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R G Coffey

Publications and source records attributed to R G Coffey.

At least 37 records · Page 2Linked to original sources
PubMed1989

Acute effects of phorbol esters on receptor-mediated IP3, cAMP, and progesterone levels in rat granulosa cells.

Luteinizing hormone (LH) stimulates the formation of adenosine 3',5'-cyclic monophosphate (cAMP) and inositol trisphosphate (IP3) in rat granulosa cells. This report describes the effects of protein kinase C activators on second messenger generation in isolated rat granulosa cells. The protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA) completely inhibited LH-stimulated inositol phosphate accumulation. The inhibitory effects of TPA were rapid (5-15 min) and concentration dependent with 50 nM TPA producing maximally inhibitory effects. However 30-min incubations with 10-100 nM TPA had no effect on LH-stimulated cAMP or progesterone levels. The inhibitory effect of TPA could not be overcome by high concentrations of LH. TPA also inhibited gonadotropin-releasing hormone-stimulated phospholipase C activity, although to a much lesser extent. Increased inositol phosphate degradation and reduced inositol phospholipid synthesis were unlikely explanations for the effects of TPA. The results indicate that phorbol esters modulate the inositol phospholipid-phospholipase C transmembrane signaling system in rat granulosa cells. The results suggest that phorbol esters may alter the coupling of the hormone receptor complex to phospholipase C.

Animals↗
PubMed1988

Stimulation of guanylate cyclase activity and reduction of adenylate cyclase activity by granulocyte-macrophage colony-stimulating factor in human blood neutrophils.

Human neutrophils were incubated with granulocyte-macrophage (GM)-CSF and examined for changes in second messenger systems. Twofold increases in cGMP but not cAMP were measured after 5 to 20 min with 100 U/ml GM-CSF. Guanylate cyclase activities in membrane and cytosol fractions were increased to the same extent whether measured in the presence of Mg2+ or Mn2+, or in the cytosol with Mg2+ + N-methyl-N'-nitro-N-nitroso-guanidine. Kinetic studies of the cytosol enzyme showed no changes in the Km values for Mg2+ and Mn2+dependent guanylate cyclase activities (0.91 and 0.022 mM, respectively), whereas Vm values were increased after treating intact cells with GM-CSF. Two peaks of guanylate cyclase activity were observed, one at 10 and another at 60 min after adding 100 U/ml GM-CSF, whereas only one peak at 5 min occurred with 1 U/ml. Adenylate cyclase activity was reduced by nearly 50% after adding 100 U/ml GM-CSF for 10 to 30 min. These effects were also seen in the presence of several hormonal and nonhormonal adenylate cyclase stimulators. In contrast, small increases in adenylate cyclase activity occurred after adding 1 U/ml GM-CSF. In experiments to examine the pathway of guanylate cyclase activation by GM-CSF, we observed no changes in inositol phosphates, intracellular calcium ion, or cytosolic protein kinase C. The augmentation of chemotactic peptide-induced superoxide production by GM-CSF concentrations, may be related to the effects of the higher levels of GM-CSF to stimulate late increases in guanylate cyclase or decreases in adenylate cyclase.

Adenylyl Cyclases↗
PubMed1987

Interleukin II increases cyclic GMP levels in immature thymocytes and mitogen-primed T-lymphocytes.

Interleukin II, also called T-cell growth factor, induces proliferation of immature peanut agglutinin positive murine thymocytes (PNA+) and renders them responsive to concanavalin A. It also, as shown by others, provides a second signal to induce phytohemagglutinin-primed mature human T-lymphocytes to enter DNA synthesis. Both actions are associated with early increases (2-60 min) in cellular levels of cyclic 3'5' guanosine monophosphate (cyclic GMP) without change of cyclic 3'5' adenosine monophosphate (cyclic AMP) levels. Cyclic GMP is postulated to represent part of the mechanism by which IL-2 acts.

Animals↗
PubMed1986

Phosphatidylserine and phorbol myristate acetate stimulation of human lymphocyte guanylate cyclase.

Guanylate cyclase activities of human lymphocyte membrane and cytosol preparations are stimulated up to three-fold by the direct addition of phosphatidylserine. Phorbol 12-myristate 13-acetate (PMA) greatly augments the effect of phosphatidylserine, but has only a small effect when added alone. Stimulation involves an increase in Vmax, with no change in Km. Inhibitor studies suggest that stimulation may be mediated by protein kinase C, but not by phospholipase or lipoxygenase.

Adult↗
PubMed1986

Stimulatory effects of muramyl dipeptide and its butyl ester derivative on the proliferation and activation of macrophages in vitro.

Muramyl dipeptide (MDP) and the butyl ester derivative, N-acetylmuramyl-L-alanyl-D-glutamine-alpha-n-butyl ester (MDP[Gln]OnBu), were shown to induce the in vitro proliferation of oil-induced guinea pig peritoneal exudate cells (PEC). Both agents induced 10-20 fold increases in tritiated thymidine incorporation in PEC cultures. The maximal effects occurred in 72 h cultures stimulated with either 0.1 microgram MDP or 10 micrograms MDP[Gln]OnBu. The mitogenic effects of MDP appeared to be mediated by a macrophage product detected in the supernatants of MDP-stimulated cultures. Supernatants of MDP- or MDP[Gln]OnBu-stimulated PEC cultures were also inhibitory to normal fibroblast growth and cytotoxic to L929 tumor cells. These results indicated that these agents may stimulate macrophages by modulating secretory functions. In addition, either peptidoglycan was capable of activating bactericidal activity in in vitro macrophage cultures. Initial studies of possible mechanisms of action revealed an early increase in the level of cyclic GMP. The possible role of cyclic GMP in mediating the stimulation of macrophage secretory processes is discussed.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1985

Neurotransmitters, hormones, and cyclic nucleotides in lymphocyte regulation.

Lymphocytes bear receptors for a wide variety of neurotransmitters, hormones, and other mediators that influence cellular functions in part through alterations in cyclic nucleotide metabolism. A sizable list of agents that increase cyclic AMP levels now includes adenosine (Ra), epinephrine (beta), glucocorticosteroids, histamine (H2), prostaglandins (A, E), and bacterial products (lipopolysaccharide, cholera toxin). We have found no evidence for lymphocyte cyclic AMP responses to adenosine Ri agonists or to enkephalins. Present data suggest a role for cyclic AMP in promoting the differentiation of immature lymphocytes, whereas elevated cyclic AMP levels are associated with inhibition of mature, differentiated lymphocyte functions. Opposing these effects of cyclic AMP are those of cyclic GMP and an expanding collection of compounds that increase its levels: acetylcholine (muscarinic), ascorbate, calcium ionophore, hydroperoxides of arachidonic acid, hypoxanthine derivatives, interleukin 1, serotonin, thymic hormones, and plant lectin mitogens. The biochemical pathways mediating cyclic GMP increases and mechanisms by which cyclic GMP may enhance immunological responses are being intensively studied.

Acetylcholine↗
PubMed1984

Selective inhibition by NPT 15392 of lymphocyte cyclic GMP phosphodiesterase.

Cyclic nucleotide phosphodiesterases were measured in mouse spleen and thymus lymphocyte membranes and soluble fractions and in extracts of canine tracheal smooth muscle. The immunostimulant erythro-9(2-hydroxy,3-nonyl) hypoxanthine (NPT 15392) was found to be a potent and relatively selective inhibitor of mouse lymphocyte cyclic GMP phosphodiesterase, with IC50 values 15-180 times greater for cyclic AMP than cyclic GMP phosphodiesterases. The greatest inhibition by NPT 15392 was found using 10 microM substrate, and inhibition was greater in membrane than soluble forms of phosphodiesterase. Spleen soluble enzymes were separated by DEAE Bio-Gel A column into six peaks. A major form of cyclic GMP phosphodiesterase was inhibited effectively by NPT 15392 in a competitive manner (Ki = 50 microM). Cyclic AMP phosphodiesterase activity in the same fraction, but representing only a fifth of the total activity, was also inhibited (Ki = 70 microM). Other soluble enzymes were not affected significantly. Membrane bound enzymes were solubilized and separated into three peaks. One with high affinity for cyclic GMP was strongly inhibited (Ki = 10 microM) by NPT 15392. Inosine and isoprinosine were one-tenth to one-hundredth as effective as NPT 15392 as cyclic nucleotide phosphodiesterase inhibitors. Incubation of mouse splenic lymphocytes with NPT 15392 for 48 hr resulted in enzymes with altered responsiveness to the drug in broken cell assays: inhibition of cyclic GMP hydrolysis was enhanced while that of cyclic AMP hydrolysis was decreased. Among three separated and characterized forms of tracheal smooth muscle phosphodiesterase, NPT 15392 inhibited the low Km cyclic GMP phosphodiesterase 6-10 times more effectively than the other enzymes. These data suggest that the immunopharmacologic activities of NPT 15392 may include specific cyclic GMP phosphodiesterase inhibition as one of several possible mechanisms.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1982

Effect of phorbol myristate acetate and a lymphokine on cyclic 3':5'-guanosine monophosphate levels and proliferation of macrophages.

The tumor promoter phorbol myristate acetate (PMA) was compared to a lymphokine macrophage mitogenic factor (MMF) for its ability to induce replication of guinea pig peritoneal and alveolar macrophages. Like MMF, PMA induces DNA synthesis of both cell populations with peak thymidine incorporation at 72 hr of culture. Optimal concentrations of PMA for the peritoneal and alveolar cells were 1.6 x 10(-7) and 1.6 x 10(-9) M, respectively. The magnitude of the effect is slightly less than MMF but greater than that of phytohemagglutinin or concanavalin A. Indomethacin added to inhibit prostaglandin synthesis potentiates the effects of MMF but has little effect on the actions of PMA and the other mitogens. Potentiation by indomethacin of the effects of PMA on the peritoneal cell was observed only at the suboptimal concentration of PMA (1.6 x 10(-8) M). By adherence criteria and density gradient fractionation, the cell responding to PMA is confirmed to be the macrophage. Cell counts and nuclear radioautography confirm that replication in this system is reasonably well reflected by thymidine incorporation. The effects of PMA and its analogs as macrophage mitogens correlate with their tumor-promoting effects. Both PMA and MMF induce early increases in peritoneal macrophage levels of cyclic 3':5'-guanosine monophosphate without changes in the levels of cycles 3':5'-adenosine monophosphate. These studies indicate that PMA offers a useful probe of macrophage function.

Animals↗
PubMed1980

Effects of BM 12,531 (azimexon) on in vitro lymphocyte and macrophage proliferation.

BM 12,531 (azimexon) is an experimental immunomodulating agent which augments cellular immune responses in vivo. This study indicates that BM 12,531, while not directly mitogenic for human peripheral blood lymphocytes nor guinea pig peritoneal macrophages, potentiates the proliferative effects of phytohemagglutinin and a lymphokine, respectively. The optimal effects (0.001--0.01 microgram/ml) are somewhat greater in magnitude than those of levamisole. Unlike levamisole, BM 12,531 has no effect on cyclic 3',5' GMP levels or on guanylate cyclase activity of lymphocytes. The data suggest that both the thymus-derived lymphocyte and the monocyte-derived macrophage are cell targets of BM 12,531 action at concentrations achievable in vivo.

Adjuvants, Immunologic↗
PubMed1978

Thymopoietin enhances the allogeneic response and cyclic GMP levels of mouse peripheral, thymus-derived lymphocytes.

The action of the purified thymic factor, thymopoietin, on populations of post-thymic lymphocytes has been studied. Thymopoietin, at concentrations as low as 1.5 ng/ml, uniquely enhanced the proliferative response of peripheral T cells from lymph node and spleen to allogeneic stimulation. Enhancement of the allogeneic response (MLR) was not produced by several polypeptide hormones, including insulin, ACTH, HCG, or Ubiquitin. Treatment of spleen cells with anti-Thy-1 antiserum almost completely abolished the MLR. Thymopoietin's stimulatory effects could not reverse this. Thymopoietin treatment of Thy-1+-enriched spleen cell populations enhanced the MLR even when thymopoietin was removed as early as 2 min after incubation with responding cells. The interaction of thymopoietin with peripheral Thy-1+ cell populations produced a rapid and transient rise in cyclic GMP levels and slightly decreased cyclic AMP levels. These results suggest that thymopoietin interacts with one or more Thy-1+ subpopulations and that this interaction involves early changes in cyclic nucleotide metabolism.

Animals↗