Distribution and Acute Stressor-Induced Activation of Corticotrophin-Releasing Hormone Neurones in the Central Nervous System of Xenopus laevis

In mammals, corticotrophin-releasing hormone (CRH) and related peptides are known to play essential roles in the regulation of neuroendocrine, autonomic and behavioural responses to physical and emotional stress. In nonmammalian species, CRH-like peptides are hypothesized to play similar neuroendocrine and neurocrine roles. However, there is relatively little detailed information on the distribution of CRH neurones in the central nervous system (CNS) of nonmammalian vertebrates, and there are currently no comparative data on stress-induced changes in CRH neuronal physiology. We used a specific, affinity-purified antibody raised against synthetic Xenopus laevis CRH to map the distribution of CRH in the CNS of juvenile South African clawed frogs . We then analysed stress-induced changes in CRH immunoreactivity (CRH-ir) throughout the CNS. We found that CRH-positive cell bodies and fibres are widely distributed throughout the brain and rostral spinal cord of juvenile X. laevis . Strong CRH-immunoreactovity (ir) was found in cell bodies and fibres in the anterior preoptic area (POA, an area homologous to the mammalian paraventricular nucleus) and the external zone of the median eminence. Specific CRH-ir cell bodies and fibres were also identified in the septum, pallium and striatum in the telencephalon; the amygdala, bed nucleus of the stria terminalis and various hypothalamic and thalamic nuclei in the diencephalon; the tectum, torus semicircularis and tegmental nuclei of the mesencephalon; the cerebellum and locus coeruleus in the rhombencephalon; and the ventral horn of the rostral spinal cord. To determine if exposure to an acute physical stressor alters CRH neuronal physiology, we exposed juvenile frogs to shaking/handling and conducted morphometric analysis. Plasma corticosterone was significantly elevated by 30 min after exposure to the stressor and continued to increase up to 6 h. Morphometric analysis of CRH-ir after 4 h of stress showed a significant increase in CRH-ir in parvocellular neurones of the anterior preoptic area, the medial amygdala and the bed nucleus of the stria terminalis, but not in other brain regions. The stress-induced increase in CRH-ir in the POA was associated with increased Fos-like immunoreactivity (Fos-LI), and confocal microscopy showed that CRH-ir colocalized with Fos-LI in a subset of Fos-LI-positive neurones. Our results support the view that the basic pattern of CNS CRH expression arose early in vertebrate evolution and lend further support to earlier studies suggesting that amphibians may be a transitional species for descending CRH-ergic pathways. Furthermore, CRH neurones in the frog brain exhibit changes in response to a physical stressor that parallel those seen in mammals, and thus are likely to play an active role in mediating neuroendocrine, behavioural and autonomic stress responses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73585/1/j.1365-2826.2004.01246.x.pd

Differentiation dependent expression of urocortin’s mRNA and peptide in human osteoprogenitor cells: influence of BMP-2, TGF-beta-1 and dexamethasone

Urocortin-1 (UCN) a corticotropin releasing-factor (CRF) related peptide, has been found to be expressed in many different tissues like the central nervous system, the cardiovascular system, adipose tissue, and skeletal muscle. The effects of UCN are mediated via stimulation of CRF-receptors 1 and 2 (CRFR1 and 2, CRFR’s) with a high affinity for CRFR2. It has been shown that the CRF-related peptides and CRFR’s are involved in the regulation of stress-related endocrine, autonomic and behavioural responses. Using immunocytochemistry, immunohistochemistry and RT–PCR, we now can show the differentiation dependent expression of UCN mRNA and peptide in human mesenchymal progenitor cells (MSCs) directed to the osteoblastic phenotype for the first time. UCN expression was down regulated by TGF-beta and BMP-2 in the early proliferation phase of osteoblast development, whereas dexamethasone (dex) minimally induced UCN gene expression during matrix maturation after 24 h stimulation. Stimulation of MSCs for 28 days with ascorbate/beta-glycerophosphate (asc/bGp) induced UCN gene expression at day 14. This effect was prevented when using 1,25-vitamin D3 or dex in addition. There was no obvious correlation to osteocalcin (OCN) gene expression in these experiments. In MSCs from patients with metabolic bone disease (n = 9) UCN gene expression was significantly higher compared to MSCs from normal controls (n = 6). Human MSCs did not express any of the CRFR’s during differentiation to osteoblasts. Our results indicate that UCN is produced during the development of MSCs to osteoblasts and differentially regulated during culture as well as by differentiation factors. The expression is maximal between proliferation and matrix maturation phase. However, UCN does not seem to act on the osteoblast itself as shown by the missing CRFR’s. Our results suggest new perspectives on the role of urocortin in human skeletal tissue in health and disease

Intratumoral CRH modulates immuno-escape of ovarian cancer cells through FasL regulation

Although corticotropin-releasing hormone (CRH) and Fas ligand (FasL) have been documented in ovarian carcinoma, a clear association with tumour progression and immuno-escape has not been established. FasL plays an important role in promoting tumour cells' ability to counterattack immune cells. Here, we examined immunohistochemically the expression of CRH, CRHR1, CRHR2 and FasL in 47 human ovarian cancer cases. The ovarian cancer cell lines OvCa3 and A2780 were further used to test the hypothesis that CRH might contribute to the immune privilege of ovarian tumours, by modulating FasL expression on the cancer cells. We found that CRH, CRHR1, CRHR2 and FasL were expressed in 68.1, 70.2, 63.8 and 63.8% of the cases respectively. Positivity for CRH or FasL expression was associated with higher tumour stage. Finally, CRH increased the expression of FasL in OvCa3 and A2780 cells through CRHR1 thereby potentiated their ability to induce apoptosis of activated peripheral blood lymphocytes. Corticotropin-releasing hormone produced by human ovarian cancer might favour survival and progression of the tumour by promoting its immune privilege. These findings support the hypothesis that CRHR1 antagonists could potentially be used against ovarian cancer