Inhibitory Effects of Neferine on Na_v1.5 Channels Expressed in HEK293 Cells

Neferine, a bisbenzylisoquinoline alkaloid in Lotus Plumule, was proved to have a wide range of biological activities. In the present study, using whole-cell patch-clamp technique, we investigated the effects of neferine on Nav1.5 channels that are stably expressed in HEK 293 cells. We found that neferine potently and reversibly inhibited Nav1.5 currents in a concentration dependent manner with a half-maximal inhibition（IC50） being 26.15 μmol/L. The inhibitory effects of neferine on Nav1.5 currents were weaker than those of quinidine at the same concentration. The steady-state inactivation curve was significantly shifted towards hyperpolarizing direction in the presence of 30 μmol/L neferine, while the voltage-dependent activation was unaltered. Neferine prolonged the time to peak of activation, increased the inactivation time constants of Nav1.5 currents and markedly slowed the recovery from inactivation. The inhibitory effect of neferine could be potentiated in a frequency-dependent manner. These results suggested that neferine can block Nav1.5 channels under the open state and inactivating state and it is an open channel blocker of Nav1.5 channels.

Cellular Oxidative Damage of HEK293T Cells Induced by Combination of CdCl_2 and Nano-TiO_2

This study investigated the conjoined cellular oxidative damage of human embryo kidney 293T（HEK293T） cells induced by cadmium chloride（CdCl2） and nanometer titanium dioxide（nano-TiO2）.RT-PCR technique was used to detect the expressions of Heme oxygenase-1（HO-1） and 8-oxoguanine DNA glycosylase（OGG1）.The activities of superoxide dismutase（SOD） and catalase enzyme（CAT） and concentrations of reactive oxygen species（ROS） and maldondialdehyde（MDA） were measured by different approaches.The results showed that CdCl2 and nano-TiO2 at a low concen-tration of 0.75 total toxic unit（TU） exerted an additive effects on HO-1 gene expression,CAT activities and MDA concentrations.When the total TU was increased to 1 or 1.25 TU,the interaction was syner-getic.Moreover,the mixture with high proportion of CdCl2 produced an additive effect on the OGG1 gene expression,and the interaction was changed to be synergetic when the concentration of CdCl2 was lower than or equal to that of nano-TiO2.Synergetic effects of CdCl2 and nano-TiO2 on cellular oxida-tive damage of HEK293T cells were found as indicated by the changes in the SOD activities and ROS concentrations.It was concluded that CdCl2 and nano-TiO2 exerts synergistic effects on the cellular oxidative damage of HEK293T cells,and the sensitivity of these indicators of oxidative damage varies with the proportion of CdCl2 and nano-TiO2 in the mixture.

Protective Effect of Reduced Glutathione C_(60) Derivative against Hydrogen Peroxide-induced Apoptosis in HEK 293T Cells

Hydrogen peroxide（H_2O_2） and free radicals cause oxidative stress, which induces cellular injuries, metabolic dysfunction, and even cell death in various clinical abnormalities. Fullerene（C_（60）） is critical for scavenging oxygen free radicals originated from cell metabolism, and reduced glutathione（GSH） is another important endogenous antioxidant. In this study, a novel water-soluble reduced glutathione fullerene derivative（C_（60）-GSH） was successfully synthesized, and its beneficial roles in protecting against H_2O_2-induced oxidative stress and apoptosis in cultured HEK 293 T cells were investigated. Fourier Transform infrared spectroscopy and 1H nuclear magnetic resonance were used to confirm the chemical structure of C_（60）-GSH. Our results demonstrated that C_（60）-GSH prevented the reactive oxygen species（ROS）-mediated cell damage. Additionally, C_（60）-GSH pretreatment significantly attenuated H_2O_2-induced superoxide dismutase（SOD） consumption and malondialdehyde（MDA） elevation. Furthermore, C_（60）-GSH inhibited intracellular calcium mobilization, and subsequent cell apoptosis via bcl-2/bax-caspase-3 signaling pathway induced by H_2O_2 stimulation in HEK 293 T cells. Importantly, these protective effects of C_（60）-GSH were superior to those of GSH. In conclusion, these results suggested that C_（60）-GSH has potential to protect against H_2O_2-induced cell apoptosis by scavenging free radicals and maintaining intracellular calcium homeostasis without evident toxicity.

Electrophysiology of hyperpolarization-activated cyclic nucleotidegated cation channel 2 and hyperpolarization-activated cyclic nucleotide-gated cation channel 4 expressed in HEK293 cells

The action potential of pacemaker cells in the sino-atrial node forms the automatic rhythm of the heart. The automatic depolarization in phase 4 is me DaSlS of the automaticity in pacemaker cells. Many currents are included in phase 4, such as calcium current, TTX-sensitive sodium current, sustained inward current （Isi）, decay of delayed rectifier potassium current, etc. Funny current （If） has long been recognized as important in this phase and is activated at hyperpolarized potentials during cell diastole and in turn activates other currents to form automatic depolarization.

Expression of fluorescent tagged recombinant erythroferrone protein

Objective: To produce fluorescent tagged recombinant erythroferrone protein(ERFE_eGFP) for laboratory investigations. Methods: Erythroferrone(ERFE) gene was fused to green fluorescent protein(eGFP) gene and cloned in a pSecTag2Hygro plasmid. The constructed plasmid was amplified in Escherichia coli DH5α and the eGFP-fused ERFE(ERFE_eGFP) protein was expressed in human embryonic kidney(HEK293T) cell line. Results: The plasmid constructed from colony C6 contained ERFE_eGFP with the correct restriction sizes of 4.2 kb and expressed secretory ERFE_eGFP fusion protein(approximately size of 75 kDa) in HEK293T cell line. Conclusions: ERFE_eGFP recombinant protein is successfully expressed as a secretory functional protein and could be sensitively detected using fluorometry. This fusion protein might benefit future applications for localization of cellular ERFE receptors and competitive immunoassay of ERFE concentration.

Construction of recombinant human nerve growth factor beta adenovirus and evaluation of its function An in vitro and in vivo study

Exogenous delivery of nerve growth factor （NGF） promotes neural regeneration. However, the short half-life limits delivery efficacy. Therefore, a long-term, efficient, local delivery tool or scheme is needed. The purpose of this study was to construct a functioning, recombinant, adenoviral vector carrying human NGF-β （hNGF-β） DNA, and to measure expression of the constructed vector in vitro and in vivo. rhNGF-β adenoviral vector containing full-length hNGF-β cDNA was generated by homologous recombination in Escherichia CoIL The rhNGF-β adenovirus was packaged and amplified in human embryonic kidney HEK293 cells. Transformation efficiency, expression and function of rhNGF-β adenovirus for primary Schwann cells, Schwann cell lines, human embryonic kidney HEK 293 cells, CRH myoblasts, and NIH3T3 fibroblasts were evaluated. Subsequently, expression of rhNGF-β adenovirus at the peripheral nerve of rat was also assessed. Recombinant adenoviral vector carrying hNGF-β was successfully constructed and confirmed by restriction endonuclease analysis and DNA sequence analysis. Green fluorescent protein expression was observed in 90% of rhNGF-β adenovirus-infected cells （primary Schwann cells, Schwann cell line, human embryonic kidney HEK 293 cells, CRH myoblasts, and NIH3T3 fibroblasts） compared with non-infected cells. Total mRNA isolated from rhNGF-β adenovirus-infected cells exhibited strong expression. Maximum NGF release was induced by primary cultured Schwann cells at 4 days after infection, which steadily continued for 14 days. PC-12 cells exposed to media conditioned with rhNGF-β adenovirus-infected Schwann cells exhibited increased neurite extension. In vivo experiment revealed that the injected rhNGF-β adenovirus was transfected into the cells at the injected site and promoted expression of NGF, p75NTR and brain derived neurotrophic factor at the sciatic nerve and dorsal root ganglia.

Construction of eukaryotic expression vector of humanarresten gene and its secreted expression in HEK 293 cells

The eukaryotic expression vector of human arresten gene was constructed and its secretive expression in human embryonic kidney(HEK 293)cells was detected.Human arresten gene was amplified from recombinant plasmid pGEM-Arr by polymerase chain reaction(PCR),and then digested with restriction endonucleases BamH I and EcoR I.The target fragment was inserted into the BamH I and EcoR I restriction sites of eukaryotic expression vector pSecTag2 to construct pST-AT.Restric-tion analysis and DNA sequencing indicated that the arresten gene was successfully inserted into pSecTag2.The recombinant plasmid was subsequently transfected into HEK 293 cells with LipofectAMINETM2000 Reagent,and the expression of the target gene was detected.Reverse transcription PCR(RT-PCR)revealed that the mRNA of the target gene was transcribed in the transfected HEK 293 cells.Western blot analysis verified that the recombinant protein in supernatants was correct.The supernatants of transfected cells were prepared,and 3-(4,5)-dimethylthiazol(-2-y1)-3,5-di-phenyltetrazoliumbromide(MTT)assay was carried out to assess their effects on the proliferation of human umbilical vein endothelial cells,which showed that the recombinant protein could significantly suppress the proliferation of human umbilical vein endothelial cells in vitro.These results provided a solid foundation to explore the usage of arresten in tumor anti-angiogenic gene therapy.

Cytotoxicity assessment of a gold nanoparticle-chitosan nanocomposite as an efficient support for cell immobilization:comparison with chitosan hydrogel and chitosan-gelatin

Cell-based biosensors have become a research hotspot in the biosensors and bioelectronics fields. The main feature of cell-based biosensors is immobilization of living cells on the surface of transducers. Different types of polymers which are used as scaffolds for cell growth should be biocompatible and should have reac- tive functional groups for further attachment of biomolecules. In this work, cell attachment and proliferation on chitosan hydrogel, chitosan-gelatin and gold nanoparticle-chitosan nanocomposite membranes was stud- ied. Characterization of the membranes was performed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Cytotoxicity assessment on HEK293 cells was carried out for all mem- branes using the MTT assay. Cell morphology and viability were assessed to evaluate cell attachment and pro- liferation. Regarding cell studies, the findings revealed that none of the membranes induced cytotoxic effects. However, the data showed that gold nanoparticle nanocomposite membranes improved HEK293 attachment and adhesion more than other membranes, indicating that it provides an effective surface for immobilizing cells for sensing applications.

Heterologous expression and cell membrane localization of dinoflagellate opsins (rhodopsin proteins) in mammalian cells

Rhodopsins are now found in all domains of life,and are classified into two large groups:type II,found in animals and type I found in microbes including Bacteria,Archaea,and Eukarya.While type II rhodopsin functions in many photodependent signaling processes including vision,type 1 among others contains rhodopsins that function as a light-driven proton pump to convert light into ATP as in proteobacteria(named proteorhodopsin).Proteorhodopsin homologs have been documented in dinoflagellates,but their subcellular localizations and functions are still poorly understood.Even though sequence analyses suggest that it is a membrane protein,experimental evidence that dinoflagellate rhodopsins are localized on the plasma membrane or endomembranes is still lacking.As no robust dinoflagellate gene transformation tool was available,we used HEK 293T cells to construct a mammalian expression system for two dinoflagellate rhodopsin genes.The success of expressing these genes in the system shows that this mammalian cell type is suitable for expressing dinoflagellate genes.Immunofluorescence of the expressed protein locates these dinoflagellate rhodopsins on the cell membrane.This result indicates that the protein codons and membrane targeting signal of the dinoflagellate genes are compatible with the mammalian cells,and the proteins'subcellular localization is consistent with proton pump rhodopsins.