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De Leon DD, Arnoux JB, Banerjee I, Bergada I, Bhatti T, Conwell LS, Fu J, Flanagan SE, Gillis D, Meissner T, Mohnike K, Pasquini TL, Shah P, Stanley CA, Vella A, Yorifuji T, Thornton PS. International Guidelines for the Diagnosis and Management of Hyperinsulinism. Horm Res Paediatr 2023; 97:279-298. [PMID: 37454648 PMCID: PMC11124746 DOI: 10.1159/000531766] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 05/16/2023] [Indexed: 07/18/2023] Open
Abstract
BACKGROUND Hyperinsulinism (HI) due to dysregulation of pancreatic beta-cell insulin secretion is the most common and most severe cause of persistent hypoglycemia in infants and children. In the 65 years since HI in children was first described, there has been a dramatic advancement in the diagnostic tools available, including new genetic techniques and novel radiologic imaging for focal HI; however, there have been almost no new therapeutic modalities since the development of diazoxide. SUMMARY Recent advances in neonatal research and genetics have improved our understanding of the pathophysiology of both transient and persistent forms of neonatal hyperinsulinism. Rapid turnaround of genetic test results combined with advanced radiologic imaging can permit identification and localization of surgically-curable focal lesions in a large proportion of children with congenital forms of HI, but are only available in certain centers in "developed" countries. Diazoxide, the only drug currently approved for treating HI, was recently designated as an "essential medicine" by the World Health Organization but has been approved in only 16% of Latin American countries and remains unavailable in many under-developed areas of the world. Novel treatments for HI are emerging, but they await completion of safety and efficacy trials before being considered for clinical use. KEY MESSAGES This international consensus statement on diagnosis and management of HI was developed in order to assist specialists, general pediatricians, and neonatologists in early recognition and treatment of HI with the ultimate aim of reducing the prevalence of brain injury caused by hypoglycemia. A previous statement on diagnosis and management of HI in Japan was published in 2017. The current document provides an updated guideline for management of infants and children with HI and includes potential accommodations for less-developed regions of the world where resources may be limited.
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Affiliation(s)
- Diva D. De Leon
- Congenital Hyperinsulinism Center and Division of Endocrinology and Diabetes, Department of Pediatrics, Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Jean Baptiste Arnoux
- Reference Center for Inherited Metabolic Diseases, Necker-Enfants Malades Hospital, AP-HP, University of Paris-Cité, Paris, France
| | - Indraneel Banerjee
- Paediatric Endocrinology, Royal Manchester Children’s Hospital, University of Manchester, Manchester, UK
| | - Ignacio Bergada
- Centro de Investigaciones Endocrinológicas “Dr. César Bergadá” (CONICET – FEI), Division de Endrocrinología, Hospital de Niños Ricardo Gutiérrez, Buenos Aires, Argentina
| | - Tricia Bhatti
- Department of Clinical Pathology and Laboratory Medicine, Children’s Hospital of Philadelphia and Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Louise S. Conwell
- Australia and Children’s Health Queensland Clinical Unit, Department of Endocrinology and Diabetes, Queensland Children’s Hospital, Children’s Health Queensland, Greater Brisbane Clinical School, Medical School, Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
| | - Junfen Fu
- National Clinical Research Center for Child Health, Department of Endocrinology, The Children’s Hospital of Zhejiang University School of Medicine, Hangzhou, China
| | - Sarah E. Flanagan
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, UK
| | - David Gillis
- Hadassah Medical Center, Department of Pediatrics, Ein-Kerem, Jerusalem and Faculty of Medicine, Hebrew-University, Jerusalem, Israel
| | - Thomas Meissner
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children’s Hospital, Medical Faculty, Heinrich Heine University, Duesseldorf, Germany
| | - Klaus Mohnike
- Department of General Pediatrics, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Tai L.S. Pasquini
- Research and Policy Director, Congenital Hyperinsulinism International, Glen Ridge, NJ, USA
| | - Pratik Shah
- Pediatric Endocrinology, The Royal London Children’s Hospital, Queen Mary University of London, London, UK
| | - Charles A. Stanley
- Congenital Hyperinsulinism Center and Division of Endocrinology and Diabetes, Department of Pediatrics, Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Adrian Vella
- Division of Diabetes, Endocrinology and Metabolism, Mayo Clinic, Rochester, MN, USA
| | - Tohru Yorifuji
- Pediatric Endocrinology and Metabolism, Children’s Medical Center, Osaka City General Hospital, Osaka, Japan
| | - Paul S. Thornton
- Congenital Hyperinsulinism Center, Cook Children’s Medical Center and Texas Christian University Burnett School of Medicine, Fort Worth, TX, USA
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Dickerson MT, Dadi PK, Zaborska KE, Nakhe AY, Schaub CM, Dobson JR, Wright NM, Lynch JC, Scott CF, Robinson LD, Jacobson DA. G i/o protein-coupled receptor inhibition of beta-cell electrical excitability and insulin secretion depends on Na +/K + ATPase activation. Nat Commun 2022; 13:6461. [PMID: 36309517 PMCID: PMC9617941 DOI: 10.1038/s41467-022-34166-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 10/17/2022] [Indexed: 12/25/2022] Open
Abstract
Gi/o-coupled somatostatin or α2-adrenergic receptor activation stimulated β-cell NKA activity, resulting in islet Ca2+ fluctuations. Furthermore, intra-islet paracrine activation of β-cell Gi/o-GPCRs and NKAs by δ-cell somatostatin secretion slowed Ca2+ oscillations, which decreased insulin secretion. β-cell membrane potential hyperpolarization resulting from Gi/o-GPCR activation was dependent on NKA phosphorylation by Src tyrosine kinases. Whereas, β-cell NKA function was inhibited by cAMP-dependent PKA activity. These data reveal that NKA-mediated β-cell membrane potential hyperpolarization is the primary and conserved mechanism for Gi/o-GPCR control of electrical excitability, Ca2+ handling, and insulin secretion.
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Affiliation(s)
- Matthew T Dickerson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Prasanna K Dadi
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Karolina E Zaborska
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Arya Y Nakhe
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Charles M Schaub
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Jordyn R Dobson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Nicole M Wright
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Joshua C Lynch
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Claire F Scott
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Logan D Robinson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - David A Jacobson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA.
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McClellan K, Chen EY, Kardosh A, Lopez CD, Del Rivero J, Mallak N, Rocha FG, Koethe Y, Pommier R, Mittra E, Pegna GJ. Therapy Resistant Gastroenteropancreatic Neuroendocrine Tumors. Cancers (Basel) 2022; 14:4769. [PMID: 36230691 PMCID: PMC9563314 DOI: 10.3390/cancers14194769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/24/2022] [Accepted: 09/28/2022] [Indexed: 11/16/2022] Open
Abstract
Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a heterogenous group of malignancies originating from neuroendocrine cells of the gastrointestinal tract, the incidence of which has been increasing for several decades. While there has been significant progress in the development of therapeutic options for patients with advanced or metastatic disease, these remain limited both in quantity and durability of benefit. This review examines the latest research elucidating the mechanisms of both up-front resistance and the eventual development of resistance to the primary systemic therapeutic options including somatostatin analogues, peptide receptor radionuclide therapy with lutetium Lu 177 dotatate, everolimus, sunitinib, and temozolomide-based chemotherapy. Further, potential strategies for overcoming these mechanisms of resistance are reviewed in addition to a comprehensive review of ongoing and planned clinical trials addressing this important challenge.
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Affiliation(s)
- Kristen McClellan
- School of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Emerson Y. Chen
- Division of Hematology Oncology, Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Adel Kardosh
- Division of Hematology Oncology, Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Charles D. Lopez
- Division of Hematology Oncology, Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Jaydira Del Rivero
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nadine Mallak
- Division of Molecular Imaging and Therapy, Oregon Health & Science University, Portland, OR 97239, USA
| | - Flavio G. Rocha
- Division of Surgical Oncology, Department of Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Yilun Koethe
- Dotter Department of Interventional Radiology, Oregon Health & Science University, Portland, OR 97239, USA
| | - Rodney Pommier
- Division of Surgical Oncology, Department of Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Erik Mittra
- Division of Molecular Imaging and Therapy, Oregon Health & Science University, Portland, OR 97239, USA
| | - Guillaume J. Pegna
- Division of Hematology Oncology, Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA
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Cuff H, Lord K, Ballester L, Scully T, Stewart N, De Leon DD. The Use of Lanreotide in the Treatment of Congenital Hyperinsulinism. J Clin Endocrinol Metab 2022; 107:e3115-e3120. [PMID: 35587448 DOI: 10.1210/clinem/dgac322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Indexed: 11/19/2022]
Abstract
CONTEXT Congenital hyperinsulinism (HI) results in severe, persistent hypoglycemia and is associated with high risk of neurodevelopmental deficits. Sixty percent of HI cases are unresponsive to diazoxide, the only Food and Drug Administration-approved drug. Somatostatin analogs are used off-label as second-line treatment; the long-acting somatostatin analogue, lanreotide, has been used to treat HI over the past decade. Existing reports are limited to small case series. OBJECTIVE To assess the effectiveness and safety of lanreotide in individuals with HI. DESIGN Retrospective cohort study of individuals with HI treated with lanreotide between 2015 and 2020. SETTING The Congenital Hyperinsulinism Center at The Children's Hospital of Philadelphia. PATIENTS Fifty-four individuals with hyperinsulinism treated with lanreotide. MAIN OUTCOME MEASURES Fasting duration with plasma glucose > 70 mg/dL; frequency of lanreotide-associated side effects. RESULTS The median duration of lanreotide therapy was 28.7 (2.8-64.5) months. Thirty-four patients (63%) had HI due to inactivating mutations of the adenosine 5'-triphosphate (ATP) sensitive potassium channel (KATP-HI), and 39% had undergone a pancreatectomy. Of 52 patients receiving other HI therapies, 22 (42%) were able to discontinue other treatments and were managed on lanreotide alone. Fasting duration with plasma glucose > 70 mg/dL was significantly longer during therapy with lanreotide compared to prior to lanreotide initiation (8.6 ± 6.5 vs 5.1 ± 4.7 hours, P = 0.001). The most common side effects were subcutaneous nodules (26%) and gallstones (11%). CONCLUSIONS Lanreotide is a well-tolerated treatment for patients with HI. It results in a longer duration of fasting and a simplification of treatment regimens.
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Affiliation(s)
- Heather Cuff
- Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Congenital Hyperinsulinism Center, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Katherine Lord
- Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Congenital Hyperinsulinism Center, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Lance Ballester
- Biostatistics and Data Management Core, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Tryce Scully
- Biostatistics and Data Management Core, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Nicole Stewart
- Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Congenital Hyperinsulinism Center, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Diva D De Leon
- Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Congenital Hyperinsulinism Center, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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Dicitore A, Saronni D, Gaudenzi G, Carra S, Cantone MC, Borghi MO, Persani L, Vitale G. Long-term effects of somatostatin analogues in rat GH-secreting pituitary tumor cell lines. J Endocrinol Invest 2022; 45:29-41. [PMID: 34128215 PMCID: PMC8741688 DOI: 10.1007/s40618-021-01609-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 06/03/2021] [Indexed: 11/18/2022]
Abstract
PURPOSE First-generation somatostatin analogs, octreotide (OCT) and lanreotide, are the cornerstone for the medical treatment of growth hormone (GH)-secreting pituitary tumors. A new multireceptor analog, such as pasireotide (PAS), showed better activity than OCT in long-term treatment of patients with acromegaly, but modulation of intracellular key processes is still unclear in vitro. In this study, we evaluated the antitumor activity of OCT and PAS in two GH-secreting pituitary tumor cell lines, GH3 and GH4C1, after a long-term incubation. METHODS The effects of PAS and OCT on the cell viability, cell cycle, apoptosis, GH secretion, and tumor-induced angiogenesis have been evaluated through a colorimetric method (MTS Assay), DNA flow cytometry with propidium iodide, and Annexin V-FITC/propidium iodide staining, ELISA assay and zebrafish platform, respectively. RESULTS PAS showed a more potent antitumor activity compared to OCT in GH3 cell line exerted through inhibition of cell viability, perturbation of cell cycle progression, and induction of apoptosis after 6 days of incubation. A concomitant decrease in GH secretion has been observed after 2 days of incubation only with PAS. No effect on tumor-induced angiogenesis has been reported after treatment with OCT or PAS in zebrafish/tumor xenograft model. CONCLUSION Long-term incubation with PAS showed a more potent antitumor activity than that reported after OCT in GH3 cells, mainly modulated by a cell cycle perturbation and a relevant induction in apoptosis.
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Affiliation(s)
- A Dicitore
- Laboratory of Geriatric and Oncologic Neuroendocrinology Research, Istituto Auxologico Italiano, IRCCS, Via Zucchi 18, 20095, Cusano Milanino, MI, Italy
| | - D Saronni
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - G Gaudenzi
- Laboratory of Geriatric and Oncologic Neuroendocrinology Research, Istituto Auxologico Italiano, IRCCS, Via Zucchi 18, 20095, Cusano Milanino, MI, Italy
| | - S Carra
- Laboratory of Endocrine and Metabolic Research, Istituto Auxologico Italiano, IRCCS, Milan, Italy
| | - M C Cantone
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - M O Borghi
- Experimental Laboratory of Immuno-rheumatology, Istituto Auxologico Italiano, IRCCS, Milan, Italy
- Department of Clinical Sciences and Community Health (DISCCO), University of Milan, Milan, Italy
| | - L Persani
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
- Laboratory of Endocrine and Metabolic Research, Istituto Auxologico Italiano, IRCCS, Milan, Italy
| | - G Vitale
- Laboratory of Geriatric and Oncologic Neuroendocrinology Research, Istituto Auxologico Italiano, IRCCS, Via Zucchi 18, 20095, Cusano Milanino, MI, Italy.
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.
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Zaid NRR, Kletting P, Winter G, Prasad V, Beer AJ, Glatting G. A Physiologically Based Pharmacokinetic Model for In Vivo Alpha Particle Generators Targeting Neuroendocrine Tumors in Mice. Pharmaceutics 2021; 13:2132. [PMID: 34959413 PMCID: PMC8703774 DOI: 10.3390/pharmaceutics13122132] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/04/2021] [Accepted: 12/07/2021] [Indexed: 12/13/2022] Open
Abstract
In vivo alpha particle generators have great potential for the treatment of neuroendocrine tumors in alpha-emitter-based peptide receptor radionuclide therapy (α-PRRT). Quantitative pharmacokinetic analyses of the in vivo alpha particle generator and its radioactive decay products are required to address concerns about the efficacy and safety of α-PRRT. A murine whole-body physiologically based pharmacokinetic (PBPK) model was developed for 212Pb-labeled somatostatin analogs (212Pb-SSTA). The model describes pharmacokinetics of 212Pb-SSTA and its decay products, including specific and non-specific glomerular and tubular uptake. Absorbed dose coefficients (ADC) were calculated for bound and unbound radiolabeled SSTA and its decay products. Kidneys received the highest ADC (134 Gy/MBq) among non-target tissues. The alpha-emitting 212Po contributes more than 50% to absorbed doses in most tissues. Using this model, it is demonstrated that α-PRRT based on 212Pb-SSTA results in lower absorbed doses in non-target tissue than α-PRRT based on 212Bi-SSTA for a given kidneys absorbed dose. In both approaches, the energies released in the glomeruli and proximal tubules account for 54% and 46%, respectively, of the total energy absorbed in kidneys. The 212Pb-SSTA-PBPK model accelerates the translation from bench to bedside by enabling better experimental design and by improving the understanding of the underlying mechanisms.
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Affiliation(s)
- Nouran R. R. Zaid
- Medical Radiation Physics, Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (P.K.); (G.G.)
- Biophysics and Medical Imaging Program, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, An-Najah National University, Nablus 44839, Palestine
| | - Peter Kletting
- Medical Radiation Physics, Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (P.K.); (G.G.)
- Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (G.W.); (V.P.); (A.J.B.)
| | - Gordon Winter
- Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (G.W.); (V.P.); (A.J.B.)
| | - Vikas Prasad
- Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (G.W.); (V.P.); (A.J.B.)
| | - Ambros J. Beer
- Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (G.W.); (V.P.); (A.J.B.)
| | - Gerhard Glatting
- Medical Radiation Physics, Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (P.K.); (G.G.)
- Department of Nuclear Medicine, Ulm University, 89081 Ulm, Germany; (G.W.); (V.P.); (A.J.B.)
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Iida H, Komagata T, Tanaka H, Nagasawa R, Nishio T, Shono T, Kitagawa J, Ogawara KI, Shinozaki K, Seki A, Bruce M, Ohno T. Novel Platform for Predicting Drug Effects in Patients with Acromegaly: Translational Exposure-Response Evaluation of Growth Hormone-Inhibitory Effect of Octreotide after Growth Hormone-Releasing Hormone Stimulation. J Pharmacol Exp Ther 2021; 379:400-408. [PMID: 34599040 DOI: 10.1124/jpet.121.000769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 09/29/2021] [Indexed: 11/22/2022] Open
Abstract
Acromegaly is a chronic systemic disease characterized by facial and peripheral changes caused by soft tissue overgrowth and is associated with multiple comorbidities. Despite available surgical and medical therapies, suitable treatments for acromegaly are still lacking. Efficient drug development requires an understanding of the exposure-response (E-R) relationship based on nonclinical and early clinical studies. We aimed to establish a platform to facilitate the development of novel drugs to treat acromegaly. We evaluated the E-R relationship of the growth hormone (GH)-inhibitory effect of the somatostatin analog octreotide under growth hormone-releasing hormone + arginine stimulation in healthy participants and compared the results with historical data for patients with acromegaly. This randomized five-way crossover study included two placebo and three active-treatment periods with different doses of octreotide acetate. GH secretion in the two placebo periods was comparable, which confirmed the reproducibility of the response with no carryover effect. GH secretion was inhibited by low-, medium-, and high-dose octreotide acetate in a dose-dependent manner. We also examined the E-R relationship in monkeys as a preclinical drug evaluation study and in rats as a more convenient and simple system for screening candidate drugs. The E-R relationships and EC50 values were similar among animals, healthy participants, and patients with acromegaly, which suggests that GH stimulation studies in early research and development allowed simulation of the drug response in patients with acromegaly. SIGNIFICANCE STATEMENT: This study demonstrated similar exposure-response relationships in terms of the growth hormone-inhibitory effect of octreotide after growth hormone-releasing hormone stimulation among healthy participants, monkeys, and rats. The research methods and analyses utilized in this study will be useful for simulating the dosages and therapeutic effects of drugs for acromegaly and will facilitate the research and development of novel therapeutic agents with similar modes of action.
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Affiliation(s)
- Hiroyuki Iida
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Tatsuya Komagata
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Hirotaka Tanaka
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Ryusuke Nagasawa
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Takuya Nishio
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Tomoyuki Shono
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Junsaku Kitagawa
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Ken-Ichi Ogawara
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Koji Shinozaki
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Akiteru Seki
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Mark Bruce
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
| | - Tomoya Ohno
- Ono Pharmaceutical Co., Ltd., Osaka, Japan (H.I., T.K., H.T., R.N., T.N., T.S., J.K., K.S., A.S., T.O.); Laboratory of Pharmaceutics, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Japan (H.I., K.O.); and Ono Pharma UK Ltd., London, United Kingdom (M.B.)
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Somatostatin-Dopamine Chimeric Molecules in Neuroendocrine Neoplasms. J Clin Med 2021; 10:jcm10030501. [PMID: 33535394 PMCID: PMC7867079 DOI: 10.3390/jcm10030501] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 12/12/2022] Open
Abstract
Neuroendocrine neoplasms (NENs) are a widely heterogeneous family of neoplasms arising from neuroendocrine cells, which are interspersed throughout the body. Despite NENs are relatively rare, their incidence and prevalence are constantly increasing probably due to the improvement in earlier diagnosis and patients’ management. When surgery is not curative, particularly for patients with metastatic disease, several medical options are available. Somatostatin analogues (SSA) are the first-line medical therapy for well-differentiated NENs. Interestingly, the heterodimerization of somatostatin receptors (SSTs) with dopamine receptors (DRs) has been discovered in NENs. This phenomenon results in hybrid receptors with enhanced functional activity. On these bases, chimeric molecules embracing somatostatin and dopamine features have been recently developed. The aim of this review is to provide a comprehensive overview of the available preclinical and clinical data regarding chimeric somatostatin-dopamine agonists as a new class of “magic bullet” in the therapy of NENs.
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9
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Olsen C, Memarzadeh K, Ulu A, Carr HS, Bean AJ, Frost JA. Regulation of Somatostatin Receptor 2 Trafficking by C-Tail Motifs and the Retromer. Endocrinology 2019; 160:1031-1043. [PMID: 30822353 PMCID: PMC6462214 DOI: 10.1210/en.2018-00865] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 02/25/2019] [Indexed: 12/15/2022]
Abstract
The Gi-coupled somatostatin receptor 2 (SST2) is a G protein-coupled receptor (GPCR) that mediates many of somatostatin's neuroendocrine actions. Upon stimulation, SST2 is rapidly internalized and transported to early endosomes before being recycled to the plasma membrane. However, little is known about the intracellular itinerary of SST2 after it moves to the early endosomal compartment or the cytoplasmic proteins that regulate its trafficking. As postsynaptic density protein/discs large 1/zonula occludens-1 (PDZ) domain interactions often regulate the trafficking and signaling potential of GPCRs, we examined the role of the SST2 PDZ ligand and additional C-terminal residues in controlling its intracellular trafficking. We determined that SST2 can recycle to the plasma membrane via multiple pathways, including a LAMP1/Rab7-positive late endosome to the trans-Golgi network (TGN) pathway. Trafficking from the late endosome to the TGN is often regulated by the retromer complex of endosomal coat proteins, and disrupting the retromer components sorting nexins 1/2 inhibits the budding of SST2 from late endosomes. Moreover, trafficking through the late endosomal/TGN pathway is dependent on an intact PDZ ligand and C-terminal tail, as truncating either the 3 or 10 C-terminal amino acids of SST2 alters the pathway through which it recycles to the plasma membrane. Moreover, addition of these amino acids to a heterologous receptor is sufficient to redirect it from a degradation pathway to a recycling itinerary. Our results demonstrate that endosomal trafficking of SST2 is dependent on numerous regulatory mechanisms controlled by its C terminus and the retromer machinery.
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Affiliation(s)
- Courtney Olsen
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
| | - Kimiya Memarzadeh
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas
| | - Arzu Ulu
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Heather S Carr
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Andrew J Bean
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas
- Department of Pediatrics, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Jeffrey A Frost
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
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10
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Riedemann T, Sutor B. Long-lasting actions of somatostatin on pyramidal cell excitability in the mouse cingulate cortex. Neurosci Lett 2019; 698:217-223. [PMID: 30668961 DOI: 10.1016/j.neulet.2019.01.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/10/2019] [Accepted: 01/18/2019] [Indexed: 02/07/2023]
Abstract
Many neurological diseases are related to disturbances of somatostatin- (SOM-) expressing interneurons in the cingulate cortex. Therefore, their role within the circuitry of the cingulate cortex needs to be investigated. We describe here the physiological time course of SOM effects onto pyramidal cell excitability and action potential discharge pattern. Furthermore, we show that the GRK2 inhibitor Gallein had no effect on the reduced SOM-induced response following repetitive SOM applications.
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Affiliation(s)
- Therese Riedemann
- Biomedical Center, Ludwig-Maximilians-Universität, Physiological Genomics, Großhaderner Str. 9, 82152 Planegg-Martinsried, Germany.
| | - Bernd Sutor
- Biomedical Center, Ludwig-Maximilians-Universität, Physiological Genomics, Großhaderner Str. 9, 82152 Planegg-Martinsried, Germany
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11
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Treppiedi D, Peverelli E, Giardino E, Ferrante E, Calebiro D, Spada A, Mantovani G. Somatostatin Receptor Type 2 (SSTR2) Internalization and Intracellular Trafficking in Pituitary GH-Secreting Adenomas: Role of Scaffold Proteins and Implications for Pharmacological Resistance. Horm Metab Res 2017; 49:259-268. [PMID: 27632151 DOI: 10.1055/s-0042-116025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AbstractSomatostatin receptor type 2 (SSTR2), together with SSTR5, represents the main
target of medical treatment for growth hormone (GH)-secreting pituitary tumors,
since it is expressed in most of these tumors and exerts both antiproliferative
and cytostatic effects, and reduces hormone secretion, as well. However,
clinical practice indicates a great variability in the frequency and entity of
favorable responses of acromegalic patients to long-acting somatostatin
analogues (SSAs), but the molecular mechanisms regulating this pharmacological
resistance are not completely understood. So far, several potentially implied
mechanisms have been suggested, including impaired expression of SSTRs, or
post-receptor signal transduction alterations. More recently, new studies
exploited the molecular factors involved in SSTRs intracellular trafficking
regulation, this being a critical point for the modulation of the available
active G-coupled receptors (GPCRs) amount at the cell surface. In this respect,
the role of the scaffold proteins such as β-arrestins, and the cytoskeleton
protein Filamin A (FLNA), have become of relevant importance for GH-secreting
pituitary tumors. In fact, β-arrestins are linked to SSTR2 desensitization and
internalization, and FLNA is able to regulate SSTR2 trafficking and stability at
the plasma membrane. Therefore, the present review will summarize emerging
evidence highlighting the role of β-arrestins and FLNA, as possible novel
players in the modulation of agonist activated-SSTR2 receptor trafficking and
response in GH-secreting pituitary tumors.
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Affiliation(s)
- D Treppiedi
- Endocrine Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - E Peverelli
- Endocrine Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - E Giardino
- Endocrine Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - E Ferrante
- Endocrine Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - D Calebiro
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, Würzburg, Germany
| | - A Spada
- Endocrine Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - G Mantovani
- Endocrine Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
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12
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Bronstein MD, Jallad RS. Pasireotide for treating acromegaly. Expert Opin Orphan Drugs 2016. [DOI: 10.1517/21678707.2016.1167593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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13
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Lucas SJ, Armstrong DL. Protein phosphatase modulation of somatostatin receptor signaling in the mouse hippocampus. Neuropharmacology 2015. [PMID: 26196943 DOI: 10.1016/j.neuropharm.2015.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Many inhibitory interneurones in the hippocampus release the neuropeptide somatostatin (SST) which inhibits neuronal excitability through Gi/Go-coupled receptors. To investigate the signaling pathways underlying the SST inhibition of neuronal excitability in the hippocampus, we performed perforated patch-clamp recordings from CA1 pyramidal neurones in acute brain slices from P14-P18 mice. Bath application of 1 μM SST reversibly reduces the frequency of action potential firing in response to depolarising current steps, and is associated with neuronal hyperpolarisation and a reduction in membrane resistance. This effect is mediated by potassium channels with KCNK-like pharmacology. In addition, in slices that have been cultured in vitro for seven days or more, SST also produces a hyperpolarisation independent reduction in action potential firing, which can be also observed in acute slices when the Ser/Thr protein phosphatases PP2A and PP4 are inhibited selectively with fostriecin. This hyperpolarisation independent effect of SST appears to be mediated by G-protein-activated inwardly rectifying K+ (GIRK) channels. Knockdown of protein phosphatase 5, by Cre recombinase mediated deletion of the floxed Ppp5c gene, blocks the hyperpolarisation independent effect of SST, and reduces the hyperpolarisation dependent effect in a manner consistent with increased SST receptor desensitisation. Thus, reversible protein phosphorylation provides a mechanism to enhance or diminish the inhibitory effect of SST, which could allow system level regulation of circuit excitability in the hippocampus.
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Affiliation(s)
- Sarah J Lucas
- Lab. Neurobiology, National Institute of Environmental Health Sciences, NIH, Durham, NC, 27709, USA.
| | - David L Armstrong
- Lab. Neurobiology, National Institute of Environmental Health Sciences, NIH, Durham, NC, 27709, USA
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14
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Azevedo AW, Doan T, Moaven H, Sokal I, Baameur F, Vishnivetskiy SA, Homan KT, Tesmer JJG, Gurevich VV, Chen J, Rieke F. C-terminal threonines and serines play distinct roles in the desensitization of rhodopsin, a G protein-coupled receptor. eLife 2015; 4. [PMID: 25910054 PMCID: PMC4438306 DOI: 10.7554/elife.05981] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 04/23/2015] [Indexed: 12/31/2022] Open
Abstract
Rod photoreceptors generate measurable responses to single-photon activation of individual molecules of the G protein-coupled receptor (GPCR), rhodopsin. Timely rhodopsin desensitization depends on phosphorylation and arrestin binding, which quenches G protein activation. Rhodopsin phosphorylation has been measured biochemically at C-terminal serine residues, suggesting that these residues are critical for producing fast, low-noise responses. The role of native threonine residues is unclear. We compared single-photon responses from rhodopsin lacking native serine or threonine phosphorylation sites. Contrary to expectation, serine-only rhodopsin generated prolonged step-like single-photon responses that terminated abruptly and randomly, whereas threonine-only rhodopsin generated responses that were only modestly slower than normal. We show that the step-like responses of serine-only rhodopsin reflect slow and stochastic arrestin binding. Thus, threonine sites play a privileged role in promoting timely arrestin binding and rhodopsin desensitization. Similar coordination of phosphorylation and arrestin binding may more generally permit tight control of the duration of GPCR activity. DOI:http://dx.doi.org/10.7554/eLife.05981.001 ‘Rod’ cells in the eye enable us to see in starlight. Inside these cells, a protein called rhodopsin is activated by light, which leads to an electrical signal being produced that travels to the brain. The duration of the electrical signal depends on the time it takes for the rhodopsin to be deactivated. Rhodopsin is a member of a large class of receptor proteins known as G protein-coupled receptors that regulate many processes throughout the body. Previous studies have shown that rhodopsin is deactivated by the attachment of phosphate groups to the protein. This allows another protein called arrestin to bind to rhodopsin. The phosphates can be attached to particular amino acids—the building blocks of proteins—at one end of rhodopsin. Three of these are a type of amino acid called serine. Previous work has shown that light increases the speed at which phosphate groups are added to these serines, suggesting that they are important for producing rapid electrical signals. The other three amino acids are of a different type—called threonine—but it is less clear what role they play in deactivating rhodopsin. Here, Azevedo et al. studied mutant forms of rhodopsin that were missing the serines or threonines in mice. The experiments show that loss of the serines only slightly slowed the electrical signals. However, loss of the threonines resulted in much slower electrical signals that ended at random times. This was due to rhodopsin being less able to bind to arrestin. Azevedo et al. propose a new model for how rhodopsin is deactivated. Once light activates the protein, phosphate groups are rapidly added to the serines, which begins to lower the activity of rhodopsin. However, it is the slower addition of phosphates to the threonines that is essential to promote arrestin binding and fully deactivate the protein. Other proteins belonging to the G protein-coupled receptor family also have these serines and threonines, and thus, may be regulated in a similar way. DOI:http://dx.doi.org/10.7554/eLife.05981.002
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Affiliation(s)
- Anthony W Azevedo
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Thuy Doan
- Department of Ophthalmology, University of Washington, Seattle, United States
| | - Hormoz Moaven
- Departments of Cell & Neurobiology and Ophthalmology, Zilkha Neurogenetic Institute, Keck School of Medicine of University of Southern California, Los Angeles, United States
| | - Iza Sokal
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Faiza Baameur
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, United States
| | - Sergey A Vishnivetskiy
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, United States
| | - Kristoff T Homan
- Life Sciences Institute, Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, United States
| | - John J G Tesmer
- Life Sciences Institute, Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, United States
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, United States
| | - Jeannie Chen
- Departments of Cell & Neurobiology and Ophthalmology, Zilkha Neurogenetic Institute, Keck School of Medicine of University of Southern California, Los Angeles, United States
| | - Fred Rieke
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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15
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Abstract
The somatostatin (SRIF) system, which includes the SRIF ligand and receptors, regulates anterior pituitary gland function, mainly inhibiting hormone secretion and to some extent pituitary tumor cell growth. SRIF-14 via its cognate G-protein-coupled receptors (subtypes 1-5) activates multiple cellular signaling pathways including adenylate cyclase/cAMP, MAPK, ion channel-dependent pathways, and others. In addition, recent data have suggested SRIF-independent constitutive SRIF receptor activity responsible for GH and ACTH inhibition in vitro. This review summarizes current knowledge on ligand-dependent and independent SRIF receptor molecular and functional effects on hormone-secreting cells in the anterior pituitary gland.
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Affiliation(s)
- Tamar Eigler
- Division of EndocrinologyDiabetes and Metabolism, Department of Medicine, Pituitary Center, Cedars Sinai Medical Center, Davis Building, Room 3066, 8700 Beverly Boulevard, Los Angeles, California 90048, USA
| | - Anat Ben-Shlomo
- Division of EndocrinologyDiabetes and Metabolism, Department of Medicine, Pituitary Center, Cedars Sinai Medical Center, Davis Building, Room 3066, 8700 Beverly Boulevard, Los Angeles, California 90048, USA
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16
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Reubi JC, Schonbrunn A. Illuminating somatostatin analog action at neuroendocrine tumor receptors. Trends Pharmacol Sci 2013; 34:676-88. [PMID: 24183675 DOI: 10.1016/j.tips.2013.10.001] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 09/26/2013] [Accepted: 10/03/2013] [Indexed: 02/08/2023]
Abstract
Somatostatin analogs for the diagnosis and therapy of neuroendocrine tumors (NETs) have been used in clinical applications for more than two decades. Five somatostatin receptor subtypes have been identified and molecular mechanisms of somatostatin receptor signaling and regulation have been elucidated. These advances increased understanding of the biological role of each somatostatin receptor subtype, their distribution in NETs, as well as agonist-specific regulation of receptor signaling, internalization, and phosphorylation, particularly for the sst2 receptor subtype, which is the primary target of current somatostatin analog therapy for NETs. Various hypotheses exist to explain differences in patient responsiveness to somatostatin analog inhibition of tumor secretion and growth as well as differences in the development of tumor resistance to therapy. In addition, we now have a better understanding of the action of both first generation (octreotide, lanreotide, Octreoscan) and second generation (pasireotide) FDA-approved somatostatin analogs, including the biased agonistic character of some agonists. The increased understanding of somatostatin receptor pharmacology provides new opportunities to design more sophisticated assays to aid the future development of somatostatin analogs with increased efficacy.
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Affiliation(s)
- Jean Claude Reubi
- Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Berne, Switzerland.
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17
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Kozhemyakin M, Rajasekaran K, Todorovic MS, Kowalski SL, Balint C, Kapur J. Somatostatin type-2 receptor activation inhibits glutamate release and prevents status epilepticus. Neurobiol Dis 2013; 54:94-104. [PMID: 23473742 DOI: 10.1016/j.nbd.2013.02.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/06/2013] [Accepted: 02/25/2013] [Indexed: 02/07/2023] Open
Abstract
Newer therapies are needed for the treatment of status epilepticus (SE) refractory to benzodiazepines. Enhanced glutamatergic neurotransmission leads to SE, and AMPA receptors are modified during SE. Reducing glutamate release during SE is a potential approach to terminate SE. The neuropeptide somatostatin (SST) is proposed to diminish presynaptic glutamate release by activating SST type-2 receptors (SST2R). SST exerts an anticonvulsant action in some experimental models of seizures. Here, we investigated the mechanism of action of SST on excitatory synaptic transmission at the Schaffer collateral-CA1 synapses and the ability of SST to treat SE in rats using patch-clamp electrophysiology and video-EEG monitoring of seizures. SST reduced action potential-dependent EPSCs (sEPSCs) at Schaffer collateral-CA1 synapses at concentrations up to 1μM; higher concentrations had no effect or increased the sEPSC frequency. SST also prevented paired-pulse facilitation of evoked EPSCs and did not alter action-potential-independent miniature EPSCs (mEPSCs). The effect of SST on EPSCs was inhibited by the SST2R antagonist cyanamid-154806 and was mimicked by the SST2R agonists, octreotide and lanreotide. Both SST and octreotide reduced the firing rate of CA1 pyramidal neurons. Intraventricular administration of SST, within a range of doses, either prevented or attenuated pilocarpine-induced SE or delayed the median time to the first grade 5 seizure by 11min. Similarly, octreotide or lanreotide prevented or attenuated SE in more than 65% of animals. Compared to the pilocarpine model, octreotide was highly potent in preventing or attenuating continuous hippocampal stimulation-induced SE in all animals within 60min of SE onset. Our results demonstrate that SST, through the activation of SST2Rs, diminishes presynaptic glutamate release and attenuates SE.
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Affiliation(s)
- Maxim Kozhemyakin
- Department of Neurology and Neuroscience, University of Virginia Health Sciences Center, Charlottesville, VA 22908, USA
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18
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Sreenivasan VKA, Kim EJ, Goodchild AK, Connor M, Zvyagin AV. Targeting somatostatin receptors using in situ-bioconjugated fluorescent nanoparticles. Nanomedicine (Lond) 2012; 7:1551-60. [DOI: 10.2217/nnm.12.42] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Aim: The author’s group report, for the first time, on the development of a quantum dot (QD)-based fluorescent somatostatin (somatotropin release-inhibiting factor [SRIF]) probe that enables specific targeting of somatostatin receptors. Receptor-mediated endocytosis of SRIF was imaged using this probe. Materials & methods: Biotinylated SRIF-analog (SRIF-B) and streptavidin (Sav)-coated QDs were used for the probe synthesis. A dye-labeled streptavidin complex was used to evaluate the effect of Sav binding on the activity of SRIF-B. Results: A preconjugated probe of the form SRIF-B:Sav-QD, was inactive and unable to undergo receptor-mediated endocytosis. An alternative in situ bioconjugation strategy, where SRIF-B and Sav-QD were added in two consecutive steps, enabled visualization of the receptor-mediated endocytosis. The process of Sav binding appeared to be responsible for the inactivity in the first case. Conclusion: The in situ two-step bioconjugation strategy allowed QDs to be targeted to somatostatin receptors. This strategy should enable flexible fluorescent tagging of SRIF for the investigation of molecular trafficking in cells and targeted delivery in live animals. Original submitted 14 November 2011; Revised submitted 27 February 2012; Published online 20 July 2012
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Affiliation(s)
| | - Eun J Kim
- Department of Science Education – Chemical Education Major, Daegu University, Gyeonbuk, Republic of Korea
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19
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Waser B, Cescato R, Liu Q, Kao YJ, Körner M, Christ E, Schonbrunn A, Reubi JC. Phosphorylation of sst2 receptors in neuroendocrine tumors after octreotide treatment of patients. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 180:1942-9. [PMID: 22538189 DOI: 10.1016/j.ajpath.2012.01.041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 01/13/2012] [Accepted: 01/26/2012] [Indexed: 12/18/2022]
Abstract
Somatostatin analogues, which are used to treat neuroendocrine tumors, target the high levels of somatostatin receptor subtype 2 (SSTR1; alias sst2) expressed in these cancers. However, some tumors are resistant to somatostatin analogues, and it is unknown whether the defect lies in sst2 activation or downstream signaling events. Because sst2 phosphorylation occurs rapidly after receptor activation, we examined whether sst2 is phosphorylated in neuroendocrine tumors. The sst2 receptor phosphorylation was evaluated by IHC and Western blot analysis with the new Ra-1124 antibody specific for the sst2 receptor phosphorylated at Ser341/343 in receptor-positive neuroendocrine tumors obtained from 10 octreotide-treated and 7 octreotide-naïve patients. The specificity, time course, and subcellular localization of sst2 receptor phosphorylation were examined in human embryo kinase-sst2 cell cultures by immunofluorescence and confocal microscopy. All seven octreotide-naïve tumors displayed exclusively nonphosphorylated cell surface sst2 expression. In contrast, 9 of the 10 octreotide-treated tumors contained phosphorylated sst2 that was predominantly internalized. Western blot analysis confirmed the IHC data. Octreotide treatment of human embryo kinase-sst2 cells in culture demonstrated that phosphorylated sst2 was localized at the plasma membrane after 10 seconds of stimulation and was subsequently internalized into endocytic vesicles. These data show, for the first time to our knowledge, that phosphorylated sst2 is present in most gastrointestinal neuroendocrine tumors from patients treated with octreotide but that a striking variability exists in the subcellular distribution of phosphorylated receptors among such tumors.
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MESH Headings
- Antineoplastic Agents, Hormonal/pharmacology
- Antineoplastic Agents, Hormonal/therapeutic use
- Carcinoma, Neuroendocrine/drug therapy
- Carcinoma, Neuroendocrine/metabolism
- Carcinoma, Neuroendocrine/surgery
- Chemotherapy, Adjuvant
- Humans
- Microscopy, Confocal
- Microscopy, Fluorescence
- Neoplasm Proteins/drug effects
- Neoplasm Proteins/metabolism
- Octreotide/pharmacology
- Octreotide/therapeutic use
- Phosphorylation/drug effects
- Receptors, Somatostatin/drug effects
- Receptors, Somatostatin/metabolism
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Affiliation(s)
- Beatrice Waser
- Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Berne, Switzerland
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20
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Elberg D, Turman MA, Pullen N, Elberg G. Prostaglandin E2 stimulates cystogenesis through EP4 receptor in IMCD-3 cells. Prostaglandins Other Lipid Mediat 2012; 98:11-6. [PMID: 22503965 DOI: 10.1016/j.prostaglandins.2012.03.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 03/21/2012] [Accepted: 03/30/2012] [Indexed: 10/28/2022]
Abstract
Previously, we demonstrated that prostaglandin E(2) (PGE(2)) induced cAMP and cyst formation through PGE(2) receptor-2 (EP2) activity in human autosomal-dominant polycystic kidney disease (ADPKD) epithelial cells. In this study, we determined the role of EP2 and EP4 receptors in mediating PGE(2) stimulation of cAMP signaling and cystogenesis in mouse renal epithelial cells using the inner medullary collecting duct-3 (IMCD-3) cell line. In contrast to human ADPKD cells, using novel EP2 and EP4 antagonists, we found that IMCD-3 cells expressed functional EP4 but not EP2, which stimulated cAMP formation and led to cyst formation in 3D culture system. The involvement of EP4 receptors in IMCD-3 cells was further supported by the specific effect of EP4 siRNA that inhibited PGE(2)-induced cystogenesis. We also observed different cellular localization of EP2 or EP4 receptors in IMCD-3 transfected cells. Collectively, our results suggest an important role of different expression of EP2 or EP4 receptors in the regulation of cystogenesis.
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Affiliation(s)
- Dorit Elberg
- Department of Pediatrics, Section of Nephrology, the University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States
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21
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Abstract
The neuropeptide somatostatin (SRIF) is an important modulator of neurotransmission in the central nervous system and acts as a potent inhibitor of hormone and exocrine secretion. In addition, SRIF regulates cell proliferation in normal and tumorous tissues. The six somatostatin receptor subtypes (sst1, sst2A, sst2B, sst3, sst4, and sst5), which belong to the G protein-coupled receptor (GPCR) family, share a common molecular topology: a hydrophobic core of seven transmembrane-spanning α-helices, three intracellular loops, three extracellular loops, an amino-terminus outside the cell, and a carboxyl-terminus inside the cell. For most of the GPCRs, intracytosolic sequences, and more particularly the C-terminus, are believed to interact with proteins that are mandatory for either exporting neosynthesized receptor, anchoring receptor at the plasma membrane, internalization, recycling, or degradation after ligand binding. Accordingly, most of the SRIF receptors can traffic not only in vitro within different cell types but also in vivo. A picture of the pathways and proteins involved in these processes is beginning to emerge.
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Affiliation(s)
- Zsolt Csaba
- INSERM, Unité Mixte de Recherche U676, Paris, France
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Cakir M, Dworakowska D, Grossman A. Somatostatin receptor biology in neuroendocrine and pituitary tumours: part 1--molecular pathways. J Cell Mol Med 2011; 14:2570-84. [PMID: 20629989 PMCID: PMC4373477 DOI: 10.1111/j.1582-4934.2010.01125.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Neuroendocrine tumours (NETs) may occur at many sites in the body although the majority occur within the gastroenteropancreatic axis. Non-gastroenteropancreatic NETs encompass phaeochromocytomas and paragangliomas, medullary thyroid carcinoma, anterior pituitary tumour, broncho-pulmonary NETs and parathyroid tumours. Like most endocrine tumours, NETs also express somatostatin (SST) receptors (subtypes 1–5) whose ligand SST is known to inhibit endocrine and exocrine secretions and have anti-tumour effects. In the light of this knowledge, the idea of using SST analogues in the treatment of NETs has become increasingly popular and new studies have centred upon the development of new SST analogues. We attempt to review SST receptor (SSTR) biology primarily in neuroendocrine tissues, focusing on pituitary tumours. A full data search was performed through PubMed over the years 2000–2009 with keywords ‘somatostatin, molecular biology, somatostatin receptors, somatostatin signalling, NET, pituitary’ and all relevant publications have been included, together with selected publications prior to that date. SSTR signalling in non-neuroendocrine solid tumours is beyond the scope of this review. SST is a potent anti-proliferative and anti-secretory agent for some NETs. The successful therapeutic use of SST analogues in the treatment of these tumours depends on a thorough understanding of the diverse effects of SSTR subtypes in different tissues and cell types. Further studies will focus on critical points of SSTR biology such as homo- and heterodimerization of SSTRs and the differences between post-receptor signalling pathways of SSTR subtypes.
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Affiliation(s)
- Mehtap Cakir
- Selcuk University, Meram School of Medicine, Division of Endocrinology and Metabolism, Konya, Turkey.
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Kao YJ, Ghosh M, Schonbrunn A. Ligand-dependent mechanisms of sst2A receptor trafficking: role of site-specific phosphorylation and receptor activation in the actions of biased somatostatin agonists. Mol Endocrinol 2011; 25:1040-54. [PMID: 21493671 DOI: 10.1210/me.2010-0398] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The somatostatin receptor subtype 2A (sst2A) mediates many of somatostatin's neuroendocrine actions and is the primary therapeutic target for the stable somatostatin analogs used to inhibit hormone secretion by pituitary and gastroenteropancreatic tumors. Two new multireceptor targeting somatostatin analogs currently under clinical investigation, the multisomatostatin receptor agonist cyclo-[diaminoethylcarbamoyl-HydroxyPro-Phenylglycine-D-Trp-Lys-(4-O-benzyl)Tyr-Phe] (SOM230) (Pasireotide) and pan-somatostatin receptor agonist Tyr-cyclo-[D-diaminobutyric acid-Arg-Phe-Phe-D-Trp-Lys-Thr-Phe] (KE108), behave as functionally selective ligands at the sst2A receptor, mimicking some of somatostatin's actions but antagonizing others. Further, SOM230 and KE108 are less able to induce receptor internalization than somatostatin, indicating that they exhibit functional selectivity for receptor regulation as well as signaling. Here, we identify agonist-specific differences in the molecular events regulating sst2A receptor endocytosis. SOM230 and KE108 were less potent and less effective than somatostatin at stimulating sst2A receptor phosphorylation at two pairs of residues, Ser341/343 and Thr353/354. Only the pattern of Thr353/354 phosphorylation correlated with receptor internalization, consistent with the known importance of Thr phosphorylation for sst2A receptor endocytosis. As expected, arrestin recruitment to membrane receptors was reduced with SOM230 and KE108. In addition, both receptor dephosphorylation and receptor recycling occurred more rapidly with SOM230 and KE108 than with somatostatin. Surprisingly, however, SOM230 and KE108 also altered sst2A internalization in a phosphorylation-independent manner, because these analogs were less effective than somatostatin at stimulating the endocytosis of a phosphorylation-negative receptor mutant. These results show that the decreased receptor internalization produced by SOM230 and KE108 compared with somatostatin result from phosphorylation-independent effects as well as reduced site-specific receptor phosphorylation and receptor-arrestin association.
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Affiliation(s)
- Yachu J Kao
- Department of Integrative Biology and Pharmacology, University of Texas, Health Science Center-Houston, Houston, Texas 77030, USA
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24
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Ghosh M, Schonbrunn A. Differential temporal and spatial regulation of somatostatin receptor phosphorylation and dephosphorylation. J Biol Chem 2011; 286:13561-73. [PMID: 21343287 DOI: 10.1074/jbc.m110.215723] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The G(i)-coupled somatostatin 2A receptor (sst2A) mediates many of the neuromodulatory and neuroendocrine actions of somatostatin (SS) and is targeted by the SS analogs used to treat neuroendocrine tumors. As for other G protein-coupled receptors, agonists stimulate sst2A receptor phosphorylation on multiple residues, and phosphorylation at different sites has distinct effects on receptor internalization and uncoupling. To elucidate the spatial and temporal regulation of sst2A receptor phosphorylation, we examined agonist-stimulated phosphorylation of multiple receptor GPCR kinase sites using phospho-site-specific antibodies. SS increased receptor phosphorylation sequentially, first on Ser-341/343 and then on Thr-353/354, followed by receptor internalization. Reversal of receptor phosphorylation was determined by the duration of prior agonist exposure. In acutely stimulated cells, in which most receptors remained on the cell surface, dephosphorylation occurred only on Thr-353/354. In contrast, both Ser-341/343 and Thr-353/354 were rapidly dephosphorylated when cells were stimulated long enough to allow receptor internalization before agonist removal. Consistent with these observations, dephosphorylation of Thr-353/354 was not affected by either hypertonic sucrose or dynasore, which prevent receptor internalization, whereas dephosphorylation of Ser-341/343 was completely blocked. An okadaic acid- and fostriecin-sensitive phosphatase catalyzed the dephosphorylation of Thr-353/354 both intracellularly and at the cell surface. In contrast, dephosphorylation of Ser-341/343 was insensitive to these inhibitors. Our results show that the phosphorylation and dephosphorylation of neighboring GPCR kinase sites in the sst2A receptor are subject to differential spatial and temporal regulation. Thus, the pattern of receptor phosphorylation is determined by the duration of agonist stimulation and compartment-specific enzymatic activity.
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Affiliation(s)
- Madhumita Ghosh
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas 77225, USA
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25
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War SA, Somvanshi RK, Kumar U. Somatostatin receptor-3 mediated intracellular signaling and apoptosis is regulated by its cytoplasmic terminal. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:390-402. [PMID: 21194548 DOI: 10.1016/j.bbamcr.2010.12.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/25/2010] [Accepted: 12/13/2010] [Indexed: 12/25/2022]
Abstract
In the present study, we describe the role of cytoplasmic terminal (C-tail) domain in regulating coupling to adenylyl cyclase, signaling, and apoptosis in human embryonic kidney (HEK-293) cells transfected with wild type (wt)-hSSTR3 and C-tail deleted mutants. Cells transfected with wt-hSSTR3 and C-tail mutants show comparable membrane expression; however, display decreased expression in presence of agonist. wt-hSSTR3 exists as preformed homodimer at cell surface in basal conditions and decreases in response to agonist. Cells expressing C-tail mutants also show evidence of homodimerization with the same intensity as wt-hSSTR3. The agonist-dependent inhibition of cyclic adenosine monophosphate (cAMP) was lost in cells expressing C-tail mutants. Agonist treatment in cells expressing wt-hSSTR3 resulted in inhibition of cell proliferation, increased expression of PARP-1, and TUNEL positivity in proliferating cell nuclear antigen (PCNA)-positive cells. The agonist mediated increase in membrane expression of protein tyrosine phosphatase (PTP) seen with wt-hSSTR3 was diminished in C-tail mutants, which was accompanied with the loss of receptor's ability to induce apoptosis. Taken together, our data provide new insights into C-tail-dependent regulation of cell signaling and apoptosis by hSSTR3.
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Affiliation(s)
- Sajad A War
- Faculty of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, The University of British Columbia, Vancouver, BC V6T1Z3, Canada
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26
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Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
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27
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Ben-Shlomo A, Melmed S. Pituitary somatostatin receptor signaling. Trends Endocrinol Metab 2010; 21:123-33. [PMID: 20149677 PMCID: PMC2834886 DOI: 10.1016/j.tem.2009.12.003] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 12/09/2009] [Accepted: 12/10/2009] [Indexed: 12/27/2022]
Abstract
Somatotropin-release inhibitory factor (SRIF) is a major regulator of pituitary function, mostly inhibiting hormone secretion and to a lesser extent pituitary cell growth. Five SRIF receptor subtypes (SSTR1-5) are ubiquitously expressed G-protein coupled receptors. In the pituitary, SSTR1, 2, 3 and 5 are expressed, with SSTR2 and SSTR5 predominating. As new SRIF analogs have recently been introduced for treatment of pituitary disease, we evaluate the current knowledge of cell-specific pituitary SRIF receptor signaling and highlight areas of future research for comprehensive understanding of these mechanisms. Elucidating pituitary SRIF receptor signaling enables understanding of pituitary hormone secretion and cell growth, and also encourages future therapeutic development for pituitary disorders.
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Affiliation(s)
- Anat Ben-Shlomo
- Pituitary Center, Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90048, USA
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28
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C-tail mediated modulation of somatostatin receptor type-4 homo- and heterodimerizations and signaling. Cell Signal 2009; 21:1396-414. [PMID: 19426801 DOI: 10.1016/j.cellsig.2009.04.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Revised: 04/23/2009] [Accepted: 04/30/2009] [Indexed: 12/26/2022]
Abstract
Somatostatin receptors show great diversity in response to agonist mediated receptor-specific homo- and heterodimerizations. Here, using photobleaching-fluorescence resonance energy transfer, immunocytochemistry, western blot and co-immunoprecipitation, we investigated dimerization, trafficking, coupling to adenylyl cyclase and signaling of human somatostatin receptor-4 (hSSTR4) in HEK-293 cells. We also determined the role of the C-tail of hSSTR4 on physiological responses of the cells. wt-hSSTR4 exogenously expressed in HEK-293 cells exhibits constitutive dimerization, inhibits forskolin-stimulated cAMP, and displays agonist dependent changes in pERK1/2 and pERK5 expressions. Upon C-tail deletion, the receptor loses membrane expression and ability to dimerize and inhibition of cAMP and pERK5 however, displays several-fold increases in the expression of pERK1/2. Chimeric hSSTR4 with the C-tail of hSSTR5 functions like wt-hSSTR4, in contrast, with the C-tail of hSSTR1 functions like C-tail deleted hSSTR4. hSSTR4 dimerization and signaling are associated with increased cyclin-dependent-kinase p27(kip1) expression and inhibition of the cell proliferation. We also report heterodimerization between hSSTR4/hSSTR5, but not between hSSTR4/hSSTR1, with significant changes in receptor functions. Taken together, these data define a novel mechanism for the role of hSSTR4 in cell proliferation and modulation of signaling pathways.
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29
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Liu Q, Bee MS, Schonbrunn A. Site specificity of agonist and second messenger-activated kinases for somatostatin receptor subtype 2A (Sst2A) phosphorylation. Mol Pharmacol 2009; 76:68-80. [PMID: 19389921 DOI: 10.1124/mol.108.054262] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Somatostatin receptor subtype 2A (sst2A) mediates many of the endocrine and neuronal actions of somatostatin and is the target of somatostatin analogs in cancer therapy. As with many G-protein-coupled receptors, agonist stimulation causes sst2A receptor desensitization and internalization, events that require receptor phosphorylation. Furthermore, heterologous receptor activation of protein kinase C (PKC) also increases sst2A receptor phosphorylation and internalization. Here we analyzed a series of sst2A receptor mutants biochemically to identify residues in the receptor carboxyl terminus that were phosphorylated upon agonist stimulation, and we then generated four phosphorylation-sensitive antibodies to those residues. Once the selectivity of each antibody for its phosphorylated and nonphosphorylated target sequence was determined, the phospho-site-specific antibodies were used to demonstrate that somatostatin treatment of Chinese hamster ovary (CHO) cells expressing the wild type sst2A receptor increased phosphorylation on five residues in the receptor C terminus: Ser341, Ser343, Ser348, Thr353, and Thr354. Phorbol 12-myristate 13-acetate (PMA) increased receptor phosphorylation only on Ser343. Inhibition of PKC blocked PMA but not somatostatin stimulation, showing that different kinases catalyzed Ser343 phosphorylation. In contrast, somatostatin-stimulated sst2A receptor phosphorylation was inhibited by knockdown of G-protein coupled receptor kinase-2 with siRNA. Somatostatin increased sst2A receptor phosphorylation on the same five residues in GH4C1 pituitary cells as in CHO cells. However, PMA stimulated sst2A receptor phosphorylation on both Ser343 and Ser348 in GH4C1 cells. These results characterize the complex pattern of sst2A receptor phosphorylation by agonist and second messenger-activated kinases for the first time and indicate that cell type-specific regulation of sst2A receptor phosphorylation occurs.
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Affiliation(s)
- Qisheng Liu
- Department of Integrative Biology and Pharmacology, University of Texas-Houston, School of Medicine, Houston, TX 77225, USA
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30
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He X, Fang L, Wang J, Yi Y, Zhang S, Xie X. Bryostatin-5 blocks stromal cell-derived factor-1 induced chemotaxis via desensitization and down-regulation of cell surface CXCR4 receptors. Cancer Res 2008; 68:8678-86. [PMID: 18974109 DOI: 10.1158/0008-5472.can-08-0294] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The chemokine receptor CXCR4 and its ligand, stromal cell-derived factor-1 (SDF-1), play important roles in hematopoiesis regulation, lymphocyte activation, and trafficking, as well as in developmental processes, including organogenesis, vascularization, and embryogenesis. The receptor is also involved in HIV infection and tumor growth and metastasis. Antagonists of CXCR4 have been widely evaluated for drugs against HIV and tumors. In an effort to identify novel CXCR4 antagonists, we screened a small library of compounds derived from marine organisms and found bryostatin-5, which potently inhibits chemotaxis induced by SDF-1 in Jurkat cells. Bryostatin-5 is a member of the macrolactones, and its analogue bryostatin-1 is currently being evaluated in clinical trials for its chemotherapeutic potential. The involvement of bryostatins in the SDF-1/CXCR4 signaling process has never been reported. In this study, we found that bryostatin-5 potently inhibits SDF-1-induced chemotaxis but does not affect serum-induced chemotaxis. Further studies indicate that this inhibitory effect is not due to receptor antagonism but rather to bryostatin-5-induced receptor desensitization and down-regulation of cell surface CXCR4. We also show that these effects are mediated by the activation of conventional protein kinase C.
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Affiliation(s)
- Xing He
- National Center for Drug Screening, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Graduate University of the Chinese Academy of Sciences, Shanghai, China
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31
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Biondi C, Ferretti ME, Lunghi L, Medici S, Cervellati F, Abelli L, Bertoni F, Adinolfi E, Vesce F, Bartolini G, Papi A, D'Andrea S, Berton S, Baldassarre G. Somatostatin as a regulator of first-trimester human trophoblast functions. Placenta 2008; 29:660-70. [PMID: 18617261 DOI: 10.1016/j.placenta.2008.05.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 05/09/2008] [Accepted: 05/31/2008] [Indexed: 12/19/2022]
Abstract
We have tested the hypothesis that human early trophoblast is a target for somatostatin (SRIF) regulatory actions. We report for the first time that SSTR2A and 2B transcripts and proteins are present in first-trimester human chorionic villi and the trophoblast-derived HTR-8/SVneo and JAR cells. In both cell lines, SSTR are functional since SRIF inhibits cyclic AMP pathway, stimulates arachidonic acid release and enhances cell proliferation. Moreover, in HTR-8/SVneo cells, considered a good model of first-trimester EVT, SRIF also enhances migration. An involvement of the cyclic AMP pathway in mediating SRIF effects on proliferation and migration is suggested. Our data support the idea that SRIF regulates early trophoblast functions mainly through an interaction with SSTR2.
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Affiliation(s)
- C Biondi
- Department of Biology and Evolution, Sections of General Physiology, University of Ferrara, 44100 Ferrara, Italy
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32
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Vezzosi D, Bennet A, Courbon F, Caron P. Short- and long-term somatostatin analogue treatment in patients with hypoglycaemia related to endogenous hyperinsulinism. Clin Endocrinol (Oxf) 2008; 68:904-11. [PMID: 18031316 DOI: 10.1111/j.1365-2265.2007.03136.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND The long-term efficacy of somatostatin analogues on insulinomas has not been studied. DESIGN A prospective study to evaluate the response of octreotide in 21 patients with hypoglycaemia related to endogenous hyperinsulinism who were not treated by surgery. RESULTS Reasons for not undergoing surgery were: refusal (n = 3), old age with multiple diseases (n = 5), unlocalized insulinomas (n = 2), malignant unresectable insulinomas (n = 5), multiple insulinomas (n = 3) and diffuse beta-cell disease (n = 3). Hypoglycaemia was responsive to octreotide in 14 of the 21 patients. A short 100-microg octreotide test correctly predicted the efficacy of treatment in six patients with benign insulinomas. Octreoscan scintigraphy was positive in 6 of the 16 patients of whom three were responsive and three unresponsive to octreotide. Octreoscan scintigraphy was negative in 10 of the 16 patients, eight of whom were responsive to octreotide. Subcutaneous octreotide treatment was prolonged for > 6 months (7-144 months, 67 +/- 47 months) in 11 responsive patients. No tachyphylaxis was observed. However, the octreotide dose had to be increased in two patients after 3 and 18 months, respectively. Only one patient suffered from symptomatic biliary lithiasis after 3 years of treatment. CONCLUSION Long-term octreotide treatment can be used to control hypoglycaemia in patients with endogenous hyperinsulinism who are not eligible for surgery; octreotide efficacy on hypoglycaemia could be predicted by a short 100 microg-octreotide test in patients with benign insulinomas, but was not correctly predicted by Octreoscan scintigraphy.
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Affiliation(s)
- D Vezzosi
- Department of Endocrinology, Centre Hospitalier Universitaire, Toulouse, France
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33
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Jacobs S, Schulz S. Intracellular trafficking of somatostatin receptors. Mol Cell Endocrinol 2008; 286:58-62. [PMID: 18045773 DOI: 10.1016/j.mce.2007.10.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Revised: 09/03/2007] [Accepted: 10/10/2007] [Indexed: 01/28/2023]
Abstract
The somatostatin receptor subtypes 1-5 (sst(1)-sst(5)) exhibit different intracellular trafficking and endosomal sorting after agonist exposure. The internalization of the somatostatin receptor subtypes sst(2), sst(3) and sst(5) occurs to a much higher extent after somatostatin exposure than of sst(1) or sst(4). After endocytosis, sst(2) and sst(5) recycle to the plasma membrane, whereas sst(3) is predominantly down-regulated. This review will focus on the molecular mechanisms of the differential intracellular trafficking of sst(2), sst(3) and sst(5), and discusses our current knowledge on somatostatin receptor interacting proteins.
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Affiliation(s)
- Stefan Jacobs
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, Würzburg, Germany
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34
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Schonbrunn A. Selective agonism in somatostatin receptor signaling and regulation. Mol Cell Endocrinol 2008; 286:35-9. [PMID: 18006219 PMCID: PMC2435097 DOI: 10.1016/j.mce.2007.09.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 09/25/2007] [Indexed: 12/13/2022]
Abstract
The five somatostatin receptor subtypes, named sst1-sst5, activate both distinct and common signaling pathways and exhibit different patterns of receptor regulation. Until recently it was believed that once a particular somatostatin receptor was activated by an agonist, all the down-stream signaling and regulatory effects characteristic of that receptor subtype in that cellular environment would be triggered. Thus, differences in the actions of somatostatin analogs between tissues were attributed to variability in the nature and concentration of the sst receptor subtypes and effectors expressed in different targets. However, agonists have recently been shown to exhibit functional selectivity at individual sst receptors such that they can elicit a subset of that receptor's potential effects, a property known as biased agonism. This review will summarize the evidence for functionally selective somatostatin receptor agonists and discuss the implications and promise of these new findings.
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Affiliation(s)
- Agnes Schonbrunn
- Department of Integrative Biology and Pharmacology, University of Texas-Houston, School of Medicine, Houston, TX 77225, USA.
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35
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Zhu T, Fang LY, Xie X. Development of a universal high-throughput calcium assay for G-protein- coupled receptors with promiscuous G-protein Galpha15/16. Acta Pharmacol Sin 2008; 29:507-16. [PMID: 18358098 DOI: 10.1111/j.1745-7254.2008.00775.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
AIM To develop a universal high-throughput screening assay based on Galpha15/16- mediated calcium mobilization for the identification of novel modulators of Gprotein- coupled receptors (GPCR). METHODS In the present study, CHO-K1 or HEK293 cells were co-transfected with plasmids encoding promiscuous G-protein Galpha15/16 and various receptors originally coupled to Galphas, Galphai, or Galphaq pathways. Intracellular calcium change was monitored with fluorescent dye Fluo-4. RESULTS We found out for all the receptors tested, Galpha15/16 could shift the receptorso coupling to the calcium mobilization pathway, and the EC50 values of the ligands generated with this method were comparable with reported values that were obtained using traditional methods. This assay was validated and optimized with the zeta-opioid receptor, which originally coupled to Galphai and was recently found to play important roles in neurodegenerative and autoimmune diseases. A largescale screening of 48 000 compounds was performed based on this system. Several new modulators were identified and confirmed with the traditional GTPgammaS binding assay. CONCLUSION This cell-based calcium assay was proved to be robust and easy to automate, and could be used as a universal method in searching for GPCR modulators.
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Affiliation(s)
- Ting Zhu
- The National Center for Drug Screening, Chinese Academy of Sciences, Shanghai 201203, China
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36
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Liu Q, Dewi DA, Liu W, Bee MS, Schonbrunn A. Distinct phosphorylation sites in the SST2A somatostatin receptor control internalization, desensitization, and arrestin binding. Mol Pharmacol 2007; 73:292-304. [PMID: 17981995 DOI: 10.1124/mol.107.038570] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The somatostatin subtype 2A (sst2A) receptor, a member of the G protein-coupled receptor superfamily, mediates many of the neuroendocrine and neuromodulatory actions of somatostatin, and it represents the primary target for somatostatin analogs used in cancer therapy and tumor localization. Agonist stimulation leads to the rapid phosphorylation, endocytosis, and desensitization of the sst2A receptor; however, little is known about the role of phosphorylation in sst2A regulation. sst2A phosphorylation occurs on serine and threonine residues in the third intracellular loop and carboxyl terminus. Therefore, we generated mutant receptors in which serine (Ser-), threonine (Thr-), or both (Ser-/Thr-) residues in these regions were mutated to alanine. In contrast to the wild-type receptor, somatostatin treatment did not stimulate the phosphorylation of the Ser-/Thr- mutant, and it did not produce desensitization. Furthermore, internalization of the Ser-/Thr- mutant occurred 5 times more slowly than with the wild-type receptor. Mutating only the Ser residues did not inhibit either internalization or desensitization. In contrast, mutating only the Thr residues inhibited receptor endocytosis to the same extent as in the full mutant, but it did not affect receptor desensitization. In both the wild-type and Ser- receptors, agonist binding produced a stable arrestin-receptor complex that was maintained during receptor trafficking, whereas arrestin was not recruited to either the Thr- or the Ser-/Thr- receptors. These results demonstrate that agonist-stimulated receptor phosphorylation is necessary for both desensitization and rapid internalization of the sst2A receptor. However, sst2A receptor internalization and uncoupling can occur independently, involve different receptor phosphorylation sites, and exhibit different requirements for stable arrestin association.
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Affiliation(s)
- Q Liu
- Department of Integrative Biology and Pharmacology, School of Medicine, University of Texas-Houston, P.O. Box 20708, Houston, TX 77225, USA
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37
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Gonsiorek W, Lunn CA, Fan X, Deno G, Kozlowski J, Hipkin RW. Sch35966 is a potent, selective agonist at the peripheral cannabinoid receptor (CB2) in rodents and primates. Br J Pharmacol 2007; 151:1262-71. [PMID: 17603556 PMCID: PMC2189839 DOI: 10.1038/sj.bjp.0707336] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE The peripheral cannabinoid receptor (CB(2)) is expressed on peripheral immune cells and is thought to have a role in the immunosuppressive effects of cannabinoids. Historically, there have been few potent, CB(2)-selective agonists to assess the contribution of CB(2) to this phenomenon. The studies presented here describe the synthesis of 8,10-bis[(2,2-dimethyl-1-oxopropyl)oxy]-11-methyl-1234-tetrahydro-6H-benzo[beta]quinolizin-6-one (Sch35966), which binds with low nanomolar potency to CB(2) in both primates and rodents. EXPERIMENTAL APPROACH The affinity, potency and efficacy of Sch35966 and other cannabinoid ligands at CB(2) was assessed using competition binding assays vs [(3)H]CP55,940, [(35)S]GTPgammaS exchange, cAMP accumulation and cell chemotaxis assays. KEY RESULTS We showed that Sch35966 has >450-fold selectivity for CB(2) binding vs the central cannabinoid receptor (CB(1)) in primates (humans and cynomolgus monkeys) and rodents (rats and mice). Sch35966 is an agonist as it effectively inhibited forskolin-stimulated cAMP synthesis in CHO-hCB(2) cells, stimulated [(35)S]GTPgammaS exchange and directed chemotaxis in cell membranes expressing CB(2). In all species examined, Sch35966 was more potent, more efficacious and more selective than JWH-015 (a commonly used CB(2)-selective agonist). CONCLUSIONS AND IMPLICATIONS Taken together, the data show that Sch35966 is a potent and efficacious CB(2)-selective agonist in rodents and primates.
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Affiliation(s)
- W Gonsiorek
- Department of Inflammation, Schering-Plough Research Institute Kenilworth, NJ, USA
| | - C A Lunn
- Department of New Lead Discovery, Schering-Plough Research Institute Kenilworth, NJ, USA
| | - X Fan
- Department of Inflammation, Schering-Plough Research Institute Kenilworth, NJ, USA
| | - G Deno
- Department of Inflammation, Schering-Plough Research Institute Kenilworth, NJ, USA
| | - J Kozlowski
- Department of Chemistry, Schering-Plough Research Institute Kenilworth, NJ, USA
| | - R W Hipkin
- Department of Inflammation, Schering-Plough Research Institute Kenilworth, NJ, USA
- Author for correspondence:
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Yang SK, Parkington HC, Epelbaum J, Keating DJ, Chen C. Somatostatin decreases voltage-gated Ca2+ currents in GH3 cells through activation of somatostatin receptor 2. Am J Physiol Endocrinol Metab 2007; 292:E1863-70. [PMID: 17327372 DOI: 10.1152/ajpendo.00047.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The secretion of growth hormone (GH) is inhibited by hypothalamic somatostatin (SRIF) in somatotropes through five subtypes of the somatostatin receptor (SSTR1-SSTR5). We aimed to characterize the subtype(s) of SSTRs involved in the Ca2+ current reduction in GH3 somatotrope cells using specific SSTR subtype agonists. We used nystatin-perforated patch clamp to record voltage-gated Ca2+ currents, using a holding potential of -80 mV in the presence of K+ and Na+ channel blockers. We first established the presence of T-, L-, N-, and P/Q-type Ca2+ currents in GH3 cells using a variety of channel blockers (Ni+, nifedipine, omega-conotoxin GVIA, and omega-agatoxin IVA). SRIF (200 nM) reduced L- and N-type but not T- or P/Q-type currents in GH3 cells. A range of concentrations of each specific SSTR agonist was tested on Ca2+ currents to find the maximal effective concentration. Activation of SSTR2 with 10(-7) and 10(-8) M L-797,976 decreased the voltage-gated Ca2+ current and abolished any further decrease by SRIF. SSTR1, SSTR3, SSTR4, and SSTR5 agonists at 10(-7) M did not modify the voltage-gated Ca2+ current and did not affect the Ca2+ current response to SRIF. These results indicate that SSTR2 is involved mainly in regulating voltage-gated Ca2+ currents by SRIF, which contributes to the decrease in intracellular Ca2+ concentration and GH secretion by SRIF.
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Affiliation(s)
- Seung-Kwon Yang
- Prince Henry's Institute of Medical Research, PO Box 5152, Clayton, Victoria 3168, Australia
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Gonsiorek W, Fan X, Hesk D, Fossetta J, Qiu H, Jakway J, Billah M, Dwyer M, Chao J, Deno G, Taveras A, Lundell DJ, Hipkin RW. Pharmacological characterization of Sch527123, a potent allosteric CXCR1/CXCR2 antagonist. J Pharmacol Exp Ther 2007; 322:477-85. [PMID: 17496166 DOI: 10.1124/jpet.106.118927] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In neutrophils, growth-related protein-alpha (CXCL1) and interleukin-8 (CXCL8), are potent chemoattractants (Cytokine 14:27-36, 2001; Biochemistry 42:2874-2886, 2003) and can stimulate myeloperoxidase release via activation of the G protein-coupled receptors CXCR1 and CXCR2. The role of CXCR1 and CXCR2 in the pathogenesis of inflammatory responses has encouraged the development of small molecule antagonists for these receptors. The data presented herein describe the pharmacology of 2-hydroxy-N,N-dimethyl-3-{2-[[(R)-1-(5-methyl-furan-2-yl)-propyl]amino]-3,4-dioxo-cyclobut-1-enylamino}-benzamide (Sch527123), a novel antagonist of both CXCR1 and CXCR2. Sch527123 inhibited chemokine binding to (and activation of) these receptors in an insurmountable manner and, as such, is categorized as an allosteric antagonist. Sch527123 inhibited neutrophil chemotaxis and myeloperoxidase release in response to CXCL1 and CXCL8 but had no effect on the response of these cells to C5a or formyl-methionyl-leucyl-phenylalanine. The pharmacological specificity of Sch527123 was confirmed by testing in a diversity profile against a panel of enzymes, channels, and receptors. To measure compound affinity, we characterized [(3)H]Sch527123 in both equilibrium and nonequilibrium binding analyses. Sch527123 binding to CXCR1 and CXCR2 was both saturable and reversible. Although Sch527123 bound to CXCR1 with good affinity (K(d) = 3.9 +/- 0.3 nM), the compound is CXCR2-selective (K(d) = 0.049 +/- 0.004 nM). Taken together, our data show that Sch527123 represents a novel, potent, and specific CXCR2 antagonist with potential therapeutic utility in a variety of inflammatory conditions.
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Affiliation(s)
- Waldemar Gonsiorek
- Department of Inflammation, K15 E332C-3945, Schering-Plough Research Institute, 2015 Galloping Hill Rd, Kenilworth, NJ 07033-0539, USA
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Sharif N, Gendron L, Wowchuk J, Sarret P, Mazella J, Beaudet A, Stroh T. Coexpression of somatostatin receptor subtype 5 affects internalization and trafficking of somatostatin receptor subtype 2. Endocrinology 2007; 148:2095-105. [PMID: 17272399 DOI: 10.1210/en.2006-1266] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The somatostatin [somatotropin release-inhibiting factor (SRIF)] receptor subtypes sst(2A) and sst(5) are frequently coexpressed in SRIF-responsive cells, including endocrine pituitary cells. We previously demonstrated that sst(2A) and sst(5) exhibit different subcellular localizations and regulation of cell surface expression, although they have similar signaling properties. We investigated here whether sst(2A) and sst(5) functionally interact in cells coexpressing the two receptor subtypes. We stimulated both transfected cells stably expressing sst(2A) alone (CHO-sst(2A)) or together with sst(5) (CHO-sst(2A+5)) and the pituitary cell line AtT20, which endogenously expresses the two receptor subtypes, with either the nonselective agonist [D-Trp(8)]-SRIF-14 or the sst(2)-selective agonist L-779,976. In CHO-sst(2A) cells, stimulation with either ligand resulted in the loss of approximately 75% of cell surface SRIF binding sites and massive internalization of sst(2A) receptors. The cells were desensitized to subsequent stimulation with [D-Trp(8)]-SRIF-14, which failed to inhibit forskolin-evoked cAMP accumulation. Similarly, in CHO-sst(2A+5) and AtT20 cells, [D-Trp(8)]-SRIF-14 induced the loss of 60-70% of SRIF binding sites as well as massive sst(2A) endocytosis. By contrast, in cells expressing both sst(2A) and sst(5), selective stimulation of sst(2A) with L-779,976 resulted in only 20-40% loss of cell surface binding and markedly reduced sst(2A) internalization. Consequently, whereas CHO-sst(2A+5) and AtT20 cells stimulated with [D-Trp(8)]-SRIF-14 were desensitized to a second stimulation with the same agonist, cells prestimulated with L-779,976 were not desensitized to subsequent [D-Trp(8)]-SRIF-14 stimulation. These findings indicate that the presence of sst(5) in the same cells modulates trafficking and cell surface regulation of sst(2A) and cellular desensitization to the effects of SRIF.
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Affiliation(s)
- Nadder Sharif
- Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada H3A 2B6
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Abstract
The experimental data reviewed in the present paper deal with the molecular events underlying the agonist-dependent regulation of the distinct somatostatin receptor subtypes and may suggest important clues about the clinical use of somatostatin analogs with different pattern of receptor specificity for the in vivo targeting of tumoral somatostatin receptors. Somatostatin receptor subtypes are characterized by differential beta-arrestin trafficking and endosomal sorting upon agonist binding due, at least in part, to the differences in their C-terminal tails. Moreover, the subcellular expression pattern of somatostatin receptor subtypes and their activity in response to agonist treatment are affected by intracellular complements, such as proteins involved in intracellular vesicle trafficking. Different somatostatin analogs may induce distinct conformations of the receptor/ligand complex, preferentially coupled to either receptor signaling or receptor endocytosis.
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Dwyer MP, Yu Y, Chao J, Aki C, Chao J, Biju P, Girijavallabhan V, Rindgen D, Bond R, Mayer-Ezel R, Jakway J, Hipkin RW, Fossetta J, Gonsiorek W, Bian H, Fan X, Terminelli C, Fine J, Lundell D, Merritt JR, Rokosz LL, Kaiser B, Li G, Wang W, Stauffer T, Ozgur L, Baldwin J, Taveras AG. Discovery of 2-hydroxy-N,N-dimethyl-3-{2-[[(R)-1-(5- methylfuran-2-yl)propyl]amino]-3,4-dioxocyclobut-1-enylamino}benzamide (SCH 527123): a potent, orally bioavailable CXCR2/CXCR1 receptor antagonist. J Med Chem 2007; 49:7603-6. [PMID: 17181143 DOI: 10.1021/jm0609622] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structure-activity studies on lead cyclobutenedione 3 led to the discovery of 4 (SCH 527123), a potent, orally bioavailable CXCR2/CXCR1 receptor antagonist with excellent cell-based activity. Compound 4 displayed good oral bioavailability in rat and may be a potential therapeutic agent for the treatment of various inflammatory diseases.
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Affiliation(s)
- Michael P Dwyer
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA.
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Durán-Prado M, Bucharles C, Gonzalez BJ, Vázquez-Martínez R, Martínez-Fuentes AJ, García-Navarro S, Rhodes SJ, Vaudry H, Malagón MM, Castaño JP. Porcine somatostatin receptor 2 displays typical pharmacological sst2 features but unique dynamics of homodimerization and internalization. Endocrinology 2007; 148:411-21. [PMID: 17053026 DOI: 10.1210/en.2006-0920] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Somatostatin (SRIF) exerts its multiple actions, including inhibition of GH secretion and of tumoral growth, through a family of five receptor subtypes (sst1-sst5). We recently reported that an sst2-selective agonist markedly decreases GH release from pig somatotropes, suggesting important roles for this scarcely explored receptor, psst2. Here, functional expression of psst2 in Chinese hamster ovary-K1 and human embryonic kidney-293-AD cell lines was employed to determine its pharmacological features and functional ability to reduce cAMP, and to examine its homodimerization and internalization dynamics in real time in single living cells. Results show that psst2 is a high-affinity receptor (dissociation constant = 0.27 nM) displaying a typical sst2 profile (nM affinity for SRIF-14> or =SRIF-28>cortistatin>MK678>octreotide) and high selectivity (EC(50) = 1.1 nM) for the sst2 agonist l-779,976, but millimolar or undetectable affinity to other sst-specific agonists (sst3>sst1>sst5>>>sst4). Accordingly, SRIF dose-dependently inhibited forskolin-stimulated cAMP with high potency (EC(50) = 6.55 pm) and modest efficacy (maximum 29.1%) via psst2. Cotransfection of human embryonic kidney-293 and Chinese hamster ovary-K1 cells with two receptor constructs modified with distinct fluorescent tags (psst2-YFP/psst2-CFP) enabled fluorescence resonance energy transfer measurement of physical interaction between psst2 receptors and also receptor internalization in single living cells. This revealed that under basal conditions, psst2 forms constitutive homodimers/homomultimers, which dissociate immediately (11 sec) upon SRIF binding. Interestingly, contrary to human sst2, psst2 rapidly reassociates (110.5 sec) during a subsequent process that temporally overlaps with receptor internalization (half-maximal = 95.1 sec). Therefore, psst2 is a potent inhibitory receptor displaying a unique set of interrelated dynamic features of agonist-dependent dimerization, dissociation, internalization, and reassociation, a cascade of events that might be critical for receptor function.
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Affiliation(s)
- Mario Durán-Prado
- Department of Cell Biology, University of Córdoba, E-14014 Córdoba, Spain
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Lattuada D, Casnici C, Crotta K, Mastrotto C, Franco P, Schmid HA, Marelli O. Inhibitory effect of pasireotide and octreotide on lymphocyte activation. J Neuroimmunol 2007; 182:153-9. [PMID: 17113654 DOI: 10.1016/j.jneuroim.2006.10.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 10/10/2006] [Accepted: 10/11/2006] [Indexed: 11/29/2022]
Abstract
Somatostatin (SST) regulates the function of the central and peripheral nervous system, the endocrine and exocrine organs, as well as the vascular and immune system. These actions are mediated by five specific membrane somatostatin receptors. This study compares the effects on human lymphocytes of two long-acting somatostatin analogues that have different receptor affinity: octreotide and pasireotide. Both analogues have an antiproliferative effect on human lymphocyte proliferation, but they act at different concentration and, while octreotide enhances IL10 and inhibits gamma IFN pasireotide inhibits IL2 and gamma IFN. In both sets of experiment the different behaviour of the two analogues could be due to their different affinity to the SSTR subtypes. Finally this study suggest that the growth inhibitory action of somatostatin analogues is an apoptotic phenomenon and it can be mediated by SSTR2a, in the case of octreotide, and by SSTR3 when pasireotide is used or it can be mediated by the heterodimerization of the two receptor.
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Affiliation(s)
- D Lattuada
- Department of Pharmacology, School of Medicine, University of Milan, Italy.
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Fan X, Patera AC, Pong-Kennedy A, Deno G, Gonsiorek W, Manfra DJ, Vassileva G, Zeng M, Jackson C, Sullivan L, Sharif-Rodriguez W, Opdenakker G, Van Damme J, Hedrick JA, Lundell D, Lira SA, Hipkin RW. Murine CXCR1 is a functional receptor for GCP-2/CXCL6 and interleukin-8/CXCL8. J Biol Chem 2006; 282:11658-66. [PMID: 17197447 DOI: 10.1074/jbc.m607705200] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Functional interleuin-8 (IL-8) receptors (IL-8RA and IL-8RB: CXCR1 and CXCR2, respectively) have been described in human, monkey, dog, rabbit, and guinea pig. Although three IL-8R homologues have been found in rat, only one of these, rat CXCR2, appears to be functional based on responsiveness to ligands. Similarly, CXC chemokines induce biological responses through the murine homolog of CXCR2, but the identification of functional rodent CXCR1 homologues has remained elusive. We have identified and characterized the mouse CXCR1 homologue (mCXCR1). Murine CXCR1 shares 68 and 88% amino acid identity with its human and rat counterparts, respectively. Similar to the tissue distribution pattern of rat CXCR1, we found murine CXCR1 mRNA expression predominantly in lung, stomach, bone marrow, and leukocyte-rich tissues. In contrast to previous reports, we determined that mCXCR1 is a functional receptor. We show predominant engagement of this receptor by mouse GCP-2/CXCL6, human GCP-2, and IL-8/CXCL8 by binding, stimulation of GTPgammaS exchange, and chemotaxis of mCXCR1-transfected cells. Furthermore, murine CXCR1 is not responsive to the human CXCR2 ligands ENA-78/CXCL5, NAP-2/CXCL7, GRO-alpha, -beta, -gamma/CXCL1-3, or rat CINC-1-3. In addition, we show concomitant elevation of mCXCR1 and its proposed major ligand, GCP-2, positively correlated with paw swelling in murine collagen-induced arthritis. This report represents the first description of a functional CXCR1-like receptor in rodents.
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Affiliation(s)
- Xuedong Fan
- Inflammation Department, Discovery Technologies Department, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA
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Pintér E, Helyes Z, Szolcsányi J. Inhibitory effect of somatostatin on inflammation and nociception. Pharmacol Ther 2006; 112:440-56. [PMID: 16764934 DOI: 10.1016/j.pharmthera.2006.04.010] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Accepted: 04/27/2006] [Indexed: 10/24/2022]
Abstract
The present review focuses on promising new opportunities for anti-inflammatory and analgesic therapy. The theoretical background is an original observation based on our own experimental results. These data demonstrate that somatostatin is released from capsaicin-sensitive, peptidergic sensory nerve endings in response to noxious heat and chemical stimuli such as vanilloids, protons or lipoxygenase products. It reaches distant parts of the body via the circulation and exerts systemic anti-inflammatory and analgesic effects. Somatostatin binds to G-protein-coupled membrane receptors (sst(1)-sst(5)) and diminishes neurogenic inflammation by prejunctional action on sensory-efferent nerve terminals, as well as by postjunctional mechanisms on target cells. It decreases the release of pro-inflammatory neuropeptides from sensory nerve endings and also acts on receptors of vascular endothelial, inflammatory and immune cells. Analgesic effect is mediated by an inhibitory action on peripheral terminals of nociceptive neurons, since circulating somatostatin cannot exert central action. Somatostatin itself is not suitable for drug development because of its broad spectrum and short elimination half life, stable, receptor-selective agonists have been synthesized and investigated. The present overview is aimed at summarizing the physiological importance of somatostatin and sst receptors, pharmacological significance of synthetic agonists and their potential in the development of novel anti-inflammatory and analgesic drugs. These compounds might provide novel perspectives in the pharmacotherapy of acute and chronic painful inflammatory diseases, as well as neuropathic conditions.
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Affiliation(s)
- Erika Pintér
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs, H-7624 Pécs, Szigeti u. 12, Hungary.
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Gonsiorek W, Hesk D, Chen SC, Kinsley D, Fine JS, Jackson JV, Bober LA, Deno G, Bian H, Fossetta J, Lunn CA, Kozlowski JA, Lavey B, Piwinski J, Narula SK, Lundell DJ, Hipkin RW. Characterization of Peripheral Human Cannabinoid Receptor (hCB2) Expression and Pharmacology Using a Novel Radioligand, [35S]Sch225336. J Biol Chem 2006; 281:28143-51. [PMID: 16754676 DOI: 10.1074/jbc.m602364200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Studies to characterize the endogenous expression and pharmacology of peripheral human cannabinoid receptor (hCB2) have been hampered by the dearth of authentic anti-hCB2 antibodies and the lack of radioligands with CB2 selectivity. We recently described a novel CB2 inverse agonist, N-[1(S)-[4-[[4-methoxy-2-[(4methoxyphenyl)sulfonyl] phenyl]sulfonyl] phenyl]ethyl]methane-sulfonamide (Sch225336), that binds hCB2 with high affinity and excellent selectivity versus hCB1. The precursor primary amine of Sch225336 was prepared and reacted directly with [(35)S]mesyl chloride (synthesized from commercially obtained [(35)S]methane sulfonic acid) to generate [(35)S]Sch225336. [(35)S]Sch225336 has high specific activity (>1,400 Ci/mmol) and affinity for hCB2 (65 pm). Using [(35)S]Sch225336, we assayed hemopoietic cells and cell lines to quantitate the expression and pharmacology of hCB2. Lastly, we used [(35)S]Sch225336 for detailed autoradiographic analysis of CB2 in lymphoid tissues. Based on these data, we conclude that [(35)S]Sch225336 represents a unique radioligand for the study of CB2 endogenously expressed in blood cells and tissues.
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Affiliation(s)
- Waldemar Gonsiorek
- Department of Inflammation, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA
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Huang HC, Wang SS, Lee FY, Chang FY, Lin HC, Hou MC, Yang YY, Lee SD. Lanreotide on collateral response to endothelin-1 and vasopressin in cirrhotic rats. J Chin Med Assoc 2006; 69:397-403. [PMID: 17051749 DOI: 10.1016/s1726-4901(09)70281-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
BACKGROUND Portosystemic collaterals in cirrhosis are often complicated with hemorrhage. Endothelin-1 (ET-1) and arginine vasopressin (AVP) have been shown to directly constrict collaterals of portal hypertensive rats. Furthermore, octreotide, a long-acting somatostatin analog, enhances ET-1-related collateral vasoconstriction if administered in the perfusate before ET-1 incubation. However, long-term effects of somatostatin analogs on collateral response to ET-1 and AVP remain unclarified. This study investigated the effects of lanreotide (a longer-acting somatostatin analog when compared with octreotide) on the portosystemic collateral vascular reactiveness to ET-1 and AVP in cirrhotic rats. METHODS Liver cirrhosis was induced in Sprague-Dawley rats by common bile duct ligation (BDL). On the 33rd day after BDL, rats received 1 intramuscular injection with lanreotide (10 mg/kg) or distilled water. On the 43rd day after BDL, systemic, and portal hemodynamics were evaluated. By an in situ perfusion model, ET-1 (10(-10) - 10(-7) mol/L) and AVP (10(-10) - 3 x 10(-7) mol/L) were applied to assess the collateral responses. RESULTS Heart rate, mean arterial pressure, and portal pressure were not modified by lanreotide. Lanreotide pretreatment enhanced collateral vascular response to ET-1 and reached statistical significance at 10(-7) mol/L without inducing changes to AVP. CONCLUSION Lanreotide augmented the collateral vascular responsiveness to ET-1 but not to AVP in cirrhotic rats.
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Affiliation(s)
- Hui-Chun Huang
- Division of Gastroenterology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
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Watt HL, Kumar U. Colocalization of somatostatin receptors and epidermal growth factor receptors in breast cancer cells. Cancer Cell Int 2006; 6:5. [PMID: 16519802 PMCID: PMC1479379 DOI: 10.1186/1475-2867-6-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 03/06/2006] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Somatostatin receptor (SSTR) expression is positively correlated with tumor size and inversely correlated with epidermal growth factor receptor (ErbB) levels and tumor differentiation. In the present study, we compared SSTR1-5 and ErbB1-4 mRNA and protein expression in two breast cancer cell lines: MCF-7 (ER+) and MDA-MB-231 (ERalpha-). RESULTS All five SSTRs and four ErbBs were variably expressed as both cell surface and cytoplasmic proteins. In both cell lines, SSTR4 and SSTR1 were highly expressed, followed by SSTR2 and SSTR5 with SSTR3 being the least expressed subtype, at the protein level. ErbBs were variably expressed with ErbB1 as the predominant subtype in both cell lines. ErbB1 is followed by ErbB3, ErbB2 and ErbB4 in MCF-7 at both the protein and mRNA levels. In MDA-MB-231 cells, ErbB1 is followed by ErbB2, ErbB4 and ErbB3. Our results indicate significant correlations at the level of mRNA and protein expression in a cell and receptor-specific manner. Using indirect immunofluorescence, we found that, in MCF-7 cells, SSTR5 was the most prominent subtype coexpressed with ErbBs followed by SSTR3, SSTR4, SSTR1 and SSTR2, respectively. In MDA-MB-231 cells, SSTR1 colocalized strongly with ErbBs followed by SSTR5, SSTR4, SSTR3 and SSTR2. ErbBs displayed higher levels of colocalization amongst themselves in MCF-7 cells than in MDA-MB-231 cells. CONCLUSION These findings may explain the poor response to endocrine therapy in ER-cancer. Differential distribution of SSTR subtypes with ErbBs in breast cancer cells in a receptor-specific manner may be considered as a novel diagnosis for breast tumors.
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Affiliation(s)
- Heather L Watt
- Fraser Laboratories For Diabetes Research, Department of Medicine, Royal Victoria Hospital, McGill University, Montreal, Quebec, H3A 1A1, Canada
| | - Ujendra Kumar
- Faculty of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, The University of British Columbia, Vancouver, BC, Canada
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Vezzosi D, Bennet A, Rochaix P, Courbon F, Selves J, Pradere B, Buscail L, Susini C, Caron P. Octreotide in insulinoma patients: efficacy on hypoglycemia, relationships with Octreoscan scintigraphy and immunostaining with anti-sst2A and anti-sst5 antibodies. Eur J Endocrinol 2005; 152:757-67. [PMID: 15879362 DOI: 10.1530/eje.1.01901] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
OBJECTIVE We studied the efficacy of octreotide treatment on hypoglycaemia in patients with insulinoma and its relationships with Octreoscan scintigraphy and the presence of tumoral somatostatin receptors sst2A and sst5. DESIGN AND METHODS 17 patients with insulinoma were evaluated using (i) evaluation of blood glucose, insulin and C-peptide during a short 100 mug octreotide test in fasting patients and/or treatment over 8 days-8 months with octreotide, (ii) Octreoscan scintigraphy and (iii) immunostaining of the tumor with anti-sst2A and anti-sst5. RESULTS Octreotide was effective on hypoglycaemia in 10/17 patients. Octreoscan scintigraphy detected 4/17 insulinomas. sst2A receptor was detected in 7/17 insulinomas and sst5 in 15/17 insulinomas. Octreotide was effective on hypoglycaemia in those seven patients with sst2A receptor-expressing insulinoma, and in three patients with undetectable sst2A receptor and detectable sst5; it was ineffective in six patients whose tumor expressed the sst5 receptor with undetectable sst2A and in one patient with undetectable sst2A and sst5 receptor. CONCLUSIONS Octreotide is an effective treatment of hypoglycaemia in more than 50% of patients with insulinoma. Detection of responsive patients was better based on a positive short test with subcutaneous octreotide than on the results of Octreoscan scintigraphy. Positive anti-sst2 receptor immunostaining is associated with efficacy of octreotide treatment, but does not account for all cases of responsiveness to octreotide. Expression of sst5 receptor does not appear to explain per se the efficacy of octreotide on sst2A-negative insulinomas.
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