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Subcutaneous Administration of Muscarinic Antagonists and Triple-Immunostaining of the Levator Auris Longus Muscle in Mice
07:09

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Expression and function of muscarinic receptor subtypes on human cornea and conjunctiva

Shaohui Liu1, Jing Li, Donald T H Tan

  • 1Singapore Eye Research Institute, National University of Singapore, Singapore.

Investigative Ophthalmology & Visual Science
|June 27, 2007
PubMed
Abstract

Insights

All five muscarinic receptor (MR) subtypes are present on ocular surface cells. These receptors regulate epithelial cell growth by activating p42/44 mitogen-activated protein kinase (MAPK).

Area of Science:

  • Ophthalmology
  • Cell Biology
  • Molecular Biology

Background:

  • Muscarinic receptors (MRs) are G protein-coupled receptors involved in various physiological processes.
  • Their presence and function on the ocular surface, particularly in epithelial cell growth, remain incompletely understood.

Purpose of the Study:

  • To determine the cellular distribution of muscarinic receptor (MR) subtypes m1-m5 on the ocular surface.
  • To investigate the role of these MRs in regulating ocular surface epithelial cell growth.

Main Methods:

  • Isolation and culture of human limbal, conjunctival epithelial cells, and conjunctival fibroblasts.
  • Analysis of MR subtype expression using RT-PCR, real-time PCR, immunostaining, and Western blot.
  • Assessment of cell proliferation via BrdU incorporation and MAPK activation using Western blot in response to MR agonists and antagonists.

Main Results:

  • All five MR subtypes (m1-m5) were detected at both mRNA and protein levels in ocular surface cells and tissues.
  • MR subtype m5 showed the highest mRNA levels across all cell types.
  • Carbachol, an MR agonist, stimulated conjunctival epithelial cell proliferation and activated p42/44 MAPK, which was inhibited by specific antagonists and U0126.

Conclusions:

  • The ocular surface expresses all five muscarinic receptor subtypes.
  • MRs play a significant role in regulating ocular surface epithelial cell proliferation.
  • This proliferation is mediated through the activation of the p42/44 MAPK signaling pathway.

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