Differential regulation of human dopamine D2 and somatostatin receptor subtype expression by glucocorticoids in vitro

Dopamine agonists (DA) and somatostatin (SS) analogues have been proposed in the treatment of ACTH-producing neuro-endocrine tumours that cause Cushing's syndrome. Inversely, glucocorticoids (GCs) can differentially influence DA receptor D2 or SS receptor subtype (sst) expression in rodent models. If this also occurs in human neuro-endocrine cells, then cortisol-lowering therapy could directly affect the expression of these target receptors. In this study, we investigated the effects of the GC dexamethasone (DEX) on D2 and sst expression in three human neuro-endocrine cell lines: BON (carcinoid) and TT (medullary thyroid carcinoma) versus DMS (small cell lung cancer), which is severely GC resistant. In BON and TT, sst2 mRNA was strongly down-regulated in a dose-dependent manner (IC50 0.84 nM and 0.16 nM), whereas sst5 and especially D2 were much more resistant to DEX treatment. Sst2 down-regulation was abrogated by a GC receptor antagonist and reversible in time upon GC withdrawal. At the protein level, DEX also induced a decrease in the total number of SS (−52%) and sst2-specific (−42%) binding sites. Pretreatment with DEX abrogated calcitonin inhibition by sst2-preferring analogue octreotide in TT. In DMS, DEX did not cause significant changes in the expression of these receptor subtypes. In conclusion, we show that GCs selectively down-regulate sst2, but not D2 and only to a minor degree sst5 in human neuro-endocrine BON and TT cells. This mechanism may also be responsible for the low expression of sst2 in corticotroph adenomas and underwrite the current interest in sst5 and D2 as possible therapeutic targets for a medical treatment of Cushing's disease.

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Ghrelin Receptor (GHS-R1a) and Its Constitutive Activity in Somatotroph Adenomas: A New Co-targeting Therapy Using GHS-R1a Inverse Agonists and Somatostatin Analogs

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2014-2753 ◽

2014 ◽

Vol 99 (12) ◽

pp. E2463-E2471 ◽

Cited By ~ 4

Author(s):

Yves Mear ◽

Marie-Pierre Blanchard ◽

Céline Defilles ◽

Thierry Brue ◽

Dominique Figarella-Branger ◽

...

Keyword(s):

Somatostatin Receptor ◽

Somatostatin Analogs ◽

Inverse Agonist ◽

Receptor Subtype ◽

Dependent Manner ◽

Constitutive Activity ◽

Targeting Therapy ◽

Ghrelin Receptor ◽

Gh Secretion

Context: The ghrelin receptor GHS-R1a is highly expressed in human somatotroph adenomas and exhibits unusually high basal signaling activity. In humans, the suppression of this constitutive activity by mutation induces a short stature. Objective: Using a GHS-R1a inverse agonist, modified substance P (MSP), we explored the role of GHS-R1a constitutive activity in GH hypersecretion from somatotroph adenomas and as a putative therapeutic target. Design: The effects of MSP were assessed on GH secretion from 19 human somatotroph tumors in vitro. Moreover, these effects were compared with those of octreotide (somatostatin receptor subtype 2 [sst2] agonist) and with the combination of both drugs. Expression and localization of GHS-R1a and sst2 were studied. Results: For all tumors, MSP inhibited GH secretion in a dose-dependent manner from 13 to 64%. Moreover, MSP enhanced octreotide-induced GH inhibition. For five tumors, the effects of combined MSP plus octreotide treatment were significantly higher than the sum of effects of each drug alone. MSP increased the membrane localization of GHS-R1a and of microdomains colocalizing sst2-GHS-R1a, highlighting the cooperation between the two drugs. Conclusions: The GHS-R1a inverse agonist could open new therapeutic options for acromegalic patients, particularly patients partially sensitive to octreotide whose GH secretion is not completely controlled by the sst2 agonist.

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Microinjection of exogenous somatostatin in the dorsal vagal complex inhibits pancreatic secretion via somatostatin receptor-2 in rats

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00174.2006 ◽

2007 ◽

Vol 292 (3) ◽

pp. G746-G752 ◽

Cited By ~ 10

Author(s):

Zhuan Liao ◽

Zhao-Shen Li ◽

Yan Lu ◽

Wei-Zhong Wang

Keyword(s):

Pancreatic Secretion ◽

Exocrine Pancreas ◽

Feedback Inhibition ◽

Somatostatin Receptor ◽

Inhibitory Effect ◽

Receptor Subtype ◽

Dependent Manner ◽

Dorsal Vagal Complex ◽

Somatostatin Receptor Antagonist ◽

Dose Dependent

Previous studies have suggested that somatostatin inhibits pancreatic secretion at a central vagal site, and the dorsal vagal complex (DVC) is involved in central feedback inhibition of the exocrine pancreas. The aim of this study was to investigate the effect of exogenous somatostatin in the DVC on pancreatic secretion and the somatostatin receptor subtype(s) responsible for the effect. The effects of somatostatin microinjected into the DVC on pancreatic secretion stimulated by cholecystokinin octapeptide (CCK-8) or 2-deoxy-d-glucose (2-DG) were examined in anesthetized rats. To investigate the somatostatin inhibitory action site, a somatostatin receptor antagonist [SRA; cyclo(7-aminoheptanoyl-Phe-d-Trp-Lys-Thr)] was microinjected into the DVC before intravenous infusion of somatostatin and CCK-8/2-DG. The effects of injection of a somatostatin receptor-2 agonist (seglitide) and combined injection of somatostatin and a somatostatin receptor-2 antagonist (CYN 154806) in the DVC on the pancreatic secretion were also investigated. Somatostatin injected into the DVC significantly inhibited pancreatic secretion evoked by CCK-8 or 2-DG in a dose-dependent manner. SRA injected into the DVC completely reversed the inhibitory effect of intravenous administration of somatostatin. Seglitide injected into the DVC also inhibited CCK-8/2-DG-induced pancreatic protein secretion. However, combined injection of somatostatin and CYN 154806 did not affect the CCK-8/2-DG-induced pancreatic secretion. Somatostatin in the DVC inhibits pancreatic secretion via somatostatin receptor-2, and the DVC is the action site of somatostatin for its inhibitory effect.

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Effect of GHRH and GHRP-2 treatment in vitro on GH secretion and levels of GH, pituitary transcription factor-1, GHRH-receptor, GH-secretagogue-receptor and somatostatin receptor mRNAs in ovine pituitary cells

Acta Endocrinologica ◽

10.1530/eje.0.1500235 ◽

2004 ◽

pp. 235-242 ◽

Cited By ~ 18

Author(s):

M Yan ◽

M Hernandez ◽

R Xu ◽

C Chen

Keyword(s):

Transcription Factor ◽

Somatostatin Receptor ◽

Receptor Subtypes ◽

Pituitary Cells ◽

Dependent Manner ◽

Gh Secretion ◽

Somatostatin Receptor Subtypes ◽

Transcription Factor 1

OBJECTIVE: Growth hormone (GH)-releasing hormone (GHRH) and GH-releasing peptides (GHRPs) stimulate the release of GH through their specific receptors on somatotropes. Combined GHRH and GHRP administration causes a synergistic GH release in vivo by an unknown mechanism. The current study focuses on the direct action of GHRH and GHRP on several molecular targets in somatotropes. DESIGN AND METHODS: To clarify the mechanism of action, ovine somatotropes were used to measure the expression of mRNAs encoding for GH, pituitary transcription factor-1 (Pit-1), GH-secretagogue receptor (GHS-R), GHRH-R, somatostatin receptor subtypes (sst-1 and sst-2) and GH release after GHRH and GHRP-2 treatment for 0.5, 1, 1.5 and 2 h. RESULTS: GHRH (10 nM), GHRP-2 (100 nM) and combined GHRH-GHRP-2 increased the levels of GH mRNA and GH release from 0.5 to 2 h in a time-dependent manner. The levels of Pit-1, GHRH-R and GHS-R mRNA were increased after 0.5 h treatment of cells with GHRH and GHRP-2. The levels of sst-1 but not sst-2 mRNA were significantly increased after 0.5 and 1 h of GHRH treatment. In contrast, both sst-1 and sst-2 mRNA expression was inhibited after 0.5-2 h of GHRP treatment. CONCLUSIONS: These data demonstrate a direct in vitro modification of ovine somatotropes by GHRH and GHRP-2 resulting in altered GHRH-R, GHS-R, Pit-1, sst-1, sst-2 and GH gene expression; this may underlie the regulatory action of GHRH and GHRP-2 on GH secretion.

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Effect of the Gintonin-Enriched Fraction on Glucagon-Like-Protein-1 Release

Molecules ◽

10.3390/molecules26206298 ◽

2021 ◽

Vol 26 (20) ◽

pp. 6298

Author(s):

Rami Lee ◽

Sun-Hye Choi ◽

Han-Sung Cho ◽

Hongik Hwang ◽

Hyewhon Rhim ◽

...

Keyword(s):

Western Blotting ◽

Receptor Activation ◽

Receptor Subtype ◽

Receptor Subtypes ◽

Dependent Manner ◽

Receptor Ligands ◽

Lpa Receptor ◽

Beneficial Effects

Ginseng-derived gintonin reportedly contains functional lysophosphatidic acids (LPAs) as LPA receptor ligands. The effect of the gintonin-enriched fraction (GEF) on in vitro and in vivo glucagon-like protein-1 (GLP-1) secretion, which is known to stimulate insulin secretion, via LPA receptor(s) remains unclear. Accordingly, we examined the effects of GEF on GLP-1 secretion using human enteroendocrine NCI-H716 cells. The expression of several of LPA receptor subtypes in NCI-H716 cells using qPCR and Western blotting was examined. LPA receptor subtype expression was in the following order: LPA6 > LPA2 > LPA4 > LPA5 > LPA1 (qPCR), and LPA6 > LPA4 > LPA2 > LPA1 > LPA3 > LPA5 (Western blotting). GEF-stimulated GLP-1 secretion occurred in a dose- and time-dependent manner, which was suppressed by cAMP-Rp, a cAMP antagonist, but not by U73122, a phospholipase C inhibitor. Furthermore, silencing the human LPA6 receptor attenuated GEF-mediated GLP-1 secretion. In mice, low-dose GEF (50 mg/kg, peroral) increased serum GLP-1 levels; this effect was not blocked by Ki16425 co-treatment. Our findings indicate that GEF-induced GLP-1 secretion could be achieved via LPA6 receptor activation through the cAMP pathway. Hence, GEF-induced GLP secretion via LPA6 receptor regulation might be responsible for its beneficial effects on human endocrine physiology.

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Coexpression of Dopamine and Somatostatin Receptor Subtypes in Corticotroph Adenomas

Endocrinology ◽

10.1210/endo.150.3.9998 ◽

2009 ◽

Vol 150 (3) ◽

pp. 1558-1559 ◽

Cited By ~ 2

Author(s):

Christiaan de Bruin ◽

Alberto M. Pereira ◽

Richard A. Feelders ◽

Johannes A. Romijn ◽

Ferdinand Roelfsema ◽

...

Keyword(s):

Somatostatin Receptor ◽

Receptor Subtypes ◽

Medical Centers ◽

Somatostatin Receptor Subtypes ◽

Transsphenoidal Adenomectomy ◽

Adenoma Tissue ◽

Vitro Analysis ◽

Corticotroph Adenomas ◽

In Vitro Analysis

Abstract Context: Previous studies have demonstrated the expression of somatostatin receptor subtypes (mainly sst5) and dopamine (DA) receptor subtypes (mainly D2) in smaller series of human corticotroph adenomas. In line with these findings, sst5 and D2-targeting agents have already been used clinically in patients with Cushing’s disease (CD) and have shown promising results in subsets of patients. To what extent these receptor subtypes are coexpressed within individual adenomas, is not known however. Objective: The aim of the study was to investigate the (co-)expression of both sst and DA receptors in a large series of human corticotroph adenomas. Design: We conducted in vitro analysis of corticotroph adenoma tissue obtained via transsphenoidal adenomectomy. Setting: The study was conducted at two university medical centers. Patients: Thirty patients with CD participated in the study. Results: Analyzed by quantitative RT-PCR, D2 and sst5 were significantly (co-) expressed in the majority (60%) of adenomas, whereas 23% of adenomas only expressed D2, but not sst5. The remaining 17% of adenomas did not significantly express either sst5 or D2. Overall, expression of sst1–4 and D4 was low to nondetectable. Corticotroph adenomas with invasive growth invariably showed loss of sst5 and D2 expression. Autoradiography revealed clear D2 and/or SS-14 binding in a subset of cases, which correlated well with their respective mRNA data. Conclusions: sst5 and especially D2 are highly expressed in the majority of human corticotroph adenomas, with coexpression of sst5 and D2 being a common phenomenon. These findings support the current studies with sst5 and D2-targeting agents in patients with CD and highlight the rationale behind sst5-D2 combination therapy.

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Expression and Functional Analysis of Dopamine Receptor Subtype 2 and Somatostatin Receptor Subtypes in Canine Cushing’s Disease

Endocrinology ◽

10.1210/en.2008-0244 ◽

2008 ◽

Vol 149 (9) ◽

pp. 4357-4366 ◽

Cited By ~ 18

Author(s):

C. de Bruin ◽

J. M. Hanson ◽

B. P. Meij ◽

H. S. Kooistra ◽

A. M. Waaijers ◽

...

Keyword(s):

Medical Treatment ◽

Dopamine Receptor ◽

Anterior Pituitary ◽

Dopamine Agonists ◽

Somatostatin Receptor ◽

Somatostatin Analogs ◽

Receptor Subtype ◽

Receptor Subtypes ◽

Somatostatin Receptor Subtypes ◽

Corticotroph Adenomas

Cushing’s disease (CD) is a severe disorder characterized by chronic hypercortisolism due to an ACTH-secreting pituitary adenoma. Transsphenoidal adenomectomy is the treatment of choice in humans with CD, but recurrences occur frequently. Finding an effective and safe medical treatment for CD may improve long-term clinical outcome. The recent demonstration of expression of somatostatin receptor subtypes (mainly sst5) and dopamine receptor subtype 2 (D2) in human corticotroph adenomas offers the possibility for medical treatment of CD with novel somatostatin analogs and dopamine agonists. Investigation of the effects of these drugs is hampered by the low incidence of CD in humans. Interestingly, CD is a frequent disorder in dogs with striking clinical similarities with CD in humans. Therefore, we investigated the expression and functional role of D2 and somatostatin receptors in corticotroph adenoma cells from 13 dogs with active CD that underwent therapeutic hypophysectomy and normal anterior pituitary cells from five dogs. Quantitative RT-PCR and immunohistochemistry revealed that both in CD and normal anterior pituitary, sst2 was the predominant receptor subtype expressed, whereas D2 was modestly expressed and sst5 was expressed only at very low levels. In primary cultures of canine adenomas (n = 7), the sst2-preferring agonist octreotide also showed the strongest ACTH-suppressive effects. In conclusion, canine corticotroph adenomas provide an interesting model to study CD, but differences in somatostatin and dopamine receptor expression between humans and dogs should be taken into account when using dogs with CD as a model to evaluate efficacy of novel somatostatin analogs and dopamine agonists for human CD.

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Coexpression of Dopamine and Somatostatin Receptor Subtypes in Corticotroph Adenomas

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2008-2101 ◽

2009 ◽

Vol 94 (4) ◽

pp. 1118-1124 ◽

Cited By ~ 71

Author(s):

Christiaan de Bruin ◽

Alberto M. Pereira ◽

Richard A. Feelders ◽

Johannes A. Romijn ◽

Ferdinand Roelfsema ◽

...

Keyword(s):

Somatostatin Receptor ◽

Receptor Subtypes ◽

Medical Centers ◽

Somatostatin Receptor Subtypes ◽

Transsphenoidal Adenomectomy ◽

Adenoma Tissue ◽

Vitro Analysis ◽

Corticotroph Adenomas ◽

In Vitro Analysis

Abstract Context: Previous studies have demonstrated the expression of somatostatin receptor subtypes (mainly sst5) and dopamine (DA) receptor subtypes (mainly D2) in smaller series of human corticotroph adenomas. In line with these findings, sst5 and D2-targeting agents have already been used clinically in patients with Cushing’s disease (CD) and have shown promising results in subsets of patients. To what extent these receptor subtypes are coexpressed within individual adenomas, is not known however. Objective: The aim of the study was to investigate the (co-)expression of both sst and DA receptors in a large series of human corticotroph adenomas. Design: We performed in vitro analysis of corticotroph adenoma tissue obtained via transsphenoidal adenomectomy. Setting: The study was conducted at two university medical centers. Patients: Adenoma tissue from 30 patients with CD was analyzed in this study. Results: Analyzed by quantitative RT-PCR, D2 and sst5 were significantly (co-) expressed in the majority (60%) of adenomas, whereas 23% of adenomas only expressed D2, but not sst5. The remaining 17% of adenomas did not significantly express either sst5 or D2. Overall, expression of sst1–4 and D4 was low to nondetectable. Corticotroph adenomas with invasive growth invariably showed loss of sst5 and D2 expression. Autoradiography revealed clear D2 and/or SS-14 binding in a subset of cases, which correlated well with their respective mRNA data. Conclusions: Sst5 and especially D2 are highly expressed in the majority of human corticotroph adenomas, with coexpression of sst5 and D2 being a common phenomenon. These findings support the current studies with sst5 and D2-targeting agents in patients with CD and highlight the rationale behind sst5-D2 combination therapy.

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Prostaglandin F2α Facilitates Platelet Activation by Acting on Prostaglandin E2 Receptor Subtype EP3 and Thromboxane A2 Receptor TP in Mice

Thrombosis and Haemostasis ◽

10.1055/s-0039-1688906 ◽

2019 ◽

Vol 119 (08) ◽

pp. 1311-1320 ◽

Cited By ~ 3

Author(s):

Hitoshi Kashiwagi ◽

Koh-ichi Yuhki ◽

Yoshitaka Imamichi ◽

Fumiaki Kojima ◽

Shima Kumei ◽

...

Keyword(s):

Platelet Function ◽

Prostaglandin F2α ◽

Receptor Subtype ◽

Receptor Subtypes ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Pge2 Receptor ◽

Induced Aggregation

AbstractPlatelets play an important role in both physiological hemostasis and pathological thrombosis. Thromboxane (TX) A2 and prostaglandin (PG) I2 are well known as a potent stimulator and an inhibitor of platelet function, respectively. Recently, PGE2 has also been reported to regulate platelet function via PGE2 receptor subtypes. However, the effect of PGF2α on platelet function remains to be determined. The aim of the present study was to clarify the effect of PGF2α on murine platelet function both in vitro and in vivo. Platelets prepared from wild-type mice (WT platelets) expressed several types of prostanoid receptors, including the PGE2 receptor subtype EP3 and the TXA2 receptor TP, while expression of the PGF2α receptor FP was not detected. In WT platelets, PGF2α potentiated adenosine diphosphate-induced aggregation in a concentration-dependent manner, while PGF2α alone did not induce aggregation. In platelets prepared from mice lacking FP, however, PGF2α-induced potentiation was not significantly different from that in WT platelets. Interestingly, the potentiation was significantly blunted in platelets lacking EP3 or TP and disappeared completely in platelets lacking both EP3 and TP. Accordingly, PGF2α decreased the cyclic adenosine monophosphate level via EP3 and increased the inositol triphosphate level via TP in WT platelets. Intravenously administered PGF2α significantly shortened the bleeding time and aggravated arachidonic acid-induced acute thromboembolism in WT mice, suggesting that PGF2α works as a platelet stimulator also in vivo. In conclusion, PGF2α potentiates platelet aggregation in vitro via EP3 and TP but not FP. Accordingly, PGF2α facilitates hemostasis and thromboembolism in vivo.

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Activation of NTS A1adenosine receptors inhibits regional sympathetic responses evoked by activation of cardiopulmonary chemoreflex

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00164.2012 ◽

2012 ◽

Vol 303 (5) ◽

pp. R539-R550 ◽

Cited By ~ 10

Author(s):

Tomoko K. Ichinose ◽

Zeljka Minic ◽

Cailian Li ◽

Donal S. O'Leary ◽

Tadeusz J. Scislo

Keyword(s):

Adenosine Receptors ◽

Right Atrial ◽

Volume Control ◽

Receptor Subtype ◽

Receptor Subtypes ◽

Dependent Manner ◽

Severe Hypotension ◽

Before And After ◽

Sympathetic Responses ◽

Dose Dependent

Previously we have shown that adenosine operating via the A1receptor subtype may inhibit glutamatergic transmission in the baroreflex arc within the nucleus of the solitary tract (NTS) and differentially increase renal (RSNA), preganglionic adrenal (pre-ASNA), and lumbar (LSNA) sympathetic nerve activity (ASNA>RSNA≥LSNA). Since the cardiopulmonary chemoreflex and the arterial baroreflex are mediated via similar medullary pathways, and glutamate is a primary transmitter in both pathways, it is likely that adenosine operating via A1receptors in the NTS may differentially inhibit regional sympathetic responses evoked by activation of cardiopulmonary chemoreceptors. Therefore, in urethane-chloralose-anesthetized rats ( n = 37) we compared regional sympathoinhibition evoked by the cardiopulmonary chemoreflex (activated with right atrial injections of serotonin 5HT3receptor agonist phenylbiguanide, PBG, 1–8 μg/kg) before and after selective stimulation of NTS A1adenosine receptors [microinjections of N6-cyclopentyl adenosine (CPA), 0.033–330 pmol/50 nl]. Activation of cardiopulmonary chemoreceptors evoked differential, dose-dependent sympathoinhibition (RSNA>ASNA>LSNA), and decreases in arterial pressure and heart rate. These differential sympathetic responses were uniformly attenuated in dose-dependent manner by microinjections of CPA into the NTS. Volume control ( n = 11) and blockade of adenosine receptor subtypes in the NTS via 8-( p-sulfophenyl)theophylline (8-SPT, 1 nmol in 100 nl) ( n = 9) did not affect the reflex responses. We conclude that activation of NTS A1adenosine receptors uniformly inhibits neural and cardiovascular cardiopulmonary chemoreflex responses. A1adenosine receptors have no tonic modulatory effect on this reflex under normal conditions. However, when adenosine is released into the NTS (i.e., during stress or severe hypotension/ischemia), it may serve as negative feedback regulator for depressor and sympathoinhibitory reflexes integrated in the NTS.

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Oxygenation of 18-hydroxycorticosterone as the final reaction for aldosterone biosynthesis

Acta Endocrinologica ◽

10.1530/acta.0.1070395 ◽

1984 ◽

Vol 107 (3) ◽

pp. 395-400 ◽

Cited By ~ 9

Author(s):

Itaru Kojima ◽

Etsuro Ogata ◽

Hiroshi Inano ◽

Bun-ichi Tamaoki

Keyword(s):

Carbon Monoxide ◽

Hydroxysteroid Dehydrogenase ◽

Dependent Manner ◽

In Vitro Production ◽

Mitochondrial Preparation ◽

Final Reaction ◽

Vitro Production ◽

Dose Dependent ◽

Cytochrome P 450

Abstract. Incubation of 18-hydroxycorticosterone with the sonicated mitochondrial preparation of bovine adrenal glomerulosa tissue leads to the production of aldosterone, as measured by radioimmunoassay. The in vitro production of aldosterone from 18-hydroxycorticosterone requires both molecular oxygen and NADPH, and is inhibited by carbon monoxide. Cytochrome P-450 inhibitors such as metyrapone, SU 8000. SU 10603, SKF 525A, amphenone B and spironolactone decrease the biosynthesis of aldosterone from 18-hydroxycorticosterone. These results support the conclusion that the final reaction in aldosterone synthesis from 18-hydroxycorticosterone is catalyzed by an oxygenase, but not by 18-hydroxysteroid dehydrogenase. By the same preparation, the production of [3H]aldosterone but not [3H]18-hydroxycorticosterone from [1,2-3H ]corticosterone is decreased in a dose-dependent manner by addition of non-radioactive 18-hydroxycorticosterone.

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