Discovery and characterization of potent and selective inhibitors against the PEA-hydrolyzing enzyme, N-acylethanolamine-hydrolyzing acid amidase.

摘要

The fatty acid ethanolamides (FAEs) are a family of signaling lipids involved in regulating various physiological processes such as feeding, pain and inflammation. The best characterized member of this family is anandamide, which exerts its multiple effects by activating cannabinoid receptors, type-1 and type-2. Despite the structural similarity of two other members of this class, palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), their effects are not mediated by activation of cannabinoid receptors, but rather activation of the nuclear receptor peroxisome proliferator-activated receptor type-alpha (PPAR-alpha). PEA is a potent anti-inflammatory compound that was first isolated from plant and animal tissues over 50 years ago. Though the pharmacological actions of PEA are well understood, its endogenous roles remain unclear.In the present dissertation, I used a biochemical and pharmacological approach to elucidate the intrinsic roles of PEA in the regulation of the inflammatory response. In chapter 3, I found that PEA levels in immune cells are markedly reduced by inflammatory stimuli, and in collaboration with medicinal and computational chemists, I discovered the first potent and selective inhibitors of the PEA-hydrolyzing enzyme, N-acylethanolamine-hydrolyzing acid amidase (NAAA). This class of NAAA inhibitors, derived from a beta-lactone active warhead, normalizes PEA levels in activated immune cells and exerts marked anti-inflammatory effects. In chapter 4, we optimized the potency of this class of compounds by structure activity relationships, and identified (S)-N-(2-oxo-3-oxetanyl)-4-biphenylamide, which inhibits NAAA with an IC50 value of 115nM, and blunts inflammatory reactions induced by carrageenan in vivo.Together, insights into the regulation of PEA levels by activated immune cells, and the marked anti-inflammatory effects of agents which prevent PEA hydrolysis, suggest that PEA is an intrinsic anti-inflammatory signal, which negatively regulates the activation of immune cells by inflammatory triggers. This role distinguishes PEA from other known lipid mediators, which either incite inflammatory reactions (i.e. prostaglandins) or terminate it by promoting resolution and tissue healing (i.e. lipoxins and resolvins). My work has contributed to our understanding of the endogenous roles of PEA, and provides the basis for future studies investigating its role in chronic inflammatory conditions, which could result in novel therapeutic strategies against such diseases.