Low-dose ketamine attenuates microcirculatory deficits after traumatic brain injury in mice via microglial NF-κB/iNOS pathway / 中华神经医学杂志

ABSTRACT

Objective:To investigate the effect of low-dose ketamine on neuroinflammation and microcirculation in mice with traumatic brain injury (TBI).Methods:Sixty adult male C57BL/6 mice, weighing 22-28 g, were randomly divided into sham-operated group, TBI group, Sham+ketamine group, and TBI+ketamine group ( n=15). A controlled cortical impingement (CCI) method was used to establish TBI models in the later 2 groups. Sham+ketamine group and TBI+ketamine group were intraperitoneally injected with 30 mg/kg ketamine once daily for 3 d at 30 min after TBI; sham-operated group and TBI group were intraperitoneally injected same amount of saline at the same time points. Cerebral cortical blood flow in 6 mice from each group was measured by laser speckle contrast imaging (LSCI) before, immediately after, 30 min after, 1 d after and 3 d after modeling, respectively. Three d after modeling, immunohistochemical staining and immunofluorescent double label staining were used to detect the nuclear translocation of microglia markers, ionized calcin-antibody-1 (Iba-1) and nuclear factor (NF)-κB p65 in damaged cortical brain tissues in 6 mice from each group. The remaining 3 mice in each group were sacrificed and tissue plasma was extracted 3 d after modeling; levels of NF-κB p65, phosphorylated (p)-NF-κB p65, p-IκB and inducible nitric oxide synthase (iNOS) in cortical brain tissues were detected by Western blotting. Expressions of tumor necrosis factor-α (TNF-α), interleukin-1-β (IL-1β) and interleukin-6 (IL-6), iNOS, reactive oxygen species (ROS) and reactive nitrogen species (RNS) in cortical brain tissues were detected by ELISA. Results:LSCI indicated that, 3 d after modeling, relative blood flow in local cerebral microcirculation of TBI+ketamine group was significantly increased compared with that of TBI group ( P<0.05). Immunohistochemical staining indicated that compared with the sham-operated group and Sham+ketamine group, the TBI group and TBI+ketamine group had significantly increased number of Iba-1 positive cells in the cerebral cortex ( P<0.05); compared with the TBI group, the TBI+ketamine group had significantly decreased number of Iba-1 positive cells ( P<0.05). ELISA indicated that compared with the sham-operated group and Sham+ketamine group, the TBI group and TBI+ketamine group had significantly increased expressions of TNF-α, IL-1β, IL-6, iNOS, ROS and RNS in damaged cortical brain tissues ( P<0.05); compared with the TBI group, the TBI+ ketamine group had significantly decreased expressions of TNF-α, IL-1β, IL-6, iNOS, ROS and RNS in damaged cortical brain tissues ( P<0.05). Immunofluorescent double label staining indicated obviously inhibited NF-κB p65 nuclear translocation in TBI+ketamine group when it was compared with TBI group. Western blotting indicated that compared with the sham-operated group and Sham+ketamine group, the TBI+ketamine group had significantly increased iNOS, NF-κB p65, p-NF-κB p65 and P-IκB protein expressions in damaged cortical brain tissues ( P<0.05); compared with the TBI group, the TBI+ketamine group had significantly decreased protein expressions of iNOS, NF-κB p65, p-NF-κB p65 and p-IκB in damaged cortical brain tissues ( P<0.05). Conclusion:Low-dose ketamine reduces neuroinflammation and improves cerebral microcirculatory blood flow after open TBI, whose mechanism may be related to inhibition of microglia NF-κB/iNOS pathway.