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Intestinal Alkaline Phosphatase Regulates Tight Junction Protein Levels
Wei Liu, Sulaiman R. Hamarneh, Weifeng Zhang, Haizhong Huo, Dong Hu, Sarah S. Gul, Sarah Morrison, Mohammad Hadi Gharedaghi, *Richard A. Hodin
Massachusetts General Hospital, Boston, MA

Objective: Intestinal alkaline phosphatase (IAP) plays a pivotal role in maintaining gut health and well being. Oral supplementation of IAP improves gut barrier function and prevents luminal pro-inflammatory factors from gaining access to the circulation.We sought to elucidate the role of IAP in tight junction protein (TJP) functions.

Design: IAP knockout mice and wild type mice were used to study gut permeability and intestinal tight junction protein expression.The effect of IAP deletion on TJP levels was studied in mouse embryonic fibroblasts generated from IAP-KO and WT mice. IAP overexpressing cells were generated by transfecting the human colon cancer T84 cells with Ds-Red1 plasmid with human IAP gene as an insert. TJP levels were measured by RT q-PCR using RNA isolates from IAP-overexpressing T84 cells compared to cells transfected with empty vector.

Results: Intestinal permeability to 4kD and 10KD FITC-dextran were >2-fold higher in the IAP KO vs WT mice (p< 0.05). The relative expression of TJP (ZO-1, ZO-2, Ocludin, Claudin-1, Claudin-3) were >8-fold lower in IAP KO vs. WT mice (p< 0.05). Furthermore, IAP-KO MEFs had significantly lower levels of ZO-1, ZO-2 and Occludin compared to WT controls. Overexpression of IAP gene resulted in two fold increases in the levels of ZO-1 and ZO-2 proteins in T84 cells.

Conclusion: IAP is a major regulator of gut mucosal permeability and its function is in part through improving TJP levels.

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