23 - Control of protein cysteine oxidation in lung fibrosis via a coordinated network of protein disulfide oxidoreductases

Abstract

Pulmonary fibrosis (IPF) is a devastating progressive disease that is fatal within 3-5 years of diagnosis. We recently demonstrated increases in protein S-glutathionylation (PSSG) in lungs from patients with IPF which correlated with loss of lung function (Anathy, Nature Medicine 2018). We have also shown that PSSG in lung epithelial cells is controlled by glutaredoxin (GLRX) glutathione S-transferase P (GSTP), and protein disulfide isomerase A3 (PDIA3). Assessment of transcripts of these oxidoreductases in IPF lung tissues and controls revealed small but statistically significant increases in mRNA levels of PDIA3, whereas expression of GSTPand GLRXmRNAs was unchanged in IPF patients compared to controls. Despite the lack of GSTPmRNA expression changes in IPF, we have observed robust expression of GSTP in hyperplastic type II epithelial cells and in regions of disease progression in IPF.Pharmacological inhibition of GSTP, using TLK117, a clinically applicable inhibitor of GSTP, protected against the progression of bleomycin-induced fibrosis in association with decreased S-glutathionylation (McMillan JCI Insight 2016). Despite slight changes in GLRXmRNA, GLRX enzymatic activity was strongly attenuated in lungs from patients with IPF. Administration of recombinant active Glrx to mice with pre-existing bleomycin or TGFB1-induced fibrosis reversed the existing increases in fibrosis in association with decreased S-glutathionylation. Similarly, epithelial specific ablation of Pdia3, or pharmacological inhibition of PDIs also attenuated bleomycin-induced lung epithelial apoptosis and fibrosis in mice. Collectively these findings suggest that multiple redox enzymes (PDIA3, GSTP, GLRX) act in concert to control the extent of S-glutathionylation, apoptosis and fibrogenesis. Coordinated targeting of this enzyme axis may provide a powerful strategy to restore redox homeostasis and reverse fibrosis. Our findings also indicate that global transcriptomics analyses in lung tissue homogenates may not identify relevant targets for pharmacological manipulation, given that PDIA3, GSTP, and GLRX activities, were found be a strong determinants of disease progression, instead of mRNA expression.