advertisement
Abstract #14036 Published in IGR 8-3
Human trabecular meshwork cells express functional serotonin-2A (5HT2A) receptors: role in IOP reduction
Sharif NA; Kelly CR; McLaughlin MInvestigative Ophthalmology and Visual Science 2006; 47: 4001-4010
See also comment(s) by Douglas Rhee •
PURPOSE: To apply a multidisciplinary approach to the identification and pharmacological characterization of the serotonin (5HT) receptors that mediate functional responses in human trabecular meshwork (h-TM) cells. To correlate in vitro findings with intraocular pressure (IOP) changes in conscious ocular hypertensive cynomolgus monkeys. METHODS: Documented methods were used, including reverse transcription-polymerase chain reaction (RT-PCR), phosphoinositide (PI) turnover, and intracellular Ca2+ ([Ca2+ ]i ) mobilization. IOP was measured using standard applanation pneumatonometry. RESULTS: h-TM cells expressed robust mRNA signals for 5HT2A and 5HT2B receptors. 5HT and its analogues stimulated PI turnover and [Ca2+ ]i mobilization in h-TM cells from multiple donors (20/24 donors' TM cells responded). The agonist potencies (EC50 ) of compounds in mobilizing [Ca2+ ]i were (nM): 5-methoxy tryptamine, 8 ± 4; (R)-DOI, 18 ± 6; α-methyl-5HT, 22 ± 3; 5HT, 40 ± 7; 5-methoxy-dimethyl tryptamine, 64 ± 27; and BW-723C86, 1213 ± 210. These effects were potently blocked by the 5HT2A -receptor-selective antagonist, M-100907 (Ki = 1 ± 0.3 nM), but weakly by antagonists of 5HT2B and 5HT2C receptors. Only 5HT2 receptor agonists such as (R)-DOI (300 μg lowered IOP 34.4% from baseline of 38.2 mmHg; P < 0.001) and α-methyl-5HT (250 μg lowered IOP 30.8% from baseline of 41.8 mmHg; P < 0.001) lowered IOP in ocular hypertensive cynomolgus monkeys. CONCLUSIONS: Strong signals for 5HT2A and 5HT2B receptor mRNAs were detected in h-TM cells. The receptors that coupled to PI hydrolysis and [Ca2+ ]i mobilization in h-TM cells were the 5HT2A receptor subtype, which also significantly lowered IOP in a primate model. These receptors may mediate the ocular hypotensive actions of 5HT2A agonists.
Dr. N.A. Sharif, Ophthalmology Discovery Research, Alcon Research, Ltd., Fort Worth, TX, USA
Classification:
3.8 Pharmacology (Part of: 3 Laboratory methods)
2.5.1 Trabecular meshwork (Part of: 2 Anatomical structures in glaucoma > 2.5 Meshwork)
3.5 Molecular biology incl. SiRNA (Part of: 3 Laboratory methods)
5 Experimental glaucoma; animal models
