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R Snyderman

Publications and source records attributed to R Snyderman.

At least 145 records · Page 8Linked to original sources
PubMed1983

Activation of the respiratory burst enzyme in human polymorphonuclear leukocytes by chemoattractants and other soluble stimuli. Evidence that the same oxidase is activated by different transductional mechanisms.

Chemoattractant-receptor coupling triggers several biologic responses in phagocytic cells including activation of the respiratory burst. Prior evidence in intact cells implied that stimulation of the respiratory burst by chemoattractants was by a mechanism different from other soluble agents suggesting the possibility that different oxidative enzymes were responsible. We now show that the chemoattractants N-formyl-methionyl-leucyl-phenylalanine and a split fragment of the fifth component of complement (C5a) stimulate an NADPH oxidase activity, measured in the 50,000-g particulate fraction from human polymorphonuclear leukocytes (PMN). Levels of oxidase activity stimulated by the chemoattractants were both time and dose dependent and required the presence of cytochalasin B during stimulation. In contrast, activation by two nonchemotactic stimuli, the ionophore A23187 and phorbol myristate acetate (PMA), did not require cytochalasin B. Temporal patterns of oxidase activation suggested that different stimuli follow different transductional pathways. Chemoattractant-mediated activation was immediate (no lag); peaked by 45 s and declined rapidly to approximately 50% of maximal by 2 min. In contrast, activation by A23187 or PMA had a 15-30-s lag and increased more slowly. Stimulation by A23187 peaked at 5 min, then declined. Stimulation by PMA plateaued at 20 min and did not decline by 90 min. Comparison of Km values for NADPH and NADH obtained by Lineweaver-Burk analysis of the oxidase activity stimulated by N-formyl-methionyl-leucyl-phenylalanine, A23187, and PMA suggested that the same enzyme was activated by all stimuli. Thus, chemoattractants and other soluble stimuli appear to activate the same respiratory burst enzyme in PMN but they utilize different transductional mechanisms and are regulated differently.

Calcimycin↗
PubMed1983

Guanine nucleotides modulate the binding affinity of the oligopeptide chemoattractant receptor on human polymorphonuclear leukocytes.

The oligopeptide chemoattractant receptor on human polymorphonuclear leukocyte (PMN) membranes exists in two affinity states. Since guanine nucleotides regulate the binding affinity and transductional activity of several other types of receptors, we examined the effect of nucleotides on the binding of N-formyl-methionyl peptides to their receptors on human PMN membranes. The addition of guanylylimidodiphosphate (0.1 mM), a nonhydrolyzable derivative of guanosine triphosphate (GTP), to PMN membrane preparations reduced the fraction of high-affinity receptors detected in equilibrium binding studies from 21.3 +/- 0.13 to 11.8 +/- 0.05% (P less than 0.03), without altering the binding affinities. Since the total number of receptors remained unchanged, the effect of guanylylimidodiphosphate was to convert a portion of the receptors from the high-affinity state to the low-affinity state. At the maximal concentration of guanine nucleotide tested, approximately 50% of the high-affinity sites were converted to low-affinity sites. The findings obtained by equilibrium binding were supported by kinetic studies since the dissociation of the radiolabeled oligopeptide chemoattractant N-formyl-methionyl-leucyl-[3H]phenylalanine from PMN membranes was accelerated in the presence of guanine nucleotide. The effect of guanine nucleotides was reversed upon washing, indicating that affinity conversion is bidirectional. The guanine nucleotide effects were greatest with nonhydrolyzable derivatives of GTP followed by GTP then guanosine diphosphate. Neither guanosine monophosphate nor any adenine nucleotide tested had an effect on receptor binding. These data suggest a role for guanine nucleotides in the regulation of stimulus-receptor coupling of chemoattractant receptors on human PMN.

Chemotaxis, Leukocyte↗
PubMed1983

Hormonal activation of adenylate cyclase in macrophage membranes is regulated by guanine nucleotides.

Many macrophage functions such as chemotaxis, phagocytosis, enzyme secretion, and cytotoxicity are influenced by intracellular cyclic nucleotide levels, but the regulatory mechanisms involved are poorly defined. We have developed methods that allowed us to study the activation of AC in isolated guinea pig (g.p.) macrophage membranes. AC in these membrane preparations could be stimulated approximately twofold by guanine nucleotides. We could not obtain any hormonal activation of membrane-bound AC in the absence of guanine nucleotides. In the presence of GTP, however, the hormones isoproterenol and PGE1 elicited an additional threefold rise in AC activity, which subsided after approximately 15 min. As little as 10(-8) M concentrations of these two hormones induced significant elevations of AC activity. Replacement of GTP by its nonhydrolyzable analogue Gpp(NH)p resulted in a persistent hormone-independent activation of AC, and addition of hormones enhanced this level of activation. Thus, GTP-ase activity is present in macrophage membrane preparations and serves to regulate AC activation. Hormonal stimulation of AC was receptor mediated, because the effect of the beta-adrenergic agonist isoproterenol, but not PGE1, was inhibited by the beta-adrenergic blocker propranolol. In addition, the potency series of PG corresponded to that observed for stimulation of cAMP production in intact g.p. macrophages, i.e., PGE1 = PGE2 greater than PGA1 greater than PGF2 alpha. AC activation by PG in the membrane preparation was inhibited by an alpha-adrenergic agonist, thus demonstrating one means for down regulating cAMP production in g.p. macrophages. Our studies also showed that certain hormones (e.g., beta-adrenergic agonists, PG) can exert their effect on cAMP production by stimulation of membrane-bound AC, whereas other agents such as lectins or arachidonic acid require additional intracellular components to elevate cAMP levels in macrophages. The mechanism of activation of AC by hormones in g.p. macrophage membranes appears to fit the model of a ternary complex, the components of which include the hormone receptor, AC, and guanine nucleotide regulatory protein, which transmits the signal from the receptor to AC.

Adenylyl Cyclases↗
PubMed1982

Transmethylation reactions regulate affinity and functional activity of chemotactic factor receptors on macrophages.

Methylation mediated by S-adenosyl-L-methionine is required for the chemotaxis of mononuclear leukocytes. We investigated whether transmethylation reactions are required for normal functioning of chemotactic factor receptors. Three chemoatractant-mediated functions in macrophages, chemotaxis, the stimulated release of arachidonic acid from membrane phospholipids and superoxide production, are markedly depressed by agents that inhibit cellular methylation reactions. Treatment of macrophages with methylation inhibitors decreased the affinity of the N-formylated chemoattractant receptor present on these cells by a factor of 4.5, but did not significantly alter the total receptor on macrophages can exist in more than one affinity state and that an ongoing methylation reaction is required for the maintenance of the receptor in its higher affinity form. Inhibition of methylation lowers the affinity of the receptor and renders it nonfunctional or "uncoupled" in its ability to produce chemotaxis, superoxide and the release of a arachidonic acid from leukocyte membranes.

Adenosine↗
PubMed1982

Induction of cellular immunity to Coccidioides immitis after sensitization with dinitrochlorobenzene.

A patient had progressive disseminated coccidioidomycosis and depressed cellular immunity to Coccidioides immitis. He developed a large nasal coccidioidal lesion that was unresponsive to conventional therapy. Application of dinitrochlorobenzene (DNCB) to the nasal lesion was temporally associated with resolution of the lesion and stabilization of the systemic disease. In addition, DNCB application was followed by signs of cellular immunity to C. immitis. These included development of delayed cutaneous hypersensitivity to coccidioidin, as well as lymphokine production and lymphoproliferative responses to coccidioidin. Similar forms of DNCB immunotherapy may prove useful in other patients with fungal disease and depressed cellular immunity.

Adult↗
PubMed1982

Cyclic nucleotides regulate the morphologic alterations required for chemotaxis in monocytes.

The initial morphologic response of human monocytes to chemoattractants is a change in shape from round to a triangular "motile" configuration (polarization). At doses chemotactic in vitro, chemoattractants induced rapid (t 1/2 = 45 sec), sustained (greater than 40 min) polarization of monocytes in suspension. Extracellular Ca++ was not required for polarization induced by chemoattractants, but in the absence of Ca++ kinetics were slowed (t 1/2 = 6.5 min). Phenylephrine, carbamycholine, serotonin, and ascorbate also caused rapid polarization of monocytes. Unlike chemoattractants, polarization by the pharmacologic agents was unsustained (less than 15 min), absolutely required extracellular Ca++, and affected about 50% of the cells responsive to chemoattractants. Based on relative sensitivities to alpha 1- and alpha 2-adrenergic agonists and antagonists, polarization caused by adrenergic agents was mediated by alpha 2-receptors. Muscarinic and alpha 2-adrenergic agonists, serotonin, and ascorbate enhanced the rate and number of monocytes polarizing to suboptimal doses of chemoattractants. Thus, the initial morphologic changes induced by chemoattractants appear to utilize an activation pathway shared with a variety of agents that enhance cGMP levels and inhibit adenylate cyclase. In contrast, theophylline, histamine, and isoproterenol, all agents that activate adenylate cyclase and elevate cAMP levels, inhibited monocyte polarization to chemoattractants. As in PMN, pharmacologic agents that increase cAMP levels inhibited monocyte chemotaxis in vitro, whereas those that inhibit adenylate cyclase and increase cGMP enhanced monocyte chemotactic responses. Thus, the initial morphologic response of monocytes to chemoattractants as well as the processes required for sustained directional motility are modulated by cyclic nucleotides.

Adrenergic beta-Agonists↗
PubMed1982

Amphotericin B alters the affinity and functional activity of the oligopeptide chemotactic factor receptor on human polymorphonuclear leukocytes.

Leukocyte chemotaxis is initiated by the binding of chemotactic factors to specific, high-affinity receptors. Amphotericin B, a polyene antibiotic that binds to membrane cholesterol, inhibits human neutrophil (PMN) chemotaxis. We examined the effects of this drug on PMN functions mediated by the oligopeptide chemotactic factor receptor. The antibiotic irreversibly inhibited chemotaxis and depressed the binding of the radiolabeled chemoattractant, fMet-Leu-[3H]Phe, to its receptor without affecting the receptor's specificity. The drug lowered the binding affinity of the receptor by up to fivefold and slightly increased its number. Doses of amphotericin B that depressed receptor affinity and inhibited chemotaxis did not diminish lysosomal enzyme secretion or superoxide anion production. Nystatin, a less potent polyene antibiotic, also diminished chemotactic factor binding, but to a lesser degree than amphotericin B did. A chemically unrelated antifungal agent had no effect on either binding or chemotaxis. Thus, pharmacologic manipulation can alter the affinity of the chemotactic factor receptor on human PMN; this alteration is associated with a change in receptor function. The data suggest that receptor affinity regulates or at least reflects its functional state, and that the transduction mechanisms for various biologic responses mediated by the chemoattractant receptor are heterogeneous. By pharmacologic alterations of receptor affinity, one may be able to modulate specific biologic responses elicited by chemoattractant receptor-ligand interactions.

Amphotericin B↗
PubMed1981

Molecular and cellular mechanisms of leukocyte chemotaxis.

The application of modern scientific methods to the study of leukocyte function has begun to reveal the molecular and cytostructural bases of the chemotactic responses of these cells. Leukocyte chemotaxis is initiated by the binding of chemoattractants to distinct plasma membrane receptors; this finding alters transmembrane potential and activates ionic fluxes. The subsequent sequence of metabolic processes leads to a rearrangement of cytoskeletal elements that is manifested by orientation and migration of the cells toward the source of the chemotactic gradient.

Animals↗
PubMed1981

Alterations of new methylated phospholipid synthesis in the plasma membranes of macrophages exposed to chemoattractants.

Chemotactic factors have been shown to inhibit the methylation of phosphatidylethanolamine in macrophages without affecting total phospholipid synthesis. It would thus be anticipated that newly synthesized membranes of macrophages exposed to chemoattractants would have an increased ratio of phosphatidylethanolamine to its methylated derivatives. These ratios were measured directly in newly synthesized phospholipids of plasma membranes isolated from guinea pig peritoneal macrophages. The phosphatidylethanolamine: methylated phospholipid ratio in such plasma membranes was increased by 53 to 111% upon exposure of the cells to chemotactic factors. This increase was due to decreased synthesis of methylated phospholipids and not to altered formation of phosphatidylethanolamine or activation of phospholipases. Methylated phospholipid ratios were also studied in the leading front lamellipodia isolated from macrophages migrating under chemotactic and nonchemotactic conditions. The phosphatidylethanolamine:methylated phospholipid ratios were increased up to fourfold in lamellipodia of macrophages migrating towards chemotactic agents when compared to those from cells migrating randomly. Biophysical changes in the plasma membrane produced by an increase in the ratio of phosphatidylethanolamine:methylated phospholipids as a result of exposure of cells to chemoattractants may be required for sustained directed migration.

Animals↗
PubMed1981

Monocyte responsiveness to chemotactic stimuli is a property of a subpopulation of cells that can respond to multiple chemoattractants.

The chemotactic migration of leukocytes is preceded by an alteration in the cells' shape from round to a characteristic polar configuration. We have developed an assay that shows that human monocytes, when exposed to chemoattractant in suspension, assume this polarized shape. The three types of chemo-attractants studied, a chemotactic lymphokine, complement-activated serum, and the N-formylated oligopeptides, all induced polarization in a time, temperature, and dose-dependent fashion. Nonchemotactic agents such as mitogens or phorbol myristate acetate did not induce polarization. At 37 degrees C, polarization was rapid (<1 min) and was inhibitable by cytochalasin B, sodium azide, or low temperature. A series of N-formylated oligopeptides were studied and their activity in inducing polarization correlated closely (r > 0.99) with their chemotactic activity. Of the entire population of circulating monocytes there is a subpopulation of cells that is capable of polarizing in response to chemotactic stimuli. The maximum percentage of monocytes which polarized to any chemotactic factor was approximately 60%. Furthermore, the combination of several chemotactic factors could not increase the percentage of polarized monocytes above the maximum obtained with an optimal dose of any single chemoattractant. The data also demonstrate that high doses of a chemoattractant can induce a state of cross-desensitization in monocytes that blocks the response of the cells to other types of chemotactic factors. These results support the concept that the monocytes that do respond to chemotactic stimuli are capable of responding to any of several attractants.

Blood Physiological Phenomena↗
PubMed1981

Inhibitors of monocyte responses to chemotaxins are present in human cancerous effusions and react with monoclonal antibodies to the P15(E) structural protein of retroviruses.

Individuals with cancer have previously been shown to have abnormal chemotactic responsiveness. Surgical removal of the tumor often resulted in normalization of monocyte function, which suggests that human neoplasms might inhibit monocyte chemotaxis by release of soluble mediators. We therefore examined the effects of cancerous effusions on monocyte polarization, i.e., the rapid change in monocyte morphology from round to a triangular "motile" configuration in response to chemoattractants. All 17 malignant effusions, representing 15 tumor types, inhibited monocyte polarization induced by the chemoattractant N-formyl-methionyl-leucyl-phenylalanine by 45-89% (mean 55.9 +/- 12.7%, P less than 0.01) in blinded assays. None of 17 benign effusions signigicantly inhibited polarization (0-15%, mean 6.2 +/- 4.2%). Dilutions of cancerous effusions as low as 1:200 produced inhibition that was time, temperature, and dose dependent . Monocyte polarization induced by activated serum or by chemotactic lymphokine was also blocked by cancerous effusions. The inhibitory activity affected the monocyte directly, and did not destroy the chemoattractant or block the polarization of granulocytes to chemotactic factors. High pressure liquid chromatography of five cancerous fluids revealed three peaks of inhibitory activity: greater than or equal to 200,000, 46,000 +/- 13,000, and 21,000 +/- 3,000 daltons. Fractionation of noncancerous effusions revealed only small amounts of the highest molecular weight inhibitory activity. The inhibitory activity in cancerous effusion was heat stable (56 degrees C, 30 min), trypsin sensitive, and could be absorbed by three different monoclonal antibodies reactive to P15(E), a structural component of type C retroviruses. In contrast, six monoclonal antibodies with other specificities had no effect on the inhibitors of polarization. This study demonstrates that human cancerous effusions contain novel proteins that are potent inhibitors of monocyte function and that are recognized by antibodies reactive to the P15(E) component of retroviruses. By producing such factors, tumor cells may subvert monocyte-mediated surveillance.

Adult↗
PubMed1981

Transmethylation reactions are required for initial morphologic and biochemical responses of human monocytes to chemoattractants.

Transmethylation reactions mediated by S-adenosyl-L-methionine are required for the chemotaxis of mononuclear leukocytes. It is not yet known, however, whether methylation reactions participate in the initial transduction of the chemotactic signals that lead to the alterations in cellular morphology required for chemotaxis and/or whether they are necessary for the subsequent biochemical events needed for sustained directed migration. We therefore investigated the effects of inhibiting methylation on 2 early responses induced by chemoattractant-receptor occupancy in human monocytes; the rapid morphologic alteration from round to a triangular, motile cell configuration (polarization) and the release of [3H]-arachidonic acid from membrane phospholipids. Both of these initial responses to 3 types of chemoattractants were severely depressed in monocytes treated with the methylation inhibitors, erythro-9-[2-hydroxy-3-nonyl]adenine (EHNA) plus adenosine and L-homocysteine or by 3-deazaadenosine plus L-homocysteine. These findings indicate that methylation reactions are required for the transduction of signals after chemotactic factor receptor occupancy in monocytes, which lead to a motile cellular configuration and release of arachidonic acid from membrane phospholipids. Activation of phospholipases with destruction of cell-associated phosphatidylinositol appears to account for the major source of arachidonic acid released by monocytes exposed to chemoattractants. This pathway for arachidonic acid release requires a transmethylation reaction since it is blocked by inhibitors of methylation.

Adenine↗
PubMed1981

The role of transmethylation reactions in regulating the binding of BCG-activated murine macrophages to neoplastic target cells.

The ability of BCG-activated macrophages from C57BL/6J mice to lyse neoplastic targets was depressed by inhibitors of methyltransferase reactions (10(-4) M adenosine, 10(-5) M EHNA, and 10(-4) M L-homocysteine or 10(-5) M DZA). Binding of P815 mastocytoma targets to BCG-activated macrophages, which has been shown to be a necessary event in cytolysis of those targets, was also inhibited by adenosine, EHNA, and L-homocysteine or by DZA at the above concentrations. Inhibition of binding was obtained when macrophages were pretreated with the inhibitors, whereas pretreatment of targets with the inhibitors did not alter binding. The inhibitors were not toxic to the macrophages, as judged by morphology and viability of the macrophage cultures as well as by ability of macrophages to bind antibody-coated P815 targets or to secrete plasminogen activator. The inhibitors, at concentrations that inhibited cytolysis and binding, also depressed one type of S-adenosyl-L-methionine-mediated methylation reaction (protein carboxy-O-methylation) in BCG macrophages. The data suggest that transmethylation reactions are essential for the ability of BCG activated murine macrophages to bind and, hence, to destroy P815 tumor cells.

Animals↗
PubMed1981

Differential anti-inflammatory effects of LPS in susceptible and resistant mouse strains.

Most mouse strains are highly susceptible to endotoxin (LPS) lethality and are responsive to LPS stimulation in vitro (e.g., B cell mitogenesis, macrophage activation). They are, however, capable of mounting only a small inflammatory response to LPS when it is injected i.p. The present study demonstrates that LPS is in fact a potent, anti-inflammatory agent in all of the five normally LPS susceptible strains tested. LPS was also anti-inflammatory in F1 hybrid mice from susceptible (C3HeB/FeJ) x-resistant (C3H/HeJ) parents. Anti-inflammatory effects of LPS in susceptible strains were achieved by either i.v. or i.p. treatment and were observed toward a variety of phlogistic stimuli including mitogens, C-activating substances, and nonspecific irritants. The most dramatic inhibitory effect of LPS was directed toward the accumulation of inflammatory macrophages. Kinetic studies indicated that the anti-inflammatory effect of a single dose of LPS persisted for at least 72 hr but was maximal when LPS was given simultaneously with the inflammatory stimulus. In contrast to normal mice, two mutant, LPS resistant strains (C3H/HeJ and C57BL10/ScCR) responded to increasing doses of LPS i.p. with a progressively increasing influx of inflammatory cells. In addition, in resistant strains, LPS often enhanced and never depressed the inflammatory response to other phlogistic agents. These studies demonstrate that the genetic regulation of the inflammatory responses to LPS also controls the anti-inflammatory effects of LPS. These responses may be another relevant parameter in determining strain susceptibility to LPS lethality.

Animals↗