Spinal sigma-1 receptor activation increases the production of d-serine in astrocytes which contributes to the development of mechanical allodynia in a mouse model of neuropathic pain

Ji Young Moon, Sheu Ran Choi, Dae Hyun Roh, Seo Yeon Yoon, Soon Gu Kwon, Hoon Seong Choi, Suk Yun Kang, Ho Jae Han, Hyun Woo Kim, Alvin J. Beitz, Seog Bae Oh, Jang Hern Lee

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

We have previously demonstrated that activation of the spinal sigma-1 receptor (Sig-1R) plays an important role in the development of mechanical allodynia (MA) via secondary activation of the N-methyl-d-aspartate (NMDA) receptor. Sig-1Rs have been shown to localize to astrocytes, and blockade of Sig-1Rs inhibits the pathologic activation of astrocytes in neuropathic mice. However, the mechanism by which Sig-1R activation in astrocytes modulates NMDA receptors in neurons is currently unknown. d-serine, synthesized from l-serine by serine racemase (Srr) in astrocytes, is an endogenous co-agonist for the NMDA receptor glycine site and can control NMDA receptor activity. Here, we investigated the role of d-serine in the development of MA induced by spinal Sig-1R activation in chronic constriction injury (CCI) mice. The production of d-serine and Srr expression were both significantly increased in the spinal cord dorsal horn post-CCI surgery. Srr and d-serine were only localized to astrocytes in the superficial dorsal horn, while d-serine was also localized to neurons in the deep dorsal horn. Moreover, we found that Srr exists in astrocytes that express Sig-1Rs. The CCI-induced increase in the levels of d-serine and Srr was attenuated by sustained intrathecal treatment with the Sig-1R antagonist, BD-1047 during the induction phase of neuropathic pain. In behavioral experiments, degradation of endogenous d-serine with DAAO, or selective blockade of Srr by LSOS, effectively reduced the development of MA, but not thermal hyperalgesia in CCI mice. Finally, BD-1047 administration inhibited the development of MA and this inhibition was reversed by intrathecal treatment with exogenous d-serine. These findings demonstrate for the first time that the activation of Sig-1Rs increases the expression of Srr and d-serine in astrocytes. The increased production of d-serine induced by CCI ultimately affects dorsal horn neurons that are involved in the development of MA in neuropathic mice.

Original languageEnglish (US)
Article number2916
Pages (from-to)353-364
Number of pages12
JournalPharmacological Research
Volume100
DOIs
StatePublished - Oct 1 2015

Keywords

  • Astrocyte
  • D-serine
  • Mechanical allodynia
  • Neuropathic paina
  • Sig-1R

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