[Effect of secretin on the expression of cPLA2 and mPGEs-1 in mouse endometrial stromal cell during early pregnancy].

Secretin, a gastrointestinal peptide, has been found to be expressed in mouse endometrial stromal cells (mESCs) during early pregnancy. In order to further investigate the function of secretin during embryo implantation, the expression levels of secretin, secretin receptor, cytosolic phospholipase A2 (cPLA2) and membrane prostaglandin E synthase 1 (mPGEs-1) were detected in the mice uterus from day 4 to 8 of pregnancy by real-time PCR, ELISA and in situ hybridization. mESCs isolated and cultured from day 4 of pregnancy were transfected with secretin expression vectors or treated with H89, a PKA inhibitor. Then the expression levels of cPLA2, mPGEs-1 and cAMP responsive element-binding protein (CREB) were detected by real-time PCR and Western blot. The concentration of prostaglandin E2 (PGE2) in the supernatant was determined by ELISA. The result showed that secretin, cPLA2 and mPGEs-1 mRNA expression increased gradually in implantation sites from day 5 to day 7 of pregnancy with the same tendency. The secretin levels in serum were significantly higher on days 6, 7 and 8 of pregnancy than that on day 5 of pregnancy. The concentration of secretin was significantly higher in implantation sites on days 6, 7 than that in non-implantation site on day 5. Transfection of secretin expression vector promoted cPLA2, p-cPLA2 and mPGEs-1 expressions in mESCs, but not PGE2 level in the supernatant. H89 could effectively inhibit the expression of CREB, p-CREB, p-cPLA2 and cPLA2 induced by secretin. The results showed that the increased secretin expression in mESCs during embryo implantation may promote p-cPLA2, cPLA2 and mPGEs-1 expression, and the promotion may be through PKA signaling pathway.

Multi-scale modeling identifies the role of p53-Gys2 negative feedback loop in cellular homeostasis.

The transcription factor p53 is a tumor suppressor and strictly controlled p53 protein abundance coordinates cellular outcomes in response to various stresses. The glycogen synthase 2 (Gys2) and p53 generates a novel negative feedback circuit in which p53 represses Gys2 expression whereas Gys2 can stabilize p53 by competitive binding with MDM2. However, the dynamic role of p53-Gys2 negative feedback is still elusive. In current work, we recapitulated the main experimental findings using multi-scale modeling and emphasized the pivotal role of p53-Gys2 negative feedback loop to main cellular homeostasis. The multi-scale modeling strategy was used to simulate both in vitro and in vivo experimental findings. We found that expression of a key oncoprotein HBx may facilitate cancer progression. Gys2 overexpression can inhibit hepatocellular carcinoma progression whereas Gys2 knockdown advanced cancer development. We also applied oscillatory and impulse disturbance to p53 signaling pathway and the results showed that optimal p53-Gys2 negative feedback loop was highly resistant to oscillatory or impulse disturbances. Instead, the canonical p53-MDM2 negative feedback circuit can significantly affect the dynamics of p53 and therefore effectively shaped pulsatile patterns. Therefore, the dual negative feedback loops in p53 signaling can provide features of both robustness and tunability. These dynamic features are critical for cellular homeostasis against tumor progression in p53 signaling pathway.