Mediation of gastrointestinal stress responses by corticotropin-releasing factor

Stress and gene expression of individuals with chronic abdominal pain

BACKGROUND

Research examining the role of stress in gastrointestinal (GI) symptoms such as chronic abdominal pain (CAP) is controversial. The purpose of this study was to examine the expression of genes involved in metabolic stress and toxicity in men and women with high and low levels of perceived stress with and without CAP.

METHODS

Data and samples were collected and the expression of genes involved in metabolic stress and toxicity was analyzed in 26 individuals who had consented to participate in a natural history protocol. Subjects completed the 10-item Perceived Stress scale (PSS). Fasting participants' peripheral whole blood was collected for proteomic and genomic studies. Polymerase chain reaction (PCR) array was used to analyze the expression of 84 key genes involved in human stress and toxicity plus 5 housekeeping genes. Plasma interleukin-1 alpha (IL-1α) protein was quantified via enzyme-linked immunosorbent assay (ELISA).

RESULTS

Interleukin-1 alpha gene (IL1A) was upregulated in females with high stress versus females with low stress by 2.58-fold (95% CI [0.88, 4.28]). IL1A was upregulated in participants with high stress and CAP versus those with low stress and CAP by 3.47-fold (95% CI [1.14, 5.80]).

CONCLUSIONS

An upregulation of the gene coding the pro-inflammatory cytokine IL-1α suggests that the mechanism behind stress-related changes in GI symptoms is pro-inflammatory in nature. The results of this study contribute to the knowledge of the mechanism behind stress-related CAP symptoms and gender differences associated with these disorders.

Basal and stimulated hypothalamic-pituitary-adrenal axis activity in patients with functional gastrointestinal disorders and healthy controls

OBJECTIVE

The aim of this study was to investigate alterations of pituitary-adrenal activity under both stimulated and unstimulated conditions in patients with functional gastrointestinal disorders.

METHODS

Thirty subjects who fulfilled the Rome Diagnostic Criteria for either irritable bowel syndrome or nonulcer dyspepsia and 24 healthy controls took part in the study. Free salivary morning cortisol and diurnal cortisol profiles were obtained for all subjects. On a second day, a low-dose dexamethasone suppression test was applied. Additionally, in all subjects a corticotropin-releasing hormone (CRH) challenge test was performed.

RESULTS

The results show attenuated unstimulated cortisol levels in patients compared with controls. After CRH challenge, blunted adrenocorticotropic hormone and cortisol responses were observed. These findings suggest lower pituitary and adrenocortical activity in patients with functional gastrointestinal disorders.

CONCLUSION

The observed pituitary-adrenal reactivity in these patients is discussed as a possible consequence of lower adrenocortical activity, possibly resulting in a disinhibition of CRH in the brain.

Cocaine-amphetamine-regulated transcript (CART) acts in the central nervous system to inhibit gastric acid secretion via brain corticotropin-releasing factor system

Recent study has indicated that cocaine-amphetamine-regulated transcript (CART) is an anorectic chemical in the brain. In the present study, we examined the hypothesis that CART may act in the central nervous system to alter gastric function. Food consumption, gastric acid secretion, and gastric emptying were measured after injection of CART into the cerebrospinal fluid in 24-h fasted Sprague Dawley rats. Central injection of CART inhibited food intake, gastric acid secretion, and gastric emptying. In contrast, ip injection of CART failed to inhibit gastric acid secretion and gastric emptying, suggesting that CART acts in the brain to suppress gastric acid secretion and gastric emptying. In the vagotomized animals, centrally administered CART did inhibit pentagastrin-stimulated gastric acid secretion. The CART-induced acid inhibition was also observed in rats treated with indomethacin, a cyclooxygenase inhibitor. In contrast, pretreatment with central administration of a CRF receptor antagonist, alpha-helical CRF9-41, completely blocked the central CART-induced inhibition of gastric acid secretion. All these results suggest that CART acts in the brain to inhibit gastric function via brain CRF system. The vagal pathway and the prostaglandin system are not involved in the acid inhibition.

Corticotropin-releasing hormone mimics stress-induced colonic epithelial pathophysiology in the rat

We examined the effect of stress on colonic epithelial physiology, the role of corticotropin-releasing hormone (CRH), and the pathways involved. Rats were restrained or injected intraperitoneally with CRH or saline. Colonic segments were mounted in Ussing chambers, in which ion secretion and permeability (conductance and probe fluxes) were measured. To test the pathways involved in CRH-induced changes, rats were pretreated with hexamethonium, atropine, bretylium, doxantrazole, alpha-helical CRH-(9-41) (all intraperitoneally), or aminoglutethimide (subcutaneously). Restraint stress increased colonic ion secretion and permeability to ions, the bacterial peptide FMLP, and horseradish peroxidase (HRP). These changes were prevented by alpha-helical CRH-(9-41) and mimicked by CRH (50 microgram/kg). CRH-induced changes in ion secretion were abolished by alpha-helical CRH-(9-41), hexamethonium, atropine, or doxantrazole. CRH-stimulated conductance was significantly inhibited by alpha-helical CRH-(9-41), hexamethonium, bretylium, or doxantrazole. CRH-induced enhancement of HRP flux was significantly reduced by all drugs but aminoglutethimide. Peripheral CRH reproduced stress-induced colonic epithelial pathophysiology via cholinergic and adrenergic nerves and mast cells. Modulation of stress responses may be relevant to the management of colonic disorders.

Microinfusion of corticotropin-releasing factor into the locus coeruleus/subcoeruleus nuclei inhibits gastric acid secretion via spinal pathways in the rat

Brain corticotropin-releasing factor (CRF) is involved in stress-related alterations of gastric acid secretion. CRF in the locus coeruleus has been shown to induce anxiogenic behavioral responses and to mimic stress-induced alterations of colonic motor function. Whether the locus coeruleus/subcoeruleus nucleus (LC/SC) is a site of action for CRF to alter gastric acid secretion was investigated in urethane-anesthetized gastric fistula rats. In sham-operated animals, CRF (126-420 pmol) microinfused bilaterally into the LC/SC induced a dose-dependent inhibition of pentagastrin (PG)-stimulated gastric acid secretion of 60-81% within the first hour after microinjection. At the 420 pmol dose, this inhibitory effect of CRF into the LC/SC lasted throughout the whole observation period of 120 min. After bilateral vagotomy, basal and PG-stimulated gastric acid secretion at microinjection of vehicle was reduced. Nevertheless, microinfusion of 420 pmol CRF into the LC/SC still inhibited significantly gastric acid secretion by 62.1%. In contrast, in spinal cord transected animals bilateral microinfusion of 420 pmol CRF into the LC/SC did not reduce PG-stimulated gastric acid secretion. These data indicate that CRF acts in the LC/SC to induce a long lasting inhibition of peripherally stimulated gastric acid secretion via spinal pathways. These findings suggest a possible role of the LC/SC in the regulation of gastric secretion and of endogenous CRF at these sites in the stress-related inhibition of gastric acid secretion by affecting autonomic nervous system activity.

Regulation of canine gallbladder motility by brain peptides

BACKGROUND

Brain peptides alter most gastrointestinal functions, but their effects on gallbladder motility have not been examined in detail.

METHODS

Studies were conducted in awake, male beagle dogs.

RESULTS

Of 30 brain peptides evaluated, thyrotropin-releasing hormone (TRH) and calcitonin gene-related peptide (CGRP) inhibited CCK- and meal-induced gallbladder contraction. These responses were abolished by ganglionic blockade. Truncal vagotomy prevented the central inhibitory action of TRH but not that of CGRP, whereas noradrenergic blockade prevented the central inhibitory action of CGRP but not that of TRH. Muscarinic blockade did not prevent the relaxing effect of cerebral TRH but pretreatment with the vasoactive intestinal peptide (VIP) antagonist, (4Cl-D-Phe6-Leu17)VIP, significantly attenuated gallbladder relaxation induced by cerebral TRH: the combination of both VIP and muscarinic antagonists abolished TRH-induced gallbladder relaxation. alpha-Adrenergic receptor blockade but neither beta-adrenergic blockade nor adrenalectomy abolished gallbladder relaxation induced by cerebral CGRP. Intravenous infusion of VIP and norepinephrine inhibited CCK-induced gallbladder contraction and these responses were abolished dose dependently by intravenous infusion of (4Cl-D-Phe6-Leu17)VIP and phentolamine, respectively.

CONCLUSIONS

Cerebral TRH inhibits canine gallbladder contraction by stimulation of vagal outflow and subsequent release of VIP acting via its specific receptor whereas cerebral CGRP inhibits gallbladder contraction by stimulation of sympathetic, noradrenergic outflow via alpha-adrenergic receptors.

The neurobiology of stress ulcers

We have reviewed the neurobiology of stress ulcers from animal models to potential pharmacotherapeutic mechanisms. The evidence strongly supports the hypothesis that certain stress-related gastric lesions are 'brain-driven' events which may be more effectively managed through central manipulations than by altering local, gastric factors. Recent advances in the use of anxiolytic and antidepressant drugs in the management of stress-related gastric mucosal injury further supports the contention that a brain-gut axis, which may have nervous, peptidergic and classic monoaminergic components, modulates the intricate and complicated pattern of communication between the brain and the stomach. Delineation of the precise pathways which make up this communication as well as their manipulation by various pharmacological agents will be the focus of future research endeavour.