Tight Junction in the Intestinal Epithelium: Its Association with Diseases and Regulation by Phytochemicals

Figure 1

Functions of the small intestine. The small intestinal epithelium plays a role in the absorption of nutrients through transcellular (nutrients passing through the cells), facilitated and active (nutrients passing through the membrane via transport proteins), and paracellular (nutrients passing between the tight junction (TJ) between cells) transports. The small intestinal epithelium also performs barrier functions because of the presence of TJ and the xenobiotic detoxification system. TJ acts as a physical barrier to pathogens and large harmful molecules while enzymes involved in xenobiotic metabolism detoxify harmful compounds. Furthermore, intestinal cells expressing toll-like receptors (TLRs) and cytokine receptors respond to lipopolysaccharides (LPS) and proinflammatory cytokines (interleukin-1 beta, tumor necrosis factor-alpha, and interferon gamma) triggering intracellular signaling pathways.