Endothelin 1 in iron handling in sickle cell disease

Sickle cell disease (SCD) is an inherited chronic hemolytic anemia characterized by vaso-occlusive episodes and end organ damage. Up to 80% of patients with SCD will develop chronic kidney disease (CKD), with 30% mortality ascribed to kidney failure. This devastating health outcome exists because there are numerous gaps in our understanding of complex mechanisms underlying SCD nephropathy. In patients and murine SCD, an increased renal iron deposition occurs primarily in proximal tubules (PT), and correlates with albuminuria, an early marker of CKD. Kidney-specific etiology of iron accumulation is purely a consequence of intravascular hemolysis, not chronic blood transfusion. Current interventional strategies are limited to the chelation of transfusion-mediated iron overload only. Classic iron chelators are nephrotoxic, and there are no available strategies targeting kidney iron overload, thus there is an unmet need for novel iron overload-modifying reno-protective strategies. However, molecular mechanisms of renal-specific iron handling remain to be elucidated. My preliminary studies indicate that ET-1 promotes PT iron accumulation. I observed a strong positive correlation between plasma ET-1 levels and renal iron accumulation in both mice and patients with SCD. Furthermore, selective ETA receptor antagonist reduces iron deposition in the kidney, at the same time increasing urinary iron excretion and serum iron levels in SCD mice. Third, my in vitro data show that ET-1 directly increases the expression of transferrin-1 receptor (iron uptake transporter) and decreases the expression of ferroportin-1 (FPN-1, iron exporter) in mouse PT cells. Together, these observations point to ET-1/ETA signaling as a novel regulator of renal iron handling in SCD. Based on these novel preliminary findings, we hypothesize that ET- 1/ETA activation promotes renal iron overload via direct increase in heme/iron uptake and/or inhibition of iron export in SCD. Using primary mouse and human PT cells, we will determine whether ET-1/ETA receptor activation increases heme/iron uptake via direct and/or HIF-1a-mediated activation of NF-kB signaling pathway. Using novel humanized SCD mice lacking PT ETA expression, we will determine the effect of ETA receptors deletion on renal iron burden and kidney health. Second, we will define specific ET-1/ETA-dependent control of FPN-1 and iron export in vitro, and in vivo mechanisms contributing to ETA-mediated renal iron recycling using acute hemolysis model. Lastly, we will determine the effect of ETA receptor antagonism on iron recycling and/or urinary excretion in SCD patients. We aim to unveil these molecular mechanisms with the following aims: Specific Aim 1: Determine the mechanism(s) by which ET-1/ETA signaling promotes iron uptake by PT and its subsequent contribution to SCD nephropathy. Specific Aim 2: Determine the mechanism(s) by which ET-1/ETA signaling reduces PT iron export, subsequently leading to iron accumulation in SCD. Specific Aim 3: Assess the relationship between renal iron handling and ETA antagonism in SCD patients. Project Number: 1R01HL173038-01A1 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Malgorzata Kasztan | Institution: UNIV OF NORTH CAROLINA CHAPEL HILL, CHAPEL HILL, NC | Award Amount: $573,821 | Activity Code: R01 | Study Section: Hemostasis, Thrombosis, Blood Cells and Transfusion Study Section[HTBT] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01HL17303801A1