catechol-O-methyltransferase Activity Research Articles

The Catechol-O-methyltransferase Val(108/158)Met Genetic Polymorphism cannot be Recommended as a Biomarker for the Prediction of Venlafaxine Efficacy in Patients Treated in Psychiatric Settings.

The antidepressant venlafaxine is known to increase the turnover of cerebral monoamines, which are catabolized by the catechol-O-methyltransferase (COMT). The COMT (Val(108/158)Met, rs4680) genetic polymorphism affects the cerebral COMT activity. But whether this genetic polymorphism is associated with response to venlafaxine remains unclear. We assessed the impact of the COMT Val(108/158)Met, rs4680 genetic polymorphism on the efficacy of venlafaxine in depressed patients. This study was nested in the METADAP cohort, a real-world naturalistic treatment study in psychiatric settings. A total of 206 Caucasian patients with a unipolar major depressive episode (DSM-IVTR) treated with venlafaxine and evaluated with the Hamilton Depression Rating Scale (HDRS) were studied. One hundred and eighty patients were genotyped for the COMT Val(108/158)Met, rs4680 genetic polymorphism and classified into three genotype subgroups: Val/Val, Val/Met and Met/Met. The COMT genotype was the explanatory variable, and the variables to be explained were HDRS score, HDRS score improvement over time, response rate and remission rate. Venlafaxine had a trend to higher efficacy in the Val/Val patients as compared to Met/Met carriers, as shown by the HDRS score improvement after 3months of treatment, but this result was not significant in mixed models [Val/Val: 59.78% (±22.4); Val/Met: 51.64% (±26.3); Met/Met: 39.52% (±27.6)]. The percentage of responders and remitters after 3months of treatment was not significantly different in the three genotype groups, although coherent trends were shown. The COMT Val(108/158)Met, rs4680 genetic polymorphism cannot be recommended as a biomarker for the prediction of venlafaxine efficacy in patients treated in psychiatric settings.

A single- and multiple-dose study to investigate the pharmacokinetics and pharmacodynamics of opicapone, a novel COMT inhibitor, in rat

Opicapone is a novel catechol-O-methyltransferase (COMT) inhibitor that emerged to fulfil the need of a safer and more efficacious COMT inhibitor. The present study was carried out in order to assess and compare the pharmacokinetics and pharmacodynamics (COMT inhibition) of opicapone after single and multiple oral administrations (30 mg/kg) to Wistar rats. For this purpose, at predefined time points up to 72 h post-dosing, blood, liver and kidneys were collected and, then, the concentrations of opicapone and its active metabolite (BIA 9–1079) were determined in plasma and in liver and kidney tissues, as well as the erythrocyte, liver and kidney COMT activity. No systemic, renal or hepatic accumulation of opicapone was observed following repeated administration. Furthermore, the tissue-systemic exposure relationships to opicapone suggested a low drug exposure in the liver and kidneys. After single-dosing, COMT inhibition profiles were reasonably comparable in all the studied matrices; although similar results were found after multiple-dosing, a higher degree of inhibition was observed, indicating a continuous peripheral COMT inhibition when opicapone is administered once-daily. Despite having a short elimination half-life (≤2.94 h), opicapone showed a strong and long-lasting COMT inhibition in both studies, since more than 50% of the COMT activity was still inhibited at 24 h post-dosing.

An Optimized Two-Photon Fluorescent Probe for Biological Sensing and Imaging of Catechol-O-Methyltransferase.

A practical two-photon fluorescent probe was developed for highly sensitive and selective sensing of the activities of catechol-O-methyltransferase (COMT) in complex biological samples. To this end, a series of 3-substituted 7,8-dihydroxycoumarins were designed and synthesized. Among them, 3-BTD displayed the best combination of selectivity, sensitivity, reactivity, and fluorescence response following COMT-catalyzed 8-O-methylation. The newly developed two-photon fluorescent probe 3-BTD can be used for determining the activities of COMT in complex biological samples and bio-imaging of endogenous COMT in living cells and tissue slices with good cell permeability, low cytotoxicity, and high imaging resolution. All these findings suggest that 3-BTD holds great promise for developing therapeutic molecules that target COMT, as well as for exploring COMT-associated biological processes and its biological functions in living systems. Furthermore, the strategy also sheds new light on the development of fluorescent probes for other conjugative enzymes.

Remote memories are enhanced by COMT activity through dysregulation of the endocannabinoid system in the prefrontal cortex.

The prefrontal cortex (PFC) is a crucial hub for the flexible modulation of recent memories (executive functions) as well as for the stable organization of remote memories. Dopamine in the PFC is implicated in both these processes and genetic variants affecting its neurotransmission might control the unique balance between cognitive stability and flexibility present in each individual. Functional genetic variants in the catechol-O-methyltransferase (COMT) gene result in a different catabolism of dopamine in the PFC. However, despite the established role played by COMT genetic variation in executive functions, its impact on remote memory formation and recall is still poorly explored. Here we report that transgenic mice overexpressing the human COMT-Val gene (COMT-Val-tg) present exaggerated remote memories (>50 days) while having unaltered recent memories (<24 h). COMT selectively and reversibly modulated the recall of remote memories as silencing COMT Val overexpression starting from 30 days after the initial aversive conditioning normalized remote memories. COMT genetic overactivity produced a selective overdrive of the endocannabinoid system within the PFC, but not in the striatum and hippocampus, which was associated with enhanced remote memories. Indeed, acute pharmacological blockade of CB1 receptors was sufficient to rescue the altered remote memory recall in COMT-Val-tg mice and increased PFC dopamine levels. These results demonstrate that COMT genetic variations modulate the retrieval of remote memories through the dysregulation of the endocannabinoid system in the PFC.

Delayed O-methylation of l-DOPA in MB-COMT-deficient mice after oral administration of l-DOPA and carbidopa

1. Catechol-O-methyltransferase (COMT) is involved in the O-methylation of l-DOPA, dopamine, and other catechols. The enzyme is expressed in two isoforms: soluble (S-COMT), which resides in the cytoplasm, and membrane-bound (MB-COMT), which is anchored to intracellular membranes.2. To obtain specific information on the functions of COMT isoforms, we studied how a complete MB-COMT deficiency affects the total COMT activity in the body, peripheral l-DOPA levels, and metabolism after l-DOPA (10 mg kg−1) plus carbidopa (30 mg kg−1) administration by gastric tube in wild-type (WT) and MB-COMT-deficient mice. l-DOPA and 3-O-methyl-l-DOPA (3-OMD) levels were assayed in plasma, duodenum, and liver.3. We showed that the selective lack of MB-COMT did not alter the total COMT activity, COMT enzyme kinetics, l-DOPA levels, or the total O-methylation of l-DOPA but delayed production of 3-OMD in plasma and peripheral tissues.

A Novel Sensitive Method to Measure Catechol-O-Methyltransferase Activity Unravels the Presence of This Activity in Extracellular Vesicles Released by Rat Hepatocytes.

There is a clear need for drug treatments to be selected according to the characteristics of an individual patient, in order to improve efficacy and reduce the number and severity of adverse drug reactions. One of the main enzymes to take into account in pharmacogenomics is catechol O-methyltransferase (COMT), which catalyzes the transfer of a methyl group from S-adenosylmethionine to catechols and catecholamines, like the neurotransmitters dopamine, epinephrine, and norepinephrine. Although, most of this enzyme is associated to intracellular vesicles, recently it has also been detected in extracellular vesicles secreted by hepatocytes and in serum circulating vesicles. COMT has implications in many neurological and psychiatric disorders like Parkinson's disease, chronic fatigue, pain response, schizophrenia, and bipolar disorders. Remarkably, genetic variations of COMT affect its activity and are associated to various human disorders from psychiatric diseases to estrogen-induced cancers. Consequently, the establishment of new methods to evaluate COMT activity is an important aspect to investigate the biology of this drug-metabolizing enzyme. Herein, we have developed a sensitive and selective method to determine COMT activity. We first optimized the activity in rat liver incubated with two different substrates; norepinephrine and dopamine. The enzymatically formed products (normetanephrine and 3-methoxytyramine, respectively) were extracted by solid-phase extraction using weak cation exchange cartridges, chromatographically separated, and detected and quantified using a mass spectrometer. The range of quantitation for both products was from 0.005 to 25 μg/mL. This methodology offers acceptable recovery for both enzymatic products (≥75%) and good accuracy and precision (≤15%). The lower limit of quantifications were 0.01 and 0.005 μM for 3-methoxytyramine and normetanephrine, respectively. Importantly, this sensitive assay was able to detect the presence of COMT activity in extracellular vesicles secreted by hepatocytes supporting a potential role of these vesicles in catecholamines and catecholestrogens metabolisms. In addition, the presence of COMT activity in extracellular vesicles opens new possibilities to develop tools to evaluate personalized drug response in a low invasive manner.

Common functional pain syndromes

### Key points When a patient presents with pain of no obvious organic origin, they are often labelled as having ‘functional’ pain. The exact diagnosis is derived from the organ system displaying the predominant symptoms e.g. musculoskeletal pain in fibromyalgia (FM) or visceral pain in irritable bowel syndrome (IBS). The worldwide prevalence of all functional pain syndromes (FPS) is 15–20%. World Health Organization (WHO) surveys reveal that ∼10% of primary care patients develop a chronic pain condition within 12 months of initial registration. Of these, at least 50% continue to have symptoms beyond 1 yr. FPS cause enormous economic burden on society with concurrent ramifications for the individual's family in particular and society in general. FM alone has been estimated to cost around £4000 per patient per year. There has been a paradigm shift in the understanding of FPS. The old model of multiple discrete chronic pain conditions is being replaced by a more overarching, although no less complex, state of central sensitivity syndrome (CSS). Evidence is being accrued that FPS represent the phenotypic output of a complex interplay between genetic susceptibility, gene–environment interactions, and environmental triggers. Four common FPS will be reviewed in this article: FM, IBS, temporomandibular dysfunction (TMD), and chronic cardiac chest pain (CCCP). The pathophysiology and management of each will be examined and the case presented for a shared underlying mechanism called CSS. Once this new mechanism is adopted more widely, it will allow for future novel management options to be …

Catechins Variously Affect Activities of Conjugation Enzymes in Proliferating and Differentiated Caco-2 Cells.

The knowledge of processes in intestinal cells is essential, as most xenobiotics come into contact with the small intestine first. Caco-2 cells are human colorectal adenocarcinoma that once differentiated, exhibit enterocyte-like characteristics. Our study compares activities and expressions of important conjugation enzymes and their modulation by green tea extract (GTE) and epigallocatechin gallate (EGCG) using both proliferating (P) and differentiated (D) caco-2 cells. The mRNA levels of the main conjugation enzymes were significantly elevated after the differentiation of Caco-2 cells. However, no increase in conjugation enzymes’ activities in differentiated cells was detected in comparison to proliferating ones. GTE/EGCG treatment did not affect the mRNA levels of any of the conjugation enzymes tested in either type of cells. Concerning conjugation enzymes activities, GTE/EGCG treatment elevated glutathione S-transferase (GST) activity by approx. 30% and inhibited catechol-O-methyltransferase (COMT) activity by approx. 20% in differentiated cells. On the other hand, GTE as well as EGCG treatment did not significantly affect the activities of conjugation enzymes in proliferating cells. Administration of GTE/EGCG mediated only mild changes of GST and COMT activities in enterocyte-like cells, indicating a low risk of GTE/EGCG interactions with concomitantly administered drugs. However, a considerable chemo-protective effect of GTE via the pronounced induction of detoxifying enzymes cannot be expected as well.

Genotype-Dependent Effects of COMT Inhibition on Cognitive Function in a Highly Specific, Novel Mouse Model of Altered COMT Activity.

Catechol-O-methyltransferase (COMT) modulates dopamine levels in the prefrontal cortex. The human gene contains a polymorphism (Val158Met) that alters enzyme activity and influences PFC function. It has also been linked with cognition and anxiety, but the findings are mixed. We therefore developed a novel mouse model of altered COMT activity. The human Met allele was introduced into the native mouse COMT gene to produce COMT-Met mice, which were compared with their wild-type littermates. The model proved highly specific: COMT-Met mice had reductions in COMT abundance and activity, compared with wild-type mice, explicitly in the absence of off-target changes in the expression of other genes. Despite robust alterations in dopamine metabolism, we found only subtle changes on certain cognitive tasks under baseline conditions (eg, increased spatial novelty preference in COMT-Met mice vs wild-type mice). However, genotype differences emerged after administration of the COMT inhibitor tolcapone: performance of wild-type mice, but not COMT-Met mice, was improved on the 5-choice serial reaction time task after tolcapone administration. There were no changes in anxiety-related behaviors in the tests that we used. Our findings are convergent with human studies of the Val158Met polymorphism, and suggest that COMT's effects are most prominent when the dopamine system is challenged. Finally, they demonstrate the importance of considering COMT genotype when examining the therapeutic potential of COMT inhibitors.

A highly selective fluorescent probe for sensing activities of catechol-O-methyltransferase in complex biological samples

Catechol-O-methyltransferase (COMT), one of the most important phase II drug metabolizing enzymes, plays important roles in the metabolism of endogenous and xenobiotic catechols. In this study, a highly selective fluorescent probe for sensing activities of catechol-O-methyltransferase in complex biological samples was discovered and well characterized. Under physiological conditions, COMT selectively catalyzes the conversion of the probe (7,8-dihydroxy-4-methylcoumarin, DHMC) to 7-hydroxy-8-methoxy-4-methylcoumarin (HMMC), which brings a strong turn-on fluorescence signal at 520nm. The probe substrate has been used for monitoring the real activities of COMT in complex biological samples, as well as for rapid screening of potential COMT inhibitors which are useful in the treatment of Parkinson's diseases Furthermore, the probe has been successfully used to monitor endogenous COMT in living cells for the first time, and the results demonstrate that DHMC is cell membrane permeable and low toxic to the cells. All these features of DHMC suggested that this probe holds great promise for COMT-related regulation and inhibition assays in drug discovery, as well as for further investigation on the biological functions of COMT in living cells.

Anti-stress Activity of Ocimum sanctum: Possible Effects on Hypothalamic-Pituitary-Adrenal Axis.

The present study investigated anti-stress potential of Ocimum sanctum in chronic variable stress (CVS) paradigm. Further, the possible mechanism of anti-stress was explored in vitro using cell and cell-free assays. Rats were administered O. sanctum followed by CVS regimen for a period of 16 days. On days 4, 8, 12, and 16, body weight and immobility time in forced swim test were measured. In addition, the possible inhibitory effect of O. sanctum and ursolic acid on cortisol release and CRHR1 receptor activity were studied in cell-based assays, while inhibitory effects on 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and catechol-O-methyltransferase (COMT) were studied in cell-free assays. CVS group demonstrated less body weight gain and higher immobility time than O. sanctum administered groups, while oral administration of O. sanctum significantly increased body weight gain and decreased the immobility time. Further, O. sanctum and its constituents inhibited cortisol release and exhibited a significant CRHR1 receptor antagonist activity. Also, they had specific inhibitory activity towards 11β-HSD1 and COMT activity. Thus, O. sanctum was found to be effective in the management of stress effects, and anti-stress activity could be due to inhibition of cortisol release, blocking CRHR1 receptor, and inhibiting 11β-HSD1 and COMT activities. Copyright © 2016 John Wiley & Sons, Ltd.

Yokukansan, a Traditional Japanese Medicine, Enhances the L-DOPA-Induced Rotational Response in 6-Hydroxydopamine-Lesioned Rats: Possible Inhibition of COMT.

The aim of the present study was to investigate the effects of the traditional Japanese medicine yokukansan (YKS) on the function of dopamine (DA) in the rat nigrostriatal system. Unilateral 6-hydroxydopamine lesions were produced in the rat nigrostriatal system. Despite a marked loss in the striatal immunoreactivity of tyrosine hydroxylase on the lesion side, striatal serotonin (5-HT) immunoreactivity was not affected. Treatment using L-3,4-dihydroxyphenylalanine (L-DOPA) in conjunction with benserazide for 15 d induced abnormal involuntary movements (AIMs) such as locomotive (rotational response), axial, forelimb, and orolingual movements in the lesioned rats. The L-DOPA-induced locomotive and axial, but not forelimb and orolingual, AIMs were significantly increased and prolonged by the pre-administration of YKS. We next investigated the effects of YKS on the production of DA from L-DOPA in 5-HT synthetic RIN 14B cells. RIN 14B cells produced DA and its metabolite, 3-methoxytyramine (3-MT), following L-DOPA treatment. YKS significantly augmented DA production and inhibited its metabolism to 3-MT in a manner similar to the catechol-O-methyltransferase (COMT) inhibitor entacapone. YKS and some alkaloids (corynoxeine: CX, geissoschizine methyl ether: GM) in Uncaria hook, a constituent herb of YKS, also inhibited COMT activity, indicating that the augmenting effect of YKS on L-DOPA-induced DA production in 5-HT synthetic cells was due to the inhibition of COMT by CX and GM. Our results suggest that YKS facilitates the DA supplemental effect of L-DOPA, and that COMT inhibition by CX and GM contributes, at least in part, to the effects of YKS.

Abstract 14360: Gene Transfer of Sarco/Endoplasmic reticulum Ca2+-ATPase 2a Restores Pulmonary Artery Endothelial Catechol-O-Methyltransferase Activity to Decrease Norepinephrine Levels in Pulmonary Hypertension

Elevated levels of norepinephrine (NE) may occur in pulmonary hypertension (PH), in part, when activity of catechol- O -methyltransferase (COMT) is decreased. COMT is expressed by pulmonary artery endothelial cells (PAEC), degrades NE, and is negatively regulated by aldosterone (ALDO) and cytosolic Ca 2+ . Expression of the cardiac isoform of the sarco/endoplasmic Ca 2+ -ATPase (SERCA2a) modulates ALDO and cytosolic Ca 2+ and is downregulated in pulmonary arteries in PH. We hypothesized that gene transfer of SERCA2a to pulmonary arteries would prevent the decrease in COMT activity and lower NE levels. Accordingly, human PAEC were infected with an adenovirus encoding SERCA2a to increase expression 4.2-fold (p&lt;0.01) or control virus and exposed to ALDO (10 -7 mol/L), which decreases COMT activity by 59.2 ± 6.2% (p&lt;0.01). Compared to controls, SERCA2a overexpression in PAEC had no effect on COMT mRNA or protein levels but increased COMT activity by 148.8 ± 14.5% (p&lt;0.01) by decreasing cytosolic Ca 2+ levels by 38.2 ± 6.7% (p&lt;0.05). This resulted in a decrease in NE levels in the medium (229.4 ± 20.6 vs. 139.9 ± 14.8 vs. pg/mg protein, p&lt;0.01) and collagen I expression. To examine the in vivo relevance of SERCA2a gene transfer on COMT activity, the rat monocrotaline model of PH was treated with inhaled adeno-associated virus 1 carrying SERCA2a (AAV1.SERCA2a). There was no difference in COMT expression in AAVI.SERCA2a-treated or saline control PH-rats; however, lung COMT activity was increased 139.8 ± 8.2% (p&lt;0.01) while lung levels of NE (366.7 ± 38.6 vs. 504 ± 30.2 pg/ml/mg, p&lt;0.01), serum ALDO, and pulmonary artery collagen 1 were decreased by AAV1.SERCA2a. In the pig pulmonary vein banding model of PH, inhaled AAV1.SERCA2a gene therapy decreased mean pulmonary artery pressure (54 ± 20 vs. 29 ± 5 mmHg, p&lt;0.03); increased COMT activity by 121.1 ± 6.2% (p&lt;0.05); and decreased levels of ALDO by 43.3 ± 4.6% (p&lt;0.03), NE by 43.3 ± 4.6% (p&lt;0.03), and collagen I in remodeled vessels. Taken together, these data indicate that gene therapy with inhaled AAV1.SERCA2a increases COMT activity by decreasing intracellular Ca 2+ , thereby decreasing NE levels. This extends the actions of SERCA2a beyond pulmonary vascular remodeling in PH to modulating levels of circulating catecholamines.

Effect of 3 Single-Dose Regimens of Opicapone on Levodopa Pharmacokinetics, Catechol-O-Methyltransferase Activity and Motor Response in Patients With Parkinson Disease.

This study determined the effects of single doses of opicapone (OPC), a novel third-generation catechol-O-methyltransferase (COMT) inhibitor, on levodopa and 3-O-methyl-levodopa (3-OMD) pharmacokinetics (PK), COMT activity and motor fluctuations in patients with Parkinson disease (PD). Subjects received, in a double-blind manner, 25, 50, and 100 mg OPC or placebo (PLC) in 4 separate treatment periods. The washout period between doses was at least 10 days. During each period, the OPC/PLC capsules were to be coadministered with the morning dose of 100/25 mg levodopa/carbidopa (LC) or levodopa/benserazide (LB) on day 3. In relation to PLC, levodopa exposure increased 3.7%, 16.4%, and 34.8% following 25, 50, or 100 mg OPC, respectively. Maximum S-COMT inhibition (Emax ) ranged from 67.8% (25 mg OPC) to 100% (100 mg OPC). Peak and extent of S-COMT inhibition were dose-dependent. Maximum decrease in the plasma 3-OMD was observed following administration of 100 mg OPC. Opicapone administered concomitantly with standard-release 100/25 mg LC or LB improved motor performance. Treatments were generally well tolerated and safe. It was concluded that OPC is a new COMT inhibitor that significantly decreased COMT activity and increased systemic exposure to levodopa in PD patients with motor fluctuations.

Opicapone pharmacokinetics and pharmacodynamics comparison between healthy Japanese and matched white subjects.

Opicapone (OPC) is a novel third-generation catechol-O-methyltransferase (COMT) inhibitor. This randomized, double-blind, parallel, placebo-controlled and multiple ascending dose study in 3 sequential groups of up to 38 (19 Japanese plus 19 white subjects) aimed to compare the pharmacokinetics (PK) and pharmacodynamics (PD; COMT activity) of opicapone between healthy Japanese and matched white subjects. Enrolled subjects received a once-daily morning administration of OPC (5, 25, or 50 mg) or placebo for 10 days, with plasma and urine concentrations of opicapone and its metabolites measured up to 144 hours postdose, including S-COMT activity. Geometric mean ratios (GMRs) and confidence intervals (95%CIs) for the main PK and PD parameters of OPC were evaluated between populations. Both the PK and PD of OPC were similar in the Japanese and white populations. Overall, only minimal differences were noted between the 2 populations, which were not deemed to be statistically significant. When both populations were separated based on their COMT genotype, the observed PK and PD differences were also negligible. In conclusion, the PK and PD profiles of OPC were similar in the Japanese and white populations. Thus, ethnicity and COMT polymorphisms had no significant impact on the OPC PK and PD in the conditions of the study.

Fetal Val108/158Met catechol-O-methyltransferase (COMT) polymorphism and placental COMT activity are associated with the development of preeclampsia

To evaluate the association between fetal and maternal catechol-O-methyltransferase (COMT) Val158Met and methyl tetrahydrofolate reductase (MTHFR) C677T functional polymorphisms and preeclampsia, examining its influence on placental COMT and in maternal 2-methoxyestradiol (2-ME) plasma levels. Prospective case-control study. University hospital. A total of 53 preeclamptic and 72 normal pregnant women. Maternal and cord blood samples and placental tissue samples were obtained. Maternal and fetal COMT and MTHFR polymorphisms were genotyped. Maternal plasma 2-ME and homocysteine levels, and expression and activity of placental COMT were measured. The odds ratio for the risk of preeclampsia for fetal COMT Met/Met was 3.22, and it increased to 8.65 when associated with fetal MTHFR TT. Placental COMT activity and expression were influenced by genotype, but COMT activity in preeclamptic placentas did not differ from control pregnancies. There was no association between any genotypes and maternal 2-ME. Homocysteine levels were higher in women with preeclampsia than in normal pregnancies, and were inversely correlated with 2-ME plasma levels, indicating that its altered metabolism may lower COMT activity in vivo. Fetal Met-Met COMT genotype reduces COMT placental expression and activity in vitro and increases preeclampsia, risk but it does not explain the difference in maternal 2-ME levels between preeclamptic and normal pregnancies. However, the preeclamptic patients had elevated homocysteine levels that correlated inversely with 2-ME, indicating that an altered methionine-homocysteine metabolism may contribute to reduce COMT activity in vivo and explain the decreased levels of 2-ME in preeclamptic women.

Analytical Methods for the Measurement of Catechol-O-Methyltransferase Activity in Animal Tissues

Catechol-O-methyltransferase (COMT) catalyzes the transfer of a methyl group from Sadenosyl- L-methionine to catechols. Because COMT has an important role in the metabolism of catecholamines, catechol estrogens, and drugs with a catechol moiety such as L-Dopa, measurement of COMT activity in several tissues is important. Furthermore, COMT inhibitors are used clinically in the treatment of Parkinson’s disease, and activation of COMT can control high blood pressure. Hence, high-throughput screening methods for COMT inhibitors and activators are needed. In this methodological article, two analytical methods for the measurement of COMT activity are described. One is very sensitive, and the other is a rapid assay. Norepinephrine, an endogenous compound was used as the substrate, and the enzymatic product (normetanephrine) was quantified with highperformance liquid chromatography-fluorescence or chemiluminescence detection. Keywords: Chemiluminescence, enzyme, fluorescence, HPLC, Parkinson’s disease, substrate.

COMT gene locus: new functional variants.

Catechol-O-methyltransferase (COMT) metabolizes catecholaminergic neurotransmitters. Numerous studies have linked COMT to pivotal brain functions such as mood, cognition, response to stress, and pain. Both nociception and risk of clinical pain have been associated with COMT genetic variants, and this association was shown to be mediated through adrenergic pathways. Here, we show that association studies between COMT polymorphic markers and pain phenotypes in 2 independent cohorts identified a functional marker, rs165774, situated in the 3' untranslated region of a newfound splice variant, (a)-COMT. Sequence comparisons showed that the (a)-COMT transcript is highly conserved in primates, and deep sequencing data demonstrated that (a)-COMT is expressed across several human tissues, including the brain. In silico analyses showed that the (a)-COMT enzyme features a distinct C-terminus structure, capable of stabilizing substrates in its active site. In vitro experiments demonstrated not only that (a)-COMT is catalytically active but also that it displays unique substrate specificity, exhibiting enzymatic activity with dopamine but not epinephrine. They also established that the pain-protective A allele of rs165774 coincides with lower COMT activity, suggesting contribution to decreased pain sensitivity through increased dopaminergic rather than decreased adrenergic tone, characteristic of reference isoforms. Our results provide evidence for an essential role of the (a)-COMT isoform in nociceptive signaling and suggest that genetic variations in (a)-COMT isoforms may contribute to individual variability in pain phenotypes.

Inhibition of catechol-O-methyl transferase (COMT) by tolcapone restores reductions in microtubule-associated protein 2 (MAP2) and synaptophysin (SYP) following exposure of neuronal cells to neurotropic HIV.

This investigation aimed to assess whether inhibition of cathecol-O-methyl transferase (COMT) by tolcapone could provide neuroprotection against HIV-associated neurodegenerative effects. This study was conducted based on a previous work, which showed that a single nucleotide polymorphism (SNP) at position 158 (val158met) in COMT, resulted in 40 % lower COMT activity. Importantly, this reduction confers a protective effect against HIV-associated neurocognitive disorders (HAND), which have been linked to HIV-associated brain changes. SH-SY5Y-differentiated neurons were exposed to macrophage-propagated HIV (neurotropic MACS2-Br strain) in the presence or absence of tolcapone for 6 days. RNA was extracted, and qPCR was performed using Qiagen RT2 custom array consisting of genes for neuronal and synaptic integrity, COMT and pro-inflammatory markers. Immunofluorescence was conducted to validate the gene expression changes at the protein level. Our findings demonstrated that HIV significantly increased the messenger RNA (mRNA) expression of COMT while reducing the expression of microtubule-associated protein 2 (MAP2) (p = 0.0015) and synaptophysin (SYP) (p = 0.012) compared to control. A concomitant exposure of tolcapone ameliorated the perturbed expression of MAP2 (p = 0.009) and COMT (p = 0.024) associated with HIV. Immunofluorescence revealed a trend reduction of SYP and MAP2 with exposure to HIV and that concomitant exposure of tolcapone increased SYP (p = 0.016) compared to HIV alone. Our findings demonstrated in vitro that inhibition of COMT can ameliorate HIV-associated neurodegenerative changes that resulted in the decreased expression of the structural and synaptic components MAP2 and SYP. As HIV-associated dendritic and synaptic damage are contributors to HAND, inhibition of COMT may represent a potential strategy for attenuating or preventing some of the symptoms of HAND.

Effect of intracerebral hydroxytyrosol and its nitroderivatives on striatal dopamine metabolism: A study by in vivo microdialysis.

The natural phenolic oil compound hydroxytyrosol (HTy) is widely studied because of its antioxidant and neuroprotective properties. Nitroderivatives of HTy have been studied in order to evaluate their putative effects on catechol-O-methyltransferase (COMT) activity. To study its effect on dopamine metabolism, nitrohydroxytyrosol and its lipophilic derivatives (nitrohydroxytyrosyl acetate and ethyl nitrohydroxytyrosyl ether), were administered into the rat corpus striatum through a microdialysis probe. Other catechols (HTy and the known COMT inhibitor Ro 41-0960) were also studied for comparison. The olive oil phenolic compounds (nitroderivatives and HTy) increased extracellular levels of 3,4-dihydroxyphenylacetic acid during the perfusion with similar maximum values to that of Ro 41-0960 when comparing to basal dialysate levels (approximately 140%). None of the compound series produced a decrease in the homovanillic acid extracellular levels below 75%. Among all novel compounds studied, both lipophilic nitrocatechols (nitrohydroxytyrosyl acetate and ethyl nitrohydroxytyrosyl ether) showed a long-acting effect over time once the perfusion through the microdialysis probe ended. In accordance with the actual design of novel COMT inhibitors with a long profile, our results suggest a certain influence of the side chain substituent on the COMT activity that could provide new lipophilic COMT inhibitors.