Objectives: To characterize diarrhoeal mechanisms in HIV-infected patients, epithelial transport and barrier function of the duodenal mucosa was investigated in vitro. Patients: Twenty-one HIV-seropositive patients (13 asymptomatic and eight with diarrhoea) and 12 controls from an urban referral-based tertiary care centre in Berlin who underwent duodenoscopy. Methods: A new miniaturized Ussing chamber allowed measurements on duodenal forceps biopsies. Epithelial barrier function was characterized by alternating current impedance analysis, which allows differentiation of epithelial and subepithelial resistance and by 3 H-lactulose and 3 H-mannitol flux measurements. Na + -glucose cotransport was quantified as phlorizin-sensitive short circuit current (I SC ) and active ion secretion by baseline and bumetanide-sensitive I SC . Results: Duodenal biopsies from asymptomatic HIV-infected patients were no different from controls, whereas biopsies from HIV-infected patients with diarrhoea showed a decrease in epithelial resistance from 21.2±1.9 to 12.9±1.3 Ωcm 2 (P< 0.01). Concomitantly, mucosal-to-serosal lactulose flux increased from 0.29 ± 0.02 to 0.40 ± 0.03 μmol (hcm 2 ) (P < 0.01). Phlorizin-sensitive I SC indicating Na + -glucose cotransport, as well as baseline and bumetanide-sensitive I SC . indicating active electrogenic chloride secretion were not different between the three groups. Conclusions: A miniaturized Ussing device was developed for electrophysiological investigations of duodenal forceps biopsies, which allowed characterization of active ion transport mechanisms and epithelial barrier function. Duodenum of HIV-infected patients with diarrhoea showed no evidence for active ion secretion or Na + -glucose malabsorption, but showed an impaired epithelial barrier function, which could contribute to diarrhoea by a leak flux mechanism.

HIV heterogeneity and disease progression in AIDS: a model of continuous virus adaptation.

Yersinia enterocolitica induces epithelial barrier dysfunction through regional tight junction changes in colonic HT-29/B6 cell monolayers.

Background and aims: Little is known of the permeability of ileoanal pouches. Hence the aim of the present study was to determine changes in permeability and mucosal function after ileo-pouchanal anastomosis (IPAA) in patients with ulcerative colitis.

Materials and methods: Biopsies were taken from 43 patients (male:female ratio 28:15; mean age 35.2 (12.5) years) prior to colectomy (ileum prior to pouch), prior to closure of ileostomy (deviation), and after closure of ileostomy (intact pouch) in the case of pouchitis, and from 14 healthy controls. Tissues were mounted in a miniaturised Ussing chamber. Epithelial and subepithelial resistance was determined by transmural impedance analysis. Active Na+-glucose cotransport was measured as change in short circuit current after stepwise addition of glucose, and active Cl− secretion was measured after stimulation with theophylline and prostaglandin E2.

Results: Neither epithelial resistance nor mannitol fluxes were significantly altered compared with intact controls, indicating no barrier defect in pouchitis. Subepithelial resistances of intact pouches and pouchitis were increased compared with deviation (18.2 (1.6) and 24.3 (1.5) v 13.6 (1.0) Ω×cm2) consistent with an adaptive thickening of the subepithelial layer. In contrast, active Cl− secretion of pouchitis tissues was reduced versus intact pouch and controls (1.4 (0.3) v 4.3 (0.7) and 4.6 (0.7) μmol/h/cm2), and Na+-glucose cotransport of pouchitis was reduced compared with intact pouch and controls (1.8 (0.5) v 4.2 (0.8) and 8.8 (1.3) μmol/h/cm2).

Conclusions: Ileal mucosa in pouchitis and terminal ileum prior to IPAA exhibit impaired secretory and absorptive transport functions whereas the epithelial barrier function remains unchanged. This differs from findings in ulcerative colitis. Thus the hypothesis that pouchitis represents a remanifestation of ulcerative colitis has to be questioned.

https://gut.bmj.com/content/gutjnl/50/6/821.full.pdf

Impairment of epithelial transport but not of barrier function in idiopathic pouchitis after ulcerative colitis

The relative abundance of various claudin proteins of LLC-PK(1) renal epithelial tight junctions (TJs) is modulated by culturing the cells in a medium that is sharply reduced in the sulfur-containing amino acids, cysteine, cystine, and methionine. The functional result is an epithelial barrier that has a higher transepithelial electrical resistance and a decreased paracellular leak to D-mannitol (i.e., improved barrier function). This is accomplished without affecting the culture's confluent cell density, its short circuit current, or its hallmark differentiated property, Na(+)-dependent sugar transport. The implications of being able to enhance epithelial TJ barrier function by nutritional means are discussed, particularly in light of the ability of methionine-restrictive diets to enhance life span and forestall age-related morbidity.

Modification of Tight Junction Structure and Permeability by Nutritional Means

Infection with Yersinia enterocolitica causes acute diarrhea in early childhood. A mouse infection model presents new findings on pathological mechanisms in the colon. Symptoms involve diarrhea with watery feces and weight loss that have their functional correlates in decreased transepithelial electrical resistance and increased fluorescein permeability. Y. enterocolitica was present within the murine mucosa of both ileum and colon. Here, the bacterial insult was of focal nature and led to changes in tight junction protein expression and architecture. These findings are in concordance with observations from former cell culture studies and suggest a leak flux mechanism of diarrhea.

Yersinia enterocolitica Affects Intestinal Barrier Function in the Colon

Gogarten W, Kockerling A, Fromm M, Riecken EO, Schulzke JD. Effect of acute Yersinia enterocolitica infection on intestinal barrier function in the mouse. Scand J Gastroenterol 1994;29:814-819.Background: Yersinia enterocolitica is an important cause of diarrhea, but little is known about the underlying mechanisms. We therefore studied the impact of acute Y. enterocolitica infection on intestinal barrier function in a mouse model. Methods: For this purpose CD-I mice were infected with Y. enterocolitica (serotype 08; 6 × 107 viable bacteria), and alternating current impedance analysis was performed on days 1, 2, 3, 5, and 8 after infection. Results: The infection resulted in a decrease in epithelial resistance from 18.0 ± 0.9 ωcm2 (controls) to 12.1 ± 0.5 ωcm2 (day 1, p < 0.001), from which the animals recovered by day 5. To locate this loss in barrier function, the horizontal distribution of local conductances was measured by voltage scanning, yielding two results. First, conductance was homogeneously dis...

Effect of acute Yersinia enterocolitica infection on intestinal barrier function in the mouse

In ulcerative colitis and polyposis coli, creation of an ileal pouch with ileoanal anastomosis after proctocolectomy has become a common surgical method. The aim of our study was to characterize the adaptation of the epithelial ion transport function in the pouch by using electrophysiologic techniques. Proctocolectomy and ileoanal anastomosis was performed in rats either with (pouch) or without (control) creation of an ileal J-pouch. To characterize the epithelial barrier function, impedance analysis was performed 6 months after surgery. Epithelial resistance was 29 ± 2 Ω · cm2 in controls and was unchanged in the pouch (28 ± 4 Ω · cm2; NS). In contrast, subepithelial resistance increased from 33 ± 3 Ω · cm2 to 54 ± 5 Ω · cm2 (p < 0.01) owing to work hypertrophy of the muscle layers in the pouch. To detect changes in net ion transport, ion tracer fluxes were measured in the Ussing chamber. In control ileum, absorptive net Na and Cl fluxes of similar magnitude were present, indicating that electroneutral N...

Epithelial Ion Transport in the Heal J-Pouch after Proctocolectomy in the Rat

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Effect of acute Yersinia enterocolitica infection on intestinal barrier function in the mouse

Epithelial Ion Transport in the Heal J-Pouch after Proctocolectomy in the Rat