Ultrashort Cationic Lipopeptides and Lipopeptoids Selectively Induce Cytokine Production in Macrophages

Brandon Findlay,Frank Schweizer,Neeloffer Mookherjee,Claudio M Costa-Neto

doi:10.1371/journal.pone.0054280

Brandon Findlay, Frank Schweizer + Show 2 more

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https://doi.org/10.1371/journal.pone.0054280

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Abstract

A series of ultrashort lipopeptides and lipopeptoids were tested for their ability to induce cytokine production in macrophages. Fourteen compounds were found to strongly induce production of chemokines Groα and IL-8, with a structural bias that was absent from previous antibacterial activity investigations. Compounds based on LysGlyLys and NLysGlyNLys sequences did not induce cytokine production, whereas those based on LysLysLys and NLysNLysNLys were active only when linked to a lipid tail at least sixteen carbons long. Three lipopeptides induced high levels of IL-8 production, above that of equivalent concentrations of cathelicidin LL-37, while no compound induced production of the pro-inflammatory cytokine TNF-α at or below 100 µM. Two compounds, peptoids C16OH-NLysNLysNLys and C16OH-NHarNHarNHar, were selective for IL-8 production and did not induce TNF-α or IL-1β. These compounds may prove beneficial for in vivo treatment of infectious disease, with improved bioavailability over LL-37 due to their protease-resistant scaffold.

Highlights

It is well established that the prevalence of antibiotic resistance is rising in pathogenic bacteria, in part due to selective pressure from human antibiotic use and from the use of antibiotics as growth promoters in livestock [1,2]
Our compound synthesis was biased towards these properties (General Chemical Procedures, Supplementary Materials), with LysGlyLys or LysLysLys based amphiphiles (NLysGlyNLys and NLysNLysNLys for the lipopeptoids) and lipid tails eleven to twenty carbons in length (Figure 1, Table 1, Table S1)
Increasing the strength of the cationic charge has been found to improve antibacterial activity [28], and so each of the LysLysLys and NLysNLysNLys compounds was mirrored by a homoarginine analogue (Har or NHar), to determine if immunomodulatory properties would be enhanced

Summary

Introduction

It is well established that the prevalence of antibiotic resistance is rising in pathogenic bacteria, in part due to selective pressure from human antibiotic use and from the use of antibiotics as growth promoters in livestock [1,2]. The urgent need for new antibiotics has driven research into new scaffolds and unconventional modes of action, with the field of cationic antimicrobial peptides (CAMPs) of particular interest [4]. Unlike classical antibiotics, which derive their activity through inhibition of specific enzymes or processes, CAMPs largely interact with the cell through nonspecific interactions driven by a mix of electrostatic and hydrophobic effects [6]. Researchers were interested in the effect of CAMPs on bacterial and mammalian membranes, as many compounds were found to form membrane pores at sufficiently high concentrations and it was thought that a membrane-specific mode of action had reduced potential for resistance development [7,8]

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