| Background:Intra-abdominal hypertension(IAH)refers to a continuous or repetitive pathological increase of intra-abdominal pressure(IAP)?12mmHg.Abdominal compartment syndrome(ACS)refers to IAP persistence ?20mmHg with new organ dysfunction or disorders.IAH/ACS can be divided into primary IAH/ACS and secondary IAH/ACS.Primary IAH/ACS is mainly caused by primary abdominal or pelvic disease/injury.Secondary IAH/ACS is mainly caused by systemic inflammatory response syndrome,ischemic shock,and large-scale burns.Most secondary IAH/ACS are characterized by hypovolemia requiring massive fluid resuscitation.The pathological process includes ischemia-reperfusion injury,release of inflammatory factors,increasing of blood capillary permeability,fluid leakage,and abdominal edema.IAH/ACS not only causes abdominal organ damage,but also leads to increased intracranial pressure,which further induces brain damage.The mechanism may be related to the destruction of the blood-brain barrier(BBB).In clinic,severe patients with traumatic brain injury(TBI)are usually associated with IAH/ACS.The two interact with each other so that brain injury is aggravated,affecting the prognosis of patients.Basic fibroblast growth factor(bFGF)has a wide range of biological effects,e.g.,it plays a positive role in angiogenesis,wound healing,tissue repair,and nerve growth.Studies have found that in brain hemorrhage models,bFGFs can bind to fibroblast growth factor receptors(FGFRs),up-regulate the expression of tight junction(TJ)and adheren junction(AJ)proteins,and protect the blood-brain barrier,but the mechanism is unclear yet.There are few studies in literature on the blood-brain barrier after TBI combined with IAH/ACS.Our experiment aimed to investigate the effect of TBI combined with IAH on the blood-brain barrier and intracranial pressure,analyze the role of bFGF on the injured blood-brain barrier and explore its mechanism.We established a rat model for in vivo experiments(in this model,cortical control injury was induced to simulate TBI and massive fluid resuscitation combined with intraperitoneal nitrogen injection after hemorrhagic shock was performed to simulate secondary IAH/ACS),and in vitro cultured human brain microvascular endothelial cells for oxygen-glucose deprivation/reoxygenation induction experiment.To be specific,there were three experiments:(1)Experiment 1,to establish a secondary IAH/ACS model of rats and analyze its effect on the blood-brain barrier;(2)Experiment 2,to investigate the effect of bFGF on the blood-brain barrier after TBI combined with IAH and explore the mechanism;(3)Experiment 3,to study the effect of bFGF on the permeability and apoptosis of human brain microvasculature endothelial cells after oxygen-glucose deprivation / reoxygenation and explore the mechanism.This study revealed that TBI combined with secondary IAH can disrupt the blood-brain barrier and it also provided a theoretical basis for the application of bFGF in managing blood-brain barrier damage.Methods:1.Establishment of secondary IAH/ACS rat model and its effect on blood-brain barrierIn this study,we performed massive fluid resuscitation and intraperitoneal nitrogen injection in rats with hemorrhagic shock to establish a secondary IAH/ACS model(IAH?12mmHg,ACS?20mmHg),and then observed intracranial pressure,general morphology of brain tissue,brain MRI,brain water content,and permeability of the blood-brain barrier.The expression of ZO-1,?-catenin,MMP2 and IL-1? in the blood-brain barrier of the rat model was detected by the western blotting and PCR,and the damage to the blood-brain barrier at different intra-abdominal pressures and the pathological process of intracranial pressure changes were evaluated in order to find potential therapeutic targets and provide new perspectives for clinical application.2.Effect and mechanism of bFGF on the blood-brain barrier after TBI combined with IAHBased on the previously constructed secondary IAH model,cortical control injury was induced to simulate TBI.The rats were divided into control group,combined injury(TBI + IAH)group,combined injury+ bFGF group,combined injury+ bFGF + PD173074 group,and combined injury+ bFGF + PD98059 group.The intracranial pressure,brain water content and blood-brain barrier permeability were measured after injury in each group.The immunofluorescence,Western blotting and PCR were used to detect the expression of FGFR1/p-FGFR1,FGFR2/ p-FGFR2,ZO-1,claudin-5,occludin,?-catenin,MMP9,MMP12,IL-1?,and TNF-? on the blood-brain barrier in each group.The protective effect of bFGF on the blood-brain barrier after TBI and IAH was explored,as well as its mechanism,including the binding receptors and activated downstream signaling pathways,so as to provide an experimental reference for clinical treatment.3.Effect of bFGF on human brain microvascular endothelial cells(HBMECs)after oxygen-glucose deprivation / reoxygenation(OGD/ R)and its mechanismIn vivo experiments showed that the blood-brain barrier was damaged after TBI combined with IAH,and the administration of bFGF increased the specific protein expression of BMECs,thereby reducing the permeability of the blood-brain barrier,brain edema and intracranial pressure.In an in vitro experiment,HBMECs were divided into control group,OGD/R group,OGD/R + bFGF group,OGD/R + bFGF+PD173074 group,and OGD/R + bFGF+ PD98059 group.The permeability,apoptosis and vitality of HBMECs under OGD/R were observed.The expression of FGFR1/p-FGFR1,FGFR2/p-FGFR2,ZO-1,claudin-5,occludin,?-catenin,MMP2,MMP9,BAX,Bcl-2,and Caspase-3 on the blood-brain barrier in each group were detected by the immunofluorescence,Western blotting and PCR.The effect of bFGF on the permeability,apoptosis and vitality of HBMECs after OGD/R was analyzed to provide new perspectives for treatment.Results:1.The secondary IAH/ACS model of rats was successfully established and the result showed that IAH/ACS can cause damage to the blood-brain barrier and increase intracranial pressure.The secondary IAH/ACS model was successfully established by massive fluid resuscitation against hemorrhagic shock and intraperitoneal nitrogen injection.The ACS model had a higher mortality compared with the IAH model.Both IAH group and ACS group had elevated intracranial pressure and increased cerebral edema and brain water content,leading to increased permeability of the blood-brain barrier,decreased expression of junction proteins(ZO1,?-catenin)on the blood-brain barrier,and increased expression of MMP2 and inflammatory factor(IL-1?)which caused damage to the blood-brain barrier.There were no significant differences between the two groups with regard to increased intracranial pressure and destruction of the blood-brain barrier.2.bFGF protects the blood-brain barrier damaged by TBI and IAH and reduces intracranial pressure,which may be due to that bFGF binds to FGFR1 in BMECs,activating the downstream ERK pathway.The combination of TBI and IAH results in the increase of intracranial pressure,brain water content and blood-brain barrier permeability.The expression of p-FGFR1 in BMECs constituting the blood-brain barrier showed a significant change.The administration of bFGF can activate p-FGFR1 and downstream p-ERK,up-regulate AJ proteins(ZO-1,Claudin-5,occludin),TJ protein(?-catenin),down-regulate MMPs(MMP9,MMP12)and IL-1?,and reduce brain water content,permeability of the blood-brain barrier and intracranial pressure.The administration of FGFR1 antagonist(PD173074)and ERK antagonist(PD98059)can reverse the protective effect of bFGF.3.bFGF improves the permeability and apoptosis of human brain microvascular endothelial cells after oxygen-glucose deprivation/reoxygenation(OGD/R).The mechanism is as follow: bFGF binds to FGFR1 in HBMECs,activating the downstream ERK pathway.OGD/R leads to the increased permeability and apoptosis of HBMECs,but produces little effect on vitality.After OGD/R in HBMECs,the expression of p-FGFR1 showed significant change compared with pre-OGD/R level,but p-FGFR2 expression showed no change.The administration of bFGF can activate p-FGFR1 and downstream p-ERK,up-regulate AJ proteins(ZO-1,Claudin-5,occludin),TJ protein(?-catenin)and Bcl-2,down-regulate MMPs(MMP9,MMP12),BAX and caspase-3,and reduce the permeability of the blood-brain barrier and apoptotic cells.The administration of FGFR1 antagonist(PD173074)and ERK antagonist(PD98059)can reverse the protective effect of bFGF.Conclusions:1.We successfully established the animal model and confirmed the relationship between different intra-abdominal pressures and brain injury.The results showed that IAH/ACS can increase intracranial pressure through damaging the blood-brain barrier.The rat model has the advantages of small size,simple operation,low cost,close homology with human genes,and easy preparation of reagents,which is suitable for this study.2.TBI combined with IAH causes damage to the blood-brain barrier,brings cerebral edema,and increases intracranial pressure.bFGF can protect the blood-brain barrier,reduce brain edema and decrease intracranial pressure by up-regulating the expression of TJs,AJs proteins in the blood-brain barrier and reducing the expression of MMP and inflammatory factors.The protective effect of bFGF may be achieved through FGFR1 and the downstream ERK signaling pathways.3.The in vitro cultured HBMECs showed increased permeability and apoptosis under OGD/R.By binding to FGFR1,bFGF activates the ERK pathway,up-regulates AJ and TJ proteins,and regulates MMP and apoptotic proteins(Bcl-2,BAX,caspase-3),reduces the permeability of HBMECs and the number of apoptotic cells,thereby it has protective effect on HBMECs damage. |
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