title: Plate reader-based cell viability assays for glioprotection using primary rat optic nerve head astrocytes.
abstract: Optic nerve head astrocytes (ONHAs) are the major glia cell type in the non-myelinated optic nerve head where they contribute critically to extracellular matrix synthesis during development and throughout life. In glaucoma, and in related disorders affecting the optic nerve and the optic nerve head, pathological changes include altered astrocyte gene and protein expression resulting in their activation and extracellular matrix remodeling. ONHAs are highly sensitive to mechanical and oxidative stress resulting in the initiation of axon damage early during pathogenesis. Furthermore, ONHAs are crucial for the maintenance of retinal ganglion cell physiology and function. Therefore, glioprotective strategies with the goal to preserve and/or restore the structural and functional viability of ONHA in order to slow glaucoma and related pathologies are of high clinical relevance. Herein, we describe the development of standardized methods that will allow for the systematic advancement of such glioprotective strategies. These include isolation, purification and culture of primary adult rat ONHAs, optimized immunocytochemical protocols for cell type validation, as well as plate reader-based assays determining cellular viability, proliferation and the intracellular redox state. We validated and standardized our protocols by performing a glioprotection study using primary ONHAs. Specifically, we measured protection against exogenously-applied oxidative stress using tert-butylhydroperoxide (tBHP) as a model of disease-mediated oxidative stress in the retina and optic nerve head by the prototypic antioxidant, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). Levels of oxidative stress were increased in the response to exogenously applied tBHP and were assessed by 6-carboxy-2', 7' dichlorodihydrofluorescein diacetate (DCFDA) fluorescence. Normalized DCFDA fluorescence showed a maximal 5.1-fold increase; the half-maximal effect (EC50) for tBHP was 212 ± 25 μM. This was paralleled very effectively in the assays measuring cell death and cell viability with half-maximal effects of 241 ± 20 μM and 194 ± 5 μM for tBHP in the lactate dehydrogenase (LDH) release and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion assays, respectively. Pre-treatment with 100 μM Trolox decreased the sensitivity of ONHAs to tBHP. Half-maximal effects increased to 396 ± 12 μM tBHP in the LDH release assay and to 383 ± 3 μM tBHP in the MTT assay. Vehicle treatment (0.1% v/v ethanol) did not significantly affect cellular responses to tBHP. Antioxidant treatment increases ONHA viability and reduces the deleterious effects of oxidative stress. Our experiments provide important feasibility data for utilizing primary rat ONHAs in plate reader-based assays assessing novel therapeutics for glioprotection of the optic nerve and the optic nerve head in glaucoma and related disorders. Furthermore, our novel, standardized protocols have the potential to be readily adapted to high-throughput and high-content testing strategies.
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Simon
authors.initials: S
authors.lastname: Kaja
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Payne
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Naumchuk
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Levy
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Danish H
authors.initials: DH
authors.lastname: Zaidi
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Alexa M
authors.initials: AM
authors.lastname: Altman
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Saba
authors.initials: S
authors.lastname: Nawazish
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Jasleen K
authors.initials: JK
authors.lastname: Ghuman
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Bryan C
authors.initials: BC
authors.lastname: Gerdes
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Moore
authors.affiliation: Vision Research Center, Department of Ophthalmology, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA; Department of Basic Medical Science, University of Missouri - Kansas City, School of Medicine, 2411 Holmes St., Kansas City, MO 64108, USA. Electronic address: koulenp@umkc.edu.
authors.forename: Peter
authors.initials: P
authors.lastname: Koulen
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D018929:Cell Culture Techniques; D049109:Cell Proliferation / Q000502:physiology; D002470:Cell Survival; D008297:Male; D000066829:Neuroprotection / Q000502:physiology*; D009898:Optic Disk / Q000166:cytology*; D018384:Oxidative Stress; D051381:Rats; D011914:Rats, Inbred BN; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D015415:Biomarkers; D017382:Reactive Oxygen Species
keywords: Cell viability; Drug discovery; Glaucoma; Glioprotection; Immunocytochemistry; Lactate dehydrogenase; Optic nerve head astrocytes; Oxidative stress