Expression of Toll-like receptors on human platelets.
BACKGROUND
Platelets play a crucial role in arterial thrombosis, which is the main cause of acute coronary syndrome. Some mycobacteriums, such as Chlamydia pneumoniae, were associated with progression of atherosclerosis and they are interacted with Toll-like receptors (TLRs), which have been defined as pathogen-associated molecular pattern recognition molecules in innate immunity. In the present study, we examined whether human platelets express TLRs.


METHODS
Human platelets were obtained from healthy volunteers and the mRNA and protein level of TLRs on platelets and Meg-01 cells, megakaryoblastic cell line, were investigated.


RESULTS
Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated that TLR1 and TLR6 mRNA were expressed in platelets and Meg-01 cells. Furthermore, interferon-gamma up-regulated their mRNA levels in dose and time dependent manners after stimuli. Both TLR1 and TLR6 proteins in platelets were detected by Western blotting, and their expression of platelets was more than that of Meg-01 cells. Flow cytometry analysis revealed the expression of TLR1 and TLR6 on the cell surface of Meg-01 cells. Furthermore, immunohistochemical analysis using human coronary thrombi obtained from patients with acute coronary syndrome confirmed the expression of TLR1 and TLR6 on platelets.


CONCLUSIONS
In summary, we demonstrated that human platelets and Meg-01 cells expressed a family of TLRs for the first time, and our findings indicated that platelets might recognize antigens directly via TLRs. Our findings suggest a possibility that platelets have the ability to recognize the antigens via TLRs and that there are mechanistic relations between infectious inflammation and atherosclerotic vascular diseases.
Shiraki
Rio
R
Division of Cardiovascular and Respiratory Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo, Kobe 650-0017, Japan.
Inoue
Nobutaka
N
Kawasaki
Satoru
S
Takei
Asumi
A
Kadotani
Makoto
M
Ohnishi
Yoshio
Y
Ejiri
Junya
J
Kobayashi
Seiichi
S
Hirata
Ken-Ichi
K
Kawashima
Seinosuke
S
Yokoyama
Mitsuhiro
M
D015415:Biomarkers / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003328:Coronary Thrombosis / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007947:Leukemia, Megakaryoblastic, Acute / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D051194:Toll-Like Receptor 1; D051216:Toll-Like Receptor 6; D051193:Toll-Like Receptors
D015415:Biomarkers; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495368:TLR6 protein, human; D051194:Toll-Like Receptor 1; D051216:Toll-Like Receptor 6; D051193:Toll-Like Receptors