Effects of fluoranthene, a polycyclic aromatic hydrocarbon, on cAMP-dependent anion secretion in human airway epithelia

Effects of dietary fluoranthene on tissue-specific responses of carboxylesterases, acetylcholinesterase and heat shock protein 70 in two forest lepidopteran species

In this study, responses of carboxylesterases, acetylcholinesterase, and stress protein Hsp70 were examined in the midgut and midgut tissue, and brain of fifth instar larvae of Lymantria dispar L. and Euproctis chrysorrhoea L. following chronic exposure to dietary fluoranthene. Specific carboxylesterase activity increased significantly in the midgut tissue of E. chrysorrhoea larvae treated with a lower fluoranthene concentration. The specific patterns of isoforms expression, recorded in larvae of both species, enable efficient carboxylesterase activity as a significant part of defense mechanisms. Increased Hsp70 concentration in the brain of L. dispar larvae points to a response to the proteotoxic effects of a lower fluoranthene concentration. Decreased Hsp70 in the brain of E. chrysorrhoea larvae in both treated groups can suggest induction of other mechanisms of defense. The results indicate the importance of the examined parameters in larvae of both species exposed to the pollutant, as well as their potential as biomarkers.

Biological effects of carbon black nanoparticles are changed by surface coating with polycyclic aromatic hydrocarbons

Background

Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both.

Methods

Printex^®90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea.

Results

All particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 μg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo.

Conclusions

Our results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-017-0189-1) contains supplementary material, which is available to authorized users.

A community study of the effect of polycyclic aromatic hydrocarbon metabolites on heart rate variability based on the Framingham risk score

OBJECTIVES

To investigate the effects of the urinary metabolite profiles of background exposure to the atmospheric pollutants polycyclic aromatic hydrocarbon (PAH) and Framingham risk score (FRS), which assesses an individual's cardiovascular disease risk, on heart rate variability (HRV).

METHODS

The study conducted from April to May 2011 in Wuhan, China, included 1978 adult residents with completed questionnaires, physical examinations, blood and urine samples, and 5-min HRV indices (including SD of all normal to normal intervals (SDNN), root mean square successive difference (rMSSD), low frequency (LF), high frequency (HF) and their ratio (LF/HF), and total power) obtained from 3-channel Holter monitor. 12 urinary PAH metabolites were measured by gas chromatography-mass spectrometry. FRS was calculated by age, sex, lipid profiles, blood pressure, diabetes and smoking status. Linear regression models were constructed after adjusting for potential confounders.

RESULTS

Elevated total concentration of hydroxynaphthalene (ΣOHNa) was significantly associated, in a dose-responsive manner, with decreased SDNN and LF/HF (ptrend=0.014 and 0.007, respectively); elevated total concentration of hydroxyfluorene (ΣOHFlu) was significantly associated with reduced SDNN, LF and LF/HF (ptrend=0.027, 0.003, and <0.0001, respectively); and elevated total concentration of all PAH metabolites (ΣOH-PAHs) was associated with decreased LF and LF/HF (ptrend=0.005 and <0.0001, respectively). Moreover, increasing quartiles of FRS were significantly associated with decreased HRV indices, except LF/HF (all ptrend<0.0001). Interestingly, individuals in low-risk subgroups had greater decreases in SDNN, LF and LF/HF in relation to ΣOH-PAHs, ΣOHNa and ΣOHFlu than those in high-risk subgroups (all p<0.05).

CONCLUSIONS

Environmental PAH exposure may differentially affect HRV based on individual coronary risk profiles.

Repeated exposure to polycyclic aromatic hydrocarbons and asthma: effect of seroatopy

BACKGROUND

Exposure to traffic-related air pollutants, including polycyclic aromatic hydrocarbons (PAHs), can induce asthma. However, the effects of early repeated PAH exposure over time on different asthma phenotypes have not been examined.

OBJECTIVE

To assess associations between repeated PAH exposure, measured from prenatal personal and residential indoor monitors in children's homes, and asthma in an inner-city cohort.

METHODS

Prenatal exposure was assessed by personal air monitoring during 48 hours and exposure at 5 to 6 years of age by 2-week residential monitoring in the Columbia Center for Children's Environmental Health cohort. PAH was dichotomized into pyrene (representative semivolatile PAH) and the sum of 8 nonvolatile PAHs. High exposure to each was defined as measures above the median at both repeated time points. Asthma and wheeze were determined by validated questionnaires at ages 5 to 6 years. Children with specific IgE levels greater than 0.35 IU/mL to any of 5 indoor allergens were considered seroatopic.

RESULTS

Among all 354 children, repeated high exposure to pyrene was associated with asthma (odds ratio [OR], 1.90; 95% confidence interval [CI], 1.13-3.20). Among 242 nonatopic children, but not those sensitized to indoor allergens (n = 87) or with elevated total IgE levels (n = 171), high pyrene levels were associated positively with asthma (OR, 2.89; 95% CI, 1.77-5.69), asthma medication use (OR, 2.28; 95% CI, 1.13-4.59), and emergency department visits for asthma (OR, 2.43; 95% CI, 1.20-4.91). Associations between the levels of the 8 nonvolatile PAHs and asthma were not observed, even when stratifying by seroatopy.

CONCLUSION

Nonatopic children may be more susceptible to the respiratory consequences of early pyrene exposures.

Effects of Cordyceps sinensis, Cordyceps militaris and their isolated compounds on ion transport in Calu-3 human airway epithelial cells

AIM OF THE STUDY

The traditional Chinese medicine Cordyceps sinensis (CS) (Clavicipitaceae) improves pulmonary function and is used to treat respiratory disease. Here, we compare the efficacy and mechanisms of action of Cordyceps sinensis and Cordyceps militaris (CM) (Clavicipitaceae) in Calu-3 human airway epithelial monolayer model.

MATERIAL AND METHODS

The extracts of Cordyceps sinensis and Cordyceps militaris, as well as their isolated compounds, cordycepin and adenosine, stimulated ion transport in a dose-dependent manner in Calu-3 monolayers. In subsequent experiments, transport inhibitor bumetanide and carbonic anhydrase inhibitor acetazolamide were added after Cordyceps sinensis and Cordyceps militaris extracts to determine their effects on Cl- and HCO3- movement.

RESULTS

The results suggested that Cordyceps sinensis and Cordyceps militaris extracts may affect the anion movement from the basolateral to apical compartments in the airway epithelia.

CONCLUSIONS

Basolateral Na+-K+-2Cl- cotransporter and apical cAMP-dependent cystic fibrosis transmembrane conductance regulator Cl- channel are involved in the process. The results provide the first evidence for the pharmacological mechanism of Cordyceps sinensis and Cordyceps militaris on respiratory tract.

Down-regulation of early ionotrophic glutamate receptor subunit developmental expression as a mechanism for observed plasticity deficits following gestational exposure to benzo(a)pyrene

The focus of this study was to characterize the impact of gestational exposure to benzo(a)pyrene [B(a)P] on modulation of glutamate receptor subunit expression that is critical for the maintenance of synaptic plasticity mechanisms during hippocampal or cortical development in offspring. Previous studies have demonstrated that hippocampal and/or cortical synaptic plasticity (as measured by long-term potentiation and S1-cortex spontaneous/evoked neuronal activity) and learning behavior (as measured by fixed-ratio performance operant testing) is significantly impaired in polycyclic aromatic or halogenated aromatic hydrocarbon-exposed offspring as compared to controls. These previous studies have also revealed that brain to body weight ratios are greater in exposed offspring relative to controls indicative of intrauterine growth retardation which has been shown to manifest as low birth weight in offspring. Recent epidemiological studies have identified an effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons on neurodevelopment in the first 3 years of life among inner-city children [Perera FP, Rauh V, Whyatt RM, Tsai WY, Tang D, Diaz D, et al. Effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons on neurodevelopment in the first 3 years of life among inner-city children. Environ Health Perspect 2006;114:1287-92]. The present study utilizes a well-characterized animal model to test the hypothesis that gestational exposure to B(a)P causes dysregulation of developmental ionotropic glutamate receptor subunit expression, namely the N-methyl-d-aspartate receptor (NMDAR) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate receptor (AMPAR) both critical to the expression of synaptic plasticity mechanisms. To mechanistically ascertain the basis of B(a)P-induced plasticity perturbations, timed pregnant Long-Evans rats were exposed in an oral subacute exposure regimen to 0, 25 and 150mug/kg BW B(a)P on gestation days 14-17. The first sub-hypothesis tested whether gestational exposure to B(a)P would result in significant disposition in offspring. The second sub-hypothesis tested whether gestational exposure to B(a)P would result in down-regulation of early developmental expression of NMDA and AMPA receptor subunits in the hippocampus of offspring as well as in primary neuronal cultures. The results of these studies revealed significant: (1) disposition to the hippocampus and cortex, (2) down-regulation of developmental glutamate receptor mRNA and protein subunit expression and (3) voltage-dependent decreases in the amplitude of inward currents at negative potentials in B(a)P-treated cortical neuronal membranes. These results suggest that plasticity and behavioral deficits produced as a result of gestational B(a)P exposure are at least, in part, a result of down-regulation of early developmental glutamate receptor subunit expression and function at a time when excitatory synapses are being formed for the first time in the developing central nervous system. The results also predict that in B(a)P-exposed offspring with reduced early glutamate receptor subunit expression, a parallel deficit in behaviors that depend on normal hippocampal or cortical functioning will be observed and that these deficits will be present throughout life.

A polyomic approach to elucidate the fluoranthene-degradative pathway in Mycobacterium vanbaalenii PYR-1

Mycobacterium vanbaalenii PYR-1 is capable of degrading a wide range of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs), including fluoranthene. We used a combination of metabolomic, genomic, and proteomic technologies to investigate fluoranthene degradation in this strain. Thirty-seven fluoranthene metabolites including potential isomers were isolated from the culture medium and analyzed by high-performance liquid chromatography, gas chromatography-mass spectrometry, and UV-visible absorption. Total proteins were separated by one-dimensional gel and analyzed by liquid chromatography-tandem mass spectrometry in conjunction with the M. vanbaalenii PYR-1 genome sequence (http://jgi.doe.gov), which resulted in the identification of 1,122 proteins. Among them, 53 enzymes were determined to be likely involved in fluoranthene degradation. We integrated the metabolic information with the genomic and proteomic results and proposed pathways for the degradation of fluoranthene. According to our hypothesis, the oxidation of fluoranthene is initiated by dioxygenation at the C-1,2, C-2,3, and C-7,8 positions. The C-1,2 and C-2,3 dioxygenation routes degrade fluoranthene via fluorene-type metabolites, whereas the C-7,8 routes oxidize fluoranthene via acenaphthylene-type metabolites. The major site of dioxygenation is the C-2,3 dioxygenation route, which consists of 18 enzymatic steps via 9-fluorenone-1-carboxylic acid and phthalate with the initial ring-hydroxylating oxygenase, NidA3B3, oxidizing fluoranthene to fluoranthene cis-2,3-dihydrodiol. Nonspecific monooxygenation of fluoranthene with subsequent O methylation of dihydroxyfluoranthene also occurs as a detoxification reaction.

Paradoxical effects of hydrogen peroxide on human airway anion secretion

The present study concerns intriguing effects of hydrogen peroxide (H2O2) on cAMP-mediated anion secretion in polarized human airway epithelia. Although H2O2 applied to the apical and basolateral membrane increases short-circuit currents (ISC) with analogous properties, it has opposite effects on subsequent cAMP-activated ISC responses. Namely, forskolin (FK)-induced ISC responses were down-regulated by the apical presence of H2O2, whereas they were up-regulated by its basolateral presence. Despite this contrasting effect, oxidative stimuli from either aspect of the monolayer hindered FK-induced increments in cytosolic cAMP levels and apical membrane Cl- conductance. The site-dependent effects of H2O2 were reproduced in the responses to 8-bromo-cAMP. Estimation of the anionic composition of the ISC revealed that the FK up-regulated both bumetanide [an Na+-K+-2Cl- cotransporter (NKCC1) inhibitor]-sensitive and 4,4'-dinitrostilbene-2,2'-disulfonic acid [an HCO3--dependent anion transporter (NBC1/AE2) inhibitor]-sensitive ISC in the control, whereas the up-regulation evidently favored bumetanide-sensitive ISC in the basolateral presence of H2O2. The FK-induced NKCC1 augmentation after exposure to basolateral H2O2 was counteracted by cytochalasin D, an inhibitor of microfilament function, but not by charybdotoxin, a blocker of the intermediate conductance Ca2+-activated K+ channel, whose activation could be related to NKCC1-mediated Cl- secretion. These observations suggest that basolaterally but not apically applied H2O2 potentiates subsequent cAMP-mediated Cl- secretion by an increase in Cl- uptake via basolateral NKCC1, whose sensitivities to cAMP/protein kinase A are up-regulated, overcoming the H2O2-induced inhibition of cAMP-mediated apical anion conductance. The basolateral membrane-specific effects of H2O2 may be relevant to the basolateral cytoskeleton, which is believed to interact with NKCC1.

Ion transport regulated by protease-activated receptor 2 in human airway Calu-3 epithelia

We examined the mechanisms underlying anion secretion mediated by protease-activated receptor 2 (PAR2) and its role in the regulation of ion transport, using polarized human airway Calu-3 cells. PAR2 stimulation by trypsin and a PAR2-activating peptide (PAR2AP), especially from the basolateral aspect, caused transient Cl(-) secretion due to cytosolic Ca(2+) mobilization. Antagonists of PI-PLC (U73122, ET-18-OCH(3)) and inositol 1,4,5-triphosphate (xestospongin C (Xest C)) were without effect on the PAR2AP-mediated Cl(-) secretion, whereas it was attenuated by D609 (a PC-PLC inhibitor) and phorbol 12-myristate 13 acetate (PMA, a PKC activator). Even 30 min after removal of PAR2AP after a 10-min-exposure, cells were still poorly responsive to PAR2 stimulation, but the reduced responsiveness was upregulated by a PKC inhibitor, GF109203X (GFX). Pretreatment with PAR2AP did not affect responses to anion secretagogues, such as isoproterenol, forskolin, thapsigargin, 1-ethyl-2-benzimdazolinone, and adenosine, but ATP-induced responses were significantly reduced. Nystatin permeabilization studies revealed that the presence of PAR2AP prevented ATP-induced increments in basolateral membrane K(+) conductance without affecting apical membrane Cl(-) conductance. ATP-elicited Ca(2+) mobilization, which was sensitive to D609 and PMA, was inhibited by the pretreatment with PAR2AP, and this inhibition was blunted by the presence of GFX. Collectively, stimulation of PAR2 generates a brief response of Cl(-) secretion through PC-PLC-mediated pathway, followed by not only auto-desensitization of PAR2 itself but also cross-desensitization of a PC-PLC-coupled purinoceptor. The two types of desensitization seem likely to have PKC-mediated downregulation of PC-PLC in common.

DCEBIO stimulates Cl- secretion in the mouse jejunum

We investigated the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one(DCEBIO) on the Cl- secretory response of the mouse jejunum using the Ussing short-circuit current (Isc) technique. DCEBIO stimulated a concentration-dependent, sustained increase in Isc (EC50 41 +/- 1 microM). Pretreating tissues with 0.25 microM forskolin reduced the concentration-dependent increase in Isc by DCEBIO and increased the EC50 (53 +/- 5 microM). Bumetanide blocked (82 +/- 5%) the DCEBIO-stimulated Isc consistent with Cl- secretion. DCEBIO was a more potent stimulator of Cl- secretion than its parent molecule, 1-ethyl-2-benzimidazolinone. Glibenclamide or NPPB reduced the DCEBIO-stimulated Isc by >80% indicating the participation of CFTR in the DCEBIO-stimulated Isc response. Clotrimazole reduced DCEBIO-stimulated Isc by 67 +/- 15%, suggesting the participation of the intermediate conductance Ca2+-activated K+ channel (IKCa) in the DCEBIO-activated Isc response. In the presence of maximum forskolin (10 microM), the DCEBIO response was reduced and biphasic, reaching a peak response of the change in Isc of 43 +/- 5 microA/cm2 and then falling to a steady-state response of 17 +/- 10 microA/cm2 compared with DCEBIO control tissues (61 +/- 6 microA/cm2). The forskolin-stimulated Isc in the presence of DCEBIO was reduced compared with forskolin control tissues. Similar results were observed with DCEBIO and 8-BrcAMP where adenylate cyclase was bypassed. H89, a PKA inhibitor, reduced the DCEBIO-activated Isc, providing evidence that DCEBIO increased Cl- secretion via a cAMP/PKA-dependent manner. These data suggest that DCEBIO stimulates Cl- secretion of the mouse jejunum and that DCEBIO targets components of the Cl- secretory mechanism.

Reduction of airway anion secretion via CFTR in sphingomyelin pathway

The present study concerns the involvement of the ceramide produced through sphingomyelinase (SMase)-mediated catalysis in airway anion secretion of Calu-3 cells. Short-circuit current (Isc) measurement revealed that isoproterenol (ISO, 0.1 microM)-induced anion secretion was prevented by pretreatment with SMase (0.3 U/ml, for 30 min) from the basolateral but not the apical side, although basal and 1-ethyl-2-benzimidazolinone (1-EBIO, a Ca2+-activated K+ channel opener)-induced Isc were unaffected. The effects of SMase were reproduced in responses to forskolin (20 microM) or 8-bromo-cAMP (2 mM). C2-ceramide, a cell-permeable analog, also repressed the 8-bromo-cAMP-induced responses. Nystatin permeabilization studies confirmed that the SMase- and C2-ceramide-induced repressions were due to hindrance of augmentation of cystic fibrosis transmembrane conductance regulator (CFTR)-mediated conductance across the apical membrane. Further, SMase failed to influence K+ conductance across the basolateral membrane. These results suggest that the ceramide originating from basolateral sphingomyelin acts on activated CFTR from the cytosolic side, hindering anion secretion.