George J. Jakab

The Effects of Ozone on Immune Function

A review of the literature reveals that ozone (O3) exposure can either suppress or enhance immune responsiveness. These disparate effects elicited by O3 exposure depend, in large part, on the experimental design used, the immune parameters examined as well as the animal species studied. Despite the apparent contradictions, a general pattern of response to O3 exposure can be recognized. Most studies indicate that continuous O3 exposure leads to an early (days 0-3) impairment of immune responsiveness followed, with continued exposures, by a form of adaptation to O3 that results in a re-establishment of the immune response. The effects of O3 exposure on the response to antigenic stimulation also depend on the time at which O3 exposure occurred. Whereas O3 exposure prior to immunization is without effect on the response to antigen, O3 exposure subsequent to immunization suppresses the response to antigen. Although most studies have focused on immune responses in the lung, numerous investigators have provided functional and anatomical evidence to support the hypothesis that O3 exposure can have profound effects on systemic immunity.

The effects of acrolein exposure on pulmonary antibacterial defenses

Inhalation exposure to acrolein induced a dose-dependent impairment of pulmonary antibacterial defenses in mice. Animals exposed to 3 or 6 ppm of acrolein were increasingly less effective in inactivation of aerogenic challenges of 32P-labeled Staphylococcus aureus. Acrolein concentrations greater than 6 ppm caused increased sensory irritations, but no additional impairment of lung antibacterial resistance. Influenza A viral pneumonia in mice also suppressed pulmonary bacterial activity. Mice convalescing from moderate viral pneumonia became severely deficient in antibacterial defenses when exposed to acrolein. Whether the viral-induced impairment in pulmonary defense delayed the inactivation or allowed the proliferation of bacteria was dependent upon the dose of acrolein. The present study demonstrated that an underlying infectious disease process compounded the pulmonary toxicity of acrolein such that normally moderate toxicity was elevated to a virtual abolition of antibacterial defense mechanisms.

Concomitant exposure to carbon black particulates enhances ozone‐induced lung inflammation and suppression of alveolar macrophage phagocytosis

The goal of this study was to investigate whether coexposures to carbon black and O3 result in a toxicologic interaction in the lungs as quantitated by the inflammatory response and alveolar macrophage (AM) phagocytosis. This aim was accomplished through inhalation coexposures of Swiss mice for 4 h to target concentrations of 10 mg/m3 of carbon black and 1.5 ppm O3, or exposure to either agent alone. As a control for the coexposure experiments, mice were also exposed for 4 h to carbon black, followed immediately thereafter by exposure for 4 h to O3, or vice versa. At 24 h after exposure, the lungs of the animals were lavaged for quantitation of total and differential cell counts and assessment of AM Fc-receptor-mediated phagocytosis. Exposure to carbon black did not result in an inflammatory response, nor had it any effect on AM phagocytosis. Ozone exposure resulted in an inflammatory response in the lungs and suppression of AM phagocytosis. Both biologic parameters were significantly enhanced following combined exposure to the particle and the gas. Carbon black exposure either before or after O3 had no significant effect on AM phagocytosis as compared to O3 exposure alone. These data demonstrate the toxicologic interaction of coexposures to an inert particle and O3 on well-accepted biologic markers pulmonary toxicity. The mechanism for the enhanced biologic effect may be that the carbon black particle acts as a carrier mechanism for O3 to areas in the distal lung not accessible to O3 in the gaseous phase or that O3 alters the physicochemistry of the particulate from a nontoxic to a toxic form.

Aerosol transmission of experimental rotavirus infection.

Several aspects of the epidemiology of rotavirus suggest the possibility that transmission may occur by nonenteral routes. We utilized the mouse model of rotavirus infection to investigate the experimental transmission of rotavirus infection by respiratory droplets. Following exposure to a defined dose of aerosolized rotavirus, the kinetics of viral replication within the lung and gastrointestinal tract was studied using a double antibody enzyme immunoassay and indirect immunofluorescence. These studies documented the efficient transmission of rotavirus infection by means of aerosol in all exposed animals. Rotavirus antigen was detected as early as 12 hours after infection in the pulmonary and gastrointestinal tracts of the infected animals and antigen remained detectable in both sites for at least 8 days following infection. Gastrointestinal illness was clearly demonstrable in the animals while pulmonary pathology was not evident. These studies document that rotavirus infection can be transmitted by aerosol droplets under experimental conditions.

Suppression and recovery of the alveolar macrophage phagocytic system during continuous exposure to 0.5 ppm ozone.

Short-term exposures to ozone (O3) are known to impair pulmonary antibacterial defenses and alveolar macrophage (AM) phagocytosis in a dose-related manner. To determine the effect of prolonged O3 exposure, Swiss mice were exposed continuously to 0.5 ppm O3. At 1, 3, 7, and 14 days, intrapulmonary killing was assessed by inhalation challenge with Staphylococcus aureus or Proteus mirabilis and by comparing the number of viable bacteria remaining in the lungs at 4 h between O3-exposed and control animals. To evaluate the effects of O3 on the functional capacity of the AMs, Fc-receptor mediated phagocytosis was assessed. Ozone exposure impaired the intrapulmonary killing of S. aureus at 1 and 3 days; however, with prolonged exposure, the bactericidal capacity of the lungs returned to normal. This trend of an initial suppression followed by recovery was reflected in the phagocytic capacity of the AMs. In contrast to S. aureus, when P. mirabilis was used as the challenge organism, O3 exposure had no suppressive effect on pulmonary bactericidal activity, which correlated with an increase in the phagocytic cell population in the lungs. Morphologic examination of the lavaged macrophages showed that after 1 day of O3 exposure, the AMs were more foamy, and contained significantly more vacuoles. There was also a significant increase in binucleated cells at 3 days. These studies demonstrate that continuous exposure to O3 modulates AM-dependent lung defenses and points to the importance of the challenge organism and exposure protocol in establishing the adverse effect of O3.

Modulation of pulmonary defense mechanisms by acute exposures to nitrogen dioxide

The effect of acute exposures to NO2 on the antibacterial defenses of the murine lung was assessed following inhalation challenges with Staphylococcus aureus, Proteus mirabilis, and Pasteurella pneumotropica. Animals were challenged with the bacteria and exposed for 4 hr to increasing concentrations of NO2 after which pulmonary bactericidal activity was quantitated. With S. aureus pulmonary antibacterial defenses were suppressed at NO2 levels of 4.0 ppm and greater. Exposure to 10.0 ppm enhanced the intrapulmonary killing of P. mirabilis which correlated with an increase in the phagocytic cell populations lavaged from the lungs; at 20.0 ppm bactericidal activity against P. mirabilis was impaired. Pulmonary antibacterial defenses against P. pneumotropica were impaired at 10.0 ppm which correlated with a decrease in the retrieved phagocytic lung cell population. Reversing the order of treatment (ie., NO2 exposure prior to bacterial challenge) raised the threshold concentration for NO2-induced impairment of intrapulmonary bacterial killing. With S. aureus the effect was not observed at 5.0 ppm but at 10.0 ppm and with P. mirabilis not at 20.0 ppm but at 30.0 ppm intrapulmonary killing was enhanced. Exposures up to 20.0 ppm of NO2 did not effect the physical translocation mechanisms of the lung as quantitated by declines in pulmonary radiotracer activity following aerogenic challenge with 32P-labeled staphylococci. These studies demonstrate that NO2 modulates pulmonary antibacterial defenses and points to the importance of the challenge organism and the exposure protocol in establishing a threshold dose for the adverse effect.

Inhalation of acid coated carbon black particles impairs alveolar macrophage phagocytosis

A flow-past nose-only inhalation system was used for the co-exposure of mice to carbon black aerosols (CBA) and sulfur dioxide (SO2) at varying relative humidities (RH). The conversion of SO2 to sulfate (SO4(-2)) on the CBA, at a fixed aerosol concentration, was dependent on RH and SO2 concentration. The effect of the aerosol-gas mixture on alveolar macrophage (AM) phagocytosis was assessed three days following exposure for 4 h. Exposure to 10 mg/m3 CBA alone at low RH (10%) and high RH (85%), to 10 ppm SO2 alone at both RH, and to the mixture at low RH had no effect on AM phagocytosis. In contrast, AM phagocytosis was significantly suppressed following co-exposure at 85% RH, the only circumstance in which significant chemisorption of the gas by the aerosol and oxidation to SO4(-2) occurred. The results suggest that fine carbon particles can be an effective vector for the delivery of toxic amounts of SO4(-2) to the periphery of the lung.

Reduction of influenza virus pathogenesis by exposure to 0.5 ppm ozone

Continuous exposure to 0.5 ppm ozone during the course of murine influenza A/PR8/34 virus infection reduced the severity of the disease as quantitated by histologic (morphometric), biochemical (serum albumin in lavage fluid), and gravimetric (lung wt/dry weight ratios) parameters of lung injury. The ozone-mediated abatement of the lung injury was independent of peak pulmonary virus titers. However, determination of the sites of virus multiplication indicated that exposure to ozone resulted in a less widespread infection of the lung parenchyma. Furthermore, ozone exposure reduced the antiviral immune response as shown by reduced numbers of phenotypically quantitated T- and B-lymphocytes recovered from lung tissues and reduction of serum antibody titers. Since the pathogenesis of influenza virus infection depends on both the site of viral replication and the antiviral immune response, these studies suggest that redistribution of virus growth in murine lungs and immunosuppressive mechanisms are factors in the ozone-reduced disease severity.

Relationship Between Carbon Black Particulate-Bound Formaldehyde, Pulmonary Antibacterial Defenses, and Alveolar Macrophage Phagocytosis

AbstractThe goal of this study was to investigate whether exposure to formaldehyde vapors decreases resistance to respiratory infections through dysfunctions of the alveolar macrophage phagocytic system. Additionally, the study explored whether the interactions of formaldehyde and respirable carbon black particles result in an altered susceptibility through delivery of the absorbed formaldehyde to the deep lung with the inhaled particle. This aim was accomplished through in vivo studies of alveolar macrophage-dependent intrapulmonary killing of Staphylococcus au-reus and ex vivo alveolar macrophage k-receptor-mediated phagocytosis. Exposure to 15 ppm formaldehyde impaired lung antibacterial defenses when exposure followed bacterial challenge; however, this effect was found at 1 ppm when formaldehyde exposure preceded and was continued after bacterial challenge. Coexposure to target concentration of 3.5 mg/m3 carbon black and 2.5 ppm formaldehyde or 10 mg/m3 carbon black and 5 ppm formaldehyde for 4 h afte...

Inhalation Coexposure to Carbon Black and Acrolein Suppresses Alveolar Macrophage Phagocytosis and Tnf-α Release and Modulates Peritoneal Macrophage Phagocytosis

AbstractAcrolein, a hydrophilic vapor that is efficiently absorbed in the upper respiratory tract, is often emitted with respirable particles by combustion sources. If acrolein is adsorbed on respirable particles it may be deposited in the deep lung and interact with cells in the lung parenchyma. To test this hypothesis, mice were coexposed to target concentrations of 10 mg/m3 of carbon black and 2.5 ppm acrolein for 4 hours/day for 4 days and alveolar macrophage (AM) phagocytosis and lipopolysaccharide (LPS)-induced tumor necrosis factor-α (TNF-α) production were assessed. AM phagocytosis was suppressed at 1 through 11 days after exposure, with recovery of phagocytic activity at day 20. TNF-a production was a/so initially impaired but was reestablished by day 20. Suppression of AM phagocytosis and TNF-α production were not observed following exposure to either agent alone. Coexposure to target concentrations of 10 mg/m3 of carbon black and 5 ppm of acrolein for 4 hours/day for either 2, 4, 6, or 8 days w...