Down-regulation of high mobility group-I(Y) protein contributes to the inhibition of nitric-oxide synthase 2 by transforming growth factor-beta1.
The inducible isoform of nitric-oxide synthase (NOS2) catalyzes the production of nitric oxide (NO), which participates in the pathophysiology of systemic inflammatory diseases such as sepsis. NOS2 is transcriptionally up-regulated by endotoxin and inflammatory cytokines, and down-regulated by transforming growth factor (TGF)-beta1. Recently we have shown that high mobility group (HMG)-I(Y) protein, an architectural transcription factor, contributes to NOS2 gene transactivation by inflammatory mediators. The aim of the present study was to determine whether regulation of HMG-I(Y) by TGF-beta1 contributes to the TGF-beta1-mediated suppression of NOS2. By Northern blot analysis, we show that TGF-beta1 decreased cytokine-induced HMG-I(Y) mRNA levels in vascular smooth muscle cells and macrophages in vitro and in vivo. Western analysis confirmed the down-regulation of HMG-I(Y) protein by TGF-beta1. To determine whether the down-regulation of HMG-I(Y) contributed to a decrease in NOS2 gene transactivation by TGF-beta1, we performed cotransfection experiments. Overexpression of HMG-I(Y) was able to restore cytokine inducibility of the NOS2 promoter that was suppressed by TGF-beta1. The effect of TGF-beta1 on NOS2 gene transactivation was not related to a decrease in binding of HMG-I(Y) to the promoter of the NOS2 gene, but due to a decrease in endogenous HMG-I(Y) protein. These data provide the first evidence that cytokine-induced HMG-I(Y) can be down-regulated by TGF-beta1. This down-regulation of HMG-I(Y) contributes to the TGF-beta1-mediated decrease in NOS2 gene transactivation by proinflammatory stimuli.
Pellacani
A
A
Cardiovascular and Pulmonary and Critical Care Divisions, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Wiesel
P
P
Razavi
S
S
Vasilj
V
V
Feinberg
M W
MW
Chin
M T
MT
Reeves
R
R
Perrella
M A
MA
D000818:Animals; D001011:Aorta; D002460:Cell Line; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D025741:HMGA1a Protein; D006609:High Mobility Group Proteins / Q000235:genetics* / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D008264:Macrophages / Q000201:enzymology; D008297:Male; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D010750:Phosphoproteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D015533:Transcriptional Activation; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D006609:High Mobility Group Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D025741:HMGA1a Protein; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat