Impacts of Mild Hypothermia on LPS-Mediated TLR4/NF-κB Signaling Pathway in Microglia

摘要

Background : Existing studies have found that some inflammatory factors cause brain cell damage through the TLR4/NF-κB pathway, and that mild hypothermia has a protective effect on nerve cells. It is not clear whether the mild hypothermic brain protection is achieved through the TLR4/NF-κB pathway in microglia. Objective : To investigate the impacts of mild hypothermia on lipopolysaccharide (LPS)-mediated TLR4/NF-κB signaling pathway in microglia. Method : The cultured microglia cells in vitro were divided into the NS group and the LPS group at 33?C and 37?C, respectively; quantitative RT-PCR was performed to detect the expressions of TLR4 and NF-κB mRNA in the microglia, Western blot was used to detect the expressions of TLR4 and NF-κB protein in the microglia, and ELISA was performed to detect the levels of tumor necrosis factor α (TNF-α ) and interleukin-10 (IL-10) in the culture medium. Results : Under the LPS stimulation, the mRNA and protein expressions of TLR4 and NF-κB at different time points had significant changes between the normothermia group and the mild hypothermia group, in which the expressions in the former group were firstly increased and then decreased, while those in the latter showed a continuous increasing trend (P < 0.01); and the expressions of TNF-α in all the groups presented the trend of first-increasing then-decreasing, while IL-10 exhibited one slow linear increasing trend (P < 0.01). Conclusions : Mild hypothermia could inhibit the mRNA and protein expressions of LPS-mediated TLR4/NF-κB signaling pathway in the microglia, and inhibit the production and release of downstream inflammatory cytokines (TNF-α and IL-10).