Intestinal Alkaline Phosphatase Regulates Tight Junction Protein Levels.
Intestinal alkaline phosphatase (IAP) plays a pivotal role in maintaining gut health and well-being. Oral supplementation with IAP in mice improves gut barrier function and prevents luminal proinflammatory factors from gaining access to the circulation. In this study, we sought to explore the relationship between IAP and tight junction protein (TJP) expression and function.



The effect of IAP deletion on TJP levels was studied in mouse embryonic fibroblasts (MEFs) generated from IAP-knockout and wild type mice. Regulation of TJPs by IAP was assayed in the human colon cancer Caco-2 and T84 cells by overexpressing the human IAP gene. Tight junction protein levels and localization were measured by using RT q-PCR and antibodies targeting the specific TJPs. Finally, the effect of IAP on inflammation-induced intestinal permeability was measured by in vitro trans-well epithelial electrical resistance (TEER).



Intestinal alkaline phosphatase gene deletion in MEFs resulted in significantly lower levels of ZO-1, ZO-2, and Occludin compared with levels in wild-type control cells; IAP overexpression in Caco-2 and T84 cells resulted in approximate 2-fold increases in the mRNA levels of ZO-1 and ZO-2. The IAP treatment ameliorated lipopolysaccharide-induced increased permeability in the Caco-2 trans-well system. Furthermore, IAP treatment preserved the localization of the ZO-1 and Occludin proteins during inflammation and was also associated with improved epithelial barrier function.



Intestinal alkaline phosphatase is a major regulator of gut mucosal permeability and appears to work at least partly through improving TJP levels and localization. These data provide a strong foundation to develop IAP as a novel therapy to maintain gut barrier function.
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Wei
W
Liu
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Dong
D
Hu
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Haizhong
H
Huo
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Weifeng
W
Zhang
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Fatemeh
F
Adiliaghdam
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Sarah
S
Morrison
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Juan M
JM
Ramirez
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Sarah S
SS
Gul
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Sulaiman R
SR
Hamarneh
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA. Electronic address: rhodin@mgh.harvard.edu.
Richard A
RA
Hodin
D000469:Alkaline Phosphatase / Q000172:deficiency / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D018938:Caco-2 Cells; D015536:Down-Regulation; D017097:Electric Impedance; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010539:Permeability; D060888:Real-Time Polymerase Chain Reaction; D019108:Tight Junctions / Q000378:metabolism*; D015854:Up-Regulation
D015415:Biomarkers; D000469:Alkaline Phosphatase