RESUMEN
In this study thirteen 2-aminopyrimidine derivatives were synthesised and screened as potential antagonists of adenosine A1 and A2A receptors in order to further investigate the structure activity relationships of this class of compounds. 4-(5-Methylfuran-2-yl)-6-[3-(piperidine-1-carbonyl)phenyl]pyrimidin-2-amine (8m) was identified as a compound with high affinities for both receptors, with an A2AKi value of 6.34 nM and an A1Ki value of 9.54 nM. The effect of selected compounds on the viability of cultured cells was assessed and preliminary results indicate low cytotoxicity. In vivo efficacy at A2A receptors was illustrated for compounds 8k and 8m since these compounds attenuated haloperidol-induced catalepsy in rats. A molecular docking study revealed that the interactions between the synthesised compounds and the adenosine A2A binding site most likely involve Phe168 and Asn253, interactions which are similar for structurally related adenosine A2A receptor antagonists.
Asunto(s)
Antagonistas del Receptor de Adenosina A1/farmacología , Antagonistas del Receptor de Adenosina A2/farmacología , Pirimidinas/farmacología , Receptor de Adenosina A1/metabolismo , Receptor de Adenosina A2A/metabolismo , Antagonistas del Receptor de Adenosina A1/síntesis química , Antagonistas del Receptor de Adenosina A1/química , Antagonistas del Receptor de Adenosina A2/síntesis química , Antagonistas del Receptor de Adenosina A2/química , Animales , Catalepsia/inducido químicamente , Catalepsia/prevención & control , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Relación Dosis-Respuesta a Droga , Haloperidol , Células HeLa , Humanos , Masculino , Simulación del Acoplamiento Molecular , Estructura Molecular , Pirimidinas/síntesis química , Pirimidinas/química , Ratas , Ratas Sprague-Dawley , Relación Estructura-ActividadRESUMEN
The aim of this study was to design drug-like molecules with multiple neuroprotective mechanisms which would ultimately inhibit N-methyl-D-aspartate (NMDA) receptors, block L-type voltage gated calcium channels (VGCC) and inhibit apoptotic processes as well as the monoamine oxidase-B (MAO-B) enzyme in the central nervous system. These types of compounds may act as neuroprotective and symptomatic drugs for disorders such as Alzheimer's and Parkinson's disease. In designing the compounds we focused on the structures of rasagiline and selegiline, two well known MAO-B inhibitors and proposed neuroprotective agents. Based on this consideration, the compounds synthesised all contain the propargylamine functional group of rasagiline and selegiline or a derivative thereof, conjugated to various polycyclic cage moieties. Being non-polar, these polycyclic moieties have been shown to aid in the transport of conjugated compounds across the blood-brain barrier, as well as cell membranes and have secondary positive neuroprotective effects. All novel synthesised polycyclic derivatives proved to have significant anti-apoptotic activity (p < 0.05) which was comparable to the positive control, selegiline. Four compounds (12, 15 and 16) showed promising VGCC and NMDA receptor channel inhibitory activity ranging from 18% to 59% in micromolar concentrations and compared favourably to the reference compounds. In the MAO-B assay, 8-phenyl-ethynyl-8-hydroxypentacycloundecane (10), exhibited MAO-B inhibition of 73.32% at 300 µM. This compound also reduced the percentage of apoptotic cells by as much as 40% when compared to the control experiments.
Asunto(s)
Acetileno/química , Acetileno/farmacología , Fármacos Neuroprotectores/química , Fármacos Neuroprotectores/farmacología , Pargilina/análogos & derivados , Propilaminas/química , Propilaminas/farmacología , Apoptosis/efectos de los fármacos , Bloqueadores de los Canales de Calcio/química , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio Tipo L/metabolismo , Humanos , Modelos Moleculares , Monoaminooxidasa/química , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Pargilina/química , Pargilina/farmacología , Conformación Proteica , Receptores de N-Metil-D-Aspartato/metabolismoRESUMEN
OBJECTIVES: Caffeine represents a useful scaffold for the design of monoamine oxidase (MAO) type B inhibitors. Specifically, substitution on the C8 position yields structures which are high-potency MAO-B inhibitors. To explore the structure-activity relationships of MAO-B inhibition by caffeine-derived compounds, this study examines the MAO inhibitory properties of a series of phenylalkylcaffeine analogues. METHODS: Employing the recombinant human enzymes, the potencies (IC50 values) by which the caffeine analogues inhibit MAO-A and MAO-B were measured. The reversibility of inhibition of a selected inhibitor was determined by measuring the recovery of enzyme activity after dilution and dialysis of enzyme-inhibitor mixtures. KEY FINDINGS: The results document that the phenylalkylcaffeine analogues are reversible and selective MAO-B inhibitors with a competitive mode of inhibition. The most potent analogue, 8-(7-phenylheptyl)caffeine, exhibits IC50 values for the inhibition of MAO-A and MAO-B of 3.01 µm and 0.086 µm, respectively. Increasing the length of the alkyl side chain leads to enhanced MAO-A and MAO-B inhibitory potency while introduction of a carbonyl group reduces MAO-B inhibitory potency. CONCLUSIONS: Phenylalkylcaffeines represent a new class of high-potency MAO-B inhibitors with the longer alkyl side chains yielding enhanced inhibitory activity. Such compounds may represent useful leads for the development of anti-parkinsonian therapies.
Asunto(s)
Cafeína/farmacología , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/metabolismo , Cafeína/análogos & derivados , Humanos , Concentración 50 Inhibidora , Modelos Moleculares , Enfermedad de Parkinson/tratamiento farmacológico , Relación Estructura-ActividadRESUMEN
The validity of the chalcone scaffold for the design of inhibitors of monoamine oxidase has previously been illustrated. In a systematic attempt to investigate the effect of heterocyclic substitution on the monoamine oxidase inhibitory properties of this versatile scaffold, a series of furanochalcones were synthesized. The results demonstrate that these furan substituted phenylpropenones exhibited moderate to good inhibitory activities towards MAO-B, but showed weak or no inhibition of the MAO-A enzyme. The most active compound, 2E-3-(5-chlorofuran-2-yl)-1-(3-chlorophenyl)prop-2-en-1-one, exhibited an IC50 value of 0.174 µM for the inhibition of MAO-B and 28.6 µM for the inhibition of MAO-A. Interestingly, contrary to data previously reported for chalcones, these furan substituted derivatives acted as reversible inhibitors, while kinetic analysis revealed a competitive mode of binding.
Asunto(s)
Chalconas/química , Chalconas/farmacología , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Furanos/química , Furanos/farmacología , Humanos , Monoaminooxidasa/metabolismo , Proteínas Recombinantes/metabolismoRESUMEN
Based on recent reports that the small molecules, isatin and phthalimide, are suitable scaffolds for the design of high potency monoamine oxidase (MAO) inhibitors, the present study examines the MAO inhibitory properties of a series of phthalide [2-benzofuran-1(3H)-one] analogues. Phthalide is structurally related to isatin and phthalimide and it is demonstrated here that substitution at C6 of the phthalide moiety yields compounds endowed with high binding affinities to both human MAO isoforms. Among the nineteen homologues evaluated, the lowest IC(50) values recorded for the inhibition of MAO-A and -B were 0.096 and 0.0014 µM, respectively. In most instances, C6-substituted phthalides exhibit MAO-B specific inhibition. Among a series of 6-benzyloxyphthalides bearing substituents on the para position of the phenyl ring the general order of potency was CF(3) > I > Br > Cl > F > CH(3) > H. The results also show that the binding modes of representative phthalides are reversible and competitive at both MAO isoforms. Based on these data, C6-substituted phthalides may serve as leads for the development of therapies for neurodegenerative disorders such as Parkinson's disease.
Asunto(s)
Benzofuranos/química , Benzofuranos/farmacología , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/química , Monoaminooxidasa/metabolismo , Benzofuranos/síntesis química , Sitios de Unión , Humanos , Inhibidores de la Monoaminooxidasa/síntesis química , Unión Proteica , Relación Estructura-ActividadRESUMEN
In a previous study we have investigated the monoamine oxidase (MAO) inhibitory properties of a series of 8-sulfanylcaffeine analogues. Among the compounds studied, 8-[(phenylethyl)sulfanyl]caffeine (IC(50) = 0.223 µM) was found to be a particularly potent inhibitor of the type B MAO isoform. In an attempt to discover potent MAO inhibitors and to further examine the structure-activity relationships (SAR) of MAO inhibition by 8-sulfanylcaffeine analogues, in the present study a series of 8-[(phenylethyl)sulfanyl]caffeine analogues were synthesized and evaluated as inhibitors of human MAO-A and -B. The results document that substitution on C3 and C4 of the phenyl ring with alkyl groups and halogens yields 8-[(phenylethyl)sulfanyl]caffeine analogues which are potent and selective MAO-B inhibitors with IC(50) values ranging from 0.017 to 0.125 µM. The MAO inhibitory properties of a series of 8-sulfinylcaffeine analogues were also examined. The results show that, compared to the corresponding 8-sulfanylcaffeine analogues, the 8-sulfinylcaffeins are weaker MAO-B inhibitors. Both the 8-sulfanylcaffeine and 8-sulfinylcaffeine analogues were found to be weak MAO-A inhibitors. This study also reports the MAO inhibition properties of selected 8-[(phenylpropyl)sulfanyl]caffeine analogues.
Asunto(s)
Cafeína/análogos & derivados , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/metabolismo , Cafeína/química , Cafeína/farmacología , Humanos , Modelos Moleculares , Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/química , Unión Proteica , Relación Estructura-ActividadRESUMEN
A recent study has reported that a series of 8-benzyloxycaffeines are potent and reversible inhibitors of both human monoamine oxidase (MAO) isoforms, MAO-A and -B. In an attempt to discover additional caffeine derivatives with potent MAO inhibitory activities, and to contribute to the known structure-activity relationships of MAO inhibition by caffeine derived compounds, the present study investigates the MAO inhibitory potencies of series of 8-phenoxymethylcaffeine and 8-[(phenylsulfanyl)methyl]caffeine derivatives. The results document that the 8-phenoxymethylcaffeine derivatives act as potent reversible inhibitors of MAO-B, with IC(50) values ranging from 0.148 to 5.78 µM. In contrast, the 8-[(phenylsulfanyl)methyl]caffeine derivatives were found to be weak inhibitors of MAO-B, with IC(50) values ranging from 4.05 to 124 µM. Neither the 8-phenoxymethylcaffeine nor the 8-[(phenylsulfanyl)methyl]caffeine derivatives exhibited high binding affinities for MAO-A. While less potent than the 8-benzyloxycaffeines as MAO-B inhibitors, this study concludes that 8-phenoxymethylcaffeines may act as useful leads for the design of MAO-B selective inhibitors. Such compounds may find application in the therapy of neurodegenerative disorders such as Parkinson's disease. Using molecular docking experiments, this study also proposes possible binding orientations of selected caffeine derivatives in the active sites of MAO-A and -B.
Asunto(s)
Cafeína/análogos & derivados , Inhibidores de la Monoaminooxidasa/química , Monoaminooxidasa/química , Sitios de Unión , Cafeína/síntesis química , Dominio Catalítico , Simulación por Computador , Humanos , Cinética , Monoaminooxidasa/genética , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/síntesis química , Isoformas de Proteínas/antagonistas & inhibidores , Isoformas de Proteínas/metabolismo , Proteínas Recombinantes/antagonistas & inhibidores , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Relación Estructura-ActividadRESUMEN
It was recently reported that a series of C5-substituted phthalimides are remarkably potent reversible inhibitors of recombinant human monoamine oxidase (MAO) B. Modeling studies suggested that the phthalimide ring forms numerous polar interactions with the polar region of the MAO-B substrate cavity while the C5 side chain extends to, and interacts via Van der Waals interactions with the hydrophobic regions of the enzyme entrance cavity. Interactions with both cavities appear to be requirements for high affinity binding. In the present study we have examined an analogs series of C4-substituted phthalonitriles as potential human MAO inhibitors. The phthalonitriles were found to be highly potent reversible MAO-B inhibitors with most analogs exhibiting IC(50) values in the low nM range. The phthalonitriles also interacted with human MAO-A, although with lower binding affinities compared to MAO-B. Modeling studies suggest that the high binding affinities of the phthalonitriles to MAO-B may depend, at least in part, on the formation of polar interactions between the nitrile functional groups and the enzyme substrate cavity. Examination of a homologs series of benzonitriles established that the phthalonitrile moiety is more optimal for MAO-B inhibition than the corresponding benzonitrile moiety, and that C3-substituted benzonitriles are better MAO-B inhibitors than C4-substituted benzonitriles. Since elimination of the nitrile functional group yielded compounds with only moderate MAO-B inhibition potencies, it may be concluded that this functional group is privileged for MAO-B inhibition.
Asunto(s)
Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/química , Ftalimidas/química , Ftalimidas/farmacología , Sitios de Unión , Dominio Catalítico , Simulación por Computador , Activación Enzimática/efectos de los fármacos , Humanos , Cinética , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/síntesis química , Nitrilos/química , Ftalimidas/síntesis químicaRESUMEN
In a recent study it was shown that 8-benzyloxycaffeine analogues act as potent reversible inhibitors of human monoamine oxidase (MAO) A and B. Although the benzyloxy side chain appears to be particularly favorable for enhancing the MAO inhibition potency of caffeine, a variety of other C8 oxy substituents of caffeine also lead to potent MAO inhibition. In an attempt to discover additional C8 substituents of caffeine that lead to potent MAO inhibition and to explore the importance of the ether oxygen for the MAO inhibition properties of C8 oxy-substituted caffeines, a series of 8-sulfanyl- and 8-aminocaffeine analogues were synthesized and their human MAO-A and -B inhibition potencies were compared to those of the 8-oxycaffeines. The results document that the sulfanylcaffeine analogues are reversible competitive MAO-B inhibitors with potencies comparable to those of the oxycaffeines. The most potent inhibitor, 8-{[(4-bromophenyl)methyl]sulfanyl}caffeine, exhibited an IC(50) value of 0.167 µM towards MAO-B. While the sulfanylcaffeine analogues also exhibit affinities for MAO-A, they display in general a high degree of MAO-B selectivity. The aminocaffeine analogues, in contrast, proved to be weak MAO inhibitors with a number of analogues exhibiting no binding to the MAO-A and -B isozymes. The results of this study are discussed with reference to possible binding orientations of selected caffeine analogues within the active site cavities of MAO-A and -B. MAO-B selective sulfanylcaffeine derived inhibitors may act as lead compounds for the design of antiparkinsonian therapies.
Asunto(s)
Cafeína/análogos & derivados , Cafeína/farmacología , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/metabolismo , Aminas/química , Aminas/farmacología , Dominio Catalítico , Humanos , Modelos Moleculares , Monoaminooxidasa/química , Relación Estructura-Actividad , Compuestos de Sulfhidrilo/química , Compuestos de Sulfhidrilo/farmacologíaRESUMEN
A series of anilide derivatives were synthesized and evaluated as inhibitors of recombinant human monoamine oxidase (MAO) A and B. The most potent inhibitors among the derivatives that were initially evaluated were (2E)-N-(3-chlorophenyl)-3-phenylprop-2-enamide (2c) and (2E)-N-(3-bromophenyl)-3-phenylprop-2-enamide (2d) with IC(50) values of 0.53 µM and 0.45 µM, respectively. These derivatives exhibited reversible and selective inhibition of MAO-B with binding affinities 37 fold higher for MAO-B than for MAO-A. Analysis of the possible binding interactions of these inhibitors with active site models of human MAO-A and -B led to the design of phenolic and benzonitrile derivatives of 2c and 2d. Among these were (2E)-N-(3-chlorophenyl)-3-(4-hydroxyphenyl)prop-2-enamide (7c) and (2E)-N-(3-bromophenyl)-3-(4-hydroxyphenyl)prop-2-enamide (7d) which inhibited MAO-B selectively and reversibly with IC(50) values of 0.032 µM and 0.026 µM, respectively. These inhibitors were at least 14 fold more potent than 2c and 2d. This study concludes that N,3-diphenylprop-2-enamide is a suitable scaffold for the design of selective MAO-B inhibitors and structural modifications to enhance the binding affinities of the inhibitors for the MAO-B active site include substitution with halogens on the N-phenyl ring and substitution with hydroxyl and nitrile functional groups on the para and meta positions, respectively, of the C3 phenyl ring. Possible binding modes of these structures within the MAO-B active site are proposed with the emphasis on the interactions of the inhibitor halogens and the hydroxyl and nitrile functional groups with active site residues and water molecules.
Asunto(s)
Anilidas/química , Anilidas/farmacología , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/metabolismo , Anilidas/síntesis química , Dominio Catalítico , Humanos , Concentración 50 Inhibidora , Modelos Moleculares , Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/síntesis química , Unión Proteica , Proteínas Recombinantes/antagonistas & inhibidores , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismoRESUMEN
This is a case report of adrenomyeloneuropathy (AMN), the adult variant of adrenoleukodystryphy (ALD). The diagnoses in the patient, aged 34, was confirmed via increased serum very long chain fatty acid concentration (VLCFA). Treatment started with the cholesterol lowering drug, atorvastatin, followed by add-on therapy with Lorenzo's oil (LO) and finally supplementation with docosahexaenoic acid (DHA). The magnetic resonance imaging (MRI) scan of the AMN patient before DHA treatment, already showed abnormal white matter in the brain. Although the MRI showed no neurological improvement after 6 months of DHA treatment, no selective progression of demyelination was detected in the AMN patient. Contrary to what was expected, LO failed to sustain or normalize the VLCFA levels or improve clinical symptoms. It was however, shown that DHA supplementation in addition to LO, increased DHA levels in both plasma and red blood cells (RBC). Additionally, the study showed evidence that the elongase activity in the elongation of eicosapentaenoic acid (EPA) to docosapentaenoic acid (DPA) might have been significantly compromised, due to the increased DHA levels.
Asunto(s)
Adrenoleucodistrofia/dietoterapia , Adrenoleucodistrofia/tratamiento farmacológico , Suplementos Dietéticos , Ácidos Docosahexaenoicos/uso terapéutico , Ácidos Erucicos/uso terapéutico , Hipolipemiantes/uso terapéutico , Trioleína/uso terapéutico , Adrenoleucodistrofia/sangre , Adrenoleucodistrofia/fisiopatología , Adulto , Anticolesterolemiantes/uso terapéutico , Atorvastatina , Terapia Combinada , Progresión de la Enfermedad , Ácidos Docosahexaenoicos/sangre , Combinación de Medicamentos , Quimioterapia Combinada , Ácidos Heptanoicos/uso terapéutico , Humanos , Masculino , Pirroles/uso terapéutico , Resultado del TratamientoRESUMEN
Literature reports that isatin as well as C5- and C6-substituted isatin analogues are reversible inhibitors of human monoamine oxidase (MAO) A and B. In general, C5- and C6-substitution of isatin leads to enhanced binding affinity to both MAO isozymes compared to isatin and in most instances result in selective binding to the MAO-B isoform. Crystallographic and modeling studies suggest that the isatin ring binds to the substrate cavities of MAO-A and -B and is stabilized by hydrogen bond interactions between the NH and the C2 carbonyl oxygen of the dioxoindolyl moiety and water molecules present in the substrate cavities of MAO-A and -B. Based on these observations and the close structural resemblances between isatin and its phthalimide isomer, a series of phthalimide analogues were synthesized and evaluated as MAO inhibitors. While phthalimide and N-aryl-substituted phthalimides were found to be weak MAO inhibitors, phthalimide homologues containing C5 substituents were potent reversible inhibitors of recombinant human MAO-B with IC(50) values ranging from 0.007 to 2.5 µM and moderately potent reversible inhibitors of recombinant human MAO-A with IC(50) values ranging from 0.22 to 9.0 µM. By employing molecular docking the importance of hydrogen bonding between the active sites of MAO-A and -B and the phthalimide inhibitors are highlighted.
Asunto(s)
Isatina/química , Inhibidores de la Monoaminooxidasa/síntesis química , Monoaminooxidasa/química , Ftalimidas/química , Animales , Evaluación Preclínica de Medicamentos , Humanos , Insectos , Isatina/análogos & derivados , Isatina/farmacología , Modelos Moleculares , Conformación Molecular , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/análisis , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Ftalimidas/farmacología , Unión Proteica , Relación Estructura-Actividad , Factores de TiempoRESUMEN
Recently it was reported that a series of 8-benzyloxycaffeine analogues are potent reversible inhibitors of human monoamine oxidase (MAO) A and B. In an attempt to discover additional C8 oxy substituents of caffeine that lead to potent MAO inhibition, a series of related 8-aryl- and alkyloxycaffeine analogues were synthesized and their MAO-A and -B inhibition potencies were compared to those of the 8-benzyloxycaffeines. The results document that while the 8-substituted-oxycaffeine analogues inhibited both human MAO isoforms, they displayed a high degree of selectivity for MAO-B. 8-(3-Phenylpropoxy)caffeine, 8-(2-phenoxyethoxy)caffeine and 8-[(5-methylhexyl)oxy]caffeine were found to be the especially potent MAO-B inhibitors with IC(50) values ranging from 0.38 to 0.62 µM. These inhibitors are therefore 2.5-4.6 fold more potent MAO-B inhibitors than is 8-benzyloxycaffeine (IC(50) = 1.77 µM). It is also demonstrated that, analogous to 8-benzyloxycaffeine, halogen substitution on the phenyl ring of the C8 substituent significantly enhances MAO binding affinity. For example, the most potent MAO-B inhibitor of the present series is 8-[2-(4-bromophenoxy)ethoxy]caffeine with an IC(50) value of 0.166 µM. This study also reports possible binding orientations of selected oxy caffeines within the active site cavities of MAO-A and MAO-B.
Asunto(s)
Cafeína/síntesis química , Inhibidores de la Monoaminooxidasa/síntesis química , Monoaminooxidasa/metabolismo , Unión Proteica/efectos de los fármacos , Psicotrópicos/síntesis química , Proteínas Recombinantes/metabolismo , Alquilación , Animales , Sitios de Unión , Cafeína/análogos & derivados , Cafeína/farmacología , Halógenos/química , Humanos , Concentración 50 Inhibidora , Cinética , Kinuramina/metabolismo , Ratones , Modelos Moleculares , Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Enfermedades Neurodegenerativas/tratamiento farmacológico , Enfermedades Neurodegenerativas/fisiopatología , Trastornos Psicóticos/tratamiento farmacológico , Trastornos Psicóticos/fisiopatología , Psicotrópicos/farmacología , Proteínas Recombinantes/química , Relación Estructura-ActividadRESUMEN
Previous studies have shown that (E)-5-styrylisatin and (E)-6-styrylisatin are reversible inhibitors of human monoamine oxidase (MAO) A and B. Both homologues are reported to exhibit selective binding to the MAO-B isoform with (E)-5-styrylisatin being the most potent inhibitor. To further investigate these structure-activity relationships (SAR), in the present study, additional C5- and C6-substituted isatin analogues were synthesized and evaluated as inhibitors of recombinant human MAO-A and MAO-B. With the exception of 5-phenylisatin, all of the analogues examined were selective MAO-B inhibitors. The C5-substituted isatins exhibited higher binding affinities to MAO-B than the corresponding C6-substituted homologues. The most potent MAO-B inhibitor, 5-(4-phenylbutyl)isatin, exhibited an IC(50) value of 0.66nM, approximately 13-fold more potent than (E)-5-styrylisatin and 18,500-fold more potent than isatin. The most potent MAO-A inhibitor was found to be 5-phenylisatin with an IC(50) value of 562nM. The results document that substitution at C5 with a variety of substituents is a general strategy for enhancing the MAO-B inhibition potency of isatin. Possible binding orientations of selected isatin analogues within the active site cavities of MAO-A and MAO-B are proposed.
Asunto(s)
Isatina/farmacología , Inhibidores de la Monoaminooxidasa/farmacología , Cristalografía por Rayos X , Isatina/análogos & derivados , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Inhibidores de la Monoaminooxidasa/química , Espectrometría de Masa por Ionización de Electrospray , Espectrofotometría Ultravioleta , Relación Estructura-ActividadRESUMEN
Exposure to the industrial solvent, styrene, induces locomotor and cognitive dysfunction in rats, and parkinsonian-like manifestations in man. The antipsychotic, haloperidol (HP), well known to induce striatal toxicity in man and animals, and styrene share a common metabolic pathway yielding p-fluoro phenylglyoxylic acid and phenylglyoxylic acid (PGA), respectively. Using an exposure period of 30 days and the vacous chewing movement (VCM) model as an expression of striatal-motor toxicity, we found that incremental PGA dosing (220-400 mg/kg) significantly increased VCMs up to day 25, but decreased to control levels shortly after reaching maximum dose. However, a diminishing dose of PGA (400-200 mg/kg) did not evoke an immediate worsening of VCMs but precipitated a significant increase in VCMs following dosage reduction to 200 mg/kg on day 22. PGA exposure, therefore, compromises striatal-motor function that is especially sensitive to changes in exposure dose. Longer alternating dose exposure studies are needed to establish whether motor dysfunction is progressive in severity or longevity. These findings are of significance for the environmental toxicology of styrene in the chemical industry.
Asunto(s)
Glioxilatos/administración & dosificación , Glioxilatos/toxicidad , Sustancias Peligrosas/administración & dosificación , Sustancias Peligrosas/toxicidad , Ácidos Mandélicos/administración & dosificación , Ácidos Mandélicos/toxicidad , Masticación/efectos de los fármacos , Trastornos del Movimiento , Estireno/metabolismo , Animales , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
The parkinsonian inducing agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its corresponding five-membered ring analogue 1-methyl-3-phenyl-3-pyrroline are cyclic tertiary allylamines and good substrates of monoamine oxidase B (MAO-B). The MAO-B catalyzed 2-electron alpha-carbon oxidation of this class of substrates appears to be dependent on the presence of the allylic pi-bond since the corresponding saturated piperidinyl analogue of MPTP is reported not to be an MAO-B substrate. The only saturated cyclic tertiary amine known to act as an MAO-B substrate is the 3,4-cyclopropyl analogue of MPTP, 3-methyl-6-phenyl-3-azabicyclo[4.1.0]heptane. As part of our ongoing studies we have examined the MAO-B substrate properties of the corresponding pyrrolidinyl analogue, 1-methyl-3-phenylpyrrolidine, and the 3,4-cyclopropyl analogue, 3-methyl-1-phenyl-3-azabicyclo[3.1.0]hexane. The results document that both the pyrrolidinyl analogue [K(m)=234microM; V(max)=8.37nmol/(min-mg mitochondrial protein)] and the 3,4-cyclopropyl analogue [K(m)=148microM; V(max)=16.9nmol/(min-mg mitochondrial protein)] are substrates of baboon liver mitochondrial MAO-B. We also have compared the neurotoxic potential of these compounds in the C57BL/6 mouse. The results led us to conclude that these compounds are not MPTP-type neurotoxins.
Asunto(s)
Hexanos/metabolismo , Monoaminooxidasa/metabolismo , Pirrolidinas/metabolismo , Animales , Cinética , Ratones , Ratones Endogámicos C57BL , Mitocondrias Hepáticas/enzimología , Síndromes de Neurotoxicidad , PapioRESUMEN
Based on recent reports that several (E)-8-styrylcaffeinyl analogues are potent reversible inhibitors of monoamine oxidase B (MAO-B), a series of 8-benzyloxycaffeinyl analogues were synthesized and evaluated as inhibitors of baboon liver MAO-B and recombinant human MAO-A and -B. The 8-benzyloxycaffeinyl analogues were found to inhibit reversibly both MAO isoforms with enzyme-inhibitor dissociation constants (K(i) values) ranging from 0.14 to 1.30 microM for the inhibition of human MAO-A, and 0.023-0.59 microM for the inhibition of human MAO-B. The most potent MAO-A inhibitor was 8-(3-methylbenzyloxy)caffeine while 8-(3-bromobenzyloxy)caffeine was the most potent MAO-B inhibitor. The analogues inhibited human and baboon MAO-B with similar potencies. A quantitative structure-activity relationship (QSAR) study indicated that the MAO-B inhibition potencies of the 8-benzyloxycaffeinyl analogues are dependent on the Hansch lipophilicity (pi) and Hammett electronic (sigma) constants of the substituents at C-3 of the benzyloxy ring. Electron-withdrawing substituents with a high degree of lipophilicity enhance inhibition potency. These results are discussed with reference to possible binding orientations of the inhibitors within the active site cavities of MAO-A and -B.
Asunto(s)
Cafeína/química , Cafeína/farmacología , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/metabolismo , Animales , Humanos , Modelos Moleculares , Monoaminooxidasa/química , Papio , Unión Proteica , Relación Estructura-Actividad CuantitativaRESUMEN
Previous studies have shown that (E)-8-(3-chlorostyryl)caffeine (CSC) is a specific reversible inhibitor of human monoamine oxidase B (MAO-B) and does not bind to human MAO-A. Since the small molecule isatin is a natural reversible inhibitor of both MAO-B and MAO-A, (E)-5-styrylisatin and (E)-6-styrylisatin analogues were synthesized in an attempt to identify inhibitors with enhanced potencies and specificities for MAO-B. The (E)-styrylisatin analogues were found to exhibit higher binding affinities than isatin with the MAO preparations tested. The (E)-5-styrylisatin analogues bound more tightly than the (E)-6 analogue although the latter exhibits the highest MAO-B selectivity. Molecular docking studies with MAO-B indicate that the increased binding affinity exhibited by the (E)-styrylisatin analogues, in comparison to isatin, is best explained by the ability of the styrylisatins to bridge both the entrance cavity and the substrate cavity of the enzyme. Experimental support for this model is shown by the weaker binding of the analogues to the Ile199Ala mutant of human MAO-B. The lower selectivity of the (E)-styrylisatin analogues between MAO-A and MAO-B, in contrast to CSC, is best explained by the differing relative geometries of the aromatic rings for these two classes of inhibitors.
Asunto(s)
Isatina/análogos & derivados , Isatina/química , Inhibidores de la Monoaminooxidasa/síntesis química , Monoaminooxidasa/química , Unión Competitiva , Encéfalo/metabolismo , Química Farmacéutica/métodos , Diseño de Fármacos , Humanos , Concentración 50 Inhibidora , Isatina/farmacología , Cinética , Modelos Químicos , Estructura Molecular , Inhibidores de la Monoaminooxidasa/farmacología , Mutación , Relación Estructura-ActividadRESUMEN
Based on a recent report that 1-methyl-3-phenylpyrrolyl analogues are moderately potent reversible inhibitors of the enzyme monoamine oxidase B (MAO-B), a series of structurally related N-methyl-2-phenylmaleimidyl analogues has been prepared and evaluated as inhibitors of MAO-B. In general, the maleimides were more potent competitive inhibitors than the corresponding pyrrolyl analogues. N-Methyl-2-phenylmaleimide was found to be the most potent inhibitor with an enzyme-inhibitor dissociation constant (K(i) value) of 3.49 microM, approximately 30-fold more potent than 1-methyl-3-phenylpyrrole (K(i)=118 microM). This difference in activities may be dependent upon the ability of the maleimidyl heterocyclic system to act as a hydrogen bond acceptor. This is in correspondence with literature reports which suggest that hydrogen bond formation is involved in stabilizing inhibitor-MAO-B complexes. Also reported here is a brief kinetic study of the hydrolysis of the N-methyl-2-phenylmaleimidyl analogues in aqueous solution. The findings of the inhibition studies are discussed with reference to the rate and extent of hydrolysis.
Asunto(s)
Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Inhibidores de la Monoaminooxidasa/química , Inhibidores de la Monoaminooxidasa/farmacología , Monoaminooxidasa/química , Animales , Sitios de Unión , Catálisis , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/metabolismo , Humanos , Cinética , Mitocondrias Hepáticas/enzimología , Monoaminooxidasa/metabolismo , Inhibidores de la Monoaminooxidasa/síntesis química , Inhibidores de la Monoaminooxidasa/metabolismo , Papio , Relación Estructura-ActividadRESUMEN
The parkinsonian inducing agent, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is a cyclic tertiary allylamine exhibiting good monoamine oxidase B (MAO-B) substrate properties. MAO-B catalyzes the ring alpha-carbon 2-electron bioactivation of MPTP to yield the 1-methyl-4-phenyl-2,3-dihydropyridinium species (MPDP(+)). The corresponding 5-membered ring MPTP analogue, 1-methyl-3-phenyl-3-pyrroline, also undergoes MAO-B-catalyzed oxidation to give the 2-electron oxidation product, 1-methyl-3-phenylpyrrole. Here we report the kinetic deuterium isotope effects on V(max) and V(max)/K(m) for the steady-state oxidation of 1-methyl-3-phenyl-3-pyrroline and 1-methyl-3-(4-fluorophenyl)-3-pyrroline by baboon liver MAO-B, using the corresponding pyrroline-2,2,4,5,5-d(5) analogues as the deuterated substrates. The apparent isotope effects for the two substrates were 4.29 and 3.98 on V(max), while the isotope effects on V(max)/K(m) were found to be 5.71 and 3.37, respectively. The values reported for the oxidation of MPTP by bovine liver MAO-B with MPTP-6,6-d(2), as deuterated substrate, are (D)(V(max))=3.55; (D)(V(max)/K(m))=8.01. We conclude that the mechanism of the MAO-B-catalyzed oxidation of pyrrolinyl substrates is similar to that of the tetrahydropyridinyl substrates and that a carbon-hydrogen bond cleavage step is, at least partially, rate determining.