RESUMO
Cannabinoids exert anti-cancer actions; however, the underlying cytotoxic mechanisms and the cannabinoid receptors (CBRs) involved remain unclear. In this study, CBRs were characterized in several cancer cell lines. Radioligand binding screens surprisingly revealed specific binding only for the non-selective cannabinoid [3H]WIN-55,212-2, and not [3H]CP-55,940, indicating that the expressed CBRs exhibit atypical binding properties. Furthermore, [3H]WIN-55,212-2 bound to a single site in all cancer cells with high affinity and varying densities. CBR characteristics were next compared between human prostate cancer cell lines expressing low (PC-3) and high (DU-145) CBR density. Although mRNA for canonical CBRs was detected in both cell lines, only 5 out of 15 compounds with known high affinity for canonical CBRs displaced [3H]WIN-55,212-2 binding. Functional assays further established that CBRs in prostate cancer cells exhibit distinct signaling properties relative to canonical Gi/Go-coupled CBRs. Prostate cancer cells chronically exposed to both CBR agonists and antagonists/inverse agonists produced receptor downregulation, inconsistent with actions at canonical CBRs. Treatment of DU-145 cells with CBR ligands increased LDH-release, decreased ATP-dependent cell viability, and produced mitochondrial membrane potential depolarization. In summary, several cancer cell lines express CBRs with binding and signaling profiles dissimilar to canonical CBRs. Drugs selectively targeting these atypical CBRs might exhibit improved anti-cancer properties.
Assuntos
Canabinoides , Neoplasias da Próstata , Canabinoides/farmacologia , Morte Celular , Humanos , Masculino , Próstata/metabolismo , Receptores de Canabinoides/metabolismo , Transdução de SinaisRESUMO
AIMS: Characterizing cannabinoid receptors (CBRs) expressed in Ewing sarcoma (EWS) cell lines as potential targets for anti-cancer drug development. MAIN METHODS: CBR affinity and function were examined by competitive binding and G-protein activation, respectively. Cannabinoid-mediated cytotoxicity and cell viability were evaluated by LDH, and trypan blue assays, respectively. KEY FINDINGS: qRT-PCR detected CB1 (CB1R) and CB2 receptor (CB2R) mRNA in TC-71 cells. However, binding screens revealed that CBRs expressed exhibit atypical properties relative to canonical receptors, because specific binding in TC-71 could only be demonstrated by the established non-selective CB1/CB2R radioligand [3H]WIN-55,212-2, but not CB1/CB2R radioligand [3H]CP-55,940. Homologous receptor binding demonstrated that [3H]WIN-55,212-2 binds to a single site with nanomolar affinity, expressed at high density. Further support for non-canonical CBRs expression is provided by subsequent binding screens, revealing that only 9 out of 28 well-characterized cannabinoids with high affinity for canonical CB1 and/or CB2Rs were able to displace [3H]WIN-55,212-2, whereas two ligands enhanced [3H]WIN-55,212-2 binding. Five cannabinoids producing the greatest [3H]WIN-55,212-2 displacement exhibited high nanomolar affinity (Ki) for expressed receptors. G-protein modulation and adenylyl cyclase assays further indicate that these CBRs exhibit distinct signaling/functional profiles compared to canonical CBRs. Importantly, cannabinoids with the highest affinity for non-canonical CBRs reduced TC-71 viability and induced cytotoxicity in a time-dependent manner. Studies in a second EWS cell line (A-673) showed similar atypical binding properties of expressed CBRs, and cannabinoid treatment produced cytotoxicity. SIGNIFICANCE: Cannabinoids induce cytotoxicity in EWS cell lines via non-canonical CBRs, which might be a potential therapeutic target to treat EWS.
Assuntos
Antineoplásicos/farmacologia , Benzoxazinas/farmacologia , Canabinoides/farmacologia , Morfolinas/farmacologia , Naftalenos/farmacologia , Receptor CB1 de Canabinoide/metabolismo , Receptor CB2 de Canabinoide/metabolismo , Sarcoma de Ewing/metabolismo , Ligação Competitiva , Linhagem Celular Tumoral , Citotoxinas/farmacologia , Desenvolvimento de Medicamentos , Humanos , Ligantes , Receptor CB1 de Canabinoide/agonistas , Receptor CB2 de Canabinoide/agonistasRESUMO
Synthetic indole cannabinoids characterized by a 2',2'-dimethylindan-5'-oyl group at the indole C3 position constitute a new class of ligands possessing high affinity for human CB2 receptors at a nanomolar concentration and a good selectivity index. Starting from the neutral antagonist 4, the effects of indole core modification on the pharmacodynamic profile of the ligands were investigated. Several N1 side chains afforded potent and CB2-selective neutral antagonists, notably derivatives 26 (R1 = n-propyl, R2 = H) and 35 (R1 = 4-pentynyl, R2 = H). Addition of a methyl group at C2 improved the selectivity for the CB2 receptor. Moreover, C2 indole substitution may control the CB2 activity as shown by the functionality switch in 35 (antagonist) and 49 (R1 = 4-pentynyl, R2 = CH3, partial agonist).
Assuntos
Indóis/síntese química , Indóis/farmacologia , Receptor CB2 de Canabinoide/antagonistas & inibidores , Técnicas de Química Sintética , Relação Dose-Resposta a Droga , Humanos , Indóis/química , Relação Estrutura-AtividadeRESUMO
A series of N-benzyl-7-azaindolequinuclidinone (7-AIQD) analogs have been synthesized and evaluated for affinity toward CB1 and CB2 cannabinoid receptors and identified as a novel class of cannabinoid receptor ligands. Structure-activity relationship (SAR) studies indicate that 7-AIQD analogs are dual CB1/CB2 receptor ligands exhibiting high potency with somewhat greater selectivity towards CB2 receptors compared to the previously reported indolequinuclidinone (IQD) analogs. Initial binding assays showed that 7-AIQD analogs 8b, 8d, 8f, 8g and 9b (1 µM) produced more that 50% displacement of the CB1/CB2 non-selective agonist CP-55,940 (0.1 nM). Furthermore, Ki values determined from full competition binding curves showed that analogs 8a, 8b and 8g exhibit high affinity (110, 115 and 23.7 nM, respectively) and moderate selectivity (26.3, 6.1 and 9.2-fold, respectively) for CB2 relative to CB1 receptors. Functional studies examining modulation of G-protein activity demonstrated that 8a acts as a neutral antagonist at CB1 and CB2 receptors, while 8b exhibits inverse agonist activity at these receptors. Analogs 8f and 8g exhibit different intrinsic activities, depending on the receptor examined. Molecular docking and binding free energy calculations for the most active compounds (8a, 8b, 8f, and 8g) were performed to better understand the CB2 receptor-selective mechanism at the atomic level. Compound 8g exhibited the highest predicted binding affinity at both CB1 and CB2 receptors, and all four compounds were shown to have higher predicted binding affinities with the CB2 receptor compared to their corresponding binding affinities with the CB1 receptor. Further structural optimization of 7-AIQD analogs may lead to the identification of potential clinical agents.
Assuntos
Compostos Aza/farmacologia , Indóis/farmacologia , Quinuclidinas/farmacologia , Receptor CB1 de Canabinoide/antagonistas & inibidores , Receptor CB2 de Canabinoide/antagonistas & inibidores , Compostos Aza/síntese química , Compostos Aza/química , Relação Dose-Resposta a Droga , Humanos , Indóis/síntese química , Indóis/química , Ligantes , Estrutura Molecular , Quinuclidinas/síntese química , Quinuclidinas/química , Receptor CB1 de Canabinoide/metabolismo , Receptor CB2 de Canabinoide/metabolismo , Relação Estrutura-AtividadeRESUMO
AKB48 and its fluorinated derivative 5F-AKB48 are synthetic cannabinoids (SCs) which have caused hospitalizations and deaths in human users. Abuse of SCs is dangerous because users may mistake them for natural cannabis, which is generally considered to be unlikely to elicit adverse effects. The present studies were designed to investigate the in vitro oxidative metabolism of 5F-AKB48 by human microsomal fractions from different organs and sexes as well as recombinant human cytochrome P450s (P450s). Mass spectrometry data tentatively provides evidence for the existence of mono-, di-, and trihydroxylated metabolites in a successive metabolism. Experiments utilizing P450s revealed that the most active enzymes (CYP2D6, CYP2J2, CYP3A4, and CYP3A5) effectively produced mono- and dihydroxylated metabolites, while CYP3A4/5 also produced significant amounts of the trihydroxylated metabolite. Moreover, although the affinity and potency of Phase I metabolite 4OH-5F-AKB48 is reduced when compared to that of the parent drug, this metabolite nevertheless retains similar high affinity for CB1 receptors, and greater efficacy for G protein activation, when compared to THC. Finally, 5F-AKB48 produced time- and dose-dependent cannabimimetic effects in mice which were more potent, but shorter acting, than those of Δ9-THC, and were attenuated by prior treatment with the CB1 antagonist rimonabant. Based on our data, we hypothesize that while many cases of toxicity result from genetic mutations, which can lead to a decrease or even absence of activity for Phase I drug-metabolizing enzymes, other P450s could potentially increase their role in the metabolism of these SCs. Because many metabolites of SCs remain biologically active, they could contribute to the deleterious effects of these substances.
Assuntos
Adamantano/análogos & derivados , Indazóis/metabolismo , Indazóis/toxicidade , Receptor CB1 de Canabinoide/agonistas , Receptor CB1 de Canabinoide/metabolismo , Adamantano/metabolismo , Adamantano/toxicidade , Animais , Antagonistas de Receptores de Canabinoides/farmacologia , Citocromo P-450 CYP2D6/genética , Citocromo P-450 CYP2D6/metabolismo , Citocromo P-450 CYP3A/genética , Citocromo P-450 CYP3A/metabolismo , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/metabolismo , Oxirredução/efeitos dos fármacos , Polimorfismo Genético , Ligação Proteica , Proteínas Recombinantes/metabolismo , Rimonabanto/farmacologia , Fatores SexuaisRESUMO
Recently, there has been a rise in abuse of synthetic cannabinoids (SCBs). The consumption of SCBs results in various effects and can induce toxic reactions, including paranoia, seizures, tachycardia and even death. 1-Naphthyl 1-(4-fluorobenzyl)-1H-indole-3-carboxylate (FDU-PB-22) is a third generation SCB whose metabolic pathway has not been fully characterized. In this study, we conducted in vitro pharmacokinetic analysis of FDU-PB-22 metabolism. Metabolic reactions containing FDU-PB-22 and human liver microsomes (HLMs) were independent of NADPH but not UDP-glucuronic acid (UDPGA), suggesting that UDP-glucuronosyltransferases (UGTs) are the primary enzymes involved in this metabolism. It was further determined that the metabolite extensively formed after incubating FDU-PB-22 with UDPGA in HLMs was the glucuronide of FDU-PB-22 3-carboxyindole (FBI-COOH). Various hepatic UGTs showed enzymatic activity for FBI-COOH. A series of UGT inhibitors showed moderate to strong inhibition of FBI-COOH-glucuronidation in HLMs, suggesting that multiple UGT isoforms are involved in FBI-COOH-glucuronidation in the liver. Interestingly, an extra-hepatic isoform, UGT1A10, exhibited the highest activity with a Km value of 38 µM and a Vmax value of 5.90 nmol/min/mg. Collectively, these results suggest that both genetic mutations of and the co-administration of inhibitors for FDU-PB-22-metabolizing UGTs will likely increase the risk of FDU-PB-22-induced toxicity.
Assuntos
Canabinoides/química , Canabinoides/farmacocinética , Indóis/química , Indóis/farmacocinética , Microssomos Hepáticos/enzimologia , Inibidores Enzimáticos/farmacologia , Glucuronosiltransferase/antagonistas & inibidores , Glucuronosiltransferase/genética , Glucuronosiltransferase/metabolismo , Humanos , Drogas Ilícitas/metabolismo , Drogas Ilícitas/farmacocinética , Inativação Metabólica , Microssomos Hepáticos/efeitos dos fármacos , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Uridina Difosfato Ácido Glucurônico/metabolismoRESUMO
A simple and reproducible procedure was developed to measure the volume of liquid microinjected into cells. A calibration curve of droplet fluorescence intensity versus volume was constructed by injecting a fluorescent dextran solution through a 125-150⯵m diameter micropipette into an oil-filled culture dish to create a spray of varied-sized droplets. The droplets retained a spherical shape because they were in an oil medium and they settled onto a glass surface coated with a superhydrophobic surface. Fluorescent micrographs of the droplets were obtained and analyzed with Image-J software to quantify the fluorescence intensity and radius of each spherical droplet to produce the calibration curve. Subsequently, Dut-145 human prostate carcinoma cells were microinjected with the same fluorescent dextran solution and fluorescent micrographs of the cells were obtained using the identical exposure conditions used to photograph the droplets. The measured fluorescence intensity of the microinjected cells was entered into the formula for the regression line that was fit to the calibration curve allowing determination of the volume of solution injected into each cell. Thus, a mixture consisting of known concentrations of a test material of test material (macromolecules, drugs, etc.) and a fluorescent dextran, volumetric, tracer can be used to quantify the relationship between the amount of a microinjected material and subsequent effects on cells.
Assuntos
Calibragem , Microinjeções , Microscopia de Fluorescência , Linhagem Celular Tumoral , Dextranos , Fluorescência , Corantes Fluorescentes/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Microscopia de Fluorescência/métodos , Propriedades de SuperfícieRESUMO
Acute liver injury is a debilitating disorder associated with loss of synthetic and detoxifying functions of the liver. This investigation was designed to assess cytoprotective efficacy of daily oral tiron (300 mg/kg) and daily oral methyl palmitate (300 mg/kg) against acetaminophen-induced acute liver injury. Rats were orally pretreated with either tiron or methyl palmitate at doses (300 mg/kg) for 7 days prior to oral acetaminophen (3 g/kg). Biochemical assay of markers of hepatotoxicity indices and oxidative stress was undertaken. Expression of inflammatory cytokine IL-6 was also evaluated. Histopathological examination of liver specimens was carried out as well. Both methyl palmitate and tiron significantly reversed the acetaminophen-induced elevation of biochemical markers (ALT, AST, and ALP) with restoration of SOD levels. Serum albumin levels and GSH liver contents increased, but in a nonsignificant manner. Moreover, methyl palmitate and tiron significantly decreased the level of serum LDH and serum IL-6 levels. Histopathology revealed that tiron markedly reduced the extent of acetaminophen-induced necrosis and methyl palmitate moderately decreased the necrosis in liver tissue. Methyl palmitate (300 mg/kg) and tiron (300 mg/kg) demonstrated promising hepatoprotective effects against acetaminophen-induced acute liver injury via modulation of inflammatory response and alleviation of the oxidative stress, allowing the preservation of hepatic functions.