MOJ ISSN: 2471-139X MOJAP

Anatomy & Physiology
Mini Review
Volume 2 Issue 5 - 2016
Physiology of Gonadotropin-Releasing Hormone (GnRH): Beyond the Control of Reproductive Functions
Roberto Maggi*
Department of Pharmacological and Biomolecular Sciences, Universita degli Studi di Milano, Italy
Received: May 07, 2016 | Published: July 05, 2016
*Corresponding author: Roberto Maggi, Department of Pharmacological and Biomolecular Sciences, Universita degli Studi di Milano, Via G Balzaretti, 20133 Milano (MI) - Italy, Tel: +39 02 50318233; Fax: +39 02 50318204; Email:
Citation: Maggi R (2016) Physiology of Gonadotropin-Releasing Hormone (Gnrh): Beyond the Control of Reproductive Functions. MOJ Anat & Physiol 2(5): 00063. DOI: 10.15406/mojap.2016.02.00063

Abstract

GnRH is the hypothalamic main regulator of the hypothalamic-pituitary-gonadal reproductive axis, but it was found to exert additional functions due to the wide distribution of its receptors both in central nervous system (from cortex to spinal cord) and in peripheral organs and tissues. The possible activity of GnRH/GnRHR system at the level of the hippocampus has raised the interest on the effects of the decapeptide and its analogues on neurogenesis and neuronal functions. Recently, it has been observed that GnRH is decreased in mouse hypothalamic ageing and that restoring normal GnRH levels may attenuate brain and systemic aging processes.

Other studies have also pointed out on neurogenic and neuro protective actions of GnRH in several models of neurodegeneration, as in Alzheimer's disease and in spinal cord injury models. A direct effect of GnRH on cholesterol and estrogen synthesis in human neuronal-like cells has been also proposed as a mechanism involved in neuro protective activity. Since GnRH analogues are known to be safe and effective, a new possible lines of therapeutic intervention to control some of the defects present in aging and neurodegenerative diseases may be delineated.

In conclusion, brain GnRH/GnRHR system is a novel and extremely interesting target, since it mediates several actions possibly integrated in a complex control of reproductive functions with neurogenesis, neuroprotection, sex behavior and cognition.

Keywords: Gonadotropin Releasing Hormone; Physiology; Neuroprotection; Neurogenesis; analogues

Abbreviations

cAMP: Cyclic Adenosine Monophosphate; DAG: Diacylglycerol; IP3: Inositol 1,4,5-Triphosphate; HPG: Hypothalamic-Pituitary-Gonadal; APP: Amyloid Precursor Protein; MAPK: Mitogen-Activated Protein Kinase; ERK1/2: Extracellular Signal-Regulated Kinase; PI3K: Phosphatidylinositol-3-Kinase; EGR1: Early Growth Response 1; PP: Phosphotyrosine Phosphatase; NF-Kb: Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B Cells; DHCR24: 3-Betahydroxysterol Delta-24-Reductase; St AR: Steroidogenic Acute Regulatory Protein; IKK-β: Inhibitor of Nuclear Factor Kappa-B Kinase Subunit Beta; Aβ: Amyloid Beta Peptide

Introduction

Gonadotropin releasing hormone (GnRH) is 35-year-old neuropeptide recognized as the central regulator of reproductive functions [1]. It was actually one of the earliest hypothalamic-releasing hormones sequenced and characterized and led its discoverer Andrew Schally to be awarded by the Nobel prize in 1977 [2]. The peptide is a sequence of ten aminoacids (Figure 1A) with a cyclized proline at the N-terminal and a glycine-amide residue at C-terminal, which confer some resistance to terminal peptidases.

Figure 1: Aminoacid sequence of GnRH (A) and the hypotalamo-pituitary–gonadal axis organization (B).

In mammals, GnRH is mainly produced by a limited number of hypothalamic neurons, which do not form a defined nucleus but show a dispersed organization in the mediobasal hypothalamus. Making axonal contacts with the hypothalamo-hypophyseal portal vessels, GnRH neurons release the decapeptide in the bloodstream directed to the adenohypophysis in a pulsatile manner [3]. At the pituitary level, the decapeptide interact with specific G protein-coupled receptors (GnRHR) present on gonadotrope cells inducing the release of the two gonadotropins (LH, luteinizing hormone and FSH, follicle stimulating hormones) which in turn coordinate male and female gonadal functions promoting the folliculogenesis and the ovulation in female, the spermatogenesis in male, and the production of sex steroid hormones (estrogen, progesterone and testosterone) [4,5] (Figure 1B).

GnRHR may be coupled either to Gaq/11 or Gas subunits which activate different intracellular responses including cAMP and DAG/IP3 pathways, as well as the mitogen-activated protein kinase (MAPK) cascades [6]. The separate activation of Gaq/11 or Gas subunits, by changes in the frequency of decapeptide pulsatile release, is the basis for the differential control of gonadotropin release [7]. The actions of GnRH on reproductive functions cover the whole lifespan and characterize the maturation, the pubertal activation and the adult functions of the hormonal hypothalamo-pituitary-gonadal axis. Because of its importance on reproductive functions, a series of synthetic analogues, with agonist or antagonist activities have been developed soon after GnRH identification [8,9] (Table 1).

GnRH

pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Arg8-Pro9-Gly10- NH2

Agonists

Buserelin

pGlu1-His2-Trp3-Ser4-Tyr5-D-Ser(tBu)6-Leu7-Arg8-Pro9 - NHEt

Leuprolide

pGlu1-His2-Trp3-Ser4-Tyr5-D-Leu6-Leu7-Arg8-Pro9- NHEt

Antagonists

Cetrorelix

Ac-D-Nal1-D-Cpa2-D-Pal3-Ser4-Tyr5-D-Cit6-Leu7-Arg8-Pro9-D-Ala10-NH2

Table 1: Sequences of some GnRH analogues.

tBu: Tert-Butyl; Et: Ethyl; Cpa: Chlorophenylalanine; Pal: 3-pyridylalanine; Cit: citrulline; Nal: 2-naphtylamine.

The pharmacological approach with GnRH analogues has been so far limited to the induction of puberty or, more in general, for recovery of fertility through a pulsatile administration; on the contrary, a continuous administration of GnRH agonists or antagonist is used to block the gonadotropin release and the reproductive axis (chemical castration) [1].

Discussion

Since 1979 it has become increasingly clear that, in mammals, GnRH could also exert extrapituitary functions [10]. In fact, GnRH/GnRHR systems were also found to be expressed in peripheral organs, in particular in the female reproductive tract [11], and in several tumors [12], where their activation is associated with a strong antiproliferative/antimetastatic activity [13,14]. These findings gave a further impulse to the development of new GnRH analogs for the therapy of gynecological diseases and endocrine tumors (see [1,14]). More recently, GnRHR were found also in human lung epithelial cells and their activation by GnRH improves the chloride transport defect present in cystic fibrosis, suggesting a new therapeutic use of GnRHR analogs [15]. Extrapituitary GnRHRs share the same mRNA sequence and protein molecular size with the pituitary receptor [16,17] although some of them, particularly those present in peripheral organs, may show a different pharmacological profile, leaving the assessment of their identity a still open question [18-21]. It has been also reported that pituitary and peripheral GnRHR differ in terms of activated intracellular signaling pathway [22]; GnRHR present in peripheral and tumoral tissues are generally coupled with the Gai subunit, and their activation leads to a decrease of intracellular cAMP levels. Different intracellular signaling cascades, such as MAPK (p38, ERK1/2, and JNK), PI3K and PP are linked to this pathway activation and involved to mediate the growth/survival effects of GnRH analogues [23].

Recent findings have focused the attention also on the possible role of GnRH in neuronal functions. GnRHR show a well documented wide distribution in the central nervous system, in particular at the level of the limbic system (hippocampus, amygdala), a region involved in cognitive and sexual behavior, as well as in entorhinal and frontal cortex, subiculum, septum and in spinal cord motor neurons. Although genetic identification of the GnRHR in the different brain areas indicates a similarity, their activation may elicit different intracellular responses, suggesting a possible differential effect on brain functions [24]. Acting as neuromodulator, GnRH might play therefore important additional functions on brain physiology other than the control of gonadotropin secretion, even if its exact role in different brain structures has not been completely defined.

The expression of brain GnRHR occurs after birth and is restricted to postmitotic neurons [25]; this excludes their involvement in neuronal embryonic development and suggests a possible role in postnatal development or in brain plasticity. Actually, activation of GnRHR alters the electrical properties of hippocampal neurons through a protein kinase C-dependent action [10] and exerts a significant control of synaptic plasticity. In fact, the activation of GnRH receptors with the analog leuprolide was found to increase the intrinsic neuronal excitability of pyramidal neurons (of region CA1 and CA3) [26] and an enhancement of synaptic transmission mediated by ionotropic glutamate receptors [27]. GnRH was found to regulate the expression of pre- and post-synaptic markers spinophilin, synaptophisin and Egr1 in neurons obtained from hippocampus [25,28]. Hippocampal GnRHR has been implicated in the regulation of aromatase activity [28], suggesting that the observed neurotrophic effect of GnRH could be mediated by a possible intervention on local synthesis of estrogen, known to affect synaptogenesis and expression of both spinophilin and synaptophisin [29]. This observation also suggests that estrus cycle - dependent synaptogenesis, occurring in the rat female hippocampus, may be regulated by the cyclic release of hypothalamic GnRH. However, GnRH projections may be widespread in the brain [10] and GnRH might reach the hippocampal region from cerebrospinal fluid or from neurons located in other brain regions; GnRH fibers have been found in the hippocampus and a population of septal GnRH neurons were found to project axons through a septo hippocampal tract [30-32]. From a physiological point of view, GnRH signaling was found to modify some specific behaviors (i.e., sexual behavior); moreover, it was reported that administration of the GnRH agonist leuprolide improves cognitive function in a mouse model of dementia [33].

Aging is an inexorable process through which both physiological and pathophysiological events occur and the hypothalamus may play a key role in aging development. In a very elegant study, Zhang et al. [34] described how infection-unrelated inflammatory changes in the mediobasal hypothalamus are implicated in programming systemic aging in mice. This appears due to an over activation of the immunity nuclear factor NF-kB. Further studies revealed that IKK-b and NF-kB might mediate an ageing-related hypothalamic decline by the inhibition of GnRH production. Accordingly, systemic GnRH treatment of mice displaying an over activation of NF-kB, associated to cognitive impairment and reduced neurogenesis, may abrogate this pro-aging phenotype promoting neurogenesis and delaying many effects of systemic ageing (skin atrophy, bone, muscle and cognitive decay, improving health and lifespan). In addition, the increase of b-sitosterol, a phytosterol with anti-inflammatory property, into the neuronal plasma membrane could also prevent the decrease of GnRH production induced by tumor necrosis factor-a (TNF-a)-NF-kB activated pathway [35]. Therefore, the hypothalamus has a role in ageing development by an immune–neuroendocrine integration, and anti-inflammatory/GnRHa associated therapies could have a potential role to counteract ageing-related health problems [34].

A relationship between GnRH and Alzheimer's Disease (AD) has also been reported. Alzheimer disease (AD), a complex, neurodegenerative disease characterized by synaptic dysfunction, memory loss, neuroinflammation and neuronal cell death, is one of the most common forms of dementia owing to the pathophysiological class of aging-related disorders. Senile plaques and neurofibrillary tangles are the two main histological brain lesions making definitive the post-mortem diagnosis of an AD patient. A change in the production of gonadal steroids (e.g. at the end of reproductive life) may be associated with cognitive senescence and it has been proposed to be implicated in the neuropathology of AD. Actually, in brains of aged hypogonadal hpg mice (carrying an inactivating genetic mutation in the GnRH gene with consequent deficiency of gonadotropins and gonadal sex hormones) were found high levels of AD markers, like presenilin 1, APP C-terminal fragment, and Ab; these changes are limited to the hippocampal region and have been linked to the androgen depletion present in this animal model [36].

Although, as stated above, GnRH has been described to exert a control on synaptic plasticity in the hippocampus, a brain region strongly affected in AD, the relation GnRH-AD has been so far mainly described in term of its regulatory action on gonadal steroid hormone production, which may predispose to AD. However, the evidence that modifications of the brain and serum LH levels may change biochemical and cellular markers consistent with the neurodegenerative modifications observed in the AD brain [37,38] call into question the hypothesis on gonadal steroid-dependent AD susceptibility. Moreover, the observation that GnRH treatment abrogated the aging phenotype observed in mice studied by Zhang et al. [34], whereas sex steroids did not, support the notion that GnRH may be involved in AD independently of its hormonal activity. Actually, studies using GnRHa leuprolide therapy, aimed at down regulating peripheral LH, show a decrease the toxic Ab load in the brain and a significant improvements in cognitive performance [33,37,39]. Animal studies utilizing GnRHR antagonists, (cetrorelix), which also lowers serum levels of LH, also show cognitive improvements [40].

More recently, it has been reported a higher hippocampal level of GnRH and GnRHR mRNA in both male and female plaque-bearing AD transgenic mice (tgArcSwe), respect to age matched controls [41]. The treatment of these animals with the GnRHa leuprolide caused sex-related significant down-regulation of the expression of both the peptide and of its receptor, even though without significant changes in the plaque load; this may be suggestive of an insufficient effect of GnRHR activation in a more severe and advanced stage of the disease or an effect of GnRHa weaker than the transgene phenotype of the animal model [41]. Finally, clinical trials using leuprolide acetate has been shown to stabilize cognition in women with mild-to-moderate AD [42]. These findings clearly support the role of GnRH as a potential regulator of AD pathogenesis and lead to view the hypothalamic GnRH-NF-kB axis as an interesting mediator of aging-related neurodegenerative processes. Despite a series of reports suggesting the possible utilization of GnRHa in AD, some negative effect of the analogs on cognitive functions have been reported [43] thatwillhave to be accurately considered in further clinical investigations. Nevertheless, the premise exists that GnRH may be involved in AD and GnRH-based therapeutics could be considered among the potential future treatments for AD.

GnRH may exert additional effects on steroidogenesis; it has been found that exposure of human neuronal-like cells (SH-SY5Y neuroblastoma cells) to nanomolar concentration of GnRH up-regulates the expression of enzymes involved in cholesterol (DHCR24) and sterol (StAR) synthesis, enhancing both cell cholesterol and estrogen levels [44]. Notably, DHCR24 is a crucial enzyme for cholesterol biosynthesis also called seladin-1 (for SELective Alzheimer's Disease INdicator-1) since has been found downregulated in brain areas affected by AD [45]. However, high levels of DHCR24 may also exert neuro protective functions in several models conferring resistance against oxidative stress, protecting neurons from apoptosis, by modulation of caspases and conferring resistance against Ab-mediated toxicity [22,45,46]. These last observations suggest a possible mechanism of GnRH-induced neuroprotection through the induction of DHCR24 and are indicative of a possible relationship among GnRH action and the neuronal sterol environment.

Finally, a neurotropic effect of GnRH has been proposed. GnRH was shown to induce changes in neurite outgrowth and length in rat cortical neurons in vitro [47]. GnRHR, have been also described in the spinal cord motorneurons [48,49] and their activation with GnRHa increases the expression of neurofilaments and myelin basic protein with partial improvement of locomotor activity and bladder function in rats with spinal cord injury [50]. The treatment with the GnRHa leuprolide has also been shown to decrease the severity of clinical signs on locomotion of rats with experimental autoimmune encephalomyelitis, suggesting its possible utilization for the therapy of multiple sclerosis [51]. A promising approach to repair of spinal cord injury includes the administration of neurotropic factors together to immunomodulators and in this context leuprolide would be a potential treatment of spinal cord damages because of its safety and lack of significant side effects [52].

Conclusion

In conclusion, GnRH seems to play a physiological role in the hypothalamic control of ageing and in hippocampal neuronal homeostasis; the restoration of GnRH levels in these brain regions might represent a potential strategy for age-related health problems. GnRH peptide is an extremely interesting target since it exerts pleiotropic actions; actually, it is involved in the control of reproduction, by regulating gonadotropin secretion, and may affect both hypothalamic and hippocampal neurogenesis.

Since GnRH analogues are known to be safe, effective and able to cross the blood-brain barrier, a new possible line of therapeutic intervention to control some of the defects present in aging and neurodegenerative diseases may be delineated. For instance, an important aspect to take into consideration when reasoning on possible therapeutic strategies for AD is that both inhibition of neurodegeneration and regeneration of the brain are necessary. At this regard, GnRH system is an extremely interesting target since it might exert both actions.

These findings open new insights on the role of hypothalamic GnRH in the mechanisms of aging, in neuroprotection and in neurogenesis that go beyond its functions on HPG axis but that may be strongly coordinated by a complex integrated control of the reproductive success.

References

  1. Maggi R, Cariboni AM, Marelli MM, Moretti RM, Andre V, et al. (2016) GnRH and GnRH receptors in the pathophysiology of the human female reproductive system. Hum Reprod Update 22(22).  
  2. Matsuo H, Baba Y, Nair RM, Arimura A, Schally AV (1971) Structure of the porcine LH- and FSH-releasing hormone. I. The proposed amino acid sequence. Biochem Biophys Res Commun 43(43): 1334-1339.
  3. Marshall JC, Dalkin AC, Haisenleder DJ, Paul SJ, Ortolano GA, et al. (1991) Gonadotropin-releasing hormone pulses: regulators of gonadotropin synthesis and ovulatory cycles. Recent Prog Horm Res 47(47): 155-187.
  4. Conn PM, Crowley WF (1994) Gonadotropin-releasing hormone and its analogs. Annu Rev Med 45(45): 391-405.
  5. Millar RP (2005) GnRHs and GnRH receptors. Anim Reprod Sci 88(88): 5-28.
  6. Kraus S, Naor Z, Seger R (2001) Intracellular signaling pathways mediated by the gonadotropin-releasing hormone (GnRH) receptor. Arch Med Res 32(32): 499-509.
  7. Tsutsumi R, Webster NJ (2009) GnRH pulsatility, the pituitary response and reproductive dysfunction. Endocr J 56(56): 729-737.
  8. Schally AV, Kastin AJ, Arimura A, Coy D, Coy E, et al. (1973) Basic and clinical studies with luteinizing hormone-releasing hormone (LH-RH) and its analogues. J Reprod Fertil Suppl 20(20): 119-136.
  9. Kiesel LA, Rody A, Greb RR, Szilágyi A (2002) Clinical use of GnRH analogues. Clin Endocrinol (Oxf) 56(56): 677-687.
  10. Skinner DC, Albertson AJ, Navratil A, Smith A, Mignot M, et al. (2009) Effects of gonadotrophin-releasing hormone outside the hypothalamic-pituitary-reproductive axis. J Neuroendocrinol 21(21): 282-292.
  11. Hsueh AJ, Erickson GF (1979) Extrapituitary action of gonadotropin-releasing hormone: direct inhibition ovarian steroidogenesis. Science 204(204): 854-855.
  12. Hierowski MT, Altamirano P, Redding TW, Schally AV (1983) The presence of LHRH-like receptors in Dunning R3327H prostate tumors. FEBS Lett 154(154): 92-96.
  13. Limonta P, Montagnani Marelli M, Moretti RM (2001) LHRH analogues as anticancer agents: pituitary and extrapituitary sites of action. Expert Opin Investig Drugs 10(10): 709-720.
  14. Manea M, Marelli MM, Moretti RM, Maggi R, Marzagalli M, et al. (2014) Targeting hormonal signaling pathways in castration resistant prostate cancer. Recent Pat Anticancer Drug Discov 9(9): 267-285.
  15. Benz N, Le Hir S, Norez C, Kerbiriou M, Calvez ML, et al. (2014) Improvement of chloride transport defect by gonadotropin-releasing hormone (GnRH) in cystic fibrosis epithelial cells. PLoS One 9(9): e88964.
  16. Limonta P, Moretti RM, Marelli MM, Dondi D, Parenti M, et al. (1999) The luteinizing hormone-releasing hormone receptor in human prostate cancer cells: messenger ribonucleic acid expression, molecular size, and signal transduction pathway. Endocrinology 140(140): 5250-5256.
  17. Limonta P, Marelli MM, Mai S, Motta M, Martini L, et al. (2012) GnRH Receptors in Cancer: From Cell Biology to Novel Targeted Therapeutic Strategies. Endocrine Reviews 33(33): 784-811.
  18. Dondi D, Limonta P, Moretti RM, Marelli MM, Garattini E, et al. (1994) Antiproliferative effects of luteinizing hormone-releasing hormone (LHRH) agonists on human androgen-independent prostate cancer cell line DU 145: evidence for an autocrine-inhibitory LHRH loop. Cancer Res 54(54): 4091-4095.
  19. Irmer G, Burger C, Muller R, Ortmann O, Peter U, et al. (1995) Expression of the messenger RNAs for luteinizing hormone-releasing hormone (LHRH) and its receptor in human ovarian epithelial carcinoma. Cancer Res 55(55): 817-822.
  20. Kleinman D, Douvdevani A, Schally AV, Levy J, Sharoni Y (1994) Direct growth inhibition of human endometrial cancer cells by the gonadotropin-releasing hormone antagonist SB-75: role of apoptosis. Am J Obstet Gynecol 170(170): 96-102.
  21. Rama S, Rao AJ (2001) Embryo implantation and GnRH antagonists: the search for the human placental GnRH receptor. Hum Reprod 16(16): 201-205.
  22. Millar RP, Pawson AJ, Morgan K, Rissman EF, Lu ZL (2008) Diversity of actions of GnRHs mediated by ligand-induced selective signaling. Front Neuroendocrinol 29(29): 17-35.
  23. Kim KY, Choi KC, Park SH, Chou CS, Auersperg N, et al. (2004) Type II gonadotropin-releasing hormone stimulates p38 mitogen-activated protein kinase and apoptosis in ovarian cancer cells. J Clin Endocrinol Metab 89(89): 3020-3026.
  24. Badr M, Pelletier G (1987) Characterization and autoradiographic localization of LHRH receptors in the rat brain. Synapse 1(1): 567-571.
  25. Schang AL, Counis R, Magre S, Bleux C, Granger A, et al. (2011) Reporter transgenic mouse models highlight the dual endocrine and neural facet of GnRH receptor function. Ann N Y Acad Sci 1220(1220): 16-22.
  26. Meethal SV, Smith MA, Bowen RL, Atwood CS (2005) The gonadotropin connection in Alzheimer's disease. Endocrine 26(26): 317-326.
  27. Lu F, Yang JM, Wu JN, Chen YC, Kao YH, et al. (1999) Activation of gonadotropin-releasing hormone receptors produces neuronal excitation in the rat hippocampus. Chin J Physiol 42(42): 67-71.
  28. Prange-Kiel J, Jarry H, Schoen M, Kohlmann P, Lohse C, et al. (2008) Gonadotropin-releasing hormone regulates spine density via its regulatory role in hippocampal estrogen synthesis. J Cell Biol 180(180): 417-426.
  29. Prange-Kiel J, Fester L, Zhou L, Jarry H, Rune GM (2009) Estrus cyclicity of spinogenesis: underlying mechanisms. J Neural Transm (Vienna) 116(116): 1417-1425.
  30. Witkin JW, Paden CM, Silverman AJ (1982) The luteinizing hormone-releasing hormone (LHRH) systems in the rat brain. Neuroendocrinology 35(35): 429-438.
  31. Skynner MJ, Slater R, Sim JA, Allen ND, Herbison AE (1999) Promoter transgenics reveal multiple gonadotropin-releasing hormone-I-expressing cell populations of different embryological origin in mouse brain. J Neurosci 19(19): 5955-5966.
  32. Ferris JK, Tse MT, Hamson DK, Taves MD, Ma C, et al. (2015) Neuronal Gonadotrophin-Releasing Hormone (GnRH) and Astrocytic Gonadotrophin Inhibitory Hormone (GnIH) Immunoreactivity in the Adult Rat Hippocampus. J Neuroendocrinol 27(27): 772-786.
  33. Casadesus G, Webber KM, Atwood CS, Pappolla MA, Perry G, et al. (2006) Luteinizing hormone modulates cognition and amyloid-beta deposition in Alzheimer APP transgenic mice. Biochim Biophys Acta 1762(1762): 447-452.
  34. Zhang G, Li J, Purkayastha S, Tang Y, Zhang H, et al. (2013) Hypothalamic programming of systemic ageing involving IKK-β, NF-κB and GnRH. Nature 497(497): 211-216.
  35. Shi C, Luo X, Wang J, Long D (2015) Incorporation of β-sitosterol into the membrane prevents tumor necrosis factor-α-induced nuclear factor-κB activation and gonadotropin-releasing hormone decline. Steroids 96(96): 1-6.
  36. Drummond ES, Martins RN, Handelsman DJ, Harvey AR (2012) Altered expression of Alzheimer's disease-related proteins in male hypogonadal mice. Endocrinology 153(153): 2789-2799.
  37. Bowen RL, Verdile G, Liu T, Parlow AF, Perry G, et al. (2004) Luteinizing hormone, a reproductive regulator that modulates the processing of amyloid-beta precursor protein and amyloid-beta deposition. J Biol Chem 279(279): 20539-20545.
  38. Blair JA, Bhatta S, McGee H, Casadesus G (2015) Luteinizing hormone: Evidence for direct action in the CNS. Horm Behav 76(76): 57-62.
  39. Wilson AC, Salamat MS, Haasl RJ, Roche KM, Karande A, et al. (2006) Human neurons express type I GnRH receptor and respond to GnRH I by increasing luteinizing hormone expression. J Endocrinol 191(191): 651-663.
  40. Telegdy G, Tanaka M, Schally AV (2009) Effects of the LHRH antagonist Cetrorelix on the brain function in mice. Neuropeptides 43(43): 229-234.
  41. Nuruddin S, Syverstad GH, Lillehaug S, Leergaard TB, Nilsson LN, et al. (2014) Elevated mRNA-levels of gonadotropin-releasing hormone and its receptor in plaque-bearing Alzheimer's disease transgenic mice. PLoS One 9(9): e103607.
  42. Bowen RL, Perry G, Xiong C, Smith MA, Atwood CS (2015) A clinical study of lupron depot in the treatment of women with Alzheimer's disease: preservation of cognitive function in patients taking an acetylcholinesterase inhibitor and treated with high dose lupron over 48 weeks. J Alzheimers Dis 44(44): 549-560.
  43. Green HJ, Pakenham KI, Headley BC, Yaxley J, Nicol DL, et al. (2002) Altered cognitive function in men treated for prostate cancer with luteinizing hormone-releasing hormone analogues and cyproterone acetate: a randomized controlled trial. BJU Int 90(90): 427-432.
  44. Rosati F, Sturli N, Cungi MC, Morello M, Villanelli F, et al. (2011) Gonadotropin-releasing hormone modulates cholesterol synthesis and steroidogenesis in SH-SY5Y cells. J Steroid Biochem Mol Biol 124(124): 77-83.
  45. Greeve I, Hermans-Borgmeyer I, Brellinger C, Kasper D, Gomez-Isla T, et al. (2000) The human DIMINUTO/DWARF1 homolog seladin-1 confers resistance to Alzheimer's disease-associated neurodegeneration and oxidative stress. J Neurosci 20(20): 7345-7352.
  46. Crameri A, Biondi E, Kuehnle K, Lutjohann D, Thelen KM, et al. (2006) The role of seladin-1/DHCR24 in cholesterol biosynthesis, APP processing and Abeta generation in vivo. EMBO J 25(25): 432-443.
  47. Quintanar JL, Salinas E (2008) Neurotrophic effects of GnRH on neurite outgrowth and neurofilament protein expression in cultured cerebral cortical neurons of rat embryos. Neurochem Res 33(33): 1051-1056.
  48. Dolan S, Evans NP, Richter TA, Nolan AM (2003) Expression of gonadotropin-releasing hormone and gonadotropin-releasing hormone receptor in sheep spinal cord. Neurosci Lett 346(346): 120-122.
  49. Quintanar JL, Salinas E, González R (2007) Expression of gonadotropin-releasing hormone receptor in cerebral cortical neurons of embryos and adult rats. Neurosci Lett 411(411): 22-25.
  50. Calderón-Vallejo D, Quintanar JL (2012) Gonadotropin-releasing hormone treatment improves locomotor activity, urinary function and neurofilament protein expression after spinal cord injury in ovariectomized rats. Neurosci Lett 515(515): 187-190.
  51. Guzmán-Soto I, Salinas E, Hernández-Jasso I, Quintanar JL (2012) Leuprolide acetate, a GnRH agonist, improves experimental autoimmune encephalomyelitis: a possible therapy for multiple sclerosis. Neurochem Res 37(37): 2190-2197.
  52. Díaz Galindo C, Gómez-González B, Salinas E, Calderón-Vallejo D, Hernández-Jasso I, et al. (2015) Leuprolide acetate induces structural and functional recovery of injured spinal cord in rats. Neural Regen Res 10(10): 1819-1824.
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