The effect of phospholipids and fatty acids on tight-junction permeability and bacterial translocation

Abstract

The activity of phospholipase A2 (PLA2) is elevated in the intestinal epithelia of patients with inflammatory bowel disease (IBD). We recently reported that PLA2 mediates hydrolysis of phosphatidylcholine (PC) to lysophosphatidylcholine (L-PC) when both are applied to the apical surface of cultured EC monolayers, resulting in increased bacterial translocation (BT) and decreased transepithelial electrical resistance (TEER). Free fatty acids (FFA) are the other products of this reaction, however, their effect on Caco-2 cell permeability has not been reported. In addition to PC, other luminal phospholipids are present at the surface of the enterocyte. PLA2 may also mediate the hydrolysis of luminal phospholipids other than PC. The aim of this study was to examine the effects of phospholipids other than PC and common FFA on intestinal epithelial permeability and BT. Human Caco-2 enterocytes were grown to confluence on porous filters in the apical chamber of a two-chamber cell-culture system. Monolayer integrity and tight-junction permeability were measured as TEER. First, common FFA released by PC hydrolysis were determined using thin-layer chromatography (TLC). In separate experiments, monolayers were treated with phosphatidylethanolamine (PE), lysophosphatidylethanolamine (L-PE), or palmitoleic acid, oleic acids, linoleic acids, and arachidonic acid solubilized in solution with PC. The magnitude of BT was determined 2 h after treatment by adding Escherichia coli C25 to the apical chamber followed by quantitatively culturing basal-chamber samples. Statistical analysis was by the Kurosaki-Wallis test. TLC of PC samples incubated with PLA2 on the apical surface of Caco-2 monolayers demonstrated the production of palmitoleic acid, oleic acids, linoleic acids, and arachidonic acid. L-PE significantly decreased TEER compared to controls, but to a lesser degree than L-PC alone. L-PE had no effects on BT. Palmitoleic acid and oleic acid likewise significantly decreased TEER compared to controls, however, less than L-PC. All FFA tested had no effect on BT. Phospholipids applied to the apical surface of enterocytes, such as those found in vivo in mucus, can be hydrolyzed by the enzyme PLA2 resulting in lysophospholipid and FFA species that can alter enterocyte monolayer permeability. However, FFA and L-PL, other than L-PC, appear to have no effect to stimulate BT. This observation may have clinical implications in the pathogenesis and treatment strategies for IBD patients in whom enterocyte PLA2 activity has been shown to be elevated.

The nutritional background of the host alters the disease course in a fish–myxosporean system

“…Other possible changes in the cellular architecture and composition of the digestive tract might favour parasite entrance and proliferation in the intestinal epithelium, through changes at the host-parasite interface (Yoshino et al, 2001), alterations of the gut barrier or the mucosal immunity (Kasper and Buzoni-Gatel, 2001), or alterations of the biochemical makeup of the cell membrane lipid rafts/caveolae microdomains (Chapkin et al, 2008). In fact, the effect of PLs, FAs and soybean meal on tight-junction permeability and therefore in bacterial translocation (Sawai et al, 2001), on fish intestinal mucus and bacterial adhesion (BakkeMcKellep et al, 2007;Schroers et al, 2008) have been reported. Thus, further studies are needed to determine the effect of vegetable diets in the distribution and composition of enzymes, other molecules of interest and leucocyte populations in the intestinal tract.…”

Establishment of an in vitro brain barrier epithelial transport system for pharmacological and toxicological study

“…Fatty acids are the major constituents of the phospholipid bilayer of the epithelial cell membrane and have been suggested to play a role in modulating the permeability of the epithelial cells [29]. Yamagata and his colleagues [42] recently reported that EPA and glinolenic acid (GLA), by modulating protein kinase C and tyrosine kinase activity, increased the expression of occludin mRNA in porcine brain capillary endothelial cells, leading to an increased TEER in their barrier model.…”

New insights into the role of fatty acids in the pathogenesis and resolution of inflammatory bowel disease

“…Another study using cultured enterocytes showed that PLA 2 (which is increased in IBD patients), converts PC to LPC, leading to increased tight junction permeability and bacterial translocation. 51 Several animal studies have shown protection from experimental colitis when given exogenous sources of PC in the diet. 52,53 Another key component of mucus is mucin (a glycoprotein) that has also been found to be selectively abnormal in UC patients, but not those with colitis from CD, infection, or ischemia.…”