Intralesional Infiltrations of Arteriosclerotic Tissue Cells-Free Filtrate Reproduce Vascular Pathology in Healthy Recipient Rats

Lower-extremity arterial disease is a major health problem with increasing prevalence, often leading to non-traumatic amputation, disability and mortality. The molecular mechanisms underpinning abnormal vascular wall remodeling are not fully understood. We hypothesized on the existence of a vascular tissue memory that may be transmitted through soluble signaling messengers, transferred from humans to healthy recipient animals, and consequently drive the recapitulation of arterial wall thickening and other vascular pathologies. We examined the effects of the intralesional infiltration for 6 days of arteriosclerotic popliteal artery-derived homogenates (100 µg of protein) into rats’ full-thickness wounds granulation tissue. Animals infiltrated with normal saline solution or healthy brachial arterial tissue homogenate obtained from traumatic amputation served as controls. The significant thickening of arteriolar walls was the constant outcome in two independent experiments for animals receiving arteriosclerotic tissue homogenates. This material induced other vascular morphological changes including an endothelial cell phenotypic reprogramming that mirrored the donor’s vascular histopathology. The immunohistochemical expression pattern of relevant vascular markers appeared to match between the human tissue and the corresponding recipient rats. These changes occurred within days of administration, and with no cross-species limitation. The identification of these “vascular disease drivers” may pave novel research avenues for atherosclerosis pathobiology.

d-Amino acid substitutions and dimerization increase the biological activity and stability of an IL-15 antagonist peptide

Interleukin (IL)-15 plays an important role in several inflammatory diseases. We have previously identified an IL-15 antagonist called P8 peptide, which binds specifically to IL-15 receptor alpha subunit. However, the P8 peptide rapidly degraded by proteases, limiting its therapeutic application. Thus, we replaced each P8 peptide l-amino acid by its corresponding d-isomers. First, we determined the biological activity of the resulting peptides in a proliferation assay by using CTLL-2 cells. The substitution of l-Ala by d-Ala ([A4a]P8 peptide) increased the inhibitory effect of the P8 peptide in CTLL-2 cells in five-fold. In addition to that, the [A4a]P8 peptide dimer showed the most inhibitory effect. To protect the [A4a]P8 peptide and its dimer against exopeptidase activity, we acetylated the N-terminal of these peptides. At least a three-fold reduction in antagonist activity of acetylated peptides was exhibited. However, the substitution of the N-terminal l-Lys residue of [A4a]P8 peptide and its dimer by d-Lys ([K1k;A4a]P8 peptide) did not affect the antagonist effect of the aforementioned peptides. The [K1k;A4a]P8 peptide dimer was stable to the degradation of trypsin, chymotrypsin, and pepsin up until 48 min. Also, the safety and immunogenicity studies in healthy BALB/c mice demonstrated that the administration of this peptide did not affect the clinical parameters of the animals nor generated antipeptide antibodies. Our findings reveal that two distinct d-amino acid substitutions and dimerization increase the biological activity and stability of P8 peptide. The resulting peptide constitutes a novel IL-15 antagonist with potential applicability in inflammatory diseases.

In vitro and in vivo characterization of an interleukin-15 antagonist peptide by metabolic stability, 99m Tc-labeling, and biological activity assays

Interleukin (IL)-15 is an inflammatory cytokine that constitutes a validated therapeutic target in some immunopathologies, including rheumatoid arthritis (RA). Previously, we identified an IL-15 antagonist peptide named [K6T]P8, with potential therapeutic application in RA. In the current work, the metabolic stability of this peptide in synovial fluids from RA patients was studied. Moreover, [K6T]P8 peptide was labeled with ^99m Tc to investigate its stability in human plasma and its biodistribution pattern in healthy rats. The biological activity of [K6T]P8 peptide and its dimer was evaluated in CTLL-2 cells, using 3 different additives to improve the solubility of these peptides. The half-life of [K6T]P8 in human synovial fluid was 5.88 ± 1.73 minutes, and the major chemical modifications included peptide dimerization, cysteinylation, and methionine oxidation. Radiolabeling of [K6T]P8 with ^99m Tc showed a yield of approximately 99.8%. The ^99m Tc-labeled peptide was stable in a 30-fold molar excess of cysteine and in human plasma, displaying a low affinity to plasma proteins. Preliminary biodistribution studies in healthy Wistar rats suggested a slow elimination of the peptide through the renal and hepatic pathways. Although citric acid, sucrose, and Tween 80 enhanced the solubility of [K6T]P8 peptide and its dimer, only the sucrose did not interfere with the in vitro proliferation assay used to assess their biological activity. The results here presented, reinforce nonclinical characterization of the [K6T]P8 peptide, a potential agent for the treatment of RA and other diseases associated with IL-15 overexpression.

Cm-p5: an antifungal hydrophilic peptide derived from the coastal mollusk Cenchritis muricatus (Gastropoda: Littorinidae)

Antimicrobial peptides form part of the first line of defense against pathogens for many organisms. Current treatments for fungal infections are limited by drug toxicity and pathogen resistance. Cm-p5 (SRSELIVHQRLF), a peptide derived from the marine mollusk Cenchritis muricatus peptide Cm-p1, has a significantly increased fungistatic activity against pathogenic Candida albicans (minimal inhibitory concentration, 10 µg/ml; EC50, 1.146 µg/ml) while exhibiting low toxic effects against a cultured mammalian cell line. Cm-p5 as characterized by circular dichroism and nuclear magnetic resonance revealed an α-helical structure in membrane-mimetic conditions and a tendency to random coil folding in aqueous solutions. Additional studies modeling Cm-p5 binding to a phosphatidylserine bilayer in silico and isothermal titration calorimetry using lipid monophases demonstrated that Cm-p5 has a high affinity for the phospholipids of fungal membranes (phosphatidylserine and phosphatidylethanolamine), only moderate interactions with a mammalian membrane phospholipid, low interaction with ergosterol, and no interaction with chitin. Adhesion of Cm-p5 to living C. albicans cells was confirmed by fluorescence microscopy with FITC-labeled peptide. In a systemic candidiasis model in mice, intraperitoneal administration of Cm-p5 was unable to control the fungal kidney burden, although its low amphiphaticity could be modified to generate new derivatives with improved fungicidal activity and stability.

LPS inmobilization on porous and non-porous supports as an approach for the isolation of anti-LPS host-defense peptides

Lipopolysaccharides (LPSs) are the major molecular component of the outer membrane of Gram-negative bacteria. This molecule is recognized as a sign of bacterial infection, responsible for the development of local inflammatory response and, in extreme cases, septic shock. Unfortunately, despite substantial advances in the pathophysiology of sepsis, there is no efficacious therapy against this syndrome yet. As a consequence, septic shock syndrome continues to increase, reaching mortality rates over 50% in some cases. Even though many preclinical studies and clinical trials have been conducted, there is no Food and Drug Administration-approved drug yet that interacts directly against LPS. Cationic host-defense peptides (HDPs) could be an alternative solution since they possess both antimicrobial and antiseptic properties. HDPs are small, positively charged peptides which are evolutionarily conserved components of the innate immune response. In fact, binding to diverse chemotypes of LPS and inhibition of LPS-induced pro-inflammatory cytokines from macrophages have been demonstrated for different HDPs. Curiously, none of them have been isolated by their affinity to LPS. A diversity of supports could be useful for such biological interaction and suitable for isolating HDPs that recognize LPS. This approach could expand the rational search for anti-LPS HDPs.

Functional characterization of a synthetic hydrophilic antifungal peptide derived from the marine snail Cenchritis muricatus

Antimicrobial peptides have been found in mollusks and other sea animals. In this report, a crude extract of the marine snail Cenchritis muricatus was evaluated against human pathogens responsible for multiple deleterious effects and diseases. A peptide of 1485.26 Da was purified by reversed-phase HPLC and functionally characterized. This trypsinized peptide was sequenced by MS/MS technology, and a sequence (SRSELIVHQR), named Cm-p1 was recovered, chemically synthesized and functionally characterized. This peptide demonstrated the capacity to prevent the development of yeasts and filamentous fungi. Otherwise, Cm-p1 displayed no toxic effects against mammalian cells. Molecular modeling analyses showed that this peptide possible forms a single hydrophilic α-helix and the probable cationic residue involved in antifungal activity action is proposed. The data reported here demonstrate the importance of sea animals peptide discovery for biotechnological tools development that could be useful in solving human health and agribusiness problems.