N-methyl D-aspartate receptor subtype 2B antagonist, Ro 25-6981, attenuates neuropathic pain by inhibiting postsynaptic density 95 expression

Ling-Er Huang,Yong-Xing Yao,Yan Yang,Shao-Hui Guo,Lalita Thitiseranee,Yan-Feng Zhou

doi:10.1038/s41598-018-26209-7

Abstract

Postsynaptic density-95 (PSD-95) is a synaptic scaffolding protein that plays a crucial role in the development of neuropathic pain. However, the underlying mechanism remains unclear. To address the role of PSD-95 in N-methyl-D-aspartate receptor subtype 2B (NR2B) -mediated chronic pain, we investigated the relationship between PSD-95 activation and NR2B function in the spinal cord, by using a rat model of sciatic nerve chronic constriction injury (CCI). We demonstrate that the expression levels of total PSD-95 and cAMP response element binding protein (CREB), as well as phosphorylated NR2B, PSD-95, and CREB, in the spinal dorsal horn, and the interaction of NR2B with PSD-95 were increased in the CCI animals. Intrathecal injection of the selective NR2B antagonist Ro 25-6981 increased paw withdrawal latency, in a thermal pain assessment test. Moreover, repeated treatment with Ro 25-6981 markedly attenuated the thermal hypersensitivity, and inhibited the CCI-induced upregulation of PSD-95 in the spinal dorsal horn. Furthermore, intrathecal injection of the PSD-95 inhibitor strikingly reversed the thermal and mechanical hyperalgesia. Our results suggest that blocking of NR2B signaling in the spinal cord could be used as a therapeutic candidate for treating neuropathic pain.

Highlights

Neuropathic pain, usually caused by a primary lesion in the nervous system, is a serious worldwide public health problem[1,2]
The results showed that the N-methyl-D-aspartate receptor subtype 2B (NR2B) protein was enriched in the spinal dorsal horn (DH) than the ventral horn (VH); no NR2B signal was detected in the dorsal root ganglion (DRG) of healthy rats (Fig. 1A,B)
To test whether NR2B was expressed in neurons, microglia, or astrocytes cells, we labeled the sections using antibodies for neuronal nuclear protein (NeuN), ionized calcium binding adaptor molecule 1 (Iba-1), and glial fibrillary acidic protein (GFAP), respectively

Summary

Introduction

Neuropathic pain, usually caused by a primary lesion in the nervous system, is a serious worldwide public health problem[1,2]. Some studies have shown that spinal NR2B expression increases upon partial constrictive injury of the sciatic nerve in rats[16], while others have suggested that pain transmission signals are not induced by NR2B protein alterations[17,18,19,20]. These discrepancies prompted us to further study the mechanism by which NR2B and PSD-95 mediate neuropathic pain. We hypothesized that CCI induces activation of spinal cord NR2B/PSD-95/cAMP response element binding protein (CREB) signaling and that perturbing NR2B function might attenuate pain hypersensitivity

Objectives

Methods

Results

Conclusion