Naphthalene Research Articles

Ascorbic Acid Enhances the Accumulation of Polycyclic Aromatic Hydrocarbons (PAHs) in Roots of Tall Fescue (Festuca arundinacea Schreb.)

Plant contamination by polycyclic aromatic hydrocarbons (PAHs) is crucial to food safety and human health. Enzyme inhibitors are commonly utilized in agriculture to control plant metabolism of organic components. This study revealed that the enzyme inhibitor ascorbic acid (AA) significantly reduced the activities of peroxidase (POD) and polyphenol oxidase (PPO), thus enhancing the potential risks of PAH contamination in tall fescue (Festuca arundinacea Schreb.). POD and PPO enzymes in vitro effectively decomposed naphthalene (NAP), phenanthrene (PHE) and anthracene (ANT). The presence of AA reduced POD and PPO activities in plants, and thus was likely responsible for enhanced PAH accumulation in tall fescue. This conclusion is supported by the significantly enhanced uptake of PHE in plants in the presence of AA, and the positive correlation between enzyme inhibition efficiencies and the rates of metabolism of PHE in tall fescue roots. This study provides a new perspective, that the common application of enzyme inhibitors in agricultural production could increase the accumulation of organic contaminants in plants, hence enhancing risks to food safety and quality.

Characteristic molecular signature for the early detection and prediction of polycyclic aromatic hydrocarbons in rat liver

Predictions of toxicity are central for the assessment of chemical toxicity, and the effects of environmental toxic compounds are still a major issue for predicting potential human health risks. Among the various environmental toxicants, polycyclic aromatic hydrocarbons (PAHs) are an important class of environmental pollutant, and many PAHs are known or suspected carcinogens. In the present study, to investigate whether characteristic expression profiles of PAHs exist in rat liver and whether a characteristic molecular signature can discriminate and predict among different PAHs at an early exposure time, we analyzed the genome-wide expression profiles of rat livers exposed to PAHs [benzo[a]anthracene (BA), benzo[a]pyrene (BP), phenanthrene (PA) and naphthalene (NT)]. At early time-point PAH exposure, large-scale gene expression analysis resulted in characteristic molecular signatures for each PAH, and supervised analysis identified 1183 outlier genes as a distinct molecular signature discerning PAHs from the normal control group. We identified 158 outlier genes as early predictive and surrogate markers for predicting each tested PAH by combination of two different multi-classification algorithms with 100% accuracy through a leave-one out cross-validation method. In conclusion, the characteristic gene expression signatures from a rat model system could be used as predictable and discernible gene-based biomarkers for the detection and prediction of PAHs, and these molecular markers may provide insights into the underlying mechanisms for genotoxicity of exposure to PAHs from environmental aspect.

Longitudinal variations in indoor VOC concentrations after moving into new apartments and indoor source characterization

This study examined the indoor concentrations of a wide range of volatile organic compounds (VOCs) in currently built new apartments every month over a 24-month period and the source characteristics of indoor VOCs. The indoor total VOC (TVOC) concentrations exhibited a decreasing tendency over the 24-month follow-up period. Similar to TVOCs, the median indoor concentrations of 33 of 40 individual VOCs (all except for naphthalene and six halogenated VOCs) revealed decreasing tendencies. In contrast, the indoor concentrations of the six halogenated VOCs did not reveal any definite trend with time. Moreover, the indoor concentrations of those halogenated VOCs were similar to the outdoor concentrations, suggesting the absence of any notable indoor sources of halogenated VOCs. For naphthalene (NT), the indoor concentrations were significantly higher than the outdoor concentrations, suggesting the presence of indoor NT source(s). The floor/wall coverings (39 %) were the most influential indoor source of indoor VOCs, followed by household cleaning products (32 %), wood paneling/furniture (17 %), paints (7 %), and moth repellents (5 %).

Prediction of rate constants for the gas phase reactions of triphenylene with OH and NO3 radicals using a relative rate method in CCl4 liquid phase-system

The kinetics of CCl4 liquid-phase reactions of ten kinds of polycyclic aromatic compounds (PACs) including triphenylene (TP) with NO3 radicals have been investigated at 273K by a relative rate method using naphthalene (NA) as a reference compound. The obtained relative reaction rates of the tested PACs to NA in CCl4 were as follows: 2.57±0.24 (acenaphthene), 2.11±0.30 (2,3-dimethylnaphthalene), 1.21±0.13 (fluoranthene), 0.56±0.07 (fluorene), 1.85±0.19 (1-methylnaphthalene), 1.77±0.12 (2-methylnaphthalene), 0.11±0.03 (1-nitronaphthalene), 1.59±0.23 (phenanthrene), 2.40±0.29 (pyrene), 0.22±0.04 (TP). TP is a semi-volatile PAC with four aromatic rings and it is chemically changed into mutagenic 2-nitrotriphenylene (2-NTP) via the gas-phase OH or NO3 radical-initiated reactions. On the basis of the relative reactivity of the PACs in the CCl4 liquid phase-system, the rate constants of the gas-phase reactions of TP with OH and NO3 radicals at 298K were predicted to be (8.6±1.2)×10−12cm3molecule−1s−1 and (6.6±1.5)×10−29[NO2]cm3molecule−1s−1, respectively. Based on the ambient concentrations of TP and 2-NTP and the obtained rate constant for the reaction of TP with OH radicals, the atmospheric loss rate of 2-NTP was also evaluated.

Correlation between atmospheric polycyclic aromatic hydrocarbons exposure and urinary hydroxyl metabolites of polycyclic aromatic hydrocarbons in elderly population in Tianjin, China

To identify suitable hydroxyl polycyclic aromatic hydrocarbons (OH-PAHs) for co-evaluation of internal exposure level of PAHs by simultaneous determination of a variety of OH-PAHs in urine. The 24-h individual particulate matter and morning urine samples of 112 subjects were collected during June 2011. PAHs carried by individual particulate matter samples and OH-PAHs in urine samples were detected by gas chromatography-mass spectrometry. Seven OH-PAHs were detected in urine samples, among which 1-hydroxy-naphthalene (1-OHNap) concentration was the highest [(20.54 ± 28.94) µmol/mol Cr], while 1-hydroxy-pyrene (1-OHP) concentration was the lowest [(0.73 ± 0.63) µmol/mol Cr]. The concentrations of these seven OH-PAHs decreased in the following order: 1-hydroxy-naphthalene (1-OHNap) > 9-hydroxy-fluorene (9-OHFlu) > 2-hydroxy-naphthalene (2-OHNap) > 3-hydroxy-fluorene (3-OHFlu) > 2-hydroxy-fluorene (2-OHFlu) > 6-hydroxy-chrysene (6-OHChr) > 1-hydroxy-pyrene (1-OHP). The effects of gender and smoking upon the contents of OH-PAHs in urine samples were not significant. There was a good correlation between total hydroxy-naphthalene (ΣOHNap) and 1-OHNap (r = 0.948), and a good correlation was also showed between total hydroxy-fluorene (ΣOHFlu) and 9-OHFlu (r = 0.975). Naphthalene carried by atmospheric particulate matters demonstrated better correlation with 1-OHNap than 2-OHNap, while fluorene carried by atmospheric particulate matters showed better correlation with 9-OHFlu than 3-OHFlu and 2-OHFlu. The correlation coefficients of ΣOHNap, ΣOHFlu and 6-OHChr with 1-OHP were 0.427, 0.543 and 0.655, respectively, and the correlations were not strong. It cannot reflect internal exposure level of PAHs to use 1-OHP as the only biomarker, while 1-OHNap and 9-OHFlu can be well predictive of the exposure levels of corresponding total OH-PAHs, suggesting that simultaneous determination of 1-OHNap, 9-OHFlu and 1-OHP can be more accurate and comprehensive in evaluating the internal exposure level of PAHs.

Adsorption characteristics of 1,2,4-trichlorobenzene, 2,4,6-trichlorophenol, 2-naphthol and naphthalene on graphene and graphene oxide

Adsorption of 1,2,4-trichlorobenzene (TCB), 2,4,6-trichlorophenol (TCP), 2-naphthol and naphthalene (NAPH) on graphene (G) and graphene oxide (GO) was investigated using a batch equilibration method and micro-Fourier transform infrared spectroscopy. All adsorption isotherms of four aromatics on G and GO were nonlinear, indicating that except for hydrophobic interaction, some specific interactions were involved in adsorption. For G, four aromatics had similar adsorption capacity at pH 5.0 in despite of their different chemical properties. A series of pH-dependent experimental results showed that 2-naphthol had higher adsorption capacity on G at alkaline pH than that at acidic pH. Theoretical calculation ascribed this to higher π-electron density of anionic 2-naphthol than that of neutral 2-naphthol, which facilitated the π–π interaction formation with G. For GO, the adsorption affinity of four aromatics increased in the order: NAPH<TCB<TCP<2-naphthol. FTIR results revealed that TCB, TCP and 2-naphthol were adsorbed on G mainly via π–π interaction. In contrast, high adsorption of TCP and 2-naphthol on GO was attributed to the formation of H-bonding between hydroxyl groups of TCP and 2-naphthol and O-containing functional groups on GO.

Characteristics of nano-/ultrafine particle-bound PAHs in ambient air at an international airport

Concentrations of 22 polycyclic aromatic hydrocarbons (PAHs) were estimated for individual particle-size distributions at the airport apron of the Taipei International Airport, Taiwan, on 48 days in July, September, October, and December of 2011. In total, 672 integrated air samples were collected using a micro-orifice uniform deposition impactor (MOUDI) and a nano-MOUDI. Particle-bound PAHs (P-PAHs) were analyzed by gas chromatography with mass selective detector (GC/MSD). The five most abundant species of P-PAHs on all sampling days were naphthalene (NaP), phenanthrene (PA), fluoranthene (FL), acenaphthene (AcP), and pyrene (Pyr). Total P-PAHs concentrations were 152.21, 184.83, and 188.94 ng/m(3) in summer, autumn, and winter, respectively. On average, the most abundant fractions of benzo[a]pyrene equivalent concentration (BaPeq) in different molecular weights were high-weight PAHs (79.29 %), followed by medium-weight PAHs (11.57 %) and low-weight PAHs (9.14 %). The mean BaPeq concentrations were 1.25 and 0.94 (ng/m(3)) in ultrafine particles (<0.1 μm) and nano-particles (<0.032 μm), respectively. The percentages of total BaPeq in nano- and ultrafine particulate size ranges were 52.4 % and 70.15 %, respectively.

Polycyclic Aromatic Hydrocarbon (PAH) and Soot Formation in the Pyrolysis of Acetylene and Ethylene: Effect of the Reaction Temperature

The formation of soot and polycyclic aromatic hydrocarbons (PAHs) has been studied during the pyrolysis of acetylene and ethylene at different reaction temperatures (1073–1423 K) in a tubular flow reactor at atmospheric pressure. The 16 PAHs classified by the United States Environmental Protection Agency (U.S. EPA) as priority compounds, together with light gases present at the outlet gas stream, were quantified by a chromatographic method. Soot formed was collected on a filter at the reactor outlet and later quantified. In this way, the relationship between PAH, gas, and soot formation can be discussed. The distribution of the target PAHs in the different phases (at the gas phase, adsorbed on soot, and/or sticked on reactor walls) is also analyzed. The speciation of the individual PAH compounds was achieved by a combination of Soxhlet extraction, extract concentration by a rotary evaporator, and gas chromatography coupled to mass spectrometry (GC–MS). The present study shows that, in the pyrolysis of both acetylene and ethylene, while soot formation is enhanced by increasing the temperature, the PAH yield exhibits a maximum in the evaluated temperature range, and such a maximum value depends upon the hydrocarbon used (ethylene or acetylene). However, the PAH distribution in the different phases does not seem to be influenced by hydrocarbon used. PAHs from ethylene and acetylene pyrolysis are seen to be mainly adsorbed on soot preferably than on other places, except for naphthalene (NAPH) in the pyrolysis of ethylene, in which case a higher concentration was found at the gas phase.

Synthesis of branched naphthoquinones from castor oil

The naphthoquinones are cyclic aromatic α,β-dienonas with a basic framework derived from naphthalene. They are also found in many higher plants, algae, fungi and as the product of the metabolism of some bacteria having large biologica activity described in the literature such as antibacterial, anti-inflammatory, antitumor, anticancer and trypanocidal [1-3]. Castor oil is an abundant raw material in Brazil of great versatility and, it is present in biodiesel production, surfactants, cosmetics and others. Considering the importance of naphthoquinones and, the availability of the ricinoleic acid from castor oil, the aim of this study was the preparation of new branched naphthoquinones in order to test their trypanocidal activity. Castor oil was submitted to saponification with sodium hydroxide, ethanol and water under reflux for 6 h. We then carried out an acid hydrolysis with hydrochloric acid and the formed ricinoleic acid was extracted with ethyl acetate. Following, through Kochi-Anderson addition reaction it was performed the alkylation of a naphthoquinone 1 and 2 , using ammonium persulfate, silver nitrate, acetonitrile and water, under heating at 70-80 ° C during 3 h, to give the branched naphthoquinones 4 and 5 (scheme 1). The naphthoquinone 3 will be similarly submitted to this procedure. The naphthoquinones 4 and 5 were purified by column chromatography on silica gel using hexane as the eluent. The compounds were characterized by mass spectrometry and 1 H and 13 CNMR spectroscopy.

Effects of three different PAHs on nitrogen-fixing bacterial diversity in mangrove sediment

Polycyclic aromatic hydrocarbons (PAHs) are of great environmental and human health concerns due to their widespread occurrence, persistence and carcinogenic properties. There is now compelling evidence that the mangrove sediment microbial structure is susceptible to PAHs contamination. The study aimed to assess the effects of PAHs on the nitrogen-fixing bacterial community of mangrove sediment. Three types of PAHs, naphthalene (NAP), a two-ring PAH; fluorene (FLU), a three-ring PAH; and pyrene (PYR), a four-ring PAH; were applied at three doses. After 7 and 24 days of incubation, the nitrogen-fixing bacterial population and diversity were evidenced in the nifH gene polymerase chain reaction denaturing gradient gel electrophoresis profile. DGGE pattern shows that the nitrogen-fixing bacterial community changed significantly with the types and doses of PAHs, and the incubation time. As far as single PAH is concerned, high concentration of PAH has larger impact on the nitrogen-fixing bacteria than low concentration of PAH. Besides, among the three types of PAHs, NAP has the greatest short term toxicity; PYR has the strongest long-term impact, whereas FLU has relatively higher long-time effect. Multidimensional scaling analysis and correspondence analysis are two reliable multivariate analysis methods for investigating the relationship between the nitrogen-fixing bacterial community and PAHs contamination. Investigating the effect of PAHs on the nitrogen-fixing bacterial diversity could yield useful information for understanding the process of biogeochemical cycling of nitrogen in mangrove sediment. The present study reveals that nitrogen-fixing bacterial community can be used as an important parameter indicating the impact of PAHs on mangrove sediment ecosystem.

Short-term toxic effects of naphthalene and pyrene on the common prawn (Palaemon serratus) assessed by a multi-parameter laboratorial approach: mechanisms of toxicity and impairment of individual fitness

The short-term (96 h) toxic effects of two polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAP) and pyrene (PYR), on the common prawn (Palaemon serratus) were investigated in laboratory bioassays, including a fitness related assay based on the post-exposure swimming velocity. Other effect criteria were biomarkers of neurotoxicity, oxidative stress and bioenergetics, and mortality. In the range of concentrations tested (NAP: 0.13–8 mg/L; PYR: 0.006–0.4 mg/L), both PAHs impaired the swimming velocity, induced oxidative stress and damage, and changed the activity of lactate dehydrogenase and isocitrate dehydrogenase. NAP also caused mortality (96 h-LC50 = 3.5 mg/L). Thus, both PAHs were able to cause toxic effects on P. serratus after a short period of exposure through the water, including the reduction of individual fitness. PYR was five folds more effective in reducing the swimming velocity of P. serratus than NAP. These findings are of interest for the marine ecological risk assessment of oil spills.

Preliminary evaluation of the human relevance of respiratory tumors observed in rodents exposed to naphthalene

Inhalation bioassays in mice and rats exposed to naphthalene (NA) show incidences of lung and nasal cancer, respectively. This paper describes a preliminary mode of action (MOA)/human relevance (HR) framework for NA. Species differences in both carcinogenic and cytotoxic responses between the rodent and human have been noted based on qualitative and quantitative differences in metabolism. Some occur at the initial oxidation of NA in the rat through CYP2F, versus CYP2A13 metabolism in the human respiratory system and which results in a difference in the specific naphthoquinone formed. Normally, subsequent reactive metabolites are then conjugated through glutathione, but high dose exposures, as in the rat bioassay, result in glutathione depletion, and the availability of 1,2-naphthoquinone for other conjugation. In the rat nose, it is proposed that a naphthoquinone imine is formed via a species and site-specific aryl amidase acting on an amino acid conjugate of the quinone. Such a quinone imine is believed to be the active agent in Alachlor and phenacetin, resulting in the same profile of respiratory tumors in the rat as NA. Based on the MOA and the limited epidemiological data indicating no human evidence of nasal or lung tumor risk, the carcinogenic response observed in rats does not appear relevant to the human.

Sorption of acidic organic solute onto kaolinitic soils from methanol-water mixtures

The fate of the acidic organic solute from the soil-water-solvent system is not well-understood. In this study, the effect of the acidic functional group of organic solute in the sorption from cosolvent system was evaluated. The sorption of naphthalene (NAP) and 1-naphthoic acid (1-NAPA) by three kaolinitic soils and two model sorbents (kaolinite and humic acid) were measured as functions of the methanol volume fractions (f c ≤ 0.4) and ionic compositions (CaCl2 and KCl). The solubility of 1-NAPA was also measured in various ionic compositions. The sorption data were interpreted using the cosolvency-induced sorption model. The K m values (= the linear sorption coefficient) of NAP with kaolinitic soil for both ionic compositions was log linearly decreased with f c. However, the K m values of 1-NAPA with both ionic compositions remained relatively constant over the f c range. For the model sorbent, the K m values of 1-NAPA with kaolinite for the KCl system and with humic acid for both ionic compositions decreased with f c, while the sorption of 1-NAPA with kaolinite for the CaCl2 system was increased with f c. From the solubility data of 1-NAPA with f c, no significant difference was observed with the different ionic compositions, indicating an insignificant change in the aqueous activity of the liquid phase. In conclusion, the enhanced 1-NAPA sorption, greater than that predicted from the cosolvency-induced model, was due to an untraceable interaction between the carboxylate and hydrophilic soil domain in the methanol-water system. Therefore, in order to accurately predict the environmental fate of acidic pesticides and organic solutes, an effort to quantitatively incorporate the enhanced hydrophilic sorption into the current cosolvency-induced sorption model is required.

Adsorption and separation of poly-aromatic hydrocarbons by a hydrogen-bonded coordination polymer

A residual-host prepared by thermal removal of naphthalene (NA) from the inclusion compound [Ni(SCN)(2)(isonicotinic acid)(2)]·(NA)(0.5) was found to function as an adsorbent for aromatic molecules and exhibit method-dependent selectivity.

Effect of Ligands on the Dispersion of Ni Nanoparticles in Ni/SBA-15 Hydrogenation Catalysts

ABSTRACTIn the present work, a comparison study of the Ni catalysts supported on SBA-15 silica support prepared with and without the addition of organic ligands (citric acid and ethylenediaminetetraacetic acid (EDTA) was undertaken. The aim of this study was to inquire on the effect of the addition of organic ligands on the characteristics of the supported NiO and Ni nanoparticles and on their activity and selectivity in hydrogenation (HYD) of aromatics. Catalysts with different metal loadings (5, 10 and 20 wt. % of Ni) were prepared, characterized by nitrogen physisorption, small-angle and powder XRD, TPR, UV-vis DRS, and HRTEM, and tested in HYD of naphthalene (NP). It was found that Ni(II)-Ligand complexes were formed in aqueous solutions of Ni(NO3)2 containing citric acid (CA) or EDTA. Catalysts prepared from impregnation solutions with and without ligands had different textural characteristics and dispersion of NiO particles after calcination at 500 °C for 4 h. As it was shown by XRD, DRS and TPR, dispersion of NiO particles significantly increased when EDTA was used, whereas it noticeably decreased after the addition of CA. Similar trends were observed in the dispersion of metallic Ni particles after reduction of the NiO/SBA-15 precursors (HRTEM). In line with the characterization results, catalytic activity tests revealed strong differences in the activity of the prepared Ni/SBA-15 catalysts in hydrogenation of naphthalene. Catalysts prepared with the addition of EDTA were more active than those prepared without ligands. On the contrary, the HYD activity of a series of the Ni catalysts prepared with citric acid was lower than of other corresponding samples. The reasons of such a different behavior of the catalysts prepared with two organic ligands used are discussed on the basis of the obtained characterization results.

Thermodynamic Modeling For The Ternary Mixture CO2-Naphtalene-Phenanthrene At High Pressure

The present work is concerned with the modelling of the solubility of solid compounds like Phenanthrene (PH), and Naphtalene (NA), as well as their mixtures, in supercritical fluids such as carbon dioxide.For the first two binary systems i.e. PH-CO2, the model combines the cubic Soave equation of state (EOS) and Redlich Kwong EOS and Peng Robinson EOS with the mixing rule (MR) of van der Waals (VDW) at constant temperature of 308.2K and a pressure range of 87.5-308.2 Bars.The obtained solubility of NA in supercritical carbon dioxide has been found to be higher than that of PH. This can be explained by the differences in the intermolecular interactions which are relatively weak for the case of NA. However, the model PR-VDW provides a better correlation than the others models for the solubility of Naphthalene and phenanthrene in supercritical CO2.

Genome Shuffling of &amp;lt;i&amp;gt;Pseudomonas&amp;lt;/i&amp;gt; Sp. Ioca11 for Improving Degradation of Polycyclic Aromatic Hydrocarbons

A Pseudomonas sp. strain IOCa11 exhibiting broad substrate profile for polycyclic aromatic hydrocarbons (PAHs) degradation was isolated by enrichment techniques from oil-contaminated soil. We applied genome shuffling of Pseudomonas sp. strain IOCa11 to achieve improved degradation of PAHs. The initial mutant population was generated by nitrosoguanidine treatment and population exhibiting improved phenotype was subjected to multiple round of protoplast fusion in order to allow recombination between genomes. Mutant, designated as SF-IOC11-16A, obtained after recursive protoplast fusion showed substantial improvement in ability to degrade PAHs in liquid media. It could degrade 98% DBT in 72 hours in comparison to 74% by the wild parent strain. Similar improvement in degradation of the naphthalene (NAP), phenanthrene (PHE), and benzo (α) pyrene (BAP) was also observed in shuffled strain. The shuffled strain was also able to grow at higher concentration of PAHs and degrade them efficiently. The results indicate that genome shuffling can successfully be used to improve the PAHs degradation capability of bacteria.

Nasal epithelial lesions in F344 rats following a 90-day inhalation exposure to naphthalene

Naphthalene (NA) was shown to be carcinogenic, causing respiratory epithelial adenoma in the nasal cavity of male F344 rats and olfactory epithelial neuroblastoma in female F344 rats at exposure concentrations of 10–60 ppm in a 2-year inhalation study conducted by the National Toxicology Program. To explore the exposure-response relationship and threshold for nasal epithelial effects in F344 rats, a 90-day (6 h/d, 5 d/wk) inhalation study was conducted at 0, 0.1, 1, 10 and 30 ppm NA vapor. Group size for nasal cavity histopathology was 10/sex with an additional 10/sex evaluated 4 wk post-exposure. NA exposure concentrations were measured by GC/MS, and aerosol testing verified that solid NA particles were not present. There were no NA exposure-related clinical observations and mild decreases in body weight (<10%) and food/water consumption were observed primarily in the 30 ppm rats. Rat heads were cross-sectioned at six levels for microscopic examination. There were no nasal cavity lesions related to NA exposure in rats of the 0.1 ppm group. Minimal hyperplasia was observed in the transitional/respiratory epithelium of rats exposed to 1 ppm. Mild hyperplasia and minimal squamous metaplasia were observed in the respiratory epithelium of rats exposed to 10 or 30 ppm. Lesions in the olfactory epithelium were observed only in rats of the 10 or 30 ppm groups and consisted of degeneration, necrosis, areas of re-epithelialization and basal cell hyperplasia. There was remarkable recovery of effects after 4 weeks, but residual olfactory epithelial degeneration and basal cell hyperplasia were still evident.

Sorption of aromatic hydrocarbons onto montmorillonite as affected by norfloxacin

Effect of norfloxacin (Nor) on the sorption of 1,3-dinitrobenzene (1,3-DNB), and PAHs (naphthalene (NAPH), phenanthrene (PHEN) and pyrene (PYR)) to K +-montmorillonite was studied. Nor suppressed 1,3-DNB sorption due to their competition for the same sorption sites. 1,3-DNB was sorbed on K +-montmorillonite surface via cation–polar interaction and n–π electron donor–acceptor interaction. Nor also was sorbed on these sites through cation exchange, cation bridging and/or surface complexation. Nor increased three PAHs sorption on montmorillonite and the enhanced magnitude was positively correlated with the π-donor strength of three PAHs. The enhanced sorption of PAHs by Nor was primarily attributed to π–π interaction between π-electron-depleted quinoline ring of Nor and π-electron-rich PAHs. Compared with cation (Nor +) and anion (Nor −), zwitterion (Nor ±) of Nor increased PHEN and PYR sorption more pronounced due to additional cation–π interaction between the sorbed Nor ± and PAHs. 1H NMR spectrum provided direct evidence for π–π and cation–π complexation between PAHs and Nor + in solution by ring-current-induced upfield chemical shifts of amino group and methylene group of Nor +.

Epithelial cell senescence impairs repair process and exacerbates inflammation after airway injury

BackgroundGenotoxic stress, such as by exposure to bromodeoxyuridine (BrdU) and cigarette smoke, induces premature cell senescence. Recent evidence indicates that cellular senescence of various types of cells is accelerated in COPD patients. However, whether the senescence of airway epithelial cells contributes to the development of airway diseases is unknown. The present study was designed to test the hypothesis that premature senescence of airway epithelial cells (Clara cells) impairs repair processes and exacerbates inflammation after airway injury.MethodsC57/BL6J mice were injected with the Clara-cell-specific toxicant naphthalene (NA) on days 0, 7, and 14, and each NA injection was followed by a daily dose of BrdU on each of the following 3 days, during which regenerating cells were allowed to incorporate BrdU into their DNA and to senesce. The p38 MAPK inhibitor SB202190 was injected 30 minutes before each BrdU dose. Mice were sacrificed at different times until day 28 and lungs of mice were obtained to investigate whether Clara cell senescence impairs airway epithelial regeneration and exacerbates airway inflammation. NCI-H441 cells were induced to senesce by exposure to BrdU or the telomerase inhibitor MST-312. Human lung tissue samples were obtained from COPD patients, asymptomatic smokers, and nonsmokers to investigate whether Clara cell senescence is accelerated in the airways of COPD patients, and if so, whether it is accompanied by p38 MAPK activation.ResultsBrdU did not alter the intensity of the airway epithelial injury or inflammation after a single NA exposure. However, after repeated NA exposure, BrdU induced epithelial cell (Clara cell) senescence, as demonstrated by a DNA damage response, p21 overexpression, increased senescence-associated β-galactosidase activity, and growth arrest, which resulted in impaired epithelial regeneration. The epithelial senescence was accompanied by p38 MAPK-dependent airway inflammation. Senescent NCI-H441 cells impaired epithelial wound repair and secreted increased amounts of pro-inflammatory cytokines in a p38 MAPK-dependent manner. Clara cell senescence in COPD patients was accelerated and accompanied by p38 MAPK activation.ConclusionsSenescence of airway epithelial cells impairs repair processes and exacerbates p38 MAPK-dependent inflammation after airway injury, and it may contribute to the pathogenesis of COPD.