Shoki Ro

Urocortin 1 reduces food intake and ghrelin secretion via CRF2 receptors

Although it is known that urocortin 1 (UCN) acts on both corticotropin-releasing factor receptors (CRF(1) and CRF(2)), the mechanisms underlying UCN-induced anorexia remain unclear. In contrast, ghrelin, the endogenous ligand for the growth hormone secretagogue receptor, stimulates food intake. In the present study, we examined the effects of CRF(1) and CRF(2) receptor antagonists (CRF(1)a and CRF(2)a) on ghrelin secretion and synthesis, c-fos mRNA expression in the caudal brain stem, and food intake following intracerebroventricular administration of UCN. Eight-week-old, male Sprague-Dawley rats were used after 24-h food deprivation. Acylated and des-acylated ghrelin levels were measured by enzyme-linked immunosorbent assay. The mRNA expressions of preproghrelin and c-fos were measured by real-time RT-PCR. The present study provided the following important insights into the mechanisms underlying the anorectic effects of UCN: 1) UCN increased acylated and des-acylated ghrelin levels in the gastric body and decreased their levels in the plasma; 2) UCN decreased preproghrelin mRNA levels in the gastric body; 3) UCN-induced reduction of plasma ghrelin and food intake were restored by CRF(2)a but not CRF(1)a; 4) UCN-induced increase of c-fos mRNA levels in the caudal brain stem containing the nucleus of the solitary tract (NTS) was inhibited by CRF(2)a; and 5) UCN-induced reduction of food intake was restored by exogenous ghrelin and rikkunshito, an endogenous ghrelin secretion regulator. Thus, UCN increases neuronal activation in the caudal brain stem containing NTS via CRF(2) receptors, which may be related to UCN-induced inhibition of both ghrelin secretion and food intake.

Histamine Mediates the Stimulatory Action of Ghrelin on Acid Secretion in Rat Stomach

Ghrelin, a novel growth hormone-releasing peptide, is present in the rat and human stomach and is known to stimulate acid secretion and stomach motility. However, the mechanism of action of ghrelin is not fully understood. In the present study, we attempted to elucidate the role of histamine in ghrelin-induced acid secretion in rat stomach. Intravenous administration of ghrelin at 0.8 to 20 μg/kg dose dependently increased gastric acid secretion, as measured by the gastric lumen perfusion method. The maximum response was almost equal to that of gastrin (20 μg/kg). These actions were abolished by bilateral subdiaphragmatic vagotomy. Famotidine (0.33 mg/kg) also completely inhibited the effects of ghrelin. Furthermore, ghrelin increased histidine decarboxylase (HDC) messenger RNA (mRNA) levels, as measured by real-time reverse transcription-polymerase chain reaction using LightCycler. The action of ghrelin on HDC mRNA was abolished by vagotomy. Ghrelin did not affect histamine release from isolated vascularly perfused rat stomach. Taken together, these results suggest that ghrelin stimulates gastric acid secretion via a mechanism involving activation of vagal efferent nerve and histamine release from gastric enterochromaffin-like cells.

Expression of c-Fos protein in the brain after intravenous injection of ghrelin in rats

In this study, we surveyed central neurons that might be activated after peripheral administration of a gut-brain peptide ghrelin, by examining neurons expressing c-Fos protein. First, we examined the relationship between the dose of ghrelin and the amount of gastric acid secreted. Ghrelin induced a significant increase in the amount of gastric acid secretion in a dose-dependent manner. Secondly, we examined central neurons that expressed c-Fos protein after intravenous injection of ghrelin. We found that intravenously injected ghrelin induced the neural expression of c-Fos protein in several nuclei and circumventricular organs in the brain. These results suggest that ghrelin released into the circulation may stimulate central neurons that have some role in the control mechanism for gastric acid secretion.

Effects of interleukin-8 and Helicobacter pylori on histamine release from isolated canine gastric mucosal mast cells.

Background. In recent studies, the involvement of mast cells in the pathogenesis of Helicobacter pylori infection was suggested. In the present study, using isolated canine gastric mucosal mast cells, we undertook to elucidate the effects of interleukin-8 (IL-8) and H. pylori on histamine release from these cells. Methods. Enriched canine gastric mucosal mast cells (50% target cells) were incubated in Hanks medium with IL-8, or water extract or sonicate of H. pylori for 15 min at 37°C. The content of histamine in the supernatants and the cell pellets after centrifugation was assayed with a histamine radioimmunoassay (RIA) kit. Results. IL-8 (50 ng/ml) and concanavalin A (20 μg/ml) significantly increased histamine release from enriched gastric mucosal mast cells. Dose-dependent stimulation of histamine release by IL-8 (5–50 ng/ml) was also seen. Water extract and sonicate of H. pylori (108 bacteria) increased histamine release from mast cells. A concentration-dependent stimulation of histamine release by water extract or sonicate was also seen. The maximal response of histamine release was seen at the highest concentration of the water extract or sonicate. Conclusions. The results indicated that IL-8 and H. pylori had stimulatory effects on histamine release from canine gastric mucosal mast cells. The results imply that IL-8 and soluble factors of H. pylori may accelerate inflammation of the gastric mucosa via histamine release from mast cells.

Evaluation for transvaginal and transgastric NOTES cholecystectomy in human and animal natural orifice translumenal endoscopic surgery

BACKGROUND/PURPOSE Natural orifice translumenal endoscopic surgery (NOTES) is a novel concept using an endoscope via a translumenal access for abdominal surgery. This study was designed to evaluate the feasibility and technical aspects of NOTES cholecystectomy from our experience on humans and animals. METHODS NOTES cholecystectomies were performed in 12 animal experiments, including 8 pigs (6 by transgastric and 2 by transvaginal accesses) and 4 dogs (4 transvaginal accesses), and a human female cadaver. RESULTS The entire gallbladder could be removed under direct vision in all experiments. The average time was 60 min by transgastric and 40 min by transvaginal in animals. It was 87 min for human transvaginal cholecystectomy. In all animal and human procedures, there was no major complication concerning the operation. DISCUSSION The transvaginal route may be the easiest route for abdominal NOTES. Percutaneous endoscopic gastrostomy (PEG) allowed the safe performance of a controlled gastric perforation and shortened the time. The hybrid method allowed performance of a safe procedure and shortened the time. CONCLUSIONS Transvaginal and transgastric NOTES cholecystectomy is technically feasible and safe in both humans and animals. New instrumentation needs to be developed to perform a pure NOTES cholecystectomy without transabdominal assistance.

Water extract of Helicobacter pylori stimulates interleukin-8 secretion by a human gastric epithelial cell line (JR-St) through protein tyrosine phosphorylation

Background : Infection by Helicobacter pylori induces cytokine production in gastric mucosal cells. Production of interleukin‐8 (IL‐8) is known to be markedly increased and is believed to play an important role in gastric mucosal inflammation. The aim of this study was to elucidate the effects of soluble factors of H. pylori on IL‐8 production in a gastric epithelial cell line, JR‐St.

Distribution of c-Fos immunoreactive neurons in the brain after intraperitoneal injection of apelin-12 in Wistar rats

The present study surveyed activation of central neurons following peripheral administration of apelin-12 (AP12), an apelin peptide homologue, by examining the distribution of neurons expressing c-Fos protein. AP12 is known to induce gastric acid secretion among other physiological functions such as regulation of circulation. It was recently reported that apelin counteracted the effect of arginine vasopressin (AVP) in the maintenance of body fluid homeostasis. We attempted to clarify which neurons in the central nervous system express c-Fos protein after intraperitoneal injection of AP12. Intraperitoneally administered AP12 induced expression of c-Fos protein in several nuclei throughout the brain. In the paraventricular nucleus of the hypothalamus (PAH), lateral hypothalamic area (LH), paraventricular nucleus of the thalamus (PVT), periaqueductal gray matter (PAG), bed nucleus of the stria terminalis (BNST), locus coeruleus (LC), lateral parabrachial nucleus (Pbl), the complex of the solitary tract nucleus (NTS) and dorsal motor nucleus of the vagus nerve (DMX), numbers of neurons expressing c-Fos protein were much higher in test than in control experiments. These findings suggest that AP12 stimulates central neurons that may play roles in the regulation of gastric acid, and hypothalamic neurons that may play roles in the maintenance of body fluid homeostasis as well as other physiological functions.

Interleukin-8 Enhances Tetragastrin-Stimulated Acid Secretion In Vivo

Recent studies have demonstrated a relationshipbetween cytokines and gastric acid secretion. However,details of the mechanism underlying that relationshiphave not been elucidated. For this study, an in vivo experiment was undertaken toinvestigate the possibility that IL-8 would be involvedin the mechanism of gastric acid secretion. Gastriclumen-perfused rats were prepared and the stomachs wereperfused with a saline solution. The effluent wascollected at 15-min intervals and assayed for titratableacid against 0.01 M NaOH. IL-8 (200 ng/rat) givenintravenously did not influence basal acid output inrats. However, when IL-8 was administered byinjection during continuous tetragastrin infusion (4mug/kg/hr) acid output increased significantly (P <0.01). The acid output during the first hour following IL-8 injection was 43.6% higher than prior tothe injection. Acid output during the second hour waslower than during the first hour. However, successiveinjection of IL-8 again increasedtetragastrin-stimulated acid output by 23.4% (P < 0.05). IL-8injection did not change histamine-stimulated acidoutput. The results indicate that IL-8 has the effect ofenhancing gastrin-stimulated acid secretion and might have an important role in the pathophysiologyof gastric acid secretion in vivo.

Apelin-12 stimulates acid secretion through an increase of histamine release in rat stomachs

BACKGROUND Apelin is a peptide that was originally isolated from bovine stomach extract and has been demonstrated to be an endogenous ligand for orphan receptor APJ. Both apelin and the APJ receptor are widely distributed in the whole body. Apelin is supposed to have important regulatory roles in the function of many organs such as in the cardiovascular system; however, the mechanism of apelin function has not been elucidated. In this study, we studied the action of apelin in acid secretion and demonstrated its mechanism of action. METHODS Gastric lumen-perfused rats were prepared and their stomachs were perfused with a saline solution using a peristaltic pump. Apelin-12, 36 or Pyr(1)-apelin-13, were intravenously injected to examine their effects on acid secretion in rats. In some experiments, rats were pretreated with famotidine (0.33 mg/kg) or atropine sulfate (0.1mg/kg) intravenously injected 5 or 15 min before apelin injection. Furthermore, isolated vascularly perfused rat stomachs were prepared to examine the effect of apelin on histamine release, which was assayed in the effluent by radioimmunoassay. Messenger RNA of histidine decarboxylase (HDC) in gastric mucosa of isolated stomach was measured by real-time RT-PCR. RESULTS Apelin-12 (20-100 μg/kg) dose-dependently increased gastric acid secretion, with a maximum of 203% at 100 μg/kg (n=5). Neither Pyr(1)-apelin-13 nor apelin-36 caused a significant increase in acid secretion. Famotidine completely blocked the stimulatory action of apelin on acid secretion. Apelin-12 (100 μg/20 ml/10 min) markedly increased histamine release from isolated vascularly perfused rat stomachs by 278%, and also increased the mRNA of HDC by 480% of the control. Atropine sulfate did not abolish the effect of apelin on the secretion of gastric acid. Apelin-12 amplified an increase of acid secretion stimulated by gastrin injection. CONCLUSION These results indicate that apelin-12 stimulates gastric acid secretion through an increase in histamine release and synthesis from gastric mucosa, suggesting that apelin might play a role in the secretion of gastric acid or serve as a regulating factor of the secretion of gastric acid.

Neutrophil-derived hydroxyl radicals mediate interleukin-8-induced increases in tetragastrin-stimulated acid secretion in rats.

Until recently, the secretion of gastric acid, which plays an important role in the pathogenesis of peptic ulcer, was thought to be controlled by diet, the autonomic nerves and gut hormones. However, peptic ulcer is now known to be caused by the infection with Helicobacter pylori (H. pylori), so it is possible that inflammation modifies the secretion of gastric acid. We used gastric-lumen-perfused rats to first examine the effect of interleukin-8 (IL-8) on acid secretion and then the involvement of free radicals and neutrophils in the action of IL-8. IL-8 enhanced tetragastrin-stimulated acid secretion and free radical scavengers or inhibitors and the pretreatment with anti-rat neutrophil serum inhibited this effect, which indicates that IL-8 enhances gastrin-stimulated acid secretion and that neutrophil-derived hydroxyl radicals mediate the IL-8-induced increase in acid secretion.