Ischemic preconditioning blocks BAD translocation, Bcl-x _L cleavage, and large channel activity in mitochondria of postischemic hippocampal neurons

Abstract

Transient forebrain or global ischemia induces delayed neuronal death in vulnerable CA1 pyramidal cells with many features of apoptosis. A brief period of ischemia, i.e., ischemic preconditioning, affords robust protection of CA1 neurons against a subsequent more prolonged ischemic challenge. Here we show that preconditioning acts via PI3K/Akt signaling to block the ischemia-induced cascade involving mitochondrial translocation of Bad, assembly of Bad with Bcl-x L , cleavage of Bcl-x L to form its prodeath fragment, ΔN-Bcl-x L , activation of large-conductance channels in the mitochondrial outer membrane, mitochondrial release of cytochrome c and Smac/DIABLO (second mitochondria-derived activator of caspases/direct IAP-binding protein with low pI), caspase activation, and neuronal death. These findings show how preconditioning acts to prevent the release of cytochrome c and Smac/DIABLO from mitochondria and to preserve the integrity of the mitochondrial membrane. The specific PI3K inhibitor LY294002 administered in vivo 1 h before or immediately after ischemia or up to 120 h later significantly reverses preconditioning-induced protection, indicating a requirement for sustained PI3K signaling in ischemic tolerance. These findings implicate PI3K/Akt signaling in maintenance of the integrity of the mitochondrial outer membrane.

Heat Acclimation Provides Sustained Improvement in Functional Recovery and Attenuates Apoptosis after Traumatic Brain Injury

“…As both proand antiapoptotic Bcl-2 proteins may be regulated by transcription, phosphorylation, dimerization, translocation, degradation, and cleavage (Gross et al, 1999), it is plausible that increased Bcl-xL levels in HA animals are associated with posttranscriptional modifications, subcellular compartmentalization, or reduced degradation/cleavage rate. This notion is supported by previous reports indicating that injurious stimuli in the brain promote proteolytic cleavage of full length Bcl-xL to create a strong proapoptotic product that acts within the mitochondria (Bonanni et al, 2006;Miyawaki et al, 2008). Bad protein levels were also measured in the mitochondria and cytosol of sham, noninjured mice and at various time intervals after TBI.…”

Heme Oxygenase-1 Mediates Neuroprotection Conferred by Argon in Combination with Hypothermia in Neonatal Hypoxia–Ischemia Brain Injury

“…Efforts were made to minimise the used number and/or suffering of animals throughout. Drug administration in vivo: LY294002 (Calbiochem, 0.2 mol/L in 5 μl of PBS) or the PBS vehicle (PBS) was injected intracerebroventricularly before gas treatment, as described previously 16,17 . were incubated with the two primary antibodies overnight, followed by the two secondary antibodies.…”

Molecular Mechanisms of Development of Cerebral Tolerance to Ischemia (Review. Part 2)

“…Помимо этого, ПреК предотвращало формирование каналов в наружной мембране митохондрий и, следовательно, сопрово-ждалось менее интенсивным выходом цитохрома С из межмембранного пространства митохондрий. Как следствие, в мозге животных, подвергнутых ПреК, отме-чалась меньшая активность каспаз и меньшая интенсив-ность апоптоза [2].…”

“…Кроме того, под действием ПреК происходит стабилизация митохондри-ального мембранного потенциала, снижается высвобож-дение митохондриального цитохрома С, а также умень-шается интенсивность синтеза каспазы 3 и снижается активность ядерного белка p53 [1]. На модели четырех-сосудистой ишемии ГМ у крыс было показано, что меха-низмы предотвращения апоптоза нейронов СА1-зоны гиппокампа под действием ишемического ПреК вклю-чают активацию фосфатидилинозитол-3ОН-киназы (PI3K) и протеинкиназы В с последующей блокировкой сигнальных путей апоптоза [2]. В частности, ишемиче-ское ПреК предотвращало транслокацию в митохон-дрии проапоптотического фактора BAD, его связывание с BCL-X L и расщепление последнего с образованием проа-поптотического фрагмента ∆N-Bcl-X L .…”