| Objective:Subarachnoid hemorrhage(SAH)is a kind of nervous system critical disease with high mortality and high disability.SAH is a clinical disease caused by ruptured blood vessels and blood flowing into the subarachnoid space.The rupture of autonomic aneurysms is the most common cause.The cerebral vasospasm(CVS)caused by SAH is widely believed to be the cause of death and disability.With further research,more and more evidence points to early brain injury(EBI),suggesting that EBI is the main cause of poor prognosis in SAH patients.EBI refers to a series of pathophysiological changes that occur in the brain within72 h after SAH,including elevated intracranial pressure,blood-brain barrier destruction(BBB),brain edema,microcirculation disorders,and brain cell apoptosis,among which inflammatory cascade reactions play a key role.It was reported that triggering receptor expressed on myeloid cells-1(TREM-1)is a key mediator that is mainly expressed on the surface of neutrophils and can lead to the occurrence and amplification of inflammatory reactions and may be involved in the formation of EBI.Our previous study found that the expression of soluble TREM-1(sTREM-1)was elevated in cerebrospinal fluid(CFS)of SAH patients,and was closely related to the severity and prognosis of the patients.We also found that the level of sTREM-1 in CSF was positively correlated with the levels of tumor necrosis factor(TNF-?)and interleukin-6(IL-6),suggesting that TREM-1 may be related to the formation of early inflammatory cascade after SAH,but specific mechanisms are unclear.Therefore,the purpose of this study was to investigate the TREM-1 specific inhibitor LP17 after intervention in SAH rats,to observe the expression of TREM-1,inflammatory reaction and EBI degree in rat brain tissue.The expression of p38mitogen-activated protein kinase(p38MAPK)? Extracellular signal-regulated kinase1/2(ERK1/2)and matrix metalloproteinase-9(MMP-9)and zonula occludens-1(ZO-1)in the downstream after inhibition of TREM-1 expression.Explore the role of TREM-1 in EBI formation after SAH,and to provide new targets for the formation of clinical prevention and treatment EBI.Methods:SD adult male rats weighing 250-300 g,were selected from the Animal Laboratory Center of Shanxi Medical University.The endovascular perforation model of SAH was produced and 72 rats were randomly divided into 4 groups as sham,SAH+vehicle(saline intervention group),SAH+LP17-1.0mg/kg(low dose intervention group)and SAH+LP17-3.5mg/kg(high dose intervention group).Rats brain tissue was taken 24 h after modeling to analyze the degree of brain edema and BBB destruction,and TREM-1,p38mitogen-activated protein kinase(p38MAPK),matrix metalloproteinase-9(MMP-9)and zonula occludens-1(ZO-1)level changes were analyzed by Western blot.Using the same approach,48 rats were randomly divided into 4 groups as sham,SAH+vehicle(saline intervention group),SAH+LP17-1.0mg/kg(low dose intervention group)and SAH+LP17-3.5mg/kg(high dose intervention group).Rats brain tissue was taken 72 h after modeling for analysis of brain water content and BBB destruction.LP17 is a competitive inhibitor of TREM-1,dissolved in 0.5 ml of saline and administered by intraperitoneal injection 1 h after modeling.Before the animals were put to death,the neurological scores were performed separately;rast mortality was recorded throughout the experiment to assess the severity of the EBI.All rats were given a SAH a score of less than 8,indicating that the model was not successful,excluded and remodeled by new rats.Results:1.A total of 153 rats were used in this experiment.To produce models killed at 24 hours post operation,89 rats were used and 17 rats died(19.1%),and no statisticaldifference of mortality was found among vehicle group(28.0%,7 of 25 rats),low-dose group(25.0%,6 of 24 rats)and high-dose group(18.1%,4 of 22 rats)groups,there was no significant difference in mortality among the three groups(P>0.05).When producing models sacrificed at 72 hours after operation,64 rats were used and 16 rats died(25.0%),among which 7 of 19 rats(36.8%)died in the vehicle group,5 of 17 rats(29.4%)died in low-dose group and 4 of 16 rats(25.0%)died in high-dose group.No significant difference of mortality existed among the 3 groups(P > 0.05).Statistical analysis shows,SAH grade was similar among the 3 groups at both 24 hours and 72 hours post eSAH(P>0.05).2.The study found,the neurological scores of vehicle,low-dose and high-dose groups at both 24 hours and 72 hours post-SAH were significantly lower than that of sham group(P<0.001).However,high-dose of LP17 obviously prevented neurological impairment at 72 hours post eSAH(P<0.05).3.Vehicle-treated group showed more remarkable BBB disruption in all brain regions at both 24 hours and 72 hours after surgery than that in the sham group(P<0.05).However,high-dose treatment significantly reduced the BBB disruption in the perforation-sided hemisphere at 24 hours and even in all brain regions at 72 hours after eSAH(P<0.05).Low-dose of LP17 treatment did not prevent BBB disruption in any brain regions(P>0.05).4.Western blot analysis showed that the TREM-1 levels were statistically higher in all SAH groups than that it was in the sham group at after eSAH(P<0.05).But high-dose and low-dose of LP17 treatment significantly reduced the TREM-1 levels.In vehicle group,p38MAPK/MMP-9 ? ERK1/2 levels were statistically higher and ZO-1 was more significantly degraded(P<0.05);but only high-dose of LP17 treatment statistically attenuated the p38MAPK/MMP-9 ? ERK1/2 induction and reduced ZO-1degradation(P<0.05).Conclusion:TREM-1 may participate in the pathogenesis of SAH-induced EBI via promotingp38MAPK/MMP-9?ERK1/2 activation and ZO-1 degradation,while TREM-1 inhibition attenuated the EBI severity obviously,providing a novel approach for the treatment of EBI. |
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