Abstract
Oral supplementation of anthocyanins-rich haskap (Lonicera caerulea) berry (HB) reduces 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis, cytotoxicity, DNA damage, and modulated inflammation in vitro and in vivo. The procarcinogen NNK is metabolically activated by cytochrome P450 (P450) enzymes, producing reactive metabolites that induce lung carcinogenesis. Hypothesis: Therefore, we hypothesized that the HB-modulated protective effect against NNK could be due to its ability to suppress P450 enzymes. Methods: HB (6 mg of cyanidin-3-O-glucoside [C3G] in 0.2 g of HB/mouse/day) was given to A/J mice as a dietary supplement following subsequent administration of NNK (100 mg/kg body weight). The liver tissues of mice were analyzed to determine the expression of P450s and metabolites. Results: HB upregulated the expression of cyp2a4 and cyp2a5 mRNA and nuclear receptor/transcription factor (PPARα) in NNK-deprived hepatic tissues. With NNK, HB downregulated the expression of cyp2a4 and cyp2a5 and facilitated the formation of non-carcinogenic NNK metabolites. Molecular docking indicated a high binding affinity and strong hydrophobic interactions between C3G and its major metabolites, peonidin-3-O-glucoside, petunidin-3-O-glucoside, peonidin and cyanidin with Cyp2a5 and with human P450 homologue CYP2A13. Conclusions: HB could be a potential dietary supplement to inhibit the P450 activated NNK carcinogenic metabolites formation. Hence, inhibiting the activation of NNK by lung CYP2A13 through dietary HB supplementation could be a strategy to reduce lung carcinogenesis among smokers. Understanding the effect of HB on the activity of CYP2A13 in human studies is necessary before recommending these natural compounds as therapeutics.