Effects of 16,16-dimethyl prostaglandin E2 on glycoprotein and lipid synthesis of gastric epithelial cells grown in a primary culture

Development of the PC-NSAID technology: From contact angle to Vazalore®

We describe strategies in drug development to reduce the gastrointestinal (GI) toxicity of nonsteroidal anti-inflammatory drugs (NSAIDs). We then provide an overview of the experiments that led to the development of PC-NSAIDs, a novel family of NSAIDs associated with phosphatidylcholine (PC) that have reduced GI toxicity and full therapeutic activity. Furthermore, we describe the evidence showing: that the stomach possesses hydrophobic properties that are attributable to phospholipids lining the mucus gel layer; and that NSAIDs chemically associate with intrinsic PC, thereby attenuating the tissue's hydrophobic properties. Further, pre-associating NSAIDs with PC reduces the GI toxicity of these drugs, both in rodent ulcer models and in human subjects, without affecting the drugs' therapeutic activity. Finally, we discuss the commercialization and launch of Aspirin-PC, an over-the-counter (OTC) drug with the brand name Vazalore®.

Sodium caprate-induced increases in intestinal permeability and epithelial damage are prevented by misoprostol

Epithelial damage caused by intestinal permeation enhancers is a source of debate concerning safety. The medium chain fatty acid, sodium caprate (C10), causes reversible membrane perturbation at high dose levels required for efficacy in vivo, so the aim was to model it in vitro. Exposure of Caco-2 monolayers to 8.5mM C10 for 60min followed by incubation in fresh buffer led to (i) recovery in epithelial permeability (i.e. transepithelial electrical resistance (TEER) and apparent permeability coefficient (Papp) of [(14)C]-mannitol), (ii) recovery of cell viability parameters (monolayer morphology, plasma membrane potential, mitochondrial membrane potential, and intracellular calcium) and (iii) reduction in mRNA expression associated with inflammation (IL-8). Pre-incubation of monolayers with a mucosal prostaglandin cytoprotectant was attempted in order to further decipher the mechanism of C10. Misoprostol (100nM), inhibited C10-induced changes in monolayer parameters, an effect that was partially attenuated by the EP1 receptor antagonist, SC51322. In rat isolated intestinal tissue mucosae and in situ loop instillations, C10-induced respective increases in the [(14)C]-mannitol Papp and the AUC of FITC-dextran 4000 (FD-4) were similarly inhibited by misoprostol, with accompanying morphological damage spared. These data support a temporary membrane perturbation effect of C10, which is linked to its capacity to mainly increase paracellular flux, but which can be prevented by pre-exposure to misoprostol.

Fetal rat glandular stomach epithelial cells differentiate into surface mucous cells which express cathepsin E in the absence of mesenchymal cells in primary culture

It is well established that the differentiation of glandular stomach epithelial cells is affected by many factors including epithelial-mesenchymal interactions. To clarify the control mechanism of their differentiation, we developed a primary culture system for fetal rat glandular stomach epithelial cells, and examined their differentiation in the absence of mesenchyme. Pure glandular stomach epithelial tissues obtained from 16.5-day fetal rats proliferated rapidly, increasing their number about 20 times in the first 7 days. The epithelial nature of the cells was confirmed by the presence of cytokeratin in the cells. Glandular stomach epithelial cells formed simple cuboidal/squamous epithelia with many mucous granules in their cytoplasm, and exhibited epithelial polarity with microvilli on the luminal surface, basal lamina-like material on the basal surface, and junctional complexes in the apical region. Biochemical analysis showed that the cells expressed acid protease activity in culture. Previous studies showed that glandular stomach epithelial cells specifically expressed two types of acid proteases: pepsinogens in chief and mucous neck cells, and cathepsin E in surface mucous cells. Immunohistochemical studies using specific antibodies showed that the cultured cells expressed cathepsin E but not pepsinogens, and the result was confirmed by zymogram and Western blotting analysis. We thus concluded that fetal rat glandular stomach epithelial cells differentiated into surface mucous cells that expressed cathepsin E in primary culture in the absence of mesenchyme.

The effect of 16,16-dimethyl prostaglandin E2 on proliferation of an intestinal goblet cell line and its synthesis and secretion of mucin glycoproteins

The effect of 16,16'-dimethyl prostaglandin E2 (dmPGE2) on the human colonic adenocarcinoma derived mucus-secreting goblet cell line HT29-18N2 was investigated. The proliferation rate of HT29-18N2 was increased by exposure to 10 or 100 microM dmPGE2. Exposure to 10 or 100 microM dmPGE2 caused a significant decrease in the rate of radiolabeled glucosamine incorporation into newly synthesized glycoproteins during an 8 or 24 h exposure. At concentrations as low as 1 microM, dmPGE2 accelerated the secretion of mucin glycoproteins as assessed by the release of newly synthesized radiolabeled glycoproteins, a mucin-specific enzyme-linked immunoassay and a whole-mount immunofluorescence assay. A 1 h exposure to dmPGE2 did not, however, result in a morphometrically detectable decrease in intracellular mucous granule stores or elicit any other readily detectable morphological change. The experimental results suggest elevated levels of PGs may contribute to the previously recognized decreases in intracellular mucin stores and shifts in the types of mucins species present at sites of mucosal inflammation in ulcerative colitis patients.

Effect of 16,16-dimethyl prostaglandin E2 on lipidic organelles of rat gastric surface mucous cells

BACKGROUND

We examined the effect of 16,16-dimethyl prostaglandin E2 (dmPGE2) on the subcellular distribution of phospholipids in rat gastric surface mucous cells (SMCs) using the cytochemical stain, iodoplatinate (IP).

METHODS

The volume of a number of subcellular organelles and the density of IP reactivity within these organelles was determined by modified vertical section stereology.

RESULTS

The volume occupied by most of the subcellular organelles was not affected by dmPGE2 treatment, with the exception that the volume fraction of two classes of large infranuclear inclusion bodies (LIIB1 and LIIB2, organelles we have previously shown to contain hydrophobic lipids), were significantly expanded by a factor of 3-4-fold. The distribution of IP reactivity among the various subcellular compartments appeared to undergo a shift in response to dmPGE2 treatment. Once again the major prostanoid effect was seen in the infranuclear inclusion bodies, as the volume density of IP reactivity was increased 2-24-fold in LIIB1 and 9-10-fold in LIIB2 in comparison to control values.

CONCLUSION

dmPGE2 administration to rats induces an increase in the volume and IP reactivity of a family of lipid-containing organelles, which may underlie its ability to increase the hydrophobic surface properties of the stomach.