Ascorbic Acid Modulation of Iron Homeostasis and Lysosomal Function in Trabecular Meshwork Cells
Publication: Journal of Ocular Pharmacology and Therapeutics
Volume 30, Issue Number 2-3
Abstract
Purpose: To investigate the antioxidant properties and biological functions of ascorbic acid (AA) on trabecular meshwork (TM) cells.
Methods: Primary cultures of porcine TM cells were supplemented for 10 days with increasing concentrations of AA. Antioxidant properties against cytotoxic effect of H2O2 were evaluated by monitoring cell viability. Redox-active iron was quantified using calcein-AM. Intracellular reactive oxygen species (iROS) production was quantified using H2DCFDA. Ferritin and cathepsin protein levels were analyzed by Western blot. Autophagy was evaluated by monitoring lipidation of LC3-I to LC3-II. Lysosomal proteolysis and cathepsins activities were quantified using specific fluorogenic substrates.
Results: AA exerts a dual effect against oxidative stress in TM cells, acting as an anti-oxidant or a pro-oxidant, depending on the concentration used. The pro-oxidant effect of AA was mediated by free intracellular iron and correlated with increased protein levels of ferritin and elevated iROS. In contrast, antioxidant properties correlated with lower ferritin and basal iROS content. Ascorbic acid supplementation also caused induction of autophagy, as well as increased lysosomal proteolysis, with the latter resulting from higher proteolytic activation of lysosomal cathepsins in treated cultures.
Conclusions: Our results suggest that the reported decrease of AA levels in plasma and aqueous humor can compromise lysosomal degradation in the outflow pathway cells with aging and contribute to the pathogenesis of glaucoma. Restoration of physiological levels of vitamin C inside the cells might improve their ability to degrade proteins within the lysosomal compartment and recover tissue function.
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Information & Authors
Information
Published In
Journal of Ocular Pharmacology and Therapeutics
Volume 30 • Issue Number 2-3 • March/April 2014
Pages: 246 - 253
PubMed: 24552277
Copyright
Copyright 2014, Mary Ann Liebert, Inc.
History
Published online: 3 April 2014
Published in print: March/April 2014
Published ahead of print: 19 February 2014
Accepted: 13 December 2013
Received: 1 September 2013
Authors
Author Disclosure Statement
No competing financial interests exist.
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