Toll-like receptor 9 signaling is critical for early experimental deep vein thrombosis resolution.
OBJECTIVE
Toll-like receptors (TLR) bridge innate immunity and host responses, including inflammation. Sterile inflammation such as a venous thrombus (Vt) may involve TLR signaling, including TLR9.


RESULTS
TLR9 signaling on thrombus resolution was investigated using a mouse model of stasis Vt. Vt were significantly larger in TLR9-/- mice compared with wild-type (WT) at 2 and 8 days, despite a 2-fold increase in thrombus polymorphonucleic neutrophils at 2 days and monocytes at 8 days, whereas thrombus collagen and neovascularization was 55% and 37% less, respectively, at 8 days. Coincidently, decreased fibrinogen and increased thrombin-antithrombin complex were observed in TLR9-/- mouse thrombi. Vein wall interferon-α, interleukin-1α, and interleukin-2 were significantly reduced in TLR9-/- mice compared with WT. Thrombus cell death pathway markers were not significantly altered at 2 days, but caspase-1 was reduced in TLR9-/- thrombi at 8 days. MyD88 confers TLR9 intracellular signaling, but MyD88-/- mice had Vt resolution similar to that of WT. However, inhibition of the NOTCH ligand δ-like 4 was associated with larger Vt. Finally, stimulation with a TLR9 agonist was associated with smaller Vt.


CONCLUSIONS
TLR9 signaling is integral for early and mid-Vt resolution through modulation of sterile inflammation, maintaining a TH1 milieu, and effects on the thrombosis pathway.
Henke
Peter K
PK
CVC-5463, Ann Arbor, MI 48109, USA. henke@umich.edu
Mitsuya
Mayo
M
Luke
Catherine E
CE
Elfline
Megan A
MA
Baldwin
Joseph F
JF
Deatrick
K Barry
KB
Diaz
Jose A
JA
Sood
Vikram
V
Upchurch
Gilbert R
GR
Wakefield
Thomas W
TW
Hogaboam
Cory
C
Kunkel
Steven L
SL
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000990:Antithrombin III / Q000378:metabolism; D001777:Blood Coagulation; D002135:Calcium-Binding Proteins; D003094:Collagen / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005340:Fibrinogen / Q000378:metabolism; D007249:Inflammation / Q000097:blood / Q000235:genetics / Q000276:immunology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000276:immunology; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D010447:Peptide Hydrolases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D018417:Th1 Cells / Q000276:immunology; D013916:Thrombelastography; D013997:Time Factors; D051217:Toll-Like Receptor 9 / Q000819:agonists / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020246:Venous Thrombosis / Q000097:blood / Q000235:genetics / Q000276:immunology*
D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D016207:Cytokines; C519665:DLL4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D009838:Oligodeoxyribonucleotides; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; C046193:antithrombin III-protease complex; D000990:Antithrombin III; D005340:Fibrinogen; D003094:Collagen; D010447:Peptide Hydrolases