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Temporin L (TempL) is a 13 residue Host Defense Peptide (HDP) isolated from the skin of frogs. It has a strong affinity for lipopolysaccharides (LPS), which is related to its high activity against Gram-negative bacteria and also to its strong tendency to neutralize the pro-inflammatory response caused by LPS release from inactivated bacteria. A designed analog with the Q3K substitution shows an enhancement in both these activities. In the present paper, Molecular Dynamics (MD) simulations have been used to investigate the origin of these improved properties. To this end, we have studied the behavior of the peptides both in water solution and in the presence of LPS lipid-A bilayers, demonstrating that the main effect through which the Q3K substitution improves the peptide activities is the destabilization of peptide aggregates in water., Competing Interests: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Background: The goals of treating ulcerative colitis (UC) have shifted from clinical remission to mucosal healing. Non-invasive biomarkers are required to assess mucosal healing as endoscopic assessment is inconvenient for patients. Enhanced expression of trefoil factor 3 (TFF3, a mucin-associated peptide) is observed after injury of the gastrointestinal tract. The present study was designed to evaluate TFF3 as a biomarker of mucosal healing in patients with UC., Methods: This cross-sectional study included consecutive patients with UC (18-65 years old, disease duration >3 months, either left-sided colitis or pancolitis) who had a Simple Clinical Colitis Activity Index (SCCAI) <6. Colonoscopy was done to assess the presence or absence of mucosal healing (defined using the Baron score) in all patients. Serum level of TFF3 was assessed in all patients and 20 healthy controls., Results: Seventy-four patients were included [mean age 37.2±10.9 years, 47 males, median disease duration 4.8 years (IQR 3-8.3), median SCCAI = 0] in the study. Forty-three patients had mucosal healing (Baron score 0 or 1) and 31 did not (Baron score 2 or 3). Median TFF3 level in patients without mucosal healing was significantly higher than that in patients with mucosal healing [1.5 (IQR 1.2-1.9) vs 1.1 (IQR 0.8-1.3) ng/ml, p = 0.01] and healthy controls [0.85 (IQR 0.7-1.2) ng/ml, p < 0.001]. A serum TFF3 level of <1.27 ng/ml (as determined by the receiver operating characteristic curve; area under the curve 0.73) had sensitivity, specificity, positive predictive value and negative predictive value of 70, 68, 75 and 62%, respectively, for identifying patients with mucosal healing., Conclusion: Serum TFF3 can potentially be used as a biomarker to assess mucosal healing in UC patients., (Copyright © 2015 European Crohn’s and Colitis Organisation (ECCO). Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

To understand the influence of different hydrophobic amino acids at "a" and "d" positions of a heptad repeat sequence on antimicrobial, cytotoxic, and antiendotoxin properties, four 15-residue peptides with leucine (LRP), phenylalanine (FRP), valine (VRP), and alanine (ARP) residues at these positions were designed, synthesized, and characterized. Although valine is similarly hydrophobic to leucine and phenylalanine, VRP showed significantly lesser cytotoxicity than LRP and FRP; further, the replacement of leucines with valines at "a" and "d" positions of melittin-heptads drastically reduced its cytotoxicity. However, all four peptides exhibited significant antimicrobial activities that correlate well with their interactions with mammalian and bacterial cell membranes and the corresponding lipid vesicles. LRP most efficiently neutralized the LPS-induced pro-inflammatory mediators like NO, TNF-α, and IL-6 in macrophages followed by FRP, VRP, and ARP. The results could be useful for designing short antimicrobial and antiendotoxin peptides with understanding the basis of their activity.

KvAP is a voltage-gated tetrameric K(+) channel with six transmembrane (S1-S6) segments in each monomer from the archaeon Aeropyrum pernix. The objective of the present investigation was to understand the plausible role of the S6 segment, which has been proposed to form the inner lining of the pore, in the membrane assembly and functional properties of KvAP channel. For this purpose, a 22-residue peptide, corresponding to the S6 transmembrane segment of KvAP (amino acids 218-239), and a scrambled peptide (S6-SCR) with rearrangement of only hydrophobic amino acids but without changing its composition were synthesized and characterized structurally and functionally. Although both peptides bound to the negatively charged phosphatidylcholine/phosphatidylglycerol model membrane with comparable affinity, significant differences were observed between these peptides in their localization, self-assembly, and aggregation properties onto this membrane. S6-SCR also exhibited reduced helical structures in SDS micelles and phosphatidylcholine/phosphatidylglycerol lipid vesicles as compared with the S6 peptide. Furthermore, the S6 peptide showed significant membrane-permeabilizing capability as evidenced by the release of calcein from the calcein-entrapped lipid vesicles, whereas S6-SCR showed much weaker efficacy. Interestingly, although the S6 peptide showed ion channel activity in the bilayer lipid membrane, despite having the same amino acid composition, S6-SCR was significantly inactive. The results demonstrated sequence-specific structural and functional properties of the S6 wild type peptide. The selected S6 segment is probably an important structural element that could play an important role in the membrane interaction, membrane assembly, and functional property of the KvAP channel.

A 13-residue frog antimicrobial peptide Temporin L (TempL) possesses versatile antimicrobial activities and is considered a lead molecule for the development of new antimicrobial agents. To find out the amino acid sequences that influence the anti-microbial property of TempL, a phenylalanine zipper-like sequence was identified in it which was not reported earlier. Several alanine-substituted analogs and a scrambled peptide having the same composition of TempL were designed for evaluating the role of this motif. To investigate whether leucine residues instead of phenylalanine residues at 'a' and/or 'd' position(s) of the heptad repeat sequence could alter its antimicrobial property, several TempL analogs were synthesized after replacing these phenylalanine residues with leucine residues. Replacing phenylalanine residues with alanine residues in the phenylalanine zipper sequence significantly compromised the anti-endotoxin property of TempL. This is evident from the higher production of tumor necrosis factor-α and interleukin- 6 in lipopolysaccharide (LPS)-stimulated rat bone-marrow-derived macrophage cells in the presence of its alanine-substituted analogs than TempL itself. However, replacement of these phenylalanine residues with leucine residues significantly augmented anti-endotoxin property of TempL. A single alanine-substituted TempL analog (F8ATempL) showed significantly reduced cytotoxicity but retained the antibacterial activity of TempL, while the two single leucine-substituted analogs (F5L-TempL and F8L-TempL), although exhibiting lower cytotoxicity, were able to retain the antibacterial activity of the parent peptide. The results demonstrate how minor amino acid substitutions in the identified phenylalanine zipper sequence in TempL could yield analogs with better antibacterial and/or anti-endotoxin properties with their plausible mechanism of action. [ABSTRACT FROM AUTHOR]

The bee venom antimicrobial peptide, melittin, besides showing versatile activity against microorganisms also neutralizes lipopolysaccharide (LPS)-induced proinflammatory responses in macrophage cells. However, how the amino acid sequence of melittin contributes in its anti-inflammatory properties is mostly unknown. To determine the importance of the leucine zipper sequence of melittin in its neutralization of LPS-induced inflammatory responses in macrophages and interaction with LPS, anti-inflammatory properties of melittin and its three analogues and their interactions with LPS were studied in detail. Two of these analogues, namely melittin Mut-1 (MM-1) and melittin Mut-2 (MM-2), possess leucine to alanine substitutions in the single and double heptadic leucine residue(s) of melittin, respectively, whereas the third analogue is a scrambled peptide (Mel-SCR) that contains the amino acid composition of melittin with minor rearrangement in its leucine zipper sequence. Although MM-1 partly inhibited the production of proinflammatory cytokines in RAW 264.7 and rat primary macrophage cells in the presence of LPS, MM-2 and Mel-SCR were negligibly active. A progressive decrease in interaction of melittin with LPS, aggregation in LPS, and dissociation of LPS aggregates with alteration in the leucine zipper sequence of melittin was observed. Furthermore, with alteration in the leucine zipper sequence of melittin, these analogues failed to exhibit cellular responses associated with neutralization of LPS-induced inflammatory responses in macrophage cells by melittin. The data indicated a probable important role of the leucine zipper sequence of melittin in neutralizing LPS-induced proinflammatory responses in macrophage cells as well as in its interaction with LPS. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic, prevalent, immune-mediated, inflammatory, joint disorder affecting millions of people worldwide. Despite current treatment options, many patients remain unable to achieve remission and suffer from comorbidities. Because of several comorbidities as well as its chronic nature, it diminishes the quality of patients' life and intensifies socioeconomic cargo. Consolidating peptides with immensely effective drug delivery systems has the ability to alleviate adverse effects associated with conventional treatments. Peptides are widely used as targeting moieties for the delivery of nanotherapeutics. The use of novel peptide-based nanotherapeutics may open up new avenues for improving efficacy by promoting drug accumulation in inflamed joints and reducing off-target cytotoxicity. Peptide therapeutics have grabbed significant attention due to their advantages over small drug molecules as well as complex targeting moieties. In light of this, the market for peptide-based medications is growing exponentially. Peptides can provide the versatility required for the successful delivery of drugs due to their structural diversity and their capability to lead drugs at the site of inflammation while maintaining optimum therapeutic efficacy. This comprehensive review aims to provide an enhanced understanding of recent advancements in the arena of peptide-based nanotherapeutics to strengthen targeted delivery for the effective management of rheumatoid arthritis. Additionally, various peptides having therapeutic roles in rheumatoid arthritis are summarized along with regulatory considerations for peptides. [Display omitted] • Rheumatoid arthritis is a chronic, autoimmune, inflammatory joint disease. • Peptides are widely used as targeting moieties for delivery of nanotherapeutics. • Peptides have advantages like bioactivity, specificity and low immunogenicity. • Peptide-based nanotherapeutics have been described for Rheumatoid Arthritis. [ABSTRACT FROM AUTHOR]

Recently, peptides have attracted tremendous attention among researchers attributed to their high target specificity and efficacy compared to conventional therapeutics. The ease of self-administration and non-invasiveness confers oral as the most desirable route. However, numerous challenges associated with peptide delivery through the oral route like harsh gastrointestinal environment, enzymatic degradation, and absorption barriers hinder its clinical translation. Protease activity is more pronounced in the proximal segments of the gastrointestinal tract (GIT). Distal segments like the colon possess lower proteolytic activity, enhanced retention time, etc. which could facilitate easy absorption. However, traversing of the upper segments to reach the colon requires the circumvention of the pitfalls of the GIT. The advent of nanomedicine strategies could help in overcoming the said challenges associated with oral delivery, colon-specific targeting, and improving stability and bioavailability at the active site. Furthermore, the classification of peptides and various nanomedicine strategies for oral delivery of peptides to the colon has been conveyed. Regulatory hurdles and ways to accomplish clinical translation have been addressed. [Display omitted] • Prevalence and classification of oral colonic peptides have been conveyed. • Nanomedicine strategies could help in circumventing oral peptide delivery to colon. • Nanocarriers for oral colonic peptide delivery have been described. • Regulatory considerations for hastening clinical translation have been revealed. [ABSTRACT FROM AUTHOR]