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PubMed1998

Abnormal accumulation of endotoxin in biliary epithelial cells in primary biliary cirrhosis and primary sclerosing cholangitis.

BACKGROUNDS/AIMS: Previous studies have revealed the involvement of Kupffer cells and hepatocytes in the metabolism of endotoxin in the liver. The aim of this study was to investigate the in vivo localization of endotoxin in liver cells, including Kupffer cells, hepatocytes, and biliary epithelial cells, in primary biliary cirrhosis and primary sclerosing cholangitis. We also examined the effect of ursodeoxycholic acid on the intrahepatic distribution of endotoxin in primary biliary cirrhosis. METHODS: The immunohistochemical localization of endotoxin was examined in liver specimens from 30 cases of primary biliary cirrhosis and seven of primary sclerosing cholangitis using a monoclonal antibody against lipid A. Controls were seven cases of obstructive jaundice, ten of hepatitis C virus-related liver cirrhosis, 14 of chronic hepatitis C, and five histologically normal liver cases. Semi-quantitative analysis of endotoxin accumulation was performed to measure the intensity of fluorescence for endotoxin. Nine of the 30 patients with primary biliary cirrhosis underwent a second liver biopsy for evaluation of the ursodeoxycholic acid treatment. RESULTS: In primary biliary cirrhosis and primary sclerosing cholangitis, biliary epithelial cells showed strong immunostaining for endotoxin as well as hepatocytes and Kupffer cells. Biliary epithelial cells of primary biliary cirrhosis and primary sclerosing cholangitis showed more intense immunoreactivity than those of other controls. In primary biliary cirrhosis, ursodeoxycholic acid reduced the immunoreactivity to endotoxin in biliary epithelial cells, and increased the immunoreactivity to endotoxin in Kupffer cells, but did not affect that in hepatocytes. CONCLUSIONS: Our results revealed that in primary biliary cirrhosis and primary sclerosing cholangitis, endotoxin accumulates abnormally in biliary epithelial cells. In addition, we found that ursodeoxycholic acid treatment in primary biliary cirrhosis may provide a beneficial effect on the intrahepatic metabolism of endotoxin.

Adult↗
PubMed1990

Insulin and beta adrenergic effects during endotoxin shock: in vivo myocardial interactions.

STUDY OBJECTIVE - Catecholamine concentrations are raised during endotoxin shock and may be responsible for myocardial insulin resistance in such a condition. The purpose of the investigation was to examine the effect of insulin on myocardial contractility and glucose uptake in the presence of beta adrenergic blockade during endotoxin shock. DESIGN - Endotoxin shock was obtained in dogs by giving S Typhimurium endotoxin intravenously (1 mg.kg-1) and the cardiac responses to insulin were determined under hyperinsulinaemic (4 U.min-1) euglycaemic clamp conditions during continuous beta adrenergic blockade (propranolol 150 micrograms.kg-1 + 5 micrograms.kg-1.min-1). SUBJECTS - 19 mongrel dogs of either sex, weight 20-25 kg, were studied under pentobarbitone anaesthesia. Seven dogs received endotoxin plus propranolol, and seven others received propranolol alone (control group). Five dogs received endotoxin but no propranolol or insulin. All other procedures were the same in each group. MEASUREMENTS and RESULTS - The exposed heart was prepared for coronary sinus blood sampling and measurements of circumflex artery blood flow (Q), instantaneous left ventricular pressure, and left ventricular wall thickness. Glucose uptake was calculated from product of Q and aortic-coronary sinus concentration difference. End systolic pressure-dimension relationship was used to assess contractility. Myocardial performance was assessed from left ventricular dP/dtmax. Basal shock measurements were made 60 min post endotoxin. beta Adrenergic blockade did not interfere with insulin stimulated glucose uptake in controls, but was unable to restore the uptake response during endotoxin shock. Contractility was increased during endotoxin shock and this effect was abolished by beta adrenergic blockade. In controls the only variable affected by beta adrenergic blockade was left ventricular dP/dtmax (decreased). Insulin increased contractility during beta adrenergic blockade in controls but not in shock. Myocardial performance was depressed during shock. In controls, insulin increased myocardial performance; in shock this response was attenuated. CONCLUSIONS - The findings confirm that the myocardium becomes less responsive to the glucose uptake stimulating and positive inotropic effects of insulin during endotoxin shock. The data show that beta adrenergic activity is responsible for the increased contractile state of the heart during acute endotoxin shock, but is not the cause of the observed insulin resistant state.

Animals↗
PubMed2003

Ozone exposure enhances endotoxin-induced mucous cell metaplasia in rat pulmonary airways.

Coexposure to different airborne pollutants can be more toxic to airway epithelium than an inhalation exposure to a single pollutant. We have previously reported that coexposure to ozone, the primary oxidant gas in photochemical smog, and unique inflammatory biogenic substances such as allergens or bacterial endotoxin, results in augmented epithelial and inflammatory responses in rat nasal airways (M. V. Fanucchi et al., 1998, Toxicol. Appl. Pharmacol. 152, 1-9; J. G. Wagner et al., 2002a, Toxicol. Sci.67, 284-294). In the present study, we investigated the toxic interaction of ozone and endotoxin on the respiratory epithelium in the pulmonary airways of laboratory rodents. F344 rats were intranasally instilled with 0, 2, or 20 microg endotoxin dissolved in sterile saline (150 microl/nasal passage). Six h after instillation rats were exposed to air or 1 ppm ozone for 8 h. One day later, endotoxin and ozone exposures were repeated. Three days after the last exposure, rats were sacrificed, the lungs were lavaged with saline, and the collected bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cells and secreted mucosubstances (mucin 5AC). Lung tissues were processed for light microscopic examination and morphometric analysis of numeric density of epithelial cell populations and volume densities of intraepithelial mucosubstances (IM). Conducting airways were microdissected and analyzed by quantitative RT-PCR to determine steady-state mucin gene (rMuc5AC) mRNA levels in respiratory epithelium. Endotoxin instillation caused a dose-dependent increase in BALF neutrophils that was further increased twofold in ozone-exposed rats given 20 microg endotoxin. Mucin glycoprotein 5AC was elevated in BALF from rats exposed to 20 microg, but not 2 microg endotoxin. Exposure to ozone alone did not cause mucus hypersecretion, but ozone potentiated mucus secretion in rats given 2 or 20 microg endotoxin. Airways of rats exposed to air or ozone alone had scant amounts of IM. Endotoxin instillation induced a dose-dependent increase in IM in airway epithelium that was significantly increased (twofold) in rats that were also exposed to ozone. Expression of rMuc5AC was induced in axial pulmonary airways by 2 and 20 microg endotoxin, and was increased further by ozone-exposure in rats instilled with 20 microg endotoxin. These data demonstrate that ozone exposure potentiates neutrophilic inflammation and mucus production and secretion elicited by a biogenic substance in rat pulmonary airways.

Administration, Intranasal↗
PubMed1998

The relationships among nitric oxide production, bacterial translocation, and intestinal injury after endotoxin challenge in vivo.

BACKGROUND: This study examines the hypothesis that there is a relationship among endotoxin-induced bacterial translocation (BT) and increased nitric oxide (NO) production and that inhibition of excessive NO production with NG-monomethyl-L-arginine (L-NMMA) is beneficial. METHODS: Rats received 0, 1, or 4 mg/kg endotoxin intraperitoneally, and 6 or 18 hours later, they were killed and BT, NO production (as reflected in nitrite/nitrate levels), and calcium-dependent nitric oxide synthase and calcium-independent nitric oxide synthase (iNOS) activities were measured in tissues (ileum, liver, and mesenteric lymph nodes) and blood. In a second set of experiments, the animals received the NOS inhibitor L-NMMA (100 mg/kg) intravenously either 15 minutes before or 2 hours after endotoxin challenge (4 mg/kg) and the same parameters were measured. RESULTS: The incidence of BT was higher in rats receiving 4 mg/kg endotoxin (62.5%) than in the control group (0%, p < 0.05), and the 1 mg/kg endotoxin group had intermediate incidence (25%). The animals receiving 4 mg/kg endotoxin had higher tissue (mesenteric lymph nodes, liver) and blood nitrite/nitrate levels than the control or 1 mg/kg endotoxin groups. The increased NO production was mainly attributable to an elevated level of iNOS activity. The administration of L-NMMA before but not after endotoxin challenge reduced iNOS activity, NO production, and BT to control levels at 6 hours but not 18 hours after endotoxin administration. CONCLUSION: Endotoxin-induced mucosal injury and BT are associated with iNOS activity and increased NO production. Inhibition of iNOS activity with L-NMMA before treatment prevented endotoxin-induced ileal mucosal injury and BT.

Animals↗
PubMed1970

Characteristics of Endotoxin-Altering Fractions Derived from Normal Serum III. Isolation and Properties of Horse Serum alpha(2)-Macroglobulin.

The endotoxin-altering activity of fractions isolated from normal horse serum was examined by incubation of Salmonella typhosa strain 0-901 endotoxin (Boivin) in a solution of the fraction, and subsequent quantitation of any diminution in the capacity of endotoxin to be precipitated by specific anti-endotoxin antiserum. The horse serum fraction isolated by precipitation with ammonium sulfate at a concentration between 1.6 and 2.7 m was incubated with Pronase PA and then with trypsin. When this partly digested fraction was passed twice through a Sephadex G-200 column and eluted with 0.2 m tris(hydroxymethyl)aminomethane buffer, most of the endotoxinaltering activity was found in the first protein peak designated F-1a. F-1a was found to be homogeneous and corresponded to an alpha(2)-macroglobulin by the techniques of electrophoresis, immunodiffusion, and ultracentrifugation. Approximately 100-fold more F-1a than endotoxin was needed to reduce the antigenicity of the endotoxin by one-half. Alteration was increased when F-1a was incubated with the endotoxin at acid pH or at 45 C rather than at 37 C and was lost after heating F-1a at 56 C for 30 min. N-ethylmaleimide increased the endotoxin-altering activity of horse serum, F-1a, and human plasma fraction III(0), whereas p-chloromercuribenzoate did not. On the other hand, diazonium-1-H-tetrazole, iodoacetic acid, and benzylchloride suppressed the activity of F-1a. When the interaction of endotoxin and F-1a was examined by immunodiffusion techniques, depolymerization of the endotoxin molecule was indicated. The endotoxin-altering factor of horse serum is discussed in relation to the mechanisms of other known reagents, such as deoxycholate and sodium lauryl sulfate.

Journal Article↗
PubMed2001

Free radical-induced contractile protein dysfunction in endotoxin-induced sepsis.

Recent studies have indicated that sepsis is associated with enhanced generation of several free-radical species (nitric oxide [NO], superoxide, hydrogen peroxide) in skeletal muscle. It is also known that this enhanced free-radical generation results in reductions in skeletal muscle force-generating capacity, but the precise mechanism(s) by which free radicals exert this effect in sepsis has not been determined. We postulated that free radicals might react directly with the contractile proteins in this condition, altering contractile protein force-generating capacity. To test this theory, we compared the force generation of single Triton-skinned diaphragmatic fibers (Triton skinning exposes the contractile apparatus, permitting direct assessment of contractile protein function) from the following groups of rats: (1) control animals; (2) endotoxin-treated animal; (3) animals given endotoxin plus polyethylene glycol- superoxide dismutase (PEG-SOD), a superoxide scavenger; (4) animals given endotoxin plus N(omega)-nitro-L-arginine methylester (L-NAME), a NO synthase inhibitor; (5 ) animals given only PEG-SOD or L-NAME; and (6 ) animals given endotoxin plus denatured PEG-SOD. We found that endotoxin administration produced both a reduction in the maximum force-generating capacity (Fmax) (i.e., a decrease in Fmax) of muscle fibers and a reduction in fiber calcium sensitivity (i.e., an increase in the Ca2+ concentration required to produce half-maximal activation [Ca50]). L-NAME and PEG-SOD administration preserved Fmax and Ca50 in endotoxin-treated animals; neither drug affected these parameters in non-endotoxin treated animals. Denatured PEG-SOD failed to inhibit endotoxin-related alterations in contractile protein function. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of skinned fibers from endotoxin-treated animals revealed a selective depletion of several proteins; administration of L-NAME or PEG-SOD to endotoxin-treated animals prevented this protein depletion, paralleling the effect of these two agents to prevent a reduction in contractile protein force-generating capacity. These data indicate that free radicals (superoxide, NO, or daughter species of these radicals) play a central role in altering skeletal muscle contractile protein force-generating capacity in endotoxin-induced sepsis.

Animals↗
PubMed2002

Regulation of endotoxin-induced keratitis by PECAM-1, MIP-2, and toll-like receptor 4.

PURPOSE: Bacterial lipopolysaccharide (LPS, endotoxin) is a potent stimulator of inflammatory responses and is likely to contribute to microbial keratitis and to the pathogenesis of sterile corneal ulcers. The purpose of the present study was to identify specific mediators of endotoxin-induced keratitis. METHODS: The corneal epithelium of BALB/c, C3H/HeJ, and C3H/HeN mice was abraded, and Pseudomonas aeruginosa endotoxin (10 microg in 1 microL) was added. Stromal thickness and haze were measured by in vivo scanning confocal microscopy, and neutrophil recruitment determined by immunohistochemistry. RESULTS: Pseudomonas endotoxin induced a significant increase in stromal thickness and haze compared with untreated control corneas at each time point examined, and the severity coincided with neutrophil infiltration into the corneal stroma. Furthermore, systemic depletion of neutrophils completely abrogated endotoxin-induced increases in stromal thickness and haze, indicating an essential role for these cells. Expression of platelet endothelial cell adhesion molecule (PECAM)-1 on vascular endothelium and production of macrophage inflammatory protein (MIP)-2 in the corneal stroma were also significantly elevated after exposure to endotoxin, and antibody blockade inhibited neutrophil recruitment to the cornea and abrogated endotoxin-induced increases in stromal thickness and haze. In LPS-hyporesponsive C3H/HeJ mice, PECAM-1 and MIP-2 were not upregulated after exposure to endotoxin, and endotoxin-induced keratitis did not develop in these mice. CONCLUSIONS: These findings demonstrate that endotoxin-induced keratitis is regulated by toll-like receptor-4 (TLR4)-dependent expression of PECAM-1 and MIP-2, which are essential for recruitment of neutrophils to this site and for development of endotoxin-induced stromal disease.

Animals↗
PubMedDate not supplied

Protection against fatal endotoxin shock in mice by antihistamines.

Protection against endotoxin shock by antihistamines and similar pharmacologic agents has been reported in the literature. The authors tested the validity of this form of treatment by animal experiments which were conducted in three phases. During the first phase, 10 mice each were treated intravenously with various doses of gram negative endotoxin to determine the dose of endotoxin which would kill 80% of the animals (LD80). This dose was determined to be 36 mg/kg bodyweight. During the second phase, 10 mice each were pretreated with various doses of either diphenhydramine (Benadryl) or of hydroxyzine HCI (Atarax) one hour prior to the administration of the LD80 of endotoxin. It appeared that high doses of diphenhydramine as well as of hydroxyzine were highly fatal to most animals by causing severe convulsions within 3 to 6 hours at doses of 40 or 50 mg/kg. Doses of less than 1 mg/kg appeared to have no protective effect, while doses of 2.5 and of 5 mg/kg, given one hour prior to the LD80 of endotoxin, had some protective value. In the case of diphenhydramine, 60% of the animals survived with 5 mg/kg pretreatment. Hydroxyzine hydrochloride protected 100% of the 10 animals so treated during the initial experiment and 90% during a subsequent experiment, if given 1 hour before the endotoxin. The third phase of this experiment was designed to determine the optimal time at which hydroxyzine needs to be given to protect against fatal endotoxin shock. Given 6 hours before endotoxin, hydroxyzine appeared to protect half of the animals, 1 hour prior to endotoxin, 5 mg/kg of hydroxyzine protected 90% of animals; if given simultaneously, it protected all animals. When hydroxyzine was given 1 hour after endotoxin there was a 70% survival and, if given 3 hours after endotoxin, a 40% survival.

Animals↗
PubMed1994

Endotoxin tolerance: effects on lethality and macrophage thromboxane (B2) and interleukin 6 production.

The effects of endotoxin pretreatment on induction of in vivo tolerance to endotoxin lethality, and on in vitro stimulated peritoneal macrophage mediators, thromboxane (TX)B2 and interleukin 6 (IL-6) were investigated. Rats were given i.p. injections of S. enteritidis endotoxin on days 1 (100 micrograms/kg) and 2 (500 micrograms/kg), respectively. After 5 days, or after 2-8 weeks of initial pretreatment, either endotoxin-induced mortality was assessed, or peritoneal cells were harvested for the in vitro studies. Endotoxin tolerant rats were resistant (p < .05) to endotoxin lethality for 2 weeks after initial induction of tolerance. In vitro studies with peritoneal macrophages demonstrated that endotoxin or monophosphoryl lipid A stimulated (p < .05) TXB2 production. However, peritoneal cells harvested from endotoxin tolerant rats exhibited suppressed (*p < .05) TXB2 production to both stimuli which persisted for at least 8 weeks. Endotoxin stimulated (p < .05) in vitro levels of IL-6 in control cells, but in contrast to the suppressed TXB2 production in tolerance, also stimulated (p < .05) in vitro IL-6 in the endotoxin tolerant group. Paradoxically, lipid A did not induce IL-6 production in either group. These composite observations suggest that during endotoxin tolerance neither in vitro peritoneal macrophage TXB2 nor IL-6 synthesis temporally correlate with in vivo resistance to lethality.

Animals↗
PubMed1989

The effect of endotoxin on glucose metabolism in skeletal muscle requires the presence of plasma.

The administration of endotoxin in vivo results in an increase in glucose utilization through an as yet undetermined mechanism. This study evaluated (1) the contribution of blood to the increased glucose utilization noted following endotoxemia, (2) the direct action of endotoxin on skeletal muscle glucose uptake in an isolated hindlimb perfusion system and in incubated muscle, and (3) the possibility that the increased glucose uptake in skeletal muscle mediated by endotoxin requires the presence of plasma. Incubation of blood with 50 and 100 mg/L of endotoxin increased glucose uptake and lactate production in a dose-dependent manner. Muscle incubations and perfusions in the absence of plasma and white blood cells showed that glucose uptake and lactate production were not affected by the presence of 50 to 250 mg/L of endotoxin, while 500 mg/L of endotoxin produced a 26.2% decrease in glucose uptake. In contrast, incubation of muscle in the presence of plasma and endotoxin increased glucose uptake by 37%. These findings suggest that (1) the increased glucose utilization of endotoxemia is only partially explained by increased glucose metabolism by blood, (2) endotoxin does not have a direct effect on the glucose uptake of skeletal muscle, and (3) an interaction of endotoxin with a component of plasma is required for an endotoxin-mediated increase in glucose utilization by skeletal muscle.

Animals↗
PubMed1985

Modulation of endotoxin-induced neutrophil alveolitis by captopril and by hyperoxia.

We compared survival and the intensity of bronchoalveolar inflammation reflected by lung lavage after the intraperitoneal injection of endotoxin from Escherichia coli serotype 055B5 in rats breathing air and those breathing 60% oxygen for six days after endotoxin injection. Survival following 7.5 mg/kg of endotoxin was comparable in air-breathing rats (50%) and in oxygen-breathing rats (63%). Endotoxin caused a dose-dependent increase in the recovery of polymorphonuclear leukocytes from the lung. Oxygen breathing reduced the percentage of neutrophils recovered by lavage 24 hr after endotoxin from 17% to 9% after 2.5 mg/kg of endotoxin and from 34% to 12% after 7.5 mg/kg of endotoxin. The absolute number of neutrophils recovered was also significantly decreased in oxygen-breathing rats. The activity of pulmonary angiotensin-converting enzyme (ACE) has been reported to be affected by oxygen tension, and ACE degrades bradykinin, a proinflammatory mediator. Therefore, we questioned whether the salutary effect of increased inspired oxygen tension on the magnitude of neutrophil influx into the airspaces could be related to changes in ACE activity. We found that after 48 hr of peroral pretreatment of the rats with captopril, a specific ACE inhibitor, there was increased recovery of neutrophils by lavage 24 hr after injection of endotoxin in air-breathing rats. Captopril pretreatment also increased the chemotactic activity of bronchoalveolar lavage fluid (BALF). There was no concomitant alteration in the accumulation of 125I albumin in the lung following captopril pretreatment either in endotoxin-treated rats or in controls. Thus, breathing 60% oxygen decreased the accumulation of neotrophils in airspaces after intraperitoneal endotoxin injection and pharmacologic inhibition of ACE had the opposite effect. Alterations in the activity of pulmonary angiotensin-converting enzyme related to alveolar oxygen tension is a potential speculative mechanism for modulation of alveolar inflammation by the inspired oxygen concentration in this model.

Animals↗
PubMed1997

Induction of endotoxin tolerance depletes nuclear factor-kappaB and suppresses its activation in rat alveolar macrophages.

To investigate the mechanism of endotoxin tolerance in macrophages, a rat alveolar macrophage cell line (NR8383) was rendered endotoxin tolerant by treatment with endotoxin at 40 ng/mL for 48 h. This treatment induced a state of tolerance such that subsequent exposure to high-dose endotoxin (5 microg/mL) resulted in decreased production of macrophage inflammatory protein-2, tumor necrosis factor alpha, and nitric oxide compared to endotoxin-sensitive cells. Suppressed mediator production by endotoxin-tolerant cells was associated with impaired activation of nuclear factor-kappaB (NF-kappaB) in response to treatment with 5 microg/mL of endotoxin. This impairment of NF-kappaB activation was found to be associated with depletion of latent NF-kappaB (both RelA and p50) in the cytoplasm of endotoxin-tolerant cells. These data suggest that a mechanism of endotoxin tolerance is depletion of RelA/p50, which could limit the amount of NF-kappaB available for activation by subsequent stimuli and thereby inhibit transcription of NF-kappaB-dependent genes. Limiting NF-kappaB-dependent inflammatory gene transcription by inducing endotoxin tolerance is a potential therapeutic strategy for diseases where excessive production of inflammatory mediators leads to tissue injury.

Animals↗
PubMed2004

Extraction of cyanobacterial endotoxin.

To simplify our efforts in acquiring toxicological information on endotoxins produced by cyanobacteria, a method development study was undertaken to identify relatively hazard-free and efficient procedures for their extraction. One article sourced and two novel methods were evaluated for their ability to extract lipopolysaccharides (LPSs) or endotoxins from cyanobacteria. The Limulus polyphemus amoebocyte lysate (LAL) assay was employed to compare the performance of a novel method utilizing a 1-butanol-water (HBW) solvent system to that of Westphal's (1965) phenol-water system (HPW) for the extraction of endotoxin from various cyanobacteria. The traditional HPW method extracted from 3- to 12-fold more endotoxin from six different cyanobacterial blooms and culture materials than did the novel HBW method. In direct contrast, the novel HBW method extracted ninefold more endotoxin from a non-microcystin producing Microcystis aeruginosa culture as compared to the HPW method. A solvent system utilizing N,N'-dimethylformamide-water (HDW) was compared to both the HPW and HBW methods for the extraction of endotoxin from natural samples of Anabaena circinalis, Microcystis flos-aquae, and a 1:1 mixture of Microcystis aeruginosa/Microcystisflos-aquae. The LAL activities of these extracts showed that the novel HDW method extracted two- and threefold more endotoxin from the Anabaena sample that did the HBW and HPW methods, respectively. The HDW method also extracted approximately 1.5-fold more endotoxin from the Microcystis flos-aquae sample as compared to both the HBW and HPW methods. On the other hand, the HBW method extracted 2- and 14-fold more endotoxin from the Microcystis flos-aquae/Microcystis aeruginosa mixture than did the HPW and HDW methods, respectively. Results of this study demonstrate that significant disparities exist between the physicochemical properties of the cell wall constituents not only of different cyanobacterial species but also of different strains of the same cyanobacterial species, as showing by the varying effectiveness of the solvent systems investigated. Therefore, a sole method cannot be regarded as universal and superior for the extraction of endotoxins from cyanobacteria. Nevertheless, the ability of the novel HBW and HDW methods to utilize easily handled organic solvents that are less hazardous than phenol render them attractive alternatives to the standard HPW method.

Biological Assay↗
PubMed1991

Impaired calcium uptake by cardiac sarcoplasmic reticulum and its underlying mechanism in endotoxin shock.

Effects of endotoxin administration on the ATP-dependent Ca2+ uptake by canine cardiac sarcoplasmic reticulum (SR) were investigated. Results obtained 4 h after endotoxin administration show that ATP-dependent Ca2+ uptake by cardiac SR was decreased by 27-43% (p less than 0.05). Kinetic analysis indicates that the Vmax values for Ca2+ and for ATP were significantly decreased while the S0.5 and the Hill coefficient values were not affected during endotoxin shock. Magnesium (1-5 mM) stimulated while vanadate (25-250 microM) inhibited the ATP-dependent Ca2+ uptake, but the Mg(2+)-stimulated and the vanadate-inhibited activities remained significantly lower in the endotoxin-treated animals. Phosphorylation of SR by the exogenously added catalytic subunit of the cAMP-dependent protein kinase or by the addition of calmodulin stimulated the ATP-dependent Ca2+ uptake activities both in the control and endotoxin-injected dogs. However, the phosphorylation-stimulated activities remained significantly lower in the endotoxin-injected dogs. Dephosphorylation of SR decreased the ATP-dependent Ca2+ uptake, but the half-time required for the maximal dephosphorylation was reduced by 31% (p less than 0.05) 4 h post-endotoxin. These data indicate that endotoxin administration impairs the ATP-dependent Ca2+ uptake in canine cardiac SR and the endotoxin-induced impairment in the SR calcium transport is associated with a mechanism involving a defective phosphorylation and an accelerated dephosphorylation of SR membrane protein. Since ATP-dependent Ca2+ uptake by cardiac SR plays an important role in the regulation of the homeostatic levels of the contractile calcium, our findings may provide a biochemical explanation for myocardial dysfunction that occurs during endotoxin shock.

Adenosine Triphosphate↗
PubMed1977

Fever in rats after intravenous E. coli endotoxin administration.

In conscious unrestrained rats, at an ambient temperature of 22 degrees C, oesophageal temperature was measured and temperature effect of single and repeated intravenous injection of E. coli endotoxin was examined. The first injection of endotoxin in a dose of 10.0 mug/rat did not change the rat body temperature. The second injection of this dose in the same animals repeated after 48 h produced fever. With following injections the fevers observed were less pronounced. The absence of fever after a single injection of endotoxin was accompanied by the rapid loss of pyretic activity of the rat plasma samples (bioassayed in rabbits). When fever was observed (48 h interval between endotoxin injections) the pyretic activity of the rat plasma remained unchanged for 90 min following endotoxin injection. It was concluded that after a single injection endotoxin is rapidly detoxified in the rat circulation while this process does not take place after the second endotoxin injection (48 h interval). The process of endotoxin detoxification can be depressed by the pretreatment with nitrogen mustard. Analysis of changes of skin temperature following endotoxin injections and the influence of aspirin on endotoxin-induced fever suggest that the fever observed was of central origin.

Animals↗
PubMed1991

Specific assay for endotoxin using immobilized histidine and Limulus amebocyte lysate.

The LAL test is inhibited or enhanced by many substances. To overcome these problems, we have developed a specific endotoxin assay method using an ultrafiltration unit, a fluorometric LAL reagent, and immobilized histidine (which is a specific adsorbent for endotoxins). This method is composed of two steps. The first step is the adsorption of endotoxins. Using immobilized histidine, endotoxins are quantitatively adsorbed on the adsorbent, and the adsorbed endotoxins are separated from LAL-inhibiting or -enhancing substances by the ultrafiltration unit. The second step is the reaction of adsorbed endotoxins with the LAL reagent. The endotoxins adsorbed on immobilized histidine are directly reacted with the LAL reagent in a filter cup and show enough activity for assay. The reproducibility and the accuracy of this method are high, and the recovery of endotoxins from a sample solution is more than 95%. The new endotoxin assay method using immobilized histidine can be utilized for the determination of endotoxins in a solution containing LAL-inhibiting or -enhancing substances such as amino acids and antibiotics instead of requiring employment of the more common gel-clot technique.

Adsorption↗
PubMed1987

A new method for reduction of endotoxin contamination from protein solutions.

A method of reducing endotoxin contamination in protein-containing solutions is described here using a combination of polymyxin B-Sepharose 4B (PB-Seph 4B) affinity binding and endotoxin-protein dissociation with the dialyzable surfactant, octyl-beta-D-glucopyranoside (OBDG). Using the limulus amoebocyte lysate (LAL) assay to detect endotoxin, greater than 1000-fold reduction of endotoxin reactivity could be accomplished from a contaminated commercial preparation of bovine catalase. Importantly, this occurred with only a 24% protein loss and an 11% loss of catalase enzymatic activity after treatment. The treated catalase appeared to be largely endotoxin-free since it no longer elicited a pyrogenic response in rabbits or primed for intravascular coagulation of the generalized Shwartzman reaction. Of interest, OBDG treatment of Salmonella minnesota Re595 lipopolysaccharide enhanced its ability to bind to serum high density lipoproteins which might contribute to decreased in vivo toxicity. In quantitative studies using radiolabeled endotoxin, the OBDG was shown to be capable of dissociating protein-bound endotoxin thereby facilitating its binding to the PB-Seph 4B adduct. The technique was also useful in removing radiolabeled endotoxin added to human IgG. The methodology described here would be expected to have general usefulness in reducing endotoxin contamination of macromolecular solutions that can bind and retain endotoxin.

Catalase↗
PubMed1984

Endotoxin-mediated inhibition of human platelet aggregation.

A variety of endotoxins, when added to human platelet-rich plasma (PRP) or to suspensions of washed platelets (WP), demonstrated an inhibitory effect on platelet aggregation induced by various aggregating agents. Endotoxin blocked the release of 14C serotonin from platelets but had no influence on cyclic AMP production. Endotoxin did not interfere with thromboxane generation by platelets. However, endotoxin-treated platelets failed to respond to added thromboxane. The inhibitory effect of endotoxin on platelet aggregation was more pronounced in the presence of ionophore A23187 as compared to other aggregating agents and was effectively reversed by calcium but not by magnesium, another divalent cation. Furthermore, endotoxin failed to inhibit the ristocetin-induced agglutination of formaldehyde-fixed platelets; a non-calcium dependent phenomenon. These findings appear to suggest that endotoxin-mediated inhibitory activity of platelet aggregation is related to the interference in the role of calcium. The antiaggregatory activity of endotoxin appears to be due to a direct and rapid action on platelets and not due to a non-specific binding, as the effect was not abolished by washing the endotoxin-incubated platelets. Endotoxin-mediated alteration of platelet function may contribute to bleeding diathesis in septecemic and endotoxemic patients.

Blood Platelets↗