Toll-like receptor stimulation in cardiomyoctes decreases contractility and initiates an NF-kappaB dependent inflammatory response.
OBJECTIVE
The transmembrane receptor family of Toll-like receptors (TLRs) may play a role in initiating early inflammatory and functional responses to danger signals arising from ischemia-reperfusion and inflammatory stimuli. We determined whether Toll-like receptors are expressed in cardiac tissue and whether stimulation with cognate ligands would result in a pro-inflammatory response and decreased cardiomyocyte contractility.


RESULTS
We observed mRNA expression of TLR2, TLR3, TLR4, TLR5, TLR7 and TLR9 in both whole heart tissue and a murine cardiomyocyte cell line (HL-1). Ligand activation of TLR2, TLR4 and TLR5, but not TLR3, TLR7 or TLR9, resulted in cardiomyocyte expression of the inflammatory cytokine IL-6, the chemokines KC and MIP-2, and the cell surface adhesion molecule ICAM-1. Activation of these Toll-like receptors was associated with decreased cardiomyocyte contractility. Using transfection of a nuclear factor kappa B (NF-kappaB)-Luciferase reporter plasmid, we found significantly increased NF-kappaB transcriptional activity in response to TLR2, TLR4 and TLR5 activation in cardiomyocytes. Further, a chemical inhibitor of NF-kappaB, pyrrolidine dithiocarbamate (PDTC), as well as transfection using a dominant negative form of IKKbeta, resulted in profound reduction of the TLR-initiated pro-inflammatory response.


CONCLUSIONS
Cardiomyocytes express most known Toll-like receptors. Of these, TLR2, TLR4 and TLR5 signal via NF-kappaB, resulting in decreased contractility and a concerted inflammatory response.
Boyd
John H
JH
Critical Care Research Laboratories, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada, V6Z 1Y6.
Mathur
Sumeet
S
Wang
Yingjin
Y
Bateman
Ryon M
RM
Walley
Keith R
KR
D000328:Adult; D000818:Animals; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D004452:Echocardiography; D006801:Humans; D051550:I-kappa B Kinase / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008024:Ligands; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009205:Myocarditis / Q000276:immunology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051196:Toll-Like Receptor 3 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D051198:Toll-Like Receptor 5 / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000378:metabolism; D051193:Toll-Like Receptors / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection / Q000379:methods
D016207:Cytokines; D008024:Ligands; D016328:NF-kappa B; C495344:TLR3 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051198:Toll-Like Receptor 5; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors; D018799:Intercellular Adhesion Molecule-1; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse