Prostaglandin E(2) stimulates rat and human colonic mucin exocytosis via the EP(4) receptor

Area of Science:

• Gastroenterology
• Immunology
• Cell Biology

Background:

• Mucins are key components of the innate immune system in the intestines, protecting against pathogens and irritants.
• The regulation of mucin secretion during inflammation is not well understood.
• Prostaglandin E(2) (PGE(2)) is a significant mediator during intestinal inflammation.

Purpose of the Study:

• To investigate the receptor-signaling pathway of prostaglandin E(2) (PGE(2)) in regulating mucin exocytosis.
• To determine the role of specific prostaglandin E(2) receptors (EP) in colonic mucin secretion.
• To elucidate the downstream signaling mechanisms, including cyclic adenosine monophosphate (cAMP), involved in PGE(2)-mediated mucin release.

Main Methods:

• Identification of EP receptors using reverse-transcription polymerase chain reaction (RT-PCR) and [(3)H]PGE(2) binding assays.
• Quantification of intracellular cyclic adenosine monophosphate ([cAMP](i)) via enzyme immunoassay.
• Measurement of mucin secretion using metabolic labeling, column chromatography, immunoblot analysis, and density gradient centrifugation.

Main Results:

• EP(2), EP(3), and EP(4) receptors were identified in colonic epithelial cells.
• PGE(2) and specific EP receptor agonists (EP(4) and EP(3)/EP(4)) dose-dependently stimulated mucin secretion and [cAMP](i) production.
• Inhibition of adenylate cyclase blocked the stimulatory effects, confirming the involvement of the cAMP pathway.
• EP(4) receptor activation was confirmed to be linked to mucin exocytosis in vivo using rat colon models.

Conclusions:

• Prostaglandin E(2) (PGE(2)) stimulates mucin exocytosis through coupling to the EP(4) receptor.
• This process is dependent on the elevation of intracellular cyclic adenosine monophosphate (cAMP) levels.
• The EP(4) receptor-cAMP pathway represents a significant mechanism for regulating mucin secretion in the colon.