Protective Effect Of Omega-3 Polyunsaturated Fatty Acids On Brain Injury Induced By Lipopolysaccharide In Newborn Rats

Background:Postnatal infection of preterm infants is a common problem in neonates.However,for a long time,people have paid more attention to the correlation between intrauterine infection(i.e.,prenatal infection)and brain injury of premature infants,while few researches have been conducted on the correlation between postnatal infection and brain injury of premature infants.At present,the clinical treatment of infection in premature infants mainly focuses on how to effectively fight infection,and there is no measure to prevent and control the brain injury related to infection/inflammation in premature infants.Omega-3 polyunsaturated fatty acids(omega-3 polyunsaturated fatty acids,omega-3 PUFAs)have anti-inflammatory and antiapoptotic effect,has been used in the treatment of diseases of the nervous system,but its mechanism is not fully clear.Perinatal supplementation of omega-3 PUFAs can inhibit the death of neurons and alleviate hypoxic ischemic brain injury by promoting the formation of phosphatidylserine and the AKT signaling pathway.The PI3K/AKT signaling pathway may be associated with brain injury caused by postnatal infection.Therefore,the present study explored the brain protective mechanism of omega-3 PUFAs in the nerve injury induced by Lipopolysaccharide(LPS)through in vivo and in vitro experiments.Methods:In vivo experiments,SD newborn rats were intraperitoneally injected with LPS to establish the brain injury model.Rats were assigned into 5 groups randomly:control(saline),saline+?-3 PUFAs,saline+LPS(1.0 mg/kg),saline+LPS(1.0 mg/kg)+?-3 PUFAs(50 mg/kg),saline+LPS(1.0 mg/kg)+?-3 PUFAs(250 mg/kg).All the chemicals were injected intraperitoneally,while the injection volume of saline and LPS was strigently equal.TUNEL and BrdU were used to detect the proliferation and apoptosis of hippocampal nerve cells.The effect omega-3 PUFAs on LPS-induced long-term enhancement(Long-term action,LTP)damage was analyzed by patch-clamp technique.And qPCR and Western Blot were used to detect the expressions of PI3K,?-catenin,AKT and p-AKT in different treatment groups.In vitro,PC 12 cells were induced by LPS to construct the damaged cell model and were randomly divided into five groups:control group,control+omega-3 PUFAs group,LPS group,LPS+omega-3 PUFAs group,LPS+agonist(740 Y-P)group and LPS+omega-3 PUFAs+740 Y-P group.Proliferation,apoptosis and migration of cells in different groups were detected by CCK8,flow cytometry,EdU and Transwell,respectively,and the expressions of PI3K,AKT,p-AKT and ?-catenin in PC12 cells in different treatment groups were detected by qPCR and Western Blot.Results:The brain injury model of newborn rats was successfully induced by LPS in vivo.LPS can promote the increase of nerve cell apoptosis in the hippocampal tissue and inhibit the proliferation ability of nerve cells.However,after intraperitoneal injection of omega-3 PUFAs with high dose,it can enhance the proliferation ability of nerve cells in the hippocampal tissue and inhibit the apoptosis.LPS can cause damage to LTP in newborn rats.When omega-3 PUFAs is injected intraperitoneally,it can effectively reverse the damage of LPS to LTP and thus protect nerve cells.Subsequently,qPCR and Western blot analysis showed that after intraperitoneal injection of LPS in newborn rats,the mRNA and protein expression levels of PI3K and ?-catenin in brain tissues were significantly decreased(P<0.05),while the phosphorylation of AKT was significantly inhibited(P<0.05).However,after intraperitoneal injection of omega-3 PUFAs in newborn rats,the mRNA and protein expression levels of PI3K and ?-catenin in the brain tissues of newborn rats were significantly up-regulated(P<0.05),while phosphorylation of AKT was activated(P<0.05).In vitro experiments,we found that LPS could inhibit the proliferation and migration of PC 12 cells and promote cell apoptosis,while omega-3 PUFAs and 740 Y-P could reverse the inhibition of LPS on cell proliferation and migration,reduce the apoptosis of PC 12 cells and promote cell proliferation.We found that omega-3 PUFAs can up-regulate the mRNA and protein expression levels of PI3K and ?-catenin in cells,activate the phosphorylation of AKT in cells,and reverse the inhibitory effect of LPS on PI3K/AKT/?-catenin signal molecules,and omega-3 PUFAs and 740 Y-P have synergistic effects.Conclusion:Omega-3 PUFAs may through PI3K/AKT/?-catenin signaling pathway positively regulation the expression of PI3K and further caused the phosphorylation of AKT activated,and then upregulate the expression of ?-catenin.Thus,it can promote the proliferation and migration of nerve cells,inhibit the apoptosis of nerve cells,and finally exert the therapeutic effect on the damaged brain tissue and nerve cells.It suggests that omega-3 PUFAs may be a PI3K/AKT/?-catenin signaling axis agonist with potential application value in the treatment of premature brain injury.