Evidence for multiple P2Y receptors in trabecular meshwork cells

Area of Science:

• Ophthalmology
• Cell Biology
• Pharmacology

Background:

• The trabecular meshwork (TM) is crucial for regulating intraocular pressure.
• Purinergic signaling via P2 receptors plays diverse roles in cellular function.
• Understanding P2 receptor presence in TM cells is key to their physiological function.

Purpose of the Study:

• To investigate the presence and function of purinergic P2 receptors in human (HTM-3) and bovine trabecular meshwork cells.
• To determine the effects of P2 receptor activation on intracellular calcium (Ca2+) levels and extracellular signal-regulated kinase (ERK1/2) signaling.
• To identify specific P2Y receptor subtypes expressed in TM cells.

Main Methods:

• Cell culture of HTM-3 and bovine TM cells.
• Stimulation with various P2 receptor agonists (ATP, UTP, ADP, 2-MeS-ATP, UDP).
• Measurement of intracellular Ca2+ levels and ERK1/2 activation.
• Use of specific receptor antagonists (MRS-2179) and signaling pathway inhibitors (U-0126, chelerythrine chloride).
• Reverse transcription-polymerase chain reaction (RT-PCR) for P2Y receptor mRNA expression analysis.

Main Results:

• ATP, UTP, ADP, and 2-MeS-ATP increased intracellular Ca2+ in a concentration-dependent manner; UDP had no effect.
• The P2Y(1) antagonist MRS-2179 blocked ADP- and 2-MeS-ATP-induced Ca2+ increases, but not those induced by ATP or UTP.
• ADP, 2-MeS-ATP, ATP, and UTP activated the ERK1/2 pathway, inhibited by U-0126 and chelerythrine chloride, but not MRS-2179.
• RT-PCR detected P2Y(1), P2Y(4), and P2Y(11) receptor mRNA in HTM-3 cells.
• Ca2+ mobilization is linked to P2Y(1) and P2Y(4) activation, while ERK1/2 activation involves P2Y(4) alone.

Conclusions:

• Trabecular meshwork cells express multiple functional P2Y receptors, including P2Y(1), P2Y(4), and P2Y(11) subtypes.
• P2Y(1) and P2Y(4) receptors mediate Ca2+ mobilization, while P2Y(4) receptors alone activate the ERK1/2 pathway.
• The precise role of P2Y(11) receptors requires further investigation, but they may also contribute to Ca2+ mobilization or ERK1/2 activation.