Death signaling pathway induced by pyrrolidine dithiocarbamate-Cu2+ complex in the cultured rat cortical astrocytes

The chelating and antioxidant effects of pyrrolidine dithiocarbamate (PDTC) have been investigated extensively for preventing cell death induced by di fferent insults. However, the toxic effects of PDTC have been studied only recently and fewer studies on the toxic effects on astrocytes have been rep orted. In our study, we demonstrated that both PDTC and Cu2+ alone were rat ed as only weakly toxic in inducing cell death in cortical astrocytes with IC50 of 300 mu M and 180 mu M, respectively. However, PDTC and Cu2+ in the complex form markedly potentiated with each other by about 1,000-fold with ICS, of 0.3 mu M PDTC plus 10 mu M Cu-2+ Other metals at concentrations of 3-10 mu M (VO45+, Cr6+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Pb2+, Bi2+, Ba2+, UO2 +, Cs+, SeO42-, La3+) had no such potentiating effects on PDTC. Changes in morphology (nuclear condensation), apoptotic body formation, and hypodiploi dity of DNA suggested that the PDTC-Cu2+ complex induced cell death through an apoptotic process. Further studies showed that the PDTC-Cu2+ complex de creased mitochondrial membrane potential, increased hydrogen peroxide produ ction, and depleted GSH contents. After the increased oxidative stress, PDT C-Cu2+ complex differentially activated JNKs, ERK, p38 and caspase 3, which caused PARP degradation in a time-dependent manner. All these effects were consistent with the increased cellular Cu contents. The nonpermeable coppe r-specific chelator bathocuproine disulfonate (BCPS), but not the permeable Cu2+ chelator neocuproine, abolished all the observed effects. Antioxidant s (N-acetylcysteine [NAC], vitamin C), catalase, and Cu2+-binding proteins (albumin, hemoglobin, and higher serum) reduced the cytotoxic effects of PD TC-Cu2+ complex. We concluded that the death signaling pathway of PDTC-Cu2 complex was mediated by oxidative stress and subsequent JNK activation. Th ese findings imply that PDTC, a widely used pesticide and medicine that is capable of penetrating the blood-brain barrier, may cause neurotoxicity thr ough astrocyte dysfunction. (C) 2000 Wiley-Liss, Inc.