Affiliation:
1. Department of Cancer Biology Wake Forest University School of Medicine Winston‐Salem North Carolina USA
2. Atrium Health Wake Forest Baptist Comprehensive Cancer Center Winston‐Salem North Carolina USA
3. Department of Internal Medicine‐Gerontology and Geriatric Medicine Wake Forest University School of Medicine Winston‐Salem North Carolina USA
4. Sticht Center for Healthy Aging and Alzheimer's Prevention Wake Forest University School of Medicine Winston‐Salem North Carolina USA
Abstract
AbstractGut microbiome dysbiosis is a major contributing factor to several pathological conditions. However, the mechanistic understanding of the communication between gut microbiota and extra‐intestinal organs remains largely elusive. Extracellular vesicles (EVs), secreted by almost every form of life, including bacteria, could play a critical role in this inter‐kingdom crosstalk and are the focus of present study. Here, we present a novel approach for isolating lipopolysaccharide (LPS)+ bacterial extracellular vesicles (bEVLPS) from complex biological samples, including faeces, plasma and the liver from lean and diet‐induced obese (DIO) mice. bEVLPS were extensively characterised using nanoparticle tracking analyses, immunogold labelling coupled with transmission electron microscopy, flow cytometry, super‐resolution microscopy and 16S sequencing. In liver tissues, the protein expressions of TLR4 and a few macrophage‐specific biomarkers were assessed by immunohistochemistry, and the gene expressions of inflammation‐related cytokines and their receptors (n = 89 genes) were measured using a PCR array. Faecal samples from DIO mice revealed a remarkably lower concentration of total EVs but a significantly higher percentage of LPS+ EVs. Interestingly, DIO faecal bEVLPS showed a higher abundance of Proteobacteria by 16S sequencing. Importantly, in DIO mice, a higher number of total EVs and bEVLPS consistently entered the hepatic portal vein and subsequently reached the liver, associated with increased expression of TLR4, macrophage markers (F4/80, CD86 and CD206), cytokines and receptors (Il1rn, Ccr1, Cxcl10, Il2rg and Ccr2). Furthermore, a portion of bEVLPS escaped liver and entered the peripheral circulation. In conclusion, bEV could be the key mediator orchestrating various well‐established biological effects induced by gut bacteria on distant organs.