Cilia and mucus transport as determinants of the response of lung to air pollutants

Airway hydration and COPD

Chronic obstructive pulmonary disease (COPD) is one of the prevalent causes of worldwide mortality and encompasses two major clinical phenotypes, i.e., chronic bronchitis (CB) and emphysema. The most common cause of COPD is chronic tobacco inhalation. Research focused on the chronic bronchitic phenotype of COPD has identified several pathological processes that drive disease initiation and progression. For example, the lung's mucociliary clearance (MCC) system performs the critical task of clearing inhaled pathogens and toxic materials from the lung. MCC efficiency is dependent on: (1) the ability of apical plasma membrane ion channels such as the cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial Na(+) channel (ENaC) to maintain airway hydration; (2) ciliary beating; and (3) appropriate rates of mucin secretion. Each of these components is impaired in CB and likely contributes to the mucus stasis/accumulation seen in CB patients. This review highlights the cellular components responsible for maintaining MCC and how this process is disrupted following tobacco exposure and with CB. We shall also discuss existing therapeutic strategies for the treatment of chronic bronchitis and how components of the MCC can be used as biomarkers for the evaluation of tobacco or tobacco-like-product exposure.

Herd-level risk factors for infectious diseases in Swedish dairy calves aged 0–90 days

The effect of environmental factors and management routines on the risk of diarrhoea, respiratory disease and other infectious diseases was investigated in 3081 heifer calves 0-90 days old in 122 Swedish dairy herds. The farmers kept records on cases of diseases in their heifer calves and in addition, project veterinarians clinically examined all calves every 2-3 months. At each visit, the veterinarians also measured the ammonia concentration and relative air humidity in the housing facilities for the calves. The cleanliness of the animals and their environment was recorded as a measure of the hygienic status of the farm. The presence or absence of draught (i.e. wind velocity>0.5 m/s) was recorded twice during the study period. The effect of these factors, as well as the placing of the calf pens, the nature of the pen walls, air volume per animal, management factors (such as the status of the caretaker and feeding routines) and presence or absence of a bovine viral diarrhoea virus (BVDV) infection in the herd, was evaluated by means of a two-level variance component logistic model. The placing of calf pens along an outer wall was significantly associated with the risk of diarrhoea (odds ratio (OR): 1.92, P<0.01). The risk for respiratory disease was significantly associated with an ammonia concentration below 6 ppm (OR: 0.42, P<0.05) while the odds ratio for moderately to severely increased respiratory sounds was significantly associated with a BVDV infection in the herd (OR: 2.39, P<0.05) and draught (OR: 3.7, P<0.02). Absence of draught was significantly associated with the risk for infectious diseases other than diarrhoea and respiratory disease (OR: 0.42, P<0.01).

Twenty-four-hour tracheal pH monitoring--a simple and non-hazardous investigation

Prolonged oesophageal pH monitoring is commonly used in the investigation of gastro-oesophageal reflux. In contrast, tracheal pH monitoring is virtually unknown. We report a simple technique of measuring tracheal pH where the pH probe is inserted under local anaesthetic and can be left in position for 24 h to allow prolonged monitoring. Ten control individuals were studied. All completed the study without complication. One patient with mixed connective tissue disease, failed hiatal hernia repair and subsequent recurrent aspiration pneumonia was studied, on and off ranitidine, using simultaneous tracheal and oesophageal pH monitoring. This method showed evidence of gastro-oesophageal reflux and tracheal aspiration off treatment. When repeated with the patient taking ranitidine, the frequency of significant gastro-oesophageal reflux was reduced and no episodes of tracheal acid aspiration were recorded. Prolonged tracheal pH monitoring is a simple and non-hazardous technique. It is sensitive in detecting tracheal aspiration and may be more sensitive than pre-existing radiolabelled isotope techniques.

Acute inflammatory lung injury retards pulmonary particle clearance

The deposition, retention, and clearance of inhaled cobalt oxide particles from the lungs of calves with acute inflammatory lung injury induced by parainfluenza-3 virus (PI-3) were examined. Acute pulmonary inflammation was induced by nebulization with 10(9) TCID50 of PI-3 virus on two successive days, and animals were subsequently exposed to an aerosol of particulate cobalt oxide (geometric mean diameter 0.54-0.65 microns) seven days post-virus infection (dpi). Pulmonary lesions at 7 dpi were typical of PI-3 pneumonitis and were characterized by patchy aveolitis and bronchiolitis with accumulations of neutrophils, macrophages, fibrin, and inflammatory debris. Calves were killed at 0, 7, and 21 days post-aerosol exposure (dpe) to evaluate particle clearance and retention by assay for cobalt in lung tissues, bronchoalveolar washings, and tracheobronchial lymph nodes. Control animals had a typically biphasic clearance pattern with rapid initial clearance of 50% of the initial lung burden (ILB) by 7 dpe followed by slower prolonged clearance. Clearance was significantly retarded (P less than 0.05) in calves with viral-induced acute inflammatory lung injury; 90% of the ILB was retained at 7 dpe. Essentially all particles recoverable by bronchoalveolar lavage were intracellular within pulmonary alveolar macrophages (PAM) in both experimental and control groups, but interstitial sequestration of particles within PAM was commonly observed only in the lungs of calves with viral pneumonitis. Pneumonic calves also exhibited retarded translocation of particles to regional lymph nodes. The results document impaired particulate clearance from acutely inflamed lungs, and implicate decreased mucociliary clearance and interstitial sequestration within PAM as the major contributing factors. These functional alterations would be expected to enhance the progression of virus-induced acute pulmonary inflammatory injury.

Different virulence of influenza A virus strains and susceptibility to pneumococcal otitis media in chinchillas

We have previously shown that chinchillas infected with a multiply passaged laboratory strain of influenza A/NWS/33 (H1N1) develop negative middle-ear pressure; polymorphonuclear leukocyte oxidative, bactericidal, and chemotactic dysfunction; and increased susceptibility to pneumococcal otitis media. Because influenza A virus strains show different virulence in humans, three such strains were compared in the chinchilla model. Negative middle-ear pressure and tympanic membrane inflammation developed significantly more often in chinchillas infected with wild-type H3N2 virus than with either wild-type H1N1 virus or an attenuated, cold-adapted H3N2 vaccine strain, CR29. Marked depression in polymorphonuclear leukocyte chemiluminescent activity also developed significantly more often in H3N2 infected animals than in H1N1- or CR29-infected animals. Intranasal challenge of influenza virus-infected animals with type 7 Streptococcus pneumoniae resulted in a significantly greater occurrence of pneumococcal otitis media in H3N2-infected animals than in H1N1-, CR29-, or non-influenza-infected control animals. Clearance of pneumococci from nasal washings of animals infected with wild-type H3N2 was significantly delayed in comparison with the other groups. Thus, the previously demonstrated increased susceptibility to otitis media among children infected with H3N2 influenza virus may relate to the capacity of this strain to induce negative middle-ear pressure, polymorphonuclear leukocyte dysfunction, and alteration in the mucosal clearance of pneumococci.

Inhaled aerosols: lung deposition and clinical applications

Although aerosol deposition in the lungs is often considered in the context of industrial hygiene, aerosols also play an important clinical role. Three principal mechanisms (inertial impaction, gravitational sedimentation and Brownian diffusion) account for the majority of aerosol deposition in the lungs. Deposition depends upon the mode of inhalation, the nature of the particles and physical characteristics of the subject inhaling the particles. Radioaerosols are widely employed in measurements of total and regional deposition, and topographical distribution may also be determined. Aerosols play an important role in the treatment of various forms of respiratory disease, with bronchodilators for the therapy of asthma being particularly important. On average only 10% of the therapeutic aerosol dose actually reaches the lungs. The rate of removal of insoluble radioaerosols deposited in the lungs may be used as an index of mucociliary transport. Aerosols are also used in a variety of other diagnostic and research procedures, particularly for ventilation scanning, alveolar clearance, measurement of alveolar permeability, and for measuring the size of pulmonary air space.

Experimental otitis media after nasal inoculation of Streptococcus pneumoniae and influenza A virus in chinchillas

Otitis media developed in 67% of chinchillas inoculated intranasally with type 7 Streptococcus pneumoniae and influenza A virus. Only 4% of chinchillas inoculated with influenza alone and 21% of chinchillas inoculated with S. pneumoniae alone developed otitis media. Among the chinchillas that developed otitis media after inoculation with both pneumococcus and influenza, 73% of the affected ears contained effusion, and 27% of the affected ears showed tympanic membrane inflammation without middle ear effusion obtained on paracentesis. Although a majority of the ears with effusion yielded S. pneumoniae on culture, one-third of the effusions were sterile for aerobic bacteria. This model resembles conditions accompanying otitis media in humans and suggests that respiratory viral infection contributes significantly to the pathogenesis of acute otitis media.

Regional lung clearance of excessive bronchial secretions during chest physiotherapy in patients with stable chronic airways obstruction

Clearance of excessive bronchial secretions labelled with inhaled radioactive polystyrene particles has been directly measured with a gamma-camera linked to a computer. Chest physiotherapy significantly increased clearance from central, intermediate, and peripheral lung regions and sputum yield. These findings confirm the value of this form of treatment, which has hitherto been in doubt, in removing excessive bronchial secretions from all lung regions and in aiding their expectoration.

The effects of asbestos on macrophages

The exact role of the alveolar macrophage in the pathogenesis of asbestosis is not known. Most studies of the effect of asbestos on macrophages have been concerned with the in vitro biochemical or cytotoxic properties of the dust and have made use of peritoneal macrophages. In general, chrysotile had a toxic effect on the macrophages, whereas amphibole varieties did not. Most forms of absetos, however, are actively fibrogenic in man and animals, and there is no clear correlation between in vitro cytotoxicity of various forms of asbestos and their fibrogenicity. Recent experiments in which animals are exposed to asbestos in vivo provide evidence of alteration of macrophage activity, as demonstrated by changes in surface morphology and IgG receptor sites, as well as released of various secretory products. Deposition of complement components found on the surface of alveolar marcophages from animals exposed to asbestos could be a manifestation of a humoral immune response directed against an altered cell. The capacity of macrophages to participate in inflammation, tissue repair, and immunity suggests an immunopathogenic concept for the development of asbestosis.

Sulfur dioxide and tracheobronchial clearance in man

Tracheobronchial clearance was measured in nine healthy, nonsmoking adults. Technetium Tc 99m albumin aerosol (mass median diameter, 3 mu; geometric standard deviation, 1.6) was inhaled as a bolus under controlled conditions to achieve reproducible deposition in large airways. Each subject was studied in three seperate three-hour experiments: twice under control conditions and once exposed to 5 ppm sulfur dioxide (pollutant exposure after aerosol inhalation). Lung retention of activity was measured using a gamma camera interfaced to a data storage and retrieval system. The study showed that (1) Both deposition and clearance were highly reproducible in individuals in repeat control studies. (2) Acute exposure to 5 ppm sulfur dioxide had no significant effect (P greater than .05) on mucocillary clearance in resting healthy subjects, except perhaps for a small transient change (P=.05) after one hour. (3) Pulmonary function tests showed a decrease in maximal midexpiratory flow (P less than .01) but no other significant changes.

Effect of parainfluenza-3 virus neuraminidase on the structure of the gel phase of bovine nasal secretion

The gel phase of bovine nasal secretion was separated from the liquid phase and exposed to parainfluenza-3 virus or Vibrio cholerae neuraminidase under optimal in vitro conditions. N-Acetylneuraminic acid was released from the gel by either neuraminidase. The release of N-acetylneuraminic acid was accompanied by a decrease in the net negative charge of the gel, as evidenced by free zone electrophoresis. Scanning electron microscopy showed that after exposure to neuraminidases the regular network structure of the untreated gel attained a coarse, irregular structure. Samples of gel incubated with 0.15 M sodium chloride under similar conditions did not show changes in the net charge or morphology.

Role of immunity in viral-induced bacterial superinfections of the lung

Although viral illnesses are predisposing causes for pulmonary bacterial infections, the interrelationships of viral virulence and host immunity to alterations in susceptibility to bacterial infection are incompletely understood. We used two mutant strains of encephalomyocarditis virus (minimally virulent Mengo-37A and a highly virulent Columbia SK [Col-SK]) to investigate these interrelationships. Mice that had been immunized to Mengo-37A, and nonimmunized controls, were challenged with aerosols containing 10(4) plaque-forming units of Mengo-37A or Col-SK per liter. The effect of each viral infection on pulmonary antibacterial activity was assessed 3 days later by measuring the capacity of the lungs to kill inhaled radiophosphorus ((32)P)-labeled Staphylococcus aureus. The degree of antibacterial dysfunction found was proportional to the virulence of the infecting virus. If the host was immune to the infecting virus, bactericidal function was not impaired by viral challenge. Neither mutant caused significant pulmonary damage; therefore: (i) viral-induced impairment in bactericidal activity reflects, quantitatively, the virulence of the virus and (ii) viral immunity protects pulmonary bacterial defenses by preventing damage to the phagocyte from the virus or its attendant metabolic abnormalities.

Immunity against parainfluenza-3 virus in cattle: anti-neuraminidase activity in serum and nasal secretion

The antigenicity of two parainfluenza=3 virus strains, a "neuraminidasestrong" and a "neuraminidase-weak," was compared. For both strains the amount of hemagglutinin units was equal. The antibody responses to neuraminidase and hemagglutinin were measured on samples of serum and nasal secretion and were found to be similar, irrespective of the strain used for immunization. Anti-neuraminidase activity was demonstrated in the gel phase of nasal secretion of immunized cattle. Immunglobulin A was found attached to the peplomers of inhibited virus by immuno-electron microscopy.

Murine resistance to inhaled Neisseria meningitidis after infection with an encephalomyocarditis virus

A reduction in pulmonary anti-bacterial activity due to a preceding viral illness has been suggested as the mechanism responsible for some meningococcal infections of the lung. We investigated this proposed pathogenesis by infecting mice with airborne encephalomyocarditis virus (EMC) and then challenging them 1, 4, and 7 days later with aerosols of Neisseria meningitidis. Meningococcal clearance was assessed by comparing the numbers of bacteria present immediately after inhaling the aerosols with the numbers present 3 hr later. To insure that EMC virus adequately depressed murine defense mechanisms, we also determined staphylococcal killing rates at 4 hr by using radiophosphorus-labeled staphylococcal aerosols. Viral infection depressed murine pulmonary antimeningococcal activity at 1 and 4 days (P < 0.01) but not at 7 days. Intrapulmonary staphylococcal killing was impaired on day 4 (P < 0.01) but not on days 1 or 7. Pulmonary viral titers decreased rapidly from 10(7) to 10(3) plaque-forming units/ml of lung during the experimental period. According to these data viral disease transiently depresses resistance to meningococcal infection. This impairment in host resistance is present while the viral titer is decreasing and follows a relatively similar pattern to the transient decrease noted for staphylococci.

The effect of Sendai virus infection on bactericidal and transport mechanisms of the murine lung

Pulmonary virus infections predispose to bacterial infections in the lung. The mechanism of this effect was studied by quantitative comparison of the effects of airborne acute viral infection on pulmonary transport vs. in situ bactericidal mechanisms in mice. Animals infected by aerosol with 10(4) TCID(50) of Sendai virus developed pathologic pulmonary changes of interstitial pneumonitis, bronchial epithelial desquamation, and peribronchial mononuclear cell infiltration 7 days later. At that time, the mice were challenged with an aerosol of viable (32)P-labeled Staphylococcus aureus. Pulmonary bactericidal activity and physical transport by the lung were determined by the determination of viable staphylococcal and (32)P radiotracer counts respectively at 4, 24, 48, and 72 hr after bacterial challenge. Infected mice showed a significant decrease from normal in the rate of reduction of viable bacterial counts in the first 4 hr after challenge followed by a proliferation of the staphylococci. By contrast, radiotracer removal rates at 4 and 24 hr were similar in infected and noninfected mice. There was a small but significant retention of (32)P in the lungs of the infected animals at the later periods. These data demonstrate that bacterial multiplication associated with virus infection of lungs is related to defects in in situ bactericidal (phagocytic) mechanisms rather than transport mechanisms of the lung, despite histologic evidence of extensive destruction of bronchial-ciliated epithelium.