• The Korean Journal of Physiology and Pharmacology
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• v.1 no.1
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• pp.97-105
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• 1997

The regulatory role of cyclic nucleotides in the expression of neutrophil responses has been examined. fMLP-stimulated superoxide production in neutrophils was inhibited by dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), histamine, adenosine + theophylline, cAMP elevating agents, and 8-bromoguanosine 3' ,5' -cyclic monophosphate (8-BrcGMP) and sodium nitroprusside, cGMP elevating agents. Staurosporine, a protein kinase C inhibitor, genistein, a protein tyrosine kinase inhibitor and chlorpromazine, a calmodulin inhibitor, inhibited superoxide production by fMLP, but they did not further affect the action of DBcAMP on the stimulatory action of fMLP. DBcAMP, histamine, adenosine+theophylline and genistein inhibited myeloperoxidease release evoked by fMLP, whereas BrcGMP, sodium nitroprusside and staurosporine did not affect it. The elevation of $[Ca^{2+}]_i$ evoked by fMLP was inhibited by genistein and chlorpromazine but was not affected by staurosporine. DBcAMP exerted little effect on the initial peak in $[Ca^{2+}]_i$ response to fMLP but effectively inhibited the sustained rise. On the other hand, BrcGMP significantly inhibited both phases. fMLP-induced $Mn^{2+}$ influx was inhibited by either DBcAMP or BrcGMP. These results suggest that fMLP-stimulated neutrophil responses may be regulated by cAMP more than cGMP. cAMP and cGMP appear not affect stimulated responses by direct protein kinase C activation. Their regulatory action on the stimulated neutrophil responses may be not influenced by other activation processes.

• Animal cells and systems
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• v.10 no.4
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• pp.237-241
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• 2006

Chemotactic behavior is essential for the survival of animals. However, the mechanism by which animals carry out chemotaxis is poorly understood. To explore the biochemical events underlying chemotaxis, we isolated C. elegans mutants that displayed abnormal chemotactic responses to cAMP, a strong attractant for C. elegans. Based on their responses to other chemoattractants, the mutant animals could be classified into five groups: (1) animals with defective chemotaxis to cAMP only; (2) animals with defective chemotaxis to both cAMP and cGMP; (3) animals with defective chemotaxis to water-soluble attractants; (4) animals with defective chemotaxis to both water-soluble and volatile attractants; and (5) animals with enhanced chemotactic responses. We expect that analyses of these mutants will help understand the molecular mechanisms underlying chemotaxis in C. elegans.

• YAKHAK HOEJI
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• v.51 no.1
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• pp.35-43
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• 2007

To investigate the immunomodulatory roles of cyclic AMP (CAMP) on macrophage- and T lymphocyte-mediated immune responses, CAMP elevating agents were employed and carefully re-examined under the activation conditions of the cells. Various inhibitors tested dose-dependently blocked tumor necrosis factor (TNF)-${\alpha}$ production with IC$_{50}$ values ranged from 0.04 to 300 ${\mu}$M. Of the inhibitors, cAMP-elevating agents showed lower cytotoxicity assessed by lactate dehydrogenase (LDH) release, suggesting less toxic and more selective. In particular co-treatment of dbcAMP with a protein kinase C inhibitor staurosporine displayed the synergistic inhibition of TNF-${\alpha}$ production. The modulatory effect of dbcAMP on TNF-${\alpha}$ and nitric oxide (NO) was significantly affected by treatment time of dbcAMP. Thus, post-treatment of dbcAMP (three hours before LPS) abrogated dbcAMP's inhibitory activity and rather enhanced TNF-${\alpha}$ level up to 60%. In contrast, additional NO production was shown at the co-treatment of dbcAMP with LPS. Unlike simultaneous treatment of phorbol 12-myristate 13-acetate (PMA) and interferon (IFN)-${\gamma}$co-treatment, the combination of dbcAMP with other NO-inducing stimuli did not show drastic overproduction of NO. cAMP elevating agents also diminished splenocyte proliferation stimulated by concanavalin (Con) A, phytohemaglutinin A (PHA) and lipopolysaccharide (LPS). In addition, dbcAMP but not rolipram strongly suppressed CD8$^+$ T cells (CTLL-2). Finally, cAMP elevating agents were differentially involved in regulating CD98-mediated cell-cell adhesion. Thus, dbcAMP and rolipram significantly enhanced the cell-cell adhesion, whereas forskolin blocked. Therefore, our results suggest that CAMP elevating agents participate in various immune responses mediated by macrophages and T cells with a different fashion depending on cellular environments and activation signals.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.442-446
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• 2010

Adenosine 3',5'-cyclic monophosphate (cAMP) is a second messenger responsible for a multitude of cellular responses. In this study, we utilized $\beta$-cyclodextrin ($\beta$-CD) as an artificial receptor with a hydrophobic cavity to elucidate the inclusion kinetics of cAMP in a hydrophobic environment using the ultrasonic relaxation method. The results revealed that the interaction of cAMP with $\beta$-CD followed a single relaxation curve as a result of host-guest interactions. The inclusion of cAMP into the $\beta$-CD cavity was found to be a diffusion-controlled reaction. The dissociation of cAMP from the $\beta$-CD cavity was slower than that of adenosine 5'-monophosphate (AMP). The syn and anti glycosyl conformations of adenine nucleotides are considered to play an important role in formation of the inclusion complex. Taken together, our findings indicate that hydrophobic interactions are involved in the inclusion complex formation of cAMP with $\beta$-CD and provide insight into the interactions of cAMP with cAMP-binding proteins.

• The Korean Journal of Pharmacology
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• v.31 no.3
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• pp.333-344
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• 1995

The effects of adenosine and $N^6-cyclopentyladenosine$ (CPA) on superoxide production, myeloperoxidase release and $Ca^{2+}$ mobilization stimulated by fMLP in neutrophils were investigated. The effects were also observed on the stimulatory actions of C5a and PMA and the responses in lipopolysaccharide-primed neutrophils. In addition, the involvement of cAMP in the inhibitory action of adenosine was examined. The fMLP-stimulated neutrophil respiratory burst, degranulation and intracellular $Ca^{2+}$ mobilization may be regulated by activation of adenosine receptors. Adenosine may not affect the stimulated neutrophil responses due to activation of protein kinase C. fMLP-stimulated respiratory burst in lipopolysaccharide-primed neutrophils may be less sensitive to adenosine, compared with nonprimed cells. The inhibitory effect of theophylline in the presence of adenosine on neutrophil responses appears to be ascribed to accumulation of intracellular cAMP.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.207.2-207.2
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• 2003

cAMP acts as a second messenger in the functional responses of various cells to hormones, cytokines and other agents. In turn, this nucleotide also modulates the signal transduction processes regulated by a range of cytokines and growth factors. The intracellular level of cAMP is regulated by a G protein coupled adenylyl cyclase and degradation is mediated by the phosphodiesterases (PDEs), a superfamily of enzymes that catalyze the hydrolysis of cAMP. (omitted)

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.1
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• pp.9-14
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• 2009

We cultured canine kidney(MDCK) cells stably expressing aquaporin-2(AQP2) on collagen-coated permeable membrane filters and examined the effect of extracellular ATP on arginine vasopressin(AVP)-stimulated fluid transport and cAMP production. Exposure of cell monolayers to basolateral AVP resulted in stimulation of apical to basolateral net fluid transport driven by osmotic gradient which was formed by addition of 500 mM mannitol to basolateral bathing solution. Pre-exposure of the basolateral surface of cell monolayers to ATP(100 ${\mu}M$) for 30 min significantly inhibited the AVP-stimulated net fluid transport. In these cells, AVP-stimulated cAMP production was suppressed as well. Profile of the effects of different nucleotides suggested that the $P2Y_2$ receptor is involved in the action of ATP. ATP inhibited the effect of isoproterenol as well, but not that of forskolin to stimulate cAMP production. The inhibitory effect of ATP on AVP-stimulated fluid movement was attenuated by a protein kinase C inhibitor, calphostin C or pertussis toxin. These results suggest that prolonged activation of the P2 receptors inhibits AVP-stimulated fluid transport and cAMP responses in AQP2 transfected MDCK cells. Depressed responsiveness of the adenylyl cyclase by PKC-mediated modification of the pertussis-toxin sensitive $G_i$ protein seems to be the underlyihng mechanism.

• The Korean Journal of Physiology and Pharmacology
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• v.11 no.5
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• pp.175-182
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• 2007

Members of prostaglandin(PG) E-series elicit cellular effects mainly through adenylyl cyclase-cAMP signaling. The role of $PGE_2$-induced increase in cAMP has been shown to be compartmentalized in the cardiac myocytes: $PGE_2$-induced increase of cAMP is not involved in the control of cardiomyocytic contraction. The purpose of the present study was to define the effect of $PGE_1$ on the cGMP levels and the role of $PGE_1$ in the atrial secretory function. Experiments were performed in perfused beating rabbit atria and atrial contractile responses, cGMP and cAMP efflux, and atrial natriuretic peptide(ANP) secretion were measured. $PGE_1$ increased cGMP as well as cAMP efflux concentration in a concentration-dependent manner, however, no significant changes in atrial secretory responses were observed(with $1.0{\mu}M\;PGE_1$; for cGMP, $144.76{\pm}37.5%$, n=11 versus $-16.81{\pm}4.76%$, n=6, control, p<0.01; for cAMP, $187.60{\pm}41.52%$, n=11 versus $7.38{\pm}19.44%$, n=6, control, p<0.01). $PGE_1$ decreased atrial dynamics slightly but transiently, whereas $PGE_2$ showed similar effects but with lower potency. Isoproterenol increased atrial cAMP efflux(with 2.0 nM; $145.71{\pm}41.89$, n=5 versus $7.38{\pm}19.44%$, n=6, control, p<0.05) and mechanical dynamics and decreased ANP secretion. The $PGE_1$-induced increase in cGMP efflux showed a bell-shaped concentration-response curve. $PGE_1$-induced increase of cGMP efflux was not observed in the presence of L-NAME, an inhibitor of nitric oxide(NO) synthase, or ODQ, an inhibitor of NO-sensitive guanylyl cyclase. L-NAME and ODQ showed no significant effect on the $PGE_1$-induced transient decrease of atrial dynamics. These data indicate that $PGE_1$ increases cGMP levels via NO-soluble GC signaling in the cardiac atrium and also show that $PGE_1$-induced increases in cGMP and cAMP levels are not involved in the regulation of atrial secretory and contractile functions.

• The Journal of Internal Korean Medicine
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• v.26 no.2
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• pp.398-408
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• 2005

Objective: Graves' disease encompasses hyperthyroidism and diffused goiter associated with auto-antibodies to the thyroid stimulating hormone(TSH) receptors. In clinical environment, treatments of Graves' disease have many side effects such as recurrence and hypothyroidism. We've studied the effects of Sipyukmiyukieum on DNA synthesis, cAMP synthesis, and MHC-class II expression of FRTL-5 thyroid cells were studied. Methods: DNA synthesis was investigated by using BrdU staining and cAMP synthesis by ELISA kit, and expression of $interferon-{\gamma}$ activated MHC class II by Flow cytometer. Results: After introduction of Sipyukmiyukieum, significant inhibition of DNA synthesis. cAMP synthesis, and expression of $interferon-{\gamma}$ activated MHC class II of FRTL-5 thyroid cells was observed. Conclusions: Judging from these results, Sipyukmiyukieum has potential as a potent herbal treatment for inhibiting the enlargement of goiter, synthesis of abnormal thyroidal hormones, and autoimmuine responses of Graves' disease.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.3
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• pp.189-195
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• 2021

Fluoxetine (FLX), a selective serotonin reuptake inhibitor antidepressant, exhibits various other mechanisms of action in numerous cell types and has been shown to induce cell death in cancer cells, paving the way for its potential use in cancer therapy. The aim of this study was to determine the off-target effects of the anti-depressant drug FLX, on the human ovarian granulosa tumor COV434 cells stimulated by forskolin (FSK), by measuring the real-time kinetics of intracellular cyclic AMP (cAMP), ATP level, cytoplasmic calcium ([Ca2+]cyt) and survival of COV434 cells. We show that incubating COV434 cells with FLX (between 0.6 and 10 μM) induces a decrease in intracellular cAMP response to FSK, a drop in ATP content and stimulates cytoplasmic Ca2+ accumulation in COV434 cells. Only the highest concentrations of FLX (5-10 μM) diminished cell viability. The present report is the first to identify an action mechanism of FLX in human tumor ovarian cells COV434 cells and thus opening the way to potential use of fluoxetine as a complementary tool, in granulosa tumor treatments.