Hepatocyte-secreted extracellular vesicles modify blood metabolome and endothelial function by an arginase-dependent mechanism

Abstract

Hepatocytes release extracellular vesicles (EVs) loaded with signaling molecules and enzymes into the bloodstream. Although the importance of EVs in the intercellular communication is already recognized, the metabolic impact of the enzymes carried by these vesicles is still unclear. We evaluated the global effect of the enzymatic activities of EVs by performing untargeted metabolomic profiling of serum samples after their exposure to EVs. This approach revealed a significant change in the abundance of 94 serum metabolic signals. Our study shows that these vesicles modify the concentration of metabolites of different chemical nature including metabolites related to arginine metabolism, which regulates vascular function. To assess the functional relevance of this finding, we examined the levels of arginase-1 protein and its activity in the hepatic EVs carrying the exosomal markers CD81 and CD63. Remarkably, the arginase activity was also detected in EVs isolated from the serum in vivo, and this vesicular activity significantly increased under liver-damaging conditions. Finally, we demonstrated that EVs secreted by hepatocytes inhibited the acetylcholine-induced relaxation in isolated pulmonary arteries, via an arginase-dependent mechanism. In summary, our study demonstrates that the hepatocyte-released EVs are metabolically active, affecting a number of serum metabolites involved in oxidative stress metabolism and the endothelial function.

Abundance of Cytochromes in Hepatic Extracellular Vesicles Is Altered by Drugs Related With Drug‐Induced Liver Injury

“…In addition, alteration of the metabolism of arginine was also observed, as judged by the increased levels of the enzymes argininosuccinate synthase 1 and arginase 1 (Arg1) (Fig. and Supporting Table ), previously shown to be active in EVs and associated with endothelial regulation . Asparagine and aspartate metabolism involved cellular proliferation was also affected by all treatments, as suggested by the increased levels of L‐asparaginase (also known as 60 kDa lysophospholipase, LPP60) (Fig.…”

“…Remarkably, Cyp2d1 was highly enriched in the same fraction, strongly suggesting that this enzyme was associated with extracellular vesicles. We have demonstrated in hepatocyte‐secreted EVs the presence of not only the protein but also the activity for the Arg1, Ces1d, and Comt enzymes . Here, we addressed the question of whether the Cyp2d1 enzyme, detected in EVs, is active.…”

A new role for extracellular vesicles: how small vesicles can feed tumors' big appetite

“…EVs also contain miRNA that are known to target proteins implicated in metabolism (81) and recent studies point out the presence of metabolites in EVs (13,82,83). Moreover, enzymes carried by hepatocyte vesicles can modify serum metabolome, and especially metabolites involved in oxidative stress (84,85). Collectively, these studies suggest that regulation of cell metabolism by EVs could be multifactorial.…”

Summary of the ISEV workshop on extracellular vesicles as disease biomarkers, held in Birmingham, UK, during December 2017

“…Interestingly, liver injury often leads to changes in liver-specific enzymes, and these remain catalytically active when released within EVs. Addition of hepatocyte EVs to serum results in a host of new metabolites, such as ornithine, due to the catalytic activities of EV-associated arginase [23]. Hence, the assessment of liver injury can be inferred from profiling EVs and the repertoire of metabolites within biofluids [24].…”