Possible contribution of hepatocyte secretion to the elevation of plasma exosomal arginase-1 in high-fat diet-fed mice

Arginase-1 in Plasma-Derived Exosomes as Marker of Metastasis in Patients with Head and Neck Squamous Cell Carcinoma

Immunoregulatory Arginase-1 (Arg-1) is present in the tumor microenvironment of solid tumors. Its association to clinicopathology and its prognostic impact are inconsistent among different tumor types and biological fluids. This study evaluated Arg-1 protein levels in tumors and the circulation of patients with head and neck squamous cell carcinoma (HNSCC) in relation to clinical stage and prognosis. Tumor Arg-1 expression was monitored via immunohistochemistry while plasma Arg-1 levels via ELISA in 37 HNSCC patients. Arg-1 presence in plasma-derived exosomes was assessed using Western blots in 20 HNSCC patients. High tumor Arg-1 expression correlated with favorable clinicopathology and longer recurrence-free survival (RFS), while high plasma Arg-1 levels were associated with unfavorable clinicopathology. All patients with low tumor and high plasma Arg-1 had nodal metastases and developed recurrence. This discrepancy was attributed to the presence of Arg-1-carrying exosomes. Arg-1 was found in plasma-derived exosomes from all HNSCC patients. High exosomal Arg-1 levels were associated with positive lymph nodes and short RFS. Circulating Arg-1+ exosomes represent a mechanism of active Arg-1 export from the tumor to the periphery. Exosomes reflected biologically relevant Arg-1 levels in metastatic HNSCC and emerged as potentially more accurate biomarkers of metastatic disease and RFS than tissue or plasma Arg-1 levels.

An Overview of Inter-Tissue and Inter-Kingdom Communication Mediated by Extracellular Vesicles in the Regulation of Mammalian Metabolism

Obesity and type 2 diabetes are associated with defects of insulin action in different tissues or alterations in β-cell secretory capacity that may be triggered by environmental challenges, inadequate lifestyle choices, or an underlying genetic predisposition. In addition, recent data shows that obesity may also be caused by perturbations of the gut microbiota, which then affect metabolic function and energy homeostasis in the host. Maintenance of metabolic homeostasis in complex organisms such as mammals requires organismal-level communication, including between the different organs and the gut microbiota. Extracellular vesicles (EVs) have been identified in all domains of life and have emerged as crucial players in inter-organ and inter-kingdom crosstalk. Interestingly, EVs found in edible vegetables or in milk have been shown to influence gut microbiota or tissue function in mammals. Moreover, there is a multidirectional crosstalk mediated by EVs derived from gut microbiota and body organs that has implications for host health. Untangling this complex signaling network may help implement novel therapies for the treatment of metabolic disease.

TMAO-Activated Hepatocyte-Derived Exosomes Impair Angiogenesis via Repressing CXCR4

Objective: Trimethylamine-N-oxide (TMAO) was found to play crucial roles in vascular endothelial function. However, the exact molecular mechanisms are not yet entirely clear. Recently, we found that exosomes (Exos) isolated from TMAO-treated hepatocytes (TMAO-Exos) contained a distinctive profile of miRNAs compared to those from the TMAO-free group (Control-Exos). Furthermore, TMAO-Exos could notably promote inflammation, damage vascular endothelial cells (VECs), and impair endothelium-dependent vasodilation. This study aimed to further evaluate the effects of TMAO-Exos on VECs and explore the underlying mechanisms.

Methods: Exos were isolated from the hepatocyte culture supernatant with or without TMAO, using differential centrifugation. Then, VECs were treated with these Exos for 48 h and subjected to RNA-sequencing for detecting the changes of alternative polyadenylation (APA) and mRNA. After validation by qPCR and western blotting, the recombinant viruses were used to mediate the overexpression of C-X-C motif chemokine receptor 4 (CXCR4). The in vitro VEC function was evaluated by cell migration and tube formation, and in vivo angiogenesis was investigated in hindlimb ischemia models.

Results: Exos released from hepatocytes were differentially regulated by TMAO; both could be taken up by VECs; and furthermore, TMAO-Exos significantly reduced cell migration and tube formation in vitro and impaired perfusion recovery and angiogenesis after hindlimb ischemia, by down-regulating the CXCR4 expression. However, TMAO-Exos failed to regulate the splicing events, at least in this experimental setting, which suggested that TMAO-Exos may affect CXCR4 expression via an APA-independent manner.

Conclusions: Our findings revealed a novel indirect mechanism by which TMAO impaired endothelial function through stimulating hepatocytes to produce Exos that possessed distinctive activity. The crosstalk between the liver and vascular endothelial mediated by these Exos may offer a new target for restraining the harmful effects induced by TMAO.

Dietary modulation of large extracellular vesicles: the good and the bad for human health

Extracellular vesicles (EVs) encompassing nanovesicles derived from the endosome system and generated by plasmatic membrane shedding are of increasing interest in view of their ability to sustain cell-to-cell communication and the possibility that they could be used as surrogate biomarkers of healthy and unhealthy trajectories. Nutritional strategies have been developed to preserve health, and the impact of these strategies on circulating EVs is arousing growing interest. Data available from published studies are now sufficient for a first integration to better understand the role of EVs in the relationship between diet and health. Thus, this review focuses on human intervention studies investigating the impact of diet or its components on circulating EVs. Because of analytical bias, only large EVs have been assessed so far. The analysis highlights that poor-quality diets with elevated fat and sugar content increase levels of circulating large EVs, and these can be partly counteracted by healthy food or some food micronutrients and bioactive compounds. However, knowledge of the content and the biological functions of these diet-induced EVs is still missing. It is important to address these aspects in new research in order to state if EVs are mediators of the effects of diet on health.