Glutathione-diethyl ester (reduced)

The effect of reduced glutathione, reduced glutathione monoethyl ester and reduced glutathione diethyl ester on the cellular concentration of reduced glutathione and cysteine in P388D1 macrophages in vitro, and the cellular and extracellular de-esterification of reduced glutathione esters, was investigated. At 1 mM reduced glutathione derivative, only reduced glutathione diester markedly increased the cellular concentration of reduced glutathione. There was little delivery of reduced glutathione monoethyl ester into the cells. Reduced glutathione, and monoethyl and diethyl ester derivatives all increased the cellular concentration of cysteine; reduced glutathione diethyl ester also increased the cellular concentration of gamma-glutamylcysteine. Reduced glutathione diethyl ester also increased the cellular concentration of gamma-glutamylcysteine. Reduced glutathione esters were de-esterified intracellularly where the diester was rapidly converted to the monoester. The diester was also converted to the monoester extracellularly by interaction with cell surface esterases and by a much slower spontaneous hydrolysis. This indicates that the diester of reduced glutathione was a much more effective vehicle for delivery of reduced glutathione into cells than the monoester. Reduced glutathione diester also increased the cellular concentrations of cysteine and gamma-glutamylcysteine, suggesting that de novo synthesis of reduced glutathione was also stimulated.

Ammonia is responsible for cerebral edema associated with acute liver failure, but the role of the vasogenic mechanism has been a matter of dispute. Here, we tested the hypothesis that ammonia induces changes in blood-brain barrier (BBB) permeability by a mechanism coupled to oxidative/nitrosative stress (ONS) evoked in the BBB-forming cerebral capillary endothelial cells. Treatment of a rat brain endothelial cell line with ammonia (5 mmol/L, 24 h) caused accumulation of ONS markers: reactive oxygen species, nitric oxide and peroxidation products of phospholipid-bound arachidonic acid, F2-isoprostanes. Concurrently, ammonia increased the activity of extracellular matrix metalloproteinases (MMP-2/MMP-9), increased cell permeability to fluorescein isothiocyanate-dextran (40 kDa), and increased the expression of y+LAT2, a transporter that mediates the uptake to the cells of the nitric oxide precursor, arginine. The increase of cell permeability was ameliorated upon co-treatment with a MMP inhibitor, SB-3CT and with an antioxidant, glutathione diethyl ester, which also reduced F2-isoprostanes. Ammonia-induced ONS was attenuated by cytoprotective agents l-ornithine, phenylbutyrate, and their conjugate l-ornithine phenylbutyrate, an ammonia-trapping drug used to treat hyperammonemia. The results support the concept that ONS and ONS-related activation of MMPs in cerebral capillary endothelial cells contribute to the alterations in BBB permeability and to the vasogenic component of cerebral edema associated with acute liver failure.

Cisplatin-induced hearing loss is experienced by a high percentage of patients with squamous cell carcinoma undergoing cisplatin chemotherapy. A novel nano-construct capable of sequestering extracellular cisplatin was developed to combat this problem. The nano-construct consisted of superparamagnetic iron oxide nanoparticles (SPIONs) entrapped within polymeric micelles, which were formed from a glutathione diethyl ester-conjugated amphiphilic diblock copolymer. The glutathione-micelles were analyzed at the cellular level and in an organotypic study for safety evaluation. All utilized methods indicated that the micelles do not cause cellular toxicity or organ damage. The micelles' ability to reduce cisplatin-induced cytotoxicity was then probed in an in vitro model. Cisplatin was pre-treated with the novel nano-construct before being added to growing cells. When compared to cells that were exposed to untreated cisplatin, cells in the pre-treated cisplatin group showed a significant increase in cell viability. This clearly demonstrates that the construct is able to protect the cells from cisplatin cytotoxicity and makes it highly likely that the novel nano-construct will be able to play a role in the protection of the inner ear from cisplatin-induced ototoxicity.