Phosphodiesterase I Research Articles

Stimulatory effects of purified macrophage colony-stimulating factor on murine resident peritoneal macrophages

A purified preparation of macrophage colony-stimulating factor (M-CSF) free of interferon and endotoxin activity was studied for its effects on resident murine peritoneal macrophages. M-CSF was found to induce profound morphologic alterations in resident macrophages. These changes included a marked increase in cell size, membrane ruffling, and cytoplasmic vacuolization. Further, after 72 hr of incubation with 1000 U/ml of M-CSF, there were significant increases in macrophage DNA synthesis as measured by autoradiography ( P < 0.001), and in macrophage monolayer protein content ( P < 0.01). None of these changes was seen in control macrophages or those exposed to recombinant interferon-γ (IFN). Low activity levels of the ectoenzymes 5′-nucleotidase (5′NTD) and alkaline phosphodiesterase I (APD) have been associated with certain macrophage functions, particularly the expression of tumor cytotoxicity. Macrophage monolayers exposed to M-CSF demonstrated an unaltered level of 5′NTD activity from controls and a significantly increased level of APD activity ( P < 0.01) and did not demonstrate an increased ability to kill tumor cells, as measured by the 51Cr-release assay. On the other hand, IFN caused significant decreases in both 5′NTD ( P < 0.05) and APD ( P < 0.01) and also induced marked tumoricidal activity in macrophage monolayers. These results indicate that purified M-CSF induces highly specific alterations in the functional activity and morphologic appearance of resident macrophages and these changes are distinct from those induced by IFN.

Alkaline phosphodiesterase I release from eucaryotic plasma membranes by phosphatidylinositol-specific phospholipase C. II. The release from brush border membranes of porcine intestine

T. Nakabayashi and H. Ikezawa. Alkaline phosphodiesterase I release from eucaryotic plasma membranes by phosphatidylinositol-specific phospholipase C. II. The release from brush border membranes of porcine intestine. Toxicon 24, 975 – 984, 1986. — Ectoenzyme release from porcine intestinal brush border membranes by phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis was studied. Alkaline phosphodiesterase I, alkaline phosphatase and 5′-nucleotidase were released from both slices and brush border membranes. The pattern of alkaline phosphodiesterase I release was the same as that of alkaline phosphatase. The release of alkaline phosphodiesterase I induced by phospholipase C was dependent on, or proportional to, the reaction time and the concentration of phospholipase C. The Arrhenius plot for phosphodiesterase I release showed a single break at 30°C for brush border membranes. Only 40% of alkaline phosphodiesterase I present in the brush border membranes were solubilized by phosphatidylinositol-specific phospholipase C treatment. The data indicate the presence of two forms of phosphodiesterase I, which are different in their sensitivity to phospholipase C. The released alkaline phosphodiesterase I had a molecular weight of 240,000 and was activated by Mg 2+ and Ca 2+, but strongly inhibited by EDTA.

Alkaline phosphodiesterase I release from eucaryotic plasma membranes by phosphatidylinositol-specific phospholipase C. I. The release from rat organs.

From various rat organs, alkaline phosphodiesterase I was liberated by the action of phosphatidylinositol-specific phospholipase C obtained from Bacillus thuringiensis. Especially, a large amount of alkaline phosphodiesterase I was released from slices of small intestine, testis, lung, and kidney, but not from pancreas and liver. The release of the enzyme induced by phospholipase C was dependent on, or proportional to, the reaction time and the concentrations of the phospholipase C and the weight of the slices of small intestine or testis. Furthermore, little enzyme was released from the homogenate of pancreas. These results suggest an important role of phosphatidylinositol in the binding of alkaline phosphodiesterase I to the plasma membranes of rat small intestine and pancreas. The alkaline phosphodiesterase I released from slices of rat small intestine and testis had a molecular weight of about 240,000, and was activated by Mg2+ and Ca2+ but inhibited by EDTA. The enzyme hydrolyzed the phosphodiester linkage of p-nitrophenyl-thymidine 5'-monophosphate at pH 8.9, having the Km values of 0.36 mM (small intestine) and 0.25 mM (testis). The intestinal enzyme differed from the testis enzyme in pI values, thermostability, and Arrhenius plot having a single breakpoint.

The Physiological Action of Bacterial Phosphatidylinositol-Specific Phospholipase C the Release of Ectoenzymes and Other Effects

AbstractPhosphatidylinositol-specific phospholipase C catalyzes the hydrolysis of phosphatidylinositol, resulting in diglycerides and myoinositol phosphates. This enzyme has been found in the culture broth of Staphylococcus aureus, Bacillus cereus, Bacillus thurinqiensis and Clostridium novyi. In this review, the properties and the physiological actions of bacterial phosphatidylinositol-specific phospholipase C are described. Especially, the phospholipase C releases the ectoenzymes such as alkaline phosphatase, 5′-nucleotidase, alkaline phosphodiesterase I, acetylcholinesterase, trehalase, acid ATPase, nucleoside diphosphatase and so forth from the eucaryotic membranes including plasma membranes, microsomal membranes and lysosomal membranes. From several studies on the enzyme release by phosphatidylinositol-specific phospholipase C, it is concluded that phosphatidylinositol in the eucaryotic membranes serves as a hydrophobic anchor for these membrane-bound enzymes to associate with other membrane phosphol...

Biliary excretion of iron from hepatocyte lysosomes in the rat. A major excretory pathway in experimental iron overload.

In these experiments, we assessed the role of hepatocyte lysosomes in biliary excretion of iron. We loaded rats with iron by feeding 2% carbonyl iron and collected bile for 24 h via bile fistulae from iron-loaded and control rats. In additional rats, bile was collected before and after the administration of colchicine. Rats were then killed and their livers were homogenized and fractionated for biochemical analyses or processed for electron microscopy and x-ray microanalysis. Inclusion of 2% carbonyl iron in the diet caused a 45-fold increase (P less than 0.001) in hepatic iron concentration compared with controls (1,826 +/- 159 vs. 38 +/- 6.7 micrograms/g liver, mean +/- SE). Electron microscopy with quantitative morphometry and x-ray microanalysis showed that the excess iron was sequestered in an increased number of lysosomes concentrated in the pericanalicular region of the hepatocyte. Iron loading was also associated with a twofold increase in biliary iron excretion (4.06 +/- 0.3 vs. 1.75 +/- 0.1 micrograms/g liver/24 h; P less than 0.001). In contrast, the biliary outputs of three lysosomal enzymes were significantly lower (P less than 0.0005) in iron-loaded rats compared with controls (mean +/- SE) expressed as mU/24 h/g liver: N-acetyl-beta-glucosaminidase, 26.7 +/- 4.6 vs. 66.2 +/- 13.4; beta-glucuronidase, 10.1 +/- 1.3 vs. 53.2 +/- 17.9; beta-galactosidase, 8.9 +/- 1.0 vs. 15.4 +/- 2.3. In iron-loaded rats but not in controls, biliary iron excretion was coupled to the release into bile of each of the three lysosomal hydrolases as assessed by linear regression analysis (P less than 0.001). In contrast, no relationships were found between biliary iron excretion and the biliary outputs of a plasma membrane marker enzyme (alkaline phosphodiesterase I) or total protein. After administration of colchicine, there was a parallel increase in biliary excretion of iron and lysosomal enzymes in iron-loaded rats, but not controls. We interpret these data to indicate that, in the rat, biliary iron excretion from hepatocyte lysosomes is an important excretory route for excess hepatic iron.

Nonlysosomal granules in peritoneal macrophages: Subcellular localization of neutral .ALPHA.-glucosidase.

Neutral α-glucosidase in mouse peritoneal macrophages was shown to be associated with granules distinct from lysosomes. When post-nuclear supernatants were centrifuged in a Percoll density gradient containing 20units/ml of heparin and 10mM Tris-HCl (pH 7.2), neutral α-glucosidase activity was clearly separated from β-glucuronidase activity. Activity peaks for alkaline phosphodiesterase, a plasma membrane enzyme, and for UDP-galactosyl transferase activity, a Golgi enzyme, were detected in different fractions. Release of the enzyme activities into extracellular medium depending on phagocytosis or pharmacological stimuli, was also different. These observations suggested that neutral α-glucosidase localize in nonlysosomal granules in macrophages.

Macrophage activation by trehalose dimycolate requirement for an expression signal in vitro for antitumoral activity; biochemical markers distinguishing primed and fully activated macrophages.

It was possible to define the effects of trehalose dimycolate (TDM), a glycolipid extracted from Mycobacterium tuberculosis, on mouse peritoneal macrophages more precisely using endotoxin-free culture conditions. TDM-elicited macrophages, when assayed in vitro in the absence of endotoxin, were unable to limit tumor growth; however, after a short treatment (4 h) with low doses of lipopolysaccharide (LPS; 1-10 ng/ml), they exhibited a strong cytostatic capacity against P815 mastocytoma cells. Thus, TDM injected in vivo did not activate macrophages fully but it primed them to respond in vitro to low doses of LPS, which provided the final stimulus for activation to antitumor competence. Macrophages elicited by an injection of killed group C Streptococci were also in a primed state; in contrast, thioglycollate-elicited macrophages were in a nonreceptive state. Besides LPS, concanavalin A (5 micrograms/ml), MDP (0.2-1 microgram/ml) and the ionophore A23187 (5 microM) can deliver the activation signal to TDM-primed macrophages. Primed macrophages were found to express several biochemical markers previously described as specific for activated macrophages (low levels of alkaline phosphodiesterase and beta-galactosidase, for example) and, although they were not cytotoxic for tumor cells, they had the capacity to release large amounts of H2O2. However, when pulsed by LPS or MDP, primed macrophages responded by further modifications in their metabolism: the rate of glucose consumption and the labeling of glycoproteins by D-[2-3H]mannose were greatly increased and the secretion of a polypeptide of 22 kDa was enhanced. The activation-associated biochemical markers are thus acquired in two steps. The ability to produce activated oxygen species is expressed earlier than the antitumoral activity.

Immuno-isolation of a plasma membrane fraction from the Fao cell.

A plasma membrane was immuno-isolated from a post-nuclear supernatant of a cultured rat hepatocyte, the Fao cell, using a cellulose immuno-adsorbent and antibodies raised against a variety of endogenous antigens of hepatocytes: 5'-nucleotidase, a plasma membrane fraction and the whole Fao cell. The antibodies which recognize antigens on the cell surface were selected from the total serum by first binding the antiserum to suspension cells. Alternatively, the plasma membrane and Fao antisera were affinity purified on a column prepared from a Triton X-114 extract of a plasma membrane fraction. The immuno-isolation was most efficient when carried out with either the plasma membrane or the Fao anti-serum. When alkaline phosphodiesterase I or 5'-nucleotidase was used as the plasma membrane marker, 40-60% of the plasma membrane of the post-nuclear supernatant was isolated representing a maximum 34-fold increase in the specific activity of the enzymes in the bound material. Using the NaB-[3H]4-labelled glycoproteins of the plasma membrane or the IgG bound to the plasma membrane as alternative markers, an 80% isolate of the plasma membrane of the post-nuclear supernatant was achieved, resulting in an estimated 40-fold purification. The non-specific binding was low despite the use of a post-nuclear supernatant as the input fraction. The characterization of the bound materials suggested that the whole plasma membrane was immuno-isolated and not a particular domain.

Antibacterial resistance, macrophage influx, and activation induced by bacterial rRNA with dimethyldioctadecylammonium bromide

Intraperitoneally injected rRNA from Pseudomonas aeruginosa combined with dimethyldioctadecylammonium bromide (DDA) increased nonspecifically the resistance of mice against an intraperitoneal challenge with extracellular (P. aeruginosa, Escherichia coli) and intracellular (Listeria monocytogenes) bacteria. This study concerns the mechanism underlying the nonspecific resistance. RNA with DDA (RNA-DDA) induced a cell influx and activated peritoneal macrophages (M phi) as judged by the decreased 5'-nucleotidase and alkaline phosphodiesterase activities in M phi lysates, the enhanced O2- release, and the increased antitumor activity in comparison with unstimulated M phi. RNA without DDA did not enhance the resistance and did not influence the peritoneal cell numbers or M phi properties. DDA without RNA enhanced the resistance of mice only slightly; it induced a cell influx, yielding elicited M phi as judged by the decreased 5'-nucleotidase activity and increased alkaline phosphodiesterase activity, the slightly enhanced O2- release, and the absence of increased antitumor activity. Both RNA-DDA and DDA M phi showed an enhanced capacity to ingest and kill L. monocytogenes in vitro, DDA M phi being slightly less effective than RNA-DDA M phi with respect to killing. We conclude that the enhanced killing capacity of M phi for L. monocytogenes is characteristic of both elicited DDA M phi and activated RNA-DDA M phi. The relationship between nonspecific resistance, peritoneal cell numbers, and antibacterial M phi activity is discussed. In addition, it is shown that RNA and DDA retain their activity when they are injected apart, suggesting that they activate M phi by sequential action.

Subfractionation of hepatic endosomes in Nycodenz gradients and by free-flow electrophoresis. Separation of ligand-transporting and receptor-enriched membranes.

The complexity of rat liver endosome fractions containing internalized radioiodinated asialotransferrin, asialo-(alkaline phosphatase), insulin and prolactin was investigated by using free-flow electrophoresis and isopycnic centrifugation in Nycodenz gradients. Two subfractions were separated by free-flow electrophoresis. Both subfractions contained receptors for asialoglycoprotein and insulin. Glycosyltransferase activities were associated with the more electronegative vesicles, whereas 5'-nucleotidase and alkaline phosphodiesterase activities were associated with the less electronegative vesicles. Three subfractions were separated on Nycodenz gradients. Two subfractions, previously shown to become acidified in vitro, contained the ligands. At short intervals after uptake (1-2 min), ligands were mainly in subfraction DN-2 (density 1.115 g/cm3), but movement into subfraction DN-1 (density 1.090 g/cm3) had occurred 10-15 min after internalization. Low amounts of glycosyltransferase activities were associated with subfraction DN-2, and 5'-nucleotidase and alkaline phosphodiesterase activities were mainly located in subfraction DN-1. The binding sites for asialoglycoproteins and insulin were distributed towards the higher density range in the Nycodenz gradients, thus indicating a segregation of receptor-enriched vesicles and those vesicles containing the various ligands 10-15 min after internalization. Electron microscopy of the subfractions separated on Nycodenz gradients indicated that whereas the ligand-transporting fractions consisted mainly of empty vesicles (average diameter 100-150 nm), the receptor-enriched component was more granular and smaller (average diameter 70-95 nm). The properties of the endosome subfraction are used to assign their origin to the regions of the endocytic compartment where ligand-receptor dissociation and separation occur.

Subcellular localization of a membrane-associated transglutaminase activity in rat liver

Fractionation of rat liver by homogenization and differential centrifugation revealed that only about 83% of the transglutaminase activity in the tissue is in a soluble form, and that the remainder is associated with the particulate fraction. This latter activity remained with the membranes even after they were extensively washed to remove 99% of such soluble enzymes as lactate dehydrogenase and aldolase. Subsequent fractionation of the membranes by isopycnic density gradient centrifugation in sucrose resulted in a single band of transglutaminase activity at a density of 1.194 g/cm 3. This activity was coincident with the major band of plasma membranes, which was identified by its content of 5′-nucleotidase, alkaline phosphodiesterase I, alkaline phosphatase and leucine aminopeptidase activities. After treatment with digitonin and fractionation on sucrose gradients, the transglutaminase activity and the plasma membrane marker enzyme activities were found at a new density of 1.210 g/cm 3, while the enzyme markers for the other membrane fractions remained unchanged. From these data, we conclude that approximately 17% of the transglutaminase activity in rat liver is specifically associated with the plasma membranes.

Differential ability of human blood monocyte subsets to release various cytokines.

We have shown that two human monocyte subsets can be isolated from the peripheral blood of healthy donors; these subsets possess different morphological, cytochemical, functional, and in vivo trafficking properties [1]. In this report, these two subsets were further characterized. One subset (intermediate monocytes, IM) has been shown to have significantly lower acid phosphatase activity and total cellular protein content as well as lower peroxidase activity when compared with another subset (regular monocytes, RM). The overall activation status of the two subsets (as determined by their alkaline phosphodiesterase activity) was identical. We also examined the capacity of these subsets to release various cytokines with or without polyriboinosinic and polyribocytidylic acid (Poly I:C) stimulation. There was no appreciable difference in their ability to release interferon (IFN), interleukin 1 (IL-1), and prostaglandin E (PGE) without stimulation, while IM produced slightly, but significantly, higher amounts of colony-stimulating factor (CSF) than RM. The amount of IFN released by IM in response to poly I:C was approximately three times higher than the amount of IFN released by RM. IL-1 was also released in higher amounts by IM than by RM in response to poly I:C. IM were also found to release more CSF than RM in response to poly I:C. In contrast, it was noted that IM secrete significantly less PGE response to poly I:C than do RM. These findings indicate that two purified human monocyte subsets, distinguishable by maturation markers, differ significantly in their ability to release various cytokines after stimulation; this difference may be relevant to potential in vivo roles of these immunoregulatory cells.

Isolation of plasma membranes from the bovine retinal pigment epithelium

Retinal pigment epithelium plasma membranes have been isolated by differential and density gradient centrifugation of glass-bead-bound, collagenase-treated cells. Electron microscopic evidence indicates that the glass-bead-bound cells were devoid of red blood cells, rod outer segments and other ocular cell contaminants. The plasma membranes were recovered in 4–6 μg/eye yields and purified 10-fold by 5′-nucleotidase and alkaline phosphodiesterase 1, and 6.5-fold by (Na + + K +)-ATPase. Plasma membrane purity as measured by covalent labeling of the epithelial cell plasma membrane proteins with p-(diazonium) benzene[ 32S]sulfonic acid was 8–19-fold. In purified plasma membranes contamination by mitochondria was undetectable and lysosomal contamination reduced 100-fold, while endoplasmic reticulum was 2-fold enriched. SDS-polyacrylamide gel electrophoresis of the plasma membrane proteins revealed 23–26 major bands by Coomassie blue staining and 12–16 major bands by radioactive labeling. The plasma membranes exhibited a 3-fold lower concentration of docosahexaenoic acid, a 3-fold higher cholesterol/phosphate ratio, and were 10-fold enriched in cholesterol per μg protein when compared to the whole cell fraction. Retinal epithelial plasma membranes contain an average of 1 mol cholesterol per mol of lipid phosphorus, a high palmitic acid concentration (39 mol%) and a low concentration of docosahexaenoic acid (2 mol%). The lipid profile of the retinal pigment epithelial plasma membranes indicates that they are typical of plasma membranes from many other cell types and that they appear to be less fluid than total rod outer segment membranes.

Analytical study of microsomes and isolated subcellular membranes from rat liver. IX. Nicotinamide adenine dinucleotide glycohydrolase: a plasma membrane enzyme prominently found in Kupffer cells.

The distribution of nicotinamide adenine dinucleotide (NAD) glycohydrolase in rat liver was investigated by subcellular fractionation and by isolation of hepatocytes and sinusoidal cells. The behavior of NAD glycohydrolase in subcellular fractionation was peculiar because, although the enzyme was mainly microsomal, plasma membrane preparations contained distinctly more NAD glycohydrolase than could be accounted for by their content in elements derived from the endoplasmic reticulum or the Golgi complex identified by glucose-6-phosphatase and galactosyltransferase, respectively. When microsomal and plasmalemmal preparations were brought to equilibrium in a linear-density gradient, NAD glycohydrolase differed from these enzymes and behaved like 5'-nucleotidase and alkaline phosphodiesterase I. NAD glycohydrolase was markedly displaced towards higher densities after treatment with digitonin. This behavior in density-gradient centrifugation strongly suggests that NAD glycohydrolase is an exclusive enzyme of the plasma membrane. NAD glycohydrolase differed clearly from other plasmalemmal enzymes when the liver was fractionated into hepatocytes and sinusoidal cells; its specific activity was considerably greater in sinusoidal cell than in hepatocyte preparations. Further subfractionation of sinusoidal cell preparations into endothelial and Kupffer cells by counterflow elutriation showed that NAD glycohydrolase is more active in Kupffer cells. We estimate that the specific activity of NAD glycohydrolase activity is at least 65-fold higher at the periphery of Kupffer cells than at the periphery of hepatocytes. As the enzyme shows not structure-linked latency and is an exclusive constituent of the plasma membranes, we conclude that it is an ectoenzyme that cannot lead to a rapid turnover of the cytosolic pyridine nucleotides.

Studies on antineoplastic activity of naphthomycin, a naphthalenic ansamycin, and its mode of action.

An antibiotic, identical with naphthomycin, was isolated from a soil Streptomyces. The antibiotic displayed significant therapeutic activity by ip administration against murine tumors: Ehrlich carcinoma and IMC carcinoma implanted ip. The maximum increase of life-span was more than 169% in Ehrlich carcinoma, and 128% in IMC carcinoma. The antibiotic exhibited a potent cytotoxicity against murine leukemic cells: P388, L1210, and L5178Y. IC50 was 0.4-1.3 microgram/ml in culture. The activity of naphthomycin was reversed by SH compounds: 2-mercaptoethanol, dithiothreitol, and glutathione. DNA and RNA syntheses were more markedly inhibited by naphthomycin than protein synthesis in L5178Y cells. Approximately 50% inhibition of nucleic acid syntheses was observed at an antibiotic concentration of 2 micrograms/ml. Naphthomycin blocked alkaline phosphodiesterase obtained from L5178Y cells: IC50 was ca. 7.6 micrograms/ml. The antibiotic neither caused metaphase arrest nor prevented tubulin polymerization. The results suggest that the mechanism of cytotoxicity of naphthomycin is the inhibition of various SH enzymes, particularly those involved in nucleic acid biosynthesis. The mode of action is unique in the ansamycin group of antibiotics.

Effects of particulate glucan on murine peritoneal macrophage 5'-nucleotidase leucine aminopeptidase and alkaline phosphodiesterase ectoenzyme activities

Effects of particulate glucan on murine peritoneal macrophage 5'-nucleotidase leucine aminopeptidase and alkaline phosphodiesterase ectoenzyme activities

Serum alkaline phosphodiesterase I in experimental biliary obstruction in the rat.

Alkaline phosphodiesterase I was present in rat liver at approx. 100-fold greater activity than alkaline phosphatase, and in rat bile at approx. 25-fold greater activity. Rat serum alkaline phosphodiesterase I was increased 6-fold whilst serum alkaline phosphatase was increased only 2-fold 96 h after bile duct ligation. In contrast to alkaline phosphatase, hepatic alkaline phosphodiesterase I was not affected by bile duct ligation, suggesting its raised serum activity was due to bile regurgitation rather than overspill of the enzyme from liver into blood. Gel filtration showed that 8 and 96 h after bile duct ligation the serum contained a high molecular weight form of alkaline phosphodiesterase I. It is suggested that alkaline phosphodiesterase I offers a potentially useful indicator of biliary obstruction in the rat.

Identification of some plasma membrane proteins of cultured rat pigment epithelial cells by labeling with 125I

Cultured rat retinal pigment epithelial (PE) cells were labeled with 125I by lactoperoxidase (LPO)-catalyzed radioiodination. Examination of 125I-labeled cells by electron microscopic autoradiography suggested that 125I was incorporated into proteins at both the apical and basal surfaces of the PE cells, and into the extracellular matrix (ECM). Analysis of labeled cells by SDS-polyacrylamide gel electrophoresis and autoradiography showed that 125I was incorporated into at least 15 polypeptides. In order to determine which of these labeled proteins were derived from the plasma membrane, 125I-labeled cells were subjected to differential detergent extraction. Triton X-100 (2% v/v), which removed the cell plasma membrane, solubilized only three of the labeled proteins (1 52 000, 1 38 000, 1 23 000 daltons). SDS (0·25 % w/v) completely removed cells from the tissue culture dish and solubilized all but four of the labeled proteins (225 000, 173 000, 87 000 and 72 100 daltons). When 125I-labeled PE cells were mechanically disrupted, and the resulting cell fractions separated by sucrose density gradient centrifugation, labeled proteins separated into two subcellular fractions. One fraction was especially enriched in the 1 52 000, 1 38 000 and 1 23 000 dalton labeled proteins, in addition to the plasma membrane marker enzymes Na +, K +-ATPase, and alkaline phosphodiesterase I. The second fraction was enriched in the 225 000, 1 96 000 and 1 73 000 dalton labeled proteins, the ECM proteins laminin and fibronectin, and the 43 000 actin band. It is proposed that 125I-labeled proteins in the former cell fraction are truly plasma membrane proteins, while those found in the latter cell fraction are a mixture of 125I-labeled ECM and basal plasma membrane proteins. The 1 52 000, 1 38 000 and 1 23 000 dalton labeled proteins of the plasma membrane fraction are glycoproteins and become firmly anchored to the Triton X-100 insoluble cytoskeleton when labeled cells are treated with concanavalin A.

Stimulation of phagocytosis in bone marrow-derived mouse macrophages by bacterial lipopolysaccharide: correlation with biochemical and functional parameters.

It has been shown that low concentrations of E. coli lipopolysaccharides (LPS) greatly and selectively stimulate phagocytosis and related functions in mouse bone marrow-derived macrophages. Culture in the presence of 50 ng/ml LPS induced on average a 10-fold enhancement of phagocytosis of IgG-coated sheep erythrocytes. Activation was in two stages--a small increase observed during the first 8 to 12 hr, and the major increase noted between 16 and 24 hr. Phagocytic activity remained at the maximal level for 24 hr and then declined progressively. Stimulation by LPS was dose-dependent; significant effects could be observed at 0.8 ng/ml and the maximum was reached at 10 ng/ml. LPS-treated cells also showed a markedly increased tendency to form colonies. All these effects could be prevented by the addition of 100 ng/ml polymyxin B together with LPS, indicating that the active principle is lipid A. The LPS-dependent increase in phagocytic activity is probably mediated by increased Fc receptor capacity because both parameters were influenced in parallel by the stimulus. Phagocytosis-related events, such as enhanced hexose monophosphate shunt activity, H2O2 formation, and nitroblue tetrazolium reduction were also stimulated by LPS. By contrast, pinocytosis was unaffected. Measurements of cell-associated enzyme activities showed that lactate dehydrogenase, acid phosphatase, and cathepsin D were significantly increased. Beta-glucuronidase, beta-galactosidase, alkaline phosphodiesterase, and aminopeptidase were unchanged and NAD nucleosidase was markedly decreased after LPS treatment. 5'-Nucleotidase and glucosamine uptake were undetectable both in control and LPS-stimulated cells. LPS treatment induced a significant increase in cell-associated protein, but did not result in cell proliferation or increased cell loss as shown by the DNA content that remained constant. LPS-induced changes were dependent on de novo protein synthesis; cycloheximide prevented enhancement of phagocytosis, Fc receptor capacity, and colony formation.

Characterization of a monoclonal antibody defining a macrophage activation-specific cell surface antigen

Macrophages have been obtained from the peritoneal cavities of C57BL/6 mice following treatment with C . parvum , MVE-2, mineral oil, or thioglycollate. Cell populations were primarily composed of mononudear phagocytes as determined by a latex bead uptake assay. Macrophages obtatned from C . parvum or MVE-2 were activated as judged by enhanced cytostatic activity against two tumor cell target lines. Thioglycollate-elicited macrophages demonstrated much lower cytostatic ability. Rats were immunized with activated MVE-2 macrophages. Hybridomas were prepared by fusion with a non-secreting myeloma cell line followed by cloning. Cell supernates were selected on the basis of binding to activated but not elicited macrophages. The monoclonal antibody produced has been characterized by flow cytometry. The antibody does not react with syngeneic erythrocytes, thymocytes, or spleen cells. Reaction with thioglycollate macrophages is very low. Alternatively, intense binding is found on activated macrophages. This antigen which accompanies macrophage activation for tumor ce11 cytostasis is designated as macrophage activation antigen-1 (MAA-1). Several important physiological changes accompany the process of macrophage activation. For example, activated macrophages demonstrate enhanced microbicidal, phagocytic, secretory, and tumoricidal activity (for reviews see refs. 1,2). Concommitant alterations in cell surface properties have been observed. These include: (a) changes in surface morphology and spreading (3–5), (b) altered lipid and protein content (6,7), (c) decreases in 5'-nucleotidase activity and alkaline phosphodiesterase (8), increases in leucine aminopeptidase (8), decreases in mannose receptors (11,12), and antigen F4/80 (11), (d) increases in la antigens (11,12), and (e) increased tumor cell binding (13). These structural and functional modifications indicate that activated macrophages represent a unique class of functionally differentiated cells (9). Antigenic modifications accompanying macrophage differentiation are of special interest. Markers for specific macrophage classes might be useful in defining differentiation pathways, dissecting type-specific functional activities such as tumor cytotoxicity, and providing a means to identify macrophage subsets in heterogeneous cell populations. In the present work we have taken the first step in this direction by defining a cell surface macrophage activation antigen.