Taurine chloramine induces heme oxygenase-1 expression via Nrf2 activation in murine macrophages

Abstract

Taurine chloramine (TauCl) is produced abundantly in activated neutrophils by a reaction between the stored taurine and the newly produced HOCl by the myeloperoxidase system, and is much less oxidizing or toxic than HOCl. TauCl has been shown to provide cytoprotection against inflammatory tissue injury by inhibiting the overproduction of inflammatory mediators. The result of this study shows that TauCl upregulated the expression of heme oxygenase (HO)-1 and increased HO activity in RAW 264.7 macrophages, while taurine had no effect. TauCl by itself generated reactive oxygen species (ROS) in macrophages and diminished total glutathione (GSH) level initially. TauCl increased the nuclear translocation of NF-E2-related factor 2 (Nrf2) and enhanced its binding to the anti-oxidant response element (ARE). This, in turn, was responsible for the upregulation of HO-1 expression. In summary, TauCl generated ROS in RAW 264.7 macrophages and decreased cellular GSH level initially. This was responsible for the nuclear translocation of Nrf2 and its binding to ARE promoted the expression of HO-1 and increased HO activity. Thus, TauCl-derived elevation of HO activity may play an essential role in the adaptive cytoprotection of inflammatory tissues.