Cellular senescence involves stochastic processes causing loss of expression of differentiated function genes: Visualization by in situ hybridization for steroid 17α-hydroxylase in bovine adrenocortical cells

Ryan, Robert F.; Hancock, J. P.; McDonald, J. Tyson; Hornsby, Peter J.

doi:10.1016/0014-4827(89)90210-3

Cited by 20 publications

(2 citation statements)

References 19 publications

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“…The same authors also found co-localization of P450C17 protein and mRNA in the same tissue section. When bovine cell cultures prepared from adrenal zona fasciculatareticularis were analyzed for the presence of P450C17 by immunofluorescence and hybridization in situ, those cells that were positive for immunofluorescence were also positive for hybridization (Ryan et al 1989), indicating that the P450C17 mRNA was effectively translated into protein. A decrease in immunofluorescent staining from the ZF to the ZR for P450C17 was reported for the guinea pig (Shinzawa et al 1988) and pig (Sasano et al 1989) adrenal cortices.…”

Section: Discussionmentioning

confidence: 99%

Immunolocalization and Biochemical Determination of Cytochrome P450C17 in Adrenals of Hamsters Treated with ACTH

Brière

Martel

Cloutier

et al. 1997

J Histochem Cytochem.

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SUMMARYWe used an anti-rat adrenal cytochrome P450C17 (P450C17) antibody to perform immunofluorescence and also immunogold electron microscopic studies to determine the zonal and intracellular distribution of P450C17 in hamster adrenals. Because P450C17 activity is regulated mainly by adrenocorticotropin (ACTH), its zonal and intracellular localization was also analyzed after ACTH treatment. The effect of ACTH treatment on protein concentration was also investigated by Western blotting analysis. By immunofluorescence, we found P450C17 to be confined to the zona fasciculata (ZF) in the hamster, in contrast to other small rodents, which do not express P450C17 in their adrenals. After treatment with ACTH, the thickness of the ZF remained unchanged compared to that of control animals, whereas a marked increase in fluorescence intensity was observed. In addition, dispersed cells in the zona reticularis (ZR) showed positive staining after ACTH treatment. Immunocytochemistry with colloidal gold showed P450C17 to be localized and importantly increased only in the cytoplasmic areas between the mitochondria of ZF cells of ACTH-treated animals. These areas are predominantly occupied by elements of the endoplasmic reticulum and other unidentified organelles. Immunoblotting analysis of whole glands revealed a single protein band at approximately 55 kD, which reacted with the 450C17 antibody. After stimulation with ACTH injected at 5-hr intervals over a period of 20 hr, P450C17 protein concentrations were considerably greater than in control animals. In conclusion, P450C17 is located not over mitochondria but probably in the endoplasmic reticulum of the ZF cells in hamster adrenals. Treatment with ACTH induced expression of cytochrome P450C17 in ZF cells, increasing its production in these cells without stimulating cell proliferation.

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Section: Discussionmentioning

confidence: 99%

Immunolocalization and Biochemical Determination of Cytochrome P450C17 in Adrenals of Hamsters Treated with ACTH

Brière

Martel

Cloutier

et al. 1997

J Histochem Cytochem.

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“…At the same time, several investigators have reported changes in the transcriptional activity of specific genes in several organisms (14,34,35,41,46,47). In many cases, transcriptional activity is reduced during aging because of the dependence of some genes on hormonal control.…”

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T-kininogen gene expression is induced during aging.

Sierra¹,

Fey²,

Guigoz³

1989

Mol. Cell. Biol.

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We have constructed a cDNA library from senescent (24-month-old) rat liver mRNA and, by differential screening, have selected clones corresponding to mRNA species with increased abundance in aging rats. Direct sequencing of the inserts indicated that most of the clones (9 of 10) contained sequences coding for T-kininogen, also called major acute-phase protein, cysteine protease inhibitor, or thiostatin. Nuclear elongation experiments showed that the increase in mRNA concentration was controlled at the transcriptional level. RNase mapping and Si analysis indicated that the age-dependent induction operated preferentially at one of the three transcriptional start sites of the gene(s). The acute-phase reaction (inflammation) is known to also induce these genes at the level of transcription; however, two of the three start sites are induced by inflammation. Transcription from one of these sites was induced by both phenomena, aging and inflammation.During the past few years, major efforts have been made to understand developmental processes at the molecular level. Although many researchers have directed their efforts toward an understanding of the changes in gene expression that accompany early development, surprisingly little is known about the molecular changes that occur as the ultimate result of development, namely, senescence.We are particularly interested in the process of aging as well as the factors that might be able to affect this process. The phenomenon of aging is the result of an interplay of various components, both extrinsic (such as nutritional status or physical exercise) and intrinsic. The intrinsic processes can in turn be subdivided into two distinct classes: random events, which are usually triggered by extrinsic events such as UV irradiation or free-radical formation, and programmed events, which are inherently associated with the developmental pathway of the species in question. These programmed events include, for example, the changes in gene expression associated with the loss of hormonal balance (32,34). We are directing our efforts toward an understanding of the programmed changes in gene expression and metabolism that are normally associated with the process of aging.It has been observed for some time that aging is accompanied by an overall deregulation of gene activity (10,29,30,45). At the same time, several investigators have reported changes in the transcriptional activity of specific genes in several organisms (14,34,35,41,46,47). In many cases, transcriptional activity is reduced during aging because of the dependence of some genes on hormonal control. One such example is the extinction of expression of the a2U-globulin gene in aging animals (34). In this case, it has been shown that the gene is turned off not only because of a diminishing level of several controlling hormones but also because the receptors for these hormones appear to diminish with age (33). In addition, a recent report has shown that in aging animals, the a2U-globulin genes are detached from the nuclear matrix (28)....

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Modulation of mRNA levels during human keratinocyte differentiation

Younus

Gilchrest

1992

Journal Cellular Physiology

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Cultures of human keratinocytes provide an excellent model system in which to study differentiation. Using the phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA) and calcium, two agents known to induce keratinocyte differentiation in vitro, we examined the expression of the genes encoding c-fos, c-myc, and c-jun; involucrin, a protein precursor of the keratinocyte cornified envelope; and L-7, a ribosomal protein. Overall, at the doses studied, TPA induced a more rapid and profound differentiation than did calcium, as evaluated by culture morphology and northern blot analysis. Our studies showed a constant low level of c-fos and c-jun expression in unstimulated cells with no significant change after addition of either TPA or calcium except when transcript breakdown was inhibited by cycloheximide. The c-myc proto-oncogene, known to have a high constitutive expression in actively proliferating cells, was strongly downregulated by TPA, but calcium had no effect over a 32 hour period, consistent with the greater growth inhibition of TPA in this system. Involucrin was induced about ninefold by both TPA and calcium as early as 8 hours after stimulation, suggesting transcriptional regulation of this gene during differentiation. L-7, recently demonstrated to be downregulated in late passage human fibroblasts in an in vitro model of senescence, was also strongly downregulated by either TPA or calcium, consistent with an interrelationship between the basic cellular processes of aging and differentiation. These finding expand our knowledge of the differentiation process in human keratinocytes.

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Cellular senescence involves stochastic processes causing loss of expression of differentiated function genes: Visualization by in situ hybridization for steroid 17α-hydroxylase in bovine adrenocortical cells

Cited by 20 publications

References 19 publications

Immunolocalization and Biochemical Determination of Cytochrome P450C17 in Adrenals of Hamsters Treated with ACTH

Immunolocalization and Biochemical Determination of Cytochrome P450C17 in Adrenals of Hamsters Treated with ACTH

T-kininogen gene expression is induced during aging.

Modulation of mRNA levels during human keratinocyte differentiation

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