Tight junctions and tissue barriers.

The integrity and function of many vertebrate organs depend on cellular barriers that are mainly formed by intercellular protein complexes of the plasma membrane. These cell-cell contacts, tight junctions (TJs), exhibit the most apical localization in the lateral membrane; they regulate the permeability of the paracellular space between opposing epithelial and endothelial cells. This Forum reviews the currently available data on the influence of oxidative stress and the effects of antioxidative mechanisms on TJ proteins and on tissue barrier functions inseparably linked to these proteins. The contributions are focused on the most important transmembranal and membrane-associated TJ proteins and on tissue barriers characterized by predominant involvement of the TJs, and alterations at the molecular and functional levels induced by redox signaling are also discussed. This Forum demonstrates that cell barriers are highly sensitive to oxidative stress but also respond to antioxidative intervention. However, our knowledge of the molecular basis of the specific mechanisms responsible for functional disturbances remains limited and needs further investigations.