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Varamini P, Mansfeld FM, Giddam AK, Steyn F, Toth I. New gonadotropin-releasing hormone glycolipids with direct antiproliferative activity and gonadotropin-releasing potency. Int J Pharm 2017; 521:327-336. [PMID: 28232269 DOI: 10.1016/j.ijpharm.2017.02.054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 02/10/2017] [Accepted: 02/19/2017] [Indexed: 11/19/2022]
Affiliation(s)
- Pegah Varamini
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia.
| | - Friederike M Mansfeld
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Ashwini Kumar Giddam
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Frederik Steyn
- The University of Queensland Centre for Clinical Research and the School of Biomedical Sciences, Brisbane, Australia
| | - Istvan Toth
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia; School of Pharmacy, The University of Queensland, Brisbane, Australia; Institute for Molecular Biosciences, The University of Queensland, Brisbane, Australia
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2
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Mansfeld FM, Toth I. Lipidated analogues of luteinizing hormone-releasing hormone (LHRH) reduce serum levels of follicle-stimulating hormone (FSH) after oral administration. Int J Pharm 2012; 439:216-22. [DOI: 10.1016/j.ijpharm.2012.09.038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 09/11/2012] [Accepted: 09/17/2012] [Indexed: 11/24/2022]
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3
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Therapeutic effects of leuprorelin microspheres on endometriosis and uterine leiomyomata. Adv Drug Deliv Rev 1997. [DOI: 10.1016/s0169-409x(97)00055-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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4
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Van Leusden HA. Impact of different GnRH analogs in benign gynecological disorders related to their chemical structure, delivery systems and dose. Gynecol Endocrinol 1994; 8:215-22. [PMID: 7847108 DOI: 10.3109/09513599409072458] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
This review addresses the question of whether the different gonadotropin releasing hormone (GnRH) agonists in clinical use might have different impacts, related to their chemical structure, delivery system and dose. Impact was investigated in benign gynecological disorders, i.e. endometriosis and leiomyoma. Arguments are presented indicating that a difference in impact of different analogs can be expected. All currently used intranasal, daily subcutaneous and depot preparations finally give rise to low levels of serum estradiol. The number of days before the first ovulatory menstruation after discontinuation of GnRH agonist treatment is remarkably constant. Four weeks after the last impact of the agonist, there is resumption of follicle growth. This phenomenon is independent of chemical structure, delivery system and dose. One should realize, however, that it generally takes about 30 days before the impact of a depot preparation disappears. Consequently, the impact of a depot preparation lasts 4 weeks longer than that of an otherwise applied agonist. Thus resumption of pituitary activity after discontinuation of a depot formulation takes 4 weeks longer than after discontinuation of non-depot formulations. All agonists have an impressive effect on endometriosis, independent of their chemical structure and delivery system. However, there are no studies comparing different agonists with the same delivery system in comparable endometriosis groups. Similarly, all agonists considerably reduce myoma volume, independently of their chemical structure and delivery system.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H A Van Leusden
- Department of Obstetrics and Gynaecology, Rijnstate-EG Hospital, Arnhem, The Netherlands
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5
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Contijoch AM, Advis JP. Median eminence and anterior pituitary degradation of luteinizing hormone releasing hormone in hens undergoing changes in luteinizing hormone secretion. Poult Sci 1993; 72:1756-63. [PMID: 8234136 DOI: 10.3382/ps.0721756] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Studies described in this report provide physiological evidence for a possible involvement of median eminence (ME) and anterior pituitary (AP) luteinizing hormone releasing hormone degrading activity (LHRH-DA) in the genesis of the hen's preovulatory surge of luteinizing hormone (LH). Serum LH and progesterone (P4), ME LHRH content and LHRH-DA, and AP LHRH-DA were determined in laying hens in the following reproductive conditions: 1) a "spontaneous" preovulatory LH surge; 2) a "premature" preovulatory LH surge; and 3) an ovulatory failure induced by feed withdrawal. The premature preovulatory surge of LH occurred 3 h after P4 administration and was preceded by an increase in both ME and AP LHRH-DA and by a decrease in ME LHRH content 1 h after P4 administration. However, the premature preovulatory LH surge was associated with a decrease in LHRH-DA back to control levels as ME LHRH content increased, even though LHRH was presumably being released from the ME at this time to maintain the preovulatory surge of LH. Although similar changes in LHRH-DA (an increase in both ME and AP LHRH-DA, followed by a decrease) also preceded the spontaneous preovulatory surge of LH, its profile was significantly blunted and no changes in ME LHRH content were associated with this LH surge. In contrast, ovulatory failure was correlated with a decrease in ME LHRH content but no changes in LHRH-DA. Therefore, in the hen, ME and AP enzymatic degradation of LHRH I might be involved in the genesis of a premature preovulatory surge of LH.
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Affiliation(s)
- A M Contijoch
- Department of Animal Sciences, Rutgers University, New Brunswick, New Jersey 08903
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6
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Miró F, Sampaio MC, Tarin JJ, Pellicer A. Steroidogenesis in vitro of human granulosa-luteal cells pretreated in vivo with two gonadotropin releasing hormone analogs employing different protocols. Gynecol Endocrinol 1992; 6:77-84. [PMID: 1502933 DOI: 10.3109/09513599209046389] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have previously observed impaired progesterone accumulation in vitro in response to human chorionic gonadotropin (hCG) by cells pretreated in vivo with a gonadotropin releasing hormone analog (GnRH-a). The present study was conducted in order to evaluate different protocols for GnRH-a in in vitro fertilization (IVF), employing two different available analogs. Granulosa-luteal cells were collected at ovum pick-up and stimulated with hCG. Buserelin (Bus) was employed as long (Bus-L) and short (Bus-S) protocol, and Leuprolide (Leu) was also used as long (Leu-L) and short (Leu-S) protocol. Progesterone accumulation in vitro was compared with cells treated with clomiphene citrate (CC) and gonadotropins. Maximal progesterone production was observed on culture day 6 using Bus-L in comparison to day 4 when clomiphene citrate was employed. While Leu-S showed a similar pattern of progesterone accumulation to clomiphene citrate, Leu-L and Bus-S had an intermediate pattern. The response to hCG was maximal on day 4 for the clomiphene citrate- and Leu-S-treated cells, while the rest of the protocols had a peak on day 6. In addition, hCG consistently stimulated progesterone production in all protocols except in Bus-L. These results confirm an altered progesterone accumulation in vitro when GnRH-a are used. The effect seems to be more evident in long protocols, especially when buserelin is used, suggesting a higher accumulation of the analog in follicular fluid.
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Affiliation(s)
- F Miró
- Instituto Valenciano de Infertilidad, Valencia University School of Medicine, Spain
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8
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Affiliation(s)
- P M Conn
- Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242-1109
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9
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Qayum A, Gullick WJ, Waxman J. Gonadotrophin-releasing hormone: physiological significance and relevance to cancer. PROGRESS IN GROWTH FACTOR RESEARCH 1991; 3:115-30. [PMID: 1663406 DOI: 10.1016/s0955-2235(05)80003-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Gonadotrophin releasing hormone (GnRH) is a decapeptide released by the hypothalamus. The binding of the peptide to pituitary receptors leads to the activation of second messenger systems. The physiological outcome of the exposure of pituitary cells to GnRH is the release of luteinising hormone (LH) and follicle-stimulating hormone (FSH). Continued exposure of these receptors to high concentrations of the peptide desensitises the receptor, thus inhibiting the release of gonadotrophins. This paradoxical effect has proved to be beneficial in the clinic where long-acting and enzyme-resistant analogues are used to inhibit the pituitary-gonadal axis, for example in the treatment of advanced prostatic cancer. In addition GnRH-analogues may affect tumour cells directly as observed in vitro. These direct effects have been described as inhibitory but recent data suggests that low concentrations of GnRH-analogues may stimulate short term growth of prostatic cancer cells in vitro. GnRH shares many other common characteristics with peptide growth factors, including common second messenger systems and receptor desensitisation on prolonged exposure to the ligand. It is possible that the direct inhibitory effects of GnRH-analogues are mediated through the desensitisation of tumour GnRH receptors, as suggested by recent observations. The nature and mechanism of the direct anti-tumour effect is important to understand and to promote the therapeutic efficacy of GnRH-analogues in the clinic.
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Affiliation(s)
- A Qayum
- Department of Clinical Oncology, Hammersmith Hospital, London, U.K
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10
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O'Cuinn G, O'Connor B, Elmore M. Degradation of thyrotropin-releasing hormone and luteinising hormone-releasing hormone by enzymes of brain tissue. J Neurochem 1990; 54:1-13. [PMID: 2104543 DOI: 10.1111/j.1471-4159.1990.tb13276.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this article, the enzymes of brain and associated tissues that can degrade thyrotropin-releasing hormone (TRH) and luteinising hormone-releasing hormone (LH-RH) are reviewed. As both TRH and LH-RH are considered to act as neurotransmitters or neuromodulators in the CNS, attention is paid to the subcellular location of the enzymes described and how their topographies and substrate specificities fit them to playing roles as inactivating agents for TRH and LH-RH or as regulators of intracellular concentrations of TRH and LH-RH. Consideration is also given to enzymes involved in biotransformation of TRH to secondary metabolites that exhibit biological activity and to enzymes involved in the metabolism of secondary metabolites.
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Affiliation(s)
- G O'Cuinn
- Department of Life Sciences, Regional Technical College, Galway, Ireland
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11
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Møss J, Bundgaard H. Prodrugs of peptides. 5. Protection of the pyroglutamyl residue against pyroglutamyl aminopeptidase by bioreversible derivatization with glyoxylic acid derivatives. Int J Pharm 1989. [DOI: 10.1016/0378-5173(89)90228-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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12
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Frohman LA, Downs TR, Heimer EP, Felix AM. Dipeptidylpeptidase IV and trypsin-like enzymatic degradation of human growth hormone-releasing hormone in plasma. J Clin Invest 1989; 83:1533-40. [PMID: 2565342 PMCID: PMC303858 DOI: 10.1172/jci114049] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The plasma enzyme responsible for primary proteolytic cleavage of growth hormone-releasing hormone (GRH) at the 2-3 amino acid bond was characterized. Native GRH[GRH(1-44)-NH2 and GRH(1-40)-OH], and COOH-terminally shortened fragments [GRH(1-32)-NH2 and GRH(1-29)-NH2] were rapidly cleaved, while GRH(2-32)-NH2 was not degraded at this site. Moreover, degradation to GRH(3-44)-NH2 was unaffected by an aminopeptidase inhibitor, indicating that this metabolite was generated from a single step cleavage by a dipeptidylpeptidase (DPP) rather than sequential aminopeptidase cleavages. Conversion to GRH(3-44)-NH2 was blocked by diprotin A, a DPP type IV (DPP IV) competitive inhibitor. D-Amino acid substitution at either position 1 or 2 also prevented hydrolysis, characteristic of DPP IV. Analysis of endogenous plasma GRH immunoreactivity from a human GRH transgenic pig revealed that the major peak coeluted with GRH(3-44)-NH2. Native GRH exhibited trypsin-like degradation at the 11-12 position but cleavage at the 12-13 site occurred only with GRH(1-32)-NH2 and GRH(1-29)-NH2. Formation of these metabolites was independent of prior DPP IV hydrolysis but was greatly reduced by trypsin inhibitors. Evaluation of plasma stability of potential GRH super analogues, designed to resist degradation by these enzymes, confirmed that GRH degradation in plasma occurs primarily by DPP IV, and to a lesser extent by trypsin-like enzyme(s).
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Affiliation(s)
- L A Frohman
- Department of Internal Medicine, University of Cincinnati College of Medicine, Ohio 45267
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13
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KELLY JULIEA, GRIFFITHS EC. A Comparison of TRH and Analogue Degradation by Rat Spinal Cord, Brain Stem, and Cortex. Ann N Y Acad Sci 1989. [DOI: 10.1111/j.1749-6632.1989.tb46698.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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14
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KELLY JULIEA, GRIFFITHS EC. A Comparison of TRH and Analogue Degradation by Rat Spinal Cord, Brain Stem, and Cortex. Ann N Y Acad Sci 1989. [DOI: 10.1111/j.1749-6632.1989.tb54544.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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15
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Suen CS, Wilk S. Regulation of thyrotropin releasing hormone degrading enzymes in rat brain and pituitary by L-3,5,3'-triiodothyronine. J Neurochem 1989; 52:884-8. [PMID: 2563758 DOI: 10.1111/j.1471-4159.1989.tb02537.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effect of treatment with L-3,5,3'-triiodothyronine (T3) on the levels of pyroglutamyl peptidase I and pyroglutamyl peptidase II in rat brain regions, pituitary, and serum was studied. Pyroglutamyl peptidase I cleaves pyroglutamyl peptides such as thyrotropin releasing hormone (TRH), luteinizing hormone releasing hormone, neurotensin, and bombesin, whereas pyroglutamyl peptidase II appears to be specific for TRH. Acute administration of T3 did not affect pyroglutamyl peptidase I in any of the regions studied, whereas pyroglutamyl peptidase II was significantly elevated in frontal cortex and pituitary. Treatment with T3 for 10 or 14 days significantly elevated pyroglutamyl peptidase I in pituitary, hypothalamus, olfactory bulb, hippocampus, and thalamus. Chronic T3 treatment elevated pyroglutamyl peptidase II in frontal cortex and in serum. These studies demonstrate regulation of neuropeptide degrading enzymes by thyroid hormones in vivo. This regulation may play a role in the negative feedback control of thyroid status by T3.
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Affiliation(s)
- C S Suen
- Department of Pharmacology, Mount Sinai School of Medicine, City University of New York, New York 10029
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16
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GRIFFITHS EC, KELLY JULIEA, ASHCROFT ALISON, WARD DJ, ROBSON B. PART V. TRH METABOLISM: Comparative Metabolism and Conformation of TRH and Its Analogues. Ann N Y Acad Sci 1989. [DOI: 10.1111/j.1749-6632.1989.tb54491.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Griffiths EC, Kelly JA, Ashcroft A, Ward DJ, Robson B. Comparative metabolism and conformation of TRH and its analogues. Ann N Y Acad Sci 1989; 553:217-31. [PMID: 2497673 DOI: 10.1111/j.1749-6632.1989.tb46645.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- E C Griffiths
- Department of Physiological Sciences, University of Manchester, England
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18
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Bundgaard H, Møss J. Prodrugs of peptides. IV: Bioreversible derivatization of the pyroglutamyl group by N-acylation and N-aminomethylation to effect protection against pyroglutamyl aminopeptidase. J Pharm Sci 1989; 78:122-6. [PMID: 2565975 DOI: 10.1002/jps.2600780210] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Various N-acyl derivatives and N-Mannich bases of the model compound L-pyroglutamyl benzylamide were synthesized to assess their suitability as prodrug forms for the N-terminal pyroglutamyl residue occurring in several peptides, with the aim of improving peptide delivery characteristics. Whereas pyroglutamyl benzylamide was rapidly hydrolyzed by pyroglutamyl aminopeptidase, the N-acyl derivatives and N-Mannich bases (N-aminomethyl derivatives) were totally resistant to cleavage by the enzyme. On the other hand, these derivatives are readily bioreversible, the conversion to the parent pyroglutamyl amide taking place either by spontaneous hydrolysis at physiological pH, as demonstrated for the N-Mannich bases, or by plasma enzymes, as shown for the N-acyl derivatives. The results suggest that by appropriate N-acylation or N-aminomethylation it may be feasible to protect pyroglutamyl-containing peptides against cleavage by pyroglutamyl aminopeptidase and to obtain a release of the parent peptide in the organism, hence improving the delivery characteristics of such peptides.
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Affiliation(s)
- H Bundgaard
- Royal Danish School of Pharmacy, Department of Pharmaceutical Chemistry AD, Copenhagen, Denmark
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19
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Harvey S, Foltzer-Jourdainne C, Karmann H, Mialhe P. Thyrotrophin-releasing hormone-induced growth hormone secretion in ducks: independence of peripheral plasma somatostatin, insulin, and glucagon. Gen Comp Endocrinol 1988; 70:374-81. [PMID: 2901384 DOI: 10.1016/0016-6480(88)90111-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In young, but not old, ducks the iv infusion of thyrotrophin-releasing hormone (TRH) markedly increased peripheral plasma growth hormone (GH) concentrations, which remained elevated throughout the 30-min period of infusion. This GH response to TRH was suppressed by the simultaneous infusion of somatostatin, which increased the level of circulating somatostatin-like immunoreactivity (SLI) to supraphysiological levels. Basal concentrations of plasma SLI in both young and old birds were suppressed by TRH infusion. Concentrations of glucagon-like immunoreactivity (GLI) were increased by the infusion of TRH in young birds but not in adults, whereas plasma immunoreactive insulin (IRI) was decreased in young birds and increased in adults following TRH infusion. These results indicate that TRH-induced GH secretion in ducks is unrelated to changes in peripheral plasma SLI, GLI, or IRI induced by TRH infusion.
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Affiliation(s)
- S Harvey
- Department of Physiology, University of Alberta, Edmonton, Canada
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20
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Abstract
The application of steroid-modifying drugs as a strategy for the treatment of hormone-dependent cancers has gained increasing popularity during the past decade. However, it is important to point out and emphasize that very few of the agents were originally designed for their current application. Most were designed for other purposes, predominantly fertility control (e.g. LHRH agonists and the antiestrogens). Nevertheless, now it is possible to integrate their actions to design rational therapies. There are many reasons for the current interest in antisteroidal drugs. The initial euphoria over the potential ability of combination chemotherapy to cure breast and prostatic carcinoma has proved to be premature. Combination chemotherapy has many severe side-effects which limits patient acceptability, especially if the patient realizes that the likelihood of a cure is remote. In the main, antisteroidal therapies do not have many side-effects and those that do, e.g. aminoglutethimide, are the focus of increased efforts in drug design to produce increased drug specificity. Finally, there is a growing realization that hormone-dependent cancer control with a nontoxic, antisteroidal therapy may be the most acceptable approach currently available for early disease management. Chemotherapy would then be reserved as the final option for treatment. The description of drug metabolism has been central to the development of synthetic LHRH analogs and an understanding of the mode of action of nonsteroidal antiestrogens and antiandrogens. The discovery of steroid synthetic pathways has been essential for the development of the aromatase inhibitors. This whole area of endeavor has now become a major focus of attention for the medicinal chemist. A new generation of agents is entering clinical evaluation which will provide a wealth of valuable information about the successful (or unsuccessful?) methods to control hormone-dependent disease. Since the success or failure of a drug can often depend upon formulation, pharmacokinetics, bioavailability or metabolism, it is our hope that this overview might help solve some of the future problems.
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Affiliation(s)
- S P Robinson
- Department of Human Oncology, University of Wisconsin Clinical Cancer Center, Madison 53792
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Amir S, Harel M, Rivkind AI. Thyrotropin-releasing hormone potently reverses epinephrine-stimulated hyperglycemia in mice. Brain Res 1987; 435:112-22. [PMID: 3123010 DOI: 10.1016/0006-8993(87)91592-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Intracerebroventricular microinjection of thyrotropin-releasing hormone (TRH) potently blocked the development of, as well as promptly reversed, epinephrine-stimulated hyperglycemia in mice. The central antihyperglycemic effect was dose-related (0.1-10 micrograms), could be reproduced by an intravenous injection of a large dose of the peptide (100 micrograms), was independent of experimental factors such as stress and age, was effective against other hyperglycemic stimuli, and appeared to be unique to TRH, as it could not be mimicked by many other centrally active peptides known to influence glucoregulation in normoglycemic animals. Moreover, the antihyperglycemic effect of TRH appeared to depend on the structural integrity of the peptide molecule but seemed to be unrelated to the peptide's hypophysiotropic actions or to interaction of the peptide with previously characterized TRH receptors, as it could be mimicked by various analogs devoid of thyrotropin- and prolactin-releasing influences or by peptides resembling TRH in amino acid composition but lacking substantial binding affinity to TRH receptors. Furthermore, the effect of TRH to reverse epinephrine-stimulated hyperglycemia appeared to be mediated by combined action of peripheral sympathetic and parasympathetic mechanisms to stimulate insulin release from the pancreas, since only complete blockade of the central autonomic outflow, but not selective perturbation of the sympathetic or parasympathetic outflow, or depletion of pancreatic insulin could substantially attenuate the antihyperglycemic action. Taken together, these results suggest a new physiologic role of TRH as a central glucoregulatory neuropeptide involved in autonomic modulation of insulin secretion and prevention of hyperglycemia.
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Affiliation(s)
- S Amir
- Center for Neurosciences and Behavioral Research, Weizmann Institute of Science, Rehovot, Israel
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22
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Ward DJ, Finn PW, Griffiths EC, Robson B. Comparative conformation-activity relationships for hormonally- and centrally-acting TRH analogues. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1987; 30:263-74. [PMID: 2824390 DOI: 10.1111/j.1399-3011.1987.tb03334.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Empirical energy calculations have been applied to a series of thyrotrophin-releasing hormone (TRH) analogues in an attempt to incorporate the conformational parameter into traditional Quantitative Structure-Activity Relationships (QSAR). A search was made of the potential surface of each analogue using a SIMPLEX technique coupled with a model representing solvent effects as a dielectric continuum. Conformers of TRH can be described in terms of the distance between the pyroglutamyl, imidazole and prolyl rings, and presented as two-dimensional descriptor coordinates using multidimensional scaling. This process was repeated for stable and metastable conformers of all the TRH analogues investigated and correlated with experimental data on receptor affinity, relative stability and biological potency of the analogues. The results obtained suggest that modifications to the TRH structure can lead to greater potency in addition to improved stability, and that providing the appropriate theoretical approach is taken, it is possible to apply QSAR-based design procedures to conformationally-flexible drugs.
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Affiliation(s)
- D J Ward
- Department of Biochemistry & Molecular Biology, School of Biological Sciences, University of Manchester, England
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23
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Abstract
The antinociceptive action of the 2 main metabolites of thyrotropin-releasing hormone (TRH), pyroglutamyl-histidyl-proline (TRH-OH) and histidyl-proline-diketopiperazine or cyclo(His-Pro), were studied using mechanical (Haffner's test) and chemical (phenyl-p-benzoquinone writhing test) stimuli. TRH has previously been shown to be active against both these stimuli. TRH-OH showed an antinociceptive action against both stimuli, while cyclo(His-Pro) had a dose-dependent effect only against a mechanical stimulus. Both metabolites of TRH were less effective than TRH. The antinociception induced by TRH does not appear to depend on the biotransformation of TRH to its metabolites since they are less active than TRH itself.
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Abstract
The particulate fraction of brain homogenates contains an enzyme that cleaves the pyroglutamyl-histidyl bond of thyrotropin-releasing hormone (TRH) but is clearly distinct from the more widely distributed pyroglutamyl peptidase (EC 3.4.19.3). This particulate enzyme is highly localized to brain where it is found on synaptosomal membranes. It exhibits an unusual degree of substrate specificity. For example, it does not cleave the pyroglutamyl-histidyl bond of luteinizing hormone-releasing hormone (LHRH) or the pyroglutamyl histidyl bond of the chromogenic substrate pyroglutamyl-histidyl-2-naphthylamide. Evidence is reviewed supporting the possibility that this enzyme, first detected in serum and originally referred to as "thyroliberinase", may be the first neuropeptide-specific peptidase to be characterized.
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Hedger MP, Robertson DM, Tepe SJ, Browne CA, de Kretser DM. Degradation of luteinizing hormone-releasing hormone (LHRH) and an LHRH agonist by the rat testis. Mol Cell Endocrinol 1986; 46:59-70. [PMID: 3519317 DOI: 10.1016/0303-7207(86)90070-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Degradation of LHRH and [D-Ser(tBu)6,des-Gly-NH10(2)]LHRH ethylamide (LHRH-A), during incubation with high-speed supernatants of rat testes, as assessed by reversed-phase (RP)-HPLC fractionation of the iodinated peptides and by radioimmunoassays for LHRH or LHRH-A, was principally due to a neutral 43 000 Da peptidase with apparent Km values at 25 degrees C of 0.15 microM for LHRH and 1.19 microM for LHRH-A. The peptidase was inhibited by sulphydryl reagents, TLCK, 1,10-phenanthroline, EDTA, bacitracin, other LHRH analogues, oxytocin, [Lys8]vasopressin and somatostatin. It was predomantly located in seminiferous tubule supernatants (98% of recovered activity), with much lower levels in interstitial fluid (2%), interstitial tissue or testicular particulate fractions (less than 0.8%). Extracts of cultured immature Sertoli cells produced LHRH- and LHRH-A-degradation profiles, as assessed by RP-HPLC, that were identical to those produced by testicular supernatants. Similar levels of peptidase activity/mg protein were observed in immature and adult rat testes. These studies indicate that the principal LHRH-peptidase in the rat testis is produced by cells of the seminiferous epithelium, chiefly the Sertoli cell, and may play an important role in regulating the activity of LHRH and other peptide hormones in the testis.
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Bramley TA, Menzies GS. Subcellular fractionation of the human corpus luteum: distribution of GnRH agonist binding sites. Mol Cell Endocrinol 1986; 45:27-36. [PMID: 3084319 DOI: 10.1016/0303-7207(86)90079-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We have investigated the subcellular localization of GnRH agonist (GnRHA) binding sites in the human corpus luteum. Corpora lutea (CL) were obtained from 13 women undergoing laparotomy during the luteal phase of the menstrual cycle. CL homogenates were subjected to subcellular fractionation by either differential rate centrifugation or by sucrose density gradient fractionation with or without digitonin perturbation. Fractions were then assayed for a number of marker activities characteristic of the major intracellular organelles and cell-surface membranes, and for specific binding of [125I]GnRHA. Specific binding of [125I]GnRH agonist was greatest in regions of the gradient (density, 1.12-1.15 g/cm3) enriched in cell-surface and endoplasmic reticulum membrane markers. Little or no GnRHA binding was associated with fractions enriched in nuclei, mitochondria or lysosomes. Digitonin treatment demonstrated that the majority of GnRHA binding sites were associated with luteal cell plasma-membranes: however, some GnRHA binding was also associated with endoplasmic reticulum. These results indicate that: (i) human luteal GnRHA binding sites were not associated with lysosomal proteases, (ii) a significant fraction (59%) of GnRHA binding sites was localised on the luteal cell-surface membrane. Specific GnRHA binding to both cell-surface and endoplasmic reticulum membranes may indicate an extensive turnover of membrane binding sites.
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Chapter 6. Formation and Degradation of Neuropeptides. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1986. [DOI: 10.1016/s0065-7743(08)61116-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Amir S, Rivkind AI, Harel M. Central thyrotropin-releasing hormone elicits systemic hypoglycemia in mice. Brain Res 1985; 344:387-91. [PMID: 3930002 DOI: 10.1016/0006-8993(85)90821-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Thyrotropin-releasing hormone (TRH), injected into the central nervous system (CNS) in rats, has been shown to elicit systemic hyperglycemia. In the present study, central TRH administration significantly decreased the plasma glucose in mice. The hypoglycemic response could be blocked by pretreatment with the muscarinic cholinergic antagonist, atropine methyl bromide, or the diabetogenic beta-cytotoxin, alloxan, implicating the involvement of the parasympathetic system and insulin-secreting cells in the endocrine pancreas. The role of TRH in the CNS in the autonomic regulation of glucose homeostasis is discussed.
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Griffiths EC, Baris C, Visser TJ, Klootwijk W. Thyrotrophin-releasing hormone inactivation by human postmortem brain. REGULATORY PEPTIDES 1985; 10:145-55. [PMID: 3922011 DOI: 10.1016/0167-0115(85)90009-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The mechanisms of inactivation of thyrotrophin-releasing hormone (TRH) by peptidases in several areas of normal human postmortem brain have been investigated by radioimmunoassay and high-performance liquid chromatography. Of the several brain regions studied, the cerebral cortex (Brodman's area, BA10) had the highest TRH-degrading activity in both subcellular fractions. Deamidated-TRH (TRH-OH) was the only product formed by the soluble fraction whereas the histidyl-proline diketopiperazine, cyclo(His-Pro), and a small amount of TRH-OH were formed by the particulate fraction. Several centrally acting TRH analogues showed varying degrees of resistance to degradation by the peptidases in the two fractions, the most stable analogue being RX77368 (pGlu-His-3,3'-dimethyl(ProNH2]. Areas of human postmortem brain appear to contain two of the enzymes capable of degrading TRH, a proline endopeptidase forming TRH-OH and a pyroglutamyl aminopeptidase forming cyclo(His-Pro). The use of the assay procedures in further studies on the inactivation of TRH by peptidases from brain areas of patients with neurological disorders may provide complementary information on the dynamics of TRH in these disorders. The stability of the centrally acting TRH analogues may prove useful in examining their therapeutic potential.
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Sharp T, Bennett GW, Marsden CA, Tulloch IF. A comparison of the locomotor effects induced by centrally injected TRH and TRH analogues. REGULATORY PEPTIDES 1984; 9:305-15. [PMID: 6441196 DOI: 10.1016/0167-0115(84)90083-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Thyrotrophin-releasing hormone (TRH) and its stable analogues CG3509 and RX77368 were injected directly into the nucleus accumbens, septum and striatum of the rat and locomotor activity was recorded. TRH (5-20 micrograms) caused a dose-dependent increase in locomotor activity when injected into the nucleus accumbens. TRH (20 micrograms) also increased locomotor activity after administration into the septum but not when put into the striatum. Both the TRH analogues (0.1 and 1.0 microgram) produced closely related increases in activity when injected into either the nucleus accumbens or septum but CG3509 was more potent with a longer lasting effect. Also, in contrast with TRH (20 micrograms), both TRH analogues stimulated locomotor activity when injected into the striatum at a dose of 1 microgram but the effect was less marked and delayed in onset compared to the nucleus accumbens and septum response. Dopamine (100 micrograms) injected into the accumbens or septum also produced significant increases in locomotor activity. The locomotor effects of the peptides are discussed in relation to a possible dopamine-mediated mechanism which contrasts with the actions of TRH and the analogues on barbiturate anaesthesia.
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McDermott JR, Kidd AM. Ion-exchange, gel-filtration and reversed-phase high-performance liquid chromatography in the isolation of neurotensin-degrading enzymes from rat brain. J Chromatogr A 1984; 296:231-9. [PMID: 6480742 DOI: 10.1016/s0021-9673(01)96416-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Brain and pituitary peptidases involved in the metabolism of neurotensin were identified by ion-exchange (TSK-545 DEAE) and gel-filtration (TSK-G4000 SW) high-performance liquid chromatography (HPLC). Reversed-phase HPLC on radial compression cartridges was used in a rapid assay of neurotensin-hydrolysing activity in column fractions and at the same time the bond specificity of the activity was determined. Semipreparative isolation of the major enzyme which cleaves neurotensin at Arg8-Arg9 was carried out and some of its characteristics were determined.
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Johnson AL, Dickerman RW, Advis JP. Comparative ability of chicken and mammalian LHRH to release LH from rooster pituitary cells in vitro. Life Sci 1984; 34:1847-51. [PMID: 6376990 DOI: 10.1016/0024-3205(84)90678-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Biological properties of homogeneous solutions of chicken (c) and mammalian (m) LHRH were compared by their ability to release LH, in vitro, from a rooster pituitary cell incubation system. Homogeneity of the two LHRH species was confirmed by High Performance Liquid Chromatography (HPLC) using linear gradients of acetonitrile and phosphate buffer. A clear HPLC separation of [Gln8]-LHRH ( cLHRH ) and [Arg8]-LHRH ( mLHRH ) was obtained, with the former having a consistently longer retention time than the latter. cLHRH cause a greater (p less than .025) in vitro release of LH at low doses (less than 1 ng/2 X 10(5) live pituitary cells), but not at high doses (greater than 10 ng/2 X 10(5) live pituitary cells), than that caused by mLHRH . Our results indicate that rooster pituitary cells are significantly more sensitive to low doses of cLHRH than to similar doses of mLHRH , when assessed by their ability to release LH in vitro.
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