Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The intracellular ratio of adenosine 3',5'-cyclic monophosphate (cyclic AMP) to guanosine 3',5'-cyclic monophosphate (cyclic GMP) may control the developmental pathway followed by antibody-forming cell (AFC) precursors. The evidence for this is derived from several different types of experiments. First lipopolysaccharide (LPS) which is mitogenic for B lymphocytes, stimulates rapid, transient changes in intracellular levels of cyclic GMP but not cyclic AMP when added to mouse spleen cultures. Cyclic GMP itself stimulates DNA synthesis in these cultures, suggesting that the intracellular changes in cyclic GMP levels are involved in the mitogenic signal delivered by LPS to cells. The absolute amounts of cyclic nucleotides may vary widely in different cells under various conditions, however, the intracellular ratio of cyclic AMP to cyclic GMP is always high in nondividing cells and low in dividing cells. AFC precursors appear to respond to antigen in the absence of T-cell activity by inactivation (1-7). In the response to antigen in the presence of specific T cells, precursor cells proliferate and mature to AFC. Raising intracellular levels of cyclic AMP inhibits cell proliferation and leads to precursor cell inactivation (14, 15). It is suggested that the interaction of antigen with immunoglobulin receptors on the surface of precursors cells leads to the stimulation of adenylate cyclase activity and initiates the inactivation pathway. Since cyclic GMP stimulates immune responses in T-cell-depleted cultures (14, 15) and increasing cyclic GMP levels appear to be involved in the delivery of a mitogenic signal to cells, it is suggested that T-helper cells deliver a signal to precursor cells via the stimulation of guanylate cyclase to initiate the inductive pathway. It is suggested that it is the intracellular ratio of cyclic AMP to cyclic GMP that regulates the fate of precursor cells, not the absolute level of one cyclic nucleotide.
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PMID:The influence of intracellular levels of cyclic nucleotides on cell proliferation and the induction of antibody synthesis. 16 86

BALB/c spleen cells (5 x 10(6)) were cultured in 1 ml of serum-free RPMI 1640 medium for 3 days in order to examine the effect of cholera enterotoxin (CN) and its spontaneously formed toxoid (CD) on lymphocyte stimulation. Stimulation was assessed after addition of [3H] thymidine for the last 16 hours of culture. One microgram of CN per culture markedly reduced the baseline of [3H] thymidine incorporation and the stimulation due to phytohaemagglutinin (PHA), concanavalin A (con A) and bacterial lipopolysaccharide (LPS). One microgram of CD diminished the base-line to half, abolished the response to PHA, reduced the response to con A and had very little effect on the LPS-induced stimulation. One-tenth the amount (0-1 mug) of both CN and CD affected only the PHA reaction. A secondary response to haemocyanin in vitro was not decreased by this lower dose. The effect of 1 mug on CN on the LPS response could be reduced by pretreatment of the cells with CD, whereas the PHA reaction remained markedly diminished. Dibutyryl-cAMP added to culture tubes had a similar effect ot 1 mug of CN, affecting the PHA response much more than the response to LPS. Spleen cells of mice immunized with CD gave a significant proliferative response to both 1 mug of CD and CN. The results are interpreted as indicating a strong inhibitory effect of CN mediated by accumulation of intracellular cAMP. CD-immunized cells contain specific receptors for both CD and CN which probably compete with the sites responsible for adenylate cyclase stimulation by CN.
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PMID:The differential effect of cholera toxin on the lymphocyte stimulation induced by various mitogens. 16 98

Lipopolysaccharides (endotoxins) from Escherichia coli, Serratia marcesens and Salmonella typhosa stimulated steroid production in Y-1 adrenal tumor cells in culture with a latent period of 3-4 h. Lipid A, derived from Escherichia coli lipopolysaccharide, also stimulated steroidogenesis. Lipopolysaccharides and lipid A also stimulate adenylate cyclase activity and cause rounding of the cells. In contrast, lipopolysaccharides do not stimulate steroidogenesis in receptor-deficient adrenal tumor cells (OS-3) or Leydig tumor cells (I-10). This tends to rule out contamination by enterotoxin to which these lines respond. Although both hormone and lipopolysaccharide responses are lost in these lines, there was no interaction between these sites as judged by the failure of lipopolysaccharides to block, during their latency, the response to corticotropin in Y-1 cells. The possibility that the lipopolysaccharide effect is one on membrane conformation is discussed.
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PMID:Endotoxic lipopolysaccharides stimulate steroidogenesis and adenylate cyclase in adrenal tumor cells. 17 55

The adenyl cyclase-activating enterotoxin of Vibrio cholerae was shown to contain two types of subunit: six smaller units (L) that are responsible for the binding to cell membrane receptors and a larger unit (H) that mediates the toxic action. The receptor was identified as the ganglioside GM1 (galactosyl-N-acetylgalactosaminyl [sialosyl] lactosyl ceramide), and the results suggested that penetration of the toxin molecule into the membrane follows the rapid binding to GM1. The relationship of these findings to the mechanism of protective immunity, which is mediated by antibodies to the enterotoxin as well as those to the cell wall lipopolysaccharide of V. cholerae, was investigated. The antitoxic antibodies were directed mainly against the L subunit and protected by preventing binding of toxin; the antibacterial antibodies probably interfered with adhesion of V. cholerae to the intestine. The finding that the immune responses to toxin and bacteria act synergistically in protection against experimental cholera indicates that an improved cholera vaccine should contain both toxoid and lipopolysaccharide as antigens. In the rabbit, either subcutaneous or enteral immunization gave rise to intestinal synthesis of specific antibodies to V. cholerae.
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PMID:Mechanisms of disease and immunity in cholera: a review. 19 73

Endotoxin lipopolysaccharide (LPS) from Acinetobacter 199A induced aggregation of blood platelets from immune adherence-positive species (rat, rabbit) but not from immune adherence-negative species such as pig and man. Aggregation occurred in 2 phases: the first was not accompanied by secretion of platelet constituents, was apparently a consequence of C3 activation, and was selectively inhibited by EGTA. The second phase of aggregation was associated with secretion of platelet granule contents, and with a lesser amount of cytoplasmic leakage. Secondary aggregation was abolished by the sulphydryl alkylating agent N-ethylmaleimide, and by agents which increased the level of cyclic AMP in platelets, such as prostaglandin E1 (a stimulator of adenylate cyclase) and methyl xanthines (inhibitors of phosphodiesterase). Secondary aggregation was partly inhibited by agents which block platelet prostaglandin biosynthesis (e.g. aspirin, indomethacin). Primary aggregation was unaffected by these inhibitors at concentrations which blocked secondary aggregation.
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PMID:Endotoxin-induced platelet aggregation and secretion. I. Morphological changes and pharmacological effects. 20 8

The effects of Escherichia coli lipopolysaccharide (LPS) on adenylate cyclase have been tested using renal tubular membranes and renal glomeruli isolated from rats. E. Coli LPS did not stimulate glomerular and tubular basal adenylate cyclase activity whereas it was an activator in the presence of fluoride. The effect of E. Coli LPS was immediate but was greater after 20 min preincubation. Maximum stimulation of both glomerular and tubular fluoride sensitive adenylate cyclase occurred at 125 microgram/ml of E. Coli LPS with an apparent Km (dose corresponding to 50% of maximum stimulation) of 30 microgram/ml. Above 125 microgram/ml there was a decrease in adenylate cyclase activity. E. Coli LPS produced an increase in the maximum velocity of both enzymes but did not affect their affinity for adenosine triphosphate. E. Coli LPS did not potentiate the effect of parathyroid hormone on glomerular and tubular adenylate cyclase. The lipid A moiety which is common to all LPS whatever the original strain gave results similar to those obtained with the entire LPS. This effect was specific and did not depend on the phospholipidic structure in general since no activation was obtained in the presence of phosphatidylserine.
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PMID:Effects of Escherichia coli lipopolysaccharide on renal glomerular and tubular adenylate cyclase. 33 75

The capability of elevated intracellular cyclic AMP concentration to activate IL-1 gene expression and protein production was examined in human peripheral blood monocytes. In accordance with previous studies it was observed that the transiently elevated cyclic AMP (induced either with prostaglandin E2 or with the direct adenylate cyclase activator, forskolin) was not a sufficient signal to activate IL-1 production. However, if the degradation of cyclic AMP was inhibited with isobutyl-methyl-xanthine (IBMX), IL-1 production was strongly activated. This prostaglandin E2 plus IBMX effect could also be mimicked with high concentrations of the cell permeant structural cyclic AMP analogue, dibutyryl cyclic AMP. The cyclic AMP-induced IL-1 production differed in some aspects from the bacterial lipopolysaccharide-induced IL-1 production: (1) the kinetics of both IL-1 gene expression and protein production was much slower; (2) the IL-1 beta gene expression was superinducible by inhibiting the protein synthesis with cycloheximide. Thus these data suggest that prolonged elevation of cyclic AMP is alone a sufficient signal to activate IL-1 production.
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PMID:Prolonged elevation of intracellular cyclic AMP activates interleukin-1 production in human peripheral blood monocytes. 131 Aug 16

We previously showed that human immunoglobulin preparation for intravenous use (IGIV) suppresses the in vitro production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) by rabbit peritoneal exudate cells (PEC) stimulated with lipopolysaccharide (LPS). In this study we investigated the mechanism of the suppression. IGIV treated at pH4 (pH4-G) was used as IGIV. Fc fragments of pH4-G, as well as untreated pH4-G, suppressed TNF-alpha and IL-1 production by rabbit PEC stimulated with LPS. The interaction of pH4-G with PEC also resulted in generation of cyclic adenosine 3':5'-monophosphate (cAMP), known to be an intracellular second messenger. N6, 2'-0-dibutyryl cAMP (BtcAMP), a lipid-soluble derivative of cAMP, and cholera toxin (CT), an adenylate cyclase activating agent, also suppressed the production of TNF-alpha and IL-1. Further N-[2-(methylamino) ethyl]-5-isoquinolinesulphonamide dihydrochloride (H-8), an inhibitor of cAMP-dependent protein kinases, abrogated the suppression by pH4-G of the productions. These results indicate that the binding of IGIV to PEC via Fc gamma receptors (Fc gamma R) induces the elevation of intracellular cAMP levels, resulting in the suppression of LPS-induced TNF-alpha and IL-1 productions.
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PMID:Human immunoglobulin preparation for intravenous use induces elevation of cellular cyclic adenosine 3':5'-monophosphate levels, resulting in suppression of tumour necrosis factor alpha and interleukin-1 production. 164 26

Treatment of murine peritoneal macrophages with 100 nM prostaglandin E2 (PGE2) produced a rapid biphasic increase in intracellular cAMP that was maximal at 1 min and sustained through 20 min. Pretreatment of macrophages with 100 ng/ml of lipopolysaccharide (LPS) for 60 min prior to PGE2 decreased the magnitude of cAMP elevation by 50%, accelerated the decrease of cAMP to basal levels, and abolished the sustained phase of cAMP elevation. The effect of LPS was concentration-dependent, with maximal effect at 10 ng/ml in cells incubated in the presence of 5% fetal calf serum and at 1 microgram/ml in the absence of fetal calf serum. LPS also inhibited cAMP accumulation in cells treated with 100 microM forskolin, but the decrease was about half that seen in cells treated with PGE2. LPS concentrations that inhibited cAMP accumulation produced a 30% increase in soluble low Km cAMP phosphodiesterase activity while having no effect on particulate phosphodiesterase activity. The nonspecific phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, as well as the more specific inhibitors rolipram and Ro-20-1724 were effective in inhibiting soluble phosphodiesterase activity in vitro, producing synergistic elevation of cAMP in PGE2-treated cells, and blocking the ability of LPS to inhibit accumulation of cAMP. Separation of the phosphodiesterase isoforms in the soluble fraction by DEAE chromatography indicated that LPS activated a low Km cAMP phosphodiesterase. The enzyme(s) present in this peak could be activated 6-fold by cGMP and were potently inhibited by low micromolar concentrations of Ro-20-1724 and rolipram. Using both membranes from LPS-treated cells and membranes incubated with LPS, no decrease in adenylylcyclase activity could be attributed to LPS. Although effects of LPS on the rate of synthesis of cAMP cannot be excluded, the present evidence is most consistent with a role for phosphodiesterase activation in the inhibitory effects of LPS on cAMP accumulation in murine peritoneal macrophages.
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PMID:Inhibition of prostaglandin E2-stimulated cAMP accumulation by lipopolysaccharide in murine peritoneal macrophages. 164 47

The macrophage activation for tumor cytotoxicity with lipopolysaccharide (LPS) was remarkably inhibited by adding indomethacin (5 x 10(-6) M) or 10mM LiCl which is known to inhibit adenylate cyclase activity. The tumor cytotoxicity of macrophages inhibited with these agents was recovered by adding dibutyryl cyclic adenosine 3',5'-monophosphate (cAMP) (10(-4) or 10(-5) M) and furthermore tumor cell killing activity was augmented as compared with LPS-activated macrophage. Macrophages showed a 5 to 6 times increased intracellular cAMP concentration over the control within 30 min when incubated with LPS. However, the increased intracellular cAMP concentration was decreased by adding LiCl (10 mM). Thus, these findings indicate that there is an important relation between intracellular cAMP concentration and the mechanism of macrophage activation. One can then conclude that at least the initial enhancement of intracellular cAMP was important for tumor cell killing as a signal transmission in macrophage activated by LPS.
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PMID:Elevation of intracellular cyclic adenosine 3',5'-monophosphate levels in macrophages activated with lipopolysaccharide for tumor cell killing. 165 23


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