Upregulation of interleukin-6 on Ca3.2 T-type calcium channels in dorsal root ganglion neurons contributes to neuropathic pain in rats with spinal nerve ligation.

The T-type calcium channels Ca3.2, one of the low voltage-activated (LVA) calcium channels, have been found to play important roles in the neuronal excitability. Recently, we and others have demonstrated that accumulation of Ca3.2 channels in the dorsal root ganglion (DRG) neurons and sensory nerves contributes to neuropathic pain after peripheral nerve injury. In the present study, we aimed to further investigate the regulation of Ca3.2 channels by interleukin-6 (IL-6) in DRG neurons in neuropathic pain rats after spinal nerve ligation (SNL). The results showed that Ca3.2 channel protein expression in L5 DRG neurons was upregulated and blockade of this channel decreased the hyperexcitability of DRG neurons and mechanical allodynia in SNL neuropathic pain rats. Furthermore, inhibition of IL-6 trans-signaling reduced the upregulation of Ca3.2 T-type channel induced by FIL-6 (a fusion protein of IL-6 and sIL-6R) in primary cultured DRG neurons in vitro. In vivo, inhibition of IL-6 trans-signaling reversed the upregulation of Ca3.2, reduced the hyperexcitability of L5 DRG neurons and alleviated mechanical allodynia in SNL rats. Our results suggest that IL-6 upregulates Ca3.2 T-type channels expression and function through the IL-6/sIL-6R trans-signaling pathway in DRG neurons, thus contributes to the development of neuropathic pain in SNL rats.