gms | German Medical Science

Introduction: Intestinal epithelial barrier breakdown and consecutive bacterial translocation promotes inflammatory response in septic patients. Convincing therapeutic approaches to stabilize intestinal epithelial barrier properties are still missing. Therefore we tested here whether inhibition of phosphodiesterase-4 (PD-4-I) is effective to prevent inflammation-induced breakdown of the intestinal barrier.

Material and methods: Adult rats were anaesthetized and systemic inflammation was induced by intravenous injection of Lipopolysaccharide (LPS; n=6). Another group was treated by i.v. injection with PD-4-I rolipram (LPS+PD-4-I group; n= 6) while controls were left untreated (n=5). After the end of the experimental procedures, morphologic alterations of tissue sections of the intestine were analyzed in H.E. staining. Additionally immunostaining for tight junction proteins claudin1, claudin5 and of adherens junction protein E-cadherin was performed in these sections. In our in vitro model of the intestinal barrier i.e. in differentiated Caco2 monolayers permeability measurements and immunostaining were performed after incubation with LPS or LPS+PD-4-I, Tumor necrosis factor-α (TNF-α) or TNF- α+PDI-4-I (n>4 each), respectively while controls were left untreated.

Results: In LPS-treated animals the intestinal epithelial barrier was significantly compromised as revealed by reduced staining of claudin1, claudin5 and E-cadherin at intercellular junctions of enterocytes lining the intestine. In contrast, LPS+PD-4-I treatment resulted in regular staining pattern of both tight- and adherens junction proteins comparable to control conditions. To test whether PD-4-I could have direct effects on intestinal epithelial barrier functions we performed permeability measurements in our vitro system of differentiated Caco2 cells. Application of LPS and of TNF-α significantly increased permeability as revealed by measurement of 4 kDa FITC-dextran flux across Caco2 monolayers. Similar to the in vivo situation this was completely blocked by simultaneous treatment with PD-4-I.

Conclusion: Taken together these data suggest that PD-4-I is capable to block inflammation-induced disruption of junctional proteins and thereby prevents breakdown of the intestinal barrier.