MicroRNAs: protective regulators for neuron growth and development.

MicroRNAs (miRNAs) play an important regulatory role in neuronal growth and development. Different miRNAs target different genes to protect neurons in different ways, such as by avoiding apoptosis, preventing degeneration mediated by conditional mediators, preventing neuronal loss, weakening certain neurotoxic mechanisms, avoiding damage to neurons, and reducing inflammatory damage to them. The high expression of miRNAs in the brain has significantly facilitated their development as protective targets for therapy, including neuroprotection and neuronal recovery. miRNA is indispensable to the growth and development of neurons, and in turn, is beneficial for the development of the brain and checking the progression of various diseases of the nervous system. It can thus be used as an important therapeutic target for models of various diseases. This review provides an introduction to the protective effects of miRNA on neurons in case of different diseases or damage models, and then provides reference values and reflections on the relevant treatments for the benefit of future research in the area.

α- and ß-adrenoceptors of zebrafish in melanosome movement: a comparative study between embryo and adult melanophores.

Zebrafish, like other teleosts, display rapid skin color change in response to the background through sympathetic nerves. Here, the α- and ß-adrenoceptors of melanophores were studied pharmacologically both in zebrafish embryo and adult scale. In vitro experiments on adult scale melanophores demonstrated that both α1- and α2-adrenoceptors are functional in melanosome aggregation, the α2 subtype being predominant. Most melanophores in zebrafish embryos were able to concentrate melanosomes to α2-adrenergic agonist α-methylnorepinephrine when they first appeared. This ability increased at least in the following 48 h, showing melanophores at these stages have developed functional adrenoceptors and these receptors increase independently before sympathetic innervation. However, even high concentration (10(-3) M) of α1-adrenoceptor agonist phenylephrine was not able to evoke any paling of the embryos. In adult scales, propranolol enhanced the melanosome-aggregating response of epinephrine and isoproterenol, but not norepinephrine, indicating ß-adrenoceptor mediates melanosome-dispersing response in adult zebrafish. Similar response was not observed in embryos until 60 h post-fertilization (hpf). The melanophore adrenoceptor blocking effects of phentolamine and propranolol in embryos were much lower than that in adult zebrafish, suggesting these adrenoceptors in developing melanophores are less sensitive to the classical antagonists.

Development and applications of a nasopharyngeal carcinoma Tet-Off cell line.

The conditional activation and inactivation of target gene expression in a nasopharyngeal carcinoma (NPC) cell line is beneficial for the study of the roles of NPC-related genes. Based on the Tet-Off Advanced system, a NPC S18 Tet-Off cell line was developed by stable transfection of a pTet-Off Advanced vector (regulator plasmid in Tet-Off Advanced system) into NPC S18 cells. Doxycycline-dependent regulators expressed in the S18 Tet-Off cells were examined by transient and stable transfection of pTRE-Tight-Luc. The S18 Tet-Off-Luc clone selected by stable transfection of pTRE-Tight-Luc into S18 Tet-Off cells expressed firefly luciferase under tight control of doxycycline in a time- and dose-dependent manner. To test applications of the S18 Tet-Off cell line in the study of gene function, the impact of ferritin heavy chain (FTH1) gene on NPC cell growth was examined. The S18 Tet-Off-FTH1 clone was developed by stably transfecting pTRE-Tight-FTH1 (response plasmid harboring FTH1) into S18 Tet-Off cells. FTH1 levels in the S18 Tet-Off-FTH1 clone were semi-quantitatively regulated in response to varying concentrations of doxycycline. A cell proliferation assay showed that a high expression of FTH1 (cells grown in the absence of doxycycline) reduced cell growth, while moderate FTH1 overexpression (cells grown in 0.1 ng/ml doxycycline) had no adverse effect on cell growth. In conclusion, the S18 Tet-Off cell line provides a proven genetic background for convenient access to controllable gene expression in NPC.

Sodium benzoate exposure downregulates the expression of tyrosine hydroxylase and dopamine transporter in dopaminergic neurons in developing zebrafish.

BACKGROUND: Recent data have demonstrated that treatment with sodium benzoate (SB) leads to significant developmental defects in motor neuron axons and neuromuscular junctions in zebrafish larvae, thereby implying that SB can be neurotoxic. This study examined whether SB affects the development of dopaminergic neurons in the zebrafish brain. METHODS: Zebrafish embryos were exposed to different concentrations of SB for various durations, during which the survival rates were recorded, the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the neurons in the ventral diencephalon were detected by in situ hybridization and immunofluorescence, and the locomotor activity of larval zebrafish was measured. RESULTS: The survival rates were significantly decreased with the increase of duration and dose of SB-treatment. Compared to untreated clutch mates (untreated controls), treatment with SB significantly downregulated expression of TH and DAT in neurons in the ventral diencephalon of 3-day post-fertilization (dpf) zebrafish embryos in a dose-dependent manner. Furthermore, there was a marked decrease in locomotor activity in zebrafish larvae at 6dpf in response to SB treatment. CONCLUSIONS: The results suggest that SB exposure can cause significantly decreased survival rates of zebrafish embryos in a time- and dose-dependent manner and downregulated expression of TH and DAT in dopaminergic neurons in the zebrafish ventral diencephalon, which results in decreased locomotor activity of zebrafish larvae. This study may provide some important information for further elucidating the mechanism underlying SB-induced developmental neurotoxicity.