The recent observation that in vivo administration of interleukin- 1 (IL-1) or of interleukin-2 (IL-2) results in increases of plasma adrenocorticotropic hormone or corticotropin (ACTH) indicates that monokines and lymphokines affect neuroendocrine function. Our results demonstrating an enhanced level of proopiomelanocortin (POMC) mRNA in IL-1 and IL-2 treated pituitary cells indicate that these immune response modifiers have activity in pituitary cells not unlike that of corticotropin releasing hormone (CRF). THe goal of this project is to further characterize the effects of monokines and lymphokines on corticotrophs. We will use radioimmunoassays to determine if, like CRF, IL-1 and IL-2 as well as other monokines or lymphokines stimulate the release of ACTH and endorphin from pituitary cells. This will be achieved using the corticotropoic cell line, AtT-20 and confirmed in primary cultures of rat pituitary cells. Further studies will determine if monokines or lymphokines specifically affect corticotrophs or if they also cause release of hormones from other pituitary cell populations such as thyrotrophs (thyrotropin), somatotrophs (growth hormone), or gonadotrophs (luteinizing hormone). We will also determine the effects of immune response modifiers on the expression of the POMC gene in AtT-20 cells and in normal rat pituitary cells. The levels of POMC-mRNA in teated cells will be assessed by hybridization to a nick translated 32P-POMC-cDNA. Nuclear runoff experiments will determine if like CRF, IL-1 and IL-2 stimulate and enhanced transcription of the POMC gene. We also propose to examine the expression of the IL-2 receptor (IL-2R) on AtT-20 cells and rat pituitary cells. Our preliminary results using a monoclonal antibody to the murine IL-2R have indicated that the IL-2R is expressed by AtT-20 cells. We have also detected IL-2 receptor message in AtT-20 cells and in rat pituitary cells using an IL-2R cDNA probe. We will further characterize the expression of IL- 2R by these cells by flow cytometry, saturation binding assays with 125I-IL-2 and the utilization of IL-2R cDNA probe to correlate receptor expression with transcription of the IL-2R gene by pituitary cells. Finally, we will determine if like CRF, monokines and lymphokines stimulate cAMP generation in pituitary cells. These studies will determine if molecules of divergent origin produce common effects through similar mechanisms.
| Smith, L R; Brown, S L; Blalock, J E (1989) Interleukin-2 induction of ACTH secretion: presence of an interleukin-2 receptor alpha-chain-like molecule on pituitary cells. J Neuroimmunol 21:249-54 |
