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Sung Wook Park, Shawna D Persaud, Stanislas Ogokeh, Tatyana A Meyers, DeWayne Townsend and Li-Na Wei

Excessive and/or persistent activation of calcium-calmodulin protein kinase II (CaMKII) is detrimental in acute and chronic cardiac injury. However, intrinsic regulators of CaMKII activity are poorly understood. We find that cellular retinoic acid-binding protein 1 (CRABP1) directly interacts with CaMKII and uncover a functional role for CRABP1 in regulating CaMKII activation. We generated Crabp1-null mice (CKO) in C57BL/6J background for pathophysiological studies. CKO mice develop hypertrophy as adults, exhibiting significant left ventricular dilation with reduced ejection fraction at the baseline cardiac function. Interestingly, CKO mice have elevated basal CaMKII phosphorylation at T287, and phosphorylation on its substrate phospholamban (PLN) at T17. Acute isoproterenol (ISO) challenge (80 mg/kg two doses in 1 day) causes more severe apoptosis and necrosis in CKO hearts, and treatment with a CaMKII inhibitor KN-93 protects CKO mice from this injury. Chronic (30 mg/kg/day) ISO challenge also significantly increases hypertrophy and fibrosis in CKO mice as compared to WT. In wild-type mice, CRABP1 expression is increased in early stages of ISO challenge and eventually reduces to the basal level. Mechanistically, CRABP1 directly inhibits CaMKII by competing with calmodulin (CaM) for CaMKII interaction. This study demonstrates increased susceptibility of CKO mice to ISO-induced acute and chronic cardiac injury due to, at least in part, elevated CaMKII activity. Deleting Crabp1 results in reduced baseline cardiac function and aggravated damage challenged with acute and persistent β-adrenergic stimulation. This is the first report of a physiological role of CRABP1 as an endogenous regulator of CaMKII, which protects the heart from ISO-induced damage.

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Wenqi Chen, Siyu Lu, Chengshun Yang, Na Li, Xuemei Chen, Junlin He, Xueqing Liu, Yubin Ding, Chao Tong, Chuan Peng, Chen Zhang, Yan Su, Yingxiong Wang and Rufei Gao

Previous research on the role of insulin has focused on metabolism. This study investigated the effect of insulin on angiogenesis in endometrial decidualization. High insulin-treated mouse model was constructed by subcutaneous injection of insulin. Venous blood glucose, serum insulin, P4, E2, FSH and LH levels in the pregnant mice were detected by ELISA. Decidual markers, angiogenesis factors and decidual vascular network were detected during decidualization in the pregnant mouse model and an artificially induced decidualization mouse model. Tube formation ability and angiogenesis factors expression were also detected in high insulin-treated HUVECS cells. To confirm whether autophagy participates in hyperinsulinemia-impaired decidual angiogenesis, autophagy was detected in vivo and in vitro. During decidualization, in the condition of high insulin, serum insulin and blood glucose were significantly higher, while ovarian steroid hormones were also disordered (P < 0.05), decidual markers BMP2 and PRL were significantly lower (P < 0.05). Uterine CD34 staining showed that the size of the vascular sinus was significantly smaller than that in control. Endometrial VEGFA was significantly decreased after treatment with high insulin in vivo and in vitro (P < 0.05), whereas ANG-1 and TIE2 expression was significantly increased (P < 0.05). In addition, aberrant expression of autophagy markers revealed that autophagy participates in endometrial angiogenesis during decidualization (P < 0.05). After treatment with the autophagy inhibitor 3-MA in HUVEC, the originally damaged cell tube formation ability and VEGFA expression were repaired. This study suggests that endometrial angiogenesis during decidualization was impaired by hyperinsulinemia in early pregnant mice.

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Yan Su, Sujuan Guo, Chunyan Liu, Na Li, Shuang Zhang, Yubin Ding, Xuemei Chen, Junlin He, Xueqing Liu, Yingxiong Wang and Rufei Gao

Embryo implantation is essential for normal pregnancy. Decidualization is known to facilitate embryo implantation and maintain pregnancy. Uterine stromal cells undergo transformation into decidual cells after embryo attachment to the endometrium. Pyruvate kinase M2 (PKM2) is a rate limiting enzyme in the glycolysis process which catalyzes phosphoenolpyruvic acid into pyruvate. However, little is known regarding the role of PKM2 during endometrial decidualization. In this study, PKM2 was found to be mainly located in the uterine glandular epithelium and luminal epithelium on day 1 and day 4 of pregnancy and strongly expressed in the decidual zone after embryo implantation. PKM2 was dramatically increased with the onset of decidualization. Upon further exploration, PKM2 was found to be more highly expressed at the implantation sites than at the inter-implantation sites on days 5 to 7 of pregnancy. PKM2 expression was also significantly increased after artificial decidualization both in vivo and in vitro. After PKM2 expression was knocked down by siRNA, the number of embryo implantation sites in mice on day 7 of pregnancy was significantly reduced, and the decidualization markers BMP2 and Hoxa10 were also obviously downregulated in vivo and in vitro. Downregulated PKM2 could also compromise cell proliferation in primary endometrial stromal cells and in Ishikawa cells. The migration rate of Ishikawa cells was also obviously suppressed by si-PKM2 according to the wound healing assay. In conclusion, PKM2 might play an important role in decidualization during early pregnancy, and cell proliferation might be one pathway for PKM2 regulated decidualization.