Enhancing the permeation of marker compounds and enaminone anticonvulsants across Caco-2 monolayers by modulating tight junctions using zonula occludens toxin

Zonula occludens toxin (Zot), a protein elaborated from Vibrio cholerae, has been shown to be capable of reversibly opening tight junctions between intestinal cells The objective of this study was to examine the effect of Zot on the flux of various molecules across Caco-2 cell monolayers. In addition, the transport of a series of anticonvulsants, the enaminones was also evaluated in the presence of Zot. The flux of [C-14] mannitol, [C-14] inulin and various enaminones across Caco-2 cell monolayers (n = 6) was examined after pre-incubation for 1 h with Zot (0 or 4000 ng/ml) or phosphate-buffered saline (PBS). At the end of the incubation period, the flux of radiolabeled compounds or enaminones (1 X 10(-4) M) was assessed over a 2-h period. In addition, dose-response studies with Zot (0, 1000, 2000 or 4000 ng/ml) were performed using mannitol. The flux of both mannitol and inulin significantly increased (P < 0.05) in the presence of Zot. The transport of the enaminones with Zot ranged from 9.42 to 26.83 x 10(-5) cm/s vs. 4.68 to 13.83 x 10(-5) cm/s without Zot. Zot significantly increased the transport of all agents tested. This suggests that the co-administration of drugs with Zot may be a useful delivery strategy to increase the intestinal permeability and hence oral absorption of poorly bioavailable agents. (C) 2001 Elsevier Science B.V. All rights reserved.