Abstract
A significant loss and remodeling of the lamina cribrosa tissue leading to the excavation of the optic nerve is seen in glaucoma. Elevated endothelin-1 (ET-1) levels are detected in the aqueous humor of patients of open-angle glaucoma and in the plasma of patients with normal-tension glaucoma. Optic nerve damage, including axonal loss, can be mimicked by ET-1 injection near the optic nerve. ET-1 is produced from its precursor Big ET-1 (38 amino acids) by endothelin-converting enzyme (ECE). Although ET-1 and its receptors have been identified in the retina, little is known of the distribution of ECE at the optic nerve. Presently, ET-1 receptors and Big ET-1 converting activities were characterized in bovine optic nerve and the retina. The ETB receptor was detected in both the optic nerve and retina by immunoblotting and cross-linking, using 125I-ET-1. However, the ETA receptor was detected only in the retina. Big ET-1 conversion activities were detected in the plasma membrane (PM) of bovine retina, but not in the PM of the optic nerve. The retinal PM Big ET-1 converting activity was inhibited by phosphoramidon, thiorphan, and acidification. Furthermore, ECE cytosolic activities were detected in both the optic nerve and retina. Unlike the PM-ECE, cytosolic Big ET-1 converting activities were activated by acidification (pH 6.4), suggesting the involvement of ECE-2-like activity and/or cathepsin activity. Pepstatin, a potent inhibitor of cathepsins, inhibited the optic nerve (ON) cytosolic conversion of Big ET-1 peptide by 50%, and the combination of pepstatin and phosphoramidon, a potent inhibitor of ECE, inhibited the ON cytosolic activity by 86%. By contrast, the combination of both inhibitors weakly inhibited the cytosolic retinal Big ET-1 converting activity. Western blotting revealed the presence of ECE-1 at the PM of the retina not the ON. ECE-2 and cathpesins B, D, and L were detected only in the cytosol of both the retina and ON. In summary, it appears that ET-1 could be produced in the retina and optic nerve by at least two ECE subtypes and, perhaps, cathepsins. Big ET-1 converting activity may be an important target in preventing ET-1-induced optic nerve pathology.
| Original language | English |
|---|---|
| Pages (from-to) | 288-297 |
| Number of pages | 10 |
| Journal | Journal of Ocular Pharmacology and Therapeutics |
| Volume | 21 |
| Issue number | 4 |
| DOIs | |
| State | Published - 1 Aug 2005 |
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Localization of endothelin-converting enzyme in bovine optic nerve and retina. / Dibas, Adnan; Prasanna, Ganesh; Yorio, Thomas.
In: Journal of Ocular Pharmacology and Therapeutics, Vol. 21, No. 4, 01.08.2005, p. 288-297.Research output: Contribution to journal › Article
TY - JOUR
T1 - Localization of endothelin-converting enzyme in bovine optic nerve and retina
AU - Dibas, Adnan
AU - Prasanna, Ganesh
AU - Yorio, Thomas
PY - 2005/8/1
Y1 - 2005/8/1
N2 - A significant loss and remodeling of the lamina cribrosa tissue leading to the excavation of the optic nerve is seen in glaucoma. Elevated endothelin-1 (ET-1) levels are detected in the aqueous humor of patients of open-angle glaucoma and in the plasma of patients with normal-tension glaucoma. Optic nerve damage, including axonal loss, can be mimicked by ET-1 injection near the optic nerve. ET-1 is produced from its precursor Big ET-1 (38 amino acids) by endothelin-converting enzyme (ECE). Although ET-1 and its receptors have been identified in the retina, little is known of the distribution of ECE at the optic nerve. Presently, ET-1 receptors and Big ET-1 converting activities were characterized in bovine optic nerve and the retina. The ETB receptor was detected in both the optic nerve and retina by immunoblotting and cross-linking, using 125I-ET-1. However, the ETA receptor was detected only in the retina. Big ET-1 conversion activities were detected in the plasma membrane (PM) of bovine retina, but not in the PM of the optic nerve. The retinal PM Big ET-1 converting activity was inhibited by phosphoramidon, thiorphan, and acidification. Furthermore, ECE cytosolic activities were detected in both the optic nerve and retina. Unlike the PM-ECE, cytosolic Big ET-1 converting activities were activated by acidification (pH 6.4), suggesting the involvement of ECE-2-like activity and/or cathepsin activity. Pepstatin, a potent inhibitor of cathepsins, inhibited the optic nerve (ON) cytosolic conversion of Big ET-1 peptide by 50%, and the combination of pepstatin and phosphoramidon, a potent inhibitor of ECE, inhibited the ON cytosolic activity by 86%. By contrast, the combination of both inhibitors weakly inhibited the cytosolic retinal Big ET-1 converting activity. Western blotting revealed the presence of ECE-1 at the PM of the retina not the ON. ECE-2 and cathpesins B, D, and L were detected only in the cytosol of both the retina and ON. In summary, it appears that ET-1 could be produced in the retina and optic nerve by at least two ECE subtypes and, perhaps, cathepsins. Big ET-1 converting activity may be an important target in preventing ET-1-induced optic nerve pathology.
AB - A significant loss and remodeling of the lamina cribrosa tissue leading to the excavation of the optic nerve is seen in glaucoma. Elevated endothelin-1 (ET-1) levels are detected in the aqueous humor of patients of open-angle glaucoma and in the plasma of patients with normal-tension glaucoma. Optic nerve damage, including axonal loss, can be mimicked by ET-1 injection near the optic nerve. ET-1 is produced from its precursor Big ET-1 (38 amino acids) by endothelin-converting enzyme (ECE). Although ET-1 and its receptors have been identified in the retina, little is known of the distribution of ECE at the optic nerve. Presently, ET-1 receptors and Big ET-1 converting activities were characterized in bovine optic nerve and the retina. The ETB receptor was detected in both the optic nerve and retina by immunoblotting and cross-linking, using 125I-ET-1. However, the ETA receptor was detected only in the retina. Big ET-1 conversion activities were detected in the plasma membrane (PM) of bovine retina, but not in the PM of the optic nerve. The retinal PM Big ET-1 converting activity was inhibited by phosphoramidon, thiorphan, and acidification. Furthermore, ECE cytosolic activities were detected in both the optic nerve and retina. Unlike the PM-ECE, cytosolic Big ET-1 converting activities were activated by acidification (pH 6.4), suggesting the involvement of ECE-2-like activity and/or cathepsin activity. Pepstatin, a potent inhibitor of cathepsins, inhibited the optic nerve (ON) cytosolic conversion of Big ET-1 peptide by 50%, and the combination of pepstatin and phosphoramidon, a potent inhibitor of ECE, inhibited the ON cytosolic activity by 86%. By contrast, the combination of both inhibitors weakly inhibited the cytosolic retinal Big ET-1 converting activity. Western blotting revealed the presence of ECE-1 at the PM of the retina not the ON. ECE-2 and cathpesins B, D, and L were detected only in the cytosol of both the retina and ON. In summary, it appears that ET-1 could be produced in the retina and optic nerve by at least two ECE subtypes and, perhaps, cathepsins. Big ET-1 converting activity may be an important target in preventing ET-1-induced optic nerve pathology.
UR - http://www.scopus.com/inward/record.url?scp=23944496195&partnerID=8YFLogxK
U2 - 10.1089/jop.2005.21.288
DO - 10.1089/jop.2005.21.288
M3 - Article
C2 - 16117692
AN - SCOPUS:23944496195
VL - 21
SP - 288
EP - 297
JO - Journal of Ocular Pharmacology and Therapeutics
JF - Journal of Ocular Pharmacology and Therapeutics
SN - 1080-7683
IS - 4
ER -