title: Adenosine A(2a) receptor stimulation prevents hepatocyte lipotoxicity and non-alcoholic steatohepatitis (NASH) in rats.
abstract: NEFA (non-esterified 'free' fatty acid)-mediated lipotoxicity plays a critical role in the pathogenesis of NASH (non-alcoholic steatohepatitis). In the light of the growing need for new therapeutic options for NASH, we investigated the action of A2aR (adenosine A(2a) receptor) stimulation against lipotoxicity. The effects of the A(2a)R agonist CGS21680 [2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxyamidoadenosine] were evaluated 'in vitro' in liver cells exposed to SA (stearic acid) and 'in vivo' in rats with NASH induced by 8 weeks of feeding with an MCD diet (methionine/choline-deficient diet). In cultured hepatocytes, SA promoted apoptosis by inducing MKK4 (mitogen-activated protein kinase kinase 4)/SEK1 (stress-activated protein kinase/extracellular-signal-regulated kinase kinase-1) and JNK-1/2 (c-Jun N-terminal kinase-1/2) activation. CGS21680 addition prevented JNK-1/2 activation and reduced apoptosis without interfering with lipid accumulation. CGS21680 action required PI3K (phosphoinositide 3-kinase)/Akt-mediated block of MKK4/SEK1. Consistently, PI3K inhibition with wortmannin abolished the cytoprotective action of CGS21680 and reverted MKK4 inhibition. SA lipotoxicity was also prevented by transfecting HTC cells with a specific MKK4/SEK1 siRNA (small interfering RNA). In rats receiving the MCD diet, the development of NASH was associated with MKK4/SEK1 and JNK-1/2 activation. CGS21680 (0.5 mg/kg of body weight, intraperitoneal) administration to MCD-fed rats prevented JNK-1/2 activation by acting on MKK4/SEK1. CGS21680 also effectively reduced NASH-associated ALT (alanine aminotransferase) release, hepatocyte apoptosis, liver inflammation and fibrosis without affecting hepatic steatosis. Taken together, these results demonstrate that, by inhibiting JNK-1/2, A(2a)R stimulation reduces lipotoxicity and ameliorates NASH, giving a rationale to investigate A(2a)R agonists as possible new therapeutic agents in preventing fatty liver progression to NASH.
authors.affiliation: Department of Health Sciences, University 'A. Avogadro', Novara 28100, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Imarisio
authors.forename: Elisa
authors.initials: E
authors.lastname: Alchera
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sutti
authors.forename: Guido
authors.initials: G
authors.lastname: Valente
authors.forename: Francesca
authors.initials: F
authors.lastname: Boccafoschi
authors.forename: Emanuele
authors.initials: E
authors.lastname: Albano
authors.forename: Rita
authors.initials: R
authors.lastname: Carini
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D058908:Adenosine A2 Receptor Agonists / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D002478:Cells, Cultured; D004334:Drug Administration Schedule; D005234:Fatty Liver / Q000378:metabolism / Q000517:prevention & control*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D007274:Injections, Intraperitoneal; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D065626:Non-alcoholic Fatty Liver Disease; D010627:Phenethylamines / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D043683:Receptors, Adenosine A2 / Q000378:metabolism; D013229:Stearic Acids / Q000633:toxicity
chemical_list: D058908:Adenosine A2 Receptor Agonists; D015415:Biomarkers; D010627:Phenethylamines; D043683:Receptors, Adenosine A2; D013229:Stearic Acids; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C031183:stearic acid; D048031:JNK Mitogen-Activated Protein Kinases; D000241:Adenosine