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PubMed2000

Tumor necrosis factor alpha inhibits type I collagen synthesis through repressive CCAAT/enhancer-binding proteins.

Extracellular matrix (ECM) formation and remodeling are critical processes for proper morphogenesis, organogenesis, and tissue repair. The proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) inhibits ECM accumulation by stimulating the expression of matrix proteolytic enzymes and by downregulating the deposition of structural macromolecules such as type I collagen. Stimulation of ECM degradation has been linked to prolonged activation of jun gene expression by the cytokine. Here we demonstrate that TNF-alpha inhibits transcription of the gene coding for the alpha2 chain of type I collagen [alpha2(I) collagen] in cultured fibroblasts by stimulating the synthesis and binding of repressive CCAAT/enhancer proteins (C/EBPs) to a previously identified TNF-alpha-responsive element. This conclusion was based on the concomitant identification of C/EBPbeta and C/EBPdelta as TNF-alpha-induced factors by biochemical purification and expression library screening. It was further supported by the ability of the C/EBP-specific dominant-negative (DN) protein to block TNF-alpha inhibition of alpha2(I) collagen but not TNF-alpha stimulation of the MMP-13 protease. The DN protein also blocked TNF-alpha downregulation of the gene coding for the alpha1 chain of type I collagen. The study therefore implicates repressive C/EBPs in the TNF-alpha-induced signaling pathway that controls ECM formation and remodeling.

Amino Acid Sequence↗
PubMed2003

Effect of indocyanine green and illumination on gene expression in human retinal pigment epithelial cells.

PURPOSE: To investigate the biological effects of indocyanine green (ICG) and acute illumination on human retinal pigment epithelial (RPE) cells. METHODS: Three concentrations (0, 0.25, and 2.5 mg/mL) of ICG were applied to ARPE19 cells for 1 minute. After isotonic rinsing, the cells were irradiated with a light beam with a wavelength spectrum from 400 to 800 nm and an output of 1850 lumens for 15 minutes. The cells were collected at timed intervals for the investigation of cell death and expression of stress-response genes by reverse transcription-polymerase chain reaction, immunofluorescence, and Western blot analysis. RESULTS: After ICG incubation, photoreactive changes were observed in the RPE cells. A reduction in cellular viability and considerable shrinkage of the cells were observed. The expressions of the apoptosis-related genes p53 and bax and the cell cycle arrest protein p21 were upregulated in cells treated with both ICG and light. Of the early-response genes, the expression of c-fos was specifically enhanced by light, with additive effects from the presence of ICG. Such stimulatory effects on these gene expressions were greater at 2.5 mg/mL than at 0.25 mg/mL ICG. CONCLUSIONS: ICG in the presence of acute illumination can elicit cell-cycle arrest and even apoptosis in RPE cells. The establishment of a safety level in the application of ICG in the region of 0.25 mg/mL is recommended.

Apoptosis↗
PubMed2003

CD11c gene expression in hairy cell leukemia is dependent upon activation of the proto-oncogenes ras and junD.

Hairy cell leukemia (HCL) is a chronic lymphoproliferative disease, the cause of which is unknown. Diagnostic of HCL is abnormal expression of the gene that encodes the beta2 integrin CD11c. In order to determine the cause of CD11c gene expression in HCL the CD11c gene promoter was characterized. Transfection of the CD11c promoter linked to a luciferase reporter gene indicated that it is sufficient to direct expression in hairy cells. Mutation analysis demonstrated that of predominant importance to the activity of the CD11c promoter is its interaction with the activator protein-1 (AP-1) family of transcription factors. Comparison of nuclear extracts prepared from hairy cells with those prepared from other cell types indicated that hairy cells exhibit abnormal constitutive expression of an AP-1 complex containing JunD. Functional inhibition of AP-1 expressed by hairy cells reduced CD11c promoter activity by 80%. Inhibition of Ras, which represents an upstream activator of AP-1, also significantly inhibited the CD11c promoter. Furthermore, in the hairy cell line EH, inhibition of Ras signaling through mitogen-activated protein kinase/extracellular signal-regulated kinase kinases 1 and 2 (MEK1/2) reduced not only CD11c promoter activity but also reduced both CD11c surface expression and proliferation. Expression in nonhairy cells of a dominant-positive Ras mutant activated the CD11c promoter to levels equivalent to those in hairy cells. Together, these data indicate that the abnormal expression of the CD11c gene characteristic of HCL is dependent upon activation of the proto-oncogenes ras and junD.

Antigens, CD↗
PubMed1995

Glutathione transferase P1-1 expression in human melanoma metastases: correlation to N-RAS mutations and expression.

Expression of the detoxication enzyme glutathione transferase P1-1 (GST P1-1) at elevated levels has been noted in many types of human tumors, including melanomas. The products of the human H-RAS, K-RAS and N-RAS genes play a key role in intracellular signal transduction leading to transcriptional activation of AP-1 (Fos/Jun) responsive genes. The oncogenic mutated forms of the ras proteins are constitutively active and interfere with normal signal transduction. Mutated RAS genes as well as increased expression of wild-type ras proteins are common features in human tumors including melanoma. We have characterized 30 melanoma metastases from 23 melanoma patients with reference to N-RAS expression and mutation as well as to GST P1 expression (immunohistochemistry and genetic analysis). Twenty-three of 30 samples (70%) had high N-Ras p21 and/or N-RAS codon 61 mutations and 18 of these 23 samples also had high GST P1-1 immunoreactivity. Seven of 30 (23%) samples had low N-Ras p21 immunoreactivity and no detectable N-RAS codon 61 mutations. Six of these 7 samples (86%) also had low GST P1-1 immunoreactivity. The results indicate a statistically significant correlation (Spearman correlation coefficient, r = 0.56, p = 0.001, 2-tailed test) and provide, for the first time, indirect evidence for a possible coregulation of N-RAS and GST P1 in human malignant melanoma which should be further evaluated.

Biomarkers, Tumor↗
PubMedDate not supplied

Pref-1, SF-1 and adrenocortical zonation.

The stimulation of the zona glomerulosa phenotype by a low sodium diet is characterised by increased expression of aldosterone synthase accompanied by increases in (pro)renin, bFGF, c-fos and c-jun gene transcription. In contrast ACTH diminishes the specific glomerulosa phenotype. The EGF related transmembrane protein preadipocyte factor 1 (Pref-1) is specifically found in the zona glomerulosa and medulla of the adult rat adrenal as well as being expressed in fetal tissue. In addition the orphan nuclear receptor SF-1/Ad4bp considered to be an important factor in fetal adrenocortical development and differentiation may also have a role in zonal differentiation in the adult. To investigate their roles, adrenals were taken from adult Wistar rats maintained on a low sodium diet or ACTH treated (enhancing or diminishing zona glomerulosa function respectively) and compared with untreated controls. Localisation of Pref-1 was carried out by immunocytochemistry using the polyclonal antibody ZOG (anti Pref-1) and of SF-1 using a rabbit antiserum to SF-1. The experimental treatment resulted in a decrease and increase in Pref-1 expression in ACTH treated and low sodium diet treated rats respectively, in accordance with changes in abundance of glomerulosa cells. SF-1 expression was expected throughout the adrenal cortex, without zonal differentiation, though somewhat decreased by ACTH treatment. Of these two factors, only Pref-1 can be considered to have a role in zonal differentiation.

Adrenal Cortex↗
PubMed1998

Effect of ionizing radiation on wild-type and mutant mouse leukemia L1210 cells.

Wild-type (WT) mouse leukemia L1210 cells express steady-state levels of p53 mRNA and protein. However, the p53 expressed by the wild-type L1210 cells was found to be a mutant form of p53 (relative to normal mouse fibroblast p53 sequence) having a point mutation in the DNA binding domain of p53. A deoxyadenosine-resistant L1210 cell line (Y8) derived from the parental WT cells had previously been shown to lack the expression of p53 but to respond to cycloheximide (CHX) treatment by superinduction of p53 mRNA. The mRNA for p53 induced by CHX had the same sequence as the p53 from normal mouse fibroblasts. Although the Y8 cells had no constitutive levels of p53 mRNA or protein, the Y8 cells expressed constitutive levels of WAF1 mRNA and protein. Gadd45 mRNA was also present in the Y8 cells. Subjecting the WT or Y8 cells to ionizing radiation did not result in a G0/G1 cell cycle block; the cells blocked in G2/M. The Y8 cells were much more sensitive to the irradiation treatment than the WT cells, resulting in marked increases in apoptosis in the Y8 cells. Although radiation treatment induced p53 mRNA, but no p53 protein, in the Y8 cells, WAF1 mRNA was induced in the Y8 cells. These data indicate that there are p53-independent pathway(s) that may still involve WAF1 and Gadd45 with respect to cell cycle control and apoptosis.

Animals↗
PubMed1999

Space flight modulates signal transduction pathway of growth factor receptors in rat osteoblasts.

Bone metabolism is regulated by the balance of bone formation and resorption. Osteoblasts serves primarily for bone formation. Microgravity deteriorates osteoblastic function and inhibit bone formation. Growth factors regulate osteoblast function via receptors. Binding of EGF and PDGF to the receptors activates receptor tyrosine kinase and rapid association of adapter proteins Shc and Grb2, and evokes the Ras/MAP kinase cascade. Signals from various chemical and physical stimuli are transmitted to the nucleus, and induce c-fos and c-jun gene expression. However, effects of microgravity on the molecular events in osteoblasts remain unknown. The purpose of this study is to investigate the mRNA levels for PDGF-beta receptor, EGF receptor, Shc, and c-fos in rat osteoblasts during space flight.

Animals↗
PubMed1992

Stable expression of HB24, a diverged human homeobox gene, in T lymphocytes induces genes involved in T cell activation and growth.

A diverged homeobox gene, HB24, which is known to be induced following lymphocyte activation, was introduced into Jurkat T cells under the control of a constitutive promoter. Stable transfectants of HB24 were established that expressed high levels of HB24 mRNA and possessed an altered phenotype suggestive of activated T cells. A number of genes known to be induced following T cell activation and associated with cell growth were increased in the transfectants, including c-fos, c-myc, c-myb, HLA-DR, lck, NF-kappa B, interleukin-2 and interleukin-2 receptor alpha (IL-2R alpha). Analysis of IL-2R alpha expression by transient transfection of IL-2R alpha promoter constructs into the HB24 transfectants revealed constitutive expression (about 60% of phytohemagglutinin- and phorbol ester-activated Jurkat cells) that was dependent on the kappa B site in the IL-2R alpha promoter. Furthermore, as a consequence of the increased HB24 mRNA levels, the Jurkat HB24 transfectants proliferated more rapidly than control cell lines. Thus, stable expression of HB24 confers an activation phenotype on a human T cell line, implicating this gene as an important transcriptional factor during T cell activation and growth.

Base Sequence↗
PubMed1992

Retinoic acid inhibits interleukin-6-induced macrophage differentiation and apoptosis in a murine hematopoietic cell line, Y6.

We established a radiation-induced murine hematopoietic cell line, Y6, that could be induced to differentiate into macrophages by interleukin-6 (IL-6). IL-6 also induced growth inhibition and apoptosis in Y6 cells. Retinoic acid (RA) inhibited such effects of IL-6 on Y6 cells. The inhibitory effect of RA on the effects of IL-6 was not caused by the downregulation of the IL-6 receptor, because RA neither affected the expression of IL-6 receptor mRNA nor the expression of IL-6 receptor molecule on the cell surface. Furthermore, RA did not inhibit the IL-6-induced expression of junB mRNA, indicating that the expression of functionally active IL-6 receptor and the signal transduction pathway activating the junB gene are not inhibited by RA. IL-6-induced macrophage differentiation of Y6 cells was preceded by the downregulation of the c-myc gene, which was also prevented by RA. Because the inhibitory effect of RA on Y6 cells was reversible and seemed not to require de novo protein synthesis, the RA receptor by itself might be directly involved in the inhibition of the IL-6 signal transduction pathway. The results indicated that the IL-6 signal transduction pathways leading to the induction of macrophage differentiation and junB gene expression can be dissected by RA.

Animals↗
PubMed1994

Signals transduced via insulin-like growth factor I receptor (IGF(R)) mediate resistance to retinoic acid-induced cell growth arrest in a human neuroblastoma cell line.

Retinoic Acid (RA) has been shown to control growth and induce differentiation in a number of human neuroblastoma (NB) cell lines. However, a number of NB cell lines may be termed resistant to RA as they fail to growth arrest and differentiate. In studying the mechanism mediating RA-resistance, we noted that invariably RA-resistant NB cell lines constitutively express Insulin-like Growth Factor 2 (IGF2) (Gaetano, 1991b). The NB cell line LAN-1-15N (15N) represented an interesting model in which to study the development of RA-resistance as initially 15N cells are growth arrested by RA, however with prolonged culture (8-10 days) cells begin to proliferate. Coincidentally, RA induces IGF2 mRNA and protein secretion in 15N NB cells (Matsumoto, 1992). In this study we isolated RA-resistant 15N cell lines and analyzed their growth properties and changes in cell cycle related (cdc2, cdk2, cyclins A, B, D and E) and early response (fos and jun) gene expression to evaluate the role IGF2 may play in mediating RA resistance. We found that exogenous IGF2 stimulates growth in 15N and is capable of altering RA induced inhibition of NB cell growth. Finally we show that by blocking the Insulin-like Growth Factor Receptor (IGF1(R)) with a monoclonal antibody (alpha-IR3) in the presence of RA the growth of RAR cell lines could be completely blocked. These data are consistent with the concept that signals by IGF2 and transduced via the IGF1(R) can mediate resistance to the growth inhibiting properties of RA.

Journal Article↗
PubMed1993

Involvement of immediate-early gene expression in the synergistic effects of steel factor in combination with granulocyte-macrophage colony-stimulating factor or interleukin-3 on proliferation of a human factor-dependent cell line.

Steel factor (SLF) synergizes with granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) to stimulate proliferation of human factor-dependent cell line, MO7e. To elucidate molecular mechanisms underlying this synergism, induction of immediate-early genes was studied. Treatment of MO7e cells with SLF, GM-CSF, and IL-3 induced/enhanced expression of c-fos, junB, egr-1, and c-myc genes. SLF treatment of MO7e cells led to higher expression of c-fos, junB, and egr-1 genes than did treatment with GM-CSF or IL-3. However, GM-CSF and IL-3 had more prolonged effects on enhancement of the c-myc gene than SLF. Using optimal dosages for cell proliferation, induction of c-fos and junB was greater than additive with SLF plus GM-CSF or IL-3, as compared with each factor alone. Using suboptimal amounts of SLF with optimal GM-CSF or IL-3, induction of c-fos, junB, egr-1, and c-myc genes was greater than additive. De novo protein synthesis was not required for greater induction of these immediate-early genes by the combination of SLF plus GM-CSF. Based on nuclear run-on and actinomycin D experiments, the data suggest that the synergistic effects of SLF plus GM-CSF on the induction of immediate-early genes may be mediated in part at the level of transcription and mRNA stabilization for c-fos, at the level of mRNA stabilization for junB, and at the level of transcription for egr-1.

Cell Division↗
PubMed1994

Impairment of ligand binding and growth signaling of mutant IL-2 receptor gamma-chains in patients with X-linked severe combined immunodeficiency.

The IL-2R gamma-chain is an indispensable subunit for the functional IL-2R. Recently, mutations of the gamma-chain have been reported to be closely associated with X-linked severe combined immunodeficiency (XSCID). The present study reveals that three patients with XSCID have three different mutations in the gamma-chain; a point mutation, a two consecutive-base deletion, and lack of the second exon in mRNA. The point mutation that we have detected is C to T, which results in one amino acid substitution of valine for alanine in the extracellular domain of the IL-2R gamma-chain (named AV mutant). The two-base deletion detected causes a frame shift of the coding region in the SH2 subdomain in the cytoplasmic domain (named tSH mutant). Transfection studies performed with the mutant gamma-chains demonstrated that the AV mutant and tSH mutant failed to bind to IL-2 and to transduce growth signals, respectively. These findings indicate that the gamma-chain gene mutations that accompany XSCID induce loss of the gamma-chain function, possibly resulting in stagnation of the differentiation and development of T cells.

Base Sequence↗
PubMed1993

DNA damage, gene expression, growth arrest and cell death.

The sequence of biochemical and molecular events that mediate growth arrest and cell death in tumor cells exposed to agents that induce DNA damage is poorly defined. This commentary exploits the recent explosion of information regarding oncogenes, tumor suppressor genes, and cell-cycle regulatory genes to develop a model for growth arrest/cell death. The model focuses on changes in the expression of these genes, in the level and phosphorylation of their protein products, and in the interaction(s) between these proteins. It is recognized that such a model is, of necessity, incomplete, since new gene functions associated with the cellular response to DNA damage will continuously be uncovered; in addition, the proposed sequence of events will likely require modification as the relationships between the functions of the discrete gene products are clarified. Nevertheless, it is hoped that this commentary will provide a conceptual framework within which to fit currently available information as well as future findings relating to the expression and function of DNA-damage-responsive genes, and that the sections of the model that are incomplete will provide a springboard for the development of research approaches designed to answer specific questions regarding the nature of the cellular response to DNA damage.

Animals↗
PubMed1993

Mitogenic signaling mechanisms of human cementum-derived growth factors.

Cementum-derived growth factor (CGF) is a M(r) 23,000 protein, which is sequestered in the mineralized matrix of tooth cementum. We have investigated the mitogenic signaling reactions induced by CGF using quiescent human gingival fibroblasts as target cells. Cells activated with CGF were compared with those treated with CGF plus epidermal growth factor (EGF) and other growth factors. CGF caused a transient increase in cytoplasmic Ca2+ concentration, and this was accompanied by enhancement of membrane protein kinase C activity, myelin basic protein and S6 kinase activities, inositol phosphate levels, and activation of c-fos and jun-B gene expression. Membranes obtained from cells activated with CGF contained several protein bands, which cross-reacted with antiphosphotyrosine antibody; however, proteins corresponding to a putative phosphorylated CGF receptor were not detected. DNA synthesis induced by CGF was inhibited by 65% in cells treated with pertussis toxin but only 25-29% in cultures exposed to H7 or 12-O-tetradecanoylphorbol-13-acetate; these values were different from those obtained when EGF, PDGF, or fetal bovine serum were used as mitogens. CGF and TGF-beta, but not EGF, caused an increase of PDGF-A chain mRNA expression 4 h after mitogen addition. However, while CGF was mitogenic for gingival fibroblasts, TGF-beta was not. Kinetics of DNA stimulation and experiments with anti-PDGF antibodies indicated that PDGF-A expression does not contribute significantly to CGF-induced DNA synthesis. When the stimulation of various signaling pathways induced by CGF and other growth factors was compared, the pattern of stimulation by CGF was different from other growth factors. The characteristic signaling reactions of CGF are likely to be important components of the mechanisms that regulate the formation and regeneration of cementum and adjacent connective tissues.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Control of liver growth.

The liver is an excellent tissue for the study of growth regulation because of its ability to regenerate by a process of compensatory growth following surgical resection or toxic injury. Much of the investigation on the mechanisms of hepatic growth has been done in partially hepatectomized animals in vivo and in hepatocytes in primary culture. Almost immediately after partial hepatectomy there are major changes in the binding capacity of transcription activators and in the expression of a relatively large number of genes. Many of the immediate early response gene products are themselves transcription activators and thus can multiply and propagate the initial gene activation process. An important issue in the regulation of liver growth is to identify growth factors that may play a role in hepatocyte replication in vivo. In addition to substances that are adjuvants in the mitogenic response at least three growth factors, EGF, TGF alpha, and HGF, are complete mitogens for hepatocytes in culture and appear to play important roles as stimulators of liver growth. We discuss data that indicate that none of these growth factors seems capable of causing a significant increase in DNA synthesis in quiescent hepatocytes in vivo. In contrast, EGF, TGF alpha, and HGF (both the monomer and the heterodimer) increase DNA synthesis in vivo in hepatocytes that have become "competent" to proliferate. We suggest that the competence process involves the activation of transcription factors and protooncogenes, and that during liver regeneration at least some of these changes precede rather than follow growth factor/ligand signaling. The available data suggest that the three growth factors by themselves may not trigger regeneration in strictly quiescent hepatocytes. There is now extensive evidence from work on TGF alpha in developing and regenerating liver as well as studies with transgenic animals to indicate that the factor may act as a cell cycle progression agent. We suggest that "priming" of hepatocytes after partial hepatectomy might have similarities to the widespread activation of genes observed in response to stimuli such as heat shock, ionic imbalances, and changes in redox potentials, and that TGF alpha and also probably the other growth factors act to make primed cells progress through the cycle and undergo DNA synthesis. TGF beta 1 is a potent antagonist to the mitogenic effects of these growth factors on cultured hepatocytes and could be an important factor for terminating the proliferative response of hepatocytes after partial hepatectomy. Although we have moved closer to finding "on" and "off" switches for regeneration, their precise identities and mechanisms remain elusive.

Animals↗