Evidence of Dual Mechanisms of Glutathione Uptake in the Rodent Lens: A Novel Role for Vitreous Humor in Lens Glutathione Homeostasis

• Published in: Investigative ophthalmology & visual science 2016-07, Vol.57 (8), p.3914-3925
• Main Authors: Whitson, Jeremy A, Sell, David R, Goodman, Michael C, Monnier, Vincent M, Fan, Xingjun
• Format: Article
• Language: English
• Subjects: Animals; Biological Transport - physiology; Cells, Cultured; Diffusion; Glutathione - biosynthesis; Glutathione - metabolism; Homeostasis - physiology; Lens; Lens, Crystalline - metabolism; Mice; Mice, Knockout; Permeability; Vitreous Body - metabolism
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.16-19592

Lens glutathione synthesis knockout (LEGSKO) mouse lenses lack de novo glutathione (GSH) synthesis but still maintain >1 mM GSH. We sought to determine the source of this residual GSH and the mechanism by which it accumulates in the lens. Levels of GSH, glutathione disulfide (GSSG), and GSH-related compounds were measured in vitro and in vivo using isotope standards and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Wild-type (WT) lenses could accumulate GSH from γ-glutamylcysteine and glycine or from intact GSH, but LEGSKO lenses could only accumulate GSH from intact GSH, indicating that LEGSKO lens GSH content is not due to synthesis by a salvage pathway. Uptake of GSH in cultured lenses occurred at the same rate for LEGSKO and WT lenses, could not be inhibited, and occurred primarily through cortical fiber cells. In contrast, uptake of GSH from aqueous humor could be competitively inhibited and showed an enhanced Km in LEGSKO lenses. Mouse vitreous had >1 mM GSH, whereas aqueous had