NF-κB-Associated Pain-Related Neuropeptide Expression in Patients with Degenerative Disc Disease.

Aisha Ahmed,Kanar Alkass,Henrik Druid,David Hart,Camilla Svensson,Eva Kosek,Svante Berg

doi:10.3390/ijms20030658

Abstract

The role of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) has been highlighted in mechanisms underlying inflammatory and neuropathic pain processes. The present study was designed to investigate whether NF-κB signaling is associated with pain-related neuropeptide expression in patients with chronic back pain related to degenerative disc disease (DDD). Intervertebral disc (IVD) tissues were collected from forty DDD patients undergoing disc replacement or fusion surgery, and from eighteen postmortem (PM) control subjects. RELA, NFKB1, CGRP, TAC1, TRPV1, and MMP-3 gene expression were analyzed by RT-qPCR, while NF-κB subunit RelA and NF-κB1–DNA binding in nuclear extracts and calcitonin gene related peptide (CGRP), substance P (SP), and transient receptor potential, subfamily V, member 1 (TRPV1) protein levels in cytosolic extracts of tissues were assessed by enzyme-linked immunosorbent assay (ELISA). An upregulated NF-κB1–DNA binding, and higher CGRP and TRPV1 protein levels were observed in DDD patients compared to PM controls. In DDD patients, NF-κB1–DNA binding was positively correlated with nuclear RelA levels. Moreover, NF-κB1–DNA binding was positively associated with TRPV1 and MMP-3 gene and SP and TRPV1 protein expression in DDD patients. Our results indicate that the expression of SP and TRPV1 in IVD tissues was associated with NF-κB activation. Moreover, NF-κB may be involved in the generation or maintenance of peripheral pain mechanisms by the regulation of pain-related neuropeptide expression in DDD patients.

Highlights

Degenerative disc disease (DDD) is an important cause of chronic low back pain [1]
We have quantified NF-κB1–DNA binding and nuclear RelA levels, as well as studied the expression of calcitonin gene related peptide (CGRP), substance P (SP), and TRPV1 both at the mRNA and protein levels in Intervertebral disc (IVD) tissues collected from degenerative disc disease (DDD) patients and postmortem (PM) controls
The main findings of the present studies are that NF-κB1–DNA binding and CGRP and TRPV1 levels were higher in IVD tissues extracted from DDD patients compared to PM controls

Summary

Introduction

Degenerative disc disease (DDD) is an important cause of chronic low back pain [1]. DDD is characterized by the loss of extracellular matrix, initiated by an imbalance between catabolic and anabolic mediator expression in the chondrocytes and in matrix [2]. An upregulated expression of calcitonin gene related peptide (CGRP) and substance P (SP) along with nerve growth factor (NGF) in sensory nerves innervating IVD has been reported in DDD patients [6,7]. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is one of numerous signaling pathways reported to play a critical role in inflammatory degenerative processes [10,11]. Activation of NF-κB, as measured by the upregulated expression of RelA, has been reported in IVD tissues extracted from patients with DDD [17]. By blocking nuclear RelA translocation with specific inhibitors, it has been shown that the process of IVD degeneration was decreased in a rat model of DDD [18], suggesting a role for NF-κB in IVD degenerative processes. The role of NF-κB signaling on SP expression or NF-κB-related processes in human IVD tissues likely influencing nociceptive signaling in DDD patients have, to our knowledge, not been studied before

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