Upregulation of Cav3.2 T-type calcium channels targeted by endogenous hydrogen sulfide contributes to maintenance of neuropathic pain

Abstract

Hydrogen sulfide (H(2)S) formed from l-cysteine by multiple enzymes including cystathionine-gamma-lyase (CSE) is now considered a gasotransmitter in the mammalian body. Our previous studies have shown that H(2)S activates/sensitizes Ca(v)3.2 T-type Ca(2+) channels, leading to facilitation of somatic and visceral nociception, and that CSE-derived endogenous H(2)S participates in inflammatory pain. Here, we show novel evidence for involvement of the endogenous H(2)S-Ca(v)3.2 pathway in neuropathic pain. In the rat subjected to the right L5 spinal nerve cutting (L5SNC), a neuropathic pain model, i.p. administration of dl-propargylglycine (PPG) and beta-cyanoalanine, irreversible and reversible CSE inhibitors, respectively, strongly suppressed the neuropathic hyperalgesia/allodynia. The anti-hyperalgesic effect of PPG was reversed by intraplantar administration of NaHS, a donor for H(2)S, in the L5SNC rat. Intraplantar administration or topical application of mibefradil, a T-type Ca(2+) channel blocker, reversed hyperalgesia in the L5SNC rat. The protein levels of Ca(v)3.2, but not CSE, in the ipsilateral L4, L5 and L6 dorsal root ganglia were dramatically upregulated in the L5SNC rat. Finally, silencing of Ca(v)3.2 in DRG by repeated intrathecal administration of Ca(v)3.2-targeting siRNA significantly attenuated the neuropathic hyperalgesia in the L5SNC rat. In conclusion, our data suggest that Ca(v)3.2 T-type Ca(2+) channels in sensory neurons are upregulated and activated/sensitized by CSE-derived endogenous H(2)S after spinal nerve injury, contributing to the maintenance of neuropathic pain. We thus propose that Ca(v)3.2 and CSE could be targets for the development of therapeutic drugs for the treatment of neuropathic pain.

T-type Calcium Channels: Functional Regulation and Implication in Pain Signaling

“…Involvement of T-channels in cancer chemotherapy-induced neuropathy was first suggested by a report showing that systemic administration of ethosuximide, a classic T-channel inhibitor, alleviated mechanical and cold allodynia/ hyperalgesia in rats with paclitaxel-or vincristineinduced neuropathy (31). We have confirmed that paclitaxel-induced neuropathic hyperalgesia is abolished by more selective inhibitors of T-channels and by Ca v 3.2 gene silencing, although expression levels of Ca v 3.2 in DRG do not change in this neuropathic pain model (32), differing from the spinal nerve injury-induced neuropathic pain models in which Ca v 3.2 is dramatically upregulated in DRG (28). It is also noteworthy that the paclitaxel-induced neuropathy is reversed by an inhibitor of CSE, suggesting involvement of functional upregulation of the CSE/H 2 S/Ca v 3.2 pathway.…”

“…Interestingly, the neuropathic pain caused by spinal nerve injury is also abolished by two distinct inhibitors of CSE, an H 2 S forming enzyme, suggesting that in addition to the upregulation of Ca v 3.2, sensitization of Ca v 3.2 by CSE-derived endogenous H 2 S through interaction with Zn 2+ , as described in Section 2.1. and shown in Fig. 1, contributes to the neuropathic pain (28). In addition to Ca v 3.2, Ca v 3.1 and Ca v 3.3 may be involved in the pathophysiology of neuropathic pain, considering evidence that neuropathic pain induced by L5 spinal nerve ligation is attenuated in Ca v 3.1-defective mice (29) and that Ca v 3.3, as well as Ca v 3.2, is upregulated at mRNA levels in the spinal cord of the rats with neuropathy induced by chronic compression of DRG (30).…”

“…There is evidence for upregulation of T-channel current density in small DRG cells isolated from rats with neuropathic pain due to chronic constrictive injury (CCI) of the sciatic nerve (27) and that genetic silencing of Ca v 3.2 channels reverses CCI-induced neuropathic pain (17). We have demonstrated upregulation of Ca v 3.2 at protein levels in the DRG of rats with neuropathy induced by spinal nerve injury and that pharmacological inhibition or genetic silencing of Ca v 3.2 reverses the established neuropathic hyperalgesia/allodynia (28). Interestingly, the neuropathic pain caused by spinal nerve injury is also abolished by two distinct inhibitors of CSE, an H 2 S forming enzyme, suggesting that in addition to the upregulation of Ca v 3.2, sensitization of Ca v 3.2 by CSE-derived endogenous H 2 S through interaction with Zn 2+ , as described in Section 2.1. and shown in Fig.…”

Targeting Calcium Channels to Block Tumor Vascularization

“…Moreover, mibefradil suppressed the phosphorylation of ERK induced by the infusion of NaHS, a pronociceptive stimulus in the pancreatic duct, albeit at higher concentrations than those reported above (500 nM/rat) [46]. Finally, the neuropathic allodynia/hyperalgesia induced in rats by damaging the right L5 spinal nerve [47] or by systemic injection of paclitaxel [48], an anticancer drug, was strongly attenuated by either mibefradil or CSE inhibitors, or by antisense ODNs against rat CaV3.2. In addition, CaV3.2 was significantly up-regulated in the ipsilateral L4, L5, and L6 dorsal root ganglia of rats subjected to spinal nerve injury, but not treated with paclitaxel [48].…”

Gasotransmitters in Vascular Complications of Diabetes

“…Conversely, reduction of H 2 S reduced the tactile allodynia developed in course of diabetes. The T-type voltage-gated calcium channel Ca V 3.2 is sensitized by H 2 S, leading to increased pain sensitivity (101). An increased H 2 S tissue content and hyperactivity (102).…”