Pseudomonas aeruginosa pyocyanin: discruption of ultrastructure of human respiratory mucosa in vitro

Abstract

Purpose Previous studies showed that adenosine triphosphate (ATP) is depleted from human respiratory epithelium in the presence of pyocyanin. The latter was also associated with an increase in oxidative stress in intracellular structures. It is postulated that mitochondrial ultrastructure would be affected by pyocyanin. Method The human respiratory mucosa was obtained without anaesthetic from the inferior turbinate of 6 healthy subjects, and suspended in M199 which contained 0 and 20mg/mL of pyocyanin. After 4 hrs incubation, the cells were fixed with 2.5% cacodylate-buffered glutaraldehyde and post-fixed in 1% osmium tetroxide. This was followed by standard serial dehydration through alcohols and embedding in araldite. An ultrathin section (70 to 90 nm) through the central portion of each specimen was examined with TEM at a magnification of x3000, which is the lowest magnification for mitochondria to be recognized. Ten digital images from each treatment were captured for every subject. Total mitochondrial volume of each ultrathin section was measured to be the area within the electronically traced area using the Photopro plus programme. Results Paired Sample t-test showed that there were significantly more swollen mitochondria in TEM sections in the pyocyanin-treated epithelial cells (p < 0.0001). Besides an increase in mitochondrial swelling, there was no damage of cell junctions or loss of cilia and the orientation of cilia were normal in the pyocyanin-treated epithelial cells. Conclusion It is concluded that pyocyanin causes mitochondrial ultrastructure damage.