The effects of acute hydrogen peroxide exposure on respiratory cilia motility and viability.

COVID-19 has seen the propagation of alternative remedies to treat respiratory disease, such as nebulization of hydrogen peroxide (H 2 O 2 ). As H 2 O 2 has known cytotoxicity, it was hypothesised that H 2 O 2 inhalation would negatively impact respiratory cilia function. To test this hypothesis, mouse tracheal samples were incubated with different H 2 O 2 concentrations (0.1-1%) then cilia motility, cilia generated flow, and cell death was assessed 0-120 min following H 2 O 2 treatment. 0.1-0.2% H 2 O 2 caused immediate depression of cilia motility and complete cessation of cilia generated flow. Higher H 2 O 2 concentrations (≥0.5%) caused immediate complete cessation of cilia motility and cilia generated flow. Cilia motility and flow was restored 30 min after 0.1% H 2 O 2 treatment. Cilia motility and flow remained depressed 120 min after 0.2-0.5% H 2 O 2 treatment. No recovery was seen 120 min after treatment with ≥1% H 2 O 2 . Live/dead staining revealed that H 2 O 2 treatment caused preferential cell death of ciliated respiratory epithelia over non-ciliated epithelia, with 1% H 2 O 2 causing 35.3 ± 7.0% of the ciliated epithelia cells to die 120 min following initial treatment. This study shows that H 2 O 2 treatment significantly impacts respiratory cilia motility and cilia generated flow, characterised by a significant impairment in cilia motility even at low concentrations, the complete cessation of cilia motility at higher doses, and a significant cytotoxic effect on ciliated respiratory epithelial cells by promoting cell death. While this data needs further study using in vivo models, it suggests that extreme care should be taken when considering treating respiratory diseases with nebulised H 2 O 2 .