Disruption of the Cox-1 gene slows repair of microscopic lesions in the mouse gastric epithelium

Abstract

Cyclooxygenase-1 (Cox-1) contributes to gastric defense of healthy tissue, but the role in the protection of the gastric epithelium after minor, acute damage has been difficult to study in vivo. Using 710-nm two-photon light absorption to create microscopic gastric damage in anesthetized mice with the gastric mucosal surface surgically exposed and perfused on the microscope stage, the acute response of surface cells to injury could be monitored using in vivo microscopy within seconds after injury. Using exogenous (Cl-NERF) and endogenous fluorophores, extracellular pH and cell death were monitored in real time during the entire damage and repair cycle. Two-photon damage was initiated by scanning approximately 200 microm(2) of gastric surface cells with high laser intensity, causing rapid bleaching of NAD(P)H fluorescence in optically targeted cells. In both Cox-1(+/-) and Cox-1(-/-) mice, a similar initial damage area expanded to include bystander epithelial cells over the next 2-5 min, with larger maximal damage noted in Cox-1(-/-) mice. The maximal damage size seen in Cox-1(-/-) mice could be reduced by exogenous dimethyl-PGE(2). All damaged cells exfoliated, and the underlying epithelium was coincidently repaired over a time interval that was briefer in Cox-1(+/-) (12 +/- 2 min, n = 12) than in Cox-1(-/-) (24 +/- 4 min, n = 14) mice. Directly after damage, pH increased transiently in the juxtamucosal layer (maximal at 3-6 min). A smaller peak pH change was noted in Cox-1(-/-) mice (DeltapH = 0.3 +/- 0.04) than in Cox-1(+/-) mice (DeltapH = 0.6 +/- 0.2). Recovery to normal surface pH took longer in Cox-1(-/-) mice (27 +/- 5 min) than in Cox-1(+/-) mice (12 +/- 1 min). In conclusion, constitutive loss of Cox-1 leaves the gastric mucosa more prone to damage and slowed repair of microlesions.

Trefoil Factor 2 Requires Na/H Exchanger 2 Activity to Enhance Mouse Gastric Epithelial Repair

“…Live Tissue Imaging and Inducing Focal Lesions in Gastric Surface Epithelium-Our methods for confocal/two-photon imaging of the exposed gastric mucosa and creation of microscopic lesions in the surface epithelium by two-photon photodamage have been reported previously (25,30,31). Briefly, the mucosal surface of the gastric corpus was observed using a Zeiss C-Apo ϫ40 objective, and data were collected in a time series.…”

“…The damagerepair cycle was measured independently several times per animal in different locations of the corpus. As described previously (25,30,31), post-acquisition image analysis (Metamorph software, Molecular Devices, Downington, PA) measured the lesioned area as defined by cellular loss of NAD(P)H autofluorescence in direct comparison with simultaneously recorded confocal reflectance images that confirmed location of cellular structures. The changing size of the damaged area over time was used to estimate rates of epithelial restitution, by fitting data to a single exponential decay curve as described and reporting the rate constant of repair as a measure of the restitution rate (25).…”

“…The changing size of the damaged area over time was used to estimate rates of epithelial restitution, by fitting data to a single exponential decay curve as described and reporting the rate constant of repair as a measure of the restitution rate (25). Extracellular pH near the gastric surface was measured from Cl-NERF ratio images as described previously (25,27,28,31).…”

Prostaglandin E2 Prevents Helicobacter-Induced Gastric Preneoplasia and Facilitates Persistent Infection in a Mouse Model

“…In seeming contrast to the protective effect of exogenously added PGE 2 , we observe elevated endogenous PGE 2 in mice with established atrophy. We believe that this PGE 2 , which may be COX-1 derived, is secreted by the gastric mucosa in an effort to repair the mucosal damage, 36 but is insufficient to act on T-cells and to prevent further damage or to reverse pre-established lesions.…”

Genetic ablation of carbonic anhydrase IX disrupts gastric barrier function via claudin‐18 downregulation and acid backflux

“…Another parameter that has been shown to reflect intact gastric defence mechanisms is the assessment of the juxtamucosal pH directly above the epithelial cells 41, 42. In the present study, the juxtamucosal pH was significantly lower in the absence of CAIX in the presence of a luminal acid load, which may reflect lower rates of base permeation either via the apical membrane of the surface cells or via the anion‐selective tight junctional pathway (Fig.…”