anandamide and Peripheral-Nervous-System-Diseases

Cisplatin (CIS) is an effective antineoplastic agent used in the treatment of several cancer types. Peripheral neuropathy is a major dose-limiting side-effect in CIS therapy. Cannabinoids may alleviate this painful side effect. This study investigated the analgesic effects of anandamide (AN) on CIS-induced peripheral neuropathy, in vitro effects of AN in CIS neurotoxicity, and the contribution of nitric oxide (NO) in this effect.. This is an experimental animal study. Primary dorsal root ganglion (DRG) cultures were prepared from one-day-old rats for in vitro investigations. DRG cells were incubated with CIS (100–300 M), and AN (10, 50, 100, and 500 μM) was administered with the submaximal concentration of CIS. Female Sprague Dawley rats were divided into control, CIS, CIS+AN, CIS+AN+L-NG-nitro arginine methyl ester (LNAME). CIS was administered 3 mg/kg i.p once weekly for 5 weeks. AN (1 mg/kg i.p) or in combination with 10 mg/kg i.p LNAME was administrated 30 min before CIS injection. Mechanical allodynia, thermal hyperalgesia, and tail clip tests were performed. After intracardiac perfusion, sciatic nerves (SN), and DRGs were isolated and semi-thin sections were stained with toluidine blue and investigated histologically. SPSS v. 21.0 and Sigma STAT 3.5 were used for statistical analysis. One/two way ANOVA, Kruskal–Wallis, and Wilcoxon signed ranks tests were used. A p-value of 0.05 was accepted as significant.. CIS caused significant mechanical allodynia. AN and AN+LNAME significantly increased hind paw withdrawal latency in mechanical allodynia test. The degenerated axons significantly increased in CIS group, while decreased in AN group. The frequency of larger neurons seemed to be higher in CIS+AN group.. AN may be a therapeutic alternative for the treatment of CIS-induced peripheral neuropathy. However, its central adverse effects must be considered.

Topics: Animals; Arachidonic Acids; Cisplatin; Endocannabinoids; Female; Hyperalgesia; NG-Nitroarginine Methyl Ester; Peripheral Nervous System Diseases; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley

Painful neuropathy frequently develops as a consequence of commonly used chemotherapy agents for cancer treatment and is often a dose-limiting side effect. Currently available analgesic treatments are often ineffective on pain induced by neurotoxicity. Although peripheral administration of cannabinoids, endocannabinoids, and inhibitors of endocannabinoid hydrolysis has been effective in reducing hyperalgesia in models of peripheral neuropathy, including chemotherapy-induced peripheral neuropathy (CIPN), few studies have examined cannabinoid effects on responses of nociceptors in vivo. In this study we determined whether inhibition of fatty acid amide hydrolase (FAAH), which slows the breakdown of the endocannabinoid anandamide (AEA), reduced sensitization of nociceptors produced by chemotherapy. Over the course of a week of daily treatments, mice treated with the platinum-based chemotherapy agent cisplatin developed robust mechanical allodynia that coincided with sensitization of cutaneous C-fiber nociceptors as indicated by the development of spontaneous activity and increased responses to mechanical stimulation. Administration of the FAAH inhibitor URB597 into the receptive field of sensitized C-fiber nociceptors decreased spontaneous activity, increased mechanical response thresholds, and decreased evoked responses to mechanical stimuli. Cotreatment with CB1 (AM281) or CB2 (AM630) receptor antagonists showed that the effect of URB597 was mediated primarily by CB1 receptors. These changes following URB597 were associated with an increase in the endocannabinoid anandamide in the skin. Our results suggest that enhanced signaling in the peripheral endocannabinoid system could be utilized to reduce nociceptor sensitization and pain associated with CIPN.

Topics: Amidohydrolases; Animals; Arachidonic Acids; Benzamides; Cannabinoid Receptor Antagonists; Carbamates; Cisplatin; Endocannabinoids; Hydrolysis; Indoles; Male; Mice; Morpholines; Nerve Fibers, Unmyelinated; Nociception; Nociceptors; Peripheral Nervous System Diseases; Polyunsaturated Alkamides; Pyrazoles; Skin

Cisplatin, a platinum-derived chemotherapeutic agent, produces mechanical and coldallodynia reminiscent of chemotherapy-induced neuropathy in humans. The endocannabinoid system represents a novel target for analgesic drug development. The endocannabinoid signaling system consists of endocannabinoids (e.g. anandamide (AEA) and 2-arachidonoylglycerol (2-AG)), cannabinoid receptors (e.g. CB(1) and CB(2)) and the enzymes controlling endocannabinoid synthesis and degradation. AEA is hydrolyzed by fatty-acid amide hydrolase (FAAH) whereas 2-AG is hydrolyzed primarily by monoacylglycerol lipase (MGL). We compared effects of brain permeant (URB597) and impermeant (URB937) inhibitors of FAAH with an irreversible inhibitor of MGL (JZL184) on cisplatin-evoked behavioral hypersensitivities. Endocannabinoid modulators were compared with agents used clinically to treat neuropathy (i.e. the opioid analgesic morphine, the anticonvulsant gabapentin and the tricyclic antidepressant amitriptyline). Cisplatin produced robust mechanical and cold allodynia but did not alter responsiveness to heat. After neuropathy was fully established, groups received acute intraperitoneal (i.p.) injections of vehicle, amitriptyline (30 mg/kg), gabapentin (100 mg/kg), morphine (6 mg/kg), URB597 (0.1 or 1 mg/kg), URB937 (0.1 or 1 mg/kg) or JZL184 (1, 3 or 8 mg/kg). Pharmacological specificity was assessed by coadministering each endocannabinoid modulator with either a CB(1) (AM251 3 mg/kg), CB(2) (AM630 3 mg/kg), TRPV1 (AMG9810 3 mg/kg) or TRPA1 (HC030031 8 mg/kg) antagonist. Effects of cisplatin on endocannabinoid levels and transcription of receptors (CB(1), CB(2), TRPV1, TRPA1) and enzymes (FAAH, MGL) linked to the endocannabinoid system were also assessed. URB597, URB937, JZL184 and morphine reversed cisplatin-evoked mechanical and cold allodynia to pre-cisplatin levels. By contrast, gabapentin only partially reversed the observed allodynia while amitriptyline, administered acutely, was ineffective. CB(1) or CB(2) antagonists completely blocked the anti-allodynic effects of both FAAH (URB597, URB937) and MGL (JZL184) inhibitors to mechanical and cold stimulation. By contrast, the TRPV1 antagonist AMG9810 blocked the anti-allodynic efficacy of both FAAH inhibitors, but not the MGL inhibitor. By contrast, the TRPA1 antagonist HC30031 did not attenuate anti-allodynic efficacy of any endocannabinoid modulator. When the levels of endocannabinoids were examined, cisplatin increased both anandami

Topics: Amidohydrolases; Analgesics; Animals; Antineoplastic Agents; Arachidonic Acids; Benzamides; Benzodioxoles; Cannabinoids; Carbamates; Cisplatin; Endocannabinoids; Enzyme Inhibitors; Ganglia, Spinal; Glycerides; Hyperalgesia; Lipid Metabolism; Male; Monoacylglycerol Lipases; Peripheral Nervous System Diseases; Piperidines; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; RNA, Messenger; Spinal Cord; TRPV Cation Channels

Painful peripheral neuropathy is a dose-limiting complication of chemotherapy. Cisplatin produces a cumulative toxic effect on peripheral nerves, and 30-40% of cancer patients receiving this agent experience pain. By modeling cisplatin-induced hyperalgesia in mice with daily injections of cisplatin (1 mg/kg, i.p.) for 7 d, we investigated the anti-hyperalgesic effects of anandamide (AEA) and cyclohexylcarbamic acid 3'-carbamoyl-biphenyl-3-yl ester (URB597), an inhibitor of AEA hydrolysis. Cisplatin-induced mechanical and heat hyperalgesia were accompanied by a decrease in the level of AEA in plantar paw skin. No changes in motor activity were observed after seven injections of cisplatin. Intraplantar injection of AEA (10 μg/10 μl) or URB597 (9 μg/10 μl) transiently attenuated hyperalgesia through activation of peripheral CB₁ receptors. Co-injections of URB597 (0.3 mg/kg daily, i.p.) with cisplatin decreased and delayed the development of mechanical and heat hyperalgesia. The effect of URB597 was mediated by CB₁ receptors since AM281 (0.33 mg/kg daily, i.p.) blocked the effect of URB597. Co-injection of URB597 also normalized the cisplatin-induced decrease in conduction velocity of Aα/Aβ-fibers and reduced the increase of ATF-3 and TRPV1 immunoreactivity in dorsal root ganglion (DRG) neurons. Since DRGs are a primary site of toxicity by cisplatin, effects of cisplatin were studied on cultured DRG neurons. Incubation of DRG neurons with cisplatin (4 μg/ml) for 24 h decreased the total length of neurites. URB597 (100 nM) attenuated these changes through activation of CB₁ receptors. Collectively, these results suggest that pharmacological facilitation of AEA signaling is a promising strategy for attenuating cisplatin-associated sensory neuropathy.

Topics: Activating Transcription Factor 3; Animals; Antineoplastic Agents; Arachidonic Acids; Benzamides; Cannabinoid Receptor Modulators; Carbamates; Cells, Cultured; Cisplatin; Disease Models, Animal; Drug Interactions; Endocannabinoids; Enzyme Inhibitors; Ganglia, Spinal; Hyperalgesia; Male; Mice; Mice, Inbred C3H; Morpholines; Motor Activity; Neurites; Neurotoxicity Syndromes; Peripheral Nervous System Diseases; Polyunsaturated Alkamides; Pyrazoles; Receptor, Cannabinoid, CB1; TRPV Cation Channels

The production of nitric oxide (NO) from l-arginine is catalyzed by NO synthase (NOS), which exists as the following three isoforms: endothelial (eNOS), neuronal (nNOS), and inducible (iNOS). The participation of this pathway in peripheral antinociception has been extensively established by our group with the use of several types of drugs, including opioids, cannabinoids, cholinergic, and α(2C) adrenoceptor agonists and nonsteroidal anti-inflammatory drugs (NSAIDS), and even non-pharmacological procedures such as electroacupuncture. In this study, we aimed to refine the previous data to investigate which type of NOS isoform is involved in the peripheral antinociception mechanism induced by anandamide, morphine, SNC80, bremazocine, acetylcholine, xylazine, baclofen, dipyrone, and diclofenac. After hyperalgesia was induced by intraplantar injection of prostaglandin E(2) in male Wistar rats, we measured peripheral nociception with the paw pressure test. All drugs that were used induced a peripheral antinociception effect that was completely blocked by injection of the selective neuronal NO synthase inhibitor, L-NPA (24μg/paw). The exception was the GABA(B) agonist baclofen, which induced an effect that was not antagonized. We used the inhibitors L-NIO and -NIL (24μg/paw) to exclude the involvement of endothelial and inducible NO synthase, respectively. These drugs were ineffective against the antinociception effect induced by all analgesic drugs that we utilized. Based on the experimental evidence, we conclude that the local injection of analgesic drugs activates nNOS to release NO and induce peripheral antinociception.

Topics: Acetylcholine; Analgesics; Animals; Arachidonic Acids; Arginine; Dinoprostone; Endocannabinoids; Enzyme Inhibitors; Hyperalgesia; Isoenzymes; Male; Nitric Oxide; Nitric Oxide Synthase Type I; Pain Measurement; Peripheral Nervous System Diseases; Polyunsaturated Alkamides; Rats; Rats, Wistar

Peripheral cannabinoid receptors exert a powerful inhibitory control over pain initiation, but the endocannabinoid signal that normally engages this intrinsic analgesic mechanism is unknown. To address this question, we developed a peripherally restricted inhibitor (URB937) of fatty acid amide hydrolase (FAAH), the enzyme responsible for the degradation of the endocannabinoid anandamide. URB937 suppressed FAAH activity and increased anandamide levels outside the rodent CNS. Despite its inability to access brain and spinal cord, URB937 attenuated behavioral responses indicative of persistent pain in rodent models of peripheral nerve injury and inflammation and prevented noxious stimulus-evoked neuronal activation in spinal cord regions implicated in nociceptive processing. CB₁ cannabinoid receptor blockade prevented these effects. These results suggest that anandamide-mediated signaling at peripheral CB₁ receptors controls the access of pain-related inputs to the CNS. Brain-impenetrant FAAH inhibitors, which strengthen this gating mechanism, might offer a new approach to pain therapy.

Topics: Amidohydrolases; Animals; Arachidonic Acids; Cannabinoid Receptor Modulators; Cannabinoids; Carrageenan; Chromatography, Liquid; Disease Models, Animal; Drug Administration Routes; Drug Administration Schedule; Endocannabinoids; Enzyme Inhibitors; Escape Reaction; Ethylene Glycols; Feeding Behavior; Formaldehyde; Gene Expression Regulation; Hyperalgesia; Indoles; Male; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Knockout; Monoacylglycerol Lipases; Motor Activity; Oncogene Proteins v-fos; Pain; Pain Measurement; Pain Threshold; Peripheral Nervous System Diseases; Piperidines; Polyunsaturated Alkamides; PPAR alpha; Pyrazoles; Rats; Rats, Sprague-Dawley; Rimonabant; Sciatica; Spinal Cord; Statistics, Nonparametric; Time Factors; Tissue Distribution; Tritium

Direct-acting cannabinoid receptor agonists are well known to reduce hyperalgesic responses and allodynia after nerve injury, although their psychoactive side effects have damped enthusiasm for their therapeutic development. Alternatively, inhibiting fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), the principal enzymes responsible for the degradation of the respective endogenous cannabinoids, anandamide (AEA) and 2-arachydonylglycerol (2-AG), reduce nociception in a variety of nociceptive assays, with no or minimal behavioral effects. In the present study we tested whether inhibition of these enzymes attenuates mechanical allodynia, and acetone-induced cold allodynia in mice subjected to chronic constriction injury of the sciatic nerve. Acute administration of the irreversible FAAH inhibitor, cyclohexylcarbamic acid 3'-carbamoylbiphenyl-3-yl ester (URB597), or the reversible FAAH inhibitor, 1-oxo-1-[5-(2-pyridyl)-2-yl]-7-phenylheptane (OL-135), decreased allodynia in both tests. This attenuation was completely blocked by pretreatment with either CB(1) or CB(2) receptor antagonists, but not by the TRPV1 receptor antagonist, capsazepine, or the opioid receptor antagonist, naltrexone. The novel MAGL inhibitor, 4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184) also attenuated mechanical and cold allodynia via a CB(1), but not a CB(2), receptor mechanism of action. Whereas URB597 did not elicit antiallodynic effects in FAAH(-/-) mice, the effects of JZL184 were FAAH-independent. Finally, URB597 increased brain and spinal cord AEA levels, whereas JZL184 increased 2-AG levels in these tissues, but no differences in either endo-cannabinoid were found between nerve-injured and control mice. These data indicate that inhibition of FAAH and MAGL reduces neuropathic pain through distinct receptor mechanisms of action and present viable targets for the development of analgesic therapeutics.

Topics: Amidohydrolases; Analgesics, Non-Narcotic; Animals; Arachidonic Acids; Benzamides; Benzodioxoles; Cannabinoid Receptor Modulators; Carbamates; Cold Temperature; Endocannabinoids; Enzyme Inhibitors; Glycerides; Hyperalgesia; Male; Mice; Mice, Inbred C57BL; Monoacylglycerol Lipases; Narcotic Antagonists; Pain; Pain Measurement; Peripheral Nervous System Diseases; Piperidines; Polyunsaturated Alkamides; Pyridines; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; TRPV Cation Channels

An attractive alternative to the use of direct agonists at the cannabinoid receptor type 1 (CB1) in the control of neuropathic pain may be to potentiate the actions of endogenous cannabinoids. Thus, the effects of AM404, an inhibitor of anandamide uptake, were assessed in an experimental model of neuropathic pain in rats. Daily treatment with AM404 prevented, time- and dose-dependently, the development of thermal hyperalgesia and mechanical allodynia in neuropathic rats. Antagonists at cannabinoid CB1 or CB2 receptors, or at the transient receptor potential vanilloid type 1 receptor, each partially reversed effects induced by AM404. A complete reversal was obtained when the three antagonists were given together, suggesting that all three receptors are involved. AM404 treatment affected two pathways involved in the generation and maintenance of neuropathic pain, one mediated by nitric oxide (NO) and the other by cytokines. AM404 completely prevented the overproduction of NO and the overexpression of nNOS, inhibited the increase in tumour necrosis factor alpha (TNFalpha) and enhanced the production of interleukin-10. Both NO and TNFalpha are known to contribute to the apoptotic process, which plays an important role in the establishment of chronic pain states. AM404 treatment prevented the increase in the ratio between pro- and anti-apoptotic gene bax/bcl-2 expression observed in the spinal cord of neuropathic rats. Taken together, these findings suggest that inhibition of endocannabinoid uptake, by blocking the putative anandamide carrier, results in the relief of neuropathic pain and may represent a novel strategy for treating chronic pain.

Topics: Analgesics; Animals; Apoptosis; Arachidonic Acids; bcl-2-Associated X Protein; Behavior, Animal; Blotting, Western; Calcium Channel Blockers; Cannabinoid Receptor Antagonists; Cytokines; Endocannabinoids; Genes, bcl-2; Hot Temperature; Hyperalgesia; Male; Motor Activity; NF-kappa B; Nitrates; Nitrites; Pain; Peripheral Nervous System Diseases; Physical Stimulation; Polyunsaturated Alkamides; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction