Reen Wu

Repeated episodes of ozone inhalation amplifies the effects of allergen sensitization and inhalation on airway immune and structural development in Rhesus monkeys

Twenty-four infant rhesus monkeys (30 days old) were exposed to 11 episodes of filtered air (FA), house dust mite allergen aerosol (HDMA), ozone (O3), or HDMA + O3 (5 days each followed by 9 days of FA). Ozone was delivered for 8 h/day at 0.5 ppm. Twelve of the monkeys were sensitized to house dust mite allergen (Dermatophagoides farinae) at ages 14 and 28 days by subcutaneous inoculation (SQ) of HDMA in alum and intraperitoneal injection of heat-killed Bordetella pertussis cells. Sensitized monkeys were exposed to HDMA aerosol for 2 h/day on days 3-5 of either FA (n = 6) or O3 (n = 6) exposure. Nonsensitized monkeys were exposed to either FA (n = 6) or O3 (n = 6). During the exposure regimen, parameters of allergy (i.e., serum IgE, histamine, and eosinophilia), airways resistance, reactivity, and structural remodeling were evaluated. Eleven repeated 5-day cycles of inhaling 0.5 ppm ozone over a 6-month period had only mild effects on the airways of nonsensitized infant rhesus monkeys. Similarly, the repeated inhalation of HDMA by HDMA-sensitized infant monkeys resulted in only mild airway effects, with the exception of a marked increase in proximal airway and terminal bronchiole content of eosinophils. In contrast, the combined cyclic inhalation of ozone and HDMA by HDMA sensitized infants monkeys resulted in a marked increase in serum IgE, serum histamine, and airways eosinophilia. Furthermore, combined cyclic inhalation of ozone and HDMA resulted in even greater alterations in airway structure and content that were associated with a significant elevation in baseline airways resistance and reactivity. These results suggest that ozone can amplify the allergic and structural remodeling effects of HDMA sensitization and inhalation.

Effects of exposure to environmental tobacco smoke on a human tracheobronchial epithelial cell line

BEAS-2B cells, a human bronchial epithelial line immortalized by viral transformation, were exposed to sidestream tobacco smoke (STS) as a surrogate for environmental tobacco smoke (ETS) under biphasic culture conditions where the apical portion of the cells was in direct contact with the gas phase. Dose-dependent cytotoxicity was observed. In addition, induction of an as yet uncharacterized protein of molecular weight 45,000 was associated with exposure to STS. This protein might be part of a protective response of exposed cells, which do not show a classical heat shock response when exposed to STS. We conclude that STS and ETS can be directly cytotoxic to human airway epithelial cells in biphasic culture at concentrations not unreasonable for smoky indoor atmospheres. The model system described in this paper should be useful for studying the detailed mechanisms of cytotoxicity of, and protection from, ETS exposure in the human cells most directly exposed to ETS in vivo.

In vitro exposure of tracheobronchial epithelial cells and of tracheal explants to ozone

An in vitro system for exposing respiratory epithelial cells or explant tissues to ozone has been developed and characterized. This system is designed to generate and monitor consistent, reproducible levels of ozone, over a range of concentrations, in a humidified atmosphere, and to allow an exposure time of 24 h or longer. Based on chemical analysis, highly reproducible concentrations of ozone are delivered throughout the chamber, with a coefficient of variation of < 5% between five replicate vials exposed to 0.5 ppm of ozone for 50 min. The viability of cultured human tracheobronchial epithelial cells, as measured by the ability to oxidize a vital dye, and of rat tracheal epithelium, as measured by total numbers of necrotic cells in tracheal explants, after ozone exposure was examined in this system. Responses of cultured cells to ozone exposure as measured by bioassay were consistent with the observed low level of variability of ozone concentration between replicate incubation dishes or vials. Responses of cultured cells to ozone were proportional to duration of exposure and inversely proportional to the volume of medium covering the cells. We conclude that this newly developed in vitro exposure system will allow relatively simple and convenient exposure of cultured cells or organs to ozone or other gaseous agents under highly controlled and reproducible conditions.

Asthma: a comparison of animal models using stereological methods

Asthma is a worldwide health problem that affects 300 million people, as estimated by the World Health Organization. A key question in light of this statistic is: “what is the most appropriate laboratory animal model for human asthma?” The present authors used stereological methods to assess airways in adults and during post-natal development, and their response to inhaled allergens to compare rodents and nonhuman primates to responses in humans. An epithelial–mesenchymal trophic unit was defined in which all of the compartments interact with each other. Asthma manifests itself by altering not only the epithelial compartment but also other compartments (e.g. interstitial, vascular, immunological and nervous). All of these compartments show significant alteration in an airway generation-specific manner in rhesus monkeys but are limited to the proximal airways in mice. The rhesus monkey model shares many of the key features of human allergic asthma including the following: 1) allergen-specific immunoglobulin (Ig)E and skin-test positivity; 2) eosinophils and IgE+ cells in airways; 3) a T-helper type 2 cytokine profile in airways; 4) mucus cell hyperplasia; 5) subepithelial fibrosis; 6) basement membrane thickening; and 7) persistent baseline hyperreactivity to histamine or methacholine. In conclusion, the unique responses to inhaled allergens shown in rhesus monkeys make it the most appropriate animal model of human asthma.