Role of thromboxane, prostaglandins and leukotrienes in endotoxic and septic shock

Molecular mechanisms in septic shock (Review)

Sepsis is a clinical syndrome defined by the presence of infection and systemic inflammatory response to infection and results from a complex interaction between the host and infectious agents. It is characterized by the activation of multiple inflammatory pathways, with an increased risk of mortality. The incidence of sepsis has been on an ever-increasing pathway in recent years. Sepsis can be induced by several clinical situations that predispose to its occurrence: malignant tumors, organ transplantation, AIDS, radiation therapy, burns, sores, polytrauma, diabetes mellitus, hepatic failure, renal failure, malnutrition, catheters or different invasive devices, and urinary catheters. The microorganisms involved in the pathogenesis of sepsis are Gram-positive cocci (Staphylococci, Streptococci) and Gram-negative bacilli (Klebsiella, Pseudomonas aeruginosa, E. coli), fungi (Candida), parasites, and viruses. Among mechanisms involved in septic shock production, two pathological phenomena appear: the profound decompensation of circulation and metabolic disturbances that evolve towards an irreversible state. The intimate mechanism of shock involves the activation of monocytes, macrophages and neutrophils by lipopolysaccharides of Gram-negative bacteria. The microvascular bed is directly involved in the etiopathogenesis of disorders of acute inflammatory states associated with or without sepsis. A better comprehension of sepsis pathophysiology, especially the molecular mechanisms of septic shock, allows for new therapeutic perspectives.

Acute fibrinolysis shutdown occurs early in septic shock and is associated with increased morbidity and mortality: results of an observational pilot study

BACKGROUND

Septic coagulopathy represents a very dynamic disease entity, tilting from initial hypercoagulability towards a subsequent hypocoagulable disease state, entitled overt disseminated intravascular coagulation. Acute fibrinolysis shutdown has recently been described to be a crucial component of initial hypercoagulability in critically ill patients, although the underlying pathomechanisms, the specific temporal kinetics and its outcome relevance in patients with sepsis remain to be determined.

METHODS

In total, 90 patients (30 with septic shock, 30 surgical controls and 30 healthy volunteers) were enrolled. Blood samples were collected at sepsis onset or prior and immediately after the surgical procedure as well as 3 h, 6 h, 12 h, 24 h, 48 h and 7 d later, whereas blood samples from healthy volunteers were collected once. Besides viscoelastic and aggregometric point-of-care testing (POCT), enzyme-linked immunosorbent and thrombin generation assays and liquid chromatography-mass spectrometry-based measurements were performed.

RESULTS

As assessed by viscoelastic POCT, fibrinolysis shutdown occurred early in sepsis. Significant increases in tissue plasminogen activator had no effect on thromboelastometrical lysis indices (LIs). Contrariwise, plasminogen activator inhibitor-1 was already significantly increased at sepsis onset, which was paralleled by significantly increased LIs in patients suffering from septic shock in comparison with both control groups. This effect persisted throughout the 7-day observation period and was most pronounced in severely ill as well as non-surviving septic patients. Thromboelastometrical LI, therefore, proved to be suitable for early diagnosis [e.g. LI 45 min: area under the curve (AUC) up to 0.933] as well as prognosis (e.g. LI 60 min: AUC up to 1.000) of septic shock.

CONCLUSIONS

Early inhibition of plasminogen activation leads to acute fibrinolysis shutdown with improved clot stability and is associated with increased morbidity and mortality in septic patients. Trial registration This study was approved by the local ethics committee (Ethics Committee of the Medical Faculty of Heidelberg; Trial-Code No. S247-2014/German Clinical Trials Register (DRKS)-ID: DRKS00008090; retrospectively registered: 07.05.2015). All study patients or their legal representatives signed written informed consent.

The use of nonsteroidal anti-inflammatory drugs in critically ill horses

OBJECTIVE

To review the physiology of the cyclooxygenase (COX) enzymes with reference to the beneficial effects of nonsteroidal anti-inflammatory drugs (NSAIDs) related to their analgesic and antiendotoxic properties as well as the mechanisms responsible for adverse gastrointestinal, renal, and coagulation effects.

DATA SOURCES

Human and veterinary peer reviewed literature

VETERINARY DATA SYNTHESIS

NSAIDs are frequently administered to critically ill horses for their analgesic and anti-inflammatory effects. However, NSAIDs have significant side effects principally on the gastrointestinal mucosa and kidneys. These side effects may be exacerbated in critically ill horses if they have gastrointestinal damage or are volume depleted

CONCLUSIONS

This review provides important information for equine veterinarians and criticalists on the advantages and disadvantages of using traditional NSAIDs and newer equine COX-2 selective NSAIDs for the management of different conditions in critically ill horses.

Interactions between platelet activating factor and eicosanoids during endotoxic shock in anaesthetized pigs

The effects of platelet activating factor (PAF) on eicosanoid release during endotoxic shock was investigated in anaesthetized pigs receiving 5 μg kg⁻¹ Escherichia coli endotoxin (LPS) into the superior mesenteric artery over a 60 min period, by measuring plasma levels of a variety of mediators. Fifteen of the 31 animals infused with LPS and not treated with BN 52021, a PAF receptor antagonist, died within 30 min after the commencement of LPS infusion (non-survivors), while the other 16 survived the experimental period of 3 h, though in a state of shock (survivors). No alterations were observed in plasma concentrations of eicosanoids in the non-survivors. A significant, though transient, increase in eicosanoid concentrations occurred only in the survivors. Treatment with BN 52021 (4 mg kg-1, i.v.) injected 5 min prior to LPS infusion, failed to exert any effect on the survival rate. However, pretreatment with BN 52021 prevented circulatory collapse in the survivors and reduced the concentration of cyclooxygenase enzyme products, without affecting LTB₄ release. Exogenous administration of PAF (0.01 μg kg⁻¹) caused hypotension and increased TXB₂ levels although 6-keto PGF_1α and LTB₄ concentrations were unchanged. The data suggest that prostanoid formation may be secondary to PAF release in circulatory collapse evoked by LPS infusion in survivors, and give further support to the suggestion that PAF prostanoid interaction is important during endotoxic shock. However, their role in early death seems to be negligible, indicating the importance of other mediators.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Dose-response investigation of oral ketoprofen in pigs challenged with Escherichia coli endotoxin

In order to determine the effective dose, the effects of orally administered ketoprofen were evaluated in pigs following intravenous challenge with Escherichia coli endotoxin. One hour after the challenge, five groups of pigs were treated with either tap water or ketoprofen (0.5 mg/kg, 1 mg/kg, 2 mg/kg or 4 mg/kg). The body temperature was measured and a total clinical score was calculated after assessing the general behaviour, respiratory rate and locomotion of the pigs. Thromboxane B(2) and ketoprofen concentrations were analysed from blood samples. Ketoprofen treatment significantly reduced the rectal temperature and total clinical scores, and lowered blood thromboxane B(2) concentrations when compared with the control group. Ketoprofen plasma concentrations were lower than previously reported in healthy pigs after similar doses. The appropriate dose of orally administered ketoprofen in pigs in this model is 2 mg/kg, as the higher dose of 4 mg/kg failed to provide an additional benefit.

Cyclooxygenase inhibition in sepsis: is there life after death?

Prostaglandins are important mediators and modulators of the inflammatory response to infection. The prostaglandins participate in the pathogenesis of hemodynamic collapse, organ failure, and overwhelming inflammation that characterize severe sepsis and shock. In light of this, cyclooxygenase (COX) inhibiting pharmacological agents have been extensively studied for their capacity to ameliorate the aberrant physiological and immune responses during severe sepsis. Animal models of sepsis, using the systemic administration of pathogen-associated molecular patterns (PAMPs) or live pathogens, have been used to examine the effectiveness of COX inhibition as a treatment for severe sepsis. These studies have largely shown beneficial effects on mortality. However, human studies have failed to show clinical utility of COX inhibitor treatment in severely septic patients. Why this approach “worked” in animals but not in humans might reflect differences in the controlled nature of animal investigations compared to human studies. This paper contrasts the impact of COX inhibitors on mortality in animal models of sepsis and human studies of sepsis and examines potential reasons for differences between these two settings.

Adult Dirofilaria immitis excretory/secretory antigens upregulate the production of prostaglandin E2 and downregulate monocyte transmigration in an "in vitro" model of vascular endothelial cell cultures

Canine and feline cardiopulmonary dirofilariosis caused by Dirofilaria immitis is a chronic and potentially fatal disease. Adult worms live in the pulmonary arteries of infected immunocompetent hosts for years. The aim of the present study is the identification of the influence of the metabolic products (excretory/secretory antigens, DiE/S) of D. immitis on the vascular endothelial cells, because the vascular endothelium interplays in a direct manner with the parasite and their products. For this purpose, HAAE-1 vascular endothelial cells were treated with DiE/S, using non-treated cultures as negative controls. Significant increases in the COX-2, 5-LO expression and PGE(2) level were detected in the treated cells compared with the control cells. Moreover, DiE/S decreases monocyte transmigrations across vascular endothelial cell monolayers. Treatment with DiE/S does not have a cytotoxic effect and do not alter apoptosis, necrosis or cell cycle of vascular endothelial cells. These results suggest that the DiE/S stimulates the production of mediators and mechanisms that favor the survival of the parasite, in vascular endothelial cells, contributing to restrict vascular and lung damages in the infected host, without altering the basic physiologic processes of endothelial cells.

E-prostanoid 3 receptor deletion improves pulmonary host defense and protects mice from death in severe Streptococcus pneumoniae infection

Prostaglandins (PGs) are potent lipid mediators that are produced during infections and whose synthesis and signaling networks present potential pharmacologic targets for immunomodulation. PGE(2) acts through the ligation of four distinct G protein-coupled receptors, E-prostanoid (EP) 1-4. Previous in vitro and in vivo studies demonstrated that the activation of the G(alphas)-coupled EP2 and EP4 receptors suppresses inflammatory responses to microbial pathogens through cAMP-dependent signaling cascades. Although it is speculated that PGE(2) signaling via the G(alphai)-coupled EP3 receptor might counteract EP2/EP4 immunosuppression in the context of bacterial infection (or severe inflammation), this has not previously been tested in vivo. To address this, we infected wild-type (EP3(+/+)) and EP3(-/-) mice with the important respiratory pathogen Streptococcus pneumoniae or injected mice i.p. with LPS. Unexpectedly, we observed that EP3(-/-) mice were protected from mortality after infection or LPS. The enhanced survival observed in the infected EP3(-/-) mice correlated with enhanced pulmonary clearance of bacteria; reduced accumulation of lung neutrophils; lower numbers of circulating blood leukocytes; and an impaired febrile response to infection. In vitro studies revealed improved alveolar macrophage phagocytic and bactericidal capacities in EP3(-/-) cells that were associated with an increased capacity to generate NO in response to immune stimulation. Our studies underscore the complex nature of PGE(2) immunomodulation in the context of host-microbial interactions in the lung. Pharmacological targeting of the PGE(2)-EP3 axis represents a novel area warranting greater investigative interest in the prevention and/or treatment of infectious diseases.

High levels of serum thromboxane B2 are generated during human pulmonary dirofilariosis

The canine parasite Dirofilaria immitis can infect humans. Patients with pulmonary dirofilariosis develop significantly higher thromboxane B2 levels than healthy individuals living in areas where dirofilariosis is endemic and in areas where dirofilariosis is not endemic. The possible role of Wolbachia bacteria in the appearance of this eicosanoid is discussed.

A human in vitro model system for investigating genome-wide host responses to SARS coronavirus infection

Background

The molecular basis of severe acute respiratory syndrome (SARS) coronavirus (CoV) induced pathology is still largely unclear. Many SARS patients suffer respiratory distress brought on by interstitial infiltration and frequently show peripheral blood lymphopenia and occasional leucopenia. One possible cause of this could be interstitial inflammation, following a localized host response. In this study, we therefore examine the immune response of SARS-CoV in human peripheral blood mononuclear cells (PBMCs) over the first 24 hours.

Methods

PBMCs from normal healthy donors were inoculated in vitro with SARS-CoV and the viral replication kinetics was studied by real-time quantitative assays. SARS-CoV specific gene expression changes were examined by high-density oligonucleotide array analysis.

Results

We observed that SARS-CoV was capable of infecting and replicating in PBMCs and the kinetics of viral replication was variable among the donors. SARS-CoV antibody binding assays indicated that SARS specific antibodies inhibited SARS-CoV viral replication. Array data showed monocyte-macrophage cell activation, coagulation pathway upregulation and cytokine production together with lung trafficking chemokines such as IL8 and IL17, possibly activated through the TLR9 signaling pathway; that mimicked clinical features of the disease.

Conclusions

The identification of human blood mononuclear cells as a direct target of SARS-CoV in the model system described here provides a new insight into disease pathology and a tool for investigating the host response and mechanisms of pathogenesis.

Lepeophtheirus salmonis: characterization of prostaglandin E2 in secretory products of the salmon louse by RP-HPLC and mass spectrometry

Lepeophtheirus salmonis is an ectoparasitic copepod that causes serious disease outbreaks in both wild and farmed salmonids. As the relationship between L. salmonis and its hosts is not well understood, the current investigation was undertaken to investigate whether any immunomodulatory compounds could be identified from secretions of L. salmonis. By incubating live L. salmonis adults with the neurotransmitter dopamine in seawater, we were able to obtain secretions from the parasite. These were analyzed by RP-HPLC column, as well as LC-MS. L. salmonis secretions contained a compound with the same retention time and mass of PGE(2). The identity of this compound as PGE(2) was confirmed by MS-in source dissociation. The concentrations of PGE(2) in L. salmonis secretions ranged from 0.2 to 12.3 ng/individual and varied with incubation temperature and time kept off the host. Prostaglandin E(2) is a potent vasodilator and thought to aid in parasite evasion from host immune responses. This is the first reported evidence of prostaglandin production in parasitic copepod secretions and its implications for the host-parasite relationship are discussed.

Simultaneous activation of apoptosis and inflammation in pathogenesis of septic shock: a hypothesis

Sepsis, a widely prevalent disease with increasing morbidity and mortality, is thought to result from uncontrolled inflammatory responses to microbial infection and/or components. However, failure of several experimental anti-inflammatory therapies has necessitated re-evaluation of the paradigm underlying the pathogenesis of this complex disorder. Apoptotic cell death forms a second dominant feature of septic shock in patients and animal models. Anti-apoptotic strategies may protect animals from septic death. However, simultaneous occurrence of apoptosis and inflammation is necessary for septic death. At the cellular level, apoptosis plays a central role in the development of the lymphoid system and regulation of immune responses. Immune activation renders cells refractory to apoptosis while apoptosis of activated lymphocytes is an important immunoregulatory mechanism. Factors such as complement factor 5a, caspase-1 and mitogen-activated protein kinase, which participate in apoptosis as well as pro-inflammatory pathways, may be responsible for simultaneous activation of apoptosis and inflammation in sepsis. Further identification of other similar biochemical events capable of co-activating inflammation and apoptosis may provide new targets for therapy of this hitherto untreatable disease.

Protective effect of FK506 and Thromboxane synthase inhibitor on ischemia-reperfusion injury in non-heart-beating donor in rat orthotopic liver transplantation

The study investigated the possibility of pharmacologically modulating hepatic allograft function from non-heart-beating donors (NHBDs) using male Lewis rats. The donors were divided into 4 groups: Group 1 in which the vehicle was administered, Group 2 in which FK506 (tacrolimus; a powerful immunosuppressive agent) was administered, Group 3 in which OKY046 (a specific thromboxane synthetase inhibitor) was administered and Group 4 in which FK506 and OKY046 were administered. The recipients received orthotopic liver transplantation. The survival rates differed significantly between the recipients that had received liver transplantation from Groups 1 and 4. The serum liver enzyme and inflammatory cytokine concentrations of the recipients which had received liver transplantation from Groups 2, 3 and 4 were significantly lower than those of the recipients that had received liver transplantation from Group 1. Although there was no significant difference, all parameters were better in the recipients that had received transplantation from Group 4 than those that had received transplantation from Groups 2 and 3. The action mechanisms of FK506 and OKY046 are completely different. Therefore, concomitant use of FK506 and OKY046 might have additive effects on liver transplantation from NHBDs. In conclusion, we demonstrated that pretreatment of NHBDs using FK506 and OKY046 ameliorated graft viability.

Thromboxane synthesis is increased by upregulation of cytosolic phospholipase A2 and cyclooxygenase-2 in peripheral polymorphonuclear leukocytes during bacterial infection in childhood

Prostaglandins (PGs) and thromboxane (TX) are important mediators of inflammation. Recent studies revealed that PG and TX synthesis is controlled by the regulation of PG- and TX-synthesizing enzymes. In this study, we examined the TX synthesis and the expression of TX-synthesizing enzymes in activated peripheral polymorphonuclear leukocytes (PMNs) obtained from children with bacterial infection. Blood samples were obtained from controls and patients with bacterial infection. A23187-stimulated production of TXB(2), a stable metabolite of TXA(2) in PMNs, was measured by a specific radioimmunoassay. The mRNA expression of cytosolic phospholipase A(2) (cPLA(2)), cyclooxygenase (COX)-1, COX-2, and TXA(2) synthase was determined by RT-PCR. The synthesis of TXB(2) in PMNs was significantly increased in the patients [925.0 (550.0-1100.0) pg/10(6) cells], compared with the controls [550.0 (450.0-775.0) pg/10(6) cells]. The mRNA expression for cPLA(2) and COX-2 in PMNs was also enhanced in the patients. The results indicate that TX production in PMNs is significantly increased through possible transcriptional mechanisms of cPLA(2) and COX-2 during bacterial infection in children. The upregulation of TXA(2) synthesis may contribute to the process of acute inflammatory reaction caused by bacterial infection.

Prostacyclin is neither sufficient alone nor necessary to cause pulmonary dysfunction: results from infusions of prostacyclin and antiprostacyclin antibody in porcine septic shock

OBJECTIVE

This study evaluated whether prostacyclin is a necessary mediator of inflammation in graded bacteremia or is sufficient alone in pathophysiologic concentrations to cause the pulmonary derangement of bacteremic shock.

DESIGN

Experimental.

SETTING

Laboratory.

SUBJECTS

Twenty-three anesthetized adult swine. INTERVENSIONS: Swine were studied in four groups for 4 hrs: a) an anesthesia control group (n = 6); b) a septic control group (n = 6), in which 1010/mL Aeromonas hydrophila was infused intravenously at 0.2 mL.kg-1.hr-1 and increased to 4.0 mL.kg-1.hr-1 over 3 hrs; c) a prostacyclin infusion group (n = 6), which received prostacyclin infusion to match septic control plasma concentrationsclm without bacteremia; and d) an antiprostacyclin antibody group (n = 5), which received continuous Aeromonas hydrophila infusion plus antiprostacyclin antibody infusion.

MEASUREMENTS AND MAIN RESULTS

Pulmonary hemodynamics, arterial blood gases, and plasma concentrations of arachidonate metabolites were measured hourly over a 4-hr period. In the septic control group and antiprostacyclin antibody group, elevated pulmonary vascular resistance index and pulmonary artery pressure with decreased Pao2, as well as lower pH, were documented after 1 and 3 hrs of graded bacteremia compared with the anesthesia control group and prostacyclin infusion group (p <.05). Thromboxane B2 concentration increased significantly in all groups during septic shock. In the antiprostacyclin antibody group, leukotriene B4 increased immediately after starting antiprostacyclin antibody infusion and reached significance at 3 hrs compared with the septic control group (p <.05). The prostacyclin infusion group had consistently lower concentrations of leukotrienes C4, D4, and E4 than all other groups.

CONCLUSIONS

Prostacyclin does not mediate blood gas changes, alterations of pulmonary hemodynamics, or platelet abnormalities in porcine septic shock, because antiprostacyclin antibody infusion did not change the pulmonary hypertension and hypoxemia, and infusion of prostacyclin to pathophysiologic blood concentrations did not reproduce such changes. Antiprostacyclin blockade during bacteremia significantly increased concentrations of leukotrienes C4, D4, and E4 and leukotriene B4, whereas prostacyclin infusion suppressed concentrations of leukotrienes C4, D4, and E4, suggesting that endogenous prostacyclin may blunt leukotriene release.

Lipid mediators in the pathophysiology of critical illness

Inflammatory lipid mediators are produced by the metabolism of membrane phospholipids following a number of different stimuli. These mediators lead to a variety of cellular and systemic responses which contribute to the manifestations of the systemic inflammatory response syndrome in the critically ill patient. These mediators include platelet-activating factor and the eicosanoids, including prostaglandins, thromboxanes, leukotrienes, and HETEs. This review seeks to evaluate the current role of these mediators in the pathophysiology of critical illness. We will focus on recent studies concerning the modulation of these pathways as a potential therapeutic strategy for management of these critically ill patients. This includes the gamut from nutritional strategies to alter the cellular membrane lipid composition, thereby effecting the substrate available to produce these lipid byproducts, to intracellular inhibitors to alter production of these mediators, to receptor blockage and enhanced clearance to inhibit their effects.

Alteration of n-3 fatty acid composition in lung tissue after short-term infusion of fish oil emulsion attenuates inflammatory vascular reaction

OBJECTIVES

To investigate whether modulation of the fatty acid profile can be achieved by the short-term infusion of a fish oil emulsion which may attenuate the pulmonary response to inflammatory stimulation. Changes of fatty acid pattern in-lung tissue and perfusate were analyzed and correlated with physiologic data after a 3-hr infusion of fish oil in comparison with a soybean oil preparation.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Experimental laboratory in a university teaching hospital.

SUBJECTS

Forty standard breed rabbits of either gender.

INTERVENTIONS

Isolated lungs from anesthetized rabbits were ventilated and recirculation-perfused (200 mL/min) with 200 mL of cell-free buffer solution to which either 2 mL of saline (control, n = 6), 2 mL of a 10% soybean oil preparation (n = 6), or 2 mL of a 10% fish oil emulsion (n = 6) were added. Samples of perfusate and lung tissue were collected for analysis of fatty acid composition. Tissue and perfusate fatty acid composition were analyzed by capillary gas chromatography. To study metabolic alterations in states of inflammatory stimulation, lungs of each group were stimulated with small doses of the calcium ionophore, A23187 (10(-8) M), during the 180-min lipid perfusion period and again after washing out the lipids by exchanging the perfusion fluid. Pulmonary arterial pressure and lung weight gain were monitored, and eicosanoids were analyzed in the perfusate.

MEASUREMENTS AND MAIN RESULTS

Free eicosapentaenoic acids increased several-fold in lung tissue and perfusate during a 3-hr infusion with fish oil. The intravenously administered n-3 fatty acids were rapidly hydrolyzed, as indicated by the appearance of substantial quantities of eicosapentaenoic acid in the perfusate free fatty acid fraction. This increase of perfusion levels of eicosapentaenoic acid was paralleled by an attenuated pressure increase and edema formation due to calcium ionophore challenge and an altered eicosanoid spectrum determined in the perfusate compared with soybean oil-treated lungs.

CONCLUSION

Short-term n-3 lipid application (fish oil emulsion) exerts anti-inflammatory effects on lung vasculature, which may be due to the metabolism of eicosapentaenoic acid resulting in the generation of less potent inflammatory eicosanoids.

Induction mechanism of small intestinal lesions caused by intravenous injection of endotoxin in rats

The pathogenesis of intestinal damage caused by bolus intravenous injection of endotoxin (ETX; 3 mg/kg) was investigated. Administration of ETX to rats induced reddish discoloration suggestive of bleeding, increased hemoglobin amounts, and leakage of plasma protein in the intestine. However, light microscopic examination of the intestine demonstrated blood congestion of the microvessels. Plasma accumulation was partially inhibited by combined pretreatment with a histamine H1 antagonist and a serotonin (5-HT) antagonist. Neither a 5-lipoxygenase inhibitor, a soybean trypsin inhibitor, nor atropine was observed to inhibit plasma accumulation. Both the intestinal leakage of plasma and the accumulation of hemoglobin were completely inhibited by indomethacin, a selective thromboxane A synthetase inhibitor (OKY 1581), and a stable PGI2 analogue (beraprost). Intravital microscopic observation of the microvessels of the small intestinal villi demonstrated microthrombus formation within several minutes after the injection of ETX, and pretreatment with OKY 1581 attenuated the formation of microthrombus. Platelet counts decreased significantly 10 min after ETX administration, and the decrease was not inhibited by pretreatment with either OKY 1581 or beraprost. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were not prolonged. These observations thus suggest that microcirculatory disturbances by platelet thrombus, which are mediated by thromboxane A2 at least in part, play an important role in ETX-induced intestinal damage.

Endotoxic shock after long-term resuscitation of hemorrhage/reperfusion injury decreased splanchnic blood flow and eicosanoid release

OBJECTIVE

The authors examine the hypothesis that hemorrhage/reperfusion injury predisposes the splanchnic bed to decreased prostacyclin (PGl2) release and blood flow after subsequent endotoxin challenge.

SUMMARY BACKGROUND DATA

Prostacyclin is a potent vasodilator that has been demonstrated to be an important regulator of splanchnic blood flow. Previous studies have demonstrated that during resuscitation from severe hemorrhage, there is a marked reduction in intestinal PGl2 levels, which is associated with reduced splanchnic perfusion.

METHODS

Anesthetized Sprague-Dawley rats underwent hemorrhage to a mean arterial pressure of 30 mmHg for 30 minutes followed by the reinfusion of shed blood. Then the animals were maintained on total parenteral nutrition (TPN) for 10 days, after which time they received 20 mg/kg Escherichia coli endotoxin intraperitoneally. Aortic and superior mesenteric artery (SMA) blood flow was monitored with a Doppler flow probe. The splanchnic bed was excised and perfused in vitro for measurement of venous effluent eicosanoid concentrations. Controls consisted of animals that received TPN and endotoxin but did not undergo hemorrhage and resuscitation (sham).

RESULTS

Total parenteral nutrition support of sham animals followed by endotoxin challenge did not alter splanchnic eicosanoid release or blood flow. Hemorrhage/reperfusion animals supported by long-term TPN and challenged with endotoxin demonstrated a threefold decrease in splanchnic prostacyclin metabolite (6-keto-PGF1 alpha) release and a 50% decrease in SMA blood flow.

CONCLUSIONS

Hemorrhage/reperfusion injury predisposes the splanchnic bed from rats sustained with long-term TPN to decreased release of PGl2 and SMA blood flow when challenged with endotoxin as a second injury.

Role of platelet-activating factor and prostanoids in hemodynamic changes in rat experimental endotoxic shock

The present experiments were conducted to elucidate the role of platelet-activating factor (PAF) and cyclooxygenase products in the cardiovascular responses to endotoxin in anesthetized rats. Endotoxin (10 mg/kg, i.v.) induced hypotension that was accompanied by a decrease in cardiac output and an increase in calculated total peripheral resistance, suggesting that this hypotension mainly resulted from the reduced cardiac output. The endotoxin-induced decrease in cardiac output and hemoconcentration was significantly attenuated by TCV-309 (a PAF receptor antagonist), ibuprofen (a cyclooxygenase inhibitor) or S-1452 (a thromboxane A2/prostaglandin H2-receptor antagonist). During the 3-hr observation period following endotoxin administration, ibuprofen and S-1452 showed only early protection and TCV-309 showed late attenuation of the endotoxin-induced hypotension. Tachycardiac responses to endotoxin were only blocked by ibuprofen but not by TCV-309 or S-1452. These results suggest that both PAF and cyclooxygenase product(s), including thromboxane A2, mediate the decrease in cardiac output and hypotension in rat experimental endotoxic shock. Cyclooxygenase product(s) other than thromboxane A2 or prostaglandin endoperoxide may be involved in the endotoxin-induced increase in heart rate.

Long-term resuscitation of hemorrhage/reperfusion injury (H/R) stimulates renal PGE2 release

This study examines the hypothesis that long-term resuscitation with hyperalimentation (TPN) following acute hemorrhage/reperfusion (H/R) injury stimulates renal release of PGE2. Male Sprague-Dawley rats were anesthetized and subjected to sham or hemorrhage to 30 mmHg for 30 min followed by reperfusion. All rats were placed on TPN for 5 days, then underwent laparotomy for in vivo renal artery and aortic blood flow for 60 min. The kidney was perfused in vitro with Krebs-Henseleit buffer at 3 ml/min (pH 7.4, 37 degrees C) and venous effluent was collected for analysis of PGE2, 6-keto-PGF1 alpha and thromboxane B2 by EIA. Hemorrhage/reperfusion followed by TPN for 5 days increased renal PGE2 2-fold and decreased in vivo renal artery blood flow by 50% compared to the sham group. Hemorrhage/reperfusion followed by TPN did not alter release of the other eicosanoids measured. These data suggest that the kidney has a limited capacity to maintain renal blood flow by increasing release of PGE2 when the animal is subjected to long-term resuscitation with TPN following mild hemorrhage/reperfusion injury.

Indomethacin and thromboxane A2/prostaglandin H2 antagonist SQ29,548 impair in vitro contractions of aortic rings of ex vivo-treated lipopolysaccharide rats

Lipopolysaccharide treated rats (25 mg/kg i.v.) were killed after 60 min and rat aortic rings were mounted in an isolated organ bath for measurement of isometric contractions in response to phenylephrine (0.01-10 microM) or potassium chloride (10 mM). Aortic rings from lipopolysaccharide-treated rats showed reduced contractility to phenylephrine and potassium chloride when compared to those from saline-treated rats. Indomethacin 10 microM, added in vitro further impaired phenylephrine-induced contraction of aortic rings from lipopolysaccharide ex vivo treated rats but was ineffective on aortic rings from saline treated rats. A similar pattern was observed when potassium chloride was used. Administration in vitro of thromboxane A2 receptor antagonist SQ29,548 gave a similar effect to indomethacin. Aortic rings collected from rat treated in vivo with dexamethasone (10 mg/kg) showed a reduction in phenylephrine induced contractions that was not further reduced by in vitro treatment with indomethacin (10 microM). Similarly, when rat aortic rings were incubated in vitro (60 min) with lipopolysaccharide (0.4 mg/ml) a reduction of phenylephrine- and potassium chloride-induced contraction was observed, but addition of either indomethacin or SQ29,548 did not further reduce contraction. Our results suggest that under these experimental conditions, in the early phase of endotoxin shock, synthesis of cyclooxygenase products (such as endoperoxides or thromboxane A2) occurs probably as a compensatory mechanism to lipopolysaccharide induced hypocontractility from the interaction, in vivo, between lipopolysaccharide, endothelium, circulating cells and vascular smooth muscles.

Differential effects of acute thermal injury on rat splanchnic and renal blood flow and prostanoid release

This study examines the hypothesis that acute thermal injury decreases renal and splanchnic blood flow which correlates with altered endogenous vasodilator eicosanoid release. Anesthetized male Wistar rats were subjected to sham or a non-resuscitated 30% total body surface area burn. At 1, 2, 4, 8, and 24 h post-burn mean arterial pressure as well as superior mesenteric and renal artery in vivo blood flow were measured. The superior mesenteric and renal arteries were cannulated and perfused in vitro with their end organs with Krebs buffer (pH 7.4, 37 degrees C). Renal and splanchnic 6-keto-PGF1 alpha (PGI2), PGE2, and thromboxane B2 (TXB2) release were measured by EIA at 15 min of perfusion. Renal and superior mesenteric artery blood flow decreased by 40% or more at 1 and 2 h post-burn despite mean arterial pressure remaining unchanged. The major eicosanoids released were PGI2 from the splanchnic bed and PGI2 and PGE2 from the kidney. Splanchnic PGI2 and TXB2 release and renal TXB2 increased 2-3 fold at 1 h post-burn but returned to the sham level at 2 h post-burn. By 24 h post-burn the vasodilator eicosanoids were increased in both the splanchnic and renal vascular beds. These data show that decreased renal and splanchnic blood flow was associated with increased endogenous release of the potent vasoconstrictor TXB2. By 2 h post-burn, renal and splanchnic blood flow began returning toward the sham level as endogenous release of TXB2 from both organs fell to sham levels. These data suggest that increased endogenous release of TXB2 may contribute to the short-term decrease in renal and splanchnic blood flow in the immediate post-burn period and thus may contribute to ischemia of both vascular beds.

Acute burn down regulates rabbit splanchnic and renal prostanoid release

This study examines the hypothesis that acute thermal injury decreases renal and splanchnic vasodilator eicosanoids. Anesthetized rabbits were subjected to sham or a 25% total body surface area burn and fluid resuscitated. At 2, 4, 6, 12, and 24 h postburn the superior mesenteric and renal arteries were cannulated and perfused in vitro with their end organs with Krebs buffer (pH 7.4, 37 degrees C). Renal and splanchnic prostaglandins (PGs) 6-keto-PGF1 alpha (PGI2), and PGE2, and thromboxane B2 (TxB2) release were measured by EIA at 15 min of perfusion. The major eicosanoids released were PGI2 from the splanchnic bed and PGI2 and PGE2 from the kidney. Renal PGE2 and PGI2 and splanchnic PGI2 release were decreased by 50% or more 12 h postburn (p < 0.01) but were restored to sham burn levels 24 h postburn. Loss of these endogenous renal and splanchnic vasodilators 12 h postburn may contribute to ischemia of both vascular beds at this critical time period following acute burn injury.

Incidence and pathophysiological relevance of postoperative endotoxemia

Patients who underwent surgical procedures usually develop elevated body temperature, changes of plasma levels of some proteins, and leucocytosis. These alterations are summarized as the postoperative acute-phase reaction. Also endotoxin can induce the described phenomena suggesting that endotoxin may play a role concerning the induction of the acute phase reaction. In order to test that hypothesis we determined endotoxin plasma levels preoperatively and daily postoperatively in patients who were operated on because of goiter (n = 20), colonic, pancreatic and gastric diseases (n = 58). A significant increase of endotoxin plasma levels was found at the first and third day after abdominal surgery whereas after goiter surgery the increase revealed to be only very slight. However, the decrease between the first and second postoperative day in the latter group was again statistically significant suggesting postoperative endotoxemia even after minor operations. Furthermore a correlation between the amount of circulating endotoxin and pulmonary or infectious complications could be established in patients after major operations even at the first postoperative day suggesting a pathogenetic relevance of postoperative endotoxemia.

Renal impairment after spontaneous bacterial peritonitis in cirrhosis: incidence, clinical course, predictive factors and prognosis

Although spontaneous bacterial peritonitis is considered a precipitating factor of renal impairment in cirrhosis, no study specifically addressing this problem has been reported. This study was aimed at assessing the incidence, clinical course, predictive factors and prognosis of renal impairment in cirrhotic patients with peritonitis. Therefore, 252 consecutive episodes of spontaneous bacterial peritonitis in 197 patients were analyzed. Clinical and laboratory data obtained before and after diagnosis of peritonitis were considered as possible predictors of renal impairment and hospital mortality. Renal impairment occurred in 83 (33%) episodes, and in every instance it fulfilled the criteria of functional kidney failure. Renal impairment was progressive in 35 episodes, steady in 27 and transient in 21. Blood urea nitrogen and serum sodium concentration before peritonitis and band neutrophils count in blood at diagnosis were independent predictors for the development of renal impairment. Renal impairment was the strongest independent predictor of mortality during hospitalization. Other independent prognostic factors were blood urea nitrogen level before peritonitis, age, positive ascitic fluid culture and serum bilirubin level during infection. These results indicate that renal impairment is a frequent event in cirrhotic patients with spontaneous bacterial peritonitis that occurs mainly in patients with kidney failure before infection. Renal impairment is the most important predictor of hospital mortality in cirrhotic patients with spontaneous bacterial peritonitis.

Cyclooxygenase inhibitors enhance tumour necrosis factor production and mortality in murine endotoxic shock

Intraperitoneal administration of E. coli lipopolysaccharide (5-15 mg/kg) produced a dose-related increase in mortality which was maximal 72 h after induction of shock. Using a suboptimal dose of LPS (10 mg/kg i.p.), pretreatment with indomethacin (0.1-10 mg/kg p.o) or ibuprofen (1-100 mg/kg p.o) 30 min prior to induction of shock led to a significant enhancement of mortality. This enhancement was associated with a 2-3 fold increase in the peak circulating levels of tumour necrosis factor (TNF-alpha) in the serum of animals treated with indomethacin or ibuprofen compared to vehicle-treated control animals. These results indicate that TNF-alpha production is modulated by endogenous prostaglandins in vivo and that enhanced production of TNF-alpha by cyclooxygenase inhibitors may lead to exacerbation of some inflammatory processes.

Binding of lysozyme to lipopolysaccharide suppresses tumor necrosis factor production in vivo

Endotoxin (lipopolysaccharide [LPS]) released during gram-negative bacterial infection induces varieties of cytokines which directly and/or indirectly cause shock, disseminated intravascular coagulation, and death. We previously showed that lysozyme (LZM) was an LPS-binding protein and inhibited various immunomodulating activities of LPS. In this study, we examined the effect of LZM on the LPS-triggered septic shock model induced by carrageenan treatment and assessed by tumor necrosis factor production. The data presented in this report strongly suggest that LZM-LPS complex formation completely abrogates tumor necrosis factor production and the mortality caused by LPS and that LZM may be useful for the treatment of endotoxin shock.

Amelioration of respiratory and circulatory changes in established endotoxic shock by ketoprofen

In an intensive-care setting we studied the effects of ketoprofen, a dual inhibitor of cyclooxygenase and lipoxygenase, on circulatory and respiratory changes during established endotoxic shock in sheep. Two groups (n = 7 in each) were exposed to E. coli endotoxin, which caused a sharp increase in pulmonary artery pressure (200%; PAP), intrapulmonary shunt fraction (300%; QS/QT%), and oxygen extraction ratio (50%; VO2/DO2%). There was also a significant decrease in mean arterial pressure (25%; MAP), respiratory compliance (60%; CT), arterial oxygen tension (65%; PaO2), and oxygen delivery index (15%; DO2) in both groups. After 30 min of endotoxin infusion, group K received ketoprofen, 2.5 mg/kg b.w. i.v., while group E served as shock controls. After 4 h there had been a significant improvement in MAP, PaO2, DO2, QS/QT%, and CT in the ketoprofen-treated group compared with the controls (P < 0.01). In addition, the oxygen extraction ratio normalised in group K, but remained 70-100% increased in group E (P < 0.01). The wet-to-dry weight ratios of the lungs and the liver were significantly lower in the ketoprofen-treated group compared with the controls (P < 0.05). It was concluded that ketoprofen significantly ameliorated the respiratory and circulatory effects of established endotoxic shock in sheep.

Inhibition of the production of nitric oxide and vasodilator prostaglandins attenuates the cardiovascular response to bacterial endotoxin in adrenalectomized rats

Bacterial lipopolysaccharide (LPS) is the toxic moiety of the gram-negative bacterial outer membrane which is responsible for many of the pathophysiological events that occur during endotoxic shock. Here we investigate the hypothesis that endogenous glucocorticoids modulate the formation of nitric oxide (NO) and of vasodilator cyclooxygenase metabolites in response to LPS. Intravenous administration of a small dose of Escherichia coli LPS (0.1 mg kg-1) to normal Wistar rats caused a moderate fall in blood pressure, and 120 min of endotoxaemia was not associated with an attenuation of the rise in blood pressure elicited by intravenous injection of noradrenaline (NA; vascular hyporeactivity). When adrenalectomized (ADX) rats, which lack endogenous glucocorticoids, were subjected to the same dose of LPS, they developed a much more severe form of circulatory shock, which was characterized by a profound fall in blood pressure and a vascular hyporeactivity to NA. Both hypotension and vascular hyporeactivity were prevented by pre-treatment with dexamethasone. Inhibition of NO biosynthesis with NG-methyl-L-arginine significantly attenuated the hypotension and the vascular hyporeactivity to NA caused by LPS in ADX rats. Similarly, the cyclooxygenase inhibitor indomethacin significantly attenuated the circulatory failure elicited by LPS in the ADX rats. Interestingly, 120 min of endotoxaemia resulted in a de novo biosynthesis of an induced isoform of NO synthase in the lungs of ADX, but not normal Wistar, rats. This induction of NO synthase was prevented by dexamethasone pre-treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Endotoxic shock has differential effects on renal and splanchnic eicosanoid synthesis

This study examined the differential effects of endotoxin on renal and splanchnic vascular (SV + SI) eicosanoid synthesis. Dogs were anesthetized and subjected to a challenge of 1 mg/kg (i.v.) bolus of B-lipopolysaccharide endotoxin followed by a 3 h infusion of endotoxin at 0.5 mg/kg/h. The kidney and SV + SI were cannulated and perfused in vitro with Krebs buffer. The venous effluent from the kidney and SV + SI were assayed for 6-keto-PGF1a (PGI2), PGE2, Leukotriene B4 (LTB4), LTC4, and thromboxane B2 (TXB2) by enzyme immunoassay. Endotoxin treatment markedly increased splanchnic PGI2 release (splanchnic vasodilator) two fold and decreased release of all other measured eicosanoids. Endotoxin treatment markedly increased renal PGE2 (renal vasodilator) but did not significantly increase PGI2. These data showed that endotoxin treatment stimulated both the splanchnic vascular bed and kidney to increase synthesis and release of their major endogenous vasodilator eicosanoids.

Burn injury decreased splanchnic PGI2 release is restored by treatment with lazaroid

This study examined the hypothesis that burn injury inhibits the release of splanchnic PGI2, a potent endogenous vasodilator of the splanchnic vascular bed. Male Hartley Guinea Pigs (350 grams) were anesthetized, shaved and subjected to a full thickness scald burn comprising 45% of the total body surface area (or sham burn). The animals were treated with intravenous or topical lazaroid, a 21-aminosteroid U75412E. After recovery for 24 hours, the animals were anesthetized, and the superior mesenteric artery was cannulated and removed with its intact intestine (SV + SI). The SV + SI was perfused in vitro with oxygenated Krebs buffer. The venous effluent was assayed for 6-keto-PGF1 alpha, PGE2 and thromboxane B2 by enzyme immunoassay. Acute burn injury decreased SV + SI release of 6-keto-PGF1 alpha by 57% but did not alter release of PGE2 or thromboxane B2. Treatment of the animals with topical lazaroid and not intravenous lazaroid restored SV+SI 6-keto-PGF1 alpha release to control levels. These data showed that topical lazaroid therapy maintained endogenous splanchnic PGI2 release following acute burn injury. Maintaining endogenous splanchnic PGI2 release by topical lazaroid treatment may be one strategy to avoid splanchnic ischemia following acute thermal injury.

Cecal ligation and puncture is associated with pulmonary injury in the rat: role of cyclooxygenase pathway products

The present studies evaluated the role cyclooxygenase products play in bacterial sepsis induced pulmonary injury in the rat. Lung injury was assessed by determining the pulmonary capillary filtration coefficient (Kf) and the lung lavage protein concentration four and 18 hours after cecal ligation and puncture. Four hours after cecal ligation, the Kf was unchanged from control, however, by 18 hours, the Kf was increased 171% (p < .05). Similarly, lung lavage protein levels were unchanged four hours after cecal ligation but were significantly (p < .05) elevated at 18 hours. On the other hand, pulmonary lavage immunoreactive thromboxane B2 (iTXB2) levels were increased both four and 18 hours after the initiation of sepsis. In order to determine if cyclooxygenase products played a role in the sepsis associated lung injury, ibuprofen was administered prior to cecal ligation. Ibuprofen pretreatment prevented the sepsis associated increase in both Kf and lung lavage protein concentration. These studies suggest that bacterial sepsis in the rat is associated with pulmonary injury and that early administration of ibuprofen ameliorates this damage.

Ibuprofen intervention in canine septic shock: reduction of pathophysiology without decreased cytokines

This study was undertaken to evaluate the effect of a cyclooxygenase inhibitor, ibuprofen, at various time intervals in a live Escherichia coli model of canine septic shock. Group I (control) animals (n = 5) received a LD100 dose of 10(9) live E. coli per kilogram were given no further treatment. Group II animals (n = 5) received a 10 mg/kg bolus of ibuprofen 10 min prior to bacterial infusion. Group III animals (n = 5) received ibuprofen 15 min after the bacterial infusion. Statistical analysis revealed the following: Group II animals had significantly higher MABP and significantly lower levels of serum fluorescent products (superoxide radical activity), plasma thromboxane B2, prostaglandin E2, and endotoxin levels compared to Group I animals (P less than 0.05). Plasma levels of tumor necrosis factor (TNF) and interleukin-6 (IL-6) were significantly elevated (P less than 0.05) from baseline in all animals (Groups I, II, and III), but ibuprofen treatment failed to either increase or decrease these levels. This study demonstrates that ibuprofen treatment can significantly reverse the deleterious hemodynamic and metabolic effects commonly seen in live E. coli septic shock without depressing the endogenous production of TNF or IL-6. These data support the hypothesis that sepsis initiates a cascade of mediators with the cytokines TNF and IL-6 being proximal events which in turn stimulate the next level, with ibuprofen probably exerting its inhibitory effect distal to this point in the cascade.

Endogenous glucocorticoids regulate an inducible cyclooxygenase enzyme

The effect of endogenous glucocorticoids on the expression of the cyclooxygenase enzyme was studied by contrasting cyclooxygenase expression and prostanoid synthesis in adrenalectomized and sham-adrenalectomized mice with or without the concurrent administration of endotoxin. Peritoneal macrophages obtained from adrenalectomized mice showed a 2- to 3-fold induction in cyclooxygenase synthesis and activity when compared to sham controls. Intravenous injection of a sublethal dose of endotoxin (5 micrograms/kg) further stimulated cyclooxygenase synthesis, resulting in a 4-fold increase in prostaglandin production. Similar cyclooxygenase induction can be achieved in macrophages obtained from normal mice but only after high doses of endotoxin (2.5 mg/kg) that are 100% lethal to adrenalectomized mice. Restoration of glucocorticoids in adrenalectomized animals with dexamethasone completely inhibited the elevated cyclooxygenase and protected these animals from endotoxin-induced death. In contrast, no signs of cyclooxygenase induction were observed in the kidneys of the adrenalectomized mice, even when treated with endotoxin. Dexamethasone did not affect the constitutive cyclooxygenase activity and prostaglandin production present in normal and adrenalectomized kidneys. These data indicate the existence of a constitutive cyclooxygenase that is normally present in most cells and tissues and is unaffected by steroids and of an inducible cyclooxygenase that is expressed only in the context of inflammation by proinflammatory cells, like macrophages, and that is under glucocorticoid regulation. Under normal physiological conditions glucocorticoids maintain tonic inhibition of inducible cyclooxygenase expression. Depletion of glucocorticoids or the presence of an inflammatory stimulus such as endotoxin causes rapid induction of this enzyme, resulting in an exacerbated inflammatory response that is often lethal.

The effect of elevated levels of thromboxane on host response to tumor

Previous studies have demonstrated that human malignancies can synthesize large amounts of thromboxane. It has also been reported that thromboxane can significantly alter multiple components of physiologic and immunologic function. We investigated the effect of elevated levels of thromboxane on host response to tumor using multiple rat models, and the long acting thromboxane analogue U-46619. Administration of the thromboxane analogue was not found to significantly alter the growth of primary tumors or peritoneal metastases. The analogue was found to significantly decrease mean survival time with a pulmonary metastases model. The thromboxane analogue failed to alter macrophage cytotoxicity, lymphocyte cytotoxicity, T lymphocyte subset numbers, or lymphocyte blastogenic response. Administration of the thromboxane analogue decreased the rate of lymphocyte metabolism of glucose and decreased lymphocyte intracellular adenosine deaminase activity. In conclusion, elevated thromboxane levels do not appear to alter primary tumor growth or host immune function, but do decrease resistance to pulmonary metastases.