[Effects of acute fear stress on spatial memory and neuronal plasticity in the medial prefrontal cortex in mice].

The purpose of this study was to investigate the effects of acute fear stress on the spatial memory and neuronal plasticity of medial prefrontal cortex (mPFC) neurons in mice, and to elucidate the mechanisms underlying mPFC plasticity and post-stress memory regulation. Male C57BL/6 mice (6 weeks old) were randomly divided into control group and stress group. Foot shock stress was applied to establish an acute fear stress model. Changes in spatial memory were examined by the Morris water maze test, and the dynamic changes in the spike encoding of pyramidal neurons and GABAergic neurons in the prelimbic cortex (PrL) and infralimbic cortex (IL) of mPFC were detected by whole-cell recording. The results showed that acute fear stress significantly enhanced the percentage of freezing and the number of freezing, reduced the average speed, decreased the escape latency during acquisition phase, extended the probing time in the first quadrant and shortened the probing time in the third quadrant during probe trial, increased inter-spike interval, energy barrier and absolute refractory period of GABAergic neurons in the PrL and pyramidal neurons in the IL, while decreased inter-spike interval, energy barrier and absolute refractory period of pyramidal neurons in the PrL and GABAergic neurons in the IL. These results suggest that acute fear stress can enhance the spatial memory of mice, elevate the excitability and function of the PrL, while deteriorate the excitability and function of the IL, and the underlying mechanism may involve the role of mPFC microcircuitry plasticity in spatial memory after stress.

[MicroRNA-218 promotes osteosarcoma cell apoptosis by down-regulating oncogene B lymphoma mouse Moloney leukemia virus insertion region 1].

OBJECTIVE: To investigate the tumor-suppressing effect of microRNA-218 (miR-218) in osteosarcoma (OS) and explore its molecular mechanism. METHODS: We examined the expression levels of miR-218 in 68 pairs of OS and adjacent tissue samples using qRT-PCR. Cultured human OS cell line Saos-2 was transfected with miR-218 mimics or anti-miR-218 mimics, and the cell apoptosis was assessed using CCK-8 assay, annexin V-FITC staining and Western blotting. We also analyzed the potential functional targets of miR-218 in Saos-2 cells using luciferase assay, qRT-PCR and Western blotting. RESULTS: The expression level of miR-218 was lowered by at least 8 folds in OS tissues as compared with the adjacent tissues. In cultured Saos-2 cells, transfection with miR-218 mimics for 24, 36, and 48 h resulted in a significant reduction in the cell viability, while transfection with anti-miR-218 mimics significantly increased the cell viability. The cells transfected with miR-218 mimics showed an obviously enhanced expression of cleaved poly(ADP-ribose) polymerase (C-PARP) as compared with the cells transfected with anti-miR-218 mimics and the control cells. Flow cytometry demonstrated obviously increased apoptosis of the cells following miR-218 mimics transfection. We identified the oncogene B lymphoma mouse Moloney leukemia virus insertion region 1 (BMI-1) as a specific target of miR-218 in Saos-2 cells. BMI-1 expressions at both the mRNA and protein levels were significantly reduced in Saos-2 cells overexpressing miR-218 but increased in the cells with miR-218 knockdown as compared to the control cells. Luciferase reporter assay indicated that miR-218 directly inhibited the expression of BMI-1 via binding to its 3'-UTR in OS cells. CONCLUSION: miR-218 can promote OS cell apoptosis and plays the role as a tumor suppressor by down-regulating BMI-1.