Discovery of medium ring thiophosphorus based heterocycles as antiproliferative agents.

Hydrogen sulfide (H2S) has been investigated for its potential in therapy. Recently, we reported novel H2S donor molecules based on a thiophosphorus core, which slowly release H2S and have improved anti-proliferative activity in cancer cell lines compared to the most widely studied H2S donor GYY4137 (1). Herein, we have prepared new thiophosphorus organic H2S donors with different ring sizes and evaluated them in two solid tumor cell lines and one normal cell line. A seven membered ring compound, 17, was found to be the most potent with sub-micromolar IC50s in breast (0.76µM) and ovarian (0.76µM) cancer cell lines. No significant H2S release was detected in aqueous solution for this compound. However, confocal imaging showed that H2S was released from 17 inside cells at a similar level to the widely studied H2S donor GYY4137, which was shown to release 10µM H2S after 12h at a concentration of 400µM. Comparison of 17 with its non-sulfur oxygen analogue, 26, provided evidence that the sulfur atom is important for its potency. However, the significant potency observed for 26 (5.94-11.0µM) indicates that the high potency of 17 is not entirely due to release of H2S. Additional mechanism(s) appear to be responsible for the observed activity, hence more detailed studies are required to better understand the role of H2S in cancer with potent thiophosphorus agents.

A novel slow-releasing hydrogen sulfide donor, FW1256, exerts anti-inflammatory effects in mouse macrophages and in vivo.

Exogenous hydrogen sulfide (H2S) is known to exert anti-inflammatory effects both in macrophages and in animal models. In this study, we first showed that NaHS caused a concentration dependent reduction in TNFα and IL-6 secretion in LPS-stimulated RAW264.7 macrophages in the absence of cell death. Thereafter, we screened a series of novel slow H2S donors for similar activity. One such compound, FW1256, concentration dependently decreased TNFα, IL-6, PGE2 and NO generation in LPS-stimulated RAW264.7 macrophages and BMDMs. FW1256 also significantly reduced IL-1ß, COX-2 and iNOS mRNA and protein in LPS-stimulated RAW264.7 macrophages. Mechanistically, FW1256 decreased NFκB activation as evidenced by reduced cytosolic phospho-IκBα levels and reduced nuclear p65 levels in LPS-stimulated RAW264.7 macrophages treated with FW1256. Using a H2S fluorescent probe in FW1256-treated RAW264.7 macrophages, H2S release from FW1256 was apparent over a period of 24h in these cells. Moreover, the effect of FW1256 on TNFα and IL-6 by FW1256 in LPS-stimulated RAW264.7 macrophages was reversed by treatment with the H2S scavenger, vitamin B12a. FW1256 had no cytotoxic effect on LPS-stimulated RAW264.7 macrophages or BMDMs. In vivo, FW1256 administration also reduced IL-1ß, TNFα, nitrate/nitrite and PGE2 levels in LPS-treated mice. We show here a novel slow H2S-releasing compound that exerts anti-inflammatory effects in macrophages and in vivo. FW1256 may be a useful tool to study the biological effects of exogenous H2S and could also have future therapeutic value in inflammatory conditions.