Protection of Ischemic Postconditioning against Neuronal Apoptosis Induced by Transient Focal Ischemia Is Associated with Attenuation of NF-κB/p65 Activation

Abstract

Background and PurposeAccumulating evidences have demonstrated that nuclear factor κB/p65 plays a protective role in the protection of ischemic preconditioning and detrimental role in lethal ischemia-induced programmed cell death including apoptosis and autophagic death. However, its role in the protection of ischemic postconditioning is still unclear.MethodsRat MCAO model was used to produce transient focal ischemia. The procedure of ischemic postconditioning consisted of three cycles of 30 seconds reperfusion/reocclusion of MCA. The volume of cerebral infarction was measured by TTC staining and neuronal apoptosis was detected by TUNEL staining. Western blotting was used to analyze the changes in protein levels of Caspase-3, NF-κB/p65, phosphor- NF-κB/p65, IκBα, phosphor- IκBα, Noxa, Bim and Bax between rats treated with and without ischemic postconditioning. Laser scanning confocal microscopy was used to examine the distribution of NF-κB/p65 and Noxa.ResultsIschemic postconditioning made transient focal ischemia-induced infarct volume decrease obviously from 38.6%±5.8% to 23.5%±4.3%, and apoptosis rate reduce significantly from 46.5%±6.2 to 29.6%±5.3% at reperfusion 24 h following 2 h focal cerebral ischemia. Western blotting analysis showed that ischemic postconditioning suppressed markedly the reduction of NF-κB/p65 in cytoplasm, but elevated its content in nucleus either at reperfusion 6 h or 24 h. Moreover, the decrease of IκBα and the increase of phosphorylated IκBα and phosphorylated NF-κB/p65 at indicated reperfusion time were reversed by ischemic postconditioning. Correspondingly, proapoptotic proteins Caspase-3, cleaved Caspase-3, Noxa, Bim and Bax were all mitigated significantly by ischemic postconditioning. Confocal microscopy revealed that ischemic postconditioning not only attenuated ischemia-induced translocation of NF-κB/p65 from neuronal cytoplasm to nucleus, but also inhibited the abnormal expression of proapoptotic protein Noxa within neurons.ConclusionsWe demonstrated in this study that the protection of ischemic postconditioning on neuronal apoptosis caused by transient focal ischemia is associated with attenuation of the activation of NF-κB/p65 in neurons.

The role of inflammasomes in ischemic stroke - from pathophysiology to treatments

“…A major finding of this present study is that both NF-κB and MAPK(s) signaling pathways played a major role in the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons, and that the expression and activation of neuronal NLRP1 and NLRP3 inflammasomes was able to be attenuated by treatment with either NF-κB and MAPKs inhibitors under simulated in vitro ischemic conditions. Several previous studies have provided evidence that activation of both NF-κB and MAPK(s) signaling pathways occur in neurons following ischemic stroke Gladbach et al, 2014;Liang et al, 2014;Liu et al, 2009;. In the present study, we again provide supporting evidence that activation of both NF-κB and MAPK(s) signaling pathways are detrimental to neuronal survival and pharmacological inhibition of either the NF-κB and MAPK(s) signaling pathways were able to significantly protect neurons under ischemic conditions.…”

Immediate Remote Ischemic Postconditioning Reduces Brain Nitrotyrosine Formation in a Piglet Asphyxia Model

“…RIPostC is the application of “brief intermittent cycles of ischemia alternating with reperfusion” [ 26 ] in the limbs after an ischemic insult. RIPostC has been shown to reduce cerebral ischemia-induced infarct size and neuronal apoptosis in rats [ 27 ] and could be similarly effective in neonates. Whilst the underlying neuroprotective mechanism is yet to be understood, RIPostC may interfere with apoptotic pathways by reducing oxidative stress to indirectly inhibit NF- κ B activity [ 27 ].…”

Endothelial Progenitor Cells Modulate Inflammation-Associated Stroke Vasculome

“…IKB-alpha constitutes its inhibitory effect onto NF-kB through binding tightly to NF-kB dimers, forming a complex, masking the nuclear localization signals (NLS) and keeping the NF-kB sequestered in the cytoplasm [ 50 ]. Due to stressors like ischemia or hypoxia, during the acute phase there IkB-alpha gets activated when phosphorylated by IkB kinase (IKK) causing their eventual degradation by proteasomes [ 51 , 52 ]. The ischemia-induced increase of active IkB-alpha expression in the brain allows increased NF-kB expression and leads to neuroinflammatory responses, which can cause harmful post-stroke injury [ 53 ].…”

“…Various studies have attempted to determine how eliminating the upregulation of phosphorylated IkB-alpha and its subsequent degradation can affect post-ischemia recovery. Interestingly, several studies have shown that ischemic post conditioning, the use of flavonoids and stem cells therapy can reversed the phosphorylation and degradation levels of IkB-alpha caused by ischemia [ 51 , 52 , 54 , 55 ]. These studies support our finding whereby EPC graphs were able to reduce the overexpression of active IkB-alpha, typically seen after ischemic injury, in the peri-infarct area of cortex and striatum as depicted by immunofluorescent and further validated by protein analysis of the whole ipsilateral hemisphere.…”