p53- and Bax-mediated apoptosis in injured rat spinal cord

Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, One Illini Drive, Peoria, IL 61656, USA.
Neurochemical Research (Impact Factor: 2.55). 07/2011; 36(11):2063-74. DOI: 10.1007/s11064-011-0530-2

ABSTRACT Spinal cord injury (SCI) induces a series of endogenous biochemical changes that lead to secondary degeneration, including apoptosis. p53-mediated mitochondrial apoptosis is likely to be an important mechanism of cell death in spinal cord injury. However, the signaling cascades that are activated before DNA fragmentation have not yet been determined. DNA damage-induced, p53-activated neuronal cell death has already been identified in several neurodegenerative diseases. To determine DNA damage-induced, p53-mediated apoptosis in spinal cord injury, we performed RT-PCR microarray and analyzed 84 DNA damaging and apoptotic genes. Genes involved in DNA damage and apoptosis were upregulated whereas anti-apoptotic genes were downregulated in injured spinal cords. Western blot analysis showed the upregulation of DNA damage-inducing protein such as ATM, cell cycle checkpoint kinases, 8-hydroxy-2'-deoxyguanosine (8-OHdG), BRCA2 and H2AX in injured spinal cord tissues. Detection of phospho-H2AX in the nucleus and release of 8-OHdG in cytosol were demonstrated by immunohistochemistry. Expression of p53 was observed in the neurons, oligodendrocytes and astrocytes after spinal cord injury. Upregulation of phospho-p53, Bax and downregulation of Bcl2 were detected after spinal cord injury. Sub-cellular distribution of Bax and cytochrome c indicated mitochondrial-mediated apoptosis taking place after spinal cord injury. In addition, we carried out immunohistochemical analysis to confirm Bax translocation into the mitochondria and activated p53 at Ser(3)(9)(2). Expression of APAF1, caspase 9 and caspase 3 activities confirmed the intrinsic apoptotic pathway after SCI. Activated p53 and Bax mitochondrial translocation were detected in injured spinal neurons. Taken together, the in vitro data strengthened the in vivo observations of DNA damage-induced p53-mediated mitochondrial apoptosis in the injured spinal cord.

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Available from: Rama P Kotipatruni, Aug 19, 2015
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    • "The Bax pro-apoptotic protein is a Bcl-2 protein family, which participate in the intrinsic pathway of apoptosis [8]. When subjected to certain stimuli such as excitotoxicity, this protein activates proteases that cause apoptosis [3] [7] [9] [10]. "
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    • "Our data show that VPA increased the expression of HSP27, HSP70, and phosphorylation of Akt, which are known to function as survival factors after SCI and ischemia (see Fig. 6d and e) (Lee et al. 2004; Yune et al. 2008b; van der et al. 2010). However, VPA attenuated the increase of p53 level (Saito et al. 2000; Kotipatruni et al. 2011), which is known to be involved in apoptotic cell death after SCI. Taken together, our data suggest that VPA might also exert its neuroprotective effect in part by modulating the expression of HSP27, HSP70, and p53, and phosphorylating Akt under epigenetic control after SCI. "
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