Mitochondrial Transmembrane Potential In Cells Research Articles

Nano-silicon Dioxide Affects Apoptosis of Alveolar Macrophages via PI3K/AKt Signaling Pathway

To investigate the effect of phosphatidyl inositol 3-kinase/protein kinase B (PI3K/AKt) signaling pathway on the apoptosis of alveolar macrophages (AM) induced by nano-silica (NS) dust. After exposure to different concentrations of NS suspension, CCK-8 assay was used to detect the AM viability; the cellular morphology of apoptotic AM was observed under fluorescence microscopy; the apoptosis rate and mitochondrial transmembrane potential of cells were detected by flow cytometry before and after pretreatment with phosphatidyl inositol 3-kinase (PI3K) inhibitor LY294002; Western blot was used to detect the expression of apoptosis-related proteins Bax, Bcl-2, p-PI3K and p-AKt. The survival rate of AM was decreased in a time-dose relationship after NS exposure. With LY294002 pretreatment, the mitochondrial transmembrane potential level and the expressions of p-PI3K, p-AKt and Bcl-2 were decreased, the expression of Bax and the apoptosis rate were increased. Our data suggested that the activation of PI3K/AKt signaling pathway played an important role in NS-induced apoptosis in alveolar macrophages.

Organoruthenium Complexes with C^N Ligands are Highly Potent Cytotoxic Agents that Act by a New Mechanism of Action.

Our study demonstrates that four novel kinetically inert C,N-cyclometalated RuII complexes of the type [Ru(C^N)(N^N)2 ][PF6 ] containing a handle for functionalization on the C^N ligand are very potent cytotoxic agents against several different human cancer cell lines and are up to 400-fold more potent than clinically used cisplatin. In addition, the investigated ruthenium complexes are less cytotoxic in noncancerous cells, and exhibit higher selectivity for cancer cells than conventional platinum anticancer drugs. The high potency of the investigated ruthenium compounds can be attributed to several factors, including enhanced internalization and their capability to change mitochondrial transmembrane potential in cells. The new ruthenium complexes also interfere with protein synthesis with a markedly higher potency than conventional inhibitors of DNA translation. Notably, the latter mechanism has not been hitherto described for other cytotoxic Ru compounds and cisplatin.

Resveratrol Suppresses Oxidised Low-Density Lipoprotein-Induced Macrophage Apoptosis through Inhibition of Intracellular Reactive Oxygen Species Generation, LOX-1, and the p38 MAPK Pathway

Background/Aim: Resveratrol (RSV) may have therapeutic potential for various diseases. Here we investigated the effect of RSV on oxidised low-density lipoprotein- (ox-LDL) induced apoptosis in RAW264.7 macrophages. Methods: Apoptosis of macrophages following incubation with ox-LDL (with or without RSV pre-treatment) was detected by flow cytometry. Western blotting was used to assess the protein expression of Bax, Bcl-2, and caspase-3 as well as ox-LDL receptor 1 (LOX-1) and p38 mitogen-activated protein kinase (MAPK) phosphorylation. Reactive oxygen species (ROS) generation was evaluated by 2', 7'-dichlorofluorescein diacetate, and JC-1 probe was used to determine the mitochondrial transmembrane potential of cells. Results: Ox-LDL significantly reduced viability and increased the rate of apoptosis (P < 0.05) in RAW264.7 cells. However, pre-treatment with RSV resulted in a remarkable decrease in this apoptotic effect. Moreover, ox-LDL caused the up-regulation of Bax and the down-regulation of Bcl-2, as well as the activation of caspase-3. Expression of LOX-1, phosphorylation of p38 MAPK, and intracellular ROS production also increased after ox-LDL stimulation. Strikingly, these effects were abolished by pre-treatment of cells with RSV. Conclusion: RSV suppresses ox-LDL-induced macrophage apoptosis. These beneficial effects might be exerted through inhibition of ROS generation, LOX-1, and the p38 MAPK signalling pathway.

Neuroprotective effect of melatonin against ischemia/reperfusion-induced neuronal apoptosis in mouse cerebellum

Background Some experiments have demonstrated that melatonin (N-aceyl-5-methoxytryptamine, Mel) has antioxidation. However, whether it has neuroprotective effect in the ischemia/reperfusion injury of central nervous system is unclear. Objective To observe the protective effect of Mel on ischemia/reperfusion-induced cerebellar neuronal apoptosis of rats, and the action mechanism. Design Controlled observation experiment. Setting Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology. Materials Eight Sprague-Dawley rats aged 7–8 days and weighing 10–12 g were provided by Medical Experimental Animal Center, Tongji Medical College, Huazhong University of Science and Technology. Anti-cytochrome C monoclonal antibody was purchased from R & D Company; 7-dichlorodihydrofluorescein diacetate(DCFH-DA), rhodamine 123 and Mel were purchased from Sigma Company (USA). Lactate dehydrogenase (LDH) kit was purchased from Nanjing Jiancheng Bioengineering Institute. Methods This experiment was carried out in the laboratory for Department of Biochemistry and Molecule Biology, Tongji Medical College between October 2002 and March 2004. Cerebellar neurons of rats were cultured in vitro. After oxygen-glucose deprivation (OGD) for 90 minutes, 1×10 −4,1×10 −6, 1×10 −9 mol/L Mel was added, respectively, namely high-, middle-, and low-concentration Mel groups. Cells, which were cultured by OGD, served as model group, and control group, in which OGD intervention was omitted, was set. ▪Cytochrome C level of mitochondrial cells in each group was detected by ELISA method. ▪LDH activity in the cell culture fluid was measured, and cell membrane permeability change was analyzed. The cells in the Mel group with the lowest LDH activity served as Mel treatment group, i.e. cells were cultured with OGD, and then Mel was added; Meanwhile, Mel prevention group was set, i.e. Mel was added before OGD. Intervention was not changed in the model group and control group. ▪ DNA level was analyzed and cell apoptosis was observed by agarose gel electrophoresis(AGE). ▪Mitochondrial transmembrane potential of cells, and apoptotic way in each group were analyzed by confocal laser scanning microscopy. Main Outcome Measures ▪Mitochondrial cytochrome C level of cerebellar nerve cells. ▪LDH activity of cerebellar nerve cells. ▪ DNA AGE results. ▪Mitochondrial transmembrane potential change. Results ▪Mitochondrial cytochrome C level of cerebellar nerve cells: cytochrome C was obviously released at 6 hours of OGD-reperfusion. Mel inhibited the release of cytochrome C in dose-dependent manner. ▪LDH activity of cerebellar nerve cells: LDH activity ( A value) was significantly lower in the high- and middle-concentration Mel groups than in the model group ( P < 0.05). LDH activity ( A value) in the low-concentration Mel group was 0.415 0±0.012 9, indicating that Mel could decrease LDH activity of OGD-treated cell supernatant and promote membrane stablization in dose-dependent manner. ▪AGE results of DNA: 1×10 −9 mol/L was considered as the best concentration of melatonin. Cell DNA was extracted for AGE. Results presented typical ladder shape, indicating apoptosis appeared, while apoptosis was lessened in the Mel treatment group and Mel prevention group. ▪Mitochondrial transmembrane potential change: Experimental results showed that green fluorescein was evenly distributed in cerebellar granule cells cultured normally, and the axons of neurons were very clear. The body of neurons was condensed and the axons disappeared after cerebellar granule cells undergoing OGD injury. Mel could completely reverse the effect of OGD. Conclusion Mel can enhance cerebellar neuronal membrane stabilization of rats in dose-dependent manner, and suppress OGD-induced apoptosis of cerebellar granule cells by preventing against mitochondrial apoptosis.

Amino acid signaling through the mammalian target of rapamycin (mTOR) pathway: Role of glutamine and of cell shrinkage

Mammalian target of rapamycin (mTOR) mediates a signaling pathway that couples amino acid availability to S6 kinase (S6K) activation, translational initiation and cell growth rate, participating to a versatile checkpoint that inspects the energy status of the cell. The pathway is activated by branched-chain amino acids (BCAA), leucine being the most effective, whereas amino acid dearth and ATP shortage lead to its deactivation. Glutamine- or amino acid-deprivation and hyperosmotic stress induce a fast cell shrinkage (with marked decrease of the intracellular water volume) associated to mTOR-dependent S6K1 dephosphorylation. Using cultured Jurkat cells, we have measured the changes of cell content and intracellular concentration of ATP, of relevant amino acids (BCAA) and of ninhydrin-positive substances (NPS, as measure of NH(2)-bearing organic osmolytes) under conditions that deactivate (leucine-deprivation, glutamine-deprivation, amino acid withdrawal, sorbitol-induced hyperosmotic stress) or reactivate a previously deactivated, mTOR-S6K1 pathway. We have also assessed the mitochondrial function by measurements of mitochondrial transmembrane potential in cells subjected to hypertonic stress. Our results indicate that diverse control signals converge on the mTOR-S6K1 signaling pathway. In the presence of adequate energy resources, the pathway senses the amino acid availability as inward transport of effective amino acids (as BCAA and especially leucine), but its activation occurs only in the presence of an extracellular amino acid complement, with glutamine as obligatory component, and does not tolerate decrements of cell water volume incapable of maintaining adequate intracellular physicochemical conditions.

The production of nitric oxide in EL4 lymphoma cells overexpressing growth hormone

Growth hormone (GH) is produced by immunocompetent cells and has been implicated in the regulation of a multiplicity of functions in the immune system involved in growth and activation. However, the actions of endogenous or lymphocyte GH and its contribution to immune reactivity when compared with those of serum or exogenous GH are still unclear. In the present study, we overexpressed lymphocyte GH in EL4 lymphoma cells, which lack the GH receptor (GHR), to determine the role of endogenous GH in nitric oxide (NO) production and response to genotoxic stress. Western blot analysis demonstrated that the levels of GH increased approximately 40% in cells overexpressing GH (GHo) when compared with cells with vector alone. The results also show a substantial increase in NO production in cells overexpressing GH that could be blocked by N G-monomethyl- l-arginine ( l-NMMA), an l-arginine analogue that competitively inhibits all three isoforms of nitric oxide synthase (NOS). No evidence was obtained to support an increase in peroxynitrite in cells overexpressing GH. Overexpression of GH increased NOS activity, inducible nitric oxide synthase (iNOS) promoter activity, and iNOS protein expression, whereas endothelial nitric oxide synthase and neuronal nitric oxide synthase protein levels were essentially unchanged. In addition, cells overexpressing GH showed increased arginine transport ability and intracellular arginase activity when compared with control cells. GH overexpression appeared to protect cells from the toxic effects of the DNA alkylating agent methyl methanesulfonate. This possibility was suggested by maintenance of the mitochondrial transmembrane potential in cells overexpressing GH when compared with control cells that could be blocked by l-NMMA. Taken together, the data support the notion that lymphocyte GH, independently of the GH receptor, may play a key role in the survival of lymphocytes exposed to stressful stimuli via the production of NO.

19] Quantitation of mitochondrial transmembrane potential in cells and in isolated mitochondria

19] Quantitation of mitochondrial transmembrane potential in cells and in isolated mitochondria