Increased C-fos Gene Expression Research Articles

The role of C1473G polymorphism in triptophanhydroxylase-2 gene in the acute ethanol effects on <i>c-fos</i> gene expression and metabolism of biogenic amines in brain of mice

Tryptophan hydroxylase-2 is a key enzyme in the synthesis of the neurotransmitter serotonin, which plays an important role in the mechanisms of regulation of a wide range of physiological functions and behaviors. In this work, we studied the effect of acute ethanol administration on the expression of the c-fos early response gene and the metabolism of serotonin and catecholamines in the brain structures of B6-1473C and B6-1473G congenic mice, which differ in the C1473G single-nucleotide substitution in the Tph2 gene and enzyme activity. Acute alcoholization led to a significant increase in c-fos gene expression in the frontal cortex and striatum of B6-1473G mice and the hippocampus of B6-1473C mice. The introduction of ethanol caused a decrease in the index of serotonin metabolism in the nucleus accumbens in B6-1473C mice, as well as in the hippocampus and striatum of B6-1473G mice. Also, ethanol led to a decrease in the level of norepinephrine in the hypothalamus in B6-1473C mice. Thus, the C1473G polymorphism in the Tph2 gene has a significant effect on changes in the c-fos gene expression pattern and metabolism of biogenic amines in the brain induced by acute ethanol administration.

LGG-17. Preventing recurrence: targeting molecular mechanisms driving tumor growth rebound after MAPKi withdrawal in pediatric low-grade glioma

Pediatric low-grade gliomas, a diverse group of WHO grade 1 and 2 glial or glioneural tumors, comprise the most common category of primary brain tumors in children. The majority of these tumors are driven by alterations in the MAPK pathway, making them in principle susceptible to MAPKi therapy. While patients often benefit from MAPKi during treatment, tumor rebound may occur once treatment is stopped, constituting a significant clinical challenge. BT-40, patient-derived cells with molecular features of pleomorphic xanthoastrocytoma (BRAFV600E, CDKN2Adel), were used to model the rebound growth in vitro, based on viable cell counts in response to treatment and withdrawal of the clinically relevant BRAFV600E specific inhibitor dabrafenib. Standard-of-care chemotherapy (vincristine and carboplatin) was used as a reference. MAPK pathway reactivation upon withdrawal was assessed by WB and qPCR analysis. Based on the observed cell-regrowth and MAPK-reactivation pattern, key-timepoints during withdrawal were identified, which are currently being further analyzed through RNAseq and phospho-/proteomics. BT-40 cells started to proliferate again two days after dabrafenib withdrawal, and earliest five days after chemotherapy withdrawal. MAPK pathway activity, based on Mek and Erk phosphorylation, reached baseline levels three hours after dabrafenib withdrawal, this was associated with 2.5-fold increased c-Fos gene expression two hours after withdrawal. The earlier cell regrowth after dabrafenib withdrawal compared to chemotherapy withdrawal matches clinical observations, making the model suitable to study the rebound. The observed MAPK overactivation suggests the growth rebound might not only be caused by a fast reactivation of the pathway but also by other mechanisms, e.g. accumulation of upstream activators due to loss of negative feedback or parallel pathways. To investigate this, key-timepoints during treatment withdrawal will be analyzed using a multi-omics approach. Based on these findings, possible rebound-driving mechanisms will be identified and further validated using BT-40 and additional PXA models in vitro and in vivo.

Neonatal Lipopolysaccharide Challenge Induces Long-lasting Spatial Cognitive Impairment and Dysregulation of Hippocampal Histone Acetylation in Mice

Neonatal inflammation induces long-term effects on brain function. We investigated the effects of systematic neonatal inflammation using lipopolysaccharide (LPS) injection at postnatal day 3 (P3) and P5 in a mouse model of spatial memory capacity measured using a Morris water maze (MWM) task in adulthood. Subsequently, we assessed histone acetylation and immediate-early response gene expression (c-Fos and brain-derived neurotrophic factor) in the hippocampus in response to MWM acquisition training. The LPS-treated mice exhibited a significant spatial cognitive impairment, which was accompanied by insufficient histone acetylation of the H4K12-specific lysine residue and repressed c-Fos gene expression immediately after acquisition training. Moreover, the enrichment of acetyl-H4K12 on the c-Fos promoter following acquisition training was decreased in LPS-treated mice. Administration of trichostatin A (TSA), a histone deacetylase inhibitor, 2 h before each MWM acquisition training session effectively enhanced hippocampal histone acetylation levels and enrichment of acetyl-H4K12 on the c-Fos promoter following acquisition training in LPS-treated mice. TSA also increased c-Fos gene expression underlying synaptic plasticity and memory formation, and consequently rescued impaired spatial cognitive function. These results indicate that the dysregulation of H4K12 acetylation during the ongoing process of memory formation plays a key role in the spatial cognitive impairment associated with a neonatal LPS challenge. The histone deacetylase inhibitor TSA exhibits therapeutic potential for treating cognitive impairment induced by neonatal inflammation, by means of improving hippocampal histone acetylation and downstream c-Fos gene expression in response to a learning task.

Role of the paraventricular nucleus in the reflex diuresis to pulmonary lymphatic obstruction in rabbits.

The changes in urine flow and renal sympathetic nerve activity (RSNA) due to pulmonary lymphatic obstruction (PLO) were examined in anesthetized, artificially ventilated New Zealand white rabbits. PLO was produced by pressurizing an isolated pouch created in the right external jugular vein at the points of entry of the right lymphatic ducts. During this maneuver, urine flow increased from 8.5 ± 0.3 mL/10 min to 12 ± 0.5 mL/10 min (P < 0.0001) and RSNA increased from 24.0 ± 4 to 40.0 ± 5 μV·s (P < 0.0001). Bilateral lesioning of the paraventricular nucleus (PVN) of the hypothalamus or cervical vagotomy abolished these responses. PLO increased c-fos gene expression in the PVN. The increase in urine flow due to PLO was attenuated by muscimol and abolished by kynurenic acid microinjections into the PVN. The results show that (i) neurons in the PVN are an important relay site in the reflex arc, which is activated by PLO; and (ii) this activation is regulated by glutamatergic and partly by GABAergic input to the PVN.

Molecular neuroimaging of post-injury plasticity.

Nerve injury induces long-term changes in neuronal activity in the primary somatosensory cortex (S1), which has often been implicated as the origin of sensory dysfunction. However, the cellular mechanisms underlying this phenomenon remain unclear. C-fos is an immediate early gene, which has been shown to play an instrumental role in plasticity. By developing a new platform to image real-time changes in gene expression in vivo, we investigated whether injury modulates the levels of c-fos in layer V of S1, since previous studies have suggested that these neurons are particularly susceptible to injury. The yellow fluorescent protein, ZsYellow1, under the regulation of the c-fos promoter, was expressed throughout the rat brain. A fiber-based confocal microscope that enabled deep brain imaging was utilized, and local field potentials were collected simultaneously. In the weeks following limb denervation in adult rats (n=10), sensory stimulation of the intact limb induced significant increases in c-fos gene expression in cells located in S1, both contralateral (affected, 27.6±3 cells) and ipsilateral (8.6±3 cells) to the injury, compared to controls (n=10, 13.4±3 and 1.0±1, respectively, p value<0.05). Thus, we demonstrated that injury activates cellular mechanisms that are involved in reshaping neuronal connections, and this may translate to neurorehabilitative potential.

Effects of Stress on Corticosterone Levels, Expression of the c-fos Gene, and Serotonin Metabolism in the Brains of Mice with a Genetic Predisposition to Catalepsy

Freezing reactions, or catalepsy, constitute a passive defensive reaction to stress. The involvement of brain serotonin (5-HT) in the regulation of catalepsy has been demonstrated. The main gene controlling the predisposition to catalepsy in CBA mice is located on the 59–70 cM fragment of chromosome 13 in mice. This fragment was transferred from CBA mice to the genome of the non-cataleptic AKR strain to create the congenic strain AKR.CBA-D13Mit76 (D13). The aim of the present work was to compare the effects of acute stress (restraint, 1 h) on the plasma corticosterone level, expression of the c-fos gene (a stress neuromarker), and serotonin catabolism in the brain in mice of the catalepsy-resistant strain AKR and its congenic cataleptic strain D13. Corticosterone levels in stress were significantly lower (p < 0.001) in D13 mice than in AKR animals. Acute stress led to similar increases in c-fos gene expression in the hypothalamus and midbrain of mice of both strains. Stress increased (p < 0.05) serotonin metabolism in the midbrain in mice of congenic strain D13, but not in AKR mice. Thus, the fragment of chromosome 13 containing the main catalepsy gene is involved in regulating hormonal responses and serotonin metabolism in acute stress.

Lack of elevations in glucocorticoids correlates with dysphoria-like behavior after repeated social defeat

Activity of the hypothalamic–pituitary–adrenocortical (HPA) axis is often abnormal in depression and could hold clues for better treatment of this debilitating disease. However, it has been difficult to use HPA activity as a depression biomarker because both HPA hyperactivity and HPA hypoactivity have been reported in depression. Melancholic depression has typically been associated with HPA hyperactivity, while atypical depression has been linked with HPA hypoactivity. Many animal models of chronic stress recapitulate behavioral aberrations and elevated HPA activity that could represent a model for melancholic depression. However, there are no animal models that could be used to elucidate the etiology or treatment of atypical depression. We have used repeated social defeat in mice to test the hypothesis that this chronic stress would induce dysphoria-like behavior associated with HPA hypoactivity in a subset of subjects. Intruder mice were placed in the home cage of an aggressive resident mouse for 5min/d for 30days. The majority of intruder mice had elevated basal plasma corticosterone (High Morning Corticosterone, or HMC) and adrenal 11β hydroxylase mRNA levels relative to control mice that were handled daily. However, a subset of intruder mice (Low Morning Corticosterone; LMC) exhibited basal plasma corticosterone and 11β hydroxylase mRNA levels that were indistinguishable from control levels. Significant changes in emotional behavior only occurred in LMC mice, which exhibited anxiety-like increases in activity and defecation during tail suspension and anhedonia-like decreases in sucrose preference. Relative to HMC mice, LMC mice also showed increases in gene expression of mineralocorticoid receptor in CA2 hippocampus, consistent with the possibility that HPA activity in this group is constrained by increased sensitivity to glucocorticoid negative feedback. LMC mice also exhibited increased c-fos gene expression compared to HMC mice in the paraventricular hypothalamus and lateral septum suggesting that central pathways fail to habituate to chronic stress even though adrenocortical activity is not stimulated. We conclude that LMC mice showed adrenocortical hyporesponsiveness, which in combination with the behavioral abnormalities in this group may represent a model for the HPA hypoactivity associated with atypical depression.

Centrally administered relaxin-3 induces Fos expression in the osmosensitive areas in rat brain and facilitates water intake

The expression of the relaxin-3 gene, detected as a new member of the insulin superfamily using human genomic databases, is abundantly present in the brain and testis. Intracerebroventricularly (icv) administered relaxin-3 stimulates food intake. Icv administered relaxin (identical to relaxin-2 in humans) affects the secretion of vasopressin and drinking behavior. Relaxin-3 partly binds relaxin family peptide receptor 1, which is a specific receptor to relaxin. Thus, we hypothesized that relaxin-3 would have physiological effects in the body fluid balance. However, the effects of relaxin-3 in the body fluid balance remain unknown. In the present study, we revealed that icv administered relaxin-3 induced dense Fos-like immunoreactivity (Fos-LI) in the rat hypothalamus and circumventricular organs including the organum vasculosum of the lamina terminalis, the median preoptic nucleus, supraoptic nucleus (SON), the subfornical organ (SFO) and the paraventricular nucleus (PVN), that are related to the central regulation of body fluid balance. Icv administered relaxin-3 (54, 180 and 540 pmol/rat) also induced a significant increase in c-fos gene expression in a dose-dependent manner in the SON, SFO and PVN. Further, icv administered relaxin-3 (180 pmol/rat) significantly increased water intake, and the effect was as strong as that of relaxin-2 (180 pmol/rat). These results suggest that icv administered relaxin-3 activates osmosensitive areas in the brain and plays an important role in the regulation of body fluid balance.

C-Fos gene expression pattern in the hypothalamus and the preoptic area of defeminized rats

The object of the present study was to determine the c-fos gene expression pattern in the hypothalamus (HYP) and the preoptic area (POA) after estradiol and testosterone priming during the critical period of sexual differentiation of the rat brain. Three-day-old female rats were injected s.c. with a single dose of 17β-estradiol (200 μg), testosterone enantate (200 μg) or vehicle (corn oil). HYP and POA were dissected 2 h, 24 h and 14 days after treatments and on the day of vaginal opening (VO). Other animals, previously treated as above, were acutely injected with 17β-estradiol (5 μg) on the day of VO; HYP and POA were obtained 3 h later. Total RNA was extracted and processed for semiquantitative RT-PCR. We observed that c-fos gene expression was markedly increased in POA of the animals treated with estradiol or testosterone 2 h after treatments, while a non-significant increase in c-fos gene expression was observed in the HYP of these animals. We found a significant increase in c-fos expression in HYP and POA on the day of VO in both estradiol and testosterone defeminized rats. Interestingly, the acute estradiol administration on the day of VO did not induce c-fos gene expression in either HYP or POA of defeminized animals, instead a diminution in its expression was observed in animals treated with testosterone in POA. The overall results suggest that estradiol and testosterone imprinting during critical postnatal period of sexual differentiation of the brain permanently modifies the regulation of c-fos gene expression.

Activation of p38 MAP kinase and ERK are required for ultraviolet-B induced c-fos gene expression in human keratinocytes.

The effects of p38 MAP kinase and ERK on UVB induced c-fos gene expression were studied in a human keratinocyte cell line, FL30. UVB significantly increased c-fos gene expression at both the transcriptional and protein levels. p38 and ERK were also significantly activated after UVB irradiation. Treating the cells with p38 inhibitor SB202190 inhibited p38 activation, but not ERK; treating the cells with MEK-1 inhibitor PD98059 inhibited ERK activation without suppressing p38 activation. The kinase activation was determined by Western blots using phospho-p38 or ERK antibodies, or an in vivo p38 activity assay. Further studies demonstrated that blocking p38 almost completely abrogated UVB induced c-fos gene transcription and c-Fos protein synthesis. Inhibiting ERK partially abrogated UVB induced c-fos transcriptional and protein levels. Suppression of both p38 and ERK not only completely blocked UVB induced c-fos expression, but also decreased c-fos gene basal expression. Our data indicated that p38 may play a more important role than ERK in UVB induced c-fos expression in human keratinocytes. Since c-fos expression may play an important role in UVB induced AP-1 activation, and AP-1 activation is known to play a role in tumor promotion, both p38 and ERK could be potential targets for chemoprevention of skin cancer.

PACAP(6-38) is a PACAP receptor antagonist for breast cancer cells.

The effects of pituitary adenylate cyclase activating polypeptide (PACAP) analogs were investigated using breast cancer cells. 125I-PACAP-27 bound with high affinity (Kd = 5 nM) to T47D cells (Bmax = 29,000 per cell). Specific 125I-PACAP-27 binding was inhibited half maximally by PACAP-27, PACAP-38, PACAP(6-38) and PACAP(28-38) with IC50) values of 8, 17, 750 and >3000 nM, respectively. By RT-PCR, PACAP receptor mRNA was present in MCF-7 and T47D cell lines. Polyclonal antibodies to a PACAP receptor fragment (A-8-C) were elicited. The antibodies were affinity purified, recognized a 60-kDa protein by western blot, and stained malignant cells in breast cancer biopsy specimens by immunohistochemistry. PACAP-27 elevated the cAMP in T47D cells and the increase in cAMP caused by PACAP was inhibited by PACAP(6-38). PACAP-27 stimulated c-fos mRNA in T47D cells and the increase in c-fos gene expression caused by PACAP was reversed by PACAP(6-38). PACAP(6-38) inhibited colony formation using a soft agar assay and inhibited breast cancer xenograft growth in nude mice. These data suggest that PACAP(6-38) functions as a breast cancer PACAP receptor antagonist.

UVB Irradiation-induced Activator Protein-1 Activation Correlates with Increased c-fos Gene Expression in a Human Keratinocyte Cell Line

The effects of UVB irradiation on transcription factor activator protein-1 (AP-1) DNA binding and AP-1 transactivation were studied in a human keratinocyte cell line, HaCaT. UVB-induced AP-1 binding to a consensus AP-1 binding site was observed by gel shift assays with maximum stimulation at 12 h after UVB irradiation. A promoter region of the human collagenase-1 gene containing the same AP-1 binding sequence linked to a luciferase reporter gene was stably transfected into HaCaT cells. UVB irradiation significantly increased luciferase activity in these stably transfected cells, with maximum activity observed at 24 h after UVB irradiation. c-Fos and Jun D were identified by antibody clearing assays as the main components of the bound AP-1 complexes. Inhibition of transcription with actinomycin D and inhibition of protein synthesis with cycloheximide significantly abrogated the effect of UVB on AP-1 DNA binding, indicating that transcription and translation were required for AP-1 activation. Northern and Western analyses revealed a correlation between increased AP-1 activity and accumulation of c-fos mRNA and c-Fos protein after UVB irradiation. UVB irradiation increased c-fos transcription in HaCaT cells stably transfected with a plasmid containing the human c-fos promoter driving a luciferase reporter gene. These results suggest that increased c-fos expression may play an important role in UVB-induced AP-1 activation in HaCaT cells.

C-fos expression pattern in the hypothalamus and the preoptic area of the rat during proestrus

c-fos gene expression in the hypothalamus, the preoptic area, the hippocampus and the frontal cerebral cortex of the rat was determined every two hours from 09:00 h to 19:00 h on the day of proestrus by using reverse transcription coupled to polymerase chain reaction. Rats under a 14:10 h light-dark cycle, with lights on at 06:00 h were used. We found a marked increase in c-fos gene expression in the studied regions but the hippocampus at 13:00 h, followed by a significant diminution in the subsequent hours of proestrus day. The high expression of c-fos gene at 13:00 could be associated to the increase in estradiol seric levels observed both at 11:00 h and at 13:00 h. Our results correlate with the increase in the number of FOS immunoreactive cells in some forebrain areas in proestrus afternoon related to gonadotropin releasing hormone secretion.

(Arg 15, Arg 21) VIP: Evaluation of Biological Activity and Localization to Breast Cancer Tumors

Moody, T. W., J. Leyton, E. Unsworth, C. John, L. Lang and W. C. Eckelman. (Arg 15, Arg 21) VIP: Evaluation of biological activity and localization to breast cancer tumors. Peptides 19(3) 585–592, 1998.—VIP analogs, which contain a single lysine amino acid, were synthesized and evaluated using breast cancer cells. (Arg 15, Arg 20) VIP, (Arg 15, Arg 21) VIP, and (Arg 20, Arg 21) VIP inhibited 125I-VIP binding to T47D cells with high affinity (IC 50 values of 1.2, 1.0, and 0.8 nM, respectively). The VIP analogs elevated cAMP in T47D cells with ED 50 values ranging from 0.1–1 nM. Because (Arg 15, Arg 21) VIP was the most potent at elevating cAMP, it was characterized further. (Arg 15, Arg 21) VIP transiently increased c-fos gene expression in breast cancer cells. N-Succinimidyl-4- 18F (fluoromethly) benzoate was prepared in one chemical step from N-succinimidyl-4-(4-nitrobenzenesulfonyl)oxomethyl)benzoate by adding 18F in acetone at room temperature. This prosthetic group was then reacted with (Arg 15, Arg 21) VIP ((RR) VIP). ( 18F-RR) VIP bound with high affinity to T47D cells and was rapidly internalized. ( 18F-RR) VIP was injected intravenously into nude mice bearing breast cancer xenografts and after 4 h, the density of ( 18F-RR) VIP was elevated in the tumors relative to normal organs. These data suggest that VIP receptors may be used to localize breast cancer tumors.

Protein tyrosine kinase, mitogen-activated protein kinase and protein kinase C are involved in the mitogenic signaling of platelet-activating factor (PAF) in HEC-1A cells

We have recently demonstrated that the phospholipid platelet-activating factor (PAF) mediates an autocrine proliferative loop in the endometrial adenocarcinoma cell line HEC-1A. In the present study we investigated the signaling pathways involved in PAF-mediated increase of proliferation in these cells. In particular, we studied the effect of PAF on protein tyrosine phosphorylation and mitogen-activated protein kinase (MAPK) activity, as well as the effect of protein tyrosine kinase (PTK) and protein kinase C (PKC) inhibition on PAF-induced increase of c-fos gene expression and thymidine incorporation in HEC-1A cells. We found that PAF induced a rapid, time- and dose-dependent increase of tyrosine phosphorylation of a subset of proteins of 42, 44, 78, 99, and 150 kDa molecular weight. We also found that PAF increased tyrosine phosphorylation and activity of p42 MAPK, suggesting the involvement of this important intermediary enzyme in the proliferative effect of PAF. The effect of PAF on c-fos gene expression was not prevented by pre incubation with the PTK inhibitors genistein or methyl-2,5-dihydroxycinnamate, whereas was strongly affected by PKC down regulation after long term incubation with PMA or by PKC inhibition with sangivamycin. We also found that genistein and methyl 2,5-dihydroxycinnamate decreased both basal and PAF-stimulated [ 3H]thymidine uptake in these cells. Similar results were obtained with PD 098059, a specific inhibitor of MAP kinase cascade. PAF-stimulated [ 3H]thymidine uptake was also prevented by PKC down regulation after long term exposure to PMA and PKC inhibition with the two inhibitors sangivamycin and bis-indolylmaleimide. In conclusion, our results indicate that PAF-induced mitogenesis in HEC-1A cells is mediated by the activation of multiple signaling pathways, involving PTK, MAPK, and PKC activation.

Extracellular ATP induces immediate-early gene expression but not cellular hypertrophy in neonatal cardiac myocytes.

It is well-documented that norepinephrine (NE) induces the expression of immediate-early genes (IEGs), such as c-fos, c-jun, and jun-B, in cultured neonatal heart cells and leads to cell growth without cell division (ie, hypertrophy). Although purinergic receptors activated by ATP are present on cardiac myocytes and ATP is coreleased with NE from sympathetic nerve endings within the heart, the potential role of the purinergic system in the cascade of events that leads to cardiac hypertrophy is unknown. We report in the present study that stimulation of purinergic receptors by micromolar concentrations of extracellular ATP increased the levels of c-fos and jun-B mRNA as well as FOS and JUN-B proteins in neonatal cardiac myocytes. The magnitude of response to micromolar ATP was comparable to that elicited by NE. The increase in IEG expression induced by ATP was preceded by a rapid transient increase in cytosolic Ca2+. Pretreatment of myocytes with the intracellular Ca2+ chelator BAPTA-AM prevented the ATP-stimulated increase in cytosolic Ca2+ and attenuated the ATP-stimulated increase in c-fos expression. In contrast, NE did not increase cytosolic Ca2+ in quiescent myocytes, and pretreatment with BAPTA-AM did not inhibit the NE-stimulated increase in c-fos gene expression. Furthermore, although NE markedly increased [14C]phenylalanine incorporation into protein and myocyte hypertrophy measured by cell size, ATP did not. These results demonstrate that stimulation of purinergic receptors by ATP activates IEGs via a Ca(2+)-dependent pathway in cardiac myocytes that differs from the NE stimulated activation of these genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of c-fos Gene Expression by Arabinofuranosylcytosine in Human KG-1 Leukemia Cells

Previous studies have demonstrated that the c-fos proto-oncogene is expressed during induction of differentiation and as an immediate early response to growth factors. The present results demonstrate that exposure of human KG-1 myeloid leukemic cells to 1-beta-D-arabinofuranosylcytosine (ara-C) was associated with increases in c-fos gene expression. This effect was dependent on the concentration and time of ara-C treatment. The level of c-fos transcripts was maximal after 6 hr of exposure to 5 x 10(-6) M ara-C and subsequently declined to that in untreated cells. Nuclear run-on assays demonstrated low to undetectable levels of c-fos gene transcription in untreated KG-1 cells. In contrast, treatment with 5 x 10(-6) M ara-C for 6 hr was associated with increases in transcription of this gene. Although superinduction of c-fos expression has been observed at the post-transcriptional level in the presence of protein synthesis inhibition, this effect was not detectable in ara-C-treated KG-1 cells. These combined results demonstrate that ara-C increased c-fos mRNA levels in KG-1 cells and that this effect was associated with transcriptional activation of the c-fos gene.

β-Adrenergic regulation of c-fos gene expression in an epithelial cell line

Stimulation of β-adrenoreceptors in the RSMT-A5 epithelial cell line is accompanied by an early and transient increase in the expression of the proto-oncogene c-fos. Maximal induction was at 30 min, returning to basal levels after 2 h. Similar results were obtained when cells were incubated with 8-bromo-cAMP. The induction of c-fos is specific since the expression of p53, a transformation-related gene, is not modulated by isoproterenol or 8-bromo-cAMP. The increase in c-fos gene expression is not associated with proliferative activity in these epithelial cells.

C-fos expression in human skin fibroblasts by reperfusion after oxygen deficiency: a recovery change of human skin fibroblasts after oxygen deficiency stress.

A dramatic and specific induction of c-fos mRNA was observed in human skin fibroblasts in vitro culture by oxygen reperfusion after oxygen deficiency treatment. C-fos mRNA reached a maximum about 30-60 min after oxygen reperfusion and declined to basal level after 120 min. And this phenomenon was duration of oxygen deficiency-dependent, and remarkably observed for 0.5-2 hr of oxygen deficiency. More long duration of oxygen deficiency induced a decreasing tendency of c-fos mRNA overexpression due to essential and irreversible cellular damage. Thus increased c-fos gene expression might be an early event in cellular recovery process in particularly human skin fibroblasts with oxygen deficiency.

Mapping patterns of c-fos expression in the central nervous system after seizure.

A dramatic and specific induction of c-fos was observed in identifiable neuronal populations in vivo after administration of the convulsant Metrazole. This effect was time- and dose-dependent and was abolished by prior treatment with the anticonvulsant drugs diazepam or pentobarbital. About 60 minutes after administration of Metrazole, c-fos messenger RNA reached a maximum and declined to basal levels after 180 minutes. A further decrease below that in normal brain was observed before a return to basal levels after 16 hours. While Metrazole still elicited seizures during this period, reinduction of c-fos was largely refractory. At 90 minutes, c-fos protein was observed in the nuclei of neurons in the dentate gyrus, and in the pyriform and cingulate cortices. Subsequently, c-fos protein appeared throughout the cortex, hippocampus, and limbic system. Thus, seizure activity results in increased c-fos gene expression in particular subsets of neurons.