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Tight junctions and the experimental modifications of lipid content
V Calderón1, A Lázaro, R G Contreras
1Department of Biochemistry, Biophysics and Neuroscience of the Center for Research & Advanced Studies, Apartado Postal 14-740, México, D.F. 07000 México.
The Journal of Membrane Biology
|June 24, 1998
Summary
Altering lipid composition of tight junctions (TJs) did not change strand structure or electrical resistance. However, linoleic acid enrichment significantly increased dextran flux, suggesting TJs may have mobile mechanisms.
Area of Science:
- Cell Biology
- Biophysics
- Membrane Biology
Background:
- Tight junctions (TJs) form seals between cells, crucial for tissue integrity.
- The molecular composition of TJ strands (proteins vs. lipids) remains debated.
- Understanding TJ permeability is vital for drug delivery and disease research.
Purpose of the Study:
- Investigate the role of lipid composition in TJ structure and function.
- Determine if TJ strands are solely resistive or involve mobile mechanisms.
- Analyze the impact of lipid modification on TJ permeability and occludin distribution.
Main Methods:
- Cultured Madin-Darby canine kidney (MDCK) monolayers with altered lipid composition.
- Measured transepithelial electrical resistance (TER) to assess TJ sealing.
- Assessed paracellular permeability using 4 kD fluorescent dextran (JDEX) flux.
- Examined TJ strand structure via freeze fracture electron microscopy.
- Analyzed occludin protein distribution in modified TJ.
Main Results:
- Modifying total phospholipids, sphingolipids, cholesterol, and fatty acid content did not alter TER or TJ strand structure.
- Enrichment with linoleic acid increased JDEX flux by 631% without decreasing TER.
- Occludin distribution remained unaffected by lipid composition changes.
- TJ strand structure was preserved despite significant lipid alterations.
Conclusions:
- TJ strand structure and sealing (TER) are largely independent of bulk lipid composition.
- Increased permeability (JDEX flux) with linoleic acid suggests TJs possess mobile transport mechanisms, not just passive barriers.
- Lipid environment may influence TJ function through dynamic processes rather than static structural roles.
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