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P045. Direct effects of infliximab (IFX) on intestinal mucosa: Exploring mechanisms of mucosal healing

F. Scaldaferri1, L.R. Lopetuso1, V. Petito2, V. Gerardi1, V. Arena2, E. Stigliano2, M. Pizzoferrato1, S. Pecere1, L. Laterza1, A. Papa3, V. Cufino2, A. Amato4, G. Cammarota1, A. Sgambato2, A. Gasbarrini1

1Catholic University of Rome, Internal Medicine Department/Gastroenterology Division, Rome, Italy; 2Catholic University of Rome, Pathology Department, Rome, Italy; 3Catholic University of Rome, Internal Medicine and Gastroenterology Complesso Integrato Columbus, Rome, Italy; 4Catholic University of Rome, Anesthesiology Department, Rome, Italy

Background: Mucosal healing is one of the biggest issues on the management of IBD, as it seems to be determined by certain categories of drugs, including biologics. Mechanisms of these drugs are still not clear. Aim of our study is to identify the effect of IFX on intestinal epithelial cells in order to induce mucosal healing, using in vitro and in vivo models.

Methods: Human intestinal mucosal biopsies from active IBD patients were cultured for 48 h with/wo IFX (50 ng/ml), and supernatants were assessed for cytokines content and histology performed.

Effect of IFX was explored in C57BL/6 mice exposed for 7 days to 2.5% of DSS. IFX was administered iv (5 mg/Kg) at day 5 or by daily enema (300 mg/200 ml) for 3 days starting at day 5. At day 9 mice were sacrificed and histology was taken.

To explore the effect of IFX on intestinal epithelial cells, a scratch assay was performed on CT26 and Caco2 cell line monolayer. Precice scratches were obtained by seading cells in micro-CHAMBER formed by culture inserts. Cells were exposed for 24 h to IFX (50 ng/ml) and/or TNF‑a (100 U/ml), or to supernatants of PBMC or fibroblast treated or not for 24 h with IFX and/or TNF‑a. Seriated pictures were taken for 24 h following the stimulation and analized by computer software.

Results: Human biopsies exposed to IFX show a decrease in TNF‑a content, as well as of innate and adaptive immunity cytokines. At histology IFX-treated biopsies showed a decreased immune cells infiltration.

In vivo, IFX iv or given as enema ameliorated the severity of colitis in mice, by lowering the disease activity index (DAI) and the loss of body weight. At day 9 a reduction of intestinal inflammatory infiltrate was observed in treated mice.

At scratch assay, TNF‑a slightly decreased the healing process, while IFX alone or in combination did not. TNF‑a exposed PBMC supernatants decreased epithelial healing; TNF‑a fibroblast supernatants slowed the healing process but adding IFX the healing process was restored.

Conclusions: IFX acts locally at mucosa level, as shown by the decrease in inflammatory infiltrate and cytokines contents. The effect of IFX is partially dependent on direct effect on epithelial cells. IFX seems to ameliorate epithelial cell healing by blocking the detrimental capacity of TNF‑a pre-treated fibroblast on intestinal epithelial cells. More data are necessary to unravel molecular pathways of these observations, in order also to clarify mechanisms of loss of responses to it as well as new targets for potential new therapies.