Oxidative damage is thought to be a major cause of the progression of dopamine (DA)rgic neurodegeneration as in Parkinson's disease. We have previously reported that tetrahydrobiopterin (BH4), an endogenous molecule required for DA synthesis, exerts oxidative stress to DA-producing cells and facilitates the production of DA quinone. It is known that aconitase, present in both mitochondrial and cytosolic forms, act as an reactive oxygen species (ROS) sensor, and that their inactivation leads to further generation of ROS. In the present study we investigated whether the BH4-associated vulnerability of DA cells might involve aconitase. In DArgic cell line CATH.a, BH4 treatment caused reduction of activity of both mitochondrial and cytosolic aconitases, and this appeared to be due to direct inactivation of the pre-existing enzyme molecules. Although most of the activity reduced by BH4 was increased upon reactivation reaction under a reducing condition, the restoration was not complete, suggesting that irreversible and covalent modification has occurred. The aconitase inactivation was exacerbated in the presence of DA and attenuated in the presence of tyrosine hydroxylase inhibitor a-methyl-p-tyrosine, suggesting the involvement of DA. The degree of inactivation increased when the cells were treated with the quinone reductase inhibitor dicoumarol and decreased in the presence of quinone reductase inducer sulforaphane. Taken together, BH4 appeared to lead to both reversible and irreversible inactivation of aconitase and that this is facilitated by the presence of DA and accumulation of DA quinone.
Aconitate Hydratase ; Benzoquinones ; Biopterin ; Cell Line ; Cytosol ; Dicumarol ; Dopamine ; NAD(P)H Dehydrogenase (Quinone) ; Oxidative Stress ; Parkinson Disease ; Reactive Oxygen Species ; Thiocyanates ; Tyrosine 3-Monooxygenase

Ascorbic acid has been reported to extend replicative life span of human embryonic fibroblast (HEF). Since the detailed molecular mechanism of this phenomenon has not been investigated, we attempted to elucidate. Continuous treatment of HEF cells with ascorbic acid (at 200 micrometer) from 40 population doubling (PD) increased maximum PD numbers by 18% and lowered SA-beta-gal positive staining, an aging marker, by 2.3 folds, indicating that ascorbic acid extends replicative life span of HEF cells. Ascorbic acid treatment lowered DCFH by about 7 folds and Rho123 by about 70%, suggesting that ascorbic acid dramatically decreased ROS formation. Ascorbic acid also increased aconitase activity, a marker of mitochondrial aging, by 41%, indicating that ascorbic acid treatment restores age-related decline of mitochondrial function. Cell cycle analysis by flow cytometry revealed that ascorbic acid treatment decreased G1 population up to 12%. Further western blot analysis showed that ascorbic acid treatment decreased levels of p53, phospho-p53 at ser 15, and p21, indicating that ascorbic acid relieved senescence-related G1 arrest. Analysis of AP (apurinic/apyrimidinic) sites showed that ascorbic acid treatment decreased AP site formation by 35%. We also tested the effect of hydrogen peroxide treatment, as an additional oxidative stress. Continuous treatment of 20 micrometer of hydrogen peroxide from PD 40 of HEF cells resulted in premature senescence due to increased ROS level, and increased AP sites. Taken together, the results suggest that ascorbic acid extends replicative life span of HEF cells by reducing mitochondrial and DNA damages through lowering cellular ROS.
Aconitate Hydratase ; Aging ; Ascorbic Acid* ; Blotting, Western ; Cell Cycle ; DNA Damage ; DNA* ; Fibroblasts* ; Flow Cytometry ; Humans* ; Hydrogen Peroxide ; Oxidative Stress ; Reactive Oxygen Species

OBJECTIVE: Both constitutive and inducible forms of nitric oxide synthase exist in endothelial cells. Disorders that produce acute lung injury frequently release endotoxin and cytoknes, such as interferon(IFNgamma) and tumor necrosis factor (TNFalpha). Endotoxin and these cytokines likely act as important mediators of cell injury. Because nitric oxide (NO) avidly reacts with iron, it may affect the activity of key enzymes, such as mitochondrial aconitase, which contain an iron-sulfur structure as a prosthetic group. METHOD: We studied the effect of IFNgamma, TNFalpha and E. coli lipopolysaccharide(LPS) on NO production and mitochondrial aconitase activity in cultured rat lung microvascular endothelial cells(RLMVC). RESULT: Exposing RLMVC for 24 hours to IFNgamma(500 U/mL), TNFalpha(300 U/mL) and LPS(5 microgram/mL) significantly increases nitrite production to 20+/-1 micrometer compared to 0.07 micrometer in control cells(P<0.05, n=4). Cytokine treatment also reduced mitochondrial aconitase activity from 196+/-8 to 102+/-34 nmole/min/mg of cell protein(P<0.05, n=4). Treatment with the inhibitor of nitric oxide synthase N-monomethyl-L-arginine(NMMA) (0.5 mM) not only significantly blunted the cytokine-mediated increase in nitrite formation (3+/-0.5 micrometer vs 20+/-1 micrometer with cytokines, P<0.05, n=4), but also prevented the cytokine-mediated drop in aconitase activity (161+/- 24 vs. 196+/-8 nmole/min/mg of cell protein, NS). CONCLUSION: Exposing RLMVC to IFNgamma, TNFalpha and E. coli LPS substantially decreases mitochondrial aconitase activity. Nitric oxide appears to mediate this effect. Our results suggest that the excessive production of NO by endothelial cells, in response to cytokines and endotoxin, may inhibit the function of the endothelial cell itself.
Aconitate Hydratase* ; Acute Lung Injury ; Animals ; Cytokines* ; Endothelial Cells* ; Iron ; Lung* ; Nitric Oxide Synthase ; Nitric Oxide* ; Rats* ; Tumor Necrosis Factor-alpha

PURPOSE: Zinc is one of the trace minerals in the body and is known to have an anticancer effect by inducing apoptosis in prostate cancer. We aimed to investigate the antiproliferative effects of a zinc-citrate compound in bladder cancer. MATERIALS AND METHODS: A bladder cancer cell line (MBT-2) was treated with a zinc-citrate compound at different time intervals and concentrations. Mitochondrial (m)-aconitase activity was determined by use of the aconitase assay. DNA laddering analysis was performed to investigate apoptosis of MBT-2 cells. The molecular mechanism of apoptosis was investigated by Western blot analysis of p53, p21waf1, Bcl-2, Bcl-xL, and Bax and also by caspase-3 activity analysis. RESULTS: Treatment with the zinc-citrate compound resulted in a time- and dose-dependent decrease in cell number of MBT-2 cells. M-aconitase activity was significantly decreased. DNA laddering analysis indicated apoptosis of MBT-2 cells. The zinc-citrate compound increased the expression of p21waf1 and p53 and reduced the expression of Bcl-2 and Bcl-xL proteins but induced expression of Bax protein. The zinc-citrate compound induced apoptosis of MBT-2 cells by activation of the caspase-3 pathway. CONCLUSIONS: We have shown that a zinc-citrate compound induces apoptotic cell death in a bladder cancer cell line, MBT-2, by caspase-3 activation through up-regulation of apoptotic proteins and down-regulation of antiapoptotic proteins.
Aconitate Hydratase ; Apoptosis ; bcl-2-Associated X Protein ; bcl-X Protein ; Blotting, Western ; Caspase 3 ; Cell Count ; Cell Death ; Cell Line ; DNA ; Down-Regulation ; Minerals ; Prostatic Neoplasms ; Proteins ; Up-Regulation ; Urinary Bladder ; Urinary Bladder Neoplasms ; Zinc

OBJECTIVE: Human seminal plasma has diverse biological activities including cytotoxic effect. It contains high concentrations of zinc and citric acid. Zinc inhibits several carcinoma cell growths through induction of cell cycle arrest and apoptosis. We tried to investigate the effects of zinc-citrate compound (CIZAR(R)) on normal human ovarian epithelial (NOSE) cells and human epithelial ovarian cancer cells, OVCAR-3. METHODS: To investigate the potential effect of CIZAR(R) on cell growth and survival, cells were treated with different dose and exposed to different time. Mitochondrial(m)-aconitase activity was determined in cell extracts using aconitase assay. The flow cytometric assay, DNA laddering, telomerase activity and morphological analysis were done to investigate apoptosis of OVCAR-3 cells. Molecular mechanism of apoptosis was investigated by p53, Bcl-XL, Bcl-2, Bax protein, and caspase activity. RESULTS: Treatment of OVCAR-3 cells with CIZAR(R) resulted in a time- and dose-dependent decrease in cell number in comparison with NOSE cells. M-aconitase activity was significantly decreased in OVCAR-3 cells but relatively constant in NOSE cells. The flow cytometric assay, DNA laddering and morphological analysis indicated apoptosis of OVCAR-3 cells. CIZAR(R) did not affect p53 but increased the expression of p21waf1 upon the indicated times and induced reduction of telomerase activity. CIZAR(R) reduced expression of Bcl-2 and Bcl-xL proteins but induced expression of Bax protein. CIZAR(R) induced apoptosis of OVCAR-3 cells by activation of caspase-3 pathway. CONCLUSION: These results show that CIZAR(R) prevent the proliferation of OVCAR-3 cells by inactivation of m-aconitase activity and induce apoptosis by induction of apoptotic genes and repression of antiapoptotic genes without adverse effect on normal ovarian epithelial cells. These results will offer new window in prevention and treatment of epithelial ovarian cancer.
Aconitate Hydratase ; Apoptosis ; bcl-2-Associated X Protein ; bcl-X Protein ; Caspase 3 ; Cell Count ; Cell Cycle Checkpoints ; Cell Extracts ; Citric Acid ; DNA ; Epithelial Cells ; Humans* ; Nose ; Ovarian Neoplasms* ; Repression, Psychology ; Semen ; Telomerase ; Zinc

BACKGROUND AND PURPOSE: Hypoxia, or ischemia, is a common cause of neurological deficits in the elderly. This study elucidated the mechanisms underlying ischemia-induced brain injury that results in neurological sequelae. METHODS: Cerebral ischemia was induced in male Sprague-Dawley rats by transient ligation of the left carotid artery followed by 60 min of hypoxia. A two-dimensional differential proteome analysis was performed using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry to compare changes in protein expression on the lesioned side of the cortex relative to that on the contralateral side at 0, 6, and 24 h after ischemia. RESULTS: The expressions of the following five proteins were up-regulated in the ipsilateral cortex at 24 h after ischemia-reperfusion injury compared to the contralateral (i.e., control) side: aconitase 2, neurotensin-related peptide, hypothetical protein XP-212759, 60-kDa heat-shock protein, and aldolase A. The expression of one protein, dynamin-1, was up-regulated only at the 6-h time point. The level of 78-kDa glucose-regulated protein precursor on the lesioned side of the cerebral cortex was found to be high initially, but then down-regulated by 24 h after the induction of ischemia-reperfusion injury. The expressions of several metabolic enzymes and translational factors were also perturbed soon after brain ischemia. CONCLUSIONS: These findings provide insights into the mechanisms underlying the neurodegenerative events that occur following cerebral ischemia.
Aconitate Hydratase ; Aged ; Anoxia ; Brain Injuries ; Brain Ischemia ; Carotid Arteries ; Cerebral Cortex* ; Dynamin I ; Fructose-Bisphosphate Aldolase ; Geriatrics ; Heat-Shock Proteins ; Humans ; Ischemia ; Ligation ; Male ; Mass Spectrometry ; Proteome ; Proteomics ; Rats, Sprague-Dawley ; Reperfusion Injury*

To explore the role of nitric oxide (NO) in the pathogenesis and effect on regulation of iron metabolism in anemia of chronic disease (ACD) and provide experimental evidence for prevention and treatment of ACD. On the basis of traditional animal model of rheumatoid arthritis, an ACD rat model was established by repeated injection of Freund's complete adjuvant. The relationship between NO concentration and iron metabolism was observed in ACD rats with and without NO synthase inhibitor, L-NAME, (N omega-nitro-L-arginine methyl ester L-NAME). The results showed that anemia was induced in the rat model. In the ACD group, NO concentration and NO synthase activity in serum increased; iron, total iron binding capacity (TIBC) and transferrin saturation (TS) in serum and ferritin in erythrocytes (rFn) decreased; transferrin receptor (TfR) and iron in bone marrow cells decreased; ferritin in serum and iron in liver increased and meanwhile the acotinase activity in liver decreased. After administration of L-NAME, anemia was improved, when NO, NO-synthase activity, liver iron and serum ferritin decreased, but serum iron, TS, TIBC, rFn, TfR, iron in marrow cells and liver acotinase activity elevated. The levels of parameters for iron metabolism in ACD + L-NAME group were situated between ACD and control groups. It is concluded that NO plays an important role in pathogenesis of ACD and influences the regulation of iron in ACD. Decrease of NO level as early as possible will benefit to block the development of anemia, that will provide a new strategy of therapy for ACD.
Aconitate Hydratase ; metabolism ; Anemia ; metabolism ; Animals ; Chronic Disease ; Hemoglobins ; analysis ; Iron ; metabolism ; Male ; NG-Nitroarginine Methyl Ester ; pharmacology ; Nitric Oxide ; physiology ; Nitric Oxide Synthase ; blood ; Rats ; Rats, Sprague-Dawley

AIMTo investigate the possible role of manganese in the regulation of mitochondrial aconitase (mACON) activity human prostate carcinoma cell line PC-3 cells.

METHODSThe mACON enzymatic activities of human prostate carcinoma cell line PC-3 cells were determined using a reduced nicotinamide adenine dinucleotide-coupled assay. Immunoblot and transient gene expression assays were used to study gene expression of the mACON. The putative response element for gene expression was identified using reporter assays with site-directed mutagenesis and electrophoretic mobility-shift assays.

RESULTSIn vitro study revealed that manganese chloride (MnCl2) treatment for 16 h inhibited the enzymatic activity of mACON, which induced the inhibition of citrate utility and cell proliferation of PC-3 cells. Although results from transient gene expression assays showed that MnCl2 treatment upregulated gene translation by approximately 5-fold through the iron response element pathway, immunoblot and reporter assays showed that MnCl2 treatments inhibited protein and gene expression of mACON. This effect was reversed by co-treatment with ferric ammonium citrate. Additional reporter assays with site-directed mutagenesis and electrophoretic mobility-shift assays suggested that a putative metal response element in the promoter of the mACON gene was involved in the regulation of MnCl2 on the gene expression of mACON.

CONCLUSIONThese findings suggest that manganese acts as an antagonist of iron, disrupting the enzymatic activity and gene expression of mACON and citrate metabolism in the prostate.

Aconitate Hydratase ; antagonists & inhibitors ; genetics ; Actins ; genetics ; Adenosine Triphosphate ; metabolism ; Cell Line, Tumor ; Chlorides ; pharmacology ; Citrates ; metabolism ; DNA Primers ; Gene Expression Regulation, Enzymologic ; drug effects ; Gene Expression Regulation, Neoplastic ; drug effects ; Genes, Reporter ; Humans ; Iron ; metabolism ; Male ; Manganese Compounds ; pharmacology ; Mitochondria ; enzymology ; Prostatic Neoplasms ; enzymology