Yonsei Med J.  2016 May;57(3):748-753. 10.3349/ymj.2016.57.3.748.

Efficacy of Anti-NaV1.7 Antibody on the Sensory Nervous System in a Rat Model of Lumbar Intervertebral Disc Injury

• Nojima D
• Inage K
• Sakuma Y
• Sato J
• Orita S
• Yamauchi K
• Eguchi Y
• Ochiai N
• Kuniyoshi
• Aoki Y
• Nakamura J
• Miyagi M
• Suzuki M
• Kubota G
• Sainoh T
• Fujimoto K
• Shiga Y
• Abe K
• Kanamoto H
• Inoue G
• Takahashi
• Ohtori S

• KMID: 2374097
• DOI: http://doi.org/10.3349/ymj.2016.57.3.748

Abstract

PURPOSE
The pathophysiology of discogenic low back pain is not fully understood. Tetrodotoxin-sensitive voltage-gated sodium (NaV) channels are associated with primary sensory nerve transmission, and the NaV1.7 channel has emerged as an analgesic target. Previously, we found increased NaV1.7 expression in dorsal root ganglion (DRG) neurons innervating injured discs. This study aimed to examine the effect of blocking NaV1.7 on sensory nerves after disc injury.
MATERIALS AND METHODS
Rat DRG neurons innervating the L5/6 disc were labeled with Fluoro-Gold (FG) neurotracer. Twenty-four rats underwent intervertebral disc puncture (puncture group) and 12 rats underwent sham surgery (non-puncture group). The injury group was divided into a saline infusion group (puncture+saline group) and a NaV1.7 inhibition group, injected with anti-NaV1.7 antibody (puncture+anti-NaV1.7 group); n=12 per group. Seven and 14 days post-surgery, L1 to L6 DRGs were harvested and immunostained for calcitonin gene-related peptide (CGRP) (an inflammatory pain marker), and the proportion of CGRP-immunoreactive (IR) DRG neurons of all FG-positive neurons was evaluated.
RESULTS
The ratio of CGRP-IR DRG neurons to total FG-labeled neurons in the puncture+saline group significantly increased at 7 and 14 days, compared with the non-puncture group, respectively (p<0.05). Application of anti-NaV1.7 into the disc significantly decreased the ratio of CGRP-IR DRG neurons to total FG-labeled neurons after disc puncture at 7 and 14 days (40% and 37%, respectively; p<0.05).
CONCLUSION
NaV1.7 antibody suppressed CGRP expression in disc DRG neurons. Anti-NaV1.7 antibody is a potential therapeutic target for pain control in patients with lumbar disc degeneration.

Keyword

Low back pain; NaV1.7; intervertebral disc; CGRP; rat

MeSH Terms

Animals
Antibodies
Calcitonin Gene-Related Peptide/metabolism
Disease Models, Animal
Ganglia, Spinal/*metabolism
Intervertebral Disc/*drug effects/*injuries
Intervertebral Disc Degeneration/metabolism
Low Back Pain/*physiopathology
Lumbar Vertebrae/injuries
Male
NAV1.7 Voltage-Gated Sodium Channel/*metabolism
Neurons/*metabolism
Pain/metabolism
Rats
Rats, Sprague-Dawley
Stilbamidines
Antibodies
Calcitonin Gene-Related Peptide
Stilbamidines

Figure

• 

  Fig. 1 FG-labeled (A, B, and C) and CGRP-IR (D, E, and F) DRG neurons among 3 group. FG-labeled (A) and CGRP-IR (D) DRG neurons in the non-puncture group. FG-labeled (B) and CGRP-IR (E) DRG neurons in the puncture+saline group. FG-labeled (C) and CGRP-IR (F) DRG neurons in the puncture+anti-NaV1.7 antibody group. Arrowheads indicate FG-labeled/CGRP-IR DRG neurons. Magnification rate is ×400. FG, Fluoro-Gold; CGRP-IR, calcitonin gene-related peptide-immunoreactive; DRG, dorsal root ganglion; NaV, voltage-gated sodium.

• 

  Fig. 2 Ratio of FG-labeled/CGRP-IR DRG neurons to FG-labeled DRG neurons in the non-puncture, puncture+saline, and puncture+anti-NaV1.7 antibody groups on day 7. The ratio at levels L1 to L6 in the puncture+saline group was significantly greater than the non-puncture and the puncture+NaV1.7 antibody groups (*p<0.05). The ratio at levels L5 and L6 in the puncture+NaV1.7 antibody group was significantly greater than the non-puncture group (†p<0.05). FG, Fluoro-Gold; CGRP-IR, calcitonin gene-related peptide-immunoreactive; DRG, dorsal root ganglion; NaV, voltage-gated sodium.

• 

  Fig. 3 Ratio of FG-labeled/CGRP-IR DRG neurons to FG-labeled DRG neurons in the non-puncture, puncture+saline, and puncture+anti-NaV1.7 antibody groups on day 14. The ratio at levels L1 to L6 in the puncture+saline group was significantly greater than in the non-puncture and the puncture+NaV1.7 antibody groups (*p<0.05). The ratio in the puncture+NaV1.7 antibody group was not significantly different than the non-puncture group (p>0.05). FG, Fluoro-Gold; CGRP-IR, calcitonin gene-related peptide-immunoreactive; DRG, dorsal root ganglion; NaV, voltage-gated sodium.

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