TY - JOUR
T1 - Dexamethasone regulates endothelin-1 and endothelin receptors in human non-pigmented ciliary epithelial (HNPE) cells
AU - Zhang, Xinyu
AU - Krishnamoorthy, Raghu R.
AU - Prasanna, Ganesh
AU - Narayan, Santosh
AU - Clark, Abbot
AU - Yorio, Thomas
N1 - Funding Information:
This work was supported by a grant from NEI/NIH (Grant number: EY11979) and the Texas Higher Education Coordinating Board Advanced Technology Program. The authors would like to thank Dr Michael Martin and Dr Simecka Jerry for their expert technical assistance with the binding studies and quantitative PCR respectively.
PY - 2003/3/1
Y1 - 2003/3/1
N2 - Endothelin-1 (ET-1) lowers intraocular pressure (IOP) in animal models by regulating aqueous humour dynamics through both inflow and outflow mechanisms. Moreover, ET's concentration is elevated in glaucoma patients and in animal models of glaucoma. Glucocorticoid therapy often can lead to increase IOP in susceptible individuals including patients with primary open angle glaucoma (POAG). In this study, we examined the effects of dexamethasone (Dex), a frequently used anti-inflammatory glucocorticoid, on the synthesis and release of endothelin-1 and on the expression of endothelin receptors in human non-pigmented ciliary epithelial (HNPE) cells, an established source for ET-1 in the anterior chamber. As measured by ET-1 immunoreactivity, ET-1 was concentration-dependently increased following 24hr Dex treatment, with a maximum concentration (100nM) causing a threefold increase of ET-1 release. Western blot analysis of HNPE cells showed the expression of endothelin receptor A (ETA) and endothelin receptor B (ETB) with approximate molecular weights of 40kDa. Dex treatment decreased ETA receptor expression at all Dex doses, but up-regulated ETB receptors with 10nM Dex having the greatest effect. Quantitative PCR demonstrated that Dex also increased the mRNA of pre-pro-ET-1 (ppET-1) and ETB but decreased the mRNA of ETA. RU486, a glucocorticoid receptor antagonist, was able to block Dex's actions on ET release and ETB receptor expression, but did not block its action on ETA receptor expression. Endothelin receptors were minimally expressed in HNPE cells as determined in binding experiments (Bmax: ETA 17, ETB 25fmolmg-1 membrane protein). However Dex treatment stimulated a dramatic increase in ETB receptor density while decreasing ETA receptors (Bmax: ETA 11, ETB 116fmolmg-1 membrane protein). The regulation of endothelin and its receptors could be a novel mechanism associated with glucocorticoid's effects on intraocular pressure. The increase in ET-1 and disproportionate regulation in ET receptor expression by Dex could promote dysregulation in ET's mechanism on both inflow and outflow, thus affecting aqueous humour dynamics in the anterior chamber of the eye.
AB - Endothelin-1 (ET-1) lowers intraocular pressure (IOP) in animal models by regulating aqueous humour dynamics through both inflow and outflow mechanisms. Moreover, ET's concentration is elevated in glaucoma patients and in animal models of glaucoma. Glucocorticoid therapy often can lead to increase IOP in susceptible individuals including patients with primary open angle glaucoma (POAG). In this study, we examined the effects of dexamethasone (Dex), a frequently used anti-inflammatory glucocorticoid, on the synthesis and release of endothelin-1 and on the expression of endothelin receptors in human non-pigmented ciliary epithelial (HNPE) cells, an established source for ET-1 in the anterior chamber. As measured by ET-1 immunoreactivity, ET-1 was concentration-dependently increased following 24hr Dex treatment, with a maximum concentration (100nM) causing a threefold increase of ET-1 release. Western blot analysis of HNPE cells showed the expression of endothelin receptor A (ETA) and endothelin receptor B (ETB) with approximate molecular weights of 40kDa. Dex treatment decreased ETA receptor expression at all Dex doses, but up-regulated ETB receptors with 10nM Dex having the greatest effect. Quantitative PCR demonstrated that Dex also increased the mRNA of pre-pro-ET-1 (ppET-1) and ETB but decreased the mRNA of ETA. RU486, a glucocorticoid receptor antagonist, was able to block Dex's actions on ET release and ETB receptor expression, but did not block its action on ETA receptor expression. Endothelin receptors were minimally expressed in HNPE cells as determined in binding experiments (Bmax: ETA 17, ETB 25fmolmg-1 membrane protein). However Dex treatment stimulated a dramatic increase in ETB receptor density while decreasing ETA receptors (Bmax: ETA 11, ETB 116fmolmg-1 membrane protein). The regulation of endothelin and its receptors could be a novel mechanism associated with glucocorticoid's effects on intraocular pressure. The increase in ET-1 and disproportionate regulation in ET receptor expression by Dex could promote dysregulation in ET's mechanism on both inflow and outflow, thus affecting aqueous humour dynamics in the anterior chamber of the eye.
KW - Aqueous humour dynamics
KW - Ciliary epithelium
KW - Dexamethasone
KW - Endothelin receptor A
KW - Endothelin receptor B
KW - Endothelin-1
KW - Glucocorticoid receptor
KW - Intraocular pressure
KW - RU486
UR - http://www.scopus.com/inward/record.url?scp=0037374514&partnerID=8YFLogxK
U2 - 10.1016/S0014-4835(02)00323-8
DO - 10.1016/S0014-4835(02)00323-8
M3 - Article
C2 - 12573655
AN - SCOPUS:0037374514
SN - 0014-4835
VL - 76
SP - 261
EP - 272
JO - Experimental Eye Research
JF - Experimental Eye Research
IS - 3
ER -