Manganese-Stimulated Kisspeptin Is Mediated by the IGF-1/Akt/Mammalian Target of Rapamycin Pathway in the Prepubertal Female Rat

Low-dose administration of manganese chloride (MnCl2) causes release of hypothalamic LH-releasing hormone (LHRH) and advances puberty in rat. Recently, this element was shown to up-regulate mammalian target of rapamycin (mTOR), kisspeptin gene (KiSS-1), and LHRH gene expressions in the brain preoptic area (POA)/anteroventral periventricular (AVPV) nucleus. Because these genes are critical for puberty, this study was conducted to identify the upstream mechanism by which Mn activates the mTOR/KiSS-1 pathway. On day 12, immature female rats began receiving a daily supplemental dose of 10 mg/kg of MnCl2 or saline by gavage, and POA/AVPV tissues were collected on day 29 for specific protein assessments. Another experiment assessed in vitro IGF-1 release in response to Mn and assessed signal transduction pathways in the POA/AVPV region after Mn delivery into the third ventricle. Chronic Mn exposure increased (P < .05) basal expressions of mTOR and kisspeptin proteins. Mn increased protein kinase B (Akt) and Ras homolog enriched in brain, both capable of activating mTOR. Central Mn delivery increased expressions of phosphorylated IGF-1 receptor (IGF-1R) (P < .05) and Akt (P < .01) in the POA/AVPV region. The previous central delivery of JB1, an IGF-1R antagonist, blocked Mn-induced expressions of both phosphorylated IGF-1R and Akt. Downstream to Akt, centrally administered Mn increased tuberous sclerosis complex 2 (P < .05), Ras homolog enriched in brain (P < .01), mTOR (P < .05), and kisspeptin (P < .05). Finally, we observed that the early puberty induced by Mn was blocked by the administration of an mTOR inhibitor. These results suggest that Mn acts, at least in part, through the IGF-1/Akt/mTOR pathway to influence prepubertal kisspeptin and LHRH.

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Pituitary receptors for LH-releasing hormone (LHRH) and responsiveness to LHRH in adult female rats after neonatal monosodium l-glutamate treatment

Journal of Endocrinology ◽

10.1677/joe.0.1070009 ◽

1985 ◽

Vol 107 (1) ◽

pp. 9-13 ◽

Cited By ~ 5

Author(s):

S. E. Inkster ◽

R. N. Clayton ◽

S. A. Whitehead

Keyword(s):

Adult Female ◽

Female Rats ◽

Serum Prolactin ◽

Female Rat ◽

Releasing Hormone ◽

Old Rats ◽

Lh Releasing Hormone ◽

Ovarian Cyclicity ◽

Pituitary Receptors

ABSTRACT The effects of neonatal monosodium l-glutamate (MSG) treatment on pituitary responsiveness to LH-releasing hormone (LHRH) and on pituitary LHRH receptors have been investigated in the intact adult female rat. Three- to four-month-old rats treated with MSG (4 mg/g body wt) on days 2, 4, 6, 8 and 10 after birth had significantly reduced ovarian and pituitary weights, showed an absence or disruption of ovarian cyclicity after puberty, and had significantly higher concentrations of serum prolactin despite normal levels of LH. In-vitro pituitary LH responses to LHRH were in the normal range for one group of treated animals whilst in a second group the LH responses were markedly enhanced. In contrast, the total number of pituitary LHRH receptors were significantly reduced in all MSG-treated animals showing that the increased pituitary responsiveness of MSG-treated animals is not attributable to an increase in pituitary LHRH receptors. J. Endocr. (1985) 107, 9–13

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Targeting mammalian target of rapamycin: prospects for the treatment of inflammatory bowel diseases

Current Medicinal Chemistry ◽

10.2174/0929867327666200504081503 ◽

2020 ◽

Vol 27 ◽

Author(s):

Naser-Aldin Lashgari ◽

Nazanin Momeni Roudsari ◽

Saeideh Momtaz ◽

Negar Ghanaatian ◽

Parichehr Kohansal ◽

...

Keyword(s):

Signaling Pathway ◽

Mammalian Target Of Rapamycin ◽

Mtor Pathway ◽

Mtor Signaling ◽

Target Of Rapamycin ◽

In Vivo Studies ◽

Cochrane Library ◽

Mtor Signaling Pathway ◽

Inflammatory Bowel

: Inflammatory bowel disease (IBD) is a general term for a group of chronic and progressive disorders. Several cellular and biomolecular pathways are implicated in the pathogenesis of IBD, yet the etiology is unclear. Activation of the mammalian target of rapamycin (mTOR) pathway in the intestinal epithelial cells was also shown to induce inflammation. This review focuses on the inhibition of the mTOR signaling pathway and its potential application in treating IBD. We also provide an overview on plant-derived compounds that are beneficial for the IBD management through modulation of the mTOR pathway. Data were extracted from clinical, in vitro and in vivo studies published in English between 1995 and May 2019, which were collected from PubMed, Google Scholar, Scopus and Cochrane library databases. Results of various studies implied that inhibition of the mTOR signaling pathway downregulates the inflammatory processes and cytokines involved in IBD. In this context, a number of natural products might reverse the pathological features of the disease. Furthermore, mTOR provides a novel drug target for IBD. Comprehensive clinical studies are required to confirm the efficacy of mTOR inhibitors in treating IBD.

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IN-VITRO STUDIES OF THE EFFECTS OF OESTROGEN PRETREATMENT ON THE SENSITIVITY OF THE IMMATURE FEMALE RAT PITUITARY GLAND TO STIMULATION WITH GONADOTROPHIN RELEASING HORMONE

Journal of Endocrinology ◽

10.1677/joe.0.0740011 ◽

1977 ◽

Vol 74 (1) ◽

pp. 11-21 ◽

Cited By ~ 2

Author(s):

M. WILKINSON ◽

D. DE ZIEGLER ◽

DANIELLE CASSARD ◽

K. B. RUF

Keyword(s):

Pituitary Gland ◽

Brain Lesion ◽

Culture Technique ◽

Female Rats ◽

Female Rat ◽

Immature Female ◽

Releasing Hormone ◽

Gonadotrophin Releasing Hormone ◽

Unilateral Brain Lesion

The effects of oestrogen priming on the sensitivity of the anterior pituitary gland to stimulation with gonadotrophin releasing hormone (GnRH) was investigated in immature female rats using a new organ culture technique. Hemipituitary glands obtained from animals primed with a single dose of oestradiol benzoate (OB; 20 μg/100 g body weight) released significantly more LH when pulsed with GnRH (4 nmol/l) than did control hemipituitary glands. This potentiating effect was detectable as early as 5 days after birth. After a second stimulation, LH secretion remained high. These results were compared with those obtained from animals treated to induce increased levels of endogenous oestrogen on day 26 of life. Thus, hemipituitary glands were obtained from animals given two injections of OB, an injection of pregnant mare serum gonadotrophin (PMSG) or a unilateral brain lesion placed in the basal hypothalamus. Pituitary tissue was stimulated as before with a pulse of GnRH. Two injections of OB enhanced the sensitivity to stimulation. Conversely, both PMSG and lesion treatment severely reduced the sensitivity to GnRH, although PMSG-treated and lesioned animals have been used as models for the study of ovulation.

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T-2 Toxin Exposure Induces Apoptosis in TM3 Cells by Inhibiting Mammalian Target of Rapamycin/Serine/Threonine Protein Kinase(mTORC2/AKT) to Promote Ca2+Production

International Journal of Molecular Sciences ◽

10.3390/ijms19113360 ◽

2018 ◽

Vol 19 (11) ◽

pp. 3360 ◽

Cited By ~ 4

Author(s):

Ji Wang ◽

Chenglin Yang ◽

Zhihang Yuan ◽

Jine Yi ◽

Jing Wu

Keyword(s):

Cell Injury ◽

Mammalian Target Of Rapamycin ◽

Annexin V ◽

Target Of Rapamycin ◽

Dependent Manner ◽

Toxin Exposure ◽

Concentration Changes ◽

Vitro Model ◽

Induced Apoptosis

Although mTOR (the mammalian target of rapamycin) can regulate intracellular free Ca2+concentration in normal cultured podocytes, it remains elusive as to how mTORC2/AKT-mediated Ca2+participates in the process of T-2 toxin-induced apoptosis. The potential signaling responsible for intracellular Ca2+ concentration changes was investigated using immunoblot assays in an in vitro model of TM3 cell injury induced by T-2 toxin. Changes in Ca2+ were assessed using the Ca2+-sensitive fluorescent indictor dye Fura 2-AM. The cytotoxicity of TM3 cells was assessed with an MTT bioassay, and apoptosis was measured using Annexin V-FITC staining. Following T-2 toxin treatment, the growth of cells, phospho-mTORSer2481, phospho-mTORSer2448, and phospho-AktSer473 were significantly decreased in a time-dependent manner, whereas Ca2+ and apoptosis were increased. T-2 toxin-induced apoptosis was prevented by BAPTA-AM (a Ca2+chelator) and MHY1485 (an mTOR activator), and the application of mTOR activator MHY1485 also prevented the increase of intracellular free Ca2+concentration in TM3 cells. Our results strongly suggest that T-2 toxin exposure induces apoptosis in TM3 cells by inhibiting mTORC2/AKT to promote Ca2+ production.

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REGULATION OF THE METABOLISM OF PITUITARY NUCLEIC ACIDS IN FEMALE RATS

Journal of Endocrinology ◽

10.1677/joe.0.0850001 ◽

1980 ◽

Vol 85 (1) ◽

pp. 1-8 ◽

Cited By ~ 12

Author(s):

J. BÍRÓ

Keyword(s):

Nucleic Acids ◽

Intraperitoneal Injection ◽

Anterior Pituitary ◽

Rna Metabolism ◽

Female Rats ◽

Biphasic Effect ◽

Lh Rh ◽

Lh Releasing Hormone

SUMMARY Ovariectomy caused an increase in the metabolism of pituitary nucleic acids. This effect was reversed in vivo by a biphasic action of oestradiol-17β which first facilitated RNA metabolism after 8 h and then inhibited it 16 h after intraperitoneal injection. To analyse the origin of this biphasic effect the roles of LH releasing hormone (LH-RH) and hysterectomy were examined. Incorporation of uridine into the RNA of the anterior pituitary gland of female rats was inhibited both in vivo and in vitro by LH-RH. Hysterectomy augmented the increase in the RNA metabolism caused by ovariectomy whereas steroid-free uterine extracts inhibited the increase significantly. We have concluded that extrapituitary factors may be involved in the effects of oestrogen on the metabolism of pituitary nucleic acids.

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Direct Stimulatory Effects of Oxytocin in Female Rat Gonadotrophs and Somatotrophs In Vitro: Comparison With Lactotrophs

Endocrinology ◽

10.1210/en.2014-1543 ◽

2014 ◽

Vol 156 (2) ◽

pp. 600-612 ◽

Cited By ~ 17

Author(s):

Arturo E. Gonzalez-Iglesias ◽

Patrick A. Fletcher ◽

José A. Arias-Cristancho ◽

Ruth Cristancho-Gordo ◽

Cleyde V. Helena ◽

...

Keyword(s):

Receptor Antagonist ◽

Cell Types ◽

Pituitary Hormones ◽

Prolactin Secretion ◽

Female Rats ◽

Pituitary Cells ◽

Female Rat ◽

Dependent Manner ◽

Rat Pituitary Cells

The peptide oxytocin (OT) is secreted by hypothalamic neurons and exerts numerous actions related to reproduction. OT stimulation of prolactin secretion in female rats is important during the estrous cycle, pregnancy, and lactation. Here we report that OT also stimulates transients of intracellular Ca2+ concentration in somatotrophs and gonadotrophs as well as the release of GH and LH in a dose-dependent manner with EC50 values that closely correspond to the ligand affinity of the OT receptor (OTR). Remarkably, the hormone-releasing effect of OT in these two cell types is 2 orders of magnitude more sensitive than that in lactotrophs. The specific OTR agonist [Thr4,Gly7]-oxytocin acutely stimulated the release of LH, GH, and prolactin from female rat pituitary cells in primary culture and increased intracellular Ca2+ concentration in gonadotrophs, somatotrophs, and lactotrophs. In these three cell types, the effects on hormone release and intracellular Ca2+ of both OT and [Thr4,Gly7]oxytocin were abolished by the specific OT receptor antagonist desGly-NH2-d(CH2)5[D-Tyr2,Thr4]OVT but not by the highly selective vasopressin V1a receptor antagonist, d(CH2)5[Tyr(Me)2,Dab5]AVP. Furthermore, 10 nM arginine vasopressin stimulated LH and GH release comparably with a dose of OT that was at least 10 times lower. Finally, the presence of the OTR-like immunoreactivity could be observed in all three cell types. Taken together, these results show that OT directly stimulates gonadotrophs, somatotrophs, and lactotrophs through OT receptors and suggest that OT signaling may serve to coordinate the release of different pituitary hormones during specific physiological conditions.

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Targeting TORC2 in multiple myeloma with a new mTOR kinase inhibitor

Blood ◽

10.1182/blood-2010-05-285726 ◽

2010 ◽

Vol 116 (22) ◽

pp. 4560-4568 ◽

Cited By ~ 86

Author(s):

Bao Hoang ◽

Patrick Frost ◽

Yijiang Shi ◽

Eileen Belanger ◽

Angelica Benavides ◽

...

Keyword(s):

Multiple Myeloma ◽

Kinase Inhibitor ◽

Mammalian Target Of Rapamycin ◽

Target Of Rapamycin ◽

Phosphatase And Tensin Homolog ◽

Akt Phosphorylation ◽

Tensin Homolog ◽

Complex Protein ◽

Preclinical Work

Although preclinical work with rapalogs suggests potential in treatment of multiple myeloma (MM), they have been less successful clinically. These drugs allostearically inhibit the mammalian target of rapamycin kinase primarily curtailing activity of the target of rapamycin complex (TORC)1. To assess if the mammalian target of rapamycin within the TORC2 complex could be a better target in MM, we tested a new agent, pp242, which prevents activation of TORC2 as well as TORC1. Although comparable to rapamycin against phosphorylation of the TORC1 substrates p70S6kinase and 4E-BP-1, pp242 could also inhibit phosphorylation of AKT on serine 473, a TORC2 substrate, while rapamycin was ineffective. pp242 was also more effective than rapamycin in achieving cytoreduction and apoptosis in MM cells. In addition, pp242 was an effective agent against primary MM cells in vitro and growth of 8226 cells in mice. Knockdown of the TORC2 complex protein, rictor, was deleterious to MM cells further supporting TORC2 as the critical target for pp242. TORC2 activation was frequently identified in primary specimens by immunostaining for AKT phosphorylation on serine 473. Potential mechanisms of up-regulated TORC2 activity in MM were stimulation with interleukin-6 or insulin-like growth factor 1, and phosphatase and tensin homolog or RAS alterations. Combining pp242 with bortezomib led to synergistic anti-MM effects. These results support TORC2 as a therapeutic target in MM.

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The Rapamycin-Binding Domain Governs Substrate Selectivity by the Mammalian Target of Rapamycin

Molecular and Cellular Biology ◽

10.1128/mcb.22.21.7428-7438.2002 ◽

2002 ◽

Vol 22 (21) ◽

pp. 7428-7438 ◽

Cited By ~ 77

Author(s):

Lloyd P. McMahon ◽

Kin M. Choi ◽

Tai-An Lin ◽

Robert T. Abraham ◽

John C. Lawrence

Keyword(s):

Translation Initiation ◽

Mammalian Target Of Rapamycin ◽

Mrna Translation ◽

Binding Domain ◽

Target Of Rapamycin ◽

Substrate Selectivity ◽

Hydrophobic Amino Acid ◽

Translational Regulators ◽

Mtor Activity

ABSTRACT The mammalian target of rapamycin (mTOR) is a Ser/Thr (S/T) protein kinase, which controls mRNA translation initiation by modulating phosphorylation of the translational regulators PHAS-I and p70S6K. Here we show that in vitro mTOR is able to phosphorylate these two regulators at comparable rates. Both (S/T)P sites, such as Thr36, Thr45, and Thr69 in PHAS-I and the h(S/T)h site (where h is a hydrophobic amino acid) Thr389 in p70S6K, were phosphorylated. Rapamycin-FKBP12 inhibited mTOR activity. Surprisingly, the extent of inhibition depended on the substrate. Moreover, mutating Ser2035 in the rapamycin-binding domain (FRB) not only decreased rapamycin sensitivity as expected but also dramatically affected the sites phosphorylated by mTOR. The results demonstrate that mutations in Ser2035 are not silent with respect to mTOR activity and implicate the FRB in substrate recognition. The findings also impose new limitations on interpreting results from experiments in which rapamycin and/or rapamycin-resistant forms of mTOR are used to investigate mTOR function in cells.

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Flurothyl-induced convulsions delay the onset of sexual maturation in the female rat

Journal of Endocrinology ◽

10.1677/joe.0.0950037 ◽

1982 ◽

Vol 95 (1) ◽

pp. 37-41 ◽

Cited By ~ 2

Author(s):

M. Wilkinson ◽

R. Bhanot ◽

J. A. Pincock ◽

L. Donald

Keyword(s):

Sexual Maturation ◽

Serum Levels ◽

Female Rats ◽

Female Rat ◽

Basal Serum ◽

Age Related ◽

Lh Release ◽

Gonadotrophin Releasing Hormone ◽

Related Increase

We have investigated whether sexual maturation in female rats is affected by repeated flurothyl-induced convulsions. This treatment had no effect on the normal age-related increase in body weight though puberty (vaginal opening) was significantly delayed when compared with non-convulsed control rats. In an attempt to probe the mechanism of this delaying effect we observed that (1) anterior pituitary response to gonadotrophin releasing hormone in vitro was normal in terms of LH release but FSH secretion was impaired and (2) progesterone injection in oestrogen-primed convulsed rats failed to generate an ovulatory-type surge of LH or FSH. Basal serum levels and basal in-vitro secretion of LH and FSH were normal. We conclude that repeated convulsions adversely affect the hypothalamo-pituitary-gonadotrophin system of immature female rats.

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