Modulating the activity of short arginine-tryptophan containing antibacterial peptides with N-terminal metallocenoyl groups

Abstract

SummaryA series of small synthetic arginine and tryptophan containing peptides was prepared and analyzed for their antibacterial activity. The effect of N-terminal substitution with metallocenoyl groups such as ferrocene (FcCO) and ruthenocene (RcCO) was investigated. Antibacterial activity in different media, growth inhibition, and killing kinetics of the most active peptides were determined. The toxicity of selected derivatives was determined against erythrocytes and three human cancer cell lines. It was shown that the replacement of an N-terminal arginine residue with a metallocenoyl moiety modulates the activity of WRWRW-peptides against Gram-positive and Gram-negative bacteria. MIC values of 2–6 µM for RcCO-W(RW)2 and 1–11 µM for (RW)3 were determined. Interestingly, W(RW)2-peptides derivatized with ferrocene were significantly less active than those derivatized with ruthenocene which have similar structural but different electronic properties, suggesting a major influence of the latter. The high activities observed for the RcCO-W(RW)2- and (RW)3-peptides led to an investigation of the origin of activity of these peptides using several important activity-related parameters. Firstly, killing kinetics of the RcCO-W(RW)2-peptide versus killing kinetics of the (RW)3 derivative showed faster reduction of the colony forming units for the RcCO-W(RW)2-peptide, although MIC values indicated higher activity for the (RW)3-peptide. This was confirmed by growth inhibition studies. Secondly, hemolysis studies revealed that both peptides did not lead to significant destruction of erythrocytes, even up to 500 µg/mL for (RW)3 and 250 µg/mL for RcCO-W(RW)2. In addition, toxicity against three human cancer cell lines (HepG2, HT29, MCF7) showed that the (RW)3-peptide had an IC50 value of ~140 µM and the RcW(RW)2 one of ~90 µM, indicating a potentially interesting therapeutic window. Both the killing kinetics and growth inhibition studies presented in this work point to a membrane-based mode of action for these two peptides, each having different kinetic parameters.

Small cationic antimicrobial peptides delocalize peripheral membrane proteins

“…That MP196 affected DPPG but not DPPE implies a preference for negatively charged over neutral lipids and could explain the preference for bacterial over erythrocyte membranes. This supposition is consistent with the known low hemolytic activity of MP196 (18). A preference for negatively charged phospholipids has been shown previously for other very small RWrich peptides, Combi-1 (Ac-RRWWRF-NH 2 ) and LfcinB 4-9 (RRWQWR-NH 2 ), using the same method (reviewed in ref.…”

“…S1 for structure) was synthesized for TEM and atomic absorption spectrometry studies. The ruthenocene substitution did not affect antibacterial activity negatively (18), and ruthenium alone is not toxic.…”

“…S1 for structure) as a model representing the minimal pharmacophore of positively charged and hydrophobic amino acids (16,17). It is effective against Grampositive bacteria including methicillin-resistant Staphylococcus aureus strains, is moderately effective against Gram-negative bacteria, has low toxicity against human cell lines, and displays low hemolytic activity (18). MP196 therefore is a promising lead structure for derivatization and already has yielded peptides with improved activities and altered pharmacological properties (19).…”

Synthesis and antibacterial activity of trivalent ultrashort Arg-Trp-based antimicrobial peptides (AMPs)

“…Against Gram-positive bacteria all compounds show good to high activity. Especially compound 10b has MIC values (7.3-1.8 mM) that are as good as the linear hexapeptide H-RWRWRW-NH 2 (RW) 3 (5.3-1.3 mM) 8 which was the lead structure for the trivalent peptide conjugates. As it was shown before making the linear peptide longer than six amino acids does not necessarily lead to a better activity.…”

Stable and Persistent Acyclic Diaminocarbenes with Cycloalkyl Substituents and Their Transformation to β‐Lactams by Uncatalysed Carbonylation with CO

“…MIC tests : Compounds were tested against Escherichia coli DSM 30083, Acinetobacter baumannii DSM 30007, Pseudomonas aeruginosa DSM 50071, Bacillus subtilis DSM 402, Staphylococcus aureus DSM 20231 and Staphylococcus aureus ATCC 43300 (MRSA) in a microtiter plate assay according to CLSI guidelines, as described in ref . E. coli , A. baumannii , S. aureus and B. subtilis were grown in Mueller Hinton broth, P. aeruginosa in cation‐adjusted Mueller Hinton II.…”