503. In vitro Evaluation of Sitagliptin-HIV-1 Trans-activator Transcription Peptide Nano-formula for Antiviral Activity Against SARS-CoV-2: Drug Repurposing Approach

Background

The outbreak of COVID-19 pandemic in China regarded as a major health/economic hazard. The importance of coming up with mechanisms for preventing or treating COVID-19 has been felt across the world. This work aimed at examining the efficiency of Sitagliptin (SIT) and human immunodeficiency virus type 1 (HIV-1) trans-activator transcription peptide (TAT) against SARS-CoV-2.

Methods

SIT-TAT nano-conjugates were prepared according to a full three-factor bi-level (2³) factorial design. SIT concentration (mM, X1), TAT concentration (mM, X2), and pH (X3) were selected as the factors. Particle size (nm, Y1) and zeta potential (mV, Y2) were assessed as responses. Characterization of the optimized formula for Fourier-transformed infrared (FTIR) and Transmission electron microscope was carried out. In addition, IC50 in Vero E6 cells, In vitro 3CL-protease inhibition and docking tests were investigated.

Results

The prepared complex’s formula was as follows 1: 1 SIT: TAT molar ratio, whereas zeta potential and particle size values were at 34.17 mV and 97.19 nm, respectively. This combination did exhibit its antiviral potentiality against SARS-CoV-2 via IC50 values of 9.083 5.415, and 16.14 µM for TAT, SIT-TAT, and SIT, respectively. In addition, the complex SIT-TAT showed a significant (P < 0.001) viral-3CL-protease inhibitory effect (IC50 = 3.959 µM ± 0.011) in comparison to isolated components (IC50 = 10.93 µM ± 0.25) and TAT (IC50 = 8.128 µM ± 0.42). This was further confirmed via in silico study. Molecular docking investigation has shown promising binding affinity of the formula components towards SARS-CoV-2 main protease (3-CL).

Conclusion

While offering significant binding interactions with protein’s key pocket residues, an optimized formulation of SIT-TAT could guarantee both the enhanced delivery to the target cells and the improved cellular uptake. The presented findings would guarantee further investigations regarding formula optimization against SARS-CoV-2.

Disclosures

All Authors: No reported disclosures

pH-Induced Changes in the Surface Viscosity of Unsaturated Phospholipids Monitored Using Active Interfacial Microrheology

Lipid membranes, a major component of cells, are subjected to significant changes in pH depending on their location in the cell: the outer leaflet of the cell membrane is exposed to a pH of 7.4 whereas lipid membranes that make up late endosomes and lysosomes are exposed to a pH of as low as 4.4. The purpose of this study is to evaluate how changes in the environmental pH within cells alter the fluidity of phospholipid membranes. Specifically, we studied pH-induced alterations in the surface arrangement of monounsaturated lipids with zwitterionic headgroups (phosphoethanolamine (PE) and phosphocholine (PC)) that are abundant in plasma membranes as well as anionic lipids (phosphatidylserine (PS) and phosphatidylglycerol (PG)) that are abundant in inner membranes using a combination of techniques including surface tension vs area measurements, interfacial microrheology, and fluorescence/atomic force microscopy. Using an active interfacial microrheology technique, we find that phospholipids with zwitterionic headgroups show a significant increase in their surface viscosity at acidic pH. This increase in surface viscosity is also found to depend on the size of the lipid headgroup, with a smaller headgroup showing a greater increase in viscosity. The observed pH-induced increase in viscosity is also accompanied by an increase in the cohesion pressure between zwitterionic molecules at acidic pH and a decrease in the average molecular area of the lipids, as measured by fitting the surface pressure isotherms to well-established equations of state. Because fluorescent images show no change in the phase of the lipids, we attribute this change in surface viscosity to the pH-induced reorientation of the P^--N⁺ dipoles that form part of the polar lipid headgroup, resulting in increased lipid-lipid interactions. Anionic PG headgroups do not demonstrate this pH-induced change in viscosity, suggesting that the presence of a net negative charge on the headgroup causes electrostatic repulsion between the headgroups. Our results also show that active interfacial microrheology is a sensitive technique for detecting minute changes in the lipid headgroup orientation induced by changes in the local membrane environment, even in unsaturated phospholipids where the surface viscosity is close to the experimental detection limit.

Targeted gene silencing of CCL2 inhibits triple negative breast cancer progression by blocking cancer stem cell renewal and M2 macrophage recruitment

Triple negative breast cancers are an aggressive subtype of breast cancer, characterized by the lack of estrogen receptor, progesterone receptor and Her2 expression. Triple negative breast cancers are non-responsive to conventional anti-hormonal and Her2 targeted therapies, making it necessary to identify new molecular targets for therapy. The chemokine CCL2 is overexpressed in invasive breast cancers, and regulates breast cancer progression through multiple mechanisms. With few approaches to target CCL2 activity, its value as a therapeutic target is unclear. In these studies, we developed a novel gene silencing approach that involves complexing siRNAs to TAT cell penetrating peptides (Ca-TAT) through non-covalent calcium cross-linking. Ca-TAT/siRNA complexes penetrated 3D collagen cultures of breast cancer cells and inhibited CCL2 expression more effectively than conventional antibody neutralization. Ca-TAT/siRNA complexes targeting CCL2 were delivered to mice bearing MDA-MB-231 breast tumor xenografts. In vivo CCL2 gene silencing inhibited primary tumor growth and metastasis, associated with a reduction in cancer stem cell renewal and recruitment of M2 macrophages. These studies are the first to demonstrate that targeting CCL2 expression in vivo may be a viable therapeutic approach to treating triple negative breast cancer.