Aryl hydrocarbon hydroxylase activity and psoriasis

Aryl hydrocarbon hydroxylase (AHH) has been measured in the skin, jejunum and liver of normal and psoriatic individuals. We have been unable to confirm previous reports of an abnormality in AHH activity in patients with psoriasis. Re-examination of the laboratory records on which the original reports were based leads us to doubt their veracity and validity.     

Aryl hydrocarbon hydroxylase activity induced by cannabis resin: analysis for polycyclic hydrocarbons

Crude cannabis resin was fractionated on silica gel plates with benzene as developer. Twenty-four hr after oral administration of 500 mg/kg of the crude resin or of 500 mg/kg of reconstituted resin after fractionation, pulmonary and hepatic aryl hydrocarbon hydroxylase activity was enhanced in male rats (80 – 100 g). The material from 4 zones with R_f values of (1) 0.82 – 0.96; (2) 0.62 – 0.78; (3) 0.20 – 0.60 and (4) 0.00 – 0.20 was isolated from the silica gel plates and given orally to rats at a dose of 200 mg/kg. All but the most polar fraction induced pulmonary aryl hydrocarbon hydroxylase activity. The least polar fraction (R_f 0.82 – 0.96) was analyzed for polycyclic hydrocarbons by thin-layer chromatography and gas chromatography. Benzo[a]-pyrene was found to be present in quantities of 11 ng/mg of original resin; no evidence for the presence of 3-methylcholanthrene, 1,2,3,4-dibenzanthracene or 1,2,5,6-dibenzanthracene was found. Although benzo[a]pyrene is a recognized carcinogen, it would not seem that its presence in cannabis resin ought to evoke undue concern, since present patterns of cannabis ingestion would not provide more of it than might be found in certain foods.     

Aryl hydrocarbon hydroxylase induction in rat lung, liver, and male reproductive organs following inhalation exposure to diesel emission

Due to increasing use of diesel-powered vehicles, it has become necessary to assess adverse biological effects of diesel emissions in our environment. The present data describe the effects of inhalation exposure of diesel emission on the specific activities of aryl hydrocarbon hydroxylase (AHH) and epoxide hydrase (EH) in rat lung, liver, testis, and prostate gland. Adult CD strain, Sprague-Dawley male rats (8–10 weeks old) were exposed to diesel emission (1:13 dilution) containing 14.2 ppm ($\text{v}\text{v}$) total hydrocarbon, 20 hr/day for 42 days. Although liver exhibited the greatest overall AHH activity among the organs tested, the percentage increase over control values was highest in the prostate gland. On Day 15 of exposure, AHH activity had increased to 4.5-fold that of the control and remained elevated throughout the entire exposure period. In contrast, AHH induction in liver and lung occurred on Day 33 of exposure, and the maximum AHH induction was observed on Day 42 (1.4- and 1.3-fold increase in lung and liver, respectively). In all the organs tested, EH activity was not changed significantly during the experimental period.     

Induction of aryl hydrocarbon hydroxylase in rat tissue following intratracheal instillation of diesel particulate extract and benzo[a]pyrene

The potential for aryl hydrocarbon hydroxylate (AHH) induction by inhaled diesel particles was assessed by intratracheal administration. Benzo[a]pyrene, (B[a]P) a reference compound, or an extract of particles, dissolved in gelatin-saline solution was administered to Fischer 344 rats at several dose levels. Twenty-four hours after administration of B[a]P or diesel particulate extract, the AHH activity increased in a dose-response manner in the lung, but not in liver. The maximum increase in the AHH activity in the lung was observed 12 h after intratracheal instillation of B[a]P (5 mg/kg), and the levels remained elevated for seven days. The AHH activity in the liver reached the maximum 24 h after the administration, and returned rapidly to control values. In contrast, intratracheal instillation of diesel particulate extract resulted in a significant increase of AHH activity in the lungs only after doses greater than 6 mg kg-1. The activity, however, declined rapidly and returned to control values within 75 h. The liver AHH activity in this instance, remained unchanged throughout the experimental period. These data indicate that in the lung, hydrocarbons extracted from diesel particles are weak enzyme inducers and exposure to these compounds by intratracheal administration did not result in AHH induction in the liver. The results suggest that doses higher than those normally expected from occupational exposures will be required to induce AHH activity in organs examined.     

Aryl hydrocarbon hydroxylase induction in rat pulmonary alveolar macrophages (PAMs) by diesel particulates and their extracts

The Aryl hydrocarbon hydroxylase (AHH) activity in the lavaged PAMs was investigated in male Fischer rats after inhalation of diluted diesel exhaust (DE), and compared with intratracheal instillation of the organic solvent extract of hydrocarbons adsorbed on the particulate surface. Animals were exposed to concentrations of 1500 micrograms/m3 or 6000 micrograms/m3 of diesel particulates, 20 hrs/day, 7 days/wk for 2 days up to 28 days, or treated with a single intratracheal dose of DE extract or benzo[a]pyrene (B[a]P) dissolved in gelatin-saline solution. The counts of lavageable PAM and polymorphonuclear leukocytes (PMN) were significantly elevated in the exposed rats. However, a decrease of AHH activity was found in the PAM cells after four weeks of exposure to both particulate concentrations. The AHH activity in the PAMs from rats injected intratracheally with 5 mg/kg of B[a]P was slightly increased; no change was observed in PAMs similarly treated with DE extract. Enzyme induction is not noted because of absence of sufficient quantities of hydrocarbons need for induction. This could be further potentiated that macrophages metabolize and perhaps reduce hydrocarbon levels by translocation.     

Effects of volatile constituents of rosemary extract on lung inflammation induced by diesel exhaust particles

Epidemiological and experimental studies have implicated that diesel exhaust particles are involved in increases in morbidity and mortality from lung diseases. Recently, we have demonstrated that rosmarinic acid, a polyphenolic liquid component in perilla, inhibits lung inflammation induced by diesel exhaust particles in vivo, partly through its antioxidative property. We have also shown the antioxidative activities of volatile constituents of rosemary extract, the gaseous component in perilla, in vitro. The purpose of this study was to evaluate the effects of intratracheal administration of volatile rosemary extract on lung inflammation induced by diesel exhaust particles. ICR mice were treated with intratracheal administration of volatile rosemary extract before intratracheal exposure to diesel exhaust particles. Twenty-four hr later, diesel exhaust particles exposure elicited lung inflammation characterized by the infiltration of neutrophils and eosinophils, which was confirmed by cellular profile of bronchoalveolar lavage fluid and histological examination. Diesel exhaust particles enhanced the protein expressions of interleukin-1beta, macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant in the lung. Pretreatment with rosemary extract significantly inhibited the diesel exhaust particles-induced lung inflammation. Rosemary extract treatment also suppressed the diesel exhaust particles-enhanced lung expression of macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant. These results suggest that intratracheal administration of rosemary extract can prevent lung inflammation induced by diesel exhaust particles. The preventive effect is mediated, at least partly, through the inhibition of the enhanced lung expressions of macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractants.     

Pulmonary function testing of animals chronically exposed to diluted diesel exhaust

The purpose of this work was to assess the potential effect that chronic inhalation of diesel exhaust may have on lung mechanics and lung volume. Noninvasive pulmonary function tests that produced data on lung air flows and volumes have been conducted repeatedly on 25 male Fischer-344 rats exposed to diesel exhaust at a particulate concentration of 1500 micrograms m-3, 20 h per day, 5 1/2 days per week, for 612 days. The same tests were conducted on 25 clean air control animals. When the data were normalized, the majority of tests did not reveal any significant deviation from the norm for the first year of exposure. In the second year, the functional residual capacity and its component volumes - expiratory reserve and residual volume, maximum expiratory flow at 40% of vital capacity, maximum expiratory flow at 20% of vital capacity and the forced expiratory volume in 0.1 s - were significantly greater in the diesel exposed animals. The data are inconsistent with known clinically significant adverse health effects. Although the lung volume changes in the diesel exposed animals could be indicative of emphysema or other forms of chronic obstructive lung disease, this interpretation is contradicted by the air flow data which suggest simultaneous lowering of the resistance of the smaller airways. The observations are not consistent with documented clinical lung disease in man.     

The induction of rat lung aryl hydrocarbon hydroxylase by diluted smoke from commercial cigarettes

Induction of pulmonary aryl hydrocarbon hydroxylase (AHH) by cigarette smoke in small rodents is well established. However, studies on dose-response relationships particularly at the lower ends of such relationships are few indeed. Availability of the British-American Tobacco Co. (B.-A.T.)-Mason inhalation system, in which precisely-calibrated dilutions of cigarette smoke can be released into an inhalation chamber, enables excellent dose-response relationships to be established. Using this inhalation system and cigarettes delivering tar (total particulate matter, water and nicotine free) equal to 1, 4 and 20 mg/cigarette, it has been shown that induction of AHH in male Sprague-Dawley rat lung is an extremely sensitive system to inhaled cigarette smoke. AHH induction was observed at a 200-s exposure to 40 puffs of a 1 : 5 dilution of smoke from an ultra mild cigarette delivering 1 mg tar. At this low concentration, it is not even possible to accurately weigh the TPM from diluted smoke in the exposure chamber. This extremely sensitive rat pulmonary enzyme system may prove valuable in the biological testing of modern low tar cigarettes.     

Anti-estrogenic activity of diesel exhaust particles

Estrogenic and anti-estrogenic activities of diesel exhaust particles (DEP) were evaluated using yeast cells expressing the human estrogen receptor and the responsive element regulating the expression of the receptor gene for beta-galactosidase (Routledge and Sumpter, 1996). It was found that a suspension of whole DEP suspension is not estrogenic but that this preparation possesses the ability to reduce the estrogen-dependent reporter activity. DEP were serially extracted with hexane, benzene, dichloromethane, methanol, and 1 M ammonia, and the estrogenic and anti-estrogenic activities of these preparations were determined. None of the extracts of DEP were estrogenic, but the extracts of benzene, dichloromethane and methanol possessed anti-estrogenic activity, and the activity of estrogen in the presence of hexane extract was slightly decreased. These results indicated that DEP contain heterologous compounds having anti-estrogenic activity. It is thought that those compounds in DEP can modulate the activity of estrogen, leading to the distruption of balance between estrogen and androgen. In this paper, the environmental effects of DEP in relation to the endocrine disrupting effect of organic compounds in DEP are discussed.     

Systemic and vascular effects of circulating diesel exhaust particulate matter

Abstract

Objective: Numerous studies have found an association between transiently increased particulate matter air pollution and acute adverse cardiovascular health effects; however, the mechanisms underlying these effects are not clear. Translocation of ultra-fine ambient particulate matter has been proposed to play a key role in these acute side effects. This study was designed to determine the contribution of circulating (translocated) diesel exhaust particles (DEPs) to the systemic and vascular effects.

Methods: C57 mice (10-week) received intravenous DEPs via tail vein injection. Following 1-h post-injection, inflammatory cytokines (IL-1β, IL-6 and TNF-α), peripheral blood cell counts, band cell counts, aortic endothelial function and vascular constriction were assessed. Thoracic aortae were isolated, and endothelial function was examined by measuring acetylcholine (ACh) and sodium nitroprusside (SNP)-stimulated vascular relaxation using a wire myograph. In addition, phenylephrine (PE)-stimulated vasoconstriction was also measured. The amount of DEPs deposited and trapped in tissues (the spleen, liver, lungs and heart) were quantified.

Results: Acute systemic DEP exposure caused a significant increase in TNF-α, peripheral neutrophil and band cell counts. ACh and SNP-induced relaxation were not affected by acute systemic DEP exposure, neither was PE-stimulated constriction. There was a significantly increased DEP deposition in the spleen as well as in the liver. No significantly increased DEPs were detected in the lung and heart.

Conclusion: Here we show that circulating DEPs induce a systemic response characterized by increased TNF-α, peripheral granulocytes, but does not impact endothelial function. Our study also suggests that circulating particles are rapidly removed from the circulation and predominantly sequestered in the spleen and liver.     

Experimental conditions in GMR chronic inhalation studies of diesel exhaust

A chronic inhalation exposure study was initiated to study the potential health effects of diesel exhaust on laboratory animals. Test atmospheres of clean air (control) or freshly diluted diesel exhaust at nominal particulate concentrations of 250, 750 and 1500 micrograms m-3 were supplied to four large volume inhalation chambers in which individually housed Fischer 344 albino rats (Rattus norvegicus) and Hartley guinea pigs (Cavia porcellus) were exposed for 20 h per day, 51/2 days per week. The diesel aerosol concentration, chamber temperature and relative humidity were continually monitored and controlled to maintain the exposure dose levels and an environment of 22 +/- 2 degrees C and 50 +/- 20% relative humidity. Animals were randomly sampled from the chambers for physiological, biochemical and pathological studies throughout the exposure period. The study was continued without interruption for 24 months with the mean diesel particle mass concentrations within 6% of the target values. The standard deviation of the mass concentration measurements was approximately 30% of the mean.     

Cacao liquor proanthocyanidins inhibit lung injury induced by diesel exhaust particles

Epidemiological and experimental studies have suggested that diesel exhaust particles (DEPs), which generate reactive oxygen species, may be involved in the recent increase in the prevalence of lung diseases. Cacao liquor proanthocyanidins (CPs) are naturally occurring polyphenols with antioxidative activities. We carried out a study in mice to investigate the effects of dietary supplementation of CPs on lung injury induced by intratracheal administration of DEPs (500 microg/body). Dietary supplementation with 1.0 percent CPs inhibited DEP-induced lung injury, characterized by neutrophil sequestration and edema. Immunohistochemical analyses showed that CPs prevented enhanced expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 caused by DEPs in the lung injury. Numerous adducts of nitrotyrosine, N-(hexanonyl) lysine, 4-hydroxy-2-nonenal, and 8-OHdG were also observed immunohistochemically in the lungs of mice treated with DEPs. However, these indicators of oxidative stress were barely visible in mice pretreated with CP supplementation. In addition, the level of thiobarbituric acid reactive substances in the lung was decreased by CP supplementation in the presence of DEPs. These results suggest that CPs inhibit DEP-induced lung injury by reducing oxidative stress, in association with a reduction in the expression of adhesion molecules.     

Aryl hydrocarbon hydroxylase (AHH) induction by polybrominated biphenyls (PBBs): enchancement by photolysis

Irradiation of the commercial polybrominated biphenyl (PBB( mixture, fireMaster BP-6, in cyclohexane solution at 300 nm for 930 min resulted in a marked diminution of the major components of the mixture. Administration of the photolyzed PBB mixture of fireMaster BP-6 to immature male Wistar rats caused both dose-related decreases in thymus weight and increase in hepatic microsomal benzo[a]pyrene hydroxylase (AHH), 4-dimethylaminoantipyrine N-demethylase and NADPH-cytochrome c reductase activities and cytochrome P-450 content. The dose effecting half-maximal AHH induction for the photolyzed PBBs (9 mg . KG-1) was approximately 6 times lower than that of fireMaster BP-6 (50 mg. kg-1). Furthermore, the concentration of photolyzed PBBs (2 micrometers) required to displace 50% of the specifically-bound [3H] TCDD from its high-affinity cytosolic Ah receptor was approximately 150 times lower than that required for fireMaster BP-6 (300 micrometers), as measured by sucrose density gradient centrifugation analysis. The results suggest that the photolysis of the commercial PBB mixture yields products which possess increased biologic activity.     

Species differences in release of arachidonate metabolites in response to inhaled diluted diesel exhaust

In life-span studies in CD-1 mice and F344/Crl rats, inhaled diluted diesel exhaust was highly fibrogenic in rats but not in mice. This was the case despite the higher lung burden, in mg soot/g lung, achieved in mice compared to rats. We tested the hypothesis that the greater fibrogenicity of the soot in rats was due in part to greater release of mediators of inflammation from alveolar cells in rats compared to mice. Female F344/rats and B6C3F1 mice were exposed for up to 17 days to diluted diesel exhaust containing 3.5 mg/m3 of soot. The lungs of control and soot-exposed animals were lavaged after 2, 12 or 17 days of exposure. The presence of leukotriene (LT)B4, LTC4, prostaglandin (PG)E2, PGF2 alpha and thromboxane (TX) B2 in the lavage fluids and LTB4 and PGF2 alpha in cultured lavage cell supernatants was determined. The total amount of each lavage fluid constituent was normalized to lung weight for species comparisons. Control rats had higher levels of TXB2 (16-fold), and LTB4 (6-fold) and PGE2 (2-fold) than control mice, but control mice had higher amounts of LTC4 (4-fold). Control rats and mice had approximately the same amounts of PGF2 alpha/g lung in bronchoalveolar lavage fluid (BALF). Rats exposed to diesel exhaust had increases in BALF PGF2 alpha and LTB4 that were highest after 2 days of exposure and decreased thereafter. Mice had lesser increases in both parameters. Rat cells recovered from lavage fluid released larger amounts of LTB4 into culture supernatants than mouse cells. The data were consistent with the hypothesis that soot-laden rat alveolar cells release greater quantities of mediators of inflammation than do the alveolar cells in mice.     

Heterozygosity in the glutathione synthesis gene Gclm increases sensitivity to diesel exhaust particulate induced lung inflammation in mice

Context: Inhalation of ambient fine particulate matter (PM_2.5) is associated with adverse respiratory and cardiovascular effects. A major fraction of PM_2.5 in urban settings is diesel exhaust particulate (DEP), and DEP-induced lung inflammation is likely a critical event mediating many of its adverse health effects. Oxidative stress has been proposed to be an important factor in PM_2.5-induced lung inflammation, and the balance between pro- and antioxidants is an important regulator of this inflammation. An important intracellular antioxidant is the tripeptide thiol glutathione (GSH). Glutamate cysteine ligase (GCL) carries out the first step in GSH synthesis. In humans, relatively common genetic polymorphisms in both the catalytic (Gclc) and modifier (Gclm) subunits of GCL have been associated with increased risk for lung and cardiovascular diseases.

Objective: This study was aimed to determine the effects of Gclm expression on lung inflammation following DEP exposure in mice.

Materials and methods: We exposed Gclm wild type, heterozygous, and null mice to DEP via intranasal instillation and assessed lung inflammation as determined by neutrophils and inflammatory cytokines in lung lavage, inflammatory cytokine mRNA levels in lung tissue, as well as total lung GSH, Gclc, and Gclm protein levels.

Results: The Gclm heterozygosity was associated with a significant increase in DEP-induced lung inflammation when compared to that of wild type mice.

Discussion and conclusion: This finding indicates that GSH synthesis can mediate DEP-induced lung inflammation and suggests that polymorphisms in Gclm may be an important factor in determining adverse health outcomes in humans following inhalation of PM_2.5.     

Differences in airway-inflammation development by house dust mite and diesel exhaust inhalation among mouse strains

Three mouse strains (BALB/c, ICR, and C3H/He) were injected intratracheally with house dust mites (Der f) four times at 2-week intervals during exposure to diesel exhaust (DE) or clean air for 8 weeks. Der f treatment caused eosinophilic inflammation and proliferation of goblet cells in the airways of the three strains. DE + Der f caused a further increase of eosinophils in BALB/c and ICR mice, but not in C3H/He mice. DE + Der f significantly increased interleukin (IL)-5; regulated on activation, normal T cell expressed, and presumably secreted (RANTES); eotaxin, monocyte chemotactic protein-1 (MCP-1); and macrophage-inflammatory protein-1 alpha (MIP-1 alpha) in all three strains. However, the protein of IL-5 decreased more in C3H/He mice treated with DE + Der f than in mice treated with Air + Der f. The levels of IL-5 in lung tissues corresponded to the pathological changes by Der f and/or DE treatment. The levels of MCP-1 and MIP-1 alpha in the three strains corresponded to the accumulation of lymphocytes in the airway. The adjuvant effect of DE on IgG1 production was observed in the ICR and C3H/He mice. These results suggest that the murine strain differences in the production of eosinophilic airway inflammation by DE + Der f is related to differences in local expression of IL-5, eotaxin, and IgG1 production. The enhancing effects of DE exposure may be mediated mainly by local IL-5.     

Alteration of peripheral blood monocyte gene expression in humans following diesel exhaust inhalation

Context: Epidemiologic associations between acutely increased cardiorespiratory morbidity and mortality and particulate air pollution are well established, but the effects of acute pollution exposure on human gene expression changes are not well understood.

Objective: In order to identify potential mechanisms underlying epidemiologic associations between air pollution and morbidity, we explored changes in gene expression in humans following inhalation of fresh diesel exhaust (DE), a model for particulate air pollution.

Materials and methods: Fourteen ethnically homogeneous (white males), young, healthy subjects underwent 60-min inhalation exposures on 2 separate days with clean filtered air (CA) or freshly generated and diluted DE at a concentration of 300 μg/m³ PM_2.5. Prior to and 24?h following each session, whole blood was sampled and fractionated for peripheral blood mononuclear cell (PBMC) isolation, RNA extraction, and generation of cDNA, followed by hybridization with Agilent Whole Human Genome (4X44K) arrays.

Results: Oxidative stress and the ubiquitin proteasome pathway, as well as the coagulation system, were among hypothesized pathways identified by analysis of differentially expressed genes. Nine genes from these pathways were validated using real-time polymerase chain reaction (PCR) to compare fold change in expression between DE exposed and CA days. Quantitative gene fold changes generated by real-time PCR were directionally consistent with the fold changes from the microarray analysis.

Discussion and conclusion: Changes in gene expression connected with key oxidative stress, protein degradation, and coagulation pathways are likely to underlie observed physiologic and clinical outcomes and suggest specific avenues and sensitive time points for further physiologic exploration.