Influence of cytokines on Dmt1 iron transporter and ferritin expression in insulin-secreting cells

Abstract

Free intracellular ferrous iron (Fe 2C ) is essential for the generation of the extremely toxic hydroxyl radicals, which contribute to b-cell destruction by cytokines. Therefore the expression of the different divalent metal transporter 1 (Dmt1) isoforms and ferritin (Ft) subunits, responsible for iron import and chelation, was analyzed under pro-inflammatory conditions (IL1b alone or together with TNFaCIFNg). The Dmt1 isoforms (1A/1B and CIRE/ KIRE) and the total Dmt1 expression in insulin-producing cells (RINm5F and INS-1E), in primary rat islets and, for comparison, in the neuroendocrine PC12 cell line were quantified by qRT-PCR. In addition, the expression of the light (L-Ft) and heavy Ft (H-Ft) subunits and the mitochondrial Ft isoform (Mtft) in insulin-producing cells under control conditions and after cytokine treatment was estimated. The 1B isoform was the predominant Dmt1 mRNA in all insulin-producing cells, accounting for almost 100% of the 1A/1B isoform expression. For the IRE variants, CIRE expression was higher than KIRE expression. Pro-inflammatory cytokines accelerated the expression of Dmt1 isoforms significantly with an overall 2.5-to 3-fold increase in the total Dmt1 expression. In contrast, the expression of the iron-buffering ferritin subunits L-and H-Ft was unaffected by IL1b and only slightly induced by the cytokine mixture. Mtft expression was also not increased. Dmt1 expression was significantly elevated through pro-inflammatory cytokines, whereas Ft expression was marginally increased. This imbalance between the increased iron transport capacity and the almost unaffected iron storage capacity can foster cytokine-mediated formation of hydroxyl radicals and thus pro-inflammatory cytokine toxicity through elevated free iron concentrations.

Endometrial expression and in vitro modulation of the iron transporter divalent metal transporter-1: implications for endometriosis

“…Regarding IL-1b, our in vitro results show that this cytokine induced an increase in DMT-80 and DMT-50 expression and a reduction in DMT-65 expression in ESCs. It has been reported that IL-1b induces an increase in DMT1 expression in rat primary neurons, microglia, and the pancreatic cell line RINm5F (26,28,29). This, together with the results shown here, can be explained because IL-1b is a well-known inducer of NF-kB activation (68,69).…”

“…Excessive intracellular iron is stored in ferritin, a multimeric protein conformed by 24 subunits of either heavy or light chains, ferritin light chain (Fn-L) being the structure where nucleation sites for iron crystal formation are present (20). In a cell-specific response, inflammation is a stimulus for the regulation of DMT1 and Fn-L protein synthesis (21)(22)(23)(24)(25)(26)(27)(28)(29).…”

In Situ OH Generation from O2− and H2O2 Plays a Critical Role in Plasma-Induced Cell Death

“…Findings from previous studies suggested that plasma treatment could provide both H 2 O 2 and O 2 − species at μM concentrations. Cells typically express several iron proteins such as ferroportin [ 29 , 30 ], lactoferrin receptor [ 31 ], transferrin [ 32 , 33 ], divalent metal transporter 1 [ 34 , 35 ], and ferritin [ 36 , 37 ], among others. These proteins could conceivably catalyze H 2 O 2 and O 2 − radicals into a highly reactive OH radical that has more potent biological effects.…”

Anaemia of Chronic Disease: An In-Depth Review

“…Activation of this pathway leads to production of intracellular factors which enhance apoptosis by regulating transcription and eventual myelosuppression. IFN-γ stimulates ferritin transcription on the one hand and inhibits transferrin receptor (TfR) mRNA expression via an iron-regulatory element-protein-independent process [ 20 , 21 , 22 ]. It also increases expression of DMT-1, which is involved in the active transport of ferrous molecules from the lumen to the duodenal endothelial cell cytoplasm [ 21 ].…”