Expression of vesicular glutamate transporters VGLUT1 and VGLUT2 in the rat dental pulp and trigeminal ganglion following inflammation.

Eun Sun Yang,Yun Sook Kim,Tae Heon Kim,So Young Choi,Yi Sul Cho,Myoung Uk Jin,Yong Chul Bae,Jae Hyun Hong,Alexander Binshtok

doi:10.1371/journal.pone.0109723

Abstract

BackgroundThere is increasing evidence that peripheral glutamate signaling mechanism is involved in the nociceptive transmission during pathological conditions. However, little is known about the glutamate signaling mechanism and related specific type of vesicular glutamate transporter (VGLUT) in the dental pulp following inflammation. To address this issue, we investigated expression and protein levels of VGLUT1 and VGLUT2 in the dental pulp and trigeminal ganglion (TG) following complete Freund’s adjuvant (CFA) application to the rat dental pulp by light microscopic immunohistochemistry and Western blot analysis.ResultsThe density of VGLUT2− immunopositive (+) axons in the dental pulp and the number of VGLUT2+ soma in the TG increased significantly in the CFA-treated group, compared to control group. The protein levels of VGLUT2 in the dental pulp and TG were also significantly higher in the CFA-treated group than control group by Western blot analysis. The density of VGLUT1+ axons in the dental pulp and soma in the TG remained unchanged in the CFA-treated group.ConclusionsThese findings suggest that glutamate signaling that is mediated by VGLUT2 in the pulpal axons may be enhanced in the inflamed dental pulp, which may contribute to pulpal axon sensitization leading to hyperalgesia following inflammation.

Highlights

There is increasing evidence that glutamate, a major excitatory neurotransmitter in the central nervous system, plays an essential role in the transmission of pain signals by the peripheral nervous system under normal and pathological conditions
The peripheral signaling mechanism for pulpal inflammatory pain, and involvement of specific type of vesicular glutamate transporter (VGLUT) in it, is largely unknown. To address this gap in knowledge, we investigated the expression of VGLUT1 and VGLUT2 in the rat dental pulp and trigeminal ganglion (TG) in a model of dental pulp inflammation, induced by complete Freund’s adjuvant (CFA), using light microscopic immunohistochemistry, quantitative analysis of VGLUT12 and VGLUT22 immunopositive axons and somata, and Western blot analysis
VGLUT1 and VGLUT2 expression in the dental pulp In the dental pulp of controls, VGLUT1 and VGLUT2 were expressed in axons (Fig. 1A, B)

Summary

Introduction

There is increasing evidence that glutamate, a major excitatory neurotransmitter in the central nervous system, plays an essential role in the transmission of pain signals by the peripheral nervous system under normal and pathological conditions. There is increasing evidence that peripheral glutamate signaling mechanism is involved in the nociceptive transmission during pathological conditions. Little is known about the glutamate signaling mechanism and related specific type of vesicular glutamate transporter (VGLUT) in the dental pulp following inflammation. To address this issue, we investigated expression and protein levels of VGLUT1 and VGLUT2 in the dental pulp and trigeminal ganglion (TG) following complete Freund’s adjuvant (CFA) application to the rat dental pulp by light microscopic immunohistochemistry and Western blot analysis

Methods

Results

Conclusion