Tumor promoter-induced changes in the permeability of epithelial cell tight junctions

Area of Science:

• Cell biology
• Epithelial biology
• Biochemistry

Background:

• The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) is known to induce various cellular responses.
• Epithelial tight junctions regulate paracellular transport and maintain tissue integrity.
• Understanding TPA's effects on epithelial cells is crucial for cancer research.

Purpose of the Study:

• To investigate the effects of TPA on the permeability and morphology of kidney epithelial cells (MDCK).
• To determine the role of plasminogen activator (PA) in TPA-induced changes.
• To examine the involvement of cytoskeletal components in TPA's action.

Main Methods:

• Treatment of MDCK cells with TPA.
• Measurement of transepithelial permeability.
• Analysis of cell morphology using microscopy.
• Assessment of plasminogen activator (PA) synthesis.
• Inhibition of PA synthesis and cytoskeletal function using specific drugs.

Main Results:

• TPA significantly increased tight junction permeability and altered cell morphology within 2-4 hours.
• TPA stimulated a 10-20 fold increase in PA synthesis and secretion.
• Inhibition of PA synthesis did not prevent TPA-induced morphological changes or increased permeability.
• Drugs inhibiting cytoskeletal function prevented morphological changes but not increased permeability.

Conclusions:

• TPA's effects on tight junction permeability and cell morphology are complex and occur early.
• Plasminogen activator (PA) is not involved in the early TPA-induced changes in tight junctions or cell morphology.
• TPA may act directly on epithelial tight junctions and cytoskeletal components.