Abstract
Background
Endothelin-1 (ET-1) is known to induce contraction of trabecular meshwork (TM) and is probably involved in the pathogenesis of glaucoma. Calcium (Ca2+)-independent contraction has been shown in TM, and its inhibition may represent an interesting way of influencing outflow facility, and thus intraocular pressure (IOP). This study investigates the role of ET-1 and its receptors ET-A and ET-B (ET-AR and ET-BR) in TM Ca2+-independent contractility.
Methods
Isometric tension measurements of bovine TM (BTM) strips were performed using a force-length transducer system. Intra- and extracellular Ca2+ buffering was achieved by means of EGTA and BAPTA-AM. Under Ca2+-free conditions, ET-1-induced contractility of TM was assessed also in the presence of the specific inhibitors for ET-AR and ET-BR, BQ123 and BQ788 respectively. In order to clarify the intracellular mediators of Ca2+-independent contractility induced by ET-1, TM contraction was further measured in the presence of Y-27632, a selective inhibitor of Rho-associated kinases (ROCKs). The expression of ROCK1 and of its activating protein RhoA in BTM cells was investigated using western blot analysis.
Results
ET-1 induced a significant contraction of native BTM after intra- and extracellular Ca2+-depletion (45% ± 8% of the maximally inducible contraction). Both endothelin receptor inhibitors BQ123 and BQ788 significantly reduced TM Ca2+-independent contraction in response to ET-1 (8.4 ± 3.3% and 20.3 ± 4.8% respectively). In the presence of the ROCK inhibitor Y-27632, ET-1-induced contraction of TM under Ca2+-free conditions was almost completely abolished (4.3% ± 1.7%, p < 0.001). A clear signal for RhoA at 24 kDa and ROCK1 at 160 kDa could be detected in lysates of native tissue and cultured BTM cells with western blot.
Conclusions
This study shows evidence that a significant portion of ET-1-induced contraction of TM is Ca2+-independent. In this contraction pathway, both ET-AR and ET-BR are involved with RhoA and its kinases as intracellular mediators. Ca2+-independent contraction of TM in response to ET-1 may represent a specific target to modulate IOP.
Similar content being viewed by others
References
Yanagisawa M, Kurihara H, Kimura S, Tomobe Y, Kobayashi M, Mitsui Y, Yazaki Y, Goto K, Masaki T (1988) A novel potent vasoconstrictor peptide produced by vascular endothelial cells [see comments]. Nature 332:411–415
Yorio T, Krishnamoorthy R, Prasanna G (2002) Endothelin: is it a contributor to glaucoma pathophysiology? J Glaucoma 11:259–270
Haefliger IO, Flammer J, Luscher TF (1992) Nitric oxide and endothelin-1 are important regulators of human ophthalmic artery. Invest Ophthalmol Vis Sci 33:2340–2343
Wiederholt M, Thieme H, Stumpff F (2000) The regulation of trabecular meshwork and ciliary muscle contractility. Prog Retin Eye Res 19:271–295
Lepple-Wienhues A, Becker M, Stahl F, Berweck S, Hensen J, Noske W, Eichhorn M, Wiederholt M (1992) Endothelin-like immunoreactivity in the aqueous humor and in conditioned medium from cultured ciliary epithelial cells. Curr Eye Res 11:1041–1046
Noske W, Hensen J, Wiederholt M (1997) Endothelin-like immunoreactivity in aqueous humor of patients with primary open-angle glaucoma and cataract. Graefes Arch Clin Exp Ophthalmol 235:551–552
Lepple-Wienhues A, Stahl F, Willner U, Schafer R, Wiederholt M (1991) Endothelin-evoked contractions in bovine ciliary muscle and trabecular meshwork: interaction with calcium, nifedipine and nickel. Curr Eye Res 10:983–989
Wiederholt M, Bielka S, Schweig F, Lutjen-Drecoll E, Lepple-Wienhues A (1995) Regulation of outflow rate and resistance in the perfused anterior segment of the bovine eye. Exp Eye Res 61:223–234
Thieme H, Stumpff F, Ottlecz A, Percicot CL, Lambrou GN, Wiederholt M (2001) Mechanisms of action of unoprostone on trabecular meshwork contractility. Invest Ophthalmol Vis Sci 42:3193–3201
Thieme H, Schimmat C, Munzer G, Boxberger M, Fromm M, Pfeiffer N, Rosenthal R (2006) Endothelin antagonism: effects of FP receptor agonists prostaglandin F2alpha and fluprostenol on trabecular meshwork contractility. Invest Ophthalmol Vis Sci 47:938–945
Thieme H, Nuskovski M, Nass JU, Pleyer U, Strauss O, Wiederholt M (2000) Mediation of Calcium-Independent Contraction in Trabecular Meshwork through Protein Kinase C and Rho-A. Invest Ophthalmol Vis Sci 41:4240–4246
Lepple-Wienhues A, Stahl F, Wiederholt M (1991) Differential smooth muscle-like contractile properties of trabecular meshwork and ciliary muscle. Exp Eye Res 53:33–38
Lepple Wienhues A, Stahl F, Wunderling D, Wiederholt M (1992) Effects of endothelin and calcium channel blockers on membrane voltage and intracellular calcium in cultured bovine trabecular meshwork cells. Germ J Ophthalmol 1:159–163
Thieme H, Nass JU, Nuskovski M, Bechrakis NE, Stumpff F, Strauss O, Wiederholt M (1999) The effects of protein kinase C on trabecular meshwork and ciliary muscle contractility. Invest Ophthalmol Vis Sci 40:3254–3261
Pang IH, Yorio T (1997) Ocular actions of endothelins. Proceedings of the Society for Experimental Biology and Medicine 215:21–34
Prasanna G, Narayan S, Krishnamoorthy RR, Yorio T (2003) Eyeing endothelins: a cellular perspective. Mol Cell Biochem 253:71–88
Choritz L, Rosenthal R, Fromm M, Foerster MH, Thieme H (2005) Pharmacological and functional characterization of endothelin receptors in bovine trabecular meshwork and ciliary muscle. Ophthalmic Res 37:179–187
Rosenthal R, Choritz L, Zorn R, Munzer G, Fromm M, Pfeiffer N, Thieme H (2007) Endothelin receptor B in trabecular meshwork. Exp Eye Res 85:482–491
Orgul S, Cioffi GA, Bacon DR, Van Buskirk EM (1996) An endothelin-1-induced model of chronic optic nerve ischemia in rhesus monkeys. J Glaucoma 5:135–138
Chauhan BC, LeVatte TL, Jollimore CA, Yu PK, Reitsamer HA, Kelly ME, Yu DY, Tremblay F, Archibald ML (2004) Model of endothelin-1-induced chronic optic neuropathy in rat. Invest Ophthalmol Vis Sci 45:144–152
Sugiyama T, Moriya S, Oku H, Azuma I (1995) Association of endothelin-1 with normal tension glaucoma: clinical and fundamental studies. Survey Ophthalmol 39(Suppl 1):S49–S56
Henry E, Newby DE, Webb DJ, Hadoke PW, O’Brien CJ (2006) Altered endothelin-1 vasoreactivity in patients with untreated normal-pressure glaucoma. Invest Ophthalmol Vis Sci 47:2528–2532
Nicolela MT, Ferrier SN, Morrison CA, Archibald ML, LeVatte TL, Wallace K, Chauhan BC, LeBlanc RP (2003) Effects of cold-induced vasospasm in glaucoma: the role of endothelin-1. Invest Ophthalmol Vis Sci 44:2565–2572
Emre M, Orgul S, Haufschild T, Shaw SG, Flammer J (2005) Increased plasma endothelin-1 levels in patients with progressive open angle glaucoma. Br J Ophthalmol 89:60–63
Galassi F, Renieri G, Sodi A, Ucci F, Vannozzi L, Masini E (2004) Nitric oxide proxies and ocular perfusion pressure in primary open angle glaucoma. Br J Ophthalmol 88:757–760
Zhang X, Clark AF, Yorio T (2003) Interactions of endothelin-1 with dexamethasone in primary cultured human trabecular meshwork cells. Invest Ophthalmol Vis Sci 44:5301–5308
Toris CB, Zhan G, Camras CB (2004) Increase in outflow facility with unoprostone treatment in ocular hypertensive patients. Arch Ophthalmol 122:1782–1787
Toris CB, Zhan G, Fan S, Dickerson JE, Landry TA, Bergamini MV, Camras CB (2007) Effects of travoprost on aqueous humor dynamics in patients with elevated intraocular pressure. J Glaucoma 16:189–195
Tamura M, Iwamoto Y, Nakatsuka K, Yamanouchi U (1989) Immunofluorescence studies of the cytoskeletal and contractile elements in cultured human trabecular cells. Jpn J Ophthalmol 33:95–102
Rosenthal R, Choritz L, Schlott S, Bechrakis NE, Jaroszewski J, Wiederholt M, Thieme H (2005) Effects of ML-7 and Y-27632 on carbachol- and endothelin-1-induced contraction of bovine trabecular meshwork. Exp Eye Res 80:837–845
Harnett KM, Biancani P (2003) Calcium-dependent and calcium-independent contractions in smooth muscles. Am J Med 115(Suppl 3A):24S–30S
Civelek M, Ainslie K, Garanich JS, Tarbell JM (2002) Smooth muscle cells contract in response to fluid flow via a Ca2+-independent signaling mechanism. J Appl Physiol 93:1907–1917
Andrea J, Walsh MP (1992) Protein kinase C of smooth muscle. Hypertension 20:585–594
Allen BG, Walsh MP (1994) The biochemical basis of the regulation of smooth muscle contraction. Trends Pharmacol Sci 15:362–368
Noma K, Oyama N, Liao JK (2006) Physiological role of ROCKs in the cardiovascular system. Am J Physiol Cell Physiol 290:C661–C668
Nakajima E, Nakajima T, Minagawa Y, Shearer TR, Azuma M (2005) Contribution of ROCK in contraction of trabecular meshwork: proposed mechanism for regulating aqueous outflow in monkey and human eyes. J Pharm Sci 94:701–708
Rao PV, Deng PF, Kumar J, Epstein DL (2001) Modulation of aqueous humor outflow facility by the Rho kinase-specific inhibitor Y-27632. Invest Ophthalmol Vis Sci 42:1029–1037
Honjo M, Tanihara H, Inatani M, Kido N, Sawamura T, Yue BY, Narumiya S, Honda Y (2001) Effects of rho-associated protein kinase inhibitor Y-27632 on intraocular pressure and outflow facility. Invest Ophthalmol Vis Sci 42:137–144
McNair LL, Salamanca DA, Khalil RA (2004) Endothelin-1 promotes Ca2+antagonist-insensitive coronary smooth muscle contraction via activation of epsilon-protein kinase C. Hypertension 43:897–904
Chuman H, Chuman T, Nao-i N, Sawada A (2000) The effect of L-arginine on intraocular pressure in the human eye. Curr Eye Res 20:511–516
Acknowledgements
The authors wish to thank Marianne Boxberger and Ingrid Lichtenstein for expert technical support. This work was partly supported by DFG grant Th 751/4-1.
Author information
Authors and Affiliations
Corresponding author
Additional information
Grant: Deutsche Forschungsgemeinschaft (DFG Th751/4-1)
The authors have full control of all primary data and they agree to allow Graefe’s Archive for Clinical and Experimental Ophthalmology to review their data upon request.
Rights and permissions
About this article
Cite this article
Renieri, G., Choritz, L., Rosenthal, R. et al. Effects of endothelin-1 on calcium-independent contraction of bovine trabecular meshwork. Graefes Arch Clin Exp Ophthalmol 246, 1107–1115 (2008). https://doi.org/10.1007/s00417-008-0817-4
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00417-008-0817-4