Expression of Toll-like receptor 4 induced by extravasated IgG and peripheral LPS in rat brains / 解剖学报

ABSTRACT

ObjectiveTo investigate the effect of immunoglobulin G (IgG) extravasated from blood circulation on the expression of toll-like receptor 4 (TLR4) induced by peripheral lipopolysaccharide (LPS) in rat brain. Methods The rats were divided into four groups in random, 5 rats in each. Group one received LPS 100μg/kg by intraperitoneal administration, normal saline was given by intravenous injection 6 hours later; group two was injected with adrenalin (AD) 15μg/kg intravenously; group three was treated with LPS intraperitoneally, AD was injected 6 hours later; group four was injected normal saline intravenously as control. For all groups, the animals were sacrificed 30 min after the last injection, and the brains were taken for investigation of the TLR4 expressions by immunofluorescence staining and RT-PCR. Result Immunofluorescence staining showed that IgG immunoreactive product was patch-like, distributed in the brain parenchyma in all the animals that received AD. In the LPS+normal saline group, IgG was found merely around the blood vessels. Meanwhile, in LPS+AD animals, TLR4 immunoreactive product coexisted with microglia marker Iba-1 within the IgG extravasated area. The double-labeled cells dispersed in the brain parenchyma and near to the cerebral vessels. In the LPS+saline group, TLR4 positive cells were endothelial-like. RT-PCR results indicated that the expression level of TLR4 in the LPS+AD group were significantly higher than that in the LPS+saline group or AD group or the saline control (P<0.01). Conclusion Extravasated circulating IgG may enhance the TLR4 expression in the rat brain induced by peripheral LPS.