Oxidative stress induces proorphanin FQ and proenkephalin gene expression in astrocytes through p38‐ and ERK‐MAP kinases and NF‐κB

Abstract

Oxidative stress has been implicated in the pathogenesis of stroke, traumatic brain injuries, and neurodegenerative diseases affecting both neuronal and glial cells in the CNS.In this study we have demonstrated that reactive oxygen species (ROS) dramatically induce the expression of two neuropeptide genes, the opioid proenkephalin (pENK) and the opioid-related proorphanin FQ (pOFQ; also known as pronociceptin) in primary astrocytes. Hydrogen peroxide (H 2 O 2 ) treatment dose-dependently increased pENK and pOFQ mRNA levels with a maximal effect (,15-fold increase) being detected at 50 mM concentration. Exposing the astrocyte cultures to hypoxia and subsequent re-oxygenation also led to a profound elevation of pOFQ and pENK mRNA levels. Western blot analysis and immunocytochemistry revealed that H 2 O 2 treatment elicited the phosphorylation and nuclear translocation of ERK 1/2 and p38 MAP kinases. Blockade of the p38 or the ERK MAP kinase pathways (by SB202190 and PD98059, respectively) prevented the H 2 O 2 -induced increase in pENK and pOFQ mRNA levels indicating a central role for these cascades in the regulation of pOFQ and pENK genes in response to oxidative stress. Regulation of pOFQ and pENK gene expression by ERK and p38 activation may be mediated through the transcription factor cAMP-response element binding protein (CREB). We observed CREB phosphorylation in response to H 2 O 2 , which was also prevented by SB202190 and PD98059. The nuclear factor-kB (NF-kB) pathway appears to be involved exclusively in the induction of pOFQ transcription by H 2 O 2 , as NF-kB inhibitors antagonized the effect of oxidative stress on pOFQ, but not on pENK expression. The profound induction of these genes by oxidative stress and these other factors may suggest a role for orphanin FQ and enkephalin in injury and stress responses of the CNS and neuropathophysiological conditions involving reactive oxygen species.

Mitochondrial-dependent manganese neurotoxicity in rat primary astrocyte cultures

“…ERK activation can contribute to neurotoxicity, particularly in the context of oxidative insults (Chu et al, 2004). ERK1/2 stimulation by ROS has been described in neurons (Samanta et al, 1998) and neuroprotection by MEK inhibition against oxidative stress in both neurons and in astrocytes (Satoh et al, 2000;Rosenberger et al, 2001). Although numerous reports have implicated ERK in neuronal cell survival (Xia et al, 1995;Yujiri et al, 1998;de Bernardo et al, 2003), it has been proposed that the precise pattern of ERK1/2 activation ultimately determines whether the kinase participates in cell death-promoting or cell survival pathway (Stanciu et al, 2000;Chang and Karin 2001;Stanciu and DeFranco 2002;Chu et al, 2004).…”

Xanthoceraside Inhibits Pro-inflammatory Cytokine Expression in Aβ25–35/IFN-γ–Stimulated Microglia Through the TLR2 Receptor, MyD88, Nuclear Factor-κB, and Mitogen-Activated Protein Kinase Signaling Pathways

“…Intracellular ROS could activate diverse downstream signaling molecules, such as protein kinase C, MAPK, and NF-kB, to regulate the expression of genes encoding various pro-inflammatory factors (36,37); and the inflammatory effects might result in the accumulation of intracellular ROS (38). IFN-g could up-regulate ROS production in microglia via transcribed subunits of the nicotinamide adenine dinucleotide phosphate oxidase complex (39).…”

NF-κB activity in distinct neural subtypes of the rat hippocampus: Influence of time and GABA antagonism in acute slice preparations

“…Critically, during this period, slices are essentially experiencing in vitro ischemia. NF-B has been shown to be up-regulated in response to products of ischemia such as H 2 O 2 ‫מ‬ (Schreck et al 1991;Rosenberger et al 2001;Shen et al 2003). Secondly, hippocampal slices may undergo NMDAmediated excitotoxicity immediately post-cutting (Feig and Lipton 1990), triggering an NF-B-dependent anti-apoptotic cascade (Hardingham and Bading 2003).…”