RESUMO
Gastrointestinal toxicity, such as late-onset diarrhea, is a significant concern in irinotecan hydrochloride (CPT-11)-containing regimens. Prophylaxis of late-onset diarrhea has been reported with use of Japanese traditional (Kampo) medicine containing baicalin and with the antibiotic cefixime, and this has been explained in terms of inhibition of bacterial deconjugation of SN-38-glucuronide since unconjugated SN-38 (active metabolite of CPT-11) is responsible for the gastrointestinal toxicity. It is also prerequisite for SN-38 to be accumulated in intestinal tissues to exert toxicity. Based on the fact that liver-specific organic anion transporting polypeptide (OATP)1B1, a member of the same family as OATP2B1, is known to be involved in hepatic transport of SN-38, we hypothesized that intestinal transporter OATP2B1 contributes to the accumulation of SN-38 in gastrointestinal tissues, and its inhibition would help prevent associated toxicity. We found that uptake of SN-38 by OATP2B1-expressing Xenopus oocytes was significantly higher than that by control oocytes. OATP2B1-mediated uptake of SN-38 was saturable, pH dependent, and decreased in the presence of baicalin, cefixime, or fruit juices such as apple juice. In vivo gastrointestinal toxicity of SN-38 in mice caused by oral administration for consecutive 5 days was prevented by coingestion of apple juice. Thus, OATP2B1 contributes to the uptake of SN-38 by intestinal tissues, triggering gastrointestinal toxicity. So, in addition to the reported inhibition of bacterial ß-glucuronidase by cefixime or baicalin, inhibition of OATP2B1 may also contribute to prevention of gastrointestinal toxicity. Apple juice may be helpful for prophylaxis of late-onset diarrhea observed in CPT-11 therapy without disturbance of the intestinal microflora.
Assuntos
Antineoplásicos/toxicidade , Camptotecina/análogos & derivados , Diarreia/induzido quimicamente , Absorção Intestinal , Intestinos/efeitos dos fármacos , Transportadores de Ânions Orgânicos/metabolismo , Administração Oral , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/metabolismo , Bactérias/efeitos dos fármacos , Bactérias/enzimologia , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/metabolismo , Camptotecina/administração & dosagem , Camptotecina/metabolismo , Camptotecina/toxicidade , Cefixima/farmacologia , Diarreia/metabolismo , Diarreia/microbiologia , Diarreia/prevenção & controle , Inibidores Enzimáticos/farmacologia , Feminino , Flavonoides/farmacologia , Interações Alimento-Droga , Sucos de Frutas e Vegetais , Microbioma Gastrointestinal , Técnicas de Transferência de Genes , Glucuronidase/antagonistas & inibidores , Glucuronidase/metabolismo , Concentração de Íons de Hidrogênio , Mucosa Intestinal/metabolismo , Intestinos/microbiologia , Irinotecano , Cinética , Malus , Camundongos Endogâmicos C57BL , Oócitos , Transportadores de Ânions Orgânicos/genética , Xenopus laevisRESUMO
Clinical studies have shown that moderate whisky consumption increased renal excretion of urate into urine and decreased serum urate level, but the mechanism involved has not been established. Because renal reabsorption influences serum urate level, the effects of the whisky congeners on urate transporters, urate transporter 1 (URAT1), and voltage-driven urate transporter (URATv1) involved in reabsorptive transport of urate were examined. In transporter-expressing Xenopus oocytes, 12-year-old and 18-year-old whisky congeners inhibited urate uptake by URAT1 with IC50 values of 0.08 ± 0.01 and 0.04 ± 0.01 mg/mL, respectively, while urate uptake by URATv1 was inhibited only at 1 mg/mL. Decreased serum urate level after whisky consumption may be mainly due to inhibition of URAT1 by the congeners.
Assuntos
Bebidas Alcoólicas , Transportadores de Ânions Orgânicos/metabolismo , Proteínas de Transporte de Cátions Orgânicos/metabolismo , Ácido Úrico/metabolismo , Animais , Transporte Biológico , Humanos , Concentração Inibidora 50 , Oócitos/metabolismo , Ácido Úrico/sangue , XenopusRESUMO
We examined the effect of 0-20% back pressure, which functions as a resistance to emulsification in a high-pressure homogenizer, on emulsification of lipid nanodispersions (emulsion and liposomes) less than 100 nm in diameter. Back pressure in the range of 0.9-3.8% of the emulsification pressure enhanced the emulsification, and the particle diameter of lipid nanodispersion was the smallest at 2% back pressure. The back pressure effect was independent of the actual pressure, which was regarded as the difference between the emulsification and the back pressures. The mechanism of the back pressure effect was considered to be enhancement of emulsification by suppression of collapse cavitation in the high-pressure emulsification module. This back pressure effect appeared in emulsification of emulsion and liposomes, and was seen predominantly in the early emulsification phase (within 10 passages). The particles of lipid nanodispersions prepared at 2% back pressure with adequate re-circulation achieved physicochemically optimal diameter with a narrow size distribution, and were more stable at 60°C for 7 days than particles prepared with 20% back pressure. Our results indicate that emulsification with a low level of back pressure is effective for production of stable lipid nanodispersions with narrow size distribution.
Assuntos
Lecitinas/química , Nanopartículas , Nanotecnologia , Óleo de Soja/química , Tecnologia Farmacêutica/métodos , Química Farmacêutica , Composição de Medicamentos , Emulsões , Desenho de Equipamento , Lipossomos , Nanotecnologia/instrumentação , Tamanho da Partícula , Pressão , Tecnologia Farmacêutica/instrumentação , Temperatura , Fatores de TempoRESUMO
Induction of the breast cancer resistance protein (BCRP/ABCG2) expression has been found in various tissues and cell-types after exposure to chemicals including 17ß-estradiol, rosiglitazone, imatinib, as well as aryl hydrocarbon receptor (AhR) activators such as 2,3,7,8-tetrachlorodibenzodioxin, 3-methylcholanthrene (3MC), and omeprazole. However, the mechanism(s) underlying AhR-related induction of ABCG2 is largely unknown. Here, we demonstrate the AhR-dependent induction of ABCG2 expression in human colon adenocarcinoma LS174T cells. Importantly, a novel distal AhR-responsive element (AhRE5) located -2357/-2333bp upstream of the ABCG2 transcriptional start site has been identified and characterized as a functional unit pivotal to 3MC-mediated induction of ABCG2. Cell-based reporter assays revealed that deletion of AhRE5 and 4 dramatically attenuated 3MC-induced activation of ABCG2 reporter activity, while further deletion of the proximal AhRE3 and 2 only moderately changed the luciferase activities. Notably, site-directed mutation of the AhRE5 in the BCRP-3.8kb reporter construct alone resulted in approximately 80% decrease in 3MC activation of the ABCG2 promoter; additional mutation of the AhRE4 site had negligible effect on the ABCG2 promoter activity. Moreover, chromatin immunoprecipitation assays demonstrated that treatment with 3MC significantly enhanced the recruitment of AhR to the AhRE5 occupied region, and mutation of the AhRE5 site clearly dissociated AhR protein from this promoter region. Together, these data show that the novel distal AhRE5 is critical for AhR-mediated transcriptional activation of ABCG2 gene expression in LS174T cells, and it may offer new strategies for early identification of ABCG2 inducers, which would be of benefit for preventing transporter-associated drug-drug interactions.
Assuntos
Transportadores de Cassetes de Ligação de ATP/biossíntese , Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Proteínas de Neoplasias/biossíntese , Receptores de Hidrocarboneto Arílico/fisiologia , Xenobióticos/farmacologia , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Linhagem Celular Tumoral , Técnicas de Silenciamento de Genes , Ginkgo biloba , Humanos , Metilcolantreno/farmacologia , Proteínas de Neoplasias/genética , Extratos Vegetais/farmacologia , Elementos de Resposta/efeitos dos fármacos , Elementos de Resposta/fisiologia , Ativação Transcricional/efeitos dos fármacos , Ativação Transcricional/fisiologiaRESUMO
PURPOSE: Vorinostat [suberoylanilide hydroxamic acid (SAHA)] is a potent histone deacetylase inhibitor with promising clinical efficacy as an anticancer agent. In this preclinical study, we evaluated combining cytosine arabinoside [1-beta-D-arabinofuranosylcytosine (ara-C)] and/or etoposide with vorinostat for use in the treatment of acute leukemias. EXPERIMENTAL DESIGN: Cell survival was examined in vitro in HL-60 human myeloid leukemia cells and K562 myeloid blast crisis chronic myelogenous leukemia cells, using the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt and/or fluorescein diacetate/propidium iodide assays. Drug interactions were analyzed by the combination index method (CalcuSyn) and by a novel statistical method that we developed (SynStat). Cell cycle phase distribution was measured by flow cytometry. RESULTS: Cytotoxic antagonism resulted when vorinostat was combined concomitantly with ara-C; however, when vorinostat was given first followed by a drug-free interval before ara-C treatment, this sequential combination was mostly synergistic. Etoposide combined with vorinostat was additive to synergistic, and the synergism became more pronounced when etoposide was given after vorinostat. Cell cycle analyses revealed that the sequence-dependent interaction of vorinostat and ara-C or etoposide reflected the arrest of cells in G1 or G2 phase during vorinostat treatment and recovery into S phase after removal of vorinostat. CONCLUSIONS: These findings using two independent methods to assess drug combination effects provide a preclinical rationale for phase I trials of the sequential combination of vorinostat followed by ara-C and etoposide in patients with advanced or refractory leukemias. CalcuSyn findings were concordant with those of SynStat, validating the use of the latter in analyzing drug interactions.