• Molecular & Cellular Toxicology
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• v.4 no.2
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• pp.157-163
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• 2008

Formation of ${\beta}$-amyloid $(A{\beta})$ fibrils has been identified as one of the major characteristics of Alzheimer's disease (AD). Inhibition of $A{\beta}$ fibril formation in the CNS would be attractive therapeutic targets for the treatment of AD. Several small compounds that inhibit amyloid formation or amyloid neurotoxicity in vitro have been known. Citrate has surfactant function effect because of its molecular structure having high anionic charge density, in addition to the well-known antibacterial and antioxidant properties. Therefore, we hypothesized that citrate might have the inhibitory effect against $A{\beta}$ fibril formation in vitro and have the protective effect against $A{\beta}$-induced neurotoxicity in PC12 cells. We examined the effect of citrate against the formation of $A{\beta}$ fibrils by measuring the intensity of fluorescence in thioflavin-T (Th-T) assay of between $A{\beta}_{25-35}$ groups treated with citrate and the control with $A{\beta}_{25-35}$ alone. The neuroprotective effect of citrate against $A{\beta}$-induced toxicity in PC12 cells was investigated using the WST-1 assay. Fluorescence spectroscopy showed that citrate inhibited dose-dependently the formation of $A{\beta}$ fibrils from ${\beta}$-amyloid peptides. The inhibition percentages of $A{\beta}$ fibril formation by citrate (1, 2.5, and 5 mM) were 31%, 60%, and 68% at 7 days, respectively in thioflavin-T (Th-T) assay. WST-1 assay revealed that the toxic effect of $A{\beta}_{25-35}$ was reduced, in a dose-dependent manner to citrate. The percentages of neuroprotection by citrate (1, 2.5, and 5 mM) against $A{\beta}-induced$ toxicity were 19%, 31 %, and 34%, respectively. We report that citrate inhibits the formation of $A{\beta}$ fibrils in vitro and has neuroprotective effect against $A{\beta}$-induced toxicity in PC12 cells. Neuroprotective effects of citrate against $A{\beta}$ might be, to some extent, attributable to its inhibition of $A{\beta}$ fibril formation. Although the mechanism of anti-amyloidogenic activity is not clear, the possible mechanism is that citrate might have two effects, salting-in and surfactant effects. These results suggest that citrate could be of potential therapeutic value in Alzheimer's disease.

• Resources Recycling
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• v.17 no.2
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• pp.3-15
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• 2008

Different toxic wastes are disposed of in our surroundings and these will ultimately threaten the existence of living organisms. Biohydrometallurgy, which includes the processes of bioleaching and bioremediation through the activities of microorganisms such as bacterial or fungal species, is a technology that has the potential to overcome many environmental problems at a reasonable economic cost. Bioleaching were carried out for dissolution of metals from different materials using most important metal mobilizing bacteria such as Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Laptospirillum ferrooxidans. According to the reaction, bioleaching is parted as direct and indirect mechanism. In direct mechanism the bacteria oxidize the sulphides minerals by accepting electron and producing sulphuric acid in leaching media for their growth and metabolism. In other hand the indirect bioleaching is demonstrated as the oxidation of sulphides mineral by the oxidant like $Fe^{3+}$ produced by the iron oxidizing bacteria. Through this process, substantial amount of metal can be recovered from low-grade ores, concentrates, industrial wastes like sludge, tailings, fly ash, slag, electronic scrap, spent batteries and spent catalysts. This may be alternative technology to solve the high deposition of waste, which moves toward a healthy environment and green world.

• YAKHAK HOEJI
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• v.40 no.6
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• pp.705-712
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• 1996

We have previously shown that determination of glucose uptake using ${\alpha}$-methylglucose(${\alpha}$-MG) is very sensitive and rapid parameter for the assessment of loss of cellular fu nction in renal cell line($LLC-PK_1$). The present study was designed to elucidate the mechanism of inhibition of ${\alpha}$-MG uptake and the intracellular site of toxic action of cisplatin(CIS). $LLC-PK_1$ cells were exposed to various concentrations(5 ${\mu}$M-l00 ${\mu}$M) of CIS for 5 hrs or 24 hrs and ${\alpha}$-MG uptake was determined. Mitochondrial function was evaluated by measuring intracellular ATP content and MTT reduction. The activities of marker enzymes for the basolateral membrane(Na$^+$-K$^+$ ATPase) and brush border membrane (alkaline phosphatase: ALP) were also measured. CIS treatment significantly inhibited the ${\alpha}$-MG uptake in a time- and dose-dependent manner above 25 ${\mu}$M for 5 hrs. Intracellular ATP content and MTT reduction were affected by 24 hr-treatment of 50 ${\mu}$M CIS. The activities of Na$^+$-K$^+$ ATPase and ALP were significantly decreased at 10 ${\mu}$M and 5 ${\mu}$M of CIS for 24 hrs, respectively. The incubation with CIS for 5 hrs had no effects on the intracellular ATP content, MTT reduction and the activities of marker enzymes up to 100 ${\mu}$M. These results partly indicate that inhibition of ${\alpha}$-MG uptake by CIS may not be attributed to the disturbance of mitochondrial function or inhibition of the activity of Na$^+$-K$^+$ ATPase and can be resulted from direct effect of CIS on the Na$^+$/glucose cotransporter in brush border membrane. This study shows that additional mechanistic information, indicating the intracellular site of nephrotoxic action, can be gained by coupling the ${\alpha}$-MG uptake and ATP content or the activity of Na$^+$-K$^+$ ATPase.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.24-24
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• 2017

Heavy metals at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to oxidative stress in plants. The present study was performed to explore the metal tolerance mechanism in Sorghum seedling. Morpho-physiological and metal ions uptake changes were observed prominently in the seedlings when the plants were subjected to different concentrations of $CuSO_4$ and $CdCl_2$. The observed morphological changes revealed that the plants treated with Cu and Cd displayed dramatically altered shoot lengths, fresh weights, and relative water content. In addition, the concentration of Cu and Cd was markedly increased by treatment with Cu and Cd, and the amount of interacting ions taken up by the shoots and roots was significantly and directly correlated with the applied level of Cu and Cd. Using the 2-DE method, a total of 24 and 21 differentially expressed protein spots from sorghum leaves and roots respectively, 33 protein spots from sorghum leaves under Cd stress were analyzed using MALDI-TOF/TOF MS. However, the over-expression of GAPDH plays a significant role in assisting Sorghum bicolor to attenuate the adverse effects of oxidative stress caused by Cu, and the proteins involved in resistance to stress helped the sorghum plants to tolerate high levels of Cu. Significant changes were absorbed in the levels of proteins known to be involved in carbohydrate metabolism, transcriptional regulation, translation and stress responses. In addition, the up-regulation of glutathione S-transferase and cytochrome P450 may play a significant role in Cd-related toxicity and stress responses. The results obtained from the present study may provide insights into the tolerance mechanism of seedling leaves and roots in Sorghum under heavy metal stress.

• Proceedings of the Korean Society of Toxicology Conference
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• 2006.11a
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• pp.46-54
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• 2006

The methylmercury (MeHg) is a toxic environmental pollutant, causing serious neurological and developmental effects in humans. Recent epidemiological studies have indicated that ingestion of MeHg in fish during pregnancy can result in neuroethological effects in the offspring. However, the mechanism underlying the MeHg-toxicity is not fully understood. To elucidate the mechanisms of toxicity of MeHg and of defense against MeHg, we searched for factors that determine the sensitivity of yeast cells to MeHg, and found that overexpression of Cdc34, a ubiquitin-conjugating enzyme (E2) that is a component of the ubiquitin-proteasome (UP) system, induces a resistance to MeHg toxicity in both yeast and human cells. The UP system is involved in the intracellular degradation of proteins. When Cdc34 is overexpressed in cells, ubiquitination reactions are activated and the degradation of certain proteins by the UP system is enhanced. Therefore, it seems likely that certain as-yet-unidentified proteins that increase MeHg toxicity might exist in cons and that toxicity might be reduced by the enhanced degradation of such proteins, mediated by the UP system, when Cdc34 is overexpressed. SCF ubiquitin-ligase is a component of UP system and consists of Skpl, the scaffold protein Cdc53, the RING-finger protein Hrt1, and one member of the family of F-box proteins. The F-box proteins directly bind to the substrates and are the determinants of substrate specificity of SCF. Therefore, we searched for the f-box protein that cofers resistance to MeHg, and found that overexpression of Hrt3 or Yi1224w induced resistance to MeHg toxicity in yeast cells. Since the protein(5) that enhance toxicity of MeHg might plausibly be induced in substrates of both f-box proteins, we next searched for substrate proteins that are recognized by Hrt3 or Y1r224w using two-hybrid screen. We found that Did3 or Crsl interacts with Hrt3; and Eno2 interacts with Yir224w. The yeast cells that overexpressed each those proteins showed hypersensitivity to MeHg, respectively, indicating that those proteins enhance the MeHg toxicity. Both Dld3 and Eno2 are proteins involved in the synthesis of pyruvate, and overexpression of both proteins might induce increase in interacellular levels of pyruvate. Deletion of Yi1006w that transports pyruvate into the mitochondria induced aresistance to MeHg. These results suggest that the promotion of the pyruvate irdlowinto the mitochondria might enhance MeHg toxicity. This study providesimportant keyfor the elucidauon of the molecular mechanism of MeHg toxicity.

• Childhood Kidney Diseases
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• v.2 no.2
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• pp.138-144
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• 1998

Purpose : The use of cyclosporine and mitomycin in various immunologic or neoplastic disorders has been known to cause wide-ranged nephrotoxic effects including thrombotic microangiopathy. However, the mechanism of nephrotoxicity of these drugs has not been studied adequately, so that present experimental study has been undertaken to find out whether these drugs can cause direct damage to the kidney and to clarify the pathogenetic mechanism of nephrotoxic effect of these drugs. Materials and methods : Sprague-Dawley rats weighing 250-300 gm were used for experimental animals and unilateral renal perfusion technique, modified from the method described by Hoyer et al was used. Isolation of left kidney from systemic circulation was made by clamping aorta and left renal vein and a hole was punctured in the anterior wall of the left renal vein. Cyclosporine (2.5 mg in 4 ml solution) and mitomycin (1.6 mg in 4ml solution) were infused through left renal artery and normal saline was used in control rats. Forty-eight hours after infusion of the drugs, animals were sacrificed and left kidney removed and processed for histologic examination. Total ischemic time of left kidney was less than 15 minutes: Results : Cyclosporine-perfused group showed severe swelling of glomerular endothelial ceil along with swelling of glomerular epithelial cell and interstitial vascular endothelial cell. Mitomycin-perfused group also showed severe swelling of glomerular endothelial and epithelial cells. And in addition to these findings, they demonstrated platelets aggregation, swelling and degranulation of platelets and fibrin accumulation in some of the capillaries, indicating occurrance of thrombotic microangiopathy. Conclusion : present experiment indicates that cyclosporine and mitomycin can cause direct toxic injury to renal endothelial cell. And this direct toxic damage to endothelial cell seems to be an important initiating event for the development of thrombotic microangiopathy.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.69-75
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• 2006

Improper disposal of petroleum and spills from underground storage tanks have created large areas with highly toxic contamination of the soil and groundwater. Methyl tert-butyl ether (MTBE) is widely used as a fuel additive because of its advantageous properties of increasing the octane value and reducing carbon monoxide and hydrocarbon exhausts. However, MTBE is categorized as a possible human carcinogen. This research investigated the Modified Photo-Fenton system which is based on the Modified Fenton reaction and UV light irradiation. The Modified Fenton reaction is effective for MTBE degradation near a neutral pH, using the ferric ion complex composed of a ferric ion and environmentally friendly organic chelating agents. This research was intended to treat high concentrations of MTBE; thus, 1,000 mg/L MTBE was chosen. The objectives of this research are to find the optimal reaction conditions and to elucidate the kinetic and mechanism of MTBE degradation by the Modified Photo-Fenton reaction. Based on the results of experiments, citrate was chosen among eight chelating agents as the candidate for the Modified Photo-Fenton reaction because it has a relatively higher final pH and MTBE removal efficiency than the others, and it has a relatively low toxicity and is rapidly biodegradable. MTBE degradation was found to follow pseudo-first-order kinetics. Under the optimum conditions, [$Fe^{3+}$] : [Citrate] = 1 mM: 4 mM, 3% $H_2O_2$, 17.4 kWh/L UV dose, and initial pH 6.0, the 1000 ppm MTBE was degraded by 86.75% within 6 hours and 99.99% within 16 hours. The final pH value was 6.02. The degradation mechanism of MTBE by the Modified Photo-Fenton Reaction included two diverse pathways and tert-butyl formate (TBF) was identified to be the major degradation intermediate. Attributed to the high solubility, stability, and reactivity of the ferric-citrate complexes in the near neutral condition, this Modified Photo-Fenton reaction is a promising treatment process for high concentrations of MTBE under or near a neutral pH.

• Tuberculosis and Respiratory Diseases
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• v.43 no.4
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• pp.579-589
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• 1996

Background : Activation of neutrophil is critical for the clearance of microorganisms and toxic host mediators during sepsis. Unfortunately the activated neutrophil and its toxic byproducts can produce tissue injury and organ dysfunction. The leucocyte CD11/18 adhesion complex regulates neutrophil-endothelial cell adhesion, the first step in neutrophil migration to sites of injection and inflammation. To investigate the potential of neutrophil inhibition as a treatment strategy for sepsis, we evaluated the effects of monoclonal antibody against CD11b (MAb 1B6) in rats intrabronchial challenged with Escherichia coli. Methods : Animals were randomly assigned to receive monoclonal antibody against CD11b (1 mg/kg, sc) and bovine serum albumin(BSA, 1 mg/kg, sc) 6 hr before, at 0 and 6 hr after intrabronchial challenge of $20x10^9$ CFU/kg E. coli 0111. Animals were randomized to treat either 24, 60 or 90% oxygen after bacterial challenge and begining 4 hr after inoculation, all animals were received 100 mg/kg ceftriaxone qd for 3 days. Peripheral and alveolar neutrophil(by bronchoalveolar lavage) counts and lung injury parameters such as alveolar-arte rial $PO_2$ difference, wet to dry lung weight ratio and protein concentration of alveolar fluid were measured in survived rats at 12 hr and 96 hr. Results : Monoclonal antibody against CD11b decreased circulating and alveolar neutrophil especially more in 12 hr than in 96 hr The lung injury parameters of antibody-treated animals were not different from those of BSA-treated animals. but It was meaningless due to small number of survived animals. The early(6 hr) mortality rate was significantly increased in antibody-treated group(51%) compared to BSA-treated group(31%) (P=0.02) but late(from 12 hr to 72 hr) mortality rate was not different in antibody-treated group(44%) from BSA-treated group(36%) (P =0.089). Conclusion : Leucocyte CD11b/18 adhesion molecule is known to regulate neutrophil migration to the site of infection and inflammation. The monoclonal antibody against CD11b decreased alveolar neutrophil in rats with pulmonary sepsis and increased early mortality rate. Therefore, we can speculate that monoclonal antibody against CD11b blocks of alveolar recruitment of neutrophils, impairs host defense mechanism and increases early mortality rate of pulmonary sepsis in rat.

• Journal of Digital Convergence
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• v.15 no.11
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• pp.285-295
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• 2017

This study aims to provide basic data on useful functional ingredients in red ginseng by studying the anti-inflammatory and anti-cancer effects of convergence of ginsenoside Rh2(Rh2) and compound K(CK) isolated from amplified red ginseng. Therefore we examined cytotoxicity in Hep3B, activity of IL-6 induced STAT3 luciferase and survival concentration of cells in B16F10 and HaCa T. According to the experimental results, when the Rh2 and CK mixture were 10 ug/ml, there was no cytotoxicity in Hep3B cells and the anti-inflammatory effect of IL-6 reduction ratio was 102%. In addition, Rh2 and CK mixture were observed to be toxic in melanoma cell line B16F10 and HaCa T (human keratinocyte) at 50 uM. FACS(fluorescence activated cell sorting) analysis showed that annexin V was not expressed and melanoma cells and keratinocyte were desorbed and killed. It can be assumed that the mechanism of killing through this phenomenon is due to the cell death of anoikis-type, and it is necessary to study the changes of cell adhesion proteins in the future in order to clarify the cell death signal system.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.12
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• pp.667-675
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• 2016

Nanoscale zero-valent iron (nZVI) has been effectively applied for environmental remediation due to its ability to reduce various toxic compounds. However, quantification of nZVI reactivity has not yet been standardized. Here, we adapted colorimetric assays for determining reductive activity of nZVIs. A modified indophenol method was suggested to determine reducing activity of nZVI. The method was originally developed to determine aqueous ammonia concentration, but it was further modified to quantify phenol and aniline. The assay focused on analysis of reduction products rather than its mother compounds, which gave more accurate quantification of reductive activity. The suggested color assay showed superior selectivity toward reduction products, phenol or aniline, in the presence of mother compounds, 4-chlorophenol or nitrobenzene. Reaction conditions, such as reagent concentration and reaction time, were optimized to maximize sensitivity. Additionally, pretreatment step using $Na_2CO_3$ was suggested to eliminate the interference of residual iron ions. Monometallic nZVI and bimetallic Ni/Fe were investigated with the reaction. The substrates showed graduated reactivity, and thus, reduction potency and kinetics of different materials and reaction mechanism was distinguished. The colorimetric assay based on modified indophenol reaction can be promises to be a useful and simple tool in various nZVI related research topics.