Increased prostacyclin and PGE2 stimulated cAMP production by macrophages from endotoxin-tolerant rats

1998 ◽  
Vol 274 (5) ◽  
pp. C1238-C1244 ◽  
Author(s):  
Michel A. Makhlouf ◽  
Lawrence P. Fernando ◽  
Thomas W. Gettys ◽  
Perry V. Halushka ◽  
James A. Cook
Keyword(s):  
Inflammatory Mediator ◽  
Phosphodiesterase Inhibitors ◽  
Mrna Levels ◽  
Cytokine Release ◽  
Camp Production ◽  
Receptor Mrna ◽  
Ep4 Receptor ◽  
Ip Receptor ◽  
Camp Levels ◽  
Camp Formation

Sublethal administration of lipopolysaccharide (LPS) renders rats tolerant to multiple lethal stimuli. Tolerant macrophages exhibit differential alterations in LPS-stimulated cytokine and inflammatory mediator release. Increased cAMP levels stimulated by PGE2 or prostacyclin (PGI2) result in differential effects on LPS-induced cytokine release and protect against the pathophysiological changes of endotoxemia. In the present studies, we sought to determine whether PGE2- and PGI2-stimulated cAMP levels are altered in tolerant macrophages. Incubation of macrophages with cicaprost or 11-deoxy-PGE1 in the presence of phosphodiesterase inhibitors resulted in significantly higher (2.5- to 6.5-fold) cAMP concentrations in tolerant macrophages compared with control. In contrast, isoproterenol-stimulated cAMP levels were not significantly different between control and tolerant cells. Also, incubation of tolerant macrophages with LPS did not result in significantly elevated cAMP levels. Prostacyclin (IP) receptor mRNA levels were significantly increased in tolerant cells compared with controls, whereas [3H]PGE2binding and PGE2 EP4 receptor mRNA levels were not significantly changed. These studies suggest that LPS tolerance induces selective alterations in eicosanoid regulation of cAMP formation.

Mechanism of action of γ-aminobutyric acid on frog melanotrophs

1995 ◽  
Vol 14 (1) ◽  
pp. 1-12 ◽  
Author(s):  
L Desrues ◽  
H Vaudry ◽  
M Lamacz ◽  
M C Tonon
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Inhibitory Effect ◽  
Aminobutyric Acid ◽  
Calcium Stores ◽  
Camp Production ◽  
Biphasic Effect ◽  
Camp Levels ◽  
Camp Formation ◽  
Stimulation Of

ABSTRACT We have previously demonstrated that γ-aminobutyric acid (GABA) is a potent regulator of secretory and electrical activity in melanotrophs of the frog pituitary. The aim of the present study was to investigate the intracellular events which mediate the response of melanotrophs to GABA. We first observed that GABA (1–100 μm inhibited both basal and forskolin-stimulated cyclic AMP (cAMP) formation. The inhibitory effect of GABA on cAMP levels was mimicked by the GABAB receptor agonist baclofen (100 μm) and totally abolished by a 4-h pretreatment with pertussis toxin (01 μg/ml). In contrast, the specific GABAA agonist 3-aminopropane sulphonic acid (3APS) did not affect cAMP production. Both GABA and 3APS (100 μm each) induced a biphasic effect on α-MSH release from perifused frog neurointermediate lobes, i.e. a transient stimulation followed by an inhibition of α-MSH secretion. Administration of forskolin (10 μm) prolonged the stimulatory phase and attenuated the inhibitory phase evoked by GABA and 3APS, indicating that cAMP modulates the response of melanotrophs to GABAA agonists. Ejection of 3APS (1 μm) in the vicinity of cultured melanotrophs caused a massive increase in intracellular calcium concentration ([Ca2+]i). The stimulatory effect of 3APS on [Ca2+]i was abolished when the cells were incubated in a chloride-free medium. The formation of inositol trisphosphate was not affected by 3APS, suggesting that the increase in [Ca2+]i cannot be ascribed to mobilization of intracellular calcium stores. ω-Conotoxin did not alter the secretory response of frog neurointermediate lobes to 3APS, while nifedipine blocked the stimulation of α-MSH secretion induced by 3APS. In conclusion, the present data indicate that, in frog pituitary melanotrophs, (i) the stimulatory phase evoked by GABAA agonists can be accounted for by an influx of calcium through L-type calcium channels, (ii) the inhibitory effect evoked by GABAB agonists can be ascribed to inhibition of adenylate cyclase activity and (iii) cAMP attenuates the inhibitory phase evoked by GABAA agonists. Taken together, these data suggest that activation of GABAB receptors may modulate GABAA receptor function.

Alpha 2-adrenoceptor stimulation and cellular cAMP levels in microdissected rat glomeruli

1986 ◽  
Vol 250 (1) ◽  
pp. F103-F108
Author(s):  
S. Umemura ◽  
D. D. Smyth ◽  
W. A. Pettinger
Keyword(s):  
Adenylate Cyclase ◽  
Phosphodiesterase Inhibitor ◽  
Camp Accumulation ◽  
Camp Production ◽  
Camp Concentration ◽  
Adrenoceptor Agonist ◽  
Dose Dependent Fashion ◽  
Camp Levels ◽  
Dose Dependent ◽  
Camp Formation

A functional role for the numerically predominant glomerular alpha 2-adrenoceptors is unknown. In other tissues, activation of alpha 2-adrenoceptors inhibits adenylate cyclase activity. We therefore examined the effect of alpha 2-adrenoceptor stimulation with (-)-epinephrine (E) on the cellular cAMP concentration in glomeruli isolated by microdissection. Parathyroid hormone (1-34 PTH), prostaglandin E2 (PGE2), histamine, serotonin, or adenosine, in the presence of 3-isobutyl-1-methylxanthine (phosphodiesterase inhibitor) and propranolol, was used to activate adenylate cyclase in single intact rat glomeruli. alpha 2-Adrenoceptors were activated with varying concentrations of E (37 degrees C, 2 min). In the presence of PTH-stimulated cAMP production, alpha 2-adrenoceptor activation with E (5 X 10(-7) to 5 X 10(-6) M) suppressed cellular cAMP levels in a dose-dependent fashion with the maximum at 30%. This suppression by E was inhibited by 5 X 10(-6) M yohimbine but not by 5 X 10(-6) M prazosin, confirming alpha 2-adrenoceptor mediation of this effect of E. Consistent with the above findings, the specific alpha 2-adrenoceptor agonist BHT933 inhibited PTH-stimulated cAMP accumulation. E also inhibited cAMP accumulation stimulated by serotonin. However, E did not suppress the PGE2-, histamine-, or adenosine-stimulated increase in cellular cAMP in the glomerulus. Activation of alpha 2-adrenoceptors inhibits cAMP formation stimulated by PTH or serotonin but not by PGE2, histamine, or adenosine in the rat glomerulus. Thus, the ability of alpha 2-adrenoceptors to inhibit adenylate cyclase appears to be hormone and probably function specific.

scholarly journals A major role for the EP4 receptor in regulation of renin

2011 ◽  
Vol 301 (5) ◽  
pp. F1035-F1041 ◽  
Author(s):  
Carie S. Facemire ◽  
Mytrang Nguyen ◽  
Leigh Jania ◽  
William H. Beierwaltes ◽  
Hyung-Suk Kim ◽  
...  
Keyword(s):  
Macula Densa ◽  
Mrna Levels ◽  
Wild Type ◽  
Targeted Disruption ◽  
Ep4 Receptor ◽  
Ip Receptor ◽  
Renin Mrna ◽  
Cox 2 ◽  
Wild Type Control ◽  
Stimulation Of

Prostaglandins have been implicated as paracrine regulators of renin secretion, but the specific pathways and receptor(s) carrying out these functions have not been fully elucidated. To examine the contributions of prostanoid synthetic pathways and receptors to regulation of renin in the intact animal, we used a panel of mice with targeted disruption of several key genes: cyclooxygenase-2 (COX-2), microsomal PGE synthases 1 and 2 (mPGES1, mPGES2), EP2 and EP4 receptors for PGE2, and the IP receptor for PGI2. To activate the macula densa signal for renin stimulation, mice were treated with furosemide over 5 days and renin mRNA levels were determined by real-time RT-PCR. At baseline, there were no differences in renin mRNA levels between wild-type and the various strains of mutant mice. Furosemide caused marked stimulation of renin mRNA expression across all groups of wild-type control mice. This response was completely abrogated in the absence of COX-2, but was unaffected in mice lacking mPGES1 or mPGES2. The absence of Gs/cAMP-linked EP2 receptors had no effect on stimulation of renin by furosemide and there was only a modest, insignificant reduction in renin responses in mice lacking the IP receptor. By contrast, renin stimulation in EP4−/− mice was significantly reduced by ∼70% compared with wild-type controls. These data suggest that stimulation of renin by the macula densa mechanism is mediated by PGE2 through a pathway requiring COX-2 and the EP4 receptor, but not EP2 or IP receptors. Surprisingly, mPGES1 or mPGES2 are not required, suggesting other alternative mechanisms for generating PGE2 in response to macula densa stimulation.

A type I collagen substrate increases PTH/PTHrP receptor mRNA expression and suppresses PTHrP mRNA expression in UMR106–06 osteoblast-like cells

1996 ◽  
Vol 150 (2) ◽  
pp. 299-308 ◽  
Author(s):  
S Celic ◽  
P J Chilco ◽  
J D Zajac ◽  
T J Martin ◽  
D M Findlay
Keyword(s):  
Retinoic Acid ◽  
Mrna Expression ◽  
Mrna Stability ◽  
Type I Collagen ◽  
Type I ◽  
Mrna Levels ◽  
Receptor Mrna ◽  
Pthrp Receptor ◽  
Camp Levels ◽  
In Cells

Abstract We have previously shown that the response of osteoblasts to parathyroid hormone (PTH) can be influenced at the receptor level by growth on the physiological substrate, type I collagen, or by treatment with retinoic acid. We have also shown differential expression of genes when cells of the osteoblast lineage are grown on type I collagen. The aim of this study was therefore to examine the effect of retinoic acid and growth on type I collagen on PTH/PTH-related protein (PTHrP) receptor mRNA expression in the osteosarcoma osteoblast-like cell line UMR106–06. PTH/PTHrP receptor mRNA levels, as assessed by Northern blot, of cells grown on collagen were increased up to 2-fold compared with cells on plastic and in a concentration-dependent manner with respect to collagen. An increase was seen as early as 6 h and was maintained over a 24 h period. This was not due to increased mRNA stability. Retinoic acid decreased the level of receptor mRNA on both plastic and collagen at each time but did not alter mRNA stability. For all treatments PTH/PTHrP receptor mRNA abundance, relative to glyceraldehyde-3-phosphate dehydrogenase, increased steadily over 24 h after subculture of cells. In contrast, PTHrP mRNA levels were reduced in cells on collagen, compared with plastic. PTH-stimulated cAMP levels of cells grown on collagen were increased compared with plastic at 24 h, but not earlier. Consistent with the mRNA data, retinoic acid decreased the amplitude of cAMP responses in cells on plastic and collagen. There was no evidence for changes in adenylate cyclase per se, since forskolin-induced cAMP levels did not change with either treatment. This study shows that known modulators of osteoblast maturation also affect signal transduction in these cells by regulating gene expression of the PTH/PTHrP receptor as well as the PTHrP ligand. Journal of Endocrinology (1996) 150, 299–308

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

scholarly journals Significant association of interleukin 10 receptor mRNA levels with renal cell carcinoma metastasis

2008 ◽  
Vol 29 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Hideyuki ABE ◽  
Tomonori YAMANISHI ◽  
Tomoko MASHIDORI ◽  
Kyoko ARAI ◽  
Takao KAMAI
Keyword(s):  
Renal Cell Carcinoma ◽  
Cell Carcinoma ◽  
Renal Cell ◽  
Interleukin 10 ◽  
Mrna Levels ◽  
Receptor Mrna ◽  
Renal Cell Carcinoma Metastasis ◽  
Carcinoma Metastasis

Prostanoid signaling, localization, and expression of IP receptors in rat thick ascending limb cells

1998 ◽  
Vol 275 (6) ◽  
pp. F904-F914 ◽  
Author(s):  
Richard L. Hébert ◽  
Tim O’Connor ◽  
Chris Neville ◽  
Kevin D. Burns ◽  
Odette Laneuville ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Rat Kidney ◽  
Receptor Expression ◽  
Molecular Evidence ◽  
Thick Ascending Limb ◽  
Renal Epithelial Cells ◽  
Receptor Mrna ◽  
Ip Receptor ◽  
Receptor Cdna ◽  
Nucleotide Binding Proteins

It is widely held that only one prostacyclin (IP) receptor exists that can couple to guanine stimulatory nucleotide binding proteins (Gs) leading to activation of adenyl cyclase. Although IP receptor mRNA is expressed in vascular arterial smooth muscle cells and platelets, with lower level expression in mature thymocytes, splenic lymphocytes, and megakaryocytes, there is no molecular evidence for IP receptor expression in renal epithelial cells. The purpose of the present study was to obtain molecular evidence for the expression and localization of the IP receptor and to study the signaling pathways of IP receptor in rat medullary thick ascending limb (MTAL). Biochemical studies showed that IP prostanoids do not increase cAMP in rat MTAL. However, in the presence of vasopressin, inhibition of cAMP formation by prostacyclin (PGI2) analogs is pertussis toxin sensitive and does not activate protein kinase C. In situ hybridization studies localized IP receptor mRNA expression to MTAL in the rat kidney outer medulla. The results of RT-PCR of freshly isolated RNA from MTAL, with primers specific for the mouse IP receptor cDNA, produced an amplification product of the correct predicted size that contained an expected Nco I endonuclease restriction site. We conclude that rat renal epithelial cells express the IP receptor, coupled to inhibition of cAMP production.

scholarly journals Characterization and Regulation of Type A Endothelin Receptor Gene Expression in Bovine Luteal Cell Types

Endocrinology ◽  
1999 ◽  
Vol 140 (5) ◽  
pp. 2110-2116 ◽  
Author(s):  
Roni Mamluk ◽  
Nitzan Levy ◽  
Bo Rueda ◽  
John S. Davis ◽  
Rina Meidan
Keyword(s):  
Gene Expression ◽  
Receptor Gene ◽  
Cell Types ◽  
Cell Populations ◽  
Mrna Levels ◽  
Factor I ◽  
Receptor Mrna ◽  
Progesterone Production ◽  
Eta Receptor ◽  
Receptor Gene Expression

Abstract Our previous studies demonstrated that endothelin-1 (ET-1), a 21-amino acid vasoconstrictor peptide, has a paracrine regulatory role in bovine corpus luteum (CL). The peptide is produced within the gland where it inhibits progesterone production by acting via the selective type A endothelin (ETA) receptors. The present study was designed to characterize ETA receptor gene expression in different ovarian cell types and its hormonal regulation. ETA receptor messenger RNA (mRNA) levels were high in follicular cells as well as in CL during luteal regression. At this latter stage, high ETA receptor expression concurred with low prostaglandin F2α receptor mRNA. The ETA receptor gene was expressed by all three major cell populations of the bovine CL; i.e. small and large luteal cells, as well as in luteal endothelial cells. Among these various cell populations, the highest ETA receptor mRNA levels were found in endothelial cells. cAMP elevating agents, forskolin and LH, suppressed ETA receptor mRNA expression in luteinized theca cells (LTC). This inhibition was dose dependent and was evident already after 24 h of incubation. In luteinized granulosa cells (LGC), 10 and 100 ng/ml of insulin-like growth factor I and insulin (only at a concentration of 2000 ng/ml) markedly decreased ETA receptor mRNA levels. In both LGC and LTC there was an inverse relationship between ETA receptor gene expression and progesterone production; insulin (in LGC) and forskolin (in LTC) enhanced progesterone production while inhibiting ETA receptor mRNA levels. Our findings may therefore suggest that, during early stages of luteinization when peak levels of both LH and insulin-like growth factor I exist, the expression of ETA receptors in the gland are suppressed. This study demonstrates physiologically relevant regulatory mechanisms controlling ETA receptor gene expression and further supports the inhibitory role of ET-1 in CL function.

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