Effects of trigeminal nerve injury on the expression of galanin and its receptors in the rat trigeminal ganglion

doi:10.1016/j.npep.2020.102098

Neuropeptides

Volume 84, December 2020, 102098

https://doi.org/10.1016/j.npep.2020.102098 Get rights and content

Abstract

In the spinal nervous system, the expression of galanin (GAL) and galanin receptors (GALRs) that play important roles in the transmission and modulation of nociceptive information can be affected by nerve injury. However, in the trigeminal nervous system, the effects of trigeminal nerve injury on the expression of GAL are controversy in the previous studies. Besides, little is known about the effects of trigeminal nerve injury on the expression of GALRs. In the present study, the effects of trigeminal nerve injury on the expression of GAL and GALRs in the rat trigeminal ganglion (TG) were investigated by using quantitative real-time reverse transcription-polymerase chain reaction and immunohistochemistry. To identify the nerve-injured and nerve-uninjured TG neurons, activating transcription factor 3 (ATF3, the nerve-injured neuron marker) was stained by immunofluorescence. The levels of GAL mRNA in the rostral half and caudal half of the TG dramatically increased after transection of infraorbital nerve (ION) and inferior alveolar nerve (IAN), respectively. Immunohistochemical labeling of GAL and ATF3 revealed that GAL level was elevated in both injured and adjacent uninjured small and medium-sized TG neurons after ION/IAN transection. In addition, the levels of GAL₂R-like immunoreactivity were reduced in both injured and adjacent uninjured TG neurons after ION/IAN transection, while levels of GAL₁R and GAL₃R-like immunoreactivity remained unchanged. Furthermore, the number of small to medium-sized TG neurons co-expressing GAL- and GAL₁R/GAL₂R/GAL₃R-like immunoreactivity was significantly increased after ION/IAN transection. In line with previous studies in other spinal neuron systems, these results suggest that GAL and GALRs play functional roles in orofacial neuropathic pain and trigeminal nerve regeneration after trigeminal nerve injury.

Introduction

Galanin (GAL), a neuropeptide consisting of 29 amino acids (30 in humans) (Tatemoto et al. 1983), is widely distributed in the central and peripheral nervous system (Ichikawa and Helke 1993; Melander et al. 1986; Skofitsch and Jacobowitz 1985). In the brain and spinal cord of rats, GAL is expressed in various types of neurons and nerve fiber terminals and associated with modulation of action potentials (Bai et al. 2018; Ch'ng et al. 1985; Simpson et al. 1999; Yue et al. 2011). In the dorsal root ganglion (DRG) and trigeminal ganglion (TG) of rats, GAL is mainly expressed by small sensory neurons that can propagate nociceptive signals (Coronel et al. 2008; Deguchi et al. 2006). Previous studies have reported GAL is involved in the neuropathic pain caused by nerve injury with excitatory and inhibitory effects (Lang et al. 2015). Following peripheral nerve injury, spontaneous and evoked neuropathic pain behaviors are compromised in GAL knockout mice, which suggests endogenous GAL has pro-nociceptive function (Kerr et al. 2000). However, there is evidence that the spinal administration of exogenous GAL can also inhibit mechanical and cold allodynia in rats after partial sciatic nerve injury (Hao et al. 1999). In addition, GAL has been shown to accelerate the repair and regeneration of the injured nerve (Brumovsky et al. 2006; Hobson et al. 2006). Meanwhile, the axotomy and ligation of sciatic nerve significantly increase the content of GAL and its mRNA in the rat dorsal root ganglion (Ma and Bisby, 1997, Ma and Bisby, 1999; Villar et al. 1989).

GAL exerts its biologic effects via three known metabotropic and G-protein-coupled receptors: GAL₁R, GAL₂R, and GAL₃R (Habert-Ortoli et al. 1994; Howard et al. 1997; Wang et al. 1997). Previous studies have also demonstrated GAL receptors (GALRs) are expressed in the central and peripheral nervous systems of rodent animals and associated with pronociceptive and analgesic functions (Duan et al. 2015; Hulse et al. 2011; Lemons and Wiley 2011; Liu and Hokfelt 2002a; Lyu et al. 2020; Sipkova et al. 2017; Waters and Krause 2000). For instance, the upregulation of GAL in rat DRG neurons following nerve injury results in antinociception via stimulation of GAL₁R in the dorsal horn interneurons, while the pro-nociceptive effect of GAL is related to presynaptic GAL₂R on primary afferents (Brumovsky et al. 2006; Landry et al. 2006; Liu and Hokfelt 2002a; Yue et al. 2011). Furthermore, nerve injury can affect the expression of GALRs in the spinal cord and sensory ganglia (Brumovsky et al. 2006; Lyu et al. 2020; Xu et al. 1996). After the transection of sciatic nerve, the level of GAL₁R and GAL₂R mRNA was decreased in the rat DRG (Sten Shi et al. 1997; Xu et al. 1996). In the rat TG, GAL₁R is expressed in TG neurons (Suzuki et al. 2002). However, the expression and distribution of GAL₂R and GAL₃R in the TG have not been reported.

The infraorbital nerve (ION) and inferior alveolar nerve (IAN) are derived from the maxillary and mandibular branches of trigeminal nerve, respectively. Previous studies have demonstrated an inconclusive expression of GAL after damage of different trigeminal branches. No significant difference in the level of GAL in TG neurons was observed between the ipsilateral and contralateral TG after ION transection in mice (Lynds et al. 2017). Transection of IAN increased GAL and its mRNA in the ipsilateral TG of rats (Zhang et al. 1996). However, transection of IAN with ligation at the mesial nerve ending reduced GAL level in the ferret TG (Elcock et al. 2001). Therefore, the effects of nerve injury on GAL expression in the TG may be different based on the different trigeminal nerve branches and different types of nerve injuries involved. Furthermore, it is unknown whether the damage of trigeminal nerve regulates the expression of GAL and GALRs in injured and uninjured TG neurons. We hypothesized that expression of GAL and GALRs in the TG will be affected by nerve injury, further suggesting a role for the GAL signaling system in the modulation of neuronal activity, nociceptive transduction, and regeneration.

Therefore, the present study examined possible changes in the level of GAL mRNA and peptide immunoreactivity in the rat TG after ION/IAN transection by quantitative real-time reverse transcription-polymerase chain reaction (RT-qPCR) and immunohistochemical methods, respectively. Changes in GAL expression in nerve-injured and nerve-uninjured TG neurons were also investigated by double immunofluorescence labeling of GAL and activating transcription factor 3 (ATF3), a marker for nerve-injured neurons (Tsujino et al. 2000). In addition, a trichrome immunofluorescence staining for GAL, GALRs, and ATF3 was performed to understand the effects of nerve injury on the expression of GAL and GALRs in nerve-injured and nerve-uninjured TG neurons. The specificity of different receptor antisera was checked by pre-absorption test. The major findings of this study were that ION and IAN transections upregulated the levels of GAL mRNA and peptide in both injured and adjacent uninjured small to medium-sized TG neurons, without affecting distant intact TG neurons. In addition, GAL₁R, GAL₂R, and GAL₃R were predominantly located in small to medium-sized TG neurons, and GAL₂R was decreased in injured and adjacent uninjured TG neurons, while GAL₁R and GAL₃R remained unchanged after ION and IAN transections. In line with previous studies in other spinal neuron systems, these results suggest that GAL, GAL₁R, GAL₂R, and GAL₃R play functional roles in orofacial neuropathic pain and trigeminal nerve regeneration after trigeminal nerve injury.

Section snippets

Animals and axotomy

A total of 32 male Wistar rats (180–250 g) were used in this study. Transection of the left ION or IAN was performed on the rats under deep anesthesia with a mixture of medetomidine hydrochloride (0.04 mg/kg), midazolam (0.3 mg/kg), and butorphanol tartrate (0.4 mg/kg) (i.p.). The left ION of 8 rats was exposed through an incision of skin and subcutaneous layer in the infraorbital region. For IAN transection (n = 8), the left mandibular skin, subcutaneous layer, and the masseter muscle were

Levels of GAL mRNA increased in the TG after trigeminal nerve injury

To investigate the effects of ION/IAN transection on levels of GAL mRNA in the caudal and rostral halves of the TG, RT-qPCR was performed. In sham-operated rats, the expression of GAL mRNA in the caudal and rostral halves of the TG was similar after sham operations for ION or IAN injury (Fig. 1A and B). However, the level of GAL mRNA was higher in the rostral half (R1/2) of the TG than that of the caudal half (C1/2) of the TG after transection of ION (C1/2 vs. R1/2 = 22.8 ± 5.2 vs. 32.4 ± 3.7,

Discussion

The present study demonstrated that the transection of ION/IAN increased both GAL mRNA and peptide levels in the rat TG. This is consistent with several previous studies observed that transection or crush of nerves increases the expression of GAL mRNA and peptide in the rodent TG, DRG, pelvic ganglia, superior cervical ganglion (SCG), facial nucleus, spinal cord, and brain stem (Bodie et al. 1997; Burazin and Gundlach 1998; Girard et al. 2012; Makwana et al. 2010; Schreiber et al. 1994; Villar

CRediT authorship contribution statement

Fei Liu: Conceptualization, Data curation, Investigation, Methodology, Writing - original draft, Writing - review & editing. Takehiro Yajima: Formal analysis, Methodology, Writing - review & editing. Min Wang: Validation, Writing - review & editing. Jie-Fei Shen: Validation, Writing - review & editing. Hiroyuki Ichikawa: Conceptualization, Resources, Supervision, Validation, Writing - review & editing. Tadasu Sato: Data curation, Methodology, Software, Project administration.

Declaration of Competing Interest

The authors declare that there is no conflict of interest.

Acknowledgment

We thank all the members in our laboratory for their helpful assistance and comments.

References (89)

F. Amaya et al.
Local inflammation increases vanilloid receptor 1 expression within distinct subgroups of DRG neurons
Brain Res.
(2003)
Y.F. Bai et al.
Activation of galanin receptor 1 inhibits locus coeruleus neurons via GIRK channels
Biochem. Biophys. Res. Commun.
(2018)
P. Brumovsky et al.
Differential distribution and regulation of galanin receptors- 1 and −2 in the rat lumbar spinal cord
Brain Res.
(2006)
P. Brumovsky et al.
Neuropeptide tyrosine and pain
Trends Pharmacol. Sci.
(2007)
M.J. Caterina et al.
Sense and specificity: a molecular identity for nociceptors
Curr. Opin. Neurobiol.
(1999)
J.L. Ch'ng et al.
Distribution of galanin immunoreactivity in the central nervous system and the responses of galanin-containing neuronal pathways to injury
Neuroscience
(1985)
L.A. Colvin et al.
Primary afferent-evoked release of immunoreactive galanin in the spinal cord of the neuropathic rat
Br. J. Anaesth.
(1998)
M.F. Coronel et al.
Differential galanin upregulation in dorsal root ganglia and spinal cord after graded single ligature nerve constriction of the rat sciatic nerve
J. Chem. Neuroanat.
(2008)
R.A. Cridland et al.
Effects of intrathecal administration of neuropeptides on a spinal nociceptive reflex in the rat: VIP, galanin, CGRP, TRH, somatostatin and angiotensin II
Neuropeptides
(1988)
C. Elcock et al.
Neuropeptide expression in the ferret trigeminal ganglion following ligation of the inferior alveolar nerve
Arch. Oral Biol.
(2001)

T. Goto et al.

Neuropeptides and ATP signaling in the trigeminal ganglion

The Japanese dental science review

(2017)

T. Hokfelt et al.

Increase of galanin-like immunoreactivity in rat dorsal root ganglion cells after peripheral axotomy

Neurosci. Lett.

(1987)

A.D. Howard et al.

Molecular cloning and characterization of a new receptor for galanin

FEBS Lett.

(1997)

H. Ichikawa et al.

Distribution, origin and plasticity of galanin-immunoreactivity in the rat carotid body

Neuroscience

(1993)

J.M. Jimenez-Andrade et al.

Mechanism by which peripheral galanin increases acute inflammatory pain

Brain Res.

(2005)

N. Kerekes et al.

The effect of NGF, BDNF and bFGF on expression of galanin in cultured rat dorsal root ganglia

Brain Res.

(1997)

L.L. Lemons et al.

Galanin receptor-expressing dorsal horn neurons: role in nociception

Neuropeptides

(2011)

H. Liu et al.

Effect of intrathecal galanin and its putative antagonist M35 on pain behavior in a neuropathic pain model

Brain Res.

(2000)

H.X. Liu et al.

The participation of galanin in pain processing at the spinal level

Trends Pharmacol. Sci.

(2002)

H.X. Liu et al.

The participation of galanin in pain processing at the spinal level

Trends Pharmacol. Sci.

(2002)

K.J. Livak et al.

Analysis of relative gene expression data using real-time quantitative PCR and the 2(T)(−Delta Delta C) method

Methods

(2001)

C. Lyu et al.

A preliminary study on DRGs and spinal cord of a galanin receptor 2-EGFP transgenic mouse

Neuropeptides

(2020)

W. Ma et al.

Differential expression of galanin immunoreactivities in the primary sensory neurons following partial and complete sciatic nerve injuries

Neuroscience

(1997)

W. Ma et al.

Increase of galanin mRNA in lumbar dorsal root ganglion neurons of adult rats after partial sciatic nerve ligation

Neurosci. Lett.

(1999)

M.S. Rao et al.

Leukemia inhibitory factor mediates an injury response but not a target-directed developmental transmitter switch in sympathetic neurons

Neuron

(1993)

R.C. Schreiber et al.

Galanin expression increases in adult rat sympathetic neurons after axotomy

Neuroscience

(1994)

A.M. Shadiack et al.

Galanin induced in sympathetic neurons after axotomy is anterogradely transported toward regenerating nerve endings

Neuropeptides

(1998)

G. Skofitsch et al.

Galanin-like immunoreactivity in capsaicin sensitive sensory neurons and ganglia

Brain Res. Bull.

(1985)

K.E. Smith et al.

Cloned human and rat galanin GALR3 receptors. Pharmacology and activation of G-protein inwardly rectifying K+ channels

J. Biol. Chem.

(1998)

W.D. Snider et al.

Tackling pain at the source: new ideas about nociceptors

Neuron

(1998)

T.J. Sten Shi et al.

Expression and regulation of galanin-R2 receptors in rat primary sensory neurons: effect of axotomy and inflammation

Neurosci. Lett.

(1997)

H. Suzuki et al.

Expression of galanin receptor-1 (GALR1) in the rat trigeminal ganglia and molar teeth

Neurosci. Res.

(2002)

M. Takeda et al.

Activation of interleukin-1beta receptor suppresses the voltage-gated potassium currents in the small-diameter trigeminal ganglion neurons following peripheral inflammation

Pain

(2008)

M. Takeda et al.

Inflammation enhanced brain-derived neurotrophic factor-induced suppression of the voltage-gated potassium currents in small-diameter trigeminal ganglion neurons projecting to the trigeminal nucleus interpolaris/caudalis transition zone

Neuroscience

(2014)

K. Tatemoto et al.

Galanin - a novel biologically active peptide from porcine intestine

FEBS Lett.

(1983)

Y. Terada et al.

NGF and BDNF expression in mouse DRG after spared nerve injury

Neurosci. Lett.

(2018)

Y. Tsuboi et al.

Alteration of the second branch of the trigeminal nerve activity following inferior alveolar nerve transection in rats

Pain

(2004)

H. Tsujino et al.

Activating transcription factor 3 (ATF3) induction by axotomy in sensory and motoneurons: a novel neuronal marker of nerve injury

Mol. Cell. Neurosci.

(2000)

M.J. Villar et al.

Neuropeptide expression in rat dorsal root ganglion cells and spinal cord after peripheral nerve injury with special reference to galanin

Neuroscience

(1989)

M.J. Villar et al.

Further studies on galanin-, substance P-, and CGRP-like immunoreactivities in primary sensory neurons and spinal cord: effects of dorsal rhizotomies and sciatic nerve lesions

Exp. Neurol.

(1991)

S. Wang et al.

Cloning and expressional characterization of a novel galanin receptor. Identification of different pharmacophores within galanin for the three galanin receptor subtypes

J Biol Chem

(1997)

R. Amir et al.

Chemically mediated cross-excitation in rat dorsal root ganglia

J. Neurosci.

(1996)

D. Bodie et al.

Organization, development, and effects of infraorbital nerve transection on galanin binding sites in the trigeminal brainstem complex

Somatosensory & motor research

(1997)

T.C. Burazin et al.

Inducible galanin and GalR2 receptor system in motor neuron injury and regeneration

J. Neurochem.

(1998)

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¹: Permanent Address: State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Department II of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, No. 14, Section 3, Renminnan Road, Chengdu, Sichuan 610,041, China

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Effects of trigeminal nerve injury on the expression of galanin and its receptors in the rat trigeminal ganglion

Abstract

Introduction

Section snippets

Animals and axotomy

Levels of GAL mRNA increased in the TG after trigeminal nerve injury

Discussion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgment

Brain Res.

Biochem. Biophys. Res. Commun.

Brain Res.

Trends Pharmacol. Sci.

Curr. Opin. Neurobiol.

Neuroscience

Br. J. Anaesth.

J. Chem. Neuroanat.

Neuropeptides

Arch. Oral Biol.

The Japanese dental science review

Neurosci. Lett.

FEBS Lett.

Neuroscience

Brain Res.

Brain Res.

Neuropeptides

Brain Res.

Trends Pharmacol. Sci.

Trends Pharmacol. Sci.

Methods

Neuropeptides

Neuroscience

Neurosci. Lett.

Neuron

Neuroscience

Neuropeptides

Brain Res. Bull.

J. Biol. Chem.

Neuron

Neurosci. Lett.

Neurosci. Res.

Pain

Neuroscience

FEBS Lett.

Neurosci. Lett.

Pain

Mol. Cell. Neurosci.

Neuroscience

Exp. Neurol.

J Biol Chem

Chemically mediated cross-excitation in rat dorsal root ganglia

J. Neurosci.

Organization, development, and effects of infraorbital nerve transection on galanin binding sites in the trigeminal brainstem complex

Somatosensory & motor research

Inducible galanin and GalR2 receptor system in motor neuron injury and regeneration

J. Neurochem.