RESUMEN
Potential chemopreventive agents exist in foods. Artepillin C in Brazilian propolis was investigated for its effects on colon carcinogenesis. We had found that artepillin C was a bioavailable antioxidant, which could be incorporated into intestinal Caco-2 and hepatic HepG2 cells without any conjugation and inhibited the oxidation of intracellular DNA. Artepillin C was then added to human colon cancer WiDr cells. It dose-dependently inhibited cell growth, inducing G(0)/G(1) arrest. The events involved a decrease in the kinase activity of a complex of cyclin D/cyclin-dependent kinase 4 and in the levels of retinoblastoma protein phosphorylated at Ser 780 and 807/811. The inhibitors of the complex, Cip1/p21 and Kip1/p27, increased at the protein level. On the other hand, Northern blotting showed that artepillin C did not affect the expression of Kip1/p27 mRNA. According to the experiments using isogenic human colorectal carcinoma cell lines, artepillin C failed to induce G(0)/G(1) arrest in the Cip1/p21-deleted HCT116 cells, but not in the wild-type HCT116 cells. Artepillin C appears to prevent colon cancer through the induction of cell-cycle arrest by stimulating the expression of Cip1/p21 and to be a useful chemopreventing factor in colon carcinogenesis.
Asunto(s)
Neoplasias del Colon/tratamiento farmacológico , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Fase G1/efectos de los fármacos , Inhibidores de la Síntesis del Ácido Nucleico/farmacología , Fenilpropionatos/farmacología , Própolis/química , Fase de Descanso del Ciclo Celular/efectos de los fármacos , Northern Blotting , Proliferación Celular/efectos de los fármacos , Neoplasias del Colon/metabolismo , Neoplasias del Colon/patología , Ciclina D , Quinasa 4 Dependiente de la Ciclina/metabolismo , Inhibidor p27 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p27 de las Quinasas Dependientes de la Ciclina/metabolismo , Ciclinas/metabolismo , Citometría de Flujo , Células HCT116 , Humanos , Inmunoprecipitación , Fosforilación/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteína de Retinoblastoma/metabolismoRESUMEN
Propolis has strong antioxidative activity. We investigated here whether this activity was available in intestinal Caco-2 and hepatic HepG2 cells. Phenolics in Brazilian propolis, extracted with ethyl acetate after the removal of resin and wax with 90% methanol, included artepillin C at 21 mmol/100 g, p-coumaric acid and cinnamic acid relatives 24mmol, kaempferol and its derivatives 9.4 mmol, naringenin 2.8 mmol, isosakuranetin 0.9 mmol, chrysin at 0.8 mmol/100 g, and several minor components. When the extract was added to the apical side of Caco-2 monolayers, artepillin C was specifically incorporated into the cells and released to the basolateral side mostly without conjugation. Then, artepillin C was added to HepG2 cells and exposed to reactive oxygens. Artepillin C prevented oxidative damage dose-dependently, and suppressed lipid peroxidation evaluated with thiobarbituric acid reactive substances by 16% and the formation of 8-hydroxy-2'-deoxyguanosine in DNA by 36% at a concentration of 20microM. Artepillin C is a bioavailable antioxidant.