Polymyxin B antagonizing biological activity of lipopolysaccharide.
OBJECTIVE
To investigate the mechanism of polymyxin B (PMB) antagonizing the biological activity of lipopolysaccharide (LPS).


METHODS
The affinity of PMB for LPS and lipid A was assayed by biosensor, and the neutralization of PMB for LPS (2 ng/ml) was detected by kinetic turbidimetric limulus test. The releases of TNF-alpha and IL-6 in murine peritoneal macrophages a (PMphi) after exposure to LPS (100 ng/ml) were detected, and the expression levels of TLR4, TNF-alpha and IL-6 mRNA in PMphi induced by LPS (100 ng/ml) were measured by RT-PCR.


RESULTS
PMB had high-affinity to LPS and lipid A with dissociation equilibrium constants of 18.9 nmol/L and 11.1 nmol/L, respectively, and neutralized LPS in a dose-dependent manner. Furthermore, PMB could markedly inhibit the expressions of TLR4, TNF-alpha and IL-6 mRNA and the release of cycokines in LPS-stimulated murine peritoneal macrophages.


CONCLUSIONS
PMB neutralizes LPS and inhibites the expression and release of cycokines in macrophages, in which the affinity of PMB for lipid A plays an important role.
Guo
Yi-bin
YB
Medical Research Center, Southwest Hospital, Third Military Medical University, Chongqing 400038, China.
Chen
Li-ping
LP
Cao
Hong-wei
HW
Wang
Ning
N
Zheng
Jiang
J
Xiao
Guang-xia
GX
D000818:Animals; D016207:Cytokines / Q000032:analysis; D008033:Limulus Test; D008050:Lipid A / Q000037:antagonists & inhibitors; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors*; D008264:Macrophages / Q000737:chemistry; D051379:Mice; D011112:Polymyxin B / Q000494:pharmacology*
D016207:Cytokines; D008050:Lipid A; D008070:Lipopolysaccharides; D011112:Polymyxin B