Neuropathic Allodynia Involves Spinal Neurexin-1β-dependent Neuroligin-1/Postsynaptic Density-95/NR2B Cascade in Rats.
BACKGROUND
Neuroligin-1 (NL1) forms a complex with the presynaptic neurexin-1β (Nrx1b), regulating clustering of N-methyl-D-aspartate receptors with postsynaptic density-95 (PSD-95) to underlie learning-/memory-associated plasticity. Pain-related spinal neuroplasticity shares several common features with learning-/memory-associated plasticity. The authors thereby investigated the potential involvement of NL1-related mechanism in spinal nerve ligation (SNL)-associated allodynia.


METHODS
In 626 adult male Sprague-Dawley rats, the withdrawal threshold and NL1, PSD-95, phosphorylated NR2B (pNR2B) expressions, interactions, and locations in dorsal horn (L4 to L5) were compared between the sham operation and SNL groups. A recombinant Nrx1b Fc chimera (Nrx1b Fc, 10 μg, 10 μl, i.t., bolus), antisense small-interfering RNA targeting to NL1 (10 μg, 10 μl, i.t., daily for 4 days), or NR2B antagonist (Ro 25-6981; 1 μM, 10 μl, i.t., bolus) were administered to SNL animals to elucidate possible cascades involved.


RESULTS
SNL-induced allodynia failed to affect NL1 or PSD-95 expression. However, pNR2B expression (mean ± SD from 13.1 ± 2.87 to 23.1 ± 2.52, n = 6) and coexpression of NL1-PSD-95, pNR2B-PSD-95, and NL1-total NR2B were enhanced by SNL (from 10.7 ± 2.27 to 22.2 ± 3.94, 11.5 ± 2.15 to 23.8 ± 3.32, and 8.9 ± 1.83 to 14.9 ± 2.27 at day 7, n = 6). Furthermore, neuron-localized pNR2B PSD-95-pNR2B double-labeled and NL1/PSD-95/pNR2B triple-labeled immunofluorescence in the ipsilateral dorsal horn was all prevented by Nrx1b Fc and NL1-targeted small-interfering RNA designed to block and prevent NL1 expression. Without affecting NL1-PSD-95 coupling, Ro 25-6981 decreased the SNL-induced PSD-95-pNR2B coprecipitation (from 18.7 ± 1.80 to 14.7 ± 2.36 at day 7, n = 6).


CONCLUSIONS
SNL-induced allodynia, which is mediated by the spinal NL1/PSD-95/pNR2B cascade, can be prevented by blockade of transsynaptic Nrx1b-NL1 interactions.
From the Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan (T.-B.L.); Graduate Institute of Basic Medical Science, College of Medicine, China Medical University, Taichung, Taiwan (T.-B.L.); Department of Biotechnology, Asia University, Taichung, Taiwan (T.-B.L.); Department of Medicine, Mackay Medical College, New Taipei, Taiwan (C.-Y.L., M.-C.H., J.-L.J., J.-K.C., Y.-P.C., H.-Y.P.); Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan (C.-Y.L.); Department of Physiology, School of Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan (M.-C.H.); Department of Anesthesiology, Mackay Memorial Hospital, New Taipei, Taiwan (J.-K.C.); School of Medicine, Fu-Jen Catholic University, New Taipei, Taiwan (T.R.); and Department of Obstetrics and Gynecology, Chung-Shan Medical University Hospital, Chung-Shan Medical University, Taichung, Taiwan (G.-D.C.).
Tzer-Bin
TB
Lin
Cheng-Yuan
CY
Lai
Ming-Chun
MC
Hsieh
Jian-Lin
JL
Jiang
Jen-Kun
JK
Cheng
Yat-Pang
YP
Chau
Ting
T
Ruan
Gin-Den
GD
Chen
Hsien-Yu
HY
Peng
D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000096:biosynthesis*; D000076122:Disks Large Homolog 4 Protein; D006930:Hyperalgesia / Q000378:metabolism* / Q000473:pathology; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis*; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D009437:Neuralgia / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis*; D015398:Signal Transduction / Q000502:physiology; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology; D013127:Spinal Nerves / Q000293:injuries
D015816:Cell Adhesion Molecules, Neuronal; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D016194:Receptors, N-Methyl-D-Aspartate; C093438:neuroligin 1; C086959:neurexin Ibeta