Mechanistic predictions of the influence of collagen-binding domain sequences on human LL37 interactions with model lipids using quartz crystal microbalance with dissipation

Recognition of the interaction between the bioactive peptide Val-Pro-Pro and the minimal promoter region of genes SOD and CAT using QCM-D and docking studies

Bioactive peptides are biomolecules involved in very diverse mechanisms in vivo. It has been reported that bioactive peptides play a very important role in the regulation of physiological functions such as oxidative stress, hypertension, cancer and inflammation. It's been reported that the milk derived peptide (VPP) prevents the progress of hypertension in different animal models and human beings with mild hypertension. It has also been shown that oral administration of VPP produces an anti-inflammatory effect in adipose tissue of mouse models. Currently there are no reports on the possible interaction of VPP with the enzymes superoxide dismutase (SOD) and catalase (CAT), the main regulators of oxidative stress. This study analyzes the interaction between VPP and specific domains in the minimal promoter region of the genes SOD and CAT in blood samples of obese children using a QCM-D type piezoelectric biosensor. We also used molecular modeling (docking) to determine the interaction between the peptide VPP and the minimal promoter region of both genes. With QCM-D, we detected the interaction of VPP with the nitrogenous base sequences that comprise the minimal promoter regions of both genes CAT and SOD. These experimental interactions were explained at the atomic level by molecular docking simulations showing how the peptides are capable of reaching the DNA structures by means of hydrogen bonds with favored free energy values. It is possible to conclude that the combined use of docking and QCM-D allows for the determination of the interaction of small peptides (VPP) with specific sequences of genes.

Alginate Affects Bioactivity of Chimeric Collagen-Binding LL37 Antimicrobial Peptides Adsorbed to Collagen-Alginate Wound Dressings

Chronic infected wounds cause more than 23,000 deaths annually. Antibiotics and antiseptics are conventionally used to treat infected wounds; however, they can be toxic to mammalian cells, and their use can contribute to antimicrobial resistance. Antimicrobial peptides (AMPs) have been utilized to address the limitations of antiseptics and antibiotics. In previous work, we modified the human AMP LL37 with collagen-binding domains from collagenase (cCBD) or fibronectin (fCBD) to facilitate peptide tethering and delivery from collagen-based wound dressings. We found that cCBD-LL37 and fCBD-LL37 were retained and active when bound to 100% collagen scaffolds. Collagen wound dressings are commonly made as composites with other materials, such as alginate. The goal of this study was to investigate how the presence of alginate affects the tethering, release, and antimicrobial activity of LL37 and CBD-LL37 peptides adsorbed to commercially available collagen-alginate wound dressings (FIBRACOL Plus-a 90% collagen and 10% alginate wound dressing). We found that over 85% of the LL37, cCBD-LL37, and fCBD-LL37 was retained on FIBRACOL Plus over a 14-day release study (90.3, 85.8, and 98.6%, respectively). Additionally, FIBRACOL Plus samples loaded with peptides were bactericidal toward Pseudomonas aeruginosa, even after 14 days in release buffer but demonstrated no antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis. The presence of alginate in solution induced conformational changes in the cCBD-LL37 and LL37 peptides, resulting in increased peptide helicity, and reduced antimicrobial activity against P. aeruginosa. Peptide-loaded FIBRACOL Plus scaffolds were not cytotoxic to human dermal fibroblasts. This study demonstrates that CBD-mediated LL37 tethering is a viable strategy to reduce LL37 toxicity, and how substrate composition plays a crucial role in modulating the antimicrobial activity of tethered AMPs.