title: Role of cannabinoid receptors in alcoholic hepatic injury: steatosis and fibrogenesis are increased in CB2 receptor-deficient mice and decreased in CB1 receptor knockouts.
abstract: BACKGROUND
  Alcohol is a common cause of hepatic liver injury with steatosis and fibrosis. Cannabinoid receptors (CB) modulate steatosis, inflammation and fibrogenesis. To investigate the differences between CB(1) and CB(2) in the hepatic response to chronic alcohol intake, we examined CB knockout mice (CB(1)(-/-), CB(2)(-/-)).
  
  
  METHODS
  Eight- to 10-week-old CB(1)(-/-), CB(2)(-/-) and wild-type mice received 16% ethanol for 35 weeks. Animals receiving water served as controls. We analysed triglyceride and hydroxyproline contents in liver homogenates. mRNA levels of CBs, pro-inflammatory cytokines [tumour necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1, interleukin (IL)-1β] and profibrotic factors [α-smooth muscle actin (α-SMA), procollagen-Ia, platelet-derived growth factor β receptor (PDGFβ-R)] were analysed by reverse transcription-polymerase chain reaction (RT-PCR). Histology (hemalaun and eosin, oil-red O, CD3, CD45R, CD45, F4/80, Sirius red) characterized hepatic steatosis, inflammation and fibrosis. Activation of lipogenic pathways, activation and proliferation of hepatic stellate cell (HSC) were assessed by western blot [fatty acid synthase (FAS), sterol regulatory element binding protein 1c (SREBP-1c), α-SMA, proliferating cell nuclear antigen (PCNA), cathepsin D].
  
  
  RESULTS
  Hepatic mRNA levels of the respective CBs were increased in wild-type animals and in CB(1)(-/-) mice after ethanol intake. Ethanol intake in CB(2)(-/-) mice induced much higher steatosis (SREBP-1c mediated) and inflammation (B-cell predominant infiltrates) compared with wild-type animals and CB(1)(-/-) mice. HSC activation and collagen production were increased in all groups after forced ethanol intake, being most pronounced in CB(2)(-/-) mice and least pronounced in CB(1)(-/-) mice.
  
  
  CONCLUSIONS
  The fact that CB(2) receptor knockout mice exhibited the most pronounced liver damage after ethanol challenge indicates a protective role of CB(2) receptor expression in chronic ethanol intake. By contrast, in CB(1) knockouts, the effect of ethanol was attenuated, suggesting aggravation of fibrogenesis and SREBP-1c-mediated steatosis via CB(1) receptor expression after ethanol intake.
authors.affiliation: Department of Internal Medicine I, University of Bonn, Bonn, Germany. jonel.trebicka@ukb.uni-bonn.de
authors.forename: Jonel
authors.initials: J
authors.lastname: Trebicka
authors.forename: Ildiko
authors.initials: I
authors.lastname: Racz
authors.forename: Sören V
authors.initials: SV
authors.lastname: Siegmund
authors.forename: Erlind
authors.initials: E
authors.lastname: Cara
authors.forename: Michaela
authors.initials: M
authors.lastname: Granzow
authors.forename: Robert
authors.initials: R
authors.lastname: Schierwagen
authors.forename: Sabine
authors.initials: S
authors.lastname: Klein
authors.forename: Alexandra
authors.initials: A
authors.lastname: Wojtalla
authors.forename: Martin
authors.initials: M
authors.lastname: Hennenberg
authors.forename: Sebastian
authors.initials: S
authors.lastname: Huss
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Fischer
authors.forename: Jörg
authors.initials: J
authors.lastname: Heller
authors.forename: Andreas
authors.initials: A
authors.lastname: Zimmer
authors.forename: Tilman
authors.initials: T
authors.lastname: Sauerbruch
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D049109:Cell Proliferation; D004195:Disease Models, Animal; D000431:Ethanol / Q000097:blood; D005235:Fatty Liver, Alcoholic / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D055166:Hepatic Stellate Cells / Q000378:metabolism / Q000473:pathology; D006519:Hepatitis, Alcoholic / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D006909:Hydroxyproline / Q000378:metabolism; D018836:Inflammation Mediators / Q000378:metabolism; D008099:Liver / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D008104:Liver Cirrhosis, Alcoholic / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000172:deficiency* / Q000235:genetics; D043885:Receptor, Cannabinoid, CB2 / Q000172:deficiency* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D015415:Biomarkers; D018836:Inflammation Mediators; D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D014280:Triglycerides; D000431:Ethanol; D006909:Hydroxyproline