PKC-NF-κB are involved in CCL2-induced Nav1.8 expression and channel function in dorsal root ganglion neurons.

Rui Zhao,Rui Cong,Tong Tian,Cheng-Wu Zang,Guo-Xian Pei,Hang Zhang

doi:10.1042/bsr20140005

Abstract

CCL2 [chemokine (C–C motif) ligand 2] contributes to the inflammation-induced neuropathic pain through activating VGSC (voltage-gated sodium channel)-mediated nerve impulse conduction, but the underlying mechanism is currently unknown. Our study aimed to investigate whether PKC (protein kinase C)–NF-κB (nuclear factor κB) is involved in CCL2-induced regulation of voltage-gated sodium Nav1.8 currents and expression. DRG (dorsal root ganglion) neurons were prepared from adult male Sprague–Dawley rats and incubated with various concentration of CCL2 for 24 h. Whole-cell patch-clamps were performed to record the Nav1.8 currents in response to the induction by CCL2. After being pretreated with 5 and10 nM CCL2 for 16 h, CCR2 [chemokine (C–C motif) receptor 2] and Nav1.8 expression significantly increased and the peak currents of Nav1.8 elevated from the baseline 46.53±4.53 pA/pF to 64.28±3.12 pA/pF following 10 nM CCL2 (P<0.05). Compared with the control, significant change in Nav1.8 current density was observed when the CCR2 inhibitor INCB3344 (10 nM) was applied. Furthermore, inhibition of PKC by AEB071 significantly eliminated CCL2-induced elevated Nav1.8 currents. In vitro PKC kinase assays and autoradiograms suggested that Nav1.8 within DRG neurons was a substrate of PKC and direct phosphorylation of the Nav1.8 channel by PKC regulates its function in these neurons. Moreover, p65 expression was significantly higher in CCL2-induced neurons (P<0.05), and was reversed by treatment with INCB3344 and AEB071. PKC–NF-κB are involved in CCL2-induced elevation of Nav1.8 current density by promoting the phosphorylation of Nav1.8 and its expression.

Highlights

Peripheral nerve injury, tissue inflammation and neuropathic disorders often result in neuropathic pain, which affects approximately 7 % of the general populations and is insufficiently treated with currently available drugs [1]
Our study aimed to investigate the role of chemokine ligand 2 (CCL2)/chemokine receptor 2 (CCR2) in Nav1.8 modulation in rat dorsal root ganglion (DRG), to clarify whether the regulation of CCL2 on Nav1.8 is dependent on protein kinase C (PKC) activation, and to make determine if the nuclear factor κB (NF-κB) pathway is involved in the regulation of Nav1.8 expression
CCL2–CCR2 are involved in the regulation of Nav1.8 currents in DRG neurons Using a whole-cell patch-clamp configuration, we evaluated the effects of CCL2–CCR2 on the density and kinetic properties of Nav1.8 sodium currents in DRG neurons

Summary

Introduction

Peripheral nerve injury, tissue inflammation and neuropathic disorders often result in neuropathic pain, which affects approximately 7 % of the general populations and is insufficiently treated with currently available drugs [1]. Chemokines and cytokines secreted by infiltrating immune cells, such as macrophages, lymphocytes and neutrophils, enhance the activity of nociceptive DRG (dorsal root ganglion neurons), eventually leading to hyperpathia of afferent neurons [3]. The chemokine CCL2 [chemokine (C– C motif) ligand]was shown to play a key role in spinal nociceptive processing, mainly by sensitizing primary afferent neurons via binding to its preferred receptor CCR2 [chemokine (C–C motif) receptor 2] to enhance the pain hypersensitivity [4,5]. CCR2 is expressed in primary afferent DRG neurons, and the antagonists or blocking antibodies of CCR2 successfully inhibited the nociceptive signalling in peripheral neurons [6]. VGSCs (voltage-gated sodium channels) are very important for electrogenesis and nerve impulse conduction, and are suggested to be involved in the pathogenesis of chronic pain in primary sensory neurons [7].

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