Sulfur compounds block MCP-1 production by Mycoplasma fermentans-infected macrophages through NF-kB inhibition

Background and aims: Hydrogen sulfide (H2S), together with nitric oxide (NO) and carbon monoxide (CO), belongs to a family of endogenous signaling mediators termed "gasotransmitters". Recent studies suggest that H2S modulates many cellular processes and it has been recognized to play a central role in inflammation, in the cardiovascular and nervous systems. By infecting monocytes/macrophages with Mycoplasma fermentans (M.F.), a well-known pro-inflammatory agent, we evaluated the effects of H2S. Methods: M.F.-infected cells were analyzed by ELISA and real time RT-PCR to detect the M.F. effects on MCP-1 and on MMP-12 expression. The role of two different H2S donors (NaHS and GYY4137) on MF-infected cells was determined by treating infected cells with H2S and then testing the culture supernatants for MCP-1 and on MMP-12 production by ELISA assay. In order to identify the pathway/s mediating H2S-anti-inflammatory activity, cells were also treated with specific pharmaceutical inhibitors. Cytoplasmic and nuclear accumulation of NF-kB heterodimers was analyzed. Results: We show that H2S was able to reduce the production of pro-inflammatory cytokine MCP-1, that was induced in monocytes/macrophages during M.F. infection. Moreover, MCP-1 was induced by M.F. through Toll-like receptor (TLR)-mediated nuclear factor-kB (NF-kB) activation, as demonstrated by the fact that TLR inhibitors TIRAP and MyD88 and NF-kB inhibitor IKK were able to block the cytokine production. In contrast H2S treatment of M.F. infected macrophages reduced nuclear accumulation of NF-kB heterodimer p65/p52. Conclusions: Our data demonstrate that under the present conditions H2S is effective in reducing Mycoplasma-induced inflammation by targeting the NF-kB pathway. This supports further studies for possible clinical applications.