Molecular mechanisms of pulmonary response progression in crystalline silica exposed rats

An understanding of the mechanisms underlying diseases is critical for their prevention. Excessive exposure to crystalline silica is a risk factor for silicosis, a potentially fatal pulmonary disease. Male Fischer 344 rats were exposed by inhalation to crystalline silica (15 mg/m³, six hours/day, five days) and pulmonary response was determined at 44 weeks following termination of silica exposure. Additionally, global gene expression profiling in lungs and BAL cells and bioinformatic analysis of the gene expression data were done to understand the molecular mechanisms underlying the progression of pulmonary response to silica. A significant increase in lactate dehydrogenase activity and albumin content in BAL fluid (BALF) suggested silica-induced pulmonary toxicity in the rats. A significant increase in the number of alveolar macrophages and infiltrating neutrophils in the lungs and elevation in monocyte chemoattractant protein-1 (MCP-1) in BALF suggested the induction of pulmonary inflammation in the silica exposed rats. Histological changes in the lungs included granuloma formation, type II pneumocyte hyperplasia, thickening of alveolar septa and positive response to Masson's trichrome stain. Microarray analysis of global gene expression detected 94 and 225 significantly differentially expressed genes in the lungs and BAL cells, respectively. Bioinformatic analysis of the gene expression data identified significant enrichment of several disease and biological function categories and canonical pathways related to pulmonary toxicity, especially inflammation. Taken together, these data suggested the involvement of chronic inflammation as a mechanism underlying the progression of pulmonary response to exposure of rats to crystalline silica at 44 weeks following termination of exposure.

Pulmonary toxicity and global gene expression changes in response to sub-chronic inhalation exposure to crystalline silica in rats

Exposure to crystalline silica results in serious adverse health effects, most notably, silicosis. An understanding of the mechanism(s) underlying silica-induced pulmonary toxicity is critical for the intervention and/or prevention of its adverse health effects. Rats were exposed by inhalation to crystalline silica at a concentration of 15 mg/m³, 6 hr/day, 5 days/week for 3, 6 or 12 weeks. Pulmonary toxicity and global gene expression profiles were determined in lungs at the end of each exposure period. Crystalline silica was visible in lungs of rats especially in the 12-week group. Pulmonary toxicity, as evidenced by an increase in lactate dehydrogenase (LDH) activity and albumin content and accumulation of macrophages and neutrophils in the bronchoalveolar lavage (BAL), was seen in animals depending upon silica exposure duration. The most severe histological changes, noted in the 12-week exposure group, consisted of chronic active inflammation, type II pneumocyte hyperplasia, and fibrosis. Microarray analysis of lung gene expression profiles detected significant differential expression of 38, 77, and 99 genes in rats exposed to silica for 3-, 6-, or 12-weeks, respectively, compared to time-matched controls. Among the significantly differentially expressed genes (SDEG), 32 genes were common in all exposure groups. Bioinformatics analysis of the SDEG identified enrichment of functions, networks and canonical pathways related to inflammation, cancer, oxidative stress, fibrosis, and tissue remodeling in response to silica exposure. Collectively, these results provided insights into the molecular mechanisms underlying pulmonary toxicity following sub-chronic inhalation exposure to crystalline silica in rats.

Comparison of cell counting methods in rodent pulmonary toxicity studies: automated and manual protocols and considerations for experimental design

Pulmonary toxicity studies often use bronchoalveolar lavage (BAL) to investigate potential adverse lung responses to a particulate exposure. The BAL cellular fraction is counted, using automated (i.e. Coulter Counter®), flow cytometry or manual (i.e. hemocytometer) methods, to determine inflammatory cell influx. The goal of the study was to compare the different counting methods to determine which is optimal for examining BAL cell influx after exposure by inhalation or intratracheal instillation (ITI) to different particles with varying inherent pulmonary toxicities in both rat and mouse models. General findings indicate that total BAL cell counts using the automated and manual methods tended to agree after inhalation or ITI exposure to particle samples that are relatively nontoxic or at later time points after exposure to a pneumotoxic particle when the response resolves. However, when the initial lung inflammation and cytotoxicity was high after exposure to a pneumotoxic particle, significant differences were observed when comparing cell counts from the automated, flow cytometry and manual methods. When using total BAL cell count for differential calculations from the automated method, depending on the cell diameter size range cutoff, the data suggest that the number of lung polymorphonuclear leukocytes (PMN) varies. Importantly, the automated counts, regardless of the size cutoff, still indicated a greater number of total lung PMN when compared with the manual method, which agreed more closely with flow cytometry. The results suggest that either the manual method or flow cytometry would be better suited for BAL studies where cytotoxicity is an unknown variable.

Oxidative stress and reduced responsiveness of challenged circulating leukocytes following pulmonary instillation of metal-rich particulate matter in rats

Welding fume is an exposure that consists of a mixture of metal-rich particulate matter with gases (ozone, carbon monoxide) and/or vapors (VOCs). Data suggests that welders are immune compromised. Given the inability of pulmonary leukocytes to properly respond to a secondary infection in animal models, the question arose whether the dysfunction persisted systemically. Our aim was to evaluate the circulating leukocyte population in terms of cellular activation, presence of oxidative stress, and functionality after a secondary challenge, following welding fume exposure. Rats were intratracheally instilled (ITI) with PBS or 2 mg of welding fume collected from a stainless steel weld. Rats were sacrificed 4 and 24 h post-exposure and whole blood was collected. Whole blood was used for cellular differential counts, RNA isolation with subsequent microarray and Ingenuity Pathway Analysis, and secondary stimulation with LPS utilizing TruCulture technology. In addition, mononuclear cells were isolated 24 h post-exposure to measure oxidative stress by flow cytometry and confocal microscopy. Welding fume exposure had rapid effects on the circulating leukocyte population as identified by relative mRNA expression changes. Instillation of welding fume reduced inflammatory protein production of circulating leukocytes when challenged with the secondary stimulus LPS. The effects were not related to transcription, but were observed in conjunction with oxidative stress. These findings support previous studies of an inadequate pulmonary immune response following a metal-rich exposure and extend those findings showing leukocyte dysfunction occurs systemically.

Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis

Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO2) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO2 on the pulmonary system in a rat model. Specific pathogen-free male Sprague-Dawley rats were exposed to CeO2 and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO2 induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO2 and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ, respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO2, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP+CeO2 were significantly larger than CeO2 or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP+CeO2 reflects the combination of DEP-exposure plus CeO2-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO2 induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO2 in the combined exposure. Using CeO2 as diesel fuel catalyst may cause health concerns.

Genotoxicity of multi-walled carbon nanotubes at occupationally relevant doses

Carbon nanotubes are commercially-important products of nanotechnology; however, their low density and small size makes carbon nanotube respiratory exposures likely during their production or processing. We have previously shown mitotic spindle aberrations in cultured primary and immortalized human airway epithelial cells exposed to single-walled carbon nanotubes (SWCNT). In this study, we examined whether multi-walled carbon nanotubes (MWCNT) cause mitotic spindle damage in cultured cells at doses equivalent to 34 years of exposure at the NIOSH Recommended Exposure Limit (REL). MWCNT induced a dose responsive increase in disrupted centrosomes, abnormal mitotic spindles and aneuploid chromosome number 24 hours after exposure to 0.024, 0.24, 2.4 and 24 μg/cm² MWCNT. Monopolar mitotic spindles comprised 95% of disrupted mitoses. Three-dimensional reconstructions of 0.1 μm optical sections showed carbon nanotubes integrated with microtubules, DNA and within the centrosome structure. Cell cycle analysis demonstrated a greater number of cells in S-phase and fewer cells in the G2 phase in MWCNT-treated compared to diluent control, indicating a G1/S block in the cell cycle. The monopolar phenotype of the disrupted mitotic spindles and the G1/S block in the cell cycle is in sharp contrast to the multi-polar spindle and G2 block in the cell cycle previously observed following exposure to SWCNT. One month following exposure to MWCNT there was a dramatic increase in both size and number of colonies compared to diluent control cultures, indicating a potential to pass the genetic damage to daughter cells. Our results demonstrate significant disruption of the mitotic spindle by MWCNT at occupationally relevant exposure levels.

Lung toxicity and biodistribution of Cd/Se-ZnS quantum dots with different surface functional groups after pulmonary exposure in rats

BACKGROUND

The potential use of quantum dots (QD) in biomedical applications, as well as in other systems that take advantage of their unique physiochemical properties, has led to concern regarding their toxicity, potential systemic distribution, and biopersistence. In addition, little is known about workplace exposure to QD in research, manufacturing, or medical settings. The goal of the present study was to assess pulmonary toxicity, clearance, and biodistribution of QD with different functional groups in rats after pulmonary exposure.

METHODS

QD were composed of a cadmium-selenide (CdSe) core (~5nm) with a zinc sulfide (ZnS) shell functionalized with carboxyl (QD-COOH) or amine (QD-NH2) terminal groups. Male Sprague-Dawley rats were intratracheally-instilled (IT) with saline, QD-COOH, or QD-NH2 (12.5, 5.0, or 1.25 μg/rat). On days 0, 1, 3, 5, 7, 14, and 28 post-IT, the left lung, lung-associated lymph nodes (LALN), heart, kidneys, spleen, liver, brain, and blood were collected for metal analysis of Cd content by neutron activation to evaluate clearance and biodistribution. One right lobe was ligated and fixed for microscopy and histopathological analysis. The remaining right lobes from rats in each group were subjected to bronchoalveolar lavage (BAL) to retrieve BAL fluid and cells for analysis of injury and inflammation.

RESULTS

Lung injury and inflammation was found to be dose-dependent and peaked at days 7 and 14 post-exposure for both forms of QD, with slight variations in degree of toxicity at early and later time points. Both QD appeared to lose their fluorescent properties and destabilize after 1 week in the lung. Cd persisted up to 28 days for both forms of QD; however, clearance rate was slightly greater for QD-COOH over time. No Cd was detected in the liver, spleen, heart, brain, or blood at any time point. Cd appeared in the LALN and kidneys beginning at 1-2 weeks post-exposure.

CONCLUSIONS

QD-COOH and QD-NH2 differed in clearance rate and differed slightly in degree of toxicity at different time points; however, the overall pattern of toxicity and biodistribution was similar between the two particles. Toxicity may be dependent on the dissolution rate and bioavailability of free Cd.

Adjuvant effect of zymosan after pulmonary treatment in a mouse ovalbumin allergy model

An association has been observed between indoor mold contamination and lung allergy and asthma. This relationship is not fully understood. 1→3-β-Glucan is the major cell wall component of fungi and a good marker of fungi exposure. The objective was to evaluate the adjuvant effect of zymosan, a crude yeast cell wall preparation of 1→3-β-glucan, during ovalbumin (OVA) sensitization in an allergy model. BALB/c mice were sensitized by pharyngeal aspiration with saline, 50 μg of OVA, or OVA with 1, 10, 50, or 75 μg of zymosan on days 0, 7, and 14. One week after sensitization, each sensitized animal group was challenged with an aspiration dose of 50 μg of OVA once a week for 2 weeks. At 1 day after the last aspiration, bronchoalveolar lavage fluid and blood was collected, and markers of lung allergy and inflammation were assessed. An adjuvant effect of zymosan on OVA allergy during sensitization was observed as indicated by significant elevations in lung eosinophils, serum OVA-specific IgE, and lung IL-5 in the groups sensitized with zymosan and OVA. Pulmonary treatment with zymosan also amplified lung inflammation. Elevations were observed in lung neutrophils, TNF-α, and parameters of lung injury in the groups primed with both zymosan and OVA. In nearly all parameters, a non-linear dose-response relationship was observed in the groups primed with OVA and zymosan. The optimum adjuvant dose of zymosan was 10 μg. This study demonstrated an adjuvant effect of zymosan when exposures occurred during the sensitization phase in an OVA-induced allergy model in BALB/c mice.

Transcriptomics analysis of lungs and peripheral blood of crystalline silica-exposed rats

Minimally invasive approaches to detect/predict target organ toxicity have significant practical applications in occupational toxicology. The potential application of peripheral blood transcriptomics as a practical approach to study the mechanisms of silica-induced pulmonary toxicity was investigated. Rats were exposed by inhalation to crystalline silica (15 mg/m(3), 6 h/day, 5 days) and pulmonary toxicity and global gene expression profiles of lungs and peripheral blood were determined at 32 weeks following termination of exposure. A significant elevation in bronchoalveolar lavage fluid lactate dehydrogenase activity and moderate histological changes in the lungs, including type II pneumocyte hyperplasia and fibrosis, indicated pulmonary toxicity in the rats. Similarly, significant infiltration of neutrophils and elevated monocyte chemotactic protein-1 levels in the lungs showed pulmonary inflammation in the rats. Microarray analysis of global gene expression profiles identified significant differential expression [>1.5-fold change and false discovery rate (FDR) p < 0.01] of 520 and 537 genes, respectively, in the lungs and blood of the exposed rats. Bioinformatics analysis of the differentially expressed genes demonstrated significant similarity in the biological processes, molecular networks, and canonical pathways enriched by silica exposure in the lungs and blood of the rats. Several genes involved in functions relevant to silica-induced pulmonary toxicity such as inflammation, respiratory diseases, cancer, cellular movement, fibrosis, etc, were found significantly differentially expressed in the lungs and blood of the silica-exposed rats. The results of this study suggested the potential application of peripheral blood gene expression profiling as a toxicologically relevant and minimally invasive surrogate approach to study the mechanisms underlying silica-induced pulmonary toxicity.

Single-Walled Carbon Nanotubes Induce Fibrogenic Effect by Disturbing Mitochondrial Oxidative Stress and Activating NF-κB Signaling

Single-walled carbon nanotubes (SWCNTs) are newly discovered material of crystalline carbon that forms single-carbon layer cylinders with nanometer diameters and varying lengths. Although SWCNTs are potentially suitable for a range of novel applications, their extremely small size, fiber-like shape, large surface area, and unique surface chemistry raise potential hazard to humans, including lung toxicity and fibrosis. The molecular mechanisms by which SWCNTs cause lung damage remain elusive. Here we show that SWCNTs dose and time-dependently caused toxicity in cultured human bronchial epithelial (BEAS-2B), alveolar epithelial (A549), and lung fibroblast (WI38) cells. At molecular levels, SWCNTs induced significant mitochondrial depolarization and ROS production at subtoxic doses. SWCNTs stimulated the secretion of proinflammatory cytokines and chemokines TNFα, IL-1β, IL-6, IL-10 and MCP1 from macrophages (Raw 264.7), which was attributed to the activation of the canonical signaling pathway of NF-κB by SWCNT. Finally, SWCNTs stimulated profibrogenic growth factors TGFβ1 production and fibroblast-to-myofibroblast-transformation. These results indicate that SWCNTs has a potential to induce human lung damage and fibrosis by damaging mitochondria, generating ROS, and stimulating production of proinflammatory and profibrogenic cytokines and growth factors.

Abstract 5464: Genotoxicity of multi-walled carbon nanotubes at occupationally relevant doses

Carbon nanotubes represent a creative alternative for applications in medicine as therapeutic vectors, imaging and controlled release of active molecules. Although the low density and small size of carbon nanotubes makes respiratory exposures to workers likely during the production or use of commercial products, the potential genotoxicity of multi-walled carbon nanotubes has not been investigated. We have previously shown mitotic spindle aberrations in cultured primary and immortalized human airway epithelial cells exposed to single-walled carbon nanotubes (SWCNT). In order to investigate whether genetic damage was unique to SWCNT, we examined mitotic spindle aberrations following dosing of cells to multi-walled carbon nanotubes (MWCNT) at concentrations anticipated in the workplace. Immortalized and primary respiratory epithelial cells were exposed to 0.024, 0.24, 2.4, and 24μg/cm2 carbon nanotubes. The minimal dose of MWCNT considered for this research was based on the permissible exposure limit for particles with an aerodynamic diameter of less than 5 microns (Occupation Safety and Health Administration). MWCNT induced a dose response of disrupted centrosomes, mitotic spindles and aneuploid chromosome number. The data further showed that monopolar mitotic spindles comprised 95% of the disrupted mitoses. The monopolar phenotype of the disrupted mitotic spindles is in sharp contrast to the multi-polar spindle of SWCNT-induced disruption. Three-dimensional reconstructions showed carbon nanotubes integrated with the microtubules, the DNA and within the centrosome structure. The lower doses did not cause cytotoxicity or apoptosis 24 hours after exposure; however, after 72 hours, significant cytotoxicity was observed in the MWCNT-exposed cells. Disruption of the centrosome is common in many solid tumors including lung cancer. The resulting aneuploidy is a key event in the progression of cancer and is correlated with tumor stage. Our results demonstrate significant disruption of the mitotic spindle by MWCNT at occupationally relevant doses. These results suggest caution should be used in the handling and processing of carbon nanotubes.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5464. doi:1538-7445.AM2012-5464

Factoring-in agglomeration of carbon nanotubes and nanofibers for better prediction of their toxicity versus asbestos

Background

Carbon nanotubes (CNT) and carbon nanofibers (CNF) are allotropes of carbon featuring fibrous morphology. The dimensions and high aspect ratio of CNT and CNF have prompted the comparison with naturally occurring asbestos fibers which are known to be extremely pathogenic. While the toxicity and hazardous outcomes elicited by airborne exposure to single-walled CNT or asbestos have been widely reported, very limited data are currently available describing adverse effects of respirable CNF.

Results

Here, we assessed pulmonary inflammation, fibrosis, oxidative stress markers and systemic immune responses to respirable CNF in comparison to single-walled CNT (SWCNT) and asbestos. Pulmonary inflammatory and fibrogenic responses to CNF, SWCNT and asbestos varied depending upon the agglomeration state of the particles/fibers. Foci of granulomatous lesions and collagen deposition were associated with dense particle-like SWCNT agglomerates, while no granuloma formation was found following exposure to fiber-like CNF or asbestos. The average thickness of the alveolar connective tissue - a marker of interstitial fibrosis - was increased 28 days post SWCNT, CNF or asbestos exposure. Exposure to SWCNT, CNF or asbestos resulted in oxidative stress evidenced by accumulations of 4-HNE and carbonylated proteins in the lung tissues. Additionally, local inflammatory and fibrogenic responses were accompanied by modified systemic immunity, as documented by decreased proliferation of splenic T cells ex vivo on day 28 post exposure. The accuracies of assessments of effective surface area for asbestos, SWCNT and CNF (based on geometrical analysis of their agglomeration) versus estimates of mass dose and number of particles were compared as predictors of toxicological outcomes.

Conclusions

We provide evidence that effective surface area along with mass dose rather than specific surface area or particle number are significantly correlated with toxicological responses to carbonaceous fibrous nanoparticles. Therefore, they could be useful dose metrics for risk assessment and management.

Systemic immune cell response in rats after pulmonary exposure to manganese-containing particles collected from welding aerosols

Welding fume inhalation affects the immune system of exposed workers. Manganese (Mn) in welding fume may induce immunosuppressive effects. The goal was to determine if Mn in welding fume alters immunity by reducing the number of circulating total leukocytes and specific leukocyte sub-populations. Sprague-Dawley rats were treated by intratracheal instillation (ITI) with either a single dose (2.00 mg/rat) or repeated doses (0.125 or 2.00 mg/rat for 7 weeks) with welding fumes that contained different levels of Mn. Additional rats were treated by ITI once a week for 7 weeks with the two doses of manganese chloride (MnCl₂). Bronchoalveolar lavage was performed to assess lung inflammation. Also, whole blood was recovered, and the number of circulating total leukocytes, as well as specific lymphocyte subsets, was determined by flow cytometry. The welding fume highest in Mn content significantly increased lung inflammation, injury, and production of inflammatory cytokines and chemokines compared to all other treatment groups. In addition, the same group expressed significant decreases in the number of circulating CD4⁺ and CD8⁺ T-lymphocytes after a single exposure, and significant reductions in the number of circulating total lymphocytes, primarily CD4⁺ and CD8⁺ T-lymphocytes, after repeated exposures (compared to control values). Repeated MnCl₂ exposure led to a trend of a reduction (but not statistically significant) in circulating total lymphocytes, attributable to the changes in the CD4⁺ T-lymphocyte population levels. The welding fume with the lower concentration of Mn had no significant effect on the numbers of blood lymphocytes and lymphocyte subsets compared to control values. Evidence from this study indicates that pulmonary exposure to certain welding fumes cause decrements in systemic immune cell populations, specifically circulating T-lymphocytes, and these alterations in immune cell number are not dependent exclusively on Mn, but likely a combination of other metals present in welding fume.

Multiwalled carbon nanotubes induce a fibrogenic response by stimulating reactive oxygen species production, activating NF-κB signaling, and promoting fibroblast-to-myofibroblast transformation

Carbon nanotubes (CNTs) are novel materials with unique electronic and mechanical properties. The extremely small size, fiberlike shape, large surface area, and unique surface chemistry render their distinctive chemical and physical characteristics and raise potential hazards to humans. Several reports have shown that pulmonary exposure to CNTs caused inflammation and lung fibrosis in rodents. The molecular mechanisms that govern CNT lung toxicity remain largely unaddressed. Here, we report that multiwalled carbon nanotubes (MWCNTs) have potent, dose-dependent toxicity on cultured human lung cells (BEAS-2B, A549, and WI38-VA13). Mechanistic analyses were carried out at subtoxic doses (≤20 μg/mL, ≤ 24 h). MWCNTs induced substantial ROS production and mitochondrial damage, implicating oxidative stress in cellular damage by MWCNT. MWCNTs activated the NF-κB signaling pathway in macrophages (RAW264.7) to increase the secretion of a panel of cytokines and chemokines (TNFα, IL-1β, IL-6, IL-10, and MCP1) that promote inflammation. Activation of NF-κB involved rapid degradation of IκBα, nuclear accumulation of NF-κBp65, binding of NF-κB to specific DNA-binding sequences, and transactivation of target gene promoters. Finally, MWCNTs induced the production of profibrogenic growth factors TGFβ1 and PDGF from macrophages that function as paracrine signals to promote the transformation of lung fibroblasts (WI38-VA13) into myofibroblasts, a key step in the development of fibrosis. Our results revealed that MWCNTs elicit multiple and intertwining signaling events involving oxidative damage, inflammatory cytokine production, and myofibroblast transformation, which potentially underlie the toxicity and fibrosis in human lungs by MWCNTs.

Pulmonary exposure of rats to ultrafine titanium dioxide enhances cardiac protein phosphorylation and substance P synthesis in nodose ganglia

The inhalation of engineered nanoparticles stimulates the development of atherosclerosis and impairs vascular function. However, the cardiac effects of inhaled engineered nanoparticles are unknown. Here, we investigate the effects of ultrafine titanium dioxide (UFTiO(2)) on the heart, and we define the possible mechanisms underlying the measured effects. Pulmonary exposure of rats to UFTiO(2) increased the phosphorylation levels of p38 mitogen-activated protein kinase and cardiac troponin I, but not Akt, in the heart and substance P synthesis in nodose ganglia. Circulatory levels of pro-inflammatory cytokines, and blood cell counts and differentials were not significantly changed after pulmonary exposure. Separately, the incubation of cardiac myocytes isolated from naïve adult rat hearts in vitro with UFTiO(2) did not alter the phosphorylation status of the same cardiac proteins. In conclusion, the inhalation of UFTiO(2) enhanced the phosphorylation levels of cardiac proteins. Such responses are likely independent of systemic inflammation, but may involve a lung-neuron-regulated pathway.

Direct effects of carbon nanotubes on dendritic cells induce immune suppression upon pulmonary exposure

Pharyngeal aspiration of single-walled carbon nanotubes (SWCNTs) caused inflammation, pulmonary damage, and an altered cytokine network in the lung. Local inflammatory response in vivo was accompanied by modified systemic immunity as documented by decreased proliferation of splenic T cells. Preincubation of naïve T cells in vitro with SWCNT-treated dendritic cells reduced proliferation of T cells. Our data suggest that in vivo exposure to SWCNT modifies systemic immunity by modulating dendritic cell function.

Short-term inhalation of stainless steel welding fume causes sustained lung toxicity but no tumorigenesis in lung tumor susceptible A/J mice

Debate exists as to whether welding fume is carcinogenic, but epidemiological evidence suggests that welders are an at-risk population for development of lung cancer. Our objective was to expose, by inhalation, lung tumor susceptible (A/J) and resistant C57BL/6J (B6) mice to stainless steel (SS) welding fume containing carcinogenic metals and characterize the lung-inflammatory and tumorigenic response. Male mice were exposed to air or gas metal arc (GMA)-SS welding fume at 40 mg/m(3)×3 h/day for 6 and 10 days. At 1, 4, 7, 10, 14, and 28 days after 10 days of exposure, bronchoalveolar lavage (BAL) was done. Lung cytotoxicity, permeability, inflammatory cytokines, and cell differentials were analyzed. For the lung tumor study, gross tumor counts and histopathological changes were assessed in A/J mice at 78 weeks after 6 and 10 days of exposure. Inhalation of GMA-SS fume caused an early, sustained macrophage and lymphocyte response followed by a gradual neutrophil influx and the magnitudes of these differed between the mouse strains. Monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-2 (MIP-2), and tumor necrosis factor-α (TNF-α) were increased in both strains while the B6 also had increased interleukin-6 (IL-6) protein. BAL measures of cytotoxicity and damage were similar between the strains and significantly increased at all time points. Histopathology and tumorigenesis were unremarkable at 78 weeks. In conclusion, GMA-SS welding fume induced a significant and sustained inflammatory response in both mouse strains with no recovery by 28 days. Under our exposure conditions, GMA-SS exposure resulted in no significant tumor development in A/J mice.

Blood gene expression profiling detects silica exposure and toxicity

Blood gene expression profiling was investigated as a minimally invasive surrogate approach to detect silica exposure and resulting pulmonary toxicity. Rats were exposed by inhalation to crystalline silica (15 mg/m³, 6 h/day, 5 days), and pulmonary damage and blood gene expression profiles were determined after latency periods (0-16 weeks). Silica exposure resulted in pulmonary toxicity as evidenced by histological and biochemical changes in the lungs. The number of significantly differentially expressed genes in the blood, identified by microarray analysis, correlated with the severity of silica-induced pulmonary toxicity. Functional analysis of the differentially expressed genes identified activation of inflammatory response as the major biological signal. Induction of pulmonary inflammation, as suggested by the blood gene expression data, was supported by significant increases in the number of macrophages and infiltrating neutrophils as well as the activity of pro-inflammatory chemokines observed in the lungs of the silica-exposed rats. A gene expression signature developed using the blood gene expression data predicted the exposure of rats to lower, minimally toxic and nontoxic concentrations of silica. Taken together, our findings suggest the potential application of peripheral blood gene expression profiling as a minimally invasive surrogate approach to detect pulmonary toxicity induced by silica in the rat. However, further research is required to determine the potential application of our findings specifically to monitor human exposure to silica and the resulting pulmonary effects.

Single pre-exposure to a high dose of zymosan enhances lung defense mechanisms and accelerates the pulmonary clearance of a bacterial pathogen in rats

The present study examines the effects of pre-exposure to zymosan (a 1 --> 3-beta-glucan from baker yeast) on lung defense against bacterial infection. Rats received a single dose of zymosan A (0.6, 1.2, or 2.5 mg/kg body weight [bw]) or vehicle control (saline) via intratracheal instillation 3 days prior to intratracheal inoculation with 5 x 10(5) Listeria monocytogenes. Left lungs were homogenized and cultured to assess bacterial clearance, and bronchoalveolar lavage was performed on the right lungs to monitor lung inflammation and injury. Prior to bacterial infection, zymosan exposure resulted in elevated inflammation and oxidant production in the lungs. Zymosan treatment followed by infection led to an accelerated pulmonary clearance of bacteria when compared to the saline control group in a dose-dependent fashion. In addition, lower levels of injury and inflammation were associated with the enhanced bacteria clearance observed in zymosan-infected rats. Our findings suggest that zymosan exposure may enhance the lung immune response by activating alveolar macrophages prior to infection, and stimulating T cells involved in the adaptive immune response early after infection, thus resulting in a heightened pulmonary immune response.

Titanium dioxide (TiO2) nanoparticles induce JB6 cell apoptosis through activation of the caspase-8/Bid and mitochondrial pathways

Titanium dioxide (TiO(2)), a commercially important material, is used in a wide variety of products. Although TiO(2) is generally regarded as nontoxic, the cytotoxicity, pathogenicity, and carcinogenicity of TiO(2) nanoparticles have been recently recognized. The present study investigated TiO(2) nanoparticle-induced cell apoptosis and molecular mechanisms involved in this process in a mouse epidermal (JB6) cell line. Using the 3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay, TiO(2) nanoparticles were found to exhibit higher cytotoxicity than fine particles. YO-PRO-1 iodide (YP) staining demonstrated that both TiO(2) nanoparticles and fine particles induced cell death through apoptosis. The signaling pathways involved in TiO(2) particle-induced apoptosis were investigated. Western-blot analysis showed an activation of caspase-8, Bid, BAX, and caspase-3 and a decrease of Bcl-2 in JB6 cells treated with TiO(2) particles. Time-dependent poly(ADP)ribose polymerase (PARP) cleavage induced by TiO(2) nanoparticles was observed. TiO(2) particles also induced cytochrome c release from mitochondria to cytosol. Further studies demonstrated that TiO(2) nanoparticles induced significant changes in mitochondrial membrane permeability, suggesting the involvement of mitochondria in the apoptotic process. In conclusion, evidence indicated that TiO(2) nanoparticles exhibit higher cytotoxicity and apoptotic induction compared to fine particles in JB6 cells. Caspase-8/Bid and mitochondrial signaling may play a major role in TiO(2) nanoparticle-induced apoptosis involving the intrinsic mitochondrial pathway. Unraveling the complex mechanisms associated with these events may provide further insights into TiO(2) nanoparticle-induced pathogenicity and potential to induce carcinogenicity.

Pulmonary Exposure to 1→3-β-Glucan Alters Adaptive Immune Responses in Rats

1 --> 3-beta-glucans have been associated with increased pulmonary inflammation in fungal-related indoor air problems. Epidemiological studies have shown a correlation between increases in T-cell proliferation and decreases in CD4+/CD8+ ratio after exposure to fungi. The objective of the present investigation was to determine the mechanisms by which 1 --> 3-beta-glucans affect immune responses using an animal model. Rats received a single dose of zymosan A (2.5 mg/kg body weight) via intratracheal instillation (IT) and were euthanized on days 1, 4, 6, 8, and 10 post IT. Bronchoalveolar lavage was performed at each time point post-IT. Inflammation and lung injury were assessed by measuring neutrophil infiltration into bronchoalveolar lavage fluid (BALF) and by measuring albumin and lactate dehydrogenase levels in BALF, respectively. Alveolar macrophage activation was determined by chemiluminescence. Immune response was characterized via immunophenotyping of bronchoalveolar lavage cells and lymphocytes isolated from the lung-associated lymph nodes. Upon challenge with zymosan, rats exhibited increased inflammation and injury at early time points (days 1 and 4) post IT exposure. Although elevations in neutrophil infiltration and chemiluminescence had returned to control levels on day 4, lymphocytes recovered from lung-associated lymph nodes continued to proliferate and reached a maximum on day 6. The CD4+/CD8+ T cell ratio from lymph nodes was lower in zymosan-treated rats than in control rats. Zymosan treatment increased tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10, and IL-12p70 secretion in BALF on day 1. In summary, rats exposed to zymosan had an increase in acute inflammation, and the altered lymphocyte profiles were consistent with the findings of epidemiology studies.

Pulmonary inflammation and tumor induction in lung tumor susceptible A/J and resistant C57BL/6J mice exposed to welding fume

Background

Welding fume has been categorized as "possibly carcinogenic" to humans. Our objectives were to characterize the lung response to carcinogenic and non-carcinogenic metal-containing welding fumes and to determine if these fumes caused increased lung tumorigenicity in A/J mice, a lung tumor susceptible strain. We exposed male A/J and C57BL/6J, a lung tumor resistant strain, by pharyngeal aspiration four times (once every 3 days) to 85 μg of gas metal arc-mild steel (GMA-MS), GMA-stainless steel (SS), or manual metal arc-SS (MMA-SS) fume, or to 25.5 μg soluble hexavalent chromium (S-Cr). Shams were exposed to saline vehicle. Bronchoalveolar lavage (BAL) was done at 2, 7, and 28 days post-exposure. For the lung tumor study, gross tumor counts and histopathological changes were assessed in A/J mice at 48 and 78 weeks post-exposure.

Results

BAL revealed notable strain-dependent differences with regards to the degree and resolution of the inflammatory response after exposure to the fumes. At 48 weeks, carcinogenic metal-containing GMA-SS fume caused the greatest increase in tumor multiplicity and incidence, but this was not different from sham. By 78 weeks, tumor incidence in the GMA-SS group versus sham approached significance (p = 0.057). A significant increase in perivascular/peribronchial lymphoid infiltrates for the GMA-SS group versus sham and an increased persistence of this fume in lung cells compared to the other welding fumes was found.

Conclusion

The increased persistence of GMA-SS fume in combination with its metal composition may trigger a chronic, but mild, inflammatory state in the lung possibly enhancing tumorigenesis in this susceptible mouse strain.

PGJ2 inhibition of LPS-induced inflammatory mediator expression from rat alveolar macrophages

Studies suggested that 15-deoxy-delta-(12,14)-prostaglandin J2 (PGJ2) may exert anti-inflammatory effects, including in the lung. Thus, in vitro studies were conducted to (1) investigate whether PGJ2 inhibited the production of inflammatory mediators from lipopolysaccharide (LPS)-exposed primary rat alveolar macrophages (AM), and (2) investigate possible mechanisms underlying PGJ2-mediated inhibition of inflammatory mediator production. These studies determined that PGJ2 inhibited LPS-induced nitric oxide (NO) production in a concentration- and time-dependent manner. PGJ2-mediated inhibition of NO, as well as of tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2), was also determined to be dependent on the time of addition of PGJ2 relative to LPS, and suggested the PGJ2 inhibitory mechanism is an early event. PGJ2 was shown not to interfere with binding or internalization of LPS by AM, indicating this was not responsible for PGJ2 inhibitory effects. Another possible mechanism underlying PGJ2-mediated inhibition was via peroxisome proliferator-activated receptor-gamma (PPAR-gamma). However, biochemical studies suggested that PGJ2-mediated inhibition was not occurring through PPAR-gamma dependent mechanism, and molecular studies further established that both LPS and PGJ2 decrease PPAR-gamma mRNA expression. A third possible mechanism underlying PGJ2-mediated inhibition was by alteration of nuclear factor (NF)-kappaB. Molecular studies confirmed that LPS stimulated NF-kappaB mRNA expression, and PGJ2 reduced this stimulation, which is consistent with PGJ2 effect on LPS-induced production of NO, TNF-alpha and MIP-2. Thus, data in this study established that PGJ2 inhibited LPS-induced inflammatory mediator production in rat AM, and this inhibition is mediated, at least in part, by reducing the expression of NF-kappaB mRNA.

A comparison of the pulmonary inflammatory potential of different components of yeast cell wall

1-->3-Beta-glucan has been associated with pulmonary inflammation induced by exposure to fungal or yeast cell wall dust. 1-->3-Beta-glucan is the major cell wall component of yeast or fungi. However, the yeast cell wall contains several other components besides 1-->3-beta-glucans, such as mannan and chitin. Few studies evaluated the contribution of these other cell wall components to pulmonary inflammation. The present study compares a crude particulate yeast cell wall preparation (zymosan A) to purified yeast glucan, purified yeast glucan mannan, or purified yeast glucan chitin particles for their potency to induce mouse pulmonary inflammation after in vivo exposure. Mannan is the second most abundant polysaccharide in the yeast cell wall, whereas chitin content is a minor component. The results show that pulmonary injury is mediated by both chitin and 1-->3-beta-glucan and to a lesser degree by mannan. There is also evidence that zymosan is more potent than purified 1-->3-beta-glucan alone. Evidence indicates that 1-->3-beta-glucan is the major inflammatory component in yeast and fungal cell walls.

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.

Effect of stainless steel manual metal arc welding fume on free radical production, DNA damage, and apoptosis induction

Questions exist concerning the potential carcinogenic effects after welding fume exposure. Welding processes that use stainless steel (SS) materials can produce fumes that may contain metals (e.g., Cr, Ni) known to be carcinogenic to humans. The objective was to determine the effect of in vitro and in vivo welding fume treatment on free radical generation, DNA damage, cytotoxicity and apoptosis induction, all factors possibly involved with the pathogenesis of lung cancer. SS welding fume was collected during manual metal arc welding (MMA). Elemental analysis indicated that the MMA-SS sample was highly soluble in water, and a majority (87%) of the soluble metal was Cr. Using electron spin resonance (ESR), the SS welding fume had the ability to produce the biologically reactive hydroxyl radical (*OH), likely as a result of the reduction of Cr(VI) to Cr(V). In vitro treatment with the MMA-SS sample caused a concentration-dependent increase in DNA damage and lung macrophage death. In addition, a time-dependent increase in the number of apoptotic cells in lung tissue was observed after in vivo treatment with the welding fume. In summary, a soluble MMA-SS welding fume was found to generate reactive oxygen species and cause DNA damage, lung macrophage cytotoxicity and in vivo lung cell apoptosis. These responses have been shown to be involved in various toxicological and carcinogenic processes. The effects observed appear to be related to the soluble component of the MMA-SS sample that is predominately Cr. A more comprehensive in vivo animal study is ongoing in the laboratory that is continuing these experiments to try to elucidate the potential mechanisms that may be involved with welding fume-induced lung disease.

Cardiovascular effects of pulmonary exposure to single-wall carbon nanotubes

BACKGROUND

Engineered nanosized materials, such as single-wall carbon nanotubes (SWCNT), are emerging as technologically important in different industries.

OBJECTIVE

The unique physical characteristics and the pulmonary toxicity of SWCNTs raised concerns that respiratory exposure to these materials may be associated with cardiovascular adverse effects.

METHODS

In these studies we evaluated aortic mitochondrial alterations by oxidative stress assays, including quantitative polymerase chain reaction of mitochondrial (mt) DNA and plaque formation by morphometric analysis in mice exposed to SWCNTs.

RESULTS

A single intrapharyngeal instillation of SWCNTs induced activation of heme oxygenase-1 (HO-1), a marker of oxidative insults, in lung, aorta, and heart tissue in HO-1 reporter transgenic mice. Furthermore, we found that C57BL/6 mice, exposed to SWCNT (10 and 40 mug/mouse), developed aortic mtDNA damage at 7, 28, and 60 days after exposure. mtDNA damage was accompanied by changes in aortic mitochondrial glutathione and protein carbonyl levels. Because these modifications have been related to cardiovascular diseases, we evaluated whether repeated exposure to SWCNTs (20 mug/mouse once every other week for 8 weeks) stimulates the progression of atherosclerosis in ApoE(-/-) transgenic mice. Although SWCNT exposure did not modify the lipid profiles of these mice, it resulted in accelerated plaque formation in ApoE(-/-) mice fed an atherogenic diet. Plaque areas in the aortas, measured by the en face method, and in the brachiocephalic arteries, measured histopathologically, were significantly increased in the SWCNT-treated mice. This response was accompanied by increased mtDNA damage but not inflammation.

CONCLUSIONS

Taken together, the findings are of sufficient significance to warrant further studies to evaluate the systemic effects of SWCNT under workplace or environmental exposure paradigms.

Welding fume exposure and associated inflammatory and hyperplastic changes in the lungs of tumor susceptible a/j mice

It has been suggested that welding fume (WF) exposure increases lung cancer risk in welders. Epidemiology studies have failed to conclude that WF alone causes lung cancer and animal studies are lacking. We examined the course of inflammation, damage, and repair in the lungs of A/J mice, a lung tumor susceptible strain, caused by stainless steel WF. Mice were exposed by pharyngeal aspiration to 40 mg/kg of WF, silica, or saline. Bronchoalveolar lavage (BAL) was performed 24 hours, 1 and 16 weeks to assess lung injury and inflammation and histopathology was done 1, 8, 16, 24, and 48 weeks postexposure. Both exposures increased inflammatory cells, lactate dehydrogenase and albumin at 24 hr and 1 week. At 16 weeks, these parameters remained elevated in silica-exposed but not WF-exposed mice. Histopathologic evaluation at 1 week indicated that WF induced bronchiolar epithelial hyperplasia with associated cellular atypia, alveolar bronchiolo-alveolar hyperplasia (BAH) in peribronchiolar alveoli, and peribronchiolar lymphogranulomatous inflammation. Persistent changes included foci of histiocytic inflammation, fibrosis, atypical bronchiolar epithelial cells, and bronchiolar BAH. The principle changes in silica-exposed mice were histiocytic and suppurative inflammation, fibrosis, and alveolar BAH. Our findings that WF causes persistent bronchiolar and peribronchiolar epithelial changes, suggest a need for studies of bronchiolar changes after WF exposure.

Phosphatidylinositol 3-kinase regulates Ca2+ signaling in pancreatic acinar cells through inhibition of sarco(endo)plasmic reticulum Ca2+-ATPase

Calcium is a key mediator of hormone-induced enzyme secretion in pancreatic acinar cells. At the same time, abnormal Ca(2+) responses are associated with pancreatitis. We have recently shown that inhibition of phosphatidylinositol 3-kinase (PI3-kinase) by LY-294002 and wortmannin, as well as genetic deletion of PI3-kinase-gamma, regulates Ca(2+) responses and the Ca(2+)-sensitive trypsinogen activation in pancreatic acinar cells. The present study sought to determine the mechanisms of PI3-kinase involvement in Ca(2+) responses induced in these cells by CCK and carbachol. The PI3-kinase inhibitors inhibited both Ca(2+) influx and mobilization from intracellular stores induced by stimulation of acini with physiological and pathological concentrations of CCK, as well as with carbachol. PI3-kinase inhibition facilitated the decay of cytosolic free Ca(2+) concentration ([Ca(2+)](i)) oscillations observed in individual acinar cells. The PI3-kinase inhibitors decreased neither CCK-induced inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)] production nor Ins(1,4,5)P(3)-induced Ca(2+) mobilization, suggesting that the effect of PI3-kinase inhibition is not through Ins(1,4,5)P(3) or Ins(1,4,5)P(3) receptors. PI3-kinase inhibition did not affect Ca(2+) mobilization induced by thapsigargin, a specific inhibitor of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA). Moreover, SERCA blockade with thapsigargin abolished the effects of pharmacological and genetic PI3-kinase inhibition on [Ca(2+)](i) signals, suggesting SERCA as a downstream target of PI3-kinase. Both pharmacological PI3-kinase inhibition and genetic deletion of PI3-kinase-gamma increased the amount of Ca(2+) in intracellular stores during CCK stimulation. Finally, addition of the PI3-kinase product phosphatidylinositol 3,4,5-trisphosphate to permeabilized acini significantly attenuated Ca(2+) reloading into the endoplasmic reticulum. The results indicate that PI3-kinase regulates Ca(2+) signaling in pancreatic acinar cells through its inhibitory effect on SERCA.

Partially opened triple helix is the biologically active conformation of 1-->3-beta-glucans that induces pulmonary inflammation in rats

1-->3-beta-Glucans produce pulmonary inflammation in rats and are commonly found in indoor air dust samples. Conformation is an important factor determining the biological activity of 1-->3-beta-glucans. The partially opened triple-helix conformation induced by NaOH treatment and the annealed triple-helix conformation have been identified by fluorescence resonance energy transfer spectroscopy in our previous study. The objective of this study was to examine the role of these conformations of 1-->3-beta-glucans in the induction of pulmonary inflammation in rats. A partially opened triple-helix conformation of the known inflammatory 1-->3-beta-glucan zymosan was prepared by treating zymosan with NaOH followed by neutralization and dialysis. The annealed triple-helix conformation was prepared by allowing the partially opened triple-helix conformation to anneal for 9 d at room temperature. Rats were exposed to fresh or annealed NaOH-treated zymosan via intratracheal instillation. The results show that the zymosan-induced pulmonary inflammatory responses were significantly reduced after the 9-d annealing period, which suggests that this inflammatory response was dependent on the conformation of zymosan. Freezing NaOH-treated zymosan (for 7 d) inhibited the annealing process. Exposure of rats to thawed preparations of zymosan resulted in the same inflammatory responses as the freshly prepared partially opened triple-helix zymosan. In contrast, the potency of untreated zymosan did not change significantly following a 7-d annealing period, indicating that annealing occurs only after the conformation has been modified by NaOH treatment. This study indicates that the partially opened triple helix of 1-->3-beta-glucans is more active than the closed conformation in inducing pulmonary inflammation in rats.

Exposure to particulate 1-->3-beta-glucans induces greater pulmonary toxicity than soluble 1-->3-beta-glucans in rats

1-->3-beta-Glucans, derived from the inner cell wall of yeasts and fungi, are commonly found in indoor air dust samples and have been implicated in organic dust toxic syndrome. In a previous study, it was reported that 1-->3-beta-glucan (zymosan A) induced acute pulmonary inflammation in rats. This study investigates which form of 1-->3-beta-glucans, particulate or soluble, is more potent in inducing pulmonary inflammation. Zymosan A was suspended in 0.25 N NaOH for 30 min, neutralized, dialyzed for 2 d using deionized water, and particulate and soluble fractions were collected. Male Sprague-Dawley rats were exposed via intratracheal instillation to NaOH-soluble or NaOH-insoluble zymosan A. At 18 h postexposure, various indicators of pulmonary response were monitored, including indicators of lung damage, such as serum albumin concentration and lactate dehydrogenase (LDH) activity in acellular bronchoalveolar lavage fluid. Inflammation was characterized by an increase in lavageable polymorphonuclear leukocytes (PMN). Pulmonary irritation (breathing frequency increase) and oxidant production (nitric oxide and chemiluminescence, CL) were also monitored. Exposure to the particulate form of NaOH-treated zymosan produced a significant increase in all these indicators. In contrast, rats exposed to the NaOH-soluble fraction were not markedly affected except for LDH, PMN, and CL. However, these increases were significantly less than with exposure to NaOH-insoluble zymosan. Therefore, results demonstrate that particulate zymosan A is more potent in inducing pulmonary inflammation and damage in rats than the soluble form of this beta-glucan.

Outsourcing and benchmarking in a rural public hospital: does economic theory provide the complete answer?

INTRODUCTION

The ideology and pronouncements of the Australian Government in introducing 'competitive neutrality' to the public sector has improved efficiency and resource usage. In the health sector, the Human Services Department directed that non-clinical and clinical areas be market tested through benchmarking services against the private sector, with the possibility of outsourcing. These services included car parking, computing, laundry, engineering, cleaning, catering, medical imaging (radiology), pathology, pharmacy, allied health and general practice. Managers, when they choose between outsourcing, and internal servicing and production, would thus ideally base their decision on economic principles. Williamson's transaction cost theory studies the governance mechanisms that can be used to achieve economic efficiency and proposes that the optimal organisation structure is that which minimises transaction costs or the costs of exchange. Williamson proposes that four variables will affect such costs, namely: (i) frequency of exchange; (ii) asset specificity; (iii) environmental uncertainty; and (iv) threat of opportunism. This paper provides evidence from a rural public hospital and examines whether Williamson's transaction cost theory is applicable.

METHOD

Case study research operates within the interpretivism paradigm and is used in this research to uncover why the outsourcing decision was made. Such research aims to study real-life experiences by examining the way people think and act and, in contrast to positivism, allows the interviewer to participate to better understand the details and features of the experiences. In the present research, individual interviews were conducted with managers of the hospital and owners and staff of the vendor organisations using semi- and unstructured questions to ascertain the extent of, and processes used in, outsourcing specific functional areas, and areas that were not outsourced.

RESULTS

Pathology, radiology, dental technician services and lawn mowing were outsourced while food services was retained internally. The outsourcing of radiology was due to the hospital being unable (or unwilling) to finance new equipment and the problematical relationship between the existing radiologists, and hospital management and staff. Outsourcing resulted in increased staff morale, upgraded capital equipment and improved services. The outsourcing of pathology and dental technical services aimed to increase labour flexibility, thereby decreasing costs. Additional drivers in pathology were the changing nature of the funding arrangements rendering it profitable for the private sector to move into the provision of pathology and the increasing power of the medical scientists' union. The outsourcing of lawn mowing was simply to reduce costs. Food services was not outsourced because there was a lack of evidence that costs could be reduced. In addition, the existing relationships with food services staff were regarded as important because they had previously made immense changes to work practices, reduced staff numbers and decreased costs.

CONCLUSION

Transaction costs are important when analysing how managers make the outsourcing decision, but the evidence from this case is that not all transaction costs are included in the decision, and that such costs are more complex than can be included in the type of analysis often undertaken by decision-makers. Taking into account Williamson's variables, the research shows that the outsourcing of services did not comply solely with the levels of transaction frequency or the requirement of asset specificity. In addition, opportunistic behaviour was evident on the part of all parties and was used in some cases as a reason for outsourcing, and in others to sway the decision to the manager's predisposed choice. A variety of arrangements were used to reduce environmental uncertainty, such as the transfer of staff to the contractor and the use of long-term contracts. Indeed the case shows that relationships between the hospital, its staff and the vendor are an important consideration that may not always be factored into an analysis that relies solely on transaction costs.

Modified endotoxin responses in rats pretreated with 1-->3-beta-glucan (zymosan A)

The present study investigates whether 1-->3-beta-glucans (zymosan particles) modify the pulmonary response of rats to endotoxin (lipopolysaccharide, LPS). Initial experiments were conducted to establish appropriate doses of LPS and regimens for exposure to zymosan and LPS. Interaction between zymosan and LPS exposures was determined to be the deviation from the sum of the individual effects of these agents. Treatment with zymosan on Day 1 and LPS on Day 2 modified several indices of pulmonary responsiveness, including tumor necrosis factor-alpha, albumin, and lactate dehydrogenase activity (LDH) in first acellular lavage fluid as well as the levels of chemiluminescence (CL), NO-dependent CL, and nitric oxide production in cultured lavaged alveolar macrophage cells determined 1 day after exposure. No significant deviation from additivity was found for breathing rate increase and polymorphonuclear leukocytes infiltration. Simultaneous administration of zymosan and LPS or administration of LPS before zymosan did not change these indices of pulmonary responsiveness. These data suggest that the inhibitory effect of 1-->3-beta-glucans on pulmonary responsiveness to endotoxin exposure was apparent only when rats were pretreated with 1-->3-beta-glucan. These results suggest that complex interaction of components may exist in exposure to organic dusts. Therefore, hazard may not be defined by measuring endotoxin or 1-->3-beta-glucans alone.

Acute inflammation and recovery in rats after intratracheal instillation of a 1-->3-beta-glucan (zymosan A)

Although endotoxin is a known potent stimulant of inflammatory responses, the magnitude of pulmonary response following exposure to various organic dusts does not always correlate with endotoxin content of the dusts alone. Other components, such as 1-->3-beta-glucans, derived from the inner cell wall of yeasts and fungi, have been implicated in organic dust toxic syndrome. However, animal studies report conflicting results concerning the inflammatory potency of 1-->3-beta-glucan. In this experiment, the pulmonary reaction of rats to 1-->3-beta-glucan (zymosan A) exposure was assessed. Male Sprague-Dawley rats were exposed via intratracheal instillation (IT) to zymosan A (dose range 0-5 mg/kg body weight). Rats were sacrificed 1-7 d postexposure and the following pulmonary responses were monitored: (1) breathing frequency, (2) differential cell counts of hronchoalveolar lavage (BAL) cells, (3) chemiluminescence (CL) as a measure of alveolar macrophage activation, (4) nitric oxide production by alveolar macrophages, (5) albumin levels, and (6) lactate dehydrogenase (LDH) activity in the first acellular lavage fluid. Upon challenge with zymosan A, rats exhibited a dose-dependent pulmonary response at 1 d post IT that was significantly higher than the control level at a dose of 1-2.5 mg/kg body weight for each of these pulmonary parameters. Post-IT enhancement of breathing frequencies and polymorphonuclear leukocytes (PMN) obtained by BAL both correlated very well with zymosan A concentration (r = .95 and .99, respectively). Elevation of albumin levels and LDH activity of the acellular BAL fluid also correlated (r = .80) with the dose of zymosan. The recovery from a single intratracheal administration of zymosan A (2.5 mg/kg body weight) was monitored over 7 d. PMN and CL showed significant recovery from d 1 level by 3 d postexposure. Breathing frequencies and nitric oxide production showed significant recovery from d 1 level by 4 d postexposure. A good correlation (r2= .8) between recovery of PMN in BAL, CL, or nitric oxide production and the days postexposure was observed.

Rapid protein kinase D translocation in response to G protein-coupled receptor activation. Dependence on protein kinase C

Protein kinase D (PKD)/protein kinase C (PKC) mu is a serine/threonine protein kinase that can be activated by physiological stimuli like growth factors, antigen-receptor engagement and G protein-coupled receptor (GPCR) agonists via a phosphorylation-dependent mechanism that requires PKC activity. In order to investigate the dynamic mechanisms associated with GPCR signaling, the intracellular translocation of a green fluorescent protein-tagged PKD was analyzed by real-time visualization in fibroblasts and epithelial cells stimulated with bombesin, a GPCR agonist. We found that bombesin induced a rapidly reversible plasma membrane translocation of green fluorescent protein-tagged PKD, an event that can be divided into two distinct mechanistic steps. The first step, which is exclusively mediated by the cysteine-rich domain in the N terminus of PKD, involved its translocation from the cytosol to the plasma membrane. The second step, i.e. the rapid reverse translocation of PKD from the plasma membrane to the cytosol, required its catalytic domain and surprisingly PKC activity. These findings provide evidence for a novel mechanism by which PKC coordinates the translocation and activation of PKD in response to bombesin-induced GPCR activation.

Agonists of proteinase-activated receptor 1 induce plasma extravasation by a neurogenic mechanism

Thrombin, generated in the circulation during injury, cleaves proteinase-activated receptor 1 (PAR1) to stimulate plasma extravasation and granulocyte infiltration. However, the mechanism of thrombin-induced inflammation in intact tissues is unknown. We hypothesized that thrombin cleaves PAR1 on sensory nerves to release substance P (SP), which interacts with the neurokinin 1 receptor (NK1R) on endothelial cells to cause plasma extravasation. PAR1 was detected in small diameter neurons known to contain SP in rat dorsal root ganglia by immunohistochemistry and in situ hybridization. Thrombin and the PAR1 agonist TFLLR-NH(2) (TF-NH(2)) increased [Ca(2+)](i) >50% of cultured neurons (EC(50)s 24 mu ml(-1) and 1.9 microM, respectively), assessed using Fura-2 AM. The PAR1 agonist completely desensitized responses to thrombin, indicating that thrombin stimulates neurons through PAR1. Injection of TF-NH(2) into the rat paw stimulated a marked and sustained oedema. An NK1R antagonist and ablation of sensory nerves with capsaicin inhibited oedema by 44% at 1 h and completely by 5 h. In wild-type but not PAR1(-/-) mice, TF-NH(2) stimulated Evans blue extravasation in the bladder, oesophagus, stomach, intestine and pancreas by 2 - 8 fold. Extravasation in the bladder, oesophagus and stomach was abolished by an NK1R antagonist. Thus, thrombin cleaves PAR1 on primary spinal afferent neurons to release SP, which activates the NK1R on endothelial cells to stimulate gap formation, extravasation of plasma proteins, and oedema. In intact tissues, neurogenic mechanisms are predominantly responsible for PAR1-induced oedema.

Agonist-dependent immobilization of chimeric bombesin/GRP receptors: dependence on c-Src activity and dissociation from internalization

G-protein-coupled receptors (GPCRs) are membrane proteins that exhibit a decreased mobile fraction compared to a freely mobile plasma membrane protein. Recently, interest has focused on proteins other than heterotrimeric G-proteins that interact with GPCRs as scaffolding structures that affect receptor signal transduction. In order to investigate the physical state of receptors before and after agonist, we used fluorescence recovery after photobleaching of the bombesin/gastrin-releasing peptide (GRP) receptor fused to the intrinsically fluorescent green fluorescent protein (GFP-GRP receptor) expressed in KNRK cells to measure both the fraction of mobile receptors and their diffusion rate before and after agonist stimulation. In live cells at 37 degrees C, addition of GRP (100 nM) caused a rapid decrease in GFP-GRP receptor mobile fraction from 0.8 +/- 0.1 to 0.49 +/- 0.05, which was independent of endocytosis. Concurrently, the remaining mobile GFP-GRPreceptors showed an increase in the diffusion rate with the half-time of fluorescent recovery, tau(1/2) = 46 +/- 7 s for untreated cells, decreasing to tau(1/2) = 30 +/- 6 s for cells treated with GRP. Prior treatment with the Src-specific inhibitor PP-2 (10 microM) blocked GFP-GRP receptor immobilization while treatment with the inactive analog PP-3 (10 microM) did not affect receptor immobilization. These data suggest that agonist-bound GPCR have increased plasma membrane diffusion rates but an increased affinity for immobilization into a multiprotein complex that is mediated by Src activity.

Molecular mechanism of tumor necrosis factor-alpha production in 1-->3-beta-glucan (zymosan)-activated macrophages

The molecular details of 1-->3-beta-glucans, a fungal cell wall component, induced inflammatory responses are not well understood. In the present study, we conducted a systematic analysis of the molecular events leading to tumor necrosis factor (TNF)-alpha production after glucan stimulation of macrophages. We demonstrated that activation of nuclear factor kappaB (NF-kappaB) is essential in zymosan A (a source of 1-->3-beta-glucans)-induced TNF-alpha production in macrophages (RAW264.7 cells). Zymosan A-induced TNF-alpha protein production was associated with an increase in the TNF-alpha gene promoter activity. Activation of the TNF-alpha gene promoter was dependent on activation of NF-kappaB. Time course studies indicated that DNA binding activity of NF-kappaB preceded TNF-alpha promoter activity. Inhibition of NF-kappaB activation led to a dramatic reduction in both TNF-alpha promoter activity and TNF-alpha protein production in the response to zymosan A. Mutation of a major NF-kappaB binding site (kappa3) in the gene promoter resulted in a significant decrease in the induction of the gene promoter by zymosan A, while mutation of Egr or CRE sites failed to inhibit the response to zymosan. Together, these results strongly suggest that NF-kappaB is involved in signal transduction of 1-->3-beta-glucans-induced TNF-alpha expression.

Activation of mitogen-activated protein kinase p38 and extracellular signal-regulated kinase is involved in glass fiber-induced tumor necrosis factor-alpha production in macrophages

In a previous study, we demonstrated that the length of glass fibers was a critical determinant of fiber potency in induction of tumor necrosis factor (TNF)-alpha and that activation of NF-kappaB was an important factor in this response. In the present study, we analyzed the role of mitogen-activated protein (MAP) kinases in the induction of TNF-alpha by glass fibers. Glass fibers induced phosphorylation of MAP kinases, p38, and ERK in primary rat alveolar macrophages, and this phosphorylation was associated with TNF-alpha gene expression. Long fibers were more potent than short fibers in activation of MAP kinases. Results from mechanistic analysis support that MAP kinases activate transcription factor c-Jun. The activated c-Jun acts on the TNF-alpha gene promoter through two binding sites, the cyclic AMP response element and the activator protein 1-binding site. These results suggest that in addition to the NF-kappaB pathway for TNF-alpha production, glass fibers are able to activate c-Jun through MAP kinase pathways that lead to induction of TNF-alpha expression.

Dorsal ulnar cutaneous nerve conduction studies in an asymptomatic population

OBJECTIVES

To establish the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve under controlled temperature and settings.

DESIGN

Dorsal ulnar cutaneous nerve conduction studies were performed with a bar electrode between the fourth and fifth metacarpals. The nerve was stimulated at 8 and 10cm from the active electrode. The temperature of the limbs under study was kept at 32 degrees C to 35 degrees C.

PARTICIPANTS

Fifty-four arms of 27 subjects were studied.

RESULTS

Results showed that distal sensory latencies were normally distributed. The average distal sensory latencies at 8cm and 10cm were 1.84 +/- .20msec and 2.09 +/- .21msec, respectively, with average amplitudes of 26.5 +/- 9.7microV and 23.5 +/- 8.8microV. Comparison with a previously reported study in which the limb temperature was not controlled showed a statistically significant difference.

CONCLUSION

It is important to use standardized technique and to measure and maintain optimal temperature of the arm under study to prevent erroneous results and misdiagnosis.

Observation of a partially opened triple-helix conformation in 1-->3-beta-glucan by fluorescence resonance energy transfer spectroscopy

This study used fluorescence resonance energy transfer (FRET) spectroscopy as an indirect method to investigate the effect of NaOH treatment on the conformation of a triple-helix (1-->3)-beta-D-glucan and then evaluated the effect of conformation on biological activity. Previous studies have suggested that treatment of the triple-helix glucans with NaOH produces single-helix conformers. FRET spectra of the triple-helix glucan, laminarin, doubly labeled with 1-aminopyrene as donor probe and fluorescein-5-isothiocyanate as acceptor probe attached at the reducing end, showed that a partially opened triple-helix conformer was formed on treatment with NaOH. Increasing degrees of strand opening was associated with increasing concentrations of NaOH. Based on these observations we propose that a partially opened triple-helix rather than a single helix, is formed by treating the triple-helix glucans with NaOH. After neutralizing the NaOH, changes in FRET indicated that the partially opened conformer gradually reverts to the triple-helix over 8 days. Laminarian was stabilized at different degrees of partial opening and its biological activity examined using the Limulus amebocyte lysate assay and nitric oxide production by alveolar macrophage. Both Limulus amebocyte lysate activity and nitric oxide production were related to the degree of opening of the triple-helix. Partially open conformers were more biologically active than the intact triple-helix.

Mechanical activation of dorsal root ganglion cells in vitro: comparison with capsaicin and modulation by kappa-opioids

The aim of this study was to characterize plasma membrane pathways involved in the intracellular calcium ([Ca(2+)](i)) response of small DRG neurons to mechanical stimulation and the modulation of these pathways by kappa-opioids. [Ca(2+)](i) responses were measured by fluorescence video microscopy of Fura-2 labeled lumbosacral DRG neurons obtained from adult rats in short-term primary culture. Transient focal mechanical stimulation of the soma, or brief superfusion with 300 nM capsaicin, resulted to [Ca(2+)](i) increases which were abolished in Ca(2+)-free solution, but unaffected by lanthanum (25 microM) or tetrodotoxin (10(-6) M). 156 out of 465 neurons tested (34%) showed mechanosensitivity while 55 out of 118 neurons (47%) were capsaicin-sensitive. Ninty percent of capsaicin-sensitive neurons were mechanosensitive. Gadolinium (Gd(3+); 250 microM) and amiloride (100 microM) abolished the [Ca(2+)](i) transient in response to mechanical stimulation, but had no effect on capsaicin-induced [Ca(2+)](i) transients. The kappa-opioid agonists U50,488 and fedotozine showed a dose-dependent inhibition of mechanically stimulated [Ca(2+)](i) transients but had little effect on capsaicin-induced [Ca(2+)](i) transients. The inhibitory effect of U50,488 was abolished by the kappa-opioid antagonist nor-Binaltorphimine dihydrochloride (nor-BNI; 100 nM), and by high concentrations of naloxone (30-100 nM), but not by low concentrations of naloxone (3 nM). We conclude that mechanically induced [Ca(2+)](i) transients in small diameter DRG somas are mediated by influx of Ca(2+) through a Gd(3+)- and amiloride-sensitive plasma membrane pathway that is co-expressed with capsaicin-sensitive channels. Mechanical-, but not capsaicin-mediated, Ca(2+) transients are sensitive to kappa-opioid agonists.

Agonists of proteinase-activated receptor 2 induce inflammation by a neurogenic mechanism

Trypsin and mast cell tryptase cleave proteinase-activated receptor 2 and, by unknown mechanisms, induce widespread inflammation. We found that a large proportion of primary spinal afferent neurons, which express proteinase-activated receptor 2, also contain the proinflammatory neuropeptides calcitonin gene-related peptide and substance P. Trypsin and tryptase directly signal to neurons to stimulate release of these neuropeptides, which mediate inflammatory edema induced by agonists of proteinase-activated receptor 2. This new mechanism of protease-induced neurogenic inflammation may contribute to the proinflammatory effects of mast cells in human disease. Thus, tryptase inhibitors and antagonists of proteinase-activated receptor 2 may be useful anti-inflammatory agents.

Calcium waves in colonic myocytes produced by mechanical and receptor-mediated stimulation

The mechanisms underlying intracellular Ca2+ waves induced by either mechanical or receptor-mediated stimulation of myocytes isolated from the longitudinal muscle layer of the rabbit distal colon were compared using fura 2 and fluorescence videomicroscopy. Light focal mechanical deformation of the plasma membrane or focal application of substance P resulted in localized intracellular Ca2+ concentration ([Ca2+]i) transients that propagated throughout the cell. In both cases, the Ca2+ response consisted of a transient peak response followed by a delayed-phase response. Substance P-mediated [Ca2+]i responses involved generation of inositol 1,4, 5-trisphosphate and release of Ca2+ from thapsigargin-sensitive stores, whereas mechanically induced responses were partially (29%) dependent on La3+-sensitive influx of extracellular Ca2+ and partially on release of intracellular Ca2+ from thapsigargin-insensitive stores gated by ryanodine receptors. The delayed-phase response in both cases was dependent on extracellular Ca2+. However, although the response to substance P was sensitive to La3+, that after mechanical stimulation was not. In the later case, the underlying mechanism may involve capacitative Ca2+ entry channels that are activated after mechanical stimulation but not by substance P.

Chemical signaling from colonic smooth muscle cells to DRG neurons in culture

Transduction mechanisms between target cells within the intestinal wall and peripheral terminals of extrinsic primary afferent neurons are poorly understood. The purpose of this study was to characterize the interactions between smooth muscle cells from the rat distal colon and lumbar dorsal root ganglion (DRG) neurons in coculture. DRG neurons visually appeared to make contact with several myocytes. We show that brief mechanical stimulation of these myocytes resulted in intracellular Ca2+ concentration ([Ca2+]i) transients that propagated into 57% of the contacting neurites. Direct mechanical stimulation of DRG neurites cultured without smooth muscle had no effect. We also show that colonic smooth muscle cells express multiple connexin mRNAs and that these connexins formed functional gap junctions, as evidenced by the intercellular transfer of Lucifer yellow. Furthermore, thapsigargin pretreatment and neuronal heparin injection abolished the increase in neurite [Ca2+]i, indicating that the neuronal Ca2+ signal was triggered by inositol 1,4, 5-trisphosphate-mediated Ca2+ release from intracellular stores. Our results provide evidence for intercellular chemical communication between DRG neurites and intestinal smooth muscle cells that mediates the exchange of second messenger molecules between different cell types.

Apolipoprotein B-100: conservation of lipid-associating amphipathic secondary structural motifs in nine species of vertebrates

Development of a computer program called LOCATE allowed us to show that human apolipoprotein B-100 is composed of five domains, NH2-alpha1-beta1-alpha2-beta2-alpha3-COOH, enriched, alternately, in amphipathic alpha helixes and amphipathic beta strands. Using updated versions of this program, here we compare the complete sequence of human apolipoprotein B-100 with partial sequences from eight additional species of vertebrates (chicken, frog, hamster, monkey, mouse, pig, rat, and rabbit). The lipid-associating amphipathic alpha helixes cluster in domains alpha2 (between residues 2075 +/- 25 and 2575 +/- 25) and alpha3 (between residues 4100 +/- 100 and 4550 +/- 50) in all species for which those regions have been sequenced but with little conservation of individual helixes. Lipid-associating amphipathic beta strands cluster in domains beta1 (approximately residues 827-2000) and beta2 (approximately residue 2571 to residue 4000 +/- 50) in all species for which these regions have been sequenced, with conservation of several individual amphipathic beta strands. Hydrophobic segments are present in apolipoprotein B-100 sequences of all nine species but the frequency of occurrence is no greater than generally found in beta sheet-containing proteins. We conclude that four alternating lipid-associating domains, -beta1-alpha2-beta2-alpha3-COOH, are common supramolecular features of apolipoprotein B-100 in nine vertebrate species.