Estrogen decrease in tight junctional resistance involves matrix-metalloproteinase-7-mediated remodeling of occludin

Area of Science:

• Endocrinology
• Cell Biology
• Molecular Biology

Background:

• Estrogen plays a crucial role in modulating cellular functions, including the regulation of epithelial barrier integrity.
• Tight junctions are critical for maintaining paracellular permeability, and their disruption is implicated in various physiological and pathological processes.
• Occludin is a key protein component of tight junctions, and its remodeling affects barrier function.

Purpose of the Study:

• To elucidate the molecular mechanisms by which estrogen modulates tight junctional resistance and occludin remodeling.
• To investigate the role of matrix-metalloproteinase-7 (MMP-7) in estrogen-mediated effects on epithelial barrier function.

Main Methods:

• Experiments were conducted using human normal vaginal-cervical epithelial cells.
• Investigated constitutive and estrogen-stimulated secretion of MMP-7.
• Utilized inhibitors of Golgi transport (monensin) and vesicular exocytosis (bafilomycin A1) to probe cellular mechanisms.
• Assessed MMP-7 activation, phosphorylation, and co-localization with cellular markers (GPP130, SNAP-25).

Main Results:

• Human vaginal-cervical epithelial cells constitutively secrete MMP-7, which is necessary and sufficient for estrogen's effects on tight junctions and occludin.
• Estrogen stimulates intracellular activation and secretion of MMP-7, acting at the Golgi apparatus and involving soluble N-ethylmaleimide sensitive fusion factor attachment protein receptor (SNARE)-dependent exocytosis.
• Estrogen's modulation of MMP-7 phosphorylation appears secondary to changes in cellular MMP-7 mass, and luminal acidification may counteract MMP-7 activation.

Conclusions:

• Estrogen up-regulates intracellular activation of MMP-7 at the Golgi and enhances its secretion via SNARE-dependent exocytosis, thereby modulating tight junctional resistance.
• These findings reveal a novel pathway for estrogen's regulation of epithelial barrier function involving MMP-7.
• The interplay between intracellular MMP-7 activation and luminal conditions is crucial for controlling estrogen's effects on paracellular permeability in vivo.