Inhibitory Effect of Flavonoids on the Efflux of 𝑁-Acetyl 5-Aminosalicylic Acid Intracellularly Formed in Caco-2 Cells

• Main Authors: Shin Yoshimura, Kentaro Kawano, Ryusuke Matsumura, Narumi Sugihara, Koji Furuno
• Format: Article
• Language: English
• Published: Hindawi Limited 2009-01-01
• Series: Journal of Biomedicine and Biotechnology
• Online Access: http://dx.doi.org/10.1155/2009/467489

𝑁-acetyl 5-aminosalicylic acid (5-AcASA) that was intracellularly formed from 5-aminosalicylic acid (5-ASA) at 200 𝜇M was discharged 5.3, 7.1, and 8.1-fold higher into the apical site than into the basolateral site during 1, 2, and 4-hour incubations, respectively, in Caco-2 cells grown in Transwells. The addition of flavonols (100 𝜇M) such as fisetin and quercetin with 5-ASA remarkably decreased the apically directed efflux of 5-AcASA. When 5-ASA (200 𝜇M) was added to Caco-2 cells grown in tissue culture dishes, the formation of 5-AcASA decreased, and, in addition, the formed 5-AcASA was found to be accumulated within the cells in the presence of such flavonols. Thus, the decrease in 5-AcASA efflux by such flavonols was attributed not only to the inhibition of 𝑁-acetyl-conjugation of 5-ASA but to the predominant cellular accumulation of 5-AcASA. Various flavonoids also had both of the effects with potencies that depend on their specific structures. The essential structure of flavonoids was an absence of a hydroxyl substitution at the C5 position on the A-ring of flavone structure for the inhibitory effect on the 𝑁-acetyl-conjugation of 5-ASA, and a presence of hydroxyl substitutions at the C3 or C4 position on the B-ring of flavone structure for the promoting effect on the cellular accumulation of 5-AcASA. Both the decrease in 5-AcASA apical efflux and the increase in 5-AcASA cellular accumulation were also caused by MK571 and indomethacin, inhibitors of MRPs, but not by quinidine, cyclosporin A, P-glycoprotein inhibitors, and mitoxantrone, a BCRP substrate. These results suggest that certain flavonoids suppress the apical efflux of 5-AcASA possibly by inhibiting MRPs pumps located on apical membranes in Caco-2 cells.