Cell death by 1-chloro-2,4-dinitrobenzene, an inhibitor of thioredoxin reductase and its dual regulation by nitric oxide in rats

Thioredoxin (Trx), the oxidized form of which is converted to a reduced form by Trx reductase, regulates cell proliferation and survival. We investigated the effect of 1-chloro-2,4-dinitrobenzene (DNCB), an inhibitor of Trx reductase, on cell death in neuronal PC12 cells and rat glial cells. In both types of cells, culture with DNCB for 4 h stimulated lactate dehydrogenase (LDH) leakage. LDH leakage by DNCB was inhibited by an inhibitor of caspases. Addition of 2,2-(hydroxynitrosohydrazino)bis-ethanamine, of which 50% decays and releases nitric oxide (NO) in 21 h, inhibited DNCB-induced LDH leakage. Addition of 10 μM N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethanamine (NOC-12), of which 50% decays and releases NO in 100 min, inhibited DNCB-induced LDH leakage, although 0.2 mM NOC-12 enhanced the leakage in PC12 cells. These findings suggest that DNCB induces cell death of neuronal and glial cells accompanied by caspase(s) activation. NO inhibits DNCB-induced cell death in both types of cells, although excess NO showed a toxic effect.