Hyperglycemia suppresses c-fos mRNA expression following transient cerebral ischemia in gerbils.

The c-fos proto-oncogene is activated by transient cerebral ischemia. This activation may signify a specific genetic response to ischemia affecting tolerance to ischemia and ultimate cell survival. Hyperglycemia, which enhances brain injury from transient ischemia, was studied for its effects on this gene system in gerbils by measuring c-fos mRNA 2 h after 20 min of bilateral carotid artery occlusion. Brain c-fos mRNA was increased by ischemia (11.7 +/- 5.0, p less than or equal to 0.05, fold increase) compared to nonischemic controls (1.0 +/- 1.3). Pretreatment with 1 g/kg of glucose partially reduced postischemic c-fos mRNA (6.3 +/- 1.6, p less than or equal to 0.05) while 4 g/kg of glucose completely suppressed postischemic c-fos expression (0.7 +/- 0.3, p less than or equal to 0.05). These data indicate that hyperglycemia suppresses normal postischemic gene expression and suggest the possibility that such suppression is a predictor or even a contributor to hyperglycemia-enhanced ischemic brain damage.     

Cocaine modulates mu-opioid receptor mRNA but not c-fos mRNA levels in primary cortical astrocytes

Cocaine is known to modulate the opioid system in several brain regions, including the cortex. Glial cells that are derived from the neonatal cortex have been shown to express opioid peptides and opioid receptors. In this study we investigated the effects of cocaine on c-fos and mu-opioid receptor mRNA levels in primary cortical astrocyte cultures, using RT-PCR and quantitative solution hybridization assays. Astrocyte cultures from 1-day-old Fischer rats were untreated or treated with cocaine for 30min, 2h, or 5h. While c-fos mRNA levels did not change at any time, mu-opioid receptor mRNA levels decreased by 75% after 2 and 5h of cocaine treatments. Our data suggest that cocaine differentially modulates c-fos and opioid signaling in astrocyte cell culture.     

Acute glucocorticoid pretreatment suppresses stress-induced hypothalamic-pituitary-adrenal axis hormone secretion and expression of corticotropin-releasing hormone hnRNA but does not affect c-fos mRNA or fos protein expression in the paraventricular nucleus of the hypothalamus

Corticosterone regulates both basal and stress-induced hypothalamic-pituitary-adrenal (HPA) axis activity in a negative-feedback fashion. However, the cellular and molecular mechanisms of this negative feedback have yet to be explicitly characterized. By comparing stress-induced c-fos and corticotropin-releasing hormone (CRH) expression in the paraventricular nucleus (PVN), we may be able to determine whether acute glucocorticoid treatment affects the net neural excitatory input to the PVN (represented primarily by c-fos mRNA expression) or directly affects the ability of cells in the PVN to respond to that input (represented primarily by CRH hnRNA expression). In the following studies, we observed the effect of acute glucocorticoid (RU28362) treatment on subsequent HPA axis reactivity by measuring stress-induced plasma hormone concentration [corticosterone and adrenocorticotropic hormone (ACTH)] and gene expression (c-fos and CRH) in the PVN. First, we examined the dose-response relationship between systemically administered RU28362 (1-150 microg/kg, i.p) and suppression of the stress-induced corticosterone response. We then confirmed central nervous system access of the maximally suppressive dose of RU28362 (150 microg/kg) by an ex vivo radioligand binding assay. RU28362 selectively occupied the majority of glucocorticoid receptors in the hippocampus and hypothalamus while having no effect on mineralocorticoid receptors. In separate studies, RU28362 (150 microg/kg) and corticosterone (5 mg/kg) were injected i.p. 1 h before restraint stress. Compared to vehicle-treated controls, rats treated with RU28362 and corticosterone had substantially blunted stress-induced corticosterone and ACTH production, respectively. Furthermore, treatment with RU28362 significantly blunted stress-induced CRH hnRNA expression in the PVN. By contrast, neither RU28362 nor corticosterone treatment had an effect on stress-induced neuronal activation as measured by c-fos mRNA and its protein product in the PVN. This dissociation between c-fos and CRH gene expression suggests that glucocorticoid suppression of HPA activity within this time-frame is not a result of decreased excitatory neural input to the PVN, but instead depends on some direct effect of RU28362 on cells intrinsic to the HPA axis.     

Activation of adenosine receptors induces c-fos, but not c-jun, expression in neuron-glia hybrids and fibroblasts

Extracellular adenosine acts through specific cell surface receptors to modulate numerous physiological processes in both the CNS and peripheral tissues (e.g. neurotransmitter release and blood flow). Activation of A1 or A2 adenosine receptors leads to decreased or increased intracellular cAMP levels, respectively. Fos and Jun are nuclear proto-oncogene products, which, like cAMP, appear to act as intermediates in a number of signal transduction pathways. Since increases in both adenosine release and Fos and Jun expression occur in the brain following seizures, we wanted to determine whether Fos and Jun induction might occur as a result of adenosine receptor activation. 3T3 fibroblasts and NG108-15 neuroblastoma-glioma hybrid cells were chosen for study, since they were known to respond to adenosine agonists with changes in cAMP levels. The membranes of NG108-15 cells were shown to have A2-like binding activity in a competitive binding assay. Cultures of each cell line were treated with the adenosine agonists, CHA (A1-selective) and NECA (non-selective adenosine agonist). Both lines responded with a concentration-dependent transient increase in c-fos, but not c-jun, mRNA content after treatment with either agonist. The kinetics of the response were much more rapid for 3T3 cells (peak between 15 and 30 min) than for NG cells (peak between 60 and 90 min). The slower, more prolonged response in the NG108-15 cells is more similar to the time interval between adenosine release and the peak of c-fos mRNA induction in brains of animals following the administration of seizure-promoting drugs.(ABSTRACT TRUNCATED AT 250 WORDS)     

c-fos proto-oncogene expression in astrocytes associated with differentiation or proliferation but not depolarization

Expression of the c-fos proto-oncogene in rat neocortical astrocytes in culture was examined using Northern blotting and immunocytochemistry. Marked induction of c-fos mRNA in astrocytes was observed after treatment with epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), dibutyryl cyclic AMP (db-cAMP), and phorbol diester (TPA; 12-O-tetra-decanoylphorbol 13-acetate), which are known to induce the proliferation or differentiation of astrocytes. Increase of c-fos protein immunoreactivity (IR) was obtained after treatment with fetal calf serum, EGF, bFGF, db-cAMP and TPA. High concentrations of calcium ionophore A23187, which were lethal to cultured astrocytes, also increased c-fos protein-IR. Treatment with lower concentrations of calcium ionophore (which slightly increase Ca2+ uptake), high K+ and nerve growth factor had no detectable effect on c-fos expression. These results show that depolarization does not induce c-fos in astrocytes and suggest that c-fos may play a role in differentiation and proliferation of astrocytes.     

Valproic acid induces microglial dysfunction,not apoptosis,in human glial cultures

Valproic acid (VPA) is widely used for the treatment of mood disorders and epilepsy, but its mechanism of action is unclear. In vivo and in vitro studies using rodent models have demonstrated that VPA has both neuroprotective and neurotrophic effects. These beneficial effects are, in part, through modulation of glial cell function. Recently, we and others have shown that VPA selectively induces caspase-3 mediated apoptosis in rodent microglial cells. However, the effect of VPA on human microglia has not been tested. In this study, using microglia derived from adult human brains, we demonstrate that VPA does not induce microglial apoptosis as determined by the absence of caspase-3 cleavage. However, VPA does partially decrease the expression of the microglial markers PU.1 and CD45, as well as dramatically reducing microglial phagocytosis. Due to the many roles of microglia in the brain, these VPA-induced alterations in microglial phenotype could potentially have major effects on physiological and pathological actions of these cells.     

大鼠疼痛模型中类固醇对c-fos mRNA和c-fos蛋白表达的调节

目的:探讨偏头痛三叉神经血管机制中,三叉神经疼痛刺激诱导c-fos mRNA、c-fos蛋白表达和类固醇激素之间的关系。方法:选择了与偏头痛发病机制相关的电刺激大鼠三叉神经根的疼痛模型。电刺激组:用电脉冲持续刺激三叉神经根10分钟(n=15)。然后分别在30(n=5),60(n=5),120(n=5)分钟后断头处死动物。类固醇治疗组:电刺激同时在颈动脉鞘旁注射强地松龙混悬液1.25mg/kg(n=5),对照组:仅做麻醉处理(n=4)。结果:中缝核和三叉神经脊束核神经元c-fos mRNA、c-fos的表达数量随时间的延长逐渐增加(P<0.01)。注射强地松龙混悬液120分钟后两者的表达细胞数量增多,(P<0.05)。结论:类固醇可以正向调节c-fos mRNA、和 c-fos表达。其原因可能由于激活了不同的c-fos mRNA、和c-fos表达通道所致,包括疼痛刺激反应和疼痛调节通道。这种作用可能是类固醇激素在临床上治疗偏头痛长期疗效的基础。     

High-frequency discharge of dentate granule cells, but not long-term potentiation, induces c-fos protein

Competence genes, such as c-fos, may play key roles in information storage in the nervous system by linking relatively brief extracellular signals to long-term changes in the neuron. In support of this idea we, and others, have shown that the c-fos protein occurs in adult mammalian neurons and that higher levels of the protein are induced in certain brain regions after kindled or metrazol-induced seizures in mice and rats, sensory stimulation and mechanical damage in spinal cord neurons, and after depolarization in PC12 cells. Here we report that a massive induction of c-fos protein is observed in dentate granule cells in four conditions that result in repetitive firing: localized seizure discharges; high frequency antidromic activation; orthodromic activation in the presence of iontophoresed bicuculline; and frequency potentiation. However, stimulation of the perforant path with high frequency trains that produced long-term potentiation at the perforant path-granule cell synapse did not reliably induce c-fos in the dentate gyrus. These findings suggest that c-fos induction can follow repetitive neuronal discharge but is not involved in long-term potentiation.     

Suppression of c-fos induction in the nucleus accumbens prevents acquisition but not expression of morphine-conditioned place preference

The c-fos immediate-early gene is induced by morphine and other drugs of abuse in the nucleus accumbens (NAc), a mesolimbic region implicated in drug abuse and reward. This study examined the role of c-fos in the acquisition and expression of the conditioned place paradigm (CPP) in the rat by suppressing Fos protein expression with c-fos antisense oligodeoxynucleotides (ODNs). CPP was completely prevented by c-fos antisense ODN infused bilaterally into the NAc prior to each systemic morphine injection, whereas sense and missense NAc injections had no effect on CPP. NAc administration of c-fos antisense ODN after the last systemic morphine conditioning session did not affect the expression of morphine-CPP. These results suggest that c-fos expression in NAc is necessary for the acquisition but not expression of morphine-CPP, and they have important implications for understanding conditioned behaviours and drug craving and addiction.     

Adenosinergic modulation of caffeine-induced c-fos mRNA expression in mouse brain

The adenosine receptor antagonist, caffeine, transiently induced proto-oncogene c-fos mRNA in mouse brain in a dose-dependent fashion. In situ hybridization revealed that caffeine-induced c-fos expression was high in caudate-putamen and olfactory tubercle at both subconvulsive and convulsive doses. The pattern of c-fos mRNA distribution following caffeine administration differs from that reported after seizures induced by electroconvulsive shock (ECS) or other chemical convulsants, and closely parallels the distribution of adenosine A₂ receptors. Furthermore, the potent adenosine A₂ receptor agonist,5′-N-ethylcarboxamide adenosine (NECA) blocked caffeine-induced c-fos expression whereas the adenosine A₁ receptor ligand, N⁶-cyclohexyladenosine (CHA), had no effect. This study suggests that the caffeine-induced expression of c-fos mRNA may be mediated by the adenosine A₂ receptor in mouse brain.     

Early postnatal exposure of rats to lamotrigine, but not phenytoin, reduces seizure threshold in adulthood

In view of previous reports of changes in seizure susceptibility in adult rats exposed to phenobarbital or diazepam as pups, we examined the effects of early life exposure to lamotrigine and phenytoin, two commonly used antiepileptic drugs (AEDs), for their effect on seizure threshold in adult rats. We found that pups exposed to lamotrigine for 6 days during the second postnatal week had a significantly lower threshold for pentylenetetrazole-evoked seizures when tested as adults. In contrast, phenytoin exposure during the second postnatal week was without a significant effect on seizure threshold in adults. Seizure scores at threshold were comparable across all groups tested. The dose of lamotrigine used in our study (20 mg/kg) was below that required to cause developmental neuronal apoptosis, whereas the dose of phenytoin used (50 mg/kg) was above that required for developmental neurotoxicity. Therefore, our findings suggest that neurodevelopmental alterations in seizure susceptibility may occur via mechanisms that are independent of those responsible for neural injury or teratogenesis. Our findings support the possibility that therapy with certain AEDs during pregnancy or infancy may alter seizure susceptibility later in life, a possibility that should be taken into account when examining early life factors that contribute to seizure susceptibility in adulthood.     

Alterations in cytokine but not chemokine mRNA expression during three distinct Theiler's virus infections

DA, GDVII and H101 are neurovirulent strains of Theiler's murine encephalomyelitis virus that cause very different neuropathology and CNS disease when inoculated into SJL/J mice. DA virus causes a chronic demyelinating disease, GDVII virus causes an acute fatal polioencephalomyelitis, and H101 virus causes an acute pachymeningitis with hydrocephalus. Performing RNase protection assays, we detected the same pattern of chemokine (RANTES, MCP-1, IP-10, MIP-1beta, MIP-1alpha and MIP-2) mRNA expression in brain and spinal cord during all three infections. In contrast, IFN-beta and IL-6 mRNA were highly expressed only in GDVII virus infection, whereas high levels of LT-alpha mRNA were only found during DA virus infection. Our study demonstrates that proinflammatory cytokines are involved in the neuropathogenesis of CNS disease and modulate the acute and chronic process underlying different pathologic features of disease.     

Peripheral, but not central, axotomy induces neuropilin-1 mRNA expression in adult large diameter primary sensory neurons

Neuropilin-1 (NP-1) is a component of the receptor for semaphorin3a (Sema3a), a member of a large family of molecules with widespread expression and demonstrable influence (via their ability to repel growing axons) on nervous system development. Recent studies have shown that some types of adult mammalian neurons retain the capacity to respond to Sema3a, particularly in relation to neuronal injury and regeneration. Although variations in expression of Sema3a mRNA have been revealed in neurons in both the central and peripheral nervous systems in this context, relatively little is known about NP-1 expression patterns. In this study we investigated the expression of NP-1 mRNA in adult dorsal root ganglion (DRG) neurons in intact and lesioned animals. We compared the effect of unilateral lesioning of the sciatic nerve or unilateral dorsal rhizotomy at lumbar levels L4/5, and bilateral dorsal funiculus lesioning at thoracic levels T10/11 on NP-1 mRNA expression in the cell bodies of lumbar DRGs. A significantly increased level of NP-1 mRNA expression was detected only following sciatic nerve lesioning (P < 0.001), but not after rhizotomy or dorsal funiculus lesioning. Furthermore, this upregulation was mainly confined to large diameter neurons of DRGs at lumbar levels L4/5, which provide the main sensory contribution to the sciatic nerve. These results suggest a role for NP-1 in the axonal response to peripheral nerve injury, which may be specific to a particular subset of primary sensory neurons.     

Valproic acid, curly hair and weight gain

Gain of weight may be observed in up to 20% of patients treated with valproic acid, while changes in hair texture may be found in up to 9%. The author describes the case of a female patient aged 19 years who gained 13 kg and had her hair changed from light, fine blonde to thicker, darker and curly while on valproate acid 1000 mg daily, with a serum level of 138.9 micrograms/ml. After reduction to 500 mg daily, with a serum level of 80.5 micrograms/ml she lost 7 kg but the hair remained unchanged. The patient chose to continue the drug due to complete control of absence, myoclonic and tonic-clonic seizures, which had not been obtained with any other drug before.