An Important Role for N-Acylethanolamine Acid Amidase in the Complete Freunds Adjuvant Rat Model of Arthritis

Abstract

The endogenous lipid amides, palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), exert marked antinociceptive and anti-inflammatory effects in animal models by engaging nuclear peroxisome proliferator-activated receptor-a. PEA and OEA are produced by macrophages and other host-defense cells and are deactivated by the cysteine amidase, N-acylethanolamine acid amidase (NAAA), which is highly expressed in macrophages and B-lymphocytes. In the present study, we examined whether a) NAAA might be involved in the inflammatory reaction triggered by injection of complete Freund's adjuvant (CFA) into the rat paw and b) administration of 4-cyclohexylbutyl-N-[(S)-2-oxoazetidin-3-yl]-carbamate (ARN726), a novel systemically active NAAA inhibitor, attenuates such reaction. Injection of CFA into the paw produced local edema and heat hyperalgesia, which were accompanied by decreased PEA and OEA content (assessed by liquid chromatography/mass spectrometry) and increased NAAA levels (assessed by Western blot and ex vivo enzyme activity measurements) in paw tissue. Administration of undec-10-ynyl-N-[(3S)-2-oxoazetidin-3-yl] carbamate (ARN14686), a NAAA-preferring activity-based probe, revealed that NAAA was catalytically active in CFA-treated paws. Administration of ARN726 reduced NAAA activity and restored PEA and OEA levels in inflamed tissues, and significantly decreased CFAinduced inflammatory symptoms, including pus production and myeloperoxidase activity. The results confirm the usefulness of ARN726 as a probe to investigate the functions of NAAA in health and disease and suggest that this enzyme may provide a new molecular target for the treatment of arthritis.

The N-Acylethanolamine Acid Amidase Inhibitor ARN077 Suppresses Inflammation and Pruritus in a Mouse Model of Allergic Dermatitis

“…As previously shown with other inflammatory stimuli, such as carrageenan (Solorzano et al, 2009), lipopolysaccharide (Ribeiro et al, 2015), and complete Freund's adjuvant (Bonezzi et al, 2016), local application of DNFB decreased PEA content in mouse ear tissue (Figure 3a) (P < 0.001, n ¼ 9). By contrast, no change was observed in the levels of oleoylethanolamide (OEA), another lipid amide agonist of PPAR-a ( Figure 3b) (Fu et al, 2003).…”

“…Despite their rapid clearance, (S)-OOPP and ARN077 have been shown to suppress macrophage activation in vitro and to attenuate local inflammatory and nociceptive responses in vivo (Sasso et al, 2013b; Solorzano et al, 2009). NAAA inhibitors with greater metabolic stability, such as the b-lactam ARN726 and isothiocyanate AM9053, display significant anti-inflammatory activity after systemic administration in mouse models of lung (Ribeiro et al, 2015), joint (Bonezzi et al, 2016), and colon inflammation (Alhouayek et al, 2015).…”

“…In both experimental animals and humans, acute and chronic inflammatory states are accompanied by a dramatic decrease in PEA levels (Ribeiro et al, 2015;Richardson et al, 2008;Sasso et al, 2013b;Solorzano et al, 2009), resulting from a combination of impaired biosynthesis and heightened NAAAmediated degradation (Zhu et al, 2011). That these changes might be functionally significant is suggested by the finding that administration of the systemically active NAAA inhibitor, ARN726, counters the inflammatory responses elicited by bacterial lipopolysaccharide or complete Freund's adjuvant in mice (Bonezzi et al, 2016;Ribeiro et al, 2015). Local application of exogenous PEA also attenuates skin inflammation in animals (Lo Verme et al, 2005;Noli et al, 2015) and humans (Eberlein et al, 2008) through a mechanism that requires PPAR-a activation (Lo Verme et al, 2005).…”

Molecular mechanism of activation of the immunoregulatory amidase NAAA

“…NAEs are primarily inactivated by hydrolysis to ethanolamine and fatty acid (8,9) carried out by two enzymes: fatty acid amide hydrolase (FAAH) (10) and N-acylethanolamine acid amidase (NAAA) (9). FAAH is widely distributed (11) although it is most abundant in the brain and liver (12), whereas NAAA is almost exclusively expressed in immune cells (13,14) such as monocytes and tissue macrophages (15,16) but is also found in prostate epithelium (13,17). In light of the analgesic and antiinflammatory actions of PEA, multiple NAAA inhibitors have been developed over the last decade (18,19) and shown to exhibit beneficial effects in a range of rodent models of human disease, including inflammation (20)(21)(22)(23)(24)(25), allergic contact dermatitis (26), spinal cord trauma (27), neuropathic pain (28,29), chronic pain (30), inflammatory bowel disease (31), lung inflammation (25,32), arthritis (14), and multiple sclerosis (33).…”

N-Palmitoylethanolamine Maintains Local Lipid Homeostasis to Relieve Sleep Deprivation–Induced Dry Eye Syndrome

“…We found that mRNA levels of NAAA, the specific hydrolase of PEA, remained constant during 10 days after SD. NAAA is almost exclusively expressed in immune cells (Bonezzi et al, 2016;Bottemanne et al, 2018) and is catalytically active at the acidic pH present during inflammation. In the SDE mouse model, no obvious inflammatory cell infiltration was found in ocular surfaces or LGs, which might explain why NAAA enzyme was not highly expressed.…”