Antinociceptive effects of the N-acylethanolamine acid amidase inhibitor ARN077 in rodent pain models

Abstract

Fatty acid ethanolamides (FAEs), which include palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), are endogenous agonists of peroxisome proliferator-activated receptor-α (PPAR-α) and important regulators of the inflammatory response. They are degraded in macrophages by the lysosomal cysteine amidase, N-acylethanolamine acid amidase (NAAA). Previous studies have shown that pharmacological inhibition of NAAA activity suppresses macrophage activation in vitro and causes marked anti-inflammatory effects in vivo, which is suggestive of a role for NAAA in the control of inflammation. It is still unknown, however, whether NAAA-mediated FAE deactivation might regulate pain signaling. In the present study, we examined the effects of ARN077, a potent and selective NAAA inhibitor recently disclosed by our group, in rodent models of hyperalgesia and allodynia caused by inflammation or nerve damage. Topical administration of ARN077 attenuated, in a dose-dependent manner, heat hyperalgesia and mechanical allodynia elicited in mice by carrageenan injection or sciatic nerve ligation. The anti-nociceptive effects of ARN077 were prevented by the selective PPAR-α antagonist GW6471 and did not occur in PPAR-α-deficient mice. Furthermore, topical ARN077 reversed the allodynia caused by ultraviolet B-radiation in rats, and this effect was blocked by pretreatment with GW6471. Sciatic nerve ligation or application of the pro-inflammatory phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) decreased FAE levels in sciatic nerve and skin tissue, respectively. ARN077 reversed these biochemical effects. The results identify ARN077 as a potent inhibitor of intracellular NAAA activity, which is active in vivo by topical administration. The findings further suggest that NAAA regulates peripheral pain initiation by interrupting endogenous FAE signaling at PPAR-α.

Synthesis and Structure–Activity Relationship (SAR) of 2-Methyl-4-oxo-3-oxetanylcarbamic Acid Esters, a Class of Potent N-Acylethanolamine Acid Amidase (NAAA) Inhibitors

“…46 Moreover, in rodent models of hyperalgesia and allodynia caused by inflammation or nerve damage, 4 administered by the topical route partially normalized FAE levels in the skin and sciatic nerve, which were reduced by inflammation and surgical ligation, respectively, and attenuated nociception through a mechanism that required PPAR-α activation. 46 We identified compound 4 starting from the serine-derived 2-oxo-3-oxetanylamide, (S)-OOPP (2), which inhibits NAAA with a median inhibitory concentration (IC 50 ) of 0.42 μM. 24 The (S)-configuration at position 3 in the β-lactone ring of 2 is essential for inhibitory potency, as indicated by the substantially lower activity of its enantiomer, (R)-OOPP (IC 50 = 6.0 μM).…”

“…46 In vitro experiments have shown that compound 4 inhibits rat NAAA through a mechanism that is rapid, noncompetitive, and fully reversible after overnight dialysis. 46 Moreover, in rodent models of hyperalgesia and allodynia caused by inflammation or nerve damage, 4 administered by the topical route partially normalized FAE levels in the skin and sciatic nerve, which were reduced by inflammation and surgical ligation, respectively, and attenuated nociception through a mechanism that required PPAR-α activation. 46 We identified compound 4 starting from the serine-derived 2-oxo-3-oxetanylamide, (S)-OOPP (2), which inhibits NAAA with a median inhibitory concentration (IC 50 ) of 0.42 μM.…”

“…33,46 In our simulations, the four compounds were truncated and modeled as methyl carbamate, and the sulfur atom was provided by cysteamine (see Computational Methods under Experimental Section). Starting from the noncovalent complex, we performed a scan on the potential energy surface, using as reaction coordinate the distance between the sulfur atom of the cysteamine molecule and the carbon atom of the carbonyl group of the β-lactone ring.…”

Endogenous N -acyl taurines regulate skin wound healing

“…Previous studies have shown that two FAAH substrates present in the skin, PEA and OEA, modulate local inflammatory responses by activating the nuclear receptor PPAR-α (8,37). Like NAT formation after wounding, the production of PEA and OEA is suppressed by proinflammatory stimuli (38)(39)(40), suggesting that different classes of lipid amides may regulate distinct phases of the healing response in a coordinated manner. Answering these questions may help uncover possible roles of NAT-mediated signaling in pathological impairments of skin repair, such as those consequent to aging, diabetes, and immunosuppression, and might guide the development of new strategies for the management of chronic nonresolving wounds.…”

Therapeutic Potential of Fatty Acid Amide Hydrolase, Monoacylglycerol Lipase, and N-Acylethanolamine Acid Amidase Inhibitors

“…The compound (10% in acetone) was effective in TPA-induced edema and CCI mouse models. 135 Modification of the phenylpentyl moiety of 111 was performed. Removal of the phenyl ring or modification of the carbon chain length of the phenylpentyl group appeared to result in a notable decease of inhibition ( Figure 42).…”