Antimicrobial and Biophysical Properties of Surfactant Supplemented with an Antimicrobial Peptide for Treatment of Bacterial Pneumonia

Abstract

e Antibiotic-resistant bacterial infections represent an emerging health concern in clinical settings, and a lack of novel developments in the pharmaceutical pipeline is creating a "perfect storm" for multidrug-resistant bacterial infections. Antimicrobial peptides (AMPs) have been suggested as future therapeutics for these drug-resistant bacteria, since they have potent broad-spectrum activity, with little development of resistance. Due to the unique structure of the lung, bacterial pneumonia has the additional problem of delivering antimicrobials to the site of infection. One potential solution is coadministration of AMPs with exogenous surfactant, allowing for distribution of the peptides to distal airways and opening of collapsed lung regions. The objective of this study was to test various surfactant-AMP mixtures with regard to maintaining pulmonary surfactant biophysical properties and bactericidal functions. We compared the properties of four AMPs (CATH-1, CATH-2, CRAMP, and LL-37) suspended in bovine lipid-extract surfactant (BLES) by assessing surfactant-AMP mixture biophysical and antimicrobial functions. Antimicrobial activity was tested against methillicin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. All AMP/surfactant mixtures exhibited an increase of spreading compared to a BLES control. BLES؉CATH-2 mixtures had no significantly different minimum surface tension versus the BLES control. Compared to the other cathelicidins, CATH-2 retained the most bactericidal activity in the presence of BLES. The BLES؉CATH-2 mixture appears to be an optimal surfactant-AMP mixture based on in vitro assays. Future directions involve investigating the potential of this mixture in animal models of bacterial pneumonia.

Differential susceptibility of transgenic mice expressing human surfactant protein B genetic variants to Pseudomonas aeruginosa induced pneumonia

“…Surfactant activity of large aggregates of BALF from infected and sham mice was analyzed by the Constrained Drop Surfactometer (CDS) [18,19,20]. The results indicated that uninfected hSP-B-T and hSP-B-C mice (sham) had similar surface activity, i.e., minimum surface tension (γ min ) about 1.8–2.2 (mN/m) (Fig.…”

“…and the supernatant was then centrifuged for 15 min at 40,000xg, 4°C. After centrifugation, the pellet containing surfactant large aggregates was resuspended in 0.3 ml of saline for surface tension study as previous description [18,19]. The phospholipid concentration of the large aggregates was determined using phosphate assays to be around 1 mg/mL.…”

Physical-Chemical Studies of the Effect of Antibiotic Incorporation in the Structure and Molecular Organization of Clinical-Grade Lung Surfactant Monolayers and Membrane Models at the Air-Water Interface

“…and fluidize the DPPC film. Banaschewski et al(BANASCHEWSKI et al, 2015) found that the presence of microbiotic peptides accelerated the formation of natural lung surfactant films and affected little its biophysical function under high concentrations. However, the antimicrobiotic activity of most tested peptides was inhibited in the presence of natural lung surfactant due to electrostatic interactions between the polar groups of phospholipids and peptides.…”

“…Lung surfactant has actually been used in vivo as a drug carrier (BANASCHEWSKI et al, 2015;FAJARDO et al, 1998;HERTING et al, 1999;KHARASCH et al, 1991;NATARAJAN et al, 2016;VAN'T VEEN et al, 1996;VAN 'T VEEN et al, 1996;YEH et al, 2008), including for the transport of antibiotics to the lung(DALLOW et al, 2014; GEORGIEV; GEORGIEV;…”

“…Hence, before attempts are made to employ the lung surfactant with a specific drug in in vivo tests, it makes sense to verify whether the surfactant will remain stable upon interacting with the drug. Such a study can be made with Langmuir monolayers representing the lung surfactant (BANASCHEWSKI et al, 2015;BENSIKADDOUR et al, 2008b;BERQUAND et al, 2005;BANERJEE, 2005a, 2005b, 2005c, PINHEIRO et al, 2013a, 2013b, which allows for determining the molecularlevel interactions between the surfactant constituents and the drug. and fluidize the DPPC film.…”