Kidney Week

Abstract: SA-PO223

ET-1-Dependent Impairment of Renal Iron Handling Leads to Iron Overload-Associated Tubular Injury in Sickle Cell Nephropathy

Session Information

• Anemia and Iron Metabolism: Basic
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Anemia and Iron Metabolism

• 201 Anemia and Iron Metabolism: Basic

Authors

• Kasztan, Malgorzata, University of Alabama at Birmingham, Birmingham, Alabama, United States

Malgorzata Kasztan,

• Hyndman, Kelly A., University of Alabama at Birmingham, Birmingham, Alabama, United States

Kelly A. Hyndman,

• Pollock, David M., University of Alabama at Birmingham, Birmingham, Alabama, United States

David M. Pollock,

Background

Iron overload, a major consequence of the sickle cell disease (SCD), promotes renal iron deposition that correlates with albuminuria in SCD patients. Also, elevated plasma endothelin-1 (ET-1) levels reported in SCD correlate with microalbuminuria. Excessive renal iron deposition in humanized sickle cell (HbSS) mice is attenuated by endothelin A receptor (ET_A) blockade.Thus, we hypothesize that elevated ET-1 via ET_A receptor activity leads to dysfunctional tubular iron handling, iron overload, and resultant tubular injury in SCD nephropathy.

Methods

C57BL/6 mouse primary tubule (PT) cells and 14 weeks old HbSS mice were utilized in this study.

Results

ET-1 directly increased the expression of iron trafficking mediators in mouse PT cells. This includes transferrin receptor 1 (TfR-1) for cellular uptake and H-ferritin for storage. ET-1 also, decreases the expression of the iron exporter, ferroportin-1 ((FPN-1) and increases the expression of FPN-1 regulator, hepcidin (HAMP). Exposure of PT cells to 50 nM ET-1 and 0.1 μM heme for 24h increased cellular heme uptake compared to untreated cells (19.31±2.51 vs. 1.85±0.26 μM/mg protein). The ET_A antagonist, BQ123, prevented ET-1-induced alterations in all iron trafficking mediators. Moreover, plasma ET-1 concentrations were positively correlated with renal iron deposition in HbSS mice (R²=0.72, p<0.0001). HbSS mice showed altered PT iron transporter expressions consistent with promoting PT iron accumulation. 10-week in vivo treatment with an ET_A receptor antagonist prevented the induction of cellular iron uptake transporter, DMT-1, preserved FPN-1, and reduced HAMP expression in PT cells from HbSS mice. A potential mechanism(s) of ET-1-mediated iron overload-associated tubular damage may involve ROS and/or mitochondrial dysfunction. PT cells exposed to FeS (500 μg/mL) have increased ROS production (12.52±1.31 vs. 0.14±0.01 AUCx10³/mg protein). PT cells from HbSS mice exhibit mitochondrial dysfunction indicated by doubled expression of markers of mitochondrial stress PTEN-induced kinase 1 (PINK1), heat-shock protein 40 (mtHSP40), and mitochondrial fission 1 protein (Fis1).

Conclusion

These results uncover a novel role for ET-1 in PT iron trafficking and provide rationale for use of selective ET_A receptor blockade as a potential therapeutic approach in SCD nephropathy.

Funding

• NIDDK Support