Prospecting for new catechol-O-methyltransferase (COMT) inhibitors as a potential treatment for Parkinson's disease: a study by molecular dynamics and structure-based virtual screening.

Parkinson's disease (PD) is a neurodegenerative, chronic, and progressive disease, common in the elderly. The catechol-O-methyltransferase (COMT) is a monomeric enzyme involved in dopamine (DA) degradation, the neurotransmitter in deficit in patients with PD. The reference treatment of PD consists of levodopa (L-dopa) administration, which is the precursor of DA. The inhibition of COMT is an adjuvant treatment in PD since it keeps DA levels constant. The goal of this study was to identify drug candidates capable of inhibiting COMT for the treatment of PD and identify important fragments of these molecules. Initially, we analyzed the flexibility of COMT and defined its main conformations in solution regarding the absence (system I) and presence of the S-adenosyl-L-methionine (SAM) cofactor (system II) through molecular dynamics (MD) simulations. Two regions in these structures were selected for molecular docking, firstly the entire cavity where the cofactor and substrates are bound and secondly the specific biding region of the enzyme substrates. Based on the conformations of the MD, the virtual screening (VS) was performed against FDA Approved and Zinc Natural Products databases aiming at the selection of the best compounds. Subsequently, the absorption, distribution, metabolization, excretion, and toxicity (ADMET) properties, as well as drug-score and drug-likeness indexes of the most promising compounds were analyzed. After a detailed analysis of the compounds selected by structure-based VS, it was possible to highlight the fragments most frequently involved in their stability: 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole, 9H-Benz(c)indole(3,2,1-ij)(1,5)naphthyridin-9-one and (10R,13S)-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17dodecahydrocyclopenta[a]phenanthren-3-one. The identification of these potential fragments is essential for the prospection of more specific inhibitors against COMT using the technique of Fragment-based lead discovery (FBLD). Besides, this study allowed us to identify the potential COMT inhibitors through a complete understanding of molecular-level interactions based on the flexibility of this protein.Communicated by Ramaswamy H. Sarma.

Entacapone improves saccharification without affecting lignin and maize growth: An in silico, in vitro, and in vivo approach.

Caffeate 3-O-methyltransferase (COMT) catalyzes the methylation of the 3-hydroxyl group of caffeate to produce ferulate, an important precursor of the lignin biosynthesis. As a crucial drawback for biofuel production, lignin limits the enzymatic hydrolysis of polysaccharides to result in fermentable sugars. We hypothesized that a controlled inhibition of maize COMT can be an efficient approach to reduce ferulate and lignin, thus improving the saccharification process. First, we applied in silico techniques to prospect potential inhibitors of ZmaysCOMT, and the nitrocatechol entacapone was selected. Second, in vitro assays confirmed the inhibitory effect of entacapone on maize COMT. Finally, in vivo experiments revealed that entacapone reduced the contents of cell-wall-esterified hydroxycinnamates and increased saccharification of stems (18%) and leaves (70%), without negatively affecting maize growth and lignin biosynthesis. This non-genetically modified approach can be an alternative strategy to facilitate the enzymatic hydrolysis of biomass polysaccharides and increase saccharification for bioethanol production.

Respuesta ultrarrápida de tecnología sanitaria: opicapona / Ultrafast response of healthcare technology: opicapona

INTRODUCCIÓN: Levodopa es el tratamiento más efectivo para el manejo de EP. Sin embargo, muchos pacientes que reciben tratamiento prolongado con dicha droga desarrollan fluctuaciones musculares y disquinesia. Los pacientes reportan que presentan varias horas por día en estado off y esto afecta su calidad de vida. Por este motivo, el control de las fluctuaciones motoras es un objetivo importante en muchos pacientes. Las fluctuaciones motoras de final de dosis se asocian a la vida media corta del tratamiento con levodopa vía oral (60-90 minutos aproximadamente). TECNOLOGÍA: Opicapona: Opicapona es un inhibidor periférico, selectivo y reversible de la catecol-Ometiltransferasa (COMT), dotado de una unión de alta afinidad que se traduce en una tasa de disociación del complejo lenta y una duración de acción in vivo larga y constante (>24 horas). En presencia de un inhibidor de la DOPA descarboxilasa (IDDC), la COMT se convierte en la principal enzima metabolizante de la levodopa, catalizando su conversión en 3-O-metildopa (3-OMD) en el cerebro y la periferia. En pacientes que toman levodopa y un IDDC periférico, como carbidopa o benserazida, la opicapona aumenta los niveles plasmáticos de levodopa, mejorando así la respuesta clínica a levodopa. La dosis recomendada de opicapona es de 50 mg una vez por día. Opicapona aumenta los efectos de la levodopa. Se debe administrar como adyuvante al tratamiento con levodopa. EPIDEMIOLOGÍA: La Enfermedad de Parkinson es un proceso degenerativo de presentación generalmente esporádica. La causa es desconocida, aunque probablemente es multifactorial, siendo los principales factores etiológicos de naturaleza genética y ambiental. La EP ataca varones y mujeres de todas las razas, ocupaciones y países. La media de edad en que comienza es de unos 60 años, pero se han identificado casos en individuos que tienen entre 20 y 29 años y otros todavía más jóvenes. La frecuencia con que aparece la enfermedad aumenta con el envejecimiento. La EP es la segunda enfermedad neurodegenerativa (después de la enfermedad de Alzheimer), con una tasa de incidencia media anual estandarizada por edad en países de altos ingresos de 14/100.000 habitantes de la población total y 160/100.000 personas ≥65 años. Desde el punto de vista clínico, la enfermedad de Parkinson se caracteriza por temblor en reposo, rigidez, bradicinesia y deficiencias de la locomoción conocidas como los "signos cardinales" de la misma. Otras manifestaciones incluyen rigidez de la marcha, inestabilidad postural, dificultad del habla, perturbaciones del sistema autónomo, alteraciones de la función sensitiva, cambios en el ánimo, insomnio, deficiencias cognitivas y demencia senil. CONCLUSIÓN: Opicapona es un inhibidor de catecol-o-metiltransferasa que se utiliza como adyuvante de Levodopa para tratamiento de fluctuaciones motoras de final de dosis y fenómeno on-off, en adultos con enfermedad de Parkinson. La eficacia de opicapona fue estudiada en dos estudios fase 3, cuyo objetivo primario fue el estudio de fenómenos on-off según registro de los pacientes. Se demostró que una dosis diaria de opicapona 50 mg comparada con placebo otorga una mejoría medida en minutos de tiempo off de -55,3 (IC95% -92,0 a -18,6) y -52,4 (IC95% -89,1 a -15,7) en cada estudio respectivamente. Respecto de la seguridad, los eventos adversos más frecuentes fueron disquinesias, constipación, boca seca, e insomnio. Este fármaco no constituye la única opción para el tratamiento de la enfermedad y su indicación debe ser valorada en función del beneficio agregado probable y en pacientes que no responden al tratamiento disponible. Nada obsta para su importación, quedando su uso adecuado y en ámbito adecuado, bajo estricta responsabilidad de su médico tratante.

Dopamine is metabolised by different enzymes along the rat nephron.

The purpose of this study was to determine the basal levels of dopamine (DA) and to examine the enzymes involved in DA metabolism in different microdissected nephron segments from rat kidneys. Segments were incubated with DA (50 nM) or DA plus monoamine oxidase (MAO) or catechol-O-methyl transferase (COMT) inhibitors. Basal DA levels were higher in the proximal convoluted tubule (PCT, 10.8+/-3.7 pg/mm) and in the medullary collecting duct (MCD, 10.9+/-4.0 pg/mm) than in the medullary thick ascending limb of Henle's loop (MTAL, 4.9+/-0.9 pg/mm) (P<0.05). The percentage of exogenously added DA that was not metabolised was similar in both PCT (67+/-13%) and MCD (65+/-5%) and lower in MTAL (35+/-7%), suggesting that MTAL is a major site of DA metabolism. Inhibition of MAO (pargyline 1 mM) significantly increased the basal content of DA and the percentage of the added non-metabolised DA (to 95+/-10%) in PCT but had no effect on MTAL or MCD. Conversely, inhibition of COMT (nitecapone or Ro-41-0960, both 1 mM) slightly increased the basal levels of DA only in MTAL, whereas the percentage of added DA not metabolised rose to 97+/-10% in MTAL and to 91+/-15% in MCD. COMT inhibition had no effect in PCT. In conscious rats pargyline (50 mg/kg) increased urinary DA from 680+/-34 to 1,128+/-158 ng/d/100 g BW (P<0.01) while nitecapone (40 mg/kg) produced a slight non-significant increment. Our results show that DA is present all along the rat nephron and that renal DA is metabolised continuously and predominantly by MAO in proximal segments, and by COMT in the more distal ones.

Uptake and metabolism of 3H-(+/-)-noradrenaline in the isolated perfused rat liver.

The influence of inhibitors of metabolism and uptake of noradrenaline on the 3H-noradrenaline removal from the perfusion fluid by the isolated rat liver was studied. Livers were perfused with 3 nmol/l 3H-noradrenaline and 3H-noradrenaline and 3H-metabolites were determined in effluent, liver and bile. After the perfusion with 14,900 +/- 920 dpm.g-1.min-1 during 90 min, cumulative removal of tritium was 323,574 +/- 63,103 dpm/g. 3H-metabolites recovered from the liver after 90 min perfusion represented 71.1 +/- 9.0% of total metabolite formation. Only the OMDA-fraction appeared in the perfusate; its approach to steady state of efflux was slow. The inhibition either of MAO or COMT changed neither the total removal of tritium nor the 3H-metabolites recovered from the liver. Cocaine (10 mumol/l) reduced the accumulation of 3H-noradrenaline in the liver. The uptake2 inhibitor corticosterone (30 mumol/l) diminished total removal of tritium and the 3H-metabolites recovered from the liver without changing the accumulation of 3H-noradrenaline. The hypothesis of two different compartments, one responsible for the metabolism and the other for the accumulation of the amine is discussed.

Response of the atrial pacemaker to dobutamine.

The action of dobutamine, (+/-)-4- [2- [[3-(p-hydroxyphenyl)-1-methylpropyl]amino]ethyl] pyrocatechol hydrochloride was studied on the pacemaker of the isolated rat atria. The dose-chronotropic response curve showed a typical bell-dome shape of the sympathomimetic amines. Reserpinization of the animals did not change the curve of the agonist. Cocaine (6.7 microgram/ml) induced a decrease of the sensitivity of the rat atria pacemaker for dobutamine (p less than 0.001). Propranolol (3 X 10(-8) and 10(-7) M) provoked a shift to the right of the dose-response curve for dobutamine. Also, the last concentration of the antagonist depressed the maxima (p less than 0.01). Phentolamine failed to prove a possible alpha-adrenergic action of the drug on the pacemaker. The response to dobutamine was not affected when monoaminoxidase was inhibited by pretreatment with pargyline, or when catechol-O-methyltransferase was inhibited by exposure to U-0521 (3,4 dihydroxy-alpha-methylpropiophenone). These results indicate that dobutamine: a) is a beta-adrenergic agent, b) is not a good substrate of MAO, c) is a direct-acting sympathomimetic amine.