Involvement of N-acylethanolamine-hydrolyzing acid amidase in the degradation of anandamide and other N-acylethanolamines in macrophages

Abstract

Bioactive N-acylethanolamines including the endocannabinoid anandamide are known to be hydrolyzed to fatty acids and ethanolamine by fatty acid amide hydrolase (FAAH). In addition, we recently cloned an isozyme termed ''N-acylethanolamine-hydrolyzing acid amidase (NAAA)'', which is active only at acidic pH [Tsuboi, Sun, Okamoto, Araki, Tonai, Ueda, J. Biol. Chem. 285 (2005) 11082 -11092]. However, physiological roles of NAAA remained unclear. Here, we examined a possible contribution of NAAA to the degradation of various Nacylethanolamines in macrophage cells. NAAA mRNA as well as FAAH mRNA was detected in several macrophage-like cells, including RAW264.7, and mouse peritoneal macrophages. The homogenates of RAW264.7 cells showed both the NAAA and FAAH activities which were confirmed with the aid of their respective specific inhibitors, N-cyclohexanecarbonylpentadecylamine (CCP) and URB597. As analyzed with intact cells, RAW264.7 cells and peritoneal macrophages degraded anandamide, N-palmitoylethanolamine, N-oleoylethanolamine, and Nstearoylethanolamine. Pretreatment of the cells with CCP or URB597 partially inhibited the degradation, and a combination of the two compounds caused more profound inhibition. In contrast, the anandamide hydrolysis in mouse brain appeared to be principally attributable to FAAH despite the expression of NAAA in the brain. These results suggested that NAAA and FAAH cooperatively degraded various N-acylethanolamines in macrophages. D

Endogenous Molecules Stimulating N-Acylethanolamine-Hydrolyzing Acid Amidase (NAAA)

“…In agreement with the preference of PEA in vitro, the selective NAAA inhibitor N-[(3S)-2-oxo-3-oxetanyl]-3-phenylpropanamide increased the endogenous level of PEA in ionomycin-stimulated NAAAoverexpressing human embryonic kidney 293 (HEK293) cells but not that of AEA in lipopolysaccharide-stimulated NAAAoverexpressing HEK293 cells. 35 However, since macrophage cells endogenously expressing NAAA degraded 14 C-labeled PEA, OEA, and AEA at similar rates in the presence of the FAAH inhibitor URB597, 31 we cannot rule out a possibility that unknown endogenous factors affect the substrate specificity of NAAA.…”

“…These results were similar to our previous results analyzed by conventional reverse transcription-PCR. 31 When the NAAA levels were compared between wild-type and FAAH −/− mice, there were no significant differences in all the tissues. These results suggest that FAAH −/− mice do not have a molecular mechanism by which the accumulating NAEs enhance the levels of NAAA mRNA and are in agreement with the previous reports that endogenous levels of NAEs, including PEA, dramatically increase in the brain and other tissues of FAAH −/− mice.…”

“…30 NAAA is detected in various tissues with its predominant expression in macrophages. 31,32 Among human tissues, prostate showed a relatively high expression level of NAAA. 33 Several selective NAAA inhibitors have been reported.…”

Identification of intracellular carriers for the endocannabinoid anandamide

“…FABPs may also provide a means for rapid substrate delivery to other enzymes with distinct subcellular localizations capable of metabolizing AEA to a minor degree (34,52,53). Relative to other AEA uptake models, the proposed mechanism of simple diffusion across the plasma membrane and subsequent cytosolic trafficking by FABPs provides the most temporally efficient mode of AEA delivery to FAAH.…”

Oral Palmitoylethanolamide Treatment Is Associated with Reduced Cutaneous Adverse Effects of Interferon-β1a and Circulating Proinflammatory Cytokines in Relapsing–Remitting Multiple Sclerosis

“…The inactivation of NAEs (AEA, OEA, and PEA) occurs essentially by enzymatic hydrolysis by FAAH and NAAA [35][36][37][38][39]. Thus, it is possible that um-PEA administration reduces the degradation of AEA and OEA by substrate competition.…”