Activation of toll-like receptor 3 protects against DSS-induced acute colitis.
BACKGROUND
Mimetics of bacterial DNA, given orally or subcutaneously, protect mice from experimental colitis via a toll-like receptor (TLR)-9-dependent mechanism. The goal of the study was to define whether synthetic viral RNA, polyinosinic acid:cytidylic acid [poly(I:C)], which is also a potent immunomodulator, might also affect murine colitis and, if so, define whether such effects were mediated by TLR3, which is one of at least 4 known receptors for this viral RNA analog.


METHODS
Mice (C57BL6, IL-10KO, or TLR3 KO) were administered 1.5% dextran sodium sulfate (DSS) in drinking water for 7 days. Two hours before treatment with DSS, mice were given phosphate-buffered saline (PBS) or poly(I:C) 20 mug subcutaneously (s.c.), or 100 mug intragastrically (i.g.).


RESULTS
In wildtype mice s.c. administration of poly(I:C) dramatically protected against DSS-induced colitis as assessed by every parameter analyzed, which included body weight, rectal bleeding, colonic myeloperoxidase, histopathology, serum keratinocyte-derived chemokine, serum amyloid A, and lipocalin-2. In contrast, i.g. administration of poly(I:C) offered no protection in this colitis model nor did its administration activate the innate immune system as assessed by serologic parameters. Subcutaneous poly(I:C) protected against DSS-induced colitis equally well in C57BL6 and IL-10KO mice, indicating that this antiinflammatory cytokine is not required for such protection. Protection against colitis given by poly(I:C) treatment was ablated in TLR3 KO, indicating that the protective action of this viral RNA analog was mediated by this receptor.


CONCLUSIONS
Activation of TLR3 on cells that are accessible by systemic, but not oral, administration of synthetic viral RNA results in protection against the acute inflammation that can ensue upon damage of the gut epithelium. Thus, this viral RNA analog, which is under clinical trials for other inflammatory disorders (e.g., lupus), may also have therapeutic value for inflammatory bowel disease.
Vijay-Kumar
Matam
M
Department of Pathology and Laboratory Medicine, Epithelial Pathobiology Unit, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Wu
Huixia
H
Aitken
Jesse
J
Kolachala
Vasantha L
VL
Neish
Andrew S
AS
Sitaraman
Shanthi V
SV
Gewirtz
Andrew T
AT
D000818:Animals; D003092:Colitis / Q000139:chemically induced / Q000276:immunology / Q000517:prevention & control*; D003106:Colon / Q000378:metabolism / Q000473:pathology; D016264:Dextran Sulfate; D004333:Drug Administration Routes; D005260:Female; D007369:Interferon Inducers / Q000008:administration & dosage / Q000627:therapeutic use*; D016753:Interleukin-10 / Q000172:deficiency / Q000235:genetics / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011070:Poly I-C / Q000008:administration & dosage / Q000627:therapeutic use*; D051196:Toll-Like Receptor 3 / Q000172:deficiency / Q000378:metabolism*
D007369:Interferon Inducers; C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3; D016753:Interleukin-10; D016264:Dextran Sulfate; D011070:Poly I-C