Hyaluronan fragments stimulate endothelial recognition of injury through TLR4.
Tissues must quickly recognize injury to respond to the rapid pace of microbial growth. In skin, dermal microvascular endothelial cells must also react to danger signals from the surrounding tissue and immediately participate by initiating the wound repair process. Components of the extracellular matrix such as hyaluronan are rapidly broken down into smaller molecular weight oligosaccharides in a wound, and these can activate a variety of biological processes. This study set out to determine if hyaluronan fragments released following injury can stimulate endothelial cells and what mechanism is responsible for this response. Using genechip microarray analysis, a response to hyaluronan fragments was detected in endothelial cells with the most significant increase observed for the chemokine IL-8. This observation was verified with qualitative reverse transcriptase-PCR and ELISA in human endothelial cell culture, and in a mouse model by observing serum levels of MIP-2 and KC following hyaluronan fragment administration in vivo. Activation was TLR4-dependent, as shown by use of TLR4 blocking antibody and TLR4-deficient mice, but not due to the presence of undetected contaminants as shown by inactivation following digestion with the hyaluronan-degrading enzyme chondroitinase ABC or incubation with the hyaluronan-specific blocking peptide Pep-1. Inactivation of LPS activity failed to diminish the action of hyaluronan fragments. These observations suggest that endogenous components of the extracellular matrix can stimulate endothelia to trigger recognition of injury in the initial stages of the wound defense and repair response.
Taylor
Kristen R
KR
Department of Dermatology, University of California, San Diego and Veterans Affairs Medical Center, San Diego, California 92161, USA.
Trowbridge
Janet M
JM
Rudisill
Jennifer A
JA
Termeer
Christian C
CC
Simon
Jan C
JC
Gallo
Richard L
RL
D000818:Animals; D002478:Cells, Cultured; D019765:Chondroitin ABC Lyase / Q000378:metabolism; D020405:Dermis / Q000166:cytology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry* / Q000494:pharmacology*; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008833:Microcirculation; D020411:Oligonucleotide Array Sequence Analysis; D010455:Peptides / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014945:Wound Healing
D016209:Interleukin-8; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D010455:Peptides; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D006820:Hyaluronic Acid; D019765:Chondroitin ABC Lyase