1
|
Mitra S, Chandersekhar B, Li Y, Coopershlyak M, Mahoney ME, Evans B, Koenig R, Hall SCL, Klösgen B, Heinrich F, Deslouches B, Tristram-Nagle S. Novel non-helical antimicrobial peptides insert into and fuse lipid model membranes. SOFT MATTER 2024; 20:4088-4101. [PMID: 38712559 PMCID: PMC11109824 DOI: 10.1039/d4sm00220b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 04/26/2024] [Indexed: 05/08/2024]
Abstract
This research addresses the growing menace of antibiotic resistance by exploring antimicrobial peptides (AMPs) as alternatives to conventional antibiotics. Specifically, we investigate two linear amphipathic AMPs, LE-53 (12-mer) and LE-55 (16-mer), finding that the shorter LE-53 exhibits greater bactericidal activity against both Gram-negative (G(-)) and Gram-positive (G(+)) bacteria. Remarkably, both AMPs are non-toxic to eukaryotic cells. The heightened effectiveness of LE-53 is attributed to its increased hydrophobicity (H) compared to LE-55. Circular dichroism (CD) reveals that LE-53 and LE-55 both adopt β-sheet and random coil structures in lipid model membranes (LMMs) mimicking G(-) and G(+) bacteria, so secondary structure is not the cause of the potency difference. X-ray diffuse scattering (XDS) reveals increased lipid chain order in LE-53, a potential key distinction. Additionally, XDS study uncovers a significant link between LE-53's upper hydrocarbon location in G(-) and G(+) LMMs and its efficacy. Neutron reflectometry (NR) confirms the AMP locations determined using XDS. Solution small angle X-ray scattering (SAXS) demonstrates LE-53's ability to induce vesicle fusion in bacterial LMMs without affecting eukaryotic LMMs, offering a promising strategy to combat antibiotic-resistant strains while preserving human cell integrity, whereas LE-55 has a smaller ability to induce fusion.
Collapse
Affiliation(s)
- Saheli Mitra
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Bhairavi Chandersekhar
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Yunshu Li
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Mark Coopershlyak
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Margot E Mahoney
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Brandt Evans
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Rachel Koenig
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Stephen C L Hall
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Beate Klösgen
- University of Southern Denmark, Dept. Physics, Chemistry & Pharmacy, PhyLife, Campusvej 55, Odense M5230, Denmark
| | - Frank Heinrich
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Berthony Deslouches
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Stephanie Tristram-Nagle
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| |
Collapse
|
2
|
Jennings J, Ašćerić D, Semeraro EF, Lohner K, Malanovic N, Pabst G. Combinatorial Screening of Cationic Lipidoids Reveals How Molecular Conformation Affects Membrane-Targeting Antimicrobial Activity. ACS APPLIED MATERIALS & INTERFACES 2023; 15:40178-40190. [PMID: 37602460 PMCID: PMC10472336 DOI: 10.1021/acsami.3c05481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 08/04/2023] [Indexed: 08/22/2023]
Abstract
The search for next-generation antibacterial compounds that overcome the development of resistance can be facilitated by identifying how to target the cell membrane of bacteria. Understanding the key molecular features that enable interactions with lipids and lead to membrane disruption is therefore crucial. Here, we employ a library of lipid-like compounds (lipidoids) comprising modular structures with tunable hydrophobic and hydrophilic architecture to shed light on how the chemical functionality and molecular shape of synthetic amphiphilic compounds determine their activity against bacterial membranes. Synthesized from combinations of 8 different polyamines as headgroups and 13 acrylates as tails, 104 different lipidoids are tested for activity against a model Gram-positive bacterial strain (Bacillus subtilis). Results from the combinatorial screening assay show that lipidoids with the most potent antimicrobial properties (down to 2 μM) have intermediate tail hydrophobicity (i.e., c log P values between 3 and 4) and lower headgroup charge density (i.e., longer spacers between charged amines). However, the most important factor appeared to be the ability of a lipidoid to self-assemble into an inverse hexagonal liquid crystalline phase, as observed by small-angle X-ray scattering (SAXS) analysis. The lipidoids active at lowest concentrations, which induced the most significant membrane damage during propidium iodide (PI) permeabilization assays, were those that aggregated into highly curved inverse hexagonal liquid crystal phases. These observations suggest that the introduction of strong curvature stress into the membrane is one way to maximize membrane disruption and lipidoid antimicrobial activity. Lipidoids that demonstrated the ability to furnish this phase consisted of either (i) branched or linear headgroups with shorter linear tails or (ii) cyclic headgroups with 4 bulky nonlinear tails. On the contrary, lipidoids previously observed to adopt disc-like conformations that pack into bicontinuous cubic phases were significantly less effective against B. subtilis. The discovery of these structure-property relationships demonstrates that it is not simply a balance of hydrophobic and hydrophilic moieties that govern membrane-active antibacterial activity, but also their intrinsic curvature and collective behavior.
Collapse
Affiliation(s)
- James Jennings
- Institute
of Molecular Biosciences, University of
Graz, NAWI Graz, 8010 Graz, Austria
- Field
of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Dunja Ašćerić
- Institute
of Molecular Biosciences, University of
Graz, NAWI Graz, 8010 Graz, Austria
- Field
of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Enrico Federico Semeraro
- Institute
of Molecular Biosciences, University of
Graz, NAWI Graz, 8010 Graz, Austria
- Field
of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Karl Lohner
- Institute
of Molecular Biosciences, University of
Graz, NAWI Graz, 8010 Graz, Austria
- Field
of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Nermina Malanovic
- Institute
of Molecular Biosciences, University of
Graz, NAWI Graz, 8010 Graz, Austria
- Field
of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Georg Pabst
- Institute
of Molecular Biosciences, University of
Graz, NAWI Graz, 8010 Graz, Austria
- Field
of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| |
Collapse
|
3
|
Jennings J, Ašćerić D, Malanovic N, Pabst G. Structure-Activity Relationships of Cationic Lipidoids against Escherichia coli. Antibiotics (Basel) 2023; 12:1300. [PMID: 37627720 PMCID: PMC10451255 DOI: 10.3390/antibiotics12081300] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/02/2023] [Accepted: 08/05/2023] [Indexed: 08/27/2023] Open
Abstract
Membrane-active molecules provide a promising strategy to target and kill pathogenic bacteria. Understanding how specific molecular features drive interactions with membrane components and subsequently cause disruption that leads to antimicrobial activity is a crucial step in designing next-generation treatments. Here, we test a library of lipid-like compounds (lipidoids) against Gram-negative bacteria Escherichia coli to garner in-depth structure-activity relationships using antimicrobial assays. Modular lipidoid molecules were synthesized in high-throughput, such that we could analyze 104 compounds with variable combinations of hydrophobic tails and cationic headgroups. Antibacterial activity was strongly correlated to specific structural features, including tail hydrophobicity and headgroup charge density, and also to the overall molecular shape and propensity for self-assembly into curved liquid crystalline phases. Dye permeabilization assays showed that E. coli membranes were permeabilized by lipidoids, confirming their membrane-active nature. The reduced permeabilization, as compared to Gram-positive Bacillus subtilis, alludes to the challenge of permeabilizing the additional outer membrane layer of E. coli. The effect of headgroup solubility in gemini-type lipidoids was also demonstrated, revealing that a headgroup with a more hydrophilic spacer between amine groups had enhanced activity against B. subtilis but not E. coli. This provides insight into features enabling outer membrane penetration and governing selectivity between bacterial species.
Collapse
Affiliation(s)
- James Jennings
- Institute of Molecular Biosciences, University of Graz, NAWI Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Dunja Ašćerić
- Institute of Molecular Biosciences, University of Graz, NAWI Graz, 8010 Graz, Austria
| | - Nermina Malanovic
- Institute of Molecular Biosciences, University of Graz, NAWI Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Georg Pabst
- Institute of Molecular Biosciences, University of Graz, NAWI Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| |
Collapse
|
4
|
Ön A, Vejzovic D, Jennings J, Parigger L, Cordfunke RA, Drijfhout JW, Lohner K, Malanovic N. Bactericidal Activity to Escherichia coli: Different Modes of Action of Two 24-Mer Peptides SAAP-148 and OP-145, Both Derived from Human Cathelicidine LL-37. Antibiotics (Basel) 2023; 12:1163. [PMID: 37508259 PMCID: PMC10376646 DOI: 10.3390/antibiotics12071163] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 07/05/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023] Open
Abstract
OP-145 and SAAP-148, two 24-mer antimicrobial peptides derived from human cathelicidin LL-37, exhibit killing efficacy against both Gram-positive and Gram-negative bacteria at comparable peptide concentrations. However, when it comes to the killing activity against Escherichia coli, the extent of membrane permeabilization does not align with the observed bactericidal activity. This is the case in living bacteria as well as in model membranes mimicking the E. coli cytoplasmic membrane (CM). In order to understand the killing activity of both peptides on a molecular basis, here we studied their mode of action, employing a combination of microbiological and biophysical techniques including differential scanning calorimetry (DSC), zeta potential measurements, and spectroscopic analyses. Various membrane dyes were utilized to monitor the impact of the peptides on bacterial and model membranes. Our findings unveiled distinct binding patterns of the peptides to the bacterial surface and differential permeabilization of the E. coli CM, depending on the smooth or rough/deep-rough lipopolysaccharide (LPS) phenotypes of E. coli strains. Interestingly, the antimicrobial activity and membrane depolarization were not significantly different in the different LPS phenotypes investigated, suggesting a general mechanism that is independent of LPS. Although the peptides exhibited limited permeabilization of E. coli membranes, DSC studies conducted on a mixture of synthetic phosphatidylglycerol/phosphatidylethanolamine/cardiolipin, which mimics the CM of Gram-negative bacteria, clearly demonstrated disruption of lipid chain packing. From these experiments, we conclude that depolarization of the CM and alterations in lipid packing plays a crucial role in the peptides' bactericidal activity.
Collapse
Affiliation(s)
- Ayse Ön
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Djenana Vejzovic
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - James Jennings
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Lena Parigger
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Robert A Cordfunke
- Department of Immunology, Leiden University Medical Center, 2333 Leiden, The Netherlands
| | - Jan Wouter Drijfhout
- Department of Immunology, Leiden University Medical Center, 2333 Leiden, The Netherlands
| | - Karl Lohner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
- BioTechMed Graz, 8010 Graz, Austria
| | - Nermina Malanovic
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
- BioTechMed Graz, 8010 Graz, Austria
| |
Collapse
|
5
|
Beck K, Nandy J, Hoernke M. Membrane permeabilization can be crucially biased by a fusogenic lipid composition - leaky fusion caused by antimicrobial peptides in model membranes. SOFT MATTER 2023; 19:2919-2931. [PMID: 37010846 DOI: 10.1039/d2sm01691e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Induced membrane permeabilization or leakage is often taken as an indication for activity of membrane-active molecules, such as antimicrobial peptides (AMPs). The exact leakage mechanism is often unknown, but important, because certain mechanisms might actually contribute to microbial killing, while others are unselective, or potentially irrelevant in an in vivo situation. Using an antimicrobial example peptide (cR3W3), we illustrate one of the potentially misleading leakage mechanisms: leaky fusion, where leakage is coupled to membrane fusion. Like many others, we examine peptide-induced leakage in model vesicles consisting of binary mixtures of anionic and zwitterionic phospholipids. In fact, phosphatidylglycerol and phosphatidylethanolamine (PG/PE) are supposed to reflect bacterial membranes, but exhibit a high propensity for vesicle aggregation and fusion. We describe the implications of this vesicle fusion and aggregation for the reliability of model studies. The ambiguous role of the relatively fusogenic PE-lipids becomes clear as leakage decreases significantly when aggregation and fusion are prevented by sterical shielding. Furthermore, the mechanism of leakage changes if PE is exchanged for phosphatidylcholine (PC). We thus point out that the lipid composition of model membranes can be biased towards leaky fusion. This can lead to discrepancies between model studies and activity in true microbes, because leaky fusion is likely prevented by bacterial peptidoglycan layers. In conclusion, choosing the model membrane might implicate the type of effect (here leakage mechanism) that is observed. In the worst case, as with leaky fusion of PG/PE vesicles, this is not directly relevant for the intended antimicrobial application.
Collapse
Affiliation(s)
- Katharina Beck
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| | - Janina Nandy
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| |
Collapse
|
6
|
Semeraro EF, Pajtinka P, Marx L, Kabelka I, Leber R, Lohner K, Vácha R, Pabst G. Magainin 2 and PGLa in bacterial membrane mimics IV: Membrane curvature and partitioning. Biophys J 2022; 121:4689-4701. [PMID: 36258677 PMCID: PMC9748257 DOI: 10.1016/j.bpj.2022.10.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/10/2022] [Accepted: 10/12/2022] [Indexed: 12/15/2022] Open
Abstract
We previously reported that the synergistically enhanced antimicrobial activity of magainin 2 (MG2a) and PGLa is related to membrane adhesion and fusion. Here, we demonstrate that equimolar mixtures of MG2a and L18W-PGLa induce positive monolayer curvature stress and sense, at the same time, positive mean and Gaussian bilayer curvatures already at low amounts of bound peptide. The combination of both abilities-membrane curvature sensing and inducing-is most likely the base for the synergistically enhanced peptide activity. In addition, our coarse-grained simulations suggest that fusion stalks are promoted by decreasing the free-energy barrier for their formation rather than by stabilizing their shape. We also interrogated peptide partitioning as a function of lipid and peptide concentration using tryptophan fluorescence spectroscopy and peptide-induced leakage of dyes from lipid vesicles. In agreement with a previous report, we find increased membrane partitioning of L18W-PGLa in the presence of MG2a. However, this effect does not prevail to lipid concentrations higher than 1 mM, above which all peptides associate with the lipid bilayers. This implies that synergistic effects of MG2a and L18W-PGLa in previously reported experiments with lipid concentrations >1 mM are due to peptide-induced membrane remodeling and not their specific membrane partitioning.
Collapse
Affiliation(s)
- Enrico F Semeraro
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | - Peter Pajtinka
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic; Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Lisa Marx
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | - Ivo Kabelka
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Regina Leber
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | - Karl Lohner
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | - Robert Vácha
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic; Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Brno, Czech Republic.
| | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Graz, Austria; BioTechMed Graz, Graz, Austria.
| |
Collapse
|
7
|
Shi S, Fan H, Hoernke M. Leaky membrane fusion: an ambivalent effect induced by antimicrobial polycations. NANOSCALE ADVANCES 2022; 4:5109-5122. [PMID: 36504745 PMCID: PMC9680940 DOI: 10.1039/d2na00464j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/24/2022] [Indexed: 05/28/2023]
Abstract
Both antimicrobial peptides and their synthetic mimics are potential alternatives to classical antibiotics. They can induce several membrane perturbations including permeabilization. Especially in model studies, aggregation of vesicles by such polycations is often reported. Here, we show that unintended vesicle aggregation or indeed fusion can cause apparent leakage in model studies that is not possible in most microbes, thus potentially leading to misinterpretations. The interactions of a highly charged and highly selective membrane-active polycation with negatively charged phosphatidylethanolamine/phosphatidylglycerol (PE/PG) vesicles are studied by a combination of biophysical methods. At low polycation concentrations, apparent vesicle aggregation was found to involve exchange of lipids. Upon neutralization of the negatively charged vesicles by the polycation, full fusion and leakage occurred and leaky fusion is suspected. To elucidate the interplay of leakage and fusion, we prevented membrane contacts by decorating the vesicles with PEG-chains. This inhibited fusion and also leakage activity. Leaky fusion is further corroborated by increased leakage with increasing likeliness of vesicle-vesicle contacts. Because of its similar appearance to other leakage mechanisms, leaky fusion is difficult to identify and might be overlooked and more common amongst polycationic membrane-active compounds. Regarding biological activity, leaky fusion needs to be carefully distinguished from other membrane permeabilization mechanisms, as it may be less relevant to bacteria, but potentially relevant for fungi. Furthermore, leaky fusion is an interesting effect that could help in endosomal escape for drug delivery. A comprehensive step-by-step protocol for membrane permeabilization/vesicle leakage using calcein fluorescence lifetime is provided in the ESI.
Collapse
Affiliation(s)
- Shuai Shi
- Chemistry and Pharmacy, Albert-Ludwigs-Universität 79104 Freiburg i.Br. Germany
| | - Helen Fan
- Leslie Dan Faculty of Pharmacy, University of Toronto Toronto Canada
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität 79104 Freiburg i.Br. Germany
| |
Collapse
|
8
|
Vejzovic D, Iftic A, Ön A, Semeraro EF, Malanovic N. Octenidine's Efficacy: A Matter of Interpretation or the Influence of Experimental Setups? Antibiotics (Basel) 2022; 11:1665. [PMID: 36421309 PMCID: PMC9686575 DOI: 10.3390/antibiotics11111665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 07/30/2023] Open
Abstract
With its broad antimicrobial spectrum and non-specific mode of action via membrane disruption, any resistance to octenidine (OCT) seems unlikely and has not been observed in clinical settings so far. In this study, we aimed to investigate the efficacy of OCT against Escherichia coli and mutants lacking specific lipid head groups which, due to altered membrane properties, might be the root cause for resistance development of membrane-active compounds. Furthermore, we aimed to test its efficacy under different experimental conditions including different solvents for OCT, bacterial concentration and methods for analysis. Our primary goal was to estimate how many OCT molecules are needed to kill one bacterium. We performed susceptibility assays by observing bacterial growth behavior, using a Bioscreen in an analogous manner for every condition. The growth curves were recorded for 20 h at 420-580 nm in presence of different OCT concentrations and were used to assess the inhibitory concentrations (IC100%) for OCT. Bacterial concentrations given in cell numbers were determined, followed by Bioscreen measurement by manual colony counting on agar plates and QUANTOMTM cell staining. This indicated a significant variance between both methods, which influenced IC100% of OCT, especially when used at low doses. The binding capacity of OCT to E. coli was investigated by measuring UV-absorbance of OCT exposed to bacteria and a common thermodynamic framework based on Bioscreen measurements. Results showed that OCT's antimicrobial activity in E. coli is not affected by changes at the membrane level but strongly dependent on experimental settings in respect to solvents and applied bacterial counts. More OCT was required when the active was dissolved in phosphate or Hepes buffers instead of water and when higher bacterial concentration was used. Furthermore, binding studies revealed that 107-108 OCT molecules bind to bacteria, which is necessary for the saturation of the bacterial surface to initiate the killing cascade. Our results clearly demonstrate that in vitro data, depending on the applied materials and the methods for determination of IC100%, can easily be misinterpreted as reduced bacterial susceptibility towards OCT.
Collapse
Affiliation(s)
- Djenana Vejzovic
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Azra Iftic
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Ayse Ön
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Enrico F. Semeraro
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
- Bio TechMed Graz, 8010 Graz, Austria
| | - Nermina Malanovic
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
- Bio TechMed Graz, 8010 Graz, Austria
| |
Collapse
|
9
|
Vejzovic D, Piller P, Cordfunke RA, Drijfhout JW, Eisenberg T, Lohner K, Malanovic N. Where Electrostatics Matter: Bacterial Surface Neutralization and Membrane Disruption by Antimicrobial Peptides SAAP-148 and OP-145. Biomolecules 2022; 12:biom12091252. [PMID: 36139091 PMCID: PMC9496175 DOI: 10.3390/biom12091252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/30/2022] [Accepted: 09/04/2022] [Indexed: 11/22/2022] Open
Abstract
The need for alternative treatment of multi-drug-resistant bacteria led to the increased design of antimicrobial peptides (AMPs). AMPs exhibit a broad antimicrobial spectrum without a distinct preference for a specific species. Thus, their mechanism, disruption of fundamental barrier function by permeabilization of the bacterial cytoplasmic membrane is considered to be rather general and less likely related to antimicrobial resistance. Of all physico-chemical properties of AMPs, their positive charge seems to be crucial for their interaction with negatively charged bacterial membranes. Therefore, we elucidate the role of electrostatic interaction on bacterial surface neutralization and on membrane disruption potential of two potent antimicrobial peptides, namely, OP-145 and SAAP-148. Experiments were performed on Escherichia coli, a Gram-negative bacterium, and Enterococcus hirae, a Gram-positive bacterium, as well as on their model membranes. Zeta potential measurements demonstrated that both peptides neutralized the surface charge of E. coli immediately after their exposure, but not of E. hirae. Second, peptides neutralized all model membranes, but failed to efficiently disrupt model membranes mimicking Gram-negative bacteria. This was further confirmed by flow cytometry showing reduced membrane permeability for SAAP-148 and the lack of OP-145 to permeabilize the E. coli membrane. As neutralization of E. coli surface charges was achieved before the cells were killed, we conclude that electrostatic forces are more important for actions on the surface of Gram-negative bacteria than on their cytoplasmic membranes.
Collapse
Affiliation(s)
- Djenana Vejzovic
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | - Paulina Piller
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | - Robert A. Cordfunke
- Department of Immunology, Leiden University Medical Center, 2300 ZA Leiden, The Netherlands
| | - Jan W. Drijfhout
- Department of Immunology, Leiden University Medical Center, 2300 ZA Leiden, The Netherlands
| | - Tobias Eisenberg
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
- Bio TechMed Graz, 8010 Graz, Austria
| | - Karl Lohner
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
- Department of Immunology, Leiden University Medical Center, 2300 ZA Leiden, The Netherlands
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Nermina Malanovic
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
- Bio TechMed Graz, 8010 Graz, Austria
- Correspondence:
| |
Collapse
|
10
|
Semeraro EF, Marx L, Mandl J, Letofsky-Papst I, Mayrhofer C, Frewein MPK, Scott HL, Prévost S, Bergler H, Lohner K, Pabst G. Lactoferricins impair the cytosolic membrane of Escherichia coli within a few seconds and accumulate inside the cell. eLife 2022; 11:e72850. [PMID: 35670565 PMCID: PMC9352351 DOI: 10.7554/elife.72850] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 06/06/2022] [Indexed: 12/29/2022] Open
Abstract
We report the real-time response of Escherichia coli to lactoferricin-derived antimicrobial peptides (AMPs) on length scales bridging microscopic cell sizes to nanoscopic lipid packing using millisecond time-resolved synchrotron small-angle X-ray scattering. Coupling a multiscale scattering data analysis to biophysical assays for peptide partitioning revealed that the AMPs rapidly permeabilize the cytosolic membrane within less than 3 s-much faster than previously considered. Final intracellular AMP concentrations of ∼80-100 mM suggest an efficient obstruction of physiologically important processes as the primary cause of bacterial killing. On the other hand, damage of the cell envelope and leakage occurred also at sublethal peptide concentrations, thus emerging as a collateral effect of AMP activity that does not kill the bacteria. This implies that the impairment of the membrane barrier is a necessary but not sufficient condition for microbial killing by lactoferricins. The most efficient AMP studied exceeds others in both speed of permeabilizing membranes and lowest intracellular peptide concentration needed to inhibit bacterial growth.
Collapse
Affiliation(s)
- Enrico F Semeraro
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
| | - Lisa Marx
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
| | - Johannes Mandl
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
| | - Ilse Letofsky-Papst
- Institute of Electron Microscopy and Nanoanalysis and Center for Electron Microscopy, Graz University of Technology, NAWI GrazGrazAustria
| | | | - Moritz PK Frewein
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
- Institut Laue-LangevinGrenobleFrance
| | - Haden L Scott
- Center for Environmental Biotechnology, University of TennesseeKnoxvilleUnited States
- Shull Wollan Center, Oak Ridge National LaboratoryOak RidgeUnited States
| | | | - Helmut Bergler
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
| | - Karl Lohner
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
| | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, NAWI GrazGrazAustria
- BioTechMed GrazGrazAustria
- Field of Excellence BioHealth – University of GrazGrazAustria
| |
Collapse
|
11
|
Kabelka I, Georgiev V, Marx L, Pajtinka P, Lohner K, Pabst G, Dimova R, Vácha R. Magainin 2 and PGLa in bacterial membrane mimics III: Membrane fusion and disruption. Biophys J 2022; 121:852-861. [PMID: 35134334 PMCID: PMC8943694 DOI: 10.1016/j.bpj.2021.12.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/27/2021] [Accepted: 12/22/2021] [Indexed: 11/30/2022] Open
Abstract
We previously speculated that the synergistically enhanced antimicrobial activity of Magainin 2 and PGLa is related to membrane adhesion, fusion, and further membrane remodeling. Here we combined computer simulations with time-resolved in vitro fluorescence microscopy, cryoelectron microscopy, and small-angle X-ray scattering to interrogate such morphological and topological changes of vesicles at nanoscopic and microscopic length scales in real time. Coarse-grained simulations revealed formation of an elongated and bent fusion zone between vesicles in the presence of equimolar peptide mixtures. Vesicle adhesion and fusion were observed to occur within a few seconds by cryoelectron microscopy and corroborated by small-angle X-ray scattering measurements. The latter experiments indicated continued and time-extended structural remodeling for individual peptides or chemically linked peptide heterodimers but with different kinetics. Fluorescence microscopy further captured peptide-dependent adhesion, fusion, and occasional bursting of giant unilamellar vesicles a few seconds after peptide addition. The synergistic interactions between the peptides shorten the time response of vesicles and enhance membrane fusogenic and disruption properties of the equimolar mixture compared with the individual peptides.
Collapse
Affiliation(s)
- Ivo Kabelka
- CEITEC – Central European Institute of Technology, Masaryk University, Brno, Czech Republic,National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Vasil Georgiev
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, Potsdam, Germany
| | - Lisa Marx
- Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz, Austria,BioTechMed Graz, Graz, Austria
| | - Peter Pajtinka
- CEITEC – Central European Institute of Technology, Masaryk University, Brno, Czech Republic,National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic,Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Karl Lohner
- Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz, Austria,BioTechMed Graz, Graz, Austria
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz, Austria,BioTechMed Graz, Graz, Austria
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, Potsdam, Germany
| | - Robert Vácha
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic; Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Brno, Czech Republic.
| |
Collapse
|
12
|
Shi S, Markl AM, Lu Z, Liu R, Hoernke M. Interplay of Fusion, Leakage, and Electrostatic Lipid Clustering: Membrane Perturbations by a Hydrophobic Antimicrobial Polycation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2379-2391. [PMID: 35148117 DOI: 10.1021/acs.langmuir.1c03445] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Membrane active compounds are able to induce various types of membrane perturbations. Natural or biomimetic candidates for antimicrobial treatment or drug delivery scenarios are mostly designed and tested for their ability to induce membrane permeabilization, also termed leakage. Furthermore, the interaction of these usually cationic amphiphiles with negatively charged vesicles often causes colloidal instability leading to vesicle aggregation or/and vesicle fusion. We show the interplay of these modes of membrane perturbation in mixed phosphatidyl glycerol (PG)/phosphatidyl ethanolamine (PE) by the statistical copolymer MM:CO comprising, both, charged and hydrophobic subunits. MM:CO is a representative of partially hydrophobic, highly active, but less selective antimicrobial polycations. Cryo-electron microscopy indicates vesicle fusion rather than vesicle aggregation upon the addition of MM:CO to negatively charged PG/PE (1:1) vesicles. In a combination of fluorescence-based leakage and fusion assays, there is support for membrane permeabilization and pronounced vesicle fusion activity as distinct effects. To this end, membrane fusion and aggregation were prevented by including lipids with polyethylene glycol attached to their head groups (PEG-lipids). The leakage activity of MM:CO is very similar in the absence and presence of PEG-lipids. Vesicle aggregation and fusion however are largely suppressed. This strongly suggests that MM:CO induces leakage by asymmetric packing stress because of hydrophobically driven interactions which could lead to leakage. As a further membrane perturbation effect, MM:CO causes lipid clustering in model vesicles. We address potential artifacts and misinterpretations of experiments characterizing leakage and fusion. Additional to the leakage activity, the pronounced fusogenic activity of the polymer and potentially of many other similar compounds likely has implications for antimicrobial activity and beyond.
Collapse
Affiliation(s)
- Shuai Shi
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, 79104 Freiburg i.Br., Germany
| | - Anja Madleine Markl
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, 79104 Freiburg i.Br., Germany
| | - Ziyi Lu
- State Key Laboratory of Bioreactor Engineering, Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Runhui Liu
- State Key Laboratory of Bioreactor Engineering, Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, 79104 Freiburg i.Br., Germany
| |
Collapse
|
13
|
Marx L, Frewein MPK, Semeraro EF, Rechberger GN, Lohner K, Porcar L, Pabst G. Antimicrobial peptide activity in asymmetric bacterial membrane mimics. Faraday Discuss 2021; 232:435-447. [PMID: 34532723 PMCID: PMC8704130 DOI: 10.1039/d1fd00039j] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 07/21/2021] [Indexed: 11/21/2022]
Abstract
We report on the response of asymmetric lipid membranes composed of palmitoyl oleoyl phosphatidylethanolamine and palmitoyl oleoyl phosphatidylglycerol, to interactions with the frog peptides L18W-PGLa and magainin 2 (MG2a), as well as the lactoferricin derivative LF11-215. In particular we determined the peptide-induced lipid flip-flop, as well as membrane partitioning of L18W-PGLa and LF11-215, and vesicle dye-leakage induced by L18W-PGLa. The ability of L18W-PGLa and MG2a to translocate through the membrane appears to correlate with the observed lipid flip-flop, which occurred at the fastest rate for L18W-PGLa. The higher structural flexibility of LF11-215 in turn allows this peptide to insert into the bilayers without detectable changes of membrane asymmetry. The increased vulnerability of asymmetric membranes to L18W-PGLa in terms of permeability, appears to be a consequence of tension differences between the compositionally distinct leaflets, but not due to increased peptide partitioning.
Collapse
Affiliation(s)
- Lisa Marx
- University of Graz, Institute of Molecular Biosciences, NAWI Graz, 8010 Graz, Austria.
- Field of Excellence BioHealth, University of Graz, Graz, Austria
| | - Moritz P K Frewein
- University of Graz, Institute of Molecular Biosciences, NAWI Graz, 8010 Graz, Austria.
- Field of Excellence BioHealth, University of Graz, Graz, Austria
- Institut Laue-Langevin, 38043 Grenoble, France
| | - Enrico F Semeraro
- University of Graz, Institute of Molecular Biosciences, NAWI Graz, 8010 Graz, Austria.
- Field of Excellence BioHealth, University of Graz, Graz, Austria
| | - Gerald N Rechberger
- University of Graz, Institute of Molecular Biosciences, NAWI Graz, 8010 Graz, Austria.
- Field of Excellence BioHealth, University of Graz, Graz, Austria
| | - Karl Lohner
- University of Graz, Institute of Molecular Biosciences, NAWI Graz, 8010 Graz, Austria.
- Field of Excellence BioHealth, University of Graz, Graz, Austria
| | | | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, NAWI Graz, 8010 Graz, Austria.
- Field of Excellence BioHealth, University of Graz, Graz, Austria
| |
Collapse
|