Abstract
Purpose::
Rapid responses to aldosterone have been demonstrated in secretory epithelia1. We have previously shown rapid activation by aldosterone of Mitogen-Activated Protein Kinase (MAPK) in human non-pigmented epithelial (HNPE) cells2. Aldosterone causes increased expression of genes coding for Na+-K+-ATPase, sgkand ENaC3 and also activates genes involved in fibrosis, inflammation and calcification4.Our aim was to examine the hypothesis that aldosterone could rapidly regulate the expression of MAPK related genes in HNPE cells.
Methods::
The cell line ODM-Cl2 was cultured in standard conditions. Cells were treated with 10nM aldosterone for 20 minutes. Poly-A-RNA was extracted, labelled with α32P-CTP and hybridised with "GEArray Q Series Human MAP Kinase Signalling Pathways Gene Array" membrane (Superarray). Results were analysed using the manufacturer’s recommended software and normalised using housekeeping genes on both membranes.
Results::
The expression of 33 genes was changed after aldosterone treatment. There was a 2-fold increase in expression of eight genes, including the Epithelial Growth Factor Receptor (EGFR) and MAPK isoforms, in the treated cells. There was a 2-fold decrease in expression of one gene - CDKN1C, a cell cycle kinase. There were also 24 genes affected by 1.5-2-fold changes in expression; 22 increased, while 2 decreased.All affected genes were MAPK isoforms, members of the MAPK kinase, and kinase kinase groups of enzymes, activated transcription factors, cell cycle proteins, scaffolding and anchoring proteins.
Conclusions::
This is the first evidence that aldosterone has a rapid effect on gene expression in HNPE cells. Also, gene expression has not previously been reported in ocular tissue so early after hormonal treatment. We have shown that aldosterone has both a stimulatory and inhibitory effect on a variety of MAPK related genes. MAPK pathways play a key role in the regulation of gene expression, cell growth, inflammation and apoptosis. These are novel areas of action for aldosterone, whose activity classically relates to ion transport.References:1. Maguire, D., et al., Steroids, 1999. 64(1-2): p. 51-63.2. O’Colmain, U., et al., ARVO, 2004.2. Gumz, M.L., et al., Am J Physiol Renal Physiol, 2003. 285(4): p. F664-73.3. Okoshi MP., et al., J Card Fail, 2004. 10(6): p. 511-8.
Keywords: gene microarray • ciliary body • signal transduction: pharmacology/physiology