Folate deprivation induces cell cycle arrest at G0/G1 phase and apoptosis in hippocampal neuron cells through down-regulation of IGF-1 signaling pathway.
Folate deficiency contributes to impaired adult hippocampal neurogenesis, yet the mechanisms remain unclear. Here we use HT-22 hippocampal neuron cells as model to investigate the effect of folate deprivation (FD) on cell proliferation and apoptosis, and to elucidate the underlying mechanism. FD caused cell cycle arrest at G0/G1 phase and increased the rate of apoptosis, which was associated with disrupted expression of folate transport and methyl transfer genes. FOLR1 and SLC46A1 were (P<0.01) down-regulated, while SLC19A1 was up-regulated (P<0.01) in FD group. FD cells exhibited significantly (P<0.05) higher protein content of BHMT, MAT2b and DNMT3a, as well as increased SAM/SAH concentrations and global DNA hypermethylation. The expression of the total and all the 3 classes of IGF-1 mRNA variants was significantly (P<0.01) down-regulated and IGF-1 concentration was decreased (P<0.05) in the culture media. IGF-1 signaling pathway was also compromised with diminished activation (P<0.05) of STAT3, AKT and mTOR. CpG hypermethylation was detected in the promoter regions of IGF-1 and FOLR1 genes, while higher SLC19A1 mRNA corresponded to hypomethylation of its promoter. IGF-1 supplementation in FD media significantly abolished FD-induced decrease in cell viability. However, IGF-1 had limited effect in rescuing the cell phenotype when added 24h after FD. Taken together, down-regulation of IGF-1 expression and signaling is involved in FD-induced cell cycle arrest and apoptosis in HT-22 hippocampal neuron cells, which is associated with an abnormal activation of methyl transfer pathway and hypermethylation of IGF-1 gene promoter.
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Yang
Y
Yang
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Xi
X
Li
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Qinwei
Q
Sun
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Bin
B
He
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Yimin
Y
Jia
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Demin
D
Cai
Key Laboratory of Animal Physiology & Biochemistry, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China; Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing 210095, PR China. Electronic address: zhao.ruqian@gmail.com.
Ruqian
R
Zhao
D000818:Animals; D017209:Apoptosis; D001692:Biological Transport; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D058975:Folate Receptor 1 / Q000235:genetics; D005492:Folic Acid / Q000378:metabolism; D005494:Folic Acid Deficiency / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D058972:Folic Acid Transporters / Q000235:genetics; D059585:G1 Phase Cell Cycle Checkpoints; D006624:Hippocampus / Q000473:pathology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000473:pathology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D058978:Reduced Folate Carrier Protein / Q000235:genetics; D016192:Resting Phase, Cell Cycle; D015398:Signal Transduction
D058975:Folate Receptor 1; D058972:Folic Acid Transporters; C520574:Folr1 protein, mouse; D058978:Reduced Folate Carrier Protein; D007334:Insulin-Like Growth Factor I; D005492:Folic Acid
Apoptosis; Cell cycle arrest; Folate; Hippocampal neuron cells; IGF-1