BiochemistryGlutathione ester prevents buthionine sulfoximine-induced cataracts and lens epithelial cell damage [mitochondria/glutathione mono(glycyl) Contributed by Alton Meister, August 30, 1989 ABSTRACT Treatment of newborn rats and mice with buthionine sulfoximine, an inhibitor of glutathione synthesis, leads to development of cataracts, which are not prevented by treatment with glutathione, but they are prevented by treatment with glutathione monoester. Cataracts are associated with glutathione deficiency in the lens epithelium, which undergoes severe degeneration. The findings indicate that glutathione normally functions in the protection of the lens and lens epithelium against oxidative injury, suggesting that procedures that increase lens glutathione levels might be useful for prevention of other types of cataracts. Relatively low doses of buthionine sulfoximine produce cataracts in newborn animals, and treatment of pregnant mice with buthionine sulfoximine during the last part of gestation leads to cataract formation in the offspring. The high sensitivity of the developing lens to the effects of glutathione deficiency suggests that this tissue may be a useful model for studies on glutathione function.

Upon exposure to 0.25 mM cystine dimethyl ester, normal and cystinotic leukocytes accumulate substantially more intracellular cystine than is present endogenously in cystinotic cells. Leukocytes loaded by exposure to cystine dimethyl ester may have abnormally lucent and distended lysosomes, and the cystine is compartmentalized within the granular fraction of the cells. After the cells are exposed to cystine dimethyl ester, cystine clearance from normal leukocytes is much faster than from cystinotic cells. The ratios of labeled cysteine-N-ethylmaleimide to cystine are also greater in normals than in cystinotics 60 min after termination of loading. No overlap in ranges of cystine clearance half-times or cysteine-N-ethylmaleimide to cystine ratios was observed in normal compared to cystinotic leukocytes. Limited experiments with fibroblasts exposed to cystine dimethyl ester suggest a correspondingly prolonged cystine clearance for cystinotic cells. These experiments provide evidence for defective clearance of cystine from cystinotic lysosomes in situ.In classical cystinosis, an autosomal recessive disorder (1, 2), progressive kidney disease usually leads to death before age 10 unless renal transplantation is performed. Many cystinotic tissues, including leukocytes and cultured fibroblasts, have greatly increased concentrations offree cystine (1-4), with cystine compartmentalization in lysosomes (1, 2, 5-7).Although the fundamental metabolic defect remains unknown, one possibility is that cystinotic cells lack a mechanism for disposal ofcystine from their lysosomes. However, there is no direct evidence for defective efflux ofcystine from cystinotic lysosomes, despite attempts to assess transcellular uptake or efflux in whole cystinotic cells in comparison with normal cells (8,9). Examinations of subcellular transport have been limited by the inability to load normal cells or lysosomes to cystine concentrations approximating the cystinotic.Goldman and Kaplan (10) and Reeves (11) have demonstrated that certain amino acid methyl esters can be used to load isolated rat liver lysosomes with high concentrations of the corresponding amino acid. Apparently, the methyl esters penetrate lysosomal membranes and are hydrolyzed by esterases to free amino acids, which accumulate because of slow efflux from the lysosomes. Using radioactive amino acid methyl esters, Reeves characterized the efflux of certain amino acids from rat liver lysosomes (11). We have used related techniques to study amino acid efflux from isolated normal and cystinotic human leukocyte lysosomes (12)(13)(14).In this report, we demonstrate that intact normal and cystinotic human leukocytes incubated with cystine dimethyl ester accumulate cystine, primarily within lysosomes, in concentrations far exceeding those present endogenously in cystinotic cells. Loaded cystinotic leukocytes exhibited retarded cystine clearance when compared to normal cells. These observations strongly suggest that cystinotic lysosomes in situ are defective in their capacity t...

The observation that high-dose oral vitamin E supplementation (800 IU per day) improved red-cell survival in two rare disorders associated with increased red-cell susceptibility to oxidative stress prompted a similar trial in 23 patients with Mediterranean glucose-6-phosphate dehydrogenase (G6PD) deficiency. Three months of vitamin E administration resulted in decreased chronic hemolysis as evidenced by improved red-cell life span (P less than 0.025), with an improvement in red-cell half-life from 22.9 +/- 0.7 days to 25.1 +/- 0.6 days (mean +/- S.E.M.), increased hemoglobin concentration (P less than 0.001), and decreased reticulocytosis (P less than 0.001) as compared with base-line values. Evaluation after one year of vitamin E administration demonstrated sustained improvement in all these indexes. Controlled clinical trials of vitamin E supplementation may be warranted to examine its efficacy in ameliorating acute hemolytic crises or in reducing morbidity from neonatal jaundice in this relatively common genetic disorder.

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