RESUMO
The µ-opioid receptor (µOR) is a well-established target for analgesia1, yet conventional opioid receptor agonists cause serious adverse effects, notably addiction and respiratory depression. These factors have contributed to the current opioid overdose epidemic driven by fentanyl2, a highly potent synthetic opioid. µOR negative allosteric modulators (NAMs) may serve as useful tools in preventing opioid overdose deaths, but promising chemical scaffolds remain elusive. Here we screened a large DNA-encoded chemical library against inactive µOR, counter-screening with active, G-protein and agonist-bound receptor to 'steer' hits towards conformationally selective modulators. We discovered a NAM compound with high and selective enrichment to inactive µOR that enhances the affinity of the key opioid overdose reversal molecule, naloxone. The NAM works cooperatively with naloxone to potently block opioid agonist signalling. Using cryogenic electron microscopy, we demonstrate that the NAM accomplishes this effect by binding a site on the extracellular vestibule in direct contact with naloxone while stabilizing a distinct inactive conformation of the extracellular portions of the second and seventh transmembrane helices. The NAM alters orthosteric ligand kinetics in therapeutically desirable ways and works cooperatively with low doses of naloxone to effectively inhibit various morphine-induced and fentanyl-induced behavioural effects in vivo while minimizing withdrawal behaviours. Our results provide detailed structural insights into the mechanism of negative allosteric modulation of the µOR and demonstrate how this can be exploited in vivo.
Assuntos
Analgésicos Opioides , Avaliação Pré-Clínica de Medicamentos , Naloxona , Receptores Opioides mu , Bibliotecas de Moléculas Pequenas , Animais , Humanos , Masculino , Camundongos , Regulação Alostérica/efeitos dos fármacos , Analgésicos Opioides/antagonistas & inibidores , Analgésicos Opioides/farmacologia , Sítios de Ligação/efeitos dos fármacos , Microscopia Crioeletrônica , Fentanila/antagonistas & inibidores , Fentanila/farmacologia , Cinética , Ligantes , Modelos Moleculares , Morfina/antagonistas & inibidores , Morfina/farmacologia , Naloxona/administração & dosagem , Naloxona/química , Naloxona/metabolismo , Naloxona/farmacologia , Antagonistas de Entorpecentes/administração & dosagem , Antagonistas de Entorpecentes/química , Antagonistas de Entorpecentes/metabolismo , Antagonistas de Entorpecentes/farmacologia , Overdose de Opiáceos/tratamento farmacológico , Conformação Proteica/efeitos dos fármacos , Estabilidade Proteica/efeitos dos fármacos , Receptores Opioides mu/agonistas , Receptores Opioides mu/antagonistas & inibidores , Receptores Opioides mu/química , Receptores Opioides mu/metabolismo , Células Sf9 , Transdução de Sinais/efeitos dos fármacos , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/farmacologia , Camundongos Endogâmicos C57BLRESUMO
Mitragynine, an alkaloid present in the leaves of Mitragyna speciosa (kratom), has a complex pharmacology that includes low efficacy agonism at µ-opioid receptors (MORs). This study examined the activity of mitragynine at adrenergic α2 receptors (Aα2Rs) in vitro and in vivo. Mitragynine displaced a radiolabeled Aα2R antagonist ([3H]RX821002) from human Aα2ARs in vitro with lower affinity (Ki = 1260 nM) than the agonists (-)-epinephrine (Ki = 263 nM) or lofexidine (Ki = 7.42 nM). Mitragynine did not significantly stimulate [35S]GTPγS binding at Aα2ARs in vitro, but in rats trained to discriminate 32 mg/kg mitragynine from vehicle (intraperitoneally administered; i.p.), mitragynine exerted an Aα2R agonist-like effect. Both α2R antagonists (atipamezole and yohimbine) and MOR antagonists (naloxone and naltrexone) produced rightward shifts in mitragynine discrimination dose-effect function and Aα2R agonists lofexidine and clonidine produced leftward shifts. In the mitragynine trained rats, Aα2R agonists also produced leftward shifts in discrimination dose-effect functions for morphine and fentanyl. In a separate rat cohort trained to discriminate 3.2 mg/kg i.p. morphine from vehicle, naltrexone produced a rightward shift, but neither an Aα2R agonist or antagonist affected morphine discrimination. In a hypothermia assay, both lofexidine and clonidine produced marked effects antagonized by yohimbine. Mitragynine did not produce hypothermia. Together, these data demonstrate that mitragynine acts in vivo like an Aα2R agonist, although its failure to induce hypothermia or stimulate [35S]GTPγS binding in vitro, suggests that mitragynine maybe a low efficacy Aα2R agonist.
Assuntos
Mitragyna , Receptores Adrenérgicos alfa 2 , Alcaloides de Triptamina e Secologanina , Animais , Alcaloides de Triptamina e Secologanina/farmacologia , Masculino , Humanos , Ratos , Receptores Adrenérgicos alfa 2/metabolismo , Mitragyna/química , Ratos Sprague-Dawley , Agonistas de Receptores Adrenérgicos alfa 2/farmacologia , Antagonistas de Receptores Adrenérgicos alfa 2/farmacologia , Células CHO , Receptores Opioides mu/agonistas , Receptores Opioides mu/metabolismo , Receptores Opioides mu/antagonistas & inibidoresRESUMO
Kappa opioid receptors (KORs) are implicated in the pathophysiology of various psychiatric and neurological disorders creating interest in targeting the KOR system for therapeutic purposes. Accordingly, navacaprant (NMRA-140) is a potent, selective KOR antagonist being evaluated as a treatment for major depressive disorder. In the present report, we have extended the pharmacological characterization of navacaprant by further demonstrating its selective KOR antagonist properties and confirming its lack of agonist activity at KORs and related targets involved in opioid-related abuse. Using CHO-K1 cells expressing human KOR, mu (MOR), or delta (DOR) opioid receptors, navacaprant demonstrated selective antagonist properties at KOR (IC50 = 0.029 µM) versus MOR (IC50 = 3.3 µM) and DOR (IC50 > 10 µM) in vitro. In vivo, navacaprant (10-30 mg/kg, i.p.) dose-dependently abolished KOR-agonist induced analgesia in the mouse tail-flick assay. Additionally, navacaprant (10, 30 mg/kg, p.o.) significantly reduced KOR agonist-stimulated prolactin release in mice and rats, confirming KOR antagonism in vivo. Navacaprant showed no agonist activity at any opioid receptor subtype (EC50 > 10 µM) in vitro and exhibited no analgesic effect in the tail-flick assays at doses ≤100 mg/kg, p.o. thereby confirming a lack of opioid receptor agonist activity in vivo. Importantly, navacaprant did not alter extracellular dopamine concentrations in the nucleus accumbens shell of freely-moving rats following doses ≤100 mg/kg, p.o., whereas morphine (10, 20 mg/kg, i.p.) significantly increased dopamine levels. These results demonstrate that navacaprant is a KOR-selective antagonist with no pharmacological properties implicated in opioid-related abuse.
Assuntos
Analgésicos Opioides , Cricetulus , Receptores Opioides kappa , Receptores Opioides kappa/agonistas , Receptores Opioides kappa/antagonistas & inibidores , Animais , Células CHO , Humanos , Masculino , Camundongos , Ratos , Analgésicos Opioides/farmacologia , Cricetinae , Transtornos Relacionados ao Uso de Opioides/tratamento farmacológico , Antagonistas de Entorpecentes/farmacologia , Relação Dose-Resposta a Droga , Ratos Sprague-Dawley , Receptores Opioides delta/antagonistas & inibidores , Receptores Opioides delta/agonistas , Receptores Opioides mu/agonistas , Receptores Opioides mu/antagonistas & inibidores , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Camundongos Endogâmicos C57BL , Dopamina/metabolismoRESUMO
In recent years, synthetic opioids have emerged as a predominant cause of drug-overdose-related fatalities, causing the "opioid crisis." To design safer therapeutic agents, we accidentally discovered µ-opioid receptor (MOR) antagonists based on fentanyl with a relatively uncomplicated chemical composition that potentiates structural modifications. Here, we showed the development of novel atropisomeric fentanyl analogues that exhibit more potent antagonistic activity against MOR than naloxone, a morphinan MOR antagonist. Derivatives displaying stable axial chirality were synthesized based on the amide structure of fentanyl. The aS- and aR-enantiomers exerted antagonistic and agonistic effects on the MOR, respectively, and each atropisomer interacted with the MOR by assuming a distinct binding mode through molecular docking. These findings suggest that introducing atropisomerism into fentanyl may serve as a key feature in the molecular design of future MOR antagonists to help mitigate the opioid crisis.
Assuntos
Fentanila , Receptores Opioides mu , Receptores Opioides mu/antagonistas & inibidores , Receptores Opioides mu/metabolismo , Fentanila/farmacologia , Fentanila/análogos & derivados , Fentanila/química , Estereoisomerismo , Humanos , Simulação de Acoplamento Molecular , Relação Estrutura-Atividade , Animais , Antagonistas de Entorpecentes/química , Antagonistas de Entorpecentes/farmacologia , Conformação Molecular , Analgésicos Opioides/farmacologia , Analgésicos Opioides/química , Analgésicos Opioides/síntese química , Células CHO , CricetulusRESUMO
PURPOSE: Mu-opioid receptors (MORs) are widely expressed in the central nervous system (CNS), peripheral organs, and immune system. This study measured the whole body distribution of MORs in rhesus macaques using the MOR selective radioligand [11C]carfentanil ([11C]CFN) on the PennPET Explorer. Both baseline and blocking studies were conducted using either naloxone or GSK1521498 to measure the effect of the antagonists on MOR binding in both CNS and peripheral organs. METHODS: The PennPET Explorer was used for MOR total-body PET imaging in four rhesus macaques using [11C]CFN under baseline, naloxone pretreatment, and naloxone or GSK1521498 displacement conditions. Logan distribution volume ratio (DVR) was calculated by using a reference model to quantitate brain regions, and the standard uptake value ratios (SUVRs) were calculated for peripheral organs. The percent receptor occupancy (%RO) was calculated to establish the blocking effect of 0.14 mg/kg naloxone or GSK1521498. RESULTS: The %RO in MOR-abundant brain regions was 75-90% for naloxone and 72-84% for GSK1521498 in blocking studies. A higher than 90% of %RO were observed in cervical spinal cord for both naloxone and GSK1521498. It took approximately 4-6 min for naloxone or GSK1521498 to distribute to CNS and displace [11C]CFN from the MOR. A smaller effect was observed in heart wall in the naloxone and GSK1521498 blocking studies. CONCLUSION: [11C]CFN total-body PET scans could be a useful approach for studying mechanism of action of MOR drugs used in the treatment of acute and chronic opioid use disorder and their effect on the biodistribution of synthetic opioids such as CFN. GSK1521498 could be a potential naloxone alternative to reverse opioid overdose.
Assuntos
Fentanila , Macaca mulatta , Tomografia por Emissão de Pósitrons , Receptores Opioides mu , Imagem Corporal Total , Animais , Fentanila/análogos & derivados , Fentanila/farmacologia , Fentanila/farmacocinética , Receptores Opioides mu/metabolismo , Receptores Opioides mu/antagonistas & inibidores , Tomografia por Emissão de Pósitrons/métodos , Masculino , Naloxona/farmacologia , Naloxona/farmacocinética , Radioisótopos de Carbono , Distribuição Tecidual , Pirrolidinas/farmacocinética , Pirrolidinas/farmacologia , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , BenzamidasRESUMO
The number of opioid-related overdose deaths and individuals that have suffered from opioid use disorders have significantly increased over the last 30 years. FDA approved maintenance therapies to treat opioid use disorder may successfully curb drug craving and prevent relapse but harbor adverse effects that reduce patient compliance. This has created a need for new chemical entities with improved patient experience. Previously our group reported a novel lead compound, NAT, a mu-opioid receptor antagonist that potently antagonized the antinociception of morphine and showed significant blood-brain barrier permeability. However, NAT belongs to thiophene containing compounds which are known structural alerts for potential oxidative metabolism. To overcome this, 15 NAT derivatives with various substituents at the 5'-position of the thiophene ring were designed and their structure-activity relationships were studied. These derivatives were characterized for their binding affinity, selectivity, and functional activity at the mu opioid receptor and assessed for their ability to antagonize the antinociceptive effects of morphine in vivo. Compound 12 showed retention of the basic pharmacological attributes of NAT while improving the withdrawal effects that were experienced in opioid-dependent mice. Further studies will be conducted to fully characterize compound 12 to examine whether it would serve as a new lead for opioid use disorder treatment and management.
Assuntos
Receptores Opioides mu , Animais , Relação Estrutura-Atividade , Camundongos , Receptores Opioides mu/metabolismo , Receptores Opioides mu/antagonistas & inibidores , Humanos , Estrutura Molecular , Tiofenos/química , Tiofenos/farmacologia , Tiofenos/síntese química , Tiofenos/uso terapêutico , Masculino , Relação Dose-Resposta a Droga , Analgésicos Opioides/farmacologia , Analgésicos Opioides/química , Antagonistas de Entorpecentes/farmacologia , Antagonistas de Entorpecentes/química , Morfina/farmacologiaRESUMO
The design of bifunctional compounds is a promising approach toward the development of strong analgesics with reduced side effects. We here report the optimization of the previously published lead peptide KGFF09, which contains opioid receptor agonist and neuropeptide FF receptor antagonist pharmacophores and is shown to induce potent antinociception and reduced side effects. We evaluated the novel hybrid peptides for their in vitro activity at MOP, NPFFR1, and NPFFR2 and selected four of them (DP08/14/32/50) for assessment of their acute antinociceptive activity in mice. We further selected DP32 and DP50 and observed that their antinociceptive activity is mostly peripherally mediated; they produced no respiratory depression, no hyperalgesia, significantly less tolerance, and strongly attenuated withdrawal syndrome, as compared to morphine and the recently FDA-approved TRV130. Overall, these data suggest that MOP agonist/NPFF receptor antagonist hybrids might represent an interesting strategy to develop novel analgesics with reduced side effects.
Assuntos
Receptores de Neuropeptídeos , Receptores Opioides mu , Animais , Receptores Opioides mu/agonistas , Receptores Opioides mu/antagonistas & inibidores , Receptores Opioides mu/metabolismo , Camundongos , Receptores de Neuropeptídeos/agonistas , Receptores de Neuropeptídeos/antagonistas & inibidores , Receptores de Neuropeptídeos/metabolismo , Masculino , Analgésicos/farmacologia , Analgésicos/química , Analgésicos/uso terapêutico , Analgésicos/síntese química , Humanos , Relação Estrutura-Atividade , Analgésicos Opioides/farmacologia , Analgésicos Opioides/químicaRESUMO
Transcutaneous electrical nerve stimulation (TENS) activates various pathways to induce antinociceptive effects, based on the frequencies used. This study evaluates the preemptive analgesic effects and their duration of low- (LT: 4 Hz) and high-frequency TENS (HT: 100 Hz) using a rat model of acute inflammatory pain. Acute inflammation was induced by injecting 1% formalin into the hind paws of rats. LT or HT was applied for 30 min before formalin injection. Pain-related behaviors, such as licking, flinching, and lifting, were recorded for 60 min postinjection. Immunohistochemistry was used to assess the number of phosphorylated extracellular signal-regulated kinase (pERK)- and c-fos-positive cells in the spinal cord. Naloxone, a µ-opioid receptors (MORs) antagonist, and naltrindole, a δ-opioid receptors (DORs) antagonist, were administered before TENS application. Pain behavior duration and pERK- and c-fos-positive cell expression were then measured. LT and HT pretreatment significantly reduced both pain behaviors and the number of pERK- and c-fos-positive cells postformalin injection. Naloxone and naltrindole partially reversed the effects of LT and HT, respectively. Notably, HT's analgesic effect lasted up to 120 min whereas that of LT persisted for 90 min. LT and HT effectively exerted their preemptive analgesic effects on acute inflammatory pain by inhibiting pERK and c-fos expression in the spinal cord. HT presented a longer-lasting effect compared to LT. MOR and DOR activation may contribute to LT and HT's analgesic mechanisms, respectively.
Assuntos
Inflamação , Naloxona , Proteínas Proto-Oncogênicas c-fos , Ratos Sprague-Dawley , Estimulação Elétrica Nervosa Transcutânea , Animais , Estimulação Elétrica Nervosa Transcutânea/métodos , Masculino , Naloxona/farmacologia , Ratos , Proteínas Proto-Oncogênicas c-fos/metabolismo , Dor Aguda/terapia , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Antagonistas de Entorpecentes/farmacologia , Naltrexona/farmacologia , Naltrexona/análogos & derivados , Medula Espinal/metabolismo , Medula Espinal/efeitos dos fármacos , Receptores Opioides mu/metabolismo , Receptores Opioides mu/antagonistas & inibidores , Manejo da Dor/métodos , Fosforilação/efeitos dos fármacos , Modelos Animais de DoençasAssuntos
Antagonistas de Entorpecentes , Constipação Induzida por Opioides , Receptores Opioides mu , Humanos , Receptores Opioides mu/antagonistas & inibidores , Criança , Antagonistas de Entorpecentes/uso terapêutico , Antagonistas de Entorpecentes/efeitos adversos , Constipação Induzida por Opioides/tratamento farmacológico , Analgésicos Opioides/efeitos adversos , Analgésicos Opioides/uso terapêutico , Constipação Intestinal/tratamento farmacológico , Constipação Intestinal/induzido quimicamente , Resultado do TratamentoRESUMO
The synthesis and pharmacological activity of a new series of dual ligands combining activities towards the α2δ-1 subunit of voltage-gated calcium channels (Cavα2δ-1) and the µ-opioid receptor (MOR) as novel pain therapeutics are reported. A careful exploration of the pharmacophores related to both targets, which in principle had few common characteristics, led to the design of novel compounds exhibiting both activities. The construction of the dual ligands started from published Cavα2δ-1 ligands, onto which MOR ligand pharmacophoric elements were added. This exercise led to new amino-acidic substances with good affinities on both targets as well as good metabolic and physicochemical profiles and low potential for drug-drug interactions. A representative compound, (2S,4S)-4-(4-chloro-3-(((cis)-4-(dimethylamino)-4-phenylcyclohexyl)methyl)-5-fluorophenoxy)pyrrolidine-2-carboxylic acid, displayed promising analgesic activities in several inâ vivo pain models as well as a reduced side-effect profile in relation to morphine.
Assuntos
Analgésicos , Canais de Cálcio , Dor , Receptores Opioides mu , Animais , Humanos , Masculino , Ratos , Analgésicos/farmacologia , Analgésicos/química , Analgésicos/síntese química , Canais de Cálcio/metabolismo , Canais de Cálcio/química , Relação Dose-Resposta a Droga , Ligantes , Estrutura Molecular , Dor/tratamento farmacológico , Receptores Opioides mu/metabolismo , Receptores Opioides mu/antagonistas & inibidores , Relação Estrutura-AtividadeRESUMO
Ten new indole alkaloids (1-10) as well as eleven known analogs (11-21) were isolated from the stems and hooks of Uncaria rhynchophylla. Their structure elucidation was based on extensive NMR studies, MS and ECD data, with the essential aid of DFT prediction of ECD spectra. Compound 1 was determined as a 17,19-seco-cadambine-type alkaloid, and compound 3 was confirmed to be a 3,4-seco-tricyclic monoterpene indole alkaloid, which are the first seco-alkaloids possessing such cleavage positions from U. rhynchophylla. All the isolated compounds were evaluated for their bioactivities on dopamine D2 and Mu opioid receptors for discovering natural therapeutic drugs targeting central nervous system (CNS) diseases. Compounds 1, 2, 4, 5, 20 and 21 showed antagonistic bioactivities on the D2 receptor (IC50 0.678-15.200 µM), and compounds 1, 3, 6, 9, 10, 13, 18, 19 and 21 exhibited antagonistic effects on the Mu receptor (IC50 2.243-32.200 µM). Among them, compounds 1 and 21 displayed dual-target activities. Compound 1 showed conspicuous antagonistic activity on D2 and Mu receptors with the IC50 values of 0.678 ± 0.182 µM and 13.520 ± 2.480 µM, respectively. Compound 21 displayed moderate antagonistic activity on the two receptors with the IC50 values at 15.200 ± 1.764 µM and 32.200 ± 5.695 µM, respectively.
Assuntos
Antagonistas dos Receptores de Dopamina D2 , Alcaloides Indólicos , Uncaria , Alcaloides/química , Alcaloides/farmacologia , Dopamina/metabolismo , Alcaloides Indólicos/farmacologia , Alcaloides Indólicos/química , Receptores Opioides mu/antagonistas & inibidores , Uncaria/química , Antagonistas dos Receptores de Dopamina D2/química , Antagonistas dos Receptores de Dopamina D2/farmacologia , Antagonistas de Entorpecentes/química , Antagonistas de Entorpecentes/farmacologiaRESUMO
To develop safer and potent analgesics, we designed, synthesized, and evaluated a new series of benzylaminofentanyl derivates as bifunctional µ opioid receptor (MOR) and σ1 receptor (σ1R) ligands. Compound 68 (Tao-191) showed desirable MOR agonism (Ki = 6.5 nΜ; EC50 = 48.5 nΜ, Emax = 66.3%) and σ1R antagonism (Ki = 35.7 nM) in vitro, and exerted powerful analgesic effects in the abdominal constriction test (ED50 = 0.32 mg/kg, in mice), formalin-induced pain test (phase II, ED50 = 2.26 mg/kg, in rats), and paclitaxel-induced neuropathic pain model (ED50 = 0.30 mg/kg, in mice). The contributions of MOR and σ1R to its antinociceptive effect were verified by combined administration with the MOR antagonist naloxone and the σ1R agonist PRE-084, respectively. At equianalgesic doses, compound 68 induced fewer MOR-related side effects-including physical and psychological dependence, respiratory depression, constipation, and acute hyperlocomotion-than fentanyl. The results provide a rationale for further exploration of the action and safety of dual MOR/σ1R ligands as a promising avenue for the development of potent and safe analgesics.
Assuntos
Analgésicos , Neuralgia , Receptores Opioides mu , Receptores sigma , Analgésicos/farmacologia , Animais , Ligantes , Camundongos , Naloxona/farmacologia , Ratos , Receptores Opioides mu/agonistas , Receptores Opioides mu/antagonistas & inibidores , Receptores sigma/agonistas , Receptores sigma/antagonistas & inibidores , Receptor Sigma-1RESUMO
The lateral hypothalamus (LH) sends neural pathways to structures involved on predatorrelated defensive behaviours, escape and antinociception. The aim of this study was to investigate the role played by µ-opioid receptors located on LH neurons in defensive behaviour and unconditioned fearinduced antinociception elicited by electric stimulation of LH. To achieve the goals, the µ1-opioid receptor selective antagonist naloxonazine was administered at different concentrations in the LH, and the defensive behaviour and fearinduced antinociception elicited by electrical stimulation of LH were evaluated. The electrical stimulation of LH caused escape behaviour followed by defensive antinociception. Microinjections of naloxonazine in a concentration of 5.0 µg/0.2 µL in the LH decreased the aversive stimulusinduced escape behaviour thresholds, but diminished defensive antinociception. These findings suggest that µ-opioid receptors of LH can be critical to panic attackrelated symptoms and facilitate the unconditioned fearinduced antinociception produced by LH neurons activation.
Assuntos
Comportamento Animal , Região Hipotalâmica Lateral , Transtorno de Pânico , Receptores Opioides mu , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Bicuculina/farmacologia , Medo/fisiologia , Região Hipotalâmica Lateral/efeitos dos fármacos , Região Hipotalâmica Lateral/metabolismo , Naloxona/análogos & derivados , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Nociceptividade , Pânico/fisiologia , Transtorno de Pânico/metabolismo , Transtorno de Pânico/psicologia , Ratos , Ratos Wistar , Receptores Opioides mu/antagonistas & inibidores , Receptores Opioides mu/metabolismoRESUMO
Ingestion of alkaloid metabolites from the bark of Galbulimima (GB) sp. leads to psychotropic and excitatory effects in humans1-4. Limited, variable supply of GB alkaloids5, however, has impeded their biological exploration and clinical development6. Here we report a solution to the supply of GB18, a structural outlier and putative psychotropic principle of Galbulimima bark. Efficient access to its challenging tetrahedral attached-ring motif required the development of a ligand-controlled endo-selective cross-electrophile coupling and a diastereoselective hydrogenation of a rotationally dynamic pyridine. Reliable, gram-scale access to GB18 enabled its assignment as a potent antagonist of κ- and µ-opioid receptors-the first new targets in 35 years-and lays the foundation to navigate and understand the biological activity of Galbulimima metabolites.
Assuntos
Alcaloides , Magnoliopsida , Alcaloides/síntese química , Alcaloides/farmacologia , Técnicas de Química Sintética , Humanos , Hidrogenação , Ligantes , Magnoliopsida/química , Casca de Planta/química , Piridinas , Receptores Opioides kappa/antagonistas & inibidores , Receptores Opioides mu/antagonistas & inibidoresRESUMO
Opioid-related fatalities involving synthetic opioids have reached unprecedented levels. This study evaluated the respiratory depressant effects of seven fentanyl analogs that have either emerged in the illicit drug supply or been identified in toxicological analyses following fatal or non-fatal intoxications. Adult male Swiss Webster mice were administered fentanyl analogs (isobutyrylfentanyl, crotonylfentanyl, para-methoxyfentanyl, para-methoxybutyrylfentanyl, 3-furanylfentanyl, thiophenefentanyl, and benzodioxolefentanyl) and their effects on minute volume as compared to mu-opioid receptor (MOR) agonist standards (fentanyl, morphine, and buprenorphine) were measured using whole body plethysmography (WBP). All drugs elicited significant (p ≤ 0.05) hypoventilation relative to vehicle for at least one dose tested: morphine (1, 3.2, 10, 32 mg/kg), buprenorphine, (0.032, 0.1, 0.32, 1, 3.2 mg/kg), fentanyl (0.0032, 0.01, 0.032, 0.1, 1, 32 mg/kg), isobutyrylfentanyl (0.1, 0.32, 1, 3.2, 10 mg/kg), crotonylfentanyl (0.1, 0.32, 1, 3.2, 10 mg/kg), para-methoxyfentanyl (0.1, 0.32, 1, 3.2, 10 mg/kg), para-methoxybutyrylfentanyl (0.32, 1, 3.2, 10 mg/kg), 3-furanylfentanyl (0.1, 0.32, 1, 3.2, 10 mg/kg), thiophenefentanyl (1, 3.2, 10, 32, 100 mg/kg), and benzodioxolefentanyl (3.2, 10, 32, 100 mg/kg). The ED50 values for hypoventilation showed a rank order of potency as follows: fentanyl (ED50 = 0.96 mg/kg) > 3-furanylfentanyl (ED50 = 2.60 mg/kg) > crotonylfentanyl (ED50 = 2.72 mg/kg) > para-methoxyfentanyl (ED50 = 3.31 mg/kg) > buprenorphine (ED50 = 10.8 mg/kg) > isobutyrylfentanyl (ED50 = 13.5 mg/kg) > para-methoxybutyrylfentanyl (ED50 = 16.1 mg/kg) > thiophenefentanyl (ED50 = 18.0 mg/kg) > morphine (ED50 = 55.3 mg/kg) > benzodioxolefentanyl (ED50 = 10,168 mg/kg). A naloxone pretreatment (10 mg/kg) attenuated the hypoventilatory effects of all drugs. These results establish that the respiratory depressant effects of these fentanyl analogs are at least in part mediated by the MOR.
Assuntos
Fentanila/análogos & derivados , Hipoventilação/prevenção & controle , Naloxona/farmacologia , Receptores Opioides mu/antagonistas & inibidores , Animais , Fentanila/química , Fentanila/toxicidade , Hipoventilação/induzido quimicamente , Hipoventilação/fisiopatologia , Masculino , Camundongos , Estrutura Molecular , Antagonistas de Entorpecentes/farmacologia , Pletismografia/métodos , Receptores Opioides mu/fisiologia , Mecânica Respiratória/efeitos dos fármacos , Mecânica Respiratória/fisiologiaRESUMO
BACKGROUND: Xanthomicrol is one of the methoxylated flavones and a promising cancer chemopreventive agent, but its anti-migration and anti-invasion ability on human hepatocellular carcinoma (HCC) remains unknown. OBJECTIVES: This study aims to explore Xanthomicrol's effects on migration and invasion ability of the human HCC Huh7 cell line. METHODS: Viability of Huh7 cells was measured by cell counting kit-8 (CCK8) assay. Cell apoptosis was assayed with flow cytometry analysis. The ability of migration and invasion of Huh7 cells was then detected through Transwell assays. Epithelial-mesenchymal transition (EMT)-related proteins were also detected through Western blot. KEY FINDINGS: Xanthomicrol inhibits the migration and invasion of Huh7 cells. The overexpression of Μu-opioid receptor (MOR) increases Huh7 cells' proliferation and enhances migration and invasion ability, while xanthomicrol treatment decreases the expression of MOR. Moreover, xanthomicrol can reverse migration, invasion and EMT-related protein expression by overexpressed MOR. CONCLUSIONS: These results suggest that xanthomicrol is a potential MOR antagonist, and it possesses potent anti-migration and anti-invasion ability on Huh7 cells.
Assuntos
Carcinoma Hepatocelular , Movimento Celular/efeitos dos fármacos , Flavonas/farmacologia , Neoplasias Hepáticas , Invasividade Neoplásica/prevenção & controle , Receptores Opioides mu/antagonistas & inibidores , Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Carcinoma Hepatocelular/tratamento farmacológico , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Transição Epitelial-Mesenquimal/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Neoplasias Hepáticas/tratamento farmacológico , Neoplasias Hepáticas/patologiaRESUMO
A new series of enkephalin-like tetrapeptide analogs modified at the C-terminus by an N-(3,4-dichlorophenyl)-N-(piperidin-4-yl)propionamide (DPP) moiety were designed, synthesized, and tested for their binding affinities at opioid receptors and monoamine transporters to evaluate their potential multifunctional activity for the treatment of chronic pain. Most ligands exhibited high binding affinities in the nanomolar range at the opioid receptors with a slight delta-opioid receptor (DOR) selectivity over mu-opioid receptor (MOR) and kappa-opioid receptor (KOR) and low binding affinities in the micromolar range at the monoamine transporters, SERT and NET. Ligands of which the positions 1 and 4 were substituted by Dmt and Phe(4-X) residues, respectively, showed the excellent binding affinities at three opioid receptors. Among them, Dmt-d-Tic-Gly-Phe(4-F)-DPP was the most promising considering its excellent opioid affinities, particularly unexpected high binding affinity (Ki = 0.13 nM) at the KOR, and moderate interactions with serotonin/norepinephrine reuptake inhibitors (SNRIs). Docking studies revealed that the ligand was a good fit for the KOR binding pocket (binding score = 8,750).
Assuntos
Amidas/farmacologia , Oligopeptídeos/farmacologia , Receptores Opioides kappa/antagonistas & inibidores , Receptores Opioides mu/antagonistas & inibidores , Amidas/química , Relação Dose-Resposta a Droga , Humanos , Ligantes , Modelos Moleculares , Estrutura Molecular , Oligopeptídeos/síntese química , Oligopeptídeos/química , Receptores Opioides kappa/metabolismo , Receptores Opioides mu/metabolismo , Relação Estrutura-AtividadeRESUMO
Opioid overdose is a leading cause of death in the United States. The only treatment available currently is the competitive antagonist, naloxone (Narcan® ). Although naloxone is very effective and has saved many lives, as a competitive antagonist it has limitations. Due to the short half-life of naloxone, renarcotization can occur if the ingested opioid agonist remains in the body longer. Moreover, because antagonism by naloxone is surmountable, renarcotization can also occur in the presence of naloxone if a relatively larger dose of opioid agonist is taken. In such circumstances, a long-lasting, non-surmountable antagonist would offer an improvement in overdose treatment. Methocinnamox (MCAM) has been reported to have a long duration of antagonist action at mu opioid receptors in vivo. In HEK cells expressing the human mu opioid receptor, MCAM antagonism of mu agonist-inhibition of cAMP production was time-dependent, non-surmountable and non-reversible, consistent with (pseudo)-irreversible binding. In vivo, MCAM injected locally into the rat hindpaw antagonized mu agonist-mediated inhibition of thermal allodynia for up to 96 h. By contrast, antagonism by MCAM of delta or kappa agonists in HEK cells and in vivo was consistent with simple competitive antagonism. Surprisingly, MCAM also shifted the concentration-response curves of mu agonists in HEK cells in the absence of receptor reserve in a ligand-dependent manner. The shift in the [D-Ala2 ,N-MePhe4 ,Gly-ol5 ]-enkephalin (DAMGO) concentration-response curve by MCAM was insensitive to naloxone, suggesting that in addition to (pseudo)-irreversible orthosteric antagonism, MCAM acts allosterically to alter the affinity and/or intrinsic efficacy of mu agonists.
Assuntos
Cinamatos/farmacologia , Derivados da Morfina/farmacologia , Antagonistas de Entorpecentes/farmacologia , Receptores Opioides mu/antagonistas & inibidores , Regulação Alostérica/efeitos dos fármacos , Animais , AMP Cíclico/metabolismo , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Células HEK293 , Humanos , Ligantes , Masculino , Naloxona/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores Opioides mu/metabolismo , Fatores de TempoRESUMO
AIMS: Dezocine and pentazocine, widely prescribed in China for postoperative pain, were initially considered as mixed agonist/antagonist targeting µ-opioid receptors (MORs) and κ-opioid receptors (KORs). However, dezocine has been revealed to alleviate chronic neuropathic pain through MOR activation and norepinephrine reuptake inhibition (NRI). This study investigated dezocine- and pentazocine-induced antinociception and physical dependence development, compared to the typical MOR-NRI opioid tapentadol. MAIN METHODS: Calcium mobilization assay was conducted to assess the potency of the drugs while hot-plate test was performed to compare the antinociception. Physical dependence development was compared with morphine. KEY FINDINGS: Treatment with dezocine, pentazocine and tapentadol stimulated calcium mobilization in HEK293 cells stably expressed MORs but not KORs, whereas dezocine and pentazocine inhibited KOR activities. Subcutaneously injected dezocine-, tapentadol- and pentazocine-induced antinociception dose-dependently, in hot-plate test. Intrathecally injected MOR antagonist CTAP, norepinephrine depletor 6-OHDA and α2-adrenoceptor (α2-AR) antagonist yohimbine partially antagonized dezocine, pentazocine and tapentadol antinociception. Whereas specific KOR antagonist GNTI did not alter their antinociception, the putative inverse KOR agonist nor-BNI reduced dezocine and pentazocine antinociception. Moreover, combined CTAP and 6-OHDA or yohimbine blocked dezocine and tapentadol antinociception but displayed the same partial inhibition on pentazocine antinociception as CTAP alone. Furthermore, compared to morphine and pentazocine, long-term treatment with dezocine and tapentadol produced much less physical dependence-related withdrawal signs, which were restored by spinal 6-OHDA or yohimbine treatment. SIGNIFICANCE: Our findings illustrated that dezocine and tapentadol, but not pentazocine, exert remarkable antinociception in nociceptive pain with less abuse liability via dual mechanisms of MOR activation and NRI.
Assuntos
Analgésicos Opioides/farmacologia , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Dor Nociceptiva/tratamento farmacológico , Pentazocina/farmacologia , Receptores Opioides mu/agonistas , Tapentadol/farmacologia , Tetra-Hidronaftalenos/farmacologia , Inibidores da Captação Adrenérgica/química , Inibidores da Captação Adrenérgica/farmacologia , Analgésicos Opioides/química , Analgésicos Opioides/uso terapêutico , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/química , Compostos Bicíclicos Heterocíclicos com Pontes/uso terapêutico , Agonismo de Drogas , Antagonismo de Drogas , Células HEK293 , Humanos , Camundongos , Pentazocina/química , Pentazocina/uso terapêutico , Receptores Adrenérgicos/metabolismo , Receptores Opioides kappa/agonistas , Receptores Opioides kappa/antagonistas & inibidores , Receptores Opioides mu/antagonistas & inibidores , Tapentadol/química , Tapentadol/uso terapêutico , Tetra-Hidronaftalenos/química , Tetra-Hidronaftalenos/uso terapêuticoRESUMO
PURPOSE OF REVIEW: Opioids are still the most effective and widely used treatments for acute and chronic pain in cancer patients. This review focuses on the impact of opioids and mu-opioid receptors (MOR) on tumor progression and providing new ideas for targeting the MOR in cancer treatment. RECENT FINDINGS: Studies estimated that opioids facilitate tumor progression and are related to the worse prognosis in cancer patients. As the primary receptor of opioids, MOR is involved in the regulation of malignant transformation of tumors and participating in proliferation, invasion, metastasis, and angiogenesis. MOR may be a new molecular marker of malignant tumors and thus become a new target for cancer therapy, which may be beneficial to the outcomes of cancer patients.