scholarly journals Telomerase activity in primary cultures of normal adrenocortical cells

2001 ◽  
Vol 170 (3) ◽  
pp. 677-684 ◽  
Author(s):  
T Suwa ◽  
L Yang ◽  
PJ Hornsby
Keyword(s):  
Primary Culture ◽  
Adrenal Cortex ◽  
Cell Cultures ◽  
Primary Cultures ◽  
Telomerase Activity ◽  
Adrenocortical Cell ◽  
Isolated Cells ◽  
Adrenocortical Cells ◽  
Human Telomerase Reverse Transcriptase ◽  
In Cells

Telomerase activity was measured in isolated cells from bovine and human adrenal cortex, in cells in primary culture, in cells in later passages in culture, and in cells genetically modified by expression of hTERT (human telomerase reverse transcriptase). Telomerase activity in freshly isolated bovine adrenocortical cells and in human adrenal cells from donors of various ages (6-79 years) was very low or undetected. However, primary bovine adrenocortical cell cultures were strongly positive for telomerase activity, and primary human adrenocortical cell cultures were weakly positive. Both cell types proliferate in primary culture but proliferation of bovine cells is much more vigorous. When primary bovine cells were subcultured to make successively secondary and tertiary cultures, telomerase activity declined strongly, and was undetected by the third passage. There was only a slight decrease in growth rate over this period. Levels of the telomerase RNA component did not change with passage number when assessed by semi-quantitative competitive RT-PCR. When both bovine and human cells were infected with a retrovirus encoding hTERT, telomerase activity in the cells was very high. We conclude that in the adrenal cortex, as in some other tissues, TERT expression is regulated and upregulation of telomerase activity is associated with rapid proliferation in primary culture. Telomerase activity is not maintained, and introduction of TERT is required for stable telomerase activity and for immortalization.

Contact behaviour during the reassociation of dissociated epithelial cells in primary culture

1987 ◽  
Vol 88 (4) ◽  
pp. 521-526
Author(s):  
R.M. Brown ◽  
C.A. Middleton
Keyword(s):  
Epithelial Cells ◽  
Chick Embryo ◽  
Primary Culture ◽  
Cell Cultures ◽  
Corneal Epithelium ◽  
Time Lapse ◽  
Cell Types ◽  
Epidermal Cells ◽  
Isolated Cells ◽  
Contact Behaviour

The behaviour in culture of dissociated epithelial cells from chick embryo pigmented retina epithelium (PRE), corneal epithelium (CE) and epidermis has been studied using time-lapse cinematography. The analysis concentrated on the contact behaviour of 60 previously isolated cells of each type during a 24 h period starting 3.5 h after the cells were plated out. During the period analysed the number of isolated cells in cultures of all three types gradually decreased as they became incorporated into islands and sheets of cells. However, there were significant differences in behaviour between the cell types during the establishment of these sheets and islands. In PRE cell cultures, islands of cells developed because, throughout the period of analysis, collisions involving previously isolated cells almost invariably resulted in the development of a stable contact. Once having established contact with another cell these cells rarely broke away again to become reisolated. In contrast the contacts formed between colliding CE and epidermal cells were, at least initially, much less stable and cells of both these types were frequently seen to break away and become reisolated after colliding with other cells. Sheets and islands of cells eventually developed in these cultures because the frequency with which isolated cells become reisolated decreased with increasing time in culture. The possible reasons underlying the different behaviour of PRE cells, when compared with that of CE and epidermal cells, are discussed. It is suggested that the decreasing tendency of isolated CE and epidermal cells to become reisolated may be related to the formation of desmosomes.

scholarly journals Derepression of hTERT gene expression promotes escape from oncogene-induced cellular senescence

2016 ◽  
Vol 113 (34) ◽  
pp. E5024-E5033 ◽  
Author(s):  
Priyanka L. Patel ◽  
Anitha Suram ◽  
Neena Mirani ◽  
Oliver Bischof ◽  
Utz Herbig
Keyword(s):  
Dna Damage ◽  
Cancer Progression ◽  
Ectopic Expression ◽  
Telomerase Activity ◽  
Early Event ◽  
Telomere Dysfunction ◽  
Telomeric Dna ◽  
Human Telomerase Reverse Transcriptase ◽  
Htert Gene ◽  
In Cells

Oncogene-induced senescence (OIS) is a critical tumor-suppressing mechanism that restrains cancer progression at premalignant stages, in part by causing telomere dysfunction. Currently it is unknown whether this proliferative arrest presents a stable and therefore irreversible barrier to cancer progression. Here we demonstrate that cells frequently escape OIS induced by oncogenic H-Ras and B-Raf, after a prolonged period in the senescence arrested state. Cells that had escaped senescence displayed high oncogene expression levels, retained functional DNA damage responses, and acquired chromatin changes that promoted c-Myc–dependent expression of the human telomerase reverse transcriptase gene (hTERT). Telomerase was able to resolve existing telomeric DNA damage response foci and suppressed formation of new ones that were generated as a consequence of DNA replication stress and oncogenic signals. Inhibition of MAP kinase signaling, suppressing c-Myc expression, or inhibiting telomerase activity, caused telomere dysfunction and proliferative defects in cells that had escaped senescence, whereas ectopic expression of hTERT facilitated OIS escape. In human early neoplastic skin and breast tissue, hTERT expression was detected in cells that displayed features of senescence, suggesting that reactivation of telomerase expression in senescent cells is an early event during cancer progression in humans. Together, our data demonstrate that cells arrested in OIS retain the potential to escape senescence by mechanisms that involve derepression of hTERT expression.

Protein kinase C-induced activin A switches adrenocortical steroidogenesis to aldosterone by suppressing CYP17A1 expression

2013 ◽  
Vol 305 (6) ◽  
pp. E736-E744 ◽  
Author(s):  
Johannes Hofland ◽  
Jacobie Steenbergen ◽  
Leo J. Hofland ◽  
Peter M. van Koetsveld ◽  
Marco Eijken ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Adrenal Cortex ◽  
Cell Lines ◽  
Cell Cultures ◽  
Activin A ◽  
Type I ◽  
Adrenocortical Cell ◽  
Adrenal Cell ◽  
Kinase C

Functional zonation of the adrenal cortex is a consequence of the zone-specific expression of P450c17 ( CYP17A1) and its cofactors. Activin and inhibin peptides are differentially produced within the zones of the adrenal cortex and have been implicated in steroidogenic control. In this study, we investigated whether activin and inhibin can function as intermediates in functional zonation of the human adrenal cortex. Activin A suppressed CYP17A1 expression and P450c17 function in adrenocortical cell lines as well as in primary adrenal cell cultures. Inhibin βA-subunit mRNA and activin A protein levels were found to be increased up to 1,900-fold and 49-fold, respectively, after protein kinase C (PKC) stimulation through PMA or angiotensin II in H295R adrenocortical carcinoma cells. This was confirmed in HAC15 cells and for PMA in primary adrenal cell cultures. Both PMA and Ang II decreased CYP17A1 expression in the adrenocortical cell lines, whereas PMA concurrently suppressed CYP17A1 levels in the primary cultures. Inhibition of activin signaling during PKC stimulation through silencing of the inhibin βA-subunit or blocking of the activin type I receptor opposed the PMA-induced downregulation of CYP17A1 expression and P450c17 function. In contrast, PKA stimulation through adrenocorticotrophin or forskolin increased expression of the inhibin α-subunit and betaglycan, both of which are antagonists of activin action. These data indicate that activin A acts as a PKC-induced paracrine factor involved in the suppression of CYP17A1 in the zona glomerulosa and can thereby contribute to functional adrenocortical zonation.

scholarly journals Telomerase Activation by Human Papillomavirus Type 16 E6 Protein: Induction of Human Telomerase Reverse Transcriptase Expression through Myc and GC-Rich Sp1 Binding Sites

2001 ◽  
Vol 75 (12) ◽  
pp. 5559-5566 ◽  
Author(s):  
Stephen T. Oh ◽  
Saturo Kyo ◽  
Laimonis A. Laimins
Keyword(s):  
Reverse Transcriptase ◽  
Binding Sites ◽  
Telomerase Activity ◽  
Telomerase Reverse Transcriptase ◽  
Htert Promoter ◽  
Htert Expression ◽  
Human Telomerase Reverse Transcriptase ◽  
Htert Transcription ◽  
Human Telomerase ◽  
In Cells

ABSTRACT High-risk human papillomaviruses (HPVs) immortalize keratinocytes by disrupting the retinoblastoma protein (Rb)/p16 pathway and activating telomerase. The E7 oncoprotein targets Rb, while the E6 oncoprotein induces telomerase activity in human keratinocytes. This study has examined the mechanism by which E6 activates telomerase. Expression of human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase, was found to be increased in keratinocytes stably expressing HPV type 16 E6, suggesting that E6 acts to increase hTERT transcription. hTERT expression and telomerase activity were activated to significantly higher levels in cells expressing both E6 and E7 than in cells expressing E6 alone. This indicates that E7 may augment E6-mediated activation of hTERT transcription. In transient-transfection assays using hTERT reporters, the induction of hTERT expression by E6 was found to be mediated by a 258-bp fragment of the hTERT promoter, proximal to the ATG initiation codon. Previous studies have demonstrated that overexpression of Myc can activate hTERT expression, suggesting that Myc may be a mediator of E6-mediated hTERT induction. However, in cells stably expressing E6, no strict correlation between the level of Myc and the activation of hTERT was found. Consistent with this observation, mutation of the two Myc binding sites in the hTERT promoter only modestly reduced responsiveness to E6 in transient reporter assays. This indicates that activation of Myc-dependent transcription is not essential for E6-mediated upregulation of hTERT expression. The hTERT promoter also contains five GC-rich elements that can bind Sp1. Mutation of these sites within the 258-bp fragment partially reduced hTERT induction by E6. However, when mutations in the Sp1 sites were combined with the mutated Myc binding sites, all activation by E6 was lost. This indicates that it is the combinatorial binding of factors to Myc and Sp1 cis elements that is responsible for hTERT induction by E6.

Dose-dependent effects of angiotensin II, acetylcholine and vasopressin on the cytosolic concentration of Ca2+ in suspension primary cultures of zona fasciculata/reticularis cells from bovine adrenal cortex

1991 ◽  
Vol 6 (2) ◽  
pp. 197-203 ◽  
Author(s):  
S. W. Walker ◽  
M. W. J. Strachan ◽  
M. Nicol ◽  
B. C. Williams ◽  
I. M. Bird
Keyword(s):  
Angiotensin Ii ◽  
Suspension Culture ◽  
Adrenal Cortex ◽  
Primary Cultures ◽  
Intracellular Concentration ◽  
Zona Fasciculata ◽  
Adrenocortical Cells ◽  
Intracellular Pool ◽  
Intracellular Ca ◽  
Dose Dependent

ABSTRACT The effects of angiotensin II (AII), acetylcholine and vasopressin on the intracellular concentration of Ca2+ have been little studied in adrenocortical cells from the zona fasciculata/reticularis (ZFR). Primary cultures of bovine ZFR cells maintained in suspension culture for 72 h produce cortisol in response to AII (0·1 μm), acetylcholine (0·1 mm) and vasopressin (1 μm). This response is accompanied by a breakdown of membrane phosphoinositides from [3H]inositol-prelabelled cells. Using cells loaded with the Ca2+ indicator fura-2, the intracellular concentration of Ca2+ was measured in response to increasing doses of all three agonists and found to increase in a graded fashion in each case. The basal intracellular concentration of Ca2+ was 75±3 nm (mean±s.e.m., n=52), rising to a maximum 1·82±0·14-fold (n=6) for AII (0·1 μm), 1·35±0·05-fold (n=7) for acetylcholine (0·1 mm) and 1·27±0·10-fold (n=6) for vasopressin (1 μm). In the case of AII and acetylcholine, agonists were added sequentially in medium of normal extracellular Ca2+ concentration (1·2 mm) or in medium in which the Ca2+ concentration was buffered to approximate to the intracellular concentration of Ca2+ (75–100 nm). Evidence was thereby obtained that both AII and acetylcholine mobilize a common intracellular pool of Ca2+. Our findings suggest that these three agonists, all of which stimulate phospholipase C, increase intracellular Ca2+ through a mechanism which depends, at least in part, on the release of Ca2+ from a common intracellular pool.

Adrenocortical Ultrastructure in Ectopic Acth Syndrome

1976 ◽  
Vol 34 ◽  
pp. 238-239
Author(s):  
K. Kovacs ◽  
E. Horvath ◽  
W. Singer
Keyword(s):  
Adrenal Cortex ◽  
Zona Glomerulosa ◽  
Ectopic Acth Syndrome ◽  
Pituitary Neoplasms ◽  
Electron Microscopic ◽  
Adrenocortical Cells ◽  
Cell Hyperplasia ◽  
Ectopic Acth ◽  
Ectopic Acth Production ◽  
Microscopic Findings

Secretion of ACTH by non-pituitary neoplasms is recognized with increasing frequency. While the clinical and biochemical changes associated with ectopic ACTH production have been extensively studied recently, relatively little attention was focused on the morphology of the adrenal cortex and, to our knowledge, the fine structure of the adrenocortical cells in cases of ectopic ACTH syndrome has not been described so far. We report here the electron microscopic findings in the adrenal cortex of a 50-year-old man with a pancreatic apudoma. The patient showed the characteristic clinical and biochemical features of ectopic ACTH syndrome and because of extensive hypercorticism, underwent bilateral adrenalectomy.By light microscopy, the adrenal cortices showed extensive compact cell hyperplasia and lipid depletion. The zona glomerulosa was present in small foci and, except for a few places, fasciculata cells were noted under the fibrous capsule.

scholarly journals Coregulatory protein–orphan nuclear receptor interactions in the human adrenal cortex

2005 ◽  
Vol 186 (1) ◽  
pp. 33-42 ◽  
Author(s):  
Sinead N Kelly ◽  
T Joseph McKenna ◽  
Leonie S Young
Keyword(s):  
Transcriptional Regulation ◽  
Adrenal Cortex ◽  
Nuclear Receptor ◽  
Tumour Cell Line ◽  
Zona Fasciculata ◽  
Orphan Nuclear Receptor ◽  
Response Element ◽  
Coregulatory Proteins ◽  
Coregulatory Protein ◽  
In Cells

The capacity of the adrenal to produce steroids is controlled in part through the transcriptional regulation of steroid enzymes. The orphan nuclear receptor steroidogenic factor 1 (SF-1) is central to the transcriptional regulation of all steroid hydroxylase enzymes, whereas nur77 can preferentially regulate steroid enzyme genes relevant to cortisol production. We hypothesised that, in the presence of secretagogues, SF-1 and nur77 may differentially interact with coregulatory proteins in the human adrenal cortex. Both coregulatory proteins, steroid receptor coactivator (SRC-1) and silencing mediator for retinoid and thyroid hormones (SMRT), were found to be expressed in the zona fasciculata and reticularis in the human adrenal cortex, but were largely absent from the zona glomerulosa. Both coregulatory proteins were colocalised with SF-1 and nur77. In the H295R adrenal tumour cell line, SF-1 and nur77 transcripts were increased in cells in the presence of forskolin, whereas nur77 mRNA was also induced with angiotensin II (AII). The coactivator SRC-1 mRNA was increased in the presence of both forskolin and AII. Forskolin induced recruitment of SRC-1 to the SF-1 response element and induced SRC-1–SF-1 interactions, whereas AII increased recruitment of SRC-1 to the nur77 response element and induced SRC-1–nur77 interactions. The corepressor SMRT interacted with SF-1 in the presence of AII and with nur77 in cells treated with forskolin. Orphan nuclear receptor–coregulatory protein interactions may have consequences for the regulation of key steroidogenic enzymes in the human adrenal cortex.

Contribution of apoptosis to the phenotypic changes of adrenocortical cells in primary culture

1995 ◽  
Vol 110 (1-2) ◽  
pp. 175-184 ◽  
Author(s):  
A. Negoescu ◽  
F. Labat-Moleur ◽  
G. Defaye ◽  
P. Mezin ◽  
C. Drouet ◽  
...  
Keyword(s):  
Primary Culture ◽  
Adrenocortical Cells ◽  
Phenotypic Changes

Expression of viral p21ras during acquisition of a transformed phenotype by rat adrenal cortex cells infected with Kirsten murine sarcoma virus

1986 ◽  
Vol 6 (1) ◽  
pp. 342-346
Author(s):  
A MacAuley ◽  
N Auersperg ◽  
T Pawson
Keyword(s):  
Adrenal Cortex ◽  
Adrenocortical Cells ◽  
Murine Sarcoma Virus ◽  
Sarcoma Virus ◽  
Murine Sarcoma ◽  
Oncogenic Form

Rat adrenal cortex cells infected with Kirsten murine sarcoma virus acquire a transformed phenotype in a progressive fashion. The expression of the viral p21ras does not appear to correlate with the degree of transformation of the adrenocortical cells but rather is produced at similar levels as the culture becomes transformed. This indicates that the expression of an oncogenic form of p21ras is not of itself sufficient to completely transform rat adrenal cortex cells.

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