Regulation of TGFbeta1-mediated collagen formation by LOX-1: studies based on forced overexpression of TGFbeta1 in wild-type and lox-1 knock-out mouse cardiac fibroblasts.
Transforming growth factor beta(1) (TGFbeta(1)) activation leads to tissue fibrosis. Here, we report on the role of LOX-1, a lectin-like 52-kDa receptor for oxidized low density lipoprotein, in TGFbeta(1)-mediated collagen expression and underlying signaling in mouse cardiac fibroblasts. TGFbeta(1) was overexpressed in wild-type (WT) and LOX-1 knock-out mouse cardiac fibroblasts by transfection with adeno-associated virus type 2 vector carrying the active TGFbeta(1) moiety (AAV/TGFbeta (ACT)(1)). Transfection of WT mouse cardiac fibroblasts with AAV/TGFbeta (ACT)(1) markedly enhanced the expression of NADPH oxidases (p22(phox), p47(phox), and gp91(phox) subunits) and LOX-1, formation of reactive oxygen species, and collagen synthesis, concomitant with an increase in the activation of p38 and p44/42 mitogen-activated protein kinases (MAPK). The TGFbeta(1)-mediated increase in collagen synthesis was markedly attenuated in the LOX-1 knock-out mouse cardiac fibroblasts as well as in WT mouse cardiac fibroblasts treated with a specific anti-LOX-1 antibody. Treatment with anti-LOX-1 antibody also reduced NADPH oxidase expression and MAPK activation. The NADPH oxidase inhibitors and gp91phox small interfering RNA reduced LOX-1 expression, MAPK activation, and collagen formation. The p38 MAPK inhibitors as well as the p44/42 MAPK inhibitors reduced collagen formation without affecting LOX-1 expression in cardiac fibroblasts. These observations suggest that collagen synthesis in cardiac fibroblasts involves a facilitative interaction between TGFbeta(1)-NADPH oxidase and LOX-1. Further, the activation of MAPK pathway appears to be downstream of TGFbeta(1)-reactive oxygen species-LOX-1 cascade.
Hu
Changping
C
Cardiovascular Medicine, University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, Arkansas 72205-7199, USA.
Dandapat
Abhijit
A
Sun
Liuqin
L
Khan
Junaid A
JA
Liu
Yong
Y
Hermonat
Paul L
PL
Mehta
Jawahar L
JL
D000818:Animals; D003094:Collagen / Q000378:metabolism*; D003573:Cytochrome b Group / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D020935:MAP Kinase Signaling System; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism; D017382:Reactive Oxygen Species; D051127:Scavenger Receptors, Class E / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
D003573:Cytochrome b Group; D008562:Membrane Glycoproteins; C495138:Olr1 protein, mouse; D017382:Reactive Oxygen Species; D051127:Scavenger Receptors, Class E; D053773:Transforming Growth Factor beta1; D003094:Collagen; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C515614:Cyba protein, mouse; C060505:neutrophil cytosolic factor 1