Injury‐induced apoptosis of neurons in adult brain is mediated by p53‐dependent and p53‐independent pathways and requires bax

Abstract

The mechanisms of injury-induced apoptosis of neurons within the CNS are not understood. We used a model of cortical injury in rat and mouse to induce retrograde neuronal apoptosis in thalamus. In this animal model, unilateral ablation of the occipital cortex causes unequivocal apoptosis of corticopetal projection neurons in the dorsal lateral geniculate nucleus (LGN) by 7 days postlesion. We tested the hypothesis that p53 and Bax regulate this retrograde neuronal apoptosis. We found, by using immunocytochemistry, that p53 accumulates in nuclei of neurons destined to undergo apoptosis. By immunoblotting, p53 levels increase ( approximately 150% of control) in nuclear-enriched fractions of the ipsilateral LGN by 5 days after occipital cortex ablation. p53 is functionally activated in nuclear fractions of the ipsilateral LGN at 5 days postlesion, as shown by DNA binding assay (approximately fourfold increase) and by immunodetection of phosphorylated p53. The levels of procaspase-3 increase at 4 days postlesion, and caspase-3 is activated prominently at 5 days postlesion. To identify whether neuronal apoptosis in the adult brain is dependent on p53 and Bax, cortical ablations were done on p53 and bax null mice. Neuronal apoptosis in the dorsal LGN is significantly attenuated (approximately 34%) in p53(-/-) mice. In lesioned p53(+/+) mice, Bax immunostaining is enhanced in the ipsilateral dorsal LGN and Bax immunoreactivity accumulates at perinuclear locations in dorsal LGN neurons. The enhancement and redistribution of Bax immunostaining is attenuated in lesioned p53(-/-) mice. Neuronal apoptosis in the dorsal LGN is blocked completely in bax(-/-) mice. We conclude that neuronal apoptosis in the adult thalamus after cortical injury requires Bax and is modulated by p53.

Apoptotic Mediators are Upregulated in the Skeletal Muscle of Chronic/Progressive Mouse Model of Parkinson's Disease

“…P53 mediates apoptosis (Benchimol, 2001;Shen and White, 2001;Martin et al, 2001;Liu et al, 2013). Previous studies have demonstrated p53 overexpression in PD brain (De La Monte et al, 1998;Mogi et al, 2007;Da Costa et al, 2009).…”

Adult Motor Neuron Apoptosis Is Mediated by Nitric Oxide and Fas Death Receptor Linked by DNA Damage and p53 Activation

“…Sections were selected with a random start and systematically sampled (every ninth section) to generate a subsample of sections from each mouse lumbar spinal cord that were mounted on glass slides and stained with cresyl violet for neuronal counting. Neuronal counts in the ipsilateral and contralateral ventral horns were made at 1000ϫ magnification using the stereological optical disector method as described previously (Calhoun et al, 1996;Martin et al, 1999). MNs without apoptotic structural changes were counted using strict morphological criteria.…”

“…Phosphorylated p53 was detected with a rabbit antibody to serine-15 phosphorylated p53 (Cell Signaling). The specificities of these antibodies were evaluated by immunoblotting or have been evaluated previously (Northington et al, 1996;Martin et al, 2001;Martin and Liu, 2002a;Graham et al, 2004). Negative control sections were incubated in comparable dilutions of IgG or with the primary or secondary antibody omitted.…”

“…Hydroxyl radical damage to DNA and RNA was detected with monoclonal antibodies to 8-hydroxy-2-deoxyguanosine (OHdG), obtained from QED Bioscience (San Diego, CA) and OXIS International (Portland, OR). These antibodies to OHdG have been evaluated for specificity by multiple approaches (Al-Abdulla and Martin, 1998;Martin et al, 1999). In competition experiments, sections were reacted with an antibody to OHdG that was incubated at 4°C for 24 h with 1000-fold concentrations of OHdG, 8-hydroxyguanosine, or guanosine .…”

“…Serial sections from each mouse and rat spinal cord were mounted on glass slides and stained with cresyl violet for neuronal counting. MN counts in the ipsilateral and contralateral sides were determined by an operator unaware of sample experimental history at 1000ϫ magnification using the stereological optical disector method (Calhoun et al, 1996;Martin et al, 1999). Neuronal counts were used to determine group means and variances, and comparisons among groups were performed using a one-way ANOVA and a post hoc Newman-Keuls test.…”