Vagal afferents mediate antinociception of estrogen in a rat model of visceral pain: the involvement of intestinal mucosal mast cells and 5-hydroxytryptamine 3 signaling.

UNLABELLED: Estrogen reportedly facilitates visceral nociception at the spinal or supraspinal level. The present study was aimed to investigate whether estrogen modulates visceral pain through the vagal pathway. Ovariectomized rats received estradiol, which was administered subcutaneously (to act through both the vagal and spinal pathways) or intraduodenally (to preferentially act through the vagal pathway). Luminally applied estradiol induced a rapid and significant decrease in the visceromotor response to colorectal distension, with increased c-Fos expression in nodose ganglion neurons. Systemically injected estradiol increased visceromotor response and c-Fos expression in both nodose and dorsal root ganglion (T6-12) neurons. The antinociceptive effect of estrogen was abolished by surgical vagotomy or chemical denervation of vagal afferents. Both luminally and systemically administered estradiol elicited selective 5-hydroxytryptamine secretion from the duodenum. Granisetron, a 5-hydroxytryptamine 3 receptor antagonist, reversed the antinociceptive effect of estrogen. Intestinal mucosal mast cell stabilizers prevented estradiol-induced antinociception and 5-hydroxytryptamine secretion. Ultrastructural analysis revealed that estradiol caused piecemeal degranulation of intestinal mucosal mast cells. The actions of estradiol were inhibited by an estrogen receptor ß antagonist and mimicked by an estrogen receptor ß agonist. These results suggest that estrogen can trigger vagus-mediated antinociception, which is masked by its spinally mediated pronociception. PERSPECTIVE: This study is the first to show a vagus-mediated estrogenic antinociception, in which the nongenomic estrogen receptor ß-mediated, intestinal mucosal mast cell-derived 5-hydroxytryptamine/5-hydroxytryptamine 3 receptor pathway is involved. This work may provide new insights into the sex hormone modulation of visceral sensitivity related to irritable bowel syndrome and indicate potential therapeutic targets to manage this disease.

Small interfering RNA against the apurinic or apyrimidinic endonuclease enhances the sensitivity of human pancreatic cancer cells to gemcitabine in vitro.

OBJECTIVE: To investigate whether the downregulation of human apurinic or apyrimidinic endonuclease/redox factor-1 gene (APE1/Ref-1) expression by ribonucleic acid interference (RNAi) would increase the sensitivity of SW1990 cells to gemcitabine. METHODS: Chemically synthesized small interfering RNA (siRNA) directed against human APE1/Ref-1 (si-APE1) was transfected into SW1990 cells through transfection reagents. The mRNA expression of APE1/Ref-1 was detected by semi-quantitative RT-PCR and the protein expression of APE1/Ref-1 was detected by Western blot; cell proliferation and apoptosis were studied by a Cell Counting Kit 8 (CCK-8) and flow cytometry (FCM) and fluorescence microscopy. RESULTS: After transfecting the SW1990 cells with siRNA directed against human APE1/Ref-1, the mRNA expression of APE1/Ref-1 of these cells was reduced, and its protein expression was reduced by 55.41 +/- 3.58%. The CCK-8 assay showed that the absorbance and the inhibition of cell growth transfected with si-APE1 were significantly different from the blank (cultured with Dulbecco's modified Eagle's medium) and negative control (given 50 nmol/L scrambled control siRNA). The inhibition rates of cell growth of the si-APE1 group at 24, 48, 72 h were 41.69 +/- 2.78%, 24.83 +/- 3.70% and 21.27 +/- 9.82%, respectively. A FCM analysis and cell morphology study showed that the apoptotic rate of SW1990 cells transfected with si-APE1 combined with gemcitabine treatment was significantly different from the blank control and others. CONCLUSION: To knock down APE1/Ref-1 gene expression may significantly sensitize the SW1990 cells to gemcitabine and enhance cell apoptosis.

Effect of domperidone therapy on nocturnal dyspeptic symptoms of functional dyspepsia patients.

AIM: To investigate the incidence of nocturnal dyspeptic symptoms in patients with functional dyspepsia (FD) and whether prokinetic drugs can alleviate them. METHODS: Eighty-five consecutive Chinese patients with FD were included in this study. One week after single-blinded placebo run-in treatment, baseline nocturnal intragastric pH, bile reflux and nocturnal dyspeptic symptoms of eligible patients, including epigastric pain or discomfort, abdominal distention and belching, were investigated with questionnaires. Patients exhibiting nocturnal dyspeptic symptoms were randomly and double-blindly assigned to domperidone group or placebo group. Nocturnal intragastric pH and percentage of duodenogastric bile reflux time were determined after treatment. RESULTS: Of the 85 FD patients, 2 females without nocturnal symptoms, who responded to placebo run-in treatment, were excluded from the study, 30 (36.1%) exhibited nocturnal dyspeptic symptoms with increased duodenogastric bile reflux time (intragastric bilirubin absorbance > 0.14) and mean gastric pH (confirming the existence of bile reflux) (P = 0.021, 0.023) at night were included in the study. Of these 30 patients, 21 (70%) had overt nocturnal duodenogastric bile reflux, which was significantly higher than that of those without nocturnal symptoms (P = 0.026). The 30 patients were allocated to domperidone group or placebo group (n = 15). The nocturnal duodenogastric bile reflux and gastric pH were significantly decreased after domperidone treatment (P = 0.015, 0.021). The severity score of nocturnal dyspeptic symptoms was also significantly decreased after domperidone treatment (P = 0.010, 0.015, 0.026), which was positively correlated with the reduced nocturnal bile reflux or gastric pH (r = 0.736, 0.784, 0.753 or r = 0.679, 0.715, 0.697, P = 0.039, 0.036, 0.037 or P = 0.043, 0.039, 0.040). CONCLUSION: A subgroup of Chinese FD patients show overt nocturnal dyspeptic symptoms, which may be correlated with the excessive nocturnal duodenogastric bile reflux. Domperidone therapy can alleviate these symptoms.

Effects of thalidomide in experimental models of post-endoscopic retrograde cholangiopancreatography pancreatitis.

BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha) plays a central role in the pathogenesis of acute pancreatitis and related systemic complications. The authors hypothesized that it may also play an important role in the development of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP). The aim of the study was to evaluate the effectiveness of thalidomide, an immunomodulator that exerts an inhibitory action on TNF-alpha by enhancing mRNA degradation, in reducing post-ERCP pancreatitis in a rat model. METHODS: A total of 200 mg/kg thalidomide was given intragastric once a day (total 8 days) before the experimental models of post-ERCP pancreatitis were established. After 24 h, histology and edema of pancreas, serum amylase, and TNF-alpha mRNA in the pancreatic tissue were evaluated. RESULTS: Intraductal contrast infusion caused increases in serum amylase, edema, histological grade, and TNF-alpha mRNA of pancreas. The prophylactic use of thalidomide significantly reduced serum amylase, pancreatic edema and the histologic grade of pancreatitis accompanied by a decrease in mRNA expression of TNF-alpha in the pancreatic tissue. CONCLUSIONS: Prophylactic intragastric administration of thalidomide provides a protective effect in post-ERCP pancreatitis. The mechanism of the protective effects of thalidomide seems to be the reduction of expression of TNF-alpha mRNA in pancreatic tissue.

Gastric distention enhances FOS and calcitonin gene-related peptide expression in the spinal cord and brain of rats.

OBJECTIVE: The purpose of this study was to determine the pathway and mode of transmission of visceral stimuli by investigating the distribution of the FOS and calcitonin gene-related peptide (CGRP) proteins in the central nervous system. METHODS: Twenty-four Sprague-Dawley rats were divided into three groups: study group (n = 12), sham control group (n = 6), and normal control group (n = 6). A balloon was implanted into the stomach of the rats in the study and sham control groups. After 48 h, the rats in the study group had the stomach distended (80 mmHg) for 2 h, after which they were killed and the antrum, thoracic spinal cord and brain were isolated or dissected. The expression of Fos and CGRP in these tissues was detected immunohistochemically. RESULTS: FOS expression in the dorsal horn of the spinal cord, dorsal nucleus of the vagal nerve, nucleus of the solitary tract in the study rats was significantly higher than in the sham and normal controls. However, no difference was found between the three groups in FOS expression in the myenteric plexus. Similarly, gastric distention enhanced CGRP expression significantly in the spinal cord and medulla oblongata and correlated closely with FOS expression in these two areas. CONCLUSIONS: Gastric distention can activate the limbic system, and CGRP plays an important role in the input of visceral stimuli.

Effects of bile reflux on gastric mucosal lesions in patients with dyspepsia or chronic gastritis.

AIM: To investigate the influences of bile reflux on profiles of gastric mucosal lesions in patients with dyspepsia or chronic gastritis. METHODS: A total of 49 patients diagnosed with dyspepsia and chronic gastritis underwent 24-h ambulatory and simultaneous monitoring of intragastric bilirubin absorbance and pH values, and then they were divided into bile reflux positive group and bile reflux negative group. Severity of pathological changes in gastric mucosa including active inflammation, chronic inflammation, intestinal metaplasia, atrophy and dysplasia as well as Helicobacter pylori (H pylori) infection at the corpus, incisura and antrum were determined respectively according to update Sydney system criteria. The profiles of gastric mucosal lesions in the two groups were compared, and correlations between time-percentage of gastric bilirubin absorbance >0.14 and severity of gastric mucosal lesions as well as time-percentage of gastric pH >4 were analyzed respectively. RESULTS: Thirty-eight patients (21 men and 17 women, mean age 44.2 years, range 25-61 years) were found existing with bile reflux (gastric bilirubin absorbance >0.14) and 11 patients (7 men and 4 women, mean age 46.2 years, range 29-54 years) were bile reflux negative. In dyspepsia patients with bile reflux, the mucosal lesions such as active inflammation, chronic inflammation, intestinal metaplasia, atrophy or H pylori infection in the whole stomach, especially in the corpus and incisura, were significantly more severe than those in dyspepsia patients without bile reflux. Moreover, the bile reflux time was well correlated with the severity of pathological changes of gastric mucosa as well as H pylori colonization in the near-end stomach, especially in the corpus region. No relevance was found between the time of bile reflux and pH >4 in gastric cavity. CONCLUSION: Bile reflux contributes a lot to mucosal lesions in the whole stomach, may facilitate H pylori colonization in the corpus region, and has no influence on acid-exposing status of gastric mucosa in patients with dyspepsia or chronic gastritis.

Nitric oxide synthase distribution in esophageal mucosa and hemodynamic changes in rats with cirrhosis.

AIM:To observe the nitric oxide synthase (NOS) distribution in the esophageal mucosa and hemodynamic changes in cirrhotic rats.METHODS:NOS distribution in the lower esophagus of rats with carbon tetrachloride-induced cirrhosis was assessed by using NADPH-diaphorase (NADPH-d) histochemical method.Concentration of NO in serum were measured by fluorometric assay. Mean arterial pressure (MAP), cardiac output (CO), cardiac index (CI), splanchnic vascular resistance (SVR), and splanchnic blood flow (SBF) were also determined using (57)Co-labled microsphere technique.RESULTS:Intensity of NOS staining in the esophageal epithelium of cirrhotic rats was significantly stronger than that in controls. There was a NOS-positive staining area in the endothelia of esophageal submucosal vessels of cirrhotic rats, but the NOS staining was negative in normal rats. NO concentration of serum in cirrhotic rats were significantly higher in comparison with that of controls. Cirrhotic rats had significantly lower MAP, SVR and higher SBF than those of the controls.CONCLUSION:Splanchnic hyperdynamic circulatory state was observed in rats with cirrhosis. The endogenous NO may play an important role in development of esophageal varices and in changes of hemodynamics in cirrhosis.