Interferon alpha-induced apoptosis on rat preneoplastic liver is mediated by hepatocytic transforming growth factor beta(1).
In previous work we showed that interferon alfa-2b (IFN-alpha2b) increases apoptosis on rat hepatic preneoplastic foci. The aim of this study was to determine if transforming growth factor beta1 (TGF-beta1) was involved in the programmed cell death on the foci. Animals were divided into 6 groups: subjected to a 2-phase model (diethylnitrosamine plus 2-acetylaminofluorene) of preneoplasia development (group 1); treated with IFN-alpha2b during the 2 phases (group 2); treated with IFN-alpha2b during initiation with diethylnitrosamine (group 3); treated with IFN-alpha2b during 2-acetylaminofluorene administration (group 4); subjected only to an initiation stage (group 5); and treated with IFN-alpha2b during the initiation period (group 6). Serum TGF-beta1 levels were increased in IFN-alpha2b-treated rats. Immunohistochemical studies showed that IFN-alpha2b significantly increased the quantity of TGF-beta1-positive hepatocytes in groups 2 to 4. Phosphorylated-Smads-2/3 (p-Smads-2/3) proteins in liver nuclear extracts were significantly elevated. To determine the source of TGF-beta1, isolated hepatocytes, Kupffer cells, and peritoneal macrophages from animals in groups 1 and 5 were cultured with or without IFN-alpha2b. IFN-alpha2b stimulus induced several-fold increases of TGF-beta1 secretion from hepatocytes. Neither Kupffer cells nor peritoneal macrophages secreted detectable TGF-beta1 levels when they were treated with IFN-alpha2b. IFN-alpha2b-stimulated cultured hepatocytes from preneoplastic livers showed enhanced apoptosis, measured by fluorescence microscopy and caspase-3 activity. They presented higher nuclear accumulation of p-Smads-2/3, indicating increased TGF-beta1 signaling. When anti-TGF-beta1 was added to the culture media, TGF-beta1 activation and apoptosis induced by IFN-alpha2b were blocked. In conclusion, IFN-alpha2b-induced production of TGF-beta1 by hepatocytes from preneoplastic liver is involved in the apoptotic elimination of altered hepatic foci.
de Luján Alvarez
María
M
Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina.
Ronco
María Teresa
MT
Ochoa
J Elena
JE
Monti
Juan A
JA
Carnovale
Cristina E
CE
Pisani
Gerardo B
GB
Lugano
María Cristina
MC
Carrillo
María Cristina
MC
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003470:Culture Media / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology*; D008114:Liver Neoplasms, Experimental / Q000503:physiopathology*; D008297:Male; D010766:Phosphorylation; D011230:Precancerous Conditions / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000097:blood / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D003470:Culture Media; D004268:DNA-Binding Proteins; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D011994:Recombinant Proteins; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051900:Smad3 Protein; C497787:Smad3 protein, rat; C508962:Tgfb1 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases