Endocrine Abstracts

Folliculostellate (FS) cells are non-hormone producing cells that represent up to 10% of the anterior pituitary gland and may mediate the response of the hypothalamic pituitary adrenal axis to inflammation. Adenosine, released during stress and inflammation, acts at A2b receptors to stimulate growth and secretion of IL-6 from a mouse FS cell line, TtT/GF. We have now extended these studies and investigated how NECA (universal adenosine receptor agonist; 10 micromolar) stimulates the function of TtT/GF cells over 30 minutes and 2 hour time points using DNA microarray analysis (Affymetrix MG-U74A ver.2 chips).

Of the 12,436 genes on the chip, 6,553 are expressed by TtT/GF cells. Applying two-tailed heteroscedastic t-tests and a P value of less than 0.01, 14 and 20 genes were up-regulated and 3 and 139 were down-regulated at respectively 30 minutes and 2 hours. The down-regulated genes included those associated with a) immune function: interferon-gamma receptor (1.6 fold), leukaemia inhibitory factor receptor (1.4 fold) and glucocorticoid attenuated response gene (GARG-49, 3.6 fold) and b) cell cycle proliferation: early growth response genes 1 and 2 (13 and 10 fold), GADD45 (4.9 fold) and cdk inhibitor 2b (4.5 fold). Examples of up-regulated genes included IL-6 (108 fold), chemokine orphan receptor (6.1 fold), SOCS 3 (15.4 fold), thrombomodulin (3.6 fold) and endothelial protein C receptor (1.8 fold). 25-30% of the up-regulated and up to 45% of the down-regulated genes were of unknown function (expressed sequence tags).

These findings demonstrate that NECA stimulates IL-6 mRNA expression as well as protein secretion in a pituitary FS cell line, an effect likely mediated via A2b adenosine receptors based on our previous observations. Several of the transcripts that had altered expression can be associated with inflammation or cell growth. These data have additionally identified novel pathways linked to adenosine receptor signalling.