Palmitoylethanolamide (PEA) is an endogenous lipid that is thought to be involved in endogenous protective mechanisms activated as a result of stimulation of inflammatory response. In spite of the well demonstrated anti-inflammatory properties of PEA, its involvement in controlling pain pathways still remains poorly characterized. On this basis, we tested the efficacy of PEA in vivo against a peculiar persistent pain, such as neuropathic one. PEA was administered i.p. to mice with chronic constriction injury of sciatic nerve (CCI) once a day for one week starting the day after the lesion. This therapeutic regimen evoked a relief of both thermal hyperalgesia and mechanical allodynia in neuropathic mice. Various selective receptor antagonists were used in order to clarify the relative contribution of cannabinoid, vanilloid and peroxisome proliferator-activated receptor to PEA-induced effects. The results indicated that CB(1), PPARgamma and TRPV1 receptors mediated the antinociception induced by PEA, suggesting that the most likely mechanism might be the so-called "entourage effect" due to the PEA-induced inhibition of the enzyme catalyzing the endocannabinoid anandamide (AEA) degradation that leads to an enhancement of its tissue levels thus increasing its analgesic action. In addition, the hypothesis that PEA might act through the modulation of local mast cells degranulation is sustained by our findings showing that PEA significantly reduced the production of many mediators such as TNFalpha and neurotrophic factors, like NGF. The findings presented here, in addition to prove the beneficial effects of PEA in chronic pain, identify new potential targets for analgesic medicine.

Neuropathic pain remains a prevalent clinical problem because it is often poorly responsive to the currently used analgesics, thus it is crucial the identification of new potential targets and drugs. Recent evidence indicated that microglial cells in the spinal cord are critically involved in the development and maintenance of neuropathic pain, with a pivotal role of toll-like receptor 4 (TLR4). Binding of an endogenous ligand to TLR4 might be considered an important step in the regulation of microglia activity in pain facilitation, suggesting that a mechanism aimed to inhibit such a binding could be effective against neuropathic pain. We have synthesized new ligands to TLR4 with antagonistic activity. In the present work we evaluated the efficacy of the most potent TLR4 antagonist synthesized by us (FP-1), administered in mice with painful neuropathy. The repeated treatment of neuropathic mice with FP-1 (5-10 mg/kg, i.p.) evoked a relief of both thermal hyperalgesia and mechanical allodynia, whereas the administration of the highest dose to TLR4 knockout neuropathic mice revealed that in the absence of TLR4 receptor, the compound lost its efficacy. As consequence of TLR4 binding, the repeated treatment with FP-1 prevented the activation of the transcription factor NF-kB and the TNFalpha overproduction in the spinal cord. Together, our findings support the previous evidence indicative for a contribution of glial TLR4 to the initiation of neuropathic pain, suggest it as potential innovative target to treat this debilitating disease, and propose FP-1 as lead compound for the development of new effective drugs.

Background and purpose: 2-arachidonoylglycerol (2-AG) is an endocannabinoid whose hydrolysis is predominantly catalysed by the enzyme monoacylglycerol lipase (MAGL). The development of MAGL inhibitors could offer an opportunity to investigate the anti-inflammatory and anti-nociceptive role of 2-AG, which have not yet been elucidated. On these bases, URB602, a MAGL inhibitor, was tested in a murine model of inflammation/inflammatory pain. Experimental approach: Acute inflammation was induced by intraplantar injection of l-carrageenan into mice. The highest dose to be employed has been selected performing the tetrad assays for cannabimimetic activity in mice. URB602 antiinflammatory and anti-nociceptive efficacy (assessed by plethysmometer and plantar test, respectively) was evaluated both in a preventive regimen (drug administered 30 min before carrageenan) and in a therapeutic regimen (URB602 administered 30 min after carrageenan). To elucidate the cannabinoid receptor involvement, rimonabant and SR144528, CB 1 and CB 2 selective antagonists, respectively, were given 15 min before URB602. Key results: Systemic administration of URB602 elicited a dose-dependent anti-oedemigen and anti-nociceptive effect that was reversed exclusively by the CB 2 receptor antagonist. The efficacy of URB602 persisted also when the compound was administered in a therapeutic regimen, suggesting the ability of URB602 to improve established disease. Conclusions and implications:The present report highlighted the ability of the selective MAGL inhibitor, URB602, to prevent and treat an acute inflammatory disease without producing adverse psychoactive effects. The data presented herein also contributed to clarify the physiological role of 2-AG in respect to inflammatory reactions, suggesting its protective role in the body.

This study aimed to give a rationale for the employment of phytocannabinoid formulations to treat neuropathic pain. It was found that a controlled cannabis extract, containing multiple cannabinoids, in a defined ratio, and other non-cannabinoid fractions (terpenes and flavonoids) provided better antinociceptive efficacy than the single cannabinoid given alone, when tested in a rat model of neuropathic pain. The results also demonstrated that such an antihyperalgesic effect did not involve the cannabinoid CB1 and CB2 receptors, whereas it was mediated by vanilloid receptors TRPV1. The non-psychoactive compound, cannabidiol, is the only component present at a high level in the extract able to bind to this receptor: thus cannabidiol was the drug responsible for the antinociceptive behaviour observed. In addition, the results showed that after chronic oral treatment with cannabis extract the hepatic total content of cytochrome P450 was strongly inhibited as well as the intestinal P-glycoprotein activity. It is suggested that the inhibition of hepatic metabolism determined an increased bioavailability of cannabidiol resulting in a greater effect. However, in the light of the well known antioxidant and antiinflammatory properties of terpenes and flavonoids which could significantly contribute to the therapeutic effects, it cannot be excluded that the synergism observed might be achieved also in the absence of the cytochrome P450 inhibition.

New glycolipids and a benzylammonium lipid were rationally designed by varying the chemical structure of a D-glucose-derived hit compound active as lipid A antagonist. We report the synthesis of these compounds, their in vitro activity as lipid A antagonists on HEK cells, and the capacity to inhibit LPS-induced septic shock in vivo. The lack of toxicity and the good in vivo activity suggest the use of some compounds of the panel as hits for antisepsis drug development.