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The expression and activities of corticotrophinreleasing factor (CRF), urocortin (UCN), the CRF-binding protein (CRF-BP) and CRF receptors in rat brain have been well documented; however, information regarding their peripheral distributions remains incomplete. Given the multiple immunomodulatory effects of peripherally administered CRF and UCN and the high levels of CRF receptor type 2 (CRF-R2) mRNA and protein expressed in the heart, the lymphoid organs and heart have become targets for some of the latest CRF-related research. Here we demonstrate the presence of UCN mRNA in both the rat spleen and human Jurkat T-lymphoma cells using 3 -RACE (rapid amplication of cDNA ends) PCR. Following on from these initial results, we used semiquantitative RT-PCR to carry out a comprehensive study assessing the relative amounts of CRF, UCN, CRF-R1, CRF-R2 and CRF-BP mRNAs in the brain, thymus, spleen and heart of normal, untreated rats. The rank orders of mRNA abundance in each of the tissue types were as follows: for CRF, brain> >thymus=spleen=heart; for UCN, heartdbrain>thymus>spleen; for CRF-R1, brain> >thymus>spleen (absent in heart); for CRF-R2, brain=heart>thymus>spleen; and CRF-BP was only detectable in the brain. We have provided evidence for the existence of CRF, UCN, CRF-R1 and CRF-R2 expression in resting immune cells, with UCN expression being particularly predominant in the rat thymus and human Jurkat cells. Additionally, the high levels of UCN mRNA detected in heart corresponded to the high expression of CRF-R2 mRNA, suggesting an important role for UCN/CRF-R2 coupling in this tissue.

In comparison to the embryo, very little work has been carried out on the expression and role of Hox genes in the adult animal. An expression profile of all 39 vertebrate Hox genes on a select panel of adult human tissues reveals that in fact these genes are widely expressed throughout the adult human and a colinear pattern of expression is displayed similar to that of the developing embryo. Of particular interest is the abundance of Hox genes that are expressed within the adult adrenal gland. Adrenal cortical cells are continuously renewed to sustain production of zonal steroids. Cell proliferation occurs at the periphery of the cortex and cells are then displaced centripetally, phenotypically switching as they migrate through the gland before undergoing apoptosis at the zona reticularis/medullary boundary. It is still unclear which mechanisms cause the cells to differentiate as they cross the zonal boundaries and we hypothesise that Hox genes may be involved in the phenotypic switching of the adrenocortical cells. In situ hybridisation experiments were carried out on adult rat adrenal gland sections and Hox gene expression was localized within the zonal borders, coinciding with the localization of cells that undergo phenotypic differentiation, and thus supporting our hypothesis that Hox genes may be involved in the phenotypic switching of the adrenocortical cells. As in the developing embryo, the genes display colinear expression with the 3' Hox genes being expressed within the outer gland and the 5' genes within the inner zones.

In view of the reported inflammatory effects of corticotrophin-releasing factor (CRF) and the associated regulatory elements in the gene of its binding protein (BP), we postulate that both BP as well as novel BP-ligands other than CRF may be involved in inflammatory disease. We have investigated BP in the blood of patients with arthritis and septicaemia and have attempted to identify CRF and other BP-ligands in synovial fluid. The BP was found to be significantly elevated in the blood of patients with rheumatoid arthritis and septicaemia. There was less BP-ligand and CRF in synovial fluid from patients with rheumatoid arthritis that from those with osteo- or psoriatic arthritis. There was at least 10-fold more BP-ligand than CRF in the fluid of all three groups of patients. A small amount of immunoreactive human (h)CRF, eluting in the expected position of CRF-41, was detected after high-pressure liquid chromatography of arthritic synovial fluid; however, the bulk of material with BP-ligand binding activity eluted earlier, suggesting that synovial fluid contained novel peptides that interacted with the BP. These results would suggest that the BP and its ligands could play an endocrine immunomodulatory role in inflammatory disease.

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