Corticotropin-releasing hormone receptors mediate opposing effects in cholestasis-induced liver cell apoptosis

Activation of corticotropin releasing factor receptors up regulates collagen production by hepatic stellate cells via promoting p300 expression

Liver fibrosis is characterized with the over expression and excessive accumulation of extracellular matrix proteins, including collagens. The causative factors in the over production of collagens are not fully understood. This study aims to test a hypothesis that activation of corticotropin releasing factor receptors up regulates the expression of collagen in hepatic stellate cells. In this study, human hepatic stellate cell line, LX-2 cells were cultured. Expression of collagens by LX-2 cells was assessed by real time RT-PCR, Western blotting. The results showed that, upon exposure to urocortin in the culture, LX-2 cells (a human hepatic stellate cell line) increased the expression of collagen IV (Col4) markedly. The exposure to urocortin also enhanced the levels of pTip60, H3K9, RNA polymerase II and forkhead box protein 3 at the collagen promoter locus as well as increase in the expression of Col4 mRNA and protein in the cells. Blocking p300 efficiently suppressed the urocortin-induced Col4 expression in LX-2 cells and unveiled an apoptosis-inducing effect of urocortin. In conclusion, activation of CRF receptors is capable of enforcing the production of Col4 by LX-2 cells via up regulating the p300 pathway, which may contribute to the development of liver fibrosis.

Corticotropin-releasing factor (CRF) system localization in human fetal heart

OBJECTIVE

The corticotropin-releasing factor (CRF) family consists of the neuropeptides CRF, Ucn I, II and III and the binding sites CRFR1, CRFR2 and CRF-BP. It regulates stress response and the homeostasis of an organism. In this study, we examined the presence of the CRF system in the human hearts of normal and pathological fetuses.

DESIGN

Heart tissues from 40 archival human fetuses were divided into Group A (without pathology, 'normal'), Group B (with chromosomal abnormalities) and Group C (with congenital disorders). Immunohistochemistry was used to localize the CRF system. Results correlated to gestational trimester and pathology.

RESULTS

Immunoreactivity for all antigens was found in cardiac myocytes of all groups, in almost all samples, except Ucn III which was present in almost half of the fetuses of Groups B and C and was not detected at all in Group A. Ucn III was more often present during the earlier stage of development (<21 weeks) and in fetuses with congenital disorders. In a fetus diagnosed with heart pathology, all but Ucn III antigens were also present.

CONCLUSIONS

We localized a complete CRF system in the human fetal heart and correlated the presence of Ucn III to development and pathology. More studies are needed to verify and clarify the exact role of the CRF system in the human fetal heart.

Corticotropin-releasing factor family peptide signaling in feline bladder urothelial cells

Corticotropin-releasing factor (CRF) plays a central role in the orchestration of behavioral and neuroendocrine responses to stress. The family of CRF-related peptides (CRF and paralogs: urocortin (Ucn)-I, -II, and -III) and associated receptors (CRFR1 and CRFR2) are also expressed in peripheral tissues such as the skin and gastrointestinal tract. Local signaling may exert multiple effects of stress-induced exacerbation of many complex syndromes, including psoriasis and visceral hypersensitivity. Interstitial cystitis/painful bladder syndrome (IC/PBS), a chronic visceral pain syndrome characterized by urinary frequency, urgency, and pelvic pain, is reported to be exacerbated by stress. Functional changes in the epithelial lining of the bladder, a vital blood-urine barrier called the urothelium, may play a role in IC/PBS. This study investigated the expression and functional activity of CRF-related peptides in the urothelium of normal cats and cats with feline interstitial cystitis (FIC), a chronic idiopathic cystitis exhibiting similarities to humans diagnosed with IC/PBS. Western blots analysis showed urothelial (UT) expression of CRFR1 and CRFR2. Enzyme immunoassay revealed release of endogenous ligands (CRF and Ucn) by UT cells in culture. Evidence of functional activation of CRFR1 and CRFR2 by receptor-selective agonists (CRF and UCN3 respectively) was shown by i) the measurement of ATP release using the luciferin-luciferase assay and ii) the use of membrane-impermeant fluorescent dyes (FM dyes) for fluorescence microscopy to assess membrane exocytotic responses in real time. Our findings show evidence of CRF-related peptide signaling in the urothelium. Differences in functional responses between FIC and normal UT indicate that this system is altered in IC/PBS.

Corticotropin-releasing factor receptor type-2 is involved in the cocaine-primed reinstatement of cocaine conditioned place preference in rats

Here we explored the in vivo role of brain corticotropin-releasing factor receptor type-2 (CRFR2) in cocaine-primed reinstatement of drug seeking. Conditioned place preference (CPP) procedure was used to assess the acquisition, extinction and reinstatement of cocaine-seeking behavior in rats. First, expressions of CRFR2 were shown to be affected in a brain region-specific manner within cocaine-induced CPP and cocaine-extinct CPP models. Bilateral blockade of CRFR2 in the dorsal portion of the medial prefrontal cortex (mPFC), or hippocampus (HP) was partially inhibited, but in the dorsal striatum (DS) did not affect, the cocaine-primed reinstatement of cocaine CPP.

CRHR1 mediates p53 transcription induced by high altitude hypoxia through ERK 1/2 signaling in rat hepatic cells

We have previously reported that hypoxia activates corticotrophin-releasing hormone (CRH) and the expression of its type-1 receptor (CRHR1) and induces disorders of the brain-endocrine-immune network. p53 is activated by hypoxia and involved in tumorigenesis and apoptosis. Whether CRHR1 regulates p53 transactivation to further influence apoptotic genes remains unclear. Here, we showed that hypoxia at a simulated altitude of 5km or 7km for 8 and 24h increased p53 protein and mRNA, and reduced apoptotic bax and IGFBP3 gene expression while upregulating the cell-arrest gene p21 for 8h in rat liver cells. The upregulation of p53 mRNA and downregulation of bax mRNA induced by hypoxia were blocked by pretreatment with the specific CRHR1 antagonist CP-154,526, but the downregulation of IGFBP3 and upregulation of p21 mRNA were not. Furthermore, CRH stimulated p53 mRNA via the ERK 1/2 pathway in the BRL-3A cell line and this was blocked by the ERK 1/2 antagonist U0126. These data provide novel evidence that the CRHR1-triggered ERK 1/2 pathway is involved in the activation of p53 and suppression of the apoptotic bax gene by hypoxia in rat liver.

Corticotropin-releasing factor receptor subtype 2 in human colonic mucosa: Down-regulation in ulcerative colitis

AIM: To assess corticotropin-releasing factor receptor 2 (CRF₂) expression in the colon of healthy subjects and patients with ulcerative colitis (UC).

METHODS: We examined CRF₂ gene and protein expression in the distal/sigmoid colonic mucosal biopsies from healthy subjects and patients with UC (active or disease in remission), human immunodeficiency virus (HIV) and functional bowel disease (FBD) by reverse transcription-polymerase chain reaction and immunofluorescence.

RESULTS: Gene expression of CRF₂ was demonstrated in the normal human colonic biopsies, but not in the human colorectal adenocarcinoma cell line Caco2. Receptor protein localization showed immunoreactive CRF₂ receptors in the lamina propria and in the epithelial cells of the distal/sigmoid biopsy samples. Interestingly, CRF₂ immunoreactivity was no longer observed in epithelial cells of patients with mild-moderately active UC and disease in remission, while receptor protein expression did not change in the lamina propria. No differences in CRF₂ expression profile were observed in distal/sigmoid intestinal biopsies from HIV infection and FBD patients, showing no signs of inflammation.

CONCLUSION: The down-regulation of the CRF₂ receptor in the distal/sigmoid biopsies of UC patients is indicative of change in CRF₂ signalling associated with the process of inflammation.

The corticotropin releasing factor system in cancer: expression and pathophysiological implications

Malignant tumors express multiple factors that have some role in the regulating networks supporting their ectopic growth. Recently, increased interest has been developing in the expression and biological role of the neuropeptides and receptors of the corticotropin releasing factor (CRF) system, the principal neuroendocrine mediator of the stress response, especially in the light of several R&D programs for small molecule antagonists that could present some anticancer therapeutic benefit. In the present article, we review the literature suggesting that the CRF system could be involved in the regulation of human cancer development. Potential implication in growth, metastasis, angiogenesis, or immune parameters via activation of locally expressed receptors could be clinically exploited by presenting targets of new therapeutic approaches.