title: Limonene and its ozone-initiated reaction products attenuate allergic lung inflammation in mice.
abstract: Inhalation of indoor air pollutants may cause airway irritation and inflammation and is suspected to worsen allergic reactions. Inflammation may be due to mucosal damage, upper (sensory) and lower (pulmonary) airway irritation due to activation of the trigeminal and vagal nerves, respectively, and to neurogenic inflammation. The terpene, d-limonene, is used as a fragrance in numerous consumer products. When limonene reacts with the pulmonary irritant ozone, a complex mixture of gas and particle phase products is formed, which causes sensory irritation. This study investigated whether limonene, ozone or the reaction mixture can exacerbate allergic lung inflammation and whether airway irritation is enhanced in allergic BALB/cJ mice. Naïve and allergic (ovalbumin sensitized) mice were exposed via inhalation for three consecutive days to clean air, ozone, limonene or an ozone-limonene reaction mixture. Sensory and pulmonary irritation was investigated in addition to ovalbumin-specific antibodies, inflammatory cells, total protein and surfactant protein D in bronchoalveolar lavage fluid and hemeoxygenase-1 and cytokines in lung tissue. Overall, airway allergy was not exacerbated by any of the exposures. In contrast, it was found that limonene and the ozone-limonene reaction mixture reduced allergic inflammation possibly due to antioxidant properties. Ozone induced sensory irritation in both naïve and allergic mice. However, allergic but not naïve mice were protected from pulmonary irritation induced by ozone. This study showed that irritation responses might be modulated by airway allergy. However, aggravation of allergic symptoms was observed by neither exposure to ozone nor exposure to ozone-initiated limonene reaction products. In contrast, anti-inflammatory properties of the tested limonene-containing pollutants might attenuate airway allergy.
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Jitka S
authors.initials: JS
authors.lastname: Hansen
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Asger W
authors.initials: AW
authors.lastname: Nørgaard
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Ismo K
authors.initials: IK
authors.lastname: Koponen
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Jorid B
authors.initials: JB
authors.lastname: Sørli
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Maya D
authors.initials: MD
authors.lastname: Paidi
authors.affiliation: b Institute of Molecular Medicine, University of Southern Denmark , Odense , Denmark.
authors.forename: Søren W K
authors.initials: SW
authors.lastname: Hansen
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Per Axel
authors.initials: PA
authors.lastname: Clausen
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Gunnar D
authors.initials: GD
authors.lastname: Nielsen
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Peder
authors.initials: P
authors.lastname: Wolkoff
authors.affiliation: a The National Research Centre for the Working Environment , Copenhagen , Denmark.
authors.forename: Søren Thor
authors.initials: ST
authors.lastname: Larsen
mesh_terms: D016902:Air Pollution, Indoor / Q000009:adverse effects; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000276:immunology*; D053138:Cyclohexenes / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D007073:Immunoglobulin E; D007509:Irritants / Q000276:immunology*; D000077222:Limonene; D008168:Lung / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D010126:Ozone / Q000276:immunology*; D011014:Pneumonia / Q000276:immunology*; D013729:Terpenes / Q000276:immunology*
chemical_list: D000893:Anti-Inflammatory Agents; D053138:Cyclohexenes; D016207:Cytokines; D007509:Irritants; D013729:Terpenes; D007073:Immunoglobulin E; D010126:Ozone; D000077222:Limonene; D051547:Heme Oxygenase-1
keywords: Allergy; IgE; anti-inflammatory; indoor air; irritants; mouse model; respiration