Effect Of Alpha 1-antitrypsin On White Matter Injury In Premature Birth

Background Currently,11.4 percent of all births in the united states are premature,and 3.4percent are born prior to 34 weeks gestation.Each year,about 1.8 million premature infants were born in China and it has an increasing trend.Compare to term infants,prematurity is associated with an increased risk of motor,cognitive,and behavioral deficits.With the improvement of perinatal medicine care,the mortality rate of premature infants,especially in very low birth weight infants,has been decreasing year by year,but the survival rate has increased.The complications associated with brain injury,especially the white matter injury,have become more prominent in premature infants.White matter injury(WMI)in premature infants is the most common forms of brain injury in premature infants,which can become periventricular leukomalacia(PVL).White matter injury occurs most frequently in premature infants born between 23 and 32 weeks of age,the pathogenesis is still unclear now,but It is thought to be affected by certain factors,such as intrauterine infection,hypoxia-ischemia(HI)and so on.Due to the lack of specific clinical manifestations and effective treatment measures for white matter injury of premature infants,the mortality rate is high,and the survivors are often left with moderate or severe neurodevelopmental disorders,such as cerebral palsy,mental deficit and so on,which seriously affect the quality of premature infant’s life and bring extremely heavy burden to the family and society.According to research,there are about345,000 preterm infants with moderate or severe neurodevelopmental disorder among13 million preterm infants around the world every year,and the risk of cerebral palsy in preterm infants with PVL exceeds 50%. Alpha1-antitrypsin(AAT)is a protease inhibitor,which belongs to the serine protease superfamily and has the function of inhibiting the activity of various proteases.AAT is mainly synthesized by human liver and released into blood.In recent years,studies have shown that various proteases,such as trypsin and tryptase,can activate the protease-activated receptor 2(PAR2),which is widely distributed in the central nervous system and is involved in the pathological processes of central nervous system injury and degenerative diseases.In vitro experiments showed that trypsin could activate protease-activated receptor 2 on the surface of astrocytes and promote the synthesis and release of NO.Tryptase can activate PAR2 on the surface of microglial cells,cause microglial cell activation,release cytokines such as TNF-α,cause inflammatory reaction and apoptosis of peripheral neurons.As a broad-spectrum protease inhibitor,AAT is difficult to complete through the blood-brain barrier.But,study shows that after intravenous injection of exogenous hAAT in the adult rat stroke model,hAAT were significantly increased in vivo,which result as reduce the degree of brain injury and improve the sensory and motor function of rats.These results suggest that when blood-brain barrier permeability is increased or damaged,AAT can enter brain tissue through blood-brain barrier and play a neuroprotective role.In addition,experiments confirmed that AAT can inhibit neutrophil protease in circulating blood system,reduce the damage of blood brain barrier caused by hypoxia and ischemia,inhibit the migration and infiltration of inflammatory cells into brain,and reduce inflammatory brain injury.These results also suggest that AAT has indirect neuroprotective effect.Based on our previous plasma proteomics studies,the results showed that the plasma AAT level of premature infants with PVL was significantly lower than that of premature infants without nervous system injury,the plasma AAT level of preterm infants with PVL and cerebral palsy was significantly lower than that of preterm infants only with PVL,which suggested that the down-regulation of AAT expression plays an important role in the occurrence and development of white matter injury in preterm infants.Materials and methods Use PND5 C57BL/6J mice to establish hypoxia ischemia induced white matter injury model.In order to choose the best drug injection way,we inject exogenous AAT through the nose or intraperitoneal approach,test the AAT concentration within brain tissue in different time points after hypoxia ischemia,evaluate AAT pharmacokinetic in brain tissue through different drug injection way.Mice were sacrificed at PND12 and collected the brain samples after perfusion.The short-term neuroprotective effect of AAT was evaluated by MBP and MAP2 staining.Result It was found that AAT could penetrate the injured blood-brain barrier in the white matter injury mice model,and the concentration of AAT in brain tissue after intraperitoneal injection was higher than that in the brain tissue after nasal injection,so intraperitoneal injection was adopted.MAP2 staining results showed that brain tissue loss volume was 21.933±11.984 mm~3 in the saline control group and15.411±11.420 mm~3 in the AAT drug injection group in day 7 after hypoxic ischemia,and AAT effectively reduced the brain injury after hypoxic ischemia(P=0.017).The results of MBP staining showed that the volume of subcortical white matter loss(0.169±0.106mm~3)in AAT group was significantly lower than that in saline group(0.235±0.104mm~3),and AAT effectively reduced the subcortical white matter injury(P=0.022).Conclusion AAT can effectively reduce the white matter injury in neonatal mice after hypoxic ischemia,and play a neuroprotective role,which can be used as a potential new strategy for the treatment of cerebral white matter injury in premature infants and do further research.