The depletion of intracellular zinc with N,N,N 0 ,N 0 -tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) induces protein synthesis-dependent apoptosis. Here we examined the involvement of caspase induction in apoptosis. Among the examined caspases, only caspase-11 was increased by TPEN. Caspase-11 activity also increased, which resulted in caspase-3 activation. Cycloheximide or actinomycin D blocked caspase-11 induction, reduced caspase-11 and -3 activation, and attenuated TPEN-induced neuronal apoptosis. Blockade of caspase-11 by a chemical inhibitor or genetic deletion attenuated TPEN-induced apoptosis, indicating a critical role of caspase-11 in TPEN-induced apoptosis. Although mitochondria-mediated caspase-9/-3 activation also contributed to TPEN-induced apoptosis, caspase-11 is likely a key inducible apoptosis-inducing protein.

a b s t r a c tDepletion of intracellular zinc with N,N,N 0 ,N 0 -tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) induces protein synthesis-dependent apoptosis. In this study, we examined the requirement for p53 as an upstream transcription factor in TPEN-induced neuronal apoptosis. Chemical or genetic blockade of p53 markedly attenuated TPEN-induced neuronal apoptosis, while the stability and activity of p53 were increased by TPEN. In addition, expression of proapoptotic genes, PUMA and NOXA, and activation of caspase-11 were increased by TPEN in a p53-dependent manner. Inhibition of p53 blocked cytochrome C release from mitochondria to cytosol and prevented caspase-3 activation. Therefore, p53 may be an essential regulatory factor for TPEN-induced neuronal apoptosis.

Depletion of intracellular zinc by N,N,N′,N′-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN) induces p53-mediated protein synthesis-dependent apoptosis of mouse cortical neurons. Here, we examined the requirement for poly(ADP-ribose) polymerase (PARP)-1 as an upstream regulator of p53 in zinc depletion-induced neuronal apoptosis. First, we found that chemical inhibition or genetic deletion of PARP-1 markedly attenuated TPEN-induced apoptosis of cultured mouse cortical neurons. Poly(ADP-ribosyl)ation of p53 occurred starting 1 h after TPEN treatment. Suggesting the critical role of PARP-1, the TPEN-induced increase of stability and activity of p53 as well as poly(ADP-ribosyl)ation of p53 was almost completely blocked by PARP inhibition. Consistent with this, the induction of downstream proapoptotic proteins PUMA and NOXA was noticeably reduced by chemical inhibitors or genetic deletion of PARP-1. TPEN-induced cytochrome C release into the cytosol and caspase-3 activation were also blocked by inhibition of PARP-1. Taken together, these findings indicate that PARP-1 is essential for TPEN-induced neuronal apoptosis.