Protein cohesion induced by metal ions observed with fluorescence correlation spectroscopy.

Nine metal ions were evaluated in the point of denaturating action of proteins. When some metal ions were added to the diluted protein solutions, aggregates appear: stronger denaturation causes the appearance of the larger-size aggregate. The size of the aggregatates are determined by fluorescence correlation spectroscopy (FCS). Green fluorescent protein (ZsGreen) and PE(phycoerythrin)-conjugated human-antibody monoclonal protein were employed as the target protein, of which solution was diluted 100-500 times and mixed with metal ions. According to this process, the denaturation power of metal ions is in the order of Mn(2+)≈ Fe(2+)< Co(2+)< Ni(2+)< Tl(+)< Cd(2+)< Cu(+)< Cu(2+)< Pb(2+)for ZsGreen, and Tl(+)≈ Ni(2+)< Cd(2+)< Fe(2+)< Cr(3+)≪ Pb(2+)for PE-conjugated antibody protein. Pb(2+)exhibits the strongest power of denaturation. In the case of ZsGreen, the denaturation power of metal ions is on the order of the Irving-Williams series, which provide the coordination tendency against ligands possessing nitrogen and oxygen. The present method with FCS is effective to evaluate the denaturation power of metal ions against proteins.

Evaluation of hydrogenated resin acids as molecular markers for tire-wear debris in urban environments.

To propose new molecular markers for tire-wear emissions, four dihydroresin acids, that is, 8-isopimaren-18-oic acid (I), 8-pimaren-18-oic acid (II), 13ß(H)-abieten-18-oic acid (III), and 13α(H)-abiet-8-en-18-oic acid (IV), were identified and investigated for source specificities, distributions, and environmental stabilities. The absence of I-IV in natural sources and the linear correlations between dihydroresin acids with different skeletons in tires and in environmental samples demonstrated that I-IV are specific markers for synthetic rubbers. The ratio of III + IV to the sum of III + IV plus abietic acid showed the resin acids distribution between different environmental compartments receiving contributions from traffic and natural sources. The physicochemical properties and results of photolysis experiments suggested that I-IV can set lower limits for tire-wear contributions to environmental loads of particulate matter (PM) and polycyclic aromatic hydrocarbons with molecular weight ≥202. By comparing III + IV concentrations or (III+IV)/pyrene or (III+IV)/benzo[a]pyrene ratios in tires and those in environmental matrices, the contributions of tire-wear emissions to PM, pyrene, and benzo[a]pyrene were estimated to be 0.68 ± 0.54%, 6.9 ± 4.8%, and 0.37 ± 0.18% in roadside PM and 0.83 ± 0.21%, 0.88 ± 0.52%, and 0.08 ± 0.06% in rooftop PM.

Optical parameter dependence of fluorescence correlation spectrometry without using magnification tools.

The performance of fluorescence correlation spectrometry (FCS) was examined for studying the solutions suspended with the fluorescent particles of various sizes from 50 nm to 10 microm in diameter and for different sizes of pinholes: the particles were made to move by simply stirring the solution in the quartz fluorescence cuvette. Without using any magnification tool for the optical image, this FCS system successfully distinguishes images with a size of smaller than 1 microm. This system was applied for determination of the sizes of microalgae.

Evaluation of immunotoxic and immunodisruptive effects of inorganic arsenite on human monocytes/macrophages.

A trivalent inorganic arsenic, arsenite, has been causing chronic inflammation in humans through the consumption of contaminated well water. The total peripheral blood arsenic concentrations of chronic arsenic-exposed patients, who had inflammatory-like immune responses, are less than 1 microM, thus, nM concentrations may be very important regarding the chronic inflammatory effects by arsenite. However, there are few reports about the biological effects of low concentrations of arsenite in mammalian cells, especially in normal immune effector cells. In this study, we examined whether arsenite has any biological and/or toxicological effects on the differentiation of human peripheral blood monocytes into macrophages using the colony-stimulating factor (CSF) in vitro compared with that of other metallic compounds, and found that arsenite sensitively inhibited the CSF-induced in vitro maturation of monocytes into macrophages at nM levels, and it also induced small, nonadhesive and CD14-positive abnormal macrophage generation from monocytes with granulocyte-macrophage CSF (GM-CSF) at 50-500 nM without cell death. The addition of other metallic compounds, including chromium, selenium, mercury, cadmium, nickel, copper, zinc, cobalt, manganese and other human pentavalent arsenic metabolites, such as inorganic arsenate, monomethylarsonic acid and dimethylarsinic acid, could not induce the same abnormal cell generation from monocytes with CSFs at any concentration and any additional time schedules; they showed only simple cytolethality in monocytes and macrophages at any concentration and any additional time schedules; they showed only simple cytolethality in monocytes and macrophages at n-mM levels accompanied by cell death. This work may have implications in the arsenic-induced chronic inflammation in humans.

Evaluation of in vivo acute immunotoxicity of a major organic arsenic compound arsenobetaine in seafood.

In this study, we observed the in vivo acute immunotoxicity of a trimethyl arsenic compound, arsenobetaine (AsBe), which is present in large quantities in various marine animals that are daily ingested as seafood in many countries. The synthetic pure AsBe was orally administered to CDF(1) mice at a dose of 1.625 g/kg mouse weight once a day on days -6, -4, -2 and 0 (four times, total 6.5 g/kg mouse weight), and its effect on the immune organs and immune effector cells were assessed until day 8. Orally administered AsBe was temporally distributed to the immune organs, such as the spleen and thymus, but was not very toxic both quantitatively and qualitatively on these immune organs and immune effector cells, splenocytes, thymocytes, Peyer's patch lymphocytes and peritoneal macrophages. This finding suggests that the ingestion of AsBe contained in marine animals is relatively safe to the health of people who often consume marine animals in their daily diet.

Evaluation of immunotoxic and immunodisruptive effects of inorganic arsenite on human monocytes/macrophages.

A trivalent inorganic arsenic, arsenite, has been causing chronic inflammation in humans through the consumption of contaminated well water. The total peripheral blood arsenic concentrations of chronic arsenic-exposed patients, who had inflammatory-like immune responses, are less than 1 microM, thus, nM concentrations may be very important regarding the chronic inflammatory effects by arsenite. However, there are few reports about the biological effects of low concentrations of arsenite in mammalian cells, especially in normal immune effector cells. In this study, we examined whether arsenite has any biological and/or toxicological effects on the differentiation of human peripheral blood monocytes into macrophages using the colony-stimulating factor (CSF) in vitro compared with that of other metallic compounds, and found that arsenite sensitively inhibited the CSF-induced in vitro maturation of monocytes into macrophages at nM levels, and it also induced small, nonadhesive and CD14-positive abnormal macrophage generation from monocytes with granulocyte-macrophage CSF (GM-CSF) at 50-500 nM without cell death. The addition of other metallic compounds, including chromium, selenium, mercury, cadmium, nickel, copper, zinc, cobalt, manganese and other human pentavalent arsenic metabolites, such as inorganic arsenate, monomethylarsonic acid and dimethylarsinic acid, could not induce the same abnormal cell generation from monocytes with CSFs at any concentration and any additional time schedules; they showed only simple cytolethality in monocytes and macrophages at n-mM levels accompanied by cell death. This work may have implications in the arsenic-induced chronic inflammation in humans.

Chemical sensing of metal ions using a silica-micelle mesophase doubly functionalized by a fluorogenic ionophore and a masking agent.

We report on a chemical-sensing method based on the silica-micelle mesophase wherein both a fluoroionophore and a masking agent are embedded. Using this method, a highly selective detection of metal ions in an aqueous solution has been successfully demonstrated. Furthermore, simultaneous analyses of multisamples using a sensor array composed of functionalized mesoporous thin films were demonstrated for the first time.

Comparison of fluorescence correlation spectrometry with the ordinary fluorescence optical configuration with flow cytometry as a tool for micrometer-level size determination.

As a tool for micrometer-level size determination, fluorescence correlation spectroscopy (FCS), performed based on our previous report, was compared to flow cytometry (FCM). For this purpose, standard fluorescent beads were subjected to both methods. And hence, it was found that our FCS is a useful method with satisfactory precision for size determinations of individual particles at micrometer size levels, while providing the average size for a mixture of two kinds of particles with different sizes.

Size-dependent toxicity of silica nano-particles to Chlorella kessleri.

SiO(2) nano-particles were found to exhibit size-dependent toxicity toward the alga, Chlorella kessleri. Small SiO(2) nano-particles exhibit stronger toxicity: 50% inhibitory concentrations (IC(50)) value for 5 nm = 0.8 +/- 0.6%, 26 nm = 7.1 +/- 2.8%, and 78 nm = 9.1 +/- 4.7%. Enlargement of the cell body was observed by flow cytometry, which is due to the presence of structures that obstructed cell division. Optical and transmission microscopes were used to observe coagulated cells with incomplete division. Although the physiological effect of SiO(2) nano-particles was not clear, SiO(2) nano-particles are toxic, at least for algae in aquatic media. Under the transmission electron microscope, several amorphous structures appeared in the cells that were exposed to 5-nm silica nano-particles.

Effects of derivatization on solar-induced decomposition of polycyclic aromatic hydrocarbons in aqueous media.

The solar-induced decomposition of 10 polycyclic aromatic hydrocarbons (PAHs) was observed in aqueous media. All 10 PAHs observed were half-decomposed within 120 min. Among anthracene derivatives, the decomposition rates were: anthracene = 1-methylanthracene < 2-methylanthracene < 9-methylanthracene < 9,10-dimethylanthracene approximately 2-aminoanthracene. The addition of commercial humic acid had no effect on the decomposition rates of these PAHs. Deuterium water also hastened the decomposition of PAH. The products obtained by the solar radiation of PAH after extraction to DCM were mainly ketone and hydroxyl derivatives. To explain these results, reactivities and electron charges at the constituent carbon atoms in each anthracene derivative were examined by an ab initio molecular orbital calculation method.

Compound class specific 14C analysis of polycyclic aromatic hydrocarbons associated with PM10 and PM1.1 aerosols from residential areas of suburban Tokyo.

Compound class specific radiocarbon analysis (CCSRA) was performed for polycyclic aromatic hydrocarbons (PAHs) associated with airborne particulate matter (APM) with diameter <10 microm (PM10) and <1.1 microm (PM1.1) collected from a residential area of suburban Tokyo, Japan, and seasonal and particle-size radiocarbon variations were investigated. Source diagnostic isomer pair ratios indicated mixed contributions from petroleum combustion and from biomass and coal combustion to the PAHs in APM. The delta14C- PAHs in APM, ranging from -787 to -514 per thousand, indicated dominance of fossil fuel combustion. The delta14C of 5-6 rings (HMW) PAHs were higher than the 3-4 rings (LMW) species in both PM10 and PM1.1 samples. The delta14C of HMW-PAHs indicated greater biomass-burning contributions in summer than in winter and no apparent particle-size variation. Conversely, the delta14C of LMW species showed a greater contribution from fossil sources in summer and in larger particles (PM10). This finding could be tentatively attributed to the recondensation of fossil-PAHs vaporized from petroleum sources. A 14C isotopic mass balance approach estimated that biomass burning contributes 17-45% of the PAH burden in suburban Tokyo, and that the increase in the biomass-PAH accounts for approximately 27% and 22% of winter-time elevation of LMW- and HMW-PAHs, respectively. These are far exceeding what is expected from the emission statistics for CO2 and combusted materials in Japan and emphasizing the importance of biomass-burning as a source of PAHs; which, in turn, demonstrates the utility and the significance of field-based source assessment by using CCSRA for an effective regulation of atmospheric pollution by PAHs.

Inorganic arsenite alters macrophage generation from human peripheral blood monocytes.

Inorganic arsenite has caused severe inflammatory chronic poisoning in humans through the consumption of contaminated well water. In this study, we examined the effects of arsenite at nanomolar concentrations on the in vitro differentiation of human macrophages from peripheral blood monocytes. While arsenite was found to induce cell death in a culture system containing macrophage colony stimulating factor (M-CSF), macrophages induced by granulocyte-macrophage CSF (GM-CSF) survived the treatment, but were morphologically, phenotypically, and functionally altered. In particular, arsenite-induced cells expressed higher levels of a major histocompatibility complex (MHC) class II antigen, HLA-DR, and CD14. They were more effective at inducing allogeneic or autologous T cell responses and responded more strongly to bacterial lipopolysaccharide (LPS) by inflammatory cytokine release as compared to cells induced by GM-CSF alone. On the other hand, arsenite-induced cells expressed lower levels of CD11b and CD54 and phagocytosed latex beads or zymosan particles less efficiently. We also demonstrated that the optimum amount of cellular reactive oxygen species (ROS) induced by nM arsenite might play an important role in this abnormal monocyte differentiation. This work may have implications in chronic arsenic poisoning because the total peripheral blood arsenic concentrations of these patients are at nM levels.

Preventive mechanism of cellular glutathione in monomethylarsonic acid-induced cytolethality.

Human pentavalent arsenic metabolic intermediate, monomethylarsonic acid (MMAs(V)), is a major arsenic type found in the blood in chronic arsenic poisoning patients, but little information is available on its toxicity potential or mechanisms of action. In this study, we investigated the molecular mechanisms of in vitro cytolethality of MMAs(V) using rat liver TRL 1215 cells. Cellular arsenic concentrations reached the nanomolar range in TRL 1215 cells when cells were exposed to millimolar levels of MMAs(V), and most of the MMAs(V) was not metabolized during the 48-h incubation. Under these conditions, MMAs(V) showed significant cytolethality when cellular reserves of reduced glutathione (GSH) were depleted. Morphological and biochemical evidence confirmed that MMAs(V) induced both necrosis and apoptosis in the cellular GSH-depleted cells. MMAs(V) significantly enhanced cellular caspase 3 activity in the cellular GSH-depleted cells, and a caspase 3 inhibitor blocked MMAs(V)-induced apoptosis. MMAs(V) also enhanced the production of cellular reactive oxygen species (ROS) in the cellular GSH-depleted cells, and addition of a membrane-permeable radical trapping reagent completely prevented both MMAs(V)-induced cellular caspase 3 activation and cytolethality in these cells. These observations suggest that MMAs(V) typically generates harmful ROS in cells, and cellular GSH prevents cytolethality by scavenging these toxic ROS. However, when cellular GSH levels are decreased, MMAs(V) induces oxidative stress in the cells, and this leads to apoptosis and/or necrosis depending on the cellular ROS/GSH ratio.

Benzothiazolamines as tire-derived molecular markers: sorptive behavior in street runoff and application to source apportioning.

Wash-off and sorptive behaviors of two benzothiazolamines (BTs) [i.e., 2-(4-morpholinyl)benzothiazole (24MoBT) and N-cyclohexyl-2-benzothiazolamine (NCBA)] have been investigated as possible molecular markersfortire debris and/or road dust transported in highway runoff water. Sum of dissolved and particulate 24MoBT and NCBA concentrations in runoff water ranged from 15 to 417ng/L and from 22to 508ng/L, respectively. Proportions of NCBA in particulate (>0.7microm) phase (<9-79%) were larger than that of 24MoBT (<1-14%), which was consistent with their experimentally determined octanol/water partition coefficients (Kow; 10(4.23+/-0.14) for NCBA; 10(2.42+/-0.03) for 24MoBT). The organic carbon-normalized in-situ partition coefficient (Koc') observed in runoff events (10(4.69+/-0.28) for NCBA; 10(3.42+/-0.23) for 24MoBT) were 1 order of magnitude higher than those expected from their Kow, indicating strong affinity of BTs to suspended particulate matter (SPM) in runoff water. Furthermore, in desorption experiments lasting 24 h, we observed almost the same levels of Koc' as those in runoff events, implying that significant fractions of BTs are strongly associated with runoff particles and not easily available to equilibrium partitioning. NCBA was ubiquitous in sediments from the Nogawa River receiving runoff from the Chuo Highway, whereas many of those samples had undetectable levels of 24MoBT. All of above results indicate that NCBA would be more suitable than 24MoBT as a molecular marker for runoff particles loading the aquatic environment. By using SPM-weighted mean concentration of particulate NCBA, at least 3.3+/-1.6% of the mass in the Nogawa sediments is estimated to be from runoff SPM.

Cellular glutathione prevents cytolethality of monomethylarsonic acid.

Inorganic arsenicals are clearly toxicants and carcinogens in humans. In mammals, including humans, inorganic arsenic often undergoes methylation, forming compounds such as monomethylarsonic acid (MMAs(V)) and dimethylarsinic acid (DMAs(V)). However, much less information is available on the in vitro toxic potential or mechanisms of these methylated arsenicals, especially MMAs(V). We studied the molecular mechanisms of in vitro cytolethality of MMAs(V) using a rat liver epithelial cell line (TRL 1215). MMAs(V) was not cytotoxic in TRL 1215 cells even at concentrations exceeding 10 mM, but it became weakly cytotoxic and induced both necrotic and apoptotic cell death when cellular reduced glutathione (GSH) was depleted with the glutathione synthase inhibitor, l-buthionine-[S,R]-sulfoximine (BSO), or the glutathione reductase inhibitor, carmustine. Similar results were observed in the other mammalian cells, such as human skin TIG-112 cells, chimpanzee skin CRT-1609 cells, and mouse metallothionein (MT) positive and MT negative embryonic cells. Ethacrynic acid (EA), an inhibitor of glutathione S-transferase (GST) that catalyses GSH-substrate conjugation, also enhanced the cytolethality of MMAs(V), but aminooxyacetic acid (AOAA), an inhibitor of beta-lyase that catalyses the final breakdown of GSH-substrate conjugates, had no effect. Both the cellular GSH levels and the cellular GST activity were increased by the exposure to MMAs(V) in TRL 1215 cells. On the other hand, the addition of exogenous extracellular GSH enhanced the cytolethality of MMAs(V), although cellular GSH levels actually prevented the cytolethality of combined MMAs(V) and exogenous GSH. These findings indicate that human arsenic metabolite MMAs(V) is not a highly toxic compound in mammalian cells, and the level of cellular GSH is critical to its eventual toxic effects.

Role of glutathione in dimethylarsinic acid-induced apoptosis.

Inorganic arsenicals are clearly toxicants and carcinogens in humans. In mammals, including humans, inorganic arsenicals often undergo methylation, forming compounds such as dimethylarsinic acid (DMAs(V)). Recent evidence indicates that DMAs(V) is a complete carcinogen in rodents although evidence for inorganic arsenicals as carcinogens in rodents remains equivocal. Thus, we studied the molecular mechanisms of in vitro cytolethality of DMAs(V) using a rat liver epithelial cell line (TRL 1215). DMAs(V) selectively induced apoptosis in TRL 1215 cells; its LC(50) value after 48 h exposure was 4.5 mM. The addition of a glutathione synthase inhibitor, L-buthionine-[S,R]-sulfoximine (BSO), actually decreased DMAs(V)-induced apoptosis. DMAs(V) exposure temporarily decreased cellular reduced glutathione (GSH) levels and enhanced cellular glutathione S-transferase (GST) activity from 6 h after the exposure when the cells were still alive. Also, DMAs(V) exposure activated cellular caspase 3 activity with a peak at 18 h after the exposure when apoptosis began, and BSO treatment completely inhibited this enzyme activity. The additions of inhibitors of caspase 3, caspase 8, and caspase 9 significantly reduced DMAs(V)-induced apoptosis. Taken together, these data indicate that cellular GSH was required for DMAs(V)-induced apoptosis to occur, and activation of cellular caspases after conjugation of DMAs(V) with cellular GSH appears to be of mechanistic significance. Further research will be required to determine the role of intracellular GSH and methylation in the toxicity of arsenicals in chronic arsenic poisoning or in cases where arsenicals are used as chemotherapeutics.