Fenglan Li

Polymorphism H558R in the Human Cardiac Sodium Channel SCN5A Gene is Associated with Atrial Fibrillation

Atrial fibrillation (AF) is one of the most common sustained cardiac arrhythmias and its prevalence is increasing worldwide in line with the growing elderly population. Many single nucleotide polymorphisms and mutations are associated with AF, including the common loss-of-function histidine-558-to-arginine (H558R) polymorphism of the human cardiac sodium channel, voltage-gated, type V, α subunit (encoded by the SCN5A gene). The H558R polymorphism results from the T-C transition in the SCN5A gene. This study recruited 135 patients with AF and 296 healthy controls to scan for and perform targeted genotyping of the H558R polymorphism of the SCN5A gene. Logistic regression analysis showed that the TC and CC genotypes (i.e. genotypes that result in the R558 polymorphism) were significantly associated with an increased risk of developing AF. The R558 polymorphism conferred an odds ratio for AF of 3.451 (95% confidence interval 1.718, 6.931). In conclusion, this study provided evidence for the role of the H558R polymorphism of the SCN5A gene in increasing the susceptibility to AF.

MicroRNA-30b-5p Is Involved in the Regulation of Cardiac Hypertrophy by Targeting CaMKIIδ

Background MicroRNAs (miRNAs) participate in the regulation of cardiac hypertrophy. However, it remains largely unknown as to how miRNAs are integrated into the hypertrophic program. Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a hypertrophic signaling marker. It is not yet clear which miRNAs can regulate CaMKIIδ. Purpose In this study, we identified which miRNAs could regulate CaMKIIδ and how to regulate CaMKIIδ. Methods Through computational and expression analyses, miR-30b-5p was identified as a candidate regulator of CaMKIIδ. Quantitative expression analysis of hypertrophic models demonstrated significant down-regulation of miR-30b-5p compared with control groups. Luciferase reporter assay showed that miR-30b-5p could significantly inhibit the expression of CaMKIIδ. Moreover, through gain-of-function and loss-of-function approaches, we found miR-30b-5p could negatively regulate the expression of CaMKIIδ and miR-30b-5p was a regulator of cardiac hypertrophy. Conclusion Our study demonstrates that the expression of miR-30b-5p is down-regulated in cardiac hypertrophy, and restoration of its function inhibits the expression of CaMKIIδ, suggesting that miR-30b-5p may act as a hypertrophic suppressor.

A mutually beneficial relationship between hepatocytes and cardiomyocytes mitigates doxorubicin-induced toxicity

Use of doxorubicin (DOX) is limited by its toxicity in multiple organs. However, the relationship between different organs in response to DOX-induced injury is not well understood. We found that partial hepatectomy correlated with increased DOX-induced heart injury in vivo while supernatant prepared from DOX-treated hepatocytes mitigated DOX-induced cytotoxicity of cardiomyocytes in vitro. Meanwhile, the supernatant of DOX-treated cardiomyocytes mitigated DOX-induced cytotoxicity of hepatocytes. Investigation of the molecular mechanisms underlying these effects found that interleukin 6 (IL-6) was significantly up-regulated in DOX-treated tissues and cells, and supernatant from IL-6 treated cells had a similar effect to that from DOX-treated cells. Although the concentration of secreted IL-6 in supernatant from DOX-treated cells did not significantly differ, blockade of IL-6 signaling, by overexpressing SOCS3, suppressed expression of the downstream molecules trefoil factor family 3 (TFF3) and hepatocyte growth factor (HGF), impaired the mutually beneficial relationship between hepatocytes and cardiomyocytes. In conclusion, our study shows that a mutually beneficial relationship exists between hepatocytes and cardiomyocytes during the acute injury induced by DOX. Moreover, it demonstrates that this phenomenon may be indirectly caused by increased IL-6 expression and the activation of the downstream molecular mediators TFF3 and HGF in hepatocytes and cardiomyocytes, respectively.

MicroRNA‐328 is involved in the effect of selenium on hydrogen peroxide‐induced injury in H9c2 cells

Oxidative stress induces apoptosis in cardiac cells, and antioxidants attenuate the injury. MicroRNAs (miRNAs) are also involved in cell death; therefore, this study aimed to investigate the role of miRNAs in the effect of selenium on oxidative stress‐induced apoptosis. The effects of sodium selenite were analyzed via cell viability, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) concentration. Flow cytometry was used to evaluate cell apoptosis. Fura‐2AM was used to calculate intracellular Ca2+ concentration. Sodium selenite could ameliorate hydrogen peroxide (H2O2)‐induced cell apoptosis and improve expression levels of glutathione peroxidase and thioredoxin reductase. Pretreatment with sodium selenite improved SOD activity and reduced MDA concentration. Treatments with H2O2 or sodium selenite decreased miR‐328 levels. MiR‐328 overexpression enhanced cell apoptosis, reduced ATP2A2 levels, and increased intracellular Ca2+ concentration, while inhibition produced opposite effects. MiR‐328 might be involved in the effect of sodium selenite on H2O2‐induced cell death in H9c2 cells.

Dishevelled-1 (Dvl-1) Protein: a Potential Participant of Oxidative Stress Induced by Selenium Deficiency

Oxidative stress induced by selenium deficiency has been shown to be associated with cardiovascular diseases. Nevertheless, the mechanism associated with oxidative stress induced by selenium deficiency is poorly understood. In the present study, 36 weaning C57BL/6 mice were randomly divided into 4 groups as follows: control (n = 9), 4-week selenium deficiency (n = 9), 8-week selenium deficiency (n = 9), and 12-week selenium deficiency (n = 9). The levels of myocardial glutathione peroxidase (GPx), superoxide dismutase (SOD), and malondialdehyde (MDA) were determined by Western blotting or commercial kits. Real-time PCR was performed to detect the mRNA expression of dishevelled-1 (Dvl-1) protein. Western blotting was conducted to evaluate the protein expression levels of Dvl-1 and β-catenin. Our results demonstrated that the levels of GPx and SOD were significantly reduced, along with an increase in MDA in selenium-deficient mice. Importantly, Dvl-1 and β-catenin were clearly upregulated under oxidative stress. Collectively, our findings indicate that Dvl-1 may be an underlying participant of oxidative stress induced by selenium deficiency.

Recombinant Escherichia coli Trx-JZTX-III represses the proliferation of mouse hepatocellular carcinoma cells through induction of cell cycle arrest

The aim of the present study was to investigate the effects of recombinant Escherichia coli (E. coli) Trx-jingzhaotoxin (JZTX)-III on cell growth in the mouse hepatocellular carcinoma (HCC) cell line Hepa1-6. The JZTX-III gene sequence was synthesized and cloned into the pET-32a(+) vector to construct the recombinant fusion protein Trx-JZTX-III, which was subsequently purified. Hepa1-6 cells were treated with 0 to 1,000-µg/ml concentrations of Trx-JZTX-III; this was demonstrated to affect cell viability, as determined by the 3-(4,5-dimethylthiazol‑2-yl)-2,5-diphenyltetra-zolium bromide (MTT) assay. The expression of the proliferating cell nuclear antigen (PCNA) protein was investigated using western blot analysis. A colony formation assay was used to determine Hepa1-6 cell proliferation, and the migration ability of cells was determined using a wound‑healing assay. Additionally, flow cytometry was employed to observe changes in the cell cycle. The MTT assay and quantification of PCNA expression indicated that recombinant E. coli Trx-JZTX-III significantly repressed the proliferation of Hepa1-6 cells. Colony formation and the migration of malignant cells was inhibited following treatment with recombinant E. coli Trx-JZTX-III. Flow cytometry showed that recombinant E. coli Trx-JZTX-III induced G0/G1 cell cycle arrest. In conclusion, recombinant E. coli Trx-JZTX-III functions as a tumor suppressor drug in mouse HCC and its underlying mechanism may involve the induction of G0/G1 cell cycle arrest.

The role of Sep (O-phosphoserine) tRNA: Sec (selenocysteine) synthase (SEPSECS) in proliferation, apoptosis and hormone secretion of trophoblast cells

OBJECTIVES To investigate whether Sep (O-phosphoserine) tRNA: Sec (selenocysteine) synthase (SEPSECS), which plays an essential role in the synthesis of selenoprotein, affects proliferation, apoptosis and hormone secretion of human trophoblast cells. METHODS Human trophoblast JEG-3 cells were divided into four groups: control group, SEPSECS silenced-expression group, empty vector group and SEPSECS over-expression group. Over-expression and silenced-expression were achieved by transfection with plasmid DNA or RNA oligonucleotide, respectively. 3-[4,5-dimethylthiazol-2-yl] -2,5-diphenyltetrazolium bromide (MTT) and colony formation assays were performed to investigate cell proliferation, while apoptosis was tested by annexin V-FITC, PI double staining and caspases-3 activation assays, enzyme-linked immunosorbent assay (ELISA) was used to determine the level of progesterone (PG) and human chorionic gonadotropin (hCG). RESULTS SEPSECS silenced-expression clearly inhibited proliferation of JEG-3 cells (p < 0.05), significantly induced cell apoptosis (p < 0.01) and reduced the production of PG and hCG (p < 0.05). On the contrary, SEPSECS over-expression significantly promoted both cell proliferation (p < 0.01) and secretion of PG and hCG (p < 0.05). CONCLUSIONS SEPSECS significantly affects proliferation, apoptosis and hormone secretion of human trophoblast cells, suggesting that a potential relationship exists among SEPSECS, cell proliferation, apoptosis and hormone production of human placental trophoblast cells. Furthermore, this may provide a clue to uncover the relationship between selenium and human placental in association with an emphasis on the importance of selenium adequacy during pregnancy.

Aberrant expression profiles of isoproterenol-induced endoplasmic reticulum stress response genes in mouse myocardium†

In this study, we identified the aberrant expression profiles of isoproterenol‐ (ISO; synthetic catecholamine)induced endoplasmic reticulum (ER) stress response genes in mouse myocardium. Mouse models of acute catecholamine cardiotoxicity were induced by ISO for 6, 12, and 24 h. We performed whole genome oligo microarrays of damaged mouse cardiac tissues, and we found 26 ER stress‐related genes whose expression changed significantly for at least one time point. The functional analysis of those genes indicated that myocardial cells were protected by increasing folding capacity, inhibiting general protein translation, and promoting the degradation of misfolded proteins; however, some of them underwent apoptosis in the early stage of ER stress after ISO induced.

Knockdown of Trnau1ap inhibits the proliferation and migration of NIH3T3, JEG-3 and Bewo cells via the PI3K/Akt signaling pathway

The tRNA selenocysteine 1 associated protein 1 (Trnau1ap, initially named SECp43) is involved in Selenocysteine (Sec) biosynthesis and incorporation into selenoproteins, which play a key role in biological processes, such as embryonic development. We previously reported that downregulation of Trnau1ap inhibited proliferation of cardiomyocyte-like H9c2 cells. However, the effects of Trnau1ap on cell proliferation and migration of embryonic development are not known, and the mechanisms remain elusive. Herein, lentiviral shRNA vectors were transfected in NIH3T3, JEG-3 and Bewo cells (embryonic, trophoblast and placental cells). We found that knockdown of Trnau1ap resulted in reduced expression levels of selenoproteins. The data of Cell Count Kit-8 (CCK-8) assay and wound scratch assay revealed the proliferation and migration rates were reduced in the Trnau1ap-shRNA groups. Furthermore, western blot analysis showed that the phosphorylation level of Akt in the phosphatidylinositol 3-kinase (PI3K)/Akt pathway was attenuated. These results indicate that Trnau1ap plays an important role in regulation of cell proliferation and migration through the PI3K/Akt signaling pathway, as well as being essential for embryonic development by regulating the expression of selenoproteins.