title: Inhibition of natural killer cells protects the liver against acute injury in the absence of glycine N-methyltransferase.
abstract: Glycine N-methyltransferase (GNMT) catabolizes S-adenosylmethionine (SAMe), the main methyl donor of the body. Patients with cirrhosis show attenuated GNMT expression, which is absent in hepatocellular carcinoma (HCC) samples. GNMT(-/-) mice develop spontaneous steatosis that progresses to steatohepatitis, cirrhosis, and HCC. The liver is highly enriched with innate immune cells and plays a key role in the body's host defense and in the regulation of inflammation. Chronic inflammation is the major hallmark of nonalcoholic steatohepatitis (NASH) progression. The aim of our study was to uncover the molecular mechanisms leading to liver chronic inflammation in the absence of GNMT, focusing on the implication of natural killer (NK) / natural killer T (NKT) cells. We found increased expression of T helper (Th)1- over Th2-related cytokines, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-R2/DR5, and several ligands of NK cells in GNMT(-/-) livers. Interestingly, NK cells from GNMT(-/-) mice were spontaneously activated, expressed more TRAIL, and had strong cytotoxic activity, suggesting their contribution to the proinflammatory environment in the liver. Accordingly, NK cells mediated hypersensitivity to concanavalin A (ConA)-mediated hepatitis in GNMT(-/-) mice. Moreover, GNMT(-/-) mice were hypersensitive to endotoxin-mediated liver injury. NK cell depletion and adoptive transfer of TRAIL(-/-) liver-NK cells protected the liver against lipopolysaccharide (LPS) liver damage.
  
  
  CONCLUSIONS
  Our data allow us to conclude that TRAIL-producing NK cells actively contribute to promote a proinflammatory environment at early stages of fatty liver disease, suggesting that this cell compartment may contribute to the progression of NASH.
authors.affiliation: Department of Metabolomics, CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (Ciberedh), Technology Park of Bizkaia, 48160-Derio, Bizkaia, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Gomez-Santos
authors.forename: Zigmund
authors.initials: Z
authors.lastname: Luka
authors.forename: Conrad
authors.initials: C
authors.lastname: Wagner
authors.forename: Sara
authors.initials: S
authors.lastname: Fernandez-Alvarez
authors.forename: Shelly C
authors.initials: SC
authors.lastname: Lu
authors.forename: Jose M
authors.initials: JM
authors.lastname: Mato
authors.forename: Maria L
authors.initials: ML
authors.lastname: Martinez-Chantar
authors.forename: Naiara
authors.initials: N
authors.lastname: Beraza
mesh_terms: D000208:Acute Disease; D019264:Adoptive Transfer; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D056486:Chemical and Drug Induced Liver Injury / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D003208:Concanavalin A / Q000633:toxicity; D004195:Disease Models, Animal; D005234:Fatty Liver / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D050938:Glycine N-Methyltransferase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007694:Killer Cells, Natural / Q000276:immunology* / Q000473:pathology; D008070:Lipopolysaccharides / Q000633:toxicity; D008212:Lymphocyte Depletion; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008934:Mitogens / Q000633:toxicity; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D008934:Mitogens; D053221:TNF-Related Apoptosis-Inducing Ligand; C505654:Tnfsf10 protein, mouse; D003208:Concanavalin A; D050938:Glycine N-Methyltransferase; C494511:Gnmt protein, mouse