Intestinal epithelial cell accumulation of the cancer preventive polyphenol ellagic acid: Extensive covalent binding to protein and DNA Alexander C. Whitley, Gary D. Stoner, Thomas Walle. Medical University of South Carolina, Charleston, SC; School of Public Health and Comprehensive Cancer Center, The Ohio State University, Columbus, OH. Ellagic acid (EA), a polyphenol present in many berries, has been demonstrated to be preventive of esophageal cancer in animals both at the initiation and promotion stages. To be able to extrapolate these findings to humans we have studied the transcellular absorption and epithelial cell accumulation of [14C]EA in the human intestinal Caco-2 cells. The apical (mucosal) to basolateral (serosal) transcellular transport of 10 mM [14C]EA was minimal with a Papp of only 0.13 x 10-6 cm/sec, which is less than for the paracellular transport marker mannitol. In contrast, Caco-2 cell uptake studies showed high accumulation of EA in the cells (1054 ± 136 pmol/mg protein), indicating facile transport across the apical membrane. Preliminary experiments indicate this to involve a sodium-dependent transporter. Surprisingly, as much as 93% of the cellular uptake was irreversibly bound to macromolecules (982 ± 151 pmol/mg protein). To confirm the irreversible nature of the binding, Caco-2 cells treated with 10 mM [14C]EA were subjected to SDS-PAGE analysis. This resulted in radiolabeled bands trapped in the stacking gel, consistent with [14C]EA-crosslinked proteins. Treatment of Caco-2 cells with 10 mM [14C]EA also revealed irreversible binding of EA to cellular DNA which was as much as 5 times higher than for protein (5020 ± 773 pmol/mg DNA). Together these observations suggest that EA, after entering the Caco-2 cell, is efficiently oxidized, presumably by reactive oxygen species (ROS) to intermediates, which rapidly bind covalently to protein and DNA. This also limits its transcellular absorption. Thus, EA may accumulate in the epithelial cells of the aerodigestive tract, where its cancer preventive actions may be displayed by binding to specific signaling proteins and/or specific DNA sequences. Presenter: Alexander C. Whitley Affiliation: Medical University of South Carolina, Charleston, SC . Email: whitleac@musc.edu AACR Abstract Number: R863, 2003 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.