Toll-like receptor 9 expression and activation in acute coronary syndrome patients on dual anti-platelet therapy.
BACKGROUND
The Toll-like receptor 9 (TLR9) pathway can activate platelets but its role in acute coronary syndromes (ACS) is unknown. This study examined TLR9 expression and platelet activation in response to ODN2006, a TLR9 agonist, in healthy subjects and in ACS subjects treated with dual anti-platelet therapy (DAPT).


METHODS
TLR9 expression was examined in both resting and thrombin receptor activator peptide (TRAP)-activated platelets (1 and 10μM) from healthy and ACS subjects by flow cytometry. In both cohorts, ODN2006-mediated platelet activation (5μM) was examined in whole blood (WB) and platelet-rich plasma (PRP) using cell-surface CD62p and CD63 expression by flow cytometry.


RESULTS
Baseline TLR9 expression was significantly greater in ACS subjects compared to healthy subjects (p<0.01). Following TRAP activation, TLR9 expression increased dose-dependently in healthy subjects. However, no difference in TLR9 expression was seen in ACS platelets following TRAP activation. ODN2006 treatment resulted in significant increases in cell-surface expression of CD62p and CD63 in both WB (all p<0.001) and PRP (all p<0.001) in comparison to unstimulated platelets in healthy subjects. Despite DAPT, ODN2006 treatment produced significant increases in both activation markers in the ACS cohort across WB and PRP (all p<0.0001). Elevated baseline expression of TLR9 in ACS platelets may indicate increased sensitivity to TLR9 agonists and contribute to increased platelet activation in these patients. Furthermore, ODN2006 stimulation can activate platelets in ACS subjects despite treatment with DAPT.


CONCLUSIONS
This study demonstrates TLR9 expression and activation to be of potential therapeutic importance in ASC patients.
School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand; Wellington Cardiovascular Research Group, Wellington, New Zealand. Electronic address: hallykath@myvuw.ac.nz.
Kathryn E
KE
Hally
School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand; Wellington Cardiovascular Research Group, Wellington, New Zealand.
Anne C
AC
La Flamme
School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand; Wellington Cardiovascular Research Group, Wellington, New Zealand; Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.
Peter D
PD
Larsen
School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand; Wellington Cardiovascular Research Group, Wellington, New Zealand; Department of Cardiology, Wellington Hospital, Wellington, New Zealand.
Scott A
SA
Harding
D054058:Acute Coronary Syndrome / Q000188:drug therapy* / Q000473:pathology; D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000187:drug effects* / Q000473:pathology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D015539:Platelet Activation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D053657:Platelet-Rich Plasma / Q000187:drug effects; D051217:Toll-Like Receptor 9 / Q000819:agonists / Q000032:analysis*
C000615642:ODN2006; D009838:Oligodeoxyribonucleotides; D010975:Platelet Aggregation Inhibitors; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9
Acute coronary syndromes; Anti-platelet therapy; Innate immunity; Platelets; Toll-like receptor 9