Metabolic drug interactions with new psychotropic agents

New psychotropic drugs introduced in clinical practice in recent years include new antidepressants, such as selective serotonin reuptake inhibitors (SSRI) and 'third generation' antidepressants, and atypical antipsychotics, i.e. clozapine, risperidone, olanzapine, quetiapine, ziprasidone and amisulpride. These agents are extensively metabolized in the liver by cytochrome P450 (CYP) enzymes and are therefore susceptible to metabolically based drug interactions with other psychotropic medications or with compounds used for the treatment of concomitant somatic illnesses. New antidepressants differ in their potential for metabolic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, while nefazodone is a potent inhibitor of CYP3A4. These antidepressants may be involved in clinically significant interactions when coadministered with substrates of these isoforms, especially those with a narrow therapeutic index. Other new antidepressants including sertraline, citalopram, venlafaxine, mirtazapine and reboxetine are weak in vitro inhibitors of the different CYP isoforms and appear to have less propensity for important metabolic interactions. The new atypical antipsychotics do not affect significantly the activity of CYP isoenzymes and are not expected to impair the elimination of other medications. Conversely, coadministration of inhibitors or inducers of the CYP isoenzymes involved in metabolism of the various antipsychotic compounds may alter their plasma concentrations, possibly leading to clinically significant effects. The potential for metabolically based drug interactions of any new psychotropic agent may be anticipated on the basis of knowledge about the CYP enzymes responsible for its metabolism and about its effect on the activity of these enzymes. This information is essential for rational prescribing and may guide selection of an appropriate compound which is less likely to interact with already taken medication(s).     

Large GABAergic neurons form a distinct subclass within the mouse dorsal cortex of the inferior colliculus with respect to intrinsic properties,synaptic inputs,sound responses,and projections

Neurons in the inferior colliculus (IC) show a remarkable diversity in their responses to sound, but it has been difficult to relate these responses to their morphology. Large cells, which are found in all subdivisions of the IC, may form an exception. We found that large neurons of the mouse dorsal cortex of the IC were GABAergic and were contacted by vesicular glutamate transporter 2‐containing somatic terminals, as previously observed for the rat IC. Large cells, which were targeted under two‐photon guidance, typically had a low input resistance in comparison with the other cells in the dorsal cortex of the IC. Large cells received short‐latency excitatory inputs and had short first‐spike latencies. These excitatory inputs were often followed by long‐latency inhibitory postsynaptic potentials. In four cells, it was possible to reconstruct the ascending axon following labeling with biocytin. We found evidence that they projected to both the ventral and the dorsal divisions of the medial geniculate body of the thalamus, but they also branched off large collaterals while passing through the brachium of the IC. Our data indicate that, owing to their somatic glutamatergic inputs, large GABAergic tectothalamic projection neurons can generate short‐latency, well‐timed, feed‐forward inhibition, which affects not only the thalamus, but also other ascending nuclei. Their remarkably homogeneous properties, which generally differed from those of the other cells in the dorsal cortex of the IC, suggest that large neurons form a distinct subclass within the dorsal cortex of the IC. J. Comp. Neurol. 521:189–202, 2013. © 2012 Wiley Periodicals, Inc.     

Alterations in the motor neuron–renshaw cell circuit in the Sod1G93A mouse model

Motor neurons become hyperexcitable during progression of amyotrophic lateral sclerosis (ALS). This abnormal firing behavior has been explained by changes in their membrane properties, but more recently it has been suggested that changes in premotor circuits may also contribute to this abnormal activity. The specific circuits that may be altered during development of ALS have not been investigated. Here we examined the Renshaw cell recurrent circuit that exerts inhibitory feedback control on motor neuron firing. Using two markers for Renshaw cells (calbindin and cholinergic nicotinic receptor subunit alpha2 [Chrna2]), two general markers for motor neurons (NeuN and vesicular acethylcholine transporter [VAChT]), and two markers for fast motor neurons (Chondrolectin and calcitonin‐related polypeptide alpha [Calca]), we analyzed the survival and connectivity of these cells during disease progression in the Sod1^G93A mouse model. Most calbindin‐immunoreactive (IR) Renshaw cells survive to end stage but downregulate postsynaptic Chrna2 in presymptomatic animals. In motor neurons, some markers are downregulated early (NeuN, VAChT, Chondrolectin) and others at end stage (Calca). Early downregulation of presynaptic VAChT and Chrna2 was correlated with disconnection from Renshaw cells as well as major structural abnormalities of motor axon synapses inside the spinal cord. Renshaw cell synapses on motor neurons underwent more complex changes, including transitional sprouting preferentially over remaining NeuN‐IR motor neurons. We conclude that the loss of presynaptic motor axon input on Renshaw cells occurs at early stages of ALS and disconnects the recurrent inhibitory circuit, presumably resulting in diminished control of motor neuron firing. J. Comp. Neurol. 521:1449–1469, 2013. © 2012 Wiley Periodicals, Inc.     

Olfactory identification deficits and associated response inhibition in obsessive-compulsive disorder: On the scent of the orbitofronto–striatal model

Olfactory identification ability implicates the integrity of the orbitofrontal cortex (OFC). The fronto–striatal circuits including the OFC have been involved in the neuropathology of Obsessive Compulsive Disorder (OCD). However, only a few studies have examined olfactory function in patients with OCD. The Brief Smell Identification Test (B-SIT) and tests from the Cambridge Neuropsychological Automated Battery (CANTAB) were administered to 25 patients with OCD and to 21 healthy matched controls. OCD patients showed a significant impairment in olfactory identification ability as well as widely distributed cognitive deficits in visual memory, executive functions, attention, and response inhibition. The degree of behavioural impairment on motor impulsivity (prolonged response inhibition Stop-Signal Reaction Time) strongly correlated with the B-SIT score. Our study is the first to indicate a shared OFC pathological neural substrate underlying olfactory identification impairment, impulsivity, and OCD. Deficits in visual memory, executive functions and attention further indicate that regions outside of the orbitofronto–striatal loop may be involved in this disorder. Such results may help delineate the clinical complexity of OCD and support more targeted investigations and interventions. In this regard, research on the potential diagnostic utility of olfactory identification deficits in the assessment of OCD would certainly be useful.     

Structure and Biological Properties of Ribosome-Inactivating Proteins and Lectins from Elder (Sambucus nigra L.) Leaves

Ribosome-inactivating proteins (RIPs) are a group of proteins with rRNA N-glycosylase activity that catalyze the removal of a specific adenine located in the sarcin–ricin loop of the large ribosomal RNA, which leads to the irreversible inhibition of protein synthesis and, consequently, cell death. The case of elderberry (Sambucus nigra L.) is unique, since more than 20 RIPs and related lectins have been isolated and characterized from the flowers, seeds, fruits, and bark of this plant. However, these kinds of proteins have never been isolated from elderberry leaves. In this work, we have purified RIPs and lectins from the leaves of this shrub, studying their main physicochemical characteristics, sequences, and biological properties. In elderberry leaves, we found one type 2 RIP and two related lectins that are specific for galactose, four type 2 RIPs that fail to agglutinate erythrocytes, and one type 1 RIP. Several of these proteins are homologous to others found elsewhere in the plant. The diversity of RIPs and lectins in the different elderberry tissues, and the different biological activities of these proteins, which have a high degree of homology with each other, constitute an excellent source of proteins that are of great interest in diagnostics, experimental therapy, and agriculture.     

Metal Ions and Chemical Modification Reagents Inhibit the Enzymatic Activity of Lecithin-Dependent Hemolysin from Vibrio parahaemolyticus

Lecithin-dependent thermolabile hemolysin (LDH) is a virulence factor excreted by Vibrio parahaemolyticus, a marine bacterium that causes important losses in shrimp farming. In this study, the function of LDH was investigated through its inhibition by metal ions (Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺) and chemical modification reagents: β-mercaptoethanol (βME), phenylmethylsulfonyl fluoride (PMSF) and diethyl pyrocarbonate (DEPC). LDH was expressed in the Escherichia coli strain BL-21, purified under denaturing conditions, and the enzymatic activity was evaluated. Cu²⁺, Ni²⁺, Co²⁺ and Ca²⁺ at 1 mmol/L inhibited the LDH esterase activity by 20–95%, while Mg²⁺ and Mn²⁺ slightly increased its activity. Additionally, PMSF and DEPC at 1 mmol/L inhibited the enzymatic activity by 40% and 80%, respectively. Dose-response analysis showed that DEPC was the best-evaluated inhibitor (IC₅₀ = 0.082 mmol/L), followed by Cu²⁺ > Co²⁺ > Ni²⁺ and PMSF (IC₅₀ = 0.146–1.5 mmol/L). Multiple sequence alignment of LDH of V. parahaemolyticus against other Vibrio species showed that LDH has well-conserved GDSL and SGNH motifs, characteristic of the hydrolase/esterase superfamily. Additionally, the homology model showed that the conserved catalytic triad His-Ser-Asp was in the LDH active site. Our results showed that the enzymatic activity of LDH from V. parahaemolyticus was modulated by metal ions and chemical modification, which could be related to the interaction with catalytic amino acid residues such as Ser153 and/or His 393.     

The PRB-dependent FOXO1/IGFBP-1 axis is essential for progestin to inhibit endometrial epithelial growth

Progestin inhibits the growth of normal and cancerous endometria via the progesterone receptor (PR), but the distinct functions and signalings of PR subtypes have not been fully understood. The aim of the present study was to dissect the key pathways of progestin to inhibit endometrial epithelial growth. Immortalized endometrial epithelial cells (EM-E6/E7/TERT) with stable PRA or PRB expression were established and used for the experiments. In vitro growth inhibition by progestin was mainly observed in EM-E6/E7/TERT cells with PRB rather than those with PRA. RT-PCR assay confirmed that FOXO1, a key gene for progestin action, was up-regulated by progestin in a PRB-dependent manner. cDNA microarray analysis identified IGFBP-1, which contains FOXO1 binding sites on its promoter, to be induced by medroxyprogesterone acetate (MPA) in EM-E6/E7/TERT cells with PRB but not with PRA. siRNA knockdown of FOXO1 disturbed the induction of IGFBP-1 by MPA, while IGFBP-1 knockdown showed no effect on MPA-induced FOXO1 expression, indicating that FOXO1 is an upstream regulator of IGFBP-1. Luciferase reporter assays showed that MPA activated the IGFBP-1 promoter, which was cancelled by FOXO1 knockdown. Chromatin immunoprecipitation assay confirmed the in vivo binding of FOXO1 to the core promoter of IGFBP-1. IGFBP-1 knockdown significantly attenuated the growth inhibitory effects of MPA. The FOXO1/IGFBP-1 axis is essential for PRB-dependent growth inhibition of endometrial epithelial cells, offering a potential therapeutic clue to enhance the progestin effect.     

多囊卵巢综合征患者血清抑制素B水平的分析

目的：探讨抑制素B（inhibin,INH-B）水平在多囊卵巢综合征（PCOS）患者血清中的变化及其与体重指数（BMI）的关系。方法：筛选PCOS患者40例,根据体重指数（BMI）分为肥胖组和非肥胖组并检测血清中的抑制素B（INH-B）、胰岛素生长因子-I（IGF-I）、空腹胰岛素（In）、瘦素（leptin）、黄体生成素（LH）、卵泡刺激素（FSH）、人体催乳素（PRL）、雌二醇（E2）和睾酮（T）,另取40例排卵正常、无怀孕妇女做对照分析。结果：PCOS患者肥胖组leptin、In、LH、T水平明显高于非肥胖组,INH-B、IGF水平则明显低于非肥胖组,差异有统计学意义（P〈0.05）;且肥胖组的LH与INH-B呈负相关（r=-0.735,P〈0.05）,非肥胖组的LH与INH-B无明显相关性。非肥胖组INH-B、IGF、LH、T水平明显高于对照组,差异有统计学意义（P〈0.05）。结论：INH-B与多囊卵巢综合征（PCOS）发生有关,且作为PCOS特征的肥胖又影响着INH-B的作用和水平。     

蛇葡萄素在大鼠肝微粒体中的代谢动力学及药用辅料对其抑制作用的研究

目的 研究蛇葡萄素在大鼠肝微粒体的代谢规律及药用辅料对其代谢的影响。方法 建立UPLC-MS/MS方法学体系,通过检测代谢反应体系的蛇葡萄素剩余浓度进行体外代谢反应条件的筛选和代谢规律的评价。结果 反应体系的孵育时间、肝微粒体浓度及蛇葡萄素浓度均对代谢产生影响,大鼠肝细胞色素P450亚酶CYP3A、CYP1A1/2和CYP2E1对蛇葡萄素代谢起主要作用。药用辅料对蛇葡萄素代谢的抑制作用呈剂量依赖性,其中聚氧乙烯氢化蓖麻油40、吐温80、聚维酮K30、羟丙基β环糊精、普朗尼克F68以混合竞争模式显著抑制蛇葡萄素的代谢。结论 这些药用辅料有望通过抑制代谢作用来提高蛇葡萄素的口服生物利用度。