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      Regulation of Corticotropin-Releasing Factor Receptor Type 2β Messenger Ribonucleic Acid by Interleukin-1β in Rat Vascular Smooth Muscle Cells

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          Objective: Corticotropin-releasing factor receptor type 2 (CRF R2) messenger RNA (mRNA) expression in the rodent heart or vessels is modulated by exposure to urocortin and glucocorticoids. In addition, we previously found that incubation with a variety of cytokines, such as interleukin (IL)-1 and IL-6, and tumor necrosis factor-α also reduced CRF R2β mRNA expression, with IL-1β being the most effective. In this study, we further explored the regulation of CRF R2β mRNA levels by IL-1β in the rat vascular smooth muscle A7r5 cells. Methods: A7r5 cells were incubated with IL-1β, urocortin, or both for 6 h, after pre-incubating with or without anti-IL-1β antibody (Ab) for 30 min, and then CRF R2β mRNA levels were measured by RNase protection assay. Cells were incubated with lipopolysaccharides, IL-1β, IL-6 , dexamethasone, forskolin, or urocortin for 20 min, and then intracellular cAMP was measured by cAMP RIA. Results: IL-1β produced a significant time-dependent decrease in CRF R2β mRNA levels. Combined urocortin and IL-1β administration did not have synergistic effects on the decrease in CRF R2β mRNA levels. IL-1β Ab failed to block the ability of urocortin to regulate CRF R2β mRNA levels, suggesting that urocortin regulated CRF R2β mRNA levels via another pathway than IL-1β production. Urocortin induced the intracellular cAMP production in A7r5 cells, while IL-1β failed to induce it. Conclusion: The multifactorial regulation of CRF R2β mRNA expression in the A7r5 cells serves to limit the inotropic and chronotropic effects of CRF R2 agonists such as urocortin during prolonged physical or immune challenge.

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          Most cited references 6

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          Urocortin, a mammalian neuropeptide related to fish urotensin I and to corticotropin-releasing factor.

          Corticotropin-releasing factor (CRF), a peptide first isolated from mammalian brain, is critical in the regulation of the pituitary-adrenal axis, and in complementary stress-related endocrine, autonomic and behavioural responses. Fish urotensin I and amphibian sauvagine were considered to be homologues of CRF until peptides even more closely related to CRF were identified in these same vertebrate classes. We have characterized another mammalian member of the CRF family and have localized its urotensin-like immunoreactivity to, and cloned related complementary DNAs from, a discrete rat midbrain region. The deduced protein encodes a peptide that we name urocortin, which is related to urotensin (63% sequence identity) and CRF (45% sequence identity). Synthetic urocortin evokes secretion of adrenocorticotropic hormone (ACTH) both in vitro and in vivo and binds and activates transfected type-1 CRF receptors, the subtype expressed by pituitary corticotropes. The coincidence of urotensin-like immunoreactivity with type-2 CRF receptors in brain, and our observation that urocortin is more potent than CRF at binding and activating type-2 CRF receptors, as well as at inducing c-Fos (an index of cellular activation) in regions enriched in type-2 CRF receptors, indicate that this new peptide could be an endogenous ligand for type-2 CRF receptors.
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            Urocortin expression in rat brain: evidence against a pervasive relationship of urocortin-containing projections with targets bearing type 2 CRF receptors.

            Histochemical and axonal transport methods were used to clarify the central organization of cells and fibers that express urocortin (UCN), a recently discovered corticotropin-releasing factor (CRF)-related neuropeptide, which has been proposed as an endogenous ligand for type 2 CRF receptors (CRF-R2). Neurons that display both UCN mRNA and peptide expression were found to be centered in the Edinger-Westphal (EW), lateral superior olivary (LSO), and supraoptic nuclei; lower levels of expression are seen in certain cranial nerve and spinal motoneurons and in small populations of neurons in the forebrain. Additional sites of UCN mRNA and peptide expression detected only in colchicine-treated rats are considered to be minor ones. UCN-immunoreactive projections in brain are predominantly descending and largely consistent with central projections attributed to the EW and LSO, targeting principally accessory optic, precerebellar, and auditory structures, as well as the spinal intermediate gray. Although neither the EW nor LSO are known to project to the forebrain, UCN-ir neurons in the EW were identified that project to the lateral septal nucleus, which houses a prominent UCN-ir terminal field. Although substantial UCN-ir projections were observed to several brainstem cell groups that express CRF-R2, including the dorsal raphe and interpeduncular nuclei and the nucleus of the solitary tract (NTS), most prominent seats of CRF-R2 expression were found to contain inputs immunopositive for piscine urotensin I, but not rat UCN. The results define a central UCN system whose organization suggests a principal involvement in motor control and sensorimotor integration; its participation in stress-related mechanisms would appear to derive principally by virtue of projections to the spinal intermediolateral column, the NTS, and the paraventricular nucleus. Several observations, including the lack of a pervasive relationship of UCN-ir projections with CRF-R2-expressing targets, support the existence of still additional CRF-related peptides in mammalian brain. Copyright 1999 Wiley-Liss, Inc.
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              Urocortin protects against ischemic and reperfusion injury via a MAPK-dependent pathway.

              Urocortin (UCN) is a peptide related to hypothalamic corticotrophin-releasing hormone and binds with high affinity to corticotrophin-releasing hormone receptor-2beta, which is expressed in the heart. In this study, we report that UCN prevented cell death when administered to primary cardiac myocyte cultures both prior to simulated hypoxia/ischemia and at the point of reoxygenation after simulated hypoxia/ischemia. UCN-mediated cell survival was measured by trypan blue exclusion, 3'-OH end labeling of DNA (TUNEL), annexin V, and fluorescence-activated cell sorting. To explore the mechanisms that could be responsible for this effect, we investigated the involvement of MAPK-dependent pathways. UCN caused rapid phosphorylation of ERK1/2-p42/44, and PD98059, which blocks the MEK1-ERK1/2-p42/44 cascade, also inhibited the survival-promoting effect of UCN. Most important, UCN reduced damage in isolated rat hearts ex vivo subjected to regional ischemia/reperfusion, with the protective effect being observed when UCN was given either prior to ischemia or at the time of reperfusion after ischemia. This suggests a novel function of UCN as a cardioprotective agent that could act when given after ischemia, at reperfusion.

                Author and article information

                S. Karger AG
                May 2002
                28 May 2002
                : 9
                : 6
                : 326-332
                Third Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Japan
                59390 Neuroimmunomodulation 2001;9:326–332
                © 2002 S. Karger AG, Basel

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                Page count
                Figures: 4, References: 40, Pages: 7
                Original Paper


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