Membrane-targeted synergistic activity of docosahexaenoic acid and lysozyme against Pseudomonas aeruginosa.
Antimicrobial polypeptides, including lysozymes, have membrane perturbing activity and are well-documented effector molecules of innate immunity. In cystic fibrosis, a hereditary disease with frequent lung infection with Pseudomonas aeruginosa, the non-esterified fatty acid DA (docosahexaenoic acid), but not OA (oleic acid), is decreased, and DA supplementation has been shown to improve the clinical condition in these patients. We hypothesized that DA may, either alone or in conjunction with lysozyme, exert antibacterial action against Ps. aeruginosa. We found that DA and lysozyme synergistically inhibit the metabolic activity of Ps. aeruginosa, in contrast with OA. Electron microscopy and equilibrium dialysis suggest that DA accumulates in the bacterial membrane in the presence of lysozyme. Surface plasmon resonance with live bacteria and differential scanning calorimetry studies with bacterial model membranes reveal that, initially, DA facilitates lysozyme incorporation into the membrane, which in turn allows influx of more DA, leading to bacterial cell death. The present study elucidates a molecular basis for the synergistic action of non-esterified fatty acids and antimicrobial polypeptides, which may be dysfunctional in cystic fibrosis.
Martinez
Jose G
JG
Department of Biological Sciences, California State University Los Angeles, 5151 State University Drive, Los Angeles, CA 90032, USA.
Waldon
Michael
M
Huang
Qiyu
Q
Alvarez
Sandra
S
Oren
Ami
A
Sandoval
Natalie
N
Du
Ming
M
Zhou
Feimeng
F
Zenz
Alexandra
A
Lohner
Karl
K
Desharnais
Robert
R
Porter
Edith
E
D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D046529:Microscopy, Electron, Transmission; D009113:Muramidase / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000648:ultrastructure*; D020349:Surface Plasmon Resonance
D004281:Docosahexaenoic Acids; D009113:Muramidase