| Object i ve Traumatic brain injury(TBI) is a common and highly dangerous disease.The process of brain damage does not finish in a short time after the primary injury and the secondary injury is the major pathological process of traumatic encephalopathy with ischemia as the major mechanism of this secondary damage.Apoptosis is a common form of cell death.Recently,related studies of mechanism of apoptosis have demonstrated that apoptosis participates in the pathogenesis of secondary brain damage after TBI.Most injured cells undergo necrosis in the central area of contusion.However,in the boundary of contusion, named " ischemic penumbra " ,the hurt is less severe and most injured cells undergo apoptosis.The ischemic penumbra may alter according to the changes of outside condition.When the condition is better, it can be reversed to the normal perfusion region(reversible);on the contrary,when the condition becomes worse,it will be exacerbated into a necrosis region(irre- versible),and neurological dysfunction will be aggravated. Apoptosis is a complex cascade of cellular suicide,and induced mainly by the activation of proteases of caspase family. Among this family,caspase-3 is a key enzyme in mammalian cell apoptosis,which initiates the executive phase of apoptosis.Solid clinical studies indicated that hyperbaric oxygen(HBO) is a effective treatment for TBI.HBO can increase signi- ficantly the oxygen concentration in blood and distance of oxygen diffusion,and augment blood flow in ischemic regions.In addition,HBO can improve aerobic metabolism level and the ability of damaged mitochondria to utilize the oxygen,rectify acid toxin,and reduce the formation of edema.HBO can also accelerate the regeneration of capillary and the foundation ofcolleteral circulation,and therefore,protect the neurons in ischemic penumbra surrounding the injury region.There have been no studies,however, to demonstrate the relationship between the effect of HBO and neuronal apoptosis induced by TBI.To explore the molecular mechanism of HBO treatment effect using the established animal models of moderate cortical contusion injury,we investigated the influences of HBO, hyperbaric air(HBA) and normobaric hyperoxia(NHO) on the neuronal apoptosis and the expression of caspase-3 after TBI.Methodes 40 healthy female SD rats(250 + 30g) were divided into five groups(n=8 each).The five groups were treated differently as followings: group A,sham-injured group;group B,TBI group; group C,TBI+HBA group;group D,TBI+NHO group;group E,TBI+HBO group.The controlled moderate cortical contusion injury models were made with Teeney' s method in group B,C,D,and E.The sham-injured animals(group A) underwent the same surgical procedure as other groups,but did not receive impact injury. The rats in group B received no additional treatments after TBI. The rats in group C,D,E were treated respectively with HBA(0.25Mpa), NHO(O.lMpa) and HBO(0.25Mpa) 30 minutes after TBI,and the treatments were performed every 12 hours with time length of 1 hour every time. 48 hours later from the operation,every rat was anesthetized and perfused transcardially with 4% phosphate-buffered paraformal- dehyde,and the brain tissues were removed and placed in the forementioned fixative overnight. Adjacently fixed,paraffin sections were made.Apoptotic neurons were detected by using TUNEL staining method.The number of positive stained cells in every 100 neurons was regarded as apoptosis index.Immunohistochemistrical method was used for detecting the expression of caspase-3 . Statistical analysis was performed with the software package(SPSSl0.0).ResuIts (1) TUNEL Staining: There are few TUNEL positive neurons in sham-operated animals.After TBI,The TUNEL-positive neuronal cells increased significantly(P<0.05,compared with group A).HBO sharply decreased the number of TUNEL-positive neuronal cells induced by TBI(P<0.05,compared with group B),which is,however, more than that of group A(P<0.05).There was no significant distinctions in number of TUNEL-positive neuronal cells between grouop C,D... |
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