Potent analgesic effects of a store-operated calcium channel inhibitor

Abstract

Chronic pain often accompanies immune responses and immune cells are known to be involved in chronic pain. Store-operated calcium (SOC) channels are calcium-selective cation channels and play an important role in the immune system. YM-58483, a potent SOC channel inhibitor, has been shown to inhibit cytokine production from immune cells and attenuate antigen-induced hypersensitivity reactions. Here, we report that YM-58483 has analgesic actions in chronic pain and produces antinociceptive effects in acute pain and prevents the development of chronic pain in mice. Oral administration of 10mg/kg or 30 mg/kg YM-58483 dramatically attenuated complete Freund adjuvant (CFA)-induced thermal hyperalgesia and prevented the development of thermal and mechanical hypersensitivity in a dose-dependent manner. Analgesic effects were observed when YM-58483 was administered systemically, intrathecally and intraplantarly. YM-58483 decreased spared nerve injury (SNI)-induced thermal and mechanical hypersensitivity and prevented the development of SNI-induced pain hypersensitivity. Pretreatment with YM-58483 strongly reduced both the first and second phases of formalin-induced spontaneous nocifensive behavior in a dose-dependent manner. YM-58483 produced antinociception in acute pain induced by heat or chemical or mechanical stimuli at a dose of 30 mg/kg. YM-58483 diminished CFA-induced paw edema, and reduced production of TNF-α, IL-1β and PGE2 in the CFA-injected paw. In vitro, SOC entry in nociceptors was more robust than in nonnociceptors, and the inhibition of SOC entry by YM-58483 in nociceptors was much greater than in nonnociceptors. Our findings indicate that YM-58483 is a potent analgesic and suggest that SOC channel inhibitors may represent a novel class of therapeutics for pain.

Keywords: Dorsal root ganglia; Inflammation; Pain; Store-operated calcium channels; Tumor necrosis factor alpha; YM-58483.

Fig. 1

YM-58483 reverses complete Freund's adjuvant (CFA)-induced pain hypersensitivity. (A) Time-dependent effects of YM-58483 (YM) on CFA-induced thermal hyperalgesia measured 72 hrs after CFA injection in CD-1 mice (n = 6-7). (B) Time-dependent effects of YM-58483 on CFA-induced mechanical allodynia measured 72 hrs after CFA injection in C57BL/6 mice (n=6-7). *P <.05 compared with vehicle control

Fig. 2

YM-58483 prevents the development of pain hypersensitivity. (A) Effects of YM-58483 and indomethacin (ind) on CFA-induced thermal hyperalgesia measured 2 and 24 hrs after CFA injection in CD-1 mice (n = 4-7). (B) Effects of YM-58483 and indomethacin on CFA-induced mechanical allodynia measured 2 and 24 hrs after CFA injection in C57BL/6 mice (n = 4-7). *P < .05 compared with vehicle control.

Fig. 3

YM-58483 decreases complete Freund's adjuvant (CFA)-induced inflammation and TNF-α, IL-1β and PGE₂ production in CD-1 mice. (A) Effects of YM-58483 (YM) and indomethacin (Ind) on CFA-induced paw edema measured at 3 and 24 hrs after CFA injection (n=4-7, *P < .05 compared with vehicle control). (B-D) The effect of YM-58483 on CFA-induced increase in TNF-α (B), IL-1β (C) and PGE₂ (D). Control animals were intraplantarly injected with saline. The measurements were performed 24 hrs after CFA injection (n=4-6). * P <.05 compared with saline; ^# P <.05 compared with CFA.

Fig. 4

YM-58483 has both peripheral and central analgesic effects on CFA-induced thermal hyperalgesia in CD-1 mice. (A) Time-dependent effects of intraplantar injection of YM-58483 on CFA-induced thermal hyperalgesia measured 72 hrs after CFA injection (n = 6-7). (B) Effects of intraplantar administration of YM-58483 (YM) on CFA-induced paw edema measured at 3 hrs after CFA injection (n = 6-7). (C) Time-dependent effects of YM-58483 by intrathecal injection on CFA-induced thermal hyperalgesia measured 72 hrs after CFA injection (n = 6-7). *P <.05 compared with vehicle control).

Fig. 5

YM-58483 attenuates formalin-induced nociceptive behavior in C57BL/6 mice. (A) The time course of nociceptive behavior after subcutaneous injection of formalin (2%, 20 μL) into the hind paw following pretreatment with vehicle or YM-58483 (n = 4-6). (B) Total time spent in nociceptive behavior during the first (0-10 min) and second (15-60 min) phases of the formalin-induced spontaneous behavior with vehicle or YM-58483 (n=4-6). *P <.05 compared with vehicle control.

Fig. 6

YM-58483 reduces spared nerve injury (SNI)-induced pain hypersensitivity. (A) Time-dependent effects of YM-58483 on SNI-induced thermal hyperalgesia measured 7 days after surgery in CD-1 mice (n = 6-7). (B) Time-dependent effects of YM-58483 on SNI-induced mechanical allodynia measured 7 days after surgery in C57BL/6 mice (n=6-7). (C, D) Effects of YM-58483 on the development of SNI-induced thermal and mechanical hypersensitivity (n = 6-7). *P <.05 compared with vehicle control.

Fig. 7

YM-58483 diminishes acute pain induced by mechanical, heat and chemical stimuli. (A) Effects of YM-58483 on basal mechanical sensitivity in C57BL/6 mice (n=6-7). (B) Effects of YM-58483 on paw pressure-induced pain in C57BL/6 mice (n = 10). (C) Effects of YM-58483 on radiant heat-induced pain in CD-1 mice (n = 5). (D) Effects of YM-58483 on capsaicin-induced spontaneous nociceptive behavior in CD-1 mice (n=10-11). *P<.05 compared with vehicle control.

Fig. 8

YM-58483 inhibits store-operated calcium (SOC) entry in cultured adult CD-1 mouse dorsal root ganglion (DRG) neurons. (A) Representative traces of 10 μM cyclopiazonic acid-induced SOC entry in large, small and capsaicin positive (capsaicin+) DRG neurons. (B) Summary of SOC entry in large, small and capsaicin positive DRG neurons (n = 34-66 neurons each), * P<.05 compared with large neurons. (C) Representative traces of SOC entry blocked by YM-58483. (D) Summary of YM-58483-induced inhibition of SOC entry in large, small and capsaicin-positive DRG neurons (n = 27-35 neurons each). * P<.05 compared to control; ^#P<.05 compared with large neurons.