Epidermal growth factor and prostaglandin E(2) accelerate mucosal recovery from stress-induced gastric lesions via inhibition of apoptosis.

The repair of damaged gastric mucosa is a complex process involving prostaglandins (PG) and mucosal growth factors such as epidermal growth factor (EGF). Recently, we postulated that the increased occurrence of apoptosis in the gastric epithelium might be of pathophysiological importance in the development of stress lesions. The aim of the present study was to assess the effect of the pretreatment of rats, exposed to 3.5 h of water immersion and restraint stress (WRS), with EGF and PG (16,16 dmPGE(2)) on the number of stress lesions, recovery of gastric mucosa from stress and the expression of apoptosis related genes such as caspase-3 and antiapoptotic bcl-2. Rats were divided in following groups: (1) vehicle; (2) EGF 100 microg/kg i.p.; (3) 16,16 dm-PGE(2) (5 microg/kg i.g.) and caspase-1 inhibitor (ICE-I; 100 microg/kg i.p.). One hour later, the rats were exposed to 3.5 h of WRS and then sacrificed immediately (0 h) or at 6, 12, or 24 h after WRS. The number of acute gastric lesions was determined. Gastric epithelial apoptosis was assessed by TUNEL staining. In addition, mRNA expression of caspase-3, Bcl-2 and proinflammatory cytokines (IL-1 beta, TNFalpha) was assessed by RT-PCR. PGE(2) generation in gastric mucosa and luminal EGF were determined by RIA. Exposure to WRS resulted in the development of multiple acute stress erosions ( approximately 18) which almost completely healed during 24 h. The gastric blood flow was significantly reduced (approximately 70% of intact mucosa) immediately after WRS. The expression of mRNA for IL-1 beta and TNF alpha reached their peak at 12 h after stress exposure. The apoptosis rate was highest at 6 h after WRS and was accompanied by the highest caspase-3 expression. In rats pretreated with EGF or 16,16 dm-PGE(2), a significant decrease in caspase-3 mRNA and upregulation of bcl-2 mRNA as observed as compared to vehicle controls. Caspase-1 inhibitor significantly reduced the number of stress lesions. We conclude that EGF and PGE(2) accelerate healing of stress-induced lesions due to the attenuation of apoptosis via upregulation of bcl-2 in gastric mucosa. Inhibitors of apoptosis accelerate healing of stress lesions and may be potentially effective agents in the healing of damaged gastric mucosa.     

Apoptosis in gastric mucosa with stress-induced gastric ulcers.

The maintenance of gastric mucosal integrity depends upon the interplay between epithelial cell proliferation and apoptosis (programmed cell death). The Bcl-2 family of proteins plays a central role in the regulation of apoptotic cell death by suppressing the apoptosis while some others such as Bax proteins promote this process. Stress-induced gastric ulcerations are accompanied by the fall in gastric mucosal cell proliferation but little is known about the influence of the stress on the apoptosis in gastric mucosa. In the present study, the gastric epithelial apoptosis was determined by means of expression of Bax and Bcl-2 mRNA in the gastric mucosa following acute stress. Wistar rats were exposed to mild water immersion and restraint stress (WRS) for 3.5 h and then sacrificed at 0, 2, 4, 6, 12 and 24 h after the termination of WRS. At each time interval after WRS, the gastric blood flow (GBF) and the proliferating cell nuclear antigen (PCNA) labeling were determined. The apoptosis rate in the gastric mucosa was determined by the terminal deoxynucleotidyl transferase (TDT) mediated 2-deoxyuridine 5-triphosphate (dUTP)-biotin nick end-labeling (TUNEL) staining method and the expression of Bax and Bcl-2 mRNA was analyzed by RT-PCR and southern blot hybridization. WRS produced multiple erosions accompanied by the fall in GBF and PCNA index and by a dramatic enhancement in gastric epithelial apoptosis rate reaching maximum at 4 h after exposure to WRS. Following 6 and 12 h after the end of WRS the apoptotis declined but even 24 h after WRS it failed to reach the value recorded in intact gastric mucosa. The PCNA index was still significantly inhibited at 2 h after WRS but then showed significant rise at 6 and 12 h to reach at 24 h after WRS, the level similar to that measured in intact gastric mucosa. The expression of Bax mRNA was detected in intact gastric mucosa and gradually increased in first 4 h after WRS to decline at 24 h to the level not significantly different from that observed in the intact mucosa. In contrast, the expression of Bcl-2 mRNA was almost undetectable during first 4 h but showed strong signal at 6 and 12 h to decline to the control level 24 h after WRS. We conclude that: 1. Healing of WRS lesions involves an increase in GBF and mucosal cell proliferation and 2. The enhancement in gastric epithelial apoptosis accompanies the mucosal damage induced by stress and this appears to be triggered by the shift from the cell death effector Bax to the cell death repressor Bcl-2 protein.     

Exogenous and endogenous ghrelin in gastroprotection against stress-induced gastric damage

Ghrelin, identified in the gastric mucosa has been involved in control of food intake and growth hormone (GH) release but little is known about its influence on gastric secretion and mucosal integrity. The effects of ghrelin on gastric secretion, plasma gastrin and gastric lesions induced in rats by 75% ethanol or 3.5 h of water immersion and restraint stress (WRS) were determined. Exogenous ghrelin (5, 10, 20, 40 and 80 microg/kg i.p.) increased gastric acid secretion and attenuated gastric lesions induced by ethanol and WRS and this was accompanied by the significant rise in plasma ghrelin level, gastric mucosal blood flow (GBF) and luminal NO concentrations. Ghrelin-induced protection was abolished by vagotomy and attenuated by suppression of COX, deactivation of afferent nerves with neurotoxic dose of capsaicin or CGRP(8-37) and by inhibition of NOS with L-NNA but not influenced by medullectomy and administration of 6-hydroxydopamine. We conclude that ghrelin exerts a potent protective action on the stomach of rats exposed to ethanol and WRS, and these effects depend upon vagal activity, sensory nerves and hyperemia mediated by NOS-NO and COX-PG systems.     

Epidermal growth factor and prostaglandin E2 accelerate mucosal recovery from stress-induced gastric lesions via inhibition of apoptosis

The repair of damaged gastric mucosa is a complex process involving prostaglandins (PG) and mucosal growth factors such as epidermal growth factor (EGF). Recently, we postulated that the increased occurence of apoptosis in the gastric epithelium might be of pathophysiological importance in the development of stress lesions. The aim of the present study was to assess the effect of the pretreatment of rats, exposed to 3.5 h of water immersion and restraint stress (WRS), with EGF and PG (16,16 dmPGE₂) on the number of stress lesions, recovery of gastric mucosa from stress and the expression of apoptosis related genes such as caspase-3 and antiapoptotic bcl-2. Rats were divided in following groups: (1) vehicle; (2) EGF 100 μg/kg i.p.; (3) 16,16 dm-PGE₂ (5 μg/kg i.g.) and caspase-1 inhibitor (ICE-I; 100 μg/kg i.p.). One hour later, the rats were exposed to 3.5 h of WRS and then sacrificed immediately (0 h) or at 6, 12, or 24 h after WRS. The number of acute gastric lesions was determined. Gastric epithelial apoptosis was assessed by TUNEL staining. In addition, mRNA expression of caspase-3, Bcl-2 and proinflammatory cytokines (IL-1β, TNFα) was assessed by RT-PCR. PGE₂ generation in gastric mucosa and luminal EGF were determined by RIA. Exposure to WRS resulted in the development of multiple acute stress erosions (18) which almost completely healed during 24 h. The gastric blood flow was significantly reduced (70% of intact mucosa) immediately after WRS. The expression of mRNA for IL-1β and TNFα reached their peak at 12 h after stress exposure. The apoptosis rate was highest at 6 h after WRS and was accompanied by the highest caspase-3 expression. In rats pretreated with EGF or 16,16 dm-PGE₂, a significant decrease in caspase-3 mRNA and upregulation of bcl-2 mRNA as observed as compared to vehicle controls. Caspase-1 inhibitor significantly reduced the number of stress lesions. We conclude that EGF and PGE₂ accelerate healing of stress-induced lesions due to the attenuation of apoptosis via upregulation of bcl-2 in gastric mucosa. Inhibitors of apoptosis accelerate healing of stress lesions and may be potentially effective agents in the healing of damaged gastric mucosa.     

Histamine in stress ulcer prophylaxis in rats.

BACKGROUND: Gastrin and its analogues increase the gastric acid secretion, but also enhance mucosal defense mechanisms. On the other hand, increased formation of histamine leading to an increase in gastric acid secretion is accompanied with gastroprotection and acceleration of gastric ulcer healing. AIM: Of this study was to examine the effect of histamine on stress induced gastric ulcers in rats. METHODS: Male Wistar rats were exposed to water immersion and restrain stress (WRS) for 3.5 h at 23 degrees C. Before WRS rats were pretreated with saline, histamine, ranitidine or omeprazole. RESULTS: WRS produces gastric lesions which were strongly reduced by ranitidine or omeprazole. Also treatment with histamine markedly reduced ulcer area evoked by WRS. Addition of histamine to ranitidine or omeprazole caused an additional reduction in ulcer area. Gastroprotective effect of histamine was accompanied with the increase in gastric blood flow (GBF). Administration of omeprazole or ranitidine alone was without significant effect on GBF. Histamine caused an slight decrease in gastric luminal pH, whereas ranitidine or omeprazole significantly increased gastric luminal pH. Plasma interleukin-1beta was significantly reduced after administration of omeprazole, ranitidine, or histamine, however, the effect of histamine was less pronounced. DNA synthesis was increased after administration of omeprazole, ranitidine or histamine when compared with WRS alone. Administration of histamine in combination with ranitidine or omeprazole caused an additional increase in DNA synthesis. CONCLUSIONS: Histamine exhibits protective effect and increases gastroprotective effect of ranitidine and omeprazole against stress-induced gastric lesions. This effect of histamine seems to be independent on gastric acid secretion but related to the increase in gastric blood flow and the reduction in activation of cytokine cascade.     

Gastroprotective action of orexin-A against stress-induced gastric damage is mediated by endogenous prostaglandins, sensory afferent neuropeptides and nitric oxide

Orexin-A, identified in the neurons and endocrine cells in the gut, has been implicated in control of food intake and sleep behavior but little is known about its influence on gastric secretion and mucosal integrity. The effects of orexin-A on gastric secretion and gastric lesions induced in rats by 3.5 h of water immersion and restraint stress (WRS) or 75% ethanol were determined. Orexin-A (5-80 microg/kg i.p.) increased gastric acid secretion and attenuated gastric lesions induced by WRS and this was accompanied by the significant rise in plasma orexin-A, CGRP and gastrin levels, the gastric mucosal blood flow (GBF), luminal NO concentration and an increase in mRNA for CGRP and overexpression of COX-2 protein and the generation of PGE(2) in the gastric mucosa. Orexin-A-induced protection was abolished by selective OX-1 receptor antagonist, vagotomy and attenuated by suppression of COX-1 and COX-2, deactivation of afferent nerves with neurotoxic dose of capsaicin, pretreatment with CCK(2)/gastrin antagonist, CGRP(8-37) or capsazepine and by inhibition of NOS with L-NNA. This study shows for the first time that orexin-A exerts a potent protective action on the stomach of rats exposed to non-topical ulcerogens such as WRS or topical noxious agents such as ethanol and these effects depend upon hyperemia mediated by COX-PG and NOS-NO systems, activation of vagal nerves and sensory neuropeptides such as CGRP released from sensory nerves probably triggered by an increase in gastric acid secretion induced by this peptide.     

The effect of sialoadenectomy on gastric mucosal integrity in the rat: roles of epidermal growth factor and prostaglandin E2

Removal of the salivary glands (SALX) in rats has been shown to increase the susceptibility of gastric mucosa to ulcerogens. In the present study, we have investigated the role of specific salivary glands in this response. In addition, we have examined whether a functional link exists between the salivary glands, epidermal growth factor (EGF), and prostaglandin E2 (PGE2) by determining whether SALX decreases the responsiveness of the mucosa to the protective actions of either of both of these agents. Removal of the parotid salivary glands did not significantly increase ulceration in response to intragastric administration of 100% w/v ethanol. Animals were examined 60 min after ethanol administration. Removal of the submandibular-sublingual gland complexes was associated with a significant increase in the area of mucosal damage and a decrease in gastric pit depth in ethanol-treated animals when compared with sham-operated control rats. Furthermore, in both SALX and control animals, exogenous PGE2 and EGF resulted in a dose-dependent reduction in both groups of animals, although the protective effects of PGE2 and EGF were attenuated in SALX rats. PGE2 and EGF administered in combination resulted in the same degree of protection in both SALX and control rats. Sialoadenectomy resulted in a reduction in mucosal PGE2 synthesis. EGF administration did not consistently increase mucosal PGE2 synthesis. Conversely, sialoadenectomy did not reduce mucosal levels of EGF nor did exogenous PGE2 consistently increase salivary or mucosal content of EGF.(ABSTRACT TRUNCATED AT 250 WORDS)     

New satiety hormone nesfatin-1 protects gastric mucosa against stress-induced injury: Mechanistic roles of prostaglandins,nitric oxide,sensory nerves and vanilloid receptors

Nesfatin-1 belongs to a family of anorexigenic peptides, which are responsible for satiety and are identified in the neurons and endocrine cells within the gut. These peptides have been implicated in the control of food intake; however, very little is known concerning its contribution to gastric secretion and gastric mucosal integrity. In this study the effects of nesfatin-1 on gastric secretion and gastric lesions induced in rats by 3.5 h of water immersion and restraint stress (WRS) were determined. Exogenous nesfatin-1 (5–40 μg/kg i.p.) significantly decreased gastric acid secretion and attenuated gastric lesions induced by WRS, and this was accompanied by a significant rise in plasma NUCB2/nefatin-1 levels, the gastric mucosal blood flow (GBF), luminal NO concentration, generation of PGE₂ in the gastric mucosa, an overexpression of mRNA for NUBC2 and cNOS, as well as a suppression of iNOS and proinflammatory cytokine IL-1β and TNF-α mRNAs. Nesfatin-1-induced protection was attenuated by suppression of COX-1 and COX-2 activity, the inhibition of NOS with L-NNA, the deactivation of afferent nerves with neurotoxic doses of capsaicin, and the pretreatment with capsazepine to inhibit vanilloid VR1 receptors. This study shows for the first time that nesfatin-1 exerts a potent protective action in the stomach of rats exposed to WRS and these effects depend upon decrease in gastric secretion, hyperemia mediated by COX-PG and NOS-NO systems, the activation of vagal and sensory nerves and vanilloid receptors.     

Reduction of EGF is associated with the delay of ulcer healing by cigarette smoking

Cigarette smoking is associated with peptic ulcer diseases. Smokers have lower levels of salivary epidermal growth factor (EGF) than nonsmokers. We investigated whether reduction of EGF is involved in the delay of gastric ulcer healing by cigarette smoking. Rats with acetic acid-induced ulcers were exposed to cigarette smoke (0, 2, or 4% vol/vol) 1 day after ulcer induction. EGF level was elevated 1 day after ulcer induction in salivary glands and serum, and 4 days after ulcer induction in the gastric mucosa. However, cigarette smoke depressed these beneficial effects and EGF mRNA expression in salivary glands and gastric mucosa. Cigarette smoke delayed gastric ulcer healing and reduced cell proliferation, angiogenesis, and mucus synthesis. Exogenous EGF (10 and 20 microg/kg i.v.) before smoke exposure reversed the adverse effects of cigarette smoke, whereas vascular endothelial growth factor level and nitric oxide synthase activity were unaffected. It is concluded that the detrimental effect of cigarette smoke on ulcer healing is a consequence of reduction of angiogenesis, cell proliferation, and mucus secretion through the depressive action on EGF biosynthesis and its mRNA expression in salivary glands and gastric mucosa.     

Interactions between sialoadenectomy and capsaicin-sensitive afferent fibers on gastric acid secretion in rats

In this study we have investigated the relative influence of capsaicin-sensitive afferents and sialoadenectomy on gastric acid secretion. Sialoadenectomized (SALX) rats showed a decrease in gastric acid secretion and an increase in gastric calcitonin gene-related peptide-like immunoreactivity (CGRP-li) as compared to sham-operated animals. Capsaicin pretreatment (50 + 100 mg kg-1 in two days) markedly decreased gastric CGRP-li in both sham and SALX-operated rats and increased acid concentration and output only in SALX animals. In this latter case the concomitant absence of two potent endogenous antisecretory agents (CGRP and epidermal growth factor; EGF) may contribute to the observed hypersecretion. Gastric content of vasoactive intestinal polypeptide (VIP)-li was unaffected in SALX and capsaicin-treated rats. Capsaicin-sensitive afferents and EGF contained in the salivary glands may interact in the regulation of the gastric acid secretion.     

Expression of cyclooxygenase (COX)-1 and COX-2 in adaptive cytoprotection induced by mild stress.

Prostaglandins (PG) derived from COX-1 play an important role in the maintenance of mucosal integrity but the role of COX-2-derived products in mucosal defence mechanism has not been fully explained. Mild stress is known to prevent gastric mucosal lesions induced by severe stress via the phenomenon of adaptive cytoprotection but it remains unknown which COX is involved in this adaptation. In this study, the mucosal expression of COX-1 and COX-2 was examined and the inhibitors of these enzymes were used to determine the contribution of these enzymes in adaptive cytoprotection induced by mild stress. Male Wistar rats were exposed to mild water immersion and restraint stress (WRS) at various time intervals ranging from 5 min up to 2 h followed 1 h later by exposure to severe 3.5 h WRS with or without pretreatment with: 1) NS-398 (10 mg x kg(-1) i.g.), a selective COX-2 inhibitor; 2) resveratrol (5 mg x kg(-1) i.g.), a selective COX-1 inhibitor; 3) meloxicam (2 mg x kg(-1) i.g.), preferential COX-2 inhibitor; and 4) indomethacin (5 mg x kg(-1) i.p), non-selective inhibitor of COX. The number of WRS lesions was counted, gastric blood flow (GBF) was measured by H2-gas clearance technique, mucosal biopsy samples were taken for the assessment of PGE2 by radioimmunoassay, and the expression of COX-1 and COX-2 mRNA by RT-PCR. WRS for 3.5 h produced numerous gastric lesions, decreased GBF by 48% and inhibited formation of PGE2 by 68% as compared to intact mucosa. Exposure to mild WRS during 5-30 min by itself failed to affect mucosal integrity but significantly attenuated gastric lesions induced by exposure to severe 3.5 h stress; the maximal protective effect being achieved with mild WRS during 15 min. This protective effect was accompanied by the rise in GBF and the generation of PGE2 in the gastric mucosa. After extension of mild WRS from 15 min up to 1 or 2 h before more severe 3.5 h WRS, the loss of cytoprotective effect of mild WRS against severe stress accompanied by significant fall in the GBF were observed. Pretreatment with NS-398 (10 mg x kg(-1) i.g.) that failed to affect mucosal PGE2 generation, reduced significantly the protection and accompanying rise in GBF produced by mild WRS whereas resveratrol partly reduced the protection and the rise in GBF induced by mild WRS. Meloxicam or indomethacin significantly inhibited PGE2 generation and completely abolished the hyperemia and protection induced by mild WRS against more severe stress. The protective and hyperemic effects of mild WRS were completely restored by the addition of 16,16 dm PGE2 (5 microg x kg(-1) i.g.) to NS-398 or resveratrol, while the deleterious effects of meloxicam and indomethacin were significantly attenuated by the concomitant treatment with this PGE2 analogue. We conclude that PG derived from both, COX-1 and COX-2 appear to be involved in adaptive cytoprotection developed in response to mild stressors.     

Interactions of EGF and ornithine decarboxylase activity in the regulation of gastric mucus synthesis in cigarette smoke exposed rats

Cigarette smoking has been shown to aggravate ulceration and delay ulcer healing. Smokers had a lower level of mucus in their stomachs. In the present study, we examined whether cigarette smoke or its extract reduced mucus production through the suppression of epidermal growth factor (EGF) associated with the reduction of polyamine biosynthesis both in vivo and in vitro. Ornithine decarboxylase (ODC) activities and mucus synthesis were determined in rat gastric mucosa and in human MKN-28 cells. Incubation of MKN-28 cells with EGF (0.01-1.00 ng/mL) significantly increased mucus synthesis in vitro, which was accompanied by an increase of ODC activity. Removal of salivary glands decreased the circulated EGF level and induced a significant reduction of mucus-secreting layer thickness in the gastric mucosa. Cigarette smoke or its extract markedly decreased mucus synthesis in vivo and in vitro, both of which could be completely reversed by intravenous administration of EGF (20 microg/kg) in rats or co-incubation with EGF (1 and 2 ng/mL) in MKN-28 cells. However, ODC activities, which were suppressed by cigarette smoke or its extract, were unaffected by intravenous administration of EGF in rats, or only partially reversed by co-incubation with EGF in MKN-28 cells. These findings indicate that both EGF and ODC activity represent two different entities in the modulation of cigarette smoking on gastric mucus synthesis. The action of EGF on mucus synthesis may only be partially if not dependent on ODC activity in the stomach.     

Effects of reactive oxygen species action on gastric mucosa in various models of mucosal injury.

BACKGROUND: The exposure of gastric mucosa to damaging factors, such as ethanol, water restraint stress, or ischemia followed by reperfusion, produces pathological changes: inflammatory process, hemorrhagic erosions, even acute ulcers. The base of these changes is a disturbance of protective mechanisms and disrupture of gastric mucosal barrier. Previous studies pointed out the role of disturbances of gastric blood flow, mucus secretion and involvement of prostaglandins and nitric oxide formation in the pathomechanism of gastric mucosa lesions. The role of reactive oxygen species (ROS) in these processes has been little studied. Aim: The purpose of our present investigations is to explain the participation of ROS in acute gastric mucosal damage by various irritants. MATERIAL AND METHODS: Experiments were carrying out on 80 male Wistar rats. To assess gastric blood flow (GBF) laser Doppler flowmeter was used. The area of gastric lesions was established by planimetry. The levels of proinflammatory cytokines were measured by ELISA technique. The colorimetric assays were used to determine of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) as well as superoxide dismutase (SOD) activity. RESULTS: We demonstrated that 3.5 h of water immersion and restraint stress (WRS), 30 min of gastric ischemia followed by 60 min of reperfusion or intragastric administration of 100% ethanol, all resulted in appearance of acute gastric mucosal lesions accompanied by a significant decrease of gastric blood flow. These lesions are also accompanied by the significant increase of proinflammatory cytokines including interleukin-1 beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) plasma level. Biological effects of ROS were estimated by measuring tissue level of MDA and 4-HNE, the products of lipid peroxydation by ROS, as well as the activity of SOD, the scavanger of ROS. It was established that 3.5 h of WRS, ischemia-reperfusion and 100% ethanol lead to significant increase of MDA and 4-HNE mucosal level, accompanied by a decrease of SOD activity (significant in WRS and ethanol application). CONCLUSIONS: The pathogenesis of experimental mucosal damage in rat stomach includes the generation of ROS that seem to play an important role, namely due to generation of lipid peroxides, accompanied by impairment of antioxidative enzyme activity of cells.     

Role of parasympathetic overactivity in water immersion stress-induced gastric mucosal lesion in rat.

Stress ulcer is clinically prevalent, but the underlying mechanisms are not well understood. This study aimed to investigate the role of sympathovagal imbalance in the development of water immersion restraint stress (WRS)-induced gastric mucosal lesion. Wistar rats were subjected to either restraint stress (RS) (n = 7) or WRS (n = 7) for 5 h. Linear parameters of heart rate variability and Poincaré plot were analyzed on the basis of the surface ECGs. Gastric mucosal lesion was evaluated by gross anatomy and histology. Mean R-R intervals significantly increased (P < 0.001) in a time-dependent manner in the WRS group but slightly decreased (P < 0.001) in the RS group. Root mean square of successive differences of R-R intervals and high-frequency norm (high-frequency power normalized by the total frequency power) were significantly higher in the WRS group than the RS group (P < 0.001). Low-frequency norm and low-to-high-frequency ratio increased significantly 1 h after stress and then declined to similar levels in both groups. The Poincaré plots of R-R intervals in the WRS group shifted right-upwardly and showed dispersed patterns compared with the RS group. Gastric mucosae showed serious hemorrhage, effusion, and structural collapse in the WRS group but remained normal in the RS group. Bilateral cervical vagotomy suppressed the increase of heart rate variability and prevented the gastric mucosal lesion induced by WRS. We conclude that parasympathetic overactivity is the predominant autonomic response to WRS and is most probably the leading mechanism of WRS-induced gastric mucosal lesion in rat.     

Role of capsaicin sensory nerves and EGF in the healing of gastric ulcer in rats

Accumulating evidence indicates that capsaicin sensitive afferent fibers play a pivotal role not only in gastroprotection but also in ulcer healing. Denervation of capsaicin sensitive afferent fibers exerts an adverse action on these effects. However, whether such an action is mediated through a depression on epidermal growth factor (EGF) is undefined. In this study, the effects of denervation of sensory neurons with capsaicin (100 mg/kg, s.c.) on acetic acid-induced chronic gastric ulcers and their relationship with the EGF expression in salivary glands, serum and gastric mucosa were investigated. Capsaicin significantly increased ulcer size, decreased gastric mucosal cell proliferation at the ulcer margin, angiogenesis in the granulation tissue and also gastric mucus content. Ulcer induction by itself dramatically elevated EGF levels in salivary glands and serum on day 1 and 4, and also in the gastric mucosa on day 4. However, capsaicin completely abolished these effects. It is concluded that stimulation of EGF expression in salivary glands and serum may be one of the mechanisms by which capsaicin sensitive nerves contribute to the gastroprotective and ulcer healing actions in the stomach.     

Immunoreactivities for epidermal growth factor (EGF) and for EGF receptors in rats with gastric ulcers

Summary The present study was aimed at assessing whether epidermal growth factor (EGF) and its receptors are present in the gastric mucosa during the healing of gastric ulcers. Immunohistochemical, immunochemical and functional studies were performed in rats after induction of ulcers in the oxyntic mucosa. Controls, which included non-operated and sham-operated animals, displayed only rare cells in the bottom of the oxyntic glands showing EGF-like immunoreactivity. Within one day after ulcer induction, a markedly increased number of chief cells in undamaged mucosa showed intense staining. Concomitantly, there was an increased immunoreactivity for EGF receptors in the mucous neck cells. Maximal immunostaining for both compounds was observed at 3 days after ulcer induction; augmented staining was still demonstrable after 3 weeks. RIA revealed significantly increased EGF concentration in the oxyntic mucosa three days after ulcer induction, and at this stage stimulated gastric acid secretion, measured in a parallel group of chronic fistula rats, indicated significant inhibition. The transient increases in EGF-like and EGF receptor immunoreactivities may stimulate gland cell proliferation. The local release of EGF-like substances may also serve to reduce gastric acidity and thereby promote ulcer healing.     

应激状态下NO的胃粘膜保护作用及其与壁细胞泌酸的关系

目的:探讨应激状态下一氧化氮(NO)的胃粘膜保护作用及其与壁细胞泌酸的关系.方法:采用水浸-束缚应激(WRS)方法制备应激性溃疡(SU)动物模型,检测胃粘膜溃疡指数(UI)、胃粘膜NO含量和壁细胞H ,K -ATPase活性,观察L-硝基精氨酸甲酯(L-NAME)和L-精氨酸(L-Arg)对应激后大鼠壁细胞H ,K -ATPase活性及胃粘膜损伤的影响.结果:L-NAME(20 mg·kg-1)可使胃粘膜NO含量减少(P＜0.01),壁细胞H ,K -AT-Pase活性增加(P＜0.05),并加重应激所致的胃粘膜损伤;L-Arg(300 mg·kg-1)则使胃粘膜NO含量增加(P＜0.01),壁细胞H ,K -ATPase活性下降(P＜0.05),减轻应激所致胃粘膜损伤.结论:NO对应激状态下大鼠胃粘膜具有保护作用,其机制与抑制壁细胞H ,K -ATPase活性有关.     

Ultrastructure of cells of proper gastric glands and their stroma in hemorrhagic shock in the rat.

Ultrastructural changes in the cells of the proper gastric glands and their stroma are biphasic in the hemorrhagic shock. First phase: "paralysis" of the capillary vessels with an oedema of their stroma, an intracellular oedema with hydropic degeneration of the parietal cells and a degranulation of the argentaffin and argentaffin-like cells. Second phase: ischemia of the gastric mucosa with ultrastructural features of: a) the increased secretion of the parietal cells, b) the degranulation of the chief gastric cells, c) the increased secretion processes in the mucous neck cells. These findings suggest that at last 2 factors coincide in the pathogenesis of so-called stress gastric ulcerations: biphasic disturbances of blood circulation initially damage the gastric mucosa and are followed the digestive hyperactivity of the gastric juice finally resulting stress ulceration.     

Endoplasmic reticulum stress response is involved in the pathogenesis of stress induced gastric lesions in rats

Stress gastric ulcer is a serious complication, but the mechanism involved is not fully clarified. It is well known that mucosal cell apoptosis plays a crucial role in the pathogenesis of gastric ulceration. Recent studies have shown that endoplasmic reticulum (ER) stress is an important pathway leading to cellular apoptosis. To investigate the role of ER stress in the pathogenesis of stress gastric ulcer, we studied the alteration in the expression of ER stress markers GRP78 (glucose-regulated protein 78) and caspase-12 (an ER stress-specific proapoptotic molecule) and their relations with gastric mucosal apoptosis during development of stress gastric lesions in the water-immersion and restraint stress (WRS) model in rats. Rats developed severe gastric lesions after 6 h of WRS. Typical apoptosis was observed at the edge cells of WRS induced gastric lesions. Western blot analysis showed that GRP78 and activated caspase-12 were over-expressed in the gastric tissues of WRS rats. Immunohistochemical analysis demonstrated that increased GRP78 and caspase-12 were distributed only under the lesions. In addition, dithiothreitol and tunicamycin (ER stress inducers), which increased the expression of GRP78 and activated caspase-12, caused gastric mucosal injury and mucosal cell apoptosis in vitro. These findings suggest that ER stress might be involved in the development of stress gastric ulcer through an apoptotic mechanism.     

Capsaicin effects on stress pathology and gastric acid secretion in rats

The effects of capsaicin on stress ulcer formation, plasma corticosterone levels and gastric acid secretion were examined in rats. Capsaicin desensitization did not affect restraint stress ulcer formation but was associated with markedly elevated corticosterone levels, even in non-stressed rats. Acute, orally administered capsaicin augmented ulcer formation only if its administration was followed immediately by restraint stress. Delays of 1, 2, or 3 h between drug administration and stress produced ulceration comparable to control values. Capsaicin did not affect basal (non-stimulated) gastric acid secretion but substantially decreased pentagastrin-stimulated acid output.