Anethole dithiolethione, a putative neuroprotectant, increases intracellular and extracellular glutathione levels during starvation of cultured astroglial cells

Astroglial cells protect neurons against oxidative damage. The antioxidant glutathione plays a pivotal role in the neuroprotective action of astroglia l cells which is impaired following loss of glutathione. Anethole dithiolet hlone (ADT), a sulfur-containing compound which is used in humans as a secr etagogue, increases glutathione levels in cultured astroglial cells under " physiological" conditions and is thought thereby to protect against oxidati ve damage. Presently we report the effect of ADT (3-100 mu M) on glutathion e content of and efflux from rat primary astroglia-rich cultures under "pat hological" conditions, i.e., extended deprivation of glucose and amino acid s. Although cellular viability was not affected significantly, starvation of t hese cultures for 24 h in a bicarbonate buffer lacking glucose and amino ac ids led to a decrease in glutathione and protein content of approximately 4 3% and 40%, respectively. Although no effect on the protein loss occurred, the presence of ADT during starvation counteracted the starvation-induced l oss of intracellular glutathione in a concentration-dependent way. At a con centration of 100 mu M ADT even a significant increase in astroglial glutat hione content was noted after 24 h of starvation. Alike intracellular gluta thione levels, the amount of glutathione found in the buffer was elevated s ubstantially if ADT was present during starvation. This ADT-mediated, appar ent increase in glutathione efflux was additive to the stimulatory effect o n extracellular glutathione levels of acivicin (100 mu M), an inhibitor of extracellular enzymatic glutathione breakdown. However, the ADT-induced ele vation of both intra- and extracellular glutathione content during starvati on was prevented completely by coincubation with buthionine sulfoximine (10 mu M), an inhibitor of glutathione synthesis. These results demonstrate that, most likely through stimulation of glutathi one synthesis, ADT enables astroglial cells to maintain higher intra- and e xtracellular levels of glutathione under adverse conditions. Considering th e lowered glutathione levels in neurodegenerative syndromes, we conclude th at further evaluation of the therapeutic potential of the compound is warra nted.