APPS November 2002 Meeting Abstract 1153


Ralph N. Watts, Des Richardson, Iron Metabolism and Chelation Group, The Heart Research Institute, Sydney, NSW.

Iron (Fe) plays a crucial role in cellular metabolism, being found in a variety of essential proteins and enzymes. Recently, nitrogen monoxide (NO) has been shown to mobilize Fe from cells. Indeed, the cytotoxicity of activated macrophages is at least partially mediated by the production of NO that targets vital Fe-containing molecules and results in Fe release. The mechanism of NO-mediated Fe mobilization from cells remains unclear, but recently we have shown that it is dependent on temperature as well as ATP and glutathione levels1 We have now further examined the mechanism of NO-mediated Fe efflux from cells. Since Fe release by NO and Fe chelators have similar characteristics, we examined whether these molecules target the same intracellular pools by pre-labeling cells with 59Fe-transferrin (Tf). The cells were then incubated with Fe chelators in the presence or absence of NO-generators. For all chelators tested, no additive effect on Fe efflux was observed when co-incubated with NO. Further experiments were performed to determine if the addition of non-membrane permeable Fe chelators could increase NO-mediated Fe efflux by creating an extracellular Fe “sink”. However, no enhancement of NO-mediated Fe mobilization was observed. The ability of NO to mobilize Fe from cell lysates was also examined in comparison to the Fe chelator desferrioxamine. In contrast to whole cells, NO had little influence on mobilising Fe from lysates, being less effective than desferrioxamine. We have also shown that NO targets ferritin-Fe levels by inhibiting incorporation of Fe into this molecule and indirectly inducing Fe release. Our data suggests that NO removes Fe from the same intracellular pool as Fe chelators and that this appears to occur by an energy-dependent process that is independent of simple diffusion.

(1) Watts RN, Richardson DR. Journal of Biological Chemistry. 2001;276:4727-4732.

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