Introductory paragraph Panic disorder is a severe anxiety disorder with recurrent, debilitating panic attacks. In subjects with panic disorder there is evidence of decreased central GABAergic activity as well as marked increases in autonomic and respiratory responses following intravenous infusions of 0.5M sodium lactate1–3. In an animal model of panic disorder, chronic inhibition of GABA synthesis in the dorsomedial/perifornical hypothalamus of rats produces anxiety-like states and a similar vulnerability to sodium lactate-induced cardioexcitatory responses4–9. The dorsomedial/perifornical hypothalamus is enriched in orexin (ORX, also known as hypocretin)-containing neurons10 that play a critical role in arousal10,11, vigilance10 and central autonomic mobilization12, all of which are key components of panic. Here, we demonstrate that activation of the ORX neurons is necessary for developing a panic-prone state in the animal model, and either silencing the hypothalamic ORX gene (Hcrt) product with RNA interference or systemic ORX1 antagonists blocks the panic responses. Moreover, we show that subjects with panic anxiety have elevated levels of ORX in the cerebrospinal fluid compared to subjects without panic anxiety. Taken together our results suggest that the ORX system may be involved in the pathophysiology of panic anxiety, and that ORX antagonists constitute a potential novel treatment strategy for panic disorder.

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Methylphenidate is an important stimulant prescribed to treat attention-deficit hyperactivity disorder. It has two chiral centers, but most current commercial formulations consist of the racemic mixture of the threo pair of methylphenidate isomers (d-, l-threo-methylphenidate). The d-isomer is the pharmacologically active component. Numerous studies reported that oral administration of the methylphenidate racemate undergoes first-pass, stereoselective clearance in humans with l-methylphenidate being eliminated faster than d-methylphenidate. Accordingly, the kinetics of hydrolysis of individual enantiomers by purified native and recombinant human liver carboxylesterases CES1A1 and CES2 and a colon isoenzyme CES3 were examined with a liquid chromatography/mass spectrometry assay. The expression of CES1A1, CES2, and CES3 in Sf9 cells and the methods for purification of the three isoenzymes are reported. CES1A1 has a high catalytic efficiency for both d-and l-enantiomers of methylphenidate. No catalytic activity was detected with CES2 and CES3 for either enantiomer. The catalytic efficiency of CES1A1 for l-methylphenidateHence, the catalytic efficiency of CES1A1 for methylphenidate enantiomers agrees with stereoselective clearance of methylphenidate reported in human subjects. Both enantiomers of methylphenidate can be fit into the three-dimensional model of CES1A1 to form productive complexes in the active site. We conclude that CES1A1 is the major enzyme responsible for the first-pass, stereoselective metabolism of methylphenidate.

Capecitabine is an oral prodrug of 5-fluorouracil that is indicated for the treatment of breast and colorectal cancers. A three-step in vivo-targeted activation process requiring carboxylesterases, cytidine deaminase, and thymidine phosphorylase converts capecitabine to 5-fluorouracil. Carboxylesterases hydrolyze capecitabine's carbamate side chain to form 5Ј-deoxy-5-fluorocytidine (5Ј-DFCR). This study examines the steady-state kinetics of recombinant human carboxylesterase isozymes carboxylesterase (CES) 1A1, CES2, and CES3 for hydrolysis of capecitabine with a liquid chromatography/mass spectroscopy assay. Additionally, a spectrophotometric screening assay was utilized to identify drugs that may inhibit carboxylesterase activation of capecitabine. CES1A1 and CES2 hydrolyze capecitabine to a similar extent, with catalytic efficiencies of 14.7 and 12.9 min Ϫ1 mM Ϫ1

Carboxylesterases belong to Phase I group of drug metabolizing enzymes. They hydrolyze a variety of drug esters, amides, carbamates and similar structures. There are five 'carboxylesterase' genes listed in the Human Genome Organization database. In this review, we will focus on the CES1, CES2 and CES3 genes and their protein products that have been partially characterized. Several variants of these three CESs result from alternate splicing, single nucleotide polymorphisms and multiple copy variants. The three CESs, are largely localized to tissues that are major sites of drug metabolism like the mucosa of the gastrointestinal tract, lungs and liver but, they differ in tissue-specific expression. The amino acid alignment of the three CESs reveals important conserved catalytic and structural residues. There are interesting insertions and deletions that may affect enzymatic function as determined by homology modeling of CES3 using the CES1 three-dimensional structure. A comparison of the substrate specificity of CES1 versus CES2 reveals broad but distinct substrate preferences. There is little information on the substrate specificity of CES3 but it seems to have a lower catalytic efficiency than the other two CESs for selected substrates.

Repeated maternal separation of pups from dams is often used as an early life stressor that causes profound neurochemical and behavioral changes in the pups that persist into adulthood. The effects of maternal separation on both the dams and the treated pups as adults on cocaine self-administration were examined using four separation conditions: 15-or 180-min separation (MS15 and MS180), brief handling without separation (MS0), and a nonhandled group (NH). The separations and handling occurred daily on postnatal days 2 to 15. The acquisition of cocaine self-administration (0.0625-1.0 mg/kg/infusion) was evaluated in the treated pups as adults. The MS180 group acquired cocaine self-administration at the lowest dose tested (0.0625 mg/kg/infusion), whereas the MS15s did not respond for cocaine at rates greater than that seen with saline administration. The NH group received the greatest number of infusions and intake at the highest doses. After self-administration, no differences were observed between groups in activity of two liver carboxylesterases involved in the inactivation of cocaine, ES10 and ES4. Maternal separation affected cocaine self-administration in the dams as well. Although there was an overall significant affect of treatment on cocaine self-administration, the length of separation (15 or 180 min) did not affect cocaine self-administration on the dams. The MS0 dams averaged a greater number of infusions per session than NH group during the 1st week of acquisition. These data suggest that in addition to the profound changes that occur in pups as result of maternal separation, the dams are also susceptible to alterations in behaviors.Traumatic or stressful events experienced in childhood can have profound behavioral effects in adults. Therefore, it is not surprising that early adverse events in humans are associated with increased vulnerability to drug abuse as adults. McFarlane et al. (2005) found an association of adverse early life experiences with nicotine dependence. Felitti et al. (1998) found a strong relationship between household dysfunction during childhood and drug abuse, and others have had similar results (Dube et al., 2003). Because of the relatively common and serious nature of this problem, developing an animal model has been important.Animal models of early life stress, such as maternal separation and neonatal isolation, have been developed in an attempt to elucidate the neurochemical and behavioral alterations resulting from exposure to the early life stressor. In animal models, perinatal stress affects behavioral response to various drugs of abuse. Neonatal isolation and prolonged maternal separation alter the self-administration of cocaine in rats (Matthews et al., 1999;Flagel et al., 2003;Kosten et al., 2004;Zhang et al., 2005). Early life stress also alters conditioned place preference for amphetamine (Campbell and Spear, 1999), cocaine-induced locomotor activity (Brake et al., 2004), behavioral sensitization to cocaine (Li et al., 2003), ethanol preference and consumptio...

ABSTRACT:Carboxylesterases metabolize ester, thioester, carbamate, and amide compounds to more soluble acid, alcohol, and amine products. They belong to a multigene family with about 50% sequence identity between classes. CES1A1 and CES2 are the most studied human isoenzymes from class 1 and 2, respectively. In this study,

S-Nitrosoglutathione reductase (GSNOR) is an alcohol dehydrogenase involved in the regulation of S-nitrosothiols (SNOs) in vivo. Knock-out studies in mice have shown that GSNOR regulates the smooth muscle tone in airways and the function of ␤-adrenergic receptors in lungs and heart. GSNOR has emerged as a target for the development of therapeutic approaches for treating lung and cardiovascular diseases. We report three compounds that exclude GSNOR substrate, S-nitrosoglutathione (GSNO) from its binding site in GSNOR and cause an accumulation of SNOs inside the cells. The new inhibitors selectively inhibit GSNOR among the alcohol dehydrogenases. Using the inhibitors, we demonstrate that GSNOR limits nitric oxide-mediated suppression of NF-B and activation of soluble guanylyl cyclase. Our findings reveal GSNOR inhibitors to be novel tools for regulating nitric oxide bioactivity and assessing the role of SNOs in vivo.