Expression of c-fos mRNA after cortical ablation in rat brain is modulated by basic fibroblast growth factor (bFGF) and the NMDA receptor is involved in c-fos expression

A metabotropic glutamate receptor antagonist, alpha-methyl-4-carboxyphenylglycine, attenuates immediate early gene mRNA expression following traumatic injury in cultured rat cortical glial cells

The effects of three glutamate receptor antagonists, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (MK-801) for the N-methyl-D-aspartate receptor, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f] quinoxaline-7-sulfonamide (NBQX) for the alpha-amino-3-hydroxy-5methyl-4-isoxazole propionate /kinate receptor and (S)-alpha-methyl-4-carboxyphenylglycine (MCPG) for the metabotropic receptor, on c-fos and c-jun mRNA expression were investigated in cultured cortical glial cells following traumatic scratch injury. Expression of the two genes along the edges of wounds detected by in situ hybridization was not affected by MK-801 and NBQX. However, 100 and 500 microM of MCPG remarkably reduced the hybridization signals for both c-fos and c-jun mRNAs. The present results suggest that group I metabotropic glutamate receptors might have some association with immediate early gene induction after in vitro traumatic injury in glial cells.

CROC-4: a novel brain specific transcriptional activator of c-fos expressed from proliferation through to maturation of multiple neuronal cell types

A novel, brain-specific cDNA, denoted CROC-4, was cloned from human brain by a contingent replication of cDNA procedure capable of detecting transcriptional activators of the human c-fos proto-oncogene promoter. CROC-4 encoded an 18-kDa serine/threonine-rich polypeptide containing a P-loop motif and an SH3-binding region with phosphorylation sites for a variety of protein kinases (cdc2, CDK2, MAPK, CDK5, protein kinase C, Ca(2+)/calmodulin protein kinase 2, casein kinase 2) involved in cell proliferation and differentiation. Immunohistochemistry revealed that during early development, expression was associated with proliferating and migrating cells throughout the rodent brain, initially appearing in the proliferative ventricular zones. During late development and in adult human brain, CROC-4 was expressed in diverse brain regions including the thalamus, subthalamic nucleus, corpus callosum, substantia nigra, caudate nucleus, amygdala, and hippocampus. The association of CROC-4 expression with proliferating regions of developing brain and retention in regions of the adult brain, as well as the punctate nuclear location, suggest that CROC-4 participates in brain-specific c-fos signaling pathways involved in cellular remodeling of brain architecture.

BDNF atelocollagen mini-pellet accelerates facial nerve regeneration

We investigated the effect of BDNF mini-pellet on the GAP-43 mRNA expression and functional status of facial nerve in a rat model of facial nerve transection and immediate repair. The facial function started to recover at 17 days in the placebo group and 14 days in the BDNF group. BDNF group had shorter period of increased GAP-43 mRNA expression than the placebo group. Topically applied BDNF may accelerate the facial nerve regeneration.

Inducible and constitutive transcription factors in the mammalian nervous system: control of gene expression by Jun, Fos and Krox, and CREB/ATF proteins

This article reviews findings up to the end of 1997 about the inducible transcription factors (ITFs) c-Jun, JunB, JunD, c-Fos, FosB, Fra-1, Fra-2, Krox-20 (Egr-2) and Krox-24 (NGFI-A, Egr-1, Zif268); and the constitutive transcription factors (CTFs) CREB, CREM, ATF-2 and SRF as they pertain to gene expression in the mammalian nervous system. In the first part we consider basic facts about the expression and activity of these transcription factors: the organization of the encoding genes and their promoters, the second messenger cascades converging on their regulatory promoter sites, the control of their transcription, the binding to dimeric partners and to specific DNA sequences, their trans-activation potential, and their posttranslational modifications. In the second part we describe the expression and possible roles of these transcription factors in neural tissue: in the quiescent brain, during pre- and postnatal development, following sensory stimulation, nerve transection (axotomy), neurodegeneration and apoptosis, hypoxia-ischemia, generalized and limbic seizures, long-term potentiation and learning, drug dependence and withdrawal, and following stimulation by neurotransmitters, hormones and neurotrophins. We also describe their expression and possible roles in glial cells. Finally, we discuss the relevance of their expression for nervous system functioning under normal and patho-physiological conditions.

Expression of immediate early gene c-fos in rat brain following increased intracranial pressure

No attention has been given to an influence of the intracranial pressure (ICP) elevation on the brain at the level of the gene. In the present study, we originally attempted to evaluate the molecular biological changes of the brain, especially the expression of c-fos mRNA as a marker of cellular response, caused by increased ICP. Our results confirm that the neurons and non-neuronal cells are well able to tolerate the stress of increased ICP at the level of the gene, under the condition that cerebral blood flow (CBF) is maintained. A severe increase in ICP, which reduces CBF, enhances the c-fos mRNA expression in a similar fashion as in a forebrain ischemia model, except in the choroid plexus.

Differential induction of immediate early gene mRNAs following cryogenic and impact trauma with/without craniotomy in rats

Expression of immediate early gene (IEG) mRNAs following traumatic brain injury in 3 different models-cryogenic injury, impact injury with craniotomy and impact injury without craniotomy-was investigated using in situ hybridization. Cryogenic brain injury resulted in c-fos and c-jun mRNA expression throughout the ipsilateral cortex, piriform cortex and dentate gyrus on the injured side, with peak at 30 min to 1 h post-injury. Impact injury with craniotomy was associated with hybridization signals in the same areas and also in the subcortical white matter or ependyma underlying the impact site at 30 min post-injury. The expression was rather more prolonged than with cryogenic injury. Impact injury without craniotomy induced the expression of both mRNAs throughout the ipsilateral cortex, piriform cortex and dentate gyrus at 30 min post-injury, but this was promptly attenuated by 1 h post-injury, except for bilateral elevation in the dentate gyrus. The present study, thus, demonstrated that regional and temporal expression of IEG mRNAs is influenced by the intensity, quality and manner of application of the insult. Differences in the expression of IEGs may alter the late response gene expression and affect the succeeding events.

Temporal changes in gene expression following cryogenic rat brain injury

Expression of 18 genes was examined at 8 different time points between 1 h and 28 days following cryogenic rat brain injury. The genes include thymidine kinase (TK), p53 tumor suppressor, c-fos, renin, myelin basic protein (MBP), proteolipid protein (PLP), transferrin, transferrin receptor, platelet-derived growth factor A (PDGF A), platelet-derived growth factor B (PDGF B), platelet-derived growth factor receptor alpha (PDGF alpha receptor), platelet-derived growth factor receptor beta (PDGF beta receptor), glial fibrillary acidic protein (GFAP), transforming growth factor-beta 1 (TGF-beta 1), basic fibroblast growth factor (bFGF), fibroblast growth factor receptor-1 (FGF-R1), insulin-like growth factor-1 (IGF-1), and somatostatin. Time courses of gene expression were determined for RNAs derived from hippocampus and cortex. Genes were divided into categories based upon those in which statistically significant changes in expression were first observed at or before 24 h (early genes) and those in which changes were first observed at or after 72 h (late genes). In the present model, many genes demonstrate elevated RNA levels in the cortex prior to hippocampus, following injury. RNAs transcribed from late genes tend to be elevated concurrently in cortex and hippocampus.

Expression of growth inhibitory factor mRNA after focal ischemia in rat brain

Growth inhibitory factor (GIF) is a small protein belonging to the metallothionein family that has the capacity to inhibit neuronal survival and neurite formation in vitro. This study was conducted to investigate the role of GIF in the brain afflicted with ischemic injury. We used the in situ hybridization technique and Northern blot analysis to study the changes in GIF messenger RNA (mRNA) expression in a rat focal ischemia model. On the first day, the expression tended to decrease in the hemisphere ipsilateral to the injury. It returned to normal levels on the second day except for the central area of the middle cerebral artery (MCA) territory. On the third and fourth day, the expression increased diffusely in the hemisphere of the affected side, including the subcortical area. Two weeks after ischemia, the GIF mRNA expression increased again but only in the peri-infarcted area. Down-regulation of GIF on the first day in the cortex ipsilateral to the infarction might promote neurite sprouting. The subsequent increase in GIF mRNA expression on the third and fourth day might be a symptom of neurons attempting to inhibit excessive neurite outgrowth, or to protect themselves against toxicity caused by oxygen radicals. The later increase in the limited area around the infarction may be related to astroglial reaction. Growth inhibitory factor may play an important role in regulating the central nervous system after ischemic insults.

The role of inducible transcription factors in apoptotic nerve cell death

Recent studies have shown that certain types of nerve cell death in the brain occur by an apoptotic mechanism. Researchers have demonstrated that moderate hypoxic-ischemic (HI) episodes and status epilepticus (SE) can cause DNA fragmentation as well as other morphological features of apoptosis in neurons destined to die, whereas more severe HI episodes lead to neuronal necrosis and infarction. Although somewhat controversial, some studies have demonstrated that protein synthesis inhibition prevents HI-and SE-induced nerve cell death in the brain, suggesting that apoptotic nerve cell death in the adult brain is de novo protein synthesis-dependent (i.e., programmed). The identity of the proteins involved in HI-and SE-induced apoptosis in the adult brain is unclear, although based upon studies in cell culture, a number of potential cell death and anti-apoptosis genes have been identified. In addition, a number of studies have demonstrated that inducible transcription factors (ITFs) are expressed for prolonged periods in neurons undergoing apoptotic death following HI and SE. These results suggest that prolonged expression of ITFs (in particular c-jun) may form part of the biological cascade that induces apoptosis in adult neurons. These various studies are critically discussed and in particular the role of inducible transcription factors in neuronal apoptosis is evaluated.

Expression of growth inhibitory factor mRNA following cortical injury in rat

Growth inhibitory factor (GIF) inhibits survival and neurite formation of cortical neurons in vitro and is found abundantly in the normal human brain. The role of GIF is still obscure, although it is reported to decrease in the brain in Alzheimer's disease. We examined changes in GIF mRNA expression in a rat cortical-ablation model with the aid of an in situ hybridization technique. In sham-operated animals, the GIF mRNA was expressed consistently in the cerebral cortex, hippocampus, and thalamus. One day after cortical ablation of the left somatosensory cortex, the expression tended to decrease in the cortex ipsilateral to the injury. Four days after surgery, it increased markedly in the affected cortex and thereafter returned to the level of the control animals except for the area surrounding the injury, where GIF mRNA again increased 2 to 3 weeks after ablation. The transient increase in GIF mRNA expression may reflect efforts to inhibit excessive sprouting of neurites. We also studied the effect of topically applied basic fibroblast growth factor (bFGF), which has a range of neurotrophic effects, on GIF mRNA expression. Topically applied bFGF enhanced the suppression of GIF at 1 day after surgery, though it did not affect the subsequent response. GIF can therefore be assumed to affect the outgrowth of injured neurites and might play a major role in maintenance of the neuronal network in cooperation with other trophic factors. Modification of these factors may be the key to improve neuronal damage after injury.