Neurotoxicity of 2-bromopropane and 1-bromopropane, alternative solvents for chlorofluorocarbons

To clarify the neurotoxicity of 2-bromopropane (2-BP) in comparison with 1-bromopropane (1-BP), 36 Wistar strain male rats were divided into 4 groups of 9 and exposed daily to 100-ppm 2-BP, 1000-ppm 2-BP, 1000-ppm 1-BP, or fresh air for 8 h a day. Exposure to 1000 ppm of 1-BP was discontinued after 5 or 7 weeks' exposure because of the unexpected appearance of incomplete hindlimb paralysis followed by serious emaciation. The other groups were sacrificed at the end of 12 weeks' exposure. Exposure to 1000 ppm of 2-BP resulted in significant decreases in body weight and motor nerve conduction velocity (MCV) and elongation in distal latency (DL). A ball-like enlargement of myelin sheaths was observed. Significant reductions in the number of erythrocytes, platelets, and leukocytes, testicular germ cell loss, and seminiferous atrophy were also observed in this group, but not in 100-ppm 2-BP group. Exposure to 1000 ppm of 1-BP for 5 or 7 weeks caused a significant decrease in body weight and MCV and elongation in DL. Linearly arranged ovoid- or bubble-like debris of the axons and myelin sheaths in the teased tibial nerves and axonal swelling in gracilis nucleus were found in this group. No significant changes in hematological indices or histopathological findings of the testis were found in this group. In conclusion, 2-BP is neurotoxic to the peripheral nerves in addition to its toxic effects on the reproductive and hematopoietic systems at 1000 ppm. No noticeable changes were found in the rats exposed to 100 ppm of 2-BP. 1-BP is a potent neurotoxicant at 1000 ppm for 5 or 7 weeks, while testicular and hematopoietic toxicity was not found.     

Enhancement of antibody response in Japanese quails by acute NO2 exposure

The effect of acute exposure to nitrogen dioxide (NO2) on anti-SRBC antibody response in two lines of Japanese quails, high and low responder, was investigated. Mean survival time of 11- to 13-week-old quails after exposure to 20 ppm NO2 was 12.0 hr. The high responder line lived longer than the low responder line. Changes of spleen weights of both lines were not observed in 10- and 20-ppm NO2 exposure for 4 hr. Anti-SRBC antibody response in high responder quail was significantly enhanced by 20-ppm NO2 exposure for 4 hr and the response in low responder quail was slightly enhanced. A similar, although somewhat less pronounced, tendency was observed also after 10-ppm NO2 exposure. These results suggest that acute NO2 exposure enhances the antibody response of Japanese quails.     

Pulmonary response to exposure to ozone of emphysematous rats

Rats were treated with a single intratracheal instillation of 6.5 units elastase or normal saline. Seven weeks after treatment, the animals were exposed for 24 hr to filtered air or 1 ppm O3, and their lung functions were measured. The exposure to O3 resulted in functional changes depending mainly on peripheral airway obstruction, and the direction and degree of those functional changes were in general similar between the saline- and elastase-treated animals. Another group of saline- or elastase-treated rats were exposed to 3 ppm O3 for 3 hr and the edematous response of their lungs was again similar. These results indicate that elastase-treated lungs responded to the exposure to O3 in a fashion similar to normal lungs in rats, but lung damage caused by the exposure to O3 superimposed over preexisting emphysematous damage, resulted in an additional lessening of the margin of pulmonary reserve capacity.     

Genomic and proteomic profiling of responses to toxic metals in human lung cells

Examining global effects of toxic metals on gene expression can be useful for elucidating patterns of biological response, discovering underlying mechanisms of toxicity, and identifying candidate metal-specific genetic markers of exposure and response. Using a 1,200 gene nylon array, we examined changes in gene expression following low-dose, acute exposures of cadmium, chromium, arsenic, nickel, or mitomycin C (MMC) in BEAS-2B human bronchial epithelial cells. Total RNA was isolated from cells exposed to 3 M Cd(II) (as cadmium chloride), 10 M Cr(VI) (as sodium dichromate), 3 g/cm2 Ni(II) (as nickel subsulfide), 5 M or 50 M As(III) (as sodium arsenite), or 1 M MMC for 4 hr. Expression changes were verified at the protein level for several genes. Only a small subset of genes was differentially expressed in response to each agent: Cd, Cr, Ni, As (5 M), As (50 M), and MMC each differentially altered the expression of 25, 44, 31, 110, 65, and 16 individual genes, respectively. Few genes were commonly expressed among the various treatments. Only one gene was altered in response to all four metals (hsp90), and no gene overlapped among all five treatments. We also compared low-dose (5 M, noncytotoxic) and high-dose (50 M, cytotoxic) arsenic treatments, which surprisingly, affected expression of almost completely nonoverlapping subsets of genes, suggesting a threshold switch from a survival-based biological response at low doses to a death response at high doses.     

Epigenetic alterations in liver of C57BL/6J mice after short-term inhalational exposure to 1,3-butadiene

Background

1,3-Butadiene (BD) is a high-volume industrial chemical and a known human carcinogen. The main mode of BD carcinogenicity is thought to involve formation of genotoxic epoxides.

Objectives

In this study we tested the hypothesis that BD may be epigenotoxic (i.e., cause changes in DNA and histone methylation) and explored the possible molecular mechanisms for the epigenetic changes.

Methods and Results

We administered BD (6.25 and 625 ppm) to C57BL/6J male mice by inhalation for 2 weeks (6 hr/day, 5 days a week) and then examined liver tissue from these mice for signs of toxicity using histopathology and gene expression analyses. We observed no changes in mice exposed to 6.25 ppm BD, but glycogen depletion and dysregulation of hepatotoxicity biomarker genes were observed in mice exposed to 625 ppm BD. We detected N-7-(2,3,4-trihydroxybut-1-yl)guanine (THB-Gua) adducts in liver DNA of exposed mice in a dose-responsive manner, and also observed extensive alterations in the cellular epigenome in the liver, including demethylation of global DNA and repetitive elements and a decrease in histone H3 and H4 lysine methylation. In addition, we observed down-regulation of DNA methyltransferase 1 (Dnmt1) and suppressor of variegation 3–9 homolog 1, a histone lysine methyltransferase (Suv39h1), and up-regulation of the histone demethylase Jumonji domain 2 (Jmjd2a), proteins responsible for the accurate maintenance of the epigenetic marks. Although the epigenetic effects were most pronounced in the 625-ppm exposure group, some effects were evident in mice exposed to 6.25 ppm BD.

Conclusions

This study demonstrates that exposure to BD leads to epigenetic alterations in the liver, which may be important contributors to the mode of BD carcinogenicity.     

Effect of inhaled ozone on lung histamine in conscious guinea pigs

The effect of short-term ozone (O3) exposure on pulmonary mast cell function was examined. Guinea pigs were continuously exposed to 1.0 ppm O3 for 2, 4, and 8 hr. O3 exposure produced a significant decrease in lung histamine concentration. Two-hour exposure to O3 caused a 22.4 +/- 7.0% decrease in lung histamine concentration compared with controls. Ozone exposures of 4 and 8 hr caused lung histamine concentrations to decrease by 43.7 +/- 7.7 and 49.0 +/- 7.5% (P less than 0.05), respectively, without significant changes in lung water or protein, or evidence of cytotoxicity. These results suggest that O3 or its metabolites affect pulmonary mast cell function by stimulating the release of histamine from the lung.     

荧蒽暴露致小鼠肺损伤及肺组织转录组分析

目的 本研究旨在评估苯并［b］荧蒽（Benzo［b］ fluoranthene, BbF）暴露导致小鼠肺组织的损伤,并运用转录组学（RNA-Seq）技术探讨潜在的相关基因及信号通路。 方法 对C57BL/6J 雄性小鼠采用非暴露式气管滴注不同剂量苯并［b］荧蒽14天,牺牲小鼠后提取肺组织进行H&E病理检测,提取肺组织总RNA制备cDNA文库,采用Illumina二代高通量测序平台检测小鼠肺组织差异表达基因,并进行GO富集分析和KEGG富集分析。 结果 H&E染色结果显示,与对照组比较,苯并［b］荧蒽暴露组表现为急、慢性炎症细胞浸润、泡沫细胞及组织细胞增生,残存肺泡腔可见炎性坏死物,并且随着暴露剂量增加炎性细胞浸润程度增强。转录组学分析共筛选到188个表达差异显著的基因,不同剂量苯并［b］荧蒽暴露组关键基因表达不相同,提示不同基因在肺部损伤中可能发挥着不同生物学功能。韦恩图显示有25个差异基因在不同剂量苯并［b］荧蒽暴露导致的肺损伤中共表达,Chil1、Retnla、Lcn2、Ccl6、Mmp12等基因可能参与了肺损伤的调控过程。GO富集分析显示差异表达基因主要与炎症和免疫反应相关。KEGG富集分析显示IL-17信号通路富集到的差异表达基因最多;随着暴露剂量增加,KEGG富集通路从细胞因子、炎症相关信号通路发展为疾病相关信号通路。 结论 苯并［b］荧蒽暴露会造成小鼠肺组织损伤和炎症反应,进而引起炎症、免疫及肺部疾病相关基因差异表达及信号通路的变化。     

The effects of ozone inhalation on the immunological response of selenium- and vitamin E-deprived rats

Deficiencies in vitamin E (E) or Se result in immune alterations, possibly due to reduction of antioxidant activity. Such reductions might greatly compromise the ability of the immune system to deal with additional oxidant stress, as encountered during exposure to air pollutants such as ozone (O3). To study possible interactions of these oxidative stresses on immune function, male Long-Evans hooded rats were maintained 5 weeks on torula yeast-based diets, with or without the addition of E or Se. Each dietary group was subdivided into O3-exposed and nonexposed groups. Two different regimens of O3 exposure were used: continuous (1.0 ppm, 8 hr/day for 7 days) or intermittent (2.0 ppm, 8 hr/day for 4 days, 2-4 days in ambient air followed by 1 day of exposure prior to sacrifice). Exposure to O3 in either regimen resulted in increased numbers of cells recovered by pulmonary lavage. With continuous exposure this increase was due to macrophage influx and, with intermittent exposure, due to influx of both macrophages and neutrophils. Combined deficiency of E and Se led to an enhanced ability of spleen and lung cells to mediate antibody-dependent cell-mediated cytotoxicity (ADCMC). In animals deficient in E, but not Se, O3 exposure depressed spleen cell ADCMC. Deficiencies of either E or Se also depressed lymphocyte response to mitogens. Although intermittent exposure to O3 caused no changes in mitogen response, in animals exposed continuously to O3 there was a significant enhancement of this response.     

Experimental suppression of tolerance to ozone and of cross-tolerance (NO2O3) in rats by actinomycin D and colchicine

Rats were initially exposed to 2 ppm ozone or 16–20 ppm NO₂ for 3 hr in order to induce a certain tolerance to ozone during 3 days after the initial exposure. After the initial exposure, the y were intraperitoneally administered actinomycin D or colchicine at a scheduled interval. Twenty-four hours after the administration, the induction of tolerance was assayed by the response of lung weight to challenge exposure to 5.6 ppm ozone for 3 hr. Either actinomycin D or colchicine administered immediately after the initial exposure suppressed the induction of tolerance (O₃O₃) and of cross-tolerance (NO₂O₃), while the tolerance was not suppressed by the inhibitors administered 12 to 24 hr following the initial exposure. Normal tolerance to ozone was induced 12 to 24 hr after the initial exposure. It was thus shown that the induction of tolerance could not be suppressed by the inhibitors administered after the lungs became fully tolerant; we tentatively interpret these results to suggest that no tolerance is induced without pulmonary cell proliferation stimulated by the initial exposure.     

纳米氧化钕致SD大鼠肺部炎症反应中 miR-498-5p的表达及意义

目的 探讨纳米氧化钕（NPs-Nd2 O3 ）致SD大鼠肺部炎症反应中miR-498-5p的表达水平及意义。方法 将42只SPF级健康雄性SD大鼠随机分为对照组和NPs-Nd2 O3 染毒组,按照100 mg/kg浓度,采用非暴露式气管内一次性滴注法对大鼠进行NPs-Nd2 O3 染毒处理,在染毒第7、14和28 d后处死大鼠。计算肝脏、脑、肾脏、脾脏、睾丸、肺脏的脏器系数;采用电感耦合等离子体质谱法（ICP-MS）检测肝脏、脑、肾脏、脾脏、睾丸、肺脏中钕元素的含量;酶联免疫吸附法（ELISA）测定血清、肺泡灌洗液及肺组织中肿瘤坏死因子-α（TNF-α）和白细胞介素-6（IL-6）的含量;实时荧光定量PCR检测大鼠肺组织中miR-498-5p的相对表达水平; TargetScan、 mireap、miRanda网站预测与miR-498-5p相互作用的下游靶基因; Pearson相关分析miR-498-5p与炎症因子TNF-α、IL-6的相关性。结果 NPs-Nd2 O3 染毒后,大鼠肺脏的脏器系数增加（t=-3.408,P=0.005）;肝脏、脑、肾脏、脾脏、睾丸、肺脏中均检测到钕元素;血清、肺泡灌洗液及肺组织中TNF-α、IL-6的含量升高（P<0.05）;NPs-Nd2 O3 染毒第7、14和28 d后肺组织中miR-498-5p的相对表达水平升高（7 d组: t= -21.236,P<0.001;14 d组: t= -4.631,P=0.010;28 d组: t= -6.132,P=0.001）,miR-498-5p表达与TNF-α含量呈正相关（ r =0.787,P=0.012）,与IL-6含量呈正相关（ r =0.708,P<0.033）;KEGG富集分析发现与miR-498-5p作用的靶基因其中有27个mRNAs参与JAK/STAT通路,19个mRNAs参与NF-κB通路。结论 NPs-Nd2 O3 经呼吸道进入体内可引起肺部明显炎症反应;NPs-Nd2 O3 染毒组大鼠肺组织中miR-498-5p表达水平升高,并与TNF-α、IL-6含量呈正相关;MiR-498-5p可能通过JAK/STAT通路和NF-κB通路参与NPs-Nd2 O3 诱导的肺部炎症。     

DNA microarray analysis of human gene expression induced by a non-lethal dose of cadmium

Cadmium (Cd) is a hazardous heavy metal present in working and living environments. Cd affects many cellular functions, but little is known about the mechanisms of its toxicity and cellular defense against it. Recently, advanced gene expression analysis employing DNA microarrays provided us the means to profile the expression of thousands of genes simultaneously. We describe here a study of Cd-induced gene expression profile. Messenger RNA was prepared from HeLa cells exposed to a non-lethal dose of CdSO4, and analyzed by the use of an array consisting of 7,075 human cDNAs. Many stress response genes including those coding for metallothioneins and heat shock proteins were observed to be induced by Cd. The cellular metabolism inclined toward the synthesis of cysteine and glutathione after Cd exposure. Anti-oxidant genes also appeared to be induced to protect cell components and to quench reactive oxygen species. Ubiquitin pathway was activated as well probably to degrade proteins which might not be renatured. These data suggest that human cells mobilize every genomic resource (induction of some genes and repression of others) to overcome cytotoxicity caused by Cd.     

Effects of Acute Exposure to Nitrogen Dioxide on Primary Antibody Response

The effects of acute exposure to nitrogen dioxide on primary humoral antibody response to sheep red blood cells in mice were studied. Mice were exposed to 5 ppm, 20 ppm, and 40 ppm nitrogen dioxide for 12 hr. An exposure of 20 ppm or 40 ppm resulted in a significant suppression of antibody responses, but 5 ppm did not affect antibody response. This immunosuppression resulting from nitrogen dioxide exposure was more apparent in males than females. Exposures to 20 ppm nitrogen dioxide for various time intervals revealed that the strongest suppression effect was observed in the group exposed 2 days after antigen injection. A decreased total cell number in the spleen, and more strikingly, in the thymus, was also caused by acute exposure to nitrogen dioxide.     

Effects of short- and long-term exposure to ozone on heart rate and blood pressure of emphysematous rats

Electrocardiogram and arterial blood pressure of elastase-treated emphysematous rats (E rats) and saline-treated control rats (S rats) were recorded continuously during exposure to either 1 ppm ozone (O3) for 3 hr or 0.5 ppm O3 for 6 hr. The heart rates (HRs) of both groups decreased to about 50 and 65% of the initial levels at the end of 1 ppm and 0.5 ppm O3 exposure, respectively. Mean arterial blood pressures (MAPs) also decreased to about 76 and 82%, respectively. There was no significant difference in these responses between E and S rats, although the levels of HRs and MAPs of the E rats were always a little lower than those of the S rats. Another group of E and S rats was continuously exposed to 0.2 ppm O3 for 4 weeks. The HRs of both E and S groups decreased to about 81 and 88% of the initial levels on the first day, respectively, although they recovered completely by the third day. No significant difference in the variation of HRs during exposure was noted between E and S rats. However, the HR responses of these rats to a challenge exposure of 0.8 ppm O3 for 1.5 hr appeared to be different. That is, S rats were more tolerant of the challenge exposure to O3 for 1.5 hr than the E rats.     

A dose-response study of healthy, heavily exercising men exposed to ozone at concentrations near the ambient air quality standard

Twenty-four healthy, well-conditioned young adult male volunteers, free of asthma or clinical respiratory allergies, were exposed to purified air containing ozone (O3) at 0.16, 0.14, 0.12, 0.10, 0.08, and 0.00 part per million (ppm). Exposures were separated by 2-week intervals, occurred in random order, and lasted 2 hours each. Temperature was 32 +/- 1 degree C and relative humidity was 38 +/- 3%, simulating Los Angeles area smog conditions. Subjects exercised 15 minutes of each half hour, attaining ventilation rates averaging 68 L/min (approximately 35 L/min per m2 body surface area). Lung function was measured pre-exposure and after 1 hr and 2 hr of exposure. Airway responsiveness to a cold-air challenge was measured immediately following the 2-hr exposure. Symptoms were recorded before, during, and for one-week periods following exposures. For the group as a whole, no meaningful untoward effects were found except for a mild typical respiratory irritant response after 2 hr exposure to 0.16 ppm O3. Two individual subjects showed possible responses at 0.14 ppm, and one of them also at 0.12 ppm. In comparison to some previous investigations, this study showed generally less response to O3. The comparative lack of response may relate to the favorable clinical status of the subjects, the pattern of exercise during exposure, or some other factor not yet identified.     

Subchronic lead exposure, immunotoxicology and increased disease resistance in Japanese quail (Corturnix coturnix japonica)

The present study investigated the effects of lead (Pb) on immune responses in quail (Coturnix coturnix japonica) and the pathological impact of exposure to an infectious agent (E. coli O2). Fifty-four, 4-week-old quail were exposed to lead acetate in drinking water at 5 or 50 ppm. All birds were vaccinated with Newcastle Vaccine (NDV) during the third week of contaminant (Pb) exposure. In the fourth week, several arms of the immune response were tested using the T cell based phytohemagglutinin (PHA) skin test, the B cell mediated antibody response to NVD, and the chemiluminescence assay measuring innate immunity. Immunohistochemistry (IHC) was used to determine the expression of toll like receptor-3 (TLR-3) in the bursa of Fabricius. In the fifth week, quail were challenged with 200 μL of E. coli O2 (1×10⁴ colony forming units (CFU)/mL).No clinical signs of Pb toxicity were observed. Morbidity/mortality subsequent to E. coli exposure was lowest in the high exposure group (27.8%) compared to low exposure (44.4%) and control (55.5%) groups. There was no difference in the T-cell-mediated PHA response, primary or secondary immune response or the innate response in Pb exposed groups; however, bursal TLR-3 increased (p<0.05) with higher Pb exposure.No evidence supported that subchronic Pb exposure was immunotoxic to quail at 5 or 50 ppm in drinking water. In contrast, our results provide evidence of a hormetic effect, with Pb exposed birds having lower morbidity and better survival than controls. Subchronic Pb exposure may be immunostimulatory rather than suppressive as predicted in earlier studies based on testing individual immune parameters.     

Synergism between rhinovirus infection and oxidant pollutant exposure enhances airway epithelial cell cytokine production

Of the several factors believed to exacerbate asthmatic symptoms, air pollution and viral infections are considered to be particularly important. Although evidence indicates that each of these respiratory insults individually can increase asthma severity in susceptible individuals, we know little about the extent to which exposure to environmental oxidant pollutants can influence the course of respiratory viral infection and its associated inflammation. To investigate the interaction of these two stimuli within their common epithelial cell targets in the upper and lower respiratory tracks, we infected primary human nasal epithelial cells and cells of the BEAS-2B line grown at the air-liquid interface with human rhinovirus type 16 (RV16) and exposed them to NO2 (2.0 ppm) or O3 (0.2 ppm) for 3 hr. Independently, RV16, NO2, and O3 rapidly increased release of the inflammatory cytokine interleukin-8 through oxidant-dependent mechanisms. The combined effect of RV16 and oxidant ranged from 42% to 250% greater than additive for NO2 and from 41% to 67% for O3. We abrogated these effects by treating the cells with the antioxidant N-acetylcysteine. Surface expression of intercellular adhesion molecule 1 (ICAM-1) underwent additive enhancement in response to combined stimulation. These data indicate that oxidant pollutants can amplify the generation of proinflammatory cytokines by RV16-infected cells and suggest that virus-induced inflammation in upper and lower airways may be exacerbated by concurrent exposure to ambient levels of oxidants commonly encountered the indoor and outdoor environments.     

Dietary exposure to Aroclor 1254 alters gene expression in Xenopus laevis frogs

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that contribute to worldwide health problems. Despite data associating PCBs with adverse health effects, decisions to clean up contaminated sites remain controversial. Cleanup decisions are typically based on risk assessment methods that are not sensitive enough to detect subtle changes in health. We have recently shown that gene expression signatures can serve as sensitive molecular biomarkers of exposure and related health effects. Our initial studies were carried out with developing Xenopus laevis tadpoles that were exposed to the PCB mixture Aroclor 1254 (A1254) for 2 days. A1254 was dissolved in dimethyl sulfoxide and added to the aquarium water for rapid loading of PCBs into the tadpole tissue. These studies showed that increases in the expression of specific genes occurred independent of adverse health effects, and decreases in specific genes correlated with the appearance of observable health effects, including decreased survival and gross morphological and behavioral abnormalities. In this report, we extend our previous work to test the use of gene expression signatures as biomarkers in frogs exposed to PCBs through the diet from early tadpole stages through metamorphosis. This work showed that chronic low-dose exposure to A1254 (24 ppm) in food produced tissue levels of 17 ppm and increased gene expression of nerve growth factor and proopiomelanocortin independent of adverse health effects. Exposure to higher doses of A1254 (200 ppm) produced tissue levels of 80 ppm and increased expression of p450 1A1, also, independent of adverse health effects. This work provides further evidence for the use of gene expression changes as biomarkers of exposure to PCBs.