Inhibition of growth of OV-1063 human epithelial ovarian cancers and c- jun and c- fos oncogene expression by bombesin antagonists

Receptors for bombesin are present on human ovarian cancers and bombesin-like peptides could function as growth factors in this carcinoma. Therefore, we investigated the effects of bombesin/gastrin-releasing peptide (GRP) antagonists RC-3940-II and RC-3095 on the growth of human ovarian carcinoma cell line OV-1063, xenografted into nude mice. Treatment with RC-3940-II at doses of 10 microg and 20 microg per day s.c. decreased tumour volume by 60.9% (P< 0.05) and 73.5% (P< 0.05) respectively, after 25 days, compared to controls. RC-3095 at a dose of 20 microg per day reduced the volume of OV-1063 tumours by 47.7% (P = 0.15). In comparison, luteinizing hormone-releasing hormone (LH-RH) antagonist Cetrorelix at a dose of 100 microg per day caused a 64.2% inhibition (P< 0.05). RT-PCR analysis showed that OV-1063 tumours expressed mRNA for bombesin receptor subtypes BRS-1, BRS-2, and BRS-3. In OV-1063 cells cultured in vitro, GRP(14-27) induced the expression of mRNA for c- jun and c- fos oncogenes in a time-dependent manner. Antagonist RC-3940-II inhibited the stimulatory effect of GRP(14-27) on c- jun and c- fos in vitro. In vivo, the levels of c- jun and c- fos mRNA in OV-1063 tumours were decreased by 43% (P< 0.05) and 45% (P = 0. 05) respectively, after treatment with RC-3940-II at 20 microg per day. Exposure of OV-1063, UCI-107 and ES-2 ovarian carcinoma cells to RC-3940-II at 1 microM concentration for 24 h in vitro, extended the latency period for the development of palpable tumours in nude mice. Our results indicate that antagonists of bombesin/GRP inhibit the growth of OV-1063 ovarian cancers by mechanisms that probably involve the downregulation of c- jun and c- fos proto-oncogenes.

[Screening the trans-action factors binding to the enhancer element of rat GST-P by yeast one-hybrid system]

OBJECTIVE

To investigate the diversity of the mechanisms of rat glutathione S-transferase P (GST-P) gene expression regulation and the relation between rat GST-P gene expression and carcinogenesis. To search the trans-action factors binding to the enhancer element of rat GST-P (glutathione S-transferase P enhancer, GPE I).

METHODS

We searched the trans-action factors binding to GPE I using yeast one-hybrid system, and analyzed the DNA sequence by sequencing and computer search.

RESULTS

Two positive clones pYGPE1 and pYGPE2 were obtained. The homologies of the insert sequence of pYGPE1 nucleotide and amino acid sequences with rat c-jun cDNA were 99% and 100% respectively; the homologies of the insert sequence of pYGPE2 nucleotide and amino acid sequences with rat mitochondrial adenine nucleotide translocase cDNA were 99% and 100% respectively.

CONCLUSIONS

Rat c-Jun and mitochondrial adenine nucleotide translocase can bind to the GPE I core sequence, and they perhaps are the trans-action factors of GPE I.

Role of suppressors of cytokine signaling (Socs) in leukemia inhibitory factor (LIF) -dependent embryonic stem cell survival

Mouse embryonic stem (ES) cells remain pluripotent in vitro when grown in the presence of leukemia inhibitory factor (LIF). LIF withdrawal results in progressive ES cell differentiation. Here we show that during this differentiation process, part of the cells undergo apoptosis concomitant with an activation of the p38 MAP kinase. To gain insight into events mediated by LIF in ES cells, the expression of potential candidate genes was analyzed in the absence or presence of this cytokine by using a semiquantitative RT-PCR assay. We focused on early response genes and on a new type of cytokine repressors (the Socs proteins), some of which exhibit anti-apoptotic properties. We found that expression of c-Fos, c-Jun, and JunB was induced upon LIF treatment whereas that of JunD, the tyrosine phosphatase ESP, and the components of the LIF receptor remained unaffected. Expression of Socs-3, but not Socs-1 or Socs-2, was stimulated in the presence of LIF. Finally, uncontrolled overexpression of Socs-1 and Socs-3 led to repression of LIF-dependent transcription and severely reduced cell viability, suggesting that the disturbance of a well balanced Socs protein content has adverse effects on cell survival.

Differential immediate-early gene responses to shear stress and intraluminal pressure in intact human conduit vessels

We have previously shown distinct effects of shear stress and pressure on transcription of several potent vascular mediators. In the present study, we tested the hypothesis that c-jun and c-fos are regulated differentially by shear and pressure. Intact human umbilical veins were perfused with various combinations of shear and pressure during 1.5, 3 and 6 h. Protein and gene expressions were assessed by immunofluorescence and real-time reverse transcription PCR, respectively. Shear stress and pressure exert differential temporal effects on c-jun and c-fos gene and protein expression, and these immediate-early gene responses appear to be cell-type specific for endothelial and smooth muscle cells.

Tumor necrosis factor-alpha enhances mRNA expression and secretion of interleukin-6 in cultured human airway smooth muscle cells

Airway smooth muscle (ASM) is considered to be an end-target cell for the effects of mediators released during airway wall inflammation. Several reports suggest that activated ASM may be capable of generating various proinflammatory cytokines. We investigated the effects of tumor necrosis factor (TNF)-alpha, a potent proinflammatory cytokine, on cultured human ASM cells by examining the expression and release of the cytokine interleukin (IL)-6, cell proliferation, and the expression pattern of c-fos and c-jun, two nuclear proto-oncogenes constituting the activator protein-1 transcription factor. Growth-arrested cell monolayers were stimulated with human recombinant TNF-alpha in a concentration- and time-dependent manner. TNF-alpha stimulated the expression of IL-6 messenger RNA (mRNA), which was detected after 15 min, reaching a maximum at 1 h. IL-6 protein was readily detected in ASM cell-conditioned medium after 2 h of TNF-alpha stimulation. Protein levels increased in a time- and concentration-dependent manner. Release of IL-6 elicited by TNF-alpha was significantly inhibited by dexamethasone, cycloheximide, and nordihydroguaiaretic acid (NDGA). TNF-alpha did not alter DNA biosynthesis up to 48 h or cell numbers up to 120 h. Northern blot analysis of proto-oncogene expression revealed that c-fos and c-jun mRNA levels were elevated after 30 min of TNF-alpha incubation with maximum levels at 1 h and 45 min, respectively. Expression of c-fos mRNA was downregulated by NDGA. Four hours of TNF-alpha treatment resulted in translocation of c-jun immunofluorescence from the cytoplasm to the nucleus in human ASM cells. Our results suggest that despite the lack of a mitogenic response to TNF-alpha, upregulation of primary response genes in human ASM cells may account for the induction of proinflammatory cytokines, such as IL-6, in human airways.

Studies on hepatic gene expression in different liver regenerative models

We have investigated the expression of several growth-related genes in the liver after partial hepatectomy in three experimental models: normal, Dexamethasone-pretreated, and hypophysectomized rats. Dexamethasone and hypophysectomy resulted in a delay in the peak of cell replication in 6 and 18 h, respectively, when compared to the normal animals. TGFalpha mRNA expression was shifted together with the DNA synthesis, but the expression of c-myc, c-fos, c-jun, HGF, TGFbeta1, IL1beta did not delay. This result suggests that liver-derived TGFalpha but not the other factors are important in the timing of the proliferative response after partial hepatectomy.

Transcriptional regulation in response to exercise

Much progress has been made in recent years into understanding molecular mechanisms by which transcription is regulated following changes in physiological stimuli. This review has tried to focus on what is known about four specific physiological challenges--mechanical load, intracellular calcium, hypoxia, and redox state. Because of our biased interest in exercise, it was our goal to review these relatively well-studied systems so that we might provide insight into potential mechanisms that govern exercise-induced transcriptional changes. What becomes obvious, when reaching the end of this review, is that there are many common themes among the different physiological responses described. Some examples include the activation of IEGs, such as c-jun and c-fos, the phosphorylation of the transcription factor CREB, and the importance of the serum response element and the serum response factor. These commonalities across the different physiological systems suggest a certain redundancy or shared mechanism(s) for regulating transcription in response to physiological stimuli. While very little is known at this time about how exercise regulates transcription, it is an exciting time in this field of research. The recent growth in the molecular biological research literature of more physiologically-based studies provides exciting new molecular and cellular tools for those researchers willing to take on the challenge of understanding the complex mechanisms of exercise-induced adaptations.

Apoptosis induced by hydrogen peroxide under serum deprivation and its inhibition by antisense c-jun in F-MEL cells

Under serum deprivation F-MEL cells die by apoptosis. We previously showed that apoptosis induced by serum deprivation was suppressed by inhibition of c-jun expression using antisense c-jun transfected cell line, c-junAS. To elucidate the underlying mechanisms we examined the species which is responsible for apoptosis under serum deprivation. When catalase and N-acetyl-L-cysteine (NAC) were included in the medium, cell death under serum deprivation was effectively suppressed in F-MEL cells. Intracellular generation of hydrogen peroxide (H(2)O(2)) was also detected under serum deprivation in parental F-MEL cells, but it was suppressed in c-junAS (+) cells, in which antisense c-jun was expressed and c-Jun protein expression was inhibited as shown by Western blot. When H(2)O(2) was directly applied to F-MEL cells at 3 mM, apoptotic cell death was induced, whereas it was suppressed in c-junAS (+) cells. Induction of apoptosis by H(2)O(2) and its inhibition by antisense c-jun was confirmed by detection of internucleosomal fragmentation of DNA, TdT-mediated dUTP nick end labeling (TUNEL)-positive cells and morphological alteration of nuclei. These results indicate that apoptosis induced by serum deprivation in F-MEL cells is mediated by H(2)O(2) and c-jun expression is essential to apoptosis induced by H(2)O(2) in F-MEL cells.

Cadmium induces c-myc, p53, and c-jun expression in normal human prostate epithelial cells as a prelude to apoptosis

Cadmium is a suspected human prostatic carcinogen shown to induce prostatic tumors and proliferative lesions in rats. The carcinogenic mechanism of cadmium is unknown, but its poor mutagenicity points toward an epigenetic mechanism. Here we studied the effect of cadmium on genes involved in growth regulation of prostate epithelial cell using the human prostate epithelial cell line RWPE-1, which is immortalized but not transformed and is androgen-responsive. Treatment with 10 microM cadmium resulted in transient increases in c-myc and p53 mRNA levels that peaked at 2-fold and 1.4-fold, respectively, compared to control after 2 h. In contrast, c-jun mRNA levels were increased >3-fold after 2, 4, and 6 h and 20-fold after 24 h. DNA synthesis decreased after 24 h of cadmium exposure. Further study revealed a significant increase in apoptosis after 48 h of cadmium exposure. However, approximately 35% of the cells were still viable and appeared normal, indicating this subpopulation was more resistant to cadmium. Furthermore, these resistant cells had 2.5-fold more metallothionein than untreated control cells. This suggests that cadmium could act to select for apoptotic-defective cells in vivo, thereby increasing the likelihood of tumor formation. This work represents the first description of cadmium affecting oncogene expression in a human cell model of a potential in vivo target site of cadmium carcinogenesis.

mRNA expression of proto-oncogenes and platelet-derived growth factor in proliferative vitreoretinal diseases

PURPOSE

To detect the expression of mRNA of protooncogenes ets-1, c-jun, c-fos, and platelet-derived growth factor (PDGF) in proliferative membranes of patients with proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR).

METHODS

cDNA was synthesized from mRNA of proliferative membranes from patients with PDR, PVR, premacular fibrosis (PMF), acute retinal necrosis (ARN), and age-related macular degeneration (ARMD). Ets-1, c-jun, c-fos, PDGF-A, and PDGF-B cDNA were amplified using reverse transcriptase-polymerase chain reaction (PCR).

RESULTS

Proto-oncogene mRNA was highly expressed in membranes from patients with severe PDR, grade D PVR. PDGF mRNA was expressed in almost all samples.

CONCLUSIONS

Our results suggest that not only PDGF mRNA was expressed in the membranes of patients with PDR and PVR, but proto-oncogenes ets-1, c-jun, and c-fos mRNA were also expressed.

Hepatitis B virus surface (S) transactivator with DNA-binding properties

Chronic infection with hepatitis B virus (HBV) in humans is strongly linked to the development of hepatocellular carcinoma (HCC). Activation of growth-regulatory genes may play a crucial role in carcinogenesis. Proto-oncogene expression has been shown to be higher in HCC tissue with integrated HBV DNA than in the normal liver. Earlier, we showed that the 3' end of the HBV major surface gene (S) (426-855 nucleotides of the S region) is a transactivator of the X promoter-enhancer regulatory element in co-transfection experiments. This region expresses a truncated carboxy terminal S protein extending from amino acid residues 102 to 226. In this study, the truncated S protein (trc-S) was examined for its enhancing activity on several viral and cellular regulatory elements. The results indicate that trc-S activates rous sarcoma virus long terminal repeat (LTR), human T-lymphotropic virus 2 LTR, human immunodeficiency virus 1 LTR, and the c-jun and c-fos promoters. Electrophoretic mobility shift assays carried out to investigate its DNA-binding properties established that trc-S binds to HBV X promoter and oligonucleotides representing binding sites for the AP1 and TFIID transcription factors. The specificity of this interaction was confirmed by using competition experiments and supershift assays. These experiments suggest that trc-S is a transactivator of several cellular and viral promoters and that this activity is mediated by direct interaction with DNA.

Conditional cell transformation by doxycycline-controlled expression of the ASV17 v-jun allele

To investigate the molecular basis of oncogenesis induced by the v-jun oncogene of avian sarcoma virus 17 (ASV17), we developed a conditional cell transformation system in which transcription of the ASV17 v-jun allele is controlled by a doxycycline-sensitive transactivator (tTA) or a reverse (doxycycline-dependent) transactivator (rtTA), respectively. Permanent cell lines of quail embryo fibroblasts conditionally transformed by a doxycycline-controlled v-jun allele revert to the normal phenotype within 3 days and lose their ability to grow in soft agar, strictly dependent on the addition or removal of the drug, respectively. The reverted cells are rapidly retransformed on conditional activation of v-jun. While full-level synthesis of v-jun mRNA and v-Jun protein in these cells is established within 2 and 14 h, respectively, after switching to the permissive conditions, the first morphological alterations are observed after 24 h, and as early as 2 days later the morphology has changed entirely from flat cells resembling normal fibroblasts to spindle-shaped fusiform cells showing a typical jun-transformed phenotype. Kinetic expression analysis revealed that transcriptional activation of the direct jun target gene BKJ precisely coincides with the establishment of full-level v-Jun protein synthesis. Furthermore, we have analyzed the expression of a novel candidate v-jun target gene, termed JAC, which shows no sequence homology to known genes. Similar to BKJ, JAC is specifically activated in jun-transformed fibroblasts, and induction of JAC is tightly linked to the conditional expression of oncogenic v-Jun. These results demonstrate the high stringency of the doxycycline-controlled v-jun expression system, and they also indicate that expression of v-jun in these cells is indispensable for enhanced proliferation, cell transformation, and the induction of specific expression patterns of downstream target genes.

Electrically stimulated induction of hsp70 gene expression in mouse astroglia and fibroblast cells

Mouse astroglial cells, which were cultured on an electrode, were found responsive to an electric stimulation of sine wave potential in enhancing hsp70 mRNA resulting from an activation of hsp70 gene expression. On the basis of this finding, electrically responsive cells were established by transfecting mouse 3T3-L1 cells with a constructed plasmid encoding hsp70 promoter and the firefly luciferase gene. A stable cell line has been established through selection of heat-stimulated luciferase expression. A 1-h electric stimulation of the cells resulted in activation of luciferase expression, which was confirmed to produce an increase in light emission. The sequential pattern of the electrically stimulated expression of luciferase was found different from that of the heat stimulation. Furthermore, the promoter was activated depending on the potential and duration of the stimulation applied. Consequently, the electric stimulation has proven effective on activating hspP70 promoter. This cell line is feasible in expressing the gene of interest by electrical stimulation, which lead us to construct environment responsive cells in general.

Angiotensin II-stimulated vascular endothelial growth factor expression in bovine retinal pericytes

PURPOSE

Angiotensin II (AII) has been shown to play a role in many vascular diseases. In the study described, the effect of AII on vascular endothelial growth factor (VEGF) expression and related intracellular signaling mechanism was investigated in bovine retinal microcapillary pericytes.

METHODS

Cultured bovine retinal microvascular endothelial cells and pericytes were prepared. VEGF expression was determined by Northern blot analysis and immunoprecipitation assay. Cell proliferation was assessed by DNA content growth assay. Reporter gene studies were performed to identify the AII responsible transcription-activating region of VEGF gene.

RESULTS

Angiotensin II induced a significant increase in VEGF mRNA in a time- and dose-dependent manner. Angiotensin II type I receptor antagonist inhibited this effect. Angiotensin II activates the transcription of VEGF gene without changing the mRNA half-life, and the AII responsible region was found in the 5'-flanking region of the VEGF gene. Angiotensin II also increased the expression of c-fos and c-jun mRNA, and antisense oligonucleotides against c-Fos blocked the AII-induced VEGF mRNA expression. The conditioned media of AII-stimulated pericyte cultures had a growth-promoting effect on endothelial cells, and this effect was inhibited almost completely by VEGF neutralizing antibody.

CONCLUSIONS

These findings suggest that AII might induce angiogenic activity through a paracrine function of VEGF in retinal microvascular cells.

Constitutive expression and regulation of collagenase-3 in human breast cancer cells

Matrix metalloproteinases (MMPs) are a family of secreted or transmembrane proteins that have been implicated in multiple physiological and pathological processes related to extracellular matrix turnover. Recent evidence strongly suggests a role for collagenase-3 (MMP-13) in tumor metastasis and invasion. We report here that collagenase-3 is constitutively expressed in the breast cancer cell line MDA-MB231 (MDA) and outline the molecular mechanism regulating its expression. Functional analysis of the collagenase-3 promoter showed that both the activator protein-1 (AP-1) site and the runt domain (RD) binding site were required for maximal constitutive expression of collagenase-3 in MDA cells. Determination of factors binding to those sites by Northern analysis and transient transfections identified the requirement of Fra-1, c-Jun, and Cbfa1 for basal collagenase-3 promoter activity in MDA cells.

The early response genes c-jun and HSP-70 are induced in regional cardiac stunning in conscious mammals

OBJECTIVES

A reversible contractile dysfunction without necrosis after transient myocardial ischemia has been termed stunning. The molecular mechanisms underlying this phenomenon are only now beginning to be unraveled. It is conceivable that the expression of early-response genes may play a crucial role in stunning.

METHODS

The expression of HSP-70, c-jun, and GRP-94 was investigated in a chronically instrumented dog model (n = 9). The left anterior descending coronary artery was occluded temporarily for 10 minutes after the animals had fully recovered from instrumentation. The wall thickening fraction was measured in the left anterior descending coronary artery and the nonischemic ramus circumflex of the left coronary artery-perfused region. When the wall thickening fraction of the left anterior descending coronary artery had recovered to 50% of preocclusion values, tissue samples were obtained from the areas perfused by the left anterior descending coronary artery and the nonischemic ramus circumflex of the left coronary artery.

RESULTS

The messenger RNA of HSP-70 was increased to 214% +/- 26% in the area perfused by the left anterior descending artery compared with that perfused by the nonischemic ramus circumflex of the left coronary artery. There was no difference in the messenger RNA of GRP-94. The HSP-70 content was elevated to 130% +/- 14% in the left anterior descending artery compared with the area perfused by the ramus circumflex of the left coronary artery, and the c-jun protein content was 70% +/- 25% higher in the ischemic area compared with the control area.

CONCLUSIONS

The induction of early-response genes observed here may indicate that they play an adaptive role in myocardial stunning, even in conscious mammals.

Immediate early gene expression in PC12 cells exposed to lead: requirement for protein kinase C

We previously demonstrated induction of c-fos mRNA in PC12 cells exposed to lead that was dependent on new transcription. In the current work, we examined two signal transduction mechanisms that are activated by lead and have been shown to mediate induction of c-fos mRNA. One mechanism involves protein kinase C, and the other requires calmodulin-dependent protein kinase II. Significant increases in the levels of c-fos, c-jun, and egr-1 but not NGFIB mRNA were observed in PC12 cells exposed to lead or phorbol 12-myristate 13-acetate. In contrast, PC12 cells depolarized with 56 mM K+ displayed an increase in c-fos, egr-1, and NGFIB but not c-jun mRNA. Similar to other activators of protein kinase C, lead increased AP-1 and Egr-1 DNA binding activity. Additionally, lead increased luciferase activity in cerebellar granule cells transfected with an AP-1 luciferase reporter construct. Lead did not increase c-fos mRNA in PC12 cells that were depleted of protein kinase C by a 24-h treatment with phorbol 12,13-dibutyrate or incubated with the protein kinase C inhibitor H-7. In contrast, an inhibitor of calmodulin-dependent protein kinase, KN-62, and an inhibitor of calmodulin, W-7, did not block the induction of c-fos mRNA by lead. An increase in serum-response element DNA-binding activity was observed in nuclear extracts from PC12 cells exposed to lead. It is interesting that lead activated protein kinase C isoforms delta and epsilon, but not isoforms alpha and beta. In conclusion, lead appears to induce the expression of immediate early genes by a mechanism that requires protein kinase C.

Sodium restriction decreases AP-1 activation after nephron reduction in the rat: role in the progression of renal lesions

Renal hyperplasia and hypertrophy are early events after nephron reduction which precede progressive destruction of the remnant kidney. Restriction of dietary sodium content was shown to reduce renal lesions following nephron reduction. AP-1 is a transcription factor, resulting from heterodimerization of fos and jun proteins, which mediates the effects of mitogenic growth factors. To elucidate the role of AP-1 in growth processes involved in renal deterioration, we evaluated whether restriction of dietary sodium content (0.25 vs. 0.50% sodium w/w) affected AP-1-DNA binding and hyperplasia in the remnant kidney after nephron reduction (70% nephrectomy). Cell proliferation, evaluated by PCNA immunostaining, increased progressively from day 7 to day 60 in glomeruli, proximal and distal tubules and loops of Henle of nephrectomized (Nx) rats compared to control sham-operated (C) animals. AP-1-DNA binding activity increased 7 and 14 days after surgery, but it was reduced below C values at day 60. c-fos and c-jun expression were also reduced in Nx rats at day 60. Sodium restriction significantly reduced the number of PCNA-stained cells in glomeruli and tubules at days 14 and 60, but not at day 7, whereas it decreased AP-1 activation at all times of the study. This effect was associated to a marked reduction of renal lesions in Nx rats. In conclusion, we showed that, after nephron reduction, the beneficial effect of sodium restriction was associated with a reduction of hyperplasia and AP-1 activation, but that the latter did not parallel delayed cell proliferation rate in remaining nephrons. Thus, we propose that different transduction pathways are involved in cell proliferation after nephron reduction, according to the time of evolution of renal lesions.

Gene expression and cytokine and enzyme activation in the liver after a burn injury

The liver plays a critical role in the inflammatory response to injury; however, the mechanisms by which the liver is affected and how it influences the rest of the immune system are not well understood. Partial hepatectomy is a direct injury to the liver, whereas a burn is an indirect injury to liver, but both injuries appear to produce damage to the liver. In this study, we used a mouse model of 25% total body surface area and 40% total body surface area full-thickness burns to investigate the mechanism of liver damage and response to burn injury by measuring levels of c-Jun messenger (m)RNA, NFkappaB nuclear protein, interleukin-6, transaminases, and liver tissue histology over time. c-Jun and NFkappaB are 2 transcription factors that are induced by partial hepatectomy and related to hepatocyte injury and growth. In both groups of mice with burns, expression of c-Jun mRNA and NFkappaB nuclear protein was activated within 30 minutes after the burn injury, followed by increased levels of interleukin-6 and, finally, elevated enzyme levels. Liver injuries were similar in both groups despite the magnitude of the burns. We believe that these gene products are initiated in the hepatocyte injury after a burn and that they precede other inflammatory responses such as cytokine release, plasma transaminase levels, and histologic changes.

Prostaglandin E(2) (PGE(2)) induces the c-fos and c-jun expressions via the EP(1) subtype of PGE receptor in mouse osteoblastic MC3T3-E1 cells

This study examined which subtype(s) of PGE receptors is involved in the induction of c-fos and c-jun by PGE(2) in MC3T3-E1 cells. We also investigated the possibility that the induction of these genes is involved in the growth and differentiation of this cell line. PGE(2) dose-dependently induced c-fos and c-jun mRNA expressions in MC3T3-E1 cells. Of the PGE analogs, 17-phenyl-omega-trinor PGE(2) (EP(1) agonist) and sulprostone (EP(1)/EP(3) agonist) were far more potent than butaprost (EP(2) agonist) and 11-deoxy PGE(1) (EP(2)/EP(4) agonist) in inducing c-fos and c-jun mRNA expressions. Since MC3T3-E1 cells do not express the EP(3) subtype, these results suggest that PGE(2) induces c-fos and c-jun mRNA expressions through the EP(1) subtype of its receptor. In order to study the functional relevance of these protooncogenes, we then studied the effect of inhibition of their synthesis by the use of antisense oligonucleotide. Alkaline phosphatase (ALP) suppression by 17-phenyl-omega-trinor PGE(2) was reversed by antisense oligonucleotide for either c-fos or c-jun. These results suggest that PGE(2), via the EP(1) subtype of the PGE receptor, negatively modulates the transition from proliferation to the matrix maturation stage through the induction of c-fos and c-jun. However, antisense oligonucleotide for c-fos or c-jun did not alter the prostaglandin G/H synthase-2 mRNA expression induced by EP(1). Thus, it is possible that c-fos and c-jun inductions do not account for all the EP(1)-mediated PGE(2) actions in MC3T3-E1 cells.

Expression of the immediate early genes c-Fos and c-Jun after head injury in man

Immediate early genes (IEC) are expressed in a variety of experimental paradigms including cerebral ischemia and trauma. There is a paucity of information on whether the results of laboratory experiments can be extrapolated from animals into man. To examine this further we hypothesized that expression of c-Fos and c-Jun occurs after contusional head injury in man. We also sought to identify whether there was an association between the level of immediate early gene expression and 1. the outcome one year after head injury, 2. the timing of surgery after head injury. IEG expression was examined using in situ hybridization and immunocytochemistry in brain tissue therapeutically removed in 14 patients with head injury 6 h to 6 days after contusional injury. IEG expression was also examined in tissue removed during elective non-traumatic neurosurgery for comparative purposes. Expression of c-fos and c-jun mRNA was observed in 50% and 64% of head-injured patients respectively. Protein immunoreactivity for these IEGs was evident in 67% of head injured patients. The expression of c-Fos and c-Jun was associated with final outcome. Patients with poorer outcomes had higher levels of gene expression (p = 0.08 for c-Fos and p = 0.006 for c-Jun). No correlation between the timing of surgery and the intensity of gene expression was evident in the trauma patients (r2 = 0.09 and 0.10 for c-Fos and c-Jun respectively). In the non-trauma patients 36% expressed c-fos and 73% expressed c-jun mRNA, with all patients studied expressing c-Fos and c-Jun proteins. We conclude that differential expression of c-Fos and c-Jun occurs in the patients with cerebral contusions. The difference in expression rates between mRNA and protein emphasises the need for analysis of gene products when investigating gene expression. These results support the hypothesis that IEGs may be involved in the pathogenetic mechanisms of contusional head injury. Observations of IEG expression in human brain injury are important in steering animal experimental programmes towards studies that may yield information directly applicable to human brain injury.

Altered molecular response to adrenoreceptor-induced cardiac hypertrophy in Egr-1-deficient mice

Unmanipulated early growth response-1 (Egr-1)-deficient -/- mice have similar heart-to-body weight ratios but express lower amounts of atrial natriuretic factor (ANF), beta-myosin heavy chain (beta-MHC), skeletal actin, NGF1-A binding protein (NAB)-2, Sp1, c-fos, c-jun, GATA-4, and Nkx2.5 than +/+ or +/- mice. alpha-MHC, tubulin, and NAB-1 expression was similar. Isoproterenol (Iso) and phenylephrine (PE) infusion into +/+ and -/- mice increased heart weight, ANF, beta-MHC, skeletal actin, Sp1, NAB-2, c-fos, and c-jun expression, but induction in -/- mice was lower. Only Iso + PE-treated +/+ mice showed induction of NAB-1, GATA-4, and Nkx2.5. Foci of fibrosis were found in Iso + PE-treated -/- and +/+ mice. Surprisingly, vehicle-treated -/- mice displayed fibrosis and increased Sp1, skeletal actin, Nkx2.5, and GATA-4 expression without hypertrophy. Minipump removal caused the agonist-treated hearts and gene expression to regress to control or near-control levels. Thus Egr-1 deficiency caused a blunted catecholamine-induced hypertrophy response and increased sensitivity to stress.

A short region containing an AP-1 binding site is essential for transforming growth factor-beta-induced c-jun gene expression in osteoblastic cells

Transforming growth factor-beta (TGF-beta) is a multifunctional regulatory peptide that elicits different responses in different cell types. Much remains unknown about the pathway of intracellular TGF-beta signal transduction, but TGF-beta is known to induce expression of several genes by way of the transcription factor AP-1. We studied the mechanism that mediates TGF-beta-induced gene expression of c-jun, a component of AP-1, in MC3T3-E1 osteoblastic cells. To map in detail the corresponding responsive elements in the rat c-jun promoter, we generated a series of 5' deletion promoter/luciferase reporter gene constructs. Transient cell transfection assays identified the region located between positions -79 and -59 as being critical for the TGF-beta response and for the basal activity of the promoter. Gel mobility shift assays indicated specific binding of nuclear proteins to this 21-bp region of the c-jun promoter containing an AP-1 binding site. These results show that the AP-1-dependent mechanism is involved in TGF-beta-induced increase of c-jun induction, suggesting positive autoregulation of AP-1.

Activation of immediate early gene, c-fos, and c-jun in the rat small intestine after ischemia/reperfusion

BACKGROUND

Activated immediate early genes (IEGs) play key roles in mediating cellular response after ischemia/reperfusion (I/R) injuries in some organs such as liver, heart and kidney. However, there is no report investigating an association between the activation of IEGs and cellular regeneration or programmed cell death after I/R in small intestine.

METHODS

We examined a sequential expression of c-fos and c-jun after I/R in rat small intestine using reverse transcription-polymerase chain reaction and Northern blot analysis, and compared the patterns with coexistent two parameters: (1) regeneration determined by immunohistochemical detection of proliferating cell nuclear antigen, (2) programmed cell death determined with the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) method and DNA fragmentation.

RESULTS

The expression of c-fos and c-jun mRNA increased markedly 15 min after reperfusion and was, respectively, 6.3 and 4.4 times higher than in controls. Proliferating cell nuclear antigen expression was significantly elevated between 5 min and 4 hr, peaking at 30 min after reperfusion. Apoptosis showed a peak 60 min after reperfusion. Apoptosis after I/R was detected in the nuclei of absorptive epithelial cells by the TUNEL method, and these apoptotic signals were consistent with the expression of c-Fos and c-Jun proteins using an immunohistochemical method.

CONCLUSIONS

These results suggest that overexpression of c-fos and c-jun after I/R in the small intestine correlates with programmed cell death and subsequent cellular regeneration.

c-Src activates the DNA binding and transcriptional activity of Stat3 molecules: serine 727 is not required for transcriptional activation under certain circumstances

Stat3 proteins are constitutively activated in cells transformed by v-Src and the proteins have been shown to interact directly. Subsequent studies have shown that Stat3 is required for cellular transformation of NIH fibroblasts by v-Src, suggesting a potential role for Stat3 in aberrant cell growth. Stat3 is phosphorylated on a single tyrosine (tyrosine 705) which is required for effective dimer formation. An additional phosphorylation event (serine 727) is believed to be required for full transcriptional activity of Stat1 and Stat3 molecules. Here we report that c-Src activates the DNA binding activity of Stat3alpha, Stat3beta, and three Stat3 mutants, one in which serine 727 was replaced by alanine (Stat3alphaS727A) and C-terminal truncated molecules Delta48 and Delta55. Consistent with this finding is a general increase in the tyrosine 705-phosphorylated Stat3 in cells cotransfected with c-Src. Furthermore, transcription from an alpha-2 macroglobulin reporter gene is activated by Stat3alphaS727A to the same magnitude as compared to Stat3alpha and Stat3beta in the presence of c-Src. These results suggest that serine 727, contained in a consensus MAP kinase recognition site and shown to be the only serine in Stat3 phosphorylated in epidermal growth factor (EGF) treated cells, is not necessary for transcriptional activity comparable to wild-type Stat3alpha or Stat3beta when activated by c-Src in COS-7 cells.