Although nitric oxide (NO) induces neuronal cell death under some conditions, it also can prevent apoptosis resulting from growth factor withdrawal. We investigated the molecular mechanism by which NO protects undifferentiated and differentiated PC12 cells from trophic factor deprivation-induced apoptosis. PC12 cells underwent apoptotic death in association with increased caspase-3-like activity, DNA fragmentation, poly(ADP-ribose) polymerase (PARP) cleavage, and cytochrome c release after 24 hr of serum withdrawal. The apoptosis of PC12 cells was inhibited by the addition of NO-generating donor S-nitroso-N-acetylpenicillamine (SNAP) (5-100 microM) and the specific caspase-3-like protease inhibitor Ac-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-cho) but not the YVADase (or caspase-1-like protease) inhibitor N-acetyl-Tyr-Val-Ala-Asp-aldehyde (Ac-YVAD-cho). SNAP and Ac-DEVD-cho prevented the increase in DEVDase (caspase-3-like protease) activity. The SNAP-mediated suppression of DEVDase activity was only minimally reversed by the incubation of cell lysate with dithiothreitol, indicating that NO did not S-nitrosylate caspase-3-like proteases in PC12 cells. Western blot analysis showed that NO inhibited the proteolytic activation of caspase-3. The cGMP analog 8-bromo-cGMP (8-Br-cGMP) blocked apoptotic cell death, caspase-3 activity and activation, and cytochrome c release. The soluble guanylyl cyclase inhibitor 1-H-oxodiazol-[1,2,4]-[4,3-a] quinoxaline-1-one (CODQ) significantly attenuated NO-mediated, but not 8-Br-cGMP-dependent, inhibition of apoptotic cell death, PARP cleavage, cytochrome c release, and DEVDase activity. Furthermore, the protein kinase G inhibitor KT5823 reversed both SNAP- and 8-Br-cGMP-mediated anti-apoptotic events. All these apoptotic phenomena were also suppressed by NO production through neuronal NO synthase gene transfer into PC12 cells. Furthermore, similar findings were observed in differentiated PC12 cells stimulated to undergo apoptosis by NO donors and NGF deprivation. These findings indicate that NO protects against PC12 cell death by inhibiting the activation of caspase proteases through cGMP production and activation of protein kinase G.

A solution-phase synthetic protocol to form two-dimensional (2D) single-layer transition-metal chalcogenides (TMCs) has long been sought; however, such efforts have been plagued with the spontaneous formation of multilayer sheets. In this study, we discovered a solution-phase synthetic protocol, called "diluted chalcogen continuous influx (DCCI)", where controlling the chalcogen source influx (e.g., H2S) during its reaction with the transition-metal halide precursor is the critical parameter for the formation of single-layer sheets as examined for the cases of group IV TMCs. The continuous influx of dilute H2S throughout the entire growth period is necessary for large sheet formation through the exclusive a- and b-axial growth processes. By contrast, the burst influx of highly concentrated H2S in the early stages of the growth process forms multilayer TMC nanodiscs. Our DCCI protocol is a new synthetic concept for single-layer TMCs and, in principle, can be operative for wide range of TMC nanosheets.

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Recent studies show that dysregulated miRNAs play an important role in breast cancer initiation and progression. Here, we identified upregulated expression of miR-1307-3p in breast cancer tissues and that increased level of miR-1307-3p was closely correlated with lower survival rate in breast cancer patients. Consistent with clinical data, our in vitro data show that expression level of miR-1307-3p was significantly increased in breast cancer cell lines compared to human mammary epithelial cell line MCF10A. Overexpression of miR-1307-3p in MCF10A stimulated cell proliferation and caused their growth in soft agar and tumor formation in nude mice. In contrast, inhibition of miR-1307-3p suppressed breast cancer cell proliferation and their growth in soft agar and inhibited tumor formation in nude mice. Further, we identified that miR-1307-3p plays its oncogenic role through targeting SET and MYND domain-containing 4 (SMYD4) expression in breast cancer. Taken together, our findings suggest that miR-1307-3p is a oncogenic miRNA that significantly contributes to breast cancer development and progression, and inhibition of miR-1307-3p may be a novel strategy for inhibits breast cancer initiation and progression.