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Exp Gerontol. 2011 Nov;46(11):877-83. doi: 10.1016/j.exger.2011.07.007. Epub 2011 Jul 27.

Opposing effects of cortisol and dehydroepiandrosterone on the expression of the receptor for Activated C Kinase 1: implications in immunosenescence.

Author information

1
Department of Drug Sciences-Pharmacology Section, Center of Excellence in Applied Biology, University of Pavia, Viale Taramelli 14, Pavia, Italy.

Abstract

Aging is associated to a decline in immune functions that are in part related to a defective protein kinase C dependent signal transduction machinery. RACK-1 (Receptor for Activated C Kinase 1) is a scaffold protein for different kinases and membrane receptors. We have previously demonstrated, in the elderly, a defective PCKβII (Protein Kinase C βII) translocation related to a decrease in RACK-1 protein expression, which is correlated to the age-associated decline in DHEA (dehydroepiandrosterone) levels. As a consequence of this signal transduction impairment, a significant decrease in immune cells functionality was observed. Furthermore, we could demonstrate that in vivo and in vitro DHEA administration restored RACK-1 level and immune functions, indicating that this hormone behaved as a positive RACK-1 regulator. We have most recently characterized the human GNB2L1 promoter region, coding for RACK-1 protein. Although no direct DHEA responsive elements were found, a glucocorticoid responsive element (GRE) was identified. The purpose of this work was to investigate, in the human pro-myelocytic cell line THP-1, whether physiological cortisol concentrations were able to modulate GNB2L1 promoter activity, RACK-1 transcription as well as cytokine production. As DHEA is endowed of anti-glucocorticoid properties in several cellular systems, and as cortisol:DHEA ratio imbalance is relevant in aging, we also investigated their possible interaction at the RACK-1 expression level. We could demonstrate that cortisol acted in a dose-related manner as a GNB2L1 promoter repressor, reducing RACK-1 mRNA expression and protein level. Probably by interfering with glucocorticoid receptor binding to GRE sequence, prolonged DHEA exposure counteracted cortisol effects, restoring RACK-1 levels and cytokine production, as assessed by LPS-induced TNF-α release.

PMID:
21820043
DOI:
10.1016/j.exger.2011.07.007
[Indexed for MEDLINE]

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