Aihua Gong

Synthesis of highly photoluminescent carbon dots via citric acid and Tris for iron(III) ions sensors and bioimaging

In this work, high quantum yield and strong photoluminescent carbon quantum dots (C-QDs) are successfully synthesized via a facile and green hydrothermal method using citric acid and Tris as precursors. The as-synthesized C-QDs with a quantum yield (QY) as high as 52% were characterized by UV, FT-IR, TEM, XPS and fluorescence spectroscope. TEM results show that C-QDs are mono-dispersed spherical particles and the diameter distribution of C-QDs is 2.8±1.1 nm. The extraordinary photoluminescent properties and low cytotoxicity of C-QDs were obtained through optical property characterization and cytotoxicity assay. In addition, we found that the as-prepared C-QDs had a high affinity for Fe(3+) ions and the response toward Fe(3+) ions was highly linear (R(2)=0.997) over the concentration range from 2 to 50 μM, which could provide an effective platform for portable detection of Fe(3+) ions. Also, it is demonstrated that the photoluminescent C-QDs display hypotoxicity and are biocompatible for use as biosensors in living cells.

Economical and green synthesis of bagasse- derived fluorescent carbon dots for biomedical applications

Carbon quantum dots (CDs) are promising nanomaterials in biomedical, photocatalytical and photoelectronic applications. However, determining how to explore an ideal precursor for a renewable carbon resource is still an interesting challenge. Here, for the first time, we report that renewable wastes of bagasse as a new precursor were prepared for fluorescent CDs by a hydrothermal carbonization (HTC) process. The characterization results show that such bagasse-derived CDs are monodispersed, contain quasi spherical particles with a diameter of about 1.8 nm and exhibit favorable photoluminescence properties, super-high photostability and good dispersibility in water. Most importantly, bagasse-derived CDs have good biocompatibility and can be easily and quickly internalized by living cancer cells; they can also be used for multicolour biolabeling and bioimaging in cancer cells. It is suggested that bagasse-derived CDs might have potential applications in biomedical and photoelectronic fields.

Role of histone methylation in zygotic genome activation in the preimplantation mouse embryo

Numerous previous studies demonstrated that gene expression was influenced by histone modifications. However, little information is available about the relation of histone methylation with embryonic gene expression. Here, we examine the significance of histone H3 dimethyl-lysine 4 (H3K4me2) during mouse zygotic genome activation (ZGA) by inhibiting demethylation with the specific histone H3 lysine 4 demethylase inhibitor bisguanidine 1c (1c). A 1c treatment of one-cell embryos did not significantly affect the level of eIF-4C transcripts but did affect Oct4 levels by the two-cell stage. Furthermore, 1c treatment significantly inhibited cleavage of the embryos to the four-cell stage (from 82.7% to 18.2%), and the inhibitory effect was identified to be irreversible. These results suggest that histone methylation may be closely correlated with the formation of a transcriptionally repressive state during ZGA and that the repressive state actually dictates the appropriate pattern of gene expression required for further development.

Dynamic patterns of histone H3 lysine 4 methyltransferases and demethylases during mouse preimplantation development

Extensive and dynamic chromatin remodeling occurs after fertilization, including DNA methylation and histone modifications. These changes underlie the transition from gametic to embryonic chromatin and are thought to facilitate early embryonic development. Histone H3 lysine 4 methylation (H3K4me) is an important epigenetic mechanism that associates with gene-specific activation and functions in development. However, dynamic regulation of H3K4me during early embryonic development remains unclear. Herein, the authors examined the dynamic changes of H3K4me and its key regulators (Ash1l, Ash2l, Kmt2a, Kmt2b, Kmt2c, Setd1a, Setd7, Kdm1a, Kdm1b, Kdm5a, Kdm5b, Kdm5c, and Kdm5d) in mouse oocytes and preimplantation embryos. An increase in levels of H3K4me2 and me3 was observed at the one- to two-cell stages (P < 0.05), corresponding to the period of embryonic genome activation (EGA). Subsequently, the H3K4me2 level dramatically decreased at the four-cell stage and remained at low level until the blastocyst stage (P < 0.05), whereas the H3K4me3 level transiently decreased in the four-cell embryos but steadily increased to the peak in the blastocysts (P < 0.05). The high level of H3K4me2 during the EGA was coinciding with a peak expression of its methyltransferase, ASH2L, which may stabilize this methylation level during this period. Correspondingly, a concomitant decrease in levels of its demethylases, KDM5B and KDM1A, was observed. H3K4me3 was correlated to the expression of its methyltransferase (KMT2B) and demethylase (KDM5A). Thus, these enzymes may function for the EGA and the first lineage segregation in preimplantation mouse embryos.

Fibrin Scaffolds Containing Ectomesenchymal Stem Cells Enhance Behavioral and Histological Improvement in a Rat Model of Spinal Cord Injury

Fibrin has been widely used in wound healing. However, its benefit for spinal cord injury (SCI) is limited. In this study, we investigated the impact of fibrin scaffolds containing ectomesenchymal stem cells (EMSCs) on histological and behavioral recovery after SCI and compared it with fibrin alone. To achieve this, EMSCs derived from adult rat nasal respiratory mucosa were cultured, characterized and transfected with green fluorescent protein adenovirus before transplantation. Then, Sprague-Dawley host rats were randomly assigned into four groups: the control group (laminectomy); the SCI group (laminectomy and transection of spinal cords); the fibrin group (fibrin was transplanted immediately after SCI), and the fibrin cell (FC) group (fibrin scaffolds containing EMSCs were transplanted after SCI). Three days after the operation, a TUNEL assay indicated less apoptotic cells in the FC group than in the fibrin group. Two weeks after SCI, fluorescence staining demonstrated not only the survival and migration of EMSCs into the lesion sites, but also a higher number of nerve fibers in the FC group than in the fibrin group. Histological examination including immunohistochemistry and transmission electron microscopy 12 weeks after the operation showed more nerve fibers and a thicker myelin sheath in the FC group compared to the fibrin group. Western blotting confirmed these morphological results. Consistent with the histological results, Basso, Beattie and Bresnahan locomotor scores of the FC group were higher than those of the fibrin group. These results suggest that fibrin scaffolds containing EMSCs can improve the behavioral and histological recovery after SCI better than fibrin alone.

Autophagy contributes to ING4-induced glioma cell death

Previous studies suggest that ING4, a novel member of ING (inhibitor of growth) family, can inhibit brain tumor growth. However, whether autophagy is involved in ING4-induced cell death still remains unknown. In this study, we found that in addition to apoptosis, autophagy also contributed to cell death induced by ING4. Autophagy levels were elevated following the exposure to Ad-ING4, including enhanced fluorescence intensity of monodansylcadervarine (MDC), a specific in vivo marker for autophagic vacuoles, and increased expression levels of the LC3-II and Beclin-1, wheras the autophagic levels were attenuated following the pretreatment of 3-MA, the inhibitor of autophagy, which significantly decreased the Ad-ING4-induced cell death compared with caspase inhibitor zVAD. Furthermore, ING4 also induced mitochondrial dysfunction, such as mitophagy, collapse of mitochondrial membrane potential and the intracellular ROS, which indicated that mitochondria might be associated with the process of autophagic cell death of glioma cells. Finally, the relationship among Bax, Bcl-2, Beclin-1 and caspase family proteins levels were analyzed in glioma cells U251MG and LN229 infected with Ad-ING4 or Ad-lacZ. It is suggested that both autophagy and apoptosis could contribute to ING4-induced glioma cell death, and mitochondria might play an important role in this process. Our findings reveal novel aspects of the autophagy in glioma cells that underlie the cytotoxic action of ING4, possibly providing new insights in the development of combinatorial therapies for gliomas.

Lysine-specific demethylase 1 mediates epidermal growth factor signaling to promote cell migration in ovarian cancer cells

Epigenetic abnormalities play a vital role in the progression of ovarian cancer. Lysine-specific demethylase 1 (LSD1/KDM1A) acts as an epigenetic regulator and is overexpressed in ovarian tumors. However, the upstream regulator of LSD1 expression in this cancer remains elusive. Here, we show that epidermal growth factor (EGF) signaling upregulates LSD1 protein levels in SKOV3 and HO8910 ovarian cancer cells overexpressing both LSD1 and the EGF receptor. This effect is correlated with a decrease in the dimethylation of H3K4, a major substrate of LSD1, in an LSD1-dependent manner. We also show that inhibition of PI3K/AKT, but not MEK, abolishes the EGF-induced upregulation of LSD1 and cell migration, indicating that the PI3K/PDK1/AKT pathway mediates the EGF-induced expression of LSD1 and cell migration. Significantly, LSD1 knockdown or inhibition of LSD1 activity impairs both intrinsic and EGF-induced cell migration in SKOV3 and HO8910 cells. These results highlight a novel mechanism regulating LSD1 expression and identify LSD1 as a promising therapeutic target for treating metastatic ovarian cancer driven by EGF signaling.

Engineering iodine-doped carbon dots as dual-modal probes for fluorescence and X-ray CT imaging

X-ray computed tomography (CT) is the most commonly used imaging technique for noninvasive diagnosis of disease. In order to improve tissue specificity and prevent adverse effects, we report the design and synthesis of iodine-doped carbon dots (I-doped CDs) as efficient CT contrast agents and fluorescence probe by a facile bottom-up hydrothermal carbonization process. The as-prepared I-doped CDs are monodispersed spherical nanoparticles (a diameter of ~2.7 nm) with favorable dispersibility and colloidal stability in water. The aqueous solution of I-doped CDs showed wavelength-dependent excitation and stable photoluminescence similar to traditional carbon quantum dots. Importantly, I-doped CDs displayed superior X-ray attenuation properties in vitro and excellent biocompatibility. After intravenous injection, I-doped CDs were distributed throughout the body and excreted by renal clearance. These findings validated that I-doped CDs with high X-ray attenuation potency and favorable photoluminescence show great promise for biomedical research and disease diagnosis.

MicroRNA-29c/PTEN Pathway is Involved in Mice Brain Development and Modulates Neurite Outgrowth in PC12 Cells

Growing evidence indicates that microRNAs (miRNAs) are important mediators of brain development and neurite growth. However, the affected signaling mechanisms are not clearly clarified. In the present study, we confirm that miR-29c is expressed during mice brain development and increases neurite outgrowth via decreasing PTEN expression. We first screen the picked-out miR-29c up-regulated in PC12 cells induced by nerve growth factor (NGF). In silico analysis of possible miR-29c targets, VEGFA, MAPK3, PDGFB, and PTEN mRNA are proposed as relatively likely putative binding sites for miR-29c. Subsequently, we detect that miR-29c is involved in brain development and has a negative relationship with the expression of PTEN. Then, using luciferase reporter assay,we demonstrate that miR-29c could directly target to the 3′-UTR of PTEN mRNA and result in down-expression of PTEN. By infecting PC12 cells with lentiviral pLKO-miR-29c or control, we also find that increasing levels of miR-29c markedly increase Akt phosphorylation level, and thus, promote neurite outgrowth of PC12 cells. Together, our results identify that miR-29c is required for mice brain development and modulates neurite outgrowth in PC12 cells via targeting PTEN and has a promising therapeutic target for neural disease.

Egr-1 promotes hypoxia-induced autophagy to enhance chemo-resistance of hepatocellular carcinoma cells.

Previous studies suggest that early growth response gene-1 (Egr-1) plays an important role in hypoxia-induced drug-resistance. However, the mechanism still remains to be clarified. Herein, we investigated the role of Egr-1 in hypoxia-induced autophagy and its resulted hypoxia-driven chemo-resistance in Hepatocellular Carcinoma (HCC) cells. Our data demonstrated that Egr-1 was overexpressed in HCC tissues and cells and conferred them drug resistance under hypoxia. Mechanistically, Egr-1 transcriptionally regulated hypoxia-induced autophagy by binding to LC3 promoter in HCC cells, which resulted in resistance of HCC cells to chemotherapeutic agents; while dominant negative Egr-1 could inhibit autophagy level, and thus enhanced the sensitivity of HCC cells to chemotherapeutic agents, indicating that hypoxia-induced Egr-1 expression enhanced drug resistance of HCC cells likely through autophagy. Accordingly, it is suggested that a mechanism of hypoxia/Egr-1/autophagy axis might be involved in drug resistance in HCC.