ABSTRACT
Objective To observe the effects of exogenous basic fibroblast growth factor (bFGF) on radiation-induced apoptosis of C17.2 neural stem cells(NSCs) and explore the relationship between bFGF and Hes1,RBP-JK protein.Methods The cell viability was assessed using the MTT assay.After the cells attach to the flasks they were irradiated by the linear accelerator.And 5 min later,different concentrations of bFGF in accordance with the experimental design and cultured cells 48 h.Extracted total protein of each group and Western blot analysis showed the changes of the Hes1,RBP-JK protein.Results Compared with the control group,irradiation group cell growth was inhibited,the OD of 0 ng/ml bFGF group was 0.61±0.81,the OD of 80 ng/ml bFGF group was 1.21±1.01 and the control group was 1.51± 1.13.Compared with the control group,all groups showed statistically significant difference (P＜ 0.05).Western blot analysis showed that with the increasing concentrations of bFGF,RBP-JK expression gradually decreased,but Hes1 expression gradually increased.Conclusion Exogenous basic fibroblast growth factor (bFGF) can inhibit apoptosis of C17.2 NSCs.bFGF can regulate Notch signaling pathway downstream proteins Hes1,RBP-JK expression and inhibit neural stem cell apoptosis which were irradiated.
ABSTRACT
Low density lipoprotein receptor (LDLR) plays an important role in the cholesterol homeostasis. We examined the possible circadian regulation of LDLR and mechanism(s) underlying it. In mice, blood glucose and plasma triglyceride, total and high density lipoprotein cholesterol varied distinctively throughout a day. In addition, LDLR mRNA oscillated in the liver in a functional clock-dependent manner. Accordingly, analysis of human LDLR promoter sequence revealed three putative E-boxes, raising the possible regulation of LDLR expression by E-box-binding transcription factors. To test this possibility, human LDLR promoter reporter constructs were transfected into HepG2 cells and the effects of CLOCK/BMAL1, Hes1, and Hes6 expression were analyzed. It was found that positive circadian transcription factor complex CLOCK/BMAL1 upregulated human LDLR promoter activity in a serum-independent manner, while Hes family members Hes1 and Hes6 downregulated it only under serum-depleted conditions. Both effects were mapped to proximal promoter region of human LDLR, where mutation or deletion of well-known sterol regulatory element (SRE) abolished only the repressive effect of Hes1. Interestingly, hes6 and hes1 mRNA oscillated in an anti-phasic manner in the wild-type but not in the per1-/-per2-/- mouse. Comparative analysis of mouse, rat and human hes6 genes revealed that three E-boxes are conserved among three species. Transfection and site-directed mutagenesis studies with hes6 reporter constructs confirmed that the third E-box in the exon IV is functionally induced by CLOCK/BMAL1. Taken together, these results suggest that LDLR expression is under circadian control involving CLOCK/BMAL1 and Hes family members Hes1 and Hes6.