NAAA inhibitor F96 attenuates BBB disruption and secondary injury after traumatic brain injury (TBI)

Traumatic brain injury (TBI) is a leading cause of death worldwide, for which there is currently no comprehensive treatment available. Preventing blood-brain barrier (BBB) disruption is crucial for TBI treatment. N-acylethanolamine acid amidase (NAAA)-regulated palmitoylethanolamide (PEA) signaling play an important role in the control of inflammation. However, the role of NAAA in BBB dysfunction following TBI remains unclear. In the present study, we found that TBI induces the increase of PEA levels in the injured cortex, which prevent the disruption of BBB after TBI. TBI also induces the infiltration of NAAA-contained neutrophils, increasing the contribution of NAAA to the PEA degradation. Neutrophil-derived NAAA weakens PEA/PPARα-mediated BBB protective effects after TBI, facilitates the accumulation of immune cells, leading to secondary expansion of tissue injury. Inactivation of NAAA increased PEA levels in injured site, prevents early BBB damage and improves secondary injury, thereby eliciting long-term functional improvements after TBI. This study identified a new role of NAAA in TBI, suggesting that NAAA is a new important target for BBB dysfunction related CNS diseases.

Palmitoylethanolamide (PEA) reduces postoperative adhesions after experimental strabismus surgery in rabbits by suppressing canonical and non-canonical TGFβ signaling through PPARα

Postoperative adhesions and scarring are the particular complication after strabismus surgery, for which there is currently no comprehensive treatment available. Preventing inflammation and fibrosis in the extraocular muscle are crucial for treatment of postoperative adhesions. In the present study, we found that administration of palmitoylethanolamide (PEA) attenuated postoperative inflammation and fibroproliferation through activating peroxisome proliferator-activated receptor α (PPARα), thus prevented scar formation. Inhibition of PEA degradation by N-Acylethanolamine acid amidase (NAAA) inhibitor F96 led to the same pharmacological results. PPARα activation suppressed both canonical and non-canonical TGFβ signaling. Mechanistically, we found that PPARα directly bound to TGFβ-activated kinase 1 (TAK1), thus preventing its hyperphosphorylation and the activation of downstream p38 and JNK1/2 signaling. Taken together, current study suggested that PEA could be a novel therapeutic approach for postoperative adhesions after strabismus surgery.

Advances in the discovery of fatty acid amide hydrolase inhibitors: what does the future hold?

INTRODUCTION

Fatty acid amide hydrolase (FAAH) is a membrane-bound enzyme, that inactivates endogenous signaling lipids of the fatty acid amide family, including the endocannabinoid anandamide (N-arachidonoylethanolamine, AEA). The latter compound has been shown to regulate a number of important pathophysiological conditions in humans, like feeding, obesity, immune response, reproductive events, motor coordination, and neurological disorders. Hence, direct manipulation of the endocannabinoid tone is thought to have therapeutic potential. A new opportunity to develop effective drugs may arise from multi-target directed ligand (MTDL) strategies, which brings the concept that a single compound can recognize different targets involved in the cascade of pathophysiological events.

AREAS COVERED

This review reports the latest advances in the development of new single targeted and dual-targeted FAAH inhibitors over the past 5 years.

EXPERT OPINION

In recent years, several FAAH inhibitors have been synthesized and investigated, yet to date none of them has reached the market as a systemic drug. Due to the diligence of inherent redundancy and robustness in many biological networks and pathways, multitarget inhibitors present a new prospect in the pharmaceutical industry for treatment of complex diseases.

A perspective review on fatty acid amide hydrolase (FAAH) inhibitors as potential therapeutic agents

Fatty acid amide hydrolase (FAAH) is an important enzyme creditworthy of hydrolyzing endocannabinoids and related-amidated signalling lipids, discovery of which has pioneered novel arena of pharmacological canvasses to unwrap its curative potency in various diseased circumstances. It presents contemporary basis for understanding molecules regulating and mediating inflammatory reactions, pain, anxiety, depression, and neurodegeneration. FAAH inhibitors form vital approach for discovery of therapeutic agents that are concerned with local elevation of endocannabinoids under certain stimuli, debarring adverse/unwanted secondary effects from global activation of cannabinoid receptors by exogenous cannabimimetics. During past decades, several molecules with excellent potency developed through tailor-made approaches entered into clinical trials, but none could reach market. Hence, hunt for novel, non-toxic and selective FAAH inhibitors are on horizon. This review summarizes present perception on FAAH in conjunction with its structure, mechanism of catalysis and biological functions. It also foregrounds recent development of molecules belonging to diverse chemical classes as potential FAAH inhibitors bobbing up from in-depth chemical, mechanistic and computational studies published since 2015-November 2019, focusing on their potency. This review will assist readers to obtain rationale on FAAH as potential target for addressing various disease conditions, acquiring significant knowledge on recently established inhibitor scaffolds and their development potentials. New technologies including MD-MM simulations and 3D-QSAR studies allow mechanistic characterization of enzyme. Assessment of in-vitro and in-vivo efficacy of existing FAAH inhibitors will facilitate researchers to design novel ligands utilizing modern drug design methods. The discussions will also impose precaution in decision making process, quashing possibility of late stage failure.

N-Acylethanolamine acid amidase (NAAA) inhibitor F215 as a novel therapeutic agent for osteoarthritis

Osteoarthritis (OA), characterized by cartilage damage, synovitis inflammation and chronic pain, is a common degenerative joint disease that may lead to physical disability. In the present study, we first explored the association between N-Acylethanolamine acid amidase (NAAA) and OA progression, and then examined the capability of the NAAA inhibitor F215 to attenuate osteoarthritis. Increased NAAA expressions and decreased PEA levels in synovial membrane and lumbar spinal cord were observed in MIA induced osteoarthritic rats. F215 (i.a., and i.p.) significantly protected against cartilage damage and synovial inflammation by directly increasing PEA levels in joints, or normalization of PEA levels and resolution of inflammation in spinal cord. Moreover, F215 also markedly alleviated osteoarthritic pain in rats, and the therapeutic effects of F215 were blocked by the PPAR-α antagonist MK886. The results revealed that NAAA may has been implicated in OA progression, and treatment with NAAA inhibitor F215 alleviated OA development by preventing cartilage damage, reducing inflammation, and alleviating pain. Our study suggested that NAAA inhibitor might be a novel therapeutic agent for OA treatment.

Synthesis, biological evaluation, and structure activity relationship (SAR) study of pyrrolidine amide derivatives as N-acylethanolamine acid amidase (NAAA) inhibitors

N-Acylethanolamine acid amidase (NAAA) is one of the key enzymes involved in the degradation of fatty acid ethanolamides (FAEs), especially for palmitoylethanolamide (PEA). Pharmacological blockage of NAAA restores PEA levels, providing therapeutic benefits in the management of inflammation and pain. In the current work, we showed the structure-activity relationship (SAR) studies for pyrrolidine amide derivatives as NAAA inhibitors. A series of aromatic replacements or substituents for the terminal phenyl group of pyrrolidine amides were examined. SAR data showed that small lipophilic 3-phenyl substituents were preferable for optimal potency. The conformationally flexible linkers increased the inhibitory potency of pyrrolidine amide derivatives but reduced their selectivity toward fatty acid amide hydrolase (FAAH). The conformationally restricted linkers did not enhance the inhibitor potency toward NAAA but improved the selectivity over FAAH. Several low micromolar potent NAAA inhibitors were developed, including 4g bearing a rigid 4-phenylcinnamoyl group. Dialysis and kinetic analysis suggested that 4g inhibited NAAA via a competitive and reversible mechanism. Furthermore, 4g showed high anti-inflammatory activities in lipopolysaccharide (LPS) induced acute lung injury (ALI) model, and this effect was blocked by pre-treatment with the PPAR-α antagonist MK886. We anticipate that 4g (E93) will enable a new agent to treat inflammation and related diseases.