Hsp70 Overexpression Sequesters AIF and Reduces Neonatal Hypoxic/Ischemic Brain Injury

Abstract

Apoptosis is implicated in neonatal hypoxic/ischemic (H/I) brain injury among various forms of cell death. Here we investigate whether overexpression of heat shock protein (Hsp) 70, an antiapoptotic protein, protects the neonatal brain from H/I injury and the pathways involved in the protection. Postnatal day 7 (P7) transgenic mice overexpressing rat Hsp70 (Tg) and their wild-type littermates (Wt) underwent unilateral common carotid artery ligation followed by 30 mins exposure to 8% O(2). Significant neuroprotection was observed in Tg versus Wt mice on both P12 and P21, correlating with a high level of constitutive but not inducible Hsp70 in the Tg. More prominent injury was observed in Wt and Tg mice on P21, suggesting its continuous evolution after P12. Western blot analysis showed that translocation of cytochrome c, but not the second mitochondria-derived activator of caspase (Smac)/DIABLO and apoptosis-inducing factor (AIF), from mitochondria into cytosol was significantly reduced in Tg 24 h after H/I compared with Wt mice. Coimmunoprecipitation detected more Hsp70 bound to AIF in Tg than Wt mice 24 h after H/I, inversely correlating with the amount of nuclear, but not cytosolic, AIF translocation. Our results suggest that interaction between Hsp70 and AIF might have reduced downstream events leading to cell death, including the reduction of nuclear AIF translocation in the neonatal brains of Hsp70 Tg mice after H/I.

Physical interaction of apoptosis-inducing factor with DNA and RNA

“…We found that AIF binds to heat shock protein 70 (HSP70) and that this interaction can prevent AIF from translocating to the nucleus (Gurbuxani et al, 2003), where it exerts its proapoptotic action. This neutralizing interaction has been confirmed in vivo (Matsumori et al, 2005). We also found that AIF binds to cyclophilin A.…”

Influence of duration of focal cerebral ischemia and neuronal nitric oxide synthase on translocation of apoptosis-inducing factor to the nucleus

“…In neurons, AIF translocation to the nucleus appears to play an important role in NMDA and kainate excitotoxicity (Yu et al, 2002;Wang et al, 2004;Cheung et al, 2005) and in oxygenglucose deprivation (Cao et al, 2003;Plesnila et al, 2004;Culmsee et al, 2005). In brain, nuclear AIF translocation has been reported after hypoglycemic coma (Ferrand-Drake et al, 2003), global cerebral ischemia (Cao et al, 2003), hypoxia-ischemia in postnatal rats and mice (Matsumori et al, 2005), and traumatic brain injury (Zhang et al, 2002).…”

Analysis of the NMDA in Focal Cerebral Ischemia in Rats

“…S e v e r a l morphometric changes are detected in the affected cerebral area after experimental cerebral ischemia, including neuronal and glial cell death by necrosis and apoptosis (Thorburn, 2004;Matsumori et al, 2005;Siegelin et al, 2005;Zhang et al, 2006). After minutes of a focal ischemic stroke occurring, the core of brain tissue exposed to the most dramatic blood flow reduction is fatally injured and subsequently undergoes necrotic cell death that is surrounded by a zone of less severely affected tissue but metabolically active known as "ischemic penumbra" and represents the region in which there is opportunity for salvage via poststroke therapy (Broughton et al, 2009).…”