[Study on the natural ligand(s) of triggering receptor expressed on myeloid cell-1 on bacteria cell wall].
OBJECTIVE
To look for the natural ligand(s) of human triggering receptor expressed on myeloid cell-1 (TREM-1), in order to provide the theoretical basis for elucidation of the pathogenesis of sepsis.


METHODS
Neutrophils and monocytes isolated from human peripheral blood were treated with heat-inactivated Staphylococcus aureus, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Staphylococcus aureus L-form or Pseudomonas aeruginosa L-form respectively for 24 hours. The cell wall was extracted from Staphylococcus aureus, Pseudomonas aeruginosa and Mycobacterium tuberculosis by ultrasound. Neutrophils and monocytes were isolated and treated with the cell wall respectively for 24 hours. Neutrophils and monocytes were isolated and treated with three main components from bacterial cell wall (polysaccharides, lipids and proteins) respectively for 24 hours. The level of TREM-1 mRNA was measured with fluorescent quantitative polymerase chain reaction (PCR), and the concentrations of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) were measured with enzyme-linked immunosorbent assay (ELISA).


RESULTS
The TREM-1 mRNA level and the concentrations of TNF-alpha and IL-1 beta in cell supernatant of neutrophils and monocytes were upgraded when treated with cell, cell wall and cell wall polysaccharides of Staphylococcus aureus and Pseudomonas aeruginosa. Compared with the blank control group, the TREM-1 mRNA level of neutrophils and monocytes was upgraded to (3.86+/-0.20)-fold and (5.15+/-0.56)-fold respectively when treated with cell wall polysaccharides of Staphylococcus aureus (both P<0.05); the TREM-1 mRNA level of neutrophils and monocytes was upgraded to (4.03+/-0.15)-fold and (7.22+/-0.73)-fold respectively when treated with cell wall polysaccharides of Pseudomonas aeruginosa (both P<0.05). The effect could be attenuated by the addition of LP17 which could bind TREM-1 ligand. This attenuating effect was not found when the cells were treated with cell, cell wall or cell wall polysaccharides of Mycobacterium tuberculosis.


CONCLUSIONS
The study provides the evidence that TREM-1 natural ligand(s) is present on cell wall of bacteria including Staphylococcus aureus and Pseudomonas aeruginosa, and it might be polysaccharides.
Yu
Zhi-hui
ZH
The First Affiliated Hospital of Guangzhou Medical College, Guangzhou Institute of Respiratory Disease, Guangzhou 510120, Guangdong, China.
Huang
Hong-chuan
HC
Mao
Pu
P
Liu
Dong-dong
DD
Mo
Hong-ying
HY
He
Wei-qun
WQ
Liu
Xiao-qing
XQ
Li
Yi-min
YM
D001419:Bacteria / Q000737:chemistry*; D002473:Cell Wall / Q000737:chemistry*; D002478:Cells, Cultured; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism; D008024:Ligands; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D000073871:Triggering Receptor Expressed on Myeloid Cells-1; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D053583:Interleukin-1beta; D008024:Ligands; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; C408842:TREM1 protein, human; D000073871:Triggering Receptor Expressed on Myeloid Cells-1; D014409:Tumor Necrosis Factor-alpha