Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Archives of Toxicology (v.76, #5-6)
No Title by Ricarda Thier; Thomas Brüning; Peter H. Roos; Hermann M. Bolt (pp. 249-256).
Alcohol consumption and tobacco smoking are major causes of head and neck cancers, and regional differences point to the importance of research into gene-environment interactions. Much interest has been focused on polymorphisms of CYP1A1 and of GSTM1 and GSTT1, but a number of studies have not demonstrated significant effects. This has mostly been ascribed to small sample sizes. In general, the impact of polymorphisms of metabolic enzymes appears inconsistent, with some reports of weak-to-moderate associations, and with others of no elevation of risks. The classical cytochrome P450 isoenzyme considered for metabolic activation of polycyclic aromatic hydrocarbons (PAH) is CYP1A1. A new member of the CYP1 family, CYP1B1, was cloned in 1994, currently representing the only member of the CYP1B subfamily. A number of single nucleotide polymorphisms of the CYP1B1 gene have been reported. The amino acid substitutions Val432Leu (CYP1B1*3) and Asn453Ser (CYP1B1*4), located in the heme binding domain of CYP1B1, appear as likely candidates to be linked with biological effects. CYP1B1 activates a wide range of PAH, aromatic and heterocyclic amines. Very recently, the CYP1B1 codon 432 polymorphism (CYP1B1*3) has been identified as a susceptibility factor in smoking-related head-and-neck squamous cell cancer. The impact of this polymorphic variant of CYP1B1 on cancer risk was also reflected by an association with the frequency of somatic mutations of the p53 gene. Combined genotype analysis of CYP1B1 and the glutathione transferases GSTM1 or GSTT1 has pointed to interactive effects. This provides new molecular evidence that tobacco smoke-specific compounds relevant to head and neck carcinogenesis are metabolically activated through CYP1B1 and is consistent with a major pathogenetic relevance of PAH as ingredients of tobacco smoke.
Keywords: CYP1B1 Head and neck cancer Laryngeal cancer Enzyme polymorphisms Gene–environment interactions Tobacco smoking
No Title by Richard Schreurs; Peter Lanser; Willem Seinen; Bart van der Burg (pp. 257-261).
In the past decade the list of chemicals in the environment that are able to mimic the natural hormone estrogen, thereby disrupting endocrine function, has grown rapidly. These chemicals are able to bind to estrogen receptors (ERs) and influence estrogen signalling pathways, although several of them have structures that differ substantially from the endogenous hormone 17β-estradiol. In this study, six extensively used ultraviolet (UV) filters were assessed for transcriptional activation of estrogen receptors. Because of their high lipophilicity, these UV filters tend to bioaccumulate in the environment. They have been found in surface waters, fish, and in human milk fat. Using a sensitive in vitro reporter gene assay, we found that all six compounds induce estrogenic activity towards ERα, while four out of six compounds induced transcriptional activity of ERβ. Zebrafish, in which an estrogen responsive luciferase reporter gene has been stably introduced, were used for in vivo testing. In this transgenic zebrafish assay none of the compounds showed estrogenic activity. Our findings suggest that one should be aware of over-interpretation when predicting in vivo effects from weak in vitro data. However, it can not be ruled out that these UV filters have long-term effects in the environment.
Keywords: UV filters Estrogen receptors Estrogenicity Transgenic zebrafish
No Title by Andrea Trevisan; Christine Marzano; Patrizia Cristofori; Matteo Borella Venturini; Lorena Giovagnini; Dolores Fregona (pp. 262-268).
A new palladium(II)-dithiocarbamate complex, [Pd(ESDT)Cl]n, was synthesised and its chemical characteristics are discussed. This complex was examined for its cytotoxic properties in human tumour cell lines; for comparison, the cytotoxicity of cisplatin was evaluated under the same experimental conditions. In particular, Pd(II)-complex cytotoxicity on ovarian carcinoma C13 cells, resistant to cisplatin, showed that there seemed to be no cross-resistance between [Pd(ESDT)Cl]n and cisplatin. The effects on the kidney were also studied. Biochemical investigation on urinary parameters showed that the effects after a single injection are similar to those of cisplatin, with an increase of urinary proteins and enzyme excretion in urine, and a significant decrease of glutamine synthetase activity in the renal tissue. In addition, the Pd(II)-complex caused a significant decrease of p-aminohippuric acid uptake in renal cortical slices relative to cisplatin. On the other hand, histopathological findings showed that the effects of the Pd(II)-complex are more severe and diffuse than the damage caused by cisplatin. Biochemical and histopathological findings show that the Pd(II)-complex affects the pars recta and pars convoluta, in contrast to cisplatin, which only affects the pars recta.
Keywords: Cisplatin Palladium complexes Chemical synthesis Biological assay Nephrotoxicity
No Title by Swaran J. Flora; Gurusamy M. Kannan; Bhagwat P. Pant; Devendra K. Jaiswal (pp. 269-276).
Gallium arsenide (GaAs), a group III-VA intermetallic semiconductor, possesses superior electronic and optical properties and has a wide application in the electronics industry. Exposure to GaAs in the semiconductor industry is a potential occupational hazard because cleaning and slicing GaAs ingots to yield the desired wafer could generate GaAs particles. The ability of GaAs to induce oxidative stress has not yet been reported. The present study reports the role of oxidative stress in GaAs-induced haematological and liver disorders and its possible reversal overturn by administration of meso-2,3-dimercaptosuccinic acid (DMSA) and one of its analogue, monoisoamyl DMSA (MiADMSA), either individually or in combination with oxalic acid. While DMSA and MiADMSA are potential arsenic chelators, oxalic acid is reported to be an effective gallium chelator. Male rats were exposed to 10 mg/kg GaAs orally, 5 days a week for 8 weeks. GaAs exposure was then stopped and rats were given a 0.5 mmol/kg dose of succimers (DMSA or MiADMSA), oxalic acid or a combination of the two, intraperitoneally once daily for 5 consecutive days. We found a significant fall in blood δ-aminolevulinic acid dehydratase (ALAD) activity and blood glutathione (GSH) level, and an increased urinary excretion of δ-aminolevulinic acid (ALA) and an increased malondialdehyde (MDA) level in erythrocytes of rats exposed to GaAs. Hepatic GSH levels decreased, whereas there was an increase in GSSG and MDA levels. The results suggest a role of oxidative stress in GaAs-induced haematological and hepatic damage. Administration of DMSA and MiADMSA produced effective recovery in most of the above variables. However, a greater effectiveness of the chelation treatment (i.e. removal of both gallium and arsenic from body organs) could be achieved by combined administration of succimer (DMSA) with oxalic acid since, after MiADMSA administration, a marked loss of essential metals (copper and zinc) is of concern.
Keywords: Gallium arsenide Oxidative stress Chelation therapy Oxalic acid Thiol chelators Combined treatment
No Title by Flemming R. Cassee; Hans Muijser; Evert Duistermaat; Jan J. Freijer; Kees B. Geerse; Jan C. Marijnissen; Josje H. Arts (pp. 277-286).
The relative importance of the three particulate matter (PM) size fractions in ambient air, i.e. coarse (2.5–10 µm), fine (0.1–2.5 µm) and ultrafine (<0.1 µm) fractions, on the induction of adverse health effects is still unknown. Moreover, there is no straightforward relationship between ambient concentration levels, exposure (external dose) and the dose delivered to the target site (internal dose). Recently, a human and a rat airway PM deposition model (MPPDep V1.1) have been developed by CIIT Centers for Health Research and the National Institute of Public Health and the Environment (RIVM), based on the work of O.G. Raabe et al. (1977, In: W.H. Walton, editor, Inhaled Particles IV/2; Pergamon, Oxford) and S. Anjilvel and B. Asgharian (1995, Fundam Appl Toxicol 28:41–50). This paper describes studies using cadmium chloride (CdCl2) as a model for toxic aerosol particles to (1) investigate the role of particle size in the development of pulmonary effects, and (2) evaluate the MPPDep model, by comparing predicted deposition with measured deposition of CdCl2 in the respiratory tract. Rats (ten per group) were exposed for a single 4-h period to CdCl2 particles at various sizes, i.e. 33, 170, 637 and 1495 nm, all at a target concentration of 1 mg/m3. Immediately after exposure, four of ten rats per group were killed and trachea, lung lobes, heart, liver and kidneys were collected and preserved to determine the amount of CdCl2 present in each of these organs. CdCl2-induced toxicity, as measured by lactate dehydrogenase (LDH), N-acetyl glucosaminidase (NAG) and protein levels in bronchoalveolar lavage fluid, was determined in the remaining six rats per group the day after exposure. Animals exposed to 33 nm particles showed the highest level of respiratory toxicity, followed by animals exposed to 637 nm particles, then to 170 nm particles and finally by those exposed to 1495 nm particles. Pulmonary cadmium levels showed a similar relationship. The results from the present study suggest that the induction of pulmonary toxicity following inhalation exposure to soluble CdCl2 particles in the range 30–1500 nm depends on the amount of deposited material, which in its turn depends on the initial (aerodynamic) particle size. In addition, the MPPDep model accurately predicted the measured CdCl2 deposition. Conclusively, for soluble particles the deposited pulmonary mass (dose) of particles is important for toxicity and is dependent of particle size. These findings may have serious impact on the evaluation of the role of various particle sizes in PM10-associated health effects.
Keywords: Particles Dosimetry Cadmium chloride Electrospaying Lung Particulate matter Toxicity
No Title by Masashi Iwanari; Miki Nakajima; Ryoichi Kizu; Kazuichi Hayakawa; Tsuyoshi Yokoi (pp. 287-298).
Nitropolycyclic aromatic hydrocarbons (NPAHs) are found in diesel exhaust and ambient air. NPAHs as well as polycyclic aromatic hydrocarbons (PAHs) are known to have mutagenicity, carcinogenicity, and endocrine-disruptive effects. In the present study, the inducibility of the human cytochrome P450-1 (CYP1) family by NPAHs was compared with those produced by their parent PAHs and some reductive metabolites, amino-PAHs. Furthermore, to investigate the differences in the inducibility of the CYP1 family in human tissues, various human tissue-derived cell lines, namely HepG2 (hepatocellular carcinoma), ACHN (renal carcinoma), A549 (lung carcinoma), MCF-7 (breast carcinoma), LS-180 (colon carcinoma), HT-1197 (bladder carcinoma), HeLa (cervix of uterus adenocarcinoma), OMC-3 (ovarian carcinoma), and NEC14 (testis embryonal carcinoma), were treated with NPAHs, PAHs, or amino-PAHs. The mRNA levels of CYP1A1, CYP1A2, and CYP1B1 were determined with reverse transcription-polymerase chain reaction (RT-PCR). The cell lines were classified into two groups: CYP1 inducible cell lines, comprising HepG2, MCF-7, LS-180, and OMC-3 cells, and CYP1 non-inducible cell lines, comprising ACHN, A549, HT-1197, HeLa, and NEC14 cells. In inducible cell lines, the induction profile of chemical specificity was similar for CYP1A1, CYP1A2, and CYP1B1, although the extent of induction differed among the cell lines and for the CYP isoforms. Pyrene, 1-nitropyrene, 1-aminopyrene, 1,3-, 1,6-, and 1,8-dinitropyrenes slightly induced CYP1 mRNAs, but 1,3-dinitropyrene produced a 6-fold induction of CYP1A1 mRNA in MCF-7 cells. 2-Nitrofluoranthene and 3-nitrofluoranthene exhibited stronger inducibility than fluoranthene in the inducible cell lines. 6-Nitrochrysene induced CYP1 mRNAs to the same extent or more potently than chrysene. The induction potencies of 6-nitrobenzo[a]pyrene and 7-nitrobenz[a]anthracene were weaker than those of their parents benzo[a]pyrene and benz[a]anthracene, respectively. This study demonstrated that NPAHs as well as PAHs induced human CYP1A1, CYP1A2, and CYP1B1 in a chemical-, CYP isoform-, and cell-specific manner. Furthermore, the cell-specific induction of the CYP1 family was not related to the expression levels of aryl hydrocarbon receptor, aryl hydrocarbon nuclear translocator, or estrogen receptors α and β.
Keywords: Cytochrome P450 Induction Nitropolycyclic aromatic hydrocarbon Aryl hydrocarbon receptor Estrogen receptor
No Title by G. Csanády; H. Oberste-Frielinghaus; B. Semder; C. Baur; K. Schneider; J. Filser (pp. 299-305).
Physiological toxicokinetic (PT) models are used to simulate tissue burdens by chemicals in animals and humans. A prerequisite for a PT model is the knowledge of the chemical's distribution among tissues. This depends on the blood flow and also on the free fraction of the substance and its tissue:blood partition coefficients. In the present study we determined partition coefficients in human tissues at 37°C for the two selected xenoestrogens bisphenol A (BA) and daidzein (DA), and their unspecific binding to human serum proteins. Partition coefficients were obtained by incubating blood containing BA or DA with each of the following tissues: brain, liver, kidney, muscle, fat, placenta, mammary gland, and adrenal gland. Blood samples were analysed by HPLC. For BA and DA, all partition coefficients in non-adipose tissues were similar (average values: BA 1.4, DA 1.2). However, the lipophilic properties of both compounds diverge distinctly. Fat:blood partition coefficients were 3.3 (BA) and 0.3 (DA). These values indicate that with the exception of fat both compounds are distributed almost equally among tissues. In dialysis experiments, the unspecific binding of BA and DA with human serum proteins was measured by HPLC. For BA, the total concentration of binding sites and the apparent dissociation constant were calculated as 2000 and 100 nmol/ml, respectively. Because of the limited solubility of DA, only the ratio of the bound to the free DA concentration could be determined and was found to be 7.2. These values indicate that at low concentrations only small percentages of about 5% (BA) and 12% (DA) are as unbound free fractions in plasma. Since only the unbound fraction can bind to the estrogen receptor, binding to serum proteins represents a mechanism that limits the biological response in target tissues.
Keywords: Bisphenol A Daidzein Partition coefficient Protein binding
No Title by Toshiaki Yoshida; Katashi Andoh; Hiroshi Kosaka; Shinji Kumagai; Ichiro Matsunaga; Susumu Akasaka; Sei-ichi Nakamura; Hajime Oda; Morio Fukuhara (pp. 306-315).
Inhalation toxicokinetics of p-dichlorobenzene (p-DCB) in humans was evaluated, and the amounts of daily absorption and internal accumulation were estimated in order to obtain fundamental data for the risk assessment of chronic low-level exposure in the general population. Seven male subjects continuously inhaled about 2.5 ppm of p-DCB vapor for 1 h, and the concentration-time courses of p-DCB in their exhaled air and serum and of urinary 2,5-dichlorophenol (2,5-DCP), a major metabolite of p-DCB, were examined. The toxicokinetics of p-DCB was evaluated on the basis of the time courses using a linear two-compartment model. The amounts of p-DCB absorbed daily and the internal accumulation in chronic low-level exposure were extrapolated using the estimated toxicokinetic parameters. p-DCB was transferred from inhaled air to the body with a constant high absorption rate during exposure. The major route for elimination from the body was urinary excretion followed by metabolism, not exhalation. However, during 9–11 h after the start of exposure, the fraction of p-DCB excreted in urine was only 5–16% of the amount absorbed. Furthermore, most of the absorbed p-DCB seemed to be distributed rapidly to the tissues, such as fat, according to toxicokinetic analysis. Consequently, p-DCB seems to require a long time to be completely eliminated from the body. The amounts of daily absorption and internal accumulation were extrapolated to average 0.27 mg/day and 2.9 mg, respectively, in the subjects exposed chronically to 1 ppb of p-DCB. The amount absorbed daily agreed approximately with that extrapolated from rats which inhaled p-DCB in our previous study.
Keywords: p-Dichlorobenzene General population Inhalation toxicokinetics Daily absorption Internal accumulation
No Title by Alexandra Geusau; Sabine Schmaldienst; Kurt Derfler; Olaf Päpke; Klaus Abraham (pp. 316-325).
In spring 1998, two women were diagnosed with severe 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) intoxication. Over the following 3 years, TCDD levels were monitored under various attempts to enhance its elimination, and the half-lives were evaluated. Olestra, a non-digestible, non-absorbable dietary fat substitute, was continuously administered to the patients either as pure substance or in potato-chips. Additionally, in the more severely contaminated patient, we studied whether low-density lipoprotein (LDL)-apheresis, an extracorporeal means of blood lipid elimination, was effective in reducing the TCDD body burden. The blood concentrations initially measured in spring 1998 were 144,000 pg/g blood fat in patient 1 and 26,000 pg/g in patient 2, the highest levels ever measured in adults. In March 2001, concentrations in blood fat were 35,900 and 9,500 pg/g, corresponding to overall elimination half-lives of 560 days (1.5 years) in patient 1 and 1050 days (2.9 years) in patient 2, which are considerably shorter than median values of 7–9 years reported for background and moderate exposure levels. Calculations of the TCDD half-lives and measurements of TCDD elimination via different routes allowed the calculation of an unidentified route of elimination, representing 78 and 62% of the overall elimination in patient 1 and 2, respectively, probably due to an induced hepatic metabolism caused by the high TCDD exposure. As previously reported, administration of olestra was found to be effective in increasing the fecal excretion of TCDD. Due to the short half-lives in our patients, the effect of olestra on the overall elimination was relatively small, but is expected to be much greater for 'normal' half-lives. LDL-apheresis was shown to eliminate TCDD, corresponding to the eliminated blood fat. When employed twice a week, the amount of TCDD excreted by this method was comparable to fecal excretion. In view of costs and time involved, LDL-apheresis does not seem to be justified for enhancement of TCDD elimination.
Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin TCDD Dioxin Kinetics Lipid-apheresis Olestra
No Title by Peter H. Roos; Sebastian Tschirbs; Peter Welge; Alfons Hack; Dirk Theegarten; Grigori Mogilevski; Michael Wilhelm (pp. 326-334).
We have used the minipig as a prospective animal model for human risk characterization to study primary biochemical alterations upon oral contaminant intake. The effects of three orally administered soils containing polycyclic aromatic hydrocarbons (PAH) on the expression pattern of the cytochrome P450 enzyme CYP1A1 in various organs have been analyzed. Dependent on the soil sample, subchronic daily oral PAH doses ranged from 0.38 to 1.90 mg PAHEPA/kg body weight. In all cases, soil administration lead to significant CYP1A1 induction in several organs of minipigs to a different extent, following the order liver ≈ duodenum >lung >kidney ≈ spleen. Hepatic ethoxyresorufin-O-deethylase activities were elevated to 310, 1250 and 1780 compared with a background level of 200 pmol resorufin/mg protein per min. Induced duodenal activities appear to be even higher than in the liver, namely 405, 1280 and 2500 compared with a basal activity of 11 pmol resorufin/mg protein per min. CYP1A1 induction in several organs is clear evidence for successful contaminant mobilization and absorption in the duodenum and subsequent distribution of contaminant into diverse body compartments. As is shown in one case, impairment of CYP1A1 induction in the liver and thus breakdown of its PAH-metabolizing activity appears to have no effect on induced CYP1A1 levels in other organs. It appears important with respect to risk assessment that induction of CYP1A1 is particularly sensitive in the duodenum of minipigs and is achieved with soil doses which are in the range of amounts ingested by playing children due to hand-to-mouth activities. Induced duodenal CYP1A1 activities obtained in minipigs by oral exposure to PAH largely exceed maximal duodenal activities so far observed in rats. This is equally relevant for risk assessment and for selection of a suitable animal model that reflects effects of PAH exposure in humans.
Keywords: Minipig Oral exposure Polycyclic aromatic hydrocarbons (PAH) Cytochrome P450 CYP1A1 Duodenum Kidney liver Induction Biomarker of effect Contaminated soil
No Title by Shin-ichi Tsukumo; Makoto Iwata; Chiharu Tohyama; Keiko Nohara (pp. 335-343).
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and its structural analogs are widespread environmental contaminants and highly toxic. TCDD is reported to reduce thymocyte numbers and skew the lineage commitment of thymocytes toward CD4–CD8+ T (CD8 T) cells. The extracellular signal-related kinase (ERK) pathway has been suggested as critical for physiological thymocyte differentiation and apoptosis, and to be activated by TCDD in some types of cells. In the present study, we used a chemical inhibitor and mouse fetal thymus organ cultures (FTOCs) to investigate whether activation of the ERK pathway is involved in the TCDD-induced alteration of thymocytes. On days 4 and 6 of culture, the numbers of total cells and CD4+CD8+ (DP) cells were significantly decreased by TCDD. By contrast, the number of mature CD8 T cells was increased on day 4, confirming that TCDD induces differentiation to CD8 T cells. We then assessed the effects of U0126, an ERK pathway inhibitor, on the TCDD-induced alterations on day 4 of FTOC. The TCDD-induced increase in mature CD8 T cell number was not observed in the presence of the inhibitor, although total and DP cell reductions were not significantly affected. Furthermore, U0126 did not suppress the induction of CYP1A1 mRNA by TCDD in thymocytes of adult mice, confirming that the inhibitor does not suppress the activation of aryl hydrocarbon receptor. In conclusion, our results suggest that activation of the ERK pathway is required for TCDD-induced differentiation to mature CD8 T cells, but not for reduction of thymocyte numbers.
Keywords: 2,3,7,8-Tetrachlorodienzo-p-dioxin Fetal thymus organ culture Extracellular signal-related kinase pathway U0126
No Title by David Shaw; Rebecca Lee; Ruth A. Roberts (pp. 344-350).
Diisononylphthalate (DINP) is one of the group of dialkyl phthalate esters used widely to impart flexibility to polyvinyl chloride (PVC) products. However, DINP and other phthalates are rodent peroxisome proliferators (PPs), a class of compounds that cause rodent hepatic peroxisome proliferation, induction of DNA synthesis and suppression of apoptosis leading to liver tumours. Despite these adverse effects in rodent liver, humans appear to be nonresponsive to the adverse effects of PPs. Here, we have examined species differences in the response of rat and human hepatocytes to MINP, a principle metabolite of DINP and the proximal peroxisome proliferator. In rat hepatocytes in vitro, MINP caused a concentration-dependent induction of peroxisomal β-oxidation. Similarly, MINP caused a concentration-dependent suppression of apoptosis and induction of DNA synthesis. In contrast to the pleiotropic response noted in rat hepatocytes, MINP did not cause induction of β-oxidation, stimulation of DNA synthesis or suppression of apoptosis in human hepatocytes. These data provide evidence for species differences in the hepatic response to the phthalate ester DINP, confirming that human hepatocytes are refractory to the adverse effects noted in rodents.
Keywords: Apoptosis Diisononylphthalate (DINP) DNA synthesis Phthalate esters Peroxisome proliferation Human risk assessment Hepatocarcinogenesis Species differences
No Title by Yen-Chou Chen; Shing-Chuan Shen; Woan-Rouh Lee; Hui-Yi Lin; Ching-Huai Ko; Chun-Ming Shih; Ling-Ling Yang (pp. 351-359).
Wogonin and fisetin are flavonoids, which are widely distributed in plants. Our recent study demonstrated that, among seven structurally related flavonoids, wogonin and fisetin showed the most potent apoptosis-inducing activities in human promyeloleukemic cells HL-60. In the present investigation, we performed molecular studies to assess the apoptotic effects of wogonin and fisetin on hepatocellular carcinoma cells SK-HEP-1. Both wogonin and fisetin showed dose-dependent cytotoxic effects on SK-HEP-1 cells, accompanied by DNA fragmentation. Microscopic observation under Giemsa staining showed that wogonin and fisetin, at the dose of 80 µM, induced cellular swelling and the appearance of apoptotic bodies, characteristics of apoptosis, in SK-HEP-1 cells. Furthermore, flow cytometry analysis showed an increase of hypodiploid cells in wogonin- and fisetin-treated SK-HEP-1 cells. These data demonstrated that wogonin and fisetin were effective inducers of apoptosis in SK-HEP-1 cells. Treatment with an apoptosis-inducing concentration of wogonin or fisetin caused induction of caspase 3/CPP32 activity, but not of caspase 1 activity. In addition, a caspase 3 inhibitor, Ac-DEVD-CHO, but not the caspase 1 inhibitor Ac-YVAD-CHO, reversed the cytotoxic effects of wogonin and fisetin on SK-HEP-1 cells. Further, cleavage of caspase 3 substrates including poly(ADP-ribose) polymerase (PARP) and D4-GDI protein, and decrease of pro-caspase 3 protein were detected in wogonin- and fisetin-treated SK-HEP-1 cells. Increase of p53 protein was associated with wogonin- and fisetin-induced apoptosis; however, a p53-controlled gene, p21Waf/Cip-1, was only induced in wogonin- (not fisetin-) treated SK-HEP-1 cells. Serum starvation elevated p21Waf/Cip-1 protein expression, and enhanced the apoptotic induction activity of wogonin (not fiseitn) in SK-HEP-1 cells. Our study has provided molecular evidence to demonstrate that wogonin and fisetin had effective cytotoxic effects through apoptosis induction in hepatocellular carcinoma cells SK-HEP-1; activation of caspase 3 cascade, induction of p53 protein and alternative expression of p21Waf/Cip-1 protein were involved.
Keywords: Wogonin Fisetin Apoptosis Protein p53 Protein p21 Caspase 3
No Title by Kai Riecke; Daniela Grimm; Mehdi Shakibaei; Peter Kossmehl; Gundula Schulze-Tanzil; Martin Paul; Ralf Stahlmann (pp. 360-366).
Epidemiological studies have suggested an association between exposure to dioxins and cardiovascular morbidity and mortality. However, cardiotoxic effects of low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in animals have not been reported so far. We studied the hearts of male marmosets (Callithrix jacchus) after treatment with single subcutaneous doses of 1, 10 or 100 ng TCDD/kg body weight or vehicle (toluene/DMSO 1+2 v/v, 100 µl/kg body weight). The animals were killed 2 or 4 weeks after treatment. Tissue samples of left ventricular myocardium were stained with picrosirius red and examined histologically along with quantitative image analysis. Extracellular matrix proteins were additionally analysed by western blotting. Monkeys showed no overt signs of toxicity nor did their relative heart weights differ significantly depending on treatment. Histology revealed an increase of picrosirius red-positive area above control values in 2 of 4 (1 ng TCDD/kg body weight), 6 of 12 (10 ng/kg) and 6 of 10 (100 ng/kg) marmosets. Western blotting confirmed these histological findings showing an increase of collagen, fibronectin and laminin in the hearts of TCDD-treated animals. Western blotting additionally showed an increased concentration of transforming growth factor β1 (TGF-β1) as well as TGF-β receptor type I which could be a functional link to the effects on extracellular matrix. Our findings might explain the association of TCDD exposure with increased cardiovascular mortality observed in epidemiological studies and should stimulate further research on the role of changes in the extracellular matrix in the toxic effects of dioxins and related substances on other organs.
Keywords: Extracellular matrix Growth factors Dioxin Marmoset Myocardial fibrosis
No Title by Angelo Moretto; Marcello Lotti (pp. 367-375).
Species differences have been observed between hen and human clinical manifestations of isofenphos toxicities. Hens treated with the insecticide isofenphos (90 mg/kg p.o.) developed severe cholinergic toxicity followed by mild organophosphate-induced delayed polyneuropathy (OPIDP). However, a patient developed severe OPIDP, which was preceded by very mild cholinergic signs, after an attempted suicide with a commercial formulation containing isofenphos and phoxim, an insecticide not causing OPIDP (estimated doses were 500 and 125 mg/kg, respectively). To explain this difference the following hypotheses were tested: (1) phoxim is a promoter of isofenphos-induced OPIDP; (2) whereas neuropathy target esterase (NTE) is thought to be the target of OPIDP, activation of isofenphos by liver microsomes causes the formation of more potent NTE inhibitor(s) in humans than in hens; (3) in contrast to hen NTE, the sensitivity of the human enzyme to such inhibitor(s) is higher than that of acetylcholinesterase (AChE), the target of cholinergic toxicity. Results showed that phoxim (22.5 mg/kg p.o.) was not a promoter of OPIDP in hens and that the ratio AChE inhibition:NTE inhibition by microsome-activated isofenphos was similar for both hen and human enzymes. The schedule of antidotal treatment in hens is the likely explanation for the observed difference from the patient. Peak AChE inhibition was maintained in hen brain up to 6 days after a single dose of isofenphos, suggesting prolonged pharmacokinetics. However, the AChE reactivator pyridine-2-aldoxime (2-PAM) was given to hens before isofenphos and then every 8 h, whereas continuous 2-PAM infusion was provided to the patient. When 2-PAM was given to hens every hour after isofenphos (90 mg/kg p.o.), the birds remained asymptomatic. Since other organophosphates may have a prolonged pharmacokinetics, testing procedures for the potential of these insecticides to cause OPIDP may underestimate the risk for humans.
Keywords: Isofenphos Cholinergic toxicity Delayed polyneuropathy Human Activation