Cyclooxygenase-2 expression in Barrett's esophagus

Barrett's epithelium is a recognized premalignant condition for esophageal adenocarcinoma. Nonsteroidal antiinflammatory drugs (NSAIDs) decrease the relative risk of colon cancer in humans and the esophageal tumor load in carcinogen-treated mice. Previous studies provided conflicting results for COX-2 activity in Barrett's mucosa. Pinch mucosal biopsies were collected from Barrett's and adjacent normal esophageal mucosa from 17 patients with Barrett's esophagus. Low-grade dysplasia was found in seven patients. COX-2 protein was undetectable in normal esophageal mucosa. COX-1 protein expression did not vary between normal and Barrett's epithelium. Increased COX-2 protein was detected in Barrett's epithelium in seven patients (41%) but did not differ with or without dysplasia (43% vs 40%). In conclusion, COX-2 protein is increased in 41% of patients with Barrett's epithelium compared to normal esophageal mucosa but did not differ with or without dysplasia. COX-2 induction may be an early event in the development of Barrett's esophagus.

Low endogenous prostaglandin E2 predisposes to relapsing inflammation in experimental rat enterocolitis

Intramural injection of peptidoglycan-polysaccharide (PG-PS) induces acute enterocolitis that spontaneously relapses in Lewis but not Fischer rats. Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) induce prostaglandin E2 (PGE2) secretion, which inhibits secretion of these cytokines by macrophages, suggesting an inhibitory feedback mechanism. We postulate that Lewis rat susceptibility to relapse is due to an imbalance between protective prostaglandins and cytokines. Female Fischer and Lewis rats were injected with PG-PS (37.5 microg/g) or human serum albumin intramurally. Tissue IL-1alpha and PGE2 immunoreactivities and myeloperoxidase (MPO) activity were determined. Relapsing rats had lower PGE2 and PGE2/IL-1alpha ratios than nonrelapsing rats (P < 0.05). In Fischer rats, 2 mg/kg/day of indomethacin potentiated cecal MPO and IL-1alpha concentrations above PG-PS alone (P < 0.05). Misoprostol treatment blocked PG-PS induced IL-1alpha and MPO and inhibited the potentiating effect of indomethacin on MPO and IL-1alpha (P < 0.05). In conclusion, increased endogenous PG may be protective against relapsing inflammation in PG-PS induced enterocolitis, at least partially via inhibition of proinflammatory cytokines. Imbalance between protective prostaglandins and proinflammatory cytokines may be involved in the pathogenesis of chronic relapsing inflammation in genetically susceptible hosts.

Low endogenous prostaglandin E2 predisposes to relapsing inflammation in experimental rat enterocolitis

Intramural injection of peptidoglycan-polysaccharide (PG-PS) induces acute enterocolitis that spontaneously relapses in Lewis but not Fischer rats. Interleukin-1 (IL-1) and tumor-necrosis factor-alpha (TNF-alpha) induce prostaglandin E2 (PGE2) secretion, which inhibits secretion of these cytokines by macrophages, suggesting an inhibitory feedback mechanism. We postulate that Lewis rat susceptibility to relapse is due to an imbalance between protective prostaglandins and cytokines. Female Fischer and Lewis rats were injected with PG-PS (37.5 microg/g) or human serum albumin intramurally. Tissue IL-1alpha and PGE2 immunoreactivities and myeloperoxidase (MPO) activity were determined. Relapsing rats had lower PGE2 and PGE2:IL-1alpha ratios than nonrelapsing rats (P < 0.05). In Fischer rats, 2 mg/kg/day indomethacin potentiated cecal MPO and IL-1alpha concentrations above PG-PS alone (P < 0.05). Misoprostol treatment blocked PG-PS-induced IL-1alpha and MPO and inhibited the potentiating effect of indomethacin on MPO and IL-1alpha (P < 0.05). In conclusion, increased endogenous PG may be protective against relapsing inflammation in PG-PS induced enterocolitis, at least partially via inhibition of proinflammatory cytokines. An imbalance between protective prostaglandins and proinflammatory cytokines may be involved in the pathogenesis of chronic relapsing inflammation in genetically susceptible hosts.

L-glutamine and L-asparagine stimulate ODC activity and proliferation in a porcine jejunal enterocyte line

We studied the effect of L-glutamine (Gln), the principal intestinal fuel, on proliferation of a porcine jejunal cell line, IPEC-J2. In cells synchronized by serum deprivation for 4 h, Gln stimulated ornithine decarboxylase (ODC; EC 4.1.1.17) in a dose- and time-dependent manner, with maximal effects at 10 mM in 3 h (P < 0.01). Similar effects were seen for the structurally related amino acid L-asparagine and serum. The Gln effect on ODC was specific, as isosmolar mannitol, glucose, methyl-beta-D-glucoside, L-phenylalanine, ammonia, and aminoisobutyric acid were ineffective. The alanine aminotransferase inhibitor aminooxyacetate (AO) inhibited the ODC stimulation by Gln in a dose-dependent manner (half-maximal inhibitory concentration = 0.5 mM). AO was not toxic to cells, as determined by propidium iodide uptake into nuclei. In addition, Gln stimulated a twofold increase of cellular 24-h [3H]thymidine incorporation above rates of control cells bathed in standard media (P < 0.01); this effect was also blocked by AO. Gln and phorbol 12-myristate 13-acetate stimulated ODC in a synergistic manner. The Na+/H+ exchange inhibitor methylisobutyl amiloride blocked the enhancement of ODC by Gln. Gln also induced the mRNA of the immediate-early gene c-jun. Gln stimulates proliferation in a porcine jejunal cell line through a mechanism requiring transamination and intact Na+/H+ exchange. This stimulation of enterocyte proliferation by Gln suggests that therapeutic Gln administration could facilitate epithelial recovery in the injured small intestine.

Oral transforming growth factor-alpha enhances jejunal mucosal recovery and electrical resistance in piglet rotavirus enteritis

A randomized, investigator-masked trial determined the effects of oral recombinant human transforming growth factor-alpha (TGF alpha) on jejunal mucosal recovery in 75 piglets with rotavirus diarrhea. Rotavirus inoculation of artificially reared piglets induced subtotal (approximately 50%) villus atrophy and watery diarrhea. Dietary TGF alpha was associated with significant restoration of villus surface area by 4 d postinoculation (p.i.) and complete restoration by 8 d p.i., whereas saline-treated animals required 12 d for recovery. Jejunal segments from clinically recovered TGF alpha-treated piglets showed an increase in electrical resistance across the epithelial barrier in vitro which was proportional to villus height. TGF alpha treatment for 12 d also produced a 30-50% increase in jejunal mucosal mass (protein content and wet weight), compared with the corresponding values in saline-treated piglets and in uninfected controls. However, oral TGF alpha did not hasten the resolution of diarrhea, enhance the specific activities of jejunal mucosal digestive enzymes, or increase jejunal glucose-stimulated Na+ absorption in vitro. We conclude that dietary TGF alpha stimulates jejunal mucosal hypertrophy, improves barrier function, and enhances regrowth of villi in rotavirus enteritis; however, it does not facilitate the restoration of functional activity or mucosal digestive enzymes. Oral TGF alpha can facilitate intestinal epithelial recovery in diseases associated with mucosal damage.

Tumour necrosis factor alpha changes porcine intestinal ion transport through a paracrine mechanism involving prostaglandins

Prostaglandins stimulate electrogenic anion secretion and inhibit sodium chloride absorption in cryptosporidium induced pig diarrhoea. Because tumour necrosis factor alpha (TNF alpha) is an early mediator of inflammation and stimulates prostaglandin secretion, we investigated its effect on intestinal ion transport. Cryptosporidium infected pig ileum showed higher macrophage infiltration and tissue TNF alpha-like activity than uninfected tissues (p < 0.05, n = 4 and p < 0.05, n = 12, respectively). TNF alpha treatment of control porcine ileal mucosa increased the short circuit current (Isc), a measurement of net anion secretion in this model (p < 0.001, n = 23). This effect was blocked by 10(-6) M indomethacin and Cl- replacement. Neither acute treatment nor preincubation of colonic intestinal epithelial cell monolayers (T84) with TNF alpha stimulated the Isc. However, co-mounting of TNF alpha preincubated pig jejunal fibroblasts (P2JF) monolayers back to back with untreated T84 monolayers dose-dependently induced an indomethacin sensitive increase in Isc compared with values in untreated co-mounted monolayers (p < 0.001, n = 11). These data suggest that in infectious diarrhoea, TNF alpha may induce Cl- secretion through a paracrine mechanism involving prostaglandin release from subepithelial cells, for example fibroblasts.