Differential Behaviour of Fluid Liposomes Toward Mammalian Epithelial Cells and Bacteria: Restriction of Fusion to Bacteria

Abstract

Previous work demonstrated that fluid liposomes developed in our laboratory are able to fuse with bacterial outer membranes. This fusion improved the penetration and activity of liposome-encapsulated antibiotics and antisense oligonucleotides into the bacterial cells. Because it is anticipated that fluid liposome encapsulated antibiotics will be administered by aerosols to patients with chronic pulmonary infections or cystic fibrosis (CF), we conducted comparative studies in E. coli, P. aeruginosa and human lung epithelial cells using lipid-mixing assays to investigate the possibility that fluid liposomes might fuse with surrounding epithelial cells. After a 2 h incubation at 4 and 37 degrees C, no fusion between fluid liposomes and human lung epithelial cells was observed, whereas mean levels of 71 and 37% of fusion were observed at 37 degrees C with E. coli and P. aeruginosa cells, respectively. No fusion was observed at 4 degrees C in any cells. A kinetic study where temperature was gradually increased from 7 to 37 degrees C indicated that the fusion process in the two bacteria starts between 28 and 31 degrees C with a mean fusion rate of 0.60%/min at 31 degrees C to reach 1.18%/min at 37 degrees C. The present work suggests that it is unlikely that fluid liposomes fuse with host cells lining the human respiratory tract and further elucidates the fusogenic properties of fluid liposomes with respect to prokaryotes and eukaryotes.

Liposomal N-acetylcysteine Modulates the Pathogenesis of P. aeruginosa Isolated from the Lungs of Cystic Fibrosis Patient

“…On the other hand, when exposed to F-NAC cells were less viable. This might be due to the ability of liposomes to reduce toxicity of drugs by decreasing their availability within the cell membrane; thus moderates cell toxicity [73]. Then we studied the ability of L-NAC to reduce bacterial adhesion to lung cells (A549) in vitro.…”

Nanomaterials and molecular transporters to overcome the bacterial envelope barrier: Towards advanced delivery of antibiotics

“…show that fusion with bacterial membranes may occur to some extent using non-DOPE liposomes. Although there is no PE in the liposomes, there is a high amount of PE in the Gramnegative OM that may mediate fusion [55,228]. Indeed DPPC/DMPG liposomes cannot fuse with the more rigid cytoplasmic membrane of human cells (which contain cholesterol and have PC as the major lipid on their membrane surface and a minor amount of PE sheltered in the inner CM's leaflet) [55,228].…”

“…Although there is no PE in the liposomes, there is a high amount of PE in the Gramnegative OM that may mediate fusion [55,228]. Indeed DPPC/DMPG liposomes cannot fuse with the more rigid cytoplasmic membrane of human cells (which contain cholesterol and have PC as the major lipid on their membrane surface and a minor amount of PE sheltered in the inner CM's leaflet) [55,228]. However, DPPC/DMPG liposomes could fuse with Gramnegative bacteria and the higher the PE content of the bacterial OM, the better fusion occured [213,228].…”

“…Indeed DPPC/DMPG liposomes cannot fuse with the more rigid cytoplasmic membrane of human cells (which contain cholesterol and have PC as the major lipid on their membrane surface and a minor amount of PE sheltered in the inner CM's leaflet) [55,228]. However, DPPC/DMPG liposomes could fuse with Gramnegative bacteria and the higher the PE content of the bacterial OM, the better fusion occured [213,228]. When PE (in the form of DOPE) is also included in liposomes, composed for instance of DPPC/DMPG liposomes [218], DPPC/Chol hemisuccinate liposomes [217] or PC/Octadecylamine [209], the tendency for fusion between bacteria and liposomes is further enhanced, as seen by the significant improvement of the antibiotics efficacy [212,217,218].…”

Nanotechnology Formulations for Antibacterial Free Fatty Acids and Monoglycerides

“…Fusogenic liposomes that encapsulate traditional antibiotics exhibit strong antibacterial activity, even with only sub-MIC (minimum inhibitory concentration) concentrations of encapsulated antibiotic [61]. The fusogenic liposomes have been shown to fuse with bacterial cell membranes [62], offering a pathway to rescue the antibacterial properties of antibiotics against bacterial strains that have become resistant to the free form of the said antibiotic due to, e.g., decreased membrane permeability or highly functional bacterial cell membrane transporters [63]. Historically, Gram-positive bacteria have been more susceptible to antibiotics, as compared to Gram-negative bacteria, which possess an additional outer membrane.…”