Proposition 2, which requires that egg-laying hens be confined only in ways that allow these animals to lie down, stand up, fully extend their limbs and turn around freely, was passed by the voters of California in 2008. These new housing requirements were introduced in the USA and European Union without considering the potential impact of changes in layer hen housing on the health of poultry workers in the new facilities. Particles were collected from ambient air inside a large layer hen complex featuring separate barns with conventional battery caging, enriched caging, or 'free range' (aviary) housing during winter, spring, and summer seasons over one year. Toxicity of the particles was evaluated by analysis of inflammatory cell influx into lung lavage fluid after intratracheal instillation into mice. Capacity of the particles to elicit oxidative stress was evaluated using a macrophage cell line engineered with a reporter gene sensitive to nuclear factor κB activation. We observed similar pro-inflammatory and pro-oxidant effects of the particles collected from different types of barns and over different seasons, suggesting that standard industrial hygiene techniques for evaluating respirable particles in ambient air can adequately monitor worker risk. Based on particle concentrations found in ambient air in the barns, we can rank the facilities for worker exposure to particles as conventional caging (now banned) approximately equal to enriched caging (permitted under Proposition 2). Aviary housing is associated with increased exposure of workers to particulate matter and, therefore, to greater risk of allergic reactions and/or decreased respiratory function.

Objectives and design

The function of the airway nitric oxide synthase (NOS) isoforms and the lung cell types responsible for its production are not fully understood. We hypothesized that NO homeostasis in the airway is important to control inflammation, which requires upregulation, of NOS2 protein expression by an NOS3-dependent mechanism.

Materials or subjects

Mice from a C57BL/6 wild-type, NOS1(-/-), NOS2(-/-), and NOS3(-/-) genotypes were used. All mice strains were systemically sensitized and exposed to filtered air or ovalbumin (OVA) aerosol for two weeks to create a subchronic model of allergen-induced airway inflammation.

Methods

We measured lung function, lung lavage inflammatory and airway epithelial goblet cell count, exhaled NO, nitrate and nitrite concentration, and airway NOS1, NOS2, and NOS3 protein content.

Results

Deletion of NOS1 or NOS3 increases NOS2 protein present in the airway epithelium and smooth muscle of air-exposed animals. Exposure to allergen significantly reduced the expression of NOS2 protein in the airway epithelium and smooth muscle of the NOS3(-/-) strain only. This reduction in NOS2 expression was not due to the replacement of epithelial cells with goblet cells as remaining epithelial cells did not express NOS2. NOS1(-/-) animals had significantly reduced goblet cell metaplasia compared to C57Bl/6 wt, NOS2(-/-), and NOS3(-/-) allergen-exposed mice.

Conclusion

The airway epithelial and smooth muscle cells maintain a stable airway NO concentration under noninflammatory conditions. This "homeostatic" mechanism is unable to distinguish between NOS derived from the different constitutive NOS isoforms. NOS3 is essential for the expression of NOS2 under inflammatory conditions, while NOS1 expression contributes to allergen-induced goblet cell metaplasia.

Ras, a small GTPase protein, is thought to mediate Th2-dependent eosinophilic inflammation in asthma. Ras requires cell membrane association for its biological activity, and this requires the posttranslational modification of Ras with an isoprenyl group by farnesyltransferase (FTase) or geranylgeranyltransferase (GGTase). We hypothesized that inhibition of FTase using FTase inhibitor (FTI)-277 would attenuate allergic asthma by depleting membrane-associated Ras. We used the OVA mouse model of allergic inflammation and human airway epithelial (HBE1) cells to determine the role of FTase in inflammatory cell recruitment. BALB/c mice were first sensitized then exposed to 1% OVA aerosol or filtered air, and half were injected daily with FTI-277 (20 mg/kg per day). Treatment of mice with FTI-277 had no significant effect on lung membrane-anchored Ras, Ras protein levels, or Ras GTPase activity. In OVA-exposed mice, FTI-277 treatment increased eosinophilic inflammation, goblet cell hyperplasia, and airway hyperreactivity. Human bronchial epithelial (HBE1) cells were pretreated with 5, 10, or 20 μM FTI-277 prior to and during 12 h IL-13 (20 ng/ml) stimulation. In HBE1 cells, FTase inhibition with FTI-277 had no significant effect on IL-13-induced STAT6 phosphorylation, eotaxin-3 peptide secretion, or Ras translocation. However, addition of exogenous FPP unexpectedly augmented IL-13-induced STAT6 phosphorylation and eotaxin-3 secretion from HBE1 cells without affecting Ras translocation. Pharmacological inhibition of FTase exacerbates allergic asthma, suggesting a protective role for FTase or possibly Ras farnesylation. FPP synergistically augments epithelial eotaxin-3 secretion, indicating a novel Ras-independent farnesylation mechanism or direct FPP effect that promotes epithelial eotaxin-3 production in allergic asthma.