Selective inhibition of Ca _V 3.2 channels reverses hyperexcitability of peripheral nociceptors and alleviates postsurgical pain

Abstract

Pain-sensing sensory neurons of the dorsal root ganglion (DRG) can become sensitized or hyperexcitable in response to surgically induced peripheral tissue injury. We investigated the potential role and molecular mechanisms of nociceptive ion channel dysregulation in acute pain conditions such as those resulting from skin and soft tissue incision. We used selective pharmacology, electrophysiology, and mouse genetics to link increased current densities arising from the Ca3.2 isoform of T-type calcium channels (T-channels) to nociceptive sensitization using a clinically relevant rodent model of skin and deep tissue incision. Furthermore, knockdown of the Ca3.2-targeting deubiquitinating enzyme USP5 or disruption of USP5 binding to Ca3.2 channels in peripheral nociceptors resulted in a robust antihyperalgesic effect in vivo and substantial T-current reduction in vitro. Our study provides mechanistic insight into the role of plasticity in Ca3.2 channel activity after surgical incision and identifies potential targets for perioperative pain that may greatly decrease the need for narcotics and potential for drug abuse.

Novel neuroactive steroid with hypnotic and T‐type calcium channel blocking properties exerts effective analgesia in a rodent model of post‐surgical pain

“…In order to further study the mechanisms of inhibitory effects of 3β‐OH on T‐currents, we applied 3β‐OH in a concentration of 10 μM on HEK cells expressing Ca V 3.2 channel, a T‐channel subtype important for the development of incisional pain (Joksimovic et al, ). This concentration of 3β‐OH was used since it blocked potently T‐currents in DRG cells (Todorovic et al, ).…”

“…We have previously shown that Ca V 3.2 channels are essential for the development of post‐surgical pain in rodents (Joksimovic et al, ). In order to investigate if Ca V 3.2 isoform of T‐channels represents a target for the in vivo analgesic effects of 3β‐OH post‐incision, we applied neurosteroid (16 μg i.t.)…”

“…in WT mice and in mice lacking Ca V 3.2 calcium channels (Ca V 3.2 KO mice). The treatment was applied on the second day post‐incision (Joksimovic et al, ), and the effects of the treatment were measured at time points of 30, 60 and 90 min after the injection (Figure a). We found that 3β‐OH significantly reduced mechanical hyperalgesia post‐incision in WT mice, but not in KO mice (Figure b).…”

“…The supportive role of Ca V 3.2 isoform of T‐channels in pain pathways has been relatively well established since blocking peripheral T‐channels leads to very potent antinociceptive effects in the various pain models (Choi et al, ; Todorovic et al, ; Todorovic, Meyenburg, & Jevtovic‐Todorovic, ; Todorovic, Rastogi, & Jevtovic‐Todorovic, ). Furthermore, our recent study (Joksimovic et al, ) has implicated Ca V 3.2 channels in hyperalgesia using postsurgical pain model in rodents.…”

“…Whenever possible, studies were designed to generate groups of equal size, using randomization and blinded analysis. In our behaviour experiments, we used the vehicle in the same fashion as previously published (Joksimovic et al, ) and we have previously shown that this vehicle does not exert any effect on hyperalgesia. Therefore, to be in accordance with the 3R principle (replace, reduce and refine), we minimized the use of animals for well‐established experiments, due to which a smaller group of animals received vehicle as compared to the treatment groups.…”