Proteomic analysis of the monkey hippocampus for elucidating ischemic resistance

It is well-known that the cornu Ammonis 1 (CA1) sector of hippocampus is vulnerable for the ischemic insult, whereas the dentate gyrus (DG) is resistant. Here, to elucidate its underlying mechanism, alternations of protein oxidation and expression of DG in the monkey hippocampus after ischemia-reperfusion by the proteomic analysis were studied by comparing CA1 data. Oxidative damage to proteins such as protein carbonylation interrupt the protein function. Carbonyl modification of molecular chaperone, heat shock 70 kDa protein 1 (Hsp70.1) was increased remarkably in CA1, but slightly in DG. In addition, expression levels of nicotinamide adenine dinucleotide (NAD)-dependent protein deacetylase sirtuin-2 (SIRT2) was significantly increased in DG after ischemia, but decreased in CA1. Accordingly, it is likely that SIRT2 upregulation and negligible changes of carbonylation of Hsp70.1 exert its neuroprotective effect in DG. On the contrary, carbonylation level of dihydropyrimidinase related protein 2 (DRP-2) and l-lactate dehydrogenase B chain (LDHB) were slightly increased in CA1 as shown previously, but remarkably increased in DG after ischemia. It is considered that DRP-2 and LDHB are specific targets of oxidative stress by ischemia insult and high carbonylation levels of DRP-2 may play an important role in modulating ischemic neuronal death.

Functionalized Surface-Charged SiO2 Nanoparticles Induce Pro-Inflammatory Responses, but Are Not Lethal to Caco-2 Cells

Nanoparticles (NPs) are widely used in food, and analysis of their potential gastrointestinal toxicity is necessary. The present study was designed to determine the effects of silica dioxide (SiO₂), titanium dioxide (TiO₂), and zinc oxide (ZnO) NPs on cultured THP-1 monocyte-derived macrophages and human epithelial colorectal adenocarcinoma (Caco-2) cells. Exposure to ZnO NPs for 24 h increased the production of redox response species (ROS) and reduced cell viability in a dose-dependent manner in THP-1 macrophages and Caco-2 cells. Although TiO₂ and SiO₂ NPs induced oxidative stress, they showed no apparent cytotoxicity against both cell types. The effects of functionalized SiO₂ NPs on undifferentiated and differentiated Caco-2 cells were investigated using fluorescently labeled SiO₂ NPs with neutral, positive, or negative surface charge. Exposure of both types of cells to the three kinds of SiO₂ NPs significantly increased their interaction in a dose-dependent manner. The largest interaction with both types of cells was noted with exposure to more negatively surface-charged SiO₂ NPs. Exposure to either positively or negatively, but not neutrally, surface-charged SiO₂ NPs increased NO levels in differentiated Caco-2 cells. Exposure of differentiated Caco-2 cells to positively or negatively surface-charged SiO₂ NPs also upregulated interleukin-8 expression. We conclude that functionalized surface-charged SiO₂ NPs can induce pro-inflammatory responses but are noncytotoxic.

NF‑κB inhibitor DHMEQ inhibits titanium dioxide nanoparticle‑induced interleukin‑1β production: Inhibition of the PM2.5‑induced inflammation model

PM2.5 is a particle with a diameter <2.5 µm that is often involved in air pollution. Nanoparticles <100 nm are thought to invade the trachea and lungs to cause inflammation, possibly through the activation of macrophages. On the other hand, titanium dioxide (TiO2) particles can be used in models of nano‑micro‑sized particles, as one can prepare the particles with such sizes. TiO2 particles are classified into Rutile, Anatase, and Brookite types by their crystal structure. Among them, Anatase‑type TiO2 particles with a primary diameter of 50 nm (A50) were reported to induce interleukin (IL)‑1β production and secretion effectively in phorbol 12‑myristate 13‑acetate‑treated human monocytic leukemia THP‑1 cells (THP‑1 macrophages). We previously designed and synthesized dehydroxymethyl‑epoxyqinomicin (DHMEQ) as an inhibitor of NF‑κB. The present study investigated whether the NF‑κB inhibitor DHMEQ inhibits TiO2 nanoparticle‑induced IL‑1β production in THP‑1 macrophages, and determined the mechanism. As a result, DHMEQ inhibited A50‑induced IL‑1β secretion in ELISA assays at nontoxic concentrations. It decreased the expression of IL‑1β mRNA, which was dependent on NF‑κB. Although NLR family pyrin domain containing 3 (NLRP3)‑inflammasome‑caspase‑1 activation is required for the maturation of IL‑1β, and DHMEQ reduced the NLRP3 mRNA expression and caspase‑1 activity; a caspase‑1 inhibitor did not influence the A50‑induced IL‑1β production. Therefore, it is likely that inhibition of pro‑IL‑1β expression by DHMEQ may be sufficient to inhibit mature IL‑1β production. Thus, DHMEQ may be useful for the amelioration of inflammation in the trachea and lungs caused by inhalation of PM2.5.

Single- and double-walled carbon nanotubes enhance atherosclerogenesis by promoting monocyte adhesion to endothelial cells and endothelial progenitor cell dysfunction

BACKGROUND

The use of carbon nanotubes has increased lately. However, the cardiovascular effect of exposure to carbon nanotubes remains elusive. The present study investigated the effects of pulmonary exposure to single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) on atherosclerogenesis using normal human aortic endothelial cells (HAECs) and apolipoprotein E-deficient (ApoE^-/-) mice, a model of human atherosclerosis.

METHODS

HAECs were cultured and exposed to SWCNTs or DWCNTs for 16 h. ApoE^-/- mice were exposed to SWCNTs or DWCNTs (10 or 40 μg/mouse) once every other week for 10 weeks by pharyngeal aspiration.

RESULTS

Exposure to CNTs increased the expression level of adhesion molecule (ICAM-1) and enhanced THP-1 monocyte adhesion to HAECs. ApoE^-/- mice exposed to CNTs showed increased plaque area in the aorta by oil red O staining and up-regulation of ICAM-1 expression in the aorta, compared with vehicle-treated ApoE^-/- mice. Endothelial progenitor cells (EPCs) are mobilized from the bone marrow into the circulation and subsequently migrate to the site of endothelial damage and repair. Exposure of ApoE^-/- mice to high-dose SWCNTs or DWCNTs reduced the colony-forming units of EPCs in the bone marrow and diminished their migration function.

CONCLUSION

The results suggested that SWCNTs and DWCNTs enhanced atherosclerogenesis by promoting monocyte adhesion to endothelial cells and inducing EPC dysfunction.

Zn(II) released from zinc oxide nano/micro particles suppresses vasculogenesis in human endothelial colony-forming cells

Zinc oxide (ZnO) nanoparticles have been widely used in industry, cosmetics, and biomedicine. Recent studies suggested that these nanoparticles could have a major impact on the cardiovascular system. Endothelial progenitor cells (EPCs) contribute to postnatal endothelial repair and regeneration. The present study dissected the effects of ZnO nanoparticles on vasculogenesis using human endothelial colony forming cells (ECFCs), which participate in post-natal vasculogenesis. Two types of ZnO particles were used (nano and micro), in addition to zinc chloride solutions with zinc ion concentrations equal to those in ZnO nanoparticles. Twenty-four-hour exposure induced cytotoxicity in a dose-dependent manner and increased ECFCs apoptosis in all groups. The exposure also reduced the functional capacity of ECFCs on Matrix gel to form tubules, compared with the control cells. These effects were associated with downregulation of expression of vascular endothelial growth factor receptor, VEGFR2 and CXC chemokine receptor, CXCR4. The results suggest that ZnO nanoparticles suppress vasculogenesis from ECFCs through downregulation of the expression of receptors related to vasculogenesis. These effects are based the concentration of released Zn(II).

Copper Oxide Nanoparticles Reduce Vasculogenesis in Transgenic Zebrafish Through Down-Regulation of Vascular Endothelial Growth Factor Expression and Induction of Apoptosis

The present study investigated the effects of exposure to metal oxide nanoparticles on vasculogenesis/angiogenesis using transgenic zebrafish. The study also examined the potential mechanisms involved in those effects using human umbilical vein endothelial cells (HUVEC). TG (nacre/fli1:EGFP) zebrafish were exposed to nano-sized titanium dioxide (TiO2), silica dioxide (SiO2), and copper oxide (CuO) particles at 0.01, 1 and 100 µg/ml concentrations from 1 to 5 dpf (day-post-fertilization). Angiogenesis was evaluated morphologically at the end of exposure. Exposure to CuO nanoparticles reduced the number of transversely-running subintestinal vessels in TG zebrafish. Exposure to CuO nanoparticles down-regulated the expression of vascular endothelial growth factor (VEGF) and VEGF receptor in endothelial cells sorted by Fluorescence Activated Cell Sorter (FACS). Exposure of HUVEC to CuO nanoparticles reduced cell viability and increased apoptotic index in a dose-dependent manner. The results suggested that CuO nanoparticles inhibit vasculogenesis through reduction of VEGF expression and induction of apoptosis.

Synergistic effect of bolus exposure to zinc oxide nanoparticles on bleomycin-induced secretion of pro-fibrotic cytokines without lasting fibrotic changes in murine lungs

Zinc oxide (ZnO) nanoparticles are widely used in various products, and the safety evaluation of this manufactured material is important. The present study investigated the inflammatory and fibrotic effects of pulmonary exposure to ZnO nanoparticles in a mouse model of pulmonary fibrosis. Pulmonary fibrosis was induced by constant subcutaneous infusion of bleomycin (BLM). Female C57BL/6Jcl mice were divided into BLM-treated and non-treated groups. In each treatment group, 0, 10, 20 or 30 µg of ZnO nanoparticles were delivered into the lungs through pharyngeal aspiration. Bronchoalveolar lavage fluid (BALF) and the lungs were sampled at Day 10 or 14 after administration. Pulmonary exposure by a single bolus of ZnO nanoparticles resulted in severe, but transient inflammatory infiltration and thickening of the alveolar septa in the lungs, along with the increase of total and differential cell counts in BLAF. The BALF level of interleukin (IL)-1β and transforming growth factor (TGF)-β was increased at Day 10 and 14, respectively. At Day 10, the synergistic effect of BLM and ZnO exposure was detected on IL-1β and monocyte chemotactic protein (MCP)-1 in BALF. The present study demonstrated the synergistic effect of pulmonary exposure to ZnO nanoparticles and subcutaneous infusion of BLM on the secretion of pro-fibrotic cytokines in the lungs.

Serial changes in adipocytokines and cardiac function in a rat model of the metabolic syndrome

Obesity is associated with high chronic cardiac workload due to the need to supply more blood to peripheral tissue, and frequently leads to left ventricular (LV) dysfunction. The present study examined serial changes in cardiac function in the SHR/NDmcr-cp (SHR/cp) strain, an experimental model of obesity plus hypertension and metabolic syndrome. Transthoracic echocardiography was used to define cardiac dimensions and function in male spontaneously hypertensive rats (SHR/lean), SHR/cp and Wistar-Kyoto rats. We also assessed age-related changes in plasma and LV adipocytokine levels in this model. Although there were no significant differences in LV end-diastolic diameter and end-systolic diameter among the three rat strains until 24 weeks of age, these parameters were significantly higher and LV fractional shortening (%FS) was significantly lower in SHR/cp compared with SHR/lean at 32 weeks of age. At the same age, pronounced interstitial fibrosis and infiltration of macrophages and T lymphocytes into the LV was noted in SHR/cp relative to the other strains. In the myocardium, adiponectin levels were significantly lower and resistin levels and the expression of proinflammatory cytokines (tumour necrosis factor-α and interleukin-6) were significantly higher in SHR/cp than SHR/lean at 32 weeks of age. Using echocardiography, we demonstrated reduced systolic function in 32-week-old SHR/cp. Changes in myocardial cytokine concentrations could be involved in worsening of cardiac function in our animal model of metabolic syndrome.

Zinc oxide nanoparticles induce migration and adhesion of monocytes to endothelial cells and accelerate foam cell formation

Metal oxide nanoparticles are widely used in industry, cosmetics, and biomedicine. However, the effects of exposure to these nanoparticles on the cardiovascular system remain unknown. The present study investigated the effects of nanosized TiO2 and ZnO particles on the migration and adhesion of monocytes, which are essential processes in atherosclerogenesis, using an in vitro set-up of human umbilical vein endothelial cells (HUVECs) and human monocytic leukemia cells (THP-1). We also examined the effects of exposure to nanosized metal oxide particles on macrophage cholesterol uptake and foam cell formation. The 16-hour exposure to ZnO particles increased the level of monocyte chemotactic protein-1 (MCP-1) and induced the migration of THP-1 monocyte mediated by increased MCP-1. Exposure to ZnO particles also induced adhesion of THP-1 cells to HUVECs. Moreover, exposure to ZnO particles, but not TiO2 particles, upregulated the expression of membrane scavenger receptors of modified LDL and increased cholesterol uptake in THP-1 monocytes/macrophages. In the present study, we found that exposure to ZnO particles increased macrophage cholesterol uptake, which was mediated by an upregulation of membrane scavenger receptors of modified LDL. These results suggest that nanosized ZnO particles could potentially enhance atherosclerogenesis and accelerate foam cell formation.

Identification of a glutamic acid repeat polymorphism of ALMS1 as a novel genetic risk marker for early-onset myocardial infarction by genome-wide linkage analysis

BACKGROUND

Myocardial infarction (MI) is a leading cause of death worldwide. Given that a family history is an independent risk factor for coronary artery disease, genetic variants are thought to contribute directly to the development of this condition. The identification of susceptibility genes for coronary artery disease or MI may thus help to identify high-risk individuals and offer the opportunity for disease prevention.

METHODS AND RESULTS

We designed a 5-step protocol, consisting of a genome-wide linkage study followed by association analysis, to identify novel genetic variants that confer susceptibility to coronary artery disease or MI. A genome-wide affected sib-pair linkage study with 221 Japanese families with coronary artery disease yielded a statistically significant logarithm of the odds score of 3.44 for chromosome 2p13 and MI. Further association analysis implicated Alström syndrome 1 gene (ALMS1) as a candidate gene within the linkage region. Validation association analysis revealed that representative single-nucleotide polymorphisms of the ALMS1 promoter region were significantly associated with early-onset MI in both Japanese and Korean populations. Moreover, direct sequencing of the ALMS1 coding region identified a glutamic acid repeat polymorphism in exon 1, which was subsequently found to be associated with early-onset MI.

CONCLUSIONS

The glutamic acid repeat polymorphism of ALMS1 identified in the present study may provide insight into the pathogenesis of early-onset MI.

Endocrine disruptors found in food contaminants enhance allergic sensitization through an oxidative stress that promotes the development of allergic airway inflammation

In the past few decades, there has been a significant increase in incidence of allergic diseases. The hygiene hypothesis may provide some clues to explain this rising trend, but it may also be attributable to other environmental factors that exert a proallergic adjuvant effects. However, there is limited information on the risks of developing allergic asthma and related diseases through the ingestion of environmental chemicals found in food contaminants. In the present study, we have shown that oral administration of tributyltin, used as a model environmental chemical, induced oxidative-stress status in the bronchial lymph node, mesenteric lymph node and spleen, but not in the lung, where the initial step of allergic asthma pathogenesis takes place. Mice exposed to tributyltin exhibited heightened Th2 immunity to the allergen with more severe airway inflammation. Tributyltin also induced Treg cells apoptosis preferentially over non-Treg cells. All these effects of tributyltin exposure were canceled by the administration of glutathione monoethyl ester. Meanwhile, tributyltin did not affect airway inflammation of mice transferred with allergen-specific Th2 cells. Collectively, these results suggest that tributyltin exerts its pathological effect during the sensitization phase through oxidative stress that enhances the development of allergic diseases. The current study dissects the pathogenic role of oxidative stress induced by oral exposure to an environmental chemical during the sensitization phase of allergic airway inflammation and would be important for developing therapeutics for prevention of allergic diseases.

Altered gene and protein expression in liver of the obese spontaneously hypertensive/NDmcr-cp rat

BACKGROUND

It is difficult to study the mechanisms of the metabolic syndrome in humans due to the heterogeneous genetic background and lifestyle. The present study investigated changes in the gene and protein profiles in an animal model of the metabolic syndrome to identify the molecular targets associated with the pathogenesis and progression of obesity related to the metabolic syndrome.

METHODS

We extracted mRNAs and proteins from the liver tissues of 6- and 25-week-old spontaneously hypertensive/NIH -corpulent rat SHR/NDmcr-cp (CP), SHR/Lean (Lean) and Wistar Kyoto rats (WKY) and performed microarray analysis and two-dimensional difference in gel electrophoresis (2D-DIGE) linked to a matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS).

RESULTS

The microarray analysis identified 25 significantly up-regulated genes (P < 0.01; log10 > 1) and 31 significantly down-regulated genes (P < 0.01; log10 < -1) in 6- and 25-week-old CP compared with WKY and Lean. Several of these genes are known to be involved in important biological processes such as electron transporter activity, electron transport, lipid metabolism, ion transport, transferase, and ion channel activity. MALDI-TOF/TOF MS identified 31 proteins with ±1.2 fold change (P < 0.05) in 6- and 25-week-old CP, compared with age-matched WKY and Lean. The up-regulated proteins are involved in metabolic processes, biological regulation, catalytic activity, and binding, while the down-regulated proteins are involved in endoplasmic reticulum stress-related unfolded protein response.

CONCLUSION

Genes with significant changes in their expression in transcriptomic analysis matched very few of the proteins identified in proteomics analysis. However, annotated functional classifications might provide an important reference resource to understand the pathogenesis of obesity associated with the metabolic syndrome.

[Preferential induction of apoptosis in regulatory T cells by tributyltin: possible involvement in the exacerbation of allergic diseases]

OBJECTIVES

Tributyltin (TBT) has been recognized as a particularly important pollutant. Human exposure to TBT persists via consumption of TBT-containing meat and fish products. Although it is well known that high-dose TBT exerts immunotoxic effects such as thymic atrophy, the effect of low-dose TBT exposure on immune responses remains elusive. Our previous studies demonstrated that TBT at environmentally relevant doses promoted T helper (Th)2 polarization via enhancement of Th2 differentiation and preferential induction of apoptosis in Th1, which is associated with the exacerbation of Th2-driven allergic airway inflammation. In the present study, we explored the possibility that TBT might preferentially induce apoptosis in Foxp3(+) regulatory T cells (Treg), which play an indisputable role in the negative regulation of immune responses.

METHODS

We established several independent Treg and Th2 clones and their susceptibilities to TBT-induced apoptosis were examined. To examine whether the susceptibility to TBT-induced apoptosis may be due to the level of glutathione (GSH), we measured the basal GSH levels in Treg and Th2 clones. Intracellular GSH level was measured using high-performance liquid chromatography (HPLC) with a gold electrode.

RESULTS

We show that TBT preferentially induces apoptosis in Treg clones rather than in Th2 clones. The basal levels of GSH in Treg clones were significantly lower than those in Th2 clones.

CONCLUSIONS

The increased susceptibility of Treg clones to TBT-induced apoptosis appeared to result from lower GSH levels in Treg clones, which may detoxify the reactive oxygen species (ROS) induced by TBT treatment. Our results suggest that the preferential induction of apoptosis in Treg over Th2 contributes to the exacerbation of Th2-driven allergic diseases by TBT.

Pre-operative intracellular glutathione levels of peripheral monocytes as a biomarker to predict survival of colorectal cancer patients

The ability to predict anti-tumor immune responses at local tumor growing sites using only peripheral blood specimens would be helpful in determining therapeutic options for patients with solid tumors. Here, we show that the glutathione intracellular content (icGSH) of peripheral monocytes (Mo) correlates positively with T cell infiltration within tumor islets and overall survival in patients with colorectal carcinoma. IcGSH redox status was determined in CD14(+) Mo prior to surgery by staining with monochlorobimane. The tumor-infiltrating T cells (TIL) were quantified as CD45RO(+) T cells in resected tumors using paraffin sections. A positive association was found between the GSH index and TIL in tumor islets (P < 0.001). The 50% cut-off value for the GSH index, that is the determinant between TIL presence or absence in tumor islets, was calculated to be almost 0.7 through logistic regression analysis. Mo with a GSH index of > or =0.7 were termed reductive (R)-Mo, and those with <0.7 were designated as oxidative (O)-Mo. Cox's proportional hazards regression analysis of patients with R-Mo or O-Mo prior to surgery, and the presence or absence of TIL, was found to correlate significantly with the overall survival rate of stage II and III patients. Kaplan-Meier analysis also showed a significant correlation. These results indicate that the Mo icGSH index is a useful biomarker parameter for better understanding the host/tumor relationship prior to surgery, thereby enabling the development of an individual patient-oriented therapeutic strategy.

Romidepsin (FK228), a potent histone deacetylase inhibitor, induces apoptosis through the generation of hydrogen peroxide

Romidepsin (FK228) is a potent histone deacetylase (HDAC) inhibitor, which has a potent anticancer activity, but its molecular mechanism is unknown. We investigated the mechanism of FK228-induced apoptosis in the human leukemia cell line HL-60 and its hydrogen peroxide (H(2)O(2))-resistant sub-clone, HP100, and the human colon cancer cell line Caco-2. Cytotoxicity and DNA ladder formation induced by FK228 could be detected in HL-60 cells after a 24-h incubation, whereas they could not be detected in HP100 cells. Trichostatin A (TSA), an HDAC inhibitor, induced DNA ladder formation in both HL-60 and HP100 cells. In contrast, FK228 inhibited HDAC activity in both HL-60 and HP100 cells to a similar extent. These findings suggest that FK228-induced apoptosis involves H(2)O(2)-mediated pathways and that TSA-induced apoptosis does not. Flow cytometry revealed H(2)O(2) formation and a change in mitochondrial membrane potential (Δψm) in FK228-treated cells. FK228 also induced apoptosis in Caco-2 cells, which was prevented by N-acetyl-cysteine, suggesting that reactive oxygen species participate in apoptosis in various types of tumor cells. Interestingly, in a cell-free system, FK228 generated superoxide (O(2)(-)) in the presence of glutathione, suggesting that H(2)O(2) is derived from dismutation of O(2)(-) produced through redox-cycle of FK228. Therefore, in addition to HDAC inhibition, H(2)O(2) generated from FK228 may participate in its apoptotic effect.

Proteomic identification of carbonylated proteins in the monkey hippocampus after ischemia-reperfusion

Reactive oxygen species (ROS) are known to participate in neurodegeneration after ischemia-reperfusion. With the aid of ROS, the calpain-induced lysosomal rupture provokes ischemic neuronal death in the cornu Ammonis (CA) 1 of the hippocampus; however, the target proteins of ROS still remain unknown. Here a proteomic analysis was done to identify and characterize ROS-induced carbonyl modification of proteins in the CA1 of the macaque monkey after transient whole-brain ischemia followed by reperfusion. We found that carbonyl modification of heat shock 70-kDa protein 1 (Hsp70-1), a major stress-inducible member of the Hsp70 family, was extensively increased before the neuronal death in the CA1 sector, and the carbonylation site was identified to be Arg469 of Hsp70-1. The CA1 neuronal death conceivably occurs by calpain-mediated cleavage of carbonylated Hsp70 that becomes prone to proteolysis with the resultant lysosomal rupture. In addition, the carbonyl levels of dihydropyrimidinase-like 2 isoform 2, glial fibrillary acidic protein, and beta-actin were remarkably increased in the postischemic CA1. Therefore, ischemia-reperfusion-induced oxidative damage to these proteins in the CA1 may lead to loss of the neuroprotective function, which contributes to neuronal death.

The mechanisms of oxidative DNA damage and apoptosis induced by norsalsolinol, an endogenous tetrahydroisoquinoline derivative associated with Parkinson's disease

Tetrahydroisoquinoline (TIQ) derivatives are putative neurotoxins that may contribute to the degeneration of dopaminergic neurons in Parkinson's disease. One TIQ, norsalsolinol (NorSAL), is present in dopamine-rich areas of human brain, including the substantia nigra. Here, we demonstrate that NorSAL reduces cell viability and induces apoptosis via cytochrome c release and caspase 3 activation in SH-SY5Y human neuroblastoma cells. Cytochrome c release, caspase 3 activation, and apoptosis induction were all inhibited by the antioxidant N-acetylcysteine. Thus, reactive oxygen species (ROS) contribute to apoptosis induced by NorSAL. Treatment with NorSAL also increased levels of oxidative damage to DNA, a stimulus for apoptosis, in SH-SY5Y. To clarify the mechanism of intracellular DNA damage, we examined the DNA damage caused by NorSAL using (32)P-5'-end-labeled isolated DNA fragments. NorSAL induced DNA damage in the presence of Cu(II). Catalase and bathocuproine, a Cu(I) chelator, inhibited this DNA damage, suggesting that ROS such as the Cu(I)-hydroperoxo complex derived from the reaction of H(2)O(2) with Cu(I), promote DNA damage by NorSAL. In summary, NorSAL-generated ROS induced oxidative DNA damage, which led to caspase-dependent apoptosis in neuronal cells.

H2O2 accelerates cellular senescence by accumulation of acetylated p53 via decrease in the function of SIRT1 by NAD+ depletion

It has been reported that p53 acetylation, which promotes cellular senescence, can be regulated by the NAD(+)-dependent deacetylase SIRT1, the human homolog of yeast Sir2, a protein that modulates lifespan. To clarify the role of SIRT1 in cellular senescence induced by oxidative stress, we treated normal human diploid fibroblast TIG-3 cells with H(2)O(2) and examined DNA cleavage, depletion of intracellular NAD(+), expression of p21, SIRT1, and acetylated p53, cell cycle arrest, and senescence-associated beta-galactosidase (SA-beta-gal) activity. DNA cleavage was observed immediately in TIG-3 cells treated with H(2)O(2), though no cell death was observed. NAD(+) levels in TIG-3 cells treated with H(2)O(2) were also decreased significantly. Pre-incubation with the poly (ADP-ribose) polymerase (PARP) inhibitor resulted in preservation of intracellular NAD(+) levels. The amount of acetylated p53 was increased in TIG-3 cells at 4h after H(2)O(2) treatment, while there was little to no decrease in SIRT1 protein expression. The expression level of p21 was increased at 12h and continued to increase for up to 24h. Additionally, exposure of TIG-3 cells to H(2)O(2) induced cell cycle arrest at 24h and increased SA-beta-gal activity at 48h. This pathway likely plays an important role in the acceleration of cellular senescence by oxidative stress.

Mechanism for manganese enhancement of dopamine-induced oxidative DNA damage and neuronal cell death

Although the cause of dopaminergic cell death in Parkinson's disease is still poorly understood, there is accumulating evidence suggesting that metal ions can be involved in the processes. We investigated the effect of manganese on cell death and DNA damage in PC12 cells treated with dopamine. Mn(II) enhanced cell death induced by dopamine. Mn(II) also increased the 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) contents of DNA in PC12 cells treated with dopamine. To clarify the mechanism of cellular DNA damage, we investigated DNA damage induced by dopamine and Mn(II) using (32)P-labeled DNA fragments. Mn(II) enhanced Cu(II)-dependent DNA damage by dopamine. The Mn(II)-enhanced DNA damage was greatly increased by NADH. Piperidine and formamidopyrimidine-DNA glycosylase treatment induced cleavage sites mainly at T and G of the 5'-TG-3' sequence, respectively. Bathocuproine, a Cu(I) chelator, and catalase inhibited the DNA damage. Oxygen consumption and UV-visible spectroscopic measurements showed that Mn(II) enhanced autoxidation of dopamine with H(2)O(2) formation. These results suggest that reactive species derived from the reaction of H(2)O(2) with Cu(I) participates in Mn(II)-enhanced DNA damage by dopamine plus Cu(II). Therefore, it is concluded that oxidative DNA damage induced by dopamine in the presence of Mn(II), NADH, and Cu(II) is possibly linked to the degeneration of dopaminergic neurons.

iNOS-dependent DNA damage via NF-kappaB expression in hamsters infected with Opisthorchis viverrini and its suppression by the antihelminthic drug praziquantel

Inflammation-mediated DNA damage triggered by Opisthorchis viverrini (OV) infection is a major risk factor of cholangiocarcinoma (CCA). We have recently reported that nitrative and oxidative DNA damage participates in CCA development caused by repeated infection with OV [Pinlaor et al., Carcinogenesis 2004; 25:1535-42]. Therefore, to clarify the preventive effect of the antihelminthic drug praziquantel against cholangiocarcinogenesis, we assessed the effect of this drug on nitrative and oxidative DNA damage, including the formation of 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), and the expression of inducible nitric oxide synthase (iNOS) by immunohistochemistry in OV-infected hamsters. We also examined the expression of nuclear factor-kappaB (NF-kappaB), which functions as a tumor promoter in inflammation-associated cancer. Our results showed that although 1-week treatment with praziquantel did not kill parasites completely in hamsters on days 14 and 30, this drug dramatically reduced inflammatory cell infiltration. Double immunofluorescence staining showed that drug treatment almost completely diminished OV-induced 8-nitroguanine and 8-oxodG formation in bile duct epithelial cells. Quantitative analysis using an electrochemical detector coupled to HPLC revealed that 8-oxodG level in the liver of OV-infected hamsters was significantly decreased by drug treatment (p<0.05). Western blotting and immunohistochemistry revealed that the expression of NF-kappaB and iNOS in bile duct epithelium was reduced by drug treatment. The amount of nitrate plus nitrite in the liver and plasma was significantly decreased after drug treatment. It is concluded that praziquantel can exhibit a preventive effect against OV-induced cholangiocarcinoma by inhibiting iNOS-dependent DNA damage through not only elimination of parasites but also a potential antiinflammatory effect.

Endocrine disruptors that deplete glutathione levels in APC promote Th2 polarization in mice leading to the exacerbation of airway inflammation

Endocrine-disrupting chemicals (EDC) are ubiquitous in environment and may have various undesirable effects on human health. In the present study, we have shown that some EDC [benzophenone, p-octylphenol, and tributyltin chloride (TBT)] promoted strong Th2 polarization via suppression and augmentation of Th1 and Th2 development, respectively, from naive CD4+ T cells primed with anti-CD3 and splenic antigen-presenting cells (APC). The effect was indicated to be indirect via suppression of IL-12 production and augmentation of IL-10 production of APC, which are critical for the Th1 and Th2 development, respectively. Such modulation of cytokine production by EDC was associated with reduction of intracellular glutathione levels in APC. IL-10 deprivation or the addition of N-acetylcysteine, which replenishes intracellular glutathione level during priming, cancelled the effect of EDC on the promotion of Th2 polarization. Oral administration of TBT, which most effectively promoted Th2 polarization in vitro, exacerbated airway inflammation in a murine model of allergic asthma with concomitant enhancement of Th2-type immunity. Collectively these results suggest that EDC such as benzophenone, p-octylphenol, and TBT promote Th2 polarization indirectly via the depletion of glutathione in APC and subsequent modulation of IL-10 and IL-12 production that might result in the exacerbation of allergic diseases.

Opisthorchis viverrini antigen induces the expression of Toll-like receptor 2 in macrophage RAW cell line

Opisthorchis viverrini infection induces inflammation in and around the bile duct, leading to cholangiocarcinoma in humans. To examine the mechanism of O. viverrini-induced inflammatory response, we assessed the expression of Toll-like receptors (TLRs) in RAW 264.7 macrophage cell line treated with an extract of O. viverrini antigen. Flow cytometry and immunocytochemistry showed that O. viverrini antigen induced the expression of TLR2 but not TLR4. Western blotting and immunocytochemistry revealed that nuclear factor-kappaB (NF-kappaB), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were expressed in RAW 264.7 cells treated with O. viverrini antigen in a dose-dependent manner. These results suggest that O. viverrini induces inflammatory response through TLR2-mediated pathway leading to NF-kappaB-mediated expression of iNOS and COX-2.

Mechanism of apoptosis induced by doxorubicin through the generation of hydrogen peroxide

The main anticancer action of doxorubicin (DOX) is believed to be due to topoisomerase II inhibition and free radical generation. Our previous study has demonstrated that TAS-103, a topoisomerase inhibitor, induces apoptosis through DNA cleavage and subsequent H(2)O(2) generation mediated by NAD(P)H oxidase activation [H. Mizutani et al. J. Biol. Chem. 277 (2002) 30684-30689]. Therefore, to clarify whether DOX functions as an anticancer drug through the same mechanism or not, we investigated the mechanism of apoptosis induced by DOX in the human leukemia cell line HL-60 and the H(2)O(2)-resistant sub-clone, HP100. DOX-induced DNA ladder formation could be detected in HL-60 cells after a 7 h incubation, whereas it could not be detected under the same condition in HP100 cells, suggesting the involvement of H(2)O(2)-mediated pathways in apoptosis. Flow cytometry revealed that H(2)O(2) formation preceded the increase in Delta Psi m and caspase-3 activation. Poly(ADP-ribose) polymerase (PARP) and NAD(P)H oxidase inhibitors prevented DOX-induced DNA ladder formation in HL-60 cells. Moreover, DOX significantly induced formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an indicator of oxidative DNA damage, in HL-60 cells at 1 h, but not in HP100 cells. DOX-induced apoptosis was mainly initiated by oxidative DNA damage in comparison with the ability of other topoisomerase inhibitors (TAS-103, amrubicin and amrubicinol) to cause DNA cleavage and apoptosis. These results suggest that the critical apoptotic trigger of DOX is considered to be oxidative DNA damage by the DOX-induced direct H(2)O(2) generation, although DOX-induced apoptosis may involve topoisomerase II inhibition. This oxidative DNA damage causes indirect H(2)O(2) generation through PARP and NAD(P)H oxidase activation, leading to the Delta Psi m increase and subsequent caspase-3 activation in DOX-induced apoptosis.

Vacuolar H+-ATPase inhibitor induces apoptosis via lysosomal dysfunction in the human gastric cancer cell line MKN-1

We investigated the mechanism of apoptosis induced by bafilomycin A(1), an inhibitor of vacuolar H(+)-ATPase. Bafilomycin A(1) significantly inhibited the growth of MKN-1 human gastric cancer cells. Bafilomycin A(1) induced apoptosis as demonstrated by DNA ladder formation and the TUNEL method. We designed a flow cytometric assay to detect the alteration in lysosomal pH using a fluorescent probe, fluorescein isothiocyanate-conjugated dextran. This assay revealed that bafilomycin A(1) dramatically increased lysosomal pH. However, bafilomycin A(1) induced neither significant decrease in mitochondrial transmembrane potential nor the release of mitochondrial cytochrome c into the cytoplasm. Western blotting showed that cathepsin D, but not cathepsin L, was released into the cytoplasm. The activity of caspase-3 was significantly increased by bafilomycin A(1). However, cathepsin D did not directly cleave procaspase-3. These findings suggest that bafilomycin A(1)-induced apoptosis in MKN-1 cells is mediated by other proteases released after lysosomal dysfunction followed by activation of caspase-3 in a cytochrome c-independent manner. The present study showed that flow cytometric analysis of lysosomal pH can be useful to evaluate lysosomal protease-mediated apoptosis.

Mechanism for generation of hydrogen peroxide and change of mitochondrial membrane potential during rotenone-induced apoptosis

Rotenone, an inhibitor of NADH dehydrogenase complex, is a naturally occurring insecticide, which is capable of inducing apoptosis. Rotenone-induced apoptosis is considered to contribute to its anticancer effect and the etiology of Parkinson's disease (PD). We demonstrated that rotenone induced internucleosomal DNA fragmentation, DNA ladder formation, in human cultured cells, HL-60 (promyelocytic leukemia) and BJAB cells (B-cell lymphoma). Flow cytometry showed that rotenone induced H2O2 generation, followed by significant changes in the mitochondrial membrane potential (DeltaPsim). Caspase-3 activity increased in HL-60 cells in a time-dependent manner. These apoptotic events were delayed in HP100 cells, an H2O2-resistant clone of HL-60, confirming the involvement of H2O2 in apoptosis. Expression of anti-apoptotic protein, Bcl-2, in BJAB cells drastically inhibited DeltaPsim change and DNA ladder formation but not H2O2 generation, confirming the participation of mitochondrial dysfunction in apoptosis. NAD(P)H oxidase inhibitors prevented H2O2 generation and DNA ladder formation. These results suggest that rotenone induces O2(-)-derived H2O2 generation through inhibition of NADH dehydrogenase complex and/or activation of NAD(P)H oxidase, and H2O2 generation causes the disruption of mitochondrial membrane in rotenone-induced apoptosis.

Epstein-Barr virus BHRF1 functions downstream of Bid cleavage and upstream of mitochondrial dysfunction to inhibit TRAIL-induced apoptosis in BJAB cells

We have previously reported that TNF-related apoptosis inducing ligand (TRAIL) causes cleavage of Bid via activation of caspase-8 and the loss of mitochondrial membrane potential (DeltaPsim), resulting in apoptosis. Experiments with BJAB clones expressing Epstein-Barr virus (EBV) anti-apoptotic protein BHRF1 showed that BHRF1 drastically inhibited TRAIL-mediated apoptosis. Although Western blot analysis demonstrated that TRAIL-induced Bid cleavage was not inhibited by BHRF1, the decrease in DeltaPsim caused by TRAIL was effectively blocked by BHRF1. These findings suggest that in BJAB cells, BHRF1 acts downstream of Bid cleavage and upstream of mitochondrial damage, resulting in inhibition of TRAIL-induced apoptosis.

Mechanism of apoptosis induced by a new topoisomerase inhibitor through the generation of hydrogen peroxide

TAS-103, a new anticancer drug, induces DNA cleavage by inhibiting the activities of topoisomerases I and II. We investigated the mechanism of TAS-103-induced apoptosis in human cell lines. Pulsed field gel electrophoresis revealed that in the leukemia cell line HL-60 and the H(2)O(2)-resistant subclone, HP100, TAS-103 induced DNA cleavage to form 1-2-Mb fragments at 1 h to a similar extent, indicating that the DNA cleavage was induced independently of H(2)O(2). TAS-103-induced DNA ladder formation in HP100 cells was delayed compared with that seen at 4 h in HL-60 cells, suggesting the involvement of H(2)O(2)-mediated pathways in apoptosis. Flow cytometry revealed that H(2)O(2) formation preceded increases in mitochondrial membrane potential (DeltaPsim) and caspase-3 activation. Inhibitors of poly(ADP-ribose) polymerase (PARP) prevented both TAS-103-induced H(2)O(2) generation and DNA ladder formation. The levels of NAD(+), a PARP substrate, were significantly decreased in HL-60 cells after a 3-h incubation with TAS-103. The decreases in NAD(+) levels preceded both increases in DeltaPsim and DNA ladder formation. Inhibitors of NAD(P)H oxidase prevented TAS-103-induced apoptosis, suggesting that NAD(P)H oxidase is the primary enzyme mediating H(2)O(2) formation. Expression of the antiapoptotic protein, Bcl-2, in BJAB cells drastically inhibited TAS-103-induced apoptosis, confirming that H(2)O(2) generation occurs upstream of mitochondrial permeability transition. Therefore, these findings indicate that DNA cleavage by TAS-103 induces PARP hyperactivation and subsequent NAD(+) depletion, followed by the activation of NAD(P)H oxidase. This enzyme mediates O(2)(-)-derived H(2)O(2) generation, followed by the increase in DeltaPsim and subsequent caspase-3 activation, leading to apoptosis.

Site-specific DNA damage at the GGG sequence by UVA involves acceleration of telomere shortening

Telomere shortening is associated with cellular senescence. We investigated whether UVA, which contributes to photoaging, accelerates telomere shortening in human cultured cells. The terminal restriction fragment (TRF) from WI-38 fibroblasts irradiated with UVA (365-nm light) decreased with increasing irradiation dose. Furthermore, UVA irradiation dose-dependently increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in both WI-38 fibroblasts and HL-60 cells. To clarify the mechanism of the acceleration of telomere shortening, we investigated site-specific DNA damage induced by UVA irradiation in the presence of endogenous photosensitizers using (32)P 5'-end-labeled DNA fragments containing the telomeric oligonucleotide (TTAGGG)(4). UVA irradiation with riboflavin induced 8-oxodG formation in the DNA fragments containing telomeric sequence, and Fpg protein treatment led to chain cleavages at the central guanine of 5'-GGG-3' in telomere sequence. The amount of 8-oxodG formation in DNA fragment containing telomere sequence [5'-CGC(TTAGGG)(7)CGC-3'] was approximately 5 times more than that in DNA fragment containing nontelomere sequence [5'-CGC(TGTGAG)(7)CGC-3']. Catalase did not inhibit this oxidative DNA damage, indicating no or little participation of H(2)O(2) in DNA damage. These results indicate that the photoexcited endogenous photosensitizer specifically oxidizes the central guanine of 5'-GGG-3' in telomere sequence to produce 8-oxodG probably through an electron-transfer reaction. It is concluded that the site-specific damage in telomere sequence induced by UVA irradiation may participate in the increase of telomere shortening rate.

Caspase-3 activation by lysosomal enzymes in cytochrome c-independent apoptosis in myelodysplastic syndrome-derived cell line P39

In most cases, apoptosis is considered to involve mitochondrial dysfunction with sequential release of cytochrome c from mitochondria, resulting in activation of caspase-3. However, we found that etoposide induced apoptosis in P39 cells, a myelodysplastic syndrome-derived cell line, without the release of cytochrome c. Furthermore, in etoposide-treated P39 cells, no changes in mitochondrial membrane potential (delta psi m) were detected by flow cytometry. Flow cytometry using a pH-sensitive probe demonstrated that lysosomal pH increased during early apoptosis in P39 cells treated with etoposide. A reduction in the ATP level preceded the elevation of lysosomal pH. In addition, specific inhibitors of vacuolar H+-ATPase induced apoptosis in P39 cells but not in HL60 cells. Although etoposide-induced activation of caspase-3 was followed by DNA ladder formation in P39 cells, E-64d, an inhibitor of lysosomal thiol proteases, specifically suppressed etoposide-induced activation of caspase-3. Western blotting analysis provided direct evidence for the involvement of a lysosomal enzyme, cathepsin L. These findings indicate that lysosomal dysfunction induced by a reduction in ATP results in leakage of lysosomal enzymes into the cytosolic compartment and that lysosomal enzyme(s) may be involved in activation of caspase-3 during apoptosis in P39 cells treated with etoposide.

DNA damage by dimethylformamide: role of hydrogen peroxide generated during degradation

Dimethylformamide (DMF) has been suspected to associate with cancers in exposed workers, whereas there has been inadequate evidence for carcinogenicity in experimental animals. We demonstrated that H(2)O(2) was generated during the degradation of DMF under aerobic conditions, and that the amount of H(2)O(2) was enhanced by exposure to solar light or by the contamination of trace metal. Experiments using (32)P-5'-end-labeled DNA fragments revealed that the degraded DMF induced DNA damage in the presence of Cu(II). However, purified DMF did not induce DNA damage even in the presence of Cu(II). Addition of purified DMF enhanced DNA damage induced by H(2)O(2) in the presence of Cu(II). The degraded DMF caused Cu(II)-mediated DNA cleavage frequently at thymine and cytosine residues. The similar pattern of site-specific DNA damage was observed with purified DMF and H(2)O(2). Bathocuproine and catalase inhibited the DNA damage, indicating the involvement of Cu(I) and H(2)O(2). A typical free hydroxy radical scavenger showed no inhibitory effect on the DNA damage. Addition of purified DMF enhanced about 3-4-fold 8-oxo-7, 8-dihydro-2'-deoxyguanosine formation induced by H(2)O(2) and Cu(II). ESR spectroscopic study demonstrated that carbon-centered radicals and nitrogen-centered radicals were generated in the reaction mixture of DMF, H(2)O(2), and Cu(II). Inhibitory effects of scavengers on radical formation and DNA damage suggest that carbon-centered radicals and/or nitrogen-centered radicals may contribute to the DNA damage. These results suggest that H(2)O(2) generation during DMF degradation is related to the possible carcinogenic activity of DMF.

TRAIL causes cleavage of bid by caspase-8 and loss of mitochondrial membrane potential resulting in apoptosis in BJAB cells

A new member of the TNF family, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), has been shown to induce apoptosis. However, the mechanism for TRAIL-induced apoptosis remains to be clarified. SDS-PAGE and Western blot analysis showed that cleavage of Bid was induced by a 1-h incubation of BJAB cells with TRAIL and was blocked by a caspase-8 inhibitor. Flow cytometry demonstrated that loss of mitochondrial membrane potential in BJAB cells began about 1.5 h after the treatment with TRAIL and was apparent at 2 h in comparison with the control. DNA ladder formation, which is characteristic for apoptosis, in the cells treated with TRAIL was detected at 2 h and observed most effectively at 3 h. The time course study suggests that TRAIL causes cleavage of Bid via activation of caspase-8, subsequently the loss of mitochondrial membrane potential, resulting in apoptosis in BJAB cells.

N-acetylcysteine, a cancer chemopreventive agent, causes oxidative damage to cellular and isolated DNA

Although N-acetylcysteine is an antioxidant which has been expected to be a cancer chemopreventive agent, its safety and risk assessment have not been evaluated. N-acetylcysteine increased the amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a characteristic oxidative DNA lesion, in human leukemia cell line HL-60, whereas the amount of 8-oxodG in HP100, which is a hydrogen peroxide (H(2)O(2))-resistant cell line derived from HL-60, was not increased. To clarify the mechanism of cellular DNA damage, we investigated DNA damage and its site specificity induced by N-acetylcysteine, using (32)P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene. N-acetylcysteine induced extensive DNA damage in the presence of Cu(II). The DNA cleavage was enhanced by piperidine treatment, suggesting that N-acetylcysteine plus Cu(II) caused not only deoxyribose phosphate backbone breakage but also base modification. N-acetylcysteine plus Cu(II) frequently modified thymine and guanine residues. Bathocuproine, a specific Cu(I) chelator, and catalase inhibited the DNA damage, indicating the participation of Cu(I) and H(2)O(2) in the DNA damage. Typical hydroxyl radical scavengers did not inhibit N-acetylcysteine plus Cu(II)-induced DNA damage, whereas methional completely inhibited it. These results suggest that reactive species derived from the reaction of H(2)O(2) with Cu(I) participates in N-acetylcysteine plus Cu(II)-induced DNA damage. The content of 8-oxodG in calf thymus DNA was increased by N-acetylcysteine in the presence of Cu(II). The present study has demonstrated that N-acetylcysteine could induce metal-dependent H(2)O(2) generation and, subsequently, damage to cellular and isolated DNA. Therefore, it is reasonable to consider that N-acetylcysteine may have the dual function of carcinogenic and anti-carcinogenic potentials. This work requires further studies on safety and risk assessment of N-acetylcysteine.

Generation of hydrogen peroxide precedes loss of mitochondrial membrane potential during DNA alkylation-induced apoptosis

Pulsed field gel electrophoresis showed that the initiation time of DNA breakage induced by the DNA alkylating agent duocarmycin A, which is not a redox-cycling agent, was almost the same in the human leukemia cell line HL-60 and its H2O2-resistant clone HP100. Catalase activity of HP100 cells was much higher than that of HL-60 cells. Duocarmycin A-mediated DNA ladder formation in HP100 cells was delayed compared with that in HL-60 cells, suggesting the involvement of H2O2 in duocarmycin A-induced apoptosis. Flow cytometry demonstrated that peroxide formation preceded loss of mitochondrial membrane potential (delta psi m) in cells treated with duocarmycin A. Then, caspase-3 was activated, followed by DNA ladder formation. These findings suggest that DNA damage by duocarmycin A induces H2O2 generation, which causes delta psi m loss and subsequently caspase-3 activation, resulting in apoptosis.

Role of ultraviolet A-induced oxidative DNA damage in apoptosis via loss of mitochondrial membrane potential and caspase-3 activation

UVA has been implicated in multistage photocarcinogenesis. HPLC analysis revealed that the 7,8-dihydro-8-oxo-2'-deoxyguanosine content of DNA in HL-60 cells increased immediately after UVA irradiation. Pulsed field gel electrophoresis showed that cellular DNA strand breakage was induced at 1 h after UVA irradiation. Flow cytometry showed that mitochondrial membrane potential (delta psi m) decreased time-dependently in cells exposed to UVA. The activity of caspase-3 and DNA ladder formation increased at 2 h after UVA irradiation. These results suggest that UVA irradiation induces oxidative DNA damage, followed by the loss of delta psi m and subsequent activation of caspase-3, resulting in apoptosis.