BackgroundFatty acid binding proteins (FABPs) serve as intracellular carriers that deliver endocannabinoids and N-acylethanolamines to their catabolic enzymes. Inhibition of FABPs reduces endocannabinoid transport and catabolism in cells and FABP inhibitors produce antinociceptive and anti-inflammatory effects in mice. Potential analgesic effects in mice lacking FABPs, however, have not been tested.FindingsMice lacking FABP5 and FABP7, which exhibit highest affinities for endocannabinoids, possessed elevated levels of the endocannabinoid anandamide and the related N-acylethanolamines palmitoylethanolamide and oleoylethanolamide. There were no compensatory changes in the expression of other FABPs or in endocannabinoid-related proteins in the brains of FABP5/7 knockout mice. These mice exhibited reduced nociception in the carrageenan, formalin, and acetic acid tests of inflammatory and visceral pain. The antinociceptive effects in FABP5/7 knockout mice were reversed by pretreatment with cannabinoid receptor 1, peroxisome proliferator-activated receptor alpha, and transient receptor potential vanilloid 1 receptor antagonists in a modality specific manner. Lastly, the knockout mice did not possess motor impairments.ConclusionsThis study demonstrates that mice lacking FABPs possess elevated levels of N-acylethanolamines, consistent with the idea that FABPs regulate the endocannabinoid and N-acylethanolamine tone in vivo. The antinociceptive effects observed in the knockout mice support a role for FABPs in regulating nociception and suggest that these proteins should serve as targets for the development of future analgesics.

The therapeutic properties of cannabinoids have been well demonstrated but are overshadowed by such adverse effects as cognitive and motor dysfunction, as well as their potential for addiction. Recent research on the natural lipid ligands of cannabinoid receptors, also known as endocannabinoids, has shed light on the mechanisms of intracellular transport of the endocannabinoid anandamide by fatty acid-binding proteins (FABPs) and subsequent catabolism by fatty acid amide hydrolase. These findings facilitated the recent development of SBFI26, a pharmacological inhibitor of epidermal- and brain-specific FABP5 and FABP7, which effectively increases anandamide signaling. The goal of this study was to examine this compound for any possible rewarding and addictive properties as well as effects on locomotor activity, working/recognition memory, and propensity for sociability and preference for social novelty (SN) given its recently reported anti-inflammatory and analgesic properties. Male C57BL mice were split into four treatment groups and conditioned with 5.0, 20.0, 40.0 mg/kg SBFI26, or vehicle during a conditioned place preference (CPP) paradigm. Following CPP, mice underwent a battery of behavioral tests [open field, novel object recognition (NOR), social interaction (SI), and SN] paired with acute SBFI26 administration. Results showed that SBFI26 did not produce CPP or conditioned place aversion regardless of dose and did not induce any differences in locomotor and exploratory activity during CPP- or SBFI26-paired open field activity. We also observed no differences between treatment groups in NOR, SI, and SN. In conclusion, as SBFI26 was shown previously by our group to have significant analgesic and anti-inflammatory properties, here we show that it does not pose a risk of dependence or motor and cognitive impairment under the conditions tested.

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PurposePentane extract of the Peruvian plant Lepidium meyenii (Maca) has been demonstrated to possess neuroprotective activity in previous studies. This extract contains several macamides that might act on the endocannabinoid system. The aim of this study is to characterize the inhibitory activity of four maccamides (N‐benzylstearamide, N‐benzyloleamide, N‐benzyloctadeca‐9Z,12Z‐dienamide, and N‐benzyloctadeca‐9Z,12Z,15Z‐trienamide) on fatty acid amide hydrolase (FAAH), an enzyme that is responsible for the endocannabinoid degradation in the nervous system. The enhancement of endocannabinoid activity by inhibition of FAAH enzyme results in analgesic, anxiolytic, anti‐depressant and neuroprotectant effects, avoiding unwanted side effects of cannabinoid receptor activation such as weight gain and motor cognitive impairments.MethodsThe four compounds at concentrations from 1 to 100 μM were tested using a FAAH inhibitor screening assay method. This assay is based on fluorescence produced upon the hydrolysis of a substrate, 7‐amino‐4‐methylcoumarin‐arachidonamide (AMC‐AA) by the FAAH enzyme to the 7‐amino‐4‐methylcoumarin (AMC) which is measured 60 min following substrate addition at 37ºC with excitation and emission of 360 and 460 nm, respectively. To study the time dependence effect on the FAAH enzyme inhibition, the previous assay was repeated using different pre‐incubation times (0, 60 and 120 min) before substrate addition at 37ºC. To evaluate whether macamides are purely inhibitors or might be substrates of FAAH, LC/MS/MS was used to analyze the 60 min incubation of N‐benzyloctadeca‐9Z,12Z‐dienamide with and without FAAH enzyme at 37ºC. The benzylamine was used as a standard to determine the possible degradation of N‐benzyloctadeca‐9Z,12Z‐dienamide by FAAH enzyme.ResultsThe four macamides studied demonstrated concentration‐dependent FAAH inhibitory activity. Double bonds appeared to have an important impact on FAAH inhibitory activity. The macamides containing oleic, linoleic and linolenic acids produced FAAH inhibition of 64, 73, and 54%, respectively, while the macamide containing stearic acid and lacking a double bond produced only 13% inhibition at 100 μM. N‐Benzyloctadeca‐9Z,12Z‐dienamide (two double bonds) demonstrated the greatest inhibitory activity, indicating that two double bonds significantly influence the inhibition of FAAH. Pre‐incubation studies showed significant differences in the FAAH inhibitory activity of N‐benzyloctadeca‐9Z,12Z‐dienamide, N‐benzyloleamide, and N‐benzylstearamide, indicating that the inhibitory mechanism of these compounds is time‐dependent. Incubation of N‐benzyloctadeca‐9Z,12Z‐dienamide with FAAH enzyme for 60 min resulted in a 44% degradation, when analyzed by LC/MS/MS. This result indicates that N‐benzyloctadeca‐9Z,12Z‐dienamide likely acts as a slow substrate for the FAAH enzyme.ConclusionN‐Benzyloctadeca‐9Z,12Z‐dienamide is the most active macamide. The presence of double bonds in macamides significantly increases FAAH inhibition, which could improve the potential neuroprotective and analgesic activities. These results will provide useful information regarding the development of new compounds with FAAH inhibitory activity.Support or Funding InformationKing Saud ben Abdulaziz University for Health Sciences (KSAU‐HS)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.