Reactive nitrogen species switch on early extracellular matrix remodeling via induction of MMP1 and TNFalpha.
OBJECTIVE
Liver injury leads to generation of reactive oxygen and nitrogen species, which can react to produce peroxynitrite (ONOO-). We investigated whether ONOO- and its metabolites modulate extracellular matrix remodeling.


METHODS
Stellate cells (HSC) were incubated with pure ONOO- or SIN-1 (a ONOO- donor). Western blot, nuclear in vitro transcription, Northern blot, qPCR, and promoter transactivation analysis for COL1A1 and COL1A2 were carried out. Rats were fed alcohol or injected with CCl4 to cause alcohol-induced liver injury and an early fibrogenic response.


RESULTS
HSC incubated with ONOO- or SIN-1 showed similar viability, proliferation, COL1A1 and COL1A2 transcription rates, and mRNA levels as controls. There was a time- and dose-dependent down-regulation of collagen I and alpha-Sma proteins and up-regulation of MMP1 and TNFalpha, indicating decreased HSC activation. These effects were blocked by ONOO- scavengers. SIN-1 or ONOO- increased nitrosylation of MMP1/MMP13 and transactivation of the MMP1, MMP13, and TNFalpha promoters. A TNFalpha neutralizing antibody or GSH-ethyl ester blocked MMP1 promoter transactivation; whereas TNFalpha or l-buthionine sulfoximine, which depletes GSH, further enhanced it. Pretreatment with SIN-1 or ONOO- reduced the TGFbeta pro-fibrogenic response in HSC. In vivo experiments validated the protective role of ONOO- on the early fibrogenic response. However, highly activated HSC, such as myofibroblasts and HSC from chronic alcohol-fed rats, were resistant to the anti-fibrogenic actions of ONOO- due to higher levels of GSH, a ONOO- scavenger, overproduction of pro-fibrogenic TGFbeta, and reactive oxygen species.


CONCLUSIONS
ONOO- could induce a protective mechanism in HSC in early stages of liver injury.
Urtasun
Raquel
R
Department of Medicine, Division of Liver Diseases, Mount Sinai School of Medicine, New York, New York 10029, USA.
Cubero
Francisco Javier
FJ
Vera
María
M
Nieto
Natalia
N
D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002251:Carbon Tetrachloride; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D000090602:Collagen Type I, alpha 1 Chain; D004195:Disease Models, Animal; D005109:Extracellular Matrix / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D008103:Liver Cirrhosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism*; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D030421:Peroxynitrous Acid / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D026361:Reactive Nitrogen Species / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D000199:Actins; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D020030:Nitric Oxide Donors; D026361:Reactive Nitrogen Species; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D030421:Peroxynitrous Acid; C002385:linsidomine; D003094:Collagen; D002251:Carbon Tetrachloride; D008981:Molsidomine; D020781:Matrix Metalloproteinase 1