Controlled Decompression Alleviates Motor Dysfunction By Regulating Microglial Polarization Via HIF-1α Signaling Pathway In Intracranial Hypertension

ObjectiveAcute intracranial hypertension is one of the most common causes of death and disability after severe craniocerebral trauma and stroke,and emergency debulking decompression is commonly performed in these patients.Previous studies by our group have shown that controlled decompression(CDC)is more effective than conventional rapid decompression(RDC)in reducing the incidence of surgical complications and improving the prognosis of traumatic brain injury,but the underlying mechanisms are unclear.In this study,we explored whether CDC regulates microglia polarization through the HIF-1α signaling pathway after intracranial hypertension to reduce intracranial hypertension-induced neuroinflammation and motor dysfunction by establishing an acute intracranial hypertension(AIH)model.MethodsFirst,SD rats were randomly divided into five groups,including sham-operated group(Sham group),controlled decompression group(CDC group),rapid decompression group(RDC group),rapid decompression + 2-ME2 group(RDC + 2-ME2 group)and controlled decompression + DMOG group(CDC + DMOG group).Acute intracranial hypertension(AIH)model was established by placing an embolic balloon and injecting water into the left epidural of SD rats.The behavioral methods of cylinder test,rotarod test,irregular ladder walking and modified neurological severity score were used to compare the CDC and RDC treated AIH models.The neuromotor function of CDC was evaluated by comparing the changes in neuromotor function of the corresponding groups of rats after 24 h of different treatments of AIH model with RDC.Then,the neuromotor protective effects of CDC were evaluated using Nissl staining,Terminal deoxynucleotidyl transferase d UTP nick-end labeling(TUNEL),Immunofluorescence(IF)and EnzymeLinked Immunosorbent Assay(ELA).The neuronal apoptosis,microglia polarization and inflammation level in the stressed cortical region were observed by CDC treatment in AIH rat model after 24 h.The expression of hypoxia inducible factor-1α(HIF-1α)in the AIH rat model and the expression of HIF-1α in the stressed cortical region after CDC treatment were also detected by western blot(WB).Finally,the effects of 2-ME2 and DMOG on microglial polarization phenotype,inflammation and inflammation were evaluated by IF,ELISA,TUNEL and behavioral methods in the experimental animals of the respective groups.The effects of 2-ME2 and DMOG on microglia polarization phenotype,inflammatory factor levels and motor dysfunction were evaluated by IF,ELISA,TUNEL and behavioral methods respectively.Results1.The results of behavioral methods showed that the CDC group significantly promoted the recovery of motor function in the AIH rat model compared with the RDC group.2.The results of Nissl staining and Neu N/TUNEL co-staining showed that the number of Nissl-positive cells in the damaged cortex was significantly reduced and the number of Neu N/TUNEL double-positive cells was significantly increased in the CDC group compared with the RDC group.These data suggest that the CDC intervention attenuated neuronal apoptosis after AIH compared with the RDC group.3.ELISA results showed that AIH increased the levels of TNF-α,IL-1β and IL-6 proinflammatory factors.Compared with the RDC group,the CDC group attenuated the AIH-induced increase in the levels of these pro-inflammatory factors,while increasing the levels of the anti-inflammatory factors IL-10,IL-4 and TGF-β.4.Changes in M1 phenotype(CD32,i NOS and TNF-α)and M2 phenotype(Arg-1,CD206 and IL-10)microglia markers after AIH were detected using IF,WB and q PCR.the results of IF,WB and q PCR showed that AIH induced increased expression of M1 phenotype microglia in a rat model of cranial hypertension;compared with RDC,CDC could promote its polarization to M2 phenotype microglia and decreased the expression level of M1 microglia.5.The expression of HIF-1α in the pressurized cortical region of the AIH model was measured by WB during the 7-day postoperative observation period,and the highest expression of HIF-1α in the pressurized cortical brain tissue of the RDC group was observed at 24 hours.The expression level of HIF-1α was reduced after the CDC intervention compared to the RDC group.Similarly,the protein expression level of HIF-1α was significantly reduced in the RDC+2-ME2 group after treatment of the RDC group with 2-ME2.6.IF and ELISA results suggested that HIF-1α inhibitor(2-ME2)intervention reduced M1-type glial cell polarization and attenuated the level of inflammation after AIH,while the neuroprotective effect of CDC on AIH was blocked by administration of HIF-1α agonist(DMOG).7.Results of IF,Neu N/TUNEL co-staining and behavioral test showed that administration of DMOG blocked the neuroprotective effect of CDC on AIH and did not improve neuronal apoptosis and motor dysfunction after AIH.ConclusionIn summary,CDC effectively alleviated AIH pathology-induced neuroinflammation,neuronal apoptosis and motor dysfunction by regulating HIF-1α-mediated polarization of microglia toward the M2 type.The results will contribute to further understanding of the neuroprotective mechanisms of CDC in cranial hypertension and facilitate clinical translation studies of HIF-1α in cranial hypertension.