Pharmacological in vivo inhibition of S-nitrosoglutathione reductase attenuates bleomycin-induced inflammation and fibrosis

Interstitial lung disease (ILD) characterized by pulmonary fibrosis and inflammation poses a substantial biomedical challenge due to often negative disease outcomes combined with the need to develop better, more effective therapies. We assessed the in vivo effect of administration of a pharmacological inhibitor of S-nitrosoglutathione reductase, SPL-334, in a mouse model of ILD induced by intratracheal instillation of bleomycin (BLM). Daily intraperitoneal administration of SPL-334 alone at 0.3 mg/kg, 1.0 mg/kg, or 3.0 mg/kg had no effect on animal body weight, appearance, behavior, total and differential bronchoalveolar lavage (BAL) cell counts, or collagen accumulation in the lungs, showing no toxicity of our investigational compound. Similar administration of SPL-334 for 7 days before and for an additional 14 days after BLM instillation resulted in a preventive protective effect on the BLM challenge-induced decline in total body weight and changes in total and differential BAL cellularity. In the therapeutic treatment regimen, SPL-334 was administered at days 7-21 after BLM challenge. Such treatment attenuated the BLM challenge-induced decline in total body weight, changes in total and differential BAL cellularity, and magnitudes of histological changes and collagen accumulation in the lungs. These changes were accompanied by an attenuation of BLM-induced elevations in pulmonary levels of profibrotic cytokines IL-6, MCP-1, and TGF-β. Experiments in cell cultures of primary normal human lung fibroblast have demonstrated attenuation of TGF-β-induced upregulation in collagen by SPL-334. It was concluded that SPL-334 is a potential therapeutic agent for ILD.