Plasma Corticotropin-Releasing Factor Receptors and B7-2⁺ Extracellular Vesicles in Blood Correlate with Irritable Bowel Syndrome Disease Severity

Extracellular vesicles (EVs) are composed of bilayer membranes that are released by different cell types and are present in bodily fluids, such as blood, urine, and bile. EVs are thought to play a key role in intracellular communication. Based on their size and density, EVs are classified into small, medium, or large EVs. Cargo composition in EVs reflects physiological changes in health and disease. Patients with irritable bowel syndrome (IBS) exhibit visceral hypersensitivity and mood disorders. Stressful episodes often precede disease symptoms in IBS patients. Stress-induced symptoms include, but are not limited to, abdominal pain and mood swings. Perceived stress responses are mediated by two known G protein-coupled receptors (GPCRs), corticotropin-releasing factor receptor 1 and 2 (CRFRs). CRFRs belong to the Class B secretin receptor family of GPCRs. Here, we show that CRFRs were present in human and murine plasma, and in EVs purified from mouse serum. CRFRs were present in plasma from IBS patients and healthy controls. EVs secreted from immune cells influence both adaptive and innate immune responses via exchange of EVs between different immune cell types. B7-2 (CD86), a plasma membrane antigen-presenting protein, is present on EVs secreted from dendritic, B-, and mast cells, whereas CD9 is present on EVs secreted from dendritic and intestinal epithelial cells. We found that plasma CRFR levels positively correlated with B7-2+ EVs (R = 0.8597, p < 0.0001), but no association was seen with CD9+ EVs. Plasma CRFRs expression negatively correlated with IBS severity scores. Our data suggests that plasma EVs from immune cells carry CRFRs as cargos and influence cell-cell communication in health and disease.

Characterization of CRF1 receptor antagonists with differential peripheral vs central actions in CRF challenge in rats

The aim of this study was to investigate peripheral and central roles of corticotropin-releasing factor (CRF) in endocrinological and behavioral changes. Plasma adrenocorticotropin (ACTH) concentration was measured as an activity of hypothalamic-pituitary-adrenal (HPA) axis. As behavioral changes, locomotion and anxiety behavior were measured after CRF challenge intravenously (i.v.) for the peripheral administration or intracerebroventricularly (i.c.v.) for the central administration. Plasma ACTH concentration was significantly increased by both administration routes of CRF; however, hyperlocomotion and anxiety behavior were induced only by the i.c.v. administration. In the drug discovery of CRF₁ receptor antagonists, we identified two types of compounds, Compound A and Compound B, which antagonized peripheral CRF-induced HPA axis activation to the same extent, but showed different effects on the central CRF signal. These had similar in vitro CRF₁ receptor binding affinities (15 and 10nM) and functional activities in reporter gene assay (15 and 9.5nM). In the ex vivo binding assays using tissues of the pituitary, oral treatment with Compound A and Compound B at 10mg/kg inhibited [¹²⁵I]-CRF binding, whereas in the assay using tissues of the frontal cortex, treatment of Compound A but not Compound B inhibited [¹²⁵I]-CRF binding, indicating that only Compound A inhibited central [¹²⁵I]-CRF binding. In the peripheral CRF challenge, increase in plasma ACTH concentration was significantly suppressed by both Compound A and Compound B. In contrast, Compound A inhibited the increase in locomotion induced by the central CRF challenge while Compound B did not. Compound A also reduced central CRF challenge-induced anxiety behavior and c-fos immunoreactivity in the cortex and the hypothalamic paraventricular nucleus. These results indicate that the central CRF signal, rather than the peripheral CRF signal would be related to anxiety and other behavioral changes, and CRF₁ receptor antagonism in the central nervous system may be critical for identifying drug candidates for anxiety and mood disorders.

Intracerebroventricular administration of novel glucagon-like peptide suppresses food intake in chicks

Glucagon-related peptides such as glucagon, glucagon-like peptide-1, and oxyntomodulin suppress food intake in mammals and birds. Recently, novel glucagon-like peptide (GCGL) was identified from chicken brain, and a comparatively high mRNA expression level of GCGL was detected in the hypothalamus. A number of studies suggest that the hypothalamus plays a critical role in the regulation of food intake in mammals and birds. In the present study, we investigated whether GCGL is involved in the central regulation of food intake in chicks. Male 8-day-old chicks (Gallus gallus) were used in all experiments. Intracerebroventricular administration of GCGL in chicks significantly suppressed food intake. Plasma glucose level was significantly decreased by GCGL, whereas plasma corticosterone level was not affected. Central administration of a corticotrophin-releasing factor (CRF) receptor antagonist, α-helical CRF, attenuated GCGL-suppressed food intake. It seems likely that CRF receptor is involved in the GCGL-induced anorexigenic pathway. All our findings suggest that GCGL functions as an anorexigenic peptide in the central nervous system of chicks.

Differential behavioural effects of chronic infusion of CRH 1 and CRH 2 receptor antisense oligonucleotides into the rat brain

The purpose of this study was to investigate the functional role the two corticotropin-releasing hormone (CRH) receptor subtypes play in regulating the behavioural performance of rats in various well-defined test situations. Antisense oligodeoxynucleotides (ODNs) corresponding to either the rat CRH1 or CRH2 receptor mRNA were infused chronically into the lateral ventricle of male rats via osmotic minipumps (5 microg/0.5 microl/h over 6 days). Control groups received infusions of either a scrambled sequence ODN or mixed bases ODN or vehicle. On day 4 after surgery, the rats were subjected to 10 min of social defeat and immediately afterwards tested on the elevated plus-maze. Compared to a scrambled sequence control ODN, CRH1 receptor antisense ODN infusion was found to exert an anxiolytic-like effect whereas CRH2 receptor antisense ODN infusion had no effect on defeat-induced anxiety-related behaviour. In contrast, the CRH2 receptor antisense ODN increased immobility in a forced swim test whereas CRH1 receptor ODN-treated rats did not differ from controls. No influence of either ODN was found on general locomotor activity in an open field or on short-term memory performance in a social discrimination test. Furthermore, the CRH2 receptor antisense ODN did not affect spatial learning in a Morris water maze task. An additional experiment comparing a mixture of both missense ODNs and a vehicle control group confirmed that the former failed to induce non-specific (toxic) side effects, further substantiating the specificity of the respective antisense effects measured in this study. The results support the hypothesis that the two CRH receptor subtypes selectively mediate differential effects of endogenous CRH or CRH-related peptides at the brain level with the CRHI receptor contributing predominantly to emotional behaviour and the CRH2 receptor being involved in the regulation of stress coping behaviour.