Production of reactive oxygen and nitrogen species in phagocytes is regulated by taurine chloramine

Taurine is abundantly present in phagocytic cells and provides protection against cytotoxicity caused by reactive oxygen species (ROS). The reaction between taurine and HOCl, a toxic product of the myeloperoxidase (MPO) system, generates a more stable and less toxic product, taurine chloramine (TauCl). TauCl has also been shown to inhibit the production of superoxide anion (O2-) and nitric oxide (NO). In this review, we compare the effect of taurine and TauCl on the production of these reactive species in phagocytes. First, TauCl inhibit PMA-derived O2- production and this is associated with inhibition of p47phox phosphorylation and of p47phox and p67phox translocation. Second, TauCl inhibits LPS-induced iNOS expression and NO production. This occurs by direct inhibition of Ras activation, ERK1/2 phosphorylation and NF-kappaB activation. Third, TauCl by itself increases the expression of heme oxygenase-1 (HO-1) and enhances HO activity. Carbon monoxide (CO), a product of HO activity, is able to inhibit both O2- and NO production. Combined, these effects of TauCl appear to provide cytoprotection against the inadvertent cytotoxicity caused by overproduction of O2- and NO.