Cultured rat and human astrocytes and rat neurones were shown to release reduced glutathione (GSH). In addition, GSH oxidation was retarded by the concomitant release of a factor from the cells. One possibility is that this factor is extracellular superoxide dismutase (SOD). In support of this, the factor was found to bind heparin, have a molecular mass estimated to be between 50 and 100 kDa, and CuZn-type SOD protein and cyanide sensitive enzyme activity were demonstrated in the cell-conditioned medium. In addition, supplementation of native medium with exogenous CuZn-type SOD suppressed GSH oxidation. We propose that preservation of released GSH is essential to allow for maximal up-regulation of GSH metabolism in neurones. Furthermore, cytokine stimulation of astrocytes increased release of the extracellular SOD, and enhanced stability of GSH. This may be a protective strategy occurring in vivo under conditions of oxidative stress, and suggests that SOD mimetics may be of therapeutic use.

No abstract

No abstract

Like all known parasitic protozoa, Trvpanosomu are auxotrophic for purines and therefore need to salvage purines from their environment. The first step in purine salvage, the transport of nucleosides across the cell membrane is achieved in Trypunosorna brucei brucei by at least two high affinity transporters (P1 and P2) with overlapping permeant specificities. Furthermore, the P2 transporter has also been implicated in the transport of trypanocidal drugs and loss or alteration of its function results in drug resistance. Whereas the P2 adenosine transporter in a wild type strain of T equiperdurn has similar kinetic properties to those determined in 7: brucei, a drug resistant derivative (PBR) has a greatly reduced affinity. To determine the molecular basis for this change in affinity, we have cloned the P2 transporter from wild type and drug-resistant (PBR) T equiperdurn. Cloning was accomplished using a PCR approach based on the recent sequence of the gene TbATI, that encodes the T. brucei P2 transporter. Sequencing and identification of the mutations leading to the altered phenotype are currently underway, as is heterologous expression in S. cerevisiae JL is in receipt of a BBSRC postgraduate studentship 96 A human astrocytoma cell line releases and preserves reduced glutathione. Reduced glutathione (GSH) plays a major role in protection against reactive oxygen species. GSH may predominantly be located to glial cells. However, neurones, when cocultured with astrocytes, have been shown to be less susceptible to oxidative stress than when cultured alone. We have previously published data showing efflux of reduced glutathione from cultured rodent astrocytes. In addition, GSH was also shown to be more stable in astrocyte-conditioned medium than in unconditioned minimal medium. Our recent findings show that the human astrocytoma cell line 1321N1 also releases GSH into extracellular medium over a 4 hour time period, at a comparable rate to cultured rat astrocytes. In addition to this, the stability of GSH is increased when added to medium previously exposed to the human astrocytoma cell line. However in the absence of human astrocytoma cells, GSH decays rapidly. Results from this human cell line data supports our previously published findings using primary rodent astrocytes. The release and preservation of GSH by both primary astrocyte cultures and a human astrocytoma cell line may suggest the presence of an astrocyte-derived factor that prevents oxidation of the released GSH, and may be important in limiting neuronal damage from astrocyte-derived oxidizing species such as nitric oxide. Rebecca Stone is funded by the Brain Research Trust (UK).Peptaibols are antibiotic pemdes, which range from 7 to 20 amino acids. Peptaibols contain the unusual amino acid a-aminoisobutyric acid (Aib) and have a C-terminal alcohol residue. Most of the peptides are isolated from fungal sources and are able to form channels in membranes through self-association, which can create a leakage of cytoplasmic material out of the cell, ultimatel...