title: Nitration of pollen aeroallergens by nitrate ion in conditions simulating the liquid water phase of atmospheric particles.
abstract: Pollen aeroallergens are present in atmospheric particulate matter (PM) where they can be found in coarse biological particles such as pollen grains (aerodynamic diameter dae>10μm), as well as fragments in the finest respirable particles (PM2.5; dae<2.5μm). Nitration of tyrosine residues in pollen allergenic proteins can occur in polluted air, and inhalation and deposition of these nitrated proteins in the human respiratory tract may lead to adverse health effects by enhancing the allergic response in population. Previous studies investigated protein nitration by atmospheric gaseous pollutants such as nitrogen dioxide and ozone. In this work we report, for the first time, a study on protein nitration by nitrate ion in aqueous solution, at nitrate concentrations and pH conditions simulating those occurring in the atmospheric aerosol liquid water phase. Experiments have been carried out on the Bovine serum albumin (BSA) protein and the recombinant Phleum pratense allergen (Phl p 2) both in the dark and under UV-A irradiation (range 4-90Wm-2) to take into account thermal and/or photochemical nitration processes. For the latter protein, modifications in the allergic response after treatment with nitrate solutions have been evaluated by immunoblot analyses using sera from grass-allergic patients. Experimental results in bulk solutions showed that protein nitration in the dark occurs only in dilute nitrate solutions and under very acidic conditions (pH<3 for BSA; pH<2.2 for Phl p 2), while nitration is always observed (at pH0.5-5) under UV-A irradiation, both in dilute and concentrated nitrate solutions, being significantly enhanced at the lowest pH values. In some cases, protein nitration resulted in an increase of the allergic response.
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy. Electronic address: alessandra.ghiani@unimib.it.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Ghiani
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bruschi
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Citterio
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy.
authors.forename: Ezio
authors.initials: E
authors.lastname: Bolzacchini
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ferrero
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Sangiorgi
authors.affiliation: Ambulatorio di Allergologia, Clinica San Carlo, Paderno Dugnano, Milan, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Asero
authors.affiliation: Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126 Milan, Italy. Electronic address: grazia.perrone@unimib.it.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Perrone
mesh_terms: D000485:Allergens / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D009566:Nitrates / Q000737:chemistry*; D031784:Phleum / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011058:Pollen / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry
chemical_list: D000485:Allergens; D009566:Nitrates; D010940:Plant Proteins; D012710:Serum Albumin, Bovine
keywords: Acidic aerosol; Allergenicity; DRH; Slot Blot; Tyrosine nitration; UV-A irradiation