Experimental colitis increases small intestine permeability in the rat.

Small intestine permeability is frequently altered in patients with Crohn's disease and is thought to play a pathogenic role. The aim of this study was to investigate the permeability and structure of small intestine tight junctions (TJ) in an animal model of chronic distal colitis. Seven days after colitis induction with trinitrobenzenesulfonic acid/ethanol, the duodenal and ileal TJ were studied by means of transmission electron microscopy using lanthanum nitrate, freeze fractures, and immunohistochemistry of occludin, ZO-1, and cingulin. Animals treated with intrarectal ethanol alone served as controls. In controls, 7.5% of duodenal and 9.6% of ileal TJ were permeable to lanthanum, whereas in colitis, permeability increased significantly (79.5% and 72.9%, respectively; p < 0.001, both segments compared with controls). In colitis, the percentage of "leaky" junctions in duodena as well as in terminal ilea correlated positively with the macroscopic colon damage score (p < 0.02 and p < 0.005, respectively). Freeze-fracture analysis and immunohistochemistry of cingulin and ZO-1 did not reveal any difference between control and treated animals, whereas the signal of the transmembrane protein occludin was found to be disrupted and irregular in both small intestine segments. Distal colitis induces an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. Alterations in the transmembrane protein occludin seem to be responsible for the observed changes. Further investigation is needed to elucidate the mechanism of TJ alterations by a remote focus of inflammation.

Fries W ，Mazzon E ，Squarzoni S ，Martin A ，Martines D ，Micali A ，Sturniolo GC ，Citi S ，Longo G ... -  《LABORATORY INVESTIGATION》

5-lipoxygenase modulates the alteration of paracellular barrier function in mice ileum during experimental colitis.

Small intestine permeability is frequently altered in inflammatory bowel disease and may be caused by the translocation of intestinal toxins through leaky small intestine tight junctions (TJs) and adherence. Recently, it has been shown that 5-lipoxygenase (5-LO) plays an important role in the development of various inflammatory conditions like inflammatory bowel disease. In the present study, by comparing the responses in wild-type mice (5-LOWT) with those of mice lacking the 5-lipoxygenase (5-LOKO), we investigated the role played by this enzyme in the permeability and structure of small intestine TJs in an animal model of experimental colitis. To address this question, we used an experimental model of colitis, induced by dinitrobenzene sulfonic acid (DNBS). Four days after colitis induction by DNBS, the ileal TJs were studied by means of transmission electron microscopy using lanthanum nitrate and immunohistochemistry of occludin and ZO-1. When compared with DNBS-treated 5-LOWT mice, DNBS-treated 5-LOKO mice experienced a reduced rate of the extent and severity of the histological signs of colon injury. After administration of DNBS, 5-LOWT mice showed a significant increase of ileal permeability (88.3% +/- 1.2%) compared with sham (5.6% +/- 0.5%). In colitis, the percentage of "leaky" junctions in terminal ilea correlated positively with the macroscopic colon damage score. Distal colitis in 5-LOWT mice induces an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. On the contrary, a significant reduction of (1) the degree of colon injury, (2) the alteration of ZO-1 and occludin localization (immunohistochemistry), and (3) ileal permeability (8.1% +/- 0.7%) caused by DNBS in the colon was observed in 5-LOKO mice. Similarly, the treatment of 5-LOWT with zileuton (50 mg/kg per oral gavage twice a day), a 5-LO inhibitor, resulted in a significant reduction of all the previously described parameters. Taken together, our results clearly demonstrate that 5-LO modulates small intestinal permeability in experimental colitis through the regulation of TJ protein.

Mazzon E ，Sautebin L ，Caputi AP ，Cuzzocrea S ... -  《SHOCK》

Thalidomide treatment reduces the alteration of paracellular barrier function in mice ileum during experimental colitis.

Small intestine permeability is frequently altered in inflammatory bowel diseases and may be caused by the translocation of intestinal toxins through leaky small intestine tight junctions (TJs) and adherence. Thus, the aim of the present study was to examine the effects of thalidomide treatment on the permeability and structure of small intestine TJs in an animal model of experimental colitis induced by dinitrobenzene sulfonic acid (DNBS). Four days after colitis induction with DNBS, the ileal TJs were studied by means of transmission electron microscopy using lanthanum nitrate and immunohistochemistry of occludin and zonula occludens 1. When compared with DNBS-treated mice, thalidomide-treated (200 mg/kg orally starting 30 min after the administration of DNBS) mice subjected to DNBS-induced colitis experienced a significantly reduced rate of the extent and severity of the histological signs of colon injury associated with a significant reduction of plasma and colon tumor necrosis factor alpha levels. After administration of DNBS to the mice induced a significant increase of ileal permeability was observed. Distal colitis in mice induced an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. In particular, we have observed that thalidomide treatment resulted in a significant reduction of the following: (1) the degree of colon injury, (2) the alteration of zonula occludens 1 and occludin localization (immunohistochemistry), and (3) intestinal permeability caused by DNBS in the colon. Taken together, our results clearly show that thalidomide treatment reduced small intestinal permeability in experimental colitis through the regulation of TJ protein.

Mazzon E ，Cuzzocrea S 《SHOCK》

Loss of the tight junction protein ZO-1 in dextran sulfate sodium induced colitis.

Inflammatory bowel disease (IBD) is associated with increased intestinal permeability and decreased expression of tight junction (TJ) proteins in the inflamed mucosa. Whether this alteration in TJ expression is a prerequisite for the development of intestinal inflammation or a secondary result of that inflammation is unknown. This study looked at the expression of the TJ protein ZO-1 and the corresponding permeability changes in dextran sulfate sodium (DSS) induced colitis in a mouse model. BALB/c mice were fed 3% DSS or water for 1, 3, 5, or 7 days. The animals were weighed, stool was checked for blood, and the colon length measured. Segments of the colon were used for histology, immunohistochemistry for ZO-1, or Western blot for TJ proteins. Colonic permeability was measured using Evan's Blue dye. DSS treated animals had heme positive stools, colitis by histology, significant weight loss, and colon shortening. There was an absence of ZO-1 by Western blot in the 7-day DSS treated animals, double the amount of claudin-1 and normal cytokeratin. The loss of ZO-1 started after 1 d of DSS treatment and was followed by a significant increase in permeability to Evan's blue by day 3. The loss of ZO-1 and increased permeability preceded the development of significant intestinal inflammation suggesting that in DSS colitis alterations in the TJ complex occur before the intestinal inflammation and not as a consequence of it. These changes in the TJ complex may facilitate the development of the inflammatory infiltrate seen in colitis.

Poritz LS ，Garver KI ，Green C ，Fitzpatrick L ，Ruggiero F ，Koltun WA ... -  《JOURNAL OF SURGICAL RESEARCH》

Absence of functional peroxisome proliferator-activated receptor-alpha enhanced ileum permeability during experimental colitis.

The aim of the present study was to examine the role of endogenous peroxisome proliferator-activated receptor-alpha (PPAR-alpha) ligand on the permeability and structure of small intestine tight junctions (TJs) in an animal model of experimental colitis, induced by dinitrobenzene sulfuric acid (DNBS). Four days after colitis induction with DNBS, the ileal TJs were studied by means of transmission electron microscopy using lanthanum nitrate and immunohistochemistry of occludin, zonula occludens 1, and claudin 2. Administration of DNBS to wild-type mice induced colon injury associated with a significant increase of plasma and colon tumor necrosis factor-alpha levels and with a significant increase of ileal permeability. Distal colitis in mice induced an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. Small intestinal permeability was associated with the presence of apoptosis (evaluated by FAS ligand expression and terminal deoxynucleotidyltransferase-mediated UTP nick end labeling coloration), which was associated with a significantly increased expression of proapoptotic Bax and decreased ileum content of antiapoptotic Bcl-2. Absence of a functional PPAR-alpha gene in PPAR-alpha knockout mice resulted in a significant augmentation of all the above-described parameters. Taken together, our results clearly demonstrate that endogenous PPAR-alpha ligands reduced small intestinal permeability in experimental colitis through the regulation of apoptosis and TJ protein.

Mazzon E ，Cuzzocrea S 《SHOCK》