. Nuclear morphological alterations were detected by Hoechst staining and caspase‑3 activity was measured using biochemical methods. The expression levels of Bax and Bcl‑2, and the phosphorylation and expression levels of Axl, Akt, IκB‑α, p65, c‑Jun N‑terminal protein kinase (JNK), extracellular signal‑regulated kinase (ERK) and p38 were determined by western blotting. Furthermore, immunofluorescence analysis was performed to visualize translocation of NF‑κB p65. The results demonstrated that Gas6 suppressed TNF‑α release and inhibited cell apoptosis, and attenuated nuclear factor (NF)‑κB and mitogen‑activated protein kinase (MAPK) activation via the Axl/PI3K/Akt pathway. Furthermore, the cardioprotective properties of Gas6 on the suppression of LPS‑induced TNF‑α release and apoptosis were abolished by treatment with TP‑0903 (an Axl inhibitor) and Wortmannin (a PI3K inhibitor). Pretreatment with TP‑0903 and Wortmannin abrogated the effects of Gas6 on phosphorylated‑IκB‑α, IκB‑α, NF‑κB, ERK1/2, JNK and p38 MAPK. These findings suggested that activation of Axl/PI3K/Akt signaling by Gas6 may inhibit LPS‑induced TNF‑α expression and apoptosis, as well as MAPK and NF‑κB activation.

Phenylephrine Attenuated Sepsis-Induced Cardiac Inflammation and Mitochondrial Injury Through an Effect on the PI3K/Akt Signaling Pathway

OBJECTIVE

To investigate whether phenylephrine (PE) inhibits sepsis-induced cardiac dysfunction, cardiac inflammation, and mitochondrial injury through the PI3K/Akt signaling pathway.

METHODS

A rat model of sepsis was established by cecal ligation and puncture. PE and/or wortmannin (a PI3K inhibitor) were administered to investigate the role of PI3K/Akt signaling in mediating the effects of PE on inhibiting sepsis-induced cardiac dysfunction, cardiac inflammation, and mitochondrial injury. Hematoxylin-eosin staining, echocardiography, and Langendorff system were used to examine the myocardial injury and function. The concentrations of TNF-α and IL-6 were analyzed by enzyme-linked immunosorbent assay. Intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), myeloperoxidase, mitochondria-related fusion/fission proteins, and PI3K/Akt signaling pathway-associated proteins were analyzed by Western blotting.

RESULTS

PE improved the cardiac function and survival in septic rats. PE decreased TNF-α, IL-6, ICAM-1, VCAM-1, and myeloperoxidase contents in the myocardium of septic rats. Meanwhile, PE increased the fusion-related proteins and decreased the fission-related proteins in the myocardial mitochondria of septic rats. On the other hand, PE activated the PI3K/Akt signaling pathway in the cecal ligation and puncture-treated rats, and all the protective effects of PE were abolished by wortmannin.

CONCLUSIONS

PE attenuated sepsis-induced cardiac dysfunction, cardiac inflammation, and mitochondrial injury through the PI3K/Akt signaling pathway.

Pathophysiology of Septic Shock

Fundamental features of septic shock are vasodilation, increased permeability, hypovolemia, and ventricular dysfunction. Vasodilation owing to increased nitric oxide and prostaglandins is treated with vasopressors (norepinephrine first). Increased permeability relates to several pathways (Slit/Robo4, vascular endothelial growth factor, angiopoietin 1 and 2/Tie2 pathway, sphingosine-1-phosphate, and heparin-binding protein), some of which are targets for therapies. Hypovolemia is common and crystalloid is recommended for fluid resuscitation. Cardiomyocyte-inflammatory interactions decrease contractility and dobutamine is recommended to increase cardiac output. There is benefit in decreasing heart rate in selected patients with esmolol. Ivabradine is a novel agent for heart rate reduction without decreasing contractility.

Low tidal volume ventilation ameliorates left ventricular dysfunction in mechanically ventilated rats following LPS-induced lung injury

Background

High tidal volume ventilation has shown to cause ventilator-induced lung injury (VILI), possibly contributing to concomitant extrapulmonary organ dysfunction. The present study examined whether left ventricular (LV) function is dependent on tidal volume size and whether this effect is augmented during lipopolysaccharide(LPS)-induced lung injury.

Methods

Twenty male Wistar rats were sedated, paralyzed and then randomized in four groups receiving mechanical ventilation with tidal volumes of 6 ml/kg or 19 ml/kg with or without intrapulmonary administration of LPS. A conductance catheter was placed in the left ventricle to generate pressure-volume loops, which were also obtained within a few seconds of vena cava occlusion to obtain relatively load-independent LV systolic and diastolic function parameters. The end-systolic elastance / effective arterial elastance (Ees/Ea) ratio was used as the primary parameter of LV systolic function with the end-diastolic elastance (Eed) as primary LV diastolic function.

Results

Ees/Ea decreased over time in rats receiving LPS (p = 0.045) and high tidal volume ventilation (p = 0.007), with a lower Ees/Ea in the rats with high tidal volume ventilation plus LPS compared to the other groups (p < 0.001). Eed increased over time in all groups except for the rats receiving low tidal volume ventilation without LPS (p = 0.223). A significant interaction (p < 0.001) was found between tidal ventilation and LPS for Ees/Ea and Eed, and all rats receiving high tidal volume ventilation plus LPS died before the end of the experiment.

Conclusions

Low tidal volume ventilation ameliorated LV systolic and diastolic dysfunction while preventing death following LPS-induced lung injury in mechanically ventilated rats. Our data advocates the use of low tidal volumes, not only to avoid VILI, but to avert ventilator-induced myocardial dysfunction as well.

Advances in Sepsis Research

Recent research has identified promising targets for therapeutic interventions aimed at modulating the inflammatory response in sepsis. Herein, the authors describe mechanisms involved in the clearance of pathogen toxin from the circulation and potential interventions aimed at enhancing clearance mechanisms. The authors also describe advances in the understanding of the innate immune response as potential therapeutic targets. Finally, novel potential treatment strategies aimed at decreasing vascular leak are discussed.

Enhanced monocyte chemoattractant protein-1 production in aging mice exaggerates cardiac depression during endotoxemia

Introduction

Endotoxemia and the systemic inflammatory response syndrome have a significant impact on post-surgery outcome, particularly in the elderly. The cytokine response to endotoxin is altered by aging. We tested the hypothesis that vulnerability to endotoxemic cardiac depression increases with aging due to age-related augmentation of myocardial inflammatory responses.

Methods

Adult (4 to 6 months) and old (20 to 22 months) C57/BL6 mice were treated with endotoxin (0.5 mg/kg, iv). Left ventricle (LV) function was assessed using a microcatheter system. Chemokines and cytokines in plasma and myocardium were analyzed by enzyme-linked immunosorbent assay (ELISA). Mononuclear cells in the myocardium were examined using immunofluorescence staining.

Results

Old mice displayed worse LV function (cardiac output: 3.0 ± 0.2 mL/min versus 4.4 ± 0.3 mL/min in adult mice) following endotoxin treatment. The exaggerated cardiac depression in old mice was associated with higher levels of monocyte chemoattractant protein-1 (MCP-1) and keratinocyte chemoattractant (KC) in plasma and myocardium, greater myocardial accumulation of mononuclear cells, and greater levels of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β) and interleukin 6 (IL-6) in plasma and myocardium. Neutralization of MCP-1 resulted in greater reductions in myocardial mononuclear cell accumulation and cytokine production, and greater improvement in LV function in old mice while neutralization of KC had a minimal effect on LV function.

Conclusion

Old mice have enhanced inflammatory responses to endotoxemia that lead to exaggerated cardiac functional depression. MCP-1 promotes myocardial mononuclear cell accumulation and cardiodepressant cytokines production, and plays an important role in the endotoxemic cardiomyopathy in old mice. The findings suggest that special attention is needed to protect the heart in the elderly with endotoxemia.

α₁ adrenoceptor activation by norepinephrine inhibits LPS-induced cardiomyocyte TNF-α production via modulating ERK1/2 and NF-κB pathway

Cardiomyocyte tumour necrosis factor α (TNF-α) production contributes to myocardial depression during sepsis. This study was designed to observe the effect of norepinephrine (NE) on lipopolysaccharide (LPS)-induced cardiomyocyte TNF-α expression and to further investigate the underlying mechanisms in neonatal rat cardiomyocytes and endotoxaemic mice. In cultured neonatal rat cardiomyocytes, NE inhibited LPS-induced TNF-α production in a dose-dependent manner. α₁- adrenoceptor (AR) antagonist (prazosin), but neither β₁- nor β₂-AR antagonist, abrogated the inhibitory effect of NE on LPS-stimulated TNF-α production. Furthermore, phenylephrine (PE), an α₁-AR agonist, also suppressed LPS-induced TNF-α production. NE inhibited p38 phosphorylation and NF-κB activation, but enhanced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and c-Fos expression in LPS-treated cardiomyocytes, all of which were reversed by prazosin pre-treatment. To determine whether ERK1/2 regulates c-Fos expression, p38 phosphorylation, NF-κB activation and TNF-α production, cardiomyocytes were also treated with U0126, a selective ERK1/2 inhibitor. Treatment with U0126 reversed the effects of NE on c-Fos expression, p38 mitogen-activated protein kinase (MAPK) phosphorylation and TNF-α production, but not NF-κB activation in LPS-challenged cardiomyocytes. In addition, pre-treatment with SB202190, a p38 MAPK inhibitor, partly inhibited LPS-induced TNF-α production in cardiomyocytes. In endotoxaemic mice, PE promoted myocardial ERK1/2 phosphorylation and c-Fos expression, inhibited p38 phosphorylation and IκBα degradation, reduced myocardial TNF-α production and prevented LPS-provoked cardiac dysfunction. Altogether, these findings indicate that activation of α₁-AR by NE suppresses LPS-induced cardiomyocyte TNF-α expression and improves cardiac dysfunction during endotoxaemia via promoting myocardial ERK phosphorylation and suppressing NF-κB activation.

The effects of tumor necrosis factor-alpha on systolic and diastolic function in rat ventricular myocytes

The proinflammatory cytokine tumor necrosis factor-alpha (TNF-α) is associated with myocardial dysfunction observed in sepsis and septic shock. There are two fundamental components to this dysfunction. (1) systolic dysfunction; and (2) diastolic dysfunction. The aim of these experiments was to determine if any aspect of whole-heart dysfunction could be explained by alterations to global intracellular calcium ([Ca²⁺]_i), contractility, and [Ca²⁺]_i handling, by TNF-α, at the level of the individual rat myocyte. We took an integrative approach to simultaneously measure [Ca²⁺]_i, contractility and sarcolemmal Ca fluxes using the Ca indicator fluo-3, video edge detection, and the perforated patch technique, respectively. All experiments were performed at 37°C. The effects of 50 ng/mL TNF-α were immediate and sustained. The amplitude of systolic [Ca²⁺]_i was reduced by 31% and systolic shortening by 19%. Diastolic [Ca²⁺]_i, myocyte length and relaxation rate were not affected, nor were the activity of the [Ca²⁺]_i removal mechanisms. The reduction in systolic [Ca²⁺]_i was associated with a 14% reduction in sarcoplasmic reticulum (SR) content and a 11% decrease in peak L-type Ca current (I_Ca-L). Ca influx was decreased by 7% associated with a more rapid I_Ca-L inactivation. These data show that at the level of the myocyte, TNF-α reduces SR Ca which underlies a reduction in systolic [Ca²⁺]_i and thence shortening. Although these findings correlate well with aspects of systolic myocardial dysfunction seen in sepsis, in this model, acutely, TNF-α does not appear to provide a cellular mechanism for sepsis-related diastolic myocardial dysfunction.

Inflammation in myocardial diseases

Inflammatory processes underlie a broad spectrum of conditions that injure the heart muscle and cause both structural and functional deficits. In this article, we address current knowledge regarding 4 common forms of myocardial inflammation: myocardial ischemia and reperfusion, sepsis, viral myocarditis, and immune rejection. Each of these pathological states has its own unique features in pathogenesis and disease evolution, but all reflect inflammatory mechanisms that are partially shared. From the point of injury to the mobilization of innate and adaptive immune responses and inflammatory amplification, the cellular and soluble mediators and mechanisms examined in this review will be discussed with a view that both beneficial and adverse consequences arise in these human conditions.

Translational research in sepsis - an ultimate challenge?

In the era of evidence-based medicine, large, randomized, controlled, multicenter studies represent the "summit of evidence". In contrast to specialties like cardiology, the majority of randomized, controlled trials in critical care medicine, however, have failed to demonstrate a survival benefit; notably, despite encouraging results from experimental and phase-II clinical studies. The difficulty in translating our theoretical knowledge into successful multicenter randomized, controlled trials and subsequent treatment recommendations may represent one reason, why the mortality of septic shock still averages between 40-60%, although our knowledge about the underlying pathophysiology has considerably increased and international guidelines have widely been implemented. The present article elucidates some of the difficulties in translating research from bench to bedside.

Effect of erythromycin on biological activities induced by clostridium perfringens alpha-toxin

Clostridium perfringens alpha-toxin, an important agent of gas gangrene with inflammatory myopathies, possesses lethal, hemolytic, and necrotic activities. Here, we show that alpha-toxin-induced lethality in mice was inhibited by i.v. preadministration of erythromycin (ERM). Administration of ERM resulted in a drastic reduction in the release of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 and systemic hemolysis induced by alpha-toxin, whereas the administration of kitasamycin did not. Furthermore, the lethality and systemic hemolysis caused by alpha-toxin were blocked by the preinjection of anti-TNF-alpha, but not the anti-IL-1beta- or anti-IL-6-antibody. In addition, TNF-alpha-deficient mice were resistant to alpha-toxin, indicating that TNF-alpha plays an important role in the lethality. ERM inhibited the toxin-induced release of TNF-alpha from neutrophils and phosphorylation of toropomyosin-related kinase receptor A (TrkA) and extracellular-regulated kinase (ERK) 1/2. Furthermore, K252a, a TrkA inhibitor, and PD98059 (2'-amino-3'-methoxyflavone), an ERK1/2 inhibitor, inhibited the toxin-induced release of TNF-alpha from neutrophils. The observation shows that the toxin-induced release of TNF-alpha is dependent on the activation of ERK/mitogen-activated protein kinase signal transduction via TrkA in neutrophils and that ERM specifically blocks the toxin-induced events through the activation of neutrophils.

S100A8 and S100A9 mediate endotoxin-induced cardiomyocyte dysfunction via the receptor for advanced glycation end products

Cardiovascular dysfunction as a result of sepsis is the leading cause of death in the critically ill. Cardiomyocytes respond to infectious pathogens with a Toll-like receptor-initiated proinflammatory response in conjunction with a decrease in contractility, although the downstream events linking Toll-like receptor activation and reduced cardiac contractility remain to be elucidated. Using microarray analysis of cardiac tissue exposed to systemic lipopolysaccharide (LPS), we discovered that 2 small calcium-regulating proteins (S100A8 and S100A9) are highly upregulated. HL-1 cardiomyocytes, isolated primary cardiomyocytes, and live mice were exposed to LPS, whereas beating HL-1 cells had S100A8 and S100A9 overexpressed and their calcium flux quantified. Using in vivo microbubble technology, we delivered S100A8 and S100A9 to normal mouse hearts; using the same technology, we inhibited S100A9 production in mouse hearts and subsequently exposed them to LPS. Coimmunoprecipitation of S100A8 and S100A9 identified interaction with RAGE (the receptor for advanced glycation end products), the cardiac function and postreceptor signaling of which were investigated. HL-1 cardiomyocytes, isolated primary cardiomyocytes, and whole hearts exposed to LPS have large increases in S100A8 and S100A9. Cardiac overexpression of S100A8 and S100A9 led to a RAGE-dependent decrease in calcium flux and, in the intact mouse, to a decreased cardiac ejection fraction, whereas knockdown of S100A9 attenuated LPS-induced cardiac dysfunction. Cardiomyocytes exposed to LPS express S100A8 and S100A9, leading to a RAGE-mediated decrease in cardiomyocyte contractility. This finding provides a novel mechanistic link between circulating pathogen-associated molecular products and subsequent cardiac dysfunction.

Toxin gamma from Tityus serrulatus scorpion venom plays an essential role in immunomodulation of macrophages

Fraction number II obtained from Sephadex G-50 gel filtration of the soluble venom from the Brazilian scorpion Tityus serrulatus (TSV) stimulates macrophage function in vitro. The aim of this study was to identify which one of the several components of this fraction was responsible for the main stimulatory activity on macrophages. This component was identified as sub-fraction II-11, also known by the name of gamma toxin or simply abbreviated Ts1, which stands for toxin 1 of T. serrulatus venom. The effect of Ts1 was analyzed by detection of inflammatory mediators. Several functional bioassays were performed: TNF activity was assayed by measuring its cytotoxicity on L929 cells, whereas IL-1, IL-6, IFN-gamma and IL-10 were assayed by enzyme-linked immunosorbent assay. The levels of NO were evaluated by Griess colorimetric reactions in supernatants of macrophages in culture exposed to Ts1 and compared with FII. Macrophages exposed to Ts1 increase the production of mediators. With respect to the pro-inflammatory cytokines, an increment of IL-1alpha, IL-1beta was observed after 12 h; the maximum levels of IL-6 and TNF were observed after 24 h; the highest levels of IFN-gamma and NO were observed after 72 h. In contrast, the highest levels of anti-inflammatory cytokines such as IL-10 were observed after 120 h. With respect to the balance of pro- and anti-inflammatory cytokines, IL-1alpha/IL-10 and IL-6/IL-10 ratios appear incremented between 12 and 48 h in macrophages exposed to Ts1. IL-1beta/IL-10 and TNF/IL-10 ratios were increased in macrophages exposed to Ts1 for 12 h. IFN-gamma/IL-10 ratios increased up to 48 h, decaying thereafter. Elevated IL-6/TNF ratios were observed up to 24 h. These ratios may possibly reflect the inflammatory status during exposition to the venom. In conclusion, these data indicate that Ts1 has an important immunomodulatory effect on macrophages, and add important knowledge for understanding scorpion envenomation. It also opens the field for further research about the intoxication phenomenon as it is discussed here.

Albumin resuscitation improves ventricular contractility and myocardial tissue oxygenation in rat endotoxemia

OBJECTIVE

Fluid resuscitation to improve delivery of oxygen to vital organs is a principal clinical intervention for septic patients. We previously reported that albumin resuscitation in rat endotoxemia improved contractility in isolated cardiomyocytes, but whether this effect occurs in vivo is unknown. We hypothesized that albumin resuscitation would improve decreased ventricular contractility and myocardial tissue oxygenation in vivo.

DESIGN

Randomized, controlled, prospective animal study.

SETTING

University animal laboratory.

SUBJECTS

Male Sprague-Dawley rats (250-350 g).

INTERVENTIONS

Rats were randomized into three groups: control with no lipopolysaccharide (n = 8), lipopolysaccharide (10 mg/kg) without albumin resuscitation (n = 8), and lipopolysaccharide with albumin resuscitation (n = 6). Five hours after lipopolysaccharide injection, animals were resuscitated with 10 mL/kg 5% rat albumin in 0.9% saline. Six hours after 10 mL/kg lipopolysaccharide, a pressure-volume conductance catheter (MIKRO-Tip 2.0-Fr, Millar Instruments, Houston, TX) was inserted into the left ventricle to quantify maximum elastance as an index of contractility. Myocardial tissue Po2 was measured using a fiberoptic oxygen probe.

MEASUREMENTS AND MAIN RESULTS

Maximum elastance decreased after lipopolysaccharide relative to control (47%, from 5.9 +/- 0.8 to 3.1 +/- 0.4 mm Hg/microL, p < .05). Albumin resuscitation prevented the lipopolysaccharide-induced decrease in maximum elastance (7.0 +/- 1.2 mm Hg/microL, p < .05 vs. lipopolysaccharide). Myocardial tissue Po2 was reduced in endotoxemia compared with control (53%, from 10.1 +/- 0.9 to 4.7 +/- 0.6 mm Hg, p < .05), and albumin resuscitation improved the lipopolysaccharide-induced tissue hypoxia toward the control value (9.0 +/- 1.4 mm Hg, p < .05).

CONCLUSIONS

Albumin resuscitation improved decreased ventricular contractility and myocardial oxygenation in endotoxemic rats. This result suggests that albumin resuscitation may improve ventricular dysfunction by improving myocardial hypoxia.

Balance between pro- and anti-inflammatory cytokines in mice treated with Centruroides noxius scorpion venom

CSV consists of a very complex of molecules and demonstrates significant cellular activities capable of stimulating immune functions in vivo. The purpose of this study was to analyze the effects of CSV on sex, weight, route of injection and the balance of pro- and anti-inflammatory cytokines in mice. The susceptibility and route of injection were analyzed by lethal (LD(50)) determination. The effects of CSV were also analyzed in blood from immunized mice using detection by means of antibodies and mediators production. Several functional bioassays were employed: TNF activity was assayed by measuring its cytotoxic activity in L929 cells, and other cytokines were assayed by enzyme-linked immunosorbent assay, whereas nitric oxide levels were detected by Griess colorimetric reactions in sera from BALB/c mice. After injecting subcutaneously, the LD(50) presented an increase of the CSV correlation and similar levels of susceptibility were obtained for female and male from BALB/c mice. Significant differences were observed in the time-course of cytokine levels. The balance of pro- and anti-inflammatory cytokines TNF/IL-10 and IL-6/IL-10 ratios were significantly higher in injected mice group when compared with those obtained for non-injected group. The CSV is poor in antigenic composition and it is difficult to get antibodies specific to neutralizing the lethal factor. The effect of immunization with 0.5 LD(50) of CSV on the balance of pro- and anti-inflammatory cytokines was measured. The maximum levels of TNF and IL-6, IFN-gamma and NO were observed on days 7 and 21 after immunization, respectively. IL-10 levels peaked between days 21 and 28 after immunization with CSV. With respect, to balance of pro- and anti-inflammatory cytokines it was possible to observe that negative correlation between serum levels of IL-6/IL-10 and TNF/IL-10 exists. These ratios may possibly reflect the balance of pro- and anti-inflammatory cytokines in serum, which may by manifested in the inflammatory status during the envenoming processes. In conclusion, an increase in the serum levels of TNF and IL-6 may be a useful marker for scorpion envenomation.

Activation of peroxisome proliferator-activated receptor-alpha by fenofibrate prevents myocardial dysfunction during endotoxemia in rats

OBJECTIVE

To investigate the effects of fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, on cardiac function in a rat endotoxemia model.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Three-month-old male Wistar rats.

INTERVENTIONS

Animals were fed with standard diet containing no drug or fenofibrate (0.2%) for 14 days. They were then injected intravenously with either 5 mg/kg lipopolysaccharide (LPS and fenofibrate + LPS groups) or saline (control and fenofibrate groups).

MEASUREMENTS AND MAIN RESULTS

In the LPS group, body weight loss, metabolic acidosis, and thrombocytopenia confirmed presence of systemic endotoxemia. LPS administration resulted in an early peak in plasma tumor necrosis factor-alpha, decreased cardiac contractility (isolated and perfused heart), reduced myofilament Ca2+ sensitivity (Triton-skinned cardiac fibers), and increased left ventricular nitric oxide (NO) end-oxidation products (NO(x) and NO2), without evidence of myocardial oxidative stress (thiobarbituric acid-reactive substances and antioxidant enzyme activities). Fenofibrate pretreatment (fenofibrate + LPS group) did not alter signs of endotoxemia but prevented reductions in both cardiac contractility and myofilament Ca2+ sensitivity. The peak of plasma tumor necrosis factor-alpha was attenuated, whereas myocardial NO(x) and NO2 remained similar to the LPS group. Oxidative stress was suggested from moderate increase in cardiac thiobarbituric acid-reactive substances and reduced glutathione peroxidase activity.

CONCLUSION

Fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, may prevent endotoxemia-induced cardiac dysfunction and reduction in myofilament Ca2+ sensitivity. Our data also suggest a mediating role for early peak plasma tumor necrosis factor-alpha, but not for myocardial NO production or oxidative stress.

Toll-like receptor 2 activation by bacterial peptidoglycan-associated lipoprotein activates cardiomyocyte inflammation and contractile dysfunction

OBJECTIVE

Although cardiac dysfunction plays an important role in the pathogenesis of sepsis, the mechanisms that underlie cardiac dysfunction in sepsis remain poorly understood. Bacterial peptidoglycan-associated lipoprotein (PAL), an outer-membrane protein of Gram-negative bacteria, was recently found to be released into the bloodstream in sepsis and to cause inflammation and death in mice. The present studies assessed the effects of PAL on cardiomyocyte function and its signal transduction in cardiomyocytes.

DESIGN

Randomized prospective animal study.

SETTING

Research laboratory.

SUBJECTS

Male C57BL/6 mice, B6;129S-Tnfrsf1a(tm1Imx) Tnfrsf1b(tm1Imx)/J knockout mice, Toll-like receptor 2 (TLR2) knockout mice, and myeloid differentiation factor 88 (MyD88) knockout mice.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Immunohistochemical staining and immunoblot analysis indicated that intravenously injected PAL bound to myocardium. Injection of PAL decreased cardiac function in vivo. Challenge with PAL altered cell shortening and Ca2+ transients in isolated mouse cardiomyocytes but not in cardiomyocytes isolated from TLR2 -/- and MyD88 -/- mice. Cytokine profiling arrays demonstrated that tumor necrosis factor-alpha (TNFalpha), granulocyte colony-stimulating factor, and interferon-gamma-production were elevated in PAL-treated cardiomyocytes. Increased TNFalpha production was abolished in MyD88 -/- cardiomyocytes but restored by adenovirally mediated expression of MyD88. PAL did not affect cell shortening and Ca2+ cycling in cardiomyocytes obtained from mice deficient for TNFalpha receptor (TNFR) 1 and TNFR2 (TNFR1/2 -/-).

CONCLUSION

Our data reveal that PAL uses the TLR2/MyD88 signaling cascade to induce cardiomyocyte dysfunction and inflammatory responses and that TNFalpha is a major mediator of PAL-induced dysfunction in cardiomyocytes. These studies suggest that circulating PAL and other TLR2 agonists may contribute to cardiac dysfunction in sepsis.

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.

E. Coli Sepsis Induces Profound Mechanoenergetic Inefficiency in the Porcine Left Ventricle

Myocardial dysfunction is believed to be a central part of septic multiorgan manifestations. The aim of the present study was to assess whether E. coli sepsis in an in vivo model would induce a dysfunction in the relationship between mechanical work and energy consumption in the left ventricle (LV). Accordingly, we measured hemodynamics, left ventricular pressure-volume area (PVA), and myocardial oxygen consumption (MVo2) in deeply anesthetized pigs. Eight pigs received 2.0 +/- 0.5 x 10(9) E. coli bacteria intravenously, and seven served as controls. Compared with baseline and the control group, no alternations were observed in LV diastolic function or indices of contractility in the septic group. The MVo2-PVA relationship was highly linear in both groups (all r2 = 0.96-0.99). At 5 h, the y-axis intercept of the MVo2-PVA relationship (nonmechanical MVo2) had increased in the sepsis group by 70% compared with baseline (P = 0.004) and by 60% compared with the control group (P = 0.003). Contractile efficiency (the inverse of the MVo2-PVA slope) remained unchanged over time and between groups. The study demonstrates a profound increase in nonmechanical oxygen consumption during E. coli sepsis in the LV.

Interleukin-1beta, interleukin-6, tumour necrosis factor-alpha and interferon-gamma released by a viral infection and an aseptic inflammation reduce CYP1A1, 1A2 and 3A6 expression in rabbit hepatocytes

Inflammation reduces activity and expression of hepatic cytochrome P450 (P450) and therefore diminishes drug biotransformation. This study aimed to identify the serum mediators triggered by a viral infection and an aseptic inflammation that downregulate P450 isoforms. Incubation of hepatocytes with serum from rabbits with a turpentine-induced inflammation or humans with a viral infection decreased the amount of cytochrome 1A1 (CYP1A1), 1A2 and 3A6 mRNA and apoproteins. By serum fractionation and immuno-neutralization, we showed that in the aseptic inflammation, interleukin-6 and, to a lesser degree, interleukin-1beta are involved in the downregulation of all three isoforms. In serum from humans with a viral infection, interleukin-1beta, interleukin-6, interferon-gamma and tumour necrosis factor-alpha contribute to the downregulation of P450 isoforms. CYP1A1 and 1A2 are regulated by serum mediators at the transcriptional level, while the expression of CYP3A6 appears to be under the control of pre- and posttranscriptional mechanisms.

Delayed dilated cardiomyopathy for major burn injuries

PURPOSE

The early impact on the heart of severe burns has all been well documented previously. Here, we report on the late effects of burns upon the heart, and dilated cardiomyopathy, such aspects having been little reported previously in the literature.

METHODS

Over the past 8 years (June 1991 to December 1998), 55 scalded or flame-burnt patients for whom the total burnt body surface area (TBSA) exceeded 50% were treated. Seventeen patients survived and were followed up. The mean age was 44 years. The mean follow-up period was 47.3 months; four patients displayed a previous history of heart disease. We used several parameters to evaluate and follow cardiac status to see the late effect of burns upon the heart.

RESULTS

Of 17 patients, 3 patients (17.7%) were found to exhibit dilated cardiomyopathies after a mean time of 6 months post-injury. A dramatic recovery from symptoms and roentgenographic findings were observed for all patients following symptomatic treatment.

CONCLUSION

Here we report three cases of delayed dilated cardiomyopathy, a condition that has been little reported in the past. There may be many causating factors. Several recommendations are described.

Albumin resuscitation increases cardiomyocyte contractility and decreases nitric oxide synthase II expression in rat endotoxemia

OBJECTIVE

Hypotension and hypoperfusion during septic shock may contribute to tissue hypoxia and the intramyocardial inflammatory response that results in myocardial dysfunction. Therefore, we hypothesized that crystalloid or colloid resuscitation may alter myocardial dysfunction.

DESIGN

Randomized, controlled, prospective animal study.

SETTING

University animal laboratory.

SUBJECTS

Sprague-Dawley rats (250-300 g, n = 6/group).

INTERVENTIONS

Rats received an intraperitoneal injection of 10 mg/kg lipopolysaccharide or control. One hour later, rats were randomized to intravenous resuscitation and received either 30 mL/kg normal saline, 10 mL/kg 10% pentastarch, 10 mL/kg 5% rat albumin, or no volume.

MEASUREMENTS AND MAIN RESULTS

We measured fractional shortening of cardiomyocytes isolated 5 hrs after lipopolysaccharide or control injection. In separate identical experiments, we measured myocardial interleukin-6, macrophage inhibitory protein-2, and nitric oxide synthase II protein and messenger RNA expression. Control fractional shortening of 24.1 +/- 2.2% was decreased by lipopolysaccharide to 18.8 +/- 1.2% (p <.001). Volume resuscitation after lipopolysaccharide significantly improved fractional shortening (p <.001). In particular, albumin resuscitation increased fractional shortening to 23.5 +/- 0.9%, which was more than either saline (fractional shortening 20.1 +/- 1.7%,p <.01) or pentastarch (fractional shortening 21.4 +/- 0.9%,p <.01). Myocardial macrophage inhibitory protein-2 protein and interleukin-6 and macrophage inhibitory protein-2 messenger RNA expression and neutrophil content were elevated following lipopolysaccharide (p <.05) but were not altered by volume resuscitation. Myocardial nitric oxide synthase II protein and messenger RNA expression increased following lipopolysaccharide (p <.01) and decreased with albumin resuscitation.

CONCLUSIONS

We conclude that following lipopolysaccharide injection, volume resuscitation improves cardiomyocyte fractional shortening. Albumin resuscitation is particularly beneficial in preventing reduced cardiomyocyte contractility, and this benefit may be related to an albumin-induced reduction in nitric oxide synthase II protein and messenger RNA expression following endotoxin injection.

Myocardial dysfunction in the patient with sepsis

The nature of myocardial dysfunction during sepsis and septic shock has been investigated for more than half a century. This review traces the evolution of scientific thought regarding this phenomenon during this period with particular emphasis on the current understanding of both the clinical manifestations and the molecular/cellular basis of septic myocardial dysfunction in critically ill patients. Current data suggest, contrary to older literature, that patients with septic shock develop a hyperdynamic circulatory state after fluid resuscitation and maintain this hyperdynamic circulatory state until death or recovery. Overt myocardial depression, as manifested by decreased cardiac output, is decidedly uncommon, even in the preterminal phase. Nonetheless, myocardial depression, as evidenced by biventricular dilation and depression of the ejection fraction, can be demonstrated in most patients with septic shock by using either radionuclide cineangiography or echocardiography. Depression is reversible over the course of 7 to 10 days in survivors. Available evidence suggests that myocardial hypoperfusion is not responsible for septic myocardial depression, because examination of humans with septic shock demonstrates increased myocardial perfusion, and animal models of septic shock appear to maintain myocardial high-energy phosphates. A circulating factor or factors, including the cytokines tumor necrosis factor alpha and interleukin-1beta, appear to have a significant role in the phenomenon. In addition, septic myocardial depression appears to be mediated in part through combinations of nitric oxide-dependent and -independent alterations of basal and catecholamine-stimulated cardiac myocyte contractility.

Do blood transfusions improve outcomes related to mechanical ventilation?

BACKGROUND

Correcting the decrease in oxygen delivery from anemia using allogeneic RBC transfusions has been hypothesized to help with increased oxygen demands during weaning from mechanical ventilation. However, it is also possible that transfusions hinder the process because RBCs may not be able to adequately increase oxygen delivery. In this study, we determined whether a liberal RBC transfusion strategy improved outcomes related to mechanical ventilation.

METHODS

Seven hundred thirteen patients receiving mechanical ventilation, representing a subgroup of patients from a larger trial, were randomized to either a restrictive transfusion strategy, receiving allogeneic RBC transfusions at a hemoglobin concentration of 7.0 g/dL (and maintained between 7.0 g/dL and to 9.0 g/dL), or to a liberal transfusion strategy, receiving RBCs at 10.0 g/dL (and maintained between 10.0 g/dL and 12.0 g/dL). The larger trial was designed to evaluate transfusion practice rather than weaning per se.

RESULTS

Baseline characteristics in the restrictive-strategy group (n = 357) and the liberal-strategy group (n = 356) were comparable. The average durations of mechanical ventilation were 8.3 +/- 8.1 days and 8.3 +/- 8.1 days (95% confidence interval [CI] around difference, - 0.79 to 1.68; p = 0.48), while ventilator-free days were 17.5 +/- 10.9 days and 16.1 +/- 11.4 days (95% CI around difference, - 3.07 to 0.21; p = 0.09) in the restrictive-strategy group vs the liberal-strategy group, respectively. Eighty-two percent of the patients in the restrictive-strategy group were considered successfully weaned and extubated for at least 24 h, compared to 78% for the liberal-strategy group (p = 0.19). The relative risk (RR) of extubation success in the restrictive-strategy group compared to the liberal-strategy group, adjusted for the confounding effects of age, APACHE (acute physiology and chronic health evaluation) II score, and comorbid illness, was 1.07 (95% CI, 0.96 to 1.26; p = 0.43). The adjusted RR of extubation success associated with restrictive transfusion in the 219 patients who received mechanical ventilation for > 7 days was 1.1 (95% CI, 0.84 to 1.45; p = 0.47).

CONCLUSION

In this study, there was no evidence that a liberal RBC transfusion strategy decreased the duration of mechanical ventilation in a heterogeneous population of critically ill patients.

Tumor necrosis factor-alpha (TNF-alpha) plays a protective role in acute viralmyocarditis in mice: A study using mice lacking TNF-alpha

BACKGROUND

It has been reported that tumor necrosis factor-alpha (TNF-alpha) is expressed in the heart with viral myocarditis and that its expression aggravates the condition. The pathophysiological effects of TNF-alpha on viral myocarditis, however, have not been fully elucidated.

METHODS AND RESULTS

To investigate the role of TNF-alpha in the progression of viral myocarditis, we used TNF-alpha gene-deficient mice (TNF-alpha(-/-)) and induced acute myocarditis by infection with encephalomyocarditis virus (EMCV). The survival rate of TNF-alpha(-/-) mice after EMCV infection was significantly lower than that of TNF-alpha(+/+) mice (0% versus 67% on day 14). Injection of recombinant human TNF-alpha (0.2 to 4.0 microg/mouse IV) improved the survival of TNF-alpha(-/-) mice in a dose-dependent manner, indicating that TNF-alpha is essential for protection against viral myocarditis. The levels of viral titer and viral genomic RNA of EMCV in the myocardium were significantly higher in TNF-alpha(-/-) than in TNF-alpha(+/+) mice. Histopathological examination showed that the inflammatory changes of the myocardium were less marked in TNF-alpha(-/-) than in TNF-alpha(+/+) mice. Immunohistochemical analysis revealed that the levels of immunoreactivity of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in the myocardium were decreased in TNF-alpha(-/-) mice compared with TNF-alpha(+/+) mice.

CONCLUSIONS

These observations suggested that TNF-alpha is necessary for adhesion molecule expression and to recruit leukocytes to inflammatory sites, and thus, the lack of this cytokine resulted in failure of elimination of infectious agents. We concluded that TNF-alpha plays a protective role in the acute stage of viral myocarditis.

Endotoxin infusion in rats induces apoptotic and survival pathways in hearts

Inflammatory mediators of sepsis induce apoptosis in many cell lines. We tested the hypothesis that lipopolysaccharide (LPS) injection in vivo results in induction of early apoptotic and survival pathways as well as evidence of late-stage apoptosis in the heart. Hearts were collected from control rats and at 6, 12, and 24 h after LPS injection (4 mg/kg). Activation of an apoptotic pathway was identified by a 1,000-fold increase in caspase-3 activity at 24 h (P < 0.05). Confirmation of these results occurred when terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining identified myocardial cells undergoing DNA fragmentation with significant levels at 24 h post-LPS injection. LPS also caused early proapoptotic mRNA (Bax) to increase (16% at 24 h, P < 0.05), whereas the Bax protein initially decreased (35% at 6 h, P < 0.05) and then returned to baseline values by 24 h. Six hours after LPS injection, Bcl-2 (early prosurvival) mRNA levels increased, whereas its protein levels decreased (70%, P < 0.05) and then returned to baseline levels by 24 h. Mitochondrial cytochrome c levels decreased, suggestive of mitochondrial involvement. Thus involvement of proapoptotic and prosurvival pathways in the heart occurs during a septic inflammatory response.

Cytochrome P450 inactivation by serum from humans with a viral infection and serum from rabbits with a turpentine-induced inflammation: the role of cytokines

Serum from humans with an acute upper respiratory viral infection and from rabbits with turpentine-induced inflammation reduce the catalytic activity of hepatic cytochrome P450 (P450). The aim of this study was to identify the serum mediators responsible for the decrease in P450 activity. Rabbit and human sera were fractionated by size exclusion chromatography and the fractions tested for their ability to reduce the activity and amount of P450 after 4 h of incubation with hepatocytes from turpentine-treated rabbits (H(INF)). Rabbit and human sera decreased P450 activity by around 40% without any change in the amount of CYP1A1 and 1A2 apoproteins. In rabbit serum, the fraction containing proteins of M(r) 23-15 kDa decreased P450 content by 41%, but did not alter the amount of the apoproteins. Anti-IL-6 antibody added to the M(r) 23-15 kDa fraction restored P450 content to 97% of control values, while anti-IL-1beta, TNF-alpha and IFN-gamma antibodies had no effect. Supporting the role of IL-6, incubation of H(INF) in the presence of IL-6 for 4 h reduced P450 content by 40%. In human serum, the fraction containing proteins of M(r) >95 kDa lowered P450 content by 43% without modifying the amounts of CYP1A1/2. Neutralization experiments showed that IFN-gamma, IL-6, and IL-1beta contributed to the decrease in P450 content. In conclusion, the present results demonstrate that IL-6, and IFN-gamma, IL-6 and IL-1beta are the serum mediators released in vivo by a turpentine-induced inflammatory reaction in the rabbit and an upper respiratory viral infection in humans, respectively, inactivating hepatic P450.

Nitric oxide modulation of TNF-alpha-induced cardiac contractile dysfunction is concentration dependent

Whereas previous studies suggest that tumor necrosis factor-alpha (TNF-alpha) induces cardiac contraction-relaxation deficits, the mechanisms remain unclear. Our recent studies have implicated cardiac-derived nitric oxide (NO). This study examined the detrimental and protective effects of NO donors S-nitroso-N-acetyl-penicillamine (SNAP) or (Z)-1- [N-(3-ammonio-propyl)-N-(n-propyl)amino]diazen-1-ium- 1,2diolate (PAPA/NO) on TNF-alpha-related changes in cardiac contractile function (Langendorff), cellular injury, and intracellular myocyte Ca(2+) concentration ([Ca(2+)](i)). Myocytes were incubated in the presence/absence of TNF-alpha (200-500 pg/ml x 10(5) cells) for 3 h; subsets of myocytes were incubated with one of several concentrations of SNAP or PAPA/NO (0.1, 0.3, 0.5, and 1.5 mM) for 15 min before TNF-alpha challenge. Supernatant creatine kinase (CK), cell viability (Trypan blue dye exclusion), and myocyte [Ca(2+)](i) (fura 2-acetoxymethyl ester) were measured. In parallel experiments, cardiac function (Langendorff) was examined after TNF-alpha challenge in the presence or absence of SNAP or PAPA/NO (0.1 and 1.5 mM). TNF-alpha in the absence of an NO donor impaired cardiac contraction and relaxation and produced cardiomyocyte injury. Pretreating perfused hearts or isolated cardiomyocytes with a low concentration of either SNAP or PAPA/NO decreased TNF-alpha-mediated cardiac injury and improved contractile dysfunction, whereas high concentrations of NO donor exacerbated TNF-alpha-mediated cardiac effects. These data provide one explanation for the conflicting reports of beneficial versus detrimental effects of NO in the face of inflammation and suggest that the effects of NO on organ function are concentration dependent; low concentrations of NO are cardioprotective, whereas high concentrations of NO are deleterious.

Increased cardiomyocyte intracellular calcium during endotoxin-induced cardiac dysfunction in guinea pigs

Septic shock is a complex pathophysiologic state characterized by circulatory insufficiency, multiple system organ dysfunction, and frequent mortality. Although profound cardiac dysfunction occurs during sepsis, the pathogenesis of this dysfunction remains poorly understood. To determine whether abnormalities in intramyocyte calcium accumulation might contribute to the development of cardiac dysfunction, we measured myocyte intracellular calcium during peak cardiac dysfunction after an endotoxin challenge. Intraperitoneal administration of Escherichia coli lipopolysaccharide 4 mg/kg to adult guinea pigs resulted in significantly impaired cardiac performance (Langendorff preparation) 18 h after challenge compared with control. This included diminished left ventricular pressure development (56 +/- 7 versus 95 +/- 4 mm Hg, p < 0.05), maximal rate of left ventricular pressure rise (998 +/- 171 versus 1784 +/- 94 mm Hg/s, p < 0.05) and left ventricular pressure fall (1014 +/- 189 versus 1621 +/- 138 mm Hg/s, p < 0.05). Assay of intracellular calcium in fura-2AM-loaded cardiac myocytes demonstrated increased intracellular calcium concentration in myocytes obtained from lipopolysaccharide-challenged animals compared with controls (234 +/- 18 versus 151 +/- 6 nM, p < 0.05). Inhibition of calcium-release channel (ryanodine receptor) opening by administration of dantrolene prevented the increase in intracytoplasmic calcium (159 +/- 8 versus 234 +/- 18 nM, p < 0.05) and partially ameliorated systolic and diastolic ventricular dysfunction. These data indicate that abnormalities of intracellular calcium contribute to the development of endotoxin-induced myocardial dysfunction.

Cardiac contractility is not depressed in early canine endotoxic shock

We investigated effects of acute endotoxemia (Escherichia coli endotoxin, 1 mg/kg, intravenously) on left ventricular (LV) function in the first 4 h after induction of endotoxic shock in anesthetized canine preparations (n = 7 each, endotoxin and control groups). LV pressure and conductance (volume) catheters were used to construct pressure-volume loops. Transient inferior vena cava occlusion was used to rapidly and reversibly alter LV end-diastolic volume. LV contractility was assessed from the slope of the LV end-systolic pressure-volume relationship (Ees) and from preload-recruitable stroke work (PRSW), and from their change (DeltaEes and DeltaPRSW, respectively, measured at 2 and 4 h only), in response to a dobutamine infusion (5 microg/kg/min). Diastolic function and arterial tone were assessed as the maximal negative change in filling pressure versus time (max -dP/dt), filling rate, and arterial elastance (Ea), respectively. Ees, PRSW, Ea, diastolic function, and hemodynamics were measured hourly. Endotoxemia induced an immediate hypotensive, hyperdynamic, tachycardic state with progressive lactic acidosis. By 2.5 h after endotoxin infusion, heart rate returned to preendotoxin and control levels, but the other changes remained. However, no change occurred in LV Ees, DeltaEes, PRSW, DeltaPRSW, diastolic function, or Ea during the 4-h measurement interval. The cardiovascular collapse seen during the first 4 h of endotoxemia is therefore not due even partly to alterations in LV contractility.

Myocardial oxygen consumption during dobutamine infusion in endotoxemic pigs

PURPOSE

Dobutamine infusion is used to increase whole-body oxygen delivery in septic patients to satisfy unmet oxygen demand of hypoxic tissues. However, dobutamine infusion also increases myocardial work and myocardial oxygen consumption. Our goal was to determine the importance of this effect as a fraction of the increase in whole-body oxygen consumption, in a porcine model of septic shock.

MATERIALS AND METHODS

Four hours after a 50 microg/kg infusion of Escherichia coli endotoxin (0111: B4, Sigma) in eight anesthetized pigs, whole-body oxygen delivery and myocardial oxygen delivery and consumption were calculated from blood flow and arterial and venous oxygen content measurements. We directly measured whole-body oxygen consumption by analysis of inhaled and exhaled gases using a metabolic cart. Then dobutamine 10 and 20 microg/kg/min was infused and measurements were repeated.

RESULTS

Dobutamine infusion increased whole-body oxygen delivery but did not increase metabolic cart measured whole-body oxygen consumption. Dobutamine infusion of 10 and 20 microg/kg/min increased myocardial oxygen consumption by 7.0 +/- 0.6 (80 +/-10%) and 12.0 +/- 2.0 mL O2/min (142 +/- 30%), respectively (P < .01).

CONCLUSIONS

In this porcine model of sepsis, dobutamine infusion significantly increases myocardial oxygen consumption. Because whole-body oxygen consumption does not change, dobutamine infusion may fail to increase and may decrease oxygen consumption by other organs.

Activated macrophages decrease rat cardiac myocyte contractility: importance of ICAM-1-dependent adhesion

Macrophages are found in the heart as part of the inflammatory response. To determine whether macrophages could contribute to myocardial dysfunction, rat ventricular myocytes were isolated and cocultured with elicited peritoneal macrophages in media containing tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, or endotoxin for 4 h. Cardiac myocytes were electrically stimulated, and fractional shortening was determined using videomicroscopy. When myocytes alone or myocytes in coculture with macrophages separated by a membrane were challenged with TNF-alpha, lipopolysaccharide, or IL-1, fractional shortening did not decrease. When macrophages were allowed to contact myocytes, fractional shortening decreased from 20. 1 +/- 0.9% in unchallenged macrophage-myocyte cocultures to 15.5 +/- 0.9, 16.3 +/- 0.8, and 15.8 +/- 0.6% when challenged for 4 h with TNF-alpha, endotoxin, or IL-1beta, respectively (P < 0.05). Myocytes had a mean adherence of 4.2 +/- 0.2 macrophages after TNF-alpha challenge compared with 2.6 +/- 0.3 for controls (P < 0.05). The number of adherent macrophages was associated with the decrease in fractional shortening. Anti-intercellular adhesion molecule-1 (ICAM-1) reduced macrophage adherence and prevented the decrease in fractional shortening. This decrease was also prevented by desferoxamine, superoxide dismutase, and nitro-L-arginine methyl ester. This suggests that activated macrophages adhere to myocytes via ICAM-1, and adherent macrophages decrease their contractile function via TNF-alpha, oxygen free radicals, and nitric oxide.

IL-1ra administration does not improve cardiac function in patients with severe sepsis

PURPOSE

The purpose of this study was to investigate the effects of interleukin-1 receptor antagonist (IL-1ra) on myocardial function in septic patients.

MATERIALS AND METHODS

A subgroup of patients from a prospective, randomized, double-blind, placebo-controlled, multicenter trial was studied from 63 academic medical centers in the United States, Canada, and Europe. A subgroup of 71 patients with severe sepsis in whom vasoactive support was little altered during the study was included. The patients were randomized to receive either placebo (n = 29) or IL-1ra at a dose of 1 mg/kg/h (n = 20) or 2 mg/kg/h (n = 22).

RESULTS

Hemodynamic measurements were taken at baseline, and 1, 2, 3, 4, 8, and 12 hours after placebo or IL-1ra administration. No significant differences in hemodynamic parameters were observed between the groups or over time during the study period.

CONCLUSIONS

IL-1ra administration has no effect on cardiac function in septic patients.

Tumor necrosis factor depresses myocardial contractility in endotoxemic swine

BACKGROUND

Depression of myocardial contractility occurs in septic shock.

METHODS

Fourteen pigs were instrumented to measure cardiopulmonary dynamics after a challenge of Escherichia coli endotoxin (lipopolysaccharide endotoxin, LPS). A volumetric Swan-Ganz catheter was placed via the jugular vein, and a carotid arterial line was placed into the aortic root. Eight pigs received LPS alone and six pigs received tumor necrosis factor monoclonal antibody (TNF MAb) 15 minutes before the administration of LPS. Pulmonary artery and aortic root blood were sampled for amounts of TNF. Ninety minutes after LPS administration, thoracotomy was performed to biopsy the right and left ventricles for TNF levels. Contractility was determined from the end systolic pressure-volume relationships of pressure-volume diagrams.

RESULTS

Right ventricular end diastolic volume index nearly doubled and myocardial contractility decreased by 40% from baseline in the pigs receiving only LPS. Pigs that received TNF MAb had no change in myocardial contractility or right ventricular end diastolic volume index from baseline. There was a higher level of TNF in the aortic sample than in the pulmonary samples at 60 minutes. Right ventricular tissue TNF levels were significantly higher in the LPS-alone group. There was no such difference in left ventricular tissue.

CONCLUSION

The left and right ventricles have different susceptibilities to TNF MAb. TNF may decrease myocardial contractility in sepsis. Blockade of TNF with TNF MAb reverses the depression of myocardial contractility and the right ventricular dilatation associated with septic shock.

Biphasic changes in left ventricular function during hyperdynamic endotoxemia

Cardiac contractility was studied in a clinically relevant conscious swine model simulating human hemodynamics during endotoxemia. The slope of the end-systolic pressure-volume relationship [end-systolic elastance (EES)] was used as a load-independent contractility index. Chronic instrumentation in 10 pigs included two pairs of endocardial ultrasonic crystals for measuring internal major and minor axial dimensions of the left ventricle, a micromanometer for left ventricular pressure measurement, and a thermodilution pulmonary artery catheter. After a 10-day recovery period, control measurements of cardiac hemodynamic function were obtained. The following week, Escherichia coli endotoxin (10 micrograms . kg-1. h-1) was administered intravenously for 24 h. EES increased 1 h after endotoxin infusion and decreased beyond 7 h. The later hemodynamic changes resembled human cardiovascular performance during endotoxemia more closely than the changes during the acute phase. EES decreased in the later phase. A similar biphasic response of EES has been reported during a tumor necrosis factor-alpha (TNF) challenge. Even though plasma TNF was highest at 1 h and declined thereafter in this study, no consistent relationship between TNF and EES was identified, and TNF levels did not correlate directly with the changes in EES.

L-2-Oxothiazolidine-4-carboxylic acid prevents endotoxin-induced cardiac dysfunction

We tested the hypothesis that treatment with the glutathione repleting agent, L-2-oxothiazolidine-4-carboxylic acid (OTZ), could prevent endotoxin-induced ventricular dysfunction. Rabbits were treated with OTZ 2.4 g/kg (10% solution subcutaneously), or an equal volume and osmolality of saline, 24 h prior to, and again (intravenously) just prior to, infusion of 1 mg/kg E. coli endotoxin (or vehicle control). Ventricular contractility was measured in isolated hearts perfused by support rabbits. Contractility did not change in control groups (Saline/Control [n = 7] or OTZ/Control [n = 7]) over 6 h. However, Emax decreased in the Saline/Endotoxin group (-16.1 +/- 4.5% from baseline, n = 7, p < 0.05) and this was prevented by pretreatment with OTZ in the OTZ/ Endotoxin group (+6.3 +/- 4.1%, n = 7, p < 0.05 by analysis of variance). To better understand the mechanism of this effect we measured myocardial glutathione concentration and found it to be greater in OTZ/Endotoxin animals (104 +/- 4 ng/g) than in the Saline/Endotoxin animals (80 +/- 3 ng/g, p < 0.05). OTZ did not appreciably alter the endotoxin-induced increase in serum concentration of tumor necrosis factor (TNF) or the endotoxin-induced increase in myocardial leukocyte content. We conclude that oxygen radicals contribute to the early decrease in left ventricular contractility after endotoxin infusion and this decrease may be prevented by OTZ.

Cardiac failure in transgenic mice with myocardial expression of tumor necrosis factor-alpha

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional cytokine that has been detected in several human cardiac-related conditions, including congestive heart failure and septic cardiomyopathy. In these conditions, the origin of TNF-alpha secretion is, at least in part, cardiac myocytes.

METHODS AND RESULTS

To determine the consequences of TNF-alpha production by cardiac myocytes in vivo, we developed transgenic mice in which expression of a murine TNF-alpha coding sequence was driven by the murine alpha-myosin heavy chain promoter. Four transgenic founders developed an identical illness consisting of tachypnea, decreased activity, and hunched posture. In vivo, ECG-gated MRI of symptomatic transgenic mice documented a severe impairment of cardiac function evidenced by biventricular dilatation and depressed ejection fractions. All transgenic mice died prematurely. Pathological examination of affected animals revealed a globular dilated heart, bilateral pleural effusions, myocyte apoptosis, and transmural myocarditis in both the right and left ventricular free walls, septum, and atrial chambers. In all terminally ill animals, there was significant biventricular fibrosis and atrial thrombosis.

CONCLUSIONS

This is the first report detailing the effects of tissue-specific production of TNF-alpha by cardiac myocytes in vivo. These findings indicate that production of TNF-alpha by cardiac myocytes is sufficient to cause severe cardiac disease and support a causal role for this cytokine in the pathogenesis of human cardiac disease.