The S1PR2-CCL2-BDNF-TrkB pathway mediates neuroinflammation and motor incoordination in hyperammonaemia

Autores de CIPF

• 

  Yaiza Arenas Ortiz

  Autor

• Tiziano Balzano

  Autor

• Gergana Mincheva Ganeva

  Autor

• 

  Marta Llansola Gil

  Autor

• 

  Vicente Felipo Orts

  Autor

Grupos de Investigación

• Laboratorio de Neurobiología

  

  Jefe/a de Grupo

  Vicente Felipo Orts

Abstract

Aims Chronic hyperammonaemia and inflammation synergistically induce neurological impairment, including motor incoordination, in hepatic encephalopathy. Hyperammonaemic rats show neuroinflammation in the cerebellum which enhances GABAergic neurotransmission leading to motor incoordination. We aimed to identify underlying mechanisms. The aims were (1) to assess if S1PR2 is involved in microglial and astrocytic activation in the cerebellum of hyperammonaemic rats; (2) to identify pathways by which enhanced S1PR2 activation induces neuroinflammation and alters neurotransmission; (3) to assess if blocking S1PR2 reduces neuroinflammation and restores motor coordination in hyperammonaemic rats. Methods We performed ex vivo studies in cerebellar slices from control or hyperammonaemic rats to identify pathways by which neuroinflammation enhances GABAergic neurotransmission in hyperammonaemia. Neuroinflammation and neurotransmission were assessed by immunochemistry/immunofluorescence and western blot. S1PR2 was blocked by intracerebral treatment with JTE-013 using osmotic mini-pumps. Motor coordination was assessed by beam walking. Results Chronic hyperammonaemia enhances S1PR2 activation in the cerebellum by increasing its membrane expression. This increases CCL2, especially in Purkinje neurons. CCL2 activates CCR2 in microglia, leading to microglial activation, increased P2X4 membrane expression and BDNF in microglia. BDNF enhances TrkB activation in neurons, increasing KCC2 membrane expression. This enhances GABAergic neurotransmission, leading to motor incoordination in hyperammonaemic rats. Blocking S1PR2 in hyperammonaemic rats by intracerebral administration of JTE-013 normalises the S1PR2-CCL2-CCR2-BDNF-TrkB-KCC2 pathway, reduces glial activation and restores motor coordination in hyperammonaemic rats. Conclusions Enhanced S1PR2-CCL2-BDNF-TrkB pathway activation mediates neuroinflammation and incoordination in hyperammonaemia. The data raise a promising therapy for patients with hepatic encephalopathy using compounds targeting this pathway.

Keywords

• CCL2; hyperammonaemia; neuroinflammation; Purkinje neurons; S1PR2