Correlation Between LOX-1/NF-κB Expression In Respirable Fine Particulate Matter Induced Brain Tissue And Ischemic Stroke

Objective:In recent years,numerous epidemiological studies have found a strong association between PM2.5 and ischaemic stroke(IS).In this study,the effects of PM2.5 exposure on cerebral infarct volume,neurological function scores,intracerebral LOX-1 and NF-κB p65 expression and internal carotid artery vasculature in ischemia-reperfused(I/R)rats were observed to provide a theoretical basis for exploring the mechanisms by which PM2.5aggravates cerebral ischemic injury.Methods:Ninety male Sprague-Dawley(SD)rats,weighing 200g-250 g,were randomly divided into five groups after 1 week in the SPF class laboratory,with group 1 being the sham-operated group,in which the rats were given sterile saline in the nasal cavity,and group 2 being the I/R group,in which the rats were given middle cerebral artery embolization(MCAO)after 4 weeks in the nasal cavity.The remaining 3 groups were I/R + PM2.5 low concentration group,I/R +PM2.5 medium concentration group and I/R + PM2.5 high concentration group.The rats were treated with MCAO after 4 weeks of nasal drip of PM2.5 staining solution at the concentration of 1.25mg/ml,6.25mg/ml and 31.25mg/ml respectively.A volume of 20 ul of drug was administered in the nasal cavity of the rats at a frequency of once every other day.The rats in each group were scored for neurological deficits at 24 and 48 hours postoperatively according to the zea-Longa scale.The rats were stained with 2,3,5-triphenyltetrazolium chloride(TTC)to detect the volume of cerebral infarction,and the expression of LOX-1 and NF-κB p65 in the ischemic half dark zone was detected by Western blotting.Expression of LOX-1 and NF-κB in rat brain tissue in the ischemic semidark zone detected by immunofluorescence.Chemical kit to detect Reactiveoxygenspecies and Superoxide Dismutase in the ischemic hemispheric zone of brain tissue.Enzyme-Linked Immuno Sorbent Assay(ELISA)for the detection of the inflammatory factors Interleukin(IL)-1α,IL-1β,IL-18 and Tumour Necrosis Factor-α(TNF-α)in rat serum.Hematoxylin-eosin(HE)staining for endothelial injury and atherosclerosis in rat internal carotid arteries.Results:1.Rat neurological deficit score:The rats in the sham-operated group underwent the same surgical procedure but without middle cerebral artery embolization and had a neurological deficit score of 0.Rats in the I/R and PM2.5-stained groups showed signs of neurological deficits compared to the sham-operated group(P<0.001).The symptoms of neurological deficits were relatively worse in rats after medium and high PM2.5 exposure compared to the I/R group(P<0.05).No significant differences were seen in the neurological deficits in the low PM2.5 exposed rats compared to the I/R group.2.Cerebral infarct volume in rats:No infarct foci were seen after TTC staining in the sham-operated group of rats.Significant infarct foci were observed in the brain tissue of the I/R and PM2.5-stained rats compared to the sham-operated group(P<0.001).Relative increase in brain infarct volume in rats after medium and high PM2.5 exposure compared to the I/R group(P<0.05).No significant difference was seen in brain infarct volume after low PM2.5 exposure compared to the I/R group.3.Serum inflammatory factor expression in rats : Compared with the sham-operated group,the I/R group and the PM2.5-stained group significantly increased the expression of IL-1a,IL-1β,IL-18 and TNF-a inflammatory factors in rat serum(P<0.05).Compared with the I/R group,the expression levels of IL-1a,IL-1β,IL-18 and TNF-a inflammatory factors in rat serum were further increased after medium and high concentrations of PM2.5 exposure(P<0.05),and TNF-a expression levels in serum were selectively increased after low concentrations of PM2.5exposure(P<0.05).4.Expression of ROS and SOD in rat brain tissue:Compared with the sham-operated group,brain tissue ROS expression was significantly higher and SOD activity was significantly lower in the I/R and PM2.5-stained rats(P<0.05).Compared with the I/R group,the expression of ROS in the brain tissue of rats was relatively increased and the activity of SOD was relatively decreased in all groups after PM2.5 exposure(P<0.05).5.Expression of LOX-1 and NF-κB p65 in rat brain tissue:Compared with the shamoperated group,the expression of LOX-1 and NF-κB p65 protein in brain tissues of I/R and PM2.5-stained rats was increased(P<0.001),and further up-regulated after PM2.5 exposure compared with the I/R group(P<0.001).6.HE staining of rat internal carotid artery:No significant atherosclerosis was found in the internal carotid arteries of the rats in each group.However,compared to the Contr and I/R groups,the internal carotid arteries of the rats exposed to PM2.5 showed varying degrees of endothelial damage and elastic fibre disruption.Conclusion:1.PM2.5 exposure exacerbated cerebral ischemia-reperfusion injury,increased neurological deficit scores,and increased the size of cerebral infarct foci.2.PM2.5 exposure increased inflammatory factor expression in serum,increased oxidative stress damage in the brain,and upregulated LOX-1 and NF-κB p65 protein expression in brain tissue,and the higher the concentration of PM2.5 exposure,the higher the expression level of each factor.3.The damaging effects of PM2.5 exposure on brain tissue and neurological function may be related to the pro-inflammatory and pro-oxidative effects of inflammatory mediators through upregulation of LOX-1 and NF-κB p65.4.The internal carotid arteries of the rats did not develop significant atherosclerosis after4 weeks of exposure to different concentrations of PM2.5,but showed varying degrees of pathological damage.