Tight Junctions PDF

Preface

A major function of polarized epithelia is to separate tissue spaces and regulate the exchange of material between them. The tight junction (TJ) creates the paracellular component of this barrier. In the past, the TJ was considered to be a permanent structure whose only function was to block the passage of substances between the cells. We now know the barrier is regulated and highly variable among different types. Its regulation occurs in response to physiologic, pharmacologic, and pathologic conditions. The first edition of this book, published a decade ago, was the first attempt to systematically review all aspects of the biology of TJs. Since its publication there has been an unprecedented expansion of information, including enumeration of the TJs' molecular components. This has provided new insights into the regulation of permeability, cell signaling, and disease. This new information is coming from researchers in traditionally separate fields; thus we felt this was an appropriate time and valuable effort to again collect these many viewpoints in a second edition.

The first part of this book (Chapters 1 through 9) serves as a general introduction to the structure and physiology of the tight junction. This material is best appreciated in the context of the biology of epithelial cells; consequently, we include discussion of cell polarity, protein sorting, and other types of intercellular junctions. We felt it was also important to present the relevant theoretical and technical issues required to study tight junctions. The second part of the book (Chapters 10 through 21) reviews more focused aspects of the TJ, but those that can still be generalized to TJs in all cell types. This includes discussion of its molecular components, and cellular mechanisms for regulating permeability and cell signaling. The final part (Chapters 22 through 33) deals with the role of tight junctions in pathologic conditions or issues that are unique to specific organs. Among other topics, this includes genetic diseases and the effects of bacterial toxins and inflammation. Within this last section are chapters addressing the practical question of whether paracellular permeability could be manipulated for therapeutic purposes such as to enhance drug absorption.

We have convened a group of the world's leading experts to address these topics. A few are veterans of the first edition. They attacked their assignments with enthusiasm and we are humbled by and grateful for their outstanding efforts. We would like to thank all the authors and Ms. Dorothy Franco and Elizabeth del Oso for their success in keeping all 69 of us on track and on time.