Interaction of Pexiganan (MSI-78)-Derived Analogues Reduces Inflammation and TLR4-Mediated Cytokine Secretion: A Comparative Study

Abstract

Antibiotic-resistant bacterial infections have increased the prevalence of sepsis and septic shock mortality worldwide and have become a global concern. Antimicrobial peptides (AMPs) show remarkable properties for developing new antimicrobial agents and host response modulatory therapies. A new series of AMPs derived from pexiganan (MSI-78) were synthesized. The positively charged amino acids were segregated at their N- and C-termini, and the rest of the amino acids created a hydrophobic core surrounded by positive charges and were modified to simulate the lipopolysaccharide (LPS). The peptides were investigated for their antimicrobial activity and LPS-induced cytokine release inhibition profile. Various biochemical and biophysical methods were used, including attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, microscale thermophoresis (MST), and electron microscopy. Two new AMPs, MSI-Seg-F2F and MSI-N7K, preserved their neutralizing endotoxin activity while reducing toxicity and hemolytic activity. Combining all of these properties makes the designed peptides potential candidates to eradicate bacterial infection and detoxify LPS, which might be useful for sepsis treatment.

Development of Nontoxic Peptides for Lipopolysaccharide Neutralization and Sepsis Treatment

“…It is well-known from previous studies that LPS forms aggregates in solution . We performed a transmission electron microscopy (TEM) analysis to investigate the LPS conformation in the absence and in the presence of the peptides.…”

“…This unregulated stimulation can result in an excessive release of inflammatory cytokines, leading to systemic inflammation, blood clotting in blood vessels, and organ dysfunction, as observed in sepsis . It has been reported that some peptides have been shown to possess additional functions, including anticancer activity, complement activation, direct activation of TLRs, and neutralizing LPS toxicity. ,,− Despite this extensive repertoire of diverse AMPs, there is still limited knowledge on how to separate LPS-neutralizing activity from the systemic toxicity associated with antimicrobial peptides. LPS creates supramolecular aggregates in aqueous environments when exceeding the critical micellar concentration .…”

“…Due to its significant role in causing septic shock, researchers are actively seeking new molecules to counteract the exaggerated immune response triggered by LPS. Among these, AMPs, such as MSI-78, LL-37, and amphipathic- d , are appealing due to their ability to interact with and neutralize LPS, offering hope in preventing sepsis. , In the present study, we investigated a group of peptides inspired and designed from the TLR-derived peptides and alanine-leucine sequences to assess their capacity to neutralize LPS and evaluate their toxicity. Our findings demonstrated that the effectiveness of LPS neutralization was strongly influenced by peptide hydrophobicity, length, and the number of charges.…”

“…Most studies examined the interactions of the peptides with lipid A, the hydrophobic anchor of LPS to the membrane. These studies emphasized the interaction of the positive charges on the peptides with the phosphate head groups on the lipid A as well as the hydrophobic interaction of the peptide backbone with the acyl chains of the lipid A. ,, Other research groups have focused on the aggregation state of LPS upon association with neutralizing HDPs. ,, We have previously focused on hydrophobicity and charge as more general parameters defining LPS neutralization. , Taken together, it has become clear that endotoxin neutralization properties of peptides are much more complex than simple binding to LPS. To date, despite extensive research, the exact properties correlating LPS neutralization and antimicrobial activity of peptides are still not fully understood. , Previous studies conducted in our laboratory demonstrated that transmembrane domain (TMD) TLRs inhibit the immune response. − These TMD-TLR-derived peptides share a common feature, characterized by a high hydrophobic core and positively charged lysines at the termini of the peptides.…”