Nitric oxide production by rat bronchoalveolar macrophages or polymorphonuclear leukocytes following intratracheal instillation of lipopolysaccharide or silica

Extended Exhaled Nitric Oxide Analysis in Interstitial Lung Diseases: A Systematic Review

Fractional exhaled nitric oxide (FeNO) is a well-known and widely accepted biomarker of airways inflammation that can be useful in the therapeutic management, and adherence to inhalation therapy control, in asthmatic patients. However, the multiple-flows assessment of FeNO can provide a reliable measurement of bronchial and alveolar production of NO, supporting its potential value as biomarker also in peripheral lung diseases, such as interstitial lung diseases (ILD). In this review, we first discuss the role of NO in the pathobiology of lung fibrosis and the technique currently approved for the measurement of maximum bronchial flux of NO (J'awNO) and alveolar concentration of NO (CaNO). We systematically report the published evidence regarding extended FeNO analysis in the management of patients with different ILDs, focusing on its potential role in differential diagnosis, prognostic evaluation and severity assessment of disease. The few available data concerning extended FeNO analysis, and the most common comorbidities of ILD, are explored too. In conclusion, multiple-flows FeNO analysis, and CaNO in particular, appears to be a promising tool to be implemented in the diagnostic and prognostic pathways of patients affected with ILDs.

The time-dependent health and biochemical effects in rats exposed to stainless steel welding dust and its soluble form

Welding processes that generate fumes containing toxic metals, such as hexavalent chromium (Cr(VI)), manganese (Mn), and nickel (Ni), have been implicated in lung injury, inflammation, and lung tumor promotion in animal models. The principal objective of this study was to determine the dynamics of toxic effects of inhalation exposure to morphologically rated welding dust from stainless steel welding and its soluble form in TSE System with a dynamic airflow. We assessed the pulmonary toxicity of welding dust in Wistar rats exposed to 60.0 mg/m³ of respirable-size welding dust (mean diameter 1.17 µm) for 2 weeks (6 h/day, 5 days/week); the aerosols were generated in the nose-only exposure chambers (NOEC). An additional aim included the study of the effect of betaine supplementation on oxidative deterioration in rat lung during 2 weeks of exposure to welding dust or water-soluble dust form. The animals were divided into eight groups (n = 8 per group): control, dust, betaine, betaine + dust, soluble-form dust, soluble-form dust + betaine, saline and saline + betaine groups. Rats were euthanized 1 or 2 weeks after the last exposure for assessment of pulmonary toxicity. Differential cell counts, total protein concentrations and cellular enzyme (lactate dehydrogenase-LDH) activities were determined in bronchoalveolar lavage (BAL) fluid, and corticosterone and thiobarbituric acid reactive substances (TBARS) concentrations were assessed in serum. The increase in polymorphonuclear (PMN) leukocytes in BAL fluid (a cytological index of inflammatory responses of the lung) is believed to reflect pulmonary toxicity of heavy metals. Biomarkers of toxicity assessed in bronchoalveolar fluids indicate that the level of the toxic effect depends mainly on the solubility of studied metal compounds; biomarkers that showed treatment effects included: total cell, neutrophil and lymphocyte counts, total protein concentrations, and cellular enzyme (lactate dehydrogenase) activity. Betaine supplementation at 250 mg/kg/day in all study rats groups attenuated stress indices, and corticosterone and TBARS serum levels, and simultaneously stimulated increase of polymorphonuclear cells in BALF of rats. The study confirmed deleterious effect of transitory metals and particles during experimental inhalation exposure to welding dusts, evidenced in the lungs and brain by increased levels of total protein, higher cellular influx, rise of LDH in BALF, elevated TBARS and increased corticosterone in serum of rats. Our result confirm also the hypothesis about the effect of the welding dusts on the oxidative stress responsible for disturbed systemic homeostasis and impairment of calcium regulation.

Eupatorium lindleyanum DC. sesquiterpenes fraction attenuates lipopolysaccharide-induced acute lung injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Eupatorium lindleyanum DC. is widely used for its efficiency in treating cough, tracheitis and tonsillitis. Acute lung injury (ALI) induced by lipopolysaccharide (LPS) in mice was used to investigate therapeutic effects and possible mechanism of the sesquiterpenes fraction of E. lindleyanum DC. (EUP-SQT).

MATERIALS AND METHODS

Mice were orally administrated with EUP-SQT (15, 30 and 60mg/kg) per day for 7 days consecutively before LPS challenge. The lung specimens and bronchoalveolar lavage fluid (BALF) were harvested for histopathological examinations and biochemical analysis at 6h and 24h after LPS challenge. The level of complement 3 (C3) and complement 3c (C3c) in serum was quantified by a sandwich ELISA kit.

RESULTS

Pretreatment with EUP-SQT could significantly decrease lung wet-to-dry weight (W/D) ratio, nitric oxide (NO) and protein concentration in BALF, which was exhibited together with the lowered myeloperoxidase (MPO) activity, the increased superoxide dismutase (SOD) activity and down-regulation the level of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in ALI model. Additionally, EUP-SQT attenuated lung histopathological changes and significantly reduced complement deposition with decreasing the level of C3 and C3c in serum.

CONCLUSIONS

These results showed that EUP-SQT significantly attenuated LPS-induced ALI via reducing productions of pro-inflammatory mediators and decreasing the level of complement, indicating it as a potential therapeutic agent for ALI.

Embelia ribes ameliorates lipopolysaccharide-induced acute respiratory distress syndrome

ETHNOPHARMACOLOGICAL RELEVANCE

Embelia ribes Burm. f. (Fam. Myrsinaceae) locally known as Vidanga have been used for treating tumors, ascites, bronchitis, jaundice, diseases of the heart and brain in traditional Indian medicine. However, no scientific studies providing new insights in its pharmacological properties with respect to acute respiratory distress syndrome have been investigated.

AIM

The present investigation aimed to elucidate the effectiveness of Embelin isolated from Embelia ribes seeds on attenuation of LPS-induced acute respiratory distress syndrome in murine models.

METHODS

Embelin (5, 10 and 20 mg/kg/day, i.p.) and Roflumilast (1 mg/kg/day, p.o.) were administered for four days and prior to LPS in rats (i.t.). Four hour after LPS challenge animals were anesthesized and bronchoalveolar lavage was done with ice-cold phosphate buffer. Assessment of BAL fluid was done for albumin, total protein, total cell and neutrophil count, TNF-α levels, nitrosoative stress. Superior lobe of right lung was used for histopathologic evaluation. Inferior lobe of right lung was used to obtain lung edema. Left lung was used for myeloperoxidase estimation. Arterial blood was collected immediately and analyzed for pH, pO2 and pCO2 were estimated.

RESULTS

Pretreatment with embelin (5, 10 and 20 mg/kg, i.p.) decreased lung edema, mononucleated cellular infiltration, nitrate/nitrite, total protein, albumin concentrations, TNF-α in the bronchoalveolar lavage fluid and myeloperoxidase activity in lung homogenate. Embelin markedly prevented pO2 down-regulation and pCO2 augmentation. Additionally, it attenuated lung histopathological changes in acute respiratory distress syndrome model.

CONCLUSION

The study demonstrates the effectiveness of Embelia ribes Burm. f. (Fam. Myrsinaceae) seeds in acute respiratory distress syndrome possibly related to its anti-inflammatory and protective effect against LPS induced airway inflammation by reducing nitrosative stress, reducing physiological parameters of blood gas change, TNF-α and mononucleated cellular infiltration indicating it as a potential therapeutic agent for acute respiratory distress syndrome.

Rabdosia japonica var. glaucocalyx Flavonoids Fraction Attenuates Lipopolysaccharide-Induced Acute Lung Injury in Mice

Rabdosia japonica var. glaucocalyx (Maxim.) Hara, belonging to the Labiatae family, is widely used as an anti-inflammatory and antitumor drug for the treatment of different inflammations and cancers. Aim of the Study. To investigate therapeutic effects and possible mechanism of the flavonoids fraction of Rabdosia japonica var. glaucocalyx (Maxim.) Hara (RJFs) in acute lung injury (ALI) mice induced by lipopolysaccharide (LPS). Materials and Methods. Mice were orally administrated with RJFs (6.4, 12.8, and 25.6 mg/kg) per day for 7 days, consecutively, before LPS challenge. Lung specimens and the bronchoalveolar lavage fluid (BALF) were isolated for histopathological examinations and biochemical analysis. The level of complement 3 (C3) in serum was quantified by a sandwich ELISA kit. Results. RJFs significantly attenuated LPS-induced ALI via reducing productions of the level of inflammatory mediators (TNF- α , IL-6, and IL-1 β ), and significantly reduced complement deposition with decreasing the level of C3 in serum, which was exhibited together with the lowered myeloperoxidase (MPO) activity and nitric oxide (NO) and protein concentration in BALF. Conclusions. RJFs significantly attenuate LPS-induced ALI via reducing productions of proinflammatory mediators, decreasing the level of complement, and reducing radicals.

High glucose enhances LPS-stimulated human PMVEC hyperpermeability via the NO pathway

Chronic hyperglycemia is an established risk factor for endothelial damage. It remains unclear, however, whether brief hyperglycemic exposure exacerbates the damage to vascular endothelial cells induced by endotoxin. We hypothesize that brief hyperglycemic exposure enhances the permeability of the endothelium following stimulation with lipopolysaccharide (LPS). Correlations between modulation of nitric oxide synthase (NOS) pathways and altered endothelial homeostasis have been studied and demonstrated in various pathophysiological conditions. NOS activities are regulated by endogenous inhibitors, including asymmetric dimethylarginine (ADMA), which is metabolized by dimethylarginine dimethylaminohydrolase (DDAH). Since previous data demonstrated that endothelial dysfunction may be related to reduced expression and/or activity of DDAH, in this study, we aimed to determine the effect of increased glucose levels on pulmonary microvascular endothelial cell (PMVEC) permeability, including effects on the NOS pathways. Human PMVECs were incubated with normal (5.5 mM) and high (33 mM) concentrations of D-glucose for 5 days to create a monolayer of cells prior to LPS stimulation (10 μg/ml) for 12 h. When stimulated with LPS, cells incubated with a high glucose (HG) concentration had significant microfilament rearrangement compared with cells incubated with a normal glucose concentration, as determined by immunofluorescence. Scanning electron microscopy revealed a larger average diameter and increased number of fenestrae on the hyperglycemic PMVECs when stimulated with LPS, compared with PMVECs cultured with a normal glucose concentration. The results demonstrated that a high concentration of glucose increases the LPS-stimulated horseradish peroxidase (HRP) permeability compared with a normal concentration of glucose. Furthermore, a HG concentration upregulated LPS-stimulated inducible NOS (iNOS) production and down-regulated endothelial NOS (eNOS) and DDAH-2 expression. Hyperglycemia significantly increased LPS-stimulated nitrite/nitrate production (stable NO end-products). Our results, thus, demonstrate that in vitro HG concentrations exacerbate LPS-stimulated cytoskeletal rearrangement and hyperpermeability of an endothelial monolayer, and cause further imbalance of the NO pathway. These results suggest that it is important to manage even short-term increases in blood glucose, particularly following acute infection.

5-Lipoxygenase deficiency impairs innate and adaptive immune responses during fungal infection

5-lipoxygenase-derived products have been implicated in both the inhibition and promotion of chronic infection. Here, we sought to investigate the roles of endogenous 5-lipoxygenase products and exogenous leukotrienes during Histoplasma capsulatum infection in vivo and in vitro. 5-LO deficiency led to increased lung CFU, decreased nitric oxide production and a deficient primary immune response during active fungal infection. Moreover, H. capsulatum-infected 5-LO^−/− mice showed an intense influx of neutrophils and an impaired ability to generate and recruit effector T cells to the lung. The fungal susceptibility of 5-LO^−/− mice correlated with a lower rate of macrophage ingestion of IgG-H. capsulatum relative to WT macrophages. Conversely, exogenous LTB4 and LTC4 restored macrophage phagocytosis in 5-LO deficient mice. Our results demonstrate that leukotrienes are required to control chronic fungal infection by amplifying both the innate and adaptive immune response during histoplasmosis.

Bupleurum chinense DC polysaccharides attenuates lipopolysaccharide-induced acute lung injury in mice

Bupleurum chinense DC had hepato-protective, anti-inflammatory, antipyretic, analgesic, and immunomodulatory effect in traditional Chinese medicine. This study was to determine whether the crude polysaccharides isolated from the roots of Bupleurum chinense DC (BCPs) attenuated lipopolysaccharide (LPS)-induced acute lung injury in mice. Mice were challenged with LPS intratracheally 2h before BCPs (20, 40 and 80 mg/kg) administration. The bronchoalveolar lavage fluid (BALF) was collected 24h after LPS challenge. Treatment with BCPs reduced lung wet-to-dry weight ratio. The elevated number of total cells and protein concentration in BALF was reduced. The increased level of myeloperoxidase (MPO), tumor necrosis factor-α (TNF-α) in BALF, and serum nitric oxide (NO) were also inhibited. BCPs significantly attenuated lung injury with improved lung morphology and reduced complement deposition. These results suggested that the effect of BCPs against ALI might be related with its inhibitory effect on excessive activation of complement and on the production of proinflammatory mediators.

Alveolar macrophage inducible nitric oxide synthase-dependent pulmonary microvascular endothelial cell septic barrier dysfunction

Inducible nitric oxide (NO) synthase (iNOS) from neutrophils and alveolar macrophages (AM) contributes to the pathophysiology of murine septic acute lung injury (ALI). It is not known if AM iNOS has a direct effect on septic pulmonary microvascular endothelial cell (PMVEC) permeability. We hypothesized that AM iNOS mediates PMVEC permeability in vitro under septic conditions through NO and peroxynitrite. 100,000 confluent PMVEC on cell-culture inserts were co-incubated with iNOS+/+ vs. iNOS-/- AM, in various ratios of AM to PMVEC. PMVEC injury was assessed by trans-PMVEC Evans Blue-labelled albumin flux in the presence or absence of cytomix (equimolar TNF-alpha, IL-1beta and IFN-gamma). Cytomix stimulation dose-dependently increased trans-PMVEC EB-albumin flux, which was exaggerated (1.4+/-0.1% vs. 0.4+/-0.1% in unstimulated PMVEC, p<0.05) in the presence of iNOS+/+, but not iNOS-/-, AM in the upper compartment. Similarly, iNOS+/+, but not iNOS-/-, AM in the lower compartment also enhanced septic trans-PMVEC albumin leak. The mechanism of iNOS-dependent septic PMVEC permeability was pursued through pharmacologic studies with inhibitors of NOS, and scavengers of NO, superoxide, and peroxynitrite, and treatment of PMVEC with the NO donor, DETA-NONOate. Septic iNOS+/+ AM-dependent trans-PMVEC albumin leak was significantly attenuated by pharmacologic iNOS inhibition (L-NAME and 1400W), and scavenging of either NO (oxyhemoglobin), superoxide (PEG-SOD), or peroxynitrite (FeTPPS). Exogenous NO (DETA-NONOate) had no effect on PMVEC permeability. These data are consistent with a direct role of AM iNOS in septic PMVEC barrier dysfunction, which is likely mediated, in part, through peroxynitrite.

Effects of hyperoxia and nitric oxide on endogenous nitric oxide production in polymorphonuclear leukocytes

BACKGROUND

Exposure to hyperoxia and nitric oxide (NO) occur frequently during the treatment of neonatal hypoxic pulmonary failure.

OBJECTIVE

The aim of the study was to quantify the endogenous synthesis of NO in neonatal polymorphonuclear neutrophils following exposure to hyperoxia and NO in vitro.

METHODS

Neonatal cord blood was exposed to room air, 25, 30 and 100% oxygen and 10 or 20 ppm NO added to the different oxygen concentrations for up to 30 min. 4,5-Diaminofluorescein diacetate (DAF-2 DA) is an intracellular dye used to measure real-time changes in NO levels in vivo. The molecular structure of DAF-2 DA changes upon contact with NO to its oxidized and fluorescent form diaminofluorescein-triazol (DAF-2T) and after being hydrolyzed by intracellular esterases cannot leave the cell. DAF-2 DA signals following equilibration with room air were used as controls.

RESULTS

Exposure to 100% oxygen increased NO production significantly when compared to 20 ppm NO plus 100% oxygen (p = 0.031) and to 20 ppm NO alone (p = 0.006). 10 ppm NO produced a similar effect. Significant increases in NO production were also noticed following exposure to 25% oxygen. This increase was already present after 10 min of oxygen exposure.

CONCLUSION

These findings support the propagated avoidance of hyperoxia not only in preterm infants, but also in term neonates.

Comparison of the effects of erdosteine and N-acetylcysteine on apoptosis regulation in endotoxin-induced acute lung injury

This study was carried out to investigate comparatively the frequency of apoptosis in lung epithelial cells after intratracheal instillation of endotoxin [lipopolysaccharide (LPS)] in rats and the role of tumor necrosis factor alpha (TNF-alpha) on apoptosis, and the effects of erdosteine and N-acetylcysteine on the regulation of apoptosis. Female Wistar rats were given oral erdosteine (10-500 mg kg(-1)) or N-acetylcysteine (10-500 mg kg(-1)) once a day for 3 consecutive days. Then the rats were intratracheally instilled with LPS (5 mg kg(-1)) to induce acute lung injury. The rats were killed at 24 h after LPS administration. Lung tissue samples were stained with hematoxylin-eosin for histopathological assessments. The apoptosis level in the lung bronchial and bronchiolar epithelium was determined using the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick endlabelling) method. Cytoplasmic TNF-alpha was evaluated by immunohistochemistry. Pretreatment with erdosteine and pretreatment with N-acetylcysteine at a dose of 10 mg kg(-1) had no protective effect on LPS-induced lung injury. When the doses of drugs increased, the severity of the lung damage caused by LPS decreased. It was found that as the pretreatment dose of erdosteine was increased, the rate of apoptosis induced by LPS in lung epithelial cells decreased and this decrease was statistically significant in doses of 300 mg kg(-1) and 500 mg kg(-1). Pretreatment with N-acetylcysteine up to a dose of 500 mg kg(-1) did not show any significant effect on apoptosis regulation. It was noticed that both antioxidants had no significant effect on the local production level of TNF-alpha. These findings suggest that erdosteine could be a possible therapeutic agent for acute lethal lung injury and its mortality.

Reduction in alveolar macrophages attenuates acute ventilator induced lung injury in rats

OBJECTIVE

Alveolar macrophages are the sentinel cell for activation of the inflammatory cascade when the lung is exposed to noxious stimuli. We investigated the role of macrophages in mechanical lung injury by comparing the effect of high-volume mechanical ventilation with or without prior depletion of macrophages.

DESIGN AND SETTING

Randomized sham-controlled animal study in anesthetized rats.

METHODS

Lung injury was induced by 15 min of mechanical ventilation (intermittent positive pressure ventilation) using high peak pressures and zero end-expiratory pressure. The mean tidal volume was 40+/-0.7 ml/kg. One group of animals was killed immediately after this period of volutrauma (HV), while in a second group normoventilation was continued for 2 h at a tidal volume less than 10 ml/kg (HV-LV). One-half of the animals were depleted of alveolar macrophages by pretreatment with intratracheal liposomal clodronate (CL2MDP).

MEASUREMENTS

Arterial blood gas, blood pressure. After kill: lung static pressure volume curves, bronchoalveolar fluid concentration for protein, macrophage inflammatory protein 2, tumor necrosis factor alpha, and wet/dry lung weight ratio (W/D).

RESULTS

During HV and HV+LV oxygenation, lung compliance, and alveolar stability were better preserved in animals pretreated with CL2MDP. In both groups W/D ratio was significantly greater in ventilated than in nonventilated animals (4.5+/-0.6), but the increase in W/D was significantly less in CL2MDP treated HV and HV-LV groups (6.1+/-0.4, 6.6+/-0.6) than in the similarly ventilated nontreated groups (8.7+/-0.2 and 9.2+/-0.5).

CONCLUSIONS

Alveolar macrophages participate in the early phase of ventilator-induced lung injury.

Soluble metals in residual oil fly ash alter innate and adaptive pulmonary immune responses to bacterial infection in rats

The soluble metals of the pollutant, residual oil fly ash (ROFA), have been shown to alter pulmonary bacterial clearance in rats. The goal of this study was to determine the potential effects on both the innate and adaptive lung immune responses after bacterial infection in rats pre-exposed to the soluble metals in ROFA. Sprague-Dawley rats were intratracheally dosed (i.t.) at day 0 with ROFA (R-Total) (1.0 mg/100 g body weight), the soluble fraction of ROFA (R-Soluble), the soluble sample subject to a chelator (R-Chelex), or phosphate-buffered saline (Saline). On day 3, rats were administered an i.t. dose of 5 x 10(4)Listeria monocytogenes. On days 6, 8, and 10, bacterial pulmonary clearance was monitored and bronchoalveolar lavage (BAL) was performed on days 3 (pre-infection), 6, 8, and 10. A concentrated first fraction of lavage fluid was retained for analysis of lactate dehydrogenase and albumin to assess lung injury. BAL cell number, phenotype, and production of reactive oxygen (ROS) and nitrogen species (RNS) were assessed, and a variety of cytokines were measured in the BAL fluid. Rats pre-treated with R-Soluble showed elevated lung injury/cytotoxicity and increased cellular influx into the lungs. R-Soluble-treatment also altered ROS, RNS, and cytokine levels, and caused a degree of macrophage and T cell inhibition. These effects of R-Soluble result in increased pulmonary bacterial burden after infection. The results suggest that soluble metals in ROFA increase lung injury and inflammation, and alter both innate and adaptive pulmonary immune responses.

Structural and biological study of carboxymethylated Phellinus linteus polysaccharides

Polysaccharides isolated from Phellinus linteus were chemically modified by carboxymethylation, and the structural and physiological properties of the derivative were investigated. 13C NMR spectroscopy showed that the polysaccharides extracted from P. linteus contained (1-3)-beta-glucans with a (1-6)-linkage. The carboxymetehylation of the P. linteus polysaccharides was confirmed by Fourier transform infrared spectroscopy, and the degree of substitution was obtained by the potentiometric titration, which was calculated to be 0.63. The bronchoalveolar lavage experiments showed that the carboxymethylated derivative raised the nitric oxide production. In addition, the carboxymethylation stimulated in vitro cytotoxic activity against the HT1080 cell line. Thus, the derivative exhibited the enhanced activity of immune systems, which would be explained by the improved water solubility and structural changes by carboxymethylation. However, a slight decrease in the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of the derivative was observed.

Cell- and isoform-specific increases in arginase expression in acute silica-induced pulmonary inflammation

Arginase induction was reported in several inflammatory lung diseases, suggesting that this may be a common feature underlying the pathophysiology of such diseases. As little is known regarding arginase expression in silicosis, the induction and cellular localization of arginase were elucidated in lungs of Sprague-Dawley rats 24 h following exposure to varying doses of silica by intratracheal instillation. Arginase expression was evaluated by activity assay, quantification of arginase I and arginase II mRNA levels using real-time polymerase chain reaction (PCR), and immunohistochemistry. Analyses of cells and fluid obtained by bronchoalveolar lavage (BAL) showed that markers of pulmonary inflammation, tissue damage, activation of alveolar macrophages (AM) and NO production were significantly increased by all silica doses. Arginase activity was increased also in AMs isolated from BAL fluid of silica-treated rats. Silica produced two- and three-fold increases in arginase activity of whole lung at doses of 1 and 5 mg/100 g body weight, respectively. Levels of arginase I mRNA, but not of arginase II mRNA, were similarly elevated. In control lungs, arginase I immunoreactivity was observed only in AMs sparsely dispersed throughout the lung; no inducible nitric oxide synthase (iNOS) immunoreactivity was detected. In silica-treated lungs, arginase I and iNOS were co-expressed in most AMs that were abundantly clustered at inflammatory foci. The rapid induction of arginase I expression in inflammatory lung cells, similar to induction of arginase in other inflammatory lung diseases, implicates elevated arginase activity as a factor in the development of lung damage following exposure to silica.

Exposure in vivo to silica or lipopolysaccharide produces transient or sustained upregulation, respectively, of PYPAF7 and MEFV genes in bronchoalveolar lavage cells in rats

A family of proteins containing PAAD [for PYRIN, AIM (absent in melanoma), apoptosis-associated protein speck-like protein containing a caspase recruitment domain, and death domain] domain was found to be involved in modulating inflammatory responses, by its ability to regulate nuclear factor (NF)-kappaB and procaspase-1 activation. In this study, intratracheal instillation of silica in rats was found to produce transient upregulation of mRNA levels of the PAAD family of proteins, PYPAF7 (PYRIN containing Apaf1-like protein; Apaf stands for apoptosis activating factor) and MEFV (for Mediterranean fever), in bronchoalveolar lavage (BAL) cells. The levels were markedly elevated at 4 h, returning to basal levels by 24 h. In contrast, intratracheal instillation of LPS produced a sustained upregulation of the two genes in BAL cells. In vitro exposure of BAL cells to silica or lipopolysaccharide (LPS) produced no changes in the expression of these genes, indicating that silica or LPS exposure in vivo induces some factors that are responsible for the upregulation of PYPAF7 and MEFV. The mRNA levels of these two genes in peripheral blood monocytes and PMN following LPS exposure did not change, indicating that AM and peripheral blood cells show similar response to LPS exposure in vitro. This study provides the basis for a physiological model to study the effects of these two genes in modulating the inflammatory response after particle exposure.

Nitric Oxide and Reactive Oxygen Species Production Causes Progressive Damage in Rats after Cessation of Silica Inhalation

Our laboratory has previously reported results from a rat silica inhalation study which determined that, even after silica exposure ended, pulmonary inflammation and damage progressed with subsequent fibrosis development. In the present study, the relationship between silica exposure, nitric oxide (NO) and reactive oxygen species (ROS) production, and the resultant pulmonary damage is investigated in this model. Rats were exposed to silica (15 mg/m3, 6 h/day) for either 20, 40, or 60 days. A portion of the rats from each exposure were sacrificed at 0 days postexposure, while another portion was maintained without further exposure for 36 days to examine recovery or progression. The major findings of this study are: (1) silica-exposed rat lungs were in a state of oxidative stress, the severity of which increased during the postexposure period, (2) silica-exposed rats had significant increase in lung NO production which increased in magnitude during the postexposure period, and (3) the presence of silica particle(s) in an alveolar macrophage (AM) was highly associated with inducible nitric oxide synthase (iNOS) protein. These data indicate that, even after silica exposure has ended, and despite declining silica lung burden, silica-induced pulmonary NO and ROS production increases, thus producing a more severe oxidative stress. A quantitative association between silica and expression of iNOS protein in AMs was also determined, which adds to our previous observation that iNOS and NO-mediated damage are associated anatomically with silica-induced pathological lesions. Future studies will be needed to determine whether the progressive oxidative stress, and iNOS activation and NO production, is a direct result of silica lung burden or a consequence of silica-induced biochemical mediators.

The crucial role of particle surface reactivity in respirable quartz-induced reactive oxygen/nitrogen species formation and APE/Ref-1 induction in rat lung

Persistent inflammation and associated excessive oxidative stress have been crucially implicated in quartz-induced pulmonary diseases, including fibrosis and cancer. We have investigated the significance of the particle surface reactivity of respirable quartz dust in relation to the in vivo generation of reactive oxygen and nitrogen species (ROS/RNS) and the associated induction of oxidative stress responses in the lung. Therefore, rats were intratracheally instilled with 2 mg quartz (DQ12) or quartz whose surface was modified by either polyvinylpyridine-N-oxide (PVNO) or aluminium lactate (AL). Seven days after instillation, the bronchoalveolar lavage fluid (BALF) was analysed for markers of inflammation (total/differential cell counts), levels of pulmonary oxidants (H₂O₂, nitrite), antioxidant status (trolox equivalent antioxidant capacity), as well as for markers of lung tissue damage, e.g. total protein, lactate dehydrogenase and alkaline phosphatase. Lung homogenates as well as sections were investigated regarding the induction of the oxidative DNA-lesion/oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) using HPLC/ECD analysis and immunohistochemistry, respectively. Homogenates and sections were also investigated for the expression of the bifunctional apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1) by Western blotting and immunohistochemistry. Significantly increased levels of H₂O₂ and nitrite were observed in rats treated with non-coated quartz, when compared to rats that were treated with either saline or the surface-modified quartz preparations. In the BALF, there was a strong correlation between the number of macrophages and ROS, as well as total cells and RNS. Although enhanced oxidant generation in non-coated DQ12-treated rats was paralleled with an increased total antioxidant capacity in the BALF, these animals also showed significantly enhanced lung tissue damage. Remarkably however, elevated ROS levels were not associated with an increase in 8-OHdG, whereas the lung tissue expression of APE/Ref-1 protein was clearly up-regulated. The present data provide further in vivo evidence for the crucial role of particle surface properties in quartz dust-induced ROS/RNS generation by recruited inflammatory phagocytes. Our results also demonstrate that quartz dust can fail to show steady-state enhanced oxidative DNA damage in the respiratory tract, in conditions were it elicits a marked and persistent inflammation with associated generation of ROS/RNS, and indicate that this may relate to compensatory induction of APE/Ref-1 mediated base excision repair.

Nitrite enhances neutrophil-induced DNA strand breakage in pulmonary epithelial cells by inhibition of myeloperoxidase

Chronic inhalation of environmental particles is associated with pulmonary carcinogenesis. Although the mechanism has not yet been fully elucidated, influx of inflammatory cells, including neutrophils, is suggested to play a major role in this process. Typically, in the particle-exposed lung, influx of neutrophils is accompanied by an accumulation of nitrite. Previous studies indicated that nitrite may affect the toxicity of neutrophils, involving an interaction with neutrophil-derived myeloperoxidase (MPO). To evaluate the possible consequences of this interaction for inflammation-mediated genotoxicity, we investigated the effect of nitrite on neutrophil-induced DNA damage in pulmonary target cells. Therefore, activated neutrophils were co-cultured with alveolar type II epithelial cells (RLE), and DNA strand breakage was evaluated using single-cell gel electrophoresis (comet assay). In this system, addition of nitrite caused an increase in neutrophil-induced DNA strand breakage in RLE cells, which was associated with an inhibition of MPO activity. Similar results were obtained by co-culturing RLE cells with neutrophils in the presence of the specific MPO inhibitor 4-aminobenzoic acid hydrazide (4-ABAH). To further investigate the mechanism underlying these observations, in vitro experiments were performed using mixtures of nitrite, MPO and its substrate H2O2. DNA strand breakage by reagent H2O2 was inhibited when it was allowed to react with MPO before addition to the RLE cells. However, when MPO and H2O2 were pre-mixed in the presence of nitrite or 4-ABAH, the inhibitory effect of MPO on resultant DNA damage was reversed. Further studies using catalase indicated that DNA strand breakage by the pre-mixtures of MPO, H2O2 and nitrite was H2O2-specific, suggesting that nitrite prevents consumption of H2O2 by MPO. Collectively, our results show that nitrite enhances neutrophil-induced DNA strand breakage in pulmonary epithelial cells. This effect is probably due to an inhibition of MPO activity, which increases the availability of its DNA strand breaking substrate H2O2.

Inflammatory and immunological responses to subchronic exposure to endotoxin-contaminated metalworking fluid aerosols in F344 rats

Rats were exposed for 6 h per day in inhalation chambers to a 10 mg/m(3) concentration of metalworking fluid (MWF) contaminated with endotoxin at concentrations of 1813 (low dose) and 20,250 eu/m(3) (high dose) 5 days per week for 8 weeks. It was found that 94.7% of the MWF aerosol particles had diameters in the range of 0.42-4.6 microm, with geometric mean diameter of 1.56 microm. The body weight and pulmonary function parameters were measured every week during the 8 weeks of exposure, whereas bronchoalveolar lavage (BAL) fluid was prepared to measure the inflammatory markers and cytokines after the 8 weeks of exposure. There were no changes in body weight and respiratory function (tidal volume and respiratory frequency) during the 8 weeks of exposure to the MWF containing endotoxins, yet lung weight increased significantly (P < 0.05) in the rats exposed to the MWF both with and without endotoxins. The number of polymorphonuclear (PMN) cells in the BAL fluid increased significantly (P < 0.05) in the rats exposed to MWF with endotoxins, and the levels of cytokines such as IL-4, INF-gamma, IL-1beta, and TNF-alpha also were significantly increased (P < 0.05) compared to the control. The NOx production activity of the BAL cells increased significantly (P < 0.05) in the rats exposed to the MWF with and without endotoxins. Increases in lung weight, number of PMN cells, and levels of extracellular cytokines and NOx were all more significant in the rats exposed to the MWF with endotoxins rather than in those exposed to MWF without endotoxins. In spleen cell cultures, T-cell proliferation activity was decreased, yet cytokine levels (INF-gamma, IL-1beta, IL-4, and TNF-alpha) remained unchanged after repeated exposure to MWF with and without endotoxins. Although the levels of total IgG(1), IgG(2a), and IgE antibodies in the serum were not changed, the levels of endotoxin-specific antibodies, including IgG(2a) and IgE, were increased significantly (P < 0.05) in the rats exposed to endotoxins, but there was not a significant increase in endotoxin-specific IgG(1). When taken together, the results indicate that lung inflammatory responses can be induced without changing pulmonary function after repeated exposure to MWFs contaminated with endotoxins. In addition, endotoxin-specific IgG(2a) and IgE may be effective biomarkers for workers exposed to MWFs contaminated with endotoxins in the workplace.

Respiratory effect of acute and subacute exposure to endotoxin-contaminated metal working fluid (MWF) aerosols on Sprague-Dawley rats

Male Sprague-Dawley rats were exposed to a water-soluble metal working fluid (MWF) (5% v/v) contaminated with endotoxins (10,000 eu/ml or 100,000 eu/ml) at 10 mg/m3 for six hours per day for three days (acute exposure) or two weeks (subacute exposure). The geometric mean diameter of the MWF aerosols was 1.56 microm, and the airborne endotoxin concentrations ranged from 1,231 to 2,173 eu/m3 (10,000 eu/ml in the bulk MWF) for the low dose and 19,263-27,386 eu/m3 (100,000 eu/ml in the bulk MWF) for the high dose. Minimal effects were observed after exposure to 10 mg/m3 of the MWF without endotoxins for three days or two weeks. However, an increase in the number of polymorphonuclear cells (PMNs) and the level of protein was noted in the bronchoalveolar lavage (BAL) fluid from the rats acutely exposed to the MWF with endotoxins. The acute exposure produced a greater increase in the number of PMNs and total cell number in the BAL fluid than the subacute exposure. The number of white blood cells in the peripheral blood and the weight of the lungs both increased after the subacute exposure to the MWF aerosol with endotoxins, indicating increased vascular permeability in response to the endotoxin exposure. The levels of cyotokines such as IL-4, INF-gamma, and IL-1beta in the BAL fluid from the rats exposed to the MWF with or without endotoxins remained unchanged. Although the level of nitric oxide (NO(x)) in the BAL supernatant did not show any change, the induction of NO(x) from the alveolar macrophages increased in the rats acutely or subacutely exposed to the MWF contaminated with endotoxins. The ConA-induced proliferation response showed no change, yet the LPS-induced proliferation response was significantly increased in the splenocytes from the rats subacutely exposed to the MWF with and without endotoxins. The level of TNF-alpha in the spleen cell culture obtained from the rats exposed to the MWF with or without endotoxins increased without changing the levels of IL-1beta, IL-4, and INF-gamma. The level of endotoxin-specific IgE in the serum obtained from the rats exposed to the MWF with endotoxins increased dose-dependently, while the levels of total immunoglobulins (IgG(1), IgG(2a) and IgE) and endotoxin-specific IgG(1) and IgG(2a) remained unchanged. Accordingly, the current results indicate that lung inflammation can be immediately induced by acute or subacute exposure to an MWF contaminated with endotoxins, and macrophages would appear to play a role in the induction of inflammation along with B-cell functions rather than T-cell functions, after subacute exposure to an MWF with endotoxins. In addition, endotoxin-specific IgE is an early marker for endotoxin exposure in the workplace.

The sources of inflammatory mediators in the lung after silica exposure

The expression of 10 genes implicated in regulation of the inflammatory processes in the lung was studied after exposure of alveolar macrophages (AMs) to silica in vitro or in vivo. Exposure of AMs to silica in vitro up-regulated the messenger RNA (mRNA) levels of three genes [interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2)] without a concomitant increase in the protein levels. AMs isolated after intratracheal instillation of silica up-regulated mRNA levels of four additional genes [granulocyte/macrophage-colony stimulating factor (GM-CSF), IL-1beta, IL-10, and inducible nitric oxide synthase]. IL-6, MCP-1, and MIP-2 protein levels were elevated in bronchoalveolar lavage fluid. Fibroblasts under basal culture conditions express much higher levels of IL-6 and GM-CSF compared with AMs. Coculture of AMs and alveolar type II cells, or coculture of AMs and lung fibroblasts, in contact cultures or Transwell chambers, revealed no synergistic effect. Therefore, such interaction does not explain the effects seen in vivo. Identification of the intercellular communication in vivo is still unresolved. However, fibroblasts appear to be an important source of inflammatory mediators in the lung.

New genes implicated in the protection of anaerobically grown Escherichia coli against nitric oxide

Nitric oxide produced by activated macrophages plays a key role as one of the immune system's weapons against pathogens. Because the lifetime of nitric oxide is short in aerobic conditions, whereas in anaerobic conditions the cytotoxic effects of nitric oxide are greatly increased as in the infection/inflammation processes, it is important to establish which systems are able to detoxify nitric oxide under anaerobic conditions. In the present work a new set of Escherichia coli K-12 genes conferring anaerobic resistance to nitric oxide is presented, namely the gene product of YtfE and a potential transcriptional regulator of the helix-turn-helix LysR-type (YidZ). The crucial role of flavohemoglobin for anaerobic nitric oxide protection is also demonstrated. Furthermore, nitric oxide is shown to cause a significant alteration of the global E. coli gene transcription profile that includes the increase of the transcript level of genes encoding for detoxification enzymes, iron-sulfur cluster assembly systems, DNA-repairing enzymes, and stress response regulators.