Effects of lipopolysaccharide on human endothelial cells in culture

Ethyl pyruvate diminishes the endotoxin-induced inflammatory response of bovine mammary endothelial cells

The endotoxin-induced inflammatory response during coliform mastitis is difficult to control with the currently available therapeutics. Endothelial cells are among the first cell type to be engaged in the inflammatory response and can modulate the severity of inflammation by producing proinflammatory mediators upon endotoxin exposure. Ethyl pyruvate, an ethyl ester of pyruvic acid, can ameliorate endotoxin-induced inflammatory responses by inhibiting the production of proinflammatory mediators in several in vitro and in vivo endotoxemia models. The objective of this study was to determine the effect of ethyl pyruvate on the production of vascular proinflammatory mediators that are associated with the pathogenesis of coliform mastitis. The ability of ethyl pyruvate to reduce the expression of proinflammatory mediators was evaluated in cultured bovine mammary endothelial cells (BMEC) stimulated with endotoxin. Treatment of endotoxin-stimulated BMEC with ethyl pyruvate significantly reduced gene expression of IL-6, IL-8, and intercellular adhesion molecule 1 as well as expression of eicosanoid-producing enzymes, including cyclooxygenase 2 and 15-lipoxygenase 1. This is the first time that the effect of ethyl pyruvate was evaluated in an in vitro BMEC model of coliform mastitis. The ability of ethyl pyruvate to effectively inhibit gene and protein expression of potent vascular proinflammatory mediators in vitro warrants further investigations to assess in vivo efficacy. Ethyl pyruvate is safe for human consumption, and it may be an attractive candidate as a therapeutic in ameliorating the severe pathogenesis associated with coliform mastitis.

Human kidney histopathology in acute obstructive jaundice: a prospective study

INTRODUCTION

Cholemia and bacterial translocation with portal endotoxemia are integral in the pathogenesis of obstructive jaundice (OJ). There is sufficient experimental data about hemodynamic and histopathological consequences of OJ. In contrast, pathological information of renal changes in patients with OJ is still lacking. Therefore; the primary objective of this prospective study is to show the specific histopathological changes in kidneys of patients with short-term biliary tract obstruction receiving a standard perioperative medical treatment protocol.

MATERIALS AND METHODS

Twenty consecutive patients with biliary obstruction were included in the study. Fluid replacement, prevention of biliary sepsis, and portal endotoxemia were mainstays of the perioperative treatment protocol. Fluid and electrolyte balance was maintained by twice daily body weight calculations, central venous pressure, and mean arterial pressure monitoring. Renal function was assessed by glomerular filtration rate estimation by modification of diet in renal disease-7 formula. Kidney biopsy evaluation was focused on tubular changes, thrombotic microangiopathy, endothelial damage, and peritubular capillary (PTC) dilatation with or without C4d staining. Fresh frozen sections were evaluated with immunofluorescence microscopy for glomerular IgG, IgA, IgM, C3, and C1q staining.

RESULTS

The mean duration of OJ was 15.5 ± 1.4 days. Body weight increased before surgery through volume expansion (P = 0.001). All patients have shown mean arterial pressure ≥ 70 and ≤ 120 mmHg and renal function was very well preserved in all but one subject during the perioperative period. Despite those favorable figures, dilatation of peritubular venules and acute tubular necrosis were shown synchronously in all cases. C4d staining in PTC and arterioles and thrombotic microangiopathy were entirely absent in the study group. Immune complex deposits in PTCs and in glomeruli were not detected. Three patients had isolated glomerular C4d deposition without accompanying thrombotic microangiopathy and IgG, IgA, IgM, C3, and C1q staining of glomerular capillaries in I immunofluorescence microscopy.

DISCUSSION

This study is the first in the literature to address the histopathological changes that occur in humans with short-term biliary obstruction. Acute tubular necrosis and venous dilatation was observed in all biopsies, without exception, despite the maintenance of strict volume control in all patients. The adequacy of volume control may not be implicated in those results; rather a possible mechanism related to untrapped endotoxin in the gut lumen or systemic circulation might lead to prolonged PTC dilatation and hypoperfusion with synchronous acute tubular necrosis. Absolute recovery of renal function in all patients and the demonstration of solitary acute tubular necrosis with no microvascular-glomerular-interstitial inflammation or injury, suggests that the perioperative treatment regime in this study is fairly efficacious in short-term OJ.

Effects of ibuprofen on the viability and proliferation of rainbow trout liver cell lines and potential problems and interactions in effects assessment

Under some conditions ibuprofen was either cytotoxic or cytostatic to rainbow trout cell lines: RTL-W1 (liver) and RTH-149 (hepatoma). Ibuprofen at up to 15 microg/mL was not cytotoxic, regardless of dosing protocols, exposure conditions, viability endpoints, or cell lines. Responses to higher ibuprofen concentrations depended on the test methodology. No cytotoxicity was seen when stock ibuprofen solutions had been prepared in ethanol. For stock solutions in dimethylsulfoxide (DMSO), ibuprofen from 50 to 1500 microg/mL elicited little cytotoxicity in cultures in which the final DMSO concentration was 0.05% (v/v), but was consistently cytotoxic after 24 h for cultures with 0.5% DMSO (v/v). Cytotoxicity was evaluated with alamar Blue (AB) and carboxyfluoroscein diacetate acetoxymethyl ester (CFDA-AM) as measures respectively of metabolic activity and membrane integrity. Effective concentrations (EC50s) for ibuprofen with AB and CFDA-AM depended on whether the stock solution was dosed directly into a culture well or mixed in medium prior to being added to a well. For indirect dosing, ibuprofen was more cytotoxic in medium without fetal bovine serum (FBS), whereas for direct dosing ibuprofen was equally cytotoxic in medium with or without FBS. As judged by AB and CFDA-AM EC50s, dosing ibuprofen was directly 10 to 30 times more cytotoxic. In FBS-containing cultures, which was dosed with increasing ibuprofen and DMSO at 0.05% (v/v), cell proliferation was impaired at 50 and 150 microg/mL ibuprofen. Lipopolysaccharide (LPS) at 50 microg/mL had little influence on these cytotoxic and cytostatic effects of ibuprofen in medium with FBS.

Activation by C5a of endothelial cell caspase 8 and cFLIP

OBJECTIVES AND DESIGN

In this study, we examine the relationship between C5a and activation of cysteine aspartic acid protease 8 (caspase 8) in human umbilical vein endothelial cells (HUVEC).

MATERIALS OR SUBJECTS

Primary cultures of HUVEC were used.

TREATMENTS

Recombinant human C5a (50 ng/ml) was used in the presence or absence of 10 microg/ml cycloheximide (CHX).

METHODS

HUVEC were treated with C5a alone and in the presence of CHX, then monitored for cell viability, poly- ADP-ribose 1 (PARP-1) and caspase 8 activities. Gene and protein expressions were assessed for caspase 8 and the caspase 8 homologue, FLICE -inhibitory protein (cFLIP).

RESULTS

We found a 43.1 +/- 6.9 percent reduction in viability of HUVEC stimulated for 18 h with 50 ng/ml C5a in the presence of 10 microg/ml CHX (p < 0.05). In contrast, the cell viability of cells stimulated for 18 h with 50 ng/ml C5a or 10 microg/ml CHX alone was not significantly different compared to the non-stimulated control. Treatment of HUVEC with C5a induced an increase in caspase 8 activity but did not significantly affect cFLIP levels.

CONCLUSIONS

These data suggest caspase 8 activation induced by C5a leads to cell death if protein synthesis of antiapoptotic protein(s) is blocked.

Functional characterization of bovine TIRAP and MyD88 in mediating bacterial lipopolysaccharide-induced endothelial NF-kappaB activation and apoptosis

Mastitis is a prevalent disease in dairy cows. Gram-negative bacteria, which express the pro-inflammatory molecule lipopolysaccharide (LPS), are responsible for the majority of acute clinical cases of mastitis. Previous studies have identified differential susceptibility of human and bovine endothelial cells (EC) to the pro-inflammatory and injury-inducing effects of LPS. The Toll-like receptor (TLR)-4 signaling pathway, which is activated by LPS, has been well studied in humans, but not in ruminants. Human myeloid differentiation-factor 88 (MyD88) and TIR-domain containing adaptor protein (TIRAP) are critical proteins in the LPS-induced NF-kappaB and apoptotic signaling pathways. To assess the role of the bovine orthologs of these proteins in bovine TLR-4 signaling, dominant-negative constructs were expressed in bovine EC, and LPS-induced NF-kappaB activation and apoptosis evaluated. The results from this study indicate that bovine MyD88 and TIRAP play functional roles in transducing LPS signaling from TLR-4 to downstream effector molecules involved in NF-kappaB activation, and that TIRAP promotes apoptotic signaling.

The toll-like receptor-4 (TLR-4) pathway and its possible role in the pathogenesis of Escherichia coli mastitis in dairy cattle

Mastitis is one of the most costly production diseases in the dairy industry that is caused by a wide array of microorganisms. In this review, we focus on the Gram-negative Escherichia coli infections that often occur at periods when the innate immune defence mechanisms are impaired (i.e., parturition through the first 60 days of lactation). There is substantial evidence demonstrating that at these periods, the expected influx of polymorphonuclear neutrophil leukocytes (PMN) into the mammary gland is delayed during inflammation after intramammary infection with E. coli. Here, we provide some hypotheses on the potential mechanisms of action on how the disease may develop under circumstances of immunosuppression, and describe the potential involvement of the toll-like receptor-4 signal transduction pathway in the pathogenesis of E. coli mastitis. In addition, some ideas are proposed to help prevent E. coli mastitis and potentially other diseases caused by Gram-negative infections in general.

Anti-vascular permeability of the cleaved reactive center loop within the carboxyl-terminal domain of C1 inhibitor

C1 inhibitor (C1INH), a member of the serine proteinase inhibitor (serpin) family, functions as an inhibitor of the complement and contact systems. Cleavage of the reactive center loop (RCL) within the carboxyl-terminal domain of C1INH (iC1INH), lacking of serpin function, induces a conformational change in the molecule. Our previous data demonstrated that active, intact C1INH prevents vascular permeability induced by gram-negative bacterial lipopolysaccharide (LPS). In this study, we investigate the role of RCL-cleaved, inactive C1INH (iC1INH) in vascular endothelial activation. In the cultured primary human umbilical vein endothelial cell (HUVEC) monolayer, iC1INH blocked LPS-induced cell injury by evaluated as transendothelial flux, cell detachment, and cytoskeletal disorganization. LPS-induced upregulation of vascular cell adhesion molecule-1 (VCAM-1) could be suppressed by treatment with iC1INH. Studies exploring the underlying mechanism of iC1INH-mediated suppression in VCAM-1 expression were related to reduction of NF-kappaB activation and nuclear translocation in an I kappa B alpha-dependent manner. The inhibitory effect was associated with stabilization of the NF-kappaB inhibitor I kappa B and reduction of inhibitor I kappa B kinase activity. In the model of endotoxin-induced mice, increased plasma leakage in local abdominal skin in response to LPS was reversed by treatment with iC1INH. Furthermore, systemic administration of LPS to mice resulted in increased microvascular permeability in multiple organs, which was reduced by iC1INH. These data provide evidence that iC1INH has an anti-vascular permeability independent on the serpin function.

C1 inhibitor prevents Gram-negative bacterial lipopolysaccharide-induced vascular permeability

Gram-negative bacterial endotoxemia may lead to the pathological increase of vascular permeability with systemic vascular collapse, a vascular leak syndrome, multiple organ failure (MOF), and/or shock. Previous studies demonstrated that C1 inhibitor (C1INH) protects mice from lipopolysaccharide (LPS)-induced lethal septic shock via a direct interaction with LPS. Here, we report that C1INH blocked the LPS-induced increase in transendothelial flux through an endothelial monolayer. In addition, LPS-mediated detachment of cultured endothelial cells was prevented with C1INH. C1INH also inhibited LPS-induced endothelial cell apoptosis as demonstrated by suppression of DNA fragmentation and annexin V expression. As illustrated by laser scanning confocal microscopy, C1INH completely blocked the binding of fluorescein isothiocyanate (FITC)-LPS to human umbilical vein endothelial cells (HUVECs). C1INH protected from localized LPS-induced increased plasma leakage in C57BL/6J mice and in C1INH-deficient mice. Local vascular permeability in response to LPS was increased to a greater extent in C1INH-deficient mice compared with wild-type littermate controls and was reversed by treatment with C1INH. Systemic administration of LPS to mice resulted in increased vascular permeability, which was reduced by C1INH. Therefore, these studies demonstrate that C1INH, in addition to its role in suppression of LPS-mediated macrophage activation, may play an important role in the prevention of LPS-mediated increased vascular permeability, endothelial cell injury, and multiple organ failure.

The antiangiogenic factor 16K PRL induces programmed cell death in endothelial cells by caspase activation

We asked whether the antiangiogenic action of 16K human PRL (hPRL), in addition to blocking mitogen-induced vascular endothelial cell proliferation, involved activation of programmed cell death. Treatment with recombinant 16K hPRL increased DNA fragmentation in cultured bovine brain capillary endothelial (BBE) and human umbilical vein endothelial (HUVE) cells in a time- and dose-dependent fashion, independent of the serum concentration. The activation of apoptosis by 16K hPRL was specific for endothelial cells, and the activity of the peptide could be inhibited by heat denaturation, trypsin digestion, and immunoneutralization, but not by treatment with the endotoxin blocker, polymyxin-B. 16K hPRL-induced apoptosis was correlated with the rapid activation of caspases 1 and 3 and was blocked by pharmacological inhibition of caspase activity. Caspase activation was followed by inactivation of two caspase substrates, poly(ADP-ribose) polymerase (PARP) and the inhibitor of caspase-activated deoxyribonuclease (DNase) (ICAD). Furthermore, 16K hPRL increased the conversion of Bcl-X to its proapoptotic form, suggesting that the Bcl-2 protein family may also be involved in 16K hPRL-induced apoptosis. These findings support the hypothesis that the antiangiogenic action of 16K hPRL includes the activation of programmed cell death of vascular endothelial cells.

Reduction in lipopolysaccharide-induced thrombocytopenia by triflavin in a rat model of septicemia

BACKGROUND

Thrombocytopenia frequently occurs early in the course of Gram-negative bacterial infections. Triflavin, an Arg-Gly-Asp-containing disintegrin, has been suggested to interfere with the interaction of fibrinogen with the glycoprotein IIb/IIIa complex. The present study was undertaken to determine whether triflavin could prevent thrombocytopenia in lipopolysaccharide (LPS)-treated rats.

METHODS AND RESULTS

In this study, 51Cr-labeled platelets were used to assess blood and tissue platelet accumulation after LPS challenge. The administration of LPS (4 mg/kg IV bolus) for 4 hours induced a reduction in radiolabeled platelets in blood and an obvious accumulation of platelets in liver. Triflavin (500 microg/kg) but not GRGDS (20 mg/kg) significantly prevented the alteration of radiolabeled platelet distribution in blood and liver when induced by LPS. Furthermore, triflavin but not GRGDS markedly suppressed the elevation in plasma thromboxane B2 concentration within the 4-hour period of LPS administration. In LPS-treated rats, the 5-hydroxytryptamine level was lower in the blood and higher in the liver compared with levels in normal saline-treated rats. Pretreatment with triflavin (500 microg/kg) significantly reversed the 5-hydroxytryptamine concentration in blood and liver of LPS-treated rats. In histological examinations and platelet adhesion assay, triflavin markedly inhibited the adhesion of platelets to subendothelial matrixes in vivo and in vitro.

CONCLUSIONS

The results indicate that triflavin effectively prevents thrombocytopenia, possibly through the following 2 mechanisms: (1) Triflavin markedly inhibits platelet aggregation, resulting in decreased thromboxane A2 formation. (2) It inhibits the adhesion of platelets to subendothelial matrixes, thereby leading to a reversal in the distribution of platelets in blood and liver in LPS-treated rats.

Additive effect of tumor necrosis factor-alpha and endotoxin on bilirubin cytotoxicity

Clinical observations suggest that sepsis may enhance the risk of kernicterus. This study investigated the combined effects of bilirubin, endotoxin, and tumor necrosis factor-alpha (TNF-alpha), which simulate sepsis in a jaundiced mouse fibroblast cell line. The horseradish peroxidase oxidation method was applied for bilirubin-albumin titration studies to test the effect of endotoxin and TNF-alpha on bilirubin-albumin binding. A modified 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide method was used to study cytotoxicity. Bilirubin caused cytotoxicity in a dose-dependent manner in the cultured mouse fibroblasts. Such an effect was significantly amplified by TNF-alpha and endotoxin. TNF-alpha and endotoxin had no effect on the bilirubin-albumin titration curves. Our results have shown that TNF-alpha and endotoxin increase the cytotoxicity of bilirubin. These findings provide supportive evidence that sepsis would increase the risk of tissue damage by bilirubin.

Chlamydia pneumoniae but not cytomegalovirus antibodies are associated with future risk of stroke and cardiovascular disease: a prospective study in middle-aged to elderly men with treated hypertension

BACKGROUND AND PURPOSE

Several cross-sectional and prospective studies have indicated that high titers of antibodies to Chlamydia pneumoniae and cytomegalovirus (CMV) are associated with coronary heart disease. The aim of the present study was to examine whether elevated titers of antibodies to these pathogens are predictive of not only coronary but also cerebrovascular disease.

METHODS

Serum titers of antibodies to C pneumoniae (IgM, IgG, IgA, IgG immune complex) and CMV (IgG) were determined at baseline (n=130) and after 3.5 years (n=111) in a total sample of 152 men. All individuals had treated hypertension and at least 1 additional risk factor for cardiovascular disease (hypercholesterolemia, smoking, or diabetes mellitus) and constituted 93% of a randomly selected subgroup (n=164) of patients participating in a multiple risk factor intervention study.

RESULTS

Elevations of any or both of the IgA or IgG titers to C pneumoniae at entry or after 3.5 years were found in 84 cases (55%). Of those with high titers at entry, 97% remained high at the 3.5 year reexamination. After 6.5 years of follow-up, high titers to C pneumoniae at entry were associated with an increased risk for future stroke (relative risk [RR], 8.58; P=0.043; 95% CI, 1.07 to 68.82) and for any cardiovascular event (RR, 2.69; P=0.042; 95% CI, 1.04 to 6.97). A high serum titer of antibodies to CMV was found in 125 cases (85%), and this was not associated with an increased risk of future cardiovascular events.

CONCLUSIONS

Seropositivity for C pneumoniae, but not for CMV, was associated with an increased risk for future cardiovascular disease and, in particular, stroke.

Bacterial lipopolysaccharide disrupts endothelial monolayer integrity and survival signaling events through caspase cleavage of adherens junction proteins

Bacterial lipopolysaccharide or endotoxin induces actin reorganization, increased paracellular permeability, and endothelial cell detachment from the underlying extracellular matrix in vitro. We studied the effect of endotoxin on transendothelial albumin flux and detachment of endothelial cells cultured on gelatin-impregnated filters. The endotoxin-induced changes in endothelial barrier function and detachment occurred at doses and times that were compatible with endotoxin-induced apoptosis. Since the actin cytoskeleton and cell-cell and cell-matrix adhesion all participate in the regulation of the paracellular pathway and cell-matrix interactions, we studied whether protein components of the actin-linked adherens junctions were modified in response to endotoxin. Components of cell-cell (beta- and gamma-catenin) and cell-matrix (focal adhesion kinase and p130(Cas)) adherens junctions were cleaved by caspases activated during apoptosis with dose and time requirements that paralleled those seen for barrier dysfunction and detachment. Cleavage of focal adhesion kinase led to its dissociation from the focal adhesion-associated signaling protein, paxillin, resulting in reduced paxillin tyrosine phosphorylation. Inhibition of caspase-mediated cleavage of these proteins protected against detachment but not opening of the paracellular pathway. Therefore, endotoxin-induced disruption of endothelial monolayer integrity and survival signaling events is mediated, in part, through caspase cleavage of adherens junction proteins.

Selectivity of endotoxin-induced defect in endothelial calcium mobilization

BACKGROUND

We hypothesized that endotoxin (LPS) would impair bradykinin (BK)-induced calcium (Ca2+) mobilization in aortic endothelial cells, perhaps due to cytotoxicity or via stimulation of nitric oxide (NO) synthesis. As well, we sought to define contributions of LPS-stimulated Ca2+ mobilization to these effects.

METHODS

LPS- or BK-induced increments of intracellular Ca2+ were assessed by microspectrofluorimetry with fura-2 in passaged bovine aortic endothelial cells. Time- and dose-dependent effects of LPS exposure (+/- inhibitors of NO or prostaglandin synthesis) on subsequent BK-induced Ca2+ mobilization and on attached cell counts were determined.

RESULTS

LPS (0.1 to 1.0 mg/ml) led to rapid increments of Ca2+, while Ca2+ responses were delayed following LPS (1 to 10 microg/ml) and lower doses were without effect. By contrast, LPS more potently (1.0 pg to 1.0 microg/ml) led to dose- and time-dependent impairment of subsequent BK-induced Ca2+ mobilization, with peak effect at four to six hours, persisting for at least 18 hours. This delayed effect on BK-response was unaltered by inhibition of either NO synthase or cyclooxygenase. The effect of LPS on BK-responsivity depended importantly on cell confluence, as it was not observed in subconfluent cells. By contrast, LPS-induced cell detachment, which was observed only at doses > or = 1.0 microg/ml, did not depend on confluence.

CONCLUSIONS

Different mechanisms lead to endothelial cytotoxicity and to impaired BK-response following LPS. Only the former effect, occurring at higher doses, might depend on initial LPS-induced Ca2+ mobilization.

Increased plasma von Willebrand factor in the systemic inflammatory response syndrome is derived from generalized endothelial cell activation

OBJECTIVES

Von Willebrand factor antigen (vWf) is an essential hemostatic protein. Increased plasma levels have been documented in patients suffering from the systemic inflammatory response syndrome (SIRS) and resulted presumably from endothelial cell damage specific to the site of injury. We hypothesize that increased plasma levels result from systemic endothelial cell activation and degranulation.

DESIGN

We compared immunohistochemical vWf staining in dermal biopsy specimens from patients with SIRS to healthy control subjects in the presence and absence of recombinant human tumor necrosis factor (rhTNF)-alpha. Also, we quantified plasma levels of vWf in these groups using a newly available antibody.

SETTING

A tertiary care surgical intensive care unit in a university teaching hospital.

SUBJECTS

Patients with SIRS and healthy controls.

INTERVENTIONS

Biopsies and blood samples were obtained from study groups.

MEASUREMENTS AND MAIN RESULTS

Decreased baseline vWf staining was noted in SIRS patients. The rhTNF-alpha caused a statistically significant decrease in vWf staining in control subjects but not in SIRS patients. Plasma vWf levels were increased an average of 11-fold in SIRS patients compared with control subjects.

CONCLUSION

We postulate that the increased plasma levels of vWf and the decreased staining in the peripheral dermal plexus represent the generalized activation and degranulation of endothelium in vascular beds remote from the original inflammatory focus.

Chlamydia pneumoniae and occlusive vascular disease: identification and characterization

Chlamydia pneumoniae, a respiratory pathogen, has been associated with occlusive vascular disease, including atherosclerosis and intimal hyperplasia, through seroepidemiologic studies. Furthermore, using immunohistochemistry (IHC), polymerase chain reaction (PCR), transmission electron microscopy (TEM), and in situ hybridization, this association has been reconfirmed by detecting this organism in atherosclerotic vascular tissue. This review summarizes and critically analyzes these findings and also discusses various mechanisms of how Chlamydia pneumoniae could be involved in the pathogenesis of occlusive vascular disease. Although more studies are needed to reproduce these results and, possibly, uncover a mechanism, the current literature fails to include detailed methodologies for studying Chlamydia pneumoniae. Therefore, to provide a general standard, we have also outlined specific protocols for IHC, PCR, and TEM. These protocols incorporate essential components from various studies and are presented in a concise and easily adaptable format.

Modulation of endothelial cell apoptosis: mechanisms and pathophysiological roles

Apoptosis is a mode of cell death in which intrinsic cellular mechanisms participate in the demise of the cell. The modulation of endothelial apoptosis may play a role in atherosclerosis, angiogenesis, vascular remodeling and other pathophysiological states. Control of cell death is mediated by the state of activation of a death pathway as well as by the levels of anti apoptotic proteins. The final common pathway of many, if not all, triggers of apoptosis involves activation of cysteine proteases. The Bcl 2 family, in contrast, appears to play a major role in protection against apoptosis. The role of these mechanisms in modulating endothelial cell apoptosis under various conditions is discussed.

In vitro susceptibility of human vascular wall cells to infection with Chlamydia pneumoniae

Chlamydia pneumoniae is a common respiratory pathogen. Recent studies have demonstrated the presence of C. pneumoniae in coronary and aortic atherosclerotic lesions. To study the role of C. pneumoniae in atherosclerosis, we investigated the susceptibilities of three different cells of the human vascular wall to infection with C. pneumoniae AR-39. These cell types were endothelial cells, smooth muscle cells, and macrophages derived from peripheral blood monocytes. Infection was assessed by using a direct fluorescent antibody to assess inclusion counts. Duplicate cell samples were harvested 3 days postinfection and were passed in HL cells, a susceptible human epithelial cell line, to determine if infectious organisms were produced. Endothelial cells, smooth muscle cells, and macrophages were capable of supporting C. pneumoniae growth in vitro. These results showed that three different cell types known to be important in atherogenesis are susceptible to infection with C. pneumoniae.

Soluble CD14 in serum mediates LPS-induced increase in permeability of bovine pulmonary arterial endothelial cell monolayers in vitro

Lipopolysaccharide (LPS) is a mediator of septic shock and acute respiratory distress syndrome (ARDS), conditions which are characterized by high-permeability pulmonary edema. LPS increases endothelial permeability both directly and indirectly via the pro-inflammatory cytokines produced by monocytes and macrophages. We investigated the role of soluble CD14 in serum in the increased endothelial permeability induced by LPS. Bovine pulmonary artery endothelial cells were grown to confluence on a microporous filter and the 125I-albumin clearance rate across the monolayer was determined. Even a high concentration of LPS (1 microgram/ml) did not increase endothelial permeability under a serum-free condition. In the presence of more than 3% normal human serum, LPS increased endothelial permeability. The presence of neutralizing anti-CD14 monoclonal antibody eliminated the serum-dependent effect of LPS. The addition of recombinant sCD14 completely replaced the requirement for serum. LPS-binding protein (LBP) did not enhance the rsCD14-mediated LPS effect, and anti-LBP antibody did not attenuate the serum-dependent LPS effect. These findings suggest that sCD14 in serum mediates the permeability-increasing effect on LPS on endothelial cells but that LBP is not necessary for this effect.

Elevated promotion of prostacyclin production by synthetic lipid A analogs in aged human endothelial cells in culture

We examined the effects of E. coli lipopolysaccharide (LPS) and synthetic analogs of lipid A, a bioactive moiety of LPS, on the prostacyclin (PGI2) production by young and old human endothelial cells in vitro. PGI2 production by endothelial cells has been shown to decrease during in vitro cellular senescence as well as in vivo. LPS and all the analogs tested in this study did not stimulate PGI2 production by young endothelial cells more than twofold. However, LPS and the majority of the lipid A analogs examined stimulated the PGI2 production by old cells more than twofold (approximately two- to sixfold). These results indicate that the responses to certain stimuli sometimes differ markedly between young and old cells, and this should be carefully considered when evaluating the biological effects of various compounds. Furthermore, these results suggest that certain synthetic lipid A analogs can be used as drugs to prevent some age-related vascular diseases.

Lipopolysaccharide (LPS)-binding protein and soluble CD14 function as accessory molecules for LPS-induced changes in endothelial barrier function, in vitro

Bacterial LPS induces endothelial cell (EC) injury both in vivo and in vitro. We studied the effect of Escherichia coli 0111:B4 LPS on movement of 14C-BSA across bovine pulmonary artery EC monolayers. In the presence of serum, a 6-h LPS exposure augmented (P < 0.001) transendothelial 14C-BSA flux compared with the media control at concentrations > or = 0.5 ng/ml, and LPS (10 ng/ml) exposures of > or = 2-h increased (P < 0.005) the flux. In the absence of serum, LPS concentrations of up to 10 micrograms/ml failed to increase 14C-BSA flux at 6 h. The addition of 10% serum increased EC sensitivity to the LPS stimulus by > 10,000-fold. LPS (10 ng/ml, 6 h) failed to increase 14C-BSA flux at serum concentrations < 0.5%, and maximum LPS-induced increments could be generated in the presence of > or = 2.5%. LPS-binding protein (LBP) and soluble CD14 (sCD14) could each satisfy this serum requirement; either anti-LBP or anti-CD14 antibody each totally blocked (P < 0.00005) the LPS-induced changes in endothelial barrier function. LPS-LBP had a more rapid onset than did LPS-sCD14. The LPS effect in the presence of both LBP and sCD14 exceeded the effect in the presence of either protein alone. These data suggest that LBP and sCD14 each independently functions as an accessory molecule for LPS presentation to the non-CD14-bearing endothelial surface. However, in the presence of serum both molecules are required.

Application of immunogold labelling for light and electron microscopic localization of endothelial leukocyte adhesion molecule 1 (ELAM-1) on cultured human endothelial cells

This study describes the expression characteristics of E-selectin molecules using immunogold histochemical techniques on cultured human umbilical vein endothelial cells (HUVEC). The expression of E-selectin was induced by tumour necrosis factor-alpha (TNF-alpha, 300 U/ml), phorbol ester (PMA, 10 ng/ml) and bacterial lipopolysaccharide (LPS, 4 micrograms/ml). No expression was demonstrated on control cells. Using the silver-enhanced colloidal gold-labelling technique, at the light microscopical level, HUVEC could be distinctively subdivided into three staining types. The cell labelling index, expressed as the number of 'positively' stained cells as a proportion of all viewed cells was the highest in the LPS group. For transmission electron microscopy (TEM) the preembedding immunocytochemical staining method and embedding in epoxy resin (Agar 100) according to standard procedures was used. In TEM gold particles were localized in close association with the apical plasma membrane, as well as on the surface of microvillus-like projections (the latter by TNF-alpha group). For high resolution scanning electron microscopy (HR-SEM) the secondary (SEI) and the backscattered electron imaging (BEI) modes were used. Gold particles were randomly distributed over the whole cell surface, although they appeared to be denser in the perinuclear zone. The quantitative evaluation on SE and BE viewing (the number of gold particles per cell area in microns 2) demonstrated the highest density of labelling in the LPS-treated group, but there was only a significant difference between LPS and TNF-alpha groups (P < 0.01, t-test). Furthermore, the ultrastructural studies indicated that treatment with substances which up-regulate E-selectin expression was not related to toxic cell damage or significant alterations of cellular ultrastructure.

Comparison of the potency of various serotypes of E. coli lipopolysaccharides in stimulating PGI2 production and suppressing ACE activity in cultured human umbilical vein endothelial cells

We investigated the potency of various serotypes of lipopolysaccharides (LPS) by examining LPS-induced stimulation of PGI2 production and suppression of ACE activity in cultured human umbilical vein endothelial cells (HUVEC). HUVEC which had been incubated with E. coli 055:B5 and 0111:B4 for 24 h produced more prostacyclin (PGI2) in response to thrombin than HUVEC incubated with E. coli 026:B6. Also, angiotensin converting enzyme activity (ACE) in cell lysates of HUVEC incubated for 24 h with 055:B5 or 0111:B4 was suppressed significantly compared to control HUVEC or HUVEC incubated with 026:B6. From these experimental results, E. coli 055:B5 and 0111:B4 appear to be more potent than 026:B6. It is concluded that this difference in potency among various serotypes of LPS should be taken into account when experiments are designed to examine the effect of LPS on endothelial cell function.

Bacterial lipopolysaccharide induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in pulmonary vascular endothelial cells: concurrent F-actin depolymerization and new actin synthesis

Bacterial lipopolysaccharide (LPS) influences pulmonary vascular endothelial barrier function in vitro. We studied whether LPS regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to Escherichia coli 0111:B4 LPS 10 ng/ml or media for up to 6 h and evaluated for: 1) transendothelial 14C-albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the DNAse 1 inhibition assay. LPS induced increments in 14C-albumin flux (P < 0.001) and intercellular gap formation at > or = 2-6 h. During this same time period the endothelial F-actin pool was not significantly changed compared to simultaneous media controls. Mean (+/- SE) G-actin (micrograms/mg total protein) was significantly (P < 0.002) increased compared to simultaneous media controls at 2, 4, and 6 h but not at 0.5 or 1 h. Prior F-actin stabilization with phallicidin protected against the LPS-induced increments in G-actin (P = 0.040) as well as changes in barrier function (P < 0.0001). Prior protein synthesis inhibition unmasked an LPS-induced decrement in F-actin (P = 0.0044), blunted the G-actin increment (P = 0.010), and increased LPS-induced changes in endothelial barrier function (P < 0.0001). Therefore, LPS induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. Over the same time period, LPS increased total actin (P < 0.0001) and new actin synthesis (P = 0.0063) which may be a compensatory endothelial cell response to LPS-induced F-actin depolymerization.

Chlamydia pneumoniae-specific circulating immune complexes in patients with chronic coronary heart disease

BACKGROUND

An association of chronic Chlamydia pneumoniae infection to coronary heart disease has been suggested recently. In a recent study, we demonstrated circulating immune complexes containing chlamydial genus-specific lipopolysaccharide in patients with coronary heart disease. The objective of the present study was to investigate whether C. pneumoniae species-specific immune complexes are present in chronic coronary heart disease.

METHODS AND RESULTS

The presence of Chlamydia-specific circulating immune complexes was studied in 46 patients with chronic coronary heart disease and in control subjects. Chlamydial lipopolysaccharide-containing immune complexes were detected with the antigen-specific capture method, and they were present in 41% of patients and 15% of control subjects (p < 0.01). The presence of C. pneumoniae antibodies in circulating immune complexes was studied by testing the specificity of antibodies derived from isolated and dissociated immune complexes by microimmunofluorescence testing and immunoblotting. The C. pneumoniae indexes based on the relative amount of immune complex-derived antibodies and free antibodies were significantly higher among patients compared with control subjects (median, 1/8 versus 1/16; p < 0.001). Immune complex bound antibodies showed specificity for 98-kd and 42-kd proteins of C. pneumoniae.

CONCLUSIONS

The results suggest that the majority of the patients with chronic coronary heart disease have a chronic C. pneumoniae infection in which chlamydial components have an easy access to circulation to form immune complexes with preexisting antibodies. These findings give further evidence for the association of chronic C. pneumoniae infection with coronary heart disease.

A simple assay to detect endothelial cell injury; measurement of released thrombomodulin from cells

A simple assay to determine the degree of endothelial cell injury has been developed using released thrombomodulin as the index. Thrombomodulin is a cell surface protein on endothelial cells which is released from the cell upon injury. In this assay, bovine arterial endothelial cells were cultured in serum free medium with the test substances and the amount of thrombomodulin released into the culture medium was measured by enzyme immunoassay. Substances which are known to injure cells such as H2O2, prostaglandin A2, lipopolysaccharide, and elastase released significant amounts of thrombomodulin. The sensitivity of this assay for mild injury was superior or at least equal to the traditional 51Cr release method. Since this method does not require the use of radioisotopes, it seems to be advantageous and suitable for the detection of endothelial cell injury during routine examination.

Shiga toxin-associated hemolytic uremic syndrome: combined cytotoxic effects of shiga toxin and lipopolysaccharide (endotoxin) on human vascular endothelial cells in vitro

This study explores the in vitro relationship between Shiga toxin-producing Shigella spp. and Escherichia coli and the development of vascular complications in humans following bacillary dysentery. We propose that lipopolysaccharide (LPS; endotoxin) may combine with Shiga toxin to facilitate vascular damage characteristic of hemolytic uremic syndrome. We have examined the direct cytotoxic effects of Shiga toxin and LPS on human umbilical vein endothelial cells (HUVEC) in culture. Shiga toxin alone was cytotoxic to HUVEC, whereas LPS was noncytotoxic at concentrations at or below 10 micrograms/ml. Combinations of LPS with Shiga toxin resulted in a synergistic cytotoxic effect. The synergistic cytotoxic response of HUVEC to Shiga toxin plus LPS was dose dependent for both agents and was maximal at 24 h of exposure. This synergistic response was enhanced by preincubation of HUVEC with LPS. LPS (1 micrograms/ml) alone depressed HUVEC protein synthesis in a transient manner and enhanced the protein synthesis-inhibiting activity of Shiga toxin. The synergistic cytotoxic activity of LPS analogs was as follows, in decreasing order: complete LPS = diphosphoryl lipid A greater than monophosphoryl lipid A greater than deacylated LPS. These results are consistent with a role for Shiga toxin and LPS in the development of hemolytic uremic syndrome at the level of the vascular endothelium in humans.

Anti-myeloperoxidase antibodies stimulate neutrophils to damage human endothelial cells

Anti-myeloperoxidase autoantibodies are found in association with idiopathic necrotizing glomerulonephritis and systemic vasculitis. It is not known if their presence is an epiphenomen or an integral part of the pathogenic process. To further delineate their hypothesized pathogenicity, we studied their ability to stimulate neutrophils to damage human umbilical vein endothelial cells in vitro. Anti-myeloperoxidase antibodies from human, rabbit and mouse sources were utilized. These antibodies stimulated neutrophils to damage endothelial cells as determined by 51Cr release. The effect was dependent on priming the neutrophils with tumor necrosis factor-alpha, and further enhanced with the addition of endotoxin. The amount of endothelial cell damage was dependent on the dose of anti-myeloperoxidase, the source of the neutrophils, the concentration of TNF, and the presence of endotoxin. Under identical conditions, control antibodies did not stimulate neutrophils to damage endothelial cells. The effect was confirmed by labeling the endothelial cells with 3H-adenine which yielded the same results. These results provide further in vitro evidence that anti-myeloperoxidase autoantibodies may play a significant role in the pathogenesis of idiopathic pauci-immune glomerulonephritis and vasculitis.

Lipopolysaccharides decrease angiotensin converting enzyme activity expressed by cultured human endothelial cells

Angiotensin converting enzyme (ACE) is present on endothelial cells and plays a role in regulating blood pressure in vivo by converting angiotensin I to angiotensin II and metabolizing bradykinin. Since ACE activity is decreased in vivo in sepsis, the ability of lipopolysaccharide (LPS) to suppress endothelial cell ACE activity was tested by culturing human umbilical vein endothelial cells (HUVEC) for 0-72 hr with or without LPS and then measuring ACE activity. ACE activity in intact HUVEC monolayers incubated with LPS (10 micrograms/ml) decreased markedly with time and was inhibited by 33%, 71%, and 76% after 24 hr, 48 hr, and 72 hr, respectively, when compared with control, untreated cells. The inhibitory effect of LPS was partially reversible upon removal of the LPS and further incubation in the absence of LPS. The LPS-induced decrease in ACE activity was dependent on the concentrations of LPS (IC50 = 15 ng/ml at 24 hr) and was detectable at LPS concentrations as low as 1 ng/ml. That LPS decreased the Vmax of ACE in the absence of cytotoxicity and without a change in Km suggests that LPS decreased the amount of ACE present on the HUVEC cell membrane. While some LPS serotypes (Escherichia coli 0111:B4 and 055:B5, S. minnesota) were more potent inhibitors of ACE activity than others (E. coli 026:B6 and S. marcescens), all LPS serotypes tested were inhibitory. These finding suggest that LPS decreases endothelial ACE activity in septic patients; in turn, this decrease in ACE activity may decrease angiotensin II production and bradykinin catabolism and thus play a role in the pathogenesis of septic shock.

Cyclosporine-induced synthesis of endothelin by cultured human endothelial cells

Endothelin (ET), a peptide synthesized by endothelial cells (EC), causes a decreased renal blood flow and glomerular filtration rate and an increased mean arterial pressure when infused in animals. In tissue culture, ET causes smooth muscle cell (SMC) proliferation and contraction by influx of extracellular calcium, which is inhibited by calcium channel antagonists. Infusion of cyclosporine (CSA) hemodynamically parallels ET action, and knowing that CSA effects EC, we hypothesize that the vasoconstrictive effects of CSA are a result of ET synthesis by EC. Varying concentrations of CSA were incubated with EC resulting in ET present in the supernatants in a dose-dependent manner peaking at 75% above basal activity. Coincubation of either cremophor alone or cycloheximide with CSA resulted in minimal ET present in the EC supernatants (P less than 0.01 each). Incubation of conditioned media from CSA-treated EC with SMC caused proliferation at 114% above basal activity, which did not occur in the presence of CSA alone (P less than 0.01). This activity is specifically inhibited in the presence of an anti-ET antibody or nonspecifically in the presence of calcium channel antagonists (P less than 0.01 each). Therefore, CSA stimulates EC synthesis of ET which in turn causes SMC proliferation. This action is inhibited by the coincubation of a specific antibody to ET or a calcium channel antagonist. These findings may help in the understanding of CSA-induced hypertension and vasculopathy.

Endotoxin-induced endothelial injury and subendothelial accumulation of fibronectin in rat aorta

Endotoxin (lipopolysaccharide, LPS) induces endothelial injury in arterial vessels. Fibronectin is known to be involved in cell attachment and wound repair. The present study was designed to elucidate the effect of LPS on the production and distribution of fibronectin in relation to injury and repair in rat aortic endothelium. Male Sprague-Dawley rats were sacrificed for ultrastructural and immunocytochemical evaluations at 1, 3, 6, 24, and 48 hr after a single intravenous injection of 1.5 or 3 mg/kg body weight E. coli LPS. Apparent morphological signs of endothelial injury, including cell detachment, denudation, cell death, and edema were observed 1-48 hr after injection. Parietal thrombosis and leukocyte diapedesis were also observed in the aorta. A profound increase in subendothelial fibronectin was found following LPS treatment. However, no distinct change in intracellular fibronectin was observed in the same endothelium until 24 hr after injection. Using horseradish peroxidase (HRP) and anti-fibronectin-HRP antibody as tracers, LPS was also found to increase permeability and extravasation of plasma proteins (fibronectin) of the aortic endothelium. The increase of subendothelial fibronectin possibly resulted from increased influx and sequestration of plasma fibronectin. This increase may provide a firm substratum for reendothelialization after vascular injury.

Endotoxic shock. Part I: A review of causes

Endotoxic shock is a complex phenomenon resulting from systemic release of inflammatory mediators. Endotoxin interacts with inflammatory cells, platelets, and vascular endothelium. Cytokines, such as tumor necrosis factor and interleukins, and lipid mediators (platelet activating factor, thromboxane, prostacyclin, leukotrienes) are released. These primary mediators act synergistically to cause many of the harmful effects associated with endotoxemia. Multiple secondary mediators are released in response to the primary mediators, compounding the damage. The end result is the species-specific clinical syndrome recognized as endotoxemia.

Effects of serum and endotoxin in experimental lung injury

Lipopolysaccharide (LPS) is in large part responsible for the lung injury that occurs in the sepsis syndrome. Recent work has shown the ability of LPS alone to induce injury in endothelial monolayers, though the LPS effect is enhanced in the presence of serum. We previously demonstrated that low-dose LPS (50 ng/mL) can lead to lung injury in an isolated perfused rabbit lung model. To examine the effect of serum on LPS-induced injury rabbit lungs were perfused with increasing doses of rabbit serum in the presence and absence of LPS. There was no increase in total weight gained by the lung,Qf, with either 5% serum, 10% serum, or 10% serum with LPS. However vascular permeability as measured by hydraulic conductance was increased with increasing doses of serum. This effect was not enhanced by the addition of LPS. These results provide evidence that serum alone may cause lung injury, perhaps through the activation of complement or other mediators.

Thromboxane and prostacyclin release after endotoxin infusion in the rat

To determine in the rat whether pulmonary artery hypertension accompanies thromboxane release, we sequentially monitored pulmonary and systemic artery pressures and cardiac output. We measured pulmonary and aortic plasma levels of TxB2 as well as 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in awake unrestrained adult male Sprague-Dawley rats given a single infusion of endotoxin at the relatively high dose commonly administered to this endotoxin-resistant species. At 40 min after endotoxin infusion, both pulmonary and aortic TxB2 and 6-keto-PGF1 alpha levels increased nine-fold and seven-fold above baseline, respectively. In the pulmonary artery, 40 min after infusion, both mediator levels differed significantly from baseline (p less than 0.05), whereas in the aorta, because of marked variance in the response of different animals, only the 6-keto-PGF1 alpha levels achieved significance (p less than 0.05). These changes were associated with a fall in systemic blood pressure and cardiac output, but no demonstrable rise in pulmonary artery pressure (PAP). Despite ultrastructural evidence of vascular injury, these data indicate that in the rat thromboxane and prostacyclin release following a single infusion of endotoxin is not associated with pulmonary hypertension and that increased prostacyclin production may contribute to systemic hypotension.

Antilipopolysaccharide factor from horseshoe crab, Tachypleus tridentatus, inhibits lipopolysaccharide activation of cultured human endothelial cells

Antilipopolysaccharide (anti-LPS) factor is a basic protein that is purified from the hemocyte lysate of the Japanese and American horseshoe crabs (Tachypleus tridentatus and Limulus polyphemus). Anti-LPS factor has previously been reported to inhibit LPS-mediated activation of limulus factor C, lyse endotoxin-sensitized erythrocytes, and inhibit the growth of some gram-negative bacteria. In this study, we examine the ability of anti-LPS factor purified from T. tridentatus to inhibit the activation of cultured human endothelial cells by LPS. Anti-LPS factor inhibited the stimulation of endothelial adhesiveness for neutrophils by LPS in a dose-dependent manner. Maximum inhibition was achieved when anti-LPS factor was mixed with LPS prior to addition to the endothelial cell monolayers. Anti-LPS factor inhibited endothelial cell activation by LPS derived from Salmonella minnesota Re and Rc mutants as well as from the wild type (smooth), suggesting that it recognizes the lipid A moiety of LPS.

Human endothelial cell response to lipopolysaccharide, interleukin-1, and tumor necrosis factor is regulated by protein synthesis

In this study we assessed the viability of cultured human umbilical vein endothelial cells (HUVE) treated with bacterial lipopolysaccharide (LPS), recombinant human interleukin-1 (rhIL-1), or recombinant human tumor necrosis factor-alpha (rhTNF-alpha) during inhibition of RNA or protein synthesis. Cytotoxicity was determined by 51Cr activity retained in labeled HUVE monolayers after exposure to LPS, rhIL-1 or rhTNF-alpha, and cycloheximide (Cx) or actinomycin D (Act D). Lipopolysaccharide (150 ng/ml), rhIL-1 (100 pg/ml), or rhTNF-alpha (20 ng/ml) alone was not toxic to HUVE in an 18-hr incubation. Cycloheximide alone (1 microgram/ml for 18 hr) or Act D alone (1 microgram/ml for 6 hr) was also not toxic to HUVE. However, coincubation of HUVE with Cx and LPS (150 ng/ml), rhIL-1 (10 pg/ml), or rhTNF-alpha (20 ng/ml) produced significant cytotoxicity at 18 hr (70 +/- 4% for LPS, 75 +/- 5% for rhIL-1, and 52 +/- 5% for rhTNF-alpha; mean +/- SEM of 18, 16, and 19 separate experiments, respectively). Similarly, coincubation of HUVE with Act D and LPS, rhIL-1, or rhTNF-alpha resulted in 82 +/- 5%, 85 +/- 3%, and 67 +/- 4% cytotoxicity, respectively, at 6 hr (mean +/- SEM of 5 separate experiments for LPS, and 7 separate experiments each for rhIL-1 and rhTNF-alpha). At the highest concentrations of LPS, rhIL-1, or rhTNF-alpha, cytotoxicity during coincubation with Cx or Act D was detected as early as 2 hr and was near maximal by 6 hr. In contrast to LPS, rhIL-1, or rhTNF-alpha, recombinant human interferon-gamma (up to 100 U/ml), or human alpha-thrombin (up to 10 U/ml), produced no cytotoxicity in the presence of Cx. Recombinant human lymphotoxin (up to 50 ng/ml) had a detectable cytotoxic effect in the presence of Cx although it was significantly less than that seen with rhTNF-alpha. Furthermore, coincubation of human fibroblasts and human smooth muscle cells with Cx and LPS, rhIL-1, or rhTNF-alpha produced no cytotoxicity. We conclude that under these culture conditions, LPS, rhIL-1, or rhTNF-alpha produces a lethal injury to HUVE when de novo RNA or protein synthesis is inhibited. These results suggest that LPS, rhIL-1, and rhTNF-alpha may act via a common pathway in endothelial cells and that protein synthesis is important in regulating the response to these stimuli.

In vitro effects of endotoxin on bovine and sheep lung microvascular and pulmonary artery endothelial cells

A single infusion of Escherichia coli endotoxin into sheep results in structural evidence of pulmonary endothelial injury, increases in both prostacyclin and prostaglandin E2 (PGE2) in lung lymph, and an increase in pulmonary microvascular permeability. Endotoxin-induced lung endothelial damage can also be induced in vitro, but to date these studies have utilized endothelium from large pulmonary vessels. In the present study, we have grown endothelial cells from peripheral lung vessels of cows and sheep and exposed these microvascular endothelial cells to endotoxin. Controls included lung microvascular endothelium without endotoxin and endothelial cells from bovine and sheep main pulmonary artery with and without addition of endotoxin. We found that endotoxin caused significant increases in release of prostacyclin and PGE2 from both bovine and sheep lung microvascular and pulmonary artery endothelium. Normal bovine and sheep pulmonary artery and bovine lung microvascular endothelium released greater levels of prostacyclin than PGE2 (ng/ng); release of PGE2 from the microvascular cells was greater than from the pulmonary artery endothelium in both species. Exposure of endothelial cells from cow and sheep main pulmonary artery to endotoxin results in endothelial cell retraction and pyknosis, a loss of barrier function, increased release of prostacyclin and PGE2 and eventual cell lysis. In lung microvascular cells, the increases in prostanoids were accompanied by changes in cell shape but occurred in the absence of either detectable alterations in barrier function or cytolysis. Thus, while endotoxin causes alterations to endothelial cells from both large and small pulmonary vessels, the effects are not identical suggesting site specific phenotypic expression of endothelial cells even within a single vessel. To determine whether the response of either the large or small pulmonary vessel endothelial cells in culture mimics most closely the in vivo response of the lung to endotoxin requires further study.

Haemophilus influenzae lipopolysaccharide-induced blood brain barrier permeability during experimental meningitis in the rat

The factors responsible for blood-brain barrier (BBB) injury during bacterial meningitis are incompletely defined. We evaluated the role of Haemophilus influenzae type b (Hib) lipopolysaccharide (LPS) in the alteration of blood-brain barrier permeability (BBBP) in an adult, normal and leukopenic, rat model of meningitis. Intracisternal inoculation of Hib LPS resulted in (a) dose-dependent increases in BBBP from 2 pg to 20 ng, with significant attenuation in the peak response after challenge with 500 ng and 1 microgram; (b) time-dependent increases in BBBP, with a delayed onset of at least 2 h, maximum alteration at 4 h, and complete reversal at 18 h; (c) greater BBBP than after challenge with the live parent strain; (d) and a close correlation (r = 0.86) between CSF pleocytosis and BBBP at 4 h. The LPS effect was significantly inhibited by preincubation with Polymyxin B and neutrophil acyloxyacyl hydrolase, however two different oligosaccharide-specific monoclonal antibodies did not inhibit activity. No change in BBBP after inoculation with Hib LPS occurred in leukopenic rats. Hib LPS, in the setting of an intact leukocyte response, exerts profound effects on BBBP.

Functional heterogeneity of vascular endothelial cells

This review has highlighted some of the well-described differences in endothelial cells derived from different sites of the vascular tree. In presenting a select group of endothelial properties, there was no intention to imply that these are the only properties of endothelial cells that exhibit heterogeneity. Nonetheless, having described endothelial heterogeneity in regard to a number of defined properties, we are left with persistent questions including: Are these divergent properties of endothelial cells fixed? Alternatively, can we alter the properties of endothelial cells by affecting the signals from the environment? A number of reports strongly suggest that endothelial cells are capable of acquiring new properties. Stewart and Wiley investigated the role of the neural tissue environment on the differentiation of brain capillary endothelial cells. These authors transplanted ectopic sites, i.e. vascular segments of brain from very young quail embryos to chick coeliac cavity, and a quail somites to chick brain ventricles. The distinctive morphology of quail cells provided a cell marker to differentiate host from graft. The results of this study demonstrated that mesenteric or somatic vessels growing into grafted brain developed functional, structural and histochemical features specific for neural capillaries. Conversely, capillaries in mesodermal tissue that had been grafted to the brain were devoid of the neural capillary characteristics, indicating that brain vessels do not form a barrier when they are made to vascularize non-neural tissue. Milici and Carley reported that bovine adrenal capillary cells cultured on plastic exhibited occasional diaphragmed fenestrations and no transendothelial channels. However, if these same cells were cultured on a basement membrane (matrix) laid down by MDCK cells (a canine nephron epithelial cell line), the cells responded by increasing the number of diaphragmed fenestrations and transendothelial channels. This cell culture study supported an earlier whole animal study in which the importance of the epithelium and/or epithelial basal lamina in the maintenance of endothelial ultrastructure was demonstrated in a developmental study of rat intestinal capillaries. In this earlier study, it was noted that epithelial development coincided with the formation of fenestrations by the endothelium. Enzymatic activities of endothelial cells can also be altered by environmental signals. For example, primary cerebral microvascular endothelial cells exhibit barrier features and are enriched in gamma-glutamyl transpeptidase activity, yet rapidly lose the activity when subcultured.(ABSTRACT TRUNCATED AT 400 WORDS)

Endotoxin alters arachidonate metabolism in pulmonary endothelial cells

Endotoxin and lipid A dose dependently (1 ng/ml to 10 micrograms/ml) and time dependently (6-24 h) stimulated the generation of large amounts of prostacyclin in cultured pig pulmonary artery endothelial cells. This effect occurred in the absence of cell detachment and overt cell damage. The presence of at least 1% serum was required but the activation of the complement cascade was not. Endotoxin-treated endothelial cells generated increased amounts of prostacyclin upon stimulation with A23187 and arachidonic acid. Endotoxin-induced activation of arachidonate metabolism could be reduced by 10(-10) M glucocorticoids but not by progesterone. It was further affected by inhibitors of protein and RNA synthesis and calmodulin function. In addition, exposure of endothelial cells to endotoxin resulted in an enhanced synthesis of cyclooxygenase and in a higher enzymatic capacity of prostacyclin synthase. The data indicate that endotoxin in concentrations occurring in the plasma of patients profoundly alters arachidonic acid metabolism in endothelial cells.

Endotoxin increases superoxide dismutase in cultured bovine pulmonary endothelial cells

Manganous (Mn) and copper zinc (CuZn) superoxide dismutase (SOD) concentrations and glutathione peroxidase (GSH-Px) and catalase (CAT) activities were measured in cultured bovine pulmonary endothelial cells with and without exposure to Escherichia coli endotoxin (10(-1) micrograms/ml) over intervals of 0.5-24 h. The activities of two mitochondrial marker enzymes, fumarase and cytochrome-c oxidase, were also measured. Endotoxin exposure caused a marked increase (9-fold) in endothelial cell Mn SOD content without significant effects on GSH-Px, CAT, fumarase, or cytochrome-c oxidase activities. Endotoxin induced a slight decrease in CuZn SOD content over 24 h. This is the first report of a selective effect of endotoxin on Mn SOD in pulmonary endothelial cells. The response appears to be independent of an increase in mitochondrial activity (no change was observed in cytochrome-c oxidase or fumarase activities). These findings support the notion that endotoxin increases generation of toxic oxygen metabolites within pulmonary endothelial cells. An endotoxin-induced increase in Mn SOD could contribute to the reported protective effect of endotoxin against oxygen toxicity in these cells.

Endotoxin enhances tissue factor and suppresses thrombomodulin expression of human vascular endothelium in vitro

Endotoxemia is frequently associated clinically with disseminated intravascular coagulation (DIC); however, the mechanism of endotoxin action in vivo is unclear. Modulation of tissue factor (TF) and thrombomodulin (TM) expression on the endothelial surface may be relevant pathophysiologic mechanisms. Stimulation of human umbilical vein endothelial cells with endotoxin (1 microgram/ml) increased surface TF activity from 1.52 +/- 0.84 to 11.89 +/- 8.12 mU/ml-10(6) cells at 6 h (n = 11) which returned to baseline by 24 h. Repeated stimulation at 24 h resulted in renewed TF expression. Endotoxin (1 microgram/ml) also caused a decrease in TM expression to 55.0 +/- 6.4% of control levels at 24 h (n = 10) that remained depressed at 48 h. Both effects were dose and serum dependent. A temporary rise in TF expression accompanied by a sustained fall in TM expression comprise a shift in the hemostatic properties of the endothelium that would favor intravascular coagulation and may contribute to the pathogenesis of DIC in gram-negative septicemia.