The Role And Mechanisms Of NLRP3 Inflammasome Underlying LPS-induced Cognitive Dysfunction

Objective:Gram-negative bacteria are the common pathogenic bacteria in clinics.Lipopolysaccharide（LPS）is the cell wall component of Gram-negative bacteria and the main pathogen.In physiological status,the circμLating level of LPS is very low,but woμLd be boosted in pathological states such as sepsis which may cause cognitive dysfunction.Neuroinflammation is currently known to play a critical role in LPS-induced cognitive dysfunction.However,the pathological mechanisms by which LPS induces acute cognitive dysfunction have not been fμLly elucidated.NLRP3（NOD-like receptor pyrin domain-containing protein）is an important component of innate immune for inducing inflammation and eliminating invading pathogens.LPS can activate the NLRP3 inflammasome in sepsis throμgh the canonical mode and non-canonical mode which triggers an inflammatory cascade.However,it is unclear whether LPS induces cognitive dysfunction by activating the NLRP3 inflammasome.This study will investigate the role,the mechanism and related applications regarding NLRP3inflammasomes in the LPS-induced cognitive dysfunction.Methods:1.To investigate the role of NLRP3 inflammasome in the LPS-induced Sepsis-associated encephalopathy（SAE）.By collecting blood samples and clinical data from septic patients with Gram-negative bacteria infection,the patient divided into SAE and Non-SAE according to the presence or absence of encephalopathy.MμLtiple cytokines were used to detect the changes of inflammatory factors in the blood of all the patients.The correlation between the encephalopathy-increased cytokines and Glasglow score were analyzed;q RT-PCR were used to verify the relationship between NLRP3 inflammasome and cognitive dysfunction in sepsis.2.To explore the mechanism of NLRP3 inflammasome in LPS-induced cognitive dysfunction.The effect of different concentrations of LPS on cerebrospinal fluid and serum cytokines were analyzed in vivo.The changes of cognitive function,newborn neurons,microglia and cytokines in WT mice and Nlrp3^-/-,Asc^-/-,Gsdmd^-/-mice were analyzed after intraperitoneal injecting 10 mg/kg LPS.The effects of NLRP3inflammasome on cytokines,A1 toxic astrocyte marker C3 and cortical neurons in different glial cells were analyzed in vitro.3.To investigate the effect and mechanism of NLRP3inflammasome inhibitor baicalein on LPS-induced cognitive dysfunction.After an intervention of baicalein,the behavior of WT and Nlrp3^-/-mice,the changes of IL-1βand IL-1αin microglia and the level of A1 astrocyte marker C3 were analyzed with a challenge of LPS.ResμLts:1.In the SAE group,the scores of APACHE-II and GCS,the time staying in ICU were significantly higher than those in the non-SAE group.The secretion of IL-12p70,IL-10,IL-8,IL-1βand IL-18was significantly higher in the SAE group than in the non-SAE group.Spearman correlation analysis showed that downstream IL-1βand IL-18of NLRP3 activation were negatively correlated with GCS score.NLRP3inflammasome expression was enhanced in SAE group.2.LPS（10 mg/kg）can promote the secretion of IL-1βin cerebrospinal fluid and serum in mice,and decrease the ability of new object recognition and spatial learning and memory.By activating NLRP3 inflammasome in microglia,LPS can promote the secretion of IL-1βand IL-1ɑ,neo-neuron decline,C3 expression and increase neuronal cell mortality.Deletion of NLRP3,ASC and GSDMD genes ameliorates LPS-induced behavioral abnormalities,neuron damage,and inhibiting microglial activation and C3 expression.3.Baicalein ameliorates LPS-induced cognitive dysfunction by inhibiting NLRP3 inflammasome in microglia and reducing the secretion of IL-1βand IL-1ɑand transformation of A1 astrocyte.Conclusion:LPS induces cognitive dysfunction throμgh activation of NLRP3inflammasome in microglia,which promotes the transformation of A1astrocytes.NLRP3 inflammasome inhibitor baicalein is an effective drμg in the treatment of this disease.