The Inhibitory Effect Of Dipyrithione On Lipopolysaccharide-induced INOS Expression And Its Mechanism In RAW264.7 Cells

Lipopolysaccharide (LPS), a constituent of the gram-negative bacterial cell wall, induces inflammatory responses when administered to cells or animals, which is similar to those seen in septic shock, a serious circulatory disorder with a high mortality rate of 30-90%, indicating an apparent inefficiency of its current treatment. Pro-inflammatory cells, mainly activated macrophages, are responsible for most of the cellular and molecular pathophysiology of sepsis by producing cytokines and other pro-inflammatory molecules including platelet-activating factor, prostaglandins, enzymes, and free radicals, such as nitric oxide (NO). Among a variety of inflammatory mediators, NO has been implicated as important mediators in endotoxemia and inflammatory conditions. NO reacts with superoxide anion (O^2-) readily and then yields peroxynitrite (ONOO^-) to result in DNA damage, low-density lipoprotein (LDL) oxidation and tyrosine nitration. NO may regulate almost all stages in the development of inflammation, in particular, the early stages of inflammatory cell transmigration to the sites of inflammation. In inflammation, over-production of NO is mainly produced by iNOS that can be up-regulated in macrophages by LPS stimulation. Compounds that inhibit iNOS expression or iNOS activity possess anti-inflammatory properties. In various cells including macrophages, LPS stimulates toll-like receptor 4 (TLR-4) to activate nuclear factorκB (NF-κB) that is an important transcription factor for iNOS. Another transcription factor involved in LPS-induced iNOS expression is the signal transducer and activator of transcription 1 (STAT1), which is activated through the Janus kinase (JAK) - STAT-pathway. LPS also had been shown to activate mitogen-activated protein kinases (MAPKs) pathways to enhance iNOS gene expression in macrophages.Dipyrithione (2, 2' -dithiobispyridine-1, 1' -dioxide, PTS2) (CAS number: 3696-28-4), a pyrithione derivate, is usually used as antibacterial and antifungal drug. Pyrithione (PTO), the monomer of PTS2, which inhibits the growth of fungi, yeast, mold and bacteria, is widely used in cosmetics and shampoo. Recently, we reported that PTS2 induced HeLa cells apoptosis through activating MAPKs pathway. Here we show the evidence that PTS2 inhibits LPS-induced iNOS expression and NO production in macrophages. We also found the reduction of STAT1 phosphorylation is involved in the inhibitory effect of PTS2 on iNOS expression in RAW264.7 cells. These results strongly suggest that PTS2 might exert anti-inflammatory activities in LPS-induced inflammation.