| Background and aimsPost-CA syndrome after successful cardiopulmonary resuscitation(CPR)is a unique and complicated pathophysiological process that involves brain injury,myocardial dysfunction,and systemic ischemia/reperfusion response.Post-CA brain injury,which is named as hypoxic ischemic encephalopathy(HIE)clinically,takes great responsible for the high mortality and disability rate of patients who initially achieve ROSC after cardiac arrest,however,studies of pathological mechanism and available intervention strategies for HIE are remain limited.Recent studies found that excessive inflammatory response produced after cardiac arrest and cardiopulmonary resuscitation(CA/CPR)is one of major causes of cerebral injury.High mobility group box 1(HMGB1),a well-known pro-inflammatory cytokine,plays an important role in a variety of inflammatory related disease,and it is considered as an ideal target to alleviate the nervous system inflammation and brain damage.However,its role in brain injury after CA/CPR is unknown.Herein we investigate serum HMGB1 level after CA/CPR and whether blocking HMGB1 signaling could ease brain injury after CA/CPR in rats,which is of great significance for founding effective pharmaceutical drug,curing the disease and reducing the mortality.Methods1.8 min asphyxia CA model of male Sprague-Dawley rats were used.2.Using enzyme-linked immunosorbent assay(ELISA)kit for HMGB1,we have detected HMGB1 level in serum of patients and rats after successfully resuscitation.3.To investigate whether blocking HMGB1 confers salutary effect on post-CA brain,rats were randomly divided into four groups:sham-oprated group,CA/CPR group,HMGB1 binding Heptamer Peptide(HBHP)and Scramble group,followed by observation of survival rate,neurological outcome(validated scale of neurologic deficit score),neuronal degenerations(Nissl staining),microglial and astrocyte activation(immunohistochemical staining)as well as inflammatory cytokines expression(PCR/Westem blot).4.In the mechanism study,rats were randomly allocated and intracerebroventricularly(i.c.v.)injected with TAK-242(specific inhibitor of TLR4)or vehicle Dimethyl Sulphoxide(DMSO)at 30 min before CA onset.Histological changes and the protein expressions were then observed.Results1、Serum HMGB1 Expression Levels were Increased in Patients and Rats after CA/CPRThe ELISA data revealed both resuscitated patients and animals had elevated HMGB1 level in sera,compared with the healthy volunteers and Sham operative rats,respectively(P<0.01).2、HBHP Improved Survival and Ameliorates Brain Injury in Rats after CA/CPRHBHP treatment significantly increased the survival rate compared with Scramble group(80.77%vs 53.85%,P<0.05)and NDSs of HBHP group was significantly lower than those in Scramble group at 24h,72h,and 7-day after ROSC(P<0.05,P<0.01,P<0.05).Besides,HBHP treatment could obviously prevent the loss of CA1 Neurons(38± 3 vs 18 ± 3,P<0.001),partly rescued the loss of MAP2-postive fibers in CA/CPR rats(P<0.05),and suppressed activation state of microglia(P<0.001)and astrocytes(P<0.001,P<0.01)in hippocampal CA1 and cortex.Moreover,HBHP downregulated mRNA level of IL-1β in hippocampus and TNF-a in cortex,and reduced expressions of iNOS and COX-2 in the hippocampus(P<0.05).3、TAK-242 Attenuated the Neuronal Degenerations and the Activation of NF-κB Signaling in Hippocampal CA1 of Resuscitated RatsTAK-242 treatment obviously attenuated the loss of neurons(54 ± 6 vs 28 ± 3,P<0.01)and dendrites(P<0.05)induced by CA/CPR in hippocampal CA1 region compared with vehicle DMSO,and partly suppressed the activation of NF-κB P65.ConclusionIn summary,CA/CPR can induce HMGB1 release to serum.Blocking HMGB1 signaling with peptide may improve survival and attenuate post-resuscitation brain injury in the rat model of CA/CPR.TLR4 antagonist may also offer neuroprotective effects through weakening HMGB1-mediated proinflammatory reactions and HMGB1/TLR4/NF-κB signialing may involved in post-C A brain injury.These findings should aid in the development of therapeutic strategies for the treatment of HIE. |
