Neuroprotection against Focal Ischemic Brain Injury by Inhibition of c-Jun N-Terminal Kinase and Attenuation of the Mitochondrial Apoptosis-Signaling Pathway

Abstract

c-Jun N-terminal kinase (JNK) is an important stress-responsive kinase that is activated by various forms of brain insults. In this study, we have examined the role of JNK activation in neuronal cell death in a murine model of focal ischemia and reperfusion; furthermore, we investigated the mechanism of JNK in apoptosis signaling, focusing on the mitochondrial-signaling pathway. We show here that JNK activity was induced in the brain 0.5 to 24 h after ischemia. Systemic administration of SP600125, a small molecule JNK-specific inhibitor, diminished JNK activity after ischemia and dose-dependently reduced infarct volume. c-Jun N-terminal kinase inhibition also attenuated ischemia-induced expression of Bim, Hrk/DP5, and Fas, but not the expression of Bcl-2 or FasL. In strong support of a role for JNK in promoting the mitochondrial apoptosis-signaling pathway, JNK inhibition prevented ischemia-induced mitochondrial translocation of Bax and Bim, release of cytochrome c and Smac, and activation of caspase-9 and caspase-3. The potential mechanism by which JNK promoted Bax translocation after ischemia was further studied using coimmunoprecipitation, and the results revealed that JNK activation caused serine phosphorylation of 14-3-3, a cytoplasmic sequestration protein of Bax, leading to Bax disassociation from 14-3-3 and subsequent translocation to mitochondria. These results confirm the role of JNK as a critical cell death mediator in ischemic brain injury, and suggest that one of the mechanisms by which JNK triggers the mitochondrial apoptosis-signaling pathway is via promoting Bax and Bim translocation.

SP600125, a selective JNK inhibitor, aggravates hepatic ischemia-reperfusion injury

“…For example, the attenuation of hepatic I/R injury by a p38 MAPK inhibitor identifies p38 M APK as a therapeutic target in I/R injury (Kobayashi et al, 2002). JNK has also been suggested as a therapeutic target in reperfusion injury of major organs, such as the brain (Gao et al, 2005) and the lung (Ishii et al, 2004) because it was found that chemical JNK inhibitors attenuate reperfusion injury in these organs. Uehara et al, (2005) recently reported that several novel JNK inhibitors successfully attenuated hepatic I/R injury and increased the survival rate of rats subjected to partial hepatic I/R and resectioning of the remaining non-ischemic lobes.…”

“…SP600125, a reversible ATP-competitive inhibitor, selectively inhibits JNK activity (Bennett et al, 2001), reduces ischemia-reperfusion injury in the brain (Gao et al, 2005) and the lungs (Ishii et al, 2004), and protects hepatocytes from apoptosis due to TNF- (Marderstein et al, 2003). Therefore, we attempted to determine whether SP600125 attenuates hepatic I/R injury in vivo using a partial hepatic I/R model in mice.…”

Prevention of JNK Phosphorylation as a Mechanism for Rosiglitazone in Neuroprotection after Transient Cerebral Ischemia: Activation of Dual Specificity Phosphatase

“…4 Inhibition of either activated JNK or p38 MAPK, by drugs or by gene therapy, can protect against cell death after ischemia. [5][6][7] Stress-activated protein kinase signaling pathways contain various checkpoints for regulation. Many studies have demonstrated that phosphorylation of upstream kinases is significant in regulating the signaling cascade.…”

Bim and Noxa Are Candidates to Mediate the Deleterious Effect of the NF-κB Subunit RelA in Cerebral Ischemia

“…However, we found a reproducible upregulation of the proapoptotic BH3-only genes Bik, Bim, and Noxa by cerebral ischemia. The induction of Bim by cerebral ischemia has been reported previously (Shibata et al, 2002;Gao et al, 2005).…”