Extracellular high mobility group box-1 (HMGB1) inhibits enterocyte migration via activation of Toll-like receptor-4 and increased cell-matrix adhesiveness.
Toll-like receptor-4 (TLR4) is the receptor for bacterial lipopolysaccharide, yet it may also respond to a variety of endogenous molecules. Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in newborn infants and is characterized by intestinal mucosal destruction and impaired enterocyte migration due to increased TLR4 signaling on enterocytes. The endogenous ligands for TLR4 that lead to impaired enterocyte migration remain unknown. High mobility group box-1 (HMGB1) is a DNA-binding protein that is released from injured cells during inflammation. We thus hypothesize that extracellular HMGB1 inhibits enterocyte migration via activation of TLR4 and sought to define the pathways involved. We now demonstrate that murine and human NEC are associated with increased intestinal HMGB1 expression, that serum HMGB1 is increased in murine NEC, and that HMGB1 inhibits enterocyte migration in vitro and in vivo in a TLR4-dependent manner. This finding was unique to enterocytes as HMGB1 enhanced migration of inflammatory cells in vitro and in vivo. In seeking to understand the mechanisms involved, TLR4-dependent HMGB1 signaling increased RhoA activation in enterocytes, increased phosphorylation of focal adhesion kinase, and increased phosphorylation of cofilin, resulting in increased stress fibers and focal adhesions. Using single cell force traction microscopy, the net effect of HMGB1 signaling was a TLR4-dependent increase in cell force adhesion, accounting for the impaired enterocyte migration. These findings demonstrate a novel pathway by which TLR4 activation by HMGB1 delays mucosal repair and suggest a novel potential therapeutic target in the amelioration of intestinal inflammatory diseases like NEC.
Dai
Shipan
S
Division of Pediatric Surgery, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15207, USA.
Sodhi
Chhinder
C
Cetin
Selma
S
Richardson
Ward
W
Branca
Maria
M
Neal
Matthew D
MD
Prindle
Thomas
T
Ma
Congrong
C
Shapiro
Richard A
RA
Li
Bin
B
Wang
James H-C
JH
Hackam
David J
DJ
D000199:Actins / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects* / Q000235:genetics; D002633:Chemotaxis / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D020345:Enterocolitis, Necrotizing / Q000378:metabolism; D020895:Enterocytes / Q000166:cytology* / Q000187:drug effects; D005434:Flow Cytometry; D024243:HMGB1 Protein / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000502:physiology; D051379:Mice; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D024243:HMGB1 Protein; D051197:Toll-Like Receptor 4; D020742:rhoA GTP-Binding Protein