scholarly journals Transcriptional activation by growth hormone of HNF-6-regulated hepatic genes, a potential mechanism for improved liver repair during biliary injury in mice

2008 ◽  
Vol 295 (2) ◽  
pp. G357-G366 ◽  
Author(s):  
Minhua Wang ◽  
Michael Chen ◽  
Guoqiang Zheng ◽  
Barney Dillard ◽  
Mike Tallarico ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Recombinant Adenovirus ◽  
Hepatic Function ◽  
Hepatocyte Proliferation ◽  
Expression Vectors ◽  
Sham Operation ◽  
Duct Ligation ◽  
Liver Repair

Growth hormone (GH) function is mediated through multiple endocrine pathways. In the liver, GH also transcriptionally activates hepatocyte nuclear factor-6 (HNF-6; OC-1), a liver-enriched transcription factor that regulates the expression of genes essential to hepatic function. We hypothesize that GH modulates hepatic function in the normal and injured liver through HNF-6 and HNF-6 target genes. CD1 mice received PBS or GH for the 1-, 7-, and 28-day course of Sham operation or bile duct ligation (BDL). Proliferation-, metabolic-, and profibrotic-specific hepatic functions were assessed with a focus on candidate HNF-6 transcriptional target genes. Confirmation of HNF-6 regulation was done by analysis of target gene expression in liver infected with recombinant adenovirus AdHNF-6 expression vectors. GH administration upregulated HNF-6 expression throughout the course of liver injury. This was associated with increased expression of HNF-6 proliferative target genes cyclin D1 and metabolic gene Cyp7A1 and downregulation of profibrogenic TGFb2R. Hepatic function improved such as enhanced hepatocyte proliferation, higher cholesterol clearance throughout the course of injury, and attenuated fibrogenic response at day 28 of BDL. GH treatment also transcriptionally increased albumin expression in an HNF-6-independent manner. This was associated with enhanced serum albumin levels. In conclusion, the GH/HNF-6 axis is a potential in vivo mechanism underlying GH diverse function in the liver to modulate the liver repair response to BDL.

scholarly journals The Lack of Nrf2 Causes Hepatocyte Dedifferentiation and Reduced Albumin Production in an Experimental Extrahepatic Cholestasis Model

2021 ◽  
Author(s):  
Guo-Ying Wang ◽  
Veronica Garcia ◽  
Joonyong Lee ◽  
Jennifer Yanum ◽  
Huaizhou Jiang ◽  
...  
Keyword(s):  
Epithelial Differentiation ◽  
Hepatocyte Proliferation ◽  
Sham Operation ◽  
Wild Type ◽  
Ductular Reaction ◽  
Extrahepatic Cholestasis ◽  
Liver Size ◽  
Duct Ligation ◽  
Albumin Production ◽  
In The Wild

AbstractThe transcription factor Nrf2 modulates the initiation and progression of a number of diseases including liver disorders. The aim of this study was to evaluate whether Nrf2 mediates hepatic adaptive responses to cholestasis. Wild-type and Nrf2-null mice were subjected to bile duct ligation (BDL) or a sham operation. Various assessments were performed at different days after surgery. Significant genotype-dependent changes in liver size, biliary ductular reaction, hepatocyte proliferation, and fibrotic response were not observed. However, as cholestasis progressed to Day 15 post-BDL, hepatocytes in the wild-type mice exhibited a tendency to dedifferentiate, indicated by the very weak expression of hepatic progenitor markers: CD133 and fibroblast growth factor-inducible 14 (Fn14). During the same period, Nrf2 deficiency augmented this tendency, manifested by higher CD133 expression, earlier, stronger, and continuous induction of Fn14 expression, and markedly reduced albumin production. Remarkably, as cholestasis advanced to the late stage (40 days after BDL), hepatocytes in the wild-type mice exhibited a Fn14+ phenotype and strikingly upregulated the expression of deleted in malignant brain tumor 1 (DMBT1), a protein essential for epithelial differentiation during development. In contrast, at this stage, hepatocytes in the Nrf2-null mice entirely inhibited the upregulation of DMBT1 expression, displayed a strong CD133+/Fn14+ phenotype indicative of severe dedifferentiation, and persistently reduced albumin production. Collectively, our studies revealed that Nrf2 maintains hepatocytes in the differentiated state potentially via the increased activity of the Nrf2/DMBT1 pathway during cholestasis. These findings enable us to gain novel insight into how hepatocytes respond to cholestasis.New and NoteworthyWe found that, when hepatocytes are exposed to cholestasis, they exhibit a tendency of dedifferentiation. In this case, Nrf2 is highly activated to markedly up-regulate the expression of epithelial differentiation gene DMBT1, which potentially prevent hepatocytes from dedifferentiation. Our findings revealed a plastic property of hepatocytes in response to cholestasis and demonstrated a novel Nrf2/DMBT1 pathway likely controlling this property of hepatocytes.

Abstract P257: Isoform-Specific Effects of the Transcription Factor Sister-of-Mammalian Grainyhead on Endothelial Cells and in Vivo

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Arne Mlynek ◽  
Margarete Lukosz ◽  
Martin Graf ◽  
Christoph Winkler ◽  
Judith Haendeler ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Transcription Factor ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Protein Isoforms ◽  
Expression Vectors ◽  
Luciferase Expression ◽  
Reporter System ◽  
Active Transcription

Apoptosis and reduced migratory capacity of human endothelial cells (EC) are hallmarks for the development of atherosclerosis. TNFalpha has been described as one apoptotic stimulus, which is increased during cardiovascular disease. However, recent findings support the hypothesis that TNFalpha can induce survival genes before committing cells to apoptosis. In a screen for anti-apoptotic genes regulated by TNFalpha we have identified the transcription factor Sister-of-Mammalian Grainyhead/Grainyhead-like 3 (SOM/GRHL3). In humans two RNAs are transcribed from the gene, one of which is alternatively spliced, yielding the protein isoforms SOM1 and SOM3, the latter being an N-terminally truncated version. We have found that both isoforms are expressed in EC. Since nothing is known about the function of these proteins in EC, we investigated their functional properties and role in migration and apoptosis. To analyze their transcription factor activity we established a SOM-dependent reporter system by inserting tandem SOM binding sites and corresponding mutants upstream of a minimal promoter driving luciferase expression. To assess transcriptional activation by SOM1 and SOM3 we cotransfected these reporters with expression vectors for both proteins. In contrast to previously published work, in which isolated SOM domains fused to a Gal4 DNA binding domain were used, we found that both full length proteins are active transcription factors. We next investigated the influence of SOM1 and SOM3 on EC functions. Surprisingly, overexpression of isoform 1 induced migration and inhibited apoptosis, whereas isoform 3 had opposite effects. Along the same lines, SOM1, but not SOM3 activated endothelial nitric oxide synthase and Akt. To investigate whether these isoforms have different functions also in vivo, we overexpressed them in zebrafish embryos. SOM3 but not SOM1 overexpression led to increased lethality, a strong reduction in normal phenotype and a 10 fold higher frequency in heavy deformations. The effects observed on EC migration and apoptosis as well as on zebrafish development suggest that these isoforms activate different sets of target genes, which we are currently identifying by microarray analysis.

scholarly journals Rearranged NFKB-2 genes in lymphoid neoplasms code for constitutively active nuclear transactivators.

1995 ◽  
Vol 15 (9) ◽  
pp. 5180-5187 ◽  
Author(s):  
C C Chang ◽  
J Zhang ◽  
L Lombardi ◽  
A Neri ◽  
R Dalla-Favera
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Heterologous Protein ◽  
Chromosomal Rearrangements ◽  
Expression Vectors ◽  
Nf Kappa B ◽  
Lymphoid Neoplasms ◽  
Related Transcription Factor ◽  
Functional Consequences

The NFKB-2 gene codes for an NF-kappa B-related transcription factor containing rel-polyG-ankyrin domains. Chromosomal rearrangements of the NFKB-2 locus have been found in various types of lymphoid neoplasms, suggesting that they may contribute to lymphomagenesis. Rearrangements cluster within the 3'-terminal ankyrin-encoding domain of the NFKB-2 gene and lead to the production of C-terminally truncated proteins which, in some cases, are fused to heterologous protein domains. In order to determine the functional consequences of these alterations, we have analyzed the subcellular localization, DNA binding, and transcriptional activity of two representative tumor-associated mutants in which the ankyrin domain is either terminally truncated (NFKB-2p85) or truncated and joined to an out-of-frame immunoglobulin C alpha domain (lyt-10C alpha). Immunofluorescence studies performed on cells transfected with p85 or lyt-10C alpha expression vectors showed that both the abnormal proteins were constitutively localized in the nucleus. Immunoprecipitation analysis of UV-cross-linked DNA-protein adducts showed that p85 can bind kappa B sites in its unprocessed form. Cotransfection of p85 or lyt-10C alpha expression vectors with kappa B-driven reporter plasmids showed that both p85 and lyt-10C alpha have retained the ability to mediate transcriptional activation via heterodimerization with Rel-Ap65 but have lost the transrepression activity associated with homodimeric DNA binding. Furthermore, both p85 and lyt-10C alpha were capable of independent transactivation of kappa B-reporter genes and this activity could not be further stimulated by Bcl-3. These abnormal proteins may contribute to lumphomagenesis by determining a constitutive activation of the NF-kappa B system and, in particular, of NFKB-2 target genes.

A new method for the experimental induction of secundary biliary cirrhosis in wistar rats

2001 ◽  
Vol 16 (2) ◽  
pp. 75-81 ◽  
Author(s):  
Gracinda De Lourdes Jorge ◽  
Luiz Sergio Leonardi ◽  
Ilka de Fatima Santana Ferreira Boin ◽  
Orlando de Castro e Silva Jr ◽  
Cecilia Amelia Fazzio Escanhoela
Keyword(s):  
Bile Duct ◽  
Morphological Study ◽  
Wistar Rats ◽  
Hepatic Duct ◽  
Control Group ◽  
Sham Operation ◽  
Biliary Cirrhosis ◽  
Technical Failure ◽  
Duct Obstruction ◽  
Duct Ligation

The aim of this study was to describe a method for the induction of experimental secondary biliary fibrosis (SBF). Forty-seven Wistar rats were submitted to hepatic duct obstruction (OB group) for thirty days without ligature, section or cannulization causing interruption of biliary flow. This technique was carried out by simple traction of the bile duct passing it through the xiphoid appendix. Nine rats were submitted to a sham operation for bile duct stricture and seven rats comprised the control group. Blood samples were collected for the measurement of total bilirubin (TB), alkaline phosphatase (AP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Liver fragments were removed for morphological study. Thirty days after surgery TB, AP, ALT and AST levels were significantly increased in the hepatic duct ligation group compared to the sham operated group and the presence of SBF in the OB group was confirmed by morphological study of the liver. There was technical failure in 31.92% cases. The survival was 100% at fifteen days and 82.97% at the end of the experiment. We concluded that this simple surgical technique may be used to study the consequence of bile duct obstruction which could be a reversible process depending on the obstruction time. This technique can be carried out from cholestasis to fibrosis.

scholarly journals The Non-Canonical Aspects of MicroRNAs: Many Roads to Gene Regulation

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1465 ◽  
Author(s):  
Christiaan J. Stavast ◽  
Stefan J. Erkeland
Keyword(s):  
Rna Polymerase Ii ◽  
Transcriptional Activation ◽  
Small Rnas ◽  
Target Genes ◽  
Biological Functions ◽  
Rnase Iii ◽  
Mrna Targets ◽  
Argonaute Proteins ◽  
Epigenetic Modifiers ◽  
Encoding Genes

MicroRNAs (miRNAs) are critical regulators of gene expression. As miRNAs are frequently deregulated in many human diseases, including cancer and immunological disorders, it is important to understand their biological functions. Typically, miRNA-encoding genes are transcribed by RNA Polymerase II and generate primary transcripts that are processed by RNase III-endonucleases DROSHA and DICER into small RNAs of approximately 21 nucleotides. All miRNAs are loaded into Argonaute proteins in the RNA-induced silencing complex (RISC) and act as post-transcriptional regulators by binding to the 3′- untranslated region (UTR) of mRNAs. This seed-dependent miRNA binding inhibits the translation and/or promotes the degradation of mRNA targets. Surprisingly, recent data presents evidence for a target-mediated decay mechanism that controls the level of specific miRNAs. In addition, several non-canonical miRNA-containing genes have been recently described and unexpected functions of miRNAs have been identified. For instance, several miRNAs are located in the nucleus, where they are involved in the transcriptional activation or silencing of target genes. These epigenetic modifiers are recruited by RISC and guided by miRNAs to specific loci in the genome. Here, we will review non-canonical aspects of miRNA biology, including novel regulators of miRNA expression and functions of miRNAs in the nucleus.

Early increase in pulsatile growth hormone release after unilateral nephrectomy in adult rats

1994 ◽  
Vol 266 (4) ◽  
pp. F628-F632 ◽  
Author(s):  
A. Haramati ◽  
M. D. Lumpkin ◽  
S. E. Mulroney
Keyword(s):  
Growth Hormone ◽  
Early Time ◽  
Peak Level ◽  
Unilateral Nephrectomy ◽  
Sham Operation ◽  
Renal Growth ◽  
Adult Rats ◽  
Compensatory Renal Growth ◽  
Jugular Veins ◽  
Hypertrophic Response

Removal of one kidney results, within days, in accelerated growth of the remaining kidney. However, the mechanisms that underlie this compensatory renal hypertrophic response, particularly in the early time period following nephrectomy, are not understood. In this study we tested the hypothesis that removal of one kidney leads to a change in the pulsatile release of growth hormone (GH), which facilitates compensatory renal growth. Adult Wistar rats were implanted with Silastic cannulas in jugular veins and underwent either unilateral nephrectomy (UNX) or sham operation. Plasma levels of GH were determined 24 and 48 h after sham operation or UNX. Blood samples were taken every 20 min over a 6-h period from conscious, unrestrained animals. Pulsatile GH release was markedly elevated 24 h after UNX in both the amplitude of the surges as well as in the duration of release. Peak GH levels after 24 h were three- to fourfold higher in UNX rats compared with sham controls (417 +/- 75 vs. 119 +/- 23 ng/ml, P < 0.05). However, this enhanced release of GH appeared to be of short duration and began declining by 48 h post-UNX (peak level of 227 +/- 37 ng/ml, P < 0.05 vs. both 24 h UNX and sham controls). To examine whether this rise in GH release post-UNX contributed to the compensatory renal growth, rats underwent UNX and were immediately treated with an antagonist to GH-releasing factor (GRF-AN; i.e., [N-Ac-Tyr1,D-Arg2]GRF-(1-29) amide, 200 micrograms/kg twice daily), and the effects on GH release and renal growth were determined. Administration of GRF-AN significantly suppressed the increase in GH release post-UNX and was associated with a significant attenuation in renal growth 48 h post-UNX in GRF-AN-treated rats (8.7 +/- 2.6% vs. 22.7 +/- 3.0% in UNX controls, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Glucocorticoid Receptor Phosphorylation Differentially Affects Target Gene Expression

2008 ◽  
Vol 22 (8) ◽  
pp. 1754-1766 ◽  
Author(s):  
Weiwei Chen ◽  
Thoa Dang ◽  
Raymond D. Blind ◽  
Zhen Wang ◽  
Claudio N. Cavasotto ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Transcriptional Activation ◽  
Leucine Zipper ◽  
Target Genes ◽  
Divalent Cations ◽  
Phosphorylation Site ◽  
Transcriptional Response ◽  
Receptor Occupancy ◽  
Wild Type ◽  
Interacting Protein

Abstract The glucocorticoid receptor (GR) is phosphorylated at multiple sites within its N terminus (S203, S211, S226), yet the role of phosphorylation in receptor function is not understood. Using a range of agonists and GR phosphorylation site-specific antibodies, we demonstrated that GR transcriptional activation is greatest when the relative phosphorylation of S211 exceeds that of S226. Consistent with this finding, a replacement of S226 with an alanine enhances GR transcriptional response. Using a battery of compounds that perturb different signaling pathways, we found that BAPTA-AM, a chelator of intracellular divalent cations, and curcumin, a natural product with antiinflammatory properties, reduced hormone-dependent phosphorylation at S211. This change in GR phosphorylation was associated with its decreased nuclear retention and transcriptional activation. Molecular modeling suggests that GR S211 phosphorylation promotes a conformational change, which exposes a novel surface potentially facilitating cofactor interaction. Indeed, S211 phosphorylation enhances GR interaction with MED14 (vitamin D receptor interacting protein 150). Interestingly, in U2OS cells expressing a nonphosphorylated GR mutant S211A, the expression of IGF-binding protein 1 and interferon regulatory factor 8, both MED14-dependent GR target genes, was reduced relative to cells expressing wild-type receptor across a broad range of hormone concentrations. In contrast, the induction of glucocorticoid-induced leucine zipper, a MED14-independent GR target, was similar in S211A- and wild-type GR-expressing cells at high hormone levels, but was reduced in S211A cells at low hormone concentrations, suggesting a link between GR phosphorylation, MED14 involvement, and receptor occupancy. Phosphorylation also affected the magnitude of repression by GR in a gene-selective manner. Thus, GR phosphorylation at S211 and S226 determines GR transcriptional response by modifying cofactor interaction. Furthermore, the effect of GR S211 phosphorylation is gene specific and, in some cases, dependent upon the amount of activated receptor.

scholarly journals In vitro expression of long and short ovine prolactin receptors: activation of Jak2/STAT5 pathway is not sufficient to account for prolactin signal transduction to the ovine beta-lactoglobulin gene promoter

1999 ◽  
Vol 23 (2) ◽  
pp. 125-136 ◽  
Author(s):  
C Bignon ◽  
N Daniel ◽  
L Belair ◽  
J Djiane
Keyword(s):  
Tyrosine Phosphorylation ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Gene Promoter ◽  
Janus Kinase ◽  
Prolactin Receptors ◽  
Milk Protein Gene ◽  
Prolactin Signaling ◽  
Beta Lactoglobulin

The recent finding that sheep had long (l-oPRLR) and short (s-oPRLR) prolactin receptors provided new tools to further explore prolactin signaling to target genes. Here we used CHO cells transfected with l-oPRLR or s-oPRLR cDNAs to compare the activation of known key steps of prolactin signaling by the two receptors. We found that prolactin stimulated l-oPRLR tyrosine phosphorylation, although it lacked the last tyrosine residue found in other long prolactin receptors. In addition, l-oPRLR and s-oPRLR both responded to prolactin stimulation by (1) Janus kinase 2 (Jak2) tyrosine phosphorylation, (2) DNA-binding activation of signal transducer and activator of transcription 5 (STAT5), (3) stimulation of transcription from a promoter made of six repeats of STAT5-responsive sequence. However, although it contains STAT5-binding consensus sequences, the ovine beta-lactoglobulin promoter (-4000 to +40) was transactivated by l-oPRLR, but not by s-oPRLR. Taken together, our results indicate that activation of Jak2/STAT5 pathway alone is not sufficient to account for prolactin-induced transcription of this milk protein gene, and that sequences of its promoter, other than STAT5-specific sequences, account for the opposite transcriptional activation capabilities of l-oPRLR and s-oPRLR.

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