Bleomycin-induced lung fibrosis and dysfunction is exacerbated by G6PD deficiency

Pulmonary fibrosis (PF) is a major cause of morbidity and mortality. Although increased oxidative stress and altered metabolism are implicated in PF pathobiology, our knowledge regarding the contribution of the glucose metabolism to the synthesis of extracellular matrix (ECM) is still incomplete. Therefore, our objective was to determine altered metabolic pathways that contribute to bleomycin sulfate (BLM; 5 mg/kg)-induced PF in rats. We determined the effects of nebulized BLM on PF in CRISPR-edited rats expressing glucose-6-phosphate dehydrogenase (G6PD) variant (S188F; G6PD S188F ) and their wild-type (WT) littermates. Unexpectedly, application of BLM increased lung tissue volume in G6PD S188F rats as compared to WT littermates. Masson’s Trichrome staining and Ashcroft scoring revealed increased collagen in perivascular regions and around the airways and hydroxyproline within the lungs of G6PD S188F + BLM as compared to WT + BLM rats. In addition, mass-spectrometry-based proteomics and spatial proteomics confirmed increased expression of pro-fibrotic proteins, including collagen1a1 and baculoviral IAP Repeat Containing 5, in the lungs of G6PD S188F + BLM rats compared to WT + BLM rats. Since BLM increased expression of KEAP1, we suggest that BLM inactivated NRF2 and increased oxidized glutathione, an indicator of oxidative stress that increases ECM, in lungs of G6PD S188F rats. Finally, unbiased metabolomics revealed down-regulated spermidine, a polyamine pathway metabolite that decreases BLM-induced collagen deposition, in the lungs of G6PD S188F + BLM rats. Therefore, we propose that dysregulated polyamine pathway and antioxidant state exacerbated BLM-induced synthesis of ECM-related proteins in G6PD S188F variant rats as compared to their WT littermates.