Elsevier

Brain Research

Volume 1243, 3 December 2008, Pages 10-18
Brain Research

Research Report
Factors that regulate KiSS1 gene expression in the hippocampus

https://doi.org/10.1016/j.brainres.2008.09.031Get rights and content

Abstract

Kisspeptin is a C-terminally amidated peptide encoded by the KiSS1 gene. The peptide and its receptor GPR54 are abundant in the hypothalamus and have been implicated as gatekeepers for the onset of puberty and the development of the reproductive system. Interestingly, GPR54 is also highly expressed in granule cells of the hippocampal dentate gyrus, and in a previous study we showed that kisspeptin enhances excitatory synaptic transmission in these cells. The present study examined how expression of KiSS1 and GPR54 is regulated in rat hippocampus, using in vivo and in vitro preparations. In animals, a 3 h period of kainate-induced seizures significantly altered expression of both genes. KiSS1 mRNA showed a 3–4 fold increase which peaked 1–3 days post-seizure and subsided after one week. GPR54 mRNA, on the other hand, was reduced by 20–30% at 6–24 h. In organotypic hippocampal slice cultures, brief exposure to kainate produced a significant increase in KiSS1 mRNA with a time course comparable to that in vivo, and the effect was blocked by tetrodotoxin and CNQX. Chronic (7-day) treatment with picrotoxin, which induced a persistent four-fold increase in spike activity in multi-electrode recordings, caused a similar size but more persistent upregulation in KiSS1 mRNA. As in other studies, kainate and picrotoxin induced an upsurge in BDNF expression, but BDNF mRNA was also significantly increased when slice cultures were treated with kisspeptin. Taken together, KiSS1 expression is upregulated by neuronal activity and activation of GPR54 by kisspeptin may in turn contribute to sustain basal BDNF levels required for hippocampal function. In additional experiments, KiSS1 mRNA was found to be increased after orchidectomy and thus expression may be regulated also by gonadal hormones.

Introduction

The KiSS1 gene was originally identified in melanomas as conferring suppression of metastasis (Lee et al., 1996), and a peptide encoded by this gene was subsequently shown to influence migration and other cellular processes in a wide range of cells (Lee and Welch, 1997, Masui et al., 2004). The primary translation product of the KiSS1 gene is processed proteolytically to yield a 54-amino acid carboxy-terminally amidated sequence that appears to be the primary active peptide and is variously named metastin, kisspeptin, or kisspeptin-54. However, shorter fragments containing the same C-terminus, but only 14, 13, or 10 amino acids, have been detected in tissues and found to be active with equal or higher affinity than the parent peptide (Kotani et al., 2001, Ohtaki et al., 2001).

In 2001, several laboratories (Ohtaki et al., 2001, Muir et al., 2001, Kotani et al., 2001) discovered that the effects of these peptides are mediated by a G-protein coupled receptor that had been named GPR54 in rats (Lee et al., 1999). Activation of GPR54 in most cell lines appears to couple to Gαq/11 and increase cytosolic calcium via stimulation of phospholipase C and phosphatidylinositol turnover (Kotani et al., 2001, Muir et al., 2001, Brailoiu et al., 2005). GPR54 is expressed in a wide range of tissues that include the brain, placenta, liver, and pancreas. In the brain, GPR54 was found to be particularly abundant in regions of the hypothalamus that regulate reproduction, and subsequent studies led to the discovery that the kisspeptin/GPR54 system plays a central role in controlling release of gonadotropin releasing hormone (GnRH) from hypothalamic neurons (Seminara et al., 2003, Funes et al., 2003, Gottsch et al., 2004, Navarro et al., 2004, Han et al., 2005). The importance of this system for the maturation of the gonadal organs has been illustrated most vividly by the discovery that some forms of hypogonadism are the result of mutations in GPR54 that render the receptor inactive (de Roux et al., 2003, Seminara et al., 2003, Semple et al., 2005). Kisspeptin receptors on GnRH-releasing neurons are therefore now considered a key factor for controlling sexual maturation and estrous cycles. Moreover, given that kisspeptin is also present in ovaries (Castellano et al., 2006) and that GPR54 controls trophoblast insertion into the uterine wall during pregnancy (Bilban et al., 2004), it is now widely thought that controlling reproduction is the primary role of this peptide system.

GPR54 is expressed at high density also in specific brain regions outside the hypothalamus, such as in the amygdala and in the hippocampal dentate gyrus (Lee et al., 1999), but there is as yet little information about the function of this peptide system in these areas. In a recent study we have shown that activation of GPR54 in dentate gyrus granule cells produces a dramatic increase in the amplitude of excitatory synaptic responses (Arai et al., 2005). The effect was abolished by the G-protein inhibitor GDP-β-S and the calcium chelator BAPTA, as well as by inhibitors of MAP kinases, calcium-calmodulin dependent kinase II (CaMK II) and tyrosine kinases. Analysis of miniature events indicated that kisspeptin increased event amplitude, but not event frequency, indicating that it acted post-synaptically. Kisspeptin did not affect membrane properties, and thus its mode of action in the dentate gyrus appears to be different from that in hypothalamic neurons where kisspeptin causes depolarization and enhanced spiking even when excitatory synaptic transmission is blocked (Han et al., 2005, Pielecka-Fortuna et al., 2008).

In our previous study we also showed by using RT-PCR that mRNA for KiSS1 is present in the dentate gyrus (Arai et al., 2005). The purpose of the present study has been to examine how expression of receptor and peptide is regulated. In the hypothalamus, KiSS1 expression is controlled by feedback from gonadal hormones (Smith et al., 2005). However, the most common factor of gene regulation in the brain is the level of neuronal activity. To test this, limbic seizures were induced by peripheral injection of kainate, using an experimental paradigm that has been widely employed to examine how neuronal activity influences gene expression in the hippocampus (Gall, 1988, Gall, 1993, Sperk, 1994). Parallel experiments were conducted with organotypic hippocampal slice cultures in which activity was enhanced by applying kainate or by blocking GABAergic inhibition with picrotoxin. Both in vivo and in vitro studies suggest that KiSS1 mRNA is substantially upregulated by neuronal activity.

Section snippets

Comparison of KiSS1 mRNA content across brain regions

Kisspeptin immunoreactivity has been reported to be low or undetectable in cortex and hippocampus (Brailoiu et al., 2005), but we have previously shown that the hippocampus does express KiSS1 mRNA (Arai et al., 2005). To obtain an estimate for regional differences in the density of KiSS1 expression, we compared mRNA in the hippocampus with that of the hypothalamus and amygdala, using semi-quantitative RT-PCR. As shown in Fig. 1A, the hippocampus was found to contain about 50 to 100 times lower

Discussion

The main finding of this study has been that expression of kisspeptin is strongly regulated by neuronal activity. By far the largest changes in kisspeptin expression were obtained after limbic seizures induced with kainate. However, significant increases were also observed when kainate was briefly applied to hippocampal cultures and when neuronal activity was increased in a sustained manner with picrotoxin. The time course of the response to kainate was similar in vivo and in vitro, with mRNA

Kainate-induced seizures

All studies were carried out in accordance with a protocol approved by the Animal Care and Use Committee of the Southern Illinois University School of Medicine. Male Sprague–Dawley rats (7–10 week old) from the same litter were injected intraperitoneally with kainate (8–12 mg/kg). Behavior was observed for 3 h and a seizure score was given according to a modified Racine's scale (Racine, 1972), as follows: 0, no change in behavior; 1, staring with immobility; 2, wet dog shake/head bobbing; 3,

Acknowledgments

This work was supported by a grant from the Whitehall Foundation (2007-05-119) and by funds from the Central Research Committee of the Southern Illinois University School of Medicine. We would like to thank Nancy Johnston, DVM, and Andrea M. Frazier from the animal care facility for providing surgical services for orchidectomy.

References (45)

  • MasuiT. et al.

    Metastin and its variant forms suppress migration of pancreatic cancer cells

    Biochem. Biophys. Res. Comm.

    (2004)
  • MonaghanD.T. et al.

    Distribution of [3H]AMPA binding sites in rat brain as determined by quantitative autoradiography

    Brain Res.

    (1984)
  • MuirA.I. et al.

    AXOR12, a novel human G protein-coupled receptor, activated by the peptide KiSS-1

    J. Biol. Chem.

    (2001)
  • PoulsenF.R. et al.

    Differential expression of brain-derived neurotrophic factor transcripts after pilocarpine-induced seizure-like activity is related to mode of Ca2+ entry

    Neuroscience

    (2004)
  • RacineR.J.

    Modification of seizure activity by electrical stimulation II. Motor seizure

    Electroencephalogr. Clin. Neurophysiol.

    (1972)
  • RoutbortM.J. et al.

    Seizure, cell death, and mossy fiber sprouting in kainic acid-treated organotypic hippocampal cultures

    Neuroscience

    (1999)
  • SperkG.

    Kainic acid seizures in the rat

    Prog. Neurobiol.

    (1994)
  • StoppiniL. et al.

    A simple method for organotypic cultures of nervous tissue

    J. Neurosci. Methods

    (1991)
  • AraiA.C. et al.

    Effects of a memory enhancing drug on AMPA receptor currents and synaptic transmission in hippocampus

    J. Pharmacol. Exp. Ther.

    (1996)
  • AraiA.C. et al.

    Cancer metastasis-suppressing peptide metastin upregulates excitatory synaptic transmission in hippocampal dentate granule cells

    J. Neurophysiol.

    (2005)
  • BilbanM. et al.

    Kisspeptin-10, a KiSS-1/metastin-derived decapeptide, is a physiological invasion inhibitor of primary human trophoblasts

    J. Cell Sci.

    (2004)
  • BrailoiuG.C. et al.

    KiSS-1 expression and metastin-like immunoreactivity in the rat brain

    J. Comp. Neurol.

    (2005)
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