Gut最新文献

Background: Plasmablast-derived HBV surface antigen (HBsAg)-specific monoclonal antibody (mAb) and structural basis for binding to native HBsAg are poorly known.

Objective: We aimed to identify plasmablast-derived HBsAg-specific mAbs, evaluate their antiviral activities and resolve their structure for binding to native HBsAg.

Design: A previously vaccinated volunteer was enrolled in this study, who was boosted with a dose of recombinant hepatitis B vaccine and donated the blood sample. Activated plasmablasts were sorted from fresh peripheral blood mononuclear cells and mAbs were expressed. Their gene features, cross-genotypic binding activities and antiviral functions in vitro and in vivo were comprehensively analysed. The cryo-electron microscopy (cryo-EM) was used to determine the structure of representative mAb bound to the native HBsAg.

Results: In this study, we cloned a series of HBsAg-specific mAbs directly from clonally expanded plasmablasts from a vaccinated individual. Most of the mAbs displayed cross-reactivities of binding to different genotype HBsAg proteins and antiviral functions such as neutralisation and antibody-dependent cellular phagocytosis. These human anti-HBsAg mAbs, especially SY-4-class and SY-23-class, could be good candidates for antibody drugs. The cryo-EM structure of SY-23 bound to the dimeric HBsAg was determined, revealing its binding mechanism and unprecedented structural detail of the major antigenic loop (AGL) of HBsAg.

Conclusion: Overall, our work has uncovered the diverse gene features and varied anti-HBV activities of plasmablast-derived mAbs, providing a series of antibody drug candidates and the long-sought-after atomic model of AGL has paved the way for a wholistic characterisation of the AGL's dynamic conformation during HBV infection and immune response.

Background: Liver metastasis is a common and fatal event for patients with pancreatic ductal adenocarcinoma (PDAC). Dysregulated mitochondrial dynamics reshape biological processes, including metabolism reprogramming, which disrupts immune cell function and promotes metastatic progression.

Objective: To identify key drivers that reprogramme PDAC mitochondrial function and its role in remodelling the immunosuppressive tumour microenvironment (TME) during PDAC liver colonisation.

Design: Genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) loss-of-function screening, in vivo mouse model screening and in vitro anoikis-resistant cell selection were employed to identify key drivers during PDAC liver colonisation. PDAC organoids, metabolic flux analysis, single-cell RNA sequencing, spatial metabolomics and glutathione S-transferase (GST) pull-down assay were used to explore the regulation of mitochondrial fission process protein 1 (MTFP1) on PDAC liver colonisation and unravel the underlying mechanism.

Results: We revealed MTFP1, a protein that plays an important role in cell viability and mitochondrial dynamics, as a driver of PDAC liver colonisation. Mechanistically, MTFP1 is recognised as a novel ATP synthase modulator through its interaction with numerous ATP synthase subunits, thereby enhancing oxidative phosphorylation (OXPHOS). Increased mitochondrial fission and subsequent redox signalling (ROS production) upregulates solute carrier family A1 member 5 (SLC1A5) expression by activating the PI3K/AKT/c-MYC pathway, competing for glutamine uptake and impaired antitumour responses of CD8⁺ T cells. By performing virtual screening, we identified KPT 9274 (ATG-019) as an effective inhibitor of MTFP1. Limitation of glutamine uptake in PDAC cells or MTFP1 inhibition reverses the immunosuppressive TME and reduces liver colonisation of PDAC.

Conclusion: Our data demonstrate that the enhanced MTFP1 expression leads to an upregulated glutamine-OXPHOS axis in PDAC liver colonisation. This metabolic shift is triggered by the ROS/PI3K/AKT/c-MYC/SLC1A5 pathway. Targeting MTFP1 may be a potential therapeutic strategy for PDAC patients with liver metastasis.

Background: Gastric cancer (GC) is one of the most common malignancies worldwide and it is the third leading cause of cancer-related death in China. While Helicobacter pylori is a known GC pathogen, its abundance declines in tumours and the role of other bacteria in GC metastasis remains unclear.

Objective: We aim to investigate the mechanisms of other bacteria influencing GC progression and metastasis.

Design: Integrated intratumoural microbiome-metabolome analysis identified GC-associated microbes and metabolites. We then demonstrated the pro-metastatic role of Acinetobacter baumannii (A. baumannii, Ab) and its metabolite nicotinic acid (NA) using genetic, molecular and in vivo approaches.

Results: The abundance of A. baumannii was significantly increased in GC tissues, correlating with advanced tumour stage and intratumoural NA levels. Fluorescence in situ hybridisation confirmed its colonisation in GC tumours. In co-culture systems, A. baumannii increased NA levels, enhancing nicotinamide adenine dinucleotide (NAD) metabolism and increasing 1-Methylnicotinamide accumulation in tumour cells. Mutagenesis of the bacterial NA synthase gene pncA confirmed that A. baumannii excreted an NA-dependent pro-metastasis effect. Mechanically, A. baumannii promotes GC metastasis by reprogramming tumour cell glucose metabolism, reducing oxidative phosphorylation while enhancing glycolysis and activating the hypoxia-inducible factor-1 pathway in GC cells through metabolites both in vivo and in vitro.

Conclusions: This study elucidates the role of A. baumannii in enhancing NAD metabolism in GC cells through NA synthesis, consequently promoting GC metastasis. These findings establish a microbiota-metabolism axis as a mechanistic foundation for developing targeted therapeutic strategies against GC metastasis.

Background: Stroke induces complex pathophysiological responses that extend beyond the brain, yet the mechanisms through which peripheral signals influence stroke recovery remain largely unclear.

Objective: Here, we identify a novel gut-brain neural circuit that promotes stroke recovery via kynurenic acid (KYNA) signalling.

Design: In a training cohort (30 patients with acute ischaemic stroke (AIS) and 30 controls), untargeted metabolomics profiled intestinal metabolites and the key metabolite KYNA was validated in an independent cohort (100 patients with AIS and 100 controls) using targeted metabolomics and assessed for its 3-month prognostic value. In stroke mouse models, KYNA was administered to evaluate therapeutic effects. Mechanistic studies combined neuronal calcium imaging, enteric neuron receptor manipulation, vagotomy, neuronal tracing, electrophysiology and immunofluorescence to delineate the KYNA-mediated gut-brain neural circuit regulating stroke recovery.

Results: Our study demonstrates a significant reduction of intestinal KYNA in patients with AIS and validates its prognostic value for neurological recovery at 3 months poststroke in both the training and validation cohorts. Oral KYNA supplementation markedly improves poststroke cerebral injury by activating G protein-coupled receptor 35 (GPR35) on enteric neurons, initiating vagal nerve signalling. Mechanistically, KYNA-GPR35 interaction activates vagal afferents, transmitting signals through the nucleus tractus solitarius to hippocampal and hypothalamic regions. This GPR35-vagus nerve signalling pathway, further validated with the selective GPR35 agonist Zaprinast, confers neuroprotection by shifting microglial polarisation towards the anti-inflammatory M2 phenotype and enhancing neuronal α7 nicotinic acetylcholine receptor activity.

Conclusion: KYNA acts through an intestinal GPR35-vagus neural pathway to influence stroke recovery, highlighting this gut-brain signalling axis as a promising therapeutic avenue.