Ischemic Preconditioning Mediates Cyclooxygenase-2 Expression Via Nuclear Factor-Kappa B Activation in Mixed Cortical Ne
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ORIGINAL ARTICLE
Ischemic Preconditioning Mediates Cyclooxygenase-2 Expression Via Nuclear Factor-Kappa B Activation in Mixed Cortical Neuronal Cultures Eun Joo Kim & Ami P. Raval & Nina Hirsch & Miguel A. Perez-Pinzon
Received: 6 October 2009 / Revised: 21 November 2009 / Accepted: 4 December 2009 / Published online: 26 January 2010 # Springer Science+Business Media, LLC 2010
Abstract Nuclear factor-kappaB (NF-κB) activation occurs following ischemic preconditioning (IPC) in brain. However, the upstream signaling messengers and downstream targets of NF-κB required for induction of IPC remain undefined. In a previous study, we demonstrated that epsilon protein kinase c (εPKC) was a key mediator of IPC in brain. Activation of εPKC induced cyclooygenase-2 (COX-2) expression and conferred ischemic tolerance in the neuronal and hippocampal slice models. Here, we hypothesized that IPC-mediated COX-2 expression was mediated by NF-κB. We tested this hypothesis in mixed cortical neuron/astrocyte cell cultures. To simulate IPC or ischemia, cell cultures were exposed to 1 or 4 h of oxygen– glucose deprivation, respectively. Our results demonstrated translocation of p65 and p50 subunits of NF-κB into nucleus following IPC or εPKC activation. NF-κB inhibition with pyrrolidine dithiocarbamate (10 μM) abolished IPC or εPKC activator-mediated neuroprotection indicating that NF-κB activation was involved in ischemic tolerance. In parallel studies, inhibition of either εPKC or the extracellular signal-regulated kinase (ERK 1/2) pathway reduced IPC-induced NF-κB activation. Finally, inhibition of NF-κB blocked IPC-induced COX-2 expression. In conclusion, we demonstrated that IPC-signaling cascade comprises εPKC activation→ERK1/2 activation→NF-κB translocation to nucleus→COX-2 expression resulting in neuroprotection in mixed neuronal culture. E. J. Kim : A. P. Raval : N. Hirsch : M. A. Perez-Pinzon (*) Cerebral Vascular Disease Research Center, Department of Neurology and Neuroscience Program (D4-5), University of Miami Miller School of Medicine, P.O. Box 016960, Miami, FL 33101, USA e-mail: [email protected]
Keywords Cerebral ischemia . Ischemic tolerance . Epsilon protein kinase C . Extracellular signal-regulated kinase (ERK1/2) . Neuroprotection . Mixed cortical neuron/astrocyte cell cultures
Introduction Ischemic preconditioning (IPC) is an intrinsic neuroprotective mechanism invoked by sublethal ischemic insults prior to a subsequent lethal ischemic insult. The resulting state of ischemic tolerance has gained attention as a potentially robust prophylactic approach with the potential for clinical use in humans having a high risk for pathological cerebrovascular events and for patients anticipating neurosurgical procedures. More importantly, therapies based on endogenous neuroprotective mechanisms may as well have less intense and fewer side effects. Therefore, the main emphasis in the field of IPC is to better understand signaling mechanisms of initiation, induction, and maintenance. The induction of IPC requires activatio
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