Megakaryocytic IGF1 coordinates activation and ferroptosis to safeguard hematopoietic stem cell regeneration after radiation injury.

BACKGROUND: Hematopoietic stem cell (HSC) regeneration underlies hematopoietic recovery from myelosuppression, which is a life-threatening side effect of cytotoxicity. HSC niche is profoundly disrupted after myelosuppressive injury, while if and how the niche is reshaped and regulates HSC regeneration are poorly understood. METHODS: A mouse model of radiation injury-induced myelosuppression was built by exposing mice to a sublethal dose of ionizing radiation. The dynamic changes in the number, distribution and functionality of HSCs and megakaryocytes were determined by flow cytometry, immunofluorescence, colony assay and bone marrow transplantation, in combination with transcriptomic analysis. The communication between HSCs and megakaryocytes was determined using a coculture system and adoptive transfer. The signaling mechanism was investigated both in vivo and in vitro, and was consolidated using megakaryocyte-specific knockout mice and transgenic mice. RESULTS: Megakaryocytes become a predominant component of HSC niche and localize closer to HSCs after radiation injury. Meanwhile, transient insulin-like growth factor 1 (IGF1) hypersecretion is predominantly provoked in megakaryocytes after radiation injury, whereas HSCs regenerate paralleling megakaryocytic IGF1 hypersecretion. Mechanistically, HSCs are particularly susceptible to megakaryocytic IGF1 hypersecretion, and mTOR downstream of IGF1 signaling not only promotes activation including proliferation and mitochondrial oxidative metabolism of HSCs, but also inhibits ferritinophagy to restrict HSC ferroptosis. Consequently, the delicate coordination between proliferation, mitochondrial oxidative metabolism and ferroptosis ensures functional HSC expansion after radiation injury. Importantly, punctual IGF1 administration simultaneously promotes HSC regeneration and hematopoietic recovery after radiation injury, representing a superior therapeutic approach for myelosuppression. CONCLUSIONS: Our study identifies megakaryocytes as a last line of defense against myelosuppressive injury and megakaryocytic IGF1 as a novel niche signal safeguarding HSC regeneration.

Clustered Cobalt Nanodots Initiate Ferroptosis by Upregulating Heme Oxygenase 1 for Radiotherapy Sensitization.

High cobalt (Co) levels in tumors are associated with good clinical prognosis. An anticancer regimen that increases intratumoral Co through targeted nanomaterial delivery is proposed in this study. Bovine serum albumin and cobalt dichloride are applied to prepare cobaltous oxide nanodots using a facile biomineralization strategy. After iRGD peptide conjugation, the nanodots are loaded into dendritic mesoporous silica nanoparticles, generating a biocompatible product iCoDMSN. This nanocomposite accumulates in tumors after intravenous injection by deep tissue penetration and can be used for photoacoustic imaging. Proteomics research and molecular biology experiments reveal that iCoDMSN is a potent ferroptosis inducer in cancer cells. Mechanistically, iCoDMSNs upregulate heme oxygenase 1 (HMOX1), which increases transferrin receptors and reduces solute carrier family 40 member 1 (SLC40A1), resulting in Fe2+ accumulation and ferroptosis initiation. Furthermore, upregulated nuclear factor erythroid 2-related factor 2 (NRF2), arising from the reduction in Kelch-like ECH-associated protein 1 (KEAP1) expression, is responsible for HMOX1 enhancement after iCoDMSN treatment. Owing to intensified ferroptosis, iCoDMSN acts as an efficient radiotherapy enhancer to eliminate cancer cells in vitro and in vivo. This study demonstrates a versatile Co-based nanomaterial that primes ferroptosis by expanding the labile iron pool in cancer cells, providing a promising tumor radiotherapy sensitizer.

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.

Inflammasomes and the Maintenance of Hematopoietic Homeostasis: New Perspectives and Opportunities.

Hematopoietic stem cells (HSCs) regularly produce various blood cells throughout life via their self-renewal, proliferation, and differentiation abilities. Most HSCs remain quiescent in the bone marrow (BM) and respond in a timely manner to either physiological or pathological cues, but the underlying mechanisms remain to be further elucidated. In the past few years, accumulating evidence has highlighted an intermediate role of inflammasome activation in hematopoietic maintenance, post-hematopoietic transplantation complications, and senescence. As a cytosolic protein complex, the inflammasome participates in immune responses by generating a caspase cascade and inducing cytokine secretion. This process is generally triggered by signals from purinergic receptors that integrate extracellular stimuli such as the metabolic factor ATP via P2 receptors. Furthermore, targeted modulation/inhibition of specific inflammasomes may help to maintain/restore adequate hematopoietic homeostasis. In this review, we will first summarize the possible relationships between inflammasome activation and homeostasis based on certain interesting phenomena. The cellular and molecular mechanism by which purinergic receptors integrate extracellular cues to activate inflammasomes inside HSCs will then be described. We will also discuss the therapeutic potential of targeting inflammasomes and their components in some diseases through pharmacological or genetic strategies.

Irradiation pretreatment enhances the therapeutic efficacy of platelet-membrane-camouflaged antitumor nanoparticles.

BACKGROUND: Cell membrane-based nanocarriers are promising candidates for delivering antitumor agents. The employment of a simple and feasible method to improve the tumor-targeting abilities of these systems is appealing for further application. Herein, we prepared a platelet membrane (PM)-camouflaged antitumor nanoparticle. The effects of irradiation pretreatment on tumor targeting of the nanomaterial and on its antitumor action were evaluated. RESULTS: The biomimetic nanomaterial constructed by indocyanine green, poly(d,l-lactide-co-glycolide), and PM is termed PINPs@PM. A 4-Gy X-ray irradiation increased the proportions of G2/M phase and Caveolin-1 content in 4T1 breast cancer cells, contributing to an endocytic enhancement of PINPs@PM. PINPs@PM produced hyperthermia and reactive oxygen species upon excitation by near-infrared irradiation, which were detrimental to the cytoplasmic lysosome and resulted in cell death. Irradiation pretreatment thus strengthened the antitumor activity of PINPs@PM in vitro. Mice experiments revealed that irradiation enhanced the tumor targeting capability of PINPs@PM in vivo. When the same dose of PINPs@PM was intravenously administered, irradiated mice had a better outcome than did mice without X-ray pretreatment. CONCLUSION: The study demonstrates an effective strategy combining irradiation pretreatment and PM camouflage to deliver antitumor nanoparticles, which may be instrumental for targeted tumor therapy.

Yeast Microcapsule-Mediated Targeted Delivery of Diverse Nanoparticles for Imaging and Therapy via the Oral Route.

Targeting of nanoparticles to distant diseased sites after oral delivery remains highly challenging due to the existence of many biological barriers in the gastrointestinal tract. Here we report targeted oral delivery of diverse nanoparticles in multiple disease models, via a "Trojan horse" strategy based on a bioinspired yeast capsule (YC). Diverse charged nanoprobes including quantum dots (QDs), iron oxide nanoparticles (IONPs), and assembled organic fluorescent nanoparticles can be effectively loaded into YC through electrostatic force-driven spontaneous deposition, resulting in different diagnostic YC assemblies. Also, different positive nanotherapies containing an anti-inflammatory drug indomethacin (IND) or an antitumor drug paclitaxel (PTX) are efficiently packaged into YC. YCs containing either nanoprobes or nanotherapies may be rapidly endocytosed by macrophages and maintained in cells for a relatively long period of time. Post oral administration, nanoparticles packaged in YC are first transcytosed by M cells and sequentially endocytosed by macrophages, then transported to neighboring lymphoid tissues, and finally delivered to remote diseased sites of inflammation or tumor in mice or rats, all through the natural route of macrophage activation, recruitment, and deployment. For the examined acute inflammation model, the targeting efficiency of YC-delivered QDs or IONPs is even higher than that of control nanoprobes administered at the same dose via intravenous injection. Assembled IND or PTX nanotherapies orally delivered via YCs exhibit remarkably potentiated efficacies as compared to nanotherapies alone in animal models of inflammation and tumor, which is consistent with the targeting effect and enhanced accumulation of drug molecules at diseased sites. Consequently, through the intricate transportation route, nanoprobes or nanotherapies enveloped in YC can be preferentially delivered to desired targets, affording remarkably improved efficacies for the treatment of multiple diseases associated with inflammation.

Self-Assembly of pH-Responsive Microspheres for Intestinal Delivery of Diverse Lipophilic Therapeutics.

Targeted delivery of therapeutics to the intestine is preferred for the management of many diseases due to its diverse advantages. Currently, there are still challenges in creating cost-effective and translational pH-responsive microspheres for intestinal delivery of various hydrophobic drugs. Herein we report a multiple noncovalent interactions-mediated assembly strategy in which carboxyl-bearing compounds (CBCs) are guest molecules, while poly(N-isopropylacrylamide) (PNIPAm) serves as a host polymer. Formation of microparticles and therapeutic packaging can be achieved simultaneously by this assembly approach, leading to well-shaped microspheres with extremely higher drug loading capacity as compared to microspheres based on two FDA-approved materials of poly(d,l-lactide-co-glycolide) (PLGA) and an enteric coating polymer EudragitS 100 (S100). Also, carboxyl-deficient hydrophobic drugs can be effectively entrapped. These assembled microspheres, with excellent reconstitution capability as well as desirable scalability, could selectively release drug molecules under intestinal conditions. By significantly enhancing drug dissolution/release in the intestine, these pH-responsive assemblies may notably improve the oral bioavailability of loaded therapeutics. Moreover, the assembled microspheres possessed superior therapeutic performance in rodent models of inflammation and tumor over the control microspheres derived from PLGA and S100. Therapy with newly developed microspheres did not cause undesirable side effects. Furthermore, in vivo evaluation in mice revealed the carrier material PNIPAm was safe for oral delivery at doses as high as 10 g/kg. Collectively, our findings demonstrated that this type of pH-responsive microsphere may function as superior and translational intestine-directed delivery systems for a diverse array of therapeutics.

Enhanced Intracellular Delivery and Tissue Retention of Nanoparticles by Mussel-Inspired Surface Chemistry.

Nanomaterials have been broadly studied for intracellular delivery of diverse compounds for diagnosis or therapy. Currently it remains challenging for discovering new biomolecules that can prominently enhance cellular internalization and tissue retention of nanoparticles (NPs). Herein we report for the first time that a mussel-inspired engineering approach may notably promote cellular uptake and tissue retention of NPs. In this strategy, the catechol moiety is covalently anchored onto biodegradable NPs. Thus, fabricated NPs can be more effectively internalized by sensitive and multidrug resistant tumor cells, as well as some normal cells, resulting in remarkably potentiated in vitro activity when an antitumor drug is packaged. Moreover, the newly engineered NPs afford increased tissue retention post local or oral delivery. This biomimetic approach is promising for creating functional nanomaterials for drug delivery, vaccination, and cell therapy.

Application of a derivative of human defensin 5 to treat ionizing radiation-induced enterogenic infection.

Enterogenic infection is a common complication for patients with radiation injury and requires efficient therapeutics in the clinic. Herein, we evaluated the promising drug candidate T7E21RHD5, which is a peptide derived from intestinal Paneth cell-secreted human defensin 5. Oral administration of this peptide alleviated the diarrhea symptoms of mice that received total abdominal irradiation (TAI, γ-ray, 12 Gy) and improved survival. Pathologic analysis revealed that T7E21RHD5 elicited an obvious mitigation of ionizing radiation (IR)-induced epithelial damage and ameliorated the reduction in the levels of claudin, zonula occluden 1 and occludin, three tight junction proteins in the ileum. Additionally, T7E21RHD5 regulated the gut microbiota in TAI mice by remodeling ß diversity, manifested as a reversal of the inverted proportion of Bacteroidota to Firmicutes caused by IR. T7E21RHD5 treatment also decreased the abundance of pathogenic Escherichia-Shigella but significantly increased the levels of Alloprevotella and Prevotellaceae_NK3B31, two short-chain fatty acid-producing bacterial genera in the gut. Accordingly, the translocation of enterobacteria and lipopolysaccharide to the blood, as well as the infectious inflammatory responses in the intestine after TAI, was all suppressed by T7E21RHD5 administration. Hence, this versatile antimicrobial peptide possesses promising application prospects in the treatment of IR-induced enterogenic infection.

P-selectin Facilitates SARS-CoV-2 Spike 1 Subunit Attachment to Vesicular Endothelium and Platelets.

SARS-CoV-2 infection starts from the association of its spike 1 (S1) subunit with sensitive cells. Vesicular endothelial cells and platelets are among the cell types that bind SARS-CoV-2, but the effectors that mediate viral attachment on the cell membrane have not been fully elucidated. Herein, we show that P-selectin (SELP), a biomarker for endothelial dysfunction and platelet activation, can facilitate the attachment of SARS-CoV-2 S1. Since we observe colocalization of SELP with S1 in the lung tissues of COVID-19 patients, we perform molecular biology experiments on human umbilical vein endothelial cells (HUVECs) to confirm the intermolecular interaction between SELP and S1. SELP overexpression increases S1 recruitment to HUVECs and enhances SARS-CoV-2 spike pseudovirion infection. The opposite results are determined after SELP downregulation. As S1 causes endothelial inflammatory responses in a dose-dependent manner, by activating the interleukin (IL)-17 signaling pathway, SELP-induced S1 recruitment may contribute to the development of a "cytokine storm" after viral infection. Furthermore, SELP also promotes the attachment of S1 to the platelet membrane. Employment of PSI-697, a small inhibitor of SELP, markedly decreases S1 adhesion to both HUVECs and platelets. In addition to the role of membrane SELP in facilitating S1 attachment, we also discover that soluble SELP is a prognostic factor for severe COVID-19 through a meta-analysis. In this study, we identify SELP as an adhesive site for the SARS-CoV-2 S1, thus providing a potential drug target for COVID-19 treatment.

Intrinsically bioactive and biomimetic nanoparticle-derived therapies alleviate asthma by regulating multiple pathological cells.

Asthma is a serious global public health concern. Airway neutrophilic inflammation is closely related to severe asthma, for which effective and safe therapies remain to be developed. Here we report nanotherapies capable of simultaneously regulating multiple target cells relevant to the pathogenesis of neutrophilic asthma. A nanotherapy LaCD NP based on a cyclic oligosaccharide-derived bioactive material was engineered. LaCD NP effectively accumulated in the injured lungs of asthmatic mice and mainly distributed in neutrophils, macrophages, and airway epithelial cells after intravenous or inhalation delivery, thereby ameliorating asthmatic symptoms and attenuating pulmonary neutrophilic inflammation as well as reducing airway hyperresponsiveness, remodeling, and mucus production. Surface engineering via neutrophil cell membrane further enhanced targeting and therapeutic effects of LaCD NP. Mechanistically, LaCD NP can inhibit the recruitment and activation of neutrophils, especially reducing the neutrophil extracellular traps formation and NLRP3 inflammasome activation in neutrophils. Also, LaCD NP can suppress macrophage-mediated pro-inflammatory responses and prevent airway epithelial cell death and smooth muscle cell proliferation, by mitigating neutrophilic inflammation and its direct effects on relevant cells. Importantly, LaCD NP showed good safety performance. Consequently, LaCD-derived multi-bioactive nanotherapies are promising for effective treatment of neutrophilic asthma and other neutrophil-associated diseases.

Hydrogel Transformed from Nanoparticles for Prevention of Tissue Injury and Treatment of Inflammatory Diseases.

Functional hydrogels responsive to physiological and pathological signals have extensive biomedical applications owing to their multiple advanced attributes. Herein, engineering of functional hydrogels is reported via transformable nanoparticles in response to the physiologically and pathologically acidic microenvironment. These nanoparticles are assembled by a multivalent hydrophobic, pH-responsive cyclodextrin host material and a multivalent hydrophilic guest macromolecule. Driven by protons, the pH-responsive host-guest nanoparticles can be transformed into hydrogel, resulting from proton-triggered hydrolysis of the host material, generation of a hydrophilic multivalent host compound, and simultaneously enhanced inclusion interactions between host and guest molecules. By in situ forming a hydrogel barrier, the orally delivered transformable nanoparticles protect mice from ethanol- or drug-induced gastric injury. In addition, this type of nanoparticles can serve as responsive and transformable nanovehicles for therapeutic agents to achieve triggerable and sustained drug delivery, thereby effectively treating typical inflammatory diseases, including periodontitis and arthritis in rats. With combined advantages of nanoparticles and hydrogels, together with their good in vivo safety, the engineered transformable nanoparticles hold great promise in tissue injury protection and site-specific/local delivery of molecular and cellular therapeutic agents.

Selenium nanoparticles alleviate ischemia reperfusion injury-induced acute kidney injury by modulating GPx-1/NLRP3/Caspase-1 pathway.

Rationale: Acute kidney injury (AKI) is a common critical illness in the clinic and currently lacks effective treatment options. Ischemia reperfusion injury (IRI) is a major pathogenic factor for AKI. Due to the deficiency of selenium (Se) in AKI patients, we intended to treat IRI-induced AKI using a Se rebalancing strategy in the present study. Methods: Sodium selenate, ascorbic acid, and bovine serum albumin (BSA) were employed to prepare nanomaterials termed Se@BSA nanoparticles (NPs) using a simple method. Experiments with human renal tubular epithelial HK-2 cells exposed to hypoxia/reoxygenation (H/R) and IRI-AKI mice were used to evaluate the therapeutic efficiency of Se@BSA NPs. Transcriptome sequencing, further molecular biology experiments, and pathologic analysis were performed to investigate the underlying mechanisms. Results: Se@BSA NPs accumulated in mouse kidneys and could be endocytosed by renal tubular epithelial cells after intravenous administration. In vitro studies showed that Se@BSA NP treatment markedly increased the levels of glutathione peroxidase (GPx)-1 and suppressed NLRP3 inflammasome activation in H/R cells, which resulted in reductions in the proteolytic cleavage of pro-Caspase-1 into active Caspase-1 and the maturation of inflammatory factors. Mouse experiments confirmed these findings and demonstrated an inspiring mitigative effect of Se@BSA NPs on IRI-induced AKI. Owing to modulation of the GPx-1/NLRP3/Caspase-1 pathway, Se@BSA NPs dramatically inhibited fibrosis formation after AKI. Conclusion: This study provides an effective therapeutic option by applying easy-to-produce Se-containing nanomaterials to remedy Se imbalance and impede inflammatory responses in the kidney, which is a promising candidate for AKI treatment.

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.

Renal Klotho and inorganic phosphate are extrinsic factors that antagonistically regulate hematopoietic stem cell maintenance.

The composition and origin of extrinsic cues required for hematopoietic stem cell (HSC) maintenance are incompletely understood. Here we identify renal Klotho and inorganic phosphate (Pi) as extrinsic factors that antagonistically regulate HSC maintenance in the bone marrow (BM). Disruption of the Klotho-Pi axis by renal Klotho deficiency or Pi excess causes Pi overload in the BM niche and Pi retention in HSCs, leading to alteration of HSC maintenance. Mechanistically, Pi retention is mediated by soluble carrier family 20 member 1 (SLC20A1) and sensed by diphosphoinositol pentakisphosphate kinase 2 (PPIP5K2) to enhance Akt activation, which then upregulates SLC20A1 to aggravate Pi retention and augments GATA2 activity to drive the expansion and megakaryocyte/myeloid-biased differentiation of HSCs. However, kidney-secreted soluble Klotho directly maintains HSC pool size and differentiation by restraining SLC20A1-mediated Pi absorption of HSCs. These findings uncover a regulatory role of the Klotho-Pi axis orchestrated by the kidneys in BM HSC maintenance.

Polyphenol-assisted facile assembly of bioactive nanoparticles for targeted therapy of heart diseases.

It remains a great challenge for targeted therapy of heart diseases. To achieve desirable heart targeting, we developed a polyphenol-assisted nanoprecipitation/self-assembly approach for facile engineering of functional nanoparticles. Three different materials were employed as representative carriers, while gallic acid, catechin, epigallocatechin gallate, and tannic acid (TA) served as typical polyphenols with varied numbers of phenolic hydroxyl groups. By optimizing different parameters, such as polyphenol types and the weight ratio of carrier materials and polyphenols, well-defined nanoparticles with excellent physicochemical properties can be easily prepared. Regardless of various carrier materials, TA-derived nanoparticles showed potent reactive oxygen species-scavenging activity, especially nanoparticles produced from a cyclodextrin-derived bioactive material (TPCD). By internalization into cardiomyocytes, TPCD/TA nanoparticles (defined as TPTN) effectively protected cells from hypoxic-ischemic injury. After intravenous injection, TPTN considerably accumulated in the injured heart in two murine models of ventricular fibrillation cardiac arrest in rats and myocardial hypertrophy in mice. Correspondingly, intravenously delivered TPTN afforded excellent therapeutic effects in both heart diseases. Preliminary experiments also revealed good safety of TPTN. These results substantiated that TPTN is a promising nanotherapy for targeted treatment of heart diseases, while polyphenol-assisted self-assembly is a facile but robust strategy to develop heart-targeting delivery systems.

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.

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.

A Prognostic Signature Constructed by CTHRC1 and LRFN4 in Stomach Adenocarcinoma.

BACKGROUND: Stomach adenocarcinoma (STAD) is the most common histological type of stomach cancer, which causes a considerable number of deaths worldwide. This study aimed to identify its potential biomarkers with the notion of revealing the underlying molecular mechanisms. METHODS: Gene expression profile microarray data were downloaded from the Gene Expression Omnibus (GEO) database. The "limma" R package was used to screen the differentially expressed genes (DEGs) between STAD and matched normal tissues. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used for function enrichment analyses of DEGs. The STAD dataset from The Cancer Genome Atlas (TCGA) database was used to identify a prognostic gene signature, which was verified in another STAD dataset from the GEO database. CIBERSORT algorithm was used to characterize the 22 human immune cell compositions. The expression of LRFN4 and CTHRC1 in tissues was determined by quantitative real-time PCR from the patients recruited to the present study. RESULTS: Three public datasets including 90 STAD patients and 43 healthy controls were analyzed, from which 44 genes were differentially expressed in all three datasets. These genes were implicated in biological processes including cell adhesion, wound healing, and extracellular matrix organization. Five out of 44 genes showed significant survival differences. Among them, CTHRC1 and LRFN4 were selected for construction of prognostic signature by univariate Cox regression and stepwise multivariate Cox regression in the TCGA-STAD dataset. The fidelity of the signature was evaluated in another independent dataset and showed a good classification effect. The infiltration levels of multiple immune cells between high-risk and low-risk groups had significant differences, as well as two immune checkpoints. TIM-3 and PD-L2 were highly correlated with the risk score. Multiple signaling pathways differed between the two groups of patients. At the same time, the expression level of LRFN4 and CTHRC1 in tissues analyzed by quantitative real-time PCR were consistent with the in silico findings. CONCLUSION: The present study constructed the prognostic signature by expression of CTHRC1 and LRFN4 for the first time via comprehensive bioinformatics analysis, which provided the potential therapeutic targets of STAD for clinical 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.