DNA damage-inducible transcript 3 positively regulates RIPK1-mediated necroptosis.

DNA damage-inducible transcript 3 (DDIT3) is a well-known transcription factor that regulates the expression of apoptosis-related genes for promoting apoptosis during endoplasmic reticulum stress. Here, we report an unrecognized role of DDIT3 in facilitating necroptosis. DDIT3 directly binds and competitively prevents the p38 MAPK-MK2 interaction and thereby blocking MK2 activation while stimulating p38 MAPK activation. This blockage of MK2 activation initially prevents RIPK1 phosphorylation at Ser320 (inactivation), subsequently relieving its suppression of RIPK1 activation. Consequently, p38 MAPK facilitates RIPK1 phosphorylation at Ser166 (activation) through DDIT3 phosphorylation-related mechanisms, leading to necroptosis. Mechanistically, a 10-amino acid segment (Glu19-Val28) within DDIT3's N-terminus is identified to account for its pro-necroptotic function. In vivo studies demonstrate that forced expression of DDIT3 induces necroptosis, whereas deletion of DDIT3 alleviates necroptosis in mouse hearts under stress. These findings shed light on a novel regulatory mechanism by which DDIT3 promotes RIPK1 activation and subsequent necroptosis.

Structural characterization, anti-aging activity and mechanisms investigation in vivo of a polysaccharide from Anthriscus sylvestris.

Anthriscus sylvestris (L.) Hoffm has a long history of use for anti-aging, although the anti-aging properties of its decoction ingredients have been seldom explored. This study marks the first detailed examination of the in vivo anti-aging activity of A. sylvestris roots polysaccharide (AP). Structural analyses revealed that AP is a neutral heteropolysaccharide with an average molecular weight (Mw) of 34.17 kDa, comprising glucose, xylose, galactose, mannose, and arabinose, with a backbone primarily of 1,4-α-D-Glc and minor branching at 1,4,6-α-D-Man. Its advanced structure is characterized by stable triple-helical chains and nanoscale agglomerated spherical particles. Using a D-gal-induced aging mouse model, further investigation showed that AP boosts the activity of various antioxidant enzymes via the Nrf2/HO-1/NQO1 signaling pathway. Aging-related immune decline was also mitigated by an increase in lymphocyte production in thymus. Moreover, AP reduced inflammation and downregulated aging genes p53 and p21 in hippocampus and liver tissues, enhanced the cholinergic system, and improved liver functions and lipid metabolism. The collective impact of these mechanisms underscores the robust anti-aging properties of AP. These findings highlight the anti-aging and immunomodulatory potential of A. sylvestris polysaccharide, broadening the understanding of its active components.

Crystal structure and nucleic acid binding mode of CPV NSP9: implications for viroplasm in Reovirales.

Cytoplasmic polyhedrosis viruses (CPVs), like other members of the order Reovirales, produce viroplasms, hubs of viral assembly that shield them from host immunity. Our study investigates the potential role of NSP9, a nucleic acid-binding non-structural protein encoded by CPVs, in viroplasm biogenesis. We determined the crystal structure of the NSP9 core (NSP9ΔC), which shows a dimeric organization topologically similar to the P9-1 homodimers of plant reoviruses. The disordered C-terminal region of NSP9 facilitates oligomerization but is dispensable for nucleic acid binding. NSP9 robustly binds to single- and double-stranded nucleic acids, regardless of RNA or DNA origin. Mutagenesis studies further confirmed that the dimeric form of NSP9 is critical for nucleic acid binding due to positively charged residues that form a tunnel during homodimerization. Gel migration assays reveal a unique nucleic acid binding pattern, with the sequential appearance of two distinct complexes dependent on protein concentration. The similar gel migration pattern shared by NSP9 and rotavirus NSP3, coupled with its structural resemblance to P9-1, hints at a potential role in translational regulation or viral genome packaging, which may be linked to viroplasm. This study advances our understanding of viroplasm biogenesis and Reovirales replication, providing insights into potential antiviral drug targets.

Prophylactic efficacy of an intranasal spray with 2 synergetic antibodies neutralizing Omicron.

BACKGROUNDAs Omicron is prompted to replicate in the upper airway, neutralizing antibodies (NAbs) delivered through inhalation might inhibit early-stage infection in the respiratory tract. Thus, elucidating the prophylactic efficacy of NAbs via nasal spray addresses an important clinical need.METHODSThe applicable potential of a nasal spray cocktail containing 2 NAbs was characterized by testing its neutralizing potency, synergetic neutralizing mechanism, emergency protective and therapeutic efficacy in a hamster model, and pharmacokinetics/pharmacodynamic (PK/PD) in human nasal cavity.RESULTSThe 2 NAbs displayed broad neutralizing efficacy against Omicron, and they could structurally compensate each other in blocking the Spike-ACE2 interaction. When administrated through the intranasal mucosal route, this cocktail demonstrated profound efficacy in the emergency prevention in hamsters challenged with authentic Omicron BA.1. The investigator-initiated trial in healthy volunteers confirmed the safety and the PK/PD of the NAb cocktail delivered via nasal spray. Nasal samples from the participants receiving 4 administrations over a course of 16 hours demonstrated potent neutralization against Omicron BA.5 in an ex vivo pseudovirus neutralization assay.CONCLUSIONThese results demonstrate that the NAb cocktail nasal spray provides a good basis for clinical prophylactic efficacy against Omicron infections.TRIAL REGISTRATIONwww.chictr.org.cn, ChiCTR2200066525.FUNDINGThe National Science and Technology Major Project (2017ZX10202203), the National Key Research and Development Program of China (2018YFA0507100), Guangzhou National Laboratory (SRPG22-015), Lingang Laboratory (LG202101-01-07), Science and Technology Commission of Shanghai Municipality (YDZX20213100001556), and the Emergency Project from the Science & Technology Commission of Chongqing (cstc2021jscx-fyzxX0001).

Aloe-emodin: Progress in Pharmacological Activity, Safety, and Pharmaceutical Formulation Applications.

Aloe-emodin (AE) is an anthraquinone derivative and a biologically active component sourced from various plants, including Rheum palmatum L. and Aloe vera. Known chemically as 1,8-dihydroxy-3-hydroxymethyl-anthraquinone, AE has a rich history in traditional medicine and is esteemed for its accessibility, safety, affordability, and effectiveness. AE boasts multiple biochemical and pharmacological properties, such as strong antibacterial, antioxidant, and antitumor effects. Despite its array of benefits, AE's identity as an anthraquinone derivative raises concerns about its potential for liver and kidney toxicity. Nevertheless, AE is considered a promising drug candidate due to its significant bioactivities and cost efficiency. Recent research has highlighted that nanoformulated AE may enhance drug delivery, biocompatibility, and pharmacological benefits, offering a novel approach to drug design. This review delves into AE's pharmacological impacts, mechanisms, pharmacokinetics, and safety profile, incorporating insights from studies on its nanoformulations. The goal is to outline the burgeoning research in this area and to support the ongoing development and utilization of AE-based therapies.

Anthriscus sylvestris: An overview on Bioactive Compounds and Anticancer Mechanisms from a Traditional Medicinal Plant to Modern Investigation.

Anthriscus sylvestris (L.) Hoffm. Gen. is a biennial or perennial herb commonly found in China. It has a long history of use in traditional Chinese medicine to treat various ailments such as cough, gastric disorders, spleen deficiency, and limb weakness. Recently, its potential as an anticancer agent has gained considerable attention and has been the subject of extensive research focusing on extract efficacy, identification of active compounds, and proposed molecular mechanisms. Nevertheless, further high-quality research is still required to fully evaluate its potential as an anticancer drug. This review aims to comprehensively summarize the anticancer properties exhibited by the active components found in Anthriscus sylvestris. We conducted a comprehensive search, collation, and analysis of published articles on anticancer activity and active compounds of A. sylvestris using various databases that include, but are not limited to, PubMed, Web of Science, Science Direct and Google Scholar. The primary chemical composition of A. sylvestris consists of phenylpropanoids, flavonoids, steroids, fatty acids, and organic acids, showcasing an array of pharmacological activities like anticancer, antioxidant, anti-aging, and immunoregulatory properties. Thus, this review highlights the active compounds isolated from A. sylvestris extracts, which provide potential leads for the development of novel anticancer drugs and a better understanding of the plant's pharmacological effects, particularly its anticancer mechanism of action.

Characterization of N-glycosylation and its functional role in SIDT1-Mediated RNA uptake.

The mammalian SID-1 transmembrane family members, SIDT1 and SIDT2, are multipass transmembrane proteins that mediate the cellular uptake and intracellular trafficking of nucleic acids, playing important roles in the immune response and tumorigenesis. Previous work has suggested that human SIDT1 and SIDT2 are N-glycosylated, but the precise site-specific N-glycosylation information and its functional contribution remain unclear. In this study, we use high-resolution liquid chromatography tandem mass spectrometry to comprehensively map the N-glycosites and quantify the N-glycosylation profiles of SIDT1 and SIDT2. Further molecular mechanistic probing elucidates the essential role of N-linked glycans in regulating cell surface expression, RNA binding, protein stability, and RNA uptake of SIDT1. Our results provide crucial information about the potential functional impact of N-glycosylation in the regulation of SIDT1-mediated RNA uptake and provide insights into the molecular mechanisms of this promising nucleic acid delivery system with potential implications for therapeutic applications.

Nicotinamide mononucleotide as a therapeutic agent to alleviate multi-organ failure in sepsis.

BACKGROUND: Sepsis-caused multi-organ failure remains the major cause of morbidity and mortality in intensive care units with limited therapeutics. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD+), has been recently reported to be protective in sepsis; however, its therapeutic effects remain to be determined. This study sought to investigate the therapeutic effects of NMN in septic organ failure and its underlying mechanisms. METHODS: Sepsis was induced by feces-injection-in-peritoneum in mice. NMN was given after an hour of sepsis onset. Cultured neutrophils, macrophages and endothelial cells were incubated with various agents. RESULTS: We demonstrate that administration of NMN elevated NAD+ levels and reduced serum lactate levels, oxidative stress, inflammation, and caspase-3 activity in multiple organs of septic mice, which correlated with the attenuation of heart dysfunction, pulmonary microvascular permeability, liver injury, and kidney dysfunction, leading to lower mortality. The therapeutic effects of NMN were associated with lower bacterial burden in blood, and less ROS production in septic mice. NMN improved bacterial phagocytosis and bactericidal activity of macrophages and neutrophils while reducing the lipopolysaccharides-induced inflammatory response of macrophages. In cultured endothelial cells, NMN mitigated mitochondrial dysfunction, inflammation, apoptosis, and barrier dysfunction induced by septic conditions, all of which were offset by SIRT3 inhibition. CONCLUSION: NAD+ repletion with NMN prevents mitochondrial dysfunction and restrains bacterial dissemination while limiting inflammatory damage through SIRT3 signaling in sepsis. Thus, NMN may represent a therapeutic option for sepsis.

Mechanism of a rabbit monoclonal antibody broadly neutralizing SARS-CoV-2 variants.

Due to the continuous evolution of SARS-CoV-2, the Omicron variant has emerged and exhibits severe immune evasion. The high number of mutations at key antigenic sites on the spike protein has made a large number of existing antibodies and vaccines ineffective against this variant. Therefore, it is urgent to develop efficient broad-spectrum neutralizing therapeutic drugs. Here we characterize a rabbit monoclonal antibody (RmAb) 1H1 with broad-spectrum neutralizing potency against Omicron sublineages including BA.1, BA.1.1, BA.2, BA.2.12.1, BA.2.75, BA.3 and BA.4/5. Cryo-electron microscopy (cryo-EM) structure determination of the BA.1 spike-1H1 Fab complexes shows that 1H1 targets a highly conserved region of RBD and avoids most of the circulating Omicron mutations, explaining its broad-spectrum neutralization potency. Our findings indicate 1H1 as a promising RmAb model for designing broad-spectrum neutralizing antibodies and shed light on the development of therapeutic agents as well as effective vaccines against newly emerging variants in the future.

Mechanism of an RBM-targeted rabbit monoclonal antibody 9H1 neutralizing SARS-CoV-2.

The COVID-19 pandemic, caused by SARS-CoV-2, has led to over 750 million infections and 6.8 million deaths worldwide since late 2019. Due to the continuous evolution of SARS-CoV-2, many significant variants have emerged, creating ongoing challenges to the prevention and treatment of the pandemic. Therefore, the study of antibody responses against SARS-CoV-2 is essential for the development of vaccines and therapeutics. Here we perform single particle cryo-electron microscopy (cryo-EM) structure determination of a rabbit monoclonal antibody (RmAb) 9H1 in complex with the SARS-CoV-2 wild-type (WT) spike trimer. Our structural analysis shows that 9H1 interacts with the receptor-binding motif (RBM) region of the receptor-binding domain (RBD) on the spike protein and by directly competing with angiotensin-converting enzyme 2 (ACE2), it blocks the binding of the virus to the receptor and achieves neutralization. Our findings suggest that utilizing rabbit-derived mAbs provides valuable insights into the molecular interactions between neutralizing antibodies and spike proteins and may also facilitate the development of therapeutic antibodies and expand the antibody library.

Structural Insight Into hnRNP A2/B1 Homodimerization and DNA Recognition.

Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) has been identified as a nuclear DNA sensor. Upon viral infection, hnRNP A2/B1 recognizes pathogen-derived DNA as a homodimer, which is a prerequisite for its translocation to the cytoplasm to activate the interferon response. However, the DNA binding mechanism inducing hnRNP A2/B1 homodimerization is unknown. Here, we show the crystal structure of the RNA recognition motif (RRM) of hnRNP A2/B1 in complex with a U-shaped ssDNA, which mediates the formation of a newly observed protein dimer. Our biochemical assays and mutagenesis studies confirm that the hnRNP A2/B1 homodimer forms in solution by binding to pre-generated ssDNA or dsDNA with a U-shaped bulge. These results depict a potential functional state of hnRNP A2/B1 in antiviral immunity and other cellular processes.

Enhancement of Escherichia coli Ribonuclease R Cytosine-Sensitive Activity by Single Amino Acid Substitution.

Exoribonucleases are frequently used as nuclei acids detection tools for their sequences, modifications, and structures. Escherichia coli ribonuclease R (EcR) is the prototypical exoribonuclease of the RNase II/RNB family degrading RNA in the 3'-5' direction. Different from RNase II, EcR is capable of degrading structured RNA efficiently, which makes it a potential analysis tool for various RNA species. In this work, we examined the nuclease activity of EcR degrading a series of RNA substrates with various sequences. Our biochemical work reveals that EcR is significantly sensitive to cytosine compared with other bases when catalyzing RNA degradation. EcR shows higher cytosine sensitivity compared to its homolog RNase II when degrading RNAs, and the hydrolysis process of EcR is transiently halted and produces apparent intermediate product when the 1-nt upstream of C is A or U, or G. Furthermore, the substitution of glycine with proline (G273P) in EcR enhances its cytosine sensitivity. These findings expand our understanding of EcR enzymatic activities. The EcR G273P mutant bearing higher cytosine sensitivity could help enrich cytosine trails in RNAs and will have potential implications in the detection and analysis of various RNA species especially small RNAs in biological and clinical samples.

Sustained over-expression of calpain-2 induces age-dependent dilated cardiomyopathy in mice through aberrant autophagy.

Calpains have been implicated in heart diseases. While calpain-1 has been detrimental to the heart, the role of calpain-2 in cardiac pathology remains controversial. In this study we investigated whether sustained over-expression of calpain-2 had any adverse effects on the heart and the underlying mechanisms. Double transgenic mice (Tg-Capn2/tTA) were generated, which express human CAPN2 restricted to cardiomyocytes. The mice were subjected to echocardiography at age 3, 6, 8 and 12 months, and their heart tissues and sera were collected for analyses. We showed that transgenic mice over-expressing calpain-2 restricted to cardiomyocytes had normal heart function with no evidence of cardiac pathological remodeling at age 3 months. However, they exhibited features of dilated cardiomyopathy including increased heart size, enlarged heart chambers and heart dysfunction from age 8 months; histological analysis revealed loss of cardiomyocytes replaced by myocardial fibrosis and cardiomyocyte hypertrophy in transgenic mice from age 8 months. These cardiac alterations closely correlated with aberrant autophagy evidenced by significantly increased LC3BII and p62 protein levels and accumulation of autophagosomes in the hearts of transgenic mice. Notably, injection of 3-methyladenine, a well-established inhibitor of autophagy (30 mg/kg, i.p. once every 3 days starting from age 6 months for 2 months) prevented aberrant autophagy, attenuated myocardial injury and improved heart function in the transgenic mice. In cultured cardiomyocytes, over-expression of calpain-2 blocked autophagic flux by impairing lysosomal function. Furthermore, over-expression of calpain-2 resulted in lower levels of junctophilin-2 protein in the heart of transgenic mice and in cultured cardiomyocytes, which was attenuated by 3-methyladenine. In addition, blockade of autophagic flux by bafilomycin A (100 nM) induced a reduction of junctophilin-2 protein in cardiomyocytes. In summary, transgenic over-expression of calpain-2 induces age-dependent dilated cardiomyopathy in mice, which may be mediated through aberrant autophagy and a reduction of junctophilin-2. Thus, a sustained increase in calpain-2 may be detrimental to the heart.

MLKL-mediated necroptosis is a target for cardiac protection in mouse models of type-1 diabetes.

BACKGROUND: Cardiomyocyte death contributes to cardiac pathology of diabetes. Studies have shown that the RIPK3/MLKL necroptosis signaling is activated in diabetic hearts. Deletion of RIPK3 was reported to attenuate myocardial injury and heart dysfunction in streptozocin (STZ)-induced diabetic mice, suggesting a potential role of necroptosis in diabetic cardiomyopathy. This study characterized cardiomyocyte necroptosis in diabetic hearts and investigated whether MLKL-mediated necroptosis is a target for cardiac protection in diabetes. METHODS: Type 1 diabetes was induced in RIPK3 knockout, MLKL knockout and wild-type mice. Akita Type-1 diabetic mice were injected with shRNA for MLKL. Myocardial function was assessed by echocardiography. Immuno-histological analyses determined cardiomyocyte death and fibrosis in the heart. Cultured adult mouse cardiomyocytes were incubated with high glucose in the presence of various drugs. Cell death and phosphorylation of RIPK3 and MLKL were analysed. RESULTS: We showed that the levels of phosphorylated RIPK3 and MLKL were higher in high glucose-stimulated cardiomyocytes and hearts of STZ-induced type-1 diabetic mice, akita mice and type-1 diabetic monkeys when compared to non-diabetic controls. Inhibition of RIPK3 by its pharmacological inhibitor or gene deletion, or MLKL deletion prevented high glucose-induced MLKL phosphorylation and attenuated necroptosis in cardiomyocytes. In STZ-induced type-1 diabetic mice, cardiomyocyte necroptosis was present along with elevated cardiac troponin I in serum and MLKL oligomerization, and co-localized with phosphorylated MLKL. Deletion of RIPK3 or MLKL prevented MLKL phosphorylation and cardiac necroptosis, attenuated serum cardiac troponin I levels, reduced myocardial collagen deposition and improved myocardial function in STZ-injected mice. Additionally, shRNA-mediated down-regulation of MLKL reduced cardiomyocyte necroptosis in akita mice. Interestingly, incubation with anti-diabetic drugs (empagliflozin and metformin) prevented phosphorylation of RIPK3 and MLKL, and reduced cell death in high glucose-induced cardiomyocytes. CONCLUSIONS: We have provided evidence that cardiomyocyte necroptosis is present in diabetic hearts and that MLKL-mediated cardiomyocyte necroptosis contributes to diabetic cardiomyopathy. These findings highlight MLKL-mediated necroptosis as a target for cardiac protection in diabetes.

The Third dose of CoronVac vaccination induces broad and potent adaptive immune responses that recognize SARS-CoV-2 Delta and Omicron variants.

The waning humoral immunity and emerging contagious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants resulted in the necessity of the booster vaccination of coronavirus disease 2019 (COVID-19). The inactivated vaccine, CoronaVac, is the most widely supplied COVID-19 vaccine globally. Whether the CoronaVac booster elicited adaptive responses that cross-recognize SARS-CoV-2 variants of concern (VoCs) among 77 healthy subjects receiving the third dose of CoronaVac were explored. After the boost, remarkable elevated spike-specific IgG and IgA responses, as well as boosted neutralization activities, were observed, despite 3.0-fold and 5.9-fold reduced neutralization activities against Delta and Omicron strains compared to that of the ancestral strain. Furthermore, the booster dose induced potent B cells and memory B cells that cross-bound receptor-binding domain (RBD) proteins derived from VoCs, while Delta and Omicron RBD-specific memory B cell recognitions were reduced by 2.7-fold and 4.2-fold compared to that of ancestral strain, respectively. Consistently, spike-specific circulating follicular helper T cells (cTfh) significantly increased and remained stable after the boost, with a predominant expansion towards cTfh17 subpopulations. Moreover, SARS-CoV-2-specific CD4+ and CD8+ T cells peaked and sustained after the booster. Notably, CD4+ and CD8+ T cell recognition of VoC spike was largely preserved compared to the ancestral strain. Individuals without generating Delta or Omicron neutralization activities had comparable levels of CD4+ and CD8+ T cells responses as those with detectable neutralizing activities. Our study demonstrated that the CoronaVac booster induced broad and potent adaptive immune responses that could be effective in controlling SARS-CoV-2 Delta and Omicron variants.

Structures of Omicron spike complexes and implications for neutralizing antibody development.

The emergence of the SARS-CoV-2 Omicron variant is dominant in many countries worldwide. The high number of spike mutations is responsible for the broad immune evasion from existing vaccines and antibody drugs. To understand this, we first present the cryo-electron microscopy structure of ACE2-bound SARS-CoV-2 Omicron spike. Comparison to previous spike antibody structures explains how Omicron escapes these therapeutics. Secondly, we report structures of Omicron, Delta, and wild-type spikes bound to a patient-derived Fab antibody fragment (510A5), which provides direct evidence where antibody binding is greatly attenuated by the Omicron mutations, freeing spike to bind ACE2. Together with biochemical binding and 510A5 neutralization assays, our work establishes principles of binding required for neutralization and clearly illustrates how the mutations lead to antibody evasion yet retain strong ACE2 interactions. Structural information on spike with both bound and unbound antibodies collectively elucidates potential strategies for generation of therapeutic antibodies.

Structural basis for replicase polyprotein cleavage and substrate specificity of main protease from SARS-CoV-2.

The main protease (Mpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a key enzyme, which extensively digests CoV replicase polyproteins essential for viral replication and transcription, making it an attractive target for antiviral drug development. However, the molecular mechanism of how Mpro of SARS-CoV-2 digests replicase polyproteins, releasing the nonstructural proteins (nsps), and its substrate specificity remain largely unknown. Here, we determine the high-resolution structures of SARS-CoV-2 Mpro in its resting state, precleavage state, and postcleavage state, constituting a full cycle of substrate cleavage. The structures show the delicate conformational changes that occur during polyprotein processing. Further, we solve the structures of the SARS-CoV-2 Mpro mutant (H41A) in complex with six native cleavage substrates from replicase polyproteins, and demonstrate that SARS-CoV-2 Mpro can recognize sequences as long as 10 residues but only have special selectivity for four subsites. These structural data provide a basis to develop potent new inhibitors against SARS-CoV-2.

Crystal Structures of Wolbachia CidA and CidB Reveal Determinants of Bacteria-induced Cytoplasmic Incompatibility and Rescue.

Cytoplasmic incompatibility (CI) results when Wolbachia bacteria-infected male insects mate with uninfected females, leading to embryonic lethality. "Rescue" of viability occurs if the female harbors the same Wolbachia strain. CI is caused by linked pairs of Wolbachia genes called CI factors (CifA and CifB). The co-evolution of CifA-CifB pairs may account in part for the incompatibility patterns documented in insects infected with different Wolbachia strains, but the molecular mechanisms remain elusive. Here, we use X-ray crystallography and AlphaFold to analyze the CI factors from Wolbachia strain wMel called CidAwMel and CidBwMel. Substituting CidAwMel interface residues with those from CidAwPip (from strain wPip) enables the mutant protein to bind CidBwPip and rescue CidBwPip-induced yeast growth defects, supporting the importance of CifA-CifB interaction in CI rescue. Sequence divergence in CidAwPip and CidBwPip proteins affects their pairwise interactions, which may help explain the complex incompatibility patterns of mosquitoes infected with different wPip strains.