HMGB1 B box increases the permeability of Caco-2 enterocytic monolayers and impairs intestinal barrier function in mice.
OBJECTIVE
High mobility group (HMG) B1 is a nonhistone nuclear protein that was recently identified as a late-acting mediator of lipopolysaccharide-induced lethality in mice. The proinflammatory actions of HMGB1 have been localized to a region of the molecule called the B box.


METHODS
To determine whether HMGB1 or B box are capable of causing derangements in intestinal barrier function, we incubated cultured Caco-2 human enterocytic monolayers with recombinant human HMGB1 or a 74-residue truncated form of the protein consisting of the B box domain.


RESULTS
Both HMGB1 and B box increased the permeability of Caco-2 monolayers to fluorescein isothiocyanate-labeled dextran (FD4) in a time- and dose-dependent fashion. The increase in permeability was reversible following removal of the recombinant protein. Exposure of Caco-2 cells to B box resulted in increased expression of inducible nitric oxide synthase messenger RNA and increased production of NO. When we used various pharmacologic strategies to inhibit NO production or scavenge NO or peroxynitrite (ONOO(-)), we abrogated B box-induced hyperpermeability. Administration of B box to wild-type mice increased both ileal mucosal permeability to FD4 and bacterial translocation to mesenteric lymph nodes. These effects were not observed in inducible nitric oxide synthase knockout mice.


CONCLUSIONS
These data support the view that HMGB1 and B box are capable of causing alterations in gut barrier function via a mechanism that depends on the formation of NO and ONOO(-).
Department of Critical Care Medicine, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15261, USA.
Penny L
PL
Sappington
Runkuan
R
Yang
Huan
H
Yang
Kevin J
KJ
Tracey
Russell L
RL
Delude
Mitchell P
MP
Fink
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D018938:Caco-2 Cells / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism*; D024243:HMGB1 Protein / Q000737:chemistry / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D007082:Ileum / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000172:deficiency / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010539:Permeability / Q000187:drug effects; D030421:Peroxynitrous Acid / Q000502:physiology; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000276:immunology
D000906:Antibodies; D024243:HMGB1 Protein; D016328:NF-kappa B; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse