Tight junction overview

Abstract This chapter attempts to give an overview on the properties of the intestinal epithelium with regard to both, barriers to transcellular (transporter and efflux systems) and paracellular (tight junctional complex) drug absorption and transport systems and tight junction modulation. A short introduction into the relation between the innate immune system and modulation of paracellular permeability is equally given. 

An overview of several possible transport routes is given in Figure 10.2. During various disease states, alterations in the levels or distribution of transporters can be seen. Tight junctions limit the paracellular diffusion of molecules and the formation of extracellular fluid [47]. 

Cell communication can be studied between cells by direct or indirect contact. Indirect cell contact allows the study of soluble, diffusible factors to influence cell communication while direct cell contact introduces the additional factor of cell-cell contact through tight junctions, gap junctions, and adhesion proteins (Loewenstein 1981, Takeichi 1990). This section will provide a brief overview of cocultures involving both types of cell communication in the context of 2D and 3D systems. Figure 21.1 provides an overview of these coculture systems. 

---