Interaction with epithelial cells modifies airway macrophage response to ozone.

The initial innate immune response to ozone (O3) in the lung is orchestrated by structural cells, such as epithelial cells, and resident immune cells, such as airway macrophages (Macs). We developed an epithelial cell-Mac coculture model to investigate how epithelial cell-derived signals affect Mac response to O3. Macs from the bronchoalveolar lavage (BAL) of healthy volunteers were cocultured with the human bronchial epithelial (16HBE) or alveolar (A549) epithelial cell lines. Cocultures, Mac monocultures, and epithelial cell monocultures were exposed to O3 or air, and Mac immunophenotype, phagocytosis, and cytotoxicity were assessed. Quantities of hyaluronic acid (HA) and IL-8 were compared across cultures and in BAL fluid from healthy volunteers exposed to O3 or air for in vivo confirmation. We show that Macs in coculture had increased markers of alternative activation, enhanced cytotoxicity, and reduced phagocytosis compared with Macs in monoculture that differed based on coculture with A549 or 16HBE. Production of HA by epithelial cell monocultures was not affected by O3, but quantities of HA in the in vitro coculture and BAL fluid from volunteers exposed in vivo were increased with O3 exposure, indicating that O3 exposure impairs Mac regulation of HA. Together, we show epithelial cell-Mac coculture models that have many similarities to the in vivo responses to O3, and demonstrate that epithelial cell-derived signals are important determinants of Mac immunophenotype and response to O3.

Phenotypic modification of human airway epithelial cells in air-liquid interface culture induced by exposure to the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

The nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent tobacco-specific carcinogen. We used an air-liquid interface epithelial cell culture system to model changes associated with NNK exposure relative to pathologies documented in human tobacco-related illnesses. Although in vitro systems exhibit certain limitations, they often offer accentuation of subtle pathologies. While the distribution of cell types in control cultures typically favors the ciliated cell phenotype, NNK-exposed cultures transitioned to non-ciliated cell phenotypes as well as reflecting features consistent with squamous metaplasia. We conclude that NNK impacts normal growth and differentiation of human airway epithelium in a short interval of time in vitro.

Culturing of human nasal epithelial cells at the air liquid interface.

In vitro models using human primary epithelial cells are essential in understanding key functions of the respiratory epithelium in the context of microbial infections or inhaled agents. Direct comparisons of cells obtained from diseased populations allow us to characterize different phenotypes and dissect the underlying mechanisms mediating changes in epithelial cell function. Culturing epithelial cells from the human tracheobronchial region has been well documented, but is limited by the availability of human lung tissue or invasiveness associated with obtaining the bronchial brushes biopsies. Nasal epithelial cells are obtained through much less invasive superficial nasal scrape biopsies and subjects can be biopsied multiple times with no significant side effects. Additionally, the nose is the entry point to the respiratory system and therefore one of the first sites to be exposed to any kind of air-borne stressor, such as microbial agents, pollutants, or allergens. Briefly, nasal epithelial cells obtained from human volunteers are expanded on coated tissue culture plates, and then transferred onto cell culture inserts. Upon reaching confluency, cells continue to be cultured at the air-liquid interface (ALI), for several weeks, which creates more physiologically relevant conditions. The ALI culture condition uses defined media leading to a differentiated epithelium that exhibits morphological and functional characteristics similar to the human nasal epithelium, with both ciliated and mucus producing cells. Tissue culture inserts with differentiated nasal epithelial cells can be manipulated in a variety of ways depending on the research questions (treatment with pharmacological agents, transduction with lentiviral vectors, exposure to gases, or infection with microbial agents) and analyzed for numerous different endpoints ranging from cellular and molecular pathways, functional changes, morphology, etc. In vitro models of differentiated human nasal epithelial cells will enable investigators to address novel and important research questions by using organotypic experimental models that largely mimic the nasal epithelium in vivo.

DNA methylation in nasal epithelial cells from smokers: identification of ULBP3-related effects.

We previously demonstrated that, in nasal epithelial cells (NECs) from smokers, methylation of an antiviral gene was associated with impaired antiviral defense responses. To expand these findings and better understand biological mechanisms underlying cigarette smoke (CS)-induced modifications of host defense responses, we aimed to compare DNA methylation of genes that may play a role in antiviral response. We used a two-tiered analytical approach, where we first implemented a genome-wide strategy. NECs from smokers differed in the methylation levels of 390 genes, the majority (84%) of which showed decreased methylation in smokers. Secondly, we generated an a priori set of 161 antiviral response-related genes, of which five were differentially methylated in NEC from smokers (CCL2, FDPS, GSK3B, SOCS3, and ULBP3). Assessing these genes at the systems biology level revealed a protein interaction network associated with CS-induced epigenetic modifications involving SOCS3 and ULBP3 signaling, among others. Subsequent confirmation studies focused on SOCS3 and ULBP3, which were hypomethylated and hypermethylated, respectively. Expression of SOCS3 was increased, whereas ULBP3 expression was decreased in NECs from smokers. Addition of the demethylating agent 5-Aza-2-deoxycytidine enhanced ULBP3 expression in NECs from smokers. Furthermore, infection of differentiated NECs with influenza virus resulted in significantly lower levels of ULBP3 in cells from smokers. Taken together, our findings show that genomic DNA methylation profiles are altered in NECs from smokers and that these changes are associated with decreased antiviral host defense responses, indicating that epigenenic dysregulation of genes such as SOCS3 and ULBP3 likely impacts immune responses in the epithelium.

Correlative ultrastructural investigations of airway epithelium following experimental exposure to defined air pollutants and lifestyle exposure to tobacco smoke.

CONTEXT: Investigations of cell/molecular level effects of in vivo exposure of airway mucosa of experimental animals to common irritant gases have demonstrated structural and physiological changes reflective of breaches in epithelial barrier function, presence of inflammatory cell infiltrate and compromised ciliary function. These experimental animal studies provided useful perspectives of plausible, but more subtle pathologic outcomes having relevance to lifestyle exposure to gaseous environmental irritants including tobacco smoke. METHODS: Freeze-fracture technology was applied to ultrastructural examination of large airway epithelium, with appropriate controls, from guinea pigs exposed to ozone and of nasal mucosa of human subjects exposed to ozone or sulfur dioxide, and nasal mucosa of active smokers. RESULTS: We documented substantive membrane structural changes to tight junctional complexes and cilia as well as an infiltrate of neutrophils into the surface mucosal layer in exposed animals. These patterns also were evident but not as pervasive among human subjects acutely exposed experimentally to irritant gases and those chronically exposed by their lifestyle to tobacco smoke. DISCUSSION: Our intent was to characterize respiratory tract mucosal membrane disorganization associated with high level acute irritant exposures in an experimental animal model and to evaluate evidence of similar but perhaps more subtle pathologic change associated with lower level experimental or lifestyle exposures. Our studies demonstrate continuity, albeit subtle, of pathologic change from high dosage experimental animal exposure to low dosage human exposures. CONCLUSIONS: This study represents the first report of ultrastructural airway epithelial membrane anomalies associated with lifestyle exposure to tobacco smoke irritants.

Ozone exposed epithelial cells modify cocultured natural killer cells.

Ozone (O3) causes significant adverse health effects worldwide. Nasal epithelial cells (NECs) are among the first sites within the respiratory system to be exposed to inhaled air pollutants. They recruit, activate, and interact with immune cells via soluble mediators and direct cell-cell contacts. Based on our recent observation demonstrating the presence of natural killer (NK) cells in nasal lavages, the goal of this study was to establish a coculture model of NECs and NK cells and examine how exposure to O3 modifies this interaction. Flow cytometry analysis was used to assess immunophenotypes of NK cells cocultured with either air- or O3-exposed NECs. Our data show that coculturing NK cells with O3-exposed NECs decreased intracellular interferon-γ (IFN-γ), enhanced, albeit not statistically significant, IL-4, and increased CD16 expression on NK cells compared with air controls. Additionally, the cytotoxicity potential of NK cells was reduced after coculturing with O3-exposed NECs. To determine whether soluble mediators released by O3-exposed NECs caused this shift, apical and basolateral supernatants of air- and O3-exposed NECs were used to stimulate NK cells. While the conditioned media of O3-exposed NECs alone did not reduce intracellular IFN-γ, O3 enhanced the expression of NK cell ligands ULBP3 and MICA/B on NECs. Blocking ULBP3 and MICA/B reversed the effects of O3-exposed NECs on IFN-γ production in NK cells. Taken together, these data showed that interactions between NECs and NK cells in the context of O3 exposure changes NK cell activity via direct cell-cell interactions and is dependent on ULBP3/MICA/B expressed on NECs.

Influenza enhances caspase-1 in bronchial epithelial cells from asthmatic volunteers and is associated with pathogenesis.

BACKGROUND: The leading cause of asthma exacerbation is respiratory viral infection. Innate antiviral defense pathways are altered in the asthmatic epithelium, yet involvement of inflammasome signaling in virus-induced asthma exacerbation is not known. OBJECTIVE: This study compared influenza-induced activation of inflammasome and innate immune signaling in human bronchial epithelial cells from volunteers with and without asthma and investigated the role of caspase-1 in epithelial cell antiviral defense. METHODS: Differentiated primary human bronchial epithelial cells from volunteers with and without asthma were infected with influenza A virus. An inflammasome-specific quantitative real-time polymerase chain reaction array was used to compare baseline and influenza-induced gene expression profiles. Cytokine secretion, innate immune gene expression, and viral replication were compared between human bronchial epithelial cells from volunteers with and without asthma. Immunofluorescence microscopy was used to evaluate caspase-1 and PYCARD colocalization. Tracheal epithelial cells from caspase-1-deficient or wild-type mice were infected with influenza and assessed for antiviral gene expression and viral replication. RESULTS: Human bronchial epithelial cells from asthmatic volunteers had altered influenza-induced expression of inflammasome-related and innate immune signaling components, which correlated with enhanced production of IL-1ß, IL-6, and TNF-α. Specifically, influenza-induced caspase-1 expression was enhanced and localization differed in human bronchial epithelial cells from asthmatic volunteers compared to volunteers without asthma. Influenza-infected tracheal epithelial cells from caspase-1-deficient mice had reduced expression of antiviral genes and viral replication. CONCLUSION: Caspase-1 plays an important role in the airway epithelial cell response to influenza infection, which is enhanced in asthmatic volunteers, and may contribute to the enhanced influenza-related pathogenesis observed in vivo.

Live attenuated influenza virus (LAIV) induces different mucosal T cell function in nonsmokers and smokers.

Smokers are more susceptible to respiratory infections, including influenza. To explore the effect of smoking on influenza-induced responses within the nasal mucosa, we have developed a protocol using inoculation with live attenuated influenza virus (LAIV) vaccine followed by sampling of the nasal mucosa. Mucosal cell populations were harvested through superficial biopsy of the nasal inferior turbinate pre and post LAIV inoculation and analyzed using flow cytometry. The majority of nasal biopsy CD45+ immune cells at baseline were CD3+ T lymphocytes. Following LAIV, these lymphocytes increased in nonsmokers but not in smokers. A subset of individuals was negative for helper T cell marker CD4 and cytotoxic T cell marker CD8 but positive for the γδ T cell receptor (TCR). Increases in γδ TCR+ cells were greater in nonsmokers, than in smokers. Thus, LAIV-induced changes in CD3 T as well as γδ T lymphocyte percentages are suppressed in smokers compared to nonsmokers.

Epithelial cells from smokers modify dendritic cell responses in the context of influenza infection.

Epidemiologic evidence suggests that cigarette smoking is a risk factor for infection with influenza, but the mechanisms underlying this susceptibility remain unknown. To ascertain if airway epithelial cells from smokers demonstrate a decreased ability to orchestrate an influenza-induced immune response, we established a model using differentiated nasal epithelial cells (NECs) from nonsmokers and smokers, co-cultured with peripheral blood monocyte-derived dendritic cells (mono-DCs) from nonsmokers. NEC/mono-DC co-cultures were infected with influenza A virus and analyzed for influenza-induced immune responses 24 hours after infection. We observed that NECs from smokers, as well as mono-DCs co-cultured with NECs from smokers, exhibited suppressed influenza-induced, interferon-related proteins interferon regulatory factor-7, Toll-like receptor-3, and retinoic acid inducible gene-1, likely because of the suppressed production of IFNα from the NECs of smokers. Furthermore, NEC/mono-DC co-cultures using NECs from smokers exhibited suppressed concentrations of T-cell/natural killer cell chemokine interferon gamma-induced protein 10 (IP-10) after infection with influenza, indicating that NECs from smokers may skew early influenza-induced Th1 responses. In contrast, NEC/mono-DC co-cultures using NEC from smokers contained increased influenza-induced concentrations of the Th2 chemokine thymic stromal lymphopoeitin (TSLP). In addition, NECs from smokers cultured alone had increased influenza-induced concentrations of the Th2 chemokine thymus and activation-regulated chemokine (TARC). Using this model, we demonstrated that in the context of infection with influenza, NECs obtained from smokers create an overall cytokine microenvironment that suppresses the interferon-mediated Th1 response and enhances the TSLP-TARC-mediated Th2 response, with the potential to modify the responses of DCs. Smoking-induced alterations in the Th1/Th2 balance may play a role in developing underlying susceptibilities to respiratory viral infections, and may also promote the likelihood of acquiring Th2 proallergic diseases.

Lateral cell membranes and shunt resistance in rabbit esophageal epithelium.

BACKGROUND AND AIMS: The structures that contribute to shunt resistance (Rs) in esophageal epithelium are incompletely understood, with 35-40% of Rs known to be calcium-dependent, reflecting the role of e-cadherin. Two calcium-independent candidates for the remaining approximately 60% of Rs have been identified: the glycoprotein matrix (GPM) within stratum corneum of esophageal epithelium, and the lateral cell membranes (LCMs) from neighboring cells. METHODS: To determine the contribution of GPM and LCMs to Rs, rabbit esophageal epithelium was mounted in Ussing chambers so that transepithelial resistance (R(T)), a marker of Rs, could be monitored during luminal exposure to either glycosidases for disruption of the GPM or to hypertonic urea for separation of the LCMs. RESULTS: Glycosidases had no effect on R(T). In contrast, hypertonic urea reduced R(T), increased fluorescein flux and widened the intercellular spaces. That urea reduced R(T), and so Rs, by widening the intercellular spaces, and not by altering the e-cadherin-dependent apical junctional complex, was supported by the ability of: (a) calcium-free solution to reduce R(T) beyond that produced by urea, (b) hypertonic urea to reduce R(T) beyond that produced by calcium free solution, (c) hypertonic sucrose to collapse the intercellular spaces and raise R(T), and (d) empigen, a zwitterionic detergent, to non-osmotically widen the intercellular spaces and reduce R(T). CONCLUSION: These data indicate that the LCMs from neighboring cells are a major contributor to shunt resistance in esophageal epithelium. As resistor, they are distinguishable from the apical junctional complex by their sensitivity to (luminal) hypertonicity and insensitivity to removal of calcium.

Reduced expression of IRF7 in nasal epithelial cells from smokers after infection with influenza.

Smokers are more susceptible to respiratory viral infections, including influenza virus, but the mechanisms mediating this effect are unknown. To determine how epithelial cells contribute to the enhanced susceptibility seen in smokers, we established an in vitro model of differentiated nasal epithelial cells (NECs) from smokers, which showed enhanced mucin expression. The NECs from smokers responded to influenza infection with greater cytotoxicity, release of interleukin-6, and viral shedding than NECs from nonsmokers. Focusing on type I interferon (IFN) expression, we observed that influenza-infected NECs from smokers produced significantly less IFN-alpha than NECs from nonsmokers. Similarly, the expression of IRF7, a key transcription factor controlling the expression of IFN-alpha, was significantly decreased in influenza-infected and IFN-beta-stimulated NECs from smokers. Furthermore, our data indicate that the DNA methylation of the IRF7 gene and expression of the DNA (cytosine-5-)-methyltransferase 1 was enhanced in NECs from smokers. To confirm these findings in vivo, we initiated a study in which smoking and nonsmoking healthy volunteers were inoculated nasally with the live-attenuated influenza virus (LAIV) vaccine, and nasal biopsies were obtained before and after the administration of LAIV. The LAIV-induced expression of IRF7 was lower in the nasal epithelium from smokers, supporting our in vitro observations. These data demonstrate that infection with influenza results in the reduced expression of transcription factor IRF7 in NECs from smokers, and that these effects may be mediated by an epigenetic modification of the IRF7 gene, thus providing a potential mechanism rendering smokers more susceptible to respiratory virus infections.

MRT letter: Auto-fluorescence by human alveolar macrophages after in vitro exposure to air pollution particles.

Macrophages from smokers demonstrate an increased auto-fluorescence. Similarly, auto-fluorescence follows in vitro exposure of macrophages to cigarette smoke condensate (i.e., the particulate fraction of cigarette smoke). The composition of particles in cigarette smoke can be comparable to air pollution particles. We tested the postulate that macrophages exposed to air pollution particles could demonstrate auto-fluorescence. Healthy nonsmoking and healthy smoking volunteers (both 18-40 years of age) underwent fiberoptic bronchoscopy with bronchoalveolar lavage and alveolar macrophages isolated. Macrophages were incubated at 37 degrees C in 5% CO(2) with either PBS or 100 microg/mL particle for both 1 and 24 h. Particles included a residual oil fly ash, Mt. St. Helens volcanic ash, and ambient air particles collected from St. Louis, Missouri and Salt Lake City, Utah. At the end of incubation, 50 microL of the cell suspension was cytocentrifuged and examined at modes for viewing fluorescein isothiocyanate (FITC) and rhodamine fluorescence. Both emission source air pollution particles demonstrated FITC and rhodamine auto-fluorescence at 1 and 24 h, but the signal following incubation of the macrophages with oil fly ash appeared greater. Similarly, the ambient particles were associated with auto-fluorescence by the alveolar macrophages and this appeared to be dose-dependent. We conclude that exposure of macrophages to air pollution particles can be associated with auto-fluorescence in the FITC and rhodamine modes.

Exacerbation of allergic inflammation in mice exposed to diesel exhaust particles prior to viral infection.

BACKGROUND: Viral infections and exposure to oxidant air pollutants are two of the most important inducers of asthma exacerbation. Our previous studies have demonstrated that exposure to diesel exhaust increases the susceptibility to influenza virus infections both in epithelial cells in vitro and in mice in vivo. Therefore, we examined whether in the setting of allergic asthma, exposure to oxidant air pollutants enhances the susceptibility to respiratory virus infections, which in turn leads to increased virus-induced exacerbation of asthma. Ovalbumin-sensitized (OVA) male C57BL/6 mice were instilled with diesel exhaust particles (DEP) or saline and 24 hours later infected with influenza A/PR/8. Animals were sacrificed 24 hours post-infection and analyzed for markers of lung injury, allergic inflammation, and pro-inflammatory cytokine production. RESULTS: Exposure to DEP or infection with influenza alone had no significant effects on markers of injury or allergic inflammation. However, OVA-sensitized mice that were exposed to DEP and subsequently infected with influenza showed increased levels of eosinophils in lung lavage and tissue. In addition Th2-type cytokines, such as IL-4 and IL-13, and markers of eosinophil chemotaxis, such as CCL11 and CCR3, were increased in OVA-sensitized mice exposed to DEP prior to infection with influenza. These mice also showed increased levels of IL-1alpha, but not IL-10, RANTES, and MCP-1 in lung homogenates. CONCLUSION: These data suggest that in the setting of allergic asthma, exposure to diesel exhaust could enhance virus-induced exacerbation of allergic inflammation.

Localization of type I interferon receptor limits interferon-induced TLR3 in epithelial cells.

Previous studies have shown that influenza infections increase Toll-like receptor 3 (TLR3) expression and that type I interferons (IFNs) may play a role in this response. This study aimed to expand on the role of type I IFNs in the influenza-induced upregulation of TLR3 and determine whether and how the localization of the IFN-alpha/beta receptor (IFNAR) in respiratory epithelial cells could modify IFN-induced responses. Using differentiated primary human airway epithelial cells this study demonstrates that soluble mediators secreted in response to influenza infection upregulate TLR3 expression in naive cells. This response was associated with an upregulation of type I IFNs and stimulation with type I, but not type II, IFNs enhanced TLR3 expression. Interestingly, although influenza infection results in IFN-beta release both toward the apical and basolateral sides of the epithelium, TLR3 expression is only enhanced in cells stimulated with IFN-beta from the basolateral side. Immunohistochemical analysis demonstrates that IFNAR expression is limited to the basolateral side of differentiated human airway epithelial cells. However, non- or poorly differentiated epithelial cells express IFNAR more toward the apical side. These data demonstrate that restricted expression of the IFNAR in the differentiated airway epithelium presents a potential mechanism of regulating type I IFN-induced TLR3 expression.

Transcriptional profiling of mucociliary differentiation in human airway epithelial cells.

When cultured at an air-liquid interface (ALI) in the appropriate medium, primary human airway epithelial cells form a polarized, pseudostratified epithelium composed of ciliated and mucus-secreting cells. This culture system provides a useful tool for the in vitro study of airway epithelial biology and differentiation. We have performed microarray analysis on ALI cultures of human bronchial epithelial cells (HBECs) grown over a 28-d period to identify genes involved in mucociliary differentiation. We identified over 2,000 genes that displayed statistically significant 2-fold or greater changes in expression during the time course. Of the genes showing the largest increases, many are involved in processes associated with airway epithelial biology, such as cell adhesion, immunity, transport, and cilia formation; however, many novel genes were also identified. We compared our results with data from proteomic analyses of the ciliary axoneme and identified candidate genes that may have roles in cilia formation or function. Gene networks were generated using Ingenuity Pathways Analysis (Ingenuity Systems, Redwood City, CA) to identify signaling pathways involved in mucociliary cell differentiation or function. Networks containing genes involved in TGF-beta, WNT/beta-catenin, and epidermal growth factor receptor (EGFR) pathways were identified, suggesting potential roles for these families in airway epithelia. Microarray results were validated by real-time RT-PCR for a number of representative genes. This work has provided extensive information about gene expression changes during differentiation of airway epithelial cells, and will be a useful resource for researchers interested in respiratory function, pathology, and toxicology.

Diesel exhaust enhances influenza virus infections in respiratory epithelial cells.

Several factors, such as age and nutritional status, can affect the susceptibility to influenza infections. Moreover, exposure to air pollutants, such as diesel exhaust (DE), has been shown to affect respiratory virus infections in rodent models. Influenza virus primarily infects and replicates in respiratory epithelial cells, which are also a major targets for inhaled DE. Using in vitro models of human respiratory epithelial cells, we determined the effects of an aqueous-trapped solution of DE (DE(as)) on influenza infections. Differentiated human nasal and bronchial epithelial cells, as well as A549 cells, were exposed to DE(as) and infected with influenza A/Bangkok/1/79. DE(as) enhanced the susceptibility to influenza virus infection in all cell models and increased the number of influenza-infected cells within 24 h post-infection. This was not caused by suppressing antiviral mediator production, since interferon (IFN) beta levels, IFN-dependent signaling, and IFN-stimulated gene expression were also enhanced by exposure to DE(as). Many of the adverse effects induced by DE exposure are mediated by oxidative stress. Exposure to DE(as) used in these studies generated oxidative stress in respiratory epithelial cells, and addition of the antioxidant glutathione-ethylester (GSH-ET) reversed the effects of DE(as) on influenza infections. Furthermore, DE(as) increased influenza virus attachment to respiratory epithelial cells within 2 h post-infection. Taken together, the results presented here suggest that in human respiratory epithelial cells oxidative stress generated by DE(as) increases the susceptibility to influenza infection and that exposure to DE(as) increases the ability of the virus to attach to and enter respiratory epithelial cells.

3-nitrotyrosine attenuates respiratory syncytial virus infection in human bronchial epithelial cell line.

3-nitrotyrosine (NO2Tyr), an L-tyrosine derivative during nitrative stress, can substitute the COOH-terminal tyrosine of alpha-tubulin, posttranslationally altering microtubular functions. Because infection of the cells by respiratory syncytial virus (RSV) may require intact microtubules, we tested the hypothesis that NO2Tyr would inhibit RSV infection and intracellular signaling via nitrotyrosination of alpha-tubulin. A human bronchial epithelial cell line (BEAS-2B) was incubated with RSV with or without NO2Tyr. The release of chemokines and viral particles and activation of interferon regulatory factor-3 (IRF-3) were measured. Incubation with NO2Tyr increased nitrotyrosinated alpha-tubulin, and NO2Tyr colocalized with microtubules. RSV-infected cells released viral particles, RANTES, and IL-8 in a time- and dose-dependent manner, and intracellular RSV proteins coprecipitated with alpha-tubulin. NO2Tyr attenuated the RSV-induced release of RANTES, IL-8, and viral particles by 50-90% and decreased alpha-tubulin-associated RSV proteins. 3-chlorotyrosine, another L-tyrosine derivative, had no effects. NO2Tyr also inhibited the RSV-induced shift of the unphosphorylated form I of IRF-3 to the phosphorylated form II. Pre-exposure of the cells to NO(2) (0.15 ppm, 4 h), which produced diffuse protein tyrosine nitration, did not affect RSV-induced release of RANTES, IL-8, or viral particles. NO2Tyr did not affect the potential of viral spreading to the neighboring cells since the RSV titers were not decreased when the uninfected cells were cocultured with the preinfected cells in NO2Tyr-containing medium. These results indicate that NO2Tyr, by replacing the COOH-terminal tyrosine of alpha-tubulin, attenuated RSV infection, and the inhibition appeared to occur at the early stages of RSV infection.

Oxidative stress activates anion exchange protein 2 and AP-1 in airway epithelial cells.

Anion exchange protein 2 (AE2) is a membrane-bound protein that mediates chloride-bicarbonate exchange. In addition to regulating intracellular pH and cell volume, AE2 exports superoxide (O.) to the extracellular matrix in an HCO-dependent process. Given this ability to export O., we hypothesized that expression of AE2 in the lung is regulated by oxidative stress. AE2 mRNA and protein expression was measured by RT-PCR and Western blot analysis, respectively, in differentiated human bronchial epithelial cells exposed to H(2)O(2) (100 microM). Alterations in in vivo AE2 protein expression were evaluated in lung tissue of rats exposed to 70% O(2). The role of transcription factor activator protein (AP)-1 in oxidant regulation of AE2 was evaluated by EMSA and by immunoblotting of nuclear phospho-c-jun. Results show increased AE2 mRNA and protein expression after oxidant exposure. This was preceded by transient increases in DNA binding of AE2-specific AP-1 and phosphorylation of c-jun. This study demonstrates that AE2 expression is regulated by oxidative stress in airway epithelial cells and that this regulation correlates with activation of AP-1.