Journal
JOURNAL OF NEUROINFLAMMATION
Volume 17, Issue 1, Pages -Publisher
BMC
DOI: 10.1186/s12974-020-01746-z
Keywords
Hyperammonemia; Neuroinflammation; TNF-a; Purkinje neurons; TNFR1
Categories
Funding
- Ministerio de Ciencia e Innovacion Spain [SAF2014-51851-R, SAF2017-82917-R]
- Conselleria Educacion Generalitat Valenciana [PROMETEOII/2014/033, PROMETEOII/2018/051]
- European Regional Development Funds (ERDF)
- Ministerio de Ciencia e Innovacion, Spain [PRE2018-084770]
- Generalitat Valenciana [APOSTD/2018/002]
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Background Patients with liver cirrhosis may develop hepatic encephalopathy. Rats with chronic hyperammonemia exhibit neurological alterations mediated by peripheral inflammation and neuroinflammation. Motor incoordination is due to increased TNF-a levels and activation of its receptor TNFR1 in the cerebellum. The aims were to assess (a) whether peripheral inflammation is responsible for TNF-a induction in hyperammonemic rats, (b) the cell type(s) in which TNF-a is increased, (c) whether this increase is associated with increased nuclear NF-kappa B and TNFR1 activation, (d) the time course of TNF-a induction, and (e) if TNF-a is induced in the Purkinje neurons of patients who die with liver cirrhosis. Methods We analyzed the level of TNF-a mRNA and NF-kappa B in microglia, astrocytes, and Purkinje neurons in the cerebellum after 1, 2, and 4 weeks of hyperammonemia. We assessed whether preventing peripheral inflammation by administering an anti-TNF-a antibody prevents TNF-a induction. We tested whether TNF-a induction is reversed by R7050, which inhibits the TNFR1-NF-kappa B pathway, in ex vivo cerebellar slices. Results Hyperammonemia induced microglial and astrocyte activation at 1 week. This was followed by TNF-a induction in both glial cell types at 2 weeks and in Purkinje neurons at 4 weeks. The level of TNF-a mRNA increased in parallel with the TNF-a protein level, indicating that TNF-a was synthesized in Purkinje cells. This increase was associated with increased NF-kappa B nuclear translocation. The nuclear translocation of NF-kappa B and the increase in TNF-a were reversed by R7050, indicating that they were mediated by the activation of TNFR1. Preventing peripheral inflammation with an anti-TNF-a antibody prevents TNF-a induction. Conclusion Sustained (4 weeks) but not short-term hyperammonemia induces TNF-a in Purkinje neurons in rats. This is mediated by peripheral inflammation. TNF-a is also increased in the Purkinje neurons of patients who die with liver cirrhosis. The results suggest that hyperammonemia induces TNF-a in glial cells and that TNF-a released by glial cells activates TNFR1 in Purkinje neurons, leading to NF-kappa B nuclear translocation and the induction of TNF-a expression, which may contribute to the neurological alterations observed in hyperammonemia and hepatic encephalopathy.
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