Epithelial cell proliferation in the digestive tract induced by space restriction and water-immersion stress

Peripheral infusion of nociceptin/orphanin FQ influences the response of rat gastric and colonic mucosa to repeated stress

The 17-amino acid peptide nociceptin/orphanin FQ (N/OFQ) plays a role in the regulation of stress responses and of emotional disorders. The objective of this study is to evaluate whether long-term peripheral N/OFQ could dose- and time-dependently influence the responses to repeated cold-restraint stress on the rat gastric and colonic mucosa. Rats were exposed to cold-restraint stress for 3h per day for 1, 2 and 3 consecutive days. N/OFQ was administered at doses of 0.1, 1 and 10 microg/kg/h via Alzet osmotic minipumps. In the gastric fundus, N/OFQ exerted dose-dependent beneficial effects against acute and repeated stress but, after prolonged treatment, became damaging in non-stressed rats. In the distal colon, N/OFQ exerted a protective effect against damage by acute and repeated stress with no influence on epithelial integrity in non-stressed rats. In both regions, the peptide itself dose- and time-dependently reduced intraepithelial mucins. The reduction in mucin content caused by stress was effectively counteracted by N/OFQ, 0.1 microg/kg/h, in the distal colon only. N/OFQ did not modify basal mucosal cell proliferation. The peptide at 0.1 and 1 microg/kg/h had no influence while at 10 microg/kg/h abolished stress-induced increase in cell proliferation. The present results provide evidence that N/OFQ is implicated in the regulation of resting and stress-challenged mucosal integrity and activity of mucin-producing cells.

Proliferation of intestinal crypt cells by gastrin-induced ornithine decarboxylase

AIM: To determine whether the gastrin stimulated intestinal crypt cell (IEC-6) proliferation by induction of ornithine decarboxylase (ODC).

METHODS: IEC-6 cells were grown in DMEM containing 50 mL·L^-1 dialyzed fetal bovine serum for 24 h and then were treated with gastrin. The proliferative capability of the cells was monitored subsequently on d 1, 2, 3, and 4 after treatment with MTT assay at aborbance 570 nm. The cellular ODC mRNA expression, ODC activity, and putrescine content were examined by RT-PCR method, radiometric technique and high-performance liquid chromatography(HPLC) analysis respectively after 12 h of treatment.

RESULTS: On d1 after exposure of IEC-6 cells to pentagastrin, the proliferation increased initially and reached a peak on d3 at 250 μg·L^-1 concentration. Pentagastrin 500 μg·L^-1 increased cell proliferation on day 1 and day 2, and then decreased. Compared with control group, pentagastrin 250 μg·L^-1 increased ODC mRNA level by 1.09-fold (P < 0.05), ODC activity by 1.71-fold(P < 0.01), and putrescine content 5.30-fold (P < 0.01), respectively. Similarly, pentagastrin of 500 μg·L^-1 also increased ODC mRNA level by 1.16-fold (P < 0.05), ODC activity 1.63-fold(P < 0.05), and putrescine content 4.41-fold (P < 0.01), respectively. But there was not significant difference between them.

CONCLUSION: Gastrin is an agent which promotes IEC-6 cell proliferation involved in regulating ODC activity mechanism.

Intestinal perfusion induces rapid activation of immediate-early genes in weaning rats

C-fos and c-jun are immediate-early genes (IEGs) that are rapidly expressed after a variety of stimuli. Products of these genes subsequently bind to DNA regulatory elements of target genes to modulate their transcription. In rat small intestine, IEG mRNA expression increases dramatically after refeeding following a 48-h fast. We used an in vivo intestinal perfusion model to test the hypothesis that metabolism of absorbed nutrients stimulates the expression of IEGs. Compared with those of unperfused intestines, IEG mRNA levels increased up to 11 times after intestinal perfusion for 0.3-4 h with Ringer solutions containing high (100 mM) fructose (HF), glucose (HG), or mannitol (HM). Abundance of mRNA returned to preperfusion levels after 8 h. Levels of c-fos and c-jun mRNA and proteins were modest and evenly distributed among enterocytes lining the villi of unperfused intestines. HF and HM perfusion markedly enhanced IEG mRNA expression along the entire villus axis. The perfusion-induced increase in IEG expression was inhibited by actinomycin-D. Luminal perfusion induces transient but dramatic increases in c-fos and c-jun expression in villus enterocytes. Induction does not require metabolizable or absorbable nutrients but may involve de novo gene transcription in cells along the villus.

Role of mast cells in chronic stress induced colonic epithelial barrier dysfunction in the rat

BACKGROUND AND AIMS

Stress may be an important factor in exacerbating inflammatory bowel disease but the underlying mechanism is unclear. Defective epithelial barrier function may allow uptake of luminal antigens that stimulate an immune/inflammatory response. Here, we examined the effect of chronic stress on colonic permeability and the participation of mast cells in this response.

METHODS

Mast cell deficient Ws/Ws rats and +/+ littermate controls were submitted to water avoidance stress or sham stress (one hour/day) for five days. Colonic epithelial permeability to a model macromolecular antigen, horseradish peroxidase, was measured in Ussing chambers. Epithelial and mast cell morphology was studied by light and electron microscopy.

RESULTS

Chronic stress significantly increased macromolecular flux and caused epithelial mitochondrial swelling in +/+ rats, but not in Ws/Ws rats, compared with non-stressed controls. Stress increased the number of mucosal mast cells and the proportion of cells showing signs of activation in +/+ rats. No mast cells or ultrastructural abnormalities of the epithelium were present in Ws/Ws rats. Increased permeability in +/+ rats persisted for 72 hours after stress cessation.

CONCLUSIONS

Chronic stress causes an epithelial barrier defect and epithelial mitochondrial damage, in parallel with mucosal mast cell hyperplasia and activation. The study provides further support for an important role for mast cells in stress induced colonic mucosal pathophysiology.

Prostacyclin analog prevents stress-induced expression of immediate early genes and gastric mucosal lesions in the rat stomach

Water immersion-restraint induced the expression of immediate early genes (IEGs) in the epithelial cells and smooth muscle cells of gastric wall of rats, in addition to its well-known effects of mucosal erosion. Pretreatment with a prostacyclin analog (beraprost), a proton pump inhibitor (lansoprazole) or a histamine H2 receptor antagonist (famotidine) prevented formation of gastric mucosal erosion, while only the prostacyclin analog inhibited expression of IEGs. The prostacyclin analog may prevent mucosal damages as well as molecular changes by ameliorating the mucosal microcirculation, and may have potential therapeutic applications.