Irradiation accelerates SARS-CoV-2 infection by enhancing sphingolipid metabolism.

Cancer patients who receive radiotherapy have a high risk of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, but the concrete reason remains unclear. Herein, we investigated the influence of irradiation on the vulnerability of cancer cells to SARS-CoV-2 using S pseudovirions and probed the underlying mechanism via RNA-seq and other molecular biology techniques. Owing to the enhancement of sphingolipid metabolism, irradiation accelerated pseudovirion infection. Mechanistically, irradiation induced the expression of acid sphingomyelinase (ASM), which catalyses the hydrolysis of sphingomyelin to ceramide, contributing to lipid raft formation and promoting SARS-CoV-2 invasion. Inhibition of lipid raft formation with methyl-ß-cyclodextrin (MßCD) or the tyrosine kinase inhibitor genistein and ASM suppression through small interfering RNA or amitriptyline (AMT) treatment abolished the enhancing effect of irradiation on viral infection. Animal experiments supported the finding that irradiation promoted SARS-CoV-2 S pseudovirion infection in A549 cell tumour-bearing BALB/c nude mice, whereas AMT treatment dramatically decreased viral infection. This study discloses the role of sphingolipid metabolism in irradiation-induced SARS-CoV-2 infection, thus providing a potential target for clinical intervention to protect patients receiving radiotherapy from COVID-19.

γ-Core Guided Antibiotic Design Based on Human Enteric Defensin 5.

An increase in the number of infections caused by resistant bacteria worldwide necessitates the development of alternatives to antibiotics. Human defensin (HD) 5 is an innate immune peptide with broad-spectrum antibacterial activity, but its complicated structure makes its preparation difficult. Herein, we truncated the HD5 structure by extracting the highly conserved γ-core motif. A structure-activity study showed that this motif was ineffective in killing bacteria in the absence of specific spatial conformation. Notably, after the introduction of two intramolecular disulfide bonds, its antibacterial activity was markedly improved. Glu and Ser residues were then replaced with Arg to create the derivative RC18, which exhibited stronger potency than HD5, particularly against methicillin-resistant S. aureus (MRSA). Mechanistically, RC18 bound to lipid A and lipoteichoic acid at higher affinities than HD5. Furthermore, RC18 was more efficient than HD5 in penetrating the bacterial membranes. Molecular dynamics simulation revealed that five Arg residues, Arg1, Arg7, Arg9, Arg15, and Arg18, mediated most of the polar interactions of RC18 with the phospholipid head groups during membrane penetration. In vivo experiments indicated that RC18 decreased MRSA colonization and dramatically improved the survival of infected mice, thus demonstrating that RC18 is a promising drug candidate to treat MRSA infections.

An angiotensin-converting enzyme-2-derived heptapeptide GK-7 for SARS-CoV-2 spike blockade.

The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is a global concern and necessitates efficient drug antagonists. Angiotensin-converting enzyme-2 (ACE2) is the main receptor of SARS-CoV-2 spike 1 (S1), which mediates viral invasion into host cells. Herein, we designed and prepared short peptide inhibitors containing 4-6 critical residues of ACE2 that contribute to the interaction with SARS-CoV-2 S1. Among the candidates, a peptide termed GK-7 (GKGDFRI), which was designed by extracting residues ranging from Gly353 to Ile359 in the ligand-binding domain of ACE2, exhibited the highest binding affinity (25.1 nM) with the SARS-CoV-2 spike receptor-binding domain (RBD). GK-7 bound to the RBD and decreased SARS-CoV-2 S1 attachment to A549 human alveolar epithelial cells. Owing to spike blockade, GK-7 inhibited SARS-CoV-2 spike pseudovirion infection in a dose-dependent manner, with a half-maximal inhibitory concentration of 2.96 µg/mL. Inspiringly, pulmonary delivery of GK-7 by intranasal administration did not result in toxicity in mice. This study revealed an easy-to-produce peptide inhibitor for SARS-CoV-2 spike blockade, thus providing a promising candidate for COVID-19 treatment.

Human Cathelicidin Inhibits SARS-CoV-2 Infection: Killing Two Birds with One Stone.

SARS-CoV-2 infection begins with the association of its spike 1 (S1) protein with host angiotensin-converting enzyme-2 (ACE2). Targeting the interaction between S1 and ACE2 is a practical strategy against SARS-CoV-2 infection. Herein, we show encouraging results indicating that human cathelicidin LL37 can simultaneously block viral S1 and cloak ACE2. LL37 binds to the receptor-binding domain (RBD) of S1 with high affinity (11.2 nM) and decreases subsequent recruitment of ACE2. Owing to the RBD blockade, LL37 inhibits SARS-CoV-2 S pseudovirion infection, with a half-maximal inhibitory concentration of 4.74 µg/mL. Interestingly, LL37 also binds to ACE2 with an affinity of 25.5 nM and cloaks the ligand-binding domain (LBD), thereby decreasing S1 adherence and protecting cells against pseudovirion infection in vitro. Intranasal administration of LL37 to C57 mice infected with adenovirus expressing human ACE2 either before or after pseudovirion invasion decreased lung infection. The study identified a versatile antimicrobial peptide in humans as an inhibitor of SARS-CoV-2 attachment using dual mechanisms, thus providing a potential candidate for coronavirus disease 2019 (COVID-19) prevention and treatment.

Membrane Nanoparticles Derived from ACE2-Rich Cells Block SARS-CoV-2 Infection.

The ongoing COVID-19 pandemic worldwide necessitates the development of therapeutics against SARS-CoV-2. ACE2 is the main receptor of SARS-CoV-2 S1 and mediates viral entry into host cells. Herein, membrane nanoparticles (NPs) prepared from ACE2-rich cells were discovered to have potent capacity to block SARS-CoV-2 infection. The membranes of human embryonic kidney-239T cells highly expressing ACE2 were applied to prepare NPs using an extrusion method. The nanomaterials, termed ACE2-NPs, contained 265.1 ng mg-1 ACE2 on the surface and acted as baits to trap S1 in a dose-dependent manner, resulting in reduced recruitment of the viral ligand to HK-2 human renal tubular epithelial cells. Aside from affecting receptor recongnition, S1 translocated to the cytoplasm and induced apoptosis by reducing optic atrophy 1 expression and increasing cytochrome c release, which was also inhibited by ACE2-NPs. Further investigations revealed that ACE2-NPs efficiently suppressed SARS-CoV-2 S pseudovirions entry into host cells and blocked viral infection in vitro and in vivo. This study characterizes easy-to-produce memrbane nanoantagonists of SARS-CoV-2 that enrich the existing antiviral arsenal and provide possibilities for COVID-19 treatment.