N-Acetyl-L-cysteine in the Presence of Cu2+ Induces Oxidative Stress and Death of Granule Neurons in Dissociated Cultures of Rat Cerebellum.

Addition into the culture medium of the antioxidant N-acetylcysteine (NAC, 1 mM) in the presence of Cu2+ (0.0005-0.001 mM) induced intensive death of cultured rat cerebellar granule neurons, which was significantly decreased by the zinc ion chelator TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine). However, the combined action of NAC and Zn2+ did not induce destruction of the neurons. Measurement of the relative intracellular concentration of Zn2+ with the fluorescent probe FluoZin-3 AM or of free radical production using a CellROX Green showed that incubation of the culture for 4 h with Cu2+ and NAC induced an intensive increase in the fluorescence of CellROX Green but not of FluoZin-3. Probably, the protective effect of TPEN in this case could be mediated by its ability to chelate Cu2+. Incubation of cultures in a balanced salt solution in the presence of 0.01 mM Cu2+ caused neuronal death already after 1 h if the NAC concentration in the solution was within 0.005-0.05 mM. NAC at higher concentrations (0.1-1 mM) together with 0.01 mM Cu2+ did not cause the death of neurons. These data imply that the antioxidant NAC can be potentially harmful to neurons even in the presence of nanomolar concentrations of variable valence metals.