endothelin-1 and Escherichia-coli-Infections

Acute kidney injury (AKI) in septic patients drastically increases the mortality to 50-80%. Sepsis is characterized by hemodynamic perturbations as well as overwhelming induction of proinflammatory cytokines. Since ghrelin has been shown to have anti-inflammatory properties, we hypothesized that ghrelin may afford renal protection during endotoxemia-induced AKI. Studies were conducted in a normotensive endotoxemia-induced AKI model in mice by intraperitoneal injection of 3.5 mg/kg LPS. Serum ghrelin levels were increased during endotoxemia accompanied by increased ghrelin receptor (GHSR-1a) protein expression in the kidney. Ghrelin administration (1.0 mg/kg sc 6 h and 30 min before and 14 h after LPS) significantly decreased serum cytokine levels (TNF-alpha, IL-1beta, and IL-6) and serum endothelin-1 levels which had been induced by LPS. The elevated serum nitric oxide (NO) levels and renal inducible NO synthase expression were also decreased by ghrelin. Renal TNF-alpha levels were also increased significantly in response to LPS and ghrelin significantly attenuated this increase. When administrated before LPS, ghrelin protected against the fall in glomerular filtration rate at 16 h (172.9 +/- 14.7 vs. 90.6 +/- 15.2 microl/min, P < 0.001) and 24 h (147.2 +/- 20.3 vs. 59.4 +/- 20.7 microl/min, P < 0.05) as well as renal blood flow at 16 h (1.65 +/- 0.07 vs. 1.47 +/- 0.04 ml/min, P < 0.01) and 24 h (1.56 +/- 0.08 vs. 1.22 +/- 0.03 ml/min, P < 0.05) after LPS administration without affecting mean arterial pressure. Ghrelin remained renal protective even when it was given after LPS. In summary, ghrelin offered significant protection against endotoxemia-induced AKI. The renal protective effect of ghrelin was associated with an inhibition of the proinflammatory cytokines. Of particular importance was the suppression of TNF-alpha both in the circulation and kidney tissues. Thus, ghrelin may be a promising peptide in managing endotoxemia-induced AKI.

Topics: Acute Kidney Injury; Animals; Body Weight; Cyclic GMP; Endothelin-1; Endotoxemia; Escherichia coli Infections; Ghrelin; HMGB1 Protein; Kidney; Kidney Function Tests; Lipopolysaccharides; Male; Mice; Mice, Inbred C57BL; Nitric Oxide; Nitric Oxide Synthase Type II; Receptors, Ghrelin; Tumor Necrosis Factor-alpha

Studies in vitro reveal that endothelin-1 (ET-1) activates the alpha isoform of protein kinase C (PKC-alpha) in cultures of endothelial cells, thereby deranging cellular integrity. Sepsis and endotoxemia are associated with increased plasma concentrations of ET-1 that induce acute lung injury (ALI). We recently reported that non-selective ET-1 receptor blockade attenuates ALI in sheep by reducing the endotoxin-induced increase in extravascular lung water index (EVLWI). The aim of this study was to find out whether this attenuation is associated with reduced translocation of PKC-alpha from the cytosolic to the membrane fraction of lung tissue homogenate.. Seventeen awake, instrumented sheep were randomly assigned to a sham-operated group (n = 3), a lipopolysaccharide (LPS) group (n = 7) receiving an intravenous infusion of Escherichia coli 15 ng/kg per min for 24 hours, and a tezosentan group (n = 7) subjected to LPS and, from 4 hours, an intravenous injection of tezosentan 3 mg/kg followed by infusion at 1 mg/kg per hour for the reminder of the experiment. Pulmonary micro-occlusion pressure (Pmo), EVLWI, plasma concentrations of ET-1, tumor necrosis factor-a (TNF-a), and interleukin-8 (IL-8) were determined every 4 hours. Western blotting was used to assess PKC-alpha.. In non-treated sheep a positive correlation was found between the plasma concentration of ET-1 and Pmo in the late phase of endotoxemia (12 to 24 hours). A positive correlation was also noticed between Pmo and EVLWI in the LPS and the LPS plus tezosentan groups, although the latter was significantly reduced in comparison with LPS alone. In both endotoxemic groups, plasma concentrations of ET-1, TNF-alpha, and IL-8 increased. In the LPS group, the cytosolic fraction of PKC-alpha decreased by 75% whereas the membrane fraction increased by 40% in comparison with the sham-operated animals. Tezosentan completely prevented the changes in PKC-alpha in both the cytosolic and the membrane fractions, concomitantly causing a further increase in the plasma concentrations of ET-1, TNF-alpha, and IL-8.. In endotoxemic sheep, ET-1 receptor blockade alleviates lung injury as assessed by a decrease in EVLWI paralleled by a reduction in Pmo and the prevention of activation of PKC-alpha.

Topics: Animals; Endothelin A Receptor Antagonists; Endothelin-1; Endotoxemia; Enzyme Activation; Escherichia coli Infections; Interleukin-8; Protein Kinase C; Pyridines; Respiratory Distress Syndrome; Sheep; Tetrazoles; Tumor Necrosis Factor-alpha; Vasodilator Agents

To investigate whether adenosine protects against endotoxin-induced increments in extravascular lung water content.. Prospective, randomized, animal study.. University research laboratory.. Twenty-one anesthetized juvenile pigs.. The animals were divided into two groups subjected to endotoxin infusion: Endotoxin alone (n = 7), or endotoxin combined with adenosine infusion (n = 7) administered during the whole experimental period. Two other groups were exposed to anesthesia alone (n = 4) or adenosine infusion alone (n = 3), respectively.. Central hemodynamic variables and extravascular lung water, as assessed by the thermal dye dilution double indicator technique, were monitored. Plasma endothelin-1 concentrations were measured hourly. Extravascular lung water increased significantly in response to endotoxemia (p <.001) along with an increase in pulmonary microvascular pressure (P(mv) [p <.01]). Although the Pmv increased less in endotoxemic animals exposed to adenosine infusion, no intergroup difference was found. From 4 through 6 hrs, adenosine-treated pigs displayed only half of the extravascular lung water content of nontreated animals (p <.01). The latter did not differ from that of anesthetized controls receiving anesthesia or adenosine alone. Adenosine administered alone had no effect on P(mv). In pigs receiving adenosine alone, extravascular lung water content reached nadir after 3 hrs. In both endotoxin groups, plasma endothelin-1 concentration increased two-fold, peaking 4-6 hrs after the start of endotoxin infusion (p <.001).. The endotoxin-induced increase in lung extravascular water was hampered by intravenously infused adenosine in the presence of a nonsignificantly reduced microvascular pressure. This leaves reduced microvascular permeability the most likely reason for the beneficial effect of adenosine.

Topics: Adenosine; Analysis of Variance; Animals; Blood Pressure; Capillary Permeability; Endothelin-1; Endotoxemia; Escherichia coli Infections; Extravascular Lung Water; Hemodynamics; Lung; Microcirculation; Pulmonary Gas Exchange; Random Allocation; Respiratory Distress Syndrome; Swine; Vasodilator Agents

Acute lung injury is a common complication of gram-negative sepsis. Pulmonary hypertension and increased lung vascular permeability are central features of lung injury following experimental bacteremia. Platelet-activating factor is a prominent proinflammatory mediator during bacterial sepsis. Our previous studies have demonstrated that exogenous administration of platelet-activating factor (PAF) induces pulmonary edema without causing pulmonary hypertension. Interestingly, inhibition of PAF activity during Escherichia coli bacteremia prevents the development of both pulmonary hypertension and pulmonary edema. These data suggest that PAF contributes to pulmonary hypertension during sepsis, but that this is unlikely to be a direct vascular effect of PAF. The goal of the present study was to investigate the mechanism by which acute E. coli bacteremia induces pulmonary injury and to define the role that PAF plays in this injury. We hypothesized that the effects of PAF on pulmonary hypertension during bacteremia are due to the effects of PAF on other vascular mediators. Several studies suggest that PAF induces the expression of endothelin-1 (ET), a potent peptide vasoconstrictor. Further, our previous studies have implicated ET as a central mediator of systemic vasoconstriction during bacteremia. We therefore sought to assess whether ET is modulated by PAF. E. coli has also been demonstrated to increase endothelial production of nitric oxide (NO), which contributes to maintenance of basal vascular tone in the pulmonary circulation. We hypothesized that PAF might increase pulmonary vascular resistance during bacteremia by activating neutrophils, increasing expression of ET, and decreasing the tonic release of NO. Furthermore, we hypothesized that hypoxic vasoconstriction did not contribute to pulmonary vasoconstriction during the first 120 min of E. coli bacteremia.. Pulmonary artery pressure (PAP), blood pressure (BP), heart rate (HR), and arterial blood gases (ABG) were measured in anesthetized spontaneously breathing adult male Sprague-Dawley rats. E. coli (10(9) CFU/100 g body wt) was injected at t = 0, and hemodynamic data were obtained at 10-min intervals and ABG data at 30-min intervals for a total of 120 min. Sham animals were treated equally but received normal saline in place of E. coli. In treatment groups, a 2.5 mg/kg dose of WEB 2086, a PAF receptor antagonist, was administered intravenously 15 min prior to the onset of sepsis or sham sepsis. The groups were (1) intravenous E. coli (n = 5); (2) intravenous WEB 2086 pretreatment + intravenous E. coli (n = 5); (3) intravenous WEB 2086 alone (n = 5); and (4) intravenous normal saline (n = 6). Nitric oxide metabolites (NOx) and ET concentrations were assayed from arterial serum samples obtained at the end of the protocol. Lung tissue was harvested for measurement of myeloperoxidase (MPO) activity and pulmonary histology.. E. coli bacteremia increased HR, PAP, and respiratory rate early during sepsis (within 20 min), while hypoxemia, hypotension, and hemoconcentration were not manifest until the second hour. Pretreatment with WEB 2086 completely abrogated all of these changes. E. coli bacteremia increased the activity of serum ET, lung MPO, and neutrophil sequestration in the lung parenchyma via a PAF-dependent mechanism. However, the mechanism of increased production of NO appears to be PAF independent.. These data support the hypothesis that E. coli bacteremia rapidly induces pulmonary hypertension stimulated by PAF and mediated at least in part by endothelin-1 and neutrophil activation and sequestration in the lung. Microvascular injury with leak is also mediated by PAF during E. coli bacteremia, but the time course of resultant hypoxemia and hemoconcentration is slower than that of pulmonary hypertension. The contribution of hypoxic vasoconstriction in exacerbating pulmonary hypertension in gram-negative sepsis is probably a late

Topics: Animals; Bacteremia; Endothelin-1; Escherichia coli Infections; Hemodynamics; Hemoglobins; Hypertension, Pulmonary; Male; Neutrophils; Nitric Oxide; Oxygen; Peroxidase; Platelet Activating Factor; Rats; Rats, Sprague-Dawley

Shiga toxin, produced by Escherichia coli O157:H7, is important for the pathogenicity of the epidemic form of hemolytic uremic syndrome (HUS). This toxin has recently been found to stimulate endothelin-1 synthesis in cultured endothelial cells in vitro.. We investigated endothelin and cytokine levels in sera during a large outbreak of E. coli O157:H7 infection in Osaka, Japan, in 1996. Eleven patients with HUS and 9 patients with hemorrhagic colitis at the onset of E. coli O157:H7 infection were studied.. Serum IL-6 (p < 0.01), IL-8 (p < 0.05), IL-10 (p < 0.001) and endothelin (p < 0.001) levels were significantly increased in patients with HUS compared to those with colitis only. The serum thrombomodulin level, a molecular marker of endothelial damage, also showed a significant positive correlation with serum IL-6 (p < 0.01), IL-8 (p < 0.01), IL-10 (p < 0.01) and endothelin (p < 0.001) levels. In a HUS patient, the increase in serum IL-10 and endothelin levels reached a plateau prior to the peak of serum creatinine levels.. Increased serum endothelin synthesis by Shiga toxin in vivo was proven in HUS secondary to E. coli O157:H7 infection. Increased serum endothelin and IL-10 levels were speculated to be associated with the development of HUS through vascular endothelial damage caused by E. coli O157:H7 infection.

Topics: Case-Control Studies; Colitis; Creatinine; Disease Outbreaks; Endothelin-1; Escherichia coli Infections; Escherichia coli O157; Female; Gastrointestinal Hemorrhage; Hemolytic-Uremic Syndrome; Humans; Interleukin-10; Interleukin-6; Interleukin-8; Japan; Male; Thrombomodulin; Time Factors

During systemic inflammation, elevated levels of endothelin (ET)-1 have been reported. The aim of this study was to investigate the effects of ET-1 on neutrophil (PMN) respiratory burst, phagocytosis, and elimination of Escherichia coli from blood and tissues.. Prospective, randomized, controlled trial.. Experimental laboratory in a university hospital.. A total of 18 female chinchilla rabbits.. To quantify the clearance process, defined numbers (10(8) colony-forming units) of E. coli were injected intravenously into anesthetized rabbits, 60 mins after onset of continuous 0.2 microg/kg/min ET-1 administration (n = 9) and after saline infusion (control group, n = 9), respectively. To evaluate potential effects of ET-1 on bacterial elimination and killing, blood clearance of E. coli and colonization of different organs were investigated.. Variables monitored were neutrophil respiratory burst and phagocytosis activity, rates of bacterial elimination from the blood, arterial blood pressure, blood gases, serum lactate concentrations, and nitrite and nitrate levels. The animals were killed 3 hrs after bacterial injection and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts.. Compared with the control group, ET-1 significantly impaired PMN respiratory burst (p < .05) and prolonged elimination of injected E. coli from the blood (p < .01), whereas phagocytosis functions remained unaltered. The reduced PMN burst activity after ET-1 was associated with a higher bacterial colonization of all organs (lung, p < .01; spleen, p < .05). Endothelin-1 induced increases in mean arterial pressure (p < .01) and serum lactate concentrations, whereas nitrite and nitrate levels remained unaltered.. Endothelin-1 impairs respiratory burst and bacterial clearance from the blood and tissue. Thus, elevated levels of ET-1 during sepsis could induce organ hypoperfusion and cause disturbances in immune functions, increasing the risk of bacterial infections.

Topics: Animals; Endothelin-1; Escherichia coli; Escherichia coli Infections; Female; Immune Tolerance; Neutrophils; Phagocytosis; Rabbits; Respiratory Burst

As elevated endothelin-1 (ET-1) levels have been reported in systemic inflammatory diseases, the role of ET-1 as a promoter of inflammatory reactions is currently under investigation. The purpose of this study was to investigate the potential influence of ET-1 on systemic vascular pressure and immune function in terms of blood clearance and organ distribution of injected Escherichia coli in a rabbit model. To enable quantification of the clearance process, defined numbers of exogenous E. coli (10(8) cfu) were injected intravenously 60 min after starting the infusion of ET-1 (0.2 microgram kg-1 min-1; n = 9) or after saline infusion (controls, n = 9). Parameters monitored were arterial blood pressure, airway pressure, serum lactate concentrations and rates of bacterial elimination from the blood. At 180 min after E. coli injection, the animals were killed, and tissue samples of liver, kidney, spleen and lung were collected for bacterial counts. ET-1 infusion produced an increase in mean arterial pressure (83.9 +/- 3.9 mmHg vs. 50.1 +/- 4.1 mmHg at 120 min; P < 0.01) associated with higher serum lactate concentrations (12.6 +/- 1.3 vs. 5.4 +/- 0.3 mg dL-1; P < 0.001) and a delayed bacterial elimination from the blood compared with controls. Furthermore, there was increased colonization of the lungs (3.6 +/- 0.5 x 10(3) cfu vs. 745 +/- 120 cfu; P < 0.01), spleen (142.4 +/- 45.4 x 10(3) cfu vs. 227 +/- 5.2 x 10(3) cfu; P < 0.05) and kidney (758 +/- 329 vs. 357 +/- 151 cfu; NS), reflecting a reduced bacterial killing function.

Topics: Animals; Blood Pressure; Colony Count, Microbial; Endothelin-1; Endotoxins; Escherichia coli; Escherichia coli Infections; Female; Hemodynamics; Hemoglobins; Kidney; Kinetics; Lactic Acid; Lipopolysaccharides; Liver; Lung; Male; Rabbits; Spleen

This study was performed to integratively investigate the vasoregulatory response during standardized splanchnic hypoperfusion in pigs. Splanchnic perfusion was reduced to 50% of baseline by: haemorrhage by 20 and 40% of the estimated total blood volume; femoral venous infusion of live E. coli to establish sepsis of systemic origin; portal venous infusion of live E. coli to establish sepsis of splanchnic origin. Invasive haemodynamic monitoring and radioimmunoassay analyses of arterial plasma concentrations of angiotensin II, endothelin-1 and atrial natriuretic peptide were carried out. Acute hypovolaemia reduced systemic and splanchnic vascular resistances following transient increases and increased angiotensin II levels (+587%), whereas endothelin-1 and atrial natriuretic peptide levels did not change significantly. Systemic sepsis following femoral venous infusion of E. coli resulted in increased splanchnic vascular resistance and increased levels of angiotensin II (+274%), endothelin-1 (+134%) and atrial natriuretic peptide (+185%). Infusion of E. coli via the portal venous route induced an increase in splanchnic vascular resistance associated with particularly elevated levels of angiotensin II (+1770%) as well as increased endothelin-1 (+201%) and atrial natriuretic peptide (+229%) concentrations. Hypovolaemia and sepsis, although standardized with a predefined level of splanchnic hypoperfusion, elicited differentiated cardiovascular and vasopeptidergic responses. Sepsis, particularly of portal origin, notably increased splanchnic vascular resistance related to increased production of the vasoconstrictors angiotensin II and endothelin-1. The role of atrial natriuretic peptide as a vasodilator seems to be of subordinate importance in hypovolaemia and sepsis.

Topics: Acute Disease; Anesthesia; Angiotensin II; Animals; Atrial Natriuretic Factor; Endothelin-1; Escherichia coli Infections; Female; Femoral Vein; Hemorrhage; Hypovolemia; Male; Neuropeptides; Portal Vein; Sepsis; Splanchnic Circulation; Swine; Vasoconstrictor Agents

We have performed a series of experiments to study the effects of a newly developed antisense homology box-derived endothelin (ET) antagonist peptide (ETR-P1/fl) on the early hemodynamic changes in a hyperdynamic endotoxemic dog model. Mean arterial pressure (MAP), cardiac output (CO) and myocardial contractility (MC) were measured in closed-chest animals. Plasma levels of ET-1,2 were determined by radioimmunassay. A hyperdynamic circulatory response was elicited with a 2-hour infusion of 5.3 micrograms/kg of E. coli endotoxin (ETX). Control and ETX-treated animals received an infusion of ETR-P1/fl (0.1 mg/kg) i.v. ETX treatment decreased MAP and MC, increased initially CO, and a long lasting elevation in the plasma ET level was observed. In ETX-treated animals the administration of ETR-P1/fl significantly prolonged the increase in CO and inhibited the depression of MC. Our results suggest that treatment with the ET antagonist ETR-P1/fl may be advantageous in the early phase of endotoxemia.

Topics: Animals; Blood Circulation; Blood Pressure; Cardiac Output; Disease Models, Animal; Dogs; Endothelin Receptor Antagonists; Endothelin-1; Endothelin-2; Endotoxemia; Endotoxins; Escherichia coli; Escherichia coli Infections; Heart Rate; Hemodynamics; Infusions, Intravenous; Intercellular Signaling Peptides and Proteins; Myocardial Contraction; Peptides; Ventricular Function, Left; Ventricular Pressure

Big-endothelin (big-ET) is one of the endothelium-derived vasoactive substances that plays an important role in regulating the vascular tone. Because the role of this agent in bacteremia remains unknown, we investigated whether bacteremia induces the release of big-ET in a subhuman primate model and whether tumor necrosis factor (TNF) is an important mediator of big-ET release. To study this, we infused 8 male baboons (17 to 19 kg body weight) intravenously for 2 hours with Escherichia coli (5 x 10(8) CFU/kg) and observed them for 72 hours. Plasma was obtained at various intervals and assayed for big-ET by using immunoassay. Four bacteremic animals given vehicle only showed a peak big-ET plasma concentration of 15.1 +/- 4.6 fmol/ml at 10 hours, as compared with a baseline concentration of 0.9 +/- 0.5 fmol/ml. Administration of anti-TNF monoclonal antibodies (CB6, 15 mg/kg) 2 hours before E. coli infusion in additional animals prevented the rise in plasma TNF levels (5.7 +/- 2.5 ng/ml versus nondetectable) and significantly (p < 0.01) attenuated the release of big-ET. Hemodynamic measurements revealed the typical pattern of sepsis, with generally more stable circulatory conditions in the anti-TNF-treated animals. Moreover, the mortality rate decreased from 100% to 0% with anti-TNF treatment. These studies, therefore, lead us to conclude that TNF, directly or indirectly through another mediator, plays an important role in the endothelin production/release during bacteremia and that neutralization of circulating TNF appears to be beneficial for improving the survival after bacteremia.

Topics: Animals; Bacteremia; Endothelin-1; Endothelins; Endotoxins; Escherichia coli; Escherichia coli Infections; Hemodynamics; Male; Papio; Protein Precursors; Survival Analysis; Tumor Necrosis Factor-alpha