WWL70 protects against chronic constriction injury-induced neuropathic pain in mice by cannabinoid receptor-independent mechanisms

Abstract

BackgroundTargeting the endocannabinoid system has emerged as an effective strategy for the treatment of inflammatory and neurological diseases. Unlike the inhibition of the principal 2-arachidonyl glycerol (2-AG) hydrolytic enzyme monoacylglycerol lipase (MAGL), which leads to 2-AG overload and cannabinoid receptor desensitization, selective inhibition of the minor 2-AG hydrolytic enzyme alpha, beta-hydrolase domain 6 (ABHD6) can provide therapeutic benefits without producing cannabimimetic side effects. We have shown that inhibition of ABHD6 significantly reduces neuroinflammation and exerts neuroprotection in animal models of traumatic brain injury and multiple sclerosis. However, the role of ABHD6 inhibition on neuropathic pain has not been explored.MethodsNeuropathic pain was induced by chronic constriction injury (CCI) of the mouse sciatic nerve and examined by Hargreaves and Von Frey tests. Activation of inflammatory cells and the production of cytokines and chemokines in the spinal cord dorsal horn, dorsal root ganglion (DRG), and sciatic nerve were assessed by qRT-PCR, enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry. The levels of 2-AG and arachidonic acid (AA) in sciatic nerve were quantified by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS).ResultsTreatment with the selective ABHD6 inhibitor WWL70 significantly alleviated CCI-induced thermal hyperalgesia and mechanical allodynia. Microglia activation, macrophage infiltration, and the production of nociceptive mediators were reduced in the ipsilateral lumbar spinal cord dorsal horn, DRG, and sciatic nerve of WWL70-treated animals. The diminished cytokine and chemokine production is likely due to the inhibitory effect of WWL70 on NF-κB phosphorylation. Surprisingly, the anti-nociceptive and anti-inflammatory effects of WWL70 were not reversed by addition of the cannabinoid receptor antagonists. Treatment with WWL70 did not alter the levels of 2-AG, AA, and the phosphorylation of cytosolic phospholipase A2 (cPLA2), but significantly reduced the production of prostaglandin E2 (PGE2) and the expression of cyclooxygenase-2 (COX-2) and prostaglandin E synthase-2 (PGES2) in the injured sciatic nerve.ConclusionsThis study reveals a novel mechanism for the antinociceptive effect of the 2-AG catabolic enzyme ABHD6 inhibitor WWL70. Understanding the interaction between endocannabinoid and eicosanoid pathways might provide a new avenue for the treatment of inflammatory and neuropathic pain.

Curcumin Diglutaric Acid, a Prodrug of Curcumin Reduces Pain Hypersensitivity in Chronic Constriction Injury of Sciatic Nerve Induced-Neuropathy in Mice

“…Peripheral nerve injury, i.e., CCI, can also activate resident spinal glia indicated by the excessive release of inflammatory mediators, leading to the sensitization of second-order neurons, known as central sensitization [ 4 , 5 ]. This activation is characterized by the increase of microglia marker (ionized calcium-binding adaptor molecule 1; iba1), astrocyte marker (glial fibrillary acidic protein; GFAP), as well as the release of pro-inflammatory mediators, including TNF-α and IL-6, produced by glial cells [ 45 ]. As reported, these cytokines involve spinal sensitization via enhancing excitatory neurotransmission and suppressing inhibitory neurotransmission [ 46 ].…”

Therapeutic Effect of the Substrate-Selective COX-2 Inhibitor IMMA in the Animal Model of Chronic Constriction Injury

“…The surgical procedure for partial sciatic nerve ligation was carried out as described previously (Bennett and Xie, 1988) with slight modifications (Wen et al, 2018). Mice were anesthetized with isoflurane (3.5% for induction and 2.0% for maintenance) and the middle to lower back above the dorsal left thigh were shaved and cleaned with iodine and 75% ethanol in preparation for surgery.…”

“…The thermal escape latency was determined using the Hargreaves type thermal escape testing system (Plantar Analgesia Meter, IITC Life Science Inc.) as we previously described (Wen et al, 2018). Briefly, mice were placed individually in Plexiglas cubicles on a glass surface and allowed to acclimate for 30 min.…”

Targeting Endocannabinoid Metabolism: an Arrow with Multiple Tips Against Multiple Sclerosis

“…Moreover, PGE2 biosynthetic enzymes were designated as targets of WWL70, thus providing more solid elucidation of its anti‐inflammatory and therapeutic effects in EAE. Similarly, WWL70 (10 mg/kg, i. p.) exerted CBRs‐independent anti‐nociceptive activity in animal models of neuropathic pain [175] . Microglia activation, macrophage infiltration, and the production of nociceptive mediators were reduced in treated animals, along with COX‐2 and PGES2 expression, but the use of CBRs antagonists did not affect these processes and the levels of 2‐AG were not increased.…”