Different Biological Activities of Histidine-Rich Peptides Are Favored by Variations in Their Design

The Inhibitory Effect and Mechanism of the Histidine-Rich Peptide rAj-HRP from Apostichopus japonicus on Human Colon Cancer HCT116 Cells

Colon cancer is a common and lethal malignancy, ranking second in global cancer-related mortality, highlighting the urgent need for novel targeted therapies. The sea cucumber (Apostichopus japonicus) is a marine organism known for its medicinal properties. After conducting a bioinformatics analysis of the cDNA library of Apostichopus japonicus, we found and cloned a cDNA sequence encoding histidine-rich peptides, and the recombinant peptide was named rAj-HRP. Human histidine-rich peptides are known for their anti-cancer properties, raising questions as to whether rAj-HRP might exhibit similar effects. To investigate whether rAj-HRP can inhibit colon cancer, we used human colon cancer HCT116 cells as a model and studied the tumor suppressive activity in vitro and in vivo. The results showed that rAj-HRP inhibited HCT116 cell proliferation, migration, and adhesion to extracellular matrix (ECM) proteins in vitro. It also disrupted the cytoskeleton and induced apoptosis in these cells. In vivo, rAj-HRP significantly inhibited the growth of HCT116 tumors in BALB/c mice, reducing tumor volume and weight without affecting the body weight of the tumor-bearing mice. Western blot analysis showed that rAj-HRP inhibited HCT116 cell proliferation and induced apoptosis by upregulating BAX and promoting PARP zymogen degradation. Additionally, rAj-HRP inhibited HCT116 cell adhesion and migration by reducing MMP2 levels. Further research showed that rAj-HRP downregulated EGFR expression in HCT116 cells and inhibited key downstream molecules, including AKT, P-AKT, PLCγ, P38 MAPK, and c-Jun. In conclusion, rAj-HRP exhibits significant inhibitory effects on HCT116 cells in both in vitro and in vivo, primarily through the EGFR and apoptosis pathways. These findings suggest that rAj-HRP has the potential as a novel targeted therapy for colon cancer.

Antioxidant activities of Saudi honey samples related to their content of short peptides

This study explored the effect of geographical and floral origins on the antioxidant activities of Saudi honey samples related to their content of short peptides originated from honeybee proteins. The studied antioxidants were the total protein concentration, catalase activity, phenolic acids and flavonoids. The antioxidant activity assays included were the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, the ferric reducing antioxidant power (FRAP) assay and Ascorbic acid Equivalent Antioxidant Capacity (AEAC). The studied honey samples were obtained from the southwestern region of Saudi Arabia, namely Asir (65) and Jazan (25). The floral origins of the honey samples were Acacia (51), Ziziphus (4) and polyfloral (35). The LC/MS technique was used to detect the short peptides and the mascot database was used to identify the short peptides, their precursor proteins and the protease enzymes that produce them. Jazan honey was characterized by high number of short peptides. The short peptides were originated from honeybee proteins by the action of proteases from the honeybees and bacteria. The antioxidant activity of the honey samples increase with the increase of their content of short peptides and proteins. The amino acids type and sequence of the short peptides qualify them to act as antioxidant, antimicrobial, anti-diabetic, anti-hypertension, immunomodulatory and cholesterol lowering peptides.

N-terminal modification of an LAH4-derived peptide increases mRNA delivery in the presence of serum

The recently developed mRNA-based coronavirus SARS-CoV-2 vaccines highlighted the great therapeutic potential of the mRNA technology. Although the lipid nanoparticles used for the delivery of the mRNA are very efficient, they showed, in some cases, the induction of side effects as well as the production of antibodies directed against particle components. Thus, the development of alternative delivery systems is of great interest in the pursuit of more effective mRNA treatments. In the present work, we evaluated the mRNA transfection capacities of a series of cationic histidine-rich amphipathic peptides derived from LAH4. We found that while the LAH4-A1 peptide was an efficient carrier for mRNA, its activity was highly serum sensitive. Interestingly, modification of this cell penetrating peptide at the N-terminus with two tyrosines or with salicylic acid allowed to confer serum resistance to the carrier.

Chitosan/Hesperidin Nanoparticles for Sufficient, Compatible, Antioxidant, and Antitumor Drug Delivery Systems

One flavonoid glycoside with demonstrated therapeutic potential for several illnesses, including cancer, is hesperidin. However, because of its limited bioavailability and solubility, it is only marginally absorbed, necessitating a delivery mechanism to reach the intended therapeutic target. Additionally, the cytoskeleton of crustaceans yields chitosan, a naturally occurring biopolymer with mucoadhesive properties that has been used to improve the absorption of advantageous chemical substances like flavonoids. Chitosan/hesperidin nanoparticles (Hes-Nanoparticles) were made using the ion gelation technique. The synthesis of Hes-Nanoparticles was confirmed by several characterization methods, including the swelling test, zeta potential, particle size, FTIR, XRD, TEM, and SEM. DPPH and ABTS were used to demonstrate radical scavenging activity in antioxidant assays of chitosan, hesperidin, and the synthesized Hes-Nanoparticles. In addition, by a viability assay against MDA-MB-231, the anticancer efficacies of chitosan, hesperidin, and the synthesized Hes-Nanoparticles were assessed. Furthermore, annexin-V/PI double staining and the cycle of cell analysis were determined by flow cytometry. The results displayed that Hes-Nanoparticles have higher antioxidant activity than chitosan and hesperidin alone. Also, it has been demonstrated that Hes-Nanoparticles are more effective in early cell cycle arrest, suppressing the viability of cancer cells, and increasing cell apoptosis than chitosan and hesperidin alone. In conclusion, Hes-Nanoparticles demonstrated more antioxidant and antitumor activities than chitosan and hesperidin alone. Moreover, it has been established that Hes-Nanoparticles, in a highly soluble form, increase activity in contrast to the poorly soluble form of hesperidin alone.

Deciphering Structural Determinants Distinguishing Active from Inactive Cell-Penetrating Peptides for Cytosolic mRNA Delivery

The formation of noncovalent complexes by mixing of positively charged polymers with negatively charged oligonucleotides (ONs) is a widely explored concept in nanomedicine to achieve cellular delivery of ONs. Uptake of ON complexes occurs through endocytosis, which then requires release of ON from endosomes. As one type of polymer, cell-penetrating peptides (CPPs) are being used which are peptides of about 8-30 amino acids in length. However, only a few CPPs yield effective cytosolic ON delivery and activity. Several strategies have been devised to increase cellular uptake and enhance endosomal release, among which an increase of osmotic pressure through the so-called proton sponge effect, disruption of membrane integrity through membrane activity, and disulfide-mediated polymerization. Here, we address the relevance of these concepts for mRNA delivery by incorporating structural features into the human lactoferrin-derived CPP, which shows uptake but not delivery. The incorporation of histidines was explored to address osmotic pressure and structural motifs of the delivery-active CPP PepFect14 (PF14) to address membrane disturbance, and finally, the impact of polymerization was explored. Whereas oligomerization increased the stability of polyplexes against heparin-induced decomplexation, neither this approach nor the incorporation of histidine residues to promote a proton-sponge effect yielded activity. Also, the replacement of arginine residues with lysine or ornithine residues, as in PF14, was without effect, even though all polyplexes showed cellular uptake. Ultimately, sufficient activity could only be achieved by transferring amphipathic sequence motifs from PF14 into the hLF context with some benefit of oligomerization demonstrating overarching principles of delivery for CPPs, lipid nanoparticles, and other types of delivery polymers.

Host–Bacterial Interactions: Outcomes of Antimicrobial Peptide Applications

The bacterial membrane is part of a secretion system which plays an integral role to secrete proteins responsible for cell viability and pathogenicity; pathogenic bacteria, for example, secrete virulence factors and other membrane-associated proteins to invade the host cells through various types of secretion systems (Type I to Type IX). The bacterial membrane can also mediate microbial communities’ communication through quorum sensing (QS), by secreting auto-stimulants to coordinate gene expression. QS plays an important role in regulating various physiological processes, including bacterial biofilm formation while providing increased virulence, subsequently leading to antimicrobial resistance. Multi-drug resistant (MDR) bacteria have emerged as a threat to global health, and various strategies targeting QS and biofilm formation have been explored by researchers worldwide. Since the bacterial secretion systems play such a crucial role in host–bacterial interactions, this review intends to outline current understanding of bacterial membrane systems, which may provide new insights for designing approaches aimed at antimicrobials discovery. Various mechanisms pertaining interaction of the bacterial membrane with host cells and antimicrobial agents will be highlighted, as well as the evolution of bacterial membranes in evasion of antimicrobial agents. Finally, the use of antimicrobial peptides (AMPs) as a cellular device for bacterial secretion systems will be discussed as emerging potential candidates for the treatment of multidrug resistance infections.

Analyzing siRNA Concentration, Complexation and Stability in Cationic Dendriplexes by Stem-Loop Reverse Transcription-qPCR

RNA interference (RNAi) is a powerful therapeutic approach for messenger RNA (mRNA) level regulation in human cells. RNAi can be triggered by small interfering RNAs (siRNAs) which are delivered by non-viral carriers, e.g., dendriplexes. siRNA quantification inside carriers is essential in drug delivery system development. However, current siRNA measuring methods either are not very sensitive, only semi-quantitative or not specific towards intact target siRNA sequences. We present a novel reverse transcription real-time PCR (RT-qPCR)-based application for siRNA quantification in drug formulations. It enables specific and highly sensitive quantification of released, uncomplexed target siRNA and thus also indirect assessment of siRNA stability and concentration inside dendriplexes. We show that comparison with a dilution series allows for siRNA quantification, exclusively measuring intact target sequences. The limit of detection (LOD) was 4.2 pM (±0.2 pM) and the limit of quantification (LOQ) 77.8 pM (±13.4 pM) for uncomplexed siRNA. LOD and LOQ of dendriplex samples were 31.6 pM (±0 pM) and 44.4 pM (±9.0 pM), respectively. Unspecific non-target siRNA sequences did not decrease quantification accuracy when present in samples. As an example of use, we assessed siRNA complexation inside dendriplexes with varying nitrogen-to-phosphate ratios. Further, protection of siRNA inside dendriplexes from RNase A degradation was quantitatively compared to degradation of uncomplexed siRNA. This novel application for quantification of siRNA in drug delivery systems is an important tool for the development of new siRNA-based drugs and quality checks including drug stability measurements.

VirPorters: Insights into the action of cationic and histidine-rich cell-penetrating peptides

The utilization of nanoparticles for the intracellular delivery of theranostic agents faces one substantial limitation. Sequestration in intracellular vesicles prevents them from reaching the desired location in the cytoplasm or nucleus to deliver their cargo. We investigated whether three different cell-penetrating peptides (CPPs), namely, octa-arginine R8, polyhistidine KH27K and histidine-rich LAH4, could promote cytosolic and/or nuclear transfer of unique model nanoparticles-pseudovirions derived from murine polyomavirus. Two types of CPP-modified pseudovirions that carry the luciferase reporter gene were created: VirPorters-IN with CPPs genetically attached to the capsid interior and VirPorters-EX with CPPs noncovalently associated with the capsid exterior. We tested their transduction ability by luciferase assay and monitored their presence in subcellular fractions. Our results confirmed the overall effect of CPPs on the intracellular destination of the particles and suggested that KH27K has the potential to improve the cytosolic release of pseudovirions. None of the VirPorters caused endomembrane damage detectable by the Galectin-3 assay. Remarkably, a noncovalent modification was required to promote high transduction of the reporter gene and cytosolic delivery of pseudovirions mediated by LAH4. Together, CPPs in different arrangements have demonstrated their potential to improve pseudovirion invasion into cells, and these findings could be useful for the development of other nanoparticle-based delivery systems.