James Guy Breitenbucher

Inhibition of fatty acid amide hydrolase produces analgesia by multiple mechanisms

British Journal of Pharmacology (2006) 148, 114. doi:10.1038/sj.bjp.0706773

Inhibition of fatty acid amide hydrolase produces analgesia by multiple mechanisms: Mechanisms of analgesia by FAAH inhibition

1 The reversible fatty acid amide hydrolase (FAAH) inhibitor OL135 reverses mechanical allodynia in the spinal nerve ligation (SNL) and mild thermal injury (MTI) models in the rat. The purpose of this study was to investigate the role of the cannabinoid and opioid systems in mediating this analgesic effect. 2 Elevated brain concentrations of anandamide (350 pmol g−1 of tissue vs 60 pmol g−1 in vehicle‐treated controls) were found in brains of rats given OL135 (20 mg kg−1) i.p. 15 min prior to 20 mg kg−1 i.p. anandamide. 3 Predosing rats with OL135 (2–60 mg kg−1 i.p.) 30 min before administration of an irreversible FAAH inhibitor (URB597: 0.3 mg kg−1 intracardiac) was found to protect brain FAAH from irreversible inactivation. The level of enzyme protection was correlated with the OL135 concentrations in the same brains. 4 OL135 (100 mg kg−1 i.p.) reduced by 50% of the maximum possible efficacy (MPE) mechanical allodynia induced by MTI in FAAH+/+mice (von Frey filament measurement) 30 min after dosing, but was without effect in FAAH−/− mice. 5 OL135 given i.p. resulted in a dose‐responsive reversal of mechanical allodynia in both MTI and SNL models in the rat with an ED50 between 6 and 9 mg kg−1. The plasma concentration at the ED50 in both models was 0.7 μM (240 ng ml−1). 6 In the rat SNL model, coadministration of the selective CB2 receptor antagonist SR144528 (5 mg kg−1 i.p.), with 20 mg kg−1 OL135 blocked the OL135‐induced reversal of mechanical allodynia, but the selective CB1 antagonist SR141716A (5 mg kg−1 i.p.) was without effect. 7 In the rat MTI model neither SR141716A or SR144528 (both at 5 mg kg−1 i.p.), or a combination of both antagonists coadministered with OL135 (20 mg kg−1) blocked reversal of mechanical allodynia assessed 30 min after dosing. 8 In both the MTI model and SNL models in rats, naloxone (1 mg kg−1, i.p. 30 min after OL135) reversed the analgesia (to 15% of control levels in the MTI model, to zero in the SNL) produced by OL135.

Biochemical and Biological Properties of 4-(3-phenyl-[1,2,4] thiadiazol-5-yl)-piperazine-1-carboxylic acid phenylamide, a Mechanism-Based Inhibitor of Fatty Acid Amide Hydrolase

Fatty acid amide hydrolase (FAAH) is an integral membrane enzyme within the amidase-signature family. It catalyzes the hydrolysis of several endogenous biologically active lipids, including anandamide (arachidonoyl ethanolamide), oleoyl ethanolamide, and palmitoyl ethanolamide. These endogenous FAAH substrates have been shown to be involved in a variety of physiological and pathological processes, including synaptic regulation, regulation of sleep and feeding, locomotor activity, pain and inflammation. Here we describe the biochemical and biological properties of a potent and selective FAAH inhibitor, 4-(3-phenyl-[1,2,4]thiadiazol-5-yl)-piperazine-1-carboxylic acid phenylamide (JNJ-1661010). The time-dependence of apparent IC50 values at rat and human recombinant FAAH, dialysis and mass spectrometry data indicate that the acyl piperazinyl fragment of JNJ-1661010 forms a covalent bond with the enzyme. This bond is slowly hydrolyzed, with release of the piperazinyl fragment and recovery of enzyme activity. The lack of inhibition observed in a rat liver esterase assay suggests that JNJ-1661010 is not a general esterase inhibitor. JNJ-1661010 is >100-fold preferentially selective for FAAH-1 when compared to FAAH-2. JNJ-1661010 dose-dependently increases arachidonoyl ethanolamide, oleoyl ethanolamide, and palmitoyl ethanolamide in the rat brain. The compound attenuates tactile allodynia in the rat mild thermal injury model of acute tissue damage and in the rat spinal nerve ligation (Chung) model of neuropathic pain. JNJ-1661010 also diminishes thermal hyperalgesia in the inflammatory rat carrageenan paw model. These data suggest that FAAH inhibitors with modes of action similar to JNJ-1661010 may be useful clinically as broad-spectrum analgesics.

Role of CCK and potential utility of CCK1 receptor antagonism in the treatment of pancreatitis induced by biliary tract obstruction

Background and purpose: Cholecystokinin (CCK) stimulates the release of amylase and lipase from the normal pancreas. However, it is not clear to what extent this occurs in the early stages of pancreatitis induced by biliary tract obstruction in the rat and whether CCK initiates an inflammatory cascade in this condition.