FIG. 6.
Effect of NGF or GSH ethyl ester addition on cytochrome c release from NGF-deprived mouse sympathetic neurons. In the original experiments, cells were maintained in medium containing the broad-spectrum caspase inhibitor BAF to prevent death. This treatment does not alter the time course of cytochrome c redistribution but prevents death of all cells for at least 48 h (47). About 90% of BAF-maintained cells had released cytochrome c from mitochondria by 48 h after NGF withdrawal (solid line). Addition of NGF or GSH ethyl ester to the culture medium at 24 h after deprivation blocked further release (dashed line for both). Treatment of these cells at 24 h after withdrawal with the GR inhibitor BCNU completely blocked the ability of GSH ethyl ester or NGF to inhibit cytochrome c release in the succeeding 24 h (dotted line for both). It had no effect on cytochrome c release in control cells. These data suggest a role for NGF activation of glutathione redox cycling in short-term prevention of cytochrome c redistribution by NGF readdition.