Nuclear Factor-κB Modulates the p53 Response in Neurons Exposed to DNA Damage

Abstract

Previous studies have shown that DNA damage-evoked death of primary cortical neurons occurs in a p53 and cyclin-dependent kinasedependent (CDK) manner. The manner by which these signals modulate death is unclear. Nuclear factor-B (NF-B) is a group of transcription factors that potentially interact with these pathways. Presently, we show that NF-B is activated shortly after induction of DNA damage in a manner independent of the classic IB kinase (IKK) activation pathway, CDKs, ATM, and p53. Acute inhibition of NF-B via expression of a stable IB mutant, downregulation of the p65 NF-B subunit by RNA interference (RNAi), or pharmacological NF-B inhibitors significantly protected against DNA damage-induced neuronal death. NF-B inhibition also reduced p53 transcripts and p53 activity as measured by the p53-inducible messages, Puma and Noxa, implicating the p53 tumor suppressor in the mechanism of NF-B-mediated neuronal death. Importantly, p53 expression still induces death in the presence of NF-B inhibition, indicating that p53 acts downstream of NF-B. Interestingly, neurons cultured from p65 or p50 NF-B-deficient mice were not resistant to death and did not show diminished p53 activity, suggesting compensatory processes attributable to germline deficiencies, which allow p53 activation still to occur. In contrast to acute NF-B inhibition, prolonged NF-B inhibition caused neuronal death in the absence of DNA damage. These results uniquely define a signaling paradigm by which NF-B serves both an acute p53-dependent pro-apoptotic function in the presence of DNA damage and an anti-apoptotic function in untreated normal neurons.

Roles for NF-κB in nerve cell survival, plasticity, and disease

“…[92][93][94] It has been reported that NF-kB is rapidly activated following DNA damage in cultured neurons in an IKK-ATM-and p53-independent manner. 95 Data in the latter study suggested that NF-kB acts upstream of p53 in acute cell death induced by DNA damage, but, on the other hand, NF-kB promotes cell survival when activated over a longer time period in the absence of severe DNA damage. However, in another study, DNA-damaging agents reduced NF-kB activity in cultured neurons and treatment with a p53 inhibitor resulted in preservation of NF-kB activity.…”

Parkin is transcriptionally regulated by ATF4: evidence for an interconnection between mitochondrial stress and ER stress

“…Briefly, neurons from each embryo were plated individually, into six-well dishes (B3 million cells/well) coated with poly-D-lysine (100 mg/ml) in serum-free medium (MEM/F12 (1:1) supplemented with 6 mg/ml D-glucose, 100 mg/ml transferrin, 25 mg/ml insulin, 20 nM progesterone, 60 mM putrescine and 30 nM selenium) as described previously. 38 At 2 days in vitro, cortical neurons were treated with TM (3 mg/ml) for 8 h. Stock solutions of TM were prepared in DMSO (Sigma Aldrich, Oakville, ON, Canada) and diluted in culture media immediately before addition. Total RNA was isolated from cells at indicated time points using TRIzol reagent as per manufacturer's instructions (Invitrogen).…”

Bim and Noxa Are Candidates to Mediate the Deleterious Effect of the NF-κB Subunit RelA in Cerebral Ischemia

“…An indirect mechanism through which NF-B is able to regulate Noxa gene transcription was suggested by Aleyasin et al (2004). These authors found that, when DNA had been damaged, NF-B stimulated Noxa and Puma gene transcription through induction of p53 expression.…”