Quercetin代謝產物抑制benzo[a]pyrene單獨或合併 β-胡蘿蔔素所誘發的傷害:ex vivo及體內試驗

Abstract

Quercetin, a flavonoid, is found ubiquitously in the vegetables and fruits. It possesses antioxidant and anti-inflammatory activity in vitro. However, the conjugated metabolites rather than quercetin aglycone present in blood in human after consumption of foods rich in quercetin. Whether the metabolites of quercetin possess the beneficial effects as their parent compound remains unclear. Therefore, this thesis work was divided into two parts to investigate whether the metabolites of quercetin present in plasma of gerbils, which were fed with quercetin by gavage, prevent the harmful effects of bezo[a]pyrene ( BaP ) or BaP+β-carotene. Part 1. In the ex vivo study, the A549 cells were preincubated with quercetin or the quercetin-metabolite-enriched plasma ( QP; 10% ), alone or combined with 20 μM β-carotene for 4 h, and then, the cells were treated with 20 μM of BaP for 24 h. The QP was obtained from gerbils at 2 h after fed with quercetin at 100mg/kgw/week, while the control plasma was obtained from gerbils administered vehicle only. Several quercetin metabolites were observed in QP, including quercetin-3-glucuronide, quercetin-3'-sulfate and methylquercetin. At 2 h after oral administration of quercetin, the total quercetin concentration of the plasma in gerbils was significantly increased and reached to a maximum ( ~ 5 μM ). QP significantly increased the cell viability and decreased DNA damage in A549 cells incubated with BaP or BaP+ β-carotene, and the efficiency of QP was similar to those of quercetin at 2 and 5 μM. QP also significantly decreased the ratio of phosphor-Jun/total Jun in A549 cells incubated with BaP or BaP+ β-carotene. Part 2. In the in vivo study, we fed gerbil by gavage with β-carotene ( 10 mg/kgw, 3 time/week ), quercetin ( 100 mg/kgw, 3 time/week ) and BaP ( 8 μmole/time, 2 time/week ) alone or combined for 6 months. After sacrificed, bronchoalveolar lavage fluid ( BALF ) and plasma were collected to determine cell profile or/and the levels of pro-inflammatory cytokine, TNF-α ( tumor necrosis factor-α ) and IL-1β ( Interleukin-1β ). The activation of JNK ( Jun N-terminal kinase ) and c-Jun proteins in lung was also determined by western blotting. The results showed BaP significantly increased the numbers of total cell and the macrophage as well as the levels of pro-inflammatory cytokine in BALF. β-carotene -administration significantly enhanced such an effect; in contrast, quercetin- administration significantly decreased the pro-inflammatory effects of BaP or BaP+ β-carotene. BaP also significantly increased the ratio of phospho-JNK/total JNK and that of phospho-Jun/total Jun in lung in gerbils. Similarly, β-carotene-administration significantly enhanced such an effect while quercetin- administration had a significant suppressed effect. The results of these two parts studies demonstrated that the metabolites of quercetin possess the bioactivity for protect cells against the damages of BaP or BaP + β-carotene, suggesting that they may interact with β-carotene. The mechanisms were associated with the down-regulation of the activation of JNK and Jun.