The Role Of NLRP3/ASC/Caspase-1 Pyroptosis Pathway In PM_2.5-Induced Cognitive Impairment In Mice

Objective To investigate the role of NLRP3/ASC/Caspase-1 signaling pathway in the neuroinflammatory response and neuronal scorching in mice exposed to atmospheric PM_2.5.To provide scientific basis for deeper understanding of the molecular mechanism of cognitive impairment caused by PM_2.5 exposure.Methods Sixty healthy adult 8-week-old C57BL/6 mice were randomly divided into control,PM_2.5,CY-09 and PM_2.5+CY-09 groups after one week of adaptive feeding.PM_2.5was infected with the online concentration of fine particles and animal poisoning system.The CY-09 group and the PM_2.5+CY-09 group were intraperitoneally injected with the inflammatory body inhibitor CY-09 before poisoning,and the control group and PM_2.5groups were injected with saline.Mice in the PM_2.5 group and PM_2.5+CY-09 group were placed in a poisoning cabinet and exposed to PM_2.5.The concentration of PM_2.5 was set 6times to the concentration of PM_2.5 in the outdoor atmospheric environment for 8 hours a day and 5 days a week.The changes in body weight of mice were recorded in the clean room and the outdoor atmosphere during the period of toxicity,and the water maze and open field experiments were performed after the end of toxicity.The m RNA expression levels of NLRP3,ASC,Caspase-1,GSDMD,IL-1βand IL-18 in hippocampal tissues were measured by RT-q PCR and the protein expression levels of NLRP3,ASC,Caspase-1,GSDMD,IL-1βand IL-18 in hippocampal tissues were measured by Western blot.Results 1.The average PM_2.5 concentrations in the outdoor air,clean room and cabinets during the contamination period were（48.80±29.03）μg/m³,（23.58±20.60）μg/m³ and（287.26±175.95）μg/m³ respectively.2.Compared to the control group,mice in the PM_2.5group had reduced body weight at weeks 3 and 4,and mice in the PM_2.5+CY-09 group had reduced body weight at week 3（P<0.05）;compared to the CY-09 group,mice in the PM_2.5group had reduced body weight at weeks 2,3 and 4,and mice in the PM_2.5+CY-09 group had reduced body weight at weeks 2 and 3（P<0.05）;compared to the PM_2.5 group the body weight of mice in the PM_2.5+CY-09 group decreased at week 4（P<0.05）.3.Compared with the control group,mice in the PM_2.5 group had a longer escape latency（P<0.05）;compared with mice in the CY-09 group,mice in the PM_2.5 group had a longer escape latency on day1,2 and 3 of training,and mice in the PM_2.5+CY-09 group had a longer escape latency on day 1 of training（P<0.05）;compared with the PM_2.5 group,mice in the PM_2.5+CY-09 group had a shorter escape latency on day 1,2 and 3 of training（P<0.05）.Compared with the control group,the target quadrant time was prolonged in the CY-09 group and shortened in the PM_2.5 group（P<0.05）;compared with the CY-09 group,mice in the PM_2.5 group crossed the platform less frequently and the target quadrant time was significantly shorter in the PM_2.5 and PM_2.5+CY-09 groups（P<0.05）;compared with the PM_2.5 group,the target quadrant time was prolonged in the PM_2.5+CY-09 group（P<0.05）.4.In the open field experiment,compared with the control group,the CY-09 group showed an increase in the total distance of locomotion,a decrease in the central zone dwell time in the PM_2.5 and PM_2.5+CY-09 groups,and a decrease in the number of central zone entries in the PM_2.5 group;compared with the CY-09 group,the PM_2.5 and PM_2.5+CY-09 groups showed a decrease in the total distance of locomotion,a decrease in the central zone dwell time,and a decrease in the number of central zone entries in the PM_2.5 and PM_2.5+CY-09 groups.Compared with the PM_2.5 group,the PM_2.5+CY-09 group showed a decrease in total distance travelled,a decrease in central zone dwell time and a decrease in the number of central zone entries（P<0.05）.5.In the PM_2.5 group,hippocampal neurons were morphologically altered,with nuclear consolidation,pore formation in the cell membrane and more release of cell contents;in the control,CY-09 and PM_2.5+CY-09 groups,nuclei were normal,cell membrane integrity increased and less release of cell contents.6.Compared with the control group and CY-09group,serum IL-1βand IL-18 levels were increased in the PM_2.5 group,compared with the PM_2.5 group,serum IL-1βand IL-18 levels were decreased in the PM_2.5+CY-09 group（P<0.05）.7.Compared with the control group,the m RNA expression levels of GSDMD in the hippocampal tissues of mice in the CY-09 group were elevated;the m RNA expression levels of NLRP3,ASC,Caspase-1,GSDMD,IL-1βand IL-18 in the hippocampal tissues of mice in the PM_2.5 group were elevated;the m RNA expression levels of ASC,GSDMD,IL-1βand IL-18 in the hippocampal tissues of mice in the PM_2.5+CY-09 group were elevated（P<0.05）.The m RNA expression levels of ASC,Caspase-1,IL-1βand IL-18 were increased in the hippocampal tissue of mice in the PM_2.5 group compared with the CY-09 group（P<0.05）;the m RNA expression levels of ASC and IL-18 were increased in the hippocampal tissue of mice in the PM_2.5+CY-09 group compared with the CY-09 group（P<0.05）.The m RNA expression levels of NLRP3 and Caspase-1 in hippocampal tissues of mice in the PM_2.5+CY-09 group were decreased compared with those in the PM_2.5 group（P<0.05）.8.Compared with the control group,the protein expression levels of NLRP3 and IL-18 in the hippocampus of mice in the CY-09 group were elevated;the protein expression levels of NLRP3,ASC,Caspase-1,GSDMD,IL-1βand IL-18 in the hippocampal tissues of mice in the PM_2.5 group were elevated;the protein expression levels of NLRP3,IL-1βand IL-18 in the hippocampal tissues of mice in the PM_2.5+CY-09 group were elevated（P<0.05）.Compared with the CY-09 group,the protein expression levels of NLRP3,ASC,Caspase-1,GSDMD,IL-1βand IL-18 in the hippocampus of the PM_2.5 groups of mice increased,and the protein expression of NLRP3 and IL-1βin the hippocampus of the PM_2.5+CY-09 group increased.Compared with the PM_2.5 group,the protein expression levels of ASC,Caspase-1,GSDMD and IL-18 in the hippocampus of the PM_2.5+CY-09 group decreased（P<0.05）.Conclusion 1.PM_2.5 exposure triggered neuroinflammatory responses and ultrastructural changes in mouse hippocampal tissue.2.PM_2.5 exposure increased the expression of NLRP3/ASC/Caspase-1 signaling pathway and its receptors in mouse brain hippocampus.3.CY-09 inhibited the expression of inflammatory vesicles and ameliorated the effects of PM_2.5 contamination on learning memory capacity and inflammatory responses in mice.Figure 6;Table 13;Reference 142...