Neuroligin1 Contributes to Neuropathic Pain by Promoting Phosphorylation of Cofilin in Excitatory Neurons.

Junlin Ouyang,Xiaohu Zhu,Changbin Ke,Xinhua Yu,Xiaohui Li,Xiaping Chen,Shanchun Su,Xueqin Xu

doi:10.3389/fnmol.2021.640533

Junlin Ouyang, Xiaohu Zhu + Show 6 more

Open Access

https://doi.org/10.3389/fnmol.2021.640533

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Abstract

Neuropathic pain is a kind of chronic pain that remains difficult to treat due to its complicated underlying mechanisms. Accumulating evidence has indicated that enhanced synaptic plasticity of nociceptive interneurons in the superficial spinal dorsal horn contributes to the development of neuropathic pain. Neuroligin1 (NL1) is a type of excitatory postsynaptic adhesion molecule, which can mediate excitatory synaptic activity, hence promoting neuronal activation. Vglut2 is the most common marker of excitatory glutamatergic neurons. To explore the role of NL1 in excitatory neurons in nociceptive regulation, we used transgenic mice with cre recombinase expression driven by the Vglut2 promoter combined with viral vectors to knockdown the expression of NL1 in excitatory neurons in the spinal dorsal horn. We found that NL1 was upregulated in the L4–L6 spinal dorsal horn in Vglut2-cre+/– mouse subjected to spared nerve injury (SNI). Meanwhile, the expression of phosphorylated cofilin (p-cofilin) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit 1 (GluR1) was also increased. Spinal microinjection of a cre-dependent NL1-targeting RNAi in Vglut2-cre+/– mouse alleviated the neuropathic pain-induced mechanical hypersensitivity and reduced the increase in p-cofilin and GluR1 caused by SNI. Taken together, NL1 in excitatory neurons regulates neuropathic pain by promoting the SNI-dependent increase in p-cofilin and GluR1 in the spinal dorsal horn. Our study provides a better understanding of the role of NL1 in excitatory neurons, which might represent a possible therapeutic target for alleviating neuropathic pain.

Highlights

Neuropathic pain is a worldwide problem that can be caused by a lesion or disease of the somatosensory system (Jensen et al, 2011; Colloca et al, 2017; Song et al, 2020)
Real-time Polymerase Chain Reaction (PCR) (Figure 2C) and western blot analysis showed that both mRNA and protein levels of NL1 were remarkably downregulated by NL1-Associated Virus (AAV) (p < 0.05), but not by native control adeno-associated virus (NC-AAV)
Real-time PCR (Figure 5C) and western blot analysis suggested that the expression of GluR1 was remarkably increased in mice subjected to spared nerve injury (SNI) as compared with sham-operated mice (p < 0.05), and this was substantially reversed by recombinant RNAi adeno-associated virus targeting NL1 (NL1-AAV) (p < 0.05) but not by NC-AAV

Summary

INTRODUCTION

Neuropathic pain is a worldwide problem that can be caused by a lesion or disease of the somatosensory system (Jensen et al, 2011; Colloca et al, 2017; Song et al, 2020). A previous study determined that EYFP positive dorsal horn neurons are glutamatergic excitatory neurons and mediate nociceptive transmission (Wang et al, 2018). Extensive studies have shown that NL1 is associated with pain regulation and hypersensitivity (Guo et al, 2018; Zhao et al, 2018), how NL1 in excitatory neurons participates in nociceptive transmission is not fully known. Neuroligin may regulate neuropathic pain differently in excitatory and inhibitory neurons. We used transgenic mice with Cre recombinase expression driven by the Vglut promoter combined with viral vectors to knockdown the expression of NL1 in excitatory neurons in order to examine the effects of NL1 in excitatory neurons in neuropathic pain regulation and the relevant mechanisms

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION

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