title: Crystallins are regulated biomarkers for monitoring topical therapy of glaucomatous optic neuropathy.
abstract: Optic nerve atrophy caused by abnormal intraocular pressure (IOP) remains the most common cause of irreversible loss of vision worldwide. The aim of this study was to determine whether topically applied IOP-lowering eye drugs affect retinal ganglion cells (RGCs) and retinal metabolism in a rat model of optic neuropathy. IOP was elevated through cauterization of episcleral veins, and then lowered either by the daily topical application of timolol, timolol/travoprost, timolol/dorzolamide, or timolol/brimonidine, or surgically with sectorial iridectomy. RGCs were retrogradely labeled 4 days prior to enucleation, and counted. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption ionization mass spectrometry, Western blotting, and immunohistochemistry allowed the identification of IOP-dependent proteomic changes. Genomic changes were scrutinized using microarrays and qRT-PCR. The significant increase in IOP induced by episcleral vein cauterization that persisted until 8 weeks of follow-up in control animals (p<0.05) was effectively lowered by the eye drops (p<0.05). As anticipated, the number of RGCs decreased significantly following 8 weeks of elevated IOP (p<0.05), while treatment with combination compounds markedly improved RGC survival (p<0.05). 2D-PAGE and Western blot analyses revealed an IOP-dependent expression of crystallin cry-βb2. Microarray and qRT-PCR analyses verified the results at the mRNA level. IHC demonstrated that crystallins were expressed mainly in the ganglion cell layer. The data suggest that IOP and either topically applied antiglaucomatous drugs influence crystallin expression within the retina. Neuronal crystallins are thus suitable biomarkers for monitoring the progression of neuropathy and evaluating any neuroprotective effects.
authors.affiliation: Institute of Experimental Ophthalmology, School of Medicine, University of Münster, Albert-Schweitzer-Campus 1, Münster, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Prokosch
authors.forename: Maurice
authors.initials: M
authors.lastname: Schallenberg
authors.forename: Solon
authors.initials: S
authors.lastname: Thanos
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D003459:Crystallins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004338:Drug Combinations; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005901:Glaucoma / Q000150:complications*; D007429:Intraocular Pressure / Q000187:drug effects; D009883:Ophthalmic Solutions / Q000008:administration & dosage; D009901:Optic Nerve Diseases / Q000209:etiology* / Q000235:genetics / Q000378:metabolism*; D020543:Proteome; D040901:Proteomics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D012160:Retina / Q000187:drug effects / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000378:metabolism; D013449:Sulfonamides / Q000008:administration & dosage; D013876:Thiophenes / Q000008:administration & dosage; D013999:Timolol / Q000008:administration & dosage
chemical_list: D015415:Biomarkers; D003459:Crystallins; D004338:Drug Combinations; D009883:Ophthalmic Solutions; D020543:Proteome; D013449:Sulfonamides; D013876:Thiophenes; C479140:dorzolamide-timolol combination; D013999:Timolol