Study of the Membrane Activity of the Synthetic Peptide ∆M3 Against Extended-Spectrum ß-lactamase Escherichia coli Isolates.

Escherichia coli is the most common microorganism causing nosocomial or community-acquired bacteremia, and extended-spectrum ß-lactamase-producing Escherichia coli isolates are identified worldwide with increasing frequency. For this reason, it is necessary to evaluate potential new molecules like antimicrobial peptides. They are recognized for their biological potential which makes them promising candidates in the fight against infections. The goal of this research was to evaluate the potential of the synthetic peptide ΔM3 on several extended-spectrum ß-lactamase producing E. coli isolates. The antimicrobial and cytotoxic activity of the peptide was spectrophotometrically determined. Additionally, the capacity of the peptide to interact with the bacterial membrane was monitored by fluorescence microscopy and infrared spectroscopy. The results demonstrated that the synthetic peptide is active against Escherichia coli isolates at concentrations similar to Meropenem. On the other hand, no cytotoxic effect was observed in HaCaT keratinocyte cells even at 10 times the minimal inhibitory concentration. Microscopy results showed a permeabilizing effect of the peptide on the bacteria. The infrared results showed that ΔM3 showed affinity for the lipids of the microorganism's membrane. The results suggest that the ∆M3 interacts with the negatively charged lipids from the E. coli by a disturbing effect on membrane. Finally, the secondary structure experiments of the peptide showed a random structure in solution that did not change during the interaction with the membranes.

Biophysical Insights into the Antitumoral Activity of Crotalicidin against Breast Cancer Model Membranes.

Bioactive peptides have emerged as promising therapeutic agents with antimicrobial, antifungal, antiparasitic, and, recently, antitumoral properties with a mechanism of action based on membrane destabilization and cell death, often involving a conformational change in the peptide. This biophysical study aims to provide preliminary insights into the membrane-level antitumoral mode of action of crotalicidin, a cationic host defense peptide from rattlesnake venom, toward breast cancer cell lines. The lipid composition of breast cancer cell lines was obtained after lipid extraction and quantification to prepare representative cell membrane models. Membrane-peptide interaction studies were performed using differential scanning calorimetry and Fourier-transform infrared spectroscopy. The outcome evidences the potential antitumoral activity and selectivity of crotalicidin toward breast cancer cell lines and suggests a mechanism initiated by the electrostatic interaction of the peptide with the lipid bilayer surface and posterior conformation change with membrane intercalation between the acyl chains in negatively charged lipid systems. This research provides valuable information that clears up the antitumoral mode of action of crotalicidin.

ΔM4: Membrane-Active Peptide with Antitumoral Potential against Human Skin Cancer Cells.

Peptides have become attractive potential agents due to their affinity to cancer cells. In this work, the biological activity of the peptide ΔM4 against melanoma cancer cell line A375, epidermoid carcinoma cell line A431, and non-tumoral HaCaT cells was evaluated. The cytotoxic MTT assay demonstrates that ΔM4 show five times more activity against cancer than non-cancer cells. The potential membrane effect of ΔM4 was evaluated through lactate dehydrogenase release and Sytox uptake experiments. The results show a higher membrane activity of ΔM4 against A431 in comparison with the A375 cell line at a level of 12.5 µM. The Sytox experiments show that ΔM4 has a direct effect on the permeability of cancer cells in comparison with control cells. Infrared spectroscopy was used to study the affinity of the peptide to membranes resembling the composition of tumoral and non-tumoral cells. The results show that ΔM4 induces a fluidization effect on the tumoral lipid system over 5% molar concentration. Finally, to determine the appearance of phosphatidylserine on the surface of the cell, flow cytometry analyses were performed employing an annexin V-PE conjugate. The results suggest that 12.5 µM of ΔM4 induces phosphatidylserine translocation in A375 and A431 cancer cells. The findings of this study support the potential of ΔM4 as a selective agent for targeting cancer cells. Its mechanism of action demonstrated selectivity, membrane-disrupting effects, and induction of phosphatidylserine translocation.

Infrared Spectroscopic Study of Multi-Component Lipid Systems: A Closer Approximation to Biological Membrane Fluidity.

Membranes are essential to cellular organisms, and play several roles in cellular protection as well as in the control and transport of nutrients. One of the most critical membrane properties is fluidity, which has been extensively studied, using mainly single component systems. In this study, we used Fourier transform infrared spectroscopy to evaluate the thermal behavior of multi-component supported lipid bilayers that mimic the membrane composition of tumoral and non-tumoral cell membranes, as well as microorganisms such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. The results showed that, for tumoral and non-tumoral membrane models, the presence of cholesterol induced a loss of cooperativity of the transition. However, in the absence of cholesterol, the transitions of the multi-component lipid systems had sigmoidal curves where the gel and fluid phases are evident and where main transition temperatures were possible to determine. Additionally, the possibility of designing multi-component lipid systems showed the potential to obtain several microorganism models, including changes in the cardiolipin content associated with the resistance mechanism in Staphylococcus aureus. Finally, the potential use of multi-component lipid systems in the determination of the conformational change of the antimicrobial peptide LL-37 was studied. The results showed that LL-37 underwent a conformational change when interacting with Staphylococcus aureus models, instead of with the erythrocyte membrane model. The results showed the versatile applications of multi-component lipid systems studied by Fourier transform infrared spectroscopy.

Understanding the Biophysical Interaction of LTX-315 with Tumoral Model Membranes.

Host defense peptides are found primarily as natural antimicrobial agents among all lifeforms. These peptides and their synthetic derivatives have been extensively studied for their potential use as therapeutic agents. The most accepted mechanism of action of these peptides is related to a nonspecific mechanism associated with their interaction with the negatively charged groups present in membranes, inducing bilayer destabilization and cell death through several routes. Among the most recently reported peptides, LTX-315 has emerged as an important oncolytic peptide that is currently in several clinical trials against different cancer types. However, there is a lack of biophysical studies regarding LTX-315 and its interaction with membranes. This research focuses primarily on the understanding of the molecular bases of LTX-315's interaction with eukaryotic lipids, based on two artificial systems representative of non-tumoral and tumoral membranes. Additionally, the interaction with individual lipids was studied by differential scanning calorimetry and Fourier-transformed infrared spectroscopy. The results showed a strong interaction of LTX-315 with the negatively charged phosphatidylserine. The results are important for understanding and facilitating the design and development of improved peptides with anticancer activity.

Effect of Essential Oils on Growth Inhibition, Biofilm Formation and Membrane Integrity of Escherichia coli and Staphylococcus aureus.

Biofilm as a cellular conformation confers survival properties to microbial populations and favors microbial resistance. Here, we investigated the antimicrobial, antibiofilm, antimotility, antihemolytic activity, and the interaction with synthetic membranes of 15 essential oils (EOs) on E. coli ATCC 25922 and S. aureus ATCC 29213. Antimicrobial activity of EOs was determined through microdilution method; development of the biofilm was assessed using the crystal violet assay and SEM microscopy. Results indicate that Lippia origanoides thymol-carvacrol II chemotype (LTC II) and Thymus vulgaris (TV) exhibited a significant antibacterial activity, with MIC values of 0.45 and 0.75 mg/mL, respectively. The percentage of biofilm formation inhibition was greater than 70% at subinhibitory concentrations (MIC50) for LTC II EO. The results demonstrate that these two oils had significantly reduced the hemolytic effect of S. aureus by 54% and 32%, respectively, and the mobility capacity by swimming in E. coli with percentages of decrease of 55% and 47%, respectively. The results show that LTC II and TV EOs can interact with the hydrophobic core of lipid bilayers and alter the physicochemical properties of membranes. The findings suggest that LTC II and TV oils may potentially be used to aid in the treatment of S. aureus and E. coli infections.