Ischemia-Induced Mitochondrial Apoptosis is Significantly Attenuated by Ischemic Preconditioning

Abstract

Ischemic preconditioning (IPC) represents an important adaptation of CNS to sub-lethal ischemia, which results in increased tolerance of CNS to the lethal ischemia. Ischemia-induced mitochondrial apoptosis is considered to be an important event leading to neuronal cell death after cerebral blood flow arrest. In presented study, we have determined the effect of IPC on ischemia/reperfusion-induced mitochondrial apoptosis. Global brain ischemia was induced by permanent occlusion of vertebral arteries and temporal occlusion of carotid arteries for 15 min. Rats were preconditioned by 5 min of sub-lethal ischemia and 2 days later 15 min of lethal ischemia was induced. With respect to mitochondrial apoptosis initiation, translocation of p53 to mitochondria was observed in hippocampus but not in cerebral cortex. However, level of both apoptotic bax and anti-apoptotic bcl-xl in both hippocampal and cortical mitochondria was unchanged after global brain ischemia. Detection of genomic DNA fragmentation as well as Fluoro-Jade C staining showed that ischemia induces apoptosis in vulnerable CA1 layer of rat hippocampus. IPC abolished completely ischemia-induced translocation of p53 to mitochondria and had significant protective effect on ischemia-induced DNA fragmentation. In addition, significant decrease of Fluoro-Jade C positive cells was observed as well. Our results indicate that IPC abolished almost completely both initiation and execution of mitochondrial apoptosis induced by global brain ischemia.

Ischaemia-Induced Protein Ubiquitinylation is Differentially Accompanied with Heat-Shock Protein 70 Expression After Naïve and Preconditioned Ischaemia

“…IPC has been induced by sub-lethal ischaemia in duration of 5 min and 48 h latter lethal global brain ischaemia in duration of 15 min was induced. Such protocol is associated with significant resistance of vulnerable pyramidal neurones of hippocampal CA1 layer to ischaemic insult (Racay et al 2009) as well as inhibition of p53 translocation to mitochondria (Racay et al 2007(Racay et al , 2009. Likewise naïve ischaemia, preconditioned ischaemia is associated with increased accumulation of ubiquitinylated proteins after 1 and 3 h of reperfusion (Fig.…”

Comparison of Phosphorylated Extracellular Signal-Regulated Kinase 1/2 Immunoreactivity in the Hippocampal Ca1 Region Induced by Transient Cerebral Ischemia Between Adult and Aged Gerbils

“…Although the mechanism of delayed neuronal death has not been fully elucidated, some causes have been suggested. The delayed neuronal death is related to oxidative stress, intracellular calcium influx, glutamate receptor mediated neurotoxicity, and caspase-3 activation (Himi et al 1998;Won et al 2001;Rothstein et al 2002;Candelario-Jalil et al 2003;Al-Omar et al 2006;Kravcukova et al, 2009;Pavlíková et al, 2009;Racay et al, 2009). In addition, aging is one of the risk factors for stroke, and it is a primary factor in the development of greater ischemic neuronal damage in aged rats (Yao et al 1991;Saucier et al 2007).…”

Mechanisms of Ischemic Induced Neuronal Death and Ischemic Tolerance

“…The authors showed that SPCA activity, similar to other P-type ATPases, is also subject to ischemic damage most likely due to free radicals action (Lehotsky et al, 2002b). In addition, oxidative alterations detected in mitochondria and microsomes after IRI in our experiments, may at least partially explain functional postischemic disturbances of neuronal ion transport mechanisms (Lipton 1999;Lehotsky et al, 2002a;Obrenovitch, 2008) and inhibition of global proteosynthesis (Burda et al, 2003), which are both implicated in neuronal cell damage and/or recovery from ischemic insult, IPC-induced reduction of lipoperoxidation products and protein oxidative changes (Racay et al, 2009;Pavlikova et al, 2009). These may all be probably due to upregulation of defence mechanisms (antioxidant enzymes) against oxidative stress in the preconditioning challenge (Danielisova et al, 2005;Gidday, 2006;Obrenovitch, 2008).…”

“…In addition, IPC had significant protective effect on ischemia-induced DNA fragmentation, as well as on number of positive Fluoro-Jade C staining cells. Thus, it indicates that IPC abolished almost completely both initiation and execution of mitochondrial apoptosis induced by global brain ischemia in vulnerable CA1 layer of rat hippocampus (Racay et al, 2007(Racay et al, , 2009b. The studies showed that ischemia induced inhibition of mitochondrial complexes I and IV, however inhibition is not accompanied by a decrease of mitochondrial Ca 2+ uptake rate apparently due to the excess capacity of the complex I and complex IV.…”

“…As shown by experimental and clinical studies, IRI -induced mitochondrial pathway of apoptosis is an important event leading to neuronal cell death after blood flow arrest. Impact of IRI and ischemic preconditioning on the level of apoptotic and anti-apoptotic proteins was assessed in both cortical and hippocampal mitochondria by Western blot analysis of p53, bax, and bcl-x (Racay et al, 2007(Racay et al, , 2009b. Remarkably, IRI led to increase of p53 level in hippocampal mitochondria, with significant differences after 3 h (217.1 ± 42.2% of control), 24 h (286.8 ± 65% of control), and 72 h (232.9 ± 37.3% of control) of reperfusion.…”