Down-regulation of senescence marker protein 30 by iron-specific chelator deferoxamine drives cell senescence.

To our knowledge, this is the first study to report down-regulation of senescence marker protein 30 (SMP30) by iron-specific chelator deferoxamine (DFO) on FAO cell senescence, using a DNA microarray. Furthermore, DFO treatment increased senescence marker ß-galactosidase activity, whereas this activity was attenuated by overexpression of SMP30. Our data suggested that down-regulation of SMP30 drives cell senescence in iron-chelated condition.

Iron deficiency negatively regulates protein methylation via the downregulation of protein arginine methyltransferase.

Iron is an essential trace metal for all biological processes and plays a role in almost every aspect of body growth. Previously, we found that iron-depletion downregulated the expression of proteins, arginine methyltransferase-1 and 3 (PRMT1 and PRMT3), by an iron-specific chelator, deferoxamine (DFO), in rat liver FAO cell line using DNA microarray analysis (unpublished data). However, regulatory mechanisms underlying the association between iron deficiency and PRMT expression are unclear in vitro and in vivo. In the present study, we revealed that the treatment of cells with two iron-specific chelators, DFO and deferasirox (DFX), downregulated the gene and protein expression of PRMT1 and 3 as compared with the untreated cells. Subsequently, DFO and DFX treatments decreased protein methylation. Importantly, these effects were attenuated by a holo-transferrin treatment. Furthermore, weanling Wistar-strain rats were fed a control diet or an iron-deficient diet for 4 weeks. Dietary iron deficiency was found to decrease the concentration of hemoglobin and liver iron while increasing the heart weight. PRMT and protein methylation levels were also significantly reduced in the iron-deficient group as compared to the control group. To our knowledge, this is the first study to demonstrate that PRMT levels and protein methylation are reduced in iron-deficient models, in vitro and in vivo.

Iron deficiency induces autophagy and activates Nrf2 signal through modulating p62/SQSTM.

Iron is an essential trace metal in almost all organisms and plays an important role in the redox system. We previously reported that iron deficiency activated autophagy and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling for oxidative stress. However, regulatory mechanisms underlying the association between autophagy and Nrf2 signaling are unclear. In this study, we found that treatment of cells with an iron-specific chelator deferoxamine (DFO) increased reactive oxidative species (ROS) production by elevating the expression of p47phox and p67phox compared with that in untreated cells. The DFO treatment also induced protein aggregation and formed aggresome, which is a cellular response to misfolded protein. In addition, DFO treatment upregulated the expression of the autophagic gene p62/SQSTM1, which in turn activated intracellular proteolysis during autophagy. DFO treatment phosphorylated p62/SQSTM1 (Thr351) to activate Nrf2. However, silencing of p62/SQSTM1 followed by DFO treatment attenuated Nrf2 activation and resulted in the accumulation of carboxyl proteins compared with DFO treatment alone. These results indicated that iron deficiency activates Nrf2 signaling by modulating p62/SQSTM1 during autophagy.