Up-regulation of Cavβ3 Subunit in Primary Sensory Neurons Increases Voltage-activated Ca2+ Channel Activity and Nociceptive Input in Neuropathic Pain

Li Li,Xue-Hong Cao,Shao-Rui Chen,Hee-Dong Han,Gabriel Lopez-Berestein,Anil K Sood,Hui-Lin Pan

doi:10.1074/jbc.m111.310110

Abstract

High voltage-activated calcium channels (HVACCs) are essential for synaptic and nociceptive transmission. Although blocking HVACCs can effectively reduce pain, this treatment strategy is associated with intolerable adverse effects. Neuronal HVACCs are typically composed of α(1), β (Cavβ), and α(2)δ subunits. The Cavβ subunit plays a crucial role in the membrane expression and gating properties of the pore-forming α(1) subunit. However, little is known about how nerve injury affects the expression and function of Cavβ subunits in primary sensory neurons. In this study, we found that Cavβ(3) and Cavβ(4) are the most prominent subtypes expressed in the rat dorsal root ganglion (DRG) and dorsal spinal cord. Spinal nerve ligation (SNL) in rats significantly increased mRNA and protein levels of the Cavβ(3), but not Cavβ(4), subunit in the DRG. SNL also significantly increased HVACC currents in small DRG neurons and monosynaptic excitatory postsynaptic currents of spinal dorsal horn neurons evoked from the dorsal root. Intrathecal injection of Cavβ(3)-specific siRNA significantly reduced HVACC currents in small DRG neurons and the amplitude of monosynaptic excitatory postsynaptic currents of dorsal horn neurons in SNL rats. Furthermore, intrathecal treatment with Cavβ(3)-specific siRNA normalized mechanical hyperalgesia and tactile allodynia caused by SNL but had no significant effect on the normal nociceptive threshold. Our findings provide novel evidence that increased expression of the Cavβ(3) subunit augments HVACC activity in primary sensory neurons and nociceptive input to dorsal horn neurons in neuropathic pain. Targeting the Cavβ(3) subunit at the spinal level represents an effective strategy for treating neuropathic pain.

Highlights

We determined how nerve injury affects calcium channel ␤ (Cav␤) subunits in neuropathic pain
High Expression Levels of Cav␤3 and Cav␤4 Subunits in the dorsal root ganglion (DRG) and Spinal Cord—To determine which Cav␤ subunits are present in the DRG and dorsal spinal cord, we first used reverse transcriptase-PCR and agarose gel electrophoresis to detect the presence of Cav␤1-Cav␤4 mRNA in these tissues
We determined how nerve injury affects the expression of Cav␤ subunits in primary sensory neurons and whether such changes contribute to increased High voltage-activated calcium channels (HVACCs) cur

Summary

Background

We determined how nerve injury affects calcium channel ␤ (Cav␤) subunits in neuropathic pain. Results: Nerve injury increases Cav␤3 expression level, and Cav␤3 knockdown reduces increased calcium channel activity in primary sensory neurons and pain hypersensitivity. Our findings provide novel evidence that increased expression of the Cav␤3 subunit augments HVACC activity in primary sensory neurons and nociceptive input to dorsal horn neurons in neuropathic pain. We used a rat model of neuropathic pain to determine how nerve injury affects the expression level of Cav␤ subunits in the DRG and dorsal spinal cord. We determined the contribution of the Cav␤3 subunit to increased HVACC activity in DRG neurons and nociceptive input to the spinal cord induced by nerve injury. SiRNA knockdown of Cav␤3 greatly reduced increased HVACC activity in the DRG, glutamatergic input to the spinal cord, and pain hypersensitivity caused by nerve injury without impairing normal nociception. Targeting the Cav␤3 subunit at the spinal level represents a new strategy for treating neuropathic pain with improved therapeutic profiles

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION