The cyanotoxin cylindrospermopsin slows down cell cycle progression and extends metaphase duration in immortalised human airway epithelial cells.

Cylindrospermopsin (CYN) is a cyanobacterial toxin that occurs worldwide in aquatic environments. It is known for its delayed effects upon oral uptake in animals and humans. A less well studied route of CYN internalisation is the inhalation of CYN-contaminated aerosols. We analyzed potential effects of different CYN concentrations (1, 2.5 and 5 μmol/l) on cultures of immortalised human bronchial epithelial cells (16HBE14o). Impedance, a proxi for cell attachment to the culture support, cell spreading, cell growth and cell proliferation, was measured using an Acea iCELLigence device. Cell division rate and metaphase duration were determined using time lapse movies (Nikon Biostation II) of CYN-exposed cell cultures. Western blot studies were used to determine expression levels of cell cycle regulator proteins, the cyclins B1, D1 and A2. Our investigations revealed that exposure of cells to CYN concentrations of 1 μmol/l or higher led to a concentration- and time-dependent attenuation of impedance development as well as cell proliferation rate, and an extension of the metaphase of the cell cycle. CYN-mediated downregulation of cyclins B1 and D1 may be part of the underlying cell physiological mechanism. These results indicate that exposure of airways in humans and animals to aerosolised CYN over longer periods may be harmful.