PubMed Health⌕ Search

Biomedical subjects

R J Ulevitch

Publications and source records attributed to R J Ulevitch.

At least 127 records · Page 7Linked to original sources
PubMed1988

A family of lipopolysaccharide binding proteins involved in responses to gram-negative sepsis.

The lipopolysaccharides (LPS) of Gram-negative bacteria initiate potentially fatal processes in many host organisms. Recently published amino acid sequence data suggest that there is a family of LPS binding proteins that may participate in the host response to Gram-negative bacteremia. The first two members of the family to be identified are an LPS binding protein present in serum after an acute phase response in humans, mice, rabbits, and rats and a bactericidal/permeability increasing protein present in the primary granules of human and rabbit neutrophils. LPS binding protein and bactericidal/permeability increasing protein share an ability to bind to LPS, have homologous NH2-terminal amino acid sequences, and are immunologically cross-reactive. Nevertheless, these two molecules differ in their effects on LPS and Gram-negative bacteria, in their sites of biosynthesis, and localization in vivo.

Acute-Phase Reaction↗
PubMed1988

Kinetic analysis of the Ca2+-dependent, membrane-bound, macrophage phospholipase A2 and the effects of arachidonic acid.

The kinetics of the Ca2+-dependent, alkaline pH optimum, membrane-bound phospholipase A2 from the P388D1 macrophage-like cell line were studied using various phosphatidylcholine (PC) and phosphatidylethanolamine (PE) substrates. This enzyme exhibits "surface dilution kinetics" toward PC in Triton X-100 mixed micelles, and the "dual phospholipid model" was found to adequately describe its kinetic behavior. With substrate in the form of sonicated vesicles, the dual phospholipid model should give rise to Michaelis-Menten type kinetics. However, the hydrolysis of dipalmitoyl-PC, 1-palmitoyl-2-oleoyl-PC, and 1-stearoyl-2-arachidonoyl-PC vesicles exhibited two distinct activities. Below 10 microM, the data appeared to follow Michaelis-Menten behavior, while at higher concentrations, the data could best be fit to a Hill equation with a Hill coefficient of 2. These PCs had Vmax values for the low substrate concentration range of 0.2-0.6 nmol min-1 mg-1 and Km values of 1-2 microM. At the high substrate concentration range, the Vmax values were between 5 and 7 nmol min-1 mg-1. PC containing unsaturated fatty acids had an apparent Km, determined from the Hill equation, of about 15 microM, while the apparent Km of dipalmitoyl-PC was 0.6 microM. When 70% glycerol was included in the assays, a single Michaelis-Menten curve was obtained for both dipalmitoyl-PC and 1-stearoyl,2-arachidonoyl-PC. Possible explanations for these kinetic results include reconstitution of the membrane-bound phospholipase A2 in the phospholipid vesicle or the enzyme has tow distinct phospholipid binding function. The kinetics for both dipalmitoyl-PC and dipalmitoyl-PE hydrolysis in vesicles was very similar, indicating that the enzyme does not greatly prefer one of these head groups over the other. The enzyme also showed no preference for arachidonoyl containing phospholipid. Enzymatic activity toward PC containing saturated fatty acids was linear to about 15% hydrolysis while the hydrolysis of PC containing unsaturated fatty acids was linear to only about 5%. This loss of linearity was due to inhibition by released unsaturated fatty acids. Arachidonic acid was found to be a competitive inhibitor of dipalmitoyl PC hydrolysis with a K1 of 5 microM. This tight binding suggests a possible in vivo regulatory role for arachidonic acid. Three compounds of the arachidonic acid cascade, prostaglandin F2 alpha, 6-keto-prostaglandin F1 alpha, and thromboxane B2, showed no inhibition of enzymatic activity.

Algorithms↗
PubMed1988

Solubilization, purification, and characterization of a membrane-bound phospholipase A2 from the P388D1 macrophage-like cell line.

The release of free arachidonic acid from membrane phospholipids is believed to be the rate-controlling step in the production of the prostaglandins, leukotrienes, and related metabolites in inflammatory cells such as the macrophage. We have previously identified several different phospholipases in the macrophage-like cell line P388D1 potentially capable of controlling arachidonic acid release. Among them, a membrane-bound, alkaline pH optimum, Ca2+-dependent phospholipase A2 is of particular interest because of the likelihood that the regulatory enzyme has these properties. This phospholipase A2 has now been solubilized from the membrane fraction with octyl glucoside and partially purified. The first two steps in this purification are butanol extractions that yield a lyophilized, stable preparation of phospholipase A2 lacking other phospholipase activities. This phospholipase A2 shows considerably more activity when assayed in the presence of glycerol, regardless of whether the substrate, dipalmitoylphosphatidylcholine, is in the form of sonicated vesicles or mixed micelles with the nonionic surfactant Triton X-100. Glycerol (70%) increases both the Vmax and the Km with both substrate forms, giving a Vmax of about 15 nmol min-1 mg-1 and an apparent Km of about 60 microM for vesicles and a Vmax of about 100 nmol min-1 mg-1 and an apparent Km of about 1 mM for mixed micelles. Vmax/Km is slightly greater for vesicles than for mixed micelles. The lyophilized preparation of the enzyme is routinely purified about 60-fold and is suitable for evaluating phospholipase A2 inhibitors such as manoalide analogues. Subsequent steps in the purification are acetonitrile extraction followed by high performance liquid chromatography on an Aquapore BU-300 column and a Superose 12 column. This yields a 2500-fold purification of the membrane-bound phospholipase A2 with a 25% recovery and a specific activity of about 800 nmol min-1 mg-1 toward 100 microM dipalmitoylphosphatidylcholine in mixed micelles. When this material was subjected to analysis on a Superose 12 sizing column, the molecular mass of the active fraction was approximately 18,000 daltons.

Acetonitriles↗
PubMed1988

Participation of tumor necrosis factor in the mediation of gram negative bacterial lipopolysaccharide-induced injury in rabbits.

Macrophages are induced by LPS to release a number of products that determine the host response during gram negative sepsis. To examine the role of one such substance, tumor necrosis factor (TNF), in mediating LPS-induced injury, we employed a rabbit model of endotoxic shock to (a) determine the kinetics and extent of release of TNF into plasma after injection of LPS, and (b) to evaluate the protective effect of in vivo neutralization of LPS-induced TNF by prior infusion of anti-TNF antibody. TNF was maximally induced 45-100 min after injection of 10 micrograms i.v. parent Salmonella minnesota Re595 LPS or 250 micrograms Re595 LPS-HDL complexes. Maximal induction of TNF by LPS was associated with development of hypotension, focal hepatic necrosis, intravascular fibrin deposition and lethality. Based on (a) the peak levels of TNF observed in serum, 2.5 X 10(3) U/ml, (b) the specific activity of purified rabbit macrophage-derived TNF, 1 X 10(8) U/mg, and (c) the biphasic disappearance of intravenously injected purified TNF (t1/2 = 0.5 min, 11 min) we constructed a kinetic model showing that at least 130 micrograms of TNF (1.3 X 10(7) U) was released into plasma 30-200 min postinjection of LPS. Prior infusion of anti-TNF antibody (30-45 min before LPS injection) resulted in neutralization of the LPS-induced serum TNF activity and provided significant protection from the development of hypotension, fibrin deposition, and lethality. Thus, these results provide further evidence that TNF plays a central role mediating the pathophysiologic changes that occur during gram negative endotoxic shock.

Animals↗
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↗
PubMed1986

Isolation of a lipopolysaccharide-binding acute phase reactant from rabbit serum.

This report describes the purification of an acute phase reactant from acute phase rabbit serum, which endows normal serum with the properties of acute phase serum, insofar as LPS is concerned. The acute phase reactant is referred to as LPS-binding protein, or LBP. LBP was purified approximately 2,000-fold by chromatography of acute phase serum on Bio-Rex 70 and Mono-Q resins. The resulting preparation consisted of two glycoproteins having molecular weights of 60,500 and 58,000; the two were obtained in a variable ratio, usually near 10:1, respectively. After separation by SDS-PAGE, the N-terminal 36 amino acid sequences of the two proteins were identical. From the N-terminal sequence, as well as other properties of LBP, LBP appears to be unrelated to any known acute phase reactants. The direct interaction of LPS and LBP was inferred from two types of evidence: first, immunoprecipitation of [3H]LPS from APRS by anti-LBP sera; and second, by the 125I-labeling of LBP when APRS-containing 125I-labeled 2-(p-azidosalicylamido)ethyl 1,3'-dithiopropionyl-LPS was photolysed. The data presented here support the concept that the 60-kD glycoprotein we have termed LBP is a newly recognized acute phase reactant that may modulate the biochemical and biologic properties of LPS in vivo.

Acute-Phase Proteins↗
PubMed1986

Partial restoration of the lipopolysaccharide-induced proliferative response in splenic B cells from C3H/HeJ mice.

C3H/HeJ mice are hyporesponsive to the biologic effects of bacterial lipopolysaccharide (LPS), and their splenic B cells do not proliferate after exposure to LPS. The molecular basis of this hyporesponsiveness is unknown but it may result from defective membrane signal transduction after LPS binding. To examine this possibility, we added bioactive compounds in combination with LPS to C3H/HeJ B cell cultures in order to bypass the putative defect. The addition of PMA, monensin, or ionomycin, either alone or in combination, had no effect on C3H/HeJ B cell responses to LPS. In contrast, the addition of trypsin together with LPS resulted in a partial restoration of the proliferative response in C3H/HeJ splenic B lymphocytes. The maximal C3H/HeJ B cell response varied from 25 to 60% of the C3Heb/FeJ (LPS responder) B cell response. The trypsin-mediated enhancement of the LPS response was abrogated by pretreatment of the trypsin with the trypsin inhibitors DFP or TLCK. Pretreatment of the LPS with polymyxin B, which blocks lipid A-dependent reactions, also abrogated the trypsin effect. Because the C3H/HeJ B cell responds to all other B cell mitogens, we suggest that the defect is in an LPS-specific step and that the action of trypsin results in the restoration of the missing signal. At the present time the identity of this signal is not known, but the experiments described in this report provide a unique model to elucidate the basis of LPS hyporesponsiveness in splenic B cells from C3H/HeJ mice.

Adjuvants, Immunologic↗
PubMed1985

Phospholipase activities of the P388D1 macrophage-like cell line.

The murine macrophage (M phi) cell line, P388D1, was employed as a source of M phi phospholipases in order to characterize the enzymatic properties and subcellular localization of these enzymes because of their importance for prostaglandin biosynthesis. Phospholipase activity was assessed with dipalmitoylphosphatidylcholine (DPPC) as substrate. Phospholipases were characterized with respect to divalent cation dependence, pH optima, and localization in subcellular compartments using linear sucrose gradients. By these criteria a number of different phospholipases were identified. Most importantly, a single Ca2+-dependent activity with a pH optimum of 8.8 was identified in membrane-rich fractions (plasma membrane, mitochondria, and endoplasmic reticulum) and could be clearly separated from the remaining activities, which are Ca2+ independent and exhibit pH optima of 7.5, 5.1, and 4.2. The phospholipases with acidic pH optima may be associated with subcellular components containing lysosomal enzymes and both phospholipase A1 and phospholipase A2 activities are observed. In contrast, the phospholipase activity with a pH optimum of 7.5 sediments with the cytosolic proteins and is inhibited by 5 mM Ca2+. No significant phospholipase C activity was detected in assays performed with or without added Ca2+ at pH's 4.2, 5.1, 7.5, or 8.8 using DPPC as substrate. However, the P388D1 cells do contain a lysophospholipase that is at least 20 times more active than the phospholipase A activities identified. Its presence must be taken into account in evaluating the positional specificities and properties of the macrophage phospholipases.

Animals↗
PubMed1985

Control of lipopolysaccharide-high-density lipoprotein interactions by an acute-phase reactant in human serum.

We have recently described several phenomena involving the interactions of lipopolysaccharides (LPS) from Salmonella minnesota Re595 (Re595-LPS) with rabbit serum, which are different in and unique to acute-phase serum as compared with normal serum (P.S. Tobias and R.J. Ulevitch, J. Immunol. 131:1913-1916, 1983). To determine whether these phenomena could also be observed in acute-phase human serum (APHS), we used APHS obtained from volunteers injected with etiocholanolone. As observed in acute-phase rabbit serum, we found that (i) in APHS, Re595-LPS forms a protein complex with a density of 1.3 g/cm3 which does not form in normal human serum (NHS), (ii) in APHS, the t1/2 for LPS-high-density lipoprotein (HDL) complexation is at least a factor of 10 slower than the t1/2 for LPS-HDL complexation in NHS, (iii) when Re595-LPS serum mixtures are dialyzed against a low salt buffer, Re595-LPS precipitates in less soluble form from APHS than from NHS, and (iv) the precipitate from Re595-LPS-APHS mixtures includes a protein with a molecular weight of approximately 60,000 which does not precipitate from Re595-LPS-NHS mixtures or from NHS or APHS alone. These indications of an altered status of LPS in NHS and APHS suggest that one or more acute-phase reactants interact with Re595-LPS to modify its rate of binding to HDL.

Acute-Phase Proteins↗
PubMed1985

Acute hypotension due to platelet serotonin-induced chemoreflexes after intravenous injection of dextran sulfate in the rabbit.

The hypotension and bradycardia observed after intravenous injection of dextran sulfate in rabbits was prevented by prior depletion of circulating platelets, but was not prevented by depletion of the third component of complement or Hageman factor. Dextran sulfate injection caused immediate thrombocytopenia with temporary localization of platelets within lungs. Morphological analysis revealed platelet aggregates in lung capillaries. The platelets had changed shape and were in the process of degranulating. Serotonin and histamine levels in blood increased approximately 5-fold and 7-fold, respectively, after dextran sulfate injection. The cardiovascular events following dextran sulfate injection were mimicked by intravenous serotonin but not by intravenous histamine injection, although a combination of serotonin and histamine reproduced the pattern of blood pressure changes better than did either agent alone. Quantification of platelets trapped in lung revealed that the potential release of serotonin from trapped platelets could account for the rise in plasma serotonin concentration and the hemodynamic changes observed. Both the dextran sulfate-induced cardiovascular effects and serotonin-induced hypotension were markedly diminished by cutting vagus and depressor nerves, and were virtually abolished by carotid ligation in addition to nerve section. These results support the concept that platelet activation within rabbit lungs may cause hypotension via serotonin-induced chemoreflexes.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1985

Uptake and subcellular localization of bacterial lipopolysaccharide in the adrenal gland.

For determination of the kinetics of uptake and subcellular localization of lipopolysaccharide (LPS) from LPS-high density lipoprotein (LPS-HDL) complexes in the adrenal gland, LPS-HDL complexes were isolated by immunoaffinity chromatography of 125I-Salmonella minnesota Re595 LPS that had been incubated with 20 mM EDTA-rabbit plasma. After intravenous injection of LPS-HDL complexes in rabbits, preferential uptake of the LPS was observed in the adrenal, so that by 5 hours, adrenal-tissue-bound LPS concentrations (determined by use of 131I-BSA blood marker) exceeded all other tissues examined, including liver and spleen, by at least three-fold. For determination of the subcellular localization of LPS, cholesterol-rich (lipid droplet) fractions and cholesterol-depleted fractions were obtained by ultracentrifugation of homogenates of adrenal tissue from rabbits killed at various times after injection of LPS-HDL complexes. As much as 40% of the adrenal-tissue-bound LPS was recovered in the cholesterol-rich fraction 2.5-24 hours after injection of LPS-HDL complexes. Electron-microscopic autoradiographic and immunocytochemical analysis of adrenal cortex of animals killed 5 hours after injection of LPS-HDL complexes demonstrated specific localization of LPS in lipid droplets. These data thus provide direct evidence for the uptake of LPS into the adrenal cortex of animals with intravascular LPS-HDL complexes and indicate that further study of the effect of LPS on adrenocortical function is warranted.

Adrenal Cortex↗
PubMed1984

Ocular localization of circulating bacterial lipopolysaccharide.

A bacterial lipopolysaccharide (LPS) extracted from a rough strain of Salmonella minnesota ( Re595 ) containing primarily lipid A was used to study tissue distribution following its intravenous injection in rabbits. For this purpose, the Re595 was either labelled with 125iodine (125I) and localization quantitated by gamma radiation spectrometry and radioautography of different tissues or a fluorescein labelled antibody to Re595 was employed. Localization of [125I]- Re595 or LPS was looked for at 30 min and 2 hr after intravenous injection. [131I]-albumin was employed either to measure intravascular protein or total tissue protein and, in some studies, [131I]-albumin and [125I]-fibrinogen were used to measure protein after unlabelled Re595 . Both fractions of isotopes injected and estimates of tissue-bound Re595 were made in the whole eye, liver, spleen, kidney and lung and in isolated iris-ciliary processes, aqueous, lens, vitreous, and posterior segment (retina, choroid, and sclera). Aqueous and iris-ciliary processes, but no other tissues, showed a marked extravazation of [131I]-albumin and [125I]-fibrinogen. [125I]- Re595 was found to localize primarily in liver and spleen. At 30 min, [125I]- Re595 was found in nanogram quantities within the eye and at 2 h greater amounts of LPS were found in iris-ciliary processes and aqueous than in the posterior segment. Neither radioautography nor fluorescein-labelled antibody to Re595 showed evidence of histologic localization of LPS in the iris-ciliary processes. These results indicate that although LPS does not localize preferentially in the eye, it does accumulate in quantities sufficient to have an effect locally.

Animals↗
PubMed1984

Properties and requirements for production of a macrophage product which suppresses steroid production by adrenocortical cells.

Lipopolysaccharide-treated murine peritoneal exudate macrophages (PEM) release a factor or factors into the supernatant that suppress adrenocorticotropic hormone-induced steroidogenesis in explanted rabbit adrenocortical cells (J. C. Mathison et al., J. Immunol. 130:2757-2762, 1983). To determine the requirements for suppression, PEM supernatants (30 microliters) were added to explanted rabbit adrenocortical cells in a final volume of 120 microliters with 10 mU of adrenocorticotropic hormone per ml, and after 18 h at 37 degrees C, steroid concentrations were measured by a fluorometric assay. Supernatant from proteose peptone-elicited C3HeB/FeJ PEM (5 X 10(6) PEM per 3.5-cm well, 10 micrograms of Salmonella minnesota Re595 LPS per ml, 18 h) suppressed steroid production ca. 50%, and kinetic studies demonstrated that the appearance of suppressive activity in the supernatant was gradual over 4 to 18 h. Release of suppressive activity was not associated with decreased viability of the PEM (assessed by fluorescein diacetate staining and measurement of lactic dehydrogenase in the supernatant). Suppression was not observed when the PEM supernatant was diluted 10-fold before addition to the adrenocortical cells, whereas supernatant concentrated 20-fold (prepared with a 10,000-molecular-weight-cutoff filter) produced 75 to 80% suppression. The suppressive activity was stable at pH 4, pH 11, or 70 degrees C for 30 min but was inactivated at 100 degrees C (10 min). Suppressive activity was also induced in C3HeB/FeJ PEM by O111:B4 lipopolysaccharide or heat-killed Listeria monocytogenes. In contrast, PEM from C3H/HeJ mice did not produce detectable suppressive activity in response to Re595 lipopolysaccharide or heat-killed L. monocytogenes. Thus, these results provide additional support for the inducible, selective release of a macrophage product that could affect the host response to lipopolysaccharide by regulation of the adrenocortical response to adrenocorticotropic hormone.

Adrenal Cortex↗
PubMed1984

Regulation of the host response to bacterial lipopolysaccharides.

Bacterial endotoxins or lipopolysaccharides (LPS) are unique glycolipids present in the outer cell membrane of all gram-negative bacteria. It is now generally recognized that LPS is of primary importance in initiating the pathophysiological changes that often accompany gram-negative bacillary infections in humans including hypotensive shock, disseminated intravascular coagulation, and metabolic abnormalities. Although the biochemical mechanisms of these changes are not well understood, increasing emphasis has been placed on defining the biochemical response of the macrophage (M phi) to LPS. In this paper we describe two M phi-derived factors induced by LPS that may be important in the expression of endotoxic activity in the host. These are a procoagulant activity, which is present on the cell membrane of LPS-treated rabbit liver M phi and acts by directly activating coagulation factor X, and a factor released into the supernatant by LPS-treated peritoneal exudate M phi, which suppresses steroidogenesis in explanted adrenocortical cells. The potential role of the M phi in regulating the binding of LPS to high-density lipoproteins through the induction of acute phase proteins is also considered.

Adrenal Cortex↗
PubMed1983

Suppression of ACTH-induced steroidogenesis by supernatants from LPS-treated peritoneal exudate macrophages.

The results from a number of clinical and experimental studies have suggested that during endotoxemia, suppression of adrenocortical steroidogenesis may occur. We have examined the possibility that macrophages are the source of a factor that suppresses adrenocortical steroidogenesis. Resident and peptone-elicited peritoneal exudate macrophages (PEM) from C3HeB/FeJ mice were incubated for 4 hr at 37 degrees C in the presence or absence of T cell hybridoma-derived lymphokine (LK) that contained high concentrations of MAF activity (assessed by induction of nonspecific tumoricidal activity in PEM). The LK was removed by rinsing, and fresh medium was added, followed by Salmonella minnesota R595 LPS (final concentration 10 micrograms/ml). After 18 hr at 37 degrees C the PEM supernatants and control medium from flasks without cells were harvested and stored at -20 degrees C. Explanted rabbit adrenocortical cells in 96-well plates were exposed to 30 microliters of PEM supernatant or control medium and ACTH (10 or 100 mU/ml) in a final volume of 120 microliters for 3 consecutive days. The adrenocortical cell supernatants were harvested each day, followed by replenishment of medium, PEM supernatant, and ACTH. Fluorogenic steroid production in wells that received control medium or supernatants from PEM not treated with LPS was normal (0.22 microgram +/- 0.010 (SD) per 5 X 10(4) cells). However, as much as 75 to 95% suppression of steroidogenesis was observed in wells that received supernatants from PEM treated with LK and LPS, compared to 40% suppression in wells that received supernatant from PEM treated with LPS alone. Continued exposure (over 3 days) of adrenocortical cells to supernatants from LPS-treated PEM resulted in progressively decreasing response to ACTH. Comparable suppressive activity was observed in supernatants from LPS-treated bone marrow-derived macrophages. In further experiments, suppression was observed in wells that were pretreated (22 hr) with the appropriate PEM supernatant, and evidence was obtained that the suppressive activity was not due to carry-over LPS. Finally, results from control experiments demonstrated that suppressive PEM supernatants neither inactivate ACTH nor interfere with the assay of fluorogenic steroids. Thus, these results suggest that during endotoxemia, products from LPS-stimulated macrophages may suppress adrenocortical function.

Adrenal Cortex↗
PubMed1983

Control of lipopolysaccharide-high density lipoprotein binding by acute phase protein(s).

When Salmonella minnesota R595 lipopolysaccharide (LPS) is mixed with serum, the LPS eventually forms a complex with high density lipoprotein (HDL). Complex formation is conveniently followed by CsCl equilibrium density gradient centrifugation. When mixing 10 micrograms LPS with normal rabbit serum (NRS) at 37 degrees C in the presence of 20 mM EDTA, the half-life for LPS binding to HDL is typically 2 to 3 min. When the same experiment is performed with the use of acute phase rabbit serum (APRS; collected 24 hr post-induction with silver nitrate), the half-life for LPS binding to HDL is typically 40 to 100 min. Thus LPS binding to HDL occurs some 20- to 40-fold slower in APRS than in NRS. Two other phenomena have been found, the time dependencies of which correlate well with the time dependency of LPS binding to HDL in APRS. If LPS-APRS reaction mixtures are cooled to 4 degrees C shortly after mixing and are dialyzed against 2.5 mM HEPES, 15 mM NaCl, pH 7.4 buffer, LPS is recovered in the washed precipitates ("euglobulin precipitate") if, and only if, the LPS-HDL binding reaction is not complete. The amount of LPS in the precipitate correlates well with the amount of LPS that has not bound to HDL. The second phenomenon we observe is that the LPS-containing euglobulin precipitate prepared from LPS-acute phase serum reaction mixtures shortly after mixing also contains a protein, gp60, the concentration of which in the euglobulin precipitate correlates well with the amount of LPS in the precipitate. Thus three phenomena are kinetically well correlated in APRS: the degree of binding of LPS to HDL, the degree of appearance of LPS in a euglobulin fraction, and the concentration of protein gp60 in the euglobulin fraction. We were unable to precipitate gp60 from APRS in the absence of LPS, from APRS after the LPS has fully bound to HDL, or from normal serum in the presence or absence of LPS. The known properties of gp60 are not reminiscent of any other known acute phase reactant. These data demonstrate that APRS contains acute phase reactants that interact with LPS to modify its buoyant density, its solubility, and the rate of its binding to HDL.

Acute Disease↗
PubMed1982

Interactions of bacterial lipopolysaccharide with acute-phase rabbit serum and isolation of two forms of rabbit serum amyloid A.

Mixing lipopolysaccharide (LPS, Salmonella minnesota R595) with acute-phase rabbit serum (APRS) results in the formation of two types of complexes. The two complexes are separable from each other and from LPS by CsCl density gradient ultracentrifugation. LPS alone had density 1.38 g/cm3, complex 1.3 had density 1.3 +/- 0.02 g/cm3, and complex 1.2 had density less than 1.20 g/cm3. At 1 to 10 micrograms LPS/ml APRS, up to 23 micrograms of LPS could be found in complex 1.3, with the remainder of the LPS in complex 1.2. The capacity of complex 1.2 for LPS was 500 to 600 micrograms LPS/ml APRS. The ability of rabbit serum to form complex 1.3 rose to a maximum in 24 hr post-acute-phase induction. The two complexes were purified by equilibrium density gradient ultracentrifugation and immunoaffinity chromatography using antibodies to LPS and subjected to SDS-PAGE. Complex 1.3 had major peptides after reduction of 91, 64, 61 and 50 kilodaltons. The 61-kilodalton peptide is probably rabbit serum albumin; the others are unidentified. Complex 1.2 had major peptides after reduction whose mobility corresponded to apolipoprotein A-I and serum amyloid A. Complex 1.2 thus seems to be analogous to the LPS-high-density-lipoprotein complexes that form in normal serum except that the latter complexes do not contain serum amyloid A. Rabbit serum amyloid A (SAA) was purified by CsCl equilibrium density gradient ultracentrifugation, gel filtration, and ion-exchange chromatography into two forms, SAA-1 and SAA-2. The two forms of SAA have very similar amino acid compositions and m.w. (SAA-1, 11,526 daltons; SAA-2, 11,469 daltons). They differ primarily in their isoelectric points, 6.57 and 6.27 for SAA-1 and SAA-2, respectively. The complexes 1.2 from several individual rabbits after acute-phase induction were studied by isoelectric focusing. Seven of 10 rabbits showed both forms of SAA; three showed a single form. Two rabbits showing SAA-1 on the first acute-phase induction were reinduced; one rabbit again gave SAA-1 and the other gave SAA-2. These results suggest that SAA and perhaps other acute-phase reactants may modulate the biologic activity of LPS.

Acute Disease↗