RESUMEN
Polar auxin transport (PAT) plays key roles in the regulation of plant growth and development. Flavonoids have been implicated in the inhibition of PAT. However, the active flavonoid derivative(s) involved in this process in vivo has not yet been identified. Here, we provide evidence that a specific flavonol bis-glycoside is correlated with shorter plant stature and reduced PAT. Specific flavonoid-biosynthetic or flavonoid-glycosylating steps were genetically blocked in Arabidopsis thaliana. The differential flavonol patterns established were analyzed by high-performance liquid chromatography (HPLC) and related to altered plant stature. PAT was monitored in stem segments using a radioactive [(3)H]-indole-3-acetic acid tracer. The flavonoid 3-O-glucosyltransferase mutant ugt78d2 exhibited a dwarf stature in addition to its altered flavonol glycoside pattern. This was accompanied by reduced PAT in ugt78d2 shoots. The ugt78d2-dependent growth defects were flavonoid dependent, as they were rescued by genetic blocking of flavonoid biosynthesis. Phenotypic and metabolic analyses of a series of mutants defective at various steps of flavonoid formation narrowed down the potentially active moiety to kaempferol 3-O-rhamnoside-7-O-rhamnoside. Moreover, the level of this compound was negatively correlated with basipetal auxin transport. These results indicate that kaempferol 3-O-rhamnoside-7-O-rhamnoside acts as an endogenous PAT inhibitor in Arabidopsis shoots.
Asunto(s)
Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Quempferoles/fisiología , Arabidopsis/crecimiento & desarrollo , Transporte Biológico , Quempferoles/metabolismo , Fenotipo , Brotes de la Planta/genética , Brotes de la Planta/metabolismoRESUMEN
OATP1A2 and OATP2B1 are uptake transporters of the human organic anion transporting polypeptide (OATP) family with a broad substrate spectrum including several endogenous compounds as well as drugs such as the antihistaminic drug fexofenadine and HMG-CoA reductase inhibitors. Both transporters are localized in the apical membrane of human enterocytes. Flavonoids, abundantly occurring in plants, have previously been shown to interact with drug metabolizing enzymes and transporters. However, the impact of flavonoids on OATP1A2 and OATP2B1 transport function has not been analyzed in detail. Therefore, HEK293 cell lines stably expressing OATP1A2 and OATP2B1 were used to investigate the influence of the Ginkgo flavonoids apigenin, kaempferol, and quercetin on the transport activity of OATP1A2 and OATP2B1. K(i) values of all three flavonoids determined from Dixon plot analyses using BSP as substrate indicated a competitive inhibition with quercetin as the most potent inhibitor of OATP1A2 (22.0µM) and OATP2B1 (8.7µM) followed by kaempferol (OATP1A2: 25.2µM, OATP2B1: 15.1µM) and apigenin (OATP1A2: 32.4µM OATP2B1: 20.8µM). Apigenin, kaempferol, and quercetin led to a concentration-dependent decrease of the OATP1A2-mediated fexofenadine transport with IC(50) values of 4.3µM, 12.0µM, and 12.6µM, respectively. The OATP1A2- and OATP2B1-mediated transport of atorvastatin was also efficiently inhibited by apigenin (IC(50) for OATP1A2: 9.3µM, OATP2B1: 13.9µM), kaempferol (IC(50) for OATP1A2: 37.3µM, OATP2B1: 20.7µM) and quercetin (IC(50) for OATP1A2: 13.5µM, OATP2B1: 14.1µM). These data indicate that modification of OATP1A2 and OATP2B1 transport activity by apigenin, kaempferol, and quercetin may be a mechanism for food-drug or drug-drug interactions in humans.
Asunto(s)
Apigenina/fisiología , Quempferoles/fisiología , Transportadores de Anión Orgánico/fisiología , Péptidos/fisiología , Quercetina/fisiología , Línea Celular , Interacciones Farmacológicas , Humanos , Transportadores de Anión Orgánico/antagonistas & inhibidores , Transportadores de Anión Orgánico/metabolismo , Péptidos/metabolismo , Transporte de Proteínas/efectos de los fármacos , Transporte de Proteínas/fisiologíaRESUMEN
PURPOSE: The present study was undertaken to elucidate the chemoprotective mechanism of kaempferol, which possesses anti-oxidative and anti-apoptotic properties. METHODS: House Ear Institute-Organ of Corti 1 (HEI-OC1) cells were treated with kaempferol in the presence or absence of cisplatin. Cisplatin-induced oxidative stress was assessed by analysis of Comet assay, DNA-laddering assay and activation of caspases. Heme oxygenase-1 (HO-1), mitogen-activated protein kinase (MAPK) pathway and nuclear factor-E2-related factor 2 (Nrf2) were measured by Western blot analysis. Transfection of small interfering RNAs (siRNA), glutathione (GSH) assay and RT-PCR were performed in this study. RESULTS: Kaempferol protected cells against cisplatin-induced apoptosis in a dose-dependent manner in HEI-OC1 cells. Kaempferol-induced HO-1 expression protected against cell death though the c-Jun N-terminal kinase (JNK) pathway and by the aid of Nrf2 translocation. Kaempferol increased the cellular level of GSH and the expression of GCLC time-dependently. siRNA GCLC blocked the increase of GSH level by kaempferol and the protective effect of kaempferol against cisplatin-induced cell death. CONCLUSION: The expression of HO-1 by kaempferol inhibits cisplatin-induced apoptosis in HEI-OC1 cells, and the mechanism of protective effect is also associated with its inductive effect of GCLC expression.
Asunto(s)
Apoptosis/efectos de los fármacos , Dominio Catalítico , Cisplatino/toxicidad , Glutamato-Cisteína Ligasa/biosíntesis , Hemo-Oxigenasa 1/biosíntesis , Quempferoles/fisiología , Órgano Espiral/enzimología , Animales , Apoptosis/genética , Dominio Catalítico/efectos de los fármacos , Dominio Catalítico/genética , Línea Celular , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Cisplatino/antagonistas & inhibidores , Relación Dosis-Respuesta a Droga , Inducción Enzimática/efectos de los fármacos , Inducción Enzimática/genética , Regulación de la Expresión Génica/efectos de los fármacos , Glutamato-Cisteína Ligasa/genética , Hemo-Oxigenasa 1/genética , Ratones , Órgano Espiral/citología , Órgano Espiral/efectos de los fármacosRESUMEN
ABSTRACT Understanding the metabolic responses of the plant to a devastating foliar disease, soybean rust, caused by Phakopsora pachyrhizi, will assist in development of cultivars resistant to soybean rust. In this study, differences in phenolic metabolism were analyzed between inoculated and noninoculated plants using two susceptible and three resistant soybean genotypes with known resistance genes. Rust infection resulted in increased accumulation of isoflavonoids and flavonoids in leaves of all soybean genotypes tested. Although the soybean phytoalexin glyceollin was not detected in leaves of uninfected plants, accumulation of this compound at marked levels occurred in rust-infected leaves, being substantially higher in genotypes with a red-brown resistant reaction. In addition, there was inhibition of P. pachyrhizi spore germination by glyceollin, formononetin, quercetin, and kaempferol. However, there was no correlation between concentrations of flavonoids quercetin and kaempferol and rust-induced isoflavonoid formononetin in soybean leaves and rust resistance. Lignin synthesis also increased in all inoculated soybean genotypes whereas there was no significant difference in all noninoculated soybean genotypes. Cell wall lignification was markedly higher in inoculated resistant lines compared with inoculated susceptible lines, indicating a possible protective role of lignin in rust infection development.