Sequence of the 5' regulatory domain of the gene encoding the rat beta 2-adrenergic receptor

Transcription Factor E2F1 Regulates the Expression of ADRB2

Adrenergic beta-2-receptor (ADRB2) is highly expressed in various tissue cells, affecting the susceptibility, development, and drug efficacy of diseases such as bronchial asthma and malignant tumor. However, the transcriptional regulatory mechanism of the human ADRB2 gene remains unclear. This study aimed to clarify whether E2F transcription factor 1 (E2F1) was involved in the transcriptional regulation of the human ADRB2 gene. First, the 5' flanking region of the human ADRB2 gene was cloned, and its activity was detected using A549 and BEAS-2B cells. Second, it was found that the overexpression of E2F1 could increase promoter activity by a dual-luciferase reporter gene assay. In contrast, treatment of knockdown of E2F1 significantly resulted in a decrease in its promoter activity. Moreover, mutation of the binding site of E2F1 greatly reduced the potential of human ADRB2 promoter transcriptional activity to be regulated by E2F1 overexpression and knockdown. Additionally, by real-time quantitative PCR and Western blot analysis, we demonstrated that overexpression of E2F1 elevated the ADRB2 mRNA expression and protein levels while si-E2F1 reduced its expression. Finally, the consequence of the chromatin immunoprecipitation assay showed that E2F1 was able to bind to the promoter region of ADRB2 in vivo. These results confirmed that E2F1 upregulated the expression of the human ADRB2 gene.

Prostate gland as a target organ of thyroid hormones: advances and controversies

Thyroid hormones (THs) are involved in the development and function of the male reproductive system, but their effects on the prostate have been poorly studied. This work reviews studies related to the interrelationship between the thyroid and the prostate. The information presented here is based upon bibliographic searches in PubMed using the following search terms: prostate combined with thyroid hormone or triiodothyronine, thyroxine, hypothyroidism, hyperthyroidism, or deiodinase. We identified and searched 49 articles directly related to the issue, and discarded studies related to endocrine disruptors. The number of publications has grown in the last 20 years, considering that one of the first studies was published in 1965. This review provides information based on in vitro studies, murine models, and clinical protocols in patients with thyroid disorders. Studies indicate that THs regulate different aspects of growth, metabolism, and prostate pathology, whose global effect depends on total and/or free concentrations of THs in serum, local bioavailability, and the endocrine androgen/thyronine context.

Identification of a Novel Function of Resveratrol and Genistein as a Regulator of β2 -Adrenergic Receptor Expression in Skeletal Muscle Cells and Characterization of Promoter Elements Required for Promoter Activation

SCOPE

Modulating β₂ -adrenergic receptor (β₂ -AR) expression and activation is important for maintaining skeletal muscle function. In this study, two food factors, resveratrol (RSV) and genistein (GEN), that are able to regulate β₂ -AR promoter activity and may improve skeletal muscle function are identified.

METHODS AND RESULTS

Using luciferase reporter assay, 357 functional food factors as candidates for β₂ -AR promoter activity have been screened and subsequently RSV and GEN increase β₂ -AR promoter activity and β₂ -AR mRNA expression. Using promoter sequence analysis, it is shown that the CCAAT box and the GC box on the β₂ -AR promoter are required for the regulation of β₂ -AR expression by RSV or GEN. It is also ascertained that transcription factor NF-YA binds to the CCAAT box on the β₂ -AR promoter and that the amount of NF-YA bound to the CCAAT box is unchanged by RSV or GEN treatment. Finally, it is confirmed that a GEN-containing diet increases β₂ -AR expression in mouse skeletal muscle and increased skeletal muscle mass.

CONCLUSIONS

The findings show that food-derived molecules have the potential to influence skeletal muscle mass and function by regulating G protein-coupled receptor expression.

Epigenetic and gene expression changes related to transgenerational carcinogenesis

Transgenerational carcinogenesis refers to transmission of cancer risk to the untreated progeny of parents exposed to carcinogens before mating. Accumulated evidence suggests that the mechanism of this process is epigenetic, and might involve hormonal and gene expression changes in offspring. To begin to test this hypothesis, we utilized a mouse model (NIH Swiss) in which exposure of fathers to Cr(III) chloride 2 wk before mating can alter incidence of neoplastic and nonneoplastic changes in offspring tissues. Utilizing a MS-RDA approach, we found that the sperm of these fathers had a significantly higher percentage of undermethylated copies of the 45S ribosomal RNA gene (rRNA); this finding was confirmed by bisulfite sequencing. Because gene methylation is a known mechanism of expression control in germ cells, and ribosomal RNA levels have been linked to cancer, these findings are consistent with the hypothesis. Secondly, we observed that offspring of Cr(III)-treated fathers were significantly heavier than controls, and had higher levels of serum T3. Possible effects of T3 levels on gene expression in the offspring were examined by microarray analysis of cDNAs from liver. A total of 58 genes, including 25 named genes, had expression ratios that correlated significantly with serum T3 ratios at P </= 0.001. Some of these genes have potential roles in growth and/or tumor suppression. These results also support the hypothesis of an epigenetic and/or gene expression-based mechanism for transgenerational carcinogenesis. Published 2004 Wiley-Liss, Inc.

Identification of a glucocorticoid response element in the rat beta2-adrenergic receptor gene

Regulation of beta2-adrenergic receptor (beta2AR) levels by glucocorticoids is a physiologically important mechanism for altering beta2AR responsiveness. Glucocorticoids increase beta2AR density by increasing the rate of beta2AR gene transcription, but the cis-elements involved have not been well characterized. We now show that one of six potential glucocorticoid response elements (GREs) in the 5'-flanking region of the rat beta2AR gene is necessary for glucocorticoid-dependent stimulation of receptor gene expression. Using a nested set of deletion fragments of the rat beta2AR gene 5'-flanking region fused to a luciferase reporter gene, glucocorticoid-dependent induction of reporter gene expression in HepG2 cells was localized to a region between positions -643 and -152, relative to the transcription initiation site. In electrophoretic mobility shift assays, a double-stranded oligonucleotide incorporating a near-consensus GRE from this region (positions -379 to -365) formed complexes with the human recombinant glucocorticoid receptor, as well as with nuclear protein from dexamethasone-treated HepG2 cells. Mutation of a single base within this GRE sequence greatly diminished interaction of the mutated oligonucleotide with the human recombinant glucocorticoid receptor. The functional activity of the GRE was characterized using a luciferase reporter construct driven by a minimal thymidine kinase promoter. In HepG2 cells transfected with constructs containing the GRE, dexamethasone increased reporter gene expression approximately 3-fold, whereas a dexamethasone effect was not observed with constructs lacking the GRE. Taken together, these findings show that a GRE located at positions -379 to -365 in the 5'-flanking region of the rat beta2AR gene mediates glucocorticoid stimulation of beta2AR gene transcription.

Agonistic anti-beta1-adrenergic receptor autoantibodies from cardiomyopathy patients reduce the beta1-adrenergic receptor expression in neonatal rat cardiomyocytes

BACKGROUND

Autoantibodies directed against the beta1-adrenergic receptor have been described in patients with dilated cardiomyopathy. These autoantibodies exert an agonistic, chronotropic effect on spontaneously beating cultured neonatal rat cardiomyocytes. We studied the effect of such antibodies on beta1-adrenergic receptor expression.

METHODS AND RESULTS

Cardiomyocytes were incubated with either the beta-adrenergic agonist isoproterenol or autoantibodies for 72 hours. beta-Adrenergic receptor expression was studied on the mRNA level with semiquantitative reverse transcription-polymerase chain reaction and on the protein level with immunoblotting. Isoproterenol downregulated both mRNA and beta1- and beta2-adrenergic receptor protein subtypes, whereas the anti-beta1-adrenergic receptor autoantibodies decreased only the beta1-adrenergic receptor mRNA and protein. Long-term incubation of cultured cardiomyocytes with isoproterenol or the anti-beta1-adrenergic receptor autoantibodies reduced the acute stimulatory effect of isoproterenol on the myocytes. These effects were prevented by incubating the cells with isoproterenol in the presence of propranolol or with anti-beta1-adrenergic receptor autoantibodies in the presence of bisoprolol. Bisoprolol also abolished the reduction of the beta1-adrenergic receptor expression caused by longer-term incubation with isoproterenol and the autoantibodies.

CONCLUSIONS

We conclude that after longer-term treatment with the anti-beta1-adrenergic receptor autoantibodies, the rat cardiomyocytes showed a beta-adrenergic receptor expression similar to that observed in failing hearts from patients with dilated cardiomyopathy.

Protein kinase C-mediated down-regulation of beta1-adrenergic receptor gene expression in rat C6 glioma cells

In the current study, we investigated the mechanism by which protein kinase C (PKC) regulates the expression of beta1-adrenergic receptor (beta1AR) mRNA in rat C6 glioma cells. Exposure of the cells to 4beta-phorbol-12-myristate-13-acetate (PMA), an activator PKC, resulted in a down-regulation of both beta1AR binding sites and mRNA levels in a time- and concentration-dependent manner. This effect was not observed with phorbol esters that do not activate PKC and was blocked by bisindolylmaleimide, a specific PKC inhibitor. Activation of PKC did not reduce the half-life of beta1AR mRNA but significantly decreased the activity of the beta1AR promoter, as determined by reporter analysis. A putative response element, with partial homology to a consensus cAMP response element, was identified by mutation analysis of the promoter at positions -343 to -336, relative to the translational start site. Mutation of this putative regulatory element, referred to as a beta1AR-PKC response element, completely blocked the PKC-mediated down-regulation of beta1AR promoter activity. Gel mobility shift analysis detected two specific bands when C6 cell extracts were incubated with a labeled DNA probe containing the beta1AR-PKC response element sequence. Formation of one of these bands was inhibited by an oligonucleotide probe containing a consensus CRE and disrupted by an antibody for cAMP response element binding protein. Based on these studies, we propose that the PKC-induced down-regulation of beta1AR gene transcription in C6 cells is mediated in part by a cAMP response element binding protein-dependent mechanism acting on a novel response element.

Transcription of the beta2-adrenergic receptor gene in rat liver is regulated during early postnatal development by an upstream repressor element

As early postnatal development of the male rat proceeds, there is a decline in transcription of the beta2-adrenergic receptor gene in liver which is associated with a decline in beta2-adrenergic receptor mediated glucose mobilization. In this study, primary cultures of rat hepatocytes transiently transfected with fusion genes containing various segments of beta2-adrenergic receptor gene 5'-flanking DNA fused to a promoterless luciferase reporter gene were used to identify genetic elements that might control beta2-adrenergic receptor gene expression during the first 10 days of postnatal life. We found that 261 bp of beta2-adrenergic receptor gene 5'-flanking region (-372 to -95, start of translation is +1) was sufficient to direct high luciferase expression in fetal day 18 hepatocytes and therefore included the beta2-adrenergic receptor gene promoter. Luciferase activities in fetal day 18 hepatocytes transfected with pbeta2AR(-372/-95), pbeta2AR(-1,335/-95) and pbeta2AR(-3,349/-95) were fourfold greater than that in either postnatal day 5 or postnatal day 10 hepatocytes transfected with the same fusion genes. By use of gel mobility shift assays, we observed increased protein binding to a 50 bp segment (-372 to -323) of the beta2-adrenergic receptor gene 5'-flanking region with nuclear extracts prepared from postnatal day 5 and postnatal day 10 hepatocytes compared to fetal day 18 hepatocytes. These findings suggest the presence of a regulatory element in the 5'-flanking region of the beta2-adrenergic receptor gene that appears to be involved in suppression of transcription of the beta2-adrenergic receptor gene in liver during early postnatal development.

Beta-adrenoceptor-mediated effects in rat cultured thymic epithelial cells

1. Sympathetic nerves were visualized in sections from rat thymus by immunostaining of tyrosine hydroxylase, the rate-limiting enzyme of catecholamine biosynthesis, and by glyoxylic acid-induced fluorescence of catecholamines. Catecholaminergic nerve fibres were detected in close connection to thymic epithelial cells which therefore might be preferred target cells. To evaluate this, rat immunocytochemically defined, cultured thymic epithelial cells were investigated for adrenoceptors and adrenergic effects. 2. In rat cultured thymic epithelial cells mRNA for beta 1- and beta 2-adrenoceptors was detected by reverse transcription-polymerase chain reaction by use of sequence-specific primers. Specific, saturable binding to the cultivated cells was observed with the beta-adrenoceptor agonist CGP 12177. 3. Adrenaline, noradrenaline or the beta-adrenoceptor agonist, isoprenaline, increased intracellular adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels in cultivated thymic epithelial cells dose-dependently about 25 fold. The pharmacological properties revealed that this response was mediated by receptors of the beta 1- and the beta 2-subtypes. The selective beta 3-adrenoceptor agonist BRL 37344 had no effect on cyclic AMP levels. The increase in cyclic AMP was downregulated by preincubation with glucocorticoids like dexamethasone or cortisol which also changed the relative importance of beta 1-/beta 2-adrenoceptors to the response. 4. Incubation with isoprenaline or the adenylate cyclase activator forskolin decreased basal and serum-stimulated proliferation of thymic epithelial cells. However, adrenergic stimulation of thymic epithelial cells did not induce interleukin 1 production. Since thymic epithelial cells create a microenvironment which influences the maturation and differentiation of thymocytes to T-lymphocytes, their observed capacity to respond to catecholamines provides novel evidence for the suggestion that adrenergic stimulation may interfere with the regulation of immune functions.

Structural and functional analysis of the 5'-flanking region of the rat beta 2-adrenergic receptor gene

We have analyzed 3.4 kb of DNA from the 5'-flanking region of the rat beta 2-adrenergic receptor gene and assessed its promoter activity in A549 cells, a human lung adenocarcinoma cell line. A single transcription start site was identified approx. 223 bp upstream of the ATG start codon. A549 cells were transfected with luciferase reporter plasmids containing segments of the rat beta 2-adrenergic receptor 5'-flanking region. Our results suggest that both positive and negative cis-acting regulatory sequences are present in the 5'-flanking region of the rat beta 2-adrenergic receptor gene.