Effects of Endothelin-1 on Human Trabecular Meshwork Cell Contraction

Abstract

Trabecular meshwork (TM) cells are now considered to play an active role in the aqueous outflow mechanism, since they exhibit smooth muscle-like contractile properties. Endothelin-1 (ET-1), a potent vasoconstrictor peptide, has been proposed to play a role in the local regulation of aqueous outflow and intra-ocular pressure control. We propose an in vitro culture model as a method in the study of ET-1-induced human trabecular meshwork (HTM) cell contractility. Experiments were performed on semi-confluent HTM cells (primary cultures established from normotensive human donor eyes) at the 2nd passage with PBS as control, ET-1, sarafotoxin 6c (a selective endothelin B receptor agonist) and Y-27632 (a selective inhibitor of rho-associated kinase). The contractile status of the cells was evaluated by a morphometric analysis of the cell area, assuming that HTM cells in culture are able to reduce their area as a consequence of cytoskeletal contraction rather than regulatory volume decrease. Our data indicate that image analysis of the HTM cell area can be a reliable method in the study of TM cell contractility, since it utilizes human cells and offers versatile opportunities for the pharmacological evaluation of drugs controlling HTM cell status.

Transforming Growth Factor-β2 Induces Synthesis and Secretion of Endothelin-1 in Human Trabecular Meshwork Cells

“…A similar thesis recently has been proposed for elevated levels of ET-1 observed in AH of POAG patients. [6][7][8][9][10]15,[17][18][19][20][21][22] Whereas an association between TGF-b2 and POAG has been proposed previously, a causal relationship between TGF-b2 and ET-1 in association with the pathogenesis of POAG has not been addressed previously to our knowledge. In our study, TGF-b1 and TGF-b2 were found to be equally effective at inducing marked increases in ppET-1 mRNA expression and extracellular ET-1 peptide release by primary human TM cells as well as established transformed human TM cell lines.…”

“…[12][13][14][15][16] In vitro, experimental application of ET-1 to TM cells promotes activation of the Rho/ROCK pathway, enhances Rho-dependent phosphorylation of myosin light chain, and contraction of the actomyosin cytoskeleton. 15,[17][18][19][20][21][22] Similarly, ET-1 decreases outflow facility through bovine anterior segments in vitro. 18 An alternative pathologic mechanism that may increase IOP in POAG patients is enhanced synthesis and secretion of extracellular matrix (ECM) components by TM cells.…”

Endothelin-1 plasma levels and vascular endothelial dysfunction in primary open angle glaucoma

“…Finally, there is evidence that the increased aqueous levels of ET-1 in POAG reduce aqueous humor outflow by inducing contraction of trabecular meshwork fibers (Cellini et al, 2006).…”

Effect of Flunarizine, a Calcium Channel Blocker, on Intraocular Pressure and Aqueous Humor Dynamics in Monkeys

“…Another study shows that pretreatment with flunarizine prevented the contraction of human trabecular meshwork cells in culture by endothelin-1, a vasoactive peptide with actions mediated in part through L-type calcium channels. 30 Prevention of endothelin-1-induced contraction of the trabecular meshwork would be expected to result in relaxation of trabecular meshwork cells, enlargement in intercellular spaces, and an increase in outflow facility.…”