Extracellular Vesicles from Hyperammonemic Rats Induce Neuroinflammation and Motor Incoordination in Control Rats.

Paula Izquierdo-Altarejos,Carmina Montoliu,Vicente Felipo,Hernan Gonzalez-King,Andrea Cabrera-Pastor

doi:10.3390/cells9030572

Paula Izquierdo-Altarejos, Carmina Montoliu + Show 3 more

Open Access

https://doi.org/10.3390/cells9030572

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Abstract

Minimal hepatic encephalopathy is associated with changes in the peripheral immune system which are transferred to the brain, leading to neuroinflammation and thus to cognitive and motor impairment. Mechanisms by which changes in the immune system induce cerebral alterations remain unclear. Extracellular vesicles (EVs) seem to play a role in this process in certain pathologies. The aim of this work was to assess whether EVs play a role in the induction of neuroinflammation in cerebellum and motor incoordination by chronic hyperammonemia. We characterized the differences in protein cargo of EVs from plasma of hyperammonemic and control rats by proteomics and Western blot. We assessed whether injection of EVs from hyperammonemic to normal rats induces changes in neuroinflammation in cerebellum and motor incoordination similar to those exhibited by hyperammonemic rats. We found that hyperammonemia increases EVs amount and alters their protein cargo. Differentially expressed proteins are mainly associated with immune system processes. Injected EVs enter Purkinje neurons and microglia. Injection of EVs from hyperammonemic, but not from control rats, induces motor incoordination, which is mediated by neuroinflammation, microglia and astrocytes activation and increased IL-1β, TNFα, its receptor TNFR1, NF-κB in microglia, glutaminase I, and GAT3 in cerebellum. Plasma EVs from hyperammonemic rats carry molecules necessary and sufficient to trigger neuroinflammation in cerebellum and the mechanisms leading to motor incoordination.

Highlights

Patients with liver cirrhosis may present minimal or clinical hepatic encephalopathy (HE), a complex neuropsychiatric syndrome leading to cognitive and motor alterations which reduces quality of life and life span of the patients
The presence of surface markers typical of exosomes was evaluated by Western blot, revealing that the isolated extracellular vesicles (EVs) were positive for Hsp70, Flotillin-2, and CD9 (Figure 2B)
This study provides relevant new insights on the mechanisms by which peripheral changes are transmitted to brain to induce minimal HE (MHE)

Summary

Introduction

Patients with liver cirrhosis may present minimal or clinical hepatic encephalopathy (HE), a complex neuropsychiatric syndrome leading to cognitive and motor alterations which reduces quality of life and life span of the patients. Studies in patients and in animal models show that MHE appearance is associated with changes in the peripheral immune system that are transferred to the brain, inducing neuroinflammation, which in turn leads to cognitive and motor impairment [6,7,8,9,10,11]. Changes in the immune system lead to cerebral alterations in pathologies associated to sustained peripheral inflammation such as diabetes, rheumatoid arthritis, obesity, and chronic kidney disease, as well as neurological and neurodegenerative diseases such as schizophrenia, Parkinson’s and Alzheimer’s disease [12,13,14,15,16,17,18,19,20]. The mechanisms by which changes in the immune system induce alterations in brain in response to sustained inflammation are not well understood. EVs play a main role in the mediation of immune and inflammatory responses, and in diseases with a significant inflammatory component [23,24]

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