[Toxoplasma gondii Rhoptry Protein 17 Inhibits the Apoptosis of Mouse Macrophages via Activation of Activator Protein 1 Signaling].

Objective: To investigate the effect of Toxoplasma gondii rhoptry protein 17（ROP17） on γ-interferon (IFN-γ)-induced apoptosis of mouse J774A.1 monocyte macrophages. Methods: The J774A.1 cells were transfected with recombinant plasmid p3×Flag-CMV-14/TgROP17 or empty plasmid p3×Flag-CMV-14. After addition of IFN-γ, flow cytometry and Western blotting were performed to detect apoptosis and the protein levels of phosphorylated c-Jun and apoptosis-related proteins cleaved Caspase-3, Bcl-2, Bcl-xL and Bcl-3. The p3×Flag-CMV-14/TgROP17 plasmid and c-Jun shRNA were co-transfected into J774A.1 cells, after which IFN-γ was added to induce cell apoptosis. The levels of cleaved Caspase-3 and Bcl-3 were analyzed using Western blotting. Results: Flow cytometry showed that the apoptosis rate of cells overexpressing ROP17［（3.73±0.51）%ï¼½ was significantly lower than that of the control cells［（7.78±1.10）%, P<0.05ï¼½. Western blotting showed significant differences in protein levels of phosphorylated c-Jun（0.196±0.028 vs. 0.075±0.010）, Bcl-3（0.461±0.063 vs. 0.108±0.013） and cleaved Caspase 3（0.015±0.004 vs. 0.174±0.026） between the cells overexpressing ROP17 and control cells （all P<0.05）. However, the levels of Bcl-2 and Bcl-xL were not significantly different between the cells overexpressing ROP17 and the control. When the expression of c-Jun and phosphorylation of c-Jun were inhibited by c-Jun shRNA, the relative level of cleaved Caspase 3 in the RNA interferenced cells and control cells was 0.147±0.024 and 0.087±0.010, respectively (P<0.05), and the relative level of Bcl-3 was 0.085±0.010 and 0.162±0.011, respectively (P<0.05). Conclusion: The anti-apoptosis effect of ROP17 is dependent on the phosphorylation of c-Jun and the expression of Bcl-3.

Bioluminescence imaging of DNA synthetic phase of cell cycle in living animals.

Bioluminescence reporter proteins have been widely used in the development of tools for monitoring biological events in living cells. Currently, some assays like flow cytometry analysis are available for studying DNA synthetic phase (S-phase) targeted anti-cancer drug activity in vitro; however, techniques for imaging of in vivo models remain limited. Cyclin A2 is known to promote S-phase entry in mammals. Its expression levels are low during G1-phase, but they increase at the onset of S-phase. Cyclin A2 is degraded during prometaphase by ubiquitin-dependent, proteasome-mediated proteolysis. In this study, we have developed a cyclin A2-luciferase (CYCA-Luc) fusion protein targeted for ubiquitin-proteasome dependent degradation, and have evaluated its utility in screening S-phase targeted anti-cancer drugs. Similar to endogenous cyclin A2, CYCA-Luc accumulates during S-phase and is degraded during G2/M-phase. Using Cdc20 siRNA we have demonstrated that Cdc20 can mediate CYCA-Luc degradation. Moreover, using noninvasive bioluminescent imaging, we demonstrated accumulation of CYCA-Luc in response to 10-hydroxycamptothecin (HCPT), an S-phase targeted anti-cancer drug, in human tumor cells in vivo and in vitro. Our results indicate that a CYCA-Luc fusion reporter system can be used to monitor S-phase of cell cycle, and evaluate pharmacological activity of anti-cancer drug HCPT in real time in vitro and in vivo, and is likely to provide an important tool for screening such drugs.

Stimulation of non-neuronal muscarinic receptors enhances chemerin/ChemR23 system in dysfunctional endothelial cells.

AIMS: Endothelial cells play a pivotal role in vascular intimal inflammation during cardiovascular diseases. The chemerin/ChemR23 system in endothelial cells is one of physiological mechanisms that regulate inflammatory responses. Our previous studies indicated that stimulation of non-neuronal muscarinic receptor (NNMR) improved endothelial dysfunction. However, the relationship between the chemerin/ChemR23 signaling axis and NNMR in endothelial cell is poorly understood. Here, we first investigated whether the modulation of chemerin/ChemR23 signaling axis is involved in NNMR-mediated endothelial protection. MAIN METHODS: Cultured rat aortic endothelial cells (RAECs) were used. The ChemR23 protein expression and chemerin secretion were measured using Western blot analysis. The gene expression level of ChemR23 was examined with reverse transcriptase PCR (RT-PCR). The production of nitric oxide (NO) was determined by a nitrate reductase assay kit. KEY FINDINGS: A sharp decline of chemerin secretion and ChemR23 protein/gene expression was observed in RAECs after exposed to homocysteine at concentration of 0.5 mmol/L. Arecoline (10 µmol/L) pretreatment increased ChemR23 protein expression as well as mRNA expression, and enhanced the secretion of chemerin. Arecoline could also reverse the decreased ChemR23 mRNA expression induced by uric acid, high glucose, or oxidized low-density lipoprotein. Furthermore, the modulation of arecoline on chemerin/ChemR23 signaling axis was absolutely abolished in the presence of the nonselective muscarinic receptors antagonist atropine 1 µmol/L. Additionally, arecoline improved endothelial dysfunction by increasing the reduced NO production induced by uric acid, which was blocked by anti-ChemR23 antibody. SIGNIFICANCE: The chemerin/ChemR23 signaling axis participates in NNMR-mediated protection against endothelial dysfunction in cardiovascular system.

Chemerin/ChemR23 signaling axis is involved in the endothelial protection by K(ATP) channel opener iptakalim.

AIM: To elucidate the modulation of the chemerin/ChemR23 axis by iptakalim-induced opening of K(ATP) channels and to determine the role of the chemerin/ChemR23 axis in the iptakalim-mediated endothelial protection. METHODS: Cultured rat aortic endothelial cells (RAECs) were used. Chemerin secretion and ChemR23 protein expression were investigated using Western blot analysis. The gene expression level of ChemR23 was examined with RT-PCR. In addition, the release of nitric oxide (NO) was measured with a nitric oxide assay. RESULTS: Homocysteine, uric acid, high glucose, or oxidized low-density lipoprotein (ox-LDL) down-regulated the chemerin secretion and ChemR23 gene/protein expression in RAECs as a function of concentration and time, which was reversed by pretreatment with iptakalim (1-10 µmol/L). Moreover, these effects of iptakalim were abolished in the presence of the K(ATP) channel antagonist glibenclamide (1 µmol/L). Both iptakalim and recombinant chemerin restored the impaired NO production in RAECs induced by uric acid, and the effects were abolished by anti-ChemR23 antibodies. CONCLUSION: Iptakalim via opening K(ATP) channels enhanced the endothelial chemerin/ChemR23 axis and NO production, thus improving endothelial function.