The protective effect of vasoactive intestinal peptide (VIP) on stress-induced gastric ulceration in rats

Nervous mechanisms of restraint water-immersion stress-induced gastric mucosal lesion

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Exploring the nervous mechanisms of SGML has become a research hotspot. Restraint water-immersion stress (RWIS) can induce GML and has been widely used to elucidate the nervous mechanisms of SGML. It is believed that RWIS-induced GML is mainly caused by the enhanced activity of vagal parasympathetic nerves. Many central nuclei, such as the dorsal motor nucleus of the vagus, nucleus of the solitary tract, supraoptic nucleus and paraventricular nucleus of the hypothalamus, mediodorsal nucleus of the thalamus, central nucleus of the amygdala and medial prefrontal cortex, are involved in the formation of SGML in varying degrees. Neurotransmitters/neuromodulators, such as nitric oxide, hydrogen sulfide, vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, enkephalin, 5-hydroxytryptamine, acetylcholine, catecholamine, glutamate, γ-aminobutyric acid, oxytocin and arginine vasopressin, can participate in the regulation of stress. However, inconsistent and even contradictory results have been obtained regarding the actual roles of each nucleus in the nervous mechanism of RWIS-induced GML, such as the involvement of different nuclei with the time of RWIS, the different levels of involvement of the sub-regions of the same nucleus, and the diverse signalling molecules, remain to be further elucidated.

Resveratrol promotes myenteric neuroprotection in the ileum of rats after ischemia-reperfusion injury

AIMS

The present study evaluated the effects of resveratrol in the myenteric plexus after intestinal ischemia-reperfusion (I/R) injury caused by occluding the superior mesenteric artery for 45min, followed by 7days of reperfusion.

MAIN METHODS

Forty-two male Wistar rats were divided into seven groups: control (C group), untreated sham surgery control (SC group), sham surgery control treated with resveratrol before surgery (STA group), sham surgery control treated with resveratrol before and after surgery (STAD group), ischemic control (IRC group), ischemic treated before I/R (IRTA group), and ischemic treated before and after I/R (IRTAD group). Resveratrol (10mg/kg) was administered for 4days and 2h prior to surgery and/or 7days later. Morphometric analyses were performed, and the density of the general neuronal population (HuC/D-immunoreactive [IR]), nitrergic subpopulation (neuronal nitric oxide synthase [nNOS]-IR), vasoactive intestinal peptide (VIP)ergic varicosities (VIP-IR), and glial cells (S100-IR) was determined.

KEY FINDINGS

Injury that was caused by I/R significantly reduced (p<0.01) the HuC/D-IR general neuronal population. Treatment with resveratrol before and after ischemia had a neuroprotective effect. Morphometric changes caused by I/R in nitrergic neurons and varicosities were also attenuated by resveratrol. Ischemia/reperfusion promoted the proliferation of enteric glial cells, and resveratrol treatment before and after I/R reversed this effect.

SIGNIFICANCE

Resveratrol had neuroprotective effects, showing promise for application in intestinal surgery and transplants.

Prolonged acetylsalicylic-acid-supplementation-induced gastritis affects the chemical coding of the stomach innervating vagal efferent neurons in the porcine dorsal motor vagal nucleus (DMX)

The main goal of our research was to study the possible alterations of the chemical coding of the dorsal motor vagal nucleus (DMX) neurons projecting to the porcine stomach prepyloric region following prolonged acetylsalicylic acid supplementation. Fast Blue (FB) was injected into the studied area of the stomach. Since the seventh day following the FB injection, acetylsalicylic acid (ASA) was given orally to the experimental gilts. All animals were euthanized on the 28th day after FB injection. Medulla oblongata sections were then processed for double-labeling immunofluorescence for choline acetyltransferase (ChAT), pituitary adenylate cyclase-activating peptide (PACAP), vasoactive intestinal polypeptide (VIP), nitric oxide synthase (NOS), galanin (GAL), substance P (SP), leu enkephalin (LENK), and cocaine- and amphetamine-regulated transcript (CART). In the control DMX, only PACAP was observed in 30.08 ± 1.97 % of the FB-positive neurons, while VIP, NOS, GAL, SP, LENK, and CART were found exclusively in neuronal processes running between FB-labeled perikarya. In the ASA DMX, PACAP was revealed in 49.53 ± 5.73 % of traced vagal perikarya. Moreover, we found de novo expression of VIP in 40.32 ± 7.84 %, NOS in 25.02 ± 6.08 %, and GAL in 3.37 ± 0.85 % of the FB-labeled neurons. Our results suggest that neuronal PACAP, VIP, NOS, and GAL are mediators of neural response to aspirin-induced stomach inflammatory state.

Antioxidant activity of vasoactive intestinal peptide in HK2 human renal cells

Oxidative stress is a major mediator of tissue and cell injuries. The injury in chronic nephrotic syndrome, acute renal failure, myeloma kidney injury and other kidney diseases is initiated by oxidative stress. We have previously demonstrated that vasoactive intestinal peptide (VIP) acts as an antiproliferative agent in renal cancer cells. This study was designed to evaluate the renoprotective activity of VIP against H(2)O(2)-induced oxidative damage in a proximal tubule kidney cell line (human, non-tumor, HK2 cells) in order to investigate the potential usefulness of this peptide in the treatment of oxidative-stress related kidney diseases. HK2 cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Propidium iodide was used to identify cells undergoing apoptosis. Western blotting was performed with anti-Bcl-2, anti-Bax and anti-formyl peptide receptor (low-affinity variant FPRL-1) monoclonal antibodies whereas 2,7-dichlorofluorescein diacetate was used for measurement of levels of intracellular reactive oxygen species (ROS). HK2 cells were injured with H(2)O(2) in order to induce apoptosis: the effect was time- and dose-dependent. VIP increased the levels of the antiapoptotic protein Bcl-2 and decreased those of the proapoptotic protein Bax. VIP decreased the intracellular ROS levels reached by H(2)O(2)-induced oxidative stress. VIP effect on ROS levels involved FPLR-1 but not VPAC(1,2) receptors as evidenced by the use of the respective antagonists WRW4 and JV-1-53. Thus, VIP protects HK2 cells from apoptosis by increasing Bcl-2 levels and this effect is initiated through FPLR1 receptor. In conclusion, VIP might exert a renoprotective effect by the suppression of oxidative stress.

Differential changes in Substance P, VIP as well as neprilysin levels in patients with gastritis or ulcer

The protective effect of capsaicin-sensitive sensory nerve (CSSN) activation was recently demonstrated in human gastric mucosa. We here examined changes in neuropeptides, specifically Substance P (SP), calcitonin-gene related peptide (CGRP) and vasoactive intestinal peptide (VIP) in patients with chronic gastritis or ulcer. Furthermore changes in neprilysin levels, which hydrolyse these neuropeptides, were determined. Gastric biopsies were obtained from both lesion- and normal-appearing mucosa of 57 patients. The presence of H. pylori infection was verified with rapid urease assay. Neuronal and non-neuronal levels of SP, VIP, CGRP and neprilysin activity were determined in freshly frozen biopsies. Immunohistochemical localization of neprilysin was performed in 30 paraffin embedded specimens. We here found that neuronal SP levels decreased significantly in normally appearing mucosa of patients with gastritis while levels of non-neuronal SP increased in diseased areas of gastritis and ulcer. The presence of H. pylori led to further decreases of SP levels. The content of VIP in both disease-involved and uninvolved mucosa, and expression of neprilysin, markedly decreased in patients with gastritis or ulcer. Since VIP, as well as SP fragments, formed following hydrolysis with neprilysin is recognized to have gastroprotective effects, decreased levels of VIP, SP and neprilysin may predispose to cellular damage.

Angiotensin receptor subtype mediated physiologies and behaviors: new discoveries and clinical targets

The renin-angiotensin system (RAS) mediates several classic physiologies including body water and electrolyte homeostasis, blood pressure, cyclicity of reproductive hormones and sexual behaviors, and the regulation of pituitary gland hormones. These functions appear to be mediated by the angiotensin II (AngII)/AT(1) receptor subtype system. More recently, the angiotensin IV (AngIV)/AT(4) receptor subtype system has been implicated in cognitive processing, cerebroprotection, local blood flow, stress, anxiety and depression. There is accumulating evidence to suggest an inhibitory influence by AngII acting at the AT(1) subtype, and a facilitory role by AngIV acting at the AT(4) subtype, on neuronal firing rate, long-term potentiation, associative and spatial learning, and memory. This review initially describes the biochemical pathways that permit synthesis and degradation of active angiotensin peptides and three receptor subtypes (AT(1), AT(2) and AT(4)) thus far characterized. There is vigorous debate concerning the identity of the most recently discovered receptor subtype, AT(4). Descriptions of classic and novel physiologies and behaviors controlled by the RAS are presented. This review concludes with a consideration of the emerging therapeutic applications suggested by these newly discovered functions of the RAS.

Role of vasoactive intestinal peptide and nitric oxide in the modulation of electroacupucture on gastric motility in stressed rats

AIM: To investigate the effects and mechanisms of vasoactive intestinal peptide (VIP) and nitric oxide (NO) in the modulation of electroacupucture (EA) on gastric motility in restrained-cold stressed rats.

METHODS: An animal model of gastric motility disorder was established by restrained-cold stress. Gastric myoelectric activities were recorded by electrogastroenterography (EGG). VIP and NO concentrations in plasma and gastric mucosal and bulb tissues were detected by radioimmunoassay (RIA). VIP expression in the gastric walls was assayed using avidin-biotin-peroxidase complex (ABC) and image analysis.

RESULTS: In cold restrained stressed rats, EGG was disordered and irregular. The frequency and amplitude of gastric motility were higher than that in control group (P < 0.01). VIP and NO contents of plasma, gastric mucosal and bulb tissues were obviously decreased (P < 0.01). Following EA at “Zusanli” (ST36), the frequency and amplitude of gastric motility were obviously lowered (P < 0.01), while the levels of VIP and NO in plasma, gastric mucosal and bulb tissues increased strikingly (P < 0.01, P < 0.05) and expression of VIP in antral smooth muscle was elevated significantly (P < 0.01) in comparison with those of model group.

CONCLUSION: VIP and NO participate in the modulatory effect of EA on gastric motility. EA at “Zusanli” acupoint (ST36) can improve gastric motility of the stressed rats by increasing the levels of VIP and NO.

Neuroimmune link in the mucosa of chronic gastritis with Helicobacter pylori infection

It is suggested that different neuropeptides regulate gastric mucosal integrity and participate in the development of chronic gastritis. The aim of this study was to examine the roles and changes of immunoreactive (IR) nerves and immunocompetent cells in human gastritis. Immunohistochemical, immunocytochemical, and confocal laser microscopic methods were used. All investigated nerve fibers were found in different quantities in the mucosa of both control and gastritis samples. The number of SP, NPY, and VIP IR nerve fibers increased significantly (P < 0.05) in gastritis. No IR immunocompetent cells (lymphocytes, plasma cells, mast cells) were found in the control, however, some showed NPY (16.8%) and SP (9.4%) immunoreactivity in chronic gastritis. The distance between nerve fibers and immunocompetent cells was 200 nm to 1 microm. In conclusion, the increased number of SP, NPY, and VIP IR nerves and IR immunocytes suggests that they participate in development of neurogenic inflammation, repairing processes of chronic gastritis.

Gastroprotective activity of Nigella sativa L oil and its constituent, thymoquinone against acute alcohol-induced gastric mucosal injury in rats

AIM

To evaluate the role of reactive oxygen species in the pathogenesis of acute ethanol-induced gastric mucosal lesions and the effect of Nigella sativa L oil (NS) and its constituent thymoquinone (TQ) in an experimental model.

METHODS

Male Wistar albino rats were assigned into 4 groups. Control group was given physiologic saline orally (10 mL/kg body weight) as the vehicle (gavage); ethanol group was administrated 1 mL (per rat) absolute alcohol by gavage; the third and fourth groups were given NS (10 mL/kg body weight) and TQ (10 mg/kg body weight p.o) respectively 1 h prior to alcohol intake. One hour after ethanol administration, stomach tissues were excised for macroscopic examination and biochemical analysis.

RESULTS

NS and TQ could protect gastric mucosa against the injurious effect of absolute alcohol and promote ulcer healing as evidenced from the ulcer index (UI) values. NS prevented alcohol-induced increase in thiobarbituric acid-reactive substances (TBARS), an index of lipid peroxidation. NS also increased gastric glutathione content (GSH), enzymatic activities of gastric superoxide dismutase (SOD) and glutathione-S-transferase (GST). Likewise, TQ protected against the ulcerating effect of alcohol and mitigated most of the biochemical adverse effects induced by alcohol in gastric mucosa, but to a lesser extent than NS. Neither NS nor TQ affected catalase activity in gastric tissue.

CONCLUSION

Both NS and TQ, particularly NS can partly protect gastric mucosa from acute alcohol-induced mucosal injury, and these gastroprotective effects might be induced, at least partly by their radical scavenging activity.

Anti-stress and anti-anxiety effects of centrally acting angiotensin II AT1 receptor antagonists

The brain and the peripheral (hormonal) angiotensin II systems are stimulated during stress. Activation of brain angiotensin II AT(1) receptors is required for the stress-induced hormone secretion, including CRH, ACTH, corticoids and vasopressin, and for stimulation of the central sympathetic activity. Long-term peripheral administration of the angiotensin II AT(1) antagonist candesartan blocks not only peripheral but also brain AT(1) receptors, prevents the hormonal and sympathoadrenal response to isolation stress and prevents the formation of stress-induced gastric ulcers. The mechanisms responsible for the prevention of stress-induced ulcers by the AT(1) receptor antagonist include protection from the stress-induced ischemia and inflammation (neutrophil infiltration and increase in ICAM-1 and TNF-alpha) in the gastric mucosa and a partial blockade of the stress-induced sympathoadrenal stimulation, while the protective effect of the glucocorticoid release during stress is maintained. AT(1) receptor antagonism prevents the stress-induced decrease in cortical CRH(1) and benzodiazepine binding and is anxiolytic. Blockade of brain angiotensin II AT(1) receptors offers a novel therapeutic opportunity for the treatment of anxiety and other stress-related disorders.

Brain mast cells and therapeutic potential of vasoactive intestinal peptide in a Parkinson's disease model in rats: brain microdialysis, behavior, and microscopy

In the present study, the effect of systemically administered vasoactive intestinal peptide (VIP) (25 ng/kg i.p.) was investigated on drug-induced rotational behavior, extra-cellular dopamine levels and histology of corpus striatum in a 6-hydroxydopamine (6-OHDA)-induced rat model of Parkinson's disease. After 15 days of 6-OHDA lesion, apomorphine-induced (0.05 mg/kg s.c.) rotational behavior of the animals significantly increased and extra-cellular dopamine levels of corpus striatum were significantly reduced. VIP reversed the rotational deficits but did not alter the decrease in striatal dopamine levels. On the other hand, histological data indicate that VIP significantly reduced neuronal death and demyelination. Electron microscopic appearance of mast cells showed ultra-structural variety between VIP-treated and 6-OHDA lesioned groups. VIP activates mast cells without any evidence of typical exocytosis, and possibly mast cells could participate in neuroprotection. Our results suggest that systemically administered VIP can attenuate the motor response changes, neuronal cell death, and myelin sheet loss characteristically associated with 12 microg 6-OHDA administration into the rat striatum. Brain mast cells seem to participate in neuronal protection. Possibly, protective cues could be produced by brain mast cells.

Angiotensin II AT1 receptor blockade prevents gastric ulcers during cold-restraint stress

Cold-restraint stress reduces gastric blood flow and produces acute gastric ulcers. We studied the role of Angiotensin II (Ang II) on gastric blood flow and gastric ulceration during stress. Spontaneously hypertensive rats, a stress-sensitive strain, were pretreated for 14 days with the AT(1) receptor antagonist candesartan before cold-restraint stress. AT(1) blockade increased gastric blood flow 40% to 50%; prevented gastric ulcer formation by 70% to 80%; reduced the increase in adrenomedullary epinephrine and TH mRNA without preventing the stress-induced increase in adrenal corticosterone; decreased the stress-induced expression of tumor necrosis factor alpha (TNF-alpha) and adhesion protein ICAM-1 in arterial endothelium, and neutrophil infiltration in the gastric mucosa; and decreased PGE(2) content. AT(1) receptor blockers prevent stress-induced ulcerations by a combination of gastric blood flow protection, decreased sympathoadrenal activation, anti-inflammatory effects with reduction in TNF-alpha, and ICAM-1 expression, leading to reduced neutrophil infiltration while maintaining the protective glucocorticoid effects and PGE(2) release. Ang II has a crucial role, through stimulation of AT(1) receptors, in the production and progression of stress-induced gastric injury, and AT(1) receptor antagonists could be of therapeutic benefit.

Levels of vasoactive intestinal peptide, cholecystokinin and calcitonin gene-related peptide in plasma and jejunum of rats following traumatic brain injury and underlying significance in gastrointestinal dysfunction

AIM: To study the alterations of brain-gut peptides following traumatic brain injury (TBI) and to explore the underlying significance of these peptides in the complicated gastrointestinal dysfunction.

METHODS: Rat models of focal traumatic brain injury were established by impact insult method, and divided into 6 groups (6 rats each group) including control group with sham operation and TBI groups at postinjury 3, 12, 24, 72 h, and d 7. Blood and proximal jejunum samples were taken at time point of each group and gross observations of gastrointestinal pathology were recorded simultaneously. The levels of vasoactive intestinal peptide (VIP) in plasma, calcitonin gene-related peptide (CGRP) and cholecystokinin (CCK) in both plasma and jejunum were measured by enzyme immunoassay (EIA). Radioimmunoassay (RIA) was used to determine the levels of VIP in jejunum.

RESULTS: Gastric distension, delayed gastric emptying and intestinal dilatation with a large amount of yellowish effusion and thin edematous wall were found in TBI rats through 12 h and 72 h, which peaked at postinjury 72 h. As compared with that of control group (247.8 ± 29.5 ng/L), plasma VIP levels were significantly decreased at postinjury 3, 12 and 24 h (106.7 ± 34.1 ng/L, 148.7 ± 22.8 ng/L, 132.8 ± 21.6 ng/L, respectively), but significantly increased at 72 h (405.0 ± 29.8 ng/L) and markedly declined on d 7 (130.7 ± 19.3 ng/L). However, Plasma levels CCK and CGRP were significantly increased through 3 h and 7 d following TBI (126-691% increases), with the peak at 72 h. Compared with control (VIP, 13.6 ± 1.4 ng /g; CGRP, 70.6 ± 17.7 ng/g); VIP and CGRP levels in jejunum were significantly increased at 3 h after TBI (VIP, 35.4 ± 5.0 ng/g; CGRP, 103.8 ± 22.1 ng/g), and declined gradually at 12 h and 24 h (VIP, 16.5 ± 1.8 ng/g, 5.5 ± 1.4 ng/g; CGRP, 34.9 ± 9.7 ng/g, 18.5 ± 7.7 ng/g), but were significantly increased again at 72 h (VIP, 48.7 ± 9.5 ng/g; CGRP, 142.1 ± 24.3 ng/g), then declined in various degrees on d 7 (VIP, 3.8 ± 1.1 ng/g; CGRP, 102.5 ± 18.1 ng/g). The CCK levels in jejunum were found to change in a similar trend as that in plasma with the concentrations of CCK significantly increased following TBI (99-517% increases) and peaked at 72 h.

CONCLUSION: Traumatic brain injury can lead to significant changes of brain-gut peptides in both plasma and small intestine, which may be involved in the pathogenesis of complicated gastrointestinal dysfunction.

Computer-assisted visualization and quantitation of experimental gastric lesions in rats

INTRODUCTION

Photography is commonly used to evaluate macroscopic morphology of experimental gastric lesions. The conventional methods for quantitation of these lesions tend to be highly subjective, error-prone, and tedious. This study reports a simple and novel method for visualization of experimental gastric lesions by direct scanning of stomach samples and their quantitation by using computer-assisted image analysis.

METHODS

Gastric mucosal lesions were produced by indomethacin or ethanol in male Wistar rats. The stomachs were removed, opened along the greater curvature, and washed. The flattened stomach samples were sandwiched within a transparent plastic folder and scanned. The captured image was saved and subjected to lesion quantitation using a freely accessible image analysis program, Scion Image. A macro subroutine was optimized for automation of the entire procedure for ease in frequent applications.

RESULTS

The images obtained by direct scanning of stomach samples showed excellent morphologic visualization of gastric lesions. The standard spots having variable areas of same density, or same areas of variable densities, showed a direct relation with signal intensity (pixels). A linear correlation was observed between measured and actual values of the known standard areas. The representative samples of indomethacin- and ethanol-induced gastric ulcers showed the total lesion areas of 4.62+/-0.74 and 169.26+/-13.23 mm(2), respectively.

DISCUSSION

Direct scanning of stomach samples is a simple, cost-effective, rapid, and efficient procedure for morphologic evaluation of experimental gastric lesions. The output images of scanned stomach samples are superior to scanned photographs, and can be instantly used for quantitative assessment of mucosal injury using the image analysis program.

Anti-inflammatory effects of angiotensin II AT1 receptor antagonism prevent stress-induced gastric injury

Stress reduces gastric blood flow and produces acute gastric mucosal lesions. We studied the role of angiotensin II in gastric blood flow and gastric ulceration during stress. Spontaneously hypertensive rats were pretreated for 14 days with the AT1 receptor antagonist candesartan before cold-restraint stress. AT1 receptors were localized in the endothelium of arteries in the gastric mucosa and in all gastric layers. AT1 blockade increased gastric blood flow by 40-50%, prevented gastric ulcer formation by 70-80% after cold-restraint stress, reduced the increase in adrenomedullary epinephrine and tyrosine hydroxylase mRNA without preventing the stress-induced increase in adrenal corticosterone, decreased the stress-induced expression of TNF-alpha and that of the adhesion protein ICAM-1 in arterial endothelium, decreased the neutrophil infiltration in the gastric mucosa, and decreased the gastric content of PGE2. AT1 receptor blockers prevent stress-induced ulcerations by a combination of gastric blood flow protection, decreased sympathoadrenal activation, and anti-inflammatory effects (with reduction in TNF-alpha and ICAM-1 expression leading to reduced neutrophil infiltration) while maintaining the protective glucocorticoid effects and PGE2 release. Angiotensin II has a crucial role, through stimulation of AT1 receptors, in the production and progression of stress-induced gastric injury, and AT1 receptor antagonists could be of therapeutic benefit.

Gastroprotective effect of leptin on gastric mucosal injury induced by ischemia-reperfusion is related to gastric histamine content in rats

Leptin has cytoprotective effect to gastric mucosal injury in rats. We aimed to test the hypothesis that leptin induced histamine is involved in the prevention of ischemia-reperfusion (I/R) induced gastric mucosal injury in rats. At the end of the 30 min celiac artery occlusion and 12h reperfusion process, serum and gastric tissue samples were taken from three group of rats to measure oxidative status, histamine levels and for histological examinations. Leptin decreased ulcer and polymorphonuclear leukocyte (PMNL) index, and serum malondialdehyde (MDA) and protein carbonyl content but increased gastric tissue histamine levels. We concluded that leptin exerts a protective effect on gastric mucosa to I/R induced gastric injury probably through increasing tissue histamine content which, in turn, maintain the gastric mucosal blood flow.

Effects of the vasoactive intestinal peptide on stress-induced mucosal ulcers and modulation of methylation of histamine in gastric tissue of the rats

Vasoactive intestinal peptide (VIP) prevents stress-induced gastric ulcers, inhibits mast cell degranulation and protects gastric tissue from lipid peroxidation. Histamine has an important role in the development of gastric ulcers and mast cell derived histamine might be essential in this process.

Passage of vasoactive intestinal peptide across the blood-brain barrier

We investigated the ability of vasoactive intestinal peptide (VIP) to cross the blood-brain barrier (BBB), the interface between the peripheral circulation and central nervous system (CNS). VIP labeled with 131I (I-VIP) and injected intravenously into mice was taken up by brain as determined by multiple-time regression analysis. Excess unlabeled VIP was unable to impede the entry of I-VIP, indicating that passage is by nonsaturable transmembrane diffusion. High pressure liquid chromatography (HPLC) showed the radioactivity entering the brain to be intact I-VIP. After intracerebroventricular (i.c.v.) injection, I-VIP was sequestered by brain, slowing its efflux from the CNS. In summary, VIP crosses the BBB unidirectionally from blood to brain by transmembrane diffusion.

The antioxidative and antihistaminic properties of quercetin in ethanol-induced gastric lesions

The role of reactive oxygen species in the pathogenesis of acute ethanol-induced gastric mucosal lesions and the effects of quercetin were evaluated in an experimental model. In addition, the effects of quercetin on gastric damage were evaluated histopathologically. Rats were divided into three groups as control rats, ethanol treated rats and ethanol+quercetin treated rats. Ethanol group was given a gastric gavage containing 1 ml of 80% ethanol (v/v) prepared in distilled water. Quercetin (200 mg/kg body wt.) was given by intragastric gavage 120 min before the administration of ethanol. Gastric tissue thiobarbituric acid reactive substance levels, carbonyl compounds, histamine levels and myeloperoxidase activities were found to be increased in ethanol treated rats and quercetin treatment reversed these increases. No statistically significant changes were found between all groups in catalase activity. The superoxide dismutase activity dropped significantly after ethanol treatment and quercetin treatment increased this enzyme activity. Gastric damage was confirmed histomorphometrically by significant increases in the number of mast cells and gastric erosions in ethanol treated rats. It was also confirmed that quercetin treatment significantly decreased the number of mast cells and reduced the area of gastric erosions. The results suggest that the gastroprotective effect of quercetin in this experimental model could be due to its antiperoxidative, antioxidant and antihistaminic effects.

Circuits and systems in stress. I. Preclinical studies

This paper reviews the preclinical literature related to the effects of stress on neurobiological and neuroendocrine systems. Preclinical studies of stress provide a comprehensive model for understanding neurobiological alterations in post-traumatic stress disorder (PTSD). The pathophysiology of stress reflects long-standing changes in biological stress response systems and in systems involved in stress responsivity, learning, and memory. The neural circuitry involved includes systems mediating hypothalamic-pituitary-adrenal (HPA) axis, norepinephrine (locus coeruleus), and benzodiazepine, serotonergic, dopaminergic, neuropeptide, and central amino acid systems. These systems interact with brain structures involved in memory, including hippocampus, amygdala, and prefrontal cortex. Stress responses are of vital importance in living organisms; however excessive and/or repeated stress can lead to long-lasting alterations in these circuits and systems involved in stress responsiveness. Intensity and duration of the stressor, and timing of the stressor in life, have strong impact in this respect.

Effects of sepsis on mast cells in rat dura mater: influence of L-NAME and VIP

1. The influence of lipopolysaccharide (LPS)-induced sepsis on the various mast cell phenotypes of rat dura mater were examined both by immunohistochemical and biochemical methods. 2. Three different populations of mast cells were identified in control rats: connective tissue type mast cells (CTMC) which contain rat mast cell protease1 (RMCP1), histamine, serotonin and heparin, mucosal type mast cells (MMC) which contain RMCP2, histamine and serotonin, and intermediate type which contains both RMCP1 and RMCP2 and probably various proportions of amines and heparin. 3. LPS (25 mg kg(-1) i.p.) caused changes in the proportions of the various types of mast cells. The number of MMC and intermediate type mast cells significantly increased and the number of mast cells immunopositive for both heparin and serotonin significantly decreased. Biochemical analysis showed that the histamine concentration of dura increased while its serotonin concentration decreased. 4. While vasoactive intestinal peptide (VIP) (25 ng kg(-1) i.p.) appears to potentiate LPS effects on dura mater mast cells, non-selective inhibition of nitric oxide (NO) synthase by N(g)-nitro-L-arginine methyl ester (L-NAME) (30 mg kg(-1) i.p.) did not influence sepsis-induced mast cell changes. 5. These findings suggest that mast cells of dura mater may play a role in brain protection during sepsis.

The effect of stress and in vivo vasoactive intestinal peptide (VIP) treatment on the response of isolated rat aorta to norepinephrine, angiotensin II and vasopressin, and adventitial mast cells

The effects of cold-restraint stress, repeated over 3 days, and treatment of rats with vasoactive intestinal peptide (VIP) on the contractile responses of isolated aorta to vasoconstrictors, and on aortic adventitial mast cells were investigated. Stress significantly reduced the contractile response of rat aorta smooth muscle to norepinephrine (NE), angiotensin II (Ang II) and vasopressin (VP). Decreased sensitivity to NE, Ang II and VP may result from decreased receptor density, and affinity or reduced effector efficacy. Stress induced degranulation, decreased the number and changed the granular content of mast cells; all degranulated mast cells were stained with alcian blue, and the percentage of safranin staining cells was decreased. Given prior to stress, VIP reversed the reduced contractile responses and sensitivity of aorta to NE and Ang II but had no effect on VP subsensitivity. VIP also inhibited stress-induced degranulation of mast cells, and after VIP only alcian blue-stained mast cells were seen. When VIP was given to non-stressed rats, the contractile response of the aorta to NE, but not Ang II or VP, was increased compared with control. Mast cell count was decreased in the adventitia of non-stressed VIP treated rats. The results indicate that stress decreases the heparin content of mast cells and VIP has an additive effect. In conclusion, VIP modulates both stress-induced mast cell activity and reduced sensitivity of aorta smooth muscle to NE and Ang II. It can be suggested that VIP may moderate some effects of stress on vascular pathophysiology.

Effect of psychogenic stress on gastrointestinal function

This review summarizes the studies published over the last twenty years on the effects of psychogenic stress on gastrointestinal function, using animal models. The effects of stress on gastric ulceration have received wide attention and the central and local mechanisms of mucosal damage have been, for the most part, clearly delineated. In comparison, relatively few studies have focused on the impact of stress on intestinal and colonic physiology, even though its influence on intestinal motility, mucosal permeability and inflammation has been established. More work is necessary in this field, especially considering the importance of irritable bowel syndrome in modern society.

Vasoactive intestinal peptide inhibits degranulation and changes granular content of mast cells: a potential therapeutic strategy in controlling septic shock

Vasoactive intestinal peptide (VIP) has potent protective activity against sepsis and increases the survival rate of septic rats and mice. The present study was planned to evaluate the effect of VIP on mast cell activity, histamine and methylhistamine levels and oxidative stress in the liver and kidneys of septic rats. The effect of VIP was compared to that of nitric oxide synthesis inhibition, previously tested extensively in septic shock models, with doubtful benefit. The present study showed that endotoxic shock did not lead to oxidative stress in either liver or kidney of the rats. On the other hand, mast cells, based on their location, displayed functional heterogeneity to the septic insults. VIP possibly modulated the specific reactions of the tissues to mediators released from mast cells during septic shock. The most prominent effect of VIP as compared to nitric oxide synthesis inhibition was related to mast cells. In conclusion, the prevention of mast cell reactivity by VIP could be a potential therapeutic strategy in controlling septic shock.