Open AccessInvestigating the effects of positive charge and hydrophobicity on the cell selectivity, mechanism of action and anti‐inflammatory activity of a Trp‐rich antimicrobial peptide indolicidin
Author(s) -
Nan Yong Hai,
Park Ka Hyon,
Park Yoonkyung,
Jeon Young Jin,
Kim Yangmee,
Park IlSeon,
Hahm KyungSoo,
Shin Song Yub
Publication year - 2009
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2008.01484.x
Subject(s) - antimicrobial , mechanism of action , intracellular , antimicrobial peptides , lipopolysaccharide , nitric oxide , chemistry , biochemistry , cell membrane , membrane potential , cell , peptide , membrane , escherichia coli , biophysics , biology , gene , in vitro , organic chemistry , endocrinology
To investigate the effects of positive charge and hydrophobicity on the cell selectivity, mechanism of action and anti‐inflammatory activity of a Trp‐rich antimicrobial peptide indolicidin (IN), a series of IN analogs with Trp→Lys substitution were synthesized. All IN analogs displayed an approximately 7‐ to 18‐fold higher cell selectivity, compared with IN. IN, IN‐1 and IN‐2 depolarized (50−90%) the cytoplasmic membrane potential of Staphylococcus aureus close to minimal inhibitory concentration (5–10 μg mL −1 ). However, other IN analogs (IN‐3 and IN‐4) displayed very low ability in membrane depolarization even at 40 μg mL −1 . Confocal laser‐scanning microscopy revealed that IN‐3 and IN‐4 penetrated the Escherichia coli cell membrane, whereas IN, IN‐1 and IN‐2 did not enter the cell membrane. In the gel retardation assay, IN‐3 and IN‐4 bound more strongly to DNA compared with IN, IN‐1 and IN‐2. These findings suggest that the mechanism of antimicrobial action of IN‐3 and IN‐4 may be involved in the inhibition of intracellular functions via interference with DNA/RNA synthesis. Unlike IN, all IN analogs did not inhibit nitric oxide production or inducible nitric oxide synthase mRNA expression in lipopolysaccharide‐stimulated mouse macrophage RAW264.7 cells, indicating that the hydrophobicity of IN is more important for anti‐inflammatory activity in lipopolysaccharide‐treated macrophage cells than the positive charge.