The Mechanism Of Asiatic Acid Inhibiting The Damage Of Hippocampal And Cerebral Microglial Cells By Salmonella In Mice

Salmonella invades the central nervous system and causes irreversible inflammatory damage.Microglia in the brain activate rapidly when the central nervous system is invaded by foreign microorganisms and release various cytokines in response to inflammation.As an effective component of Centella asiatica,Asiatic acid(AA)plays an important role in anti-inflammatory,antioxidant and anticancer processes.In this study,the inhibitory effect of AA on Salmonella induced inflammation and mechanism in hippocampus and microglia of mice were explored,so as to provide theoretical basis and technical support for clinical application of AA.In this experiment,the central nervous system inflammation model of mice was constructed by giving the mice Salmonella orally to simulate the natural infection route.To investigate the effects of AA on damage and inflammation induced by Salmonella infection by intervening before infection.The body weight of mice was recorded,the behavior of mice was detected by open field test,the microscopic morphology of mice brain was observed by hematoxylin-eosin staining,and the subcellular structure of hippocampus was observed by transmission electron microscopy.It was found that AA significantly inhibited the weight loss,behavioral abnormalities,hippocampal neuron necrosis and mitochondrial swelling of mice induced by Salmonella.ELISA and qPCR analysis showed that AA significantly inhibited the expression of proinflammatory factors IL-6,IL-1β,TNF-α,IFN-γ and IL-12b in hippocampus of mice induced by Salmonella.Western blot and qPCR analysis found that AA significantly inhibited the expression of TLR2 receptor and the mRNA and protein expressions of NICD of Nocthl and Nocth2 nuclear translocation regionand the target gene Hesl induced by Salmonella.In addition,AA also exerts the inflammatory response by inhibiting the activation of NF-κB-ERK pathway in hippocampus of mice stimulated by Salmonella.Microglia-specific marker Iba1 was used to stain the hippocampus sections of mice.The microglia of Salmonella infection were activated,which showed that the cell body was enlarged and the branches were increased and thickened.AA significantly inhibited the activation of microglia induced by Salmonella.In vitro study,microglia cell line BV-2 was used to investigate the regulatory effect of AA on Salmonella induced inflammation and molecular mechanism.AA significantly inhibited the expression of proinflammatory factors IL-1β,IL-6 and IL-12b in microglia induced by Salmonella,which was detected by ELISA and qPCR.Western blot analysis detection of microglia showed that AA significantly inhibited the activation of TLR2,Notch,NF-κB and ERK pathways induced by Salmonella in microglia.Immunofluorescence and immunocoprecipitate analysis showed that the protein interaction between the p65 subunit of NF-κB pathway and the nuclear translocation region of Nocth protein NIDC in the nucleus induced by Salmonella was inhibited by AA.It was found that NF-κB and ERK,as downstream pathways,play a role in the regulation of pro-inflammatory factor transcription by AA after useing TLR2 and Notch inhibitors.In conclusion,Salmonella infection can induce weight loss,behavior abnormalities,hippocamphal neuron damage and inflammatory response,and microglia activation in mice.AA can alleviate Salmonella-induced hippocamphal damage and inflammatory response by inhibiting microglia activation,which is closely related to TLR2-Notch/NF-κB-ERK signaling pathway.