Acute intravenous exposure to silver nanoparticles during pregnancy induces particle size and vehicle dependent changes in vascular tissue contractility in Sprague Dawley rats.

The use of silver nanoparticles (AgNP) raises safety concerns during susceptible life stages such as pregnancy. We hypothesized that acute intravenous exposure to AgNP during late stages of pregnancy will increase vascular tissue contractility, potentially contributing to alterations in fetal growth. Sprague Dawley rats were exposed to a single dose of PVP or Citrate stabilized 20 or 110nm AgNP (700µg/kg). Differential vascular responses and EC50 values were observed in myographic studies in uterine, mesenteric arteries and thoracic aortic segments, 24h post-exposure. Reciprocal responses were observed in aortic and uterine vessels following PVP stabilized AgNP with an increased force of contraction in uterine artery and increased relaxation responses in aorta. Citrate stabilized AgNP exposure increased contractile force in both uterine and aortic vessels. Intravenous AgNP exposure during pregnancy displayed particle size and vehicle dependent moderate changes in vascular tissue contractility, potentially influencing fetal blood supply.

Association of urinary metabolites with radiographic progression of knee osteoarthritis in overweight and obese adults: an exploratory study.

INTRODUCTION: Metabolic factors may contribute to osteoarthritis (OA). This study employed metabolomics analyses to determine if differences in metabolite profiles could distinguish people with knee OA who exhibited radiographic progression. METHODS: Urine samples obtained at baseline and 18 months from overweight and obese adults in the Intensive Diet and Exercise for Arthritis (IDEA) trial were selected from two subgroups (n = 22 each) for metabolomics analysis: a group that exhibited radiographic progression (≥0.7 mm decrease in joint space width, JSW) and an age, gender, and body mass index (BMI) matched group who did not progress (≤0.35 mm decrease in JSW). Multivariate analysis methods, including orthogonal partial least square discriminate analysis, were used to identify metabolite profiles that separated progressors and non-progressors. Plasma levels of IL-6 and C-reactive protein (CRP) were evaluated as inflammatory markers. RESULTS: Multivariate analysis of the binned metabolomics data distinguished progressors from non-progressors. Library matching revealed that glycolate, hippurate, and trigonelline were among the important metabolites for distinguishing progressors from non-progressors at baseline whereas alanine, N,N-dimethylglycine, glycolate, hippurate, histidine, and trigonelline, were among the metabolites that were important for the discrimination at 18 months. In non-progressors, IL-6 decreased from baseline to 18 months while IL-6 was unchanged in progressors; the change over time in IL-6 was significantly different between groups. CONCLUSION: These findings support a role for metabolic factors in the progression of knee OA and suggest that measurement of metabolites could be useful to predict progression. Further investigation in a larger sample that would include targeted investigation of specific metabolites is warranted.

Cardiac Ischemia Reperfusion Injury Following Instillation of 20 nm Citrate-capped Nanosilver.

BACKGROUND: Silver nanoparticles (AgNP) have garnered much interest due to their antimicrobial properties, becoming one of the most utilized nano-scale materials. However, any potential evocable cardiovascular injury associated with exposure has not been reported to date. We have previously demonstrated expansion of myocardial infarction after intratracheal (IT) instillation of carbon-based nanomaterials. We hypothesized pulmonary exposure to Ag core AgNP induces a measureable increase in circulating cytokines, expansion of cardiac ischemia-reperfusion (I/R) injury and is associated with depressed coronary constrictor and relaxation responses. Secondarily, we addressed the potential contribution of silver ion release on AgNP toxicity. METHODS: Male Sprague-Dawley rats were exposed to 200 µl of 1 mg/ml of 20 nm citrate-capped Ag core AgNP, 0.01, 0.1, 1 mg/ml Silver Acetate (AgAc), or a citrate vehicle by intratracheal (IT) instillation. One and 7 days following IT instillation the lungs were evaluated for inflammation and the presence of silver; serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and coronary artery reactivity were assessed. RESULTS: AgNP instillation resulted in modest pulmonary inflammation with detection of silver in lung tissue and alveolar macrophages, elevation of serum cytokines: G-CSF, MIP-1α, IL-1ß, IL-2, IL-6, IL-13, IL-10, IL-18, IL-17α, TNFα, and RANTES, expansion of I/R injury and depression of the coronary vessel reactivity at 1 day post IT compared to vehicle treated rats. Silver within lung tissue was persistent at 7 days post IT instillation and was associated with an elevation in cytokines: IL-2, IL-13, and TNFα and expansion of I/R injury. AgAc resulted in a concentration dependent infarct expansion and depressed vascular reactivity without marked pulmonary inflammation or serum cytokine response. CONCLUSIONS: Based on these data, IT instillation of AgNP increases circulating levels of several key cytokines, which may contribute to persistent expansion of I/R injury possibly through an impaired vascular responsiveness.

Vascular Tissue Contractility Changes Following Late Gestational Exposure to Multi-Walled Carbon Nanotubes or their Dispersing Vehicle in Sprague Dawley Rats.

Multi-walled carbon nanotubes (MWCNTs) are increasingly used in industry and in nanomedicine raising safety concerns, especially during unique life-stages such as pregnancy. We hypothesized that MWCNT exposure during pregnancy will increase vascular tissue contractile responses by increasing Rho kinase signaling. Pregnant (17-19 gestational days) and non-pregnant Sprague Dawley rats were exposed to 100 µg/kg of MWCNTs by intratracheal instillation or intravenous administration. Vasoactive responses of uterine, mesenteric, aortic and umbilical vessels were studied 24 hours post-exposure by wire myography. The contractile responses of the vessel segments were different between the pregnant and non-pregnant rats, following MWCNT exposure. Maximum stress generation in the uterine artery segments from the pregnant rats following pulmonary MWCNT exposure was increased in response to angiotensin II by 4.9 mN/mm2 (+118%), as compared to the naïve response and by 2.6 mN/mm2 (+40.7%) as compared to the vehicle exposed group. Following MWCNT exposure, serotonin induced approximately 4 mN/mm2 increase in stress generation of the mesenteric artery from both pregnant and non-pregnant rats as compared to the vehicle response. A significant contribution of the dispersion medium was identified as inducing changes in the contractile properties following both pulmonary and intravenous exposure to MWCNTs. Wire myographic studies in the presence of a Rho kinase inhibitor and RhoA and Rho kinase mRNA/protein expression of rat aortic endothelial cells were unaltered following exposure to MWCNTs, suggesting absent/minimal contribution of Rho kinase to the enhanced contractile responses following MWCNT exposure. The reactivity of the umbilical vein was not changed; however, mean fetal weight gain was reduced with dispersion media and MWCNT exposure by both routes. These results suggest a susceptibility of the vasculature during gestation to MWCNT and their dispersion media-induced vasoconstriction, predisposing reduced fetal growth during pregnancy.

Identification of metabolites of [1,2,3-(13)C]Propargyl alcohol in mouse urine by (13)C NMR and mass spectrometry and comparison to rat.

Species differences in the metabolism of acetylenic compounds commonly used in the formulation of pharmaceuticals and pesticides have not been investigated. To better understand the in vivo reactivity of this bond, the metabolism of propargyl alcohol (PA), 2-propyn-1-ol, was examined in rats and mice. An earlier study (Banijamali, A. R.; Xu, Y.; Strunk, R. J.; Gay, M. H.; Ellis, M. C.; Putterman, G. J. J. Agric. Food Chem. 1999, 47, 1717-1729) in rats revealed that PA undergoes extensive metabolism primarily via glutathione conjugation. The current research describes the metabolism of PA in CD-1 mice and compares results for the mice to those obtained for rats. [1,2,3-(13)C;2,3-(14)C]PA was administered orally to the mice. Approximately 60% of the dose was excreted in urine by 96 h. Metabolites were identified, directly, in whole urine by 1- and 2-D (13)C NMR and HPLC/MS and by comparison with the available reference compounds. The proposed metabolic pathway involves glucuronide conjugation of PA to form 2-propyn-1-ol-glucuronide as well as oxidation of PA to the proposed intermediate 2-propynal. The aldehyde undergoes conjugation with glutathione followed by further metabolism to yield as final products 3,3-bis[(2-acetylamino-2-carboxyethyl)thio]-1-propanol, 3-[(2-acetylamino-2-carboxyethyl)thio]-3-[(2-amino-2-carboxyethyl)thi o]-1-propanol, 3,3-bis[(2-amino-2-carboxyethyl)thio]-1-propanol, 3-[(2-amino-2-carboxyethyl)thio]-2-propenoic acid, and 3-[(2-formylamino-2-carboxyethyl)thio]-2-propenoic acid. A small portion of 2-propynal is also oxidized to result in the excretion of 2-propynoic acid. On the basis of urinary metabolite data, qualitative and quantitative differences are noted between rats and mice in the formation of the glucuronide conjugate of PA and in the formation of 2-propynoic acid and metabolites derived from glutathione. These metabolites represent further variation on glutathione metabolism following its addition to the carbon-carbon triple bond compared to those described for the rat.

Identification of metabolites of [1,2,3-(13)C]Propargyl alcohol in rat urine by (13)C NMR and mass spectrometry.

Little is known about the metabolism of acetylenic (C&tbd1;C) compounds commonly used in the formulation of pesticides. To better understand the in vivo reactivity of this bond, we examined the metabolism of propargyl alcohol (PA), 2-propyn-1-ol, used extensively in the chemical industry. [1,2,3-(13)C, 2,3-(14)C]PA was administered orally to male Sprague-Dawley rats. Approximately 56% of the dose was excreted in urine by 96 h. Major metabolites were characterized, directly, in the whole urine by one- and two-dimensional (13)C NMR. To determine the complete structures of metabolites of PA, rat urine was also subjected to TLC followed by purification of separated TLC bands on HPLC. The purified metabolites were identified by (13)C NMR and mass spectrometry and by comparison with available synthetic standards. The proposed metabolic pathway involves oxidation of propargyl alcohol to 2-propynoic acid and further detoxification via glutathione conjugation to yield as final products: 3, 3-bis[(2-(acetylamino)-2-carboxyethyl)thio]-1-propanol, 3-(carboxymethylthio)-2-propenoic acid, 3-(methylsulfinyl)-2-(methylthio)-2-propenoic acid, 3-[[2-(acetylamino)-2-carboxyethyl]thio]-3-[(2-amino-2-carboxyethyl)t hio]-1-propanol and 3-[[2-(acetylamino)-2-carboxyethyl]sulfinyl]-3-[2-(acetylamino)-2-car boxyethyl]thio]-1-propanol. These unique metabolites have not been reported previously and represent the first example of multiple glutathione additions to the carbon-carbon triple bond.

Dose effects on the excretion of urinary metabolites of 2-[1,2,methoxy-13C]methoxyethanol in rats and mice.

The administration of 2-methoxyethanol (2-ME) to pregnant rats, mice, or primates results in developmental toxicity. To assess the role of metabolism in the adverse response of 2-ME, carbon-13 NMR spectroscopy was used to examine, directly in the urine, metabolites produced after administering high (250 mg/kg) and low (25 mg/kg) doses of 2-[1,2,methoxy-13C]ME to pregnant CD-1 mice and male Fischer 344 rats. The high dose elicits teratogenic effects in mice and testicular toxicity in rats. The urinary disposition was also examined after dosing pregnant CD-1 mice with a developmentally toxic level of 2-ME together with serine or acetate (known attenuators of 2-ME embryotoxicity). Seven novel metabolites were found in rat urine, consistent with those assigned in our previous studies with mice. Metabolite composition was compared for the different dosing regimens. A lower percentage of metabolites derived after conversion of 2-ME to 2-methoxyacetic acid (2-MAA) was found following concurrent administration of 2-ME with acetate, D-serine, or L-serine. These differences are mainly attributed to higher levels of ethylene glycol and/or glycolic acid that arise for the 2-ME administrations with any of the attenuators. Acetate together with 2-ME also reduced the percentage of metabolites incorporated into intermediary metabolism. These data indicate that attenuators of 2-ME teratogenic effects may alter metabolism and distribution by decreasing the conversion of 2-ME to 2-MAA, decreasing the conversion of 2-MAA to a coenzyme A thioester (2-methoxyacetyl approximately CoA), altering the utilization of the coenzyme A thioester, and/or increasing the conversion of 2-ME to ethylene glycol and its further metabolism. These changes in metabolism may contribute to the attenuating effects of these agents on 2-ME.

Monitoring exposure to acrylonitrile using adducts with N-terminal valine in hemoglobin.

Human exposure to acrylonitrile (ACN), a carcinogen in rats, may occur in industrial settings, through waste water and tobacco smoke. ACN is an electrophilic compound and binds covalently to nucleophilic sites in macromolecules. Measurements of adducts with hemoglobin could be utilized for improved exposure assessments. In this study, a method for quantification of N-(2-cyanoethyl)valine (CEVal), the product of reaction of ACN with N-terminal valine in hemoglobin has been developed. The method is based on the N-alkyl Edman procedure, which involves derivatization of the globin with pentafluorophenyl isothiocyanate and gas chromatographic-mass spectrometric analysis of the resulting thiohydantoin. An internal standard was prepared by reacting valylglycylglycine with [2H3]ACN, spiked with [14C]ACN to a known sp. act. Levels of CEVal were measured in globin from rats exposed to 3-300 p.p.m. ACN in drinking water for 105 days and from humans (four smokers and four non-smokers). CEVal was detected at all exposure levels in the drinking water study. The relationship between adduct level and water concentration was linear at concentrations of 10 p.p.m. (corresponding to an average daily uptake of c. 0.74 mg ACN/kg body wt during the 65 days prior to sacrifice) and below, with a slope of 37.7 pmol CEVal/g globin/p.p.m. At higher concentrations, adduct levels increased sublinearly, indicating saturation of a metabolic process for elimination of ACN. Comparison of adduct formation with the estimated dose (mg/kg/day) of ACN indicated that at low dose (0-10 p.p.m.) CEVal = 0.508 x ACN dose + 0.048 and at high dose (35-300 p.p.m.) CEVal = 1.142 x ACN dose - 1.098. Globin from the smokers (10-20 cigarettes/day) contained about 90 pmol CEVal/g, whereas the adduct levels in globin from non-smokers were below the detection limit. The analytical sensitivity should be sufficient to allow monitoring of occupationally exposed workers at levels well below the current Occupational Safety and Health Administration standard of 2 p.p.m.

Review of the metabolic fate of styrene.

Styrene and styrene oxide have been implicated as reproductive toxicants, neurotoxicants, or carcinogens in vivo or in vitro. The use of these chemicals in the manufacture of plastics and polymers and in the boat-building industry has raised concerns related to the risk associated with human exposure. This review describes the literature to date on the metabolic fate of styrene and styrene oxide in laboratory animals and in humans. Many studies have been conducted to assess the metabolic fate of styrene in rats, and investigations on the metabolism of styrene in humans have been of considerable interest. Limited research has been done to assess metabolism in the mouse. The metabolism of styrene to styrene oxide and further conversion to styrene glycol (via epoxide hydrolase), mandelic acid, and phenylglyoxylic acid has been given considerable attention, and is considered to be the major pathway of activation and detoxication for humans. While the hydrolysis of styrene oxide to styrene glycol historically has been the favored pathway for the rat, studies in more recent years have indicated that glutathione conjugation also is a viable and significant pathway for both the rat and the mouse. This pathway has not been established in humans. Mandelic acid and phenylglyoxylic acid have been used as urinary markers of exposure in humans exposed to styrene. Extensive investigations have been conducted on the kinetics of styrene and styrene oxide in rodents. In people, the kinetics of styrene and styrene oxide in the blood of occupationally exposed workers and volunteers have been determined. Pharmacokinetic models developed in the last decade have become increasingly complex, with the most recent physiologically based model describing the kinetics of styrene and styrene oxide. This model shows pronounced species differences in sensitivity coefficients for styrene or styrene oxide between mice, rats, and humans, where mice are the more sensitive species to the Vmax for both epoxide hydrolase and monooxygenase. This result is particularly interesting in light of the recent findings of extensive mortality and hepatotoxicity for mice exposed to relatively low levels of styrene (250 to 500 ppm), while rats and humans exhibit only nasal and eye irritations at exposure concentrations well above 500 ppm.