title: Neuronal CCL2 is upregulated during hepatic encephalopathy and contributes to microglia activation and neurological decline.
abstract: BACKGROUND
  Acute liver failure leads to systemic complications with one of the most dangerous being a decline in neurological function, termed hepatic encephalopathy. Neurological dysfunction is exacerbated by an increase of toxic metabolites in the brain that lead to neuroinflammation. Following various liver diseases, hepatic and circulating chemokines, such as chemokine ligand 2 (CCL2), are elevated, though their effects on the brain following acute liver injury and subsequent hepatic encephalopathy are unknown. CCL2 is known to activate microglia in other neuropathies, leading to a proinflammatory response. However, the effects of CCL2 on microglia activation and the pathogenesis of hepatic encephalopathy following acute liver injury remain to be determined.
  
  
  METHODS
  Hepatic encephalopathy was induced in mice via injection of azoxymethane (AOM) in the presence or absence of INCB 3284 dimesylate (INCB), a chemokine receptor 2 inhibitor, or C 021 dihydrochloride (C021), a chemokine receptor 4 inhibitor. Mice were monitored for neurological decline and time to coma (loss of all reflexes) was recorded. Tissue was collected at coma and used for real-time PCR, immunoblots, ELISA, or immunostaining analyses to assess the activation of microglia and consequences on pro-inflammatory cytokine expression.
  
  
  RESULTS
  Following AOM administration, microglia activation was significantly increased in AOM-treated mice compared to controls. Concentrations of CCL2 in the liver, serum, and cortex were significantly elevated in AOM-treated mice compared to controls. Systemic administration of INCB or C021 reduced liver damage as assessed by serum liver enzyme biochemistry. Administration of INCB or C021 significantly improved the neurological outcomes of AOM-treated mice, reduced microglia activation, reduced phosphorylation of ERK1/2, and alleviated AOM-induced cytokine upregulation.
  
  
  CONCLUSIONS
  These findings suggest that CCL2 is elevated systemically following acute liver injury and that CCL2 is involved in both the microglia activation and neurological decline associated with hepatic encephalopathy. Methods used to modulate CCL2 levels and/or reduce CCR2/CCR4 activity may be potential therapeutic targets for the management of hepatic encephalopathy due to acute liver injury.
authors.forename: Matthew
authors.initials: M
authors.lastname: McMillin
authors.forename: Gabriel
authors.initials: G
authors.lastname: Frampton
authors.forename: Michelle
authors.initials: M
authors.lastname: Thompson
authors.forename: Cheryl
authors.initials: C
authors.lastname: Galindo
authors.forename: Holly
authors.initials: H
authors.lastname: Standeford
authors.forename: Eric
authors.initials: E
authors.lastname: Whittington
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Alpini
authors.affiliation: Department of Internal Medicine, Texas A&M Health Science Center, College of Medicine, 1901 South 1st Street, Building 205, Temple, Texas, USA. demorrow@medicine.tamhsc.edu.
authors.forename: Sharon
authors.initials: S
authors.lastname: DeMorrow
mesh_terms: D000818:Animals; D001397:Azoxymethane / Q000633:toxicity; D001549:Benzamides / Q000008:administration & dosage / Q000627:therapeutic use; D001831:Body Temperature / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002273:Carcinogens / Q000633:toxicity; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000627:therapeutic use; D006501:Hepatic Encephalopathy / Q000139:chemically induced / Q000150:complications* / Q000473:pathology* / Q000517:prevention & control; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D009422:Nervous System Diseases / Q000209:etiology*; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D001549:Benzamides; C000595925:C 021 compound; D002273:Carcinogens; D018932:Chemokine CCL2; D004791:Enzyme Inhibitors; C000595924:INCB 3284; D011799:Quinazolines; D001397:Azoxymethane; D005998:Glycine