Endotoxin Infusion Research Articles

A cardioprotective role for the endothelial protein C receptor in lipopolysaccharide-induced endotoxemia in the mouse

AbstractA model of gram-negative lethal endotoxin shock, involving continuous peritoneal infusion of lipopolysaccharide (LPS), has been applied to wild-type (WT) mice and mice with a severe deficiency of endothelial protein C receptor (EPCRδ/δ). The survival of EPCRδ/δ mice was significantly diminished as compared to WT mice after administration of LPS via this route. Heart rates and central blood pressures also were significantly more depressed in EPCRδ/δ mice, indicating that the receptor-based protein C (PC) pathway functions in regulation of hemodynamic properties in the mouse. Further, heart muscle damage was more severe in EPCRδ/δ mice as compared to WT mice after endotoxin administration, as revealed by the more elevated plasma myoglobin levels in EPCRδ/δ mice and by microscopic examination of stained heart sections. Neutrophil infiltration was more pronounced in heart tissue of EPCRδ/δ mice, perhaps in response to the greatly increased expression level of the chemokine, MIP-2, which also significantly more up-regulated in the LPS-treated EPCRδ/δ mouse cohort. In conclusion, a severe deficiency of EPCR adversely affects survival of mice subjected to continuous infusion of endotoxin, via contributions of more responsive hemodynamic and cardiac alterations, thus suggesting that, among its other functions, the PC-based receptor system has a cardioprotective role after acute inflammatory challenge.

Safety of endotoxin challenge in healthy volunteers: bradycardia

which is observed by an experienced physician present in the same room. This allowed detection of one case of brady-asystole in a young male volunteer who had had an uneventful medical history and who had passed medical and laboratory screening examinations. Prior to bradycardia, endotoxin elicited nausea and vomiting in this subject, which probably contributed to a pronounced vagal reflex, resulting in brady-asystole. Brady-asystole occurred 1–2 h after endotoxin infusion and lasted for one monitor length but did not cause unconsciousness in the young man. The subject recovered spontaneously without medical intervention or sequel. Based on van Eijk’s report [4] and our own data, we can estimate that the incidence of this adverse event is approximately seen in 1 out of 600 challenged individuals. Like van Eijk et al. [4], we recommend liberal oral water intake in fasting volunteers prior to endotoxin challenge, and in most clinical trials we additionally administer physiological saline solution (200 ml/h) to maintain adequate hydration. We have not observed any serious or severe adverse events following endotoxin infusion and thus concur with their conclusion that the model is a safe and a powerful tool for studying systemic inflammation, coagulation, and potential therapeutic interventions.

Low-dose terlipressin during long-term hyperdynamic porcine endotoxemia: Effects on hepatosplanchnic perfusion, oxygen exchange, and metabolism*

To investigate whether the vasopressin analog terlipressin might induce hepatosplanchnic ischemia during long-term, hyperdynamic, volume-resuscitated porcine endotoxemia. Prospective, randomized, controlled experimental study with repeated measures. Investigational animal laboratory. Eighteen pigs were divided into two groups receiving either endotoxin alone (control group, n = 10) or endotoxin and terlipressin (n = 8). Pigs were anesthetized, mechanically ventilated, and instrumented and received a continuous intravenous infusion of Escherichia coli endotoxin. Animals were resuscitated with hydroxyethyl starch targeted to maintain mean arterial pressure >60 mm Hg. Twelve hours after the start of the endotoxin infusion, terlipressin (5-15 microg.kg.hr titrated to maintain mean arterial pressure at preendotoxin levels) or its vehicle was administered for 12 hrs. Terlipressin increased mean arterial pressure and systemic vascular resistances, which was affiliated with a decrease in cardiac output and global oxygen consumption. Terlipressin restored the hepatic artery buffer response, which led to an increase in hepatic artery flow, ultimately resulting in well-maintained liver oxygen delivery, oxygen uptake, and all other variables of regional metabolism and organ function. Terlipressin markedly attenuated the hepatosplanchnic venous acidosis but was associated with pronounced hyperlactatemia. During long-term hyperdynamic porcine endotoxemia, the well-known vasoconstrictor properties of terlipressin blunted the progressive decrease in mean arterial pressure without any detrimental effect on hepatosplanchnic perfusion, oxygen exchange, and metabolism. The marked terlipressin-induced hyperlactatemia did not originate from the hepatosplanchnic organs but from extrasplanchnic tissues, possibly muscle and skin.

Tezosentan reduces the microvascular filtration coefficient in isolated lungs from rats subjected to cecum ligation and puncture

IntroductionWe recently demonstrated that the non-selective endothelin-1 (ET-1) receptor blocker tezosentan antagonizes ovine acute lung injury (ALI) following infusion of endotoxin or ET-1 by reducing the enhanced lung microvascular pressure, although we could not exclude the possibility of a simultaneous decline in microvascular permeability. In the present study, our aim was to find out if tezosentan reverses the rise in microvascular filtration coefficient (Kfc) in rat lungs that have been isolated and perfused 12 h after cecum ligation and puncture (CLP) or infusion of ET-1.MethodsWistar rats (n = 42) were subjected to CLP. Postoperatively, rats were randomized to a CLP group (n = 7) and a CLP + tezosentan group (n = 7); the latter received tezosentan 30 mg/kg. A sham-operated group (n = 5) underwent laparotomy without CLP. Twelve hours postoperatively, the lungs were isolated and perfused with blood from similarly treated rats that also were used to assess plasma concentration of ET-1 and protein kinase Cα (PKCα) in lung tissue. Additionally, isolated blood perfused lungs from healthy rats were randomized to a control group (n = 8), an ET-1 group (n = 7) subjected to pulmonary arterial injection of ET-1 10 nM, and an ET-1 + tezosentan group (n = 7) that received tezosentan 30 mg/kg. All lung preparations received papaverine 0.1 μg/kg added to the perfusate for vasoplegia. Pulmonary hemodynamic variables, Kfc and lung compliance (CL) were assessed.ResultsAfter CLP, the plasma concentration of ET-1 increased. Papaverine abolished the vasoconstrictor response to ET-1 and the pulmonary vascular pressures remained close to baseline throughout the experiments. Both CLP and injection of ET-1 caused significant changes in Kfc and CL that were prevented in tezosentan-treated rats. Compared to sham-operated animals, CLP increased the content of PKCα by 50% and 70% in the cytosolic and the membrane fractions of lung tissue homogenates, respectively. Tezosentan prevented the upregulation of PKCα in the membrane fraction.ConclusionIn rat lungs isolated and perfused after CLP, tezosentan precludes both the increase in Kfc and the upregulation of PKCα in the membrane fraction of lung tissue.

Change of extravascular lung water in sheep with early acute respiratory distress syndrome

To determine the change of extravascular lung water (EVLW) and the effect of positive end-expiratory pressure (PEEP) and cardiac output (CO) on EVLW in the sheep with early acute respiratory distress syndrome (ARDS). The sheep ARDS model was induced by infusion of endotoxin intravenously, and then divided into ARDS model group (n = 12), PEEP group (n = 21) and dobutamine group (n = 13). The PEEP group was further divided into three subgroups: PEEP 5 cm H(2)O (n = 7), 10 cm H(2)O (n = 8) and 15 cm H(2)O groups (n = 6). EVLW was measured by the single indicator thermodilution technique. The EVLW, hemodynamics and lung mechanics parameters were observed at 6 h after sheep ARDS model was induced, 2 h after mechanical ventilation with PEEP (5, 10, 15 cm H(2)O) respectively and 2 h after CO increase >/= 50% of the base value (induced by dobutamine infusion). (1) When ARDS was induced in sheep, EVLW increased from (12.8 +/- 4.7) ml/kg to (18.1 +/- 7.1) ml/kg (P < 0.01), and EVLW had no significant change (P > 0.05) during the early phase of ARDS (6 h). PaO(2)/FiO(2) was (136.8 +/- 34.9) mm Hg at ARDS 0 h, which was higher than that before infusion of endotoxin [(444.3 +/- 127.7) mm Hg, P < 0.01]. EVLW had no relationship with PaO(2)/FiO(2), but DeltaEVLW after ARDS model induced had good correlation with DeltaPaO(2)/FiO(2) (r = -0.501, P < 0.001). When ARDS was induced, static lung compliance decreased from 26.9 +/- 8.4 to 16.4 +/- 5.0 (P < 0.01). (2) After mechanical ventilation with PEEP 2 h, EVLW in PEEP 10 cm H(2)O group and 15 cm H(2)O group were (14.7 +/- 4.5) ml/kg and (15.3 +/- 3.7) ml/kg respectively, which was significantly less than that before PEEP [(16.5 +/- 4.7) ml/kg and (18.4 +/- 6.0) ml/kg respectively, all P < 0.05]. But EVLW in 5 cm H(2)O group showed no difference during 2 h PEEP application. (3) After CO increase >/= 50% of the base value 1 h and 2 h, EVLW was (16.3 +/- 4.9) ml/kg and (16.9 +/- 6.9) ml/kg respectively, which did not differ from that of the baseline value [(15.1 +/- 4.6) ml/kg, all P > 0.05]. EVLW in ARDS sheep increased significantly and remained at the same level during the early phase of ARDS. PEEP had a markedly effect in reducing EVLW, while the increase of CO induced by dobutamine did not significantly raise EVLW.

Changes in ADAMTS13 (von-Willebrand-factor-cleaving protease) activity after induced release of von Willebrand factor during acute systemic inflammation

Von Willebrand factor (VWF) is synthesized in endothelial cells, stored in the form of high molecular weight multimers and released after stimulation. After release, the multimers are cleaved by ADAMTS13 (von-Willebrand-factor-cleaving protease). We studied healthy volunteers in a double-blind, placebo controlled inflammation model. Ten male volunteers received 2 ng/kg endotoxin intravenously, and 5 volunteers placebo. Endotoxin infusion induced systemic inflammation and coagulation activation. After 4 hours the observed increase in neutrophils reached a maximum (273+/-34% of baseline; mean+/-SEM) and the platelet count dropped (81+/-2%). These parameters returned to baseline values after 24 hours. VWF antigen increased to 259+/-16% of baseline after 4 hours, remained elevated (192+/-15%) after 24 hours and returned to baseline after 7 days. Unusually large VWF multimers occurred in the plasma 4 hours after endotoxin infusion. ADAMTS13 activity (measured with a collagen-binding assay) decreased to 64+/-5% of baseline (P<0.001) after 4 hours, was still reduced after 24 hours (86+/- %; P=0.008) and returned to normal after 7 days. VWF multimer analysis showed pronounced satellite bands in the 4-hour samples, indicating cleavage of VWF by ADAMTS13. No apparent changes of the analyzed parameters were observed in the placebo group. The reciprocal course of ADAMTS13 and VWF after short-term VWF release induced by systemic inflammation is similar to that observed after induction of VWF release by desmopressin.

P38-MAPK inhibition and endotoxin induced tubular dysfunction in men

Background: To evaluate the possibility of preventing endotoxin induced renal damage by p38-MAPK inhibition in a human model. Design and Methods: Twenty-one healthy young male volunteers received 4 ng/kg Escherichia coli endotoxin as a single dose. Four groups of volunteers received an oral dose of placebo or 350, 700 or 1400 mg RWJ-67657, a p38-MAPK inhibitor, 20 min before endotoxin infusion. Urine samples were collected at set time intervals. The urinary excretion rate of β2-microglobulin and N-acetyl-β-D-glucosaminidase, as indicators of tubular dysfunction was determined. Results: There was a significant increase of β2-microglobulin and N-acetyl-β-D-glucosaminidase urine excretion rate after endotoxin infusion in the placebo group. p38-MAPK inhibition prevented the increase of markers for tubulopathy. Conclusions: Endotoxin infusion induces measurable tubular damage. Blocking the p38-MAPK may prevent this damage. The mechanism is unclear, but blocking TNF-α release is a possible explanation.

P38-MAPK inhibition and endotoxin induced tubular dysfunction in men

To evaluate the possibility of preventing endotoxin induced renal damage by p38-MAPK inhibition in a human model. Twenty-one healthy young male volunteers received 4 ng/kg Escherichia coli endotoxin as a single dose. Four groups of volunteers received an oral dose of placebo or 350, 700 or 1400 mg RWJ-67657, a p38-MAPK inhibitor, 20 min before endotoxin infusion. Urine samples were collected at set time intervals. The urinary excretion rate of beta(2)-microglobulin and N-acetyl-beta-D-glucosaminidase, as indicators of tubular dysfunction was determined. There was a significant increase of beta(2)-microglobulin and N-acetyl-beta-D-glucosaminidase urine excretion rate after endotoxin infusion in the placebo group. p38-MAPK inhibition prevented the increase of markers for tubulopathy. Endotoxin infusion induces measurable tubular damage. Blocking the p38-MAPK may prevent this damage. The mechanism is unclear, but blocking TNF-alpha release is a possible explanation.

Cerebral Vascular and Metabolic Response to Sustained Systemic Inflammation in Ovine Traumatic Brain Injury

Traumatic brain injury (TBI) is frequently accompanied by a systemic inflammatory response secondary to multiple trauma, shock, or infections. This study investigated the impact of sustained systemic inflammation on cerebral hemodynamics and metabolism in ovine traumatic brain injury. Fifteen sheep were investigated for 14 hours. Head injury was induced with a nonpenetrating stunner in anesthetized, ventilated animals. One group (TBI/Endo, n = 6) subsequently received a continuous endotoxin infusion for 12 hours, whereas a second group (TBI, n = 6) received the carrier. Three instrumented animals served as sham controls. Head impact significantly increased intracranial pressure from 9 ± 4 mm Hg to 21 ± 15 mm Hg (TBI/Endo) and from 10 ± 3 mm Hg to 24 ± 19 mm Hg (TBI) (means ± SD). Internal carotid blood flow increased and cerebral vascular resistance decreased (P < 0.05) during the hyperdynamic inflammatory response between 10 and 14 hours in the TBI/Endo group, whereas these parameters were at baseline level in the TBI group. Intracranial pressure remained unchanged during this period, but increased during hypercapnia. The CMRO2, PaCO2, and arterial hematocrit values were identical among the groups between 10 and 14 hours. It is concluded that chronic endotoxemia in ovine traumatic brain injury was associated with cerebral vasodilation uncoupled from global brain metabolism. Different mechanisms appear to induce cerebral vasodilation in response to inflammation and hypercapnia.

Cerebral Vascular and Metabolic Response to Sustained Systemic Inflammation in Ovine Traumatic Brain Injury

Traumatic brain injury (TBI) is frequently accompanied by a systemic inflammatory response secondary to multiple trauma, shock, or infections. This study investigated the impact of sustained systemic inflammation on cerebral hemodynamics and metabolism in ovine traumatic brain injury. Fifteen sheep were investigated for 14 hours. Head injury was induced with a nonpenetrating stunner in anesthetized, ventilated animals. One group (TBI/Endo, n = 6) subsequently received a continuous endotoxin infusion for 12 hours, whereas a second group (TBI, n = 6) received the carrier. Three instrumented animals served as sham controls. Head impact significantly increased intracranial pressure from 9 +/- 4 mm Hg to 21 +/- 15 mm Hg (TBI/Endo) and from 10 +/- 3 mm Hg to 24 +/- 19 mm Hg (TBI) (means +/- SD). Internal carotid blood flow increased and cerebral vascular resistance decreased (P < 0.05) during the hyperdynamic inflammatory response between 10 and 14 hours in the TBI/Endo group, whereas these parameters were at baseline level in the TBI group. Intracranial pressure remained unchanged during this period, but increased during hypercapnia. The CMRO2, PaCO2, and arterial hematocrit values were identical among the groups between 10 and 14 hours. It is concluded that chronic endotoxemia in ovine traumatic brain injury was associated with cerebral vasodilation uncoupled from global brain metabolism. Different mechanisms appear to induce cerebral vasodilation in response to inflammation and hypercapnia.

Introduction new developments in preeclampsia

Introduction new developments in preeclampsia

Introduction new developments in preeclampsia

Introduction new developments in preeclampsia

Epinephrine induces tissue perfusion deficit in porcine endotoxin shock: evaluation by regional CO2 content gradients and lactate-to-pyruvate ratios

Epinephrine is widely used as a vasoconstrictor or inotrope in shock, although it may typically induce or augment lactic acidosis. Ongoing debate addresses the question of whether hyperlactatemia per se is a sign of tissue perfusion deficit or aerobic glycolysis. We wanted to test the hypothesis that epinephrine has selective detrimental effects on visceral perfusion and metabolism. We performed rigorous regional venous blood gas analyses as well as intraperitoneal microdialysis. We used a mathematical model to calculate regional arteriovenous CO(2) content gradients and estimated the magnitude of the Haldane effect in a porcine model of prolonged hypotensive shock induced by endotoxin infusion (mean arterial blood pressure < 60 mmHg). Subsequently, vasopressors (epinephrine or norepinephrine) were administered and adjusted to maintain systemic mean arterial pressure > 70 mmHg for 4 h. Epinephrine caused systemic hyperlactatemia and acidosis. Importantly, both systemic and regional venous lactate-to-pyruvate ratios increased. Epinephrine was associated with decreasing portal blood flow despite apparently maintained total splanchnic blood flow. Epinephrine increased gastric venous-to-arterial Pco(2) gradients and CO(2) content gradients with decreasing magnitude of the Haldane effect, and the regional gastric respiratory quotient remained higher after epinephrine as opposed to norepinephrine infusion. In addition, epinephrine induced intraperitoneal lactate and glycerol release. We did not observe these adverse hemodynamic or metabolic changes related to norepinephrine with the same arterial pressure goal. We conclude that high CO(2) content gradients with decreasing magnitude of the Haldane effect pinpoint the most pronounced perfusion deficiency to the gastric wall when epinephrine, as opposed to norepinephrine, is used in experimental endotoxin shock.

Altered monocyte function in experimental preeclampsia in the rat

In the present study, we evaluated functional activity of monocytes in experimental preeclampsia induced by low-dose endotoxin infusion. Pregnant (n = 12) and cyclic rats (n = 12) were equipped with a permanent jugular vein cannula and infused with either low-dose endotoxin or saline. One day before the infusion, and 4, 24, 72, and 168 hours after the infusion, blood samples (400 microL) were taken and white blood cell (WBC) and differential cell counts were measured. Samples were (re)stimulated with endotoxin, and the percentage of tumor necrosis factor-alpha (TNFalpha) producing monocytes was measured. During experimental preeclampsia, monocyte TNFalpha production is persistently decreased, while total WBC and granulocyte counts are persistently increased compared with normal pregnant rats. No persistent effect of endotoxin was found in cyclic rats. Because decreased endotoxin-induced TNFalpha production is a feature of activated monocytes, the present results indicate that monocytes are persistently activated in experimental preeclampsia. Increased WBC counts and granulocyte numbers in these rats also point to an activated inflammatory response.

Dobutamine compensates deleterious hemodynamic and metabolic effects of vasopressin in the splanchnic region in endotoxin shock.

Vasopressin is a potent vasopressor in septic shock, but it may impair splanchnic perfusion. We compared the effects of vasopressin alone and in combination with dobutamine on systemic and splanchnic circulation and metabolism in porcine endotoxin shock. Twelve pigs were randomized to receive either vasopressin (VASO, n = 6) or vasopressin in combination with dobutamine (DOBU, n = 6) during endotoxin shock (E. coli endotoxin infusion). Endotoxin infusion rate was increased to induce hypotension after which vasoactive drugs were started. We aimed to keep systemic mean arterial pressure (MAP) >70 mmHg by vasopressin; the goal of dobutamine infusion was to prevent decrease in cardiac output often associated with vasopressin infusion. Regional blood flows, oxygen delivery and consumption, arterial and regional lactate concentrations were measured. Mean arterial pressure >70 mmHg was achieved in both the VASO and DOBU groups. After the primary decrease of cardiac output by vasopressin, systemic blood flow remained stable in vasopressin-treated animals. However, vasopressin as a monotherapy decreased portal venous blood flow. This was prevented by dobutamine. Vasopressin also induced splanchnic lactate release and arterial hyperlactatemia, which were not observed when dobutamine was combined with vasopressin. Dobutamine prevents adverse hemodynamic and metabolic effects of vasopressin in septic shock.

New approach to an ovine model of hypodynamic endotoxaemia.

Since the moribund hypodynamic phase of septic shock has primarily been studied in small animal models, the objective of this study was to investigate the usefulness of infusing Salmonella typhosa endotoxin at incrementing doses to establish an ovine model of hypodynamic endotoxaemia. In a prospective laboratory experiment, eight adult ewes were instrumented for a chronic study. Following a baseline measurement in the healthy state, a continuous endotoxin infusion was started with 10 ng kg(-1) min(-1) and was doubled every hour seven times. Haemodynamics, key variables of oxygen transport, and arterial lactate concentrations were determined every hour. In a dose-dependent manner, endotoxin infusion caused pulmonary hypertension, decreased cardiac output and mean arterial pressure, increased heart rate, and to a certain extent, systemic vascular resistance index. Following 4h of endotoxaemia, the maximum decrease in cardiac output occurred (4.8+/-0.2 vs. 7.6+/-0.3 Lmin(-1); P < 0.001). This was accompanied by tissue dysoxia, represented by decreases in oxygen delivery (797+/-20 vs. 1041+/-28 mLmin(-1)), oxygen consumption (277+/-14 vs. 396+/-15 mLmin(-1)) and oxygen extraction rate (0.35+/-0.01 vs. 0.38+/-0.01%; each P < 0.01), as well as an increase in arterial lactate concentration (1.7+/-0.1 vs. 0.7+/-0.1 mmolL(-1); P < 0.05). This large animal model may be helpful to study the pathophysiology responsible for cardiovascular failure, and also new therapeutic approaches relevant to management of hypodynamic circulation in the common setting of progressed systemic inflammation.

New approach to an ovine model of hypodynamic endotoxaemia

Background and objective: Since the moribund hypodynamic phase of septic shock has primarily been studied in small animal models, the objective of this study was to investigate the usefulness of infusing Salmonella typhosa endotoxin at incrementing doses to establish an ovine model of hypodynamic endotoxaemia. Methods: In a prospective laboratory experiment, eight adult ewes were instrumented for a chronic study. Following a baseline measurement in the healthy state, a continuous endotoxin infusion was started with 10 ng kg−1 min−1 and was doubled every hour seven times. Haemodynamics, key variables of oxygen transport, and arterial lactate concentrations were determined every hour. Results: In a dose-dependent manner, endotoxin infusion caused pulmonary hypertension, decreased cardiac output and mean arterial pressure, increased heart rate, and to a certain extent, systemic vascular resistance index. Following 4h of endotoxaemia, the maximum decrease in cardiac output occurred (4.8 ± 0.2 vs. 7.6 ± 0.3 L min−1; P < 0.001). This was accompanied by tissue dysoxia, represented by decreases in oxygen delivery (797 ± 20 vs. 1041 ± 28 mL min−1), oxygen consumption (277 ± 14 vs. 396 ± 15 mL min−1) and oxygen extraction rate (0.35 ± 0.01 vs. 0.38 ± 0.01%; each P < 0.01), as well as an increase in arterial lactate concentration (1.7 ± 0.1 vs. 0.7 ± 0.1 mmol L−1; P < 0.05). Conclusions: This large animal model may be helpful to study the pathophysiology responsible for cardiovascular failure, and also new therapeutic approaches relevant to management of hypodynamic circulation in the common setting of progressed systemic inflammation.

Polymyxin B protects horses against induced endotoxaemia in vivo.

A safe, affordable and effective treatment for endotoxaemia in horses is needed in order to reduce the incidence of this potentially fatal condition. To evaluate the effect of polymyxin B (PMB) on signs of experimentally-induced endotoxaemia. PMB ameliorates the adverse effects of endotoxaemia without causing nephrotoxicity. Four groups of 6 healthy mature horses each received 20 ng endotoxin/kg bwt i.v. over 30 mins. Additionally, each group received one of the following i.v.; 5000 u PMB/kg bwt 30 mins before endotoxin infusion; 5000 u PMB/kg bwt 30 mins after endotoxin infusion; 1000 u PMB/kg bwt 30 mins prior to endotoxin infusion; or saline. Clinical response data and samples were collected to determine neutrophil count, serum tumour necrosis factor (TNF) activity, plasma thromboxane B2 concentration and urine gamma glutamyltranspeptidase (GGT) to creatinine ratio. Treatment with PMB before or after administration of endotoxin significantly reduced fever, tachycardia and serum TNF, compared to horses receiving saline. The differences in response to endotoxin were greatest between horses that received saline vs. those that received 5000 u PMB/kg bwt prior to endotoxin. Urine GGT:creatinine did not change significantly. This study indicates that PMB may be a safe and effective treatment of endotoxaemia, even when administered after onset. Although nephrotoxicity was not demonstrated with this model, caution should be exercised when using PMB in azotaemic patients.

Hyperoxia-induced emphysematous changes in subacute phase of endotoxin-induced lung injury in rats.

We examined the effects of prolonged hyperoxia (75% O(2)) on lung structure and collagen metabolism in the subacute phase of lung injury induced by continuous infusion of endotoxin (LPS) in a rat model. Experimental groups included control, endotoxin alone, endotoxin plus hyperoxia, and hyperoxia alone. Endotoxin-treated rats received a bolus of LPS (10 mg/kg i.v.) followed by 500 microg.kg(-1).day(-1) in continuous infusion for 10 days. The bronchoalveolar lavage (BAL) fluid/plasma albumin concentration ratio, an index of capillary permeability, and neutrophil and macrophage counts in BAL fluid were highest in the endotoxin plus hyperoxia group. On pathological examination, prolonged hyperoxia exacerbated destruction of the alveolar wall and caused most prominent emphysematous changes in the endotoxin plus hyperoxia group. Lung tissue hydroxyproline concentration was significantly decreased in the hyperoxia group and increased in the endotoxin group. The latent forms of MMP-2 and MMP-9 increased in BAL fluid of the endotoxin- and/or hyperoxia-treated groups, whereas the activities of collagenase and gelatinase, and the active form of MMP-2 were all increased in the hyperoxia-treated groups. Added to endotoxin, prolonged hyperoxia degraded collagen, the major structural component of basement membranes, and caused emphysematous changes associated with activation of collagenase and MMP-2. Our observations suggest that, in the subacute phase of endotoxin-induced lung injury, prolonged hyperoxia causes pulmonary emphysematous changes with persistent injury to the alveolar capillary barrier. Collagenase and MMP-2 activated by hyperoxia, together with MMP-9, may play prominent roles in disruption of the alveolar basement membranes and degradation of collagen lining the alveolar walls.

Induction of microparticle- and cell-associated intravascular tissue factor in human endotoxemia

AbstractThe precise role of intravascular tissue factor (TF) remains poorly defined, due to the limited availability of assays capable of measuring circulating TF procoagulant activity (PCA). As a model of inflammation-associated intravascular thrombin generation, we studied 18 volunteers receiving an infusion of endotoxin. A novel assay that measures microparticle (MP)-associated TF PCA from a number of cellular sources (but not platelets) demonstrated an 8-fold increase in activity at 3 to 4 hours after endotoxin administration (P < .001), with a return to baseline by 8 hours. TF antigen-positive MPs isolated from plasma were visualized by electron microscopy. Interindividual MP-associated TF response to lipopolysaccharide (LPS) was highly variable. In contrast, a previously described assay that measurestotal (cell and MP-borne) whole-blood TF PCA demonstrated a more modest increase, with a peak in activity (1.3-fold over baseline; P < .000 01) at 3 to 4 hours, and persistence for more than 24 hours. This surprisingly modest increase in whole-blood TF activity is likely explained by a profound although transient LPS-induced monocytopenia. MP-associated TF PCA was highly correlated with whole-blood TF PCA and total number of circulating MPs, and whole-blood TF PCA was highly correlated with TF mRNA levels. (Blood. 2004;103:4545-4553)