Basal expression of Fos, Fos-related, Jun, and Krox 24 proteins in rat hippocampus.

The basal expression of the protein products of the inducible immediate early genes (IEGs), Fos, Jun, and Krox 24, was investigated in rat hippocampus using immunocytochemical visualization methods with antisera specific for Fos only, Fos and the Fos-related antigens (FRAs), the Jun family, and Krox 24 (previously described as TIS 8, egr-1, NGF-IA or zif 268). In the normal adult rat brain basal levels of Jun, Krox 24 and Fos-related antigens but not Fos were seen within the hippocampus. More specifically very high basal levels of Jun were seen in the dentate granule cells with high basal Krox 24 levels seen in the CA1-subiculum region of the rat hippocampus. Basal FRAs but not Fos-positive cells were seen at low levels in the dentate granule cells. The implications of these results to the functioning of IEG proteins in hippocampal neurons is discussed.     

Induction of immediate-early gene proteins in dentate granule cells and somatostatin interneurons after hippocampal seizures.

The expression of the protein products of the immediate-early genes c-fos, Fos B, Fos-related proteins (FRAs), c-jun, jun B, jun D and krox-24 was investigated in the rat hippocampus at various times after electrically-induced hippocampal seizures. Hippocampal seizures induced all the immediate-early gene proteins in dentate granule cells with differing time-courses. In addition, Krox-24, Fos and Jun D were also induced in somatostatin-containing interneurons throughout the hippocampus and also in a small percentage of parvalbumin-containing interneurons. Thus, hippocampal seizures induce waves of immediate-early gene protein expression in dentate granule cells and a selective expression of krox-24, Fos and Jun D in hippocampal somatostatin interneurons. These results suggest that biochemical and/or morphological changes occurring in dentate granule cells and somatostatin interneurons after seizures may be regulated by immediate-early gene expression, and that these immediate-early gene proteins may be involved in seizure development in the nervous system.     

Fos蛋白和Jun蛋白在犬颅脑枪弹伤局部脑组织的表达

目的　研究犬颅脑枪弹伤后脑神经元早期快反应基因c fos和c jun表达产物Fos蛋白和Jun蛋白的变化规律。方法　 2 0只杂种犬 ,随机分为正常对照组、损伤组。以德国小口径步枪子弹致犬颅脑贯通伤 (PCI)模型为对象 ,采用免疫组化法检测脑组织伤后 30min、2h、6h弹道挫伤区、震荡区及脑干神经元中Fos和Jun蛋白的表达。结果　对照组脑皮质神经元中Fos和Jun蛋白弱表达 ,弹道挫伤区、震荡区及脑干神经元中Fos和Jun蛋白表达于伤后 30min开始增加 ,2h达到高峰 ,6h逐渐下降。且Fos和Jun蛋白表达在弹道震荡区较挫伤区更为明显 (P <0 .0 5 )。结论　Fos蛋白和Jun蛋白在弹道挫伤区、震荡区及脑干神经元均有表达 ,c jun在脑组织内表达的分布范围及变化趋势与c fos基本一致 ,其表达是对损伤刺激的早期反应 ,可能是由Leao播散性抑制引起 ,并与细胞内外信号转导和细胞凋亡有关。     

Selective expression of Jun proteins following axotomy and axonal transport block in peripheral nerves in the rat: evidence for a role in the regeneration process

Expression of the protein products of the immediate-early genes (IEGs), members of the fos, jun and krox families (Jun, Fos, and Krox, resp.) was investigated in the spinal cord and sensory ganglia (DRG) of normal rats; and following transection of, block of axonal transport in, or electrical stimulation of their peripheral axons. The nuclei of many moto- and DRG neurons showed a faint basal immunoreactivity (IR) for Jun proteins, but not for Fos or Krox proteins. There was a strong and selective induction of Jun-IR in moto- and DRG neurons after peripheral nerve transection or crush, or colchicine- or vinblastine-induced block of axonal transport. The Jun-IR induced by nerve transection disappeared after nerve regeneration. In contrast, Jun, Fos and Krox proteins were all induced transynaptically in spinal dorsal horn neurons following electrical stimulation of the C-fibers in the afferent nerves. Thus in differentiated neurons in vivo these IEG proteins can be expressed either independently or concomitantly depending on the type of stimulus.     

Suppression of post-ischemic-induced Fos protein expression by an antisense oligonucleotide to c-fos mRNA leads to increased tissue damage

Activation of c-fos, an immediate early gene, and the subsequent upregulation of Fos protein expression occur following neural injury, including focal cerebral ischemia (fci). Fos and Jun form a heterodimer known as activator protein 1, which regulates the expression of many late effector genes. To study the downstream effects of c-fos expression following ischemia, we suppressed the translation of c-fos by administering an antisense oligonucleotide (AO) to c-fos mRNA. Eighteen hours prior to fci, male, Long Evans (LE) rats received intraventricular injections of AO, mismatched AO (MS) or artificial cerebrospinal fluid (aCSF). Fci was induced by permanent right middle cerebral artery occlusion. At 24-h post-occlusion, neurological function was assessed, and the animals were sacrificed. The brains were removed and stained with triphenyltetrazolium chloride for infarct volume determination. Fos immunohistochemistry was performed in separate animals to determine the effects of treatment on Fos expression number of Fos positive cells. AO administration reduced the number of cells with fci-induced Fos expression by 75%. No differences in neurological scores existed between any of the groups. AO-treated LE developed larger infarcts (40.1±1.0%, mean±S.D., p<0.001) than MS- or aCSF-treated controls (34.3±1.0%, 34.6±1.0%, respectively). These results suggest that c-fos activation and subsequent Fos protein expression exerts a neuroprotective effect, which is likely via upregulation of neurotrophins, following focal cerebral ischemia. This response, among others, may contribute to brain adaptation to injury that underlies functional recovery after stroke.     

Suppression of post-ischemic-induced fos protein expression by an antisense oligonucleotide to c-fos mRNA leads to increased tissue damage.

Activation of c-fos, an immediate early gene, and the subsequent upregulation of Fos protein expression occur following neural injury, including focal cerebral ischemia (fci). Fos and Jun form a heterodimer known as activator protein 1, which regulates the expression of many late effector genes. To study the downstream effects of c-fos expression following ischemia, we suppressed the translation of c-fos by administering an antisense oligonucleotide (AO) to c-fos mRNA. Eighteen hours prior to fci, male, Long Evans (LE) rats received intraventricular injections of AO, mismatched AO (MS) or artificial cerebrospinal fluid (aCSF). Fci was induced by permanent right middle cerebral artery occlusion. At 24-h post-occlusion, neurological function was assessed, and the animals were sacrificed. The brains were removed and stained with triphenyltetrazolium chloride for infarct volume determination. Fos immunohistochemistry was performed in separate animals to determine the effects of treatment on Fos expression number of Fos positive cells. AO administration reduced the number of cells with fci-induced Fos expression by approximately 75%. No differences in neurological scores existed between any of the groups. AO-treated LE developed larger infarcts (40.1+/-1.0%, mean+/-S.D., p<0.001) than MS- or aCSF-treated controls (34.3+/-1.0%, 34.6+/-1.0%, respectively). These results suggest that c-fos activation and subsequent Fos protein expression exerts a neuroprotective effect, which is likely via upregulation of neurotrophins, following focal cerebral ischemia. This response, among others, may contribute to brain adaptation to injury that underlies functional recovery after stroke.     

Presence and induction of Fos B-like immunoreactivity in neural, but not non-neural, cells in adult rat brain

The presence and induction of Fos B, a novel growth factor-activated gene, was investigated in adult rat brain using an antiserum to Fos B and immunocytochemical methods. In normal rat brain immunoreactivity was detected in the nuclei of nerve cells scattered in the cerebral cortex, striatum, amygdala, hippocampus and dentate gyrus. This immunostaining was not present in adjacent brain sections incubated with anti-Fos B serum preadsorbed with the Fos B peptide. Furthermore, Fos B-like immunoreactivity was induced in neurons by two treatments (focal brain injury and haloperidol injection) that are known to induce Fos, however, whereas Fos levels returned to baseline 24 h after these treatments, Fos B-like immunoreactivity remained elevated at this time point. Also, although focal brain injury and rolipram injections induced Fos in ependymal and glial-like cells in rat brain, Fos B-like immunoreactivity was not detected in these non-neural cells. The implications of these results for the presence of Fos B in adult neurons is discussed.     

Is Fos protein expressed by dying striatal neurons after immature hypoxic-ischemic brain injury?

The transient induction of mRNA for the immediate-early gene c-fos has been reported following hypoxic-ischemic brain injury in the immature brain. However, no studies have examined the temporal expression of Fos protein, which is the functionally relevant product of c-fos gene expression. Increased expression of Fos protein has been linked to cell death. We therefore examined whether Fos protein is expressed by dying neurons after immature hypoxic-ischemic brain injury. A well characterized immature rat model of hypoxic-ischemic injury at postnatal day (PN) 7 was used. Three hypoxic-ischemic and three normoxic control pups were studied per time point (i.e., 0, 2, 12, 24, 48, and 72 h posttreatment). Expression of Fos within striatal and other neurons was detected immunocytochemically. Fos protein was expressed within dying striatal neurons at 0-12 h after hypoxia-ischemia. However, detection was only seen in 2 of 17 hypoxic-ischemic pups. These 2 pups had >/=80% of their striatal neurons dying within their right, hypoxic-ischemic-exposed hemisphere. Fos protein expression after severe injury may, therefore, be a response to extraordinary or extreme stress. The absence of Fos protein expression in the majority of hypoxic-ischemic pups, which all exhibited striatal neuronal death, suggests that Fos expression is not necessary for cell death to occur. Therapies directed against Fos protein expression may therefore have limited usefulness in immature hypoxic-ischemic brain injury.     

Differential time course and spatial expression of Fos,Jun, and Krox-24 proteins in spinal cord of rats undergoing subacute or chronic somatic inflammation

We have used the evoked expression of both immediate early gene (IEG)-encoded proteins (Krox-24, c-Fos, Fos B, Jun D, Jun B, c-Jun), and dynorphin to monitor sensory processing in the spinal cords of rats undergoing subacute or chronic somatic inflammation (i.e., subcutaneous inflammation of the plantar foot and monoarthritis, respectively). Behavioral and immunocytochemical approaches were conducted in parallel up to 15 weeks postinjection in order to detect possible relationships between clinical evolution and spatiotemporal pattern of IEG-encoded protein expression. Each disease had specific characteristics both in terms of their clinical evolution and pattern of evoked protein expression. All IEG proteins were expressed in both cases. Most of the staining was observed in both the superficial layers of the dorsal horn and deep dorsal horn (laminae V–VII and X). Monoarthritis was distinguished by a high level of total protein expression. Staining was especially dense in the deep dorsal horn. More labelled cells were observed at 1–2 days and at 2 weeks postinjection, corresponding to the initiation and progressive phases of the disease, respectively. Subcutaneous inflammation was characterized by a moderate level of total IEG expression. More labelled cells were observed in the first day following injection. It is the relative degree of expression of each IEG-encoded protein with regard to the others that characterized the progression of the diseases. Early stages of the diseases coincided with the expression of all Fos and Jun proteins, while late stages showed an increase in Jun D and Fos B involvement; Krox-24 was induced mostly during the early phases and/or periods of paroxysm of the diseases. Persistent stimulation was characterized by a predominant expression in deep versus superficial layers of the dorsal horn. Evoked expression of c-Jun in motoneurons was only observed in monoarthritis. The peak of dynorphin expression was late in regard to both the induction of inflammation and period of maximal IEG-encoded protein expression. The present work indicates that the neural processing that takes place during progression of these diseases can be monitored well at the spinal cord level by using the expression of an array of IEG-encoded proteins. Study of long term evolutive diseases and especially those that evolve into chronicity can largely benefit from such an approach. © 1993 Wiley-Liss, Inc.     

TGF-α overexpression induces astrocytic hypertrophy after cortical stab wound injury

Abstract

To determine the exact role of TGF-α in glial activation after traumatic brain injury, we investigated the astroglial and microglial responses after cortical stab wound injury in TGF-α overexpressing mice. Adult male B6D2-TgN (MMTVTGFA) 29RjC transgenic mice were used for the subjects. This transgenic line carries a TGF-α cDNA under the control of the dexamethasone-inducible MMTV promoter. Thus, exogenous administration of dexamethasone induces TGF-α overexpression. Male B6D2F1/J mice at the same age served as wild-type animals. After the cortical stab wound injury, expression of glial fibrilary acidic protein, CD-11b and interleukine-6 were investigated immunohistochemically. The results indicate that TGF-α might affect astrocytic hypertrophy without affecting microgliosis not only in the normal condition, but also in the pathological condition. Moreover, overexpression of TGF-α induced obvious expression of IL-6 around the lesion. This fact might indicate possible role of TGF-α in affecting neuronal function.     

Immediate Early Gene Expression in the Rat Forebrain Following Striatal Infusion of Quinolinic Acid

Expression in the rat forebrain of immediate early genes belonging to the fos and jun families was investigated at various time points following an intrastriatal infusion of quinolinic acid. Fos immunoreactivity was rapidly and transiently induced, exhibiting maximal intensity 2 h post-lesion, and was principally located in neuronal nuclei situated around the periphery of the lesioned striatum, in regions that subsequently show little, if any, neurodegeneration. Fos immunoreactivity was additionally expressed throughout the ipsilateral cortex. In contrast, Jun immunoreactivity, which remained undetectable for 12 h after the lesion, reached its maximal intensity 24 h post-lesion, at which time it was most densely distributed in neuronal nuclei found within the central lesioned areas of the striatum. In situ hybridization analysis using radiolabeled oligonucleotide probes confirmed this spatial and temporal separation between c-fos and c-jun expression within the striatum and extended it further, showing that, whilst jun mRNA displayed very similar expression characteristics to those of c-fos mRNA, both fos B mRNA and jun D mRNA exhibited induction patterns closely resembling those of c-jun mRNA. These results clearly suggest that two distinct programmes of immediate early gene expression can be induced in vivo. The rapid (2 h) and transient induction of c-fos/jun B may well be a response to NMDA receptor activation, whereas the molecular signal for the late (24 h) and sustained induction of c-jun/ fos B/jun D is currently a focus for our investigations.     

TGF-alpha overexpression induces astrocytic hypertrophy after cortical stab wound injury

To determine the exact role of TGF-alpha in glial activation after traumatic brain injury, we investigated the astroglial and microglial responses after cortical stab wound injury in TGF-alpha overexpressing mice. Adult male B6D2-TgN (MMTVTGFA) 29RjC transgenic mice were used for the subjects. This transgenic line carries a TGF-alpha cDNA under the control of the dexamethasone-inducible MMTV promoter. Thus, exogenous administration of dexamethasone induces TGF-alpha overexpression. Male B6D2F1/J mice at the same age served as wild-type animals. After the cortical stab wound injury, expression of glial fibrillary acidic protein, CD-11b and interleukine-6 were investigated immunohistochemically. The results indicate that TGF-alpha might affect astrocytic hypertrophy without affecting microgliosis not only in the normal condition, but also in the pathological condition. Moreover, overexpression of TGF-alpha induced obvious expression of IL-6 around the lesion. This fact might indicate possible role of TGF-alpha in affecting neuronal function.     

The NMDA receptor mediates cortical induction of fos and fos-related antigens following cortical injury

Cortical cavity lesions and lateral ventricular injections of quinolinic acid, a NMDA receptor agonist, induce Fos and Fos-related antigens (FRAs) throughout ipsilateral adult rat brain cortex in similar patterns. c-fos mRNA, assessed using in situ hybridization, was induced by 1 h and disappeared between 3 and 8 h following cortical lesions. Fos proteins, detected using a specific monoclonal antibody, were induced by 1 h and disappeared by 4 h after cortical lesions. FRA proteins, detected using polyclonal antibodies, were induced between 1 and 4 h and persisted for at least 72 h following focal cortical injury. Intraventricular injections of CPP, a competitive NMDA receptor antagonist, completely blocked the induction of these nuclear proteins in cortex ipsilateral to the focal cortical lesions—except around the injury site itself. Intraventricular injections of quisqualate, a non-NMDA glutamate analogue, induced Fos in hippocampus but not in cortex. These data show that NMDA receptors mediate the induction of Fos and FRAs following cortical injury. It is proposed that local cortical injury releases excitatory amino acids that act at NMDA receptors to initiate spreading depression and that the resultant depolarization induces Fos in neurons throughout the cortex. Since Fos and FRAs are proteins that regulate the expression of target genes, they could mediate long-term biochemical adaptations in neurons following cortical injury.