Polysulfides derived from the hydrogen sulfide and persulfide donor P* inhibit IL-1β-mediated inducible nitric oxide synthase signaling in ATDC5 cells: are CCAAT/enhancer-binding proteins β and δ involved in the anti-inflammatory effects of hydrogen sulfide and polysulfides?

Hydrogen sulfide (HS) emerged as an essential signaling molecule exerting beneficial effects in various cardiovascular, neurodegenerative, or musculoskeletal diseases with an inflammatory component, such as osteoarthritis. These protective effects were initially attributed to protein S-sulfhydration, a posttranslational modification of reactive cysteine residues. However, recent studies suggest that polysulfides and not HS are responsible for S-sulfhydration. To distinguish between HS and polysulfide-mediated effects in this study, we used the slow-releasing HS and persulfide donor P*, which can be decomposed into polysulfides. The effects of P* on IL-1β-induced inducible nitric oxide synthase (iNOS), a pro-inflammatory mediator in osteoarthritis, were determined by nitrite measurement, qPCR, and Western blotting in the murine chondrocyte-like cell line ATDC5. Decomposed P* significantly reduced IL-1β-induced iNOS signaling via polysulfides, independently of HS. In line with this, the fast-releasing HS donor NaHS was ineffective. In RAW 264.7 macrophages, similar results were obtained. P*-derived polysulfides further diminished IL-1β-induced CCAAT/enhancer-binding protein (C/EBP) β and δ expression in ATDC5 cells, which might play a critical role in P*-mediated iNOS decline. In conclusion, our data support the view that polysulfides are essential signaling molecules as well as potential mediators of HS signaling. Moreover, we propose that C/EBPβ/δ might be a novel target involved in HS and polysulfide-mediated anti-inflammatory signaling.