A Combined Drug Treatment That Reduces Mitochondrial Iron and Reactive Oxygen Levels Recovers Insulin Secretion in NAF-1-Deficient Pancreatic Cells

Abstract

Decreased insulin secretion, associated with pancreatic β-cell failure, plays a critical role in many human diseases including diabetes, obesity, and cancer. While numerous studies linked β-cell failure with enhanced levels of reactive oxygen species (ROS), the development of diabetes associated with hereditary conditions that result in iron overload, e.g., hemochromatosis, Friedreich's ataxia, and Wolfram syndrome type 2 (WFS-T2; a mutation in CISD2, encoding the [2Fe-2S] protein NAF-1), underscores an additional link between iron metabolism and β-cell failure. Here, using NAF-1-repressed INS-1E pancreatic cells, we observed that NAF-1 repression inhibited insulin secretion, as well as impaired mitochondrial and ER structure and function. Importantly, we found that a combined treatment with the cell permeant iron chelator deferiprone and the glutathione precursor N-acetyl cysteine promoted the structural repair of mitochondria and ER, decreased mitochondrial labile iron and ROS levels, and restored glucose-stimulated insulin secretion. Additionally, treatment with the ferroptosis inhibitor ferrostatin-1 decreased cellular ROS formation and improved cellular growth of NAF-1 repressed pancreatic cells. Our findings reveal that suppressed expression of NAF-1 is associated with the development of ferroptosis-like features in pancreatic cells, and that reducing the levels of mitochondrial iron and ROS levels could be used as a therapeutic avenue for WFS-T2 patients.

Wolfram Syndrome Type 2: A Systematic Review of a Not Easily Identifiable Clinical Spectrum

“…They showed that treatment with the ferroptosis inhibitor ferrostatin-1 improved the cellular growth of NAF-1-repressed pancreatic cells. The authors concluded that the reduction of the mitochondrial iron levels could be used as a therapeutic route for patients with WS2 within the in vitro study [ 38 ]. Human studies are needed in order to verify the efficacy of molecules that block ER stress-induced apoptosis in the treatment of WS2.…”

A VDAC1-mediated NEET protein chain transfers [2Fe-2S] clusters between the mitochondria and the cytosol and impacts mitochondrial dynamics

“…Oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were measured using a Seahorse XFp, Agilent, cell mito-stress analyzer (Agilent Technologies, Inc.) with the XF Cell Mito Stress Kit and XF Glycolysis Stress Kit (Agilent Technologies, Inc.), as previously described ( 26 ), and according to the manufacturer’s instructions ( 40 ). MDA-MB-231 cells (25,000) were grown to ∼80% confluence in complete medium overnight before the experiment.…”

“…Cells were grown on eight-well Permanox chamber slides and, upon reaching ∼80% confluence, were fixed in 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1 M cacodylate buffer (pH 7.4) for 2 h at room temperature, then prepared for transmission electron microscope (TEM) imaging as described in detail in refs. 18 and 26 . Results were evaluated from 5 to 10 different cells randomly selected, averaged over 10 to 20 fields per cell; at least 100 to 200 mitochondria were counted.…”

“…Downregulating any one of the NEET proteins, including MiNT, leads to increased accumulation of mitochondrial labile iron (mLI) and mitochondrial reactive oxygen species (mROS), as well as to disruptions in mitochondrial function and morphology ( 12 , 14 , 17 ). Mitochondrial iron and ROS accumulation were shown to affect mitochondrial respiratory capacity ( 12 , 18 – 26 ). Since mitochondria are considered to play a central role in bioenergetics, metabolism, and other cellular pathways ( 27 ), mitochondria morphodynamics are tightly linked to the overall bioenergetic function of cells ( 28 ).…”

“…Decreasing mNT or NAF-1 levels leads to a reduction of mitochondrial size indicative of a fission process in cells ( 24 , 26 ). NAF-1 and mNT were previously shown to interact; in this interaction, mNT transfers its [2Fe-2S] cluster to NAF-1 ( 17 ).…”