Extractable lipids from Phleum pratense pollen grains and their modifications by ozone exposure

International audienceGrass pollen grains are an important source of aeroallergens eliciting respiratory allergic diseases worldwide. In the field of allergology, Phleum pratense pollen is considered as a model for other grass taxa. Upon contact with the aqueous phase of mucosa membranes, lipids are co-delivered from pollen grains with allergens. Lipid molecular species have pro-allergic, pro-inflammatory and immunomodulatory effects on the cells of the allergic immune response. The quantitative analysis of Phleum pratense pollen lipids is missing in the literature. In this work, the total mass of lipids extractable by methylene chloride was determined to be 22 ± 1 µg per mg of Phleum pratense pollen. Eighteen percent of the lipidic mass was quantified and identified by gas chromatographic analysis. Identified lipids included alkanes, alkenes, saturated and unsaturated fatty acids, aldehydes and alcohols. Pollen samples harvested at different times and locations showed a very similar lipidic pattern, both qualitatively and quantitatively. Laboratory ozone exposure of pollen substantially modified its lipidic composition by reactions of ozone with alkenes leading to the production of fatty acids and aldehydes. A deeper knowledge of the lipids released by pollen grains, including pollen from polluted areas, is essential for a better understanding of the chemical environment at the cellular level where allergic reactions take place