High throughput screening identifies auranofin and pentamidine as potent compounds that lower IFN-γ-induced Nitric Oxide and inflammatory responses in mice: DSS-induced colitis and Salmonella Typhimurium-induced sepsis

Interferon-gamma (IFN-γ) is a type II interferon produced primarily by T cells and natural killer cells. IFN-γ induces the expression of inducible nitric oxide synthase (NOS2) to catalyze Nitric Oxide (NO) production in various immune and non-immune cells. Excessive IFN-γ-activated NO production is implicated in several inflammatory diseases, including peritonitis and inflammatory bowel diseases. In this study, we screened the LOPAC®1280 library in vitro on the H6 mouse hepatoma cell line to identify novel non-steroidal small molecule inhibitors of IFN-γ-induced NO production. Compounds with the highest inhibitory activity were validated, which led to identifying the lead compounds: pentamidine, azithromycin, rolipram, and auranofin. Auranofin was the most potent compound determined based on IC50 and goodness of fit analyses. Mechanistic investigations revealed that majority of the lead compounds suppress the IFN-γ-induced transcription of Nos2 without negatively affecting NO-independent processes, such as the IFN-γ-induced transcription of Irf1, Socs1 and MHC class 1 surface expression. However, all four compounds lower IFN-γ-induced reactive oxygen species amounts. In addition, auranofin significantly reduced IFN-γ-mediated NO and IL6 production in resident as well as thioglycolate-elicited peritoneal macrophages (PMs). Finally, in vivo testing of the lead compounds in the pre-clinical DSS-induced ulcerative colitis mice model revealed pentamidine and auranofin to be the most potent and protective lead compounds. Also, pentamidine and auranofin greatly increase the survival of mice in another inflammatory model: Salmonella Typhimurium-induced sepsis. Overall, this study identifies novel anti-inflammatory compounds targeting IFN-γ-induced NO-dependent processes to alleviate two distinct inflammatory models of disease.