ABSTRACT
Oxidative stress is a hallmark of numerous airway diseases, contributing to extensive cell and tissue damage. Cell membranes and the airway mucosal lining are rich in phospholipids that are particularly susceptible to oxidative attack, producing bioactive molecules including oxidized phosphatidylcholines (OxPC). With the recent discovery of elevated OxPC in asthmatic patients after allergen challenge, we hypothesized that OxPC directly contribute to disease by inducing airway epithelial cell dysfunction.
We found that OxPC induced dose-dependent cell stress and loss of viability in BEAS-2B and Calu-3 cell lines and primary human epithelial cells. These responses corresponded with significant epithelial barrier dysfunction, which was further compounded when combining OxPC with an epithelial wound. OxPC inhibited DNA synthesis and migration required to re-establish barrier function, but cells recovered if OxPC were washed off soon after treatment. OxPC induced generation of reactive oxygen species, lipid peroxidation and mitochondrial dysfunction, raising the possibility that OxPC cause pathological lipid metabolism in a self-propagating cycle. The oxidative stress induced by OxPC could not be abrogated by putative OxPC receptor blockers, but partial recovery of barrier function, proliferation and lipid peroxidation could be achieved with the antioxidant n-acetyl cysteine.
In summary, we have identified OxPC as a group of bioactive molecules that significantly impair multiple facets of epithelial cell function, consistent with pathological features of asthma. Further characterisation of the mechanisms by which OxPC affect epithelial cells could yield new insights into how oxidative stress contributes to the pathogenesis of airway disease.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Grants
Natural Sciences and Engineering Research Council, Discovery Grant (Adrian West)
Research Manitoba, New Investigator Operating Grant (Adrian West)
Research Manitoba, Postdoctoral Fellowship (Christopher Pascoe)
Canadian Respiratory Research Network, Postdoctoral Fellowship (Christopher Pascoe)
Canadian Institutes of Health Research, Banting Postdoctoral Fellowship (Christopher Pascoe)
Research Manitoba and CHRIM, Graduate Studentship (Neilloy Roy)
Research Manitoba and CHRIM, Graduate Studentship (Jignesh Vaghasiya)
Canada Research Chairs Program (Andrew Halayko)
Canadian Institutes of Health Research Emerging Network: Canadian Respiratory Research Network (Andrew Halayko)
The grant bodies had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
This version of the manuscript has been revised to add NAC recovery data (Fig 9), and add author Jignesh Vaghasiya.