RESUMO
Multitargeting ligands on enzymes and receptors may generate a profile for a potential treatment of cognitive impairment. Considering this, a set of 21 substituted aryl-alkyl-piperazines were designed, prepared and tested for their binding affinities at histamine H3 and dopamine D3 receptors (H3R and D3R, respectively) as well as acetyl- and butyrylcholinesterases (AChE/BChE) as potentially synergistic profile. Initial screening of the compounds at H3R and D3R was done at 1 or 10 µM and 100 µM at AChE and BChE assays. The most promising compounds were then evaluated in full concentration-response curves to estimate the Ki and IC50 values. Results showed that several compounds were ligands at H3R (n = 10), D3R (n = 6), AChE (n = 3), and BChE (n = 9). Compounds LINS05006 (Ki H3R 2.8 µM; D3R 0.7 µM; IC50 BChE 26.3 µM) and LINS05015 (Ki H3R 1.1 µM; D3R 3.1 µM; IC50 AChE 97.8 µM; BChE 43.7 µM) are highlighted since presented affinity in three different. These results suggest that methylpiperazine moiety led to balanced activity at all three classes of targets, and longer linker provided the best affinities. These compounds presented high ligand efficiency values (LE > 0.3) and may have adequate pharmacokinetic profile as suggested by calculated physicochemical properties.
Assuntos
Disfunção Cognitiva , Receptores Histamínicos H3 , Humanos , Histamina , Dopamina , Ligantes , Butirilcolinesterase/metabolismo , Receptores Histamínicos H3/metabolismo , Disfunção Cognitiva/tratamento farmacológico , Inibidores da Colinesterase/química , Relação Estrutura-AtividadeRESUMO
The striatum is innervated by histaminergic fibers and expresses a high density of histamine H3 receptors (H3Rs), present on medium spiny neurons (MSNs) and corticostriatal afferents. In this study, in sagittal slices from the rat dorsal striatum, excitatory postsynaptic potentials (EPSPs) were recorded in MSNs after electrical stimulation of corticostriatal axons. The effect of H3R activation and blockers of calcium and potassium channels was evaluated with the paired-pulse facilitation protocol. In the presence of the H3R antagonist/inverse agonist clobenpropit (1 µM), the H3R agonist immepip (1 µM) had no effect on the paired-pulse ratio (PPR), but in the absence of clobenpropit, immepip induced a significant increase in PPR, accompanied by a reduction in EPSP amplitude, suggesting presynaptic inhibition. The blockade of CaV2.1 (P/Q-type) channels with ω-agatoxin TK (400 nM) increased PPR and prevented the effect of immepip. The CaV2.2 (N-type) channel blocker ω-conotoxin GVIA (1 µM) also increased PPR, but did not occlude the immepip action. Functional KIR3 channels are present in corticostriatal terminals, and in experiments in which immepip increased PPR, the KIR3 blocker tertiapin-Q (30 nM) prevented the effect of the H3R agonist. These results indicate that the presynaptic modulation by H3Rs of corticostriatal synapses involves the inhibition of Cav2.1 calcium channels and the activation of KIR3 potassium channels.
Assuntos
Canais de Cálcio Tipo N , Córtex Cerebral , Ácido Glutâmico , Canais de Potássio , Receptores Histamínicos H3/metabolismo , Sinapses , Animais , Cálcio , Canais de Cálcio Tipo N/metabolismo , Córtex Cerebral/metabolismo , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G , Ácido Glutâmico/metabolismo , Ratos , Sinapses/metabolismoRESUMO
The role of histamine and acetylcholine in cognitive functions suggests that compounds able to increase both histaminergic and cholinergic neurotransmissions in the brain should be considered as promising therapeutic options. For this purpose, dual inhibitors of histamine H3 receptors (H3 R) and cholinesterases (ChEs) have been designed and assessed. In this context, this paper reviews the strategies used to obtain dual H3 R/ChEs ligands using multitarget design approaches. Hybrid compounds designed by linking tacrine or flavonoid motifs to H3 R antagonists were obtained with high affinity for both targets, and compounds designed by merging the H3 R antagonist pharmacophore with known anticholinesterase molecules were also reported. These reports strongly suggest that key modifications in the lipophilic region (including a second basic group) seem to be a strategy to reach novel compounds, allied with longer linker groups to a basic region. Some compounds have already demonstrated efficacy in memory models, although the pharmacokinetic and toxicity profile should be considered when designing further compounds. In conclusion, the key features to be considered when designing novel H3 R/ChEs inhibitors with improved pharmacological profile were herein summarized.
Assuntos
Colinesterases/química , Ligantes , Receptores Histamínicos H3/química , Sítios de Ligação , Inibidores da Colinesterase/química , Inibidores da Colinesterase/metabolismo , Inibidores da Colinesterase/uso terapêutico , Colinesterases/metabolismo , Disfunção Cognitiva/tratamento farmacológico , Disfunção Cognitiva/patologia , Desenho de Fármacos , Antagonistas dos Receptores Histamínicos/química , Antagonistas dos Receptores Histamínicos/metabolismo , Antagonistas dos Receptores Histamínicos/uso terapêutico , Humanos , Simulação de Acoplamento Molecular , Receptores Histamínicos H3/metabolismoRESUMO
Histamine acts through four different receptors (H1R-H4R), the H3R and H4R being the most explored in the last years as drug targets. The H3R is a potential target to treat narcolepsy, Parkinson's disease, epilepsy, schizophrenia and several other CNS-related conditions, while H4R blockade leads to anti-inflammatory and immunomodulatory effects. Our group has been exploring the dihydrobenzofuranyl-piperazines (LINS01 series) as human H3R/H4R ligands as potential drug candidates. In the present study, a set of 12 compounds were synthesized from adequate (dihydro)benzofuran synthons through simple reactions with corresponding piperazines, giving moderate to high yields. Four compounds (1b, 1f, 1g and 1h) showed high hH3R affinity (pKi > 7), compound 1h being the most potent (pKi 8.4), and compound 1f showed the best efficiency (pKi 8.2, LE 0.53, LLE 5.85). BRET-based assays monitoring Gαi activity indicated that the compounds are potent antagonists. Only one compound (2c, pKi 7.1) presented high affinity for hH4R. In contrast to what was observed for hH3R, it showed partial agonist activity. Docking experiments indicated that bulky substituents occupy a hydrophobic pocket in hH3R, while the N-allyl group forms favorable interactions with hydrophobic residues in the TM2, 3 and 7, increasing the selectivity towards hH3R. Additionally, the importance of the indole NH in the interaction with Glu5.46 from hH4R was confirmed by the modeling results, explaining the affinity and agonistic activity of compound 2c. The data reported in this work represent important findings for the rational design of future compounds for hH3R and hH4R.
Assuntos
Antagonistas dos Receptores Histamínicos/farmacologia , Piperazinas/farmacologia , Receptores Histamínicos H3/metabolismo , Receptores Histamínicos H4/antagonistas & inibidores , Relação Dose-Resposta a Droga , Antagonistas dos Receptores Histamínicos/síntese química , Antagonistas dos Receptores Histamínicos/química , Humanos , Ligantes , Modelos Moleculares , Estrutura Molecular , Piperazinas/síntese química , Piperazinas/química , Receptores Histamínicos H4/metabolismo , Relação Estrutura-AtividadeRESUMO
Astrocytes take up glucose via the 45â¯kDa isoform of the Glucose Transporter 1 (GLUT-1), and in this work we have investigated whether histamine regulates GLUT-1 expression in rat cerebro-cortical astrocytes in primary culture. Cultured astrocytes expressed histamine H1 and H3 receptors (H1Rs and H3Rs) as evaluated by radioligand binding. Receptor functionality was confirmed by the increase in the intracellular concentration of Ca2+ (H1R) and the inhibition of forskolin-induced cAMP accumulation (H3R). Quantitative RT-PCR showed that histamine and selective H1R and H3R agonists (1â¯h incubation) significantly increased GLUT-1 mRNA to 153⯱â¯7, 163⯱â¯2 and 168⯱â¯13% of control values, respectively. In immunoblot assays, incubation (3â¯h) with histamine or H1R and H3R agonists increased GLUT-1 protein levels to 224⯱â¯12, 305⯱â¯11 and 193⯱â¯13% of control values, respectively, an action confirmed by inmunocytochemistry. The effects of H1R and H3R agonists were blocked by the selective antagonists mepyramine (H1R) and clobenpropit (H3R). The pharmacological inhibition of protein kinase C (PKC) prevented the increase in GLUT-1 protein induced by either H1R or H3R activation. Furthermore, histamine increased ERK-1/2 phosphorylation, and the effect of H1R and H3R activation on GLUT-1 protein levels was reduced or prevented, respectively, by MEK-1/2 inhibition. These results indicate that by activating H1Rs and H3Rs histamine regulates the expression of GLUT-1 by astrocytes. The effect appears to involve the phospholipase C (PLC) â diacylglycerol (DAG)/Ca2+â PKC and PLC â DAG/Ca2+ â PKC â MAPK pathways.
Assuntos
Astrócitos/metabolismo , Córtex Cerebral/metabolismo , Transportador de Glucose Tipo 1/biossíntese , Agonistas dos Receptores Histamínicos/farmacologia , Animais , Animais Recém-Nascidos , Cálcio/metabolismo , Córtex Cerebral/citologia , Córtex Cerebral/efeitos dos fármacos , AMP Cíclico/metabolismo , Histamina/metabolismo , Imuno-Histoquímica , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Cultura Primária de Células , Inibidores de Proteínas Quinases/farmacologia , Ratos , Ratos Wistar , Receptores Histamínicos H1/efeitos dos fármacos , Receptores Histamínicos H1/metabolismo , Receptores Histamínicos H3/efeitos dos fármacos , Receptores Histamínicos H3/metabolismoRESUMO
The brain histaminergic system plays a pivotal role in energy homeostasis, through H1- receptor activation, it increases the hypothalamic release of histamine that decreases food intake and reduces body weight. One way to increase the release of hypothalamic histamine is through the use of antagonist/inverse agonist for the H3-receptor. Histamine H3-receptors are auto-receptors and heteroreceptors located on the presynaptic membranes and cell soma of neurons, where they negatively regulate the synthesis and release of histamine and other neurotransmitters in the central nervous system. Although several compounds acting as H3-receptor antagonist/inverse agonists have been developed, conflicting results have been reported and only one has been tested as anti-obesity in humans. Animal studies revealed the opposite effect in food intake, energy expeditor, and body weight, depending on the drug, spice, and route of administration, among others. The present review will explore the state of art on the effects of H3-receptor ligands on appetite and body-weight, going through the following: a brief overview of the circuit involved in the control of food intake and energy homeostasis, the participation of the histaminergic system in food intake and body weight, and the H3-receptor as a potential therapeutic target for obesity.
Assuntos
Histamina/metabolismo , Obesidade/metabolismo , Receptores Histamínicos H3/metabolismo , Animais , Histamínicos/farmacologia , Histamínicos/uso terapêutico , Humanos , Obesidade/tratamento farmacológicoRESUMO
Histamine is a transmitter that activates the four receptors H1 R to H4 R. The H3 R is found in the nervous system as an autoreceptor and heteroreceptor, and controls the release of neurotransmitters, making it a potential drug target for neuropsychiatric conditions. We have previously reported that the 1-(2,3-dihydro-1-benzofuran-2-yl)methylpiperazines (LINS01 compounds) have the selectivity for the H3 R over the H4 R. Here, we describe their pharmacological properties at the human H1 R and H2 R in parallel with the H3 R, thus providing a full analysis of these compounds as histamine receptor ligands through reporter gene assays. Eight of the nine LINS01 compounds inhibited H3 R-induced histamine responses, but no inhibition of H2 R-induced responses was seen. Three compounds were weakly able to inhibit H1 R-induced responses. No agonist responses were seen to any of the compounds at any receptor. SAR analysis shows that the N-methyl group improves H3 R affinity while the N-phenyl group is detrimental. The methoxy derivative, LINS01009, had the highest affinity.
Assuntos
Piperazinas/química , Receptores Histamínicos H1/química , Receptores Histamínicos H2/química , Receptores Histamínicos H3/química , Antagonistas dos Receptores Histamínicos/química , Antagonistas dos Receptores Histamínicos/metabolismo , Humanos , Cinética , Ligantes , Piperazinas/síntese química , Piperazinas/metabolismo , Receptores Histamínicos H1/metabolismo , Receptores Histamínicos H2/metabolismo , Receptores Histamínicos H3/metabolismo , Relação Estrutura-AtividadeRESUMO
BACKGROUND: Histamine receptors are known to participate in spinal cord nociceptive transmission, and previous studies have suggested that histaminergic receptors are involved in the analgesic effects of morphine. Herein, we investigated the effect of intrathecal injection of histaminergic agonists and antagonists in a model of acute articular inflammation and their interaction with morphine. METHODS: After carrageenan injection in the right knee joint, articular incapacitation was measured hourly, for up to 6 hours, by the paw elevation time during 1-minute periods of stimulated walking. Inflammatory edema was also assessed hourly by determining an increase in articular diameter. Spinal treatments were administered 20 minutes before knee-joint carrageenan injection and were compared with the saline-treated control group. RESULTS: Intrathecally injected histamine increased incapacitation and articular edema, whereas the H1R antagonist, cetirizine, decreased both parameters. The H3R agonist, immepip, decreased both incapacitation and edema, but the H3R antagonist, thioperamide, increased both incapacitation and edema. Morphine inhibited both incapacitation and edema. Furthermore, combining a subeffective dose of morphine with cetirizine or immepip potentiated the analgesic and antiedematogenic effect. CONCLUSIONS: Histamine seems to act at the spinal level via H1 and H3 receptors to modulate acute arthritis in rats. An H1R antagonist and H3R agonist were found to potentiate the analgesic and antiedematogenic effects of morphine, suggesting that histaminergic and opioid spinal systems may be explored for means of improving analgesia, as well as peripheral anti-inflammatory effects.
Assuntos
Analgésicos Opioides/administração & dosagem , Anti-Inflamatórios/administração & dosagem , Edema/tratamento farmacológico , Agonistas dos Receptores Histamínicos/farmacologia , Antagonistas dos Receptores Histamínicos/farmacologia , Histamina/metabolismo , Articulações/inervação , Morfina/administração & dosagem , Osteoartrite/tratamento farmacológico , Medula Espinal/efeitos dos fármacos , Animais , Carragenina , Cetirizina/farmacologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Edema/induzido quimicamente , Edema/metabolismo , Edema/fisiopatologia , Antagonistas não Sedativos dos Receptores H1 da Histamina/farmacologia , Antagonistas dos Receptores Histamínicos H3/farmacologia , Imidazóis/farmacologia , Injeções Espinhais , Masculino , Osteoartrite/induzido quimicamente , Osteoartrite/metabolismo , Osteoartrite/fisiopatologia , Piperidinas/farmacologia , Ratos Wistar , Receptores Histamínicos H1/efeitos dos fármacos , Receptores Histamínicos H1/metabolismo , Receptores Histamínicos H3/efeitos dos fármacos , Receptores Histamínicos H3/metabolismo , Medula Espinal/metabolismo , Medula Espinal/fisiopatologiaRESUMO
Desensitization is a major mechanism to regulate the functional response of G protein-coupled receptors. In this work we studied whether the human histamine H3 receptor of 445 amino acids (hH3R445) experiences heterologous desensitization mediated by PKC activation. Bioinformatic analysis indicated the presence of Serine and Threonine residues susceptible of PKC-mediated phosphorylation on the third intracellular loop and the carboxyl terminus of the hH3R445. In CHO-K1 cells stably transfected with the hH3R445 direct PKC activation by phorbol 12-myristate 13-acetate (TPA, 200 nM) abolished H3R-mediated inhibition of forskolin-stimulated cAMP accumulation. Activation of endogenous purinergic receptors by ATP (adenosine 5'-triphosphate, 10 µM) increased the free calcium intracellular concentration ([Ca(2+)]i) confirming their coupling to phospholipase C stimulation. Incubation with ATP also abolished H3R-mediated inhibition of forskolin-induced cAMP accumulation, and this effect was prevented by the PKC inhibitors Ro-31-8220 and Gö-6976. Pre-incubation with TPA or ATP reduced H3R-mediated stimulation of [(35)S]-GTPγS binding to membranes from CHO-K1-hH3R445 cells by 39.7 and 54.2 %, respectively, with no change in the agonist potency, and the effect was prevented by either Ro-31-8220 or Gö-6976. Exposure to ATP or TPA also resulted in the loss of cell surface H3Rs (-30.4 and -45.1 %) as evaluated by [(3)H]-NMHA binding to intact cells. These results indicate that the hH3R445 undergoes heterologous desensitization upon activation of receptors coupled to PKC stimulation.
Assuntos
Proteína Quinase C/metabolismo , Receptores Histamínicos H3/metabolismo , Transdução de Sinais/efeitos dos fármacos , Trifosfato de Adenosina/metabolismo , Animais , Células CHO , Carbazóis/farmacologia , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Colforsina/farmacologia , Cricetulus/metabolismo , Humanos , Indóis/farmacologia , Fosforilação/efeitos dos fármacos , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
Experiments were designed to evaluate the tissue content of tele-methylhistamine (t-MeHA) and histamine as well as H3 receptor (H3 Rs) binding and activation of the heterotrimeric guanine nucleotide binding αi/o proteins (Gαi/o) coupled to these receptors in the hippocampus and temporal neocortex of patients (n = 10) with pharmacoresistant mesial temporal lobe epilepsy (MTLE). Patients with MTLE showed elevated tissue content of t-MeHA in the hippocampus. Analyses revealed that a younger age at seizure onset was correlated with a higher tissue content of t-MeHA, lower H3 R binding, and lower efficacy of Gαi/o protein activation in the hippocampus. We conclude that the hippocampus shows a reduction in the H3 R function associated with enhanced histamine. In contrast, the temporal neocortex displayed a high efficacy of H3 Rs Gαi/o protein activation that was associated with low tissue contents of histamine and t-MeHA. These results indicate an overactivation of H3 Rs leading to decreased histamine in the temporal neocortex. However, this situation was lessened in circumstances such as a longer duration of epilepsy or higher seizure frequency. It is concluded that decrease in H3 Rs function and enhanced levels of histamine may contribute to the epileptic activity in the hippocampus and temporal neocortex of patients with pharmacoresistant MTLE.