Wanida Ittarat

A neuronal model of Alzheimer's disease: an insight into the mechanisms of oxidative stress-mediated mitochondrial injury.

Alzheimers disease (AD) is associated with beta-amyloid accumulation, oxidative stress and mitochondrial dysfunction. However, the effects of genetic mutation of AD on oxidative status and mitochondrial manganese superoxide dismutase (MnSOD) production during neuronal development are unclear. To investigate the consequences of genetic mutation of AD on oxidative damages and production of MnSOD during neuronal development, we used primary neurons from new born wild-type (WT/WT) and amyloid precursor protein (APP) (NLh/NLh) and presenilin 1 (PS1) (P264L) knock-in mice (APP/PS1) which incorporated humanized mutations in the genome. Increasing levels of oxidative damages, including protein carbonyl, 4-hydroxynonenal (4-HNE) and 3-nitrotyrosine (3-NT), were accompanied by a reduction in mitochondrial membrane potential in both developing and mature APP/PS1 neurons compared with WT/WT neurons suggesting mitochondrial dysfunction under oxidative stress. Interestingly, developing APP/PS1 neurons were significantly more resistant to beta-amyloid 1-42 treatment, whereas mature APP/PS1 neurons were more vulnerable than WT/WT neurons of the same age. Consistent with the protective function of MnSOD, developing APP/PS1 neurons have increased MnSOD protein and activity, indicating an adaptive response to oxidative stress in developing neurons. In contrast, mature APP/PS1 neurons exhibited lower MnSOD levels compared with mature WT/WT neurons indicating that mature APP/PS1 neurons lost the adaptive response. Moreover, mature APP/PS1 neurons had more co-localization of MnSOD with nitrotyrosine indicating a greater inhibition of MnSOD by nitrotyrosine. Overexpression of MnSOD or addition of MnTE-2-PyP(5+) (SOD mimetic) protected against beta-amyloid-induced neuronal death and improved mitochondrial respiratory function. Together, the results demonstrate that compensatory induction of MnSOD in response to an early increase in oxidative stress protects developing neurons against beta-amyloid toxicity. However, continuing development of neurons under oxidative damage conditions may suppress the expression of MnSOD and enhance cell death in mature neurons.

Oxidative Damage Precedes Nitrative Damage in Adriamycin-Induced Cardiac Mitochondrial Injury

The purpose of the present study was to determine if elevated reactive oxygen (ROS)/nitrogen species (RNS) reported to be present in adriamycin (ADR)-induced cardiotoxicity actually resulted in cardiomyocyte oxidative/nitrative damage, and to quantitatively determine the time course and subcellular localization of these postulated damage products using an in vivo approach. B6C3 mice were treated with a single dose of 20 mg/kg ADR. Ultrastructural damage and levels of 4-hydroxy-2-nonenal (4HNE)-protein adducts and 3-nitrotyrosine (3NT) were analyzed. Quantitative ultrastructural damage using computerized image techniques showed cardiomyocyte injury as early as 3 hours, with mitochondria being the most extensively and progressively injured subcellular organelle. Analysis of 4HNE protein adducts by immunogold electron microscopy showed appearance of 4HNE protein adducts in mitochondria as early as 3 hours, with a peak at 6 hours and subsequent decline at 24 hours. 3NT levels were significantly increased in all subcellular compartments at 6 hours and subsequently declined at 24 hours. Our data showed ADR induced 4HNE-protein adducts in mitochondria at the same time point as when mitochondrial injury initially appeared. These results document for the first time in vivo that mitochondrial oxidative damage precedes nitrative damage. The progressive nature of mitochondrial injury suggests that mitochondria, not other subcellular organelles, are the major site of intracellular injury.

Evidence for p53 as guardian of the cardiomyocyte mitochondrial genome following acute adriamycin treatment

The present study is an initial analysis of whether p53 may function as guardian of the cardiomyocyte mitochondrial genome, with mitochondrial p53 localization proposed to be involved in both mitochondrial DNA (mtDNA) repair and apoptosis. Subcellular distribution, protein levels, and possible function(s) of p53 protein in the response of cardiomyocytes to adriamycin (ADR) were analyzed. Levels and subcellular localization of proteins were determined by Western blot and immunogold ultrastructural analysis techniques. Here we demonstrate that stress caused by ADR induced upregulation of p53 protein in cardio-myocyte mitochondria and nuclei between 3 and 24 hr. Increased expression of PUMA and Bax proteins, pro-apoptotic targets of p53, was documented following ADR treatment and was accompanied by increased levels of apoptotic markers, with elevation of cytosolic cytochrome c at 24 hr and subsequent caspase-3 cleavage at 3 days. Mitochondrial p53 levels correlated with mtDNA oxidative damage. Loss of p53 in knockout mouse heart resulted in a significant increase in mtDNA vulnerability to damage following ADR treatment. Our results suggest that mitochondrial p53 could participate in mtDNA repair as a first response to oxidative damage of cardiomyocyte mtDNA and demonstrate an increase of apoptotic markers as a result of mitochondrial/nuclear p53 localization.

Manganese superoxide dismutase and inducible nitric oxide synthase modify early oxidative events in acute adriamycin-induced mitochondrial toxicity.

In the present study, we used genetically engineered B6C3 mice [mice overexpressing manganese superoxide dismutase (TgM+/+), mice in which inducible nitric oxide synthase had been inactivated (iNOSKO−/−), and crosses of these two genotypes] to study the role of manganese superoxide dismutase (MnSOD) and inducible nitric oxide synthase (iNOS) in the development of acute Adriamycin-induced cardiotoxicity. Both nontransgenic and genetically engineered mice were treated with 20 mg/kg Adriamycin and cardiac left ventricular tissues studied at 0, 3, 6, and 24 hours. Ultrastructural damage and levels of 4-hydroxy-2-nonenal (4HNE) protein adducts and 3-nitrotyrosine (3NT) were determined in cardiomyocytes using immunogold ultrastructural techniques. Our previous results showed that Adriamycin caused mitochondrial injury without significant nuclear or cytoplasmic damage at early time points. Interestingly, overexpression of MnSOD protected against acute mitochondrial injury, whereas deficiency in iNOS potentiated mitochondrial injury in comparison with levels of injury present in cardiomyocyte mitochondria of nontransgenic mice. In TgM+/+ mice, there was a significant inverse correlation between mitochondrial injury and 4HNE/3NT levels at all time points analyzed, suggesting that reactive oxygen species/reactive nitrogen species damage products directly regulated acute Adriamycin-induced mitochondrial injury in these mice. The present studies are the first to directly quantify the effects of MnSOD and iNOS on mitochondrial injury during acute Adriamycin-induced cardiotoxicity and show extensive and specific patterns of posttranslational modifications of mitochondrial proteins following Adriamycin treatment.

NF-κB-Associated MnSOD induction protects against β-amyloid-induced neuronal apoptosis

Expression of manganese superoxide dismutase (MnSOD), a nuclear-encoded mitochondrial primary antioxidant enzyme, is protective against various paradigms of oxidative stress-induced brain injury. We have shown previously that the presence of an intronic nuclear factor site, κB (NF-κB), in the MnSOD gene is essential for the induction of MnSOD by tumor necrosis factor α (TNF-α). However, whether activation of NF-κB is protective against oxidative stress-induced neuronal injury is unclear. In the present study, we demonstrate that TNF-α activates NF-κB activity in neuronal, SH-SY5Y, cells and preferentially enhances the binding of p50 and p65 to the promoter/enhancer regions of the MnSOD gene. Binding of NF-κB members to the MnSOD gene leads to the induction of MnSOD mRNA and protein levels. Consequently, induction of MnSOD by TNF-α primes neuronal cells to develop resistance against subsequent exposure to β-amyloid and FeSO4. Taken together, these results suggest that NF-κB might exert its protective function by induction of MnSOD leading to subsequent protection against oxidative stress-induced neuronal injury.

Tamoxifen enhancement of TNF-α induced MnSOD expression: modulation of NF-κB dimerization

Manganese superoxide dismutase (MnSOD) has been shown to suppress the development of cancer. Tamoxifen (TAM), a nonsteroidal anti-estrogen that is widely used in chemotherapy, is known to be a modulator of antioxidant status. However, the mechanism by which TAM mediates antioxidant enzyme induction remains unclear. In this study we investigated TAM enhancement of MnSOD induction by TNF-α. The results show that co-treatment with TAM and TNF-α increases the MnSOD promoter/enhancer driven luciferase activity, MnSOD mRNA and protein levels. Interestingly, co-treatment with TAM and TNF-α drastically decreases the binding activity of the p50/p50 homodimer and increases that of the p50/p65 heterodimer compared to TNF-α alone. This change in DNA binding could not be attributed to a decrease in the level of p50, its precursor, p105, or its inhibitors. Furthermore, TAM did not enhance degradation of IκB-α. These results suggest that p50/p50 homodimer may act as an inhibitory complex of MnSOD expression. Modulation of the DNA binding activity in favor of the p50/p65 complex may enhance NF-κB mediated induction of MnSOD by TAM. These findings reveal a potential novel mechanism for the induction of the human MnSOD gene.

Silver quartz crystal microbalance for differential diagnosis of Plasmodium falciparum and Plasmodium vivax in single and mixed infection.

The most severe form of malaria is cerebral malaria caused by Plasmodium falciparum. Standard malaria diagnosis is Giemsa stained peripheral blood smear but false negative findings are always reported. Moreover, mixed infections are underestimated by routine microscopy. Many methods have been developed to overcome these disadvantages and the most specific and sensitive is molecular diagnosis. Specific malaria genes are amplified by polymerase chain reaction (PCR) and many post-PCR methods have been created. We developed a gold fabricated quartz crystal microbalance (QCM) as a post-PCR method of malaria diagnosis. In this work a cheaper silver fabricated QCM was developed to identify both single and mixed infection of P. falciparum and Plasmodium vivax. The biotinylated malaria probe was immobilized on silver surface via specific avidin-biotin interaction. The target DNA fragment of 18s rRNA gene was amplified and hybridized with a QCM immobilized probe. Mass changes due to DNA hybridization were indicated by changes of quartz resonance frequencies. Validation showed that malaria silver QCM had high diagnostic potency. Evaluation of suspected 67 febrile blood samples from malaria endemic area demonstrated that the malaria silver QCM could identify both false negative and misdiagnosis cases of routine microscopy. The analysis cost of malaria silver QCM was

Diagnosis and genotyping of Plasmodium falciparum by a DNA biosensor based on quartz crystal microbalance (QCM)

1/sample and analysis time was 30 min after blood collection. The malaria silver QCM is stable at tropical temperature for up to 6 months. Thus, it can be transported to be used in a remote endemic area. Thus, the malaria silver QCM is accurate, precise, rapid, cheap, and field applicable.

Low cost biosensor-based molecular differential diagnosis of α-thalassemia (Southeast Asia deletion).

Abstract Background: Malaria infection with Plasmodium falciparum is an important basic health problem in the tropical and sub-tropical countries. The standard diagnostic method is blood film examination to visualize parasite morphology. However, in cases of low parasitemia or mixed infection with very low cryptic species, microscopy is not sensitive enough. Therefore, molecular techniques have been widely employed. Methods: A label-free DNA biosensor based on quartz crystal microbalance (QCM) to diagnose and genotype P. falciparum was developed. Avidin-biotin interaction was used to coat the specific biotinylated probe on the gold surface of QCM. The gene encoding merozoite surface protein 2 (msp2) was amplified and the PCR products were then cut with restriction enzyme (MwoI). Enzymatic cutting made the PCR products suitable for QCM development. Hybridization between probe and enzymatic cutting DNA fragments resulted in frequency changes of the QCM. Results: The newly developed QCM was tested for its diagnosis ability using both malaria laboratory strains and clinical isolates. The biosensor was sensitive at the sub-nanogram level, specific for only P. falciparum detection, no cross-reaction with P. vivax, and stable at room temperature for up to 6 months. Selection of msp2 as a target gene and a geno-typing marker made the QCM potentially useful for falciparum diagnosis simultaneously with genotyping. Potency was tested by genotyping two allelic families of P. falciparum, FC27 and IC1, using malaria laboratory strains, K1 and 3D7, respectively. Conclusions: The dual function QCM was successfully developed with high sensitivity and specificity, and was cost-effective, stable and field adaptable.

Quartz crystal microbalance-based biosensor for the detection of α-thalassemia 1 (SEA deletion).

Abstract Background: Thalassemias are genetic hematologic diseases which the homozygous form of α-thalassemia can cause either death in utero or shortly after birth. It is necessary to accurately identify high-risk heterozygous couples. We developed a quartz crystal microbalance (QCM) to identify the abnormal gene causing the commonly found α-thalassemia1, [Southeast Asia (SEA) deletion]. This work is an improved method of our previous study by reducing both production cost and analysis time. Methods: A silver electrode on the QCM surface was immobilized with a biotinylated probe. The α-globin gene fragment was amplified and hybridized with the probe. Hybridization was indicated by changes of quartz oscillation. Each drying step was improved by using an air pump for 30 min instead of the overnight air dry. The diagnostic potency of the silver QCM was evaluated using 70 suspected samples with microcytic hypochromic erythrocytes. Results: The silver QCM could clearly identify samples with abnormal α-globin genes, either homozygous or heterozygous, from normal samples. Thirteen out of 70 blood samples were identified as carrier of α-thalassemia1 (SEA deletion). Results were consistent with the standard agarose gel electrophoresis. Using silver instead of gold QCM could reduce the production expense 10-fold. An air pump drying the QCM surface could reduce the analysis time from 3 days to 4 h. Conclusions: The silver thalassemic QCM was specific, sensitive, rapid, cheap and field applicable. It could be used as a one-step definite diagnosis of α-thalassemia1 (SEA deletion) with no need for the preliminary screening test.