The basal domain of human colonic epithelial cells is capable of correcting oxidizing extracellular redox

The cysteine (Cys)/cystine (CySS) redox couple is a major determinant of extracellular redox status. Human colon epithelial Caco‐2 cell monolayers can regulate extremes of apical extracellular Cys/CySS redox potential (E h ) to physiologic values (~ −80 mV) observed in vivo . The current studies determined: 1) whether the basal (B) domain of Caco‐2 cells can regulate extracellular redox potential in response to oxidizing conditions; 2) whether this response differs in the apical (A) versus B domains; and 3) potential mechanisms. Caco‐2 cells were grown on Transwell membranes for selective evaluation of extracellular redox in the A and B domains. Differentiated cells were serum‐starved for 24 h, then exposed to oxidizing extracellular Cys/CySS redox condition (0 mV) for 0, 4, and 24 h. Both A and B domains demonstrated correction of extracellular thiol‐disulfide redox towards physiologic range; however, this occurred at an earlier time point and the shift toward a more reducing redox was more marked at the B domain compared to the A domain. A domain extracellular Cys/CySS E h at 4h was +20±10 mV and at 24h was −34±9 mV. In contrast, B domain Cys/CySS E h at 4h was −88±7 mV and at 24h was −116±3 mV (A vs B; P<0.05). Studies using FITC‐dextran, flavoprotein inhibitors, thiol‐reactive alkylating agents and buthionine sulfoximine showed that extracellular redox regulation was not attributable to barrier function disruption, plasma membrane Cys/CySS interconversion, or intracellular glutathione concentration, respectively. We conclude that the basal membrane domain of Caco‐2 cells has a robust capability to correct oxidizing extracellular Cys/CySS redox conditions. Support: NIH DK55850, ES009047.