Absorption of intact protein by colonic epithelial cells of the rat

Alcoholic pancreatitis: A tale of spirits and bacteria

Alcohol is a major cause of chronic pancreatitis. About 5% of alcoholics will ever suffer from pancreatitis, suggesting that additional co-factors are required to trigger an overt disease. Experimental work has implicated lipopolysaccharide, from gut-derived bacteria, as a potential co-factor of alcoholic pancreatitis. This review discusses the effects of alcohol on the gut flora, the gut barrier, the liver-and the pancreas and proposes potential interventional strategies. A better understanding of the interaction between the gut, the liver and the pancreas may provide valuable insight into the pathophysiology of alcoholic pancreatitis.

Mucosal delivery of anti-inflammatory IL-1Ra by sporulating recombinant bacteria

BACKGROUND

Mucosal delivery of therapeutic protein drugs or vaccines is actively investigated, in order to improve bioavailability and avoid side effects associated with systemic administration. Orally administered bacteria, engineered to produce anti-inflammatory cytokines (IL-10, IL-1Ra), have shown localised ameliorating effects in inflammatory gastro-intestinal conditions. However, the possible systemic effects of mucosally delivered recombinant bacteria have not been investigated.

RESULTS

B. subtilis was engineered to produce the mature human IL-1 receptor antagonist (IL-1Ra). When recombinant B. subtilis was instilled in the distal colon of rats or rabbits, human IL-1Ra was found both in the intestinal lavage and in the serum of treated animals. The IL-1Ra protein in serum was intact and biologically active. IL-1-induced fever, neutrophilia, hypoglycemia and hypoferremia were inhibited in a dose-dependent fashion by intra-colon administration of IL-1Ra-producing B. subtilis. In the mouse, intra-peritoneal treatment with recombinant B. subtilis could inhibit endotoxin-induced shock and death. Instillation in the rabbit colon of another recombinant B. subtilis strain, which releases bioactive human recombinant IL-1beta upon autolysis, could induce fever and eventually death, similarly to parenteral administration of high doses of IL-1beta.

CONCLUSIONS

A novel system of controlled release of pharmacologically active proteins is described, which exploits bacterial autolysis in a non-permissive environment. Mucosal administration of recombinant B. subtilis causes the release of cytoplasmic recombinant proteins, which can then be found in serum and exert their biological activity in vivo systemically.

Increased permeability to polyethylene glycol 4000 in rabbits with experimental colitis

Little information is available regarding colonic permeability to macromolecules in health or disease states. In vivo permeability of rabbit colon to [14C]polyethylene glycol 4000 (14C-PEG) was examined in the presence of immune complex-mediated experimental colitis and compared with that of partially treated (control) and normal rabbits. Permeability was assessed by urinary 14C-PEG excretion after intrarectal administration of 0.1 mM solution of 14C-PEG (1 ml/kg, 7.5 X 10(6) cpm/ml). Experimental colitis greatly increased colonic permeability (p less than 0.001 in two-way analysis of variance) compared with control and normal groups (2.06% +/- 0.19%, 0.14% +/- 0.04%, and 0.01% +/- 0.004%, respectively, of rectally administered counts). Gel diffusion chromatography showed that absorbed 14C-PEG was excreted into urine unchanged, demonstrating its applicability as an inert, nonmetabolizable macromolecular probe. Urinary clearance after mesenteric vein administration of 14C-PEG was similar in normal animals and animals with colitis, implicating colonic absorption as the source of the group differences. Postmortem histology confirmed the acute colitis lesions in the experimental group. These findings support the hypothesis that nonspecific colonic inflammation is associated with significant alterations of mucosal permeability.

Macromolecular transport in the fetal rat intestine

Macromolecular barrier function of the fetal rat small intestine and colon was analyzed from 16 to 22 days gestation (birth). During this period the epithelium is converted from stratified to simple columnar. To assess permeability, horseradish peroxidase (HRP) was introduced by microinjection into the lumen or into the umbilical circulation. Proximal small intestine, distal small intestine, and colon were examined after 10-20 min. Paracellular passage of HRP through occluding junctions was not observed after either intraluminal or intravascular injection. After intraluminal injection, transepithelial transport of HRP from lumen to blood occurred in all regions at all ages studied. Horseradish peroxidase was present in cytoplasmic vesicles of most cells in the primitive stratified epithelia, during epithelial conversion, and in simple columnar epithelia. After intravascular injection, HRP was present in the lamina propria and in intercellular spaces of the epithelium, but HRP did not enter tight junctions. Tracer was taken up into cytoplasmic vesicles of both stratified and simple columnar epithelial cells, but was only rarely seen in the lumen. We conclude that there is rapid transcellular, vesicle-mediated transport from lumen to blood across both stratified and simple columnar epithelia of fetal rat small intestine and colon; after intravascular injection, macromolecules may be taken up into vesicles at basolateral epithelial cell surfaces but are not rapidly transported into the lumen; paracellular passage does not occur in the fetal ages studied.