JZL184 is anti-hyperalgesic in a murine model of cisplatin-induced peripheral neuropathy

Abstract

Cisplatin has been used effectively to treat a variety of cancers but its use is limited by the development of painful peripheral neuropathy. Because the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG) is anti-hyperalgesic in several preclinical models of chronic pain, the anti-hyperalgesic effect of JZL184, an inhibitor of 2-AG hydrolysis, was tested in a murine model of cisplatin-induced hyperalgesia. Systemic injection of cisplatin (1mg/kg) produced mechanical hyperalgesia when administered daily for 7 days. Daily peripheral administration of a low dose of JZL184 in conjunction with cisplatin blocked the expression of mechanical hyperalgesia. Acute injection of a cannabinoid (CB)-1 but not a CB2 receptor antagonist reversed the anti-hyperalgesic effect of JZL184 indicating that downstream activation of CB1 receptors suppressed the expression of mechanical hyperalgesia. Components of endocannabinoid signaling in plantar hind paw skin and lumbar dorsal root ganglia (DRGs) were altered by treatments with cisplatin and JZL184. Treatment with cisplatin alone reduced levels of 2-AG and AEA in skin and DRGs as well as CB2 receptor protein in skin. Combining treatment of JZL184 with cisplatin increased 2-AG in DRGs compared to cisplatin alone but had no effect on the amount of 2-AG in skin. Evidence that JZL184 decreased the uptake of [(3)H]AEA into primary cultures of DRGs at a concentration that also inhibited the enzyme fatty acid amide hydrolase, in conjunction with data that 2-AG mimicked the effect of JZL184 on [(3)H]AEA uptake support the conclusion that AEA most likely mediates the anti-hyperalgesic effect of JZL184 in this model.

Keywords: 2-Arachidonoyl-glycerol; Anandamide; Cannabinoid receptor; Cisplatin; Dorsal root ganglion; Hyperlagesia; JZL184; Spinal cord.

Figure 1

JZL184 attenuated development of cisplatin-induced hyperalgesia in a CB1 receptor-dependent manner. Data are the mean±SEM of the average withdrawal frequency of the hind paws to a mechanical stimulus (3.9 mN, see text for details). A. The baseline (BL) measures of withdrawal frequency were made prior to drug treatment. Mechanical hyperalgesia developed in mice during treatment with cisplatin (1mg/kg of body weight, daily for 7 d, i.p., n=10). There was no change in the mechanical sensitivity of vehicle-treated mice during this period [n=6; vehicle was DMSO:Tween-80:saline,12:1:87 (v:v:v)]. Co-administration of JZL184 (10 μg, s.c., dorsal hind paw; n=14) with cisplatin attenuated the development of mechanical hyperalgesia *Different from vehicle at p<0.05, ^#different from cisplatin-treated mice at p<0.05 (Two-way ANOVA with Bonferroni test). B. The anti-hyperalgesic effect of JZL184 was mediated by CB1 receptors. AM281 (0.4mg/kg, i.p.) blocked the effect of JZL184, but AM630 (1mg/kg, i.p.) did not. *Significantly different from vehicle-treated group at p<0.02, Two-way ANOVA with Bonferroni t test, N=7-9 mice/group.

Figure 2

Local increases in 2-AG signaling attenuated the mechanical hyperalgesia produced by cisplatin. Data are the mean±SEM of the average withdrawal frequency of the hind paws to a mechanical stimulus (3.9 mN, see text for details). A single injection of JZL184 (10 μg, i.pl., A) or 2-AG (18 μg, i.pl., B) into the hind paw transiently attenuated the cisplatin-evoked hyperalgesia ipsilateral, but not contralateral (CL) to drug injection. The anti-hyperalgesic effect of each drug was blocked by the CB1 receptor antagonist, AM281 (10 μg, i.pl.) but not the CB2 receptor antagonist AM630 (4 μg, i.pl.). *Significantly different from BL at p<0.05, Two-way ANOVA with Bonferroni t test, N=6-7 mice/group, ^#Significantly different from JZL184 or 2-AG-treated groups at p<0.05, Two-way ANOVA with Bonferroni test, N=6-7 mice/group.

Figure 3

Effect of enzyme inhibitors in naive mice. Data are the mean±SEM of the withdrawal frequency of the hind paw ipsilateral to the injection to a mechanical stimulus (3.9 mN). A. The dose of JZL184 (10 μg, i.pl,) that suppressed hyperalgesia in cisplatin-treated mice at 1 h following administration had no effect on mechanical sensitivity in naive mice (p=0.54, two-way ANOVA, n=5 mice/group). The vehicle was DMSO:Tween-80:saline, 12:1:87 (v:v:v). B. In contrast, the FAAH inhibitor URB597 (9 μg, ipl.) decreased mechanical sensitivity in naive mice at 1 h following injection. *Different from vehicle (18% ethanol in saline) at p<0.001 (Two-way ANOVA, n=5 mice/group).

Figure 4

Activation of 2-AG signaling reduced [³H]AEA uptake by DRG cells. A. Co-incubation of [³H]AEA with 2-AG dose-dependently decreased uptake of [³H]AEA. V=vehicle (0.4% ethanol in HEPES buffer). B. Pretreatment with JZL184 (1 μM) decreased uptake of [³H]AEA in a time-dependent manner. The open circle represents the vehicle control for the 60 min pretreatment. V=vehicle (0.0025% DMSO in HEPES buffer). Data represent the mean±SEM of values generated in 3 independent experiments. *Different from control within each experiment at p<0.05; **different at p<0.001 (One-way ANOVA with Bonferroni t test).