Extracellular cysteine/cystine redox potential controls lung fibroblast proliferation and matrix expression through upregulation of transforming growth factor-β

Abstract

Oxidant stress has been implicated in the pathogenesis of chronic lung disorders like idiopathic pulmonary fibrosis. However, mechanisms that link oxidant stress to fibrogenesis remain partially elucidated. Emerging data suggest an important role for the extracellular thiol/disulfide redox environment. The cysteine (Cys)/cystine (CySS) redox couple represents the predominant low-molecular-weight thiol/disulfide pool found in plasma and is sensitive to aging, smoking, and other host factors. We hypothesized that an oxidized extracellular Cys/CySS redox potential (E(h) Cys/CySS) affects lung fibroblasts by inducing intracellular signals that stimulate proliferation and matrix expression. We tested this hypothesis in primary murine lung fibroblasts and found that an oxidized E(h) Cys/CySS (-46 mV) stimulated lung fibroblast proliferation. Furthermore, it stimulated their expression of fibronectin, a matrix glycoprotein highly expressed in fibrotic lung diseases and implicated in lung injury. This stimulatory effect was dependent on protein kinase C activation. Oxidant stress also increased the phosphorylation of cAMP response element binding protein, a transcription factor known for its ability to stimulate fibronectin expression, and increased the expression of mRNAs and proteins coding for the transcription factors nuclear factor (NF)-kappaB and mothers against decapentaplegic homolog 3. Fibroblasts cultured in normal (-80 mV) or reduced (-131 mV) E(h) Cys/CySS showed less induction. Furthermore, fibronectin expression in response to an oxidized E(h) Cys/CySS was associated with expression of transforming growth factor-beta1 (TGF-beta1) and was inhibited by an anti-TGF-beta1 antibody and SB-431542, a TGF-beta1 receptor inhibitor. These studies suggest that extracellular oxidant stress activates redox-sensitive pathways that stimulate lung fibroblast proliferation and matrix expression through upregulation of TGF-beta1.

Oxidation of Plasma Cysteine/Cystine and GSH/GSSG Redox Potentials by Acetaminophen and Sulfur Amino Acid Insufficiency in Humans

“…4D), suggesting that APAP could affect redox signaling mediated via E h CySS. No relevant in vivo data are available, but in vitro data show that an oxidized extracellular E h CySS in cell culture activates proinflammatory signaling Go et al, 2010), profibrotic signaling (Ramirez et al, 2007), stress signaling (Go et al, 2009), and apoptotic signaling (Jiang et al, 2005). Although speculative, the present data suggest a number of unanticipated effects of therapeutic use of APAP could occur as a consequence of effects on plasma E h CySS.…”

Nonequilibrium thermodynamics of thiol/disulfide redox systems: A perspective on redox systems biology

“…Binding of human monocytic THP1 cells to endothelial cells was enhanced at more positive E h values [82]. A lung fibroblast model relevant to pulmonary fibrosis also showed that positive E h values stimulate fibroblast proliferation and matrix expression through upregulation of transforming growth factor-β [83]. Thus, the data show that the factors controlling the balance of plasma Cys/CySS are important in determining cell function and thereby can potentially contribute to disease risk.…”

Radical-free biology of oxidative stress

“…For instance, profibrotic signaling by TGF-␤1 in pulmonary fibroblasts is stimulated by oxidized extracellular E h (145), and this suggests that conditions which oxidize plasma Cys/CySS could contribute to fibrotic disease. Platelet activation has an optimal extracellular redox potential mediated through redox changes of Cys residues in ␣IIIb␤3 (43) and could be susceptible to aberrant function due to altered plasma redox states.…”