Hyperammonemia increases the release of pathological extracellular vesicles from monocytes by impairing lysosomal function and autophagy through the TNFα-cAMP-PKA-LC3 pathway.

Background: Patients with liver cirrhosis may show minimal hepatic encephalopathy (MHE) triggered by a shift in peripheral inflammation. A main mechanism by which peripheral alterations are transmitted to the brain is the infiltration of extracellular vesicles (EV). Hyperammonemic rats are a model of MHE that reproduces cognitive impairment. Injection of EV from plasma or peripheral blood mononuclear cells (PBMC) of hyperammonemic rats to normal rats induces neuroinflammation, alterations in neurotransmission, and cognitive impairment. PBMC contain different cell types. The aims were 1) to identify which cell type produces the pathological EV in hyperammonemic rats; 2) to identify the mechanisms by which hyperammonemia increases EV release from monocytes and induces the formation of pathological EV; and 3) to analyze the role of TNFα and PKA in these mechanisms. Methods: EV were isolated from primary cultures of CD4 Results: In hyperammonemic rats, monocytes but not CD4 Conclusions: These data unveil that monocytes produce the pathological EV in hyperammonemia and the underlying mechanisms and provide the bases for new treatments to improve cognitive and motor function in hyperammonemia and MHE.