Abstract:
PURPOSE:Metabolism and transport of cysteine are critical for maintenance of the intracellular glutathione (GSH) level. In this study, transport mechanisms of L-cystine and regulation of GSH biosynthesis in the absence or presence of NO-induced oxidant stress were investigated in primary cultured rabbit conjunctival epithelial cells (RCECs). METHODS:RCECs were grown in membrane filters to exhibit tight barrier properties. Uptake and transepithelial transport of L-cystine were determined in the presence or absence of extracellular Na(+). Uptake was determined at 10 minutes after (14)C-L-cystine instillation into apical (a) or basolateral (b) bathing fluid. The effect of nitric oxide (NO) on L-cystine uptake, cellular GSH level, and expression level of two subunits of the rate-limiting enzyme gamma-glutamylcysteine synthetase (GCS) was examined after a 24-hour incubation of primary cultured RCECs with an NO donor, S-nitroso-N-acetylpenicillamine (SNAP; N-acetyl-3-(nitrosothio)-D-valine. RESULTS:Cellular uptake of L-cystine by RCECs occurred through both Na(+)-dependent and -independent mechanisms. Uptake from apical fluid was higher than that from basolateral fluid, except for the highest concentration of L-cystine tested (200 microM). Transepithelial permeability (P(app)) of L-cystine (at 2.5 microM) was three times higher in the a-to-b direction than in the b-to-a direction in the presence of Na(+), whereas the reverse was true in the absence of Na(+). Na(+)-dependent L-cystine uptake from apical fluid was significantly elevated in primary cultured RCECs treated for 24 hours with various concentrations (0.1-2.0 mM) of SNAP, with maximum uptake observed at 1 mM. A similar pattern of SNAP-induced increase of Na(+)-independent L-cystine uptake from apical fluid was observed, whereas no significant difference was observed for basolateral uptake. Concomitantly, a significant elevation of intracellular GSH (up to fivefold versus the control) was recorded, with the highest increase occurring at 0.1 to 0.25 mM SNAP. A parallel increase in the expression levels of both catalytic and regulatory subunits of GCS was observed by Western blot analysis of lysates from RCECs treated with 0.25 mM SNAP for 24 hours. CONCLUSIONS:L-Cystine is transported by both Na(+)-dependent and -independent amino acid transport systems in RCECs. At low substrate concentrations, L-cystine uptake was higher from apical than basolateral fluid. Permeability studies indicated net absorption of L-cystine across RCECs. SNAP caused significant increases in both L-cystine uptake and intracellular GSH level, which occurred concomitantly with elevation of both catalytic and regulatory subunits of GCS. Understanding sulfur amino acid precursor-dependent cellular mechanisms of GSH homeostasis would be of value in devising GSH-based treatment for conjunctival or other ocular disorders.
journal_name
Invest Ophthalmol Vis Scijournal_title
Investigative ophthalmology & visual scienceauthors
Gukasyan HJ,Kannan R,Lee VH,Kim KJdoi
10.1167/iovs.02-0409keywords:
subject
Has Abstractpub_date
2003-03-01 00:00:00pages
1202-10issue
3eissn
0146-0404issn
1552-5783journal_volume
44pub_type
杂志文章abstract::Extracellular matrix (ECM) turnover and remodeling are initiated, at least in part, by the regulated secretion of members of a family of matrix metalloproteinases. Human and bovine trabecular mesh-work in culture secrete interstitial collagenase, both the 72- and the 92-kD forms of type IV collagenase (gelatinases) an...
journal_title:Investigative ophthalmology & visual science
pub_type: 杂志文章
doi:
更新日期:1991-01-01 00:00:00
abstract:PURPOSE:Genetic modification of cells before transplantation may allow the delivery of neuroprotective and other functional molecules to patients with neurodegenerative diseases. To avoid complications associated with virally transfected cells, we have explored the use of nonviral methods to insert genetic material int...
journal_title:Investigative ophthalmology & visual science
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abstract::In their IOVS article "Rejuvenating Clinician-Scientist Training" (published March 28, 2014), Balamurali Ambati and Judd Cahoon rightly point out the dearth of new clinician-scientists in ophthalmology. Within the context of their suggestions for increasing the number of successful clinician-scientists, they claim tha...
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abstract:PURPOSE:To characterize the phagocytosis of extracellular matrix components by retinal pigment epithelial cells and to determine which receptors and signal transduction pathways are involved. METHODS:Fluorescent latex beads were coated with fibronectin (FN), collagen type I or IV, or thrombospondin and incubated with ...
journal_title:Investigative ophthalmology & visual science
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更新日期:1999-10-01 00:00:00
abstract:PURPOSE:This study determined whether adenovirus-mediated transfer of the murine interferon-beta (AdCMVIFN-beta) gene protects against liver metastases arising from intraocular melanomas in mice. METHODS:A replication-deficient adenovirus vector (AdCMVIFN-beta) was used for the in vivo transfer of the murine IFN-beta ...
journal_title:Investigative ophthalmology & visual science
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abstract:PURPOSE:The purpose of this study was to evaluate the ability of second-harmonic imaging to identify differences in corneal stromal collagen organization between normal human and keratoconus corneas. METHODS:Six normal corneas from eye bank donors and 13 corneas of patients with keratoconus, obtained after penetrating...
journal_title:Investigative ophthalmology & visual science
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abstract::Ultrastructural cytochemistry was used to analyze the polarized distribution of alkaline phosphatase (AP) on the plasma membranes of normal and regenerating retinal pigment epithelium (RPE) and the ciliary body epithelium in rabbits. The AP activity was concentrated on the basolateral plasma membrane in normal RPE. In...
journal_title:Investigative ophthalmology & visual science
pub_type: 杂志文章
doi:
更新日期:1991-12-01 00:00:00
abstract:PURPOSE:To examine the influence of reticular pseudodrusen (RPD) on retinal and visual function in intermediate AMD using multifocal electroretinography (mfERG) and microperimetry. METHODS:In a prospective cross-sectional study, microperimetry and mfERG testing, followed by color fundus photography, near-infrared refl...
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journal_title:Investigative ophthalmology & visual science
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journal_title:Investigative ophthalmology & visual science
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journal_title:Investigative ophthalmology & visual science
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journal_title:Investigative ophthalmology & visual science
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doi:
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journal_title:Investigative ophthalmology & visual science
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doi:
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