Tropical Peatland Hydrology Simulated With a Global Land Surface Model.

Tropical peatlands are among the most carbon-dense ecosystems on Earth, and their water storage dynamics strongly control these carbon stocks. The hydrological functioning of tropical peatlands differs from that of northern peatlands, which has not yet been accounted for in global land surface models (LSMs). Here, we integrated tropical peat-specific hydrology modules into a global LSM for the first time, by utilizing the peatland-specific model structure adaptation (PEATCLSM) of the NASA Catchment Land Surface Model (CLSM). We developed literature-based parameter sets for natural (PEATCLSMTrop,Nat) and drained (PEATCLSMTrop,Drain) tropical peatlands. Simulations with PEATCLSMTrop,Nat were compared against those with the default CLSM version and the northern version of PEATCLSM (PEATCLSMNorth,Nat) with tropical vegetation input. All simulations were forced with global meteorological reanalysis input data for the major tropical peatland regions in Central and South America, the Congo Basin, and Southeast Asia. The evaluation against a unique and extensive data set of in situ water level and eddy covariance-derived evapotranspiration showed an overall improvement in bias and correlation compared to the default CLSM version. Over Southeast Asia, an additional simulation with PEATCLSMTrop,Drain was run to address the large fraction of drained tropical peatlands in this region. PEATCLSMTrop,Drain outperformed CLSM, PEATCLSMNorth,Nat, and PEATCLSMTrop,Nat over drained sites. Despite the overall improvements of PEATCLSMTrop,Nat over CLSM, there are strong differences in performance between the three study regions. We attribute these performance differences to regional differences in accuracy of meteorological forcing data, and differences in peatland hydrologic response that are not yet captured by our model.

Complex association patterns for inflammatory mediators in induced sputum from subjects with asthma.

BACKGROUND: The release of various inflammatory mediators into the bronchial lumen is thought to reflect both the type and degree of airway inflammation, eosinophilic Th2, and Th9, or neutrophilic Th1, and Th17, in patients with asthma. AIMS: We investigated whether cytokines and chemokines differed in sputum from subjects with more severe compared with milder asthma and whether unbiased factor analysis of cytokine and chemokine groupings indicates specific inflammatory pathways. METHODS: Cell-free supernatants from induced sputum were obtained from subjects with a broad range of asthma severity (n = 158) and assessed using Milliplex® Cytokines/Chemokine kits I, II and III, measuring 75 individual proteins. Each cytokine, chemokine or growth factor concentration was examined for differences between asthma severity groups, for association with leucocyte counts, and by factor analysis. RESULTS: Severe asthma subjects had 9 increased and 4 decreased proteins compared to mild asthma subjects and fewer differences compared to moderate asthma. Twenty-six mediators were significantly associated with an increasing single leucocyte type: 16 with neutrophils (3 interleukins [IL], 3 CC chemokines, 4 CXC chemokines, 4 growth factors, TNF-α and CX3CL1/Fractalkine); 5 with lymphocytes (IL-7, IL-16, IL-23, IFN-α2 and CCL4/MIP1ß); IL-15 and CCL15/MIP1δ with macrophages; IL-5 with eosinophils; and IL-4 and TNFSF10/TRAIL with airway epithelial cells. Factor analysis grouped 43 cytokines, chemokines and growth factors which had no missing data onto the first 10 factors, containing mixes of Th1, Th2, Th9 and Th17 inflammatory and anti-inflammatory proteins. CONCLUSIONS: Sputum cytokines, chemokines and growth factors were increased in severe asthma, primarily with increased neutrophils. Factor analysis identified complex inflammatory protein interactions, suggesting airway inflammation in asthma is characterized by overlapping immune pathways. Thus, focus on a single specific inflammatory mediator or pathway may limit understanding the complexity of inflammation underlying airway changes in asthma and selection of appropriate therapy.

Responsiveness to oral prednisolone in severe asthma is related to the degree of eosinophilic airway inflammation.

BACKGROUND: Patients with severe asthma appear relatively corticosteroid resistant. Corticosteroid responsiveness is closely related to the degree of eosinophilic airway inflammation. The extent to which eosinophilic airway inflammation in severe asthma responds to treatment with systemic corticosteroids is not clear. OBJECTIVE: To relate the physiological and inflammatory response to systemic corticosteroids in asthma to disease severity and the baseline extent of eosinophilic inflammation. METHODS: Patients with mild/moderate and severe asthma were investigated before and after 2 weeks of oral prednisolone (Clintrials.gov NCT00331058 and NCT00327197). We pooled the results from two studies with common protocols. The US study contained two independent centres and the UK one independent centre. The effect of oral corticosteroids on FEV1 , Pc20, airway inflammation and serum cytokines was investigated. Baseline measurements were compared with healthy subjects. RESULTS: Thirty-two mild/moderate asthmatics, 50 severe asthmatics and 35 healthy subjects took part. At baseline, both groups of asthmatics had a lower FEV1 and Pc20 and increased eosinophilic inflammation compared to healthy subjects. The severe group had a lower FEV1 and more eosinophilic inflammation compared to mild/moderate asthmatics. Oral prednisolone caused a similar degree of suppression of eosinophilic inflammation in all compartments in both groups of asthmatics. There were small improvements in FEV1 and Pc20 for both mild/ moderate and severe asthmatics with a correlation between the baseline eosinophilic inflammation and the change in FEV1 . There was a ~50% reduction in the serum concentration of CXCL10 (IP-10), CCL22 (MDC), CCL17 (TARC), CCL-2 (MCP-1) and CCL-13 (MCP-4) in both asthma groups after oral corticosteroids. CONCLUSIONS AND CLINICAL RELEVANCE: Disease severity does not influence the response to systemic corticosteroids. The study does not therefore support the concept that severe asthma is associated with corticosteroid resistance. Only baseline eosinophilic inflammation was associated with the physiological response to corticosteroids, confirming the importance of measuring eosinophilic inflammation to guide corticosteroid use.

eQTL of bronchial epithelial cells and bronchial alveolar lavage deciphers GWAS-identified asthma genes.

BACKGROUND: Genome-wide association studies (GWASs) have identified various genes associated with asthma, yet, causal genes or single nucleotide polymorphisms (SNPs) remain elusive. We sought to dissect functional genes/SNPs for asthma by combining expression quantitative trait loci (eQTLs) and GWASs. METHODS: Cis-eQTL analyses of 34 asthma genes were performed in cells from human bronchial epithelial biopsy (BEC, n = 107) and from bronchial alveolar lavage (BAL, n = 94). RESULTS: For TSLP-WDR36 region, rs3806932 (G allele protective against eosinophilic esophagitis) and rs2416257 (A allele associated with lower eosinophil counts and protective against asthma) were correlated with decreased expression of TSLP in BAL (P = 7.9 × 10(-11) and 5.4 × 10(-4) , respectively) and BEC, but not WDR36. Surprisingly, rs1837253 (consistently associated with asthma) showed no correlation with TSLP expression levels. For ORMDL3-GSDMB region, rs8067378 (G allele protective against asthma) was correlated with decreased expression of GSDMB in BEC and BAL (P = 1.3 × 10(-4) and 0.04) but not ORMDL3. rs992969 in the promoter region of IL33 (A allele associated with higher eosinophil counts and risk for asthma) was correlated with increased expression of IL33 in BEC (P = 1.3 × 10(-6) ) but not in BAL. CONCLUSIONS: Our study illustrates cell-type-specific regulation of the expression of asthma-related genes documenting SNPs in TSLP, GSDMB, IL33, HLA-DQB1, C11orf30, DEXI, CDHR3, and ZBTB10 affect asthma risk through cis-regulation of its gene expression. Whenever possible, disease-relevant tissues should be used for transcription analysis. SNPs in TSLP may affect asthma risk through up-regulating TSLP mRNA expression or protein secretion. Further functional studies are warranted.

Bronchoalveolar lavage fluid concentrations of transforming growth factor (TGF)-beta1, TGF-beta2, interleukin (IL)-4 and IL-13 after segmental allergen challenge and their effects on alpha-smooth muscle actin and collagen III synthesis by primary human lung fibroblasts.

RATIONALE: Asthmatic airway remodelling is characterized by myofibroblast hyperplasia and subbasement membrane collagen deposition. We hypothesized that cytokines and growth factors implicated in asthmatic airway remodelling are increased in bronchoalveolar lavage (BAL) fluid of asthmatics after segmental allergen challenge (SAC), and that these growth factors and cytokines increase alpha-smooth muscle actin (alpha-SMA) and collagen III synthesis by human lung fibroblasts (HLFs). METHODS: Transforming growth factor (TGF)-beta1, TGF-beta2, IL-4 and IL-13 levels were measured in BAL fluid from 10 asthmatics and 9 non-asthmatic controls at baseline and then 1 day, 1 week and 2 weeks after SAC. Confluent cultures of HLFs were stimulated by exogenous addition of TGF-beta1, TGF-beta2, IL-4 or IL-13 (concentration range 0.01-10 ng/mL) over 48 h. Collagen III was measured in culture supernates and alpha-SMA in cell lysates by Western blot. RESULTS: At baseline, there was no difference in BAL fluid concentrations of TGF-beta1, IL-4 and IL-13 between asthmatics and controls; however, non-asthmatics had higher concentrations of total TGF-beta2. In asthmatics, BAL fluid concentrations of all four factors increased significantly 1 day after SAC. TGF-beta1, TGF-beta2 and IL-13 concentrations returned to baseline by 1 week after SAC, but BAL fluid IL-4 concentration remained elevated for at least 2 weeks. TGF-beta1, TGF-beta2 and IL-4 significantly increased alpha-SMA in fibroblasts, but only IL-4 caused corresponding increases in collagen III synthesis. IL-13 had no direct effects on collagen III synthesis and alpha-SMA expression. CONCLUSIONS: Because IL-4 caused a dose-dependent increase in alpha-SMA and collagen III synthesis, it may be an important cytokine mediating asthmatic airway remodelling. TGF-beta1 and TGF-beta2 may also play a role in airway remodelling by stimulating phenotypic change of fibroblasts to myofibroblasts. Additionally, collagen III synthesis appears to be independent of myofibroblast phenotype and is apparently regulated by different growth factors and cytokines.

Interactions of allergens and irritants in susceptible populations in producing lung dysfunction: implications for future research.

Environmental agents, when applied in combination or sequentially, can induce a wide variety of adverse health effects in humans. To determine the effects of sequential allergen challenge and acid exposure on human bronchial epithelial cell function, we subjected normal, nonallergic control and ragweed-allergic individuals to bronchoscopic segmental ragweed challenge in vivo. We harvested bronchial epithelial cells by brush biopsy both before challenge and 24 hr after challenge and exposed cells to an acid stress in vitro (pH 5 for 3 hr), followed by a 1-hr recovery period at normal pH. In normal, nonallergic subjects, segmental allergen challenge produced no effects on ciliary activity; pH 5 exposure produced reduced ciliary activity (a decrease in the percent of the initially active area), with significant recovery after cells were returned to a normal pH. Ciliary activity from allergic subjects was also inhibited by pH 5 exposure; however, activity was not recovered when cells were placed in medium of normal pH. Ciliary activity in allergics who developed a stress response postantigen challenge, as determined by an induction of the 27 kDa stress (heat shock) protein, displayed no ciliary dysfunction when exposed to a pH 5 stress. In this case, a stress sufficient to provoke a heat shock (stress) protein (HSP) response (but not one that produced more severe lung injury and did not provoke an HSP response) protected cells from a subsequent acid stress. Because of our observations and recent findings reported in the literature, we suggest that in order to define the wide variety of health effects of environmental agents, control as well as at-risk populations should be studied and the ability to define potentially beneficial as well as detrimental effects should be built into the experimental design. Inclusion of different and novel end points also should be considered.

Kinetics of IL-10 production after segmental antigen challenge of atopic asthmatic subjects.

BACKGROUND: IL-10 is an anti-inflammatory cytokine made by lymphocytes, monocytes-macrophages, and eosinophils, and it may have an important role in regulating the asthmatic inflammatory response. IL-10 levels have been reported to be reduced in asthmatic airways, potentially contributing to more intense inflammation. OBJECTIVE: We sought to determine whether IL-10 levels were deficient in patients with mild asthma compared with controls and to determine whether IL-10 levels were associated with the resolution of eosinophilic inflammation. METHODS: We quantified IL-10 levels in the bronchoalveolar lavage (BAL) fluid (ELISA), BAL cells (quantitative immunocytochemistry), purified alveolar macrophages-monocytes studied ex vivo (ELISA), before (day 1) and after (24 hours [day 2], 1 week [day 9], and 2 weeks [day 16]) segmental antigen challenge (SAC), and investigated the effect of glucocorticoid treatment on ex vivo macrophage-monocyte IL-10 production. RESULTS: IL-10 levels were significantly higher in the BAL fluid of mild asthmatic subjects who demonstrated a dual reaction (both early and late) after whole lung ragweed inhalation challenge compared with nonallergic, nonasthmatic control subjects before and 24 hours and 1 week after SAC. Macro-phages-monocytes obtained before and after SAC from asthmatic patients also secreted increased amounts of IL-10 ex vivo than those from controls. Dexamethasone did not significantly change spontaneous IL-10 secretion from macrophages-monocytes in vitro. Quantitative immunocytochemical analysis of BAL cells demonstrated increased IL-10 in macrophages 24 hours after SAC and a similar trend in eosinophils. CONCLUSION: IL-10 is not deficient in mild asthma. Furthermore, BAL IL-10 levels are significantly higher in asthmatic subjects with a dual response than in control subjects before and after SAC. The increase in IL-10 was coincident with the initial increase in BAL eosinophils, although BAL eosinophilia persisted after IL-10 levels had returned to baseline, suggesting that the increased IL-10 levels could not promptly terminate this localized eosinophilic response.

Effect of IL-5, glucocorticoid, and Fas ligation on Bcl-2 homologue expression and caspase activation in circulating human eosinophils.

IL-5 is a potent eosinophil viability-enhancing factor that has been strongly implicated in the pathogenesis of IgE-mediated inflammation in vivo. Recently published data have suggested that IL-5 (and related cytokines) may act by altering the expression of the anti-apoptotic regulator Bcl-2 or its homologues, but this is controversial. The behaviour of the recently described pro-apoptotic cysteine proteases (caspases) in eosinophils after IL-5 treatment has not been explored. We examined the effect of IL-5 on the expression of four major Bcl-2 homologues, as well as on the expression/activation of key members of the caspase cell death cascade in cultured circulating human eosinophils. The effect of relevant inducers of eosinophil apoptosis (glucocorticoid and Fas ligation) on these regulatory proteins was also examined. We observed baseline expression of the anti-apoptotic Mcl-1 and pro-apoptotic Bax proteins in immunoblots of eosinophil lysates, but not Bcl-x, Bcl-2. IL-5 treatment had the effect of maintaining this basal level of expression over time without altering the balance of Bcl-2 homologues. The (upstream) caspase 8 and (downstream) caspase 3 proenzymes were detected in eosinophils at baseline, and were processed during spontaneous and stimulated eosinophil death. IL-5 completely blocked caspase processing in spontaneous and dexamethasone-induced cell death, and significantly slowed processing during Fas ligation. Our data do not support the theory that IL-5 acts by altering the balance of anti-apoptotic and pro-apoptotic Bcl-2 homologues, but suggest that it may act by regulating activation of the caspase cell death cascade.

HSP27 elevated in mild allergic inflammation protects airway epithelium from H2SO4 effects.

Inflammation in allergic individuals is hypothesized to elevate stress proteins [heat shock proteins (HSP)] in airway epithelium, which may protect cells from further adverse conditions. Allergic, either asthmatic or not, and normal volunteers participated in a 2-day segmental allergen challenge bronchoscopic procedure. Bronchial epithelium was obtained before and after challenge. Epithelium was exposed to medium with H2SO4 (pH5), returned to medium at pH 7.4, and finally harvested for Western blotting with anti-27-kDa HSP (HSP27) antibody. Prechallenge epithelium of all subjects had significantly inhibited ciliary function by H2SO4 (pH 5) conditions (P < 0.001); only epithelium of normals recovered (P = 0.02). Allergic subjects with mild inflammation (< 50 micrograms/ml increase in albumin in bronchoalveolar lavage) had significantly increased HSP27 postchallenge (P = 0.01) and little ciliary dysfunction at pH 5, whereas subjects with severe inflammation (> 50 micrograms/ml increase in albumin) had little change in HSP27 and significant ciliary inhibition (P = 0.02). Normal epithelium had similar trends in HSP27 and equivalent inhibition of ciliary activity at pH 5 before and after allergen challenge. These data indicate that mild inflammation to allergen elevates HSP27 stress protein levels, thereby potentially protecting epithelial function from additional adverse conditions.

Kinetics of the development and recovery of the lung from IgE-mediated inflammation: dissociation of pulmonary eosinophilia, lung injury, and eosinophil-active cytokines.

Events occurring up to 16 d after antigen challenge were characterized using a novel protocol employing four bronchoscopies, two segmental antigen challenge (SAC) procedures (on Days 1 and 2), and six bronchoalveolar lavages (BALs) (on Days 1, 2, 9, and 16) in three groups: ragweed allergic asthmatics with dual phase airway reactions (AA-D), allergic asthmatics with a single early airway reaction (AA-S), and nonallergic nonasthmatic control subjects. In AA-D subjects, SAC produced a marked eosinophilic inflammatory response at 24 h associated with eosinophil degranulation (eosinophil cationic protein [ECP] in BAL fluid) and lung injury, which largely resolved by Day 16. When the second antigen-challenged segment (SAC performed on Day 2) was lavaged 7 d after challenge (Day 9), a persistent pulmonary eosinophilia was noted accompanied by minimal elevations in ECP and albumin. Eosinophil-active cytokines showed unique patterns: interleukin-5 (IL-5) increased in the antigen segment on Day 2 then returned to baseline after 7 d; granulocyte-macrophage colony-stimulating factor (GM-CSF) peaked at Day 2 but was persistently elevated throughout Day 16 in antigen segments, and increased in control segments at late time points; IL-3 levels were constant and similar in antigen and control segments. Changes were specific to AA-D subjects in comparison with control subjects. Elements of the IgE-mediated pulmonary inflammatory response differ markedly in their development and resolution.

Beta 2-agonist-elevated stress response in human bronchial epithelial cells in vivo and in vitro.

Recent studies report high baseline levels of stress (heat shock) proteins in bronchial epithelial cells from asthmatic individuals. The promoter of the gene encoding the 72-kDa heat shock protein has an element responsive to cAMP, which may be affected by beta-agonists. This study examined stress protein levels in subjects enrolled in a segmental lung allergen challenge study to determine whether beta-agonist medication could contribute to a stress response. Subjects were divided on the basis of no premedication (n = 17), metered dose inhalations of albuterol (n = 24), or placebo inhalation (n = 3) prior to bronchoscopy. Levels of the inducible stress protein Hsp72 and constitutive Hsp73 were quantitated in bronchial epithelial cells from brush biopsy of allergic nonasthmatic, allergic asthmatic, and normal individuals. Mean levels were increased significantly (p < 0.003 and p < 0.004, respectively) in those subjects who received albuterol premedication. No significant differences were found between clinical groups of individuals or for placebo inhalation vs nonpremedication. Albuterol in vitro increased the levels of Hsp72 and Hsp73 in epithelial cells from either nonpremedicated or placebo-treated donors; the Hsp72 levels correlated linearly with increased albuterol concentration (r = 0.81, p < 0.01). Therefore, beta-agonists elevate or prolong an elevated stress response in epithelial cells, possibly through cAMP-mediated effects.

IL-1 beta release from cultured bronchial epithelial cells and bronchoalveolar lavage cells from allergic and normal humans following segmental challenge with ragweed.

This work investigated whether interleukin 1 beta (IL-1 beta) release from epithelial cells is modulated by antigen challenge in vivo, and inflammatory cells in vitro. Bronchial epithelial cells were obtained before and after segmental allergen challenge in allergic and normal individuals, and were cultured with and without autologous bronchoalveolar lavage (BAL) cells. IL-1 beta in culture medium was quantitated by enzyme-linked immunoabsorbent assay (ELISA). Pre-challenge IL-1 beta levels from epithelial cells were similar in allergic (4.4 +/- 0.8 pg/ml, n = 32) and normal (6.8 +/- 1.7 pg/ml, n = 17) subjects. IL-1 beta levels were significantly elevated from epithelium with BAL cell co-culture vs without co-culture in both subject groups (allergic, 13.2 +/- 2.3 pg/ml, P = 0.006; normal: 16.4 +/- 4.0 pg/ml, P = 0.007). Post-challenge IL-1 beta from epithelial cells without BAL cells was increased in both groups, but significant only for allergic subjects (P = 0.003). Post-challenge IL-1 beta from epithelial with BAL cells changed little for allergic subjects (13.8 +/- 2.4 pg/ml), and increased for normal subjects (20.0 +/- 4.8 pg/ml). Decreased production of tumour necrosis factor alpha (TNF-alpha) was observed in allergic subjects (day 1: 447 pg/ml vs day 2: 258 pg/ml). Moreover, pre-challenge release of TNF-alpha and IL-1 beta levels from epithelial + BAL cells correlated well for allergic (r = 0.84) and normal subjects (r = 0.6), but post-challenge release correlated only in normal subjects (r = 0.90). These results indicate that bronchial epithelial cells and BAL cells interact, modulating release of these inflammatory cytokines.

Two types of bacteria adherent to bovine respiratory tract ciliated epithelium.

Two hundred sixty tracheas were obtained from a Philadelphia abattoir under permit from the Department of Agriculture; the tracheas were excised from predominantly Holstein calves of both sexes that weighed approximately 250 kg. Tracheas were transported in normal saline to the laboratory at Thomas Jefferson University, Philadelphia, Pennsylvania. Evidence of bacteria adherent to the tracheal epithelium was found in specimens from 20/24 of these tracheas. The epithelium from each of five tracheas was placed in glutaraldehyde fixative for transmission electron microscopic examination. Epithelium from each of 12 other tracheas was placed in formaldehyde fixative for light microscopic examination. Microscopically, 13 of these 17 bovine tracheal epithelia were observed to contain bacteria located longitudinally parallel to and between cilia and microvilli of ciliated cells. Preparations of ciliary axonemes isolated from the epithelium of seven additional bovine tracheas also contained these bacteria in sections viewed by a transmission electron microscope. These bacteria had two different ultrastructural morphologies: filamentous with a trilaminar-structured cell wall and short with a thick, homogeneously stained cell wall beneath a regularly arrayed surface layer. The short bacillus had surface carbohydrates, including mannose, galactose, and N-acetylgalactosamine, identified by lectin binding. The filamentous bacillus was apparently externally deficient in these carbohydrates. Immunogold staining revealed that the filamentous bacillus was antigenically related to cilia-associated respiratory (CAR) bacillus, which has been identified in rabbit and rodent species. Significantly decreased numbers of cilia were obtained from tracheal epithelium heavily colonized by the filamentous bacilli, suggesting a pathologic change in ciliated cells.

Effect of Pseudomonas aeruginosa rhamnolipids on mucociliary transport and ciliary beating.

Pseudomonas aeruginosa rhamnolipid causes ciliostasis and cell membrane damage to rabbit tissue, is a secretagogue in cats, and inhibits epithelial ion transport in sheep tissue. It could therefore perturb mucociliary clearance. We have investigated the effect of rhamnolipid on mucociliary transport in the anesthetized guinea pig and guinea pig and human respiratory epithelium in vitro. Application of rhamnolipid to the guinea pig tracheal mucosa reduced tracheal mucus velocity (TMV) in vivo in a dose-dependent manner: a 10-microgram bolus caused cessation of TMV without recovery; a 5-micrograms bolus reduced TMV over a period of 2 h by 22.6% (P = 0.037); a 2.5-microgram bolus caused no overall changes in TMV. The ultrastructure of guinea pig tracheal epithelium exposed to 10 micrograms of rhamnolipid in vivo was normal. Application of 1,000 micrograms/ml rhamnolipid had no effect on the ciliary beat frequency (CBF) of guinea pig tracheal rings in vitro after 30 min, but 250 micrograms/ml stopped ciliary beating after 3 h. Treatment with 100 micrograms/ml rhamnolipid caused immediate slowing of the CBF (P less than 0.01) of human nasal brushings (n = 7), which was maintained for 4 h. Mono- and dirhamnolipid had equivalent effects. The CBF of human nasal turbinate organ culture was also slowed by 100 micrograms/ml rhamnolipid, but only after 4 h (CBF test, 9.87 +/- 0.41 Hz; control, 11.48 +/- 0.27 Hz; P less than 0.05, n = 6), and there was subsequent recovery by 14 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Ciliated respiratory epithelial surface changes after formaldehyde exposure.

The investigation sought to identify alterations of specific ciliated epithelial surface components after exposure to formaldehyde (HCHO) levels that decrease respiratory ciliary function. Bovine tracheae were reacted with an analog of N-hydroxysuccinimidobiotin to label epithelial surface-accessible components before exposure to HCHO. The tracheae were then exposed to 0, 16, 33, and 66 micrograms HCHO/cm2 epithelial surface for 30 min. Cilia were isolated from the epithelium, separated into membrane and internal axonemal portions, analyzed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and either stained to detect proteins or transblotted to detect biotin-labeled components. Densitometric analysis of axoneme proteins showed a decrease in the total amount extracted with increased HCHO concentration, including axoneme-specific proteins, dynein, and tubulin. However, biotinylated proteins in the axoneme fractions proportionately increased. Membrane fractions showed little change in protein with increasing HCHO concentration. The majority of these is not biotin-labeled and thus not surface-accessible components. Biotinylated material in the membrane fractions showed a significant decrease with increased HCHO concentration, particularly of bands at 92, 98, and 105 kD. These data suggest that increasing HCHO exposure reduces both extractable ciliary axonemes and detergent-soluble surface components, possibly by stabilizing respiratory epithelial membranes. This process apparently strengthens association of certain surface components with the internal axoneme, thereby reducing subsequent solubilization in detergent.