Metabolism of purines in macrophages. Effect of functional state of the cells.

Ecto-5'-nucleotidase is known to be diminished markedly in activated compared to control mouse macrophages. The level of three purine nucleoside metabolizing enzymes, adenosine deaminase (EC 3.5.4.4), purine nucleoside phosphorylase (EC 2.4.2.1), and adenine phosphoribosyltransferase (EC 2.4.2.7) were measured in the sonicates of different populations of mouse peritoneal macrophages. Levels of adenine phosphoribosyltransferase and purine nucleoside phosphorylase in macrophages that were elicited with sodium caseinate or activated in vivo by prior intravenous injection of Listeria monocytogenes were eight times higher than those in resident cells. Levels of adenosine deaminase also tended to increase and were two times higher in elicited cells than in resident cells. The Km of each enzyme was the same in each cell population. The findings suggest that the levels of the ecto-5'-nucleotidase and of the intracellular enzymes are coordinated.

Superoxide production by phagocytic leukocytes.

Mononuclear phagocytic leukocytes, as well as polymorphonuclear leukocytes, produce and release superoxide at rest, and this is stimulated by phagocytosis. Of the mouse monocytic cells studied, alveolar macrophages released the largest amounts of superoxide during phagocytosis, followed by normal peritoneal macrophages. Casein-elicited and "activated" macrophages released smaller quantities. In the guinea pig, polymorphonuclear leukocytes and casein-elicited macrophages were shown to release superoxide during phagocytosis whereas alveolar macrophages did not. Superoxide release accounted for only a small fraction of the respiratory burst of phagocytosis in all but the normal mouse peritoneal macrophage, the guinea pig polymorphonuclear leukocyte, and probably the mouse alveolar macrophage. There are obviously considerable species differences in O2-release by various leukocytes that might reflect both the production and/or destruction (e.g. by dismutase) of that substance.

Iodinating ability of various leukocytes and their bactericidal activity.

A rapid method that employs monolayers of different phagocytic cells, primarily from guinea pigs and mice, has allowed a kinetic determination of (a) ingestion by these cells of labeled particles, (b) fixation of (131)I and (c) microbicidal activity in the cells after periods as short as 5' of exposure of bacteria to phagocytes. Phagocytes so examined included polymorphonuclear leukocytes (PMN) elicited into the peritoneal cavity, elicited peritoneal mononuclear cells (monocytes) (MN), and peritoneal macrophages (MAC) obtained simply by lavage. Circulating PMN from normal human subjects and from children afflicted with chronic granulomatous disease were also studied. The potential for generation of H(2)O(2) (a key component of the iodinating system) of all the normal cells studied, gauged by their content of cyanide-insensitive NADH oxidase, seemed comparable. Peroxidase levels varied widely, and were highest in PMN and almost undetectable in MAC. Catalase was at negligible levels in all the cell types obtained from mice. The fixation of (131)I by phagocytes ingesting (14)C-labeled dead tubercle bacilli appeared to be primarily a function of the cellular peroxidase content. Thus, mouse macrophages, with virtually no peroxidase, displayed no fixation of iodide. PMN proved far more able to fix (131)I during phagocytosis than did MN. In experiments comparing PMN from normal human subjects and from children with chronic granulomatous disease (CGD), a sex-linked condition characterized by a deficiency of H(2)O(2) production during phagocytosis and low microbicidal activity, the iodination ratio of CGD cells was dramatically less than that of normal PMN (by about two orders of magnitude). Capacity for iodination was correlated with bactericidal activity toward E. coli. At low bacterial loads (ca. 5:1), phagocytes killed efficiently, and little discrepancy in ability among cell types was apparent. Under the stress of higher loads of (14)C-labeled E. coli (ca. 100:1), differences in bactericidal activity were exaggerated, and a substantial disparity between MN and PMN was observed in favor of the latter. The hierarchy for killing efficiencies therefore agreed with that for iodination, with one notable exception: mouse MAC were consistently competent in their killing activity, more so than MN, even though they virtually lack peroxidase and the ability to iodinate ingested bacteria.

Alterations of macrophage functions by mediators from lymphocytes.

Sensitized lymphocytes were incubated in vitro with the specific antigen Supernatants from these cultures were chromatographed on Sephadex G-100 columns. Supernatant fractions containing MIF, chemotactic factor, and lymphotoxin, but free of antigen and antibody, were incubated with normal peritoneal exudate macrophages. Macrophage adherence, phagocytosis, spreading, motility, and direct hexose monophosphate oxidation were enhanced, while protein synthesis was unaffected. Thus, antigen-stimulated lymphocytes secrete a factor or factors which enhance certain macrophage functions. Implications for models of cellular immunity and cellular hypersensitivity are discussed.

Alteration of some functional and metabolic characteristics of resident mouse peritoneal macrophages by lymphocyte mediators.

Resident mouse peritoneal macrophages were incubated in Sephadex G-100 fractions of supernates from concanavalin A-stimulated lymphocytes. A significant effect of the lymphocyte supernatant fractions containing mediators on macrophage 5'-nucleotidase, glucose-1 14C oxidation, cell maintenance, and migration is reported. The 5'-nucleotidase was depressed to an extent similar to that seen in activated macrophages obtained from Listeria-infected mice. On the other hand, glucose-1-14C oxidation was enhanced, but not to the same degree as seen in the counterparts in vivo. Whereas migration inhibitory factor (MIF) and cell adherence-augmenting activity were found in a number of adjacent fractions, the metabolic effects were found predominantly in a single fraction. Resident peritoneal macrophages or those elicited by the injection of a lymphocyte-derived chemotactic factor were more responsive with respect to the biochemical changes than caseinate-elicited macrophages. On the other hand, caseinate-elicited macrophages appeared to be more sensitive with respect to the effects of mediator(s) on cell retention. A possible dissociation between MIF and cell-adherence augmenting activity, on the one hand, and the entities that stimulate glucose-1-14C oxidation is reported, based on fractionation studies, and loss of the latter activity upon storage of lymphocyte supernates.

Muramyl peptides. Variation of somnogenic activity with structure.

Sleep-promoting activities of muramyl dipeptide (MDP) (NAc-Mur-L-ala-D-isogln) and the naturally occurring muramyl peptide(s), factor S, have recently been demonstrated. We now have amplified our understanding of structural requirements for somnogenic activity. The effects of several analogs of MDP on rabbit slow-wave sleep are presented and these results are compared to the dose-response relationship for MDP. Some tentative conclusions as to structural requirements for somnogenic activity are presented; most notably, amidation of the free gamma-carboxyl of MDP and several of its analogs resulted in the loss of somnogenic activity. MDP also can induce febrile and immunostimulatory responses. In the present paper, we show that some analogs possess immunostimulatory and pyrogenic activity but not somnogenic activity, thus suggesting that these biological activities of muramyl peptides may, in part, be mediated by separate mechanisms.

Biochemical changes during growth and encystment of the cellular slime mold Polysphondylium pallidum.

The growth of the cellular slime mold, Polysphondylium pallidum, was studied on a semidefined medium in shaken suspension. When the medium contained large quantities of particulate material, growth was more rapid and the cellular size and protein content were smaller than when growth occurred on a medium containing less particulate material. The cellular levels of DNA, RNA, and protein; of lysosomal enzymes (acid phosphatase, acid proteinase); and of peroxisomal enzymes (catalase) were assayed during growth and the subsequent stationary phase that led eventually to encystment. Only DNA remained at a constant cellular level. Encystment of exponentially growing cells could also be initiated by washing them and introducing them into a soluble peptone medium. The rate of encystment was proportional to the osmolarity of this medium. The encystment process was followed with respect to the cellular levels of DNA, RNA, protein, carbohydrates, acid phosphatase, acid beta-N-Ac-glucosaminidase, and catalase. The most dramatic change occurred in the cellular cellulose content, which increased by at least an order of magnitude by the time encystment was morphologically complete. It was concluded that the encystment of this slime mold in suspension exhibits a number of biochemical similarities to the development of this and other cellular slime molds on a surface.

Phagocytosis by the cellular slime mold Polysphondylium pallidum during growth and development.

The phagocytic ability of amoebae of the cellular slime mold Polysphondylium pallidum, grown in shaken suspension, was examined. An established quantitative assay of the uptake of polystyrene (PS) beads was shown to be valid for this organism. The kinetics of phagocytosis were determined, and estimates of the concentration of PS beads necessary to achieve half-maximal phagocytic velocity (K(p)), as well as the maximal velocity itself (V(p) (max)), were made. Comparison with previously published data on Acanthamoeba and guinea pig leukocytes suggested that the P. pallidum amoebae had the lowest K(p), while the leukocytes had the highest V(p) (max). Beads approximately 1 microm in diameter appeared to be the optimal size for ingestion. Simultaneously with phagocytosis, comparable numbers of beads accumulated at the cell surface; this accumulation did not occur when phagocytosis was inhibited. Phagocytosis was depressed by protein in the medium, by increased osmolarity, and by inhibitors of aerobic metabolism. Starvation-initiated development, leading to encystment, was shown to affect the capacity of the cells to phagocytize, mainly by progressively decreasing the time span over which the cells ingested particles at a constant initial rate.

The depression of phagocytosis by exogenous cyclic nucleotides, prostaglandins, and theophylline.

The effects of agents that elevate intracellular cyclic adenosine 3',5'-monophosphate (cAMP) have been studied with respect to phagocytosis by guinea pig polymorphonuclear leukocytes. The investigation depends upon the use of a precise method for following ingestion. Theophylline, dibutyryl cAMP, and prostaglandins inhibited the phagocytosis of starch particles. The inhibitions caused by prostaglandins E(1), E(2), and F(2alpha) (PGE(1), PGE(2), and PGF(2alpha)) were synergistic with that due to theophylline. Inhibition by PGA(1) and PGA(2) was not. At equal concentrations the order of increasing inhibition of phagocytosis (assayed at 10 min) by the prostaglandins was PGE(1) < PGF(2alpha) < PGE(2) < PGA(1) = PGA(2). Our results are consistent with the hypothesis that increased intracellular levels of cAMP impair the phagocyte's ability to ingest particles. The mechanism of the inhibition has not been defined. The increment in oxidation of [1-(14)C]glucose to (14)CO(2) that normally accompanies phagocytosis was found to be depressed in the presence of PGE(1) or theophylline, together or individually as expected from the inhibition of phagocytosis. Paradoxically, oxygen consumption although depressed by theophylline or PGE(1) plus theophylline, was stimulated by PGE(1) alone.

Cytochemical demonstration of hydrogen peroxide in polymorphonuclear leukocyte phagosomes.

Phagocytosis by polymorphonuclear leukocytes (PMN) is accompanied by specific morphological and metabolic events which may result in the killing of internalized micro-organism. Hydrogen peroxide is produced in increased amounts during phagocytosis (17) and in combination with myeloperoxidase and halide ions constitute a potent, microbicidal mechanism (8,9,11). There can be direct iodination of micro-organisms (10), or alternatively, other intermediate reaction products, i.e. chloramines and aldehydes (21), can exert a microbicidal effect. The H2O2-peroxidase-halide system is presumed to operate within the phagocytic vacuole (12,18). Myeloperoxidase, present in the primary granules of PMN, enters the phagocytic vacuole during degranulation (1,4,7), and halide ions are probably derived from the extracellular medium or are present in the PMN (see 11, 18). For the operation of this system in intact cells, the presence of H2O2 in the phagocytic vacuole is necessary, and indeed this has been suggested by the work of several investigators (12, 18, 21). In the present investigation, the diaminobenzidine reaction of Graham and Karnovsky (5), modified to utilize endogenous myeloperoxidase and hydrogen peroxide, has been applied to actively phagocytizing PMN to demonstrate cytochemically the presence of H2O2 in the phagocytic vacuole.

Glycogen accumulation in polymorphonuclear leukocytes, and other intracellular alterations that occur during inflammation.

Neutrophils isolated from the blood were compared to those from inflammatory exudates in the peritoneal cavity of guinea pigs. Inflammatory neutrophils were shown to have 10-fold more glycogen than blood neutrophils. This was also reflected in the morphology of these cells. The large accumulations of glycogen in inflammatory neutrophils exists in ordered arrays of beta-granules. Other morphological changes including accumulations of lipid droplets and a decrease in the number of lysosomal granules also accompany the change from blood neutrophils to inflammatory neutrophils. These results show that there are major metabolic differences in the two types of neutrophils.

Cell surface dynamics of neutrophils stimulated with phorbol esters or retinoids.

Neutrophils undergo rapid morphological changes as well as metabolic perturbations when stimulated with certain phorbol esters. Stimulated cells initially exhibit pronounced projections emanating from the cell bodies, followed by rounding of the cells, reduction in granule number, and the appearance of intracellular vesicles. We show these vesicles to be derived, at least in part, from the plasmalemma. The experimental approach involved labeling stimulated and unstimulated cells with native ferritin and cationized ferritin, along with the cytochemical localization of ecto-5'-nucleotidase. The labeling patterns of the vesicles indicate that these structures are involved in both phorbol ester-stimulated adsorptive and fluid-phase endocytosis. Neutrophils stimulated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) exhibit two distinct rates of superoxide release in which the second, prolonged level is approximately 50% of the initial rate. All-trans-retinal, which we have recently shown to stimulate O2- release but not granule exocytosis or cell vesiculation, induces a single prolonged rate of maximal O2- release. Neutrophils treated with both all-trans-retinal and TPA exhibit only a single sustained rate of maximal O2- release similar to that observed with all-trans-retinal alone. Moreover, treatment of cells with all-trans-retinal blocks the vesiculation of neutrophils induced by TPA in a dose-dependent manner. This observation provides a possible explanation for the differences in the kinetics of superoxide release.

Localization of NADH oxidase on the surface of human polymorphonuclear leukocytes by a new cytochemical method.

The ultrastructural localization of NADH oxidase, a possible enzyme in the increased oxidative activity of polymorphonuclear leukocytes (PMN) during phagocytosis, was studied. A new cytochemical technique for the localization of H2O2, a product of NADH oxidase activity, was developed. Cerous ions, in the presence of peroxide, form an electron-dense precipitate. Resting and phagocytically stimulated PMN were exposed to cerous ions at pH 7.5 to demonstrate sites of NADH-dependent, cyanide-insensitive H2O2 production. Resting PMN exhibites slight activity on the plasma membrane; phagocytizing PMN had extensive deposits of reaction product localized within the phagosome and on the plasma membrane. Peroxide involvement was demonstrated by the inhibitory effect of catalase on cerium precipitation; the surface localization of the enzyme responsible was confirmed by using nonpenetrating inhibitors of enzymatic activity. A correlative study was performed with an NADH-dependent, tetrazolium-reduction system. As with cerium, formazan deposition on the surface of the cell was NADH dependent, cyanide insensitive, and stimulated by phagocytosis. Superoxide dismutase did not inhibit tetrazolium reduction, as observed cytochemically, indicating direct enzymatic dye reduction without superoxide interposition. These findings, combined with oxygen consumption studies on resting and stimulated PMN in the presence or absence of NADH, indicate that NADH oxidase is a surface enzyme in human PMN. It is internalized during phagocytosis and retains its peroxide-generating capacity within the phagocytic vacuole.

Measurement of rates of phagocytosis: the use of cellular monolayers.

A method has been developed for measuring the rate of phagocytosis rather than the quantity of particles ingested per cell when the process is virtually complete. The method, which is simpler and more rapid than those described previously, utilizes cellular monolayers, radioactive particles, and short incubation times. Under the conditions described, the rate of uptake of particles by either guinea-pig peritoneal or human blood leukocytes was proportional to both cell concentration and the time of incubation, and was independent of changes in the concentration of particles during the measurement. The particles were retained by the cells for at least 90 min. The most suitable particles so far used have been (32)P-labeled Salmonella typhimurium, and acetyl-(14)C- or methyl-(14)C-labeled starch particles. The oxidation of (14)C-labeled glucose has been studied under the same conditions that were used for the assays of phagocytosis: the greatest increase in formation of (14)CO(2) from glucose-1-(14)C occurred a few minutes after the most rapid period of phagocytosis.

Release of superoxide and change in morphology by neutrophils in response to phorbol esters: antagonism by inhibitors of calcium-binding proteins.

The ability of phorbol derivatives to function as stimulating agents for superoxide (O2-) release by guinea pig neutrophils has been evaluated and compared to the known ability of each compound to activate protein kinase C. Those that activate the kinase also stimulate O2- release, while those that are inactive with respect to the kinase have no effect on O2- release. The same correlation was observed with respect to the ability of phorbol esters to induce morphological changes in neutrophils, i.e., vesiculation and reduction in granule content. Certain phenothiazines and naphthalene sulfonamides that are known antagonists of calcium-binding proteins blocked both phorbol ester-induced O2- release and morphological changes in these cells.

Metabolic and morphological observations on the effect of surface-active agents of leukocytes.

Morphological and metabolic observations have been made on the effects of endotoxin, deoxycholate, and digitonin (at less than 50 microg/ml) on polymorphonuclear leukocytes and mononuclear cells. The agents stimulate the respiration and glucose oxidation of these cells in a manner similar to that seen during phagocytosis. Electron microscopy revealed no morphological changes with the first two agents, but dramatic membrane changes were seen in the case of digitonin. Here tubular projections of characteristic size and shape formed on and split off the membrane. All the agents stimulated uptake of inulin, but efforts to demonstrate increased pinocytosis by electron microscopy have not so far succeeded, probably due to limitations in present experimental techniques.

Ecto-enzyme of granulocytes: 5'-nucleotidase.

The 5'-nucleotidase of guinea pig polymorphonuclear leukocytes is localized exclusively on the plasma membrane of intact cells. The active site of this enzyme faces the external medium, not the cytoplasm.

Deficiency of reduced nicotinamide-adenine dinucleotide oxidase in chronic granulomatous disease.

Reduced nicotinamide-adenine dinucleotide oxidase of normal human polymorphonuclear leukocytes has properties that would qualify it as the enzyme responsible for the respiratory burst during phagocytosis. The enzyme was deficient in leukocytes of five patients with chronic granulomatous disease. This lack of adequate reduced nicotinamide-adenine dinucleotide oxidase could be the basis for the metabolic abnormalities characteristic of these leukocytes and for their diminished bactericidal activity.

Sleep: effects on incorporation of inorganic phosphate into brain fractions.

During sleep there is a two- to threefold increase in the incorporation of inorganic orthophosphate-(32)P into a chemical fraction of the brain of the 20-day-old rat. This increase is not in the lipids or nucleic acids, but is associated with an acid-labile phosphate entity of the tissue residue after extraction of these fractions and phosphorus-containing substances of low molecular weight.

Concomitant alterations of sodium flux and membrane phospholipid metabolism in red blood cells: studies in hereditary spherocytosis.

The role of membrane phosphatides in transport processes has been investigated in red cells from splenectomized patients with hereditary spherocytosis (HS). Incorporation of inorganic (32)phosphate into the membrane phosphatides of HS red cells was approximately twice normal, coinciding with the nearly twofold increment in flux of sodium ions in the cells.A consistent, inordinate increase in specific activity of a chromatographic fraction containing phosphatidylserine provided the bulk of the over-all increase in labeling of HS red cell phosphatides. The specific activity of phosphatidic acid was increased but not consistently. Radioactivity of the "acidic phosphatides" (phosphatidylserine and phosphatidic acid fractions) decreased, in general, when the sodium flux was low, i.e., when the cells were suspended in media of low sodium content. When the cation flux was elevated (hypotonic media), there was a marked (ca. 35%) increase in the labeling of phosphatidylserine fractions. Normal red cells whose permeability to cations was increased by exposure to 0.5 N butanol also exhibited increased labeling of acidic phosphatides. Considerations of the stoichiometry of cation transport and phosphatide labeling make it unlikely that phospholipids act directly as carrier molecules for cations in red cell membranes. On the other hand, the involvement of these lipid substances in cation movements is substantiated by correlating several different states of sodium flux with the labeling of the phosphatidic acid and phosphatidylserine fractions.