SPA: a peptide antagonist that acts as a cell-penetrating peptide for drug delivery

Design Principles for Smart Linear Polymer Ligand Carriers with Efficient Transcellular Transport Capabilities

The surface functionalization of polymer-mediated drug/gene delivery holds immense potential for disease therapy. However, the design principles underlying the surface functionalization of polymers remain elusive. In this study, we employed computer simulations to demonstrate how the stiffness, length, density, and distribution of polymer ligands influence their penetration ability across the cell membrane. Our simulations revealed that the stiffness of polymer ligands affects their ability to transport cargo across the membrane. Increasing the stiffness of polymer ligands can promote their delivery across the membrane, particularly for larger cargoes. Furthermore, appropriately increasing the length of polymer ligands can be more conducive to assisting cargo to enter the lower layer of the membrane. Additionally, the distribution of polymer ligands on the surface of the cargo also plays a crucial role in its transport. Specifically, the one-fourth mode and stripy mode distributions of polymer ligands exhibited higher penetration ability, assisting cargoes in penetrating the membrane. These findings provide biomimetic inspiration for designing high-efficiency functionalization polymer ligands for drug/gene delivery.

Biomimetic nanocarriers loaded with temozolomide by cloaking brain-targeting peptides for targeting drug delivery system to promote anticancer effects in glioblastoma cells

Glioma is the leading cancer of the central nervous system (CNS). The efficacy of glioma treatment is significantly hindered by the presence of the blood-brain barrier (BBB) and blood-brain tumour barrier (BBTB), which prevent most drugs from entering the brain and tumours. Hence, we established a novel drug delivery nanosystem of brain tumour-targeting that could self-assemble the method using an amphiphilic Zein protein isolated from corn. Zein's amphiphilicity prompted it to self-assembled into NPs, efficiently containing TMZ. This allowed us to investigate temozolomide (TMZ) for glioblastoma (GBM) treatment. To construct TMZ-encapsulated NPs (TMZ@RVG-Zein NPs), the NPs' Zein was clocked to rabies virus glycoprotein 29 (RVG29). To verify that the NPs could penetrate the BBB and precisely target and kill the GBM cancer cell line, in vitro studies were performed. The process of NPs penetrating cancer cell membranes was investigated using enzyme-linked immunosorbent assays (ELISAs) to measure the expressions of nicotinic acetylcholine receptors (nAChRs) on the U87 cell line. Therefore, effective targeted brain cancer treatment is possible by forming NP clocks, a cell-penetrating natural Zein protein with an RVG29. These NPs can penetrate the blood-brain barrier (BBB) and enter the glioblastoma (U87) cell line to release TMZ. These NPs have a distinct cocktail of biocompatibility and brain-targeting abilities, making them ideal for involving brain diseases.

Melittin kills A549 cells by targeting mitochondria and blocking mitophagy flux

Melittin, a naturally occurring polypeptide found in bee venom, has been recognized for its potential anti-tumor effects, particularly in the context of lung cancer. Our previous study focused on its impact on human lung adenocarcinoma cells A549, revealing that melittin induces intracellular reactive oxygen species (ROS) burst and oxidative damage, resulting in cell death. Considering the significant role of mitochondria in maintaining intracellular redox levels and ROS, we further examined the involvement of mitochondrial damage in melittin-induced apoptosis in lung cancer cells. Our findings demonstrated that melittin caused changes in mitochondrial membrane potential (MMP), triggered mitochondrial ROS burst (Figure 1), and activated the mitochondria-related apoptosis pathway Bax/Bcl-2 by directly targeting mitochondria in A549 cells (Figure 2). Further, we infected A549 cells using a lentivirus that can express melittin-Myc and confirmed that melittin can directly target binding to mitochondria, causing the biological effects described above (Figure 2). Notably, melittin induced mitochondrial damage while inhibiting autophagy, resulting in abnormal degradation of damaged mitochondria (Figure 5). To summarize, our study unveils that melittin targets mitochondria, causing mitochondrial damage, and inhibits the autophagy-lysosomal degradation pathway. This process triggers mitoROS burst and ultimately activates the mitochondria-associated Bax/Bcl-2 apoptotic signaling pathways in A549 cells.

Melittin induces ferroptosis and ER stress-CHOP-mediated apoptosis in A549 cells

Melittin is a natural polypeptide present in bee venom, with significant anti-tumor activity. Melittin has been reported to induce cell death in lung carcinoma cell line A549 cells, suggesting an excellent potential for treating lung cancer. However, the core mechanism underlying melittin-induced cell death in A549 cells remains unclear. This work reports that melittin induces reactive oxygen species (ROS) burst, upregulates intracellular Fe²⁺ levels, disrupts the glutathione-glutathione peroxidase 4 antioxidant system, and increases lipid peroxide accumulation, eventually inducing cell death, indicating that ferroptosis may be involved in the antitumor effects of melittin in A549 cells. Furthermore, A549 cells treated with the ferroptosis inhibitors ferrostatin-1 and deferoxamine demonstrated that these inhibitors could reverse the cell death induced by melittin, further confirming that melittin induces A549 cell death via ferroptosis. Furthermore, the results also illustrated that melittin activated the endoplasmic reticulum (ER) stress-CHOP (C/EBP homologous protein) apoptotic signal, closely associated with high-level intracellular ROS. The ER stress inhibitor, 4-Phenyl butyric acid, was used to confirm that ER stress-CHOP apoptotic signaling is another molecular mechanism of melittin-induced A549 cell death. Thus, our results demonstrate that ferroptosis and ER stress-CHOP signaling are key molecular mechanisms of melittin-induced cell death in lung cancer.Key policy highlightsMelittin upregulates intracellular Fe²⁺ levels, leading to the accumulation of lipid peroxides in A549 cells.Melittin disrupts the glutathione-glutathione peroxidase 4 antioxidant system in A549 cells.Melittin induces activation of endoplasmic reticulum stress-C/EBP homologous protein apoptosis signal.Ferroptosis and ER stress are the core molecular mechanisms underlying melittin-induced apoptosis in A549 cells.

Influence of chain length on the anticancer activity of the antimicrobial peptide CAMEL with fatty acid modification

Antimicrobial peptides (AMPs) display promising potential in cancer therapy. Modification with fatty acids is a simple and effective approach to improve the activity of AMPs. In the present study, we investigated the effects of fatty acid chain lengths on the anticancer activity, self-assembly and mechanism of action of CAMEL (CM15, KWKLFKKIGAVLKVL-NH₂), an amphipathic AMP with 15 amino acids. Conjugation of fatty acids could obviously improve the in vitro anticancer activity of CAMEL. Among the tested peptides, C12-CAMEL showed the highest anticancer activity, while C16-CAMEL killed cancer cells with the slowest kinetics. This may be related to the self-assembly of C12-CAMEL and C16-CAMEL, which could form spherical nanoparticles and tightened nanofibers, respectively. In addition, necrosis and necroptosis rather than apoptosis were the major mechanisms underlying the anticancer activity of CAMEL, C12-CAMEL and C16-CAMEL, implying that modification with fatty acids did not obviously alter the mechanism of action of CAMEL. Notably, C12-CAMEL, with high and rapid cell-killing activity, exhibited significantly stronger in vivo anticancer activity than CAMEL and C16-CAMEL. Overall, the present work suggests that the choice of a suitable fatty acid for structural modification is necessary for improving the anticancer activity of AMPs.

Antimicrobial and anti-inflammatory activities of the neuropeptide antagonist SPA

Antimicrobial peptides have received increased attention due to the increasing prevalence of antibiotic-resistant bacteria. However, the development of antimicrobial peptides for clinical applications remains a huge challenge. SPA ([D-rg¹ , D-Trp^5,7,9 , Leu¹¹ ]SP), an analog of substance P, is a broad-spectrum neuropeptide antagonist. In this study, we found that SPA could efficiently kill Gram-positive and Gram-negative bacteria by membrane disruption, similar to antimicrobial peptides. In addition, SPA showed high killing activity toward bacteria rather than mammalian cells. Our results also demonstrated that SPA could significantly decrease the expression of proinflammatory cytokines and rescue mice from lethal septic shock induced by LPS. The impressive therapeutic potential of SPA, as indicated in this study, makes it a good template for developing effective antibiotics. Meanwhile, our study provides a new idea for developing multifunctional therapeutic agents to combat bacterial infections.

Functionalized DMP-039 Hybrid Nanoparticle as a Novel mRNA Vector for Efficient Cancer Suicide Gene Therapy

Background

Gene therapy has emerged as a new strategy for cancer therapy. As an alternative nucleic acid material, messenger ribonucleic acid (mRNA) is being increasingly utilized in cancer gene therapy. However, unfulfilled requirements and a lack of ideal mRNA delivery vectors persist.

Methods

We developed an advanced mRNA delivery system, DMP-039, by fusing a cell-penetrating peptide, cRGD-R9, and a cationic nano-sized DMP backbone together. The DMP gene vector backbone was synthesized by the self-assembly of DOTAP lipid and mPEG-PCL polymer. Introduction of the cRGD-R9 peptide onto the DMP backbone was performed to elevate the mRNA delivery capacity, which resulted in a peptide-functionalized hybrid delivery system.

Results

The average size of the synthesized DMP-039 was 268.9 ± 12.4 nm (PDI = 0.382), with a potential of 17.4 ± 0.5 mV. The synthesized DMP-039 hybrid nanoparticles exhibited high mRNA delivery efficiency through multiple mechanisms during transmembrane transportation. By loading the encoding mRNA from the suicide gene Bim, a locally administered mBim/DMP-039 complex strongly inhibited growth in two colon cancer models. Moreover, intravenous administration of the mBim/DMP-039 complex efficiently suppressed C26 pulmonary metastatic tumor progression with high safety. The in vivo distribution, degradation, and excretion were also investigated in detail.

Conclusion

Our results suggest that the DMP-039 peptide-functionalized hybrid nanoparticle is an advanced candidate for mRNA-based suicide gene therapy.

Design of acid-activated cell-penetrating peptides with nuclear localization capacity for anticancer drug delivery

Camptothecin (CPT), a DNA-toxin drug, exerts anticancer activity by inhibiting topoisomerase I. Targeted delivery of CPT into the cancer cell nucleus is important for enhancing its therapeutic efficiency. In this study, a new type of acid-activated cell-penetrating peptide (CPP) with nuclear localization capacity was constructed by conjugating six histidine residues and a hydrophobic peptide sequence, PFVYLI, to the nuclear localization sequence (NLS). Our results indicated that HNLS-3 displayed significant pH-dependent cellular uptake efficiency, endosomal escape ability, and nuclear localization activity. More importantly, the HNLS-3-CPT conjugate showed obviously enhanced cytotoxicity and selectivity compared with CPT. Taken together, our findings provide an effective approach to develop efficient CPPs with both cancer- and nucleus-targeting properties.

Peptide-Based Nanoparticles for Therapeutic Nucleic Acid Delivery

Gene therapy offers the possibility to skip, repair, or silence faulty genes or to stimulate the immune system to fight against disease by delivering therapeutic nucleic acids (NAs) to a patient. Compared to other drugs or protein treatments, NA-based therapies have the advantage of being a more universal approach to designing therapies because of the versatility of NA design. NAs (siRNA, pDNA, or mRNA) have great potential for therapeutic applications for an immense number of indications. However, the delivery of these exogenous NAs is still challenging and requires a specific delivery system. In this context, beside other non-viral vectors, cell-penetrating peptides (CPPs) gain more and more interest as delivery systems by forming a variety of nanocomplexes depending on the formulation conditions and the properties of the used CPPs/NAs. In this review, we attempt to cover the most important biophysical and biological aspects of non-viral peptide-based nanoparticles (PBNs) for therapeutic nucleic acid formulations as a delivery system. The most relevant peptides or peptide families forming PBNs in the presence of NAs described since 2015 will be presented. All these PBNs able to deliver NAs in vitro and in vivo have common features, which are characterized by defined formulation conditions in order to obtain PBNs from 60 nm to 150 nm with a homogeneous dispersity (PdI lower than 0.3) and a positive charge between +10 mV and +40 mV.