Methylation-reprogrammed Wnt/?-catenin Signaling Mediated Prenatal Hypoxia-induced Brain Injury In Fetal And Offspring Rats

Objectives: This study investigated whether and how PH affected Wnt pathway in the brain.Methods: Pregnant rats were randomly divided into two groups: The control group was kept in normal atmospheric conditions(21% O2;normoxia)throughout pregnancy.The other group was exposed to hypoxia(10.5% O2;hypoxia)in a plexiglass chamber from GD 4 to 21.At GD 21,some of pregnant dams were anesthetized intraperitoneally with sodium pentobarbital(100 mg/kg,intraperitoneally),fetuses were removed through surgical hysterotomy and weighed immediately.The fetal brain was isolated and weighed,then frozen in liquid nitrogen,and stored in-80? freezer.Other pregnant rats were allowed to give birth naturally.The male offspring at 6 weeks old were used for Morris water task.The expression of m RNA and protein were detected by q-PCR and Western-blot.Moreover,the m RNA expression of related genes in PC12 cells treated with 5-aza was examined.Results: Fetal brain weight and body weight were decreased in the PH group,the ratio of brain weight to body weight was increased significantly.Prenatal hypoxia increased m RNA expression of Wnt3 a,Wnt7a,Wnt7 b,Fzd4,activated ?-catenin protein,Hif1 a and Fosl1.Among five members of the Sfrp family,Sfrp4 was down-regulated and sodium bisulfite and sequencing revealed that hyper-methylation in the promoter region of Sfrp4 gene in the fetal brain.In the methylation-regulating genes,higher m RNA expressions of Dnmt1 and Dnmt3 b was found in the PH group.The study of PC12 cells treated with 5-aza further approved showed that Dnmt1 and Dnmt3 a was decreased and Sfrp4 was increased,the protein level of active-?-catenin was down-regulated and m RNA and protein of total Catenin showed no difference between the two groups.The PH offspring showed a longer escape latency and travel distance from the 3th to 7th day.Time of crossing the target areas were decreased in the PH group.No difference in the swim speed between the two groups.In the offspring hippocampus,protein levels of Hif1 a and m RNA expression of Sfrp4 were unchanged,while Wnt signal pathway was inhibited.Conclusions: The data demonstrated that PH activated the Wnt pathway in the fetal brain,related to the hyper-methylation of Sfrp4 as well as Hif1 a signaling.Activated Wnt signaling might play acute protective roles to the fetal brain in response to hypoxia,also would result in disadvantageous influence on the offspring in long term.