The Labile Iron Pool Reacts Rapidly and Catalytically with Peroxynitrite

While investigating peroxynitrite-dependent oxidation in murine RAW 264.7 macrophage cells, we observed that removal of the Labile Iron Pool (LIP) by chelation increases the intracellular oxidation of the fluorescent indicator H2DCF, so we concluded that the LIP reacts with peroxynitrite and decreases the yield of peroxynitrite-derived oxidants. This was a paradigm-shifting finding in LIP biochemistry and raised many questions. In this follow-up study, we address fundamental properties of the interaction between the LIP and peroxynitrite by using the same cellular model and fluorescence methodology. We have identified that the reaction between the LIP and peroxynitrite has catalytic characteristics, and we have estimated that the rate constant of the reaction is in the range of 10(6) to 10(7) M(-1)s(-1). Together, these observations suggest that the LIP represents a constitutive peroxynitrite reductase system in RAW 264.7 cells.

Automated summary

Investigating the interaction between the Labile Iron Pool (LIP) and peroxynitrite in murine RAW 264.7 macrophage cells, it was found that removal of LIP increases intracellular oxidation of H2DCF, indicating that LIP reacts with peroxynitrite to decrease oxidant yield. The study further reveals that the LIP-peroxynitrite reaction has catalytic characteristics with an estimated rate constant of 10(6) to 10(7) M(-1)s(-1), suggesting LIP represents a constitutive peroxynitrite reductase system in RAW 264.7 cells.