Isolation of nitrophenols from diesel exhaust particles (DEP) as vasodilatation compounds

Nitrophenols disrupt the expression and activity of biotransformation enzymes (CYP3A and COMT) in chicken ovarian follicles in vivo and in vitro

Nitrophenols are environmental pollutants and xenobiotics, the main sources of which are diesel exhaust fumes and pesticides. The biotransformation processes that take place in the liver are defence mechanisms against xenobiotics, such as nitrophenols. Our previous study showed that the chicken ovary is an additional xenobiotic detoxification place and that nitrophenols disrupt steroidogenesis in chicken ovarian follicles. Therefore, the present study aimed to determine the in vivo and in vitro effects of 4-nitrophenol (PNP) and 3-methyl-4-nitrophenol (PNMC) on the expression and activity of phase I (CYP3A) and phase II (COMT) biotransformation enzymes in chicken ovary. In an in vivo study, hens were treated with a vehicle or 10 mg PNP or PNMC/kg b.wt. per day for 6 days. In an in vitro study, prehierarchical white and yellowish follicles, as well as the granulosa and theca layers of the three largest preovulatory follicles (F3, F2 and F1), were isolated and then incubated in a control medium or medium supplemented with PNP (10-6 M) or PNMC (10-6 M) for 24 or 48 h. Both in vivo and in vitro studies showed that nitrophenols exert tissue- and compound-dependent (PNP or PNMC) effects on CYP3A and COMT gene (real-time PCR) protein (Western blot) expression and their activity (colorimetric methods). The inhibitory effect of nitrophenols in vivo on the activity of biotransformation enzymes suggest that the ovary has the capacity to metabolise PNP and PNMC.

Exposure to air pollution and risk of ovarian cancer: a review

OBJECTIVES

Exposure to air pollution has destructive health consequences and a potential role in ovarian cancer etiology. We conducted a systematic review of the studies assessing the associations between ovarian malignancy and exposure to air pollutants.

CONTENT

The included studies were categorized based on types of measured ambient air pollutants, including particulate matter (five studies), gases (two studies), air pollutant mixtures (eight studies), and traffic indicators for air pollution (only one study). Because of the heterogeneity of quantitative data of the reviewed studies, we qualitatively reviewed the air pollution role in ovarian cancer risk with representing incidence and/or the mortality rate of ovarian cancer in related with air pollution. Nine studies were ecological study design. Except for one, all studies confirmed a positive correlation between exposure to ambient air pollution (AAP) and increased ovarian cancer risks.

SUMMARY

We concluded that prolonged air pollution exposure through possible mechanisms, estrogen-like effects, and genetic mutations might affect ovarian tumorigenesis. This research surveyed the limitations of the previous studies, including issues with ambient air pollution surveillance and assessing the exposure, determining the air pollution sources, data analysis approaches, and study designs.

OUTLOOK

Finally, the authors provide suggestions for future environmental epidemiological inquiries on the impact of exposure to ambient air pollution on ovarian malignancy.

Chitosan-supported metal nanocatalysts for the reduction of nitroaromatics

The second most abundant natural polymer in the earth's crust is chitosan (CS). The unique physical, chemical, structural, and mechanical features of this natural polymer have led to its increased application in a variety of fields such as medicine, catalysis, removal of pollutants, etc. To eliminate various pollutants, it is preferable to employ natural compounds as their use aids the removal of contaminants from the environment. Consequently, employing CS to eliminate contaminants is a viable choice. For this aim, CS can be applied as a template and support for metal nanoparticles (MNPs) and prevent the accumulation of MNPs as well as a reducing and stabilizing agent for the fabrication of MNPs. Among the pollutants present in nature, nitro compounds are an important and wide category of biological pollutants. 4-Nitrophenol (4-NP) is one of the nitro pollutants. There are different ways for the removal of 4-NP, but the best and most effective method for this purpose is the application of a metallic catalyst and a reducing agent. In this review, we report the recent developments regarding CS-supported metallic (nano)catalysts for the reduction of nitroaromatics such as nitrophenols, nitroaniline compounds, nitrobenzene, etc. in the presence of reducing agents. The metals investigated in this study include Ag, Au, Ni, Cu, Ru, Pt, Pd, etc.

Rnf20 inhibition enhances immunotherapy by improving regulatory T cell generation

BACKGROUND

Allergic disorders are common all over the world. The pathogenesis of allergy is unclear. Therapies for allergic disorders require improvement. Endoplasmic reticulum (ER) stress is one of the factors influencing immune response. The purpose of this study is to improve the effectiveness of immunotherapy for experimental respiratory allergy by targeting the ER stress signal pathway.

METHODS

Committed CD4+ T cells were isolated from blood samples collected from patients with allergic rhinitis (AR) and TCR ovalbumin transgenic mice. The effects of TCR engagement and 3-methyl-4-nitrophenol (MNP) on inducing ER stress in committed CD4+ T cells were evaluated.

RESULTS

ER stress was detected in antigen-specific CD4+ T cells (sCD4+ T cells) of AR patients. The environmental pollutant MNP increased the expression of the X-binding protein-1 (XBP1) in the committed CD4+ T cells during the TCR engagement. XBP1 mediated the effects of MNP on inhibiting regulatory T cell (Treg) generation. The effects of MNP on induction of protein 20 (Rnf20) in CD4+ T cells were mediated by XBP1. Inhibition of Rnf20 rescued the Treg development from MNP-primed sCD4+ T cells. The ablation of Rnf20 improved the immunotherapy of AR through the restoration of the Treg generation.

CONCLUSIONS

ER stress can be detected in CD4+ T cells in TCR engagement. Exposure to MNP exacerbates ER stress in committed CD4+ T cells. Regulation of the ER stress-related Rnf20 expression can restore the generation of Treg from CD4+ T cells of subjects with allergic diseases.

Variabilities in Primary N-Containing Aromatic Compound Emissions from Residential Solid Fuel Combustion and Implications for Source Tracers

Nitroaromatic compounds (NACs) not only are strongly absorbing chromophores but also adversely affect human health. NACs can be emitted from incomplete combustions and can derive secondarily through photochemical reactions. Here, emission experiments were conducted for 31 fuel-stove combinations to elucidate variations in, and influencing factors of, NAC emission factors (EF_∑NACs) and to explore potential tracers for different combustion sources. EF_∑NACs varied by 2 orders of magnitude among different combinations. Differences in fuel type contributed more than the stove difference to the observed variation. EF_∑NACs for biomass pellets was approximately 66% lower than that for raw biomass, although the bulk organic and brown carbon EFs were 95% lower. 2-Nitro-1-naphthol was the most abundant individual compound, followed by 4-nitrocatechol, while acid compounds (salicylic acid and benzoic acid) were low in abundance (<1%). Substantially different profiles were observed between coal and biomass burning emissions. Biomass burning had more single-ring-based phenolic compounds with more 4-nitrocatechol, while in coal combustion, more two-ring products were produced. This study demonstrated much lower ratios of 2-nitro-1-naphthol/4-nitrocatechol for biomass in both traditional (2.0 ± 3.5) and improved stoves (3.0 ± 2.1) than for coals (15 ± 6). Coal and biomass burning differed in not only EF_∑NACs but also compound profile, consequently leading to distinct health and climate impacts; moreover, the ratio of 2-nitro-1-naphthol/4-nitrocatechol may be used in source apportionment of NACs.

Characteristic fragmentations of nitroaromatic compounds (NACs) in Orbitrap HCD and integrated strategy for recognition of NACs in environmental samples

Nitroaromatic compounds (NACs) are high of concern due to their mutagenicity, and carcinogenicity to organisms. Here, we attempted to establish a novel searching-validation-evaluation workflow that is tailored to recognize unknown NACs in environmental samples using liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry (LC-Orbitrap-HRMS). We studied the fragmentation process of NAC standards in Orbitrap higher-energy collision dissociation (HCD) cells and observed that the mass loss of NO was the most prevalent among all NAC standards at both low and medium levels of collision energy. Thus, neutral loss of NO was considered as a diagnostic fragment of nitro groups and was used to screen out NACs in environmental samples. This technique is mass-loss-dependent, which enhances the recognition efficiency of NACs. Candidates exported from the PubChem compound database were further evaluated to obtain possible structures. This strategy was applied for the analysis of 24 surface soil, and we tentatively discovered two novel NACs in the analyzed samples. The semi-quantification results demonstrated that the concentrations of novel NACs were comparable to those of the ten targeted NACs in soil samples. This study provides an integrated strategy for the recognition of known and unknown NACs, which could be extended to other environmental matrices.

Nitrophenols are negative modulators of steroidogenesis in preovulatory follicles of the hen (Gallus domesticus) ovary: An in vitro and in vivo study

This study assessed the effects of 4-nitrophenol (PNP) and 3-methyl-4-nitrophenol (PNMC) on steroidogenesis in the granulosa layers (GLs) and theca layers (TLs) of chicken preovulatory follicles in vitro and in vivo. In the in vitro experiment, three of the largest yellow preovulatory follicles (F3 < F2 < F1) were exposed to PNP or PNMC (10^-8-10^-4 M), ovine luteinising hormone (oLH; 10 ng/mL), and combinations of oLH and PNP or PNMC (10^-6 M). In the in vivo experiment, laying hens were treated for 6 days with PNP or PNMC (10 mg/kg). In vitro experiments revealed that PNP and PNMC decreased basal and oLH-stimulated P4 secretion from the GL as well as T and E2 secretion from the TLs of F3-F1 follicles. Treatment of laying hens with nitrophenols lowered plasma concentrations of luteinising hormone and all three steroids. The reduction of steroid secretion was associated with decrease in LHR, HSD3B1 and CYP19A1 mRNA expression in the GL and/or TLs of the preovulatory follicles, both in vitro and in vivo. Moreover, PNP decreased HSD3B protein expression in the GL of F2 follicles in vitro and in vivo, while PNMC diminished its expression in the GL of F1 follicles in vivo. In vitro, nitrophenols did not affect CYP19A1 protein expression; however, nitrophenols inhibited its expression in the TLs of F3 and F2 follicles in vivo. The results obtained clearly demonstrate that nitrophenols are negative modulators of steroidogenesis in chicken preovulatory follicles and, in consequence, may not only impair ovulation process, but also affect function of the hypothalamic-pituitary-ovarian axis.

4-nitrophenol exposure in T24 human bladder cancer cells promotes proliferation, motilities, and epithelial-to-mesenchymal transition

Although health hazards of 4-nitrophenol (PNP) exposure have been reported, the adverse effects of PNP exposure on cancer biological features are still unknown. We investigated the effects of administration of PNP in T24 human bladder cancer cells. The results showed that PNP exposure promoted cellular proliferation, migration and invasion, inhibited adhesion and apoptosis in vitro. Using quantitative real-time PCR, we found that (1) the mRNA expression levels of cell-cycle regulators PCNA, cyclin D1 and COX-2 were increased in PNP-treated cells compared to controls, however, that of pro-apoptotic gene Bax was decreased; (2) the expression level of EMT-associated gene E-cadherin was decreased in PNP-treated cells, whereas those of N-cadherin, vimentin, snail, and slug were increased; (3) the expression levels of cancer-promoting genes HIF-1, IL-1β, VEGFα and K-Ras were enhanced, but those of tumor suppressors p53, PTEN and BRCA were decreased. There was a positive association between PNP exposure times and the promotion effects. Finally, we found that the expression level of PPARγ (γ1 isoform) was increased in PNP-treated T24 cells. GW9662, a specific PPARγ antagonist, attenuated PNP-induced cell migration and invasion. These findings indicate that PNP exposure may promote bladder cancer growth and progression involving PPARγ signaling. PPARγ is a potential target for development of novel intervention study on environment pollution. Environ. Mol. Mutagen. 61:316-328, 2020. © 2019 Wiley Periodicals, Inc.

Nitrophenols suppress steroidogenesis in prehierarchical chicken ovarian follicles by targeting STAR, HSD3B1, and CYP19A1 and downregulating LH and estrogen receptor expression

To assess the effects of 4-nitrophenol (PNP) and 3-methyl-4-nitrophenol (PNMC) on steroidogenesis in the chicken ovary, white (WF, 1-4 mm) and yellowish (YF, 4-8 mm) prehierarchical follicles were incubated in a medium supplemented with PNP or PNMC (10^-8-10^-4 M), ovine LH (oLH; 10 ng/mL), and combinations of oLH with PNP or PNMC (10^-6 M). Testosterone (T) and estradiol (E2) concentrations in media and mRNA expression for steroidogenic proteins (STAR, HSD3B1, and CYP19A1), and LH receptors (LHR), estrogen receptor α (ESR1) and β (ESR2) in follicles were determined by RIA and real-time qPCR, respectively. PNP and PNMC decreased T and E2 secretion by the WF and YF, and oLH-stimulated T secretion from these follicles. PNP decreased basal STAR and HSD3B1 mRNA levels both in the WF and YF, and CYP19A1 mRNAs in the WF. PNP reduced oLH-affected mRNA expression of these genes in the YF. PNMC inhibited basal STAR, HSD3B1, and CYP19A1 mRNA expression in the WF, but not in the YF. PNMC reduced oLH-stimulated STAR and CYP19A1 expression in the YF and WF, respectively. PNP decreased basal mRNA expression of LHR, ESR1, and ESR2 in the WF, but it increased ESR1 and ESR2 mRNA levels in the YF. PNMC reduced both basal and oLH-affected LHR, ESR1, and ESR2 mRNA expression in the WF; however, it did not influence expression of these genes in the YF. We suggest that nitrophenols by influencing sex steroid synthesis and transcription of LH and estrogen receptors in prehierarchical ovarian follicles may impair their development and selection to the preovulatory hierarchy.

In vitro effects of PNP and PNMC on apoptosis and proliferation in the hen ovarian stroma and prehierarchal follicles

This study aimed to examine the mRNA expression, activity, and immunolocalisation of apoptosis/proliferation regulating factors following in vitro exposure of the stroma, white (WFs), and yellowish (YFs) follicles of the chicken ovary to 4-nitrophenol (PNP) or 3-methyl-4-nitrophenol (PNMC). PNMC increased the mRNA expression of caspase-3, -8, Apaf-1, and cytochrome c in the ovarian stroma. The activity of caspase-3, -8, and -9 decreased in WFs in both nitrophenol-treated groups. PNP reduced the number of caspase-3-positive cells in the stromal connective tissue (CT) and the theca interna and externa layers of WFs. In the stroma, the proliferating index decreased in the wall of primary follicles in both nitrophenol-treated groups, however, in the CT, the effect of PNMC was opposite. In the theca interna of WFs, PNP diminished the proliferating index. These results suggest that nitrophenols might impact the development of chicken ovarian follicles by affecting cell death and proliferation.

Emissions of fine particulate nitrated phenols from various on-road vehicles in China

Nitrated phenols are receiving increasing attention due to their adverse impacts on the environment and human health. Previous measurements have revealed the non-ignorable contribution of vehicle exhaust to atmospheric nitrated phenols in urban areas. However, there is a lack of comprehensive understanding of the emission characteristics and the total emission of nitrated phenols from current on-road traffic. This study investigated the emissions from eight passenger vehicles, eight trucks, and two taxis, with fuel types including diesel, gasoline, and compressed natural gas. Exhaust emissions were collected and measured using a mobile measurement system on two testing routes. Twelve nitrated phenols in the collected fine particulate matter were detected using ultrahigh performance liquid chromatography-mass spectrometry. Overall, the emission profiles of fine particulate nitrated phenols varied with vehicle load and fuel type. The 4-nitrophenol and its methyl derivatives were dominant nitrated phenol species emitted by the vehicles with proportions of 38.4%-68.0%, which is significantly different from the proportions of nitrated phenols emitted from biomass burning and coal combustion. The emission factors also exhibited large variations across vehicle type, fuel type, and emission standards, with relatively low values for gasoline vehicles and taxis fueled by compressed natural gas and high values for diesel vehicles. Based on the emission factors of nitrated phenols from different vehicles, the estimated total emission of nitrated phenols from on-road vehicles in China was 58.9 Mg (-86%-85% within 95% confidence interval), with diesel trucks contributing the most substantial fractions. This work highlights the very high level of emissions of nitrated phenols from diesel vehicles and provides an essential basis for atmospheric modeling and effective pollution control.

Environmental persistence, hazard, and mitigation challenges of nitroaromatic compounds

Nitroaromatic compounds (NACs) are extensively used in different industries and are synthesized in large quantity due to their heavy demand worldwide. The broad use of NACs poses a serious pollution threat. The treatment processes used for the removal of NACs are not effective and sustainable, leading to their release into the environment. The nitro group attached to benzene ring makes the compounds recalcitrant due to which they persist in the environment. Being hazardous to human as well as other living organisms, NACs are listed in the USEPA's priority pollutant group. This review provides updated information on the sources of NACs, prevalence in different environmental matrices, and recent developments in methods of their detection, with emphasis on current trends as well as future prospects. The harmful effects of NACs due to exposure through different routes are also highlighted. Further, the technologies reported for the treatment of NACs, including physico-chemical and biological methods, and the challenges faced for their effective implementation are discussed. Thus, the review discusses relevant issues in detail making suitable recommendations, which can be helpful in guiding further research in this subject.

4-Nitrophenol induces activation of Nrf2 antioxidant pathway and apoptosis of the germ cells in rat testes

The potential of 4-nitrophenol (PNP) to affect testicular function of rats was assessed by intratesticular injection (IT). The protective effects of phytosterin (PS) on PNP-induced injury were assessed. Rats were sacrificed on days 1, 3, and 7 after IT of PNP (0.1 M, 50 μl). PNP induced hemorrhage in intertubular areas and denudation of germinal epithelium. The expression of caspase-3 and sperm abnormalities were significantly increased (P < 0.05). The concentrations of testosterone in serum were significantly increased (P < 0.05) on the 1st and 3rd day. PNP induced oxidative stress in testes, which manifested increased SOD, CAT, GSH-Px activities, and increases in MDA, GSH, H2O2 concentrations (P < 0.05). The Nrf2 antioxidant pathway was activated as indicated by increased expression of Nrf2, HO-1, and GCLC mRNA (P < 0.05). Moreover, supplementation with PS resulted in an amelioration of PNP-induced oxidative damage. These results suggest that PNP induced activation of Nrf2 antioxidant pathway and apoptosis of the germ cells.

Walnut Polyphenol Extract Attenuates Immunotoxicity Induced by 4-Pentylphenol and 3-methyl-4-nitrophenol in Murine Splenic Lymphocyte

4-pentylphenol (PP) and 3-methyl-4-nitrophenol (PNMC), two important components of vehicle emissions, have been shown to confer toxicity in splenocytes. Certain natural products, such as those derived from walnuts, exhibit a range of antioxidative, antitumor, and anti-inflammatory properties. Here, we investigated the effects of walnut polyphenol extract (WPE) on immunotoxicity induced by PP and PNMC in murine splenic lymphocytes. Treatment with WPE was shown to significantly enhance proliferation of splenocytes exposed to PP or PNMC, characterized by increases in the percentages of splenic T lymphocytes (CD3+ T cells) and T cell subsets (CD4+ and CD8+ T cells), as well as the production of T cell-related cytokines and granzymes (interleukin-2, interleukin-4, and granzyme-B) in cells exposed to PP or PNMC. These effects were associated with a decrease in oxidative stress, as evidenced by changes in OH, SOD, GSH-Px, and MDA levels. The total phenolic content of WPE was 34,800 ± 200 mg gallic acid equivalents/100 g, consisting of at least 16 unique phenols, including ellagitannins, quercetin, valoneic acid dilactone, and gallic acid. Taken together, these results suggest that walnut polyphenols significantly attenuated PP and PNMC-mediated immunotoxicity and improved immune function by inhibiting oxidative stress.

The environmental endocrine disruptor p-nitrophenol interacts with FKBP51, a positive regulator of androgen receptor and inhibits androgen receptor signaling in human cells

The compound p-nitrophenol, which shows the anti-androgenic activity, can easily become anthropogenic pollutants and pose a threat to the environment and human health. Previous work indicates that the anti-androgenic mechanism of p-nitrophenol is complex and may involve several components in the AR signaling pathway, but the molecular details of how p-nitrophenol inhibits AR signaling are still not quite clear. Here, we characterized p-nitrophenol binds to the FK1 domain of an AR positive regulator FKBP51 with micromolar affinity and structural analysis of FK1 domain in complex with p-nitrophenol revealed that p-nitrophenol occupies a hydrophobic FK1 pocket that is vital for AR activity enhancement. Molecular dynamics simulation indicated that p-nitrophenol is stably bound to the FK1 pocket and the hotspot residues that involved p-nitrophenol binding are mainly hydrophobic and overlap with the AR interaction site. Furthermore, we showed that p-nitrophenol inhibits the androgen-dependent growth of human prostate cancer cells, possibly through down-regulating the expression levels of AR activated downstream genes. Taken together, our data suggests that p-nitrophenol suppresses the AR signaling pathway at least in part by blocking the interaction between AR and its positive regulator FKBP51. We believe that our findings could provide new guidelines for assessing the potential health effects of p-nitrophenol.

The effect of phytosterol protects rats against 4-nitrophenol-induced liver damage

We investigated the effect of phytosterol (PS) in regard to liver damage induced by 4-nitrophenol (PNP). Twenty rats were randomly divided into four groups (Control, PS, PNP, and PNP+PS). The PS and PNP+PS groups were pretreated with PS for one week. The PNP and PNP+PS groups were injected subcutaneously with PNP for 28 days. The control group received a basal diet and was injected with vehicle alone. Treatment with PS prevented the elevation of the total bilirubin levels, as well as an increase in serum alkaline transaminase and aspartate transaminase, which are typically caused by PNP-induced liver damage. Histopathologically showed that liver damage was significantly mitigated by PS treatment. However, there was no significant change in antioxidant enzyme activities, and the Nrf2-antioxidant system was not activated after treatment with PS. These results suggest that PS could mitigate liver damage induced by PNP, but does not enhance antioxidant capacity.

Bacterial degradation of nitrophenols and their derivatives

This review intends to provide an overview of bacterial degradation of nitrophenols (NPs) and their derivatives. The main scientific focus is on biochemical and genetic characterization of bacterial degradation of NPs. Other aspects such as bioremediation and chemotaxis correlated with biodegradation of NPs are also discussed. This review will increase our current understanding of bacterial degradation of NPs and their derivatives.

Necrosis and apoptosis of renal tubular epithelial cells in rats exposed to 3-methyl-4-nitrophenol

The 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) exists in diesel exhaust particles (DEP), and is also one of the degradation products of insecticide fenitrothion. To assess potential nephrotoxicity of PNMC, male Sprague-Dawley (SD) rats were subcutaneously dosed with PNMC at 1, 10, and 100 mg/kg/day for five consecutive days. No significant changes were detected in body weights and relative weights of kidneys by the treatment of PNMC. However, the extent of cellular necrosis was found to be severe in renal tubular epithelial cells of PNMC-treated rats. In addition, PNMC exposure significantly increased the number of terminal deoxynucleotidyle transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells compared to the control in renal tubule of PNMC-treated rats. Moreover, immunohistochemical results indicated that significant decrease in the B-cell lymphoma 2 (Bcl-2) expressions andincrease in the Bcl-2 associated × protein (Bax) expression were detected in PNMC-treated rats. The ratio of Bcl-2/Bax was also reduced significantly at PNMC-treated rats dosed at 10 or 100 mg kg(-1) . Furthermore, the significant increase of FAS (CD95/APO-1) expression was found in the groups dosed at 10 or 100 mg kg(-1) of PNMC. The expression of Caspase-3 was higher in PNMC-treated rats, compared to the control group. Our results indicated that activation of mitochondria and Caspase-3 protease may contribute to the PNMC-induced apoptosis, suggesting that PNMC could cause both necrosis and apoptosis resulting in cell death of renal epithelium cells and could induce renal toxicity.

Alleviative effect of quercetin on germ cells intoxicated by 3-methyl-4-nitrophenol from diesel exhaust particles

As a component of diesel exhaust particles, 3-methyl-4-nitrophenol (4-nitro-m-cresol, PNMC) is also a metabolite of the insecticide fenitrothion and imposes hazardous effects on human health. In the present study, the alleviative effect of a common antioxidant flavonoid quercetin on mouse germ cells intoxicated by PNMC was investigated. Results showed that a single intraperitoneal injection of PNMC at 100 mg/kg induced severe testicular damage after one week. PNMC-treated mice showed a significant loss of germ cells (approximate 40% loss of round germ cells). PNMC caused an increase of hydroxyl radical and hydrogen peroxide production and lipid peroxidation, as well as a decrease in glutathione level, superoxide dismutase and glutathione peroxidase activities. Furthermore, treatment of PNMC increased expression of the pro-apoptotic protein Bax and decreased expression of the anti-apoptotic protein Bcl-XL in germ cells. In addition, testicular caspase-3 activity was significantly up-regulated and germ cell apoptosis was significantly increased in the PNMC-treated mice. In contrast, combined administration of quercetin at 75 mg/kg significantly attenuated PNMC-induced testicular toxicity. These results indicate that the antioxidant quercetin displays a remarkable protective effect on PNMC-induced oxidative damage in mouse testes and may represent an efficient supplement to attenuate reproductive toxicity by environmental toxicants to ensure healthy sperm production.

Measurement of nitrophenols in rain and air by two-dimensional liquid chromatography-chemically active liquid core waveguide spectrometry

We report a novel system to analyze atmospheric nitrophenols (NPs). Rain or air sample extracts (1 mL) are preconcentrated on a narrow bore (2 mm) aliphatic anion exchanger. In the absence of strong retention of NPs exhibited by aromatic ion exchangers, retained NPs are eluted as a plug by injection of 100 microL of 0.1 M Na(2)SO(4) on to a short (2 x 50 mm) reverse phase C-18 column packed with 2.2 mum particles. The salt plug passes through the C-18 column unretained while the NPs are separated by an ammonium acetate buffered methanol-water eluent, compatible with mass spectrometry (MS). The eluted NPs are measured with a long path Teflon AF-based liquid core waveguide (0.15 x 1420 mm) illuminated by a 403 nm light emitting diode and detected by a monolithic photodiode-operational amplifier. The waveguide is rendered chemically active by suspending it over concentrated ammonia that permeates into the lumen. The NPs ionize to the yellow anion form (lambda(max) approximately 400 nm). The separation of 4-nitrophenol, 2,4-dinitrophenol, 2-methyl-4-nitrophenol, 3-methyl-4-nitrophenol, and 2-nitrophenol (these are the dominant NPs, typically in that order, in both rain and air of Houston and Arlington, TX, confirmed by tandem MS) takes just over 5 min with respective S/N = 3 limits of detection (LODs) of 60, 12, 30, 67, and 23 pg/mL compared to MS/MS LODs of 20, 49, 11, 20, and 210 pg/mL. Illustrative air and rain data are presented.

Isolation and identification of new vasodilative substances in diesel exhaust particles

BACKGROUND, AIM, AND SCOPE

We recently developed a new isolation method for diesel exhaust particles (DEP), involving successive extraction with H(2)O, sodium bicarbonate, and sodium hydroxide, in which the sodium hydroxide extract was found to consist of phenolic components. Analysis of the extract revealed that vasodilative-active nitrophenols are in DEP in significantly higher concentrations than those estimated by an earlier method involving a combination of solvent extraction and repeated chromatography. These findings indicated that our new procedure offers a simple, efficient, and reliable method for the isolation and identification of bioactive substances in DEP. This encouraged us to extend our work toward investigating new vasodilatory substances in the sodium bicarbonate extract.

MATERIALS AND METHODS

DEP were collected from the exhaust of a 4JB1-type engine (ISUZU Automobile Co., Tokyo, Japan). GC-MS analysis was performed with a GCMS-QP2010 instrument (Shimadzu, Kyoto, Japan).

RESULTS

DEP dissolved in 1-butanol was successively extracted with water, sodium bicarbonate, and then aqueous sodium hydroxide. The sodium bicarbonate extract was neutralized and the resulting mixture of acidic components was subjected to reverse-phase (RP) column chromatography followed by RP-HPLC with fractions assayed for vasodilative activity. This led to the identification of terephthalic acid, p-hydroxybenzoic acid, isophthalic acid, phthalic acid, 3-hydroxy-4-nitrobenzoic acid, 4-hydroxy-3-nitrophenol, and 1,4,5-naphthalene tricarboxylic acid as components of DEP.

DISCUSSION

The sodium bicarbonate extract was rich in aromatic carboxylic acid components. Repeated reverse-phase chromatography resulted in the successful isolation of several acidic substances including the new vasodilative materials, 4-hydroxy-3-nitrobenzoic acid, and 3-hydroxy-4-nitrobenzoic acid.

CONCLUSIONS

Our new fractionation method for DEP has made possible the isolation of new vasodilative compounds from the sodium bicarbonate extract.

Protective effect of quercetin on the reproductive toxicity of 4-nitrophenol in diesel exhaust particles on male embryonic chickens

The 4-nitrophenol (PNP) in diesel exhaust particles (DEP) has been identified as a vasodilator and is a known degradation product of the insecticide parathion. In this study, the protective effect of quercetin, a potent oxygen free radical scavenger and metal chelator, against the oxidative damage of PNP on cultured testicular cells was studied in male embryonic chickens. Testicular cells from Day 18 embryos were cultured in serum-free McCoy's 5A medium and challenged with quercetin (1.0 microg/ml) alone or in combinations with PNP (10(-7)-10(-5) M) for 48 h. The oxidative damage was estimated by measuring cell viability, content of malondialdehyde (MDA), activity of superoxide dismutase (SOD) and glutathione peroxidation (GSH-Px) activity. The results showed that exposure to PNP (10(-5) M) induced condensed nuclei, vacuolated cytoplasm and a decrease in testicular cell viability and spermatogonial cell number. Exposure to PNP induced lipid peroxidation by elevation of the content of MDA. Exposure to PNP also decreased GSH-Px activity and SOD activity. However, simultaneous supplementation with quercetin restored these parameters to the same levels as the control. Consequently, PNP induced oxidative stress in spermatogonial cells, and dietary quercetin may attenuate the reproductive toxicity of PNP to restore the intracellular antioxidant system in the testicular cells of embryonic chickens.

Endocrine disruptive effect of 3-methyl-4-nitrophenol isolated from diesel exhaust particles in Hershberger assay using castrated immature rats

To examine the endocrine disruptive effects of 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) in diesel exhaust particles (DEP), the rat Hershberger assay was carried out using castrated immature rats. Castrated 28-d-old immature male rats were implanted with a 5-mm-long silastic tube containing crystalline testosterone and injected with PNMC subcutaneously at doses 1, 10, or 100 mg/kg for 5 consecutive d. The weights of the livers significantly decreased in the 10 and 100 mg/kg PNMC treatment groups as compared with the control group. The weights of the seminal vesicles significantly increased in the 10 mg/kg PNMC treatment group as compared with the control group. The weights of the Cowper's glands were significantly increased in 1 mg/kg PNMC treatment group compared with the control group. The concentrations of plasma testosterone significantly increased in the 10 and 100 mg/kg PNMC treatment groups, indicating that PNMC induced accumulation of bioactive testosterone released from the implanted tube in circulation. Plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels significantly decreased under all the doses in the PNMC treatment groups, indicating that PNMC acts on the hypothalamus-pituitary axis.

4-Nitrophenol isolated from diesel exhaust particles disrupts regulation of reproductive hormones in immature male rats

In previous studies, we found that 4-nitrophenol (PNP) isolated from diesel exhaust particles exhibited both estrogenic and anti-androgenic activities. This compound is also a degradation product of the insecticide parathion. Here, we investigated the in vivo effect of PNP on reproductive function in immature male rats. Twenty-eight-day-old rats were injected subcutaneously with PNP (0.01, 0.1, 1, or 10 mg/kg) daily for 14 days. Plasma concentrations of luteinizing hormone (LH) were significantly lower in all PNP dosage groups than in the control group, and follicle-stimulating hormone (FSH) was significantly decreased in rats treated with 0.1, 1, or 10 mg/kg PNP. However, plasma concentrations of testosterone were significantly increased by 10 mg/kg PNP, and plasma concentrations of immunoreactive (ir)-inhibin were also significantly increased in the 0.1, 1, and 10 mg/kg PNP groups. Plasma concentrations of prolactin were significantly increased by 10 mg/kg PNP, and plasma concentrations of corticosterone were significantly increased in all treatment groups. These findings clearly show that PNP influences the hypothalamic-pituitary-gonadal axis in immature male rats, with decreased secretion of LH and FSH and increased secretion of testosterone and inhibin. PNP, therefore, appears to disrupt endocrine activity in the immature male reproductive system.

Effects of 3-methyl-4-nitrophenol on the reproductive toxicity in female Japanese quail (Coturnix japonica)

We previously showed that 3-methyl-4-nitrophenol (4-nitro-m-cresol, PNMC), a component of diesel exhaust particles and a degradation product of the insecticide fenitrothion, has reproductive toxicity in adult male and immature female Japanese quail (Coturnix japonica). Here we investigated effects of PNMC on the reproductive toxicity of mature female Japanese quail. The experiment consists of 3 periods of pretreatment, treatment, and post-treatment for 5 d each. The birds were reared, bred naturally for 1 week, and after 5 d of pretreatment, then injected intramuscularly with PNMC at doses 1, 10, or 100 mg/kg body weight daily for 5 d. Body weight, egg weight, and hatchability did not differ among the observation periods. However, at all doses of PNMC, the egg-laying rate showed a modest decrease during the treatment period, with recovery during the post-treatment period. Plasma concentrations of luteinizing hormone (LH) and estrodiol-17beta, were significantly decreased (p<0.05), and plasma concentrations of progesterone significantly increased (p<0.05) in birds treated with 10 and 100 mg/kg PNMC. These results suggest that PNMC have acute toxicity, and inhibited LH secretion, disturbing egg-laying in mature female quail. Our findings indicate that PNMC induces endocrine malfunction at the central level and subsequently disrupts reproductive processes in mature female quails.

Improvement of an efficient separation method for chemicals in diesel exhaust particles: analysis for nitrophenols

GOAL, SCOPE, AND BACKGROUND

Diesel exhaust is believed to consist of thousands of organic constituents and is a major cause of urban pollution. We recently reported that a systematic separation procedure involving successive solvent extractions, followed by repeated column chromatography, resulted in the isolation of vasodilatory active nitrophenols. These findings indicated that the estimation of the amount of nitrophenols in the environment is important to evaluate their effect on human health. The isolation procedure, however, involved successive solvent extractions followed by tedious, repeated chromatography, resulting in poor fractionation and in a significant loss of accuracy and reliability. Therefore, it was crucial to develop an alternative, efficient, and reliable analytical method. Here, we describe a facile and efficient acid-base extraction procedure for the analysis of nitrophenols.

MATERIALS AND METHODS

Diesel exhaust particles (DEP) were collected from the exhaust of a 4JB1-type engine (ISUZU Automobile Co., Tokyo, Japan). Gas chromatography-mass spectrometry (GC-MS) analysis was performed with a GCMS-QP2010 instrument (Shimadzu, Kyoto, Japan).

RESULTS

A solution of DEP in 1-butanol was extracted with aqueous NaOH to afford a nitrophenol-rich oily extract. The resulting oil was methylated with trimethylsilyldiazomethane and subsequently subjected to GC-MS analysis, revealing that 4-nitrophenol, 3-methyl-4-nitrophenol, 2-methyl-4-nitrophenol, and 4-nitro-3-phenylphenol were present in significantly higher concentrations than those reported previously.

DISCUSSION

Simple acid-base extraction followed by the direct analysis of the resulting extract by GC-MS gave only broad peaks of nitrophenols with a poor detection limit, while the GC-MS analysis of the sample pretreated with (trimethylsilyl)diazomethane gave satisfactorily clear chromatograms with sharp peaks and with a significantly lowered detection limit (0.5 ng/ml, approximately 100 times).

CONCLUSION

The present method involving an acid-base extraction, in situ derivatization, and GC-MS analysis has shown to be a simple, efficient, and reliable method for the isolation and identification of the chemical substances in DEP.

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

Most nitroaromatic compounds are toxic and mutagenic for living organisms, but some microorganisms have developed oxidative or reductive pathways to degrade or transform these compounds. Reductive pathways are based either on the reduction of the aromatic ring by hydride additions or on the reduction of the nitro groups to hydroxylamino and/or amino derivatives. Bacterial nitroreductases are flavoenzymes that catalyze the NAD(P)H-dependent reduction of the nitro groups on nitroaromatic and nitroheterocyclic compounds. Nitroreductases have raised a great interest due to their potential applications in bioremediation, biocatalysis, and biomedicine, especially in prodrug activation for chemotherapeutic cancer treatments. Different bacterial nitroreductases have been purified and their biochemical and kinetic parameters have been determined. The crystal structure of some nitroreductases have also been solved. However, the physiological role(s) of these enzymes remains unclear. Nitroreductase genes are widely spread within bacterial genomes, but are also found in archaea and some eukaryotic species. Although studies on regulation of nitroreductase gene expression are scarce, it seems that nitroreductase genes may be controlled by the MarRA and SoxRS regulatory systems that are involved in responses to several antibiotics and environmental chemical hazards and to specific oxidative stress conditions. This review covers the microbial distribution, types, biochemical properties, structure and regulation of the bacterial nitroreductases. The possible physiological functions and the biotechnological applications of these enzymes are also discussed.

Nitrophenols isolated from diesel exhaust particles regulate steroidogenic gene expression and steroid synthesis in the human H295R adrenocortical cell line

Studies of nitrophenols isolated from diesel exhaust particles (DEPs), 3-methyl-4-nitrophenol (PNMC) and 4-nitro-3-phenylphenol (PNMPP) have revealed that these chemicals possess estrogenic and anti-androgenic activity in vitro and in vivo and that PNMC accumulate in adrenal glands in vivo. However, the impacts of exposure to these compounds on adrenal endocrine disruption and steroidogenesis have not been investigated. To elucidate the non-receptor mediated effects of PNMC and PNMPP, we investigated the production of the steroid hormones progesterone, cortisol, testosterone, and estradiol-17beta and modulation of nine major enzyme genes involved in the synthesis of steroid hormones (CYP11A, CYP11B1, CYP17, CYP19, 17betaHSD1, 17betaHSD4, CYP21, 3betaHSD2, StAR) in human adrenal H295R cells supplied with cAMP. Exposure to 10(-7) to 10(-5) M PNMC and 1 mM 8-Br-cAMP for 48 h decreased testosterone, cortisol, and estradiol-17beta levels and increased progesterone secretion. At 10(-5) M, PNMC with 1 mM 8-Br-cAMP significantly stimulated expression of the 17betaHSD4 and significantly suppressed expression of 3betaHSD2. In comparison, 10(-7) to 2 x 10(-5) M PNMPP with 1 mM 8-Br-cAMP for 48 h decreased concentrations of estradiol-17beta, increased progesterone levels, but did not affect testosterone and cortisol secretion due to the significant suppression of CYP17 and the non-significant but obvious suppression of CYP19. Our results clarified steroidogenic enzymes as candidates responsible for the inhibition or stimulation for the production of steroid hormones in the steroidogenic pathway, thus providing the first experimental evidence for multiple mechanisms of disruption of endocrine pathways by these nitrophenols.

Effects of 3-Methyl-4-Nitrophenol in Diesel Exhaust Particles on the Regulation of Reproductive Function in Immature Female Japanese Quail (Coturnix japonica)

In a previous study, we found that 3-methyl-4-nitrophenol (PNMC), a component of diesel exhaust particles and also a degradation product of the insecticide fenitrothion, exhibits reproductive toxicity in the adult male Japanese quail. The present study investigated the toxicity of PNMC in the female Japanese quail and its ability to influence reproduction in immature females. The quail (21-day-old) were injected intramuscularly (im) with PNMC at doses 0.1, 1 or 10 mg/kg body weight daily for 3 days. There was no significant difference in body growth between the PNMC-administered and control birds. However, the weights of the oviducts were significantly lower in the PNMC-treated birds at all doses. Furthermore, the plasma concentrations of luteinizing hormone (LH) and estradiol-17 beta were significantly decreased with 1 and 10 mg/kg of PNMC. These findings suggest that PNMC might influence the hypothalamo-pituitary-gonadal axis with decreasing in secretion of GnRH, LH and ovarian steroid hormones and subsequently disturb growth of the reproductive organs of immature female quail. This study indicates that PNMC induces reproductive toxicity at the central level and disrupts reproductive function in the immature female quail.

Estrogenic and anti-androgenic activities of 4-nitrophenol in diesel exhaust particles

A 4-nitrophenol (PNP) isolated from diesel exhaust particles (DEP) has been identified as a vasodilator. PNP is also a known degradation product of the insecticide parathion. We used uterotrophic and Hershberger assays to study the estrogenic and anti-androgenic activities of PNP in-vivo. In ovariectomized immature female rats injected subcutaneously with 1, 10, or 100 mg/kg PNP daily for 7 days, significant (P<0.05) increases in uterine weight were seen in only those receiving 10 or 100 mg/kg PNP. Furthermore, in castrated immature male rats implanted with a silastic tube (length, 5 mm) containing crystalline testosterone and injected subcutaneously with 0.01, 0.1, or 1 mg/kg PNP daily for 5 days, those receiving the doses of 0.1 mg/kg showed significant (P<0.05) weight decreases in seminal vesicles, ventral prostate, levator ani plus bulbocavernosus muscles, and glans penis. Plasma FSH and LH levels did not change in female rats but were significantly (P<0.05) increased in male rats treated with 0.1 mg/kg PNP. These results clearly demonstrated that PNP has estrogenic and anti-androgenic activities in-vivo. Our results therefore suggest that diesel exhaust emissions and the degradation of parathion can lead to accumulation of PNP in air, water, and soil and thus could have serious deleterious effects on wildlife and human health.

Role of reactive oxygen species on diesel exhaust particle-induced cytotoxicity in rat cardiac myocytes

Exposure to air pollution containing diesel exhaust particles (DEP) is associated with an increase in mortality rate attributed to cardiovascular diseases, but the mechanisms by which DEP produces adverse cardiovascular effects at the cellular level are not elucidated. This study investigated the cytotoxic mechanisms underlying DEP-induced neonatal rat cardiac myocytes effects in vitro, focusing on the role of reactive oxygen species (ROS). DEP extracts (DEPE) damaged cells in a concentration- and a time-dependent manner. Lactate dehydrogenase activity leaked to medium was also increased in a concentration-dependent manner after 24 h of DEPE exposure. DEPE-induced cytotoxicity was markedly reduced by treatment with superoxide dismutase, catalase, and N-(2-mercaptopropionyl)-glycine. Furthermore, superoxide was produced from both DEPE and myocardial cells. These results suggest that ROS such as superoxide, hydrogen peroxide, and hydroxyl radical are involved in DEPE-induced cardiac cell damage.

Anti-androgenic activity of 3-methyl-4-nitrophenol in diesel exhaust particles

In our continuing studies on nitrophenol derivatives as vasodilators in diesel exhaust particles, we have reported that nitrophenols in diesel exhaust particles possess not only vasodilatory activity but also estrogenic activity in vitro and in vivo, as well as anti-androgenic activity in vitro. Our efforts here were focused on the in vitro and in vivo anti-androgenic activity of 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC), known a degradation product of the insecticide fenitrothion, in diesel exhaust particles. We investigated its anti-androgenic activity using an in vitro recombinant yeast screen and in vivo Hershberger assays. Recombinant yeast screen assay showed that PNMC possesses anti-androgenic activity at low concentrations. Furthermore, castrated 28-day-old immature male rats each implanted with a 5-mm-long silastic tube containing crystalline testosterone and injected with PNMC subcutaneously at doses from as low as 0.01 and 0.1 mg/kg up to 1 mg/kg for 5 consecutive days showed significantly decreased weights of the seminal vesicles, ventral prostate, and glans penis. Plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were significantly increased in the 0.1 mg/kg PNMC treatment group. Our results demonstrate that PNMC in diesel exhaust particles clearly has anti-androgenic activity both in vitro and in vivo and can therefore be considered as an endocrine-disrupting chemical.

Correlation between suspended particles in the environmental air and causes of disease among inhabitants: cross-sectional studies using the vital statistics and air pollution data in Japan

To identify the diseases that correlate with suspended particle concentration in the ambient air, a cross-sectional epidemiological study was conducted using the annual vital statistics and air pollution estimates of 1881 points throughout Japan. The concentration of suspended particulate matters (SPMs) 10 microm or less in diameter were hypothetically converted to PM(2.5) values (converted PM(2.5) or cPM(2.5)) by using a conversion factor obtained from 25 estimates in Japan. Among various causes of death, a significant correlation was observed between both the SPM and cPM(2.5) (SPM/cPM(2.5)) levels and the age-adjusted death rates of ischemic heart disease or hypertensive heart disease in both genders. Correlation was noted with pneumonia, asthma, chronic bronchitis/emphysema, or lung cancer only in females. Unexpectedly, breast, endometrial, and ovarian cancer also showed significant increases in mortality rates related to the SPM/cPM(2.5) level, suggesting a role for suspended particles in the ambient air with or without gaseous component as a possible endocrine-disrupting, estrogenic agent. Multivariate regression analysis of confounding factors, smoking rate, population density, and hormone-related factors revealed consistent significance of SPM/cPM(2.5) in these diseases.